WorldWideScience

Sample records for single transfer reactions

  1. Study of single nucleon transfer in α + 12C reaction

    International Nuclear Information System (INIS)

    Pandey, R.; Rana, T.K.; Dey, A.; Bhattacharya, C.; Kundu, S.; Banerjee, K.; Mukherjee, G.; Ghosh, T.K.; Meena, J.K.; Pai, H.; Gohil, M.; Bhattacharya, S.; Biswas, M.

    2011-01-01

    Nucleon transfer reactions are of great significance for understanding the nuclear structure both for direct reaction studies as well as for production of nuclear states. Transfer reactions are simplest to interpret when either the initial and final state of the target nucleus has spin zero and when the conditions are such that the transition from the initial and final states occurs to a good approximation in a single step. In this paper, the measurement of angular momentum distribution and calculation of the spectroscopic factor for one nucleon transfer reaction in α + 12 C reaction have been reported

  2. Single-collision studies of energy transfer and chemical reaction

    Energy Technology Data Exchange (ETDEWEB)

    Valentini, J.J. [Columbia Univ., New York, NY (United States)

    1993-12-01

    The research focus in this group is state-to-state dynamics of reaction and energy transfer in collisions of free radicals such as H, OH, and CH{sub 3} with H{sub 2}, alkanes, alcohols and other hydrogen-containing molecules. The motivation for the work is the desire to provide a detailed understanding of the chemical dynamics of prototype reactions that are important in the production and utilization of energy sources, most importantly in combustion. The work is primarily experimental, but with an important and growing theoretical/computational component. The focus of this research program is now on reactions in which at least one of the reactants and one of the products is polyatomic. The objective is to determine how the high dimensionality of the reactants and products differentiates such reactions from atom + diatom reactions of the same kinematics and energetics. The experiments use highly time-resolved laser spectroscopic methods to prepare reactant states and analyze the states of the products on a single-collision time scale. The primary spectroscopic tool for product state analysis is coherent anti-Stokes Raman scattering (CARS) spectroscopy. CARS is used because of its generality and because the extraction of quantum state populations from CARS spectra is straightforward. The combination of the generality and easy analysis of CARS makes possible absolute cross section measurements (both state-to-state and total), a particularly valuable capability for characterizing reactive and inelastic collisions. Reactant free radicals are produced by laser photolysis of appropriate precursors. For reactant vibrational excitation stimulated Raman techniques are being developed and implemented.

  3. Single-particle and collective states in transfer reactions

    International Nuclear Information System (INIS)

    Lhenry, I.; Suomijaervi, T.; Giai, N. van

    1993-01-01

    The possibility to excite collective states in transfer reactions induced by heavy ions is studied. Collective states are described within the Random Phase Approximation (RPA) and the collectivity is defined according to the number of configurations contributing to a given state. The particle transfer is described within the Distorted Wave Born Approximation (DWBA). Calculations are performed for two different stripping reactions: 207 Pb( 20 Ne, 19 Ne) 208 Pb and 59 Co( 20 Ne, 19 F) 60 Ni at 48 MeV/nucleon for which experimental data are available. The calculation shows that a sizeable fraction of collective strength can be excited in these reactions. The comparison with experiment shows that this parameter-free calculation qualitatively explains the data. (author) 19 refs.; 10 figs

  4. Electronic state selectivity in dication-molecule single electron transfer reactions: NO(2+) + NO.

    Science.gov (United States)

    Parkes, Michael A; Lockyear, Jessica F; Schröder, Detlef; Roithová, Jana; Price, Stephen D

    2011-11-07

    The single-electron transfer reaction between NO(2+) and NO, which initially forms a pair of NO(+) ions, has been studied using a position-sensitive coincidence technique. The reactivity in this class of collision system, which involves the interaction of a dication with its neutral precursor, provides a sensitive test of recent ideas concerning electronic state selectivity in dicationic single-electron transfer reactions. In stark contrast to the recently observed single-electron transfer reactivity in the analogous CO(2)(2+)/CO(2) and O(2)(2+)/O(2) collision systems, electron transfer between NO(2+) and NO generates two product NO(+) ions which behave in an identical manner, whether the ions are formed from NO(2+) or NO. This observed behaviour is in excellent accord with the recently proposed rationalization of the state selectivity in dication-molecule SET reactions using simple propensity rules involving one-electron transitions. This journal is © the Owner Societies 2011

  5. Mass transfer with complex reversible chemical reactions I. Single reversible chemical reaction

    NARCIS (Netherlands)

    Versteeg, Geert; Kuipers, J.A.M.; van Beckum, F.P.H.; van Swaaij, Willibrordus Petrus Maria

    1989-01-01

    An improved numerical technique was used in order to develop an absorption model with which it is possible to calculate rapidly absorption rates for the phenomenon of mass transfer accompanied by a complex reversible chemical reaction. This model can be applied for the calculation of the mass

  6. Single particle transfer reactions: what can they tell us about vibrational states

    International Nuclear Information System (INIS)

    Hering, W.R.

    1975-01-01

    The topic discussed concerns single particle transfer reactions (SPTR) which are, in general, used to study SP states. However, good SP states are rare objects in nature and people who try to look for them have often to settle with something less than ideal. Indeed the picture of a pure SP state is physically not even reasonable. It means that a nucleon is moving around a core nucleus which stays in its ground state: a process which one could call equivalent to elastic scattering of a nucleon which is not free but rather in a bound state. However it is shown that inelastic scattering is a very strong competitor to elastic scattering if the nucleus possesses states of high collectivity. Thus one would expect inelastic scattering to happen also while the nucleon is bound. This is a very intuitive picture of what is called the fragmentation of SP states. A final state psi sub(B) is populated by the transfer reaction A + a → B + b where psi sub(B) = α 1 phi 1 phi sub(A)(0) + α 2 phi 2 phi sub(A)(lambda). Hence the population of psi sub(B) automatically involves the collective state phi sub(A)(lambda). A discussion of how one can get information about phi sub(A)(lambda) out of the experimental data is given. (Auth.)

  7. Mass transfer with complex reversible chemical reactions—I. Single reversible chemical reaction

    NARCIS (Netherlands)

    Versteeg, G.F.; Kuipers, J.A.M.; Beckum, F.P.H. van; Swaaij, W.P.M. van

    1989-01-01

    An improved numerical technique was used in order to develop an absorption model with which it is possible to calculate rapidly absorption rates for the phenomenon of mass transfer accompanied by a complex reversible chemical reaction. This model can be applied for the calculation of the mass

  8. Electron transfer reactions

    CERN Document Server

    Cannon, R D

    2013-01-01

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

  9. Studies of Nuclei Close to 132Sn Using Single-Neutron Transfer Reactions

    International Nuclear Information System (INIS)

    Jones, K.L.; Pain, S.D.; Kozub, R.L.; Adekola, Aderemi S.; Bardayan, Daniel W.; Blackmon, Jeff C.; Catford, Wilton N.; Chae, K.Y.; Chipps, K.; Cizewski, J.A.; Erikson, Luke; Gaddis, A.L.; Greife, U.; Grzywacz, R.K.; Harlin, Christopher W.; Hatarik, Robert; Howard, Joshua A.; James, J.; Kapler, R.; Krolas, W.; Liang, J. Felix; Ma, Zhanwen; Matei, Catalin; Moazen, Brian; Nesaraja, Caroline D.; O'Malley, Patrick; Patterson, N.P.; Paulauskas, Stanley; Shapira, Dan; Shriner, J.F. Jr.; Sikora, M.; Sissom, D.J.; Smith, Michael Scott; Swan, T.P.; Thomas, J.S.; Wilson, Gemma L.

    2009-01-01

    Neutron transfer reactions were performed in inverse kinematics using radioactive ion beams of 132Sn, 130Sn, and 134Te and deuterated polyethylene targets. Preliminary results are presented. The Q-value spectra for 133Sn, 131Sn and 135Te reveal a number of previously unobserved peaks. The angular distributions are compatible with the expected lf7/2 nature of the ground state of 133Sn, and 2p3/2 for the 3.4 MeV state in 131Sn.

  10. Electronic state selectivity in dication-molecule single electron transfer reactions: NO+ + NO

    Czech Academy of Sciences Publication Activity Database

    Parkes, M. A.; Lockyear, J. F.; Schröder, Detlef; Roithová, J.; Price, S. D.

    2011-01-01

    Roč. 13, č. 41 (2011), s. 18386-18392 ISSN 1463-9076 R&D Projects: GA ČR GA203/09/1223 Institutional research plan: CEZ:AV0Z40550506 Keywords : coincidence experiments * dications * electron transfer * energy partitioning * state selectivity Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.573, year: 2011

  11. A single residue controls electron transfer gating in photosynthetic reaction centers

    Czech Academy of Sciences Publication Activity Database

    Shlyk, O.; Samish, I.; Matěnová, M.; Dulebo, A.; Poláková, H.; Kaftan, David; Scherz, A.

    2017-01-01

    Roč. 7, MAR 16 (2017), s. 1-13, č. článku 44580. ISSN 2045-2322 R&D Projects: GA ČR GA15-00703S; GA MŠk(CZ) LO1416 Institutional support: RVO:61388971 Keywords : BACTERIAL REACTION CENTERS * INDUCED STRUCTURAL-CHANGES * ATOMIC-FORCE MICROSCOPE Subject RIV: EE - Microbiology, Virology OBOR OECD: Microbiology Impact factor: 4.259, year: 2016

  12. Nucleon transfer reactions with radioactive beams

    Science.gov (United States)

    Wimmer, K.

    2018-03-01

    Transfer reactions are a valuable tool to study the single-particle structure of nuclei. At radioactive beam facilities transfer reactions have to be performed in inverse kinematics. This creates a number of experimental challenges, but it also has some advantages over normal kinematics measurements. An overview of the experimental and theoretical methods for transfer reactions, especially with radioactive beams, is presented. Recent experimental results and highlights on shell evolution in exotic nuclei are discussed.

  13. Single and multinucleon transfer in {sup 19}F,{sup 16}O,{sup 12}C+{sup 232}Th reactions at near barrier energies

    Energy Technology Data Exchange (ETDEWEB)

    Biswas, D.C.; Choudhury, R.K.; Nayak, B.K.; Nadkarni, D.M. [Nuclear Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Ramamurthy, V.S. [Department of Science and Technology, New Delhi 110 016 (India)

    1997-10-01

    Cross sections for single (1p) and multinucleon (2p,{sup 4}He, and p{sup 4}He) transfer reactions have been measured in {sup 19}F, {sup 16}O, {sup 12}C+{sup 232}Th systems at beam energies around the Coulomb barrier. Angular distributions and energy spectra of the projectilelike particles exhibit characteristics of direct transfer reactions. The ratio of the transfer to total reaction (transfer+fusion-fission) cross section is observed to be significantly smaller for the {sup 12}C projectile, as compared to that for {sup 19}F and {sup 16}O projectiles. All the systems show large transfer cross sections relative to the total reaction cross section at subbarrier energies. The angular distribution data were analyzed in terms of transfer probabilities to derive the slope parameter ({alpha}) for the stripping of 1p and 2p in the case of {sup 16}O and {sup 12}C projectiles and for 1p, {sup 4}He and correlated (p{sup 4}He) stripping in the case of {sup 19}F projectile, for comparison with the semiclassical calculations. It is observed that the semiclassical picture is valid for 1p transfer at energies near the Coulomb barrier, whereas for correlated 2p, {sup 4}He, and (p{sup 4}He) multinucleon transfers, the experimental values of {alpha} are anomalously small as compared to the semiclassical calculations even at subbarrier energies. At the above-barrier energies, the slope anomaly can be explained after inclusion of the nuclear effects in semiclassical calculations. {copyright} {ital 1997} {ital The American Physical Society}

  14. Guanine radical reaction processes: a computational description of proton transfer in X-irradiated 9-ethylguanine single crystals.

    Science.gov (United States)

    Jayatilaka, Nayana; Nelson, William H

    2008-12-25

    Computational methods based on DFT procedures have been used to investigate proton-transfer processes in irradiated 9-ethylguanine crystals. Previous experimental results from X-irradiation and study of this system at 10 K found significant concentrations of two main products, R1, formed by N7-hydrogenation of the purine ring, and R2, the primary one-electron oxidation product (Jayatilaka, N.; Nelson, W. H. J. Phys. Chem. B 2007, 111, 7887). The objective of this work is to describe the processes leading to these products using computational methods that take into account molecular packing and bulk dielectric properties. The basic concept is that a proton will transfer following ionization if the net electronic energy of the system, consisting of the donor plus the acceptor plus any intervening molecules, becomes lower. Three approaches were used to investigate this concept, two based on energies computed for single molecules and one based on energies computed for two-molecule clusters arranged as in the crystals. The results are that the methods successfully predict the observed behavior, that it is energetically favorable on one-electron reduction for proton H1 to transfer from a neutral molecule to N7 of the neighbor, forming the N7-hydrogenated product, and that there is virtually no energy advantage for a proton to transfer upon one-electron oxidation. The results also support the proposal that the C8 H-addition radical, found only upon irradiation at 300 K, was the product of intramolecular transfer of the H7 proton to C8 in a process apparently requiring sufficient thermal energy for activation. Finally, the computations predict hyperfine couplings and tensors in very good agreement with those from experiment, thereby providing additional evidence for the success of the computations in describing the experimental observations.

  15. A unified diabatic description for electron transfer reactions, isomerization reactions, proton transfer reactions, and aromaticity.

    Science.gov (United States)

    Reimers, Jeffrey R; McKemmish, Laura K; McKenzie, Ross H; Hush, Noel S

    2015-10-14

    While diabatic approaches are ubiquitous for the understanding of electron-transfer reactions and have been mooted as being of general relevance, alternate applications have not been able to unify the same wide range of observed spectroscopic and kinetic properties. The cause of this is identified as the fundamentally different orbital configurations involved: charge-transfer phenomena involve typically either 1 or 3 electrons in two orbitals whereas most reactions are typically closed shell. As a result, two vibrationally coupled electronic states depict charge-transfer scenarios whereas three coupled states arise for closed-shell reactions of non-degenerate molecules and seven states for the reactions implicated in the aromaticity of benzene. Previous diabatic treatments of closed-shell processes have considered only two arbitrarily chosen states as being critical, mapping these states to those for electron transfer. We show that such effective two-state diabatic models are feasible but involve renormalized electronic coupling and vibrational coupling parameters, with this renormalization being property dependent. With this caveat, diabatic models are shown to provide excellent descriptions of the spectroscopy and kinetics of the ammonia inversion reaction, proton transfer in N2H7(+), and aromaticity in benzene. This allows for the development of a single simple theory that can semi-quantitatively describe all of these chemical phenomena, as well as of course electron-transfer reactions. It forms a basis for understanding many technologically relevant aspects of chemical reactions, condensed-matter physics, chemical quantum entanglement, nanotechnology, and natural or artificial solar energy capture and conversion.

  16. Probing the Energy Transfer Dynamics of Photosynthetic Reaction Center Complexes Through Hole-Burning and Single-Complex Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Riley, Kerry Joseph [Iowa State Univ., Ames, IA (United States)

    2007-01-01

    Photosynthesis is the process by which light energy is used to drive reactions that generate sugars to supply energy for cellular processes. It is one of the most important fundamental biological reactions and occurs in both prokaryotic (e.g. bacteria) and eukaryotic (e.g. plants and algae) organisms. Photosynthesis is also remarkably intricate, requiring the coordination of many different steps and reactions in order to successfully transform absorbed solar energy into a biochemical usable form of energy. However, the net reaction for all photosynthetic organisms can be reduced to the following, deceptively general, equation developed by Van Niel[1] H2 - D + Aimplieshv A - H2 + D where H2-D is the electron donor, e.g. H2O, H2S. A is the electron acceptor, e.g. CO2, and A-H2 is the synthesized sugar. Amazingly, this simple net equation is responsible for creating the oxidizing atmosphere of Earth and the recycling of CO2, both of which are necessary for the sustainment of the global ecosystem.

  17. Study of single particle properties of nuclei in the region of the "island of inversion" by means of neutron-transfer reactions

    CERN Multimedia

    Kruecken, R; Voulot, D

    2007-01-01

    We are aiming at the investigation of single particle properties of neutron-rich nuclei in the region of the "island of inversion" where intruder states from the $\\{fp}$-shell favour deformed ground states instead of the normal spherical $\\textit{sd}$-shell states. As first experiment, we propose to study single particle states in the neutron-rich isotope $^{31}$Mg. The nucleus will be populated by a one-neutron transfer reaction with a $^{30}$Mg beam at 3 MeV/u obtained from REX-ISOLDE impinging on a CD$_{2}$ target. The $\\gamma$-rays will be detected by the MINIBALL array and the particles by a newly built set-up of segmented Si detectors with a angular coverage of nearly 4$\\pi$. Relative spectroscopic factors extracted from the cross sections will enable us to pin down the configurations of the populated states. These will be compared to recent shell model calculations involving new residual interactions. This will shed new light on the evolution of single particle structure leading to the breaking of the ...

  18. Oxidative Catalysis Using the Stoichiometric Oxidant as a Reagent: An Efficient Strategy for Single-Electron-Transfer-Induced Tandem Anion-Radical Reactions

    Czech Academy of Sciences Publication Activity Database

    Kafka, František; Holan, Martin; Hidasová, Denisa; Pohl, Radek; Císařová, I.; Klepetářová, Blanka; Jahn, Ullrich

    2014-01-01

    Roč. 53, č. 37 (2014), s. 9944-9948 ISSN 1433-7851 R&D Projects: GA ČR GA13-40188S Institutional support: RVO:61388963 Keywords : cyclization * domino reactions * electron transfer * Michael addition * radical reactions Subject RIV: CC - Organic Chemistry Impact factor: 11.261, year: 2014

  19. Single Electron Transfer-Promoted Photochemical Reactions of Secondary N-Trimethylsilylmethyl-N-benzylamines Leading to Aminomethylation of Fullerene C60.

    Science.gov (United States)

    Lim, Suk Hyun; Jeong, Ho Cheol; Sohn, Youngku; Kim, Young-Il; Cho, Dae Won; Woo, Hee-Jae; Shin, Ik-Soo; Yoon, Ung Chan; Mariano, Patrick S

    2016-03-18

    Photoreactions between C60 and secondary N-trimethylsilylmethyl-N-benzylamines were explored to evaluate the feasibility of a new method for secondary aminomethylation of electron acceptors. The results show that photoreactions of C60 with these secondary amines in 10% EtOH-toluene occur to form aminomethyl-1,2-dihydrofullerenes predominantly through a pathway involving single electron transfer (SET)-promoted formation of secondary aminium radicals followed by preferential loss of the α-trimethylsilyl group. The aminomethyl radicals formed in this manner then couple with C60 or C60(•-) to form radical or anion precursors of the aminomethyl-1,2-dihydrofullerenes. In contrast to thermal and photochemical strategies developed previously, the new SET photochemical approach using α-trimethylsilyl-substituted secondary amines is both mild and efficient, and as a result, it should be useful in broadening the library of substituted fullerenes. Moreover, the results should have an impact on the design of SET-promoted C-C bond forming reactions. Specifically, introduction of an α-trimethylsilyl group leads to a change in the chemoselectivity of SET-promoted reactions of secondary amines with acceptors that typically favor aminium radical N-H deprotonation, leading to N-C bond formation. Finally, symmetric and unsymmetric fulleropyrrolidines are also generated in yields that are highly dependent on the electronic properties of arene ring substituents in amines, irradiation time, and solvent.

  20. Study of single particle properties of neutron-rich Na isotopes on the "shore of the island of inversion" by means of neutron-transfer reactions

    CERN Multimedia

    Reiter, P; Blazhev, A A; Riisager, K; Bastin, B; Tengborn, E A; Kruecken, R; Voulot, D; Jeppesen, H B; Hadinia, B; Gernhaeuser, R A; Fynbo, H O U; Georgiev, G P; Habs, D; Fraile prieto, L M; Chapman, R; Nilsson, T; Diriken, J V J; Jenkins, D G; Kroell, T; Leske, J; Huyse, M L; Patronis, N

    We aim at the investigation of single particle properties of neutron-rich Na isotopes around the "shore of the island of inversion". As first experiment of this programme, we propose to study excited states in the isotope $^{29}$Na by a one-neutron transfer reaction with a $^{28}$Na beam at 3 MeV/u obtained from REX-ISOLDE impinging on a CD$_{2}$-target. The $\\gamma$-rays will be detected by the MINIBALL array and the particles by the T-REX array of segmented Si detectors. The main physics aims are to extract from the relative spectroscopic factors information on the configurations contributing to the wave functions of the populated states and, secondly, to identify and characterize negative parity states whose excitation energies reflect directly the N= 28 gap in this region. The results will be compared to recent shell model calculations involving new residual interactions. This will shed new light on the evolution of single particle structure and help to understand the underlying physics relevant for the f...

  1. Single step synthesis of gold-amino acid composite, with the evidence of the catalytic hydrogen atom transfer (HAT) reaction, for the electrochemical recognition of Serotonin

    Science.gov (United States)

    Choudhary, Meenakshi; Siwal, Samarjeet; Nandi, Debkumar; Mallick, Kaushik

    2016-03-01

    A composite architecture of amino acid and gold nanoparticles has been synthesized using a generic route of 'in-situ polymerization and composite formation (IPCF)' [1,2]. The formation mechanism of the composite has been supported by a model hydrogen atom (H•≡H++e-) transfer (HAT) type of reaction which belongs to the proton coupled electron transfer (PCET) mechanism. The 'gold-amino acid composite' was used as a catalyst for the electrochemical recognition of Serotonin.

  2. Scattering and transfer reactions with heavy ions

    International Nuclear Information System (INIS)

    Hussein, M.S.

    From the elastic scattering analysis the input parameters are found for the inelastic scattering analysis and the transfer reactions of the heavy ion reactions. The main theme reported is the likeness and conection among these processes. (L.C.) [pt

  3. Proton transfer reaction - mass spectrometry

    International Nuclear Information System (INIS)

    Cappellin, L.

    2012-01-01

    Proton transfer reaction mass spectrometry (PTR-MS) provides on-line monitoring of volatile organic compounds (VOCs) with a low detection threshold and a fast response time. Commercially available set-ups are usually based on quadrupole analysers but recently new instruments based on time-of-flight (PTR-ToF-MS) analysers have been proposed and commercialized. PTR-MS has been successfully applied to a variety of fields including environmental science, food science and technology, plant physiology and medical science. Many new challenges arise from the newly available PTR-ToF-MS instruments, ranging from mass calibration and absolute VOC concentration determination to data mining and sample classification. This thesis addresses some of these problems in a coherent framework. Moreover, relevant applications in food science and technology are presented. It includes twelve papers published in peer reviewed journals. Some of them address methodological issues regarding PTR-ToF-MS; the others contain applicative studies of PTR-ToF-MS to food science and technology. Among them, there are the first two published applications of PTR-ToF-MS in this field. (author)

  4. Single-Molecule Interfacial Electron Transfer

    Energy Technology Data Exchange (ETDEWEB)

    Lu, H. Peter [Bowling Green State Univ., Bowling Green, OH (United States). Dept. of Chemistry and Center for Photochemical Sciences

    2017-11-28

    This project is focused on the use of single-molecule high spatial and temporal resolved techniques to study molecular dynamics in condensed phase and at interfaces, especially, the complex reaction dynamics associated with electron and energy transfer rate processes. The complexity and inhomogeneity of the interfacial ET dynamics often present a major challenge for a molecular level comprehension of the intrinsically complex systems, which calls for both higher spatial and temporal resolutions at ultimate single-molecule and single-particle sensitivities. Combined single-molecule spectroscopy and electrochemical atomic force microscopy approaches are unique for heterogeneous and complex interfacial electron transfer systems because the static and dynamic inhomogeneities can be identified and characterized by studying one molecule at a specific nanoscale surface site at a time. The goal of our project is to integrate and apply these spectroscopic imaging and topographic scanning techniques to measure the energy flow and electron flow between molecules and substrate surfaces as a function of surface site geometry and molecular structure. We have been primarily focusing on studying interfacial electron transfer under ambient condition and electrolyte solution involving both single crystal and colloidal TiO2 and related substrates. The resulting molecular level understanding of the fundamental interfacial electron transfer processes will be important for developing efficient light harvesting systems and broadly applicable to problems in fundamental chemistry and physics. We have made significant advancement on deciphering the underlying mechanism of the complex and inhomogeneous interfacial electron transfer dynamics in dyesensitized TiO2 nanoparticle systems that strongly involves with and regulated by molecule-surface interactions. We have studied interfacial electron transfer on TiO2 nanoparticle surfaces by using ultrafast single

  5. Quantifying electron transfer reactions in biological systems

    DEFF Research Database (Denmark)

    Sjulstok, Emil Sjulstok; Olsen, Jógvan Magnus Haugaard; Solov'yov, Ilia A

    2015-01-01

    to deduce the driving force for the electron transfer reaction and to establish those interactions that play the major role in propelling the electron. The suggested approach is seen as a general recipe to treat electron transfer events in biological systems computationally, and we utilize it to describe...

  6. Single-Molecule Interfacial Electron Transfer

    Energy Technology Data Exchange (ETDEWEB)

    Ho, Wilson [Univ. of California, Irvine, CA (United States)

    2018-02-03

    Interfacial electron transfer (ET) plays an important role in many chemical and biological processes. Specifically, interfacial ET in TiO2-based systems is important to solar energy technology, catalysis, and environmental remediation technology. However, the microscopic mechanism of interfacial ET is not well understood with regard to atomic surface structure, molecular structure, bonding, orientation, and motion. In this project, we used two complementary methodologies; single-molecule fluorescence spectroscopy, and scanning-tunneling microscopy and spectroscopy (STM and STS) to address this scientific need. The goal of this project was to integrate these techniques and measure the molecular dependence of ET between adsorbed molecules and TiO2 semiconductor surfaces and the ET induced reactions such as the splitting of water. The scanning probe techniques, STM and STS, are capable of providing the highest spatial resolution but not easily time-resolved data. Single-molecule fluorescence spectroscopy is capable of good time resolution but requires further development to match the spatial resolution of the STM. The integrated approach involving Peter Lu at Bowling Green State University (BGSU) and Wilson Ho at the University of California, Irvine (UC Irvine) produced methods for time and spatially resolved chemical imaging of interfacial electron transfer dynamics and photocatalytic reactions. An integral aspect of the joint research was a significant exchange of graduate students to work at the two institutions. This project bridged complementary approaches to investigate a set of common problems by working with the same molecules on a variety of solid surfaces, but using appropriate techniques to probe under ambient (BGSU) and ultrahigh vacuum (UCI) conditions. The molecular level understanding of the fundamental interfacial electron transfer processes obtained in this joint project will be important for developing efficient light harvesting

  7. Investigations of Spectroscopic Factors and Sum Rules from the Single Neutron Transfer Reaction 111Cd(d→$\\overrightarrow {\\rm{d}} $,p112Cd

    Directory of Open Access Journals (Sweden)

    Jamieson D.S.

    2014-03-01

    Full Text Available Cadmium isotopes have been presented for decades as excellent examples of vibrational nuclei, with low-lying levels interpreted as multi-phonon quadrupole, octupole, and mixed-symmetry states. A large amount of spectroscopic data has been obtained through various experimental studies of cadmiumisotopes. In the present work, the 111Cd(d→$\\overrightarrow {\\rm{d}} $,p112Cd reaction was used to investigate the single-particle structure of the 112Cd nucleus. A 22 MeV beam of polarized deuterons was obtained at the Maier-Leibnitz laboratory in Garching, Germany. The reaction ejectiles were momentum analyzed using a Q3D spectrograph, and 130 levels have been identified up to 4.2 MeV of excitation energy. Using DWBA analysis with optical model calculations, spin-parity assignments have been made for observed levels, and spectroscopic factors have been extracted from the experimental angular distributions of differential cross section and analyzing power. In this high energy resolution investigation, many additional levels have been observed compared with the previous (d,p study using 8 MeV deuterons [1]. There were a total of 44 new levels observed, and the parity assignments of 34 levels were improved.

  8. Recent Developments in Electron Transfer Reactions.

    Science.gov (United States)

    1987-05-29

    Developments in ElectronTransfer Reactions by R.A. Marcus Prepared for Publication in Nouveau J. Chimie California Institute of Technology Noyes... coordination shell of the reactants. Comparison of the various predictions with the experimental data has been described in the review with Sutin.1 Electron

  9. Chemical Transfer (Single Small-Scale) Facility

    Data.gov (United States)

    Federal Laboratory Consortium — Description/History: Chemistry laboratoryThe Chemical Transfer Facility (CTF)  is the only U.S. single small-scale  facility, a single repository for the Army’s...

  10. Intramolecular energy transfer reactions in polymetallic

    Energy Technology Data Exchange (ETDEWEB)

    Petersen, J.

    1990-11-01

    This report is concerned with intramolecular, energy-transfer reactions. The concept of preparing synthetically a complex molecular species, capable of absorbing a photon at one metal center (antenna fragment), transferring that energy to a second metal center (reactive fragment) via a bridging ligand was first reported by our group in 1979. It is now apparent that a major emphasis in inorganic chemistry in the future will involve these types of molecular ensembles. Complexes discussed include Rh, Ru, and Cu complexes. 23 refs., 14 tabs.

  11. Hydrogen transfer reaction on rare earth oxides

    International Nuclear Information System (INIS)

    Minachev, Kh.M.; Atal'yan, O.K.; Markov, M.A.

    1978-01-01

    The ketone reduction by alcohols is studied on a large group of rare earth oxides. The reactions of octanol-2 with cyclohexan one, n. butanol with dipropyl ketone and acetone have been chosen for a model. It has been shown that La,Nd,Sm,Gd,Dy,Er and Y oxides are active in the reactions of hydrogen transfer from n. butanol to dipropyl ketone and acetone and from octanol-2 to cyclohexanone the last reaction being the most selective. The comparative reactivity of ketones-acceptors of hydrogen at their interaction with n. butanol is in conformity with the values of their normal oxidative potentials. By addition of ketone to n. butanol the general degree of catalytic transformation of the latter increases and the selectivity in ketonization ratio decreases. It has been established that catalyst activity increases with the temperature rise

  12. Photoinduced electron transfer in singly labeled thiouredopyrenetrisulfonate azurin derivatives

    DEFF Research Database (Denmark)

    Borovok, N; Kotlyar, A B; Pecht, I

    1999-01-01

    efficiency. TUPS derivatives of azurin, singly labeled at specific lysine residues, were prepared and purified to homogeneity by ion exchange HPLC. Transient absorption spectroscopy was used to directly monitor the rates of the electron transfer reaction from the photoexcited triplet state of TUPS to Cu......A novel method for the initiation of intramolecular electron transfer reactions in azurin is reported. The method is based on laser photoexcitation of covalently attached thiouredopyrenetrisulfonate (TUPS), the reaction that generates the low potential triplet state of the dye with high quantum......(II) and the back reaction from Cu(I) to the oxidized dye. For all singly labeled derivatives, the rate constants of copper ion reduction were one or two orders of magnitude larger than for its reoxidation, consistent with the larger thermodynamic driving force for the former process. Using 3-D coordinates...

  13. Neutron transfer reactions in the fp-shell region

    International Nuclear Information System (INIS)

    Mahgoub, Mahmoud

    2008-01-01

    Neutron transfer reactions were used to study the stability of the magic number N=28 near 56 Ni. On one hand the one-neutron pickup (d,p) reaction was used for precision spectroscopy of single-particle levels in 55 Fe. On the other hand we investigated the two-neutron transfer mechanism into 56 Ni using the pickup reaction 58 Ni(vectorp,t) 56 Ni. In addition the reliability of inverse kinematics reactions at low energy to study exotic nuclei was tested by the neutron transfer reactions t( 40 Ar,p) 42 Ar and d( 54 Fe,p) 55 Fe using tritium and deuterium targets, respectively, and by comparing the results with those of the normal kinematics reactions. The experimental data, differential cross-section and analyzing powers, are compared to DWBA and coupled channel calculations utilizing the code CHUCK3. By performing the single-neutron stripping reaction (vectord,p) on 54 Fe the 1f 7/2 shell in the ground state configuration was found to be partly broken. The instability of the 1f 7/2 shell and the magic number N=28 was confirmed once by observing a number of levels with J π = 7/2 - at low excitation energies, which should not be populated if 54 Fe has a closed 1f 7/2 shell, and also by comparing our high precision experimental data with a large scale shell model calculation using the ANTOINE code [5]. Calculations including a partly broken 1f 7/2 shell show better agreement with the experiment. The instability of the 1f 7/2 shell was confirmed also by performing the two-neutron pick-up reaction (vectorp,t) on 58 Ni to study 56 Ni, where a considerable improvement in the DWBA calculation was observed after considering 1f 7/2 as a broken shell. To prove the reliability of inverse kinematics transfer reactions at low energies (∝ 2 AMeV), the aforementioned single-neutron transfer reaction (d,p) was repeated using a beam of 54 Fe ions and a deuteron target. From this inverse kinematics experiment we were able to reproduce the absolute cross-section and angular

  14. Studies on electron transfer reactions of Keggin-type mixed ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 121; Issue 2. Studies on electron transfer reactions of Keggin-type mixed addenda heteropolytungstovanadophosphates with NADH ... Nicotinamide adenine dinucleotide (NADH); heteropoly-tungstovanadophosphate; outer sphere electron transfer reactions.

  15. Electron transfer and reaction mechanism of laccases.

    Science.gov (United States)

    Jones, Stephen M; Solomon, Edward I

    2015-03-01

    Laccases are part of the family of multicopper oxidases (MCOs), which couple the oxidation of substrates to the four electron reduction of O2 to H2O. MCOs contain a minimum of four Cu's divided into Type 1 (T1), Type 2 (T2), and binuclear Type 3 (T3) Cu sites that are distinguished based on unique spectroscopic features. Substrate oxidation occurs near the T1, and electrons are transferred approximately 13 Å through the protein via the Cys-His pathway to the T2/T3 trinuclear copper cluster (TNC), where dioxygen reduction occurs. This review outlines the electron transfer (ET) process in laccases, and the mechanism of O2 reduction as elucidated through spectroscopic, kinetic, and computational data. Marcus theory is used to describe the relevant factors which impact ET rates including the driving force, reorganization energy, and electronic coupling matrix element. Then, the mechanism of O2 reaction is detailed with particular focus on the intermediates formed during the two 2e(-) reduction steps. The first 2e(-) step forms the peroxide intermediate, followed by the second 2e(-) step to form the native intermediate, which has been shown to be the catalytically relevant fully oxidized form of the enzyme.

  16. Single Molecule Spectroscopy of Electron Transfer

    International Nuclear Information System (INIS)

    Holman, Michael; Zang, Ling; Liu, Ruchuan; Adams, David M.

    2009-01-01

    The objectives of this research are threefold: (1) to develop methods for the study electron transfer processes at the single molecule level, (2) to develop a series of modifiable and structurally well defined molecular and nanoparticle systems suitable for detailed single molecule/particle and bulk spectroscopic investigation, (3) to relate experiment to theory in order to elucidate the dependence of electron transfer processes on molecular and electronic structure, coupling and reorganization energies. We have begun the systematic development of single molecule spectroscopy (SMS) of electron transfer and summaries of recent studies are shown. There is a tremendous need for experiments designed to probe the discrete electronic and molecular dynamic fluctuations of single molecules near electrodes and at nanoparticle surfaces. Single molecule spectroscopy (SMS) has emerged as a powerful method to measure properties of individual molecules which would normally be obscured in ensemble-averaged measurement. Fluctuations in the fluorescence time trajectories contain detailed molecular level statistical and dynamical information of the system. The full distribution of a molecular property is revealed in the stochastic fluctuations, giving information about the range of possible behaviors that lead to the ensemble average. In the case of electron transfer, this level of understanding is particularly important to the field of molecular and nanoscale electronics: from a device-design standpoint, understanding and controlling this picture of the overall range of possible behaviors will likely prove to be as important as designing ia the ideal behavior of any given molecule.

  17. Photoinduced electron transfer in singly labeled thiouredopyrenetrisulfonate azurin derivatives

    DEFF Research Database (Denmark)

    Borovok, N; Kotlyar, A B; Pecht, I

    1999-01-01

    A novel method for the initiation of intramolecular electron transfer reactions in azurin is reported. The method is based on laser photoexcitation of covalently attached thiouredopyrenetrisulfonate (TUPS), the reaction that generates the low potential triplet state of the dye with high quantum......(II) and the back reaction from Cu(I) to the oxidized dye. For all singly labeled derivatives, the rate constants of copper ion reduction were one or two orders of magnitude larger than for its reoxidation, consistent with the larger thermodynamic driving force for the former process. Using 3-D coordinates...... of the crystal structure of Pseudomonas aeruginosa azurin and molecular structure calculation of the TUPS modified proteins, electron transfer pathways were calculated. Analysis of the results revealed a good correlation between separation distance from donor to Cu ligating atom (His-N or Cys-S) and the observed...

  18. Two-nucleon transfer reactions with form factor models

    International Nuclear Information System (INIS)

    Osman, A.

    1980-04-01

    The theory of two-nucleon transfer reactions is considered. Nuclear reactions are considered with triton or 3 He particles which are used as projectiles in stripping reactions and as detected particles in pick-up reactions. In each channel we have a four-particle problem, three of them are nucleons and the fourth is a heavy particle. These transfer reactions are studied on the basis of the generaled R-matrix method. Different channel functions of the sub-clusters in the triton and 3 He particles are included. Model form factors are obtained and are used in two-nucleon transfer reactions. Differential cross-sections of different two-nucleon transfer reactions are calculated and are found in good agreement with the experimental data. The correct normalization and spectroscopic factors are obtained. (author)

  19. Theoretical studies on proton transfer reaction of 3 (5)-substituted ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 126; Issue 1. Theoretical studies on proton transfer reaction of 3(5)-substituted pyrazoles ... Abstract. The inter and intra molecular proton transfer reactions of a series of pyrazole derivatives have been studied by using density functional theory (DFT) andMP2 methods ...

  20. Variation of kinetic isotope effect in multiple proton transfer reactions

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 124; Issue 1. Variation of kinetic isotope ... An extension of this to the concerted multiple proton transfer reactions implies that the kinetic isotope effect in such reaction depends exponentially on the number of protons that are being transferred. Computational evidence ...

  1. Single particle tracking and single molecule energy transfer

    CERN Document Server

    Bräuchle, Christoph; Michaelis, Jens

    2009-01-01

    Closing a gap in the literature, this handbook gathers all the information on single particle tracking and single molecule energy transfer. It covers all aspects of this hot and modern topic, from detecting virus entry to membrane diffusion, and from protein folding using spFRET to coupled dye systems, as well recent achievements in the field. Throughout, the first-class editors and top international authors present content of the highest quality, making this a must-have for physical chemists, spectroscopists, molecular physicists and biochemists.

  2. Studies on electron transfer reactions: Reduction of heteropoly 10 ...

    Indian Academy of Sciences (India)

    Rates of electron transfer reaction of thioglycolic acid with vanadium(V) substituted Keggintype heteropolyanion, [PVVVVW10O40]5-, in acetate-acetic acid buffers have been measured spectrophotometrically at 25°C. The order of the reaction with respect to substrate and oxidant is unity. The reaction shows simple second ...

  3. Droplet heat transfer and chemical reactions during direct containment heating

    International Nuclear Information System (INIS)

    Baker, L. Jr.

    1986-01-01

    A simplified model of heat transfer and chemical reaction has been adapted to evaluate the expected behavior of droplets containing unreacted Zircaloy and stainless steel moving through the containment atmosphere during postulated accidents involving direct containment heating. The model includes internal and external diffusive resistances to reaction. The results indicate that reactions will be incomplete for many conditions characteristic of direct containment heating sequences

  4. Excited state intramolecular charge transfer reaction in 4-(1 ...

    Indian Academy of Sciences (India)

    Administrator

    Abstract. Excited state intramolecular charge transfer reaction of 4-(1-azetidinyl) benzonitrile (P4C) in deuterated and normal methanol, ethanol and acetonitrile has been studied in order to investigate the solvent isotope effects on reaction rates and yields. These quantities (reaction rates and yields) along with several.

  5. Excited state intramolecular charge transfer reaction in 4-(1 ...

    Indian Academy of Sciences (India)

    Excited state intramolecular charge transfer reaction of 4-(1-azetidinyl) benzonitrile (P4C) in deuterated and normal methanol, ethanol and acetonitrile has been studied in order to investigate the solvent isotope effects on reaction rates and yields. These quantities (reaction rates and yields) along with several other ...

  6. Bimolecular reactions of carbenes: Proton transfer mechanism

    Science.gov (United States)

    Abu-Saleh, Abd Al-Aziz A.; Almatarneh, Mansour H.; Poirier, Raymond A.

    2018-04-01

    Here we report the bimolecular reaction of trifluoromethylhydroxycarbene conformers and the water-mediated mechanism of the 1,2-proton shift for the unimolecular trans-conformer by using quantum chemical calculations. The CCSD(T)/cc-pVTZ//MP2/cc-pVDZ potential-energy profile of the bimolecular reaction of cis- and trans-trifluoromethylhydroxycarbene, shows the lowest gas-phase barrier height of 13 kJ mol-1 compared to the recently reported value of 128 kJ mol-1 for the unimolecular reaction. We expect bimolecular reactions of carbene's stereoisomers will open a valuable field for new and useful synthetic strategies.

  7. Heavy ion transfer reactions: Status and perspectives

    Indian Academy of Sciences (India)

    Abstract. With the large solid angle magnetic spectrometer (PRISMA) coupled to the γ-array (CLARA), extensive investigations of nuclear structure and reaction dynamics have been carried out. In the present paper aspects of these studies will be presented, focussing more closely on the reaction mechanism, in particular on ...

  8. Neutron transfer reactions: Surrogates for neutron capture for basic and applied nuclear science

    Energy Technology Data Exchange (ETDEWEB)

    Cizewski, J. A. [Rutgers University; Jones, K. L. [University of Tennessee; Kozub, R. L. [Tennessee Technological University; Pain, Steven D [ORNL; Peters, W. A. [Rutgers University; Adekola, Aderemi S [ORNL; Allen, J. [Rutgers University; Bardayan, Daniel W [ORNL; Becker, J. [Lawrence Livermore National Laboratory (LLNL); Blackmon, Jeff C [ORNL; Chae, K. Y. [University of Tennessee; Chipps, K. [Colorado School of Mines, Golden; Erikson, Luke [Colorado School of Mines, Golden; Gaddis, A. L. [Furman University; Harlin, Christopher W [ORNL; Hatarik, Robert [Rutgers University; Howard, Joshua A [ORNL; Jandel, M. [Los Alamos National Laboratory (LANL); Johnson, Micah [ORNL; Kapler, R. [University of Tennessee; Krolas, W. [University of Warsaw; Liang, J Felix [ORNL; Livesay, Jake [ORNL; Ma, Zhanwen [ORNL; Matei, Catalin [Oak Ridge Associated Universities (ORAU); Matthews, C. [Rutgers University; Moazen, Brian [University of Tennessee; Nesaraja, Caroline D [ORNL; O' Malley, Patrick [Rutgers University; Patterson, N. P. [University of Surrey, UK; Paulauskas, Stanley [University of Tennessee; Pelham, T. [University of Surrey, UK; Pittman, S. T. [University of Tennessee, Knoxville (UTK); Radford, David C [ORNL; Rogers, J. [Tennessee Technological University; Schmitt, Kyle [University of Tennessee; Shapira, Dan [ORNL; ShrinerJr., J. F. [Tennessee Technological University; Sissom, D. J. [Tennessee Technological University; Smith, Michael Scott [ORNL; Swan, T. P. [University of Surrey, UK; Thomas, J. S. [Rutgers University; Vieira, D. J. [Los Alamos National Laboratory (LANL); Wilhelmy, J. B. [Los Alamos National Laboratory (LANL); Wilson, Gemma L [ORNL

    2009-04-01

    Neutron capture reactions on unstable nuclei are important for both basic and applied nuclear science. A program has been developed at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory to study single-neutron transfer (d,p) reactions with rare isotope beams to provide information on neutron-induced reactions on unstable nuclei. Results from (d,p) studies on {sup 130,132}Sn, {sup 134}Te and {sup 75}As are discussed.

  9. Probing the pairing interaction through two-neutron transfer reactions

    Directory of Open Access Journals (Sweden)

    Margueron J.

    2012-12-01

    Full Text Available The treatment of the pairing interaction in mean-field-based models is addressed. In particular, the possibility to use pair transfers as A tool to better constrain this interaction is discussed. First, pairing inter-actions with various density dependencies (surface/volume mixing are used in the microscopic Hartree-Fock-Bogoliubov + quasiparticle random-phase approximation model to generate the form factors to be used in reaction calculations. Cross sections for (p,t two-neutron transfer reactions are calculated in the one-step zero-range distorted-wave Born approximation for some Tin isotopes and for incident proton energies from 15 to 35 MeV. Three different surface/volume mixings of A zero-range density-dependent pairing interaction are employed in the microscopic calculations and the sensitivity of the cross sections to the different mixings is analyzed. Differences among the three different theoretical predictions are found espacially for the nucleus 136Sn and they are more important at the incident proton energy of 15 MeV. We thus indicate (p,t two-neutron transfer reactions with very neutron-rich Sn isotopes and at proton energies around 15 MeV as good experimental cases where the surface/volume mixing of the pairing interaction may be probed. In the second part of the manuscript, ground-state to ground-state transitions are investigated. Approximations made to estimate two-nucleon transfer probabilities in ground-state to ground-state transitions and the physical interpretation of these probabilities are discussed. Probabilities are often calculated by approximating both ground states of the initial nucleus A and of the final nucleus A±2 by the same quasiparticle vacuum. We analyze two improvements of this approach. First, the effect of using two different ground states with average numbers of particles A and A±2 is quantified. Second, by using projection techniques, the role of particle number restoration is analyzed. Our analysis

  10. Debating Elective Single Embryo Transfer after in vitro Fertilization ...

    African Journals Online (AJOL)

    transfer (eSET) to reduce the risk of multiple gestation and. Debating Elective Single Embryo Transfer ... the American Society for Reproductive Medicine, elective SET is defined as “the transfer of a single embryo at ... or should they transfer just one embryo, which reduces the risk of complications and is in line with current ...

  11. Probing cluster structures through sub-barrier transfer reactions

    Directory of Open Access Journals (Sweden)

    Rafferty D. C.

    2016-01-01

    Full Text Available Multinucleon transfer probabilities and excitation energy distributions have been measured in 16,18O, 19F + 208Pb at energies between 90% - 100% of the Coulomb barrier. A strong 2p2n enhancement is observed for all reactions, though most spectacularly in the 18O induced reaction. Results are interpreted in terms of the Semiclassical model, which seems to suggest α-cluster transfer in all studied systems. The relation to cluster-states in the projectile is discussed, with the experimental results consistent with previous structure studies. Dissipation of energy in the collisions of 18O is compared between different reaction modes, with cluster transfer associated with dissipation over a large number of internal states. Cluster transfer is shown to be a long range dissipation mechanism, which will inform the development of future models to treat these dynamic processes in reactions.

  12. Charge transfer reactions in electrochemical and chemical processes

    International Nuclear Information System (INIS)

    Krishtalik, L.I.

    1986-01-01

    This book presents information on the following topics: the Bronsted relation and the activation energy of electrode reactions; the chemical potential of an electron, absolute potential drop, and solvation energy in electrochemical kinetics; kinetic equations for discharge; the discharge of hydronium ions at a mercury cathode; the evolution of hydrogen at a silver cathode; some theoretical problems; an ion in a polar solvent; the elementary act of electron transfer; quantum and classical degrees of freedom-proton transfer; the effect of the potential and the nature of proton donors on the preexponential factor and the kinetic isotope effect; the chlorine evolution reaction at ruthenium dioxide-titanium dioxide anodes; the hydrogen evolution at certain liquid alloys; proton transfer in enzymatic hydrolysis reactions - kinetic isotope effect; and simultaneous transfer of two charges - coupling of endoergic and exoergic reactions

  13. Intramolecular electron transfer in single-site-mutated azurins

    DEFF Research Database (Denmark)

    Farver, O; Skov, L K; Pascher, T

    1993-01-01

    . Natl. Acad. Sci. U.S.A. 86, 6968-6972]. The RSSR- radical produced in the above reaction was reoxidized in a slower intramolecular electron-transfer process (30-70 s-1 at 298 K) concomitant with a further reduction of the Cu(II) ion. The temperature dependence of the latter rates was determined...... and used to derive information on the possible effects of the mutations. The substitution of residue Phe114, situated on the opposite side of Cu relative to the disulfide, by Ala resulted in a rate increase by a factor of almost 2. By assuming that this effect is only due to an increase in driving force......Single-site mutants of the blue, single-copper protein, azurin, from Pseudomonas aeruginosa were reduced by CO2- radicals in pulse radiolysis experiments. The single disulfide group was reduced directly by CO2- with rates similar to those of the native protein [Farver, O., & Pecht, I. (1989) Proc...

  14. One-nucleon transfer reactions and the optical potential

    CERN Document Server

    Nunes, F M; Ross, A; Titus, L J; Charity, R J; Dickhoff, W H; Mahzoon, M H; Sarich, J; Wild, S M

    2015-01-01

    We provide a summary of new developments in the area of direct reaction theory with a particular focus on one-nucleon transfer reactions. We provide a status of the methods available for describing (d,p) reactions. We discuss the effects of nonlocality in the optical potential in transfer reactions. The results of a purely phenomenological potential and the optical potential obtained from the dispersive optical model are compared; both point toward the importance of including nonlocality in transfer reactions explicitly. Given the large ambiguities associated with optical potentials, we discuss some new developments toward the quantification of this uncertainty. We conclude with some general comments and a brief account of new advances that are in the pipeline.

  15. Transfer reactions at the neutron dripline with triton target

    CERN Multimedia

    Two-neutron transfer to $^{9}$Li will populate the ground state of $^{11}$Li as well as low-lying resonances in a way that is complementary to studies of these states performed at higher beam energies. We aim at detecting the charged particles from the transfer reactions as well as neutrons coming from the decay of possible $^{11}$Li resonances.

  16. Parallel proton transfer pathways in aqueous acid-base reactions

    NARCIS (Netherlands)

    Cox, M.J.; Bakker, H.J.

    2008-01-01

    We study the mechanism of proton transfer (PT) between the photoacid 8-hydroxy-1,3, 6-pyrenetrisulfonic acid (HPTS) and the base chloroacetate in aqueous solution. We investigate both proton and deuteron transfer reactions in solutions with base concentrations ranging from 0.25M to 4M. Using

  17. Transfer reactions at the neutron dripline with triton target

    CERN Document Server

    Borge, M J G; Fynbo, H O U; Gomez Camacho, J; Johansen, J; Johansson, H T; Jonson, B; Krücken, R; Kurcewicz, J; Martel, I; Moro, A; Mücher, D; Nilsson, T; Nyman, G; Raabe, R; Randisi, G; Riisager, K; Sambi, S; Sanchez-Benitez, AM; Tengblad, O

    2012-01-01

    Two-neutron transfer to $^{9}$Li will populate the ground state of $^{11}$Li as well as low-lying resonances in a way that is complementary to studies of these states performed at higher beam energies. We aim at detecting the charged particles from the transfer reactions as well as neutrons coming from the decay of possible $^{11}$Li resonances.

  18. Mechanism of electron transfer reaction of ternary ...

    Indian Academy of Sciences (India)

    )(OX)(H2O)]− (DPA = dipicolinate and OX = oxalate) by periodate in aqueous acidic medium has been studied spectrophotometrically over the pH range of 4.45-5.57 at different temperatures. The reaction is first order with respect to both [IO 4 ...

  19. Action spectroscopy for single-molecule reactions - Experiments and theory

    Science.gov (United States)

    Kim, Y.; Motobayashi, K.; Frederiksen, T.; Ueba, H.; Kawai, M.

    2015-05-01

    broadening of the vibrational density of states (as described by Gaussian or Lorentzian functions) manifest themselves in Y (V) near the threshold bias voltage corresponding to a vibrational excitation responsible for reactions. A prefactor of Y (V) is explicitly derived for various types of elementary processes. Our generic formula of Y (V) also underlines the need to observe Y (V) at both bias voltage polarities, which can provide additional insight into the adsorbate projected density of states near the Fermi level within a span of the vibrational energy. The theory is applied to analysis of some highlights of the experimental results: Xe transfer, hopping of a single CO molecule on Pd(1 1 0), a dissociation of a single dimethyl disulfide (CH3S)2 and a hopping of a dissociated product, i.e., single methyl thiolate CH3S on Cu(1 1 1). It underlines that an observation of Y (V) at both bias polarities permits us to certain insight into the molecular alignment with respect to the Fermi level.

  20. Mechanism of Triplet Energy Transfer in Photosynthetic Bacterial Reaction Centers.

    Science.gov (United States)

    Mandal, Sarthak; Carey, Anne-Marie; Locsin, Joshua; Gao, Bing-Rong; Williams, JoAnn C; Allen, James P; Lin, Su; Woodbury, Neal W

    2017-07-13

    In purple bacterial reaction centers, triplet excitation energy transfer occurs from the primary donor P, a bacteriochlorophyll dimer, to a neighboring carotenoid to prevent photodamage from the generation of reactive oxygen species. The B B bacteriochlorophyll molecule that lies between P and the carotenoid on the inactive electron transfer branch is involved in triplet energy transfer between P and the carotenoid. To expand the high-resolution spectral and kinetic information available for describing the mechanism, we investigated the triplet excited state formation and energy transfer pathways in the reaction center of Rhodobacter sphaeroides using pump-probe transient absorption spectroscopy over a broad spectral region on the nanosecond to microsecond time scale at both room temperature and at 77 K. Wild-type reaction centers were compared with a reaction center mutant (M182HL) in which B B is replaced by a bacteriopheophytin (Φ), as well as to reaction centers that lack the carotenoid. In wild-type reaction centers, the triplet energy transfer efficiency from P to the carotenoid was essentially unity at room temperature and at 77 K. However, in the M182HL mutant reaction centers, both the rate and efficiency of triplet energy transfer were decreased at room temperature, and at 77 K, no triplet energy transfer was observed, attributable to a higher triplet state energy of the bacteriopheophytin that replaces bacteriochlorophyll in this mutant. Finally, detailed time-resolved spectral analysis of P, carotenoid, and B B (Φ in the M182HL mutant) reveals that the triplet state of the carotenoid is coupled fairly strongly to the bridging intermediate B B in wild-type and Φ in the M182HL mutant, a fact that is probably responsible for the lack of any obvious intermediate 3 B B / 3 Φ transient formation during triplet energy transfer.

  1. Studies on electron transfer reactions of Keggin-type mixed ...

    Indian Academy of Sciences (India)

    Administrator

    (PV2) in aqueous phosphate buffer of pH 6 at ambient temperature. Electrochemical and optical studies show that the stoichiometry of the reaction is 1: 2 (NADH : HPA). EPR and optical studies show that HPA act as one electron acceptor and the products of electron transfer reactions are one elec- tron reduced heteropoly ...

  2. Comparison of dynamical aspects of nonadiabatic electron, proton, and proton-coupled electron transfer reactions

    International Nuclear Information System (INIS)

    Hatcher, Elizabeth; Soudackov, Alexander; Hammes-Schiffer, Sharon

    2005-01-01

    The dynamical aspects of a model proton-coupled electron transfer (PCET) reaction in solution are analyzed with molecular dynamics simulations. The rate for nonadiabatic PCET is expressed in terms of a time-dependent probability flux correlation function. The impact of the proton donor-acceptor and solvent dynamics on the probability flux is examined. The dynamical behavior of the probability flux correlation function is dominated by a solvent damping term that depends on the energy gap correlation function. The proton donor-acceptor motion does not impact the dynamical behavior of the probability flux correlation function but does influence the magnitude of the rate. The approximations previously invoked for the calculation of PCET rates are tested. The effects of solvent damping on the proton donor-acceptor vibrational motion are found to be negligible, and the short-time solvent approximation, in which only equilibrium fluctuations of the solvent are considered, is determined to be valid for these types of reactions. The analysis of PCET reactions is compared to previous analyses of single electron and proton transfer reactions. The dynamical behavior is qualitatively similar for all three types of reactions, but the time scale of the decay of the probability flux correlation function is significantly longer for single proton transfer than for PCET and single electron transfer due to a smaller solvent reorganization energy for proton transfer

  3. Excited state charge transfer reaction in (mixed solvent + electrolyte ...

    Indian Academy of Sciences (India)

    to the relatively more polar charge transfer (CT) state with a forward reaction rate constant, kf . Note that the. LE→CT conversion reaction in P4C is associated with an activation barrier21 of ∼ 6kB T. Subsequently, the CT state either regenerates the LE state by participating in the reverse reaction with a rate constant, kr, or, ...

  4. Electron Transfer and Reaction Mechanism of Laccases

    OpenAIRE

    Jones, Stephen M.; Solomon, Edward I.

    2015-01-01

    Laccases are part of the family of multicopper oxidases (MCOs), which couple the oxidation of substrates to the four electron reduction of O2 to H2O. MCOs contain a minimum of four Cu's divided into Type 1 (T1), Type 2 (T2), and binuclear Type 3 (T3) Cu sites that are distinguished based on unique spectroscopic features. Substrate oxidation occurs near the T1, and electrons are transferred approximately 13 Å through the protein via the Cys-His pathway to the T2/T3 trinuclear copper cluster (T...

  5. Intrinsic barriers for H-atom transfer reactions

    Energy Technology Data Exchange (ETDEWEB)

    Camaioni, D.M.; Autrey, S.T.; Franz, J.A.

    1994-08-01

    Hydrogen transfer reactions play a well-recognized role in coal liquefaction. While H-abstraction reactions between radicals and H-donors have been well-studied, understanding of structure-reactivity relationships remains surprisingly incomplete. Another form of hydrogen transfer known as radical hydrogen transfer (radical donation of H to an unsaturated compound) is currently the subject of much speculation. The barriers for identity reactions are key parameters in the Evans-Polanyi equation for estimating reaction barriers and are fundamentally significant for the insight they provide about bond reorganization energies for formation of transition state structures. Although knowable from experiment, relatively few H-abstraction identity barriers and no barriers for hydrocarbon radical hydrogen transfer reactions have been measured. This paper seeks to supplement and extend existing experimental data with results obtained by calculation. The authors have used ab initio and semiempirical molecular orbital methods (MNDO-PM3) to calculate barriers for a series of H-atom abstraction and radical-hydrogen-transfer identity reactions for alkyl, alkenyl, arylalkyl and hydroaryl systems. Details of this methodology and analyses of how barrier heights correlate with reactant and transition state properties will be presented and discussed.

  6. Graphene Charge Transfer, Spectroscopy, and Photochemical Reactions

    Energy Technology Data Exchange (ETDEWEB)

    Brus, Louis [Columbia Univ., New York, NY (United States)

    2017-01-31

    This project focused on the special electronic and optical properties of graphene and adsorbed molecular species. Graphene makes an excellent substrate for current collection in nanostructured photovoltaic designs. Graphene is almost transparent, and can be used as a solar cell window. It also has no surface states, and thus current is efficiently transported over long distances. Progress in graphene synthesis indicates that there will soon be practical methods for making large pieces of graphene for devices. We now need to understand exactly what happens to both ground state and electronically excited molecules and Qdots near graphene, if we are going to use them to absorb light in a nano-structured photovoltaic device using graphene to collect photocurrent. We also need to understand how to shift the graphene Fermi level, to optimize the kinetics of electron transfer to graphene. And we need to learn how to convert local graphene areas to semiconductor structure, to make useful spatially patterned graphenes. In this final report, we describe how we addressed these goals. We explored the question of possible Surface Enhanced Raman spectroscopy from molecular Charge Transfer onto Graphene substrates. We observed strong hole doping of graphene by adsorbed halogens as indicated by the shift of the graphene G Raman band. In the case of iodine adsorption, we also observed the anionic species made by hole doping. At low frequency in the Raman spectrum, we saw quite intense lines from I3- and I5- , suggesting possible SERS. We reported on Fresnel calculations on this thin film system, which did not show any net electromagnetic field enhancement.

  7. Two-neutron transfer reactions with heavy-deformed nuclei

    International Nuclear Information System (INIS)

    Price, C.; Landowne, S.; Esbensen, H.

    1988-01-01

    In a recent communication we pointed out that one can combine the macroscopic model for two-particle transfer reactions on deformed nuclei with the sudden limit approximation for rotational excitation, and thereby obtain a practical method for calculating transfer reactions leading to high-spin states. As an example, we presented results for the reaction 162 Dy( 58 Ni, 60 Ni) 160 Dy populating the ground-state rotational band up to the spin I = 14 + state. We have also tested the validity of the sudden limit for the inelastic excitation of high spin states and we have noted how the macroscopic model may be modified to allow for more microscopic nuclear structure effects in an application to diabolic pair-transfer processes. This paper describes our subsequent work in which we investigated the systematic features of pair-transfer reactions within the macroscopic model by using heavier projectiles to generate higher spins and by decomposing the cross sections according to the multipolarity of the transfer interaction. Particular attention is paid to characteristic structures in the angular distributions for the lower spin states and how they depend on the angular momentum carried by the transferred particles. 11 refs., 3 figs

  8. Carbene Transfer Reactions Catalysed by Dyes of the Metalloporphyrin Group

    Directory of Open Access Journals (Sweden)

    Mário M. Q. Simões

    2018-03-01

    Full Text Available Carbene transfer reactions are very important transformations in organic synthesis, allowing the generation of structurally challenging products by catalysed cyclopropanation, cyclopropenation, carbene C-H, N-H, O-H, S-H, and Si-H insertion, and olefination of carbonyl compounds. In particular, chiral and achiral metalloporphyrins have been successfully explored as biomimetic catalysts for these carbene transfer reactions under both homogeneous and heterogeneous conditions. In this work the use of synthetic metalloporphyrins (MPorph, M = Fe, Ru, Os, Co, Rh, Ir, Sn as homogeneous or heterogeneous catalysts for carbene transfer reactions in the last years is reviewed, almost exclusively focused on the literature since the year 2010, except when reference to older publications was deemed to be crucial.

  9. Study of charge transfer reactions in a microbial fuel cell

    Energy Technology Data Exchange (ETDEWEB)

    Martin, E.; Savadogo, O. [Ecole Polytechnique, Montreal, PQ (Canada). Dept. de Genie Chimique; National Research Council of Canada, Montreal, PQ (Canada). Biotechnology Research Inst.; Tartakovsky, B. [National Research Council of Canada, Montreal, PQ (Canada). Biotechnology Research Inst.

    2008-07-01

    Electron transfer reactions in a microbial fuel cell (MFC) were evaluated. The MFC was inoculated with anaerobic mesophilic sludge and operated with carbon felt, carbon cloth, and platinum (Pt) coated carbon cloth. The MFC was then fed with either acetate or glucose as a source of fuel and operated at a temperature of 25 degrees C and a pH of 7. Scanning electron microscopy (SEM) micrographs demonstrated that the micro-organisms colonized the anodes. Cyclic voltammetry and polarization tests were conducted using different fractions of the anodophilic biofilm in order to determine charge transfer routes. The study characterized the electron transfer mechanisms used by the exoelectrogenic micro-organisms to produce electricity. It was concluded that further research is needed to characterize reaction transfer routes. 2 refs., 1 fig.

  10. Tests on measuring astrophysical S-factors with transfer reactions

    CERN Document Server

    Crespo, R

    2002-01-01

    We propose a general method to test the uniqueness property of the Asymptotic Normalization Constant, ANC. We apply this method for the case of the vertex sup 1 sup 0 B -> sup 9 Be+p using a set of different proton-transfer reactions at different energies. Given the limited sets of data for peripheral transfer reactions, we underline the present difficulties in extracting astrophysical S-factors and point out the inadequacy of some of the available data. Finally, we make some suggestions for future experiments in order to make this test conclusive.

  11. Intrinsic barriers for H-atom transfer reactions involving hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Camaioni, D.M.; Autrey, S.T.; Franz, J.A.

    1994-08-01

    Intrinsic barriers (formally the barrier in the absence of driving force) for H-atom transfer reactions are key parameters in Evans-Polyanyi and Marcus equations for estimating exothermic reaction barriers and are fundamentally significant for the insight they provide about bond reorganization energies for formation of transition state structures. Although knowable from experiment, relatively few of these barriers have been measured due to experimental difficulties in measuring rates for identity reactions. Thus, the authors have used semiempirical Molecular Orbital theoretical methods (MNDO/PM3) to calculate barriers for a series of H-atom transfer identity reactions involving alkyl, alkenyl, arylalkyl and hydroaryl radicals and donors. Briefly stated, they find that barriers decrease with the degree of alkyl substitution at the radical site whereas barriers increase with the degree of conjugation with the radical site. Details of the methodology and analyses of how these barrier heights correlate with reactant and transition state properties will be presented and discussed.

  12. Effect of electrostatic interactions on electron-transfer reactions

    International Nuclear Information System (INIS)

    Hickel, B.

    1987-01-01

    Fast reactions of electron transfer are studied by pulsed radiolysis. By this technique radicals and ionic radicals with high redox potentials are created homogeneously in the solution in about 10 -8 second. For solvated electron effect of electrostatic interaction on kinetics of reactions limited by diffusion is obtained with a good approximation by the Debye equation when ion mobility is known. Deviation from the theory occurs in ion pair formation, which is evidenced experimentally in reactions between anions when cations are complexed by a cryptate. Slow reactions k 8 M -1 s -1 are more sensitive to electrostatic interactions than reactions limited by diffusion. When there is no ion pair formation the velocity constant depends upon dielectric constant of the solvent and reaction distance. 17 refs

  13. Mass transfer with complex reversible chemical reactions. II: Parallel reversible chemical reactions

    NARCIS (Netherlands)

    Versteeg, Geert; van Beckum, F.P.H.; Kuipers, J.A.M.; van Swaaij, Willibrordus Petrus Maria

    1990-01-01

    An absorption model has been developed which can be used to calculate rapidly absorption rates for the phenomenon mass transfer accompanied by multiple complex parallel reversible chemical reactions. This model can be applied for the calculation of the mass transfer rates, enhancement factors and

  14. Variation of kinetic isotope effect in multiple proton transfer reactions

    Indian Academy of Sciences (India)

    Proton transfer; promoter modes; kinetic isotope effect. 1. Introduction. Kinetic isotope effect (KIE) is the dependence of the rate constant on the mass of the isotope of the atom in a chemical reaction. The primary kinetic isotope effect is the KIE when the bonds connecting that atom to the rest of the molecular frame are broken ...

  15. Photoinduced intramolecular charge-transfer reactions in 4-amino-3 ...

    Indian Academy of Sciences (India)

    TECS

    primary amino group, shows dual emission in polar solvents. Absorption and emission ... for understanding the primary processes of vision ... demonstrated ICT in some fluoro-substituted amino benzonitrile deriva- tive and very recently Stalin et al. 10–12 reported charge-transfer reaction in p-amino benzoic acid, 3-.

  16. Electron transfer reactions involving porphyrins and chlorophyll a

    International Nuclear Information System (INIS)

    Neta, P.; Scherz, A.; Levanon, H.

    1979-01-01

    Electron transfer reactions involving porphyrins (P) and quinones (Q) have been studied by pulse radiolysis. The porphyrins used were tetraphenylporphyrin (H 2 TPP), its tetracarboxy derivative (H 2 TCPP), the sodium and zinc compounds (Na 2 TPP and ZnTPP), and chlorophyll a (Chl a). These compounds were found to be rapidly reduced by electron transfer from (CH 3 ) 2 CO - . Reduction by (CH 3 ) 2 COH was rapid in aqueous solutions but relatively slow in i-PrOH solutions. Transient spectra of the anion radicals were determined and, in the case of H 2 TCPP - ., a pK = 9.7 was derived for its protonation. Electron-transfer reactions from the anion radical of H 2 TCPP to benzoquinone, duroquinone, 9,10-anthraquinone 2-sulfonate, and methylviologen occur in aqueous solutions with rate constants approx. 10 7 -10 9 M -1 s -1 which depend on the pH and the quinone reduction potential. Reactions of Na 2 TPP - ., ZnTPP - ., and Chl a - . with anthraquinone in basic i-PrOH solutions occur with rate constants approx. 10 9 M -1 s -1 . The spectral changes associated with these electron-transfer reactions as observed over a period of approx. 1 ms indicated, in some cases, the formation of an intermediate complex [P...Q - .]. 8 figures, 2 tables

  17. Studies on electron transfer reactions: Reduction of heteropoly 10 ...

    Indian Academy of Sciences (India)

    Administrator

    Abstract. Rates of electron transfer reaction of thioglycolic acid with vanadium(V) substituted Keggin- type heteropolyanion, [PV ... By applying Rehm–Weller relationship, self exchange rate constant for the. –. SCH2COO. –. /S. •. CH2COO. – .... is much more higher than that of mono-anion. HSCH2COO–. 3.4 Marcus theory.

  18. Excited state intramolecular charge transfer reaction of 4 ...

    Indian Academy of Sciences (India)

    An intramolecular charge transfer (ICT) molecule with an extra hetero atom in its donor moiety has been synthesized in order to investigate how ICT reaction is affected by hetero atom replacement. Photo-physical and photo-dynamical properties of this molecule, 4-(morpholenyl)benzonitrile (M6C), have been studied in 20 ...

