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Sample records for asymmetric reactions forming

  1. Asymmetric Catalytic Aza-Diels-Alder/Ring-Closing Cascade Reaction Forming Bicyclic Azaheterocycles by Trienamine Catalysis.

    Science.gov (United States)

    Li, Yang; Barløse, Casper; Jørgensen, Julie; Carlsen, Bjørn Dreiø; Jørgensen, Karl Anker

    2017-01-01

    An asymmetric catalytic aza-Diels-Alder/ring-closing cascade reaction between acylhydrazones and in situ formed trienamines is presented. The reaction proceeds through a formal aza-Diels-Alder cycloaddition, followed by a ring-closing reaction forming the hemiaminal ring leading to chiral bicyclic azaheterocycles in moderate to good yield (up to 71 %), good enantio- (up to 92 % ee) and diastereoselectivity (up to >20:1 d.r.). Furthermore, transformations are presented to show the potential application of the formed product. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. An efficient catalyst for asymmetric Reformatsky reaction

    Indian Academy of Sciences (India)

    rate enantioselectivity using N,N-dialkylnorephedrines as chiral ligands. ..... temperatures also, there was no product conversion. ... Optimization of reaction conditions for asymmetric Reformatsky reaction between benzaldehyde and α-.

  3. Direct catalytic asymmetric aldol-Tishchenko reaction.

    Science.gov (United States)

    Gnanadesikan, Vijay; Horiuchi, Yoshihiro; Ohshima, Takashi; Shibasaki, Masakatsu

    2004-06-30

    A direct catalytic asymmetric aldol reaction of propionate equivalent was achieved via the aldol-Tishchenko reaction. Coupling an irreversible Tishchenko reaction to a reversible aldol reaction overcame the retro-aldol reaction problem and thereby afforded the products in high enantio and diastereoselectivity using 10 mol % of the asymmetric catalyst. A variety of ketones and aldehydes, including propyl and butyl ketones, were coupled efficiently, yielding the corresponding aldol-Tishchenko products in up to 96% yield and 95% ee. Diastereoselectivity was generally below the detection limit of 1H NMR (>98:2). Preliminary studies performed to clarify the mechanism revealed that the aldol products were racemic with no diastereoselectivity. On the other hand, the Tishchenko products were obtained in a highly enantiocontrolled manner.

  4. Asymmetric H-D exchange reactions of fluorinated aromatic ketones

    KAUST Repository

    Zhao, Yujun

    2012-01-01

    Chiral bicyclic guanidine catalyzes the asymmetric H-D exchange reactions. Up to 30% ee was achieved. DFT calculations were employed to elucidate and explain the origin of the reaction\\'s stereoselectivity. © 2012 The Royal Society of Chemistry.

  5. Asymmetric H-D exchange reactions of fluorinated aromatic ketones

    KAUST Repository

    Zhao, Yujun; Lim, XiaoZhi; Pan, Yuanhang; Zong, Lili; Feng, Wei; Tan, Choonhong; Huang, Kuo-Wei

    2012-01-01

    Chiral bicyclic guanidine catalyzes the asymmetric H-D exchange reactions. Up to 30% ee was achieved. DFT calculations were employed to elucidate and explain the origin of the reaction's stereoselectivity. © 2012 The Royal Society of Chemistry.

  6. 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)

  7. Metal Chelation in Asymmetric Diels-Alder Reaction (II)

    International Nuclear Information System (INIS)

    Chung, Kyoo Hyun; Chu, Chan Kook; Chang, Min Ho

    2004-01-01

    In the reaction, the inverse asymmetric induction has been observed by the use of either monovalent Lewis acids or divalent Lewis acids. The reaction of the acrylate of (S)-ethyl lactate with cyclopentadiene proceeded with 86% endo-S selectivity in the presence of TiCl 4 , divalent Lewis acid, whereas did with 32% endo-R selectivity in the presence of BF 3 ·Et 2 O, monovalent Lewis acid. When a chiral dienophile which was prepared from benzyl ester of (S)-proline or methyl ester of (S)-indoline-2-carboxylic acid was employed in the reaction, a similar diastereofacial selectivity was also observed. Recently, we reported the similar selectivity in the reaction of methyl (2S,5S)-(5-t-butyldimethylsilyloxypiperidin- 2-yl)ethanoatewith cyclopentadiene.

  8. Asymmetric aza-Diels-Alder reaction of Danishefsky's diene with imines in a chiral reaction medium

    Directory of Open Access Journals (Sweden)

    Pégot Bruce

    2006-09-01

    Full Text Available Abstract The asymmetric aza-Diels-Alder reaction of chiral imines with Danishefsky's diene in chiral ionic liquids provides the corresponding cycloadduct with moderate to high diastereoselectivity. The reaction has proved to perform better at room temperature in ionic liquids without either Lewis acid catalyst or organic solvent. Chiral ionic liquids are recycled while their efficiency is preserved.

  9. Asymmetric Stetter reactions catalyzed by thiamine diphosphate-dependent enzymes.

    Science.gov (United States)

    Kasparyan, Elena; Richter, Michael; Dresen, Carola; Walter, Lydia S; Fuchs, Georg; Leeper, Finian J; Wacker, Tobias; Andrade, Susana L A; Kolter, Geraldine; Pohl, Martina; Müller, Michael

    2014-12-01

    The intermolecular asymmetric Stetter reaction is an almost unexplored transformation for biocatalysts. Previously reported thiamine diphosphate (ThDP)-dependent PigD from Serratia marcescens is the first enzyme identified to catalyze the Stetter reaction of α,β-unsaturated ketones (Michael acceptor substrates) and α-keto acids. PigD is involved in the biosynthesis of the potent cytotoxic agent prodigiosin. Here, we describe the investigation of two new ThDP-dependent enzymes, SeAAS from Saccharopolyspora erythraea and HapD from Hahella chejuensis. Both show a high degree of homology to the amino acid sequence of PigD (39 and 51 %, respectively). The new enzymes were heterologously overproduced in Escherichia coli, and the yield of soluble protein was enhanced by co-expression of the chaperone genes groEL/ES. SeAAS and HapD catalyze intermolecular Stetter reactions in vitro with high enantioselectivity. The enzymes possess a characteristic substrate range with respect to Michael acceptor substrates. This provides support for a new type of ThDP-dependent enzymatic activity, which is abundant in various species and not restricted to prodigiosin biosynthesis in different strains. Moreover, PigD, SeAAS, and HapD are also able to catalyze asymmetric carbon-carbon bond formation reactions of aldehydes and α-keto acids, resulting in 2-hydroxy ketones.

  10. Asymmetric fission of 47V induced by the 23Na+24Mg reaction

    International Nuclear Information System (INIS)

    Beck, C.; Djerroud, B.; Haas, F.; Freeman, R.M.; Hachem, A.; Heusch, B.; Morsad, A.; Vuillet-A-Cilles, M.; Sanders, S.J.

    1993-01-01

    The properties of fully energy-damped processes (deep-inelastic orbiting, fusion-evaporation, and fusion-fission processes) have been investigated in the nearly mass-symmetric entrance-channel 23 Na + 24 Mg reaction leading to the 47 V compound nucleus. By comparison with previous data for the mass-asymmetric 35 Cl + 12 C reaction forming the same compound system at the same excitation energy, no entrance-channel effects are observed in either the evaporation residue or the fusion-fission yields. This is in contrast to the situation with the 28 Si + 12 C and 24 Mg + 16 O reactions where an orbiting process is evident. The asymmetrical elemental distributions of the fusion-fission fragments of the massA=47 system are well described by a transition-state model that accounts for the spin and mass-asymmetry dependence of the fission saddle point

  11. Enhancement of nuclear reaction rates in asymmetric binary ionic mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Clerouin, J.; Arnault, P.; Desbiens, N. [CEA, DAM, DIF, Arpajon (France); White, A.; Ticknor, C.; Kress, J.D.; Collins, L.A. [Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM (United States)

    2017-11-15

    Using orbital-free molecular dynamics simulations we study the structure and dynamics of increasingly asymmetric mixtures such as hydrogen-carbon, hydrogen-aluminium, hydrogen-copper, and hydrogen-silver. We show that, whereas the heavy component structure is close to an effective one-component plasma (OCP), the light component appears more structured than the corresponding OCP. This effect is related to the crossover towards a Lorentz-type diffusion triggered by strongly coupled, highly charged heavy ions, and witnessed by the change of temperature scaling laws of diffusion. This over-correlation translates into an enhancement of nuclear reaction rates much higher than its classical OCP counterpart. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  12. Asymmetric Horner-Wadsworth-Emmons Reactions with meso-Dialdehydes: Scope, Mechanism, and Synthetic Applications

    DEFF Research Database (Denmark)

    Rein, Tobias; Vares, Lauri; Kawasaki, Ikuo

    1999-01-01

    Asymmetric Homer-Wadsworth-Emmons reactions between chiral phosphonate reagents and various meso-dialdehydes have been investigated. A mechanistic model useful for rationalizing the experimentally observed stereoselectivities is presented. Furthermore; strategies for applying these reactions...

  13. Metal-catalyzed Asymmetric Hetero-Diels-Alder Reactions of Unactivated Dienes with Glyoxylates

    DEFF Research Database (Denmark)

    Johannsen, Mogens; Yao, Sulan; Graven, Anette

    1998-01-01

    The development of a catalytic asymmetric hetero-Diels-Alder methodology for the reaction of unactivated dienes with glyoxylates is presented. Several different asymmetric catalysts can be used, but copper-bisoxazolines and aluminium-BINOL give the highest yield, and the best chemo...

  14. Tourist Demand Reactions: Symmetric or Asymmetric across the Business Cycle?

    Science.gov (United States)

    Bronner, Fred; de Hoog, Robert

    2017-09-01

    Economizing and spending priorities on different types of vacations are investigated during two periods: an economic downturn and returning prosperity. Two nation-wide samples of vacationers are used: one during a downturn, the other one at the start of the recovery period. Through comparing the results, conclusions can be drawn about symmetric or asymmetric tourist demand across the business cycle. The main summer holiday has an asymmetric profile: being fairly crisis-resistant during a recession and showing considerable growth during an expansion. This does not apply to short vacations and day trips, each having a symmetric profile: during a recession they experience substantial reductions and during expansion comparable growth. So when talking about tourist demand in general , one cannot say that it is symmetric or asymmetric across the business cycle: it depends on the type of vacation. Differences in tourist demand are best explained by the role of Quality-of-Life for vacationers.

  15. Catalytic asymmetric diels-alder reaction of quinone imine ketals: a site-divergent approach.

    Science.gov (United States)

    Hashimoto, Takuya; Nakatsu, Hiroki; Maruoka, Keiji

    2015-04-07

    The catalytic asymmetric Diels-Alder reaction of quinone imine ketals with diene carbamates catalyzed by axially chiral dicarboxylic acids is reported herein. A variety of primary and secondary alkyl-substituted quinone derivatives which have not been applied in previous asymmetric quinone Diels-Alder reactions could be employed using this method. More importantly, we succeeded in developing a strategy to divert the reaction site in unsymmetrical 3-alkyl quinone imine ketals from the inherently favored unsubstituted C=C bond to the disfavored alkyl-substituted C=C bond. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Asymmetric Diels-Alder reactions with 5-menthyloxy-2(5H)-furanones

    NARCIS (Netherlands)

    Jong, Johannes Cornelis de

    2006-01-01

    At the beginning of the reseach described in this thesis the catalytic asymmetric Diels-Alder reaction had scarcely been investigated. No good catalytic processes with high enantiomeric excess were known at that time. At the same time the Diels-Alder reactions with chiral dienophiles needed further

  17. Fission dynamics of superheavy nuclei formed in uranium induced reactions

    International Nuclear Information System (INIS)

    Gurjit Kaur; Sandhu, Kirandeep; Sharma, Manoj K.

    2017-01-01

    The compound nuclear system follows symmetric fission if the competing processes such as quasi-elastic, deep inelastic, quasi-fission etc are absent. The contribution of quasi fission events towards the fusion-fission mechanism depends on the entrance channel asymmetry of reaction partners, deformations and orientations of colliding nuclei beside the dependence on energy and angular momentum. Usually the 209 Bi and 208 Pb targets are opted for the production of superheavy nuclei with Z CN =104-113. The nuclei in same mass/charge range can also be synthesized using actinide targets + light projectiles (i.e. asymmetric reaction partners) via hot fusion interactions. These actinide targets are prolate deformed which prefer the compact configurations at above barrier energies, indicating the occurrence of symmetric fission events. Here an attempt is made to address the dynamics of light superheavy system (Z CN =104-106), formed via hot fusion interactions involving actinide targets

  18. Propulsion of a Molecular Machine by Asymmetric Distribution of Reaction Products

    Science.gov (United States)

    Golestanian, Ramin; Liverpool, Tanniemola B.; Ajdari, Armand

    2005-06-01

    A simple model for the reaction-driven propulsion of a small device is proposed as a model for (part of) a molecular machine in aqueous media. The motion of the device is driven by an asymmetric distribution of reaction products. The propulsive velocity of the device is calculated as well as the scale of the velocity fluctuations. The effects of hydrodynamic flow as well as a number of different scenarios for the kinetics of the reaction are addressed.

  19. A nanojet: propulsion of a molecular machine by an asymmetric distribution of reaction--products

    Science.gov (United States)

    Liverpool, Tanniemola; Golestanian, Ramin; Ajdari, Armand

    2006-03-01

    A simple model for the reaction-driven propulsion of a small device is proposed as a model for (part of) a molecular machine in aqueous media. Motion of the device is driven by an asymmetric distribution of reaction products. We calculate the propulsive velocity of the device as well as the scale of the velocity fluctuations. We also consider the effects of hydrodynamic flow as well as a number of different scenarios for the kinetics of the reaction.

  20. Directed transverse flow and its disappearance for asymmetric reactions

    International Nuclear Information System (INIS)

    Lovejot; Gautam, S.

    2014-01-01

    We study the directed transverse flow for mass asymmetry reactions. This is done by keeping the target fixed and varying the projectile mass from 4 He to 131 Xe. We find that directed transverse flow is sensitive to the mass of the projectile. We also study the disappearance of flow at a particular impact parameter called Geometry of Vanishing Flow (GVF) for such mass asymmetry reactions. Our results indicate that GVF is sensitive to the beam energy as well as to the mass of the projectile.

  1. Heavy residues from very mass asymmetric heavy ion reactions

    International Nuclear Information System (INIS)

    Hanold, K.A.

    1994-08-01

    The isotopic production cross sections and momenta of all residues with nuclear charge (Z) greater than 39 from the reaction of 26, 40, and 50 MeV/nucleon 129 Xe + Be, C, and Al were measured. The isotopic cross sections, the momentum distribution for each isotope, and the cross section as a function of nuclear charge and momentum are presented here. The new cross sections are consistent with previous measurements of the cross sections from similar reaction systems. The shape of the cross section distribution, when considered as a function of Z and velocity, was found to be qualitatively consistent with that expected from an incomplete fusion reaction mechanism. An incomplete fusion model coupled to a statistical decay model is able to reproduce many features of these reactions: the shapes of the elemental cross section distributions, the emission velocity distributions for the intermediate mass fragments, and the Z versus velocity distributions. This model gives a less satisfactory prediction of the momentum distribution for each isotope. A very different model based on the Boltzman-Nordheim-Vlasov equation and which was also coupled to a statistical decay model reproduces many features of these reactions: the shapes of the elemental cross section distributions, the intermediate mass fragment emission velocity distributions, and the Z versus momentum distributions. Both model calculations over-estimate the average mass for each element by two mass units and underestimate the isotopic and isobaric widths of the experimental distributions. It is shown that the predicted average mass for each element can be brought into agreement with the data by small, but systematic, variation of the particle emission barriers used in the statistical model. The predicted isotopic and isobaric widths of the cross section distributions can not be brought into agreement with the experimental data using reasonable parameters for the statistical model

  2. High-Throughput Screening of the Asymmetric Decarboxylative Alkylation Reaction of Enolate-Stabilized Enol Carbonates

    KAUST Repository

    Stoltz, Brian

    2010-06-14

    The use of high-throughput screening allowed for the optimization of reaction conditions for the palladium-catalyzed asymmetric decarboxylative alkylation reaction of enolate-stabilized enol carbonates. Changing to a non-polar reaction solvent and to an electron-deficient PHOX derivative as ligand from our standard reaction conditions improved the enantioselectivity for the alkylation of a ketal-protected,1,3-diketone-derived enol carbonate from 28% ee to 84% ee. Similar improvements in enantioselectivity were seen for a β-keto-ester derived- and an α-phenyl cyclohexanone-derived enol carbonate.

  3. High-Throughput Screening of the Asymmetric Decarboxylative Alkylation Reaction of Enolate-Stabilized Enol Carbonates

    KAUST Repository

    Stoltz, Brian; McDougal, Nolan; Virgil, Scott

    2010-01-01

    The use of high-throughput screening allowed for the optimization of reaction conditions for the palladium-catalyzed asymmetric decarboxylative alkylation reaction of enolate-stabilized enol carbonates. Changing to a non-polar reaction solvent and to an electron-deficient PHOX derivative as ligand from our standard reaction conditions improved the enantioselectivity for the alkylation of a ketal-protected,1,3-diketone-derived enol carbonate from 28% ee to 84% ee. Similar improvements in enantioselectivity were seen for a β-keto-ester derived- and an α-phenyl cyclohexanone-derived enol carbonate.

  4. Asymmetric Formal Aza-Diels-Alder Reaction of Trifluoromethyl Hemiaminals with Enones Catalyzed by Primary Amines.

    Science.gov (United States)

    Zhang, Sheng; Cha, Lide; Li, Lijun; Hu, Yanbin; Li, Yanan; Zha, Zhenggen; Wang, Zhiyong

    2016-04-15

    A primary amine-catalyzed asymmetric formal aza-Diels-Alder reaction of trifluoromethyl hemiaminals with enones was developed via a chiral gem-diamine intermediate. This novel protocol allowed facile access to structurally diverse trifluoromethyl-substituted piperidine scaffolds with high stereoselectivity. The utility of this method was further demonstrated through a concise approach to biologically active 4-hydroxypiperidine. More importantly, a stepwise mechanism involving an asymmetric induction process was proposed to rationalize the positive correlation between the chirality of the gem-diamine intermediate and the formal aza-Diels-Alder product.

  5. Chiral PEPPSI Complexes: Synthesis, Characterization, and Application in Asymmetric Suzuki–Miyaura Coupling Reactions

    KAUST Repository

    Benhamou, Laure

    2014-01-13

    PEPPSI complexes incorporating chiral N-heterocyclic carbene (NHC) ligands based on 2,2-dimethyl-1-(o-substituted aryl)propan-1-amines were synthesized. Two complexes, with one saturated and one unsaturated NHC ligand, were structurally characterized. The chiral PEPPSI complexes were used in asymmetric Suzuki-Miyaura reactions, giving atropisomeric biaryl products in modest to good enantiomeric ratios. © 2013 American Chemical Society.

  6. Chiral PEPPSI Complexes: Synthesis, Characterization, and Application in Asymmetric Suzuki–Miyaura Coupling Reactions

    KAUST Repository

    Benhamou, Laure; Besnard, Cé line; Kü ndig, E. Peter

    2014-01-01

    PEPPSI complexes incorporating chiral N-heterocyclic carbene (NHC) ligands based on 2,2-dimethyl-1-(o-substituted aryl)propan-1-amines were synthesized. Two complexes, with one saturated and one unsaturated NHC ligand, were structurally characterized. The chiral PEPPSI complexes were used in asymmetric Suzuki-Miyaura reactions, giving atropisomeric biaryl products in modest to good enantiomeric ratios. © 2013 American Chemical Society.

  7. Enantioconvergent synthesis by sequential asymmetric Horner-Wadsworth-Emmons and palladium-catalyzed allylic substitution reactions

    DEFF Research Database (Denmark)

    Pedersen, Torben Møller; Hansen, E. Louise; Kane, John

    2001-01-01

    A new method for enantioconvergent synthesis has been developed. The strategy relies on the combination of an asymmetric Horner-Wadsworth-Emmons (HWE) reaction and a palladium-catalyzed allylic substitution. Different $alpha@-oxygen-substituted, racemic aldehydes were initially transformed by asy...... the allylic stereocenter and the alkene geometry. Thus, a single $gamma@-substituted ester was obtained as the overall product, in high isomeric purity. The method was applied to a synthesis of a subunit of the iejimalides, a group of cytotoxic macrolides.......A new method for enantioconvergent synthesis has been developed. The strategy relies on the combination of an asymmetric Horner-Wadsworth-Emmons (HWE) reaction and a palladium-catalyzed allylic substitution. Different $alpha@-oxygen-substituted, racemic aldehydes were initially transformed...... by asymmetric HWE reactions into mixtures of two major $alpha@,$beta@-unsaturated esters, possessing opposite configurations at their allylic stereocenters as well as opposite alkene geometry. Subsequently, these isomeric mixtures of alkenes could be subjected to palladium-catalyzed allylic substitution...

  8. Catalytic Asymmetric Total Synthesis of (+)- and (-)-Paeoveitol via a Hetero-Diels-Alder Reaction.

    Science.gov (United States)

    Li, Tian-Ze; Geng, Chang-An; Yin, Xiu-Juan; Yang, Tong-Hua; Chen, Xing-Long; Huang, Xiao-Yan; Ma, Yun-Bao; Zhang, Xue-Mei; Chen, Ji-Jun

    2017-02-03

    The first catalytic asymmetric total synthesis of (+)- and (-)-paeoveitol has been accomplished in 42% overall yield via a biomimetic hetero-Diels-Alder reaction. The chiral phosphoric acid catalyzed hetero-Diels-Alder reaction showed excellent diastereo- and enantioselectivity (>99:1 dr and 90% ee); two rings and three stereocenters were constructed in a single step to produce (-)-paeoveitol on a scale of 452 mg. This strategy enabled us to selectively synthesize both paeoveitol enantiomers from the same substrates by simply changing the enantiomer of the catalyst.

  9. Biodiesel forming reactions using heterogeneous catalysis

    Science.gov (United States)

    Liu, Yijun

    Biodiesel synthesis from biomass provides a means for utilizing effectively renewable resources, a way to convert waste vegetable oils and animal fats to a useful product, a way to recycle carbon dioxide for a combustion fuel, and production of a fuel that is biodegradable, non-toxic, and has a lower emission profile than petroleum-diesel. Free fatty acid (FFA) esterification and triglyceride (TG) transesterification with low molecular weight alcohols constitute the synthetic routes to prepare biodiesel from lipid feedstocks. This project was aimed at developing a better understanding of important fundamental issues involved in heterogeneous catalyzed biodiesel forming reactions using mainly model compounds, representing part of on-going efforts to build up a rational base for assay, design, and performance optimization of solid acids/bases in biodiesel synthesis. As FFA esterification proceeds, water is continuously formed as a byproduct and affects reaction rates in a negative manner. Using sulfuric acid (as a catalyst) and acetic acid (as a model compound for FFA), the impact of increasing concentrations of water on acid catalysis was investigated. The order of the water effect on reaction rate was determined to be -0.83. Sulfuric acid lost up to 90% activity as the amount of water present increased. The nature of the negative effect of water on esterification was found to go beyond the scope of reverse hydrolysis and was associated with the diminished acid strength of sulfuric acid as a result of the preferential solvation by water molecules of its catalytic protons. The results indicate that as esterification progresses and byproduct water is produced, deactivation of a Bronsted acid catalyst like H2SO4 occurs. Using a solid composite acid (SAC-13) as an example of heterogeneous catalysts and sulfuric acid as a homogeneous reference, similar reaction inhibition by water was demonstrated for homogeneous and heterogeneous catalysis. This similarity together with

  10. Correction: Synthesis of pyrrolidine-3-carboxylic acid derivatives via asymmetric Michael addition reactions of carboxylate-substituted enones.

    Science.gov (United States)

    Yin, Feng; Garifullina, Ainash; Tanaka, Fujie

    2018-04-25

    Correction for 'Synthesis of pyrrolidine-3-carboxylic acid derivatives via asymmetric Michael addition reactions of carboxylate-substituted enones' by Feng Yin et al., Org. Biomol. Chem., 2017, 15, 6089-6092.

  11. Direct Enantioselective Reaction between Hemiacetals and Phosphorus Ylides: Important Role of a By-Product in the Asymmetric Transformation.

    Science.gov (United States)

    Wang, Rui; Wang, Linqing; Yang, Dongxu; Li, Dan; Liu, Xihong; Wang, Pengxin; Wang, Kezhou; Zhu, Haiyong; Bai, Lutao

    2018-05-16

    By employing a simple in-situ generated magnesium catalyst, the direct asymmetric reaction between hemiacetals and P-ylides is achieved via a tandem Wittig-oxa-Michael reaction sequence. Enantioenriched chromans, isochromans and tetrahydropyrans can be obtained in good chemical yields. (-)-Erythrococcamide B can be asymmetrically synthesized through this synthetic technique. In this work, the by-product, TPO, was identified as a necessary additive in this asymmetric synthetic method. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Principles of asymmetric synthesis

    CERN Document Server

    Gawley, Robert E; Aube, Jeffrey

    2012-01-01

    The world is chiral. Most of the molecules in it are chiral, and asymmetric synthesis is an important means by which enantiopure chiral molecules may be obtained for study and sale. Using examples from the literature of asymmetric synthesis, this book presents a detailed analysis of the factors that govern stereoselectivity in organic reactions. After an explanation of the basic physical-organic principles governing stereoselective reactions, the authors provide a detailed, annotated glossary of stereochemical terms. A chapter on "Practical Aspects of Asymmetric Synthesis" provides a critical overview of the most common methods for the preparation of enantiomerically pure compounds, techniques for analysis of stereoisomers using chromatographic, spectroscopic, and chiroptical methods. The authors then present an overview of the most important methods in contemporary asymmetric synthesis organized by reaction type. Thus, there are four chapters on carbon-carbon bond forming reactions, one chapter on reductions...

  13. Influence of Asymmetric Contact Form on Contact Resistance and Schottky Barrier, and Corresponding Applications of Diode.

    Science.gov (United States)

    Zhao, Yudan; Xiao, Xiaoyang; Huo, Yujia; Wang, Yingcheng; Zhang, Tianfu; Jiang, Kaili; Wang, Jiaping; Fan, Shoushan; Li, Qunqing

    2017-06-07

    We have fabricated carbon nanotube and MoS 2 field-effect transistors with asymmetric contact forms of source-drain electrodes, from which we found the current directionality of the devices and different contact resistances under the two current directions. By designing various structures, we can conclude that the asymmetric electrical performance was caused by the difference in the effective Schottky barrier height (Φ SB ) caused by the different contact forms. A detailed temperature-dependent study was used to extract and compare the Φ SB for both contact forms of CNT and MoS 2 devices; we found that the Φ SB for the metal-on-semiconductor form was much lower than that of the semiconductor-on-metal form and is suitable for all p-type, n-type, or ambipolar semiconductors. This conclusion is meaningful with respect to the design and application of nanomaterial electronic devices. Additionally, using the difference in barrier height caused by the contact forms, we have also proposed and fabricated Schottky barrier diodes with a current ratio up to 10 4 ; rectifying circuits consisting of these diodes were able to work in a wide frequency range. This design avoided the use of complex chemical doping or heterojunction methods to achieve fundamental diodes that are relatively simple and use only a single material; these may be suitable for future application in nanoelectronic radio frequency or integrated circuits.

  14. Linear regression analysis of potentiometric titration data for asymmetric redox reactions

    International Nuclear Information System (INIS)

    Mar'yanov, B.M.; Gavrilenko, M.A.

    1997-01-01

    A statistical method of processing the curves of potentiometric titration for homogeneous asymmetric redox reactions has been suggested. The method was tested using a model titrimetric system Mohr's salt-K 2 Cr 2 O 7 and was employed for Te determination in an individual solution, semiconductor alloy and CdTe ceramics. Random error of the equivalence point evaluation by the data of a specific titration of 0.1-0.01 M solutions does not exceed 0.3% in case of titration of 0.001 M solutions it increases up to 1.2%. The value of s r varies from 0.0006 to 0.007

  15. Using chiral ionic liquid additives to enhance asymmetric induction in a Diels-Alder reaction.

    Science.gov (United States)

    Goodrich, P; Nimal Gunaratne, H Q; Hall, L; Wang, Y; Jin, L; Muldoon, M J; Ribeiro, A P C; Pombeiro, A J L; Pârvulescu, V I; Davey, P; Hardacre, C

    2017-01-31

    A bis-oxazoline ligand has been complexed using Cu(ii) and Zn(ii) trifluoromethanesulfonate and a range of chiral ionic liquid (CIL) additives based on natural products were used as a co-catalyst for a Diels-Alder reaction. The catalytic performance of these systems was compared for the asymmetric Diels-Alder reaction between N-acryloyloxazolidinone and cyclopentadiene with and without the presence of a CIL additive. In the absence of the CIL, both catalysts resulted in low enantioselectivities in conventional solvents and ionic liquids. However, whilst only a minor effect of the CIL was observed for the Cu based catalyst, in the case of the Zn based catalyst, significant enhancements in endo enantioselectivity of up to 50% were found on the addition of a CIL.

  16. A Ligand Structure-Activity Study of DNA-Based Catalytic Asymmetric Hydration and Diels-Alder Reactions

    NARCIS (Netherlands)

    Rosati, F.; Roelfes, J.G.

    A structure-activity relationship study of the first generation ligands for the DNA-based asymmetric hydration of enones and Diels-Alder reaction in water is reported. The design of the ligand was optimized resulting in a maximum ee of 83% in the hydration reaction and 75% in the Diels-Alder

  17. Enantioselective syntheses and biological studies of aeruginosin 298-A and its analogs: application of catalytic asymmetric phase-transfer reaction.

    Science.gov (United States)

    Fukuta, Yuhei; Ohshima, Takashi; Gnanadesikan, Vijay; Shibuguchi, Tomoyuki; Nemoto, Tetsuhiro; Kisugi, Takaya; Okino, Tatsufumi; Shibasaki, Masakatsu

    2004-04-13

    Aeruginosin 298-A was isolated from the freshwater cyanobacterium Microcystis aeruginosa (NIES-298) and is an equipotent thrombin and trypsin inhibitor. A variety of analogs were synthesized to gain insight into the structure-activity relations. We developed a versatile synthetic process for aeruginosin 298-A as well as several attractive analogs, in which all stereocenters were controlled by catalytic asymmetric phase-transfer reaction promoted by two-center asymmetric catalysts and catalytic asymmetric epoxidation promoted by a lanthanide-BINOL complex. Furthermore, serine protease inhibitory activities of aeruginosin 298-A and its analogs were examined.

  18. Study of fusion reactions forming Cf nuclei

    International Nuclear Information System (INIS)

    Khuyagbaatar, J.; Hinde, D. J.; Du Rietz, R.; Carter, I. P.; Dasgupta, M.; Duellmann, C. E.; Evers, M.; Wakhle, A.; Williams, E.; Yakushev, A.

    2013-01-01

    The formation of a compound nucleus in different projectile and target combinations is a powerful method for investigating the fusion process. Recently, the dominance of quasi-fission over fusion-fission has been inferred for 34 S+ 208 Pb in comparison to 36 S+ 206 Pb; both reactions lead to the compound nucleus 242 Cf*.The mass and angle distributions of the fission fragments from these reactions were studied in order to further investigate the presence of quasi-fission. (authors)

  19. Asynchronous asymmetric form of heterogeneous osteopetrosis: initial case expanded and a new case

    International Nuclear Information System (INIS)

    Young, L.W.; Lachman, R.S.

    2001-01-01

    We have discovered additional serial radiographs and clinical information on the initial case of ''regional osteopetrosis tarda'' that has been included in several editions of Caffey's Pediatric X-Ray Diagnosis. A definite second case was found after a search of radiology teaching files of other selected medical centers and the International Skeletal Dysplasia Registry. Analysis of the sequential unusual radiographic findings of the initial case and the equivalent compelling findings of the second case justifies renewed attention to an asynchronous asymmetric form of heterogeneous osteopetrosis. (orig.)

  20. Pronounced Photovoltaic Response from Multi-layered MoTe2 Phototransistor with Asymmetric Contact Form.

    Science.gov (United States)

    Liu, Junku; Guo, Nan; Xiao, Xiaoyang; Zhang, Kenan; Jia, Yi; Zhou, Shuyun; Wu, Yang; Li, Qunqing; Xiao, Lin

    2017-11-22

    In this study, we fabricate air-stable p-type multi-layered MoTe 2 phototransistor using Au as electrodes, which shows pronounced photovoltaic response in off-state with asymmetric contact form. By analyzing the spatially resolved photoresponse using scanning photocurrent microscopy, we found that the potential steps are formed in the vicinity of the electrodes/MoTe 2 interface due to the doping of the MoTe 2 by the metal contacts. The potential step dominates the separation of photoexcited electron-hole pairs in short-circuit condition or with small V sd biased. Based on these findings, we infer that the asymmetric contact cross-section between MoTe 2 -source and MoTe 2 -drain electrodes is the reason to form non-zero net current and photovoltaic response. Furthermore, MoTe 2 phototransistor shows a faster response in short-circuit condition than that with higher biased V sd within sub-millisecond, and its spectral range can be extended to the infrared end of 1550 nm.

  1. Probing short-range correlations in asymmetric nuclei with quasi-free pair knockout reactions

    Science.gov (United States)

    Stevens, Sam; Ryckebusch, Jan; Cosyn, Wim; Waets, Andreas

    2018-02-01

    Short-range correlations (SRC) in asymmetric nuclei with an unusual neutron-to-proton ratio can be studied with quasi-free two-nucleon knockout processes following the collision between accelerated ions and a proton target. We derive an approximate factorized cross section for those SRC-driven p (A ,p‧N1N2) reactions. Our reaction model hinges on the factorization properties of SRC-driven A (e ,e‧N1N2) reactions for which strong indications are found in theory-experiment comparisons. In order to put our model to the test we compare its predictions with results of 12C (p ,p‧ pn) measurements conducted at Brookhaven National Laboratory (BNL) and find a fair agreement. The model can also reproduce characteristic features of SRC-driven two-nucleon knockout reactions, like back-to-back emission of the correlated nucleons. We study the asymmetry dependence of nuclear SRC by providing predictions for the ratio of proton-proton to proton-neutron knockout cross sections for the carbon isotopes 9-15C thereby covering neutron excess values (N - Z) / Z between -0.5 and +0.5.

  2. Asymmetric Construction of Benzindoloquinolizidine: Application of An Organocatalytic Enantioselective Conjugate Addition-Cyclization Cascade Reaction

    International Nuclear Information System (INIS)

    Kim, Cheolwoong; Seo, Seung Woo; Lee, Yona; Kim, Sunggon

    2014-01-01

    We have developed the synthetic methodology of enantioenriched benzindoloquinolizidines based on the organocatalytic enantioselective conjugate addition-cyclization cascade reaction of o-N-(3-indoleacetyl)amino-cinnamaldehydes with malonates followed by an acid-catalyzed intramolecular Pictet-Spengler type cyclization. The asymmetric reaction using diphenylprolinol TMS ether as an organocatalyst produces the desired products with good to excellent yields and high enantioselectivities (up to 98% ee). The evaluation of the applications of this synthetic methodology for generating enantioenriched benzindolo-quinolizidines and studies on the biological activity of these compounds against human prostate cancer in particular are now in progress. Results of these studies will be presented in due course. Many new types of chemical reactions have been developed to facilitate easier synthesis of complex compounds. Among the strategies, domino reactions, which have been utilized for the efficient and stereoselective construction of complex molecules from simple precursors in a single process, are widely used due to their high synthetic efficiency by reducing both the number of synthetic operation required and the quantities of chemicals and solvents used

  3. Asymmetric Benzylic Allylic Alkylation Reaction of 3-Furfural Derivatives by Dearomatizative Dienamine Activation.

    Science.gov (United States)

    He, Xiao-Long; Zhao, Hui-Ru; Duan, Chuan-Qi; Han, Xu; Du, Wei; Chen, Ying-Chun

    2018-04-20

    The dearomatizative dienamine-type ortho-quinodimethane species are smoothly generated between 2-alkyl-3-furfurals and chiral secondary amine catalysts, which undergo asymmetric benzylic allylic alkylation reactions with 2-nitroallylic acetates efficiently. A spectrum of densely functionalized 3-furfural derivatives are delivered in moderate to high yields with good to excellent diastereo- and enantioselectivity (up to 98 % yield, >19:1 d.r., >99 % ee). The latent transformations allow the facile production of some enantioenriched architectures, such as 1,1,2,2-tetraarylethanes and triarylmethanes, which are not easily available from other protocols. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Evolution of magnetization due to asymmetric dimerization: theoretical considerations and application to aberrant oligomers formed by apoSOD1(2SH).

    Science.gov (United States)

    Sekhar, Ashok; Bain, Alex D; Rumfeldt, Jessica A O; Meiering, Elizabeth M; Kay, Lewis E

    2016-02-17

    A set of coupled differential equations is presented describing the evolution of magnetization due to an exchange reaction whereby a pair of identical monomers form an asymmetric dimer. In their most general form the equations describe a three-site exchange process that reduces to two-site exchange under certain limiting conditions that are discussed. An application to the study of sparsely populated, transiently formed sets of aberrant dimers, symmetric and asymmetric, of superoxide dismutase is presented. Fits of concentration dependent CPMG relaxation dispersion profiles provide measures of the dimer dissociation constants and both on- and off-rates. Dissociation constants on the order of 70 mM are extracted from fits of the data, with dimeric populations of ∼2% and lifetimes of ∼6 and ∼2 ms for the symmetric and asymmetric complexes, respectively. This work emphasizes the important role that NMR relaxation experiments can play in characterizing very weak molecular complexes that remain invisible to most biophysical approaches.

  5. Methods for forming complex oxidation reaction products including superconducting articles

    International Nuclear Information System (INIS)

    Rapp, R.A.; Urquhart, A.W.; Nagelberg, A.S.; Newkirk, M.S.

    1992-01-01

    This patent describes a method for producing a superconducting complex oxidation reaction product of two or more metals in an oxidized state. It comprises positioning at least one parent metal source comprising one of the metals adjacent to a permeable mass comprising at least one metal-containing compound capable of reaction to form the complex oxidation reaction product in step below, the metal component of the at least one metal-containing compound comprising at least a second of the two or more metals, and orienting the parent metal source and the permeable mass relative to each other so that formation of the complex oxidation reaction product will occur in a direction towards and into the permeable mass; and heating the parent metal source in the presence of an oxidant to a temperature region above its melting point to form a body of molten parent metal to permit infiltration and reaction of the molten parent metal into the permeable mass and with the oxidant and the at least one metal-containing compound to form the complex oxidation reaction product, and progressively drawing the molten parent metal source through the complex oxidation reaction product towards the oxidant and towards and into the adjacent permeable mass so that fresh complex oxidation reaction product continues to form within the permeable mass; and recovering the resulting complex oxidation reaction product

  6. Application of Carbohydrate-Templated Asymmetric Diels-Alder Reaction to the Syntheses of ent-Penicillones A and B.

    Science.gov (United States)

    Weng, Chia-Hao; Hsu, Day-Shin; Liao, Chun-Chen

    2016-11-18

    Total syntheses of ent-penicillones A (ent-1) and B (ent-2) from 3,5-dimethylcatechol (3) were accomplished in 10 and 9 synthetic steps, respectively. A carbohydrate-templated asymmetric intramolecular Diels-Alder reaction of a masked o-benzoquinone (MOB) 9 and an aqueous acid-catalyzed intramolecular aldol reaction are the key synthetic steps. In addition, the absolute configurations of the bicyclo[2.2.2]oct-5-en-2-one core obtained from the per-O-benzylated α-d-glucopyranosyl as a carbohydrate template in the intramolecular Diels-Alder reaction of MOBs were revised.

  7. Enantioselective syntheses of aeruginosin 298-A and its analogues using a catalytic asymmetric phase-transfer reaction and epoxidation.

    Science.gov (United States)

    Ohshima, Takashi; Gnanadesikan, Vijay; Shibuguchi, Tomoyuki; Fukuta, Yuhei; Nemoto, Tetsuhiro; Shibasaki, Masakatsu

    2003-09-17

    We developed a versatile synthetic process for aeruginosin 298-A as well as several attractive analogues, in which all stereocenters were controlled by a catalytic asymmetric phase-transfer reaction and epoxidation. Furthermore, drastic counteranion effects in phase-transfer catalysis were observed for the first time, making it possible to three-dimensionally fine-tune the catalyst (ketal part, aromatic part, and counteranion).

  8. Organoplatinum complex promoted the asymmetric endo stereochemically controlled Diels-Alder reaction between 3-diphenylphosphinofuran and diphenylvinylphosphine.

    Science.gov (United States)

    Liu, Fengli; Pullarkat, Sumod A; Tan, Kien-Wee; Li, Yongxin; Leung, Pak-Hing

    2009-12-07

    The organoplatinum complex containing ortho-metalated (R)-(1-(dimethylamino)ethyl)-naphthalene as the chiral auxiliary has been used efficiently to promote the asymmetric [4 + 2] Diels-Alder reaction between diphenylvinylphosphine and 3-diphenylphosphinofuran to generate two chelating diphosphine endocycloadducts in the ratio 17:1. The absolute configurations of the three newly generated stereocenters have been assigned by single-crystal X-ray analysis.

  9. DETERMINING SOIL REACTIONS AND THE VALUE OF DEVIATION FROM A LINEAR TRAJECTORY OF ASYMMETRICAL SOIL THRUST WORKING BODY

    Directory of Open Access Journals (Sweden)

    S. Kravets

    2017-12-01

    Full Text Available The construction of underground communications in urban conditions is very difficult due to the large number of existing communications. Thus, it is necessary to change the trajectory of the horizontal well during soil thrust boring. An analytical method for determining soil reactions and the deviation of the trajectory of an asymmetric soil thrust working body, which can be used to correct or control the trajectory during puncture, is suggested.

  10. Form factors in (HI,HI') direct reactions

    International Nuclear Information System (INIS)

    Chu, Y.H.

    1981-01-01

    Using the semiclassical theory, the inelastic transition form factors are analyzed. For the first order form factors, we find that: (i) In the strong absorption limit, the Austern-Blair theory is a good approximation to the inelastic form factor--even in highly mismatched reactions. (ii) In weak to moderate absorption, the amplitude of the inelastic form factor oscillates due to overlapping potential resonances. The internal part of the form factor can be expressed in a simple form, which may easily be used to analyze heavy-ion inelastic scattering. (iii) In the presence of an isolated resonance, the inelastic form factor is enhanced greatly at the resonance due to multiple reflections inside the potential well. The second order form factors contain two terms, i.e. the one-step direct process (OSD) term and the two-step process (TS) term. It is found that: (i) In the strong absorption limit, OSD and TS form factors are equally important and interfere destructively near the grazing angular momentum. The Austern-Blair theory gives satisfactory results for well-matched reactions. The angular distributions of the mutual and double excitations are out of phase compared with that of the single excitation. (ii) For the weak absorption case, the internal part of the TS form factor is so enhanced that the OSD form factor can simply be neglected. The internal TS form factor can be parameterized in a form proportional to the internal-wave elastic Smatrix, where the angular distribution shows characteristically refractive phenomenon

  11. Asymmetric recombination and electron spin relaxation in the semiclassical theory of radical pair reactions

    International Nuclear Information System (INIS)

    Lewis, Alan M.; Manolopoulos, David E.; Hore, P. J.

    2014-01-01

    We describe how the semiclassical theory of radical pair recombination reactions recently introduced by two of us [D. E. Manolopoulos and P. J. Hore, J. Chem. Phys. 139, 124106 (2013)] can be generalised to allow for different singlet and triplet recombination rates. This is a non-trivial generalisation because when the recombination rates are different the recombination process is dynamically coupled to the coherent electron spin dynamics of the radical pair. Furthermore, because the recombination operator is a two-electron operator, it is no longer sufficient simply to consider the two electrons as classical vectors: one has to consider the complete set of 16 two-electron spin operators as independent classical variables. The resulting semiclassical theory is first validated by comparison with exact quantum mechanical results for a model radical pair containing 12 nuclear spins. It is then used to shed light on the spin dynamics of a carotenoid-porphyrin-fullerene triad containing considerably more nuclear spins which has recently been used to establish a “proof of principle” for the operation of a chemical compass [K. Maeda, K. B. Henbest, F. Cintolesi, I. Kuprov, C. T. Rodgers, P. A. Liddell, D. Gust, C. R. Timmel, and P. J. Hore, Nature (London) 453, 387 (2008)]. We find in particular that the intriguing biphasic behaviour that has been observed in the effect of an Earth-strength magnetic field on the time-dependent survival probability of the photo-excited C ·+ PF ·− radical pair arises from a delicate balance between its asymmetric recombination and the relaxation of the electron spin in the carotenoid radical

  12. Polystyrene copolymer supported by substituted (1R,2R)-1,2-diphenylethane-1,2-diamine-copper(II) complexes: a recyclable catalyst for asymmetric Henry reactions

    Czech Academy of Sciences Publication Activity Database

    Androvič, L.; Drabina, P.; Panov, I.; Frumarová, Božena; Kalendová, A.; Sedlák, M.

    2014-01-01

    Roč. 25, č. 9 (2014), s. 775-780 ISSN 0957-4166 Institutional support: RVO:61389013 Keywords : cooper complexes * copolymers * asymmetric Henry reaction Subject RIV: CC - Organic Chemistry Impact factor: 2.155, year: 2014

  13. Copper(I)-Catalyzed Asymmetric Desymmetrization through Inverse-Electron-Demand aza-Diels-Alder Reaction: Efficient Access to Tetrahydropyridazines Bearing a Unique α-Chiral Silane Moiety.

    Science.gov (United States)

    Wei, Liang; Zhou, Yu; Song, Zhi-Min; Tao, Hai-Yan; Lin, Zhenyang; Wang, Chun-Jiang

    2017-04-11

    An unprecedented copper(I)-catalyzed asymmetric desymmetrization of 5-silylcyclopentadienes with in situ formed azoalkene was realized through an inverse-electron-demand aza-Diels-Alder reaction (IEDDA) pathway, in which 5-silylcyclopentadienes served as efficient enophiles. This new protocol provides a facile access to the biologically important heterocyclic tetrahydropyridazines containing a unique α-chiral silane motif and three adjoining stereogenic centers in generally good yield (up to 92 %) with exclusive regioselectivity, high diastereoselectivity (>20:1 diastereomeric ratio), and excellent enantioselectivity (up to 98 % enantiomeric excess). DFT calculations and control experiments further confirmed the proposed reaction mechanism. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Reactions of newly formed fission products in the gas phase

    International Nuclear Information System (INIS)

    Strickert, R.G.

    1976-01-01

    A dynamic gas-flow system was constructed which stopped fission products in the gas phase and rapidly separated (in less than 2 sec) volatile compounds from non-volatile ones. The filter assembly designed and used was shown to stop essentially all non-volatile fission products. Between 5 percent and 20 percent of tellurium fission-product isotopes reacted with several hydrocarbon gases to form volatile compounds, which passed through the filter. With carbon monoxide gas, volatile tellurium compound(s) (probably TeCO) were also formed with similar efficiencies. The upper limits for the yields of volatile compounds formed between CO and tin and antimony fission products were shown to be less than 0.3 percent, so tellurium nuclides, not their precursors, reacted with CO. It was found that CO reacted preferentially with independently produced tellurium atoms; the reaction efficiency of beta-produced atoms was only 27 +- 3 percent of that of the independently formed atoms. The selectivity, which was independent of the over-all reaction efficiency, was shown to be due to reaction of independently formed atoms in the gas phase. The gas phase reactions are believed to occur mainly at thermal energies because of the independence of the yield upon argon moderator mole-fraction (up to 80 percent). It was shown in some experiments that about one-half of the TeCO decomposed in passing through a filter and that an appreciable fraction (approximately 20 percent) of the tellurium atoms deposited on the filter reacted agin with CO. Other tellurium atoms on the filter surface (those formed by beta decay and those formed independently but not reacting in the gas phase) also reacted with CO, but probably somewhat less efficiently than atoms formed by TeCO decomposition. No evidence was found for formation of TeCO as a direct result of beta-decay

  15. Uranium oxidation: characterization of oxides formed by reaction with water

    International Nuclear Information System (INIS)

    Fuller, E.L. Jr.; Smyrl, N.R.; Condon, J.B.; Eager, M.H.

    1983-01-01

    Three different uranium oxide samples have been characterized with respect to the different preparation techniques. Results show that the water reaction with uranium metal occurs cyclically forming laminar layers of oxide which spall off due to the strain at the oxide/metal interface. Single laminae are released if liquid water is present due to the prizing penetration at the reaction zone. The rate of reaction of water with uranium is directly proportional to the amount of adsorbed water on the oxide product. Rapid transport is effected through the open hydrous oxide product. Dehydration of the hydrous oxide irreversibly forms a more inert oxide which cannot be rehydrated to the degree that prevails in the original hydrous product of uranium oxidation with water. 27 figures

  16. Asymmetric Synthesis of P-Chiral Diphosphines. Steric Effects on the Palladium-Complex-Promoted Asymmetric Diels-Alder Reaction between a Dimethylphenylphosphole and (E/Z)-Methyl-Substituted Diphenylvinylphosphines.

    Science.gov (United States)

    Aw, Beng-Hwee; Hor, T. S. Andy; Selvaratnam, S.; Mok, K. F.; White, Andrew J. P.; Williams, David J.; Rees, Nicholas H.; McFarlane, William; Leung, Pak-Hing

    1997-05-07

    The organopalladium complex containing ortho-metalated (S)-(1-(dimethylamino)ethyl)naphthalene as the chiral auxiliary has been used successfully to promote the asymmetric [4+2] Diels-Alder reactions between 1-phenyl-3,4-dimethylphosphole and the following coordinated dienophiles: (a) diphenylvinylphosphine; (b) (E)-diphenyl-1-propenylphosphine; (c) (Z)-diphenyl-1-propenylphosphine. Reaction a generates three carbon and one phosphorus stereogenic centers while reactions b and c each produce four carbon and one phosphorus chiral centers. In dichloromethane, all three reactions proceeded smoothly at room temperature giving the corresponding rigid diphosphines in high yields. Under similar reaction conditions, the reaction times observed for reactions a-c are 2, 3, and 50 h, respectively. Two-dimensional ROESY NMR studies confirmed that the prolonged reaction time required for reaction c is due to several major repulsive interactions between the chiral naphthylamine auxiliary and the (Z)-methyl-substituted vinylphosphine in the transition state. Nevertheless, all three reactions gave the corresponding rigid diphosphine in high yields. The absolute stereochemistries of the three bidentate phosphine ligands that were produced from the cycloaddition reactions have been assigned by 2D ROESY NMR spectroscopy. These diphosphines are powerful sequesterers of group 8 metals although they are highly air-sensitive in the free ligand form. The coordination chemistry and the absolute stereochemistry of the optically active complex [1alpha,4alpha,5alpha(S),6alpha(S),7R]-dichloro[5-(diphenylphosphino)-2,3,6-trimethy-7-phenyl-7-phosphabicyclo[2.2.1]-hept-2-ene-P(5)(),P(7)()]palladium(II) has been studied by single-crystal X-ray analysis. Crystal structure data: C(27)H(28)Cl(2)P(2)Pd, M(r) = 591.7; triclinic; space group P1; a = 8.643(3), b = 9.044(6), c = 9.058(4) Å; alpha = 102.75(4) degrees, beta = 108.59(2) degrees, gamma = 97.82(3) degrees; V = 638.0(5) Å(3); Z = 1; R(1) = 0.036.

  17. 1,2- and 1,3-dihydroxylated and hydroxynitrogenated monoterpenes as chiral ligands in the asymmetric reformatsky reaction

    International Nuclear Information System (INIS)

    Ribeiro, Carlos Magno R.; Morita, Cristina M.; Maia, Monica P.

    2008-01-01

    This study describes the use of three (-)-α-pinene derivatives, one diol-1,2 [(-)- (1R, 2R, 3S, 5R)-2,6,6-trimethylbicyclo[3.1.1]heptane-2,3-diol 4] and two pyridine-hydroxy derivatives [(+)-(1R,2S,3R,5S)-2,6,6- trimethyl-3-(2-pyridinylmethyl)bicyclo[3.1.1]heptane-3-ol 7 and (-)-(1R,2S,3R,5S)-2,6,6-trimethyl-3-[2-(2-pyridinyl) ethyl]bicyclo[3.1.1]heptane-3-ol 8]; one diol-1,3 [(-)-(1S,2R,5S)-2-(1-hydroxy-1-methylethyl)-5-methylcyclohexanol 5] derived from (+)-isopulegol 2 and one diol-1,3 [(+)-(1R,2R,5R)-2-(1-hydroxy-1-methylethyl)-5-methylcyclohexanol 6] derived from (+)-neoisopulegol 3, as ligands in the asymmetric Reformatsky reaction. The best enantiomeric excess of β-hydroxy ester obtained in the Reformatsky asymmetric reaction was 18% using ligand 6, and the chemical yield of the reactions was 65% on average. (author)

  18. Intensification of the Use of Ionic Liquids as Efficient Reaction Co-Solvents in Asymmetric Hydrogenations

    Czech Academy of Sciences Publication Activity Database

    Černá, I.; Klusoň, Petr; Bendová, Magdalena; Floriš, Tomáš; Pelantová, Helena; Pekárek, T.

    2011-01-01

    Roč. 50, č. 3 (2011), s. 264-272 ISSN 0255-2701 R&D Projects: GA AV ČR KAN400720701; GA AV ČR IAA400720710 Institutional research plan: CEZ:AV0Z40720504; CEZ:AV0Z50200510 Keywords : Ionic liquids * asymmetric hydrogenations * BmimPF6 Subject RIV: CI - Industrial Chemistry, Chemical Engineering Impact factor: 1.924, year: 2011

  19. Asymmetric septal hypertrophy of sporadic form with abnormal thallium perfusion and myocardial enzymes

    International Nuclear Information System (INIS)

    Nagata, Seiki; Minamikawa, Tetsuhiro; Park, Yung-Dae; Nishimura, Tsunehiko; Yutani, Chikao; Ohmori, Fumio; Sakakibara, Hiroshi; Nimura, Yasuharu

    1986-01-01

    Asymmetric septal hypertrophy with abnormal thallium scintigram and elevated cardiac enzymes were observed in five patients and were studied with special reference to the clinical significance of their clinicopathological features. They were not familial cardiomyopathy patients. Two of the five patients (Cases 1 and 2) exhibited the clinical features characteristic of hypertrophic cardiomyopathy without abnormal thallium perfusion and serum cardiac enzyme levels. A right endomyocardial biopsy for Case 1 disclosed myocardial fibrosis in addition to hypertrophy and disarray of myocardial fibers. The left ventricular cavities of two other patients (Cases 4 and 5) tended to be dilated with signs of impaired systolic function and asymmetric septal hypertrophy. A regional area of reduced thickness was observed in the medial portion of the left ventricular posterior wall of Case 4. The remaining case (Case 3) exhibited left ventricular dilatation and reduced left ventricular systolic function, disproportionate hypertrophy, and had clinical signs of congestive heart failure. Necropsy disclosed massive fibrosis and diffuse disarray of myocardial fibers. Some patients with familial hypertrophic cardiomyopathy progress to exhibit clinical features of dilated cardiomyopathy in the termimal stages, and have massive fibrosis of the myocardium histologically. Thallium scintigraphic abnormalities and elevated serum levels of cardiac enzymes, especially the LDH 1 isoenzyme, in patients with hypertrophic cardiomyopathy may be a meaningful indicator of such progression in its early stages. The five patients in the present study exhibited a variety of clinical and histological features which may comprise a spectrum of clinical conditions during the progression from hypertrophic cardiomyopathy to a condition like dilated cardiomyopathy, similar to that in familial patients. This progression and the factors promoting it should be studied further in the near future. (author)

  20. Solvent Effects in Asymmetric Hetero Diels-Alder and Ene Reactions

    DEFF Research Database (Denmark)

    Johannsen, Mogens; Jørgensen, Karl Anker

    1996-01-01

    The use of polar solvents such as nitromethane or 2-nitropropane leads to a significant improvement of the catalytic properties of a cationic copper-Lewis acid in the hetero Diels-Alder reaction of alkyl glyoxylates with dienes; The scope of a newly developed copper(II)-bisoxazoline catalyst...... for the hetero Diels-Alder reaction is demonstrated by the reaction of different dienes with alkyl glyoxylates in nitroalkane solvents with the formation of the hetero Diels-Alder adduct in high enantiomeric excess as the major product. The synthetic application of the reaction is exemplified by an improved...

  1. Bifunctional nanocrystalline MgO for chiral epoxy ketones via Claisen-Schmidt condensation-asymmetric epoxidation reactions.

    Science.gov (United States)

    Choudary, Boyapati M; Kantam, Mannepalli L; Ranganath, Kalluri V S; Mahendar, Koosam; Sreedhar, Bojja

    2004-03-24

    Design and development of a truly nanobifunctional heterogeneous catalyst for the Claisen-Schmidt condensation (CSC) of benzaldehydes with acetophenones to yield chalcones quantitatively followed by asymmetric epoxidation (AE) to afford chiral epoxy ketones with moderate to good yields and impressive ee's is described. The nanomagnesium oxide (aerogel prepared) NAP-MgO was found to be superior over the NA-MgO and CM-MgO in terms of activity and enantioselectivity as applicable in these reactions. An elegant strategy for heterogenization of homogeneous catalysts is presented here to evolve single-site chiral catalysts for AE by a successful transfer of molecular chemistry to surface metal-organic chemistry with the retention of activity, selectivity/enantioselectivity. Brønsted hydroxyls are established as sole contributors for the epoxidation reaction, while they add on to the CSC, which is largely driven by Lewis basic O2-sites. Strong hydrogen-bond interactions between the surface -OH on MgO and -OH groups of diethyl tartrate are found inducing enantioselectivity in the AE reaction. Thus, the nanocrystalline NAP-MgO with its defined shape, size, and accessible OH groups allows the chemisorption of TBHP, DET, and olefin on its surface to accomplish single-site chiral catalysts to provide optimum ee's in AE reactions.

  2. Dynamics of Db isotopes formed in reactions induced by 238U, 248Cm, and 249Bk across the Coulomb barrier

    Science.gov (United States)

    Kaur, Gurjit; Sandhu, Kirandeep; Kaur, Amandeep; Sharma, Manoj K.

    2018-05-01

    The dynamical cluster decay model is employed to investigate the decay of *265Db and *267Db nuclei, formed in the 27Al+238U , 18O+249Bk , and 19F+248Cm hot fusion reactions at energies around the Coulomb barrier. First, the fission dynamics of the 27Al+238U reaction is explored by investigating the fragmentation and preformation yield of the reaction. The symmetric mass distribution of the fission fragments is observed for *265Db nucleus, when static β2 i deformations are used within hot optimum orientation approach. However, the mass split gets broaden for the use of β2 i-dynamical hot configuration of the fragments and becomes clearly asymmetric for the cold-static-deformed approach. Within the application of cold orientations of fragments, a new fission channel is observed at mass asymmetry η =0.29 . In addition to 238U-induced reaction, the work is carried out to address the fission and neutron evaporation cross sections of *267Db nucleus formed via 19F+248Cm and 18O+249Bk reactions, besides a comprehensive analysis of fusion and capture processes. Higher fusion cross sections and compound nucleus formation probabilities (PCN) are obtained for the 18O+249Bk reaction, as larger mass asymmetry in the entrance channel leads to reduced Coulomb factor. Finally, the role of sticking (IS) and nonsticking (INS) moments of inertia is analyzed for the 4 n and 5 n channels of *267Db nuclear system.

