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Sample records for c-c bond-forming reaction

  1. Helical Oligourea Foldamers as Powerful Hydrogen Bonding Catalysts for Enantioselective C-C Bond-Forming Reactions.

    Science.gov (United States)

    Bécart, Diane; Diemer, Vincent; Salaün, Arnaud; Oiarbide, Mikel; Nelli, Yella Reddy; Kauffmann, Brice; Fischer, Lucile; Palomo, Claudio; Guichard, Gilles

    2017-09-13

    Substantial progress has been made toward the development of metal-free catalysts of enantioselective transformations, yet the discovery of organic catalysts effective at low catalyst loadings remains a major challenge. Here we report a novel synergistic catalyst combination system consisting of a peptide-inspired chiral helical (thio)urea oligomer and a simple tertiary amine that is able to promote the Michael reaction between enolizable carbonyl compounds and nitroolefins with excellent enantioselectivities at exceptionally low (1/10 000) chiral catalyst/substrate molar ratios. In addition to high selectivity, which correlates strongly with helix folding, the system we report here is also highly amenable to optimization, as each of its components can be fine-tuned separately to increase reaction rates and/or selectivities. The predictability of the foldamer secondary structure coupled to the high level of control over the primary sequence results in a system with significant potential for future catalyst design.

  2. Double-Diels-Alder Approach to Maoecrystal V. Unexpected C-C Bond-Forming Fragmentations of the [2.2.2]-Bicyclic Core.

    Science.gov (United States)

    Smith, Brandon R; Njardarson, Jon T

    2017-10-06

    Synthetic studies toward maoecrystal V are reported. An oxidative dearomatization/Diels-Alder cascade to assemble the natural product carbocyclic core in one step is proposed. A facile electrocyclization is shown to suppress the intramolecular allene Diels-Alder pathway. This obstacle is alleviated via a stepwise approach with an allene equivalent to access the key cyclopentadiene-fused [2.2.2]-bicyclic core. Upon treatment with Lewis acid, the proposed intramolecular hetero-Diels-Alder reaction is cleanly and unexpectedly diverted either via C-C bond-forming fragmentation to the spiro-indene product (when R = OMe) or via elimination (when R = H).

  3. An iron-catalysed C-C bond-forming spirocyclization cascade providing sustainable access to new 3D heterocyclic frameworks

    Science.gov (United States)

    Adams, Kirsty; Ball, Anthony K.; Birkett, James; Brown, Lee; Chappell, Ben; Gill, Duncan M.; Lo, P. K. Tony; Patmore, Nathan J.; Rice, Craig. R.; Ryan, James; Raubo, Piotr; Sweeney, Joseph B.

    2017-04-01

    Heterocyclic architectures offer powerful creative possibilities to a range of chemistry end-users. This is particularly true of heterocycles containing a high proportion of sp3-carbon atoms, which confer precise spatial definition upon chemical probes, drug substances, chiral monomers and the like. Nonetheless, simple catalytic routes to new heterocyclic cores are infrequently reported, and methods making use of biomass-accessible starting materials are also rare. Here, we demonstrate a new method allowing rapid entry to spirocyclic bis-heterocycles, in which inexpensive iron(III) catalysts mediate a highly stereoselective C-C bond-forming cyclization cascade reaction using (2-halo)aryl ethers and amines constructed using feedstock chemicals readily available from plant sources. Fe(acac)3 mediates the deiodinative cyclization of (2-halo)aryloxy furfuranyl ethers, followed by capture of the intermediate metal species by Grignard reagents, to deliver spirocycles containing two asymmetric centres. The reactions offer potential entry to key structural motifs present in bioactive natural products.

  4. An iron-catalysed C-C bond-forming spirocyclization cascade providing sustainable access to new 3D heterocyclic frameworks.

    Science.gov (United States)

    Adams, Kirsty; Ball, Anthony K; Birkett, James; Brown, Lee; Chappell, Ben; Gill, Duncan M; Lo, P K Tony; Patmore, Nathan J; Rice, Craig R; Ryan, James; Raubo, Piotr; Sweeney, Joseph B

    2017-04-01

    Heterocyclic architectures offer powerful creative possibilities to a range of chemistry end-users. This is particularly true of heterocycles containing a high proportion of sp 3 -carbon atoms, which confer precise spatial definition upon chemical probes, drug substances, chiral monomers and the like. Nonetheless, simple catalytic routes to new heterocyclic cores are infrequently reported, and methods making use of biomass-accessible starting materials are also rare. Here, we demonstrate a new method allowing rapid entry to spirocyclic bis-heterocycles, in which inexpensive iron(III) catalysts mediate a highly stereoselective C-C bond-forming cyclization cascade reaction using (2-halo)aryl ethers and amines constructed using feedstock chemicals readily available from plant sources. Fe(acac) 3 mediates the deiodinative cyclization of (2-halo)aryloxy furfuranyl ethers, followed by capture of the intermediate metal species by Grignard reagents, to deliver spirocycles containing two asymmetric centres. The reactions offer potential entry to key structural motifs present in bioactive natural products.

  5. Lewis-acid catalysis of carbon carbon bond forming reactions in water

    NARCIS (Netherlands)

    Engberts, JBFN; Feringa, BL; Keller, E; Otto, S

    1996-01-01

    In this article, we review the recent progress that has been made in the field of Lewis-acid catalysis of carbon carbon-bond-forming reactions in aqueous solution. Since water hampers the hard hard interactions between the catalyst and the reactant, it often complicates catalysis. However, once

  6. Phosphinocyclodextrins as confining units for catalytic metal centres. Applications to carbon–carbon bond forming reactions

    Directory of Open Access Journals (Sweden)

    Matthieu Jouffroy

    2014-10-01

    Full Text Available The capacity of two cavity-shaped ligands, HUGPHOS-1 and HUGPHOS-2, to generate exclusively singly phosphorus-ligated complexes, in which the cyclodextrin cavity tightly wraps around the metal centre, was explored with a number of late transition metal cations. Both cyclodextrin-derived ligands were assessed in palladium-catalysed Mizoroki–Heck coupling reactions between aryl bromides and styrene on one hand, and the rhodium-catalysed asymmetric hydroformylation of styrene on the other hand. The inability of both chiral ligands to form standard bis(phosphine complexes under catalytic conditions was established by high-pressure NMR studies and shown to have a deep impact on the two carbon–carbon bond forming reactions both in terms of activity and selectivity. For example, when used as ligands in the rhodium-catalysed hydroformylation of styrene, they lead to both high isoselectivity and high enantioselectivity. In the study dealing with the Mizoroki–Heck reactions, comparative tests were carried out with WIDEPHOS, a diphosphine analogue of HUGPHOS-2.

  7. C1 polymerisation and related C-C bond forming ‘carbene insertion’ reactions

    NARCIS (Netherlands)

    Jellema, E.; Jongerius, A.L.; Reek, J.N.H.; de Bruin, B.

    2010-01-01

    In this critical review we summarise the currently available ‘C1 polymerisation’ techniques as valuable alternatives for ‘C2 polymerisation’ in the preparation of saturated main-chain carbon-based polymers. C1 polymerisation involves the growth of polymers from monomers delivering only one

  8. Carbon dioxide as a carbon source in organic transformation: carbon-carbon bond forming reactions by transition-metal catalysts.

    OpenAIRE

    Tsuji, Yasushi; Fujihara, Tetsuaki

    2012-01-01

    Recent carbon-carbon bond forming reactions of carbon dioxide with alkenes, alkynes, dienes, aryl zinc compounds, aryl boronic esters, aryl halides, and arenes having acidic C-H bonds are reviewed in which transition-metal catalysts play an important role.

  9. Method for producing bio-fuel that integrates heat from carbon-carbon bond-forming reactions to drive biomass gasification reactions

    Science.gov (United States)

    Cortright, Randy D [Madison, WI; Dumesic, James A [Verona, WI

    2012-04-10

    A low-temperature catalytic process for converting biomass (preferably glycerol recovered from the fabrication of bio-diesel) to synthesis gas (i.e., H.sub.2/CO gas mixture) in an endothermic gasification reaction is described. The synthesis gas is used in exothermic carbon-carbon bond-forming reactions, such as Fischer-Tropsch, methanol, or dimethylether syntheses. The heat from the exothermic carbon-carbon bond-forming reaction is integrated with the endothermic gasification reaction, thus providing an energy-efficient route for producing fuels and chemicals from renewable biomass resources.

  10. Method for producing bio-fuel that integrates heat from carbon-carbon bond-forming reactions to drive biomass gasification reactions

    Science.gov (United States)

    Cortright, Randy D [Madison, WI; Dumesic, James A [Verona, WI

    2011-01-18

    A low-temperature catalytic process for converting biomass (preferably glycerol recovered from the fabrication of bio-diesel) to synthesis gas (i.e., H.sub.2/CO gas mixture) in an endothermic gasification reaction is described. The synthesis gas is used in exothermic carbon-carbon bond-forming reactions, such as Fischer-Tropsch, methanol, or dimethylether syntheses. The heat from the exothermic carbon-carbon bond-forming reaction is integrated with the endothermic gasification reaction, thus providing an energy-efficient route for producing fuels and chemicals from renewable biomass resources.

  11. Recent developments in enzyme promiscuity for carbon-carbon bond-forming reactions

    NARCIS (Netherlands)

    Miao, Yufeng; Rahimi, Mehran; Geertsema, Edzard M; Poelarends, Gerrit J

    Numerous enzymes have been found to catalyze additional and completely different types of reactions relative to the natural activity they evolved for. This phenomenon, called catalytic promiscuity, has proven to be a fruitful guide for the development of novel biocatalysts for organic synthesis

  12. Palladium N-Heterocyclic Carbene Complexes: Synthesis from Benzimidazolium Salts and Catalytic Activity in Carbon-carbon Bond-forming Reactions.

    Science.gov (United States)

    Sahin, Ziya; Akkoς, Senem; İlhan, İlhan Özer; Kayser, Veysel

    2017-07-30

    Detailed and generalized protocols are presented for the synthesis and subsequent purification of four palladium N-heterocyclic carbene complexes from benzimidazolium salts. Detailed and generalized protocols are also presented for testing the catalytic activity of such complexes in arylation and Suzuki-Miyaura cross-coupling reactions. Representative results are shown for the catalytic activity of the four complexes in arylation and Suzuki-Miyaura type reactions. For each of the reactions investigated, at least one of the four complexes successfully catalyzed the reaction, qualifying them as promising candidates for catalysis of many carbon-carbon bond-forming reactions. The protocols presented are general enough to be adapted for the synthesis, purification and catalytic activity testing of new palladium N-heterocyclic carbene complexes.

  13. Universal Bronsted-Evans-Polanyi Relations for C-C, C-O, C-N, N-O, N-N, and O-O Dissociation Reactions

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Shengguang

    2010-10-27

    It is shown that for all the essential bond forming and bond breaking reactions on metal surfaces, the reactivity of the metal surface correlates linearly with the reaction energy in a single universal relation. Such correlations provide an easy way of establishing trends in reactivity among the different transition metals.

  14. THE USE OF ISOTOPE CROSSOVER EXPERIMENTS IN INVESTIGATING CARBON-CARBON BOND FORMING REACTIONS OF BINUCLEAR DIALKYL COBALT COMPLEXES

    Energy Technology Data Exchange (ETDEWEB)

    Bergman, Robert G.

    1980-01-01

    Our present understanding of the mechanisms of organometallic reactions stems almost completely from investigation of complexes containing only one metal. Recently interest has been increasing in the synthesis, structure elucidation and reaction mechanisms of polynuclear clusters, complexes containing more than one metal. This attention derives partially from the possibility that polynuclear catalysts and reagents might be designed in such a way that the metals could interact, generating cooperative systems which might be much more selective than their mononuclear analogs. Another stimulant to this work has been the relationship of cluster complexes to larger multi-metal systems, such as heterogeneous catalysts. Many polynuclear clusters have been prepared and characterized, and some of these have been found to function as unique catalysts or catalyst precursors. However, very little is yet known about how chemical transformations take place at multinuclear reaction centers. Given this paucity of information, they decided a few years ago to initiate mechanistic study of simple cluster systems containing two metal centers, in which each of the metals has a {sigma}-bound organic ligand attached to it. They also choose to focus on reactions of these complexes in which new carbon-carbon or carbon-hydrogen bonds are formed. This Account describes the work on such a system: a binuclear alkyl cobalt complex capable of transferring both alkyl groups to a molecule of carbon monoxide. In this work they have adopted as one of our highest priorities the determination of whether the cluster 'holds together' during its reactions, a question that is in our opinion too often ignored in such studies. They have found that isotope crossover experiments provide a powerful tool for investigating this structural integrity questions, and in this Account they outline a number of examples in which such crossover experiments have provided important, and occasionally surprising

  15. Carbon-carbon bond-forming reactions of α-thioaryl carbonyl compounds for the synthesis of complex heterocyclic molecules.

    Science.gov (United States)

    Biggs-Houck, James E; Davis, Rebecca L; Wei, Jingqiang; Mercado, Brandon Q; Olmstead, Marilyn M; Tantillo, Dean J; Shaw, Jared T

    2012-01-06

    Strategies for the formation of carbon-carbon bonds from the α-thioaryl carbonyl products of substituted lactams are described. Although direct functionalization is possible, a two step process of oxidation and magnesium-sulfoxide exchange has proven optimal. The oxidation step results in the formation of two diastereomers that exhibit markedly different levels of stability toward elimination, which is rationalized on the basis of quantum mechanical calculations and X-ray crystallography. Treatment of the sulfoxide with i-PrMgCl results in the formation of a magnesium enolate that will undergo an intramolecular Michael addition reaction to form two new stereogenic centers. The relationship between the substitution patterns of the sulfoxide substrate and the efficiency of the magnesium exchange reaction are also described.

  16. C-C Coupling Reactions between Benzofurazan Derivatives and 1,3-Diaminobenzenes

    Directory of Open Access Journals (Sweden)

    Gabriele Micheletti

    2017-04-01

    Full Text Available Aromatic substitution reactions between 1,3-diaminobenzene and chloronitrobenzofurazan derivatives have never been reported so far. The aim of the current study was to synthesize novel electron-donor and -acceptor architectures of interest in applied fields and to provide new insights on the nucleophilic behavior of 1,3-diaminobenzenes. The reaction of 1,3-dipiperidinyl-, 1,3-dimorpholinyl-, 1,3-dipyrrolidinyl-, or 1,3-dimethylamino-benzene with 7-chloro-4,6-dinitrobenzofuroxan or with a series of chloro-nitrobenzofurazans has been carried out in mild conditions. The partners reactivity has been investigated by monitoring the reaction course through 1H-NMR spectroscopy. The reaction occurred in a regioselective way, providing in good yields the novel C-C coupling compounds. Indications on the reactivity behavior for the studied nucleophiles have been relieved.

  17. Efficient C-O and C-N bond forming cross-coupling reactions catalyzed by core-shell structured Cu/Cu2O nanowires

    KAUST Repository

    Elshewy, Ahmed M.

    2013-12-01

    Oxygen and Nitrogen containing compounds are of utmost importance due to their interesting and diverse biological activities. The construction of the C-O and C–N bonds is of significance as it opens avenues for the introduction of ether and amine linkages in organic molecules. Despite significant advancements in this field, the construction of C-O and C–N bonds is still a major challenge for organic chemists, due to the involvement of harsh reaction conditions or the use of expensive catalysts or ligands in many cases. Thus, it is a challenge to develop alternative, milder, cheaper and more reproducible methodologies for the construction of these types of bonds. Herein, we introduce a new efficient ligand free catalytic system for C-O and C-N bond formation reactions.

  18. Novel tridentate diamino organomanganese(II) complexes as homogeneous catalysts in manganese(II)/copper(I) catalyzed carbon-carbon bond forming reactions

    NARCIS (Netherlands)

    Koten, G. van; Donkervoort, J.G.; Vicario, J.L.; Jastrzebski, J.T.B.H.; Gossage, R.A.; Cahiez, G.

    1998-01-01

    The new, paramagnetic arylmanganese(II) complex Li[MnCl2(NCN)] (2, NCN [C6H3(CH2NMe2)2-2,6]−) has been obtained in high yield from the reaction of MnCl2 and [Li(NCN)]2 in a 2:1 molar ratio. In THF solution, 2 is likely an ionic species [Li(THF)n] [MnCl2(NCN)] (molecular weight determination and

  19. A two-dimensional conjugated aromatic polymer via C-C coupling reaction

    Science.gov (United States)

    Liu, Wei; Luo, Xin; Bao, Yang; Liu, Yan Peng; Ning, Guo-Hong; Abdelwahab, Ibrahim; Li, Linjun; Nai, Chang Tai; Hu, Zhi Gang; Zhao, Dan; Liu, Bin; Quek, Su Ying; Loh, Kian Ping

    2017-06-01

    The fabrication of crystalline 2D conjugated polymers with well-defined repeating units and in-built porosity presents a significant challenge to synthetic chemists. Yet they present an appealing target because of their desirable physical and electronic properties. Here we report the preparation of a 2D conjugated aromatic polymer synthesized via C-C coupling reactions between tetrabromopolyaromatic monomers. Pre-arranged monomers in the bulk crystal undergo C-C coupling driven by endogenous solid-state polymerization to produce a crystalline polymer, which can be mechanically exfoliated into micrometre-sized lamellar sheets with a thickness of 1 nm. Isothermal gas-sorption measurements of the bulk material reveal a dominant pore size of ~0.6 nm, which indicates uniform open channels from the eclipsed stacking of the sheets. When employed as an organic anode in an ambient-temperature sodium cell, the material allows a fast charge/discharge of sodium ions, with impressive reversible capacity, rate capability and stability metrics.

  20. Chiral BINOL-derived phosphoric acids: privileged Brønsted acid organocatalysts for C-C bond formation reactions.

    Science.gov (United States)

    Zamfir, Alexandru; Schenker, Sebastian; Freund, Matthias; Tsogoeva, Svetlana B

    2010-12-07

    BINOL-derived phosphoric acids have emerged during the last five years as powerful chiral Brønsted acid catalysts in many enantioselective processes. The most successful transformations carried out with chiral BINOL phosphates include C-C bond formation reactions. The recent advances have been reviewed in this article with a focus being placed on hydrocyanations, aldol-type, Mannich, Friedel-Crafts, aza-ene-type, Diels-Alder, as well as cascade and multi-component reactions.

  1. Use of N-Methylformamide as a Solvent in Indium-Promoted Barbier Reactions en Route to Enediyne and Epoxy Diyne Formation: Comparison of Rate and Stereoselectivity in C−C Bond-Forming Reactions with Water

    Science.gov (United States)

    2009-01-01

    Indium-promoted coupling reactions between propargyl aldehydes (1) and α-chloropropargylphenyl sulfide are reported. Although water has been shown to accelerate indium metal promoted reactions, the reverse pattern was observed in this series. Use of N-methylformamide (NMF), which has not previously been a solvent known for use in indium-promoted reactions, afforded an acceleration of these Barbier-style reactions compared to water. Indium-promoted reactions in this study also showed excellent regiocontrol and good stereocontrol, allowing for easy entry into the formation of epoxydiyne and enediyne skeletal structures. This paper also describes use of the Barbier Coupled product (2) as a new, and easy, entry into the formation of enediyne and epoxydiyne skeletal structures. PMID:19634900

  2. A sensitivity study of the neutral-neutral reactions C + C3 and C + C5 in cold dense interstellar clouds

    National Research Council Canada - National Science Library

    Wakelam, Valentine; Loison, Jean-Christophe; Herbst, Eric; Talbi, Dahbia; Quan, Dongui; Caralp, Françoise

    2009-01-01

    .... Of these reactions, we concentrated on those between C and C3 and between C and C5, both for their effect on specific important species such as CO and for their general effect on large numbers of species...

  3. Theoretical and Structural Analysis of Long C-C Bonds in the Adducts of Polycyanoethylene and Anthracene Derivatives and Their Connection to the Reversibility of Diels-Alder Reactions

    NARCIS (Netherlands)

    Hirsch, Anna K. H.; Reutenauer, Philippe; Le Moignan, Marc; Ulrich, Sebastien; Boul, Peter J.; Harrowfield, Jack M.; Jarowski, Peter D.; Lehn, Jean-Marie

    2014-01-01

    X-ray structure determinations on four Diels-Alder adducts derived from the reactions of cyano- and ester-substituted alkenes with anthracene and 9,10-dimethylanthracene have shown the bonds formed in the adduction to be particularly long. Their lengths range from 1.58 to 1.62 angstrom, some of the

  4. QM/MM study of the C-C coupling reaction mechanism of CYP121, an essential Cytochrome p450 of Mycobacterium tuberculosis

    OpenAIRE

    Dumas, Victoria Gisel; Defelipe, Lucas Alfredo; Petruk, Ariel Alcides; Turjanski, Adrian; Marti, Marcelo Adrian

    2016-01-01

    Among 20 p450s of Mycobacterium tuberculosis (Mt), CYP121 has received an outstanding interest, not only due to its essentiality for bacterial viability but also because it catalyzes an unusual carbon-carbon coupling reaction. Based on the structure of the substrate bound enzyme, several reaction mechanisms were proposed involving first Tyr radical formation, second Tyr radical formation, and C?C coupling. Key and unknown features, being the nature of the species that generate the first and s...

  5. Palladium(II)-Catalyzed C-H Bond Activation/C-C and C-O Bond Formation Reaction Cascade: Direct Synthesis of Coumestans.

    Science.gov (United States)

    Neog, Kashmiri; Borah, Ashwini; Gogoi, Pranjal

    2016-12-02

    A palladium catalyzed cascade reaction of 4-hydroxycoumarins and in situ generated arynes has been developed for the direct synthesis of coumestans. This cascade strategy proceeds via C-H bond activation/C-O and C-C bond formations in a single reaction vessel. This methodology affords moderate to good yields of coumestans and is tolerant of a variety of functional groups including halide. The methodology was applied to the synthesis of natural product flemichapparin C.

  6. Roles of Fe-Nx and Fe-Fe3C@C Species in Fe-N/C Electrocatalysts for Oxygen Reduction Reaction.

    Science.gov (United States)

    Kim, Jae Hyung; Sa, Young Jin; Jeong, Hu Young; Joo, Sang Hoon

    2017-03-22

    Iron and nitrogen codoped carbons (Fe-N/C) have emerged as promising nonprecious metal catalysts for the oxygen reduction reaction (ORR). While Fe-Nx sites have been widely considered as active species for Fe-N/C catalysts, very recently, iron and/or iron carbide encased with carbon shells (Fe-Fe3C@C) has been suggested as a new active site for the ORR. However, most of synthetic routes to Fe-N/C catalysts involve high-temperature pyrolysis, which unavoidably yield both Fe-Nx and Fe-Fe3C@C species, hampering the identification of exclusive role of each species. Herein, in order to establish the respective roles of Fe-Nx and Fe-Fe3C@C sites we rationally designed model catalysts via the phase conversion reactions of Fe3O4 nanoparticles supported on carbon nanotubes. The resulting catalysts selectively contained Fe-Nx, Fe-Fe3C@C, and N-doped carbon (C-Nx) sites. It was revealed that Fe-Nx sites dominantly catalyze ORR via 4-electron (4 e(-)) pathway, exerting a major role for high ORR activity, whereas Fe-Fe3C@C sites mainly promote 2 e(-) reduction of oxygen followed by 2 e(-) peroxide reduction, playing an auxiliary role.

  7. Competitive C-C and C-H bond scission in the ethanol oxidation reaction on Cu(100) and the effect of an alkaline environment.

    Science.gov (United States)

    Wu, Zhipeng; Zhang, Minhua; Jiang, Haoxi; Zhong, Chuan-Jian; Chen, Yifei; Wang, Lichang

    2017-06-14

    Direct ethanol fuel cell technology is impeded by inefficient, yet expensive anode catalysts. As such, research on effective and cheap anode catalysts towards complete ethanol oxidation reaction (EOR) is greatly needed. Herein, we report the investigations of the competitive C-C and C-H bond scissions in the EOR involving CH3CO, CH2CO, and CHCO species on Cu(100) using density functional theory and transition state theory calculations. The easiest C-C bond cleavage was found in CH2CO while the most difficult C-H bond cleavage was also found in CH2CO, both with an activation energy of 1.02 eV. The feasible C-C bond scission may take place in CH2CO with a rate constant ratio of the C-C to the C-H bond scission at 100 °C of 0.32. Furthermore, in an alkaline environment, the C-H bond scission activation barrier is considerably lowered but the C-C bond cleavage activation barrier is slightly increased for both CH3CO and CH2CO species. The reaction of CH3CO species on Cu(100) under alkaline conditions produces mainly acetic acid with a barrier of 0.49 eV and a rate constant of 4.93 × 105 s-1 at 100 °C.

  8. 27 CFR 26.68 - Bond, Form 2898-Beer.

    Science.gov (United States)

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Bond, Form 2898-Beer. 26... Liquors and Articles in Puerto Rico Bonds § 26.68 Bond, Form 2898—Beer. Where a brewer intends to withdraw, for purpose of shipment to the United States, beer of Puerto Rican manufacture from bonded storage in...

  9. 27 CFR 26.67 - Bond, Form 2897-Wine.

    Science.gov (United States)

    2010-04-01

    ... 27 Alcohol, Tobacco Products and Firearms 1 2010-04-01 2010-04-01 false Bond, Form 2897-Wine. 26... Liquors and Articles in Puerto Rico Bonds § 26.67 Bond, Form 2897—Wine. Where a proprietor intends to withdraw, for purpose of shipment to the United States, wine of Puerto Rican manufacture from bonded...

  10. C-C cross-coupling reactions of O6-alkyl-2-haloinosine derivatives and a one-pot cross-coupling/O6-deprotection procedure.

    Science.gov (United States)

    Gurram, Venkateshwarlu; Pottabathini, Narender; Garlapati, Ramesh; Chaudhary, Avinash B; Patro, Balaram; Lakshman, Mahesh K

    2012-08-01

    Reaction conditions for the CC cross-coupling of O(6)-alkyl-2-bromo- and 2-chloroinosine derivatives with aryl-, hetaryl-, and alkylboronic acids were studied. Optimization experiments with silyl-protected 2-bromo-O(6)-methylinosine led to the identification of [PdCl(2)(dcpf)]/K(3)PO(4) in 1,4-dioxane as the best conditions for these reactions (dcpf=1,1'-bis(dicyclohexylphosphino)ferrocene). Attempted O(6)-demethylation, as well as the replacement of the C-6 methoxy group by amines, was unsuccessful, which led to the consideration of Pd-cleavable groups such that C-C cross-coupling and O(6)-deprotection could be accomplished in a single step. Thus, inosine 2-chloro-O(6)-allylinosine was chosen as the substrate and, after re-evaluation of the cross-coupling conditions with 2-chloro-O(6)-methylinosine as a model substrate, one-step C-C cross-coupling/deprotection reactions were performed with the O(6)-allyl analogue. These reactions are the first such examples of a one-pot procedure for the modification and deprotection of purine nucleosides under C-C cross-coupling conditions. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Catalytic diastereoselective tandem conjugate addition-elimination reaction of Morita-Baylis-Hillman C adducts by C-C bond cleavage

    KAUST Repository

    Yang, Wenguo

    2012-02-08

    Through the cleavage of the C-C bond, the first catalytic tandem conjugate addition-elimination reaction of Morita-Baylis-Hillman C adducts has been presented. Various S N2′-like C-, S-, and P-allylic compounds could be obtained with exclusive E configuration in good to excellent yields. The Michael product could also be easily prepared by tuning the β-C-substituent group of the α-methylene ester under the same reaction conditions. Calculated relative energies of various transition states by DFT methods strongly support the observed chemoselectivity and diastereoselectivity. © 2012 Wiley-VCH Verlag GmbH&Co. KGaA, Weinheim.

  12. The new C-C bond formation in the reaction of o-amidophenolate indium(III) complex with alkyl iodides.

    Science.gov (United States)

    Piskunov, Alexandr V; Meshcheryakova, Irina N; Fukin, Georgy K; Shavyrin, Andrei S; Cherkasov, Vladimir K; Abakumov, Gleb A

    2013-08-07

    The reaction of bis(4,6-di-tert-butyl-N-(2,6-di-iso-propylphenyl)-o-amidophenolato)indium(III) anion with alkyl iodides is reported. This process includes oxidative addition of two RI (R = Me, Et) molecules to the non-transition metal complex and results in an alkyl transfer to ring carbon atoms with the formation of two new C-C bonds. The interaction proceeds at mild conditions and gives new indium(III) derivatives containing iminocyclohexa-1,4-dienolate type ligands.

  13. Lewis acid mediated tandem reaction of propargylic alcohols to tetrazoles involving C-O- and C-C-bond cleavage reactions and a C-N-bond formation.

    Science.gov (United States)

    Song, Xian-Rong; Han, Ya-Ping; Qiu, Yi-Feng; Qiu, Zi-Hang; Liu, Xue-Yuan; Xu, Peng-Fei; Liang, Yong-Min

    2014-09-15

    A novel and direct synthesis of 1-aryl-5-arylvinyl-tetrazoles from easily prepared propargylic alcohols and TMSN3 is developed in the presence of TMSCl under mild conditions (TMS = trimethylsilyl). The process involves an allenylazide intermediate, followed by a C-C-bond cleavage and C-N-bond formation to afford the desired products. Moreover, this method offers a good functional-group applicability and can be scaled-up to grams (yield up to 85 %). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Synthesis of palladium nanoparticles with leaf extract of Chrysophyllum cainito (Star apple) and their applications as efficient catalyst for C-C coupling and reduction reactions

    Science.gov (United States)

    Majumdar, Rakhi; Tantayanon, Supawan; Bag, Braja Gopal

    2017-10-01

    A simple green chemical method for the one-step synthesis of palladium nanoparticles (PdNPs) has been described by reducing palladium (II) chloride with the leaf extract of Chrysophyllum cainito in aqueous medium. The synthesis of the palladium nanoparticles completed within 2-3 h at room temperature, whereas on heat treatment (70-80 °C), the synthesis of colloidal PdNPs completed almost instantly. The stabilized PdNPs have been characterized in detail by spectroscopic, electron microscopic and light scattering measurements. The synthesized PdNPs have been utilized as a green catalyst for C-C coupling reactions under aerobic and phosphine-free conditions in aqueous medium. In addition, the synthesized PdNPs have also been utilized as a catalyst for a very efficient sodium borohydride reduction of 3- and 4-nitrophenols. The synthesized PdNPs can retain their catalytic activity for several months.

  15. Catalytic promiscuity of 4-oxalocrotonate tautomerase : discovery and characterization of C-C bond-forming activities

    NARCIS (Netherlands)

    Zandvoort, Ellen

    2012-01-01

    Het verschijnsel katalytische promiscuïteit, waarin een enzym naast zijn natuurlijke activiteit een alternatieve reactie (of reacties) katalyseert, is een krachtig, recent opgekomen concept, dat erg relevant is voor het ontwerpen van nieuwe enzymen. Enzym promiscuïteit is een veelbelovende bron van

  16. Application of “Boomerang” Linear Polystyrene-Stabilized Pd Nanoparticles to a Series of C-C Coupling Reactions in Water

    Directory of Open Access Journals (Sweden)

    Atsushi Ohtaka

    2015-02-01

    Full Text Available The application of a catch-and-release system for soluble Pd species between water (reaction medium and polystyrene (polymer support was examined in the Suzuki coupling reaction with 2-bromothiophene and the Heck reaction with styrene or bromobenzene. Although a slight increase in particle size was observed by TEM after re-stabilization of the Pd species on linear polystyrene, no agglomeration was observed.

  17. Synthesis and reactions of polymer-bound Ph3P=C=C=O: a quick route to tenuazonic acid and other optically pure 5-substituted tetramates.

    Science.gov (United States)

    Schobert, Rainer; Jagusch, Carsten; Melanophy, Claire; Mullen, Gillian

    2004-12-07

    Polystyrene-bound cumulated ylide Ph3PCCO was prepared on a large scale in two steps. It reacts with Grignard compounds, amines and alcohols to give immobilized acyl, amide and ester ylides, respectively. Their Wittig reactions lead to alkenes free of phosphane oxide. Optically pure 5-substituted tetramates were obtained from reactions of resin-bound Ph3PCCO with alpha-ammonium esters in one step. The mycotoxin (-)-tenuazonic acid was accordingly prepared in just three steps.

  18. Construction of microbial platform for an energy-requiring bioprocess: practical 2'-deoxyribonucleoside production involving a C-C coupling reaction with high energy substrates.

    Science.gov (United States)

    Horinouchi, Nobuyuki; Sakai, Takafumi; Kawano, Takako; Matsumoto, Seiichiro; Sasaki, Mie; Hibi, Makoto; Shima, Jun; Shimizu, Sakayu; Ogawa, Jun

    2012-06-15

    Reproduction and sustainability are important for future society, and bioprocesses are one technology that can be used to realize these concepts. However, there is still limited variation in bioprocesses and there are several challenges, especially in the operation of energy-requiring bioprocesses. As an example of a microbial platform for an energy-requiring bioprocess, we established a process that efficiently and enzymatically synthesizes 2'-deoxyribonucleoside from glucose, acetaldehyde, and a nucleobase. This method consists of the coupling reactions of the reversible nucleoside degradation pathway and energy generation through the yeast glycolytic pathway. Using E. coli that co-express deoxyriboaldolase and phosphopentomutase, a high amount of 2'-deoxyribonucleoside was produced with efficient energy transfer under phosphate-limiting reaction conditions. Keeping the nucleobase concentration low and the mixture at a low reaction temperature increased the yield of 2'-deoxyribonucleoside relative to the amount of added nucleobase, indicating that energy was efficiently generated from glucose via the yeast glycolytic pathway under these reaction conditions. Using a one-pot reaction in which small amounts of adenine, adenosine, and acetone-dried yeast were fed into the reaction, 75 mM of 2'-deoxyinosine, the deaminated product of 2'-deoxyadenosine, was produced from glucose (600 mM), acetaldehyde (250 mM), adenine (70 mM), and adenosine (20 mM) with a high yield relative to the total base moiety input (83%). Moreover, a variety of natural dNSs were further synthesized by introducing a base-exchange reaction into the process. A critical common issue in energy-requiring bioprocess is fine control of phosphate concentration. We tried to resolve this problem, and provide the convenient recipe for establishment of energy-requiring bioprocesses. It is anticipated that the commercial demand for dNSs, which are primary metabolites that accumulate at very low levels in the

  19. An easy access to α-aryl substituted γ-ketophosphonates: Lewis acid mediated reactions of 1,3-diketones with α-hydroxyphosphonates and tandem regioselective C-C bond cleavage.

    Science.gov (United States)

    Pallikonda, Gangaram; Chakravarty, Manab; Sahoo, Manoj K

    2014-09-28

    A range of α-aryl substituted γ-ketophosphonates is synthesised by Lewis acid mediated reactions of 1,3-diketones and easily accessible, inexpensive benzylic α-hydroxyphosphonates in an operationally simple method under solvent-free conditions without exclusion of air/moisture. A regioselective C-C bond cleavage for 1,3-diketones in a tandem fashion has also been demonstrated. Synthesis of a γ-ketophosphonate with phenol functionality at the α-position (structural analogue of raspberry ketone, a natural product) has also been presented.

  20. RATIONAL APPROACHES FOR ENGINEERING NOVEL FUNCTIONALITIES IN CARBON-CARBON BOND FORMING ENZYMES

    Directory of Open Access Journals (Sweden)

    Perrin Baker

    2012-09-01

    Full Text Available Enzymes that catalyze carbon-carbon bond formation can be exploited as biocatalyst for synthetic organic chemistry. However, natural enzymes frequently do not possess the required properties or specificities to catalyze industrially useful transformations. This mini-review describes recent work using knowledge-guided site-specific mutagenesis of key active site residues to alter substrate specificity, stereospecificity and reaction specificity of these enzymes. In addition, examples of de novo designed enzymes that catalyze C-C bond reactions not found in nature will be discussed.

  1. Palladium nanoparticles immobilized on multifunctional ‎hyperbranched polyglycerol-grafted magnetic nanoparticles as a ‎sustainable and efficient catalyst for C-C coupling reactions

    Directory of Open Access Journals (Sweden)

    Mina Amini

    2016-07-01

    Full Text Available This study offers an exclusive class of magnetic nanoparticles supported hyperbranched polyglycerol (MNP/HPG that was functionalized with citric acid (MNP/HPG-CA as a host immobilization of palladium nanoparticles. The MNP/HPG-CA/Pd catalyst was fully characterized using some different techniques such as thermogravimetric analysis (TGA, x-ray diffraction (XRD, transmission electron microscopy (TEM, scanning electron microscopy (SEM, energy-dispersive x-ray spectroscopy (EDX, inductively coupled plasma (ICP and x-ray photoelectron spectroscopy (XPS. The new catalytic system showed high activity for the Suzuki–Miyaura cross-coupling and Heck reaction under mild and green conditions. Besides, the MNP/HPG-CA/Pd was found to be a convenient catalyst for copper-free Sonogashira coupling reaction in water as a green solvent at room temperature. Moreover, the catalyst could be recovered easily and reused several times without significant loss of reactivity. Ease of preparation, oxygen insensitive, phosphine-free, air- and moisture-stable, and high reusability of this immobilized palladium catalyst are the noteworthy advantages of this catalytic system.

  2. Pd nanoparticles deposited on poly(lactic acid) grafted carbon nanotubes: synthesis, characterization and application in Heck C-C coupling reaction.

    Science.gov (United States)

    Neelgund, Gururaj M; Oki, Aderemi

    2011-05-31

    Herein we described the synthesis of a novel f-CNTs-Pd nanocatalyst by covalent grafting of poly(lactic acid) (PLA) onto carbon nanotubes (CNTs) and subsequent deposition of Pd nanoparticles. Prior to grafting of PLA, CNTs were oxidized with a mixture of HNO(3)/H(2)SO(4) and successively activated with thionyl chloride. The PLA grafted CNTs (f-CNTs) were then used as platform for in-situ deposition of Pd nanoparticles. The formation of f-CNTs-Pd nanocatalyst was analyzed by UV-vis, FTIR and Raman spectroscopy, powder XRD, energy dispersive spectroscopy and thermogravimetric analysis. The morphologies of the nanocatalyst were characterized using scanning and transmission electron microscopes. The f-CNTs stabilized Pd nanoparticles are found to be more effective in the promotion of Heck cross-coupling reaction between aryl halides and n-butyl acrylate. The f-CNTs-Pd nanocatalyst was regenerated for three cycles of reaction without any significant loss in its activity.

  3. 46 CFR Appendix D to Subpart C of... - Ocean Transportation Intermediary (OTI) Group Bond Form [FMC-69

    Science.gov (United States)

    2010-10-01

    ... Intermediary (OTI) Group Bond Form Form FMC-69 Federal Maritime Commission Ocean Transportation Intermediary.... Corporation) Agent's Address Corporate Surety Business Address (Affix Corporate Seal) By Title ...

  4. A new strategy to construct a C=C-CF3 subunit via CuBr-catalyzed domino reaction of homopropargyl amines: an efficient synthesis of trifluoromethyl containing building blocks 4-trifluoromethyl-2,3-dihydro-pyrroliums.

    Science.gov (United States)

    Ge, Guang-Cun; Huang, Xiao-Jun; Ding, Chang-Hua; Wan, Shi-Li; Dai, Li-Xin; Hou, Xue-Long

    2014-03-21

    A new strategy for the construction of a C=C-CF3 subunit has been developed via CuBr-catalyzed domino cyclization-trifluoromethylation of homopropargyl amines with Umemoto's reagent. 4-Trifluoromethyl-2,3-dihydro-pyrroliums were produced in high yields. The usefulness of these products has been demonstrated by the transformation of them into various other trifluoromethylated molecules.

  5. Fluorescence detection of cytosine/guanine transversion based on a hydrogen bond forming ligand.

    Science.gov (United States)

    Nishizawa, Seiichi; Yoshimoto, Keitaro; Seino, Takehiro; Xu, Chun-Yan; Minagawa, Masakazu; Satake, Hiroyuki; Tong, Aijun; Teramae, Norio

    2004-05-10

    In combination with abasic site (AP site)-containing oligodeoxynucleotides (ODNs), we demonstrate potential use of a hydrogen bond forming ligand, 2-amino-7-methyl-1,8-naphthyridine (AMND), for the fluorescence detection of the cytosine (C)/guanine (G) mutation sequence of the cancer repression gene p53. Our method is based on construction of the AP site in ODN duplexes, which allows small synthetic ligands to bind to target nucleobases accompanied by fluorescence signaling: an AP site-containing ODN is hybridized with a target ODN so as to place the AP site toward a target nucleobase, by which hydrophobic microenvironments are provided for ligands to recognize target nucleobases through hydrogen-bonding. In 10mM sodium cacodylate buffer solutions (pH, 7.0) containing 100mM NaCl and 1.0mM EDTA, AMND is found to strongly bind to C (K(d)=1.5x10(-6)M) in the target ODN while the binding affinity for G is relatively moderate (K(d)=50x10(-6)M). Significant fluorescence quenching of AMND is observed only when binding to C, making it possible to judge the C/G transversion with the naked eye.

  6. Direct-dynamics VTST study of hydrogen or deuterium abstraction and C-C bond formation or dissociation in the reactions of CH3 + CH4, CH3 + CD4, CH3D + CD3, CH3CH3 + H, and CH3CD3 + D

    Science.gov (United States)

    Ramazani, Shapour

    2013-05-01

    Direct-dynamics variational transition-state theory calculations are studied at the MPWB1K/6-311++G(d,p) level for the four parts of reactions. The first part is hydrogen or deuterium abstraction in the reactions of CH3 + CH4, CH3 + CD4, and CH3D + CH3. The second part involves C-C bond formation in these reactions. The third one is the reactions of CH3CH3 + H and CH3CD3 + D to form of H2, HD, and D2. The last one is the dissociation of C-C bonds in the last group of reactions. The ground-state vibrational adiabatic potential is plotted for all channels. We have carried out direct-dynamics calculations of the rate constants, including multidimensional tunneling in the temperature range T = 200-2200 K. The results of CVT/μOMT rate constants were in good agreement with the experimental data which were available for some reactions. Small-curvature tunneling and Large-curvature tunneling with the LCG4 version were used to include the quantum effects in calculation of the rate constants. To try to find the region of formation and dissociation of bounds we have also reported the variations of harmonic vibrational frequencies along the reaction path. The thermally averaged transmission probability (P(E)exp (-ΔE/RT)) and representative tunneling energy at 298 K are reported for the reactions in which tunneling is important. We have calculated kinetic isotope effect which shows tunneling and vibrational contributions are noticeable to determine the rate constant. Nonlinear least-squares fitting is used to calculate rate constant expressions in the temperature range 200-2200 K. These expressions revealed that pre-exponential factor includes two parts; the first part is a constant number which is important at low temperatures while the second part is temperature dependent which is significant at high temperatures.

  7. Rhodium-Catalyzed C-C Bond Formation via Heteroatom-Directed C-H Bond Activation

    Energy Technology Data Exchange (ETDEWEB)

    Colby, Denise; Bergman, Robert; Ellman, Jonathan

    2010-05-13

    Once considered the 'holy grail' of organometallic chemistry, synthetically useful reactions employing C-H bond activation have increasingly been developed and applied to natural product and drug synthesis over the past decade. The ubiquity and relative low cost of hydrocarbons makes C-H bond functionalization an attractive alternative to classical C-C bond forming reactions such as cross-coupling, which require organohalides and organometallic reagents. In addition to providing an atom economical alternative to standard cross - coupling strategies, C-H bond functionalization also reduces the production of toxic by-products, thereby contributing to the growing field of reactions with decreased environmental impact. In the area of C-C bond forming reactions that proceed via a C-H activation mechanism, rhodium catalysts stand out for their functional group tolerance and wide range of synthetic utility. Over the course of the last decade, many Rh-catalyzed methods for heteroatom-directed C-H bond functionalization have been reported and will be the focus of this review. Material appearing in the literature prior to 2001 has been reviewed previously and will only be introduced as background when necessary. The synthesis of complex molecules from relatively simple precursors has long been a goal for many organic chemists. The ability to selectively functionalize a molecule with minimal pre-activation can streamline syntheses and expand the opportunities to explore the utility of complex molecules in areas ranging from the pharmaceutical industry to materials science. Indeed, the issue of selectivity is paramount in the development of all C-H bond functionalization methods. Several groups have developed elegant approaches towards achieving selectivity in molecules that possess many sterically and electronically similar C-H bonds. Many of these approaches are discussed in detail in the accompanying articles in this special issue of Chemical Reviews. One approach

  8. Recent progress in the catalytic carbene insertion reactions into the silicon-hydrogen bond.

    Science.gov (United States)

    Keipour, Hoda; Carreras, Virginie; Ollevier, Thierry

    2017-07-05

    The following review will explore the historical development of Si-H bond insertion reactions, giving an up-to-date account on the metal catalysts often employed, in addition to an assessment of their strengths and weaknesses. Diazo compounds have great synthetic potential as versatile reagents for the formation of metal carbenes, allowing the selective formation of C-C and C-heteroatom bonds and thus the introduction of functional groups into organic molecules. C-Si bond-forming methods, that introduce silicon motifs into organic molecules, rely on catalysts derived from metals such as rhodium, copper, iridium, silver, ruthenium, and iron to achieve the desired activities and selectivities.

  9. Palladium Catalyst Supported on Zeolite for Cross-coupling Reactions: An Overview of Recent Advances.

    Science.gov (United States)

    Kumbhar, Arjun

    2017-02-01

    Over the last 30-40 years, Pd-catalyzed C-C bond-forming reactions have gained immense importance for their use in synthesis of biologically and pharmaceutically important organic fragments. Heterogeneous Pd catalysts supported on porous materials, especially zeolites, have many advantages as they have high surface area with tunable acidity and basicity, hydrophobic and hydrophilic character, shape and size selectivity, as well as chemical and thermal stability. They also offer very easy recovery and reusability. This review covers the literature published on the synthesis and characterization of Pd catalysts supported on zeolites and their applications in various organic transformations.

  10. Polycyclization Enabled by Relay Catalysis: One-Pot Manganese-Catalyzed C-H Allylation and Silver-Catalyzed Povarov Reaction.

    Science.gov (United States)

    Chen, Shi-Yong; Li, Qingjiang; Liu, Xu-Ge; Wu, Jia-Qiang; Zhang, Shang-Shi; Wang, Honggen

    2017-06-09

    In this study, a Mn I /Ag I -based relay catalysis process is described for the one-pot synthesis of polycyclic products by a formal [3+2] and [4+2] cycloaddition reaction cascade. A manganese(I) complex catalyzed the first example of directed C-H allylation with allenes, setting the stage for an in situ Povarov cyclization catalyzed by silver(I). The reaction proceeds with high bond-forming efficiency (three C-C bonds), broad substrate scope, high regio- and stereoselectivity, and 100 % atom economy. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Long-lived transient anion of c-C4F8O

    Science.gov (United States)

    Kočišek, J.; Janečková, R.; Fedor, J.

    2018-02-01

    We report partial cross sections for electron attachment to c-C4F8O, a gas with promising technological applications in free-electron-rich environments. The dissociative electron attachment leads to a number of anionic fragments resulting from complex bond-breaking and bond-forming processes. However, the anion with the highest abundance is the non-dissociated (transient) parent anion which is formed around 0.9 eV electron energy. Its lifetime reaches tens of microseconds. We discuss the origin of this long lifetime, the anion's strong interactions with other molecules, and the consequences for electron-scavenging properties of c-C4F8O in denser environments, in particular for its use in mixtures with CO2 and N2.

  12. Ni-Catalyzed Carbon-Carbon Bond-Forming Reductive Amination.

    Science.gov (United States)

    Heinz, Christoph; Lutz, J Patrick; Simmons, Eric M; Miller, Michael M; Ewing, William R; Doyle, Abigail G

    2018-02-14

    This report describes a three-component, Ni-catalyzed reductive coupling that enables the convergent synthesis of tertiary benzhydryl amines, which are challenging to access by traditional reductive amination methodologies. The reaction makes use of iminium ions generated in situ from the condensation of secondary N-trimethylsilyl amines with benzaldehydes, and these species undergo reaction with several distinct classes of organic electrophiles. The synthetic value of this process is demonstrated by a single-step synthesis of antimigraine drug flunarizine (Sibelium) and high yielding derivatization of paroxetine (Paxil) and metoprolol (Lopressor). Mechanistic investigations support a sequential oxidative addition mechanism rather than a pathway proceeding via α-amino radical formation. Accordingly, application of catalytic conditions to an intramolecular reductive coupling is demonstrated for the synthesis of endo- and exocyclic benzhydryl amines.

  13. An extracellular disulfide bond forming protein (DsbF) from Mycobacterium tuberculosis: Structural, biochemical and gene expression analysis

    OpenAIRE

    Chim, Nicholas; Riley, Robert; The, Juliana; Im, Soyeon; Segelke, Brent; Lekin, Tim; Yu, Minmin; Hung, Li Wei; Terwilliger, Tom; Whitelegge, Julian P.; Goulding, Celia W.

    2010-01-01

    Disulfide bond forming (Dsb) proteins ensure correct folding and disulfide bond formation of secreted proteins. Previously, we showed that Mycobacterium tuberculosis DsbE (Mtb DsbE, Rv2878c) aids in vitro oxidative folding of proteins. Here we present structural, biochemical and gene expression analyses of another putative Mtb secreted disulfide bond isomerase protein homologous to Mtb DsbE, Mtb DsbF (Rv1677). The X-ray crystal structure of Mtb DsbF reveals a conserved thioredoxin fold althou...

  14. Borane-catalyzed cracking of C-C bonds in coal; Boran-katalysierte C-C-Bindungungsspaltung in Steinkohle

    Energy Technology Data Exchange (ETDEWEB)

    Narangerel, J.; Haenel, M.W. [Max-Planck-Institut fuer Kohlenforschung, Muelheim an der Ruhr (Germany)

    1998-09-01

    Coal, especially coking coal, was reacted with hydrogen at comparatively mild reaction conditions (150-280 degrees centigrade, 20 MPa hydrogen pressure) in the presence of catalysts consisting of borange reagents and certain transition metal halides to obtaine more than 80 percent of pyridine-soluble products. The influence of the degree of coalification, catalyst and temperature on the borane-catalyzed hydrogenolysis of C-C bonds in coal was investigated. (orig.) [Deutsch] Steinkohlen, insbesondere im Inkohlungsbereich der Fettkohlen (Kokskohlen), werden in Gegenwart von Katalysatoren aus Boran-Reagentien und bestimmten Uebergangsmetallhalogeniden mit Wasserstoff bei vergleichsweise milden Reaktionsbedingungen (250-280 C, 20 MPa Wasserstoffdruck) in zu ueber 80% pyridinloesliche Produkte umgewandelt. Der Einfluss von Inkohlungsgrad, Katalysator und Temperatur auf die Boran-katalysierte C-C-Bindungshydrogenolyse in Kohle wurde untersucht. (orig.)

  15. On the outside looking in: rethinking the molecular mechanism of 1,3-dipolar cycloadditions from the perspective of bonding evolution theory. The reaction between cyclic nitrones and ethyl acrylate.

    Science.gov (United States)

    Adjieufack, A I; Ndassa, I M; Patouossa, I; Mbadcam, J K; Safont, V S; Oliva, M; Andrés, J

    2017-07-19

    In this work we report on the progress that has been made towards gaining an understanding of the molecular mechanism of 1,3-dipolar cycloadditions using the bonding evolution theory (BET). A detailed analysis of the flow of electron density along the reaction pathway of the formal 1,3-dipolar cycloaddition reaction between cyclic nitrones (pyrroline-1-oxide and 2,3,4,5-tetrahydropyridine-1-oxide) and ethyl acrylate, as a case study, allowed the nature of the molecular mechanisms to be characterized. The present study provides a deep insight into the reaction mechanism, based on the electron density rearrangements given by the structural stability domains, and their connection with the bond breaking/forming processes along the reaction pathway. The electron pushing formalism is a powerful tool to describe chemical reactivity. Here, we show how the Lewis structures can be recovered and how curly arrows describe electron density transfers in chemical reaction mechanisms based on the BET results. The reaction mechanism is described by four consecutive events taking place as the reaction progresses: (1) the population of the initial N-C double bond is transferred to the N and C atoms; (2) the population of the initial double C-C bond is transferred to the C atoms. Along the ortho pathway the next steps are: (3) the C-C bond-forming process, and (4) the O-C bond-forming process. The order of (3) and (4) is inverted in the meta channel. Based on the sequence of the structural stability domains along the intrinsic reaction coordinate, a new synchronicity index is proposed, allowing us to classify and quantify the (a)synchronicity of the 1,3-DC reactions and, therefore, the nature of the reaction mechanism.

  16. Photoinduced C-C Cross-Coupling of Aryl Chlorides and Inert Arenes

    Directory of Open Access Journals (Sweden)

    Lele Wang

    2016-01-01

    Full Text Available Here we report a facile, efficient, and catalyst-free method to realize C-C cross-coupling of aryl chlorides and inert arenes under UV light irradiation. The aryl radical upon homolytic cleavage of C-Cl bond initiated the nucleophilic substitution reaction with inert arenes to give biaryl products. This mild reaction mode can also be applied to other synthetic reactions, such as the construction of C-N bonds and trifluoromethylated compounds.

  17. Radioecological studies of {sup 137}Cs in limnological ecosystems. Analysis on the bonding forms of {sup 137}Cs in pond sediments

    Energy Technology Data Exchange (ETDEWEB)

    Miyake, Sadaaki [Saitama Inst. of Public Health (Japan); Nakamura, Fumio; Izumo, Yoshiro

    2000-02-01

    In order to investigate in more detail on the {sup 137}Cs concentration in pond sediments, we have carried out analysis on the bonding forms of {sup 137}Cs in pond sediments. The existing rate of different bonding forms of {sup 137}Cs in pond sediments was found to be below 5% for F1: exchangeable and F2: bound to carbonates, 18-24% for F3: bound to iron and manganese oxides, 14-17% for F4: bound to organic matter and 54-60% for F5: residual (mainly, bound to silicate minerals). Furthermore, we have investigated the relations among the {sup 137}Cs concentration in each place, the ignition loss, the total carbon and the carbon exchange capacity of pond sediment, respectively. We have found a tendency that the larger the ignition loss, the total carbon and the cation exchange capacity are, the higher the {sup 137}Cs concentration is. On the other hand, about 90% of {sup 40}K in pond sediments is in the form of F5, and the bonding forms of {sup 137}Cs and {sup 40}K are obviously different regardless of the fact that both are alkaline metals. (author)

  18. Palladium-Catalyzed One-Pot Reaction of Hydrazones, Dihaloarenes, and Organoboron Reagents: Synthesis and Cytotoxic Activity of 1,1-Diarylethylene Derivatives.

    Science.gov (United States)

    Roche, Maxime; Salim, Salim Mmadi; Bignon, Jérôme; Levaique, Hélène; Brion, Jean-Daniel; Alami, Mouad; Hamze, Abdallah

    2015-07-02

    A new three-component assembly reaction between N-tosylhydrazones, dihalogenated arenes, and boronic acids or boronate esters was developed, producing highly substituted 1,1-diarylethylenes in good yields. The two C-C bonds formed through this coupling have been catalyzed by a single Pd-catalyst in a one-pot fashion. It is noted that the one-pot pinacol boronate cross-coupling reaction generally provides products in high yields, offers an expansive substrate scope, and can address a broad range of aryl, styrene, vinyl, and heterocyclic olefinic targets. The scope of this one-pot coupling has been also extended to the synthesis of the 1,1-diarylethylene skeleton of the natural product ratanhine. The new compounds were evaluated for their cytotoxic activity, and this allowed the identification of compound 4ab that exhibits excellent antiproliferative activity in the nanomolar concentration range against HCT116 cancer cell lines.

  19. [Acid-base catalysis of chiral Pd complexes: development of novel asymmetric reactions].

    Science.gov (United States)

    Hamashima, Yoshitaka

    2005-10-01

    Using a unique character of the chiral palladium complexes 1 and 2, several types of novel catalytic asymmetric reactions have been developed. In contrast to the conventional Pd(0)-catalyzed reactions, these complexes function as an acid-base catalyst. Thus active methine compounds were activated to form chiral palladium enolates, which underwent the enantioselective Michael reaction and Mannich-type reaction with up to 99% ee. Interestingly, these palladium enolates acted cooperatively with a strong protic acid activating the electrophiles, formed concomitantly during the formation of the enolates, whereby the C-C bond-forming reaction was promoted. In addition, this palladium enolate chemistry was also applicable to the electrophilic asymmetric fluorination reactions, and thus various carbonyl compounds including beta-ketoesters, beta-ketophosphonates, and oxindoles were fluorinated in a highly enantioselective manner (up to 98% ee). It is advantageous that these reactions were carried out in environmentally friendly alcoholic solvents such as ethanol, and exclusion of air and moisture is not necessary.

  20. Mannich reaction: A versatile and convenient approach to bioactive ...

    Indian Academy of Sciences (India)

    tions of multifaceted Mannich reaction in the synthesis of antimalarial, antitumour, antimicrobial, antitubercu- lar, antiinflammatory and anticonvulsant molecules. 1.1 Mannich reaction and its modern variants. Mannich reaction2 is one of the most fundamental and important, C–C bond forming reactions in organic syn- thesis.

  1. Sodium dichloroiodate promoted C-C bond cleavage: An efficient ...

    Indian Academy of Sciences (India)

    SAKET B BHAGAT

    2018-02-01

    Feb 1, 2018 ... benzimidazoles/benzothiazoles/benzoxazoles under mild conditions. This tandem process involved a C-C bond cleavage and C-N bond formation. Keywords. Benzimidazole/benzothiazole/benzoxazole; β-diketones; NaICl2; C-C bond cleavage. 1. Introduction. Nitrogen-containing five-member heterocyclic ...

  2. HETERODIMERIZATION OF PROPYLENE AND VINYLARENES: FUNCTIONAL GROUP COMPATIBILITY IN A HIGHLY EFFICIENT NI-CATALYZED CARBON-CARBON BOND-FORMING REACTION. (R826120)

    Science.gov (United States)

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  3. Isolation and characterization of the carbon-phosphorus bond-forming enzyme phosphoenolpyruvate mutase from the mollusk Mytilus edulis.

    Science.gov (United States)

    Kim, A; Kim, J; Martin, B M; Dunaway-Mariano, D

    1998-02-20

    The enzyme phosphoenolpyruvate mutase was purified to homogeneity from the mollusk Mytilus edulis. The subunit size of the native homotetramer was determined to be 34,000 Da. The steady-state kinetic constants for catalysis of the conversion of phosphonopyruvate to phosphoenolpyruvate at pH 7.5 and 25 degrees C were measured at kcat = 34 s-1, phosphonopyruvate Km = 3 microM, and Mg2+ Km = 4 microM. The enzyme displayed a broad specificity for divalent metal ion activation; Co2+, Mn2+, Zn2+, and Ni2+ are activators, whereas Ca2+ is not. Analysis of the pH dependence of the Mg2+-activated mutase-catalyzed reaction of phosphonopyruvate revealed one residue that must be protonated (apparent pKa = 8.3) and a second residue that must be unprotonated (apparent pKa = 7.7) for maximal catalytic activity.

  4. Internal friction and gas desorption of {C}/{C} composites

    Science.gov (United States)

    Serizawa, H.; Sato, S.; Kohyama, A.

    1994-09-01

    {C}/{C} composites are the most promising candidates as high heat flux component materials, where temperature dependence of mechanical properties and gas desorption behavior at elevated temperature are important properties. At the beginning, the newly developed internal friction measurement apparatus, which enables the accurate measurement of dynamic elastic properties up to 1373 K along with the measurement of gas desorption behavior, was used. The materials studied were unidirectional (UD) {C}/{C} composites reinforced with mesophase pitch-based carbon fibers, which were heat treated at temperatures ranging from 1473 to 2773 K which produced a variety of graphitized microstructures. Two-dimensional (2D) {C}/{C} composites reinfored with flat woven fabrics of PAN type carbon fibers were also studied. These materials were heat treated at 1873 K. From the temperature spectrum of internal friction of 2D {C}/{C} composites, these internal friction peaks were detected and were related to gas desorption. Also the temperature dependence of Young's modulus of UD {C}/{C} composites, negative and positive dependence of Young's modulus were observed reflecting microstructure changes resulting from the heat treatments.

  5. Efficient C/C++ programming smaller, faster, better

    CERN Document Server

    Heller, Steve

    1994-01-01

    Efficient C/C++ Programming describes a practical, real-world approach to efficient C/C++ programming. Topics covered range from how to save storage using a restricted character set and how to speed up access to records by employing hash coding and caching. A selective mailing list system is used to illustrate rapid access to and rearrangement of information selected by criteria specified at runtime.Comprised of eight chapters, this book begins by discussing factors to consider when deciding whether a program needs optimization. In the next chapter, a supermarket price lookup system is used to

  6. Get more control over your C/C++ service

    CERN Multimedia

    CERN. Geneva

    2015-01-01

    Are you looking for a way to better diagnose or monitor your C/C++ programs? Find out more about CMX - a neat, lightweight library (<32Kb) which targets this need. It allows to expose information from inside a process through a simple API, enabling pre-failure detection in combination with your favourite monitoring system.

  7. On the Michael addition of water to C = C bonds

    NARCIS (Netherlands)

    Chen, B.

    2015-01-01

    ?-Hydroxy carbonyl compounds are an important class of compounds often found as a common structural motif in natural products. Although the molecules themselves look rather simple, their synthesis can be challenging. Water addition to conjugated C = C bonds opens up a straightforward route for the

  8. Ion chemistry in octafluorocyclobutane, c-C 4F 8

    Science.gov (United States)

    Jiao, C. Q.; Garscadden, A.; Haaland, P. D.

    1998-11-01

    Cross-sections for electron impact ionization of octafluorocyclobutane ( c-C 4F 8) have been measured from 10 to 200 eV by Fourier transform mass spectrometry. No parent ion is observed, and over half of the dissociative ionization yields C 2F 4+ and C 3F 5+. Eleven other fluorocarbon cations are produced with smaller cross-sections, giving a total ionization cross-section of (1.6±0.2)×10 -15 cm 2 between 80 and 200 eV. Only CF 2+ and C 2F 3+ react further with the parent molecule to yield C 3F 5+ as the primary product. No evidence of cationic polymerization was found. F - and C 4F 8- are formed by electron attachment at energies below 10 eV, but neither reacts further with c-C 4F 8.

  9. C-C bond formation and cleavage in radical enzymes, a theoretical perspective.

    Science.gov (United States)

    Himo, Fahmi

    2005-02-25

    Quantum chemical methods are today a viable tool in the study of enzyme catalysis. The development of new density functional techniques and the enormous advancement in computer power have made it possible to accurately describe active sites of enzymes. This review gives a brief account of the methods and models used in this field. Three specific enzymes are discussed: pyruvate-formate lyase (PFL), spore photoproduct lyase (SPL), and benzylsuccinate synthase (BSS). What these enzymes have in common is that they use radical chemistry to catalyze C-C bond formation or cleavage reactions.

  10. Dielectron Production in C + C and p + p Collisions with Hades

    Science.gov (United States)

    Pietraszko, J.; Agakishiev, G.; Agodi, C.; Balanda, A.; Bellia, G.; Belver, D.; Belyaev, A.; Blanco, A.; Böhmer, M.; Boyard, J. L.; Braun-Munzinger, P.; Cabanelas, P.; Castro, E.; Chernenko, S.; Christ, T.; Destefanis, M.; Díaz, J.; Dohrmann, F.; Durán, I.; Eberl, T.; Fabbietti, L.; Fateev, O.; Finocchiaro, P.; Fonte, P. J. R.; Friese, J.; Frhölich, I.; Galatyuk, T.; Garzón, J. A.; Gernhóuser, R.; Gilardi, C.; Golubeva, M.; González-Díaz, D.; Grosse, E.; Guber, F.; Hadjivasiliou, Ch.; Heilmann, M.; Hennino, T.; Holzmann, R.; Ierusalimov, A.; Iori, I.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Kanaki, K.; Karavicheva, T.; Kirschner, D.; Koenig, I.; Koenig, W.; Kolb, B. W.; Kotte, R.; Krizek, F.; Krücken, R.; Kugler, A.; Kühn, W.; Kurepin, A.; Lamas-Valverde, J.; Lang, S.; Lange, S.; Lopez, L.; Mangiarotti, A.; Marín, J.; Markert, J.; Metag, V.; Michalska, B.; Mishra, D.; Moriniere, E.; Mousa, J.; Münch, M.; Müntz, C.; Naumann, L.; Novotny, R.; Otwinowski, J.; Pachmayer, Y. C.; Palka, M.; Pechenov, V.; Pérez, T.; Pleskac, R.; Pospísil, V.; Przygoda, W.; Ramstein, B.; Reshetin, A.; Roy-Stephan, M.; Rustamov, A.; Sadovsky, A.; Sailer, B.; Salabura, P.; Schmah, A.; Senger, P.; Shileev, K.; Simon, R.; Spataro, S.; Spruck, B.; Ströbele, H.; Stroth, J.; Sturm, C.; Sudol, M.; Teilab, K.; Tlusty, P.; Traxler, M.; Trȩbacz, R.; Tsertos, H.; Veretenkin, I.; Wagner, V.; Wen, H.; Wiśniowski, M.; Wójcik, T.; Wüstenfeld, J.; Zanevsky, Y.; Zumbruch, P.

    The High Acceptance Di-Electron Spectrometer HADES1 has been constructed at the SIS accelerator (GSI Darmstadt) to investigate electron-positron pairs produced in proton, pion and heavy ion induced reactions. The main goal of these studies is to explore properties of hadrons in nuclear matter. The apparatus and the experimental results from C+C at 2.0 AGeV and 1.0 AGeV and p+p at 2.2 GeV compared with Monte-Carlo events from a generator based on known cross-sections and branching ratios are presented.

  11. Microstructure of C/C Composites with Different Matrix Carbon

    Directory of Open Access Journals (Sweden)

    LIU Hao

    2016-07-01

    Full Text Available The microstructure of carbon/carbon(C/C composites with different matrix carbon was studied by polarized light microscopy (PLM, scanning electron microscopy (SEM, transmission electron microscopy (TEM and XRD techniques respectively. PLM results indicate that the different matrix carbon exhibits different optical reactivity, and the average optical reactivity is gradually enhanced from normal pitch carbon, smooth laminar of pyrocarbon, rough laminar of pyrocarbon to mesophase pitch carbon; SEM results show that the normal pitch carbon is mainly of grapy structure, the pyrocarbon exhibits like-crinkle lamellar structure, while the mesophase pitch carbon exhibits lamellar banded structure with different shapes. Under HRTEM, the lattice fringes of the mesophase pitch carbon are arranged regularly, is a long range ordered crystal structure, and the preferred orientation is high. The degree of the graphite and the interlayer spacing of the material B (mesophase pitch-based C/C composites are better than that of the material D (pyrocarbon-based C/C composites.