  19. Hydrogen transfer reaction of cyclohexanone with 2-propanol ...

    Indian Academy of Sciences (India)

    Unknown

    Addition of ceria into zinc oxide was found to increase the catalytic activity for hydrogen transfer reaction. The catalytic activity also depended on the method of preparation. Citrate process results in uniformly dispersed mixed oxide with higher catalytic activity. Keywords. Cyclohexanone; ceria; ZnO; diffuse reflectance; EPR.

  20. Towards Neutron Drip Line via Transfer-Type Reactions

    CERN Document Server

    Penionzhkevich, Yu E; Antonenko, N V

    2005-01-01

    Possibilities of production of light neutron-rich isotopes $^{24,26}$O, $^{32}$Ne, $^{36,38}$Mg, $^{42}$Si and $^{56,58,60}$Ca in transfer-type reactions are analyzed. The optimal conditions for their production are suggested. The measurement of the excitation function can allow us to estimate the binding energy of exotic nuclei.

  1. Exploring single electrode reactions in polymer electrolyte fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Kuhn, H.; Wokaun, A.; Scherer, G.G. [Paul Scherrer Institute, Electrochemistry Laboratory, 5232 Villigen (Switzerland)

    2007-01-20

    Utilising a pseudo-reference electrode in polymer electrolyte fuel cells allows for the separation of anodic and cathodic contributions to the entire cell impedance. Modelling the impedance responses by using equivalent circuits inhibits the investigation of kinetic parameters of the basic electrochemical reactions, which take place at single electrode-electrolyte interfaces. Therefore, we evaluate single electrode impedance measurements by a kinetic model, which is based on specific reaction pathways, either for the oxygen reduction reaction (ORR) or the hydrogen oxidation reaction (HOR). As a consequence, it is possible to obtain kinetic parameters for the specific reaction of interest. Furthermore, the information gained from the single electrode impedance measurements and the kinetic model can give insight into single reactions steps. In particular, the ORR has to include a chemical step in the reaction pathway. (author)

  2. Theory of nuclear heavy-ion direct transfer reactions

    International Nuclear Information System (INIS)

    Crowley, B.J.B.

    1979-01-01

    We review the distorted-wave approach to direct transfer reactions and draw attention to some of the shortcomings of current theories. We show that a reformulated form of the distorted-wave Born approximation (DWBA) for transfer can lead to important simplifications of the theory, which are valid for nuclear heavy-ion induced reactions at energies > or approx. =MeV/nucleon. In particular, in the semiclassical limit, it leads to a new and simple formula for the transfer t-matrix which includes all the essential physics while offering several important advantages over standard ''full-recoil finite-range'' DWBA. One such advantage is that the new formula is more transparent in that it is amendable to interpretation and analytical manipulation. At high-energy it is shown to reduce to one earlier deduced using eikonal-DWBA. The conditions for the validity of the new theory are discussed in detail. They are shown to be generally well satisfied for small-mass transfer between heavy-ions at energies at or above those particularly favour transfer (> or approx. =10 MeV/nucleon for transfer of valence nucleons). The restriction to small mass is not due to any recoil approximation; in fact, it is only a necessary restriction at certain energies. The theory treats recoil exactly. Consideration of the optimum dynamical conditions for transfer leads to a set of matching conditions. The presence of hitherto neglected absorption, arising from dynamical effects of poor matching, it suggested and qualitatively discussed. Condition under which such absorption may be neglected are derived. Results of numerical calculations are presented showing that the theory is capable of good agreement with standard full-recoil finite-range DWBA, and that it is capable of giving at least as good an account of experimental data for nucleon-transfer between heavy-ions at energies approx.10 MeV/nucleon

  3. Effects of electrostatic interactions on electron transfer reactions

    International Nuclear Information System (INIS)

    Hickel, B.

    1987-01-01

    The fast reactions of electron transfer are studied by pulse radiolysis. This technique allows the creation in about 10 -8 second radicals and radical ions with high redox potentials. For solvated electrons electrostatic interaction on the kinetics of reactions limited by diffusion is described by Debye's equation when ion mobility is known. Deviation from theory can occur in ion pairs formation. This is evidenced experimentally for anions by cation complexation with a cryptate. Relatively slow reactions are more sensitive to electrostatic interactions than limited by diffusion. If ion pairs are not formed kinetics constant depends on dielectric constant of solvent and reaction radius. Experimentally is studied the effect of electrostatic interaction on the rate constants of solvated electrons with anions and cations in water-ethanol mixtures where the dielectric constant change from 80 to 25 at room temperature. 17 refs

  4. Effects of nonlocal potentials on (p ,d ) transfer reactions

    Science.gov (United States)

    Ross, A.; Titus, L. J.; Nunes, F. M.; Mahzoon, M. H.; Dickhoff, W. H.; Charity, R. J.

    2015-10-01

    Background: Although local phenomenological optical potentials have been standardly used to interpret nuclear reactions, recent studies suggest the effects of nonlocality should not be neglected. Purpose: In this work we investigate the effects of nonlocality in (p ,d ) transfer reactions using nonlocal optical potentials. We compare results obtained with the dispersive optical model to those obtained using the Perey-Buck interaction. Method: We solve the scattering and bound-state equations for the nonlocal version of the dispersive optical model. Then, using the distorted-wave Born approximation, we calculate the transfer cross section for (p ,d ) on 40Ca at Ep=20 , 35, and 50 MeV. Results: The inclusion of nonlocality in the bound state has a larger effect than that in the scattering states. The overall effect on the transfer cross section is very significant. We found an increase due to nonlocality in the transfer cross section of ≈30 - 50 % when using the Perey-Buck interaction and of ≈15 - 50 % when using the dispersive optical potential. Conclusions: Although the details of the nonlocal interaction can change the magnitude of the effects, our study shows that qualitatively the results obtained using the dispersive optical potential and the Perey-Buck interaction are consistent, in both cases the transfer cross sections are significantly increased.

  5. Reaction mechanism and spectroscopy of transfer reactions induced by heavy ions

    International Nuclear Information System (INIS)

    Lemaire, M.-C.

    1977-01-01

    The specific features displayed by data on heavy ion elastic and inelastic angular distributions are discussed, and their physical origin is pointed out from semi-classical calculations in counterpart ambiguities in the phenomenological description of the optical potential appear. Two nucleon transfer reactions induced by heavy ions successfully point out important contributions of a two-step process where the transfer is proceeding via target and residual nucleus inelastic excitation. At incident energies not too high above the Coulomb barrier, such process produces clear shape changes between different final state angular distributions. At higher incident energy, the angular distributions are forward peaked and display oscillations for both mechanisms. As for four-nucleon transfer reactions, the existing data suggest that the nucleons are well transferred into a Os relative

  6. Transfer reactions in the investigation of light-nuclei nucleosynthesis

    Energy Technology Data Exchange (ETDEWEB)

    Guimaraes, V.; Camargo, O.; Lichtenthaler, R.; Scarduelli, V. [Instituto de Fisica, Universidade de Sao Paulo, P. O. Box 66318, 05389-970 Sao Paulo (Brazil); Kolata, J. J. [Department of Physics, University of Notre Dame, Notre Dame, 46556 Indiana (United States); Amro, H.; Becchetti, F. D.; Jiang, H. [Department of Physics, University of Michigan, Ann Arbor, 48109-1120 Michigan (United States); Aguilera, E. F.; Lizcano, D.; Martinez Q, E.; Garcia, H. [ININ, La Marquesa, 52750 Estado de Mexico (Mexico)

    2008-12-15

    Cross sections for the {sup 6}Li(p,{gamma}){sup 7}Be, {sup 7}Li(n,{gamma}){sup 8}Li{sup 8}Li(n,{gamma}){sup 9}Li and {sup 8}Li(p,{gamma}){sup 9}Be capture reactions have been investigated in the framework of the potential model. The main ingredients of the potential model are the potentials used to generate the continuum and bound-state wave functions and spectroscopic factors of the corresponding bound systems. The spectroscopic factors for the {sup 7}Lin={sup 8}Li{sub gs}, {sup 8}Lin={sup 9}Li{sub gs} bound systems were obtained from a FR-DWBA analysis of neutron transfer reactions induced by {sup 8}Li radioactive beam on a {sup 9}Be target, while spectroscopic factor for the {sup 8}Lip={sup 9}Be{sub gs} bound system were obtained from a proton transfer reaction. From the obtained capture reaction cross section, reaction rate for the {sup 8}Li(n,{gamma}){sup 9}Li and {sup 8}Li(p,{gamma}){sup 9}Be direct neutron and proton capture were determined and compared with other experimental and calculated values. (Author)

  7. Two-nucleon transfer reactions uphold supersymmetry in atomic nuclei.

    Science.gov (United States)

    Barea, J; Bijker, R; Frank, A

    2005-04-22

    The spectroscopic strengths of two-nucleon transfer reactions constitute a stringent test for two-nucleon correlations in the nuclear wave functions. A set of closed analytic expressions for ratios of spectroscopic factors is derived in the framework of nuclear supersymmetry. These ratios are parameter independent and provide a direct test of the wave functions. A comparison between the recently measured 198Hg(d-->,alpha)196Au reaction and the predictions from the nuclear quartet supersymmetry lends further support to the validity of supersymmetry in nuclear physics.

  8. Reaction Gradients Viewed Inside Single Photoactive Particles

    Science.gov (United States)

    Alpert, P.; Corral Arroyo, P.; Dou, J.; Kreiger, U.; Luo, B.; Peter, T.; Ammann, M.

    2017-12-01

    In terms of chemical selectivity and spatial resolution, a technique known as scanning transmission X-ray microscopy coupled to near-edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS) is unmatched and will remain so for years into the future. We present a recent development coupling STXM/NEXAFS to a custom-built photochemical environmental reactor in which aerosol particles reside allowing for in situ chemical imaging. A laboratory investigation of metal-organic complex photochemistry was conducted. Transition metals are of great importance to atmospheric chemistry and aerosol photochemical aging due to their ability to catalyze oxidation reactions. Aerosol particles composed of mixtures of citric acid and iron citrate were probed for their organic carbon composition and iron oxidation state under atmospherically relevant conditions. At 40% relative humidity, oxygen diffusion and reaction was severely limited. Fe was reoxidized in the first 200 nm of the particle surface leaving reduced iron in the core. Similar gradients were observed at 60% RH, however waiting approximately 2 hours in the dark resulted in a recovery of the initial Fe(III) concentration. We draw two main conclusions from our findings. Frist, the oxidation gradients must have been the result of anoxic conditions at the interior of aerosol particles. This was predicted using a newly developed model for molecular diffusion through multiple layers with a reaction framework describing the photochemical processing of the metal organic matrix. Second, the lifetime of organic radicals in an anoxic diffusion limited organic matrix must be considerably long ( hours) to completely reoxidize iron as they wait for molecular oxygen. Long radical lifetimes in viscous organic aerosol in turn, could create high radical concentrations or favor radical-radical reactions in particles typically not considered when oxygen is plentiful. Our results impact predictions of aerosol physiochemical properties, e

  9. Collision Frequency for Energy Transfer in Unimolecular Reactions.

    Science.gov (United States)

    Matsugi, Akira

    2018-03-01

    Pressure dependence of unimolecular reaction rates is governed by the energy transfer in collisions of reactants with bath gas molecules. Pressure-dependent rate constants can be theoretically determined by solving master equations for unimolecular reactions. In general, master equation formulations describe energy transfer processes using a collision frequency and a probability distribution model of the energy transferred per collision. The present study proposes a novel method for determining the collision frequency from the results of classical trajectory calculations. Classical trajectories for collisions of several polyatomic molecules (ethane, methane, tetrafluoromethane, and cyclohexane) with monatomic colliders (Ar, Kr, and Xe) were calculated on potential energy surfaces described by the third-order density-functional tight-binding method in combination with simple pairwise interaction potentials. Low-order (including non-integer-order) moments of the energy transferred in deactivating collisions were extracted from the trajectories and compared with those derived using some probability distribution models. The comparison demonstrates the inadequacy of the conventional Lennard-Jones collision model for representing the collision frequency and suggests a robust method for evaluating the collision frequency that is consistent with a given probability distribution model, such as the exponential-down model. The resulting collision frequencies for the exponential-down model are substantially higher than the Lennard-Jones collision frequencies and are close to the (hypothetical) capture rate constants for dispersion interactions. The practical adequacy of the exponential-down model is also briefly discussed.

  10. Effects of delocalization on intrinsic barriers for H-atom transfer: Implications for the radical hydrogen transfer reaction

    Energy Technology Data Exchange (ETDEWEB)

    Camaioni, D.M.; Autrey, S.T.; Ferris, K.F.; Franz, J.A.

    1992-08-01

    PM3 calculations of transition states (TS) for both normal H-atom transfer and radical hydrogen transfer (RHT) reactions of a a wide-variety of hydrocarbon structures have enabled development of quantitative structure-reactivity relationships. Results indicate that activation barriers for RHT reactions are large enough that thermoneutral and endothermic reactions should not compete with alternative multistep pathways.

  11. Single-Atom Catalysts of Precious Metals for Electrochemical Reactions.

    Science.gov (United States)

    Kim, Jiwhan; Kim, Hee-Eun; Lee, Hyunjoo

    2018-01-10

    Single-atom catalysts (SACs), in which metal atoms are dispersed on the support without forming nanoparticles, have been used for various heterogeneous reactions and most recently for electrochemical reactions. In this Minireview, recent examples of single-atom electrocatalysts used for the oxygen reduction reaction (ORR), hydrogen oxidation reaction (HOR), hydrogen evolution reaction (HER), formic acid oxidation reaction (FAOR), and methanol oxidation reaction (MOR) are introduced. Many density functional theory (DFT) simulations have predicted that SACs may be effective for CO 2 reduction to methane or methanol production while suppressing H 2 evolution, and those cases are introduced here as well. Single atoms, mainly Pt single atoms, have been deposited on TiN or TiC nanoparticles, defective graphene nanosheets, N-doped covalent triazine frameworks, graphitic carbon nitride, S-doped zeolite-templated carbon, and Sb-doped SnO 2 surfaces. Scanning transmission electron microscopy, extended X-ray absorption fine structure measurement, and in situ infrared spectroscopy have been used to detect the single-atom structure and confirm the absence of nanoparticles. SACs have shown high mass activity, minimizing the use of precious metal, and unique selectivity distinct from nanoparticle catalysts owing to the absence of ensemble sites. Additional features that SACs should possess for effective electrochemical applications were also suggested. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Laser ion source for multi-nucleon transfer reaction products

    Science.gov (United States)

    Hirayama, Y.; Watanabe, Y. X.; Imai, N.; Ishiyama, H.; Jeong, S. C.; Miyatake, H.; Oyaizu, M.; Kimura, S.; Mukai, M.; Kim, Y. H.; Sonoda, T.; Wada, M.; Huyse, M.; Kudryavtsev, Yu.; Van Duppen, P.

    2015-06-01

    We have developed a laser ion source for the target-like fragments (TLFs) produced in multi-nucleon transfer (MNT) reactions. The operation principle of the source is based on the in-gas laser ionization and spectroscopy (IGLIS) approach. In the source TLFs are thermalized and neutralized in high pressure and high purity argon gas, and are extracted after being selectively re-ionized in a multi-step laser resonance ionization process. The laser ion source has been implemented at the KEK Isotope Separation System (KISS) for β-decay spectroscopy of neutron-rich isotopes with N = 126 of nuclear astrophysical interest. The simulations of gas flow and ion-beam optics have been performed to optimize the gas cell for efficient thermalization and fast transporting the TLFs, and the mass-separator for efficient transport with high mass-resolving power, respectively. To confirm the performances expected at the design stage, off-line experiments have been performed by using 56Fe atoms evaporated from a filament in the gas cell. The gas-transport time of 230 ms in the argon cell and the measured KISS mass-resolving power of 900 are consistent with the designed values. The high purity of the gas-cell system, which is extremely important for efficient and highly-selective production of laser ions, was achieved and confirmed from the mass distribution of the extracted ions. After the off-line tests, on-line experiments were conducted by directly injecting energetic 56Fe beam into the gas cell. After thermalization of the injected 56Fe beam, laser-produced singly-charged 56Fe+ ions were extracted. The extraction efficiency and selectivity of the gas cell in the presence of plasma induced by 56Fe beam injection as well as the time profile of the extracted ions were investigated; extraction efficiency of 0.25%, a beam purity of >99% and an extraction time of 270 ms. It has been confirmed that the performance of the KISS laser ion source is satisfactory to start the measurements of

  13. Direct single-molecule dynamic detection of chemical reactions.

    Science.gov (United States)

    Guan, Jianxin; Jia, Chuancheng; Li, Yanwei; Liu, Zitong; Wang, Jinying; Yang, Zhongyue; Gu, Chunhui; Su, Dingkai; Houk, Kendall N; Zhang, Deqing; Guo, Xuefeng

    2018-02-01

    Single-molecule detection can reveal time trajectories and reaction pathways of individual intermediates/transition states in chemical reactions and biological processes, which is of fundamental importance to elucidate their intrinsic mechanisms. We present a reliable, label-free single-molecule approach that allows us to directly explore the dynamic process of basic chemical reactions at the single-event level by using stable graphene-molecule single-molecule junctions. These junctions are constructed by covalently connecting a single molecule with a 9-fluorenone center to nanogapped graphene electrodes. For the first time, real-time single-molecule electrical measurements unambiguously show reproducible large-amplitude two-level fluctuations that are highly dependent on solvent environments in a nucleophilic addition reaction of hydroxylamine to a carbonyl group. Both theoretical simulations and ensemble experiments prove that this observation originates from the reversible transition between the reactant and a new intermediate state within a time scale of a few microseconds. These investigations open up a new route that is able to be immediately applied to probe fast single-molecule physics or biophysics with high time resolution, making an important contribution to broad fields beyond reaction chemistry.

  14. Pentanidium-catalyzed enantioselective phase-transfer conjugate addition reactions

    KAUST Repository

    Ma, Ting

    2011-03-09

    A new chiral entity, pentanidium, has been shown to be an excellent chiral phase-transfer catalyst. The enantioselective Michael addition reactions of tert-butyl glycinate-benzophenone Schiff base with various α,β- unsaturated acceptors provide adducts with high enantioselectivities. A successful gram-scale experiment at a low catalyst loading of 0.05 mol % indicates the potential for practical applications of this methodology. Phosphoglycine ester analogues can also be utilized as the Michael donor, affording enantioenriched α-aminophosphonic acid derivatives and phosphonic analogues of (S)-proline. © 2011 American Chemical Society.

  15. Chaotic scattering in heavy-ion reactions with mass transfer

    International Nuclear Information System (INIS)

    Rodriguez Padron, Emilio; Guzman Martinez, Fernando

    1998-01-01

    The role of the mass transfer in heavy ion collisions is analyzed in the framework of a simple semi phenomenological model searching for chaotic scattering effects. The model couples the relative motion of the ions to a collective degree of freedom. The collective degree of freedom is identified by the mass asymmetry of the system. A Saxon-Woods potential is used for nucleus-nucleus interaction whiles a harmonic potential rules the temporal behaviour of the collective degree of freedom. This model shows chaotic scattering which could be an explanation for certain types of cross-section fluctuations observed in this kind of reactions

  16. Radiolytic and electron-transfer reactions in supercritical CO2

    International Nuclear Information System (INIS)

    Bartels, D. M.; Dimitrijevic, N. M.; Jonah, C. D.; Takahashi, K.

    2000-01-01

    Using supercritical fluids as solvents is useful for both practical and theoretical reasons. It has been proposed to use supercritical CO 2 as a solvent for synthesis because it eliminates the air pollution arising from other solvents. The properties of supercritical fluids can be easily varied with only modest changes in temperature and density, so they provide a way of testing theories of chemical reactions. It has also been proposed to use supercritical fluids for the treatment of hazardous mixed waste. For these reasons the authors have studied the production of radiolytic species in supercritical CO 2 and have measured their reactivity as a function of density. They have shown that the C 2 O 4 + is formed. They also have shown that the electron transfer reactions of dimethylaniline to C 2 O 4 + and CO 2 (e - ) to benzoquinone are diffusion controlled over a considerable density range

  17. Proton transfer reactions and dynamics in protonated water clusters.

    Science.gov (United States)

    Lao-Ngam, Charoensak; Asawakun, Prapasri; Wannarat, Sornthep; Sagarik, Kritsana

    2011-03-14

    Proton transfer reactions and dynamics were theoretically studied using the hydrogen-bond (H-bond) complexes formed from H(3)O(+) and nH(2)O, n = 1-4, as model systems. The investigations began with searching for characteristics of transferring protons in the gas phase and continuum aqueous solution using DFT method at the B3LYP/TZVP level, followed by Born-Oppenheimer molecular dynamics (BOMD) simulations at 350 K. B3LYP/TZVP calculations revealed the threshold asymmetric O-H stretching frequencies (ν(OH)*) for the proton transfers in the Zundel complex (H(5)O) in the gas phase and continuum aqueous solution at 1984 and 1881 cm(-1), respectively. BOMD simulations suggested lower threshold frequencies (ν(OH,MD)* = 1917 and 1736 cm(-1), respectively), with two characteristic ν(OH,MD) being the IR spectral signatures of the transferring protons. The low-frequency band could be associated with the "oscillatory shuttling motion" and the high-frequency band with the "structural diffusion motion". These can be regarded as the spectroscopic evidences of the formations of the shared-proton structure (O···H(+)···O) and the H(3)O(+)-H(2)O contact structure (O-H(+)···O), respectively. Since the quasi-dynamic equilibrium between the Zundel and Eigen complexes was suggested to be the rate-determining step, in order to achieve an "ideal" maximum efficiency of proton transfer, a concerted reaction pathway should be taken. The most effective interconversion between the two proton states, the shared-proton structure and the H(3)O(+)-H(2)O contact structure, can be reflected from comparable intensities of the oscillatory shuttling and structural diffusion bands. The present results iterated the previous conclusions that static proton transfer potentials cannot provide complete description of the structural diffusion process and it is essential to incorporate thermal energy fluctuations and dynamics in the model calculations.

  18. On the length dependence of bridge-mediated electron transfer reactions

    International Nuclear Information System (INIS)

    Petrov, E.G.; Shevchenko, Ye.V.; May, V.

    2003-01-01

    Bridge-mediated nonadiabatic donor-acceptor (D-A) electron transfer (ET) is studied for the case of a regular molecular bridge of N identical units. It is shown that the multi-exponential ET kinetics reduces to a single-exponential transfer if, and only if, the integral population of the bridge remains small (less than 10 -2 ). An analytical expression for the overall D-A ET rate is derived and the necessary and sufficient conditions are formulated at which the rate is given as a sum of a superexchange and a sequential contribution. To describe experimental data on the N-dependence of ET reactions an approximate form of the overall transfer rate is derived. This expression is used to reproduce experimental data on distant ET through polyproline chains. Finally it is noted that the obtained analytical results can also be used for the description of more complex two-electron transfer reactions if the latter comprises separate single-electron pathways

  19. 179Ta and 180Ta structure by transfer reactions

    International Nuclear Information System (INIS)

    Warde, Elias.

    1979-01-01

    Transfer reactions (α,t); ( 3 He,d); (p,t) and (p,d) have been used to study the nuclear spectroscopy of 179 Ta and 180 Ta. In 179 Ta, 5/2 - and 9/2 - states of the 1/2(541) configuration have been identified. The core-quasiproton interaction has to be taken into account in order to explain the two-nucleon transfer intensities in the 181 Ta(p,t) 179 Ta reaction. A level scheme has been proposed for 180 Ta for the first time. Especially the ground state is identified with the (1 + ,1) level of the [7/2 + (404)sub(p), 9/2 + (624)sub(n)] configuration and spin (9 - ,9) of the configuration [9/2 - (514)sub(p), 9/2 + (624)sub(n)] has been assigned to the long-lived isomer. From the observed configurations in 180 Ta, the matrix elements of the effective residual interaction vsub(np) have been deduced and compared to theoretical predictions [fr

  20. Transfer reactions in inverse kinematics at REX-ISOLDE

    CERN Document Server

    Tengborn, E

    Research on the structure of exotic nuclei is one of the most intriguing topics in present day nuclear physics. With the use of facilities for isotope separation on-line, such as ISOLDE at CERN, short-lived isotopes can be studied experimentally. Since 2002, the REX-ISOLDE facility enables radioactive ions produced by ISOLDE to be post-accelerated, increasing the energy of the ions enough to do nuclear transfer reactions in inverse kinematics. In this thesis, transfer reactions are used to study the structure of neutron-rich lithium isotopes through a series of experiments at REX-ISOLDE. The first experiment used a 9Li beam at 2.36 MeV/u impinging on a deuterated polyethylene target to study 10Li, 9Li and 8Li. For the (d,p)-channel the resonance ground state and a first excited state are observed and the results agree with theoretical calculations. The elastic channel agrees with Optical Model, OM, calculations. For the (d,t)-channel the shape of the angular distribution agrees with Distorted Wave Born Approx...

  1. Electron transfer reactions to probe the electrode/solution interface

    Energy Technology Data Exchange (ETDEWEB)

    Capitanio, F.; Guerrini, E.; Colombo, A.; Trasatti, S. [Milan Univ., Milan (Italy). Dept. of Physical Chemistry and Electrochemistry

    2008-07-01

    The reactions that occur at the interface between an electrode and an electrolyte were examined with particular reference to the interaction of different electrode surfaces with redox couples. A semi-integration or convolution technique was used to study the kinetics of electron transfer on different electrode materials with different hydrophilic behaviour, such as Boron-Doped-Diamond (BDD), Au and Pt. Standard reversible redox couples were also investigated, including (Fe3+/2+, Fe(CN)63-/4-, Ru(NH3)63+/2+, Co(NH3)63+/2+, Ir4+/3+, V4+/5+ and V3+/2+). The proposed method proved to be simple, straightforward and reliable since the obtained kinetic information was in good agreement with data in the literature. It was concluded that the kinetics of the electrode transfer reactions depend on the chemical nature of the redox couple and electrode material. The method should be further extended to irreversible couples and other electrode materials such as mixed oxide electrodes. 3 refs., 2 figs.

  2. X-ray Crystal Structures Elucidate the Nucleotidyl Transfer Reaction of Transcript Initiation Using Two Nucleotides

    Energy Technology Data Exchange (ETDEWEB)

    M Gleghorn; E Davydova; R Basu; L Rothman-Denes; K Murakami

    2011-12-31

    We have determined the X-ray crystal structures of the pre- and postcatalytic forms of the initiation complex of bacteriophage N4 RNA polymerase that provide the complete set of atomic images depicting the process of transcript initiation by a single-subunit RNA polymerase. As observed during T7 RNA polymerase transcript elongation, substrate loading for the initiation process also drives a conformational change of the O helix, but only the correct base pairing between the +2 substrate and DNA base is able to complete the O-helix conformational transition. Substrate binding also facilitates catalytic metal binding that leads to alignment of the reactive groups of substrates for the nucleotidyl transfer reaction. Although all nucleic acid polymerases use two divalent metals for catalysis, they differ in the requirements and the timing of binding of each metal. In the case of bacteriophage RNA polymerase, we propose that catalytic metal binding is the last step before the nucleotidyl transfer reaction.

  3. Measuring one nucleon transfer reaction 24Mg( p, d)23Mg for astrophysical reaction rates

    Science.gov (United States)

    Lee, E. J.; Chae, K. Y.

    2017-12-01

    The level structure of a radionuclide 23Mg has been studied by using the 24Mg( p, d)23Mg one nucleon transfer reaction measurement for the astrophysical 19Ne(α, γ)23Mg reaction rate. A 41 MeV proton beam was produced and accelerated at the 25 MV tandem accelerator of the Holifield Radioactive Ion Beam Facility of the Oak Ridge National Laboratory in the United States. The beam particles impinged on an isotopically-enriched 24Mg solid target. Angular distributions of recoiling deuterons were extracted by using a large area silicon strip detector array. By comparing the experimentally-obtained angular distributions with zero range distorted wave Born approximation calculations, spins and parities of three energy levels of 23Mg could be constrained for the first time, which is very important information needed to understand the 19Ne(α, γ)23Mg reaction rate.

  4. Electrocatalysis of anodic and cathodic oxygen-transfer reactions

    Energy Technology Data Exchange (ETDEWEB)

    Wels, B.R.

    1990-09-21

    The electrocatalysis of oxygen-transfer reactions is discussed in two parts. In Part I, the reduction of iodate (IO{sub 3}{sup {minus}}) is examined as an example of cathodic oxygen transfer. On oxide-covered Pt electrodes (PtO), a large cathodic current is observed in the presence of IO{sub 3}{sup {minus}} to coincide with the reduction of PtO. The total cathodic charge exceeds the amount required for reduction of PtO and IO{sub 3}{sup {minus}} to produce an adsorbed product. An electrocatalytic link between reduction of IO{sub 3}{sup {minus}} and reduction of PtO is indicated. In addition, on oxide-free Pt electrodes, the reduction of IO{sub 3}{sup {minus}} is determined to be sensitive to surface treatment. The electrocatalytic oxidation of CN{sup {minus}} is presented as an example of anodic oxygen transfer in Part II. The voltametric response of CN{sup {minus}} is virtually nonexistent at PbO{sub 2} electrodes. The response is significantly improved by doping PbO{sub 2} with Cu. Cyanide is also oxidized effectively at CuO-film electrodes. Copper is concluded to serve as an adsorption site for CN{sup {minus}}. It is proposed that an oxygen tunneling mechanism comparable to electron tunneling does not occur at the electrode-solution interface. The adsorption of CN{sup {minus}} is therefore considered to be a necessary prerequisite for oxygen transfer. 201 refs., 23 figs., 2 tabs.

  5. Golden rule kinetics of transfer reactions in condensed phase: The microscopic model of electron transfer reactions in disordered solid matrices

    Science.gov (United States)

    Basilevsky, M. V.; Odinokov, A. V.; Titov, S. V.; Mitina, E. A.

    2013-12-01

    The algorithm for a theoretical calculation of transfer reaction rates for light quantum particles (i.e., the electron and H-atom transfers) in non-polar solid matrices is formulated and justified. The mechanism postulated involves a local mode (an either intra- or inter-molecular one) serving as a mediator which accomplishes the energy exchange between the reacting high-frequency quantum mode and the phonon modes belonging to the environment. This approach uses as a background the Fermi golden rule beyond the usually applied spin-boson approximation. The dynamical treatment rests on the one-dimensional version of the standard quantum relaxation equation for the reduced density matrix, which describes the frequency fluctuation spectrum for the local mode under consideration. The temperature dependence of a reaction rate is controlled by the dimensionless parameter ξ0 = ℏω0/kBT where ω0 is the frequency of the local mode and T is the temperature. The realization of the computational scheme is different for the high/intermediate (ξ0 conduction in photosensitive organic materials is considered, based on the above techniques. The electron transfer (ET) in active centers of such systems proceeds via local intra- and intermolecular modes. The active modes, as a rule, operate beyond the kinetic regimes, which are usually postulated in the existing theories of the ET. Our alternative dynamic ET model for local modes immersed in the continuum harmonic medium is formulated for both classical and quantum regimes, and accounts explicitly for the mode/medium interaction. The kinetics of the energy exchange between the local ET subsystem and the surrounding environment essentially determine the total ET rate. The efficient computer code for rate computations is elaborated on. The computations are available for a wide range of system parameters, such as the temperature, external field, local mode frequency, and characteristics of mode/medium interaction. The relation of the

  6. Incremental Identification of Reaction and Mass-Transfer Kinetics Using the Concept of Extents

    OpenAIRE

    Bhatt, Nirav; Amrhein, Michael; Bonvin, Dominique

    2011-01-01

    This paper proposes a variation of the incremental approach to identify reaction and mass-transfer kinetics (rate expressions and the corresponding rate parameters) from concentration measurements for both homogeneous and gas-liquid reaction systems. This incremental approach proceeds in two steps: (i) computation of the extents of reaction and mass transfer from concentration measurements without explicit knowledge of the reaction and mass-transfer rate expressions, and (ii) estimation of ...

  7. Charged-particle transfer reactions and nuclear astrophysics problems

    International Nuclear Information System (INIS)

    Artemov, S.V.; Yarmukhamedov, R.; Yuldashev, B.S.; Burtebaev, N.; Duysebaev, A.; Kadyrzhanov, K.K.

    2002-01-01

    In the report a review of the recent results of calculation of the astrophysical S-factors S(E) for the D(α, γ) 6 Li, 3 He(α, γ) 7 Be, 7 Be(p, γ) 8 Be, 12,13 C(p, γ) 13, 14 N and 12 C(p,γ) 16 O* reactions at extremely low energies E, including value E=0 , performed within the framework of a new method taking into account the additional information about the nuclear vertex constant (Nc) (or the respective asymptotic normalization coefficient) are presented. The required values of Nc can be obtained from an analysis of measured differential cross-sections of proton and α-particle transfer reactions (for example A( 3 He,d)B, 6 Li(d, 6 Li)d, 6 Li(α, 6 Li)α, 12 C( 6 Li, d) 16 O* etc.). A comparative analysis between the results obtained by different authors is also done. Taking into account an important role of the NVC's values for the nuclear astrophysical A(p, γ)B and A(α, γ)B reactions, a possibility of obtaining the reliable NVC values for the virtual decay B→A+p and B→A+α from the analysis of differential cross sections both sub- and above-barrier A( 3 He, d) and A( 6,7 Li, 2,3 H)B reactions is discussed in detail. In this line the use the isochronous cyclotron U-150 M, the 'DC-60' heavy ion machine and electrostatic charge-exchanging accelerator UKP-2-1 of Institute of Nuclear Physics of National Nuclear Center of the Republic of Kazakhstan for carrying out the needed experiments is considered and the possibility of the obtained data application for the astrophysical interest is also discussed

  8. Electron transfer reactions of macrocyclic compounds of cobalt

    Energy Technology Data Exchange (ETDEWEB)

    Heckman, R.A.

    1978-08-01

    The kinetics and mechanisms of reduction of H/sub 2/O/sub 2/, Br/sub 2/, and I/sub 2/ by various macrocyclic tetraaza complexes of cobalt(II), including Vitamin B/sub 12r/, were studied. The synthetic macrocycles studied were all 14-membered rings which varied in the degree of unsaturation,substitution of methyl groups on the periphery of the ring, and substitution within the ring itself. Scavenging experiments demonstrated that the reductions of H/sub 2/O/sub 2/ produce free hydroxyl radicals only in the case of Co((14)ane)/sup 2 +/ but with none of the others. In the latter instances apparently H/sub 2/O/sub 2/ simultaneously oxidizes the metal center and the ligand. The reductions of Br/sub 2/ and I/sub 2/ produce an aquohalocobalt(III) product for all reductants (except B/sub 12r/ + Br/sub 2/, which was complicated by bromination of the corrin ring). The mechanism of halogen reduction was found to involve rate-limiting inner-sphere electron transfer from cobalt to halogen to produce a dihalide anion coordinated to the cobalt center. This intermediate subsequently decomposes in rapid reactions to halocobalt(III) and halogen atom species or reacts with another cobalt(II) center to give two molecules of halocobalt(III). The reductions of halomethylcobaloximes and related compounds and diamminecobaloxime by Cr/sup 2 +/ were also studied. The reaction was found to be biphasic in all cases with the reaction products being halomethane (for the halomethylcobaloximes), Co/sup 2 +/ (in less than 100 percent yield), a Cr(III)-dimethylglyoxime species, a small amount of free dmgH/sub 2/, and a highly-charged species containing both cobalt and chromium. The first-stage reaction occurs with a stoichiometry of 1:1 producing an intermediate with an absorption maximum at 460 nm for all starting reagents. The results were interpreted in terms of inner-sphere coordination of the cobaloxime to the Cr(II) and electron transfer through the oxime N-O bond.

  9. Single-Molecule Sensing with Nanopore Confinement: from Chemical Reactions to Biological Interactions.

    Science.gov (United States)

    Lin, Yao; Ying, Yi-Lun; Gao, Rui; Long, Yi-Tao

    2018-03-25

    The nanopore can generate an electrochemical confinement for single-molecule sensing which help understand the fundamental chemical principle in nanoscale dimensions. By observing the generated ionic current, individual bond-making and bond-breaking steps, single biomolecule dynamic conformational changes and electron transfer processes that occur within pore can be monitored with high temporal and current resolution. These single-molecule studies in nanopore confinement are revealing information about the fundamental chemical and biological processes that cannot be extracted from ensemble measurements. In this concept, we introduce and discuss the electrochemical confinement effects on single-molecule covalent reactions, conformational dynamics of individual molecules and host-guest interactions in protein nanopores. Then, we extend the concept of nanopore confinement effects to confine electrochemical redox reactions in solid-state nanopores for developing new sensing mechanisms. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Single-molecule chemical reaction reveals molecular reaction kinetics and dynamics.

    Science.gov (United States)

    Zhang, Yuwei; Song, Ping; Fu, Qiang; Ruan, Mingbo; Xu, Weilin

    2014-06-25

    Understanding the microscopic elementary process of chemical reactions, especially in condensed phase, is highly desirable for improvement of efficiencies in industrial chemical processes. Here we show an approach to gaining new insights into elementary reactions in condensed phase by combining quantum chemical calculations with a single-molecule analysis. Elementary chemical reactions in liquid-phase, revealed from quantum chemical calculations, are studied by tracking the fluorescence of single dye molecules undergoing a reversible redox process. Statistical analyses of single-molecule trajectories reveal molecular reaction kinetics and dynamics of elementary reactions. The reactivity dynamic fluctuations of single molecules are evidenced and probably arise from either or both of the low-frequency approach of the molecule to the internal surface of the SiO2 nanosphere or the molecule diffusion-induced memory effect. This new approach could be applied to other chemical reactions in liquid phase to gain more insight into their molecular reaction kinetics and the dynamics of elementary steps.

  11. Mass transfer in porous media with heterogeneous chemical reaction

    Directory of Open Access Journals (Sweden)

    Souza S.M.A.G.Ulson de

    2003-01-01

    Full Text Available In this paper, the modeling of the mass transfer process in packed-bed reactors is presented and takes into account dispersion in the main fluid phase, internal diffusion of the reactant in the pores of the catalyst, and surface reaction inside the catalyst. The method of volume averaging is applied to obtain the governing equation for use on a small scale. The local mass equilibrium is assumed for obtaining the one-equation model for use on a large scale. The closure problems are developed subject to the length-scale constraints and the model of a spatially periodic porous medium. The expressions for effective diffusivity, hydrodynamic dispersion, total dispersion and the Darcy's law permeability tensors are presented. Solution of the set of final equations permits the variations of velocity and concentration of the chemical species along the packed-bed reactors to be obtained.

  12. Membrane introduction proton-transfer-reaction mass spectrometry

    International Nuclear Information System (INIS)

    Alexander, M.; Boscaini, E.; Maerk, T.; Lindinger, W.

    2002-01-01

    Proton-transfer-reaction mass spectrometry (PTR-MS) is a rapidly expanding field with multiple applications in ion physics, atmospheric chemistry, food chemistry, volatile organic compounds monitoring and biology. Initial studies that combine PTR-MS and membrane introduction mass spectrometry (MIMS) were researched and outlined. First using PTR-MS, certain fundamental physical properties of a poly-dimethylsiloxane (PDMS) membrane including solubilities and diffusion coefficients were measured. Second, it was shown how the chemical selectivity of the (PDMS) can be used to extend the capabilities of the PTR-MS instrument by eliminating certain isobaric interferences and excluding water from volatile organic compounds (VOCs). Experiments with mixtures of several VOCs (toluene, benzene, acetone, propanal, methanol) are presented. (nevyjel)

  13. the steady-state performance characteristics of single phase transfer

    African Journals Online (AJOL)

    2012-11-03

    Nov 3, 2012 ... The paper reports the derivation of the steady- state equivalent circuit of a single phase transfer ... series opposition between the two halves of the ma- ..... from its equivalent circuit of fig 6 for different values of slip. Impedance due to forward field. Zf = Rf + jXf = Rr. 2(2s - 1). + jxr. 2. (19) in parallel with jxm. 2.

  14. Multinucleon transfer in the 136Xe+208Pb reaction

    Science.gov (United States)

    Li, Cheng; Zhang, Fan; Li, Jingjing; Zhu, Long; Tian, Junlong; Wang, Ning; Zhang, Feng-Shou

    2016-01-01

    The dynamic mechanics in the multinucleon transfer reaction 136Xe+208Pb at an incident energy of Ec .m .=450 MeV is investigated by using the improved quantum molecular dynamics model (ImQMD). The lifetime of the neck directly influences the nucleon exchange and energy dissipation between the projectile and the target. The total-kinetic-energy-mass distributions and excitation energy division of primary binary fragments and the mass distributions of primary fragments at different impact parameters are calculated. The thermal equilibrium between two reaction partners has been observed at the lifetime of a neck larger than 480 fm /c . By using the statistical decay code gemini to describe the de-excitation process of the primary fragments, the isotope production cross sections from Pt to At are compared with the prediction by the dinuclear system and GRAZING model. The calculations indicate that the GRAZING model is suitable for estimating the isotope production cross sections only for Δ Z =-1 to +2; the DNS + gemini calculations underestimate the cross sections in the neutron-rich and neutron-deficient regions; and the ImQMD + gemini calculations give reasonable predictions of the isotope production cross sections for Δ Z =-3 to 0.

  15. Single bunch transfer system for the National Synchrotron Light Source

    International Nuclear Information System (INIS)

    Sheehan, J.; Singh, O.; Rambo, W.

    1983-01-01

    The accelerator system at the National Synchrotron Light Source consists of an S-band 85 MeV linac and three synchrotron rings. The electron beam from the linac is accelerated by the booster ring to 600 MeV and transferred to one of the two storage rings. The smaller of the two rings operates between 300 and 800 MeV emtting photons in the vacuum ultraviolet (VUV), while the larger storage ring operates up to 2.5 GeV and emits photons in the x-ray spectrum. A system is described for loading the storage rings by filling a single-phase space bunch in the booster ring and transferring it at the end of each booster cycle into a selected bucket in one of the storage rings. By controlling the timing of the transfer on successive transfer cycles, many fill patterns may be obtained

  16. Production of isomers in compound and transfer reactions with 4He ions

    International Nuclear Information System (INIS)

    Karamyan, S.A.; Aksenov, N.V.; Albin, Yu.A.; Bozhikov, G.A.; Dmitriev, S.N.; Starodub, G.Ya.; Vostokin, G.K.; Carroll, J.J.

    2011-01-01

    A well-known island of nuclear isomerism appears near A = 175-180 due to the deformation alignment of single-particle orbits at high angular momentum. This sometimes results in the formation of multi-quasiparticle states with record spin that are long-lived because of 'K-hindrance', i.e., symmetry rearrangement. Production methods and spectroscopic studies of these isomers remain a challenge for modern nuclear reaction and nuclear structure physics. Activities were produced by irradiation of 176 Yb(97.6%) enriched and nat Lu targets with 35-MeV 4 He ions from the internal beam of the U200 cyclotron. Induced activities were analyzed applying methods of radiochemistry and gamma spectroscopy. Yields of compound and nucleon-transfer reactions were measured and the isomer-to-ground state ratios were deduced. Calculated results were obtained using standard procedures to reproduce the (α, xn) cross sections, and the systematic behavior of the nucleon-transfer yields was established. The isomer-to-ground state ratios for direct reactions with 4 He ions were examined, resulting in a new characterization of the reaction mechanism

  17. Dinuclear Tetrapyrazolyl Palladium Complexes Exhibiting Facile Tandem Transfer Hydrogenation/Suzuki Coupling Reaction of Fluoroarylketone

    KAUST Repository

    Dehury, Niranjan

    2016-07-18

    Herein, we report an unprecedented example of dinuclear pyrazolyl-based Pd complexes exhibiting facile tandem catalysis for fluoroarylketone: Tetrapyrazolyl di-palladium complexes with varying Pd-Pd distances efficiently catalyze the tandem reaction involving transfer hydrogenation of fluoroarylketone to the corresponding alcohol and Suzuki-Miyaura cross coupling reaction of the resulting fluoroarylalcohol under moderate reaction conditions, to biaryl alcohol. The complex with the shortest Pd-Pd distance exhibits the highest tandem activity among its di-metallic analogues, and exceeds in terms of activity and selectivity the analogous mononuclear compound. The kinetics of the reaction indicates clearly that reductive transformation of haloarylketone into haloaryalcohol is the rate determining step in the tandem reaction. Interestingly while fluoroarylketone undergoes the multistep tandem catalysis, the chloro- and bromo-arylketones undergo only a single step C-C coupling reaction resulting in biarylketone as the final product. Unlike the pyrazole based Pd compounds, the precursor PdCl2 and the phosphine based relevant complexes (PPh3)2PdCl2 and (PPh3)4Pd are found to be unable to exhibit the tandem catalysis.

  18. Pair and single neutron transfer with Borromean 8He

    International Nuclear Information System (INIS)

    Lemasson, A.; Navin, A.; Rejmund, M.; Keeley, N.; Zelevinsky, V.; Bhattacharyya, S.; Shrivastava, A.; Bazin, D.; Beaumel, D.; Blumenfeld, Y.; Chatterjee, A.; Gupta, D.; France, G. de; Jacquot, B.; Labiche, M.; Lemmon, R.; Nanal, V.; Nyberg, J.; Pillay, R.G.; Raabe, R.

    2011-01-01

    Direct observation of the survival of 199 Au residues after 2n transfer in the 8 He+ 197 Au system and the absence of the corresponding 67 Cu in the 8 He+ 65 Cu system at various energies are reported. The measurements of the surprisingly large cross sections for 199 Au, coupled with the integral cross sections for the various Au residues, is used to obtain the first model-independent lower limits on the ratio of 2n to 1n transfer cross sections from 8 He to a heavy target. A comparison of the transfer cross sections for 6,8 He on these targets highlights the differences in the interactions of these Borromean nuclei. These measurements for the most neutron-rich nuclei on different targets highlight the need to probe the reaction mechanism with various targets and represent an experimental advance towards understanding specific features of pairing in the dynamics of dilute nuclear systems.

  19. Bridge mediated two-electron transfer reactions: Analysis of stepwise and concerted pathways

    International Nuclear Information System (INIS)

    Petrov, E.G.; May, V.

    2004-01-01

    A theory of nonadiabatic donor (D)-acceptor (A) two-electron transfer (TET) mediated by a single regular bridge (B) is developed. The presence of different intermediate two-electron states connecting the reactant state D -- BA with the product state DBA -- results in complex multiexponential kinetics. The conditions are discussed at which a reduction to two-exponential as well as single-exponential kinetics becomes possible. For the latter case the rate K TET is calculated, which describes the bridge-mediated reaction as an effective two-electron D-A transfer. In the limit of small populations of the intermediate TET states D - B - A, DB -- A, D - BA - , and DB - A - , K TET is obtained as a sum of the rates K TET (step) and K TET (sup) . The first rate describes stepwise TET originated by transitions of a single electron. It starts at D -- BA and reaches DBA -- via the intermediate state D - BA - . These transitions cover contributions from sequential as well as superexchange reactions all including reduced bridge states. In contrast, a specific two-electron superexchange mechanism from D -- BA to DBA -- defines K TET (sup) . An analytic dependence of K TET (step) and K TET (sup) on the number of bridging units is presented and different regimes of D-A TET are studied

  20. Numerical study for melting heat transfer and homogeneous-heterogeneous reactions in flow involving carbon nanotubes

    Science.gov (United States)

    Hayat, Tasawar; Muhammad, Khursheed; Alsaedi, Ahmed; Asghar, Saleem

    2018-03-01

    Present work concentrates on melting heat transfer in three-dimensional flow of nanofluid over an impermeable stretchable surface. Analysis is made in presence of porous medium and homogeneous-heterogeneous reactions. Single and multi-wall CNTs (carbon nanotubes) are considered. Water is chosen as basefluid. Adequate transformations yield the non-linear ordinary differential systems. Solution of emerging problems is obtained using shooting method. Impacts of influential variables on velocity and temperature are discussed graphically. Skin friction coefficient and Nusselt number are numerically discussed. The results for MWCNTs and SWCNTs are compared and examined.

  1. High performance platinum single atom electrocatalyst for oxygen reduction reaction

    Science.gov (United States)

    Liu, Jing; Jiao, Menggai; Lu, Lanlu; Barkholtz, Heather M.; Li, Yuping; Wang, Ying; Jiang, Luhua; Wu, Zhijian; Liu, Di-Jia; Zhuang, Lin; Ma, Chao; Zeng, Jie; Zhang, Bingsen; Su, Dangsheng; Song, Ping; Xing, Wei; Xu, Weilin; Wang, Ying; Jiang, Zheng; Sun, Gongquan

    2017-07-01

    For the large-scale sustainable implementation of polymer electrolyte membrane fuel cells in vehicles, high-performance electrocatalysts with low platinum consumption are desirable for use as cathode material during the oxygen reduction reaction in fuel cells. Here we report a carbon black-supported cost-effective, efficient and durable platinum single-atom electrocatalyst with carbon monoxide/methanol tolerance for the cathodic oxygen reduction reaction. The acidic single-cell with such a catalyst as cathode delivers high performance, with power density up to 680 mW cm-2 at 80 °C with a low platinum loading of 0.09 mgPt cm-2, corresponding to a platinum utilization of 0.13 gPt kW-1 in the fuel cell. Good fuel cell durability is also observed. Theoretical calculations reveal that the main effective sites on such platinum single-atom electrocatalysts are single-pyridinic-nitrogen-atom-anchored single-platinum-atom centres, which are tolerant to carbon monoxide/methanol, but highly active for the oxygen reduction reaction.

  2. Heat transfer characteristics around a single heated rod immersed in sodium pool with gas jet injection

    International Nuclear Information System (INIS)

    Hideto Niikura; Kazuo Soga; Ken-ichiro Sugiyama; Akira Yamaguchi

    2005-01-01

    In a steam generator using liquid sodium, water intensely reacts with sodium when it leaks out from a heat transfer tube. It is important to evaluate the influence of sodium-water reaction to surrounding tubes and the shell. Hence, it has been desired to develop the simulation code for the evaluation of sodium-water reaction. From this viewpoint, the Japan Nuclear Cycle is now developing the SERAPHIM code. We reported a preliminary study to establish an experimental method for a single heated rod immersed in sodium pool with steam jet impingement planned in the near future as well as to obtain a preliminary data to verify the adequacy of SERAPHIM code. We first measured local and mean heat transfer coefficients around a horizontal single heated rod immersed in a water pool and a sodium pool with a limited volume in the experimental apparatus. It was confirmed that the mean heat transfer coefficients fairly agreed with the existing data for natural convection in water and sodium. Secondary we measured local and mean heat transfer coefficients around a horizontal single heated rod with Ar gas jet impingement immersed in the limited water pool and in the limited sodium pool. It was clearly observed that the local heat transfer coefficients in the sodium pool keep almost the same values in every angle regardless of increase in Ar gas jet velocity varied from about 8.7m/s to about 78m/s. On the other hand, it was confirmed in the water pool that local heat transfer coefficients on the forward stagnation side exposed in the Ar gas jet impingement increase with increasing the jet velocity while the local heat transfer coefficients on the opposite surface keep almost same values regardless of increase in the velocity. (authors)

  3. One nucleon transfer reactions around $^{68}$Ni at REX-ISOLDE

    CERN Multimedia

    Blazhev, A A; Kruecken, R; Mertzimekis, T; Darby, I G; Lagogiannis, A; Habs, D; Diriken, J V J; Patronis, N

    2008-01-01

    We intend to investigate the single particle properties of the neutron-rich Ni isotopes in the mass region around $^{68}$Ni and at a later stage towards the doubly-magic $^{78}$Ni. As a first experiment we propose to study the single particle character of the ground and first excited states of $^{67}$Ni. This nucleus will be the projectile-like reaction product for the one-neutron transfer reaction. A $^{66}$Ni beam at 3A MeV delivered from REX-ISOLDE will be directed on a CD$_{2}$ target. Protons produced from the (d,p) reaction will be detected either in singles or in coincidence with ${\\gamma}$-rays recorded by the MINIBALL array. The particles will be detected by the newly-built Si position-sensitive barrel configuration. The objectives of this work are the unambiguous determination of the spins and parities of the first excited states of $^{67}$Ni and measurement of the relative spectroscopic factors of those states as well as of the ground state. The experimental results will be compared with those from...

  4. Neutron spectroscopic factors of 34Ar and 46Ar from (p,d) transfer reactions

    International Nuclear Information System (INIS)

    Lee, Jenny; Tsang, M.B.; Bazin, D.; Coupland, D.; Henzl, V.; Henzlova, D.; Kilburn, M.; Lynch, W. G.; Rogers, A. M.; Sanetullaev, A.; Youngs, M.; Sun, Z. Y.; Charity, R. J.; Sobotka, L. G.; Famiano, M.; Hudan, S.; Shapira, D.; O'Malley, P.; Peters, W. A.; Chae, K. Y.

    2011-01-01

    Single-neutron-transfer measurements using (p,d) reactions have been performed at 33 MeV per nucleon with proton-rich 34 Ar and neutron-rich 46 Ar beams in inverse kinematics. The extracted spectroscopic factors are compared to the large-basis shell-model calculations. Relatively weak quenching of the spectroscopic factors is observed between 34 Ar and 46 Ar. The experimental results suggest that neutron correlations have a weak dependence on the asymmetry of the nucleus over this isotopic region. The present results are consistent with the systematics established from extensive studies of spectroscopic factors and dispersive optical-model analyses of 40-49 Ca isotopes. They are, however, inconsistent with the trends obtained in knockout-reaction measurements.

  5. Nanoscale and single-molecule interfacial electron transfer

    DEFF Research Database (Denmark)

    Hansen, Allan Glargaard; Wackerbarth, Hainer; Nielsen, Jens Ulrik

    2003-01-01

    Electrochemical science and technology in the 21st century have reached high levels of sophistication. A fundamental quantum mechanical theoretical frame for interfacial electrochemical electron transfer (ET) was introduced by Revaz Dogonadze. This frame has remained for four decades as a basis...... scanning tunneling microscopy (STM) and single-electron tunneling (SET, or Coulomb blockade) in electrochemical. systems directly in aqueous electrolyte solution and at room temperature. We illustrate the new theoretical formalism and its perspectives by recent cases of electrochemical SET, negative...

  6. Conformation and energy transfer in single conjugated polymers.

    Science.gov (United States)

    Bolinger, Joshua C; Traub, Matthew C; Brazard, Johanna; Adachi, Takuji; Barbara, Paul F; Vanden Bout, David A

    2012-11-20

    In contrast to the detailed understanding of inorganic materials, researchers lack a comprehensive view of how the properties of bulk organic materials arise from their individual components. For conjugated polymers to eventually serve as low cost semiconductor layers in electronic devices, researchers need to better understand their functionality. For organics, traditional materials science measurements tend to destroy the species of interest, especially at low concentrations. However, fluorescence continues to be a remarkably flexible, relatively noninvasive tool for probing the properties of individual molecules and allows researchers to carry out a broad range of experiments based on a relatively simple concept. In addition, the sensitivity of single-molecule spectroscopy allows researchers to see the properties of an individual component that would be masked in the bulk phase. In this Account, we examine several photophysical properties of different conjugated polymers using single-molecule spectroscopy. In these experiments, we probed the relationship between the conformation of single conjugated polymer chains and the distance scale and efficiency of energy transfer within the polymer. Recent studies used polarization anisotropy measurements on single polymer chains to study chain folding following spin-casting from solution. This Account summarizes the effects of monomer regioregularity and backbone rigidity, by comparing a regiorandom phenylene vinylene (MEH-PPV) with both a regiorandom and regioregular thiophene (P3HT). Synthesis of novel polymers allowed us to explore the role of different conformation-directing inclusions in a PPV backbone. We showed that these inclusions control the conformation of individual chains and that molecular dynamics can predict these structural effects. In situ solvent vapor annealing studies explored the dynamics of polymer chains as well as the effect of solvent evaporation on the structural equilibrium of the polymer. We

  7. Mass transfer with complex chemical reaction in gas–liquid systems—I. Consecutive reversible reactions with equal diffusivities

    NARCIS (Netherlands)

    Vas Bhat, R.D.; Swaaij, W.P.M. van; Kuipers, J.A.M.; Versteeg, G.F.

    1999-01-01

    A fundamental description of gas–liquid mass transfer with reversible consecutive reaction has been derived. The Higbie penetration theory has been used and numerical simulations were carried out for isothermal absorption. Although the model can be adapted to reactions of general stoichiometric and

  8. Mass transfer with complex chemical reaction in gas–liquid systems—II : Effect of unequal diffusivities on consecutive reactions

    NARCIS (Netherlands)

    Vas Bhat, R.D.; Swaaij, W.P.M. van; Kuipers, J.A.M.; Versteeg, G.F.

    1999-01-01

    A fundamental description of gas–liquid mass transfer with reversible consecutive reaction has been given. The Higbie penetration theory has been used and numerical simulations were carried out for isothermal absorption. Although the model can be adapted to reactions of general stoichiometric and

  9. Mass transfer with complex chemical reaction in gas-liquid systems - I. Consecutive reversible reactions with equal diffusivities

    NARCIS (Netherlands)

    Vas bhat, R.D.; van Swaaij, Willibrordus Petrus Maria; Kuipers, J.A.M.; Versteeg, Geert

    1999-01-01

    A fundamental description of gas¿liquid mass transfer with reversible consecutive reaction has been derived. The Higbie penetration theory has been used and numerical simulations were carried out for isothermal absorption. Although the model can be adapted to reactions of general stoichiometric and

  10. Chemical reaction on MHD flow and heat transfer of a nanofluid ...

    African Journals Online (AJOL)

    Chemical reaction on MHD flow and heat transfer of a nanofluid near the stagnation point over a permeable stretching surface with non-uniform heat source/sink. ... and is found to be in excellent agreement. Keywords: Stagnation point flow; Chemical reaction; Heat transfer; Stretching surface; Nanofluid; Numerical solution.

  11. The (3He,α) reaction mechanism. A study of the angular momentum transfer

    International Nuclear Information System (INIS)

    Guttormsen, M.; Bergholt, L.; Ingebretsen, F.; Loevhoeiden, G.; Messelt, S.; Rekstad, J.; Tveter, T.S.; Helstrup, H.; Thorsteinsen, T.F.

    1994-01-01

    The γ-rays emitted after the 163 Dy( 3 He,αxn) reactions at E( 3 He) = 45 MeV have been measured. The transferred angular momentum in the reaction is deduced from the side-feeding γ-intensities of the ground bands in the residual 162-x Dy isotopes. With decreasing α-energy the average spin transfer increases from similar 5h to similar 11h. The ( 3 He,α) reaction at these energies is dominated by direct processes. Even at the highest spin transfer the contribution from the compound reaction channel is negligible. ((orig.))

  12. Selective population of high-j states via heavy-ion-induced transfer reactions

    International Nuclear Information System (INIS)

    Bond, P.D.

    1982-01-01

    One of the early hopes of heavy-ion-induced transfer reactions was to populate states not seen easily or at all by other means. To date, however, I believe it is fair to say that spectroscopic studies of previously unknown states have had, at best, limited success. Despite the early demonstration of selectivity with cluster transfer to high-lying states in light nuclei, the study of heavy-ion-induced transfer reactions has emphasized the reaction mechanism. The value of using two of these reactions for spectroscopy of high spin states is demonstrated: 143 Nd( 16 O, 15 O) 144 Nd and 170 Er( 16 O, 15 Oγ) 171 Er

  13. On the ultrafast kinetics of the energy and electron transfer reactions in photosystem I

    Energy Technology Data Exchange (ETDEWEB)

    Slavov, Chavdar Lyubomirov

    2009-07-09

    The subject of the current work is one of the main participants in the light-dependent phase of oxygenic photosynthesis, Photosystem I (PS I). This complex carries an immense number of cofactors: chlorophylls (Chl), carotenoids, quinones, etc, which together with the protein entity exhibit several exceptional properties. First, PS I has an ultrafast light energy trapping kinetics with a nearly 100% quantum efficiency. Secondly, both of the electron transfer branches in the reaction center are suggested to be active. Thirdly, there are some so called 'red' Chls in the antenna system of PS I, absorbing light with longer wavelengths than the reaction center. These 'red' Chls significantly modify the trapping kinetics of PS I. The purpose of this thesis is to obtain better understanding of the above-mentioned, specific features of PS I. This will not merely cast more light on the mechanisms of energy and electron transfer in the complex, but also will contribute to the future developments of optimized artificial light-harvesting systems. In the current work, a number of PS I complexes isolated from different organisms (Thermosynechococcus elongatus, Chlamydomonas reinhardtii, Arabidopsis thaliana) and possessing distinctive features (different macroorganisation, monomers, trimers, monomers with a semibelt of peripheral antenna attached; presence of 'red' Chls) is investigated. The studies are primarily focused on the electron transfer kinetics in each of the cofactor branches in the PS I reaction center, as well as on the effect of the antenna size and the presence of 'red' Chls on the trapping kinetics of PS I. These aspects are explored with the help of several ultrafast optical spectroscopy methods: (i) time-resolved fluorescence ? single photon counting and synchroscan streak camera; and (ii) ultrafast transient absorption. Physically meaningful information about the molecular mechanisms of the energy trapping in PS I is

  14. Single Electron Transfer Living Radical Polymerization via a New Initiator

    Science.gov (United States)

    Bai, Xiongxiong; Hu, Ying; Zhang, Xu; Ai, Lingling; Cheng, Chuanjie

    2014-08-01

    Research and development of novel initiating system such as single electron transfer living radical polymerization (SET-LRP) is of high importance in polymer chemistry. A new SET-LRP initiator was synthesized and applied to prepare end-functionalized poly(methyl methacrylate) (PMMA) in this study. α-Trichloromethyl benzyl alcohol was firstly synthesized, followed by preparation of PMMA under SET-LRP conditions. Conversion of MMA was 81.9%, and the molecular weight of PMMA was about 2.5 kDa at 60 °C for 1 h. Consistency of the number-average molecular weight of PMMA from NMR, GPC and theoretical calculation indicated that the polymerization featured controllable property. Broad molecular weight distribution (MWD) may be ascribed to branched polymers formed by initiation and chain transfer.

  15. Single Electron Transfer Living Radical Polymerization via a New Initiator

    International Nuclear Information System (INIS)

    Bai, Xiongxiong; Hu, Ying; Zhang, Xu; Ai, Lingling; Cheng, Chuanjie

    2014-01-01

    Research and development of novel initiating system such as single electron transfer living radical polymerization (SET-LRP) is of high importance in polymer chemistry. A new SET-LRP initiator was synthesized and applied to prepare end-functionalized poly(methyl methacrylate) (PMMA) in this study. α-Trichloromethyl benzyl alcohol was firstly synthesized, followed by preparation of PMMA under SET-LRP conditions. Conversion of MMA was 81.9%, and the molecular weight of PMMA was about 2.5 kDa at 60 °C for 1 h. Consistency of the number-average molecular weight of PMMA from NMR, GPC and theoretical calculation indicated that the polymerization featured controllable property. Broad molecular weight distribution (MWD) may be ascribed to branched polymers formed by initiation and chain transfer

  16. Condensation heat transfer of steam on a single horizontal tube

    Science.gov (United States)

    Graber, K. A.

    1983-06-01

    An experimental apparatus was designed, constructed and instrumented in an effort to systematically and carefully study the condensation heat-transfer coefficient on a single, horizontal tube. A smooth, thick-walled copper tube of length 133.5 mm, with an outside diameter of 15.9 mm and an inside diameter of 12.7 mm was instrumented with six wall thermocouples. The temperature rise across the test section was measured accurately using quartz crystal thermometers. The inside heat-transfer coefficient was determined using the Sieder-Tate correlation with leading coefficient of 0.029. Initial steam side data were taken at atmospheric pressure to test the data acquisition/reduction computer programs.

  17. Theoretical aspects of electron transfer reactions of complex molecules

    DEFF Research Database (Denmark)

    Kuznetsov, A. M.; Ulstrup, Jens

    2001-01-01

    Features of electron transfer involving complex molecules are discussed. This notion presently refers to molecular reactants where charge transfer is accompanied by large molecular reorganization, and commonly used displaced harmonic oscillator models do not apply. It is shown that comprehensive...... theory of charge transfer in polar media offers convenient tools for the treatment of experimental data for such systems, with due account of large-amplitude strongly anharmonic intramolecular reorganization. Equations for the activation barrier and free energy relationships are provided, incorporating...

  18. Single-molecule chemical reactions on DNA origami

    DEFF Research Database (Denmark)

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

    2010-01-01

    DNA nanotechnology and particularly DNA origami, in which long, single-stranded DNA molecules are folded into predetermined shapes, can be used to form complex self-assembled nanostructures. Although DNA itself has limited chemical, optical or electronic functionality, DNA nanostructures can serve...... on a DNA origami scaffold by atomic force microscopy. The high yields and chemoselectivities of successive cleavage and bond-forming reactions observed in these experiments demonstrate the feasibility of post-assembly chemical modification of DNA nanostructures and their potential use as locally...

  19. Redox-Tag Processes: Intramolecular Electron Transfer and Its Broad Relationship to Redox Reactions in General.

    Science.gov (United States)

    Okada, Yohei; Chiba, Kazuhiro

    2017-12-08

    Explosive growth in the use of open shell reactivity, including neutral radicals and radical ions, in the field of synthetic organic chemistry has been observed in the past decade, particularly since the advent of ruthenium complexes in 2008. These complexes generally induce single-electron transfer (SET) processes via visible-light absorption. Additionally, recent significant advancements in organic electrochemistry involving SET processes to provide open shell reactivity offer a complementary method to traditional polarity-driven reactions described by two-electron transfer processes. In this Review, we highlight the importance of intramolecular SET processes in the field of synthetic organic chemistry, which seem to be more elusive than the intermolecular versions, since they are net redox-neutral and thus cannot simply be regarded as oxidations or reductions. Such intramolecular SET processes can rationally be understood in combination with concomitant bond formations and/or cleavages, and are regulated by a structural motif that we call a "redox tag." In order to describe modern radical-driven reactions involving SET processes, we focus on a classical formalism in which electrons are treated as particles rather than waves, which offers a practical yet powerful approach to explain and/or predict synthetic outcomes.

  20. Observation of the one- to six-neutron transfer reactions at sub-barrier energies

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, C.L.; Rehm, K.E.; Gehring, J. [and others

    1995-08-01

    It was suggested many years ago that when two heavy nuclei are in contact during a grazing collision, the transfer of several correlated neutron-pairs could occur. Despite considerable experimental effort, however, so far only cross sections for up to four-neutron transfers have been uniquely identified. The main difficulties in the study of multi-neutron transfer reactions are the small cross sections encountered at incident energies close to the barrier, and various experimental uncertainties which can complicate the analysis of these reactions. We have for the first time found evidence for multi-neutron transfer reactions covering the full sequence from one- to six-neutron transfer reactions at sub-barrier energies in the system {sup 58}Ni + {sup 100}Mo.

  1. Reaction kinetics in open reactors and serial transfers between closed reactors

    Science.gov (United States)

    Blokhuis, Alex; Lacoste, David; Gaspard, Pierre

    2018-04-01

    Kinetic theory and thermodynamics of reaction networks are extended to the out-of-equilibrium dynamics of continuous-flow stirred tank reactors (CSTR) and serial transfers. On the basis of their stoichiometry matrix, the conservation laws and the cycles of the network are determined for both dynamics. It is shown that the CSTR and serial transfer dynamics are equivalent in the limit where the time interval between the transfers tends to zero proportionally to the ratio of the fractions of fresh to transferred solutions. These results are illustrated with a finite cross-catalytic reaction network and an infinite reaction network describing mass exchange between polymers. Serial transfer dynamics is typically used in molecular evolution experiments in the context of research on the origins of life. The present study is shedding a new light on the role played by serial transfer parameters in these experiments.

  2. Excited state charge transfer reaction in (mixed solvent+ electrolyte ...

    Indian Academy of Sciences (India)

    The reaction time constant in low polar mixtures, which becomes faster on addition of electrolyte, lengthens on increasing the mole fraction of the relatively less polar solvent component of the mixture. These observations have been qualitatively explained in terms of the measured solvent reorganization energy and reaction ...

  3. Thermodynamic chemical energy transfer mechanisms of non-equilibrium, quasi-equilibrium, and equilibrium chemical reactions

    International Nuclear Information System (INIS)

    Roh, Heui-Seol

    2015-01-01

    Chemical energy transfer mechanisms at finite temperature are explored by a chemical energy transfer theory which is capable of investigating various chemical mechanisms of non-equilibrium, quasi-equilibrium, and equilibrium. Gibbs energy fluxes are obtained as a function of chemical potential, time, and displacement. Diffusion, convection, internal convection, and internal equilibrium chemical energy fluxes are demonstrated. The theory reveals that there are chemical energy flux gaps and broken discrete symmetries at the activation chemical potential, time, and displacement. The statistical, thermodynamic theory is the unification of diffusion and internal convection chemical reactions which reduces to the non-equilibrium generalization beyond the quasi-equilibrium theories of migration and diffusion processes. The relationship between kinetic theories of chemical and electrochemical reactions is also explored. The theory is applied to explore non-equilibrium chemical reactions as an illustration. Three variable separation constants indicate particle number constants and play key roles in describing the distinct chemical reaction mechanisms. The kinetics of chemical energy transfer accounts for the four control mechanisms of chemical reactions such as activation, concentration, transition, and film chemical reactions. - Highlights: • Chemical energy transfer theory is proposed for non-, quasi-, and equilibrium. • Gibbs energy fluxes are expressed by chemical potential, time, and displacement. • Relationship between chemical and electrochemical reactions is discussed. • Theory is applied to explore nonequilibrium energy transfer in chemical reactions. • Kinetics of non-equilibrium chemical reactions shows the four control mechanisms

  4. A molecular dynamics study of intramolecular proton transfer reaction of malonaldehyde in solutions based upon mixed quantum-classical approximation. I. Proton transfer reaction in water.