  3. The asymmetric hetero-Diels-Alder reaction in the syntheses of biologically relevant compounds.

    Science.gov (United States)

    Eschenbrenner-Lux, Vincent; Kumar, Kamal; Waldmann, Herbert

    2014-10-13

    The hetero-Diels-Alder reaction is one of the most powerful transformations in the chemistry toolbox for the synthesis of aza- and oxa-heterocycles embodying multiple stereogenic centers. However, as compared to other cycloadditions, in particular the dipolar cycloadditions and the Diels-Alder reaction, the hetero-Diels-Alder reaction has been much less explored and exploited in organic synthesis. Nevertheless, this powerful transformation has opened up efficient and creative routes to biologically relevant small molecules and different natural products which contain six-membered oxygen or nitrogen ring systems. Recent developments in this field, in particular in the establishment of enantioselectively catalyzed hetero-Diels-Alder cycloadditions steered by a plethora of different catalysts and the application of the resulting small molecules in chemical biology and medicinal chemistry research, are highlighted in this Minireview. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Asymmetric Alkylation and Aldol Reactions of D-Mannitol-Derived Chiral Oxazolidin-2-one Derivatives

    International Nuclear Information System (INIS)

    Maeng, Yun Hee; Jun, Jong Gab

    2004-01-01

    In the preceding article, we have introduced a new chiral oxazolidin-2-one auxiliary (1) derived from a cheap Dmannitol, and demonstrated the chiral selectivity in alkylation, aldol reaction and β-lactam synthesis.1 The present work began with a search for useful chiral directing groups with which to control the chiral selectivity. Because the rigidity of cyclic structures contributes significantly to control of chirality,2 the 1,2:5,6-di-O-cyclohexylidene-Dmannitol (2) was used for the synthesis of oxazolidin-2-one chiral auxiliary (3) comparing the selectivity with the auxiliary (1) in alkylation and aldol reactions.

  5. (SalenMn(III Catalyzed Asymmetric Epoxidation Reactions by Hydrogen Peroxide in Water: A Green Protocol

    Directory of Open Access Journals (Sweden)

    Francesco Paolo Ballistreri

    2016-07-01

    Full Text Available Enantioselective epoxidation reactions of some chosen reactive alkenes by a chiral Mn(III salen catalyst were performed in H2O employing H2O2 as oxidant and diethyltetradecylamine N-oxide (AOE-14 as surfactant. This procedure represents an environmentally benign protocol which leads to e.e. values ranging from good to excellent (up to 95%.

  6. Rationalization of Product Selectivities in Asymmetric Horner-Wadsworth-Emmons Reactions by Use of a New Method for Transition-State Modeling

    DEFF Research Database (Denmark)

    Norrby, Per-Ola; Brandt, Peter; Rein, Tobias

    1999-01-01

    A new method for creating a transition-state force field, based on quantum chemical normal-mode analysis, is described. The force field was used to rationalize the experimentally observed product selectivities in asymmetric Horner-Wadsworth-Emmons reactions between some chiral phosphonates and ch...

  7. alpha,beta-unsaturated 2-acyl imidazoles as a practical class of dienophiles for the DNA-Based catalytic asymmetric diels-alder reaction in water

    NARCIS (Netherlands)

    Boersma, A.J.; Feringa, B.L.; Roelfes, G.

    2007-01-01

    alpha,beta-Unsaturated 2-acyl imidazoles are a novel and practical class of dienophiles for the DNA-based catalytic asymmetric Diels-Alder reaction in water. The Diels-Alder products are obtained with very high diastereoselectivities and enantioselectivities in the range of 83-98%. The catalytic

  8. Asymmetric Baylis-Hillman Reaction between Chiral Activated Alkenes and Aromatic Aldehydes in Me3N/H2O/Solvent Medium

    Institute of Scientific and Technical Information of China (English)

    Ke HE; Zheng Hong ZHOU; Hong Ying TANG; Guo Feng ZHAO; Chu Chi TANG

    2005-01-01

    Chiral activated alkene, L-menthyl acrylate and (+)-N-α-phenylethyl acrylamide,induced asymmetric Baylis-Hillman reaction of aromatic aldehydes was realized at 25℃ for 7 days in Me3N/H2O/solvent homogeneous medium. The corresponding Baylis-Hillman adducts were obtained in good chemical yield with moderate to excellent diastereoselectivity (up to 99% de).

  9. Syntheses of the hexahydroindene cores of indanomycin and stawamycin by combinations of iridium-catalyzed asymmetric allylic alkylations and intramolecular Diels-Alder reactions.

    Science.gov (United States)

    Gärtner, Martin; Satyanarayana, Gedu; Förster, Sebastian; Helmchen, Günter

    2013-01-02

    Short and concise syntheses of the hexahydroindene cores of the antibiotics indanomycin (X-14547 A) and stawamycin are presented. Key methods used are an asymmetric iridium-catalyzed allylic alkylation, a modified Julia olefination, a Suzuki-Miyaura coupling, and an intramolecular Diels-Alder reaction. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Asymmetric effect of mechanical stress on the forward and reverse reaction catalyzed by an enzyme.

    Directory of Open Access Journals (Sweden)

    Collin Joseph

    Full Text Available The concept of modulating enzymatic activity by exerting a mechanical stress on the enzyme has been established in previous work. Mechanical perturbation is also a tool for probing conformational motion accompanying the enzymatic cycle. Here we report measurements of the forward and reverse kinetics of the enzyme Guanylate Kinase from yeast (Saccharomyces cerevisiae. The enzyme is held in a state of stress using the DNA spring method. The observation that mechanical stress has different effects on the forward and reverse reaction kinetics suggests that forward and reverse reactions follow different paths, on average, in the enzyme's conformational space. Comparing the kinetics of the stressed and unstressed enzyme we also show that the maximum speed of the enzyme is comparable to the predictions of the relaxation model of enzyme action, where we use the independently determined dissipation coefficient [Formula: see text] for the enzyme's conformational motion. The present experiments provide a mean to explore enzyme kinetics beyond the static energy landscape picture of transition state theory.

  11. Dynamical Dipole and Equation of State in N/Z Asymmetric Fusion Reactions

    Directory of Open Access Journals (Sweden)

    Giaz Agnese

    2014-03-01

    Full Text Available In heavy ion reactions, in the case of N/Z asymmetry between projectile and target, the process leading to complete fusion is expected to produce pre-equilibrium dipole γ-ray emission. It is generated during the charge equilibration process and it is known as Dynamical Dipole. A new measurement of the dynamical dipole emission was performed by studying 16O + 116Sn at 12 MeV/u. These data, together with those measured at 8.1 MeV/u and 15.6 MeV/u for the same reaction, provide the dependence on the Dynamical Dipole total emission yield with beam energy and they can be compared with theoretical expectations. The experimental results show a weak increase of the Dynamical Dipole total yield with beam energies and are in agreement with the prediction of a theoretical model based on the Boltzmann–Nordheim–Vlasov (BNV approach. The measured trend with beam energy does not confirm the rise and fall behavior previously reported for the same fused compound but with a much higher dipole moment.

  12. The asymmetric reactions of mean and volatility of stock returns to domestic and international information based on a four-regime double-threshold GARCH model

    Science.gov (United States)

    Chen, Cathy W. S.; Yang, Ming Jing; Gerlach, Richard; Jim Lo, H.

    2006-07-01

    In this paper, we investigate the asymmetric reactions of mean and volatility of stock returns in five major markets to their own local news and the US information via linear and nonlinear models. We introduce a four-regime Double-Threshold GARCH (DTGARCH) model, which allows asymmetry in both the conditional mean and variance equations simultaneously by employing two threshold variables, to analyze the stock markets’ reactions to different types of information (good/bad news) generated from the domestic markets and the US stock market. By applying the four-regime DTGARCH model, this study finds that the interaction between the information of domestic and US stock markets leads to the asymmetric reactions of stock returns and their variability. In addition, this research also finds that the positive autocorrelation reported in the previous studies of financial markets may in fact be mis-specified, and actually due to the local market's positive response to the US stock market.

  13. Asymmetrical distorted structure, dynamics, and reactions of the silacyclohexane and related radical cations: ESR and ab-initio MO study

    International Nuclear Information System (INIS)

    Komaguchi, Kenji; Shiotani, Masaru; Ishikawa, Mitsuo

    1995-01-01

    The σ-type radical cations generated by one electron oxidation of the saturated hydrocarbon have been attracted much attention because of their fundamental importance as primary reactant species in radiation chemistry. Our studies on σ-type radical cations were recently extended to the silacyclohexane (cSiC5), silacyclopentane (cSiC4), and silacyclobutane (cSiC3) radical cations. Their electronic structure, dynamics, and reactions were investigated by means of low temperature matrix isolation ESR technique combined with ionizing radiation (γ-rays from 60 Co). In the preceding paper, the 1-methylsilacyclohexane (1-Me-cSiC5) radical cation has been found to take an asymmetrically distorted C 1 structure with one of two Si-C bonds elongated in which the unpaired electron mainly resides ( 2 A in C 1 ). This conclusion was based on the 4.2 K ESR spectra of radical cations of selectively deuteriated and/or methylsubstituted silacyclohexanes, i.e., cSiC5-2,2,6,6-d 4 + , 1-Me-cSiC5 + , 1-Me-cSiC5-2,2-d 2 + , 1-Me-cSiC5-2,2,6,6-d 4 + , 1,1-Me 2 -cSiC5 + , and 4,4-Me 2 -cSiC5 + , in a frozen CF 3 -cC 6 F 11 matrix. Here we report further experimental and theoretical results on 1-methylsilacyclohexane radical cation, especially on the ab initio MO results and matrix effects on the structural distortion, as well as thermal reactions of the radical cations. The results will make it clear that the distorted C 1 structure of the 1-Me-cSiC5 + is the intrinsic nature at the ground electronic state. (J.P.N.)

  14. Wave Packet Based Statistical Approach to Complex-Forming Reactions

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Hua [Univ. of New Mexico, Albuquerque, NM (United States). Dept. of Chemistry and Chemical Biology

    2017-12-06

    Combustion represents a key chemical process in energy consumption in modern societies and a clear and comprehensive understanding of the elemental reactions in combustion is of great importance to a number of challenging areas such as engine efficiency and environmental protection. In this award, we proposed to develop new theoretical tools to understand elemental chemical processes in combustion environments. With the support of this DOE grant, we have made significant advances in developing new and more efficient and accurate algorithms to characterize reaction dynamics.

  15. Chiral four-membered cyclic nitrones; asymmetric induction in the (4+2)-cycloaddition reaction of chiral ynamines and nitroalkenes

    NARCIS (Netherlands)

    van Elburg, P.A.; Honig, G.W.N.; Reinhoudt, David

    1987-01-01

    Chiral four-membered cyclic nitrones were synthesized by the asymmetric (4+2)-cycloaddition of nitroalkenes 1 and chiral ynamines 2. The subsequent stereoselective addition of nucleophiles to these nitrones enabled the synthesis of chiral N-hydroxyazetidines.

  16. Multiplicity and asymmetric fireballs from π+p, K+p, γp, e-p, and μ-p reactions

    International Nuclear Information System (INIS)

    Hoang, T.F.; Chew, C.K.; Phua, K.K.

    1979-01-01

    Negative-pion multiplicities produced by asymmetric fireballs are investigated in terms of the fireball mass M*, related to the Feynman-Yang scaling. Assuming approx. M* and making use of results of the previous analysis on pp and p-barp data, it is found that only one parameter is needed for both π + p and K + p reactions and another one for γp, e - p, and μ - p reactions. An attempt is made to analyze π production by e + e - in analogy with the analysis of p-barp annihilation in a previous work

  17. Consumer reactions to different forms of CSR communication

    OpenAIRE

    Buden, Ivana; Connett, Louise

    2016-01-01

    Aim Companies around the world are making sizeable investments into CSR initiatives, but ensuring appropriate returns on these investments remains challenging. Therefore, it is of value to study the communication of corporate CSR efforts. The purpose of this study is to investigate how consumers react to rational versus emotional message strategies in CSR communication. Two categories of consumer reactions were considered: trust and purchase intention. Methods Qualitative research with four f...

  18. High-Performance 2.6 V Aqueous Asymmetric Supercapacitors based on In Situ Formed Na0.5 MnO2 Nanosheet Assembled Nanowall Arrays.

    Science.gov (United States)

    Jabeen, Nawishta; Hussain, Ahmad; Xia, Qiuying; Sun, Shuo; Zhu, Junwu; Xia, Hui

    2017-08-01

    The voltage limit for aqueous asymmetric supercapacitors is usually 2 V, which impedes further improvement in energy density. Here, high Na content Birnessite Na 0.5 MnO 2 nanosheet assembled nanowall arrays are in situ formed on carbon cloth via electrochemical oxidation. It is interesting to find that the electrode potential window for Na 0.5 MnO 2 nanowall arrays can be extended to 0-1.3 V (vs Ag/AgCl) with significantly increased specific capacitance up to 366 F g -1 . The extended potential window for the Na 0.5 MnO 2 electrode provides the opportunity to further increase the cell voltage of aqueous asymmetric supercapacitors beyond 2 V. To construct the asymmetric supercapacitor, carbon-coated Fe 3 O 4 nanorod arrays are synthesized as the anode and can stably work in a negative potential window of -1.3 to 0 V (vs Ag/AgCl). For the first time, a 2.6 V aqueous asymmetric supercapacitor is demonstrated by using Na 0.5 MnO 2 nanowall arrays as the cathode and carbon-coated Fe 3 O 4 nanorod arrays as the anode. In particular, the 2.6 V Na 0.5 MnO 2 //Fe 3 O 4 @C asymmetric supercapacitor exhibits a large energy density of up to 81 Wh kg -1 as well as excellent rate capability and cycle performance, outperforming previously reported MnO 2 -based supercapacitors. This work provides new opportunities for developing high-voltage aqueous asymmetric supercapacitors with further increased energy density. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Direct Reaction of Amides with Nitric Oxide To Form Diazeniumdiolates

    Science.gov (United States)

    2015-01-01

    We report the apparently unprecedented direct reaction of nitric oxide (NO) with amides to generate ions of structure R(C=O)NH–N(O)=NO–, with examples including R = Me (1a) or 3-pyridyl (1b). The sodium salts of both released NO in pH 7.4 buffer, with 37 °C half-lives of 1–3 min. As NO-releasing drug candidates, diazeniumdiolated amides would have the advantage of generating only 1 equiv of base on hydrolyzing exhaustively to NO, in contrast to their amine counterparts, which generate 2 equiv of base. PMID:25210948

  20. Stereoselectivity in ene reactions with 1O2: matrix effects in polymer supports, photo-oxygenation of organic salts and asymmetric synthesis.

    Science.gov (United States)

    Griesbeck, Axel G; Bartoschek, Anna; Neudörfl, Jörg; Miara, Claus

    2006-01-01

    The ene reaction of chiral allylic alcohols is applied as a tool for the investigation of intrapolymer effects by means of the stereoselectivity of the singlet-oxygen addition. The diastereo selectivity strongly depends on the structure of the polymer, the substrate loading degree and also on the degree of conversion demonstrating additional supramolecular effects evolving during the reaction. The efficiency and the stability of polymer-bound sensitizers were evaluated by the ene reaction of singlet oxygen with citronellol. The ene reaction with chiral ammonium salts of tiglic acid was conducted under solution phase conditions or in polystyrene beads under chiral contact ion-pair conditions. The products thus obtained precipitate during the photoreaction as ammonium salts. Moderate asymmetric induction was observed for this procedure for the first time.

  1. Heterobimetallic transition metal/rare earth metal bifunctional catalysis: a Cu/Sm/Schiff base complex for syn-selective catalytic asymmetric nitro-Mannich reaction.

    Science.gov (United States)

    Handa, Shinya; Gnanadesikan, Vijay; Matsunaga, Shigeki; Shibasaki, Masakatsu

    2010-04-07

    The full details of a catalytic asymmetric syn-selective nitro-Mannich reaction promoted by heterobimetallic Cu/Sm/dinucleating Schiff base complexes are described, demonstrating the effectiveness of the heterobimetallic transition metal/rare earth metal bifunctional catalysis. The first-generation system prepared from Cu(OAc)(2)/Sm(O-iPr)(3)/Schiff base 1a = 1:1:1 with an achiral phenol additive was partially successful for achieving the syn-selective catalytic asymmetric nitro-Mannich reaction. The substrate scope and limitations of the first-generation system remained problematic. After mechanistic studies on the catalyst prepared from Sm(O-iPr)(3), we reoptimized the catalyst preparation method, and a catalyst derived from Sm(5)O(O-iPr)(13) showed broader substrate generality as well as higher reactivity and stereoselectivity compared to Sm(O-iPr)(3). The optimal system with Sm(5)O(O-iPr)(13) was applicable to various aromatic, heteroaromatic, and isomerizable aliphatic N-Boc imines, giving products in 66-99% ee and syn/anti = >20:1-13:1. Catalytic asymmetric synthesis of nemonapride is also demonstrated using the catalyst derived from Sm(5)O(O-iPr)(13).

  2. A high-performance liquid chromatography-electronic circular dichroism online method for assessing the absolute enantiomeric excess and conversion ratio of asymmetric reactions

    Science.gov (United States)

    Zhang, Xiang; Wang, Mingchao; Li, Li; Yin, Dali

    2017-03-01

    Asymmetric reactions often need to be evaluated during the synthesis of chiral compounds. However, traditional evaluation methods require the isolation of the individual enantiomer, which is tedious and time-consuming. Thus, it is desirable to develop simple, practical online detection methods. We developed a method based on high-performance liquid chromatography-electronic circular dichroism (HPLC-ECD) that simultaneously analyzes the material conversion ratio and absolute optical purity of each enantiomer. In particular, only a reverse-phase C18 column instead of a chiral column is required in our method because the ECD measurement provides a g-factor that describes the ratio of each enantiomer in the mixtures. We used our method to analyze the asymmetric hydrosilylation of β-enamino esters, and we discussed the advantage, feasibility, and effectiveness of this new methodology.

  3. The asymmetric synthesis of (+-sitophilure, the natural form of the aggregation pheromone of Sitophilus oryzae L. and Sitophilus zeamais M.

    Directory of Open Access Journals (Sweden)

    Pilli Ronaldo A.

    1999-01-01

    Full Text Available The asymmetric synthesis of (+-sitophilure, the aggregation pheromone of Sitophilus oryzae L. and Sitophilus zeamais M., was carried out in 12 steps, 18% overall yield and 82% enantiomeric excess from the enzymatic reduction of methyl 3-oxopentanoate with S. cerevisiae in the presence of ethyl chloroacetate.

  4. 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…

  5. Reaction between CO2 and phosphate to form carboxyphosphate?

    International Nuclear Information System (INIS)

    Knight, W.B.; Attwood, P.V.; Cleland, W.W.

    1986-01-01

    Carboxyphosphate (I) is thought to be an intermediate in the enzymic carboxylation of biotin by bicarbonate and MgATP, and a plausible mechanism of carboxyl transfer to the enolate of biotin involves decarboxylation to CO 2 and phosphate. Such a process would have to be reversible, however, as carboxylase reactions are reversible. To test this possibility, the authors undertook the synthesis of I under anhydrous conditions with a high mole fraction of CO 2 present. CO 2 was distilled into capillary tubes under vacuum containing dry tris-(tetrabutyl-ammonium)-phosphate in dimethylformamide. The tubes were sealed and warmed to -10 or 20 0 C and examined by 31 P NMR. Two resonances (1.7 ppm and -5.0 ppm) in addition to phosphate (3.3 ppm) were observed. The relative ratio of each peak to the phosphate one was dependent on the temperature and the concentrations of PO 4 3- and CO 2 . Upon freezing the tubes, cracking them, and release of the CO 2 , the two additional species decomposed slowly to PO 4 3- , and more rapidly to HPO 4 3- upon the addition of H 2 O. Under some conditions they observed an additional resonance (-7.0 ppm) which is most likely pyrophosphate (PP/sub i/). At high concentrations of PO 4 3- and CO 2 , PP/sub i/ was produced and precipitated from solution. The production of PP/sub i/ is most easily explained by attack of PO 4 3- on I. They are currently trying to identify the unknown species observed in the 31 P NMR spectra

  6. Dynamic structural change of the self-assembled lanthanum complex induced by lithium triflate for direct catalytic asymmetric aldol-Tishchenko reaction.

    Science.gov (United States)

    Horiuchi, Yoshihiro; Gnanadesikan, Vijay; Ohshima, Takashi; Masu, Hyuma; Katagiri, Kosuke; Sei, Yoshihisa; Yamaguchi, Kentaro; Shibasaki, Masakatsu

    2005-09-05

    The development of a direct catalytic asymmetric aldol-Tishchenko reaction and the nature of its catalyst are described. An aldol-Tishchenko reaction of various propiophenone derivatives with aromatic aldehydes was promoted by [LaLi3(binol)3] (LLB), and reactivity and enantioselectivity were dramatically enhanced by the addition of lithium trifluoromethanesulfonate (LiOTf). First, we observed a dynamic structural change of LLB by the addition of LiOTf using 13C NMR spectroscopy, electronspray ionization mass spectrometry (ESI-MS), and cold-spray ionization mass spectrometry (CSI-MS). X-ray crystallography revealed that the structure of the newly generated self-assembled complex was a binuclear [La2Li4(binaphthoxide)5] complex 6. A reverse structural change of complex 6 to LLB by the addition of one equivalent of Li2(binol) was also confirmed by ESI-MS and experimental results. The drastic concentration effects on the direct catalytic asymmetric aldol-Tishchenko reaction suggested that the addition of LiOTf to LLB generated an active oligomeric catalyst species.

  7. How asymmetrical task dependence and task interdependence interact:an individual level study into the effects on affective reactions

    OpenAIRE

    Jong, Simon B. De; Bal, P. Matthijs

    2014-01-01

    Purpose – This study investigates whether research and practice on task design and work teams could benefit from a more nuanced perspective on task (inter)dependencies among team members. Prior research often overlooked that task interdependence captures the average exchange of resources, while asymmetrical task dependence captures the inequalities within an individual's work relationships. To date, no study on work teams has combined the two aspects. Design/methodology/approach – Data was ob...

  8. Polystyrene-supported cu(II)-R-Box as recyclable catalyst in asymmetric Friedel–Crafts reaction

    KAUST Repository

    Desyatkin, V. G.

    2017-02-12

    The complex of copper(II) trifluoromethanesulfonate with chiral isopropyl bis(oxazoline) ligand (i-Pr-Box) was immobilized on accessible and inexpensive Merrifield resin according to a “click” procedure. The resulting catalyst showed high efficiency and recyclability in the asymmetric Friedel–Crafts alkylation of indole and its derivatives. The catalyst can be recycled five times without appreciable loss in activity and enantioselectivity.

  9. Synthesis of New Chiral Benzimidazolylidene–Rh Complexes and Their Application in Asymmetric Addition Reactions of Organoboronic Acids to Aldehydes

    Directory of Open Access Journals (Sweden)

    Weiping He

    2016-09-01

    Full Text Available A series of novel chiral N-heterocyclic carbene rhodium complexes (NHC–Rh based on benzimidazole have been prepared, and all of the NHC–Rh complexes were fully characterized by NMR and mass spectrometry. These complexes could be used as catalysts for the asymmetric 1,2-addition of organoboronic acids to aldehydes, affording chiral diarylmethanols with high yields and moderate enantioselectivities.

  10. Polystyrene-supported cu(II)-R-Box as recyclable catalyst in asymmetric Friedel–Crafts reaction

    KAUST Repository

    Desyatkin, V. G.; Anokhin, M. V.; Rodionov, Valentin; Beletskaya, I. P.

    2017-01-01

    The complex of copper(II) trifluoromethanesulfonate with chiral isopropyl bis(oxazoline) ligand (i-Pr-Box) was immobilized on accessible and inexpensive Merrifield resin according to a “click” procedure. The resulting catalyst showed high efficiency and recyclability in the asymmetric Friedel–Crafts alkylation of indole and its derivatives. The catalyst can be recycled five times without appreciable loss in activity and enantioselectivity.

  11. Asymmetric Diels-Alder Reaction of α,β-Unsaturated Oxazolidin-2-one Derivatives Catalyzed by a Chiral Fe(III)-Bipyridine Diol Complex.

    Science.gov (United States)

    Li, Mao; Carreras, Virginie; Jalba, Angela; Ollevier, Thierry

    2018-02-16

    An asymmetric Fe III -bipyridine diol catalyzed Diels-Alder reaction of α,β-unsaturated oxazolidin-2-ones has been developed. Among various Fe II /Fe III salts, Fe(ClO 4 ) 3 ·6H 2 O was selected as the Lewis acid of choice. The use of a low catalyst loading (2 mol % of Fe(ClO 4 ) 3 ·6H 2 O and 2.4 mol % of Bolm's ligand) afforded high yields (up to 99%) and high enantiomeric excesses (up to 98%) of endo-cycloadducts for the Diels-Alder reaction between cyclopentadiene and substituted acryloyloxazolidin-2-ones. Other noncyclic dienes led to decreased enantioselectivities. A proposed model supports the observed stereoinduction.

  12. Diagnostic capabilities of non-treponemal and treponemal reactions in the early forms of syphilis

    Directory of Open Access Journals (Sweden)

    Zakharov S.V.

    2017-12-01

    Full Text Available A comparative analysis of the sensitivity and specificity of immunoblotting against other non-treponemal and treponemal reactions was carried out in 215 patients with early forms of syphilis. A high diagnostic efficiency of immunoblotting in patients with early latent syphilis was established. It was found that only in case of primary syphilis, immunoblotting is inferior to Immunofluorescence reaction; this test can be used for differential diagnosis between hidden syphilis and false positive reactions to syphilis.

  13. Asymmetric Brønsted acid-catalyzed aza-Diels–Alder reaction of cyclic C-acylimines with cyclopentadiene

    Directory of Open Access Journals (Sweden)

    Magnus Rueping

    2012-10-01

    Full Text Available A new chiral Brønsted acid-catalyzed aza-Diels–Alder reaction of cyclic C-acylimines with cyclopentadiene has been developed. The reaction provides optically active aza-tetracycles in good yields with high diastereo- and enantioselectivities under mild reaction conditions.

  14. A Pyrene-Linked Cavity within a β-Barrel Protein Promotes an Asymmetric Diels-Alder Reaction.

    Science.gov (United States)

    Himiyama, Tomoki; Taniguchi, Naomasa; Kato, Shunsuke; Onoda, Akira; Hayashi, Takashi

    2017-10-23

    A unique π-expanded reaction cavity tethering a polycyclic moiety which provides a platform for substrate binding was constructed within the robust β-barrel structure of nitrobindin (NB). NB variants with cavities of different sizes and shapes are coupled with N-(1-pyrenyl)maleimide (Pyr) to prepare a series of NB-Pyr conjugates. The orientation of the pyrene moiety is fixed within the cavity by the coupling reaction. The fluorescent quenching analysis of NB-Pyr indicates that azachalcone (aza), which is a dienophile for a Diels-Alder (DA) reaction, is efficiently incorporated within the pyrene-linked reaction cavity by the aromatic interaction. The DA reaction between aza and cyclopentadiene proceeds within the reaction cavity of NB-Pyr in the presence of Cu II ion in high yield and high enantio- and regioselectivity. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Ultrasound-Accelerated Synthesis of Asymmetrical Thiosulfonate S-Esters by Base-Promoted Reaction of Sulfonyl Chlorides with Thiols

    DEFF Research Database (Denmark)

    Pham, Hien Thi; Nguyen, Ngoc-Lan Thi; Duus, Fritz

    2015-01-01

    Amberlyst A-26, Mg-Al hydrotalcite, potassium fluoride absorbed on alumina, triethylamine and pyridine have been tested as base catalysts and reagents for the reaction of sulfonyl chlorides with thiols to prepare thiosulfonate S-esters. The reactions were performed under solvent-free conditions...

  16. Asymmetric synthesis of α-amino acids via homologation of Ni(II) complexes of glycine Schiff bases. Part 3: Michael addition reactions and miscellaneous transformations.

    Science.gov (United States)

    Aceña, José Luis; Sorochinsky, Alexander E; Soloshonok, Vadim

    2014-09-01

    The major goal of this review is a critical discussion of the literature data on asymmetric synthesis of α-amino acids via Michael addition reactions involving Ni(II)-complexes of amino acids. The material covered is divided into two conceptually different groups dealing with applications of: (a) Ni(II)-complexes of glycine as C-nucleophiles and (b) Ni(II)-complexes of dehydroalanine as Michael acceptors. The first group is significantly larger and consequently subdivided into four chapters based on the source of stereocontrolling element. Thus, a chiral auxiliary can be used as a part of nucleophilic glycine Ni(II) complex, Michael acceptor or both, leading to the conditions of matching vs. mismatching stereochemical preferences. The particular focus of the review is made on the practical aspects of the methodology under discussion and mechanistic considerations.

  17. A novel thiamine-derived pigment, pyrizepine, formed by the Maillard reaction.

    Science.gov (United States)

    Igoshi, Asuka; Noda, Kyoko; Murata, Masatsune

    2018-04-26

    To find a Maillard pigment derived from thiamine, a solution containing glucose and thiamine was heated and analyzed with high-performance liquid chromatography equipped with diode-array detection. As a result, a unique peak showing an absorption maximum at 380 nm was detected. This peak was then isolated from a reaction solution containing glucose, lysine and thiamine, and was identified as 1-(2-methyl-6,9-dihydro-5H-pyrimido[4,5-e][1,4]diazepin-7-yl)ethan-1-one using instrumental analyses. This compound, named pyrizepine, was a novel yellow pigment having a fused ring consisting of pyrimidine and diazepine. Pyrizepine was a major low-molecular-weight pigment in the reaction solution. The structure suggests that pyrizepine is formed by condensation reaction between a degradation product of thiamine and a tetrosone derivative formed from glucose by the Maillard reaction.

  18. Direct asymmetric vinylogous aldol reaction of allyl ketones with isatins: Divergent synthesis of 3-hydroxy-2-oxindole derivatives

    KAUST Repository

    Zhu, Bo; Zhang, Wen; Lee, Richmond; Han, Zhiqiang; Yang, Wenguo; Tan, Davin; Huang, Kuo-Wei; Jiang, Zhiyong

    2013-01-01

    6 in 1: The highly enantioselective title reaction is mediated by a bifunctional catalyst and leads to E-configured vinylogous aldol products (see scheme). These products are used as common intermediates in the synthesis of six biologically active 3

  19. Diagnostic capabilities of non-treponemal and treponemal reactions in the early forms of syphilis.

    OpenAIRE

    Zakharov, S. V.

    2017-01-01

    A comparative analysis of the sensitivity and specificity of immunoblotting against other non-treponemal and treponemal reactions was carried out in 215 patients with early forms of syphilis. A high diagnostic efficiency of immunoblotting in patients with early latent syphilis was established. It was found that only in case of primary syphilis, immunoblotting is inferior to Immunofluorescence reaction; this test can be used for differential diagnosis between hidden syphilis and false positive...

  20. A simple functional form for proton-208Pb total reaction cross sections

    International Nuclear Information System (INIS)

    Majumdar, S.; Deb, P.K.; Amos, K.

    2001-01-01

    A simple functional form has been found that gives a good representation of the total reaction cross sections for the scattering from 208 Pb of protons with energies in the range 30 to 300 MeV. The ratios of the total reaction cross sections calculated under this approximations compared well (to within a few percent) to those determined from the microscopic optical model potentials

  1. The decay of hot nuclei formed in La-induced reactions at intermediate energies

    International Nuclear Information System (INIS)

    Libby, B.; Mignerey, A.C.; Madani, H.; Marchetti, A.A.; Colonna, M.; DiToro, M.

    1992-01-01

    The decay of hot nuclei formed in lanthanum-induced reactions utilizing inverse kinematics has been studied from E/A = 35 to 55 MeV. At each bombarding energy studied, the probability for the multiple emission of complex fragments has been found to be independent of target. Global features (total charge, source velocity) of the reaction La + Al at E/A = 45 MeV have been reproduced by coupling a dynamical model to study the collision stage of the reaction to a statistical model of nuclear decay

  2. P-chiral 1-phosphanorbornenes: from asymmetric phospha-Diels-Alder reactions towards ligand design and functionalisation.

    Science.gov (United States)

    Möller, Tobias; Wonneberger, Peter; Sárosi, Menyhárt B; Coburger, Peter; Hey-Hawkins, Evamarie

    2016-02-07

    The principle of stereotopic face differentiation was successfully applied to 2H-phospholes which undergo a very efficient and highly stereoselective Diels-Alder reaction giving phosphorus-chiral 1-phosphanorbornenes with up to 87% yield. The observed reaction pathway has been supported by theoretical calculations showing that the cycloaddition reaction between 2H-phosphole 3a and the dienophile (5R)-(-)-menthyloxy-2(5H)-furanone (8) is of normal electron demand. Optically pure phosphanes were obtained by separation of the single diastereomers and subsequent desulfurisation of the sulfur-protected phosphorus atom. Finally, divergent ligand synthesis is feasible by reduction of the chiral auxiliary, subsequent stereospecific intramolecular Michael addition, and various functionalisations of the obtained key compound 13a. Furthermore, the unique structural properties of phospanorbornenes are presented and compared to those of phosphanorbornanes.

  3. Lewis Acid Catalyzed Asymmetric Three-Component Coupling Reaction: Facile Synthesis of α-Fluoromethylated Tertiary Alcohols.

    Science.gov (United States)

    Aikawa, Kohsuke; Kondo, Daisuke; Honda, Kazuya; Mikami, Koichi

    2015-12-01

    A chiral dicationic palladium complex is found to be an efficient Lewis acid catalyst for the synthesis of α-fluoromethyl-substituted tertiary alcohols using a three-component coupling reaction. The reaction transforms three simple and readily available components (terminal alkyne, arene, and fluoromethylpyruvate) to valuable chiral organofluorine compounds. This strategy is completely atom-economical and results in perfect regioselectivities and high enantioselectivities of the corresponding tertiary allylic alcohols in good to excellent yields. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Analysis of reaction products formed in the gas phase reaction of E,E-2,4-hexadienal with atmospheric oxidants: Reaction mechanisms and atmospheric implications

    Science.gov (United States)

    Colmenar, I.; Martin, P.; Cabañas, B.; Salgado, S.; Martinez, E.

    2018-03-01

    An analysis of reaction products for the reaction of E,E-2,4-hexadienal with chlorine atoms (Cl) and OH and NO3 radicals has been carried out at the first time with the aim of obtaining a better understanding of the tropospheric reactivity of α,β-unsaturated carbonyl compounds. Fourier Transform Infrared (FTIR) spectroscopy and Gas Chromatography-Mass Spectrometry with a Time of Flight detector (GC-TOFMS) were used to carry out the qualitative and/or quantitative analyses. Reaction products in gas and particulate phase were observed from the reactions of E,E-2,4- hexadienal with all oxidants. E/Z-Butenedial and maleic anhydride were the main products identified in gas phase. E-butenedial calculated molar yield ranging from 4 to 10%. A significant amount of multifunctional compounds (chloro and hydroxy carbonyls) was identified. These compounds could be formed in particulate phase explaining the ∼90% of unaccounted carbon in gas phase. The reaction with Cl atoms in the presence of NOx with a long reaction time gave Peroxy Acetyl Nitrate (PAN) as an additional product, which is known for being an important specie in the generation of the photochemical smog. Nitrated compounds were the major organic products from the reaction with the NO3 radical. Based on the identified products, the reaction mechanisms have been proposed. In these mechanisms a double bond addition of the atmospheric oxidant at C4/C5 of E,E-2,4-hexadienal is the first step for tropospheric degradation.

  5. High-Throughput Assay for Enantiomeric Excess Determination in 1,2- and 1,3-Diols and Direct Asymmetric Reaction Screening.

    Science.gov (United States)

    Shcherbakova, Elena G; Brega, Valentina; Lynch, Vincent M; James, Tony D; Anzenbacher, Pavel

    2017-07-26

    A simple and efficient method for determination of the yield, enantiomeric/diasteriomeric excess (ee/de), and absolute configuration of crude chiral diols without the need of work-up and product isolation in a high throughput setting is described. This approach utilizes a self-assembled iminoboronate ester formed as a product by dynamic covalent self-assembly of a chiral diol with an enantiopure fluorescent amine such as tryptophan methyl ester or tryptophanol and 2-formylphenylboronic acid. The resulting diastereomeric boronates display different photophysical properties and allow for fluorescence-based ee determination of molecules containing a 1,2- or 1,3-diol moiety. This method has been utilized for the screening of ee in a number of chiral diols including atorvastatin, a statin used for the treatment of hypercholesterolemia. Noyori asymmetric hydrogenation of benzil was performed in a highly parallel fashion with errors products from the parallel asymmetric synthesis in real time and in a high-throughput screening (HTS) fashion. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Cinchona alkaloids in asymmetric organocatalysis

    NARCIS (Netherlands)

    Marcelli, T.; Hiemstra, H.

    2010-01-01

    This article reviews the applications of cinchona alkaloids as asymmetric catalysts. In the last few years, characterized by the resurgence of interest in asymmetric organocatalysis, cinchona derivatives have been shown to catalyze an outstanding array of chemical reactions, often with remarkable

  7. L-Selectride-Mediated Highly Diastereoselective Asymmetric Reductive Aldol Reaction: Access to an Important Subunit for Bioactive Molecules

    OpenAIRE

    Ghosh, Arun K.; Kass, Jorden; Anderson, David D.; Xu, Xiaoming; Marian, Christine

    2008-01-01

    L-Selectride reduction of a chiral or achiral enone followed by reaction of the resulting enolate with optically active α-alkoxy aldehydes proceeded with excellent diastereoselectivity. The resulting α,α-dimethyl-β-hydroxy ketones are inherent to a variety of biologically active natural products.

  8. L-selectride-mediated highly diastereoselective asymmetric reductive aldol reaction: access to an important subunit for bioactive molecules.

    Science.gov (United States)

    Ghosh, Arun K; Kass, Jorden; Anderson, David D; Xu, Xiaoming; Marian, Christine

    2008-11-06

    L-selectride reduction of a chiral or achiral enone followed by reaction of the resulting enolate with optically active alpha-alkoxy aldehydes proceeded with excellent diastereoselectivity. The resulting alpha,alpha-dimethyl-beta-hydroxy ketones are inherent to a variety of biologically active natural products.

  9. KINETIC RESOLUTION OF ALCOHOLS IN AN ASYMMETRIC MITSUNOBU REACTION USING CHIRAL NONRACEMIC 1,3,2-DIOXAPHOSPHEPANES

    NARCIS (Netherlands)

    Hulst, Ron; Basten, Arjan van; Fitzpatrick, Kevin; Kellogg, Richard M.

    1995-01-01

    Non-racemic chiral trivalent phosphorus derivatives 1 and 2 when employed under Mitsunobu reaction conditions, induce esterification between racemic alcohols and acids with moderate enantiospecificity (up to 39%). At the expense of high conversion, the alcohols can be obtained in high ee (> 99%).

  10. Uranium oxidation: Characterization of oxides formed by reaction with water by infrared and sorption analyses

    Science.gov (United States)

    Fuller, E. L.; Smyrl, N. R.; Condon, J. B.; Eager, M. H.

    1984-04-01

    Three different uranium oxide samples have been characterized with respect to the different preparation techniques. The results show that the water reaction with uranium metal occurs cyclically forming laminar layers of oxide which spall off due to the strain at the oxide/metal interface. Single laminae are released if liquid water is present due to the prizing penetration at the reaction zone. The rate of reaction of water with uranium is directly proportional to the amount of adsorbed water on the oxide product. Rapid transport is effected through the open hydrous oxide product. Dehydration of the hydrous oxide irreversibly forms a more inert oxide which cannot be rehydrated to the degree that prevails in the original hydrous product of uranium oxidation with water. Inert gas sorption analyses and diffuse reflectance infrared studies combined with electron microscopy prove valuable in defining the chemistry and morphology of the oxidic products and hydrated intermediates.

  11. Comparing Positively and Negatively Charged Distonic Radical Ions in Phenylperoxyl Forming Reactions.

    Science.gov (United States)

    Williams, Peggy E; Marshall, David L; Poad, Berwyck L J; Narreddula, Venkateswara R; Kirk, Benjamin B; Trevitt, Adam J; Blanksby, Stephen J

    2018-06-04

    In the gas phase, arylperoxyl forming reactions play a significant role in low-temperature combustion and atmospheric processing of volatile organic compounds. We have previously demonstrated the application of charge-tagged phenyl radicals to explore the outcomes of these reactions using ion trap mass spectrometry. Here, we present a side-by-side comparison of rates and product distributions from the reaction of positively and negatively charge tagged phenyl radicals with dioxygen. The negatively charged distonic radical ions are found to react with significantly greater efficiency than their positively charged analogues. The product distributions of the anion reactions favor products of phenylperoxyl radical decomposition (e.g., phenoxyl radicals and cyclopentadienone), while the comparable fixed-charge cations yield the stabilized phenylperoxyl radical. Electronic structure calculations rationalize these differences as arising from the influence of the charged moiety on the energetics of rate-determining transition states and reaction intermediates within the phenylperoxyl reaction manifold and predict that this influence could extend to intra-molecular charge-radical separations of up to 14.5 Å. Experimental observations of reactions of the novel 4-(1-carboxylatoadamantyl)phenyl radical anion confirm that the influence of the charge on both rate and product distribution can be modulated by increasing the rigidly imposed separation between charge and radical sites. These findings provide a generalizable framework for predicting the influence of charged groups on polarizable radicals in gas phase distonic radical ions. Graphical Abstract.

  12. Two neutron transfer form factor for the reaction 42Ca(p,t)40Ca

    International Nuclear Information System (INIS)

    Meyer, R.H.

    1978-01-01

    In an attempt to better interpret experimental data concerning the two-neutron pickup process 42 Ca(p,t) 40 Ca, a detailed study of the form factors associated with the reaction is carried out. A set of coupled integro-differential equations describing these form factors is derived, starting from a microscopic, model-independent Hamiltonian. These equations allow contributions to the form factors from hole terms as well as from the particle and so-called ''continuum'' states, which were previously studied. An approximate solution of the form factor equations is obtained by neglecting the coupling terms and expressing the form factor in terms of a set of Sturmian states. Form factors for the transition to the 40 Ca ground state (O 1 + ) are calculated using various sets of Sturmian states. The inclusion of hole states is found to have a major effect upon both the shape of the form factor and the size of the related cross section. Finally, a comparison is made between the O 1 + form factors calculated using Sturmian states and a O 1 + form factor obtained using Sturmian states and a O 1 + form factor obtained using the coexistence model. It is found that a form factor based on Sturmian particle and hole states is very similar to the form factor obtained from the coexistence model calculation

  13. Direct asymmetric vinylogous aldol reaction of allyl ketones with isatins: Divergent synthesis of 3-hydroxy-2-oxindole derivatives

    KAUST Repository

    Zhu, Bo

    2013-05-03

    6 in 1: The highly enantioselective title reaction is mediated by a bifunctional catalyst and leads to E-configured vinylogous aldol products (see scheme). These products are used as common intermediates in the synthesis of six biologically active 3-hydroxy-2-oxindole derivatives (e.g., CPC-1). Computational studies indicated that the observed stereoselectivity is a result of favorable secondary π-π* and H-bonding interactions in the transition state. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. INTERMEDIATE STAGES OF REACTIONS FORMING CARBIDES OF TITANIUM, ZIRCONIUM, VANADIUM, NIOBIUM, AND TANTALIUM

    Science.gov (United States)

    intermediate and final products, and also during the calculation of approximate heat values of their formation, the passage of the reaction is confirmed...for obtaining TiC, and ZrC through the stage of intermediate oxides Ti2O3, Ti3O5, TiO and Zr2O3, ZrO, respectively and also for the reaction of...forming carbides of V (from V2O3 + 5C), of Nb and Ta (from Nb2O5 + 7C and Ta205 + 7C) through the stage of intermediate oxides VO, V4O and TaO2, Ta4O. The

  15. Externally controlled anisotropy in pattern-forming reaction-diffusion systems.

    Science.gov (United States)

    Escala, Dario M; Guiu-Souto, Jacobo; Muñuzuri, Alberto P

    2015-06-01

    The effect of centrifugal forces is analyzed in a pattern-forming reaction-diffusion system. Numerical simulations conducted on the appropriate extension of the Oregonator model for the Belousov-Zhabotinsky reaction show a great variety of dynamical behaviors in such a system. In general, the system exhibits an anisotropy that results in new types of patterns or in a global displacement of the previous one. We consider the effect of both constant and periodically modulated centrifugal forces on the different types of patterns that the system may exhibit. A detailed analysis of the patterns and behaviors observed for the different parameter values considered is presented here.

  16. Homogeneous (Cu, Ni)6Sn5 intermetallic compound joints rapidly formed in asymmetrical Ni/Sn/Cu system using ultrasound-induced transient liquid phase soldering process.

    Science.gov (United States)

    Li, Z L; Dong, H J; Song, X G; Zhao, H Y; Tian, H; Liu, J H; Feng, J C; Yan, J C

    2018-04-01

    Homogeneous (Cu, Ni) 6 Sn 5 intermetallic compound (IMC) joints were rapidly formed in asymmetrical Ni/Sn/Cu system by an ultrasound-induced transient liquid phase (TLP) soldering process. In the traditional TLP soldering process, the intermetallic joints formed in Ni/Sn/Cu system consisted of major (Cu, Ni) 6 Sn 5 and minor Cu 3 Sn IMCs, and the grain morphology of (Cu, Ni) 6 Sn 5 IMCs subsequently exhibited fine rounded, needlelike and coarse rounded shapes from the Ni side to the Cu side, which was highly in accordance with the Ni concentration gradient across the joints. However, in the ultrasound-induced TLP soldering process, the intermetallic joints formed in Ni/Sn/Cu system only consisted of the (Cu, Ni) 6 Sn 5 IMCs which exhibited an uniform grain morphology of rounded shape with a remarkably narrowed Ni concentration gradient. The ultrasound-induced homogeneous intermetallic joints exhibited higher shear strength (61.6 MPa) than the traditional heterogeneous intermetallic joints (49.8 MPa). Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Multicatalyst system in asymmetric catalysis

    CERN Document Server

    Zhou, Jian

    2014-01-01

    This book introduces multi-catalyst systems by describing their mechanism and advantages in asymmetric catalysis.  Helps organic chemists perform more efficient catalysis with step-by-step methods  Overviews new concepts and progress for greener and economic catalytic reactions  Covers topics of interest in asymmetric catalysis including bifunctional catalysis, cooperative catalysis, multimetallic catalysis, and novel tandem reactions   Has applications for pharmaceuticals, agrochemicals, materials, and flavour and fragrance

  18. Excitation energy dependence of fragment-mass distributions from fission of 180,190Hg formed in fusion reactions of 36Ar + 144,154Sm

    Directory of Open Access Journals (Sweden)

    K. Nishio

    2015-09-01

    Full Text Available Mass distributions of fission fragments from the compound nuclei 180Hg and 190Hg formed in fusion reactions 36Ar + 144Sm and 36Ar + 154Sm, respectively, were measured at initial excitation energies of E⁎(Hg180=33–66 MeV and E⁎(Hg190=48–71 MeV. In the fission of 180Hg, the mass spectra were well reproduced by assuming only an asymmetric-mass division, with most probable light and heavy fragment masses A¯L/A¯H=79/101. The mass asymmetry for 180Hg agrees well with that obtained in the low-energy β+/EC-delayed fission of 180Tl, from our earlier ISOLDE(CERN experiment. Fission of 190Hg is found to proceed in a similar way, delivering the mass asymmetry of A¯L/A¯H=83/107, throughout the measured excitation energy range. The persistence as a function of excitation energy of the mass-asymmetric fission for both proton-rich Hg isotopes gives strong evidence for the survival of microscopic effects up to effective excitation energies of compound nuclei as high as 40 MeV. This behavior is different from fission of actinide nuclei and heavier mercury isotope 198Hg.

  19. 1,5-Asymmetric induction in the boron-mediated aldol reaction of β-oxygenated methyl ketones

    International Nuclear Information System (INIS)

    Dias, Luiz C.

    2007-01-01

    High levels of substrate-based 1,5-stereo induction are obtained in the boron-mediated aldol reactions of β-oxygenated methyl ketones with achiral and chiral aldehydes. Remote induction from the boron enolates gives the 1,5-anti adducts, with the enolate pi-facial selectivity critically dependent upon the nature of the beta-alkoxy protecting group. This 1,5-anti aldol methodology has been strategically employed in the total synthesis of several natural products. At present, the origin of the high level of 1,5-anti induction obtained with the boron enolates is unclear, although a model based on a hydrogen bonding between the alkoxy oxygen and the formyl hydrogen has been recently proposed. (author)

  20. Reaction mixtures formed by nitrite and selected sulfa-drugs showed mutagenicity in acidic medium

    Directory of Open Access Journals (Sweden)

    Claudia Trossero

    2009-01-01

    Full Text Available Nitrite, which is present in preserved meat and can be produced in the oral cavity by reduction of nitrate taken from vegetables, could react in stomach with nitrosatable drugs, giving genotoxic-carcinogenic N-nitroso compounds (NOC. The mutagenicity of reaction mixtures formed by sodium nitrite and selected sulfa-drugs (sulfathiazole, HST; phtalylsulfathiazole, PhST; complex Co(II-sulfathiazole, Co(II-ST in acidic medium was evaluated using the Salmonella typhimurium reverse mutation assay (Ames test, with TA98 and TA 100 strains. The reactions were carried out at room temperature, with a mole ratio [nitrite]/[sulfa-drug] > 1. The three reaction mixtures showed mutagenic effects in the considered range.

  1. Uncertainties and understanding of experimental and theoretical results regarding reactions forming heavy and superheavy nuclei

    Science.gov (United States)

    Giardina, G.; Mandaglio, G.; Nasirov, A. K.; Anastasi, A.; Curciarello, F.; Fazio, G.

    2018-02-01

    Experimental and theoretical results of the PCN fusion probability of reactants in the entrance channel and the Wsur survival probability against fission at deexcitation of the compound nucleus formed in heavy-ion collisions are discussed. The theoretical results for a set of nuclear reactions leading to formation of compound nuclei (CNs) with the charge number Z = 102- 122 reveal a strong sensitivity of PCN to the characteristics of colliding nuclei in the entrance channel, dynamics of the reaction mechanism, and excitation energy of the system. We discuss the validity of assumptions and procedures for analysis of experimental data, and also the limits of validity of theoretical results obtained by the use of phenomenological models. The comparison of results obtained in many investigated reactions reveals serious limits of validity of the data analysis and calculation procedures.

  2. Recoil properties of radionuclides formed in photospallation reactions on complex nuclei at intermediate energies

    International Nuclear Information System (INIS)

    Haba, Hiromitsu; Oura, Yasuji; Shibata, Seiichi; Furukawa, Michiaki; Fujiwara, Ichiro

    2001-01-01

    A short review is given on our studies of recoil properties of radionuclides formed in photospallation reactions induced by bremsstrahlung of end-point energies (E 0 ) from 600 to 1100 MeV, in which the thick-target thick-catcher method was employed. The measurements have been successful on 14, 24, 26, 31, 21 and 20 nuclides from nat V, nat Cu, 93 Nb, nat Ag, nat Ta, and 197 Au, respectively. Reflecting the resonance character in a photonuclear reaction, the mean ranges FW and BW in the forward and backward directions, respectively, are E 0 -independent at the studied energies and classified into two groups accounting for the (γ, xn) (x ≥ 1) and (γ, xnyp) (x, y ≥ 1) processes. The forward-to-backward ratios (F/B) are independent of the mass difference (ΔA) between a product (A p ) and a target (A t ) and also of A t . The kinematic properties of the product nuclei were analyzed by the two-step vector velocity model. The forward velocity ν after the first step of photon-reaction is quite different from that of proton-reaction at proton energies of E p ≤ 3 GeV, though the difference disappears at higher energies. On the other hand, the mean kinetic energy T of the residual nucleus in the second step is almost equal to that of proton-reaction irrespective of E p . A comparison with T values calculated by the PICA (Photon-Induced Intranuclear Cascade Analysis) code at E 0 =400 MeV was also performed. It was found that although the code well reproduces the experimental results of nat V and nat Cu, the same calculation for heavier targets gives T values lower than the experimental results, indicating some nuclear-structure effect, such as a medium effect notably at A t ≥ 100. An average kinetic energy carried off by the emitted particles ε s =T/(ΔA/A t ) of both photon- and proton-reactions seem to increase with an increase of A t up to around A t =100, and become almost constant at larger A t , implying some change in the nuclear structure effect in this

  3. Influence of hydroxylamine conformation on stereocontrol in Pd-catalyzed isoxazolidine-forming reactions.

    Science.gov (United States)

    Lemen, Georgia S; Giampietro, Natalie C; Hay, Michael B; Wolfe, John P

    2009-03-20

    Palladium-catalyzed carboamination reactions between N-Boc-O-(but-3-enyl)hydroxylamine derivatives and aryl or alkenyl bromides afford cis-3,5- and trans-4,5-disubstituted isoxazolidines in good yield with up to >20:1 dr. The diastereoselectivity observed in the formation of cis-3,5-disubstituted isoxazolidines is superior to selectivities typically obtained in other transformations, such as 1,3-dipolar cycloaddition reactions, that provide these products. In addition, the stereocontrol in the C-N bond-forming Pd-catalyzed carboamination reactions of N-Boc-O-(but-3-enyl)hydroxylamines is significantly higher than that of related C-O bond-forming carboetherification reactions of N-benzyl-N-(but-3-enyl)hydroxylamine derivatives. This is likely due to a stereoelectronic preference for cyclization via transition states in which the Boc group is placed in a perpendicular orientation relative to the plane of the developing ring, which derives from the conformational equilibria of substituted hydroxylamines.

  4. Effect of an organoclay on the reaction-induced phase-separation in a dynamically asymmetric epoxy/PCL system

    Directory of Open Access Journals (Sweden)

    J. Rotrekl

    2013-12-01

    Full Text Available The addition of layered silicates can significantly affect the phase behaviour of both immiscible thermoplastic blends and partially miscible thermoset systems that undergo reaction-induced phase separation (RIPS during curing. This study focuses on the phase behaviour of polycaprolactone (PCL/epoxy in the presence of organically modified montmorillonite (oMMT. Due to the high dynamic asymmetry caused by the differences in the molecular weights and viscosities of the PCL and the uncured epoxy, the critical point is localised at low PCL concentrations, as indicated by the pseudophase diagram. The addition of oMMT to the system led to the marked shift of the critical point towards higher concentrations of PCL, with an increase in the oMMT content occurring as a consequence of the preferential localisation of the clay in the epoxy phase, making this phase more dynamically slow. Significant changes in morphology, including phase inversion of the PCL/epoxy systems caused by the presence of oMMT, were recorded for PCL concentrations ranging from 10 to 30%.

  5. Study of the multi-fragment production in asymmetric heavy ion reactions at E/A = 600 MeV

    International Nuclear Information System (INIS)

    Hubele, J.C.

    1992-03-01

    In this thesis the fragmentation of Au projectiles in collisions with light target nuclei ( 12 C, 27 Al, 64 Cu) is studied at a projectile energy of 600 MeV per nucleon. For the description of an event three observables are used: the multiplicity M lp of the light particles, the largest observed charge Z max of the projectile fragments, as well as a newly introduced obsevable Z bound , which is defined as the sum of all charge contained in complex projectile fragments (Z ≥ 2). By means of this observable different exit channels can be identified: the formation of a heavy residual nucleus by evaporation of light particles, the binary fission, the decay into IMF's (3 ≤ Z ≤ 30) and the complete decay into light particles. At the applied incident energy in the case of Au+Cu reactions each of these decay channels can be realized. The observables Z bound and M lpp are proved as suited quantities for the reconstruction of the impact parameter. Furthermore independently on the target a universal relation between Z bound and the multiplicity distribution of medium-heavy fragments is found. By simple model assumptions it is made plausible that Z bound is correlated both with the size of the projectile residue and in the mean with its excitation energy. For the characterization of the decay into IMF's the multiplicity M imf of these fragments is applied. For all three targets with increasing centrality first an increasing of the mean fragment multiplicities to maximal values of 3-4 is observed. In the case of the Cu target and suggestively also at the Al target in the most central collisions again a decreasing of the multiplicity is found. The universal Z bound behaviour is a hint to a - at least partial - equilibration of the primary projectile residue before the decay. (HSI) [de

  6. 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.

  7. Hydrothermally formed three-dimensional hexagon-like P doped Ni(OH)2 rod arrays for high performance all-solid-state asymmetric supercapacitors

    Science.gov (United States)

    Li, Kunzhen; Li, Shikuo; Huang, Fangzhi; Lu, Yan; Wang, Lei; Chen, Hong; Zhang, Hui

    2018-01-01

    Three dimensional hexagon-like phosphrous (P) doped Ni(OH)2 rod arrays grown on Ni foam (NF) are fabricated by a facile and green one-step hydrothermal process. Ni foam is only reacted in a certain concentration of P containing H2O2 aqueous solution. The possible growth mechanism of the P doped Ni(OH)2 rod arrays is discussed. As a battery-type electrode material in situ formed on Ni foam, the binder-free P doped Ni(OH)2 rod arrays electrode displays a ultrahigh specific areal capacitance of 2.11C cm-2 (3.51 F cm-2) at 2 mA cm-2, and excellent cycling stability (95.5% capacitance retention after 7500 cycles). The assembled all-solid-state asymmetric supercapacitor (AAS) based on such P doped Ni(OH)2 rod arrays as the positive electrode and activated carbon as the negative electrode achieves an energy density of 81.3 Wh kg-1 at the power density of 635 W kg-1. The AAS device also exhibits excellent practical performance, which can easily drive an electric fan (3 W rated power) when two AAS devices are assembled in series. Thus, our synthesized P doped Ni(OH)2 rod arrays has a lot of potential applications in future energy storage prospects.

  8. Products of aqueous vitamin B5 (pantothenic acid) formed by free radical reactions

    Energy Technology Data Exchange (ETDEWEB)

    Schittl, H. [Section of Radiation Biology, Department of Nutritional Sciences, University of Vienna, Althanstr. 14, UZA II, A-1090 Vienna (Austria); Quint, R.M. [Section of Radiation Biology, Department of Nutritional Sciences, University of Vienna, Althanstr. 14, UZA II, A-1090 Vienna (Austria); Getoff, N. [Section of Radiation Biology, Department of Nutritional Sciences, University of Vienna, Althanstr. 14, UZA II, A-1090 Vienna (Austria)]. E-mail: nikola.getoff@univie.ac.at

    2007-10-15

    The radiolysis of aqueous vitamin B5 (pantothenic acid) has been investigated under various experimental conditions. The highest vitamin degradation (G=3.22) was observed in solutions saturated with N{sub 2}O, where 90% OH radicals are operating. As final products, the following were established: aldehydes, carboxylic acids and ammonia. Their yield strongly depends on the presence/absence of air as well as on N{sub 2}O (used to convert e{sub aq} {sup -} into OH) and was determined as a function of absorbed radiation dose. HPLC-analysis showed that in all media, a main product is formed, having the highest yield in aerated solutions. Based on the chemical analysis, it appears that the OH radicals are most involved in the degradation process. A precise sequence of the reaction steps could not be given presently, because of the implication of many simultaneous reactions.

  9. Products of aqueous vitamin B5 (pantothenic acid) formed by free radical reactions

    International Nuclear Information System (INIS)

    Schittl, H.; Quint, R.M.; Getoff, N.

