Science.gov

Sample records for mcmurry reaction conditions

  1. Crossed McMurry Coupling Reactions for Porphycenic Macrocycles: Non-Statistical Selectivity and Rationalisation

    PubMed Central

    Cowie, Thomas Y; Kennedy, Lorna; Żurek, Justyna M; Paterson, Martin J; Bebbington, Magnus W P

    2015-01-01

    Crossed McMurry reactions of bifuran- or bithiophenedicarbaldehydes with bipyrroledicarbaldehydes have been studied for the first time. Only those porphycenic macrocycles derived from homocoupled McMurry products were formed. The results are explained by using both density functional theory and electron propagator computations to model the electron affinity of the dialdehyde starting materials. It was predicted that bifuran\\bithiophene cross-coupling would indeed occur, and this was demonstrated by the first synthesis of a novel dioxa,dithio hetero-porphycenoid annulene. This approach will allow the prior identification of viable substrates for related crossed McMurry reactions. PMID:26213484

  2. '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...

  3. Expert system for predicting reaction conditions: the Michael reaction case.

    PubMed

    Marcou, G; Aires de Sousa, J; Latino, D A R S; de Luca, A; Horvath, D; Rietsch, V; Varnek, A

    2015-02-23

    A generic chemical transformation may often be achieved under various synthetic conditions. However, for any specific reagents, only one or a few among the reported synthetic protocols may be successful. For example, Michael β-addition reactions may proceed under different choices of solvent (e.g., hydrophobic, aprotic polar, protic) and catalyst (e.g., Brønsted acid, Lewis acid, Lewis base, etc.). Chemoinformatics methods could be efficiently used to establish a relationship between the reagent structures and the required reaction conditions, which would allow synthetic chemists to waste less time and resources in trying out various protocols in search for the appropriate one. In order to address this problem, a number of 2-classes classification models have been built on a set of 198 Michael reactions retrieved from literature. Trained models discriminate between processes that are compatible and respectively processes not feasible under a specific reaction condition option (feasible or not with a Lewis acid catalyst, feasible or not in hydrophobic solvent, etc.). Eight distinct models were built to decide the compatibility of a Michael addition process with each considered reaction condition option, while a ninth model was aimed to predict whether the assumed Michael addition is feasible at all. Different machine-learning methods (Support Vector Machine, Naive Bayes, and Random Forest) in combination with different types of descriptors (ISIDA fragments issued from Condensed Graphs of Reactions, MOLMAP, Electronic Effect Descriptors, and Chemistry Development Kit computed descriptors) have been used. Models have good predictive performance in 3-fold cross-validation done three times: balanced accuracy varies from 0.7 to 1. Developed models are available for the users at http://infochim.u-strasbg.fr/webserv/VSEngine.html . Eventually, these were challenged to predict feasibility conditions for ∼50 novel Michael reactions from the eNovalys database (originally

  4. Tamoxifen derivatives for delivery of the antitumoral (DACH)Pt group: selective synthesis by McMurry coupling, and biochemical behaviour.

    PubMed

    Top, Siden; Kaloun, El Bachir; Vessières, Anne; Leclercq, Guy; Laïos, Ioanna; Ourevitch, Michèle; Deuschel, Christine; McGlinchey, Michael J; Jaouen, Gérard

    2003-08-01

    The goal of our study was to potentiate the effects of the ((R,R)-trans-1,2-diaminocyclohexane)-platinum(II) fragment [(DACH)Pt], known for its cytotoxic properties, either with tamoxifen (Tam), the most widely used antiestrogen in the treatment of hormone-dependent breast cancers, or with its active metabolite hydroxytamoxifen (hydroxy-Tam). We coupled Tam or hydroxy-Tam derivatives bearing a malonato group at the para position of the beta aromatic ring with the (DACH)Pt fragment. The malonato-Tam and malonato-hydroxy-Tam compounds were prepared through McMurry coupling of the appropriate ketones. The presence of the malonate group resulted in a pronounced stereospecificity in the reaction, since malonato-Tam was obtained only as the Z isomer, while malonato-hydroxy-Tam was obtained as an 80/20 E/Z mixture. Attribution of the isomeric structures was achieved by 2D NMR spectroscopy. The platinum complexes (DACH)Pt-malonato-Tam and (DACH)Pt-malonato-hydroxy-Tam were then prepared by coupling the barium salts derived from the malonato-Tam and malonato-hydroxy-Tam with the nitrate derived from (DACH)PtCl(2). Study of the biochemical properties of these two platinum complexes showed that, while the hydroxy-Tam complex is satisfactorily recognized by the estrogen receptor (relative binding affinity, RBA=6.4 %), the Tam complex is less well recognized (RBA=0.5 %). The effects of these complexes on two hormone-dependent breast cancer cell lines (MCF7 and MVLN) were studied in vitro. Both complexes showed an antiproliferative effect on MCF7 cells, and an antiestrogenic effect on MVLN cells. The observed effects appear to be essentially antihormonal, since incorporation of the (DACH)Pt fragment into the tamoxifen skeleton did not cause an increase in the cytotoxicity of the complexes. PMID:12898627

  5. 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.

  6. Accelerated glass reaction under PCT conditions

    SciTech Connect

    Ebert, W.L.; Bates, J.K.; Buck, E.C.; Bradley, C.R.

    1992-01-01

    Static leach tests similar to PCT (Product Consistency Test) were performed for up to 2 years to assess long-term reaction behavior of high-level nuclear waste glasses similar to those at Defense Waste Processing Facility. These tests show the reaction rate to decrease with the reaction time from an initially high rate to a low rate, but then to accelerate to a higher rate after reaction times of about 1 year, depending on glass surface area/leachant volume ratio used. Solution concentrations of soluble glass components increase as the reaction is accelerated, while release of other glass components into solution is controlled by secondary phases. Net result is that transformation of glass to stable phases is accelerated while the solution becomes enriched in soluble components not effectively contained in secondary phases. Rate becomes linear in time after the acceleration and may be similar to the initial forward rate. A current model of glass reaction predicts that the glass reaction will be accelerated upon the formation of secondary phases which lower the silicic acid solution concentration. These tests show total Si concentration to increase upon reaction acceleration, however, which may be due to the slightly higher pH attained with the acceleration. The sudden change in the reaction rate is likely due to secondary phase formation. 17 refs, 2 tabs, 3 figs.

  7. Accelerated glass reaction under PCT conditions

    SciTech Connect

    Ebert, W.L.; Bates, J.K.; Buck, E.C.; Bradley, C.R.

    1992-12-31

    Static leach tests similar to PCT (Product Consistency Test) were performed for up to 2 years to assess long-term reaction behavior of high-level nuclear waste glasses similar to those at Defense Waste Processing Facility. These tests show the reaction rate to decrease with the reaction time from an initially high rate to a low rate, but then to accelerate to a higher rate after reaction times of about 1 year, depending on glass surface area/leachant volume ratio used. Solution concentrations of soluble glass components increase as the reaction is accelerated, while release of other glass components into solution is controlled by secondary phases. Net result is that transformation of glass to stable phases is accelerated while the solution becomes enriched in soluble components not effectively contained in secondary phases. Rate becomes linear in time after the acceleration and may be similar to the initial forward rate. A current model of glass reaction predicts that the glass reaction will be accelerated upon the formation of secondary phases which lower the silicic acid solution concentration. These tests show total Si concentration to increase upon reaction acceleration, however, which may be due to the slightly higher pH attained with the acceleration. The sudden change in the reaction rate is likely due to secondary phase formation. 17 refs, 2 tabs, 3 figs.

  8. 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 ...

  9. 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...

  10. High explosive violent reaction (HEVR) from slow heating conditions

    SciTech Connect

    Vigil, A.S.

    1999-03-01

    The high explosives (HEs) developed and used at the Los Alamos National Laboratory are designed to be insensitive to impact and thermal insults under all but the most extreme conditions. Nevertheless, violent reactions do occasionally occur when HE is involved in an accident. The HE response is closely dependent on the type of external stimulus that initiates the reaction. For example, fast heating of conventional HE will probably result in fairly benign burning, while long-term, slow heating of conventional HE is more likely to produce an HEVR that will do much more damage to the immediate surroundings. An HEVR (High Explosive Violent Reaction) can be defined as the rapid release of energy from an explosive that ranges from slightly faster than a deflagration (very rapid burning) to a reaction that approaches a detonation. A number of thermal analyses have been done to determine slow heat/cook-off conditions that produce HE self-heating that can build up to a catastrophic runaway reaction. The author specifies the conditions that control reaction violence, describes experiments that produced an HEVR, describes analyses done to determine a heating rate threshold for HEVR, and lists possible HEVR situations.

  11. Cyclodextrin-promoted Diels Alder reactions of a polycyclic aromatic hydrocarbon under mild reaction conditions

    PubMed Central

    Chaudhuri, Sauradip; Phelan, Tyler; Levine, Mindy

    2015-01-01

    Reported herein is the effect of cyclodextrins on the rates of aqueous Diels Alder reactions of 9-anthracenemethanol with a variety of N-substituted maleimides. These reactions occurred under mild reaction conditions (aqueous solvent, 40 °C), and were most efficient for the reaction of N-cyclohexylmaleimide with a methyl-β-cyclodextrin additive (94% conversion in 24 hours). These results can be explained on the basis of a model wherein the cyclodextrins bind the hydrophobic substituents on the maleimides and activate the dienophile via electronic modulation of the maleimide double bond. The results reported herein represent a new mechanism for cyclodextrin-promoted Diels Alder reactions, and have significant potential applications in the development of other cyclodextrin-promoted organic transformations. Moreover, the ability to deplanarize polycyclic aromatic hydrocarbons (PAHs) under mild conditions, as demonstrated herein, has significant applications for PAH detoxification. PMID:26692588

  12. Reactions of animals and people under conditions of brief weightlessness

    NASA Technical Reports Server (NTRS)

    Kitayev-Smik, L. A.

    1975-01-01

    It has been shown that under brief weightlessness sensory reactions arise in a number of people, mainly those under these conditions for the first time, in the form of spatial and visual illusions, motor excitation, in which tonic and motor components can be distinguished, and vestibular-vegetative disturbances (nausea, vomiting, etc.). In repeated flights with creation of weightlessness, a decrease in the extent of expression and, then, disappearance of these reactions occurred in a significant majority of those studied. Experiments in weightlessness with the vision cut off and with the absence of vestibular functions in the subjects confirm the hypothesis that spatial conceptions of people in weightlessness depend on predominance of gravireceptor or visual afferent signals under these conditions.

  13. Pathways of the Maillard reaction under physiological conditions.

    PubMed

    Henning, Christian; Glomb, Marcus A

    2016-08-01

    Initially investigated as a color formation process in thermally treated foods, nowadays, the relevance of the Maillard reaction in vivo is generally accepted. Many chronic and age-related diseases such as diabetes, uremia, atherosclerosis, cataractogenesis and Alzheimer's disease are associated with Maillard derived advanced glycation endproducts (AGEs) and α-dicarbonyl compounds as their most important precursors in terms of reactivity and abundance. However, the situation in vivo is very challenging, because Maillard chemistry is paralleled by enzymatic reactions which can lead to both, increases and decreases in certain AGEs. In addition, mechanistic findings established under the harsh conditions of food processing might not be valid under physiological conditions. The present review critically discusses the relevant α-dicarbonyl compounds as central intermediates of AGE formation in vivo with a special focus on fragmentation pathways leading to formation of amide-AGEs. PMID:27291759

  14. 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

  15. 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

  16. 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.

  17. 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...

  18. 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,…

  19. 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.

  20. New short strategy for the synthesis of the dibenz[b,f]oxepin scaffold.

    PubMed

    Moreno, David R R; Giorgi, Giorgio; Salas, Cristian O; Tapia, Ricardo A

    2013-01-01

    In this report a short and efficient synthesis of the dibenz[b,f]oxepin framework through intramolecular SNAr and McMurry reactions is described. The diaryl ethers required for the McMurry reaction have been obtained in good yields under microwave-assisted conditions of the reaction of salicylaldehydes with fluorobenzaldehydes without catalysts. Application of an intramolecular McMurry reaction to the synthesized diarylethers using TiCl4/Zn in THF gave the target dibenzo[b,f]oxepin system in 53%-55% yields. PMID:24352054

  1. Reactions to Ostracism in Adolescents with Autism Spectrum Conditions

    ERIC Educational Resources Information Center

    Sebastian, Catherine; Blakemore, Sarah-Jayne; Charman, Tony

    2009-01-01

    Little is known about how adolescents with autism spectrum conditions (ASC) experience the initial impact of ostracism. This study investigated whether a mild, short-term episode of experimentally induced ostracism (Cyberball) would affect self-reported anxiety, mood, and the extent to which four social needs (self-esteem, belonging, control and…

  2. 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.

  3. Impact of reaction conditions on architecture and rheological properties of starch graft polyacrylamide polymers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We carried out experiments examining the impact that solvent selection and reaction conditions have on the radical initiated graft polymerization reaction of acrylamide onto starch. We have also evaluated the rheological properties the starch graftpolyacrylamide product when a gel is formed in water...

  4. Formation of phenol under conditions of the reaction of oxidative carbonylation of benzene to benzoic acid

    SciTech Connect

    Kalinovsky, I.O.; Leshcheva, A.N.; Pogorelov, V.V.; Gelbshtein, A.I.

    1993-12-31

    This paper describes conditions for the oxidation of benzene to phenol. It is shown that a reaction mixture of water, carbon monoxide, and oxygen are essential to the oxidation. The oxidation is a side reaction found to occur during the oxidative carbonylation of benzene to benzoic acid in a medium of trifluoroacetic acid.

  5. Nitric oxide is consumed, rather than conserved, by reaction with oxyhemoglobin under physiological conditions

    NASA Astrophysics Data System (ADS)

    Joshi, Mahesh S.; Ferguson, T. Bruce, Jr.; Han, Tae H.; Hyduke, Daniel R.; Liao, James C.; Rassaf, Tienush; Bryan, Nathan; Feelisch, Martin; Lancaster, Jack R., Jr.

    2002-08-01

    Although irreversible reaction of NO with the oxyheme of hemoglobin (producing nitrate and methemoglobin) is extremely rapid, it has been proposed that, under normoxic conditions, NO binds preferentially to the minority deoxyheme to subsequently form S-nitrosohemoglobin (SNOHb). Thus, the primary reaction would be conservation, rather than consumption, of nitrogen oxide. Data supporting this conclusion were generated by using addition of a small volume of a concentrated aqueous solution of NO to a normoxic hemoglobin solution. Under these conditions, however, extremely rapid reactions can occur before mixing. We have thus compared bolus NO addition to NO generated homogeneously throughout solution by using NO donors, a more physiologically relevant condition. With bolus addition, multiple hemoglobin species are formed (as judged by visible spectroscopy) as well as both nitrite and nitrate. With donor, only nitrate and methemoglobin are formed, stoichiometric with the amount of NO liberated from the donor. Studies with increasing hemoglobin concentrations reveal that the nitrite-forming reaction (which may be NO autoxidation under these conditions) competes with reaction with hemoglobin. SNOHb formation is detectable with either bolus or donor; however, the amounts formed are much smaller than the amount of NO added (less than 1%). We conclude that the reaction of NO with hemoglobin under normoxic conditions results in consumption, rather than conservation, of NO.

  6. Synthetic Reactions Using Low-valent Titanium Reagents Derived from Ti(OR)4 or CpTiX3 (X = O-i-Pr or Cl) in the Presence of Me3 SiCl and Mg.

    PubMed

    Okamoto, Sentaro

    2016-04-01

    In the presence of Me3 SiCl, Ti(OR)4 or CpTiX3 (X = O-i-Pr or Cl) is reduced by Mg powder in THF to gradually generate a specific low-valent titanium (LVT) species that mediates several synthetic reactions. The LVT-catalyzed C-O bond-cleaving reactions of allyl and propargyl ethers and esters generate parent alcohols and carboxylic acids, respectively. O-allyl and propargyl carbamates are also readily deprotected by the LVT to afford parent amines. In addition, the respective reductive N-S or O-S bond cleavage of sulfonamides or sulfonyl esters mediated by the LVT was developed as a novel facile deprotection method. The reagent catalyzes intra- and intermolecular alkyne or alkyne/nitrile cycloaddition to produce substituted benzenes and pyridines, while epoxides and oxetanes are reduced to alcohols via an LVT-mediated homolytic ring opening. The McMurry coupling of aryl aldehydes and ketones proceeds with the LVT under homogeneous and mild reaction conditions and is effective for the polymerization of aromatic dialdehydes, generating conjugated polymers. Finally, imino-pinacol coupling of imines is mediated by the LVT to provide 1,2-diamines. PMID:26969349

  7. 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.

  8. 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

  9. Macromolecular crowding conditions enhance glycation and oxidation of whey proteins in ultrasound-induced Maillard reaction.

    PubMed

    Perusko, Marija; Al-Hanish, Ayah; Cirkovic Velickovic, Tanja; Stanic-Vucinic, Dragana

    2015-06-15

    High intensity ultrasound (HIUS) can promote Maillard reaction (MR). Macromolecular crowding conditions accelerate reactions and stabilise protein structure. The aim of this study was to investigate if combined application of ultrasound and macromolecular crowding can improve efficiency of MR. The presence of crowding agent (polyethylene glycol) significantly increased ultrasound-induced whey protein (WP) glycation by arabinose. An increase in glycation efficiency results only in slight change of WP structure. Macromolecular crowding intensifies oxidative modifications of WP, as well as formation of amyloid-like structures by enhancement of MR. Solubility at different pH, thermal stability and antioxidative capacity of glycated WP were increased, especially in the presence of crowding agent, compared to sonicated nonglycated proteins. The application of HIUS under crowding conditions can be a new approach for enhancement of reactions in general, enabling short processing time and mild conditions, while preserving protein structure and minimising protein aggregation. PMID:25660883

  10. 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.

  11. 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.

  12. Decarboxylation of coal model compounds under liquefaction conditions: Does decarboxylation lead to retrograde reactions?

    SciTech Connect

    Eskay, T.P.; Britt, P.F.; Buchanan, A.C. III

    1996-12-31

    In recent years, it has become clear that oxygen functional groups in low-rank coals are major actors in retrograde reactions which inhibit their efficient thermochemical processing. In the pyrolysis and liquefaction of low-rank coals, low-temperature cross-linking reactions have been correlated with the loss of carboxyl groups and the evolution of CO{sub 2} and H{sub 2}O. Pretreatments such as methylation, demineralization, or ion-exchange of the inorganic cations reduce cross-linking and CO{sub 2} evolution in pyrolysis. Cross-linking reactions also have a deleterious effect on liquefaction yields and the distribution of oils, preasphaltenes and asphaltenes. These results suggest that decarboxylation may occur by a pathway that initiates retrograde (cross-linking) reactions in the coal polymer independent of the reaction conditions. However, the decarboxylation pathways in liquefaction and pyrolysis of low-rank coals are not known, and it is not clear how decarboxylation leads to cross-linking. Radical recombination or radical addition reactions have been suggested as being involved in retrograde reactions. However, the involvement of radical pathways in thermal decarboxylation reactions has recently been brought into question. We have presented evidence that in the pyrolysis of several bibenzyls containing aromatic carboxylic acids, radical pathways are not involved in thermal decarboxylation reactions and no cross-linking or coupling products are formed. Further, Manion et al. observed that decarboxylation of benzoic acid derivatives in tetralin yielded only small amounts of aryl-aryl coupling products. To gain a better understanding of the role decarboxylation plays in cross-linking reactions during liquefaction in low-rank coals, we have studied the thermal decomposition of several bibenzyls containing aromatic carboxylic acids, and their salts, in the presence of a hydrogen donor solvent (tetrahn) and a nondonor solvent (naphthalene).

  13. 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.

  14. 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…

  15. 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.

  16. A new practical synthesis of triaryl and trisindolylmethanes under solvent-free reaction conditions.

    PubMed

    Barbero, Margherita; Cadamuro, Silvano; Dughera, Stefano; Magistris, Claudio; Venturello, Paolo

    2011-12-21

    An efficient and practical synthesis of triaryl and trisindolylmethanes is reported via the bisarylation of aryl aldehydes with activated arenes. The new method features mild solvent-free reaction conditions, in most cases nearly stoichiometric reagent ratios, catalytic amount of the readily available, easily-handled, recoverable and reusable Brønsted acid catalyst o-benzenedisulfonimide. PMID:22042519

  17. [Osmoregulatory reactions of frog erythrocytes under conditions of activation and blockade of Ca2+-channels].

    PubMed

    Skorkina, M Iu

    2012-01-01

    The kinetics of cell osmoregulatory reactions under conditions of activation and blockade of Ca2+-channels was studied on a model of frog polyfunctional nuclear erythrocyte. Both activation and blockade of Ca2+-channels has been established to promote swelling of nuclei and an increase of the nuclear-cytoplasmic ratios under conditions of hypotonic exposure. The osmoregulatory cell reactions after activation of Ca2+-channels are expressed as a decrease of the cell volume. The blockator of Ca2+-channels verapamil produces an alternated increase and decrease of the erythrocyte volume with time intervals of 30 and 60 s. The clearly expressed functional activity of the nuclear membrane in response to the hypotonic action under conditions of activation and blockade of Ca2+-channels indicates participation of Ca2+ ions in mechanisms of the nuclear-cytoplasmic transfer. PMID:22645976

  18. Kinetics of diamond-silicon reaction under high pressure-high temperature conditions

    NASA Astrophysics Data System (ADS)

    Pantea, Cristian

    In this dissertation work, the kinetics of the reaction between diamond and silicon at high pressure-high temperature conditions was investigated. This study was motivated by the extremely limited amount of information related to the kinetics of the reaction in diamond-silicon carbide composites formation. It was found that the reaction between diamond and melted silicon and the subsequent silicon carbide formation is a two-stage process. The initial stage is a result of direct reaction of melted silicon with carbon atoms from the diamond surface, the phase boundary reaction. Further growth of SiC is much more complicated and when the outer surfaces of diamond crystals are covered with the silicon carbide layer it involves diffusion of carbon and silicon atoms through the SiC layer. The reaction takes place differently for the two regions of stability of carbon. In the graphite-stable region, the reaction between diamond and melted silicon is associated with the diamond-to-graphite phase transition, while in the diamond-stable region there is no intermediary step for the reaction. The data obtained at HPHT were fitted by the Avrami-Erofeev equation. It was found that the reaction is isotropic, the beta-SiC grown on different faces of the diamond crystals showing the same reaction rate, and that the controlling mechanism for the reaction is the diffusion. In the graphite-stable region the activation energy, 402 kJ/mol is slightly higher than in the diamond-stable region, 260 kJ/mol, as the reaction between diamond and melted silicon is associated with the diamond-to-graphite phase transition, which has higher activation energy. In the diamond-stable region, the calculated activation energy is higher for micron size diamond powders (≈260 kJ/mol), while for nanocrystalline diamond powders a lower value of 170 kJ/mol was obtained. This effect was attributed to nanocrystalline structure and strained bonds within grain boundaries in SiC formed from nanosize diamond

  19. Analysis of initial reactions of MALDI based on chemical properties of matrixes and excitation condition.

    PubMed

    Lai, Yin-Hung; Wang, Chia-Chen; Chen, Chiu Wen; Liu, Bo-Hong; Lin, Sheng Hsien; Lee, Yuan Tseh; Wang, Yi-Sheng

    2012-08-16

    This investigation concerns the initial chemical reactions that affect the ionization of matrixes in matrix-assisted laser desorption/ionization (MALDI). The study focuses on the relaxations of photon energy that occur on a comparable time scale to that of ionization, in which the available laser energy is shared and the ionization condition is changed. The relaxations include fluorescence, fragmentation, and nonradiative relaxation from the excited state to the ground state. With high absorption cross section and long excited-state lifetime, photoionization of matrix plays an important role if sufficient laser energy is used. Under other conditions, thermal ionization of the molecule in the ground state is predicted to be one of the important reactions. Evidence of change in the branching ratio of initial reactions with the matrix and the excitation wavelength was obtained with α-cyano-4-hydroxycinnamic acid, sinapinic acid, 2,5-dihydroxybenzoic acid, and 2,4,6-trihydroxyacetophenone. These matrixes are studied by obtaining their mixed crystal absorption spectra, fluorescence properties, laser-induced infrared emission, and product ions. The exact ionization pathway depends on the chemical properties of matrixes and the excitation conditions. This concept may explain the diversity of experimental results observed in MALDI experiments, which provides an insight into the ensemble of chemical reactions that govern the generation of ions. PMID:22799495

  20. Reversible Reshaping of Supported Metal Nanoislands Under Reaction Conditions in a Minimalistic Lattice Model

    NASA Astrophysics Data System (ADS)

    Korobov, A.