    Science.gov (United States)

    Yamada, Atsushi; Kojima, Hidekazu; Okazaki, Susumu

    2014-08-28

    In order to investigate proton transfer reaction in solution, mixed quantum-classical molecular dynamics calculations have been carried out based on our previously proposed quantum equation of motion for the reacting system [A. Yamada and S. Okazaki, J. Chem. Phys. 128, 044507 (2008)]. Surface hopping method was applied to describe forces acting on the solvent classical degrees of freedom. In a series of our studies, quantum and solvent effects on the reaction dynamics in solutions have been analysed in detail. Here, we report our mixed quantum-classical molecular dynamics calculations for intramolecular proton transfer of malonaldehyde in water. Thermally activated proton transfer process, i.e., vibrational excitation in the reactant state followed by transition to the product state and vibrational relaxation in the product state, as well as tunneling reaction can be described by solving the equation of motion. Zero point energy is, of course, included, too. The quantum simulation in water has been compared with the fully classical one and the wave packet calculation in vacuum. The calculated quantum reaction rate in water was 0.70 ps(-1), which is about 2.5 times faster than that in vacuum, 0.27 ps(-1). This indicates that the solvent water accelerates the reaction. Further, the quantum calculation resulted in the reaction rate about 2 times faster than the fully classical calculation, which indicates that quantum effect enhances the reaction rate, too. Contribution from three reaction mechanisms, i.e., tunneling, thermal activation, and barrier vanishing reactions, is 33:46:21 in the mixed quantum-classical calculations. This clearly shows that the tunneling effect is important in the reaction.

  5. Mass driver reaction engine characteristics and performance in earth orbital transfer missions

    Science.gov (United States)

    Snow, W. R.; Dunbar, R. S.

    1982-01-01

    Configurations of a typical mass driver reaction engine (MDRE) are presented and its use for delivery of payloads to geosynchronous orbit (GEO) from low earth orbit (LEO) is discussed. Basic rocket equations are developed for LEO to GEO round-trip missions using a single exhaust velocity. It is shown that exhaust velocities in the 5-10 km/sec range (specific impulse of 500-1000 sec) are well suited for mass drivers, minimizing the overall cost of missions. Payload delivery rate fractions show that there is little to be gained by stretching out LEO to GEO transfer times from 90 to 180 days. It therefore pays to use the shorter trip time, approximately doubling the amount of delivered payload during any fixed time of use of the MDRE.

  6. Measurement of Proton-Induced Transfer Reactions with JENSA

    Science.gov (United States)

    Chatterjee, Sidharth; Chipps, Kelly; Pain, Steven; Cizewski, Jolie; Jensa Collaboration

    2017-09-01

    Reaction measurements of radioactive nuclei on light targets are important to understanding the origin of and the trends in the structure of nuclei. To efficiently measure nuclear reactions, measurements require highly localized and pure light targets and need to accommodate arrays of light charged particles, gamma rays, and recoiling heavy ions. The Jet Experiments in Nuclear Structure and Astrophysics (JENSA) jet target system was designed to facilitate high resolution, low background nuclear reaction studies. To demonstrate the capability of the JENSA system, the 20Ne(p,3He)18F reaction was studied during the commissioning phase. The radioisotope 18F is one of the galactic gamma-ray sources targeted by next-generation space-based telescopes. In addition, the 20Ne(p,3He) reaction has not been previously used for the spectroscopic study of 18F. The JENSA system gives us the opportunity to study this reaction with high resolution and low background. The measurement was performed with a proton beam from the Holifield Radioactive Ion Beam Facility tandem on a neon jet of natural isotopic abundance from JENSA. The experimental setup of JENSA and preliminary results will be discussed. Oak Ridge National Laboratory; Rutgers University Department of Physics and Astronomy.

  7. Hydrogen atom transfer reactions in thiophenol: photogeneration of two new thione isomers.

    Science.gov (United States)

    Reva, Igor; Nowak, Maciej J; Lapinski, Leszek; Fausto, Rui

    2015-02-21

    Photoisomerization reactions of monomeric thiophenol have been investigated for the compound isolated in low-temperature argon matrices. The initial thiophenol population consists exclusively of the thermodynamically most stable thiol form. Phototransformations were induced by irradiation of the matrices with narrowband tunable UV light. Irradiation at λ > 290 nm did not induce any changes in isolated thiophenol molecules. Upon irradiation at 290-285 nm, the initial thiol form of thiophenol converted into its thione isomer, cyclohexa-2,4-diene-1-thione. This conversion occurs by transfer of an H atom from the SH group to a carbon atom at the ortho position of the ring. Subsequent irradiation at longer wavelengths (300-427 nm) demonstrated that this UV-induced hydrogen-atom transfer is photoreversible. Moreover, upon irradiation at 400-425 nm, the cyclohexa-2,4-diene-1-thione product converts, by transfer of a hydrogen atom from the ortho to para position, into another thione isomer, cyclohexa-2,5-diene-1-thione. The latter thione isomer is also photoreactive and is consumed if irradiated at λ atom-transfer isomerization reactions dominate the unimolecular photochemistry of thiophenol confined in a solid argon matrix. A set of low-intensity infrared bands, observed in the spectra of UV irradiated thiophenol, indicates the presence of a phenylthiyl radical with an H- atom detached from the SH group. Alongside the H-atom-transfer and H-atom-detachment processes, the ring-opening photoreaction occurred in cyclohexa-2,4-diene-1-thione by the cleavage of the C-C bond at the alpha position with respect to the thiocarbonyl C[double bond, length as m-dash]S group. The resulting open-ring conjugated thioketene adopts several isomeric forms, differing by orientations around single and double bonds. The species photogenerated upon UV irradiation of thiophenol were identified by comparison of their experimental infrared spectra with the spectra theoretically calculated for

  8. Studies on catalysis by molten metals. X. Hydrogen transfer reactions between alcohols and ketones on liquid indium catalyst

    International Nuclear Information System (INIS)

    Miyamoto, A.; Ogino, Y.

    1976-01-01

    Hydrogen transfer reactions between alcohols and ketones were studied on liquid indium catalyst by using a pulse reaction technique, and a plausible reaction model is proposed to explain the experimental results including deuterium isotope effects. Further, the stereoselectivity observed in the transfer hydrogenation of methylcyclohexanones and the selectivities observed in the transfer hydrogenation of unsaturated ketones are discussed in terms of the proposed model

  9. Recyclable polystyrene-supported siloxane-transfer agent for palladium-catalyzed cross-coupling reactions.

    Science.gov (United States)

    Nguyen, Minh H; Smith, Amos B

    2014-04-04

    The rational design, synthesis, and validation of a significantly improved insoluble polymer-supported siloxane-transfer agent has been achieved that permits efficient palladium-catalyzed cross-coupling reactions. The cross-linked polystyrene support facilitates product purification with excellent siloxane recycling. Drawbacks of a previous polymer-supported siloxane-transfer agent, relating to reaction efficiency and polymer stability after repeated cycles, have been addressed.

  10. A reevaluation of fluid flow, heat transfer and chemical reaction in catalyst filled tubes

    OpenAIRE

    Daszkowski, Thomas; Eigenberger, Gerhart

    1992-01-01

    The problem of heat transfer through the wall in catalyst filled tubes with a tube to particle diameter ratio greater than 4 - 5 and industrial flow rates with and without chemical reaction has been reevaluated through detailed experiments and model calculations. The results confirm and extend findings of Vortmeyer et al. that reaction and heat transfer can only be modeled with independently determined parameters if the radial variation of the axial mass flow velocity is properly considered. ...

  11. The influence of phase transfer catalyst structure on reaction selectivity

    International Nuclear Information System (INIS)

    Demlov, Eh.V.

    1995-01-01

    A concise review is given of systematic studies which are concerned with the tuning of regio, frequentio-, chemo-, and diastereoselectivity by the structure or type of phase transfer catalyst. Use of MEI as an alkylating agent is described. Refs. 36, figs. 11

  12. Synthesis and Reactions of Five-Membered Heterocycles Using Phase Transfer Catalyst (PTC Techniques

    Directory of Open Access Journals (Sweden)

    Ahmed M. El-Sayed

    2014-01-01

    Full Text Available Phase transfer catalysts (PTCs have been widely used for the synthesis of organic compounds particularly in both liquid-liquid and solid-liquid heterogeneous reaction mixtures. They are known to accelerate reaction rates by facilitating formation of interphase transfer of species and making reactions between reagents in two immiscible phases possible. Application of PTC instead of traditional technologies for industrial processes of organic synthesis provides substantial benefits for the environment. On the basis of numerous reports it is evident that phase-transfer catalysis is the most efficient way for generation and reactions of many active intermediates. In this review we report various uses of PTC in syntheses and reactions of five-membered heterocycles compounds and their multifused rings.

  13. Definition and determination of the triplet-triplet energy transfer reaction coordinate

    Energy Technology Data Exchange (ETDEWEB)

    Zapata, Felipe; Marazzi, Marco; Castaño, Obis; Frutos, Luis Manuel, E-mail: luisma.frutos@uah.es [Departamento de Química Física, Universidad de Alcalá, 28871 Alcalá de Henares, Madrid (Spain); Acuña, A. Ulises [Instituto de Química Física “Rocasolano”, C.S.I.C., Serrano 119, 28006 Madrid (Spain)

    2014-01-21

    A definition of the triplet-triplet energy transfer reaction coordinate within the very weak electronic coupling limit is proposed, and a novel theoretical formalism is developed for its quantitative determination in terms of internal coordinates The present formalism permits (i) the separation of donor and acceptor contributions to the reaction coordinate, (ii) the identification of the intrinsic role of donor and acceptor in the triplet energy transfer process, and (iii) the quantification of the effect of every internal coordinate on the transfer process. This formalism is general and can be applied to classical as well as to nonvertical triplet energy transfer processes. The utility of the novel formalism is demonstrated here by its application to the paradigm of nonvertical triplet-triplet energy transfer involving cis-stilbene as acceptor molecule. In this way the effect of each internal molecular coordinate in promoting the transfer rate, from triplet donors in the low and high-energy limit, could be analyzed in detail.

  14. Definition and determination of the triplet-triplet energy transfer reaction coordinate.

    Science.gov (United States)

    Zapata, Felipe; Marazzi, Marco; Castaño, Obis; Acuña, A Ulises; Frutos, Luis Manuel

    2014-01-21

    A definition of the triplet-triplet energy transfer reaction coordinate within the very weak electronic coupling limit is proposed, and a novel theoretical formalism is developed for its quantitative determination in terms of internal coordinates The present formalism permits (i) the separation of donor and acceptor contributions to the reaction coordinate, (ii) the identification of the intrinsic role of donor and acceptor in the triplet energy transfer process, and (iii) the quantification of the effect of every internal coordinate on the transfer process. This formalism is general and can be applied to classical as well as to nonvertical triplet energy transfer processes. The utility of the novel formalism is demonstrated here by its application to the paradigm of nonvertical triplet-triplet energy transfer involving cis-stilbene as acceptor molecule. In this way the effect of each internal molecular coordinate in promoting the transfer rate, from triplet donors in the low and high-energy limit, could be analyzed in detail.

  15. The 2H(e, e' p)n reaction at large energy transfers

    NARCIS (Netherlands)

    Willering, Hendrik Willem

    2003-01-01

    At the ELSA accelerator facillity in Bonn, Germany, we have measured the deutron "breakup" reaction 2H(e,e' p)n at four-momentum transfers around Q2 = -0 .20(GeV/c)2 with an electron beam energy of E0 = 1.6 GeV. The cross section has been determined for energy transfers extending from the

  16. Mass transfer accompanied with complete reversible chemical reactions in gas-liquid systems: an overview

    NARCIS (Netherlands)

    van Swaaij, Willibrordus Petrus Maria; Versteeg, Geert

    1992-01-01

    In many processes in the chemical industry mass transfer accompanied with reversible, complex chemical reactions in gas-liquid systems are frequently encountered. In point of view of design purposes it is very important that the absorption rates of the transferred reactants can estimated

  17. Excited state intramolecular charge transfer reaction of 4 ...

    Indian Academy of Sciences (India)

    Administrator

    In spite of the above discus- sion, conclusions drawn from this work remain un- altered as the calculation of average equilibrium constant (Keq) involves only the amplitudes of the decay components, not the reaction time constants. 4. Conclusion. To summarize, the replacement of the carbon atom para to the nitrogen atom ...

  18. Excited state intramolecular charge transfer reaction in non-aqueous ...

    Indian Academy of Sciences (India)

    is found to produce a linear increase of confined solvent viscosity but leads to a non-monotonic electrolyte concentration ... The observed huge reduction in reaction rate constant is attributed to the effects of decreased solution polarity, enhanced vis- .... twisting mode while reacting inside a confined pool. We have used the ...

  19. The electron transfer reactions of NADPH: cytochrome P450 reductase with nonphysiological oxidants.

    Science.gov (United States)

    Cénas, N; Anusevicius, Z; Bironaité, D; Bachmanova, G I; Archakov, A I; Ollinger, K

    1994-12-01

    The steady-state kinetics of oxidation of rat liver NADPH: cytochrome P450 reductase (EC 1.6.2.4) by quinones, aromatic nitrocompounds, ferricyanide, Fe(EDTA)-, and cytochrome c has been studied. The logarithms of bimolecular rate constants of reduction (kcat/Km) of quinones and nitrocompounds increase with the increase in their single-electronreduction potential (E1(7)), reaching a maximum value at E1(7) > -0.15 V. The reactivities of nitroaromatics are about by an order of magnitude lower than the reactivities of quinones. For a series of nitroaromatics including the compounds with previously undetermined E1(7) values, an orthogonality was found between their reactivities toward cytochrome P450 reductase, flavocytochrome b2 (EC 1.1.2.3), and the NADPH: adrenodoxin reductase (EC 1.18.1.2)-adrenodoxin system. This indicates the absence of significant specific interactions during these reactions. The effects of ionic strength on reaction kinetics and the character of inhibition by a product of reaction, NADP+, are in accordance with the reduction of oxidants at the negatively charged site in the surroundings of FMN of P450 reductase. Quinones inactivate oxidized reductase modifying the NADP(H) binding site. The redox cycling of quinones markedly slows the inactivation. The kinetic data presented are consistent with an outer-sphere electron transfer mechanism. The analysis of kinetics of reduction of cytochrome c, ferricyanide, and Fe(EDTA)- using the model of Mauk et al. (A. G. Mauk, R. A. Scott, and H. B. Gray (1980) J. Am. Chem. Soc. 102, 4360-4363) gives calculated distances of FMN from the surface of protein globule, 0.33-0.63 nm. The data from nitroreductase reactions of cytochrome P450 reductase, flavocytochrome b2, and adrenodoxin were used for approximate evaluation of previously unknown E1(7) of nitrocompounds.

  20. Single hole spectroscopic strength in 98Ru through the 99Ru(d,t) reaction

    International Nuclear Information System (INIS)

    Rodrigues, M.R.D.; Borello-Lewin, T.; Horodynski-Matsushigue, L.B.; Duarte, J.L.M.; Rodrigues, C.L.; Barbosa, M.D.L.; Silva, G.B. da; Ukita, G.M.

    2002-01-01

    The 99 Ru(d,t) 98 Ru reaction was measured for the first time at 16 MeV incident energy with the Sao Paulo Pelletron-Enge-spectrograph facility employing the nuclear emulsion technique. In all, up to 3.5 MeV, 23 levels were detected, eight of them new; angular distributions are presented for all of them. Least squares fits of distorted wave Born approximation one-neutron pickup predictions to the rather well structured experimental angular distributions enabled the determination of l transfers and of the corresponding spectroscopic factors for 19 of these states, some being tentative attributions. Only transfers of l=0, 2, and 4 were observed. Several states were populated through single l transfers. A pure l=2 transfer is associated with the 2 1 + level and with several other states which are considered collective, as well as with the (4 + ) state at 2.277 MeV, which presents the highest spectroscopic strength. Considering five valence neutrons above the N=50 core, only 41% of the spectroscopic strength expected for 99 Ru was detected

  1. Specific Features of Intramolecular Proton Transfer Reaction in Schiff Bases

    Directory of Open Access Journals (Sweden)

    Aleksander Koll

    2003-06-01

    Full Text Available Abstract: The differences between the intramolecular proton transfer in Mannich and Schiff bases are discussed. The tautomeric forms being in equilibrium in both types of molecules are seriously different. In Mannich bases there are in equilibrium the forms of phenols and phenolates. In Schiff bases each of tautomers is strongly influenced by resonance between zwitterionic and keto structures. Despite the common opinion that the proton transfer forms in compounds with internal π-electronic coupling are mainly keto forms it is shown in this work, that in Schiff bases the content of keto structure is slightly less than zwitterionic one. Almost equal participation of both forms leads to effective resonance between them and stabilization of intramolecular hydrogen bond in this way.

  2. Modeling of mass transfer in combination with a homogeneously catalyzed reaction

    NARCIS (Netherlands)

    Hoorn, J.A.A.; Versteeg, G. F.

    The mass transfer rates of a gaseous reactant into a liquid where the reactions are catalyzed by homogeneous catalysts have been evaluated by the numerical solution of the diffusion-reaction equations according to Higbie's penetration theory. The concentration profiles as well as enhancement factors

  3. Cost-effectiveness of single versus double embryo transfer in IVF in relation to female age

    NARCIS (Netherlands)

    van Loendersloot, Laura L.; Moolenaar, Lobke M.; van Wely, Madelon; Repping, Sjoerd; Bossuyt, Patrick M.; Hompes, Peter G. A.; van der Veen, Fulco; Mol, Ben Willem J.

    2017-01-01

    Objective: To evaluate the cost-effectiveness of single embryo transfer followed by an additional frozen thawed single embryo transfer, if more embryos are available, as compared to double embryo transfer in relation to female age. Study design: We used a decision tree model to evaluate the costs

  4. Arsenate stabilized Cu₂O nanoparticle catalyst for one-electron transfer reversible reaction.

    Science.gov (United States)

    Sahoo, Ramkrishna; Dutta, Soumen; Pradhan, Mukul; Ray, Chaiti; Roy, Anindita; Pal, Tarasankar; Pal, Anjali

    2014-05-14

    The befitting capping capabilities of AsO4(3-) provide a stable Cu2O nanocatalyst from a galvanic reaction between a Cu(II) precursor salt and As(0) nanoparticles. This stable Cu2O hydrosol appears to be a suitable catalyst for the one-electron transfer reversible redox reaction between Eosin Y and NaBH4. The progress of the reaction relates to three different kinetic stages. In the presence of the new catalyst the reversible redox reaction of Eosin Y in air shows a periodic color change providing a new crowd-pleasing demonstration, i.e. a "clock reaction".

  5. Spin-transfer measurements of the π rvec d→ rvec pp reaction at energies spanning the Δ resonance

    International Nuclear Information System (INIS)

    Feltham, A.; Jones, G.; Olszewski, R.; Pavan, M.; Sevior, M.; Trelle, R.P.; Weber, P.; Lolos, G.J.; Mathie, E.L.; Papandreou, Z.; Rui, R.; Gill, D.; Healey, D.; Ottewell, D.; Sheffer, G.; Smith, G.R.; Sossi, V.; Wait, G.; Walden, P.

    1997-01-01

    The first spin-transfer experiment performed for the π rvec d→ rvec pp reaction is described. Three spin-transfer parameters for this π-absorption process were determined, K LS a , K SS a , and K NN a , which correspond to the π-production parameters, K SL p , K SS p , and K NN p , of the time-reversed rvec pp→ rvec dπ process. Each observable was measured at a single angle for a number of energies spanning the Δ resonance of this system. The results are compared with the predictions of published partial wave amplitude fits which are primarily based on existing data for the time-reversed pp→dπ reaction, and also with the predictions of two current theories. The failure of these theories to describe the fundamental features of the data clearly demonstrates the need for further theoretical work in this area. copyright 1997 The American Physical Society

  6. Spectrophotometric determination of anilines based on charge-transfer reaction

    Science.gov (United States)

    Wu, Hao; Du, Li Ming

    2007-07-01

    The molecular interactions between aniline, p-toluidines, benzidine and p-phenylenediamine as electron donors and 7,7,8,8-tetracyanoquinodimethane (TCNQ) as acceptor have been investigated by spectrophotometric method. Different variables affecting the reaction were studies and optimized. At the optimum reaction conditions Beer's law was obeyed in a concentration limit of 0.6-3.0, 0.3-3.0, 0.3-3.0 and 0.3-2.7 μg ml -1 for aniline, p-toluidines, benzidine and p-phenylenediamine. The developed methods were applied successfully for the determination of the studied compounds in waste water and relative standard deviation of the methods were 0.8-3.0%. Percentage recoveries ranged from 97.22% to 102.78%.

  7. Two-proton transfer reactions on even Ni and Zn isotopes

    International Nuclear Information System (INIS)

    Boucenna, A.; Kraus, L.; Linck, I.; Tsan Ung Chan

    1988-01-01

    Two-proton transfer reactions induced by 112 MeV 12 C ions on even Ni and Zn isotopes are found to be less selective than the analogous two-neutron transfer reactions induced on the same targets in a similar incident energy range. The additional collective aspects observed in the proton transfer are examined in view of a semiphenomenological model of two quasi-particles coupled to a triaxial asymmetric rotor. Tentative spin and parity assignments emerge from this comparison, from crude shell model calculations and from systematic trends

  8. Observation of new neutron-deficient isotopes with Z≥92 in multinucleon transfer reactions

    Directory of Open Access Journals (Sweden)

    H.M. Devaraja

    2015-09-01

    Full Text Available In deep inelastic multinucleon transfer reactions of 48Ca + 248Cm we observed about 100 residual nuclei with proton numbers between Z=82 and Z=100. Among them, there are five new neutron-deficient isotopes: 216U, 219Np, 223Am, 229Am and 233Bk. As separator for the transfer products we used the velocity filter SHIP of GSI while the isotope identification was performed via the α decay chains of the nuclei. These first results reveal that multinucleon transfer reactions together with here applied fast and sensitive separation and detection techniques are promising for the synthesis of new isotopes in the region of heaviest nuclei.

  9. Pore to core scale simulation of the mass transfer with mineral reaction in porous media

    International Nuclear Information System (INIS)

    Bekri, S.; Renard, S.; Delprat-Jannaud, F.

    2015-01-01

    Pore Network Model (PNM) is used to simulate mass transfer with mineral reaction in a single phase flow through porous medium which is here a sandstone sample from the reservoir formation of the Pakoslaw gas field. The void space of the porous medium is represented by an idealized geometry of pore-bodies joined by pore-throats. Parameters defining the pore-bodies and the pore-throats distribution are determined by an optimization process aiming to match the experimental Mercury Intrusion Capillary Pressure (MICP) curve and petrophysical properties of the rock such as intrinsic permeability and formation factor. The generated network is used first to simulate the multiphase flow by solving Kirchhoff's laws. The capillary pressure and relative permeability curves are derived. Then, reactive transport is addressed under asymptotic regime where the solute concentration undergoes an exponential evolution with time. The porosity/ permeability relationship and the three phenomenological coefficients of transport, namely the solute velocity, the dispersion and the mean reaction rate are determined as functions of Peclet and Peclet-Damkohler dimensionless numbers. Finally, the role of the dimensionless numbers on the reactive flow properties is highlighted. (authors)

  10. Recent advances in transition metal-catalyzed N -atom transfer reactions of azides

    Science.gov (United States)

    Driver, Tom G.

    2011-01-01

    Transition metal-catalyzed N-atom transfer reactions of azides provide efficient ways to construct new carbon–nitrogen and sulfur–nitrogen bonds. These reactions are inherently green: no additive besides catalyst is needed to form the nitrenoid reactive intermediate, and the by-product of the reaction is environmentally benign N2 gas. As such, azides can be useful precursors for transition metal-catalyzed N-atom transfer to sulfides, olefins and C–H bonds. These methods offer competitive selectivities and comparable substrate scope as alternative processes to generate metal nitrenoids. PMID:20617243

  11. Excitation functions for quasi-elastic transfer reactions induced with heavy ions in bismuth

    International Nuclear Information System (INIS)

    Gardes, D.; Bimbot, R.; Maison, J.; Reilhac, L. de; Rivet, M.F.; Fleury, A.; Hubert, F.; Llabador, Y.

    1977-01-01

    The excitation functions for the production of 210 Bi, 210 Po, sup(207-211)At and 211 Rn through quasi-elastic transfer reactions induced with heavy ions in 209 Bi have been measured. The corresponding reactions involved the transfer of one neutron, one proton, two and three charges from projectile to target. The projectiles used were 12 C, 14 N, 16 O, 19 F, 20 Ne, 40 Ca, 56 Fe and 63 Cu. The experimental techniques involved target irradiations and off-line α and γ activity measurements. Chemical separations were used to solve specific problems. Careful measurements of incident energies and cross sections were performed close to the reaction thresholds

  12. Recent aspects of the proton transfer reaction in H-bonded complexes

    Science.gov (United States)

    Szafran, Mirosław

    1996-07-01

    Proton transfer processes cover a very wide range of situations and time scales and they are of great interest from the viewpoint of chemical reactions in solution. These processes can occur via thermally activated crossing or tunneling. This review considers various aspects of this many-faceted field. Spectroscopic, dielectric, colligative and energetic properties and structures of various species with H-bonds are examined. Proton transfer reactions in water and organic solvents, and the contribution of various H-bonded species and ions to these processes are discussed. Among other topics, this survey includes the effects of solvent, acid-base stoichiometry, concentration, temperature and impurity on proton transfer reactions in complexes of phenols and carboxylic acids with amines, pyridines and pyridine N-oxides. The contribution of the nonstoichiometric acid-base complexes and ionic species to the reversible proton transfer mechanism is discussed.

  13. Product distributions for some thermal energy charge transfer reactions of rare gas ions

    Science.gov (United States)

    Anicich, V. G.; Laudenslager, J. B.; Huntress, W. T., Jr.; Futrell, J. H.

    1977-01-01

    Ion cyclotron resonance methods were used to measure the product distributions for thermal-energy charge-transfer reactions of He(+), Ne(+), and Ar(+) ions with N2, O2, CO, NO, CO2, and N2O. Except for the He(+)-N2 reaction, no molecular ions were formed by thermal-energy charge transfer from He(+) and Ne(+) with these target molecules. The propensity for dissociative ionization channels in these highly exothermic charge-transfer reactions at thermal energies contrasts with the propensity for formation of parent molecular ions observed in photoionization experiments and in high-energy charge-transfer processes. This difference is explained in terms of more stringent requirements for energy resonance and favorable Franck-Condon factors at thermal ion velocities.

  14. Development of Novel Electrode Materials for the Electrocatalysis of Oxygen-Transfer and Hydrogen-Transfer Reactions

    Energy Technology Data Exchange (ETDEWEB)

    Simpson, Brett Kimball [Iowa State Univ., Ames, IA (United States)

    2002-01-01

    Throughout this thesis, the fundamental aspects involved in the electrocatalysis of anodic O-transfer reactions and cathodic H-transfer reactions have been studied. The investigation into anodic O-transfer reactions at undoped and Fe(III)[doped MnO2 films] revealed that MnO2 film electrodes prepared by a cycling voltammetry deposition show improved response for DMSO oxidation at the film electrodes vs. the Au substrate. Doping of the MnO2 films with Fe(III) further enhanced electrode activity. Reasons for this increase are believed to involve the adsorption of DMSO by the Fe(III) sites. The investigation into anodic O-transfer reactions at undoped and Fe(III)-doped RuO2 films showed that the Fe(III)-doped RuO2-film electrodes are applicable for anodic detection of sulfur compounds. The Fe(III) sites in the Fe-RuO2 films are speculated to act as adsorption sites for the sulfur species while the Ru(IV) sites function for anodic discharge of H2O to generate the adsorbed OH species. The investigation into cathodic H-transfer reactions, specifically nitrate reduction, at various pure metals and their alloys demonstrated that the incorporation of metals into alloy materials can create a material that exhibits bifunctional properties for the various steps involved in the overall nitrate reduction reaction. The Sb10Sn20Ti70, Cu63Ni37 and Cu25Ni75 alloy electrodes exhibited improved activity for nitrate reduction as compared to their pure component metals. The Cu63Ni37 alloy displayed the highest activity for nitrate reduction. The final investigation was a detailed study of the electrocatalytic activity of cathodic H-transfer reactions (nitrate reduction) at various compositions of Cu-Ni alloy electrodes. Voltammetric response for NO3- at the Cu-Ni alloy electrode is superior to

  15. Excited state intramolecular charge transfer reaction in 4-(1 ...

    Indian Academy of Sciences (India)

    Administrator

    The organization of the rest of the paper is as fol- lows. Experimental details are given in ... found to be bi-exponential functions of time with one short and one long time constants, the decay in non-polar solvents (such as hexane or heptane) was single-exponential with only one long time constant. In addition, the short time ...

  16. Transfer hydrogenation reactions catalyzed by chiral half-sandwich ...

    Indian Academy of Sciences (India)

    Chiral ruthenium half-sandwich complexes were prepared using a chelating diamine made from proline with a phenyl, ethyl, or benzyl group, instead of hydrogen on one of the coordinating arms. Three of these complexes were obtained as single diastereoisomers and their configuration identified by X-ray crystallography.

  17. Imaging the electron transfer reaction of Ne2+ with Ar using position-sensitive coincidence spectroscopy

    International Nuclear Information System (INIS)

    Harper, Sarah M; Hu Wanping; Price, Stephen D

    2002-01-01

    A new experiment, employing position-sensitive detection coupled with time-of-flight mass spectrometry, has been used to investigate the single-electron transfer reaction between Ne 2+ and Ar by detecting the resulting pairs of singly charged ions in coincidence. The experimental technique allows the determination of the individual velocity vectors of the ionic products, in the centre-of-mass frame, for each reactive event detected. The experiments show that forward scattering dominates the reactivity, although a bimodal angular distribution is apparent. In addition, the spectra show that at laboratory frame collision energies from 4-14 eV the reactivity is dominated by Ne 2+ (2p 4 , 3 P) accepting an electron from an argon atom to form the ground state of Ne + together with an Ar + ion in an excited electronic level, predominantly arising from the Ar + (3s 2 3p 4 3d) configuration. The form of this reactivity, and the differences between the reactivity observed in these experiments and those performed at higher collision energies, are well reproduced by Landau-Zener theory

  18. Cryogenic Fluid Transfer Components Using Single Crystal Piezoelectric Actuators, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Cryogenic fluid transfer components using single crystal piezoelectric actuators are proposed to enable low thermal mass, minimal heat leak, low power consumption...

  19. Cryogenic Fluid Transfer Components Using Single Crystal Piezoelectric Actuators, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — Cryogenic fluid transfer components using single crystal piezoelectric actuators are proposed to enable low thermal mass, minimal heat leak, low power consumption...

  20. Bond-formation versus electron transfer: C-C-coupling reactions of hydrocarbon dications with benzene.

    Science.gov (United States)

    Roithová, Jana; Schröder, Detlef

    2007-02-14

    The bimolecular reactions of several hydrocarbon dications C(m)H(n)(2+) (m = 6-10, n = 4-9) with neutral benzene are investigated by tandem mass spectrometry using a multipole instrument. Not surprisingly, the major reaction of C(m)H(n)(2+) with benzene corresponds to electron transfer from the neutral arene to the dication resulting in the pair of monocationic products C(m)H(n)(+) + C(6)H(6)(+). In addition, also dissociative electron transfer takes place, whereas proton transfer from the C(m)H(n)(2+) dication to neutral benzene is almost negligible. Interestingly, the excess energy liberated upon electron transfer from the neutral arene to the C(m)H(n)(2+) dication is not equally partitioned in the monocationic products in that the cations arising from the dicationic precursor have a higher internal energy content than the monocations formed from the neutral reaction partner. In addition to the reactions leading to monocationic product ions, bond-forming reactions with maintenance of the two-fold charge are observed, which lead to a condensation of the C(m)H(n)(2+) dications with neutral benzene under formation of intermediate C(m+6)H(n+6)(2+) species and then undergo subsequent losses of molecular hydrogen or neutral acetylene. This reaction complements a recently proposed dicationic route for the formation of polycyclic aromatic hydrocarbons under extreme conditions such as they exist in interstellar environments.

  1. QCD tests and large momentum-transfer reactions at CBA

    International Nuclear Information System (INIS)

    Longacre, R.; Tannenbaum, M.J.

    1983-03-01

    It is desirable to try to find fundamental tests of QCD which are sensitive to the specific properties of gluons and the non-Alelian structure of the theory, which would show that the theory is computable above leading order, and which are insensitive to the extraneous parameters such as structure functions, fragmentation functions and the like. Such tests can occur when higher-order corrections produce interference effects which must be zero in lowest order. One such effect is the linear polarization of direct single photons produced in p-p collisions. It is claimed that this polarization provides a rigorous test of perturbative QCD as well as an important check on the color hypothesis. This latter aspect is particularly attractive because the polarization involves the three-gluon interaction and the equality of the quark-gluon and three-gluon coupling in an essential way. Plans for studies at the CBA are discussed

  2. Observing Proton Transfer Reactions Inside the MALDI Plume: Experimental and Theoretical Insight into MALDI Gas-Phase Reactions

    Science.gov (United States)

    Mirabelli, Mario F.; Zenobi, Renato

    2017-08-01

    We evaluated the contribution of gas-phase in-plume proton transfer reactions to the formation of protonated and deprotonated molecules in the MALDI process. A split sample holder was used to separately deposit two different samples, which avoids any mixing during sample preparation. The two samples were brought very close to each other and desorbed/ionized by the same laser pulse. By using a combination of deuterated and non-deuterated matrices, it was possible to observe exclusively in-plume proton transfer processes. The hydrogen/deuterium exchange (HDX) kinetics were evaluated by varying the delayed extraction (DE) time, allowing the desorbed ions and neutrals to interact inside the plume for a variable period of time before being extracted and detected. Quantum mechanical calculations showed that the HDX energy barriers are relatively low for such reactions, corroborating the importance of gas-phase proton transfer in the MALDI plume. The experimental results, supported by theoretical simulations, confirm that the plume is a very reactive environment, where HDX reactions could be observed from 0 ns up to 400 ns after the laser pulse. These results could be used to evaluate the relevance of previously proposed (and partially conflicting) ionization models for MALDI.

  3. Nobel Prize 1992: Rudolph A. Marcus: theory of electron transfer reactions in chemical systems

    International Nuclear Information System (INIS)

    Ulate Segura, Diego Guillermo

    2011-01-01

    A review of the theory developed by Rudolph A. Marcus is presented, who for his rating to the theory of electron transfer in chemical systems was awarded the Nobel Prize in Chemistry in 1992. Marcus theory has constituted not only a good extension of the use of a spectroscopic principle, but also has provided an energy balance and the application of energy conservation for electron transfer reactions. A better understanding of the reaction coordinate is exposed in terms energetic and establishing the principles that govern the transfer of electrons, protons and some labile small molecular groups as studied at present. Also, the postulates and equations described have established predictive models of reaction time, very useful for industrial environments, biological, metabolic, and others that involve redox processes. Marcus theory itself has also constituted a large contribution to the theory of complex transition [es

  4. Analysis of trace gases at ppb levels by proton transfer reaction mass spectrometry (PTR-MS)

    International Nuclear Information System (INIS)

    Lindinger, W.; Hansel, A.

    1996-01-01

    A proton transfer reaction mass spectrometry (PTR-MS) system has been developed which allows for on-line measurements of trace gas components with concentrations as low as 1 ppb. The method is based on reactions of H 3 O + ions, which perform non-dissociative proton transfer to most of the common organic trace constituents but do not react with any of the components present in clean air. Examples of medical information obtained by means of breath analysis, of environmental trace analysis, and examples in the field of food chemistry demonstrate the wide applicability of the method. (Authors)

  5. Characterization of Porphyrin-Co(III)-‘Nitrene Radical’ Species Relevant in Catalytic Nitrene Transfer Reactions

    OpenAIRE

    Goswami, Monalisa; Lyaskovskyy, Volodymyr; Domingos, Sérgio R.; Buma, Wybren Jan; Woutersen, Sander; Troeppner, Oliver; Ivanović-Burmazović, Ivana; Lu, Hongjian; Cui, Xin; Zhang, X. Peter; Reijerse, Edward J.; DeBeer, Serena; van Schooneveld, Matti M.; Pfaff, Florian Felix; Ray, Kallol

    2015-01-01

    To fully characterize the CoIII–‘nitrene radical’ species that are proposed as intermediates in nitrene transfer reactions mediated by cobalt(II) porphyrins, different combinations of cobalt(II) complexes of porphyrins and nitrene transfer reagents were combined, and the generated species were studied using EPR, UV–vis, IR, VCD, UHR-ESIMS, and XANES/XAFS measurements. Reactions of cobalt-(II) porphyrins 1P1 (P1 = meso-tetraphenylporphyrin (TPP)) and 1P2 (P2 = 3,5-DitBu-ChenPhyrin) with organi...

  6. Investigation of transition metal-catalyzed nitrene transfer reactions in water.

    Science.gov (United States)

    Alderson, Juliet M; Corbin, Joshua R; Schomaker, Jennifer M

    2018-04-11

    Transition metal-catalyzed nitrene transfer is a powerful method for incorporating new CN bonds into relatively unfunctionalized scaffolds. In this communication, we report the first examples of site- and chemoselective CH bond amination reactions in aqueous media. The unexpected ability to employ water as the solvent in these reactions is advantageous in that it eliminates toxic solvent use and enables reactions to be run at increased concentrations with lower oxidant loadings. Using water as the reaction medium has potential to expand the scope of nitrene transfer to encompass a variety of biomolecules and highly polar substrates, as well as enable pH control over the site-selectivity of CH bond amination. Copyright © 2018 Elsevier Ltd. All rights reserved.

  7. Interplay of break-up and transfer processes in reactions involving weakly-bound systems

    Science.gov (United States)

    Vitturi, Andrea; Moschini, Laura

    2018-02-01

    In this note we illustrate some applications of a simple model which has been devised to clarify the reaction mechanism and the interplay of different reaction channels (elastic, inelastic, transfer, break-up) in heavy-ion collisions. The model involves two potential wells moving in one dimension and few active particles; in spite of its simplicity, it is supposed to maintain the main features, the properties and the physics of the full three-dimensional case. Special attention is given to the role of continuum states in reactions involving weakly-bound systems, and different approximation schemes (as first-order or coupled-channels) as well as different continuum discretization procedures are tested. In the case of two active particles the reaction mechanism associated with two-particle transfer and the effect of pairing intearction are investigated. Work done in collaboration with Antonio Moro and Kouichi Hagino

  8. The medium reorganization energy for the charge transfer reactions in proteins.

    Science.gov (United States)

    Krishtalik, Lev I

    2011-11-01

    A low static dielectric permittivity of proteins causes the low reorganization energies for the charge transfer reactions inside them. This reorganization energy does not depend on the pre-existing intraprotein electric field. The charge transferred inside the protein interacts with its aqueous surroundings; for many globular proteins, the effect of this surroundings on the reorganization energy is comparable with the effect of reorganization of the protein itself while for the charge transfer in the middle of membrane the aqueous phase plays a minor role. Reorganization energy depends strongly on the system considered, and hence there is no sense to speak on the "protein reorganization energy" as some permanent characteristic parameter. We employed a simple algorithm for calculation of the medium reorganization energy using the numerical solution of the Poisson-Boltzmann equation. Namely, the reaction field energy was computed in two versions - all media having optical dielectric permittivity, and all the media with the static one; the difference of these two quantities gives the reorganization energy. We have calculated reorganization energies for electron transfer in cytochrome c, various ammine-ruthenated cytochromes c, azurin, ferredoxin, cytochrome c oxidase, complex of methylamine dehydrogenase with amicyanin, and for proton transfer in α-chymotrypsin. It is shown that calculation of the medium reorganization energy can be a useful tool in analysis of the mechanisms of the charge transfer reactions in proteins. 2011 Elsevier B.V. All rights reserved.

  9. Electron transfer reaction of butane -1,3-diol and cr(vi) in aqueous ...

    African Journals Online (AJOL)

    Kinetic and mechanistic studies of electron transfer reaction of butane-1,3-diol and Cr(VI) ion in aqueous acidic medium have been carried out in aqueous medium at 271°C, I = 1.0 mol dm-3 (NaCl), [H +] = 0.5mol dm-3 (HCl). The reaction was inhibited by added anions and showed negative salt effect. Spectroscopic ...

  10. Influence of the chain-transfer reactions on the emulsion post-polymerization process

    International Nuclear Information System (INIS)

    Lukhovitskij, V.I.; Polikarpov, V.V.; Pozdeeva, R.M.

    1975-01-01

    A probability of free radical exit from latex particle in the course of chain transfer reaction is defined by properties of the radical itself. In the case of emulsive post-polymerization of styrene in the presence of H-dodecylmercantane the value α for CCL 3 is about 3x10 -2 , for radical C 12 H 25 it is close to zero and for the radical generated under transfer to the monomer it is approximately 10 -2 . The effect of transfer to the monomer on the emulsive post-polymerization is discussed: it is responsible for the high degree of monomer conversion

  11. Experimental study of the $^{66}$Ni$(d,p)^{67}$Ni one-neutron transfer reaction

    CERN Document Server

    Diriken, J.; Andreyev, A.N.; Antalic, S.; Bildstein, V.; Blazhev, A.; Darby, I.G.; De Witte, H.; Eberth, J.; Elseviers, J.; Fedosseev, V.N.; Flavigny, F.; Fransen, Ch.; Georgiev, G.; Gernhauser, R.; Hess, H.; Huyse, M.; Jolie, J.; Kröll, Th.; Krücken, R.; Lutter, R.; Marsh, B.A.; Mertzimekis, T.; Muecher, D.; Orlandi, R.; Pakou, A.; Raabe, R.; Randisi, G.; Reiter, P.; Roger, T.; Seidlitz, M.; Seliverstov, M.; Sotty, C.; Tornqvist, H.; Van De Walle, J.; Van Duppen, P.; Voulot, D.; Warr, N.; Wenander, F.; Wimmer, K.

    2015-01-01

    The quasi-SU(3) sequence of the positive parity $νg_{9/2}, d_{5/2}, s_{1/2}$ orbitals above the N=40 shell gap are assumed to induce strong quadrupole collectivity in the neutron-rich Fe (Z=26) and Cr (Z=24) isotopes below the nickel region. In this paper the position and strength of these single-particle orbitals are characterized in the neighborhood of $^{68}$Ni (Z=28,N=40) through the $^{66}$Ni($d,p$)$^{67}$Ni one-neutron transfer reaction at 2.95 MeV/nucleon in inverse kinematics, performed at the REX-ISOLDE facility in CERN. A combination of the Miniball $\\gamma$-array and T-REX particle-detection setup was used and a delayed coincidence technique was employed to investigate the 13.3-$\\mu$s isomer at 1007 keV in $^{67}$Ni. Excited states up to an excitation energy of 5.8 MeV have been populated. Feeding of the $νg_{9/2}$ (1007 keV) and $νd_{5/2}$ (2207 keV and 3277 keV) positive-parity neutron states and negative parity ($νpf$) states have been observed at low excitation energy. The extracted relativ...

  12. Mass transfer model for two-layer TBP oxidation reactions: Revision 1

    International Nuclear Information System (INIS)

    Laurinat, J.E.

    1994-01-01

    To prove that two-layer, TBP-nitric acid mixtures can be safely stored in the Canyon evaporators, it must be demonstrated that a runaway reaction between TBP and nitric acid will not occur. Previous bench-scale experiments showed that, at typical evaporator temperatures, this reaction is endothermic and therefore cannot run away, due to the loss of heat from evaporation of water in the organic layer. However, the reaction would be exothermic and could run away if the small amount of water in the organic layer evaporates before the nitric acid in this layer is consumed by the reaction. Provided that there is enough water in the aqueous layer, this would occur if the organic layer is sufficiently thick so that the rate of loss of water by evaporation exceeds the rate of replenishment due to mixing with the aqueous layer. Bubbles containing reaction products enhance the rate of transfer of water from the aqueous layer to the organic layer. These bubbles are generated by the oxidation of TBP and its reaction products in the organic layer and by the oxidation of butanol in the aqueous layer. Butanol is formed by the hydrolysis of TBP in the organic layer. For aqueous-layer bubbling to occur, butanol must transfer into the aqueous layer. Consequently, the rate of oxidation and bubble generation in the aqueous layer strongly depends on the rate of transfer of butanol from the organic to the aqueous layer. This report presents measurements of mass transfer rates for the mixing of water and butanol in two-layer, TBP-aqueous mixtures, where the top layer is primarily TBP and the bottom layer is comprised of water or aqueous salt solution. Mass transfer coefficients are derived for use in the modeling of two-layer TBP-nitric acid oxidation experiments

  13. Single-molecule stochastic times in a reversible bimolecular reaction.

    Science.gov (United States)

    Keller, Peter; Valleriani, Angelo

    2012-08-28

    In this work, we consider the reversible reaction between reactants of species A and B to form the product C. We consider this reaction as a prototype of many pseudobiomolecular reactions in biology, such as for instance molecular motors. We derive the exact probability density for the stochastic waiting time that a molecule of species A needs until the reaction with a molecule of species B takes place. We perform this computation taking fully into account the stochastic fluctuations in the number of molecules of species B. We show that at low numbers of participating molecules, the exact probability density differs from the exponential density derived by assuming the law of mass action. Finally, we discuss the condition of detailed balance in the exact stochastic and in the approximate treatment.

  14. Severe immediate allergic reactions to grapes: part of a lipid transfer protein-associated clinical syndrome

    NARCIS (Netherlands)

    Vassilopoulou, Emilia; Zuidmeer, Laurian; Akkerdaas, Jaap; Tassios, Ioannis; Rigby, Neil R.; Mills, E. N. Clare; van Ree, Ronald; Saxoni-Papageorgiou, Photini; Papadopoulos, Nikolaos G.

    2007-01-01

    BACKGROUND: Grape allergy is considered rare; grape lipid transfer protein (LTP; Vit v 1), an endochitinase and a thaumatin-like protein (TLP) have been reported as grape allergens. A considerable number of patients have referred to our department for severe reactions to grapes, and several IgE

  15. Electron transfer reactions, cyanide and O2 binding of truncated hemoglobin from Bacillus subtilis

    DEFF Research Database (Denmark)

    Fernandez, Esther; Larsson, Jonas T.; McLean, Kirsty J.

    2013-01-01

    The truncated hemoglobin from Bacillus subtilis (trHb-Bs) possesses a surprisingly high affinity for oxygen and resistance to (auto)oxidation; its physiological role in the bacterium is not understood and may be connected with its very special redox and ligand binding reactions. Electron transfer...

  16. Mechanism of the Primary Charge Transfer Reaction in the Cytochrome bc1 Complex

    DEFF Research Database (Denmark)

    Barragan, Angela M; Schulten, Klaus; Solov'yov, Ilia A

    2016-01-01

    , the quinol-protein interaction, which initiates the Q-cycle, has not yet been completely described. Furthermore, the initial charge transfer reactions of the Q-cycle lack a physical description. The present investigation utilizes classical molecular dynamics simulations in tandem with quantum density...

  17. Numerical analysis of inter-phase mass transfer with chemical reaction

    African Journals Online (AJOL)

    The numerical analysis in the present study simulates inter-phase mass transfer with chemical reaction of two immiscible liquids by simultaneously solving the Higbie Penetration model. The transport equations are solved numerically for concentration and temperature profiles at the inter-phase using finite volume method ...

  18. Cluster-transfer reactions with radioactive beams: a spectroscopic tool for neutron-rich nuclei

    CERN Document Server

    AUTHOR|(CDS)2086156; Raabe, Riccardo; Bracco, Angela

    In this thesis work, an exploratory experiment to investigate cluster-transfer reactions with radioactive beams in inverse kinematics is presented. The aim of the experiment was to test the potential of cluster-transfer reactions at the Coulomb barrier, as a possible mean to perform $\\gamma$ spectroscopy studies of exotic neutron-rich nuclei at medium-high energies and spins. The experiment was performed at ISOLDE (CERN), employing the heavy-ion reaction $^{98}$Rb + $^{7}$Li at 2.85 MeV/A. Cluster-transfer reaction channels were studied through particle-$\\gamma$ coincidence measurements, using the MINIBALL Ge array coupled to the charged particle Si detectors T-REX. Sr, Y and Zr neutron-rich nuclei with A $\\approx$ 100 were populated by either triton- or $\\alpha$ transfer from $^{7}$Li to the beam nuclei and the emitted complementary charged fragment was detected in coincidence with the $\\gamma$ cascade of the residues, after few neutrons evaporation. The measured $\\gamma$ spectra were studied in detail and t...

  19. Offline thermal-desorption proton-transfer-reaction mass spectrometry to study composition of organic aerosol

    NARCIS (Netherlands)

    Timkovsky, J.; Dusek, U.|info:eu-repo/dai/nl/314134166; Henzing, J. S.; Kuipers, T. L.; Röckmann, T.|info:eu-repo/dai/nl/304838233; Holzinger, R.|info:eu-repo/dai/nl/337989338

    2015-01-01

    We present a novel approach to study the organic composition of aerosol filter samples using thermal-desorption proton-transfer-reaction mass spectrometry (TD-PTR-MS) in the laboratory. The method is tested and validated based on the comparison with in situ TD-PTR-MS measurements. In general, we

  20. Functional LH1 antenna complexes influence electron transfer in bacterial photosynthetic reaction centers.

    NARCIS (Netherlands)

    Visschers, R.W.; Vulto, S.I.E.; Jones, M.R.; van Grondelle, R.; Kraayenhof, R.

    1999-01-01

    The effect of the light harvesting 1 (LH1) antenna complex on the driving force for light-driven electron transfer in the Rhodobacter sphaeroides reaction center has been examined. Equilibrium redox titrations show that the presence of the LH1 antenna complex influences the free energy change for

  1. Functional LH1 antenna complexes influence electron transfer in bacterial photosynthetic reaction centers

    NARCIS (Netherlands)

    Visschers, R.W.; Vulto, S.I.E.; Jones, M.R.; van Grondelle, R.; Kraayenhof, R.

    1999-01-01

    The effect of the light harvesting 1 (LH1) antenna complex on the driving force for light-driven electron transfer in the Rhodobacter sphaeroides reaction center has been examined. Equilibrium redox titrations show that the presence of the LH1 antenna complex influences the free energy change for

  2. Transfer reactions in sup(32,36)S + sup(144,154)Sm

    International Nuclear Information System (INIS)

    Pacheco, A.J.; Tada, M. di; Fernandez Niello, J.; Testoni, J.E.

    1990-01-01

    The deformation of spherical nuclei in transfer reactions near to the coulomb barrier is studied. The sup(32,36)S + sup(144,154)Sm reactions were carried out using sup(32)S beams produced by TANDAR accelerator in Buenos Aires with energies of 148 MeV and 160 MeV and sup(36)S beams produced by tandem accelerator of Laboratorio Nazionale di Legnaro with energies of 142 MeV and 155 MeV. The angular distributions were measured for sup(32)S reaction using gas ionization chamber and position sensitive detector. The mass spectra of reaction products were obtained measuring time of flight between time detectors, in the sup(36)S reaction. (M.C.K.)

  3. Production and study of new neutron rich heavy nuclei in multinucleon transfer reactions

    Directory of Open Access Journals (Sweden)

    Zagrebaev V.I.

    2013-12-01

    Full Text Available Problems of production and study of new neutron-enriched heavy nuclei are discussed. Low-energy multinucleon transfer reactions are shown to be quite appropriate for this purpose. Reactions with actinide beams and targets are of special interest for synthesis of new neutron-enriched transfermium nuclei and not-yet-known nuclei with closed neutron shell N = 126 having the largest impact on the astrophysical r-process. The estimated cross sections for the production of these nuclei look very promising for planning such experiments at currently available accelerators. These experiments, however, are rather expensive and difficult to perform because of low intensities of the massive projectile beams and problems of separating and detecting the heavy reaction products. Thus, realistic predictions of the corresponding cross sections for different projectile-target combinations are definitely required. Some uncertainty still remains in the values of several parameters used for describing the low-energy nuclear dynamics. This uncertainty does not allow one to perform very accurate predictions for the productions of new heavier-than-target (trans-target nuclei in multinucle on transfer reactions. Nevertheless these predictions are rather promising (large cross sections to start such experiments at available accelerators if the problem of separation of heavy transfer reaction products would be solved.

  4. Hydride Transfer versus Deprotonation Kinetics in the Isobutane–Propene Alkylation Reaction: A Computational Study

    Science.gov (United States)

    2017-01-01

    The alkylation of isobutane with light alkenes plays an essential role in modern petrochemical processes for the production of high-octane gasoline. In this study we have employed periodic DFT calculations combined with microkinetic simulations to investigate the complex reaction mechanism of isobutane–propene alkylation catalyzed by zeolitic solid acids. Particular emphasis was given to addressing the selectivity of the alkylate formation versus alkene formation, which requires a high rate of hydride transfer in comparison to the competitive oligomerization and deprotonation reactions resulting in catalyst deactivation. Our calculations reveal that hydride transfer from isobutane to a carbenium ion occurs via a concerted C–C bond formation between a tert-butyl fragment and an additional olefin, or via deprotonation of the tert-butyl fragment to generate isobutene. A combination of high isobutane concentration and low propene concentration at the reaction center favor the selective alkylation. The key reaction step that has to be suppressed to increase the catalyst lifetime is the deprotonation of carbenium intermediates that are part of the hydride transfer reaction cycle. PMID:29226012

  5. Hydride Transfer versus Deprotonation Kinetics in the Isobutane-Propene Alkylation Reaction: A Computational Study.

    Science.gov (United States)

    Liu, Chong; van Santen, Rutger A; Poursaeidesfahani, Ali; Vlugt, Thijs J H; Pidko, Evgeny A; Hensen, Emiel J M

    2017-12-01

    The alkylation of isobutane with light alkenes plays an essential role in modern petrochemical processes for the production of high-octane gasoline. In this study we have employed periodic DFT calculations combined with microkinetic simulations to investigate the complex reaction mechanism of isobutane-propene alkylation catalyzed by zeolitic solid acids. Particular emphasis was given to addressing the selectivity of the alkylate formation versus alkene formation, which requires a high rate of hydride transfer in comparison to the competitive oligomerization and deprotonation reactions resulting in catalyst deactivation. Our calculations reveal that hydride transfer from isobutane to a carbenium ion occurs via a concerted C-C bond formation between a tert -butyl fragment and an additional olefin, or via deprotonation of the tert -butyl fragment to generate isobutene. A combination of high isobutane concentration and low propene concentration at the reaction center favor the selective alkylation. The key reaction step that has to be suppressed to increase the catalyst lifetime is the deprotonation of carbenium intermediates that are part of the hydride transfer reaction cycle.

  6. The improvement of the heat transfer model for sodium-water reaction jet code

    International Nuclear Information System (INIS)

    Hashiguchi, Yoshirou; Yamamoto, Hajime; Kamoshida, Norio; Murata, Shuuichi

    2001-02-01

    For confirming the reasonable DBL (Design Base Leak) on steam generator (SG), it is necessary to evaluate phenomena of sodium-water reaction (SWR) in an actual steam generator realistically. The improvement of a heat transfer model on sodium-water reaction (SWR) jet code (LEAP-JET ver.1.40) and application analysis to the water injection tests for confirmation of propriety for the code were performed. On the improvement of the code, the heat transfer model between a inside fluid and a tube wall was introduced instead of the prior model which was heat capacity model including both heat capacity of the tube wall and inside fluid. And it was considered that the fluid of inside the heat exchange tube was able to treat as water or sodium and typical heat transfer equations used in SG design were also introduced in the new heat transfer model. Further additional work was carried out in order to improve the stability of the calculation for long calculation time. The test calculation using the improved code (LEAP-JET ver.1.50) were carried out with conditions of the SWAT-IR·Run-HT-2 test. It was confirmed that the SWR jet behavior on the result and the influence to the result of the heat transfer model were reasonable. And also on the improved code (LEAP-JET ver.1.50), user's manual was revised with additional I/O manual and explanation of the heat transfer model and new variable name. (author)

  7. Debating elective single embryo transfer after in vitro fertilization: a ...

    African Journals Online (AJOL)

    However, despite clinical recommendations and policy statements, patients in clinical practice frequently do request for the transfer of multiple embryos in order to have twins. Such requests conflict with policy guidelines and create an ethical dilemma for physicians: Should the physician do as the couple requests, and there ...

  8. Probing surface distributions of α clusters in 20Ne via α -transfer reaction

    Science.gov (United States)

    Fukui, Tokuro; Taniguchi, Yasutaka; Suhara, Tadahiro; Kanada-En'yo, Yoshiko; Ogata, Kazuyuki

    2016-03-01

    Background: Direct evidence of the α -cluster manifestation in bound states has not been obtained yet, although a number of experimental studies were carried out to extract the information of the clustering. In particular in conventional analyses of α -transfer reactions, there exist a few significant problems on reaction models, which are insufficient to qualitatively discuss the cluster structure. Purpose: We aim to verify the manifestation of the α -cluster structure from observables. As the first application, we plan to extract the spatial information of the cluster structure of the 20Ne nucleus in its ground state through the cross section of the α -transfer reaction 16O(6Li,d )20Ne. Methods: For the analysis of the transfer reaction, we work with the coupled-channel Born approximation (CCBA) approach, in which the breakup effect of 6Li is explicitly taken into account by means of the continuum-discretized coupled-channel method based on the three-body α +d +16O model. The two methods are adopted to calculate the overlap function between 20Ne and α +16O ; one is the microscopic cluster model (MCM) with the generator coordinate method, and the other is the phenomenological two-body potential model (PM). Results: We show that the CCBA calculation with the MCM wave function gives a significant improvement of the theoretical result on the angular distribution of the transfer cross section, which is consistent with the experimental data. Employing the PM, it is discussed which region of the cluster wave function is probed on the transfer cross section. Conclusions: It is found that the surface region of the cluster wave function is sensitive to the cross section. The present work is situated as the first step in obtaining important information to systematically investigate the cluster structure.

  9. Transfer in motion discrimination learning was no greater in double training than in single training.

    Science.gov (United States)

    Huang, Jinfeng; Liang, Ju; Zhou, Yifeng; Liu, Zili

    2017-06-01

    We investigated the controversy regarding double training in motion discrimination learning. We collected data from 43 participants in a motion direction discrimination learning task with either double training (i.e., training plus exposure) or single training (i.e., no exposure). By pooling these data with those in the literature, we had data in double training from 28 participants and in single training from 36 participants. We found that, in double training, the transfer along the exposed direction was less than that along the trained direction, indicating incomplete transfer. Importantly, the transfer in double training was not reliably greater than that in single training.

  10. Cowpea Reaction to Single and Mixed Viral Infection with Blackeye ...

    African Journals Online (AJOL)

    The results of the experiment showed that mixed inoculation with the two viruses, induced greater susceptibility to the viral pathogens in the plants, compared to single virus inoculations. The study also indicated that, early viral infection at 2 WAP, was more pathogenic and resulted in higher yield losses compared with ...

  11. Pregnancy outcomes in a university hospital after legal requirement for single-embryo transfer.

    Science.gov (United States)

    Ercan, Cihangir Mutlu; Kerimoglu, Ozlem Secilmis; Sakinci, Mehmet; Korkmaz, Cem; Duru, Namik Kemal; Ergun, Ali

    2014-04-01

    To present our in vitro fertilization outcomes after implementation of the Turkish government policy limiting the number of transferred embryos to one, in women under the age of 35, and two, in women over age 35; and to demonstrate the feasibility of this policy. We retrospectively reviewed the records of 423 patients who underwent ovarian stimulation, oocyte pick-up, intracytoplasmic sperm injection and embryo transfer due to primary or secondary infertility over a 22-month time interval. Clinical pregnancy was defined as a fetal heartbeat in the seventh gestational week. Embryo transfers were carried out on day 3 or 5. Descriptive statistics are given as the number of subjects and percentages. A total of 353 embryo transfers were performed: 261 (73.9%) were single-embryo transfer (244 (69.1%) elective and 17 (4.8%) non-elective) and 92 (26.1%) were double-embryo transfer. Of the 244 elective single-embryo transfers, 6.6% (n=16) were performed using frozen-thawed embryos. The average patient age was 29.6±4.5 years in the single-embryo group and 36.5±2.4 years in the double-embryo group. The cumulative pregnancy rates per oocyte pick-up were similar in both groups: 41% (n=107) in the single-embryo group and 43.4% (n=40) in the double-embryo group (p=0.678). The cumulative live birth rate of the single-embryo group (32.1%) was not statistically different from the double-embryo group (35.8%) (p=0.518). The twin pregnancy rate after single-embro transfer was significantly lower than with double-embryo transfer (2.8% (n=3) vs. 32.5% (n=13); ppregnancies occurred in women 35 years or older who underwent double-embryo transfer. No significant difference in the spontaneous abortion rates was recorded between the single- and double-embryo transfer groups (16 (6.1%) vs. 6 (6.5%); p=0.894). Single-embryo transfer results in a pregnancy rate comparable to double-embryo transfer, with a significantly reduced multiple pregnancy rate. Double-embryo transfer in patients over

  12. Temperature-dependent kinetics of charge transfer, hydrogen-atom transfer, and hydrogen-atom expulsion in the reaction of CO+ with CH4 and CD4.

    Science.gov (United States)

    Melko, Joshua J; Ard, Shaun G; Johnson, Ryan S; Shuman, Nicholas S; Guo, Hua; Viggiano, Albert A

    2014-09-18

    We have determined the rate constants and branching ratios for the reactions of CO(+) with CH4 and CD4 in a variable-temperature selected ion flow tube. We find that the rate constants are collisional for all temperatures measured (193-700 K for CH4 and 193-500 K for CD4). For the CH4 reaction, three product channels are identified, which include charge transfer (CH4(+) + CO), H-atom transfer (HCO(+) + CH3), and H-atom expulsion (CH3CO(+) + H). H-atom transfer is slightly preferred to charge transfer at low temperature, with the charge-transfer product increasing in contribution as the temperature is increased (H-atom expulsion is a minor product for all temperatures). Analogous products are identified for the CD4 reaction. Density functional calculations on the CO(+) + CH4 reaction were also conducted, revealing that the relative temperature dependences of the charge-transfer and H-atom transfer pathways are consistent with an initial charge transfer followed by proton transfer.

  13. Isotopic resolution of fission fragments from 238U + 12C transfer and fusion reactions

    International Nuclear Information System (INIS)

    Caamano, M.; Rejmund, F.; Derkx, X.; Schmidt, K. H.; Andouin, L.; Bacri, C. O.; Barreau, G.; Benlliure, J.; Casarejos, E.; Fernandez-Dominguez, B.; Gaudefroy, L.; Golabek, C.; Jurado, B.; Lemasson, A.; Navin, A.; Rejmund, M.; Roger, T.; Shrivastava, A.; Schmitt, C.; Taieb, J.

    2010-01-01

    Recent results from an experiment at GANIL, performed to investigate the main properties of fission-fragment yields and energy distributions in different fissioning nuclei as a function of the excitation energy, in a neutron-rich region of actinides, are presented. Transfer reactions in inverse kinematics between a 238 U beam and a 12 C target produced different actinides, within a range of excitation energy below 30 MeV. These fissioning nuclei are identified by detecting the target-like recoil, and their kinetic and excitation energy are determined from the reconstruction of the transfer reaction. The large-acceptance spectrometer VAMOS was used to identify the mass, atomic number and charge state of the fission fragments in flight. As a result, the characteristics of the fission-fragment isotopic distributions of a variety of neutron-rich actinides are observed for the first time over the complete range of fission fragments. (authors)

  14. The importance of anodic discharge of H2O in anodic oxygen-transfer reactions

    International Nuclear Information System (INIS)

    Vitt, J.E.; Johnson, D.C.

    1992-01-01

    This paper discusses difference voltammetry at rotated disk electrodes which are applied to a study of several anodic O-transfer reactions that appear to occur concurrently with O 2 evolution. This voltammetric technique was useful for extracting the rotation-dependent component of the total current from the large, virtually rotation-independent current for O 2 evolution. Data for oxidation of I - at Pt, Au, Pd, Ir, and glassy carbon electrodes show that the E 1/2 for IO - 3 production is correlated with the overpotential for O 2 evolution at these electrode materials. Data obtained at an Ir electrode for various reactions with widely varying E o values reveal uniform E 1/2 values closely correlated with the potential for onset of O 2 evolution in both alkaline and acidic solutions. The results support the conclusion that the anodic discharge of H 2 O is a prerequisite of these anodic O-transfer mechanisms

  15. Digallane with redox-active diimine ligand: dualism of electron-transfer reactions.

    Science.gov (United States)

    Fedushkin, Igor L; Skatova, Alexandra A; Dodonov, Vladimir A; Chudakova, Valentina A; Bazyakina, Natalia L; Piskunov, Alexander V; Demeshko, Serhiy V; Fukin, Georgy K

    2014-05-19

    The reactivity of digallane (dpp-Bian)Ga-Ga(dpp-Bian) (1), which consists of redox-active ligand 1,2-bis[(2,6-diisopropylphenyl)imino]acenaphthene (dpp-Bian), has been studied. The reaction of 1 with I2 proceeds via one-electron oxidation of each of two dpp-Bian ligands to a radical-anionic state and affords complex (dpp-Bian)IGa-GaI(dpp-Bian) (2). Dissolution of complex 2 in pyridine (Py) gives monomeric compound (dpp-Bian)GaI(Py) (3) as a result of a solvent-induced intramolecular electron transfer from the metal-metal bond to the dpp-Bian ligands. Treatment of compound 3 with B(C6F5)3 leads to removal of pyridine and restores compound 2. The reaction of compound 1 with 3,6-di-tert-butyl-ortho-benzoquinone (3,6-Q) proceeds with oxidation of all the redox-active centers in 1 (the Ga-Ga bond and two dpp-Bian dianions) and results in mononuclear catecholate (dpp-Bian)Ga(Cat) (4) (Cat = [3,6-Q](2-)). Treatment of 4 with AgBF4 gives a mixture of [(dpp-Bian)2Ag][BF4] (5) and (dpp-Bian)GaF(Cat) (6), which both consist of neutral dpp-Bian ligands. The reduction of benzylideneacetone (BA) with 1 generates the BA radical-anions, which dimerize, affording (dpp-Bian)Ga-(BA-BA)-Ga(dpp-Bian) (7). In this case the Ga-Ga bond remains unchanged. Within 10 min at 95 °C in solution compound 7 undergoes transformation to paramagnetic complex (dpp-Bian)Ga(BA-BA) (8) and metal-free compound C36H40N2 (9). The latter is a product of intramolecular addition of the C-H bond of one of the iPr groups to the C═N bond in dpp-Bian. Diamagnetic compounds 3, 5, 6, and 9 have been characterized by NMR spectroscopy, and paramagnetic complexes 2, 4, 7, and 8 by ESR spectroscopy. Molecular structures of 2-7 and 9 have been established by single-crystal X-ray analysis.

  16. Intramolecular electron transfer in single-site-mutated azurins

    DEFF Research Database (Denmark)

    Farver, O; Skov, L K; Pascher, T

    1993-01-01

    and used to derive information on the possible effects of the mutations. The substitution of residue Phe114, situated on the opposite side of Cu relative to the disulfide, by Ala resulted in a rate increase by a factor of almost 2. By assuming that this effect is only due to an increase in driving force...... is apparently only marginally involved in electron transfer in wild-type azurin. Pathway calculations also suggest that a longer, through-backbone path is more efficient than the shorter one involving Trp48. The former pathway yields an exponential decay factor, beta, of 6.6 nm-1. Another mutation, raising...

  17. Dynamics of Reactions Involving Hydrogen Atom or Proton Transfer Symmetric Case.

    Science.gov (United States)

    1980-09-01

    rates; tunneling; atom and proton transfer. 20 ABSTRACT ( ContInuo an revese side It necoee.,y and idenlify by block moibor) / C_ -3 A method is... improve the understanding of the dynamics of the reaction and facilitate its computational treatment. If a quasi-constant of the motion does exist for a...neglect of nonadiabatic effects and (ii) use of polar coordinates to treat the dynamics. Each could be improved , e. g. , in (i) by including perturbatively

  18. Ruthenium(II) pincer complexes with oxazoline arms for efficient transfer hydrogenation reactions

    KAUST Repository

    Chen, Tao

    2012-08-01

    Well-defined P NN CN pincer ruthenium complexes bearing both strong phosphine and weak oxazoline donors were developed. These easily accessible complexes exhibit significantly better catalytic activity in transfer hydrogenation of ketones compared to their PN 3P analogs. These reactions proceed under mild and base-free conditions via protonation- deprotonation of the \\'NH\\' group in the aromatization-dearomatization process. © 2012 Elsevier Ltd. All rights reserved.