    2007-01-01

    The radiolysis of aqueous vitamin B5 (pantothenic acid) has been investigated under various experimental conditions. The highest vitamin degradation (G=3.22) was observed in solutions saturated with N 2 O, where 90% OH radicals are operating. As final products, the following were established: aldehydes, carboxylic acids and ammonia. Their yield strongly depends on the presence/absence of air as well as on N 2 O (used to convert e aq - into OH) and was determined as a function of absorbed radiation dose. HPLC-analysis showed that in all media, a main product is formed, having the highest yield in aerated solutions. Based on the chemical analysis, it appears that the OH radicals are most involved in the degradation process. A precise sequence of the reaction steps could not be given presently, because of the implication of many simultaneous reactions

  10. Asymmetric NHC-catalyzed aza-Diels-Alder reactions: Highly enantioselective route to α-amino acid derivatives and DFT calculations

    KAUST Repository

    Yang, Limin

    2014-08-01

    A facile N-heterocyclic carbene catalytic enantioselective aza-Diels-Alder reaction of oxodiazenes with α-chloroaldehydes as dienophile precursors is reported, with excellent enantioselectivity (ee > 99%) and excellent yield (up to 93%). DFT study showed that cis-TSa, formed from a top face approach of oxodiazene to cis-IIa, is the most favorable transition state and is consistent with the experimental observations. © 2014 American Chemical Society.

  11. Asymmetric ion trap

    Science.gov (United States)

    Barlow, Stephan E.; Alexander, Michael L.; Follansbee, James C.

    1997-01-01

    An ion trap having two end cap electrodes disposed asymmetrically about a center of a ring electrode. The inner surface of the end cap electrodes are conformed to an asymmetric pair of equipotential lines of the harmonic formed by the application of voltages to the electrodes. The asymmetry of the end cap electrodes allows ejection of charged species through the closer of the two electrodes which in turn allows for simultaneously detecting anions and cations expelled from the ion trap through the use of two detectors charged with opposite polarity.

  12. Recyclable enantioselective catalysts based on copper(II) complexes of 2-(pyridine-2-yl)imidazolidine-4-thione: their application in asymmetric Henry reactions

    Czech Academy of Sciences Publication Activity Database

    Nováková, G.; Drabina, P.; Frumarová, Božena; Sedlák, M.

    2016-01-01

    Roč. 358, č. 15 (2016), s. 2541-2552 ISSN 1615-4150 Institutional support: RVO:61389013 Keywords : asymmetric catalysis * enantioselectivity * heterogeneous catalysis Subject RIV: CC - Organic Chemistry Impact factor: 5.646, year: 2016

  13. Asymmetrical field emitter

    Science.gov (United States)

    Fleming, J.G.; Smith, B.K.

    1995-10-10

    A method is disclosed for providing a field emitter with an asymmetrical emitter structure having a very sharp tip in close proximity to its gate. One preferred embodiment of the present invention includes an asymmetrical emitter and a gate. The emitter having a tip and a side is coupled to a substrate. The gate is connected to a step in the substrate. The step has a top surface and a side wall that is substantially parallel to the side of the emitter. The tip of the emitter is in close proximity to the gate. The emitter is at an emitter potential, and the gate is at a gate potential such that with the two potentials at appropriate values, electrons are emitted from the emitter. In one embodiment, the gate is separated from the emitter by an oxide layer, and the emitter is etched anisotropically to form its tip and its asymmetrical structure. 17 figs.

  14. Cyclodextrins in Asymmetric and Stereospecific Synthesis

    Directory of Open Access Journals (Sweden)

    Fliur Macaev

    2015-09-01

    Full Text Available Since their discovery, cyclodextrins have widely been used as green and easily available alternatives to promoters or catalysts of different chemical reactions in water. This review covers the research and application of cyclodextrins and their derivatives in asymmetric and stereospecific syntheses, with their division into three main groups: (1 cyclodextrins promoting asymmetric and stereospecific catalysis in water; (2 cyclodextrins’ complexes with transition metals as asymmetric and stereospecific catalysts; and (3 cyclodextrins’ non-metallic derivatives as asymmetric and stereospecific catalysts. The scope of this review is to systematize existing information on the contribution of cyclodextrins to asymmetric and stereospecific synthesis and, thus, to facilitate further development in this direction.

  15. Two novel pyrrolooxazole pigments formed by the Maillard reaction between glucose and threonine or serine.

    Science.gov (United States)

    Noda, Kyoko; Murata, Masatsune

    2017-02-01

    Pyrrolothiazolate formed by the Maillard reaction between l-cysteine and d-glucose has a pyrrolothiazole skeleton as a chromophore. We searched for a Maillard pigment having a pyrrolooxazole skeleton formed from l-threonine or l-serine instead of l-cysteine in the presence of d-glucose. As a result, two novel yellow pigments, named pyrrolooxazolates A and B, were isolated from model solutions of the Maillard reaction containing l-threonine and d-glucose, and l-serine and d-glucose, respectively, and identified as (2R,3S,7aS)-2,3,7,7a-tetrahydro-6-hydroxy-2,5,7a-trimethyl-7-oxo-pyrrolo[2,1-b]oxazole-3-calboxylic acid and (3S,7aS)-2,3,7,7a-tetrahydro-6-hydroxy-5,7a-dimethyl-7-oxo-pyrrolo[2,1-b]oxazole-3-calboxylic acid by instrumental analyses. These compounds were pyrrolooxazole derivatives carrying a carboxy group, and showed the absorption maxima at 300-360 nm under acidic and neutral conditions and at 320-390 nm under alkaline conditions.

  16. Reasons of Aggressive Behaviour Against School Fellows, Its Frequency, Forms: Reaction of Schoolchildren, Teachers and Parents

    Directory of Open Access Journals (Sweden)

    Valdas Pruskus

    2011-12-01

    Full Text Available The present article, which is based on conducted research data, analyzes an attitude of schoolchildren, teachers and parents towards the reasons of schoolchildren’s aggressive behaviour, its frequency and forms. Different factors and motives that stimulate the aggressiveness of schoolchildren, who go to the city, village and different professional (arts and technology schools are examined. Schoolchildren’s approach towards violence against school fellows and themselves is being discussed, as well as reaction of teachers and parents to this phenomenon. The article reveals opinion of schoolchildren, teachers, and parents about the means used to prevent violence towards schoolchildren and existing ways that can be used to make preventive means to be more effective.

  17. Microstructural Characterization of Reaction-Formed Silicon Carbide Ceramics. Materials Characterization

    Science.gov (United States)

    Singh, M.; Leonhardt, T. A.

    1995-01-01

    Microstructural characterization of two reaction-formed silicon carbide ceramics has been carried out by interference layering, plasma etching, and microscopy. These specimens contained free silicon and niobium disilicide as minor phases with silicon carbide as the major phase. In conventionally prepared samples, the niobium disilicide cannot be distinguished from silicon in optical micrographs. After interference layering, all phases are clearly distinguishable. Back scattered electron (BSE) imaging and energy dispersive spectrometry (EDS) confirmed the results obtained by interference layering. Plasma etching with CF4 plus 4% O2 selectively attacks silicon in these specimens. It is demonstrated that interference layering and plasma etching are very useful techniques in the phase identification and microstructural characterization of multiphase ceramic materials.

  18. Impact of spin-orbit density dependent potential in heavy ion reactions forming Se nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Rajni; Sharma, Ishita; Sharma, Manoj K. [Thapar University, School of Physics and Materials Science, Patiala (India); Jain, Deepika [Mata Gujri College, Department of Physics, Fatehgarh Sahib (India)

    2017-10-15

    The Skyrme energy density formalism is employed to explore the effect of spin-orbit interaction potential by considering a two nucleon transfer process via various entrance channels such as {sup 23}Na + {sup 49}V, {sup 25}Mg + {sup 47}Ti, {sup 27}Al + {sup 45}Sc, {sup 29}Si + {sup 43}Ca and {sup 31}P + {sup 41}K, all forming the same compound system {sup 72}Se*, using both spherical as well as quadrupole deformed (β{sub 2}) nuclei. For spherical nuclei, the spin-orbit density part V{sub J} of nuclear potential remains unaffected with the transfer of two nucleons from the target to the projectile, however, show notable variation in magnitude after inclusion of deformation effects. Likewise, deformations play an important role in the spin-orbit density independent part V{sub P}, as the fusion pocket start appears, which otherwise diminish for the spherical nuclei. Further, the effect of an increase in the N/Z ratio of Se is explored on V{sub J} as well as V{sub P} and results are compared with transfer channels. In addition to this, the role of double spin-orbit parameters (W{sub 0} and W{sub 0}{sup '}) with relative contribution of the isoscalar and isovector parts of spin-orbit strength is explored in view of SkI2, SkI3 and SkI4 Skyrme forces. Beside this, the decay path of {sup 72}Se* nucleus formed in {sup 27}Al + {sup 45}Sc reaction is investigated within the framework of dynamical cluster decay model (DCM), where the nuclear proximity potential is obtained by both Skyrme energy density formalism (SEDF) and proximity pocket formula. The fusion hindrance in the {sup 27}Al + {sup 45}Sc reaction is also addressed via the barrier lowering parameter ΔV{sub B}. Finally, the contribution of spin-orbit density dependent interaction potential is estimated for the {sup 27}Al + {sup 45}Sc reaction using single (W{sub 0} or W{sub 0}{sup '}) and double spin-orbit parameters (W{sub 0} and W{sub 0}{sup '}). (orig.)

  19. Asymmetric cation-binding catalysis

    DEFF Research Database (Denmark)

    Oliveira, Maria Teresa; Lee, Jiwoong

    2017-01-01

    The employment of metal salts is quite limited in asymmetric catalysis, although it would provide an additional arsenal of safe and inexpensive reagents to create molecular functions with high optical purity. Cation chelation by polyethers increases the salts' solubility in conventional organic...... solvents, thus increasing their applicability in synthesis. The expansion of this concept to chiral polyethers led to the emergence of asymmetric cation-binding catalysis, where chiral counter anions are generated from metal salts, particularly using BINOL-based polyethers. Alkali metal salts, namely KF...... highly enantioselective silylation reactions in polyether-generated chiral environments, and leading to a record-high turnover in asymmetric organocatalysis. This can lead to further applications by the asymmetric use of other inorganic salts in various organic transformations....

  20. Asymmetric synthesis of α-amino acids via homologation of Ni(II) complexes of glycine Schiff bases. Part 2: aldol, Mannich addition reactions, deracemization and (S) to (R) interconversion of α-amino acids.

    Science.gov (United States)

    Sorochinsky, Alexander E; Aceña, José Luis; Moriwaki, Hiroki; Sato, Tatsunori; Soloshonok, Vadim

    2013-11-01

    This review provides a comprehensive treatment of literature data dealing with asymmetric synthesis of α-amino-β-hydroxy and α,β-diamino acids via homologation of chiral Ni(II) complexes of glycine Schiff bases using aldol and Mannich-type reactions. These reactions proceed with synthetically useful chemical yields and thermodynamically controlled stereoselectivity and allow direct introduction of two stereogenic centers in a single operation with predictable stereochemical outcome. Furthermore, new application of Ni(II) complexes of α-amino acids Schiff bases for deracemization of racemic α-amino acids and (S) to (R) interconversion providing additional synthetic opportunities for preparation of enantiomerically pure α-amino acids, is also reviewed. Origin of observed diastereo-/enantioselectivity in the aldol, Mannich-type and deracemization reactions, generality and limitations of these methodologies are critically discussed.

  1. Asymmetric Frontal Brain Activity and Parental Rejection

    NARCIS (Netherlands)

    Huffmeijer, R.; Alink, L.R.A.; Tops, M.; Bakermans-Kranenburg, M.J.; van IJzendoorn, M.H.

    2013-01-01

    Asymmetric frontal brain activity has been widely implicated in reactions to emotional stimuli and is thought to reflect individual differences in approach-withdrawal motivation. Here, we investigate whether asymmetric frontal activity, as a measure of approach-withdrawal motivation, also predicts

  2. Mechanochemistry assisted asymmetric organocatalysis: A sustainable approach

    Directory of Open Access Journals (Sweden)

    Pankaj Chauhan

    2012-12-01

    Full Text Available Ball-milling and pestle and mortar grinding have emerged as powerful methods for the development of environmentally benign chemical transformations. Recently, the use of these mechanochemical techniques in asymmetric organocatalysis has increased. This review highlights the progress in asymmetric organocatalytic reactions assisted by mechanochemical techniques.

  3. Fission dynamics of 240Cf* formed in 34,36S induced reactions

    Directory of Open Access Journals (Sweden)

    Jain Deepika

    2015-01-01

    Full Text Available We have studied the entrance channel effects in the decay of Compound nucleus 240Cf* formed in 34S+206Pb and 36S+204Pb reactions by using energy density dependent nuclear proximity potential in the framework of dynamical cluster-decay model (DCM. At different excitation energies, the fragmentation potential and preformation probability of decaying fragments are almost identical for both the entrance channels, which seem to suggest that decay is independent of its formation and entrance channel excitation energy. It is also observed that, with inclusion of deformation effects upto quadrupole within the optimum orientation approach, the fragmentation path governing potential energy surfaces gets modified significantly. Beside this, the fission mass distribution of Cf* isotopes is also investigated. The calculated fission cross-sections using SIII force for both the channels find nice agreement with the available experimental data for deformed choice of fragments, except at higher energies. In addition to this, the comparative analysis with Blocki based nuclear attraction is also worked out. It is observed that Blocki proximity potential accounts well for the CN decay at all energies whereas the use of EDF based nuclear potential suggests the presence of some non-compound nucleus process (such as quasi-fission (qf at higher energies.

  4. Dynamic pathways to mediate reactions buried in thermal fluctuations. I. Time-dependent normal form theory for multidimensional Langevin equation.

    Science.gov (United States)

    Kawai, Shinnosuke; Komatsuzaki, Tamiki

    2009-12-14

    We present a novel theory which enables us to explore the mechanism of reaction selectivity and robust functions in complex systems persisting under thermal fluctuation. The theory constructs a nonlinear coordinate transformation so that the equation of motion for the new reaction coordinate is independent of the other nonreactive coordinates in the presence of thermal fluctuation. In this article we suppose that reacting systems subject to thermal noise are described by a multidimensional Langevin equation without a priori assumption for the form of potential. The reaction coordinate is composed not only of all the coordinates and velocities associated with the system (solute) but also of the random force exerted by the environment (solvent) with friction constants. The sign of the reaction coordinate at any instantaneous moment in the region of a saddle determines the fate of the reaction, i.e., whether the reaction will proceed through to the products or go back to the reactants. By assuming the statistical properties of the random force, one can know a priori a well-defined boundary of the reaction which separates the full position-velocity space in the saddle region into mainly reactive and mainly nonreactive regions even under thermal fluctuation. The analytical expression of the reaction coordinate provides the firm foundation on the mechanism of how and why reaction proceeds in thermal fluctuating environments.

  5. Asymmetric collider

    International Nuclear Information System (INIS)

    Bharadwaj, V.; Colestock, P.; Goderre, G.; Johnson, D.; Martin, P.; Holt, J.; Kaplan, D.

    1993-01-01

    The study of CP violation in beauty decay is one of the key challenges facing high energy physics. Much work has not yielded a definitive answer how this study might best be performed. However, one clear conclusion is that new accelerator facilities are needed. Proposals include experiments at asymmetric electron-positron colliders and in fixed-target and collider modes at LHC and SSC. Fixed-target and collider experiments at existing accelerators, while they might succeed in a first observation of the effect, will not be adequate to study it thoroughly. Giomataris has emphasized the potential of a new approach to the study of beauty CP violation: the asymmetric proton collider. Such a collider might be realized by the construction of a small storage ring intersecting an existing or soon-to-exist large synchrotron, or by arranging collisions between a large synchrotron and its injector. An experiment at such a collider can combine the advantages of fixed-target-like spectrometer geometry, facilitating triggering, particle identification and the instrumentation of a large acceptance, while the increased √s can provide a factor > 100 increase in beauty-production cross section compared to Tevatron or HERA fixed-target. Beams crossing at a non-zero angle can provide a small interaction region, permitting a first-level decay-vertex trigger to be implemented. To achieve large √s with a large Lorentz boost and high luminosity, the most favorable venue is the high-energy booster (HEB) at the SSC Laboratory, though the CERN SPS and Fermilab Tevatron are also worth considering

  6. Origin of Nanobubbles Electrochemically Formed in a Magnetic Field: Ionic Vacancy Production in Electrode Reaction

    Science.gov (United States)

    Aogaki, Ryoichi; Sugiyama, Atsushi; Miura, Makoto; Oshikiri, Yoshinobu; Miura, Miki; Morimoto, Ryoichi; Takagi, Satoshi; Mogi, Iwao; Yamauchi, Yusuke

    2016-07-01

    As a process complementing conventional electrode reactions, ionic vacancy production in electrode reaction was theoretically examined; whether reaction is anodic or cathodic, based on the momentum conservation by Newton’s second law of motion, electron transfer necessarily leads to the emission of original embryo vacancies, and dielectric polarization endows to them the same electric charge as trans- ferred in the reaction. Then, the emitted embryo vacancies immediately receive the thermal relaxation of solution particles to develop steady-state vacancies. After the vacancy production, nanobubbles are created by the collision of the vacancies in a vertical magnetic field.

  7. Asymmetric Diels-Alder Reaction of α-Substituted and β,β-Disubstituted α,β-Enals via Diarylprolinol Silyl Ether for the Construction of All-Carbon Quaternary Stereocenters.

    Science.gov (United States)

    Hayashi, Yujiro; Bondzic, Bojan P; Yamazaki, Tatsuya; Gupta, Yogesh; Ogasawara, Shin; Taniguchi, Tohru; Monde, Kenji

    2016-10-24

    The asymmetric Diels-Alder reaction of α-substituted acrolein proceeds in the presence of the trifluoroacetic acid salt of trifluoromethyl-substituted diarylprolinol silyl ether to afford the exo-isomer with both excellent diastereoselectivity and high enantioselectivity. In the Diels-Alder reaction of a β,β-disubstituted α,β-unsaturated aldehyde, good exo-selectivity and excellent enantioselectivity was obtained when the perchloric acid salt of the bulky triisopropyl silyl ether of trifluoromethyl substituted diarylprolinol was employed as an organocatalyst in the presence of water. In both cases, all-carbon quaternary stereocenters are constructed enantioselectively. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Lipase-catalyzed asymmetric synthesis of naphtho[2,3-c]furan-1(3H)-one derivatives by a one-pot dynamic kinetic resolution/intramolecular Diels-Alder reaction: Total synthesis of (-)-himbacine.

    Science.gov (United States)

    Sugiyama, Koji; Kawanishi, Shinji; Oki, Yasuhiro; Kamiya, Marin; Hanada, Ryosuke; Egi, Masahiro; Akai, Shuji

    2018-04-01

    One-pot sequential reactions using the acyl moieties installed by enzymatic dynamic kinetic resolution of alcohols have been little investigated. In this work, the acryloyl moiety installed via the lipase/oxovanadium combo-catalyzed dynamic kinetic resolution of a racemic dienol [4-(cyclohex-1-en-1-yl)but-3-en-2-ol or 1-(cyclohex-1-en-1-yl)but-2-en-1-ol] with a (Z)-3-(phenylsulfonyl)acrylate underwent an intramolecular Diels-Alder reaction in a one-pot procedure to produce an optically active naphtho[2,3-c]furan-1(3H)-one derivative (98% ee). This method was successfully applied to the asymmetric total synthesis of (-)-himbacine. Copyright © 2017 Elsevier Ltd. All rights reserved.

  9. When the mind forms fear: embodied fear knowledge potentiates bodily reactions

    NARCIS (Netherlands)

    Oosterwijk, S.; Topper, M.; Rotteveel, M.; Fischer, A.H.

    2010-01-01

    In the present study, the authors tested whether conceptual fear knowledge can (a) evoke bodily reactions and (b) enhance subsequent bodily reactions to fearful stimuli. Participants unscrambled neutral or fear sentences and subsequently viewed fearful and neutral pictures in combination with

  10. Aerosol-Forming Reactions of Glyoxal, Methylglyoxal and Amino Acids in Clouds

    Science.gov (United States)

    de Haan, D. O.; Smith, K. W.; Stroik, D. R.; Corrigan, A. L.; Lee, F. E.; Phan, J. T.; Conley, A. C.

    2008-12-01

    Glyoxal and methylglyoxal are two common aldehydes present in fog and cloud water. Amino acids are present in clouds at similar concentrations. Here we present bulk and aerosol mass spectroscopic data demonstrating that irreversible reactions between glyoxal and amino acids, triggered by droplet evaporation, produce N-derivatized imidazole compounds along with deeply colored Maillard reaction products. These reactions can occur in the dark and in the absence of oxidants. Reactions between methylglyoxal and amino acids produce analogous methylated products plus oligomers with masses up to m/z = 1000. These reactions, which go to completion on the 10-min-timescale of cloud processing, could be significant sources of secondary organic aerosol and humic-like substances (HULIS or brown carbon).

  11. The decay of hot nuclei formed in La-induced reactions at E/A=45 MeV

    International Nuclear Information System (INIS)

    Libby, B.

    1993-01-01

    The decay of hot nuclei formed in the reactions 139 La + 27 Al, 51 V, nat Cu, and 139 La were studied by the coincident detection of up to four complex fragments (Z > 3) emitted in these reactions. Fragments were characterized as to their atomic number, energy and in- and out-of-plane angles. The probability of the decay by an event of a given complex fragment multiplicity as a function of excitation energy per nucleon of the source is nearly independent of the system studied. Additionally, there is no large increase in the proportion of multiple fragment events as the excitation energy of the source increases past 5 MeV/nucleon. This is at odds with many prompt multifragmentation models of nuclear decay. The reactions 139 La + 27 Al, 51 V, nat Cu were also studied by combining a dynamical model calculation that simulates the early stages of nuclear reactions with a statistical model calculation for the latter stages of the reactions. For the reaction 139 La + 27 Al, these calculations reproduced many of the experimental features, but other features were not reproduced. For the reaction 139 La + 51 V, the calculation failed to reproduce somewhat more of the experimental features. The calculation failed to reproduce any of the experimental features of the reaction 139 La + nat Cu, with the exception of the source velocity distributions

  12. Impact of Secondary Interactions in Asymmetric Catalysis

    OpenAIRE

    Frölander, Anders

    2007-01-01

    This thesis deals with secondary interactions in asymmetric catalysis and their impact on the outcome of catalytic reactions. The first part revolves around the metal-catalyzed asymmetric allylic alkylation reaction and how interactions within the catalyst affect the stereochemistry. An OH–Pd hydrogen bond in Pd(0)–π-olefin complexes of hydroxy-containing oxazoline ligands was identified by density functional theory computations and helped to rationalize the contrasting results obtained emplo...

  13. Chiral ferrocenes in asymmetric catalysis: synthesis and applications

    National Research Council Canada - National Science Library

    Dai, Li-Xin; Hou, Xue-Long

    2010-01-01

    .... It provides a thorough overview of the synthesis and characterization of different types of chiral ferrocene ligands, their application to various catalytic asymmetric reactions, and versatile chiral...

  14. Asymmetric Organocatalytic Cycloadditions

    DEFF Research Database (Denmark)

    Mose, Rasmus

    2016-01-01

    has gained broad recognition as it has found several applications in academia and industry. The [4+2] cycloaddition has also been performed in an enantioselective aminocatalytic fashion which allows the generation of optically active products. In this thesis it is demonstrated how trienamines can......Since the onset of the new millennium the field of organocatalysis has undergone a great expansion led by investigations in the field of aminocatalysis. This thesis will address some recent developments in aminocatalyzed cycloadditions and provide a theoretical background hereto. Cycloadditions...... undergo cascade reactions with different electron deficient dienophiles in Diels Alder – nucleophilic ring closing reactions. This methodology opens up for the direct asymmetric formation of hydroisochromenes and hydroisoquinolines which may possess interesting biological activities. It is also...

  15. Asymmetric Evolutionary Games

    Science.gov (United States)

    McAvoy, Alex; Hauert, Christoph

    2015-01-01

    Evolutionary game theory is a powerful framework for studying evolution in populations of interacting individuals. A common assumption in evolutionary game theory is that interactions are symmetric, which means that the players are distinguished by only their strategies. In nature, however, the microscopic interactions between players are nearly always asymmetric due to environmental effects, differing baseline characteristics, and other possible sources of heterogeneity. To model these phenomena, we introduce into evolutionary game theory two broad classes of asymmetric interactions: ecological and genotypic. Ecological asymmetry results from variation in the environments of the players, while genotypic asymmetry is a consequence of the players having differing baseline genotypes. We develop a theory of these forms of asymmetry for games in structured populations and use the classical social dilemmas, the Prisoner’s Dilemma and the Snowdrift Game, for illustrations. Interestingly, asymmetric games reveal essential differences between models of genetic evolution based on reproduction and models of cultural evolution based on imitation that are not apparent in symmetric games. PMID:26308326

  16. Liquid composition having ammonia borane and decomposing to form hydrogen and liquid reaction product

    Science.gov (United States)

    Davis, Benjamin L; Rekken, Brian D

    2014-04-01

    Liquid compositions of ammonia borane and a suitably chosen amine borane material were prepared and subjected to conditions suitable for their thermal decomposition in a closed system that resulted in hydrogen and a liquid reaction product.

  17. Competition of electron transfer, dissociation, and bond-forming reactions in collisions of CO22+ with neutral CO2

    Czech Academy of Sciences Publication Activity Database

    Ricketts, Claire; Schröder, Detlef; Roithová, Jana; Schwarz, H.; Thissen, R.; Dutuit, O.; Žabka, Ján; Herman, Zdeněk; Price, S. D.

    2008-01-01

    Roč. 10, č. 33 (2008), s. 5135-5143 ISSN 1463-9076 Institutional research plan: CEZ:AV0Z40550506; CEZ:AV0Z40400503 Keywords : carbon dioxide * bond -forming reactions * dications Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.064, year: 2008

  18. Manipulating the Energetics and Rates of Electron Transfer in Rhodobacter capsulatus Reaction Centers with Asymmetric Pigment Content

    Energy Technology Data Exchange (ETDEWEB)

    Faries, Kaitlyn M. [Department; Dylla, Nicholas P. [Biosciences Division, Argonne National Laboratory, Lemont, Illinois 60439, United States; Hanson, Deborah K. [Biosciences Division, Argonne National Laboratory, Lemont, Illinois 60439, United States; Holten, Dewey [Department; Laible, Philip D. [Biosciences Division, Argonne National Laboratory, Lemont, Illinois 60439, United States; Kirmaier, Christine [Department

    2017-07-17

    Seemingly redundant parallel pathways for electron transfer (ET), composed of identical sets of cofactors, are a cornerstone feature of photosynthetic reaction centers (RCs) involved in light-energy conversion. In native bacterial RCs, both A and B branches house one bacteriochlorophyll (BChl) and one bacteriopheophytin (BPh), but the A branch is used exclusively. Described herein are the results-obtained for two Rhodobacter capsulatus RCs with an unnaturally high degree of cofactor asymmetry, two BPh on the RC's B side and two BChl on the A side. These pigment changes derive, respectively, from the His(M180)Leu mutation [a BPh ((Phi(B)) replaces the B-side BChl (BB)], and the Leu(M212)His mutation [a BChl (beta(A))) replaces the A-side BPh (H-A)]. Additionally, Tyr(M208)Phe was employed to disfavor ET to the A branch; in one mutant, Val(M131)Glu creates a hydrogen bond to H-B to enhance ET to H-B. In both Phi(B) mutants, the decay kinetics of the excited primary ET donor (P*) resolve three populations with lifetimes of similar to 9 ps (50-60%), similar to 40 ps (10-20%), and similar to 200 ps (20-30%), with P+Phi(-)(B) formed predominantly from the 9 ps fraction. The 50-60% yield of P+Phi(B)- is the highest yet observed for a Phi(B)-containing RC. The results provide insight into factors needed for efficient multistep ET.

  19. Efficient Computation of Transition State Resonances and Reaction Rates from a Quantum Normal Form

    NARCIS (Netherlands)

    Schubert, Roman; Waalkens, Holger; Wiggins, Stephen

    2006-01-01

    A quantum version of a recent formulation of transition state theory in phase space is presented. The theory developed provides an algorithm to compute quantum reaction rates and the associated Gamov-Siegert resonances with very high accuracy. The algorithm is especially efficient for

  20. A new closed form expression for the total reaction cross-section of heavy ions

    International Nuclear Information System (INIS)

    Rego, R.A.; Hussein, M.S.

    1989-02-01

    A new analytical expression for the HI total reaction cross-section which exhibits the macroscopic features of the transparency factor is derived. Comparison with optical model calculation are made for the 12 C+ 208 Pb and 16 O + 208 Pb at several energies. (author)

  1. Highly Enantioselective Construction of Tertiary Thioethers and Alcohols via Phosphine-Catalyzed Asymmetric γ-Addition reactions of 5H-Thiazol-4-ones and 5H-Oxazol-4-ones: Scope and Mechanistic Understandings

    KAUST Repository

    Wang, Tianli

    2015-06-02

    Phosphine-catalyzed highly enantioselective γ-additions of 5H-thiazol-4-ones and 5H-oxazol-4-ones to allenoates have been developed for the first time. With the employment of amino-acid derived bifunctional phosphines, a wide range of substituted 5H-thiazol-4-one and 5H-oxazol-4-one derivatives bearing heteroarom (S or O)-containing tertiary chiral centers were constructed in high yields and excellent enantioselectivities. The reported method provides a facile access to enantioenriched tertiary thioether/alcohols. The mechanism of γ-addition reaction was investigated by performing DFT calculations, and the hydrogen bonding interactions between the Brønsted acid moiety of the phosphine catalysts and the “C=O” unit of donor molecules were shown to be crucial in asymmetric induction.

  2. Highly Enantioselective Construction of Tertiary Thioethers and Alcohols via Phosphine-Catalyzed Asymmetric γ-Addition reactions of 5H-Thiazol-4-ones and 5H-Oxazol-4-ones: Scope and Mechanistic Understandings

    KAUST Repository

    Wang, Tianli; Yu, Zhaoyuan; Hoon, Ding Long; Huang, Kuo-Wei; Lan, Yu; Lu, Yixin

    2015-01-01

    Phosphine-catalyzed highly enantioselective γ-additions of 5H-thiazol-4-ones and 5H-oxazol-4-ones to allenoates have been developed for the first time. With the employment of amino-acid derived bifunctional phosphines, a wide range of substituted 5H-thiazol-4-one and 5H-oxazol-4-one derivatives bearing heteroarom (S or O)-containing tertiary chiral centers were constructed in high yields and excellent enantioselectivities. The reported method provides a facile access to enantioenriched tertiary thioether/alcohols. The mechanism of γ-addition reaction was investigated by performing DFT calculations, and the hydrogen bonding interactions between the Brønsted acid moiety of the phosphine catalysts and the “C=O” unit of donor molecules were shown to be crucial in asymmetric induction.

  3. N,N'-dioxide/nickel(II)-catalyzed asymmetric inverse-electron-demand hetero-diels-alder reaction of β,γ-unsaturated α-ketoesters with enecarbamates.

    Science.gov (United States)

    Zhou, Yuhang; Zhu, Yin; Lin, Lili; Zhang, Yulong; Zheng, Jianfeng; Liu, Xiaohua; Feng, Xiaoming

    2014-12-08

    N,N'-Dioxide/nickel(II) complexes have been developed to catalyze the inverse-electron-demand hetero-Diels-Alder reaction of β,γ-unsaturated α-ketoesters with acyclic enecarbamates. After detailed screening of the reaction parameters, mild optimized reaction conditions were established, affording 3,4-dihydro-2H-pyranamines in up to 99 % yield, 99 % ee and more than 95:5 d.r. The catalytic system was also efficient for β-substituted acyclic enecarbamates, affording more challenging 2,3,4-trisubstituted 3,4-dihydro-2H-pyranamine with three contiguous stereogenic centers in excellent yields, diastereoselectivities, and enantioselectivities. The reaction could be scaled up to a gram scale with no deterioration of either enantioselectivity or yield. Based on these experiments and on previous reports, a possible transition state was proposed. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Asymmetric NHC-catalyzed aza-Diels-Alder reactions: Highly enantioselective route to α-amino acid derivatives and DFT calculations

    KAUST Repository

    Yang, Limin; Wang, Fei; Lee, Richmond; Lv, Yunbo; Huang, Kuo-Wei; Zhong, Guofu

    2014-01-01

    A facile N-heterocyclic carbene catalytic enantioselective aza-Diels-Alder reaction of oxodiazenes with α-chloroaldehydes as dienophile precursors is reported, with excellent enantioselectivity (ee > 99%) and excellent yield (up to 93%). DFT study

  5. Reaction

    African Journals Online (AJOL)

    abp

    19 oct. 2017 ... Reaction to Mohamed Said Nakhli et al. concerning the article: "When the axillary block remains the only alternative in a 5 year old child". .... Bertini L1, Savoia G, De Nicola A, Ivani G, Gravino E, Albani A et al ... 2010;7(2):101-.

  6. Arabidopsis ASYMMETRIC LEAVES2 protein required for leaf morphogenesis consistently forms speckles during mitosis of tobacco BY-2 cells via signals in its specific sequence.

    Science.gov (United States)

    Luo, Lilan; Ando, Sayuri; Sasabe, Michiko; Machida, Chiyoko; Kurihara, Daisuke; Higashiyama, Tetsuya; Machida, Yasunori

    2012-09-01

    Leaf primordia with high division and developmental competencies are generated around the periphery of stem cells at the shoot apex. Arabidopsis ASYMMETRIC-LEAVES2 (AS2) protein plays a key role in the regulation of many genes responsible for flat symmetric leaf formation. The AS2 gene, expressed in leaf primordia, encodes a plant-specific nuclear protein containing an AS2/LOB domain with cysteine repeats (C-motif). AS2 proteins are present in speckles in and around the nucleoli, and in the nucleoplasm of some leaf epidermal cells. We used the tobacco cultured cell line BY-2 expressing the AS2-fused yellow fluorescent protein to examine subnuclear localization of AS2 in dividing cells. AS2 mainly localized to speckles (designated AS2 bodies) in cells undergoing mitosis and distributed in a pairwise manner during the separation of sets of daughter chromosomes. Few interphase cells contained AS2 bodies. Deletion analyses showed that a short stretch of the AS2 amino-terminal sequence and the C-motif play negative and positive roles, respectively, in localizing AS2 to the bodies. These results suggest that AS2 bodies function to properly distribute AS2 to daughter cells during cell division in leaf primordia; and this process is controlled at least partially by signals encoded by the AS2 sequence itself.

  7. Asymmetric adjustment

    NARCIS (Netherlands)

    2010-01-01

    A method of adjusting a signal processing parameter for a first hearing aid and a second hearing aid forming parts of a binaural hearing aid system to be worn by a user is provided. The binaural hearing aid system comprises a user specific model representing a desired asymmetry between a first ear

  8. Novel binder-free forming of Al2O3 ceramics by microwave-assisted hydration reaction

    International Nuclear Information System (INIS)

    Shirai, Takashi; Yasuoka, Masaki; Watari, Koji

    2008-01-01

    A novel binder-free forming of ceramics via microwave irradiation is developed. The irradiation of microwave to an alumina green body enhances the hydration reaction strongly between water and particle surfaces, creating surface aluminum trihydroxides structure adjacent to particles that bind them together tightly. This process makes it possible to manufacture mechanically strong green bodies with excellent shape retention ability without the use of organic binders

  9. Purification of hydrogen under a free or combined form in a gaseous mixture, by chemical reactions with uranium

    International Nuclear Information System (INIS)

    Caron Charles, M.

    1988-03-01

    Within the framework of the european fusion program, we are dealing with the purification of hydrogen (tritium) under a free or combined form, from a H 2 , N 2 , NH 3 , CH 4 , O 2 , gaseous mixture. The process consists in cracking the hydrogenated molecules and absorbing the impurities by chemical reactions with uranium, without holding back hydrogen. In the temperature range: 950 K [fr

  10. (Salen)Ti(Ⅳ)-Catalyzed Asymmetric Ring-opening of meso Epoxides Using Dithiophosphorus Acid as the Nucleophile

    Institute of Scientific and Technical Information of China (English)

    Zheng Hong ZHOU; Zhao Ming LI; Bing LIU; Kang Ying LI; Li Xin WANG; Guo Feng ZHAO; Qi Lin ZHOU; Chu Chi TANG

    2006-01-01

    The asymmetric ring-opening of epoxides with dithiophosphorus acids catalyzed by a (salen)Ti(Ⅳ) complex formed in situ from the reaction of Ti(OPr-i)4 and the chiral Schiff base derived from (1R,2R)-(+)-diaminocyclohexane was realized. The resulting products were obtained with low to good enantioselectivity (up to 73% ee).

  11. Asymmetric Ashes

    Science.gov (United States)

    2006-11-01

    that oscillate in certain directions. Reflection or scattering of light favours certain orientations of the electric and magnetic fields over others. This is why polarising sunglasses can filter out the glint of sunlight reflected off a pond. When light scatters through the expanding debris of a supernova, it retains information about the orientation of the scattering layers. If the supernova is spherically symmetric, all orientations will be present equally and will average out, so there will be no net polarisation. If, however, the gas shell is not round, a slight net polarisation will be imprinted on the light. This is what broad-band polarimetry can accomplish. If additional spectral information is available ('spectro-polarimetry'), one can determine whether the asymmetry is in the continuum light or in some spectral lines. In the case of the Type Ia supernovae, the astronomers found that the continuum polarisation is very small so that the overall shape of the explosion is crudely spherical. But the much larger polarization in strongly blue-shifted spectral lines evidences the presence, in the outer regions, of fast moving clumps with peculiar chemical composition. "Our study reveals that explosions of Type Ia supernovae are really three-dimensional phenomena," says Dietrich Baade. "The outer regions of the blast cloud is asymmetric, with different materials found in 'clumps', while the inner regions are smooth." "This study was possible because polarimetry could unfold its full strength thanks to the light-collecting power of the Very Large Telescope and the very precise calibration of the FORS instrument," he adds. The research team first spotted this asymmetry in 2003, as part of the same observational campaign (ESO PR 23/03 and ESO PR Photo 26/05). The new, more extensive results show that the degree of polarisation and, hence, the asphericity, correlates with the intrinsic brightness of the explosion. The brighter the supernova, the smoother, or less clumpy

  12. Linear relations in microbial reaction systems: a general overview of their origin, form, and use.

    Science.gov (United States)

    Noorman, H J; Heijnen, J J; Ch A M Luyben, K

    1991-09-01

    In microbial reaction systems, there are a number of linear relations among net conversion rates. These can be very useful in the analysis of experimental data. This article provides a general approach for the formation and application of the linear relations. Two type of system descriptions, one considering the biomass as a black box and the other based on metabolic pathways, are encountered. These are defined in a linear vector and matrix algebra framework. A correct a priori description can be obtained by three useful tests: the independency, consistency, and observability tests. The independency are different. The black box approach provides only conservations relations. They are derived from element, electrical charge, energy, and Gibbs energy balances. The metabolic approach provides, in addition to the conservation relations, metabolic and reaction relations. These result from component, energy, and Gibbs energy balances. Thus it is more attractive to use the metabolic description than the black box approach. A number of different types of linear relations given in the literature are reviewed. They are classified according to the different categories that result from the black box or the metabolic system description. Validation of hypotheses related to metabolic pathways can be supported by experimental validation of the linear metabolic relations. However, definite proof from biochemical evidence remains indispensable.

  13. Functional properties of nisin–carbohydrate conjugates formed by radiation induced Maillard reaction

    International Nuclear Information System (INIS)

    Muppalla, Shobita R.; Sonavale, Rahul; Chawla, Surinder P.; Sharma, Arun

    2012-01-01

    Nisin–carbohydrate conjugates were prepared by irradiating nisin either with glucose or dextran. Increase in browning and formation of intermediate products was observed with a concomitant decrease in free amino and reducing sugar groups indicating occurrence of the Maillard reaction catalyzed by irradiation. Nisin–carbohydrate conjugates showed a broad spectrum antibacterial activity against Gram negative bacteria (Escherichia coli, Pseudomonas fluorescence) as well as Gram positive bacteria (Staphylococcus aureus, Bacillus cereus). Results of antioxidant assays, including that of DPPH radical-scavenging activity and reducing power, showed that the nisin–dextran conjugates possessed better antioxidant potential than nisin–glucose conjugate. These results suggested that it was possible to enhance the functional properties of nisin by preparing radiation induced conjugates suitable for application in food industry. - Highlights: ► Nisin–carbohydrate conjugates were prepared using radiation induced Maillard reaction. ► Conjugation of nisin with dextran/glucose resulted in improvement of antibacterial spectrum. ► Conjugates of nisin with dextran/glucose had significant radical scavenging activity.

  14. Identification of secondary phases formed during unsaturated reaction of UO2 with EJ-13 water

    International Nuclear Information System (INIS)

    Bates, J.K.; Tani, B.S.; Veleckis, E.

    1989-01-01

    A set of experiments, wherein UO 2 has been contacted by dripping water, has been conducted over a period of 182.5 weeks. The experiments are being conducted to develop procedures to study spent fuel reaction under unsaturated conditions that are expected to exist over the lifetime of the proposed Yucca Mountain repository site. One half of the experiments have been terminated, while one half are ongoing. Analyses of solutions that have dripped from the reacted UO 2 have been performed for all experiments, while the reacted UO 2 surfaces have been examined for the terminated experiments. A pulse of uranium release from the UO 2 solid, combined with the formation of schoepite on the surface of the UO 2 , was observed between 39 and 96 weeks of reaction. Thereafter, the uranium release decreased and a second set of secondary phases was observed. The latter phases incorporated cations from the EJ-13 water and included boltwoodite, uranophane, sklodowskite, compreignacite, and schoepite. The experiments are continuing to monitor whether additional changes in solution chemistry or secondary phase formation occurs. 6 refs., 2 figs., 2 tabs

  15. Novel dextran derivatives with unconventional structure formed in an efficient one-pot reaction.

    Science.gov (United States)

    Hotzel, Konrad; Heinze, Thomas

    2016-11-03

    An efficient one-pot synthesis of new dextran derivatives is described. The functional groups of β-alanine, i.e., the carboxyl- and amine group, are converted independently in one-step by iminium chloride to form products with a single substituent. The dextran N-[(dimethylamino)methylene]-β-alanine ester is formed selectively. The structure of the resulting polymers is unambiguously determined by means of NMR- and FTIR-spectroscopy and elemental analysis. Copyright © 2016 Elsevier Ltd. All rights reserved.

  16. Bicyclic Guanidine Catalyzed Asymmetric Tandem Isomerization Intramolecular-Diels-Alder Reaction: The First Catalytic Enantioselective Total Synthesis of (+)-alpha-Yohimbine.

    Science.gov (United States)

    Feng, Wei; Jiang, Danfeng; Kee, Choon-Wee; Liu, Hongjun; Tan, Choon-Hong

    2016-02-04

    Hydroisoquinoline derivatives were prepared in moderate to good enantioselectivities via a bicyclic guanidine-catalyzed tandem isomerization intramolecular-Diels-Alder (IMDA) reaction of alkynes. With this synthetic method, the first enantioselective synthesis of (+)-alpha-yohimbine was completed in 9 steps from the IMDA products. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Search for toroidal and bubble nuclei formed in the Au + Au reaction

    International Nuclear Information System (INIS)

    Planeta, R.; Brzychczyk, J.; Majka, Z.; Blicharska, J.; Grzeszczuk, A.; Zipper, W.; Schmidt, K.; Kowalski, S.; Cibor, J.; Hachaj, P.; Nicolis, N.

    2003-01-01

    In this contribution we present the feasibility study for the experimental observation of toroidal and bubble nuclei. This search is based on data collected by the CHIMERA collaboration for the Au + Au reaction at 15 MeV/nucleon. The beam time needed to achieve this goal is calculated for events with at least 5 heavy fragments. We found that the fraction of such events among the accumulated data is equal to 8*10 -4 . Assuming the Au beam intensity is 0.03 pnA and target thickness equals 0.3 mg/cm 2 we estimated that 450 hours of beam time is needed to record 10 6 multifragment events. Present status of the Monte-Carlo simulation predictions is shortly discussed. (A.C.)

  18. Search for toroidal and bubble nuclei formed in the Au + Au reaction

    Energy Technology Data Exchange (ETDEWEB)

    Planeta, R.; Brzychczyk, J.; Majka, Z. [M.Smoluchowski Institute of Physics, Jagellonian University, Krakow (Poland); Blicharska, J.; Grzeszczuk, A.; Zipper, W.; Schmidt, K.; Kowalski, S. [Silesian University, Institute of Physics, Katowice (Poland); Cibor, J. [Institute of Nuclear Physics, Krakow (Poland); Hachaj, P. [Cracow Univ. of Technology, Krakow (Poland); Nicolis, N. [Ioannina Univ. (Greece)

    2003-07-01

    In this contribution we present the feasibility study for the experimental observation of toroidal and bubble nuclei. This search is based on data collected by the CHIMERA collaboration for the Au + Au reaction at 15 MeV/nucleon. The beam time needed to achieve this goal is calculated for events with at least 5 heavy fragments. We found that the fraction of such events among the accumulated data is equal to 8*10{sup -4}. Assuming the Au beam intensity is 0.03 pnA and target thickness equals 0.3 mg/cm{sup 2} we estimated that 450 hours of beam time is needed to record 10{sup 6} multifragment events. Present status of the Monte-Carlo simulation predictions is shortly discussed. (A.C.)

  19. Functional properties of nisin-carbohydrate conjugates formed by radiation induced Maillard reaction

    Science.gov (United States)

    Muppalla, Shobita R.; Sonavale, Rahul; Chawla, Surinder P.; Sharma, Arun

    2012-12-01

    Nisin-carbohydrate conjugates were prepared by irradiating nisin either with glucose or dextran. Increase in browning and formation of intermediate products was observed with a concomitant decrease in free amino and reducing sugar groups indicating occurrence of the Maillard reaction catalyzed by irradiation. Nisin-carbohydrate conjugates showed a broad spectrum antibacterial activity against Gram negative bacteria (Escherichia coli, Pseudomonas fluorescence) as well as Gram positive bacteria (Staphylococcus aureus, Bacillus cereus). Results of antioxidant assays, including that of DPPH radical-scavenging activity and reducing power, showed that the nisin-dextran conjugates possessed better antioxidant potential than nisin-glucose conjugate. These results suggested that it was possible to enhance the functional properties of nisin by preparing radiation induced conjugates suitable for application in food industry.

  20. The first report of a muoniated free radical formed from reaction of Mu with Br2

    International Nuclear Information System (INIS)

    Ghandi, Khashayar; Cottrell, Stephen P.; Fleming, Donald; Johnson, Clive

    2006-01-01

    In this paper, we report preliminary data for the first direct evidence of a free radical formed from Mu reactivity with Br 2 in the gas phase, in N 2 moderator at a total pressure of 3 bar. A new experimental setup and target vessel for μSR studies of reactive compounds, such as the halogens and hydrogen halides, suitable as well for RF measurements, is described. The experimental data, obtained from a longitudinal field repolarization curve, yields a hfc of 1770 MHz. We tentatively identify this as the [BrMuBr] radical, a non-conventional bond system, arising from the combination of a van der Waals interaction and dynamics on a repulsive surface. Studies of the dynamics and hfcs of possible radicals, which in principal could form, are also outlined here

  1. Asymmetric Diels–Alder reaction with >C=P– functionality of the 2-phosphaindolizine-η1-P-aluminium(O-menthoxy dichloride complex: experimental and theoretical results

    Directory of Open Access Journals (Sweden)

    Rajendra K. Jangid

    2013-02-01

    Full Text Available The Diels–Alder reaction of the 2-phosphaindolizine-η1-P-aluminium(O-menthoxy dichloride complex with dimethylbutadiene was investigated experimentally and computationally. The >C=P– functionality of the complex reacts with 2,3-dimethylbutadiene with complete diastereoselectivity to afford [2 + 4] cycloadducts. Calculation of the model substrate, 3-methoxycarbonyl-1-methyl-2-phosphaindolizine-P-aluminium(O-menthoxy dichloride (7a, at the DFT (B3LYP/6-31+G* level reveals that the O-menthoxy moiety blocks the Re face of the >C=P– functionality, due to which the activation barrier of the Diels–Alder reaction of 7a with 1,3-butadiene, involving its attack from the Si face, is lower. It is found that in this case, the exo approach of the diene is slightly preferred over the endo approach.

  2. The direct asymmetric vinylogous aldol reaction of furanones with α-ketoesters: Access to chiral γ-Butenolides and glycerol derivatives

    KAUST Repository

    Luo, Jie; Wang, Haifei; Han, Xiao; Xu, Liwen; Kwiatkowski, Jacek; Huang, Kuo-Wei; Lu, Yixin

    2011-01-01

    Twice as good: The title reaction using the tryptophan-derived bifunctional organic catalyst 1 has been developed. The reported method led to the synthesis of chiral γ-substituted butenolides in excellent yields, with high diastereo- and enantioselectivities. Facile synthesis of chiral glycerol derivatives containing a tertiary hydroxy group has also been demonstrated. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. The direct asymmetric vinylogous aldol reaction of furanones with α-ketoesters: Access to chiral γ-Butenolides and glycerol derivatives

    KAUST Repository

    Luo, Jie

    2011-01-11

    Twice as good: The title reaction using the tryptophan-derived bifunctional organic catalyst 1 has been developed. The reported method led to the synthesis of chiral γ-substituted butenolides in excellent yields, with high diastereo- and enantioselectivities. Facile synthesis of chiral glycerol derivatives containing a tertiary hydroxy group has also been demonstrated. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Fluoride reactions with dental enamel following different forms of fluoride supply

    International Nuclear Information System (INIS)

    Hellstroem, I.; Ericsson, Y.

    1976-01-01

    The reactions with dental enamel of NaF as tablets dissolved in different beverages or supplied with NaCl, simulating domestic salt fluoridation, were studied in tests with enamel surfaces and enamel powder. It was confirmed that powdered enamel can react quite differently from enamel surfaces under certain conditions. Enamel surfaces took up much more fluoride (F) from orange juice than from water or milk, and neither the low pH nor the citrate content of the juice increased the formation of unstable CaF 2 in the enamel, as judged from a KOH leaching test. The F uptake by enamel surfaces from 0.25 mM NaF in 175 mM NaCl, corresponding to a dish prepared with salt containing 500 parts/10 6 F, was about 80 percent greater than from the same NaF concentration in water. This NaCl concentration did not increase the formation of CaF 2 in the enamel, as judged from the KOH test, while 350 mM NaCl caused a moderate increase. The investigations support the administration of NaF tablets with orange juice and the plans for domestic salt fluoridation. (author)

  5. Intramolecular carbenoid ylide forming reactions of 2-diazo-3-keto-4-phthalimidocarboxylic esters derived from methionine and cysteine

    Directory of Open Access Journals (Sweden)

    Marc Enßle

    2012-03-01

    Full Text Available Methionine, S-benzylcysteine and S-allylcysteine were converted into 2-diazo-3-oxo-4-phthalimidocarboxylic esters 8a–c in three steps. Upon rhodium-catalysed dediazoniation, two intramolecular carbenoid reactions competed, namely the formation of a cyclic sulfonium ylide and that of a six-ring carbonyl ylide. The S-methyl and S-benzyl ylides 12a and b could be isolated, while S-allyl ylide 12c underwent a [2,3]-sigmatropic rearrangement. The short-lived carbonyl ylides derived from methionine and S-benzylcysteine formed head-to-tail dimers by a [3 + 3]-cycloaddition and could be trapped with external dipolarophiles, while the S-allyl derivative 14c yielded the pentacyclic compound 17 by an intramolecular [3 + 2]-cycloaddition reaction.

  6. Spontaneous interfacial reaction between metallic copper and PBS to form cupric phosphate nanoflower and its enzyme hybrid with enhanced activity.

    Science.gov (United States)

    He, Guangli; Hu, Weihua; Li, Chang Ming

    2015-11-01

    We herein report the spontaneous interfacial reaction between copper foil with 0.01 M phosphate buffered saline (PBS) to form free-standing cupric phosphate (Cu3(PO4)2) nanoflowers at ambient temperature. The underlying chemistry was thoroughly investigated and it is found that the formation of nanoflower is synergistically caused by dissolved oxygen, chlorine ions and phosphate ions. Enzyme-Cu3(PO4)2 hybrid nanoflower was further prepared successfully by using an enzyme-dissolving PBS solution and the enzymes in the hybrid exhibit enhanced biological activity. This work provides a facile route for large-scale synthesis of hierarchical inorganic and functional protein-inorganic hybrid architectures via a simple one-step solution-immersion reaction without using either template or surfactant, thus offering great potential for biosensing application among others. Copyright © 2015 Elsevier B.V. All rights reserved.

  7. Development of indirect spectrophotometric method for quantification of cephalexin in pure form and commercial formulation using complexation reaction

    International Nuclear Information System (INIS)

    Khan, M.N.; Hussain, R.; Kalsoom, S.; Saadiq, M.

    2016-01-01

    A simple, accurate and indirect spectrophotometric method was developed for the quantification of cephalexin in pure form and pharmaceutical products using complexation reaction. The developed method is based on the oxidation of the cephalexin with Fe/sup 3+/ in acidic medium. Then 1, 10- phenanthroline reacts with Fe/sup 2+/ and a red colored complex was formed. The absorbance of the complex was measured at 510 nm by spectrophotometer. Different experimental parameters affecting the complexation reactions were studied and optimized. Beer law was obeyed in the concentration range 0.4 -10 micro gmL/sup -1/ with a good correlation of 0.992. The limit of detection and limit of quantification were found to be 0.065 micro gmL/sup -1/ and 0.218 micro gmL/sup -1/ , respectively. The method have good reproducibility with a relative standard deviation of 6.26 percent (n = 6). The method was successfully applied for the determination of cephalexin in bulk powder and commercial formulation. Percent recoveries were found to range from 95.47 to 103.87 percent for the pure form and 98.62 to 103.35 percent for commercial formulations. (author)

  8. The d(e, e'p)n reaction and the nuetron electric form factor

    International Nuclear Information System (INIS)

    Dieperink, A.E.L.

    1978-01-01

    An accurate determination of the electric form factor of the neutron, Gsub(En), is important both for our understanding of the structure of the nucleons, and for the description of electron scattering on nuclear many-body systems. At present only reliable model-independent information on Gsub(En) is available for four-momentum transfer (qsub(μ)) 2 →0 from the scattering of thermal neutrons off atoms. Electron scattering offers the possibility to obtain information at higher (qsub(μ)) 2 . However, since electrons can only be scattered off neutrons embedded in a many-body target the extraction of Gsub(En) will in general be affected by nuclear structure uncertainties. Some methods to obtain information on Gsub(En) in e-d experiments are discussed. (Auth.)

  9. Theoretical investigation of the reaction mechanism for the phosphate diester hydrolysis using an asymmetric dinuclear metal complex as a biomimetic model of the purple acid phosphatase enzyme.

    Science.gov (United States)

    Ferreira, Dalva E C; De Almeida, Wagner B; Neves, Ademir; Rocha, Willian R

    2008-12-14

    In this work we have applied quantum mechanical calculations, at the density functional theory level, to investigate the phosphate diester hydrolysis promoted by a cationic heterodinuclear Fe(III)...Zn(II) complex that mimics the structural and functional properties of the purple acid phosphatase (PAP) enzymes. The hydrolysis of the dimethyl phosphate diester was investigated in the gas phase and in solution by means of the continuum PCM model, using the B3LYP hybrid exchange-correlation functional. Our computed results showed that the hydrolysis of the dimethyl phosphate ester takes place in two steps. The first step corresponds to a slow P-O bond formation through nucleophilic attack of the coordinated (Fe(III))-OH group. The second step consists of a proton transfer process followed by the release of a methanol molecule. The first step is rate determining with activation free energy of 12.3 kcal mol(-1), which is about 3 times lower than the activation free energy for the uncatalyzed reaction. We also show that the heterodinuclear site plays an important role favoring an associative mechanism for the phosphate diester hydrolysis, favoring the formation of a high energy intermediate phosphorane, and orienting the phosphate group to the nucleophilic attack.

  10. Nucleoside adducts are formed by cooperative reaction of acetaldehyde and alcohols: Possible mechanism for the role of ethanol in carcinogenesis

    International Nuclear Information System (INIS)

    Fraenkel-Conrat, H.; Singer, B.

    1988-01-01

    The exocyclic amino groups of ribonucleosides and deoxyribonucleosides react rapidly at ambient temperature with acetaldehyde and alcohols to yield mixed acetals [-NH-CH(CH 3 )OR]. Nucleotides and nucleoside di- and triphosphates also react. Depending on the nucleoside used and on the relative amounts of aldehyde, alcohol, and water, preparative reactions reach equilibrium with yields up to 75% in a few house. The structures have been confirmed by fast atom bombardment MS and proton NMR. Half-lives at 37 degree C have been determined, and maximum stability is in the pH range of 7.5-9.5. In the absence of alcohol, acetaldehyde-nucleoside adducts could be isolated at 4 degree C, but these were too unstable to characterize except for their UV spectra, also at 4 degree C. Ethanol is often present in human blood and tissues, and acetaldehyde is its initial metabolic product, as well as being formed by many other metabolic processes. Both chemicals have separately been implicated in carcinogenic and other cytophathologic processes, but no cooperative mechanism has been proposed. The reactions reported here are of biological concern because they also occur in dilute aqueous solution. These finding supply a mechanism by which ethanol can be covalently bound to nucleic acids under physiological conditions

  11. The reaction process of the Bi-Sr-Ca-Cu-O system and the forming mechanism of the 2212 superconducting phase

    International Nuclear Information System (INIS)

    Xiong Guohong; Wang Minquan; Fan Xianping; Tang Xiaoming

    1993-01-01

    The reaction process and the reaction behavior of each component in the Bi-Sr-Ca-Cu-O system are presented in this paper. It reveals that the reaction is carried out in three different stages: forming of an insulating interphase at 680 C-790 C, forming of the 2212 superconducting phase at 790 C-860 C and forming of semiconducting phases in the presence of the liquid phase at 860 C-970 C. It is also confirmed that the 2212 superconducting phase (T c =85 K) is formed by the reaction of a trinary interphase together with CuO, SrO and CaO. A new two-step method is presented to prepare the 2212 superconducting phase by a presynthesized interphase. (orig.)

  12. The reaction process of the Bi-Sr-Ca-Cu-O system and the forming mechanism of the 2212 superconducting phase

    Science.gov (United States)

    Xiong, Guohong; Wang, Minquan; Fan, Xianping; Tang, Xiaoming

    1993-02-01

    The reaction process and the reaction behavior of each component in the Bi-Sr-Ca-Cu-O system are presented in this paper. It reveals that the reaction is carried out in three different stages: forming of an insulating interphase at 680°C 790°C, forming of the 2212 superconducting phase at 790°C 860°C and forming often semiconducting phases in the presence of the liquid phase at 860°C 970°C. It is also confirmed that the 2212 superconducting phase ( T c=85 K) is formed by the reaction of a trinary interphase together with CuO, SrO and CaO. A new two-step method is presented to prepare the 2212 superconducting phase by a presynthesized interphase.

  13. The reaction process of the Bi-Sr-Ca-Cu-O system and the forming mechanism of the 2212 superconducting phase

    Energy Technology Data Exchange (ETDEWEB)

    Xiong Guohong (Zhejiang Univ., Hangzhou (China). Dept. of Materials Science and Engineering); Wang Minquan (Zhejiang Univ., Hangzhou (China). Dept. of Materials Science and Engineering); Fan Xianping (Zhejiang Univ., Hangzhou (China). Dept. of Materials Science and Engineering); Tang Xiaoming (Zhejiang Univ., Hangzhou (China). Center for Analysis and Measurement)

    1993-02-01

    The reaction process and the reaction behavior of each component in the Bi-Sr-Ca-Cu-O system are presented in this paper. It reveals that the reaction is carried out in three different stages: forming of an insulating interphase at 680 C-790 C, forming of the 2212 superconducting phase at 790 C-860 C and forming of semiconducting phases in the presence of the liquid phase at 860 C-970 C. It is also confirmed that the 2212 superconducting phase (T[sub c]=85 K) is formed by the reaction of a trinary interphase together with CuO, SrO and CaO. A new two-step method is presented to prepare the 2212 superconducting phase by a presynthesized interphase. (orig.)