    2016-05-01

    The shape of (nano)islands is among significant factors of the catalytic activity of supported catalysts. A lattice model of the reshaping under reaction conditions is suggested and studied by means of kinetic Monte Carlo simulations. It is rooted in experimental findings and is simplified as far as possible to still demonstrate reversible compact—ramified shape transitions. This simple model with complex behavior demonstrates several reshaping regimes and is considered as a possible sub-network of more realistic networks of heterogeneous catalytic reactions.

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

    DOEpatents

    McGrail, Bernard P.; Martin, Paul F.; Lindenmeier, Clark W.

    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.

  2. 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 (μM 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

  3. Reaction paths leading from O2/+/ to water clusters under cold mesospheric conditions

    NASA Astrophysics Data System (ADS)

    McCrumb, J. L.

    1982-06-01

    Reference is made to reported D-region positive ion measurements (Arnold and Krankowsky, 1974) in which a number of new cluster ions of minor abundance were apparent. It is noted that these ions, which were attributed to clusters with N2, O2, and CO2 ligands, were observable owing to enhanced O2(+) production and the low temperatures during the flight. Consideration is given here to these in situ ion data in view of recent laboratory ion-molecule reaction experiments that shed light on the mechanism leading from O2(+) to water clusters in air mixtures. Possible intermediates are discussed in terms of ion stability and the existence of effective reaction paths under the given atmospheric conditions. The intermediates proposed here are then fitted into a coherent reaction mechanism resulting in significant new pathways for the formation of protonated water clusters. A semiquantitative measure of the importance of each of the pathways is then calculated using signal flow graph theory.

  4. 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.

  5. Reservoir-Condition Pore-Scale Imaging of Reaction in Carbonates using Synchrotron Fast Tomography

    NASA Astrophysics Data System (ADS)

    Menke, H. P.; Andrew, M. G.; Bijeljic, B.; Blunt, M. J.

    2015-12-01

    Carbon capture and storage in carbonate reservoirs is essential for mitigating climate change. Supercritical CO2 mixed with host brine is acidic and can dissolve the surrounding pore structure and change flow dynamics. However, the type, speed, and magnitude of the dissolution are dependent on both the reactive transport properties of the pore-fluid and the intrinsic properties of the rock. Understanding how changes in the pore structure, chemistry, and flow properties affect dissolution is vital for successful predictive modelling both on the pore-scale and for up-scaled reservoir simulations. Reaction in carbonates has been studied at the pore-scale but has never been imaged dynamically in situ. We present an experimental method whereby both lab-based benchtop instruments and 'Pink Beam' synchrotron radiation are used in X-ray microtomography to investigate pore structure changes during supercritical CO2 injection at reservoir conditions. Three types of pure limestone rock with broadly varying rock topology were imaged under the same reservoir conditions. Flow-rate and brine acidity was varied in successive experiments by half an order of magnitude to gain insight into the impact of flow, transport, and physical heterogeneity. The images were binarized and the magnitude of dissolution was identified on a voxel-by-voxel basis to extract pore-by-pore dissolution data. The impact of dissolution on flow characteristics was studied by computing the evolution of the pore-scale velocity fields with a flow solver. We found that increasing rock heterogeneity increased channelized flow [Figure 1] through preferential pathways and that higher flow rate increased total dissolution. Additionally, decreasing reaction rate lowered overall reaction rate and made axial flow less uniform. Experimentally measured reaction rates in real rocks are at least an order of magnitude lower when compared to batch experiments. We provide evidence that this can be due to transport limitations

  6. 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, σ, 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 μm grain size) form next to calcite and elongated palisade-shaped grains (1-6 μm 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 μm thick granular dolomite layer

  7. 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

  8. 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

  9. Hydraulic Fracturing Fluid Reaction with Shale in Experiments at Unconventional Gas Reservoir Conditions

    NASA Astrophysics Data System (ADS)

    Paukert, A. N.; Hakala, A.; Jarvis, K. B.

    2015-12-01

    Despite the marked increase in hydraulic fracturing for unconventional natural gas production over the past decade, reactions between hydraulic fracturing fluids (HFF) and shale reservoirs remain poorly reported in the scientific literature. Shale-HFF interaction could cause mineral dissolution, releasing matter from the shale, or mineral precipitation that degrades reservoir permeability. Furthermore, data are limited on whether scale inhibitors are effective at preventing mineral precipitation and whether these inhibitors adversely affect reservoir fluid chemistry and permeability. To investigate HFF-rock interaction within shale reservoirs, we conducted flow-through experiments exposing Marcellus Shale to synthetic HFF at reservoir conditions (66oC, 20MPa). Outcrop shale samples were cored, artificially fractured, and propped open with quartz sand. Synthetic HFFs were mixed with chemical additives similar to those used for Marcellus Shale gas wells in Ohio and Southwestern Pennsylvania (FracFocus.org). We evaluated differences between shale reactions with HFF made from natural freshwater and reactions with HFF made from synthetic produced water (designed to simulate produced water that is diluted and re-used for subsequent hydraulic fracturing). We also compared reactions with HFFs including hydrochloric acid (HCl) to represent the initial acid stage, and HFFs excluding HCl. Reactions were determined through changes in fluid chemistry and X-ray CT and SEM imaging of the shale before and after experiments. Results from experiments with HFF containing HCl showed dissolution of primary calcite, as expected. Experiments using HFF made from synthetic produced water had significant mineral precipitation, particularly of barium and calcium sulfates. X-ray CT images from these experiments indicate precipitation of minerals occurred either along the main fracture or within smaller splay fractures, depending on fluid composition. These experiments suggest that HFF

  10. 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

  11. Reduction of a detailed reaction mechanism for hydrogen combustion under gas turbine conditions

    SciTech Connect

    Stroehle, Jochen; Myhrvold, Tore

    2006-02-01

    The aim of this study is to find a reduced mechanism that accurately represents chemical kinetics for lean hydrogen combustion at elevated pressures, as present in a typical gas turbine combustor. Calculations of autoignition, extinction, and laminar premixed flames are used to identify the most relevant species and reactions and to compare the results of several reduced mechanisms with those of a detailed reaction mechanism. The investigations show that the species OH and H are generally the radicals with the highest concentrations, followed by the O radical. However, the accumulation of the radical pool in autoignition is dominated by HO{sub 2} for temperatures above, and by H{sub 2}O{sub 2} below the crossover temperature. The influence of H{sub 2}O{sub 2} reactions is negligible for laminar flames and extinction, but becomes significant for autoignition. At least 11 elementary reactions are necessary for a satisfactory prediction of the processes of ignition, extinction, and laminar flame propagation under gas turbine conditions. A 4-step reduced mechanism using steady-state approximations for HO{sub 2} and H{sub 2}O{sub 2} yields good results for laminar flame speed and extinction limits, but fails to predict ignition delay at low temperatures. A further reduction to three steps using a steady-state approximation for O leads to significant errors in the prediction of the laminar flame speed and extinction limit. (author)

  12. Lipase-catalyzed synthesis of ascorbyl oleate in acetone: optimization of reaction conditions and lipase reusability.

    PubMed

    Stojanović, Marija; Velićković, Dušan; Dimitrijević, Aleksandra; Milosavić, Nenad; Knežević-Jugović, Zorica; Bezbradica, Dejan

    2013-01-01

    Lipase-catalyzed ascorbyl oleate synthesis is eco-friendly and selective way of production of liposoluble biocompatible antioxidants, but still not present on an industrial level due to the high biocatalyst costs. In this study, response surface methodology was applied in order to estimate influence of individual experimental factors, identify interactions among them, and to determine optimum conditions for enzymatic synthesis of ascorbyl oleate in acetone, in terms of limiting substrate conversion, product yield, and yield per mass of consumed enzyme. As a biocatalyst, commercial immobilized preparation of lipase B from Candida antarctica, Novozym 435, was used. In order to develop cost-effective process, at reaction conditions at which maximum amount of product per mass of biocatalyst was produced (60°C, 0.018 % (v/v) of water, 0.135 M of vitamin C, substrates molar ratio 1:8, and 0.2 % (w/v) of lipase), possibilities for further increase of ester yield were investigated. Addition of molecular sieves at 4(th) hour of reaction enabled increase of yield from 16.7 mmol g⁻¹ to 19.3 mmol g⁻¹. Operational stability study revealed that after ten reaction cycles enzyme retained 48 % of its initial activity. Optimized synthesis with well-timed molecular sieves addition and repeated use of lipase provided production of 153 mmol per gram of enzyme. Further improvement of productivity was achieved using procedure for the enzyme reactivation. PMID:23985489

  13. Behavior of Supported Palladium Oxide Nanoparticles under Reaction Conditions, Studied with near Ambient Pressure XPS.

    PubMed

    Jürgensen, Astrid; Heutz, Niels; Raschke, Hannes; Merz, Klaus; Hergenröder, Roland

    2015-08-01

    Near ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) is a promising method to close the "pressure gap", and thus, study the surface composition during heterogeneous reactions in situ. The specialized spectrometers necessary for this analytical technique have recently been adapted to operate with a conventional X-ray source, making it available for routine quantitative analysis in the laboratory. This is shown in the present in situ study of the partial oxidation of 2-propanol catalyzed with PdO nanoparticles supported on TiO2, which was investigated under reaction conditions as a function of gas composition (alcohol-to-oxygen ratio) and temperature. Exposure of the nanoparticles to 2-propanol at 30 °C leads to immediate partial reduction of the PdO, followed by a continuous reduction of the remaining PdO during heating. However, gaseous oxygen inhibits the reduction of PdO below 90 °C, and the oxidation of 2-propanol to carboxylates only occurs in the presence of oxygen above 90 °C. These results support the theory that metallic palladium is the active catalyst material, and they show that environmental conditions affect the nanoparticles and the reaction process significantly. The study also revealed challenges and limitations of this analytical method. Specifically, the intensity and fixed photon energy of a conventional X-ray source limit the spectral resolution and surface sensitivity of lab-based NAP-XPS, which affect precision and accuracy of the quantitative analysis. PMID:26144222

  14. Effect of hydrothermal reaction time and alkaline conditions on the electrochemical properties of reduced graphene oxide

    NASA Astrophysics Data System (ADS)

    Vermisoglou, E. C.; Giannakopoulou, T.; Romanos, G.; Giannouri, M.; Boukos, N.; Lei, C.; Lekakou, C.; Trapalis, C.

    2015-12-01

    Reduced graphene oxide sheets (rGO) were prepared by hydrothermal treatment of aqueous dispersions of graphite oxide (GtO) applied for short (4 h) and prolonged reaction times (19-24 h). The effect of process duration as well as the alkaline conditions (pH ∼10) by addition of K2CO3 on the quality characteristics of the produced rGO materials was investigated. Both reduction and exfoliation occurred during this process as it was evidenced by FTIR and XRD data. SEM, TEM and HRTEM microscopy displayed highly exfoliated rGO materials. XPS verified that the re-establishment of the conjugated graphene network is more extensive for prolonged times of hydrothermal processing in accordance to Raman spectroscopy measurements. The sample produced under alkaline conditions bore fewer defects and almost 5 times higher BET surface area (∼181 m2/g) than the sample with no pH adjustment (∼34 m2/g) for the same hydrothermal reaction time (19 h), attributed to the developed microporosity. The specific capacitance of this material estimated by electrochemical impedance using three-electrode cell and KCl aqueous solution as an electrolyte was ∼400-500 F/g. When EDLC capacitors were fabricated from rGO materials the electrochemical testing in organic electrolyte i.e. TEABF4 in PC, revealed that the shortest hydrothermal reaction time (4 h) was more efficient resulting in capacitance around 60 F/g.

  15. Efficient and robust reforming catalyst in severe reaction conditions by nanoprecursor reduction in confined space.

    PubMed

    Dacquin, Jean-Philippe; Sellam, Djamila; Batiot-Dupeyrat, Catherine; Tougerti, Asma; Duprez, Daniel; Royer, Sébastien

    2014-02-01

    The in situ autocombustion synthesis route is shown to be an easy and efficient way to produce nanoscaled nickel oxide containing lanthanum-doped mesoporous silica composite. Through this approach, ~3 nm NiO particles homogeneously dispersed in the pores of silica are obtained, while lanthanum is observed to cover the surface of the silica pore wall. Subsequent reduction of such composite precursors under hydrogen generates Ni(0) nanoparticles of a comparable size. Control over the size and size distribution of metallic nanoparticles clearly improved catalytic activity in the methane dry reforming reaction. In addition, these composite materials exhibit excellent stability under severe reaction conditions. This was achieved through the presence of LaOx species, which reduced active-site carbon poisoning, and the confinement effect of the mesoporous support, which reduced metallic particle sintering. PMID:24323543

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

    NASA Astrophysics Data System (ADS)

    Gal, Ciprian G.; Warma, Mahamadi

    2016-08-01

    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 Hölder 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.

  17. Specificity of psychomotor reactions in the conditions of support deprivation including effects of countermeasures

    NASA Astrophysics Data System (ADS)

    Nichiporuk, Igor; Ivanov, Oleg

    Activity of the cosmonaut demands high level of psychomotor reactions (PMR) which can vary during space flight under the influences of psychophysiological state’s variability and unusual inhabitancy that causes the necessity of PMR estimation’s inclusion into quality monitoring of capacity for work (CW). A main objective of research was a study of features of visual-motor reactions (VMR) and elements of CW of the person within simulation of microgravity effects via 7-day dry immersion (DI) in healthy male-volunteers 20-35 years old. The experimental data were received which testified to peculiarities of VMR and recognition of simple figures of main colors of a visible spectrum (red, green, blue, the RGB-standard) in the conditions of the DI characterized by support deprivation and decreased proprioceptive afferentation - in a control series and in a series with use of mioelectrostimulation as a countermeasure.

  18. 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.

  19. Measurement of transverse dispersion and reaction in heterogeneous porous media under transient flow conditions

    NASA Astrophysics Data System (ADS)

    Grathwohl, P.; Piepenbrink, M.; Eberhardt, C.; Kasper, M.; Gauglitz, G.

    2005-12-01

    Natural attenuation (mainly biodegradation) of organic pollutants in groundwater often depends on mixing of electron donors and acceptors in the plume fringes, the spatial distribution of these highly reactive zones, compared to the volume of the whole plume, is quite small and characterized by steep concentration gradients. Mixing in the field is the result of transverse dispersion, which is a function of groundwater flow velocity, the typical length scale in the aquifer (e.g. grain size) as well as the aquifer heterogeneities, and the dynamics of the natural flow system. The objectives of this work are to investigate dispersion-limited reactions in well-controlled bench-scale experiments i.e. to elaborate how heterogeneities and transient conditions at the field scale (in time and space) influence the overall natural attenuation rates of organic pollutants in groundwater. Experiments in which (a) the spreading of a conservative tracer cloud or (b) the reaction of two reaction partners at the plume fringe is limited by transverse dispersion are currently investigated in the lab. As the quantification of transverse dispersivities in heterogeneous media under transient flow conditions requires monitoring with high resolution in space and time new optical tools (CCD camera) are employed for the quantitative mapping of the plumes.The first experiments were conducted at bench scale using a continuous injection of a conservative colour tracers (fluorescine), which show absorption only at a specific range of wavelengths in the visible spectrum, a quantification of this tracers is thus possible by its colour depth. Quality control of the quantification obtained by the CCD set-up is done via conventional sampling and analysis at the outlet ports during steady state flow conditions. Currently, well controlled acid-base reactions, are monitored by the colour changes of pH-indicators.This efficient spatially and time-resolved monitoring of concentration gradient changes by

  20. Calculation of the cumulative reaction probability via a discrete variable representation with absorbing boundary conditions

    SciTech Connect

    Seideman, T.; Miller, W.H. )

    1992-03-15

    A new method is suggested for the calculation of the microcanonical cumulative reaction probability {ital via} flux autocorrelation relations. The Hamiltonian and the flux operators are computed in a discrete variable representation (DVR) and a well-behaved representation for the Green's operator, {ital G}({ital E}{sup +}), is obtained by imposing absorbing boundary conditions (ABC). Applications to a one-dimensional-model problem and to the collinear H+H{sub 2} reaction show that the DVR-ABC scheme provides a very efficient method for the {ital direct} calculation of the microcanonical probability, circumventing the need to compute the state-to-state dynamics. Our results indicate that the cumulative reaction probability can be calculated to a high accuracy using a rather small number of DVR points, confined to the vicinity of the transition state. Only limited information regarding the potential-energy surface is therefore required, suggesting that this method would be applicable also to higher dimensionality problems, for which the complete potential surface is often unknown.

  1. A Molecular Dynamics Study of Chemical Reactions of Solid Pentaerythritol Tetranitrate at Extreme Conditions

    SciTech Connect

    Wu, C J; Manaa, M R; Fried, L E

    2006-05-30

    We have carried out density functional based tight binding (DFTB) molecular dynamics (MD) simulation to study energetic reactions of solid Pentaerythritol Tetranitrate (PETN) at conditions approximating the Chapman-Jouguet (CJ) detonation state. We found that the initial decomposition of PETN molecular solid is characterized by uni-molecular dissociation of the NO{sub 2}groups. Interestingly, energy release from this powerful high explosive was found to proceed in several stages. The large portion of early stage energy release was found to be associated with the formation of H{sub 2}O molecules within a few picoseconds of reaction. It took nearly four times as long for majority of CO{sub 2} products to form, accompanied by a slow oscillatory conversion between CO and CO{sub 2}. The production of N{sub 2} starts after NO{sub 2} loses its oxygen atoms to hydrogen or carbon atoms to form H{sub 2}O or CO. We identified many intermediate species that emerge and contribute to reaction kinetics, and compared our simulation with a thermo-chemical equilibrium calculation. In addition, a detailed chemical kinetics of formation of H{sub 2}O, CO, and CO{sub 2} were developed. Rate constants of formations of H{sub 2}O, CO{sub 2} and N{sub 2} were reported.

  2. The Pt(111)/electrolyte interface under oxygen reduction reaction conditions: an electrochemical impedance spectroscopy study.

    PubMed

    Bondarenko, Alexander S; Stephens, Ifan E L; Hansen, Heine A; Pérez-Alonso, Francisco J; Tripkovic, Vladimir; Johansson, Tobias P; Rossmeisl, Jan; Nørskov, Jens K; Chorkendorff, Ib

    2011-03-01

    The Pt(111)/electrolyte interface has been characterized during the oxygen reduction reaction (ORR) in 0.1 M HClO(4) using electrochemical impedance spectroscopy. The surface was studied within the potential region where adsorption of OH* and O* species occur without significant place exchange between the adsorbate and Pt surface atoms (0.45-1.15 V vs RHE). An equivalent electric circuit is proposed to model the Pt(111)/electrolyte interface under ORR conditions within the selected potential window. This equivalent circuit reflects three processes with different time constants, which occur simultaneously during the ORR at Pt(111). Density functional theory (DFT) calculations were used to correlate and interpret the results of the measurements. The calculations indicate that the coadsorption of ClO(4)* and Cl* with OH* is unlikely. Our analysis suggests that the two-dimensional (2D) structures formed in O(2)-free solution are also formed under ORR conditions. PMID:21244087

  3. Atomic-Scale Observations of Catalyst Structures under Reaction Conditions and during Catalysis.

    PubMed

    Tao, Franklin Feng; Crozier, Peter A

    2016-03-23

    Heterogeneous catalysis is a chemical process performed at a solid-gas or solid-liquid interface. Direct participation of catalyst atoms in this chemical process determines the significance of the surface structure of a catalyst in a fundamental understanding of such a chemical process at a molecular level. High-pressure scanning tunneling microscopy (HP-STM) and environmental transmission electron microscopy (ETEM) have been used to observe catalyst structure in the last few decades. In this review, instrumentation for the two in situ/operando techniques and scientific findings on catalyst structures under reaction conditions and during catalysis are discussed with the following objectives: (1) to present the fundamental aspects of in situ/operando studies of catalysts; (2) to interpret the observed restructurings of catalyst and evolution of catalyst structures; (3) to explore how HP-STM and ETEM can be synergistically used to reveal structural details under reaction conditions and during catalysis; and (4) to discuss the future challenges and prospects of atomic-scale observation of catalysts in understanding of heterogeneous catalysis. This Review focuses on the development of HP-STM and ETEM, the in situ/operando characterizations of catalyst structures with them, and the integration of the two structural analytical techniques for fundamentally understanding catalysis. PMID:26955850

  4. 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.

  5. Chemoselective Oxidation of Benzyl, Amino, and Propargyl Alcohols to Aldehydes and Ketones under Mild Reaction Conditions

    PubMed Central

    Reddy, C B Rajashekar; Reddy, Sabbasani Rajasekhara; Naidu, Shivaji

    2015-01-01

    Catalytic oxidation reactions often suffer from drawbacks such as low yields and poor selectivity. Particularly, selective oxidation of alcohols becomes more difficult when a compound contains more than one oxidizable functional group. In order to deliver a methodology that addresses these issues, herein we report an efficient, aerobic, chemoselective and simplified approach to oxidize a broad range of benzyl and propargyl alcohols containing diverse functional groups to their corresponding aldehydes and ketones in excellent yields under mild reaction conditions. Optimal yields were obtained at room temperature using 1 mmol substrate, 10 mol % copper(I) iodide, 10 mol % 4-dimethylaminopyridine (DMAP), and 1 mol % 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) in acetonitrile, under an oxygen balloon. The catalytic system can be applied even when sensitive and oxidizable groups such as alkynes, amines, and phenols are present; starting materials and products containing such groups were found to be stable under the developed conditions. PMID:25969806

  6. Chemoselective Oxidation of Benzyl, Amino, and Propargyl Alcohols to Aldehydes and Ketones under Mild Reaction Conditions.

    PubMed

    Reddy, C B Rajashekar; Reddy, Sabbasani Rajasekhara; Naidu, Shivaji

    2015-04-01

    Catalytic oxidation reactions often suffer from drawbacks such as low yields and poor selectivity. Particularly, selective oxidation of alcohols becomes more difficult when a compound contains more than one oxidizable functional group. In order to deliver a methodology that addresses these issues, herein we report an efficient, aerobic, chemoselective and simplified approach to oxidize a broad range of benzyl and propargyl alcohols containing diverse functional groups to their corresponding aldehydes and ketones in excellent yields under mild reaction conditions. Optimal yields were obtained at room temperature using 1 mmol substrate, 10 mol % copper(I) iodide, 10 mol % 4-dimethylaminopyridine (DMAP), and 1 mol % 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) in acetonitrile, under an oxygen balloon. The catalytic system can be applied even when sensitive and oxidizable groups such as alkynes, amines, and phenols are present; starting materials and products containing such groups were found to be stable under the developed conditions. PMID:25969806

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

    NASA Astrophysics Data System (ADS)

    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.

  8. Optimum reaction conditions for lead zirconate titanate thick film deposition by ultrasound-assisted hydrothermal method

    NASA Astrophysics Data System (ADS)

    Saigusa, Katsuhiro; Morita, Takeshi

    2016-07-01

    A hydrothermal method can be used to deposit lead zirconate titanate (PZT) films and has several advantages, such as a relatively low reaction temperature and high crystal quality. We developed an ultrasound-assisted hydrothermal method to promote the hydrothermal reactions, which is effective for thick-PZT-film deposition. The first ultrasound-assisted hydrothermal method we developed can synthesize a 7.5 µm PZT film on a titanium substrate. However, for a much thicker film, repeated depositions were required, and the optimum precursor solution for the first deposition was not suitable for repeated depositions. In this study, we attempted to find the optimum precursor solution for depositing a film of sufficient thickness by repeated depositions. As a result, we were able to synthesize a 23.6 µm PZT film on second deposition by changing the ratio of zirconium to titanium ions in the precursor solutions. In addition, a transverse effect transducer was fabricated under optimum conditions and its vibration properties were evaluated.

  9. 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.