  12. Dynamic analysis of C/C composite finger seal

    Directory of Open Access Journals (Sweden)

    Chen Guoding

    2014-06-01

    Full Text Available A seal device as an important component of aeroengines has decisive influence on performance, reliability, and working life of aeroengines. With the development of aeroengines, demands on the performance characteristics of seal devices are made strictly. Finger seal as a novel kind of sealing device, recently attracts more and more attentions in academic circles and engineering fields at home and abroad. Research on finger seals has been extensively developed, especially on leakage and wear performances under dynamic conditions. However, it is a pity that the work on finger seals has been limited with a single approach that is improving the performance by structural optimization; in addition, the technology of dynamic analysis on finger seals is weak. Aiming at the problems mentioned above, a distributed mass equivalent dynamic model of finger seals considering the coupling effect of overlaid laminates is established in the present paper, the dynamic performance of 2.5 dimension C/C composite finger seal is analyzed with the model, and then the effects of fiber bundle density and fiber bundle preparation direction on finger seal’s dynamic performance are discussed, as well as compared with those of Co-based alloy finger seal. The current work is about dynamic analysis of finger seals and application of C/C composite in this paper may have much academic significance and many engineering values for improving research level of finger seal dynamics and exploring feasibility of C/C composite being used for finger seals.

  13. C.C.D. Readout Of A Picosecond Streak Camera With An Intensified C.C.D.

    Science.gov (United States)

    Lemonier, M.; Richard, J. C.; Cavailler, C.; Mens, A.; Raze, G.

    1985-02-01

    This paper deals with a digital streak camera readout device. The device consists in a low light level television camera made of a solid state C.C.D. array coupled to an image intensifier associated to a video-digitizer coupled to a micro-computer system. The streak camera images are picked-up as a video signal, digitized and stored. This system allows the fast recording and the automatic processing of the data provided by the streak tube. Starting from the output screen of the streak camera, the constitutive elements are : - A fiber optic taper (A.O. Scientific Instruments) set in contact with the fiber optic output window of the streak tube achieves the image demagnification ; - A double proximity focused image intensifier (RTC - XX1410 SP) achieves the bright-ness amplification without any distortion ; - A second fiber optic taper achieves the dimensional matching between intensifier output and C.C.D. sensitive area ;

  14. C-C bond formation and related reactions at the CNC backbone in (smif)FeX (smif = 1,3-di-(2-pyridyl)-2-azaallyl): dimerizations, 3 + 2 cyclization, and nucleophilic attack; transfer hydrogenations and alkyne trimerization (X = N(TMS)2, dpma = (di-(2-pyridyl-methyl)-amide)).

    Science.gov (United States)

    Frazier, Brenda A; Williams, Valerie A; Wolczanski, Peter T; Bart, Suzanne C; Meyer, Karsten; Cundari, Thomas R; Lobkovsky, Emil B

    2013-03-18

    Molecular orbital analysis depicts the CNC(nb) backbone of the smif (1,3-di-(2-pyridyl)-2-azaallyl) ligand as having singlet diradical and/or ionic character where electrophilic or nucleophilic attack is plausible. Reversible dimerization of (smif)Fe{N(SiMe3)2} (1) to [{(Me3Si)2N}Fe]2(μ-κ(3),κ(3)-N,py2-smif,smif) (2) may be construed as diradical coupling. A proton transfer within the backbone-methylated, and o-pyridine-methylated smif of putative ((b)Me2(o)Me2smif)FeN(SiMe3)2 (8) provides a route to [{(Me3Si)2N}Fe]2(μ-κ(4),κ(4)-N,py2,C-((b)Me,(b)CH2,(o)Me2(smif)H))2 (9). A 3 + 2 cyclization of ditolyl-acetylene occurs with 1, leading to the dimer [{2,5-di(pyridin-2-yl)-3,4-di-(p-tolyl-2,5-dihydropyrrol-1-ide)}FeN(SiMe3)2]2 (11), and the collateral discovery of alkyne cyclotrimerization led to a brief study that identified Fe(N(SiMe3)2(THF) as an effective catalyst. Nucleophilic attack by (smif)2Fe (13) on (t)BuNCO and (2,6-(i)Pr2C6H3)NCO afforded (RNHCO-smif)2Fe (14a, R = (t)Bu; 14b, 2,6-(i)PrC6H3). Calculations suggested that (dpma)2Fe (15) would favorably lose dihydrogen to afford (smif)2Fe (13). H2-transfer to alkynes, olefins, imines, PhN═NPh, and ketones was explored, but only stoichiometric reactions were affected. Some physical properties of the compounds were examined, and X-ray structural studies on several dinuclear species were conducted.

  15. Detection of bond formations by DNA-programmed chemical reactions and PCR amplification.

    Science.gov (United States)

    Li, Yizhou; Zhang, Mingda; Zhang, Chi; Li, Xiaoyu

    2012-10-04

    A system capable of performing both DNA-templated chemical reactions and detection of bond formations is reported. Photocleavable DNA templates direct reactions. Products from bond-forming events re-ligate original templates, amplifiable by PCR, therefore distinguishing bond formation from background. This system provides a novel approach for discovering potential new chemical reactions.

  16. Mirrors fabricated with slightly oxidized C/C composites

    Science.gov (United States)

    Wang, Yongjie; Xu, Liang; Ding, Jiaoteng; Xie, Yongjie; Ma, Zhen

    2016-10-01

    Up to now, traditional materials, such as glass, metal and SiC ceramic, gradually begin to be unsatisfied development of the future mirrors. Designable carbon fiber reinforced composites became optimized material for large aperture lightweight mirrors. Carbon/carbon composites exhibit low thermal expansion and no moisture-absorption expansion problem, therefore, they get particular attention in the space reflector field. Ni was always employed as optical layer in the mirror, however, the coating behaved poor bond with substrate and often peeled off during optical processing. In order to solve this problem, slight oxidation was carried on the C/C composites before Ni plated. The Ni coating exhibited stronger coherence and better finish performance. Finally, a 100mm diameter plane mirror was successful fabricated.

  17. Deformation microstructure and orientation of F.C.C. crystals

    DEFF Research Database (Denmark)

    Liu, Q.; Hansen, N.

    1995-01-01

    that dependent on the crystallographic orientation of the crystal the subdividing boundaries may be nearly parallel to slip planes or they may have a non-crystallographic orientation. This difference is discussed on the basis of an analysis of potential slip planes identified by a Schmid factor analysis.......The effect of crystallographic orientation on the microstructural evolution in f.c.c. metals with medium to high stacking fault energy is analyzed. This analysis is based on a literature review of the behaviour of single crystals and polycrystals supplemented with an experimental study of cold......-rolled pure aluminium. It is generally observed that all crystallites subdivide during deformation into cell blocks and cells bounded by rotation dislocation boundaries. In general the boundaries have a macroscopic orientation with respect to the geometry of the specimen. A crystallographic analysis shows...

  18. Pd nanoclusters in C-C coupling reaction: proof of leaching

    NARCIS (Netherlands)

    Thathagar, Mehul B.; ten Elshof, Johan E.; Rothenberg, Gadi

    2006-01-01

    A simple experiment based on exclusion of Pd nanoclusters was used to identify the true catalytic species in cluster-catalyzed Heck cross-couplings. A special reactor was used in which two compartments are separated by a nanoporous membrane that allows the passage of Pd atoms and ions but not of Pd

  19. The mechanism of hydrocarbon oxygenate reforming: C-C bond scission, carbon formation, and noble-metal-free oxide catalysts.

    Science.gov (United States)

    Lykhach, Yaroslava; Neitzel, Armin; Ševčíková, Klára; Johánek, Viktor; Tsud, Nataliya; Skála, Tomáš; Prince, Kevin C; Matolín, Vladimír; Libuda, Jörg

    2014-01-01

    Towards a molecular understanding of the mechanism behind catalytic reforming of bioderived hydrocarbon oxygenates, we explore the C-C bond scission of C2 model compounds (acetic acid, ethanol, ethylene glycol) on ceria model catalysts of different complexity, with and without platinum. Synchrotron photoelectron spectroscopy reveals that the reaction pathway depends very specifically on both the reactant molecule and the catalyst surface. Whereas C-C bond scission on Pt sites and on oxygen vacancies involves intermittent surface carbon species, the reaction occurs without any carbon formation and deposition for ethylene glycol on CeO2(111). Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Silicon-based C–N Cross-coupling Reaction

    National Research Council Canada - National Science Library

    Shimizu, Kenta; Minami, Yasunori; Goto, Osamu; Ikehira, Hideyuki; Hiyama, Tamejiro

    2014-01-01

    Palladium-catalyzed C–N bond-forming cross-coupling reaction of N-trimethylsilylamines with aryl bromides and chlorides is found to proceed in the presence of a fluoride activator in 1,3-dimethyl-2-imidazolidinone (DMI...

  1. Formation of a 1D-polymeric chain of Hg building blocks through C-C coupling under ambient conditions.

    Science.gov (United States)

    Mobin, Shaikh M; Mishra, Veenu; Ram, Priti; Birla, Anil; Mathur, Pradeep

    2013-08-14

    A novel C-C coupled 1D-polymeric chain (1) is obtained by reaction of HgCl2 and hmp-H (2-(2-hydroxymethyl pyridine)) (1 : 1) in MeOH at ambient temperature. However, a new class of μ-oxo and μ-chloro bridged polymers (2) has been obtained by altering the metal : ligand ratio to 1 : 2.

  2. C-C Coupling on Single-Atom-Based Heterogeneous Catalyst.

    Science.gov (United States)

    Zhang, Xiaoyan; Sun, Zaicheng; Wang, Bin; Tang, Yu; Nguyen, Luan; Li, Yuting; Tao, Franklin Feng

    2018-01-24

    Compared to homogeneous catalysis, heterogeneous catalysis allows for ready separation of products from the catalyst and thus reuse of the catalyst. C-C coupling is typically performed on a molecular catalyst which is mixed with reactants in liquid phase during catalysis. This homogeneous mixing at a molecular level in the same phase makes separation of the molecular catalyst extremely challenging and costly. Here we demonstrated that a TiO 2 -based nanoparticle catalyst anchoring singly dispersed Pd atoms (Pd 1 /TiO 2 ) is selective and highly active for more than 10 Sonogashira C-C coupling reactions (R≡CH + R'X → R≡R'; X = Br, I; R' = aryl or vinyl). The coupling between iodobenzene and phenylacetylene on Pd 1 /TiO 2 exhibits a turnover rate of 51.0 diphenylacetylene molecules per anchored Pd atom per minute at 60 °C, with a low apparent activation barrier of 28.9 kJ/mol and no cost of catalyst separation. DFT calculations suggest that the single Pd atom bonded to surface lattice oxygen atoms of TiO 2 acts as a site to dissociatively chemisorb iodobenzene to generate an intermediate phenyl, which then couples with phenylacetylenyl bound to a surface oxygen atom. This coupling of phenyl adsorbed on Pd 1 and phenylacetylenyl bound to O ad of TiO 2 forms the product molecule, diphenylacetylene.

  3. The role of electrophilic species in the Fischer-Tropsch reaction.

    Science.gov (United States)

    Maitlis, Peter M; Zanotti, Valerio

    2009-04-07

    The heterogeneously catalysed Fischer-Tropsch (FT) synthesis converts syngas (CO+H2) into long chain hydrocarbons and is a key step in the economically important transformation of natural gas, coal, or biomass into liquid fuels, such as diesel. Catalyst surface studies indicate that the FT reaction starts when CO is activated at imperfections on the surfaces of late transition metals (Fe, Ru, Co, or Rh) and at interfaces with "islands" of promoters (Lewis acid oxides such as alumina or titania). Activation involves CO cleavage to generate a surface carbide, C(ad), which is sequentially hydrogenated to CHx(ad) species (x=1-4). An overview of practical aspects of the FT synthesis is followed by a discussion of the chief mechanisms that have been proposed for the formation of 1-alkenes by polymerisation of surface C1 species. These mechanisms have traditionally postulated rather non-polar intermediates, such as CH2(ad) and CH3(ad). However, electrophiles and nucleophiles are well-known to play key roles in the reactions of organic and organometallic compounds, and also in many reactions homogeneously catalysed by soluble metal complexes, including olefin polymerisation. We have now extended these concepts to the Fischer-Tropsch reaction, and show that the polymerisation reactions at polarising surfaces, such as oxide-metal interfaces, can be understood if the reactive chain carrier is an electrophilic species, such as the cationic methylidyne, CH(delta+)(ad). It is proposed that the key coupling step in C-C bond formation involves the interaction of the electrophilic methylidyne with an alkylidene (RCH(ad), R=H, alkyl), followed by an H-transfer to generate the homologous alkylidene: CHdelta+(ad)+RCH(ad)-->RCHCH(ad) and RCHCH(ad)+H(ad)-->RCH2CH(ad). If the reactions occur on non-polarising surfaces, an alternative C-C bond forming reaction such as the alkenyl+methylene, RCH=CH(ad)+CH2(ad)-->RCH=CHCH2(ad), can take place. This approach explains important aspects of the

  4. Dilepton analysis in the HADES spectrometer for C+C at 2 A GeV

    Science.gov (United States)

    Bielcik, J.; Agakishiev, G.; Agodi, C.; Alvarez-Pol, H.; Balanda, A.; Bellia, G.; Böhmer, M.; Boyard, J. L.; Braun-Munzinger, P.; Chernenko, S.; Christ, T.; Coniglione, R.; Djeridi, R.; Dohrmann, F.; Durán, I.; Eberl, T.; Fabbietti, L.; Fateev, O.; Finocchiaro, P.; Friese, J.; Fröhlich, I.; Garzón, J. A.; Gernhäuser, R.; Golubeva, M.; González-Daz, D.; Grosse, E.; Guber, F.; Hennino, T.; Hlavac, S.; Holzmann, R.; Ierusalimov, A.; Iori, I.; Jaskula, M.; Jurkovic, M.; Kämpfer, B.; Kanaki, K.; Karavicheva, T.; Koenig, I.; Koenig, W.; Kolb, B. W.; Kottel, R.; Kotulic-Bunta, J.; Krücken, R.; Kugler, A.; Kühn, W.; Kulessa, R.; Kurepin, A.; Lang, S.; Lehnert, J.; Maiolino, C.; Markert, J.; Metag, V.; Mousa, J.; Münch, M.; Müntz, C.; Naumann, L.; Novotny, R.; Novotny, J.; Otwinowski, J.; Pachmayer, Y. C.; Pant, L. M.; Pechenov, V.; Pérez, T.; Pietraszko, J.; Pleskac, R.; Pospísil, V.; Przygoda, W.; Rabin, N.; Ramstein, B.; Reshetin, A.; Ritman, J.; Roy-Stephan, M.; Rustamov, A.; Sadovsky, A.; Sailer, B.; Salabura, P.; Sánchez, M.; Sapienza, P.; Schmah, A.; Simon, R.; Smolyankin, V.; Smykov, L.; Spataro, S.; Spruck, B.; Stroebele, H.; Stroth, J.; Sturm, C.; Sudol, M.; Tlusty, P.; Toia, A.; Traxler, M.; Tsertos, H.; Wagner, V.; Wisniowski, M.; Wojcik, T.; Wüstenfeld, J.; Zanevsky, Y.; Zovinec, D.; Zumbruch, P.

    2005-04-01

    The high-acceptance dielectron spectrometer (HADES) has become operational at GSI Darmstadt. The primary physics programme is to study in-medium changes of light vector mesons via their e+e- decays. The methods of dilepton signal reconstruction in the HADES spectrometer and preliminary dilepton spectra for C+C reactions at 2 A GeV are presented. In the signal reconstruction, particularly important is the reduction of the huge combinatorial background arising from e+e- combinations of leptons from gamma conversion in materials with other leptons in the collision. The purity of the dilepton signal is determined by using GEANT simulations with the full HADES geometry and a realistic detector response.

  5. Comparing Amide-Forming Reactions Using Green Chemistry Metrics in an Undergraduate Organic Laboratory

    Science.gov (United States)

    Fennie, Michael W.; Roth, Jessica M.

    2016-01-01

    In this laboratory experiment, upper-division undergraduate chemistry and biochemistry majors investigate amide-bond-forming reactions from a green chemistry perspective. Using hydrocinnamic acid and benzylamine as reactants, students perform three types of amide-forming reactions: an acid chloride derivative route; a coupling reagent promoted…

  6. Synthesis of SiC decorated carbonaceous nanorods and its hierarchical composites Si@SiC@C for high-performance lithium ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Chundong [School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074 (China); Center of Super-Diamond and Advanced Films (COSDAF), Department of Physics and Materials Science, City University of Hong Kong, Hong Kong SAR (China); Li, Yi, E-mail: liyi@suda.edu.cn [College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou (China); Center of Super-Diamond and Advanced Films (COSDAF), Department of Physics and Materials Science, City University of Hong Kong, Hong Kong SAR (China); Ostrikov, Kostya [School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, Brisbane, Queensland 4000 (Australia); Plasma Nanoscience, Industrial Innovation Program, CSIRO Manufacturing Flagship, Lindfield, New South Wales 2070 (Australia); Yang, Yonggang [College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou (China); Zhang, Wenjun, E-mail: apwjzh@cityu.edu.hk [Center of Super-Diamond and Advanced Films (COSDAF), Department of Physics and Materials Science, City University of Hong Kong, Hong Kong SAR (China)

    2015-10-15

    SiC- based nanomaterials possess superior electric, thermal and mechanical properties. However, due to the tricky synthesis process, which needs to be carried out under high temperature with multi-step reaction procedures, the further application is dramatically limited. Herein, a simple as well as a controllable approach is proposed for synthesis of SiC- based nanostructures under low temperature. Phenyl-bridged polysilsesquioxane was chosen as the starting material to react with magnesium at 650 °C, following which SiC@C nanocomposites were finally obtained, and it maintains the original bent rod-like architecture of polysilsesquioxanes. The possible formation process for the nanocomposites can proposed as well. The electrochemical behaviour of nanocomposites was accessed, verifying that the synthesized SiC@C nanocomposites deliver good electrochemical performance. Moreover, SiC@C also shows to be a promising scaffold in supporting Si thin film electrode in achieving stable cycling performance in lithium ion batteries. - Highlights: • SiC@C bent nanorods were synthesized with a magnesium reaction approach. • Carbon nanorod spines studded with ultrafine β-SiC nanocrystallines was realized. • The synthesized SiC@C keeps the original rod-like structure of polysilsesquioxanes. • The possible formation process for the nanocomposites was analysed and proposed. • Si@SiC@C nanocomposites reveal good electrochemical performance in LIBs.

  7. Aliphatic C-C Bond Cleavage in α-Hydroxy Ketones by a Dioxygen-Derived Nucleophilic Iron-Oxygen Oxidant.

    Science.gov (United States)

    Bhattacharya, Shrabanti; Rahaman, Rubina; Chatterjee, Sayanti; Paine, Tapan K

    2017-03-17

    A nucleophilic iron-oxygen oxidant, formed in situ in the reaction between an iron(II)-benzilate complex and O2 , oxidatively cleaves the aliphatic C-C bonds of α-hydroxy ketones. In the cleavage reaction, α-hydroxy ketones without any α-C-H bond afford a 1:1 mixture of carboxylic acid and ketone. Isotope labeling studies established that one of the oxygen atoms from dioxygen is incorporated into the carboxylic acid product. Furthermore, the iron(II) complex cleaves an aliphatic C-C bond of 17-α-hydroxyprogesterone affording androstenedione and acetic acid. The O2 -dependent aliphatic C-C bond cleavage of α-hydroxy ketones containing no α-C-H bond bears similarity to the lyase activity of the heme enzyme, cytochrome P450 17A1 (CYP17A1). © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Influence of applied load on wear behavior of C/C-Cu composites under electric current

    Directory of Open Access Journals (Sweden)

    Jian Yin

    2017-04-01

    Full Text Available Using carbon fiber needled fabrics with Cu-mesh and graphite powder as the preform, Cu mesh modified carbon/carbon(C/C-Cu composites were prepared by chemical vapor deposition (CVD with C3H6 and impregnation-carbonization (I/C with furan resin. C/C composites, as a comparison, were also prepared. Their microstructures and wear morphologies were observed by optical microscopy (OM and scanning electron microscope (SEM, respectively. Wear behavior of C/C and C/C-Cu composites under different applied loads were investigated on a pin-on-disc wear tester. The results show that Cu meshes are well dispersed and pyrolytic carbon is in rough laminar structure. Both C/C and C/C-Cu composites had good wear properties. The current-carrying capacity of C/C-Cu composites increases and the arc discharge is hindered as the applied load increases from 40 N to 80 N. Both C/C and C/C-Cu composites had good wear properties. The mass wear rate of C/C-Cu composites under 80 N was only 4.2% of that under 60 N. In addition, C/C-Cu composites represent different wear behaviors because wear mechanisms of arc erosion, abrasive wear, adhesive wear, and oxidative wear are changing under different applied loads.

  9. Recent advances in N-heterocyclic carbene (NHC-catalysed benzoin reactions

    Directory of Open Access Journals (Sweden)

    Rajeev S. Menon

    2016-03-01

    Full Text Available N-Heterocyclic carbenes (NHCs have emerged as a powerful class of organocatalysts that mediate a variety of organic transformations. The Benzoin reaction constitutes one of the earliest known carbon–carbon bond-forming reactions catalysed by NHCs. The rapid growth of NHC catalysis in general has resulted in the development of a variety of benzoin and benzoin-type reactions. An overview of such NHC-catalysed benzoin reactions is presented.

  10. Measurements of psi -> K-Lambda(Xi)over-bar(+) + c.c. and psi -> gamma K-Lambda(Xi)over-bar(+) + c.c.

    NARCIS (Netherlands)

    Ablikim, M.; Achasov, M. N.; Ai, X. C.; Albayrak, O.; Albrecht, M.; Ambrose, D. J.; Amoroso, A.; An, F. F.; An, Q.; Bai, J. Z.; Ferroli, R. Baldini; Ban, Y.; Bennett, D. W.; Bennett, J. V.; Bertani, M.; Bettoni, D.; Bian, J. M.; Bianchi, F.; Boger, E.; Bondarenko, O.; Boyko, I.; Briere, R. A.; Cai, H.; Cai, X.; Cakir, O.; Calcaterra, A.; Cao, G. F.; Cetin, S. A.; Chang, J. F.; Chelkov, G.; Chen, G.; Chen, H. S.; Chen, H. Y.; Chen, J. C.; Chen, M. L.; Chen, S. J.; Chen, X.; Chen, X. R.; Chen, Y. B.; Cheng, H. P.; Chu, X. K.; Cibinetto, G.; Cronin-Hennessy, D.; Dai, H. L.; Dai, J. P.; Dbeyssi, A.; Dedovich, D.; Deng, Z. Y.; Denig, A.; Denysenko, I.; Destefanis, M.; De Mori, F.; Ding, Y.; Dong, C.; Dong, J.; Dong, L. Y.; Dong, M. Y.; Duan, S. X.; Duan, P. F.; Fan, J. Z.; Fang, J.; Fang, S. S.; Fang, X.; Fang, Y.; Fava, L.; Feldbauer, F.; Felici, G.; Feng, C. Q.; Fioravanti, E.; Fritsch, M.; Fu, C. D.; Gao, Q.; Gao, X. Y.; Gao, Y.; Gao, Z.; Garzia, I.; Geng, C.; Goetzen, K.; Gong, W. X.; Gradl, W.; Greco, M.; Gu, M. H.; Gu, Y. T.; Guan, Y. H.; Guo, A. Q.; Guo, L. B.; Guo, Y.; Guo, Y. P.; Haddadi, Z.; Hafner, A.; Han, S.; Han, Y. L.; Hao, X. Q.; Harris, F. A.; He, K. L.; He, Z. Y.; Held, T.; Heng, Y. K.; Hou, Z. L.; Hu, C.; Hu, H. M.; Hu, J. F.; Hu, T.; Hu, Y.; Huang, G. M.; Huang, G. S.; Huang, H. P.; Huang, J. S.; Huang, X. T.; Huang, Y.; Hussain, T.; Ji, Q.; Ji, Q. P.; Ji, X. B.; Ji, X. L.; Jiang, L. L.; Jiang, L. W.; Jiang, X. S.; Jiao, J. B.; Jiao, Z.; Jin, D. P.; Jin, S.; Johansson, T.; Julin, A.; Kalantar-Nayestanaki, N.; Kang, X. L.; Kang, X. S.; Kavatsyuk, M.; Ke, B. C.; Kliemt, R.; Kloss, B.; Kolcu, O. B.; Kopf, B.; Kornicer, M.; Kuehn, W.; Kupsc, A.; Lai, W.; Lange, J. S.; Lara, M.; Larin, P.; Leng, C.; Li, C. H.; Li, Cheng; Li, D. M.; Li, F.; Li, G.; Li, H. B.; Li, J. C.; Li, Jin; Li, K.; Li, K.; Li, Lei; Li, P. R.; Li, T.; Li, W. D.; Li, W. G.; Li, X. L.; Li, X. M.; Li, X. N.; Li, X. Q.; Li, Z. B.; Liang, H.; Liang, Y. F.; Liang, Y. T.; Liao, G. R.; Lin, D. X.; Liu, B. J.; Liu, C. X.; Liu, F. H.; Liu, Fang; Liu, Feng; Liu, H. B.; Liu, H. H.; Liu, H. H.; Liu, H. M.; Liu, J.; Liu, J. P.; Liu, J. Y.; Liu, K.; Liu, K. Y.; Liu, L. D.; Liu, P. L.; Liu, Q.; Liu, S. B.; Liu, X.; Liu, X. X.; Liu, Y. B.; Liu, Z. A.; Liu, Zhiqiang; Liu, Zhiqing; Loehner, H.; Lou, X. C.; Lu, H. J.; Lu, J. G.; Lu, R. Q.; Lu, Y.; Lu, Y. P.; Luo, C. L.; Luo, M. X.; Luo, T.; Luo, X. L.; Lv, M.; Lyu, X. R.; Ma, F. C.; Ma, H. L.; Ma, L. L.; Ma, Q. M.; Ma, S.; Ma, T.; Ma, X. N.; Ma, X. Y.; Maas, F. E.; Maggiora, M.; Malik, Q. A.; Mao, Y. J.; Mao, Z. P.; Marcello, S.; Messchendorp, J. G.; Min, J.; Min, T. J.; Mitchell, R. E.; Mo, X. H.; Mo, Y. J.; Morales, C. Morales; Moriya, K.; Muchnoi, N. Yu.; Muramatsu, H.; Nefedov, Y.; Nerling, F.; Nikolaev, I. B.; Ning, Z.; Nisar, S.; Niu, S. L.; Niu, X. Y.; Olsen, S. L.; Ouyang, Q.; Pacetti, S.; Patteri, P.; Pelizaeus, M.; Peng, H. P.; Peters, K.; Pettersson, J.; Ping, J. L.; Ping, R. G.; Poling, R.; Pu, Y. N.; Qi, M.; Qian, S.; Qiao, C. F.; Qin, L. Q.; Qin, N.; Qin, X. S.; Qin, Y.; Qin, Z. H.; Qiu, J. F.; Rashid, K. H.; Redmer, C. F.; Ren, H. L.; Ripka, M.; Rong, G.; Ruan, X. D.; Santoro, V.; Sarantsev, A.; Savrie, M.; Schoenning, K.; Schumann, S.; Shan, W.; Shao, M.; Shen, C. P.; Shen, P. X.; Shen, X. Y.; Sheng, H. Y.; Song, W. M.; Song, X. Y.; Sosio, S.; Spataro, S.; Sun, G. X.; Sun, J. F.; Sun, S. S.; Sun, Y. J.; Sun, Y. Z.; Sun, Z. J.; Sun, Z. T.; Tang, C. J.; Tang, X.; Tapan, I.; Thorndike, E. H.; Tiemens, M.; Toth, D.; Ullrich, M.; Uman, I.; Varner, G. S.; Wang, B.; Wang, B. L.; Wang, D.; Wang, D. Y.; Wang, K.; Wang, L. L.; Wang, L. S.; Wang, M.; Wang, P.; Wang, P. L.; Wang, Q. J.; Wang, S. G.; Wang, W.; Wang, X. F.; Wang, Y. D.; Wang, Y. F.; Wang, Y. Q.; Wang, Z.; Wang, Z. G.; Wang, Z. H.; Wang, Z. Y.; Weber, T.; Wei, D. H.; Wei, J. B.; Weidenkaff, P.; Wen, S. P.; Wiedner, U.; Wolke, M.; Wu, L. H.; Wu, Z.; Xia, L. G.; Xia, Y.; Xiao, D.; Xiao, Z. J.; Xie, Y. G.; Xiu, Q. L.; Xu, G. F.; Xu, L.; Xu, Q. J.; Xu, Q. N.; Xu, X. P.; Yan, L.; Yan, W. B.; Yan, W. C.; Yan, Y. H.; Yang, H. X.; Yang, L.; Yang, Y.; Yang, Y. X.; Ye, H.; Ye, M.; Ye, M. H.; Yin, J. H.; Yu, B. X.; Yu, C. X.; Yu, H. W.; Yu, J. S.; Yuan, C. Z.; Yuan, W. L.; Yuan, Y.; Yuncu, A.; Zafar, A. A.; Zallo, A.; Zeng, Y.; Zhang, B. X.; Zhang, B. Y.; Zhang, C.; Zhang, C. C.; Zhang, D. H.; Zhang, H. H.; Zhang, H. Y.; Zhang, J. J.; Zhang, J. L.; Zhang, J. Q.; Zhang, J. W.; Zhang, J. Y.; Zhang, J. Z.; Zhang, K.; Zhang, L.; Zhang, S. H.; Zhang, X. Y.; Zhang, Y.; Zhang, Y. H.; Zhang, Y. T.; Zhang, Z. H.; Zhang, Z. P.; Zhang, Z. Y.; Zhao, G.; Zhao, H. S.; Zhao, J. W.; Zhao, J. Y.; Zhao, J. Z.; Zhao, Lei; Zhao, Ling; Zhao, M. G.; Zhao, Q.; Zhao, Q. W.; Zhao, S. J.; Zhao, T. C.; Zhao, Y. B.; Zhao, Z. G.; Zhemchugov, A.; Zheng, B.; Zheng, J. P.; Zheng, W. J.; Zheng, Y. H.; Zhong, B.; Zhou, L.; Zhou, Li; Zhou, X.; Zhou, X. K.; Zhou, X. R.; Zhou, X. Y.; Zhu, K.; Zhu, K. J.; Zhu, S.; Zhu, X. L.; Zhu, Y. C.; Zhu, Y. S.; Zhu, Z. A.; Zhuang, J.; Zotti, L.; Zou, B. S.; Zou, J. H.

    2015-01-01

    Using a sample of 1.06 x 10(8) psi(3686) events produced in e(+)e(-) collisions at root s = 3.686 GeV and collected with the BESIII detector at the BEPCII collider, we present studies of the decays psi(3686) -> K-Lambda(Xi) over bar (+) + c.c. and psi(3686) -> gamma K-Lambda(Xi) over bar (+) + c.c.

  11. Application of C/C composites to the combustion chamber of rocket engines. Part 1: Heating tests of C/C composites with high temperature combustion gases

    Science.gov (United States)

    Tadano, Makoto; Sato, Masahiro; Kuroda, Yukio; Kusaka, Kazuo; Ueda, Shuichi; Suemitsu, Takeshi; Hasegawa, Satoshi; Kude, Yukinori

    1995-04-01

    Carbon fiber reinforced carbon composite (C/C composite) has various superior properties, such as high specific strength, specific modulus, and fracture strength at high temperatures of more than 1800 K. Therefore, C/C composite is expected to be useful for many structural applications, such as combustion chambers of rocket engines and nose-cones of space-planes, but C/C composite lacks oxidation resistivity in high temperature environments. To meet the lifespan requirement for thermal barrier coatings, a ceramic coating has been employed in the hot-gas side wall. However, the main drawback to the use of C/C composite is the tendency for delamination to occur between the coating layer on the hot-gas side and the base materials on the cooling side during repeated thermal heating loads. To improve the thermal properties of the thermal barrier coating, five different types of 30-mm diameter C/C composite specimens constructed with functionally gradient materials (FGM's) and a modified matrix coating layer were fabricated. In this test, these specimens were exposed to the combustion gases of the rocket engine using nitrogen tetroxide (NTO) / monomethyl hydrazine (MMH) to evaluate the properties of thermal and erosive resistance on the thermal barrier coating after the heating test. It was observed that modified matrix and coating with FGM's are effective in improving the thermal properties of C/C composite.

  12. SnTe-TiC-C composites as high-performance anodes for Li-ion batteries

    Science.gov (United States)

    Son, Seung Yeon; Hur, Jaehyun; Kim, Kwang Ho; Son, Hyung Bin; Lee, Seung Geol; Kim, Il Tae

    2017-10-01

    Intermetallic SnTe composites dispersed in a conductive TiC/C hybrid matrix are synthesized by high-energy ball milling (HEBM). The electrochemical performances of the composites as potential anodes for Li-ion batteries are evaluated. The structural and morphological characteristics of the SnTe-TiC-C composites with various TiC contents are investigated by X-ray diffraction (XRD) and high-resolution transmission electron microscopy, which reveal that SnTe and TiC are uniformly dispersed in a carbon matrix. The electrochemical performance is significantly improved by introducing TiC to the SnTe-C composite; higher TiC contents result in better performances. Among the prepared composites, the SnTe-TiC (30%)-C and SnTe-TiC (40%)-C electrodes exhibit the best electrochemical performance, showing the reversible capacities of, respectively, 652 mAh cm-3 and 588 mAh cm-3 after 400 cycles and high rate capabilities with the capacity retentions of 75.4% for SnTe-TiC (30%)-C and 82.2% for SnTe-TiC (40%)-C at 10 A g-1. Furthermore, the Li storage reaction mechanisms of Te or Sn in the SnTe-TiC-C electrodes are confirmed by ex situ XRD.

  13. JACoW SIP4C/C++ at CERN - Status and lessons learned

    CERN Document Server

    Jensen, Steen; Dworak, Andrzej; Gourber-Pace, Marine; Hoguin, Frederic; Lauener, Joel; Locci, Frank; Sigerud, Katarina; Sliwinski, Wojciech

    2018-01-01

    After 4 years of promoting the Software Improvement Process for C/C++ (SIP4C/C++) initiative at CERN, we describe the current status for tools and procedures along with how they have been integrated into our environment. Based on feedback from four project teams, we present reasons for and against their adoption. Finally, we show how SIP4C/C++ has improved development and delivery processes as well as the first-line support of delivered products.

  14. cyclopropanation reaction with ketene

    Indian Academy of Sciences (India)

    Administrator

    Smith. 15. This has motivated a large number of research groups to develop new and wide-range methods to produce cyclopropanated products. Methylene insertion by a carbenoid species into the. C=C bond is one of the most widely used methods since the recognition of the Simmons–Smith reac- tion, which is a reaction ...

  15. Measurement of low-mass e + e - pair production in 1 and 2 A GeV C-C collision with HADES

    Science.gov (United States)

    Sudol, M.; Agakishiev, G.; Agodi, C.; Balanda, A.; Bellia, G.; Belver, D.; Belyaev, A.; Bielcik, J.; Blanco, A.; Bortolotti, A.; Boyard, J. L.; Braun-Munzinger, P.; Cabanelas, P.; Chernenko, S.; Christ, T.; Coniglione, R.; Destefanis, M.; Díaz, J.; Dohrmann, F.; Durán, I.; Dybczak, A.; Eberl, T.; Fabbietti, L.; Fateev, O.; Ferreira-Marques, R.; Finocchiaro, P.; Fonte, P.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzón, J. A.; Gernhäuser, R.; Gil, A.; Gilardi, C.; Golubeva, M.; González-Díaz, D.; Grosse, E.; Guber, F.; Heilmann, M.; Heinz, T.; Hennino, T.; Holzmann, R.; Ierusalimov, A.; Iori, I.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Kanaki, K.; Karavicheva, T.; Kirschner, D.; Koenig, I.; Koenig, W.; Kolb, B. W.; Kotte, R.; Kozuch, A.; Krása, A.; Křížek, F.; Krücken, R.; Kühn, W.; Kugler, A.; Kurepin, A.; Lamas-Valverde, J.; Lang, S.; Lange, J. S.; Lapidus, K.; Lopes, L.; Lorenz, M.; Maier, L.; Maiolino, C.; Mangiarotti, A.; Marín, J.; Markert, J.; Metag, V.; Michalska, B.; Michel, J.; Morinière, E.; Mousa, J.; Münch, M.; Müntz, C.; Naumann, L.; Novotny, R.; Otwinowski, J.; Pachmayer, Y. C.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Pérez Cavalcanti, T.; Piattelli, P.; Pietraszko, J.; Pospíšil, V.; Przygoda, W.; Ramstein, B.; Reshetin, A.; Roy-Stephan, M.; Rustamov, A.; Sadovsky, A.; Sailer, B.; Salabura, P.; Sapienza, P.; Schmah, A.; Schroeder, C.; Schwab, E.; Simon, R.; Sobolev, Yu. G.; Spataro, S.; Spruck, B.; Ströbele, H.; Stroth, J.; Sturm, C.; Tarantola, A.; Teilab, K.; Tlustý, P.; Traxler, M.; Trebacz, R.; Tsertos, H.; Wagner, V.; Weber, M.; Wisniowski, M.; Wojcik, T.; Wüstenfeld, J.; Yurevich, S.; Zanevsky, Y.; Zhou, P.; Zumbruch, P.

    2009-07-01

    HADES is a secondary generation experiment operated at GSI Darmstadt with the main goal to study dielectron production in proton, pion and heavy ion induced reactions. The first part of the HADES mission is to reinvestigate the puzzling pair excess measured by the DLS collaboration in C + C and Ca + Ca collisions at 1 A GeV. For this purpose dedicated measurements with the C + C system at 1 and 2 A GeV were performed. The pair excess above a cocktail of free hadronic decays has been extracted and compared to the one measured by DLS. Furthermore, the excess is confronted with predictions of various model calculations.

  16. Thermoelectric properties of SiC/C composites from wood charcoal by pulse current sintering

    NARCIS (Netherlands)

    Fujisawa, M; Hata, T; Bronsveld, P; Castro, [No Value; Tanaka, F; Kikuchi, H; Imamura, Y

    2005-01-01

    SiC/C composites were investigated by sintering a mix of wood charcoal and SiO2 powder (32-45 mu m) at 1400, 1600 and 1800 degrees C under N-2 atmosphere with a pulse current sintering method. Thermoelectric properties of SiC/C composites were investigated by measuring the Seebeck coefficient and

  17. Observation of the decay psi -> Lambda(Sigma)over-bar(+/-) pi(-/+) + c.c

    NARCIS (Netherlands)

    Ablikim, M.; Achasov, M. N.; Ai, X. C.; Albayrak, O.; Ambrose, D. J.; An, F. F.; An, Q.; Bai, J. Z.; Ferroli, R. Baldini; Ban, Y.; Bennett, J. V.; Bertani, M.; Bian, J. M.; Boger, E.; Bondarenko, O.; Boyko, I.; Braun, S.; Briere, R. A.; Cai, H.; Cai, X.; Cakir, O.; Calcaterra, A.; Cao, G. F.; Cetin, S. A.; Chang, J. F.; Chelkov, G.; Chen, G.; Chen, H. S.; Chen, J. C.; Chen, M. L.; Chen, S. J.; Chen, X.; Chen, X. R.; Chen, Y. B.; Cheng, H. P.; Chu, X. K.; Chu, Y. P.; Cronin-Hennessy, D.; Dai, H. L.; Dai, J. P.; Dedovich, D.; Deng, Z. Y.; Denig, A.; Denysenko, I.; Destefanis, M.; Ding, W. M.; Ding, Y.; Dong, C.; Dong, J.; Dong, L. Y.; Dong, M. Y.; Du, S. X.; Fang, J.; Fang, S. S.; Fang, Y.; Fava, L.; Feng, C. Q.; Fu, C. D.; Fu, J. L.; Fuks, O.; Gao, Q.; Gao, Y.; Geng, C.; Goetzen, K.; Gong, W. X.; Gradl, W.; Greco, M.; Gu, M. H.; Gu, Y. T.; Guan, Y. H.; Guo, A. Q.; Guo, L. B.; Guo, T.; Guo, Y. P.; Guo, Y. P.; Han, Y. L.; Harris, F. A.; He, K. L.; He, M.; He, Z. Y.; Held, T.; Heng, Y. K.; Hou, Z. L.; Hu, C.; Hu, H. M.; Hu, J. F.; Hu, T.; Huang, G. M.; Huang, G. S.; Huang, J. S.; Huang, L.; Huang, X. T.; Hussain, T.; Ji, C. S.; Ji, Q.; Ji, Q. P.; Ji, X. B.; Ji, X. L.; Jiang, L. L.; Jiang, X. S.; Jiao, J. B.; Jiao, Z.; Jin, D. P.; Jin, S.; Jing, F. F.; Johansson, T.; Kalantar-Nayestanaki, N.; Kang, X. L.; Kavatsyuk, M.; Kloss, B.; Kopf, B.; Kornicer, M.; Kuehn, W.; Kupsc, A.; Lai, W.; Lange, J. S.; Lara, M.; Larin, P.; Leyhe, M.; Li, C. H.; Li, Cheng; Li, Cui; Li, D.; Li, D. M.; Li, F.; Li, G.; Li, H. B.; Li, J. C.; Li, K.; Li, K.; Li, Lei; Li, P. R.; Li, Q. J.; Li, T.; Li, W. D.; Li, W. G.; Li, X. L.; Li, X. N.; Li, X. Q.; Li, X. R.; Li, Z. B.; Liang, H.; Liang, Y. F.; Liang, Y. T.; Liao, G. R.; Lin, D. X.; Liu, B. J.; Liu, C. L.; Liu, C. X.; Liu, F. H.; Liu, Fang; Liu, Feng; Liu, H. B.; Liu, H. H.; Liu, H. M.; Liu, J.; Liu, J. P.; Liu, K.; Liu, K. Y.; Liu, P. L.; Liu, Q.; Liu, S. B.; Liu, X.; Liu, Y. B.; Liu, Z. A.; Liu, Zhiqiang; Liu, Zhiqing; Loehner, H.; Lou, X. C.; Lu, G. R.; Lu, H. J.; Lu, H. L.; Lu, J. G.; Lu, X. R.; Lu, Y.; Lu, Y. P.; Luo, C. L.; Luo, M. X.; Luo, T.; Luo, X. L.; Lv, M.; Ma, F. C.; Ma, H. L.; Ma, Q. M.; Ma, S.; Ma, T.; Ma, X. Y.; Maas, F. E.; Maggiora, M.; Malik, Q. A.; Mao, Y. J.; Mao, Z. P.; Messchendorp, J. G.; Min, J.; Min, T. J.; Mitchell, R. E.; Mo, X. H.; Moeini, H.; Morales, C. Morales; Moriya, K.; Muchnoi, N. Yu.; Nefedov, Y.; Nikolaev, I. B.; Ning, Z.; Nisar, S.; Niu, X. Y.; Olsen, S. L.; Ouyang, Q.; Pacetti, S.; Pelizaeus, M.; Peng, H. P.; Peters, K.; Ping, J. L.; Ping, R. G.; Poling, R.; Prencipe, E.; Qi, M.; Qian, S.; Qiao, C. F.; Qin, L. Q.; Qin, X. S.; Qin, Y.; Qin, Z. H.; Qiu, J. F.; Rashid, K. H.; Redmer, C. F.; Ripka, M.; Rong, G.; Ruan, X. D.; Sarantsev, A.; Schoenning, K.; Schumann, S.; Shan, W.; Shao, M.; Shen, C. P.; Shen, X. Y.; Sheng, H. Y.; Shepherd, M. R.; Song, W. M.; Song, X. Y.; Spataro, S.; Spruck, B.; Sun, G. X.; Sun, J. F.; Sun, S. S.; Sun, Y. J.; Sun, Y. Z.; Sun, Z. J.; Sun, Z. T.; Tang, C. J.; Tang, X.; Tapan, I.; Thorndike, E. H.; Toth, D.; Ullrich, M.; Uman, I.; Varner, G. S.; Wang, B.; Wang, D.; Wang, D. Y.; Wang, K.; Wang, L. L.; Wang, L. S.; Wang, M.; Wang, P.; Wang, P. L.; Wang, Q. J.; Wang, S. G.; Wang, W.; Wang, X. F.; Wang, Y. D.; Wang, Y. F.; Wang, Y. Q.; Wang, Z.; Wang, Z. G.; Wang, Z. H.; Wang, Z. Y.; Wei, D. H.; Wei, J. B.; Weidenkaff, P.; Wen, S. P.; Wiedner, U.; Wolke, M.; Wu, G. G.; Wu, L. H.; Wu, N.; Wu, W.; Wu, Z.; Xia, L. G.; Xia, Y.; Xiao, D.; Xiao, Z. J.; Xie, Y. G.; Xiu, Q. L.; Xu, G. F.; Xu, L.; Xu, Q. J.; Xu, Q. N.; Xu, X. P.; Xue, Z.; Yan, L.; Yan, W. B.; Yan, W. C.; Yan, Y. H.; Yang, H. X.; Yang, Y.; Yang, Y. X.; Ye, H.; Ye, M.; Ye, M. H.; Yu, B. X.; Yu, C. X.; Yu, H. W.; Yu, J. S.; Yu, S. P.; Yuan, C. Z.; Yuan, W. L.; Yuan, Y.; Zafar, A. A.; Zallo, A.; Zang, S. L.; Zeng, Y.; Zhang, B. X.; Zhang, B. Y.; Zhang, C.; Zhang, C. B.; Zhang, C. C.; Zhang, D. H.; Zhang, H. H.; Zhang, H. Y.; Zhang, J. J.; Zhang, J. L.; Zhang, J. Q.; Zhang, J. W.; Zhang, J. Y.; Zhang, J. Z.; Zhang, S. H.; Zhang, X. J.; Zhang, X. Y.; Zhang, Y.; Zhang, Y. H.; Zhang, Z. H.; Zhang, Z. P.; Zhang, Z. Y.; Zhao, G.; Zhao, J. W.; Zhao, Lei; Zhao, Ling; Zhao, M. G.; Zhao, Q.; Zhao, Q. W.; Zhao, S. J.; Zhao, T. C.; Zhao, X. H.; Zhao, Y. B.; Zhao, Z. G.; Zhemchugov, A.; Zheng, B.; Zheng, Y. H.; Zhong, B.; Zhou, L.; Zhou, Li; Zhou, X.; Zhou, X. K.; Zhou, X. R.; Zhou, X. Y.; Zhu, K.; Zhu, K. J.; Zhu, X. L.; Zhu, Y. C.; Zhu, Y. S.; Zhu, Z. A.; Zhuang, J.; Zou, B. S.; Zou, J. H.; Werner, M.J.; Zheng, J.P.

    2013-01-01

    Using a sample of 1:06 X 10(8) psi(3686) events collected with the BESIII detector, we present the first observation of the decays of psi(3686) -> Lambda(Sigma) over bar (+) pi(-) + c.c. and psi(3686) -> Lambda(Sigma) over bar (-) pi(+) + c.c. The branching fractions are measured to be B(psi(3686)

  18. C. C. Li (1912–2003): his science and his spirit

    Indian Academy of Sciences (India)

    Unknown

    Ching Chun Li passed away on 20 October 2003, in Pitts- burgh. He was an outstanding population geneticist, a wonderful teacher, and above all, a great human being. Devotion to work and humility were the hallmarks of. C. C. Li, who was known as C.C. to his contemporaries and colleagues, and as Dr Li to his students.

  19. 76 FR 44800 - Election of Reduced Research Credit Under Section 280C(c)(3)

    Science.gov (United States)

    2011-07-27

    ... [TD 9539] RIN 1545-BI09 Election of Reduced Research Credit Under Section 280C(c)(3) AGENCY: Internal... dates of applicability, see Sec. 1.280C- 4(c). FOR FURTHER INFORMATION CONTACT: David Selig, (202) 622... research credit under section 280C(c)(3). On July 16, 2009, a notice of proposed rulemaking (REG-130200-08...

  20. Thermodynamic and kinetic studies of the equilibration reaction between the sulfur and carbon bonded forms of a cobalt(III) complex with the ligands 2-aminoethyl-3-aminopropylsulfide and 1,1,1-tris(aminomethyl)ethane

    DEFF Research Database (Denmark)

    Springborg, J.; Kjellerup, S.; Kofod, Pauli

    1996-01-01

    A thermodn. and kinetic study of the equilibration between the Co-S bonded complex Co(tame)(S-aeaps)3+ and the Co-C bonded complex Co(tame)(C-aeaps)2+ is reported (tame = 1,1,1-tris(aminomethyl)ethane, aeaps = 2-aminoethyl-3-aminopropyl sulfide = 3-thiahexane-1,6-diamine and C-aeaps = 1,6-diamine...... the Co-alkyl complex gave complete loss of D. From the kinetic data it is estd. that the carbanion reacts with H2O 170 times faster than it is captured by Co(III)....

  1. Thermodynamic and kinetic studies of the equilibration reaction between the sulfur and carbon bonded forms of a cobalt(III) complex with the ligands 1,4,7-triazycyclononane and 1,4-diaza-7-thiacyclodecane

    DEFF Research Database (Denmark)

    Song, Y.S.; Becker, J.; Kofod, Pauli

    1996-01-01

    -sulfur complex to form the alkyl complex gave 100% loss of deuterium. It is concluded that the labile methylene proton is bound to the carbon atom which in the alkyl complex is bound to cobalt(III). From the kinetic data it is estd. that the carbanion reacts with water 270 times faster than it is captured......The new cyclic thioether 1,4-diaza-7-thiacyclodecane, dathicd, has been synthesized and used for the prepn. of the sulfur- and carbon-bonded cobalt(III) complexes: [Co(tacn)(S-dathicd)]Cl3.5H2O and [Co(tacn)(C-dathicd)](ClO4)2 (tacn, 1,4,7-triazacyclononane; C-dathicd, 1,4-diamino-7-thiacyclodecan...

  2. Controlling the ambiphilic nature of σ-arylpalladium intermediates in intramolecular cyclization reactions.

    Science.gov (United States)

    Solé, Daniel; Fernández, Israel

    2014-01-21

    The reactivity of main group organometallics, such as organolithium compounds (RLi) and Grignard reagents (RMgX), is quite straightforward. In these species the R group usually exhibits nucleophilic reactivity without any possibility of inducing electrophilic character. In contrast, in organopalladium complexes, researchers can switch the reactivity from electrophilic to nucleophilic relatively simply. Although σ-aryl and σ-vinylpalladium complexes are commonly used as electrophiles in C-C bond-forming reactions, recent research has demonstrated that they can also react with carbon-heteroatom multiple bonds in a nucleophilic manner. Nevertheless, researchers have completely ignored the issue of controlling the ambiphilic nature of such species. This Account describes our efforts toward selectively promoting the same starting materials toward either electrophilic α-arylation or nucleophilic addition reactions to different carbonyl groups. We could tune the properties of the σ-arylpalladium intermediates derived from amino-tethered aryl halides and carbonyl compounds to achieve chemoselective transformations. Therefore, chemists can control the ambiphilic nature of such intermediates and, consequently, the competition between the alternative reaction pathways by the adequate selection of the reaction conditions and additives (base, presence/absence of phenol, bidentate phosphines). The nature of the carbonyl group (aldehydes, ketones, esters, and amides) and the length of the tether connecting it to the aniline moiety also play an important role in the outcome of these processes. Our joint computational and experimental efforts to elucidate the reaction mechanism of these palladium-catalyzed transformations suggest that beyond the formation of the four-membered azapalladacycle, two major factors help to control the dual character of the palladium(II) intermediates derived from 2-haloanilines. First, their high nucleophilicity strongly modifies the interaction of

  3. Densification Behavior and Performances of C/C Composites Derived from Various Carbon Matrix Precursors

    Science.gov (United States)

    Shao, H. C.; Xia, H. Y.; Liu, G. W.; Qiao, G. J.; Xiao, Z. C.; Su, J. M.; Zhang, X. H.; Li, Y. J.

    2014-01-01

    Three types of carbon/carbon (C/C) composites were manufactured by densifying the needled carbon fiber preform through resin and pitch impregnation/carbonization repeatedly, as well as propylene pyrolysis by chemical vapor infiltration plus carbonization after the resin impregnation/carbonization. The densification behavior and performances (involving electric, thermal, and mechanical properties, as well as impurity) of the C/C composites were investigated systematically. The results show that besides the processing and testing conditions, the electric resistivity, thermal conductivity (TC), coefficient of thermal expansion (CTE), strength, and fracture, as well as impurity content and composition of the C/C composites were closely related to the fiber orientation, interfacial bonding between carbon fiber and carbon matrix, material characteristics of the three precursors and the resulting matrix carbons. In particular, the resin-carbon matrix C/C (RC/C) composites had the highest electric resistivity, tensile, and flexural strength, as well as impurity content. Meanwhile, the pitch-carbon matrix C/C (PC/C) composites possessed the highest TC and CTE in the parallel and vertical direction. And most of the performances of pyro-carbon/resin carbon matrix C/C composites were between those of the RC/C and PC/C composites except the impurity content.

  4. The role of the steps in the cleavage of the C-C bond during ethanol oxidation on platinum electrodes.

    Science.gov (United States)

    Colmati, Flavio; Tremiliosi-Filho, Germano; Gonzalez, Ernesto R; Berná, Antonio; Herrero, Enrique; Feliu, Juan M

    2009-10-28

    Ethanol oxidation has been studied on stepped platinum single crystal electrodes in acid media using electrochemical and Fourier transform infrared (FTIR) techniques. The electrodes used belong to two different series of stepped surfaces: those having (111) terraces with (100) monoatomic steps and those with (111) terraces with (110) monoatomic steps. The behaviors of the two series of stepped surfaces for the oxidation of ethanol are very different. On the one hand, the presence of (100) steps on the (111) terraces provides no significant enhancement of the activity of the surfaces. On the other hand, (110) steps have a double effect on the ethanol oxidation reaction. At potentials below 0.7 V, the step catalyzes the C-C bond cleavage and also the oxidation of the adsorbed CO species formed. At higher potentials, the step is not only able to break the C-C bond, but also to catalyze the oxidation of ethanol to acetic acid and acetaldehyde. The highest catalytic activity from voltammetry for ethanol oxidation was obtained with the Pt(554) electrode.

  5. Thermal response experiments of {SiC}/{C} and {TiC}/{C} functionally gradient materials as plasma facing materials for fusion application

    Science.gov (United States)

    Araki, M.; Sasaki, M.; Kim, S.; Suzuki, S.; Nakamura, K.; Akiba, M.

    1994-09-01

    To evaluate the applicability of a functionally gradient technique for the fabrication of the armor tile or the interface of the divertor plate element for next fusion machines such as ITER/FER, {SiC}/{C} and {TiC}/{C} functionally gradient materials (FGMs) were prepared and tested using an electron and ion beams test facilities. FGM layer with a thickness of 1.0 mm was produced by CVD process on fine grain graphite. Their thermal resistivities were evaluated under a condition for surface heat fluxes up to 70 MW/m 2 for durations up to several seconds. As the results, we confirmed that FGMs are clearly better than non-FGMs from a view point of the reduction of thermal stress. Both FGM layers on the graphite bulk material could withstand a temperature difference as high as 1500 K without cracking or melting, leading us to conceive a promising prospect for the application of the divertor plate.

  6. The Complaint before the Judge against the Prosecutor’s Resolutions or Writs for not Proceeding to Trial – Article278 (8, Letter c C.C.P

    Directory of Open Access Journals (Sweden)

    Dragu Cretu

    2010-06-01

    Full Text Available It has been noticed in the doctrine a more pronounced current trend of “privatizing” the trial, this aspect concerning a significant part of the foreign doctrine. It was proved that its most insidious form, and undoubtedly the most dangerous, is not the traditional one, of the injured person’s prior complaint, but that which is incident to the public prosecution itself. Romanian legislator gave up the prior complaint formulated in the article 279. par. 2 letter A, C.C.P., repealing these provisions through the Law no. 356/2006, thuseliminating the procedure of direct criminal proceedings. The complaint registered in the article 278 C.C.P. arousing lots of controversies, which allow almost unlimited access from the crime victim to public proceeding. Generally, the complaint governed by the provisions of the article 275 and the next C.C.P. is, in terms of legal nature, an appeal against criminal acts and measures of prosecution and a way to control their legality. According to the law, any person whose legitimate rights were affected can lodge a complaint. The law without prescribing a limitation period, the complaint can be lodged by any natural or legal person, if there is evidence of harm of her legitimate interests.

  7. Tribological Property of C/C-SiC Composites Fabricated by Isothermal Chemical Vapor Infiltration

    Directory of Open Access Journals (Sweden)

    WANG Yueming

    2017-08-01

    Full Text Available Four kinds of C/C-SiC composites were fabricated by isothermal chemical vapor infiltration (ICVI, and the 2.5D needle-punching carbon felt was taken as the preform. The volume fraction of carbon fiber in felt is 30%. The density of C/C-SiC composites is similar (1.87-1.91 g/cm3, while the weight ratio of SiC is decreased from 56% to 15%. The microstructure and phase composition of C/C-SiC composites were observed by SEM and XRD respectively. Friction and wear behavior of the C/C-SiC composites were investigated with the MM-1000 friction machine. The results show that the average macro hardness of matrix is decreased from 98.2HRA to 65.1HRA with the decrease of SiC content from 56% to 15%, and uniformity of hardness distribution is significantly decreased. Finally, by the analysis of microtopography of friction surface and wear debris, it is found that the superficial hardness has an obvious influence on mechanism of wear during braking process. The wear mechanism of the C/C-SiC composites transforms from grain wear to the combination of grain wear and adherent wear with the decrease of surface hardness. At the same time, the average friction coefficient and mass wear rate is increased obviously during breaking process.

  8. A Monte Carlo Sensitivity Analysis of CF2 and CF Radical Densities in a c-C4F8 Plasma

    Science.gov (United States)

    Bose, Deepak; Rauf, Shahid; Hash, D. B.; Govindan, T. R.; Meyyappan, M.

    2004-01-01

    A Monte Carlo sensitivity analysis is used to build a plasma chemistry model for octacyclofluorobutane (c-C4F8) which is commonly used in dielectric etch. Experimental data are used both quantitatively and quantitatively to analyze the gas phase and gas surface reactions for neutral radical chemistry. The sensitivity data of the resulting model identifies a few critical gas phase and surface aided reactions that account for most of the uncertainty in the CF2 and CF radical densities. Electron impact dissociation of small radicals (CF2 and CF) and their surface recombination reactions are found to be the rate-limiting steps in the neutral radical chemistry. The relative rates for these electron impact dissociation and surface recombination reactions are also suggested. The resulting mechanism is able to explain the measurements of CF2 and CF densities available in the literature and also their hollow spatial density profiles.

  9. Universal Brønsted-Evans-Polanyi Relations for C–C, C–O, C–N, N–O, N–N, and O–O Dissociation Reactions

    DEFF Research Database (Denmark)

    Wang, Shengguang; Temel, Burcin; Shen, Juan

    2011-01-01

    It is shown that for all the essential bond forming and bond breaking reactions on metal surfaces, the reactivity of the metal surface correlates linearly with the reaction energy in a single universal relation. Such correlations provide an easy way of establishing trends in reactivity among the ...

  10. All-carbon quaternary stereogenic centers in acyclic systems through the creation of several C-C bonds per chemical step.

    Science.gov (United States)

    Marek, Ilan; Minko, Yury; Pasco, Morgane; Mejuch, Tom; Gilboa, Noga; Chechik, Helena; Das, Jaya P

    2014-02-19

    In the past few decades, it has become clear that asymmetric catalysis is one of the most powerful methods for the construction of carbon-carbon as well as carbon-heteroatom bonds in a stereoselective manner. However, when structural complexity increases (i.e., all-carbon quaternary stereogenic center), the difficulty in reaching the desired adducts through asymmetric catalytic reactions leads to a single carbon-carbon bond-forming event per chemical step between two components. Issues of efficiency and convergence should therefore be addressed to avoid extraneous chemical steps. In this Perspective, we present approaches that tackle the stimulating problem of efficiency while answering interesting synthetic challenges. Ideally, if one could create all-carbon quaternary stereogenic centers via the creation of several new carbon-carbon bonds in an acyclic system and in a single-pot operation from simple precursors, it would certainly open new horizons toward solving the synthetic problems. Even more important for any further design, the presence of polyreactive intermediates in synthesis (bismetalated, carbenoid, and oxenoids species) becomes now an indispensable tool, as it creates consecutively the same number of carbon-carbon bonds as in a multi-step process, but in a single-pot operation.

  11. Characterization of C/C composites porosity for the fusion; Caracterisation de la porosite de composites C/C d'interet pour la fusion

    Energy Technology Data Exchange (ETDEWEB)

    Martin, C.; Ballet, A.C.; Pardanaud, C.; Roubin, P. [Universite de Provence, Centre St-Jerome, Laboratoire PIIM, 13 - Marseille (France); Beurroies, I.; Richou, M. [Universite de Provence, Centre St-Jerome, Laboratoire Madirel, 13 - Marseille (France); Brosset, C.; Pegourie, B. [Association EURATOM-CEA sur la Fusion Controlee, CE Cadarache, 13 - St-Paul-lez-Durance (France)

    2008-07-01

    In tokamaks, the composites C/C are used as components facing the plasma because of their excellent thermo-mechanical properties. In Tore Supra tokamak, analysis of particles of graphite erosion showed a big deuterium retention by the machine wall. This fuel retention will lead in ITER to a non acceptable level of tritium. As the diffusion in materials is bound to the porosity, the authors realized a study of two composites porosity: N11 and NB31. Different analysis methods have been performed and the temperature or grain size dependence studied. (A.L.B.)

  12. Efficient detection of dangling pointer error for C/C++ programs

    Science.gov (United States)

    Zhang, Wenzhe

    2017-08-01

    Dangling pointer error is pervasive in C/C++ programs and it is very hard to detect. This paper introduces an efficient detector to detect dangling pointer error in C/C++ programs. By selectively leave some memory accesses unmonitored, our method could reduce the memory monitoring overhead and thus achieves better performance over previous methods. Experiments show that our method could achieve an average speed up of 9% over previous compiler instrumentation based method and more than 50% over previous page protection based method.

  13. Why is the linking C-C bond in tetrahedranyltetrahedrane so short?

    Science.gov (United States)

    Mo, Yirong

    2006-02-02

    [structure: see text]. The block-localized wave function (BLW) method has been employed to probe the origin of the very short linking C-C bond (1.436 A) in tetrahedranyltetrahedrane. Computations show that the vicinal hyperconjugative interactions between the two tetrahedranyl groups is stronger than the conjugation in butadiene, and if there were no hyperconjugation effect, the bond distance would be 1.491 A. Thus, both the hybridization mode and hyperconjugative interactions contribute to the shortening of the central C-C bond in tetrahedranyltetrahedrane.

  14. Monitoring and Diagnostics for C/C++ Real-Time Applications

    CERN Document Server

    Fischer, Yves

    Knowledge about the internal state of computational processes is essential for problem diagnostics as well as for constant monitoring and pre-failure recognition. The CMX li- brary provides monitoring capabilities similiar to the Java Management Extensions (JMX) for C and C++ applications. This thesis provides a detailed analysis of the requirements for monitoring and diagnos- tics of the C/C++ processes at CERN. The developed CMX library enables real-time C/C++ processes to expose values with- out harming their normal execution. CMX is portable and can be integrated in different monitoring architectures.

  15. Asymmetric C-C Bond-Formation Reaction with Pd: How to Favor Heterogeneous or Homogeneous Catalysis?

    DEFF Research Database (Denmark)

    Reimann, S.; Grunwaldt, Jan-Dierk; Mallat, T.

    2010-01-01

    The enantioselective allylic alkylation of (E)-1,3-diphenylallyl acetate was studied to clarify the heterogeneous or homogeneous character of the Pd/Al2O3-(R)-BINAP catalyst system. A combined approach was applied: the catalytic tests were completed with in situ XANES measurements to follow...

  16. Di-electron measurements in C+C reactions at 2 GeVṡA with HADES

    Science.gov (United States)

    Eberl, T.; Agakishiev, G.; Agodi, C.; Alvarez-Pol, H.; Bałanda, A.; Bellia, G.; Bielcik, J.; Böhmer, M.; Boyard, J. L.; Braun-Munzinger, P.; Chernenko, S.; Christ, T.; Coniglione, R.; Djeridi, R.; Dohrmann, F.; Durán, I.; Fabbietti, L.; Fateev, O.; Finocchiaro, P.; Friese, J.; Fröhlich, I.; Garzón, J. A.; Gernhäuser, R.; Golubeva, M.; González-Díaz, D.; Grosse, E.; Guber, F.; Hennino, T.; Hlavac, S.; Holzmann, R.; Ierusalimov, A.; Iori, I.; Jaskuła, M.; Jurkovic, M.; Kämpfer, B.; Kanaki, K.; Karavicheva, T.; Koenig, I.; Koenig, W.; Kolb, B. W.; Kotte, R.; Kotulic-Bunta, J.; Krücken, R.; Kugler, A.; Kühn, W.; Kulessa, R.; Kurepin, A.; Lang, S.; Lehnert, J.; Maiolino, C.; Markert, J.; Metag, V.; Mousa, J.; Münch, M.; Müntz, C.; Naumann, L.; Novotny, R.; Novotný, J.; Otwinowski, J.; Pachmayer, Y. C.; Pant, L. M.; Pechenov, V.; Pérez, T.; Pietraszko, J.; Pleskač, R.; Pospíšil, V.; Przygoda, W.; Rabin, N.; Ramstein, B.; Reshetin, A.; Ritman, J.; Roy-Stephan, M.; Rustamov, A.; Sadovsky, A.; Sailer, B.; Salabura, P.; Sánchez, M.; Sapienza, P.; Schmah, A.; Simon, R.; Smolyankin, V.; Smykov, L.; Spataro, S.; Spruck, B.; Stroebele, H.; Stroth, J.; Sturm, C.; Sudol, M.; Tlustý, P.; Toia, A.; Traxler, M.; Tsertos, H.; Wagner, V.; Wiśniowski, M.; Wójcik, T.; Wüstenfeld, J.; Zanevsky, Y.; Žovinec, D.; Zumbruch, P.