  14. Catalytic asymmetric synthesis of the alkaloid (+)-myrtine

    NARCIS (Netherlands)

    Pizzuti, Maria Gabriefla; Minnaard, Adriaan J.; Feringa, Ben L.

    2008-01-01

    A new protocol for the asymmetric synthesis of trans-2,6-disubstituted-4-piperidones has been developed using a catalytic enantioselective conjugate addition reaction in combination with a diastereoselective lithiation-substitution sequence; an efficient synthesis of (+)-myrtine has been achieved

  15. Chlorine in solid fuels fired in pulverized fuel boilers sources, forms, reactions, and consequences: a literature review

    Energy Technology Data Exchange (ETDEWEB)

    David A. Tillman; Dao Duong; Bruce Miller [Foster Wheeler North America Corp. (United States)

    2009-07-15

    Chlorine is a significant source of corrosion and deposition, both from coal and from biomass, and in PF boilers. This investigation was designed to highlight the potential for corrosion risks associated with once-through units and advanced cycles. The research took the form of a detailed literature investigation to evaluate chlorine in solid fuels: coals of various ranks and origins, biomass fuels of a variety of types, petroleum cokes, and blends of the above. The investigation focused upon an extensive literature review of documents dating back to 1991. The focus is strictly corrosion and deposition. To address the deposition and corrosion issues, this review evaluates the following considerations: concentrations of chlorine in available solid fuels including various coals and biomass fuels, forms of chlorine in those fuels, and reactions - including reactivities - of chlorine in such fuels. The assessment includes consideration of alkali metals and alkali earth elements as they react with, and to, the chlorine and other elements (e.g., sulfur) in the fuel and in the gaseous products of combustion. The assessment also includes other factors of combustion: for example, combustion conditions including excess O{sub 2} and combustion temperatures. It also considers analyses conducted at all levels: theoretical calculations, bench scale laboratory data and experiments, pilot plant experiments, and full scale plant experience. Case studies and plant surveys form a significant consideration in this review. The result of this investigation focuses upon the concentrations of chlorine acceptable in coals burned exclusively, in coals burned with biomass, and in biomass cofired with coal. Values are posited based upon type of fuel and combustion technology. Values are also posited based upon both first principles and field experience. 86 refs., 8 figs., 7 tabs.

  16. Antioxidative, Antibacterial, and Food Functional Properties of the Half-Fin Anchovy Hydrolysates-Glucose Conjugates Formed via Maillard Reaction

    Directory of Open Access Journals (Sweden)

    Ru Song

    2016-06-01

    Full Text Available The antioxidative, antibacterial, and food functional properties of the half-fin anchovy hydrolysates (HAHp-glucose conjugates formed by Maillard reaction (MR were investigated, respectively. Results of sugar and amino acid contents loss rates, browning index, and molecular weight distribution indicated that the initial pH of HAHp played an important role in the process of MR between HAHp and glucose. HAHp-glucose Maillard reaction products (HAHp-G MRPs demonstrated enhanced antioxidative activities of reducing power and scavenging DPPH radicals compared to control groups. HAHp-G MRPs produced from the condition of pH 9.6 displayed the strongest reducing power. The excellent scavenging activity on DPPH radicals was found for HAHp(5.6-G MRPs which was produced at pH 5.6. Additionally, HAHp(5.6-G MRPs showed variable antibacterial activities against Escherichia coli, Pseudomonas fluorescens, Proteus vulgaris, Pseudomonas aeruginosa, Staphylococcus aureus, Bacillus subtilis, Bacillus megaterium, and Sarcina lutea, with the MIC values ranging from 8.3 to 16.7 μg/mL. Result of scanning electron microscopy (SEM on E. coli suggested that HAHp(5.6-G MRPs exhibited antibacterial activity by destroying the cell integrity through membrane permeabilization. Moreover, HAHp(5.6-G MRPs had excellent foaming ability and stability at alkaline conditions of pH 8.0, and showed emulsion properties at acidic pH 4.0. These results suggested that specific HAHp-G MRPs should be promising functional ingredients used in foods.

  17. Antioxidative, Antibacterial, and Food Functional Properties of the Half-Fin Anchovy Hydrolysates-Glucose Conjugates Formed via Maillard Reaction.

    Science.gov (United States)

    Song, Ru; Yang, Peiyu; Wei, Rongbian; Ruan, Guanqiang

    2016-06-20

    The antioxidative, antibacterial, and food functional properties of the half-fin anchovy hydrolysates (HAHp)-glucose conjugates formed by Maillard reaction (MR) were investigated, respectively. Results of sugar and amino acid contents loss rates, browning index, and molecular weight distribution indicated that the initial pH of HAHp played an important role in the process of MR between HAHp and glucose. HAHp-glucose Maillard reaction products (HAHp-G MRPs) demonstrated enhanced antioxidative activities of reducing power and scavenging DPPH radicals compared to control groups. HAHp-G MRPs produced from the condition of pH 9.6 displayed the strongest reducing power. The excellent scavenging activity on DPPH radicals was found for HAHp(5.6)-G MRPs which was produced at pH 5.6. Additionally, HAHp(5.6)-G MRPs showed variable antibacterial activities against Escherichia coli, Pseudomonas fluorescens, Proteus vulgaris, Pseudomonas aeruginosa, Staphylococcus aureus, Bacillus subtilis, Bacillus megaterium, and Sarcina lutea, with the MIC values ranging from 8.3 to 16.7 μg/mL. Result of scanning electron microscopy (SEM) on E. coli suggested that HAHp(5.6)-G MRPs exhibited antibacterial activity by destroying the cell integrity through membrane permeabilization. Moreover, HAHp(5.6)-G MRPs had excellent foaming ability and stability at alkaline conditions of pH 8.0, and showed emulsion properties at acidic pH 4.0. These results suggested that specific HAHp-G MRPs should be promising functional ingredients used in foods.

  18. Pre-compound neutron evaporation in heavy ion fusion reactions

    International Nuclear Information System (INIS)

    Ajay Kumar; Singh, Hardev; Rajesh Kumar; Govil, I.M.; Golda, K.S.; Rakesh Kumar; Datta, S.K.; Yogi, B.K.; Viesti, G.

    2007-01-01

    In the present investigation, exclusive neutron spectra have been measured in coincidence with the observed γ-rays characteristic to the residual nuclei 53 Fe, 55 Fe and 56 Co. In this new experimental study, we have followed the strategy of forming the compound nucleus 58 Ni at the same excitation energy through two different entrance channels viz the mass symmetric reaction 31 P + 27 Al and the mass asymmetric reaction 12 C + 46 Ti

  19. A study of the decay modes of hot systems formed in the Ar + Au and Ar + Th reactions

    International Nuclear Information System (INIS)

    Lott, B.; Cramer, B.; Ingold, G.; Jahnke, U.; Schwinn, E.; Doubre, H.; Galin, J.; Guerreau, D.; Jiang, D.X.; Morjean, M.; Piasecki, E.; Pouthas, J.; Sokolov, A.; Gatty, B.; Jacquet, D.

    1990-01-01

    Decay channels of hot systems formed in Ar + Au and Ar + Th reactions have been investigated by measuring the associated neutron multiplicity with a 4π liquid scintillator detector. The presented results show that, in contrast with the conclusion of the folding angle method, fission remains very probable as a deexcitation channel for hot systems even at 44 MeV/u, but its cross section decreases when the bombarding energy increases from 32 MeV/u to 44 MeV/u. On the opposite, the heavy residue production increases in this incident energy domain. The average IMF multiplicity per central collision is shown to be large, minimum values of 1.0 and 1.2 have been found for E inc = 44 and 77 MeV/u respectively. The possible link between the previously observed saturation in the thermal energy deposited in the system and the increasing probability for this system to avoid fissioning for increasing bombarding energies is discussed. A possible explanation could be found in an important non equilibrium emission of light particles or IMFs

  20. The magnetic form factor of the neutron, GMn, from the d(e,e'n)p reaction

    International Nuclear Information System (INIS)

    Markowitz, P.E.C.

    1992-01-01

    The author measured the d(e,e'n)p cross-section at three values of Q 2 : 0.255, 0.176 and 0.109 (GeV/c) 2 . The electrons were detected with the OHIPS magnetic spectrometer, and the neutrons were detected in a liquid mineral oil scintillator array. The measurement were made at a fixed neutron angle of θ n = 57 degrees; the Q 2 values were obtained by varying the incident electron energy and the scattering angle. These cross sections are sensitive primarily to the neutron magnetic form factor at these quasifree kinematics. The efficiency of the neutron detector was determined by the associated particle technique with the d(γ, pn) reaction for each of three neutron kinetic energies. The value of G n M extracted from the cross sections are consistent with the dipole parametrization at the two high momentum transfers; at the lowest momentum transfer the value of G n M is 10% higher than the dipole model. This enhancement at low momentum transfer is consistent with previous measurements

  1. Synthesis of New Chiral Ligands Based on Thiophene Derivatives for Use in Catalytic Asymmetric Oxidation of Sulfides

    International Nuclear Information System (INIS)

    Jeong, Yong Chul; Ahn, Dae Jun; Lee, Woo Sun; Lee, Seung Han; Ahn, Kwang Hyun

    2011-01-01

    We discovered that the vanadium complexes of new Schiff base ligands and prepared from thiophene derivatives efficiently catalyze the asymmetric oxidation of sulfides by hydrogen peroxide to provide sulfoxides with enantioselectivities up to 79% ee and in yields up to 89%. Notably, Schiff base showed better or similar enantioselectivity than the well-studied Schiff base. These results suggest possible applications of Schiff bases derived from and in other catalytic asymmetric reactions. Chiral sulfoxides are important functional groups for various applications. For example, the biological activities of sulfoxide containing drugs such as omeprazole are strongly related to the chirality of the sulfoxide group; for this reason, esomeprazole, the enantiomerically pure form of omeprazole, was later developed. There are several chiral sulfoxide based drugs that have been introduced by the pharmaceutical industry including armodafinil, aprikalim, oxisurane, and ustiloxin. Chiral sulfoxides have also been utilized as chiral auxiliaries in asymmetric syntheses of chiral intermediates

  2. EncM, a versatile enterocin biosynthetic enzyme involved in Favorskii oxidative rearrangement, aldol condensation, and heterocycle-forming reactions

    Science.gov (United States)

    Xiang, Longkuan; Kalaitzis, John A.; Moore, Bradley S.

    2004-01-01

    The bacteriostatic natural product enterocin from the marine microbe “Streptomyces maritimus” has an unprecedented carbon skeleton that is derived from an aromatic polyketide biosynthetic pathway. Its caged tricyclic, nonaromatic core is derived from a linear poly-β-ketide precursor that formally undergoes a Favorskii-like oxidative rearrangement. In vivo characterization of the gene encM through mutagenesis and heterologous biosynthesis demonstrated that its protein product not only is solely responsible for the oxidative C—C rearrangement, but also facilitates two aldol condensations plus two heterocycle forming reactions. In total, at least five chiral centers and four rings are generated by this multifaceted flavoprotein. Heterologous expression of the enterocin biosynthesis genes encABCDLMN in Streptomyces lividans resulted in the formation of the rearranged metabolite desmethyl-5-deoxyenterocin and the shunt products wailupemycins D-G. Addition of the methyltransferase gene encK, which was previously proposed through mutagenesis to additionally assist EncM in the Favorskii rearrangement, shifted the production to the O-methyl derivative 5-deoxyenterocin. The O-methyltransferase EncK seems to be specific for the pyrone ring of enterocin, because bicyclic polyketides bearing pyrone rings are not methylated in vivo. Expression of encM with different combinations of homologous actinorhodin biosynthesis genes did not result in the production of oxidatively rearranged enterocin-actinorhodin hybrid compounds as anticipated, suggesting that wild-type EncM may be specific for its endogenous type II polyketide synthase or for benzoyl-primed polyketide precursors. PMID:15505225

  3. Asymmetric Total Synthesis of Ieodomycin B

    Directory of Open Access Journals (Sweden)

    Shuangjie Lin

    2017-01-01

    Full Text Available Ieodomycin B, which shows in vitro antimicrobial activity, was isolated from a marine Bacillus species. A novel asymmetric total synthetic approach to ieodomycin B using commercially available geraniol was achieved. The approach involves the generation of 1,3-trans-dihydroxyl at C-3 and C-5 positions via a Crimmins-modified Evans aldol reaction and a chelation-controlled Mukaiyama aldol reaction of a p-methoxybenzyl-protected aldehyde, as well as the generation of a lactone ring in a deprotection–lactonization one-pot reaction.

  4. Bite angle effects of diphosphines in C-C and C-X bond forming cross coupling reactions

    NARCIS (Netherlands)

    Birkholz, M.N.; Freixa, Z.; van Leeuwen, P.W.N.M.

    2009-01-01

    Catalytic reactions of C-C and C-X bond formation are discussed in this critical review with particular emphasis on cross coupling reactions catalyzed by palladium and wide bite angle bidentate diphosphine ligands. Especially those studies have been collected that allow comparison of the ligand bite

  5. Asymmetric Gepner models (revisited)

    Energy Technology Data Exchange (ETDEWEB)

    Gato-Rivera, B. [NIKHEF Theory Group, Kruislaan 409, 1098 SJ Amsterdam (Netherlands)] [Instituto de Fisica Fundamental, CSIC, Serrano 123, Madrid 28006 (Spain); Schellekens, A.N., E-mail: t58@nikhef.n [NIKHEF Theory Group, Kruislaan 409, 1098 SJ Amsterdam (Netherlands)] [Instituto de Fisica Fundamental, CSIC, Serrano 123, Madrid 28006 (Spain)] [IMAPP, Radboud Universiteit, Nijmegen (Netherlands)

    2010-12-11

    We reconsider a class of heterotic string theories studied in 1989, based on tensor products of N=2 minimal models with asymmetric simple current invariants. We extend this analysis from (2,2) and (1,2) spectra to (0,2) spectra with SO(10) broken to the Standard Model. In the latter case the spectrum must contain fractionally charged particles. We find that in nearly all cases at least some of them are massless. However, we identify a large subclass where the fractional charges are at worst half-integer, and often vector-like. The number of families is very often reduced in comparison to the 1989 results, but there are no new tensor combinations yielding three families. All tensor combinations turn out to fall into two classes: those where the number of families is always divisible by three, and those where it is never divisible by three. We find an empirical rule to determine the class, which appears to extend beyond minimal N=2 tensor products. We observe that distributions of physical quantities such as the number of families, singlets and mirrors have an interesting tendency towards smaller values as the gauge groups approaches the Standard Model. We compare our results with an analogous class of free fermionic models. This displays similar features, but with less resolution. Finally we present a complete scan of the three family models based on the triply-exceptional combination (1,16{sup *},16{sup *},16{sup *}) identified originally by Gepner. We find 1220 distinct three family spectra in this case, forming 610 mirror pairs. About half of them have the gauge group SU(3)xSU(2){sub L}xSU(2){sub R}xU(1){sup 5}, the theoretical minimum, and many others are trinification models.

  6. Spectral studies of intermediate species formed in one-electron reactions of bovine liver catalase at room and low temperatures. A comparison with peroxidase reactions

    International Nuclear Information System (INIS)

    Metodiewa, D.; Dunford, H.B.

    1992-01-01

    The reactions of native bovine catalase with superoxide and solvated electrons have been investigated using three different methods for generating these reducing substrates: γ-radiolysis of oxygenated or deaerated buffer solutions in the presence of an OH radical scavenger; either xanthine or acetaldehyde with xanthine oxidase; and low-temperature (77 K) γ-radiolysis of buffered ethylene glycol/water solutions with subsequent annealing of samples at 183 K. (Author)

  7. Iron-platinum multilayer thin film reactions to form L1(0) iron-platinum and exchange spring magnets

    Science.gov (United States)

    Yao, Bo

    FePt films with the L10 phase have potential applications for magnetic recording and permanent magnets due to its high magnetocrystalline anisotropy energy density. Heat treatment of [Fe/Pt] n multilayer films is one approach to form the L10 FePt phase through a solid state reaction. This thesis has studied the diffusion and reaction of [Fe/Pt]n multilayer films to form the L10 FePt phase and has used this understanding to construct exchange spring magnets. The process-structure-property relations of [Fe/Pt] n multilayer films were systematically examined. The transmission electron microscopy (TEM) study of the annealed multilayers indicates that the Pt layer grows at the expense of Fe during annealing, forming a disordered fcc FePt phase by the interdiffusion of Fe into Pt. This thickening of the fcc Pt layer can be attributed to the higher solubilities of Fe into fcc Pt, as compared to the converse. For the range of film thickness studied, a continuous L10 FePt product layer that then thickens with further annealing is not found. Instead, the initial L10 FePt grains are distributed mainly on the grain boundaries within the fcc FePt layer and at the Fe/Pt interfaces and further transformation of the sample to the ordered L10 FePt phase proceeds coupled with the growth of the initial L10 FePt grains. A comprehensive study of annealed [Fe/Pt]n films is provided concerning the phase fraction, grain size, nucleation/grain density, interdiffusivity, long-range order parameter, and texture, as well as magnetic properties. A method based on hollow cone dark field TEM is introduced to measure the volume fraction, grain size, and density of ordered L10 FePt phase grains in the annealed films, and low-angle X-ray diffraction is used to measure the effective Fe-Pt interdiffusivity. The process-structure-properties relations of two groups of samples with varying substrate temperature and periodicity are reported. The results demonstrate that the processing parameters

  8. Quantifying social asymmetric structures.

    Science.gov (United States)

    Solanas, Antonio; Salafranca, Lluís; Riba, Carles; Sierra, Vicenta; Leiva, David

    2006-08-01

    Many social phenomena involve a set of dyadic relations among agents whose actions may be dependent. Although individualistic approaches have frequently been applied to analyze social processes, these are not generally concerned with dyadic relations, nor do they deal with dependency. This article describes a mathematical procedure for analyzing dyadic interactions in a social system. The proposed method consists mainly of decomposing asymmetric data into their symmetric and skew-symmetric parts. A quantification of skew symmetry for a social system can be obtained by dividing the norm of the skew-symmetric matrix by the norm of the asymmetric matrix. This calculation makes available to researchers a quantity related to the amount of dyadic reciprocity. With regard to agents, the procedure enables researchers to identify those whose behavior is asymmetric with respect to all agents. It is also possible to derive symmetric measurements among agents and to use multivariate statistical techniques.

  9. The asymmetric total synthesis of (+)- and (-)-trypargine via Noyori asymmetric transfer hydrogenation

    International Nuclear Information System (INIS)

    Pilli, Ronaldo A.; Rodrigues Junior, Manoel Trindade

    2009-01-01

    A concise and efficient total synthesis of (+)- and (-)-trypargine (6 steps and 38% overall yield), a 1-substituted β-carboline guanidine alkaloid isolated from the skin of the African frog K. senegalensis, was developed based on the construction of the b-carboline moiety via Bischler-Napieralski reaction and the enantioselective reduction of the dihydro-β-carboline intermediate via an asymmetric transfer hydrogenation reaction using Noyori's protocol. (author)

  10. Asymmetric catalysis in the cyclopropanation of olefins; Catalise assimetrica na ciclopropanacao de olefinas

    Energy Technology Data Exchange (ETDEWEB)

    Leao, Raquel A.C.; Ferreira, Vitor F.; Pinheiro, Sergio [Universidade Federal Fluminense (UFF), Niteroi, RJ (Brazil). Dept. de Quimica Organica]. E-mail: cegvito@vm.uff.br

    2007-07-01

    The main methodologies in the asymmetric cyclopropanation of alkenes with emphasis on asymmetric catalysis are covered. Examples are the Simmons-Smith reaction, the use of diazoalkanes and reactions carried out by decomposition of alpha-diazoesters in the presence of transition metals. (author)

  11. Recent Advances in Substrate-Controlled Asymmetric Cyclization for Natural Product Synthesis

    Directory of Open Access Journals (Sweden)

    Jeyun Jo

    2017-06-01

    Full Text Available Asymmetric synthesis of naturally occurring diverse ring systems is an ongoing and challenging research topic. A large variety of remarkable reactions utilizing chiral substrates, auxiliaries, reagents, and catalysts have been intensively investigated. This review specifically describes recent advances in successful asymmetric cyclization reactions to generate cyclic architectures of various natural products in a substrate-controlled manner.

  12. Chiral 1,3,2-oxazaborolidines in asymmetric synthesis: recent advances

    International Nuclear Information System (INIS)

    Glushkov, Vladimir A; Tolstikov, Alexander G

    2004-01-01

    The use of chiral 1,3,2-oxazaborolidines in asymmetric organic synthesis, particularly, in enantioselective reduction of ketones, imines and oxime ethers, asymmetric Diels-Alder reactions, aldol condensation and atroposelective reduction of lactones is reviewed. Reactions of immobilised 1,3,2-oxazaborolidines are also considered.

  13. Unexpected catalytic reactions of silyl-protected enol diazoacetates with nitrile oxides that form 5-arylaminofuran-2(3H)-one-4-carboxylates.

    Science.gov (United States)

    Xu, Xinfang; Shabashov, Dmitry; Zavalij, Peter Y; Doyle, Michael P

    2012-02-03

    Silyl-protected enol diazoacetates undergo dirhodium(II)-catalyzed reactions with nitrile oxides to form acid-labile ketenimines via dipolar cycloaddition of nitrile oxides to a donor/acceptor cyclopropene and Lossen rearrangement of the dipolar adduct; acid catalysis converts the ketenimine to the furan product. © 2012 American Chemical Society

  14. Post-column reaction for simultaneous analysis of chromatic and leuco forms of malachite green and crystal violet by high-performance liquid chromatography with photometric detection

    Science.gov (United States)

    Allen, J.L.; Meinertz, J.R.

    1991-01-01

    The chromatic and leuco forms of malachite green and crystal violet were readily separated and detected by a sensitive and selective high-performance liquid chromatographic procedure. The chromatic and leuco forms of the dyes were separated within 11 min on a C18 column with a mobile phase of 0.05 M sodium acetate and 0.05 M acetic acid in water (19%) and methanol (81%). A reaction chamber, containing 10% PbO2 in Celite 545, was placed between the column and the spectrophotometric detector to oxidize the leuco forms of the dyes to their chromatic forms. Chromatic and leuco malachite green were quantified by their absorbance at 618 nm; and chromatic and leuco Crystal Violet by their absorbance at 588 nm. Detection limits for chromatic and leuco forms of both dyes ranged from 0.12 to 0.28 ng. A linear range of 1 to 100 ng was established for both forms of the dyes.

  15. A case of asymmetrical arthrogryposis

    International Nuclear Information System (INIS)

    Hageman, G.; Vette, J.K.; Willemse, J.

    1983-01-01

    Following the introduction of the conception that arthrogryposis is a symptom and not a clinical entity, a case of the very rare asymmetric form of neurogenic arthrogryposis is presented. The asymmetry of congenital contractures and weakness is associated with hemihypotrophy. The value of muscular CT-scanning prior to muscle biopsy is demonstrated. Muscular CT-scanning shows the extension of adipose tissue, which has replaced damaged muscles and therby indicates the exact site for muscle biopsy. Since orthopaedic treatment in arthrogryposis can be unrewarding due to severe muscular degeneration, preoperative scanning may provide additional important information on muscular function and thus be of benefit for surgery. The advantage of muscular CT-scanning in other forms of arthrogryposis requires further determination. The differential diagnosis with Werdnig-Hoffmann disease is discussed. (author)

  16. How Is Nature Asymmetric?

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 7; Issue 6. How Is Nature Asymmetric? - Discrete Symmetries in Particle Physics and their Violation ... Indian Institute of Technology, Chennai. Aligarh Muslim University. University of Rajasthan, Jaipur. Indian Institute of Science, Bangalore 560012, India.

  17. Exploring asymmetric catalytic transformations

    NARCIS (Netherlands)

    Guduguntla, Sureshbabu

    2017-01-01

    In Chapter 2, we report a highly enantioselective synthesis of β-alkyl-substituted alcohols through a one-pot Cu- catalyzed asymmetric allylic alkylation with organolithium reagents followed by reductive ozonolysis. The synthesis of γ-alkyl-substituted alcohols was also achieved through Cu-catalyzed

  18. Growth behavior of LiMn{sub 2}O{sub 4} particles formed by solid-state reactions in air and water vapor

    Energy Technology Data Exchange (ETDEWEB)

    Kozawa, Takahiro, E-mail: t-kozawa@jwri.osaka-u.ac.jp [Joining and Welding Research Institute, Osaka University, 11–1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan); Yanagisawa, Kazumichi [Research Laboratory of Hydrothermal Chemistry, Faculty of Science, Kochi University, 2–5-1 Akebono-cho, Kochi 780-8520 (Japan); Murakami, Takeshi; Naito, Makio [Joining and Welding Research Institute, Osaka University, 11–1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan)

    2016-11-15

    Morphology control of particles formed during conventional solid-state reactions without any additives is a challenging task. Here, we propose a new strategy to control the morphology of LiMn{sub 2}O{sub 4} particles based on water vapor-induced growth of particles during solid-state reactions. We have investigated the synthesis and microstructural evolution of LiMn{sub 2}O{sub 4} particles in air and water vapor atmospheres as model reactions; LiMn{sub 2}O{sub 4} is used as a low-cost cathode material for lithium-ion batteries. By using spherical MnCO{sub 3} precursor impregnated with LiOH, LiMn{sub 2}O{sub 4} spheres with a hollow structure were obtained in air, while angulated particles with micrometer sizes were formed in water vapor. The pore structure of the particles synthesized in water vapor was found to be affected at temperatures below 700 °C. We also show that the solid-state reaction in water vapor is a simple and valuable method for the large-scale production of particles, where the shape, size, and microstructure can be controlled. - Graphical abstract: This study has demonstrated a new strategy towards achieving morphology control without the use of additives during conventional solid-state reactions by exploiting water vapor-induced particle growth. - Highlights: • A new strategy to control the morphology of LiMn{sub 2}O{sub 4} particles is proposed. • Water vapor-induced particle growth is exploited in solid-state reactions. • The microstructural evolution of LiMn{sub 2}O{sub 4} particles is investigated. • The shape, size and microstructure can be controlled by solid-state reactions.

  19. Growth behavior of LiMn2O4 particles formed by solid-state reactions in air and water vapor

    International Nuclear Information System (INIS)

    Kozawa, Takahiro; Yanagisawa, Kazumichi; Murakami, Takeshi; Naito, Makio

    2016-01-01

    Morphology control of particles formed during conventional solid-state reactions without any additives is a challenging task. Here, we propose a new strategy to control the morphology of LiMn 2 O 4 particles based on water vapor-induced growth of particles during solid-state reactions. We have investigated the synthesis and microstructural evolution of LiMn 2 O 4 particles in air and water vapor atmospheres as model reactions; LiMn 2 O 4 is used as a low-cost cathode material for lithium-ion batteries. By using spherical MnCO 3 precursor impregnated with LiOH, LiMn 2 O 4 spheres with a hollow structure were obtained in air, while angulated particles with micrometer sizes were formed in water vapor. The pore structure of the particles synthesized in water vapor was found to be affected at temperatures below 700 °C. We also show that the solid-state reaction in water vapor is a simple and valuable method for the large-scale production of particles, where the shape, size, and microstructure can be controlled. - Graphical abstract: This study has demonstrated a new strategy towards achieving morphology control without the use of additives during conventional solid-state reactions by exploiting water vapor-induced particle growth. - Highlights: • A new strategy to control the morphology of LiMn 2 O 4 particles is proposed. • Water vapor-induced particle growth is exploited in solid-state reactions. • The microstructural evolution of LiMn 2 O 4 particles is investigated. • The shape, size and microstructure can be controlled by solid-state reactions.

  20. One-pot regioselective synthesis of nitrophenyloxazolinyl styrene oxides by the Darzens reaction of vicarious nucleophilic substitution-formed carbanions of 2-dichloromethyl-4,4-dimethyloxazoline.

    Science.gov (United States)

    Florio, Saverio; Lorusso, Patrizia; Granito, Catia; Luisi, Renzo; Troisi, Luigino

    2004-07-23

    The vicarious nucleophilic substitution reaction of dichloromethyloxazoline 2 with nitrobenzene has been investigated. Treatment of 2 with t-BuOK followed by the addition of nitrobenzene leads to benzylic carbanions 4 or 9 depending upon the solvent used (DMSO, DMF, or THF). Subsequent treatment of 4 or 9 with aldehydes, in a Darzens-like reaction, furnishes very good yields of nitrophenyl oxazolinyloxiranes 8 and 11. 1,2-Dioxazolinyl-1,2-dinitrophenylethene 7 forms quantitatively when carbanion 4 is allowed to warm to room temperature in the absence of external electrophiles.

  1. Vortex Dynamics of Asymmetric Heave Plates

    Science.gov (United States)

    Rusch, Curtis; Maurer, Benjamin; Polagye, Brian

    2017-11-01

    Heave plates can be used to provide reaction forces for wave energy converters, which harness the power in ocean surface waves to produce electricity. Heave plate inertia includes both the static mass of the heave plate, as well as the ``added mass'' of surrounding water accelerated with the object. Heave plate geometries may be symmetric or asymmetric, with interest in asymmetric designs driven by the resulting hydrodynamic asymmetry. Limited flow visualization has been previously conducted on symmetric heave plates, but flow visualization of asymmetric designs is needed to understand the origin of observed hydrodynamic asymmetries and their dependence on the Keulegan-Carpenter number. For example, it is hypothesized that the time-varying added mass of asymmetric heave plates is caused by vortex shedding, which is related to oscillation amplitude. Here, using direct flow visualization, we explore the relationship between vortex dynamics and time-varying added mass and drag. These results suggest potential pathways for more advanced heave plate designs that can exploit vortex formation and shedding to achieve more favorable hydrodynamic properties for wave energy converters.

  2. Effect of deformations on the compactness of odd-Z superheavy nuclei formed in cold and hot fusion reactions

    Science.gov (United States)

    Kaur, Gurjit; Sandhu, Kirandeep; Sharma, Manoj K.

    2018-03-01

    Using the extended fragmentation theory, the compactness of hot and cold fusion reactions is analyzed for odd-Z nuclei ranging Z = 105- 117. The calculations for the present work are carried out at T = 0MeV and ℓ = 0 ħ, as the temperature and angular momentum effects remain silent while addressing the orientation degree of freedom (i.e. compact angle configuration). In the hot fusion, 48Ca (spherical) + actinide (prolate) reaction, the non-equatorial compact (nec) shape is obtained for Z = 113 nucleus. On the other hand, Z > 113 nuclei favor equatorial compact (ec) configuration. The distribution of barrier height (VB) illustrate that the ec-shape is obtained when the magnitude of quadrupole deformation of the nucleus is higher than the hexadecupole deformation. In other words, negligible or small -ve β4-deformations support ec configurations. On the other hand, large (+ve) magnitude of the β4-deformation suggests that the configuration appears for compact angle θc < 90 °, leading to nec structure. Similar deformation effects are observed for Bi-induced reactions, in which not belly-to-belly compact (nbbc) configurations are seen at θc = 42 °. In addition to the effect of β2 and β4-deformations, the exclusive role of octupole deformations (β3) is also analyzed. The β3-deformations do not follow the reflection symmetry as that of β2 and β4, leading to the possible occurrence of compact configuration within 0° to 180° angular range.

  3. Multipartite asymmetric quantum cloning

    International Nuclear Information System (INIS)

    Iblisdir, S.; Gisin, N.; Acin, A.; Cerf, N.J.; Filip, R.; Fiurasek, J.

    2005-01-01

    We investigate the optimal distribution of quantum information over multipartite systems in asymmetric settings. We introduce cloning transformations that take N identical replicas of a pure state in any dimension as input and yield a collection of clones with nonidentical fidelities. As an example, if the clones are partitioned into a set of M A clones with fidelity F A and another set of M B clones with fidelity F B , the trade-off between these fidelities is analyzed, and particular cases of optimal N→M A +M B cloning machines are exhibited. We also present an optimal 1→1+1+1 cloning machine, which is an example of a tripartite fully asymmetric cloner. Finally, it is shown how these cloning machines can be optically realized

  4. Asymmetric information and economics

    Science.gov (United States)

    Frieden, B. Roy; Hawkins, Raymond J.

    2010-01-01

    We present an expression of the economic concept of asymmetric information with which it is possible to derive the dynamical laws of an economy. To illustrate the utility of this approach we show how the assumption of optimal information flow leads to a general class of investment strategies including the well-known Q theory of Tobin. Novel consequences of this formalism include a natural definition of market efficiency and an uncertainty principle relating capital stock and investment flow.

  5. Asymmetric 1,8/13,2,x-M2C2B10 14-vertex metallacarboranes by direct electrophilic insertion reactions; the VCD and BHD methods in critical analysis of cage C atom positions.

    Science.gov (United States)

    McAnaw, Amelia; Lopez, Maria Elena; Ellis, David; Rosair, Georgina M; Welch, Alan J

    2014-04-07

    The isolation of six isomeric, low-symmetry, dicobaltacarboranes with bicapped hexagonal antiprismatic cage structures, always in low yield, is described from reactions in which 13-vertex cobaltacarborane anions and sources of cobalt-containing cations were present. The vertex-to-centroid distance (VCD) and boron-H distance (BHD) methods are used to locate the correct C atom positions in the cages, thus allowing the compounds to be identified as 1,13-Cp2-1,13,2,10-closo-Co2C2B10H12 (1), 1,8-Cp2-3-OEt-1,8,2,10-closo-Co2C2B10H11 (2), 1,13-Cp2-1,13,2,9-closo-Co2C2B10H12 (3), 1,8-Cp2-1,8,2,4-closo-Co2C2B10H12 (4), 1,13-Cp2-1,13,2,4-closo-Co2C2B10H12 (5) and 1,8-Cp2-1,8,2,5-closo-Co2C2B10H12 (6). It is shown that a common alternative method of cage C atom identification, using refined (as B) U(eq) values, does not work well, at least in these cases. Having identified the correct isomeric forms of the six dicobaltacarboranes, their syntheses are tentatively rationalised in terms of the direct electrophilic insertion of a {CpCo(+)} fragment into [CpCoC2B10](-) anions and it is demonstrated that compounds 1, 4, 5 and 6 can be successfully prepared by deliberately performing such reactions.

  6. Capture and dissociation in the complex-forming CH + H2 → CH2 + H, CH + H2 reactions.

    Science.gov (United States)

    González, Miguel; Saracibar, Amaia; Garcia, Ernesto

    2011-02-28

    The rate coefficients for the capture process CH + H(2)→ CH(3) and the reactions CH + H(2)→ CH(2) + H (abstraction), CH + H(2) (exchange) have been calculated in the 200-800 K temperature range, using the quasiclassical trajectory (QCT) method and the most recent global potential energy surface. The reactions, which are of interest in combustion and in astrochemistry, proceed via the formation of long-lived CH(3) collision complexes, and the three H atoms become equivalent. QCT rate coefficients for capture are in quite good agreement with experiments. However, an important zero point energy (ZPE) leakage problem occurs in the QCT calculations for the abstraction, exchange and inelastic exit channels. To account for this issue, a pragmatic but accurate approach has been applied, leading to a good agreement with experimental abstraction rate coefficients. Exchange rate coefficients have also been calculated using this approach. Finally, calculations employing QCT capture/phase space theory (PST) models have been carried out, leading to similar values for the abstraction rate coefficients as the QCT and previous quantum mechanical capture/PST methods. This suggests that QCT capture/PST models are a good alternative to the QCT method for this and similar systems.

  7. 180Ta/sup g,m/ production cross sections form the 180Hf(p,n) reaction

    International Nuclear Information System (INIS)

    Norman, E.B.; Renner, T.R.; Grant, P.J.

    1981-01-01

    Cross sections have been determined for the production of the J/sup π/ = 1 + 180 Ta/sup g/ and the J/sup π/= 9 - 180 Ta/sup m/ from the 180 Hf(p,n) reaction. The 180 Ta/sup g/ cross sections were determined from measurements of γ-rays emitted following the electron-capture and β-decay of this 8.1-hour state. Total 180 Ta production cross sections were determined from measurements of the thick-target (p,n) yield. 180 Ta/sup m/ cross sections were calculated by subtracting the 180 Ta/sup g/ cross sections from the total (p,n) cross sections. These measurements are compared with the results of a statistical-model evaporation calculation

  8. Electrochemistry of single nanobubbles. Estimating the critical size of bubble-forming nuclei for gas-evolving electrode reactions.

    Science.gov (United States)

    German, Sean R; Edwards, Martin A; Chen, Qianjin; Liu, Yuwen; Luo, Long; White, Henry S

    2016-12-12

    In this article, we address the fundamental question: "What is the critical size of a single cluster of gas molecules that grows and becomes a stable (or continuously growing) gas bubble during gas evolving reactions?" Electrochemical reactions that produce dissolved gas molecules are ubiquitous in electrochemical technologies, e.g., water electrolysis, photoelectrochemistry, chlorine production, corrosion, and often lead to the formation of gaseous bubbles. Herein, we demonstrate that electrochemical measurements of the dissolved gas concentration, at the instant prior to nucleation of an individual nanobubble of H 2 , N 2 , or O 2 at a Pt nanodisk electrode, can be analyzed using classical thermodynamic relationships (Henry's law and the Young-Laplace equation - including non-ideal corrections) to provide an estimate of the size of the gas bubble nucleus that grows into a stable bubble. We further demonstrate that this critical nucleus size is independent of the radius of the Pt nanodisk employed (gas. For example, the measured critical surface concentration of H 2 of ∼0.23 M at the instant of bubble formation corresponds to a critical H 2 nucleus that has a radius of ∼3.6 nm, an internal pressure of ∼350 atm, and contains ∼1700 H 2 molecules. The data are consistent with stochastic fluctuations in the density of dissolved gas, at or near the Pt/solution interface, controlling the rate of bubble nucleation. We discuss the growth of the nucleus as a diffusion-limited process and how that process is affected by proximity to an electrode producing ∼10 11 gas molecules per second. Our study demonstrates the advantages of studying a single-entity, i.e., an individual nanobubble, in understanding and quantifying complex physicochemical phenomena.

  9. Survey of beta-particle interaction experiments with asymmetric matter

    Science.gov (United States)

    Van Horn, J. David; Wu, Fei

    2018-05-01

    Asymmetry is a basic property found at multiple scales in the universe. Asymmetric molecular interactions are fundamental to the operation of biological systems in both signaling and structural roles. Other aspects of asymmetry are observed and useful in many areas of science and engineering, and have been studied since the discovery of chirality in tartrate salts. The observation of parity violation in beta decay provided some impetus for later experiments using asymmetric particles. Here we survey historical work and experiments related to electron (e-) or positron (e+) polarimetry and their interactions with asymmetric materials in gas, liquid and solid forms. Asymmetric interactions may be classified as: 1) stereorecognition, 2) stereoselection and 3) stereoinduction. These three facets of physical stereochemistry are unique but interrelated; and examples from chemistry and materials science illustrate these aspects. Experimental positron and electron interactions with asymmetric materials may be classified in like manner. Thus, a qualitative assessment of helical and polarized positron experiments with different forms of asymmetric matter from the past 40 years is presented, as well as recent experiments with left-hand and right-hand single crystal quartz and organic compounds. The purpose of this classification and review is to evaluate the field for potential new experiments and directions for positron (or electron) studies with asymmetric materials.

  10. The first report of a muoniated free radical formed from reaction of Mu with Br{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Ghandi, Khashayar [Department of Chemistry, Mount Allison University, 63C York Street, Sackville (Canada)]. E-mail: kghandi@mta.ca; Cottrell, Stephen P. [ISIS, CCLRC Rutherford Appleton Laboratory, Chilton (United Kingdom); Fleming, Donald [Department of Chemistry, University of British Columbia and TRIUMF, Vancouver, NB E4L 1G8 (Canada); Johnson, Clive [ISIS, CCLRC Rutherford Appleton Laboratory, Chilton (United Kingdom)

    2006-03-31

    In this paper, we report preliminary data for the first direct evidence of a free radical formed from Mu reactivity with Br{sub 2} in the gas phase, in N{sub 2} moderator at a total pressure of 3 bar. A new experimental setup and target vessel for {mu}SR studies of reactive compounds, such as the halogens and hydrogen halides, suitable as well for RF measurements, is described. The experimental data, obtained from a longitudinal field repolarization curve, yields a hfc of 1770 MHz. We tentatively identify this as the [BrMuBr] radical, a non-conventional bond system, arising from the combination of a van der Waals interaction and dynamics on a repulsive surface. Studies of the dynamics and hfcs of possible radicals, which in principal could form, are also outlined here.

  11. Side-chain interactions form late and cooperatively in the binding reaction between disordered peptides and PDZ domains

    DEFF Research Database (Denmark)

    Haq, S Raza; Chi, Celestine N; Bach, Anders

    2012-01-01

    Intrinsically disordered proteins are very common and mediate numerous protein-protein and protein-DNA interactions. While it is clear that these interactions are instrumental for the life of the mammalian cell, there is a paucity of data regarding their molecular binding mechanisms. We have here...... used short peptides as a model system for intrinsically disordered proteins. Linear free-energy relationships based on rate and equilibrium constants for the binding of these peptides to ordered target proteins, PDZ domains, demonstrate that native side-chain interactions form mainly after the rate......-limiting barrier for binding, in a cooperative fashion. This finding suggests that these disordered peptides first form a weak encounter complex with non-native interactions. The data do not support the recent notion that the affinities of intrinsically disordered proteins towards their targets are generally...

  12. Possibility of neutron electric form factor etermination in the d-vector(e,e'p-vector)n reaction

    International Nuclear Information System (INIS)

    Gakh, G.I.

    1990-01-01

    The polarization of protons produced in the vector-polarized deuteron disintegration by unpolarized electrons has been analyzed. The sensitivities of the polarization observation to the neutron electric form factor G en and also to different parametrizations of the deuteron wave functions (DWF) have been investigated in the framework of the relativistic impulse approximation. The present method of the G en determination does not require the use of the longitudinally polarized electron beams. 34 refs.; 9 figs

  13. Reaction of carbon tetrachloride with methane in a non-equilibrium plasma at atmospheric pressure, and characterisation of the polymer thus formed

    Energy Technology Data Exchange (ETDEWEB)

    Gaikwad, Vaibhav [Process Safety and Environment Protection Research Group, School of Engineering, The University of Newcastle, Callaghan, NSW 2308 (Australia); Kennedy, Eric, E-mail: Eric.Kennedy@newcastle.edu.au [Process Safety and Environment Protection Research Group, School of Engineering, The University of Newcastle, Callaghan, NSW 2308 (Australia); Mackie, John [Process Safety and Environment Protection Research Group, School of Engineering, The University of Newcastle, Callaghan, NSW 2308 (Australia); Holdsworth, Clovia [Centre for Organic Electronics, Chemistry Building, School of Environmental and Life Sciences, University of Newcastle, Callaghan, NSW 2308 (Australia); Molloy, Scott; Kundu, Sazal; Stockenhuber, Michael [Process Safety and Environment Protection Research Group, School of Engineering, The University of Newcastle, Callaghan, NSW 2308 (Australia); Dlugogorski, Bogdan [School of Engineering and Information Technology, Murdoch University, Murdoch, WA 6150 (Australia)

    2014-09-15

    Highlights: • CCl{sub 4} remediation using non-equilibrium plasma and non-oxidative conditions is proposed. • The reaction mechanism relies on experimental data and quantum chemical analysis. • Comprehensive mass balance for the reaction is provided. • CCl{sub 4} is converted to an environmentally benign and potentially useful polymer. • Characterisation of the polymer structure based on NMR and FTIR analyses is presented. - Abstract: In this paper we focus on the development of a methodology for treatment of carbon tetrachloride utilising a non-equilibrium plasma operating at atmospheric pressure, which is not singularly aimed at destroying carbon tetrachloride but rather at converting it to a non-hazardous, potentially valuable commodity. This method encompasses the reaction of carbon tetrachloride and methane, with argon as a carrier gas, in a quartz dielectric barrier discharge reactor. The reaction is performed under non-oxidative conditions. Possible pathways for formation of major products based on experimental results and supported by quantum chemical calculations are outlined in the paper. We elucidate important parameters such as carbon tetrachloride conversion, product distribution, mass balance and characterise the chlorinated polymer formed in the process.

  14. Complex chemical composition of colored surface films formed from reactions of propanal in sulfuric acid at upper troposphere/lower stratosphere aerosol acidities.

    Science.gov (United States)

    Van Wyngarden, A L; Pérez-Montaño, S; Bui, J V H; Li, E S W; Nelson, T E; Ha, K T; Leong, L; Iraci, L T

    Particles in the upper troposphere and lower stratosphere (UT/LS) consist mostly of concentrated sulfuric acid (40-80 wt %) in water. However, airborne measurements have shown that these particles also contain a significant fraction of organic compounds of unknown chemical composition. Acid-catalyzed reactions of carbonyl species are believed to be responsible for significant transfer of gas phase organic species into tropospheric aerosols and are potentially more important at the high acidities characteristic of UT/LS particles. In this study, experiments combining sulfuric acid (H 2 SO 4 ) with propanal and with mixtures of propanal with glyoxal and/or methylglyoxal at acidities typical of UT/LS aerosols produced highly colored surface films (and solutions) that may have implications for aerosol properties. In order to identify the chemical processes responsible for the formation of the surface films, attenuated total reflectance-Fourier transform infrared (ATR-FTIR) and 1 H nuclear magnetic resonance (NMR) spectroscopies were used to analyze the chemical composition of the films. Films formed from propanal were a complex mixture of aldol condensation products, acetals and propanal itself. The major aldol condensation products were the dimer (2-methyl-2-pentenal) and 1,3,5-trimethylbenzene that was formed by cyclization of the linear aldol condensation trimer. Additionally, the strong visible absorption of the films indicates that higher-order aldol condensation products must also be present as minor species. The major acetal species were 2,4,6-triethyl-1,3,5-trioxane and longer-chain linear polyacetals which are likely to separate from the aqueous phase. Films formed on mixtures of propanal with glyoxal and/or methylglyoxal also showed evidence of products of cross-reactions. Since cross-reactions would be more likely than self-reactions under atmospheric conditions, similar reactions of aldehydes like propanal with common aerosol organic species like glyoxal

  15. Utility of Hantzsch reaction for development of highly sensitive spectrofluorimetric method for determination of alfuzosin and terazosin in bulk, dosage forms and human plasma.

    Science.gov (United States)

    Hammad, Mohamed A; Omar, Mahmoud A; Salman, Baher I

    2017-09-01

    A highly sensitive, cheap, simple and accurate spectrofluorimetric method has been developed and validated for the determination of alfuzosin hydrochloride and terazosin hydrochloride in their pharmaceutical dosage forms and in human plasma. The developed method is based on the reaction of the primary amine moiety in the studied drugs with acetylacetone and formaldehyde according to the Hantzsch reaction, producing yellow fluorescent products that can be measured spectrofluorimetrically at 480 nm after excitation at 415 nm. Different experimental parameters affecting the development and stability of the reaction products were carefully studied and optimized. The fluorescence-concentration plots of alfuzosin and terazosin were rectilinear over a concentration range of 70-900 ng ml -1 , with quantitation limits 27.1 and 32.2 ng ml -1 for alfuzosin and terazosin, respectively. The proposed method was validated according to ICH guidelines and successfully applied to the analysis of the investigated drugs in dosage forms, content uniformity test and spiked human plasma with high accuracy. Copyright © 2017 John Wiley & Sons, Ltd.

  16. Surface tectonics of nanoporous networks of melamine-capped molecular building blocks formed through interface Schiff-base reactions.

    Science.gov (United States)

    Liu, Xuan-He; Wang, Dong; Wan, Li-Jun

    2013-10-01

    Control over the assembly of molecules on a surface is of great importance for the fabrication of molecule-based miniature devices. Melamine (MA) and molecules with terminal MA units are promising candidates for supramolecular interfacial packing patterning, owing to their multiple hydrogen-bonding sites. Herein, we report the formation of self-assembled structures of MA-capped molecules through a simple on-surface synthetic route. MA terminal groups were successfully fabricated onto rigid molecular cores with 2-fold and 3-fold symmetry through interfacial Schiff-base reactions between MA and aldehyde groups. Sub-molecular scanning tunneling microscopy (STM) imaging of the resultant adlayer revealed the formation of nanoporous networks. Detailed structural analysis indicated that strong hydrogen-bonding interactions between the MA groups persistently drove the formation of nanoporous networks. Herein, we demonstrate that functional groups with strong hydrogen-bond-formation ability are promising building blocks for the guided assembly of nanoporous networks and other hierarchical 2D assemblies. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Fourier synthesis of asymmetrical optical potentials for atoms

    International Nuclear Information System (INIS)

    Ritt, G.

    2007-01-01

    In this work a dissipationless asymmetrical optical potential for cold atoms was produced. In a first step a new type of optical lattice was generated, whose spatial periodicity only corresponds to a quarter of the wavelength of the light used for the generation. This corresponds to the half of the periodicity of a conventional optical lattice, which is formed by the light of the same wavelength. The generation of this new type of optical lattice was reached by the use of two degenerated raman transitions. Virtual processes occur, in which four photons are involved. In conventional optical lattices however virtual two-photon processes occur. By spatially superimposing this optical lattice with a conventional optical lattice an asymmetrical optical potential could be formed. By diffraction of a Bose Einstein condensate of rubidium atoms at the transient activated asymmetrical potential the asymmetrical structure was proven. (orig.)

  18. Asymmetric quantum cloning machines

    International Nuclear Information System (INIS)

    Cerf, N.J.

    1998-01-01

    A family of asymmetric cloning machines for quantum bits and N-dimensional quantum states is introduced. These machines produce two approximate copies of a single quantum state that emerge from two distinct channels. In particular, an asymmetric Pauli cloning machine is defined that makes two imperfect copies of a quantum bit, while the overall input-to-output operation for each copy is a Pauli channel. A no-cloning inequality is derived, characterizing the impossibility of copying imposed by quantum mechanics. If p and p ' are the probabilities of the depolarizing channels associated with the two outputs, the domain in (√p,√p ' )-space located inside a particular ellipse representing close-to-perfect cloning is forbidden. This ellipse tends to a circle when copying an N-dimensional state with N→∞, which has a simple semi-classical interpretation. The symmetric Pauli cloning machines are then used to provide an upper bound on the quantum capacity of the Pauli channel of probabilities p x , p y and p z . The capacity is proven to be vanishing if (√p x , √p y , √p z ) lies outside an ellipsoid whose pole coincides with the depolarizing channel that underlies the universal cloning machine. Finally, the tradeoff between the quality of the two copies is shown to result from a complementarity akin to Heisenberg uncertainty principle. (author)

  19. A method of the asymmetric Abel's inversion in plasma diagnosis

    International Nuclear Information System (INIS)

    Matoba, Tohru; Funahashi, Akimasa

    1975-09-01

    In the case of a noncylindrical plasma, axis symmetric components are drawn from observed projected intensities of physical quantities, assuming an asymmetric form. And the radial intensity distribution is determined by Abel's inversion method. The best fitting curve is obtained analytically from measured values by the least-square estimation of nonlinear parameters. The cylindrical symmetric Abel's inversion code ( ABELIC ) and the asymmetric Abel's inversion code ( ABELILSENP 2 ) are described. (auth.)

  20. Optimization of the pion beam for the HADES detector and determination of the η form factor in proton-proton reactions at 2.2 GeV

    International Nuclear Information System (INIS)

    Spruck, Bjoern

    2008-01-01

    This thesis contains two tasks. The first part focuses on the development and optimization of the pion beam facility for the HADES experiment. The second part describes the measurement of the electromagnetic transition form factor of the η meson in proton-proton reactions. To investigate pion-nucleon reaction, a secondary pion beam is required. The pions are produced by a heavy ion beam impinging on a beryllium target. In order to determine the profile of the beam focus, two scintillating fiber detectors have been built as part of this thesis and are read out with recently developed electronics. The measured size of the beam focus appeared to be not acceptable, which can be attributed to the achromatic magnetic focusing in the beam line. Simulations have shown, that an additional quadrupole magnet directly in front of HADES would solve this problem and improve the beam quality. A test experiment including this new quadrupole has been performed and the analysis is still in progress. Preliminary results show a significant reduction of the momentum dependency of the focus. The size of the actual beam spot has been deduced to 14 mm by using an indirect tracking approach. For deducing the electromagnetic structure of hadrons, a first step has been done by analyzing the η Dalitz decay in p+p reactions at 2.2 GeV kinetic energy to determine the electromagnetic transition form factor of the η meson. A fit to the data leads to a form factor slope of b=2.2 -1.4 +1.2 GeV -2 . This corresponds to a pole mass of λ=680 -130 +460 MeV/c 2 . It has been shown, that a semi-exclusive analysis of the η Dalitz decay within the event hypothesis framework including a kinematical fit is feasible. (orig.)

  1. Updating the asymmetric osmium-catalyzed dihydroxylation (AD) mnemonic. Q2MM modeling and new kinetic measurements

    DEFF Research Database (Denmark)

    Fristrup, Peter; Tanner, David Ackland; Norrby, Per-Ola

    2003-01-01

    The mnemonic device for predicting stereoselectivities in the Sharpless asymmetric dihydroxylation (AD) reaction has been updated based on extensive computational studies. Kinetic measurements from competition reactions validate the new proposal. The interactions responsible for the high stereose...

  2. Alternative Asymmetric Stochastic Volatility Models

    NARCIS (Netherlands)

    M. Asai (Manabu); M.J. McAleer (Michael)

    2010-01-01

    textabstractThe stochastic volatility model usually incorporates asymmetric effects by introducing the negative correlation between the innovations in returns and volatility. In this paper, we propose a new asymmetric stochastic volatility model, based on the leverage and size effects. The model is

  3. Microstructure of Reaction Zone Formed During Diffusion Bonding of TiAl with Ni/Al Multilayer

    Science.gov (United States)

    Simões, Sónia; Viana, Filomena; Koçak, Mustafa; Ramos, A. Sofia; Vieira, M. Teresa; Vieira, Manuel F.

    2012-05-01

    In this article, the characterization of the interfacial structure of diffusion bonding a TiAl alloy is presented. The joining surfaces were modified by Ni/Al reactive multilayer deposition as an alternative approach to conventional diffusion bonding. TiAl substrates were coated with alternated Ni and Al nanolayers. The nanolayers were deposited by dc magnetron sputtering with 14 nm of period (bilayer thickness). Joining experiments were performed at 900 °C for 30 and 60 min with a pressure of 5 MPa. Cross sections of the joints were prepared for characterization of their interfaces by scanning electron microscopy (SEM), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), high resolution TEM (HRTEM), energy dispersive x-ray spectroscopy (EDS), and electron backscatter diffraction (EBSD). Several intermetallic compounds form at the interface, assuring the bonding of the TiAl. The interface can be divided into three distinct zones: zone 1 exhibits elongated nanograins, very small equiaxed grains are observed in zone 2, while zone 3 has larger equiaxed grains. EBSD analysis reveals that zone 1 corresponds to the intermetallic Al2NiTi and AlNiTi, and zones 2 and 3 to NiAl.

  4. Comparative decay analysis of 179Re* and 189Au* formed in the reactions 20Ne+159Tb, 169Tm with Elab=8 MeV/A

    International Nuclear Information System (INIS)

    Manpreet Kaur; Singh, BirBikram

    2016-01-01

    The heavy ion induced reactions lead to the formation of composite systems, which subsequently decay because of high excitation energy and angular momentum. The study of decaying composite system facilitates to explore the number of nuclear characteristics and the reaction dynamics. The medium mass composite systems 164 Yb*, 176,182,188,196 Pt* and 200,202 Pb* have been studied successfully within the framework of dynamical cluster decay model (DCM). These studies show the emission of light particles, LP (or evaporation residues, ER), intermediate mass fragments, IMF, heavy mass fragments, HMF and symmetric fragments, SF along with signatures of quasi-fission, qf, process in their decay path. The decay of medium mass composite system 179 Re* has also been studied within DCM. In the present work, we investigate the comparative decay of two medium mass composite systems 179 Re* and 189 Au formed in the reactions with same projectile ( 20 Ne) having same E lab (or same E/A) on two different targets 159 Tb and 169 Tm, for which the experimental data is available

  5. Roles of the redox-active disulfide and histidine residues forming a catalytic dyad in reactions catalyzed by 2-ketopropyl coenzyme M oxidoreductase/carboxylase.

    Science.gov (United States)

    Kofoed, Melissa A; Wampler, David A; Pandey, Arti S; Peters, John W; Ensign, Scott A

    2011-09-01

    NADPH:2-ketopropyl-coenzyme M oxidoreductase/carboxylase (2-KPCC), an atypical member of the disulfide oxidoreductase (DSOR) family of enzymes, catalyzes the reductive cleavage and carboxylation of 2-ketopropyl-coenzyme M [2-(2-ketopropylthio)ethanesulfonate; 2-KPC] to form acetoacetate and coenzyme M (CoM) in the bacterial pathway of propylene metabolism. Structural studies of 2-KPCC from Xanthobacter autotrophicus strain Py2 have revealed a distinctive active-site architecture that includes a putative catalytic triad consisting of two histidine residues that are hydrogen bonded to an ordered water molecule proposed to stabilize enolacetone formed from dithiol-mediated 2-KPC thioether bond cleavage. Site-directed mutants of 2-KPCC were constructed to test the tenets of the mechanism proposed from studies of the native enzyme. Mutagenesis of the interchange thiol of 2-KPCC (C82A) abolished all redox-dependent reactions of 2-KPCC (2-KPC carboxylation or protonation). The air-oxidized C82A mutant, as well as wild-type 2-KPCC, exhibited the characteristic charge transfer absorbance seen in site-directed variants of other DSOR enzymes but with a pK(a) value for C87 (8.8) four units higher (i.e., four orders of magnitude less acidic) than that for the flavin thiol of canonical DSOR enzymes. The same higher pK(a) value was observed in native 2-KPCC when the interchange thiol was alkylated by the CoM analog 2-bromoethanesulfonate. Mutagenesis of the flavin thiol (C87A) also resulted in an inactive enzyme for steady-state redox-dependent reactions, but this variant catalyzed a single-turnover reaction producing a 0.8:1 ratio of product to enzyme. Mutagenesis of the histidine proximal to the ordered water (H137A) led to nearly complete loss of redox-dependent 2-KPCC reactions, while mutagenesis of the distal histidine (H84A) reduced these activities by 58 to 76%. A redox-independent reaction of 2-KPCC (acetoacetate decarboxylation) was not decreased for any of the

  6. Asymmetric Realized Volatility Risk

    Directory of Open Access Journals (Sweden)

    David E. Allen

    2014-06-01

    Full Text Available In this paper, we document that realized variation measures constructed from high-frequency returns reveal a large degree of volatility risk in stock and index returns, where we characterize volatility risk by the extent to which forecasting errors in realized volatility are substantive. Even though returns standardized by ex post quadratic variation measures are nearly Gaussian, this unpredictability brings considerably more uncertainty to the empirically relevant ex ante distribution of returns. Explicitly modeling this volatility risk is fundamental. We propose a dually asymmetric realized volatility model, which incorporates the fact that realized volatility series are systematically more volatile in high volatility periods. Returns in this framework display time varying volatility, skewness and kurtosis. We provide a detailed account of the empirical advantages of the model using data on the S&P 500 index and eight other indexes and stocks.