  19. Electron transfer in reactions of ketones with organolithium reagents. A carbon-14 kinetic isotope effect probe

    International Nuclear Information System (INIS)

    Yamataka, H.; Fujimura, N.; Kawafuji, Y.; Hanafusa, T.

    1987-01-01

    Kinetic isotope effects have been determined for reactions of ketones labeled with carbon-14 at the carbonyl carbon with MeLi and Me 2 CuLi in diethyl ether at 0 0 C. Observed isotope effects were as follows: (C 6 H 5 ) 2 C double bonds O + MeLi, 12 k/ 14 k = 1.000 +/- 0.002; (C 6 H 5 ) 2 C double bonds O + Me 2 CuLi, 1.029 +/- 0.005; 2,4,6-Me 3 C 6 H 2 COC 6 H 5 + MeLi, 1.023 +/- 0.004. The relative reactivities of ortho-, meta-, and para-substituted benzophenones with these reagents were also determined by the competition experiments. These results are consistent with an electron-transfer step which is followed by a carbon-carbon bond-forming step that is or is not rate determining depending on the structure of ketones and reagents. The reaction of benzophenone with MeLi proceeds via rate-determining electron transfer; the change in nucleophile from MeLi to Me 2 CuLi shifts the rate-determining step from electron transfer to recombination; the change in ketone from benzophenone to 2,4,6-trimethylbenzophenone also shifts the rate-determining step from electron transfer to recombination because the latter step becomes slower for the more hindered ketone. The extent of the geometrical change of the substrate at the electron-transfer transition state of the reaction of benzophenone with MeLi was estimated to be small on the basis of the magnitude of the KIE and the rho value of the Hammett correlation

  20. Ultrafast Single and Multiexciton Energy Transfer in Semiconductor Nanoplatelets

    Science.gov (United States)

    Schaller, Richard

    Photophysical processes such as fluorescence resonance energy transfer (FRET) enable optical antennas, wavelength down-conversion in light-emitting diodes (LEDs), and optical bio-sensing schemes. The rate and efficiency of this donor to acceptor transfer of excitation between chromophores dictates the utility of FRET and can unlock new device operation motifs including quantum-funnel solar cells and reduced gain thresholds. However, the fastest reported FRET time constants involving spherical quantum dots (QDs) (0.12-1 ns), do not outpace biexciton Auger recombination (0.01-0.1 ns), which impedes multiexciton-driven applications including electrically-pumped lasers and carrier-multiplication-enhanced photovoltaics. Precisely controlled, few-monolayer thick semiconductor nano-platelets with tens-of-nanometer diameters exhibit intense optical transitions and hundreds-of-picosecond Auger recombination, but heretofore lack FRET characterizations. We examine binary CdSe NPL solids and show that inter-plate FRET (~6-23 ps, presumably for co-facial arrangements) can occur 15-50 times faster than Auger recombination and demonstrate multiexcitonic FRET, making such materials ideal candidates for advanced technologies. This work was performed at the Center for Nanoscale Materials, a U.S. Department of Energy Office of Science User Facility under Contract No. DE-AC02-06CH11357.

  1. Spectroscopy of $^{46}$Ar by the $(t,p)$ two-neutron transfer reaction

    CERN Document Server

    Nowak, K.; Hellgartner, S.; Mücher, D.; Bildstein, V.; Diriken, J.; Elseviers, J.; Gaffney, L.P.; Gernhäuser, R.; Iwanicki, J.; Johansen, J.G.; Huyse, M.; Konki, J.; Kröll, T.; Krücken, T.; Lutter, R.; Orlandi, R.; Pakarinen, J.; Raabe, R.; Reiter, P.; Roger, T.; Schrieder, G.; Seidlitz, M.; Sorlin, O.; Van Duppen, P.; Warr, N.; De Witte, H.; Zielinska, M.

    2016-04-27

    States in the $N=28$ nucleus $^{46}$Ar have been studied by a two-neutron transfer reaction at REX-ISOLDE (CERN). A beam of radioactive $^{44}$ at an energy of 2.16~AMeV and a tritium loaded titanium target were used to populate $^{46}$ by the t($^{44}$,p) two-neutron transfer reaction. Protons emitted from the target were identified in the T-REX silicon detector array. The excitation energies of states in $^{46}$ have been reconstructed from the measured angles and energies of recoil protons. Angular distributions for three final states were measured and based on the shape of the differential cross section an excited state at 3695~keV has been identified as $J^\\pi = 0^+$. The angular differential cross section for the population of different states are compared to calculations using a reaction model employing both sequential and direct transfer of two neutrons. Results are compared to shell model calculations using state-of-the-art effective interactions.

  2. Deep-inelastic multinucleon transfer processes in the 16O+27Al reaction

    Science.gov (United States)

    Roy, B. J.; Sawant, Y.; Patwari, P.; Santra, S.; Pal, A.; Kundu, A.; Chattopadhyay, D.; Jha, V.; Pandit, S. K.; Parkar, V. V.; Ramachandran, K.; Mahata, K.; Nayak, B. K.; Saxena, A.; Kailas, S.; Nag, T. N.; Sahoo, R. N.; Singh, P. P.; Sekizawa, K.

    2018-03-01

    The reaction mechanism of deep-inelastic multinucleon transfer processes in the 16O+27Al reaction at an incident 16O energy (Elab=134 MeV) substantially above the Coulomb barrier has been studied both experimentally and theoretically. Elastic-scattering angular distribution, total kinetic energy loss spectra, and angular distributions for various transfer channels have been measured. The Q -value- and angle-integrated isotope production cross sections have been deduced. To obtain deeper insight into the underlying reaction mechanism, we have carried out a detailed analysis based on the time-dependent Hartree-Fock (TDHF) theory. A recently developed method, TDHF+GEMINI, has been applied to evaluate production cross sections for secondary products. From a comparison between the experimental and theoretical cross sections, we find that the theory qualitatively reproduces the experimental data. Significant effects of secondary light-particle emissions are demonstrated. Possible interplay among fusion-fission, deep-inelastic, multinucleon transfer, and particle evaporation processes is discussed.

  3. Electrocatalysis of anodic oxygen-transfer reactions at modified lead dioxide electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Hsiao, Yun-Lin.

    1990-09-21

    The electrocatalytic activities were compared for pure and chloride-doped beta-PbO{sub 2} (Cl-PbO{sub 2}) films on gold and platinum substrates. Rate constants were increased significantly for oxidations of Mn{sup 2+}, toluene, benzyl alcohol, dimethylsulphoxide (DMSO) and benzaldehyde in acidic media by the incorporation of Cl{sup {minus}} into the oxide films. These reactions are concluded to occur by the electrocatalytic transfer of oxygen from H{sub 2}O to the reaction products. Results of x-ray diffraction studies indicate the Cl-PbO{sub 2} film continues to have the slightly distorted rutile structure of pure beta-PbO{sub 2}. The observed electrocatalytic phenomena are concluded to be the beneficial consequence of surface defects generated when Cl{sup {minus}} serves for charge compensation within the surface matrix and, thereby, increases the number of surface sites capable of adsorbing hydroxyl radicals which are transferred in the electrocatalytic O-transfer reactions. 91 refs., 44 figs., 10 tabs.

  4. Multi-neutron and proton transfer reactions in deep inelastic heavy-ion collisions

    International Nuclear Information System (INIS)

    Yoshida, Satoshi; Patra, S.K.; Takigawa, Noboru

    1997-01-01

    We discuss the characteristics of multi-nucleon transfer reactions in deep-inelastic heavy-ion collisions. We calculate the number of transferred neutrons and protons based on a macroscopic approach using a Fokker-Planck equation, and compare with experimental data. We show that our macroscopic approach well reproduces the experimental data concerning the ratio of the mass to the proton numbers in the projectile-like fragment as a function of the energy loss from the relative motion. Our calculations, however, do not reproduce the recent data, where the transferred number of neutrons and protons are measured separately. The net flow of nucleons evolve even in opposite directions in the experimental data and in our transport theory. (author)

  5. Stagnation point flow and mass transfer with chemical reaction past a stretching/shrinking cylinder.

    Science.gov (United States)

    Najib, Najwa; Bachok, Norfifah; Arifin, Norihan Md; Ishak, Anuar

    2014-02-26

    This paper is about the stagnation point flow and mass transfer with chemical reaction past a stretching/shrinking cylinder. The governing partial differential equations in cylindrical form are transformed into ordinary differential equations by a similarity transformation. The transformed equations are solved numerically using a shooting method. Results for the skin friction coefficient, Schmidt number, velocity profiles as well as concentration profiles are presented for different values of the governing parameters. Effects of the curvature parameter, stretching/shrinking parameter and Schmidt number on the flow and mass transfer characteristics are examined. The study indicates that dual solutions exist for the shrinking cylinder but for the stretching cylinder, the solution is unique. It is observed that the surface shear stress and the mass transfer rate at the surface increase as the curvature parameter increases.

  6. Photo- and radiation chemical studies of intermediates involved in excited-state electron-transfer reactions

    International Nuclear Information System (INIS)

    Hoffman, M.Z.

    1985-01-01

    Excited-state inter- and intramolecular electron-transfer reactions lie at the heart of the most photochemical solar energy conversion schemes. The authors research, which has utilized the techniques of continuous and pulsed photolysis and radiolysis, has focused on three general aspects of these reactions involving transition metal coordination complexes and electron donor-acceptor complexes: i) the effect of solution medium on the properties and quenching of the excited states; ii) the control of the quantum yields of formation of redox products; iii) the mechanism by which reduced species interact with water to yield H 2 homogeneously and heterogeneously. EDTA is among the most popular sacrificial electron donors used in model systems. Its role is to scavenge the oxidized form of the photosensitizer in order to prevent its rapid reaction with the reduced form of the electron relay species that results from the electron-transfer quenching of the excited photosensitizer. In systems involving MV 2+ , the radicals resulting from the oxidation of EDTA can eventually lead to the generation of a second equivalent of MV + ; the reducing agent is believed to be a radical localized on the carbon atom alpha to the carboxylate group. The reaction of radiolytically-generated OH/H with EDTA produces this radical directly via H-abstraction or indirectly via deprotonation of the carbon atom adjacent to the nitrogen radical site in the oxidized amine moiety; it reduces MV 2+ with rate constants of 2.8 x 10 9 , 7.6 x 10 9 , and 8.5 x 10 6 M -1 s -1 at pH 12.5, 8.3, and 4.7, respectively. Degradative decarboxylation of EDTA-radicals and their back electron-transfer reactions are enhanced in acidic solution causing the yield of MV + to be severely diminished

  7. Energy transfer from excited cyclobutane-t chemically activated by nuclear recoil reaction

    International Nuclear Information System (INIS)

    Nogar, N.S.

    1976-01-01

    Relative energy transfer efficiencies were determined for collisions between highly excited cyclobutane-t and a number of thermal bath gases, including nitrogen, tetrafluoromethane, the noble gases, and cyclobutane. The excited cyclobutane-t was produced with a broad spectrum of energies about a mean energy of 5 eV by replacement of hydrogen with nuclear recoil tritium. The distribution of cyclobutane-t included a fraction produced at such low energies that it was not subjected to unimolecular decomposition, a fraction always found as the decomposition product, ethylene-t, and a fraction subject to competitive stabilization-decomposition reactions. The fraction of cyclobutane-t produced at such extreme energies that it was not subject to competitive unimolecular reaction was determined by curve-fitting the pressure dependence of ratio of cyclobutane-t to ethylene-t. Subsequent examination of the composition dependence of the ratio of competitive cyclobutane-t and ethylene-t yields gave energy transfer efficiencies for C 4 H 8 , CF 4 , N 2 , He, Ne, Ar, Kr, and Xe of 1.00:1.05:0.40, 0.12, 0.23, 0.24, 0.31, 0.39. The relative efficiencies found in this system are similar to those found in high energy conventional chemical activation systems, supporting this method for determination of energy transfer efficiencies following nuclear recoil activation. Cascade deactivation is demonstrated for this system and discussed with respect to energy transfer in hot atom activated systems

  8. Single-molecule detection of dihydroazulene photo-thermal reaction using break junction technique

    Science.gov (United States)

    Huang, Cancan; Jevric, Martyn; Borges, Anders; Olsen, Stine T.; Hamill, Joseph M.; Zheng, Jue-Ting; Yang, Yang; Rudnev, Alexander; Baghernejad, Masoud; Broekmann, Peter; Petersen, Anne Ugleholdt; Wandlowski, Thomas; Mikkelsen, Kurt V.; Solomon, Gemma C.; Brøndsted Nielsen, Mogens; Hong, Wenjing

    2017-05-01

    Charge transport by tunnelling is one of the most ubiquitous elementary processes in nature. Small structural changes in a molecular junction can lead to significant difference in the single-molecule electronic properties, offering a tremendous opportunity to examine a reaction on the single-molecule scale by monitoring the conductance changes. Here, we explore the potential of the single-molecule break junction technique in the detection of photo-thermal reaction processes of a photochromic dihydroazulene/vinylheptafulvene system. Statistical analysis of the break junction experiments provides a quantitative approach for probing the reaction kinetics and reversibility, including the occurrence of isomerization during the reaction. The product ratios observed when switching the system in the junction does not follow those observed in solution studies (both experiment and theory), suggesting that the junction environment was perturbing the process significantly. This study opens the possibility of using nano-structured environments like molecular junctions to tailor product ratios in chemical reactions.

  9. Catalytic effect of a single water molecule on the OH + CH2NH reaction.

    Science.gov (United States)

    Akbar Ali, Mohamad; M, Balaganesh; Lin, K C

    2018-02-07

    In recent work, there has been considerable speculation about the atmospheric reaction of methylenimine (CH 2 NH), because this compound is highly reactive, soluble in water, and sticky, thus posing severe experimental challenges. In this work, we have revisited the kinetics of the OH + CH 2 NH reaction assisted by a single water molecule. The potential energy surfaces (PESs) for the water-assisted OH + CH 2 NH reaction were calculated using the CCSD(T)//BH&HLYP/aug-cc-pVTZ levels of theory. The rate coefficients for the bimolecular reaction pathways CH 2 NHH 2 O + OH and CH 2 NH + H 2 OHO were computed using canonical variational transition state theory (CVT) with small curvature tunneling correction. The reaction without water has four elementary reaction pathways, depending on how the hydroxyl radical approaches CH 2 NH. In all cases, the reaction begins with the formation of a single pre-reactive complex before producing abstraction and addition products. When water is added, the products of the reaction do not change, and the reaction becomes quite complex, yielding four different pre-reactive complexes and eight reaction pathways. The calculated rate coefficient for the OH + CH 2 NH (water-free) reaction at 300 K is 1.7 × 10 -11 cm 3 molecule -1 s -1 and for OH + CH 2 NH (water-assisted), it is 5.1 × 10 -14 cm 3 molecule -1 s -1 . This result is similar to the isoelectronic analogous reaction OH + CH 2 O (water-assisted). In general, the effective rate coefficients of the water-assisted reaction are 2∼3 orders of magnitude smaller than water-free. Our results show that the water-assisted OH + CH 2 NH reaction cannot accelerate the reaction because the dominated water-assisted process depends parametrically on water concentration. As a result, the overall reaction rate coefficients are smaller.

  10. Mass transfer with complex chemical reactions in gas-liquid systems: two-step reversible reactions with unit stoichiometric and kinetic orders

    NARCIS (Netherlands)

    Vas bhat, R.D.; Kuipers, J.A.M.; Versteeg, Geert

    2000-01-01

    An absorption model to study gas¿liquid mass transfer accompanied by reversible two-step reactions in the liquid phase has been presented. This model has been used to determine mass transfer rates, enhancement factors and concentration profiles over a wide range of process conditions. Although

  11. Mass transfer with complex chemical reactions in gas–liquid systems : two-step reversible reactions with unit stoichiometric and kinetic orders

    NARCIS (Netherlands)

    Vas Bhat, R.D.; Kuipers, J.A.M.; Versteeg, G.F.

    2000-01-01

    An absorption model to study gas–liquid mass transfer accompanied by reversible two-step reactions in the liquid phase has been presented. This model has been used to determine mass transfer rates, enhancement factors and concentration profiles over a wide range of process conditions. Although

  12. Kinetics and mechanisms of photoinduced electron-transfer reaction of zinc myoglobin

    International Nuclear Information System (INIS)

    Tsukahara, Keiichi; Asami, Satoko; Okada, Mihoko; Sakurai, Takeshi.

    1994-01-01

    Photoinduced electron transfer (ET) between zinc myoglobin (ZnPPMb) and a variety of quenchers, such as hexacyanoferrate(III)([Fe(CN) 6 ] 3- ) and hexaammineruthenium(III)(Ru(NH 3 ) 6 ] 3+ ions, cationic viologens, copper(II) protein (stellacyanin), and metmyoglobins, has been studied in aqueous degassed solutions. The excited triplet state of ZnPPMb( * ZnPPMb) was quenched by [Fe(CN) 6 ] 3- in a self-associated complex. Both quenching rate constant and formation constant of the self-associated complex decrease with increasing ionic strengths. The thermal backward ET reaction for this system was not observed; it is most likely that the backward ET step is much faster than the quenching reaction. All of the cationic quenchers examined in this work did not form a self-associated complex with * ZnPPMb, and the intermolecular quenching occurred. The thermal backward ET reaction was observed for these cationic quenchers. Not only photoinduced ET but also thermal backward ET reactions were insensitive to the driving force of the reactions, suggesting that the reactions are controlled by conformational changes in ZnPPMb. The quenching rate constants increase with increasing ionic strength for the cationic quenchers. The effects of poly-L-lysine hydrochloride, sodium poly-L-glutamate, and sodium cyclo-hexaphosphate were also examined. The active site of the * ZnPPMb toward both anionic and cationic quenchers is assumed to be the positively charged site near the heme pocket. (author)

  13. The 9Be(8Li,9Be)8Li elastic-transfer reaction

    International Nuclear Information System (INIS)

    Camargo, O.; Guimaraes, V.; Lichtenthaeler, R.; Scarduelli, V.; Kolata, J. J.; Bertulani, C. A.; Amro, H.; Becchetti, F. D.; Jiang Hao; Aguilera, E. F.; Lizcano, D.; Martinez-Quiroz, E.; Garcia, H.

    2008-01-01

    Angular distributions for the 9 Be( 8 Li, 9 Be) 8 Li elastic-transfer reaction have been measured with a 27-MeV 8 Li radioactive nuclear beam. Spectroscopic factors for the 9 Be| 8 Li+p> bound system were obtained from the comparison between the experimental differential cross sections and finite-range distorted-wave Born approximation calculations made with the code FRESCO. The spectroscopic factors so obtained are compared with shell-model calculations and other experimental values. Using the present value for the spectroscopic factors, cross sections and reaction rates for the 8 Li(p,γ) 9 Be direct proton-capture reaction of astrophysical interest were calculated in the framework of the potential model

  14. An annular ionization detector for quasi-elastic and transfer reaction studies

    CERN Document Server

    Dinesh, B V; Nayak, B K; Biswas, D C; Saxena, A; Pant, L M; Sahu, P K; Choudhury, R K

    2000-01-01

    An annular ionization chamber detector has been developed to study quasi-elastic and transfer reactions in heavy-ion collisions at near-barrier and sub-barrier energies. The important feature of the detector is that it has a near 2 pi coverage in the azimuthal angle phi for the particles entering in the detector at a given theta direction. This feature makes the detector very useful for measurement of the differential cross-sections at backward angles with respect to the beam direction, involving low cross-section reaction channels. The split anode configuration of the detector makes it capable of both particle identification and energy measurement for heavy ions and fission fragments. The detector has been tested using heavy-ion beams from the 14 MV-pelletron accelerator at Mumbai. Results on quasi-elastic excitation function measurements and barrier distribution studies in many heavy-ion reactions using this detector setup are discussed.

  15. High-pressure catalytic reactions over single-crystal metal surfaces

    Science.gov (United States)

    Rodriguez, JoséA.; Wayne Goodman, D.

    1991-11-01

    Studies dealing with high-pressure catalytic reactions over single-crystal surfaces are reviewed. The coupling of an apparatus for the measurement of reaction kinetics at elevated pressures with an ultrahigh vacuum system for surface analysis allows detailed study of structure sensitivity, the effects of promoters and inhibitors on catalytic activity, and, in certain cases, identification of reaction intermediates by post-reaction surface analysis. Examples are provided which demonstrate the relevance of single-crystal studies for modeling the behaviour of high-surface-area supported catalysts. Studies of CO methanation and CO oxidation over single-crystal surfaces provide convincing evidence that these reactions are structure insensitive. For structure-sensitive reactions (ammonia synthesis, alkane hydrogenolysis, alkane isomerization, water-gas shift reaction, etc.) model single-crystal studies allow correlations to be established between surface structure and catalytic activity. The effects of both electronegative (S and P) and electropositive (alkali metals) impurities upon the catalytic activity of metal single crystals for ammonia synthesis, CO methanation, alkane hydrogenolysis, ethylene epoxidation and water-gas shift are discussed. The roles of "ensemble" and "ligand" effects in bimetallic catalysts are examined in light of data obtained using surfaces prepared by vapor-depositing one metal onto a crystal face of a dissimilar metal.

  16. Quantitative control of mitochondria transfer between live single cells using a microfluidic device

    Directory of Open Access Journals (Sweden)

    Ken-Ichi Wada

    2017-12-01

    Full Text Available Quantitative control of mitochondria transfer between live cells is a promising approach for genetic manipulation of mitochondrial DNA (mtDNA because single mitochondrion transfer to a mtDNA-less (ρ0 cell potentially leads to homoplasmy of mtDNA. In this paper, we describe a method for quantitative control of mitochondria transfer between live single cells. For this purpose, we fabricated novel microfluidic devices having cell paring structures with a 4.1, 5.6 or 10.0 μm-length microtunnel. When cells were fused through a microtunnel using the Sendai virus envelope-based method, a strictured cytoplasmic connection was achieved with a length corresponding to that of the microtunnel. Elongation of the cytoplasmic connection led to a decrease in mitochondria transfer to the fusion partner. Moreover, some cell pairs that fused through a 10.0 μm-length microtunnel showed single mitochondrion transfer. Fused cells were spontaneously disconnected from each other when they were recovered in a normal culture medium. These results suggest that our cell fusion method can perform quantitative control of mitochondria transfer that includes a single mitochondrion transfer.

  17. Visualization of Natural Convection Heat Transfer on a Single Sphere using the Electroplating System

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Dong Young; Chung, Bum Jin [Kyunghee University, Yongin (Korea, Republic of)

    2016-05-15

    The natural convective flows on outer sphere rise along surface. At top of sphere, the flows are lifted-up plume shape. For laminar flows, the local heat transfer shows maximum at the bottom of sphere and a monotonic decreases as flows approached to the top. The laminar natural convection heat transfer on a single sphere has been studied experimentally and numerically by several researchers. However, relatively less study has been performed for turbulent flows as it requires large facilities to achieve high Rayleigh numbers. The flows, which occur transition, is hard to experiment because of unstable. This study tried measurement of heat transfer and visualization external natural convection on a single sphere. The basic idea is that the plating patterns of copper on the sphere in mass transfer system will reveal the amount of heat transfer according to angular distance from the bottom. This study simulated natural convection on a single sphere and performed a mass transfer experiment using heat and mass transfer analogy concept. For visualization experiment, streak form plating pattern was observed. In this case, it seems that turbulence sets on the top of sphere and increases local heat transfer.

  18. Electron transfer dynamics of bistable single-molecule junctions

    DEFF Research Database (Denmark)

    Danilov, A.V; Kubatkin, S.; Kafanov, S. G.

    2006-01-01

    We present transport measurements of single-molecule junctions bridged by a molecule with three benzene rings connected by two double bonds and with thiol end-groups that allow chemical binding to gold electrodes. The I-V curves show switching behavior between two distinct states. By statistical ...... analysis of the switching events, we show that a 300 meV mode mediates the transition between the two states. We propose that breaking and reformation of a S-H bond in the contact zone between molecule and electrode explains the observed bistability....

  19. Preparation, single-molecule manipulation and energy transfer investigation of a polyfluorene-graft-DNA polymer

    DEFF Research Database (Denmark)

    Madsen, Mikael; Christensen, Rasmus S.; Krissanaprasit, Abhichart

    2017-01-01

    with the conjugated polyfluorene backbone, but the protruding single-stranded DNA provides the material with an exceptional addressability. This allows us to demonstrate controlled single polymer patterning, as well as energy transfer between two different polymer-DNA conjugates. Finally, we demonstrate highly...

  20. Single-electron transfer living radical copolymerization of SWCNT-g-PMMA via graft from approach

    Czech Academy of Sciences Publication Activity Database

    Jaisankar, S. N.; Haridharan, N.; Murali, A.; Ponyrko, Sergii; Špírková, Milena; Mandal, A. B.; Matějka, Libor

    2014-01-01

    Roč. 55, č. 13 (2014), s. 2959-2966 ISSN 0032-3861 R&D Projects: GA ČR GAP108/12/1459 Institutional support: RVO:61389013 Keywords : single electron transfer * single-walled carbon nanotubes * controlled radical polymerization Subject RIV: CD - Macromolecular Chemistry Impact factor: 3.562, year: 2014

  1. Three-nucleon transfer reactions and cluster structure in the A = 15 to A = 19 nuclei

    International Nuclear Information System (INIS)

    Martz, L.M.

    1978-01-01

    The ( 6 Li,t) and ( 6 Li, 3 He) reactions were studied on targets of 12 C, 13 C, 14 N, 15 N, and 16 O at E/sub Li/ approx. = 44 MeV and theta/sub lab/ approx. = 15 0 . A preferential population of final states was exhibited in spectra for the A = 15 to A = 19 nuclei. The strong forward peaking of angular distributions in the 13 C( 6 Li,t) 16 O and 13 C( 6 Li, 3 He) 16 N reactions can be reproduced by DWBA calculations but not by the Hauser-Feshbach model. Such indications of a primarily direct mechanism at forward angles suggest use of these three-nucleon-transfer reactions to identify candidates for 3p-nh states. A comparison with other multinucleon transfer data, e.g., those from ( 7 Li,α) and ( 7 Li,t) reactions on 13 C and 15 N targets, further tests dominant particle-hole configurations. The relationship between ( 6 Li,t) and ( 6 Li, 3 He) spectra reveals analog states, notably T = 1, T/sub z/ = 0 levels at high excitation in 16 O. Nuclear theory is used to investigate the role of triton clustering in such structure. The 2N + L = 6 band predicted by a folded-potential model of 18 O = 15 N + t shows an underlying correspondence to the experimental levels in triton-transfer data. Triton spectroscopic factors calculated from the SU(3) shell model further suggest the broad influence of clustering phenomena in this mass region. Experimental evidence of systematic behavior in the triton binding energies of proposed p/sup -n/(sd) 3 configurations was found

  2. pH-dependent electron transfer reaction and direct bioelectrocatalysis of the quinohemoprotein pyranose dehydrogenase

    Energy Technology Data Exchange (ETDEWEB)

    Takeda, Kouta [Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588 (Japan); Matsumura, Hirotoshi; Ishida, Takuya [Department of Biomaterial Sciences, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657 (Japan); Yoshida, Makoto [Department of Environmental and Natural Resource Science, Tokyo University of Agriculture and Technology, Fuchu, Tokyo 183-8509 (Japan); Igarashi, Kiyohiko; Samejima, Masahiro [Department of Biomaterial Sciences, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657 (Japan); Ohno, Hiroyuki [Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588 (Japan); Nakamura, Nobuhumi, E-mail: nobu1@cc.tuat.ac.jp [Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588 (Japan)

    2016-08-26

    A pyranose dehydrogenase from Coprinopsis cinerea (CcPDH) is an extracellular quinohemoeprotein, which consists a b-type cytochrome domain, a pyrroloquinoline-quinone (PQQ) domain, and a family 1-type carbohydrate-binding module. The electron transfer reaction of CcPDH was studied using some electron acceptors and a carbon electrode at various pH levels. Phenazine methosulfate (PMS) reacted directly at the PQQ domain, whereas cytochrome c (cyt c) reacted via the cytochrome domain of intact CcPDH. Thus, electrons are transferred from reduced PQQ in the catalytic domain of CcPDH to heme b in the N-terminal cytochrome domain, which acts as a built-in mediator and transfers electron to a heterogenous electron transfer protein. The optimal pH values of the PMS reduction (pH 6.5) and the cyt c reduction (pH 8.5) differ. The catalytic currents for the oxidation of L-fucose were observed within a range of pH 4.5 to 11. Bioelectrocatalysis of CcPDH based on direct electron transfer demonstrated that the pH profile of the biocatalytic current was similar to the reduction activity of cyt c characters. - Highlights: • pH dependencies of activity were different for the reduction of cyt c and DCPIP. • DET-based bioelectrocatalysis of CcPDH was observed. • The similar pH-dependent profile was found with cyt c and electrode. • The present results suggested that IET reaction of CcPDH shows pH dependence.

  3. Effect of NaCl Salts on the Activation Energy of Excited-State Proton Transfer Reaction of Coumarin 183.

    Science.gov (United States)

    Joung, Joonyoung F; Kim, Sangin; Park, Sungnam

    2015-12-17

    Coumarin 183 (C183) was used as a photoacid to study excited-state proton transfer (ESPT) reactions. Here, we studied the effect of ions on the ESPT of C183 in aqueous NaCl solutions using a steady-state fluorescence spectroscopy and time-correlated single photon counting (TCSPC) method. The acid dissociation equilibrium of excited-state C183 and the activation energy for the ESPT of C183 were determined as a function of NaCl concentration. The change in the equilibrium constant was found to be correlated with the solvation energy of deprotonated C183. Frequency-resolved TCSPC signals measured at several temperatures were analyzed by using a global fitting analysis method which enabled us to extract all the rate constants involving the ESPT reaction and the spectra of individual species. The activation energy for the ESPT reaction of C183 was highly dependent on NaCl concentration. Quantum chemical calculations were used to calculate the local hydrogen-bond (H-bond) configurations around C183 in aqueous NaCl solutions. It was found that the activation energy for the ESPT was determined by the local H-bond configurations around C183 which were significantly influenced by the dissolved ions.

  4. Studies of transfer reactions of photosensitized electrons involving complexes of transition metals in view of solar energy storage

    International Nuclear Information System (INIS)

    Takakubo, Masaaki

    1984-01-01

    This research thesis addresses electron transfer reactions occurring during photosynthesis, for example, photosensitized reaction in which chlorophyll is the sensitizer. More specifically, the author studied experimentally electron photo-transfers with type D sensitizers (riboflavin, phenoxazine and porphyrin), and various complexes of transition metals. After a presentation of these experiments, the author describes the photosensitisation process (photo-physics of riboflavin, oxygen deactivation, sensitized photo-oxidation and photo-reduction). The theoretical aspect of electron transfer is then addressed: generalities, deactivation of the riboflavin triplet, initial efficiency of electron transfer. Experimental results on three basic processes (non-radiative deactivation, energy transfer, electron transfer) are interpreted in a unified way by using the non-radiative transfer theory. Some applications are described: photo-electrochemical batteries, photo-oxidation and photo-reduction of the cobalt ion

  5. (Multi-nucleon transfer in the reactions 16O, 32S+208Pb

    Directory of Open Access Journals (Sweden)

    Hinde D.J.

    2011-10-01

    Full Text Available A detailed analysis of the projectile-like fragments detected at backward angles in the reactions 16O,32 S+208Pb at energies below the fusion barrier is presented. Excitation functions corresponding to nucleon transfer with ∆Z = 1 and ∆Z = 2 were extracted, indicating surprisingly large absolute probabilities at subbarrier energies. A comparison of 2p transfer probabilities with time-dependent Hartree-Fock calculations suggests strong pairing correlations between the two protons. Excitation energies in the projectile-like fragments ~15 MeV and ~25 MeV for the 16O and 32S-induced reactions, respectively, indicate the population of highly excited states in the residual nuclei. A comparison with expected optimum Q-values suggests large losses in kinetic energy of the projectile-like fragments. These highly inelastic (large excitation energies and complex (correlated few-nucleon transfer processes may be closely related to the depletion of fusion through tunnelling at sub-barrier energies.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-01-01

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

  7. Single-molecule detection of dihydroazulene photo-thermal reaction using break junction technique

    DEFF Research Database (Denmark)

    Huang, Cancan; Jevric, Martyn; Borges, Anders Christian

    2017-01-01

    a quantitative approach for probing the reaction kinetics and reversibility, including the occurrence of isomerization during the reaction. The product ratios observed when switching the system in the junction does not follow those observed in solution studies (both experiment and theory), suggesting......Charge transport by tunnelling is one of the most ubiquitous elementary processes in nature. Small structural changes in a molecular junction can lead to significant difference in the single-molecule electronic properties, offering a tremendous opportunity to examine a reaction on the single......-molecule scale by monitoring the conductance changes. Here, we explore the potential of the single-molecule break junction technique in the detection of photo-thermal reaction processes of a photochromic dihydroazulene/vinylheptafulvene system. Statistical analysis of the break junction experiments provides...

  8. Clinical characteristics of adverse reactions to nonionic low osmolality contrast media in patients transferred from the CT room to the emergency room.

    Science.gov (United States)

    Ha, Sang Ook; Kim, Dae Yong; Sohn, You Dong

    2016-01-01

    Nonionic low osmolality contrast media (LOCMs) are used universally in computed tomography (CT) imaging. Although adverse reactions due to nonionic LOCMs are a common cause of emergency room (ER) admissions, few studies have investigated these adverse reactions. In the present study, we evaluated the characteristics of patients who were transferred from the CT room to the ER due to adverse reactions to contrast media, and we determined the risk factors for severe adverse reactions. A single-center retrospective study was conducted over a 41-month period. Baseline and clinical characteristics were evaluated and analyzed according to moderate and severe severity. In particular, risk factors of severe reactions were determined using logistic regression analysis. In total, 70 patients were admitted to the ER with adverse reactions due to nonionic LOCMs. Of these, 33 developed a moderate reaction, and 37 developed a severe reaction. Compared with the moderate reaction group, the severe reaction group was older, had higher blood pressures, showed more symptoms indicating the cardiovascular and central nervous system, and developed faster reactions to LOCMs. According to the multivariate logistic regression analysis, the age of the patient and time to onset of reaction demonstrated a statistical relationship with severe adverse reactions. In the receiver operating characteristic analysis, the optimal cutoff values for age and time to onset were 60 years and 5 min. In conclusion, clinicians should be attentive to anaphylaxis due to nonionic LOCM, in particular, for elderly patients aged older than 60 years and a time to reaction onset of less than 5 min.

  9. Electron transfer reactions in the alkene mono-oxygenase complex from Nocardia corallina B-276.

    Science.gov (United States)

    Gallagher, S C; Cammack, R; Dalton, H

    1999-04-01

    Nocardia corallina B-276 possesses a multi-component enzyme, alkene mono-oxygenase (AMO), that catalyses the stereoselective epoxygenation of alkenes. The reductase component of this system has been shown by EPR and fluorescence spectroscopy to contain two prosthetic groups, an FAD centre and a [2Fe-2S] cluster. The role of these centres in the epoxygenation reaction was determined by midpoint potential measurements and electron transfer kinetics. The order of potentials of the prosthetic groups of the reductase were FAD/FAD.=-216 mV, [2Fe-2S]/[2Fe-2S].=-160 mV and FAD./FAD.=-134 mV. Combined, these data implied that the reductase component supplied the energy required for the epoxygenation reaction and allowed a prediction of the mechanism of electron transfer within the AMO complex. The FAD moiety was reduced by bound NADH in a two-electron reaction. The electrons were then transported to the [2Fe-2S] centre one at a time, which in turn reduced the di-iron centre of the epoxygenase. Reduction of the di-iron centre is required for oxygen binding and substrate oxidation.

  10. Atomic-level insights in optimizing reaction paths for hydroformylation reaction over Rh/CoO single-atom catalyst.

    Science.gov (United States)

    Wang, Liangbing; Zhang, Wenbo; Wang, Shenpeng; Gao, Zehua; Luo, Zhiheng; Wang, Xu; Zeng, Rui; Li, Aowen; Li, Hongliang; Wang, Menglin; Zheng, Xusheng; Zhu, Junfa; Zhang, Wenhua; Ma, Chao; Si, Rui; Zeng, Jie

    2016-12-22

    Rh-based heterogeneous catalysts generally have limited selectivity relative to their homogeneous counterparts in hydroformylation reactions despite of the convenience of catalyst separation in heterogeneous catalysis. Here, we develop CoO-supported Rh single-atom catalysts (Rh/CoO) with remarkable activity and selectivity towards propene hydroformylation. By increasing Rh mass loading, isolated Rh atoms switch to aggregated clusters of different atomicity. During the hydroformylation, Rh/CoO achieves the optimal selectivity of 94.4% for butyraldehyde and the highest turnover frequency number of 2,065 h -1 among the obtained atomic-scale Rh-based catalysts. Mechanistic studies reveal that a structural reconstruction of Rh single atoms in Rh/CoO occurs during the catalytic process, facilitating the adsorption and activation of reactants. In kinetic view, linear products are determined as the dominating products by analysing reaction paths deriving from the two most stable co-adsorbed configurations. As a bridge of homogeneous and heterogeneous catalysis, single-atom catalysts can be potentially applied in other industrial reactions.

  11. Kinetic mechanism of molecular energy transfer and chemical reactions in low-temperature air-fuel plasmas.

    Science.gov (United States)

    Adamovich, Igor V; Li, Ting; Lempert, Walter R

    2015-08-13

    This work describes the kinetic mechanism of coupled molecular energy transfer and chemical reactions in low-temperature air, H2-air and hydrocarbon-air plasmas sustained by nanosecond pulse discharges (single-pulse or repetitive pulse burst). The model incorporates electron impact processes, state-specific N(2) vibrational energy transfer, reactions of excited electronic species of N(2), O(2), N and O, and 'conventional' chemical reactions (Konnov mechanism). Effects of diffusion and conduction heat transfer, energy coupled to the cathode layer and gasdynamic compression/expansion are incorporated as quasi-zero-dimensional corrections. The model is exercised using a combination of freeware (Bolsig+) and commercial software (ChemKin-Pro). The model predictions are validated using time-resolved measurements of temperature and N(2) vibrational level populations in nanosecond pulse discharges in air in plane-to-plane and sphere-to-sphere geometry; temperature and OH number density after nanosecond pulse burst discharges in lean H(2)-air, CH(4)-air and C(2)H(4)-air mixtures; and temperature after the nanosecond pulse discharge burst during plasma-assisted ignition of lean H2-mixtures, showing good agreement with the data. The model predictions for OH number density in lean C(3)H(8)-air mixtures differ from the experimental results, over-predicting its absolute value and failing to predict transient OH rise and decay after the discharge burst. The agreement with the data for C(3)H(8)-air is improved considerably if a different conventional hydrocarbon chemistry reaction set (LLNL methane-n-butane flame mechanism) is used. The results of mechanism validation demonstrate its applicability for analysis of plasma chemical oxidation and ignition of low-temperature H(2)-air, CH(4)-air and C(2)H(4)-air mixtures using nanosecond pulse discharges. Kinetic modelling of low-temperature plasma excited propane-air mixtures demonstrates the need for development of a more accurate

  12. Mutations to R. sphaeroides Reaction Center Perturb Energy Levels and Vibronic Coupling but Not Observed Energy Transfer Rates.

    Science.gov (United States)

    Flanagan, Moira L; Long, Phillip D; Dahlberg, Peter D; Rolczynski, Brian S; Massey, Sara C; Engel, Gregory S

    2016-03-10

    The bacterial reaction center is capable of both efficiently collecting and quickly transferring energy within the complex; therefore, the reaction center serves as a convenient model for both energy transfer and charge separation. To spectroscopically probe the interactions between the electronic excited states on the chromophores and their intricate relationship with vibrational motions in their environment, we examine coherences between the excited states. Here, we investigate this question by introducing a series of point mutations within 12 Å of the special pair of bacteriochlorophylls in the Rhodobacter sphaeroides reaction center. Using two-dimensional spectroscopy, we find that the time scales of energy transfer dynamics remain unperturbed by these mutations. However, within these spectra, we detect changes in the mixed vibrational-electronic coherences in these reaction centers. Our results indicate that resonance between bacteriochlorophyll vibrational modes and excitonic energy gaps promote electronic coherences and support current vibronic models of photosynthetic energy transfer.

  13. Energetic efficiency of mass transfer accompanied by chemical reactions in liquid-liquid systems

    Directory of Open Access Journals (Sweden)

    Jasińska Magdalena

    2017-09-01

    Full Text Available Energetic efficiency depicting the fraction of energy dissipation rate used to perform processes of drop breakup and mass transfer in two-phase, liquid-liquid systems is considered. Results of experiments carried out earlier in two types of high-shear mixers: an in-line rotor-stator mixer and a batch rotor-stator mixer, have been applied to identify and compare the efficiency of drop breakage and mass transfer in both types of mixers. The applied method is based on experimental determination of both: the product distribution of chemical test reactions and the drop size distributions. Experimental data are interpreted using a multifractal model of turbulence for drop breakage and the model by Favelukis and Lavrenteva for mass transfer. Results show that the energetic efficiency of the in-line mixer is higher than that of the batch mixer; two stator geometries were considered in the case of the batch mixer and the energetic efficiency of the device equipped with a standard emulsor screen (SES was higher than the efficiency of the mixer equipped with a general purpose disintegrating head (GPDH for drop breakup but smaller for mass transfer.

  14. Analysis of the non-Markovianity for electron transfer reactions in an oligothiophene-fullerene heterojunction

    Science.gov (United States)

    Mangaud, E.; Meier, C.; Desouter-Lecomte, M.

    2017-09-01

    The non-Markovianity of the electron transfer in an oligothiophene-fullerene heterojunction described by a spin-boson model is analyzed using the time dependent decoherence canonical rates and the volume of accessible states in the Bloch sphere. The dynamical map of the reduced electronic system is computed by the hierarchical equations of motion methodology (HEOM) providing an exact dynamics. Transitory witness of non-Markovianity is linked to the bath dynamics analyzed from the HEOM auxiliary matrices. The signature of the collective bath mode detected from HEOM in each electronic state is compared with predictions of the effective mode extracted from the spectral density. We show that including this main reaction coordinate in a one-dimensional vibronic system coupled to a residual bath satisfactorily describes the electron transfer by a simple Markovian Redfield equation. Non-Markovianity is computed for three inter fragment distances and compared with a priori criterion based on the system and bath characteristic timescales.

  15. Mixed convection heat and mass transfer in peristaltic flow with chemical reaction and inclined magnetic field

    Science.gov (United States)

    Noreen, S.; Hayat, T.; Alsaedi, A.; Qasim, M.

    2013-09-01

    A mathematical model is constructed to investigate the mixed convective heat and mass transfer effects on peristaltic flow of magnetohydrodynamic pseudoplastic fluid in a symmetric channel. An analysis has been carried out to examine the impact of an inclined magnetic field and chemical reaction in presence of heat sink/source. Mechanics of flow and heat/mass transfer described in terms of continuity, linear momentum, energy and concentration equations are predicted by using long wavelength and low Reynolds number. Expressions for stream function, temperature, concentration and pressure gradient are derived. Numerical simulation is performed for the rise in pressure per wave length. Effects of several physical parameters on the flow quantities are analyzed.

  16. Large momentum transfer neutron pickup with the (π+,p) and (p,d) reactions

    International Nuclear Information System (INIS)

    Smith, G.R.

    1980-01-01

    The (p,d) reaction was studied for the first time at 800 MeV on seven targets ranging from 7 Li to 40 Ca. The experimental resolution (approx. 400 keV) attained was sufficient to observe many discrete levels in each of the residual nuclei. A modified version of the one-nucleon model successfully describes the magnitude and angular dependence of almost all of the transitions observed. A specific counter example to the two-nucleon model of the reaction mechanism is suggested. The calculations are also sensitive to the neutron single-particle wave function, in accordance with the expectation that the high-momentum components of this wave function are probed at higher bombarding energies. States that have never been seen before were strongly populated in the high excitation region (up to 25 MeV) of some of the residual nuclei. The relative intensities of the other levels observed suggest that coupled-channels mechanisms play an important role for some of these states. Explicit calculations were performed to confirm this for several examples. The first high-resolution measurements of the (π + ,p) reaction were also performed on 6 Li, 7 Li, 12 C, and 13 C at pion bombarding energies on and off the pion-nucleon resonance. Calculations employing a one-nucleon model of the reaction mechanism similar to the model successfully used for the (p,d) reaction are unable to account for transitions in the (π + ,p) reaction. It is, however, unclear whether this failure is due to a fundamental inadequacy of the model or improper treatment of details in the calculations. A striking similarity was observed in the spectra of the (π + ,p) and 800-MeV (p,d) reactions on the same target; this result implies a similar mechanism for the two reactions. 120 references, 97 figures, 15 tables

  17. Electron transfer reactions induced by the triplet state of thiacarbocyanine dimers

    International Nuclear Information System (INIS)

    Chibisov, Alexander K.; Slavnova, Tatyana D.; Goerner, Helmut

    2004-01-01

    The photoinduced electron transfer between either cationic 5,5 ' -dichloro-3,3 ' ,9-triethylthiacarbocyanine (1) or a structurally similar anionic dye (2) and appropriate donors, e.g. ascorbic acid, and acceptors, e.g. methyl viologen, was studied by ns-laser photolysis. In aqueous solution the dyes in the ground state are present as an equilibrated mixture of dimers and monomers, whereas the triplet state is mainly populated from dimers. The triplet states of both dimers and monomers are quenched by electron donors or acceptors and the rate constant for quenching is generally 2-4 times higher for dimers than for monomers. The kinetics of triplet decay and radical formation and decay as a result of primary and secondary electron transfer were analyzed. While the one-electron reduced dimer decays due to back reactions, the one-electron oxidized dimer rapidly dissociates into the monomer and the monomeric dye radical. For the dimeric dye/donor/acceptor systems the primary photoinduced electron transfer occurs either from the donor or to the acceptor yielding the dimeric dye radicals. The one-electron reduced dimer can be efficiently oxidized by acceptors, e.g. the rate constant for reaction of the dimeric dye radical of 1 with methyl viologen (photoreductive pathway of sensitization) is 1.6x10 9 M -1 s -1 . The photooxidative pathway of sensitization is more complicated; after dissociation of the dimeric dye radical, the monomeric dye radical is reduced in a secondary electron transfer from ascorbic acid, e.g. with a rate constant of 1x10 9 M -1 s -1 for 2, yielding the monomer. On increasing the donor concentration the photooxidative pathway of sensitization is switched to a photoreductive one

  18. Effects of mass transfer on MHD flow of casson fluid with chemical reaction and suction

    Directory of Open Access Journals (Sweden)

    S. A. Shehzad

    2013-03-01

    Full Text Available Effect of mass transfer in the magnetohydrodynamic flow of a Casson fluid over a porous stretching sheet is addressed in the presence of a chemical reaction. A series solution for the resulting nonlinear flow is computed. The skin friction coefficient and local Sherwood number are analyzed through numerical values for various parameters of interest. The velocity and concentration fields are illustrated for several pertinent flow parameters. We observed that the Casson parameter and Hartman number have similar effects on the velocity in a qualitative sense. We further analyzed that the concentration profile decreases rapidly in comparison to the fluid velocity when we increased the values of the suction parameter.

  19. Transfer reaction studies in inverse kinematics with the magnetic spectrometer PRISMA

    Directory of Open Access Journals (Sweden)

    Corradi L.

    2015-01-01

    Full Text Available The large solid angle magnetic spectrometers, in combination with large gamma arrays, allowed to perform reaction mechanism and nuclear structure studies in different regions of the nuclear chart, especially in the neutron-rich direction. By studying transfer of multiple pairs valuable information on nucleon-nucleon correlations can be derived, especially from measurements performed below the Coulomb barrier. There is growing interest in the study of the properties of the heavy binary partner, in the Pb and in the actinides regions, crucial also for astrophysics.

  20. Lifetime and g-factor measurements of excited states using Coulomb excitation and alpha transfer reactions

    Energy Technology Data Exchange (ETDEWEB)

    Guevara, Z. E., E-mail: zjguevaram@unal.edu.co; Torres, D. A., E-mail: datorresg@unal.edu.co [Physics Department, Universidad Nacional de Colombia, Bogotá D.C. (Colombia)

    2016-07-07

    In this contribution the challenges in the use of a setup to simultaneously measure lifetimes and g-factor values will be presented. The simultaneous use of the transient field technique and the Doppler Shift Attenuation Method, to measure magnetic moments and lifetimes respectively, allows to obtain a complete characterization of the currents of nucleons and the deformation in excited states close to the ground state. The technique is at the moment limited to Coulomb excitation and alpha-transfer reactions, what opens an interesting perspective to consider this type of experiments with radioactive beams. The use of deep-inelastic and fusion-evaporation reactions will be discussed. An example of a setup that makes use of a beam of {sup 106}Cd to study excited states of {sup 110}Sn and the beam nuclei itself will be presented.

  1. Charge separation in photoinitiated electron transfer reactions induced by a polyelectrolyte

    International Nuclear Information System (INIS)

    Meyerstein, D.; Rabani, J.; Matheson, M.S.; Meisel, D.

    1978-01-01

    When uncharged molecules quench the luminescence of Ru(bpy) 3 /sup 2+*/ by electron transfer to the quencher, the addition of poly(vinyl sulfate) (PVS) may, through its potential field, affect the rate of quenching, enhance the net separated charge yield, and slow the back reaction of the separated photoredox products. In all such cases that we have studied the quenching rate in the presence of PVS was reduced to about 60% of the rate measured in the absence of PVS. For two neutral species, iron(III) nitrilotriacetate (FeNTA) and cobalt(III) acetylacetonate (Co(acac) 3 ), photoreduction of the quencher was observed, and the redox yield escaping geminate recombination was substantially increased by added PVS. In the case of FeNTA the rate of the bulk back reaction was not changed appreciably by the presence of PVS owing to the rapid neutralization of Fe(NTA) - by protonation. For Co(acac) 3 the rate of the bulk back reaction was decreased by several orders of magnitude and the back reaction was shown to occur via the enolate form of the ligand which is released to the bulk solution. 4 figures, 4 tables

  2. Study of quark flavor-dependence in exclusive reactions at large momentum transfers

    International Nuclear Information System (INIS)

    Carroll, A.S.; Appel, R.; Barton, D.S.

    1988-01-01

    The measurement of exclusive reactions at large momentum transfers provides an important testing ground for models of hard quark-quark scattering. We have measured cross sections or set upper limits for 12 meson-bryon (π/sup +-/p → pπ/sup +-/, p/rho//sup +-/, π + Δ/sup +-/, K + Σ/sup +-/, π/sup /minus//p → Λ 0 /Σ 0 K 0 , K/sup +-/p → pK/sup +-/) and 2 baryon-baryon (p/sup +-/p → pp/sup /plus minus/) reactions near 90/degree/ C.M. by studying the flavor-dependence of these 2 exclusive reactions at t = -9(GeV/c)/sup 2/, we have been able to demonstrate in a perturbative QCD picture that the quark-interchange mechanism is dominant over gluon exchange and quark-antiquark annihilation. We will also present preliminary results on many of these reactions at t = -5(GeV/c)/sup 2/ with better resolution and statistical precision. 145 refs., 3 figs

  3. Oxygen atom transfer reactions from Mimoun complexes to sulfides and sulfoxides. A bonding evolution theory analysis.

    Science.gov (United States)

    González-Navarrete, Patricio; Sensato, Fabricio R; Andrés, Juan; Longo, Elson

    2014-08-07

    In this research, a comprehensive theoretical investigation has been conducted on oxygen atom transfer (OAT) reactions from Mimoun complexes to sulfides and sulfoxides. The joint use of the electron localization function (ELF) and Thom's catastrophe theory (CT) provides a powerful tool to analyze the evolution of chemical events along a reaction pathway. The progress of the reaction has been monitored by structural stability domains from ELF topology while the changes between them are controlled by turning points derived from CT which reveal that the reaction mechanism can be separated in several steps: first, a rupture of the peroxo O1-O2 bond, then a rearrangement of lone pairs of the sulfur atom occurs and subsequently the formation of S-O1 bond. The OAT process involving the oxidation of sulfides and sulfoxides is found to be an asynchronous process where O1-O2 bond breaking and S-O1 bond formation processes do not occur simultaneously. Nucleophilic/electrophilic characters of both dimethyl sulfide and dimethyl sulfoxide, respectively, are sufficiently described by our results, which hold the key to unprecedented insight into the mapping of electrons that compose the bonds while the bonds change.

  4. Two-Dimensional Resonance Raman Signatures of Vibronic Coherence Transfer in Chemical Reactions.

    Science.gov (United States)

    Guo, Zhenkun; Molesky, Brian P; Cheshire, Thomas P; Moran, Andrew M

    2017-11-02

    Two-dimensional resonance Raman (2DRR) spectroscopy has been developed for studies of photochemical reaction mechanisms and structural heterogeneity in condensed phase systems. 2DRR spectroscopy is motivated by knowledge of non-equilibrium effects that cannot be detected with traditional resonance Raman spectroscopy. For example, 2DRR spectra may reveal correlated distributions of reactant and product geometries in systems that undergo chemical reactions on the femtosecond time scale. Structural heterogeneity in an ensemble may also be reflected in the 2D spectroscopic line shapes of both reactive and non-reactive systems. In this chapter, these capabilities of 2DRR spectroscopy are discussed in the context of recent applications to the photodissociation reactions of triiodide. We show that signatures of "vibronic coherence transfer" in the photodissociation process can be targeted with particular 2DRR pulse sequences. Key differences between the signal generation mechanisms for 2DRR and off-resonant 2D Raman spectroscopy techniques are also addressed. Overall, recent experimental developments and applications of the 2DRR method suggest that it will be a valuable tool for elucidating ultrafast chemical reaction mechanisms.

  5. A Stefan model for mass transfer in a rotating disk reaction vessel

    KAUST Repository

    BOHUN, C. S.

    2015-05-04

    Copyright © Cambridge University Press 2015. In this paper, we focus on the process of mass transfer in the rotating disk apparatus formulated as a Stefan problem with consideration given to both the hydrodynamics of the process and the specific chemical reactions occurring in the bulk. The wide range in the reaction rates of the underlying chemistry allows for a natural decoupling of the problem into a simplified set of weakly coupled convective-reaction-diffusion equations for the slowly reacting chemical species and a set of algebraic relations for the species that react rapidly. An analysis of the chemical equilibrium conditions identifies an expansion parameter and a reduced model that remains valid for arbitrarily large times. Numerical solutions of the model are compared to an asymptotic analysis revealing three distinct time scales and chemical diffusion boundary layer that lies completely inside the hydrodynamic layer. Formulated as a Stefan problem, the model generalizes the work of Levich (Levich and Spalding (1962) Physicochemical hydrodynamics, vol. 689, Prentice-Hall Englewood Cliffs, NJ) and will help better understand the natural limitations of the rotating disk reaction vessel when consideration is made for the reacting chemical species.

  6. Single-Atom Catalyst of Platinum Supported on Titanium Nitride for Selective Electrochemical Reactions.

    Science.gov (United States)

    Yang, Sungeun; Kim, Jiwhan; Tak, Young Joo; Soon, Aloysius; Lee, Hyunjoo

    2016-02-05

    As a catalyst, single-atom platinum may provide an ideal structure for platinum minimization. Herein, a single-atom catalyst of platinum supported on titanium nitride nanoparticles were successfully prepared with the aid of chlorine ligands. Unlike platinum nanoparticles, the single-atom active sites predominantly produced hydrogen peroxide in the electrochemical oxygen reduction with the highest mass activity reported so far. The electrocatalytic oxidation of small organic molecules, such as formic acid and methanol, also exhibited unique selectivity on the single-atom platinum catalyst. A lack of platinum ensemble sites changed the reaction pathway for the oxygen-reduction reaction toward a two-electron pathway and formic acid oxidation toward direct dehydrogenation, and also induced no activity for the methanol oxidation. This work demonstrates that single-atom platinum can be an efficient electrocatalyst with high mass activity and unique selectivity. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Ignition and growth modeling of detonation reaction zone experiments on single crystals of PETN and HMX

    Science.gov (United States)

    White, Bradley W.; Tarver, Craig M.

    2017-01-01

    It has long been known that detonating single crystals of solid explosives have much larger failure diameters than those of heterogeneous charges of the same explosive pressed or cast to 98 - 99% theoretical maximum density (TMD). In 1957, Holland et al. demonstrated that PETN single crystals have failure diameters of about 8 mm, whereas heterogeneous PETN charges have failure diameters of less than 0.5 mm. Recently, Fedorov et al. quantitatively determined nanosecond time resolved detonation reaction zone profiles of single crystals of PETN and HMX by measuring the interface particle velocity histories of the detonating crystals and LiF windows using a PDV system. The measured reaction zone time durations for PETN and HMX single crystal detonations were approximately 100 and 260 nanoseconds, respectively. These experiments provided the necessary data to develop Ignition and Growth (I&G) reactive flow model parameters for the single crystal detonation reaction zones. Using these parameters, the calculated unconfined failure diameter of a PETN single crystal was 7.5 +/- 0.5 mm, close to the 8 mm experimental value. The calculated failure diameter of an unconfined HMX single crystal was 15 +/- 1 mm. The unconfined failure diameter of an HMX single crystal has not yet been determined precisely, but Fedorov et al. detonated 14 mm diameter crystals confined by detonating a HMX-based plastic bonded explosive (PBX) without initially overdriving the HMX crystals.

  8. Applications of a single-molecule detection in early disease diagnosis and enzymatic reaction study

    Energy Technology Data Exchange (ETDEWEB)

    Li, Jiangwei [Iowa State Univ., Ames, IA (United States)

    2008-01-01

    Various single-molecule techniques were utilized for ultra-sensitive early diagnosis of viral DNA and antigen and basic mechanism study of enzymatic reactions. DNA of human papilloma virus (HPV) served as the screening target in a flow system. Alexa Fluor 532 (AF532) labeled single-stranded DNA probes were hybridized to the target HPV-16 DNA in solution. The individual hybridized molecules were imaged with an intensified charge-coupled device (ICCD) in two ways. In the single-color mode, target molecules were detected via fluorescence from hybridized probes only. This system could detect HPV-16 DNA in the presence of human genomic DNA down to 0.7 copy/cell and had a linear dynamic range of over 6 orders of magnitude. In the dual-color mode, fluorescence resonance energy transfer (FRET) was employed to achieve zero false-positive count. We also showed that DNA extracts from Pap test specimens did not interfere with the system. A surface-based method was used to improve the throughput of the flow system. HPV-16 DNA was hybridized to probes on a glass surface and detected with a total internal reflection fluorescence (TIRF) microscope. In the single-probe mode, the whole genome and target DNA were fluorescently labeled before hybridization, and the detection limit is similar to the flow system. In the dual-probe mode, a second probe was introduced. The linear dynamic range covers 1.44-7000 copies/cell, which is typical of early infection to near-cancer stages. The dual-probe method was tested with a crudely prepared sample. Even with reduced hybridization efficiency caused by the interference of cellular materials, we were still able to differentiate infected cells from healthy cells. Detection and quantification of viral antigen with a novel single-molecule immunosorbent assay (SMISA) was achieved. Antigen from human immunodeficiency virus type 1(HIV-1) was chosen to be the target in this study. The target was sandwiched between a monoclonal capture antibody and a

  9. Radiated chemical reaction impacts on natural convective MHD mass transfer flow induced by a vertical cone

    Directory of Open Access Journals (Sweden)

    P. Sambath

    2018-03-01

    Full Text Available The consequence of thermal radiation in laminar natural convective hydromagnetic flow of viscous incompressible fluid past a vertical cone with mass transfer under the influence of chemical reaction with heat source/sink is presented here. The surface of the cone is focused to a variable wall temperature (VWT and wall concentration (VWC. The fluid considered here is a gray absorbing and emitting, but non-scattering medium. The boundary layer dimensionless equations governing the flow are solved by an implicit finite-difference scheme of Crank–Nicolson which has speedy convergence and stable. This method converts the dimensionless equations into a system of tri-diagonal equations and which are then solved by using well known Thomas algorithm. Numerical solutions are obtained for momentum, temperature, concentration, local and average shear stress, heat and mass transfer rates for various values of parameters Pr, Sc, λ, Δ, Rd are established with graphical representations. We observed that the liquid velocity decreased for higher values of Prandtl and Schmidt numbers. The temperature is boost up for decreasing values of Schimdt and Prandtl numbers. The enhancement in radiative parameter gives more heat to liquid due to which temperature is enhanced significantly. Keywords: Chemical reaction, Heat generation/absorption, MHD, Radiation, Vertical cone

  10. Gamow-Teller transitions and neutron-proton-pair transfer reactions

    Science.gov (United States)

    Van Isacker, P.; Macchiavelli, A. O.

    2018-05-01

    We propose a schematic model of nucleons moving in spin-orbit partner levels, j = l ±1/2, to explain Gamow-Teller and two-nucleon transfer data in N = Z nuclei above 40Ca. Use of the LS coupling scheme provides a more transparent approach to interpret the structure and reaction data. We apply the model to the analysis of charge-exchange, 42Ca(3He,t)42Sc, and np-transfer, 40Ca(3He,p)42Sc, reactions data to define the elementary modes of excitation in terms of both isovector and isoscalar pairs, whose properties can be determined by adjusting the parameters of the model (spin-orbit splitting, isovector pairing strength and quadrupole matrix element) to the available data. The overall agreement with experiment suggests that the approach captures the main physics ingredients and provides the basis for a boson approximation that can be extended to heavier nuclei. Our analysis also reveals that the SU(4)-symmetry limit is not realized in 42Sc.

  11. Analisa Kecepatan Transfer Data Pada Perancangan Hotspot Sederhana Dengan System Single Sign On Di Perkantoran

    Directory of Open Access Journals (Sweden)

    Bela Neziah Arum Pangesti

    2017-05-01

    Full Text Available The problems office in the utilization of wireless technology has widely used but sometimes without take into the number of users, so it is not mangkus. The networking system for small office can be use wireless simple system. Most of the office has applied hotspot but that is old system, one account for all people using internet access. Single sign-on is a system services of hotspot, this system verifying an account for each user so people have different and username dan a password. The methodology used is literature review, analysis, design, implementation, testing and analysis of the data transfer rate. The hotspot with a single sign-on system using mikrotik, and access point, the connected with networking devices in the office. Winbox tools is used to configuration. Testing with the user had been connected to the hotspot system single sign on. Methods of test to user login on the system single sign-on is the black box texting. Testing the speed of data transfer is used staff user and guest user who uploaded three types of files to the drive with diffrent bandwidth. Then the network sniffing is used tools wireshark. The results from this study is simple hotspot service with single sign-on system for office and from the analysis of the data transfer rate was known the data transfer rate on the staff user and guest user to the three types of file is a type of word files greater than PDF and PPT.

  12. Particle Transfer Reactions with the Time-Dependent Hartree-Fock Theory Using a Particle Number Projection Technique

    International Nuclear Information System (INIS)

    Simenel, Cedric

    2010-01-01

    A particle-number projection technique is used to calculate transfer probabilities in the 16 O+ 208 Pb reaction below the fusion barrier. The time evolution of the many-body wave function is obtained with the time-dependent Hartree-Fock (TDHF) mean-field theory. The agreement with experimental data for the sum of the proton-transfer channels is good, considering that TDHF has no parameter adjusted on the reaction mechanism. Some perspectives for extensions beyond TDHF to include cluster transfers are discussed.

  13. Kinetics and mechanism of bimolecular electron transfer reaction in quinone-amine systems in micellar solution

    International Nuclear Information System (INIS)

    Kumbhakar, Manoj; Nath, Sukhendu; Mukherjee, Tulsi; Pal, Haridas

    2005-01-01

    Photoinduced electron transfer (ET) reactions between anthraquinone derivatives and aromatic amines have been investigated in sodium dodecyl sulphate (SDS) micellar solutions. Significant static quenching of the quinone fluorescence due to high amine concentration in the micellar phase has been observed in steady-state measurements. The bimolecular rate constants for the dynamic quenching in the present systems k q TR , as estimated from the time-resolved measurements, have been correlated with the free energy changes ΔG 0 for the ET reactions. Interestingly it is seen that the k q TR vs ΔG 0 plot displays an inversion behavior with maximum k q TR at around 0.7 eV, a trend similar to that predicted in Marcus ET theory. Like the present results, Marcus inversion in the k q TR values was also observed earlier in coumarin-amine systems in SDS and TX-100 micellar solutions, with maximum k q TR at around the same exergonicity. These results thus suggest that Marcus inversion in bimolecular ET reaction is a general phenomenon in micellar media. Present observations have been rationalized on the basis of the two-dimensional ET (2DET) theory, which seems to be more suitable for micellar ET reactions than the conventional ET theory. For the quinone-amine systems, it is interestingly seen that k q TR vs ΔG 0 plot is somewhat wider in comparison to that of the coumarin-amine systems, even though the maxima in the k q TR vs ΔG 0 plots appear at almost similar exergonicity for both the acceptor-donor systems. These observations have been rationalized on the basis of the differences in the reaction windows along the solvation axis, as envisaged within the framework of the 2DET theory, and arise due to the differences in the locations of the quinones and coumarin dyes in the micellar phase

  14. Validated spectrophotometric methods for determination of sodium valproate based on charge transfer complexation reactions

    Science.gov (United States)

    Belal, Tarek S.; El-Kafrawy, Dina S.; Mahrous, Mohamed S.; Abdel-Khalek, Magdi M.; Abo-Gharam, Amira H.

    2016-02-01

    This work presents the development, validation and application of four simple and direct spectrophotometric methods for determination of sodium valproate (VP) through charge transfer complexation reactions. The first method is based on the reaction of the drug with p-chloranilic acid (p-CA) in acetone to give a purple colored product with maximum absorbance at 524 nm. The second method depends on the reaction of VP with dichlone (DC) in dimethylformamide forming a reddish orange product measured at 490 nm. The third method is based upon the interaction of VP and picric acid (PA) in chloroform resulting in the formation of a yellow complex measured at 415 nm. The fourth method involves the formation of a yellow complex peaking at 361 nm upon the reaction of the drug with iodine in chloroform. Experimental conditions affecting the color development were studied and optimized. Stoichiometry of the reactions was determined. The proposed spectrophotometric procedures were effectively validated with respect to linearity, ranges, precision, accuracy, specificity, robustness, detection and quantification limits. Calibration curves of the formed color products with p-CA, DC, PA and iodine showed good linear relationships over the concentration ranges 24-144, 40-200, 2-20 and 1-8 μg/mL respectively. The proposed methods were successfully applied to the assay of sodium valproate in tablets and oral solution dosage forms with good accuracy and precision. Assay results were statistically compared to a reference pharmacopoeial HPLC method where no significant differences were observed between the proposed methods and reference method.

  15. Excited state intramolecular charge transfer reaction in nonaqueous electrolyte solutions: temperature dependence.

    Science.gov (United States)

    Pradhan, Tuhin; Gazi, Harun Al Rasid; Biswas, Ranjit

    2009-08-07

    Temperature dependence of the excited state intramolecular charge transfer reaction of 4-(1-azetidinyl)benzonitrile (P4C) in ethyl acetate (EA), acetonitrile (ACN), and ethanol at several concentrations of lithium perchlorate (LiClO(4)) has been investigated by using the steady state and time resolved fluorescence spectroscopic techniques. The temperature range considered is 267-343 K. The temperature dependent spectral peak shifts and reaction driving force (-DeltaG(r)) in electrolyte solutions of these solvents can be explained qualitatively in terms of interaction between the reactant molecule and ion-atmosphere. Time resolved studies indicate that the decay kinetics of P4C is biexponential, regardless of solvents, LiClO(4) concentrations, and temperatures considered. Except at higher electrolyte concentrations in EA, reaction rates in solutions follow the Arrhenius-type temperature dependence where the estimated activation energy exhibits substantial electrolyte concentration dependence. The average of the experimentally measured activation energies in these three neat solvents is found to be in very good agreement with the predicted value based on data in room temperature solvents. While the rate constant in EA shows a electrolyte concentration induced parabolic dependence on reaction driving force (-DeltaG(r)), the former in ethanol and ACN increases only linearly with the increase in driving force (-DeltaG(r)). The data presented here also indicate that the step-wise increase in solvent reorganization energy via sequential addition of electrolyte induces the ICT reaction in weakly polar solvents to crossover from the Marcus inverted region to the normal region.

  16. Magnetization-transfer measurements of individual rate constants in the presence of multiple reactions

    Science.gov (United States)

    Uǧurbil, Kâmil

    Magnetization-transfer techniques, such as saturation or inversion transfer, are extremely useful methods for measuring chemical-exchange rate constants which are comparable to spin-lattice relaxation rate constants of the exchanging spins. Although such determinations are relatively simple for a two-site exchange case, complications arise when multisite exchanges are involved. This severely restricts the applicability of this type of measurement, especially in whole cells and tissues where many reactants are utilized by more than one enzyme. In this paper, it is shown that a multisite exchange problem can first be reduced effectively to a two-site exchange, and a single rate constant can subsequently be measured simply and unequivocally. Application of this procedure to equilibrium and nonequilibrium chemical-exchange problems are discussed.