  10. 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

  11. 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

  12. Total synthesis of Elisabethin A: intramolecular Diels-Alder reaction under biomimetic conditions.

    PubMed

    Heckrodt, Thilo J; Mulzer, Johann

    2003-04-23

    We describe the first total synthesis of the marine diterpenoid elisabethin A. The synthesis uses (S)-hydroxy-2-methyl-propionate as the chiral starting material, which is elaborated into a dienyl-iodide and added to an aryl acetic acid ester via enolate alkylation. The hydroquinoid system is oxidized to the quinone which serves as the dienophile in a highly stereocontrolled intramolecular Diels-Alder addition. This IMDA reaction, which to our knowledge is the first one to employ a terminal (Z)-diene, proceeds under biomimetic conditions (water, ferrichloride as the oxidant, room temperature) with high yield and stereoselectivity. The Diels-Alder adduct is transformed into the natural product via a three-step sequence including selective hydrogenation, base-catalyzed epimerization of the cis- into the trans-decalin system and O-demethylation. PMID:12696865

  13. 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.

  14. Development of a reaction cell for in-situ/operando studies of surface of a catalyst under a reaction condition and during catalysis.

    PubMed

    Nguyen, Luan; Tao, Franklin Feng

    2016-06-01

    Tracking surface chemistry of a catalyst during catalysis is significant for fundamental understanding of catalytic performance of the catalyst since it allows for establishing an intrinsic correlation between surface chemistry of a catalyst at its working status and its corresponding catalytic performance. Ambient pressure X-ray photoelectron spectroscopy can be used for in-situ studies of surfaces of different materials or devices in a gas. To simulate the gaseous environment of a catalyst in a fixed-bed a flowing gaseous environment of reactants around the catalyst is necessary. Here, we report the development of a new flowing reaction cell for simulating in-situ study of a catalyst surface under a reaction condition in gas of one reactant or during catalysis in a mixture of reactants of a catalytic reaction. The homemade reaction cell is installed in a high vacuum (HV) or ultrahigh vacuum (UHV) environment of a chamber. The flowing gas in the reaction cell is separated from the HV or UHV environment through well sealings at three interfaces between the reaction cell and X-ray window, sample door and aperture of front cone of an energy analyzer. Catalyst in the cell is heated through infrared laser beam introduced through a fiber optics interfaced with the reaction cell through a homemade feedthrough. The highly localized heating on the sample holder and Au-passivated internal surface of the reaction cell effectively minimizes any unwanted reactions potentially catalyzed by the reaction cell. The incorporated laser heating allows a fast heating and a high thermal stability of the sample at a high temperature. With this cell, a catalyst at 800 °C in a flowing gas can be tracked readily. PMID:27370473

  15. Development of a reaction cell for in-situ/operando studies of surface of a catalyst under a reaction condition and during catalysis

    NASA Astrophysics Data System (ADS)

    Nguyen, Luan; Tao, Franklin Feng

    2016-06-01

    Tracking surface chemistry of a catalyst during catalysis is significant for fundamental understanding of catalytic performance of the catalyst since it allows for establishing an intrinsic correlation between surface chemistry of a catalyst at its working status and its corresponding catalytic performance. Ambient pressure X-ray photoelectron spectroscopy can be used for in-situ studies of surfaces of different materials or devices in a gas. To simulate the gaseous environment of a catalyst in a fixed-bed a flowing gaseous environment of reactants around the catalyst is necessary. Here, we report the development of a new flowing reaction cell for simulating in-situ study of a catalyst surface under a reaction condition in gas of one reactant or during catalysis in a mixture of reactants of a catalytic reaction. The homemade reaction cell is installed in a high vacuum (HV) or ultrahigh vacuum (UHV) environment of a chamber. The flowing gas in the reaction cell is separated from the HV or UHV environment through well sealings at three interfaces between the reaction cell and X-ray window, sample door and aperture of front cone of an energy analyzer. Catalyst in the cell is heated through infrared laser beam introduced through a fiber optics interfaced with the reaction cell through a homemade feedthrough. The highly localized heating on the sample holder and Au-passivated internal surface of the reaction cell effectively minimizes any unwanted reactions potentially catalyzed by the reaction cell. The incorporated laser heating allows a fast heating and a high thermal stability of the sample at a high temperature. With this cell, a catalyst at 800 °C in a flowing gas can be tracked readily.

  16. Volatile-refractory element reactions and breakdown of refractory oxides under conditions of a giant impact

    NASA Astrophysics Data System (ADS)

    Tschauner, O. D.; Ma, C.

    2015-12-01

    Whereas much or most of the highly volatile elements reside in atmosphere and oceans, understanding the global budget of these elements requires knowledge about their abundance in the Earth's interior. One piece of this puzzle is the early history of the Earth where large impacts, notably giant impacts, provided conditions where both volatile and refractory elements were mixed on atomic scale in extremely hot dense fluids. Carbides and nitrides that have recently been found in mantle rock are possible remnants of such large scale dynamic pressure-temperature conditions. In particular carbides and nitrides of lithophile refractory elements like Zr, Hf, Nb, Ta may remain in the mantle for extended time and contribute to the mantle geochemical budget of these elements as well as that of C and N. In a first step towards testing such a hypothesis, we conducted a series of shock experiments. Deflagration of C-N-O-H compounds was triggered by shockwaves. The resulting reaction wave front propagated into aggregates of refractory minerals like zircon, baddeleyite, rutile. This fluid-solid mix was subjected to shock compression to shock pressures of 20-50 GPa and temperatures in the range of 0.5-1.104 K by means of reverberating shock. Recovered sample material was analyzed by synchrotron X-ray diffraction and by EPMA.

  17. Simplified models of transport and reactions in conditions of CO2 storage in saline aquifers

    NASA Astrophysics Data System (ADS)

    Suchodolska, Katarzyna; Labus, Krzysztof

    2016-04-01

    Simple hydrogeochemical models may serve as tools of preliminary assessment of CO2 injection and sequestraton impact on the aquifer and cap-rocks. In order to create models of reaction and transport in conditions of CO2 injection and storage, the TOUGHREACT simulator, and the Geochemist's Workbench software were applied. The chemical composition of waters for kinetic transport models based on the water - rock equilibrium calculations. Analyses of reaction and transport of substances during CO2 injection and storage period were carried out in three scenarios: one-dimensional radial model, and two-dimensional model of CO2 injection and sequestration, and one-dimensional model of aquifer - cap-rock interface. Modeling was performed in two stages. The first one simulated the immediate changes in the aquifer and insulating rocks impacted by CO2 injection (100 days in case of reaction model and 30 years in transport and reaction model), the second - enabled assessment of long-term effects of sequestration (20000 years). Reactions' quality and progress were monitored and their effects on formation porosity and sequestration capacity in form of mineral, residual and free phase of CO2 were calculated. Calibration of numerical models (including precipitation of secondary minerals, and correction of kinetics parameters) describing the initial stage of injection, was based on the experimental results. Modeling allowed to evaluate the pore space saturation with gas, changes in the composition and pH of pore waters, relationships between porosity and permeability changes and crystallization or dissolution minerals. We assessed the temporal and spatial extent of crystallization processes, and the amount of carbonates trapping. CO2 in mineral form. The calculated sequestration capacity of analyzed formations reached n·100 kg/m3 for the: dissolved phase - CO(aq), gas phase - CO2(g) and mineral phase, but as much as 101 kg/m3 for the supercritical phase - SCCO2. Processes of gas

  18. Kinetics of the reaction between hydrogen and sulfur under high-temperature Claus furnace conditions

    SciTech Connect

    Dowling, N.I.; Hyne, J.B. ); Brown, D.M. )

    1990-12-01

    The reaction H{sub 2} + (1/2)S{sub 2} {r equilibrium}H{sub 2}S has been studied as a function of temperature and residence time over the ranges 602--1290{degrees}C and 0.03--1.5 s in the absence of a catalyst. This paper shows that the combination of H{sub 2} and elemental sulfur vapor under the high-temperature conditions typical of a Claus sulfur recovery unit proceeds via a reversible homogeneous gas-phase reaction that is first order in both H{sub 2} and sulfur concentration and follows the rate law {minus}d(H{sub 2})/dt = k{sub 1}(H{sub 2})(S{sub 2}) {minus} k{sub 2}(H{sub 2}S) with a second-order recombination rate constant k{sub 1} = 1 {minus} 1 {times} 10{sup 3} atm{sup {minus}1} s{sup {minus}1} (A{sub 1} = (4.3 {plus minus} 0.2) {times} 10{sup 6} atm{sup {minus}1} s{sup {minus}1}; {Delta}H{sub 1} = 26 {plus minus} 1 kcal/mol) and first-order decomposition rate constant k{sub 2} = 4 {times} 10{sup {minus}4} {minus} 70 s{sup {minus}1} (A{sub 2} = (3.6 {plus minus} 1) {times} 10{sup 8} s{sup {minus}1}; {Delta}H{sub 2} = 48 {plus minus} 1 kcal/mol) over the temperature range studied. These findings can be used to exploit opportunities in acid gas processing, such as effecting improved efficiencies for O{sub 2} usage in oxygen- blown Claus units and maximizing H{sub 2} content in the tail gas.

  19. Atomistic theory of Ostwald ripening and disintegration of supported metal particles under reaction conditions.

    PubMed

    Ouyang, Runhai; Liu, Jin-Xun; Li, Wei-Xue

    2013-02-01

    Understanding Ostwald ripening and disintegration of supported metal particles under operating conditions has been of central importance in the study of sintering and dispersion of heterogeneous catalysts for long-term industrial implementation. To achieve a quantitative description of these complicated processes, an atomistic and generic theory taking into account the reaction environment, particle size and morphology, and metal-support interaction is developed. It includes (1) energetics of supported metal particles, (2) formation of monomers (both the metal adatoms and metal-reactant complexes) on supports, and (3) corresponding sintering rate equations and total activation energies, in the presence of reactants at arbitrary temperature and pressure. The thermodynamic criteria for the reactant assisted Ostwald ripening and induced disintegration are formulated, and the influence of reactants on sintering kinetics and redispersion are mapped out. Most energetics and kinetics barriers in the theory can be obtained conveniently by first-principles theory calculations. This allows for the rapid exploration of sintering and disintegration of supported metal particles in huge phase space of structures and compositions under various reaction environments. General strategies of suppressing the sintering of the supported metal particles and facilitating the redispersions of the low surface area catalysts are proposed. The theory is applied to TiO(2)(110) supported Rh particles in the presence of carbon monoxide, and reproduces well the broad temperature, pressure, and particle size range over which the sintering and redispersion occurred in such experiments. The result also highlights the importance of the metal-carbonyl complexes as monomers for Ostwald ripening and disintegration of supported metal catalysts in the presence of CO. PMID:23272702

  20. A Comparison Between the Burn Condition of Deuterium-Tritium and Deuterium-Helium-3 Reaction and Stability Limits

    NASA Astrophysics Data System (ADS)

    Motevalli, Seyed Mohammad; Fadaei, Fereshteh

    2015-02-01

    The nuclear reaction of deuterium-tritium (D-T) fusion by the usual magnetic or inertial confinement suffers from a number of difficulties and problems caused by tritium handling, neutron damage to materials and neutron-induced radioactivity, etc. The study of the nuclear synthesis reaction of deuterium-helium-3 (D-3He) at low collision energies (below 1 keV) is of interest for its applications in nuclear physics and astrophysics. Spherical tokamak (ST) reactors have a low aspect ratio and can confine plasma with β≈1. These capabilities of ST reactors are due to the use of the alternative D-3He reaction. In this work, the burn condition of D-3He reaction was calculated by using zero-dimensional particles and power equations, and, with the use of the parameters of the ST reactor, the stability limit of D-3He reaction was calculated and then the results were compared with those of D-T reaction. The obtained results show that the burn conditions of D-3He reaction required a higher temperature and had a much more limited temperature range in comparison to those of D-T reaction.

  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. Liquid metal reactions under postulated accident conditions for fission and fusion reactors

    SciTech Connect

    Muhlestein, L.D.

    1980-04-01

    Sodium and lithium reactions are considered in the context of a postulated breach of a coolant boundary. Specific topics addressed are coolant-atmosphere and coolant-material reactions which may contribute to the overall consequence of a postulated accident scenario, and coolant reaction extinguishment and effluent control which may be desirable for containment of the spilled coolant.

  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. Three-stage extraction of gelatines from tendons of abattoir cattle: 1--reaction conditions.

    PubMed

    Mokrejs, Pavel; Janacova, Dagmar; Svoboda, Petr

    2012-10-01

    Short and long tendons of abattoir cattle are collagen by-products of the meat industry. They offer no utilisation at present, being a raw material source of over 90 % protein characteristic. This contribution deals with the three-stage extraction of gelatine from short cattle tendons. The principle of treatment consists in processing degreased tendons in the first processing stage in an environment resulting in the swelling of the starting material. In the second stage, the material is treated with a proteolytic enzyme to produce such disruption of the collagen substrate that makes gelatine extraction when boiling possible in the third stage of the process. In order to study the influence of the significant parameters during the extraction process on gelatine yield, experiments were planned using a factor experiment of 2(3) types. The variables under study were the duration of the second processing stage (5-25 h), temperature in the first and second processing stages (10-40 °C) and the addition of a proteolytic enzyme (1-5 %) on the quantity of the extracted gelatine. The results were processed statistically, and statistical significance of the studied factors was thus found. Contour graphs were plotted to easily survey the influence of the observed factors on gelatine yield. The process achieves up to 71 % efficiency, runs under atmospheric pressure and mild reaction conditions, and is conducive to preparing quality gelatines. PMID:22903323

  7. Experimental studies of gas-aerosol reactions

    NASA Astrophysics Data System (ADS)

    Gupta, Anand

    1991-05-01

    The aqueous phase oxidation of SO2 by H2O2 is believed to the principle mechanism for atmospheric sulfate formation in cloud droplets. However, no studies in noncloud aerosol systems have been reported. The objective is to quantify the importance of the noncloud liquid phase reactions of SO2 by H2O2 in the atmosphere. Growth rates of submicron droplets exposed to SO2 and H2O2 were measured using the tandem differential mobility analyzer (TDMA) technique (Rader and McMurry, 1986). The technique uses differential mobility analyzers (DMA's) to generate monodisperse particles and to measure particle size after the reaction. To facilitate submicron monodisperse droplet production with the DMA, a low-ion-concentration charter capable of generating singly charged particles up to 1.0 microns was developed and experimentally evaluated. The experiments were performed using dry and deliquesced (NH4)2SO4 particles with SO2 and H2O2 concentrations from 0-860 ppb and 0-150 ppb, respectively. No growth was observed for dry particles. For droplets greater than or equal to 0.3 microns, the fractional diameter growth was independent of particle size and for droplets less than or equal to 0.2 microns, it decreased as particle size decreased. The observed decrease is due to NH3 evaporation. As ammonia evaporates, droplet pH decreases causing the oxidation rate to decrease, leading to a lower growth rate. To predict the size-dependent growth rates, a theoretical model was developed using solution thermodynamics, gas/particle equilibrium, and chemical kinetics. The experimental and theoretical results are in reasonable agreement. For dry (NH4)2SO4 particles exposed to SO2, H2O2, NH3, and H2O vapor, surface reaction-controlled growth was observed. Particle growth was very sensitive to particle composition. No growth was observed for Polystyrene latex particles, whereas (NH4)2SO4 particles doped with catalysts (Fe(2+), Fe(3+), Mn(2+) and Cu(2+)) in a molar ratio of 1:500 grew slower than

  8. 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…

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

    SciTech Connect

    Ansari-Rad, Mehdi; 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

  10. Kinetics of CaO-H{sub 2}S reaction at high temperature under pressurized conditions

    SciTech Connect

    Matsukata, M.; Ando, H.; Ueyama, K.; Hosoda, S.

    1999-07-01

    Kinetic study of H{sub 2} absorption with calcined limestone was performed under pressurized conditions (up to 20 atm) by means of a self-made pressurized thermobalance mainly consisting of a quartz spring balance and a pressure vessel. The adsorption of 200--4,200 ppm (mainly 1000 ppm) of H{sub 2}S was carried out with calcined limestone (710--1,000 {micro}m) at 1,023--1,223 K and 1--20 atm. The effect of pressure on the kinetics of H{sub 2}S adsorption was investigated. The film resistance of mass transfer was negligible when the total gas velocity was 0.53 m/s (10 SLM). The rate of H{sub 2}S adsorption decreased with increasing total pressure (H{sub 2}S pressure was kept at 0.004 atm). The level of conversion of CaO to CaS was 87% at 1 atm and 38% at 20 atm after 5 h of reaction. The used limestone samples were characterized with SEM and EDAX. Based on the SEM and EDAX observations on the cross section of limestone particles, a CaS layer was clearly developed from the surface to the interior in the progress of sulfidation in all cases. Although the authors applied the conventional shrinking-core models with different rate-determining steps for analyzing the H{sub 2}S adsorption kinetics, these SCM models failed to explain the sulfidation behavior in the early stage of sulfidation at higher pressures. Thus, they developed empirical equations to express the sulfidation behavior in the wide ranges of the solid conversion and the total pressure. Equations developed in this study can predict the sulfidation kinetics at higher pressure well.

  11. Merging Photoredox with Palladium Catalysis: Decarboxylative ortho-Acylation of Acetanilides with α-Oxocarboxylic Acids under Mild Reaction Conditions.

    PubMed

    Zhou, Chao; Li, Pinhua; Zhu, Xianjin; Wang, Lei

    2015-12-18

    A room temperature decarboxylative ortho-acylation of acetanilides with α-oxocarboxylic acids has been developed via a novel Eosin Y with Pd dual catalytic system. This dual catalytic reaction shows a broad substrate scope and good functional group tolerance, and an array of ortho-acylacetanilides can be afforded in high yields under mild conditions. PMID:26646667

  12. Kinetics of the unimolecular reaction of CH2OO and the bimolecular reactions with the water monomer, acetaldehyde and acetone under atmospheric conditions.

    PubMed

    Berndt, Torsten; Kaethner, Ralf; Voigtländer, Jens; Stratmann, Frank; Pfeifle, Mark; Reichle, Patrick; Sipilä, Mikko; Kulmala, Markku; Olzmann, Matthias

    2015-08-14

    Stabilized Criegee Intermediates (sCIs) have been identified as oxidants of atmospheric trace gases such as SO2, NO2, carboxylic acids or carbonyls. The atmospheric sCI concentrations, and accordingly their importance for trace gas oxidation, are controlled by the rate of the most important loss processes, very likely the unimolecular reactions and the reaction with water vapour (monomer and dimer) ubiquitously present at high concentrations in the troposphere. In this study, the rate coefficients of the unimolecular reaction of the simplest sCI, formaldehyde oxide, CH2OO, and its bimolecular reaction with the water monomer have been experimentally determined at T = (297 ± 1) K and at atmospheric pressure by using a free-jet flow system. CH2OO was produced by the reaction of ozone with C2H4, and CH2OO concentrations were probed indirectly by detecting H2SO4 after titration with SO2. Time-resolved experiments yield a rate coefficient of the unimolecular reaction of k(uni) = (0.19 ± 0.07) s(-1), a value that is supported by quantum-chemical and statistical rate theory calculations as well as by additional measurements performed under CH2OO steady-state conditions. A rate coefficient of k(CH2OO+H2O) = (3.2 ± 1.2) × 10(-16) cm(3) molecule(-1) s(-1) has been determined for sufficiently low H2O concentrations (<10(15) molecule cm(-3)) that allow separation from the CH2OO reaction with the water dimer. In order to evaluate the accuracy of the experimental approach, the rate coefficients of the reactions with acetaldehyde and acetone were reinvestigated. The obtained rate coefficients k(CH2OO+acetald) = (1.7 ± 0.5) × 10(-12) and k(CH2OO+acetone) = (3.4 ± 0.9) × 10(-13) cm(3) molecule(-1) s(-1) are in good agreement with literature data. PMID:26159709

  13. 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.

  14. Manganese Triazacyclononane Oxidation Catalysts Grafted under Reaction Conditions on Solid Co-Catalytic Supports

    SciTech Connect

    Schoenfeldt, Nicholas J.; Ni, Zhenjuan; Korinda, Andrew W.; Meyer, Randall J.; Notestein, Justin M.

    2012-01-23

    Manganese complexes of 1,4,7-trimethyl-1,4,7-triazacyclononane (tmtacn) are highly active and selective alkene oxidation catalysts with aqueous H{sub 2}O{sub 2}. Here, carboxylic acid-functionalized SiO{sub 2} simultaneously immobilizes and activates these complexes under oxidation reaction conditions. H{sub 2}O{sub 2} and the functionalized support are both necessary to transform the inactive [(tmtacn)Mn{sup IV}({mu}-O)3Mn{sup IV}(tmtacn)]{sup 2+} into the active, dicarboxylate-bridged [(tmtacn)Mn{sup III}({mu}-O)({mu}-RCOO){sub 2}Mn{sup III}(tmtacn)]{sup 2+}. This transformation is assigned on the basis of comparison of diffuse reflectance UV-visible spectra to known soluble models, assignment of oxidation state by Mn K-edge X-ray absorption near-edge spectroscopy, the dependence of rates on the acid/Mn ratios, and comparison of the surface structures derived from density functional theory with extended X-ray absorption fine structure. Productivity in cis-cyclooctene oxidation to epoxide and cis-diol with 2-10 equiv of solid cocatalytic supports is superior to that obtained with analogous soluble valeric acid cocatalysts, which require 1000-fold excess to reach similar levels at comparable times. Cyclooctene oxidation rates are near first order in H{sub 2}O{sub 2} and near zero order in all other species, including H{sub 2}O. These observations are consistent with a mechanism of substrate oxidation following rate-limiting H{sub 2}O{sub 2} activation on the hydrated, supported complex. This general mechanism and the observed alkene oxidation activation energy of 38 {+-} 6 kJ/mol are comparable to H{sub 2}O{sub 2} activation by related soluble catalysts. Undesired decomposition of H{sub 2}O{sub 2} is not a limiting factor for these solid catalysts, and as such, productivity remains high up to 25 C and initial H{sub 2}O{sub 2} concentration of 0.5 M, increasing reactor throughput. These results show that immobilized carboxylic acids can be utilized and understood

  15. Study of condition-dependent decomposition reactions; Part I. The thermal behaviour and decomposition of 2-nitrobenzoyl chloride.

    PubMed

    Lever, Sarah D; Papadaki, Maria

    2004-11-11

    The risks associated with batch processing in the manufacture of chemicals and pharmaceuticals via highly exothermic reactions are of special interest due to the possibility of runaway reactions. o-Nitrated benzoyl chlorides are intermediates in the production of agrochemicals and are produced via the reaction of o-nitrated carboxylic acids with thionyl chloride in a solvent mixture. ortho-Nitrated acyl chlorides have exploded violently on attempted distillation on numerous occasions. An inadequate investigation of the process prior to large-scale operation is the most likely cause. Here we present preliminary results of studies on the decomposition of 2-nitrobenzoyl chloride. This study has revealed that the decomposition reaction is strongly condition dependent. The heating rate of the sample plays a preponderant role in the course of the decomposition reaction. That renders the interpretation of differential scanning calorimetry (DSC) or adiabatic calorimetry measurements, which are routinely used to assess the thermochemistry and safety of the large-scale reactions, problematic. Following this on-going study, we report here key features of the system that have been identified. PMID:15518968

  16. In situ characterization of catalysts and membranes in a microchannel under high-temperature water gas shift reaction conditions

    NASA Astrophysics Data System (ADS)

    Cavusoglu, G.; Dallmann, F.; Lichtenberg, H.; Goldbach, A.; Dittmeyer, R.; Grunwaldt, J.-D.

    2016-05-01

    Microreactor technology with high heat transfer in combination with stable catalysts is a very attractive approach for reactions involving major heat effects such as methane steam reforming and to some extent, also the high temperature water gas shift (WGS) reaction. For this study Rh/ceria catalysts and an ultrathin hydrogen selective membrane were characterized in situ in a microreactor specially designed for x-ray absorption spectroscopic measurements under WGS conditions. The results of these experiments can serve as a basis for further development of the catalysts and membranes.

  17. 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.