    2005-04-01

    The High Acceptance DiElectron Spectrometer HADES has been recently commissioned at GSI, Darmstadt. It has been designed for systematic studies of hadron properties inside nuclear matter. We report first preliminary results on invariant masses e +e --pairs which were measured in 12C + 12C collisions at E=2 GeVṡA. The analysis methods are briefly outlined and a comparison with detailed Monte-Carlo simulations is shown.

  17. Development of a Class for Multiple Precision Arithmetic in C/C++ Language

    OpenAIRE

    福田, 宏

    1998-01-01

    We have defined a floating-point variable of arbitrary length for a calculation of high precision and have developed a set of mathematical functions of it in C/C++ language. The variable and the functions are combined into a class in C++ language. In addition, the functions can be easily converted to those in FORTRAN language.

  18. Admission chemokine (C-C motif) ligand 4 levels predict survival in pediatric septic shock.

    Science.gov (United States)

    Nowak, Jeffrey E; Wheeler, Derek S; Harmon, Kelli K; Wong, Hector R

    2010-03-01

    Stratification with an effective outcome biomarker could improve the design of interventional trials in pediatric septic shock. The objective of this study was to test the usefulness of chemokine (C-C motif) ligand 4 as an outcome biomarker for mortality in pediatric septic shock. A cross-sectional, observational study. Eighteen pediatric intensive care units in the United States. One hundred fifty-six pediatric patients with septic shock. Serum samples were obtained within 24 hrs of admission to the pediatric intensive care unit. Serum levels of chemokine (C-C motif) ligand 4 were measured by enzyme-linked immunosorbent assay and compared with mortality in a training set of 34 patients. These data were used to generate a cutoff value whose usefulness was evaluated through prospective application-without post hoc modification-to a larger validation set of 122 patients. On inspection of the training set data, a cutoff value of 140 pg/mL was chosen. When applied to the validation set, serum chemokine (C-C motif) ligand 4 levels >140 pg/mL yielded a sensitivity of 92% and a specificity of 40% for mortality. A serum level of pediatric septic shock. Exclusion of patients with a chemokine (C-C motif) ligand 4 level of pediatric septic shock could create a study population in which survival benefit from the study agent could be more readily demonstrated.

  19. 77 FR 10004 - C$ cMoney, Inc.; Order of Suspension of Trading

    Science.gov (United States)

    2012-02-21

    ... COMMISSION C$ cMoney, Inc.; Order of Suspension of Trading February 16, 2012. It appears to the Securities... the opinion that the public interest and the protection of investors require a suspension of trading... the Securities Exchange Act of 1934, that trading in the securities of the above-listed company is...

  20. Botnet C&C Traffic and Flow Lifespans Using Survival Analysis

    Directory of Open Access Journals (Sweden)

    Vaclav Oujezsky

    2017-03-01

    Based on our research we have figured out a possibility to distinguish the individual lifespans of C&C communications that are identical to each other by using survival projection curves, although it occurred in a different time course.

  1. Anti-metastatic Semi-synthetic Sulfated Maltotriose C-C Linked Dimers. Synthesis and Characterisation

    Directory of Open Access Journals (Sweden)

    Giangiacomo Torri

    2012-08-01

    Full Text Available This manuscript describes the preparation and the spectroscopic characterisation of semi-synthetic sulfated maltotriose C-C linked dimers (SMTCs where the natural C-O-C anomeric bond was substituted by one direct central C-C bond. This C-C bond induces conformation and flexibility changes with respect to the usual anomeric bond. SMTCs neutral precursors came from maltotriosyl bromide electroreduction through maltotriosyl radical intermediate dimerisation. The new C-C bond configuration, named for convenience a,a, a,b and b,b as the natural anomeric bond, dictated the statistic ratio formation of three diastereoisomers. They were separated by silica gel flash chromatography followed by semi preparative HPLC chromatography. Each diastereoisomer was exhaustively sulfated to afford the corresponding SMTCs. SMTCs were huge characterised by NMR spectroscopy which provided the sulfation degree, too. a,a and a,b were found quite homogeneous samples with a high degree of sulfation (85–95%. b,b appeared a non-homogeneous sample whose average sulfation degree was evaluated at around 78%. Mass spectroscopy experiments confirmed the sulfation degree range. Some considerations were proposed about SMTCs structure-biological properties.

  2. B-N as a C-C substitute in aromatic systems

    National Research Council Canada - National Science Library

    Bosdet, Michael J.D; Piers, Warren E

    2009-01-01

    ... electronic properties and chemistry. Since the pioneering work of Dewar some 50 years ago, the relationship between B-N and C-C and the wealth of parent all-carbon aromatics has captured the imagination of organic, inorganic, materials...

  3. The Eschenmoser coupling reaction under continuous-flow conditions

    Directory of Open Access Journals (Sweden)

    Sukhdeep Singh

    2011-08-01

    Full Text Available The Eschenmoser coupling is a useful carbon–carbon bond forming reaction which has been used in various different synthesis strategies. The reaction proceeds smoothly if S-alkylated ternary thioamides or thiolactames are used. In the case of S-alkylated secondary thioamides or thiolactames, the Eschenmoser coupling needs prolonged reaction times and elevated temperatures to deliver valuable yields. We have used a flow chemistry system to promote the Eschenmoser coupling under enhanced reaction conditions in order to convert the demanding precursors such as S-alkylated secondary thioamides and thiolactames in an efficient way. Under pressurized reaction conditions at about 220 °C, the desired Eschenmoser coupling products were obtained within 70 s residence time. The reaction kinetics was investigated and 15 examples of different building block combinations are given.

  4. Modular functionalized polyphosphines for supported materials: previously unobserved (31)P-NMR «through-space» ABCD spin systems and heterogeneous palladium-catalysed C-C and C-H arylation.

    Science.gov (United States)

    Beaupérin, Matthieu; Smaliy, Radomyr; Cattey, Hélène; Meunier, Philippe; Ou, Jun; Toy, Patrick H; Hierso, Jean-Cyrille

    2014-08-28

    The modular design of polyphosphines, diversely functionalized for facile immobilization on virtually any kind of support, is reported. Previously unobserved ABCD (31)P NMR spin-spin systems evidence the control exercised on the polyphosphines conformation. We illustrate the catalytic performance at low Pd loading of the recyclable immobilized polyphosphines in C-C bond formation reactions.

  5. Possibilities for using a temperature-controlled pyrolysis method in order to determine the bonding form of mecury in soils and sediments; Moeglichkeiten der Anwendung eines temperaturgesteuerten Pyrolyseverfahrens zur Bestimmung der Bindungsform des Quecksilbers in Boeden und Sedimenten

    Energy Technology Data Exchange (ETDEWEB)

    Biester, H.

    1994-12-31

    The bonding behaviour of mercury in solids was investigated by means of a temperature-controlled pyrolysis method. Starting from the special property of elemental mercury to evaporate already at room temperature, a method was developed which permits to characterize different mercury bonding forms on the basis of Hg evaporation behaviour from solids at continuously increased temperature. The method starts from the assumption that it is possible to thermally reduce compounded mercury and release it in elemental form. The focus of the work was on the study of Hg bonding behaviour in soils and sediments. The soil samples used were from the areas of two mercury deposits, different kyanizing sites, some former mirror factories, and a chlor-alkali electrolysis workshop. The investigated sediments are a collection of mercury-polluted samples from the rivers Elbe, Rhine, Murg, the Rio Sao Joao de Meriti (Brazil) and some brooks and rivers of the Saar-Nahe depression. (orig./EF) [Deutsch] In der vorliegenden Arbeit wurde das Bindungsverhalten von Quecksilber in Feststoffen mittels eines temperaturgesteuerten Pyrolyseverfahrens untersucht. Ausgehend von der besonderen Eigenschaften des elementaren Quecksilbers, bereits bei Zimmertemperatur zu verdampfen, wurde ein Verfahren entwickelt, das eine Charakterisierung verschiedener Quecksilberbindungsformen aufgrund des Abdampfverhaltens des Hg aus dem Feststoff unter kontinuierlicher Temperaturerhoehung zulaesst. Dem Verfahren liegt dabei die Annahme zugrunde, dass sich das Quecksilber in seinen Verbindungen thermisch reduzieren und in elementarer Form freisetzen laesst. Durch den kontinuierlichen Aufheizprozess erfolgt die Freisetzung des Quecksilbers in Abhaengigkeit von der Bindungsstaerke in unterschiedlichen Temperaturbereichen. Die Darstellung der Ergebnisse erfolgte in Form von Abdampfkurven, die die Extinktion in Abhaengigkeit von der Temperatur darstellen. Der Schwerpunkt dieser Arbeit lag auf der Untersuchung des

  6. Quick Way to Port Existing C/C++ Chemoinformatics Toolkits to the Web Using Emscripten.

    Science.gov (United States)

    Jiang, Chen; Jin, Xi

    2017-10-23

    Emscripten is a special open source compiler that compiles C and C++ code into JavaScript. By utilizing this compiler, some typical C/C++ chemoinformatics toolkits and libraries are quickly ported to to web. The compiled JavaScript files have sizes similar to native programs, and from a series of constructed benchmarks, the performance of the compiled JavaScript codes is also close to that of the native codes and is better than the handwritten JavaScript codes. Therefore, we believe that Emscripten is a feasible and practical tool for reusing existing C/C++ codes on the web, and many other chemoinformatics or molecular calculation software tools can also be easily ported by Emscripten.

  7. Thermo-mechanical and tribological properties of phenolic polymers composites and C-C composites

    Directory of Open Access Journals (Sweden)

    Virgil MARINESCU

    2010-12-01

    Full Text Available Formaldehyde resin-based composites have been an inaugural step in obtaining and usingcomposite materials and they have grown rapidly because of their multiple uses, especially inelectrical and aeronautical field.Phenolic matrix composites represent a preliminary study to obtain mezophase carbon-carboncomposites for advanced materials as potential solutions for reentry shields of cosmic vehicles andlaunch subsystems, as elements of modern braking systems in aircraft or as potential solutions for thecomponents of the combustion chamber of rockets and also as hypersonic transport solutions for thefuture. Both phenolic matrix laminated composites and C-C mezophase matrix C-C composites wereobtained.This paper presents an evaluation of the mechanical and tribological behavior of the obtainedcomposites.

  8. Stereoselective Synthesis of the C1-C9 and C11-C25 Fragments of Amphidinolides C, C2, C3, and F.

    Science.gov (United States)

    Akwaboah, Daniel C; Wu, Dimao; Forsyth, Craig J

    2017-03-03

    An efficient synthesis of the C1-C9 and the C11-C25 fragments of amphidinolides C, C2, C3, and F from a common intermediate is reported. The construction of the C1-C9 fragment involves an intramolecular hetero-Michael cyclization to form the 3,5-disubstituted trans-tetrahydrofuran moiety. The approach to prepare the C11-C25 fragment utilizes a highly stereoselective aerobic cobalt-catalyzed alkenol cyclization and a chelated Mukaiyama aldol reaction to form the C13-C14 bond and to concomitantly install the C13 hydroxyl group.

  9. Determination of material properties for short fibre reinforced C/C-SiC

    Directory of Open Access Journals (Sweden)

    Hausherr J.-M.

    2015-01-01

    Full Text Available Determining the mechanical properties of short fibre reinforced CMC using standard sized coupons has always been a challenge due to a high statistical scattering of the measured values. Although the random orientation of short fibres results in a quasi-isotropic material behavior of 2D-structures with a sufficiently large volume, the small volume typical for test coupons usually results in a non-isotropic fibre orientation in the tested volume. This paper describes a method for manufacturing unidirectional oriented short fibre reinforced CMC materials and presents material properties of UD-C/C-SiC. After verifying the fibre orientation of the CMC using micro-computed tomography, coupons were extracted to determine the orthotropic material properties. These orthotropic material properties were then used to predict the properties of C/C-SiC with randomly distributed short fibres. To validate the method, micro-computed tomography is used to quantitatively determine the fibre orientation within coupons extracted from randomly distributed short fibre C/C-SiC. After mechanical three-point-bending tests, the measured stiffness and bending strength is compared with the predicted properties. Finally, the data are used to devise a method suited for reducing the inherent large spread of material properties associated with the measurement of CMC materials with randomly distributed short fibres.

  10. A C/C++ Build System Based On Maven for the LHC Controls System

    CERN Document Server

    Nguyen Xuan, J; Dönszelmann, M

    2011-01-01

    The CERN accelerator controls system, mainly written in Java and C/C++, consists nowadays of 50 projects and 150 active developers. The controls group has decided to unify the development process and standards (e.g. project layout) using Apache Maven and Sonatype Nexus. Maven is the de-facto build tool for Java, it deals with versioning and dependency management, whereas Nexus is a repository manager. C/C++ developers were struggling to keep their dependencies on other CERN projects, as no versioning was applied, the libraries have to be compiled and available for several platforms and architectures, and finally there was no dependency management mechanism. This results in very complex Makefiles which were difficult to maintain. Even if Maven is primarily designed for Java, a plugin (Maven NAR) adapts the build process for native programming languages for different operating systems and platforms. However C/C++ developers were not keen to abandon their current Makefiles. Hence our approach was to combine the ...

  11. C/C-SiC Composites for Nozzle of Solid Propellant Ramjet

    Directory of Open Access Journals (Sweden)

    WANG Lingling

    2017-01-01

    Full Text Available Carbon fiber reinforced carbon and silicon carbide matrix composites for nozzle inner of solid propellant ramjet were prepared by using the hybrid process of "chemical vapor infiltration + precursor impregnation pyrolysis (CVI+PIP". The microstructure, flexural and anti-ablation properties of the C/C-SiC composites and hydraulic test and rocket motor hot firing test for nozzle inner of solid propellant ramjet were comprehensively investigated. The results show that when the flexural strength of the composite reachs 197 MPa, the fracture damage behavior of the composites presents typical toughness mode.Also the composites has excellent anti-ablative property, i.e., linear ablation rate is only 0.0063 mm·s-1 after 200 s ablation. The C/C-SiC component have excellent integral bearing performance with the hydraulic bursting pressure of 6.5 MPa, and the high temperature combination property of the C/C-SiC composite nozzle inner is verified through motor hot firing of solid propellant ramjet.

  12. Metal-catalyzed asymmetric aldol reactions

    Energy Technology Data Exchange (ETDEWEB)

    Dias, Luiz C.; Lucca Junior, Emilio C. de; Ferreira, Marco A. B.; Polo, Ellen C., E-mail: ldias@iqm.unicamp.br [Universidade de Campinas (UNICAMP), SP (Brazil). Inst. de Quimica

    2012-12-15

    The aldol reaction is one of the most powerful and versatile methods for the construction of C-C bonds. Traditionally, this reaction was developed in a stoichiometric version; however, great efforts in the development of chiral catalysts for aldol reactions were performed in recent years. Thus, in this review article, the development of metal-mediated chiral catalysts in Mukaiyama-type aldol reaction, reductive aldol reaction and direct aldol reaction are discussed. Moreover, the application of these catalysts in the total synthesis of complex molecules is discussed. (author)

  13. An Erbium-Based Bifuctional Heterogeneous Catalyst: A Cooperative Route Towards C-C Bond Formation

    Directory of Open Access Journals (Sweden)

    Manuela Oliverio

    2014-07-01

    Full Text Available Heterogeneous bifuctional catalysts are multifunctional synthetic catalysts enabling efficient organic transformations by exploiting two opposite functionalities without mutual destruction. In this paper we report the first Er(III-based metallorganic heterogeneous catalyst, synthesized by post-calcination MW-assisted grafting and modification of the natural aminoacid L-cysteine. The natural acid–base distance between sites was maintained to assure the cooperation. The applicability of this new bifunctional heterogeneous catalyst to C-C bond formation and the supposed mechanisms of action are discussed as well.

  14. Study of dielectron production in C+C collisions at 1A GeV

    Science.gov (United States)

    Hades Collaboration; Agakishiev, G.; Agodi, C.; Alvarez-Pol, H.; Balanda, A.; Bassini, R.; Bellia, G.; Belver, D.; Belyaev, A.; Blanco, A.; Böhmer, M.; Bortolotti, A.; Boyard, J. L.; Braun-Munzinger, P.; Cabanelas, P.; Castro, E.; Chernenko, S.; Christ, T.; Destefanis, M.; Díaz, J.; Dohrmann, F.; Dybczak, A.; Eberl, T.; Fabbietti, L.; Fateev, O.; Finocchiaro, P.; Fonte, P.; Friese, J.; Fröhlich, I.; Galatyuk, T.; Garzón, J. A.; Gernhäuser, R.; Gil, A.; Gilardi, C.; Golubeva, M.; González-Díaz, D.; Grosse, E.; Guber, F.; Heilmann, M.; Heinz, T.; Hennino, T.; Holzmann, R.; Ierusalimov, A.; Iori, I.; Ivashkin, A.; Jurkovic, M.; Kämpfer, B.; Kajetanowicz, M.; Kanaki, K.; Karavicheva, T.; Kirschner, D.; Koenig, I.; Koenig, W.; Kolb, B. W.; Kotte, R.; Kozuch, A.; Krása, A.; Krizek, F.; Krücken, R.; Kühn, W.; Kugler, A.; Kurepin, A.; Lamas-Valverde, J.; Lang, S.; Lange, J. S.; Lapidus, K.; Lopes, L.; Maier, L.; Mangiarotti, A.; Marín, J.; Markert, J.; Metag, V.; Michalska, B.; Mishra, D.; Morinière, E.; Mousa, J.; Münch, M.; Müntz, C.; Naumann, L.; Novotny, R.; Otwinowski, J.; Pachmayer, Y. C.; Palka, M.; Parpottas, Y.; Pechenov, V.; Pechenova, O.; Pérez Cavalcanti, T.; Pietraszko, J.; Pleskac, R.; Pospísil, V.; Przygoda, W.; Ramstein, B.; Reshetin, A.; Roy-Stephan, M.; Rustamov, A.; Sadovsky, A.; Sailer, B.; Salabura, P.; Schmah, A.; Schroeder, C.; Schwab, E.; Simon, R. S.; Sobolev, Yu. G.; Spataro, S.; Spruck, B.; Ströbele, H.; Stroth, J.; Sturm, C.; Sudol, M.; Tarantola, A.; Teilab, K.; Tlusty, P.; Toia, A.; Traxler, M.; Trebacz, R.; Tsertos, H.; Veretenkin, I.; Wagner, V.; Weber, M.; Wen, H.; Wisniowski, M.; Wojcik, T.; Wüstenfeld, J.; Yurevich, S.; Zanevsky, Y.; Zhou, P.; Zumbruch, P.

    2008-05-01

    The emission of ee pairs from C+C collisions at an incident energy of 1 GeV per nucleon has been investigated. The measured production probabilities, spanning from the π-Dalitz to the ρ/ω invariant-mass region, display a strong excess above the cocktail of standard hadronic sources. The bombarding-energy dependence of this excess is found to scale like pion production, rather than like eta production. The data are in good agreement with results obtained in the former DLS experiment.

  15. Tailored synthesis of various nanomaterials by using a graphene-oxide-based gel as a nanoreactor and nanohybrid-catalyzed C-C bond formation.

    Science.gov (United States)

    Biswas, Abhijit; Banerjee, Arindam

    2014-12-01

    New graphene oxide (GO)-based hydrogels that contain vitamin B2/B12 and vitamin C (ascorbic acid) have been synthesized in water (at neutral pH value). These gel-based soft materials have been used to synthesize various metal nanoparticles, including Au, Ag, and Pd nanoparticles, as well as nanoparticle-containing reduced graphene oxide (RGO)-based nanohybrid systems. This result indicates that GO-based gels can be used as versatile reactors for the synthesis of different nanomaterials and hybrid systems on the nanoscale. Moreover, the RGO-based nanohybrid hydrogel with Pd nanoparticles was used as an efficient catalyst for C-C bond-formation reactions with good yields and showed high recyclability in Suzuki-Miyaura coupling reactions. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Electron attachment, ionization and drift in c-C4F8

    Science.gov (United States)

    de Urquijo, J.; Basurto, E.

    2001-05-01

    The pulsed Townsend method has been used to measure the drift velocity ve and the density-normalized effective ionization coefficient (α-η)/N, (α and η are the ionization and attachment coefficients, respectively) in c-C4F8 over the density-normalized electric field strength E/N, 12 Td≤E/N≤43 Td and 330 Td≤E/N≤600 Td (1 Td = 10-17 V cm2), at pressures between 1 and 7.5 Torr (1 Torr = 133.3 Pa). For 12 Td≤E/N≤43 Td, the above parameters were found to be pressure independent, while for the range 330 Td≤E/N≤600 Td an inverse dependence of the above coefficients was found for gas pressures less than 2 Torr. Such dependence is believed to be due to the autodetachment of the originally formed, unstable parent negative ion c-C4F8-*. At low E/N, no previous data for ve or (α-η)/N were found for comparison with the present data. A critical field strength of E/Ncrit = 439.5 Td, for which α = η, was found to be in good agreement with previous data.

  17. Tribological properties of C/C-SiC composites for brake discs

    Science.gov (United States)

    Jang, G. H.; Cho, K. H.; Park, S. B.; Lee, W. G.; Hong, U. S.; Jang, H.

    2010-02-01

    This study examines the friction and wear of ceramic matrix composites designed for use in automotive brake discs. The composites are produced by reinforcing a SiC matrix with carbon fibers using a liquid silicon infiltration method. C/C-SiC composites with two different compositions are fabricated to examine the compositional effect on the tribological properties. The tribological properties are evaluated using a scale dynamometer with a low-steel type friction material. The results show that the coefficient of friction is determined by the composition of the composite, which affects the propensity of friction film formation on the disc surface. A stable friction film on the disc surface also improves the wear resistance by diminishing the abrasive action of the disc. On the other hand, the friction film formation on the disc is affected by the applied pressure, and stable films are obtained at high pressures. This trend is prominent with discs with high Si content. However, both C/C/-SiC composites show superior performance in terms of the friction force oscillation, which is closely related to brake-induced vibration.

  18. Would be the photon a composed particle? / Sobre a possibilidade da quantiza\\c{c}\\~ao dos fluxos de campo na radia\\c{c}\\~ao eletromagn\\'etica

    CERN Document Server

    Duarte, Celso de Araujo

    2013-01-01

    Here it is made a comparative analysis between the classical and the quantum expressions for the energy of electromagnetic radiation (ER). The comparison points to the possibility of the quantization of the magnetic and the electric field fluxes in the ER. ----- Apresenta-se uma an\\'alise comparativa entre as express\\~oes cl\\'assica e qu\\^antica para a energia da radia\\c{c}\\~ao eletromagn\\'etica (RE). A compara\\c{c}\\~ao nos aponta para a possibilidade de haver uma quantiza\\c{c}\\~ao dos fluxos dos campos magn\\'etico e el\\'etrico na RE.

  19. Architectural Visualization of C/C++ Source Code for Program Comprehension

    Energy Technology Data Exchange (ETDEWEB)

    Panas, T; Epperly, T W; Quinlan, D; Saebjornsen, A; Vuduc, R

    2006-09-01

    Structural and behavioral visualization of large-scale legacy systems to aid program comprehension is still a major challenge. The challenge is even greater when applications are implemented in flexible and expressive languages such as C and C++. In this paper, we consider visualization of static and dynamic aspects of large-scale scientific C/C++ applications. For our investigation, we reuse and integrate specialized analysis and visualization tools. Furthermore, we present a novel layout algorithm that permits a compressive architectural view of a large-scale software system. Our layout is unique in that it allows traditional program visualizations, i.e., graph structures, to be seen in relation to the application's file structure.

  20. The 3D Lima\\c{c}on: Properties and Applications

    CERN Document Server

    Kreismann, Jakob; Sinzinger, Stefan

    2016-01-01

    We perform electromagnetic wave simulations of fully three-dimensional optical Lima\\c{c}on-microcavities, one basis for their future applications in microlasers and photonic devices. The analysis of the three-dimensional modes and far-fields reveals an increase of the quality factors as compared to the two-dimensional case. The structure of the far-field in the third dimension shows pronounced maxima in the emission directionality inclined to the resonator plane which may be exploited for coupling the resonator modes to the environment. This triggers ideas for technical applications, like the suggested sensor that can detect small changes in the environment based on changes in the emission profile.

  1. Analytical modeling of the steady state ablation of a 3D C/C composite

    Energy Technology Data Exchange (ETDEWEB)

    Lachaud, J.; Aspa, Y.; Vignoles, G.L. [Universite Bordeaux 1, Laboratoire des Composites ThermoStructuraux (LCTS), 33 - Pessac (France); Aspa, Y. [Institut de Mecanique des Fluides de Toulouse (IMFT), 31 - Toulouse (France)

    2008-05-15

    Following an analysis of surface roughness features that develop on a 3D C/C composite during ablation, i.e. wall recession by oxidation and/or sublimation, a modeling strategy is set up in order to predict the composite behavior from that of its components. It relies on two changes of scale: (i) microscopic scale (fiber, matrix) to mesoscopic scale (bundle) and (ii) mesoscopic scale (bundle, matrix) to macroscopic scale (composite). The physical basis is a general model for receding surfaces under a gasification process coupled to mass transfer. At each scale, the 3D surface equation is analytically solved in steady state considering a 1-D mass transfer perpendicular to the overall surface. The models are validated by comparison to experimental data. (authors)

  2. Facile P-C/C-H Bond-Cleavage Reactivity of Nickel Bis(diphosphine) Complexes.

    Science.gov (United States)

    Zhang, Shaoguang; Li, Haixia; Appel, Aaron M; Hall, Michael B; Bullock, R Morris

    2016-07-04

    Unusual cleavage of P-C and C-H bonds of the P2 N2 ligand, in heteroleptic [Ni(P2 N2 )(diphosphine)](2+) complexes under mild conditions, results in the formation of an iminium formyl nickelate featuring a C,P,P-tridentate coordination mode. The structures of both the heteroleptic [Ni(P2 N2 )(diphosphine)](2+) complexes and the resulting iminium formyl nickelate have been characterized by NMR spectroscopy and single-crystal X-ray diffraction analysis. Density functional theory (DFT) calculations were employed to investigate the mechanism of the P-C/C-H bond cleavage, which involves C-H bond cleavage, hydride rotation, Ni-C/P-H bond formation, and P-C bond cleavage. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Continuous Casting of Single Crystal Ingots by the O.C.C. Process

    Science.gov (United States)

    Ohno, A.

    1986-01-01

    To prevent the nucleation of crystals on the mold wall in the continuous casting of metals, a heated mold that maintained that temperature above the solidification temperature of the cast metal was used instead of the conventional cold mold. The cooling of the ingot was conducted outside of the mold. Heat was conducted axially along the ingot from the mold zone to the cooling zone. The principle of the O.C.C. (Ohno Continuous Casting) Process® was applied to the horizontal casting and vertical (upward) casting of wire and platelike ingots of Sn and Al. The ingots consisted of a completely unidirectionally solidified structure. It was possible to obtain a long single crystal ingot as a result of the growth competition of crystals.

  4. Chemokine (C-C motif ligand 20, a potential biomarker for Graves' disease, is regulated by osteopontin.

    Directory of Open Access Journals (Sweden)

    Xiaoli Li

    Full Text Available CONTEXT: Graves' disease (GD is a common autoimmune disease involving the thyroid gland. The altered balance of pro- and anti-inflammatory cytokines plays an important role in the pathogenesis of GD. Chemokine (C-C motif ligand 20 (CCL20 is important for interleukin-17 (IL-17 signal activation and a potent chemoattractant for Th17 cells. Meanwhile, Osteopontin (OPN, a broadly expressed pleiotropic cytokine, has been implicated in GD through inducing Th1-involved response to enhance the production of proinflammatory cytokines and chemokines, but little is known about the role of OPN in regulating CCL20 and IL-17 signaling. OBJECTIVE: This study sought to explore the possibility of CCL20 level as a biomarker for GD, as well as investigate the role of OPN in regulating CCL20 production. METHODS: Fifty untreated GD patients, fifteen euthyroid GD patients, twelve TRAb-negative GD patients and thirty-five healthy control donors were recruited. OPN, CCL20 and other clinical GD diagnosis parameters were measured. CD4+T cells were isolated from peripheral blood mononuclear cells (PBMCs using antibody-coated magnetic beads. Enzyme-linked immune-sorbent assay and quantitative polymerase chain reaction were used to determine CCL20 expression level. RESULTS: We found that the plasma CCL20 level was enhanced in GD patients and decreased in euthyroid and TRAb-negative GD patients. In addition, CCL20 level correlated with GD clinical diagnostic parameters and plasma OPN level. Moreover, we demonstrated that recombinant OPN and plasma from untreated GD patients increased the expression of CCL20 in CD4+T cells, which could be blocked by OPN antibody. Furthermore, we found that the effect of OPN on CCL20 expression was mediated by β3 integrin receptor, IL-17, NF-κB and MAPK pathways. CONCLUSIONS: These results demonstrated that CCL20 might serve as a biomarker for GD and suggested the possible role of OPN in induction of CCL20 expression.

  5. Overview of C/C-SiC Composite Development for the Orion Launch Abort System

    Science.gov (United States)

    Allen, Lee R.; Valentine, Peter G.; Schofield, Elizabeth S.; Beshears, Ronald D.; Coston, James E.

    2012-01-01

    Past and present efforts by the authors to further understanding of the ceramic matrix composite (CMC) material used in the valve components of the Orion Launch Abort System (LAS) Attitude Control Motor (ACM) will be presented. The LAS is designed to quickly lift the Orion Crew Exploration Vehicle (CEV) away from its launch vehicle in emergency abort scenarios. The ACM is a solid rocket motor which utilizes eight throttleable nozzles to maintain proper orientation of the CEV during abort operations. Launch abort systems have not been available for use by NASA on manned launches since the last Apollo ]Saturn launch in 1975. The CMC material, carbon-carbon/silicon-carbide (C/C-SiC), is manufactured by Fiber Materials, Inc. and consists of a rigid 4-directional carbon-fiber tow weave reinforced with a mixed carbon plus SiC matrix. Several valve and full system (8-valve) static motor tests have been conducted by the motor vendor. The culmination of these tests was the successful flight test of the Orion LAS Pad Abort One (PA ]1) vehicle on May 6, 2010. Due to the fast pace of the LAS development program, NASA Marshall Space Flight Center assisted the LAS community by performing a series of material and component evaluations using fired hardware from valve and full ]system development motor tests, and from the PA-1 flight ACM motor. Information will be presented on the structure of the C/C-SiC material, as well as the efficacy of various non ]destructive evaluation (NDE) techniques, including but not limited to: radiography, computed tomography, nanofocus computed tomography, and X-ray transmission microscopy. Examinations of the microstructure of the material via scanning electron microscopy and energy dispersive spectroscopy will also be discussed. The findings resulting from the subject effort are assisting the LAS Project in risk assessments and in possible modifications to the final ACM operational design.

  6. New Concept of the Biosynthesis of 4-Alkyl-L-proline Precursors of Lincomycin, Hormaomycin and Pyrrolobenzodiazepines: Could a γ-Glutamyltransferase Cleave the C-C Bond?

    Directory of Open Access Journals (Sweden)

    Petra eJiraskova

    2016-03-01

    Full Text Available Structurally different and functionally diverse natural compounds – antitumour agents pyrrolo[1,4]benzodiazepines, bacterial hormone hormaomycin and lincosamide antibiotic lincomycin – share a common building unit, 4-alkyl-L-proline derivative (APD. APDs arise from L-tyrosine through a special biosynthetic pathway. Its generally accepted scheme, however, did not comply with current state of knowledge. Based on gene inactivation experiments and in vitro functional tests with recombinant enzymes, we designed a new APD biosynthetic scheme for the model of lincomycin biosynthesis. In the new scheme at least one characteristic in each of five final biosynthetic steps has been changed: the order of reactions, assignment of enzymes and/or reaction mechanisms. First, we demonstrate that LmbW methylates a different substrate than previously assumed. Second, we propose a unique reaction mechanism for the next step, in which a putative γ-glutamyltransferase LmbA indirectly cleaves off the oxalyl residue by transient attachment of glutamate to LmbW product. This unprecedented mechanism would represent the first example of the C-C bond cleavage catalyzed by a γ-glutamyltransferase, i.e., an enzyme that appears unsuitable for such activity. Finally, the inactivation experiments show that LmbX is an isomerase indicating that it transforms its substrate into a compound suitable for reduction by LmbY, thereby facilitating its subsequent complete conversion to APD 4-propyl-L-proline. Elucidation of the APD biosynthesis has long time resisted mainly due to the apparent absence of relevant C-C bond cleaving enzymatic activity. Our proposal aims to unblock this situation not only for lincomycin biosynthesis, but generally for all above mentioned groups of bioactive natural products with biotechnological potential.

  7. EFFECTIVE 1,4-ASYMMETRIC C-C/C-O STEREOINDUCTION IN INDIUM-PROMOTED COUPLING REACTIONS OF ALDEHYDES TO PROTECTED AND UNPROTECTED [L -(BROMOMETHYL)VINYL] ALKANOLS. (R824725)

    Science.gov (United States)

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  8. Mechanical and Chemical Characterization of a TiC/C System Synthesized Using a Focus Plasma Arc

    National Research Council Canada - National Science Library

    Mahmoodian, Reza; Hamdi, M; Hassan, M A; Akbari, Abolghasem

    2015-01-01

    Titanium carbide-graphite (TiC/C) composite was successfully synthesized from Ti and C starting elemental powders using self-propagating high-temperature synthesis technique in an ultra-high plasma inert medium in a single stage...

  9. Prediction of cutting forces in ball-end milling of 2.5D C/C composites

    Directory of Open Access Journals (Sweden)

    Shan Chenwei

    2016-06-01

    Full Text Available Machining of carbon/carbon (C/C composite materials is difficult to carry out due to its high specific stiffness, brittleness, anisotropic, non-homogeneous and low thermal conductivity, which can result in tear, burr, poor surface quality and rapid wear of cutters. Accurate and fast prediction of cutting forces is important for milling C/C composite materials with high quality. This paper presents an alternative cutting force model involving the influences of the directions of fiber. Based on the calculated and experimental results, the cutting forces’ coefficients of 2.5D C/C composites are evaluated using multiple linear regression method. Verification experiment has been carried out through a group of orthogonal tests. Results indicate that the proposed model is reliable and can be used to predict the cutting forces in ball-end milling of 2.5D C/C composites.

  10. Direct conversion of cellulose using carbon monoxide and water on a Pt-Mo2C/C catalyst

    KAUST Repository

    Li, Jing

    2014-01-01

    CO and H2O were employed as the hydrogen source for cellulose conversion to polyols. Pt-Mo2C/C tandem catalyst with the Pt-Mo 2C domain responsible for H2 and/or H production and the Pt-C domain for cellulose conversion was fabricated. Considerable polyols were obtained over this tandem Pt-Mo2C/C catalyst. This journal is © 2014 The Royal Society of Chemistry.

  11. CYP719B1 is salutaridine synthase, the C-C phenol-coupling enzyme of morphine biosynthesis in opium poppy.

    Science.gov (United States)

    Gesell, Andreas; Rolf, Megan; Ziegler, Jörg; Díaz Chávez, María Luisa; Huang, Fong-Chin; Kutchan, Toni M

    2009-09-04

    Morphine is a powerful analgesic natural product produced by the opium poppy Papaver somniferum. Although formal syntheses of this alkaloid have been reported, the morphine molecule contains five stereocenters and a C-C phenol linkage that to date render a total synthesis of morphine commercially unfeasible. The C-C phenol-coupling reaction along the biosynthetic pathway to morphine in opium poppy is catalyzed by the cytochrome P450-dependent oxygenase salutaridine synthase. We report herein on the identification of salutaridine synthase as a member of the CYP719 family of cytochromes P450 during a screen of recombinant cytochromes P450 of opium poppy functionally expressed in Spodoptera frugiperda Sf9 cells. Recombinant CYP719B1 is a highly stereo- and regioselective enzyme; of forty-one compounds tested as potential substrates, only (R)-reticuline and (R)-norreticuline resulted in formation of a product (salutaridine and norsalutaridine, respectively). To date, CYP719s have been characterized catalyzing only the formation of a methylenedioxy bridge in berberine biosynthesis (canadine synthase, CYP719A1) and in benzo[c]phenanthridine biosynthesis (stylopine synthase, CYP719A14). Previously identified phenol-coupling enzymes of plant alkaloid biosynthesis belong only to the CYP80 family of cytochromes. CYP719B1 therefore is the prototype for a new family of plant cytochromes P450 that catalyze formation of a phenol-couple.

  12. A Novel Strategy for Biomass Upgrade: Cascade Approach to the Synthesis of Useful Compounds via C-C Bond Formation Using Biomass-Derived Sugars as Carbon Nucleophiles

    Directory of Open Access Journals (Sweden)

    Sho Yamaguchi

    2016-07-01

    Full Text Available Due to the depletion of fossil fuels, biomass-derived sugars have attracted increasing attention in recent years as an alternative carbon source. Although significant advances have been reported in the development of catalysts for the conversion of carbohydrates into key chemicals (e.g., degradation approaches based on the dehydration of hydroxyl groups or cleavage of C-C bonds via retro-aldol reactions, only a limited range of products can be obtained through such processes. Thus, the development of a novel and efficient strategy targeted towards the preparation of a range of compounds from biomass-derived sugars is required. We herein describe the highly-selective cascade syntheses of a range of useful compounds using biomass-derived sugars as carbon nucleophiles. We focus on the upgrade of C2 and C3 oxygenates generated from glucose to yield useful compounds via C-C bond formation. The establishment of this novel synthetic methodology to generate valuable chemical products from monosaccharides and their decomposed oxygenated materials renders carbohydrates a potential alternative carbon resource to fossil fuels.

  13. A Novel Strategy for Biomass Upgrade: Cascade Approach to the Synthesis of Useful Compounds via C-C Bond Formation Using Biomass-Derived Sugars as Carbon Nucleophiles.

    Science.gov (United States)

    Yamaguchi, Sho; Baba, Toshihide

    2016-07-20

    Due to the depletion of fossil fuels, biomass-derived sugars have attracted increasing attention in recent years as an alternative carbon source. Although significant advances have been reported in the development of catalysts for the conversion of carbohydrates into key chemicals (e.g., degradation approaches based on the dehydration of hydroxyl groups or cleavage of C-C bonds via retro-aldol reactions), only a limited range of products can be obtained through such processes. Thus, the development of a novel and efficient strategy targeted towards the preparation of a range of compounds from biomass-derived sugars is required. We herein describe the highly-selective cascade syntheses of a range of useful compounds using biomass-derived sugars as carbon nucleophiles. We focus on the upgrade of C2 and C3 oxygenates generated from glucose to yield useful compounds via C-C bond formation. The establishment of this novel synthetic methodology to generate valuable chemical products from monosaccharides and their decomposed oxygenated materials renders carbohydrates a potential alternative carbon resource to fossil fuels.

  14. CYP96T1 of Narcissus sp. aff. pseudonarcissus Catalyzes Formation of the Para-Para’ C-C Phenol Couple in the Amaryllidaceae Alkaloids

    Directory of Open Access Journals (Sweden)

    Matthew eKilgore

    2016-02-01

    Full Text Available The Amaryllidaceae alkaloids are a family of amino acid derived alkaloids with many biological activities; examples include haemanthamine, haemanthidine, galanthamine, lycorine, and maritidine. Central to the biosynthesis of the majority of these alkaloids is a C-C phenol-coupling reaction that can have para-para’, para-ortho’, or ortho-para’ regiospecificity. Through comparative transcriptomics of Narcissus sp. aff. pseudonarcissus, Galanthus sp., and Galanthus elwesii we have identified a para-para’ C-C phenol coupling cytochrome P450, CYP96T1, capable of forming the products (10bR,4aS-noroxomaritidine and (10bS,4aR-noroxomaritidine from 4’-O-methylnorbelladine. CYP96T1 was also shown to catalyzed formation of the para-ortho’ phenol coupled product, N-demethylnarwedine, as less than 1 % of the total product. CYP96T1 co-expresses with the previously characterized norbelladine 4’-O-methyltransferase. The discovery of CYP96T1 is of special interest because it catalyzes the first major branch in Amaryllidaceae alkaloid biosynthesis. CYP96T1 is also the first phenol-coupling enzyme characterized from a monocot.

  15. CYP96T1 of Narcissus sp. aff. pseudonarcissus Catalyzes Formation of the Para-Para' C-C Phenol Couple in the Amaryllidaceae Alkaloids.

    Science.gov (United States)

    Kilgore, Matthew B; Augustin, Megan M; May, Gregory D; Crow, John A; Kutchan, Toni M

    2016-01-01

    The Amaryllidaceae alkaloids are a family of amino acid derived alkaloids with many biological activities; examples include haemanthamine, haemanthidine, galanthamine, lycorine, and maritidine. Central to the biosynthesis of the majority of these alkaloids is a C-C phenol-coupling reaction that can have para-para', para-ortho', or ortho-para' regiospecificity. Through comparative transcriptomics of Narcissus sp. aff. pseudonarcissus, Galanthus sp., and Galanthus elwesii we have identified a para-para' C-C phenol coupling cytochrome P450, CYP96T1, capable of forming the products (10bR,4aS)-noroxomaritidine and (10bS,4aR)-noroxomaritidine from 4'-O-methylnorbelladine. CYP96T1 was also shown to catalyzed formation of the para-ortho' phenol coupled product, N-demethylnarwedine, as less than 1% of the total product. CYP96T1 co-expresses with the previously characterized norbelladine 4'-O-methyltransferase. The discovery of CYP96T1 is of special interest because it catalyzes the first major branch in Amaryllidaceae alkaloid biosynthesis. CYP96T1 is also the first phenol-coupling enzyme characterized from a monocot.

  16. Reaction Automata

    OpenAIRE

    Okubo, Fumiya; Kobayashi, Satoshi; YOKOMORI, Takashi

    2011-01-01

    Reaction systems are a formal model that has been introduced to investigate the interactive behaviors of biochemical reactions. Based on the formal framework of reaction systems, we propose new computing models called reaction automata that feature (string) language acceptors with multiset manipulation as a computing mechanism, and show that reaction automata are computationally Turing universal. Further, some subclasses of reaction automata with space complexity are investigated and their la...

  17. Coupling Reactions of α-Bromocarboxylate with Non-Aromatic N-Heterocycles

    Directory of Open Access Journals (Sweden)

    Jozef Csollei

    2009-08-01

    Full Text Available The conditions for the C-N bond forming reaction (C-N coupling reaction between α-bromocarboxylate and nitrogen-containing non-aromatic heterocyclic rings under heterogeneous copper(I oxide catalysis are investigated in this paper. All the generated compounds were fully characterized by IR, NMR and MS spectroscopy. Ab initio/DFT calculations of partial charges on nitrogen atoms in all the discussed heterocycles and on C(2 of carboxylate under applied conditions were predicted. These in silico results correlate relatively with the experimental observations.

  18. Diphenyldiacetylene complexes of molybdenum(IV) and tungsten(IV). Crystal structures of PPh/sub 4/(WCl/sub 5/(Ph-C triple bond C-C triple bond C-Ph)) x CCl/sub 4/ and PPh/sub 4/(WCl/sub 5/(Ph-C triple bond C-C(Br)=C(Br)-Ph)) x CCl/sub 4/

    Energy Technology Data Exchange (ETDEWEB)

    Stahl, K.; Weller, F.; Dehnicke, K. (Marburg Univ. (Germany, F.R.). Fachbereich Chemie)

    1984-11-01

    Syntheses and i.r. spectra of the following diphenyldiacetylene complexes are reported: (MoCl/sub 4/(Ph-C triple bond C-C triple bond C-Ph))/sub 2/ (1), (WCl/sub 4/(Ph-C triple bond C-C triple bond C-Ph))/sub 2/ (2), PPh/sub 4/(WCl/sub 5/(Ph-C triple bond C-C triple bond C-Ph)) x CCl/sub 4/ (3). 1 is formed in the reaction of MoCl/sub 5/ with excess diphenylacetylene. 2 is prepared from WCl/sub 6/ and excess diphenylacetylene with additional C/sub 2/Cl/sub 4/ as a reducing agent. Reaction of 2 with PPh/sub 4/Cl in CH/sub 2/Cl/sub 2/ solution in the presence of CCl/sub 4/ yields 3. The complexes contain one of the acetylene functions bonded in a metallacyclopropene ring; the metal atoms are seven-coordinated. 2 reacts with bromine to form the dibromide (WCl/sub 4/(Ph-C triple bond C-C(Br)=C(Br)-Ph/sub 2/))/sub 2/ (4). In CH/sub 2/Cl/sub 2/ solution and in presence of CCl/sub 4/ 4 is turned into the ionic complex PPh/sub 4/(WCl/sub 5/(Ph-C triple bond C-C(Br)=C(Br)-Ph)) x CCl/sub 4/ (5) by PPh/sub 4/Cl. The complexes 3 and 5 are characterized by structural analyses on the basis of X-ray diffraction data. 3 crystallizes monoclinic in the space group P2/sub 1//n with four formula units per unit cell (2623 observed, independent reflexions, R = 5.4%). 5 crystallizes in the same space group, set P2/sub 1//c, the unit cell containing four formula units (2537 observed, independent reflexions, R = 5.4%).

  19. Study of {lambda} hyperon production in C+C collisions at 2 AGeV beam energy with the HADES spectrometer

    Energy Technology Data Exchange (ETDEWEB)

    Kanaki, K.

    2007-03-15

    The HADES spectrometer is a high resolution detector installed at the SIS/GSI, Darmstadt. It was primarily designed for studying dielectron decay channels of vector mesons. However, its high accuracy capabilities make it an attractive tool for investigating other rare probes at these beam energies, like strange baryons. Development and investigation of Multiwire Drift Chambers for high spatial resolution have been provided. One of the early experimental runs of HADES was analyzed and the {lambda} hyperon signal was successfully reconstructed for the first time in C+C collisions at 2 AGeV beam kinetic energy. The total {lambda} production cross section is contrasted with expectations from simulations and compared with measurements of the {lambda} yield in heavier systems at the same energy. In addition, the result is considered in the context of strangeness balance and the relative strangeness content of the reaction products is determined. (orig.)

  20. Microstructure and Mechanical Properties of Two Kinds of Dual-matrix C/C Composites

    Directory of Open Access Journals (Sweden)

    LIU Hao

    2017-08-01

    Full Text Available The microstructure and mechanical properties of two kinds of dual-matrix C/C composites were studied by polarized light microscopy (PLM, scanning electron microscopy (SEM and mechanical properties tests techniques respectively. PLM results indicate that the matrix carbon exhibits the smooth laminar structure of the pyrocarbon, the isotropic, mosaics and flow domains of the pitch carbon. The TEM results show the normal pitch carbon is the grape structure; the mesophase pitch carbon is the lamellar banded structure. Materials with multi-interface structure can improve the flexural strength and fracture toughness, the load-displacement curve shows the load drop is decreased for step type, the composites show a pseudo-plastic fracture characteristics. The flexural strengths of the material A and material B are 206.68MPa and 243.66MPa, the fracture toughness are 8.06MPa·m1/2 and 9.66MPa·m1/2, respectively. The flexural strength and fracture toughness of material B are both superior than that of material A.

  1. Relationships Between Metformin, Paraoxonase-1 and the Chemokine (C-C Motif) Ligand 2.

    Science.gov (United States)

    Camps, Jordi; Hernandez-Aguilera, Anna; Garcia-Heredia, Anabel; Cabre, Noemi; Luciano-Mateo, Fedra; Arenas, Meritxell; Joven, Jorge

    2016-01-01

    Metformin is a biguanide used in the treatment of type 2 diabetes mellitus and obesity. The main mechanism of action is to decrease the intestinal glucose absorption and the hepatic glucose production, however, it does not influence insulin secretion. Metformin also increases the affinity of the insulin receptor, reduces high insulin levels and improves insulin resistance. Additionally, it promotes weight loss. Metformin is a pleiotropic compound but acts, largely, by activating 5 adenosine monophosphate (AMP)-activated protein kinase (AMPK). Data suggest that the therapeutic effects of this compound are mediated, at least in part, through an upregulation of paraoxonase-1 (PON1) synthesis. PON1 is a thiolactonase that degrades lipid peroxides, and downregulates the chemokine (C-C motif) ligand 2 (CCL2) which is a pro-inflammatory chemokine that stimulates the migration of monocytes to areas of inflammation where they differentiate into macrophages. However, the prescription of metformin in patients with liver disease is controversial since, in some cases, this drug causes worsening of liver function. Patients with chronic liver disease have decreased hepatic PON1 activity. A study in mice deficient in PON1 showed that in this experimental model, metformin administration increased the severity of steatosis, increased CCL2 expression, did not activate AMPK, and increased the expression of the apoptosis marker caspase-9. These results suggest that PON1 is essential for the successful activation of AMPK in the liver, and for metformin to demonstrate its therapeutic function.

  2. Migrating C/C++ Software to Mobile Platforms in the ADM Context

    Directory of Open Access Journals (Sweden)

    Liliana Martinez

    2017-03-01

    Full Text Available Software technology is constantly evolving and therefore the development of applications requires adapting software components and applications in order to be aligned to new paradigms such as Pervasive Computing, Cloud Computing and Internet of Things. In particular, many desktop software components need to be migrated to mobile technologies. This migration faces many challenges due to the proliferation of different mobile platforms. Developers usually make applications tailored for each type of device expending time and effort. As a result, new programming languages are emerging to integrate the native behaviors of the different platforms targeted in development projects. In this direction, the Haxe language allows writing mobile applications that target all major mobile platforms. Novel technical frameworks for information integration and tool interoperability such as Architecture-Driven Modernization (ADM proposed by the Object Management Group (OMG can help to manage a huge diversity of mobile technologies. The Architecture-Driven Modernization Task Force (ADMTF was formed to create specifications and promote industry consensus on the modernization of existing applications. In this work, we propose a migration process from C/C++ software to different mobile platforms that integrates ADM standards with Haxe. We exemplify the different steps of the process with a simple case study, the migration of “the Set of Mandelbrot” C++ application. The proposal was validated in Eclipse Modeling Framework considering that some of its tools and run-time environments are aligned with ADM standards.

  3. Accurate Reaction Enthalpies and Sources of Error in DFT Thermochemistry for Aldol, Mannich, and α-Aminoxylation Reactions

    Science.gov (United States)

    Wheeler, Steven E.; Moran, Antonio; Pieniazek, Susan N.

    2009-01-01

    Enthalpies for bond-forming reactions that are subject to organocatalysis have been predicted using the high-accuracy CBS-QB3 model chemistry and six DFT functionals. Reaction enthalpies were decomposed into contributions from changes in bonding and other intramolecular effects via the hierarchy of homodesmotic reactions. The order of the reaction exothermicities (aldol < Mannich ≈ α-aminoxylation) arises primarily from changes in formal bond types mediated by contributions from secondary intramolecular interactions. In each of these reaction types, methyl substitution at the β- and γ-positions stabilizes the products relative to the unsubstituted case. The performance of six DFT functionals (B3LYP, B3PW91, B1B95, MPW1PW91, PBE1PBE, and M06-2X), MP2, and SCS-MP2 has been assessed for the prediction of these reaction enthalpies. Even though the PBE1PBE and M06-2X functionals perform well for the aldol and Mannich reactions, errors roughly double when these functionals are applied to the α-aminoxylation reactions. On the other hand, B3PW91 and B1B95, which offer modest accuracy for the aldol and Mannich reactions, yield reliable predictions for the two α-aminoxylation reactions. The excellent performance of the M06-2X and PBE1PBE functionals for aldol and Mannich reactions stems from the cancellation of sizeable errors arising from inadequate descriptions of the underlying bond transformations and intramolecular interactions. SCS-MP2/cc-pVTZ performs most consistently across these three classes of reactions, although the reaction exothermicities are systematically underestimated by 1–3 kcal mol−1. Conventional MP2, when paired with the cc-pVTZ basis set, performs somewhat better than SCS-MP2 for some of these reactions, particularly the α-aminoxylations. Finally, the merits of benchmarking DFT functionals for the set of simple chemically meaningful transformations underlying all bond-forming reactions are discussed. PMID:19711937

  4. Acetaldehyde partial oxidation on the Au(111) model catalyst surface: C-C bond activation and formation of methyl acetate as an oxidative coupling product

    Science.gov (United States)

    Karatok, Mustafa; Vovk, Evgeny I.; Shah, Asad A.; Turksoy, Abdurrahman; Ozensoy, Emrah

    2015-11-01

    Partial oxidation of acetaldehyde (CH3CHO) on the oxygen pre-covered Au(111) single crystal model catalyst was investigated via Temperature Programmed Desorption (TPD) and Temperature Programmed Reaction Spectroscopy (TPRS) techniques, where ozone (O3) was utilized as the oxygen delivery agent providing atomic oxygen to the reacting surface. We show that for low exposures of O3 and small surface oxygen coverages, two partial oxidation products namely, methyl acetate (CH3COOCH3) and acetic acid (CH3COOH) can be generated without the formation of significant quantities of carbon dioxide. The formation of methyl acetate as the oxidative coupling reaction product implies that oxygen pre-covered Au(111) single crystal model catalyst surface can activate C-C bonds. In addition to the generation of these products; indications of the polymerization of acetaldehyde on the gold surface were also observed as an additional reaction route competing with the partial and total oxidation pathways. The interplay between the partial oxidation, total oxidation and polymerization pathways reveals the complex catalytic chemistry associated with the interaction between the acetaldehyde and atomic oxygen on catalytic gold surfaces.

  5. Effects of chemokine (C-C motif) ligand 1 on microglial function.

    Science.gov (United States)

    Akimoto, Nozomi; Ifuku, Masataka; Mori, Yuki; Noda, Mami

    2013-07-05

    Microglia, which constitute the resident macrophages of the central nervous system (CNS), are generally considered as the primary immune cells in the brain and spinal cord. Microglial cells respond to various factors which are produced following nerve injury of multiple aetiologies and contribute to the development of neuronal disease. Chemokine (C-C motif) ligand 1 (CCL-1), a well-characterized chemokine secreted by activated T cells, has been shown to play an important role in neuropathic pain induced by nerve injury and is also produced in various cell types in the CNS, especially in dorsal root ganglia (DRG). However, the role of CCL-1 in the CNS and the effects on microglia remains unclear. Here we showed the multiple effects of CCL-1 on microglia. We first showed that CCR-8, a specific receptor for CCL-1, was expressed on primary cultured microglia, as well as on astrocytes and neurons, and was upregulated in the presence of CCL-1. CCL-1 at concentration of 1 ng/ml induced chemotaxis, increased motility at a higher concentration (100 ng/ml), and increased proliferation and phagocytosis of cultured microglia. CCL-1 also activated microglia morphologically, promoted mRNA levels for brain-derived neurotrophic factor (BDNF) and IL-6, and increased the release of nitrite from microglia. These indicate that CCL-1 has a role as a mediator in neuron-glia interaction, which may contribute to the development of neurological diseases, especially in neuropathic pain. Copyright © 2013 The Authors. Published by Elsevier Inc. All rights reserved.

  6. C-C Motif Chemokine Receptor 9 Exacerbates Pressure Overload-Induced Cardiac Hypertrophy and Dysfunction.

    Science.gov (United States)

    Xu, Zhengxi; Mei, Fanghua; Liu, Hanning; Sun, Cheng; Zheng, Zhe

    2016-05-04

    Maladaptive cardiac hypertrophy is a major risk factor for heart failure, which is the leading cause of death worldwide. C-C motif chemokine receptor 9 (CCR9), a subfamily of the G protein-coupled receptor supergene family, has been highlighted as an immunologic regulator in the development and homing of immune cells and in immune-related diseases. Recently, CCR9 was found to be involved in the pathogenesis of other diseases such as cardiovascular diseases; however, the effects that CCR9 exerts in cardiac hypertrophy remain elusive. We observed significantly increased CCR9 protein levels in failing human hearts and in a mouse or cardiomyocyte hypertrophy model. In loss- and gain-of-function experiments, we found that pressure overload-induced hypertrophy was greatly attenuated by CCR9 deficiency in cardiac-specific CCR9 knockout mice, whereas CCR9 overexpression in cardiac-specific transgenic mice strikingly enhanced cardiac hypertrophy. The prohypertrophic effects of CCR9 were also tested in vitro, and a similar phenomenon was observed. Consequently, we identified a causal role for CCR9 in pathological cardiac hypertrophy. Mechanistically, we revealed a lack of difference in the expression levels of mitogen-activated protein kinases between groups, whereas the phosphorylation of AKT/protein kinase B and downstream effectors significantly decreased in CCR9 knockout mice and increased in CCR9 transgenic mice after aortic binding surgery. The prohypertrophic effects of CCR9 were not attributable to the mitogen-activated protein kinase signaling pathway but rather to the AKT-mammalian target of rapamycin-glycogen synthase kinase 3β signaling cascade. © 2016 The Authors. Published on behalf of the American Heart Association, Inc., by Wiley Blackwell.

  7. C-C chemokine receptor-7 mediated endocytosis of antibody cargoes into intact cells

    Directory of Open Access Journals (Sweden)

    Xavier eCharest-Morin

    2013-09-01

    Full Text Available The C-C chemokine receptor-7 (CCR7 is a G protein coupled receptor that has a role in leukocyte homing, but that is also expressed in aggressive tumor cells. Preclinical research supports that CCR7 is a valid target in oncology. In view of the increasing availability of therapeutic monoclonal antibodies that carry cytotoxic cargoes, we studied the feasibility of forcing intact cells to internalize known monoclonal antibodies by exploiting the cycle of endocytosis and recycling triggered by the CCR7 agonist CCL19. Firstly, an anti-CCR7 antibody (CD197; clone 150503 labeled surface recombinant CCR7 expressed in intact HEK 293a cells and the fluorescent antibody was internalized following CCL19 treatment. Secondly, a recombinant myc-tagged CCL19 construction was exploited along the anti-myc monoclonal antibody 4A6. The myc-tagged ligand was produced as a conditioned medium of transfected HEK 293a cells that contained the equivalent of 430 ng/ml of immunoreactive CCL19 (average value, ELISA determination. CCL19-myc, but not authentic CCL19, carried the fluorophore-labeled antibody 4A6 into other recipient cells that expressed recombinant CCR7 (microscopy, cytofluorometry. The immune complexes were apparent in endosomal structures, colocalized well with the small GTPase Rab5 and progressed toward Rab7-positive endosomes. A dominant negative form of Rab5 (GDP-locked inhibited this endocytosis. Further, endosomes in CCL19-myc- or CCL19-stimulated cells were positive for β-arrestin2, but rarely for β-arrestin1. Following treatment with CCL19-myc and the 4A6 antibody, the melanoma cell line A375 that expresses endogenous CCR7 was specifically stained using a secondary peroxidase-conjugated antibody. Agonist-stimulated CCR7 can transport antibody-based cargoes, with possible therapeutic applications in oncology.

  8. Reduction of unsaturated compounds under interstellar conditions: chemoselective reduction of C≡C and C=C bonds over C=O functional group

    Science.gov (United States)

    Jonusas, Mindaugas; Guillemin, Jean-Claude; Krim, Lahouari

    2017-07-01

    The knowledge of the H-addition reactions on unsaturated organic molecules bearing a triple or a double carbon-carbon bond such as propargyl or allyl alcohols and a CO functional group such as propynal, propenal or propanal may play an important role in the understanding of the chemical complexity of the interstellar medium. Why different aldehydes like methanal, ethanal, propynal and propanal are present in dense molecular clouds while the only alcohol detected in those cold regions is methanol? In addition, ethanol has only been detected in hot molecular cores. Are those saturated and unsaturated aldehyde and alcohol species chemically linked in molecular clouds through solid phase H-addition surface reactions or are they formed through different chemical routes? To answer such questions, we have investigated a hydrogenation study of saturated and unsaturated aldehydes and alcohols at 10 K. We prove through this experimental study that while pure unsaturated alcohol ices bombarded by H atoms lead to the formation of the corresponding fully or partially saturated alcohols, surface H-addition reactions on unsaturated aldehyde ices exclusively lead to the formation of fully saturated aldehyde. Such results show that in addition to a chemoselective reduction of C≡C and C=C bonds over the C=O group, there is no link between aldehydes and their corresponding alcohols in reactions involving H atoms in dense molecular clouds. Consequently, this could be one of the reasons why some aldehydes such as propanal are abundant in dense molecular clouds in contrast to the non-detection of alcohol species larger than methanol.

  9. Drug Reactions

    Science.gov (United States)

    ... or diabetes. But medicines can also cause unwanted reactions. One problem is interactions, which may occur between ... more serious. Drug allergies are another type of reaction. They can be mild or life-threatening. Skin ...

  10. Research progress on trifluoromethyl-based radical reaction process

    Science.gov (United States)

    Song, Hao

    2017-12-01

    Due to the unique properties imparted by the trifluoromethyl group, such as high electron density and strong lipotropy, which effectively improve acidity, lipophilicity and metabolic stability of the molecule itself, trifluoromethyl-substituted organic compounds are becoming increasingly important as structural motifs in pharmaceuticals, agrochemicals and organic materials. In this review, we present several methods developed for the direct introduction of a trifluoromethyl group, beginning with its rich and storied history. Then the present article addresses mechanism and process in carbon-carbon bond forming reaction based on radical process which is divided into three parts according to the way of CF3 radical generation. Finally, challenges and opportunities of researches on trifluoromethylation reactions facing are prospected.

  11. Single-molecule chemical reactions on DNA origami

    DEFF Research Database (Denmark)

    Voigt, Niels Vinther; Tørring, Thomas; Rotaru, Alexandru

    2010-01-01

    as templates for building materials with new functional properties. Relatively large nanocomponents such as nanoparticles and biomolecules can also be integrated into DNA nanostructures and imaged. Here, we show that chemical reactions with single molecules can be performed and imaged at a local position...... on a DNA origami scaffold by atomic force microscopy. The high yields and chemoselectivities of successive cleavage and bond-forming reactions observed in these experiments demonstrate the feasibility of post-assembly chemical modification of DNA nanostructures and their potential use as locally......DNA nanotechnology and particularly DNA origami, in which long, single-stranded DNA molecules are folded into predetermined shapes, can be used to form complex self-assembled nanostructures. Although DNA itself has limited chemical, optical or electronic functionality, DNA nanostructures can serve...

  12. C-C and C-N Couplings Following Hydride Addition on Isocyanide Cyclopolyenyl Dimolybdenum Complexes to Give Tethered Aldimine and Aminocarbene Derivatives.

    Science.gov (United States)

    Alvarez, Belén; Alvarez, M Angeles; García, M Esther; García-Vivó, Daniel; Ruiz, Miguel A

    2017-10-09

    Reaction of [Mo2 Cp2 (μ-κ(1) :κ(1) ,η(6) -PMes*)(CO)2 ] with S or Se followed by protonation with [H(OEt2 )2 ](BAr'4 ) gave the cationic derivatives [Mo2 Cp2 {μ-κ(2)P,E :κ(1)P ,η(5) -EP(C6 H3 tBu3 )}(CNR)(CO)2 ](BAr'4 ) (E=S; R=tBu, iPr, Ph, 4-C6 H4 OMe, Xyl; or E=Se; R=tBu; Ar'=3,5-C6 H3 (CF3 )2 ). Reaction of the latter with K[BHsBu3 ] yielded the aldimine complexes [Mo2 Cp2 {μ-κ(2)P,E :κ(2)P,N ,η(4) -SP(C6 H3 tBu3 (CHNR))}(CO)2 ] and their aminocarbene isomers [Mo2 Cp2 {μ-κ(2)P,E :κ(2)P,C ,η(4) -SP(C6 H3 tBu3 (NRCH))}(CO)2 ] (R ≠ Xyl), following C-C and C-N couplings, respectively. Monitoring of these reactions revealed that the initial H(-) attack takes place at a Cp ligand to give cyclopentadiene intermediates [Mo2 Cp{μ-κ(2)P,S :κ(1)P ,η(5) -SP(C6 H3 tBu3 )}(η(4) -C5 H6 )(CNR)(CO)2 ], which then undergo C-H oxidative addition to give the hydride isomers [Mo2 Cp2 {μ-κ(2)P,S :κ(1)P ,η(3) -SP(C6 H3 tBu3 )}(H)(CNR)(CO)2 ]. In turn, the latter rearrange to give the aldimine and aminocarbene complexes. DFT calculations revealed that the hydride intermediates first undergo migratory insertion of the isocyanide ligand into the Mo-H bond to give unobservable formimidoyl intermediates, which then evolve either by nucleophilic attack of the N atom on the C6 ring (C-N coupling) or by migratory insertion of the formimidoyl ligand into the C6 ring (C-C coupling). Our data suggest that increasing the size of the substituent R at the isocyanide ligand destabilizes the aldimine isomer to a greater extent, thus favoring formation of the aminocarbene complex. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Controllable Fabricating Dielectric-Dielectric SiC@C Core-Shell Nanowires for High-Performance Electromagnetic Wave Attenuation.

    Science.gov (United States)

    Liang, Caiyun; Wang, Zhijiang

    2017-11-22

    Heterostructured dielectric-dielectric nanowires of SiC core and carbon shell (SiC@C) with high-performance electromagnetic wave absorption were synthesized by combining an interfacial in situ polymer encapsulation and carbonization process. This approach overcomes the shortcomings of previous reported methods to prepare carbon shell that both carbon shell and free carbon particles are formed simultaneously. In our developed approach, the core of SiC nanowires are first positively charged. Then the negative resorcinol-formaldehyde polymers as the carbon source are anchored on SiC nanowires under the attraction of electrostatic force, which well suppresses the nucleation of free carbon particles. The thickness of the carbon shell could be modulated from 4 to 20 nm by simply adjusting the moral ratio of resorcinol to SiC nanowires. The resulting SiC@C core-shell nanostructures without free carbon particles offer synergism among the SiC nanowires and the carbon shells, generating multiple dipolar polarization, surfaced polarization, and associated relaxations, which endow SiC@C hybrid nanowires with a minimum reflection loss (RL) value of -50 dB at the frequency of 12 GHz and an effective absorption bandwidth of 8 GHz with RL value under -10 dB at the optimized state. Our results demonstrate that SiC@C hybrid nanowires are promising candidates for electromagnetic wave absorption applications.

  14. Highly Conductive, Mechanically Robust, and Electrochemically Inactive TiC/C Nanofiber Scaffold for High-Performance Silicon Anode Batteries

    KAUST Repository

    Yao, Yan

    2011-10-25

    Silicon has a high specific capacity of 4200 mAh/g as lithium-ion battery anodes, but its rapid capacity fading due to >300% volume expansion and pulverization presents a significant challenge for practical applications. Here we report a core-shell TiC/C/Si inactive/active nanocomposite for Si anodes demonstrating high specific capacity and excellent electrochemical cycling. The amorphous silicon layer serves as the active material to store Li+, while the inactive TiC/C nanofibers act as a conductive and mechanically robust scaffold for electron transport during the Li-Si alloying process. The core-shell TiC/C/Si nanocomposite anode shows ∼3000 mAh g-1 discharge capacity and 92% capacity retention after 100 charge/discharge cycles. The excellent cycling stability and high rate performance could be attributed to the tapering of the nanofibers and the open structure that allows facile Li ion transport and the high conductivity and mechanical stability of the TiC/C scaffold. © 2011 American Chemical Society.