  7. Asymmetric Higgsino dark matter.

    Science.gov (United States)

    Blum, Kfir; Efrati, Aielet; Grossman, Yuval; Nir, Yosef; Riotto, Antonio

    2012-08-03

    In the supersymmetric framework, prior to the electroweak phase transition, the existence of a baryon asymmetry implies the existence of a Higgsino asymmetry. We investigate whether the Higgsino could be a viable asymmetric dark matter candidate. We find that this is indeed possible. Thus, supersymmetry can provide the observed dark matter abundance and, furthermore, relate it with the baryon asymmetry, in which case the puzzle of why the baryonic and dark matter mass densities are similar would be explained. To accomplish this task, two conditions are required. First, the gauginos, squarks, and sleptons must all be very heavy, such that the only electroweak-scale superpartners are the Higgsinos. With this spectrum, supersymmetry does not solve the fine-tuning problem. Second, the temperature of the electroweak phase transition must be low, in the (1-10) GeV range. This condition requires an extension of the minimal supersymmetric standard model.

  8. Nuclear structure effects in fusion-fission of compound systems 20,21,22Ne formed in 10,11B+10,11B reactions

    International Nuclear Information System (INIS)

    Singh, BirBikram; Kaur, Manpreet; Kaur, Varinderjit; Gupta, Raj K.

    2014-01-01

    The dynamical cluster-decay model (DCM) of Gupta and collaborators has been successfully applied to the decay of number of hot and rotating compound nuclei in different mass regions, formed in low-energy heavy ion reactions. Recently, its application to the binary symmetric decay (BSD) of very light mass compound systems 20,21,22 Ne formed in 10,11 B+ 10,11 B reactions at E lab =48 MeV is extended, as the experimental data for σ BSD Expt . is available, namely, for 20 Ne (∼ 270 mb), 21 Ne ( 22 Ne ( BSD DCM for the BSD of the three Ne systems is calculated, comprising fusion-fission σ ff and deep inelastic scattering/orbiting σorb contributions (evaluated empirically here) from compound nucleus CN and non-compound nucleus nCN processes, respectively. The significant observation from this study is that, of the total σ BSD DCM , σ ff contribution is very strong for the decay of 20 Ne (=195.270 mb; >70%), followed by 21 Ne (=65.723 mb; ∼50%) and 22 Ne (=8.677 mb; almost 10%). This means that the process of collective clusterization within the DCM is playing very strong role for the decay of 20 Ne

  9. Asymmetric Michael Addition Mediated by Chiral Ionic Liquids

    Science.gov (United States)

    Suzuki, Yumiko

    2018-01-01

    Chiral ionic liquids with a focus on their applications in asymmetric Michael additions and related reactions were reviewed. The examples were classified on the basis of the mode of asymmetric induction (e.g., external induction/non-covalent interaction or internal induction/covalent bond formation), the roles in reactions (as a solvent or catalyst), and their structural features (e.g., imidazolium-based chiral cations, other chiral oniums; proline derivatives). Most of the reactions with high chiral induction are Michael addition of ketones or aldehydes to chalcones or nitrostyrenes where proline-derived chiral ionic liquids catalyze the reaction through enamine/ iminium formation. Many reports demonstrate the recyclability of ionic liquid-tagged pyrrolidines. PMID:29861702

  10. Asymmetric Michael Addition Mediated by Chiral Ionic Liquids.

    Science.gov (United States)

    Suzuki, Yumiko

    2018-06-01

    Chiral ionic liquids with a focus on their applications in asymmetric Michael additions and related reactions were reviewed. The examples were classified on the basis of the mode of asymmetric induction (e.g., external induction/non-covalent interaction or internal induction/covalent bond formation), the roles in reactions (as a solvent or catalyst), and their structural features (e.g., imidazolium-based chiral cations, other chiral oniums; proline derivatives). Most of the reactions with high chiral induction are Michael addition of ketones or aldehydes to chalcones or nitrostyrenes where proline-derived chiral ionic liquids catalyze the reaction through enamine/ iminium formation. Many reports demonstrate the recyclability of ionic liquid-tagged pyrrolidines.

  11. Bianisotropic metamaterials based on twisted asymmetric crosses

    International Nuclear Information System (INIS)

    Reyes-Avendaño, J A; Sampedro, M P; Juárez-Ruiz, E; Pérez-Rodríguez, F

    2014-01-01

    The effective bianisotropic response of 3D periodic metal-dielectric structures, composed of crosses with asymmetrically-cut wires, is investigated within a general homogenization theory using the Fourier formalism and the form-factor division approach. It is found that the frequency dependence of the effective permittivity for a system of periodically-repeated layers of metal crosses exhibits two strong resonances, whose separation is due to the cross asymmetry. Besides, bianisotropic metamaterials, having a base of four twisted asymmetric crosses, are proposed. The designed metamaterials possess negative refractive index at frequencies determined by the cross asymmetry, the gap between the arms of adjacent crosses lying on the same plane, and the type of Bravais lattice. (papers)

  12. Study of the p(e,e'π+)n electro-production reaction: form factor and electromagnetic radius of pion

    International Nuclear Information System (INIS)

    Michel, Bernard

    1977-01-01

    After having recalled the definitions and theoretical knowledge on the form factor and electromagnetic radius of hadron and pion, and discussed the relationship between electro-production and form factor for the pion, this research thesis recalls some theoretical aspects of the electro-production process. The author discusses the reaction kinematics and shows how the electro-production cross section can be broken down in terms of photon polarization. Then, he focuses on the cross section dynamic structure. After having recalled the different possible choices for amplitudes, he studies their behaviour, firstly within the framework of the Born approximation, and then within the framework of commonly used models, notably to take the resonant part of the phenomenon into account. The limits of the different models are outlined. The second part addresses the study of forward electro-production. The author shows how the pion form factor can be simply optimized. The author describes the experimental arrangement: electron beam and liquid hydrogen target, detection system, normalisation device, data acquisition logics. In the next chapter, the author describes how data are recorded until the obtainment of N electro-production events. Results are then interpreted in terms of form factor and electromagnetic radius. They are also compared with published results obtained with other electro-production experiments or measurements based on other processes [fr

  13. Novel phosphonium salts and bifunctional organocatalysts in asymmetric synthesis

    OpenAIRE

    Moore, Graham

    2013-01-01

    This thesis details the syntheses of catalysts and their applications in asymmetric reactions. Initially, the project focused on phase transfer catalysts; quaternary phosphonium salts derived from diethyl tartrate or from commercially available phosphorus compounds and their use primarily in the alkylation of N,N-diphenyl methylene glycine tert-butyl ester. Although some of the salts showed the ability to catalyse the alkylation reaction, all products obtained were racemic. The project then f...

  14. Asymmetric Synthesis of Optically Active Spirocyclic Indoline Scaffolds through an Enantioselective Reduction of Indoles

    KAUST Repository

    Borrmann, Ruediger; Knop, Nils; Rueping, Magnus

    2016-01-01

    An enantioselective synthesis of spirocyclic indoline scaffolds was achieved by applying an asymmetric iridium-catalyzed hydrogenation of 3H-indoles. Low catalyst loadings and mild reaction conditions provide a broad range of differently substituted

  15. Method development of damage detection in asymmetric buildings

    Science.gov (United States)

    Wang, Yi; Thambiratnam, David P.; Chan, Tommy H. T.; Nguyen, Andy

    2018-01-01

    Aesthetics and functionality requirements have caused most buildings to be asymmetric in recent times. Such buildings exhibit complex vibration characteristics under dynamic loads as there is coupling between the lateral and torsional components of vibration, and are referred to as torsionally coupled buildings. These buildings require three dimensional modelling and analysis. In spite of much recent research and some successful applications of vibration based damage detection methods to civil structures in recent years, the applications to asymmetric buildings has been a challenging task for structural engineers. There has been relatively little research on detecting and locating damage specific to torsionally coupled asymmetric buildings. This paper aims to compare the difference in vibration behaviour between symmetric and asymmetric buildings and then use the vibration characteristics for predicting damage in them. The need for developing a special method to detect damage in asymmetric buildings thus becomes evident. Towards this end, this paper modifies the traditional modal strain energy based damage index by decomposing the mode shapes into their lateral and vertical components and to form component specific damage indices. The improved approach is then developed by combining the modified strain energy based damage indices with the modal flexibility method which was modified to suit three dimensional structures to form a new damage indicator. The procedure is illustrated through numerical studies conducted on three dimensional five-story symmetric and asymmetric frame structures with the same layout, after validating the modelling techniques through experimental testing of a laboratory scale asymmetric building model. Vibration parameters obtained from finite element analysis of the intact and damaged building models are then applied into the proposed algorithms for detecting and locating the single and multiple damages in these buildings. The results

  16. Twin Higgs Asymmetric Dark Matter.

    Science.gov (United States)

    García García, Isabel; Lasenby, Robert; March-Russell, John

    2015-09-18

    We study asymmetric dark matter (ADM) in the context of the minimal (fraternal) twin Higgs solution to the little hierarchy problem, with a twin sector with gauged SU(3)^{'}×SU(2)^{'}, a twin Higgs doublet, and only third-generation twin fermions. Naturalness requires the QCD^{'} scale Λ_{QCD}^{'}≃0.5-20  GeV, and that t^{'} is heavy. We focus on the light b^{'} quark regime, m_{b^{'}}≲Λ_{QCD}^{'}, where QCD^{'} is characterized by a single scale Λ_{QCD}^{'} with no light pions. A twin baryon number asymmetry leads to a successful dark matter (DM) candidate: the spin-3/2 twin baryon, Δ^{'}∼b^{'}b^{'}b^{'}, with a dynamically determined mass (∼5Λ_{QCD}^{'}) in the preferred range for the DM-to-baryon ratio Ω_{DM}/Ω_{baryon}≃5. Gauging the U(1)^{'} group leads to twin atoms (Δ^{'}-τ^{'}[over ¯] bound states) that are successful ADM candidates in significant regions of parameter space, sometimes with observable changes to DM halo properties. Direct detection signatures satisfy current bounds, at times modified by dark form factors.

  17. Antioxidant activity of the melanoidin fractions formed from DGlucose and D-Fructose with L-Asparagine in the Maillard reaction

    Directory of Open Access Journals (Sweden)

    A.P Echavarría

    2013-03-01

    Full Text Available Melanoidins formed at the last stage of the Maillard reaction have been shown to possess certain functional properties, such as antioxidant activity. In order to gain more insight into these functional properties, soluble model systems melanoidins from L‑Asparagine with D‑glucose or D‑fructose fractionating by ultrafiltration were analyzed. The fractionating/concentration sequence of the melanoidin fraction (1-300 kDa enabled five fractions to be produced.Additionally, the absorption of melanoidins was measured at different wavelengths (280, 325, 405 and browning at 420 nm. The fractionation effect of melanoidin systems on the color intensity, UV-absorbance scan wavelengths (nm, CIE, L*, a*, b* parameters and antioxidant activity were measured. For this purpose, antioxidant activity was evaluated through the free radical scavenging activity, including 1,1-diphenyl-2-picryl-hydrazil (DPPH and 2,20-azinobis (3-ethylbenothiazoline-6-sulfonic acid, diammonium salt (ABTS. The results showed that the absorption of the melanoidins formed from Glucose/L-Asn was higher than for those derived from Fructose/L-Asn. On the other hand, their antioxidant power was lower than that for melanoidins formed from Fructose/L-Asn systems.

  18. Antioxidant activity of the melanoidin fractions formed from D-Glucose and D-Fructose with L-Asparagine in the Maillard reaction

    Directory of Open Access Journals (Sweden)

    A.P Echavarría

    2013-01-01

    Full Text Available Melanoidins formed at the last stage of the Maillard reaction have been shown to possess certain functional properties, such as antioxidant activity. In order to gain more insight into these functional properties, soluble model systems melanoidins from L - Asparagine with D - glucose or D - fructose fractionating by ultrafiltration were analyzed. The fractionating/concentration sequence of the melanoidin fraction (1 - 300 kDa enabled five fractions to be produced. Additionally, the absorption of melanoidins was measured at different wavelengths (280, 325, 405 and browning at 420 nm. The fractionati on effect of melanoidin systems on the color intensity, UV - absorbance scan wavelengths (nm, CIE, L*, a*, b* parameters and antioxidant activity were measured. For this purpose, antioxidant activity was evaluated through the free radical scavenging activit y, including 1,1 - diphenyl - 2 - picryl - hydrazil (DPPH and 2,20 - azinobis (3 - ethylbenothiazoline - 6 - sulfonic acid, diammonium salt (ABTS. The results showed that the absorption of the melanoidins formed from Glucose/L - Asn was higher than for those derived from Fructose/L - Asn. On the other hand, their antioxidant power was lower than that for melanoidins formed from Fructose/L - Asn systems.

  19. Asymmetric threat data mining and knowledge discovery

    Science.gov (United States)

    Gilmore, John F.; Pagels, Michael A.; Palk, Justin

    2001-03-01

    Asymmetric threats differ from the conventional force-on- force military encounters that the Defense Department has historically been trained to engage. Terrorism by its nature is now an operational activity that is neither easily detected or countered as its very existence depends on small covert attacks exploiting the element of surprise. But terrorism does have defined forms, motivations, tactics and organizational structure. Exploiting a terrorism taxonomy provides the opportunity to discover and assess knowledge of terrorist operations. This paper describes the Asymmetric Threat Terrorist Assessment, Countering, and Knowledge (ATTACK) system. ATTACK has been developed to (a) data mine open source intelligence (OSINT) information from web-based newspaper sources, video news web casts, and actual terrorist web sites, (b) evaluate this information against a terrorism taxonomy, (c) exploit country/region specific social, economic, political, and religious knowledge, and (d) discover and predict potential terrorist activities and association links. Details of the asymmetric threat structure and the ATTACK system architecture are presented with results of an actual terrorist data mining and knowledge discovery test case shown.

  20. Electric form factor of the neutron from the 2H(e-->,e'n-->)1H reaction at Q2=0.255 (GeV/c)2

    International Nuclear Information System (INIS)

    T. Eden; R. Madey; W.-M. Zhang; B. D. Anderson; H. Arenhvel; A. R. Baldwin; D. Barkhuff; K. B. Beard; W. Bertozzi; J. M. Cameron; C. C. Chang; G. W. Dodson; K. Dow; M. Farkhondeh; J. M. Finn; B. S. Flanders; C. Hyde-Wright; W.-D. Jiang; D. Keane; J. J. Kelly; W. Korsch; S. Kowalski; R. Lourie; D. M. Manley; P. Markowitz; J. Mougey; B. Ni; T. Payerle; P. J. Pella; T. Reichelt; P. M. Rutt; M. Spraker; D. Tieger; W. Turchinetz; P. E. Ulmer; S. Van Verst; J. W. Watson; L. B. Weinstein; and R. R. Whitney

    1994-01-01

    We determined the electric form factor GnE of the neutron from the quasielastic 2H(e-->,e'n-->)1H reaction at a central squared four-momentum transfer Q2=0.255 (GeV/c)2 with a longitudinally polarized electron beam of 868 MeV and a low (∼0.8%) duty factor. A neutron polarimeter designed and constructed specifically for this experiment was used to measure the sideways polarization of the recoil neutron, which was detected in coincidence with the scattered electron. Theoretical calculations have established that this polarization-transfer technique for quasielastic scattering produces a value of GnE that shows little sensitivity to the influence of final-state interactions, meson-exchange currents, isobar configurations, and deuteron structure. The value for GnE from this measurement is 0.066 ± 0.036 ± 0.009

  1. Evidence for different fission behavior of hot nuclei formed in central and peripheral collisions of 40Ar + 209Bi reaction at 25 MeV/u

    International Nuclear Information System (INIS)

    Wu Enjiu; Zheng Jiwen; Xiao Zhigang; Zhang Chun; Tan Jilian; Yin Shuzhi; Wang Sufang; Jin Genming; Yin Xu; Song Mingtao; Jin Weiyang; Peng Xingping; Li Zuyu; Wu Heyu; He Zhiyong; Jiang Dongxing; Qian Xing

    1999-01-01

    Correlated fission fragments from the reaction of 25 MeV/u 40 Ar + 209 Bi and their further correlation with α particles have been studied for peripheral and central collisions simultaneously. The excitation energy at scission deduced from post scission multiplicity is about 172.5 MeV. The fission timescale deduced from prescission multiplicity is about 4 x 10 -21 s. Systematic analysis of the mass and energy distributions of fission fragments as a function of the initial temperature of hot fissioning nuclei reveals the existence of different fission behavior of hot nuclei formed in central and peripheral collisions. Experimental data demonstrate the change of fission behavior at T∼4 MeV

  2. Force on an Asymmetric Capacitor

    National Research Council Canada - National Science Library

    Bahder, Thomas

    2003-01-01

    .... At present, the physical basis for the Biefeld-Brown effect is not understood. The order of magnitude of the net force on the asymmetric capacitor is estimated assuming two different mechanisms of charge conduction between its electrodes...

  3. MECHANISMS OF THE COMPLEX FORMATION BY d-METALS ON POROUS SUPPORTS AND THE CATALYTIC ACTIVITY OF THE FORMED COMPLEXES IN REDOX REACTIONS

    Directory of Open Access Journals (Sweden)

    T. L. Rakitskaya

    2015-11-01

    Full Text Available The catalytic activity of supported complexes of d metals in redox reactions with participation of gaseous toxicants, PH3, CO, O3, and SO2, depends on their composition. Owing to the variety of physicochemical and structural-adsorption properties of available supports, their influence on complex formation processes, the composition and catalytic activity of metal complexes anchored on them varies over a wide range. The metal complex formation on sup-ports with weak ion-exchanging properties is similar to that in aqueous solutions. In this case, the support role mainly adds up to the ability to reduce the activity of water adsorbed on them. The interaction between a metal complex and a support surface occurs through adsorbed water molecules. Such supports can also affect complex formation processes owing to protolytic reactions on account of acidic properties of sorbents used as supports. The catalytic activity of metal complexes supported on polyphase natural sorbents considerably depends on their phase relationship. In the case of supports with the nonsimple structure and pronounced ion-exchanging properties, for instance, zeolites and laminar silicates, it is necessary to take into account the variety of places where metal ions can be located. Such location places determine distinctions in the coordination environment of the metal ions and the strength of their bonding with surface adsorption sites and, therefore, the catalytic activity of surface complexes formed by theses metal ions. Because of the energy surface inhomogeneity, it is important to determine a relationship between the strength of a metal complex bonding with a support surface and its catalytic activity. For example, bimetallic complexes are catalytically active in the reactions of oxidation of the above gaseous toxicants. In particular, in the case of carbon monoxide oxidation, the most catalytic activity is shown by palladium-copper complexes in which copper(II is strongly

  4. Organocatalytic Michael and Friedel–Crafts reactions in enantioselective synthesis of biologically active compounds

    International Nuclear Information System (INIS)

    Maltsev, O V; Beletskaya, Irina P; Zlotin, Sergei G

    2011-01-01

    Recent applications of organocatalytic Michael and Friedel–Crafts reactions in enantioselective synthesis of biologically active compounds: natural products, pharmaceutical agents and plant protection agents are reviewed. The key mechanisms of stereoinduction, types of organocatalysts and reagents used in these reactions are considered. The material is classified according to the type of newly formed bonds incorporating the asymmetric carbon atom, and the information for the most numerous C–C coupling reactions is systematized according to the natures of the electrophile and the nucleophile. The bibliography includes 433 references.

  5. Reaction of Pb(II) and Zn(II) with Ethyl Linoleate To Form Structured Hybrid Inorganic–Organic Complexes: A Model for Degradation in Historic Paint Films

    Energy Technology Data Exchange (ETDEWEB)

    MacDonald, Margaret G.; Palmer, Michael R.; Suchomel, Matthew R.; Berrie, Barbara H. (NGA); (Bordeaux)

    2016-09-23

    To investigate soap formation in drying oils in historic paints, the reaction between metal acetates (K+, Zn2+, Pb2+) and ethyl linoleate (EL) was studied using optical microscopy, X-ray powder diffraction, and electron microscopy. Pb(II) and Zn(II) react rapidly with EL to form highly structured, spherulitic, luminescent crystallites that aggregate. Evidence from Fourier transform infrared (FTIR) and scanning electron microscopy/energy dispersive X-ray analysis and high-resolution synchrotron powder X-ray diffraction indicates that these are organic–inorganic hybrid complexes or coordination polymers. FTIR absorbance peaks at ca. 1540 cm–1 for Pb(II) and ca. 1580 cm–1 for Zn(II) are consistent with the formation of carboxylate complexes. The complexes formed offer insight into the degradation processes observed in oil paint films, suggesting that soap formation is rapid when metal ions are solubilized and can occur with unsaturated fatty acids that are present in fresh oils. These complexes may account for the atypical luminescence observed in lead-containing cured oil paint films.

  6. Utility of Lithium in Rare-Earth Metal Reduction Reactions to Form Nontraditional Ln2+ Complexes and Unusual [Li(2.2.2-cryptand)]1+ Cations.

    Science.gov (United States)

    Huh, Daniel N; Darago, Lucy E; Ziller, Joseph W; Evans, William J

    2018-02-19

    The utility of lithium compared to other alkali metals in generating Ln 2+ rare-earth metal complexes via reduction of Ln 3+ precursors in reactions abbreviated as LnA 3 /M (Ln = rare-earth metal; A = anionic ligand; M = alkali metal) is described. Lithium reduction of Cp' 3 Ln (Cp' = C 5 H 4 SiMe 3 ; Ln = Y, Tb, Dy, Ho) under Ar in the presence of 2.2.2-cryptand (crypt) forms new examples of crystallographically characterizable Ln 2+ complexes of these metals, [Li(crypt)][Cp' 3 Ln]. In each complex, lithium is found in an N 2 O 4 donor atom coordination geometry that is unusual for the cryptand ligand. Magnetic susceptibility data on these new examples of nontraditional divalent lanthanide complexes are consistent with 4f n 5d 1 electronic configurations. The Dy and Ho complexes have exceptionally high single-ion magnetic moments, 11.35 and 11.67 μ B , respectively. Lithium reduction of Cp' 3 Y under N 2 at -35 °C forms the Y 2+ complex (Cp' 3 Y) 1- , which reduces dinitrogen upon warming to room temperature to generate the (N 2 ) 2- complex [Cp' 2 Y(THF)] 2 (μ-η 2 :η 2 -N 2 ). These results provide insight on the factors that lead to reduced dinitrogen complexes and/or stable divalent lanthanide complexes as a function of the specific reducing agent and conditions.

  7. Asymmetric Strecker Synthesis of α-Amino Acids via a Crystallization-Induced Asymmetric Transformation Using (R)-Phenylglycine Amide as Chiral Auxiliary

    NARCIS (Netherlands)

    Boesten, Wilhelmus H.J.; Seerden, Jean-Paul G.; Lange, Ben de; Dielemans, Hubertus J.A.; Elsenberg, Henk L.M.; Kaptein, Bernard; Moody, Harold M.; Kellogg, Richard M.; Broxterman, Quirinus B.

    2001-01-01

    Diastereoselective Strecker reactions based on (R)-phenylglycine amide as chiral auxiliary are reported. The Strecker reaction is accompanied by an in situ crystallization-induced asymmetric transformation, whereby one diastereomer selectively precipitates and can be isolated in 76-93% yield and dr

  8. Ion backscattering, channeling and nuclear reaction analysis study of passive films formed on FeCrNi and FeCrNiMo (100) single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Cohen, C; Schmaus, D [Paris-7 Univ., 75 (France). Groupe de Physique des Solides de l' ENS; Elbiache, A; Marcus, P [Ecole Nationale Superieure de Chimie, 75 - Paris (France)

    1990-01-01

    The compositions of passive films formed on Fe-17Fr-13Ni (at. %) and Fe-18.5Cr-14Ni-1.5Mo (100) single crystals have been determined and the structure of the alloy under the film has been investigated. The alloys were passivated in 0.05M H{sub 2}SO{sub 4} at 250 mV/SHE for 30 min. The oxygen content was measured by nuclear microanalysis using the {sup 16}O(d,p) {sup 17}O* reaction. The oxygen content in the passive film is similar for the two alloys and equal to (12{plus minus}2) 10{sup 15} O/cm{sup 2}. The cationic compositions of the passive films have been determined by {sup 4}He channeling at two incident beam energies: 0.8 and 2.0 MeV. For the two alloys studied, a total cation content of (5{plus minus}2)10{sup 15} at/cm{sup 2} is found in the passive films. The corresponding thickness is about 12 A. There is an excess of oxygen, which can be attributed to the presence of hydroxyls and sulfate. A strong chromium enrichment is found in the passive film formed on both alloys: chromium represents about 50% of the cations. There is no evidence of molybdenum enrichment in the passive film formed on the Mo-alloyed stainless steel. The comparison of the results obtained at the two different incident beam energies (0.8MeV and 2MeV) reveals the existence of defects at the alloy/passive film interface. (author).

  9. Low-coordinate rare-earth complexes of the asymmetric 2,4-di-tert-butylphenolate ligand prepared by redox transmetallation/protolysis reactions, and their reactivity towards ring-opening polymerisation.

    Science.gov (United States)

    Clark, Lawrence; Deacon, Glen B; Forsyth, Craig M; Junk, Peter C; Mountford, Philip; Townley, Josh P

    2010-08-07

    New trivalent lanthanoid aryloxide complexes have been prepared by redox transmetallation/protolysis (rtp) reactions using 2,4-di-tert-butylphenol (dbpH). Mononuclear octahedral complexes from tetrahydrofuran (thf) were of the type [Ln(dbp)(3)(thf)(3)] (Ln = La (1), Pr (2), Nd (3), Gd (4), Er (5)). The lanthanoid contraction results in the rather subtle change in stereochemistry from meridional (La, Pr, Nd, Gd) to facial (Er). An analogous reaction with neodymium in dimethoxyethane (dme), resulted in the isolation of the seven coordinate [Nd(dbp)(3)(dme)(2)] (6), and this is comparable with the thf complexes in terms of steric crowding. Dinuclear complexes of the type [Ln(2)(dbp)(6)(thf)(2)], (Ln = Nd (7), Er (8)) were obtained when 1 and 5 were recrystallised from toluene. These dimeric complexes contain two bridging and four terminal phenolates, as well as a single coordinated molecule of thf at each metal. A similar structural motif was observed for the products when the reaction was performed in diethyl ether, and in the absence of a solvent, yielding [Nd(2)(dbp)(6)(Et(2)O)(2)] (9) and [Nd(2)(dbp)(6)(dbpH)(2)] (10) respectively. Complexes 3 and 4 alone were efficient but poorly-controlled initiators for the ROP of rac-lactide, but with an excess of BnOH as a co-initiator they showed features consistent with immortal polymerisation. Use of BnNH(2) led to well-controlled, amine-initiated immortal ROP of rac-lactide, only the second report of this type of process for a group 3 or lanthanoid system.

  10. Robotized synthesis of [3-11C]-L-alanine using reaction of asymmetric alkylation of 11CH3I nickel complex of glycine Schiff base with S-2-N-(N'-benzylpropyl)aminobenzophenone

    International Nuclear Information System (INIS)

    Mosevich, I.K.; Kuznetsova, O.F.; Vasil'ev, D.A.; Anichkov, A.A.; Korsakov, M.V.

    1999-01-01

    Synthesis of [3- 11 C]-L-alanine based on 11 CH 3 I nickel complex (1) alkylation using different solvents (tetrahydrofuran, dimethylformamide, acetonitrile, acetone) and catalysts (potassium butylate, sodium hydride) was investigated. It was shown that synthesis of amino acids labelled with 11 C based on complex (1) use permits to obtain preparations with high degree of enantiomeric enrichment. The best results (enantiomeric excess of L-alanine up to 99 %) were obtained in reaction with acetonitrile as a solvent and potassium tret-butylate as a catalyst

  11. Process for fabricating PBI hollow fiber asymmetric membranes for gas separation and liquid separation

    Science.gov (United States)

    Jayaweera, Indira; Krishnan, Gopala N.; Sanjurjo, Angel; Jayaweera, Palitha; Bhamidi, Srinivas

    2016-04-26

    The invention provides methods for preparing an asymmetric hollow fiber, the asymmetric hollow fibers prepared by such methods, and uses of the asymmetric hollow fibers. One method involves passing a polymeric solution through an outer annular orifice of a tube-in-orifice spinneret, passing a bore fluid though an inner tube of the spinneret, dropping the polymeric solution and bore fluid through an atmosphere over a dropping distance, and quenching the polymeric solution and bore fluid in a bath to form an asymmetric hollow fiber.

  12. Bonds broken and formed during the mixed-linkage glucan : xyloglucan endotransglucosylase reaction catalysed by Equisetum hetero-trans-β-glucanase.

    Science.gov (United States)

    Simmons, Thomas J; Fry, Stephen C

    2017-03-08

    Mixed-linkage glucan∶xyloglucan endotransglucosylase (MXE) is one of the three activities of the recently characterised hetero-trans-β-glucanase (HTG), which among land plants is known only from Equisetum species. The biochemical details of the MXE reaction were incompletely understood - details that would promote understanding of MXE's role in vivo and enable its full technological exploitation. We investigated HTG's site of attack on one of its donor substrates, mixed-linkage (1→3),(1→4)-β-d-glucan (MLG), with radioactive oligosaccharides of xyloglucan as the acceptor substrate. Comparing three different MLG preparations, we showed that the enzyme favours those with a high content of cellotetraose blocks. The reaction products were analysed by enzymic digestion, thin-layer chromatography (TLC), high-pressure liquid chromatography (HPLC) and gel-permeation chromatography (GPC). Equisetum HTG consistently cleaved the MLG at the third consecutive β-(1→4)-bond following (towards the reducing terminus) a β-(1→3)-bond. It then formed a β-(1→4)-bond between the MLG and the non-reducing terminal glucose residue of the xyloglucan oligosaccharide, consistent with its xyloglucan endotransglucosylase/hydrolase subfamily membership. Using size-homogeneous barley MLG as the donor substrate, we showed that HTG does not favour any particular region of the MLG chain relative to the polysaccharide's reducing and non-reducing termini; rather, it selects its target cellotetraosyl unit stochastically along the MLG molecule. This work improves our understanding of how enzymes can exhibit promiscuous substrate specificities and provides the foundations to explore strategies for engineering novel substrate specificities into transglycanases. © 2017 The Author(s).

  13. Sidewall Covalent Functionalization of Single Wall Carbon Nanotubes through C-N Bond Forming Reactions of Fluoronanotubes with Urea, Guanidine and Thiourea (Preprint)

    National Research Council Canada - National Science Library

    Pulikkathara, Merlyn X; Khabashesku, Valery N

    2007-01-01

    ...) as starting materials in the reactions with either urea, thiourea, or guanidine. Through these reactions, the derivatives with terminal amide and heteroamide groups on the nanotube sidewalls have been prepared...

  14. Passive vibro-acoustic detection of a sodium-water reaction in a steam generator of a sodium-cooled fast neutrons nuclear reactor by beam forming

    International Nuclear Information System (INIS)

    Moriot, Jeremy

    2013-01-01

    This thesis deals with a new method to detect a sodium-water reaction in a steam generator of a fast sodium-cooled nuclear reactor. More precisely, the objective is to detect a micro-leak of water (flow ≤ 1 g/s) in less than 10 seconds by measuring the external shell vibrations of the component. The strong background noise in operation makes impossible the use of a detection system based on a threshold overrun. A beam forming method applied to vibrations measured by a linear array of accelerometers is developed in this thesis to increase the signal-to-noise ratio and to detect and locate the leak in the steam generator. A numerical study is first realized. Two models are developed in order to simulate the signals measured by the accelerometers of the array. The performances of the beam forming are then studied in function of several parameters, such as the source location and frequency, the damping factor, the background noise considered. The first model consists in an infinite plate in contact with a heavy fluid, excited by an acoustic monopole located in this fluid. Analyzing the transverse displacements in the wavenumber domain is useful to establish a criterion to sample correctly the vibration field of the plate. A second model, more representative of the system is also proposed. In this model, an elastic infinite cylindrical shell, filled with a heavy fluid is considered. The finite dimensions in the radial and circumferential directions lead to a modal behavior of the system which impacts the beam forming. Finally, the method is tested on an experimental mock-up which consists in a cylindrical pipe made in stainless steel and filled with water connected to hydraulic circuit. The water flow speed can be controlled by varying the speed of the pump. The acoustic source is generated by a hydro-phone. The performances of the beam forming are studied for different water flow speeds and different amplitude and frequencies of the source. (author) [fr

  15. Enantioselective solvent-free Robinson annulation reactions

    Indian Academy of Sciences (India)

    Unknown

    solvents to effect an asymmetric synthesis is an important step forward towards ... In continuation of our preliminary communication 2, we wish to ..... formation of chiral enamine 74 from the reaction of S-proline with pro-R carbonyl group.

  16. Nonperfect synchronization of bond-forming and bond-rupturing processes in the reaction H + H2 → H2 + H

    International Nuclear Information System (INIS)

    Chandra, A.K.; Rao, V.S.

    1996-01-01

    The simplest prototypical hydrogen transfer reaction, i.e., H + H 2 → H 2 + H, is studied by the quantum-mechanical ab initio methods. Results reveal that during this reaction free valence which almost equals the square of the spin density develops on the migrating hydrogen atom. Bond orders are calculated using Mayer's formalism. Both the variations of bond orders and bond lengths along the reaction path are examined. This analysis reveals that the bond formation and bond cleavage processes in this reaction are not perfectly synchronous. The bond clevage process is slightly more advanced on the reaction path. 38 refs., 6 figs., 2 tabs

  17. Does asymmetric correlation affect portfolio optimization?

    Science.gov (United States)

    Fryd, Lukas

    2017-07-01

    The classical portfolio optimization problem does not assume asymmetric behavior of relationship among asset returns. The existence of asymmetric response in correlation on the bad news could be important information in portfolio optimization. The paper applies Dynamic conditional correlation model (DCC) and his asymmetric version (ADCC) to propose asymmetric behavior of conditional correlation. We analyse asymmetric correlation among S&P index, bonds index and spot gold price before mortgage crisis in 2008. We evaluate forecast ability of the models during and after mortgage crisis and demonstrate the impact of asymmetric correlation on the reduction of portfolio variance.

  18. Organizing for Asymmetric Collaboration

    DEFF Research Database (Denmark)

    Nielsen, Jørn Flohr; Sørensen, Henrik B.

      The vision of new organizational forms consists of less-organized networks and alliances between organizations, in which collaborative capabilities are assumed to be crucial (Miles et al., 2005). The path to such new forms may go through fragile cooperative efforts. Despite the good will of many...... complexity to already complex models, we claim that our approach has practical implications: it offers rather simple diagnostic cues to change agents that are coping with the barriers to management and collaboration among loosely coupled units....

  19. Beyond public acceptance of energy infrastructure: How citizens make sense and form reactions by enacting networks of entities in infrastructure development

    International Nuclear Information System (INIS)

    Aaen, Sara Bjørn; Kerndrup, Søren; Lyhne, Ivar

    2016-01-01

    This article adds to the growing insight into public acceptance by presenting a novel approach to how citizens make sense of new energy infrastructure. We claim that to understand public acceptance, we need to go beyond the current thinking of citizens framed as passive respondents to proposed projects, and instead view infrastructure projects as enacted by citizens in their local settings. We propose a combination of sensemaking theory and actor–network theory that allows insight into how citizens enact entities from experiences and surroundings in order to create meaning and form a reaction to new infrastructure projects. Empirically, we analyze how four citizens make sense of an electricity cable project through a conversation process with a representative from the infrastructure developer. Interestingly, the formal participation process and the materiality of the cable play minor roles in citizens' sensemaking process. We conclude that insight into the way citizens are making sense of energy infrastructure processes can improve and help to overcome shortcomings in the current thinking about public acceptance and public participation. - Highlights: •Attention to citizens' sensemaking enables greater insight into the decision-making process. •A combination of sensemaking and actor-network theory (ANT) is relevant for studies of public acceptance. •Sensemaking explains why citizens facing similar situations act differently. •Complexity of citizens' sensemaking challenges the predictability of processes.

  20. Asymmetric Synthesis via Chiral Aziridines

    DEFF Research Database (Denmark)

    Tanner, David Ackland; Harden, Adrian; Wyatt, Paul

    1996-01-01

    A series of chiral bis(aziridines) has been synthesised and evaluated as chelating ligands for a variety of asymmetric transformations mediated by metals [Os (dihydroxylation), Pd (allylic alkylation) Cu (cyclopropanation and aziridination, Li (1,2-addition of organolithiums to imines)]. In the b......A series of chiral bis(aziridines) has been synthesised and evaluated as chelating ligands for a variety of asymmetric transformations mediated by metals [Os (dihydroxylation), Pd (allylic alkylation) Cu (cyclopropanation and aziridination, Li (1,2-addition of organolithiums to imines...

  1. Ideal 3D asymmetric concentrator

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Botella, Angel [Departamento Fisica Aplicada a los Recursos Naturales, Universidad Politecnica de Madrid, E.T.S.I. de Montes, Ciudad Universitaria s/n, 28040 Madrid (Spain); Fernandez-Balbuena, Antonio Alvarez; Vazquez, Daniel; Bernabeu, Eusebio [Departamento de Optica, Universidad Complutense de Madrid, Fac. CC. Fisicas, Ciudad Universitaria s/n, 28040 Madrid (Spain)

    2009-01-15

    Nonimaging optics is a field devoted to the design of optical components for applications such as solar concentration or illumination. In this field, many different techniques have been used for producing reflective and refractive optical devices, including reverse engineering techniques. In this paper we apply photometric field theory and elliptic ray bundles method to study 3D asymmetric - without rotational or translational symmetry - concentrators, which can be useful components for nontracking solar applications. We study the one-sheet hyperbolic concentrator and we demonstrate its behaviour as ideal 3D asymmetric concentrator. (author)

  2. Non-stationary probabilities for the asymmetric exclusion process

    Indian Academy of Sciences (India)

    A solution of the master equation for a system of interacting particles for finite time and particle density is presented. By using a new form of the Bethe ansatz, the totally asymmetric exclusion process on a ring is solved for arbitrary initial conditions and time intervals.

  3. Asymmetrical Modulation for Uplink Communication in Cooperative Networks

    DEFF Research Database (Denmark)

    Zhang, Qi; Fitzek, Frank H.P.; Iversen, Villy Bæk

    2008-01-01

    -range links with neighboring mobile devices to form cooperative clusters. So far the physical communication over cellular links and over short-range links are separated in time or in frequency. Beyond this state of the art, we exploit a method, referred to as asymmetrical modulation, where a mobile device...

  4. Catálise assimétrica na ciclopropanação de olefinas Asymmetric catalysis in the cyclopropanation of olefins

    Directory of Open Access Journals (Sweden)

    Raquel A. C. Leão

    2007-01-01

    Full Text Available The main methodologies in the asymmetric cyclopropanation of alkenes with emphasis on asymmetric catalysis are covered. Exemples are the Simmons-Smith reaction, the use of diazoalkanes and reactions carried out by decomposition of alpha-diazoesters in the presence of transition metals.

  5. Do Daily Retail Gasoline Prices adjust Asymmetrically?

    Energy Technology Data Exchange (ETDEWEB)

    Bettendorf, L. [Tinbergen Instituut, Amsterdam/Rotterdam (Netherlands); Van der Geest, S. [Erasmus Universiteit, Rotterdam (Netherlands); Kuper, G. [University of Groningen, Groningen (Netherlands)

    2005-04-15

    This paper analyzes adjustments in the Dutch retail gasoline prices. We estimate an error correction model on changes in the daily retail price for gasoline (taxes excluded) for the period 1996-2004 taking care of volatility clustering by estimating an EGARCH model. It turns out the volatility process is asymmetrical: an unexpected increase in the producer price has a larger effect on the variance of the producer price than an unexpected decrease. We do not find strong evidence for amount asymmetry. However, there is a faster reaction to upward changes in spot prices than to downward changes in spot prices. This implies timing or pattern asymmetry. This asymmetry starts three days after the change in the spot price and lasts for four days.

  6. Mitigation of Hydrogen Gas Generation from the Reaction of Uranium Metal with Water in K Basin Sludge and Sludge Waste Forms

    Energy Technology Data Exchange (ETDEWEB)

    Sinkov, Sergey I.; Delegard, Calvin H.; Schmidt, Andrew J.

    2011-06-08

    corrosion rates in water alone and in simulated sludge were near or slightly below the metal-in-water rate while nitrate-free sludge/Aquaset II decreased rates by about a factor of 3. Addition of 1 M nitrate to simulated sludge decreased the corrosion rate by a factor of ~5 while 1 M nitrate in sludge/Aquaset II mixtures decreased the corrosion rate by ~2.5 compared with the nitrate-free analogues. Mixtures of simulated sludge with Aquaset II treated with 1 M nitrate had uranium corrosion rates about a factor of 8 to 10 lower than the water-only rate law. Nitrate was found to provide substantial hydrogen mitigation for immobilized simulant sludge waste forms containing Aquaset II or Aquaset II G clay. Hydrogen attenuation factors of 1000 or greater were determined at 60°C for sludge-clay mixtures at 1 M nitrate. Hydrogen mitigation for tests with PC and Aquaset II H (which contains PC) were inconclusive because of suspected failure to overcome induction times and fully enter into anoxic corrosion. Lessening of hydrogen attenuation at ~80°C and ~95°C for simulated sludge and Aquaset II was observed with attenuation factors around 100 to 200 at 1 M nitrate. Valuable additional information has been obtained on the ability of nitrate to attenuate hydrogen gas generation from solution, simulant K Basin sludge, and simulant sludge with immobilization agents. Details on characteristics of the associated reactions were also obtained. The present testing confirms prior work which indicates that nitrate is an effective agent to attenuate hydrogen from uranium metal corrosion in water and simulated K Basin sludge to show that it is also effective in potential candidate solidified K Basin waste forms for WIPP disposal. The hydrogen mitigation afforded by nitrate appears to be sufficient to meet the hydrogen generation limits for shipping various sludge waste streams based on uranium metal concentrations and assumed waste form loadings.

  7. Mitigation of Hydrogen Gas Generation from the Reaction of Uranium Metal with Water in K Basin Sludge and Sludge Waste Forms

    International Nuclear Information System (INIS)

    Sinkov, Sergey I.; Delegard, Calvin H.; Schmidt, Andrew J.

    2011-01-01

    corrosion rates in water alone and in simulated sludge were near or slightly below the metal-in-water rate while nitrate-free sludge/Aquaset II decreased rates by about a factor of 3. Addition of 1 M nitrate to simulated sludge decreased the corrosion rate by a factor of ∼5 while 1 M nitrate in sludge/Aquaset II mixtures decreased the corrosion rate by ∼2.5 compared with the nitrate-free analogues. Mixtures of simulated sludge with Aquaset II treated with 1 M nitrate had uranium corrosion rates about a factor of 8 to 10 lower than the water-only rate law. Nitrate was found to provide substantial hydrogen mitigation for immobilized simulant sludge waste forms containing Aquaset II or Aquaset II G clay. Hydrogen attenuation factors of 1000 or greater were determined at 60 C for sludge-clay mixtures at 1 M nitrate. Hydrogen mitigation for tests with PC and Aquaset II H (which contains PC) were inconclusive because of suspected failure to overcome induction times and fully enter into anoxic corrosion. Lessening of hydrogen attenuation at ∼80 C and ∼95 C for simulated sludge and Aquaset II was observed with attenuation factors around 100 to 200 at 1 M nitrate. Valuable additional information has been obtained on the ability of nitrate to attenuate hydrogen gas generation from solution, simulant K Basin sludge, and simulant sludge with immobilization agents. Details on characteristics of the associated reactions were also obtained. The present testing confirms prior work which indicates that nitrate is an effective agent to attenuate hydrogen from uranium metal corrosion in water and simulated K Basin sludge to show that it is also effective in potential candidate solidified K Basin waste forms for WIPP disposal. The hydrogen mitigation afforded by nitrate appears to be sufficient to meet the hydrogen generation limits for shipping various sludge waste streams based on uranium metal concentrations and assumed waste form loadings.

  8. An asymmetric synthesis of (R)-5-(methylamino)-5,6-dihydro-4H-imidazo-[4,5,1-ij]quinolin-2(1H) -one (1) and its [2-14C]-and [6,7-3H2]-labeled forms

    International Nuclear Information System (INIS)

    Heier, R.F.; Moon, M.W.; Stolle, W.T.; Easter, J.A.; Hsi, R.S.P.

    1996-01-01

    (R)-5-(Methylamino)-5,6-dihydro-4H-imidazo [4,5,1-ij)quinolin-2(1H)-one (1) is a dopamine agonist which shows selectivity for the D2 receptor subtype, and is of interest as a potential drug for the treatment of Parkinson's disease. An asymmetric epoxidation approach has been used to prepare 1 in eleven steps (15% overall yield) from 8-nitroquinoline. An advanced intermediate in this synthesis, tert-butyl (R)-methyl(8-amino-1,2,3,4-tetrahydro-3-quinolinyl)carbamate, has been reacted with [ 14 C]phosgene to provide a two-step synthesis of 1 labeled with carbon-14 at the C-2 position (236 μCi/mg). Bromination of 1 gave the dibromo analogue which was reduced in the presence of tritium gas to give 1 labeled with tritium at the C-6 and C-7 positions (28.5 Ci/mmol). In addition to providing syntheses for labeled forms of the drug which are useful in drug disposition and receptor binding studies, this approach also provides a convenient synthesis for the unlabeled form of drug. (author)

  9. Gravity-induced asymmetric distribution of a plant growth hormone

    Science.gov (United States)

    Bandurski, R. S.; Schulze, A.; Momonoki, Y.

    1984-01-01

    Dolk (1936) demonstrated that gravistimulation induced an asymmetric distribution of auxin in a horizontally-placed shoot. An attempt is made to determine where and how that asymmetry arises, and to demonstrate that the endogenous auxin, indole-3-acetic acid, becomes asymmetrically distributed in the cortical cells of the Zea mays mesocotyl during 3 min of geostimulation. Further, indole-3-acetic acid derived by hydrolysis of an applied transport form of the hormone, indole-3-acetyl-myo-inositol, becomes asymmetrically distributed within 15 min of geostimulus time. From these and prior data is developed a working theory that the gravitational stimulus induces a selective leakage, or secretion, of the hormone from the vascular tissue to the cortical cells of the mesocotyl.

  10. Asymmetric Penning trap coherent states

    International Nuclear Information System (INIS)

    Contreras-Astorga, Alonso; Fernandez, David J.

    2010-01-01

    By using a matrix technique, which allows to identify directly the ladder operators, the coherent states of the asymmetric Penning trap are derived as eigenstates of the appropriate annihilation operators. They are compared with those obtained through the displacement operator method.

  11. JET and COMPASS asymmetrical disruptions

    Czech Academy of Sciences Publication Activity Database

    Gerasimov, S.N.; Abreu, P.; Baruzzo, M.; Drozdov, V.; Dvornova, A.; Havlíček, Josef; Hender, T.C.; Hronová-Bilyková, Olena; Kruezi, U.; Li, X.; Markovič, Tomáš; Pánek, Radomír; Rubinacci, G.; Tsalas, M.; Ventre, S.; Villone, F.; Zakharov, L.E.

    2015-01-01

    Roč. 55, č. 11 (2015), s. 113006-113006 ISSN 0029-5515 R&D Projects: GA MŠk(CZ) LM2011021 Institutional support: RVO:61389021 Keywords : tokamak * asymmetrical disruption * JET * COMPASS Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 4.040, year: 2015

  12. Asymmetric synthesis of synthetic alkaloids by a tandem biocatalysis/Ugi/Pictet-Spengler-type

    NARCIS (Netherlands)

    Znabet, A.; Zonneveld, J.; Janssen, E.; de Kanter, F.J.J.; Helliwell, M.; Turner, N.J.; Ruijter, E.; Orru, R.V.A.

    2010-01-01

    We have combined the biocatalytic desymmetrization of 3,4-cis-substituted meso-pyrrolidines with an Ugi-type multicomponent reaction followed in situ by a Pictet-Spengler-type cyclization reaction sequence for the rapid asymmetric synthesis of alkaloid-like polycyclic compounds. © The Royal Society

  13. Asymmetric chiral colour

    International Nuclear Information System (INIS)

    Cuypers, F.

    1990-01-01

    Chiral colour is considered in a general framework where the coupling constants associated with each SU(3) component are allowed to be different. To reproduce QCD at low energy, gluons and axigluons cannot then be maximally mixed. Present data form e + e - colliders contrains the axigluon mass to values between 50 GeV and 375 GeV whilst the mixing angle is bounded by 13deg and 45deg. The lower limit of the axigluon mass is a definite bound at 90% C.L., whereas the upper limit only applies if chiral colour is to explain the anomalously high rates of hadron production at TRISTAN. (orig.)

  14. A combined continuous microflow photochemistry and asymmetric organocatalysis approach for the enantioselective synthesis of tetrahydroquinolines

    Directory of Open Access Journals (Sweden)

    Erli Sugiono

    2013-11-01

    Full Text Available A continuous-flow asymmetric organocatalytic photocyclization–transfer hydrogenation cascade reaction has been developed. The new protocol allows the synthesis of tetrahydroquinolines from readily available 2-aminochalcones using a combination of photochemistry and asymmetric Brønsted acid catalysis. The photocylization and subsequent reduction was performed with catalytic amount of chiral BINOL derived phosphoric acid diester and Hantzsch dihydropyridine as hydrogen source providing the desired products in good yields and with excellent enantioselectivities.

  15. New chiral ligands in asymmetric catalysis. Application in stabilization of metal nanoparticles

    OpenAIRE

    Axet Martí, M. Rosa

    2006-01-01

    Thesis M. Rosa AxetThis thesis deals with the development and application of diphosphite ligands derived from carbohydrates to rhodium-catalysed asymmetric hydroformylation and hydrogenation reactions. The use of various carbohydrate derivative ligands as stabilisers of metal nanoparticles is also studied. The synthesis and the characterisation of the series of diphosphite ligands are described in Chapter 2. The results of the asymmetric hydroformylation of styrene and related vinyl arenes ar...

  16. An active site mutant of Escherichia coli cyclopropane fatty acid synthase forms new non-natural fatty acids providing insights on the mechanism of the enzymatic reaction.

    Science.gov (United States)

    E, Guangqi; Drujon, Thierry; Correia, Isabelle; Ploux, Olivier; Guianvarc'h, Dominique

    2013-12-01

    We have produced and purified an active site mutant of the Escherichia coli cyclopropane fatty acid synthase (CFAS) by replacing the strictly conserved G236 within cyclopropane synthases, by a glutamate residue, which corresponds to E146 of the homologous mycolic acid methyltransferase, Hma, producing hydroxymethyl mycolic acids. The G236E CFAS mutant had less than 1% of the in vitro activity of the wild type enzyme. We expressed the G236E CFAS mutant in an E. coli (DE3) strain in which the chromosomal cfa gene had been deleted. After extraction of phospholipids and conversion into the corresponding fatty acid methyl esters (FAMEs), we observed the formation of cyclopropanated FAMEs suggesting that the mutant retained some of the normal activity in vivo. However, we also observed the formation of new C17 methyl-branched unsaturated FAMEs whose structures were determined using GC/MS and NMR analyses. The double bond was located at different positions 8, 9 or 10, and the methyl group at position 10 or 9. Thus, this new FAMEs are likely arising from a 16:1 acyl chain of a phospholipid that had been transformed by the G236E CFAS mutant in vivo. The reaction catalyzed by this G236E CFAS mutant thus starts by the methylation of the unsaturated acyl chain at position 10 or 9 yielding a carbocation at position 9 or 10 respectively. It follows then two competing steps, a normal cyclopropanation or hydride shift/elimination events giving different combinations of alkenes. This study not only provides further evidence that cyclopropane synthases (CSs) form a carbocationic intermediate but also opens the way to CSs engineering for the synthesis of non-natural fatty acids. Copyright © 2013 Elsevier Masson SAS. All rights reserved.

  17. All Pseudocapacitive MXene-RuO2 Asymmetric Supercapacitors

    KAUST Repository

    Jiang, Qiu

    2018-01-23

    2D transition metal carbides and nitrides, known as MXenes, are an emerging class of 2D materials with a wide spectrum of potential applications, in particular in electrochemical energy storage. The hydrophilicity of MXenes combined with their metallic conductivity and surface redox reactions is the key for high-rate pseudocapacitive energy storage in MXene electrodes. However, symmetric MXene supercapacitors have a limited voltage window of around 0.6 V due to possible oxidation at high anodic potentials. In this study, the fact that titanium carbide MXene (Ti3C2Tx) can operate at negative potentials in acidic electrolyte is exploited, to design an all-pseudocapacitive asymmetric device by combining it with a ruthenium oxide (RuO2) positive electrode. This asymmetric device operates at a voltage window of 1.5 V, which is about two times wider than the operating voltage window of symmetric MXene supercapacitors, and is the widest voltage window reported to date for MXene-based supercapacitors. The complementary working potential windows of MXene and RuO2, along with proton-induced pseudocapacitance, significantly enhance the device performance. As a result, the asymmetric devices can deliver an energy density of 37 µW h cm−2 at a power density of 40 mW cm−2, with 86% capacitance retention after 20 000 charge–discharge cycles. These results show that pseudocapacitive negative MXene electrodes can potentially replace carbon-based materials in asymmetric electrochemical capacitors, leading to an increased energy density.

  18. Electron Jet of Asymmetric Reconnection

    Science.gov (United States)

    Khotyaintsev, Yu. V.; Graham, D. B.; Norgren, C.; Eriksson, E.; Li, W.; Johlander, A.; Vaivads, A.; Andre, M.; Pritchett, P. L.; Retino, A.; hide

    2016-01-01

    We present Magnetospheric Multiscale observations of an electron-scale current sheet and electron outflow jet for asymmetric reconnection with guide field at the subsolar magnetopause. The electron jet observed within the reconnection region has an electron Mach number of 0.35 and is associated with electron agyrotropy. The jet is unstable to an electrostatic instability which generates intense waves with E(sub parallel lines) amplitudes reaching up to 300 mV/m and potentials up to 20% of the electron thermal energy. We see evidence of interaction between the waves and the electron beam, leading to quick thermalization of the beam and stabilization of the instability. The wave phase speed is comparable to the ion thermal speed, suggesting that the instability is of Buneman type, and therefore introduces electron-ion drag and leads to braking of the electron flow. Our observations demonstrate that electrostatic turbulence plays an important role in the electron-scale physics of asymmetric reconnection.

  19. Stable walking with asymmetric legs

    International Nuclear Information System (INIS)

    Merker, Andreas; Rummel, Juergen; Seyfarth, Andre

    2011-01-01

    Asymmetric leg function is often an undesired side-effect in artificial legged systems and may reflect functional deficits or variations in the mechanical construction. It can also be found in legged locomotion in humans and animals such as after an accident or in specific gait patterns. So far, it is not clear to what extent differences in the leg function of contralateral limbs can be tolerated during walking or running. Here, we address this issue using a bipedal spring-mass model for simulating walking with compliant legs. With the help of the model, we show that considerable differences between contralateral legs can be tolerated and may even provide advantages to the robustness of the system dynamics. A better understanding of the mechanisms and potential benefits of asymmetric leg operation may help to guide the development of artificial limbs or the design novel therapeutic concepts and rehabilitation strategies.

  20. Oriented heavy ions and the choice of a cool compound nucleus reaction

    International Nuclear Information System (INIS)

    Aroumougame, R.; Gupta, R.K.

    1980-01-01

    Potential energy surfaces are calculated within the mechanism of fragmentation theory with a view to selecting the target-projectile combinations for producing new elements through cool compound nucleus formation. The orientation of the colliding nuclei is also included. It is shown that both the reaction partners of a cool compound nucleus, formed in either a central or a nearly central collision, should preferably be spherical and either nearly symmetric or extremely asymmetric. For reactions with deformed nuclei, it is suggested that polarised targets should be used. The calculations are illustrated for the compound nuclei 258 104 and 260 106. (author)

  1. Variable angle asymmetric cut monochromator

    International Nuclear Information System (INIS)

    Smither, R.K.; Fernandez, P.B.

    1993-09-01

    A variable incident angle, asymmetric cut, double crystal monochromator was tested for use on beamlines at the Advanced Photon Source (APS). For both undulator and wiggler beams the monochromator can expand area of footprint of beam on surface of the crystals to 50 times the area of incident beam; this will reduce the slope errors by a factor of 2500. The asymmetric cut allows one to increase the acceptance angle for incident radiation and obtain a better match to the opening angle of the incident beam. This can increase intensity of the diffracted beam by a factor of 2 to 5 and can make the beam more monochromatic, as well. The monochromator consists of two matched, asymmetric cut (18 degrees), silicon crystals mounted so that they can be rotated about three independent axes. Rotation around the first axis controls the Bragg angle. The second rotation axis is perpendicular to the diffraction planes and controls the increase of the area of the footprint of the beam on the crystal surface. Rotation around the third axis controls the angle between the surface of the crystal and the wider, horizontal axis for the beam and can make the footprint a rectangle with a minimum. length for this area. The asymmetric cut is 18 degrees for the matched pair of crystals, which allows one to expand the footprint area by a factor of 50 for Bragg angles up to 19.15 degrees (6 keV for Si[111] planes). This monochromator, with proper cooling, will be useful for analyzing the high intensity x-ray beams produced by both undulators and wigglers at the APS

  2. Asymmetric information and bank runs

    OpenAIRE

    Gu, Chao

    2007-01-01

    It is known that sunspots can trigger panic-based bank runs and that the optimal banking contract can tolerate panic-based runs. The existing literature assumes that these sunspots are based on a publicly observed extrinsic randomizing device. In this paper, I extend the analysis of panic-based runs to include an asymmetric-information, extrinsic randomizing device. Depositors observe different, but correlated, signals on the stability of the bank. I find that if the signals that depositors o...

  3. Asymmetric information and macroeconomic dynamics

    Science.gov (United States)

    Hawkins, Raymond J.; Aoki, Masanao; Roy Frieden, B.

    2010-09-01

    We show how macroeconomic dynamics can be derived from asymmetric information. As an illustration of the utility of this approach we derive the equilibrium density, non-equilibrium densities and the equation of motion for the response to a demand shock for productivity in a simple economy. Novel consequences of this approach include a natural incorporation of time dependence into macroeconomics and a common information-theoretic basis for economics and other fields seeking to link micro-dynamics and macro-observables.

  4. Asymmetric Synthesis of Apratoxin E.

    Science.gov (United States)

    Mao, Zhuo-Ya; Si, Chang-Mei; Liu, Yi-Wen; Dong, Han-Qing; Wei, Bang-Guo; Lin, Guo-Qiang

    2016-10-21

    An efficient method for asymmetric synthesis of apratoxin E 2 is described in this report. The chiral lactone 8, recycled from the degradation of saponin glycosides, was utilized to prepare the non-peptide fragment 6. In addition to this "from nature to nature" strategy, olefin cross-metathesis (CM) was applied as an alternative approach for the formation of the double bond. Moreover, pentafluorophenyl diphenylphosphinate was found to be an efficient condensation reagent for the macrocyclization.

  5. Comprehensive asymmetric dark matter model

    OpenAIRE

    Lonsdale, Stephen J.; Volkas, Raymond R.

    2018-01-01

    Asymmetric dark matter (ADM) is motivated by the similar cosmological mass densities measured for ordinary and dark matter. We present a comprehensive theory for ADM that addresses the mass density similarity, going beyond the usual ADM explanations of similar number densities. It features an explicit matter-antimatter asymmetry generation mechanism, has one fully worked out thermal history and suggestions for other possibilities, and meets all phenomenological, cosmological and astrophysical...

  6. CO oxidation on PtSn nanoparticle catalysts occurs at the interface of Pt and Sn oxide domains formed under reaction conditions

    KAUST Repository

    Michalak, William D.