  18. 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 μm 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

  19. 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

  20. Kinetic and products study of the gas-phase reaction of Lewisite with ozone under atmospheric conditions.

    PubMed

    Wang, Haitao; Zhang, Yuanpeng; Guo, Xiaodi; Shao, Yusheng; Gao, Runli; Liang, Dejian; Sun, Hao

    2016-02-01

    The rate constant for the gas-phase reaction of O3 and Lewisite was studied in air using the smog chamber technique. The experiments were carried out under pseudo-first-order reaction conditions with [O3]≪[Lewisite]. The observed rate constant of O3 with Lewisite was (7.83 ± 0.38) × 10(-19)cm(3)/(molecule·sec) at 298 ± 2K. Lewisite was discussed in terms of reactivity with O3 and its relationship with the ionization potential. Our results show that the rate constant for the gas-phase reaction of O3 with Lewisite is in line with the trend of the rate constants of O3 with haloalkenes. PMID:26969539

  1. Synthesis of SF5CF2-Containing Enones and Instability of This Group in Specific Chemical Environments and Reaction Conditions.

    PubMed

    Dudziński, Piotr; Matsnev, Andrej V; Thrasher, Joseph S; Haufe, Günter

    2016-06-01

    The chemistry of the SF5CF2 moiety has been scarcely investigated. In this report, we present synthetic pathways to a variety of SF5CF2-substituted compounds starting from vinyl ethers and SF5CF2C(O)Cl. In specific chemical environments and under particular reaction conditions, the SF5CF2 moiety is unstable in downstream products resulting in the elimination of the SF5(-) anion and its decomposition to SF4 and F(-). Surprisingly, the formed F(-) can attack the intermediate difluorovinyl moiety to form trifluoromethyl substituted products. This appears to happen when an intermediate neighboring group participation involving a double bond is possible. Under slightly different conditions, the reaction stops at the stage of a difluorovinyl compound. PMID:27159371

  2. A study of different indicators of Maillard reaction with whey proteins and different carbohydrates under adverse storage conditions.

    PubMed

    Leiva, Graciela E; Naranjo, Gabriela B; Malec, Laura S

    2017-01-15

    This study examined different indicators of each stage of Maillard reaction under adverse storage conditions in a system with whey proteins and lactose or glucose. The analysis of lysine loss by the o-phthaldialdehyde method can be considered a good indicator of the early stage, showing considerable differences in reactivity when systems with mono and disaccharides were analyzed. Capillary electrophoresis proved to be a sensitive method for evaluating the extent of glycosylation of the native proteins, providing valuable information when the loss of lysine was not significant. The estimation of the Amadori compound from the determination of total 5-hydroxymethyl-2-furfuraldehyde would have correlate well with reactive lysine content if the advanced stages of the reaction had not been reached. For assessing the occurrence of the intermediate and final stages, the measurement of free 5-hydroxymethyl-2-furfuraldehyde and color, proved not to be suitable for storage conditions. PMID:27542493

  3. Reaction of trimethylsilylacetylenes with antimony pentafluoride under matrix isolation conditions: experimental and computational study.

    PubMed

    Cicak, Helena; Vancik, Hrvoj; Mihalić, Zlatko

    2010-10-15

    Reaction of trimethylsilylacetylenes Me(3)SiC≡CR with SbF(5) in the solid state was investigated using matrix isolation infrared spectroscopy and quantum-mechanical calculations. Two reaction pathways were detected. Replacement of the trimethylsilyl group with SbF(4) produces neutral antimony acetylides F(4)SbC≡CR. Acetylenic bond protonation produces silyl cation 6-R, fully bridged for R = H and SiMe(3). High total charges on the bridging SiMe(3) group and low Me(3)Si-C bond orders to acetylenic moiety, both calculated at the MP4(SDQ)/6-311G(d,p) level of theory, indicate high silyl cation character of these species. PMID:20857942

  4. Organometallic derivatives of furan. LX. Reactions of di-2-furyldimethylgermane under catalytic-hydrogenation conditions

    SciTech Connect

    Lukevits, E.; Ignatovich, L.M.; Yuskovets, Zh.G.; Golender, L.O.; Shimanskaya, M.V.

    1987-11-20

    In the reaction of di-2-furyldimethylgermane with hydrogen in the presence of the homogeneous metal-complex catalyst RhH(CO)(PPh/sub 3/)/sub 3/ the selective hydrogenation of one of the furan rings occurs, but over heterogeneous catalysts (Raney Ni, Rh black, Pd/C) hydrogenation and hydrogenolysis reactions occur. Di-2-furyldimethylgermane is converted into (2-furyl)dimethyl(tetrahydro-2-furyl)-germane by the catalytic transfer of hydrogen from 2-propanol and cyclohexene. On the basis of the kinetic relations and quantum-chemical calculations of the electron structures of the original and partially hydrogenated furylgermanes a stagewise scheme is proposed of the hydrogenation of the furan ring and the further hydrogenolysis of the semihydrogenated germane molecule.

  5. Reaction norm model to describe environmental sensitivity across first lactation in dairy cattle under tropical conditions.

    PubMed

    Bignardi, Annaiza Braga; El Faro, Lenira; Pereira, Rodrigo Junqueira; Ayres, Denise Rocha; Machado, Paulo Fernando; de Albuquerque, Lucia Galvão; Santana, Mário Luiz

    2015-10-01

    Reaction norm models have been widely used to study genotype by environment interaction (G × E) in animal breeding. The objective of this study was to describe environmental sensitivity across first lactation in Brazilian Holstein cows using a reaction norm approach. A total of 50,168 individual monthly test day (TD) milk yields (10 test days) from 7476 complete first lactations of Holstein cattle were analyzed. The statistical models for all traits (10 TDs and for 305-day milk yield) included the fixed effects of contemporary group, age of cow (linear and quadratic effects), and days in milk (linear effect), except for 305-day milk yield. A hierarchical reaction norm model (HRNM) based on the unknown covariate was used. The present study showed the presence of G × E in milk yield across first lactation of Holstein cows. The variation in the heritability estimates implies differences in the response to selection depending on the environment where the animals of this population are evaluated. In the average environment, the heritabilities for all traits were rather similar, in range from 0.02 to 0.63. The scaling effect of G × E predominated throughout most of lactation. Particularly during the first 2 months of lactation, G × E caused reranking of breeding values. It is therefore important to include the environmental sensitivity of animals according to the phase of lactation in the genetic evaluations of Holstein cattle in tropical environments. PMID:26143280

  6. Reaction pathways towards the formation of dolomite-analogues at ambient conditions

    NASA Astrophysics Data System (ADS)

    Pimentel, Carlos; Pina, Carlos M.

    2016-04-01

    In this paper we present results of a study of the crystallisation behaviour of the dolomite-analogues norsethite and PbMg(CO3)2 at room temperature and atmospheric pressure. Whereas precipitation of norsethite was previously obtained by mixing solutions (Hood et al., 1974; Pimentel and Pina, 2014a,b), we report, for the first time, the synthesis of PbMg(CO3)2 by using the same method. The formation of both phases was promoted by ageing slurries for periods of time ranging from a few days (norsethite) up to 6 months (PbMg(CO3)2). The crystallisation of both norsethite and PbMg(CO3)2 occurs by sequences of dissolution-precipitation reactions involving several amorphous and crystalline precursor phases, which were identified and characterised by X-ray diffraction and scanning electron microscopy. Depending on the initial composition and Ba:Mg and Pb:Mg ratios in the slurries, different precursors and reaction kinetics were observed. This demonstrates the existence of different reaction pathways towards the formation of the investigated dolomite-analogues. Our experimental results provide new insights into the possible mechanisms of formation of dolomite and other double carbonates in nature.

  7. Detecting 5-methylcytosine using an enzyme-free DNA strand exchange reaction without pretreatment under physiological conditions.

    PubMed

    Xu, Chen; Wu, Jinjun; Liu, Wenting; Hong, Tingting; Wang, Tianlu; Zhang, Xiaoe; Fu, Boshi; Wu, Fan; Wu, Zhiguo; Zhou, Xiang

    2016-05-21

    We present here a novel and efficient method for 5mC detection using a DNA strand exchange reaction (SER) strategy. This enzyme-free method needs no pre-treatment of target DNAs and can be adapted to most of the target duplexes under physiological conditions. The high sequence selectivity of this method can distinguish 5mC from normal cytosine in an accurate manner. PMID:27139156

  8. Influences of acidic reaction and hydrolytic conditions on monosaccharide composition analysis of acidic, neutral and basic polysaccharides.

    PubMed

    Wang, Qing-Chi; Zhao, Xia; Pu, Jiang-Hua; Luan, Xiao-Hong

    2016-06-01

    Monosaccharide composition analysis is important for structural characterization of polysaccharides. To investigate the influences of acidic reaction and hydrolytic conditions on monosaccharide composition analysis of polysaccharides, we chose alginate, starch, chitosan and chondroitin sulfate as representative of acidic, neutral, basic and complex polysaccharides to compare the release degree of monosaccharides under different hydrolytic conditions. The hydrolysis stability of 10 monosaccharide standards was also explored. Results showed that the basic sugars were hard to release but stable, the acidic sugars (uronic acids) were easy to release but unstable, and the release and stability of neutral sugars were in between acidic and basic sugars. In addition, the hydrolysis process was applied to monosaccharide composition analysis of Hippocampus trimaculatus polysaccharide and the appropriate hydrolytic condition was accorded with that of the above four polysaccharides. Thus, different hydrolytic conditions should be used for the monosaccharide composition analysis of polysaccharides based on their structural characteristics. PMID:27083372

  9. 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.

  10. Housing conditions influence cortical and behavioural reactions of sheep in response to videos showing social interactions of different valence.

    PubMed

    Vögeli, Sabine; Wolf, Martin; Wechsler, Beat; Gygax, Lorenz

    2015-05-01

    Mood, as a long-term affective state, is thought to modulate short-term emotional reactions in animals, but the details of this interplay have hardly been investigated experimentally. Apart from a basic interest in this affective system, mood is likely to have an important impact on animal welfare, as bad mood may taint all emotional experience. In the present study about mood - emotion interaction, 29 sheep were kept under predictable, stimulus-rich or unpredictable, stimulus-poor housing conditions, to induce different mood states. In an experiment, the animals were confronted with video sequences of social interactions of conspecifics showing agonistic interactions, ruminating or tolerantly co-feeding as stimuli of different valences. Emotional reactions were assessed by measuring frontal brain activity using functional near-infrared spectroscopy and by recording behavioral reactions. Attentiveness of the sheep decreased from videos showing agonistic interactions to ruminating sheep to those displaying co-feeding sheep. Seeing agonistic interactions was also associated with a deactivation of the frontal cortex, specifically in animals living under predictable, stimulus-rich housing conditions. These sheep generally showed less attentiveness and locomotor activity and they had their ears in a forward position less often and in a backward position more often than the sheep from the unpredictable, stimulus-poor conditions. Housing conditions influenced how the sheep behaved, which can either be thought to be mediated by mood or by the animals' previous experience with stimulus-richness in their housing conditions. Frontal cortical activity may not depend on valence only, but also on the perceptual channel through which the stimuli were perceived. PMID:25680678

  11. 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

  12. Polymerization of Acetonitrile via a Hydrogen Transfer Reaction from CH3 to CN under Extreme Conditions.

    PubMed

    Zheng, Haiyan; Li, Kuo; Cody, George D; Tulk, Christopher A; Dong, Xiao; Gao, Guoying; Molaison, Jamie J; Liu, Zhenxian; Feygenson, Mikhail; Yang, Wenge; Ivanov, Ilia N; Basile, Leonardo; Idrobo, Juan-Carlos; Guthrie, Malcolm; Mao, Ho-Kwang

    2016-09-19

    Acetonitrile (CH3 CN) is the simplest and one of the most stable nitriles. Reactions usually occur on the C≡N triple bond, while the C-H bond is very inert and can only be activated by a very strong base or a metal catalyst. It is demonstrated that C-H bonds can be activated by the cyano group under high pressure, but at room temperature. The hydrogen atom transfers from the CH3 to CN along the CH⋅⋅⋅N hydrogen bond, which produces an amino group and initiates polymerization to form a dimer, 1D chain, and 2D nanoribbon with mixed sp(2) and sp(3) bonded carbon. Finally, it transforms into a graphitic polymer by eliminating ammonia. This study shows that applying pressure can induce a distinctive reaction which is guided by the structure of the molecular crystal. It highlights the fact that very inert C-H can be activated by high pressure, even at room temperature and without a catalyst. PMID:27561179

  13. Palladium-Catalyzed α-Arylation of Zinc Enolates of Esters: Reaction Conditions and Substrate Scope

    PubMed Central

    Hama, Takuo; Ge, Shaozhong; Hartwig, John F.

    2013-01-01

    The intermolecular α-arylation of esters by palladium-catalyzed coupling of aryl bromides with zinc enolates of esters is reported. Reactions of three different types of zinc enolates have been developed. α-Arylation of esters occurs in high yields with isolated Reformatsky reagents, with Reformatsky reagents generated from α-bromo esters and activated zinc, and with zinc enolates generated by quenching lithium enolates of esters with zinc chloride. The use of zinc enolates, instead of alkali metal enolates, greatly expands the scope of the arylation of esters. The reactions occur at room temperature or at 70 °C with bromoarenes containing cyano, nitro, ester, keto, fluoro, enolizable hydrogen, hydroxyl or amino functionality and with bromopyridines. The scope of esters encompasses acyclic acetates, propionates, and isobutyrates, α-alkoxyesters, and lactones. The arylation of zinc enolates of esters was conducted with catalysts bearing the hindered pentaphenylferrocenyl di-tert-butylphosphine (Q-phos) or the highly reactive dimeric Pd(I) complex {[P(t-Bu)3]PdBr}2. PMID:23931445

  14. Polymerization of Acetonitrile via a Hydrogen Transfer Reaction from CH3 to CN under Extreme Conditions

    DOE PAGESBeta

    Zheng, Haiyan; Li, Kuo; Cody, George D.; Tulk, Christopher A.; Dong, Xiao; Gao, Guoying; Molaison, Jamie J.; Liu, Zhenxian; Feygenson, Mikhail; Yang, Wenge; et al

    2016-08-25

    Acetonitrile (CH3CN) is the simplest and one of the most stable nitriles. Reactions usually occur on the C≡N triple bond, while the C-H bond is very inert and can only be activated by a very strong base or a metal catalyst. In this study, it is demonstrated that C-H bonds can be activated by the cyano group under high pressure, but at room temperature. The hydrogen atom transfers from the CH3 to CN along the CH···N hydrogen bond, which produces an amino group and initiates polymerization to form a dimer, 1D chain, and 2D nanoribbon with mixed sp2 and sp3more » bonded carbon. Lastly, it transforms into a graphitic polymer by eliminating ammonia. This study shows that applying pressure can induce a distinctive reaction which is guided by the structure of the molecular crystal. It highlights the fact that very inert C-H can be activated by high pressure, even at room temperature and without a catalyst.« less

  15. Synthetic applications of aqueous accelerated [3,3] sigmatropic rearrangements of allyl vinyl ethers. [1,3] sigmatropic rearrangements of allyl vinyl ethers in 3 M lithium perchlorate-diethyl ether at ambient temperature. New methods to effect the retro Diels-Alder reaction of N-alkyl-2-azanorbornenes

    SciTech Connect

    Clark, J.D.

    1992-01-01

    Claisen rearrangements employed in the synthesis of natural and unnatural products that were heretofore difficult or impossible using conventional means are realized through the agency of water. Allyl vinyl ether 35, the unprotected form of McMurry's aphidicolin intermediate 7, rearranged after 24 h in 2.5:1 water/methanol at 80[degrees]C, affording aldehyde 40 in 70--85% yield. Acetaldehyde elimination witnessed using conventional reaction conditions was suppressed when employing water. The application of a Claisen rearrangement within the molecular framework of fenestranes was realized for the first time. Fenestrene vinyl ethers 28 and 30 rearranged to form the fenestrenes 29 and 31, respectively. Noteworthy is fenestrene 29, the first fenestrane synthesized possessing a trans-ring fusion common to two five-membered rings. The medium of 3.0 M lithium perchlorate-diethyl ether has been found to induce the rarely witnessed rearrangement of allyl vinyl ethers, despite the fact that the corresponding sigmatropic rearrangement is energetically more favorable. Yields are very good; however, in some instances the sigmatropic rearrangement and elimination processes compete slightly. Results from the observed stereoselectivities, concentration effects on reaction rate, and a crossover study indicate that these shifts take place via dissociated ions followed by recombination, and that the observed stereoselectivities are a result of unequal steric effects in the transition states for recombination. Copper(II) and sulfonic acid ion exchange resins have been found to readily catalyze the heterocycloreversion of N-alkyl-2-azanorbornenes to the corresponding primary amines, eliminating the necessity of employing a reactive dienophile to trap out the released cyclopentadiene.

  16. 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.

    2008-12-01

    Chamber studies of glyoxal uptake onto neutral 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 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. These compounds are likely to be imidazoles formed by reaction of glyoxal with the ammonium sulphate seed. 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 oxidative photochemistry, similar to that found in cloud processing, was found to occur within aerosol during irradiated experiments. Organosulphates, carboxylic acids, and organic esters were identified within the aerosol. Our study suggests that both C-N compound formation and photochemical processes should be considered in models of secondary organic aerosol formation via glyoxal.

  17. 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.

  18. Hyaluronan dermal fillers via crosslinking with 1,4-butandiol diglycidyl ether: Exploitation of heterogeneous reaction conditions.

    PubMed

    La Gatta, Annalisa; Papa, Agata; Schiraldi, Chiara; De Rosa, Mario

    2016-01-01

    Most of hyaluronan (HA)-based dermal fillers currently available on the market are produced through biopolymer crosslinking with 1,4-butandiol diglycidyl ether (BDDGE). Chemical modification is usually performed on the biopolymer dissolved in a highly alkaline aqueous medium (homogeneous conditions). Heterogeneous conditions for HA reaction with BDDGE were exploited here to obtain competitive HA fillers and to assess potential improvements in production process. Optimal parameters for effective reaction accomplishment were evaluated (e.g., medium composition, temperature and time of reaction). HA was modified with increasing BDDGE/HA equivalents (7-14%) achieving 66-74% (w/w) biopolymer insolubility. Hydrogels exhibited high swelling extent and outstanding resistance to enzymatic degradation decreasing and improving according to crosslinking degree, respectively. Once suspended in physiological solution (20 mg/mL), these products directly formed easy-to-extrude gels through 27-29 G needles. Gel particle dimensions were in the range 10-1000 µm. Rheological analyses revealed decreasing viscosity with the shear rate and G' values in the range 1200-1700 Pa. Overall, results of the in vitro characterization demonstrated the attainment of crosslinked HA particles suitable for application as dermal fillers. These new gels proved superior to similar commercialized products in terms of stability to enzymatic hydrolysis. Further, the protocol assessed allowed interesting improvements over conventional manufacturing procedures. PMID:25611588

  19. The effect of reaction conditions on formation of wet precipitated calcium phosphates

    NASA Astrophysics Data System (ADS)

    Huang, Chen; Cao, Peng

    2015-03-01

    The precipitation process discussed in the present study involves the addition of alkaline solutions to an acidic calcium phosphate suspension. Several parameters (pH, pH buffer reagent, ageing and stirring) were investigated. The synthesized powders were calcined at 1000°C for 1 h in air, in order to study the thermal stability and crystalline phase compositions. X-ray diffraction (XRD) and ESEM analysis were used for sample characterization. It is found that all these processing parameters affect the crystalline phases evolved and resultant microstructures. Phase evolution occurred at an elevated pH level. The pH buffer reagent would affect both the phase composition and microstructure. Ageing was essential for the phase maturation. Stirring accelerated the reaction process by providing a homogeneous medium for precipitation.

  20. Reaction Weakening of Dunite in Friction Experiments at Hydrothermal Conditions and Its Relevance to Subduction Zones

    NASA Astrophysics Data System (ADS)

    Moore, D. E.; Lockner, D. A.

    2014-12-01

    To improve our understanding of processes occurring in the mantle wedge near the downdip limit of seismicity in subduction zones, we conducted triaxial friction tests on dunite gouge at temperatures in the range 200-350°C, 50 MPa fluid pressure and 100 MPa effective normal stress. Dunite, quartzite, and granite forcing blocks were used respectively to approximate changing rock/fluid chemistry with decreasing distance above the subduction thrust. All experiments were characterized by an initial increase in frictional strength to a peak value, followed by a decrease associated with shearing-enhanced alteration of the dunite gouge. Reaction products and the extent of weakening varied with the chemical environment. In the dunite-block experiments, strength gradually declined from the peak value to a coefficient of friction, µ ~ 0.5-0.6, consistent with the frictional strength of serpentine that formed on the shear surfaces from alteration of the gouge. Interaction of dunite gouge with quartzite and granite driving blocks resulted in significantly greater weakening, to μ ~ 0.3, at temperatures of 250°C and higher. Talc and serpentine partly replaced dunite gouge sheared between quartzite blocks, and metastable saponitic smectite clays crystallized in dunite sheared between granite blocks, as a result of fluid-assisted chemical exchange with the minerals in the wall rocks. These results suggest that rapid and substantial weakening can occur in the mantle wedge immediately overlying the subducting slab. Whichever the chemical environment, attainment of peak strength typically was accompanied by oscillatory slip with small stress drops that gradually was replaced by stable slip with increasing displacement. This oscillatory behavior in some ways resembles the tremor events that have been reported near the forearc mantle corner in subduction zones, and it may indicate the possible involvement of mineral reactions in some instances of tremor.

  1. Acetylation of bacterial cellulose catalyzed by citric acid: Use of reaction conditions for tailoring the esterification extent.

    PubMed

    Ávila Ramírez, Jhon Alejandro; Gómez Hoyos, Catalina; Arroyo, Silvana; Cerrutti, Patricia; Foresti, María Laura

    2016-11-20

    Bacterial cellulose (BC) nanoribbons were partially acetylated by a simple direct solvent-free route catalyzed by citric acid. The assay of reaction conditions within chosen intervals (i.e. esterification time (0.5-7h), catalyst content (0.08-1.01mmol/mmol AGU), and temperature (90-140°C)), illustrated the flexibility of the methodology proposed, with reaction variables which can be conveniently manipulated to acetylate BC to the required degree of substitution (DS) within the 0.20-0.73 interval. Within this DS interval, characterization results indicated a surface-only process in which acetylated bacterial cellulose with tunable DS, preserved fibrous structure and increased hydrophobicity could be easily obtained. The feasibility of reusing the catalyst/excess acylant in view of potential scale-up was also illustrated. PMID:27561540

  2. Active sites in Cu-SSZ-13 deNOx catalyst under reaction conditions: a XAS/XES perspective

    NASA Astrophysics Data System (ADS)

    Lomachenko, Kirill A.; Borfecchia, Elisa; Bordiga, Silvia; Soldatov, Alexander V.; Beato, Pablo; Lamberti, Carlo

    2016-05-01

    Cu-SSZ-13 is a highly active catalyst for the NH3-assisted selective catalytic reduction (SCR) of the harmful nitrogen oxides (NOx, x=1, 2). Since the catalytically active sites for this reaction are mainly represented by isolated Cu ions incorporated into the zeolitic framework, element-selective studies of Cu local environment are crucial to fully understand the enhanced catalytic properties of this material. Herein, we highlight the recent advances in the characterization of the most abundant Cu-sites in Cu-SSZ-13 upon different reaction-relevant conditions made employing XAS and XES spectroscopies, complemented by computational analysis. A concise review of the most relevant literature is also presented.

  3. A Novel Endo-β-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-β-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

  4. Condensation Reactions and Formation of Amides, Esters, and Nitriles Under Hydrothermal Conditions

    NASA Astrophysics Data System (ADS)

    Rushdi, Ahmed I.; Simoneit, Bernd R. T.