  17. Hydrogen Transfer during Liquefaction of Elbistan Lignite to Biomass; Total Reaction Transformation Approach

    Science.gov (United States)

    Koyunoglu, Cemil; Karaca, Hüseyin

    2017-12-01

    Given the high cost of the tetraline solvent commonly used in liquefaction, the use of manure with EL is an important factor when considering the high cost of using tetraline as a hydrogen transfer source. In addition, due to the another cost factor which is the catalyst prices, red mud (commonly used, produced as a byproduct in the production of aluminium) is reduced cost in the work of liquefaction of coal, biomass, even coal combined biomass, corresponding that making the EL liquefaction an agenda for our country is another important factor. Conditions for liquefaction experiments conducted for hydrogen transfer from manure to coal; Catalyst concentration of 9%, liquid/solid ratio of 3/1, reaction time of 60 min, fertilizer/lignite ratio of 1/3, and the reaction temperature of 400 °C, the stirred speed of 400 rpm and the initial nitrogen pressure of 20 bar was fixed. In order to demonstrate the hydrogen, transfer from manure to coal, coal is used solely, by using tetraline (also known as a hydrogen carrier) and distilled water which is not hydrogen donor as a solvent in the co-liquefaction of experiments, and also the liquefaction conditions are carried out under an inert (N2) gas atmosphere. According to the results of the obtained liquefaction test; using tetraline solvent the total liquid product conversion percentage of the oil + gas conversion was 38.3 %, however, the results of oil+gas conversion obtained using distilled water and EL combined with manure the total liquid product conversion percentage was 7.4 %. According to the results of calorific value and elemental analysis, only the ratio of (H/C)atomic of coal obtained by using tetraline increased with the liquefaction of manure and distilled water. The reason of the increase in the amount of hydrogen due to hydrogen transfer from the manure on the solid surface of the coal, and also on the surface of the inner pore of the coal during the liquefaction, brings about the evaluation of the coal as a

  18. A general theoretical model for electron transfer reactions in complex systems.

    Science.gov (United States)

    Amadei, Andrea; Daidone, Isabella; Aschi, Massimiliano

    2012-01-28

    In this paper we present a general theoretical-computational model for treating electron transfer reactions in complex atomic-molecular systems. The underlying idea of the approach, based on unbiased first-principles calculations at the atomistic level, utilizes the definition and the construction of the Diabatic Perturbed states of the involved reactive partners (i.e. the quantum centres in our perturbation approach) as provided by the interaction with their environment, including their mutual interaction. In this way we reconstruct the true Adiabatic states of the reactive partners characterizing the electron transfer process as the fluctuation of the electronic density due to the fluctuating perturbation. Results obtained by using a combination of Molecular Dynamics simulation and the Perturbed Matrix Method on a prototypical intramolecular electron transfer (from 2-(9,9'-dimethyl)fluorene to the 2-naphthalene group separated by a steroidal 5-α-androstane skeleton) well illustrate the accuracy of the method in reproducing both the thermodynamics and the kinetics of the process.

  19. Intramolecular proton transfer and tunnelling reactions of hydroxyphenylbenzoxazole derivatives in Xenon at 15 K

    Energy Technology Data Exchange (ETDEWEB)

    Walla, Peter J. [Max-Planck-Institute for Biophysical Chemistry, Department 010, Spectroscopy and Photochemical Kinetics, Am Fassberg 11, D-37077 Goettingen (Germany) and Department for Biophysical Chemistry, Technical University of Brunswick, Institute for Physical and Theoretical Chemistry, Hans-Sommerstr. 10, D-38106 Braunschweig (Germany)]. E-mail: pwalla@gwdg.de; Nickel, Bernhard [Max-Planck-Institute for Biophysical Chemistry, Department 010, Spectroscopy and Photochemical Kinetics, Am Fassberg 11, D-37077 Goettingen (Germany)

    2005-06-06

    We investigated the site dependence and the tunnelling processes of the intramolecular proton and deuteron transfer in the triplet state of the compounds 2-(2'-hydroxy-4'-methylphenyl)benzoxazole (m-MeHBO) and 2-(2'-hydroxy-3'-methylphenyl)benzoxazoles (o-MeHBO) and their deuterio-oxy analogues in a solid xenon matrix. After singlet excitation there occurs an ultrafast intramolecular enol {yields} keto proton transfer and subsequent intersystem crossing mainly to the keto triplet state. In the triplet state of m-MeHBO, the proton transfer back to the lower enol triplet state is governed by tunnelling processes. In o-MeHBO, however, the enol triplet state is higher and therefore normally no tunnel reaction can be observed. Because of the external heavy atom-effect in a xenon matrix, we were able to investigate the reverse enol-keto-tunnelling after exciting directly the enol triplet state of deuterated o-MeHBO. The time constants of the reverse enol-keto tautomerization are similar to those of the normal keto-enol tautomerization. In a xenon matrix, the observed site-selective phosphorescence spectra are very well-resolved vibrationally. This allowed the study of the tunnel rates in different well-defined sites. The vibrational energies obtained in the spectra are in good agreement with vibrational energies found in resonant Raman and IR spectra of 2-(2'-hydroxyphenyl)benzoxazole (HBO)

  20. Risk of ectopic pregnancy lowest with transfer of single frozen blastocyst.

    Science.gov (United States)

    Li, Z; Sullivan, E A; Chapman, M; Farquhar, C; Wang, Y A

    2015-09-01

    What type of transferred embryo is associated with a lower rate of ectopic pregnancy? The lowest risk of ectopic pregnancy was associated with the transfer of blastocyst, frozen and single embryo compared with cleavage stage, fresh and multiple embryos. Ectopic pregnancy is a recognized complication following assisted reproductive technology (ART) treatment. It has been estimated that the rate of ectopic pregnancy is doubled in pregnancies following ART treatment compared with spontaneous pregnancies. However, it was not clear whether the excess rate of ectopic pregnancy following ART treatment is related to the underlying demographic factors of women undergoing ART treatment, the number of embryos transferred or the developmental stage of the embryo. A population-based cohort study of pregnancies following autologous treatment cycles between January 2009 and December 2011 were obtained from the Australian and New Zealand Assisted Reproduction Technology Database (ANZARD). The ANZARD collects ART treatment information and clinical outcomes annually from all fertility centres in Australia and New Zealand. Between 2009 and 2011, a total of 44 102 pregnancies were included in the analysis. The rate of ectopic pregnancy was compared by demographic and ART treatment factors. Generalized linear regression of Poisson distribution was used to estimate the likelihood of ectopic pregnancy. Odds ratios, adjusted odds ratios (AOR) and 95% confidence intervals (CI) were calculated. The overall rate of ectopic pregnancy was 1.4% for women following ART treatment in Australia and New Zealand. Pregnancies following single embryo transfers had 1.2% ectopic pregnancies, significantly lower than double embryo transfers (1.8%) (P ectopic pregnancy rate was 1.9% for pregnancies from transfers of fresh cleavage embryo, followed by transfers of frozen cleavage embryo (1.7%), transfers of fresh blastocyst (1.3%), and transfers of frozen blastocyst (0.8%). Compared with fresh blastocyst

  1. Reaction kinetics of oxygen on single-phase alloys, oxidation of nickel and niobium alloys

    International Nuclear Information System (INIS)

    Lalauze, Rene

    1973-01-01

    This research thesis first addresses the reaction kinetics of oxygen on alloys. It presents some generalities on heterogeneous reactions (conventional theory, theory of jumps), discusses the core reaction (with the influence of pressure), discusses the influence of metal self-diffusion on metal oxidation kinetics (equilibrium conditions at the interface, hybrid diffusion regime), reports the application of the hybrid diffusion model to the study of selective oxidation of alloys (Wagner model, hybrid diffusion model) and the study of the oxidation kinetics of an alloy forming a solid solution of two oxides. The second part reports the investigation of the oxidation of single phase nickel and niobium alloys (phase α, β and γ)

  2. Single-molecule imaging of platinum ligand exchange reaction reveals reactivity distribution.

    Science.gov (United States)

    Esfandiari, N Melody; Wang, Yong; Bass, Jonathan Y; Cornell, Trevor P; Otte, Douglas A L; Cheng, Ming H; Hemminger, John C; McIntire, Theresa M; Mandelshtam, Vladimir A; Blum, Suzanne A

    2010-11-03

    Single-molecule fluorescence microscopy provided information about the real-time distribution of chemical reactivity on silicon oxide supports at the solution-surface interface, at a level of detail which would be unavailable from a traditional ensemble technique or from a technique that imaged the static physical properties of the surface. Chemical reactions on the surface were found to be uncorrelated; that is, the chemical reaction of one metal complex did not influence the location of a future chemical reaction of another metal complex.

  3. Monitoring Chemical and Biological Electron Transfer Reactions with a Fluorogenic Vitamin K Analogue Probe.

    Science.gov (United States)

    Belzile, Mei-Ni; Godin, Robert; Durantini, Andrés M; Cosa, Gonzalo

    2016-12-21

    We report herein the design, synthesis, and characterization of a two-segment fluorogenic analogue of vitamin K, B-VK Q , prepared by coupling vitamin K 3 , also known as menadione (a quinone redox center), to a boron-dipyrromethene (BODIPY) fluorophore (a lipophilic reporter segment). Oxidation-reduction reactions, spectroelectrochemical studies, and enzymatic assays conducted in the presence of DT-diaphorase illustrate that the new probe shows reversible redox behavior on par with that of vitamin K, provides a high-sensitivity fluorescence signal, and is compatible with biological conditions, opening the door to monitor remotely (i.e., via imaging) redox processes in real time. In its oxidized form, B-VK Q is non-emissive, while upon reduction to the hydroquinone form, B-VK QH 2 , BODIPY fluorescence is restored, with emission quantum yield values of ca. 0.54 in toluene. Density functional theory studies validate a photoinduced electron transfer intramolecular switching mechanism, active in the non-emissive quinone form and deactivated upon reduction to the emissive dihydroquinone form. Our results highlight the potential of B-VK Q as a fluorogenic probe to study electron transfer and transport in model systems and biological structures with optimal sensitivity and desirable chemical specificity. Use of such a probe may enable a better understanding of the role that vitamin K plays in biological redox reactions ubiquitous in key cellular processes, and help elucidate the mechanism and pathological significance of these reactions in biological systems.

  4. Study of photo-activated electron transfer reactions in the first excited singlet state by picosecond and nanosecond laser spectroscopy

    International Nuclear Information System (INIS)

    Doizi, Denis

    1983-01-01

    Picosecond laser spectroscopy has been used to study two photo-activated electron transfer reactions: - a bimolecular electron transfer reaction between a sensitizer, DODCI, and an electron acceptor, methylviologen. The two radical ions created with an electron transfer efficiency γ ≅ 0.07 have been identified in picosecond and nanosecond laser absorption spectroscopy by adding selective solutes such as para-benzoquinone (an electron acceptor) or L(+) ascorbic acid (an electron donor). - an intramolecular electron transfer reaction in a triad molecule consisting of a tetra-aryl-porphyrin covalently linked to both a carotenoid and a quinone. The photoinduced charge separation occurs within 30 ps and leads, with a yield of 25 pc, to the formation of a zwitterion whose half-life is 2.5 μs. The experimental results obtained in these two studies show an effective decrease in the recombination rate of the two radical ions created in the encounter pair. (author) [fr

  5. Humidity independent mass spectrometry for gas phase chemical analysis via ambient proton transfer reaction.

    Science.gov (United States)

    Zhu, Hongying; Huang, Guangming

    2015-03-31

    In this work, a humidity independent mass spectrometric method was developed for rapid analysis of gas phase chemicals. This method is based upon ambient proton transfer reaction between gas phase chemicals and charged water droplets, in a reaction chamber with nearly saturate humidity under atmospheric pressure. The humidity independent nature enables direct and rapid analysis of raw gas phase samples, avoiding time- and sample-consuming sample pretreatments in conventional mass spectrometry methods to control sample humidity. Acetone, benzene, toluene, ethylbenzene and meta-xylene were used to evaluate the analytical performance of present method. The limits of detection for benzene, toluene, ethylbenzene and meta-xylene are in the range of ∼0.1 to ∼0.3 ppbV; that of benzene is well below the present European Union permissible exposure limit for benzene vapor (5 μg m(-3), ∼1.44 ppbV), with linear ranges of approximately two orders of magnitude. The majority of the homemade device contains a stainless steel tube as reaction chamber and an ultrasonic humidifier as the source of charged water droplets, which makes this cheap device easy to assemble and facile to operate. In addition, potential application of this method was illustrated by the real time identification of raw gas phase chemicals released from plants at different physiological stages. Copyright © 2015 Elsevier B.V. All rights reserved.

  6. Production and study of heavy neutron rich nuclei formed in multi-nucleon transfer reactions

    Energy Technology Data Exchange (ETDEWEB)

    Zagrebaev, V. I.; Zemlyanoy, S. G., E-mail: zemlya@jinr.ru; Kozulin, E. M. [Joint Institute for Nuclear Research, FLNR (Russian Federation); Kudryavtsev, Yu. [Instituut voor Kern-en Stralingsfysica (Belgium); Fedosseev, V. [CERN (Switzerland); Bark, R. [Nat. Research Foundation, iThemba LABS (South Africa); Othman, H. A. [Menoufiya University, Physics Department, Faculty of Science (Egypt)

    2013-04-15

    A new setup is proposed to produce and investigate heavy neutron-rich nuclei located along the neutron closed shell N = 126. This 'blank spot' of the nuclear map can be reached neither in fusion-fission reactions nor in fragmentation processes widely used nowadays for the production of exotic nuclei. The present limits of the upper part of the nuclear map are very close to stability while the unexplored area of heavy neutron-rich nuclides along the neutron closed shell N = 126 is extremely important for nuclear astrophysics investigations and, in particular, for the understanding of the r-process of astrophysical nucleosynthesis. A new way was recently proposed for the production of these nuclei via low-energy multi-nucleon transfer reactions. The estimated yields of neutron-rich nuclei are found to be rather high in such reactions and several tens of new nuclides can be produced, for example, in the near-barrier collision of 136Xe with 208Pb. This setup could definitely open a new opportunity in the studies at heavy-ion facilities and will have significant impact on future experiments.

  7. Effects of breakup of weakly bound projectile and neutron transfer on fusion reactions around Coulomb barrier

    International Nuclear Information System (INIS)

    Lin, C.J.; Zhang, H.Q.; Yang, F.; Ruan, M.; Liu, Z.H.; Wu, Y.W.; Wu, X.K.; Zhou, P.; Zhang, C.L.; Zhang, G.L.; An, G.P.; Jia, H.M.; Xu, X.X.

    2007-01-01

    The excitation functions of quasielastic and elastic scattering at backward angles have been measured for the systems of 16 O+ 152 Sm, 6,7 Li+ 208 Pb and 32 S+ 90,96 Zr. The barrier distributions are extracted from these measured excitation functions and compared with the corresponding fusion barrier distributions. Except some details, the barrier distributions derived from the data of fusion and quasielastic/elastic scattering are almost the same for the tightly bound reaction systems. For the reaction systems with weakly bound projectile, the barrier distributions extracted from quasielastic scattering are obviously different from the fusion barrier distributions. However, the barrier distributions extracted from the excitation functions of the quasielastic scattering plus breakup are almost the same as the one extracted from the complete fusion data. This result means that barrier distribution not only bears the information of nuclear structures but also contains the knowledge of reaction mechanisms. Our results show that the complete fusion of the weakly bound projectile with heavy target is suppressed at the above barrier energies as compared with the model predictions. In addition, the measured barrier distribution of 32 S+ 96 Zr is broaden and extends to lower energy than in the case of 32 S+ 90 Zr due to the coupling of neutron transfer with positive Q-values, which result in a significant enhancement of fusion cross sections at the subbarrier energies

  8. Role of inelastic excitation and nucleon transfer in quasielastic reactions between 86Kr and 208Pb

    International Nuclear Information System (INIS)

    Sohlbach, H.; Freiesleben, H.; Schneider, W.F.W.; Schuell, D.; Braun-Munzinger, P.; Kohlmeyer, B.; Marinescu, M.; Puehlhofer, F.

    1986-01-01

    In order to get detailed information about the interplay between inelastic excitation and nucleon transfer the authors studied the system 86 Kr + 208 Pb at 10, 13, and 18.2 MeV/u at GSI. The GSI-magnetic spectrometer was used to determine atomic number Z, mass number A, and kinetic energies of projectile-like reaction products. The measured momentum spectra were carefully checked and were found to be free of contaminations from target impurities and slit scattering tails. The experimental energy spectra of various reaction products exhibit in addition to the quasielastic peak very distinct structures, the centroids of which shift to higher TKEL as the bombarding energy increases. A Monte Carlo simulation of sequential 1- and 2-neutron emission was performed and all the structures observed, in particular their dependence on bombarding energy, were consistently reproduced. Two main conclusions can be drawn: firstly, all structures observed in the energy spectra are accounted for by sequential decay, secondly, the centroids of these structures can only be reproduced if the excitation energy sharing is adjusted separately for each reaction channel considered

  9. Observation of Frenkel and charge transfer excitons in pentacene single crystals using spectroscopic generalized ellipsometry

    NARCIS (Netherlands)

    Qi, Dongchen; Su, Haibin; Bastjan, M.; Jurchescu, O. D.; Palstra, T. M.; Wee, Andrew T. S.; Ruebhausen, M.; Rusydi, A.; Rübhausen, M.

    2013-01-01

    We report on the emerging and admixture of Frenkel and charge transfer (CT) excitons near the absorption onset in pentacene single crystals. Using high energy-resolution spectroscopic generalized ellipsometry with in-plane polarization dependence, the excitonic nature of three lowest lying

  10. Grid to vehicle and vehicle to grid energy transfer using single ...

    African Journals Online (AJOL)

    user

    The design of the various components of proposed configuration for energy transfer from grid to vehicle and vehicle to grid consists of a single phase half bridge boost AC-DC converter, a bidirectional DC-DC boost converter, and a battery energy storage system. The detailed design of each part is given in the following ...

  11. Supramolecular Systems and Chemical Reactions in Single-Molecule Break Junctions.

    Science.gov (United States)

    Li, Xiaohui; Hu, Duan; Tan, Zhibing; Bai, Jie; Xiao, Zongyuan; Yang, Yang; Shi, Jia; Hong, Wenjing

    2017-04-01

    The major challenges of molecular electronics are the understanding and manipulation of the electron transport through the single-molecule junction. With the single-molecule break junction techniques, including scanning tunneling microscope break junction technique and mechanically controllable break junction technique, the charge transport through various single-molecule and supramolecular junctions has been studied during the dynamic fabrication and continuous characterization of molecular junctions. This review starts from the charge transport characterization of supramolecular junctions through a variety of noncovalent interactions, such as hydrogen bond, π-π interaction, and electrostatic force. We further review the recent progress in constructing highly conductive molecular junctions via chemical reactions, the response of molecular junctions to external stimuli, as well as the application of break junction techniques in controlling and monitoring chemical reactions in situ. We suggest that beyond the measurement of single molecular conductance, the single-molecule break junction techniques provide a promising access to study molecular assembly and chemical reactions at the single-molecule scale.

  12. Reducing twin pregnancy rates after IVF--elective single embryo transfer (eSET).

    LENUS (Irish Health Repository)

    Milne, P

    2010-01-01

    Multiple pregnancy is a major complication of IVF and is associated with increased maternal, fetal and neonatal morbidity. Elective single embryo transfer (eSET) during IVF, rather than the more standard transfer of two embryos (double embryo transfer or DET), has been shown to significantly reduce the multiple pregnancy rate associated with IVF, while maintaining acceptable pregnancy rates. Couples undergoing IVF in 2008 who met good prognostic criteria had eSET performed. Pregnancy and twinning rates were compared with those for similar couples in 2007 who had DET. Couples unsuccessful with a fresh cycle of treatment had subsequent frozen embryo transfer cycles with DET. The cumulative pregnancy rate was similar for each group. However there were no multiple pregnancies in the eSET group, compared to 4 twins of 5 pregnancies in the DET group. 96% of eligible couples agreed to eSET. ESET is successful in and acceptable to good prognosis Irish couples undergoing IVF.

  13. Effects of rolling on single-phase water forced convective heat transfer characteristics

    International Nuclear Information System (INIS)

    Guo Yanming; Gao Puzhen; Huang Zhen

    2010-01-01

    A series of single-phase forced circulation tests in a vertical tube with rolling motion were performed in order to investigate effects of rolling motion on thermal-hydraulic characteristics. The amplitudes of the rolling motion in the tests were 10 degree, 15 degree and 20 degree. The rolling periods were 7.5 s, 10 s, 15 s and 20 s. The Reynolds number was from 6000 to 15000. Heat transfer in the test tube is bated by the rolling motion. As the test-bed rolling more acutely, the heat transfer coefficient of the test tube becomes smaller when the mass flow rate in the test tube is a constant. The heat transfer coefficient calculated by the formula which is for stable state doesn't fit very well with that from experiments. At last a formula for calculating heat transfer in rolling motion was introduced. (authors)

  14. Reaction of single-standard DNA with hydroxyl radical generated by iron(II)-ethylenediaminetetraacetic acid

    International Nuclear Information System (INIS)

    Prigodich, R.V.; Martin, C.T.

    1990-01-01

    This study demonstrates that the reaction of Fe(II)-EDTA and hydrogen peroxide with the single-stranded nucleic acids d(pT) 70 and a 29-base sequence containing a mixture of bases results in substantial damage which is not directly detected by gel electrophoresis. Cleavage of the DNA sugar backbone is enhanced significantly after the samples are incubated at 90 degree C in the presence of piperidine. The latter reaction is used in traditional Maxam-Gilbert DNA sequencing to detect base damage, and the current results are consistent with reaction of the hydroxyl radical with the bases in single-stranded DNA (although reaction with sugar may also produce adducts that are uncleaved but labile to cleavage by piperidine). We the authors propose that hydroxyl radicals may react preferentially with the nucleic acid bases in ssDNA and that reaction of the sugars in dsDNA is dominant because the bases are sequestered within the double helix. These results have implications both for the study of single-stranded DNA binding protein binding sites and for the interpretation of experiments using the hydroxyl radical to probe DNA structure or to footprint double-stranded DNA binding protein binding sites

  15. Axial Colocalization of Single Molecules with Nanometer Accuracy Using Metal-Induced Energy Transfer.

    Science.gov (United States)

    Isbaner, Sebastian; Karedla, Narain; Kaminska, Izabela; Ruhlandt, Daja; Raab, Mario; Bohlen, Johann; Chizhik, Alexey; Gregor, Ingo; Tinnefeld, Philip; Enderlein, Jörg; Tsukanov, Roman

    2018-03-27

    Single-molecule localization based super-resolution microscopy has revolutionized optical microscopy and routinely allows for resolving structural details down to a few nanometers. However, there exists a rather large discrepancy between lateral and axial localization accuracy, the latter typically three to five times worse than the former. Here, we use single-molecule metal-induced energy transfer (smMIET) to localize single molecules along the optical axis, and to measure their axial distance with an accuracy of 5 nm. smMIET relies only on fluorescence lifetime measurements and does not require additional complex optical setups.

  16. Stability results for a reaction-diffusion system with a single measurement

    Energy Technology Data Exchange (ETDEWEB)

    Ramoul, Hichem [Centre universitaire de Khenchela, Route de Batna, BP 1252, Liberte, 40004 Khenchela (Algeria); Gaitan, Patricia [Laboratoire d' analyse, topologie, probabilites CNRS UMR 6632, Marseille (France) and Universite Aix-Marseille II (France); Cristofol, Michel [Laboratoire d' analyse, topologie, probabilites CNRS UMR 6632, Marseille, France and Universite Aix-Marseille III (France)

    2007-06-15

    For a two by two reaction-diffusion system on a bounded domain we give a simultaneous stability result for one coefficient and for the initial conditions. The key ingredient is a global Carleman-type estimate with a single observation acting on a subdomain.

  17. Quantum coherent energy transfer over varying pathways in single light-harvesting complexes.

    Science.gov (United States)

    Hildner, Richard; Brinks, Daan; Nieder, Jana B; Cogdell, Richard J; van Hulst, Niek F

    2013-06-21

    The initial steps of photosynthesis comprise the absorption of sunlight by pigment-protein antenna complexes followed by rapid and highly efficient funneling of excitation energy to a reaction center. In these transport processes, signatures of unexpectedly long-lived coherences have emerged in two-dimensional ensemble spectra of various light-harvesting complexes. Here, we demonstrate ultrafast quantum coherent energy transfer within individual antenna complexes of a purple bacterium under physiological conditions. We find that quantum coherences between electronically coupled energy eigenstates persist at least 400 femtoseconds and that distinct energy-transfer pathways that change with time can be identified in each complex. Our data suggest that long-lived quantum coherence renders energy transfer in photosynthetic systems robust in the presence of disorder, which is a prerequisite for efficient light harvesting.

  18. Site-selective oxidation, amination and epimerization reactions of complex polyols enabled by transfer hydrogenation

    Science.gov (United States)

    Hill, Christopher K.; Hartwig, John F.

    2017-12-01

    Polyoxygenated hydrocarbons that bear one or more hydroxyl groups comprise a large set of natural and synthetic compounds, often with potent biological activity. In synthetic chemistry, alcohols are important precursors to carbonyl groups, which then can be converted into a wide range of oxygen- or nitrogen-based functionality. Therefore, the selective conversion of a single hydroxyl group in natural products into a ketone would enable the selective introduction of unnatural functionality. However, the methods known to convert a simple alcohol, or even an alcohol in a molecule that contains multiple protected functional groups, are not suitable for selective reactions of complex polyol structures. We present a new ruthenium catalyst with a unique efficacy for the selective oxidation of a single hydroxyl group among many in unprotected polyol natural products. This oxidation enables the introduction of nitrogen-based functional groups into such structures that lack nitrogen atoms and enables a selective alcohol epimerization by stepwise or reversible oxidation and reduction.

  19. Predictive value of serum HCG concentrations in pregnancies achieved after single fresh or vitrified-warmed blastocyst transfer.

    Science.gov (United States)

    Oron, Galia; Shavit, Tal; Esh-Broder, Efrat; Weon-Young, Son; Tulandi, Togas; Holzer, Hananel

    2017-09-01

    Possible differences between serum HCG levels in pregnancies achieved after transfer of a single fresh or a vitrified-warmed blastocyst were evaluated. Out of 1130 single blastocyst transfers resulting in positive HCG results, 789 were single fresh blastocyst transfers and 341 single vitrified-warmed blastocyst transfers. The initial serum HCG levels of 869 clinical intrauterine pregnancies were evaluated, 638 after the transfer of a single fresh blastocysts and 231 after the transfer of a single vitrified-warmed blastocysts. The HCG levels from cycles resulting in a clinical intrauterine pregnancy were significantly higher after the transfer of a single vitrified-warmed blastocyst (383 ± 230 IU/l) versus a fresh transfer (334 ± 192 IU/l; P = 0.01). Threshold values for predicting a clinical pregnancy for a fresh blastocyst were 111 IU/l and for a vitrified-warmed blastocyst 137 IU/l. Our study shows that the overall beta-HCG levels are comparable after the transfer of a fresh or vitrified-warmed blastocyst, suggesting that vitrification most probably does not affect the ability of the embryos to produce beta-HCG. This study further shows that when clinicians counsel patients, they should take into account that higher HCG levels are needed after a vitrified-warmed blastocyst transfer to predict a clinical intrauterine pregnancy. Copyright © 2017 Reproductive Healthcare Ltd. Published by Elsevier Ltd. All rights reserved.

  20. Plastic scintillator detectors for the study of transfer and breakup reactions at intermediate energies

    International Nuclear Information System (INIS)

    Schmidt, H.R.; Bantel, M.; Chan, Y.D.; Gazes, S.M.; Kamermans, R.; Albiston, C.; Wald, S.; Stokstad, R.G.

    1984-10-01

    The detection of light particles associated with projectile like fragments can be used to separate transfer and breakup reactions provided the detectors cover a large solid angle. Three detection systems are described: (1) a π detector in the shape of a cube, 20 cm on a side, (2) a X-Y position sensitive ΔE-E detector having an area of 20 x 20 cm 2 , and (3) a multi-element detector consisting of eight position sensitive strips. The latter two detectors are of the phoswich type having the thin element of NE102 (tau = 2.5 ns) and the thick element of NE115 (tau = 225 ns). The performance characteristics of the three detectors are described. 6 references, 13 figures

  1. Evaluation of heat transfer tube failure propagation due to sodium-water reaction in steam generator

    International Nuclear Information System (INIS)

    Nei, Hiromichi

    1978-01-01

    An evaluation was made of heat transfer tube failure propagation due to sodium-water reaction wastage in a sodium heated steam generator, by comparing an empirically derived wastage equation with leak detector responses. The experimental data agreed well with the wastage equation even for different values of distance-to-nozzle diameter ratio, though the formula had been based on wastage data obtained for only one given distance. The time taken for failure propagation was estimated for a prototype steam generator, and compared with the responses characteristics of acoustic detectors and level gages. It was found that there exists a range of leak rate between 0.5 and 100 g/sec, where the level gage can play a useful role in leak detection. The acoustic detector can be expected to respond more rapidly than the cover gas pressure gage, if noise is kept below ten times the value observed in an experimental facility, SWAT-2. (auth.)

  2. Electron transfer reactions in microporous solids. Progress report, September 1990--January 1993

    Energy Technology Data Exchange (ETDEWEB)

    Mallouk, T.E.

    1993-01-01

    Basic thrust the research program involves use of microporous solids (zeolites, clays, layered and tunnel structure oxide semiconductors) as organizing media for artificial photosynthetic systems. Purpose of the microporous solid is twofold. First, it induces spatial organization of photoactive and electroactive components (sensitizers, semiconductor particles, electron relays, and catalysts) at the solid-solution interface, enhancing the quantum efficiency of charge separation and separating physically the ultimate electron donor and acceptor in the electron transport chain. Second, since the microcrystalline solid admits only molecules of a certain charge and size, it is possible to achieve permanent charge separation by sieving chemical photoproducts (e.g., H{sub 2} and I{sub 3}{sup {minus}}, or H{sub 2} and O{sub 2)} from each other. Spectroscopic and electrochemical methods are used to study the kinetics of electron transfer reactions in these hybrid molecular/solid state assemblies.

  3. Formaldehyde measurements by Proton transfer reaction – Mass Spectrometry (PTR-MS: correction for humidity effects

    Directory of Open Access Journals (Sweden)

    A. Vlasenko

    2010-08-01

    Full Text Available Formaldehyde measurements can provide useful information about photochemical activity in ambient air, given that HCHO is formed via numerous oxidation processes. Proton transfer reaction mass spectrometry (PTR-MS is an online technique that allows measurement of VOCs at the sub-ppbv level with good time resolution. PTR-MS quantification of HCHO is hampered by the humidity dependence of the instrument sensitivity, with higher humidity leading to loss of PTR-MS signal. In this study we present an analytical, first principles approach to correct the PTR-MS HCHO signal according to the concentration of water vapor in sampled air. The results of the correction are validated by comparison of the PTR-MS results to those from a Hantzsch fluorescence monitor which does not have the same humidity dependence. Results are presented for an intercomparison made during a field campaign in rural Ontario at Environment Canada's Centre for Atmospheric Research Experiments.

  4. Neutron spectroscopic factors of 55Ni hole-states from (p,d) transfer reactions

    International Nuclear Information System (INIS)

    Sanetullaev, A.; Tsang, M.B.; Lynch, W.G.; Lee, Jenny; Bazin, D.; Chan, K.P.; Coupland, D.; Henzl, V.; Henzlova, D.; Kilburn, M.; Rogers, A.M.; Sun, Z.Y.; Youngs, M.; Charity, R.J.; Sobotka, L.G.; Famiano, M.; Hudan, S.; Shapira, D.; Peters, W.A.; Barbieri, C.

    2014-01-01

    Spectroscopic information has been extracted on the hole-states of 55 Ni, the least known of the quartet of nuclei ( 55 Ni, 57 Ni, 55 Co and 57 Cu), one nucleon away from 56 Ni, the N=Z=28 double magic nucleus. Using the 1 H( 56 Ni,d) 55 Ni transfer reaction in inverse kinematics, neutron spectroscopic factors, spins and parities have been extracted for the f 7/2 , p 3/2 and the s 1/2 hole-states of 55 Ni. These new data provide a benchmark for large basis calculations that include nucleonic orbits in both the sd and pf shells. State of the art calculations have been performed to describe the excitation energies and spectroscopic factors of the s 1/2 hole-state below Fermi energy.

  5. The combined simulation of heat transfer and pyrolysis reactions in industrial cracking furnaces

    Energy Technology Data Exchange (ETDEWEB)

    Niaei, A. [Tabriz University, Tehran (Iran). Chemical Engineering Dept.; Towfighi, J.; Sadrameli, S.M.; Karimzadeh, R. [Tarbiat Modarres University, Tehran (Iran). Chemical Engineering Dept.

    2004-10-01

    Thermal cracking of hydrocarbons for olefins production is carried out in large, gas fired furnaces containing parallel reactor coils. The simulation of these coils requires detailed kinetics, based upon radical reaction schemes and a rigorous description of heat transfer in the firebox. A complete modeling of the reactor and the firebox, using a rigorous kinetic model, for the pyrolysis of naphtha has been developed and is used here for the simulation of naphtha crackers. The coupled simulation of the reactor and the radiant box by means of the zone method, results in the understanding of the behavior of the furnace. The simulation results are in good agreement with the experimental data. The model and computational scheme can be used as a guide for plant operators and as a tool for design. (author)

  6. Charge transfer reaction of O3+ + H → O2+ + H+ in low energy collision

    International Nuclear Information System (INIS)

    Yoshida, Junichi; Oohata, Kiyosi

    1983-01-01

    The total charge transfer cross-sections have been computed for the collision of O 3+ + H in the energy range of 2-240 keV. The PSS method with the classical trajectory is employed to obtain the cross-sections. The reaction channels which have the avoided crossing with the incoming channel at the internuclear distance less than 20 a.u. have been included into the calculation. The computed cross-section is found to be relatively constant as a function of the collision energy. The computed cross-sections are considerably large in comparsion with the experimental data by Phaneuf, but are of the same order of magnitude as the experimental result given by Gardner. (author)

  7. Neutron spectroscopic factors of 55Ni hole-states from (p,d transfer reactions

    Directory of Open Access Journals (Sweden)

    A. Sanetullaev

    2014-09-01

    Full Text Available Spectroscopic information has been extracted on the hole-states of 55Ni, the least known of the quartet of nuclei (55Ni, 57Ni, 55Co and 57Cu, one nucleon away from 56Ni, the N=Z=28 double magic nucleus. Using the H1(Ni56,dNi55 transfer reaction in inverse kinematics, neutron spectroscopic factors, spins and parities have been extracted for the f7/2, p3/2 and the s1/2 hole-states of 55Ni. These new data provide a benchmark for large basis calculations that include nucleonic orbits in both the sd and pf shells. State of the art calculations have been performed to describe the excitation energies and spectroscopic factors of the s1/2 hole-state below Fermi energy.

  8. Neutron spectroscopic factors of {sup 55}Ni hole-states from (p,d) transfer reactions

    Energy Technology Data Exchange (ETDEWEB)

    Sanetullaev, A. [National Superconducting Cyclotron Laboratory and Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Tsang, M.B., E-mail: tsang@nscl.msu.edu [National Superconducting Cyclotron Laboratory and Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Lynch, W.G.; Lee, Jenny; Bazin, D. [National Superconducting Cyclotron Laboratory and Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Chan, K.P. [National Superconducting Cyclotron Laboratory and Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Physics Department, Hong Kong Chinese University, Shatin, Hong Kong (China); Coupland, D.; Henzl, V.; Henzlova, D.; Kilburn, M.; Rogers, A.M. [National Superconducting Cyclotron Laboratory and Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Sun, Z.Y. [National Superconducting Cyclotron Laboratory and Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Institute of Modern Physics, CAS, Lanzhou 730000 (China); Youngs, M. [National Superconducting Cyclotron Laboratory and Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Charity, R.J.; Sobotka, L.G. [Department of Chemistry, Washington University, St. Louis, MO 63130 (United States); Famiano, M. [Department of Physics, Western Michigan University, Kalamazoo, MI 49008 (United States); Hudan, S. [Department of Chemistry, Indiana University, Bloomington, IN 47405 (United States); Shapira, D. [Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Peters, W.A. [Rutgers University, Piscataway, NJ 08854 (United States); Barbieri, C. [Department of Physics, University of Surrey, Guildford GU2 7XH (United Kingdom); and others

    2014-09-07

    Spectroscopic information has been extracted on the hole-states of {sup 55}Ni, the least known of the quartet of nuclei ({sup 55}Ni, {sup 57}Ni, {sup 55}Co and {sup 57}Cu), one nucleon away from {sup 56}Ni, the N=Z=28 double magic nucleus. Using the {sup 1}H({sup 56}Ni,d){sup 55}Ni transfer reaction in inverse kinematics, neutron spectroscopic factors, spins and parities have been extracted for the f{sub 7/2}, p{sub 3/2} and the s{sub 1/2} hole-states of {sup 55}Ni. These new data provide a benchmark for large basis calculations that include nucleonic orbits in both the sd and pf shells. State of the art calculations have been performed to describe the excitation energies and spectroscopic factors of the s{sub 1/2} hole-state below Fermi energy.

  9. Quantification of diesel exhaust gas phase organics by a thermal desorption proton transfer reaction mass spectrometer

    Science.gov (United States)

    Erickson, M. H.; Wallace, H. W.; Jobson, B. T.

    2012-02-01

    A new approach was developed to measure the total abundance of long chain alkanes (C12 and above) in urban air using thermal desorption with a proton transfer reaction mass spectrometer (PTR-MS). These species are emitted in diesel exhaust and may be important precursors to secondary organic aerosol production in urban areas. Long chain alkanes undergo dissociative proton transfer reactions forming a series of fragment ions with formula CnH2n+1. The yield of the fragment ions is a function of drift conditions. At a drift field strength of 80 Townsends, the most abundant ion fragments from C10 to C16 n-alkanes were m/z 57, 71 and 85. The PTR-MS is insensitive to n-alkanes less than C8 but displays an increasing sensitivity for larger alkanes. Higher drift field strengths yield greater normalized sensitivity implying that the proton affinity of the long chain n-alkanes is less than H2O. Analysis of diesel fuel shows the mass spectrum was dominated by alkanes (CnH2n+1), monocyclic aromatics, and an ion group with formula CnH2n-1 (m/z 97, 111, 125, 139). The PTR-MS was deployed in Sacramento, CA during the Carbonaceous Aerosols and Radiative Effects Study field experiment in June 2010. The ratio of the m/z 97 to 85 ion intensities in ambient air matched that found in diesel fuel. Total diesel exhaust alkane concentrations calculated from the measured abundance of m/z 85 ranged from the method detection limit of ~1 μg m-3 to 100 μg m-3 in several air pollution episodes. The total diesel exhaust alkane concentration determined by this method was on average a factor of 10 greater than the sum of alkylbenzenes associated with spark ignition vehicle exhaust.

  10. Reaction Coordinate, Free Energy, and Rate of Intramolecular Proton Transfer in Human Carbonic Anhydrase II.

    Science.gov (United States)

    Paul, Sanjib; Paul, Tanmoy Kumar; Taraphder, Srabani

    2018-03-22

    The role of structure and dynamics of an enzyme has been investigated at three different stages of its function including the chemical event it catalyzes. A one-pot computational method has been designed for each of these stages on the basis of classical and/or quantum mechanical-molecular mechanical molecular dynamics and transition path sampling simulations. For a pair of initial and final states A and B separated by a high free-energy barrier, using a two-stage selection process, several collective variables (CVs) are identified that can delineate A and B. However, these CVs are found to exhibit strong cross-coupling over the transition paths. A set of mutually orthogonal order parameters is then derived from these CVs and an optimal reaction coordinate, r, determined applying half-trajectory likelihood maximization along with a Bayesian information criterion. The transition paths are also used to project the multidimensional free energy surface and barrier crossing dynamics along r. The proposed scheme has been applied to the rate-determining intramolecular proton transfer reaction of the well-known enzyme human carbonic anhydrase II. The potential of mean force, F( r), in the absence of the chemical step is found to reproduce earlier results on the equilibrium population of two side-chain orientations of key residue His-64. Estimation of rate constants, k, from mean first passage times for the three different stages of catalysis shows that the rate-determining step of intramolecular proton transfer occurs with k ≃ 1.0 × 10 6 s -1 , in close agreement with known experimental results.

  11. Application of noncatalytic gas-solid reactions for a single pellet of changing size to the modeling of fluidized-bed combustion of coal char containing sulfur

    Energy Technology Data Exchange (ETDEWEB)

    Rehmat, A.; Saxena, S.C.; Land, R.H.

    1980-09-01

    A mechanistic model is developed for coal char combustion, with sulfur retention by limestone or dolomite sorbent, in a gas fluidized bed employing noncatalytic single pellet gas-solid reactions. The shrinking core model is employed to describe the kinetics of chemical reactions taking place on a single pellet; changes in pellet size as the reaction proceeds are considered. The solids are assumed to be in back-mix condition whereas the gas flow is regarded to be in plug flow. Most char combustion occurs near the gas distributor plate (at the bottom of the bed), where the bubbles are small and consequently the mass transfer rate is high. For such a case, the analysis is considerably simplified by ignoring the bubble phase since it plays an insignificant role in the overall rate of carbon conversion. Bubble-free operation is also encounterd in the turbulent regime, where the gas flow is quite high and classical bubbles do not exist. Formulation of the model includes setting up heat and mass balance equations pertaining to a single particle (1) exposed to a varying reactant concentration along the height of the bed and (2) whose size changes during reaction. These equations are then solved numerically to account for particles of all sizes in the bed in obtaining the overall carbon conversion efficiency and resultant sulfur retention. In particular, the influence on sorbent requirement of several fluid-bed variables such as oxygen concentration profile, particle size, reaction rate for sulfation reaction, and suflur adsorption efficiency are examined.

  12. Tuning Catalytic Performance through a Single or Sequential Post-Synthesis Reaction(s) in a Gas Phase

    Energy Technology Data Exchange (ETDEWEB)

    Shan, Junjun [Department; Department; Zhang, Shiran [Department; Department; Choksi, Tej [Department; Nguyen, Luan [Department; Department; Bonifacio, Cecile S. [Department; Li, Yuanyuan [Department; Zhu, Wei [Department; Department; College; Tang, Yu [Department; Department; Zhang, Yawen [College; Yang, Judith C. [Department; Greeley, Jeffrey [Department; Frenkel, Anatoly I. [Department; Tao, Franklin [Department; Department

    2016-12-05

    Catalytic performance of a bimetallic catalyst is determined by geometric structure and electronic state of the surface or even the near-surface region of the catalyst. Here we report that single and sequential postsynthesis reactions of an as-synthesized bimetallic nanoparticle catalyst in one or more gas phases can tailor surface chemistry and structure of the catalyst in a gas phase, by which catalytic performance of this bimetallic catalyst can be tuned. Pt–Cu regular nanocube (Pt–Cu RNC) and concave nanocube (Pt–Cu CNC) are chosen as models of bimetallic catalysts. Surface chemistry and catalyst structure under different reaction conditions and during catalysis were explored in gas phase of one or two reactants with ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) and extended X-ray absorption fine structure (EXAFS) spectroscopy. The newly formed surface structures of Pt–Cu RNC and Pt–Cu CNC catalysts strongly depend on the reactive gas(es) used in the postsynthesis reaction(s). A reaction of Pt–Cu RNC-as synthesized with H2 at 200 °C generates a near-surface alloy consisting of a Pt skin layer, a Cu-rich subsurface, and a Pt-rich deep layer. This near-surface alloy of Pt–Cu RNC-as synthesized-H2 exhibits a much higher catalytic activity in CO oxidation in terms of a low activation barrier of 39 ± 4 kJ/mol in contrast to 128 ± 7 kJ/mol of Pt–Cu RNC-as synthesized. Here the significant decrease of activation barrier demonstrates a method to tune catalytic performances of as-synthesized bimetallic catalysts. A further reaction of Pt–Cu RNC-as synthesized-H2 with CO forms a Pt–Cu alloy surface, which exhibits quite different catalytic performance in CO oxidation. It suggests the capability of generating a different surface by using another gas. The capability of tuning surface chemistry and structure of bimetallic catalysts was also demonstrated in restructuring of Pt–Cu CNC-as synthesized.

  13. Recent Developments in the Synthesis of Biomacromolecules and their Conjugates by Single Electron Transfer-Living Radical Polymerization.

    Science.gov (United States)

    Lligadas, Gerard; Grama, Silvia; Percec, Virgil

    2017-04-10

    Single electron transfer-living radical polymerization (SET-LRP) represents a robust and versatile tool for the synthesis of vinyl polymers with well-defined topology and chain end functionality. The crucial step in SET-LRP is the disproportionation of the Cu(I)X generated by activation with Cu(0) wire, powder, or nascent Cu(0) generated in situ into nascent, extremely reactive Cu(0) atoms and nanoparticles and Cu(II)X 2 . Nascent Cu(0) activates the initiator and dormant chains via a homogeneous or heterogeneous outer-sphere single-electron transfer mechanism (SET-LRP). SET-LRP provides an ultrafast polymerization of a plethora of monomers (e.g., (meth)-acrylates, (meth)-acrylamides, styrene, and vinyl chloride) including hydrophobic and water insoluble to hydrophilic and water soluble. Some advantageous features of SET-LRP are (i) the use of Cu(0) wire or powder as readily available catalysts under mild reaction conditions, (ii) their excellent control over molecular weight evolution and distribution as well as polymer chain ends, (iii) their high functional group tolerance allowing the polymerization of commercial-grade monomers, and (iv) the limited purification required for the resulting polymers. In this Perspective, we highlight the recent advancements of SET-LRP in the synthesis of biomacromolecules and of their conjugates.

  14. Radiated chemical reaction impacts on natural convective MHD mass transfer flow induced by a vertical cone

    Science.gov (United States)

    Sambath, P.; Pullepu, Bapuji; Hussain, T.; Ali Shehzad, Sabir

    2018-03-01

    The consequence of thermal radiation in laminar natural convective hydromagnetic flow of viscous incompressible fluid past a vertical cone with mass transfer under the influence of chemical reaction with heat source/sink is presented here. The surface of the cone is focused to a variable wall temperature (VWT) and wall concentration (VWC). The fluid considered here is a gray absorbing and emitting, but non-scattering medium. The boundary layer dimensionless equations governing the flow are solved by an implicit finite-difference scheme of Crank-Nicolson which has speedy convergence and stable. This method converts the dimensionless equations into a system of tri-diagonal equations and which are then solved by using well known Thomas algorithm. Numerical solutions are obtained for momentum, temperature, concentration, local and average shear stress, heat and mass transfer rates for various values of parameters Pr, Sc, λ, Δ, Rd are established with graphical representations. We observed that the liquid velocity decreased for higher values of Prandtl and Schmidt numbers. The temperature is boost up for decreasing values of Schimdt and Prandtl numbers. The enhancement in radiative parameter gives more heat to liquid due to which temperature is enhanced significantly.

  15. Double proton transfer reactions in the formic acid dimer in solution

    International Nuclear Information System (INIS)

    Kohanoff, J.; Estrin, D.A.; Laria, D.; Abashkin, Y.

    2000-06-01

    The issue of multiple proton transfer (PT) reactions in solution is addressed by performing molecular dynamics simulations for a formic acid dimer embedded in a water cluster. The reactant species is treated quantum mechanically, within a density functional approach, while the solvent is represented by a classical model. By constraining different distances within the dimer we analyze the PT process in a variety of situations representative of more complex environments. Free energy profiles are presented, and analyzed in terms of typical solvated configurations extracted from the simulations. A decrease in the PT barrier height upon solvation is rationalized in terms of a transition state which is more polarized than the stable states. The dynamics of the double PT process is studied in a low-barrier case and correlated with that of the polarization fluctuations of the solvent. Cooperative effects in the motion of the two protons are observed in two different situations: when the solvent polarization does not favor the transfer of one of the two protons and when the motion of the two protons is not synchronized. This body of observations is correlated with structural and dynamical local properties of the solvent in the vicinity of the reactant. (author)

  16. High-throughput microfluidic single-cell digital polymerase chain reaction.

    Science.gov (United States)

    White, A K; Heyries, K A; Doolin, C; Vaninsberghe, M; Hansen, C L

    2013-08-06

    Here we present an integrated microfluidic device for the high-throughput digital polymerase chain reaction (dPCR) analysis of single cells. This device allows for the parallel processing of single cells and executes all steps of analysis, including cell capture, washing, lysis, reverse transcription, and dPCR analysis. The cDNA from each single cell is distributed into a dedicated dPCR array consisting of 1020 chambers, each having a volume of 25 pL, using surface-tension-based sample partitioning. The high density of this dPCR format (118,900 chambers/cm(2)) allows the analysis of 200 single cells per run, for a total of 204,000 PCR reactions using a device footprint of 10 cm(2). Experiments using RNA dilutions show this device achieves shot-noise-limited performance in quantifying single molecules, with a dynamic range of 10(4). We performed over 1200 single-cell measurements, demonstrating the use of this platform in the absolute quantification of both high- and low-abundance mRNA transcripts, as well as micro-RNAs that are not easily measured using alternative hybridization methods. We further apply the specificity and sensitivity of single-cell dPCR to performing measurements of RNA editing events in single cells. High-throughput dPCR provides a new tool in the arsenal of single-cell analysis methods, with a unique combination of speed, precision, sensitivity, and specificity. We anticipate this approach will enable new studies where high-performance single-cell measurements are essential, including the analysis of transcriptional noise, allelic imbalance, and RNA processing.

  17. Pressure drop and heat transfer of lithium single-phase flow under transverse magnetic field

    International Nuclear Information System (INIS)

    Takahashi, Minoru; Aritomi, Masanori; Inoue, Akira; Matsuzaki, Mitsuo

    1996-01-01

    Pressure drop and heat transfer characteristics of a lithium single-phase flow in a rectangular channel was investigated experimentally in the presence of a magnetic field. Friction loss coefficient under non-magnetic field and skin friction coefficient under magnetic field agreed well with the Blasius formula and a simple analytical expression, respectively. Nusselt number under non-magnetic field was slightly lower than the correlation by Hartnett and Irvine. Heat transfer was enhanced by increasing magnetic field above the Hartmann number of about 200. (author)

  18. Successful pregnancy following single blastocyst transfer in a renal transplant recipient.

    Science.gov (United States)

    Muthuvel, V Arun; Ravindran, Manipriya; Chander, Aravind; Veluswamy, Chandralekha

    2016-01-01

    Numerous spontaneous pregnancies have been reported in renal transplant recipients; however, only a few pregnancies after the use of assisted reproductive techniques. The authors report a case of renal transplant recipient with secondary infertility who delivered a healthy baby without any complications. The report highlights the importance of minimal stimulation protocol during ovarian stimulation, single embryo transfer, and the need for multispecialty care for these patients. To the best of the authors' knowledge, the present report is the first such case from India and also the second in the world to report a blastocyst transfer among renal transplant recipients.

  19. Non-Markovian theory for the waiting time distributions of single electron transfers.

    Science.gov (United States)

    Welack, Sven; Yan, YiJing

    2009-09-21

    We derive a non-Markovian theory for waiting time distributions of consecutive single electron transfer events. The presented microscopic Pauli rate equation formalism couples the open electrodes to the many-body system, allowing to take finite bias and temperature into consideration. Numerical results reveal transient oscillations of distinct system frequencies due to memory in the waiting time distributions. Memory effects can be approximated by an expansion in non-Markovian corrections. This method is employed to calculate memory landscapes displaying preservation of memory over multiple consecutive electron transfers.

  20. The effect of two-step α transfer reaction in the elastic scattering of 12C+24Mg

    International Nuclear Information System (INIS)

    Lichtenthaler Filho, R.; Lepine-Szily, A.; Villari, A.C.C.; Mittig, W.; Porto, V. de J.G.; Acquadro, C.V.

    1982-06-01

    Angular distribution of the elastic scattering 24 Mg( 12 C, 12 C) 24 Mg and of the 24 Mg( 12 C, 16 O) 20 Ne transfer reaction have been measured at 40 MeV incident energy, respectively in the 20 0 0 and 20 0 0 angular regions. The elastic scattering and transfer reactions were analysed with Frahn's closed formalism as well as with optical model calculations. The influence of the two-step α-transfer channel ( 12 C+ 24 Mg → 16 O+ 20 Ne → 12 C+ 24 Mg) on the elastic scattering was calculated explicitly using the coupled channel extension of the closed formalism. This calculation shows that the coupling between the α-transfer and elastic channel can account for the intermediate angle oscillations observed in the elastic scattering angular distributions. (Author) [pt

  1. Manganese-Oxygen Intermediates in O-O Bond Activation and Hydrogen-Atom Transfer Reactions.

    Science.gov (United States)

    Rice, Derek B; Massie, Allyssa A; Jackson, Timothy A

    2017-11-21

    Biological systems capitalize on the redox versatility of manganese to perform reactions involving dioxygen and its derivatives superoxide, hydrogen peroxide, and water. The reactions of manganese enzymes influence both human health and the global energy cycle. Important examples include the detoxification of reactive oxygen species by manganese superoxide dismutase, biosynthesis by manganese ribonucleotide reductase and manganese lipoxygenase, and water splitting by the oxygen-evolving complex of photosystem II. Although these enzymes perform very different reactions and employ structurally distinct active sites, manganese intermediates with peroxo, hydroxo, and oxo ligation are commonly proposed in catalytic mechanisms. These intermediates are also postulated in mechanisms of synthetic manganese oxidation catalysts, which are of interest due to the earth abundance of manganese. In this Account, we describe our recent efforts toward understanding O-O bond activation pathways of Mn III -peroxo adducts and hydrogen-atom transfer reactivity of Mn IV -oxo and Mn III -hydroxo complexes. In biological and synthetic catalysts, peroxomanganese intermediates are commonly proposed to decay by either Mn-O or O-O cleavage pathways, although it is often unclear how the local coordination environment influences the decay mechanism. To address this matter, we generated a variety of Mn III -peroxo adducts with varied ligand environments. Using parallel-mode EPR and Mn K-edge X-ray absorption techniques, the decay pathway of one Mn III -peroxo complex bearing a bulky macrocylic ligand was investigated. Unlike many Mn III -peroxo model complexes that decay to oxo-bridged-Mn III Mn IV dimers, decay of this Mn III -peroxo adduct yielded mononuclear Mn III -hydroxo and Mn IV -oxo products, potentially resulting from O-O bond activation of the Mn III -peroxo unit. These results highlight the role of ligand sterics in promoting the formation of mononuclear products and mark an important

  2. Modeling of the interplay between single-file diffusion and conversion reaction in mesoporous systems

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jing [Iowa State Univ., Ames, IA (United States)

    2013-01-11

    We analyze the spatiotemporal behavior of species concentrations in a diffusion-mediated conversion reaction which occurs at catalytic sites within linear pores of nanometer diameter. A strict single-file (no passing) constraint occurs in the diffusion within such narrow pores. Both transient and steady-state behavior is precisely characterized by kinetic Monte Carlo simulations of a spatially discrete lattice–gas model for this reaction–diffusion process considering various distributions of catalytic sites. Exact hierarchical master equations can also be developed for this model. Their analysis, after application of mean-field type truncation approximations, produces discrete reaction–diffusion type equations (mf-RDE). For slowly varying concentrations, we further develop coarse-grained continuum hydrodynamic reaction–diffusion equations (h-RDE) incorporating a precise treatment of single-file diffusion (SFD) in this multispecies system. Noting the shortcomings of mf-RDE and h-RDE, we then develop a generalized hydrodynamic (GH) formulation of appropriate gh-RDE which incorporates an unconventional description of chemical diffusion in mixed-component quasi-single-file systems based on a refined picture of tracer diffusion for finite-length pores. The gh-RDE elucidate the non-exponential decay of the steady-state reactant concentration into the pore and the non-mean-field scaling of the reactant penetration depth. Then an extended model of a catalytic conversion reaction within a functionalized nanoporous material is developed to assess the effect of varying the reaction product – pore interior interaction from attractive to repulsive. The analysis is performed utilizing the generalized hydrodynamic formulation of the reaction-diffusion equations which can reliably capture the complex interplay between reaction and restricted transport for both irreversible and reversible reactions.

  3. Measurement of the polarization transfer coefficient K sub LS in the p vectorp yields d vector. pi. sup + reaction

    Energy Technology Data Exchange (ETDEWEB)

    Abegg, R.; Green, P.W.; Greeniaus, L.G.; Hutcheon, D.A. (TRIUMF, Vancouver, British Columbia (Canada) Centre for Subatomic Research, Univ. Alberta, Edmonton (Canada)); Yanlin, Y.; Korkmaz, E.; Mack, D.; Moss, G.A.; Olsen, W.C. (Centre for Subatomic Research, Univ. Alberta, Edmonton (Canada)); Stevenson, N.R. (Dept. of Physics, Univ. Saskatchewan, Saskatoon (Canada))

    1992-04-06

    We have measured the polarization transfer asymmetries of the reaction p vectorp{yields}d vector{pi}{sup +} from the longitudinally polarized proton to the sideways polarized deuteron for deuteron center-of-mass angles from 25deg to 140deg. Our longitudinal to sideways polarization transfer data are best represented by the partial-wave amplitude fits of Bugg et al. while several model calculations are only in qualitative agreement. (orig.).

  4. Measurement of the polarization transfer coefficient KLS in the p vectorp→d vectorπ+ reaction

    International Nuclear Information System (INIS)

    Abegg, R.; Green, P.W.; Greeniaus, L.G.; Hutcheon, D.A.; Yanlin, Y.; Korkmaz, E.; Mack, D.; Moss, G.A.; Olsen, W.C.; Stevenson, N.R.

    1992-01-01

    We have measured the polarization transfer asymmetries of the reaction p vectorp→d vectorπ + from the longitudinally polarized proton to the sideways polarized deuteron for deuteron center-of-mass angles from 25deg to 140deg. Our longitudinal to sideways polarization transfer data are best represented by the partial-wave amplitude fits of Bugg et al. while several model calculations are only in qualitative agreement. (orig.)

  5. Influences of chemical reaction and wall properties on MHD Peristaltic transport of a Dusty fluid with Heat and Mass transfer

    Directory of Open Access Journals (Sweden)

    R. Muthuraj

    2016-03-01

    Full Text Available The influence of elasticity of flexible walls on peristaltic transport of a dusty fluid with heat and mass transfer in a horizontal channel in the presence of chemical reaction has been investigated under long wavelength approximation. Expressions have been constructed for stream function, temperature and concentration by using perturbation technique. The effects of various parameters on heat and mass transfer characteristics of the flow are discussed through graphs.

  6. Transfer and breakup reactions in 16O + CsI at 16.4 MeV/n

    Directory of Open Access Journals (Sweden)

    M.J. Murphy

    1983-01-01

    Full Text Available A streamer-chamber particle-telescope system has been used to observe ejectile charge, energy, and associated charged particle multiplicity in the reaction of 16O + CsI at 16.4 MeV/n. The measurement provides relative probabilities for transfer and projectile breakup as a function of ejectile charge, and spectra for the heavy ejectiles from transfer and breakup events. The results show that the interaction energy of 16.4 MeV/n is near the threshold for breakup reactions in heavy-ion collisions.

  7. Molecular structure determination for photogenerated intermediates in photoinduced electron transfer reactions using steady-state and transient XAFS

    Energy Technology Data Exchange (ETDEWEB)

    Chen, L.X.; Wasielewski, M.R.; Rajh, T. [Argonne National Lab., IL (United States). Chemistry Div.

    1996-10-01

    Many photoinduced electron transfer reactions are accompanied by nuclear rearrangements of the molecules involved. In order to understand the reactivities of the molecules and the reaction mechanisms, precise information on the molecular structural changes accompanying the electron transfer is often required. We present here conventional XAFS and transient energy dispersive XAFS studies on structures of excited and photoinduced charge separated state of porphyrin and porphyrin based supermolecules, and structures of TiO{sub 2} colloid and the heavymetal ions that bind to the colloid surfaces during photocatalytic reductions.

  8. Insight into the kinetics and thermodynamics of the hydride transfer reactions between quinones and lumiflavin: a density functional theory study.

    Science.gov (United States)

    Reinhardt, Clorice R; Jaglinski, Tanner C; Kastenschmidt, Ashly M; Song, Eun H; Gross, Adam K; Krause, Alyssa J; Gollmar, Jonathan M; Meise, Kristin J; Stenerson, Zachary S; Weibel, Tyler J; Dison, Andrew; Finnegan, Mackenzie R; Griesi, Daniel S; Heltne, Michael D; Hughes, Tom G; Hunt, Connor D; Jansen, Kayla A; Xiong, Adam H; Hati, Sanchita; Bhattacharyya, Sudeep

    2016-09-01

    The kinetics and equilibrium of the hydride transfer reaction between lumiflavin and a number of substituted quinones was studied using density functional theory. The impact of electron withdrawing/donating substituents on the redox potentials of quinones was studied. In addition, the role of these substituents on the kinetics of the hydride transfer reaction with lumiflavin was investigated in detail under the transition state (TS) theory assumption. The hydride transfer reactions were found to be more favorable for an electron-withdrawing substituent. The activation barrier exhibited a quadratic relationship with the driving force of these reactions as derived under the formalism of modified Marcus theory. The present study found a significant extent of electron delocalization in the TS that is stabilized by enhanced electrostatic, polarization, and exchange interactions. Analysis of geometry, bond-orders, and energetics revealed a predominant parallel (Leffler-Hammond) effect on the TS. Closer scrutiny reveals that electron-withdrawing substituents, although located on the acceptor ring, reduce the N-H bond order of the donor fragment in the precursor complex. Carried out in the gas-phase, this is the first ever report of a theoretical study of flavin's hydride transfer reactions with quinones, providing an unfiltered view of the electronic effect on the nuclear reorganization of donor-acceptor complexes.

  9. Light-induced heat and mass transfer in a single-component gas in a capillary

    International Nuclear Information System (INIS)

    Chermyaninov, I. V.; Chernyak, V. G.; Vilisova, E. A.

    2007-01-01

    A theoretical analysis is presented of light-induced heat and mass transfer in a single-component gas in a capillary tube at arbitrary Knudsen numbers. Surface and collisional mechanisms of transfer are analyzed, due to differences in accommodation coefficient and collision cross section between excited-and ground-state particles, respectively. Analytical expressions for kinetic coefficients characterizing the gas drift and heat transfer in a capillary tube are obtained in the limits of low and high Knudsen numbers. Numerical computations are performed for intermediate Knudsen numbers. Both drift and heat fluxes are determined as functions of the light beam frequency. In the case of an inhomogeneously broadened absorption line, the light-induced fluxes are found to depend not only on the sign, but also on the amount, of light beam detuning from the absorption line center frequency

  10. Transfer doping of single isolated nanodiamonds, studied by scanning probe microscopy techniques

    International Nuclear Information System (INIS)

    Bolker, Asaf; Kalish, Rafi; Saguy, Cecile

    2014-01-01

    The transfer doping of diamond surfaces has been applied in various novel two-dimensional electronic devices. Its extension to nanodiamonds (ND) is essential for ND-based applications in many fields. In particular, understanding the influence of the crystallite size on transfer doping is desirable. Here, we report the results of a detailed study of the electronic energetic band structure of single, isolated transfer-doped nanodiamonds with nanometric resolution using a combination of scanning tunneling spectroscopy and Kelvin force microscopy measurements. The results show how the band gap, the valence band maximum, the electron affinity and the work function all depend on the ND’s size and nanoparticle surface properties. The present analysis, which combines information from both scanning tunneling spectroscopy and Kelvin force microscopy, should be applicable to any nanoparticle or surface that can be measured with scanning probe techniques. (paper)

  11. Reversible Hydride Transfer to N,N'-Diarylimidazolinium Cations from Hydrogen Catalyzed by Transition Metal Complexes Mimicking the Reaction of [Fe]-Hydrogenase.

    Science.gov (United States)

    Hatazawa, Masahiro; Yoshie, Naoko; Seino, Hidetake

    2017-07-17

    [Fe]-hydrogenase is a key enzyme involved in methanogenesis and facilitates reversible hydride transfer from H 2 to N 5 ,N 10 -methenyltetrahydromethanopterin (CH-H 4 MPT + ). In this study, a reaction system was developed to model the enzymatic function of [Fe]-hydrogenase by using N,N'-diphenylimidazolinium cation (1 + ) as a structurally related alternative to CH-H 4 MPT + . In connection with the enzymatic mechanism via heterolytic cleavage of H 2 at the single metal active site, several transition metal complex catalysts capable of such activation were utilized in the model system. Reduction of 1[BF 4 ] to N,N'-diphenylimidazolidine (2) was achieved under 1 atm H 2 at ambient temperature in the presence of an equimolar amount of NEt 3 as a proton acceptor. The proposed catalytic pathways involved the generation of active hydride complexes and subsequent intermolecular hydride transfer to 1 + . The reverse reaction was accomplished by treatment of 2 with HNMe 2 Ph + as the proton source, where [(η 5 -C 5 Me 5 )Ir{(p-MeC 6 H 4 SO 2 )NCHPhCHPhNH}] was found to catalyze the formation of 1 + and H 2 with high efficiency. These results are consistent with the fact that use of 2,6-lutidine in the forward reaction or 2,6-lutidinium in the reverse reaction resulted in incomplete conversion. By combining these reactions using the above Ir amido catalyst, the reversible hydride transfer interconverting 1 + /H 2 and 2/H + was performed successfully. This system demonstrated the hydride-accepting and hydride-donating modes of biologically relevant N-heterocycles coupled with proton concentration. The influence of substituents on the forward and reverse reactivities was examined for the derivatives of 1 + and 2 bearing one para-substituted N-phenyl group.

  12. g-factor of the 9/2+ isomeric state in 65Ni from transfer reaction

    International Nuclear Information System (INIS)

    Georgiev, G.; Matea, I.; Balabanski, D.L.; Daugas, J.M.; Meot, V.; Morel, P.; Oliveira Santos, F. de; Lewitowicz, M.; Franchoo, S.; Ibrahim, F.; Le Blanc, F.; Sorlin, O.; Stanoiu, M.; Verney, D.; Lo Bianco, G.; Saltarelli, A.; Lukyanov, S.; Penionzhkevich, Yu.E.; Neyens, G.; Vermeulen, N.; Yordanov, D.; Tarisien, M.

    2006-01-01

    We report a measurement of the g-factor of the I π =9/2 + , t 1/2 =22 ns isomer in 65 Ni. The state of interest was populated and spin-oriented using a single-neutron transfer on an enriched 64 Ni target. The value, which was obtained, g(9/2 + , 65m Ni)=-0.296(3) is well in agreement with the g-factors of the other 9/2 + states in the region and with large-basis shell model calculations. The known g-factor of the 9/2 + isomer in 63 Ni was used in order to verify the strength of the hyperfine field of Ni(Ni) at room temperature. (orig.)

  13. Electron transfer reactions of 1-phenyl-4-vinylpyrazole mediated by cerium(IV) ammonium nitrate

    International Nuclear Information System (INIS)

    Pitarch-Vinuesa, M.; Miranda, M.A.; Medio-Simon, M.; Sepulveda-Arques, J.

    1993-01-01

    The title compound is converted into the cyclic ethers 5 and the alcohol 6 upon treatment with ceric ammonium nitrate in acetone. Using methanol as a solvent the dimethoxy derivative 9 and the nitrate ester 10 are formed. No cross cycloaddition is observed in the presence of olefins such as ethyl vinyl ether, DMAD, or indene; however, with cyclopentadiene as co-reagent a mixture of the exo-endo Diels-Alder adducts 14 involving the vinylic system of 1 as 2π component is obtained. The results are rationalized through the intermediacy of the radical cation 1 .+ , generated by single electron transfer (SET) from the neutral precursor 1 to Ce(IV)

  14. Electron transfer behaviour of biological macromolecules towards the single-molecule level

    DEFF Research Database (Denmark)

    Zhang, Jingdong; Grubb, Mikala; Hansen, Allan Glargaard

    2003-01-01

    is combined with state-of-the-art physical electrochemistry with emphasis on single-crystal, atomically planar electrode surfaces, in situ scanning tunnelling microscopy (STM) and other surface techniques. These approaches have brought bioelectrochemistry important steps forward towards the nanoscale...... and single-molecule levels.We discuss here these advances with reference to two specific redox metalloproteins, the blue single-copper protein Pseudomonas aeruginosa azurin and the single-haem protein Saccharomyces cerevisiae yeast cytochrome c, and a short oligonucleotide. Both proteins can be immobilized...... electron transfer (ET) function retained. In situ STM can also address the microscopic mechanisms for electron tunnelling through the biomolecules and offers novel notions such as coherent multi-ET between the substrate and tip via the molecular redox levels. This differs in important respects from...

  15. Hydrogen-transfer and charge-transfer in photochemical and radiation induced reactions. Progress report, November 1, 1975--October 31, 1976

    International Nuclear Information System (INIS)

    Cohen, S.G.