  15. Synthesis and systematic evaluation of symmetric sulfonated centrally C-C bonded cyanine near-infrared dyes for protein labelling

    NARCIS (Netherlands)

    Wal, Van Der Steffen; Kuil, Joeri; Valentijn, A.R.P.M.; Leeuwen, Van Fijs W.B.

    2016-01-01

    The most commonly used near-infrared cyanine dyes contain an aryl ether that is not fully stable towards nucleophiles. Replacement of the aryl ether by a more stable carbon-carbon bond can improve the stability. In this work we have synthesized a series of four negatively-charged symmetrical C-C

  16. Computer Simulation of the E.C.C.S. Buckling Curve using a Monte-Carlo Method

    NARCIS (Netherlands)

    Strating, J.; Vos, H.

    1973-01-01

    The application of a Monte-Carlo simulation procedure to obtain the distribution function of the maximum load of a hinged column with imperfections is discussed. Buckling tests carried out by the E.C.C.S. on IPE 160 sections have been simulated. Information concerning the column variables is

  17. [Detection of HBV DNA by sensitive techniques and definition of chronic VHB infection by pre-C-C mutants].

    Science.gov (United States)

    Lebarbier, C; Williams, V; Garandeau, C; Bellaiche, G; Deny, P; Maisonneuve, L; Gordien, E

    2004-11-01

    Our purpose is to assess the question of the definition of hepatitis B virus pre-C-C mutant-chronic infection, according to the level of the viral load at the era of very sensitive techniques of quantification of HBV DNA.

  18. Page 1 Chromones—IV - 35 acetic acid (10.0 c.c.) and nitric acid (d ...

    Indian Academy of Sciences (India)

    methylchromone (I, R = R1 = Me) at 0° : 5-Methoxy-2-methyl-8-nitrochromone (III, R = R1 = Me). 5-Methoxy-2-methylchromone (1-0 g.) was cooled externally to 0°, and a cooled mixture of concentrated Sulphuric acid (5.0 c.c.) and nitric acid (d. 1.42 ...

  19. Interaction between lattice dislocations and grain boundaries in f.c.c. and ordered compounds : a computer simulation

    NARCIS (Netherlands)

    Pestman, B.J.; Hosson, J.Th.M. De; Vitek, V.; Schapink, F.W.

    1991-01-01

    The interaction of 1/2<110> screw- and 60° dislocations with symmetric [110] tilt boundaries was investigated by atomistic simulations using many-body potentials representing a pure f.c.c. metal and ordered intermetallic compounds. The calculations were performed with and without an applied shear

  20. An exploration on the synthesis and bio-applications of derivatives ...

    African Journals Online (AJOL)

    The Mannich reaction is a three-component reaction of an aldehyde, a primary or secondary amine and a ketone which is one of the most powerful C-C bond forming reactions in organic synthesis. It leads to β-amino carbonyl compounds, which are useful for the syntheses of nitrogen containing compounds, such as natural ...

  1. Phenomenological description of a three-center insertion reaction: an information-theoretic study.

    Science.gov (United States)

    Esquivel, Rodolfo O; Flores-Gallegos, Nelson; Dehesa, Jesús S; Angulo, Juan Carlos; Antolín, Juan; López-Rosa, Sheila; Sen, K D

    2010-02-04

    Information-theoretic measures are employed to describe the course of a three-center chemical reaction in terms of detecting the transition state and the stationary points unfolding the bond-forming and bond-breaking regions which are not revealed in the energy profile. The information entropy profiles for the selected reactions are generated by following the intrinsic-reaction-coordinate (IRC) path calculated at the MP2 level of theory from which Shannon entropies in position and momentum spaces at the QCISD(T)/6-311++G(3df,2p) level are determined. Several complementary reactivity descriptors are also determined, such as the dipole moment, the molecular electrostatic potential (MEP) obtained through a multipole expansion (DMA), the atomic charges and electric potentials fitted to the MEP, the hardness and softness DFT descriptors, and several geometrical parameters which support the information-theoretic analysis. New density-based structures related to the bond-forming and bond-breaking regions are proposed. Our results support the concept of a continuum of transient of Zewail and Polanyi for the transition state rather than a single state, which is also in agreement with reaction-force analyses.

  2. Impedance spectroscopy of heterojunction solar cell a-SiC/c-Si with ITO antireflection film investigated at different temperatures

    Science.gov (United States)

    Šály, V.; Perný, M.; Janíček, F.; Huran, J.; Mikolášek, M.; Packa, J.

    2017-04-01

    Progressive smart photovoltaic technologies including heterostructures a-SiC/c-Si with ITO antireflection film are one of the prospective replacements of conventional photovoltaic silicon technology. Our paper is focused on the investigation of heterostructures a-SiC/c-Si provided with a layer of ITO (indium oxide/tin oxide 90/10 wt.%) which acts as a passivating and antireflection coating. Prepared photovoltaic cell structure was investigated at various temperatures and the influence of temperature on its operation was searched. The investigation of the dynamic properties of heterojunction PV cells was carried out using impedance spectroscopy. The equivalent AC circuit which approximates the measured impedance data was proposed. Assessment of the influence of the temperature on the operation of prepared heterostructure was carried out by analysis of the temperature dependence of AC equivalent circuit elements.

  3. Impact of Intragranular Substructure Parameters on the Forming Limit Diagrams of Single-Phase B.C.C. Steels

    Directory of Open Access Journals (Sweden)

    Gérald Franz

    2013-11-01

    Full Text Available An advanced elastic-plastic self-consistent polycrystalline model, accounting for intragranular microstructure development and evolution, is coupled with a bifurcation-based localization criterion and applied to the numerical investigation of the impact of microstructural patterns on ductility of single-phase steels. The proposed multiscale model, taking into account essential microstructural aspects, such as initial and induced textures, dislocation densities, and softening mechanisms, allows us to emphasize the relationship between intragranular microstructure of B.C.C. steels and their ductility. A qualitative study in terms of forming limit diagrams for various dislocation networks, during monotonic loading tests, is conducted in order to analyze the impact of intragranular substructure parameters on the formability of single-phase B.C.C. steels.

  4. Interferon alpha and Tat involvement in the immunosuppression of uninfected T cells and C-C chemokine decline in AIDS.

    Science.gov (United States)

    Zagury, D; Lachgar, A; Chams, V; Fall, L S; Bernard, J; Zagury, J F; Bizzini, B; Gringeri, A; Santagostino, E; Rappaport, J; Feldman, M; Burny, A; Gallo, R C

    1998-03-31

    HIV type 1 (HIV-1) not only directly kills infected CD4(+) T cells but also induces immunosuppression of uninfected T cells. Two immunosuppressive proteins, interferon alpha (IFNalpha) and extracellular Tat, mediate this process because specific antibodies against these proteins prevent generation of suppressor cells in HIV-1-infected peripheral blood mononuclear cell cultures. Furthermore, the production of C-C chemokines in response to immune cell activation, initially enhanced by IFNalpha and Tat, ultimately is inhibited by these proteins in parallel with their induction of immunosuppression. The clinical corollary is the immunosuppression of uninfected T cells and the decline in C-C chemokine release found at advanced stages of HIV-1 infection paralleling rising levels of IFNalpha and extracellular Tat. We, therefore, suggest that IFNalpha and Tat may be critical targets for anti-AIDS strategies.

  5. Microstructure of C/C composites prepared by chemical vapor infiltration method with vaporized kerosene as a precursor

    Energy Technology Data Exchange (ETDEWEB)

    Wang Jiping [State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China)]. E-mail: jipingwang@gmail.com; Qian Junmin [State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Jin Zhihao [State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Qiao Guanjun [State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China)

    2006-03-15

    The microstructures of two types of C/C composites prepared from different carbon felts by a rapid densification method, thermal gradient chemical vapor infiltration with vaporized kerosene as a precursor, at 1080-1120 deg. C for 6 h were characterized by polarized light microscopy (PLM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman micro-spectrometry techniques. The experimental results show that the fibers in the two composites are both surrounded by ring-shaped pyrocarbons with rough laminar texture, but the thickness, the surface morphology of the pyrocarbons and the graphitizability of the composites depend much on the configurations of carbon felts. The C/C composite fabricated from a higher porosity carbon felt possesses larger thickness and rougher surface of pyrocarbon, and has a lower graphitizability after heat treatment at 2300 deg. C for 2 h.

  6. Effects of Preform Density on Structure and Property of C/C-SiC Composites Fabricated by Gaseous Silicon Infiltration

    Directory of Open Access Journals (Sweden)

    CAO Yu

    2016-07-01

    Full Text Available The 3-D needled C/C preforms with different densities deposited by chemical vapor infiltration (CVI method were used to fabricate C/C-SiC composites by gaseous silicon infiltration (GSI. The porosity and CVI C thickness of the preforms were studied, and the effects of preform density on the mechanical and thermal properties of C/C-SiC composites were analyzed. The results show that with the increase of preform density, the preform porosity decreases and the CVI C thickness increases from several hundred nanometers to several microns. For the C/C-SiC composites, as the preform density increases, the residual C content increases while the density and residual Si content decreases. The SiC content first keeps at a high level of about 40% (volume fraction, which then quickly reduces. Meanwhile, the mechanical properties increase to the highest values when the preform density is 1.085g/cm3, with the flexure strength up to 308.31MP and fracture toughness up to 11.36MPa·m1/2, which then decrease as the preform density further increases. The thermal conductivity and CTE of the composites, however, decrease with the increase of preform density. It is found that when the preform porosity is too high, sufficient infiltration channels lead to more residual Si, and thinner CVI C thickness results in the severe corrosion of the reinforcing fibers by Si and lower mechanical properties. When the preform porosity is relatively low, the contents of Si and SiC quickly reduce since the infiltration channels are rapidly blocked, resulting in the formation of large closed pores and not high mechanical properties.

  7. The use of ultrasmall iron(0) nanoparticles as catalysts for the selective hydrogenation of unsaturated C-C bonds.

    Science.gov (United States)

    Kelsen, Vinciane; Wendt, Bianca; Werkmeister, Svenja; Junge, Kathrin; Beller, Matthias; Chaudret, Bruno

    2013-04-28

    The performance of well-defined ultrasmall iron(0) nanoparticles (NPs) as catalysts for the selective hydrogenation of unsaturated C-C and C=X bonds is reported. Monodisperse iron nanoparticles of about 2 nm size are synthesized by the decomposition of {Fe(N[Si(CH3)3]2)2}2 under dihydrogen. They are found to be active for the hydrogenation of various alkenes and alkynes under mild conditions and weakly active for C=O bond hydrogenation.

  8. A method of quantitative characterization for the component of C/C composites based on the PLM video

    Science.gov (United States)

    Li, Y. X.; Qi, L. H.; Song, Y. S.; Li, H. J.

    2016-07-01

    PLM video is used for studying the microstructure of C/C composites, because it contains the structure and motion information at the same time. It means that PLM video could provide more comprehensive microstructure features of C/C composites, and then the microstructure could be quantitatively characterized by image processing. However, several unavoidable displacements still exist in the PLM video, which could occur during the process of image acquisition. Therefore, an image registration method was put forward to correct the displacements by the phase correlation, and further to achieve the quantitative characterization of component combined with image fusion and threshold segmentation based on the PLM video of C/C composites. Specifically, PLM video was decomposed to a frame sequence firstly. Then a series of processes was carried out on this basis, including selecting the frame as equal interval, segmenting the static and dynamic regions and correcting the relative displacements between the adjacent frames. Meanwhile, the result of image registration was verified through image fusion, and it indicates that the proposed method could eliminate the displacements effectively. Finally, some operations of image processing were used to segment the components and calculate their fractions, thus the quantitative calculation was achieved successfully.

  9. Finite Element Modeling of 3D Orthogonal Woven C/C Composite Based on Micro-Computed Tomography Experiment

    Science.gov (United States)

    Shigang, Ai; Xiaolei, Zhu; Yiqi, Mao; Yongmao, Pei; Daining, Fang

    2014-08-01

    Two-dimensional images of C/C 3D orthogonal woven composite were captured by X-ray micro-computed tomography (μCT). The μCT data reveal comprehensive meso-geometrical information about the carbon fiber tows, carbon matrix, and void defects etc. The fibers tows are characterized consisting of the cancroids of a tow, the area and aspect ratio of its cross-section. A statistical analysis of the volume fraction and positioning of the void defects in the 3D orthogonal woven architecture is performed based on 2-D micro tomography images. The tabulated statistics are sufficient to generate the virtual specimen, which shares the same statistical characteristics of the C/C composite and the void defects are included. Three-point bending experiment and simulation are carried out and the results show that the finite element model including the void defects gives more accurate results. The finite element model will give some highlights to the numerical simulation approach of the C/C textile composite under thermal, mechanical and oxygen coupled service environment. And the numerical techniques for modelling such kind materials with woven architecture and void defects are recommended.

  10. Study of Meldrum's Acid Cyclization Reactions.

    Science.gov (United States)

    Trujillo, Cristina; Goya, Pilar; Rozas, Isabel

    2018-02-27

    On the basis of the cyclization reactions reported by Danishefsky et al. of Meldrum's acid hydroxylethyl and anilinoethyl derivatives, the cyclization of the sulfamidomethylene and ureidomethylene derivatives was attempted without success. To understand the lack of reactivity of these compounds versus the successful cyclization of the ethyl derivatives, the corresponding mechanisms of reaction for both processes have been explored by means of MP2/6-311+G(d,p) calculations in an aqueous environment. The conformational analysis of all of these structures revealed that, while for the ethyl derivatives the minimum energy conformation corresponds to that of the cyclization initiating structure, for the methylene analogues the entrance channel conformations are substantially less stable than the energy minimum. Intramolecular hydrogen bonds were found in all of the energy minima as well as in the cyclization initiating conformations as determined by analysis of their electron density. The potential energy surfaces for the successful and unsuccessful cyclization processes were obtained at room temperature and 100 °C. Comparison of both processes allows rationalization that the lack of reactivity of the methylene derivatives can be thermodynamically explained based not only on the strength of the intramolecular hydrogen bond formed in their energy minima but also by the energy penalty needed to reach the entrance channel conformation and by the calculated energy barriers.

  11. Low-oxidation state indium-catalyzed C-C bond formation.

    Science.gov (United States)

    Schneider, Uwe; Kobayashi, Shu

    2012-08-21

    highly enantioselective allylation, crotylation, and α-chloroallylation reactions of hydrazones. These transformations proceeded with rare constitutional selectivities and remarkable diastereoselectivities. Furthermore, indium(I) triflate served as the most effective catalyst for allylations and propargylations of C(sp(3)) electrophiles such as O,O-acetals, N,O-aminals, and ethers, and we applied this methodology to carbohydrate chemistry. In addition, a catalyst system composed of indium(I) chloride and a chiral silver BINOL-phosphate facilitated the highly enantioselective allylation and allenylation of N,O-aminals. Overall, these discoveries demonstrate the versatility, efficiency, and sensitivity of low-oxidation state indium catalysts in organic synthesis.

  12. An Electron-Poor C64 Nanographene by Palladium-Catalyzed Cascade C-C Bond Formation: One-Pot Synthesis and Single-Crystal Structure Analysis.

    Science.gov (United States)

    Seifert, Sabine; Shoyama, Kazutaka; Schmidt, David; Würthner, Frank

    2016-05-23

    Herein, we report the one-pot synthesis of an electron-poor nanographene containing dicarboximide groups at the corners. We efficiently combined palladium-catalyzed Suzuki-Miyaura cross-coupling and dehydrohalogenation to synthesize an extended two-dimensional π-scaffold of defined size in a single chemical operation starting from N-(2,6-diisopropylphenyl)-4,5-dibromo-1,8-naphthalimide and a tetrasubstituted pyrene boronic acid ester as readily accessible starting materials. The reaction of these precursors under the conditions commonly used for Suzuki-Miyaura cross-coupling afforded a C64 nanographene through the formation of ten C-C bonds in a one-pot process. Single-crystal X-ray analysis unequivocally confirmed the structure of this unique extended aromatic molecule with a planar geometry. The optical and electrochemical properties of this largest ever synthesized planar electron-poor nanographene skeleton were also analyzed. © 2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

  13. Laser photolysis studies of ω-bond dissociation in aromatic carbonyls with a C-C triple bond stimulated by triplet sensitization.

    Science.gov (United States)

    Yamaji, Minoru; Horimoto, Ami; Marciniak, Bronislaw

    2017-07-14

    We have prepared three types of carbonyl compounds, benzoylethynylmethyl phenyl sulfide (2@SPh), (p-benzoyl)phenylethynylmethyl phenyl sulfide (3@SPh) and p-(benzoylethynyl)benzyl phenyl sulfide (4@SPh) with benzoyl and phenylthiylmethyl groups, which are interconnected with a C-C triple bond and a phenyl ring. Laser flash photolysis of 3@SPh and 4@SPh in acetonitrile provided the transient absorption spectra of the corresponding triplet states where no chemical reactions were recognized. Upon laser flash photolysis of 2@SPh, the absorption band due to the phenylthiyl radical (PTR) was obtained, indicating that the C-S bond cleaved in the excited state. Triplet sensitization of these carbonyl compounds using acetone and xanthone was conducted using laser photolysis techniques. The formation of triplet 3@SPh was seen in the transient absorption, whereas the PTR formation was observed for 2@SPh and 4@SPh, indicating that the triplet states were reactive for the C-S bond dissociation. The C-S bond dissociation mechanism for 4@SPh upon triplet sensitization is discussed in comparison with those for 2@SPh and 3@SPh.

  14. C,C Couplings in the Reactions of Unsaturated Group 4 Metal s-cis-Butadiene Complexes with 2,6-Xylyl Isocyanide

    OpenAIRE

    Hessen, Bart; Blenkers, Joop; Teuben, Jan H.; Helgesson, Göran; Jagner, Susan

    1989-01-01

    A group of electronically unsaturated (14-electron) diene complexes of Hf and Ti has been reacted with 2,6-xylyl isocyanide. Cp*Hf(diene)Cl (diene = 2,3-dimethyl-1,3-butadiene, 2-methyl-1,3-butadiene; Cp* = η-C5Me5) reacts with 2 mol of isocyanide to form the unusual heterospiro complexes Cp*Hf(Cl)N(xy)CCH2C(Me)=C(R)CH=CHN(xy) (R = H, Me; xy = 2,6-xylyl) involving a 1,2-hydrogen shift and a ring closure after insertion of isocyanide into the Hf-diene bond. In Cp*Hf(2,3-dimethyl-1,3-butadiene)...

  15. Thermal fatigue behavior of C/C composites modified by SiC-MoSi{sub 2}-CrSi{sub 2} coating

    Energy Technology Data Exchange (ETDEWEB)

    Chu Yanhui [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi' an 710072 (China); Fu Qiangang, E-mail: fuqiangang@nwpu.edu.cn [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi' an 710072 (China); Li Hejun; Li Kezhi [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi' an 710072 (China)

    2011-08-04

    Highlights: > The low-density C/C composites were modified by SiC-MoSi{sub 2}-CrSi{sub 2} multiphase coating by pack cementation. > The thermal fatigue behavior of the modified C/C composites was studied after undergoing thermal cycling for 20 times under the different environments. > The decrease of the flexural strength of the modified C/C composites during thermal cycle in air was primarily attributed to the partial oxidation of the modified C/C samples. - Abstract: Carbon/carbon (C/C) composites were modified by SiC-MoSi{sub 2}-CrSi{sub 2} multiphase coating by pack cementation, and their thermal fatigue behavior under thermal cycling in Ar and air environments was investigated. The modified C/C composites were characterized by scanning electron microscopy and X-ray diffraction. Results of tests show that, after 20-time thermal cycles between 1773 K and room temperature in Ar environment, the flexural strength of modified C/C samples decreased lightly and the percentage of remaining strength was 94.92%. While, after thermal cycling between 1773 K and room temperature in air for 20 times, the weight loss of modified C/C samples was 5.1%, and the flexural strength of the modified C/C samples reduced obviously and the percentage of remaining strength was only 75.22%. The fracture mode of modified C/C samples changed from a brittle behavior to a pseudo-plastic one as the service environment transformed from Ar to air. The decrease of the flexural strength during thermal cycle in air was primarily attributed to the partial oxidation of modified C/C samples.

  16. Method 446.0: In Vitro Determination of Chlorophylls a, b, c + c and Pheopigments in 1 2Marine And Freshwater Algae by Visible Spectrophotometry

    Science.gov (United States)

    This method provides a procedure for determination of chlorophylls a (chl a), b (chl b), c + c 1 2 (chl c + c ) and pheopigments of chlorophyll a (pheo a) 1 2 found in marine and freshwater phytoplankton. Chlorophyllide a is determined as chl a. Visible wavelength spectrophotomet...

  17. Thermal conductivity of 2D C-C composites with pyrolytic and glass-like carbon matrices

    Energy Technology Data Exchange (ETDEWEB)

    Michalowski, J. [Institute of Nuclear Physics, Cracow (Poland); Mikociak, D. [Dept. of Biomaterials, Faculty of Materials Engineering and Ceramics, AGH University of Science and Technology, Cracow (Poland); Konsztowicz, K.J. [Dept. of Industrial Engineering, Faculty of Mechanical Engineering, and IT, University of Bielsko-Biala (Poland); Blazewicz, S., E-mail: blazew@aci.agh.edu.p [Dept. of Biomaterials, Faculty of Materials Engineering and Ceramics, AGH University of Science and Technology, Cracow (Poland)

    2009-08-15

    This study examines the relationship of thermal properties of C-C composites with structural and microstructural features resulting from specific processing steps. Samples were made with the same type of fibres, but using two distinct different methods of matrix formation: liquid impregnation with phenolic resin and the P-CVI technique. In both cases, thermal treatment after densification had decisive effect on increase of composite coefficient of thermal conductivity, due to crystallization of carbon matrix material and thus increase of its own thermal conductivity. Higher values of thermal conductivity were obtained using the pyrolytic carbon matrix processing.

  18. Numerical modelling of micro-machining of f.c.c. single crystal: Influence of strain gradients

    KAUST Repository

    Demiral, Murat

    2014-11-01

    A micro-machining process becomes increasingly important with the continuous miniaturization of components used in various fields from military to civilian applications. To characterise underlying micromechanics, a 3D finite-element model of orthogonal micro-machining of f.c.c. single crystal copper was developed. The model was implemented in a commercial software ABAQUS/Explicit employing a user-defined subroutine VUMAT. Strain-gradient crystal-plasticity and conventional crystal-plasticity theories were used to demonstrate the influence of pre-existing and evolved strain gradients on the cutting process for different combinations of crystal orientations and cutting directions. Crown Copyright © 2014.

  19. Measurement of low-mass e{sup +}e{sup -} pair production in 2 AGeV C-C collisions with HADES

    Energy Technology Data Exchange (ETDEWEB)

    Sudol, Malgorzata

    2007-07-01

    The search for a modification of hadron properties inside nuclear matter at normal and/or high temperature and density is one of the most interesting issues of modern nuclear physics. Dilepton experiments, give insight into the properties of strong interaction and the nature of hadron mass generation. One of these research tools is the HADES spectrometer. HADES is a high acceptance dilepton spectrometer installed at the heavy-ion synchrotron (SIS) at GSI, Darmstadt. The main physics motivation of HADES is the measurement of e{sup +}e{sup -} pairs in the invariant-mass range up to 1 GeV/c{sup 2} in pion- and proton-induced reactions, as well as in heavy-ion collisions. The goal is to investigate the properties of the vector mesons {rho}, {omega} and of other hadrons reconstructed from e{sup +}e{sup -} decay pairs. Dileptons are penetrating probes allowing to study the in-medium properties of hadrons. However, the measurement of such dilepton pairs is difficult because of a very large background from other processes in which leptons are created. This thesis presents the analysis of the data provided by the first physics run with the HADES spectrometer. For the first time e{sup +}e{sup -} pairs produced in C+C collisions at an incident energy of 2 GeV per nucleon have been collected with sufficient statistics. This experiment is of particular importance since it allows to address the puzzling pair excess measured by the former DLS experiment at a beam energy 1.04 AGeV. The thesis consists of five chapters. The first chapter presents the physics case which is addressed in the work. In the second chapter the HADES spectrometer is introduced with the characteristic of specific detectors which are part of the spectrometer. Chapter three focusses on the issue of charged-particle identification. The fourth chapter discusses the reconstruction of the di-electron spectra in C+C collisions. In this part of the thesis a comparison with theoretical models is included as well

  20. Long live vinylidene! A new view of the H(2)C=C: --> HC triple bond CH rearrangement from ab initio molecular dynamics.

    Science.gov (United States)

    Hayes, R L; Fattal, E; Govind, N; Carter, E A

    2001-01-31

    We present complete active space self-consistent field (CASSCF) ab initio molecular dynamics (AIMD) simulations of the preparation of the metastable species vinylidene, and its subsequent, highly exothermic isomerization to acetylene, via electron removal from vinylidene anion (D(2)C=C(-) --> D(2)C=C: --> DC triple bond CD). After equilibrating vinylidene anion-d(2) at either 600 +/- 300 K (slightly below the isomerization barrier) or 1440 K +/- 720 K (just above the isomerization barrier), we remove an electron to form a vibrationally excited singlet vinylidene-d(2) and follow its dynamical evolution for 1.0 ps. Remarkably, we find that none of the vinylidenes equilibrated at 600 K and only 20% of the vinylidenes equilibrated at 1440 K isomerized, suggesting average lifetimes >1 ps for vibrationally excited vinylidene-d(2). Since the anion and neutral vinylidene are structurally similar, and yet extremely different geometrically from the isomerization transition state (TS), neutral vinylidene is not formed near the TS so that it must live until it has sufficient instantaneous kinetic energy in the correct vibrational mode(s). The origin of the delay is explained via both orbital rearrangement and intramolecular vibrational energy redistribution (IVR) effects. Unique signatures of the isomerization dynamics are revealed in the anharmonic vibrational frequencies extracted from the AIMD, which should be observable by ultrafast vibrational spectroscopy and in fact are consistent with currently available experimental spectra. Most interestingly, of those trajectories that did isomerize, every one of them violated conventional transition-state theory by recrossing back to vinylidene multiple times, against conventional notions that expect highly exothermic reactions to be irreversible. The dynamical motion responsible for the multiple barrier recrossings involves strong mode-coupling between the vinylidene CD(2) rock and a local acetylene DCC bend mode that has been

  1. A discrete event simulation model for evaluating the performances of an m/g/c/c state dependent queuing system.

    Directory of Open Access Journals (Sweden)

    Ruzelan Khalid

    Full Text Available M/G/C/C state dependent queuing networks consider service rates as a function of the number of residing entities (e.g., pedestrians, vehicles, and products. However, modeling such dynamic rates is not supported in modern Discrete Simulation System (DES software. We designed an approach to cater this limitation and used it to construct the M/G/C/C state-dependent queuing model in Arena software. Using the model, we have evaluated and analyzed the impacts of various arrival rates to the throughput, the blocking probability, the expected service time and the expected number of entities in a complex network topology. Results indicated that there is a range of arrival rates for each network where the simulation results fluctuate drastically across replications and this causes the simulation results and analytical results exhibit discrepancies. Detail results that show how tally the simulation results and the analytical results in both abstract and graphical forms and some scientific justifications for these have been documented and discussed.

  2. The C-C Chemokines CCL17 and CCL22 and Their Receptor CCR4 in CNS Autoimmunity

    Directory of Open Access Journals (Sweden)

    Stefanie Scheu

    2017-11-01

    Full Text Available Multiple sclerosis (MS is a chronic inflammatory demyelinating disease of the central nervous system (CNS. It affects more than two million people worldwide, mainly young adults, and may lead to progressive neurological disability. Chemokines and their receptors have been shown to play critical roles in the pathogenesis of experimental autoimmune encephalomyelitis (EAE, a murine disease model induced by active immunization with myelin proteins or transfer of encephalitogenic CD4+ T cells that recapitulates clinical and neuropathological features of MS. Chemokine ligand-receptor interactions orchestrate leukocyte trafficking and influence multiple pathophysiological cellular processes, including antigen presentation and cytokine production by dendritic cells (DCs. The C-C class chemokines 17 (CCL17 and 22 (CCL22 and their C-C chemokine receptor 4 (CCR4 have been shown to play an important role in homeostasis and inflammatory responses. Here, we provide an overview of the involvement of CCR4 and its ligands in CNS autoimmunity. We review key clinical studies of MS together with experimental studies in animals that have demonstrated functional roles of CCR4, CCL17, and CCL22 in EAE pathogenesis. Finally, we discuss the therapeutic potential of newly developed CCR4 antagonists and a humanized anti-CCR4 antibody for treatment of MS.

  3. First observation of the isospin violating decay $J/\\psi\\rightarrow \\Lambda\\bar{\\Sigma}^{0}+c.c.$

    CERN Document Server

    Ablikim, M; Ambrose, D J; An, F F; An, Q; An, Z H; Bai, J Z; Ban, Y; Becker, J; Berger, N; Bertani, M; Bian, J M; Boger, E; Bondarenko, O; Boyko, I; Briere, R A; Bytev, V; Cai, X; Cakir, O; Calcaterra, A; Cao, G F; Cetin, S A; Chang, J F; Chelkov, G; Chen, G; Chen, H S; Chen, J C; Chen, M L; Chen, S J; Chen, Y; Chen, Y B; Cheng, H P; Chu, Y P; Cronin-Hennessy, D; Dai, H L; Dai, J P; Dedovich, D; Deng, Z Y; Denig, A; Denysenko, I; Destefanis, M; Ding, W M; Ding, Y; Dong, L Y; Dong, M Y; Du, S X; Fang, J; Fang, S S; Fava, L; Feldbauer, F; Feng, C Q; Ferroli, R B; Fu, C D; Fu, J L; Gao, Y; Geng, C; Goetzen, K; Gong, W X; Gradl, W; Greco, M; Gu, M H; Gu, Y T; Guan, Y H; Guo, A Q; Guo, L B; Guo, Y P; Han, Y L; Hao, X Q; Harris, F A; He, K L; He, M; He, Z Y; Held, T; Heng, Y K; Hou, Z L; Hu, H M; Hu, J F; Hu, T; Huang, B; Huang, G M; Huang, J S; Huang, X T; Huang, Y P; Hussain, T; Ji, C S; Ji, Q; Ji, X B; Ji, X L; Jia, L K; Jiang, L L; Jiang, X S; Jiao, J B; Jiao, Z; Jin, D P; Jin, S; Jing, F F; Kalantar-Nayestanaki, N; Kavatsyuk, M; Kuehn, W; Lai, W; Lange, J S; Li, C H; Li, Cheng; Li, Cui; Li, D M; Li, F; Li, G; Li, H B; Li, J C; Li, K; Li, Lei; Li, N B; Li, Q J; Li, S L; Li, W D; Li, W G; Li, X L; Li, X N; Li, X Q; Li, X R; Li, Z B; Liang, H; Liang, Y F; Liang, Y T; Liao, G R; Liao, X T; Liu, B J; Liu, C L; Liu, C X; Liu, C Y; Liu, F H; Liu, Fang; Liu, Feng; Liu, H; Liu, H B; Liu, H H; Liu, H M; Liu, H W; Liu, J P; Liu, K Y; Liu, Kai; Liu, Kun; Liu, P L; Liu, S B; Liu, X; Liu, X H; Liu, Y; Liu, Y B; Liu, Z A; Liu, Zhiqiang; Liu, Zhiqing; Loehner, H; Lu, G R; Lu, H J; Lu, J G; Lu, Q W; Lu, X R; Lu, Y P; Luo, C L; Luo, M X; Luo, T; Luo, X L; Lv, M; Ma, C L; Ma, F C; Ma, H L; Ma, Q M; Ma, S; Ma, T; Ma, X Y; Ma, Y; Maas, F E; Maggiora, M; Malik, Q A; Mao, H; Mao, Y J; Mao, Z P; Messchendorp, J G; Min, J; Min, T J; Mitchell, R E; Mo, X H; Morales, C Morales; Motzko, C; Muchnoi, N Yu; Muramatsu, H; Nefedov, Y; Nicholson, C; Nikolaev, I B; Ning, Z; Olsen, S L; Ouyang, Q; Pacetti, S; Park, J W; Pelizaeus, M; Peng, H P; Peters, K; Ping, J L; Ping, R G; Poling, R; Prencipe, E; Qi, M; Qian, S; Qiao, C F; Qin, X S; Qin, Y; Qin, Z H; Qiu, J F; Rashid, K H; Rong, G; Ruan, X D; Sarantsev, A; Schaefer, B D; Schulze, J; Shao, M; Shen, C P; Shen, X Y; Sheng, H Y; Shepherd, M R; Song, X Y; Spataro, S; Spruck, B; Sun, D H; Sun, G X; Sun, J F; Sun, S S; Sun, X D; Sun, Y J; Sun, Y Z; Sun, Z J; Sun, Z T; Tang, C J; Tang, X; Tapan, X F Tang I; Thorndike, E H; Tian, H L; Toth, D; Ullrich, M; Varner, G S; Wang, B; Wang, B Q; Wang, K; Wang, L L; Wang, L S; Wang, M; Wang, P; Wang, P L; Wang, Q; Wang, Q J; Wang, S G; Wang, X L; Wang, Y D; Wang, Y F; Wang, Y Q; Wang, Z; Wang, Z G; Wang, Z Y; Wei, D H; Weidenkaff, P; Wen, Q G; Wen, S P; Werner, M; Wiedner, U; Wu, L H; Wu, N; Wu, S X; Wu, W; Wu, Z; Xia, L G; Xiao, Z J; Xie, Y G; Xiu, Q L; Xu, G F; Xu, G M; Xu, H; Xu, Q J; Xu, X P; Xu, Z R; Xue, F; Xue, Z; Yan, L; Yan, W B; Yan, Y H; Yang, H X; Yang, Y; Yang, Y X; Ye, H; Ye, M; Ye, M H; Yu, B X; Yu, C X; Yu, J S; Yu, S P; Yuan, C Z; Yuan, W L; Yuan, Y; Zafar, A A; Zallo, A; Zeng, Y; Zhang, B X; Zhang, B Y; Zhang, C C; Zhang, D H; Zhang, H H; Zhang, H Y; Zhang, J; Zhang, J Q; Zhang, J W; Zhang, J Y; Zhang, J Z; Zhang, S H; Zhang, T R; Zhang, X J; Zhang, X Y; Zhang, Y; Zhang, Y H; Zhang, Y S; Zhang, Z P; Zhang, Z Y; Zhao, G; Zhao, H S; Zhao, J W; Zhao, K X; Zhao, Lei; Zhao, Ling; Zhao, M G; Zhao, Q; Zhao, S J; Zhao, T C; Zhao, X H; Zhao, Y B; Zhao, Z G; Zhemchugov, A; Zheng, B; Zheng, J P; Zheng, Y H; Zheng, Z P; Zhong, B; Zhong, J; Zhou, L; Zhou, X K; Zhou, X R; Zhu, C; Zhu, K; Zhu, K J; Zhu, S H; Zhu, X L; Zhu, X W; Zhu, Y C; Zhu, Y M; Zhu, Y S; Zhu, Z A; Zhuang, J; Zou, B S; Zou, J H; Zuo, J X

    2012-01-01

    Using a sample of $(225.2\\pm 2.8)\\times 10^6$ $J/\\psi$ events collected with the BESIII detector, we present results of a study of $J/\\psi\\rightarrow \\gamma\\Lambda\\bar{\\Lambda}$ and report the first observation of the isospin violating decay $J/\\psi\\rightarrow\\Lambda\\bar{\\Sigma}^{0}+c.c.$, in which $\\bar{\\Sigma}^{0}$ decays to $\\gamma \\bar{\\Lambda}$. The measured branching fractions are $\\mathcal{B}(J/\\psi\\rightarrow\\bar{\\Lambda}\\Sigma^{0}$) = $(1.46\\pm0.11\\pm0.12) \\times10^{-5}$ and $\\mathcal{B}(J/\\psi\\rightarrow\\Lambda\\bar{\\Sigma^{0}}$) = $(1.37\\pm0.12\\pm0.11) \\times10^{-5}$. We search for $\\Lambda(1520) \\rightarrow \\gamma \\Lambda$ decay, and find no evident signal, and an upper limit for the product branching fraction $\\mathcal{B}(J/\\psi\\rightarrow\\Lambda\\bar{\\Lambda}(1520)+c.c.)\\times \\mathcal{B}(\\Lambda(1520)\\rightarrow\\gamma\\Lambda)<4.1 \\times10^{-6}$ is set at the 90% confidence level. We also report the observation of $\\eta_{c}\\rightarrow\\Lambda\\bar{\\Lambda}$ in $J/\\psi \\rightarrow \\gamma \\eta_{c}$...

  4. Vibrationally Excited c-C_3H_2 Re-Visited New Laboratory Measurements and Theoretical Calculations

    Science.gov (United States)

    Gupta, Harshal; Westerfield, J. H.; Baraban, Joshua H.; Changala, Bryan; Thorwirth, Sven; Stanton, John F.; Martin-Drumel, Marie-Aline; Pirali, Olivier; Gottlieb, Carl A.; McCarthy, Michael C.

    2017-06-01

    Cyclopropenylidene, c-C_3H_2, is one of the more abundant organic molecules in the interstellar medium, as evidenced from astronomical detection of its single ^{13}C and both its singly- and doubly-deuterated isotopic species. For this reason, vibrational satellites are of considerable astronomical interest, and were the primary motivation for the earlier laboratory work by Mollaaghababa and co-workers [1]. The recent detection of intense unidentified lines near 18 GHz in a hydrocarbon discharge by FT microwave spectroscopy has spurred a renewed search for the vibrational satellite transitions of c-C_3H_2. Several strong lines have been definitively assigned to the v_6 progression on the basis of follow-up measurements at 3 mm, double resonance and millimeter-wave absorption spectroscopy, and new theoretical calculations using a rovibrational VMP2 method [2] and a high-quality ab initio potential energy surface. The treatment was applied to several excited states as well as the ground state, and included deperturbation of Coriolis interactions. [1] R. Mollaaghababa, C.A. Gottlieb, J. M. Vrtilek, and P. Thaddeus, J. Chem. Phys., 99, 890-896 (1992). [2] P. B. Changala and J. H. Baraban. J. Chem. Phys., 145, 174106 (2016).

  5. The methylenetetrahydrofolate reductase c.c.677 C>T and c.c.1298 A>C polymorphisms in reproductive failures: Experience from an RSA and RIF study on a Polish population.

    Science.gov (United States)

    Nowak, Izabela; Bylińska, Aleksandra; Wilczyńska, Karolina; Wiśniewski, Andrzej; Malinowski, Andrzej; Wilczyński, Jacek R; Radwan, Paweł; Radwan, Michał; Barcz, Ewa; Płoski, Rafał; Motak-Pochrzęst, Hanna; Banasik, Małgorzata; Sobczyński, Maciej; Kuśnierczyk, Piotr

    2017-01-01

    Almost 1600 individuals from the Polish population were recruited to this study. Among them 319 were fertile couples, 289 were recurrent spontaneous abortion (RSA) couples, and 131 were in the group of recurrent implantation failure (RIF) following in vitro fertilization. The aim of this study was to evaluate the MTHFR c.c.677 C>T and c.c.1298 A>C polymorphisms' association with RSA and RIF. We used PCR-RFLP with HinfI (677 C>T) and MboII (1298 A>C) digestion. We observed a protective effect of the female AC genotype (OR = 0.64, p = 0.01) and the C allele (AC+CC genotypes; OR = 0.65, p = 0.009) against RSA. Moreover, 1298 AA/677 CT women were more frequent in RSA (31.14%) and RIF (25.20%) groups in comparison to fertile women (22.88%), although this difference was significant only in the case of RSA (p = 0.022, OR = 1.52). Male combined genotype analysis revealed no association with reproductive failure of their partners. Nevertheless, the female/male combination AA/AC of the 1298 polymorphism was more frequent in RSA couples (p = 0.049, OR = 1.49). However, the significant results became insignificant after Bonferroni correction. In addition, analysis of haplotypes showed significantly higher frequency of the C/C haplotype (1298 C/677 C) in the female control group than in the female RSA group (p = 0.03, OR = 0.77). Moreover, the association between elevated homocysteine (Hcy) level in plasma of RSA and RIF women and MTHFR polymorphisms was investigated but did not reveal significant differences. In conclusion, for clinical practice, it is better to check the homocysteine level in plasma and, if the Hcy level is increased, to recommend patients to take folic acid supplements rather than undergo screening of MTHFR for 1298 A>C and 677 C>T polymorphisms.

  6. cycloaddition reactions

    Indian Academy of Sciences (India)

    Unknown

    models of regioselectivity in pericyclic reactions. In addition, local hard and soft acid base (HSAB) princi- ples have been also employed to predict the observed regioselectivity.2 In recent years, the conceptual density functional theory has been remarkably successful in explaining the reactivity and site selectivity.3 The.

  7. Dendrimer-encapsulated Pd nanoparticles as catalysts for C-C cross-couplings in flow microreactors

    NARCIS (Netherlands)

    Ricciardi, R.; Huskens, Jurriaan; Verboom, Willem

    2015-01-01

    The inner walls of glass microreactors were functionalized with dendrimer-encapsulated Pd nanoparticles. The catalysts were efficient for the Heck–Cassar (copper-free Sonogashira) and Suzuki–Miyaura (SMC) cross-coupling reactions. For the Heck–Cassar reaction between iodobenzene and phenylacetylene,

  8. Multilevel Quantum Mechanics Theories and Molecular Mechanics Calculations of the Cl-+ CH3I Reaction in Water.

    Science.gov (United States)

    Liu, Peng; Li, Chen; Wang, Dunyou

    2017-10-19

    The Cl - + CH 3 I → CH 3 Cl + I - reaction in water was studied using combined multilevel quantum mechanism theories and molecular mechanics with an explicit water solvent model. The study shows a significant influence of aqueous solution on the structures of the stationary points along the reaction pathway. A detailed, atomic-level evolution of the reaction mechanism shows a concerted one-bond-broken and one-bond-formed mechanism, as well as a synchronized charge-transfer process. The potentials of mean force calculated with the CCSD(T) and DFT treatments of the solute produce a free activation barrier at 24.5 and 19.0 kcal/mol, respectively, which agrees with the experimental one at 22.0 kcal/mol. The solvent effects have also been quantitatively analyzed: in total, the solvent effects raise the activation energy by 20.2 kcal/mol, which shows a significant impact on this reaction in water.

  9. Mechanical and Chemical Characterization of a TiC/C System Synthesized Using a Focus Plasma Arc.

    Directory of Open Access Journals (Sweden)

    Reza Mahmoodian

    Full Text Available Titanium carbide-graphite (TiC/C composite was successfully synthesized from Ti and C starting elemental powders using self-propagating high-temperature synthesis technique in an ultra-high plasma inert medium in a single stage. The TiC was exposed to a high-temperature inert medium to allow recrystallization. The product was then characterized using field emission scanning electron microscopy (FESEM coupled with energy dispersive X-ray analysis (EDX, X-ray diffraction (XRD, Rietveld refinement, nanoindentation, and micro-hardness to determine the product's properties. The recorded micro-hardness of the product was 3660 HV, which is a 14% enhancement and makes is comparable to TiC materials.

  10. Mechanical and Chemical Characterization of a TiC/C System Synthesized Using a Focus Plasma Arc.

    Science.gov (United States)

    Mahmoodian, Reza; Hamdi, M; Hassan, M A; Akbari, Abolghasem

    2015-01-01

    Titanium carbide-graphite (TiC/C) composite was successfully synthesized from Ti and C starting elemental powders using self-propagating high-temperature synthesis technique in an ultra-high plasma inert medium in a single stage. The TiC was exposed to a high-temperature inert medium to allow recrystallization. The product was then characterized using field emission scanning electron microscopy (FESEM) coupled with energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD), Rietveld refinement, nanoindentation, and micro-hardness to determine the product's properties. The recorded micro-hardness of the product was 3660 HV, which is a 14% enhancement and makes is comparable to TiC materials.

  11. Microstructure and mechanical properties of coal tar pitch-based 2D-C/C composites with a filler addition

    Energy Technology Data Exchange (ETDEWEB)

    Chollon, G.; Siron, O.; Takahashi, J.; Yamauchi, H.; Maeda, K.; Kosaka, K. [University of Bordeaux 1, Pessac (France)

    2001-07-01

    In order to improve the flexural and the inter-laminar shear strength of coal tar pitch-based 2D-C/C composites, fillers (carbon blacks and colloidal graphite) were introduced between the UD layers before the first infiltration of pitch. Matrix parts made of the filler/pitch-based cokes showed fine mosaic microtextures. They were found at the interface between the layers. Whereas the tensile strength is not affected, the flexural strength and the ILSS were significantly increased by the addition of fillers. The original structure of the inter-layer matrix parts and the decrease of the number of flaws were found to be responsible for the improvement of the shear strength of the 0/90 degrees UD layers.

  12. libstable: Fast, Parallel, and High-Precision Computation of α-Stable Distributions in R, C/C++, and MATLAB

    Directory of Open Access Journals (Sweden)

    Javier Royuela-del-Val

    2017-06-01

    Full Text Available α-stable distributions are a family of well-known probability distributions. However, the lack of closed analytical expressions hinders their application. Currently, several tools have been developed to numerically evaluate their density and distribution functions or to estimate their parameters, but available solutions either do not reach sufficient precision on their evaluations or are excessively slow for practical purposes. Moreover, they do not take full advantage of the parallel processing capabilities of current multi-core machines. Other solutions work only on a subset of the α-stable parameter space. In this paper we present an R package and a C/C++ library with a MATLAB front-end that permit parallelized, fast and high precision evaluation of density, distribution and quantile functions, as well as random variable generation and parameter estimation of α-stable distributions in their whole parameter space. The described library can be easily integrated into third party developments.

  13. Furanose C-C-linked γ-lactones: a combined ESI FTICR MS and semi-empirical calculations study.

    Science.gov (United States)

    Madeira, Paulo J Amorim; Xavier, Nuno M; Rauter, Amélia P; Florêncio, M Helena

    2010-10-01

    Sugars that incorporate the unsaturated carbonyl motif have become important synthetic targets not only as a result of their potential biological properties but also as precursors in the synthesis of many bioactive products. Moreover, little is known about the influence of the γ-lactone moiety in the fragmentation pattern of furanose rings. Therefore, two α,β-unsaturated γ-lactones (butenolides) and two β-hydroxy γ-lactones, C-C linked to a furanose ring were studied using electrospray ionization FTICR mass spectrometry. The behaviour of the protonated and sodiated forms of the compounds under study has been compared considering their structural features. Fragmentation mechanisms were established and ion structures were proposed taking into account the MS(2) and MS(3) experiments, accurate mass measurements and semi-empirical calculations. These inexpensive methods proved to be a valuable resource for proposing protonation sites and for the establishment of fragmentation pathways. Copyright © 2010 John Wiley & Sons, Ltd.

  14. The obesity and inflammatory marker haptoglobin attracts monocytes via interaction with chemokine (C-C motif receptor 2 (CCR2

    Directory of Open Access Journals (Sweden)

    Lisi Simonetta

    2009-12-01

    Full Text Available Abstract Background Obesity is a chronic low inflammatory state. In the obesity condition the white adipose tissue (WAT is massively infiltrated with monocytes/macrophages, and the nature of the signals recruiting these inflammatory cells has yet to be fully elucidated. Haptoglobin (Hp is an inflammatory marker and its expression is induced in the WAT of obese subjects. In an effort to elucidate the biological significance of Hp presence in the WAT and of its upregulation in obesity we formulated the hypothesis that Hp may serve as a macrophage chemoattractant. Results We demonstrated by chemotaxis assay that Hp is able to attract chemokine (C-C motif receptor 2 (CCR2-transfected pre-B lymphocytes and monocytes in a dose-dependent manner. Moreover, Hp-mediated migration of monocytes is impaired by CCR2-specific inhibition or previous cell exposure to monocyte chemoattractant protein 1 (MCP1 (also known as CCR2 ligand or chemokine (C-C motif ligand 2 (CCL2. Downstream effects of Hp/CCR2 interaction were also investigated: flow cytometry proved that monocytes treated with Hp show reduced CCR2 expression on their surface; Hp interaction induces calcium release that is reduced upon pretreatment with CCR2 antagonist; extracellular signal-regulated kinase (ERK1/2, a signal transducer activated by CCR2, is phosphorylated following Hp treatment and this phosphorylation is reduced when cells are pretreated with a specific CCR2 inhibitor. Consistently, blocking the ERK1/2 pathway with U0126, the selective inhibitor of the ERK upstream mitogen-activated protein (MAP-ERK kinase (MEK, results in a dramatic reduction (by almost 100% of the capability of Hp to induce monocyte migration. Conclusions Our data show that Hp is a novel monocyte chemoattractant and that its chemotactic potential is mediated, at least in part. by its interaction with CCR2.

  15. A direct ab initio molecular dynamics (MD) study on the repair reactions of stacked thymine dimer

    Science.gov (United States)

    Tachikawa, Hiroto; Kawabata, Hiroshi

    2008-09-01

    DNA repair reactions of the thymine dimer (T) 2 following the hole capture have been investigated by means of direct ab initio molecular dynamics (MD) method in order to elucidate the mechanism of repair processes of thymine dimer interacting with a photo-enzyme. The thymine dimer has two C-C single bonds between thymine rings at neutral state expressed by (T dbnd T). After the hole capture of (T dbnd T), one of the C-C bonds was preferentially broken, while the structure of (T dbnd T) + was spontaneously changed to an intermediate having a C-C single bond expressed by (T-T) +. Time scale of the C-C bond breaking and formation of the intermediate was estimated to be 60-180 fs. The mechanism of repair reactions of the thymine dimer was discussed on the basis of theoretical results.

  16. Selective C-C and C-H bond activation/cleavage of pinene derivatives: synthesis of enantiopure cyclohexenone scaffolds and mechanistic insights.

    Science.gov (United States)

    Masarwa, Ahmad; Weber, Manuel; Sarpong, Richmond

    2015-05-20

    The continued development of transition-metal-mediated C-C bond activation/cleavage methods would provide even more opportunities to implement novel synthetic strategies. We have explored the Rh(I)-catalyzed C-C activation of cyclobutanols resident in hydroxylated derivatives of pinene, which proceed in a complementary manner to the C-C bond cleavage that we have observed with many traditional electrophilic reagents. Mechanistic and computational studies have provided insight into the role of C-H bond activation in the stereochemical outcome of the Rh-catalyzed C-C bond activation process. Using this new approach, functionalized cyclohexenones that form the cores of natural products, including the spiroindicumides and phomactin A, have been accessed.

  17. Van Der Waals heterogeneous layer-layer carbon nanostructures involving π···H-C-C-H···π···H-C-C-H stacking based on graphene and graphane sheets.

    Science.gov (United States)

    Yuan, Kun; Zhao, Rui-Sheng; Zheng, Jia-Jia; Zheng, Hong; Nagase, Shigeru; Zhao, Sheng-Dun; Liu, Yan-Zhi; Zhao, Xiang

    2017-04-15

    Noncovalent interactions involving aromatic rings, such as π···π stacking, CH···π are very essential for supramolecular carbon nanostructures. Graphite is a typical homogenous carbon matter based on π···π stacking of graphene sheets. Even in systems not involving aromatic groups, the stability of diamondoid dimer and layer-layer graphane dimer originates from C - H···H - C noncovalent interaction. In this article, the structures and properties of novel heterogeneous layer-layer carbon-nanostructures involving π···H-C-C-H···π···H-C-C-H stacking based on [n]-graphane and [n]-graphene and their derivatives are theoretically investigated for n = 16-54 using dispersion corrected density functional theory B3LYP-D3 method. Energy decomposition analysis shows that dispersion interaction is the most important for the stabilization of both double- and multi-layer-layer [n]-graphane@graphene. Binding energy between graphane and graphene sheets shows that there is a distinct additive nature of CH···π interaction. For comparison and simplicity, the concept of H-H bond energy equivalent number of carbon atoms (noted as NHEQ), is used to describe the strength of these noncovalent interactions. The NHEQ of the graphene dimers, graphane dimers, and double-layered graphane@graphene are 103, 143, and 110, indicating that the strength of C-H···π interaction is close to that of π···π and much stronger than that of C-H···H-C in large size systems. Additionally, frontier molecular orbital, electron density difference and visualized noncovalent interaction regions are discussed for deeply understanding the nature of the C-H···π stacking interaction in construction of heterogeneous layer-layer graphane@graphene structures. We hope that the present study would be helpful for creations of new functional supramolecular materials based on graphane and graphene carbon nano-structures. © 2017 Wiley Periodicals, Inc. © 2017 Wiley

  18. $K^{\\ast}(892)^0$ and $\\bar{K}^{\\ast}(892)^0$ production in central Pb+Pb, Si+Si, C+C and inelastic p+p collisions at 158$A$~GeV

    CERN Document Server

    Anticic, T.; Barna, D.; Bartke, J.; Beck, H.; Betev, L.; Bialkowska, H.; Blume, C.; Bogusz, M.; Boimska, B.; Book, J.; Botje, M.; Buncic, P.; Cetner, T.; Christakoglou, P.; Chung, P.; Chvala, O.; Cramer, J.G.; Eckardt, V.; Fodor, Z.; Foka, P.; Friese, V.; Gazdzicki, M.; Grebieszkow, K.; Hohne, C.; Kadija, K.; Karev, A.; Kolesnikov, V.I.; Kowalski, M.; Kresan, D.; Laszlo, A.; Lacey, R.; van Leeuwen, M.; Mackowiak, M.; Makariev, M.; Malakhov, A.I.; Mateev, M.; Melkumov, G.L.; Mitrovski, M.; Mrowczynski, S.; Nicolic, V.; Palla, G.; Panagiotou, A.D.; Peryt, W.; Pluta, J.; Prindle, D.; Puhlhofer, F.; Renfordt, R.; Roland, C.; Roland, G.; Rybczynski, M.; Rybicki, A.; Sandoval, A.; Schmitz, N.; Schuster, T.; Seyboth, P.; Sikler, F.; Skrzypczak, E.; Slodkowski, M.; Stefanek, G.; Stock, R.; Strobele, H.; Susa, T.; Szuba, M.; Utvic, M.; Varga, D.; Vassiliou, M.; Veres, G.I.; Vesztergombi, G.; Vranic, D.; Wlodarczyk, Z.; Wojtaszek-Szwarc, A.

    2011-01-01

    Production of the $K^{\\ast}(892)^0$ and $\\bar{K}^{\\ast}(892)^0$ resonances was studied via their $K^+ \\pi^-$ and $K^- \\pi^+$ decay modes in central Pb+Pb, Si+Si, C+C and inelastic p+p collisions at 158\\agev ($\\sqrt{s_{NN}}$ = 17.3 GeV) with the NA49 detector at the CERN SPS. Transverse momentum and rapidity distributions were measured and total yields were estimated. The yield of $K^{\\ast}$ exceeds that of $\\bar{K}^{\\ast}$ by about a factor of two in nucleus-nucleus reactions. The total yield ratios $/$ and $/$ are strongly suppressed in central Pb+Pb compared to p+p, C+C and Si+Si collisions in agreement with the expected attenuation of these short-lived resonance states in the hadronic phase of the expanding fireball. The UrQMD model, although incorporating such a scenario, does not provide a quantitative description of the experimental results. The statistical hadron gas model assuming the same freeze-out parameters for stable hadrons and resonances overestimates the $/$ ratios in central Pb+Pb collisions ...

  19. A Conjugated Microporous Polymer for Palladium-Free, Visible Light-Promoted Photocatalytic Stille-Type Coupling Reactions.

    Science.gov (United States)

    Ghasimi, Saman; Bretschneider, Simon A; Huang, Wei; Landfester, Katharina; Zhang, Kai A I

    2017-08-01

    The Stille coupling reaction is a versatile method to mainly form aromatic C-C bonds. However, up to now, the use of palladium catalysts is necessary. Here, a palladium-free and photocatalytic Stille-type coupling reaction of aryl iodides and aryl stannanes catalyzing a conjugated microporous polymer-based phototcatalyst under visible light irradiation at room temperature is reported. The novel coupling reaction mechanism occurs between the photogenerated aryl radical under oxidative destannylation of the aryl stannane, and the electron-activated aryl iodide, resulting into the aromatic C-C bond formation reaction. The visible light-promoted Stille-type coupling reaction using the polymer-based pure organic photocatalyst offers a simple, sustainable, and more economic synthetic pathway toward palladium-free aromatic C-C bond formation.

  20. Unraveling the Fischer-Tropsch mechanism: a combined DFT and microkinetic investigation of C-C bond formation on Ru.

    Science.gov (United States)

    Mirwald, Jens W; Inderwildi, Oliver R

    2012-05-21

    A combined modelling study on the Fischer-Tropsch Mechanism on Ru(0001). The DFT results presented herein approve the idea that the carbide mechanism is not the main reaction path in the synthesis of liquid hydrocarbons on Ru{0001}. The direct reaction of a CH(x)(s) species with a CO(s) species is kinetically and thermochemically preferred over CO dissociation and the hydrogenation of carbon monoxide can be seen as the initiation reaction of the hydrocarbon polymerisation process. Moreover, this study shows that CO dissociation is favoured over desorption on Ru{0001}, while on the analogue Co facet desorption is clearly favoured. This study therefore is an important further confirmation on new thinking in the Fischer-Tropsch synthesis. The fundamental insight gained in these studies will be of paramount importance for engineers optimising the FT process. Optimisation will not only lower the cost of FT fuels but simultaneously lower energy consumption and emissions.

  1. Investigation of C-C chemokine receptor type 4 (ccr4 gene polymorphism in patients with Gestational Trophoblastic diseases (GTD

    Directory of Open Access Journals (Sweden)

    S Naeimi

    2011-08-01

    Full Text Available Introduction & Objective: Gestational trophoblastic disease (GTD consists of a spectrum of disorders that are characterized by an abnormal proliferation of trophoblastic tissue, following an abnormal fertilization. CCR4 is one chemo-attractant receptors preferentially expressed on Th2 cells, and therefore, is likely to participate in the recruitment of antigen-specific Th2 cells to sites of allergen exposure. Variations in CCR4 have been reported. In this study we intended to investigate the relationship between polymorphism of this particular gene at the site of 1014 C/T and GTD. Materials & Methods: In the present study, the polymorphisms of the CCR4 gene at the sites of 1014 C/T was investigated in 100 patients at in 2010 with proved GTD and 120 age-sex matched healthy individuals. Polymorphysm of CC chemokine 4 were investigated in these two groups by PCR-RFLP.These two groups were compared in respect their genotypes and alleles. Results: Frequency of genotype TT, CT, CC patients were 34%, 62% and 4% while the frequency of the control group, were 46.7%, 35.8% and 17.5% respectively. A significant difference was seen in genotype prevalence of 1014 C/T in ccr4 gene in the two mentioned groups (P0.05(. Conclusion: Regarding the relationship between The C-C chemokine receptor type 4 and gestational trophoblastic disease (GTD, it might be possible to use this gene as a prognostic marker in identifying the susceptible patients.

  2. Trifunctional fluorescent unnatural nucleoside: Label free detection of T-T/C-C base mismatches, abasic site and bulge DNA.

    Science.gov (United States)

    Bag, Subhendu Sekhar; Pradhan, Manoj Kumar; Talukdar, Sangita

    2017-08-01

    The detection and targeting of both the mismatched and abasic DNA is highly important which would ultimately help in designing new diagnostics and chemotherapeutics. Furthermore, sensing and targeting the bulge sequence with a fluorescent probe would be useful to study the role of bulges in nucleic acid function or could have significant therapeutic potential. Thus, detection of specific bulges by small fluorescent molecules is an attractive research area since the past several years. Many attempts have been made to prepare such compounds. We report herein a label free strategy for the detection of pyrimidine base mismatches (T/T and C/C), sensing of abasic site, and pyrimidine base bulge DNA using an unnatural tetrazolylpyrene nucleoside ( TPy B Do ) as a bare fluorescent probe. The H-bonding/hydrophobic force mediated interactions allow the sensing of all three deformed DNA via an enhancement of fluorescence signal using our simple "Just-Mix and Read" strategy. The binding of the probe to all the three deformed DNA duplexes is accompanied by an increase in the thermal melting stability of the deformed DNAs. That the probe binds efficiently to the minor groove near the deformed site was evident from spectroscopic studies. All the spectral evidences open up a multitude of possibilities for using our probe, tetrazolylpyrene nucleoside, as an efficient fluorescent light-up bio-probe for label free DNA detection. Copyright © 2017. Published by Elsevier B.V.

  3. C-C motif ligand 5 promotes migration of prostate cancer cells in the prostate cancer bone metastasis microenvironment.

    Science.gov (United States)

    Urata, Satoko; Izumi, Kouji; Hiratsuka, Kaoru; Maolake, Aerken; Natsagdorj, Ariunbold; Shigehara, Kazuyoshi; Iwamoto, Hiroaki; Kadomoto, Suguru; Makino, Tomoyuki; Naito, Renato; Kadono, Yoshifumi; Lin, Wen-Jye; Wufuer, Guzailinuer; Narimoto, Kazutaka; Mizokami, Atsushi

    2017-12-30

    Chemokines and their receptors have key roles in cancer progression. The present study investigated chemokine activity in the prostate cancer bone metastasis microenvironment. Growth and migration of human prostate cancer cells were assayed in cocultures with bone stromal cells. The migration of LNCaP cells significantly increased when co-cultured with bone stromal cells isolated from prostate cancer bone metastases. Cytokine array analysis of conditioned medium from bone stromal cell cultures identified CCL5 as a concentration-dependent promoter of LNCaP cell migration. The migration of LNCaP cells was suppressed when C-C motif ligand 5 (CCL5) neutralizing antibody was added to cocultures with bone stromal cells. Knockdown of androgen receptor with small interfering RNA increased the migration of LNCaP cells compared with control cells, and CCL5 did not promote the migration of androgen receptor knockdown LNCaP. Elevated CCL5 secretion in bone stromal cells from metastatic lesions induced prostate cancer cell migration by a mechanism consistent with CCL5 activity upstream of androgen receptor signaling. © 2017 The Authors. Cancer Science published by John Wiley & Sons Australia, Ltd on behalf of Japanese Cancer Association.

  4. Differential susceptibility of BALB/c, C57BL/6N, and CF1 mice to photoperiod changes

    Directory of Open Access Journals (Sweden)

    Luísa K. Pilz

    2015-09-01

    Full Text Available Objective:Circadian disturbances common to modern lifestyles have been associated with mood disorders. Animal models that mimic such rhythm disturbances are useful in translational research to explore factors contributing to depressive disorders. This study aimed to verify the susceptibility of BALB/c, C57BL/6N, and CF1 mice to photoperiod changes.Methods:Thermochron iButtons implanted in the mouse abdomen were used to characterize temperature rhythms. Mice were maintained under a 12:12 h light-dark (LD cycle for 15 days, followed by a 10:10 h LD cycle for 10 days. Cosinor analysis, Rayleigh z test, periodograms, and Fourier analysis were used to analyze rhythm parameters. Paired Student's t test was used to compare temperature amplitude, period, and power of the first harmonic between normal and shortened cycles.Results:The shortened LD cycle significantly changed temperature acrophases and rhythm amplitude in all mouse strains, but only BALB/c showed altered period.Conclusion:These findings suggest that BALB/c, the preferred strain for stress-induced models of depression, should also be favored for exploring the relationship between circadian rhythms and mood. Temperature rhythm proved to be a useful parameter for characterizing rhythm disruption in mice. Although disruption of temperature rhythm has been successfully documented in untethered mice, an evaluation of desynchronization of other rhythms is warranted.

  5. Association of TNF -1031 C/C as a potential protection marker for leprosy development in Amazonas state patients, Brazil.

    Science.gov (United States)

    Silva, G A V; Ramasawmy, R; Boechat, A L; Morais, A C; Carvalho, B K S; Sousa, K B A; Souza, V C; Cunha, M G S; Barletta-Naveca, R H; Santos, M P; Naveca, F G

    2015-03-01

    Polymorphisms present in the TNF promoter region has shown to influence the gene transcription. Leprosy displays different clinical manifestations according to the immune responses of the individual infected with Mycobacterium leprae. In this study, we evaluated the single nucleotide polymorphisms (SNPs) -238 G/A (rs361525), -308 G/A (rs1800629), -857 C/T (rs1799724), -863 A/C (rs1800630) and -1031 T/C (rs1799964) in the promoter region of the TNF to see whether these SNPs influence host-susceptibility to leprosy and the different clinical manifestation. Nucleotide sequencing was performed with DNA samples from 108 leprosy patients and 253 control subjects. An association between -1031 C/C genotype and protection from leprosy was observed when leprosy patients were compared to controls (OR 0.11; 95% CI=0.01-0.82; p=0.012). The -857 C/T genotype may be associated with susceptibility to leprosy (OR=1.81; 95% CI=1.09-3.00; p=0.028). Similar genotype and allele frequencies for the SNPs -308 G/A and -238 G/A were observed between leprosy patients and control subjects. Altogether, TNF polymorphisms in the promoter region may be predictive of leprosy outcome. Copyright © 2015 American Society for Histocompatibility and Immunogenetics. Published by Elsevier Inc. All rights reserved.

  6. Spallation reactions; Reactions de spallation

    Energy Technology Data Exchange (ETDEWEB)

    Cugon, J.

    1996-12-31

    Spallation reactions dominate the interactions of hadrons with nuclei in the GeV range (from {approx} 0.1 to {approx} 10 GeV). They correspond to a sometimes important ejection of light particles leaving most of the time a residue of mass commensurate with the target mass. The main features of the experimental data are briefly reviewed. The most successful theoretical model, namely the intranuclear cascade + evaporation model, is presented. Its physical content, results and possible improvements are critically discussed. Alternative approaches are shortly reviewed. (author). 84 refs.

  7. A semi-homodesmotic approach for estimating ring strain energies (RSEs) of highly substituted cyclopropanes that minimizes use of acyclic references and cancels steric interactions: RSEs for c-C3R6 that make sense.