    2004-06-01

    Hydrothermal pyrolysis experiments were performed to assess condensation (dehydration) reactions to amide, ester, and nitrile functionalities from lipid precursors. Beside product formation, organic compound alteration and stability were also evaluated. Mixtures of nonadecanoic acid, hexadecanedioic acid, or hexadecanamide with water, ammonium bicarbonate, and oxalic acid were heated at 300°C for 72 h. In addition, mixtures of ammonium bicarbonate and oxalic acid solutions were used to test the abiotic formation of organic nitrogen compounds at the same temperature. The resulting products were condensation compounds such as amides, nitriles, and minor quantities of N-methylalkyl amides, alkanols, and esters. Mixtures of alkyl amide in water or oxalic acid yielded mainly hydrolysis and dehydration products, and with ammonium bicarbonate and oxalic acid the yield of condensation products was enhanced. The synthesis experiments with oxalic acid and ammonium bicarbonate solutions yielded homologous series of alkyl amides, alkyl amines, alkanes, and alkanoic acids, all with no carbon number predominances. These organic nitrogen compounds are stable and survive under the elevated temperatures of hydrothermal fluids.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. Stability and Bifurcation in a Delayed Reaction-Diffusion Equation with Dirichlet Boundary Condition

    NASA Astrophysics Data System (ADS)

    Guo, Shangjiang; Ma, Li

    2016-04-01

    In this paper, we study the dynamics of a diffusive equation with time delay subject to Dirichlet boundary condition in a bounded domain. The existence of spatially nonhomogeneous steady-state solution is investigated by applying Lyapunov-Schmidt reduction. The existence of Hopf bifurcation at the spatially nonhomogeneous steady-state solution is derived by analyzing the distribution of the eigenvalues. The direction of Hopf bifurcation and stability of the bifurcating periodic solution are also investigated by means of normal form theory and center manifold reduction. Moreover, we illustrate our general results by applications to the Nicholson's blowflies models with one- dimensional spatial domain.

  10. Biodiesel production from various oils under supercritical fluid conditions by Candida antartica lipase B using a stepwise reaction method.

    PubMed

    Lee, Jong Ho; Kwon, Cheong Hoon; Kang, Jeong Won; Park, Chulhwan; Tae, Bumseok; Kim, Seung Wook

    2009-05-01

    In this study, we evaluate the effects of various reaction factors, including pressure, temperature, agitation speed, enzyme concentration, and water content to increase biodiesel production. In addition, biodiesel was produced from various oils to establish the optimal enzymatic process of biodiesel production. Optimal conditions were determined to be as follows: pressure 130 bar, temperature 45 degrees C, agitation speed 200 rpm, enzyme concentration 20%, and water contents 10%. Among the various oils used for production, olive oil showed the highest yield (65.18%) upon transesterification. However, when biodiesel was produced using a batch system, biodiesel conversion yield was not increased over 65%; therefore, a stepwise reaction was conducted to increase biodiesel production. When a reaction medium with an initial concentration of methanol of 60 mmol was used and adjusted to maintain this concentration of methanol every 1.5 h during biodiesel production, the conversion yield of biodiesel was 98.92% at 6 h. Finally, reusability was evaluated using immobilized lipase to determine if this method was applicable for industrial biodiesel production. When biodiesel was produced repeatedly, the conversion rate was maintained at over 85% after eight reuses. PMID:19132555

  11. Synthesis of branched cores by poly-O-alkylation reaction under phase transfer conditions. A systematic study

    NASA Astrophysics Data System (ADS)

    Landeros, José M.; Silvestre, Hugo A.; Guadarrama, Patricia

    2013-04-01

    In the present paper is described a systematic study of poly-O-alkylation reactions of pentaerythritol (PE) and 1,1,1-tris(hydroxymethyl)ethane (TME) by 1,4 Michael addition, under phase transfer catalysis (PTC), considering the effect of: (1) the organophilicity of PTC (three different catalysts were tested), (2) PTC concentration (from catalytic to equimolar conditions), and (3) the regime of addition of reactants coexisting in the aqueous phase of the heterogeneous reaction system. The less organophilic transfer agent showed the best performance on these reactions. In our case, benzyltriethylammonium chloride (TEBAC) gathers the best features. The presence of NaOH as base, promotes the interfacial mechanism and not the bulk one. Out of the optimal range of concentration of NaOH (35-40%), competition between nucleophiles can occur, due to the saturation of the medium. Regarding the regime of addition of reactants, the scenario where NaOH and TEBAC are less time in contact, favors the formation of the desired products. Finally, the deprotection of tert-butyl groups of the poly-O-alkylated compounds is described, to get branched cores with terminal carboxylic acid groups in good yields (90-94%). Spectroscopic properties, such as IR, 1H and 13C NMR, of the synthesized compounds are also described.

  12. Effect of reaction conditions on size and morphology of ultrasonically prepared Ni(OH)(2) powders.

    PubMed

    Cabanas-Polo, S; Suslick, K S; Sanchez-Herencia, A J

    2011-07-01

    Modern electrochemical devices require the morphological control of the active material. In this paper the synthesis of nickel hydroxide, as common active compound of such devices, is presented. The influence of ultrasound in the synthesis of nickel hydroxide from aqueous ammonia complexes is studied showing that ultrasound allows the fabrication of flower-like particles with sizes ranging in between 0.7 and 1.0μm in contrast with the 6-8μm particles obtained in the absence of ultrasound. The influence of gas flow, temperature of the process and surfactants in the ultrasonically prepared powders is discussed in term of shape, size and agglomeration of the particles. Adjusting the experimental condition, spherical or platelet-like particles are obtained with sizes ranging from 1.3μm to 200nm. PMID:21190889

  13. 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

  14. 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.

  15. Hydrothermal processing of duckweed: effect of reaction conditions on product distribution and composition.

    PubMed

    Duan, Peigao; Chang, Zhoufan; Xu, Yuping; Bai, Xiujun; Wang, Feng; Zhang, Lei

    2013-05-01

    Influences of operating conditions such as temperature (270-380 °C), time (10-120 min), reactor loading (0.5-5.5 g), and K2CO3 loading (0-50 wt.%) on the product (e.g. crude bio-oil, water soluble, gas and solid residue) distribution from the hydrothermal processing of duckweed were determined. Of the four variables, temperature and K2CO3 loading were always the most influential factors to the relative amount of each component. The presence of K2CO3 is unfavorable for the production of bio-oil and gas. Hydrothermal processing duckweed produces a bio-oil that is enriched in carbon and hydrogen and has reduced levels of O compared with the original duckweed feedstock. The higher heating values of the bio-oil were estimated within the range of 32-36 MJ/kg. Major bio-oil constituents include ketones and their alkylated derivatives, alcohols, heterocyclic nitrogen-containing compounds, saturated fatty acids and hydrocarbons. The gaseous products were mainly CO2 and H2, with lesser amounts of CH4 and CO. PMID:23021946

  16. 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

  17. Sulfated zirconia-catalyzed synthesis of 3,4-dihydropyrimidin-2(1H)-ones (DHPMs) under solventless conditions: competitive multicomponent Biginelli vs. Hantzsch reactions.

    PubMed

    Angeles-Beltrán, Deyanira; Lomas-Romero, Leticia; Lara-Corona, Victor H; González-Zamora, Eduardo; Negrón-Silva, Guillermo

    2006-01-01

    The catalytic ability of ZrO(2)/SO(4)(2-) to promote solventless three-component condensation reactions of a diversity of aromatic aldehydes, urea or thoiurea and ethyl acetoacetate was studied. Products resulting from Hantzsch and/or Biginelli multi-component reactions are obtained in the presence of solid acid catalysts using the same reactants but different temperature conditions. The sulfated zirconia catalyst can be recovered and recycled in subsequent reactions with a gradual decrease of activity. PMID:17971749

  18. Aggregates of a hetero-oligophenylene derivative as reactors for the generation of palladium nanoparticles: a potential catalyst in the Sonogashira coupling reaction under aerial conditions.

    PubMed

    Walia, Preet Kamal; Pramanik, Subhamay; Bhalla, Vandana; Kumar, Manoj

    2015-12-18

    The utilization of Pd nanoparticles stabilized by aggregates of hetero-oligophenylene derivative 3 as an excellent catalyst in a copper/amine free Sonogashira coupling reaction under aerial conditions at room temperature has been demonstrated. PMID:26460180

  19. Size Reproducibility of Gadolinium Oxide Based Nanomagnetic Particles for Cellular Magnetic Resonance Imaging: Effects of Functionalization, Chemisorption and Reaction Conditions

    PubMed Central

    Riyahi-Alam, Sadjad; Haghgoo, Soheila; Gorji, Ensieh; Riyahi-Alam, Nader

    2015-01-01

    We developed biofunctionalized nanoparticles with magnetic properties by immobilizing diethyleneglycol (DEG) on Gd2O3, and PEGilation of small particulate gadolinium oxide (SPGO) with two methoxy-polyethyleneglycol-silane (mPEG-Silane 550 and 2000 Da) using a new supervised polyol route, described recently. In conjunction to the previous study to achieve a high quality synthesis and increase in the product yield of nanoparticles; assessment of the effects of functionalization, chemisorption and altered reaction conditions, such as NaOH concentration, temperature, reaction time and their solubility, on size reproducibility were determined as the goals of this study. Moreover, the effects of centrifugation, filtration and dialysis of the solution on the nono magnetic particle size values and their stability against aggregation have been evaluated. Optimization of reaction parameters led to strong coating of magnetic nanoparticles with the ligands which increases the reproducibility of particle size measurements. Furthermore, the ligand-coated nanoparticles showed enhanced colloidal stability as a result of the steric stabilization function of the ligands grafted on the surface of particles. The experiments showed that DEG and mPEG-silane (550 and 2000 Dalton) are chemisorbed on the particle surfaces of Gd2O3 and SPGO which led to particle sizes of 5.9 ± 0.13 nm, 51.3 ± 1.46 nm and 194.2 ± 22.1 nm, respectively. The small size of DEG-Gd2O3 is acceptably below the cutoff of 6nm, enabling easy diffusion through lymphatics and filtration from kidney, and thus provides a great deal of potential for further in-vivo and in-vitro application PMID:25561907

  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. ACCURATE TIME-DEPENDENT WAVE PACKET STUDY OF THE H{sup +}+LiH REACTION AT EARLY UNIVERSE CONDITIONS

    SciTech Connect

    Aslan, E.; Bulut, N.; Castillo, J. F.; Banares, L.; Aoiz, F. J.; Roncero, O.

    2012-11-01

    The dynamics and kinetics of the H{sup +} + LiH reaction have been studied using a quantum reactive time-dependent wave packet (TDWP) coupled-channel quantum mechanical method on an ab initio potential energy surface at conditions of the early universe. The total reaction probabilities for the H{sup +} + LiH(v = 0, j = 0) {yields} H{sup +} {sub 2} + Li process have been calculated from 5 Multiplication-Sign 10{sup -3} eV up to 1 eV for total angular momenta J from 0 to 110. Using a Langevin model, integral cross sections have been calculated in that range of collision energies and extrapolated for energies below 5 Multiplication-Sign 10{sup -3} eV. The calculated rate constants are found to be nearly independent of temperature in the 10-1000 K interval with a value of Almost-Equal-To 10{sup -9} cm{sup 3} s{sup -1}, which is in good agreement with estimates used in evolutionary models of the early universe lithium chemistry.

  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

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

    PubMed

    Kristensen, Tor E

    2015-01-01

    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

  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. Emissions of volatile organic compounds from Quercus ilex L. measured by Proton Transfer Reaction Mass Spectrometry under different environmental conditions

    NASA Astrophysics Data System (ADS)

    Holzinger, R.; Sandoval-Soto, L.; Rottenberger, S.; Crutzen, P. J.; Kesselmeier, J.

    2000-08-01

    Volatile organic compound (VOC) emissions of the Mediterranean holm oak (Quercus ilex L.) were investigated using a fast Proton Transfer Reaction Mass Spectrometry (PTR-MS) instrument for analysis. This technique is able to measure compounds with a proton affinity higher than water with a high time resolution of 1 s per compound. Hence nearly all VOCs can be detected on-line. We could clearly identify the emission of methanol, acetaldehyde, ethanol, acetone, acetic acid, isoprene, monoterpenes, toluene, and C10-benzenes. Some other species could be tentatively denominated. Among these are the masses 67 (cyclo pentadiene), mass 71 (tentatively attributed to methyl vinyl ketone (MVK) and metacrolein (MACR)), 73 (attributed to methyl ethyl ketone (MEK)), 85 (C6H12 or hexanol), and 95 (vinylfuran or phenol). The emissions of all these compounds (identified as well as nonidentified) together represent 99% of all masses detected and account for a carbon loss of 0.7-2.9% of the net photosynthesis. Of special interest was a change in the emission behavior under changing environmental conditions such as flooding or fast light/dark changes. Flooding of the root system caused an increase of several VOCs between 60 and 2000%, dominated by the emission of ethanol and acetaldehyde, which can be explained by the well described production of ethanol under anoxic conditions of the root system and the recently described subsequent transport and partial oxidation to acetaldehyde within the green leaves. However, ethanol emissions were dominant. Additionally, bursts of acetaldehyde with lower ethanol emission were also found under fast light/dark changes. These bursts are not understood.

  6. Selection of reference genes for quantitative reverse-transcription polymerase chain reaction normalization in Brassica napus under various stress conditions.

    PubMed

    Wang, Zheng; Chen, Yu; Fang, Hedi; Shi, Haifeng; Chen, Keping; Zhang, Zhiyan; Tan, Xiaoli

    2014-10-01

    Data normalization is essential for reliable output of quantitative real-time reverse-transcription polymerase chain reaction (qRT-PCR) assays, as the unsuitable choice of reference gene(s), whose expression might be influenced by exogenous treatments in plant tissues, could cause misinterpretation of results. To date, no systematic studies on reference genes have been performed in stressed Brassica napus. In this study, we investigated the expression variations of nine candidate reference genes in 40 samples of B. napus leaves subjected to various exogenous treatments. Parallel analyses by geNorm and NormFinder revealed that optimal reference genes differed across the different sets of samples. The best-ranked reference genes were PP2A and TIP41 for salt stress, TIP41 and ACT7 for heavy metal (Cr(6+)) stress, PP2A and UBC21 for drought stress, F-box and SAND for cold stress, F-box and ZNF for salicylic acid stress, TIP41, ACT7, and PP2A for methyl jasmonate stress, TIP41 and ACT7 for abscisic acid stress, and TIP41, UBC21, and PP2A for Sclerotinia sclerotiorum stress. Two newly employed reference genes, TIP41 and PP2A, showed better performances, suggesting their suitability in multiple conditions. To further validate the suitability of the reference genes, the expression patterns of BnWRKY40 and BnMKS1 were studied in parallel. This study is the first systematic analysis of reference gene selection for qRT-PCR normalization in B. napus, an agriculturally important crop, under different stress conditions. The results will contribute toward more accurate and widespread use of qRT-PCR in gene analysis of the genus Brassica. PMID:24770781

  7. Effects of Reaction Conditions on the Properties of Spherical Silver Powders Synthesized by Reduction of an Organometallic Compound

    NASA Astrophysics Data System (ADS)

    Chiang, Ying-Jung; Wang, Sea-Fue; Lu, Chun-An; Lin, Hong-Ching

    2014-09-01

    Silver powders were synthesized by reducing a silver organometallic compound, silver 2-ethylhexanoate, with di- n-octylamine. The effects of preparation conditions on the characteristics of the powders were investigated. Silver powders prepared from silver 2-ethylhexanoate and di- n-octylamine in the ratio 2:1 (MA21) at 150°C for 3 h had the best characteristics (average particle size 277 nm, narrow particle-size distribution, high tap density of 4.0 g/cm3), and were also obtained in high yield (98%). Use of an excessive amount of di- n-octylamine resulted in intense thermolysis and a low yield of silver powders of irregular morphology with a wide particle-size distribution. As the proportion of silver 2-ethylhexanoate was increased, the silver powders obtained had a bimodal particle-size distribution and a relatively low tap density. Silver films seemed to have high resistivity when the temperature used for synthesis of the silver powders was too low or reaction time was insufficient. The electrical resistivities of silver films prepared from MA21 powders and sintered at 300°C and 500°C for 30 min were 3.8 × 10-6 Ω cm and 2.3 × 10-6 Ω cm, respectively, close to that of bulk silver.

  8. 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

  9. 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.

  10. The Influence of Sorbent Properties and Reaction Conditions on Attrition of Limestone by Impact Loading in Fluidized Beds

    NASA Astrophysics Data System (ADS)

    Scala, Fabrizio; Salatino, Piero

    The extent of attrition associated with impact loading was studied for five different limestones pre-processed in fluidized bed under different reaction conditions. The experimental procedure was based on the measurement of the amount and the particle size distribution of the debris generated upon impact of sorbent samples against a target at velocities between 10 and 45 m/s. The effect of calcination, sulfation and calcination/re-carbonation on impact damage was assessed. Fragmentation by impact loading of the limestones was significant and increased with the impact velocity. Lime samples displayed the largest propensity to undergo impact damage, followed by sulfated, re-carbonated and raw limestones. Fragmentation of the sulfated samples followed a partem typical of the failure of brittle materials. On the other hand, the behavior of lime samples better conformed to a disintegration failure mode, with extensive generation of very fine fragments. Raw limestone and re-carbonated lime samples followed either of the two patterns depending on the sorbent nature. The extent of particle fragmentation increased after multiple impacts, but the incremental amount of fragments generated upon one impact decreased with the number of successive impacts.

  11. 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.

  12. Activity of Co-N multi walled carbon nanotubes electrocatalysts for oxygen reduction reaction in acid conditions

    NASA Astrophysics Data System (ADS)

    Osmieri, Luigi; Monteverde Videla, Alessandro H. A.; Specchia, Stefania

    2015-03-01

    Two catalysts are synthesized by wet impregnation of multi walled carbon nanotubes (MWCNT) with a complex formed between Co(II) ions and the nitrogen-containing molecule 2,4,6-tris(2-pyridyl)-1,3,5-triazine (TPTZ), followed by one or two identical heat treatments in N2 atmosphere at 800 °C for 3 h. Catalysts are fully characterized by FESEM, EDX, BET, XRD, FTIR, TGA, XPS analyses, and electrochemical techniques. The electrocatalytic activity towards oxygen reduction reaction (ORR) of the catalysts in acid conditions is assessed by means of a rotating disk electrode (RDE) apparatus and a specific type of cell equipped with a gas diffusion working electrode (GDE). In both testing approaches, the catalyst heat-treated twice (Co-N/MWCNT-2) exhibits higher electroactivity than the catalyst heat-treated once (Co-N/MWCNT-1). Chronoamperometries both in RDE and GDE cell are also performed, showing less electroactivity decay and better current performance for the catalyst heat-treated twice.

  13. Isolation of lipase producing thermophilic bacteria: optimization of production and reaction conditions for lipase from Geobacillus sp.

    PubMed

    Mehta, Akshita; Kumar, Rakesh; Gupta, Reena

    2012-12-01

    Lipases catalyze the hydrolysis and the synthesis of esters formed from glycerol and long chain fatty acids. Lipases occur widely in nature, but only microbial lipases are commercially significant. In the present study, thirty-two bacterial strains, isolated from soil sample of a hot spring were screened for lipase production. The strain TS-4, which gave maximum activity, was identified as Geobacillus sp. at MTCC, IMTECH, Chandigarh. The isolated lipase producing bacteria were grown on minimal salt medium containing olive oil. Maximal quantities of lipase were produced when 30 h old inoculum was used at 10% (v/v) in production medium and incubated in shaking conditions (150 rpm) for 72 h. The optimal temperature and pH for the bacterial growth and lipase production were found to be 60°C and 9.5, respectively. Maximal enzyme production resulted when mustard oil was used as carbon source and yeast extract as sole nitrogen source at a concentration of 1% (v/v) and 0.15% (w/v), respectively. The different optimized reaction parameters were temperature 65°C, pH 8.5, incubation time 10 min and substrate p-nitrophenyl palmitate. The Km and Vmax values of enzyme were found to be 14 mM and 17.86 μmol ml-1min-1, respectively, with p-nitrophenyl palmitate as substrate. All metal ions studied (1 mM) increased the lipase activity. PMID:23195552

  14. 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.

  15. Effects of changing stance conditions on anticipatory postural adjustment and reaction time to voluntary arm movement in humans.

    PubMed

    Dietz, V; Kowalewski, R; Nakazawa, K; Colombo, G

    2000-04-15

    1. The effect on reaction time (RT) and anticipatory postural adjustment (APA) of unexpectedly changing stance conditions was studied using a push or pull arm movement task. The aim was to evaluate the modifiability of RT and APA by an external perturbation associated with an automatic compensatory reaction. 2. Subjects standing on a moveable platform were asked to push or pull a rigid handle as quickly and as strongly as possible in response to the 'go-signal', a visual signal from a green or red light-emitting diode. Forward and backward translations of the platform were randomly induced at four time intervals after the go-signal. In some experiments to detect unspecific arousal there were no platform translations but an acoustic signal was given before the go-signal. Surface electromyographic activity (EMG) of upper arm and lower leg muscles was analysed. 3. During the push task both RT and the duration of APA (onset of APA till the force signal indicating hand action) were shorter during backward than during forward translation. During the pull task the effect of platform translations was the reverse. The delay between go-signal and onset of APA remained constant. Consequently, RT and APA became shorter when the platform was translated in the same direction as that in which the upper body was displaced by the push or pull movement, and longer when it was translated in the opposite direction. The effects were maximal when translations were induced 250 ms after the go-signal, but a difference was detected up to 375 ms. 4. Furthermore, with forward and backward platform translations RT was shorter when the translations were induced early rather than late after the go-signal. This was associated with a shortening of the delay between the go-signal and onset of APA, while APA duration remained constant. The shortened RT was in the range of that obtained when an acoustic signal was given just before the go-signal. 5. It is concluded that (i) both the RT and the

  16. Effect of reaction conditions on methyl red degradation mediated by boron and nitrogen doped TiO2

    NASA Astrophysics Data System (ADS)

    Galenda, A.; Crociani, L.; Habra, N. El; Favaro, M.; Natile, M. M.; Rossetto, G.

    2014-09-01

    Nowadays the employment of renewable and sustainable energy sources, and solar light as main option, becomes an urgent need. Photocatalytic processes received great attention in wastewater treatment due to their cheapness, environmental compatibility and optimal performances. Despite the general low selectivity of the photocatalysts, an accurate optimisation of the operational parameters needs to be carried out in order to maximise the process yield. Because of this reason, the present contribution aims to deepen either the knowledge in boron and/or nitrogen doped TiO2-based systems and their employment in methyl red removal from aqueous solutions. The samples were obtained by coprecipitation and characterised by XRD, SEM, BET specific surface area, UV-vis and XPS techniques. The catalytic activity was for the first time carefully evaluated with respect to methyl red photodegradation in different conditions as a function of working pH, counter-ions and pre-adsorption time. An ad-hoc study was performed on the importance of the pre-adsorption of the dye, suggesting that an extended adsorption is useless for the catalyst photoactivity, while a partial coverage is preferable. The photocatalytic tests demonstrate the positive influence of boron doping in photo-activated reactions and the great importance of the operational parameters with respect to the simple methyl red bleaching rather than the overall pollutant mineralisation. It is proved, indeed, that different working pH, acidifying means and substrate pre-adsorption time can enhance or limit the catalyst performances with respect to the complete pollutant degradation rather than its partial breakage.

  17. Two reaction regimes in the oxidation of larger cationic tantalum clusters (Tan(+), n = 13-40) under multi-collision conditions.

    PubMed

    Neuwirth, D; Eckhard, J F; Visser, B R; Tschurl, M; Heiz, U

    2016-03-21

    The reaction of cationic tantalum clusters (Tan(+), n = 13-40) with molecular oxygen is studied under multi-collision conditions and at different temperatures. Consecutive reaction proceeds in several steps upon subsequent attachment of O2. All cluster sizes exhibit fast reaction with oxygen and form a characteristic final reaction product. The time-dependent product analysis enables the fitting to a kinetic model with the extraction of all the rate constants. Determined rate constants reveal the existence of two different regimes, which are interpreted as a change in the reaction mechanism. Based on the temperature-dependent reaction behavior, it is proposed that the reaction changes from a dissociative to a molecular adsorption of oxygen on the clusters. It is found that both regimes appear for all cluster sizes, but the transition takes place at different intermediate oxides TanOx(+). In general it is observed that transition occurs later for larger clusters, which is attributed to an increased cluster surface. PMID:26924176

  18. 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

  19. Manganese(III) Acetate-Promoted Cross-Coupling Reaction of Benzothiazole/Thiazole Derivatives with Organophosphorus Compounds under Ball-Milling Conditions.