    2014-04-01

    The barrier to CO oxidation on Pt catalysts is the strongly bound adsorbed CO, which inhibits O2 adsorption and hinders CO2 formation. Using reaction studies and in situ X-ray spectroscopy with colloidally prepared, monodisperse ∼2 nm Pt and PtSn nanoparticle catalysts, we show that the addition of Sn to Pt provides distinctly different reaction sites and a more efficient reaction mechanism for CO oxidation compared to pure Pt catalysts. To probe the influence of Sn, we intentionally poisoned the Pt component of the nanoparticle catalysts using a CO-rich atmosphere. With a reaction environment comprised of 100 Torr CO and 40 Torr O2 and a temperature range between 200 and 300 C, Pt and PtSn catalysts exhibited activation barriers for CO2 formation of 133 kJ/mol and 35 kJ/mol, respectively. While pure Sn is readily oxidized and is not active for CO oxidation, the addition of Sn to Pt provides an active site for O2 adsorption that is important when Pt is covered with CO. Sn oxide was identified as the active Sn species under reaction conditions by in situ ambient pressure X-ray photoelectron spectroscopy measurements. While chemical signatures of Pt and Sn indicated intermixed metallic components under reducing conditions, Pt and Sn were found to reversibly separate into isolated domains of Pt and oxidic Sn on the nanoparticle surface under reaction conditions of 100 mTorr CO and 40 mTorr O2 between temperatures of 200-275 C. Under these conditions, PtSn catalysts exhibited apparent reaction orders in O2 for CO 2 production that were 0.5 and lower with increasing partial pressures. These reaction orders contrast the first-order dependence in O 2 known for pure Pt. The differences in activation barriers, non-first-order dependence in O2, and the presence of a partially oxidized Sn indicate that the enhanced activity is due to a reaction mechanism that occurs at a Pt/Sn oxide interface present at the nanoparticle surface. © 2014 Published by Elsevier Inc.

  7. (TIQ) Thiazole and Oxazoline Ligands for Asymmetric Henry Reactions

    African Journals Online (AJOL)

    NICO

    cDepartment of Biochemistry and Organic Chemistry, Uppsala University, SE-751 23, Uppsala, Sweden. Received 21 ... Submitted by invitation to celebrate 2011 the 'International Year of Chemistry'. ABSTRACT ..... ketone (1 g, 5 mmol, 1 eq.) ...

  8. Tourist Demand Reactions : Symmetric or Asymmetric across the Business Cycle?

    NARCIS (Netherlands)

    Bronner, Fred; de Hoog, Robert

    2017-01-01

    Economizing and spending priorities on different types of vacations are investigated during two periods: an economic downturn and returning prosperity. Two nation-wide samples of vacationers are used: one during a downturn, the other one at the start of the recovery period. Through comparing the

  9. Multifunctional Hydrogel with Good Structure Integrity, Self-Healing, and Tissue-Adhesive Property Formed by Combining Diels-Alder Click Reaction and Acylhydrazone Bond.

    Science.gov (United States)

    Yu, Feng; Cao, Xiaodong; Du, Jie; Wang, Gang; Chen, Xiaofeng

    2015-11-04

    Hydrogel, as a good cartilage tissue-engineered scaffold, not only has to possess robust mechanical property but also has to have an intrinsic self-healing property to integrate itself or the surrounding host cartilage. In this work a double cross-linked network (DN) was designed and prepared by combining Diels-Alder click reaction and acylhydrazone bond. The DA reaction maintained the hydrogel's structural integrity and mechanical strength in physiological environment, while the dynamic covalent acylhydrazone bond resulted in hydrogel's self-healing property and controlled the on-off switch of network cross-link density. At the same time, the aldehyde groups contained in hydrogel further promote good integration of the hydrogel to surrounding tissue based on aldehyde-amine Schiff-base reaction. This kind of hydrogel has good structural integrity, autonomous self-healing, and tissue-adhesive property and simultaneously will have a good application in tissue engineering and tissue repair field.

  10. Impact of the new HNO3-forming channel of the HO2+NO reaction on tropospheric HNO3, NOx, HOx and ozone

    Directory of Open Access Journals (Sweden)

    A. Kukui

    2008-07-01

    Full Text Available We have studied the impact of the recently observed reaction NO+HO2→HNO3 on atmospheric chemistry. A pressure and temperature-dependent parameterisation of this minor channel of the NO+HO2→NO2+OH reaction has been included in both a 2-D stratosphere-troposphere model and a 3-D tropospheric chemical transport model (CTM. Significant effects on the nitrogen species and hydroxyl radical concentrations are found throughout the troposphere, with the largest percentage changes occurring in the tropical upper troposphere (UT. Including the reaction leads to a reduction in NOx everywhere in the troposphere, with the largest decrease of 25% in the tropical and Southern Hemisphere UT. The tropical UT also has a corresponding large increase in HNO3 of 25%. OH decreases throughout the troposphere with the largest reduction of over 20% in the tropical UT. The mean global decrease in OH is around 13%, which is very large compared to the impact that typical photochemical revisions have on this modelled quantity. This OH decrease leads to an increase in CH4 lifetime of 5%. Due to the impact of decreased NOx on the OH:HO2 partitioning, modelled HO2 actually increases in the tropical UT on including the new reaction. The impact on tropospheric ozone is a decrease in the range 5 to 12%, with the largest impact in the tropics and Southern Hemisphere. Comparison with observations shows that in the region of largest changes, i.e. the tropical UT, the inclusion of the new reaction tends to degrade the model agreement. Elsewhere the model comparisons are not able to critically assess the impact of including this reaction. Only small changes are calculated in the minor species distributions in the stratosphere.

  11. CO oxidation on PtSn nanoparticle catalysts occurs at the interface of Pt and Sn oxide domains formed under reaction conditions

    KAUST Repository

    Michalak, William D.; Krier, James M.; Alayoglu, Selim; Shin, Jae-Yoon; An, Kwangjin; Komvopoulos, Kyriakos; Liu, Zhi; Somorjai, Gabor A.

    2014-01-01

    The barrier to CO oxidation on Pt catalysts is the strongly bound adsorbed CO, which inhibits O2 adsorption and hinders CO2 formation. Using reaction studies and in situ X-ray spectroscopy with colloidally prepared, monodisperse ∼2 nm Pt and PtSn

  12. Influence of form factors and multistep effects on the 232Th(d,t) 231Th and 230Th(d,p) 231Th reactions

    International Nuclear Information System (INIS)

    Wilcke, W.; Felix, W.; Elze, Th.W.; Huizenga, J.R.; Thompson, R.C.; Dreisler, R.M.

    1977-01-01

    Tables of spectroscopic information are given for the nuclei 233 , 235 , 237 Pa, and 229 , 231 Ac studied in the reactions 234 , 236 , 238 U, and 230 , 232 Th(t,α), including spin, parity, differential cross sections, and spectra. These quantities are discussed and plotted

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

    KAUST Repository

    Elshewy, Ahmed M.

    2013-01-01

    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

  14. Synthesis method of asymmetric gold particles.

    Science.gov (United States)

    Jun, Bong-Hyun; Murata, Michael; Hahm, Eunil; Lee, Luke P

    2017-06-07

    Asymmetric particles can exhibit unique properties. However, reported synthesis methods for asymmetric particles hinder their application because these methods have a limited scale and lack the ability to afford particles of varied shapes. Herein, we report a novel synthetic method which has the potential to produce large quantities of asymmetric particles. Asymmetric rose-shaped gold particles were fabricated as a proof of concept experiment. First, silica nanoparticles (NPs) were bound to a hydrophobic micro-sized polymer containing 2-chlorotritylchloride linkers (2-CTC resin). Then, half-planar gold particles with rose-shaped and polyhedral structures were prepared on the silica particles on the 2-CTC resin. Particle size was controlled by the concentration of the gold source. The asymmetric particles were easily cleaved from the resin without aggregation. We confirmed that gold was grown on the silica NPs. This facile method for synthesizing asymmetric particles has great potential for materials science.

  15. Asymmetric Modeling of the Industrial Heavy Water Plant (PIAP)

    International Nuclear Information System (INIS)

    Teruel, Federico; Aprea, J; Guido Lavalle, German

    2000-01-01

    Software of asymmetric stationary simulation for the Industrial Heavy Water Plant (PIAP) was developed, based on an existing symmetric simulator (Brigitte 2.0).This software allows to turn off some of the isotopic enrichment twin units present in the plant and to simulate them asymmetrically, in other words, with different selection of parameters between twins.Other incorporations were done, such as passing flows between units and entering flows in strategic points of the plant.The iterative system in which the symmetric simulator is based was insufficient to develop the asymmetric simulator, so the system was modeled according to an implicit scheme for the units that form the simulator.This type of resolution resulted in a simulator that supports a big range of boundary conditions and internal parameters.Moreover, the time of calculus is short (∼3 minutes), making it actually useful.The asymmetric simulator is at the PIAP now, for its study and validation. It shows expected tendencies and results according to the symmetric simulator already validated

  16. An artificial molecular machine that builds an asymmetric catalyst

    Science.gov (United States)

    De Bo, Guillaume; Gall, Malcolm A. Y.; Kuschel, Sonja; De Winter, Julien; Gerbaux, Pascal; Leigh, David A.

    2018-05-01

    Biomolecular machines perform types of complex molecular-level tasks that artificial molecular machines can aspire to. The ribosome, for example, translates information from the polymer track it traverses (messenger RNA) to the new polymer it constructs (a polypeptide)1. The sequence and number of codons read determines the sequence and number of building blocks incorporated into the biomachine-synthesized polymer. However, neither control of sequence2,3 nor the transfer of length information from one polymer to another (which to date has only been accomplished in man-made systems through template synthesis)4 is easily achieved in the synthesis of artificial macromolecules. Rotaxane-based molecular machines5-7 have been developed that successively add amino acids8-10 (including β-amino acids10) to a growing peptide chain by the action of a macrocycle moving along a mono-dispersed oligomeric track derivatized with amino-acid phenol esters. The threaded macrocycle picks up groups that block its path and links them through successive native chemical ligation reactions11 to form a peptide sequence corresponding to the order of the building blocks on the track. Here, we show that as an alternative to translating sequence information, a rotaxane molecular machine can transfer the narrow polydispersity of a leucine-ester-derivatized polystyrene chain synthesized by atom transfer radical polymerization12 to a molecular-machine-made homo-leucine oligomer. The resulting narrow-molecular-weight oligomer folds to an α-helical secondary structure13 that acts as an asymmetric catalyst for the Juliá-Colonna epoxidation14,15 of chalcones.

  17. LG tools for asymmetric wargaming

    Science.gov (United States)

    Stilman, Boris; Yakhnis, Alex; Yakhnis, Vladimir

    2002-07-01

    Asymmetric operations represent conflict where one of the sides would apply military power to influence the political and civil environment, to facilitate diplomacy, and to interrupt specified illegal activities. This is a special type of conflict where the participants do not initiate full-scale war. Instead, the sides may be engaged in a limited open conflict or one or several sides may covertly engage another side using unconventional or less conventional methods of engagement. They may include peace operations, combating terrorism, counterdrug operations, arms control, support of insurgencies or counterinsurgencies, show of force. An asymmetric conflict can be represented as several concurrent interlinked games of various kinds: military, transportation, economic, political, etc. Thus, various actions of peace violators, terrorists, drug traffickers, etc., can be expressed via moves in different interlinked games. LG tools allow us to fully capture the specificity of asymmetric conflicts employing the major LG concept of hypergame. Hypergame allows modeling concurrent interlinked processes taking place in geographically remote locations at different levels of resolution and time scale. For example, it allows us to model an antiterrorist operation taking place simultaneously in a number of countries around the globe and involving wide range of entities from individuals to combat units to governments. Additionally, LG allows us to model all sides of the conflict at their level of sophistication. Intelligent stakeholders are represented by means of LG generated intelligent strategies. TO generate those strategies, in addition to its own mathematical intelligence, the LG algorithm may incorporate the intelligence of the top-level experts in the respective problem domains. LG models the individual differences between intelligent stakeholders. The LG tools make it possible to incorporate most of the known traits of a stakeholder, i.e., real personalities involved in

  18. Incompressibility of asymmetric nuclear matter

    International Nuclear Information System (INIS)

    Chen, Liewen; Cai, Baojun; Shen, Chun; Ko, Cheming; Xu, Jun; Li, Baoan

    2010-01-01

    Using an isospin- and momentum-dependent modified Gogny (MDI) interaction, the Skyrme-Hartree-Fock (SHF) approach, and a phenomenological modified Skyrme-like (MSL) model, we have studied the incompressibility K sat (δ) of isospin asymmetric nuclear matter at its saturation density. Our results show that in the expansion of K sat (δ) in powers of isospin asymmetry δ, i.e., K sat (δ) = K 0 + K sat,2 δ 2 + K sat,4 δ 4 + O(δ 6 ), the magnitude of the 4th-order K sat,4 parameter is generally small. The 2nd-order K sat,2 parameter thus essentially characterizes the isospin dependence of the incompressibility of asymmetric nuclear matter at saturation density. Furthermore, the K sat,2 can be expressed as K sat,2 = K sym – 6L – J 0 /K 0 L in terms of the slope parameter L and the curvature parameter K sym of the symmetry energy and the third-order derivative parameter J 0 of the energy of symmetric nuclear matter at saturation density, and we find the higher order J 0 contribution to K sat,2 generally cannot be neglected. Also, we have found a linear correlation between K sym and L as well as between J 0 /K 0 and K 0 . Using these correlations together with the empirical constraints on K 0 and L, the nuclear symmetry energy E sym (ρ0) at normal nuclear density, and the nucleon effective mass, we have obtained an estimated value of K sat,2 = -370 ± 120 MeV for the 2nd-order parameter in the isospin asymmetry expansion of the incompressibility of asymmetric nuclear matter at its saturation density. (author)

  19. Asymmetric effects in customer satisfaction

    DEFF Research Database (Denmark)

    Füller, Johann; Matzler, Kurt; Faullant, Rita

    2006-01-01

    The results of this study on customer satisfaction in snowboard areas show that the relationship between an attribute and overall satisfaction can indeed be asymmetric. A 30-item self-administered survey was completed by snowboarders (n=2526) in 51 areas in Austria, Germany, Switzerland and Italy....... Results show that waiting time is a dissatisfier; it has a significant impact on overall customer satisfaction in the low satisfaction condition and becomes insignificant in the high satisfaction situation. Restaurants and bars are hybrids, i.e. importance does not depend on performance. Slopes, fun...

  20. Asymmetric Formal Synthesis of Azadirachtin.

    Science.gov (United States)

    Mori, Naoki; Kitahara, Takeshi; Mori, Kenji; Watanabe, Hidenori

    2015-12-01

    An asymmetric formal synthesis of azadirachtin, a potent insect antifeedant, was accomplished in 30 steps to Ley's synthetic intermediate (longest linear sequence). The synthesis features: 1) rapid access to the optically active right-hand segment starting from the known 5-hydroxymethyl-2-cyclopentenone scaffold; 2) construction of the B and E rings by a key intramolecular tandem radical cyclization; 3) formation of the hemiacetal moiety in the C ring through the α-oxidation of the six-membered lactone followed by methanolysis. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Spontaneous baryogenesis from asymmetric inflaton

    International Nuclear Information System (INIS)

    Takahashi, Fuminobu

    2015-10-01

    We propose a variant scenario of spontaneous baryogenesis from asymmetric inflaton based on current-current interactions between the inflaton and matter fields with a non-zero B-L charge. When the inflaton starts to oscillate around the minimum after inflation, it may lead to excitation of a CP-odd component, which induces an effective chemical potential for the B-L number through the current-current interactions. We study concrete inflation models and show that the spontaneous baryogenesis scenario can be naturally implemented in the chaotic inflation in supergravity.

  2. Synchronised and complementary coordination mechanisms in an asymmetric joint aiming task

    DEFF Research Database (Denmark)

    Skewes, Joshua Charles; Skewes, Lea; Michael, John

    2015-01-01

    Many forms of social interaction require that behaviour be coordinated in the here and now. Much research has been conducted on how people coordinate their actions in real time to achieve a joint goal, showing that people use both synchronised (i.e. symmetric) and complementary (i.e. asymmetric) ...... in this asymmetric task, as people synchronise better with an irregular, but adaptive partner, than with a completely predictable, but non-responsive metronome. These results show that given asymmetric task constraints, adaptability, rather than predictability facilitates coordination....

  3. Chemical reaction due to stronger Ramachandran interaction

    Indian Academy of Sciences (India)

    actions between two polarized atoms are responsible for initiating a chemical reaction, either before or after ... Chemical reaction; Ramachandran interaction; anisotropic and asymmetric polarization; ionization ..... man sequence exactly, including the generalized mech- ..... We now move on and rearrange Eq. (8) to arrive at.

  4. Organocatalytic Hydrophosphonylation Reaction of Carbonyl Groups.

    Science.gov (United States)

    Herrera, Raquel P

    2017-09-01

    This revision is covering the limited examples reported for a pivotal strategy in the formation of C-P bonds such as the asymmetric organocatalytic hydrophosphonylation of carbonyl groups (Pudovik reaction). The scope and limitations, and the proposed mechanisms for the scarce different possibilities of asymmetric induction are also shown. The recent evolution and future trends of this undeveloped approach are commented. © 2017 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. A Catalytic, Asymmetric Formal Synthesis of (+)-Hamigeran B

    KAUST Repository

    Mukherjee, Herschel

    2011-03-04

    A concise asymmetric, formal synthesis of (+)-hamigeran B is reported. A Pd-catalyzed, decarboxylative allylic alkylation, employing a trifluoromethylated derivative of t-BuPHOX, is utilized as the enantioselective step to form the critical quaternary carbon center in excellent yield and enantioselectivity. The product is converted in three steps to a late-stage intermediate previously used in the synthesis of hamigeran B.

  6. A Catalytic, Asymmetric Formal Synthesis of (+)-Hamigeran B

    KAUST Repository

    Mukherjee, Herschel; McDougal, Nolan T.; Virgil, Scott C.; Stoltz, Brian M.

    2011-01-01

    A concise asymmetric, formal synthesis of (+)-hamigeran B is reported. A Pd-catalyzed, decarboxylative allylic alkylation, employing a trifluoromethylated derivative of t-BuPHOX, is utilized as the enantioselective step to form the critical quaternary carbon center in excellent yield and enantioselectivity. The product is converted in three steps to a late-stage intermediate previously used in the synthesis of hamigeran B.

  7. 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.

  8. Production cross sections and isomeric ratios for sup(110m)In/sup(110g)In formed in Cd (d,xn) reactions

    International Nuclear Information System (INIS)

    Herreros Usher, Oscar; Maceiras de Jefimowicz, Elena; De la Vega Vedoya, Mario; Jorge Nassiff, Sonia

    1980-01-01

    Excitation functions and isomeric cross sections ratios have been measured for the 110 Cd (d,2n) and 111 Cd (d,3n) reactions in which the isomeric pair sup(110m)In/sup(110g)In is produced. Activation method was employed and the irradiations were performed at the synchrocyclotron of the Comision Nacional de Energia Atomica, Argentina, with an incident energy of 27.MeV. (author) [es

  9. Evidence for nonequilibrium particle emission before symmetric disintegration of a composite system formed in the 16O+40Ca reaction at 230 MeV

    International Nuclear Information System (INIS)

    Brzychczyk, J.; Grotowski, K.; Majka, Z.; Micek, S.; Planeta, R.; Fabris, D.; Hagel, K.; Natowitz, J.B.; Nebbia, G.; Belery, P.; Cohilis, P.; El Masri, Y.; Gregoire, G.

    1987-01-01

    Measurement of fragment-fragment correlations in the reaction of 230 MeV 16 O with 40 Ca and of 280 MeV 32 S with 24 Mg have been used to isolate processes in which symmetric decay follows nonequilibrium emission of one or two alpha particles. At the higher energy per nucleon, in contrast to previous observations for lower velocity projectiles, nonequilibrium emission followed by symmetric decay has approximately the same probability as the symmetric fission following complete fusion. (orig.)

  10. 47nm alumina–water nanofluid flow within boundary layer formed on upper horizontal surface of paraboloid of revolution in the presence of quartic autocatalysis chemical reaction

    Directory of Open Access Journals (Sweden)

    Isaac Lare Animasaun

    2016-09-01

    Full Text Available In this article, a modified version of buoyancy-induced model is considered to investigate the flow of 47nm alumina–water nanofluid along an upper surface of horizontal paraboloid of revolution in the presence of nonlinear thermal radiation, Lorentz force and quartic autocatalysis kind of homogeneous heterogeneous chemical reaction. The case of unequal diffusion coefficients of reactant A (bulk fluid and B (high concentration of catalyst at the surface in the presence of bioconvection is considered. Governing equation suitable to unravel the thermophoresis which takes place within the boundary layer is presented. Since chemical reactant B is of higher concentration at the surface more than the concept described as cubic autocatalytic, the suitable schemes are herein described as isothermal quartic autocatalytic reaction and first order reaction. The viscosity and thermal conductivity are assumed to vary with volume fraction (ϕ and suitable models for the case 0%⩽ϕ⩽0.8% are adopted. The transformed governing equations are solved numerically using Runge–Kutta fourth order along with shooting technique (RK4SM. Good agreement is obtained between the solutions of RK4SM and MATLAB bvp5c for a limiting case. The influence of some pertinent parameters on velocity, temperature, diffusion of motile microorganism, concentration of bulk fluid and catalyst is illustrated graphically and discussed.

  11. Fold catastrophe model of dynamic pillar failure in asymmetric mining

    Energy Technology Data Exchange (ETDEWEB)

    Yue Pan; Ai-wu Li; Yun-song Qi [Qingdao Technological University, Qingdao (China). College of Civil Engineering

    2009-01-15

    A rock burst disaster not only destroys the pit facilities and results in economic loss but it also threatens the life of the miners. Pillar rock burst has a higher frequency of occurrence in the pit compared to other kinds of rock burst. Understanding the cause, magnitude and prevention of pillar rock burst is a significant undertaking. Equations describing the bending moment and displacement of the rock beam in asymmetric mining have been deduced for simplified asymmetric beam-pillar systems. Using the symbolic operation software MAPLE 9.5 a catastrophe model of the dynamic failure of an asymmetric rock-beam pillar system has been established. The differential form of the total potential function deduced from the law of conservation of energy was used for this deduction. The critical conditions and the initial and final positions of the pillar during failure have been given in analytical form. The amount of elastic energy released by the rock beam at the instant of failure is determined as well. A diagrammatic form showing the pillar failure was plotted using MATLAB software. This graph contains a wealth of information and is important for understanding the behavior during each deformation phase of the rock-beam pillar system. The graphic also aids in distinguishing the equivalent stiffness of the rock beam in different directions. 11 refs., 8 figs.

  12. Field factors for asymmetric collimators

    International Nuclear Information System (INIS)

    Turner, J.R.; Butler, A.P.H.

    1996-01-01

    In recent years manufacturers have been supplying linear accelerators with either a single pair or a dual pair of collimators. The use of a model to relate off-axis field factors to on-axis field factors obviates the need for repeat measurements whenever the asymmetric collimators are employed. We have investigated the variation of collimator scatter Sc, with distance of the central ray x from the central axis for a variety of non square field sizes. Collimator scatter was measured by in-air measurements with a build-up cap. The Primaty-Off-Centre-Ratio (POCR) was measured in-air by scanning orthogonally across the beam with an ionization chamber. The result of the investigation is the useful prediction of off-axis field factors for a range of rectangular asymmetric fields using the simple product of the on-axis field factor and the POCR in air. The effect of asymmetry on the quality of the beam and hence the percent depth dose will be discussed. (author)

  13. Biomimetically inspired asymmetric total synthesis of (+)-19-dehydroxyl arisandilactone A

    Science.gov (United States)

    Han, Yi-Xin; Jiang, Yan-Long; Li, Yong; Yu, Hai-Xin; Tong, Bing-Qi; Niu, Zhe; Zhou, Shi-Jie; Liu, Song; Lan, Yu; Chen, Jia-Hua; Yang, Zhen

    2017-01-01

    Complex natural products are a proven and rich source of disease-modulating drugs and of efficient tools for the study of chemical biology and drug discovery. The architectures of complex natural products are generally considered to represent significant barriers to efficient chemical synthesis. Here we describe a concise and efficient asymmetric synthesis of 19-dehydroxyl arisandilactone A--which belongs to a family of architecturally unique, highly oxygenated nortriterpenoids isolated from the medicinal plant Schisandra arisanensis. This synthesis takes place by means of a homo-Michael reaction, a tandem retro-Michael/Michael reaction, and Cu-catalysed intramolecular cyclopropanation as key steps. The proposed mechanisms for the homo-Michael and tandem retro-Michael/Michael reactions are supported by density functional theory (DFT) calculation. The developed chemistry may find application for the synthesis of its other family members of Schisandraceae nortriterpenoids.

  14. Study of the decay of hot nuclear systems formed in Au-induced reactions at E/A=60 MeV

    International Nuclear Information System (INIS)

    Delis, D.N.; Colonna, N.; Sui, Q.; Tso, K.

    1993-01-01

    Multifragment production was measured for the 197 Au + 12 C, 27 Al, 51 V, 63 Cu and 197 Au reactions at E/A= 60 MeV. Comparison of experimental observables to calculations with a dynamical code coupled to a statistical model indicates agreement with some features of the experimental data. Furthermore the logarithms of the branching ratios for binary, ternary, quaternary, and quinary decays plotted as a function of E -1/2 show a linear dependence that ,strongly suggests a statistical competition between the various multifraigment channels. Finally, by utilizing the momentum tensor, the shape of the most central events in momentum space has been determined

  15. Fusion-fission and deep inelastic orbiting in the target-like yields from 32S formed in 20Ne+12C reaction at different excitation energies

    International Nuclear Information System (INIS)

    Singh, BirBikram; Kaur, Mandeep; Sharma, Manoj K.; Gupta, Raj K.

    2014-01-01

    A strong motivation behind this work is that, though NOC model marked large σ C Expt in the decay of 32 S or small NOC for 20 Ne+ 12 C reaction indicating equivalently possibility of nCN contribution in it, but it does not work out the amount of contributions of σ ff and σ orb separately in the total σ C and the dynamics behind it, at different centre of mass energies, E c.m. . We intend to address this question in the present work

  16. Early Universe synthesis of asymmetric dark matter nuggets

    Science.gov (United States)

    Gresham, Moira I.; Lou, Hou Keong; Zurek, Kathryn M.

    2018-02-01

    We compute the mass function of bound states of asymmetric dark matter—nuggets—synthesized in the early Universe. We apply our results for the nugget density and binding energy computed from a nuclear model to obtain analytic estimates of the typical nugget size exiting synthesis. We numerically solve the Boltzmann equation for synthesis including two-to-two fusion reactions, estimating the impact of bottlenecks on the mass function exiting synthesis. These results provide the basis for studying the late Universe cosmology of nuggets in a future companion paper.

  17. Worst Asymmetrical Short-Circuit Current

    DEFF Research Database (Denmark)

    Arana Aristi, Iván; Holmstrøm, O; Grastrup, L

    2010-01-01

    In a typical power plant, the production scenario and the short-circuit time were found for the worst asymmetrical short-circuit current. Then, a sensitivity analysis on the missing generator values was realized in order to minimize the uncertainty of the results. Afterward the worst asymmetrical...

  18. REACTIONS FORMING Cn=2,10(0,+), Cn=2,4H(0,+), AND C3H2(0,+) IN THE GAS PHASE: SEMIEMPIRICAL BRANCHING RATIOS

    International Nuclear Information System (INIS)

    Chabot, M.; Jallat, A.; Béroff, K.; Gratier, P.; Wakelam, V.

    2013-01-01

    The aim of this paper is to provide a new set of branching ratios (BRs) for interstellar and planetary chemical networks based on a semiempirical model. We applied, instead of zero-order theory (i.e., only the most exoergic decaying channel is considered), a statistical microcanonical model based on the construction of breakdown curves and using experimental high velocity collision BRs for their parameterization. We applied the model to ion-molecule, neutral-neutral, and ion-pair reactions implemented in the few popular databases for astrochemistry, such as KIDA, OSU, and UMIST. We studied the reactions of carbon and hydrocarbon species with electrons, He + , H + , CH + , CH, C, and C + leading to intermediate complexes of the type C n=2,10 , C n=2,4 H, C 3 H 2 , C n=2,10 + , C n=2,4 H + , or C 3 H 2 + . Comparison of predictions with measurements supports the validity of the model. Huge deviations with respect to database values are often obtained. Effects of the new BRs in time-dependent chemistry for dark clouds and for photodissociation region chemistry with conditions similar to those found in the Horsehead Nebula are discussed.

  19. Designing asymmetric multiferroics with strong magnetoelectric coupling

    Science.gov (United States)

    Lu, Xuezeng; Xiang, Hongjun; Rondinelli, James; Materials Theory; Design Group Team

    2015-03-01

    Multiferroics offer exciting opportunities for electric-field control of magnetism. Single-phase multiferroics suitable for such applications at room temperature need much more study. Here, we propose the concept of an alternative type of multiferroics, namely, the ``asymmetric multiferroic.'' In asymmetric multiferroics, two locally stable ferroelectric states are not symmetrically equivalent, leading to different magnetic properties between these two states. Furthermore, we predict from first principles that a Fe-Cr-Mo superlattice with the LiNbO3-type structure is such an asymmetric multiferroic. The strong ferrimagnetism, high ferroelectric polarization, and significant dependence of the magnetic transition temperature on polarization make this asymmetric multiferroic an ideal candidate for realizing electric-field control of magnetism at room temperature. Our study suggests that the asymmetric multiferroic may provide an alternative playground for voltage control of magnetism and find its applications in spintronics and quantum computing.

  20. Teaching Form as Form

    DEFF Research Database (Denmark)

    Keiding, Tina Bering

    2012-01-01

    understanding of form per se, or, to use an expression from this text, of form as form. This challenge can be reduced to one question: how can design teaching support students in achieving not only the ability to recognize and describe different form-related concepts in existing design (i.e. analytical...

  1. Heavy stable isotopes of oxyanion-forming metals and metalloids (Cr, Se, U, Sb, and Te) as indicators of redox reactions: Theory, systematics, and the outlook for practical applications.

    Science.gov (United States)

    Johnson, T. M.

    2016-12-01

    The complex chemical behaviors of Cr, Se, U, Sb, and Te present challenges as we try to understand, predict, and/or manipulate their mobility, bioavailability, and toxicity in the environment. Redox reactions are particularly important and complex. In natural systems, aqueous concentrations and speciation can be used to infer the occurrence and rates of redox reactions, but are often of limited usefulness, for example when a reaction product is insoluble and its production is not readily observed in the field. Stable isotope ratio shifts in these elements can provide direct evidence for the occurrence of reduction, a critically important process that usually renders their soluble and mobile oxidized forms insoluble (or less soluble, in the case of Sb). Reduction kinetics differ between isotopes, and the remaining unreacted, oxidized contaminant becomes progressively shifted in its isotope ratio as reduction proceeds, providing a direct indicator of reduction in natural systems. Estimates of the extent of reduction are possible, but carry considerable uncertainty: The magnitude of isotopic fractionation induced by a reaction depends on the reaction mechanism and conditions, and thus prediction of fractionation factors for specific locations is uncertain. Furthermore, the simple Rayleigh distillation model is inaccurate due to complex reactive transport dynamics in aquifers and surface water systems. Nonetheless, useful estimates of reduction rates have been made and should be increasingly helpful as they are combined with other methods in environmental studies. Oxidation is less consistent in generating isotopic fractionation; this can be understood in terms of fundamental kinetic considerations. Furthermore, the reduced forms are usually solid and this further limits isotopic fractionation during oxidation. Sorption processes in some cases induce isotopic fractionation, but generally of smaller magnitude than reduction because bonding changes are relatively small

  2. Polymer and Membrane Design for Low Temperature Catalytic Reactions

    KAUST Repository

    Villalobos, Luis Francisco; Xie, Yihui; Nunes, Suzana Pereira; Peinemann, Klaus-Viktor

    2016-01-01

    Catalytically active asymmetric membranes have been developed with high loadings of palladium nanoparticles located solely in the membrane's ultrathin skin layer. The manufacturing of these membranes requires polymers with functional groups, which can form insoluble complexes with palladium ions. Three polymers have been synthesized for this purpose and a complexation/nonsolvent induced phase separation followed by a palladium reduction step is carried out to prepare such membranes. Parameters to optimize the skin layer thickness and porosity, the palladium loading in this layer, and the palladium nanoparticles size are determined. The catalytic activity of the membranes is verified with the reduction of a nitro-compound and with a liquid phase Suzuki-Miyaura coupling reaction. Very low reaction times are observed. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Polymer and Membrane Design for Low Temperature Catalytic Reactions

    KAUST Repository

    Villalobos, Luis Francisco

    2016-02-29

    Catalytically active asymmetric membranes have been developed with high loadings of palladium nanoparticles located solely in the membrane\\'s ultrathin skin layer. The manufacturing of these membranes requires polymers with functional groups, which can form insoluble complexes with palladium ions. Three polymers have been synthesized for this purpose and a complexation/nonsolvent induced phase separation followed by a palladium reduction step is carried out to prepare such membranes. Parameters to optimize the skin layer thickness and porosity, the palladium loading in this layer, and the palladium nanoparticles size are determined. The catalytic activity of the membranes is verified with the reduction of a nitro-compound and with a liquid phase Suzuki-Miyaura coupling reaction. Very low reaction times are observed. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Comprehensive asymmetric dark matter model

    Science.gov (United States)

    Lonsdale, Stephen J.; Volkas, Raymond R.

    2018-05-01

    Asymmetric dark matter (ADM) is motivated by the similar cosmological mass densities measured for ordinary and dark matter. We present a comprehensive theory for ADM that addresses the mass density similarity, going beyond the usual ADM explanations of similar number densities. It features an explicit matter-antimatter asymmetry generation mechanism, has one fully worked out thermal history and suggestions for other possibilities, and meets all phenomenological, cosmological and astrophysical constraints. Importantly, it incorporates a deep reason for why the dark matter mass scale is related to the proton mass, a key consideration in ADM models. Our starting point is the idea of mirror matter, which offers an explanation for dark matter by duplicating the standard model with a dark sector related by a Z2 parity symmetry. However, the dark sector need not manifest as a symmetric copy of the standard model in the present day. By utilizing the mechanism of "asymmetric symmetry breaking" with two Higgs doublets in each sector, we develop a model of ADM where the mirror symmetry is spontaneously broken, leading to an electroweak scale in the dark sector that is significantly larger than that of the visible sector. The weak sensitivity of the ordinary and dark QCD confinement scales to their respective electroweak scales leads to the necessary connection between the dark matter and proton masses. The dark matter is composed of either dark neutrons or a mixture of dark neutrons and metastable dark hydrogen atoms. Lepton asymmetries are generated by the C P -violating decays of heavy Majorana neutrinos in both sectors. These are then converted by sphaleron processes to produce the observed ratio of visible to dark matter in the universe. The dynamics responsible for the kinetic decoupling of the two sectors emerges as an important issue that we only partially solve.

  5. Synthetic Applications of Asymmetric Horner-Wadsworth-Emmons Condensations: Approaches to Marine Natural Products

    DEFF Research Database (Denmark)

    Tullis, Joshua S.; Helquist, Paul; Rein, Tobias

    1999-01-01

    Asymmetric HWE condensations of meso-dialdehyde 1 with chiral phosphonates containing 8-phenylmenthol very directly generate chiral moieties that are seen in a number of cytotoxic natural products. The HWE reactions proceed in good yields with synthetically useful geometric and diastereoselectivi...

  6. Discrete-Event Simulation with Agents for Modeling of Dynamic Asymmetric Threats in Maritime Security

    National Research Council Canada - National Science Library

    Ng, Chee W

    2007-01-01

    .... Discrete-event simulation (DES) was used to simulate a typical port-security, local, waterside-threat response model and to test the adaptive response of asymmetric threats in reaction to port-security procedures, while a multi-agent system (MAS...

  7. Probabilities of symmetric and asymmetric fission in the proton bombardment of Th{sup 232}

    Energy Technology Data Exchange (ETDEWEB)

    Bowles, B J [Atomic Energy Research Establishment, Chemistry Div., Harwell (United Kingdom); Brown, F; Butler, J P

    1957-08-01

    The ratio of symmetric to asymmetric fission in the proton bombardment of Th{sup 232} does not rise steadily with increasing proton energy; a periodic decrease in superposed upon the over-all increase. This is attributed to the changing pattern of various fission reactions, (p,f), (p,nf), etc. (author)

  8. Ruthenacycles and Iridacycles as Catalysts for Asymmetric Transfer Hydrogenation and Racemisation

    NARCIS (Netherlands)

    Jerphagnon, Thomas; Haak, Robert; Berthiol, Florian; Gayet, Arnaud J.A.; Ritleng, Vincent; Holuigue, Alexandre; Pannetier, Nicolas; Pfeffer, Michel; Voelklin, Adeline; Lefort, Laurent; Verzijl, Gerard; Tarabiono, Chiara; Janssen, Dick B.; Minnaard, Adriaan J.; Feringa, Ben L.; Vries, Johannes G. de

    2010-01-01

    Ruthenacycles, which are easily prepared in a single step by reaction between enantiopure aromatic amines and [Ru(arene)Cl2]2 in the presence of NaOH and KPF6, are very good asymmetric transfer hydrogenation catalysts. A range of aromatic ketones were reduced using isopropanol in good yields with

  9. Reactivity differences of Pt0 phosphine complexes in C-C bond activation of asymmetric acetylenes

    NARCIS (Netherlands)

    Gunay, A.; Müller, C.; Lachicotte, R.J.; Brennessel, W.W.; Jones, W.D.

    2009-01-01

    Carbon-carbon bond activation reactions of asymmetric acetylene derivatives of the type L2Pt(PhC=CR) were studied with 1,2-bis(diisopropylphosphino)ethane (dippe), 1,2-bis(di-tert-butylphosphino)ethane (dtbpe), and 1-diisopropylphosphino-2-dimethylaminoethane (dippdmae) chelates.

  10. Practical Aspects and Mechanism of Asymmetric Hydrogenation with Chiral Half-Sandwich Complexes

    Czech Academy of Sciences Publication Activity Database

    Václavík, J.; Šot, P.; Vilhanová, B.; Pecháček, J.; Kuzma, Marek; Kačer, P.

    2013-01-01

    Roč. 18, č. 6 (2013), s. 6804-6828 ISSN 1420-3049 R&D Projects: GA ČR GA104/09/1497; GA ČR GAP106/12/1276 Institutional support: RVO:61388971 Keywords : asymmetric hydrogenation * ruthenium * reaction conditions Subject RIV: CC - Organic Chemistry Impact factor: 2.095, year: 2013

  11. An Asymmetric Synthetic Approach to the A-ring of the Taxol Family of Anti-Cancer Compounds

    Directory of Open Access Journals (Sweden)

    M. L. Marin

    1998-02-01

    Full Text Available A synthetic route developed for the preparation of the A-ring of Taxol family of molecules is reported. By means of an intramolecular Diels-Alder reaction an asymmetric approach to this ring has been accomplished. Also, initial studies to prepare the A ring using an intramolecular Diels-Alder reaction have been successful.

  12. Thomson scattering measurements from asymmetric interpenetrating plasma flows

    Energy Technology Data Exchange (ETDEWEB)

    Ross, J. S., E-mail: ross36@llnl.gov; Moody, J. D.; Fiuza, F.; Ryutov, D.; Divol, L.; Huntington, C. M.; Park, H.-S. [Lawrence Livermore National Laboratory, P.O. Box 808, Livermore, California 94551 (United States)

    2014-11-15

    Imaging Thomson scattering measurements of collective ion-acoustic fluctuations have been utilized to determine ion temperature and density from laser produced counter-streaming asymmetric flows. Two foils are heated with 8 laser beams each, 500 J per beam, at the Omega Laser facility. Measurements are made 4 mm from the foil surface using a 60 J 2ω probe laser with a 200 ps pulse length. Measuring the electron density and temperature from the electron-plasma fluctuations constrains the fit of the multi-ion species, asymmetric flows theoretical form factor for the ion feature such that the ion temperatures, ion densities, and flow velocities for each plasma flow are determined.

  13. Occupation probabilities and fluctuations in the asymmetric simple inclusion process

    Science.gov (United States)

    Reuveni, Shlomi; Hirschberg, Ori; Eliazar, Iddo; Yechiali, Uri

    2014-04-01

    The asymmetric simple inclusion process (ASIP), a lattice-gas model of unidirectional transport and aggregation, was recently proposed as an "inclusion" counterpart of the asymmetric simple exclusion process. In this paper we present an exact closed-form expression for the probability that a given number of particles occupies a given set of consecutive lattice sites. Our results are expressed in terms of the entries of Catalan's trapezoids—number arrays which generalize Catalan's numbers and Catalan's triangle. We further prove that the ASIP is asymptotically governed by the following: (i) an inverse square-root law of occupation, (ii) a square-root law of fluctuation, and (iii) a Rayleigh law for the distribution of interexit times. The universality of these results is discussed.

  14. Asymmetric Hardware Distortions in Receive Diversity Systems: Outage Performance Analysis

    KAUST Repository

    Javed, Sidrah; Amin, Osama; Ikki, Salama S.; Alouini, Mohamed-Slim

    2017-01-01

    This paper studies the impact of asymmetric hardware distortion (HWD) on the performance of receive diversity systems using linear and switched combining receivers. The asymmetric attribute of the proposed model motivates the employment of improper Gaussian signaling (IGS) scheme rather than the traditional proper Gaussian signaling (PGS) scheme. The achievable rate performance is analyzed for the ideal and non-ideal hardware scenarios using PGS and IGS transmission schemes for different combining receivers. In addition, the IGS statistical characteristics are optimized to maximize the achievable rate performance. Moreover, the outage probability performance of the receive diversity systems is analyzed yielding closed form expressions for both PGS and IGS based transmission schemes. HWD systems that employ IGS is proven to efficiently combat the self interference caused by the HWD. Furthermore, the obtained analytic expressions are validated through Monte-Carlo simulations. Eventually, non-ideal hardware transceivers degradation and IGS scheme acquired compensation are quantified through suitable numerical results.

  15. Asymmetric Hardware Distortions in Receive Diversity Systems: Outage Performance Analysis

    KAUST Repository

    Javed, Sidrah

    2017-02-22

    This paper studies the impact of asymmetric hardware distortion (HWD) on the performance of receive diversity systems using linear and switched combining receivers. The asymmetric attribute of the proposed model motivates the employment of improper Gaussian signaling (IGS) scheme rather than the traditional proper Gaussian signaling (PGS) scheme. The achievable rate performance is analyzed for the ideal and non-ideal hardware scenarios using PGS and IGS transmission schemes for different combining receivers. In addition, the IGS statistical characteristics are optimized to maximize the achievable rate performance. Moreover, the outage probability performance of the receive diversity systems is analyzed yielding closed form expressions for both PGS and IGS based transmission schemes. HWD systems that employ IGS is proven to efficiently combat the self interference caused by the HWD. Furthermore, the obtained analytic expressions are validated through Monte-Carlo simulations. Eventually, non-ideal hardware transceivers degradation and IGS scheme acquired compensation are quantified through suitable numerical results.

  16. Simple Closed-Form Expression for Penning Reaction Rate Coefficients for Cold Molecular Collisions by Non-Hermitian Time-Independent Adiabatic Scattering Theory.

    Science.gov (United States)

    Pawlak, Mariusz; Ben-Asher, Anael; Moiseyev, Nimrod

    2018-01-09

    We present a simple expression and its derivation for reaction rate coefficients for cold anisotropic collision experiments based on adiabatic variational theory and time-independent non-Hermitian scattering theory. We demonstrate that only the eigenenergies of the resulting one-dimensional Schrödinger equation for different complex adiabats are required. The expression is applied to calculate the Penning ionization rate coefficients of an excited metastable helium atom with molecular hydrogen in an energy range spanning from hundreds of kelvins down to the millikelvin regime. Except for trivial quantities like the masses of the nuclei and the bond length of the diatomic molecule participating in the collision, one needs as input data only the complex potential energy surface (CPES). In calculations, we used recently obtained ab initio CPES by D. Bhattacharya et al. ( J. Chem. Theory Comput. 2017 , 13 , 1682 - 1690 ) without fitting parameters. The results show good accord with current measurements ( Nat. Phys. 2017 , 13 , 35 - 38 ).

  17. Non-Classical C–H···X Hydrogen Bonding and Its Role in Asymmetric Organocatalysis

    KAUST Repository

    Ajitha, Manjaly John

    2016-08-17

    Non-classical hydrogen bonds (NCHBs) have attracted significant interest in the past decade particularly because of their important role in asymmetric catalytic systems. These weak interactions (< 4 kcal/mol) offer much flexibility in the preorganization of molecular entities required to achieve high enantioselectivity. Herein, we review some recent important organocatalytic asymmetric reactions where a NCHB serves as a critical factor in determining the stereoselectivity.

  18. Matrix product approach for the asymmetric random average process

    International Nuclear Information System (INIS)

    Zielen, F; Schadschneider, A

    2003-01-01

    We consider the asymmetric random average process which is a one-dimensional stochastic lattice model with nearest-neighbour interaction but continuous and unbounded state variables. First, the explicit functional representations, so-called beta densities, of all local interactions leading to steady states of product measure form are rigorously derived. This also completes an outstanding proof given in a previous publication. Then we present an alternative solution for the processes with factorized stationary states by using a matrix product ansatz. Due to continuous state variables we obtain a matrix algebra in the form of a functional equation which can be solved exactly

  19. Organocatalyzed Asymmetric α-Oxidation, α-Aminoxylation and α-Amination of Carbonyl Compounds

    OpenAIRE

    Worawan Bhanthumnavin; Tirayut Vilaivan

    2010-01-01

    Organocatalytic asymmetric α-oxidation and amination reactions of carbonyl compounds are highly useful synthetic methodologies, especially in generating chiral building blocks that previously have not been easily accessible by traditional methods. The concept is relatively new and therefore the list of new catalysts, oxidizing and aminating reagents, as well as new substrates, are expanding at an amazing rate. The scope of this review includes new reactions and catalysts, mechanistic aspects ...

  20. Catalytic Asymmetric Piancatelli Rearrangement: Brønsted Acid Catalyzed 4π Electrocyclization for the Synthesis of Multisubstituted Cyclopentenones

    KAUST Repository

    Cai, Yunfei; Tang, Yurong; Atodiresei, Iuliana; Rueping, Magnus

    2016-01-01

    The first catalytic asymmetric Piancatelli reaction is reported. Catalyzed by a chiral Brønsted acid, the rearrangement of a wide range of furylcarbinols with a series of aniline derivatives provides valuable aminocyclopentenones in high yields

  1. Pricing and collecting decisions in a closed-loop supply chain with symmetric and asymmetric information

    DEFF Research Database (Denmark)

    Wei, Jie; Govindan, Kannan; Li, Yongjian

    2015-01-01

    . The optimal strategies in closed form are given under the decision scenarios with symmetric information; moreover, the first order conditions that the optimal retail price, optimal wholesale price, and optimal collection rate satisfy are given under the decision scenarios with asymmetric information......The optimal decision problem of a closed-loop supply chain with symmetric and asymmetric information structures is considered using game theory in this paper. The paper aims to explore how the manufacturer and the retailer make their own decisions about wholesale price, retail price, and collection...... rate under symmetric and asymmetric information conditions. Four game models are established, which allow one to examine the strategies of each firm and explore the role of the manufacturer and the retailer in four different game scenarios under symmetric and asymmetric information structures...

  2. Investigation of nucleon electromagnetic form factors in the unphysical region by means of the N bar N → πl+l- reactions

    International Nuclear Information System (INIS)

    Dubnickova, A.Z.; Dubnicka, S.; Rekalo, M.P.

    1995-01-01

    A theoretical investigation of N bar N → πl + l - processes is carried out. First, the general structure of the differential probability of annihilation of very slow antinucleons on nucleons at rest into pion and lepton pairs is derived, then the structure of the electromagnetic current of N bar N → πγ * transition in case of the S-state annihilation is restored and general properties of the corresponding form factors are demonstrated. Next, by using the three-diagram approximation of the amplitude, those form factors are calculated explicitly and for the special process (p bar p) → π 0 γ * → π 0 l + l - they are shown to be completely described by the magnetic form factor of the proton in the unphysical region. Finally, the effective mass spectra of lepton pairs and the integral coefficients of internal conversion for the p bar p → π 0 l + l - and p bar n → π - l + l - processes are predicted. 15 refs., 7 figs

  3. Obtainment the reverse phase spinel [Zn2+0,5Fe3+0,5](Ni2+0,5Fe3+ 1,5)O4 by the method combustion reaction: the form of assessment heating

    International Nuclear Information System (INIS)

    Silva, M.C.; Costa, A.C.F.; Coutinho, J.P.; Silva, A.T.C.; Freitas, N.L.

    2011-01-01

    This paper aims to synthesize the inverse spinel phase of by combustion reaction method and to evaluate how [Zn 2+ 0,5Fe 3+ 0,5](Ni 2+ 0,5Fe 3+ 1,5)O 4 the heat source influences the structural and morphological this phase. The forms of heating were muffle oven and ceramic plate with built-in resistance and aniline as reducing agent. Comparisons were made between temperature, reaction time and physical changes undergone by the material during the combustion carried out in two warm-up. The material was characterized by XRD, SEM, and textural analysis. Based on the results showed that the spinel phase was successfully obtained, were found traces of the phases ZnO and Fe2O3. The Most crystallite size and higher reaction temperature were presented by the material produced in the plate. As for surface area and pore volume, the highest values were achieved by the material synthesized in the oven. The agglomerates were presented in the form of skeins made of pre-sintered particles. (author)

  4. Resonant thermonuclear reaction rate

    International Nuclear Information System (INIS)

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

    1986-01-01

    Basic physical principles for the resonant and nonresonant thermonuclear reaction rates are applied to find their standard representations for nuclear astrophysics. Closed-form representations for the resonant reaction rate are derived in terms of Meijer's G-function. Analytic representations of the resonant and nonresonant nuclear reaction rates are compared and the appearance of Meijer's G-function is discussed in physical terms

  5. Electrospray ionization mass spectrometric investigations of [alpha]-dicarbonyl compounds--Probing intermediates formed in the course of the nonenzymatic browning reaction of l-ascorbic acid

    Science.gov (United States)

    Schulz, Anke; Trage, Claudia; Schwarz, Helmut; Kroh, Lothar W.

    2007-05-01

    A new method is presented which allows the simultaneous detection of various [alpha]-dicarbonyl compounds generated in the course of the nonenzymatic browning reaction initiated by thermal treatment of l-ascorbic acid, namely: glyoxal, methylglyoxal, diacetyl, 3-deoxy-l-pentosone, and l-threosoneE 3-Deoxy-l-threosone was successfully identified as a new C4-[alpha]-dicarbonyl structure for the first time in the degradation of Vitamin C by application of this non-chromatographic mass spectrometric approach. Moreover, a more detailed elucidation of the mechanistic scenario with respect to the oxidative and nonoxidative pathways is presented by using dehydro-l-ascorbic acid and 2,3-diketo-l-gulonic acid instead of l-ascorbic acid as a starting material. Furthermore, the postulated pathways are corroborated with the aid of 13C-isotopic labeling studies. The investigations were extended to baby food, and the successful detection of [alpha]-dicarbonyl compounds characteristic for Vitamin C degradation proved the matrix tolerance of the introduced method.

  6. Chaos of several typical asymmetric systems

    International Nuclear Information System (INIS)

    Feng Jingjing; Zhang Qichang; Wang Wei

    2012-01-01

    The threshold for the onset of chaos in asymmetric nonlinear dynamic systems can be determined using an extended Padé method. In this paper, a double-well asymmetric potential system with damping under external periodic excitation is investigated, as well as an asymmetric triple-well potential system under external and parametric excitation. The integrals of Melnikov functions are established to demonstrate that the motion is chaotic. Threshold values are acquired when homoclinic and heteroclinic bifurcations occur. The results of analytical and numerical integration are compared to verify the effectiveness and feasibility of the analytical method.

  7. Modelling asymmetric growth in crowded plant communities

    DEFF Research Database (Denmark)

    Damgaard, Christian

    2010-01-01

    A class of models that may be used to quantify the effect of size-asymmetric competition in crowded plant communities by estimating a community specific degree of size-asymmetric growth for each species in the community is suggested. The model consists of two parts: an individual size......-asymmetric growth part, where growth is assumed to be proportional to a power function of the size of the individual, and a term that reduces the relative growth rate as a decreasing function of the individual plant size and the competitive interactions from other plants in the neighbourhood....

  8. Simultaneous analysis of multiple T helper subsets in leprosy reveals distinct patterns of Th1, Th2, Th17 and Tregs markers expression in clinical forms and reactional events.

    Science.gov (United States)

    Azevedo, Michelle de Campos Soriani; Marques, Heloisa; Binelli, Larissa Sarri; Malange, Mariana Silva Vieira; Devides, Amanda Carreira; Silva, Eliane Aparecida; Fachin, Luciana Raquel Vincenzi; Ghidella, Cassio Cesar; Soares, Cleverson Teixeira; Garlet, Gustavo Pompermaier; Rosa, Patrícia Sammarco; Belone, Andrea de Farias Fernandes; Trombone, Ana Paula Favaro

    2017-12-01

    Leprosy is a chronic infectious disease caused by Mycobacterium leprae. Previous studies have demonstrated that the difference among clinical forms of leprosy can be associated with the immune response of patients, mainly by T helper (Th) and regulatory T cells (Tregs). Then, aiming at clarifying the immune response, the expression of cytokines related to Th1, Th2, Th17 and Tregs profiles were evaluated by qPCR in 87 skin biopsies from leprosy patients. Additionally, cytokines and anti-PGL-1 antibodies were determined in serum by ELISA. The results showed that the expression of various targets (mRNA) related to Th1, Th2, Th17 and Tregs were significantly modulated in leprosy when compared with healthy individuals, suggesting the presence of a mixed profile. In addition, the targets related to Th1 predominated in the tuberculoid pole and side and Th2 and Tregs predominated in the lepromatous pole and side; however, Th17 targets showed a mixed profile. Concerning reactional events, Tregs markers were decreased and IL-15 was increased in reversal reaction and IL-17F, CCL20 and IL-8 in erythema nodosum leprosum, when compared with the respective non-reactional leprosy patients. Additionally, ELISA analysis demonstrated that IL-22, IL-6, IL-10 and anti-PGL-1 antibody levels were significantly higher in the serum of patients when compared with healthy individuals, and IL-10 and anti-PGL-1 antibodies were also increased in the lepromatous pole and side. Together, these results indicate that Th1, Th2 and Th17 are involved in the determination of clinical forms of leprosy and suggest that decreased Tregs activity may be involved in the pathogenesis of reactional events.

  9. Chemical form analysis of reaction products in Cs-adsorption on stainless steel by means of HAXPES and SEM/EDX

    Science.gov (United States)

    Kobata, M.; Okane, T.; Nakajima, K.; Suzuki, E.; Ohwada, K.; Kobayashi, K.; Yamagami, H.; Osaka, M.

    2018-01-01

    In this study, for the understandings of Cesium (Cs) adsorption behavior on structure materials in severe accidents in a light water nuclear reactor, the chemical state of Cs and its distribution on the surface of SUS304 stainless steel (SS) with different Si concentrations was investigated by hard X-ray photoelectron spectroscopy (HAXPES) and scanning electron microscope/energy dispersive X-ray spectroscopy (SEM/EDX). As a result, it was found that Cs is selectively adsorbed at the site where Si distributes with a high concentration. CsFeSiO4 is the dominant Cs products in case of low Si content, while Cs2Si2O5 and Cs2Si4O9 are formed in addition to CsFeSiO4 in case of high Si content. The chemical forms of the Cs compounds produced in the adsorption process on the SS surface have a close correlation with the concentration and chemical states of Si originally included in SS.

  10. Collaborative hierarchy maintains cooperation in asymmetric games.

    Science.gov (United States)

    Antonioni, Alberto; Pereda, María; Cronin, Katherine A; Tomassini, Marco; Sánchez, Angel

    2018-03-29

    The interplay of social structure and cooperative behavior is under much scrutiny lately as behavior in social contexts becomes increasingly relevant for everyday life. Earlier experimental work showed that the existence of a social hierarchy, earned through competition, was detrimental for the evolution of cooperative behaviors. Here, we study the case in which individuals are ranked in a hierarchical structure based on their performance in a collective effort by having them play a Public Goods Game. In the first treatment, participants are ranked according to group earnings while, in the second treatment, their rankings are based on individual earnings. Subsequently, participants play asymmetric Prisoner's Dilemma games where higher-ranked players gain more than lower ones. Our experiments show that there are no detrimental effects of the hierarchy formed based on group performance, yet when ranking is assigned individually we observe a decrease in cooperation. Our results show that different levels of cooperation arise from the fact that subjects are interpreting rankings as a reputation which carries information about which subjects were cooperators in the previous phase. Our results demonstrate that noting the manner in which a hierarchy is established is essential for understanding its effects on cooperation.

  11. Trade Credit Insurance and Asymmetric Information Problem

    Directory of Open Access Journals (Sweden)

    Sokolovska Olena

    2017-03-01

    Full Text Available The presence of different risk factors in international trade gives evidence of the necessity of support in gaps that may affect exporters’ activity. To maximize the trade volumes and in the same time to minimize the exporters’ risks the stakeholders use trade credit insurance. The paper provides analysis of conceptual background of the trade credit insurance in the world. We analyzed briefly the problems, arising in insurance markets due to asymmetric information, such as adverse selection and moral hazard. Also we discuss the main stages of development of trade credit insurance in countries worldwide. Using comparative and graphical analysis we provide a brief evaluation of the dynamics of claims and recoveries for different forms of trade credit insurance. We found that the claims related to the commercial risk for medium and long trade credits in recent years exceed the recoveries, while with the political risk the reverse trend holds. And we originally consider these findings in terms of information asymmetry in the trade credit insurance differentiated by type of risk.

  12. Decay analysis of compound nuclei formed in reactions with exotic neutron-rich 9Li projectile and the synthesis of 217At* within the dynamical cluster-decay model

    Science.gov (United States)

    Kaur, Arshdeep; Kaushal, Pooja; Hemdeep; Gupta, Raj K.

    2018-01-01

    The decay of various compound nuclei formed via exotic neutron-rich 9Li projectile is studied within the dynamical cluster-decay model (DCM). Following the earlier work of one of us (RKG) and collaborators (M. Kaur et al. (2015) [1]), for an empirically fixed neck-length parameter ΔRemp, the only parameter in the DCM, at a given incident laboratory energy ELab, we are able to fit almost exactly the (total) fusion cross section σfus =∑x=16σxn for 9Li projectile on 208Pb and other targets, with σfus depending strongly on the target mass of the most abundant isotope and its (magic) shell structure. This result shows the predictable nature of the DCM. The neck-length parameter ΔRemp is fixed empirically for the decay of 217At* formed in 9Li + 208Pb reaction at a fixed laboratory energy ELab, and then the total fusion cross section σfus calculated for all other reactions using 9Li as a projectile on different targets. Apparently, this procedure could be used to predict σfus for 9Li-induced reactions where experimental data are not available. Furthermore, optimum choice of "cold" target-projectile combinations, forming "hot" compact configurations, are predicted for the synthesis of compound nucleus 217At* with 8Li + 209Pb as one of the target-projectile combination, or another (t , p) combination 48Ca + 169Tb, with a doubly magic 48Ca, as the best possibility.