    Science.gov (United States)

    De Lio, Ashley M; Durfey, Bridget L; Gille, Austin L; Gilbert, Thomas M

    2014-08-07

    Estimation of ring strain energies (RSEs) of substituted cyclopropanes c-C(3)H(x)R(6-x) (R = F, Cl, Me; x = 0, 2, 4) using homodesmotic reaction methods has been plagued by implausible results. Prior work suggests that this stems from poorly canceled interactions between substituents on the acyclic reference molecules. We report a semi-homodesmotic approach that minimizes use of acyclic references, focusing instead on canceling substituent interactions. The method requires employing homodesmotic group equivalent reactions only for disubstituted cyclopropanes and relies solely on absolute energy calculations for more substituted rings. This provides RSEs consistent with chemical intuition regardless of the degree of substitution. We find that RSEs increase with substitution regardless of the electronic nature of R, although the increase is more dramatic when R is electron-withdrawing. The RSEs determined are consistent with QTAIM data, which show that progressive substitution always increases critical path angles. Overall, the semi-homodesmotic approach is simpler than hyperhomodesmotic reaction methods, and gives more trustworthy results.

  8. Nonaqueous and halide-free route to crystalline BaTiO3, SrTiO3, and (Ba,Sr)TiO3 nanoparticles via a mechanism involving C-C bond formation.

    Science.gov (United States)

    Niederberger, Markus; Garnweitner, Georg; Pinna, Nicola; Antonietti, Markus

    2004-07-28

    A novel nonaqueous route for the preparation of nanocrystalline BaTiO(3), SrTiO(3), and (Ba,Sr)TiO(3) has been developed. In a simple one-pot reaction process, the elemental alkaline earth metals are directly dissolved in benzyl alcohol at slightly elevated temperatures. After the addition of Ti(O(i)Pr)(4), the reaction mixture is heated to 200 degrees C, resulting in the formation of a white precipitate. XRD measurements prove the exclusive presence of the perovskite phase without any other crystalline byproducts such as BaCO(3) or TiO(2). TEM investigations reveal that the BaTiO(3) nanoparticles are nearly spherical in shape with diameters ranging from 4 to 5 nm. The SrTiO(3) particles display less uniform particle shapes, and the size varies between 5 and 10 nm. Lattice fringes observed in HRTEM measurements further prove the high crystallinity of the nanoparticles. Surprisingly, GC-MS analysis of the reaction solution after hydrothermal treatment shows that hardly any ether formation occurs during the BaTiO(3) synthesis. Instead, the presence of 4-phenyl-2-butanol in stoichiometric amounts gives evidence that the formation mechanism proceeds mainly via a novel pathway involving C-C bond formation between benzyl alcohol and the isopropanolate ligand.

  9. Unusual C-C bond cleavage in the formation of amine-bis(phenoxy) group 4 benzyl complexes: Mechanism of formation and application to stereospecific polymerization

    KAUST Repository

    Gowda, Ravikumar R.

    2014-08-11

    Group 4 tetrabenzyl compounds MBn4 (M = Zr, Ti), upon protonolysis with an equimolar amount of the tetradentate amine-tris(phenol) ligand N[(2,4-tBu2C6H2(CH 2)OH]3 in toluene from -30 to 25 °C, unexpectedly lead to amine-bis(phenoxy) dibenzyl complexes, BnCH2N[(2,4- tBu2C6H2(CH2)O] 2MBn2 (M = Zr (1), Ti (2)) in 80% (1) and 75% (2) yields. This reaction involves an apparent cleavage of the >NCH2-ArOH bond (loss of the phenol in the ligand) and formation of the >NCH 2-CH2Bn bond (gain of the benzyl group in the ligand). Structural characterization of 1 by X-ray diffraction analysis confirms that the complex formed is a bis(benzyl) complex of Zr coordinated by a newly derived tridentate amine-bis(phenoxy) ligand arranged in a mer configuration in the solid state. The abstractive activation of 1 and 2 with B(C6F 5)3·THF in CD2Cl2 at room temperature generates the corresponding benzyl cations {BnCH2N[(2,4- tBu2C6H2(CH2)O] 2MBn(THF)}+[BnB(C6F5) 3]- (M = Zr (3), Ti, (4)). These cationic complexes, along with their analogues derived from (imino)phenoxy tri- and dibenzyl complexes, [(2,6-iPr2C6H3)N=C(3,5- tBu2C6H2)O]ZrBn3 (5) and [2,4-Br2C6H2(O)(6-CH2(NC 5H9))CH2N=CH(2-adamantyl-4-MeC 6H2O)]ZrBn2 (6), have been found to effectively polymerize the biomass-derived renewable β-methyl-α-methylene- γ-butyrolactone (βMMBL) at room temperature into the highly stereoregular polymer PβMMBL with an isotacticity up to 99% mm. A combined experimental and DFT study has yielded a mechanistic pathway for the observed unusual C-C bond cleavage in the present protonolysis reaction between ZrBn4 and N[(2,4-tBu2C 6H2(CH2)OH]3 for the formation of complex 1, which involves the benzyl radical and the Zr(III) species, resulting from thermal and photochemical decomposition of ZrBn4, followed by a series of reaction sequences consisting of protonolysis, tautomerization, H-transfer, oxidation, elimination, and radical coupling. © 2014 American Chemical Society.

  10. Investigation of K{sup +} meson production in C+C collisions at 2 A GeV with HADES

    Energy Technology Data Exchange (ETDEWEB)

    Sadovsky, A.

    2007-12-28

    In this thesis the measurement of the double differential cross sections in K{sup +}V transverse momentum and rapidity in the reaction {sup 12}C+{sup 12}C{yields}K{sup +}+X at 2A GeV is described. (HSI)

  11. Localization of (photo)respiration and CO2 re-assimilation in tomato leaves investigated with a reaction-diffusion model

    OpenAIRE

    Berghuijs, Herman N. C.; Yin, Xinyou; Ho, Q. Tri; Retta, Moges A.; Verboven, Pieter; Nicola?, Bart M.; Struik, Paul C.

    2017-01-01

    The rate of photosynthesis depends on the CO2 partial pressure near Rubisco, C c, which is commonly calculated by models using the overall mesophyll resistance. Such models do not explain the difference between the CO2 level in the intercellular air space and C c mechanistically. This problem can be overcome by reaction-diffusion models for CO2 transport, production and fixation in leaves. However, most reaction-diffusion models are complex and unattractive for procedures that require a large...

  12. Electrochemical Polymerization of Iron(III) Polypyridyl Complexes through C-C Coupling of Redox Non-innocent Phenolato Ligands.

    Science.gov (United States)

    Unjaroen, Duenpen; Swart, Marcel; Browne, Wesley R

    2017-01-03

    Phenolato moieties impart redox flexibility to metal complexes due their accessible (oxidative) redox chemistry and have been proposed as functional ligand moieties in redox non-innocent ligand based transition metal catalysis. Here, the electro- and spectroelectrochemistry of phenolato based μ-oxo-diiron(III) complexes [(L 1 )Fe(μ-O)Fe(L 1 )] 2+ (1) and [(L 2 )Fe(μ-O)Fe(L 2 )] 2+ (2), where L 1 = 2-(((di(pyridin-2-yl)methyl)(pyridin-2-ylmethyl)amino)methyl)phenol and L 2 = 3,5-di-tert-butyl-2-(((di(pyridin-2-yl)methyl)(pyridin-2-ylmethyl)amino)methyl)phenol, is described. The electrochemical oxidation of 1 in dichloromethane results in aryl C-C coupling of phenoxyl radical ligand moieties to form tetra nuclear complexes, which undergo subsequent oxidation to form iron(III) phenolato based polymers (poly-1). The coupling is blocked by placing tert-butyl groups at para and ortho positions of phenol units (i.e., 2). Poly-1 shows two fully reversible redox processes in monomer free solution. Assignment of species observed during the electrochemical and chemical {(NH 4 ) 2 [Ce IV (NO 3 ) 6 ]} oxidation of 1 in acetonitrile is made by comparison with the UV-vis-NIR absorption and resonance micro-Raman spectroelectrochemistry of poly-1, and by DFT calculations, which confirms that oxidative coupling occurs in acetonitrile also. However, in contrast to that observed in dichloromethane, in acetonitrile, the oligomers formed are degraded in terms of a loss of the Fe(III)-O-Fe(III) bridge by protonation. The oxidative redox behavior of 1 and 2 is, therefore, dominated by the formation and reactivity of Fe(III) bound phenoxyl radicals, which considerably holds implications in regard to the design of phenolato based complexes for oxidation catalysis.

  13. High Levels of Chemokine C-C Motif Ligand 20 in Human Milk and Its Production by Oral Keratinocytes.

    Science.gov (United States)

    Lourenço, Alan G; Komesu, Marilena C; Duarte, Geraldo; Del Ciampo, Luiz A; Mussi-Pinhata, Marisa M; Yamamoto, Aparecida Y

    2017-03-01

    Chemokine C-C motif ligand 20 (CCL20) is implicated in the formation and function of mucosal lymphoid tissues. Although CCL20 is secreted by many normal human tissues, no studies have evaluated the presence of CCL20 in human milk or its production by oral keratinocytes stimulated by human milk. To evaluate the presence of CCL20 in breast milk and verify CCL20 secretion in vitro by oral keratinocytes stimulated with human and bovine milk, as well as its possible association with breast milk lactoferrin levels. The levels of CCL20 and lactoferrin were measured by enzyme-linked immunosorbent assay in human milk at three different stages of maturation from 74 healthy breastfeeding mothers. In vitro, oral keratinocytes were stimulated with human and bovine milk, and CCL20 was measured in their supernatant. High concentrations of CCL20 were detected in the human breast milk samples obtained during the first week (1,777.07 pg/mL) and second week postpartum (1,523.44 pg/mL), with a significantly low concentration in samples at 3-6 weeks postpartum (238.42 pg/mL; p milk at different weeks postpartum stimulated higher CCL20 secretion by oral keratinocytes compared with bovine milk (p milk lactoferrin concentration. CCl20 is present at high levels in human milk, predominantly in the first and second week postpartum, but at significantly lower levels at 3-6 weeks postpartum. Human milk is capable of stimulating CCL20 secretion by oral keratinocytes, and this induction had no association with breast milk lactoferrin concentration.

  14. Chemokine (C-C motif ligand 2 (CCL2 in sera of patients with type 1 diabetes and diabetic complications.

    Directory of Open Access Journals (Sweden)

    Ruili Guan

    2011-04-01

    Full Text Available Chemokine (C-C motif ligand 2 (CCL2, commonly known as monocyte chemoattractant protein-1 (MCP-1, has been implicated in the pathogenesis of many diseases characterized by monocytic infiltration. However, limited data have been reported on MCP-1 in type 1 diabetes (T1D and the findings are inconclusive and inconsistent.In this study, MCP-1 was measured in the sera from 2,472 T1D patients and 2,654 healthy controls using a Luminex assay. The rs1024611 SNP in the promoter region of MCP-1 was genotyped for a subset of subjects (1764 T1D patients and 1323 controls using the TaqMan-assay.Subject age, sex or genotypes of MCP-1 rs1024611SNP did not have a major impact on serum MCP-1 levels in either healthy controls or patients. While hemoglobin A1c levels did not have a major influence on serum MCP-1 levels, the mean serum MCP-1 levels are significantly higher in patients with multiple complications (mean = 242 ng/ml compared to patients without any complications (mean = 201 ng/ml (p = 3.5×10(-6. Furthermore, mean serum MCP-1 is higher in controls (mean = 261 ng/ml than T1D patients (mean = 208 ng/ml (p99(th percentile of patients or 955 ng/ml of serum MCP-1 is significantly lower in the T1D group compared to the control group (odds ratio = 0.11, p<10(-33.MCP-1 may have a dual role in T1D and its complications. While very high levels of serum MCP-1 may be protective against the development of T1D, complications are associated with higher serum MCP-1 levels within the T1D group.

  15. Comparison of Multiscale Method of Cells-Based Models for Predicting Elastic Properties of Filament Wound C/C-SiC

    Science.gov (United States)

    Pineda, Evan J.; Fassin, Marek; Bednarcyk, Brett A.; Reese, Stefanie; Simon, Jaan-Willem

    2017-01-01

    Three different multiscale models, based on the method of cells (generalized and high fidelity) micromechanics models were developed and used to predict the elastic properties of C/C-SiC composites. In particular, the following multiscale modeling strategies were employed: Concurrent multiscale modeling of all phases using the generalized method of cells, synergistic (two-way coupling in space) multiscale modeling with the generalized method of cells, and hierarchical (one-way coupling in space) multiscale modeling with the high fidelity generalized method of cells. The three models are validated against data from a hierarchical multiscale finite element model in the literature for a repeating unit cell of C/C-SiC. Furthermore, the multiscale models are used in conjunction with classical lamination theory to predict the stiffness of C/C-SiC plates manufactured via a wet filament winding and liquid silicon infiltration process recently developed by the German Aerospace Institute.

  16. Metabolic anchor reactions for robust biorefining.

    Science.gov (United States)

    Jouhten, Paula; Huerta-Cepas, Jaime; Bork, Peer; Patil, Kiran Raosaheb

    2017-03-01

    Microbial cell factories based on renewable carbon sources are fundamental to a sustainable bio-economy. The economic feasibility of producer cells requires robust performance balancing growth and production. However, the inherent competition between these two objectives often leads to instability and reduces productivity. While algorithms exist to design metabolic network reduction strategies for aligning these objectives, the biochemical basis of the growth-product coupling has remained unresolved. Here, we reveal key reactions in the cellular biochemical repertoire as universal anchor reactions for aligning cell growth and production. A necessary condition for a reaction to be an anchor is that it splits a substrate into two or more molecules. By searching the currently known biochemical reaction space, we identify 62 C-C cleaving anchor reactions, such as isocitrate lyase (EC 4.1.3.1) and L-tryptophan indole-lyase (EC 4.1.99.1), which are relevant for biorefining. The here identified anchor reactions mark network nodes for basing growth-coupled metabolic engineering and novel pathway designs. Copyright © 2017 The Authors. Published by Elsevier Inc. All rights reserved.

  17. Liderazgo de una empresa familiar que influye en el clima laboral de los trabajadores de la empresa SEDEMI S.C.C

    OpenAIRE

    Rodríguez Valenzuela, Darwin Fausto

    2015-01-01

    El presente trabajo detalla el estudio del liderazgo y su influencia en el clima organizacional de los trabajadores de la empresa familiar Sedemi S.C.C., con la fin de proponer opciones de mejora, que coadyuven al directorio de la empresa, para fomentar un ambiente laboral agradable y motivador para sus empleados, y de esta manera incrementar su desempeño laboral. La investigación se realizó en la empresa SEDEMI S.C.C. La población objetivo está conformada por los empleados administrativos y ...

  18. Mechanical performance of Hi-Nicalon/CVI-SiC composites with multilayer SiC/C interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Halverson, H.G.; Carter, R.H.; Curtin, W.A. [Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Dept. of Engineering Science and Mechanics

    1997-12-01

    The mechanical properties and interfacial characteristics of new SiC/SiC ceramic composites, composed of Hi-Nicalon fibers in a CVI-SiC matrix and having a variety of multilayer SiC/C coatings between the fibers and the matrix, are studied in detail to elucidate the roles of the coatings and fibers. Axial tension tests and unload/reload hysteresis loop measurements are performed to determine mechanical performance. All materials exhibit the strong and tough behavior characteristic of good ceramic composites, with all multilayer variants performing quite similarly. SEM microscopy demonstrates that matrix cracks penetrate through the multilayers and debond at the fiber/inner-coating interface. Analysis of the hysteretic behavior leads to values for interfacial sliding resistance {tau} {approx} 11 ksi and interfacial toughness {Gamma}{sub i} {approx} 2 J/m{sup 2} that are nearly independent of multilayer structure, and are similar to values obtained for standard pyrolitic carbon interfaces. These results all indicate debonding at the fiber surface for all coating structures, which provides a common roughness, {tau}, and {Gamma}{sub i}. Analysis of fiber fracture mirrors provides an estimate of the in-situ strength of the fibers and demonstrates the high strength retention of the Hi-Nicalon fibers. The in-situ fiber strengths are combined with the measured pullout lengths to obtain an independent determination of {tau} = 8.5 ksi that agrees well with the value found from the hysteretic behavior. Predictions of composite strength using the derived fiber strengths agree well with the measured value although the predicted failure strain is too large. This study demonstrates that Hi-Nicalon fiber/CVI-SiC composites perform well for a wide range of multilayer interface structures and that the interfaces present relatively high values of {tau} and {Gamma}{sub i}, both of which are beneficial to strength and toughness. The small carbon layer thicknesses in these multilayer

  19. Uncovering Structural Diversity of Unsaturated Fatty Acyls in Cholesteryl Esters via Photochemical Reaction and Tandem Mass Spectrometry

    Science.gov (United States)

    Ren, Jia; Franklin, Elissia T.; Xia, Yu

    2017-07-01

    Mass spectrometry analysis of cholesteryl esters (CEs) faces several challenges, with one of them being the determination of the carbon-carbon double bond (C=C) locations within unsaturated fatty acyl chains. Paternὸ-Büchi (PB) reaction, a photochemical reaction based on the addition of acetone to C=C, is capable of C=C location determination when coupled with tandem mass spectrometry (MS/MS). In this study, the PB reaction conditions were tailored for CEs and subsequent nanoelectrospray ionization (nanoESI). A solvent system containing acetone/methanol/dichloromethane/water (40/30/20/10, volume ratios) and 100 μM LiOH was determined to be optimal, resulting in reasonable PB reaction yield ( 30%) and good ionization efficiency (forming lithium adduct of CEs). Collision-induced dissociation (CID) of the PB reaction products produced characteristic fragment ions of CE together with those modified by the PB reactions, such as lithiated fatty acyl ([FA + Li]+) and its PB product ([FA - PB + Li]+). MS3 CID of [FA - PB + Li]+ led to abundant C=C diagnostic ion formation, which was used for C=C location determination and isomer quantitation. A PB-MS3 CID approach was developed and applied for CE analysis from human plasma. A series of unsaturated CEs was identified with specific C=C locations within fatty acyl chains. Absolute quantitation for each CE species was achieved including coexisting C=C location isomers, such as Δ9 and Δ11 isomers of CE 18:1 and ω-6 and ω-3 isomers of CE 18:3. These results show that PB-MS/MS is useful in uncovering structural diversity of CEs due to unsaturation in fatty acyls, which is often undetected from current lipid analysis approach.

  20. SiC/C composites prepared from wood-based carbons by pulse current sintering with SiO2 : Electrical and thermal properties

    NARCIS (Netherlands)

    Fujisawa, M; Hata, T; Bronsveld, P; Castro, [No Value; Tanaka, F; Kikuchi, H; Furuno, T; Imamura, Y

    2004-01-01

    A powder mix of wood charcoal and SiO2 was sintered into a SiC/C composite. The heat treatment temperatures were 1400-1800 degreesC, the SiO2 concentration 0, 10, 30 and 50 wt.% with respect to the dry weight of wood charcoal. The microstructure, electrical resistance and thermal conductivity were

  1. Lack of Association of C-C Chemokine Receptor 5 Delta 32 Deletion Status with Rheumatoid Arthritis, Systemic Lupus Erythematosus, Lupus Nephritis, and Disease Severity

    NARCIS (Netherlands)

    Martens, Henk A.; Gross, Sacha; van der Steege, Gerrit; Brouwer, Elisabeth; Berden, Jo H. M.; de Sevaux, Ruud; Derksen, Ronald H. W. M.; Voskuyl, Alexandre E.; Berger, Stefan P.; Navis, Gerjan J.; Kallenberg, Cees G. M.; Bijl, Marc

    2010-01-01

    Objective. C-C chemokine receptor 5 (CCR5) plays an important role in inflammation. A 32 base-pair (Delta 32) deletion in the CCR5 gene leads to a nonfunctional receptor. This deletion has been reported to have a protective effect on the development and progression of several autoimmune diseases. We

  2. CYP96T1 of Narcissus sp. aff. pseudonarcissus Catalyzes Formation of the Para-Para' C-C Phenol Couple in the Amaryllidaceae Alkaloids

    National Research Council Canada - National Science Library

    Kilgore, Matthew B; Augustin, Megan M; May, Gregory D; Crow, John A; Kutchan, Toni M

    2016-01-01

    .... Through comparative transcriptomics of Narcissus sp. aff. pseudonarcissus, Galanthus sp., and Galanthus elwesii we have identified a para-para' C-C phenol coupling cytochrome P450, CYP96T1, capable of forming the products (10bR,4aS...

  3. Intramolecular hydroalkoxylation of non-activated C=C bonds catalysed by zeolites: an experimental and theoretical study.

    Science.gov (United States)

    Pérez-Mayoral, Elena; Matos, Ines; Nachtigall, Petr; Položij, Miroslav; Fonseca, Isabel; Vitvarová-Procházková, Dana; Čejka, Jiří

    2013-06-01

    The high activity and selectivity of zeolites in the cyclisation of unsaturated alcohols is reported for the first time; the details of a reaction mechanism based on quantum chemical calculations are also provided. The high efficiency of zeolites MFI, BEA and FAU in the cyclisation of unsaturated alcohols (cis-decen-1-ol, 6-methylhept-5-en-2-ol and 2-allylphenol) to afford oxygen-containing heterocyclic rings is demonstrated. The best catalytic performance is found for zeolites with the optimum concentration of Brønsted acid sites (ca. 0.2 mmol g(-1)) and the minimum number of Lewis acid sites. It is proposed that the efficiency of the catalysts is reduced by the existence of the so-called dual site, at which a molecule of unsaturated alcohol can simultaneously interact with two acid sites (an OH group with one and the double bond with the other Brønsted site), which increases the interaction strength. The formation of such adsorption complexes leads to a decrease in the catalyst activity because of (i) an increase in the reaction barrier, (ii) an unfavourable conformation and (iii) diffusion limitations. A new procedure for the preparation of tetrahydrofurans and pyrans over zeolite catalysts provides important oxygen-containing heterocycles with numerous applications. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Factors That Control C-C Cleavage versus C-H Bond Hydroxylation in Copper-Catalyzed Oxidations of Ketones with O2.

    Science.gov (United States)

    Tsang, Althea S-K; Kapat, Ajoy; Schoenebeck, Franziska

    2016-01-20

    The Cu-catalyzed oxidation of ketones with O2 has recently been extensively utilized to cleave the α-C-C bond. This report examines the selective aerobic hydroxylation of tertiary α-C-H bonds in ketones without C-C cleavage. We set out to understand the underlying mechanisms of these two possible reactivity modes. Using experimental, in situ IR spectroscopic, and computational studies, we investigated several mechanisms. Our data suggest that both C-C cleavage and C-H hydroxylation pathways proceed via a common key intermediate, i.e., an α-peroxo ketone. The fate of this peroxide dictates the ultimate product selectivity. Specifically, we uncovered the role of hppH [=1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine] to act not only as a base in the transformation but also as a reductant of the peroxide to the corresponding α-hydroxy ketone. This reduction may also be accomplished through exogenous phosphine additives, therefore allowing the tuning of reduction efficiency toward higher driving forces, if required (e.g., for more-activated substrates). The likely competitive pathway is the cleavage of peroxide to the α-oxy radical (likely catalyzed by Cu), which is computationally predicted to spontaneously trigger C-C bond cleavage. Increasing the susceptibility of this deperoxidation step via (i) the removal of reductant (use of different base, e.g., DBU) or the modulation of (ii) the substitution pattern toward greater activation (substrate control) and (iii) the nature of Cu catalyst (counterion and solvent dependence) will favor the C-C cleavage product.

  5. Tandem Catalysis Utilizing Olefin Metathesis Reactions.

    Science.gov (United States)

    Zieliński, Grzegorz K; Grela, Karol

    2016-07-04

    Since olefin metathesis transformation has become a favored synthetic tool in organic synthesis, more and more distinct non-metathetical reactions of alkylidene ruthenium complexes have been developed. Depending on the conditions applied, the same olefin metathesis catalysts can efficiently promote isomerization reactions, hydrogenation of C=C double bonds, oxidation reactions, and many others. Importantly, these transformations can be carried out in tandem with olefin metathesis reactions. Through addition of one portion of a catalyst, a tandem process provides structurally advanced products from relatively simple substrates without the need for isolation of the intermediates. These aspects not only make tandem catalysis very attractive from a practical point of view, but also open new avenues in (retro)synthetic planning. However, in the literature, the term "tandem process" is sometimes used improperly to describe other types of multi-reaction sequences. In this Concept, a number of examples of tandem catalysis involving olefin metathesis are discussed with an emphasis on their synthetic value. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Unusual mechanisms can dominate reactions at hyperthermal energies: an example from O(3P) + HCl --> ClO + H.

    Science.gov (United States)

    Zhang, Jianming; Camden, Jon P; Brunsvold, Amy L; Upadhyaya, Hari P; Minton, Timothy K; Schatz, George C

    2008-07-16

    An unusual mechanism in the reaction, O(3P) + HCl --> ClO + H, dominates at hyperthermal collision energies. This mechanism applies to collision geometries in which the H atom in the HCl molecule is oriented toward the reagent O atom. As the Cl-O bond forms, the H atom experiences a strong repulsive force from both the O and Cl atoms. The ClO product scatters forward with respect to the initial velocity of the O atom, and the H atom scatters backward. This mechanism accounts for more than half the reactive trajectories at energies >110 kcal mol-1, but it does not involve motion near the minimum energy path, which favors an SN2-like reaction mechanism where the H atom is oriented away from the reagent O atom during the collision.

  7. Iodination of carbohydrate-derived 1,2-oxazines to enantiopure 5-iodo-3,6-dihydro-2H-1,2-oxazines and subsequent palladium-catalyzed cross-coupling reactions

    Directory of Open Access Journals (Sweden)

    Michal Medvecký

    2016-12-01

    Full Text Available Iodination of carbohydrate-derived 3,6-dihydro-2H-1,2-oxazines of type 3 using iodine and pyridine in DMF furnished 5-iodo-substituted 1,2-oxazine derivatives 4 with high efficacy. The alkenyl iodide moiety of 1,2-oxazine derivatives syn-4 and anti-4 was subsequently exploited for the introduction of new functionalities at the C-5 position by applying palladium-catalyzed carbon–carbon bond-forming reactions such as Sonogashira, Heck, or Suzuki coupling reactions as well as a cyanation reaction. These cross-coupling reactions led to a series of 5-alkynyl-, 5-alkenyl-, 5-aryl- and 5-cyano-substituted 1,2-oxazine derivatives being of considerable interest for further synthetic elaborations. This was exemplarily demonstrated by the hydrogenation of syn-21 and anti-24 and by a click reaction of a 5-alkynyl-substituted precursor.

  8. Anaphylaxis-Like Reactions

    Science.gov (United States)

    ... Home Conditions Anaphylaxis Anaphylaxis-Like Reactions Anaphylaxis-Like Reactions Make an Appointment Refer a Patient Ask a ... exposed to a foreign substance, some people suffer reactions identical to anaphylaxis, but no allergy (IgE antibody) ...

  9. Catalysis of Photochemical Reactions.

    Science.gov (United States)

    Albini, A.

    1986-01-01

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

  10. On Thermonuclear Reaction Rates

    OpenAIRE

    Haubold, H. J.; Mathai, A. M.

    1996-01-01

    Nuclear reactions govern major aspects of the chemical evolution of galaxies and stars. Analytic study of the reaction rates and reaction probability integrals is attempted here. Exact expressions for the reaction rates and reaction probability integrals for nuclear reactions in the cases of nonresonant, modified nonresonant, screened nonresonant and resonant cases are given. These are expressed in terms of H-functions, G-functions and in computable series forms. Computational aspects are als...

  11. Theoretical study of the Diels-Alder reaction between o-benzoquinone and norbornadiene

    Science.gov (United States)

    Quijano-Quiñones, Ramiro F.; Quesadas-Rojas, M.; Cuevas, Gabriel; Mena-Rejón, Gonzalo J.

    2013-06-01

    The reaction between norbornadiene and o-benzoquinone is an important step in polyalicyclic rigid structures synthesis. It has been considered that this reaction is an example of Diels-Alder (DA) and hetero-Diels-Alder (HDA) cycloadditions with o-benzoquinone acting as diene (forming C-C bonds) and heterodiene (forming O-C bonds). We have performed a Density Functional Theory study of this reaction, employing B3LYP, mPW1PW91, and B1B95 functionals and 6-31G(d,p) and 6-31+G(d,p) Gaussian type basis sets. The results indicate that Diels-Alder is a feasible mechanism for both reactions, but should not be the main route to the formation of products with C-C bonds.

  12. Reaction of β-enaminones and acetylene dicarboxylates: synthesis of substituted 1,2-dihydropyridinones.

    Science.gov (United States)

    Nagaraju, Vemu; Purnachander, Dalovai; Mangina, N S V M Rao; Suresh, Surisetti; Sridhar, Balasubramanian; Karunakar, Galla V

    2015-03-14

    Synthesis of substituted 1,2-dihydropyridinones is described in a one pot reaction of β-enaminones and acetylene dicarboxylates where new C-C and C-N bonds were formed. The title compounds were obtained in moderate to good yields.

  13. Asymmetric synthesis of quaternary α-fluoro-β-keto-amines via detrifluoroacetylative Mannich reactions.

    Science.gov (United States)

    Xie, Chen; Dai, Yanling; Mei, Haibo; Han, Jianlin; Soloshonok, Vadim A; Pan, Yi

    2015-06-04

    Efficient asymmetric detrifluoroacetylative Mannich addition reactions between 2-fluoro-1,3-di-ketones/hydrates and chiral N-sulfinyl-imines via C-C bond cleavage were reported, which afforded C-F quaternary α-fluoro-β-keto-amines with excellent yields and high diastereoselectivity.

  14. Toolbox approach to the search for effective ligands for catalytic asymmetric Cr-mediated coupling reactions.

    Science.gov (United States)

    Guo, Haibing; Dong, Cheng-Guo; Kim, Dae-Shik; Urabe, Daisuke; Wang, Jiashi; Kim, Joseph T; Liu, Xiang; Sasaki, Takeo; Kishi, Yoshito

    2009-10-28

    Chromium catalysts derived from chiral sulfonamides represented by A effect the couplings of aldehydes with vinyl, allyl, or alkyl halides. With three distinct sites for structural modification, A affords access to a structurally diverse pool of chiral sulfonamides. The Cr catalysts derived from these sulfonamides exhibit a broad range of catalyst-substrate matching profiles. A strategy is presented to search for a satisfactory chiral sulfonamide for a given substrate. In order to demonstrate the generality and effectiveness of this approach, five diverse C-C bond-forming cases have been selected from the halichondrin synthesis. For each of the cases, two ligands have been deliberately searched for, to induce the formation of (R)- and (S)-alcohols, respectively, at the arbitrarily chosen efficiency level of ">or=80% yield with >or=20:1 stereoselectivity in the presence of

  15. Log ASCII Standard (LAS) Files for Geophysical (Gamma Ray) Wireline Well Logs and Their Application to Geologic Cross Section C-C' Through the Central Appalachian Basin

    Science.gov (United States)

    Trippi, Michael H.; Crangle, Robert D.

    2009-01-01

    U.S. Geological Survey (USGS) regional geologic cross section C-C' (Ryder and others, 2008) displays key stratigraphic intervals in the central Appalachian basin. For this cross section, strata were correlated by using descriptions of well cuttings and gamma ray well log traces. This report summarizes the procedures used to convert gamma ray curves on paper well logs to the digital Log ASCII (American Standard Code for Information Interchange) Standard (LAS) format using the third-party software application Neuralog. The procedures could be used with other geophysical wireline logs also. The creation of digital LAS files from paper well logs by using Neuralog is very helpful, especially when dealing with older logs with limited or nonexistent digital data. The LAS files from the gamma ray logs of 11 wells used to construct cross section C-C' are included in this report. They may be downloaded from the index page as a single ZIP file.

  16. Esercizio dell’attività di impresa in forma societaria e disciplina di cui all’art. 230-bis c.c.: sull’asserita incompatibilità

    Directory of Open Access Journals (Sweden)

    Luigi Balestra

    2015-01-01

    Full Text Available Le Sezioni Unite (Cass., sez un., 6 novembre 2014, n. 23676 Rel. Bernabai già segnalata in questa Rivista hanno risolto il conflitto, profilatosi innanzi alla Sezione lavoro agli inizi del nuovo millennio, in ordine alla portata applicativa dell’art. 230-bis c.c., essendo state chiamate a stabilire se la fattispecie compendiata dalla norma in questione presupponga necessariamente un imprenditore persona fisica – elemento per vero non enunciato esplicitamente dalla disposizione, ma ricavabile dal comma 3 dell’art. 230-bis c.c. ove v’è il riferimento a un vincolo (di coniugio, parentela o affinità configurabile solo tra persone fisiche – o se, invece, sia prospettabile anche quando l’attività di impresa venga svolta in forma societaria.

  17. Semiconductor Photocatalysis for Chemoselective Radical Coupling Reactions.

    Science.gov (United States)

    Kisch, Horst

    2017-04-18

    Photocatalysis at semiconductor surfaces is a growing field of general photocatalysis because of its importance for the chemical utilization of solar energy. By analogy with photoelectrochemistry the basic mechanism of semiconductor photocatalysis can be broken down into three steps: photogenerated formation of surface redox centers (electron-hole pairs), interfacial electron transfer from and to substrates (often coupled with proton-transfer), and conversion of primary redox intermediates into the products. Sun driven water cleavage and carbon dioxide fixation are still in the state of basic research whereas aerial degradation reactions of pollutants have reached practical application for the cleaning of air. In addition, a great variety of organic transformations (not syntheses) have been reported. They include cis-trans isomerizations, valence isomerizations, cycloaddition reactions, intramolecular or intermolecular C-N and C-C couplings, partial oxidations, and reductions. In all cases, well-known products were formed but very rarely also isolated. As compared to conventional homogeneous organic synthesis, the photocatalytic reaction mode is of no advantage, although the opposite is quite often claimed in the literature. It is also noted that a high quantum yield does not implicate a high product yield, since it is measured at very low substrate conversion in order to minimize secondary photoreactions. That is especially important in semiconductor photocatalysis since photocorrosion of the photocatalyst often prevents long-time irradiation, as is the case for colloidal metal sulfide semiconductors, which in general are photochemically too unstable to be used in synthesis. In this Account, we first classify the numerous organic photoreactions catalyzed by semiconductor powders. The classification is based on easily obtainable experimental facts, namely the nature of the light absorbing reaction component and the reaction stoichiometry. Next we discuss the

  18. Atmospheric gas phase reactions

    Science.gov (United States)

    Platt, Ulrich

    This chapter introduces the underlying physicochemical principles and the relevance of atmospheric gas phase reactions. In particular, reaction orders, the concept of elementary reactions, definition of and factors determining reaction rates (kinetic theory of chemical reactions), and photochemical reactions are discussed. Sample applications of the pertinent reaction pathways in tropospheric chemistry are presented, particularly reactions involving free radicals (OH, NO3, halogen oxides) and their roles in the self-cleaning of the troposphere. The cycles of nitrogen and sulfur species as well as the principles of tropospheric ozone formation are introduced. Finally, the processes governing the stratospheric ozone layer (Chapman Cycle and extensions) are discussed.

  19. Search for eta and eta ' -> pi(+)e(-)(v)over-bar(e) + c.c. decays in J/psi -> phi eta and phi eta '

    NARCIS (Netherlands)

    Ablikim, M.; Achasov, M. N.; Albayrak, O.; Ambrose, D. J.; An, F. F.; An, Q.; Bai, J. Z.; Ferroli, R. Baldini; Ban, Y.; Becker, J.; Bennett, J. V.; Bertani, M.; Bian, J. M.; Boger, E.; Bondarenko, O.; Boyko, I.; Briere, R. A.; Bytev, V.; Cai, H.; Cai, X.; Cakir, O.; Calcaterra, A.; Cao, G. F.; Cetin, S. A.; Chang, J. F.; Chelkov, G.; Chen, G.; Chen, H. S.; Chen, J.C.; Chen, M.L.; Chen, S. J.; Chen, X.; Chen, Y.B.; Cheng, H. P.; Chu, Y. P.; Cronin-Hennessy, D.; Dai, H. L.; Dai, J.P.; Dedovich, D.; Deng, Z. Y.; Denig, A.; Denysenko, I.; Destefanis, M.; Ding, W. M.; Ding, Y.; Dong, L. Y.; Dong, M. Y.; Du, S. X.; Fang, J.; Fang, S. S.; Fava, L.; Feng, C. Q.; Friedel, P.; Fu, C. D.; Fu, J. L.; Gao, Y.; Geng, C.; Goetzen, K.; Gong, W. X.; Gradl, W.; Greco, M.; Gu, M. H.; Gu, Y. T.; Guan, Y. H.; Guler, N. G.; Guo, A.Q.; Guo, L. B.; Guo, T.; Guo, Y. P.; Han, Y. L.; Harris, F. A.; He, K. L.; He, M.; He, Z. Y.; Held, T.; Heng, Y. K.; Hou, Z. L.; Hu, C.; Hu, H. M.; Hu, J. F.; Hu, T.; Huang, G. M.; Huang, G. S.; Huang, J.S.; Huang, L.; Huang, X.T.; Huang, Y.; Huang, Y.P.; Hussain, T.; Ji, C. S.; Ji, Q.; Ji, Q. P.; Ji, X. B.; Ji, X. L.; Jiang, L.L.; Jiang, X. S.; Jiao, J. B.; Jiao, Z.; Jin, D. P.; Jin, S.; Jing, F. F.; Kalantar-Nayestanaki, N.; Kavatsyuk, M.; Kopf, B.; Kornicer, M.; Kuehn, W.; Lai, W.; Lange, J.S.; Leyhe, M.; Li, C. H.; Li, Cheng; Li, Cui; Li, D. M.; Li, F.; Li, G.; Li, H.B.; Li, J. C.; Li, K.; Li, Lei; Li, Q. J.; Li, S.L.; Li, W. D.; Li, W. G.; Li, X. L.; Li, X. N.; Li, X. Q.; Li, X. R.; Li, Z. B.; Liang, H.; Liang, Y. F.; Liang, Y.T.; Liao, G.R.; Liao, X. T.; Lin, D.; Liu, B. J.; Liu, Cheng; Liu, C.X.; Liu, F.H.; Liu, Fang; Liu, Feng; Liu, H.; Liu, H. B.; Liu, H. H.; Liu, H. M.; Liu, H. W.; Liu, J. P.; Liu, K.; Liu, K.Y.; Liu, Kai; Liu, P. L.; Liu, Q.; Liu, S. B.; Liu, X.; Liu, Y. B.; Liu, Z. A.; Liu, Zhiqiang; Liu, Zhiqing; Loehner, H.; Lu, G. R.; Lu, H. J.; Lu, J.G.; Lu, Q. W.; Lu, X. R.; Lu, Y. P.; Luo, C. L.; Luo, M. X.; Luo, T.; Luo, X.L.; Lv, M.; Ma, C.L.; Ma, F. C.; Ma, H. L.; Ma, Q. M.; Ma, S.; Ma, T.; Ma, X. Y.; Maas, F.E.; Maggiora, M.; Malik, Q. A.; Mao, Y. J.; Mao, Z. P.; Messchendorp, J. G.; Min, J.; Min, T. J.; Mitchell, R. E.; Mo, X. H.; Moeini, H.; Morales, C.; Morales, K. Moriya; Muchnoi, N. Yu.; Muramatsu, H.; Nefedov, Y.; Nicholson, C.; Nikolaev, I. B.; Ning, Z.; Olsen, S. L.; Ouyang, Q.; Pacetti, S.; Park, J.W.; Pelizaeus, M.; Peng, H. P.; Peters, K.; Ping, J. L.; Ping, R. G.; Poling, R.; Prencipe, E.; Qi, M.; Qian, S.; Qiao, C. F.; Qin, L. Q.; Qin, X. S.; Qin, Y.; Qin, Z. H.; Qiu, J. F.; Rashid, K. H.; Rong, G.; Ruan, X. D.; Sarantsev, A.; Sazak, H. S.; Schaefer, B. D.; Shao, M.; Shen, C. P.; Shen, X. Y.; Sheng, H. Y.; Shepherd, M. R.; Song, W.M.; Song, X. Y.; Spataro, S.; Spruck, B.; Sun, D. H.; Sun, G. X.; Sun, J.F.; Sun, S. S.; Sun, Y.J.; Sun, Y.Z.; Sun, Z.J.; Sun, Z.T.; Tang, C.J.; Tang, X.; Tapan, I.; Thorndike, E. H.; Toth, D.; Ullrich, M.; Uman, I. U.; Varner, G. S.; Wang, B.Q.; Wang, D.; Wang, D.Y.; Wang, K.; Wang, L. L.; Wang, L. S.; Wang, M.; Wang, P.; Wang, P. L.; Wang, Q. J.; Wang, S. G.; Wang, X. F.; Wang, X. L.; Wang, Y. D.; Wang, Y. F.; Wang, Y. Q.; Wang, Z.; Wang, Z. G.; Wang, Z.Y.; Wei, D. H.; Wei, J.B.; Weidenkaff, P.; Wen, Q. G.; Wen, S. P.; Wiedner, U.; Wu, L.H.; Wu, N.; Wu, S.X.; Wu, W.; Wu, Z.; Xia, L. G.; Xia, Y. X.; Xiao, Z. J.; Xie, Y. G.; Xiu, Q. L.; Xu, G. F.; Xu, G. M.; Xu, Q.J.; Xu, Q.N.; Xu, X. P.; Xu, Z. R.; Xue, F.; Xue, Z.; Yan, L.; Yan, W. B.; Yan, Y. H.; Yang, H. X.; Yang, Y.; Yang, Y. X.; Ye, H.; Ye, M.; Ye, M. H.; Yu, B. X.; Yu, C. X.; Yu, H. W.; Yu, J. S.; Yu, S. P.; Yuan, C. Z.; Yuan, Y.; Zafar, A. A.; Zallo, A.; Zang, S. L.; Zeng, Y.; Zengin, B. Z.; Zhang, B. X.; Zhang, B. Y.; Zhang, C.; Zhang, C. C.; Zhang, D. H.; Zhang, H. H.; Zhang, H. Y.; Zhang, J. Q.; Zhang, J. W.; Zhang, J. Y.; Zhang, J. Z.; Zhang, Lili; Zhang, R.; Zhang, S. H.; Zhang, X. J.; Zhang, X. Y.; Zhang, Y.; Zhang, Y. H.; Zhang, Z. P.; Zhang, Z. Y.; Zhang, Zhenghao; Zhao, G.; Zhao, H. S.; Zhao, J.W.; Zhao, K. X.; Zhao, Lei; Zhao, Ling; Zhao, M. G.; Zhao, Q.; Zhao, S.J.; Zhao, T.C.; Zhao, X. H.; Zhao, Y. B.; Zhao, Z. G.; Zhemchugov, A.; Zheng, B.; Zheng, Y. H.; Zhong, B.; Zhou, L.; Zhou, X.; Zhou, X. K.; Zhou, X.R.; Zhu, C.; Zhu, K.; Zhu, K. J.; Zhu, S.H.; Zhu, Stuart; Zhu, Y.C.; Zhu, Y.M.; Zhu, Y.S.; Zhu, Z. A.; Zhuang, J.; Zou, B. S.; Zou, J. H.; Werner, M.J.; Zheng, J.P.

    2013-01-01

    Using a sample of 225.3 million J/psi events collected with the BESIII detector at the BEPCII e(+)e(-) collider in 2009, searches for the decays of eta and eta' -> pi(+)e(-)(v) over bar (e) + c.c. in J/psi -> phi eta and phi eta' are performed. The phi signals, which are reconstructed in K+K- final

  20. Crystallographic snapshots of tyrosine phenol-lyase show that substrate strain plays a role in C-C bond cleavage.

    Science.gov (United States)

    Milić, Dalibor; Demidkina, Tatyana V; Faleev, Nicolai G; Phillips, Robert S; Matković-Čalogović, Dubravka; Antson, Alfred A

    2011-10-19

    The key step in the enzymatic reaction catalyzed by tyrosine phenol-lyase (TPL) is reversible cleavage of the Cβ-Cγ bond of L-tyrosine. Here, we present X-ray structures for two enzymatic states that form just before and after the cleavage of the carbon-carbon bond. As for most other pyridoxal 5'-phosphate-dependent enzymes, the first state, a quinonoid intermediate, is central for the catalysis. We captured this relatively unstable intermediate in the crystalline state by introducing substitutions Y71F or F448H in Citrobacter freundii TPL and briefly soaking crystals of the mutant enzymes with a substrate 3-fluoro-L-tyrosine followed by flash-cooling. The X-ray structures, determined at ~2.0 Å resolution, reveal two quinonoid geometries: "relaxed" in the open and "tense" in the closed state of the active site. The "tense" state is characterized by changes in enzyme contacts made with the substrate's phenolic moiety, which result in significantly strained conformation at Cβ and Cγ positions. We also captured, at 2.25 Å resolution, the X-ray structure for the state just after the substrate's Cβ-Cγ bond cleavage by preparing the ternary complex between TPL, alanine quinonoid and pyridine N-oxide, which mimics the α-aminoacrylate intermediate with bound phenol. In this state, the enzyme-ligand contacts remain almost exactly the same as in the "tense" quinonoid, indicating that the strain induced by the closure of the active site facilitates elimination of phenol. Taken together, structural observations demonstrate that the enzyme serves not only to stabilize the transition state but also to destabilize the ground state.

  1. Active Metal Brazing and Characterization of Brazed Joints in C-C and C-SiC Composites to Copper-Clad-Molybdenum System

    Science.gov (United States)

    Singh, M.; Asthana, R.

    2008-01-01

    Carbon/carbon composites with CVI and resin-derived matrices, and C/SiC composites reinforced with T-300 carbon fibers in a CVI SiC matrix were joined to Cu-clad Mo using two Ag-Cu braze alloys, Cusil-ABA (1.75% Ti) and Ticusil (4.5% Ti). The brazed joints revealed good interfacial bonding, preferential precipitation of Ti at the composite/braze interface, and a tendency toward delamination in resin-derived C/C composite. Extensive braze penetration of the inter-fiber channels in the CVI C/C composites was observed. The Knoop microhardness (HK) distribution across the C/C joints indicated sharp gradients at the interface, and a higher hardness in Ticusil than in Cusil-ABA. For the C/SiC composite to Cu-clad-Mo joints, the effect of composite surface preparation revealed that ground samples did not crack whereas unground samples cracked. Calculated strain energy in brazed joints in both systems is comparable to the strain energy in a number of other ceramic/metal systems. Theoretical predictions of the effective thermal resistance suggest that such joined systems may be promising for thermal management applications.

  2. Improvement of MS (multiple sclerosis) CAD (computer aided diagnosis) performance using C/C++ and computing engine in the graphical processing unit (GPU)

    Science.gov (United States)

    Suh, Joohyung; Ma, Kevin; Le, Anh

    2011-03-01

    Multiple Sclerosis (MS) is a disease which is caused by damaged myelin around axons of the brain and spinal cord. Currently, MR Imaging is used for diagnosis, but it is very highly variable and time-consuming since the lesion detection and estimation of lesion volume are performed manually. For this reason, we developed a CAD (Computer Aided Diagnosis) system which would assist segmentation of MS to facilitate physician's diagnosis. The MS CAD system utilizes K-NN (k-nearest neighbor) algorithm to detect and segment the lesion volume in an area based on the voxel. The prototype MS CAD system was developed under the MATLAB environment. Currently, the MS CAD system consumes a huge amount of time to process data. In this paper we will present the development of a second version of MS CAD system which has been converted into C/C++ in order to take advantage of the GPU (Graphical Processing Unit) which will provide parallel computation. With the realization of C/C++ and utilizing the GPU, we expect to cut running time drastically. The paper investigates the conversion from MATLAB to C/C++ and the utilization of a high-end GPU for parallel computing of data to improve algorithm performance of MS CAD.

  3. Sn-MoS2 -C@C Microspheres as a Sodium-Ion Battery Anode Material with High Capacity and Long Cycle Life.

    Science.gov (United States)

    Zheng, Fenghua; Pan, Qichang; Yang, Chenghao; Xiong, Xunhui; Ou, Xing; Hu, Renzong; Chen, Yu; Liu, Meilin

    2017-04-11

    Sodium ion batteries (SIBs) have been regarded as a prime candidate for large-scale energy storage, and developing high performance anode materials is one of the main challenges for advanced SIBs. Novel structured Sn-MoS2 -C@C microspheres, in which Sn nanoparticles are evenly embedded in MoS2 nanosheets and a thin carbon film is homogenously engineered over the microspheres, have been fabricated by the hydrothermal method. The Sn-MoS2 -C@C microspheres demonstrate an excellent Na-storage performance as an anode of SIBs and deliver a high reversible charge capacity (580.3 mAh g(-1) at 0.05 Ag(-1) ) and rate capacity (580.3, 373, 326, 285.2, and 181.9 mAh g(-1) at 0.05, 0.5, 1, 2, and 5 Ag(-1) , respectively). A high charge specific capacity of 245 mAh g(-1) can still be achieved after 2750 cycles at 2 Ag(-1) , indicating an outstanding cycling performance. The high capacity and long-term stability make Sn-MoS2 -C@C composite a very promising anode material for SIBs. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Heterogeneously Catalysed Aldol Reactions in Supercritical Carbon Dioxide as Innovative and Non-Flammable Reaction Medium

    DEFF Research Database (Denmark)

    Musko, Nikolai; Grunwaldt, Jan-Dierk

    2011-01-01

    Aldol reactions of several aldehydes have been investigated over acidic and basic catalysts in supercritical carbon dioxide at 180 bar and 100 °C. Both acidic (Amberlyst-15, tungstosilicic acid (TSA) on SiO2 and MCM-41) and basic (hydrotalcite) materials showed interesting performance...... in this preliminary study under the entitled reaction conditions. Small and linear aldehydes, such as propanal, butanal, pentanal and hexanal, react more efficiently than the branched 3-methylbutanal, which is converted much slower. Whereas Amberlyst-15 showed the highest conversion based on the catalyst mass......, tungstosilicic acid-based catalysts were significantly better if the rates were related to the number of acidic sites (>1000 h−1). The rate depends both on the dispersion and the kind of support. Strikingly, tungstosilicic acid (TSA) on MCM-41 was also an effective catalysts for the selective C=C double bond...

  5. Robust electrodes based on coaxial TiC/C-MnO2 core/shell nanofiber arrays with excellent cycling stability for high-performance supercapacitors.

    Science.gov (United States)

    Zhang, Xuming; Peng, Xiang; Li, Wan; Li, Limin; Gao, Biao; Wu, Guosong; Huo, Kaifu; Chu, Paul K

    2015-04-17

    A coaxial electrode structure composed of manganese oxide-decorated TiC/C core/shell nanofiber arrays is produced hydrothermally in a KMnO4 solution. The pristine TiC/C core/shell structure prepared on the Ti alloy substrate provides the self-sacrificing carbon shell and highly conductive TiC core, thus greatly simplifying the fabrication process without requiring an additional reduction source and conductive additive. The as-prepared electrode exhibits a high specific capacitance of 645 F g(-1) at a discharging current density of 1 A g(-1) attributable to the highly conductive TiC/C and amorphous MnO2 shell with fast ion diffusion. In the charging/discharging cycling test, the as-prepared electrode shows high stability and 99% capacity retention after 5000 cycles. Although the thermal treatment conducted on the as-prepared electrode decreases the initial capacitance, the electrode undergoes capacitance recovery through structural transformation from the crystalline cluster to layered birnessite type MnO2 nanosheets as a result of dissolution and further electrodeposition in the cycling. 96.5% of the initial capacitance is retained after 1000 cycles at high charging/discharging current density of 25 A g(-1). This study demonstrates a novel scaffold to construct MnO2 based SCs with high specific capacitance as well as excellent mechanical and cycling stability boding well for future design of high-performance MnO2-based SCs. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Nondissociative low-energy electron attachment to SF6, C6F6, C10F8, and c-C7F14: Negative ion lifetimes

    Science.gov (United States)

    Suess, L.; Parthasarathy, R.; Dunning, F. B.

    2002-12-01

    The lifetimes of long-lived parent anions formed by nondissociative electron attachment to SF6, C6F6, C10F8, and c-C7F14 are investigated. The ions are created via electron transfer in collisions with K(np) Rydberg atoms and their lifetimes determined by observing their decay using a Penning ion trap. The measured lifetimes vary widely from target to target and range from ˜10 μs for C6F6- to ˜10 ms for SF6-. The present results are compared with values obtained in earlier free-electron studies.

  7. Self assembly of dialkoxo bridged dinuclear Fe(III) complex of pyridoxal Schiff base with C-C bond formation - structure, spectral and magnetic properties

    Czech Academy of Sciences Publication Activity Database

    Murašková, V.; Szabó, N.; Pižl, M.; Hoskovcová, I.; Dušek, Michal; Huber, Š.; Sedmidubský, D.

    2017-01-01

    Roč. 461, May (2017), s. 111-119 ISSN 0020-1693 R&D Projects: GA ČR(CZ) GA15-12653S; GA MŠk LO1603 EU Projects: European Commission(XE) CZ.2.16/3.1.00/24510 Institutional support: RVO:68378271 Keywords : iron (III) dinuclear complex * dialkoxo bridged pyridoxal Schiff base * C-C bond * crystal structure * magnetic properties Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.002, year: 2016

  8. [Adverse reactions to insulin].

    Science.gov (United States)

    Liñana, J J; Montoro, F J; Hernández, M D; Basomba, A

    1997-07-01

    The prevalence of allergic reactions to insuline has decreased during the last few years. Probably this is due to the use of the newly-developed recombinant human insuline. At present, adverse reactions to insuline occur in 5-10% of patients on therapy with insuline. Adverse reactions may be local (more frequent) or systemic (rare). Insuline resistance consists in a different type of immunological reaction. Diagnosis of allergy to insuline is based on clinical history and cutaneous and serological tests. Treatment depends upon the severity of the reaction. When insuline is indispensable despite a previous allergic reaction, a desensitization protocol may be implemented.

  9. Recent advances in cholesterol chemistry.

    Science.gov (United States)

    Morzycki, Jacek W

    2014-05-01

    This review article presents advances in cholesterol chemistry since 2000. Various transformations (chemical, enzymatic, electrochemical, etc.) of cholesterol are presented. A special emphasis is given to cholesterol oxidation reactions, but also substitution of the 3β-hydroxyl group, addition to the C5-C6 double bond, C-H functionalization, and C-C bond forming reactions are discussed. Copyright © 2014 Elsevier Inc. All rights reserved.

  10. Microfluidic chemical reaction circuits

    Science.gov (United States)

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

    2012-06-26

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

  11. Allergic reactions (image)

    Science.gov (United States)

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

  12. Cosmetic tattoo pigment reaction

    National Research Council Canada - National Science Library

    Greywal, Tanya; Cohen, Philip R

    2016-01-01

    BackgroundCutaneous reactions to tattoos are most commonly granulomatous or lichenoid.PurposeWe describe a woman who developed a lymphocytic reaction following a cosmetic tattoo procedure with black dye...

  13. On equivariant embedding of Hilbert C C C modules

    Indian Academy of Sciences (India)

    equivariant unitary map T ∈ L(E1,E2). We call a (G − A) module of the form (A ⊗ H,αg ⊗ γg). (where H is a Hilbert space) a trivial G − A module. We say that (E,β) is embeddable if there is an equivariant isometry from E to A⊗H for some Hilbert space H ...

  14. Chemical transport reactions

    CERN Document Server

    Schäfer, Harald

    2013-01-01

    Chemical Transport Reactions focuses on the processes and reactions involved in the transport of solid or liquid substances to form vapor phase reaction products. The publication first offers information on experimental and theoretical principles and the transport of solid substances and its special applications. Discussions focus on calculation of the transport effect of heterogeneous equilibria for a gas motion between equilibrium spaces; transport effect and the thermodynamic quantities of the transport reaction; separation and purification of substances by means of material transport; and

  15. 14C/C measurements support Andreev's internode method to determine lichen growth rates in Cladina stygia (Fr.) Ahti

    Energy Technology Data Exchange (ETDEWEB)

    Holt, E; Bench, G

    2007-12-05

    Growth rates and the ability to date an organism can greatly contribute to understanding its population biology and community dynamics. 1n 1954, Andreev proposed a method to date Cladina, a fruticose lichen, using total thallus length and number of internodes. No research, however, has demonstrated the reliability of this technique or compared its estimates to those derived by other means. In this study, we demonstrate the utility of {sup 14}C/C ratios to determine lichen age and growth rate in Cladina stygia (Fr.) Ahti collected from northwestern Alaska, USA. The average growth rate using {sup 14}C/C ratios was 6.5 mm {center_dot} yr{sup -1}, which was not significantly different from growth rates derived by Andreev's internode method (average = 6.2 mm {center_dot} yr{sup -1}); thus, suggesting the reliability of Andreev's simple field method for dating lichens. In addition, we found lichen growth rates appeared to differ with geographic location, yet did not seem related to ambient temperature and total precipitation.

  16. A rapid fabrication of C/C composites by a thermal gradient chemical vapor infiltration method with vaporized kerosene as a precursor

    Energy Technology Data Exchange (ETDEWEB)

    Wang Jiping [State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China)]. E-mail: buickwang@hotmail.com; Qian Junmin [State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Qiao Guanjun [State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China); Jin Zhihao [State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xi' an 710049 (China)

    2007-01-15

    A thermal gradient, atmospheric pressure chemical vapor infiltration method with simultaneous vaporized kerosene as a precursor for rapid fabrication of C/C composites was studied. By this method, carbon felts (bulk density {approx}0.2 g cm{sup -3}) were densified to C/C composites with density of 1.67 and 1.71 g cm{sup -3} when prepared at 1050 and 1150 deg. C for 6 h, respectively. X-ray diffraction result indicates that the composites have a strong ability to graphitize and the higher deposition temperature leads to the increased graphitization degree. Polarized light microscope and scanning electron microscope images reveal that fibers of the composites prepared for 6 h are surrounded by ring-shaped pyrocarbon matrix with a thickness of {approx}20 {mu}m, and that the matrix is delaminated to 4-6 layer-like regions. The deposition process is analyzed by dividing the reactor into four regions associated with specific functions and the reasons for the rapid fabrication are proposed as the short convection and diffusion path for the precursor and the existing of thermal gradient across the preform.

  17. Reaction Time (Polish language)

    OpenAIRE

    Iermakov, Sergii

    2014-01-01

    Reaction time is the interval time between the presentation of a stimulus and the initiation of the muscular response to that stimulus.If there is only one possible response (simple reaction time) it will only take a short time to react. If there are several possible responses (choice reaction time) then it will take longer to determine which response to carry out.

  18. Laser enhanced chemical reactions

    Science.gov (United States)

    Included is the discussion of infrared diode lasers used to study time dependent dynamic events. Also, hot atom excitation of vibrational states of polyatomic molecules, bimolecular quenching and reactions of O(sup 1)D, bimolecular reaction studies of the OH + CO yields H + CO2 system, and the chemical dynamics of the reaction between chlorine atoms and deuterated cyclohexane are covered briefly.

  19. (MIRC) reaction w

    Indian Academy of Sciences (India)

    Sudesh Kumari

    as eco-friendly reaction media in catalyst free organic synthesis.7 Ethylene glycol has promising physical ... these properties it is used as a promising green media in many catalysed/ uncatalysed organic reactions ..... Ruijter E, Scheffelaar R and Orru R V A 2011 Multi- component Reaction Design in the Quest for Molecular ...

  20. Unconventional exo selectivity in thermal normal-electron-demand Diels-Alder reactions

    Science.gov (United States)

    Ho, Guo-Ming; Huang, Ci-Jhang; Li, Elise Yu-Tzu; Hsu, Sheng-Kai; Wu, Ti; Zulueta, Medel Manuel L.; Wu, Kevin Binchia; Hung, Shang-Cheng

    2016-10-01

    The Diels-Alder reaction is a useful tool for generating functionalized chiral molecules through the concerted cycloaddition of dienes and dienophiles leading to six-membered rings. Traditionally, the selective predictions of the products rely heavily on consideration of the secondary orbital interactions that stabilize the endo pathway. However, there remain some basic examples defying this notion and produce the exo-isomer as major product. Here we systematically evaluated of the structural features driving exo selectivity in thermal normal-electron-demand Diels-Alder reactions. Substitution at the Cβ position and the size and electronegativity of the electron-withdrawing group of the dienophile are contributing factors. Experimental and computational studies both point toward the steric and electrostatic forces between the substituents in both the diene and the dienophile that increase the likelihood of the exo pathway. For these substrates, the dominance of the endo pathway is reduced by transition state distortions and poor structural alignments of the reacting partners. We also noted the tilt of the dienophile with respect to the diene causing steric strain on the functionalities at the more advanced bond forming carbon-carbon position of the endo transition state. Insights into such factors may benefit synthetic planning and asserting control over this important named reaction.

  1. Metathesis of alkanes and related reactions

    KAUST Repository

    Basset, Jean-Marie

    2010-02-16

    (Figure Presented) The transformation of alkanes remains a difficult challenge because of the relative inertness of the C-H and C-C bonds. The rewards for asserting synthetic control over unfunctionalized, saturated hydrocarbons are considerable, however, because converting short alkanes into longer chain analogues is usually a value-adding process. Alkane metathesis is a novel catalytic and direct transformation of two molecules of a given alkane into its lower and higher homologues; moreover, the process proceeds at relatively low temperature (ambient conditions or higher). It was discovered through the use of a silica-supported tantalum hydride, (=SiO)2TaH, a multifunctional catalyst with a single site of action. This reaction completes the story of the metathesis reactions discovered over the past 40 years: olefin metathesis, alkyne metathesis, and ene-yne cyclizations. In this Account, we examine the fundamental mechanistic aspects of alkane metathesis as well as the novel reactions that have been derived from its study. The silica-supported tantalum hydride catalyst was developed as the result of systematic and meticulous studies of the interaction between oxide supports and organometallic complexes, a field of study denoted surface organometallic chemistry (SOMC). A careful examination of this surface-supported tantalum hydride led to the later discovery of aluminasupported tungsten hydride, W(H)3/Al 2O3, which proved to be an even better catalyst for alkane metathesis. Supported tantalum and tungsten hydrides are highly unsaturated, electron-deficient species that are very reactive toward the C-H and C-C bonds of alkanes. They show a great versatility in various other reactions, such as cross-metathesis between methane and alkanes, cross-metathesis between toluene and ethane, or even methane nonoxidative coupling. Moreover, tungsten hydride exhibits a specific ability in the transformation of isobutane into 2,3-dimethylbutane as well as in the metathesis of

  2. Application of the Suzuki-Miyaura Reaction in the Synthesis of Flavonoids

    Directory of Open Access Journals (Sweden)

    Fanie R. Van Heerden

    2013-04-01

    Full Text Available The application of the Suzuki-Miyaura reaction in the synthesis of flavonoids, an important class of natural products, is reviewed. This reaction has not only been employed to provide access to flavonoid nuclei, but has also been applied to the synthesis of dimeric flavonoids and in the synthesis of libraries of flavonoid derivatives for biological activity studies. The classes of flavonoids that are discussed are the chalcones, flavones, isoflavones, neoflavones, biflavones and derivatives of flavonoids obtained by C-C bond formation via the Suzuki-Miyaura reaction.

  3. Adverse reactions following routine anticholinergic eye drops in a paediatric population: an observational cohort study

    Science.gov (United States)

    van Minderhout, Helena M; Joosse, Maurits V; Grootendorst, Diana C

    2015-01-01

    Objectives To investigate the presence, nature and relationship to age, sex, ethnicity and body mass index (BMI) of adverse reactions following routine cycloplegic eye drops in children. Design Prospective observational cohort study. Setting Ophthalmology outpatient clinic Dutch metropolitan hospital; February, March and April 2009. Participants Children aged 3–14-year-old children receiving two drops of cyclopentolate 1% (C+C) or one drop of cyclopentolate 1% and one drop of tropicamide 1% (C+T). Patients were categorised by age (3–6, 7–10 and 11–14 years), sex, ethnicity and body mass index (BMI) (low, normal or high). Outcome measures Rate and nature of adverse reactions reported at 45 min following treatment. Crude and adjusted ORs for reporting an adverse reaction using stepwise regression analysis with BMI, age, ethnicity and sex. Results 912 of 915 eligible patients participated (99.7%). Adverse reactions were reported for C+C in 10.3% and in C+T in 4.8% (42/408 and 24/504, p=0.002), respectively. Central effects were present in 95% in C+C and in 92% in C+T. Compared to C+T, an increased risk was present in C+C (crude OR 2.3 (1.4 to 3.9), p=0.002). Forward adjustment showed BMI to be an influencing factor in treatment (OR 3.1 (1.7 to 5.6), p<0.001). In a multivariate model, a dose of cyclopentolate remained associated with adverse reactions. Analysis per BMI and regime and age category and regime, indicated associations with low BMI (OR C+C 21.4 (6.7 to 67.96), p<0.001, respectively, C+T 5.2 (2.1 to 12.8), p<0.001) and young age (OR C+C 8.1 (2.7 to 24.8), p<0.001). Conclusions Adverse reactions were common and almost exclusively involved the central nervous system. Both presence and severity were associated with repeated instillation of cyclopentolate 1%, low BMI and young age. In specific paediatric populations, a single dose of cyclopentolate must be considered. Vital function monitoring facilities are advisable. Adjustment of guidelines is

  4. Hypersensitivity reactions to heparins.

    Science.gov (United States)

    Gonzalez-Delgado, Purificación; Fernandez, Javier

    2016-08-01

    This article provides an update on hypersensitivity reactions to heparins and novel oral anticoagulants, with special emphasis on diagnostic methods and management of patients. Although heparins are drugs widely used, hypersensitivity reactions are uncommon. Cutaneous delayed hypersensitivity reactions after subcutaneous administration affects up to 7.5% of patients. Heparin-induced thrombocytopenia is another unusual but severe condition in which early recognition is crucial. Immediate hypersensitivity reactions to heparins have been also reported, but with the novel oral anticoagulants are much more uncommon, although reports of exanthemas have been notified.Skin tests and subcutaneous provocation test are useful tools in the diagnosis of hypersensitivity reactions, except in heparin-induced thrombocytopenia in which biopsy of lesional skin and in-vitro tests are the modalities of choice to confirm the diagnosis.Management of hypersensitivity reactions includes finding an alternative depending on the type of reaction. Fondaparinux and novel oral anticoagulants may be safe alternatives. Delayed skin lesions after subcutaneous heparin are the most common type of hypersensitivity reactions, followed by life-threatening heparin-induced thrombocytopenia. Immediate reactions are uncommon. Allergologic studies may be useful to find an alternative option in patients with skin lesions in which heparin-induced thrombocytopenia has been previously excluded, as well as in heparin immediate reactions.