    PubMed

    Li, Liang; Wang, Jun-Jie; Wang, Guan-Wu

    2016-07-01

    The first solvent-free manganese(III) acetate-promoted reaction of benzothiazole/thiazole derivatives with organophosphorus compounds including phosphine oxides, phosphinate ester, and phosphonate diester has been efficiently developed under ball-milling conditions, providing a highly efficient and green protocol to structurally diverse C2-phosphonylated benzothiazole/thiazole derivatives with remarkable functional group tolerance and excellent yields. PMID:27248000

  20. 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...

  1. 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.

  2. 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...

  3. Encouraging Conceptual Change: The Use of Bridging Analogies in the Teaching of Action-Reaction Forces and the "At Rest" Condition in Physics. Research Report

    ERIC Educational Resources Information Center

    Bryce, Tom; MacMillan, Kenneth

    2005-01-01

    The qualitative study described in this paper examined the effectiveness of bridging analogies intended to bring about conceptual change as part of a constructivist approach to teaching about action-reaction forces in the 'at rest' condition in physics. Twenty-one 15-year-old students were involved in the investigation with subgroups previously…

  4. A π-electronic covalent organic framework catalyst: π-walls as catalytic beds for Diels-Alder reactions under ambient conditions.

    PubMed

    Wu, Yang; Xu, Hong; Chen, Xiong; Gao, Jia; Jiang, Donglin

    2015-06-25

    We report a strategy for developing π-electronic covalent organic frameworks as heterogeneous catalysts that enable the use of columnar π-walls as catalytic beds to facilitate organic transformations in their one-dimensional open channels. The π-frameworks exhibit outstanding catalytic activity, promote Diels-Alder reactions under ambient conditions and are robust for cycle use. PMID:26000867

  5. 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.

  6. Mechanistic Studies Lead to Dramatically Improved Reaction Conditions for the Cu-Catalyzed Asymmetric Hydroamination of Olefins.

    PubMed

    Bandar, Jeffrey S; Pirnot, Michael T; Buchwald, Stephen L

    2015-11-25

    Enantioselective copper(I) hydride (CuH)-catalyzed hydroamination has undergone significant development over the past several years. To gain a general understanding of the factors governing these reactions, kinetic and spectroscopic studies were performed on the CuH-catalyzed hydroamination of styrene. Reaction profile analysis, rate order assessment, and Hammett studies indicate that the turnover-limiting step is regeneration of the CuH catalyst by reaction with a silane, with a phosphine-ligated copper(I) benzoate as the catalyst resting state. Spectroscopic, electrospray ionization mass spectrometry, and nonlinear effect studies are consistent with a monomeric active catalyst. With this insight, targeted reagent optimization led to the development of an optimized protocol with an operationally simple setup (ligated copper(II) precatalyst, open to air) and short reaction times (<30 min). This improved protocol is amenable to a diverse range of alkene and alkyne substrate classes. PMID:26522837

  7. Kinetic study of the reaction of sulfamethoxazole and glucose under acidic conditions: I. Effect of pH and temperature.

    PubMed

    Lucida, H; Parkin, J E; Sunderland, V B

    2000-07-20

    The kinetics of the reaction of sulfamethoxazole (SMX) in 5% w/v glucose to form the corresponding alpha- and beta-glucosylamines over the pH range of 0.80-6.88 at 37 degrees C has been investigated. The identity of the glucosylamines was determined by 1H-nuclear magnetic resonance spectroscopy of an authentic sample of the alpha-glucosylamine (USP) and the reaction products, and by interconversion of this compound to the corresponding beta-anomer. The reaction followed pseudo first-order reversible kinetics and involved specific acid and general acid-base catalysis. The pH-rate profile demonstrated that over the pH range of 0.80-2.90 and 5.50-6. 88 the reactions were dependent on H(+) concentration but pH independent between pH 3.00-5.45, which reflects the influence of ionization of SMX and the glucosylamines on the reversible reaction. Interpretation of the data with respect to kinetic models and rate equations for the formation and hydrolysis of the glucosylamines was investigated. Temperature dependence studies followed the Arrhenius equation with an Ea of 49.28 kJ mol(-1) for the forward and 63.46 kJ mol(-1) for the reverse reaction at pH 2.89 respectively. PMID:10915926

  8. Optimization of reaction conditions for enzymatic viscosity reduction and hydrolysis of wheat arabinoxylan in an industrial ethanol fermentation residue.

    PubMed

    Sørensen, Hanne R; Pedersen, Sven; Meyer, Anne S

    2006-01-01

    This study examined enzyme-catalyzed viscosity reduction and evaluated the effects of substrate dry matter concentration on enzymatic degradation of arabinoxylan in a fermentation residue, "vinasse", resulting from industrial ethanol manufacture on wheat. Enzymatic catalysis was accomplished with a 50:50 mixture of an enzyme preparation from Humicola insolens, Ultraflo L, and a cellulolytic enzyme preparation from Trichoderma reesei, Celluclast 1.5 L. This enzyme mixture was previously shown to exhibit a synergistic action on arabinoxylan degradation. The viscosity of vinasse decreased with increased enzyme dosage and treatment time at pH 5, 50 degrees C, 5 wt % vinasse dry matter. After 24 h of enzymatic treatment, 76-84%, 75-80%, and 43-47%, respectively, of the theoretically maximal arabinose, xylose, and glucose releases were achieved, indicating that the viscosity decrease was a result of enzyme-catalyzed hydrolysis of arabinoxylan, beta-glucan, and cellulose. In designed response surface experiments, the optimal enzyme reaction conditions with respect to pH and temperature of the vinasse, the vinasse supernatant (mainly soluble material), and the vinasse sediment (mainly insoluble substances) varied from pH 5.2-6.4 and 41-49 degrees C for arabinose release and from pH 4.9-5.3 and 42-46 degrees C for xylose release. Even though only limited hydrolysis of the arabinoxylan in the vinasse sediment fraction was obtained, the results indicated that the same enzyme activities acted on the arabinoxylan in the different vinasse fractions irrespective of the state of solubility of the substrate material. The levels of liberated arabinose and xylose increased with increased dry matter concentration during enzymatic hydrolysis in the vinasse and the vinasse supernatant, but at the same time, increased substrate dry matter concentrations gave corresponding linear decreases in the hydrolytic efficiency as evaluated from levels of monosaccharide release per weight unit dry

  9. 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 (δ13C) 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

  10. Sonication effect on the reaction of 4-bromo-1-methylbenzene with sodium sulfide in liquid-liquid multi-site phase-transfer catalysis condition - kinetic study.

    PubMed

    Abimannan, Pachaiyappan; Selvaraj, Varathan; Rajendran, Venugopal

    2015-03-01

    The synthesis of di-p-tolylsulfane from the reaction of 4-bromo-1-methylbenzene (BMB) with sodium sulfide was carried out using a multi-site phase-transfer catalyst (MPTC) viz., 1,4-dihexyl-1,4-diazoniabicyclo[2.2.2]octanium dibromide and ultrasonic irradiation in a liquid-liquid reaction condition. The overall reaction rate is greatly enhanced when catalyzed by multi-site phase-transfer catalyst (MPTC) combined with sonication (40 kHz, 300 W) in a batch reactor than catalyzed by MPTC without sonication. Effects on the reaction due to various operating conditions, such as agitation speed, different ultrasound frequencies, different phase-transfer catalysts, different organic solvents, the amount of MPTC, temperature, amount of sodium sulfide, effect of sodium hydroxide, volume of n-hexane and the concentration of 4-bromo-1-methylbenzene. The reaction obeys a pseudo first-order rate law and a suitable mechanism was proposed based on the experimental observation. PMID:25199442

  11. Optimization of some conditions of Neutrase-catalyzed plastein reaction to mediate ACE-inhibitory activity in vitro of casein hydrolysate prepared by Neutrase.

    PubMed

    Xu, Wei; Kong, Bao-Hua; Zhao, Xin-Huai

    2014-02-01

    Casein hydrolysate was prepared by hydrolyzing casein with Neutrase and then modified by a Neutrase-catalyzed plastein reaction. The prepared hydrolysate had a degree of hydrolysis of 13.0% and exhibited ACE inhibition in vitro with an IC50 value of 40.4 μg⋅mL(-1). With the decreased amount of free amino groups of the modified hydrolysate as the response, some conditions of the plastein reaction including substrate concentration, enzyme to substrate ratio, reaction temperature and time were studied by single factor experiments and response surface methodology, and optimized finally as 62% (w/w), 3.0 kU⋅g(-1) peptides, 30 °C and 6.3 h, respectively. The maximum decreased amount of free amino groups of the modified hydrolysate prepared under these optimized conditions was 210.0 μmol⋅g(-1) peptides, while corresponding IC50 value was lowered to 14.7 μg⋅mL(-1). The present result indicates that Neutrase-catalyzed plastein reaction was capable of enhancing ACE-inhibitory activity in vitro of casein hydrolysate, and also highlights the importance of a forthcoming study to investigate the peptide compositions of the modified hydrolysate and the role of protease used in the plastein reaction. PMID:24493884

  12. An experimental investigation of the reaction of hydrogen chloride with lead oxide under simulated hazardous waste incineration conditions

    SciTech Connect

    Shor, J.T.; Frazier, G.C.

    1996-04-01

    To simulate the behavior of lead during hazardous waste incineration, pellets of sintered lead oxide were treated with hydrogen chloride at concentrations of 2000 and 4000 ppm in air in a laboratory tube furnace. The chemical reaction kinetics and mass transfer properties of the solid-gas and solid-liquid reactions were examined at temperatures between 260 and 680{degrees}C. Lead dichloride was found to form and became more volatile at elevated temperatures. At temperatures above 300{degrees}C, chemical reaction kinetic limitations were absent and mass transfer resistance in the developing liquid lead oxide, lead dichloride eutectic phases were controlling. Above 590{degrees}C, a curious anomaly occurred: The observed global reaction rate appeared to increase slightly while the volatilization of lead dichloride dropped during the initial stages of the reaction. A thick film of a lead oxychloride compound was found which displayed low lead dichloride activity. Below 590{degrees}C, a different lead oxychloride compound was identified by x-ray diffraction in which lead dichloride activity was high, and this compound was much more volatile than the oxychloride formed above 5900{degrees}C.

  13. Spectral Quasi-linearization Method for Homogeneous-Heterogeneous Reactions on Nonlinear Convection Flow of Micropolar Fluid Saturated Porous Medium with Convective Boundary Condition

    NASA Astrophysics Data System (ADS)

    RamReddy, Chetteti; Pradeepa, Teegala

    2016-05-01

    Based on the nonlinear variation of density with temperature (NDT) in the buoyancy term, the mixed convection flow along a vertical plate of a micropolar fluid saturated porous medium is considered. In addition, the effect of homogeneous-heterogeneous reaction and convective boundary condition has been taken into account. Using lie scaling group transformations, the similarity representation is attained for the system of partial differential equations, prior to being solved by a spectral quasilinearization method. The results show that in the presence of aiding and opposing flow situations, both the species concentration and mass transfer rate decreases when the strength of homogeneous and heterogeneous reaction parameters are enhanced.

  14. Iron-promoted C-C bond cleavage of 1,3-diketones: a route to 1,2-diketones under mild reaction conditions.

    PubMed

    Huang, Lehao; Cheng, Kai; Yao, Bangben; Xie, Yongju; Zhang, Yuhong

    2011-07-15

    A conceptual method for the preparation of 1,2-diketones is reported. The selective C-C bond cleavage of 1,3-diketones affords the 1,2-diketones in high yields under mild reaction conditions in air by the use of FeCl(3) as the catalyst and tert-butyl nitrite (TBN) as the oxidant without the use of solvent. The possible reaction mechanism is discussed. This protocol provides an expeditious route to the useful 1,2-diketones. PMID:21627329

  15. Type 1 reaction in leprosy: a model for a better understanding of tissue immunity under an immunopathological condition.

    PubMed

    Andrade, Priscila Ribeiro; Pinheiro, Roberta Olmo; Sales, Anna Maria; Illarramendi, Ximena; Barbosa, Mayara Garcia de Mattos; Moraes, Milton Ozório; Jardim, Marcia Rodrigues; Nery, Jose Augusto da Costa; Sampaio, Elizabeth Pereira; Sarno, Euzenir Nunes

    2015-03-01

    Type 1 reaction (T1R) or reversal reaction is the leading cause of physical disabilities and deformities in leprosy. Leprosy patients, even after being considered cured and released from treatment, may suffer from reactional episodes for long periods of time. Early diagnosis is a great challenge for effectively treating and managing T1R. There is an urgent need to identify the most significant biomarkers to prevent recurrent T1R and to differentiate late T1R from relapse. T1R continues to be treated with corticosteroids and complications due to iatrogenic treatment remain frequent. This review aims to provide a framework from which to approach the great challenges that still persist in T1R management and debate key issues in order to reduce the distance between basic research and the clinic. PMID:25666357

  16. Nucleoside azide-alkyne cycloaddition reactions under solvothermal conditions or using copper vials in a ball mill.

    PubMed

    Cummings, Andrew J; Ravalico, Francesco; McColgan-Bannon, Kegan I S; Eguaogie, Olga; Elliott, P Alain; Shannon, Matthew R; Bermejo, Iris A; Dwyer, Angus; Maginty, Amanda B; Mack, James; Vyle, Joseph S

    2015-01-01

    Novel nucleoside analogues containing photoswitchable moieties were prepared using 'click' cycloaddition reactions between 5'-azido-5'-deoxythymidine and mono- or bis-N-propargylamide-substituted azobenzenes. In solution, high to quantitative yields were achieved using 5 mol% Cu(I) in the presence of a stabilizing ligand. 'Click' reactions using the monopropargylamides were also effected in the absence of added cuprous salts by the application of liquid assisted grinding (LAG) in metallic copper reaction vials. Specifically, high speed vibration ball milling (HSVBM) using a 3/32″ (2.38 mm) diameter copper ball (62 mg) at 60 Hz overnight in the presence of ethyl acetate lead to complete consumption of the 5'-azido nucleoside with clean conversion to the corresponding 1,3-triazole. PMID:25874944

  17. A reaction cell with sample laser heating for in situ soft X-ray absorption spectroscopy studies under environmental conditions.

    PubMed

    Escudero, Carlos; Jiang, Peng; Pach, Elzbieta; Borondics, Ferenc; West, Mark W; Tuxen, Anders; Chintapalli, Mahati; Carenco, Sophie; Guo, Jinghua; Salmeron, Miquel

    2013-05-01

    A miniature (1 ml volume) reaction cell with transparent X-ray windows and laser heating of the sample has been designed to conduct X-ray absorption spectroscopy studies of materials in the presence of gases at atmospheric pressures. Heating by laser solves the problems associated with the presence of reactive gases interacting with hot filaments used in resistive heating methods. It also facilitates collection of a small total electron yield signal by eliminating interference with heating current leakage and ground loops. The excellent operation of the cell is demonstrated with examples of CO and H2 Fischer-Tropsch reactions on Co nanoparticles. PMID:23592631

  18. 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.

  19. 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…

  20. 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

  1. Effect of Particle Morphology on Critical Conditions for Shock-Initiated Reactions in Titanium-Silicon Powder Mixtures

    NASA Astrophysics Data System (ADS)

    Frost, David; Jette, Francois; Goroshin, Samuel; Higgins, Andrew; Lee, Julian

    2009-06-01

    The effect of titanium particle morphology on the shock sensitivity of titanium-silicon powder mixtures has been investigated experimentally. The powder mixtures were tested in a planar recovery capsule, with the shock loading produced by a high explosive Tetryl booster charge placed on top of the capsule and a PMMA attenuator. Reactions were not observed for stoichiometric mixtures of large (75 -- 106 μm), spherical Ti particles with fine (< 44 μm) Si particles for incident peak shock pressures of up to 23 GPa, estimated with LS-DYNA. In contrast, mixtures with fine (< 45 μm) spherical Ti particles or irregularly-shaped fine (< 20 μm) Ti particles had critical shock pressures for reaction initiation of 7±3 GPa and 5±2 GPa, respectively. Microscopy and spectroscopy were used to identify the degree of intermixing between the particles for shock loading just below the reaction threshold. For the largest spherical Ti particles, little particle intermixing was evident. However, differential thermal analysis carried out demonstrated that even for the large Ti particles, shock loading of the samples generated microstructural effects which lowered the temperature for the onset of exothermic reaction of the shocked sample by about 80^oC.

  2. 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 ...

  3. Selectivity of competitive-consecutive reactions depending on the turbulent mixing conditions in a co-axial jet mixer

    NASA Astrophysics Data System (ADS)

    Chorny, A.; Kornev, N.; Hassel, E.

    2010-12-01

    This paper considers the numerical results on the interaction between a turbulent co-axial jet and a co-flow of incompressible fluid (Schmidt number Sc≈1000) when competitive-consecutive reactions occur in a co-axial jet mixer. Firstly, RANS modeling was performed to predict flow phenomena. Two different mixing regimes were analyzed with and without a recirculation zone near a mixer wall. To describe the problem mathematically, the two-parameter turbulence k-ɛ model and various models for the computation of the averaged mixture fraction \\skew3\\bar f and its variance σ2 were used and verified by comparing them with the experimental and large eddy simulation (LES) data. The results revealed that the decay of \\skew5\\bar f and σ2 obtained by the developed RANS mixing model with the low-Reynolds-number effects (mechanical-to-scalar time ratio and turbulent Schmidt number in the transfer equation for σ2 as a function of Ret) was similar to the one found by LES and experiment. Second, the behavior of the competitive-consecutive reactions (A+B→P, B+R→S) in the co-axial mixer was considered. To calculate averaged chemical reaction rates, the transfer equations for concentrations adopted two approaches: a model with no regard to concentration fluctuations and the Li-Toor model with the Gaussian PDF of the mixture fraction. The yield of a desired product R was found to depend strongly on the mixing regime. The regime without recirculation zone appeared to be preferable as the reaction selectivity was smaller within the whole range of Reynolds number and initial reactant concentration ratio. This means that the amount of an undesired by-product S to be formed is minimal.

  4. 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

  5. Formation of Nano-Bacteria-Like Flow Textures Formed at Oxygen-Rich Air Condition of Shock Wave Reaction

    NASA Astrophysics Data System (ADS)

    Miura, Y.; Tanosaki, T.

    2011-03-01

    Nano-flow textures with irregular shapes are obtained by shock impact on carbon-fibers with oxygen-rich air condition (not at vacuum condition), which are different with nano-bacteria texture of the martian meteorite with regular nano-flow textures.

  6. Scaling Hyporheic Flow and Biogeochemical Reactions across a Wide Range of Flow and Sediment Conditions in Aquatic Systems

    NASA Astrophysics Data System (ADS)

    Harvey, J. W.; O'Connor, B. L.

    2008-12-01

    Aquatic ecosystems are strongly influenced by advective transport from surface water into shallow sediments of the hyporheic zone. The delivery of energy and nutrient-rich materials to microbially and geochemically reactive sediment stimulates high rates of biogeochemical reactions that influence the overall metabolism of the ecosystem as well as influencing the chemistry of downstream receiving waters. Predicting hyporheic flow is difficult because of the potential involvement of many physical processes, including diffusion, shear, bedform-scale advective pumping, bed mobility and bioturbation, turbulence penetration, and head potential- driven groundwater exchange. We used published data from carefully controlled laboratory flume experiments to develop a scaling relationship that predicts hyporheic exchange based on physical descriptors (e.g. shear stress velocity, roughness height, and sediment permeability) that summarize fluid- flow and sediment characteristics. We tested the scaling relationship's predictions by comparing them with more time and labor intensive measurements of solute and reactive tracer transport made in situ in hyporheic zones. In situ measurements were acquired using the USGS MINIPOINT sampler, which allows detailed subsurface measurements without significant disturbance of sediment or the ambient surface or subsurface water fluxes. Fieldwork was undertaken in several streams that varied widely in surface water flow velocities, grain type, median grain size, sediment porosity, sediment organic content, sediment hydraulic conductivity, and groundwater specific discharge. The comparison generally supported the predictive capability of the scaling relationship in complex field settings. The value of the scaling relationship is also indicated for improving rate measurements of biogeochemical reactions in hyporheic zones (e.g. oxygen uptake, denitrification, and manganese oxidation), as well as for estimating the cumulative influence of

  7. OD(X/sup 2/II) and SD(X/sup 2/II) from reactions of D atoms with OCS under bulk and precursor geometry limited conditions

    SciTech Connect

    Haeusler, D.; Rice, J.; Wittig, C.

    1987-10-08

    Reactions of D atoms with OCS were studied by 193-nm pulsed laser photolysis of DBr as a nearly monoenergetic D-atom source. Nascent OD(X/sup 2/II) and SD(X/sup 2/II) rotational, vibrational, spin-orbit, and ..lambda..-doublet populations were obtained under single-collision bulk conditions at 300 K. The SD channel is favored energetically (..delta.. H = -43 +/- 13 and 230 +/- 13 kJ mol/sup -1/ for the SD and OD channels, respectively) and is the dominant pathway ((SD)/(OD) = 5 +/- 2). Nascent OD(X/sup 2/II) products were also obtained from a precursor geometry limited (PGL) reaction by using the weakly bound van der Waals complex SCO-DBr. The OD(X/sup 2/II) rotational distributions are the same for both bulk and PGL conditions and can be reproduced by using a statistical model. Due to experimental difficulties, SD(X/sup 2/II) distributions could not be obtained under PGL conditions. The SD(X/sup 2/II) distribution obtained under bulk conditions is very nonstatistical, suggesting that this species is not formed via a long-lived DSCO intermediate complex in which vibrational energy is randomized.

  8. Nature of Ptn/TiO2(110) Interface under Water-Gas Shift Reaction Conditions: A Constrained ab Initio Thermodynamics Study

    SciTech Connect

    Ammal, Salai Cheettu; Heyden, Andreas

    2011-10-06

    The electronic structure of small Ptn (n = 1-8) clusters supported on the stoichiometric and partially reduced rutile TiO2(110) surface have been investigated using density functional theory. Pt atoms prefer to form a close-packed structure with (111) facet near an oxygen vacancy of the TiO2 support and a less dense structure with (100) facet away from oxygen vacant sites. Themain focus of this study is on identifying a realistic catalyst model for the Pt/TiO2 interface under watergas shift (WGS) reaction conditions. Constrained ab initio thermodynamic simulations on the stability of oxygen vacancies and formation of adsorbed gas phase molecules such as oxygen, CO, and hydrogen at the metal/oxide interface reveal that under WGS reaction conditions the formation of surface oxygen vacancies are thermodynamically favorable, platinum oxide species (PtOx) can easily be reduced and should not be present, CO adsorbs only weakly on interfacial Pt atoms, and CO poisoning of these sites should be less important. While hydrogen generally interacts weakly with interfacial Pt atoms, it forms very stable hydride species on Pt atoms neighboring an oxygen vacancy of the TiO2(110) support, possibly negatively affecting the WGS reaction rate.

  9. Tailoring (n,m) structure of single-walled carbon nanotubes by modifying reaction conditions and the nature of the support of CoMo catalysts.

    PubMed

    Lolli, Giulio; Zhang, Liang; Balzano, Leandro; Sakulchaicharoen, Nataphan; Tan, Yongqiang; Resasco, Daniel E

    2006-02-01

    The (n,m) population distribution of single-walled carbon nanotubes obtained on supported CoMo catalysts has been determined by photoluminescence and optical absorption. It has been found that the (n,m) distribution can be controlled by varying the gaseous feed composition, the reaction temperature, and the type of catalyst support used. When using CO as a feed over CoMo/SiO2 catalysts, increasing the synthesis temperature results in an increase in nanotube diameter, without a change in the chiral angle. By contrast, by changing the support from SiO2 to MgO, nanotubes with similar diameter but different chiral angles are obtained. Finally, keeping the same reaction conditions but varying the composition of the gaseous feed results in different (n,m) distribution. The clearly different distributions obtained when varying catalysts support and/or reaction conditions demonstrate that the (n,m) distribution is a result of differences in the growth kinetics, which in turn depends on the nanotube cap-metal cluster interaction. PMID:16471791

  10. Dynamic transformation of small Ni particles during methanation of CO2 under fluctuating reaction conditions monitored by operando X-ray absorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Mutz, B.; Carvalho, H. W. P.; Kleist, W.; Grunwaldt, J.-D.