    1976-10-01

    The relative importance of light absorption, quenching of triplet, and hydrogen transfer repair has been examined in retardation by mercaptans of photoreduction of aromatic ketones by alcohols. In the reduction of benzophenone by 2-propanol, retardation is efficient and, after correction for the first two effects, is due entirely to hydrogen-transfer repair, as indicated by deuterium labeling. In reduction of acetophenone by α-methylbenzyl alcohol, repair by hydrogen transfer is also operative. In reduction of benzophenone by benzhydrol, retardation is less efficient and is due to quenching, as the ketyl radical does not abstract hydrogen from mercaptan rapidly in competition with coupling. Deuterium isotope effects are discussed in terms of competitive reactions. Photoreduction of benzophenone by 2-butylamine and by triethylamine is retarded by aromatic mercaptans and disulfides. Of the retardation not due to light absorption and triplet quenching by the sulfur compounds, half is due to hydrogen-transfer repair, as indicated by racemization and deuterium labeling. The remainder is attributed to quenching by the sulfur compound of the charge-transfer-complex intermediate. Photoreduction by primary and secondary amines, but not by tertiary amines, is accelerated by aliphatic mercaptans. The acceleration is attributed to catalysis of hydrogen transfer by the mercaptan in the charge-transfer complex. The effect is large in hydrocarbon solvent, less in polar organic solvents and absent in water

  16. Highly Durable Platinum Single-Atom Alloy Catalyst for Electrochemical Reactions

    DEFF Research Database (Denmark)

    Kim, Jiwhan; Roh, Chi-Woo; Sahoo, Suman Kalyan

    2018-01-01

    -doped tin oxide (Pt1/ATO) is synthesized by conventional incipient wetness impregnation, with up to 8 wt% Pt. The single atomic Pt structure is confirmed by high-angle annular dark field scanning tunneling electron microscopy images and extended X-ray absorption fine structure analysis results. Density......Single atomic Pt catalyst can offer efficient utilization of the expensive platinum and provide unique selectivity because it lacks ensemble sites. However, designing such a catalyst with high Pt loading and good durability is very challenging. Here, single atomic Pt catalyst supported on antimony...... functional theory calculations show that replacing Sb sites with Pt atoms in the bulk phase or at the surface of SbSn or ATO is energetically favorable. The Pt1/ATO shows superior activity and durability for formic acid oxidation reaction, compared to a commercial Pt/C catalyst. The single atomic Pt...

  17. Current Status of Comprehensive Chromosome Screening for Elective Single-Embryo Transfer

    OpenAIRE

    Wu, Ming-Yih; Chao, Kuang-Han; Chen, Chin-Der; Chang, Li-Jung; Chen, Shee-Uan; Yang, Yu-Shih

    2014-01-01

    Most in vitro fertilization (IVF) experts and infertility patients agree that the most ideal assisted reproductive technology (ART) outcome is to have a healthy, full-term singleton born. To this end, the most reliable policy is the single-embryo transfer (SET). However, unsatisfactory results in IVF may result from plenty of factors, in which aneuploidy associated with advanced maternal age is a major hurdle. Throughout the past few years, we have got a big leap in advancement of the genetic...

  18. Equivalence of internal and external mixture schemes of single scattering properties in vector radiative transfer.

    Science.gov (United States)

    Mukherjee, Lipi; Zhai, Peng-Wang; Hu, Yongxiang; Winker, David M

    2017-05-10

    Polarized radiation fields in a turbid medium are influenced by single-scattering properties of scatterers. It is common that media contain two or more types of scatterers, which makes it essential to properly mix single-scattering properties of different types of scatterers in the vector radiative transfer theory. The vector radiative transfer solvers can be divided into two basic categories: the stochastic and deterministic methods. The stochastic method is basically the Monte Carlo method, which can handle scatterers with different scattering properties explicitly. This mixture scheme is called the external mixture scheme in this paper. The deterministic methods, however, can only deal with a single set of scattering properties in the smallest discretized spatial volume. The single-scattering properties of different types of scatterers have to be averaged before they are input to deterministic solvers. This second scheme is called the internal mixture scheme. The equivalence of these two different mixture schemes of scattering properties has not been demonstrated so far. In this paper, polarized radiation fields for several scattering media are solved using the Monte Carlo and successive order of scattering (SOS) methods and scattering media contain two types of scatterers: Rayleigh scatterers (molecules) and Mie scatterers (aerosols). The Monte Carlo and SOS methods employ external and internal mixture schemes of scatterers, respectively. It is found that the percentage differences between radiances solved by these two methods with different mixture schemes are of the order of 0.1%. The differences of Q/I, U/I, and V/I are of the order of 10 -5 ∼10 -4 , where I, Q, U, and V are the Stokes parameters. Therefore, the equivalence between these two mixture schemes is confirmed to the accuracy level of the radiative transfer numerical benchmarks. This result provides important guidelines for many radiative transfer applications that involve the mixture of

  19. Single Molecule Spectroelectrochemistry of Interfacial Charge Transfer Dynamics In Hybrid Organic Solar Cell

    Energy Technology Data Exchange (ETDEWEB)

    Pan, Shanlin [Univ. of Alabama, Tuscaloosa, AL (United States)

    2014-11-16

    Our research under support of this DOE grant is focused on applied and fundamental aspects of model organic solar cell systems. Major accomplishments are: 1) we developed a spectroelectorchemistry technique of single molecule single nanoparticle method to study charge transfer between conjugated polymers and semiconductor at the single molecule level. The fluorescence of individual fluorescent polymers at semiconductor surfaces was shown to exhibit blinking behavior compared to molecules on glass substrates. Single molecule fluorescence excitation anisotropy measurements showed the conformation of the polymer molecules did not differ appreciably between glass and semiconductor substrates. The similarities in molecular conformation suggest that the observed differences in blinking activity are due to charge transfer between fluorescent polymer and semiconductor, which provides additional pathways between states of high and low fluorescence quantum efficiency. Similar spectroelectrochemistry work has been done for small organic dyes for understand their charge transfer dynamics on various substrates and electrochemical environments; 2) We developed a method of transferring semiconductor nanoparticles (NPs) and graphene oxide (GO) nanosheets into organic solvent for a potential electron acceptor in bulk heterojunction organic solar cells which employed polymer semiconductor as the electron donor. Electron transfer from the polymer semiconductor to semiconductor and GO in solutions and thin films was established through fluorescence spectroscopy and electroluminescence measurements. Solar cells containing these materials were constructed and evaluated using transient absorption spectroscopy and dynamic fluorescence techniques to understand the charge carrier generation and recombination events; 3) We invented a spectroelectorchemistry technique using light scattering and electroluminescence for rapid size determination and studying electrochemistry of single NPs in an

  20. Improved single particle potential for transport model simulations of nuclear reactions induced by rare isotope beams

    International Nuclear Information System (INIS)

    Xu Chang; Li Baoan

    2010-01-01

    Taking into account more accurately the isospin dependence of nucleon-nucleon interactions in the in-medium many-body force term of the Gogny effective interaction, new expressions for the single-nucleon potential and the symmetry energy are derived. Effects of both the spin (isospin) and the density dependence of nuclear effective interactions on the symmetry potential and the symmetry energy are examined. It is shown that they both play a crucial role in determining the symmetry potential and the symmetry energy at suprasaturation densities. The improved single-nucleon potential will be useful for more accurate simulation of nuclear reactions induced by rare-isotope beams within transport models.

  1. Squeezing survival and transfer in single and double electromagnetically induced transparency

    International Nuclear Information System (INIS)

    Ding, J L; Hou, B P; Wang, S J

    2010-01-01

    We investigate the propagation and storage of a squeezed vacuum as the probe light in a collection of N four-level tripod configuration atoms under the condition of single or double electromagnetically induced transparency (EIT). The squeezing of the probe light is well preserved in both the single transparency channel and the double transparency one. On the other hand, the effects of the ground state dephasing rates on the propagation and storage of the squeezed vacuum are investigated. It is found that the maximum squeezing at the transparency points is suppressed by the dephasing rates in single or double EIT. Meanwhile, the mapping of the squeezing of the probe light onto the atomic ground coherences or onto the two atomic dark-state polaritons is also studied. In the absence of the Langevin atomic noise, the quasi-ideal squeezing transfer between the squeezed vacuum and the atomic ground coherences or the dark-state polaritons can be realized in such a system. When considering the Langevin atomic noise, the quantum characteristics of the atomic coherences at resonance are submerged by the Langevin noise, while in the scenario of the dark-state polariton, it is found that squeezing transfer onto one polariton is damaged, but the squeezing transfer onto the other polariton survives even in the presence of the Langevin noise.

  2. Measurement of Neutron Reaction Cross Sections in Carbon using a Single Crystal Diamond Detector

    Energy Technology Data Exchange (ETDEWEB)

    Pillon, M.; Angelone, M. [Associazione EURATOM-ENEA sulla Fusione, ENEA C.R. Frascati, via E. Fermi, 45 0044 Frascati, Rome (Italy); Krasa, A.; Plompen, A. J. M.; Schillebeeckx, P. [European Commission, Joint Research Centre, Institute for Reference Materials and Measurements, - 2440 Geel (Belgium); Sergi, M. L. [Dipartimento di Fisica e Astronomia, Universita di Catania e INFN-Laboratori Nazionali del Sud, Catania (Italy)

    2011-12-13

    A single crystal diamond detector was exposed to the quasi mono-energetic neutron fields in the energy range from 7 MeV to 20.5 MeV produced by the Van de Graaff neutron generator of the EC-JRC-IRMM. Pulse Height Spectra (PHS) of the neutron interaction with the diamond (carbon) were recorded in order to derive the experimental response function of this detector to neutrons in view of its use as a compact fast neutron spectrometer. Several peaks produced by outgoing charged particles produced when neutrons interact with carbon were identified using the reaction Q-values. The corresponding nuclear reactions, such as (n,{alpha}), (n,p), (n,d) for different excitation states were identified in the PHS. The analysis of the peaks allows the derivation of some neutron reaction cross sections in carbon. The results are presented in this paper together with the associated uncertainties.

  3. Measurement of Neutron Reaction Cross Sections in Carbon using a Single Crystal Diamond Detector

    Science.gov (United States)

    Pillon, M.; Angelone, M.; Krása, A.; Plompen, A. J. M.; Schillebeeckx, P.; Sergi, M. L.

    2011-12-01

    A single crystal diamond detector was exposed to the quasi mono-energetic neutron fields in the energy range from 7 MeV to 20.5 MeV produced by the Van de Graaff neutron generator of the EC-JRC-IRMM. Pulse Height Spectra (PHS) of the neutron interaction with the diamond (carbon) were recorded in order to derive the experimental response function of this detector to neutrons in view of its use as a compact fast neutron spectrometer. Several peaks produced by outgoing charged particles produced when neutrons interact with carbon were identified using the reaction Q-values. The corresponding nuclear reactions, such as (n,α), (n,p), (n,d) for different excitation states were identified in the PHS. The analysis of the peaks allows the derivation of some neutron reaction cross sections in carbon. The results are presented in this paper together with the associated uncertainties.

  4. Distance dependence of the energy transfer rate from a single semiconductor nanostructure to graphene.

    Science.gov (United States)

    Federspiel, François; Froehlicher, Guillaume; Nasilowski, Michel; Pedetti, Silvia; Mahmood, Ather; Doudin, Bernard; Park, Serin; Lee, Jeong-O; Halley, David; Dubertret, Benoît; Gilliot, Pierre; Berciaud, Stéphane

    2015-02-11

    The near-field Coulomb interaction between a nanoemitter and a graphene monolayer results in strong Förster-type resonant energy transfer and subsequent fluorescence quenching. Here, we investigate the distance dependence of the energy transfer rate from individual, (i) zero-dimensional CdSe/CdS nanocrystals and (ii) two-dimensional CdSe/CdS/ZnS nanoplatelets to a graphene monolayer. For increasing distances d, the energy transfer rate from individual nanocrystals to graphene decays as 1/d(4). In contrast, the distance dependence of the energy transfer rate from a two-dimensional nanoplatelet to graphene deviates from a simple power law but is well described by a theoretical model, which considers a thermal distribution of free excitons in a two-dimensional quantum well. Our results show that accurate distance measurements can be performed at the single particle level using graphene-based molecular rulers and that energy transfer allows probing dimensionality effects at the nanoscale.

  5. Mass Transfer and Chemical Reaction Approach of the Kinetics of the Acetylation of Gadung Flour using Glacial Acetic Acid

    Directory of Open Access Journals (Sweden)

    Andri Cahyo Kumoro

    2015-03-01

    Full Text Available Acetylation is one of the common methods of modifying starch properties by introducing acetil (CH3CO groups to starch molecules at low temperatures. While most acetylation is conducted using starch as anhidroglucose source and acetic anhydride or vinyl acetate as nucleophilic agents, this work employ reactants, namely flour and glacial acetic acid. The purpose of this work are to study the effect of pH reaction and GAA/GF mass ratio on the rate of acetylation reaction and to determine its rate constants. The acetylation of gadung flour with glacial acetic acid in the presence of sodium hydroxide as a homogenous catalyst was studied at ambient temperature with pH ranging from 8-10 and different mass ratio of acetic acid : gadung flour (1:3; 1:4; and 1:5. It was found that increasing pH, lead to increase the degree of substitution, while increasing GAA/GF mass ratio caused such decreases in the degree of substitution, due to the hydrolysis of the acetylated starch. The desired starch acetylation reaction is accompanied by undesirable hydrolysis reaction of the acetylated starch after 40-50 minutes reaction time. Investigation of kinetics of the reaction observed that the value of mass transfer rate constant (Kcs is smaller than the surface reaction rate constant (k. Thus, it can be concluded that rate controlling step is mass transfer.  © 2015 BCREC UNDIP. All rights reservedReceived: 7th August 2014; Revised: 8th September 2014; Accepted: 14th September 2014How to Cite: Kumoro, A.C., Amelia, R. (2015. Mass Transfer and Chemical Reaction Approach of the Kinetics of the Acetylation of Gadung Flour using Glacial Acetic Acid. Bulletin of Chemical Reaction Engineering & Catalysis, 10 (1: 30-37. (doi:10.9767/bcrec.10.1.7181.30-37Permalink/DOI: http://dx.doi.org/10.9767/bcrec.10.1.7181.30-37

  6. Kinetics of acyl transfer reactions in organic media catalysed by Candida antarctica lipase B.

    Science.gov (United States)

    Martinelle, M; Hult, K

    1995-09-06

    The acyl transfer reactions catalysed by Candida antartica lipase B in organic media followed a bi-bi ping-pong mechanism, with competitive substrate inhibition by the alcohols used as acyl acceptors. The effect of organic solvents on Vm and Km was investigated. The Vm values in acetonitrile was 40-50% of those in heptane. High Km values in acetonitrile compared to those in heptane could partly be explained by an increased solvation of the substrates in acetonitrile. Substrate solvation caused a 10-fold change in substrate specificity, defined as (Vm/Km)ethyl octanoate/(Vm/Km)octanoic acid, going from heptane to acetonitrile. Deacylation was the rate determining step for the acyl transfer in heptane with vinyl- and ethyl octanoate as acyl donors and (R)-2-octanol as acyl acceptor. With 1-octanol, a rate determining deacylation step in heptane was indicated using the same acyl donors. Using 1-octanol as acceptor in heptane, S-ethyl thiooctanoate had a 25- to 30-fold lower Vm/Km value and vinyl octanoate a 4-fold higher Vm/Km value than that for ethyl octanoate. The difference showed to be a Km effect for vinyl octanoate and mainly a Km effect for S-ethyl thiooctanoate. The Vm values of the esterification of octanoic acid with different alcohols was 10-30-times lower than those for the corresponding transesterification of ethyl octanoate. The low activity could be explained by a low pH around the enzyme caused by the acid or a withdrawing of active enzyme by nonproductive binding by the acid.

  7. Energetic Efficiency of Mixing and Mass Transfer in Single Phase and Two-Phase Systems

    Directory of Open Access Journals (Sweden)

    Bałdyga Jerzy

    2017-03-01

    Full Text Available In this work a concept of energetic efficiency of mixing is presented and discussed; a classical definition of mixing efficiency is modified to include effects of the Schmidt number and the Reynolds number. Generalization to turbulent flows is presented as well. It is shown how the energetic efficiency of mixing as well as efficiencies of drop breakage and mass transfer in twophase liquid-liquid systems can be identified using mathematical models and test chemical reactions. New expressions for analyzing efficiency problem are applied to identify the energetic efficiency of mixing in a stirred tank, a rotor stator mixer and a microreactor. Published experimental data and new results obtained using new systems of test reactions are applied. It has been shown that the efficiency of mixing is small in popular types of reactors and mixers and thus there is some space for improvement.

  8. Modeling of mass transfer and chemical reactions in a bubble column reactor using a discrete bubble model

    NARCIS (Netherlands)

    Darmana, D.; Deen, N.G.; Kuipers, J.A.M.

    2004-01-01

    A 3D discrete bubble model is adopted to investigate complex behavior involving hydrodynamics, mass transfer and chemical reactions in a gas-liquid bubble column reactor. In this model a continuum description is adopted for the liquid phase and additionally each individual bubble is tracked in a

  9. Geographical provenancing of purple grape juices from different farming systems by proton transfer reaction mass spectrometry using supervised statistical techniques

    NARCIS (Netherlands)

    Granato, Daniel; Koot, Alex; Ruth, van S.M.

    2015-01-01

    BACKGROUND: Organic, biodynamic and conventional purple grape juices (PGJ; n = 79) produced in Brazil and Europe were characterized by volatile organic compounds (m/z 20-160) measured by proton transfer reaction mass spectrometry (PTR-MS), and classification models were built using supervised

  10. A simple approach to the solvent reorganisation Gibbs free energy in electron transfer reactions of redox metalloproteins

    DEFF Research Database (Denmark)

    Ulstrup, Jens

    1999-01-01

    We discuss a simple model for the environmental reorganisation Gibbs free energy, E-r, in electron transfer between a metalloprotein and a small reaction partner. The protein is represented as a dielectric globule with low dielectric constant, the metal centres as conducting spheres, all embedded...

  11. Proton transfer reaction-mass spectrometry volatile organic compound fingerprinting for monovarietal extra virgin olive oil identification

    NARCIS (Netherlands)

    Ruiz-Samblas, C.; Tres, A.; Koot, A.H.; Ruth, van S.M.; Gonzalez-Casado, A.; Cuadros-Rodriguez, L.

    2012-01-01

    Proton transfer reaction-mass spectrometry (PTR-MS) is a relatively new technique that allows the fast and accurate qualification of the volatile organic compound (VOC) fingerprint. This paper describes the analysis of thirty samples of extra virgin olive oil, of five different varieties of olive

  12. An experimental investigation on mass transfer in presence of chemical reactions on a graphite cylinder in crossflow

    International Nuclear Information System (INIS)

    Ogawa, M.; Stauch, B.; Moormann, R.; Katscher, W.

    1985-11-01

    In connection with analyses of hypothetical massive air ingress accidents in HTGR experiments on mass transfer and in-pore diffusion with homogeneous and heterogeneous chemical reactions were performed. Two BLMR runs and two runs in an intermediate regime between BLMR and IPDR were executed at atmospheric pressures, Reynolds numbers ranging from 533 to 2490, and cylinder temperatures from 848 0 C to 1120 0 C. The nuclear grade graphite cylinder having a diameter of 100 mm and a porosity of 21.2% was corroded in a nitrogen gas flow containing approximately 5% oxygen. Mean and local mass transfer coefficients and corrosion rates were obtained to examine the influences of the chemical reactions on the mass transfer. As a result it can be concluded that the chemical reactions and small changes in shape do not significantly influence the mass transfer under conditions to be expected in air ingress accidents and that thus the analogy between heat and mass transfer can be used for safety calculations. (orig./HP)

  13. Influence of Proton Acceptors on the Proton-Coupled Electron Transfer Reaction Kinetics of a Ruthenium-Tyrosine Complex.

    Science.gov (United States)

    Lennox, J Christian; Dempsey, Jillian L

    2017-11-22

    A polypyridyl ruthenium complex with fluorinated bipyridine ligands and a covalently bound tyrosine moiety was synthesized, and its photo-induced proton-coupled electron transfer (PCET) reactivity in acetonitrile was investigated with transient absorption spectroscopy. Using flash-quench methodology with methyl viologen as an oxidative quencher, a Ru 3+ species is generated that is capable of initiating the intramolecular PCET oxidation of the tyrosine moiety. Using a series of substituted pyridine bases, the reaction kinetics were found to vary as a function of proton acceptor concentration and identity, with no significant H/D kinetic isotope effect. Through analysis of the kinetics traces and comparison to a control complex without the tyrosine moiety, PCET reactivity was found to proceed through an equilibrium electron transfer followed by proton transfer (ET-PT) pathway in which irreversible deprotonation of the tyrosine radical cation shifts the ET equilibrium, conferring a base dependence on the reaction. Comprehensive kinetics modeling allowed for deconvolution of complex kinetics and determination of rate constants for each elementary step. Across the five pyridine bases explored, spanning a range of 4.2 pK a units, a linear free-energy relationship was found for the proton transfer rate constant with a slope of 0.32. These findings highlight the influence that proton transfer driving force exerts on PCET reaction kinetics.

  14. Four- and six-charge transfer reactions induced by 52Cr, 56Fe, 63Cu in rare-earths

    International Nuclear Information System (INIS)

    Mouchaty, G.

    1977-01-01

    The cross sections for transfer reactions in which 4 and 6 charges are gained by Sm and Nd targets have been measured, the projectiles being 52 Cr and 56 Fe at 343 and 377 MeV. These energies correspond to 1.5B, B being the interaction barrier. The results obtained indicate that the cross section increases when the number of charges transferred and the mass of the projectile are increased. The angular distributions and recoil ranges at each angle of 151 Dy produced through 52 Cr+ 148 Sm, 52 Cr+ 144 Nd, 56 Fe+ 144 Nd, 63 Cu+ 144 Nd reactions were determined for incident energies equivalent to 1.5B. After transformation into the c.m. system, the angular distributions exhibit a maximum close to 155 0 and a tail at small angles. The position of the maximum is independent of the incident ion and of the number of transferred charges. The analysis of the energy distributions indicate that the observed reactions can be explained by a two-step process: a transfer of nucleons followed by an evaporation step. The number of nucleons transferred in the 1st step and the associated excitation energies are higher for the events corresponding to the tail than for those corresponding to the maximum [fr

  15. Study of heavy ions elastic scattering and of friction phenomenon in transfer reactions induced by 28Si on 130Te

    International Nuclear Information System (INIS)

    Sim, Kwang-Souk.

    1978-01-01

    Elastic scattering of heavy-ions 16 O and 28 Si on 59 Co, 109 Ag and 130 Te have been studied at laboratory incident energies between 80 and 140MeV. The optical model was used to analyse elastic angular distributions and different methods for determining the total reaction cross section have been compared. Transfer reactions induced by 28 Si on 130 Te have been studied at incident energy superior to the Coulomb barrier in the ratio of 1.27. A study of these reactions shows the transition between the quasi-elastic reactions and deep inelastic reactions coresponding to the phenomenon of friction. The diffusion model is used for the analysis of these results [fr

  16. Reaction-diffusion systems in natural sciences and new technology transfer

    Science.gov (United States)

    Keller, André A.

    2012-12-01

    Diffusion mechanisms in natural sciences and innovation management involve partial differential equations (PDEs). This is due to their spatio-temporal dimensions. Functional semi-discretized PDEs (with lattice spatial structures or time delays) may be even more adapted to real world problems. In the modeling process, PDEs can also formalize behaviors, such as the logistic growth of populations with migration, and the adopters’ dynamics of new products in innovation models. In biology, these events are related to variations in the environment, population densities and overcrowding, migration and spreading of humans, animals, plants and other cells and organisms. In chemical reactions, molecules of different species interact locally and diffuse. In the management of new technologies, the diffusion processes of innovations in the marketplace (e.g., the mobile phone) are a major subject. These innovation diffusion models refer mainly to epidemic models. This contribution introduces that modeling process by using PDEs and reviews the essential features of the dynamics and control in biological, chemical and new technology transfer. This paper is essentially user-oriented with basic nonlinear evolution equations, delay PDEs, several analytical and numerical methods for solving, different solutions, and with the use of mathematical packages, notebooks and codes. The computations are carried out by using the software Wolfram Mathematica®7, and C++ codes.

  17. Multi-capillary-column proton-transfer-reaction time-of-flight mass spectrometry.

    Science.gov (United States)

    Ruzsanyi, Veronika; Fischer, Lukas; Herbig, Jens; Ager, Clemes; Amann, Anton

    2013-11-05

    Proton-transfer-reaction time-of-flight mass-spectrometry (PTR-TOFMS) exhibits high selectivity with a resolution of around 5000 m/Δm. While isobars can be separated with this resolution, discrimination of isomeric compounds is usually not possible. The coupling of a multi-capillary column (MCC) with a PTR-TOFMS overcomes these problems as demonstrated in this paper for the ketone isomers 3-heptanone and 2-methyl-3-hexanone and for different aldehydes. Moreover, fragmentation of compounds can be studied in detail which might even improve the identification. LODs for compounds tested are in the range of low ppbv and peak positions of the respective separated substances show good repeatability (RSD of the peak positions <3.2%). Due to its special characteristics, such as isothermal operation, compact size, the MCC setup is suitable to be installed inside the instrument and the overall retention time for a complete spectrum is only a few minutes: this allows near real-time measurements in the optional MCC mode. In contrast to other methods that yield additional separation, such as the use of pre-cursor ions other than H3O(+), this method yields additional information without increasing complexity. Copyright © 2013 The Authors. Published by Elsevier B.V. All rights reserved.

  18. The electrochemical transfer reactions and the structure of the iron|oxide layer|electrolyte interface

    International Nuclear Information System (INIS)

    Petrović, Željka; Metikoš-Huković, Mirjana; Babić, Ranko

    2012-01-01

    The thickness, barrier (protecting) and semiconducting properties of the potentiostatically formed oxide films on the pure iron electrode in an aqueous borate buffer solution were investigated by electrochemical quartz crystal nanobalance (EQCN), electrochemical impedance spectroscopy (EIS), and Mott–Schottky (MS) analysis. The thicknesses of the prepassive Fe(II)hydroxide layer (up to monolayer) nucleated on the bare iron surface and the passive Fe(II)/Fe(III) layer (up to 2 nm), deposited on the top of the first one, were determined using in situ gravimetry. Electronic properties of iron prepassive and passive films as well as ionic and electronic transfer reactions at the film|solution interface were discussed on the basis of a band structure model of the surface oxide film and the potential distribution at the interface. The anodic oxide film formation and cathodic decomposition are coupled processes and their reversible inter-conversion is mediated by the availability of free charge carriers on the electrode|solution interface. The structure of the reversible double layer at the iron oxide|solution interface was discussed based on the concept of the specific adsorption of the imidazolium cation on the negatively charged electrode surface at pH > pH pzc .

  19. Triacetone triperoxide detection using low reduced-field proton transfer reaction mass spectrometer

    Science.gov (United States)

    Shen, Chengyin; Li, Jianquan; Han, Haiyan; Wang, Hongmei; Jiang, Haihe; Chu, Yannan

    2009-08-01

    Proton transfer reaction mass spectrometry (PTR-MS) was applied to on-line detection of the explosive triacetone triperoxide (TATP) using a discharge gas of water vapor or alternative ammonia in the ion source. The dependence of ionic intensity on reduced-field in the drift tube was investigated, and the results indicate that an irregular operation using low reduced-field can enhance TATP detection due to reduced collision-induced dissociation in the drift tube. When water vapor is used as the discharge gas, the characteristic ions for TATP identification are [TATP + H]+ which are detectable at a reduced-field about 50 Td. If ammonia is the discharge gas, PTR-MS exhibits a better sensitivity, the explosive TATP can be discriminated according to the adduct ions [TATP + NH4]+, and a limit of detection at ppb level can be achieved at a reduced-field around 100 Td in this PTR-MS apparatus. PTR-MS is suggested as a potential tool for on-site detection of the explosive TATP with the advantages of rapid response and high sensitivity without sample pretreatment.

  20. Monitoring benzene formation from benzoate in model systems by proton transfer reaction-mass spectrometry

    Science.gov (United States)

    Aprea, Eugenio; Biasioli, Franco; Carlin, Silvia; Märk, Tilmann D.; Gasperi, Flavia

    2008-08-01

    The presence of benzene in food and in particular in soft drinks has been reported in several studies and should be considered in fundamental investigations about formation of this carcinogen compound as well as in quality control. Proton transfer reaction-mass spectrometry (PTR-MS) has been used here for rapid, direct quantification of benzene and to monitor its formation in model systems related to the use of benzoate, a common preservative, in presence of ascorbic acid: a widespread situation that yields benzene in, e.g., soft drinks and fruit juices. Firstly, we demonstrate here that PTR-MS allows a rapid determination of benzene that is in quantitative agreement with independent solid phase micro-extraction/gas chromatography (SPME/GC) analysis. Secondly, as a case study, the effect of different sugars (sucrose, fructose and glucose) on benzene formation is investigated indicating that they inhibit its formation and that this effect is enhanced for reducing sugars. The sugar-induced inhibition of benzene formation depends on several parameters (type and concentration of sugar, temperature, time) but can be more than 80% in situations that can be expected in the storage of commercial soft drinks. This is consistent with the reported observations of higher benzene concentrations in sugar-free soft drinks.

  1. Studies of Silyl-Transfer Photochemical Reactions of N-[(Trimethylsilyl)alkyl]saccharins

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Dae Won; Oh, Sun Wha; Park, Hea Jung; Yoon, Ung Chan [Pusan National University, Busan (Korea, Republic of); Kim, Dong Uk [Daegu National University of Education, Daegu (Korea, Republic of); Xue, Jin Ying [Harbin Normal University, Harbin (China); Mariano, Patrick S. [University of New Mexico, Albuquerque (United States)

    2010-09-15

    Photochemical studies of N-[(trimethylsilyl)alkyl]saccharins were carried out to investigate their photochemical behavior. Depending on the nature of the substrate and the solvent system employed, reactions of these substances can take place by either SET-promoted silyl migration from carbon to either the amide carbonyl or sulfonyl oxygen or by a N-S homolysis route. The results of the current studies show that an azomethine ylide, arising from a SET-promoted silyl migration pathway, is generated in photoreactions of N-[(trimethylsilyl)methyl]saccharin and this intermediate reacts to give various photoproducts depending on the conditions employed. In addition, irradiation of N-[(trimethylsily)ethyl]saccharin produces an excited state that reacts through two pathways, the relative importance is governed by solvent polarity and protic nature. Finally, photoirradiation of N-[(trimethylsilyl)propyl]saccharin in a highly polar solvent system comprised of 35% aqueous MeOH gives rise to formation of a tricyclic pyrrolizidine and saccharin that generated via competitive SET-promoted silyl transfer and γ-hydrogen abstraction pathways.

  2. Studies of Silyl-Transfer Photochemical Reactions of N-[(Trimethylsilyl)alkyl]saccharins

    International Nuclear Information System (INIS)

    Cho, Dae Won; Oh, Sun Wha; Park, Hea Jung; Yoon, Ung Chan; Kim, Dong Uk; Xue, Jin Ying; Mariano, Patrick S.

    2010-01-01

    Photochemical studies of N-[(trimethylsilyl)alkyl]saccharins were carried out to investigate their photochemical behavior. Depending on the nature of the substrate and the solvent system employed, reactions of these substances can take place by either SET-promoted silyl migration from carbon to either the amide carbonyl or sulfonyl oxygen or by a N-S homolysis route. The results of the current studies show that an azomethine ylide, arising from a SET-promoted silyl migration pathway, is generated in photoreactions of N-[(trimethylsilyl)methyl]saccharin and this intermediate reacts to give various photoproducts depending on the conditions employed. In addition, irradiation of N-[(trimethylsily)ethyl]saccharin produces an excited state that reacts through two pathways, the relative importance is governed by solvent polarity and protic nature. Finally, photoirradiation of N-[(trimethylsilyl)propyl]saccharin in a highly polar solvent system comprised of 35% aqueous MeOH gives rise to formation of a tricyclic pyrrolizidine and saccharin that generated via competitive SET-promoted silyl transfer and γ-hydrogen abstraction pathways

  3. Experimental study of quasi-elastic transfer reactions induced on bismuth by heavy ions. Influence of energetic and geometric factors

    International Nuclear Information System (INIS)

    Gardes, D.

    A systematic study of quasi-elastic transfer reactions induced on bismuth target by heavy ions ( 12 C, 14 N, 16 O, 19 F, 20 Ne, 40 Ar, 40 Ca, 56 Fe, 63 Cu, 84 Kr) was performed. Recoil techniques were applied to the collection of heavy residues of the reaction. These products were identified by their radioactive decay. The experimental data (excitation functions, projected recoil ranges, angular distributions) could be interpreted by the drastic influence of energetical parameters such as optimum Q values, and geometrical factors (minimum distances of approach). Odd-even effects of the atomic number of the projectile on the 2 proton-transfer probability was observed for light projectiles. A theoretical calculation of transfer probability has been developed and the results compared to our experimental data. General shape of excitation functions and angular distributions in the sub-Coulomb energies region have been successfully reproduced [fr

  4. Electrochemical Dynamics of a Single Platinum Nanoparticle Collision Event for the Hydrogen Evolution Reaction.

    Science.gov (United States)

    Xiang, Zhi-Peng; Deng, Hai-Qiang; Peljo, Pekka; Fu, Zhi-Yong; Wang, Su-Li; Mandler, Daniel; Sun, Gong-Quan; Liang, Zhen-Xing

    2018-03-19

    Chronoamperometry was used to study the dynamics of Pt nanoparticle (NP) collision with an inert ultramicroelectrode via electrocatalytic amplification (ECA) in the hydrogen evolution reaction. ECA and dynamic light scattering (DLS) results reveal that the NP colloid remains stable only at low proton concentrations (1.0 mm) under a helium (He) atmosphere, ensuring that the collision events occur at genuinely single NP level. Amperometry of single NP collisions under a He atmosphere shows that each discrete current profile of the collision event evolves from spike to staircase at more negative potentials, while a staircase response is observed at all of the applied potentials under hydrogen-containing atmospheres. The particle size distribution estimated from the diffusion-controlled current in He agrees well with electron microscopy and DLS observations. These results shed light on the interfacial dynamics of the single nanoparticle collision electrochemistry. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Multi-nucleon transfer reaction studies of helium-6 on carbon-12 at 30 MeV using the SHARC and TIGRESS arrays

    Science.gov (United States)

    Smalley, Duane D.

    Two multi-nucleon transfer reactions were studied using 6He on 12C with the Silicon Highly-segmented Array for Reactions and Coulex (SHARC), a compact charged particle silicon array, and the TRIUMF-ISAC γ-Ray Escape Suppressed Spectrometer (TIGRESS), a high-efficiency γ-ray detector, at the TRIUMF ISAC-II facility. First, the reaction mechanisms of the ( 6He, 4He) two-neutron transfer were studied to determine the dominant mechanism; one-step simultaneous transfer or two-step sequential transfer. Second, the multi-nucleon transfer (6He,8 Be) reaction was observed and its reaction mechanism could proceed two ways, by a two-proton transfer or an alpha transfer. The two-neutron and multi-nucleon transfer reactions were analyzed and angular distributions extracted. These angular distributions were then compared to the microscopic models investigating the effects of the simultaneous vs. sequential transfer mechanisms. Detailed simulations in GEANT4 were performed of the SHARC array to characterize detector performance. This thesis will discuss the experimental challenges, the data analysis, GEANT4 reaction simulations and interpretation of the data within the reaction models.

  6. Elective single-embryo transfer: persuasive communication strategies can affect choice in a young British population.

    Science.gov (United States)

    van den Akker, O B A; Purewal, S

    2011-12-01

    This study tested the effectiveness of the framing effect and fear appeals to inform young people about the risks of multiple births and the option of selecting elective single-embryo transfer (eSET). A non-patient student sample (age (mean±SD) 23±5.5 years; n=321) were randomly allocated to one of seven groups: (1) framing effect: (1a) gain and (1b) loss frame; (2) fear appeal: (2a) high, (2b) medium and (2c) low fear; or (3) a control group: (3a) education and (3b) non-education. The primary outcome measure was the Attitudes towards Single Embryo Transfer questionnaire, before exposure to the messages (time 1) and immediately afterwards (time 2). Results revealed participants in the high fear, medium fear and gain condition demonstrated the most positive and significant differences (Ppersuasive communication techniques on a student population to promote immediate and hypothetical eSET preferences is more successful at promoting eSET than merely reporting educational content. Future research should investigate its application in a clinical population. A multiple pregnancy is a health risk to both infant and mother following IVF treatment. The aims of this study were to test the effectiveness of two persuasive communication techniques (the framing effect and fear appeals) to inform young people about the risks of multiple births and the hypothetical option of selecting elective single-embryo transfer (eSET) (i.e., only one embryo is transferred to the uterus using IVF treatment). A total of 321 non-patient student sample (mean age 23) were randomly allocated to read a message from one of seven groups: (1) framing effect: (1a) gain and (1b) loss frame; (2) fear appeal: (2a) high, (2b) medium and (2c) low fear; or (3) a control group: education (3a) and (3b) non-education. Participants completed the Attitudes towards Single Embryo Transfer questionnaire, before exposure to the messages (time 1) and immediately afterwards (time 2). Results revealed that participants

  7. Charge transfer dynamics from adsorbates to surfaces with single active electron and configuration interaction based approaches

    Energy Technology Data Exchange (ETDEWEB)

    Ramakrishnan, Raghunathan, E-mail: r.ramakrishnan@unibas.ch [Institute of Physical Chemistry, National Center for Computational Design and Discovery of Novel Materials (MARVEL), Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel (Switzerland); Nest, Mathias [Theoretische Chemie, Technische Universität München, Lichtenbergstr. 4, 85747 Garching (Germany)

    2015-01-13

    Highlights: • We model electron dynamics across cyano alkanethiolates attached to gold cluster. • We present electron transfer time scales from TD-DFT and TD-CI based simulations. • Both DFT and CI methods qualitatively predict the trend in time scales. • TD-CI predicts the experimental relative time scale very accurately. - Abstract: We employ wavepacket simulations based on many-body time-dependent configuration interaction (TD-CI), and single active electron theories, to predict the ultrafast molecule/metal electron transfer time scales, in cyano alkanethiolates bonded to model gold clusters. The initial states represent two excited states where a valence electron is promoted to one of the two virtual π{sup ∗} molecular orbitals localized on the cyanide fragment. The ratio of the two time scales indicate the efficiency of one charge transfer channel over the other. In both our one-and many-electron simulations, this ratio agree qualitatively with each other as well as with the previously reported experimental time scales (Blobner et al., 2012), measured for a macroscopic metal surface. We study the effect of cluster size and the description of electron correlation on the charge transfer process.

  8. Kinetics of Single-Enzyme Reactions on Vesicles: Role of Substrate Aggregation

    Science.gov (United States)

    Zhdanov, Vladimir P.

    2015-03-01

    Enzymatic reactions occurring in vivo on lipid membranes can be influenced by various factors including macromolecular crowding in general and substrate aggregation in particular. In academic studies, the role of these factors can experimentally be clarified by tracking single-enzyme kinetics occurring on individual lipid vesicles. To extend the conceptual basis for such experiments, we analyze herein the corresponding kinetics mathematically with emphasis on the role of substrate aggregation. In general, the aggregation may occur on different length scales. Small aggregates may e.g. contain a few proteins or peptides while large aggregates may be mesoscopic as in the case of lipid domains which can be formed in the membranes composed of different lipids. We present a kinetic model describing comprehensively the effect of aggregation of the former type on the dependence of the reaction rate on substrate membrane concentration. The results obtained with physically reasonable parameters indicate that the aggregation-related deviations from the conventional Michaelis-Menten kinetics may be appreciable. Special Issue Comments: This theoretical article is focused on single-enzyme reactions occurring in parallel with substrate aggregation on individual vesicles. This subject is related to a few Special Issue articles concerning enzyme dynamics6,7 and function8 and mathematical aspects of stochastic kinetics.9

  9. Single particle transfer for quantitative analysis with total-reflection X-ray fluorescence spectrometry

    International Nuclear Information System (INIS)

    Esaka, Fumitaka; Esaka, Konomi T.; Magara, Masaaki; Sakurai, Satoshi; Usuda, Shigekazu; Watanabe, Kazuo

    2006-01-01

    The technique of single particle transfer was applied to quantitative analysis with total-reflection X-ray fluorescence (TXRF) spectrometry. The technique was evaluated by performing quantitative analysis of individual Cu particles with diameters between 3.9 and 13.2 μm. The direct quantitative analysis of the Cu particle transferred onto a Si carrier gave a discrepancy between measured and calculated Cu amounts due to the absorption effects of incident and fluorescent X-rays within the particle. By the correction for the absorption effects, the Cu amounts in individual particles could be determined with the deviation within 10.5%. When the Cu particles were dissolved with HNO 3 solution prior to the TXRF analysis, the deviation was improved to be within 3.8%. In this case, no correction for the absorption effects was needed for quantification

  10. Effect of surfactant on single drop mass transfer for extraction of aromatics from lubricating oils

    Science.gov (United States)

    Izza, H.; Ben Abdessalam, S.; Korichi, M.

    2018-03-01

    Solvent extraction is an effective method for the reduction of the content of aromatic of lubricating oil. Frequently, with phenol, furfural, the NMP (out of N-methyl pyrrolidone). The power solvent and the selectivity can be still to increase while using surfactant as additive which facilitates the separation of phase and increases the yeild in raffinat. Liquid-liquid mass transfer coefficients for single freely rising drops in the presence of surfactant in an extraction column have been investigated. The surfactant used in this study was sodium lauryl ether sulfate (SLES). The experiments were performed by bubbling a solvent as a series of individual drops from the top of the column containing furfural-SLES solution. The column used in this experiment was made from glass with 17 mm inner diameter and a capacity of 125ml. The effects of the concentration of surfactant on the overall coefficient of mass transfer was investigated.

  11. Numeric Simulation of Heat Transfer from a Single Round Tube Shielded with Wire Mesh

    Directory of Open Access Journals (Sweden)

    Dymo B.V.

    2015-08-01

    Full Text Available This paper presents the results of development and investigation of heat transfer at transverse flow of round tube with wire screen using the software ANSYS Fluent 3D-model. Selection of optimal parameters of the finite element model, in particular, transition shear stress transport model as well and boundary conditions are realized. Instructed and combined net is used at numerical calculations. This net is built with the help of generators grid-torus ANSYS CFX Mesh 14.0. The problem of verification of conformity of the numerical model of the heat transfer of a single screen-covered round tubes according to physical experiment for the same tubes in the range of Reynolds numbers Re = (5000...35000 was studied. We established that discrepancy between physical experiments and numerical simulation results not exceeds 5% with respect to the data of physical experiment.

  12. Single-stage reconstruction of flexor tendons with vascularized tendon transfers.

    Science.gov (United States)

    Cavadas, P C; Pérez-García, A; Thione, A; Lorca-García, C

    2015-03-01

    The reconstruction of finger flexor tendons with vascularized flexor digitorum superficialis (FDS) tendon grafts (flaps) based on the ulnar vessels as a single stage is not a popular technique. We reviewed 40 flexor tendon reconstructions (four flexor pollicis longus and 36 finger flexors) with vascularized FDS tendon grafts in 38 consecutive patients. The donor tendons were transferred based on the ulnar vessels as a single-stage procedure (37 pedicled flaps, three free flaps). Four patients required composite tendon and skin island transfer. Minimum follow-up was 12 months, and functional results were evaluated using a total active range of motion score. Multiple linear regression analysis was performed to evaluate the factors that could be associated with the postoperative total active range of motion. The average postoperative total active range of motion (excluding the thumbs) was 178.05° (SD 50°). The total active range of motion was significantly lower for patients who were reconstructed with free flaps and for those who required composite tendon and skin island flap. Age, right or left hand, donor/motor tendon and pulley reconstruction had no linear effect on total active range of motion. Overall results were comparable with a published series on staged tendon grafting but with a lower complication rate. Vascularized pedicled tendon grafts/flaps are useful in the reconstruction of defects of finger flexor tendons in a single stage, although its role in the reconstructive armamentarium remains to be clearly established. © The Author(s) 2014.

  13. Bis(pentamethylcyclopentadienyl) ytterbium: Electron-transfer reactions with organotransition metal complexes

    Energy Technology Data Exchange (ETDEWEB)

    Matsunaga, P.T.

    1991-11-01

    The divalent lanthanide complex, (Me{sub 5}C{sub 5}){sub 2}Yb, reacts with methylcopper to produce the base-free, ytterbium-methyl complex, (Me{sub 5}C{sub 5}){sub 2}YbMe. This product forms a asymmetric, methyl-bridged dimer in the solid state. The bulky alkyl complex, (Me{sub 5}C{sub 5}){sub 2}YbCH(SiMe{sub 3}){sub 2}, displays similar chemistry to (Me{sub 5}C{sub 5}){sub 2}YbMe, but at a reduced reaction rate due to the limited accessibility of the metal in (Me{sub 5}C{sub 5}){sub 2}YbCH(SiMe{sub 3}){sub 2}. Copper and silver halide salts react with (Me{sub 5}C{sub 5}){sub 2}V to produce the trivalent halide derivatives, (Me{sub 5}C{sub 5}){sub 2}VX (X + F, Cl, Br, I). The chloride complex, (Me{sub 5}C{sub 5}){sub 2}VCl, reacts with lithium reagents to form the phenyl and borohydride species. Nitrous oxide transfers an oxygen atom to (Me{sub 5}C{sub 5}){sub 2}V producing the vanadium-oxo complex, (Me{sub 5}Ce{sub 5}){sub 2}VO. The trivalent titanium species, (Me{sub 5}C{sub 5}){sub 2}TiX (X = Cl, Br, Me, BH{sub 4}), form bimetallic coordination complexes with (Me{sub 5}C{sub 5}){sub 2}Yb. The magnetic behavior of the products indicates that electron transfer has not occurred. The solid state structures of the chloride and bromide complexes show unusual bend angles for the halide bridges between ytterbium and titanium. A model based on frontier orbital theory has been proposed to account for the bending behavior in these species. The bimetallic methyl complex contains a linear methyl bridge between ytterbium and titanium.

  14. Bis(pentamethylcyclopentadienyl) ytterbium: Electron-transfer reactions with organotransition metal complexes

    Energy Technology Data Exchange (ETDEWEB)

    Matsunaga, Phillip Thomas [Univ. of California, Berkeley, CA (United States)

    1991-11-01

    The divalent lanthanide complex, (Me5C5)2Yb, reacts with methylcopper to produce the base-free, ytterbium-methyl complex, (Me5C5)2YbMe. This product forms a asymmetric, methyl-bridged dimer in the solid state. The bulky alkyl complex, (Me5C5)2YbCH(SiMe3)2, displays similar chemistry to (Me5C5)2YbMe, but at a reduced reaction rate due to the limited accessibility of the metal in (Me5C5)3YbCH(SiMe5)2. Copper and silver halide salts react with (Me5C5)2V to produce the trivalent halide derivatives, (Me5C5)2VX (X + F, Cl, Br, I). The chloride complex, (Me5C5)2VCl, reacts with lithium reagents to form the phenyl and borohydride species. Nitrous oxide transfers an oxygen atom to (Me5C5)2V producing the vanadium-oxo complex, (Me5Ce5)2VO. The trivalent titanium species, (Me5C5)2TiX (X = Cl, Br, Me, BH4), form bimetallic coordination complexes with (Me5C5)2Yb. The magnetic behavior of the products indicates that electron transfer has not occurred. The solid state structures of the chloride and bromide complexes show unusual bend angles for the halide bridges between ytterbium and titanium. A model based on frontier orbital theory has been proposed to account for the bending behavior in these species. The bimetallic methyl complex contains a linear methyl bridge between ytterbium and titanium.

  15. Analyzing conformational dynamics of single P-glycoprotein transporters by Förster resonance energy transfer using hidden Markov models.

    Science.gov (United States)

    Zarrabi, Nawid; Ernst, Stefan; Verhalen, Brandy; Wilkens, Stephan; Börsch, Michael

    2014-03-15

    Single-molecule Förster resonance energy (smFRET) transfer has become a powerful tool for observing conformational dynamics of biological macromolecules. Analyzing smFRET time trajectories allows to identify the state transitions occuring on reaction pathways of molecular machines. Previously, we have developed a smFRET approach to monitor movements of the two nucleotide binding domains (NBDs) of P-glycoprotein (Pgp) during ATP hydrolysis driven drug transport in solution. One limitation of this initial work was that single-molecule photon bursts were analyzed by visual inspection with manual assignment of individual FRET levels. Here a fully automated analysis of Pgp smFRET data using hidden Markov models (HMM) for transitions up to 9 conformational states is applied. We propose new estimators for HMMs to integrate the information of fluctuating intensities in confocal smFRET measurements of freely diffusing lipid bilayer bound membrane proteins in solution. HMM analysis strongly supports that under conditions of steady state turnover, conformational states with short NBD distances and short dwell times are more populated compared to conditions without nucleotide or transport substrate present. Copyright © 2013 Elsevier Inc. All rights reserved.

  16. Effect of micellar environment on Marcus correlation curves for photoinduced bimolecular electron transfer reactions

    Science.gov (United States)

    Kumbhakar, Manoj; Nath, Sukhendu; Mukherjee, Tulsi; Pal, Haridas

    2005-07-01

    Photoinduced electron transfer (ET) between coumarin dyes and aromatic amine has been investigated in two cationic micelles, namely, cetyltrimethyl ammonium bromide (CTAB) and dodecyltrimethyl ammonium bromide (DTAB), and the results have been compared with those observed earlier in sodium dodecyl sulphate (SDS) and triton-X-100 (TX-100) micelles for similar donor-acceptor pairs. Due to a reasonably high effective concentration of the amines in the micellar Stern layer, the steady-state fluorescence results show significant static quenching. In the time-resolved (TR) measurements with subnanosecond time resolution, contribution from static quenching is avoided. Correlations of the dynamic quenching constants (kqTR), as estimated from the TR measurements, show the typical bell-shaped curves with the free-energy changes (ΔG0) of the ET reactions, as predicted by the Marcus outersphere ET theory. Comparing present results with those obtained earlier for similar coumarin-amine systems in SDS and TX-100 micelles, it is seen that the inversion in the present micelles occurs at an exergonicity (-ΔG0>˜1.2-1.3eV) much higher than that observed in SDS and TX-100 micelles (-ΔG0>˜0.7eV), which has been rationalized based on the relative propensities of the ET and solvation rates in different micelles. In CTAB and DTAB micelles, the kqTR values are lower than the solvation rates, which result in the full contribution of the solvent reorganization energy (λs) towards the activation barrier for the ET reaction. Contrary to this, in SDS and TX-100 micelles, kqTR values are either higher or comparable with the solvation rates, causing only a partial contribution of λs in these cases. Thus, Marcus inversion in present cationic micelles is inferred to be the true inversion, whereas that in the anionic SDS and neutral TX-100 micelles are understood to be the apparent inversion, as envisaged from two-dimensional ET theory.

  17. Elastic scattering and cluster-transfer reactions of 98Rb on 7Li at REX-ISOLDE

    CERN Document Server

    Bouma, Jake

    Exotic nuclei are nuclei with unusual proton to neutron ratios that exist far away from stability. Due to their instability, these nuclei are only available for nuclear reactions as radioactive ion beams. Experiments must therefore be performed in inverse kinematics at advanced radioactive isotope separation and acceleration facilities. REX-ISOLDE at CERN is one such facility, capable of producing post-accelerated radioactive ion beams with energies up to 2.85 MeV/u. Cluster-transfer reactions in inverse kinematics with a $^{7}$Li target are proposed as a tool for the study of exotic nuclei at REX-ISOLDE. In these reactions, either the $\\alpha$ or triton clusters that make up the weakly bound $^{7}$Li nucleus can be transfered to the beam nucleus. The remaining cluster that is not transferred can be detected, and identifies the particular transfer channel. Through this mechanism it is possible to populate states of very high spin, which is useful for $\\gamma$-spectroscopy in poorly known exotic regions. Speci...

  18. Fragmentation and direct transfer reactions for 40Ar incident beam on 27Al target at 1760 MeV

    International Nuclear Information System (INIS)

    Cisse, Ousmane

    1985-01-01

    Peripheral collision studies performed with 40 Ar projectiles at 44 MeV/A and 27 Al target show that both fragmentation and transfer reactions can be discerned in this type of interaction. The experimental observation of fragments with masses charges and velocities close to those of the incident beam are the signature of transfer reactions and a detailed analysis of the energy spectra of such fragments has been carried out and interpreted in terms of a direct diffraction transfer model. On the other hand, for large mass transfer reactions, abrasion is the suitable mechanism. Inclusive fragment measurement together with the appropriate residual nuclei-fragment coincidence results then provides experimental data in good agreement with the theoretical predictions obtained from a participant spectator model. These investigations also indicate that the separation energies of the participant from the spectator nucleus, at least within the framework of the above model, can be interpreted in terms of a friction force which becomes more efficient as the projectile energy decreases. (author) [fr

  19. Studying Chemical Reactions, One Bond at a Time, with Single Molecule AFM Techniques

    Science.gov (United States)

    Fernandez, Julio M.

    2008-03-01

    The mechanisms by which mechanical forces regulate the kinetics of a chemical reaction are unknown. In my lecture I will demonstrate how we use single molecule force-clamp spectroscopy and protein engineering to study the effect of force on the kinetics of thiol/disulfide exchange. Reduction of disulfide bond via the thiol/disulfide exchange chemical reaction is crucial in regulating protein function and is of common occurrence in mechanically stressed proteins. While reduction is thought to proceed through a substitution nucleophilic bimolecular (SN2) reaction, the role of a mechanical force in modulating this chemical reaction is unknown. We apply a constant stretching force to single engineered disulfide bonds and measure their rate of reduction by dithiothreitol (DTT). We find that while the reduction rate is linearly dependent on the concentration of DTT, it is exponentially dependent on the applied force, increasing 10-fold over a 300 pN range. This result predicts that the disulfide bond lengthens by 0.34 å at the transition state of the thiol/disulfide exchange reaction. In addition to DTT, we also study the reduction of the engineered disulfide bond by the E. coli enzyme thioredoxin (Trx). Thioredoxins are enzymes that catalyze disulfide bond reduction in all organisms. As before, we apply a mechanical force in the range of 25-450 pN to the engineered disulfide bond substrate and monitor the reduction of these bonds by individual enzymes. In sharp contrast with the data obtained with DTT, we now observe two alternative forms of the catalytic reaction, the first requiring a reorientation of the substrate disulfide bond, causing a shortening of the substrate polypeptide by 0.76±0.07 å, and the second elongating the substrate disulfide bond by 0.21±0.01 å. These results support the view that the Trx active site regulates the geometry of the participating sulfur atoms, with sub-ångström precision, in order to achieve efficient catalysis. Single molecule

  20. Force-induced chemical reactions on the metal centre in a single metalloprotein molecule.

    Science.gov (United States)

    Zheng, Peng; Arantes, Guilherme M; Field, Martin J; Li, Hongbin

    2015-06-25

    Metalloproteins play indispensable roles in biology owing to the versatile chemical reactivity of metal centres. However, studying their reactivity in many metalloproteins is challenging, as protein three-dimensional structure encloses labile metal centres, thus limiting their access to reactants and impeding direct measurements. Here we demonstrate the use of single-molecule atomic force microscopy to induce partial unfolding to expose metal centres in metalloproteins to aqueous solution, thus allowing for studying their chemical reactivity in aqueous solution for the first time. As a proof-of-principle, we demonstrate two chemical reactions for the FeS4 centre in rubredoxin: electrophilic protonation and nucleophilic ligand substitution. Our results show that protonation and ligand substitution result in mechanical destabilization of the FeS4 centre. Quantum chemical calculations corroborated experimental results and revealed detailed reaction mechanisms. We anticipate that this novel approach will provide insights into chemical reactivity of metal centres in metalloproteins under biologically more relevant conditions.

  1. Measurements of Volatile Organic Compounds Using Proton Transfer Reaction - Mass Spectrometry during the MILAGRO 2006 Campaign

    Science.gov (United States)

    Fortner, E. C.; Zheng, J.; Zhang, R.; Berk Knighton, W.; Volkamer, R. M.; Sheehy, P.; Molina, L.; André, M.

    2009-01-01

    Volatile organic compounds (VOCs) were measured by proton transfer reaction - mass spectrometry (PTR-MS) on a rooftop in the urban mixed residential and industrial area North Northeast of downtown Mexico City as part of the Megacity Initiative - Local and Global Research Observations (MILAGRO) 2006 field campaign. Thirty eight individual masses were monitored during the campaign and many species were quantified including methanol, acetaldehyde, toluene, the sum of C2 benzenes, the sum of C3 benzenes, acetone, isoprene, benzene, and ethyl acetate. The VOC measurements were analyzed to gain a better understanding of the type of VOCs present in the MCMA, their diurnal patterns, and their origins. Diurnal profiles of weekday and weekend/holiday aromatic VOC concentrations showed the influence of vehicular traffic during the morning rush hours and during the afternoon hours. Plumes including elevated toluene as high as 216 parts per billion (ppb) and ethyl acetate as high as 183 ppb were frequently observed during the late night and early morning hours, indicating the possibility of significant industrial sources of the two compounds in the region. Wind fields during those peak episodes revealed no specific direction for the majority of the toluene plumes but the ethyl acetate plumes arrived at the site when winds were from the Southwest or West. The PTR-MS measurements combined with other VOC measuring techniques at the field site as well as VOC measurements conducted in other areas of the Mexico City Metropolitan Area (MCMA) will help to develop a better understanding of the spatial pattern of VOCs and its variability in the MCMA.

  2. Calibration and intercomparison of acetic acid measurements using proton transfer reaction mass spectrometry (PTR-MS)

    Science.gov (United States)

    Haase, K.B.; Keene, W.C.; Pszenny, A.A.P.; Mayne, H.R.; Talbot, R.W.; Sive, B.C.

    2012-01-01

    Acetic acid is one of the most abundant organic acids in the ambient atmosphere, with maximum mixing ratios reaching into the tens of parts per billion by volume (ppbv) range. The identities and associated magnitudes of the major sources and sinks for acetic acid are poorly characterized, due in part to the limitation in available measurement techniques. This paper demonstrates that Proton Transfer Reaction Mass Spectrometry (PTR-MS) can reliably quantify acetic acid vapor in ambient air. Three different PTR-MS configurations were calibrated at low ppbv mixing ratios using permeation tubes, which yielded calibration factors between 7.0 and 10.9 normalized counts per second per ppbv (ncps ppbv−1) at a drift tube field strength of 132 townsend (Td). Detection limits ranged from 0.06 to 0.32 ppbv with dwell times of 5 s. These calibration factors showed negligible humidity dependence. Using the experimentally determined calibration factors, PTR-MS measurements of acetic acid during the International Consortium for Atmospheric Research on Transport and Transformation (ICARTT) campaign were validated against results obtained using Mist Chambers coupled with Ion Chromatography (MC/IC). An orthogonal least squares linear regression of paired data yielded a slope of 1.14 ± 0.06 (2σ), an intercept of 0.049 ± 20 (2σ) ppbv, and an R2 of 0.78. The median mixing ratio of acetic acid on Appledore Island, ME during the ICARTT campaign was 0.530 ± 0.025 ppbv with a minimum of 0.075 ± 0.004 ppbv, and a maximum of 3.555 ± 0.171 ppbv.

  3. Few-body semiclassical approach to nucleon transfer and emission reactions

    Directory of Open Access Journals (Sweden)

    Sultanov Renat A.

    2014-04-01

    Full Text Available A three-body semiclassical model is proposed to describe the nucleon transfer and emission reactions in a heavy-ion collision. In this model the two heavy particles, i.e. nuclear cores A1(ZA1, MA1 and A2(ZA2, MA2, move along classical trajectories R→1(t${{\\vec R}_1}\\left( t \\right$ and R→2(t${{\\vec R}_2}\\left( t \\right$ respectively, while the dynamics of the lighter neutron (n is considered from a quantum mechanical point of view. Here, Mi are the nucleon masses and Zi are the Coulomb charges of the heavy nuclei (i = 1, 2. A Faddeev-type semiclassical formulation using realistic paired nuclear-nuclear potentials is applied so that all three channels (elastic, rearrangement and break-up are described in a unified manner. In order to solve the time-dependent equations the Faddeev components of the total three-body wave-function are expanded in terms of the input and output channel target eigenfunctions. In the special case, when the nuclear cores are identical (A1 ≡ A2 and also the two-level approximation in the expansion over the target (subsystem functions is used, the time-dependent semiclassical Faddeev equations are resolved in an explicit way. To determine the realistic R→1(t${{\\vec R}_1}\\left( t \\right$ and R→2(t${{\\vec R}_2}\\left( t \\right$ trajectories of the nuclear cores, a self-consistent approach based on the Feynman path integral theory is applied.

  4. Heat transfer and pressure drop at single rods with three-dimensional roughnesses

    International Nuclear Information System (INIS)

    Meyer, L.

    1981-04-01

    The results from heat transfer and pressure drop measurements at five single rods with two types of three-dimensional roughnesses on four outer tubes are reported. The friction factors and Stanton numbers were tranformed to the boundary conditions of the rough wall by different methods. A new simple method to transform the Stanton number is proposed. Stanton numbers measured in different outer tubes, transformed to a common flow cross section are a function of the wall Reynolds number only. The tested three-dimensional roughnesses showed considerably higher thermal performances than two-dimensional roughnesses. (orig.) [de

  5. COBRA-SFS predictions of single assembly spent fuel heat transfer data

    International Nuclear Information System (INIS)

    Lombardo, N.J.; Michener, T.E.; Wheeler, C.L.; Rector, D.R.

    1986-04-01

    The study reported here is one of several efforts to evaluate and qualify the COBRA-SFS computer code for use in spent fuel storage system thermal analysis. The ability of COBRA-SFS to predict the thermal response of two single assembly spent fuel heat transfer tests was investigated through comparisons of predictions with experimental test data. From these comparisons, conclusions regarding the computational treatment of the physical phenomena occurring within a storage system can be made. This objective was successfully accomplished as reasonable agreement between predictions and data were obtained for the 21 individual test cases of the two experiments

  6. Production of neutron-rich nuclides in the vicinity of N = 126 shell closure in multinucleon transfer reactions

    Directory of Open Access Journals (Sweden)

    Karpov Alexander

    2017-01-01

    Full Text Available Multinucleon transfer in low-energy nucleus-nucleus collisions is widely discussed as a method of production of yet-unknown neutron-rich nuclei hardly accessible (or inaccessible by other methods. Modeling of complicated dynamics of nuclear reactions induced by heavy ions is done within a multidimensional dynamical model of nucleus-nucleus collisions based on the Langevin equations. The model gives a continuous description of the system evolution starting from the well-separated target and projectile in the entrance channel of the reaction up to the formation of final reaction products. In this paper, rather recent sets of experimental data for the 136Xe+198Pt,208Pb reactions are analyzed together with the production cross sections for neutron-rich nuclei in the vicinity of the N = 126 magic shell.

  7. Tunable differentiation of tertiary C-H bonds in intramolecular transition metal-catalyzed nitrene transfer reactions.

    Science.gov (United States)

    Corbin, Joshua R; Schomaker, Jennifer M

    2017-04-13

    Metal-catalyzed nitrene transfer reactions are an appealing and efficient strategy for accessing tetrasubstituted amines through the direct amination of tertiary C-H bonds. Traditional catalysts for these reactions rely on substrate control to achieve site-selectivity in the C-H amination event; thus, tunability is challenging when competing C-H bonds have similar steric or electronic features. One consequence of this fact is that the impact of catalyst identity on the selectivity in the competitive amination of tertiary C-H bonds has not been well-explored, despite the potential for progress towards predictable and catalyst-controlled C-N bond formation. In this communication, we report investigations into tunable and site-selective nitrene transfers between tertiary C(sp 3 )-H bonds using a combination of transition metal catalysts, including complexes based on Ag, Mn, Rh and Ru. Particularly striking was the ability to reverse the selectivity of nitrene transfer by a simple change in the identity of the N-donor ligand supporting the Ag(i) complex. The combination of our Ag(i) catalysts with known Rh 2 (ii) complexes expands the scope of successful catalyst-controlled intramolecular nitrene transfer and represents a promising springboard for the future development of intermolecular C-H N-group transfer methods.

  8. Nonadiabatic rate constants for proton transfer and proton-coupled electron transfer reactions in solution: Effects of quadratic term in the vibronic coupling expansion

    International Nuclear Information System (INIS)

    Soudackov, Alexander V.; Hammes-Schiffer, Sharon

    2015-01-01

    Rate constant expressions for vibronically nonadiabatic proton transfer and proton-coupled electron transfer reactions are presented and analyzed. The regimes covered include electronically adiabatic and nonadiabatic reactions, as well as high-frequency and low-frequency proton donor-acceptor vibrational modes. These rate constants differ from previous rate constants derived with the cumulant expansion approach in that the logarithmic expansion of the vibronic coupling in terms of the proton donor-acceptor distance includes a quadratic as well as a linear term. The analysis illustrates that inclusion of this quadratic term in the framework of the cumulant expansion framework may significantly impact the rate constants at high temperatures for proton transfer interfaces with soft proton donor-acceptor modes that are associated with small force constants and weak hydrogen bonds. The effects of the quadratic term may also become significant in these regimes when using the vibronic coupling expansion in conjunction with a thermal averaging procedure for calculating the rate constant. In this case, however, the expansion of the coupling can be avoided entirely by calculating the couplings explicitly for the range of proton donor-acceptor distances sampled. The effects of the quadratic term for weak hydrogen-bonding systems are less significant for more physically realistic models that prevent the sampling of unphysical short proton donor-acceptor distances. Additionally, the rigorous relation between the cumulant expansion and thermal averaging approaches is clarified. In particular, the cumulant expansion rate constant includes effects from dynamical interference between the proton donor-acceptor and solvent motions and becomes equivalent to the thermally averaged rate constant when these dynamical effects are neglected. This analysis identifies the regimes in which each rate constant expression is valid and thus will be important for future applications to proton

  9. Nonadiabatic rate constants for proton transfer and proton-coupled electron transfer reactions in solution: Effects of quadratic term in the vibronic coupling expansion.

    Science.gov (United States)

    Soudackov, Alexander V; Hammes-Schiffer, Sharon

    2015-11-21

    Rate constant expressions for vibronically nonadiabatic proton transfer and proton-coupled electron transfer reactions are presented and analyzed. The regimes covered include electronically adiabatic and nonadiabatic reactions, as well as high-frequency and low-frequency proton donor-acceptor vibrational modes. These rate constants differ from previous rate constants derived with the cumulant expansion approach in that the logarithmic expansion of the vibronic coupling in terms of the proton donor-acceptor distance includes a quadratic as well as a linear term. The analysis illustrates that inclusion of this quadratic term in the framework of the cumulant expansion framework may significantly impact the rate constants at high temperatures for proton transfer interfaces with soft proton donor-acceptor modes that are associated with small force constants and weak hydrogen bonds. The effects of the quadratic term may also become significant in these regimes when using the vibronic coupling expansion in conjunction with a thermal averaging procedure for calculating the rate constant. In this case, however, the expansion of the coupling can be avoided entirely by calculating the couplings explicitly for the range of proton donor-acceptor distances sampled. The effects of the quadratic term for weak hydrogen-bonding systems are less significant for more physically realistic models that prevent the sampling of unphysical short proton donor-acceptor distances. Additionally, the rigorous relation between the cumulant expansion and thermal averaging approaches is clarified. In particular, the cumulant expansion rate constant includes effects from dynamical interference between the proton donor-acceptor and solvent motions and becomes equivalent to the thermally averaged rate constant when these dynamical effects are neglected. This analysis identifies the regimes in which each rate constant expression is valid and thus will be important for future applications to proton

  10. Study of the 18F(p,α)15O reaction by transfer reaction for application to γ-ray emission from Novae

    International Nuclear Information System (INIS)

    Sereville, N. de

    2003-12-01

    The gamma emission from novae at/or below 511 keV is due to the annihilation of the positrons produced in the beta + decay of F 18 . The interpretation of this emission through observations made by the Integral satellite for instance, requires a good knowledge of F 18 nucleosynthesis. The reaction rate of the F 18 (p,α)O 15 is the least known because of 2 resonances corresponding to the levels 6.419 and 6.449 MeV of Ne 19 whose proton widths are completely unknown. We have determined these proton widths via the study of one-nucleon transfer reaction D(F 18 ,pα)N 15 populating equivalent levels in F 19 . We have used a 14 MeV F 18 radioactive beam on a CD 2 target for inverse kinematics studies and the multi-track silicon detector LEDA. A DWBA (Distorted Wave Bound Approximation) has enabled us to determine the proton width of both resonances and has showed that they have an impact in the calculation of the reaction rate. A thorough study of the remaining uncertainties of the reaction rate has been undertaken, particularly for those concerning interferences between these resonances and a higher resonance of Ne 19 . The reaction rate that we have obtained is very similar to the previous rate used but now it rests on a more solid basis

  11. Measurement of adenosine triphosphate (ATP) content in single red blood cells using the firefly bioluminescent reaction

    Energy Technology Data Exchange (ETDEWEB)

    Kostuk, R.K.; Muhs, A.G.; Kirkpatrick, F.H.; Gabel, C.W.