  5. Los aspectos ideológicos-pedagógicos del proyecto del «Instituto Secundario C. C. Vigil» (1970-1977

    Directory of Open Access Journals (Sweden)

    María Luz Prados

    2017-01-01

    Full Text Available En el presente artículo se analizan los aspectos ideológico-pedagógicos del proyecto político-pedagógico del Instituto Secundario C. C. Vigil. Tal proyecto formó parte del complejo institucional de lo que fuera la Biblioteca Constancio C. Vigil (1959-1977, emblemática entidad de la ciudad de Rosario que llevó adelante un proyecto cultural, social, pedagógico y mutual en uno de sus barrios populares: el barrio Tablada. Esta entidad fue víctima del terrorismo de Estado y, específicamente, de la política educativa procesista (Kaufmann, 2006 desplegada durante la última dictadura cívico-militar (1976-1983 sufriendo una intervención militar en el año 1977 que puso fin a toda su labor.

  6. A review of the irradiation evolution of dispersed oxide nanoparticles in the b.c.c. Fe-Cr system: Current understanding and future directions

    Science.gov (United States)

    Wharry, Janelle P.; Swenson, Matthew J.; Yano, Kayla H.

    2017-04-01

    Thus far, a number of studies have investigated the irradiation evolution of oxide nanoparticles in b.c.c. Fe-Cr based oxide dispersion strengthened (ODS) alloys. But given the inconsistent experimental conditions, results have been widely variable and inconclusive. Crystal structure and chemistry changes differ from experiment to experiment, and the total nanoparticle volume fraction has been observed to both increase and decrease. Furthermore, there has not yet been a comprehensive review of the archival literature. In this paper, we summarize the existing studies on nanoparticle irradiation evolution. We note significant observations with respect to oxide nanoparticle crystallinity, composition, size, and number density. We discuss four possible contributing mechanisms for nanoparticle evolution: ballistic dissolution, Ostwald ripening, irradiation-enhanced diffusion, and homogeneous nucleation. Finally, we propose future directions to achieve a more comprehensive understanding of irradiation effects on oxide nanoparticles in ODS alloys.

  7. Effect of repeated alcohol exposure during the third trimester-equivalent on messenger RNA levels for interleukin-1β, chemokine (C-C motif) ligand 2, and interleukin 10 in the developing rat brain after injection of lipopolysaccharide.

    Science.gov (United States)

    Topper, Lauren A; Valenzuela, C Fernando

    2014-12-01

    Microglia undergo maturation during the third trimester of human development (equivalent to the first 1-2 weeks of postnatal life in rodents), during which these cells may be particularly sensitive to insult. Alcohol exposure during this period can activate the neuroimmune system, an effect that may contribute to the pathophysiology of fetal alcohol spectrum disorders. Here, we investigated whether repeated alcohol exposure during the third trimester-equivalent in rats has a priming effect on the neuroimmune response to injection of bacterial lipopolysaccharide (LPS). Pups were exposed to alcohol in vapor chambers for 4 h daily from postnatal day (PD)2 to PD16 (peak blood alcohol concentrations ∼150 mg/dL). On PD17, rats were injected with either saline or LPS (50 μg/kg) and the frontal cortex, cerebellar vermis, and dentate gyrus were collected 2 h later. Messenger RNA (mRNA) levels for the pro-inflammatory agents interleukin 1β (IL-1β) and chemokine (C-C) motif ligand 2 (CCL2), as well as levels of the anti-inflammatory cytokine interleukin 10 (IL-10), were measured using reverse transcriptase polymerase chain reaction. LPS consistently increased IL-1β and CCL2 mRNA levels in the dentate gyrus, frontal cortex, and cerebellum of both male and female rats. Furthermore, the LPS-induced increase of IL-1β mRNA levels was significantly blunted in the frontal cortex of alcohol-exposed female rats. Conversely, LPS only minimally affected IL-10 mRNA expression and there were no significant differences between air- and alcohol-exposed rats. Taken together with the literature regarding the effect of third-trimester alcohol exposure on the neuroimmune system, our findings suggest that chronic exposure to lower levels is less disruptive to the neuroimmune system than binge-like exposure to high doses of alcohol. Copyright © 2014 Elsevier Inc. All rights reserved.

  8. C-C chemokine receptor type 5 deficiency exacerbates alcoholic fatty liver disease through pro-inflammatory cytokines and chemokines-induced hepatic inflammation.

    Science.gov (United States)

    Park, Ju Ho; Lee, Dong Hun; Park, Mork Soon; Jung, Young Suk; Hong, Jin Tae

    2017-06-01

    Chemokines and chemokine receptors implicated with alcoholic liver disease. Studies have shown that inflammation and oxidative stress induce fat molecules aggregation in liver. We evaluated the relationship between alcoholic fatty liver disease and C-C chemokine receptor 5 (CCR5) and impact of inflammation and oxidative stress in fat molecule deposition. Lieber-DeCarli diet containing ethanol or isocaloric control diets were fed to wild-type and CCR5 knockout mice for 10 days and gavaged with a single dose of ethanol or isocaloric maltose dextrin at 11th day. Cytokine, chemokine, and reactive oxygen species levels were measured in liver tissues to study the role of CCR5 in alcoholic fatty liver disease. C-C chemokine receptor type 5 knockout mice exacerbated ethanol-induced liver injury. Serum levels of aspartate aminotransferase and alanine aminotransferase were higher in CCR5 knockout mice than wild-type mice, and CCR5 knockout mice showed more severe lipid accumulation in liver tissue than wild-type mice after ethanol feeding. Increased expressions of pro-inflammatory cytokines TNF-α and IL-6 and chemokines CCL2, CCL3, CCL4, and CCL5 result in exacerbation of hepatitis in CCR5 knockout mice after ethanol feeding. Oxidative stress induced by reactive oxygen species was more severe in CCR5 knockout mice, and increasing level of fatty acid import and decreasing level of lipid degradation resulted in lipid accumulation in ethanol-fed CCR5 knockout mice. Deficiency of CCR5 exacerbates alcoholic fatty liver disease by hepatic inflammation induced by pro-inflammatory cytokines and chemokines and oxidative stress. © 2016 Journal of Gastroenterology and Hepatology Foundation and John Wiley & Sons Australia, Ltd.

  9. Reaction kinetics of polybutylene terephthalate polycondensation reaction

    NARCIS (Netherlands)

    Darda, P. J.; Hogendoorn, J. A.; Versteeg, G. F.; Souren, F.

    2005-01-01

    The kinetics of the forward polycondensation reaction of polybutylene terephthalate (PBT) has been investigated using thermogravimetric analysis (TGA). PBT - prepolymer with an initial degree of polymerization of 5.5 was used as starting material. The PBT prepolymer was prepared from dimethyl

  10. Reactions at Solid Surfaces

    CERN Document Server

    Ertl, Gerhard

    2009-01-01

    Expanding on the ideas first presented in Gerhard Ertl's acclaimed Baker Lectures at Cornell University, Reactions at Solid Surfaces comprises an authoritative, self-contained, book-length introduction to surface reactions for both professional chemists and students alike. Outlining our present understanding of the fundamental processes underlying reactions at solid surfaces, the book provides the reader with a complete view of how chemistry works at surfaces, and how to understand and probe the dynamics of surface reactions. Comparing traditional surface probes with more modern ones, and brin

  11. Desosamine in multicomponent reactions

    NARCIS (Netherlands)

    Achatz, Sepp; Dömling, Alexander

    2006-01-01

    Desosamine occurring ubiquitously in natural products is introduced into isocyanide based multicomponent reaction chemistry. Corresponding products are of potential interest for the design of novel antibiotics. © 2006.

  12. Hybrid quantum and classical methods for computing kinetic isotope effects of chemical reactions in solutions and in enzymes.

    Science.gov (United States)

    Gao, Jiali; Major, Dan T; Fan, Yao; Lin, Yen-Lin; Ma, Shuhua; Wong, Kin-Yiu

    2008-01-01

    A method for incorporating quantum mechanics into enzyme kinetics modeling is presented. Three aspects are emphasized: 1) combined quantum mechanical and molecular mechanical methods are used to represent the potential energy surface for modeling bond forming and breaking processes, 2) instantaneous normal mode analyses are used to incorporate quantum vibrational free energies to the classical potential of mean force, and 3) multidimensional tunneling methods are used to estimate quantum effects on the reaction coordinate motion. Centroid path integral simulations are described to make quantum corrections to the classical potential of mean force. In this method, the nuclear quantum vibrational and tunneling contributions are not separable. An integrated centroid path integral-free energy perturbation and umbrella sampling (PI-FEP/UM) method along with a bisection sampling procedure was summarized, which provides an accurate, easily convergent method for computing kinetic isotope effects for chemical reactions in solution and in enzymes. In the ensemble-averaged variational transition state theory with multidimensional tunneling (EA-VTST/MT), these three aspects of quantum mechanical effects can be individually treated, providing useful insights into the mechanism of enzymatic reactions. These methods are illustrated by applications to a model process in the gas phase, the decarboxylation reaction of N-methyl picolinate in water, and the proton abstraction and reprotonation process catalyzed by alanine racemase. These examples show that the incorporation of quantum mechanical effects is essential for enzyme kinetics simulations.

  13. The diabetogenic VPS13C/C2CD4A/C2CD4B rs7172432 variant impairs glucose-stimulated insulin response in 5,722 non-diabetic Danish individuals

    DEFF Research Database (Denmark)

    Grarup, N; Overvad, M; Sparsø, T

    2011-01-01

    A genome-wide association study in the Japanese population reported two genome-wide significant loci associated with type 2 diabetes of which the VPS13C/C2CD4A/C2CD4B locus was replicated in Europeans. We looked for potential associations between the diabetogenic VPS13C/C2CD4A/C2CD4B rs7172432...

  14. One-Dimensional Stacking of Bifunctional Dithia- and Diselenadiazolyl Radicals : Preparation and Structural and Electronic Properties of 1,3-[(E2N2C)C6H4(CN2E2)] (E = S, Se)

    NARCIS (Netherlands)

    Andrews, M.P.; Douglass, D.C.; Fleming, R.M.; Glarum, S.H.; Haddon, R.C.; Marsh, P.; Oakley, R.T.; Palstra, T.T.M.; Schneemeyer, L.F.; Trucks, G.W.; Tycko, R.; Waszczak, J.V.; Young, K.M.; Zimmerman, N.M.; Cordes, A.W.

    1991-01-01

    The preparation and solid-state characterization of the 1,3-phenylene-bridged bis(dithiadiazolyl) and bis(diselenadiazolyl) diradicals 1,3-[(E2N2C)C6H4(CN2E2)] (E = S, Se) are reported. The isomorphous crystals of 1,3-[(E2N2C)C6H4(CN2E2)] so obtained are tetragonal, space group I41/a. Stacks of

  15. [Development of novel asymmetric reactions oriented to next-generation enzymatic organic syntheses].

    Science.gov (United States)

    Akai, Shuji

    2003-11-01

    Enzyme-catalyzed organic syntheses have enormous potential in the development of environmentally benign processes. In the last two decades, increased efforts have been devoted to making this a reality. However, the utility of the enzymes is generally limited. For example, although the lipases are extensively used for the kinetic resolution or the desymmetrization of alcohols and carboxylic acid derivatives, little is known about their ability to catalyze carbon-carbon bond-forming reactions. In the past several years, we have been engaged in exploiting a next-generation enzymatic synthesis by using the lipases for the construction of carbon skeletons. This review article describes the results. First, the development of a new type of acyl donor, 1-ethoxyvinyl esters (EVEs), that have significant advantages over common acyl donors (e.g., vinyl esters) for lipase-catalyzed esterification reactions. Second, the highly enantioselective desymmetrization of prochiral 1,3-propanediols and meso 1,2-diols using 1-ethoxyvinyl 2-furoate. The application of this technology for the asymmetric syntheses of fredericamycin A analogues and the oxindoles with a chiral, nonracemic quaternary carbon center has been demonstrated. Third, the first lipase-catalyzed domino reaction using EVEs possessing a suitably functionalized acyl moiety is described. The acyl moiety installed during the enzymatic kinetic resolution was used as a part of the constituent structure for the subsequent Diels--Alder reaction to product optically pure tricyclic compounds with five chiral carbon centers via a one-pot operation. The potential influence of the lipase on the Diets--Alder reaction and the domino process accompanied by the dynamic kinetic resolution are also described.

  16. Reactions to Attitudinal Deviancy.

    Science.gov (United States)

    Levine, John M.; Allen, Vernon L.

    This paper presents a critical review of empirical and theoretical treatments of group reaction to attitudinal deviancy. Inspired by Festinger's (1950) ideas on resolution of attitudinal discrepancies in groups, Schachter (1951) conducted an experiment that has greatly influenced subsequent research and theory concerning reaction to attitudinal…

  17. ORGANIC REACTION MECHANISM CONTROVERSY ...

    African Journals Online (AJOL)

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    Chemists, educators and students are entitled to their mental constructs about reaction mechanism in the classroom. What pedagogical implications have these knowledge claims for teaching and learning reaction mechanisms in organic chemistry? This is the main interest of the paper. Thus three questions were critically ...

  18. Hydrogen evolution reaction catalyst

    Science.gov (United States)

    Subbaraman, Ram; Stamenkovic, Vojislav; Markovic, Nenad; Tripkovic, Dusan

    2016-02-09

    Systems and methods for a hydrogen evolution reaction catalyst are provided. Electrode material includes a plurality of clusters. The electrode exhibits bifunctionality with respect to the hydrogen evolution reaction. The electrode with clusters exhibits improved performance with respect to the intrinsic material of the electrode absent the clusters.

  19. Applications of Reaction Rate

    Science.gov (United States)

    Cunningham, Kevin

    2007-01-01

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

  20. Insight into Group 4 Metallocenium-Mediated Olefin Polymerization Reaction Coordinates Using a Metadynamics Approach.

    Science.gov (United States)

    Motta, Alessandro; Fragalà, Ignazio L; Marks, Tobin J

    2013-08-13

    We report here the first application of the computationally efficient metadynamics approach for analyzing single-site olefin polymerization mechanisms. The mechanism of group 4 metallocenium catalysis for ethylene homopolymerization is investigated by modeling the ethylene insertion step at the cationic (η(5)-C5H5)Zr(CH3)2(+) center using molecular dynamics simulations within the Density Functional Theory (DFT) framework. In particular, the metadynamics formalism is adopted to enable theoretical characterization of covalent bond forming/breaking processes using molecular dynamics ab initio tools. Analysis of the ethylene insertion step free energy surface indicates a slightly exoergic process (-3.2 kcal/mol) with a barrier of 8.6 kcal/mol, in good agreement with conventional ab initio static calculations. Analysis of the structural and dynamic aspects of the simulated reaction coordinate reveals a preferred olefin configuration which aligns parallel to the Zr-CH3 vector in concert with insertion and a slightly bent conformation of the product n-propyl chain to avoid nonbonded repulsion between methylene groups. It is found that the unsaturated/electrophilic CpZr(CH3)2(+) center drives the insertion step, thus promoting the formation of the Zr-alkyl bond. The metadynamics analysis uniquely encompasses all energetically possible reaction coordinates, thus providing a more detailed mechanistic picture. These results demonstrate the potential of metadynamics in the conformational and geometrical analysis of transition metal-centered homogeneous catalytic processes.

  1. An unexpected ethyl transfer reaction between Et2Zn anddo(t-butyl)glyoxaldiimine (t-BuDAB).Studies of thepersistent [EtZn(t-BuDAB)] radical which is in equilibrium with its C-C coupled dimer

    NARCIS (Netherlands)

    Koten, G. van; Jastrzebski, J.T.B.H.; Klerks, J.M.; Vrieze, K.

    1981-01-01

    Whereas p-Tol{2}Zn reacts with t-BuN@?CHCH@?N-t-Bu (t-BuDAB) to give a stable 11 complex [p-Tol{2}Zn(t-BuDAB)], Et{2}Zn gives EtZnN(Et)(t-Bu)CH@?CHN-(t-Bu) via intramolecular ethyl transfer in the unstable Et{2}Zn(t-BuDAB) complex. In solution the stable persistent organozinc radical EtZn(t-BuDAB),

  2. Respiratory transfusion reactions

    Directory of Open Access Journals (Sweden)

    Ivica Marić

    2017-11-01

    Full Text Available Respiratory transfusion-related reactions are not very frequent, partly also because recognition and reporting transfusion reactions is still underemphasized. Tis article describes the most important respiratory transfusion reactions, their pathophysiology, clinical picture and treatment strategies. Respiratory transfusion related reactions can be primary or secondary. The most important primary transfusion-related reactions are TRALI - transfusion-related acute lung injury, TACO – transfusion-associated circulatory overload, and TAD - transfusion-associated dyspnea. TRALI is immuneassociated injury of alveolar basal membrane, which becomes highly permeable and causes noncardiogenic pulmonary edema. Treatment of TRALI is mainly supportive with oxygen, fluids (in case of hypotension and in cases of severe acute respiratory failure also mechanic ventilation. TACO is caused by volume overload in predisposed individuals, such as patients with heart failure, the elderly, infants, patients with anemia and patients with positive fluid balance. Clinical picture is that of a typical pulmonary cardiogenic edema, and the therapy is classical: oxygen and diuretics, and in severe cases also non-invasive or invasive mechanical ventilation. TAD is usually a mild reaction of unknown cause and cannot be classified as TACO or TRALI, nor can it be ascribed to patient’s preexisting diseases. Although the transfusion-related reactions are not very common, knowledge about them can prevent serious consequences. On the one hand preventive measures should be sought, and on the other early recognition is beneficial, so that proper treatment can take place.

  3. Organolanthanide reagents and the Mukaiyama reaction

    Energy Technology Data Exchange (ETDEWEB)

    Gong, L.

    1989-01-01

    The bis(pentamethylcyclopentadienyl) lutetium halide complex ((C/sub 5/Me/sub 5/)/sub 2/LuCl/center dot/THF) was synthesized and characterized. The crystal structure of this complex shows that the Lu is at the center of a distorted tetrahedron consisting of the centroids of two cyclopentadienyl rings, the oxygen atom of a tetrahydrofuran molecule and a chlorine atom. /sup 1/H NMR studies of toluene-d/sub 8/ solutions of (C/sub 5/Me/sub 5/LuCl(THF) + THF, (TMS/sub 2/CP)/sub 2/LuCl(THF) + THF, and (MeCp)/sub 2/LuCl(THF) + THF at various temperatures showed exchange processes between co- ordinated THF and free THF with average values of ..delta..G/sup ne/ of 13.0 /+-/ 0.3 kcal/mol, 11.1 /+-/ 0.1 kcal/mol and <11 kcal/mol at 0/degree/C, respectively. It has been found that under the influence of a catalytic amount (1--5 mol %) of (TMS/sub 2/Cp)/sub 2/YbCl dimer, silyl enol ethers (R/sub 1/R/sub 2/C = C(OR/sub 3/)OSiMe/sub 3/)) react with benzaldehyde smoothly in dichloromethane at room temperature, giving >99% of the aldol silyl ether (isolated yield: 90%) within 3 h. At /minus/78/degrees/C, the reaction gives kinetically controlled diastereoselectivity, which was not observed in the TiCl/sub 4/-mediated aldol reaction. The use of organoytterbium enolates shows promise result with respect to increased stereoselectivity, and indicates the importance of the bulky ligands on the metal center. In addition, Yb(III) species can retard retroaldol reaction owing to its mild Lewis acidity. 118 refs., 14 figs., 30 tabs.

  4. The Atypical Receptor CCRL2 (C-C Chemokine Receptor-Like 2) Does Not Act As a Decoy Receptor in Endothelial Cells.

    Science.gov (United States)

    Mazzotti, Chiara; Gagliostro, Vincenzo; Bosisio, Daniela; Del Prete, Annalisa; Tiberio, Laura; Thelen, Marcus; Sozzani, Silvano

    2017-01-01

    C-C chemokine receptor-like 2 (CCRL2) is a non-signaling seven-transmembrane domain (7-TMD) receptor related to the atypical chemokine receptor (ACKR) family. ACKRs bind chemokines but do not activate G protein-dependent signaling or cell functions. ACKRs were shown to regulate immune functions in vivo by their ability to scavenge chemokines from the local environment. This study was performed to investigate whether CCRL2 shares two of the main characteristics of ACKRs, namely the ability to internalize and scavenge the ligands. Cell membrane analysis of CCRL2-transfected cells revealed a weak, constitutive, ligand-independent internalization, and recycling of CCRL2, with a kinetics that was slower than those observed with ACKR3, a prototypic ACKR, or other chemotactic signaling receptors [i.e., chemokine-like receptor 1 and C-X-C motif chemokine receptor 2]. Intracellularly, CCRL2 colocalized with early endosome antigen 1-positive and Rab5-positive vesicles and with recycling compartments mainly characterized by Rab11-positive vesicles. CCRL2-transfected cells and activated mouse blood endothelial cells, that endogenously express CCRL2, were used to investigate the scavenging ability of CCRL2. These experiments confirmed the ability of CCRL2 to bind chemerin, the only recognized ligand, but excluded the ability of CCRL2 to perform scavenging. Collectively, these results identify unique functional properties for this member of the non-signaling 7-TMD receptor family.

  5. Potential Hazards Relating to Pyrolysis of c-C{sub 4}F{sub 8} in Selected Gaseous Diffusion Plant Operations

    Energy Technology Data Exchange (ETDEWEB)

    Trowbridge, L.D.

    1999-03-01

    As part of a program intended to replace the present evaporative coolant at the gaseous diffusion plants (GDPs) with a non-ozone-depleting alternate, a series of investigations of the suitability of candidate substitutes in under way. One issue concerning a primary candidate, c-C4F8, is the possibility that it might produce the highly toxic perfluoroisobutylene (PFIB) in high temperature environments. This study was commissioned to determine the likelihood and severity of decomposition under two specific high temperature thermal environments, namely the use of a flame test for the presence of coolant vapors and welding in the presence of coolant vapors. The purpose of the study was to develop and evaluate available data to provide information that will allow the technical and industrial hygiene staff at the GDPs to perform appropriate safety evaluations and to determine the need for field testing or experimental work. The scope of this study included a literature search and an evaluation of the information developed therefrom. Part of that evaluation consists of chemical kinetics modeling of coolant decomposition in the two operational environments. The general conclusions are that PFIB formation is unlikely in either situation but that it cannot be ruled out completely under extreme conditions. The presence of oxygen, moisture, and combustion products will tend to lead to formation of oxidation products (COF2, CO, CO2, and HF) rather than PFIB.

  6. 4-alkyl-L-(Dehydro)proline biosynthesis in actinobacteria involves N-terminal nucleophile-hydrolase activity of γ-glutamyltranspeptidase homolog for C-C bond cleavage

    Science.gov (United States)

    Zhong, Guannan; Zhao, Qunfei; Zhang, Qinglin; Liu, Wen

    2017-07-01

    γ-Glutamyltranspeptidases (γ-GTs), ubiquitous in glutathione metabolism for γ-glutamyl transfer/hydrolysis, are N-terminal nucleophile (Ntn)-hydrolase fold proteins that share an autoproteolytic process for self-activation. γ-GT homologues are widely present in Gram-positive actinobacteria where their Ntn-hydrolase activities, however, are not involved in glutathione metabolism. Herein, we demonstrate that the formation of 4-Alkyl-L-(dehydro)proline (ALDP) residues, the non-proteinogenic α-amino acids that serve as vital components of many bioactive metabolites found in actinobacteria, involves unprecedented Ntn-hydrolase activity of γ-GT homologue for C-C bond cleavage. The related enzymes share a key Thr residue, which acts as an internal nucleophile for protein hydrolysis and then as a newly released N-terminal nucleophile for carboxylate side-chain processing likely through the generation of an oxalyl-Thr enzyme intermediate. These findings provide mechanistic insights into the biosynthesis of various ALDP residues/associated natural products, highlight the versatile functions of Ntn-hydrolase fold proteins, and particularly generate interest in thus far less-appreciated γ-GT homologues in actinobacteria.

  7. Tribological Characteristics of C/C-SiC-Cu Composite and Al/SiC Composite Materials under Various Contact Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Byung-Kook; Shin, Dong-Gap; Kim, Chang-Lae; Kim, Dae-Eun [Yonsei Univ., Seoul (Korea, Republic of); Goo, Byeong-Choon [Korea Railroad Research Institute, Uiwang (Korea, Republic of)

    2017-01-15

    The surface temperature of disc brakes varies during braking, which can affect the friction and wear behavior of braking systems. In order to develop an efficient braking system, the friction and wear behaviors of brake materials need to be clearly understood. In this work, the friction and wear behavior of the C/C-SiC-Cu composite and the Al/SiC composite, which are used in disc braking systems, were investigated. Both the surface temperature and contact pressure were studied. A pin-on-reciprocating tribotester was used for this purpose, in order to control temperature and load. Results showed that the friction varied significantly with temperature and sliding distance. It was found that a transfer layer of compacted wear debris formed on the wear track of the two materials. These layers caused the surface roughness of the wear track to increase. The outcome of this work is expected to serve as a basis for the development of braking systems under various operating conditions.

  8. Ubiquitous Transgenic Overexpression of C-C Chemokine Ligand 2: A Model to Assess the Combined Effect of High Energy Intake and Continuous Low-Grade Inflammation

    Directory of Open Access Journals (Sweden)

    Esther Rodríguez-Gallego

    2013-01-01

    Full Text Available Excessive energy management leads to low-grade, chronic inflammation, which is a significant factor predicting noncommunicable diseases. In turn, inflammation, oxidation, and metabolism are associated with the course of these diseases; mitochondrial dysfunction seems to be at the crossroads of mutual relationships. The migration of immune cells during inflammation is governed by the interaction between chemokines and chemokine receptors. Chemokines, especially C-C-chemokine ligand 2 (CCL2, have a variety of additional functions that are involved in the maintenance of normal metabolism. It is our hypothesis that a ubiquitous and continuous secretion of CCL2 may represent an animal model of low-grade chronic inflammation that, in the presence of an energy surplus, could help to ascertain the afore-mentioned relationships and/or to search for specific therapeutic approaches. Here, we present preliminary data on a mouse model created by using targeted gene knock-in technology to integrate an additional copy of the CCl2 gene in the Gt(ROSA26Sor locus of the mouse genome via homologous recombination in embryonic stem cells. Short-term dietary manipulations were assessed and the findings include metabolic disturbances, premature death, and the manipulation of macrophage plasticity and autophagy. These results raise a number of mechanistic questions for future study.

  9. Carbocyclic C-C Bond Formation: Intramolecular Radical Ring Closure to Yield Diastereomerically Pure (7'S-Me- or 7'R-Me-) Carba-LNA Nucleotide Analogs.

    Science.gov (United States)

    Plashkevych, Oleksandr; Upadhayaya, Ram Shankar; Chattopadhyaya, Jyoti

    2017-06-19

    In light of the impressive gene-silencing properties of carba-LNA modified oligo DNA and RNA, both in antisense RNA and siRNA approaches, which have been confirmed as proof-of-concept for biochemical applications in post-transcriptional gene silencing, we envision the true potential of carba-LNA modifications to be revealed soon. Herein we provide detailed protocols for synthesis of carba-LNA-A, -G, -5-Me C, and -T nucleosides on a medium/large scale (gram scale), as well as important guidelines for incorporation of these modified carba-LNAs into DNA or RNA oligonucleotides. Creation of a stereoselective C-C bond during the 5-exo radical intramolecular cyclization involves trapping of a C2' radical intermediate intramolecularly by the vicinal double bond of a C4'-tethered ─CH2 -CH═CH2 group. All diastereomers of substituted carba-LNAs are now available in pure form. The present procedure allows carba-LNA to be commercialized for medicinal or biotechnological purposes. © 2017 by John Wiley & Sons, Inc. Copyright © 2017 John Wiley & Sons, Inc.

  10. The most common mutation of KRT9, c.C487T (p.R163W), in epidermolytic palmoplantar keratoderma in two large Chinese pedigrees.

    Science.gov (United States)

    Liu, Wen-Ting; Ke, Hai-Ping; Zhao, Yan; Chen, Xiao-Ling; Lu, Jia-Jun; Du, Zheng-Fang; Yu, Dan; Zhang, Xian-Ning

    2012-04-01

    Epidermolytic palmoplantar keratoderma (EPPK) is generally associated with dominant-negative mutations of the Keratin 9 gene (KRT9), and rarely with the Keratin 1 gene (KRT1). To date, a myriad of mutations has been reported with a high frequency of codon 163 mutations within the first exon of KRT9 in different populations. Notably, a distinct phenotypic heterogeneity, digital mutilation, was found recently in a 58-year-old female Japanese EPPK patient with p.R163W. Here, we report the most common mutation, c.C487T (p.R163W) of KRT9, in two large EPPK pedigrees from southeast China. The arginine residue in peptide position 163 remains almost constant in at least 47 intermediate filament proteins ranging from snail to human. A substitution in arginine alters both the charge and shape of the 1A rod domain and disrupts the function of the helix initiation motif of keratins, finally compromising the integrity of filaments and weakening their stability in the epidermis of palms and soles. We summarize the clinical symptoms of EPPK in Chinese and show that knuckle pads are associated with KRT9 mutations. We suggest that the frequency of p.R163W in Chinese EPPK patients (31.03%) is consistent with that in the general population (29.33%), and that codon 163 is truly a hotspot mutational site of KRT9. Copyright © 2012 Wiley Periodicals, Inc.

  11. Autocatalysis in Reaction Networks

    OpenAIRE

    Deshpande, Abhishek; Gopalkrishnan, Manoj

    2013-01-01

    The persistence conjecture is a long-standing open problem in chemical reaction network theory. It concerns the behavior of solutions to coupled ODE systems that arise from applying mass-action kinetics to a network of chemical reactions. The idea is that if all reactions are reversible in a weak sense, then no species can go extinct. A notion that has been found useful in thinking about persistence is that of "critical siphon." We explore the combinatorics of critical siphons, with a view to...

  12. The Reaction Wheel Pendulum

    CERN Document Server

    Block, Daniel J; Spong, Mark W

    2007-01-01

    This monograph describes the Reaction Wheel Pendulum, the newest inverted-pendulum-like device for control education and research. We discuss the history and background of the reaction wheel pendulum and other similar experimental devices. We develop mathematical models of the reaction wheel pendulum in depth, including linear and nonlinear models, and models of the sensors and actuators that are used for feedback control. We treat various aspects of the control problem, from linear control of themotor, to stabilization of the pendulum about an equilibrium configuration using linear control, t

  13. Electron transfer reactions

    CERN Document Server

    Cannon, R D

    2013-01-01

    Electron Transfer Reactions deals with the mechanisms of electron transfer reactions between metal ions in solution, as well as the electron exchange between atoms or molecules in either the gaseous or solid state. The book is divided into three parts. Part 1 covers the electron transfer between atoms and molecules in the gas state. Part 2 tackles the reaction paths of oxidation states and binuclear intermediates, as well as the mechanisms of electron transfer. Part 3 discusses the theories and models of the electron transfer process; theories and experiments involving bridged electron transfe

  14. Autocatalysis in reaction networks.

    Science.gov (United States)

    Deshpande, Abhishek; Gopalkrishnan, Manoj

    2014-10-01

    The persistence conjecture is a long-standing open problem in chemical reaction network theory. It concerns the behavior of solutions to coupled ODE systems that arise from applying mass-action kinetics to a network of chemical reactions. The idea is that if all reactions are reversible in a weak sense, then no species can go extinct. A notion that has been found useful in thinking about persistence is that of "critical siphon." We explore the combinatorics of critical siphons, with a view toward the persistence conjecture. We introduce the notions of "drainable" and "self-replicable" (or autocatalytic) siphons. We show that: Every minimal critical siphon is either drainable or self-replicable; reaction networks without drainable siphons are persistent; and nonautocatalytic weakly reversible networks are persistent. Our results clarify that the difficulties in proving the persistence conjecture are essentially due to competition between drainable and self-replicable siphons.

  15. [Adverse reactions to vaccines].

    Science.gov (United States)

    Ito Tsuchiya, F M; Rosas Vargas, M A; Zepeda Ortega, B; Río del Navarro, Blanca Estela; Sienra Monge, Juan José Luis

    2007-01-01

    Vaccination is one of the medicine's achievements to control and/or eradicate certain infectious diseases. Vaccines contain antigenic doses derived from microorganisms and/or its toxins, besides they are composed of other substances such as aluminum, gelatin, egg proteins, mercury components (as thimerosal), and antibiotics; therefore, these substances can produce hypersensitivity reactions. The above-mentioned reactions can be evidenced with itch, edema, hives, asthmatic crisis, hypotension and even anaphylactic shock. Due to the importance of vaccination, especially in childhood, it is essential to know the benefits of vaccines, their impact in morbidity and mortality decrease of certain infected-contagious diseases, as well as the adverse effects and the allergic reactions to their application. As immunizations prevent natural infections, they might contribute to a free infectious environment that would allow atopic response. This paper reviews the allergic reactions to vaccines and their influence on the development of atopic disease.

  16. Bad Reaction to Cosmetics?

    Science.gov (United States)

    ... Consumers Protect Yourself Health Fraud Bad Reactions to Cosmetics? Tell FDA! Share Tweet Linkedin Pin it More ... Radiation-Emitting Products Vaccines, Blood & Biologics Animal & Veterinary Cosmetics Tobacco Products

  17. Reactor for exothermic reactions

    Science.gov (United States)

    Smith, Jr., Lawrence A.; Hearn, Dennis; Jones, Jr., Edward M.

    1993-01-01

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

  18. Firefighter Nozzle Reaction

    DEFF Research Database (Denmark)

    Chin, Selena K.; Sunderland, Peter B.; Jomaas, Grunde

    2017-01-01

    to anchor forces, the hose becomes straight. The nozzle reaction is found to equal the jet momentum flow rate, and it does not change when an elbow connects the hose to the nozzle. A forward force must be exerted by a firefighter or another anchor that matches the forward force that the jet would exert...... on a perpendicular wall. Three reaction expressions are derived, allowing it to be determined in terms of hose diameter, jet diameter, flow rate, and static pressure upstream of the nozzle. The nozzle reaction predictions used by the fire service are 56% to 90% of those obtained here for typical firefighting hand......Nozzle reaction and hose tension are analyzed using conservation of fluid momentum and assuming steady, inviscid flow and a flexible hose in frictionless contact with the ground. An expression that is independent of the bend angle is derived for the hose tension. If this tension is exceeded owing...

  19. Chemical burn or reaction

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/article/000059.htm Chemical burn or reaction To use the sharing features on ... the burned area from pressure and friction. Minor chemical burns will generally heal without further treatment. However, if ...

  20. Adverse reaction to tetrazepam.

    Science.gov (United States)

    Palacios Benito, R; Domínguez Ortega, J; Alonso Llamazares, A; Rodríguez Morales, A; Plaza Díaz, A; Chamorro Gómez, M; Martínez-Cócera, C

    2001-01-01

    Adverse reactions caused by benzodiazepines rarely occur. We present a case of a 70-year-old man who developed a maculopapular exanthema after the ingestion of tetrazepam. For his diagnosis, skin tests were performed, including prick and patch tests, not only with the benzodiazepine implicated in the reaction, but also with benzodiazepines of other groups. Single-blind oral challenge tests were also performed in the patient, in order to assess his tolerance to other benzodiazepines.

  1. Oxygen evolution reaction catalysis

    Science.gov (United States)

    Haber, Joel A.; Jin, Jian; Xiang, Chengxiang; Gregoire, John M.; Jones, Ryan J.; Guevarra, Dan W.; Shinde, Aniketa A.

    2016-09-06

    An Oxygen Evolution Reaction (OER) catalyst includes a metal oxide that includes oxygen, cerium, and one or more second metals. In some instances, the cerium is 10 to 80 molar % of the metals in the metal oxide and/or the catalyst includes two or more second metals. The OER catalyst can be included in or on an electrode. The electrode can be arranged in an oxygen evolution system such that the Oxygen Evolution Reaction occurs at the electrode.

  2. Photoinduced Multicomponent Reactions.

    Science.gov (United States)

    Garbarino, Silvia; Ravelli, Davide; Protti, Stefano; Basso, Andrea

    2016-12-12

    The combination of multicomponent approaches with light-driven processes opens up new scenarios in the area of synthetic organic chemistry, where the need for sustainable, atom- and energy-efficient reactions is increasingly urgent. Photoinduced multicomponent reactions are still in their infancy, but significant developments in this area are expected in the near future. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Rate constants for the slow Mu + propane abstraction reaction at 300 K by diamagnetic RF resonance.

    Science.gov (United States)

    Fleming, Donald G; Cottrell, Stephen P; McKenzie, Iain; Ghandi, Khashayar

    2015-08-14

    The study of kinetic isotope effects for H-atom abstraction rates by incident H-atoms from the homologous series of lower mass alkanes (CH4, C2H6 and, here, C3H8) provides important tests of reaction rate theory on polyatomic systems. With a mass of only 0.114 amu, the most sensitive test is provided by the rates of the Mu atom. Abstraction of H by Mu can be highly endoergic, due to the large zero-point energy shift in the MuH bond formed, which also gives rise to high activation energies from similar zero-point energy corrections at the transition state. Rates are then far too slow near 300 K to be measured by conventional TF-μSR techniques that follow the disappearance of the spin-polarised Mu atom with time. Reported here is the first measurement of a slow Mu reaction rate in the gas phase by the technique of diamagnetic radio frequency (RF) resonance, where the amplitude of the MuH product formed in the Mu + C3H8 reaction is followed with time. The measured rate constant, kMu = (6.8 ± 0.5) × 10(-16) cm(3) s(-1) at 300 K, is surprisingly only about a factor of three slower than that expected for H + C3H8, indicating a dominant contribution from quantum tunneling in the Mu reaction, consistent with elementary transition state theory calculations of the kMu/kH kinetic isotope effect.

  4. Increased C-C Chemokine Receptor 2 Gene Expression in Monocytes of Severe Obstructive Sleep Apnea Patients and under Intermittent Hypoxia

    Science.gov (United States)

    Chuang, Li-Pang; Chen, Ning-Hung; Lin, Shih-Wei; Chang, Ying-Ling; Liao, Hsiang-Ruei; Lin, Yu-Sheng; Chao, I-Ju; Lin, Yuling; Pang, Jong-Hwei S.

    2014-01-01

    Background Obstructive sleep apnea (OSA) is known to be a risk factor of coronary artery disease. The chemotaxis and adhesion of monocytes to the endothelium in the early atherosclerosis is important. This study aimed to investigate the effect of intermittent hypoxia, the hallmark of OSA, on the chemotaxis and adhesion of monocytes. Methods Peripheral blood was sampled from 54 adults enrolled for suspected OSA. RNA was prepared from the isolated monocytes for the analysis of C-C chemokine receptor 2 (CCR2). The effect of intermittent hypoxia on the regulation and function of CCR2 was investigated on THP-1 monocytic cells and monocytes. The mRNA and protein expression levels were investigated by RT/real-time PCR and western blot analysis, respectively. Transwell filter migration assay and cell adhesion assay were performed to study the chemotaxis and adhesion of monocytes. Results Monocytic CCR2 gene expression was found to be increased in severe OSA patients and higher levels were detected after sleep. Intermittent hypoxia increased the CCR2 expression in THP-1 monocytic cells even in the presence of TNF-α and CRP. Intermittent hypoxia also promoted the MCP-1-mediated chemotaxis and adhesion of monocytes to endothelial cells. Furthermore, inhibitor for p42/44 MAPK or p38 MAPK suppressed the activation of monocytic CCR2 expression by intermittent hypoxia. Conclusions This is the first study to demonstrate the increase of CCR2 gene expression in monocytes of severe OSA patients. Monocytic CCR2 gene expression can be induced under intermittent hypoxia which contributes to the chemotaxis and adhesion of monocytes. PMID:25411969

  5. Chemokine (C-C Motif) Receptor 5 −2459 Genotype in Patients Receiving Highly Active Antiretroviral Therapy: Race-Specific Influence on Virologic Success

    Science.gov (United States)

    Cheruvu, Vinay K.; Blood Zikursh, Melinda J.; Benish, Rebekah L.; Lederman, Michael M.; Salata, Robert A.; Gripshover, Barbara; McComsey, Grace A.; Lisgaris, Michelle V.; Fulton, Scott; Subauste, Carlos S.; Jurevic, Richard J.; Guillemette, Chantal; Zimmerman, Peter A.; Rodriguez, Benigno

    2011-01-01

    Background. In patients receiving highly active antiretroviral therapy (HAART), antiretroviral drug–metabolizing enzyme and transporter gene polymorphisms, as well as chemokine receptor gene polymorphisms, may influence response to treatment. Methods. In a North American, treated, adherent human immunodeficiency virus (HIV)–positive cohort (self-identified whites, n = 175; blacks, n = 218), we investigated whether CYP2B6 (516G>T, 983T>C), UGT2B7 (IVS1+985A>G, 802C>T), MDR1 3435C>T, chemokine (C-C motif) receptor 2 (CCR2) 190G>A, and CCR5 (−2459G>A, Δ32) polymorphisms influenced the time to achieve virologic success (TVLS). Results. No difference in TVLS was observed between races. In Kaplan-Meier analyses, only 516G>T (log-rank P = .045 for comparison of GG, GT, and TT and P = .02 GG + GT vs TT) and −2459G>A (log-rank P = .04 for GG, GA, and AA and P = .02 for GG + GA vs AA) genotypes were significantly associated with TVLS in black patients but not in white patients. However, in the Cox proportional hazards model that included age, sex, baseline CD4+ T cell count, and baseline viral load, no significant association was observed between 516G>T and TVLS, whereas the association between −2459G>A and TVLS remained significant even after including CCR2 190G>A as well as all the drug-metabolizing enzyme and transporter genotypes. Conclusions. These findings suggest that CCR5 −2459G>A genotype had a strong, race-specific influence on TVLS in this cohort. Understanding the possible mechanisms underlying this influence requires further studies. PMID:21673041

  6. HT-XRD study of synthetic ferrian magnesian spodumene: the effect of site dimension on the P21/c-->C2/c phase transition

    Science.gov (United States)

    Cámara, F.; Iezzi, G.; Oberti, R.

    Ferrian magnesian spodumene was synthesized in the MLFSH system at P=0.4 GPa, T=700 °C, fO2=NNO+2.3. The space group at room T is P21/c [a=9.638(3) Å, b=8.709(2) Å, c=5.258(2) Å, β=109.83(3)∘, V=415.2 Å3]. The structure is topologically equivalent to that of ferrian spodumene, LiFeSi2O6, and has two symmetrically independent tetrahedral chains, A and B, and two independent octahedral sites, M1 and M2. The crystal-chemical composition was determined combining EMP, SIMS and single-crystal XRD analysis, yielding M2(Li0.85Mg0.09Fe2+0.06) M1(Fe3+0.85Mg0.15)Si2O6. Li is ordered at the M2 site and Fe3+ is ordered at the M1 site, whereas Mg (and Fe2+) distribute over both octahedral sites. Structure refinements done at different temperatures (25, 70, 95, 125, 150 and 200 °C) allowed characterization of a reversible displacive P21/c-->C2/c transition at 106 °C. Previous HT-XRD studies of Li-clinopyroxenes had shown that the transition temperature is inversely related to the size of the M1 cation. For the crystal of this work, the aggregate ionic radius at M1 is longer than that of ferrian spodumene, for which the transition temperature is -44 °C. The higher transition temperature observed can only be explained on the basis of the shorter aggregate radius at the M2 site (due to the presence of Mg substituting after Li), in keeping with the results obtained for ferromagnesian P21/c pyroxenes. The effects of all the chemical substitutions must be considered when modelling transition temperatures and thermodynamic behaviour in clinopyroxenes.

  7. Medications and Drug Allergic Reactions

    Science.gov (United States)

    ... drug allergic reactions TTR Share | Medications and Drug Allergic Reactions This article has been reviewed by Thanai Pongdee, ... your symptoms are severe, seek medical help immediately. Allergic Reactions Allergy symptoms are the result of a chain ...

  8. Regioselectivity and Reaction Mechanism of Ru-Catalyzed Hydrogenolysis of Squalane and Model Alkanes.

    Science.gov (United States)

    Nakagawa, Yoshinao; Oya, Shin-Ichi; Kanno, Daisuke; Nakaji, Yosuke; Tamura, Masazumi; Tomishige, Keiichi

    2017-01-10

    The dependence of the C-C hydrogenolysis activity on reaction parameters and the structure of the substrate alkanes was investigated for Ru/CeO2 catalyst with very small (dispersion: H/Ru=0.89) Ru particles. The substrate concentration and reaction temperature did not have a significant effect on the selectivity pattern, except that methane production was promoted at high temperatures. However, the hydrogen pressure had a marked effect on the selectivity pattern. Ctertiary -C bond dissociation, terminal Csecondary -Cprimary bond dissociation, and fragmentation to form excess methane had negative reaction order with respect to hydrogen partial pressure, whereas Csecondary -Csecondary bond dissociation had an approximately zero reaction order. Therefore, a high hydrogen pressure is essential for the regioselective hydrogenolysis of Csecondary -Csecondary bonds in squalane. Ru/SiO2 catalyst with larger Ru particles showed similar changes in the product distribution during the change in hydrogen pressure. The reaction mechanism for each type of C-C bond dissociation is proposed based on reactivity trends and DFT calculations. The proposed intermediate species for the internal Csecondary -Csecondary dissociation, terminal Csecondary -Cprimary dissociation, and Ctertiary -C dissociation is alkyls, alkylidynes, and alkenes, respectively. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Chemical kinetics of gas reactions

    CERN Document Server

    Kondrat'Ev, V N

    2013-01-01

    Chemical Kinetics of Gas Reactions explores the advances in gas kinetics and thermal, photochemical, electrical discharge, and radiation chemical reactions. This book is composed of 10 chapters, and begins with the presentation of general kinetic rules for simple and complex chemical reactions. The next chapters deal with the experimental methods for evaluating chemical reaction mechanisms and some theories of elementary chemical processes. These topics are followed by discussions on certain class of chemical reactions, including unimolecular, bimolecular, and termolecular reactions. The rema

  10. Reacciones de creación de enlaces C-N y C-C catalizadas por Pd: Síntesis de NH-1, 2, 3-triazoles y olefinas sustituidas

    OpenAIRE

    Escribano Santamaría, María

    2016-01-01

    En esta Tesis Doctoral se aborda el estudio de nuevas aplicaciones sintéticas de las reacciones de acoplamiento cruzado catalizadas por paladio. La memoria consta de dos capítulos, que hacen referencia a la creación de enlaces C-N y C-C, respectivamente: "Reacciones de formación de enlaces C-N: acoplamiento cruzado de azida de sodio con haloalquenos. Síntesis de NH-1,2,3-triazoles" y "Reacciones de formación de enlaces C-C catalizadas por paladio a partir de N-tosilhidrazonas". Este último...

  11. Projeto da reologia de concretos refratários zero-cimento no sistema Al2O3-SiC-C Rheological design of zero-cement refractory castables in the Al2O3-SiC-C system

    Directory of Open Access Journals (Sweden)

    I. R. de Oliveira

    2001-12-01

    Full Text Available Concretos refratários no sistema Al2O3-SiC-C vêm sendo utilizados principalmente no revestimento de canais de corrida de altos-fornos. A associação dessas matérias-primas tem elevado o desempenho dos concretos refratários frente às severas condições de trabalho, devido ao aumento da resistência ao choque térmico e ao ataque por escória e metal fundido. Apesar disso, o nível de conhecimento científico sobre a dispersão das partículas desse sistema multifásico é limitado. Neste trabalho, suspensões representativas da matriz de concretos refratários zero-cimento no sistema Al2O3-SiC-C foram preparadas para a avaliação da eficiência de aditivos na dispersão simultânea de diferentes matérias-primas, bem como para a análise do comportamento reológico da matriz em função do pH e teor de aditivo. Os ácidos poliacrílico e cítrico e um surfactante não iônico foram usados como dispersantes. Os valores de viscosidade aparente e tensão de escoamento obtidos foram usados para construir mapas de estabilidade da matriz. Medidas de pH e fluidez de concretos preparados com diferentes teores de aditivo mostraram que as condições iniciais de pH não foram correspondentes à região ótima de dispersão estabelecida pelos mapas de estabilidade. O uso de altos teores de ácido cítrico, bem como, o deslocamento do pH do concreto na direção da região ótima de dispersão foram eficientes para otimizar a sua fluidez.Refractory castables in the Al2O3-SiC-C system have been used mainly as linings for blast furnace runners. The association of these raw materials has enabled the development of high quality refractory castables due to improvements on their resistance to thermal shock, slag and metal corrosion. Nevertheless, the scientific knowledge regarding particle dispersion in this system is quite limited. In this work, representative suspensions of the matrix of Al2O3-SiC-C refractory castables were prepared in order to evaluate

  12. Reaction Qualifications Revisited

    DEFF Research Database (Denmark)

    Lippert-Rasmussen, Kasper

    2009-01-01

    of merit. Specifically, it preserves symmetry between negative evaluations of antimeritocratic bases of selection and negative evaluations of qualifications rooted in comparable antimeritocratic reactions. So if employers should not select among applicants on the basis of their (the employers') racial...... preferences, recipients should not respond to the applicant actually hired on the basis of their (the recipients') racial preferences. My account decomposes the meritocratic ideal into four separate norms, one of which applies to recipients rather than to selectors. Finally, it defends the view that reaction...... reaction-qualifications are entirely irrelevant from the point of view of merit, the view expounded here implies that the ideal of meritocracy and the norm of non-discrimination are less closely tied than theorists like Andrew Mason and David Miller believe.  ...

  13. Allergic reactions in anaesthesia

    DEFF Research Database (Denmark)

    Krøigaard, M; Garvey, L H; Menné, T

    2005-01-01

    BACKGROUND: The aim of this retrospective survey of possible allergic reactions during anaesthesia was to investigate whether the cause suspected by anaesthetists involved corresponded with the cause found on subsequent investigation in the Danish Anaesthesia Allergy Centre (DAAC). METHODS: Case...... notes and anaesthetic charts from 111 reactions in 107 patients investigated in the DAAC were scrutinized for either suspicions of or warnings against specific substances stated to be the cause of the supposed allergic reaction. RESULTS: In 67 cases, one or more substances were suspected. In 49...... of these (73%) the suspected cause did not match the results of subsequent investigation, either a different substance being the cause or no cause being found. Only five cases (7%) showed a complete match between suspected cause and investigation result. In the remaining 13 cases (19%) there was a partial...

  14. Hipersensitivity Reactions to Corticosteroids.

    Science.gov (United States)

    Berbegal, L; DeLeon, F J; Silvestre, J F

    2016-03-01

    Corticosteroids are widely used drugs in the clinical practice, especially by topic application in dermatology. These substances may act as allergens and produce immediate and delayed hypersensitivity reactions. Allergic contact dermatitis is the most frequent presentation of corticosteroid allergy and it should be studied by patch testing in specific units. The corticosteroids included in the Spanish standard battery are good markers but not ideal. Therefore, if those makers are positive, it is useful to apply a specific battery of corticosteroids and the drugs provided by patients. Immediate reactions are relatively rare but potentially severe, and it is important to confirm the sensitization profile and to guide the use of alternative corticosteroids, because they are often necessary in several diseases. In this article we review the main concepts regarding these two types of hypersensitivity reactions in corticosteroid allergy, as well as their approach in the clinical practice. Copyright © 2015 Elsevier España, S.L.U. and AEDV. All rights reserved.

  15. Nanoparticle Reactions on Chip

    Science.gov (United States)

    Köhler, J. M.; Kirner, Th.; Wagner, J.; Csáki, A.; Möller, R.; Fritzsche, W.

    The handling of heterogenous systems in micro reactors is difficult due to their adhesion and transport behaviour. Therefore, the formation of precipitates and gas bubbles has to be avoided in micro reaction technology, in most cases. But, micro channels and other micro reactors offer interesting possibilities for the control of reaction conditions and transport by diffusion and convection due to the laminar flow caused by small Reynolds numbers. This can be used for the preparation and modification of objects, which are much smaller than the cross section of microchannels. The formation of colloidal solutions and the change of surface states of nano particles are two important tasks for the application of chip reactors in nanoparticle technology. Some concepts for the preparation and reaction of nanoparticles in modular chip reactor arrangements will be discussed.

  16. Adverse reactions to cosmetics

    Directory of Open Access Journals (Sweden)

    Dogra A

    2003-03-01

    Full Text Available Adverse reaction to cosmetics constitute a small but significant number of cases of contact dermatitis with varied appearances. These can present as contact allergic dermatitis, photodermatitis, contact irritant dermatitis, contact urticaria, hypopigmentation, hyperpigmentotion or depigmentation, hair and nail breakage. Fifty patients were included for the study to assess the role of commonly used cosmetics in causing adverse reactions. It was found that hair dyes, lipsticks and surprisingly shaving creams caused more reaction as compared to other cosmetics. Overall incidence of contact allergic dermatitis seen was 3.3% with patients own cosmetics. Patch testing was also done with the basic ingredients and showed positive results in few cases where casual link could be established. It is recommended that labeling of the cosmetics should be done to help the dermatologists and the patients to identify the causative allergen in cosmetic preparation.

  17. Computer investigations on the asymptotic behavior of the rate coefficient for the annihilation reaction A + A → product and the trapping reaction in three dimensions.

    Science.gov (United States)

    Litniewski, Marek; Gorecki, Jerzy

    2011-06-28

    We have performed intensive computer simulations of the irreversible annihilation reaction: A + A → C + C and of the trapping reaction: A + B → C + B for a variety of three-dimensional fluids composed of identical spherical particles. We have found a significant difference in the asymptotic behavior of the rate coefficients for these reactions. Both the rate coefficients converge to the same value with time t going to infinity but the convergence rate is different: the O(t(-1/2)) term for the annihilation reaction is higher than the corresponding term for the trapping reaction. The simulation results suggest that ratio of the terms is a universal quantity with the value equal to 2 or slightly above. A model for the annihilation reaction based on the superposition approximation predicts the difference in the O(t(-1/2)) terms, but overestimates the value for the annihilation reaction by about 30%. We have also performed simulations for the dimerization process: A + A → E, where E stands for a dimer. The dimerization decreases the reaction rate due to the decrease in the diffusion constant for A. The effect is successfully predicted by a simple model.

  18. Velocity pump reaction turbine

    Science.gov (United States)

    House, P.A.

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

  19. Knockout reactions: experimental aspects

    Energy Technology Data Exchange (ETDEWEB)

    Cortina Gil, D. [Santiago de Compostela Univ. (Spain)

    2007-07-01

    The availability of radioactive beams has given rise to intense activity in the field of direct reactions. The removal of one(two)-nucleon (referred to as nucleon knockout in this text) from a fast exotic projectile has been extensively investigated. This lecture provides a general overview of the experimental results achieved using this technique. The sensitivity of the method to different experimental aspects is illustrated with a few examples. Special attention is given to the application of nucleon-knockout reactions as a general purpose spectroscopic tool. (author)

  20. Pressure-dependent kinetics of initial reactions in iso-octane pyrolysis.

    Science.gov (United States)

    Ning, HongBo; Gong, ChunMing; Li, ZeRong; Li, XiangYuan

    2015-05-07

    This study focuses on the studies of the main pressure-dependent reaction types of iso-octane (iso-C8H18) pyrolysis, including initial C-C bond fission of iso-octane, isomerization, and β-scission reactions of the alkyl radicals produced by the C-C bond fission of iso-octane. For the C-C bond fission of iso-octane, the minimum energy potentials are calculated at the CASPT2(2e,2o)/6-31+G(d,p)//CAS(2e,2o)/6-31+G(d,p) level of theory. For the isomerization and the β-scission reactions of the alkyl radicals, the optimization of the geometries and the vibrational frequencies of the reactants, transition states, and products are performed at the B3LYP/CBSB7 level, and their single point energies are calculated by using the composite CBS-QB3 method. Variable reaction coordinate transition state theory (VRC-TST) is used for the high-pressure limit rate constant calculation and Rice-Ramsperger-Kassel-Marcus/master equation (RRKM/ME) is used to calculate the pressure-dependent rate constants of these channels with pressure varying from 0.01-100 atm. The rate constants obtained in this work are in good agreement with those available from literatures. We have updated the rate constants and thermodynamic parameters for species involved in these reactions into a current chemical kinetic mechanism and also have improved the concentration profiles of main products such as C3H6 and C4H6 in the shock tube pyrolysis of iso-octane. The results of this study provide insight into the pyrolysis of iso-octane and will be helpful in the future development of branched paraffin kinetic mechanisms.

  1. Single-Site Palladium(II) Catalyst for Oxidative Heck Reaction: Catalytic Performance and Kinetic Investigations

    Energy Technology Data Exchange (ETDEWEB)

    Duan, Hui; Li, Mengyang; Zhang, Guanghui; Gallagher, James R.; Huang, Zhiliang; Sun, Yu; Luo, Zhong; Chen, Hongzhong; Miller, Jeffrey T.; Zou, Ruqiang; Lei, Aiwen; Zhao, Yanli

    2015-01-01

    ABSTRACT: The development of organometallic single-site catalysts (SSCs) has inspired the designs of new heterogeneous catalysts with high efficiency. Nevertheless, the application of SSCs in certain modern organic reactions, such as C-C bond formation reactions, has still been less investigated. In this study, a single-site Pd(II) catalyst was developed, where 2,2'-bipyridine-grafted periodic mesoporous organosilica (PMO) was employed as the support of a Pd(II) complex. The overall performance of the single-site Pd(II) catalyst in the oxidative Heck reaction was then investigated. The investigation results show that the catalyst displays over 99% selectivity for the product formation with high reaction yield. Kinetic profiles further confirm its high catalytic efficiency, showing that the rate constant is nearly 40 times higher than that for the free Pd(II) salt. X-ray absorption spectroscopy reveals that the catalyst has remarkable lifetime and recyclability.

  2. Benchmark reaction rates, the stability of biological molecules in water, and the evolution of catalytic power in enzymes.

    Science.gov (United States)

    Wolfenden, Richard

    2011-01-01

    The rates of enzyme reactions fall within a relatively narrow range. To estimate the rate enhancements produced by enzymes, and their expected affinities for transition state analog inhibitors, it is necessary to measure the rates of the corresponding reactions in water in the absence of a catalyst. This review describes the spontaneous cleavages of C-C, C-H, C-N, C-O, P-O, and S-O bonds in biological molecules, as well as the uncatalyzed reactions that correspond to phosphoryl transfer reactions catalyzed by kinases and to peptidyl transfer in the ribosome. The rates of these reactions, some with half-lives in excess of one million years, span an overall range of 10¹⁹-fold. Moreover, the slowest reactions tend to be most sensitive to temperature, with rates that increase as much as 10⁷-fold when the temperature is raised from 25° to 100°C. That tendency collapses, by many orders of magnitude, the time that would have been required for chemical evolution on a warm earth. If the catalytic effect of primitive enzymes, like that of modern enzymes and many nonenzymatic catalysts, were mainly to reduce a reaction's enthalpy of activation, then the resulting rate enhancement would have increased automatically as the surroundings cooled. By reducing the time required for early chemical evolution in a warm environment, these findings counter the view that not enough time has passed for terrestrial life to have evolved to its present level of complexity.

  3. Reaction product imaging

    Energy Technology Data Exchange (ETDEWEB)

    Chandler, D.W. [Sandia National Laboratories, Livermore, CA (United States)

    1993-12-01

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

  4. Reaction Formulation: A Bibliography.

    Science.gov (United States)

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

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

  5. Explaining competitive reaction effects

    NARCIS (Netherlands)

    Leeflang, P.S.H.; Wittink, D.R.

    Changes in promotional expenditure decisions for a brand, as in other marketing decisions, should be based on the expected impact on purchase and consumption behavior as well as on the likely reactions by competitors. Purchase behavior may be predicted from estimated demand functions. Competitive

  6. Cluster knockout reactions

    Indian Academy of Sciences (India)

    2014-04-07

    Apr 7, 2014 ... Cluster knockout reactions are expected to reveal the amount of clustering (such as that of , d and even of heavier clusters such as 12C, 16O etc.) in the target nucleus. In simple terms, incident medium high-energy nuclear projectile interacts strongly with the cluster (present in the target nucleus) as if it ...

  7. Applications of Click Chemistry Reactions to the Synthesis of Functional Materials

    Science.gov (United States)

    Accurso, Adrian A.

    This body of work focuses on the production of functional materials using the most reliable carbon-hetoratom bond-forming processes available, which are widely termed "click chemistry" reactions in the literature. This focus on function is enabled by a basis in synthetic chemistry, and where appropriate, brings in techniques from the related fields of materials science and biology to address current needs in those areas. Chapter 1 concerns the in situ production of azide and alkyne-based click chemistry adhesive polymers. Screening of a library of multivalent azides and alkynes was accomplished on a custom-built highthroughput instrument and followed up on a lap-shear testing apparatus. The conductivity of composites made of the adhesive was also explored according to standard methods. The second and third chapters explore the synthesis and function of a family of related [3.3.1]-bicyclononane dichlorides, which we have termed "WCL" electrophiles, and their potential applications for surface functionalization, the synthesis of polycations, and candidate membrane disruptive compounds. The rates of consumption of dichlorides and hydrolysis of model compounds were also explored using NMR, GC-MS, and HPLC-based methods.

  8. Transfer reactions with HELIOS

    Science.gov (United States)

    Wuosmaa, Alan H.

    2011-04-01

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

  9. Multicomponent reactions in polymer synthesis.

    Science.gov (United States)

    Kakuchi, Ryohei

    2014-01-03

    More participants, yet efficient reactions: Multicomponent reactions (MCRs) have found application in polymer chemistry both in the synthesis of multifunctional monomers and in post-polymerization modification. Examples include the Passerini three-component reaction, the Ugi four-component reaction, and the copper-catalyzed MCR. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Kinetics of Bio-Reactions

    DEFF Research Database (Denmark)

    Villadsen, John

    2015-01-01

    his chapter predicts the specific rates of reaction by means of a mathematical expression, the kinetics of the reaction. This expression can be derived through a mechanistic interpretation of an enzymatically catalyzed reaction, but it is essentially of empirical nature for cell reactions. The mo...

  11. What Is a Reaction Rate?

    Science.gov (United States)

    Schmitz, Guy

    2005-01-01

    The definition of reaction rate is derived and demonstrations are made for the care to be taken while using the term. Reaction rate can be in terms of a reaction property, the extent of reaction and thus it is possible to give a definition applicable in open and closed systems.

  12. 1,2-Dichlorohexafluoro-Cyclobutane (1,2-c-C4F6Cl2, R-316c) a Potent Ozone Depleting Substance and Greenhouse Gas: Atmospheric Loss Processes, Lifetimes, and Ozone Depletion and Global Warming Potentials for the (E) and (Z) stereoisomers

    Science.gov (United States)

    Papadimitriou, Vassileios C.; McGillen, Max R.; Smith, Shona C.; Jubb, Aaron M.; Portmann, Robert W.; Hall, Bradley D.; Fleming, Eric L.; Jackman, Charles H.; Burkholder, James B.

    2013-01-01

    The atmospheric processing of (E)- and (Z)-1,2-dichlorohexafluorocyclobutane (1,2-c-C4F6Cl2, R-316c) was examined in this work as the ozone depleting (ODP) and global warming (GWP) potentials of this proposed replacement compound are presently unknown. The predominant atmospheric loss processes and infrared absorption spectra of the R-316c isomers were measured to provide a basis to evaluate their atmospheric lifetimes and, thus, ODPs and GWPs. UV absorption spectra were measured between 184.95 to 230 nm at temperatures between 214 and 296 K and a parametrization for use in atmospheric modeling is presented. The Cl atom quantum yield in the 193 nm photolysis of R- 316c was measured to be 1.90 +/- 0.27. Hexafluorocyclobutene (c-C4F6) was determined to be a photolysis co-product with molar yields of 0.7 and 1.0 (+/-10%) for (E)- and (Z)-R-316c, respectively. The 296 K total rate coefficient for the O(1D) + R-316c reaction, i.e., O(1D) loss, was measured to be (1.56 +/- 0.11) × 10(exp -10)cu cm/ molecule/s and the reactive rate coefficient, i.e., R-316c loss, was measured to be (1.36 +/- 0.20) × 10(exp -10)cu cm/molecule/s corresponding to a approx. 88% reactive yield. Rate coefficient upper-limits for the OH and O3 reaction with R-316c were determined to be global annually averaged lifetimes for the (E)- and (Z)-R-316c isomers were calculated using a 2-D atmospheric model to be 74.6 +/- 3 and 114.1 +/-10 years, respectively, where the estimated uncertainties are due solely to the uncertainty in the UV absorption spectra. Stratospheric photolysis is the predominant atmospheric loss process for both isomers with the O(1D) reaction making a minor, approx. 2% for the (E) isomer and 7% for the (Z) isomer, contribution to the total atmospheric loss. Ozone depletion potentials for (E)- and (Z)-R-316c were calculated using the 2-D model to be 0.46 and 0.54, respectively. Infrared absorption spectra for (E)- and (Z)-R-316c were measured at 296 K and used to estimate their

  13. Laccase-catalyzed C-S and C-C coupling for a one-pot synthesis of 1,4-naphthoquinone sulfides and 1,4-naphthoquinone sulfide dimers

    CSIR Research Space (South Africa)

    Wellington, Kevin W

    2013-06-01

    Full Text Available ChemCatChem June 2013/ Vol 5 Issue 6 Laccase-catalyzed C-S and C-C coupling for a one-pot synthesis of 1,4-naphthoquinone sulfides and 1,4-naphthoquinone sulfide dimers Dr. Kevin W. Wellington1,*, Dr. Gregory E. R. Gordon1, Lindelani A. Ndlovu1...

  14. Indole-3-carbinol and 3’, 3’-diindolylmethane modulate androgen effect up-regulation on C-C chemokine ligand 2 and monocyte attraction to prostate cancer cells

    Science.gov (United States)

    Inflammation has a role in prostate tumorigenesis. Recruitment of inflammatory monocytes to the tumor site is mediated by C-C chemokine ligand 2 (CCL2) through binding to its receptor CCR2. We hypothesized that androgen could modulate CCL2 expression in hormone-responsive prostate cancer cells, and ...

  15. Geologic cross section C-C' through the Appalachian basin from Erie County, north-central Ohio, to the Valley and Ridge province, Bedford County, south-central Pennsylvania

    Science.gov (United States)

    Ryder, Robert T.; Trippi, Michael H.; Swezey, Christopher S.; Crangle, Robert D.; Hope, Rebecca S.; Rowan, Elisabeth L.; Lentz, Erika E.