    2016-05-01

    A 10 wt.-% Ni/Al2O3 catalyst with Ni particles of about 4 nm was prepared and applied in the methanation of CO2 under dynamic reaction conditions. Fast phase transformations between metallic Ni, NiO and NiCO3 were observed under changing reaction atmospheres using operando X-ray absorption spectroscopy (XAS). Removing H2 from the feed gas and, thus, simulating a H2 dropout during the methanation reaction led to oxidation of the active sites. The initial reduced state of the Ni particles could not be recovered under methanation atmosphere (H2/CO2 = 4); this was only possible with an effective reactivation step applying H2 at increased temperatures. Furthermore, the cycling of the gas atmospheres resulted in a steady deactivation of the catalyst. Operando XAS is a powerful tool to monitor these changes and the behavior of the catalyst under working conditions to improve the understanding of the catalytic processes and deactivation phenomena.

  11. 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.

  12. 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.

  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. 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

  15. Impact of Flight Enthalpy, Fuel Simulant, and Chemical Reactions on the Mixing Characteristics of Several Injectors at Hypervelocity Flow Conditions

    NASA Technical Reports Server (NTRS)

    Drozda, Tomasz G.; Baurle, Robert A.; Drummond, J. Philip

    2016-01-01

    The high total temperatures or total enthalpies required to duplicate the high-speed flight conditions in ground experiments often place stringent requirements on the material selection and cooling needs for the test articles and intrusive flow diagnostic equipment. Furthermore, for internal flows, these conditions often complicate the use of nonintrusive diagnostics that need optical access to the test section and interior portions of the flowpath. Because of the technical challenges and increased costs associated with experimentation at high values of total enthalpy, an attempt is often made to reduce it. This is the case for the Enhanced Injection and Mixing Project (EIMP) currently underway in the Arc-Heated Scramjet Test Facility at the NASA Langley Research Center. The EIMP aims to investigate supersonic combustion ramjet (scramjet) fuel injection and mixing physics, improve the understanding of underlying physical processes, and develop enhancement strategies and functional relationships between mixing performance and losses relevant to flight Mach numbers greater than 8. The experiments will consider a "direct-connect" approach and utilize a Mach 6 nozzle to simulate the combustor entrance flow of a scramjet engine. However, while the value of the Mach number is matched to that expected at the combustor entrance in flight, the maximum value of the total enthalpy for these experiments is limited by the thermal-structural limits of the uncooled experimental hardware. Furthermore, the fuel simulant is helium, not hydrogen. The use of "cold" flows and non-reacting mixtures of fuel simulants for mixing experiments is not new and has been extensively utilized as a screening technique for scramjet fuel injectors. In this study, Reynolds-averaged simulations are utilized (RAS) to systematically verify the implicit assumptions used by the EIMP. This is accomplished by first performing RAS of mixing for two injector configurations at planned nominal experimental

  16. An experimental study on evolution of fracture permeability and rate of water-rock reactions in ultramafic rocks at hydrothermal conditions

    NASA Astrophysics Data System (ADS)

    Farough, A.; Lowell, R. P.

    2015-12-01

    We have performed experiments on the evolution of fracture permeability during serpentinization of ultramafic rocks. The experiments were performed using a flow-through triaxial machine on samples of ultramafic rocks with a well-mated through-going tensile fracture at hydrothermal conditions at effective pressure of 30 MPa and temperature of 260°C. By determining the flow rate under a pore pressure gradient during the experiments and assuming a cubic law relating fracture aperture and permeability, the results showed that fracture permeability decreased by one to two orders of magnitude during the 200 to 340 hour experiments. Electron microprobe data and SEM images indicated the formation of needle-shaped crystals of serpentine composition along the walls of the fracture. Assuming the dissolution and precipitation reactions occur simultaneously along the fracture walls we found that the rate of transformation at the beginning of the experiments is ~10-4-5 (molm-2hr-1) and decreases monotonically for about an order of magnitude towards the end of experiments. The rate of transformation is converted to rate of reaction of 10-5-7 s-1 at the beginning of the experiments, which is in agreement with estimates of Martin and Fyfe, [1970] of the rate of serpentinization reactions. The results suggest that the reaction rate slowed with increasing time as available reactive surface area decreased. The results also indicate that the water-rock reactions were the main mechanism contributing to the reduction in fracture aperture and cubic law is a reasonable first approximation for understanding evolution of fracture permeability. The experimental results suggest that the fracture network in long-lived hydrothermal circulation systems can be sealed rapidly as a result of mineral precipitation, and generation of new permeability resulting from a combination of tectonic and crystallization-induced stresses is required to maintain fluid circulation.

  17. The secondary formation of inorganic aerosols in the droplet mode through heterogeneous aqueous reactions under haze conditions

    NASA Astrophysics Data System (ADS)

    Wang, Xinfeng; Wang, Wenxing; Yang, Lingxiao; Gao, Xiaomei; Nie, Wei; Yu, Yangchun; Xu, Pengju; Zhou, Yang; Wang, Zhe

    2012-12-01

    Secondary inorganic aerosols play important roles in visibility reduction and in regional haze pollution. To investigate the characteristics of size distributions of secondary sulfates and nitrates as well as their formation mechanisms under hazes, size-resolved aerosols were collected using a Micro-Orifice Uniform Deposit Impactor (MOUDI) at an urban site in Jinan, China, in all four seasons (December 2007-October 2008). In haze episodes, the secondary sulfates and nitrates primarily formed in fine particles, with elevated concentration peaks in the droplet mode (0.56-1.8 μm). The fine sulfates and nitrates were completely neutralized by ammonia and existed in the forms of (NH4)2SO4 and NH4NO3, respectively. The secondary formation of sulfates, nitrates and ammonium (SNA) was found to be related to heterogeneous aqueous reactions and was largely dependent on the ambient humidity. With rising relative humidity, the droplet-mode SNA concentration, the ratio of droplet-mode SNA to the total SNA, the fraction of SNA in droplet-mode particles and the mass median aerodynamic diameter of SNA presented an exponential, logarithmic or linear increase. Two heavily polluted multi-day haze episodes in winter and summer were analyzed in detail. The secondary sulfates were linked to heterogeneous uptake of SO2 followed by the subsequent catalytic oxidation by oxygen together with iron and manganese in winter. The fine nitrate formation was strongly associated with the thermodynamic equilibrium among NH4NO3, gaseous HNO3 and NH3, and showed different temperature-dependences in winter and summer.

  18. 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.

  19. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-08-01

    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.

    PubMed

    Gallegos, Tanya J; Han, Young-Soo; Hayes, Kim F

    2008-12-15

    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 x 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. PMID:19174913

  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. Wavelength dependence of the fluorescence emission under conditions of open and closed Photosystem II reaction centres in the green alga Chlorella sorokiniana.

    PubMed

    Rizzo, Federico; Zucchelli, Giuseppe; Jennings, Robert; Santabarbara, Stefano

    2014-06-01

    The fluorescence emission characteristics of the photosynthetic apparatus under conditions of open (F0) and closed (FM) Photosystem II reaction centres have been investigated under steady state conditions and by monitoring the decay lifetimes of the excited state, in vivo, in the green alga Chlorella sorokiniana. The results indicate a marked wavelength dependence of the ratio of the variable fluorescence, FV=FM-F0, over FM, a parameter that is often employed to estimate the maximal quantum efficiency of Photosystem II. The maximal value of the FV/FM ratio is observed between 660 and 680nm and the minimal in the 690-730nm region. It is possible to attribute the spectral variation of FV/FM principally to the contribution of Photosystem I fluorescence emission at room temperature. Moreover, the analysis of the excited state lifetime at F0 and FM indicates only a small wavelength dependence of Photosystem II trapping efficiency in vivo. PMID:24561096

  4. 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

  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 Laboratory Test Setup for in Situ Measurements of the Dielectric Properties of Catalyst Powder Samples under Reaction Conditions by Microwave Cavity Perturbation: Set up and Initial Tests

    PubMed Central

    Dietrich, Markus; Rauch, Dieter; Porch, Adrian; Moos, Ralf

    2014-01-01

    The catalytic behavior of zeolite catalysts for the ammonia-based selective catalytic reduction (SCR) of nitrogen oxides (NOX) depends strongly on the type of zeolite material. An essential precondition for SCR is a previous ammonia gas adsorption that occurs on acidic sites of the zeolite. In order to understand and develop SCR active materials, it is crucial to know the amount of sorbed ammonia under reaction conditions. To support classical temperature-programmed desorption (TPD) experiments, a correlation of the dielectric properties with the catalytic properties and the ammonia sorption under reaction conditions appears promising. In this work, a laboratory test setup, which enables direct measurements of the dielectric properties of catalytic powder samples under a defined gas atmosphere and temperature by microwave cavity perturbation, has been developed. Based on previous investigations and computational simulations, a resonator cavity and a heating system were designed, installed and characterized. The resonator cavity is designed to operate in its TM010 mode at 1.2 GHz. The first measurement of the ammonia loading of an H-ZSM-5 zeolite confirmed the operating performance of the test setup at constant temperatures of up to 300 °C. It showed how both real and imaginary parts of the relative complex permittivity are strongly correlated with the mass of stored ammonia. PMID:25211199

  7. 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 μm. 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

  8. Formation of 6-methyl-1,4-dihydronaphthalene in the reaction of the p-tolyl radical with 1,3-butadiene under single-collision conditions.

    PubMed

    Parker, Dorian S N; Dangi, Beni B; Kaiser, Ralf I; Jamal, Adeel; Ryazantsev, Mikhail; Morokuma, Keiji

    2014-12-26

    Crossed molecular beam reactions of p-tolyl (C7H7) plus 1,3-butadiene (C4H6), p-tolyl (C7H7) plus 1,3-butadiene-d6 (C4D6), and p-tolyl-d7 (C7D7) plus 1,3-butadiene (C4H6) were carried out under single-collision conditions at collision energies of about 55 kJ mol(-1). 6-Methyl-1,4-dihydronaphthalene was identified as the major reaction product formed at fractions of about 94% with the monocyclic isomer (trans-1-p-tolyl-1,3-butadiene) contributing only about 6%. The reaction is initiated by barrierless addition of the p-tolyl radical to the terminal carbon atom of the 1,3-butadiene via a van der Waals complex. The collision complex isomerizes via cyclization to a bicyclic intermediate, which then ejects a hydrogen atom from the bridging carbon to form 6-methyl-1,4-dihydronaphthalene through a tight exit transition state located about 27 kJ mol(-1) above the separated products. This is the dominant channel under the present experimental conditions. Alternatively, the collision complex can also undergo hydrogen ejection to form trans-1-p-tolyl-1,3-butadiene; this is a minor contributor to the present experiment. The de facto barrierless formation of a methyl-substituted aromatic hydrocarbons by dehydrogenation via a single event represents an important step in the formation of polycyclic aromatic hydrocarbons (PAHs) and their partially hydrogenated analogues in combustion flames and the interstellar medium. PMID:25407848

  9. A computer analysis of EEG-intersignal reactions during the development of motoric alimentary conditioned reflexes in dogs.

    PubMed

    Dumenko, V N; Kozlov, M K

    1993-01-01

    The background electrical activity of the neocortex in the interstimulus periods at the stage of generalization during the development of alimentary motor conditioned reflexes (CR) in dogs was the investigational object. It was characterized by the appearance of brief (0.1-0.3 sec) trains of high frequencies (HF), significantly exceeding the adjacent initial baseline in frequency and amplitude. The relative variance index which we had developed made it possible to distinguish this EEG phenomenon in the initial realizations of the background activity when they were inputted into a digital computer. It was not possible to evaluate the parameters of the HF chains by means of a spectral correlation analysis. Nonstandard techniques of computer analysis directed toward the decomposition of the EEG tracing into a system of oscillations and toward the obtaining of the corresponding amplitude-frequency distributions (maps) were developed by us for the purpose of accomplishing this objective. It was demonstrated that HF trains were localized in these maps in specific, quite compact regions. PMID:8487940

  10. Catalytic reduction of NO by CO over rhodium catalysts. 2. Effect of oxygen on the nature, population, and reactivity of surface species formed under reaction conditions

    SciTech Connect

    Kondarides, D.I.; Chafik, T.; Verykios, X.E.

    2000-04-01

    The effect of oxygen on the nature, population, and reactivity of surface species formed during reduction of NO by CO over Rh/TiO{sub 2} catalysts has been examined employing FTIR and transient MS techniques. It has been found that the activity of Rh is hindered by accumulation of surface oxygen originating from NO decomposition and gas-phase oxygen in the feed. Adsorbed CO and reduced TiO{sub 2{minus}x} species in the vicinity of Rh particles act as oxygen atom scavengers and, under fuel-rich conditions, remove atomic oxygen from the surface and restore the catalytic properties. Results of the present study provide additional evidence that production of N{sub 2} is related to dissociation of adsorbed Rh-NO{sup {minus}} while production of N{sub 2}O is related to the presence of Rh(NO){sub 2}. The presence of reduced RH{sup 0} sites is necessary for the formation of both reduction products. In the absence of oxygen in the feed, surface isocyanate species are also observed under reaction conditions. Their formation requires the presence of adjacent Rh{sup 0}-CO and reduced Rh{sup 0} sites. Although these species are favored under conditions in which NO conversion to reduction products is observed, there is no evidence that they are catalytically active species.

  11. Dissolution of weak acids under laminar flow and rotating disk hydrodynamic conditions: application of a comprehensive convection-diffusion-migration-reaction transport model.

    PubMed

    Neervannan, Seshadri; Southard, Marylee Z; Stella, Valentino J

    2012-09-01

    A steady-state mass transfer model that incorporates convection, diffusion, ionic migration, and ionization reaction processes was extended to describe the dissolution of weak acids under laminar flow and a rotating disk hydrodynamics. The model accurately predicted the experimental dissolution rates of benzoic acid, 2-naphthoic acid, and naproxen in unbuffered and monoprotic buffers within the physiological pH range for both hydrodynamic systems. Simulations at various flow rates indicated a cube root dependency of dissolution rate on the flow rate for a given bulk pH value for the laminar hydrodynamic system, as proposed earlier by Shah and Nelson (1975. J Pharm Sci 64(9):1518-1520) for neutral compounds. The model has limitations in its ability to accurately predict the dissolution of weak acids under certain conditions that imposed steep concentration gradients, such as high pH values, and for polyprotic buffer systems that caused the numerical solution to be unstable, suggesting that alternative numerical techniques may be required to obtain a stable numerical solution at all conditions. The model presents many advantages, most notably the ability to successfully predict the complex process under physiological conditions without simplifying assumptions, and therefore accurately representing the system in a comprehensive manner. PMID:22623113

  12. Co-formation of hydroperoxides and ultra-fine particles during the reactions of ozone with a complex VOC mixture under simulated indoor conditions

    NASA Astrophysics Data System (ADS)

    Fan, Zhihua; Weschler, Charles J.; Han, In-Kyu; Zhang, Junfeng (Jim)

    In this study we examined the co-formation of hydrogen peroxide and other hydroperoxides (collectively presented as H 2O 2*) as well as submicron particles, including ultra-fine particles (UFP), resulting from the reactions of ozone (O 3) with a complex mixture of volatile organic compounds (VOCs) under simulated indoor conditions. The VOC mixture contained 23 compounds, including two terpenes ( d-limonene and α-pinene), two unsaturated alkenes (1-decene and 1-octene), and 19 other saturated organic compounds. These compounds are commonly found in indoor air but their concentrations were higher than typical indoor levels. When O 3 was added to a 25-m 3 controlled environmental facility (CEF) containing the 23 VOC mixture, both H 2O 2* and submicron particles were formed. The 2-h average concentration of H 2O 2* was 1.89±0.30 ppb, and the average total particle number concentration was 46,000±12,000 particles cm -3. A small increase of UFP (0.02-0.1 μm) occurred 5 min after the O 3 addition (17 min after the VOC addition) and a sharp increase of UFP occurred 13 min after the O 3 addition, suggesting homogeneous nucleation. The delayed onset of this event might reflect the time required to achieve saturated concentrations of the condensable organics. When the 2 terpenes were removed from the O 3/23 VOCs mixture, no H 2O 2* or particles were formed, indicating that the reactions of O 3 with the two terpenes were the key processes contributing to the formation of H 2O 2* and submicron particles in the O 3/23 VOCs system. The present study confirmed the findings of a previous study carried out in a real-world office and generated new findings regarding co-formation of UFP. Through a comparative analysis of H 2O 2* yields under different reaction conditions, this study demonstrates that VOCs co-present with the terpenes and O 3 may play a role in producing H 2O 2*.

  13. 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

  14. 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.

  15. The impact of raw materials and baking conditions on Maillard reaction products, thiamine, folate, phytic acid and minerals in white bread.

    PubMed

    Helou, Cynthia; Gadonna-Widehem, Pascale; Robert, Nathalie; Branlard, Gérard; Thebault, Jacques; Librere, Sarah; Jacquot, Sylvain; Mardon, Julie; Piquet-Pissaloux, Agnès; Chapron, Sophie; Chatillon, Antoine; Niquet-Léridon, Céline; Tessier, Frédéric J

    2016-06-15

    The aim of this study was to develop a white bread with improved nutrient contents and reduced levels of potentially harmful Maillard reaction products such as N(ε)-carboxymethyllysine (CML) and 5-hydroxymethylfurfural (HMF). Assays were carried out through a full factorial experimental design allowing the simultaneous analysis of four factors at two levels: (1) wheat flour extraction rates (ash content: 0.60%-0.72%), (2) leavening agents (bakers' yeast - bakers' yeast and sourdough), (3) prebaking and (4) baking conditions (different sets of time and temperature). The baking conditions affected HMF and CML as well as certain mineral contents. A reduced baking temperature along with a prolonged heat treatment was found to be favourable for reducing both the CML (up to 20%) and HMF concentrations (up to 96%). The presence of sourdough decreased the formation of CML (up to 28%), and increased the apparent amounts of calcium (up to 8%) and manganese (up to 17.5%) probably through acidification of the dough. The extraction rate of flours as well as interactions between multiple factors also affected certain mineral content. However, compounds like folate, thiamine, copper, zinc, iron and phytic acid were not affected by any of the factors studied. PMID:26974195

  16. Free energy distribution and hydrothermal mineral precipitation in Hadean submarine alkaline vent systems: Importance of iron redox reactions under anoxic conditions

    NASA Astrophysics Data System (ADS)

    Shibuya, Takazo; Russell, Michael J.; Takai, Ken

    2016-02-01

    Thermodynamic calculations of mixing between hypothetical seawater and hydrothermal fluid in the Hadean deep ocean were carried out to predict saturation states of mineral precipitates and redox reactions that could occur in Hadean submarine alkaline hydrothermal systems associated with the serpentinization of ultramafic rocks. In the calculations, the seawater was assumed to be weakly acidic (pH = 5.5) and to include carbon dioxide, ferrous iron and silica, with or without nitrate, while the Hadean hydrothermal fluid was assumed to be highly alkaline (pH = 11) and to contain abundant molecular hydrogen, methane and bisulfide, based on the Archean geologic record, the modern low-temperature alkaline hydrothermal vent fluid (Lost City field), and experimental and theoretical considerations. The modeling indicates that potential mineral precipitates in the mixing zone (hydrothermal chimney structures) could consist mainly of iron sulfides but also of ferrous serpentine and brucite, siderite, and ferric iron-bearing minerals such as goethite, hematite and/or magnetite as minor phases. The precipitation of ferric iron-bearing minerals suggests that chemical iron oxidation would be made possible by pH shift even under anoxic condition. In the mixing zone, comprising an inorganic barrier precipitated at the interface of the two contrasting solutions, various redox reactions release free energy with the potential to drive endergonic reactions, assuming the involvement of coupling inorganic protoenzymes. Hydrogenotrophic methanogenesis and acetogenesis - long considered the most ancient forms of biological energy metabolisms - are able to achieve higher maximum energy yield (>0.5 kJ/kg hydrothermal fluid) than those in the modern serpentinization-associated seafloor hydrothermal systems (e.g., Kairei field). Furthermore, the recently proposed methanotrophic acetogenesis pathway was also thermodynamically investigated. It is known that methanotrophic acetogenesis would

  17. Solvent-free cross-dehydrogenative coupling reactions under high speed ball-milling conditions applied to the synthesis of functionalized tetrahydroisoquinolines.

    PubMed

    Su, Weike; Yu, Jingbo; Li, Zhenhua; Jiang, Zhijiang

    2011-11-01

    Solvent-free reaction using a high-speed ball milling technique has been first applied to cross-dehydrogenative coupling (CDC) reactions between tetrahydroisoquinolines and three types of pronucleophiles such as nitroalkanes, alkynes, and indoles. All coupling products were obtained in good yields at short reaction times (no more than 40 min). When alkynes and indoles were used as pronucleophile, the reactions can be catalyzed efficiently by recoverable copper balls without any additional metal catalyst. PMID:21961457

  18. Effect of coupled dissolution and redox reactions on Cr(VI)aq attenuation during transport in the sediments under hyperalkaline conditions.

    PubMed

    Qafoku, Nikolla P; Ainsworth, Calvin C; Szecsody, James E; Qafoku, Odeta S; Heald, Steve M

    2003-08-15

    Aluminum-rich, hyperalkaline (pH > 13.5) and saline high-level nuclear waste (HLW) fluids at elevated temperatures (>50 degrees C), that possibly contained as much as 0.41 mol L(-1) Cr(VI), accidentally leaked to the sediments at the Hanford Site, WA. These extreme conditions promote base-induced dissolution of soil minerals which may affect Cr(VI)aq mobility. Our objective was to investigate Cr(VI)aq transport in sediments leached with HLW simulants at 50 degrees C, under CO2 and O2 free conditions. Results demonstrated that Cr(VI)aq fate was closely related to dissolution, and Cr(VI)aq mass loss was negligible in the first pore volumes but increased significantly thereafter. Similar to dissolution, Cr(VI)aq attenuation increased with increasing fluid residence time and NaOH concentration but decreased with Al concentrations in the leaching solutions. Aqueous Cr(VI) removal rate half-lives varied from 1.2 to 230 h with the fastest at the highest base concentration, lowest Al concentration, greatest reaction time, and lowest Cr(VI) concentration in the leaching solution. The rate of Cr(VI) removal (normalized to 1 kg of solution) varied from 0.83 x 10(-9) (+/-0.44 x 10(-9)) to 9.16 x 10(-9) (+/-1.10 x 10(-9)) mol s(-1). The predominant mechanism responsible for removing Cr(VI) from the aqueous phase appears to be homogeneous Cr(VI) reduction to Cr(III) by Fe(II) released during mineral dissolution. Cr(VI)aq removal was time-limited probably because it was controlled by the rate of Fe(II) release into the soil solution upon mineral dissolution, which was also a time-limited process, and other processes that may act to lower Fe(II)aq activity. PMID:12953877

  19. 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

  20. 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.

  1. Combination of heterogeneous Fenton-like reaction and photocatalysis using Co-TiO₂nanocatalyst for activation of KHSO₅ with visible light irradiation at ambient conditions.

    PubMed

    Chen, Qingkong; Ji, Fangying; Guo, Qian; Fan, Jianping; Xu, Xuan

    2014-12-01

    A novel coupled system using Co-TiO₂was successfully designed which combined two different heterogeneous advanced oxidation processes, sulfate radical based Fenton-like reaction (SR-Fenton) and visible light photocatalysis (Vis-Photo), for degradation of organic contaminants. The synergistic effect of SR-Fenton and Vis-Photo was observed through comparative tests of 50mg/L Rhodamine B (RhB) degradation and TOC removal. The Rhodamine B degradation rate and TOC removal were 100% and 68.1% using the SR-Fenton/Vis-Photo combined process under ambient conditions, respectively. Moreover, based on XRD, XPS and UV-DRS characterization, it can be deduced that tricobalt tetroxide located on the surface of the catalyst is the SR-Fenton active site, and cobalt ion implanted in the TiO₂lattice is the reason for the visible light photocatalytic activity of Co-TiO₂. Finally, the effects of the calcination temperature and cobalt concentration on the synergistic performance were also investigated and a possible mechanism for the synergistic system was proposed. This coupled system exhibited excellent catalytic stability and reusability, and almost no dissolution of Co²⁺ was found. PMID:25499492

  2. 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.

  3. 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 ±2σ 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

  4. Storage conditions of blood samples and primer selection affect the yield of cDNA polymerase chain reaction products of hepatitis C virus.