    1977-01-01

    A unique optical instrument is described which uses the firefly bioluminscent reaction to measure adenosine triphosphate (ATP) levels in single red blood cells. The method allows chemical content level to be associated with individual cell features. The optical instrument consists of a phase contrast microscope to view cells, a pulsed argon-ion laser to rupture the cell membrane, and a photon counting system to measure the bioluminescent yield. The technique has been calibrated against a standard ATP measurement using bulk analysis methods. The ATP loss mechanism for blood cells in a controlled depletion experiment was also investigated.

  12. Single blastocyst transfer after ICSI from ejaculate spermatozoa, percutaneous epididymal sperm aspiration (PESA) or testicular sperm extraction (TESE)

    OpenAIRE

    Nilsson, Staffan; Waldenström, Urban; Engström, Ann-Britt; Hellberg, Dan

    2007-01-01

    Purpose: To investigate the outcome of IVF following intracytoplasmic sperm injection (ICSI) from ejaculate, percutaneous epididymal sperm aspiration (PESA) and testicular sperm extraction (TESE), with subsequent blastocyst culture and single blastocyst transfer.

  13. On the prediction of single-phase forced convection heat transfer in narrow rectangular channels

    International Nuclear Information System (INIS)

    Ghione, Alberto; Noel, Brigitte; Vinai, Paolo; Demazière, Christophe

    2014-01-01

    In this paper, selected heat transfer correlations for single-phase forced convection are assessed for the case of narrow rectangular channels. The work is of interest in the thermal-hydraulic analysis of the Jules Horowitz Reactor (JHR), which is a research reactor under construction at CEA-Cadarache (France). In order to evaluate the validity of the correlations, about 300 tests from the SULTAN-JHR database were used. The SULTAN-JHR program was carried out at CEA-Grenoble and it includes different kinds of tests for two different vertical rectangular channels with height of 600 mm and gap of 1.51 and 2.16 mm. The experimental conditions range between 2 - 9 bar for the pressure; 0.5 - 18 m/s for the coolant velocity and 0.5 - 7.5 MW/m 2 for the heat flux (whose axial distribution is uniform). Forty-two thermocouples and eight pressure taps were placed at several axial locations, measuring wall temperature and pressure respectively. The analysis focused on turbulent flow with Reynolds numbers between 5.5 x 10 3 - 2.4 x 10 5 and Prandtl numbers between 1.5 - 6. It was shown that standard correlations as the Dittus-Boelter and Seider-Tate significantly under-estimate the heat transfer coefficient, especially at high Reynolds number. Other correlations specifically designed for narrow rectangular channels were also taken into account and compared. The correlation of Popov-Petukhov in the form suggested by Siman-Tov still under-estimates the heat transfer coefficient, even if slight improvements could be seen. A better agreement for the tests with gap equal to 2.16 mm could be found with the correlation of Ma and the one of Liang. However the heat transfer coefficient when the gap is equal to 1.51 mm could not be predicted accurately. Furthermore these correlations were based on data at low Reynolds numbers (up to 13000) and low heat flux, so the use of them for SULTAN-JHR may be questionable. According to the authors’ knowledge, existing models of heat transfer

  14. Mass transfer and chemical reaction in gas-liquid-liquid systems

    NARCIS (Netherlands)

    Brilman, Derk Willem Frederik

    1998-01-01

    Gas-liquid-liquid reaction systems may be encountered in several important fields of application as e.g. hydroformylation, alkylation, carboxylation, polymerisation, hydrometallurgy, biochemical processes and fine chemicals manufacturing. However, the reaction engineering aspects of these systems

  15. Electron transfer behaviour of biological macromolecules towards the single-molecule level

    DEFF Research Database (Denmark)

    Zhang, Jingdong; Grubb, Mikala; Hansen, Allan Glargaard

    2003-01-01

    electron transfer (ET) function retained. In situ STM can also address the microscopic mechanisms for electron tunnelling through the biomolecules and offers novel notions such as coherent multi-ET between the substrate and tip via the molecular redox levels. This differs in important respects from...... is combined with state-of-the-art physical electrochemistry with emphasis on single-crystal, atomically planar electrode surfaces, in situ scanning tunnelling microscopy (STM) and other surface techniques. These approaches have brought bioelectrochemistry important steps forward towards the nanoscale...... electrochemical ET at a single metal/electrolyte interface. Similar data for a short oligonucleotide immobilized on Au(111) show that oligonucleotides can be characterized with comparable detail, with novel perspectives for addressing DNA electronic conduction mechanisms and for biological screening towards...

  16. Preparation, Single-Molecule Manipulation, and Energy Transfer Investigation of a Polyfluorene-graft-DNA polymer.

    Science.gov (United States)

    Madsen, Mikael; Christensen, Rasmus S; Krissanaprasit, Abhichart; Bakke, Mette R; Riber, Camilla F; Nielsen, Karina S; Zelikin, Alexander N; Gothelf, Kurt V

    2017-08-04

    Conjugated polymers have been intensively studied due to their unique optical and electronic properties combined with their physical flexibility and scalable bottom up synthesis. Although the bulk qualities of conjugated polymers have been extensively utilized in research and industry, the ability to handle and manipulate conjugated polymers at the nanoscale lacks significantly behind. Here, the toolbox for controlled manipulation of conjugated polymers was expanded through the synthesis of a polyfluorene-DNA graft-type polymer (poly(F-DNA)). The polymer possesses the characteristics associated with the conjugated polyfluorene backbone, but the protruding single-stranded DNA provides the material with an exceptional addressability. This study demonstrates controlled single-molecule patterning of poly(F-DNA), as well as energy transfer between two different polymer-DNA conjugates. Finally, highly efficient DNA-directed quenching of polyfluorene fluorescence was shown. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Analysis of the Ballot Shuffling Attack on Irish ballot counting for Proportional Representation by Single Transferable Vote (PR-STV)

    DEFF Research Database (Denmark)

    Cochran, Dermot Robert

    2015-01-01

    The current Irish legislation for counting of ballots does not fully comply with the true meaning of proportional representation by single transferable vote. This is due to the way in which second and subsequent transfers are handled, the legislative requirement to only count the last set of ball...

  18. Single phase flow pressure drop and heat transfer in rectangular metallic microchannels

    International Nuclear Information System (INIS)

    Sahar, Amirah M.; Özdemir, Mehmed R.; Fayyadh, Ekhlas M.; Wissink, Jan; Mahmoud, Mohamed M.; Karayiannis, Tassos G.

    2016-01-01

    Numerical simulations were performed using Fluent 14.5 to investigate single phase flow and conjugate heat transfer in copper rectangular microchannels. Two different configurations were simulated: (1) single channel with hydraulic diameter of 0.561 mm and (2) multichannel configuration consisting of inlet and outlet manifolds and 25 channels with hydraulic diameter of 0.409 mm. In the single channel configuration, four numerical models were investigated namely, 2D thin-wall, 3D thin-wall (heated from the bottom), 3D thin-wall (three side heated) and 3D full conjugate models. In the multichannel configuration, only 3D full conjugate model was used. The simulation results of the single channel configuration were validated using experimental data of water as a test fluid while the results of the multichannel configuration were validated using experimental data of R134a refrigerant. In the multichannel configuration, flow distribution among the channels was also investigated. The 3D thin-wall model simulation was conducted at thermal boundary conditions similar to those assumed in the experimental data reduction (uniform heat flux) and showed excellent agreement with the experimental data. However, the results of the 3D full conjugate model demonstrated that there is a significant conjugate effect and the heat flux is not uniformly distributed along the channel resulting in significant deviation compared to the experimental data (more than 50%). Also, the results demonstrated that there is a significant difference between the 3D thin-wall and full conjugate models. The simulation of the multichannel configuration with an inlet manifold having gradual decrease in cross sectional area achieved very reasonable uniform flow distribution among the channels which will provide uniform heat transfer rates across the base of the microchannels.

  19. Thermally reversible single-crystal to single-crystal transformation of mononuclear to dinuclear Zn(II) complexes by [2+2] cycloaddition reaction.

    Science.gov (United States)

    Medishetty, Raghavender; Yap, Terence Teck Sheng; Koh, Lip Lin; Vittal, Jagadese J

    2013-10-25

    Two Zn(II) complexes of trans-4-styrylpyridine ligands undergo [2+2] cycloaddition reaction forming Zn(II) complex dimers in a single-crystal to single-crystal (SCSC) manner which were thermally reversible. The dimers are presumed to be the stable intermediates in the formation of 1D coordination polymers upon prolonged exposure to UV light.

  20. Large work function difference driven electron transfer from electrides to single-walled carbon nanotubes

    KAUST Repository

    Menamparambath, Mini Mol

    2014-06-23

    A difference in work function plays a key role in charge transfer between two materials. Inorganic electrides provide a unique opportunity for electron transfer since interstitial anionic electrons result in a very low work function of 2.4-2.6 eV. Here we investigated charge transfer between two different types of electrides, [Ca2N]+·e- and [Ca 24Al28O64]4+·4e-, and single-walled carbon nanotubes (SWNTs) with a work function of 4.73-5.05 eV. [Ca2N]+·e- with open 2-dimensional electron layers was more effective in donating electrons to SWNTs than closed cage structured [Ca24Al28O64] 4+·4e- due to the higher electron concentration (1.3 × 1022 cm-3) and mobility (∼200 cm 2 V-1 s-1 at RT). A non-covalent conjugation enhanced near-infrared fluorescence of SWNTs as high as 52%. The field emission current density of electride-SWNT-silver paste dramatically increased by a factor of 46000 (14.8 mA cm-2) at 2 V μm-1 (3.5 wt% [Ca2N]+·e-) with a turn-on voltage of 0.85 V μm-1. This journal is © the Partner Organisations 2014.

  1. Ligand-tailored single-site silica supported titanium catalysts: Synthesis, characterization and towards cyanosilylation reaction

    International Nuclear Information System (INIS)

    Xu, Wei; Li, Yani; Yu, Bo; Yang, Jindou; Zhang, Ying; Chen, Xi; Zhang, Guofang; Gao, Ziwei

    2015-01-01

    A successive anchoring of Ti(NMe 2 ) 4 , cyclopentadiene and a O-donor ligand, 1-hydroxyethylbenzene (PEA), 1,1′-bi-2-naphthol (Binol) or 2,3-dihydroxybutanedioic acid diethyl ester (Tartrate), on silica was conducted by SOMC strategy in moderate conditions. The silica, monitored by in-situ Fourier transform infrared spectroscopy (in-situ FT-IR), was pretreated at different temperatures (200, 500 and 800 °C). The ligand tailored silica-supported titanium complexes were characterized by in-situ FT-IR, 13 C CP MAS-NMR, X-ray photoelectron spectroscopy (XPS), X-ray absorption near edge structure (XANES) and elemental analysis in detail, verifying that the surface titanium species are single sited. The catalytic activity of the ligand tailored single-site silica supported titanium complexes was evaluated by a cyanosilylation of benzaldehyde. The results showed that the catalytic activity is dependent strongly on the dehydroxylation temperatures of silica and the configuration of the ligands. - Graphical abstract: The ligand-tailored silica supported “single site” titanium complexes were synthesized by SOMC strategy and fully characterized. Their catalytic activity were evaluated by benzaldehyde silylcyanation. - Highlights: • Single-site silica supported Ti active species was prepared by SOMC technique. • O-donor ligand tailored Ti surface species was synthesized. • The surface species was characterized by XPS, 13 C CP-MAS NMR, XANES etc. • Catalytic activity of the Ti active species in silylcyanation reaction was evaluated

  2. Detection of nerve agents using proton transfer reaction mass spectrometry with ammonia as reagent gas.

    Science.gov (United States)

    Ringer, Joachim M

    2013-01-01

    The chemical warfare agents (CWA) Sarin, Soman, Cyclosarin and Tabun were characterised by proton transfer mass spectrometry (PTRMS). It was found that PTRMS is a suitable technique to detect nerve agents highly sensitively, highly selectively and in near real-time. Methods were found to suppress molecule fragmentation which is significant under PTRMS hollow cathode ionisation conditions. In this context, the drift voltage (as one of the most important system parameters) was varied and ammonia was introduced as an additional chemical reagent gas. Auxiliary chemicals such as ammonia affect ionisation processes and are quite common in context with detectors for CWAs based on ion mobility spectrometry (IMS). With both, variation of drift voltage and ammonia as the reagent gas, fragmentation can be suppressed effectively. Suppression of fragmentation is crucial particularly concerning the implementation of an algorithm for automated agent identification in field applications. On the other hand, appearance of particular fragments might deliver additional information. Degradation and rearrangement products of nerve agents are not distinctive for the particular agent but for the chemical class they belong to. It was found that switching between ammonia doped and ordinary water ionisation chemistry can easily be performed within a few seconds. Making use of this effect it is possible to switch between fragment and molecular ion peak spectra. Thus, targeted fragmentation can be used to confirm identification based only on single peak detection. PTRMS turned out to be a promising technique for future CWA detectors. In terms of sensitivity, response time and selectivity (or confidence of identification, respectively) PTRMS performs as a bridging technique between IMS and GC-MS.

  3. Exploiting the tetrazine-norbornene reaction for single polymer chain collapse

    Science.gov (United States)

    Hansell, Claire F.; Lu, Annhelen; Patterson, Joseph P.; O'Reilly, Rachel K.

    2014-03-01

    Single chain polymer nanoparticles (SCNPs) have been formed using polystyrenes decorated with pendent norbornenes and a bifunctional tetrazine crosslinker. Characterisation by size exclusion chromatography and 1H NMR gives evidence for the formation of SCNPs by the tetrazine-norbornene reaction, whilst light scattering, neutron scattering, transmission electron microscopy and atomic force microscopy show that discrete well-defined nanoparticles are formed and their size in solution calculated.Single chain polymer nanoparticles (SCNPs) have been formed using polystyrenes decorated with pendent norbornenes and a bifunctional tetrazine crosslinker. Characterisation by size exclusion chromatography and 1H NMR gives evidence for the formation of SCNPs by the tetrazine-norbornene reaction, whilst light scattering, neutron scattering, transmission electron microscopy and atomic force microscopy show that discrete well-defined nanoparticles are formed and their size in solution calculated. Electronic supplementary information (ESI) available: Further synthetic detail, 1H and 13C NMR spectra, control experiments, TEM images, SANS and DLS data. See DOI: 10.1039/c3nr06706h

  4. Microfluidic Fabrication of Porous Polymer Microspheres: Dual Reactions in Single Droplets

    KAUST Repository

    Gong, Xiuqing

    2009-06-16

    We report the microfluidic fabrication of macroporous polymer microspheres via the simultaneous reactions within single droplets, induced by LTV irradiation. The aqueous phase of the reaction is the decomposition of H 2O2 to yield oxygen, whereas the organic phase is the polymerization of NO A 61, ethylene glycol dimethacrylate (EGDMA), and tri (propylene glycol) diacrylate (TPGDA) precursors. We first used a liquid polymer precursor to encapsulate a multiple number of magnetic Fe3O 4 colloidal suspension (MCS) droplets in a core-shell structure, for the purpose of studying the number of such encapsulated droplets that can be reliably controlled through the variation of flow rates. It was found that the formation of one shell with one, two, three, or more encapsulated droplets is possible. Subsequently, the H2O2 solution was encapsulated in the same way, after which we investigated its decomposition under UV irradiation, which simultaneously induces the polymerization of the encapsulating shell. Because the H2O2 decomposition leads to the release of oxygen, porous microspheres were obtained from a combined H2O2 decomposition/polymer precursor polymerization reaction. The multiplicity of the initially encapsulated H2O 2 droplets ensures the homogeneous distribution of the pores. The pores inside the micrometer-sized spheres range from several micrometers to tens of micrometers, and the maximum internal void volume fraction can attain 70%, similar to that of high polymerized high internal phase emulsion (polyHIPE). © 2009 American Chemical Society.

  5. Study of breakup and transfer of weakly bound nucleus 6Li to explore the low energy reaction dynamics

    Directory of Open Access Journals (Sweden)

    Zhang G. L.

    2017-01-01

    In order to have a proper understanding of the influence of breakup and transfer of weakly bound projectiles on the fusion process, we performed the 6Li+89Y experiment with incident energies of 22 MeV and 34 MeV on Galileo array in cooperation with Si-ball EUCLIDES at Legnaro National Laboratory (LNL in Italy. Using particle-particle and particle-γ coincidences, the different reaction mechanisms can be clearly explored.

  6. Flow film boiling heat transfer for subcooled liquids flowing upward perpendicular to single horizontal cylinders

    International Nuclear Information System (INIS)

    Liu, Q.S.; Shiotsu, M.; Sakurai, A.

    2001-01-01

    The knowledge of flow film boiling heat transfer on a horizontal cylinder in various liquids flowing upward perpendicular to the cylinder is important as the database for the safety evaluation of the accidents such as rapid power burst and pressure reduction in the nuclear power plants. Flow film boiling heat transfer from single horizontal cylinders in water and Freon-113 flowing upward perpendicular to the cylinder under subcooled conditions was measured under wide experimental conditions. The flow velocities ranged from 0 to 1 m/s, the system pressures ranged from 100 to 500 kPa, and the surface superheats were raised up to 800 K for water and 400 K for Freon-113, respectively. Platinum horizontal cylinders with diameters ranging from 0.7 to 5 mm were used as the test heaters. The test heater was heated by direct electric current. The experimental data of film boiling heat transfer coefficients show that they increase with the increase of flow velocity, liquid subcooling, system pressure and with the decrease of cylinder diameter. Based on the experimental data, a correlation for subcooled flow film boiling heat transfer including the effects of liquid subcooling and radiation was presented, which can describe the experimental data obtained within 20% for the flow velocities below 0.7 m/s, and within -30% to +20% for the higher flow velocities. The correlation also predicted well the data by Shigechi (1983), Motte and Bromley (1957), and Sankaran and Witte (1990) obtained for the larger diameter cylinders and higher flow velocities in various liquids at the pressures of near atmospheric. The Shigechi's data were in the range from about -20% to +15%, the data of Motte and Bromley were about 30%,and the data of Sankaran and Witte were within +20 % of the curves given by the corresponding predicted values. (authors)

  7. Efficient and Adaptive Methods for Computing Accurate Potential Surfaces for Quantum Nuclear Effects: Applications to Hydrogen-Transfer Reactions.

    Science.gov (United States)

    DeGregorio, Nicole; Iyengar, Srinivasan S

    2018-01-09

    We present two sampling measures to gauge critical regions of potential energy surfaces. These sampling measures employ (a) the instantaneous quantum wavepacket density, an approximation to the (b) potential surface, its (c) gradients, and (d) a Shannon information theory based expression that estimates the local entropy associated with the quantum wavepacket. These four criteria together enable a directed sampling of potential surfaces that appears to correctly describe the local oscillation frequencies, or the local Nyquist frequency, of a potential surface. The sampling functions are then utilized to derive a tessellation scheme that discretizes the multidimensional space to enable efficient sampling of potential surfaces. The sampled potential surface is then combined with four different interpolation procedures, namely, (a) local Hermite curve interpolation, (b) low-pass filtered Lagrange interpolation, (c) the monomial symmetrization approximation (MSA) developed by Bowman and co-workers, and (d) a modified Shepard algorithm. The sampling procedure and the fitting schemes are used to compute (a) potential surfaces in highly anharmonic hydrogen-bonded systems and (b) study hydrogen-transfer reactions in biogenic volatile organic compounds (isoprene) where the transferring hydrogen atom is found to demonstrate critical quantum nuclear effects. In the case of isoprene, the algorithm discussed here is used to derive multidimensional potential surfaces along a hydrogen-transfer reaction path to gauge the effect of quantum-nuclear degrees of freedom on the hydrogen-transfer process. Based on the decreased computational effort, facilitated by the optimal sampling of the potential surfaces through the use of sampling functions discussed here, and the accuracy of the associated potential surfaces, we believe the method will find great utility in the study of quantum nuclear dynamics problems, of which application to hydrogen-transfer reactions and hydrogen

  8. Fission fragments mass distributions of nuclei populated by the multinucleon transfer channels of the 18O+232Th reaction

    Directory of Open Access Journals (Sweden)

    R. Léguillon

    2016-10-01

    Full Text Available It is shown that the multinucleon transfer reactions is a powerful tool to study fission of exotic neutron-rich actinide nuclei, which cannot be accessed by particle-capture or heavy-ion fusion reactions. In this work, multinucleon transfer channels of the 18O+232Th reaction are used to study fission of fourteen nuclei 231,232,233,234Th, 232,233,234,235,236Pa, and 234,235,236,237,238U. Identification of fissioning nuclei and of their excitation energy is performed on an event-by-event basis, through the measurement of outgoing ejectile particle in coincidence with fission fragments. Fission fragment mass distributions are measured for each transfer channel, in selected bins of excitation energy. In particular, the mass distributions of 231,234Th and 234,235,236Pa are measured for the first time. Predominantly asymmetric fission is observed at low excitation energies for all studied cases, with a gradual increase of the symmetric mode towards higher excitation energy. The experimental distributions are found to be in general agreement with predictions of the fluctuation–dissipation model.

  9. Study of the reaction of astrophysical interest 60Fe(n,γ)61Fe via (d,pγ) transfer reaction

    International Nuclear Information System (INIS)

    Giron, S.

    2011-12-01

    60 Fe is of special interest in nuclear astrophysics. Indeed the recent observations of 60 Fe characteristic gamma-ray lines by the RHESSI and INTEGRAL spacecrafts allowed to measure the total flux of 60 Fe over the Galaxy. Moreover the observation in presolar grains of an excess of the daughter-nuclei of 60 Fe, 60 Ni, gives constraints on the conditions of formation of the early solar system. However, the cross-sections of some reactions involved in 60 Fe nucleosynthesis and included to stellar models are still uncertain. The destruction reaction of 60 Fe, 60 Fe(n, γ) 61 Fe, is one of them. The total cross-section can be separate into two contributions: the direct one, involving states below the neutron separation threshold of 61 Fe, and the resonant one.We improved 61 Fe spectroscopy in order to evaluate the direct capture part of the 60 Fe(n, γ) 61 Fe reaction cross-section. 60 Fe(n, γ) 61 Fe was thus studied via d( 60 Fe, pγ) 61 Fe transfer reaction with the CATS/MUST2/EXOGAM setup at LISE-GANIL. DWBA analysis of experimental proton differential cross-sections allowed to extract orbital angular momentum and spectroscopic factors of different populated states identified below the neutron threshold. A comparison of experimental results for 61 Fe with experimental results for similar nuclei and with shell-model calculations was also performed. (author) [fr

  10. Mixed quantum classical calculation of proton transfer reaction rates: from deep tunneling to over the barrier regimes.

    Science.gov (United States)

    Xie, Weiwei; Xu, Yang; Zhu, Lili; Shi, Qiang

    2014-05-07

    We present mixed quantum classical calculations of the proton transfer (PT) reaction rates represented by a double well system coupled to a dissipative bath. The rate constants are calculated within the so called nontraditional view of the PT reaction, where the proton motion is quantized and the solvent polarization is used as the reaction coordinate. Quantization of the proton degree of freedom results in a problem of non-adiabatic dynamics. By employing the reactive flux formulation of the rate constant, the initial sampling starts from the transition state defined using the collective reaction coordinate. Dynamics of the collective reaction coordinate is treated classically as over damped diffusive motion, for which the equation of motion can be derived using the path integral, or the mixed quantum classical Liouville equation methods. The calculated mixed quantum classical rate constants agree well with the results from the numerically exact hierarchical equation of motion approach for a broad range of model parameters. Moreover, we are able to obtain contributions from each vibrational state to the total reaction rate, which helps to understand the reaction mechanism from the deep tunneling to over the barrier regimes. The numerical results are also compared with those from existing approximate theories based on calculations of the non-adiabatic transmission coefficients. It is found that the two-surface Landau-Zener formula works well in calculating the transmission coefficients in the deep tunneling regime, where the crossing point between the two lowest vibrational states dominates the total reaction rate. When multiple vibrational levels are involved, including additional crossing points on the free energy surfaces is important to obtain the correct reaction rate using the Landau-Zener formula.

  11. Final Report: The Impact of Carbonate on Surface Protonation, Electron Transfer and Crystallization Reactions in Iron Oxide Nanoparticles and Colloids

    Energy Technology Data Exchange (ETDEWEB)

    Dixon, David Adams [The University of Alabama

    2013-07-02

    This project addresses key issues of importance in the geochemical behavior of iron oxides and in the geochemical cycling of carbon and iron. For Fe, we are specifically studying the influence of carbonate on electron transfer reactions, solid phase transformations, and the binding of carbonate to reactive sites on the edges of particles. The emphasis on carbonate arises because it is widely present in the natural environment, is known to bind strongly to oxide surfaces, is reactive on the time scales of interest, and has a speciation driven by acid-base reactions. The geochemical behavior of carbonate strongly influences global climate change and CO{sub 2} sequestration technologies. Our goal is to answer key questions with regards to specific site binding, electron transfer reactions, and crystallization reactions of iron oxides that impact both the geochemical cycling of iron and CO{sub 2} species. Our work is focused on the molecular level description of carbonate chemistry in solution including the prediction of isotope fractionation factors. We have also done work on critical atmospheric species.

  12. Structure and Reactions of 11Be: Many-Body Basis for Single-Neutron Halo

    Science.gov (United States)

    Barranco, F.; Potel, G.; Broglia, R. A.; Vigezzi, E.

    2017-08-01

    The exotic nucleus 11Be has been extensively studied and much experimental information is available on the structure of this system. We treat, within the framework of renormalized nuclear field theory in both configuration and 3D space, the mixing of bound and continuum single-particle states through the coupling to collective vibrations of the 10Be core. We also take care of the Pauli principle acting not only between the single valence particle explicitly considered and those participating in the collective states, but also between fermions involved in two-phonon virtual states dressing the single-particle motion. In this way, it is possible to simultaneously and quantitatively account for the energies of the 1 /2+ , 1 /2- low-lying states, the centroid and line shape of the 5 /2+ resonance and the one-nucleon stripping and pickup absolute differential cross sections involving 11Be as either target or residual nucleus. Also for the dipole transition connecting the 1 /2+ and 1 /2- parity inverted levels as well as the isotopic shift of the charge radius. Theory provides a unified and exhaustive nuclear structure and reaction characterization of the many-body effects which are at the basis of this paradigmatic one-neutron halo system.

  13. Single cell genomics indicates horizontal gene transfer and viral infections in a deep subsurface Firmicutes population

    Directory of Open Access Journals (Sweden)

    Jessica eLabonté

    2015-04-01

    Full Text Available A major fraction of Earth's prokaryotic biomass dwells in the deep subsurface, where cellular abundances per volume of sample are lower, metabolism is slower, and generation times are longer than those in surface terrestrial and marine environments. How these conditions impact biotic interactions and evolutionary processes is largely unknown. Here we employed single cell genomics to analyze cell-to-cell genome content variability and signatures of horizontal gene transfer (HGT and viral infections in five cells of Candidatus Desulforudis audaxviator, which were collected from a three km-deep fracture water in the 2.9 Ga-old Witwatersrand Basin of South Africa. Between 0 and 32 % of genes recovered from single cells were not present in the original, metagenomic assembly of Desulforudis, which was obtained from a neighboring subsurface fracture. We found a transposable prophage, a retron, multiple clustered regularly interspaced short palindromic repeats (CRISPRs and restriction-modification systems, and an unusually high frequency of transposases in the analyzed single cell genomes. This indicates that recombination, HGT and viral infections are prevalent evolutionary events in the studied population of microorganisms inhabiting a highly stable deep subsurface environment.

  14. Experimental research on single-phase heat transfer characteristics in a vertical circular tube under marine conditions

    International Nuclear Information System (INIS)

    Du Sijia; Zhang Hong; Jia Baoshan

    2011-01-01

    Experiments have been conducted to study the heat transfer characteristics of single-phase forced circulation when the test tube was under different marine conditions. The experiments measured the wall temperature of test tube to calculate the heat transfer coefficients at different circumferential places. When the test tube was under inclined conditions, the heat transfer coefficient increased at downside and decreased at upside of test tube because of buoyancy effect. When the test tube was under rolling conditions, the heat transfer coefficients fluctuated with the rolling motions, and the Coriolis force dominated the heat transfer fluctuation during the rolling motion. CFD method was used to simulate the heat transfer phenomena under marine conditions, and the results were accord to the experimental phenomena. (authors)

  15. Charge-Transfer Reaction of Cediranib with 2,3-Dichloro- 3,5 ...

    African Journals Online (AJOL)

    CRB) and 2, 3 - dichloro-5, 6- dicyano -1, 4 - benzoquinone (DDQ) and employment of the reaction as a basis for the development of a novel 96 - microwell spectrophotometric assay for CRB. Method: The reaction of CRB and DDQ was ...

  16. Propensity approach to nonequilibrium thermodynamics of a chemical reaction network: controlling single E-coli β-galactosidase enzyme catalysis through the elementary reaction steps.

    Science.gov (United States)

    Das, Biswajit; Banerjee, Kinshuk; Gangopadhyay, Gautam

    2013-12-28

    In this work, we develop an approach to nonequilibrium thermodynamics of an open chemical reaction network in terms of the elementary reaction propensities. The method is akin to the microscopic formulation of the dissipation function in terms of the Kullback-Leibler distance of phase space trajectories in Hamiltonian system. The formalism is applied to a single oligomeric enzyme kinetics at chemiostatic condition that leads the reaction system to a nonequilibrium steady state, characterized by a positive total entropy production rate. Analytical expressions are derived, relating the individual reaction contributions towards the total entropy production rate with experimentally measurable reaction velocity. Taking a real case of Escherichia coli β-galactosidase enzyme obeying Michaelis-Menten kinetics, we thoroughly analyze the temporal as well as the steady state behavior of various thermodynamic quantities for each elementary reaction. This gives a useful insight in the relative magnitudes of various energy terms and the dissipated heat to sustain a steady state of the reaction system operating far-from-equilibrium. It is also observed that, the reaction is entropy-driven at low substrate concentration and becomes energy-driven as the substrate concentration rises.

  17. Time resolved investigations on biogenic trace gases exchanges using proton-transfer-reaction mass spectrometry

    International Nuclear Information System (INIS)

    Karl, T.

    2000-02-01

    Volatile organic compounds (VOCs) released from vegetation, including wound-induced VOCs, can have important effects on atmospheric chemistry. The analytical methods for measuring wound-induced VOCs, especially the hexenal family of VOCs (hexenals, hexenols and hexenyl esters) but also compounds like acetaldehyde, are complicated by their chemical instability and the transient nature of their formation after leaf and stem wounding. The goal of this thesis was to assess, quantify and complement our understanding on the origin of tropospheric VOCs. This thesis demonstrates that formation and emission of hexenal family compounds can be monitored on-line using proton-transfer-reaction mass spectrometry (PTR-MS), avoiding the need for preconcentration or chromatography. These measurements revealed the rapid emission of the parent compound, (Z)-3-hexenal, within 1-2 seconds of wounding of leaves from various woody and nonwoody plants, and its metabolites including (E)-2-hexenal, hexenols and hexenyl acetates. Emission of (Z)-3-hexenal from detached, drying leaves averaged 500 μg (gram dry weight)-1. PTR-MS showed to be a useful tool for the analysis of VOC emissions resulting from grazing, herbivory, harvesting and senescing leaves. The release of reactive VOCs during lawn mowing was observed in on-line ambient air measurements in July and August 1998 in the outskirts of Innsbruck. Also obtained were data on emission rates of reactive aldehydes (hexenyl compounds) and other abundant VOCs such as methanol, acetaldehyde and acetone from drying grass in various chamber experiments. Fluxes were measured after cutting of grass using eddy covariance measurements and the micrometeorological gradient method (Obhukov-Similarity-Method). Comparison of data obtained by these different methods showed satisfactory agreement. The highest fluxes for methanol during drying were 5 mg/m2h, for (Z)-3-hexenal 1.5 mg/m2h. Experiments conducted on the Sonnblick Observatory in Fall and Winter

  18. Salt-assisted clean transfer of continuous monolayer MoS2 film for hydrogen evolution reaction

    Science.gov (United States)

    Cho, Heung-Yeol; Nguyen, Tri Khoa; Ullah, Farman; Yun, Jong-Won; Nguyen, Cao Khang; Kim, Yong Soo

    2018-03-01

    The transfer of two-dimensional (2D) materials from one substrate to another is challenging but of great importance for technological applications. Here, we propose a facile etching and residue-free method for transferring a large-area monolayer MoS2 film continuously grown on a SiO2/Si by chemical vapor deposition. Prior to synthesis, the substrate is dropped with water- soluble perylene-3, 4, 9, 10-tetracarboxylic acid tetrapotassium salt (PTAS). The as-grown MoS2 on the substrate is simply dipped in water to quickly dissolve PTAS to yield the MoS2 film floating on the water surface, which is subsequently transferred to the desired substrate. The morphological, optical and X-ray photoelectron spectroscopic results show that our method is useful for fast and clean transfer of the MoS2 film. Specially, we demonstrate that monolayer MoS2 film transferred onto a conducting substrate leads to excellent performance for hydrogen evolution reaction with low overpotential (0.29 V vs the reversible hydrogen electrode) and Tafel slope (85.5 mV/decade).

  19. Leading coordinate analysis of reaction pathways in proton chain transfer: Application to a two-proton transfer model for the green fluorescent protein

    International Nuclear Information System (INIS)

    Wang Sufan; Smith, Sean C.

    2006-01-01

    The 'leading coordinate' approach to computing an approximate reaction pathway, with subsequent determination of the true minimum energy profile, is applied to a two-proton chain transfer model based on the chromophore and its surrounding moieties within the green fluorescent protein (GFP). Using an ab initio quantum chemical method, a number of different relaxed energy profiles are found for several plausible guesses at leading coordinates. The results obtained for different trial leading coordinates are rationalized through the calculation of a two-dimensional relaxed potential energy surface (PES) for the system. Analysis of the 2-D relaxed PES reveals that two of the trial pathways are entirely spurious, while two others contain useful information and can be used to furnish starting points for successful saddle-point searches. Implications for selection of trial leading coordinates in this class of proton chain transfer reactions are discussed, and a simple diagnostic function is proposed for revealing whether or not a relaxed pathway based on a trial leading coordinate is likely to furnish useful information

  20. Energy, Electron Transfer and Photocatalytic Reactions of Visible Light Absorbing Transition Metal Complexes

    Energy Technology Data Exchange (ETDEWEB)

    Schmehl, Russell H. [Tulane Univ., New Orleans, LA (United States)

    2016-03-02

    This is the final technical report for a project carried out at Tulane University of New Orleans that describes the development of light induced (solar) reactions geared toward decomposing water into its component elements : hydrogen and oxygen. Much of the work involved optimizing systems for absorbing visible light and undergoing light promoted reactions to generate very strong reducing agents that are capable of reacting with water to produce hydrogen. Additional portions of the research were collaborative efforts to put the strong reducing agents to work in reaction with hydrogen generation catalysts prepared elsewhere. Time resolved laser spectroscopic methods were used to evaluate the light induced reactions and characterize very reactive intermediate substances formed during the reactions.

  1. Determination of radiative capture cross-section for astrophysics from transfer reaction using radioactive ion beams

    CERN Document Server

    Beaumel, D

    2002-01-01

    Thermonuclear reactions are a source of stellar energy and play a crucial role for the nucleosynthesis in astrophysical sites. Among these reactions, the radiative capture process defined as: x + A -> B + gamma is a key reaction involved in all the basic astrophysical processes over the nuclear chart. In the case of the capture of charged particles like (p,gamma) reactions, cross-sections are strongly weakened due to the low incident energies as compared to the Coulomb barrier. Their measurement in laboratories is even more complicate when the capturing nucleus is radioactive, difficult or even impossible to be used as a target. Such radioactive nuclei are involved essentially in 'explosive' environments where capture reactions are fast enough to compete with the beta-decay process. Even in non-explosive situations, unstable nuclei are sometimes important as we shall see for the hydrogen burning in the sun. To circumvent the difficulties of direct measurements with radioactive nuclei, indirect methods have be...

  2. Electron transfer reactions of ruthenium(II) complexes with polyphenolic acids in micelles

    Energy Technology Data Exchange (ETDEWEB)

    Rajeswari, Angusamy [School of Chemistry, Madurai Kamaraj University, Madurai 625 021 (India); Department of Chemistry, Fatima College, Madurai 625 018 (India); Ramdass, Arumugam [School of Chemistry, Madurai Kamaraj University, Madurai 625 021 (India); Research Department of Chemistry, Aditanar College of Arts and Science, Tiruchendur 628 216 (India); Muthu Mareeswaran, Paulpandian [School of Chemistry, Madurai Kamaraj University, Madurai 625 021 (India); Department of Industrial Chemistry, Alagappa University, Karaikudi 630 003 (India); Rajagopal, Seenivasan, E-mail: rajagopalseenivasan@yahoo.com [School of Chemistry, Madurai Kamaraj University, Madurai 625 021 (India)

    2016-02-15

    The electron transfer in a microhetrogeneous system is a perfect mimic of biological electron transfer. The electron transfer between biologically important phenolic acids and ruthenium (II) complexes is systematically studied in the presence of anionic and cationic micelles. The photophysical properties of these ruthenium (II) complexes with anionic and cationic micelles and their binding abilities with these two type of micelles are also studies using absorption, emission and excited state lifetime spectral techniques. Pseudophase Ion Exchange (PIE) Model is applied to derive mechanism of electron transfer in two types of micelles. - Highlights: • Effect of microhetrogeneous system is studied using ruthenium (II) complexes and gallic acid is studied. • Pseudophase Ion exchange model is applied to derive the mechanism. • Binding constants are in the range of 10{sup 2}–10{sup 4} M{sup −1}.

  3. Effects of stimulus pair orientation and hand switching on reaction time estimates of interhemispheric transfer.

    Science.gov (United States)

    Leblanc-Sirois, Yanick; Braun, Claude M J; Elie-Fortier, Jonathan

    2018-03-26

    Two behavioral estimates of interhemispheric transfer time, the crossed-uncrossed difference (CUD) and the unilateral field advantage (UFA), are thought to, respectively, index transfer of premotor and visual information across the corpus callosum in neurotypical participants. However, no attempt to manipulate visual and motor contingencies in a set of tasks while measuring the CUD and the UFA has yet been reported. In two go/no-go comparison experiments, stimulus pair orientations were manipulated. The hand of response changed after each correct response in the second, but not the first experiment. No correlation was found between the CUD and the UFA, supporting the hypothesis that these two measures index different types of information transfer across hemispheres. An effect of manipulation of stimulus pair orientation on UFAs was attributed to the homotopy of callosal fibers transferring visual information, while an effect of hand switching on CUDs was attributed mostly to spatial compatibility.

  4. Single-Electron Transfer Living Radical Polymerization Platform to Practice, Develop, and Invent.

    Science.gov (United States)

    Lligadas, Gerard; Grama, Silvia; Percec, Virgil

    2017-10-09

    The most fundamental aspects of single-electron transfer (SET) principles are presented. They are discussed according to different definitions used by expert practitioners and are applied to SET living radical polymerization (SET-LRP) according to the definition of the division of organic chemistry of IUPAC that relies on principles elaborated by Taube, Eberson, Chanon, and Kochi. Additional definitions are also discussed to help clarify for the nonexpert contradictory literature reports. Subsequently, the principles and evolution of SET-LRP together with the methodologies currently available to practice it are discussed. It is expected that this Perspective will be able to help experts and nonexperts practice, develop, and invent new concepts and methodologies for SET-LRP to advance its status and the status of other living radical polymerization methods to the level of the most precise living polymerization methods.

  5. Hemicellulose-based multifunctional macroinitiator for single-electron-transfer mediated living radical polymerization.

    Science.gov (United States)

    Voepel, Jens; Edlund, Ulrica; Albertsson, Ann-Christine; Percec, Virgil

    2011-01-10

    A multifunctional macroinitiator for single-electron-transfer mediated living radical polymerization (SET-LRP) was designed from acetylated galactoglucomannan (AcGGM) by α-bromoisobutyric acid functionalization of the anomeric hydroxyl groups on the heteropolysaccharide backbone. This macroinitiator, with a degree of substitution of 0.15, was used in the SET-LRP of methyl acrylate, catalyzed by Cu(0)/Me(6)-TREN in DMSO, DMF, or DMSO/H(2)O in various concentrations. Kinetic analyses confirm high conversions of up to 99.98% and a living behavior of the SET-LRP process providing high molecular weight hemicelluloses/methyl acrylate hybrid copolymers with a brush-like architecture.

  6. Kinematically complete investigation of momentum transfer for single ionization in fast proton-helium collisions

    Energy Technology Data Exchange (ETDEWEB)

    Weber, T.; Mergel, V.; Jagutzki, O.; Schmidt, L.; Afaneh, F.; Schmidt-Boecking, H. [Institut fuer Kernphysik, August-Euler-Strasse 6, 60486 Frankfurt am Main (Germany); Khayyat, K. [Department of Physics, University of Missouri, Rolla, MO (United States); Doerner, R. [Fakultaet fuer Physik, Universitaet Freiburg (Germany); Gonzalez, A. [Centro Atomico Bariloche, 8400 S C de Bariloche (Argentina); Cocke, C.L. [Department of Physics, Kansas State University, Manhatten, KS (United States); Landers, A.L. [Department of Physics, Western Michigan University, Kalamazoo, MI (United States)

    2000-09-14

    The dynamics of singly ionizing proton-helium collisions have been studied experimentally for several energies of the projectile (0.2, 0.5, 1.0 and 1.3 MeV) with the technique of cold target recoil-ion momentum spectroscopy (COLTRIMS). The complete final-state distribution in momentum space of all three particles was determined by measuring the three momentum components of the emitted electron and the coincident recoiling target ion. The momentum transfer and energy loss of the outgoing projectile was determined by momentum and energy conservation laws. Doubly differential cross sections of the kinematically complete experimental investigation are presented. The present data are compared with results from fast highly charged heavy-ion impact experiments. (author)

  7. Quasifree (p , 2 p ) Reactions on Oxygen Isotopes: Observation of Isospin Independence of the Reduced Single-Particle Strength

    Science.gov (United States)

    Atar, L.; Paschalis, S.; Barbieri, C.; Bertulani, C. A.; Díaz Fernández, P.; Holl, M.; Najafi, M. A.; Panin, V.; Alvarez-Pol, H.; Aumann, T.; Avdeichikov, V.; Beceiro-Novo, S.; Bemmerer, D.; Benlliure, J.; Boillos, J. M.; Boretzky, K.; Borge, M. J. G.; Caamaño, M.; Caesar, C.; Casarejos, E.; Catford, W.; Cederkall, J.; Chartier, M.; Chulkov, L.; Cortina-Gil, D.; Cravo, E.; Crespo, R.; Dillmann, I.; Elekes, Z.; Enders, J.; Ershova, O.; Estrade, A.; Farinon, F.; Fraile, L. M.; Freer, M.; Galaviz Redondo, D.; Geissel, H.; Gernhäuser, R.; Golubev, P.; Göbel, K.; Hagdahl, J.; Heftrich, T.; Heil, M.; Heine, M.; Heinz, A.; Henriques, A.; Hufnagel, A.; Ignatov, A.; Johansson, H. T.; Jonson, B.; Kahlbow, J.; Kalantar-Nayestanaki, N.; Kanungo, R.; Kelic-Heil, A.; Knyazev, A.; Kröll, T.; Kurz, N.; Labiche, M.; Langer, C.; Le Bleis, T.; Lemmon, R.; Lindberg, S.; Machado, J.; Marganiec-Gałązka, J.; Movsesyan, A.; Nacher, E.; Nikolskii, E. Y.; Nilsson, T.; Nociforo, C.; Perea, A.; Petri, M.; Pietri, S.; Plag, R.; Reifarth, R.; Ribeiro, G.; Rigollet, C.; Rossi, D. M.; Röder, M.; Savran, D.; Scheit, H.; Simon, H.; Sorlin, O.; Syndikus, I.; Taylor, J. T.; Tengblad, O.; Thies, R.; Togano, Y.; Vandebrouck, M.; Velho, P.; Volkov, V.; Wagner, A.; Wamers, F.; Weick, H.; Wheldon, C.; Wilson, G. L.; Winfield, J. S.; Woods, P.; Yakorev, D.; Zhukov, M.; Zilges, A.; Zuber, K.; R3B Collaboration

    2018-01-01

    Quasifree one-proton knockout reactions have been employed in inverse kinematics for a systematic study of the structure of stable and exotic oxygen isotopes at the R3B /LAND setup with incident beam energies in the range of 300 - 450 MeV /u . The oxygen isotopic chain offers a large variation of separation energies that allows for a quantitative understanding of single-particle strength with changing isospin asymmetry. Quasifree knockout reactions provide a complementary approach to intermediate-energy one-nucleon removal reactions. Inclusive cross sections for quasifree knockout reactions of the type O A (p ,2 p )N-1A have been determined and compared to calculations based on the eikonal reaction theory. The reduction factors for the single-particle strength with respect to the independent-particle model were obtained and compared to state-of-the-art ab initio predictions. The results do not show any significant dependence on proton-neutron asymmetry.

  8. Ligand-tailored single-site silica supported titanium catalysts: Synthesis, characterization and towards cyanosilylation reaction

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Wei; Li, Yani; Yu, Bo; Yang, Jindou; Zhang, Ying; Chen, Xi; Zhang, Guofang, E-mail: gfzhang@snnu.edu.cn; Gao, Ziwei, E-mail: zwgao@snnu.edu.cn

    2015-01-15

    A successive anchoring of Ti(NMe{sub 2}){sub 4}, cyclopentadiene and a O-donor ligand, 1-hydroxyethylbenzene (PEA), 1,1′-bi-2-naphthol (Binol) or 2,3-dihydroxybutanedioic acid diethyl ester (Tartrate), on silica was conducted by SOMC strategy in moderate conditions. The silica, monitored by in-situ Fourier transform infrared spectroscopy (in-situ FT-IR), was pretreated at different temperatures (200, 500 and 800 °C). The ligand tailored silica-supported titanium complexes were characterized by in-situ FT-IR, {sup 13}C CP MAS-NMR, X-ray photoelectron spectroscopy (XPS), X-ray absorption near edge structure (XANES) and elemental analysis in detail, verifying that the surface titanium species are single sited. The catalytic activity of the ligand tailored single-site silica supported titanium complexes was evaluated by a cyanosilylation of benzaldehyde. The results showed that the catalytic activity is dependent strongly on the dehydroxylation temperatures of silica and the configuration of the ligands. - Graphical abstract: The ligand-tailored silica supported “single site” titanium complexes were synthesized by SOMC strategy and fully characterized. Their catalytic activity were evaluated by benzaldehyde silylcyanation. - Highlights: • Single-site silica supported Ti active species was prepared by SOMC technique. • O-donor ligand tailored Ti surface species was synthesized. • The surface species was characterized by XPS, {sup 13}C CP-MAS NMR, XANES etc. • Catalytic activity of the Ti active species in silylcyanation reaction was evaluated.

  9. Hydrogen Evolution Reaction in Alkaline Solution: From Theory, Single Crystal Models, to Practical Electrocatalysts.

    Science.gov (United States)

    Zheng, Yao; Jiao, Yan; Qiao, Shizhang; Vasileff, Anthony

    2017-12-01

    The hydrogen evolution reaction (HER) is a fundamental process in electrocatalysis and plays an important role in energy conversion for the development of hydrogen-based energy sources. However, the considerably slow rate of the HER in alkaline conditions has hindered advances in water splitting techniques for high-purity hydrogen production. Differing from well documented acidic HER, the mechanistic aspects of alkaline HER are yet to be settled. Herein, we present a critical appraisal of alkaline HER electrocatalysis, with a special emphasis on the connection between fundamental surface electrochemistry on single crystal models and the derived molecular design principle for real-world electrocatalysts. By presenting some typical examples across theoretical calculations, surface characterization, and electrochemical experiments, we try to address some key ongoing debates to deliver a better understanding of alkaline HER at the atomic level. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Single step high-speed printing of continuous silver lines by laser-induced forward transfer

    Energy Technology Data Exchange (ETDEWEB)

    Puerto, D., E-mail: puerto@lp3.univ-mrs.fr [Aix-Marseille University, CNRS, LP3 laboratory Campus de Luminy, C.917, Marseille (France); Biver, E. [Aix-Marseille University, CNRS, LP3 laboratory Campus de Luminy, C.917, Marseille (France); Oxford Lasers Ltd., Unit 8, Moorbrook Park, Didcot, OX11 7HP (United Kingdom); Alloncle, A.-P.; Delaporte, Ph. [Aix-Marseille University, CNRS, LP3 laboratory Campus de Luminy, C.917, Marseille (France)

    2016-06-30

    Highlights: • We have performed an experimental study on laser micro-printing of silver nanoparticle inks. • We have achieved the printing of lines in a single pass at velocities of 17 m/s (1 MHz laser). • The ejection dynamics has been investigated by means of a time-resolved imaging technique. • The control of the donor film properties is of prime importance to print lines at high velocities. • Continuous conductive lines of silver inks are laser-printed on PET flexible substrates. - Abstract: The development of high-speed ink printing process by Laser-Induced Forward Transfer (LIFT) is of great interest for the printing community. To address the problems and the limitations of this process that have been previously identified, we have performed an experimental study on laser micro-printing of silver nanoparticle inks by LIFT and demonstrated for the first time the printing of continuous conductive lines in a single pass at velocities of 17 m/s using a 1 MHz repetition rate laser. We investigated the printing process by means of a time-resolved imaging technique to visualize the ejection dynamics of single and adjacent jets. The control of the donor film properties is of prime importance to achieve single step printing of continuous lines at high velocities. We use a 30 ps pulse duration laser with a wavelength of 343 nm and a repetition rate from 0.2 to 1 MHz. A galvanometric mirror head controls the distance between two consecutives jets by scanning the focused beam along an ink-coated donor substrate at different velocities. Droplets and lines of silver inks are laser-printed on glass and PET flexible substrates and we characterized their morphological quality by atomic force microscope (AFM) and optical microscope.

  11. Photochemical reactions of electron-deficient olefins with N,N,N',N'-tetramethylbenzidine via photoinduced electron-transfer

    International Nuclear Information System (INIS)

    Pan Yang; Zhao Junshu; Ji Yuanyuan; Yan Lei; Yu Shuqin

    2006-01-01

    Photoinduced electron transfer reactions of several electron-deficient olefins with N,N,N',N'-tetramethylbenzidine (TMB) in acetonitrile solution have been studied by using laser flash photolysis technique and steady-state fluorescence quenching method. Laser pulse excitation of TMB yields 3 TMB* after rapid intersystem crossing from 1 TMB*. The triplet which located at 480 nm is found to undergo fast quenching with the electron acceptors fumaronitrile (FN), dimethyl fumarate (DMF), diethyl fumarate (DEF), cinnamonitrile (CN), α-acetoxyacrylonitrile (AAN), crotononitrile (CrN) and 3-methoxyacrylonitrile (MAN). Substituents binding to olefin molecule own different electron-donating/withdrawing powers, which determine the electron-deficient property (π-cloud density) of olefin molecule as well as control the electron transfer rate constant directly. The detection of ion radical intermediates in the photolysis reactions confirms the proposed electron transfer mechanism, as expected from thermodynamics. The quenching rate constants of triplet TMB by these olefins have been determined at 510 nm to avoid the disturbance of formed TMB cation radical around 475 nm. All the k q T values approach or reach to the diffusion-controlled limit. In addition, fluorescence quenching rate constants k q S have been also obtained by calculating with Stern-Volmer equation. A correlation between experimental electron transfer rate constants and free energy changes has been explained by Marcus theory of adiabatic outer-sphere electron transfer. Disharmonic k q values for CN and CrN in endergonic region may be the disturbance of exciplexs formation. e of exciplex formation

  12. Formation of T-shaped versus charge-transfer molecular adducts in the reactions between bis(thiocarbonyl) donors and Br2 and I2.

    Science.gov (United States)

    Mancini, Annalisa; Aragoni, M Carla; Bricklebank, Neil; Castellano, Carlo; Demartin, Francesco; Isaia, Francesco; Lippolis, Vito; Pintus, Anna; Arca, Massimiliano

    2013-03-01

    The reactions of 4,5,6,7-tetrathiocino-[1,2-b:3,4-b']-1,3,8,10-tetrasubstituted-diimidazolyl-2,9-dithiones (R(2),R'(2)-todit; 1: R=R'=Et; 2: R=R'=Ph; 3: R=Et, R'=Ph) with Br(2) exclusively afforded 1:1 and 1:2 "T-shaped" adducts, as established by FT-Raman spectroscopy and single-crystal X-ray diffraction in the case of complex 1·2Br(2). On the other hand, the reactions of compounds 1-3 with molecular I(2) provided charge-transfer (CT) "spoke" adducts, among which the solvated species 3·2I(2)·(1-x)I(2)·xCH(2)Cl(2) (x=0.94) and (3)(2)·7I(2)·xCH(2)Cl(2), (x=0.66) were structurally characterized. The nature of all of the reaction products was elucidated based on elemental analysis and FT-Raman spectroscopy and supported by theoretical calculations at the DFT level. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Understanding the Oxygen Reduction Reaction on a Y/Pt(111) Single Crystal

    DEFF Research Database (Denmark)

    Ulrikkeholm, Elisabeth Therese; Johansson, Tobias Peter; Malacrida, Paolo

    2014-01-01

    Polymer electrolyte membrane fuel cells (PEMFC) hold promise as a zero-emission source of power, particularly suitable for automotive vehicles. However, the high loading of Pt required to catalyse the oxygen reduction reaction (ORR) at the PEMFC cathode, prevents the commercialisation of this tec......Polymer electrolyte membrane fuel cells (PEMFC) hold promise as a zero-emission source of power, particularly suitable for automotive vehicles. However, the high loading of Pt required to catalyse the oxygen reduction reaction (ORR) at the PEMFC cathode, prevents the commercialisation...... of this technology. Improving the activity of Pt by alloying it with other metals could decrease the loading of Pt. An earlier theoretical study conducted at our laboratory identified PtxY as an active and stable catalyst for oxygen reduction. Experiments conducted on sputter-cleaned polycrystalline Pt3Y confirmed...... was significantly different from our initial expectations. In order to understand this phenomenon, we investigated a Y/Pt(111) single crystal, formed by depositing large amounts of Y om Pt(111) under ultra-high vacuum (UHV) conditions and annealing to high temperatures. We subsequently characterised the surface...

  14. A detector system for studying nuclear reactions relevant to Single Event Effects

    Energy Technology Data Exchange (ETDEWEB)

    Murin, Yu. [V.G. Khlopin Radium Institute, 2nd Murinski 28, 194021 St. Petersburg (Russian Federation)]. E-mail: murin@jinr.ru; Babain, Yu. [V.G. Khlopin Radium Institute, 2nd Murinski 28, 194021 St. Petersburg (Russian Federation); Chubarov, M. [V.G. Khlopin Radium Institute, 2nd Murinski 28, 194021 St. Petersburg (Russian Federation); Tuboltsev, Yu. [V.G. Khlopin Radium Institute, 2nd Murinski 28, 194021 St. Petersburg (Russian Federation); Pljuschev, V. [V.G. Khlopin Radium Institute, 2nd Murinski 28, 194021 St. Petersburg (Russian Federation); Zubkov, M. [V.G. Khlopin Radium Institute, 2nd Murinski 28, 194021 St. Petersburg (Russian Federation); Nomokonov, P. [High Energy Laboratory, Joint Institute for Nuclear Research, 141980 Moscow Region (Russian Federation); Voronin, A. [Moscow State University, 119992 Moscow (Russian Federation); Merkin, M. [Moscow State University, 119992 Moscow (Russian Federation); Kondratiev, V. [St. Petersburg State University, 198504 St. Petersburg (Russian Federation); Olsson, N.; Blomgren, J. [Department of Neutron Research, Uppsala University, Box 525, SE 751 20 Uppsala (Sweden); Westerberg, L. [Department of Physics, Uppsala University, Box 530, SE 751 21 Uppsala (Sweden); Ekstroem, C.; Kolozhvari, A. [The Svedberg Laboratory, Uppsala University, Box 533, SE 751 21 Uppsala (Sweden); Jaederstroem, H. [Department of Nuclear and Particle Physics, Uppsala University, Box 531, SE 751 21 Uppsala (Sweden); Jakobsson, B.; Golubev, P. [Department of Physics, Lund University, Box 118, SE 221 00 Lund (Sweden); Bargholz, Chr.; Geren, L.; Tegner, P.-E.; Zartova, I. [Department of Physics, Stockholm University, AlbaNova, SE 10691 Stockholm (Sweden); Budzanowski, A.; Czech, B.; Skwirczynska, I. [H. Niewodniczanski Institute of Nuclear Physics, PL 31 342 Cracow (Poland); Tang, H.H.K. [IBM, T.J. Watson Research Center, Yorktown Heights, NY 10598 (United States)

    2007-08-01

    We describe a device to study reactions relevant for the Single Event Effect (SEE) in microelectronics by means of 200A and 300AMeV, inverse kinematics, Si+H and Si+D reactions. The work is focused on the possibility to measure Z=2-14 projectile fragments as efficiently as possible. During commissioning and first experiments the fourth quadrant of the CELSIUS storage ring acted as a spectrometer to register fragments in two planes of Si strip detectors in the angular region 0{sup a}t -0.6{sup a}t. A combination of ring-structured and sector-structured Si strip detector planes operated at angles 0.6{sup a}t-1.1{sup a}t. For specific event tagging a Si+ phoswich scintillator wall operated in the range 3.9{sup a}t-11.7{sup a}t and Si {delta}E-E telescopes of CHICSi type operated at large angles.

  15. Reaction pathway towards formation of cobalt single chain magnets and nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Balaji, G.; Desilva, Rohini M.; Palshin, V. [Center for Advanced Microstructures and Devices, Louisiana State University, 6980 Jefferson Highway, Baton Rouge, LA 70806 (United States); Desilva, N. [Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803 (United States); Palmer, G. [Department of Biochemistry and Cell Biology, Rice University, MS 140, 6100 Main street, Houston, TX 77251 (United States); Kumar, Challa S.S.R., E-mail: ckumar1@lsu.ed [Center for Advanced Microstructures and Devices, Louisiana State University, 6980 Jefferson Highway, Baton Rouge, LA 70806 (United States)

    2010-03-15

    With the advent of molecular magnets the quest for suitable high density magnetic storage materials has fuelled further research in this area. Here in this report, we present a detailed mechanistic investigation of thermal decomposition of cyclopentadienyl cobalt [CoCp(CO){sub 2}] precursor where Cp is the cyclopentadienyl moiety. The reaction revealed the formation of cobalt nanoparticles (Co-NPs) through an isolable reaction intermediate characterized as a Single Chain Magnet (SCM), [Co(Cp){sub 2}]{sub 2}CoCl{sub 4} (1). The SQUID magnetic measurements showed the presence of very strong antiferromagnetic interactions between Co{sup 2+} ions. The zero-field cooled (ZFC) and field cooled (FC) magnetization curves branch out below 5 K and there is evidence for frequency dependent complex susceptibility along with a maximum observed around 2.5 K. The optical studies indicated that the Co{sup 2+} d-d transition is influenced by the polarity of the solvents. The cobalt nanoparticles (Co-NPs) were obtained, either directly from 1 or from its precursor. They are spherical in shape with a mean size 15 nm, have fcc crystal structure and were found to be ferromagnetic at room temperature.

  16. Characterisation of Dissolved Organic Carbon by Thermal Desorption - Proton Transfer Reaction - Mass Spectrometry

    Science.gov (United States)

    Materić, Dušan; Peacock, Mike; Kent, Matthew; Cook, Sarah; Gauci, Vincent; Röckmann, Thomas; Holzinger, Rupert

    2017-04-01

    Dissolved organic carbon (DOC) is an integral component of the global carbon cycle. DOC represents an important terrestrial carbon loss as it is broken down both biologically and photochemically, resulting in the release of carbon dioxide (CO2) to the atmosphere. The magnitude of this carbon loss can be affected by land management (e.g. drainage). Furthermore, DOC affects autotrophic and heterotrophic processes in aquatic ecosystems, and, when chlorinated during water treatment, can lead to the release of harmful trihalomethanes. Numerous methods have been used to characterise DOC. The most accessible of these use absorbance and fluorescence properties to make inferences about chemical composition, whilst high-performance size exclusion chromatography can be used to determine apparent molecular weight. XAD fractionation has been extensively used to separate out hydrophilic and hydrophobic components. Thermochemolysis or pyrolysis Gas Chromatography - Mass Spectrometry (GC-MS) give information on molecular properties of DOC, and 13C NMR spectroscopy can provide an insight into the degree of aromaticity. Proton Transfer Reaction - Mass Spectrometry (PTR-MS) is a sensitive, soft ionisation method suitable for qualitative and quantitative analysis of volatile and semi-volatile organic vapours. So far, PTR-MS has been used in various environmental applications such as real-time monitoring of volatile organic compounds (VOCs) emitted from natural and anthropogenic sources, chemical composition measurements of aerosols etc. However, as the method is not compatible with water, it has not been used for analysis of organic traces present in natural water samples. The aim of this work was to develop a method based on thermal desorption PTR-MS to analyse water samples in order to characterise chemical composition of dissolved organic carbon. We developed a clean low-pressure evaporation/sublimation system to remove water from samples and thermal desorption system to introduce

  17. Single particle tracking-based reaction progress kinetic analysis reveals a series of molecular mechanisms of cetuximab-induced EGFR processes in a single living cell.

    Science.gov (United States)

    Kim, Do-Hyeon; Kim, Dong-Kyun; Zhou, Kai; Park, Soyeon; Kwon, Yonghoon; Jeong, Min Gyu; Lee, Nam Ki; Ryu, Sung Ho

    2017-07-01

    Cellular processes occur through the orchestration of multi-step molecular reactions. Reaction progress kinetic analysis (RPKA) can provide the mechanistic details to elucidate the multi-step molecular reactions. However, current tools have limited ability to simultaneously monitor dynamic variations in multiple complex states at the single molecule level to apply RPKA in living cells. In this research, a single particle tracking-based reaction progress kinetic analysis (sptRPKA) was developed to simultaneously determine the kinetics of multiple states of protein complexes in the membrane of a single living cell. The subpopulation ratios of different states were quantitatively (and statistically) reliably extracted from the diffusion coefficient distribution rapidly acquired by single particle tracking at constant and high density over a long period of time using super-resolution microscopy. Using sptRPKA, a series of molecular mechanisms of epidermal growth factor receptor (EGFR) cellular processing induced by cetuximab were investigated. By comprehensively measuring the rate constants and cooperativity of the molecular reactions involving four EGFR complex states, a previously unknown intermediate state was identified that represents the rate limiting step responsible for the selectivity of cetuximab-induced EGFR endocytosis to cancer cells.

  18. Quasi-steady-state voltammetry of rapid electron transfer reactions at the macroscopic substrate of the scanning electrochemical microscope.

    Science.gov (United States)

    Nioradze, Nikoloz; Kim, Jiyeon; Amemiya, Shigeru

    2011-02-01

    We report on a novel theory and experiment for scanning electrochemical microscopy (SECM) to enable quasi-steady-state voltammetry of rapid electron transfer (ET) reactions at macroscopic substrates. With this powerful approach, the substrate potential is cycled widely across the formal potential of a redox couple while the reactant or product of a substrate reaction is amperometrically detected at the tip in the feedback or substrate generation/tip collection mode, respectively. The plot of tip current versus substrate potential features the retraceable sigmoidal shape of a quasi-steady-state voltammogram although a transient voltammogram is obtained at the macroscopic substrate. Finite element simulations reveal that a short tip-substrate distance and a reversible substrate reaction (except under the tip) are required for quasi-steady-state voltammetry. Advantageously, a pair of quasi-steady-state voltammograms is obtained by employing both operation modes to reliably determine all transport, thermodynamic, and kinetic parameters as confirmed experimentally for rapid ET reactions of ferrocenemethanol and 7,7,8,8-tetracyanoquinodimethane at a Pt substrate with ∼0.5 μm-radius Pt tips positioned at 90 nm-1 μm distances. Standard ET rate constants of ∼7 cm/s were obtained for the latter mediator as the largest determined for a substrate reaction by SECM. Various potential applications of quasi-steady-state voltammetry are also proposed.

  19. Tunable, Chemo- and Site-Selective Nitrene Transfer Reactions through the Rational Design of Silver(I) Catalysts.

    Science.gov (United States)

    Alderson, Juliet M; Corbin, Joshua R; Schomaker, Jennifer M

    2017-09-19

    Carbon-nitrogen (C-N) bonds are ubiquitous in pharmaceuticals, agrochemicals, diverse bioactive natural products, and ligands for transition metal catalysts. An effective strategy for introducing a new C-N bond into a molecule is through transition metal-catalyzed nitrene transfer chemistry. In these reactions, a metal-supported nitrene can either add across a C═C bond to form an aziridine or insert into a C-H bond to furnish the corresponding amine. Typical catalysts for nitrene transfer include Rh 2 L n and Ru 2 L n complexes supported by bridging carboxylate and related ligands, as well as complexes based on Cu, Co, Ir, Fe, and Mn supported by porphyrins and related ligands. A limitation of metal-catalyzed nitrene transfer is the ability to predictably select which specific site will undergo amination in the presence of multiple reactive groups; thus, many reactions rely primarily on substrate control. Achieving true catalyst-control over nitrene transfer would open up exciting possibilities for flexible installation of new C-N bonds into hydrocarbons, natural product-inspired scaffolds, existing pharmaceuticals or biorenewable building blocks. Silver-catalyzed nitrene transfer enables flexible control over the position at which a new C-N bond is introduced. Ag(I) supported by simple N-donor ligands accommodates a diverse range of coordination geometries, from linear to tetrahedral to seesaw, enabling the electronic and steric parameters of the catalyst to be tuned independently. In addition, the ligand, Ag salt counteranion, Ag/ligand ratio and the solvent all influence the fluxional and dynamic behavior of Ag(I) complexes in solution. Understanding the interplay of these parameters to manipulate the behavior of Ag-nitrenes in a predictable manner is a key design feature of our work. In this Account, we describe successful applications of a variety of design principles to tunable, Ag-catalyzed aminations, including (1) changing Ag/ligand ratios to influence

  20. Long-range versus short-range correlations in the two-neutron transfer reaction 64Ni(18O,16O)66Ni

    Science.gov (United States)

    Paes, B.; Santagati, G.; Vsevolodovna, R. Magana; Cappuzzello, F.; Carbone, D.; Cardozo, E. N.; Cavallaro, M.; García-Tecocoatzi, H.; Gargano, A.; Ferreira, J. L.; Lenzi, S. M.; Linares, R.; Santopinto, E.; Vitturi, A.; Lubian, J.

    2017-10-01

    Recently, various two-neutron transfer studies using the (18O,16O) reaction were performed with a large success. This was achieved because of a combined use of the microscopic quantum description of the reaction mechanism and of the nuclear structure. In the present work we use this methodology to study the two-neutron transfer reaction of the 18O+64Ni system at 84 MeV incident energy, to the ground and first 2+ excited state of the residual 66Ni nucleus. All the experimental data were measured by the large acceptance MAGNEX spectrometer at the Instituto Nazionale di Fisica Nucleare -Laboratori Nazionali del Sud (Italy). We have performed exact finite range cross section calculations using the coupled channel Born approximation (CCBA) and coupled reaction channel (CRC) method for the sequential and direct two-neutron transfers, respectively. Moreover, this is the first time that the formalism of the microscopic interaction boson model (IBM-2) was applied to a two-neutron transfer reaction. From our results we conclude that for two-neutron transfer to the ground state of 66Ni, the direct transfer is the dominant reaction mechanism, whereas for the transfer to the first excited state of 66Ni, the sequential process dominates. A competition between long-range and short-range correlations is discussed, in particular, how the use of two different models (Shell model and IBM's) help to disentangle long- and short-range correlations.

  1. Phosphorus-31 NMR magnetization transfer measurements of metabolic reaction rates in the rat heart and kidney in vivo

    International Nuclear Information System (INIS)

    Koretsky, A.P.

    1984-01-01

    31 P NMR is a unique tool to study bioenergetics in living cells. The application of magnetization transfer techniques to the measurement of steady-state enzyme reaction rates provides a new approach to understanding the regulation of high energy phosphate metabolism. This dissertation is concerned with the measurement of the rates of ATP synthesis in the rat kidney and of the creatine kinase catalyzed reaction in the rat heart in situ. The theoretical considerations of applying magnetization transfer techniques to intact organs are discussed with emphasis on the problems associated with multiple exchange reactions and compartmentation of reactants. Experimental measurements of the ATP synthesis rate were compared to whole kidney oxygen consumption and Na + reabsorption rates to derive ATP/O values. The problems associated with ATP synthesis rate measurements in kidney, e.g. the heterogeneity of the inorganic phosphate resonance, are discussed and experiments to overcome these problems proposed. In heart, the forward rate through creatine kinase was measured to be larger than the reverse rate. To account for the difference in forward and reverse rates a model is proposed based on the compartmentation of a small pool of ATP

  2. N2O + CO reaction over single Ga or Ge atom embedded graphene: A DFT study

    Science.gov (United States)

    Esrafili, Mehdi D.; Vessally, Esmail

    2018-01-01

    The possibility of using a single Ga or Ge atom embedded graphene as an efficient catalyst for the reduction of N2O molecule by CO is examined. We perform density functional theory calculations to calculate adsorption energies as well as analysis of the structural and electronic properties of different species involved in the N2O + CO reaction. The large activation energy for the diffusion of the single Ga or Ge atom on the C vacancy site of graphene shows the high stability of both Ga- and Ge-embedded graphene sheets in the N2O reduction. The activation energy needed for the decomposition of N2O is calculated to be 18.4 and 14.1 kcal/mol over Ga- and Ge-embedded graphene, respectively. The results indicate that the Ge-embedded graphene may serve as an effective catalyst for the N2O reduction. Moreover, the activation energy for the disproportionation of N2O molecules that generates N2 and O2 is relatively high; so, the generation of these side products may be hindered by decreasing the temperature.