    2012-01-01

    Geologic cross section C-C' is the third in a series of cross sections constructed by the U.S. Geological Survey (USGS) to document and improve understanding of the geologic framework and petroleum systems of the Appalachian basin. Cross section C-C' provides a regional view of the structural and stratigraphic framework of the Appalachian basin from north-central Ohio to the Valley and Ridge province in south-central Pennsylvania, a distance of approximately 260 miles (mi). This cross section is a companion to cross sections E-E' and D-D' that are located about 50 to 125 mi and 25 to 50 mi, respectively, to the southwest. Cross section C-C' contains much information that is useful for evaluating energy resources in the Appalachian basin. Although specific petroleum systems are not identified on the cross section, many of their key elements (such as source rocks, reservoir rocks, seals, and traps) can be inferred from lithologic units, unconformities, and geologic structures shown on the cross section. Other aspects of petroleum systems (such as the timing of petroleum generation and preferred migration pathways) may be evaluated by burial history, thermal history, and fluid flow models based on what is shown on the cross section. Cross section C-C' also provides a general framework (stratigraphic units and general rock types) for the coal-bearing section, although the cross section lacks the detail to illustrate key elements of coal systems (such as paleoclimate, coal quality, and coal rank). In addition, cross section C-C' may be used as a reconnaissance tool to identify plausible geologic structures and strata for the subsurface storage of liquid waste or for the sequestration of carbon dioxide.

  16. Reaction chemistry of cerium

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1997-01-01

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

  17. Reactions to dietary tartrazine.

    Science.gov (United States)

    David, T J

    1987-01-01

    Double blind challenges with tartrazine and benzoic acid were performed in hospital in 24 children whose parents gave a definite history of a purely behavioural immediate adverse reaction to one of these substances. The patients, whose ages ranged from 1.6 to 12.4 years, were on a diet that avoided these items, and in all there was a clear history that any lapse of the diet caused an obvious adverse behavioural reaction within two hours. In no patient was any change in behaviour noted either by the parents or the nursing staff after the administration of placebo or active substances. Twenty two patients returned to a normal diet without problems, but the parents of two children insisted on continuing the diet. While popular belief has it that additives may have harmful behavioural effects, objective verification is required to prevent overdiagnosis. PMID:3548601

  18. Enzyme catalysed tandem reactions.

    Science.gov (United States)

    Oroz-Guinea, Isabel; García-Junceda, Eduardo

    2013-04-01

    To transfer to the laboratory, the excellent efficiency shown by enzymes in Nature, biocatalysis, had to mimic several synthetic strategies used by the living organisms. Biosynthetic pathways are examples of tandem catalysis and may be assimilated in the biocatalysis field for the use of isolated multi-enzyme systems in the homogeneous phase. The concurrent action of several enzymes that work sequentially presents extraordinary advantages from the synthetic point of view, since it permits a reversible process to become irreversible, to shift the equilibrium reaction in such a way that enantiopure compounds can be obtained from prochiral or racemic substrates, reduce or eliminate problems due to product inhibition or prevent the shortage of substrates by dilution or degradation in the bulk media, etc. In this review we want to illustrate the developments of recent studies involving in vitro multi-enzyme reactions for the synthesis of different classes of organic compounds. Copyright © 2013 Elsevier Ltd. All rights reserved.

  19. CMLSnap : Animated reaction mechanisms

    OpenAIRE

    Holliday, Gemma L; Mitchell, John BO; Murray-Rust, Peter

    2004-01-01

    The authors thank the EPSRC for financial support of this project and Unilever for their support of the Centre for Molecular Science Informatics. Reactions with many steps can be represented by a single XML-based table of the atoms, bonds and electrons. For each step the complete Chemical Markup Language 1 representation of all components is obtained and a snapshot representing the end point of the step is generated. These snapshots can then be combined to give an animated description of t...

  20. Exclusive reactions in QCD

    OpenAIRE

    Pire, Bernard

    1996-01-01

    We review the theory of hard exclusive scattering in Quantum Chromodynamics. After recalling the classical counting rules which describe the leading scale dependence of form factors and exclusive cross-sections at fixed angle, the pedagogical example of the pion form factor is developped in some detail in order to show explicitely what factorization means in the QCD framework. The picture generalizes to many hard reactions which are at the heart of the ELFE project. We briefly present the con...

  1. Photochemical reaction dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Moore, B.C. [Lawrence Berkeley Laboratory, Livermore, CA (United States)

    1993-12-01

    The purpose of the program is to develop a fundamental understanding of unimolecular and bimolecular reaction dynamics with application in combustion and energy systems. The energy dependence in ketene isomerization, ketene dissociation dynamics, and carbonyl substitution on organometallic rhodium complexes in liquid xenon have been studied. Future studies concerning unimolecular processes in ketene as well as energy transfer and kinetic studies of methylene radicals are discussed.

  2. Cryochemical chain reactions

    Science.gov (United States)

    Barkalov, I. M.; Kiryukhin, D. P.

    The possibility of a chemical reaction near absolute zero has appeared doubtful since the beginning of the 1970s. The existing ideas must be revised after the radiation polymerization of formaldehyde at 4.2 K has been observed. In glassy systems, we have examined chain processes that occur under sharp (by five to six orders) changes in molecular mobility of the medium in the region of matrix devitrification. Quite unusual mechano-energetic chains of chemical conversion arise in the studied systems submerged in liquid helium. The chemical transformation initiated by local brittle fracture travels over the sample as an autowave. A series of experimental and theoretical investigations devoted to this interesting phenomenon are described. There is no generalization in this new region of chemistry up to this time. Many journal articles and reviews have been previously published only in Russian. The cycles of investigations of chain cryochemical reactions are the subject of this review. We hope that the investigation of the extraordinary peculiarities of chain cryochemical reactions should produce new ideas in chemical theory and industry.

  3. Adverse cutaneous drug reaction

    Directory of Open Access Journals (Sweden)

    Nayak Surajit

    2008-01-01

    Full Text Available In everyday clinical practice, almost all physicians come across many instances of suspected adverse cutaneous drug reactions (ACDR in different forms. Although such cutaneous reactions are common, comprehensive information regarding their incidence, severity and ultimate health effects are often not available as many cases go unreported. It is also a fact that in the present world, almost everyday a new drug enters market; therefore, a chance of a new drug reaction manifesting somewhere in some form in any corner of world is unknown or unreported. Although many a times, presentation is too trivial and benign, the early identification of the condition and identifying the culprit drug and omit it at earliest holds the keystone in management and prevention of a more severe drug rash. Therefore, not only the dermatologists, but all practicing physicians should be familiar with these conditions to diagnose them early and to be prepared to handle them adequately. However, we all know it is most challenging and practically difficult when patient is on multiple medicines because of myriad clinical symptoms, poorly understood multiple mechanisms of drug-host interaction, relative paucity of laboratory testing that is available for any definitive and confirmatory drug-specific testing. Therefore, in practice, the diagnosis of ACDR is purely based on clinical judgment. In this discussion, we will be primarily focusing on pathomechanism and approach to reach a diagnosis, which is the vital pillar to manage any case of ACDR.

  4. Modelling Tethered Enzymatic Reactions

    Science.gov (United States)

    Solis Salas, Citlali; Goyette, Jesse; Coker-Gordon, Nicola; Bridge, Marcus; Isaacson, Samuel; Allard, Jun; Maini, Philip; Dushek, Omer

    Enzymatic reactions are key to cell functioning, and whilst much work has been done in protein interaction in cases where diffusion is possible, interactions of tethered proteins are poorly understood. Yet, because of the large role cell membranes play in enzymatic reactions, several reactions may take place where one of the proteins is bound to a fixed point in space. We develop a model to characterize tethered signalling between the phosphatase SHP-1 interacting with a tethered, phosphorylated protein. We compare our model to experimental data obtained using surface plasmon resonance (SPR). We show that a single SPR experiment recovers 5 independent biophysical/biochemical constants. We also compare the results between a three dimensional model and a two dimensional model. The work gives the opportunity to use known techniques to learn more about signalling processes, and new insights into how enzyme tethering alters cellular signalling. With support from the Mexican Council for Science and Technology (CONACyT), the Public Education Secretariat (SEP), and the Mexican National Autonomous University's Foundation (Fundacion UNAM).

  5. Switching on elusive organometallic mechanisms with photoredox catalysis.

    Science.gov (United States)

    Terrett, Jack A; Cuthbertson, James D; Shurtleff, Valerie W; MacMillan, David W C

    2015-08-20

    Transition-metal-catalysed cross-coupling reactions have become one of the most used carbon-carbon and carbon-heteroatom bond-forming reactions in chemical synthesis. Recently, nickel catalysis has been shown to participate in a wide variety of C-C bond-forming reactions, most notably Negishi, Suzuki-Miyaura, Stille, Kumada and Hiyama couplings. Despite the tremendous advances in C-C fragment couplings, the ability to forge C-O bonds in a general fashion via nickel catalysis has been largely unsuccessful. The challenge for nickel-mediated alcohol couplings has been the mechanistic requirement for the critical C-O bond-forming step (formally known as the reductive elimination step) to occur via a Ni(III) alkoxide intermediate. Here we demonstrate that visible-light-excited photoredox catalysts can modulate the preferred oxidation states of nickel alkoxides in an operative catalytic cycle, thereby providing transient access to Ni(III) species that readily participate in reductive elimination. Using this synergistic merger of photoredox and nickel catalysis, we have developed a highly efficient and general carbon-oxygen coupling reaction using abundant alcohols and aryl bromides. More notably, we have developed a general strategy to 'switch on' important yet elusive organometallic mechanisms via oxidation state modulations using only weak light and single-electron-transfer catalysts.

  6. Unravelling the Mechanism of Resonant Two-Photon Photodetachment of the Vinylidene Anion, H_2C=C^-, Using Velocity-Map Photoelectron Imaging

    Science.gov (United States)

    Gerardi, H. K.; Breen, K. J.; Gardenier, G. H.; Guasco, T. L.; Laaser, J. E.; Weddle, G. H.; Johnson, M. A.

    2009-06-01

    Vinylidene, an isomer of acetylene and the simplest unsaturated carbene, has been studied extensively due to its role as a possible intermediate in a wide range of important chemical reactions. The neutral form of vinylidene is an extremely short-lived species and therefore information about its structure and potential energy surface may be gained through the study of its stable anionic form. Using velocity-map photoelectron imaging to investigate the behavior of the anion, we observe electron loss with excitation energies lower than the established electron adiabatic detachment energy (ADE). An in-depth analysis of the velocity-map images and corresponding photoelectron spectra taken at various energies within the C-H stretching region as well as at energies around the ADE provide plausible explanations for the observed behavior. The study also reveals interesting angular distributions specific to certain vibrational modes that are not trivial to understand at this point.

  7. Photo-Induced Cycloaddition Reactions of α-Diketones and Transformations of the Photocycloadducts

    Directory of Open Access Journals (Sweden)

    Yan Zhang

    2013-03-01

    Full Text Available Photocycloaddition, along with subsequent transformation of the photocycloadducts, provides expeditious ways to construct various structures. The photo-induced reactions of α-diketones have been reported to proceed via different reaction pathways with the involvement of one or two of the carbonyl groups. Photoinduced reactions of cyclic α-diketones including N-acetylisatin, phenanthrenequinone and isoquinolinetrione with different C=C containing compounds could take place via [2 + 2], [4 + 2] or [4 + 4] photocycloaddition pathways. We have investigated the photoreactions of these cyclic α-diketones with different types of alkenes and alkynes, with a focus on the unusual cascade reactions initiated by the photocycloaddition reactions of these cyclic α-diketones and the applications of these photocycloaddition reactions along with the transformation of the photocycloadducts. In this paper, we discuss the diverse photo-cycloaddition pathways found in the photocycloaddition of o-diones leading to various photocycloadducts and the potential applications of these reactions via further transformation reactions of the adducts.

  8. Well sealing via thermite reactions

    Science.gov (United States)

    Lowry, William Edward; Dunn, Sandra Dalvit

    2016-11-15

    A platform is formed in a well below a target plug zone by lowering a thermite reaction charge into the well and igniting it, whereby the products of the reaction are allowed to cool and expand to form a platform or support in the well. A main thermite reaction charge is placed above the platform and ignited to form a main sealing plug for the well. In some embodiments an upper plug is formed by igniting an upper thermite reaction charge above the main thermite reaction charge. The upper plug confines the products of ignition of the main thermite reaction charge.

  9. Insect bite reactions

    Directory of Open Access Journals (Sweden)

    Sanjay Singh

    2013-01-01

    Full Text Available Insects are a class of living creatures within the arthropods. Insect bite reactions are commonly seen in clinical practice. The present review touches upon the medically important insects and their places in the classification, the sparse literature on the epidemiology of insect bites in India, and different variables influencing the susceptibility of an individual to insect bites. Clinical features of mosquito bites, hypersensitivity to mosquito bites Epstein-Barr virus NK (HMB-EBV-NK disease, eruptive pseudoangiomatosis, Skeeter syndrome, papular pruritic eruption of HIV/AIDS, and clinical features produced by bed bugs, Mexican chicken bugs, assassin bugs, kissing bugs, fleas, black flies, Blandford flies, louse flies, tsetse flies, midges, and thrips are discussed. Brief account is presented of the immunogenic components of mosquito and bed bug saliva. Papular urticaria is discussed including its epidemiology, the 5 stages of skin reaction, the SCRATCH principle as an aid in diagnosis, and the recent evidence supporting participation of types I, III, and IV hypersensitivity reactions in its causation is summarized. Recent developments in the treatment of pediculosis capitis including spinosad 0.9% suspension, benzyl alcohol 5% lotion, dimethicone 4% lotion, isopropyl myristate 50% rinse, and other suffocants are discussed within the context of evidence derived from randomized controlled trials and key findings of a recent systematic review. We also touch upon a non-chemical treatment of head lice and the ineffectiveness of egg-loosening products. Knockdown resistance (kdr as the genetic mechanism making the lice nerves insensitive to permethrin is discussed along with the surprising contrary clinical evidence from Europe about efficacy of permethrin in children with head lice carrying kdr-like gene. The review also presents a brief account of insects as vectors of diseases and ends with discussion of prevention of insect bites and some

  10. Asymmetric catalysis in aqueous media: use of metal-chiral crown ethers as efficient chiral Lewis acid catalysts in asymmetric aldol reactions

    Directory of Open Access Journals (Sweden)

    Shu Kobayashi

    2001-01-01

    Full Text Available Metal-chiral crown ether complexes have been developed as efficient chiral Lewis acid catalysts for asymmetric aldol reactions of silyl enol ethers with aldehydes in aqueous media. While many excellent catalytic asymmetric reactions have been developed recently, most of them have to be carried out under strictly anhydrous conditions in organic solvents. This is probably due to the instability of many catalysts and/or intermediates in the presence of even a small amount of water. To address this issue, we searched for metal-crown ether complexes on the basis of our "multi-coordination" hypothesis, and found that lead(II and lanthanide(III catalysts worked well as chiral Lewis acids in aqueous media. To the best of our knowledge, these are the first examples of chiral crown-based Lewis acids that can be successfully used in catalytic asymmetric reactions. The catalysts have been characterized by X-ray diffraction, and their unique structures as chiral catalysts have been revealed. Use of water as a solvent is essential in these asymmetric catalysis, and the role of water on these reactions to explain the high reactivity and selectivity has been suggested. Another important point is that kinetic studies have shown the possibility that these types of crown ether complexes would be suitable as chiral catalysts employed in aqueous media. In addition, although the catalytic asymmetric aldol reactions are one of the most powerful carbon-carbon bond-forming methodologies and several successful examples have been reported, the use of aprotic anhydrous solvents and low reaction temperatures (-78 °C has been needed in almost all successful cases. On the other hand, the present reactions proceeded smoothly at -10-0 °C in water-alcohol solutions while retaining high levels of diastereo- and enantioselectivities.

  11. Low Energy Nuclear Reactions?

    CERN Multimedia

    CERN. Geneva; Faccini, R.

    2014-01-01

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

  12. Post-synthetic modification of metal-organic framework thin films using click chemistry: the importance of strained C-C triple bonds.

    Science.gov (United States)

    Wang, Zhengbang; Liu, Jinxuan; Arslan, Hasan K; Grosjean, Sylvain; Hagendorn, Tobias; Gliemann, Hartmut; Bräse, Stefan; Wöll, Christof

    2013-12-23

    In this work, we demonstrate that strain-promoted azide-alkyne cycloaddition (SPAAC) yields virtually complete conversion in the context of the post-synthetic modification (PSM) of metal-organic frameworks (MOFs). We use surface-anchored MOF (SURMOF) thin films, [Zn2(N3-bdc)2(dabco)], grown on modified Au substrates using liquid-phase epitaxy (LPE) as a model system to first show that, with standard click chemistry, presently, the most popular method for rendering additional functionality to MOFs via PSM, quantitative conversion yields, cannot be reached. In addition, it is virtually impossible to avoid contaminations of the product by the cytotoxic Cu(I) ions used as a catalyst, a substantial problem for applications in life sciences. Both problems could be overcome by SPAAC, where a metal catalyst is not needed. After optimization of reaction conditions, conversion yields of nearly 100% could be achieved. The consequences of these results for various applications of PSM-modified SURMOFs in the fields of membranes, optical coatings, catalysis, selective gas separation, and chemical sensing are briefly discussed.

  13. Actualizing of calibration curves of {sup 14}C/C, {sup 90}Sr/Ca, {sup 228}Th/{sup 232}Th in ivory for the determination of the post mortal interval of elephants and consequences of the radiation protection of non-human species; Aktualisierung von Kalibierkurven von {sup 14}C/C, {sup 90}Sr/Ca und {sup 228}Th/{sup 232}Th in Elefantenelfenbein zum Zwecke der Alterbestimmung und die Konsequenzen fuer den Strahlenschutz nicht-menschlicher Arten

    Energy Technology Data Exchange (ETDEWEB)

    Schupfner, R. [Regensburg Univ. (Germany). ZRN-URA Lab.

    2016-07-01

    The determination of the activity concentration of the radionuclides {sup 14}C/C and {sup 90}Sr/Ca and {sup 228}Th/{sup 232}Th applying combined radionuclide analyses methods has been proved to be a suitable tool for the purpose of an unambiguous age determination of elephant ivory [1, 2, 3, 10, 11, 12, 13]. Analysing representative and independently dated samples (N = 28) of ivory the curves fitting the post mortal interval (PMI) versus the activity concentration of the radionuclides mentioned above produced the data base enabling a more unambiguous age determination. Data from these studies origin [1, 2, 3, 10, 11, 12, 13] in analyses of ivory samples which were available up to the 2012. During the last five years there was a gap in information of the future trend of {sup 14}C/C and {sup 90}Sr/Ca. Up to this study it was not possible to assess whether the future level of {sup 14}C/C as well as {sup 90}Sr/Ca can analytically be distinguished from the level before 1954. At about 1954 the activity concentration of radionuclides from the atmospheric nuclear explosion, as {sup 14}C and {sup 90}Sr, increased in ivory significantly. This study aims in closing this information gap. The results of analyses of {sup 14}C/C, {sup 90}Sr/Ca, {sup 228}Th/{sup 232}Th in ivory with PMI values ranging from 1 to 5 years are presented and interpreted. These data enable an actualization of the calibration curves of PMI versus specific activities. This is necessary for a better understanding of the effect of blindness of {sup 14}C/C dating and its prevention. On the base of all available results form independent dated ivory sample available up to 2015 a suitable analytical procedure is suggested which aims in a more precise and reliable age determination of elephant tusks. Results of determining of radionuclides {sup 14}C/C and {sup 90}Sr/Ca and {sup 228}Th/{sup 232}Th in ivory are shown from before 1950 to 2015. These results are discussed with respect the purposes of dating as well

  14. Mass Transfer with Chemical Reaction.

    Science.gov (United States)

    DeCoursey, W. J.

    1987-01-01

    Describes the organization of a graduate course dealing with mass transfer, particularly as it relates to chemical reactions. Discusses the course outline, including mathematics models of mass transfer, enhancement of mass transfer rates by homogeneous chemical reaction, and gas-liquid systems with chemical reaction. (TW)

  15. Anaphylactic reactions to novel foods

    DEFF Research Database (Denmark)

    Ballardini, Natalia; Nopp, Anna; Hamsten, Carl

    2017-01-01

    an anaphylactic reaction. Cross-reactivity between chicken and crocodile meat was suspected to have triggered this reaction. Basophil activation and immunoglobulin E testing confirmed the boy's allergic reaction to crocodile meat proteins. Molecular analysis identified a crocodile a-parvalbumin, with extensive...

  16. Reactions inside nanoscale protein cages

    NARCIS (Netherlands)

    Bode, Saskia A.; Minten, Inge J.; Nolte, Roeland J.M.; Cornelissen, Jeroen Johannes Lambertus Maria

    2011-01-01

    Chemical reactions are traditionally carried out in bulk solution, but in nature confined spaces, like cell organelles, are used to obtain control in time and space of conversion. One way of studying these reactions in confinement is the development and use of small reaction vessels dispersed in

  17. Nuclear reactions an introduction

    CERN Document Server

    Paetz gen. Schieck, Hans

    2014-01-01

    Nuclei and nuclear reactions offer a unique setting for investigating three (and in some cases even all four) of the fundamental forces in nature. Nuclei have been shown – mainly by performing scattering experiments with electrons, muons, and neutrinos – to be extended objects with complex internal structures: constituent quarks; gluons, whose exchange binds the quarks together; sea-quarks, the ubiquitous virtual quark-antiquark pairs and, last but not least, clouds of virtual mesons, surrounding an inner nuclear region, their exchange being the source of the nucleon-nucleon interaction.   The interplay between the (mostly attractive) hadronic nucleon-nucleon interaction and the repulsive Coulomb force is responsible for the existence of nuclei; their degree of stability, expressed in the details and limits of the chart of nuclides; their rich structure and the variety of their interactions. Despite the impressive successes of the classical nuclear models and of ab-initio approaches, there is clearly no ...

  18. Reaction Time for Trimolecular Reactions in Compartment-based Reaction-Diffusion Models

    OpenAIRE

    Li, F; Chen, M; Erban, R; Cao, Y

    2016-01-01

    Trimolecular reaction models are investigated in the compartment-based (lattice-based) framework for stochastic reaction-diffusion modelling. The formulae for the first collision time and the mean reaction time are derived for the case where three molecules are present in the solution.

  19. The Glaser–Hay reaction

    DEFF Research Database (Denmark)

    Vilhelmsen, Mie Højer; Jensen, Jonas; Tortzen, Christian

    2013-01-01

    . This unfavorable change in reaction profile could be avoided by adding molecular sieves to the reaction mixture, thereby removing the water that is accumulated from the air and produced in the reaction in which dioxygen acts as the oxidizing agent. Not unexpectedly, the stirring rate, and hence uptake of air (O2......), was found to have a significant effect on the rate of the reaction: The percentage of alkyne remaining after a certain time decreased linearly with the rate of stirring. On the basis of systematic studies, the optimized conditions for the coupling reaction using CuCl/TMEDA as the catalyst system......The oxidative Glaser–Hay coupling of two terminal alkynes to furnish a butadiyne is a key reaction for acetylenic scaffolding. Although the reaction is performed under rather simple conditions [CuCl/TMEDA/O2 (air)], the mechanism is still under debate. Herein we present detailed studies...

  20. Ion-Molecule Reaction Dynamics.

    Science.gov (United States)

    Meyer, Jennifer; Wester, Roland

    2017-05-05

    We review the recent advances in the investigation of the dynamics of ion-molecule reactions. During the past decade, the combination of single-collision experiments in crossed ion and neutral beams with the velocity map ion imaging detection technique has enabled a wealth of studies on ion-molecule reactions. These methods, in combination with chemical dynamics simulations, have uncovered new and unexpected reaction mechanisms, such as the roundabout mechanism and the subtle influence of the leaving group in anion-molecule nucleophilic substitution reactions. For this important class of reactions, as well as for many fundamental cation-molecule reactions, the information obtained with crossed-beam imaging is discussed. The first steps toward understanding micro-solvation of ion-molecule reaction dynamics are presented. We conclude with the presentation of several interesting directions for future research.

  1. Bipodal surface organometallic complexes with surface N-donor ligands and application to the catalytic cleavage of C-H and C-C bonds in n -Butane

    KAUST Repository

    Bendjeriou-Sedjerari, Anissa

    2013-11-27

    We present a new generation of "true vicinal" functions well-distributed on the inner surface of SBA15: [(Sî - Si-NH 2)(≡Si-OH)] (1) and [(≡Si-NH2)2] (2). From these amine-modified SBA15s, two new well-defined surface organometallic species [(≡Si-NH-)(≡Si-O-)]Zr(CH2tBu) 2 (3) and [(≡Si-NH-)2]Zr(CH2tBu) 2 (4) have been obtained by reaction with Zr(CH2tBu) 4. The surfaces were characterized with 2D multiple-quantum 1H-1H NMR and infrared spectroscopies. Energy-filtered transmission electron microscopy (EFTEM), mass balance, and elemental analysis unambiguously proved that Zr(CH2tBu)4 reacts with these vicinal amine-modified surfaces to give mainly bipodal bis(neopentyl)zirconium complexes (3) and (4), uniformly distributed in the channels of SBA15. (3) and (4) react with hydrogen to give the homologous hydrides (5) and (6). Hydrogenolysis of n-butane catalyzed by these hydrides was carried out at low temperature (100 C) and low pressure (1 atm). While (6) exhibits a bis(silylamido)zirconium bishydride, [(≡Si-NH-)2]Zr(H) 2 (6a) (60%), and a bis(silylamido)silyloxozirconium monohydride, [(≡Si-NH-)2(≡Si-O-)]ZrH (6b) (40%), (5) displays a new surface organometallic complex characterized by an 1H NMR signal at 14.46 ppm. The latter is assigned to a (silylimido)(silyloxo)zirconium monohydride, [(≡Si-Nî)(≡Si-O-)]ZrH (5b) (30%), coexistent with a (silylamido)(silyloxo)zirconium bishydride, [(≡Si-NH-)(≡Si-O-)] Zr(H)2 (5a) (45%), and a silylamidobis(silyloxo)zirconium monohydride, [(≡Si-NH-)(≡Si-O-)2]ZrH (5c) (25%). Surprisingly, nitrogen surface ligands possess catalytic properties already encountered with silicon oxide surfaces, but interestingly, catalyst (5) with chelating [N,O] shows better activity than (6) with chelating [N,N]. © 2013 American Chemical Society.

  2. Chiral Dawson-Type Hybrid Polyoxometalate Catalyzes Enantioselective Diels-Alder Reactions.

    Science.gov (United States)

    Xuan, Wen-Jing; Botuha, Candice; Hasenknopf, Bernold; Thorimbert, Serge

    2015-11-09

    Can achiral organocatalysts linked to chiral polyanionic metal oxide clusters provide good selectivity in enantioselective C-C bond formations? The answer to this question is investigated by developing a new active hybrid polyoxometalate-based catalyst for asymmetric Diels-Alder reaction. Chirality transfer from the chiral anionic polyoxometalate to the covalently linked achiral imidazolidinone allows Diels-Alder cycloaddition products to be obtained with good yields and high enantioselectivities when using cyclopentadiene and acrylaldehydes as partners. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. A single transition state serves two mechanisms: an ab initio classical trajectory study of the electron transfer and substitution mechanisms in reactions of ketyl radical anions with alkyl halides.

    Science.gov (United States)

    Bakken, V; Danovich, D; Shaik, S; Schlegel, H B

    2001-01-10

    Molecular dynamics has been used to investigate the reaction of a series of ketyl anion radicals and alkyl halides, CH2O(*)(-) + CH3X (X = F, Cl, Br) and NCCHO(*)(-) + CH3Cl. In addition to a floppy outer-sphere transition state which leads directly to ET products, there is a strongly bound transition state that yields both electron transfer (ET) and C-alkylated (SUB(C)) products. This common transition state has significant C-- C bonding and gives ET and SUB(C) products via a bifurcation on a single potential energy surface. Branching ratios have been estimated from ab initio classical trajectory calculations. The SUB(C) products are favored for transition states with short C--C bonds and ET for long C--C bonds. ET reactivity can be observed even at short distances of r(C)(-)(C) = ca. 2.4 A as in the transition state for the reaction NCCHO(*)(-) + CH3Cl. Therefore, the ET/SUB(C) reactivity is entangled over a significant range of the C--C distance. The mechanistic significance of the molecular dynamics study is discussed.

  4. Preaggregation reactions of platelets.

    Science.gov (United States)

    Gear, A R

    1981-09-01

    Whether platelet volume increases during the morphological changes preceding aggregation has been investigated. Previous research is controversial; resistive-counting techniques reveal an increase, centrifugal methods do not. Platelets were sized with a computerized, resistive-particle counter before and after incubation with adenosine diphosphate (ADP). Resistive volume increased by 14% (p less than 0.001) in the absence of EDTA, and only 7% in its presence (ADP, 10 micro M). EDTA inhibited platelet volume changes, whether these were shrinking induced by warming or swelling by ADP. Handling of platelets, such as during centrifugation, also caused particle swelling. Particle density decreased after ADP exposure, without release of serotonin, suggesting uptake of water. Platelet shape was experimentally manipulated to test the hypothesis that resistive volume changes stem from artifacts of particle shape. Scanning electron microscopy confirmed that colchicine, chlorpromazine, and a temperature cycle of 0 degrees to 37 degrees all caused extensive alteration from the disc shape. Subsequent exposure to ADP increased resistive volume, and in the case of chlorpromazine, no long pseudopodia were extruded. It is concluded that preaggregation reactions of platelets can be associated with an increase in particle volume, and that earlier research based on centrifugation and the presence of ETA failed to reveal the increase because of inhibitory and apparent swelling effects.

  5. Adverse Reactions to Biologic Therapy.

    Science.gov (United States)

    Patel, Sheenal V; Khan, David A

    2017-05-01

    Biologic therapies are emerging as a significant therapeutic option for many with debilitating inflammatory and autoimmune conditions. As expansion in the number of FDA-approved agents continue to be seen, more unanticipated adverse reactions are likely to occur. Currently, the diagnostic tools, including skin testing and in vitro testing, to evaluate for immediate hypersensitivity reactions are insufficient. In this review, management strategies for common acute infusion reactions, injection site reactions, and immediate reactions suggestive of IgE-mediated mechanisms are discussed. Desensitization can be considered for reactions suggestive of IgE-mediated mechanisms, but allergists/immunologists should be involved in managing these patients. Copyright © 2017 Elsevier Inc. All rights reserved.

  6. The Progression of Sequential Reactions

    Directory of Open Access Journals (Sweden)

    Jack McGeachy

    2010-01-01

    Full Text Available Sequential reactions consist of linked reactions in which the product of the first reaction becomes the substrate of a second reaction. Sequential reactions occur in industrially important processes, such as the chlorination of methane. A generalized series of three sequential reactions was analyzed in order to determine the times at which each chemical species reaches its maximum. To determine the concentration of each species as a function of time, the differential rate laws for each species were solved. The solution of each gave the concentration curve of the chemical species. The concentration curves of species A1 and A2 possessed discreet maxima, which were determined through slope-analysis. The concentration curve of the final product, A3, did not possess a discreet maximum, but rather approached a finite limit.

  7. The Paterno-Buchi reaction

    DEFF Research Database (Denmark)

    Brogaard, Rasmus Yding; Schalk, Oliver; Boguslavskiy, Andrey E.

    2012-01-01

    The Paternò-Büchi (PB) reaction between an excited carbonyl compound and an alkene has been widely studied, but so far little is known about the excited-state dynamics of the reaction. In this investigation, we used a compound in which a formyl and a vinyl group are attached to a [2.......2]paracyclophane in order to obtain a model system in pre-reactive conformation for the PB reaction. We studied the excited-state dynamics of the isolated molecule in a molecular beam using femtosecond time-resolved photoelectron spectroscopy and ab initio calculations. The results show that inter-system crossing...... within two picoseconds competes efficiently with the reaction in the singlet manifold. Thus, the PB reaction in this model system takes place in the triplet state on a time scale of nanoseconds. This result stresses the importance of triplet states in the excited-state pathway of the PB reaction...

  8. Nuclear astrophysics from direct reactions

    Energy Technology Data Exchange (ETDEWEB)

    Bertulani, C. [Department of Physics, Texas A and M University, Commerce, TX 75429 (United States)]. e-mail: carlos_bertulani@tamu-commerce.edu

    2008-12-15

    Accurate nuclear reaction rates are needed for primordial nucleosynthesis and hydrostatic burning in stars. The relevant reactions are extremely difficult to measure directly in the laboratory at the small astrophysical energies. In recent years direct reactions have been developed and applied to extract low-energy astrophysical S-factors. These methods require a combination of new experimental techniques and theoretical efforts, which are the subject of this presentation. (Author)

  9. Stochastic Modeling Of Biochemical Reactions

    Science.gov (United States)

    2006-11-01

    STOCHASTIC MODELING OF BIOCHEMICAL REACTIONS Abhyudai Singh and João Pedro Hespanha* Department of Electrical and Computer Engineering University of...procedure for con- structing approximate stochastic models for chemical reactions used for modeling biochemical processes such as gene regulatory networks... biochemical reactions , the modeling tools developed in this paper can be applied to a very general class of stochastic systems, in particular

  10. [Situational reactions in suicidologic practice].

    Science.gov (United States)

    Ambrumova, A G; Vrono, E M

    1985-01-01

    The paper is devoted to the description of suicidal manifestations in mentally normal adolescents among typical behavioural disorders characteristic of situational reactions of this age. Three types of suicido-dangerous situational responses of adolescents were specified with regard to their age and auto-and heteaggressiveness ratio: reaction of deprivation, explosive reaction and reaction of auto-elimination. Suicidogenic conflicts were analyzed and spheres of age-specific suicidal conflicts were defined. It is advisable that outpatient management of mentally normal adolescents with a history of a suicidal attempt be conducted in a special room of presentive suicidological service.

  11. Dynamic Reaction Figures: An Integrative Vehicle for Understanding Chemical Reactions

    Science.gov (United States)

    Schultz, Emeric

    2008-01-01

    A highly flexible learning tool, referred to as a dynamic reaction figure, is described. Application of these figures can (i) yield the correct chemical equation by simply following a set of menu driven directions; (ii) present the underlying "mechanism" in chemical reactions; and (iii) help to solve quantitative problems in a number of different…

  12. Dinuclear Tetrapyrazolyl Palladium Complexes Exhibiting Facile Tandem Transfer Hydrogenation/Suzuki Coupling Reaction of Fluoroarylketone

    KAUST Repository

    Dehury, Niranjan

    2016-07-18

    Herein, we report an unprecedented example of dinuclear pyrazolyl-based Pd complexes exhibiting facile tandem catalysis for fluoroarylketone: Tetrapyrazolyl di-palladium complexes with varying Pd-Pd distances efficiently catalyze the tandem reaction involving transfer hydrogenation of fluoroarylketone to the corresponding alcohol and Suzuki-Miyaura cross coupling reaction of the resulting fluoroarylalcohol under moderate reaction conditions, to biaryl alcohol. The complex with the shortest Pd-Pd distance exhibits the highest tandem activity among its di-metallic analogues, and exceeds in terms of activity and selectivity the analogous mononuclear compound. The kinetics of the reaction indicates clearly that reductive transformation of haloarylketone into haloaryalcohol is the rate determining step in the tandem reaction. Interestingly while fluoroarylketone undergoes the multistep tandem catalysis, the chloro- and bromo-arylketones undergo only a single step C-C coupling reaction resulting in biarylketone as the final product. Unlike the pyrazole based Pd compounds, the precursor PdCl2 and the phosphine based relevant complexes (PPh3)2PdCl2 and (PPh3)4Pd are found to be unable to exhibit the tandem catalysis.

  13. Progress in microscopic direct reaction modeling of nucleon induced reactions

    Energy Technology Data Exchange (ETDEWEB)

    Dupuis, M.; Bauge, E.; Hilaire, S.; Lechaftois, F.; Peru, S.; Pillet, N.; Robin, C. [CEA, DAM, DIF, Arpajon (France)

    2015-12-15

    A microscopic nuclear reaction model is applied to neutron elastic and direct inelastic scatterings, and pre-equilibrium reaction. The JLM folding model is used with nuclear structure information calculated within the quasi-particle random phase approximation implemented with the Gogny D1S interaction. The folding model for direct inelastic scattering is extended to include rearrangement corrections stemming from both isoscalar and isovector density variations occurring during a transition. The quality of the predicted (n,n), (n,n{sup '}), (n,xn) and (n,n{sup '}γ) cross sections, as well as the generality of the present microscopic approach, shows that it is a powerful tool that can help improving nuclear reactions data quality. Short- and long-term perspectives are drawn to extend the present approach to more systems, to include missing reactions mechanisms, and to consistently treat both structure and reaction problems. (orig.)

  14. Formation of nitrogen-containing polycyclic cations by gas-phase and intracluster reactions of acetylene with the pyridinium and pyrimidinium ions.

    Science.gov (United States)

    Soliman, Abdel-Rahman; Hamid, Ahmed M; Attah, Isaac; Momoh, Paul; El-Shall, M Samy

    2013-01-09

    Here, we present evidence from laboratory experiments for the formation of nitrogen-containing complex organic ions by sequential reactions of acetylene with the pyridinium and pyrimidinium ions in the gas phase and within ionized pyridine-acetylene binary clusters. Additions of five and two acetylene molecules onto the pyridinium and pyrimidinium ions, respectively, at room temperature are observed. Second-order rate coefficients of the overall reaction of acetylene with the pyridinium and pyrimidinium ions are measured as 9.0 × 10(-11) and 1.4 × 10(-9) cm(3) s(-1), respectively, indicating reaction efficiencies of about 6% and 100%, respectively, at room temperature. At high temperatures, only two acetylene molecules are added to the pyridinium and pyrimidinium ions, suggesting covalent bond formation. A combination of ion dissociation and ion mobility experiments with DFT calculations reveals that the addition of acetylene into the pyridinium ion occurs through the N-atom of the pyridinium ion. The relatively high reaction efficiency is consistent with the absence of a barrier in the exothermic N-C bond forming reaction leading to the formation of the C(7)H(7)N(•+) covalent adduct. An exothermic addition/H-elimination reaction of acetylene with the C(7)H(7)N(•+) adduct is observed leading to the formation of a bicyclic quinolizinium cation (C(9)H(8)N(+)). Similar chemistry is observed in the sequential reactions of acetylene with the pyrimidinium ion. The second acetylene addition onto the pyrimidinium ion involves an exclusive addition/H-elimination reaction at room temperature leading to the formation of a bicyclic pyrimidinium cation (C(8)H(7)N(2)(+)). The high reactivity of the pyridinium and pyrimidinium ions toward acetylene is in sharp contrast to the very low reactivity of the benzene cation, which has a reaction efficiency of 10(-4)-10(-5). This indicates that the presence of a nitrogen atom within the aromatic ring enhances the ring growth

  15. Adverse Reactions to Hallucinogenic Drugs.

    Science.gov (United States)

    Meyer, Roger E. , Ed.

    This reports a conference of psychologists, psychiatrists, geneticists and others concerned with the biological and psychological effects of lysergic acid diethylamide and other hallucinogenic drugs. Clinical data are presented on adverse drug reactions. The difficulty of determining the causes of adverse reactions is discussed, as are different…

  16. Pharmacogenetics of hypersensitivity drug reactions.

    Science.gov (United States)

    Negrini, Simone; Becquemont, Laurent

    2017-04-01

    Adverse drug reactions are a significant cause of morbidity and mortality and represent a major burden on the healthcare system. Some of those reactions are immunologically mediated (hypersensitivity reactions) and can be clinically subdivided into two categories: immediate reactions (IgE-related) and delayed reactions (T-cell-mediated). Delayed hypersensitivity reactions include both systemic syndromes and organ-specific toxicities and can be triggered by a wide range of chemically diverse drugs. Recent studies have demonstrated a strong genetic association between human leukocyte antigen alleles and susceptibility to delayed drug hypersensitivity. Most notable examples include human leukocyte antigen (HLA)-B*57:01 allele and abacavir hypersensitivity syndrome or HLA-B*15:02 and HLA-B*58:01 alleles related to severe cutaneous reactions induced by carbamazepine and allopurinol, respectively. This review aims to explore our current understanding in the field of pharmacogenomics of HLA-associated drug hypersensitivities and its translation into clinical practice for predicting adverse drug reactions. Copyright © 2017 Société française de pharmacologie et de thérapeutique. Published by Elsevier Masson SAS. All rights reserved.

  17. Engineering reactors for catalytic reactions

    Indian Academy of Sciences (India)

    Extensive studies have been conducted to establish sound basis for design and engineering of reactors for practising such catalytic reactions and for realizing improvements in reactor performance. In this article, application of recent (and not so recent) developments in engineering reactors for catalytic reactions is ...

  18. Incomplete fusion reactions in Ho

    Indian Academy of Sciences (India)

    It is now generally recognized that several reaction mechanisms are operative in heavy- ion-induced reactions below 10 MeV/amu. Predominant among these are, complete fusion. (CF), deep-inelastic collision (DIC), and quasi-elastic collisions. As the projectile energy increases to 5–10 MeV/amu and above, it turns out that ...

  19. Free Radical Reactions in Food.

    Science.gov (United States)

    Taub, Irwin A.

    1984-01-01

    Discusses reactions of free radicals that determine the chemistry of many fresh, processed, and stored foods. Focuses on reactions involving ascorbic acid, myoglobin, and palmitate radicals as representative radicals derived from a vitamin, metallo-protein, and saturated lipid. Basic concepts related to free radical structure, formation, and…

  20. Dielectron Cross Section Measurements in Nucleus-Nucleus Reactions at 1.0{ital A} GeV

    Energy Technology Data Exchange (ETDEWEB)

    Porter, R.J.; Bossingham, R.; Gong, W.G.; Heilbronn, L.; Huang, H.Z.; Krebs, G.; Letessier-Selvon, A.; Matis, H.S.; Miller, J.; Naudet, C.; Roche, G.; Schroeder, L.S.; Seidl, P.; Wilson, W.K.; Yegneswaran, A. [Lawrence Berkeley National Laboratory, University of California, Berkeley, California 94720 (United States); Beedoe, S.; Carroll, J.; Huang, H.Z.; Igo, G. [University of California at Los Angeles, California 90095 (United States); Bougteb, M.; Manso, F.; Prunet, M.; Roche, G. [Universite Blaise Pascal/IN2P3, 63177 Aubiere Cedex (France); Christie, W.B.; Hallman, T.; Madansky, L.; Welsh, R.C. [The Johns Hopkins University, Baltimore, Maryland 21218 (United States); Kirk, P.; Wang, Z.F. [Louisiana State University, Baton Rouge, Louisiana 70803 (United States); Wilson, W.K. [Wayne State University, Detroit, Michigan 48201 (United States)

    1997-08-01

    We present measured dielectron production cross sections for Ca+Ca, C+C, He+Ca, and d+Ca reactions at 1.0 A GeV . Statistical uncertainties and systematic effects are smaller than in previous dilepton spectrometer (DLS) nucleus-nucleus data. For pair mass M{le}0.35 GeV/c{sup 2} we obtain (1) the Ca+Ca cross section is larger than the previous DLS measurement and current model results, (2) the mass spectra suggest large contributions from {pi}{sup 0} and {eta} Dalitz decays, and (3) d{sigma}/dM{proportional_to}A{sub P}A{sub T}. For M{gt}0.5 GeV/c{sup 2} the Ca+Ca to C+C cross section ratio is significantly larger than the ratio of A{sub P}A{sub T} values. {copyright} {ital 1997} {ital The American Physical Society}

  1. Alilação e crotilação catalítica e enantiosseletiva de aldeídos

    Directory of Open Access Journals (Sweden)

    Ângelo de Fátima

    2006-10-01

    Full Text Available The field of chiral catalysis has experienced explosive growth over the last two decades. By now, many of the classical reactions in organic synthesis can be carried out efficiently in asymmetric manner. As one of the fundamental and powerful C-C bond-forming reactions, enantioselective catalytic allylation (ECA and crotylation (ECC of aldehydes has attracted considerable attention. In this article, we present an overview about the importance of chiral Lewis acids and bases in catalytic enantioselective addition of allyl- and crotyl metals to aldehydes and the application of this methodology in the total synthesis of natural and non-natural products.

  2. Alilação e crotilação catalítica e enantiosseletiva de aldeídos

    Directory of Open Access Journals (Sweden)

    Fátima Ângelo de

    2006-01-01

    Full Text Available The field of chiral catalysis has experienced explosive growth over the last two decades. By now, many of the classical reactions in organic synthesis can be carried out efficiently in asymmetric manner. As one of the fundamental and powerful C-C bond-forming reactions, enantioselective catalytic allylation (ECA and crotylation (ECC of aldehydes has attracted considerable attention. In this article, we present an overview about the importance of chiral Lewis acids and bases in catalytic enantioselective addition of allyl- and crotyl metals to aldehydes and the application of this methodology in the total synthesis of natural and non-natural products.

  3. Refined transition-state models for proline-catalyzed asymmetric Michael reactions under basic and base-free conditions.

    Science.gov (United States)

    Sharma, Akhilesh K; Sunoj, Raghavan B

    2012-12-07

    The stereocontrolling transition state (TS) models for C-C bond formation relying on hydrogen bonding have generally been successful in proline-catalyzed aldol, Mannich, α-amination, and α-aminoxylation reactions. However, the suitability of the hydrogen-bonding model in protic and aprotic conditions as well as under basic and base-free conditions has not been well established for Michael reactions. Through a comprehensive density functional theory investigation, we herein analyze different TS models for the stereocontrolling C-C bond formation, both in the presence and absence of a base in an aprotic solvent (THF). A refined stereocontrolling TS for the Michael reaction between cyclohexanone and nitrostyrene is proposed. The new TS devoid of hydrogen bonding between the nitro group of nitrostyrene and carboxylic acid of proline, under base-free conditions, is found to be more preferred over the conventional hydrogen-bonding model besides being able to reproduce the experimentally observed stereochemical outcome. A DBU-bound TS is identified as more suitable for rationalizing the origin of asymmetric induction under basic reaction conditions. In both cases, the most preferred approach of nitrostyrene is identified as occurring from the face anti to the carboxylic acid of proline-enamine. The predicted enantio- and diastereoselectivities are in very good agreement with the experimental observations.

  4. Mechanical stimulated reaction of metal/polymer mixed powders; Kinzoku/kobunshi kongo funmatsu no kikaiteki reiki hanno

    Energy Technology Data Exchange (ETDEWEB)

    Tobita, M.; Sakakibara, A.; Takemoto, Y. [Okayama University, Okayama (Japan). Faculty of Engineering; Iwabu, H. [Kurare Co. Ltd., Osaka (Japan)

    1999-12-15

    Mechanical grinding (MG) with mechanically stimulated reaction was performed on metal/polymer mixed powders. The starting materials used in this study were the metals of Mg, Ti and Mg{sub 2}Ni powders, arid polymer of PTFE, PVC and PE powders. The MG process was investigated using XRD, IR, SEM and TEM. According to XRD results, magnesium fluoride (MgF{sub 2}, TiF{sub 2}) and chloride (MgCl{sub 2}) were detected from MG products of the Mg/PTFE, Ti/PTFE and Mg/PVC blending systems, respectively. Explosive reaction was found during MG of both Mg/PTFE and Ti/PTFE. It was also confirmed by XRD results that the production of MgF{sub 2} had already been formed just before the explosive reaction in Mg/PTFE system. It was found from IR analysis that C-C single bond in the polymers, not only both in PTFE and PVC but also in PE, changed to double bond C=C. Hydrogen produced due to decomposition of PE on blending Mg{sub 2}Ni/PE was absorbed into C-Mg{sub 2}Ni-H as amorphous solutes. These mechanically stimulated reaction was powerful method for decomposition of engineering plastics. (author)

  5. Limits for Stochastic Reaction Networks

    DEFF Research Database (Denmark)

    Cappelletti, Daniele

    Reaction systems have been introduced in the 70s to model biochemical systems. Nowadays their range of applications has increased and they are fruitfully used in dierent elds. The concept is simple: some chemical species react, the set of chemical reactions form a graph and a rate function...... of reactions. Let the rates of degradation of the intermediate species be functions of a parameter N that tends to innity. We consider a reduced system where the intermediate species have been eliminated, and nd conditions on the degradation rate of the intermediates such that the behaviour of the reduced...... is stated in the setting of multiscale reaction systems: the amounts of all the species and the rates of all the reactions of the original model can scale as powers of N. A similar result also holds for the deterministic case, as shown in Appendix IA. In Paper II, we focus on the stationary distributions...

  6. Reaction rates for reaction-diffusion kinetics on unstructured meshes

    Science.gov (United States)

    Hellander, Stefan; Petzold, Linda

    2017-02-01

    The reaction-diffusion master equation is a stochastic model often utilized in the study of biochemical reaction networks in living cells. It is applied when the spatial distribution of molecules is important to the dynamics of the system. A viable approach to resolve the complex geometry of cells accurately is to discretize space with an unstructured mesh. Diffusion is modeled as discrete jumps between nodes on the mesh, and the diffusion jump rates can be obtained through a discretization of the diffusion equation on the mesh. Reactions can occur when molecules occupy the same voxel. In this paper, we develop a method for computing accurate reaction rates between molecules occupying the same voxel in an unstructured mesh. For large voxels, these rates are known to be well approximated by the reaction rates derived by Collins and Kimball, but as the mesh is refined, no analytical expression for the rates exists. We reduce the problem of computing accurate reaction rates to a pure preprocessing step, depending only on the mesh and not on the model parameters, and we devise an efficient numerical scheme to estimate them to high accuracy. We show in several numerical examples that as we refine the mesh, the results obtained with the reaction-diffusion master equation approach those of a more fine-grained Smoluchowski particle-tracking model.

  7. Effective reaction rates for diffusion-limited reaction cycles.

    Science.gov (United States)

    Nałęcz-Jawecki, Paweł; Szymańska, Paulina; Kochańczyk, Marek; Miękisz, Jacek; Lipniacki, Tomasz

    2015-12-07

    Biological signals in cells are transmitted with the use of reaction cycles, such as the phosphorylation-dephosphorylation cycle, in which substrate is modified by antagonistic enzymes. An appreciable share of such reactions takes place in crowded environments of two-dimensional structures, such as plasma membrane or intracellular membranes, and is expected to be diffusion-controlled. In this work, starting from the microscopic bimolecular reaction rate constants and using estimates of the mean first-passage time for an enzyme-substrate encounter, we derive diffusion-dependent effective macroscopic reaction rate coefficients (EMRRC) for a generic reaction cycle. Each EMRRC was found to be half of the harmonic average of the microscopic rate constant (phosphorylation c or dephosphorylation d), and the effective (crowding-dependent) motility divided by a slowly decreasing logarithmic function of the sum of the enzyme concentrations. This implies that when c and d differ, the two EMRRCs scale differently with the motility, rendering the steady-state fraction of phosphorylated substrate molecules diffusion-dependent. Analytical predictions are verified using kinetic Monte Carlo simulations on the two-dimensional triangular lattice at the single-molecule resolution. It is demonstrated that the proposed formulas estimate the steady-state concentrations and effective reaction rates for different sets of microscopic reaction rates and concentrations of reactants, including a non-trivial example where with increasing diffusivity the fraction of phosphorylated substrate molecules changes from 10% to 90%.

  8. Reaction rates for reaction-diffusion kinetics on unstructured meshes.

    Science.gov (United States)

    Hellander, Stefan; Petzold, Linda

    2017-02-14

    The reaction-diffusion master equation is a stochastic model often utilized in the study of biochemical reaction networks in living cells. It is applied when the spatial distribution of molecules is important to the dynamics of the system. A viable approach to resolve the complex geometry of cells accurately is to discretize space with an unstructured mesh. Diffusion is modeled as discrete jumps between nodes on the mesh, and the diffusion jump rates can be obtained through a discretization of the diffusion equation on the mesh. Reactions can occur when molecules occupy the same voxel. In this paper, we develop a method for computing accurate reaction rates between molecules occupying the same voxel in an unstructured mesh. For large voxels, these rates are known to be well approximated by the reaction rates derived by Collins and Kimball, but as the mesh is refined, no analytical expression for the rates exists. We reduce the problem of computing accurate reaction rates to a pure preprocessing step, depending only on the mesh and not on the model parameters, and we devise an efficient numerical scheme to estimate them to high accuracy. We show in several numerical examples that as we refine the mesh, the results obtained with the reaction-diffusion master equation approach those of a more fine-grained Smoluchowski particle-tracking model.

  9. Insights into the Diels-Alder Reaction between 3-Vinylindoles and Methyleneindolinone without and with the Assistance of Hydrogen-Bonding Catalyst Bisthiourea: Mechanism, Origin of Stereoselectivity, and Role of Catalyst.

    Science.gov (United States)

    Yan, Chao-Xian; Yang, Fan; Yang, Xing; Zhou, Da-Gang; Zhou, Pan-Pan

    2017-03-17

    The Diels-Alder reaction between 3-vinylindoles and methyleneindolinone can proceed both under catalyst-free conditions and with bisthiourea as the catalyst. The reaction with bisthiourea is much faster and results in higher stereoselectivity of the product. The reaction mechanism, origin of stereoselectivity, and role of the catalyst were elaborated based on quantum mechanical calculations and theoretical methods of reactivity indices, NCI, QTAIM, and distortion/interaction models. In the uncatalyzed reaction, the two C-C bonds that are formed undergo conversion from noncovalent to covalent bonding via a concerted asynchronous mechanism. The weak intermolecular interactions formed in the transition state play important roles. The difference between the interaction and distortion energies is responsible for the stereoselectivity. In the catalyzed reaction, bisthiourea induces both the diene and dienophile to approach it via weak intermolecular interactions, which greatly lowers the energy barrier of the reaction and leads to the product with excellent stereoselectivity. The possible pathways of this reaction were explored, which suggested that the formation of the two C-C bonds goes through either a stepwise or concerted asynchronous mechanism. These results detail the reaction mechanism and shed light on both the significant role of the bisthiourea catalyst and the origin of stereoselectivity for this type of Diels-Alder reaction and related ones.

  10. Effect of locally delivered tetracycline hydrochloride as an adjunct to scaling and root planing on Hba1c, C-reactive protein, and lipid profile in type 2 diabetes: A clinico-biochemical study

    Directory of Open Access Journals (Sweden)

    Vidya Dodwad

    2012-01-01

    Full Text Available Aim: The aim was to assess the levels of HbA1c, C-reactive protein, and lipid profile in patients with type 2 diabetes mellitus by treating the pockets using collagen impregnated sustained release resorbable tetracycline fiber (periodontal plus AB fiber following scaling and root planing (SRP. Materials and Methods: A total of 40 patients with type 2 diabetes mellitus were randomly distributed into two groups receiving either SRP and tetracycline fiber or SRP alone. Patients were evaluated clinically with gingival index, plaque index, probing depth, and relative attachment level, and bio-chemically with HbA1c, C Reactive Protein, and lipid profile at baseline, 1 month, and 3 months. Results: Significant reduction in all the clinical parameters was seen in the tetracycline group compared to the control group. Bio-chemical analysis also revealed similar results except for cholesterol and High density lipoprotein who did not show any significant reduction. Conclusion: Locally delivered tetracycline as a better treatment modality compared to SRP alone.

  11. A theoretical study on the aromaticity of benzene and related derivatives incorporating a C-C C-C fragment

    Czech Academy of Sciences Publication Activity Database

    Sanchez-Sanz, Goar; Trujillo, Cristina; Rozas, I.; Elguero, J.

    2013-01-01

    Roč. 69, č. 35 (2013), s. 7333-7344 ISSN 0040-4020 Institutional support: RVO:61388963 Keywords : dehydroannulenes * aromaticity * NICS * chemical shifts * benzene Subject RIV: CC - Organic Chemistry Impact factor: 2.817, year: 2013

  12. Metal-Ion- and Hydrogen-Bond-Mediated Interstellar Prebiotic Chemistry: The First Step in the Formose Reaction.

    Science.gov (United States)

    Thripati, Sorakayala; Ramabhadran, Raghunath O

    2017-11-16

    The formose reaction, which offers a feasible chemical pathway for the prebiotic synthesis of sugars, is a well-studied reaction for over two hundred and 50 years. Yet huge knowledge gaps exist even in the very first step of the formose reaction. In this work, we provide a new and otherwise unintuitive reaction pathway for the gas-phase conversion of formaldehyde to glycolaldehyde (the first step in the formose reaction) occurring in the interstellar medium (ISM). Employing electronic structure calculations (CCSD(T) and DFT methods), we exhaustively probe the role of various metal ions and small molecules detected in the ISM to propose a new mechanism wherein metal-oxygen interactions and hydrogen bonds cooperatively facilitate an otherwise implausible chemical reaction. The reactions involving Mg2+ are throughout found to be barrierless, and those featuring Al+ ions are noted to only have a small barrier. The proton affinities of the small molecules, metal-oxygen interactions, and the extent of C-C-bond formation are found to be the significant factors that influence the barrier heights. The mechanism is also shown to be consistent with well-known experimental details in the terrestrial formose reaction (which could, however, proceed through a different mechanism). Future experimental and theoretical scope arising out of this paper are subsequently discussed.

  13. Automatic determination of reaction mappings and reaction center information. 2. Validation on a biochemical reaction database.

    Science.gov (United States)

    Apostolakis, Joannis; Sacher, Oliver; Körner, Robert; Gasteiger, Johann

    2008-06-01

    The correct identification of the reacting bonds and atoms is a prerequisite for the analysis of the reaction mechanism. We have recently developed a method based on the Imaginary Transition State Energy Minimization approach for automatically determining the reaction center information and the atom-atom mapping numbers. We test here the accuracy of this ITSE approach by comparing the predictions of the method against more than 1500 manually annotated reactions from BioPath, a comprehensive database of biochemical reactions. The results show high agreement between manually annotated mappings and computational predictions (98.4%), with significant discrepancies in only 24 cases out of 1542 (1.6%). This result validates both the computational prediction and the database, at the same time, as the results of the former agree with expert knowledge and the latter appears largely self-consistent, and consistent with a simple principle. In 10 of the discrepant cases, simple chemical arguments or independent literature studies support the predicted reaction center. In five reaction instances the differences in the automatically and manually annotated mappings are described in detail. Finally, in approximately 200 cases the algorithm finds alternate reaction centers, which need to be studied on a case by case basis, as the exact choice of the alternative may depend on the enzyme catalyzing the reaction.

  14. Cyanide reaction with ninhydrin: elucidation of reaction and interference mechanisms.

    Science.gov (United States)

    Drochioiu, Gabi; Mangalagiu, Ionel; Avram, Ecaterina; Popa, Karin; Dirtu, Alin Constantin; Druta, Ioan

    2004-10-01

    A new sensitive spectrophotometric method has recently been developed for the trace determination of cyanide with ninhydrin. Cyanide ion was supposed to act as a specific base catalyst. Nevertheless, this paper demonstrates that the reported assay is based on a novel reaction of cyanide with 2,2-dihydroxy-1,3-indanedione, which affords purple or blue colored salts of 2-cyano-1,2,3-trihydroxy-2H indene. Hydrindantin is merely an intermediary of the reaction. The formation of a stable and isolable ninhydrin-cyanide compound has been confirmed by its preparation in crystalline form. Also, it is thoroughly characterized by elemental as well as MS, IR, UV/VIS and 1H NMR analyses. The Ruhemann's sequence of reactions of cyanide with ninhydrin has been reconsidered and an adequate mechanism of the reaction is proposed. As a consequence, the interference of oxidizers as well as copper, silver and mercury ions with the cyanide determination has been elucidated.

  15. Rapid biocatalytic polytransesterification: reaction kinetics in an exothermic reaction

    Science.gov (United States)

    Chaudhary; Beckman; Russell

    1998-08-20

    Biocatalytic polytransesterification at high concentrations of monomers proceeds rapidly and is accompanied by an increase in the temperature of the reaction mixture due to liberation of heat of reaction during the initial phase. We have used principles of reaction calorimetry to monitor the kinetics of polymerization during this initial phase, thus relating the temperature to the extent of polymerization. Rate of polymerization increases with the concentration of monomers. This is also reflected by the increase in the temperature of the reaction mixture. Using time-temperature-conversion contours, a differential method of kinetic analysis was used to calculate the energy of activation ( approximately 15.1 Kcal/mol). Copyright 1998 John Wiley & Sons, Inc.

  16. Immunopharmacology and adverse drug reactions.

    Science.gov (United States)

    Rieder, M J

    1993-04-01

    Adverse drug reactions are common and troublesome complications of contemporary pharmacotherapy. Adverse drug reactions are frequently, and often incorrectly, referred to as "allergy". Although there are multiple mechanisms for adverse drug reactions, adverse drug reactions mediated by the immune system account for a disproportionate number of fatal and serious adverse reactions, and constitute a major clinical problem for patients and physicians. The immune system has evolved in multicellular organisms as a defence against infection. Interactions between drugs and the immune system occur as inadvertent consequences of the protective function of the immune system, with drug molecules or drug-carrier haptens being recognized as "non-self" by the immune system. The classical mechanisms for drug hypersensitivity described by Gell and Coombs (Types 1 to 4) include IgE-mediated, cytotoxic, immune complex-mediated and delayed mechanism. These mechanisms provide elegant models for drug-immune interactions that can provide mechanistic explanations for events such as urticaria associated with penicillins. However, these mechanisms do not account for many of the immunologically mediated adverse reactions commonly encountered in clinical practice. Over the last two decades, there has been an increasing awareness of the importance of reactive drug metabolites and drug-protein interactions in the initiation of immunologic events mediating adverse drug reactions. Reactive drug metabolites may produce direct and profound effects on various functions of the immune system. Although some adverse reactions mediated by the immune system occur with equal frequency among adults and children, some of these reactions appear to be markedly more common among children than adults.(ABSTRACT TRUNCATED AT 250 WORDS)

  17. Explicit formulas for reaction probability in reaction-diffusion experiments

    OpenAIRE

    Feres, Renato; Wallace, Matthew; Stern, Ari; Yablonsky, Gregory

    2015-01-01

    A computational procedure is developed for determining the conversion probability for reaction-diffusion systems in which a first-order catalytic reaction is performed over active particles. We apply this general method to systems on metric graphs, which may be viewed as 1-dimensional approximations of 3-dimensional systems, and obtain explicit formulas for conversion. We then study numerically a class of 3-dimensional systems and test how accurately they are described by model formulas obtai...

  18. Direct reactions with exotic nuclei

    Directory of Open Access Journals (Sweden)

    Obertelli A.

    2014-03-01

    Full Text Available Direct reactions have been a unique tool to address the nuclear many-body problem from the experimental side. They are now routinely used in inverse kinematics with radioactive ion beams (RIB. However, weakly bound nuclei have recently raised questions on the applicability of reaction formalisms benchmarked on stable nuclei to the study of single-particle properties and correlations in these unstable systems. The study of the most exotic species produced at low intensity have triggered new technical developments to increase the sensitivity of the setup, with a focused attention to direct reactions such as transfer at low incident energy or knockout at intermediate energies.

  19. Palladium-catalyzed coupling reactions

    CERN Document Server

    Molnár, Árpád

    2013-01-01

    This handbook and ready reference brings together all significant issues of practical importance for interested readers in one single volume. While covering homogeneous and heterogeneous catalysis, the text is unique in focusing on such important aspects as using different reaction media, microwave techniques or catalyst recycling. It also provides a comprehensive treatment of modern-day coupling reactions and emphasizes those topics that show potential for future development, such as continuous flow systems, water as a reaction medium, and catalyst immobilization, among others. With i

  20. Cosmologia e Representa\\c{c}\\~ao

    CERN Document Server

    Ribeiro, Marcelo Byrro

    2013-01-01

    This work presents a brief and non-technical description of the main results and concepts of the modern scientific cosmology, viewing it from an epistemological perspective which allows a dialog with other modes of thinking like e.g. history, philosophy, sociology and religion. This epistemological viewpoint is based on the philosophical theses advanced by Ludwig Boltzmann (1844-1906) which states that scientific theories are nothing more than representations, or images, of nature (arXiv:physics/0701308v1). By being representations one cannot know how nature really is because the intrinsic and indispensable properties that characterize nature are unreachable by science. In other words, the true essences that constitute nature are unknowable. Therefore, all answers proposed by science are partial, simplified and replaceable. Another way of putting forward this viewpoint is to state that all scientific truths are provisional, a result which naturally leads to the conclusion that the same set of phenomena, or sc...

  1. Chemical reactions of organic molecules adsorbed on ice 1. Chlorine addition to propene

    Energy Technology Data Exchange (ETDEWEB)

    Graham, J.D.; Roberts, J.T.

    2000-02-10

    Chemical reactions that are promoted or catalyzed by the surface or near surface regions of ice particles in type II polar stratospheric clouds (PSCs) have been shown to play a role in the annual sequence of events that ultimately opens the Antarctic ozone hole. A new ice-catalyzed chemical reaction is reported, namely the addition of Cl{sub 2} to the C--C double bond of propene (C{sub 3}H{sub 6}) to form 1,2-dichloropropane. The reaction, which was investigated with temperature-programmed desorption mass spectrometry (TPD), was carried out on ultrathin (10--100 monolayer thick) films of ice deposited on single-crystal metal substrates under ultrahigh vacuum. The Cl{sub 2}-addition product was identified as 1,2-dichloropropane on the basis of its fragmentation pattern in the mass spectrometer. 1,2-Dichloropropane formation occurs below 150 K, and no chlorohydrin (e.g., 2-chloro-1-propanol) evolution is ever observed. The reaction of coadsorbed propene and chlorine is very different from what occurs in aqueous solutions, where chlorohydrin formation occurs readily. Possible mechanisms of the ice-surface-catalyzed reaction are discussed.

  2. Light and dark reactions of the uptake hydrogenase in anabaena 7120.

    Science.gov (United States)

    Houchins, J P; Burris, R H

    1981-09-01

    Reactions of the uptake hydrogenase from Anabaena 7120 (A.T.C.C. 27893, Nostoc muscorum) were examined in whole filaments, isolated heterocysts, and membrane particles. Whole filaments or isolated heterocysts that contained nitrogenase consumed H(2) in the presence of C(2)H(2) or N(2) in a light-dependent reaction. If nitrogenase was inactivated by O(2) shock, filaments catalyzed H(2) uptake to an unidentified endogenous acceptor in the light. Addition of NO(3) (-) or NO(2) (-) enhanced these rates. Isolated heterocysts consumed H(2) in the dark in the presence of electron acceptors with positive midpoint potentials, and these reactions were not enhanced by light. With acceptors of negative midpoint potential, significant light enhancement of H(2) uptake occurred. Maximum rates of light-dependent uptake were approximately 25% of the maximum dark rates observed. Membrane particles prepared from isolated heterocysts showed similar specificity for electron acceptors. These particles catalyzed a cyanide-sensitive oxyhydrogen reaction that was inactivated by O(2) at O(2) concentrations above 2%. Light-dependent H(2) uptake to low potential acceptors by these particles was inhibited by dibromothymoquinone but was insensitive to cyanide. In the presence of O(2), light-dependent H(2) uptake occurred simultaneously with the oxyhydrogen reaction. The pH optima for both types of H(2) uptake were near 7.0. These results further clarify the role of uptake hydrogenase in donating electrons to both the photosynthetic and respiratory electron transport chains of Anabaena.