  13. Modeling of asymmetrical boost converters

    Directory of Open Access Journals (Sweden)

    Eliana Isabel Arango Zuluaga

    2014-01-01

    Full Text Available The asymmetrical interleaved dual boost (AIDB is a fifth-order DC/DC converter designed to interface photovoltaic (PV panels. The AIDB produces small current harmonics to the PV panels, reducing the power losses caused by the converter operation. Moreover, the AIDB provides a large voltage conversion ratio, which is required to step-up the PV voltage to the large dc-link voltage used in grid-connected inverters. To reject irradiance and load disturbances, the AIDB must be operated in a closed-loop and a dynamic model is required. Given that the AIDB converter operates in Discontinuous Conduction Mode (DCM, classical modeling approaches based on Continuous Conduction Mode (CCM are not valid. Moreover, classical DCM modeling techniques are not suitable for the AIDB converter. Therefore, this paper develops a novel mathematical model for the AIDB converter, which is suitable for control-pur-poses. The proposed model is based on the calculation of a diode current that is typically disregarded. Moreover, because the traditional correction to the second duty cycle reported in literature is not effective, a new equation is designed. The model accuracy is contrasted with circuital simulations in time and frequency domains, obtaining satisfactory results. Finally, the usefulness of the model in control applications is illustrated with an application example.

  14. Asymmetric Supercapacitor Electrodes and Devices.

    Science.gov (United States)

    Choudhary, Nitin; Li, Chao; Moore, Julian; Nagaiah, Narasimha; Zhai, Lei; Jung, Yeonwoong; Thomas, Jayan

    2017-06-01

    The world is recently witnessing an explosive development of novel electronic and optoelectronic devices that demand more-reliable power sources that combine higher energy density and longer-term durability. Supercapacitors have become one of the most promising energy-storage systems, as they present multifold advantages of high power density, fast charging-discharging, and long cyclic stability. However, the intrinsically low energy density inherent to traditional supercapacitors severely limits their widespread applications, triggering researchers to explore new types of supercapacitors with improved performance. Asymmetric supercapacitors (ASCs) assembled using two dissimilar electrode materials offer a distinct advantage of wide operational voltage window, and thereby significantly enhance the energy density. Recent progress made in the field of ASCs is critically reviewed, with the main focus on an extensive survey of the materials developed for ASC electrodes, as well as covering the progress made in the fabrication of ASC devices over the last few decades. Current challenges and a future outlook of the field of ASCs are also discussed. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Bioinspired smart asymmetric nanochannel membranes.

    Science.gov (United States)

    Zhang, Zhen; Wen, Liping; Jiang, Lei

    2018-01-22

    Bioinspired smart asymmetric nanochannel membranes (BSANM) have been explored extensively to achieve the delicate ionic transport functions comparable to those of living organisms. The abiotic system exhibits superior stability and robustness, allowing for promising applications in many fields. In view of the abundance of research concerning BSANM in the past decade, herein, we present a systematic overview of the development of the state-of-the-art BSANM system. The discussion is focused on the construction methodologies based on raw materials with diverse dimensions (i.e. 0D, 1D, 2D, and bulk). A generic strategy for the design and construction of the BSANM system is proposed first and put into context with recent developments from homogeneous to heterogeneous nanochannel membranes. Then, the basic properties of the BSANM are introduced including selectivity, gating, and rectification, which are associated with the particular chemical and physical structures. Moreover, we summarized the practical applications of BSANM in energy conversion, biochemical sensing and other areas. In the end, some personal opinions on the future development of the BSANM are briefly illustrated. This review covers most of the related literature reported since 2010 and is intended to build up a broad and deep knowledge base that can provide a solid information source for the scientific community.

  16. Reflection asymmetric shapes in nuclei

    International Nuclear Information System (INIS)

    Ahmad, I.; Carpenter, M.P.; Emling, H.

    1989-01-01

    Experimental data show that there is no even-even nucleus with a reflection asymmetric shape in its ground state. Maximum octupole- octupole correlations occur in nuclei in the mass 224 (N∼134, Z∼88) region. Parity doublets, which are the characteristic signature of octupole deformation, have been observed in several odd mass Ra, Ac and Pa nuclei. Intertwined negative and positive parity levels have been observed in several even-even Ra and Th nuclei above spin ∼8ℎ. In both cases, the opposite parity states are connected by fast El transitions. In some medium-mass nuclei intertwined negative and positive parity levels have also been observed above spin ∼7ℎ. The nuclei which exhibit octupole deformation in this mass region are 144 Ba, 146 Ba and 146 Ce; 142 Ba, 148 Ce, 150 Ce and 142 Xe do not show these characteristics. No case of parity doublet has been observed in the mass 144 region. 32 refs., 16 figs., 1 tab

  17. Lift production through asymmetric flapping

    Science.gov (United States)

    Jalikop, Shreyas; Sreenivas, K. R.

    2009-11-01

    At present, there is a strong interest in developing Micro Air Vehicles (MAV) for applications like disaster management and aerial surveys. At these small length scales, the flight of insects and small birds suggests that unsteady aerodynamics of flapping wings can offer many advantages over fixed wing flight, such as hovering-flight, high maneuverability and high lift at large angles of attack. Various lift generating mechanims such as delayed stall, wake capture and wing rotation contribute towards our understanding of insect flight. We address the effect of asymmetric flapping of wings on lift production. By visualising the flow around a pair of rectangular wings flapping in a water tank and numerically computing the flow using a discrete vortex method, we demonstrate that net lift can be produced by introducing an asymmetry in the upstroke-to-downstroke velocity profile of the flapping wings. The competition between generation of upstroke and downstroke tip vortices appears to hold the key to understanding this lift generation mechanism.

  18. Stochastic modeling of cell growth with symmetric or asymmetric division

    Science.gov (United States)

    Marantan, Andrew; Amir, Ariel

    2016-07-01

    We consider a class of biologically motivated stochastic processes in which a unicellular organism divides its resources (volume or damaged proteins, in particular) symmetrically or asymmetrically between its progeny. Assuming the final amount of the resource is controlled by a growth policy and subject to additive and multiplicative noise, we derive the recursive integral equation describing the evolution of the resource distribution over subsequent generations and use it to study the properties of stable resource distributions. We find conditions under which a unique stable resource distribution exists and calculate its moments for the class of affine linear growth policies. Moreover, we apply an asymptotic analysis to elucidate the conditions under which the stable distribution (when it exists) has a power-law tail. Finally, we use the results of this asymptotic analysis along with the moment equations to draw a stability phase diagram for the system that reveals the counterintuitive result that asymmetry serves to increase stability while at the same time widening the stable distribution. We also briefly discuss how cells can divide damaged proteins asymmetrically between their progeny as a form of damage control. In the appendixes, motivated by the asymmetric division of cell volume in Saccharomyces cerevisiae, we extend our results to the case wherein mother and daughter cells follow different growth policies.

  19. 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

  20. Asymmetric cryptography based on wavefront sensing.

    Science.gov (United States)

    Peng, Xiang; Wei, Hengzheng; Zhang, Peng

    2006-12-15

    A system of asymmetric cryptography based on wavefront sensing (ACWS) is proposed for the first time to our knowledge. One of the most significant features of the asymmetric cryptography is that a trapdoor one-way function is required and constructed by analogy to wavefront sensing, in which the public key may be derived from optical parameters, such as the wavelength or the focal length, while the private key may be obtained from a kind of regular point array. The ciphertext is generated by the encoded wavefront and represented with an irregular array. In such an ACWS system, the encryption key is not identical to the decryption key, which is another important feature of an asymmetric cryptographic system. The processes of asymmetric encryption and decryption are formulized mathematically and demonstrated with a set of numerical experiments.

  1. Asymmetrical Representation of Gender in Amharic1

    African Journals Online (AJOL)

    Administrator

    in its grammar. Gender representation in this language is asymmetrical heavily ..... In dictionaries where. Amharic appears either as the target or the source language, verbs are entered ...... The Dialects of Amharic Revisited. Semitica et.

  2. Beam-beam issues in asymmetric colliders

    International Nuclear Information System (INIS)

    Furman, M.A.

    1992-07-01

    We discuss generic beam-beam issues for proposed asymmetric e + - e - colliders. We illustrate the issues by choosing, as examples, the proposals by Cornell University (CESR-B), KEK, and SLAC/LBL/LLNL (PEP-II)

  3. Congenital asymmetric crying face: a case report

    Directory of Open Access Journals (Sweden)

    Semra Kara

    2011-12-01

    Full Text Available Congenital asymmetric crying face is an anomalia caused by unilateral absence or weakness of depressor anguli oris muscle The major finding of the disease is the absence or weakness in the outer and lower movement of the commissure during crying. The other expression muscles are normal and the face is symmetric at rest. The asymmetry in congenital asymmetric crying face is most evident during infancy but decreases by age. Congenital asymmetric crying face can be associated with cervicofacial, musclebone, respiratory, genitourinary and central nervous system anomalia. It is diagnosed by physical examination. This paper presents a six days old infant with Congenital asymmetric crying face and discusses the case in terms of diagnosis and disease features.

  4. Asymmetric total synthesis of cladosporin and isocladosporin.

    Science.gov (United States)

    Zheng, Huaiji; Zhao, Changgui; Fang, Bowen; Jing, Peng; Yang, Juan; Xie, Xingang; She, Xuegong

    2012-07-06

    The first asymmetric total syntheses of cladosporin and isocladosporin were accomplished in 8 steps with 8% overall yield and 10 steps with 26% overall yield, respectively. The relative configuration of isocladosporin was determined via this total synthesis.

  5. Magnetically Modified Asymmetric Supercapacitors, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — This Small Business Innovation Research Phase I project is for the development of an asymmetric supercapacitor that will have improved energy density and cycle life....

  6. Forecasting Performance of Asymmetric GARCH Stock Market Volatility Models

    Directory of Open Access Journals (Sweden)

    Hojin Lee

    2009-12-01

    Full Text Available We investigate the asymmetry between positive and negative returns in their effect on conditional variance of the stock market index and incorporate the characteristics to form an out-of-sample volatility forecast. Contrary to prior evidence, however, the results in this paper suggest that no asymmetric GARCH model is superior to basic GARCH(1,1 model. It is our prior knowledge that, for equity returns, it is unlikely that positive and negative shocks have the same impact on the volatility. In order to reflect this intuition, we implement three diagnostic tests for volatility models: the Sign Bias Test, the Negative Size Bias Test, and the Positive Size Bias Test and the tests against the alternatives of QGARCH and GJR-GARCH. The asymmetry test results indicate that the sign and the size of the unexpected return shock do not influence current volatility differently which contradicts our presumption that there are asymmetric effects in the stock market volatility. This result is in line with various diagnostic tests which are designed to determine whether the GARCH(1,1 volatility estimates adequately represent the data. The diagnostic tests in section 2 indicate that the GARCH(1,1 model for weekly KOSPI returns is robust to the misspecification test. We also investigate two representative asymmetric GARCH models, QGARCH and GJR-GARCH model, for our out-of-sample forecasting performance. The out-of-sample forecasting ability test reveals that no single model is clearly outperforming. It is seen that the GJR-GARCH and QGARCH model give mixed results in forecasting ability on all four criteria across all forecast horizons considered. Also, the predictive accuracy test of Diebold and Mariano based on both absolute and squared prediction errors suggest that the forecasts from the linear and asymmetric GARCH models need not be significantly different from each other.

  7. Oxidative generation of guanine radicals by carbonate radicals and their reactions with nitrogen dioxide to form site specific 5-guanidino-4-nitroimidazole lesions in oligodeoxynucleotides.

    Science.gov (United States)

    Joffe, Avrum; Mock, Steven; Yun, Byeong Hwa; Kolbanovskiy, Alexander; Geacintov, Nicholas E; Shafirovich, Vladimir

    2003-08-01

    A simple photochemical approach is described for synthesizing site specific, stable 5-guanidino-4-nitroimidazole (NIm) adducts in single- and double-stranded oligodeoxynucleotides containing single and multiple guanine residues. The DNA sequences employed, 5'-d(ACC CG(1)C G(2)TC CG(3)C G(4)CC) and 5'-d(ACC CG(1)C G(2)TC C), were a portion of exon 5 of the p53 tumor suppressor gene, including the codons 157 (G(2)) and 158 (G(3)) mutation hot spots in the former sequence with four Gs and the codon 157 (G(2)) mutation hot spot in the latter sequence with two Gs. The nitration of oligodeoxynucleotides was initiated by the selective photodissociation of persulfate anions to sulfate radicals induced by UV laser pulses (308 nm). In aqueous solutions, of bicarbonate and nitrite anions, the sulfate radicals generate carbonate anion radicals and nitrogen dioxide radicals by one electron oxidation of the respective anions. The guanine residue in the oligodeoxynucleotide is oxidized by the carbonate anion radical to form the neutral guanine radical. While the nitrogen dioxide radicals do not react with any of the intact DNA bases, they readily combine with the guanine radicals at either the C8 or the C5 positions. The C8 addition generates the well-known 8-nitroguanine (8-nitro-G) lesions, whereas the C5 attack produces unstable adducts, which rapidly decompose to NIm lesions. The maximum yields of the nitro products (NIm + 8-nitro-G) were typically in the range of 20-40%, depending on the number of guanine residues in the sequence. The ratio of the NIm to 8-nitro-G lesions gradually decreases from 3.4 in the model compound, 2',3',5'-tri-O-acetylguanosine, to 2.1-2.6 in the single-stranded oligodeoxynucleotides and to 0.8-1.1 in the duplexes. The adduct of the 5'-d(ACC CG(1)C G(2)TC C) oligodeoxynucleotide containing the NIm lesion in codon 157 (G(2)) was isolated in HPLC-pure form. The integrity of this adduct was established by a detailed analysis of exonuclease digestion

  8. Engineered Asymmetric Composite Membranes with Rectifying Properties.

    Science.gov (United States)

    Wen, Liping; Xiao, Kai; Sainath, Annadanam V Sesha; Komura, Motonori; Kong, Xiang-Yu; Xie, Ganhua; Zhang, Zhen; Tian, Ye; Iyoda, Tomokazu; Jiang, Lei

    2016-01-27

    Asymmetric composite membranes with rectifying properties are developed by grafting pH-stimulus-responsive materials onto the top layer of the composite structure, which is prepared by two novel block copolymers using a phase-separation technique. This engineered asymmetric composite membrane shows potential applications in sensors, filtration, and nanofluidic devices. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. [Reaction mechanism studies of heavy ion induced nuclear reactions]: Annual progress report, October 1987

    International Nuclear Information System (INIS)

    Mignerey, A.C.

    1987-10-01

    The experiments which this group has been working on seek to define the reaction mechanisms responsible for complex fragment emission in heavy ion reactions. The reactions studied are La + La, La + Al, and La + Cu at 46.8 MeV/u; and Ne + Ag and Ne + Au reactions at 250 MeV/u. Another experimental program at the Oak Ridge Hollifield Heavy Ion Research Facility (HHIRF) is designed to measure the excitation energy division between reaction products in asymmetric deep inelastic reactions. A brief description is given of progress to date, the scientific goals of this experiment and the plastic phoswich detectors developed for this experiment

  10. A Tunable and Enantioselective Hetero-Diels-Alder Reaction Provides Access to Distinct Piperidinoyl Spirooxindoles.

    Science.gov (United States)

    Jayakumar, Samydurai; Louven, Kathrin; Strohmann, Carsten; Kumar, Kamal

    2017-12-11

    The active complexes of chiral N,N'-dioxide ligands with dysprosium and magnesium salts catalyze the hetero-Diels-Alder reaction between 2-aza-3-silyloxy-butadienes and alkylidene oxindoles to selectively form 3,3'- and 3,4'-piperidinoyl spirooxindoles, respectively, in very high yields and with excellent enantioselectivities. The exo-selective asymmetric cycloaddition successfully regaled the construction of sp 3 -rich and highly substituted natural-product-based spirooxindoles supporting many chiral centers, including contiguous all-carbon quaternary centers. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Dynamics of {sup 47}V* formed in {sup 20}Ne + {sup 27}Al reaction in view of fusion-fission and DIC mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Grover, Neha; Sharma, Kanishka; Sharma, Manoj K. [Thapar University, School of Physics and Materials Science, Patiala (India)

    2017-12-15

    The decay mechanism of {sup 47}V* formed in direct kinematics ({sup 20}Ne + {sup 27}Al) is investigated within the collective clusterization approach of dynamical cluster decay model (DCM). All calculations are done for quadrupole (β{sub 2i}-deformed) choice of fragments by taking optimum orientations over a wide range of center of mass energies (E{sub c.m.} ∝ 83-125 MeV). According to the experimental evidence, there is a strong competition between fusion fission (FF) and deep inelastic collision (DIC) in the decay of {sup 47}V*, which are recognized as compound nucleus process and non-compound nucleus process, respectively. The decay cross sections of {sup 47}V* for both FF and DIC decay modes are addressed using DCM, and are found to be in agreement with the experimental data. It is important to mention that emitting fragments in both these decay channels maintain their homogeneity in terms of charge number, that lies in the region 3 ≤ Z ≤ 9. Hence, all possible isotopes contributing towards 3 ≤ Z ≤ 9 are taken into consideration here. Calculations of both FF and DIC are segregated on the basis of angular momentum windows, where 0 ≤ l ≤ l{sub cr} has been taken for FF and l{sub cr} < l ≤ l{sub gr} for DIC, as the later operates only due to the partial waves near grazing angular momentum. In DIC, preformation probability (P{sub 0}) is divided equally amongst the most favoured outgoing fragments. Moreover, the behavior of fragmentation potential, preformation probability, penetrability and emission time etc. is examined, in order to identify the most favorable isotopes contributing towards FF and DIC. (orig.)

  12. Constructing Asymmetric Polyion Complex Vesicles via Template Assembling Strategy: Formulation Control and Tunable Permeability

    Directory of Open Access Journals (Sweden)

    Junbo Li

    2017-11-01

    Full Text Available A strategy for constructing polyion complex vesicles (PICsomes with asymmetric structure is described. Poly(methylacrylic acid-block-poly(N-isopropylacrylamide modified gold nanoparticles (PMAA-b-PNIPAm-@-Au NPs were prepared and then assembled with poly(ethylene glycol-block-poly[1-methyl-3-(2-methacryloyloxy propylimidazolium bromine] (PEG-b-PMMPImB via polyion complex of PMMA and PMMPImB. After removing the Au NPs template, asymmetric PICsomes composed of a PNIPAm inner-shell, PIC wall, and PEG outer-corona were obtained. These PICsomes have low protein absorption and thermally tunable permeability, provided by the PEG outer-corona and the PNIPAm inner-shell, respectively. Moreover, PICsome size can be tailored by using templates of predetermined sizes. This novel strategy for constructing asymmetric PICsomes with well-defined properties and controllable size is valuable for applications such as drug delivery, catalysis and monitoring of chemical reactions, and biomimetics.

  13. Constraining Asymmetric Dark Matter through observations of compact stars

    DEFF Research Database (Denmark)

    Kouvaris, Christoforos; Tinyakov, Peter

    2011-01-01

    We put constraints on asymmetric dark matter candidates with spin-dependent interactions based on the simple existence of white dwarfs and neutron stars in globular clusters. For a wide range of the parameters (WIMP mass and WIMP-nucleon cross section), WIMPs can be trapped in progenitors in large...... numbers and once the original star collapses to a white dwarf or a neutron star, these WIMPs might self-gravitate and eventually collapse forming a mini-black hole that eventually destroys the star. We impose constraints competitive to direct dark matter search experiments, for WIMPs with masses down...

  14. Decentralization Policies for Supply Chain Investments under Asymmetric Information

    DEFF Research Database (Denmark)

    Agrell, Per Joakim; Bogetoft, Peter

    2017-01-01

    Supply chains need specific investments for improved performance in terms of lead-time, cost, and quality. We study the contractual choice of a coordinator to either centralize or delegate the investment decision in a three-stage chain. The analysis derives closed-form results for the economic...... performance of three decentralized contracting schemes under asymmetric information on investment cost, as well as the optimal full revelation results. The results show that the observed practice of tier-1 delegated investments leads to relatively poor performance because of underinvestment. We illustrate...

  15. Evaluation of the Perceptual Characteristics of a Force Induced by Asymmetric Vibrations.

    Science.gov (United States)

    Tanabe, Takeshi; Yano, Hiroaki; Iwata, Hiroo

    2017-08-29

    This paper describes the properties of proprioceptive sensations induced by asymmetric vibration using a vibration speaker-type non-grounded haptic interface. We confirm that the vibration speaker generates a perceived force that pulls or pushes a user's hand in a particular direction when an asymmetric amplitude signal that is generated by inverting a part of a sine wave is input. In this paper, to verify the system with respect to various factors of force perception caused by asymmetric vibration, we conducted six experiments and the following results were obtained. (1) The force vector can be controlled by reversing the asymmetric waves. (2) By investigating the physical characteristics of the vibration, asymmetric vibration was confirmed. (3) The presentation of vibration in the shear direction on the finger pad is effective. (4) The point of subjective equality of the perceived force can be controlled by up to 0.43 N by changing the amplitude voltage of the input signals. (5) The minimum stimulation time required for force perception is 66.7 ms. (6) When the vibration is continuously presented for 40 to 50 s, the perceived force decreases because of adaptation. Hence, we confirmed that we can control both the direction and magnitude of the reaction force by changing the input signal of the vibration speaker.

  16. Inclined asymmetric librations in exterior resonances

    Science.gov (United States)

    Voyatzis, G.; Tsiganis, K.; Antoniadou, K. I.

    2018-04-01

    Librational motion in Celestial Mechanics is generally associated with the existence of stable resonant configurations and signified by the existence of stable periodic solutions and oscillation of critical (resonant) angles. When such an oscillation takes place around a value different than 0 or π , the libration is called asymmetric. In the context of the planar circular restricted three-body problem, asymmetric librations have been identified for the exterior mean motion resonances (MMRs) 1:2, 1:3, etc., as well as for co-orbital motion (1:1). In exterior MMRs the massless body is the outer one. In this paper, we study asymmetric librations in the three-dimensional space. We employ the computational approach of Markellos (Mon Not R Astron Soc 184:273-281, https://doi.org/10.1093/mnras/184.2.273, 1978) and compute families of asymmetric periodic orbits and their stability. Stable asymmetric periodic orbits are surrounded in phase space by domains of initial conditions which correspond to stable evolution and librating resonant angles. Our computations were focused on the spatial circular restricted three-body model of the Sun-Neptune-TNO system (TNO = trans-Neptunian object). We compare our results with numerical integrations of observed TNOs, which reveal that some of them perform 1:2 resonant, inclined asymmetric librations. For the stable 1:2 TNO librators, we find that their libration seems to be related to the vertically stable planar asymmetric orbits of our model, rather than the three-dimensional ones found in the present study.

  17. Automated Quantum Mechanical Predictions of Enantioselectivity in a Rhodium-Catalyzed Asymmetric Hydrogenation.

    Science.gov (United States)

    Guan, Yanfei; Wheeler, Steven E

    2017-07-24

    A computational toolkit (AARON: An automated reaction optimizer for new catalysts) is described that automates the density functional theory (DFT) based screening of chiral ligands for transition-metal-catalyzed reactions with well-defined reaction mechanisms but multiple stereocontrolling transition states. This is demonstrated for the Rh-catalyzed asymmetric hydrogenation of (E)-β-aryl-N-acetyl enamides, for which a new C 2 -symmetric phosphorus ligand is designed. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Asymmetric Planetary Nebulae VI: the conference summary

    Science.gov (United States)

    De Marco, O.

    2014-04-01

    The Asymmetric Planetary Nebulae conference series, now in its sixth edition, aims to resolve the shaping mechanism of PN. Eighty percent of PN have non spherical shapes and during this conference the last nails in the coffin of single stars models for non spherical PN have been put. Binary theories abound but observational tests are lagging. The highlight of APN6 has been the arrival of ALMA which allowed us to measure magnetic fields on AGB stars systematically. AGB star halos, with their spiral patterns are now connected to PPN and PN halos. New models give us hope that binary parameters may be decoded from these images. In the post-AGB and pre-PN evolutionary phase the naked post-AGB stars present us with an increasingly curious puzzle as complexity is added to the phenomenologies of objects in transition between the AGB and the central star regimes. Binary central stars continue to be detected, including the first detection of longer period binaries, however a binary fraction is still at large. Hydro models of binary interactions still fail to give us results, if we make an exception for the wider types of binary interactions. More promise is shown by analytical considerations and models driven by simpler, 1D simulations such as those carried out with the code MESA. Large community efforts have given us more homogeneous datasets which will yield results for years to come. Examples are the ChanPlaN and HerPlaNe collaborations that have been working with the Chandra and Herschel space telescopes, respectively. Finally, the new kid in town is the intermediate-luminosity optical transient, a new class of events that may have contributed to forming several peculiar PN and pre-PN.

  19. Reversal modes in asymmetric Ni nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Leighton, B.; Pereira, A. [Departamento de Fisica, Universidad de Santiago de Chile (USACH), Avda. Ecuador 3493, 917-0124 Santiago (Chile); Escrig, J., E-mail: jescrigm@gmail.com [Departamento de Fisica, Universidad de Santiago de Chile (USACH), Avda. Ecuador 3493, 917-0124 Santiago (Chile); Center for the Development of Nanoscience and Nanotechnology (CEDENNA), Avda. Ecuador 3493, 917-0124 Santiago (Chile)

    2012-11-15

    We have investigated the evolution of the magnetization reversal mechanism in asymmetric Ni nanowires as a function of their geometry. Circular nanowires are found to reverse their magnetization by the propagation of a vortex domain wall, while in very asymmetric nanowires the reversal is driven by the propagation of a transverse domain wall. The effect of shape asymmetry of the wire on coercivity and remanence is also studied. Angular dependence of the remanence and coercivity is also addressed. Tailoring the magnetization reversal mechanism in asymmetric nanowires can be useful for magnetic logic and race-track memory, both of which are based on the displacement of magnetic domain walls. Finally, an alternative method to detect the presence of magnetic drops is proposed. - Highlights: Black-Right-Pointing-Pointer Asymmetry strongly modifies the magnetic behavior of a wire. Black-Right-Pointing-Pointer Very asymmetric nanowires reverse their magnetization by a transverse domain wall. Black-Right-Pointing-Pointer An alternative method to detect the presence of magnetic drops is proposed. Black-Right-Pointing-Pointer Tailoring the reversal mode in asymmetric nanowires can be useful for potential applications.

  20. Exploiting nanospace for asymmetric catalysis: confinement of immobilized, single-site chiral catalysts enhances enantioselectivity.

    Science.gov (United States)

    Thomas, John Meurig; Raja, Robert

    2008-06-01

    In the mid-1990s, it became possible to prepare high-area silicas having pore diameters controllably adjustable in the range ca. 20-200 Å. Moreover, the inner walls of these nanoporous solids could be functionalized to yield single-site, chiral, catalytically active organometallic centers, the precise structures of which could be determined using in situ X-ray absorption and FTIR and multinuclear magic angle spinning (MAS) NMR spectroscopy. This approach opened up the prospect of performing heterogeneous enantioselective conversions in a novel manner, under the spatial restrictions imposed by the nanocavities within which the reactions occur. In particular, it suggested an alternative method for preparing pharmaceutically and agrochemically useful asymmetric products by capitalizing on the notion, initially tentatively perceived, that spatial confinement of prochiral reactants (and transition states formed at the chiral active center) would provide an altogether new method of boosting the enantioselectivity of the anchored chiral catalyst. Initially, we anchored chiral single-site heterogeneous catalysts to nanopores covalently via a ligand attached to Pd(II) or Rh(I) centers. Later, we employed a more convenient and cheaper electrostatic method, relying in part on strong hydrogen bonding. This Account provides many examples of these processes, encompassing hydrogenations, oxidations, and aminations. Of particular note is the facile synthesis from methyl benzoylformate of methyl mandelate, which is a precursor in the synthesis of pemoline, a stimulant of the central nervous system; our procedure offers several viable methods for reducing ketocarboxylic acids. In addition to relying on earlier (synchrotron-based) in situ techniques for characterizing catalysts, we have constructed experimental procedures involving robotically controlled catalytic reactors that allow the kinetics of conversion and enantioselectivity to be monitored continually, and we have access to

  1. Fourier synthesis of asymmetrical optical potentials for atoms; Fourier-Synthese von asymmetrischen optischen Potentialen fuer Atome

    Energy Technology Data Exchange (ETDEWEB)

    Ritt, G.

    2007-07-13

    In this work a dissipationless asymmetrical optical potential for cold atoms was produced. In a first step a new type of optical lattice was generated, whose spatial periodicity only corresponds to a quarter of the wavelength of the light used for the generation. This corresponds to the half of the periodicity of a conventional optical lattice, which is formed by the light of the same wavelength. The generation of this new type of optical lattice was reached by the use of two degenerated raman transitions. Virtual processes occur, in which four photons are involved. In conventional optical lattices however virtual two-photon processes occur. By spatially superimposing this optical lattice with a conventional optical lattice an asymmetrical optical potential could be formed. By diffraction of a Bose Einstein condensate of rubidium atoms at the transient activated asymmetrical potential the asymmetrical structure was proven. (orig.)

  2. Instantaneous Tunneling Flight Time for Wavepacket Transmission through Asymmetric Barriers.

    Science.gov (United States)

    Petersen, Jakob; Pollak, Eli

    2018-04-12

    The time it takes a particle to tunnel through the asymmetric Eckart barrier potential is investigated using Gaussian wavepackets, where the barrier serves as a model for the potential along a chemical reaction coordinate. We have previously shown that the, in principle experimentally measurable, tunneling flight time, which determines the time taken by the transmitted particle to traverse the barrier, vanishes for symmetric potentials like the Eckart and square barrier [ Petersen , J. ; Pollak , E. J. Phys. Chem. Lett. 2017 , 9 , 4017 ]. Here we show that the same result is obtained for the asymmetric Eckart barrier potential, and therefore, the zero tunneling flight time seems to be a general result for one-dimensional time-independent potentials. The wavepacket dynamics is simulated using both an exact quantum mechanical method and a classical Wigner prescription. The excellent agreement between the two methods shows that quantum coherences are not important in pure one-dimensional tunneling and reinforces the conclusion that the tunneling flight time vanishes.

  3. Dynamic response of the ITER tokamak during asymmetric VDEs

    International Nuclear Information System (INIS)

    Schioler, Tyge; Bachmann, Christian; Mazzone, Giuseppe; Sannazzaro, Giulio

    2011-01-01

    During the operational life of ITER, it is expected that a number of vertical displacement events (VDEs) will occur. A sub-class of these events, 'slow' asymmetric VDEs, is of particular interest from a structural point of view. This is because the forces generated during such events are both substantial and sufficiently long-lasting to significantly excite the structure. It is necessary to establish that the absolute and relative displacements of components, as well as internal and external forces, stay within acceptable limits during these events. Previous studies have investigated this problem using relatively simple models and non-rotating loads. A new, more detailed, 360-degree model was developed, and used to assess the effects of asymmetric VDEs. This paper presents the main results of this investigation. It is shown that the distance between the VV and the TFC at the inboard wall can decrease by as much as 19 mm at the equatorial plane, and that the vertical reaction force in the Vacuum Vessel supports can reach 15 MN.

  4. Toward a psychology of humiliation in asymmetric conflict.

    Science.gov (United States)

    McCauley, Clark

    2017-04-01

    Humiliation is often cited in attempts to understand the origins of asymmetric conflicts, especially conflicts involving terrorism. This article reviews common usage, expert opinion, and experiences in interpersonal and intergroup conflicts to suggest a construct definition of humiliation as a combination of anger and shame. Following appraisal theory, this definition distinguishes between the situational appraisals associated with humiliation (insult and injury; failure to retaliate) and the emotional experience of humiliation (in which the combination of anger and shame may be more synergism than summation). Research on humiliation has barely begun and focuses on interpersonal relations; a crucial issue is whether interpersonal humiliation is the same experience as the intergroup humiliation salient in accounts of terrorism and terrorists. Also important is the prediction that the targets of terrorist attack will experience humiliation if the terrorists are unknown or unreachable; thus failure to retaliate may humiliate the strong as well as the weak in asymmetric conflict. Better understanding of humiliation may be useful for understanding both terrorist violence and government reactions to this violence. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

  5. Renewable resource management under asymmetric information

    DEFF Research Database (Denmark)

    Jensen, Frank; Andersen, Peder; Nielsen, Max

    2013-01-01

    Asymmetric information between fishermen and the regulator is important within fisheries. The regulator may have less information about stock sizes, prices, costs, effort, productivity and catches than fishermen. With asymmetric information, a strong analytical tool is principal-agent analysis....... In this paper, we study asymmetric information about productivity within a principal-agent framework and a tax on fishing effort is considered. It is shown that a second best optimum can be achieved if the effort tax is designed such that low-productivity agents rent is exhausted, while high-productivity agents...... receive an information rent. The information rent is equivalent to the total incentive cost. The incentive costs arise as we want to reveal the agent's type....

  6. Asymmetric synthesis II more methods and applications

    CERN Document Server

    Christmann, Mathias

    2012-01-01

    After the overwhelming success of 'Asymmetric Synthesis - The Essentials', narrating the colorful history of asymmetric synthesis, this is the second edition with latest subjects and authors. While the aim of the first edition was mainly to honor the achievements of the pioneers in asymmetric syntheses, the aim of this new edition was bringing the current developments, especially from younger colleagues, to the attention of students. The format of the book remained unchanged, i.e. short conceptual overviews by young leaders in their field including a short biography of the authors. The growing multidisciplinary research within chemistry is reflected in the selection of topics including metal catalysis, organocatalysis, physical organic chemistry, analytical chemistry, and its applications in total synthesis. The prospective reader of this book is a graduate or undergraduate student of advanced organic chemistry as well as the industrial chemist who wants to get a brief update on the current developments in th...

  7. Asymmetric catalysis in organic synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Reilly, S.D.; Click, D.R.; Grumbine, S.K.; Scott, B.L.; Watkins, J.G.

    1998-11-01

    This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The goal of the project was to prepare new catalyst systems, which would perform chemical reactions in an enantioselective manner so as to produce only one of the possible optical isomers of the product molecule. The authors have investigated the use of lanthanide metals bearing both diolate and Schiff-base ligands as catalysts for the enantioselective reduction of prochiral ketones to secondary alcohols. The ligands were prepared from cheap, readily available starting materials, and their synthesis was performed in a ''modular'' manner such that tailoring of specific groups within the ligand could be carried out without repeating the entire synthetic procedure. In addition, they have developed a new ligand system for Group IV and lanthanide-based olefin polymerization catalysts. The ligand system is easily prepared from readily available starting materials and offers the opportunity to rapidly prepare a wide range of closely related ligands that differ only in their substitution patterns at an aromatic ring. When attached to a metal center, the ligand system has the potential to carry out polymerization reactions in a stereocontrolled manner.

  8. Formation of the reduced form of furaneol® (2,5-dimethyl-4-hydroxy-tetrahydrofuran-3-one) during the Maillard reaction through catalysis of amino acid metal salts.

    Science.gov (United States)

    Nashalian, Ossanna; Wang, Xi; Yaylayan, Varoujan A

    2016-11-01

    Under pyrolytic conditions the acidity/basicity of Maillard reaction mixtures can be controlled through the use of hydrochloride or sodium salts of amino acids to generate a diversity of products. When the degradation of glucose was studied under pyrolytic conditions using excess sodium glycinate the reaction was found to generate a major unknown peak having a molecular ion at m/z 130. Subsequent in-depth isotope labelling studies indicated that acetol was an important precursor of this compound under pyrolytic and aqueous heating conditions. The dimerisation and cyclisation of acetol into 2,5-dimethyl-4-hydroxy-tetrahydrofuran-3-one was found to be catalysed by amino acid metal salts. Also, ESI/qTOF/MS studies indicated that the unknown peak has expected molecular formula of C6H10O3. Finally, a peak having the same retention time and mass spectrum was also generated pyrolytically when furaneol® was reduced with NaBH4 confirming the initial hypothesis regarding the unknown peak to be the reduced form of furaneol®. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Measurements of the neutron electric to magnetic form factor ratio GEn/GMn via the 2H(e→,e'n→)1H reaction to Q2=1.45 (GeV/c)2

    International Nuclear Information System (INIS)

    Plaster, B.; Semenov, A.Yu.; Semenova, I.A.; Aghalaryan, A.; Asaturyan, R.; Mkrtchyan, H.; Stepanyan, S.; Tadevosyan, V.; Crouse, E.; Finn, J.M.; Perdrisat, C.; Roche, J.; MacLachlan, G.; Opper, A.K.; Tajima, S.; Churchwell, S.; Howell, C.R.; Tireman, W.; Ahmidouch, A.; Anderson, B. D.

    2006-01-01

    We report values for the neutron electric to magnetic form factor ratio, G En /G Mn , deduced from measurements of the neutron's recoil polarization in the quasielastic 2 H(e→,e ' n→) 1 H reaction, at three Q 2 values of 0.45, 1.13, and 1.45 (GeV/c) 2 . The data at Q 2 =1.13 and 1.45 (GeV/c) 2 are the first direct experimental measurements of G En employing polarization degrees of freedom in the Q 2 >1 (GeV/c) 2 region and stand as the most precise determinations of G En for all values of Q 2

  10. Measurements of the neutron electric to magnetic form-factor ratio GEn/GMn via the 2H((rvec e), e(prime)(rvec n)) 1H reaction to Q2 = 1.45-(GeV/c)2

    International Nuclear Information System (INIS)

    Bradley Plaster; A.Yu. Semenov; A. Aghalaryan; Erick Crouse; Glen MacLachlan; Shigeyuki Tajima; William Tireman; Abdellah Ahmidouch; Brian Anderson; Hartmuth Arenhovel; Razmik Asaturyan; O. Baker; Alan Baldwin; David Barkhuff; Herbert Breuer; Roger Carlini; Michael Christy; Steve Churchwell; Leon Cole; Samuel Danagoulian; Donal Day; T. Eden; Mostafa Elaasar; Rolf Ent; Manouchehr Farkhondeh; Howard Fenker; John Finn; Liping Gan; Ashot Gasparian; Kenneth Garrow; Paul Gueye; Calvin Howell; Bitao Hu; Mark Jones; James Kelly; Cynthia Keppel; Mahbubul Khandaker; Wooyoung Kim; Stanley Kowalski; Allison Lung; David Mack; Richard Madey; D. Manley; Pete Markowitz; Joseph Mitchell; Hamlet Mkrtchyan; Allena Opper; Charles Perdrisat; Vina Punjabi; Brian Raue; Tilmann Reichelt; Joerg Reinhold; Julie Roche; Yoshinori Sato; Nikolai Savvinov; Irina Semenova; Wonick Seo; Neven Simicevic; Gregory Smith; Stepan Stepanyan; Vardan Tadevosyan; Liguang Tang; Shawn Taylor; Paul Ulmer; William Vulcan; John Watson; Steven Wells; Frank Wesselmann; Stephen Wood; Seunghoon Yang; Lulin Yuan; Wei-Ming Zhang; Hong Guo Zhu; Xiaofeng Zhu

    2006-01-01

    We report values for the neutron electric to magnetic form factor ratio, G En /G Mn , deduced from measurements of the neutron's recoil polarization in the quasielastic 2 H((rvec e), e(prime)(rvec n)) 1 H reaction, at three Q 2 values of 0.45, 1.13, and 1.45 (GeV/c) 2 . The data at Q 2 = 1.13 and 1.45 (GeV/c) 2 are the first direct experimental measurements of GEn employing polarization degrees of freedom in the Q 2 > 1 (GeV/c) 2 region and stand as the most precise determinations of GEn for all values of Q 2

  11. The Chiral Pool in the Pictet–Spengler Reaction for the Synthesis of β-Carbolines

    Directory of Open Access Journals (Sweden)

    Renato Dalpozzo

    2016-05-01

    Full Text Available The Pictet–Spengler reaction (PSR is the reaction of a β-arylethylamine with an aldehyde or ketone, followed by ring closure to give an aza-heterocycle. When the β-arylethylamine is tryptamine, the product is a β-carboline, a widespread skeleton in natural alkaloids. In the natural occurrence, these compounds are generally enantiopure, thus the asymmetric synthesis of these compounds have been attracting the interest of organic chemists. This review aims to give an overview of the asymmetric PSR, in which the chirality arises from optically pure amines or carbonyl compounds both from natural sources and from asymmetric syntheses to assemble the reaction partners.

  12. Asymmetric acoustic transmission in multiple frequency bands

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Hong-xiang, E-mail: jsdxshx@ujs.edu.cn [Research Center of Fluid Machinery Engineering and Technology, Jiangsu University, Zhenjiang 212013 (China); Laboratory of Modern Acoustics, Institute of Acoustics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China); State Key Laboratory of Acoustics, Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190 (China); Yuan, Shou-qi, E-mail: Shouqiy@ujs.edu.cn [Research Center of Fluid Machinery Engineering and Technology, Jiangsu University, Zhenjiang 212013 (China); Zhang, Shu-yi [Laboratory of Modern Acoustics, Institute of Acoustics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China)

    2015-11-23

    We report both experimentally and numerically that the multi-band device of the asymmetric acoustic transmission is realized by placing two periodic gratings with different periods on both sides of two brass plates immersed in water. The asymmetric acoustic transmission can exist in four frequency bands below 1500 kHz, which arises from the interaction between various diffractions from the two gratings and Lamb modes in the brass plates immersed in water. The results indicate that the device has the advantages of multiple band, broader bandwidth, and simpler structure. Our finding should have great potential applications in ultrasonic devices.

  13. Asymmetric acoustic transmission in multiple frequency bands

    International Nuclear Information System (INIS)

    Sun, Hong-xiang; Yuan, Shou-qi; Zhang, Shu-yi

    2015-01-01

    We report both experimentally and numerically that the multi-band device of the asymmetric acoustic transmission is realized by placing two periodic gratings with different periods on both sides of two brass plates immersed in water. The asymmetric acoustic transmission can exist in four frequency bands below 1500 kHz, which arises from the interaction between various diffractions from the two gratings and Lamb modes in the brass plates immersed in water. The results indicate that the device has the advantages of multiple band, broader bandwidth, and simpler structure. Our finding should have great potential applications in ultrasonic devices

  14. Exchange-rate forecasts and asymmetric loss: empirical evidence for the yen/dollar exchange rate

    DEFF Research Database (Denmark)

    Stadtmann, Georg; Pierdzioch; Rülke

    2012-01-01

    We used the yen/dollar exchange-rate forecasts of the Wall Street Journal (WSJ) poll to analyse whether exchange-rate forecasters have an asymmetric loss function. To this end, we applied an approach recently developed by Elliott et al. (2005). We found that only few forecasters seem to form...

  15. Asymmetric Synthesis of the Epimeric (3S-3-((E-Hex-1-enyl-2-methylcyclohexanones

    Directory of Open Access Journals (Sweden)

    Pierre J. De Clercq

    2007-02-01

    Full Text Available The asymmetric rhodium-catalysed 1,4-addition of alkenylzirconium reagents to 2-cyclohexenone can be useful in the synthesis of 3-alkenyl-2-methylcyclohexanones, provided that formaldehyde is used in trapping the intermediate zirconium enolates. In this manner a four-step sequence leading to the two epimeric 3-hexenyl-2-methylcyclohexanones in enantiomeric form was developed.

  16. Differential isospin-fractionation in dilute asymmetric nuclear matter

    International Nuclear Information System (INIS)

    Li Baoan; Chen Liewen; Ma Hongru; Xu Jun; Yong Gaochan

    2007-01-01

    The differential isospin-fractionation (IsoF) during the liquid-gas phase transition in dilute asymmetric nuclear matter is studied as a function of nucleon momentum. Within a self-consistent thermal model it is shown that the neutron/proton ratio of the gas phase becomes smaller than that of the liquid phase for energetic nucleons, although the gas phase is overall more neutron-rich. Clear indications of the differential IsoF consistent with the thermal model predictions are demonstrated within a transport model for heavy-ion reactions. Future comparisons with experimental data will allow us to extract critical information about the momentum dependence of the isovector strong interaction

  17. Comparison of different proximity potentials for asymmetric colliding nuclei

    International Nuclear Information System (INIS)

    Dutt, Ishwar; Puri, Rajeev K.

    2010-01-01

    Using the different versions of phenomenological proximity potential as well as other parametrizations within the proximity concept, we perform a detailed comparative study of fusion barriers for asymmetric colliding nuclei with asymmetry parameter as high as 0.23. In all, 12 different proximity potentials are robust against the experimental data of 60 reactions. Our detailed study reveals that the surface energy coefficient as well as radius of the colliding nuclei depend significantly on the asymmetry parameter. All models are able to explain the fusion barrier heights within ±10% on the average. The potentials due to Bass 80, AW 95, and Denisov DP explain nicely the fusion cross sections at above- as well as below-barrier energies.

  18. Nuclear reaction studies

    International Nuclear Information System (INIS)

    Alexander, J.M.; Lacey, R.A.

    1994-01-01

    Research focused on the statistical and dynamical properties of ''hot'' nuclei formed in symmetric heavy-ion reactions. Theses included ''flow'' measurements and the mechanism for multifragment disassembly. Model calculations are being performed for the reactions C+C, Ne+Al, Ar+Sc, Kr+Nb, and Xe+La. It is planned to study 40 Ar reactions from 27 to 115 MeV/nucleon. 2 figs., 41 refs

  19. Nuclear reactions

    International Nuclear Information System (INIS)

    Corner, J.; Richardson, K.; Fenton, N.

    1990-01-01

    Nuclear reactions' marks a new development in the study of television as an agency of public policy debate. During the Eighties, nuclear energy became a major international issue. The disasters at Three-mile Island and Chernobyl created a global anxiety about its risks and a new sensitivity to it among politicians and journalists. This book is a case-study into documentary depictions of nuclear energy in television and video programmes and into the interpretations and responses of viewers drawn from many different occupational groupings. How are the complex and specialist arguments about benefit, risk and proof conveyed through the different conventions of commentary, interview and film sequence? What symbolic associations does the visual language of television bring to portrayals of the issue? And how do viewers make sense of various and conflicting accounts, connecting what they see and hear on the screen with their pre-existing knowledge, experience and 'civic' expectations. The authors examine some of the contrasting forms and themes which have been used by programme makers to explain and persuade, and then give a sustained analysis of the nature and sources of viewers' own accounts. 'Nuclear Reactions' inquires into the public meanings surrounding energy and the environment, spelling out in its conclusion some of the implications for future media treatments of this issue. It is also a key contribution to the international literature on 'television knowledge' and the processes of active viewing. (author)

  20. Asymmetric Dielectric Elastomer Composite Material

    Science.gov (United States)

    Stewart, Brian K. (Inventor)

    2014-01-01

    Embodiments of the invention provide a dielectric elastomer composite material comprising a plurality of elastomer-coated electrodes arranged in an assembly. Embodiments of the invention provide improved force output over prior DEs by producing thinner spacing between electrode surfaces. This is accomplished by coating electrodes directly with uncured elastomer in liquid form and then assembling a finished component (which may be termed an actuator) from coated electrode components.

  1. Asymmetric Synthesis of Optically Active Spirocyclic Indoline Scaffolds through an Enantioselective Reduction of Indoles

    KAUST Repository

    Borrmann, Ruediger

    2016-11-30

    An enantioselective synthesis of spirocyclic indoline scaffolds was achieved by applying an asymmetric iridium-catalyzed hydrogenation of 3H-indoles. Low catalyst loadings and mild reaction conditions provide a broad range of differently substituted products with excellent yields and enantioselectivities. The developed methodology allows an efficient synthesis of this important spirocyclic structural motif, which is present in numerous biologically active molecules and privileged structures in medicinal chemistry.

  2. Organocatalytic asymmetric michael addition of aldehydes to beta-nitroacroleine dimethyl acetal.

    Science.gov (United States)

    Reyes, Efraim; Vicario, Jose L; Badía, Dolores; Carrillo, Luisa

    2006-12-21

    [Structure: see text] The organocatalytic asymmetric Michael addition of aldehydes to beta-nitroacroleine dimethyl acetal has been studied in detail. The reaction took place with excellent yields and high stereoselectivities when a chiral beta-amino alcohol such as L-prolinol was employed as the catalyst, leaving a formation of highly functionalized enantioenriched compounds containing two differentiated formyl groups together with a nitro moiety.

  3. Efficient Asymmetric Synthesis of S,S-2-methylsulfanyl-2-methylsulfinyl-1-indanone

    OpenAIRE

    Derisvaldo Rosa Paiva; Roberto da Silva Gomes

    2013-01-01

    Diastereoselective synthesis of SS-2-methylsulfanyl-2-methylsulfinyl-1-indanol by reduction of SS-2-methylsulfanyl-2-methylsulfinyl-1-indanone optically enriched demonstrating to be highly efficiency using the sulfanyl group as asymmetric induction control agent during an addition reaction to carbonyl group.The 2-methylsulfinyl-1-indanone was obtained for the first time in one unique step without further oxidation steps. The synthesis of SR, SS of 2-methylsulphinyl-1-indanone optically enrich...

  4. Studies Toward the Asymmetric Synthesis of the Right Part of the Mycalamides

    OpenAIRE

    Zhong, H. Marlon; Sohn, Jeong-Hun; Rawal, Viresh H.

    2007-01-01

    Described herein is the asymmetric synthesis of a functionalized, trioxadecalin unit that comprises the right-hand part of the mycalamides and related natural products. The synthetic route involves a 16-step sequence that accomplishes the formation of two heterocyclic rings and the generation of five stereocenters. The synthesis commenced with a C2 symmetric starting material, diethyl D-tartrate, and took advantage of a relay of diastereoselective reactions to extend this four-carbon chain an...

  5. The Electric Form Factor of the Neutron at Q2 = 1.17 and 1.47(GeV/c)2 from the 2H (e, en)' H reaction.

    Energy Technology Data Exchange (ETDEWEB)

    Tireman, William [Kent State Univ., Kent, OH (United States)

    2003-12-01

    The Jefferson Laboratory E93-038 collaboration measured the ratio of the electric form factor to the magnetic form factor of the neutron, g = Gne/Gnm, via recoil polarimetry from the quasielastic 2H(e,en)1 H reaction at q2 = 0.45, 1.17 and 1.47 (GeV/c)2 in Hall C of the Thomas Jefferson National Accelerator Facility. A polarimeter designed specifically for E93-038 was used to measure the up-down scattering asymmetry from the transverse component of the recoil neutron's polarization vector, and a dipole magnet located in front of the polarimeter was used to precess the polarization vector in the scattering plane through an angle of x. Sequential measurements of the scattering asymmetry with the polarization vector precessed through angles χ = 0° and χ = ±90° for Q2 = 1.47 (GeV/c)2 were made during January 2001 and through angles χ = ±40° for Q2 = 1.17 (GeV/c)2 during April 2001 and will be reported on in this dissertation. This ratio method removes the need to know the analyzing power

  6. Standards vs. labels with imperfect competition and asymmetric information

    DEFF Research Database (Denmark)

    Baltzer, Kenneth Thomas

    2012-01-01

    I demonstrate that providing information about product quality is not necessarily the best way to address asymmetric information problems when markets are imperfectly competitive. In a vertical differentiation model I show that a Minimum Quality Standard, which retains asymmetric information...

  7. Standards vs. labels with imperfect competition and asymmetric information

    DEFF Research Database (Denmark)

    Baltzer, Kenneth Thomas

    I demonstrate that providing information about product quality is not necessarily the best way to address asymmetric information problems when markets are imperfectly competitive. In a vertical dierentiation model I show that a Minimum Quality Standard, which retains asymmetric information...

  8. Directed transport in a periodic tube driven by asymmetric unbiased forces coexisting with spatially modulated noises

    International Nuclear Information System (INIS)

    Li Fengguo; Ai Baoquan

    2011-01-01

    Graphical abstract: The current J as a function of the phase shift φ and ε at a = 1/2π, b = 0.5/2π, k B T = 0.5, α = 0.1, and F 0 = 0.5. Highlights: → Unbiased forces and spatially modulated white noises affect the current. → In the adiabatic limit, the analytical expression of directed current is obtained. → Their competition will induce current reversals. → For negative asymmetric parameters of the force, there exists an optimum parameter. → The current increases monotonously for positive asymmetric parameters. - Abstract: Transport of Brownian particles in a symmetrically periodic tube is investigated in the presence of asymmetric unbiased external forces and spatially modulated Gaussian white noises. In the adiabatic limit, we obtain the analytical expression of the directed current. It is found that the temporal asymmetry can break thermodynamic equilibrium and induce a net current. Their competition between the temporal asymmetry force and the phase shift between the noise modulation and the tube shape will induce some peculiar phenomena, for example, current reversals. The current changes with the phase shift in the form of the sine function. For negative asymmetric parameters of the force, there exists an optimum parameter at which the current takes its maximum value. However, the current increases monotonously for positive asymmetric parameters.

  9. Chloroacetone photodissociation at 193 nm and the subsequent dynamics of the CH3C(O)CH2 radical—an intermediate formed in the OH + allene reaction en route to CH3 + ketene

    Science.gov (United States)

    Alligood, Bridget W.; FitzPatrick, Benjamin L.; Szpunar, David E.; Butler, Laurie J.

    2011-02-01

    We use a combination of crossed laser-molecular beam experiments and velocity map imaging experiments to investigate the primary photofission channels of chloroacetone at 193 nm; we also probe the dissociation dynamics of the nascent CH3C(O)CH2 radicals formed from C-Cl bond fission. In addition to the C-Cl bond fission primary photodissociation channel, the data evidence another photodissociation channel of the precursor, C-C bond fission to produce CH3CO and CH2Cl. The CH3C(O)CH2 radical formed from C-Cl bond fission is one of the intermediates in the OH + allene reaction en route to CH3 + ketene. The 193 nm photodissociation laser allows us to produce these CH3C(O)CH2 radicals with enough internal energy to span the dissociation barrier leading to the CH3 + ketene asymptote. Therefore, some of the vibrationally excited CH3C(O)CH2 radicals undergo subsequent dissociation to CH3 + ketene products; we are able to measure the velocities of these products using both the imaging and scattering apparatuses. The results rule out the presence of a significant contribution from a C-C bond photofission channel that produces CH3 and COCH2Cl fragments. The CH3C(O)CH2 radicals are formed with a considerable amount of energy partitioned into rotation; we use an impulsive model to explicitly characterize the internal energy distribution. The data are better fit by using the C-Cl bond fission transition state on the S1 surface of chloroacetone as the geometry at which the impulsive force acts, not the Franck-Condon geometry. Our data suggest that, even under atmospheric conditions, the reaction of OH with allene could produce a small branching to CH3 + ketene products, rather than solely producing inelastically stabilized adducts. This additional channel offers a different pathway for the OH-initiated oxidation of such unsaturated volatile organic compounds, those containing a C=C=C moiety, than is currently included in atmospheric models.

  10. Asymmetric hindwing foldings in rove beetles.

    Science.gov (United States)

    Saito, Kazuya; Yamamoto, Shuhei; Maruyama, Munetoshi; Okabe, Yoji

    2014-11-18

    Foldable wings of insects are the ultimate deployable structures and have attracted the interest of aerospace engineering scientists as well as entomologists. Rove beetles are known to fold their wings in the most sophisticated ways that have right-left asymmetric patterns. However, the specific folding process and the reason for this asymmetry remain unclear. This study reveals how these asymmetric patterns emerge as a result of the folding process of rove beetles. A high-speed camera was used to reveal the details of the wing-folding movement. The results show that these characteristic asymmetrical patterns emerge as a result of simultaneous folding of overlapped wings. The revealed folding mechanisms can achieve not only highly compact wing storage but also immediate deployment. In addition, the right and left crease patterns are interchangeable, and thus each wing internalizes two crease patterns and can be folded in two different ways. This two-way folding gives freedom of choice for the folding direction to a rove beetle. The use of asymmetric patterns and the capability of two-way folding are unique features not found in artificial structures. These features have great potential to extend the design possibilities for all deployable structures, from space structures to articles of daily use.

  11. Mixed gas plasticization phenomena in asymmetric membranes

    NARCIS (Netherlands)

    Visser, Tymen

    2006-01-01

    This thesis describes the thorough investigation of mixed gas transport behavior of asymmetric membranes in the separation of feed streams containing plasticizing gases in order to gain more insights into the complicated behavior of plasticization. To successfully employ gas separation membranes in

  12. Asymmetric conditional volatility in international stock markets

    Science.gov (United States)

    Ferreira, Nuno B.; Menezes, Rui; Mendes, Diana A.

    2007-08-01

    Recent studies show that a negative shock in stock prices will generate more volatility than a positive shock of similar magnitude. The aim of this paper is to appraise the hypothesis under which the conditional mean and the conditional variance of stock returns are asymmetric functions of past information. We compare the results for the Portuguese Stock Market Index PSI 20 with six other Stock Market Indices, namely the SP 500, FTSE 100, DAX 30, CAC 40, ASE 20, and IBEX 35. In order to assess asymmetric volatility we use autoregressive conditional heteroskedasticity specifications known as TARCH and EGARCH. We also test for asymmetry after controlling for the effect of macroeconomic factors on stock market returns using TAR and M-TAR specifications within a VAR framework. Our results show that the conditional variance is an asymmetric function of past innovations raising proportionately more during market declines, a phenomenon known as the leverage effect. However, when we control for the effect of changes in macroeconomic variables, we find no significant evidence of asymmetric behaviour of the stock market returns. There are some signs that the Portuguese Stock Market tends to show somewhat less market efficiency than other markets since the effect of the shocks appear to take a longer time to dissipate.

  13. MHD stability of vertically asymmetric tokamak equilibria

    International Nuclear Information System (INIS)

    Dalhed, H.E.; Grimm, R.C.; Johnson, J.L.

    1981-03-01

    The ideal MHD stability properties of a special class of vertically asymmetric tokamak equilibria are examined. The calculations confirm that no major new physical effects are introduced and the modifications can be understood by conventional arguments. The results indicate that significant departures from up-down symmetry can be tolerated before the reduction in β becomes important for reactor operation

  14. Asymmetric Aminalization via Cation-Binding Catalysis

    DEFF Research Database (Denmark)

    Park, Sang Yeon; Liu, Yidong; Oh, Joong Suk

    2018-01-01

    Asymmetric cation-binding catalysis, in principle, can generate "chiral" anionic nucleophiles, where the counter cations are coordinated within chiral environments. Nitrogen-nucleophiles are intrinsically basic, therefore, its use as nucleophiles is often challenging and limiting the scope of the...

  15. Volume inequalities for asymmetric Wulff shapes

    OpenAIRE

    Schuster, Franz E.; Weberndorfer, Manuel

    2012-01-01

    Sharp reverse affine isoperimetric inequalities for asymmetric Wulff shapes and their polars are established, along with the characterization of all extremals. These new inequalities have as special cases previously obtained simplex inequalities by Ball, Barthe and Lutwak, Yang, and Zhang. In particular, they provide the solution to a problem by Zhang.

  16. Quantum optics of lossy asymmetric beam splitters

    NARCIS (Netherlands)

    Uppu, Ravitej; Wolterink, Tom; Tentrup, Tristan Bernhard Horst; Pinkse, Pepijn Willemszoon Harry

    2016-01-01

    We theoretically investigate quantum interference of two single photons at a lossy asymmetric beam splitter, the most general passive 2×2 optical circuit. The losses in the circuit result in a non-unitary scattering matrix with a non-trivial set of constraints on the elements of the scattering

  17. Motion in an Asymmetric Double Well

    OpenAIRE

    Brizard, Alain J.; Westland, Melissa C.

    2016-01-01

    The problem of the motion of a particle in an asymmetric double well is solved explicitly in terms of the Weierstrass and Jacobi elliptic functions. While the solution of the orbital motion is expressed simply in terms of the Weierstrass elliptic function, the period of oscillation is more directly expressed in terms of periods of the Jacobi elliptic functions.

  18. Asymmetric output profile of Xe Laser

    NARCIS (Netherlands)

    Blok, F.J.; Rubin, P.L.; Verschuur, Jeroen W.J.; Witteman, W.J.