  3. Influence of zeolite pore structure on product selectivities for protolysis and hydride transfer reactions in the cracking of n-pentane.

    Science.gov (United States)

    Miyaji, Akimitsu; Iwase, Yasuyoshi; Nishitoba, Toshiki; Long, Nguyen Quang; Motokura, Ken; Baba, Toshihide

    2015-02-21

    The conversion of n-pentane was carried out to examine the effects of reaction conditions on changes in product selectivities at 823 K, using zeolites with 10- and 12-membered rings. We also investigated the influence of the pore structure of these zeolites on their catalytic activities for both protolysis and hydride transfer reactions. In the first half of this work, we examined the influence of acidic proton concentration and n-pentane pressure on the reaction rates for protolysis and hydride transfer reactions using ZSM-5 zeolites. The rates of hydride transfer reactions were more influenced by pentane pressure compared to protolysis reactions, and were proportional to the square of n-pentane pressure and the concentration of acidic protons. In the second half of this work, the influence of the zeolite pore structure on changes in product selectivities with n-pentane conversion and that on the rates of protolysis and the hydride transfer reactions were revealed using various zeolites with 10- and 12-membered rings. The catalytic activities of zeolites for the protolysis and hydride transfer reactions were influenced more by the spatial volume of the zeolite cavity than the acid strength of protons on the zeolite.

  4. Dynamics of excited-state intramolecular proton transfer reactions in piroxicam. Role of triplet states

    Science.gov (United States)

    Cho, Dae Won; Kim, Yong Hee; Yoon, Minjoong; Jeoung, Sae Chae; Kim, Dongho

    1994-08-01

    The picosecond time-resolved fluorescence and transient absorption behavior of piroxicam at room temperature are reported. The keto tautomer in the excited singlet state ( 1K*) formed via the fast intramolecular proton transfer (≈ 20 ps) is observed. The short-lived (7.5 ns) triplet state of keto tauomer ( 3K*) is generated from 1K * in toluene whereas it is hardly observed in ethanol. Consequently, rapid reverse proton transfer takes place from 3K * to the enol triplet state ( 3E *.

  5. Exploring chemoselective S-to-N acyl transfer reactions in synthesis and chemical biology

    Science.gov (United States)

    Burke, Helen M.; McSweeney, Lauren; Scanlan, Eoin M.

    2017-05-01

    S-to-N acyl transfer is a high-yielding chemoselective process for amide bond formation. It is widely utilized by chemists for synthetic applications, including peptide and protein synthesis, chemical modification of proteins, protein-protein ligation and the development of probes and molecular machines. Recent advances in our understanding of S-to-N acyl transfer processes in biology and innovations in methodology for thioester formation and desulfurization, together with an extension of the size of cyclic transition states, have expanded the boundaries of this process well beyond peptide ligation. As the field develops, this chemistry will play a central role in our molecular understanding of Biology.

  6. Combining MFD and PIE for accurate single-pair Förster resonance energy transfer measurements.

    Science.gov (United States)

    Kudryavtsev, Volodymyr; Sikor, Martin; Kalinin, Stanislav; Mokranjac, Dejana; Seidel, Claus A M; Lamb, Don C

    2012-03-01

    Single-pair Förster resonance energy transfer (spFRET) experiments using single-molecule burst analysis on a confocal microscope are an ideal tool to measure inter- and intramolecular distances and dynamics on the nanoscale. Different techniques have been developed to maximize the amount of information available in spFRET burst analysis experiments. Multiparameter fluorescence detection (MFD) is used to monitor a variety of fluorescence parameters simultaneously and pulsed interleaved excitation (PIE) employs direct excitation of the acceptor to probe its presence and photoactivity. To calculate accurate FRET efficiencies from spFRET experiments with MFD or PIE, several calibration measurements are usually required. Herein, we demonstrate that by combining MFD with PIE information regarding all calibration factors as well as an accurate determination of spFRET histograms can be performed in a single measurement. In addition, the quality of overlap of the different detection volumes as well as the detection of acceptor photophysics can be investigated with MFD-PIE. Bursts containing acceptor photobleaching can be identified and excluded from further investigation while bursts that contain FRET dynamics are unaffected by this analysis. We have employed MFD-PIE to accurately analyze the effects of nucleotides and substrate on the interdomain separation in DnaK, the major bacterial heat shock protein 70 (Hsp70). The interdomain distance increases from 47 Å in the ATP-bound state to 84 Å in the ADP-bound state and slightly contracts to 77 Å when a substrate is bound. This is in contrast to what was observed for the mitochondrial member of the Hsp70s, Ssc1, supporting the notion of evolutionary specialization of Hsp70s for different cellular functions in different organisms and cell organelles. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Rotational dependence of the proton-transfer reaction HBr+ + CO2-->HOCO+ + Br. I. Energy versus angular momentum effects.

    Science.gov (United States)

    Paetow, Lisa; Unger, Franziska; Beichel, Witali; Frenking, Gernot; Weitzel, Karl-Michael

    2010-05-07

    Cross sections for the endothermic proton-transfer reactions of rotationally state-selected HBr(+) and DBr(+) ions with CO(2) were measured in a guided ion beam apparatus in order to determine the influence of rotational excitation and collision energy in the center of mass (c.m.) system on the cross section. Ab initio calculations were performed to obtain energetic information about reactants, intermediates, and products. In the experiment HBr(+) and DBr(+) ions were prepared with the same mean rotational quantum number but different mean rotational energies as the rotational constants differ by about a factor of two. The mean rotational energy was varied from 1.4 to 66.3 meV for HBr(+) and from 0.7 to 43.0 meV for DBr(+). Collision energies (E(c.m.)) ranged from 0.32 to 1.00 eV. Under all conditions considered, an increase in the rotational excitation leads to a decrease in the cross section for both reactions. However, the effect is more pronounced for the higher collision energies. For E(c.m.)=1.00 and 0.85 eV; a comparison between the results for HBr(+) and DBr(+) indicates that the cross section is dominated by effects of rotational energy rather than angular momentum. For lower collision energies the cross sections for the deuteron transfer and the proton transfer are in best agreement if not compared for the same c.m. collision energy but for the same value of the difference between the collision energy and the reaction enthalpy.

  8. Can the heat transfer coefficients for single-phase flow and for convective flow boiling be equivalent?

    Science.gov (United States)

    Dorao, C. A.; Drewes, S.; Fernandino, M.

    2018-02-01

    During the past few decades, heat transfer during convective flow boiling inside pipes has been widely studied with the goal of unveiling the physics of the process. Different heat transfer mechanisms have been suggested based on different assumptions. This fact has resulted in a large number of models including different dimensionless numbers and in some cases up to a dozen of adjusted parameters. Here, we show that the convective flow boiling heat transfer coefficient is equivalent to the one for single-phase flow when the influence of the vapour velocity is taken into account.

  9. Complete transfer of populations from a single state to a preselected superposition of states using piecewise adiabatic passage: Experiment

    International Nuclear Information System (INIS)

    Zhdanovich, S.; Shapiro, E. A.; Hepburn, J. W.; Shapiro, M.; Milner, V.

    2009-01-01

    We demonstrate a method of adiabatic population transfer from a single quantum state into a coherent superposition of states. The transfer is executed with femtosecond pulses, spectrally shaped in a simple and intuitive manner, which does not require iterative feedback-controlled loops. In contrast to nonadiabatic methods of excitation, our approach is not sensitive to the exact value of laser intensity. We show that the population transfer is complete, and analyze the possibility of controlling the relative phases and amplitudes of the excited eigenstates. We discuss the limitations of the proposed control methods due to the dynamic level shifts and suggest ways of reducing their influence.

  10. Enantio- and Diastereoselective Nitro-Mannich Reaction of α-Aryl Nitromethanes with Amidosulfones Catalyzed by Phase-Transfer Catalysts.

    Science.gov (United States)

    Lu, Ning; Li, Ruxu; Wei, Zhonglin; Cao, Jungang; Liang, Dapeng; Lin, Yingjie; Duan, Haifeng

    2017-05-05

    A high-yield, highly diastereo- and enantioselective nitro-Mannich reaction of α-aryl nitromethanes with amidosulfones catalyzed by a novel chiral phase-transfer catalyst, bearing multiple H-bonding donors, derived from quinine was developed. A variety of α-aryl nitromethanes and amidosulfones were investigated; and the corresponding products were obtained in excellent yields with excellent diastereo- and enantioselectivities (up to 99% yield, > 99:1 dr and >99% ee). As a demonstration of synthetic utility, the resulting β-nitroamines could be converted to corresponding meso-symmetric and optically pure unsymmetric anti-1,2-diarylethylenediamines.

  11. Charge distribution effects in polyatomic reactants involved in simple electron transfer reactions

    Czech Academy of Sciences Publication Activity Database

    Fawcett, W. R.; Chavis, G. J.; Hromadová, Magdaléna

    2008-01-01

    Roč. 53, č. 23 (2008), s. 6787-6792 ISSN 0013-4686 Institutional research plan: CEZ:AV0Z40400503 Keywords : electron transfer kinetics * charge distribution effects * double - layer effects in electrode kinetics Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.078, year: 2008

  12. Reaction Path Averaging: Characterizing the Structural Response of the DNA Double Helix to Electron Transfer

    Czech Academy of Sciences Publication Activity Database

    Kolář, Michal H.; Kubař, T.

    2017-01-01

    Roč. 121, č. 7 (2017), s. 1520-1532 ISSN 1520-6106 Institutional support: RVO:61388963 Keywords : excited-state dynamics * excitation energy transfer * solvation dynamics Subject RIV: CF - Physical ; Theoretical Chemistry OBOR OECD: Physical chemistry Impact factor: 3.177, year: 2016

  13. Bond-formation versus electron transfer: C–C-Coupling reactions of hydrocarbon dications with benzene

    Czech Academy of Sciences Publication Activity Database

    Roithová, Jana; Schröder, Detlef

    2007-01-01

    Roč. 9, č. 6 (2007), s. 731-738 ISSN 1463-9076 R&D Projects: GA AV ČR KJB4040302 Institutional research plan: CEZ:AV0Z40550506 Keywords : benzene * C-C coupling * dications * electron transfer Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.343, year: 2007

  14. Microscopic models for proton transfer in water and strongly hydrogen-bonded complexes with a single-well proton potential

    DEFF Research Database (Denmark)

    Kuznetsov, A.M.; Ulstrup, Jens

    2004-01-01

    A new mechanism and formalism for proton transfer in donor-acceptor complexes with long hydrogen bonds introduced recently [1], is applied to a proton transfer in liquid water. "Structural diffusion" of hydroxonium ions is regarded as totally adiabatic process, with synchronous hindered translation...... of two closest water molecules to and from the reaction complex as crucial steps. The water molecules induce a "gated" shift of the proton from the donor to the acceptor in the double-well potential with simultaneous breaking/formation of hydrogen bonds between these molecules and the proton donor...... and acceptor. The short-range and long-range proton transfer as "structural diffusion" of Zundel complexes is also considered. The theoretical formalism is illustrated with the use of Morse, exponential, and harmonic molecular potentials. This approach is extended to proton transfer in strongly hydrogen...

  15. Hydrogen peroxide elimination from C4a-hydroperoxyflavin in a flavoprotein oxidase occurs through a single proton transfer from flavin N5 to a peroxide leaving group.

    Science.gov (United States)

    Sucharitakul, Jeerus; Wongnate, Thanyaporn; Chaiyen, Pimchai

    2011-05-13

    C4a-hydroperoxyflavin is found commonly in the reactions of flavin-dependent monooxygenases, in which it plays a key role as an intermediate that incorporates an oxygen atom into substrates. Only recently has evidence for its involvement in the reactions of flavoprotein oxidases been reported. Previous studies of pyranose 2-oxidase (P2O), an enzyme catalyzing the oxidation of pyranoses using oxygen as an electron acceptor to generate oxidized sugars and hydrogen peroxide (H(2)O(2)), have shown that C4a-hydroperoxyflavin forms in P2O reactions before it eliminates H(2)O(2) as a product (Sucharitakul, J., Prongjit, M., Haltrich, D., and Chaiyen, P. (2008) Biochemistry 47, 8485-8490). In this report, the solvent kinetic isotope effects (SKIE) on the reaction of reduced P2O with oxygen were investigated using transient kinetics. Our results showed that D(2)O has a negligible effect on the formation of C4a-hydroperoxyflavin. The ensuing step of H(2)O(2) elimination from C4a-hydroperoxyflavin was shown to be modulated by an SKIE of 2.8 ± 0.2, and a proton inventory analysis of this step indicates a linear plot. These data suggest that a single-proton transfer process causes SKIE at the H(2)O(2) elimination step. Double and single mixing stopped-flow experiments performed in H(2)O buffer revealed that reduced flavin specifically labeled with deuterium at the flavin N5 position generated kinetic isotope effects similar to those found with experiments performed with the enzyme pre-equilibrated in D(2)O buffer. This suggests that the proton at the flavin N5 position is responsible for the SKIE and is the proton-in-flight that is transferred during the transition state. The mechanism of H(2)O(2) elimination from C4a-hydroperoxyflavin is consistent with a single proton transfer from the flavin N5 to the peroxide leaving group, possibly via the formation of an intramolecular hydrogen bridge.

  16. The effect of intramolecular quantum modes on free energy relationships for electron transfer reactions

    DEFF Research Database (Denmark)

    Ulstrup, Jens; Jortner, Joshua

    1975-01-01

    -frequency intramolecular degrees of feedom on the free energy relationship for series of closely related reactions was investigated for various model systems involving displacement of potential energy surfaces, frequency shift, and anharmonicity effects. The free energy plots are generally found to pass through a maximum...... and to be asymmetric with a slower decrease in the transition probability with increasing energy of reaction. For high-frequency intramolecular modes this provides a rationalization of the experimental observation of ''activationless'' regions. Isotope effects are discussed as also are the oscillatory free energy...

  17. Chemical Exchange Saturation Transfer in Chemical Reactions: A Mechanistic Tool for NMR Detection and Characterization of Transient Intermediates.

    Science.gov (United States)

    Lokesh, N; Seegerer, Andreas; Hioe, Johnny; Gschwind, Ruth M

    2018-02-07

    The low sensitivity of NMR and transient key intermediates below detection limit are the central problems studying reaction mechanisms by NMR. Sensitivity can be enhanced by hyperpolarization techniques such as dynamic nuclear polarization or the incorporation/interaction of special hyperpolarized molecules. However, all of these techniques require special equipment, are restricted to selective reactions, or undesirably influence the reaction pathways. Here, we apply the chemical exchange saturation transfer (CEST) technique for the first time to NMR detect and characterize previously unobserved transient reaction intermediates in organocatalysis. The higher sensitivity of CEST and chemical equilibria present in the reaction pathway are exploited to access population and kinetics information on low populated intermediates. The potential of the method is demonstrated on the proline-catalyzed enamine formation for unprecedented in situ detection of a DPU stabilized zwitterionic iminium species, the elusive key intermediate between enamine and oxazolidinones. The quantitative analysis of CEST data at 250 K revealed the population ratio of [Z-iminium]/[exo-oxazolidinone] 0.02, relative free energy +8.1 kJ/mol (calculated +7.3 kJ/mol), and free energy barrier of +45.9 kJ/mol (ΔG ⧧ calc. (268 K) = +42.2 kJ/mol) for Z-iminium → exo-oxazolidinone. The findings underpin the iminium ion participation in enamine formation pathway corroborating our earlier theoretical prediction and help in better understanding. The reliability of CEST is validated using 1D EXSY-build-up techniques at low temperature (213 K). The CEST method thus serves as a new tool for mechanistic investigations in organocatalysis to access key information, such as chemical shifts, populations, and reaction kinetics of intermediates below the standard NMR detection limit.

  18. Formation and characterization of a reactive chromium(v)-oxo complex: mechanistic insight into hydrogen-atom transfer reactions.

    Science.gov (United States)

    Kotani, Hiroaki; Kaida, Suzue; Ishizuka, Tomoya; Sakaguchi, Miyuki; Ogura, Takashi; Shiota, Yoshihito; Yoshizawa, Kazunari; Kojima, Takahiko

    2015-02-01

    A mononuclear Cr(v)-oxo complex, [Cr V (O)(6-COO - -tpa)](BF 4 ) 2 ( 1 ; 6-COO - -tpa = N , N -bis(2-pyridylmethyl)- N -(6-carboxylato-2-pyridylmethyl)amine) was prepared through the reaction of a Cr(iii) precursor complex with iodosylbenzene as an oxidant. Characterization of 1 was achieved using ESI-MS spectrometry, electron paramagnetic resonance, UV-vis, and resonance Raman spectroscopies. The reduction potential ( E red ) of 1 was determined to be 1.23 V vs. SCE in acetonitrile based on analysis of the electron-transfer (ET) equilibrium between 1 and a one-electron donor, [Ru II (bpy) 3 ] 2+ (bpy = 2,2'-bipyridine). The reorganization energy ( λ ) of 1 was also determined to be 1.03 eV in ET reactions from phenol derivatives to 1 on the basis of the Marcus theory of ET. The smaller λ value in comparison with that of an Fe(iv)-oxo complex (2.37 eV) is caused by the small structural change during ET due to the dπ character of the electron-accepting LUMO of 1 . When benzyl alcohol derivatives (R-BA) with different oxidation potentials were employed as substrates, corresponding aldehydes were obtained as the 2e - -oxidized products in moderate yields as determined from 1 H NMR and GC-MS measurements. One-step UV-vis spectral changes were observed in the course of the oxidation reactions of BA derivatives by 1 and a kinetic isotope effect (KIE) was observed in the oxidation reactions for deuterated BA derivatives at the benzylic position as substrates. These results indicate that the rate-limiting step is a concerted proton-coupled electron transfer (PCET) from substrate to 1 . In sharp contrast, in the oxidation of trimethoxy-BA ( E ox = 1.22 V) by 1 , trimethoxy-BA radical cation was observed by UV-vis spectroscopy. Thus, it was revealed that the mechanism of the oxidation reaction changed from one-step PCET to stepwise ET-proton transfer (ET/PT), depending on the redox potentials of R-BA.

  19. Transient core characteristics of small molten salt reactor coupling problem between heat transfer/flow and nuclear fission reaction

    International Nuclear Information System (INIS)

    Yamamoto, Takahisa; Mitachi, Koshi

    2004-01-01

    This paper performed the transient core analysis of a small Molten Salt Reactor (MSR). The emphasis is that the numerical model employed in this paper takes into account the interaction among fuel salt flow, nuclear reaction and heat transfer. The model consists of two group diffusion equations for fast and thermal neutron fluexs, balance equations for six-group delayed neutron precursors and energy conservation equations for fuel salt and graphite moderator. The results of transient analysis are that (1) fission reaction (heat generation) rate significantly increases soon after step reactivity insertion, e.g., the peak of fission reaction rate achieves about 2.7 times larger than the rated power 350 MW when the reactivity of 0.15% Δk/k 0 is inserted to the rated state, and (2) the self-control performance of the small MSR effectively works under the step reactivity insertion of 0.56% Δk/k 0 , putting the fission reaction rate back on the rated state. (author)

  20. Heterogeneous Single-Atom Catalyst for Visible-Light-Driven High-Turnover CO2 Reduction: The Role of Electron Transfer.

    Science.gov (United States)

    Gao, Chao; Chen, Shuangming; Wang, Ying; Wang, Jiawen; Zheng, Xusheng; Zhu, Junfa; Song, Li; Zhang, Wenkai; Xiong, Yujie

    2018-03-01

    Visible-light-driven conversion of CO 2 into chemical fuels is an intriguing approach to address the energy and environmental challenges. In principle, light harvesting and catalytic reactions can be both optimized by combining the merits of homogeneous and heterogeneous photocatalysts; however, the efficiency of charge transfer between light absorbers and catalytic sites is often too low to limit the overall photocatalytic performance. In this communication, it is reported that the single-atom Co sites coordinated on the partially oxidized graphene nanosheets can serve as a highly active and durable heterogeneous catalyst for CO 2 conversion, wherein the graphene bridges homogeneous light absorbers with single-atom catalytic sites for the efficient transfer of photoexcited electrons. As a result, the turnover number for CO production reaches a high value of 678 with an unprecedented turnover frequency of 3.77 min -1 , superior to those obtained with the state-of-the-art heterogeneous photocatalysts. This work provides fresh insights into the design of catalytic sites toward photocatalytic CO 2 conversion from the angle of single-atom catalysis and highlights the role of charge kinetics in bridging the gap between heterogeneous and homogeneous photocatalysts. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Proton transfer and isotope-induced reaction in aniline cluster ions

    Czech Academy of Sciences Publication Activity Database

    Lengyel, Jozef; Poterya, Viktoriya; Fárník, Michal

    2015-01-01

    Roč. 50, č. 3 (2015), s. 643-649 ISSN 1076-5174 R&D Projects: GA ČR GA14-14082S Institutional support: RVO:61388955 Keywords : isotope effect * intracluster reaction * Electron ionization Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.541, year: 2015

  2. Inelastic scattering and clusters transfer in 3,4He + 9Be reactions

    Czech Academy of Sciences Publication Activity Database

    Denikin, A. S.; Lukyanov, S.; Skobelev, N. K.; Sobolev, Yu. G.; Voskoboynik, E. I.; Penionzhkevich, Y. E.; Trzaska, W. H.; Tyurin, G. P.; Burjan, Václav; Kroha, Václav; Mrázek, Jaromír; Piskoř, Štěpán; Glagolev, Vadim; Xu, Yi; Khlebnikov, S. V.; Harakeh, M. N.; Kuterbekov, K. A.; Tuleushev, Y.

    2015-01-01

    Roč. 12, č. 5 (2015), s. 703-712 ISSN 1547-4771 R&D Projects: GA MŠk(CZ) LM2011019; GA MŠk LG14004 Institutional support: RVO:61389005 Keywords : cross-section * reactions * Be Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders

  3. Investigation of 11Be structure by means of neutron transfer reaction

    International Nuclear Information System (INIS)

    Fortier, S.; Winfield, J.; Pita, S.

    1999-01-01

    The p( 11 Be, 10 Be)d reaction at 35.3 MeV/u has been studied at the GANIL-SISSI secondary beam facility. The aim of the experiment is to extract spectroscopic factors measuring the coupling of the halo neutron to the 0 + and 2 + states of the 10 Be core. (authors)

  4. Hydride transfer versus deprotonation kinetics in the isobutane−propene alkylation reaction : A computational study

    NARCIS (Netherlands)

    Liu, Chong; Van Santen, Rutger A.; Poursaeidesfahani, A.; Vlugt, T.J.H.; Pidko, Evgeny A.; Hensen, Emiel J M

    2017-01-01

    The alkylation of isobutane with light alkenes plays an essential role in modern petrochemical processes for the production of high-octane gasoline. In this study we have employed periodic DFT calculations combined with microkinetic simulations to investigate the complex reaction mechanism of

  5. Nanopore Electrochemistry: A Nexus for Molecular Control of Electron Transfer Reactions

    Science.gov (United States)

    2018-01-01

    Pore-based structures occur widely in living organisms. Ion channels embedded in cell membranes, for example, provide pathways, where electron and proton transfer are coupled to the exchange of vital molecules. Learning from mother nature, a recent surge in activity has focused on artificial nanopore architectures to effect electrochemical transformations not accessible in larger structures. Here, we highlight these exciting advances. Starting with a brief overview of nanopore electrodes, including the early history and development of nanopore sensing based on nanopore-confined electrochemistry, we address the core concepts and special characteristics of nanopores in electron transfer. We describe nanopore-based electrochemical sensing and processing, discuss performance limits and challenges, and conclude with an outlook for next-generation nanopore electrode sensing platforms and the opportunities they present. PMID:29392173

  6. Nanopore Electrochemistry: A Nexus for Molecular Control of Electron Transfer Reactions

    Directory of Open Access Journals (Sweden)

    Kaiyu Fu

    2018-01-01

    Full Text Available Pore-based structures occur widely in living organisms. Ion channels embedded in cell membranes, for example, provide pathways, where electron and proton transfer are coupled to the exchange of vital molecules. Learning from mother nature, a recent surge in activity has focused on artificial nanopore architectures to effect electrochemical transformations not accessible in larger structures. Here, we highlight these exciting advances. Starting with a brief overview of nanopore electrodes, including the early history and development of nanopore sensing based on nanopore-confined electrochemistry, we address the core concepts and special characteristics of nanopores in electron transfer. We describe nanopore-based electrochemical sensing and processing, discuss performance limits and challenges, and conclude with an outlook for next-generation nanopore electrode sensing platforms and the opportunities they present.

  7. Synthesis and Catalytic Hydrogen Transfer Reaction of Ruthenium(II) Complex

    International Nuclear Information System (INIS)

    Son, Jung Ik; Kim, Aram; Noh, Hui Bog; Lee, Hyun Ju; Shim, Yoon Bo; Park, Kang Hyun

    2012-01-01

    The ruthenium(II) complex [Ru(bpy) 2 -(PhenTPy)] was synthesized, and used for the transfer hydrogenation of ketones and the desired products were obtained in good yield. Based on the presented results, transition-metal complexes can be used as catalysts for a wide range of organic transformations. The relationship between the electro-reduction current density and temperature are being examined in this laboratory. Attempts to improve the catalytic activity and determine the transfer hydrogenation mechanism are currently in progress. The catalytic hydrogenation of a ketone is a basic and critical process for making many types of alcohols used as the final products and precursors in the pharmaceutical, agrochemical, flavor, fragrance, materials, and fine chemicals industries. The catalytic hydrogenation process developed by Noyori is a very attractive process. Formic acid and 2-propanol have been used extensively as hydrogenation sources. The advantage of using 2-propanol as a hydrogen source is that the only side product will be acetone, which can be removed easily during the workup process. Hydrogen transfer (HT) catalysis, which generates alcohols through the reduction of ketones, is an attractive protocol that is used widely. Ruthenium(II) complexes are the most useful catalysts for the hydrogen transfer (HT) of ketones. In this method, a highly active catalytic system employs a transition metal as a catalyst to synthesize alcohols, and is a replacement for the hydrogen-using hydrogenation process. The most active system is based on Ru, Rh and Ir, which includes a nitrogen ligand that facilitates the formation of a catalytically active hydride and phosphorus

  8. Synthesis and Catalytic Hydrogen Transfer Reaction of Ruthenium(II) Complex

    Energy Technology Data Exchange (ETDEWEB)

    Son, Jung Ik; Kim, Aram; Noh, Hui Bog; Lee, Hyun Ju; Shim, Yoon Bo; Park, Kang Hyun [Pusan National University, Busan (Korea, Republic of)

    2012-01-15

    The ruthenium(II) complex [Ru(bpy){sub 2}-(PhenTPy)] was synthesized, and used for the transfer hydrogenation of ketones and the desired products were obtained in good yield. Based on the presented results, transition-metal complexes can be used as catalysts for a wide range of organic transformations. The relationship between the electro-reduction current density and temperature are being examined in this laboratory. Attempts to improve the catalytic activity and determine the transfer hydrogenation mechanism are currently in progress. The catalytic hydrogenation of a ketone is a basic and critical process for making many types of alcohols used as the final products and precursors in the pharmaceutical, agrochemical, flavor, fragrance, materials, and fine chemicals industries. The catalytic hydrogenation process developed by Noyori is a very attractive process. Formic acid and 2-propanol have been used extensively as hydrogenation sources. The advantage of using 2-propanol as a hydrogen source is that the only side product will be acetone, which can be removed easily during the workup process. Hydrogen transfer (HT) catalysis, which generates alcohols through the reduction of ketones, is an attractive protocol that is used widely. Ruthenium(II) complexes are the most useful catalysts for the hydrogen transfer (HT) of ketones. In this method, a highly active catalytic system employs a transition metal as a catalyst to synthesize alcohols, and is a replacement for the hydrogen-using hydrogenation process. The most active system is based on Ru, Rh and Ir, which includes a nitrogen ligand that facilitates the formation of a catalytically active hydride and phosphorus.

  9. Accurate quantification of microRNA via single strand displacement reaction on DNA origami motif.

    Directory of Open Access Journals (Sweden)

    Jie Zhu

    Full Text Available DNA origami is an emerging technology that assembles hundreds of staple strands and one single-strand DNA into certain nanopattern. It has been widely used in various fields including detection of biological molecules such as DNA, RNA and proteins. MicroRNAs (miRNAs play important roles in post-transcriptional gene repression as well as many other biological processes such as cell growth and differentiation. Alterations of miRNAs' expression contribute to many human diseases. However, it is still a challenge to quantitatively detect miRNAs by origami technology. In this study, we developed a novel approach based on streptavidin and quantum dots binding complex (STV-QDs labeled single strand displacement reaction on DNA origami to quantitatively detect the concentration of miRNAs. We illustrated a linear relationship between the concentration of an exemplary miRNA as miRNA-133 and the STV-QDs hybridization efficiency; the results demonstrated that it is an accurate nano-scale miRNA quantifier motif. In addition, both symmetrical rectangular motif and asymmetrical China-map motif were tested. With significant linearity in both motifs, our experiments suggested that DNA Origami motif with arbitrary shape can be utilized in this method. Since this DNA origami-based method we developed owns the unique advantages of simple, time-and-material-saving, potentially multi-targets testing in one motif and relatively accurate for certain impurity samples as counted directly by atomic force microscopy rather than fluorescence signal detection, it may be widely used in quantification of miRNAs.

  10. Accurate Quantification of microRNA via Single Strand Displacement Reaction on DNA Origami Motif

    Science.gov (United States)

    Lou, Jingyu; Li, Weidong; Li, Sheng; Zhu, Hongxin; Yang, Lun; Zhang, Aiping; He, Lin; Li, Can

    2013-01-01

    DNA origami is an emerging technology that assembles hundreds of staple strands and one single-strand DNA into certain nanopattern. It has been widely used in various fields including detection of biological molecules such as DNA, RNA and proteins. MicroRNAs (miRNAs) play important roles in post-transcriptional gene repression as well as many other biological processes such as cell growth and differentiation. Alterations of miRNAs' expression contribute to many human diseases. However, it is still a challenge to quantitatively detect miRNAs by origami technology. In this study, we developed a novel approach based on streptavidin and quantum dots binding complex (STV-QDs) labeled single strand displacement reaction on DNA origami to quantitatively detect the concentration of miRNAs. We illustrated a linear relationship between the concentration of an exemplary miRNA as miRNA-133 and the STV-QDs hybridization efficiency; the results demonstrated that it is an accurate nano-scale miRNA quantifier motif. In addition, both symmetrical rectangular motif and asymmetrical China-map motif were tested. With significant linearity in both motifs, our experiments suggested that DNA Origami motif with arbitrary shape can be utilized in this method. Since this DNA origami-based method we developed owns the unique advantages of simple, time-and-material-saving, potentially multi-targets testing in one motif and relatively accurate for certain impurity samples as counted directly by atomic force microscopy rather than fluorescence signal detection, it may be widely used in quantification of miRNAs. PMID:23990889

  11. Transfer products from the reactions of heavy ions with heavy nuclei

    International Nuclear Information System (INIS)

    Thomas, K.E. III.

    1979-11-01

    Production of nuclides heavier than the target from 86 Kr- and 136 Xe-induced reactions with 181 Ta and 238 U was investigated. Attempts were made to produce new neutron-excess Np and Pu isotopes by the deep inelastic mechanism. No evidence was found for 242 Np or 247 Pu. Estimates were made for the production of 242 Np, 247 Pu, and 248 Am from heavy-ion reactions with uranium targets. Comparisons of reactions of 86 Kr and 136 Xe ions with thick 181 Ta targets and 86 Kr, 136 Xe and 238 U ions with thick 238 U targets indicate that the most probable products are not dependent on the projectile. The most probable products can be predicted by the equation Z - Z/sub target/ = 0.43 (A - A/sub target/) + 1.0. The major effect of the projectile is the magnitude of the production cross section of the heavy products. Based on these results, estimates are made of the most probable mass of element 114 produced from heavy-ion reactions with 248 Cm and 254 Es targets. These estimates give the mass number of element 114 as approx. 287 if produced in heavy-ion reactions with these very heavy targets. Excitation functions of gold and bismuth isotopes arising from 86 Kr- and 136 Xe-induced reactions with thin 181 Ta targets were measured. These results indicate that the shape and location (in Z and A above the target) of the isotopic distributions are not strongly dependent on the projectile incident energy. Also, the nuclidic cross sections are found to increase with an increase in projectile energy to a maximum at approximately 1.4 to 1.5 times the Coulomb barrier. Above this maximum, the nuclidic cross sections are found to decrease with an increase in projectile energy. This decrease in cross section is believed to be due to fission of the heavy products caused by high excitation energy and angular momentum. 111 references, 39 figures, 34 tables

  12. Tandem catalysis of ring-closing metathesis/atom transfer radical reactions with homobimetallic ruthenium–arene complexes

    Directory of Open Access Journals (Sweden)

    Yannick Borguet

    2010-12-01

    Full Text Available The tandem catalysis of ring-closing metathesis/atom transfer radical reactions was investigated with the homobimetallic ruthenium–indenylidene complex [(p-cymeneRu(μ-Cl3RuCl(3-phenyl-1-indenylidene(PCy3] (1 to generate active species in situ. The two catalytic processes were first carried out independently in a case study before the whole sequence was optimized and applied to the synthesis of several polyhalogenated bicyclic γ-lactams and lactones from α,ω-diene substrates bearing trihaloacetamide or trichloroacetate functionalities. The individual steps were carefully monitored by 1H and 31P NMR spectroscopies in order to understand the intimate details of the catalytic cycles. Polyhalogenated substrates and the ethylene released upon metathesis induced the clean transformation of catalyst precursor 1 into the Ru(II–Ru(III mixed-valence compound [(p-cymeneRu(μ-Cl3RuCl2(PCy3], which was found to be an efficient promoter for atom transfer radical reactions under the adopted experimental conditions.

  13. Does excited-state proton-transfer reaction contribute to the emission behaviour of 4-aminophthalimide in aqueous media?

    Science.gov (United States)

    Khara, Dinesh Chandra; Banerjee, Sanghamitra; Samanta, Anunay

    2014-06-23

    4-Aminophthalimide (AP) is an extensively used molecule both for fundamental studies and applications primarily due to its highly solvent-sensitive fluorescence properties. The fluorescence spectrum of AP in aqueous media was recently shown to be dependent on the excitation wavelength. A time-dependent blue shift of its emission spectrum is also reported. On the basis of these findings, the excited-state solvent-mediated proton-transfer reaction of the molecule, which was proposed once but discarded at a later stage, is reintroduced. We report on the fluorescence behaviour of AP and its imide-H protected derivative, N-BuAP, to prove that a solvent-assisted excited-state keto-enol transformation does not contribute to the steady-state and time-resolved emission behaviour of AP in aqueous media. Our results also reveal that the fluorescence of AP in aqueous media arises from two distinct hydrogen-bonded species. The deuterium isotope effect on the fluorescence quantum yield and lifetime of AP, which was thought to be a reflection of the excited-state proton-transfer reaction in the system, is explained by considering the difference in the influence of H(2)O and D(2)O on the nonradiative rates and ground-state exchange of the proton with the solvent. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Study of shell evolution around the doubly magic $^{208}$Pb via a multinucleon transfer reaction with an unstable beam

    CERN Multimedia

    This proposal aims at the study of the neutron-rich region around the doubly-magic nucleus $^{208}$Pb populated via a multinucleon transfer reaction. An unstable $^{94}$Rb beam will be delivered by HIE-ISOLDE at 5.5 MeV$\\cdot$u onto a $^{208}$Pb 13.0 mg/cm$^{2}$ target. The $\\gamma$- rays will be recorded by the MINIBALL $\\gamma$-ray spectrometer. The aim of the experiment is twofold: \\\\ \\\\ i) firstly it will represent the proof of principle that multinucleon transfer reactions with neutron-rich unstable beams is efficient to populate neutron-rich heavy binary partners and represents a competitive method to cold fragmentation \\\\ ii) secondly we aim at populating medium- to high-spin states in $^{212;214}$Pb and $^{208;210}$Hg to elucidate the existence of the 16$^{+}$ isomer in the lead isotopes and at the same time to disentangle the puzzling case of a very low energy 3$^{-}$ state in $^{210}$Hg not described by any nuclear model. \\\\ \\\\ The experimental results will be compared with large-scale shell-model ...

  15. Long-range electron transfer over graphene-based catalyst for high-performing oxygen reduction reactions: importance of size, N-doping, and metallic impurities.

    Science.gov (United States)

    Choi, Chang Hyuck; Lim, Hyung-Kyu; Chung, Min Wook; Park, Jong Cheol; Shin, Hyeyoung; Kim, Hyungjun; Woo, Seong Ihl

    2014-06-25

    N-doped carbon materials are considered as next-generation oxygen reduction reaction (ORR) catalysts for fuel cells due to their prolonged stability and low cost. However, the underlying mechanism of these catalysts has been only insufficiently identified, preventing the rational design of high-performing catalysts. Here, we show that the first electron is transferred into O2 molecules at the outer Helmholtz plane (ET-OHP) over a long range. This is in sharp contrast to the conventional belief that O2 adsorption must precede the ET step and thus that the active site must possess as good an O2 binding character as that which occurs on metallic catalysts. Based on the ET-OHP mechanism, the location of the electrode potential dominantly characterizes the ORR activity. Accordingly, we demonstrate that the electrode potential can be elevated by reducing the graphene size and/or including metal impurities, thereby enhancing the ORR activity, which can be transferred into single-cell operations with superior stability.

  16. Study of breakup and transfer of weakly bound nucleus 6Li to explore the low energy reaction dynamics

    Science.gov (United States)

    Zhang, G. L.; Zhang, G. X.; Hu, S. P.; Zhang, H. Q.; Gomes, P. R. S.; Lubian, J.; Guo, C. L.; Wu, X. G.; Yang, J. C.; Zheng, Y.; Li, C. B.; He, C. Y.; Zhong, J.; Li, G. S.; Yao, Y. J.; Guo, M. F.; Sun, H. B.; Valiente-Dobòn, J. J.; Goasduff, A.; Siciliano, M.; Galtarosa, F.; Francesco, R.; Testov, D.; Mengoni, D.; Bazzacco, D.; John, P. R.; Qu, W. W.; Wang, F.; Zheng, L.; Yu, L.; Chen, Q. M.; Luo, P. W.; Li, H. W.; Wu, Y. H.; Zhou, W. K.; Zhu, B. J.; Li, E. T.; Hao, X.

    2017-11-01

    Investigation of the breakup and transfer effect of weakly bound nuclei on the fusion process has been an interesting research topic in the past several years. However, owing to the low intensities of the presently available radioactive ion beam (RIB), it is difficult to clearly explore the reaction mechanisms of nuclear systems with unstable nuclei. In comparison with RIB, the beam intensities of stable weakly bound nuclei such as 6,7Li and 9Be, which have significant breakup probability, are orders of magnitude higher. Precise fusion measurements have already been performed with those stable weakly bound nuclei, and the effect of breakup of those nuclei on the fusion process has been extensively studied. Those nuclei indicated large production cross sections for particles other than the α + x breakup. The particles are originated from non-capture breakup (NCBU), incomplete fusion (ICF) and transfer processes. However, the conclusion of reaction dynamics was not clear and has the contradiction. In our previous experiments we have performed 6Li+96Zr and 154Sm at HI-13 Tandem accelerator of China Institute of Atomic Energy (CIAE) by using HPGe array. It is shown that there is a small complete fusion (CF) suppression on medium-mass target nucleus 96Zr different from about 35% suppression on heavier target nucleus 154Sm at near-barrier energies. It seems that the CF suppression factor depends on the charge of target nuclei. We also observed one neutron transfer process. However, the experimental data are scarce for medium-mass target nuclei. In order to have a proper understanding of the influence of breakup and transfer of weakly bound projectiles on the fusion process, we performed the 6Li+89Y experiment with incident energies of 22 MeV and 34 MeV on Galileo array in cooperation with Si-ball EUCLIDES at Legnaro National Laboratory (LNL) in Italy. Using particle-particle and particle-γ coincidences, the different reaction mechanisms can be clearly explored.

  17. Ground reaction forces and knee kinetics during single and repeated badminton lunges.

    Science.gov (United States)

    Lam, Wing Kai; Ding, Rui; Qu, Yi

    2017-03-01

    Repeated movement (RM) lunge that frequently executed in badminton might be used for footwear evaluation. This study examined the influence of single movement (SM) and RM lunges on the ground reaction forces (GRFs) and knee kinetics during the braking phase of a badminton lunge step. Thirteen male university badminton players performed left-forward lunges in both SM and RM sessions. Force platform and motion capturing system were used to measure GRFs and knee kinetics variables. Paired t-test was performed to determine any significant differences between SM and RM lunges regarding mean and coefficient of variation (CV) in each variable. The kinetics results indicated that compared to SM lunges, the RM lunges had shorter contact time and generated smaller maximum loading rate of impact force, peak knee anterior-posterior force, and peak knee sagittal moment but generated larger peak horizontal resultant forces (Ps forces (Ps < 0.05). These results suggested that the RM testing protocols had a distinct loading response and adaptation pattern during lunge and that the RM protocol showed higher within-trial reliability, which may be beneficial for the knee joint loading evaluation under different interventions.

  18. A nonlocal and periodic reaction-diffusion-advection model of a single phytoplankton species.

    Science.gov (United States)

    Peng, Rui; Zhao, Xiao-Qiang

    2016-02-01

    In this article, we are concerned with a nonlocal reaction-diffusion-advection model which describes the evolution of a single phytoplankton species in a eutrophic vertical water column where the species relies solely on light for its metabolism. The new feature of our modeling equation lies in that the incident light intensity and the death rate are assumed to be time periodic with a common period. We first establish a threshold type result on the global dynamics of this model in terms of the basic reproduction number R0. Then we derive various characterizations of R0 with respect to the vertical turbulent diffusion rate, the sinking or buoyant rate and the water column depth, respectively, which in turn give rather precise conditions to determine whether the phytoplankton persist or become extinct. Our theoretical results not only extend the existing ones for the time-independent case, but also reveal new interesting effects of the modeling parameters and the time-periodic heterogeneous environment on persistence and extinction of the phytoplankton species, and thereby suggest important implications for phytoplankton growth control.

  19. Predictive value of initial serum human chorionic gonadotropin levels for pregnancies after single fresh and frozen blastocyst transfer.

    Science.gov (United States)

    Zhao, Wei-E; Li, Yu-Jie; Ou, Jian-Ping; Sun, Peng; Chen, Wen-Qiu; Liang, Xiao-Yan

    2017-06-01

    As one of the earliest markers for predicting pregnancy outcomes, human chorionic gonadotropin (hCG) values have been inconclusive on reliability of the prediction after frozen and fresh embryo transfer (ET). In this retrospective study, patients with positive hCG (day 12 after transfer) were included to examine the hCG levels and their predictive value for pregnancy outcomes following 214 fresh and 1513 vitrified-warmed single-blastocyst transfer cycles. For patients who got clinical pregnancy, the mean initial hCG value was significantly higher after frozen cycles than fresh cycles, and the similar result was demonstrated for patients with live births (LB). The difference in hCG value existed even after adjusting for the potential covariates. The area under curves (AUC) and threshold values calculated by receiver operator characteristic curves were 0.944 and 213.05 mIU/mL for clinical pregnancy after fresh ET, 0.894 and 399.50 mIU/mL for clinical pregnancy after frozen ET, 0.812 and 222.86 mIU/mL for LB after fresh ET, and 0.808 and 410.80 mIU/mL for LB after frozen ET with acceptable sensitivity and specificity, respectively. In conclusion, single frozen blastocyst transfer leads to higher initial hCG values than single fresh blastocyst transfer, and the initial hCG level is a reliable predictive factor for predicting IVF outcomes.

  20. Modeling the radiation transfer of discontinuous canopies: results for gap probability and single-scattering contribution

    Science.gov (United States)

    Zhao, Feng; Zou, Kai; Shang, Hong; Ji, Zheng; Zhao, Huijie; Huang, Wenjiang; Li, Cunjun

    2010-10-01

    In this paper we present an analytical model for the computation of radiation transfer of discontinuous vegetation canopies. Some initial results of gap probability and bidirectional gap probability of discontinuous vegetation canopies, which are important parameters determining the radiative environment of the canopies, are given and compared with a 3- D computer simulation model. In the model, negative exponential attenuation of light within individual plant canopies is assumed. Then the computation of gap probability is resolved by determining the entry points and exiting points of the ray with the individual plants via their equations in space. For the bidirectional gap probability, which determines the single-scattering contribution of the canopy, a gap statistical analysis based model was adopted to correct the dependence of gap probabilities for both solar and viewing directions. The model incorporates the structural characteristics, such as plant sizes, leaf size, row spacing, foliage density, planting density, leaf inclination distribution. Available experimental data are inadequate for a complete validation of the model. So it was evaluated with a three dimensional computer simulation model for 3D vegetative scenes, which shows good agreement between these two models' results. This model should be useful to the quantification of light interception and the modeling of bidirectional reflectance distributions of discontinuous canopies.

  1. Single-molecule-sensitive fluorescence resonance energy transfer in freely-diffusing attoliter droplets

    Energy Technology Data Exchange (ETDEWEB)

    Rahmanseresht, Sheema; Ramos, Kieran P.; Gamari, Ben D.; Goldner, Lori S., E-mail: lgoldner@physics.umass.edu [Department of Physics, University of Massachusetts, Amherst, Massachusetts 01003 (United States); Milas, Peker [Department of Neuroscience, University of Wisconsin, Madison, Wisconsin 53705 (United States)

    2015-05-11

    Fluorescence resonance energy transfer (FRET) from individual, dye-labeled RNA molecules confined in freely-diffusing attoliter-volume aqueous droplets is carefully compared to FRET from unconfined RNA in solution. The use of freely-diffusing droplets is a remarkably simple and high-throughput technique that facilitates a substantial increase in signal-to-noise for single-molecular-pair FRET measurements. We show that there can be dramatic differences between FRET in solution and in droplets, which we attribute primarily to an altered pH in the confining environment. We also demonstrate that a sufficient concentration of a non-ionic surfactant mitigates this effect and restores FRET to its neutral-pH solution value. At low surfactant levels, even accounting for pH, we observe differences between the distribution of FRET values in solution and in droplets which remain unexplained. Our results will facilitate the use of nanoemulsion droplets as attoliter volume reactors for use in biophysical and biochemical assays, and also in applications such as protein crystallization or nanoparticle synthesis, where careful attention to the pH of the confined phase is required.

  2. Current Status of Comprehensive Chromosome Screening for Elective Single-Embryo Transfer

    Directory of Open Access Journals (Sweden)

    Ming-Yih Wu

    2014-01-01

    Full Text Available Most in vitro fertilization (IVF experts and infertility patients agree that the most ideal assisted reproductive technology (ART outcome is to have a healthy, full-term singleton born. To this end, the most reliable policy is the single-embryo transfer (SET. However, unsatisfactory results in IVF may result from plenty of factors, in which aneuploidy associated with advanced maternal age is a major hurdle. Throughout the past few years, we have got a big leap in advancement of the genetic screening of embryos on aneuploidy, translocation, or mutations. This facilitates a higher success rate in IVF accompanied by the policy of elective SET (eSET. As the cost is lowering while the scale of genome characterization continues to be up over the recent years, the contemporary technologies on trophectoderm biopsy and freezing-thaw, comprehensive chromosome screening (CCS with eSET appear to be getting more and more popular for modern IVF centers. Furthermore, evidence has showen that, by these avant-garde techniques (trophectoderm biopsy, vitrification, and CCS, older infertile women with the help of eSET may have an opportunity to increase the success of their live birth rates approaching those reported in younger infertility patients.

  3. High-Content Analysis of Breast Cancer Using Single-Cell Deep Transfer Learning.

    Science.gov (United States)

    Kandaswamy, Chetak; Silva, Luís M; Alexandre, Luís A; Santos, Jorge M

    2016-03-01

    High-content analysis has revolutionized cancer drug discovery by identifying substances that alter the phenotype of a cell, which prevents tumor growth and metastasis. The high-resolution biofluorescence images from assays allow precise quantitative measures enabling the distinction of small molecules of a host cell from a tumor. In this work, we are particularly interested in the application of deep neural networks (DNNs), a cutting-edge machine learning method, to the classification of compounds in chemical mechanisms of action (MOAs). Compound classification has been performed using image-based profiling methods sometimes combined with feature reduction methods such as principal component analysis or factor analysis. In this article, we map the input features of each cell to a particular MOA class without using any treatment-level profiles or feature reduction methods. To the best of our knowledge, this is the first application of DNN in this domain, leveraging single-cell information. Furthermore, we use deep transfer learning (DTL) to alleviate the intensive and computational demanding effort of searching the huge parameter's space of a DNN. Results show that using this approach, we obtain a 30% speedup and a 2% accuracy improvement. © 2016 Society for Laboratory Automation and Screening.

  4. The total cross sections of heavy ion reaction and the nuclear transfer

    International Nuclear Information System (INIS)

    Rego, R.A.

    1985-01-01

    The total reaction cross section of the systems 12 C + 12 C, 12 C + 40 Ca, 12 C + 90 Zr, 12 C + 208 Pb, 40 Ca + 40 Ca, 40 Ca + 208 Pb + 90 Zr + 90 Zr, 90 Zr + 208 Pb and 208 Pb + 208 Pb for a wide range of energies has been calculated microscopically. A WKB expression for the imaginary phase shift in the impact paremeter representation has been employed. The imaginary part of the optical potential has been constructed by using the first term of multiple scattering theory with the effect of Pauli blocking incorporated into it. The inclusion of the nuclear and Coulomb interactions is shown to be important. The theoretical results do not show very good agreement with the experimental data at lower energies. This is attributed to the weak absorption contained in the imaginary potential of the ''tο A ο B '' interaction, wich contained only quasifree knock-out as the dominant reaction mechanism. (author) [pt

  5. Reaction

    African Journals Online (AJOL)

    abp

    19 oct. 2017 ... Axillary block is an easy and recommended technique in children. Its use in children with acute hepatitis A is not risk free especially when associated with sedation using remifentanil and propofol. Similarly, the presence of a single hydatid cyst allows general anesthesia with mono- pulmonary ventilation.

  6. Reactions of guanine with methyl chloride and methyl bromide: O6-methylation versus charge transfer complex formation

    Science.gov (United States)

    Shukla, P. K.; Mishra, P. C.; Suhai, S.

    Density functional theory (DFT) at the B3LYP/6-31+G* and B3LYP/AUG-cc-pVDZ levels was employed to study O6-methylation of guanine due to its reactions with methyl chloride and methyl bromide and to obtain explanation as to why the methyl halides cause genotoxicity and possess mutagenic and carcinogenic properties. Geometries of the various isolated species involved in the reactions, reactant complexes (RCs), and product complexes (PCs) were optimized in gas phase. Transition states connecting the reactant complexes with the product complexes were also optimized in gas phase at the same levels of theory. The reactant complexes, product complexes, and transition states were solvated in aqueous media using the polarizable continuum model (PCM) of the self-consistent reaction field theory. Zero-point energy (ZPE) correction to total energy and the corresponding thermal energy correction to enthalpy were made in each case. The reactant complexes of the keto form of guanine with methyl chloride and methyl bromide in water are appreciably more stable than the corresponding complexes involving the enol form of guanine. The nature of binding in the product complexes was found to be of the charge transfer type (O6mG+ · X-, X dbond Cl, Br). Binding of HCl, HBr, and H2O molecules to the PCs obtained with the keto form of guanine did not alter the positions of the halide anions in the PCs, and the charge transfer character of the PCs was also not modified due to this binding. Further, the complexes obtained due to the binding of HCl, HBr, and H2O molecules to the PCs had greater stability than the isolated PCs. The reaction barriers involved in the formation of PCs were found to be quite high (?50 kcal/mol). Mechanisms of genotoxicity, mutagenesis and carcinogenesis caused by the methyl halides appear to involve charge transfer-type complex formation. Thus the mechanisms of these processes involving the methyl halides appear to be quite different from those that involve the

  7. Study of nuclear isovector spin responses from polarization transfer in (p,n) reactions at intermediate energies

    International Nuclear Information System (INIS)

    Wakasa, Tomotsugu

    1997-01-01

    We have measured a complete set of polarization transfer observables has been measured for quasi-free (p vector, n vector) reactions on 2 H, 6 Li, 12 C, 40 Ca, and 208 Pb at a bombarding energy of 346MeV and a laboratory scattering angle of 22deg (q=1.7 fm -1 ). The polarization transfer observables for all five targets are remarkably similar. These polarization observables yield separated spin-longitudinal (σ·q) and spin-transverse (σxq) nuclear responses. These results are compared to the spin-transverse responses measured in deep-inelastic electron scattering as well as to nuclear responses based on the random phase approximation. Such a comparison reveals an enhancement in the (p vector, n vector) spin-transverse channel, which masks the effect of pionic correlations in the response ratio. Second, the double differential cross sections at θ lab between 0deg and 12.3deg and the polarization transfer D NN at 0deg for the 90 Zr(p,n) reaction are measured at a bombarding energy of 295MeV. The Gamow-Teller(GT) strength B(GT) in the continuum deduced from the L=0 cross section is compared both with the perturbative calculation by Bertsch and Hamamoto and with the second-order random phase approximation calculation by Drozdz et al. The sum of B(GT) values up to 50MeV excitation becomes S β- =28.0±1.6 after subtracting the contribution of the isovector spin-monopole strength. This S β- value of 28.0±1.6 corresponds to about (93±5)% of the minimum value of the sum-rule 3(N-Z)=30. Last, first measurements of D NN (0deg) for (p vector, n vector) reactions at 295MeV yield large negative values up to 50MeV excitation for the 6 Li, 11 B, 12 C, 13 C(p vector, n vector) reactions. DWIA calculations using the Franey and Love (FL) 270MeV interaction reproduce differential cross sections and D NN (0deg) values, while the FL 325MeV interaction yield D NN (0deg) values less negative than the experimental values. (J.P.N.)

  8. Electron and ligand transfer reactions between cyclometallated platinum(II) compounds and thallium(III) carboxylates

    NARCIS (Netherlands)

    Koten, G. van; Ploeg, A.F.M.J. van der; Vrieze, K.

    1982-01-01

    Reaction of trans-[(2-Me{2}NCH{2}C{6}H{4}{2}Pt}I{}I{] with Tl}I{}I{}I{(O{2}CR){3} (R = Me, i-Pr) gave direct elimination of Tl}I{(O{2}CR) and formation of the oxidative addition product [(2-Me{2}NCH{2}C{6}H{4}){2}Pt}I{}V{ (O{2}CR){2}], in two isomeric forms. A structure with the carbon ligands in

  9. Hydride Transfer versus Deprotonation Kinetics in the Isobutane–Propene Alkylation Reaction: A Computational Study

    OpenAIRE

    Liu, Chong; van Santen, Rutger A.; Poursaeidesfahani, Ali; Vlugt, Thijs J. H.; Pidko, Evgeny A.; Hensen, Emiel J. M.

    2017-01-01

    The alkylation of isobutane with light alkenes plays an essential role in modern petrochemical processes for the production of high-octane gasoline. In this study we have employed periodic DFT calculations combined with microkinetic simulations to investigate the complex reaction mechanism of isobutane–propene alkylation catalyzed by zeolitic solid acids. Particular emphasis was given to addressing the selectivity of the alkylate formation versus alkene formation, which requires a high rate o...

  10. Single nanowire resistive nano-heater for highly localized thermo-chemical reactions: localized hierarchical heterojunction nanowire growth.

    Science.gov (United States)

    Yeo, Junyeob; Kim, Gunho; Hong, Sukjoon; Lee, Jinhwan; Kwon, Jinhyeong; Lee, Habeom; Park, Heeseung; Manoroktul, Wanit; Lee, Ming-Tsang; Lee, Bong Jae; Grigoropoulos, Costas P; Ko, Seung Hwan

    2014-12-29

    A single nanowire resistive nano-heater (RNH) is fabricated, and it is demonstrated that the RNH can induce highly localized temperature fields, which can trigger highly localized thermo-chemical reactions to grow hierarchical nanowires directly at the desired specific spot such as ZnO nanowire branch growth on a single Ag nanowire. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Examining the role of phosphate in glycosyl transfer reactions of Cellulomonas uda cellobiose phosphorylase using D-glucal as donor substrate.

    Science.gov (United States)

    Wildberger, Patricia; Brecker, Lothar; Nidetzky, Bernd

    2012-07-15

    Cellobiose phosphorylase from Cellulomonas uda (CuCPase) is shown to utilize D-glucal as slow alternative donor substrate for stereospecific glycosyl transfer to inorganic phosphate, giving 2-deoxy-α-D-glucose 1-phosphate as the product. When performed in D(2)O, enzymatic phosphorolysis of D-glucal proceeds with incorporation of deuterium in equatorial position at C-2, implying a stereochemical course of reaction where substrate becomes protonated from below its six-membered ring through stereoselective re side attack at C-2. The proposed catalytic mechanism, which is supported by results of docking studies, involves direct protonation of D-glucal by the enzyme-bound phosphate, which then performs nucleophilic attack on the reactive C-1 of donor substrate. When offered D-glucose next to D-glucal and phosphate, CuCPase produces 2-deoxy-β-D-glucosyl-(1→4)-D-glucose and 2-deoxy-α-D-glucose 1-phosphate in a ratio governed by mass action of the two acceptor substrates present. Enzymatic synthesis of 2-deoxy-β-D-glucosyl-(1→4)-D-glucose is effectively promoted by catalytic concentrations of phosphate, suggesting that catalytic reaction proceeds through a quaternary complex of CuCPase, D-glucal, phosphate, and D-glucose. Conversion of D-glucal and phosphate presents a convenient single-step synthesis of 2-deoxy-α-D-glucose 1-phosphate that is difficult to prepare chemically. Copyright © 2012 Elsevier Ltd. All rights reserved.

  12. Competition of electron transfer, dissociation, and bond-forming processes in the reaction of the CO(2)(2+) dication with neutral CO(2).

    Science.gov (United States)

    Ricketts, Claire L; Schröder, Detlef; Roithová, Jana; Schwarz, Helmut; Thissen, Roland; Dutuit, Odile; Zabka, Jan; Herman, Zdenek; Price, Stephen D

    2008-09-01

    The bimolecular reactivity of the CO(2)(2+) dication with neutral CO(2) is investigated using triple quadrupole and ion-ion coincidence mass spectrometry. Crucial for product analysis is the use of appropriate isotope labelling in the quadrupole experiments in order to distinguish the different reactive pathways. The main reaction corresponds to single-electron transfer from the neutral reagent to the dication, i.e. CO(2)(2+) + CO(2) --> 2CO(2)(+); this process is exothermic by almost 10 eV, if ground state monocations are formed. Interestingly, the results indicate that the CO(2)(+) ion formed when the dication accepts an electron dissociates far more readily than the CO(2)(+) ion formed from the neutral CO(2) molecule. This differentiation of the two CO(2)(+) products is rationalized by showing that the population of the key dissociative states of the CO(2)(+) monocation will be favoured from the CO(2)(2+) dication rather than from neutral CO(2). In addition, two bond-forming reactions are observed as minor channels, one of which leads to CO(+) and O(2)(+) as ionic products and the other affords a long-lived C(2)O(3)(2+) dication.

  13. Enhanced Single Seed Trait Predictions in Soybean (Glycine max) and Robust Calibration Model Transfer with Near-Infrared Reflectance Spectroscopy.

    Science.gov (United States)

    Hacisalihoglu, Gokhan; Gustin, Jeffery L; Louisma, Jean; Armstrong, Paul; Peter, Gary F; Walker, Alejandro R; Settles, A Mark

    2016-02-10

    Single seed near-infrared reflectance (NIR) spectroscopy predicts soybean (Glycine max) seed quality traits of moisture, oil, and protein. We tested the accuracy of transferring calibrations between different single seed NIR analyzers of the same design by collecting NIR spectra and analytical trait data for globally diverse soybean germplasm. X-ray microcomputed tomography (μCT) was used to collect seed density and shape traits to enhance the number of soybean traits that can be predicted from single seed NIR. Partial least-squares (PLS) regression gave accurate predictive models for oil, weight, volume, protein, and maximal cross-sectional area of the seed. PLS models for width, length, and density were not predictive. Although principal component analysis (PCA) of the NIR spectra showed that black seed coat color had significant signal, excluding black seeds from the calibrations did not impact model accuracies. Calibrations for oil and protein developed in this study as well as earlier calibrations for a separate NIR analyzer of the same design were used to test the ability to transfer PLS regressions between platforms. PLS models built from data collected on one NIR analyzer had minimal differences in accuracy when applied to spectra collected from a sister device. Model transfer was more robust when spectra were trimmed from 910 to 1679 nm to 955-1635 nm due to divergence of edge wavelengths between the two devices. The ability to transfer calibrations between similar single seed NIR spectrometers facilitates broader adoption of this high-throughput, nondestructive, seed phenotyping technology.

  14. The effect of driving force on intramolecular electron transfer in proteins. Studies on single-site mutated azurins

    DEFF Research Database (Denmark)

    Farver, O; Skov, L K; van de Kamp, M

    1992-01-01

    An intramolecular electron-transfer process has previously been shown to take place between the Cys3--Cys26 radical-ion (RSSR-) produced pulse radiolytically and the Cu(II) ion in the blue single-copper protein, azurin [Farver, O. & Pecht, I. (1989) Proc. Natl Acad. Sci. USA 86, 6868-6972]. To fu...

  15. Estimating protein-protein interaction affinity in single living cells using Förster resonance energy transfer measurements

    DEFF Research Database (Denmark)

    Jensen, Jens Ledet; Raarup, Merete Krog; Rubak, Ege

    Using Förster resonance energy transfer (FRET) images we study the possibility of estimating the equilibrium dissociation constant Kd and the intrinsic FRET efficiency Em from single cells. We model the measurement uncertainty in the acquired images and use the method of total least squares...

  16. The influence of the type of embryo culture medium on neonatal birthweight after single embryo transfer in IVF

    NARCIS (Netherlands)

    Vergouw, C.G.; Kostelijk, E.H.; Doejaaren, E.; Hompes, P.G.A.; Lambalk, C.B.; Schats, R.

    2012-01-01

    STUDY QUESTION Does the type of medium used to culture fresh and frozenthawed embryos influence neonatal birthweight after single embryo transfer (SET) in IVF? SUMMARY ANSWER A comparison of two commercially available culture media showed no significant influence on mean birthweight and mean

  17. Evaluation of an effective multifaceted implementation strategy for elective single-embryo transfer after in vitro fertilization

    NARCIS (Netherlands)

    Kreuwel, I.A.M.; Peperstraten, A.M. van; Hulscher, M.E.J.L.; Kremer, J.A.M.; Grol, R.P.T.M.; Nelen, W.L.D.M.; Hermens, R.P.M.G.

    2013-01-01

    STUDY QUESTION: What is the relationship between the rate of elective single-embryo transfer (eSET) and couples' exposure to different elements of a multifaceted implementation strategy? SUMMARY ANSWER: Additional elements in a multifaceted implementation strategy do not result in an increased eSET

  18. Spectrophotometric determination of quetiapine fumarate in pharmaceuticals and human urine by two charge-transfer complexation reactions

    Directory of Open Access Journals (Sweden)

    Vinay K.B.

    2012-01-01

    Full Text Available Two simple, rapid and accurate spectrophotometric procedures are proposed for the determination of quetiapine fumarate (QTF in pharmaceuticals and in spiked human urine. The methods are based on charge transfer complexation reactions of free base form of the drug (quetiapine, QTP, as n-electron donor (D, with either p-chloranilic acid (p-CAA (method A or 2,3-dichloro-5,6-dicyanoquinone (DDQ (method B as π-acceptors (A. The coloured charge transfer complexes produced exhibit absorption maxima at 520 and 540 nm, in method A and method B, respectively. The experimental conditions such as reagent concentration, reaction solvent and time have been carefully optimized to achieve the maximum sensitivity. Beer’s law is obeyed over the concentration ranges of 8.0 - 160 and 4.0 - 80.0 μg ml-1, for method A and method B, respectively. The calculated molar absorptivity values are 1.77 × 103 and 4.59 × 103 l mol-1cm-1, respectively, for method A and method B. The Sandell sensitivity values, limits of detection (LOD and quantification (LOQ have also been reported. The stoichiometry of the reaction in both cases was accomplished adopting the limiting logarithmic method and was found to be 1: 2 (D: A. The accuracy and precision of the methods were evaluated on intra-day and inter-day basis. The proposed methods were successfully applied for the determination of QTF in pharmaceutical formulations and spiked human urine.

  19. Search for proton emission in {sup 54}Ni and multi-nucleon transfer reactions in the actinide region

    Energy Technology Data Exchange (ETDEWEB)

    Geibel, Kerstin

    2012-06-15

    The first part of the thesis presents the investigation of fusion-evaporation reactions in order to verify one-proton emission from the isomeric 10{sup +} state in the proton rich nucleus {sup 54}Ni. Between the years 2006 and 2009 a series of experimental studies were performed at the Tandem accelerator in the Institut fuer Kernphysik (IKP), University of Cologne. These experiments used fusion-evaporation reactions to populate {sup 54}Ni via the two-neutron-evaporation channel of the compound nucleus {sup 56}Ni. The cross section for the population of the ground state of {sup 54}Ni was predicted to be in orders of microbarn. This required special care with respect to the sensitivity of the experimental setup, which consisted of a double-sided silicon-strip detector (DSSSD), a neutron-detector array and HPGe detectors. In two experiments the excitation functions of the reactions ({sup 32}S+{sup 24}Mg) and ({sup 28}Si+{sup 28}Si) were determined to find the optimal experimental conditions for the population of {sup 54}Ni. A final experiment employed a {sup 28}Si beam at an energy of 70 MeV, impinging on a {sup 28}Si target. With a complex analysis it is possible to obtain a background-free energy spectrum of the DSSSD. An upper cross section limit for the population of the 10{sup +} state in {sup 54}Ni is established at σ({sup 54}Ni(10{sup +})) ≤ (13.9 ± 7.8) nbarn. In the second part of the thesis the population of actinide nuclei by multi-nucleon transfer reactions is investigated. Two experiments, performed in 2007 and 2008 at the CLARA-PRISMA setup at the Laboratori Nazionali di Legnaro, are analyzed with respect to the target-like reaction products. In both experiments {sup 238}U was used as target. A {sup 70}Zn beam with 460 MeV and a {sup 136}Xe beam with 926 MeV, respectively, impinged on the target, inducing transfer reactions. Kinematic correlations between the reaction partners are used to obtain information on the unobserved target-like reaction

  20. Sensitive detection of n-alkanes using a mixed ionization mode proton-transfer-reaction mass spectrometer

    Directory of Open Access Journals (Sweden)

    O. Amador-Muñoz

    2016-11-01

    Full Text Available Proton-transfer-reaction mass spectrometry (PTR-MS is a technique that is widely used to detect volatile organic compounds (VOCs with proton affinities higher than water. However, n-alkanes generally have a lower proton affinity than water and therefore proton transfer (PT by reaction with H3O+ is not an effective mechanism for their detection. In this study, we developed a method using a conventional PTR-MS to detect n-alkanes by optimizing ion source and drift tube conditions to vary the relative amounts of different primary ions (H3O+, O2+, NO+ in the reaction chamber (drift tube. There are very few studies on O2+ detection of alkanes and the mixed mode has never been proposed before. We determined the optimum conditions and the resulting reaction mechanisms, allowing detection of n-alkanes from n-pentane to n-tridecane. These compounds are mostly emitted by evaporative/combustion process from fossil fuel use. The charge transfer (CT mechanism observed with O2+ was the main reaction channel for n-heptane and longer n-alkanes, while for n-pentane and n-hexane the main reaction channel was hydride abstraction (HA. Maximum sensitivities were obtained at low E ∕ N ratios (83 Td, low water flow (2 sccm and high O2+ ∕ NO+ ratios (Uso =  180 V. Isotopic 13C contribution was taken into account by subtracting fractions of the preceding 12C ion signal based on the number of carbon atoms and the natural abundance of 13C (i.e., 5.6 % for n-pentane and 14.5 % for n-tridecane. After accounting for isotopic distributions, we found that PT cannot be observed for n-alkanes smaller than n-decane. Instead, protonated water clusters of n-alkanes (M  ⋅  H3O+ species were observed with higher abundance using lower O2+ and higher water cluster fractions. M  ⋅  H3O+ species are probably the source for the M + H+ species observed from n-decane to n-tridecane. Normalized sensitivities to O2+ or to the sum of O2++