  3. Educational Stress: Sources, Reactions, Preventions.

    Science.gov (United States)

    Kaiser, Jeffrey S.; Polczynski, James J.

    1982-01-01

    Effects of stress on educators and efforts to understand and cope with stress are discussed. Sources of stress, common reactions to stress, the effects of stress on educator performance, and suggested preventive methods are examined. (JN)

  4. Reactions with light exotic nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Lichtenthäler, R.; Faria, P.N. de; Pires, K.C.C.; Lepine-Szily, A.; Guimaraes, V.; Mendes Junior, D.R.; Assuncao, M.; Barioni, A.; Morcelle, V.; Morais, M.C.; Camargo Junior, O.; Alcantara Nuñez, J. [Universidade de Sao Paulo (USP), Sao Paulo, SP (Brazil). Instituto de Fisica; Moro, A.M. [Departamento de FAMN, Universidad de Sevilla, Sevilla (Spain); Arazi, A. [Laboratorio Tandar, Departamento de Fisica, Comision Nacional de Energia Atomica (CNEA), Buenos Aires (Argentina); Rodriguez-Gallardo, M. [Instituto de Estructura de la Materia, CSIC, Madrid (Spain)

    2014-07-01

    Experimental cross sections for the {sup 6}He+{sup 120}Sn are analysed. Elastic scattering angular distributions and alpha particle production cross sections have been measured and are compared with the total reaction cross sections. (author)

  5. Fluctuations in catalytic surface reactions

    CERN Document Server

    Imbihl, R

    2003-01-01

    The internal reaction-induced fluctuations which occur in catalytic CO oxidation on a Pt field emitter tip have been studied using field electron microscopy (FEM) as a spatially resolving method. The structurally heterogeneous Pt tip consists of facets of different orientations with nanoscale dimensions. The FEM resolution of roughly 2 nm corresponds to a few hundred reacting adsorbed particles whose variations in the density are imaged as brightness fluctuations. In the bistable range of the reaction one finds fluctuation-induced transitions between the two stable branches of the reaction kinetics. The fluctuations exhibit a behaviour similar to that of an equilibrium phase transition, i.e. the amplitude diverges upon approaching the bifurcation point terminating the bistable range of the reaction. Simulations with a hybrid Monte Carlo/mean-field model reproduce the experimental observations. Fluctuations on different facets are typically uncorrelated but within a single facet a high degree of spatial cohere...

  6. Transfer reactions in nuclear astrophysics

    Science.gov (United States)

    Bardayan, D. W.

    2016-08-01

    To a high degree many aspects of the large-scale behavior of objects in the Universe are governed by the underlying nuclear physics. In fact the shell structure of nuclear physics is directly imprinted into the chemical abundances of the elements. The tranquility of the night sky is a direct result of the relatively slow rate of nuclear reactions that control and determines a star’s fate. Understanding the nuclear structure and reaction rates between nuclei is vital to understanding our Universe. Nuclear-transfer reactions make accessible a wealth of knowledge from which we can extract much of the required nuclear physics information. A review of transfer reactions for nuclear astrophysics is presented with an emphasis on the experimental challenges and opportunities for future development.

  7. Analysis of kinetic reaction mechanisms

    CERN Document Server

    Turányi, Tamás

    2014-01-01

    Chemical processes in many fields of science and technology, including combustion, atmospheric chemistry, environmental modelling, process engineering, and systems biology, can be described by detailed reaction mechanisms consisting of numerous reaction steps. This book describes methods for the analysis of reaction mechanisms that are applicable in all these fields. Topics addressed include: how sensitivity and uncertainty analyses allow the calculation of the overall uncertainty of simulation results and the identification of the most important input parameters, the ways in which mechanisms can be reduced without losing important kinetic and dynamic detail, and the application of reduced models for more accurate engineering optimizations. This monograph is invaluable for researchers and engineers dealing with detailed reaction mechanisms, but is also useful for graduate students of related courses in chemistry, mechanical engineering, energy and environmental science and biology.

  8. Method for conducting exothermic reactions

    Science.gov (United States)

    Smith, Jr., Lawrence; Hearn, Dennis; Jones, Jr., Edward M.

    1993-01-01

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

  9. Engineering reactors for catalytic reactions

    Indian Academy of Sciences (India)

    Chemical Engineering and Process Development Division, CSIR - National Chemical Laboratory,. Pune 411 008, India ... Abstract. Catalytic reactions are ubiquitous in chemical and allied industries. ... strategies and recent advances in process intensification/ multifunctional reactors are discussed to illustrate the approach.

  10. Thermodynamics of random reaction networks.

    Directory of Open Access Journals (Sweden)

    Jakob Fischer

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

  11. Thermodynamics of Random Reaction Networks

    Science.gov (United States)

    Fischer, Jakob; Kleidon, Axel; Dittrich, Peter

    2015-01-01

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

  12. Drug Reactions in Oral Mucosa

    Directory of Open Access Journals (Sweden)

    Emine Derviş

    2012-12-01

    Full Text Available Both immunologic and nonimmunologic drug reactions can be seen in oral mucosa. Since considerable number of these reactions heals spontaneously without being noticed by the patients, exact frequency of the lesions is unknown. Most common lesions are xerostomia, taste disorders, mucosal ulcerations and edema. In this article, oral lesions resulting from drug intake similar to those from oral lesions of local and systemic diseases, and diagnostic problems caused by these similarities, have been reviewed.

  13. Radiation reaction and relativistic hydrodynamics.

    Science.gov (United States)

    Berezhiani, V I; Hazeltine, R D; Mahajan, S M

    2004-05-01

    By invoking the radiation reaction force, first perturbatively derived by Landau and Lifschitz, and later shown by Rohrlich to be exact for a single particle, we construct a set of fluid equations obeyed by a relativistic plasma interacting with the radiation field. After showing that this approach reproduces the known results for a locally Maxwellian plasma, we derive and display the basic dynamical equations for a general magnetized plasma in which the radiation reaction force augments the direct Lorentz force.

  14. Ionic liquids made with dimethyl carbonate: solvents as well as boosted basic catalysts for the michael reaction.

    Science.gov (United States)

    Fabris, Massimo; Lucchini, Vittorio; Noè, Marco; Perosa, Alvise; Selva, Maurizio

    2009-11-16

    This article describes 1) a methodology for the green synthesis of a class of methylammonium and methylphosphonium ionic liquids (ILs), 2) how to tune their acid-base properties by anion exchange, 3) complete neat-phase NMR spectroscopic characterisation of these materials and 4) their application as active organocatalysts for base-promoted carbon-carbon bond-forming reactions. Methylation of tertiary amines or phosphines with dimethyl carbonate leads to the formation of the halogen-free methyl-onium methyl carbonate salts, and these can be easily anion-exchanged to yield a range of derivatives with different melting points, solubility, acid-base properties, stability and viscosity. Treatment with water, in particular, yields bicarbonate-exchanged liquid onium salts. These proved strongly basic, enough to efficiently catalyse the Michael reaction; experiments suggest that in these systems the bicarbonate basicity is boosted by two orders of magnitude with respect to inorganic bicarbonate salts. These basic ionic liquids used in catalytic amounts are better even than traditional strong organic bases. The present work also introduces neat NMR spectroscopy of the ionic liquids as a probe for solute-solvent interactions as well as a tool for characterisation. Our studies show that high catalytic efficacy of functional ionic liquids can be achieved by integrating their green synthesis, along with a fine-tuning of their structure. Demonstrating that ionic liquid solvents can be made by a truly green procedure, and that their properties and reactivity can be tailored to the point of bridging the gap between their use as solvents and as catalysts.

  15. Late reaction, persistent reaction and doubtful allergic reaction: The problems of interpretation

    Directory of Open Access Journals (Sweden)

    Sarma Nilendu

    2009-01-01

    Full Text Available The standard method of patch test reading is to read the test site for any positive allergy at 48hr and then again at 72/96 hr. A late reading on the seventh day is also advised to exclude the irritant reaction (IR and to notice some delayed development of allergic reaction. However, multiple visits are often difficult for the patient; therefore, this late reading is sometimes omitted. Here a case of plantar hyperkeratosis, due to allergic contact dermatitis, is reported with some insight into interpretation of the patch test. The patient showed delayed patch test reaction to formaldehyde and colophony, which has never been reported before.

  16. Feshbach resonances in the exit channel of the F + CH3OH → HF + CH3O reaction observed using transition-state spectroscopy

    Science.gov (United States)

    Weichman, Marissa L.; Devine, Jessalyn A.; Babin, Mark C.; Li, Jun; Guo, Lifen; Ma, Jianyi; Guo, Hua; Neumark, Daniel M.

    2017-10-01

    The transition state governs how chemical bonds form and cleave during a chemical reaction and its direct characterization is a long-standing challenge in physical chemistry. Transition state spectroscopy experiments based on negative-ion photodetachment provide a direct probe of the vibrational structure and metastable resonances that are characteristic of the reactive surface. Dynamical resonances are extremely sensitive to the topography of the reactive surface and provide an exceptional point of comparison with theory. Here we study the seven-atom F + CH3OH → HF + CH3O reaction using slow photoelectron velocity-map imaging spectroscopy of cryocooled CH3OHF- anions. These measurements reveal spectral features associated with a manifold of vibrational Feshbach resonances and bound states supported by the post-transition state potential well. Quantum dynamical calculations yield excellent agreement with the experimental results, allow the assignment of spectral structure and demonstrate that the key dynamics of complex bimolecular reactions can be captured with a relatively simple theoretical framework.

  17. Reaction rates for mesoscopic reaction-diffusion kinetics.

    Science.gov (United States)

    Hellander, Stefan; Hellander, Andreas; Petzold, Linda

    2015-02-01

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

  18. Reaction rates for a generalized reaction-diffusion master equation.

    Science.gov (United States)

    Hellander, Stefan; Petzold, Linda

    2016-01-01

    It has been established that there is an inherent limit to the accuracy of the reaction-diffusion master equation. Specifically, there exists a fundamental lower bound on the mesh size, below which the accuracy deteriorates as the mesh is refined further. In this paper we extend the standard reaction-diffusion master equation to allow molecules occupying neighboring voxels to react, in contrast to the traditional approach, in which molecules react only when occupying the same voxel. We derive reaction rates, in two dimensions as well as three dimensions, to obtain an optimal match to the more fine-grained Smoluchowski model and show in two numerical examples that the extended algorithm is accurate for a wide range of mesh sizes, allowing us to simulate systems that are intractable with the standard reaction-diffusion master equation. In addition, we show that for mesh sizes above the fundamental lower limit of the standard algorithm, the generalized algorithm reduces to the standard algorithm. We derive a lower limit for the generalized algorithm which, in both two dimensions and three dimensions, is of the order of the reaction radius of a reacting pair of molecules.

  19. Construction of new biopolymer (chitosan)-based pincer-type Pd(II) complex and its catalytic application in Suzuki cross coupling reactions

    Science.gov (United States)

    Baran, Talat; Menteş, Ayfer

    2017-04-01

    In this paper we described the fabrication, characterization and application of a new biopolymer (chitosan)-based pincer-type Pd(II) catalyst in Suzuki cross coupling reactions using a non-toxic, cheap, eco-friendly and practical method. The catalytic activity tests showed remarkable product yields as well as TON (19800) and TOF (330000) values with a small catalyst loading. In addition, the catalyst indicated good recyclability in the Suzuki C-C reaction. This biopolymer supported catalyst can be used with various catalyst systems due to its unique properties, such as being inert, green in nature, low cost and chemically durable.

  20. Structure and related corrosion behaviour in 1M H{sub 2}SO{sub 4} of b.c.c. 304L films prepared by ion beam sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Idiri, M.; Boubeker, B. [Faculte des Science, Casablanca (Morocco). Lab. de Controle et d' Analyse des Materiaux; Sabot, R. [Laboratoire d' Etudes des Materiaux en Milieux Agressifs, Universite de La Rochelle, Faculte des Sciences, Avenue Marillac, 17042, La Rochelle (France); Goudeau, P. [Laboratoire de Metallurgie Physique, Universite de Poitiers, UMR 6630 du CNRS, Universite de Poitiers, SP2MI, Bd 3, Teleport 2, B.P; 179, 86960, Futuroscope (France); Dinhut, J.-F.; Grosseau-Poussard, J.-L. [Laboratoire d' Etudes des Materiaux en Milieux Agressifs, Universite de La Rochelle, Faculte des Sciences, Avenue Marillac, 17042, La Rochelle (France)

    1999-12-15

    The corrosion behaviour in a non-deaered 1M H{sub 2}SO{sub 4} solution of 304L stainless steel (SS) in bulk and thin film state was investigated. In the first step, we elaborated based cubic-centred 304L stainless steel thin films onto Si and f.c.c. 304L SS bulk substrates by using a sputter deposition method. Then, the structure and residual macrostress state of the films were studied by X-ray diffraction. It was found that films are in a highly compressive state ({approx}3 GPa). Finally, corrosion tests revealed an improvement in corrosion resistance of the films with respect to the bulk 304L stainless steel. (orig.)

  1. Comportamiento mecánico y estudio in situ de la evolución del daño en el grafito y en un compuesto C/C a 77 y a 300 K

    Directory of Open Access Journals (Sweden)

    Salazar, A.

    2002-04-01

    Full Text Available The mechanical properties at 77 K and at 300 K were determined in two polycristalline graphites with different microstructures and in a C/C composite. The flexure strength and the fracture toughness were evaluated and the micromechanic failure was studied in situ with a long distance microscope. The results obtained showed that the mechanical properties of these carbon materials are not affected by the cryogenic temperatures. The porosity is the main responsible of the mechanical failure in the graphites while in the composite, the matrix/yarn interface deflect the crack nucleated in the mattrix, presenting the best mechanical behavior.

    En este trabajo se han evaluado las propiedades mecánicas a 77 y a 300 K de dos grafitos policristalinos con microestructuras muy diferentes y de un compuesto C/C. Se realizaron ensayos de flexión en tres puntos y de tenacidad, y en éstos últimos se midió in situ la iniciación y la evolución del daño en el fondo de la entalla con un microscopio de larga distancia focal. Los resultados obtenidos muestran que las temperaturas criogénicas no afectan el comportamiento mecánico de los compuestos de carbono estudiados. Además, la porosidad presente en los grafitos es el mecanismo de rotura dominante mientras que en el material compuesto, la intercara débil entre matriz y haz de fibras detiene y desvía las grietas nucleadas en la matriz, presentando el mejor comportamiento mecánico.

  2. Carbonitriding reactions of diatomaceous earth: phase evolution and reaction mechanisms

    Directory of Open Access Journals (Sweden)

    BRANKO MATOVIC

    2006-06-01

    Full Text Available The possibility of using diatomaceous earth as Si precursor for low temperature synthesis of non-oxide powders by carbothermal reduction-nitridation was studied. It was found that carbonitriding reactions produce phases of the Si–Al–O–N system. Already at 1300 °C, nanosized, non-oxide powders were obtained. The comparatively low reaction temperatures is attributred to the nano-porous nature of the raw material. The evolution of crystalline phases proceeded via many intermediate stages. The powders were characterized by X-ray and SEM investigations. The results showed that diatomaceous earth can be a very effective source for obtaining non-oxide powders.

  3. A comprehensive survey of nuclear reactions; Panorama des reactions nucleaires

    Energy Technology Data Exchange (ETDEWEB)

    Cugnon, J. [Liege Univ., IFPA, AGO Dept. (Belgium)

    2007-07-01

    The various mechanisms of nuclear reactions are surveyed and classified in different regimes, based on the notions of coherent mechanisms and hard versus soft processes. The emphasis is put on the concepts at the basis of the understanding of these regimes and on the elements of nuclear structure which are involved in these different regimes, as well as the on the possibility of extracting this information. Due to lack of space and for pedagogical reasons, the discussion is limited to nucleon-induced and light-ion-induced reactions. However, a few remarks are given concerning some specific probes, such as weakly bound projectiles or neutron-rich nuclei. (author)

  4. Biomarkers of adverse drug reactions.

    Science.gov (United States)

    Carr, Daniel F; Pirmohamed, Munir

    2017-01-01

    Adverse drug reactions can be caused by a wide range of therapeutics. Adverse drug reactions affect many bodily organ systems and vary widely in severity. Milder adverse drug reactions often resolve quickly following withdrawal of the casual drug or sometimes after dose reduction. Some adverse drug reactions are severe and lead to significant organ/tissue injury which can be fatal. Adverse drug reactions also represent a financial burden to both healthcare providers and the pharmaceutical industry. Thus, a number of stakeholders would benefit from development of new, robust biomarkers for the prediction, diagnosis, and prognostication of adverse drug reactions. There has been significant recent progress in identifying predictive genomic biomarkers with the potential to be used in clinical settings to reduce the burden of adverse drug reactions. These have included biomarkers that can be used to alter drug dose (for example, Thiopurine methyltransferase (TPMT) and azathioprine dose) and drug choice. The latter have in particular included human leukocyte antigen (HLA) biomarkers which identify susceptibility to immune-mediated injuries to major organs such as skin, liver, and bone marrow from a variety of drugs. This review covers both the current state of the art with regard to genomic adverse drug reaction biomarkers. We also review circulating biomarkers that have the potential to be used for both diagnosis and prognosis, and have the added advantage of providing mechanistic information. In the future, we will not be relying on single biomarkers (genomic/non-genomic), but on multiple biomarker panels, integrated through the application of different omics technologies, which will provide information on predisposition, early diagnosis, prognosis, and mechanisms. Impact statement • Genetic and circulating biomarkers present significant opportunities to personalize patient therapy to minimize the risk of adverse drug reactions. ADRs are a significant heath issue

  5. Fatal anaphylactic reaction during anesthesia

    Directory of Open Access Journals (Sweden)

    Izidor Kern

    2012-01-01

    Full Text Available Background: Incidence of anaphylactic reactions occuring during anesthesia is not known. They occur most often in the induction  phase and can present with different levels of severity, also as an anaphylactic shock. Neuromuscular blocking drugs are the most frequently involved substances.Case presentation: We  report a case of a 77-year old female patient with granulomatous inflammation of unknown etiology. Surgical  biopsy of a neck lymph node was indicated. During the induction of anesthesia using propofol and succinylcholine she developed severe anaphylactic reaction presented with bronchospasm and cardiac arrest. Despite 80 min continous cardiopulmonary resuscitation the patient died. Elevated tryptase level in the patient’s blood sample taken before death confirmed anaphylactic reaction. On autopsy we confirmed the tuberculous etiology of generalized granulomatous inflammation.Conclusions: It is important to recognize anaphylactic reaction during anesthesia early and to take adequate measures in order to prevent unfavorable outcome. Tryptase assay of a blood sample taken during life or postmortem may help to identify anaphylactic reaction.

  6. [Histopathology of cutaneous drug reactions].

    Science.gov (United States)

    Ortonne, Nicolas

    2018-02-01

    There are many different types of cutaneous adverse reactions. The most classical reactions are driven by T lymphocytes that specifically react towards a drug, with an individual genetic susceptibility linked to certain type I major histocompatibility complex alleles. These reactions are characterized by a wide variety of clinical and histopathological presentations, and a wide range of severity. The most frequent entity is the maculopapular rash, while the most aggressive forms are the Steven-Johnson syndrome and toxic epidermal necrolysis (SJS-TEN). The histopathological alterations associated to each of these syndromes have been better described in the literature during the past 10 years, encompassing non-specific lesions, as in most drug induced maculopapular rashes, to more specific inflammatory patterns. The finding of confluent apoptotic keratinocytes with epidermal detachment is the prototypical aspect of SJS-TEN. There are however numerous pitfalls, and a similar aspect to those observed in each cutaneous drug reactions entities can be found in other diseases. DRESS syndrome can indeed present with dense and epidermotropic T-cell infiltrate, sometimes with nuclear atypias, and thus can be difficult to distinguish from a primary or secondary cutaneous T-cell lymphoma. The diagnosis of cutaneous adverse reactions relies on a clinical-pathological confrontation and requires an accurate evaluation of drug imputability. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

  7. Combustion kinetics and reaction pathways

    Energy Technology Data Exchange (ETDEWEB)

    Klemm, R.B.; Sutherland, J.W. [Brookhaven National Laboratory, Upton, NY (United States)

    1993-12-01

    This project is focused on the fundamental chemistry of combustion. The overall objectives are to determine rate constants for elementary reactions and to elucidate the pathways of multichannel reactions. A multitechnique approach that features three independent experiments provides unique capabilities in performing reliable kinetic measurements over an exceptionally wide range in temperature, 300 to 2500 K. Recent kinetic work has focused on experimental studies and theoretical calculations of the methane dissociation system (CH{sub 4} + Ar {yields} CH{sub 3} + H + Ar and H + CH{sub 4} {yields} CH{sub 3} + H{sub 2}). Additionally, a discharge flow-photoionization mass spectrometer (DF-PIMS) experiment is used to determine branching fractions for multichannel reactions and to measure ionization thresholds of free radicals. Thus, these photoionization experiments generate data that are relevant to both reaction pathways studies (reaction dynamics) and fundamental thermochemical research. Two distinct advantages of performing PIMS with high intensity, tunable vacuum ultraviolet light at the National Synchrotron Light Source are high detection sensitivity and exceptional selectivity in monitoring radical species.

  8. Electrocardiographic changes in lepra reaction.

    Science.gov (United States)

    Zawar, P B; Chawhan, R N; Swami, R M

    1983-04-01

    The electrocardiographic (E.C.G.) changes were evaluated in 54 patients of lepra reaction. Abnormalities of the E.C.G. observed were in the form of prolongation of QTc in 24 (44.44%), ST-T changes in a (16.66%), bundle branch block and ventricular extrasystoles in 2 each (3.70%). The mean QTc interval in 64 normal adults was 0.41 second (S.D. +/- 0.03, range 0.36 to 0.44 second). It was 0.44 second (S.D. +/- 0.05, range 0.38 to 0.52 second) in patients of lepra reaction. The difference in the QTc values in the two groups was statistically significant (P less than 0.01). The E.C.G. abnormalities in patients of lepra reaction appears to be due to myocardial involvement.

  9. Effective dynamics along given reaction coordinates, and reaction rate theory.

    Science.gov (United States)

    Zhang, Wei; Hartmann, Carsten; Schütte, Christof

    2016-12-22

    In molecular dynamics and related fields one considers dynamical descriptions of complex systems in full (atomic) detail. In order to reduce the overwhelming complexity of realistic systems (high dimension, large timescale spread, limited computational resources) the projection of the full dynamics onto some reaction coordinates is examined in order to extract statistical information like free energies or reaction rates. In this context, the effective dynamics that is induced by the full dynamics on the reaction coordinate space has attracted considerable attention in the literature. In this article, we contribute to this discussion: we first show that if we start with an ergodic diffusion process whose invariant measure is unique then these properties are inherited by the effective dynamics. Then, we give equations for the effective dynamics, discuss whether the dominant timescales and reaction rates inferred from the effective dynamics are accurate approximations of such quantities for the full dynamics, and compare our findings to results from approaches like Mori-Zwanzig, averaging, or homogenization. Finally, by discussing the algorithmic realization of the effective dynamics, we demonstrate that recent algorithmic techniques like the "equation-free" approach and the "heterogeneous multiscale method" can be seen as special cases of our approach.

  10. Miniaturized continuous flow reaction vessels: influence on chemical reactions

    NARCIS (Netherlands)

    Brivio, M.; Verboom, Willem; Reinhoudt, David

    2006-01-01

    This review offers an overview of the relatively young research area of continuous flow lab-on-a-chip for synthetic applications. A short introduction on the basic aspects of lab-on-a-chip is given in the first part. Subsequently, the effects of downscaling reaction vessels as well as the advantages

  11. Reaction rate of propene pyrolysis.

    Science.gov (United States)

    Han, Peipei; Su, Kehe; Liu, Yan; Wang, Yanli; Wang, Xin; Zeng, Qingfeng; Cheng, Laifei; Zhang, Litong

    2011-10-01

    The reaction rate of propene pyrolysis was investigated based on the elementary reactions proposed in Qu et al., J Comput Chem 2009, 31, 1421. The overall reaction rate was developed with the steady-state approximation and the rate constants of the elementary reactions were determined with the variational transition state theory. For the elementary reaction having transition state, the vibrational frequencies of the selected points along the minimum energy path were calculated with density functional theory at B3PW91/6-311G(d,p) level and the energies were improved with the accurate model chemistry method G3(MP2). For the elementary reaction without transition state, the frequencies were calculated with CASSCF/6-311G(d,p) and the energies were refined with the multireference configuration interaction method MRCISD/6-311G(d,p). The rate constants were evaluated within 200-2000 K and the fitted three-parameter expressions were obtained. The results are consistent with those in the literatures in most cases. For the overall rate, it was found that the logarithm of the rate and the reciprocal temperature have excellent linear relationship above 400 K, predicting that the rate follows a typical first-order law at high temperatures of 800-2000 K, which is also consistent with the experiments. The apparent activation energy in 800-2000 K is 317.3 kJ/mol from the potential energy surface of zero Kelvin. This value is comparable with the energy barriers, 365.4 and 403.7 kJ/mol, of the rate control steps. However, the apparent activation energy, 215.7 kJ/mol, developed with the Gibbs free energy surface at 1200 K is consistent with the most recent experimental result 201.9 ± 0.6 kJ/mol. Copyright © 2011 Wiley Periodicals, Inc.

  12. Vision 2020. Reaction Engineering Roadmap

    Energy Technology Data Exchange (ETDEWEB)

    Klipstein, David H. [Reaction Design, San Diego, CA (United States); Robinson, Sharon [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2001-01-01

    The Reaction Engineering Roadmap is a part of an industry- wide effort to create a blueprint of the research and technology milestones that are necessary to achieve longterm industry goals. This report documents the results of a workshop focused on the research needs, technology barriers, and priorities of the chemical industry as they relate to reaction engineering viewed first by industrial use (basic chemicals; specialty chemicals; pharmaceuticals; and polymers) and then by technology segment (reactor system selection, design, and scale-up; chemical mechanism development and property estimation; dealing with catalysis; and new, nonstandard reactor types).

  13. Functionalized olefin cross-coupling to construct carbon-carbon bonds

    Science.gov (United States)

    Lo, Julian C.; Gui, Jinghan; Yabe, Yuki; Pan, Chung-Mao; Baran, Phil S.

    2014-12-01

    Carbon-carbon (C-C) bonds form the backbone of many important molecules, including polymers, dyes and pharmaceutical agents. The development of new methods to create these essential connections in a rapid and practical fashion has been the focus of numerous organic chemists. This endeavour relies heavily on the ability to form C-C bonds in the presence of sensitive functional groups and congested structural environments. Here we report a chemical transformation that allows the facile construction of highly substituted and uniquely functionalized C-C bonds. Using a simple iron catalyst, an inexpensive silane and a benign solvent under ambient atmosphere, heteroatom-substituted olefins are easily reacted with electron-deficient olefins to create molecular architectures that were previously difficult or impossible to access. More than 60 examples are presented with a wide array of substrates, demonstrating the chemoselectivity and mildness of this simple reaction.

  14. Reaction

    African Journals Online (AJOL)

    raoul

    12 janv. 2012 ... recours à la TEP-FDG couplée au scanner serait d'un grand apport, en différenciant masse splénique bénigne et maligne, et en identifiant d'autres sites métastatiques hypermétaboliques insoupçonnées sur l'imagerie conventionnelle. L'imagerie de la métastase splénique pourrait également bénéficier de ...

  15. Reaction

    African Journals Online (AJOL)

    raoul

    2011-05-11

    May 11, 2011 ... Open-heart surgery and coronary artery bypass grafting in Western Africa. Frank Edwin1,2,&, Kwabena Frimpong-Boateng1 .... Frimpong-Boateng K, Amoah AG, Barwasser HM, Kallen C. Cardiopulmonary bypass in sickle cell anaemia without exchange transfusion.Eur J Cardiothorac Surg. 1998 Nov ...

  16. Reactions

    DEFF Research Database (Denmark)

    Søndergaard, Morten

    2011-01-01

    ) museum. Augmentation, in this expanding digital field, is part of a production of new public spaces, as well as a new reality that affects and traverses art and institutions immanently and througout. The expanding digital field is transforming art and the art museum in a number of fundamental ways, a few...... of which I will look into in this paper. It has been suggested that ... we are in the midst of an explosion of emerging human-computer interaction techniques that redefine our understanding of both computers and interaction. We propose the notion of Reality-Based Interaction (RBI) as a unifying concept...... that ties together ... (Robert J.K. Jacob, 2008) I suggest that a negotiation between reality-based interaction and a digital dialectic (Lunenfeld, 1999)(Søndergaard M. o., 2008) is becoming still more evident, on two levels: 1) As an investigation into (the visuality of) a digital reality under...

  17. Theoretical investigation of hyperthermal reactions at the gas-liquid interface: O (3P) and squalane.

    Science.gov (United States)

    Kim, Dongwook; Schatz, George C

    2007-06-14

    Hyperthermal collisions (5 eV) of ground-state atomic oxygen [O ((3)P)] with a liquid-saturated hydrocarbon, squalane (C(30)H(62)), have been studied using QM/MM hybrid "on-the-fly" direct dynamics. The surface structure of the liquid squalane is obtained from a classical molecular dynamics simulation using the OPLS-AA force field. The MSINDO semiempirical Hamiltonian is combined with OPLS-AA for the QM/MM calculations. In order to achieve a more consistent and efficient simulation of the collisions, we implemented a dynamic partitioning of the QM and MM atoms in which atoms are assigned to QM or MM regions based on their proximity to "seed" (open-shell) atoms that determine where bond making/breaking can occur. In addition, the number of seed atoms is allowed to increase or decrease as time evolves so that multiple reactive events can be described. The results show that H abstraction is the most important process for all incident angles, with H elimination, double H abstraction, and C-C bond cleavage also being important. A number of properties of these reactive channels, as well as inelastic nonreactive scattering, are investigated, including angular and translational energy distributions, the effect of incident collision angle, variation with depth of the reactive event within the liquid, with the reaction site on the hydrocarbon, and the effect of dynamics before and after reaction (direct reaction versus trapping reaction-desorption).

  18. Transition metal tetrachloroaluminate catalysts for probe reactions simulating petroleum resids upgrading

    Energy Technology Data Exchange (ETDEWEB)

    Sasaki, M.; Song, C.; Plummer, M.A. [Pennsylvania State University, University Park, PA (USA). Fuel Science Program and Lab. for Hydrocarbon Process Chemistry

    2000-03-01

    Several transition metal tetrachloroaluminates (MCl{sub x}-(AlCl{sub 3}){sub x}) have been evaluated as catalysts for probe reactions simulating petroleum resids upgrading. Six transition metal chlorides, VCl{sub 3}, CoCl{sub 2}, NiCl{sub 2}, ZnCl{sub 2}, MoCl{sub 3} and PdCl{sub 2}, and three kinds of alkali metal chlorides, LiCl, NaCl and KCl, were used for preparing the catalysts. Four compounds were selected as models, including 4-(1-naphthlymethyl)bibenzyl (NMBB), eicosane (n-C{sub 20}), dibenzothiophene and pyrene. Batch tests were carried out at 425{degree}C for 20 min under hydrogen pressure. Very interesting results were obtained from model compounds reactions that demonstrated the unusual and promising feature of transition metal tetrachloroaluminates. For example, some of the transition metal containing catalysts were found to strongly promote hydrocracking of a long-chain paraffin to levels which are 200-300% of those achieved with alkali metal tetrachloroaluminates. Mo-containing catalysts displayed especially higher activity for desulfurization and hydrogenation. The results of NMBB reactions provided insight into reaction mechanism, and the selectivity of cleavage of C-C bonds in NMBB correlated with the i-C{sub 4}/n-C{sub 4} ratio of the gaseous products, which is a relative measure of the acidity of the catalysts. 14 refs., 7 figs., 7 tabs.

  19. Reactions of ethanol on Ru

    NARCIS (Netherlands)

    Sturm, Jacobus Marinus; Liu, Feng; Lee, Christopher James; Bijkerk, Frederik

    2012-01-01

    The adsorption and reactions of ethanol on Ru(0001) were studied with temperatureprogrammed desorption (TPD) and reflection-absorption infrared spectroscopy (RAIRS). Ethanol was found to adsorb intact onto Ru(0001) below 100 K. Heating to 250 K resulted in formation of ethoxy groups, which undergo

  20. Reaction modeling in geothermal systems

    Science.gov (United States)

    Stefansson, A.

    2012-12-01

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

  1. Isotachophoresis applied to biomolecular reactions.

    Science.gov (United States)

    Eid, C; Santiago, J G

    2017-12-19

    This review discusses research developments and applications of isotachophoresis (ITP) to the initiation, control, and acceleration of chemical reactions, emphasizing reactions involving biomolecular reactants such as nucleic acids, proteins, and live cells. ITP is a versatile technique which requires no specific geometric design or material, and is compatible with a wide range of microfluidic and automated platforms. Though ITP has traditionally been used as a purification and separation technique, recent years have seen its emergence as a method to automate and speed up chemical reactions. ITP has been used to demonstrate up to 14 000-fold acceleration of nucleic acid assays, and has been used to enhance lateral flow and other immunoassays, and even whole bacterial cell detection assays. We here classify these studies into two categories: homogeneous (all reactants in solution) and heterogeneous (at least one reactant immobilized on a solid surface) assay configurations. For each category, we review and describe physical modeling and scaling of ITP-aided reaction assays, and elucidate key principles in ITP assay design. We summarize experimental advances, and identify common threads and approaches which researchers have used to optimize assay performance. Lastly, we propose unaddressed challenges and opportunities that could further improve these applications of ITP.

  2. Teachers' Reactions to Children's Aggression

    Science.gov (United States)

    Nesdale, Drew; Pickering, Kaye

    2006-01-01

    Drawing on social schema theory (Fiske & Taylor, 1991) and social identity theory (Tajfel & Turner, 1979), this study examined the impact on teachers' reactions to children's aggression of three variables, two of which were related to the aggressors and one was related to the teachers. Experienced female elementary school teachers (N=90) each read…

  3. The Pitfalls of Precipitation Reactions.

    Science.gov (United States)

    Slade, Peter W.; Rayner-Canham, Geoffrey W.

    1990-01-01

    Described are some of the difficulties presented in these reactions by competing equilibria that are usually ignored. Situations involving acid-base equilibria, solubility product calculations, the use of ammonia as a complexing agent, and semiquantitative comparisons of solubility product values are discussed. (CW)

  4. Reactants encapsulation and Maillard Reaction

    NARCIS (Netherlands)

    Troise, A.D.; Fogliano, V.

    2013-01-01

    In the last decades many efforts have been addressed to the control of Maillard Reaction products in different foods with the aim to promote the formation of compounds having the desired color and flavor and to reduce the concentration of several potential toxic molecules. Encapsulation, already

  5. REACTIONS OF SOME CONFECTIONERY GROUNDNUT ...

    African Journals Online (AJOL)

    AGROSEARCH UIL

    some confectionery groundnut accessions reactions to plant parasitic nematodes infection. .... The soil samples, 200 cm3 per treatment were extracted using the ..... 15. Osei et al, 2013. Table 7.Days to maturity of Accessions at the four locations. Accessions. Fumesua. Wenchi. Ejura. Atebubu. ICGV 97040. 101a. 109a. 93 e.

  6. Apparent tunneling in chemical reactions

    DEFF Research Database (Denmark)

    Henriksen, Niels Engholm; Hansen, Flemming Yssing; Billing, G. D.

    2000-01-01

    A necessary condition for tunneling in a chemical reaction is that the probability of crossing a barrier is non-zero, when the energy of the reactants is below the potential energy of the barrier. Due to the non-classical nature (i.e, momentum uncertainty) of vibrational states this is, however...

  7. Allergic reactions to natural rubber.

    Science.gov (United States)

    Slater, J E

    1992-03-01

    Immediate hypersensitivity reactions to natural rubber pose a significant risk to patients with spina bifida and urogenital abnormalities, health care workers, and rubber industry workers. Other patients, outside of these high risk groups, have experienced severe allergic reactions to natural rubber as well. Awareness of this life-threatening condition by health care providers is essential if reactions are to be prevented. History alone is inadequate to identify all patients at risk, and reliable testing materials are not yet approved or widely available. Nonrubber medical devices are readily available for most uses; however, the only rubber-free condoms currently on the market do not prevent the transmission of sexually transmitted disease. The identification and detection of rubber antigens, along with mandated labeling for rubber antigen content, will contribute to the care of this growing population of patients. Efforts by the rubber industry to decrease the antigen content of natural rubber products will decrease the risk of reaction among sensitized patients and will, very likely, decrease the rate of sensitization in the future.

  8. Organic Reaction Mechanism Controversy: Pedagogical ...

    African Journals Online (AJOL)

    The paper investigated the pedagogical implications of the controversy generated by the nature of reaction mechanism in organic chemistry as to whether it can be proven or not. A conference of a chemist, chemical educator, a graduate chemistry teacher and a graduate assistant was organized. The conference lasted for ...

  9. Reaction rates when barriers fluctuate

    OpenAIRE

    Reimann, Peter

    1999-01-01

    Reaction rates when barriers fluctuate : a path integral approach / P. Hänggi and P. Reimann. - In: International Conference on Path Integrals from peV to TeV : Proceedings of the ... / eds.: R. Casalbuoni ... - Singapore u.a. : World Scientific, 1999. - S. 407-409

  10. Palladium-Catalysed Coupling Reactions

    NARCIS (Netherlands)

    de Vries, Johannes G.; Beller, M; Blaser, HU

    2012-01-01

    Palladium-catalysed coupling reactions have gained importance as a tool for the production of pharmaceutical intermediates and to a lesser extent also for the production of agrochemicals, flavours and fragrances, and monomers for polymers. In this review only these cases are discussed where it seems

  11. Molecular Reaction Dynamics and Solvation.

    Science.gov (United States)

    Kim, Seong Keun

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

  12. FOREIGN BODY REACTION TO BIOMATERIALS

    Science.gov (United States)

    Anderson, James M.; Rodriguez, Analiz; Chang, David T.

    2008-01-01

    The foreign body reaction composed of macrophages and foreign body giant cells is the end-stage response of the inflammatory and wound healing responses following implantation of a medical device, prosthesis, or biomaterial. A brief, focused overview of events leading to the foreign body reaction is presented. The major focus of this review is on factors that modulate the interaction of macrophages and foreign body giant cells on synthetic surfaces where the chemical, physical, and morphological characteristics of the synthetic surface are considered to play a role in modulating cellular events. These events in the foreign body reaction include protein adsorption, monocyte/macrophage adhesion, macrophage fusion to form foreign body giant cells, consequences of the foreign body response on biomaterials, and cross-talk between macrophages/foreign body giant cells and inflammatory/wound healing cells. Biomaterial surface properties play an important role in modulating the foreign body reaction in the first two to four weeks following implantation of a medical device, even though the foreign body reaction at the tissue/material interface is present for the in vivo lifetime of the medical device. An understanding of the foreign body reaction is important as the foreign body reaction may impact the biocompatibility (safety) of the medical device, prosthesis, or implanted biomaterial and may significantly impact short- and long-term tissue responses with tissue-engineered constructs containing proteins, cells, and other biological components for use in tissue engineering and regenerative medicine. Our perspective has been on the inflammatory and wound healing response to implanted materials, devices, and tissue-engineered constructs. The incorporation of biological components of allogeneic or xenogeneic origin as well as stem cells into tissue-engineered or regenerative approaches opens up a myriad of other challenges. An in depth understanding of how the immune system

  13. Numerical modelling of hydration reactions

    Science.gov (United States)

    Vrijmoed, Johannes C.; John, Timm

    2017-04-01

    Mineral reactions are generally accompanied by volume changes. Observations in rocks and thin section indicate that this often occurred by replacement reactions involving a fluid phase. Frequently, the volume of the original rock or mineral seems to be conserved. If the density of the solid reaction products is higher than the reactants, the associated solid volume decrease generates space for a fluid phase. In other words, porosity is created. The opposite is true for an increase in solid volume during reaction, which leads to a porosity reduction. This slows down and may even stop the reaction if it needs fluid as a reactant. Understanding the progress of reactions and their rates is important because reaction generally changes geophysical and rock mechanical properties which will therefore affect geodynamical processes and seismic properties. We studied the case of hydration of eclogite to blueschist in a subduction zone setting. Eclogitized pillow basalt structures from the Tian-Shan orogeny are transformed to blueschist on the rims of the pillow (van der Straaten et al., 2008). Fluid pathways existed between the pillow structures. The preferred hypothesis of blueschist formation is to supply the fluid for hydration from the pillow margins progressing inward. Using numerical modelling we simulate this coupled reaction-diffusion process. Porosity and fluid pressure evolution are coupled to local thermodynamic equilibrium and density changes. The first rim of blueschist that forms around the eclogite pillow increases volume to such a degree that the system is clogged and the reaction stops. Nevertheless, the field evidence suggests the blueschist formation continued. To prevent the system from clogging, a high incoming pore fluid pressure on the pillow boundaries is needed along with removal of mass from the system to accommodate the volume changes. The only other possibility is to form blueschist from any remaining fluid stored in the core of the pillow

  14. Experimental Demonstrations in Teaching Chemical Reactions.

    Science.gov (United States)

    Hugerat, Muhamad; Basheer, Sobhi

    2001-01-01

    Presents demonstrations of chemical reactions by employing different features of various compounds that can be altered after a chemical change occurs. Experimental activities include para- and dia-magnetism in chemical reactions, aluminum reaction with base, reaction of acid with carbonates, use of electrochemical cells for demonstrating chemical…

  15. KINETICS AND MECHANISM OF REACTION OF ACIDIC ...

    African Journals Online (AJOL)

    For both Nile blue and Meldola\\'s blue reactions the rates have first-order dependence on each substrate, chlorite and acid. Both reactions showed negative salt effect indicating the reaction is between the oppositely charged species, likely the substrate cation and chlorite anion. The acidic chlorite reaction with MB+ was ...

  16. Concerted O atom—proton transfer in the O—O bond forming step in water oxidation

    National Research Council Canada - National Science Library

    Zuofeng Chen; Javier J. Concepcion; Xiangqian Hu; Weitao Yang; Paul G. Hoertz; Thomas J. Meyer

    2010-01-01

    ...⁻/4H⁺ loss and O—O bond formation. Significant progress in water oxidation catalysis has been achieved recently by use of single-site Ru metal complex catalysts such as [Ru(Mebimpy)(bpy)(OH₂)]²⁺ [Mebimpy = 2,6-bis...

  17. A preliminary study on the expression and clinical value of platelet-derived growth factor BB, hypoxia inducible factor-1α and C-C motif chemokine receptor-2 in peripheral blood during the pathogenesis of Graves' disease.

    Science.gov (United States)

    Liu, Ying; Tang, Jinglan; Hu, Qiaohong; Lu, Kefeng; Hou, Chunjie

    2018-01-01

    Platelet-derived growth factor BB (PDGF-BB) plays an important role in the development of GD (Graves' disease). However, it is still unknown whether PDGF-BB is expressed in peripheral blood and whether the expression of PDGF-BB contributes to GD. We aim to study the expression of PDGF-BB, hypoxia inducible factor (HIF)-1α and C-C motif chemokine receptor (CCR)-2 in peripheral blood of patients with GD and explore its effect and potential mechanism in pathogenesis. 41 patients with GD (GD group) and forty-five healthy people (control group) were chosen. The concentration of PDGF-BB and HIF-1α in peripheral blood specimens were detected and compared between the two groups. The expression of CCR2 in macrophages in the peripheral blood specimens were examined using FCM (Flow Cytometry). Both PDGF-BB and HIF-1α were expressed in human peripheral blood from the two groups. Compared with specimens from healthy people, there were statistically increased concentrations of PDGF-BB and HIF-1α in the GD group (P BB through HIF-1α signal, and the high expression of PDGF-BB may be involved in the pathogenesis of GD.

  18. A new face of phenalenyl-based radicals in the transition metal-free C-H arylation of heteroarenes at room temperature: trapping the radical initiatorviaC-C σ-bond formation.

    Science.gov (United States)

    Ahmed, Jasimuddin; P, Sreejyothi; Vijaykumar, Gonela; Jose, Anex; Raj, Manthan; Mandal, Swadhin K

    2017-11-01

    The radical-mediated transition metal-free approach for the direct C-H bond functionalization of arenes is considered as a cost effective alternative to transition metal-based catalysis. An organic ligand-based radical plays a key role by generating an aryl radical which undergoes a subsequent functionalization process. The design principle of the present study takes advantage of a relatively stable odd alternant hydrocarbon-based phenalenyl (PLY) radical. In this study, the first transition metal-free catalyzed direct C-H arylation of a variety of heteroarenes such as azoles, furan, thiophene and pyridine at room temperature has been reported using a phenalenyl-based radical without employing any photoactivation step. This protocol has been successfully applied to the gram scale synthesis of core moieties of bioactive molecules. The phenalenyl-based radical initiator has been characterized crystallographically by trapping it via the formation of a C-C σ-bond between the phenalenyl radical and solvent-based radical species.

  19. Study of the effect of switching speed of the a-SiC/c-Si(p)-based, thyristor-like, ultra-high-speed switches, using two-dimensional simulation techniques

    Science.gov (United States)

    Dimitriadis, Evangelos I.; Georgoulas, Nikolaos

    2017-06-01

    A parametric study for a series of technological and geometrical parameters affecting rise time of Al/a-SiC/c-Si(p)/c-Si(n+)/Al thyristor-like switches, is presented here for the first time, using two-dimensional simulation techniques. By varying anode current values in simulation procedure we achieved very good agreement between simulation and experimental results for the rising time characteristics of the switch. A series of factors affecting the rising time of the switches are studied here. Two factors among all others studied here, exerting most significant influence, of more than one order of magnitude on the rising time, are a-SiC and c-Si(p) region widths, validating our earlier presented model for device operation. The above widths can be easily varied on device manufacture procedure. We also successfully simulated the rising time characteristics of our earlier presented simulated improved switch, with forward breakover voltage {V}{BF}=11 {{V}} and forward voltage drop {V}{{F}}=9.5 {{V}} at the ON state, exhibiting an ultra low rise time value of less than 10 ps, which in conjunction with its high anode current density values of 12 A/mm2 and also cheap and easy fabrication techniques, makes this switch appropriate for ESD protection as well as RF MEMS and NEMS applications.

  20. Thermodynamics of Enzyme-Catalyzed Reactions Database

    Science.gov (United States)

    SRD 74 Thermodynamics of Enzyme-Catalyzed Reactions Database (Web, free access)   The Thermodynamics of Enzyme-Catalyzed Reactions Database contains thermodynamic data on enzyme-catalyzed reactions that have been recently published in the Journal of Physical and Chemical Reference Data (JPCRD). For each reaction the following information is provided: the reference for the data, the reaction studied, the name of the enzyme used and its Enzyme Commission number, the method of measurement, the data and an evaluation thereof.

  1. Electrochemical promotion of catalytic reactions

    Science.gov (United States)

    Imbihl, R.

    2010-05-01

    The electrochemical promotion of heterogeneously catalyzed reactions (EPOC) became feasible through the use of porous metal electrodes interfaced to a solid electrolyte. With the O 2- conducting yttrium stabilized zirconia (YSZ), the Na + conducting β″-Al 2O 3 (β-alumina), and several other types of solid electrolytes the EPOC effect has been demonstrated for about 100 reaction systems in studies conducted mainly in the mbar range. Surface science investigations showed that the physical basis for the EPOC effect lies in the electrochemically induced spillover of oxygen and alkali metal, respectively, onto the surface of the metal electrodes. For the catalytic promotion effect general concepts and mechanistic schemes were proposed but these concepts and schemes are largely speculative. Applying surface analytical tools to EPOC systems the proposed mechanistic schemes can be verified or invalidated. This report summarizes the progress which has been achieved in the mechanistic understanding of the EPOC effect.

  2. Theoretical aspects of surface reactions

    Science.gov (United States)

    Nørskov, J. K.; Stoltze, P.

    1987-10-01

    A short review is given of our present understanding of the trends in the chemisorption energies and activation energies for dissociation of simple gas molecules on the transition metals. The effect of adsorbed alkali atoms on the activation energy for dissociation is also discussed. This is then used to explain the trends in activity along the transition metal rows and the promoting effect of K for the ammonia synthesis reaction. The basis for the description is the development of a kinetic model for the ammonia synthesis which can describe quantitatively the macroscopic kinetics of a commercial catalyst under industrial conditions. The model relates the reaction rate directly to the properties of the chemisorbed reactants, intermediates and product as measured for model single crystal systems under ultrahigh vacuum conditions.

  3. Investigating Reaction-Driven Cracking

    Science.gov (United States)

    Kelemen, P. B.; Hirth, G.; Savage, H. M.

    2013-12-01

    Many metamorphic reactions lead to large volume changes, and potentially to reaction-driven cracking [1,2]. Large-scale hydration of mantle peridotite to produce serpentine or talc is invoked to explain the rheology of plate boundaries, the nature of earthquakes, and the seismic properties of slow-spread ocean crust and the 'mantle wedge' above subduction zones. Carbonation of peridotite may be an important sink in the global carbon cycle. Zones of 100% magnesite + quartz replacing peridotite, up to 200 m thick, formed where oceanic mantle was thrust over carbonate-bearing metasediments in Oman. Talc + carbonate is an important component of the matrix in subduction mélanges at Santa Catalina Island , California, and the Sanbagawa metamorphic belt, Japan. Engineered systems to emulate natural mineral carbonation could provide relatively inexpensive CO2 capture and storage [3]. More generally, engineered reaction-driven cracking could supplement or replace hydraulic fracture in geothermal systems, solution mining, and extraction of tight oil and gas. The controls on reaction-driven cracking are poorly understood. Hydration and carbonation reactions can be self-limiting, since they potentially reduce permeability and armor reactive surfaces [4]. Also, in some cases, hydration or carbonation may take place at constant volume. Small changes in volume due to precipitation of solid products increases stress, destabilizing solid reactants, until precipitation and dissolution rates become equal at a steady state stress [5]. In a third case, volume change due to precipitation of solid products causes brittle failure. This has been invoked on qualitative grounds to explain, e.g., complete serpentinization of mantle peridotite [6]. Below ~ 300°C, the available potential energy for hydration and carbonation of olivine could produce stresses of 100's of MPa [2], sufficient to fracture rocks to 10 km depth or more, causing brittle failure below the steady state stress required

  4. Partner reaction following ostomy surgery.

    Science.gov (United States)

    Gloeckner, M R

    1983-01-01

    This study was conducted to obtain information regarding sexual adjustment following ostomy surgery and to explore the spouse/partner's reaction upon resuming sexual activities following surgery. Home interviews were conducted with 40 subjects who had a permanent stoma, where the mean length of time since surgery averaged 4.6 years. Retrospective perceptions of the spouse/partner's reactions were varied. A majority reported that their spouses reacted positively to the first sexual experience following ostomy surgery. However a substantial number of subjects stated that their sexual partner reacted with caution ("fear of hurting me") or in a negative manner. This and previous studies indicate that the sexual partner plays a key role in helping the person adjust following ostomy surgery.

  5. Stickland reactions of dental plaque.

    Science.gov (United States)

    Curtis, M A; Kemp, C W; Robrish, S A; Bowen, W H

    1983-01-01

    Dental plaque samples from monkeys (Macaca fascicularis) were shown to contain proline reduction activity in coupled Stickland reactions with other amino acids and also with certain end products of bacterial glucose metabolism. The unusually high concentration of bound and free proline in the oral environment may be of importance in both the production of base and in the removal of acid from the tooth surface after dietary carbohydrate ingestion. PMID:6618673

  6. Siphons in chemical reaction networks.

    Science.gov (United States)

    Shiu, Anne; Sturmfels, Bernd

    2010-08-01

    Siphons in a chemical reaction system are subsets of the species that have the potential of being absent in a steady state. We present a characterization of minimal siphons in terms of primary decomposition of binomial ideals, we explore the underlying geometry, and we demonstrate the effective computation of siphons using computer algebra software. This leads to a new method for determining whether given initial concentrations allow for various boundary steady states.

  7. Modeling the enzyme kinetic reaction.

    Science.gov (United States)

    Atangana, Abdon

    2015-09-01

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

  8. Multicomponent reactions in nucleoside chemistry

    Science.gov (United States)

    Buchowicz, Włodzimierz

    2014-01-01

    Summary This review covers sixty original publications dealing with the application of multicomponent reactions (MCRs) in the synthesis of novel nucleoside analogs. The reported approaches were employed for modifications of the parent nucleoside core or for de novo construction of a nucleoside scaffold from non-nucleoside substrates. The cited references are grouped according to the usually recognized types of the MCRs. Biochemical properties of the novel nucleoside analogs are also presented (if provided by the authors). PMID:25161730

  9. Tuberculin reaction and BCG scar

    DEFF Research Database (Denmark)

    Timmermann, Clara Amalie Gade; Biering-Sørensen, Sofie; Aaby, Peter

    2015-01-01

    rate ratio (MRR) comparing children with a BCG scar with those without was 0.42 (95% CI = 0.19; 0.93). There was a similar tendency for TST positivity: MRR = 0.47 (95% CI = 0.14; 1.54). For LBW children who had both a positive TST reaction and a scar, the MRR was 0.22 (95% CI = 0.05; 0.87). For NBW...

  10. Reaction Selectivity in Heterogeneous Catalysis

    Energy Technology Data Exchange (ETDEWEB)

    Somorjai, Gabor A.; Kliewer, Christopher J.

    2009-02-02

    The understanding of selectivity in heterogeneous catalysis is of paramount importance to our society today. In this review we outline the current state of the art in research on selectivity in heterogeneous catalysis. Current in-situ surface science techniques have revealed several important features of catalytic selectivity. Sum frequency generation vibrational spectroscopy has shown us the importance of understanding the reaction intermediates and mechanism of a heterogeneous reaction, and can readily yield information as to the effect of temperature, pressure, catalyst geometry, surface promoters, and catalyst composition on the reaction mechanism. DFT calculations are quickly approaching the ability to assist in the interpretation of observed surface spectra, thereby making surface spectroscopy an even more powerful tool. HP-STM has revealed three vitally important parameters in heterogeneous selectivity: adsorbate mobility, catalyst mobility, and selective site-blocking. The development of size controlled nanoparticles from 0.8 to 10 nm, of controlled shape, and of controlled bimetallic composition has revealed several important variables for catalytic selectivity. Lastly, DFT calculations may be paving the way to guiding the composition choice for multi-metallic heterogeneous catalysis for the intelligent design of catalysts incorporating the many factors of selectivity we have learned.

  11. SOLVENTLESS MIGRATORY-INSERTION REACTIONS OF ...

    African Journals Online (AJOL)

    Preferred Customer

    Treichel, P.M.; Shubkin, R.L.; Barnett, K.W.; Reichard, D. Inorg. Chem. 1966, 5, 1177. 9. King, R.B.; King, A.D.; Igbal, M.Z.; Frazier, C.C. J. Am. Chem. Soc. 1978, 100, 1687. 10. Forschner, T.C.; Cutler, A.R. Organometallics 1985, 4, 1247. 11. Theys, R.D.; Dudley, M.E.; Hossain, M.M. Coord. Chem. Rev. 2009, 253, 180.

  12. Chlorination of Amino Acids: Reaction Pathways and Reaction Rates.

    Science.gov (United States)

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

    2017-05-02

    Chlorination of amino acids can result in the formation of organic monochloramines or organic dichloramines, depending on the chlorine to amino acid ratio (Cl:AA). After formation, organic chloramines degrade into aldehydes, nitriles and N-chloraldimines. In this paper, the formation of organic chloramines from chlorination of lysine, tyrosine and valine were investigated. Chlorination of tyrosine and lysine demonstrated that the presence of a reactive secondary group can increase the Cl:AA ratio required for the formation of N,N-dichloramines, and potentially alter the reaction pathways between chlorine and amino acids, resulting in the formation of unexpected byproducts. In a detailed investigation, we report rate constants for all reactions in the chlorination of valine, for the first time, using experimental results and modeling. At Cl:AA = 2.8, the chlorine was found to first react quickly with valine (5.4 × 10 4 M -1 s -1 ) to form N-monochlorovaline, with a slower subsequent reaction with N-monochlorovaline to form N,N-dichlorovaline (4.9 × 10 2 M -1 s -1 ), although some N-monochlorovaline degraded into isobutyraldehyde (1.0 × 10 -4 s -1 ). The N,N-dichlorovaline then competitively degraded into isobutyronitrile (1.3 × 10 -4 s -1 ) and N-chloroisobutyraldimine (1.2 × 10 -4 s -1 ). In conventional drinking water disinfection, N-chloroisobutyraldimine can potentially be formed in concentrations higher than its odor threshold concentration, resulting in aesthetic challenges and an unknown health risk.

  13. On the investigation of resonances above and below the threshold in nuclear reactions of astrophysical interest using the Trojan Horse Method.

    Science.gov (United States)

    La Cognata, M.; Spitaleri, C.; Cherubini, S.; Gulino, M.; Indelicato, I.; Lamia, L.; Pizzone, R. G.; Romano, S.; Trippella, O.; Tumino, A.

    2017-07-01

    The occurrence of resonances in reactions of astrophysical interest might significantly enhance the astrophysical factor with respect to the direct reaction contribution, divert nucleosynthesis path and change the energy production, with significant impact on astrophysics. Moreover, the determination of resonance parameters, that is, energy, spin-parity and partial widths, allows one to perform nuclear structure studies leading, for instance, to determine the cluster structure of the state under investigation. However, nuclear reactions in stars take place at energies well below ~ 1 MeV owing to the typical temperatures characterising these environments. Therefore, the Coulomb barrier exponentially suppressing the cross section and the electron screening effect, due to the shielding of nuclear charges by atomic electrons, make it very difficult to provide accurate astrophysical factors. The THM is an indirect method allowing to overcome such difficulties. It makes use of quasi-free reactions with three particles in the exit channel, a + A → c + C + s, to deduce the cross section of the reaction of astrophysical interest, a + x → c + C, under the hypothesis that A shows a strong x + s cluster structure, right at astrophysical energies. By using a generalised R-matrix approach, the resonance parameters can be deduced from THM data allowing one to perform a full spectroscopic study of low-energy and sub-threshold resonances. In this work, we will discuss two examples of reactions of astrophysical interest, whose cross sections show a resonant behaviour: the19F(p, α)16O cross section that displays resonances at energies above the particle emission threshold and the13C(α, n)16O reaction, dominated by the -3 keV sub-threshold resonance due to the 6.356 MeV level in17O.

  14. Synthesis of 6-substituted 2-pyrrolyl and indolyl benzoxazoles by intramolecular O-arylation in photostimulated reactions.

    Science.gov (United States)

    Vaillard, Victoria A; Guastavino, Javier F; Budén, María E; Bardagí, Javier I; Barolo, Silvia M; Rossi, Roberto A

    2012-02-03

    The synthesis of a series of 6-substituted 2-pyrrolyl and 2-indolyl benzoxazoles by photostimulated C-O cyclization of anions from 2-pyrrole carboxamides, 2-indole carboxamides, or 3-indole carboxamides has been found to proceed in good to excellent yields (41-100%) in DMSO and liquid ammonia. The pyrrole and indole carboxamides are obtained in good to very good isolated yields by an amidation reaction of different 2-haloanilines with 2-carboxylic acid of pyrrole and 2- or 3-carboxylic acid of indole. To explain the regiochemical outcome of these reactions (C-O arylation vs C-N or C-C arylation), a theoretical analysis was performed using DFT methods and the B3LYP functional.

  15. Chemical reactions in solvents and melts

    CERN Document Server

    Charlot, G

    1969-01-01

    Chemical Reactions in Solvents and Melts discusses the use of organic and inorganic compounds as well as of melts as solvents. This book examines the applications in organic and inorganic chemistry as well as in electrochemistry. Organized into two parts encompassing 15 chapters, this book begins with an overview of the general properties and the different types of reactions, including acid-base reactions, complex formation reactions, and oxidation-reduction reactions. This text then describes the properties of inert and active solvents. Other chapters consider the proton transfer reactions in

  16. Molecular basis of pyrimidine 5'-nucleotidase deficiency caused by 3 newly identified missense mutations (c.187T>C, c.469G>C and c.740T>C) and a tabulation of known mutations.

    Science.gov (United States)

    Chiarelli, Laurent R; Morera, Simone M; Galizzi, Alessandro; Fermo, Elisa; Zanella, Alberto; Valentini, Giovanna

    2008-01-01

    Hereditary pyrimidine 5'-nucleotidase deficiency is the most frequent enzymopathy of red blood cell nucleotide metabolism that causes hereditary non-spherocytic hemolytic anemia. The disease is usually characterized by mild-to-moderate hemolytic anemia, reticulocytosis and hyperbilirubinemia. To date, diagnosis ultimately depends upon demonstration of a reduced level of pyrimidine 5'-nucleotidase type-I (P5'N-1) activity in red cells and detection of mutations in the P5'N-1 gene. To unravel the causes of the P5'N deficiency and to obtain data for a definitive diagnosis three newly described missense mutations (c.187T>C, c.469G>C and c.740T>C) identified in patients with hemolytic anemia have been characterized at protein level. The mutant enzymes (C63R, G157R and I247T) were obtained as recombinant forms and purified to homogeneity. The enzymes were altered, although to a different extent, in both thermal stability and catalytic efficiency. The catalytic efficiency of all mutants was reduced especially towards UMP (up to more than 200 times), owing to the increased Km values (approximately, 10-25 times higher). The G157R enzyme was severely heat unstable and lost half of its activity after about 23 min of incubation at 37 degrees C. At higher temperature C63R and I247T mutants as well were less stable than the wild-type enzyme. Therefore, although the mutations targeted different regions of the P5'N-1 structure, they produced similar effects on the molecular properties of the enzyme. Thus, all affected amino acids are functionally and structurally important for preserving the enzyme activity during the red cell life span.

  17. Human axonal survival of motor neuron (a-SMN) protein stimulates axon growth, cell motility, C-C motif ligand 2 (CCL2), and insulin-like growth factor-1 (IGF1) production.

    Science.gov (United States)

    Locatelli, Denise; Terao, Mineko; Fratelli, Maddalena; Zanetti, Adriana; Kurosaki, Mami; Lupi, Monica; Barzago, Maria Monica; Uggetti, Andrea; Capra, Silvia; D'Errico, Paolo; Battaglia, Giorgio S; Garattini, Enrico

    2012-07-27

    Spinal muscular atrophy is a fatal genetic disease of motoneurons due to loss of full-length survival of motor neuron protein, the main product of the disease gene SMN1. Axonal SMN (a-SMN) is an alternatively spliced isoform of SMN1, generated by retention of intron 3. To study a-SMN function, we generated cellular clones for the expression of the protein in mouse motoneuron-like NSC34 cells. The model was instrumental in providing evidence that a-SMN decreases cell growth and plays an important role in the processes of axon growth and cellular motility. In our conditions, low levels of a-SMN expression were sufficient to trigger the observed biological effects, which were not modified by further increasing the amounts of the expressed protein. Differential transcriptome analysis led to the identification of novel a-SMN-regulated factors, i.e. the transcripts coding for the two chemokines, C-C motif ligands 2 and 7 (CCL2 and CCL7), as well as the neuronal and myotrophic factor, insulin-like growth factor-1 (IGF1). a-SMN-dependent induction of CCL2 and IGF1 mRNAs resulted in increased intracellular levels and secretion of the respective protein products. Induction of CCL2 contributes to the a-SMN effects, mediating part of the action on axon growth and random cell motility, as indicated by chemokine knockdown and re-addition studies. Our results shed new light on a-SMN function and the underlying molecular mechanisms. The data provide a rational framework to understand the role of a-SMN deficiency in the etiopathogenesis of spinal muscular atrophy.

  18. C-C motif chemokine 22 ligand (CCL22) concentrations in sera of gastric cancer patients are related to peritoneal metastasis and predict recurrence within one year after radical gastrectomy.

    Science.gov (United States)

    Wei, Yuzhe; Wang, Tie; Song, Hongjiang; Tian, Lining; Lyu, Gongwei; Zhao, Lei; Xue, Yingwei

    2017-05-01

    Gastric cancer is a common cancer with a poor prognosis. Chemokines play important roles in the tumor microenvironments to support tumor growth and metastasis. The effects of C-C motif chemokine ligand 22 (CCL22) in gastric cancer remain unclear. Between January 1, 2014 and April 31, 2014, a total of 298 gastric cancer patients were recruited to this study. Circulating concentrations of CCL22 were measured in gastric cancer patients before surgery, at discharged and during follow-up visits. The expression of CCL22 in gastric cancer tumor beds was measured by immunohistochemistry. The proportion of CD3 + CD4 + CD25 + Foxp3 + regulatory T cells in tumor sites was assessed by flow cytometry. Gastric cancer patients had higher serum CCL22 levels compared to healthy controls (P gastric cancer tumor beds were the source of serum CCL22, as gastric cancer patients had an increased proportion of strong expression of CCL22 (P Gastric cancer tissue harbored a higher percentage of regulatory T cells compared to normal tumor-free stomach margins (P Gastric cancer patients with peritoneal metastasis showed increased levels of circulating CCL22 before surgery compared to metastasis-free patients (P Gastric cancer patients with the recurrence within the first year after surgery had elevated serum CCL22 concentrations at different time points compared to those of recurrence-free patients (P gastric cancer development presumably by increasing the percentage of regulatory T cells in the tumor microenvironments. CCL22 levels in sera have a predictive value for gastric cancer peritoneal metastasis and the early recurrence. Therefore, CCL22 may be a therapeutic target for gastric cancer. Copyright © 2016 Elsevier Inc. All rights reserved.

  19. Animation: The C.C.C.'s Socio-Cultural Development Project

    Science.gov (United States)

    Price, Clarence

    1977-01-01

    Integration into a society made for and by men, in which all his activities are meaningful, is animation's ultimate goal. "Animation", the title of the Council for Cultural Cooperation's socio-cultural development project, is described along with the policy necessary to implement it. This includes the role of the animateur, who would…

  20. Enveloping σ-C C C-algebra of a smooth Frechet algebra crossed ...

    Indian Academy of Sciences (India)

    ... enveloping -*-algebra R E ( S ( R , A ∞ , ) ) of the smooth Schwartz crossed product R S ( R , A ∞ , ) of the Frechet algebra A ∞ of C ∞ -elements of is isomorphic to the -*-crossed product R C ∗ ( R , E ( A ) , ) of the enveloping -*-algebra () of by the induced action. When is a hermitian Q -algebra, ...