    PubMed Central

    Cuypers, H T; Bresters, D; Winkel, I N; Reesink, H W; Weiner, A J; Houghton, M; van der Poel, C L; Lelie, P N

    1992-01-01

    We have noticed that suboptimal specimen processing and storage conditions may cause false-negative results in the detection of hepatitis C virus (HCV) RNA in plasma or serum. To establish the influence of specimen handling in a serological laboratory on the rate of detection of HCV RNA by the cDNA polymerase chain reaction (cDNA-PCR), we tested routine serum samples and fresh-frozen plasma samples from the same bleeding from confirmed anti-HCV-positive blood donors. When primers from the NS3/NS4 region were used, HCV RNA was detected in fresh-frozen plasma from 67% of the donors, whereas positive results were obtained with only 50% of the serum samples that had been subjected to routine serological procedures. Analysis of the same samples with primers from the highly conserved 5'-terminal region (5'-TR) revealed an HCV RNA detection rate of 92% for both the routine and the fresh-frozen samples. However, the yield of the amplification product in routine samples was strongly reduced compared with that in fresh-frozen plasma. Comparison of both primer sets for cDNA-PCR showed that the 5'-TR primer set was 10- to 100-fold more effective in detecting HCV RNA. We also analyzed the effect of storage of whole EDTA-blood and serum at room temperature and at 4 degrees C on the yield of the amplification product. A rapid decline in detectable HCV RNA of 3 to 4 log units was observed within 14 days when whole blood and serum were stored at room temperature. By contrast, no perceptible reduction in the cDNA-PCR signal was found in freshly prepared serum stored at 4 degrees C. Images PMID:1333489

  5. Fe-N-Doped Carbon Capsules with Outstanding Electrochemical Performance and Stability for the Oxygen Reduction Reaction in Both Acid and Alkaline Conditions.

    PubMed

    Ferrero, Guillermo A; Preuss, Kathrin; Marinovic, Adam; Jorge, Ana Belen; Mansor, Noramalina; Brett, Dan J L; Fuertes, Antonio B; Sevilla, Marta; Titirici, Maria-Magdalena

    2016-06-28

    High surface area N-doped mesoporous carbon capsules with iron traces exhibit outstanding electrocatalytic activity for the oxygen reduction reaction in both alkaline and acidic media. In alkaline conditions, they exhibit more positive onset (0.94 V vs RHE) and half-wave potentials (0.83 V vs RHE) than commercial Pt/C, while in acidic media the onset potential is comparable to that of commercial Pt/C with a peroxide yield lower than 10%. The Fe-N-doped carbon catalyst combines high catalytic activity with remarkable performance stability (3500 cycles between 0.6 and 1.0 V vs RHE), which stems from the fact that iron is coordinated to nitrogen. Additionally, the newly developed electrocatalyst is unaffected by the methanol crossover effect in both acid and basic media, contrary to commercial Pt/C. The excellent catalytic behavior of the Fe-N-doped carbon, even in the more relevant acid medium, is attributable to the combination of chemical functions (N-pyridinic, N-quaternary, and Fe-N coordination sites) and structural properties (large surface area, open mesoporous structure, and short diffusion paths), which guarantees a large number of highly active and fully accessible catalytic sites and rapid mass-transfer kinetics. Thus, this catalyst represents an important step forward toward replacing Pt catalysts with cheaper alternatives. In this regard, an alkaline anion exchange membrane fuel cell was assembled with Fe-N-doped mesoporous carbon capsules as the cathode catalyst to provide current and power densities matching those of a commercial Pt/C, which indicates the practical applicability of the Fe-N-carbon catalyst. PMID:27214056

  6. 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

  7. Structure-activity relationships for degradation reaction of 1-beta-o-acyl glucuronides: kinetic description and prediction of intrinsic electrophilic reactivity under physiological conditions.

    PubMed

    Baba, Akiko; Yoshioka, Tadao

    2009-01-01

    1-beta-O-Acyl glucuronides (betaGAs) are potentially reactive metabolites capable of binding to proteins, and they have been implicated in adverse drug reactions of the carboxylic acid drugs. To explore their electrophilic reactivity, we studied structure-activity relationships (SARs) to characterize the factors affecting the degradation rate constants (k values) of betaGAs and ultimately to predict k values of structurally diverse betaGAs. Twenty-seven betaGAs and four related compounds were synthesized, and their k values were determined under physiological conditions (pH 7.4 and 37 degrees C). 1-beta-O-Benzoyl glucuronide (BAGA) and glucopyranoside (BAG) showed almost the same k values, whereas their 1-alpha-O-benzoyl isomers degraded approximately 40-fold faster than BAGA and BAG. BAGA methyl ester showed almost the same rate constant as BAGA in the cleavage of their 1-beta-O-benzoyl linkages. A pH-log k profile obtained indicated kinetics catalyzed by both specific and general bases. The log k of betaGAs derived from m- and p-substituted benzoic acids correlated with Hammett's sigma constants. A similar correlation was observed with delta(COOH), (1)H NMR chemical shifts of the parent benzoic acids including ones with less sterically bulky o-substituents. Alternative descriptors of delta(CO) and delta((CO)OH), (13)C chemical shifts for ester carbonyl carbons of betaGAs and for carbonyl carbons of the parent benzoic acids, respectively, correlated well with the log k of all 16 betaGAs derived from benzoic acids including ones with bulkier o-substituents. Of the betaGA isomers derived from (2R)- and (2S)-alpha-methyl-4-biphenylylacetic acid, the (2R)-isomer degraded approximately 2-fold faster than the (2S)-isomer. The alpha-methyl group in the (2S)-isomer would encumber the intramolecular acyl migration. The log k of betaGAs derived from n-aralkyl carboxylic acids and of the (2R)-isomer correlated with their delta(COOH). However, the log k of betaGAs derived

  8. 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 (γ) of 10-4, and both γPAA and γH2O2 increase with increasing RH. The value of γPAA at 90 % RH is 5.4 ± 1.9 times that at 3 % RH, whereas γH2O2 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 γ 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.

  9. 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

  10. MOF catalysis of Fe(II)-to-Fe(III) reaction for an ultrafast and one-step generation of the Fe2O3@MOF composite and uranium(vi) reduction by iron(ii) under ambient conditions.

    PubMed

    Xiong, Yang Yang; Li, Jian Qiang; Yan, Chang Sheng; Gao, Heng Ya; Zhou, Jian Ping; Gong, Le Le; Luo, Ming Biao; Zhang, Le; Meng, Pan Pan; Luo, Feng

    2016-08-01

    Herein, we demonstrate that Zn-MOF-74 enables the ultrafast and one-step generation of the Fe2O3@MOF composite once Zn-MOF-74 contacts with FeSO4 solution. This unique reaction can be further applied in catalysis of U(vi) reduction by Fe(ii) under ambient conditions. The results provide a highly renovated strategy for U(vi) reduction by Fe(ii) just under ambient conditions, which completely subvert all established methods about U(vi) reduction by Fe(ii) in which O2- and CO2-free conditions are absolutely required. PMID:27380820

  11. Relative rate coefficient measurements of OH radical reactions with (Z)-2-hexen-1-ol and (E)-3-hexen-1-ol under simulated atmospheric conditions

    NASA Astrophysics Data System (ADS)

    Peirone, Silvina A.; Barrera, Javier A.; Taccone, Raúl A.; Cometto, Pablo M.; Lane, Silvia I.

    2014-03-01

    The relative rate technique was used to determine the rate coefficients of the reactions of OH radicals with (Z)-2-hexen-1-ol (k1), and (E)-3-hexen-1-ol (k2), at (296 ± 2) K and (750 ± 10) Torr of N2 or pure air. The reactions were investigated using a 200 L Teflon reaction chamber and a gas chromatograph coupled with flame-ionization detection. The following rate coefficients were derived, in units of cm3 mol-1 s-1: k1 = (1.1 ± 0.4) × 10-10 and k2 = (0.8 ± 0.1) × 10-10. This is the first experimental determination of k1 and k2. A comparison between the experimental rate coefficients (kexp) and the calculated rate coefficients using the structure-activity relationship (SAR) method (kSAR), for the reaction of different unsaturated alcohols with OH radicals is presented. The atmospheric lifetimes of the studied alcohols were estimated considering the rate coefficients of their reactions with OH and NO3 radicals. The radiative efficiencies (REs) were obtained from the infrared spectra of the two hexenols and the global warming potentials (GWPs) were then estimated. Atmospheric implications of the alcohols emission are briefly discussed.

  12. 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

  13. 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...

  14. 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:.

  15. Optimization of reaction conditions in selective oxidation of styrene over fine crystallite spinel-type CaFe{sub 2}O{sub 4} complex oxide catalyst

    SciTech Connect

    Pardeshi, Satish K.; Pawar, Ravindra Y.

    2010-05-15

    The CaFe{sub 2}O{sub 4} spinel-type catalyst was synthesized by citrate gel method and well characterized by thermogravimetric analysis, atomic absorption spectroscopy, Fourier-transform infrared spectroscopy, X-ray diffraction and transmission electron microscopy. The crystallization temperature of the spinel particle prepared by citrate gel method was 600 {sup o}C which was lower than that of ferrite prepared by other methods. CaFe{sub 2}O{sub 4} catalysts prepared by citrate gel method show better activity for styrene oxidation in the presence of dilute H{sub 2}O{sub 2} (30%) as an oxidizing agent. In this reaction the oxidative cleavage of carbon-carbon double bond of styrene takes place selectively with 38 {+-} 2 mol% conversion. The major product of the reaction is benzaldehyde up to 91 {+-} 2 mol% and minor product phenyl acetaldehyde up to 9 {+-} 2 mol%, respectively. The products obtained in the styrene oxidation reaction were analyzed by gas chromatography and mass spectroscopy. The influence of the catalyst, reaction time, temperature, amount of catalyst, styrene/H{sub 2}O{sub 2} molar ratio and solvents on the conversion and product distribution were studied.

  16. Catalyst-free reactions under solvent-free conditions: microwave-assisted synthesis of heterocyclic hydrazones below the melting points of neat reactants.

    PubMed

    Jeselnik, M; Varma, R S; Polanc, S; Kocevar, M

    2001-09-21

    The reaction of neat 5- or 8-oxobenzopyran-2(1H)-ones, 1-3, with a variety of aromatic and heteroaromatic hydrazines, 4, is remarkably accelerated upon irradiation in a household microwave oven in the absence of any catalyst, solid support or solvent thus providing an environmentally friendly route to several heterocyclic hydrazones. PMID:12240280

  17. Investigation of the relationship between CO2 reservoir rock property change and the surface roughness change originating from the supercritical CO2-sandstone-groundwater geochemical reaction at CO2 sequestration condition

    NASA Astrophysics Data System (ADS)

    Lee, Minhee; Wang, Sookyun; Kim, Seyoon; Park, Jinyoung

    2015-04-01

    Lab scale experiments were performed to investigate the property changes of sandstone slabs and cores, resulting from the scCO2-rock-groundwater reaction for 180 days under CO2 sequestration conditions (100 bar and 50 °C). The geochemical reactions, including the surface roughness change of minerals in the slab, resulted from the dissolution and the secondary mineral precipitation for the sandstone reservoir of the Gyeongsang basin, Korea were reproduced in laboratory scale experiments and the relationship between the geochemical reaction and the physical rock property change was derived, for the consideration of successful subsurface CO2 sequestration. The use of the surface roughness value (SRrms) change rate and the physical property change rate to quantify scCO2-rock-groundwater reaction is the novel approach on the study area for CO2 sequestration in the subsurface. From the results of SPM (Scanning Probe Microscope) analyses, the SRrms for each sandstone slab was calculated at different reaction time. The average SRrms increased more than 3.5 times during early 90 days reaction and it continued to be steady after 90 days, suggesting that the surface weathering process of sandstone occurred in the early reaction time after CO2 injection into the subsurface reservoir. The average porosity of sandstone cores increased by 8.8 % and the average density decreased by 0.5 % during 90 days reaction and these values slightly changed after 90 days. The average P and S wave velocities of sandstone cores also decreased by 10 % during 90 days reaction. The trend of physical rock property change during the geochemical reaction showed in a logarithmic manner and it was also correlated to the logarithmic increase in SRrms, suggesting that the physical property change of reservoir rocks originated from scCO2 injection directly comes from the geochemical reaction process. Results suggested that the long-term estimation of the physical property change for reservoir rocks in CO2

  18. Reaction mechanism and optimal conditions for preparation of high-quality vanadium oxide films by organic sol-gel for optoelectronic applications

    NASA Astrophysics Data System (ADS)

    Sun, Minghui; Wen, Yuejiang; Xu, Xiangdong; Wang, Meng; He, Qiong; Jiang, Yadong; Dai, Zelin; Gu, Yu; Chen, Zhegeng

    2016-03-01

    Although vanadium oxides (VO x ) are important functional materials for academic research and industrial applications, the reaction mechanism of VO x prepared by organic sol-gel remains unclear. In order to investigate this mechanism, VO x organic sols were reacted at different temperatures, by which various VO x thin films were prepared. The products were systematically characterized by infrared spectroscopy, Raman spectroscopy, UV-vis spectroscopy, thermogravimetric analysis, scanning electron microscopy, x-ray diffraction, and a high resistance meter. Results reveal that vanadium alkoxides are created through an alcoholysis reaction of V2O5 powder and isobutyl alcohol, and then a condensation reaction of the vanadium alkoxides leads to the formation of VO x networks. The as-prepared sols are strongly temperature-dependent, causing different chemical structures and physical properties for the resulting VO x films. Particularly, a moderate temperature of 110 °C prompts both alcoholysis and condensation reactions, and thus the VO x films that are produced by the sol reacted at 110 °C possess a low resistivity of 23 Ω cm, a high temperature coefficient resistance (TCR) of  -3.2% K-1, and a low average transmittance of 54% in 580-1100 nm, compared with those prepared by the sols reacted at lower or higher temperatures. Therefore, 110 °C is a desirable sol temperature for producing VO x films serving as high-quality bolometric materials for uncooled infrared detectors. This work discloses not only the reaction mechanism of VO x films prepared by organic sol-gel, but also the route to yield desirable VO x films for optoelectronic applications.

  19. 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.

  20. Mn(2+)-mediated homogeneous Fenton-like reaction of Fe(III)-NTA complex for efficient degradation of organic contaminants under neutral conditions.

    PubMed

    Li, Yifan; Sun, Jianhui; Sun, Sheng-Peng

    2016-08-01

    In this work, we report a novel Mn(2+)-mediated Fenton-like process based on Fe(III)-NTA complex that is super-efficient at circumneutral pH range. Kinetics experiments showed that the presence of Mn(2+) significantly enhanced the effectiveness of Fe(III)-NTA complex catalyzed Fenton-like reaction. The degradation rate constant of crotamiton (CRMT), a model compound, by the Fe(III)- NTA_Mn(2+) Fenton-like process was at least 1.6 orders of magnitude larger than that in the absence of Mn(2+). Other metal ions such as Ca(2+), Mg(2+), Co(2+) and Cu(2+) had no impacts or little inhibitory effect on the Fe(III)-NTA complex catalyzed Fenton-like reaction. The generation of hydroxyl radical (HO) and superoxide radical anion (O2(-)) in the Fe(III)-NTA_Mn(2+) Fenton-like process were suggested by radicals scavenging experiments. The degradation efficiency of CRMT was inhibited significantly (approximately 92%) by the addition of HO scavenger 2-propanol, while the addition of O2(-) scavenger chloroform resulted in 68% inhibition. Moreover, the results showed that other chelating agents such as EDTA- and s,s-EDDS-Fe(III) catalyzed Fenton-like reactions were also enhanced significantly by the presence of Mn(2+). The mechanism involves an enhanced generation of O2(-) from the reactions of Mn(2+)-chelates with H2O2, indirectly promoting the generation of HO by accelerating the reduction rate of Fe(III)-chelates to Fe(II)- chelates. PMID:27070388

  1. Optimization of reaction conditions towards multiple types of framework isomers and periodic-increased porosity: luminescence properties and selective CO2 adsorption over N2.

    PubMed

    Wu, Xiao-Liu; Luo, Feng; Sun, Gong-Ming; Zheng, An-Min; Zhang, Jian; Luo, Ming-Biao; Xu, Wen-Yuan; Zhu, Yan; Zhang, Xiao-Min; Huang, Shu-Yun

    2013-10-21

    Three new metal-organic frameworks (MOFs) were prepared by solvo(hydro)thermolysis and further characterized as framework isomers. The structural transformation from non-porous to porous MOFs and the purity of these products can be modulated by controlling the reaction temperature. The periodic-increased porosity observed was further confirmed by CO2 adsorption isotherms. Owing to the presence of acylamide groups in the pore walls and the flexible nature of the skeleton of these MOFs, highly selective CO2 adsorption over N2 was observed, as well as structure-dependent periodic varieties in luminescence properties. PMID:24038959

  2. Synthesis of new pentacyclo[5.4.0.0(2,6).0(3,10).0(5,9)]undecane-8,11-dione (PCU) cyanosilylated derivatives using sulphated zirconia and hydrotalcite as catalysts in microwave-assisted reactions under solvent free conditions.

    PubMed

    Guerra-Navarro, Nahí Adriana; Palacios-Grijalva, Laura Nadxieli; Angeles-Beltrán, Deyanira; Negrón-Silva, Guillermo E; Lomas-Romero, Leticia; González-Zamora, Eduardo; Gaviño-Ramírez, Rubén; Navarrete-Bolaños, Juan

    2011-01-01

    A comparison was made of the effectiveness of the functionalization reactions of pentacyclo[5.4.0.0(2,6).0(3,10).0(5,9)]undecane-8,11-dione (PCU) using sulphated zirconia in protection-deprotection reactions and Mg/Al hydrotalcite in a cyanosilylation reaction, under classical thermal conditions and imposing microwave radiation; improved yields and reaction times were considered. PMID:21818059

  3. 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...

  4. Comparison of D1´- and D1-containing PS II reaction centre complexes under different environmental conditions in Synechocystis sp. PCC 6803.

    PubMed

    Crawford, Tim S; Hanning, Kyrin R; Chua, Jocelyn P S; Eaton-Rye, Julian J; Summerfield, Tina C

    2016-08-01

    In oxygenic photosynthesis, the D1 protein of Photosystem II is the primary target of photodamage and environmental stress can accelerate this process. The cyanobacterial response to stress includes transcriptional regulation of genes encoding D1, including low-oxygen-induction of psbA1 encoding the D1´ protein in Synechocystis sp. PCC 6803. The psbA1 gene is also transiently up-regulated in high light, and its deletion has been reported to increase ammonium-induced photoinhibition. Therefore we investigated the role of D1´-containing PS II centres under different environmental conditions. A strain containing only D1´-PS II centres under aerobic conditions exhibited increased sensitivity to ammonium chloride and high light compared to a D1-containing strain. Additionally a D1´-PS II strain was outperformed by a D1-PS II strain under normal conditions; however, a strain containing low-oxygen-induced D1´-PS II centres was more resilient under high light than an equivalent D1 strain. These D1´-containing centres had chlorophyll a fluorescence characteristics indicative of altered forward electron transport and back charge recombination with the donor side of PS II. Our results indicate D1´-PS II centres are important in the reconfiguration of thylakoid electron transport in response to high light and low oxygen. PMID:26991994

  5. 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.

  6. Role of anions and reaction conditions in the preparation of uranium(VI), neptunium(VI), and plutonium(VI) borates.

    PubMed

    Wang, Shuao; Villa, Eric M; Diwu, Juan; Alekseev, Evgeny V; Depmeier, Wulf; Albrecht-Schmitt, Thomas E

    2011-03-21

    U(VI), Np(VI), and Pu(VI) borates with the formula AnO(2)[B(8)O(11)(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, AnO(2)(2+), surrounded by BO(3) triangles and BO(4) tetrahedra to create an AnO(8) 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 BO(3) triangles and BO(4) 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). PMID:21291194

  7. 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).

  8. Investigations on the Reaction of C3 and C6 α-Dicarbonyl Compounds with Hydroxytyrosol and Related Compounds under Competitive Conditions.

    PubMed

    Navarro, Marta; Atzenbeck, Lisa; Pischetsrieder, Monika; Morales, Francisco J

    2016-08-17

    α-Dicarbonyl compounds are intermediates in reactions that lead to the formation of potentially harmful advanced glycation end-products. Carbonyl-trapping capacities of antiglycative substances have been traditionally limited to C2 and C3 α-dicarbonyl structures. Glyoxal (GO)-, methylglyoxal (MGO)-, 3-deoxyglucosone (3-DG)-, 3-deoxygalactosone (3-DGal)-, 3,4-dideoxyglucoson-3-ene-, and glucosone-trapping capacities of hydroxytyrosol (HT), hydroxytyrosol acetate (HTA), and 3,4-dihydroxyphenylacetic acid (DOPAC) in simple (phenolic/dicarbonyl) and competitive model systems (phenolic/dicarbonyl1/dicarbonyl2) were investigated. HT and HTA were more effective for MGO than 3-DG and 3-DGal. Furthermore, DOPAC exerted higher trapping capacity than HT and HTA for C3 and C6 α-dicarbonyl compounds. In the competitive systems, HT-related substances did not show preference for trapping 3-DG or 3-DGal and behaved as in the simple systems. In the presence of MGO, however, HT-related substances were more effective for trapping MGO than C6 structures. The results demonstrate the C6 α-dicarbonyl-trapping capacities of HT, HTA, and DOPAC, with DOPAC exerting the highest activity. PMID:27476321

  9. Rate Constants for the Reactions of OH with CO, NO and NO2, and of HO2 with NO2 in the Presence of Water Vapour at Lower-Tropospheric Conditions

    NASA Astrophysics Data System (ADS)

    Rolletter, Michael; Fuchs, Hendrik; Novelli, Anna; Ehlers, Christian; Hofzumahaus, Andreas

    2016-04-01

    Recent studies have shown that the chemistry of gaseous nitrous acid (HONO) in the lower troposphere is not fully understood. Aside from heterogenous reactions, the daytime HONO formation in the gas-phase is not well understood (Li et al., Science, 2014). For a better understanding of HONO in the gas-phase, we have reinvestigated the reaction rate constants of important tropospheric reactions of the HOx radical family (OH and HO2) with nitrogen oxides at realistic conditions of the lower troposphere (at ambient temperature/pressure and in humid air). In this study we apply a direct pump and probe technique with high accuracy, using small radical concentrations to avoid secondary chemistry. Pulsed laser photolysis/laser-induced fluorescence (LP/LIF) was used to investigate the reaction rate constants of OH with CO, NO, NO2, and HO2 with NO2 in synthetic air at different water vapor concentrations (up to 5 x 1017 molecules cm‑3). Photolysis of ozone in the presence of gaseous water was the source of OH. The reactions took place in a flow-tube at room temperature and atmospheric pressure. The chemical decay of the radicals was monitored by laser-induced fluorescence detection in a low-pressure cell, which sampled air continuously from the end of the flow-tube. Knowing the reactant concentrations subsequently allowed to calculate the bimolecular reaction rate constants at 1 atm from the pseudo-first-order decays. In order to observe HO2 reactions, OH was converted into HO2 with an excess of CO in the flow-tube. The newly measured rate constants for OH with CO, NO and NO2 agree very well with current recommendations by NASA/JPL and IUPAC and have an improved accuracy (uncertainty < 5%). These rate coefficients are independent of the presence of water vapour. The measured rate constant of HO2 with NO2 was found to depend significantly on the water-vapour concentration (probably due to formation of HO2*H2O complexes) and to exceed current recommendations by NASA/JPL and

  10. Photoswitching Behavior of a Cyclohexene-Bridged versus a Cyclopentene-Bridged Dithienylethene System.

    PubMed

    Steenbock, Torben; Escribano, Alejandra; Heck, Jürgen; Herrmann, Carmen

    2015-05-18

    Photoswitching is an intriguing way of incorporating functionality into molecules or their subunits. Dithienylethene switches are particularly promising, but have so far mostly been studied with five-membered ring (cyclopentenyl) backbones. We aim at comparing the switching properties of backbones with five and six carbon atoms in the ring. A major advantage is that cyclohexenyl rings offer new options for chiral functionalization. A slight change in the reaction conditions of a McMurry ring closure reaction leads to the formation of dithienyl derivatives with a cyclohexene backbone in reasonable yield. Density functional theory calculations were carried out, demonstrating the similarity of both compounds. Experimental results confirm the theoretical outcomes. PMID:25704168