    2001-01-01

    A new set of asymmetric modes was recently revealed in a Xe slab laser with pronounced lens effects originating from gas heating in the discharge. The appearance of these modes is a threshold effect. Their domain of existence in the Xe laser is discussed. It is shown that mode competition can result

  19. Computing modal dispersion characteristics of radially Asymmetric ...

    African Journals Online (AJOL)

    We developed a matrix theory that applies to with non-circular/circular but concentric layers fibers. And we compute the dispersion characteristics of radially unconventional fiber, known as Asymmetric Bragg fiber. An attempt has been made to determine how the modal characteristics change as circular Bragg fiber is ...

  20. Seasonally asymmetric enhancement of northern vegetation productivity

    Science.gov (United States)

    Park, T.; Myneni, R.

    2017-12-01

    Multiple evidences of widespread greening and increasing terrestrial carbon uptake have been documented. In particular, enhanced gross productivity of northern vegetation has been a critical role leading to observed carbon uptake trend. However, seasonal photosynthetic activity and its contribution to observed annual carbon uptake trend and interannual variability are not well understood. Here, we introduce a multiple-source of datasets including ground, atmospheric and satellite observations, and multiple process-based global vegetation models to understand how seasonal variation of land surface vegetation controls a large-scale carbon exchange. Our analysis clearly shows a seasonally asymmetric enhancement of northern vegetation productivity in growing season during last decades. Particularly, increasing gross productivity in late spring and early summer is obvious and dominant driver explaining observed trend and variability. We observe more asymmetric productivity enhancement in warmer region and this spatially varying asymmetricity in northern vegetation are likely explained by canopy development rate, thermal and light availability. These results imply that continued warming may facilitate amplifying asymmetric vegetation activity and cause these trends to become more pervasive, in turn warming induced regime shift in northern land.

  1. A comparative Study of C2-Symmetric Bis(aziridine) Ligands in Some Transition Metal-Mediated Asymmetric Transformations

    DEFF Research Database (Denmark)

    Tanner, David Ackland; Johansson, Fredrik; Harden, Adrian

    1998-01-01

    A comparative study has been made of the performance of differently substituted Ca-symmetric bis(aziridine) ligands in a variety of metal-mediated asymmetric reactions. The metals studied were osmium (dihydroxylation), palladium (allylic alkylation) and copper (cyclopropanation and aziridination...

  2. High-Resolution Tracking Asymmetric Lithium Insertion and Extraction and Local Structure Ordering in SnS2.

    Science.gov (United States)

    Gao, Peng; Wang, Liping; Zhang, Yu-Yang; Huang, Yuan; Liao, Lei; Sutter, Peter; Liu, Kaihui; Yu, Dapeng; Wang, En-Ge

    2016-09-14

    In the rechargeable lithium ion batteries, the rate capability and energy efficiency are largely governed by the lithium ion transport dynamics and phase transition pathways in electrodes. Real-time and atomic-scale tracking of fully reversible lithium insertion and extraction processes in electrodes, which would ultimately lead to mechanistic understanding of how the electrodes function and why they fail, is highly desirable but very challenging. Here, we track lithium insertion and extraction in the van der Waals interactions dominated SnS2 by in situ high-resolution TEM method. We find that the lithium insertion occurs via a fast two-phase reaction to form expanded and defective LiSnS2, while the lithium extraction initially involves heterogeneous nucleation of intermediate superstructure Li0.5SnS2 domains with a 1-4 nm size. Density functional theory calculations indicate that the Li0.5SnS2 is kinetically favored and structurally stable. The asymmetric reaction pathways may supply enlightening insights into the mechanistic understanding of the underlying electrochemistry in the layered electrode materials and also suggest possible alternatives to the accepted explanation of the origins of voltage hysteresis in the intercalation electrode materials.

  3. Charge Asymmetric Cosmic Rays as a probe of Flavor Violating Asymmetric Dark Matter

    DEFF Research Database (Denmark)

    Masina, Isabella; Sannino, Francesco

    2011-01-01

    The recently introduced cosmic sum rules combine the data from PAMELA and Fermi-LAT cosmic ray experiments in a way that permits to neatly investigate whether the experimentally observed lepton excesses violate charge symmetry. One can in a simple way determine universal properties of the unknown...... component of the cosmic rays. Here we attribute a potential charge asymmetry to the dark sector. In particular we provide models of asymmetric dark matter able to produce charge asymmetric cosmic rays. We consider spin zero, spin one and spin one-half decaying dark matter candidates. We show that lepton...... flavor violation and asymmetric dark matter are both required to have a charge asymmetry in the cosmic ray lepton excesses. Therefore, an experimental evidence of charge asymmetry in the cosmic ray lepton excesses implies that dark matter is asymmetric....

  4. Ring-Contraction Strategy for the Practical, Scalable, Catalytic Asymmetric Synthesis of Versatile γ-Quaternary Acylcyclopentenes

    KAUST Repository

    Hong, Allen Y.

    2011-02-24

    Contraction action! A simple protocol for the catalytic asymmetric synthesis of highly functionalized γ-quaternary acylcyclopentenes (see schematic) in up to 91 % overall yield and 92 % ee has been developed. The reaction sequence employs a palladium-catalyzed enantioselective alkylation reaction and exploits the unusual stability of β-hydroxy cycloheptanones to achieve a general and robust method for performing two-carbon ring contractions.

  5. Ring-Contraction Strategy for the Practical, Scalable, Catalytic Asymmetric Synthesis of Versatile γ-Quaternary Acylcyclopentenes

    KAUST Repository

    Hong, Allen Y.; Krout, Michael R.; Jensen, Thomas; Bennett, Nathan B.; Harned, Andrew M.; Stoltz, Brian M.

    2011-01-01

    Contraction action! A simple protocol for the catalytic asymmetric synthesis of highly functionalized γ-quaternary acylcyclopentenes (see schematic) in up to 91 % overall yield and 92 % ee has been developed. The reaction sequence employs a palladium-catalyzed enantioselective alkylation reaction and exploits the unusual stability of β-hydroxy cycloheptanones to achieve a general and robust method for performing two-carbon ring contractions.

  6. Asymmetric switching in a homodimeric ABC transporter: a simulation study.

    Directory of Open Access Journals (Sweden)

    Jussi Aittoniemi

    2010-04-01

    Full Text Available ABC transporters are a large family of membrane proteins involved in a variety of cellular processes, including multidrug and tumor resistance and ion channel regulation. Advances in the structural and functional understanding of ABC transporters have revealed that hydrolysis at the two canonical nucleotide-binding sites (NBSs is co-operative and non-simultaneous. A conserved core architecture of bacterial and eukaryotic ABC exporters has been established, as exemplified by the crystal structure of the homodimeric multidrug exporter Sav1866. Currently, it is unclear how sequential ATP hydrolysis arises in a symmetric homodimeric transporter, since it implies at least transient asymmetry at the NBSs. We show by molecular dynamics simulation that the initially symmetric structure of Sav1866 readily undergoes asymmetric transitions at its NBSs in a pre-hydrolytic nucleotide configuration. MgATP-binding residues and a network of charged residues at the dimer interface are shown to form a sequence of putative molecular switches that allow ATP hydrolysis only at one NBS. We extend our findings to eukaryotic ABC exporters which often consist of two non-identical half-transporters, frequently with degeneracy substitutions at one of their two NBSs. Interestingly, many residues involved in asymmetric conformational switching in Sav1866 are substituted in degenerate eukaryotic NBS. This finding strengthens recent suggestions that the interplay of a consensus and a degenerate NBS in eukaroytic ABC proteins pre-determines the sequence of hydrolysis at the two NBSs.

  7. Organocatalyzed Asymmetric α-Oxidation, α-Aminoxylation and α-Amination of Carbonyl Compounds

    Directory of Open Access Journals (Sweden)

    Worawan Bhanthumnavin

    2010-02-01

    Full Text Available Organocatalytic asymmetric α-oxidation and amination reactions of carbonyl compounds are highly useful synthetic methodologies, especially in generating chiral building blocks that previously have not been easily accessible by traditional methods. The concept is relatively new and therefore the list of new catalysts, oxidizing and aminating reagents, as well as new substrates, are expanding at an amazing rate. The scope of this review includes new reactions and catalysts, mechanistic aspects and synthetic applications of α-oxidation, hydroxylation, aminoxylation, amination, hydrazination, hydroxyamination and related α-heteroatom functionalization of aldehydes, ketones and related active methylene compounds published during 2005–2009.

  8. The regio- and stereospecific synthesis of diarylpropenyllithium compounds from dimethylamino- and dimethylaminomethyl-substituted diarylacetylenes viatransmetallation reactions involving diarylpropenylmagnesium and tin compounds

    NARCIS (Netherlands)

    Koten, G. van; Hoedt, R.W.M. ten; Noltes, J.G.

    1979-01-01

    Dimethylamino- and dimethylaminomethyl-substituted diarylacetylenes were prepared by the Pd(PPh{3}){4}-catalyzed coupling reaction of dimethylamino- and dimethylaminomethyl-substituted aryl halides with arylacetylenes.Reaction of the asymmetric diarylacetylenes with methylmagnesium bromide in the

  9. SOLVENTLESS MIGRATORY-INSERTION REACTIONS OF ...

    African Journals Online (AJOL)

    Preferred Customer

    The product formed by reaction of an alkyl or aryl cyclopentadienyl metal carbonyl .... (as also observed from the NMR tube experiments) that the solventless reaction between ... As can be seen from Figure 3, the reaction rate in the melt.

  10. Noncanonical Reactions of Flavoenzymes

    Directory of Open Access Journals (Sweden)

    Pablo Sobrado

    2012-11-01

    Full Text Available Enzymes containing flavin cofactors are predominantly involved in redox reactions in numerous cellular processes where the protein environment modulates the chemical reactivity of the flavin to either transfer one or two electrons. Some flavoenzymes catalyze reactions with no net redox change. In these reactions, the protein environment modulates the reactivity of the flavin to perform novel chemistries. Recent mechanistic and structural data supporting novel flavin functionalities in reactions catalyzed by chorismate synthase, type II isopentenyl diphosphate isomerase, UDP-galactopyranose mutase, and alkyl-dihydroxyacetonephosphate synthase are presented in this review. In these enzymes, the flavin plays either a direct role in acid/base reactions or as a nucleophile or electrophile. In addition, the flavin cofactor is proposed to function as a “molecular scaffold” in the formation of UDP-galactofuranose and alkyl-dihydroxyacetonephosphate by forming a covalent adduct with reaction intermediates.

  11. Analysing mass balance of viruses in a coagulation-ceramic microfiltration hybrid system by a combination of the polymerase chain reaction (PCR) method and the plaque forming units (PFU) method.

    Science.gov (United States)

    Matsushita, T; Matsui, Y; Shirasaki, N

    2006-01-01

    Virus removal experiments using river water spiked with bacteriophages were conducted by an in-line coagulation-ceramic microfiltration hybrid system to investigate the effects of filtration flux (62.5 and 125 L/(m2 x h)) and type of virus (Qbeta and MS2) on virus removal. In addition, the mass balance of viruses through the hybrid system was analysed by quantifying the infectious and inactive viruses by a combination of the polymerase chain reaction (PCR) method and the plaque forming units (PFU) method. Even when the system was operated at high filtration flux (125 L/(m2 x h)), high virus removal (> 6 log) with short coagulation time (2.4 s) was successfully achieved by dosing polyaluminium chloride (PACI) at more than 1.08 mg-Al/L. Removal performances were different between Qbeta and MS2, although their diameters are almost the same: greater virus removal was achieved for MS2 at PACI dosing of 0.54 mg-Al/L, and for Qbeta at PACI dosing of more than 1.08 mg-Al/L. The combination of the PCR and PFU methods revealed that two phenomena, adsorption to/entrapment in aluminium floc and virucidal activity of PACI, partially account for the high virus removal in the coagulation-MF hybrid system.

  12. Brownian Motion of Asymmetric Boomerang Colloidal Particles

    Science.gov (United States)

    Chakrabarty, Ayan; Konya, Andrew; Wang, Feng; Selinger, Jonathan; Sun, Kai; Wei, Qi-Huo

    2014-03-01

    We used video microscopy and single particle tracking to study the diffusion and local behaviors of asymmetric boomerang particles in a quasi-two dimensional geometry. The motion is biased towards the center of hydrodynamic stress (CoH) and the mean square displacements of the particles are linear at short and long times with different diffusion coefficients and in the crossover regime it is sub-diffusive. Our model based on Langevin theory shows that these behaviors arise from the non-coincidence of the CoH with the center of the body. Since asymmetric boomerangs represent a class of rigid bodies of more generals shape, therefore our findings are generic and true for any non-skewed particle in two dimensions. Both experimental and theoretical results will be discussed.

  13. Dynamics of asymmetric kinetic Ising systems revisited

    International Nuclear Information System (INIS)

    Huang, Haiping; Kabashima, Yoshiyuki

    2014-01-01

    The dynamics of an asymmetric kinetic Ising model is studied. Two schemes for improving the existing mean-field description are proposed. In the first scheme, we derive the formulas for instantaneous magnetization, equal-time correlation, and time-delayed correlation, considering the correlation between different local fields. To derive the time-delayed correlation, we emphasize that the small-correlation assumption adopted in previous work (Mézard and Sakellariou, 2011 J. Stat. Mech. L07001) is in fact not required. To confirm the prediction efficiency of our method, we perform extensive simulations on single instances with either temporally constant external driving fields or sinusoidal external fields. In the second scheme, we develop an improved mean-field theory for instantaneous magnetization prediction utilizing the notion of the cavity system in conjunction with a perturbative expansion approach. Its efficiency is numerically confirmed by comparison with the existing mean-field theory when partially asymmetric couplings are present. (paper)

  14. Improved DFIG Capability during Asymmetrical Grid Faults

    DEFF Research Database (Denmark)

    Zhou, Dao; Blaabjerg, Frede

    2015-01-01

    In the wind power application, different asymmetrical types of the grid fault can be categorized after the Y/d transformer, and the positive and negative components of a single-phase fault, phase-to-phase fault, and two-phase fault can be summarized. Due to the newly introduced negative and even...... the natural component of the Doubly-Fed Induction Generator (DFIG) stator flux during the fault period, their effects on the rotor voltage can be investigated. It is concluded that the phase-to-phase fault has the worst scenario due to its highest introduction of the negative stator flux. Afterwards......, the capability of a 2 MW DFIG to ride through asymmetrical grid faults can be estimated at the existing design of the power electronics converter. Finally, a control scheme aimed to improve the DFIG capability is proposed and the simulation results validate its feasibility....

  15. Synthesis and optical properties of novel asymmetric perylene bisimides

    International Nuclear Information System (INIS)

    Tsai, Hsing-Yang; Chen, Kew-Yu

    2014-01-01

    A novel series of asymmetric perylene bisimides, 1-amino-7-nitroperylene bisimides (1a–1c), was synthesized and fully characterized. These molecules undergo an excited-state intramolecular electron transfer reaction, resulting in a unique charge transfer emission in the near-infrared region, of which the peak wavelength exhibits strong solvatochromism. The dipole moments of these compounds have been estimated using the Lippert–Mataga equation, and upon excitation, the molecules show larger dipole moment changes than those of the symmetric 1,7-diaminoperylene bisimides (2a–2c). Furthermore, these dyes undergo two quasi-reversible one-electron oxidations and two quasi-reversible one-electron reductions in dichloromethane at modest potentials. They display good thermal stability and optical stability that can be used as stable near-infrared fluorescent dyes. Their spectroscopic properties in various conditions and complementary time-dependent density functional theory calculations are reported. - Highlights: • 1-amino-7-nitroperylene bisimide dyes were synthesized. • These molecules undergo an excited-state intramolecular electron transfer reaction. • They can be used as stable near-infrared fluorescent dyes

  16. Asymmetric volatility connectedness on the forex market

    Czech Academy of Sciences Publication Activity Database

    Baruník, Jozef; Kočenda, Evžen; Vácha, Lukáš

    2017-01-01

    Roč. 77, č. 1 (2017), s. 39-56 ISSN 0261-5606 R&D Projects: GA ČR(CZ) GA16-14179S Institutional support: RVO:67985556 Keywords : volatility * connectedness * asymmetric effects Subject RIV: AH - Economics OBOR OECD: Finance Impact factor: 1.853, year: 2016 http://library.utia.cas.cz/separaty/2017/E/barunik-0478477.pdf

  17. Magnetic properties of strongly asymmetric nuclear matter

    International Nuclear Information System (INIS)

    Kutschera, M.; Wojcik, W.

    1988-01-01

    We investigate stability of neutron matter containing a small proton admixture with respect to spin fluctuations. We establish conditions under which strongly asymmetric nuclear matter could acquire a permanent magnetization. It is shown that if the protons are localized, the system becomes unstable to spin fluctuations for arbitrarily weak proton-neutron spin interactions. For non-localized protons there exists a threshold value of the spin interaction above which the system can develop a spontaneous polarization. 12 refs., 2 figs. (author)

  18. Isospin dependent properties of asymmetric nuclear matter

    OpenAIRE

    Chowdhury, P. Roy; Basu, D. N.; Samanta, C.

    2009-01-01

    The density dependence of nuclear symmetry energy is determined from a systematic study of the isospin dependent bulk properties of asymmetric nuclear matter using the isoscalar and the isovector components of density dependent M3Y interaction. The incompressibility $K_\\infty$ for the symmetric nuclear matter, the isospin dependent part $K_{asy}$ of the isobaric incompressibility and the slope $L$ are all in excellent agreement with the constraints recently extracted from measured isotopic de...

  19. Asymmetric flow events in a VEER 1000

    International Nuclear Information System (INIS)

    Horak, W.C.; Kennett, R.J.; Shier, W.; Guppy, J.G.

    1992-07-01

    This paper describes the simulation of asymmetric loss of flow events in Russian designed VVER-1000 reactors using the RETRAN-02 Mod4 computer code. VVER-1000 reactors have significant differences from United States pressurized water reactors including multi-level emergency response systems and plant operation at reduced power levels with one or more main circulation pumps inoperable. The results of these simulations are compared to similar analyses done by the designers for the Rovno plant

  20. Two particle states in an asymmetric box

    OpenAIRE

    Li, Xin; Liu, Chuan

    2004-01-01

    The exact two-particle energy eigenstates in an asymmetric rectangular box with periodic boundary conditions in all three directions are studied. Their relation with the elastic scattering phases of the two particles in the continuum are obtained. These results can be viewed as a generalization of the corresponding formulae in a cubic box obtained by L\\"uscher before. In particular, the s-wave scattering length is related to the energy shift in the finite box. Possible applications of these f...

  1. Symmetric vs. asymmetric punishment regimes for bribery

    OpenAIRE

    Engel, Christoph; Goerg, Sebastian J.; Yu, Gaoneng

    2012-01-01

    In major legal orders such as UK, the U.S., Germany, and France, bribers and recipients face equally severe criminal sanctions. In contrast, countries like China, Russia, and Japan treat the briber more mildly. Given these differences between symmetric and asymmetric punishment regimes for bribery, one may wonder which punishment strategy is more effective in curbing corruption. For this purpose, we designed and ran a lab experiment in Bonn (Germany) and Shanghai (China) with exactly the same...

  2. Predicting tensorial electrophoretic effects in asymmetric colloids

    Science.gov (United States)

    Mowitz, Aaron J.; Witten, T. A.

    2017-12-01

    We formulate a numerical method for predicting the tensorial linear response of a rigid, asymmetrically charged body to an applied electric field. This prediction requires calculating the response of the fluid to the Stokes drag forces on the moving body and on the countercharges near its surface. To determine the fluid's motion, we represent both the body and the countercharges using many point sources of drag known as Stokeslets. Finding the correct flow field amounts to finding the set of drag forces on the Stokeslets that is consistent with the relative velocities experienced by each Stokeslet. The method rigorously satisfies the condition that the object moves with no transfer of momentum to the fluid. We demonstrate that a sphere represented by 1999 well-separated Stokeslets on its surface produces flow and drag force like a solid sphere to 1% accuracy. We show that a uniformly charged sphere with 3998 body and countercharge Stokeslets obeys the Smoluchowski prediction [F. Morrison, J. Colloid Interface Sci. 34, 210 (1970), 10.1016/0021-9797(70)90171-2] for electrophoretic mobility when the countercharges lie close to the sphere. Spheres with dipolar and quadrupolar charge distributions rotate and translate as predicted analytically to 4% accuracy or better. We describe how the method can treat general asymmetric shapes and charge distributions. This method offers promise as a way to characterize and manipulate asymmetrically charged colloid-scale objects from biology (e.g., viruses) and technology (e.g., self-assembled clusters).

  3. Diagnostic implications of asymmetrical mammographic patterns

    International Nuclear Information System (INIS)

    Asenjo, M.; Ania, B.J.

    1997-01-01

    To analyze the effect of asymmetrical mammographic patterns of the diagnosis of breast cancer. In a series of 6, 476 patients referred to a Breast Imaging Diagnosis Unit, we excluded males, women with previous breast surgery, and cases in which mammography was not performed, which left 5,203 women included. Each breast was classified according to one of four patterns of mammographic parenchymal density. Asymmetry was considered to exist when a patient's breasts had different patterns. Breast cancer was confirmed histologically in 282 (5.4%) women. The mammographic pattern was asymmetrical in 8% of the women with cancer and in 2% of the women without cancer (p<0.001). Fine-needle aspiration biopsy was performed in 78% and 96% (p=0.04), respectively, of the women with and without mammographic asymmetry who had neoplasms, and in 33% and 22% (p=0.02), respectively, of the women with and without mammographic asymmetry who did not have neoplasms. Asymmetrical mammographic pattern was four times more frequent in the women with breast cancer. This asymmetry decreased the frequency of needle biopsy in women with cancer, but increased the frequency of needle biopsy in women without cancer. (Author) 11 refs

  4. Hadron scattering in an asymmetric box

    International Nuclear Information System (INIS)

    Li Xin; Chen Ying; Meng Guozhan; Feng Xu; Gong Ming; He Song; Li Gang; Liu Chuan; Liu Yubin; Ma Jianping; Meng Xiangfei; Shen Yan; Zhang Jianbo

    2007-01-01

    We propose to study hadron-hadron scattering using lattice QCD in an asymmetric box which allows one to access more non-degenerate low-momentum modes for a given volume. The conventional Luescher's formula applicable in a symmetric box is modified accordingly. To illustrate the feasibility of this approach, pion-pion elastic scattering phase shifts in the I = 2, J = 0 channel are calculated within quenched approximation using improved gauge and Wilson fermion actions on anisotropic lattices in an asymmetric box. After the chiral and continuum extrapolation, we find that our quenched results for the scattering phase shifts in this channel are consistent with the experimental data when the three-momentum of the pion is below 300MeV. Agreement is also found when compared with previous theoretical results from lattice and other means. Moreover, with the usage of asymmetric volume, we are able to compute the scattering phases in the low-momentum range (pion three momentum less than about 350MeV in the center of mass frame) for over a dozen values of the pion three-momenta, much more than using the conventional symmetric box with comparable volume

  5. Simulation of Phenix EOL Asymmetric Test

    Energy Technology Data Exchange (ETDEWEB)

    Ha, Kwi Seok; Lee, Kwi Lim; Choi, Chi Woong; Kang, Seok Hun; Chang, Won Pyo; Jeong, Hae Yong [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2012-05-15

    The asymmetric test of End-Of-Life (EOL) tests on the Phenix plant was used for the evaluation of the MARS-LMR in the Generation IV frame as a part of the code validation. The purpose of the test is to evaluate the ability of the system code to describe asymmetric situations and to identify important phenomena during asymmetrical transient such as a three dimensional effect, buoyancy influence, and thermal stratification in the hot and cold pools. 3-dimensional sodium coolant mixing in the pools has different characteristics from the one dimensional full instantaneous mixing. The velocities and temperatures at the core outlet level differ at each sub-assembly and the temperature in the center of the hot pool may be high because the driver fuels are located at the center region. The temperatures in the hot pool are not the same in the radial and axial locations due to the buoyancy effect. The temperatures in the cold pool also differ along with the elevations and azimuthal directions due to the outlet location of IHX and the thermal stratification

  6. Flatfish: an asymmetric perspective on metamorphosis.

    Science.gov (United States)

    Schreiber, Alexander M

    2013-01-01

    The most asymmetrically shaped and behaviorally lateralized of all the vertebrates, the flatfishes are an endless source of fascination to all fortunate enough to study them. Although all vertebrates undergo left-right asymmetric internal organ placement during embryogenesis, flatfish are unusual in that they experience an additional period of postembryonic asymmetric remodeling during metamorphosis, and thus deviate from a bilaterally symmetrical body plan more than other vertebrates. As with amphibian metamorphosis, all the developmental programs of flatfish metamorphosis are ultimately under the control of thyroid hormone. At least one gene pathway involved in embryonic organ lateralization (nodal-lefty-pitx2) is re-expressed in the larval stage during flatfish metamorphosis. Aspects of modern flatfish ontogeny, such as the gradual translocation of one eye to the opposite side of the head and the appearance of key neurocranial elements during metamorphosis, seem to elegantly recapitulate flatfish phylogeny. This chapter highlights the current state of knowledge of the developmental biology of flatfish metamorphosis with emphases on the genetic, morphological, behavioral, and evolutionary origins of flatfish asymmetry. Copyright © 2013 Elsevier Inc. All rights reserved.

  7. Nuclear reactions

    International Nuclear Information System (INIS)

    Lane, A.M.

    1980-01-01

    In reviewing work at Harwell over the past 25 years on nuclear reactions it is stated that a balance has to be struck in both experiment and theory between work on cross-sections of direct practical relevance to reactors and on those relevant to an overall understanding of reaction processes. The compound nucleus and direct process reactions are described. Having listed the contributions from AERE, Harwell to developments in nuclear reaction research in the period, work on the optical model, neutron capture theory, reactions at doorway states with fine structure, and sum-rules for spectroscopic factors are considered in more detail. (UK)

  8. Asymmetric Threats and Risks of the XXI Century

    International Nuclear Information System (INIS)

    Doncev, A.

    2007-01-01

    The rapid technology development in the 21st century has a great influence over the dynamic arm competition, thus threats and risks increasing. They are sublimated in different forms of international terrorism and could produce crisis in the Region, and furthermore all round the world. The international community is faced with new challenges. Now, the territories are not the only targets of attacks. The result of the theoretical and empirical research leads towards to the non-existence of national crisis management capacity. The paper identifies the international scenario which is very complex and unpredictable in the diapason of the asymmetric threats, as well as a new priorities agenda of the international community in the 21st century. Therefore, a risk management model is suggested, too.(author)

  9. Catalytic asymmetric epoxidation of alpha,beta-unsaturated amides: efficient synthesis of beta-aryl alpha-hydroxy amides using a one-pot tandem catalytic asymmetric epoxidation-Pd-catalyzed epoxide opening process.

    Science.gov (United States)

    Nemoto, Tetsuhiro; Kakei, Hiroyuki; Gnanadesikan, Vijay; Tosaki, Shin-Ya; Ohshima, Takashi; Shibasaki, Masakatsu

    2002-12-11

    The catalytic asymmetric epoxidation of alpha,beta-unsaturated amides using Sm-BINOL-Ph3As=O complex was succeeded. Using 5-10 mol % of the asymmetric catalyst, a variety of amides were epoxidized efficiently, yielding the corresponding alpha,beta-epoxy amides in up to 99% yield and in more than 99% ee. Moreover, the novel one-pot tandem process, one-pot tandem catalytic asymmetric epoxidation-Pd-catalyzed epoxide opening process, was developed. This method was successfully utilized for the efficient synthesis of beta-aryl alpha-hydroxy amides, including beta-aryllactyl-leucine methyl esters. Interestingly, it was found that beneficial modifications on the Pd catalyst were achieved by the constituents of the first epoxidation, producing a more suitable catalyst for the Pd-catalyzed epoxide opening reaction in terms of chemoselectivity.

  10. Examining the Cultural Leadership Behaviors of Schoo l Principal s within the Context of Symmetric and Asymmetric School Culture

    Directory of Open Access Journals (Sweden)

    Betül BALKAR

    2015-08-01

    Full Text Available The aim of this study is to determine the opinions of teachers on contributions of school principals’ cultural leadership behaviors to forming symmetric and asymmetric culture. The participants of the study consisted of 27 secondary school teachers working in Gaziantep province. Data of the study were collected through semi - structured interviews and analyzed through content analysis. Contributions of each cultural leader ship behavior to symmetric and asymmetric culture types were determined by taking relations between cultural leadership behaviors and symmetric and asymmetric cultures into consideration in the process of content analysis. According to the findings of the study ; supporting development of teachers and reflecting developments and innovations on schools are among the cultural leadership behaviors contributing to forming asymmetric culture at schools. Interpreting tasks and missions of school and ensuring neces sary environment for keeping social values alive at schools are among the cultural leadership behaviors contributing to forming symmetric culture at schools. Based on the results of the study, it is suggested that school principals should follow developmen ts in educational issues and transfer these developments into school practices. They should place more importance on supporting innovative behaviors of teachers in order to create asymmetric culture at schools.

  11. Game-theoretic strategies for asymmetric networked systems

    Energy Technology Data Exchange (ETDEWEB)

    Rao, Nageswara S. [ORNL; Ma, Chris Y. T. [Hang Seng Management College, Hon Kong; Hausken, Kjell [University of Stavanger, Norway; He, Fei [Texas A& M University, Kingsville, TX, USA; Yau, David K. Y. [Singapore University of Technology and Design; Zhuang, Jun [University at Buffalo (SUNY)

    2017-07-01

    Abstract—We consider an infrastructure consisting of a network of systems each composed of discrete components that can be reinforced at a certain cost to guard against attacks. The network provides the vital connectivity between systems, and hence plays a critical, asymmetric role in the infrastructure operations. We characterize the system-level correlations using the aggregate failure correlation function that specifies the infrastructure failure probability given the failure of an individual system or network. The survival probabilities of systems and network satisfy first-order differential conditions that capture the component-level correlations. We formulate the problem of ensuring the infrastructure survival as a game between anattacker and a provider, using the sum-form and product-form utility functions, each composed of a survival probability term and a cost term. We derive Nash Equilibrium conditions which provide expressions for individual system survival probabilities, and also the expected capacity specified by the total number of operational components. These expressions differ only in a single term for the sum-form and product-form utilities, despite their significant differences.We apply these results to simplified models of distributed cloud computing infrastructures.

  12. Asymmetric Catalysis with Organic Azides and Diazo Compounds Initiated by Photoinduced Electron Transfer.

    Science.gov (United States)

    Huang, Xiaoqiang; Webster, Richard D; Harms, Klaus; Meggers, Eric

    2016-09-28

    Electron-acceptor-substituted aryl azides and α-diazo carboxylic esters are used as substrates for visible-light-activated asymmetric α-amination and α-alkylation, respectively, of 2-acyl imidazoles catalyzed by a chiral-at-metal rhodium-based Lewis acid in combination with a photoredox sensitizer. This novel proton- and redox-neutral method provides yields of up to 99% and excellent enantioselectivities of up to >99% ee with broad functional group compatibility. Mechanistic investigations suggest that an intermediate rhodium enolate complex acts as a reductive quencher to initiate a radical process with the aryl azides and α-diazo carboxylic esters serving as precursors for nitrogen and carbon-centered radicals, respectively. This is the first report on using aryl azides and α-diazo carboxylic esters as substrates for asymmetric catalysis under photoredox conditions. These reagents have the advantage that molecular nitrogen is the leaving group and sole byproduct in this reaction.

  13. Multiple Hydrogen-Bond Activation in Asymmetric Brønsted Acid Catalysis

    KAUST Repository

    Liao, Hsuan-Hung

    2018-05-03

    An efficient protocol for the asymmetric synthesis of chiral tetrahydroquinolines bearing multiple stereogenic centers by means of asymmetric Brønsted acid catalysis was developed. A chiral 1,1′‐spirobiindane‐7,7′‐diol (SPINOL)‐based N‐triflylphosphoramide (NTPA) proved to be an effective Brønsted acid catalyst for the in situ generation of aza‐ortho‐quinone methides (aza‐o‐QMs) and their subsequent cycloaddition reaction with unactivated alkenes to provide the products with excellent diastereo‐ and enantioselectivities. In addition, DFT calculations provided insight into the activation mode and nature of the interactions between the N‐triflylphosphoramide catalyst and the generated aza‐o‐QMs.

  14. A DFT investigation on interactions between asymmetric derivatives of cisplatin and nucleobase guanine

    Science.gov (United States)

    Tai, Truong Ba; Nhat, Pham Vu

    2017-07-01

    The interactions of hydrolysis products of cisplatin and its asymmetric derivatives cis- and trans-[PtCl2(iPram)(Mepz)] with guanine were studied using DFT methods. These interactions are dominated by electrostatic effects, namely hydrogen bond contributions and there exists a charge flow from H-atoms of ligands to the O-atoms of guanine. The replacement of NH3 moieties by larger functional groups accompanies with a moderate reaction between PtII and guanine molecule, diminishing the cytotoxicity of the drug. The asymmetric and symmetric NH2 stretching modes of complexes having strong hydrogen bond interactions are red shifted importantly as compared to complexes without presence of hydrogen bond interactions.

  15. Multiple Hydrogen-Bond Activation in Asymmetric Brønsted Acid Catalysis

    KAUST Repository

    Liao, Hsuan-Hung; Hsiao, Chien-Chi; Atodiresei, Iuliana; Rueping, Magnus

    2018-01-01

    An efficient protocol for the asymmetric synthesis of chiral tetrahydroquinolines bearing multiple stereogenic centers by means of asymmetric Brønsted acid catalysis was developed. A chiral 1,1′‐spirobiindane‐7,7′‐diol (SPINOL)‐based N‐triflylphosphoramide (NTPA) proved to be an effective Brønsted acid catalyst for the in situ generation of aza‐ortho‐quinone methides (aza‐o‐QMs) and their subsequent cycloaddition reaction with unactivated alkenes to provide the products with excellent diastereo‐ and enantioselectivities. In addition, DFT calculations provided insight into the activation mode and nature of the interactions between the N‐triflylphosphoramide catalyst and the generated aza‐o‐QMs.

  16. A concise summary of experimental facts about the Soai reaction.

    Science.gov (United States)

    Gehring, Timo; Busch, Mark; Schlageter, Martin; Weingand, Daniel

    2010-01-01

    The Soai reaction amplifies small enantiomeric excesses in a spectacular manner. Being known for 20 years, it has drawn the attention of many scientists in different fields as it is to date the only chemical reaction offering the chance to study the phenomenon of asymmetric autocatalysis in conjunction with high amplification of enantiomeric excess (ee). This mini-review comprises an introduction to the discovery of asymmetric autocatalysis with amplification of ee and a concise summary of published experimental results showing which starting materials and reaction parameters play an important role in this reaction and which influences are understood. It is addressed especially to scientists entering the field of the Soai reaction to get a quick overview of important aspects. © 2010 Wiley-Liss, Inc.

  17. C—C bond formation in the intramolecular Diels-Alder reaction of triene amides

    Directory of Open Access Journals (Sweden)

    Abdelilah Benallou

    2018-02-01

    Full Text Available The mechanism nature of the intramolecular Diels–Alder reaction has been performed; and thus, the changes of C—C bond forming/breaking along IRC are characterized in this study. Conceptual DFT analyses of the most favorable adduct fused/exo shows that the flux electronic will take place from diene to dienophile moiety. Moreover, ELF topological analysis based on the electron density predicts that C—C bond is formed by the coupling of two pseudoradical centers generated at the most significant atoms of the molecules. However, C2 vs C3, also C1 and C4 interaction comes mainly from the global electron density transfer which takes place along the reaction. Two- stage one-step is the proposed mechanism of this reaction, the first stage aims for the formation of C2—C3 σ bond while the second stage aims for C1—C4 σ bond formation. Interestingly, the observed asynchronicity of this IMDA reaction due principally to the asymmetric reorganization of electron density at the most attractive centers.

  18. C-C bond formation in the intramolecular Diels-Alder reaction of triene amides.

    Science.gov (United States)

    Benallou, Abdelilah; El Alaoui El Abdallaoui, Habib; Garmes, Hocine

    2018-02-01

    The mechanism nature of the intramolecular Diels-Alder reaction has been performed; and thus, the changes of C-C bond forming/breaking along IRC are characterized in this study. Conceptual DFT analyses of the most favorable adduct fused/exo shows that the flux electronic will take place from diene to dienophile moiety. Moreover, ELF topological analysis based on the electron density predicts that C-C bond is formed by the coupling of two pseudoradical centers generated at the most significant atoms of the molecules. However, C2 vs C3, also C1 and C4 interaction comes mainly from the global electron density transfer which takes place along the reaction. Two- stage one-step is the proposed mechanism of this reaction, the first stage aims for the formation of C2-C3 σ bond while the second stage aims for C1-C4 σ bond formation. Interestingly, the observed asynchronicity of this IMDA reaction due principally to the asymmetric reorganization of electron density at the most attractive centers.

  19. Two-stage solar concentrators based on parabolic troughs: asymmetric versus symmetric designs.

    Science.gov (United States)

    Schmitz, Max; Cooper, Thomas; Ambrosetti, Gianluca; Steinfeld, Aldo

    2015-11-20

    While nonimaging concentrators can approach the thermodynamic limit of concentration, they generally suffer from poor compactness when designed for small acceptance angles, e.g., to capture direct solar irradiation. Symmetric two-stage systems utilizing an image-forming primary parabolic concentrator in tandem with a nonimaging secondary concentrator partially overcome this compactness problem, but their achievable concentration ratio is ultimately limited by the central obstruction caused by the secondary. Significant improvements can be realized by two-stage systems having asymmetric cross-sections, particularly for 2D line-focus trough designs. We therefore present a detailed analysis of two-stage line-focus asymmetric concentrators for flat receiver geometries and compare them to their symmetric counterparts. Exemplary designs are examined in terms of the key optical performance metrics, namely, geometric concentration ratio, acceptance angle, concentration-acceptance product, aspect ratio, active area fraction, and average number of reflections. Notably, we show that asymmetric designs can achieve significantly higher overall concentrations and are always more compact than symmetric systems designed for the same concentration ratio. Using this analysis as a basis, we develop novel asymmetric designs, including two-wing and nested configurations, which surpass the optical performance of two-mirror aplanats and are comparable with the best reported 2D simultaneous multiple surface designs for both hollow and dielectric-filled secondaries.

  20. Free-Standing Bilayered Nanoparticle Superlattice Nanosheets with Asymmetric Ionic Transport Behaviors.

    Science.gov (United States)

    Rao, Siyuan; Si, Kae Jye; Yap, Lim Wei; Xiang, Yan; Cheng, Wenlong

    2015-11-24

    Natural cell membranes can directionally and selectively regulate the ion transport, which is critical for the functioning of living cells. Here, we report on the fabrication of an artificial membrane based on an asymmetric nanoparticle superlattice bilayered nanosheet, which exhibits similar ion transport characteristics. The superlattice nanosheets were fabricated via a drying-mediated self-assembly of polystyrene-capped gold nanoparticles at the liquid-air interface. By adopting a layer-by-layer assembly process, an asymmetric nanomembrane could be obtained consisting of two nanosheets with different nanoparticle size. The resulting nanomembranes exhibit an asymmetric ion transport behavior, and diode-like current-voltage curves were observed. The asymmetric ion transport is attributed to the cone-like nanochannels formed within the membranes, upon which a simulation map was established to illustrate the relationship between the channel structure and the ionic selectivity, in consistency with our experimental results. Our superlattice nanosheet-based design presents a promising strategy for the fabrication of next-generation smart nanomembranes for rationally and selectively regulating the ion transport even at a large ion flux, with potential applications in a wide range of fields, including biosensor devices, energy conversion, biophotonics, and bioelectronics.

  1. Asymmetric Invisibility Cloaking Theory Based on the Concept of Effective Electromagnetic Fields for Photons

    Science.gov (United States)

    Amemiya, Tomo; Taki, Masato; Kanazawa, Toru; Arai, Shigehisa

    2014-03-01

    The asymmetric invisibility cloak is a special cloak with unidirectional transparency; that is, a person in the cloak should not be seen from the outside but should be able to see the outside. Existing theories of designing invisibility cloaks cannot be used for asymmetric cloaking because they are based on the transformation optics that uses Riemannian metric tensor independent of direction. To overcome this problem, we propose introducing directionality into invisibility cloaking. Our theory is based on ``the theory of effective magnetic field for photons'' proposed by Stanford University.[2] To realize asymmetric cloaking, we have extended the Stanford's theory to add the concept of ``effective electric field for photons.'' The effective electric and the magnetic field can be generated using a photonc resonator lattice, which is a kind of metamaterial. The Hamiltonian for photons in these fields has a similar form to that of the Hamiltonian for a charged particle in an electromagnetic field. An incident photon therefore experiences a ``Lorentz-like'' and a ``Coulomb-like'' force and shows asymmetric movement depending of its travelling direction.We show the procedure of designing actual invisibility cloaks using the photonc resonator lattice and confirm their operation with the aid of computer simulation. This work was supported in part by the MEXT; JSPS KAKENHI Grant Numbers #24246061, #24656046, #25420321, #25420322.

  2. Novel asymmetric chitosan/PVP/nanocellulose wound dressing: In vitro and in vivo evaluation.

    Science.gov (United States)

    Poonguzhali, R; Khaleel Basha, S; Sugantha Kumari, V

    2018-06-01

    The present study was to develop a novel chitosan based symmetric and asymmetric bionanocomposite for potential wound dressing application. Chitosan (C)/Poly (vinyl pyrrolidone) (P)/nanocellulose (NC) membrane were fabricated by salt leaching method with the addition of 3% and 5% wt of nanocellulose. To obtain asymmetric material one side of the membrane was coated by stearic acid (S) which could form hydrophobic surface and another side acts as a hydrophilic surface. Nanocellulose of size 2-10nm was synthesized and characterized by TEM analysis. SEM showed the hydrophilic surface of asymmetric bionanocomposite consists of porous structure and hydrophobic surface is smooth and homogeneous. The results revealed that the Chitosan/PVP/Nanocellulose 3%-Stearic acid (CPNC3%-S) had a moderate swelling ratio, porosity, barrier and mechanical properties. Incorporation of nanocellulose into chitosan/PVP matrix could enhance the antibacterial activity. The hydrophobic surface of the CPNC3%-S bionanocomposite shows water repellent and antiadhesion properties towards E. coli bacteria and also the hydrophilic surface exhibit excellent antibacterial property and cytotoxicity towards bacterial pathogens. In vivo wound healing test shows better re-epithelialization and wound contraction compared with control and Chitosan/PVP-stearic acid (CP-S) bionanocomposite. Asymmetric bionanocomposite Chitosan/PVP/Nanocellulose coated with 3%-Stearic acid (CPNC3%-S) exhibited very good invitro cytocompatibility and enabled a faster wound healing than symmetric dressing, hence showing great potential to be applied as wound dressings. Copyright © 2018 Elsevier B.V. All rights reserved.

  3. Observation of asymmetric electromagnetic field profiles in chiral metamaterials

    Science.gov (United States)

    Hisamoto, Nobuyuki; Ueda, Tetsuya; Sawada, Kei; Tomita, Satoshi

    2018-02-01

    We experimentally observe asymmetric electromagnetic field profiles along two-dimensional chiral metamaterials. The asymmetric field profiles depending on the chirality and the operation frequency have been reproduced well by the numerical simulation. Around a chiral meta-atom, distribution of a Poynting vector is found to be shifted asymmetrically. These results are explained in terms of an analogy with the side-jump mechanism in the electronic anomalous Hall systems.

  4. Asymmetric forecasting and commitment policy in a robust control problem

    OpenAIRE

    Taro Ikeda

    2013-01-01

    This paper provides a piece of results regarding asymmetric forecasting and commitment monetary policy with a robust control algorithm. Previous studies provide no clarification of the connection between asymmetric preference and robust commitment policy. Three results emerge from general equilibrium modeling with asymmetric preference: (i) the condition for system stability implies an average inflation bias with respect to asymmetry (ii) the effect of asymmetry can be mitigated if policy mak...

  5. Asymmetric acoustic transmission in graded beam

    Energy Technology Data Exchange (ETDEWEB)

    Jing, Li, E-mail: lj94172350@hotmail.com [School of Mechanical Engineering and State Key laboratory for Strength and Vibration of Mechanical Structures, Xi’an Jiaotong University, Xi’an, Shaanxi 710049 (China); Wu, Jiu Hui, E-mail: ejhwu@mail.xjtu.edu.cn [School of Mechanical Engineering and State Key laboratory for Strength and Vibration of Mechanical Structures, Xi’an Jiaotong University, Xi’an, Shaanxi 710049 (China); Guan, Dong; Lu, Kuan [School of Mechanical Engineering and State Key laboratory for Strength and Vibration of Mechanical Structures, Xi’an Jiaotong University, Xi’an, Shaanxi 710049 (China); Gao, Nansha [School of Marine Science and Technology, Northwestern Polytechnical University, Xi’an, Shaanxi 710072 (China); Songhua, Cao [School of Mechanical Engineering and State Key laboratory for Strength and Vibration of Mechanical Structures, Xi’an Jiaotong University, Xi’an, Shaanxi 710049 (China)

    2016-12-01

    We demonstrate the dynamic effective material parameters and vibration performance of a graded beam. The structure of the beam was composed of several unit cells with different fill factors. The dispersion relations and energy band structures of each unit cell were calculated using the finite element method (FEM). The dynamic effective material parameters in each unit cell of the graded beam were determined by the dispersion relations and energy band structures. Longitudinal wave propagation was investigated using a numerical method and FEM. The results show that the graded beam allows asymmetric acoustic transmission over a wide range of frequencies.

  6. OFFICER AND COMMANDER IN ASYMMETRIC WARFARE OPERATIONS

    Directory of Open Access Journals (Sweden)

    Giuseppe CAFORIO

    2013-01-01

    Full Text Available Starting from the data of a field research conducted among soldiers with asymmetric warfare experiences from nine different countries, the author seeks to identify and shed light on the various problems that officers with command responsibilities had to face during their missions. A picture emerges of feelings and experiences relating to their first impression upon arriving in the theatre, relations with local armed forces, relations with the local population and local authorities, relations with NGOs, relations with other armies, the impact of the rules of engagement (ROEs, training and education, and operational experiences. The paper ends with a discussion of the lessons learned.

  7. Nanotribology of Symmetric and Asymmetric Liquid Lubricants

    Directory of Open Access Journals (Sweden)

    Shinji Yamada

    2010-03-01

    Full Text Available When liquid molecules are confined in a narrow gap between smooth surfaces, their dynamic properties are completely different from those of the bulk. The molecular motions are highly restricted and the system exhibits solid-like responses when sheared slowly. This solidification behavior is very dependent on the molecular geometry (shape of liquids because the solidification is induced by the packing of molecules into ordered structures in confinement. This paper reviews the measurements of confined structures and friction of symmetric and asymmetric liquid lubricants using the surface forces apparatus. The results show subtle and complex friction mechanisms at the molecular scale.

  8. The Asymmetric Effects of Investor Sentiment

    DEFF Research Database (Denmark)

    Lutz, Chandler

    2016-01-01

    We use the returns on lottery-like stocks and a dynamic factor model to construct a novel index of investor sentiment. This new measure is highly correlated with other behavioral indicators, but more closely tracks speculative episodes. Our main new finding is that the effects of sentiment...... are asymmetric: During peak-to-trough periods of investor sentiment (sentiment contractions), high sentiment predicts low future returns for the cross section of speculative stocks and for the market overall, whereas the relationship between sentiment and future returns is positive but relatively weak during...... trough-to-peak episodes (sentiment expansions). Overall, these results match theories and anecdotal accounts of investor sentiment....

  9. On asymmetric causal relationships in Petropolitics

    Directory of Open Access Journals (Sweden)

    Balan Feyza

    2016-01-01

    Full Text Available The aim of this paper is to examine whether the First Law of Petropolitics denominated by Friedman in 2006 is valid for OPEC countries. To do this, this paper analyses the relationship between political risk and oil supply by applying the asymmetric panel causality test suggested by Hatemi-J (2011 to these countries for the period 1984-2014. The results show that the First Law of Petropolitics is valid for Angola, Iraq, Kuwait, Libya, Nigeria, Qatar, Saudi Arabia, and the UAE, given that positive oil supply shocks significantly lead to negative political stability shocks, and negative oil supply shocks significantly lead to positive shocks in political stability.

  10. Asymmetric nuclear matter and neutron star properties

    International Nuclear Information System (INIS)

    Engvik, L.; Hjorth-Jensen, M.; Osnes, E.; Bao, G.; Oestgaard, E.

    1994-06-01

    Properties of neutron stars such as mass and radius, using a relativistic Dirac-Brueckner-Hartree-Fock approach, are calculated. Modern meson-exchange potential models are used to evaluate the G-matrix for asymmetric nuclear matter. For pure neutron matter the maximum mass is found to be M max ∼ 2.4M for a radius R ∼ 12 km. With a proton fraction of 30% the result is M max ∼ 2.1M for a radius R ∼ 10.5 km, close to the experimental values. The implications are discussed. 20 refs., 3 figs

  11. Two particle states in an asymmetric box

    International Nuclear Information System (INIS)

    Li Xin; Liu Chuan

    2004-01-01

    The exact two-particle energy eigenstates in an asymmetric rectangular box with periodic boundary conditions in all three directions are studied. Their relation with the elastic scattering phases of the two particles in the continuum are obtained. These results can be viewed as a generalization of the corresponding formulae in a cubic box obtained by Luescher before. In particular, the s-wave scattering length is related to the energy shift in the finite box. Possible applications of these formulae are also discussed

  12. Intramolecular and Transannular Diels-Alder Reactions

    DEFF Research Database (Denmark)

    Tanner, David Ackland; Ascic, Erhad

    2014-01-01

    Few reactions can compete with the Diels-Alder (DA) [4+2] cycloaddition for the rapid and efficient generation of molecular complexity. The DA reaction is atom-economic and stereospecific, as well as diastereo- and regioselective. The intramolecular version (IMDA) of the DA cycloaddition and its...... and dienophile, methods for acceleration of IMDA reactions (such as use of high pressure) and catalysis (using oxophilic or carbophilic metal complexes, Brønsted acids, and enzymes). The use of furans as diene components (IMDAF), intramolecular hetero-DA (IMHDA) and IMDA reactions with inverse electron demand...... are also covered. Applications of IMDA to asymmetric synthesis (from substrate control through to enantioselective catalysis, including organocatalysis) are presented, along with tandem sequences involving IMDA cycloaddition. A theme pervading the whole chapter is the use of IMDA reactions for the total...

  13. Asymmetrical Capacitors for Propulsion and the ISR Asymmetrical Capacitator Thruster, Experimental Results and Improved Designs

    Science.gov (United States)

    Canning, Francis; Winet, Ed; Ice, Bob; Melcher, Cory; Pesavento, Phil; Holmes, Alan; Butler, Carey; Cole, John; Campbell, Jonathan

    2004-01-01

    The outline of this viewgraph presentation on asymmetrical capacitor thruster development includes: 1) Test apparatus; 2) Devices tested; 3) Circuits used; 4) Data collected (Time averaged, Time resolved); 5) Patterns observed; 6) Force calculation; 7) Electrostatic modeling; 8) Understand it all.

  14. Influence of asymmetrical drawing radius deviation in micro deep drawing

    Science.gov (United States)

    Heinrich, L.; Kobayashi, H.; Shimizu, T.; Yang, M.; Vollertsen, F.

    2017-09-01

    Nowadays, an increasing demand for small metal parts in electronic and automotive industries can be observed. Deep drawing is a well-suited technology for the production of such parts due to its excellent qualities for mass production. However, the downscaling of the forming process leads to new challenges in tooling and process design, such as high relative deviation of tool geometry or blank displacement compared to the macro scale. FEM simulation has been a widely-used tool to investigate the influence of symmetrical process deviations as for instance a global variance of the drawing radius. This study shows a different approach that allows to determine the impact of asymmetrical process deviations on micro deep drawing. In this particular case the impact of an asymmetrical drawing radius deviation and blank displacement on cup geometry deviation was investigated for different drawing ratios by experiments and FEM simulation. It was found that both variations result in an increasing cup height deviation. Nevertheless, with increasing drawing ratio a constant drawing radius deviation has an increasing impact, while blank displacement results in a decreasing offset of the cups geometry. This is explained by different mechanisms that result in an uneven cup geometry. While blank displacement leads to material surplus on one side of the cup, an unsymmetrical radius deviation on the other hand generates uneven stretching of the cups wall. This is intensified for higher drawing ratios. It can be concluded that the effect of uneven radius geometry proves to be of major importance for the production of accurately shaped micro cups and cannot be compensated by intentional blank displacement.

  15. Asymmetrically deformed states of thorium isotopes during fission process

    International Nuclear Information System (INIS)

    Blons, J.

    1982-05-01

    Some theoretical considerations are recalled on fission barriers calculated from macroscopic, microscopic or macroscopic-microscopic and ''thorium anomaly'' problem is set. Experimental techniques used to measure fission cross sections in (n,f) reactions near the threshold are described. Fission dectector is described; stray resonance problems and retrodiffused neutrons are discussed. Results obtained in experimental study of 230 Th(n,f) and 232 Th(n,f) reactions are presented. They are compared with results obtained in other laboratories. The analysis model which allows to describe a (n,f) reaction is exposed. The compound nucleus formation cross section and transmission coefficients in neutron and gamma output channel are presented according to neutron energy for each value of angular moment and parity. Cross-section analysis and angular distribution obtained respectively in 230 Th(n,f) and 232 Th(n,f) reactions is exposed. Result interpretation show new aspects of nuclei rotational spectra and new nuclear forms [fr

  16. Effect of constant and uniform heat generation on the thermal behaviour of porous solids with asymmetric boundary conditions

    International Nuclear Information System (INIS)

    Heggs, P.J.; Dare, J.

    2007-01-01

    The generation of heat due to chemical reaction will have a significant effect on the temperature profile and heat transfer within a porous body. Most forms of analysis only consider the symmetric situation or else make use of various assumptions that greatly simplify the analysis, for example: the Semenov or the Frak-kamenetskii models. The objective of this paper is to develop an improved understanding of the thermal behaviour of a porous body with uniform internal heat generation, which is in contact with two fluids at different temperatures and with different heat transfer coefficients. The mathematical representation is a one dimensional Poisson equation with asymmetric boundary conditions. The analytical solution reveals four regimes for heat flow: (a) purely conduction at zero heat generation, (b) a combination of heat flow by conduction through the body between the hot and cold fluids and all heat generated passing to the colder fluid, (c) no heat flow by conduction between the two fluids and all heat generated passing the cold flow - the so-called critical heat generation, and (d) the heat generated passes to both the cold and hot fluids and there is a maximum temperature within the body greater than that of the hot fluid, the so-called supercritical region. Expressions are developed to allow predictions of the conditions pertaining to each regime. This new representation covers the Semenov and Frank-Kamenetskii models and all possible solutions intermediate of the them. (authors)

  17. [Asymmetric hypertrophy of the masticatory muscles].

    Science.gov (United States)

    Arzul, L; Corre, P; Khonsari, R H; Mercier, J-M; Piot, B

    2012-06-01

    Hypertrophy of the masticatory muscles most commonly affects the masseter. Less common cases of isolated or associated temporalis hypertrophy are also reported. Parafunctional habits, and more precisely bruxism, can favor the onset of the hypertrophy. This condition is generally idiopathic and can require both medical and/or surgical management. A 29-year-old patient was referred to our department for an asymmetric swelling of the masticatory muscles. Physical examination revealed a bilateral hypertrophy of the masticatory muscles, predominantly affecting the right temporalis and the left masseter. Major bruxism was assessed by premature dental wearing. The additional examinations confirmed the isolated muscle hypertrophy. Benign asymmetric hypertrophy of the masticatory muscles promoted by bruxism was diagnosed. Treatment with injections of type A botulinum toxin was conducted in association with a splint and relaxation. Its effectiveness has been observed at six months. Few cases of unilateral or bilateral temporalis hypertrophy have been reported, added to the more common isolated masseter muscles hypertrophy. The diagnosis requires to rule out secondary hypertrophies and tumors using Magnetic Resonance Imaging. The condition is thought to be favoured by parafunctional habits such as bruxism. The conservative treatment consists in reducing the volume of the masticatory muscles using intramuscular injections of type A botulinum toxin. Other potential conservative treatments are wearing splints and muscle relaxant drugs. Surgical procedures aiming to reduce the muscle volume and/or the bone volume (mandibular gonioplasty) can be proposed. Copyright © 2012 Elsevier Masson SAS. All rights reserved.

  18. Asymmetric Uncertainty Expression for High Gradient Aerodynamics

    Science.gov (United States)

    Pinier, Jeremy T

    2012-01-01

    When the physics of the flow around an aircraft changes very abruptly either in time or space (e.g., flow separation/reattachment, boundary layer transition, unsteadiness, shocks, etc), the measurements that are performed in a simulated environment like a wind tunnel test or a computational simulation will most likely incorrectly predict the exact location of where (or when) the change in physics happens. There are many reasons for this, includ- ing the error introduced by simulating a real system at a smaller scale and at non-ideal conditions, or the error due to turbulence models in a computational simulation. The un- certainty analysis principles that have been developed and are being implemented today do not fully account for uncertainty in the knowledge of the location of abrupt physics changes or sharp gradients, leading to a potentially underestimated uncertainty in those areas. To address this problem, a new asymmetric aerodynamic uncertainty expression containing an extra term to account for a phase-uncertainty, the magnitude of which is emphasized in the high-gradient aerodynamic regions is proposed in this paper. Additionally, based on previous work, a method for dispersing aerodynamic data within asymmetric uncer- tainty bounds in a more realistic way has been developed for use within Monte Carlo-type analyses.

  19. D mesons in asymmetric nuclear matter

    International Nuclear Information System (INIS)

    Mishra, Amruta; Mazumdar, Arindam

    2009-01-01

    We calculate the in-medium D and D meson masses in isospin-asymmetric nuclear matter in an effective chiral model. The D and D mass modifications arising from their interactions with the nucleons and the scalar mesons in the effective hadronic model are seen to be appreciable at high densities and have a strong isospin dependence. These mass modifications can open the channels of the decay of the charmonium states (Ψ ' ,χ c ,J/Ψ) to DD pairs in dense hadronic matter. The isospin asymmetry in the doublet D=(D 0 ,D + ) is seen to be particularly appreciable at high densities and should show in observables such as their production and flow in asymmetric heavy-ion collisions in the compressed baryonic matter experiments in the future facility of FAIR, GSI. The results of the present work are compared to calculations of the D(D) in-medium masses in the literature using the QCD sum rule approach, quark meson coupling model, and coupled channel approach as well as to those from studies of quarkonium dissociation using heavy-quark potentials from lattice QCD at finite temperatures

  20. On the Collisionless Asymmetric Magnetic Reconnection Rate

    Science.gov (United States)

    Liu, Yi-Hsin; Hesse, M.; Cassak, P. A.; Shay, M. A.; Wang, S.; Chen, L.-J.

    2018-04-01

    A prediction of the steady state reconnection electric field in asymmetric reconnection is obtained by maximizing the reconnection rate as a function of the opening angle made by the upstream magnetic field on the weak magnetic field (magnetosheath) side. The prediction is within a factor of 2 of the widely examined asymmetric reconnection model (Cassak & Shay, 2007, https://doi.org/10.1063/1.2795630) in the collisionless limit, and they scale the same over a wide parameter regime. The previous model had the effective aspect ratio of the diffusion region as a free parameter, which simulations and observations suggest is on the order of 0.1, but the present model has no free parameters. In conjunction with the symmetric case (Liu et al., 2017, https://doi.org/10.1103/PhysRevLett.118.085101), this work further suggests that this nearly universal number 0.1, essentially the normalized fast-reconnection rate, is a geometrical factor arising from maximizing the reconnection rate within magnetohydrodynamic-scale constraints.