Sample records for h2o-3h exchange reaction

  1. {[GdAg 2(dtpa)(H 2O)] · 3H 2O} n : the first 2D Gd–Ag coordination polymer with Ag–Ag interaction

    Microsoft Academic Search

    Bin Zhao; Xiao-Yan Chen; Wen-Zhen Wang; Peng Cheng; Bin Ding; Dai-Zheng Liao; Shi-Ping Yan; Zong-Hui Jiang

    2005-01-01

    A novel 4d–4f coordination polymer {[GdAg2(dtpa)(H2O)]·3H2O}n (1) (dtpa=diethylenetriamine pentaacetate) was synthesized and characterized by magnetic and EPR studies. Its one-dimensional Gd–Ag ladder-like chains built upon tetranuclear rings are further connected by Ag–O bonds and Ag–Ag interactions to form a lamellar 2D packing.

  2. Metal-Containing Ligands for Mixed-Metal Polymers: Novel Cu(II)-Ag(I) Mixed-Metal Coordination Polymers Generated from [Cu(2-methylpyrazine-5-carboxylate)2(H2O)],3H2O

    E-print Network

    zur Loye, Hans-Conrad

    -dimensional mixed-metal polymer chains in the crystalline state. The magnetic susceptibilities of 2 and 3 wereMetal-Containing Ligands for Mixed-Metal Polymers: Novel Cu(II)-Ag(I) Mixed-Metal Coordination Polymers Generated from [Cu(2-methylpyrazine-5-carboxylate)2(H2O)],3H2O and Silver(I) Salts Yu-Bin Dong

  3. The Kinetics of Isotopic Exchange Reactions.

    ERIC Educational Resources Information Center

    Logan, S. R.

    1990-01-01

    Discussed are the kinetic interactions of these chemical processes and the determination of the actual order of such reactions. Included are multiple exchange, catalytic exchange with deuterium, and depletion of the original substrate. (CW)

  4. Individual Differences in Reactions to Inequitable Exchanges

    Microsoft Academic Search

    Barbara B. Ellis; Louis A. Penner

    1983-01-01

    This study investigated the role of sociopathic tendencies in reactions to inequitable exchanges. Subjects were 273 males and females classified as high or low in sociopathy. High sociopathic subjects were further divided into primary or secondary sociopaths on the basis of their levels of anxiety and guilt. Subjects read narratives of inequitable exchanges and assumed the role of the exploiter

  5. Inorganic–organic hybrid materials of p, p?-diphenylmethylenediphosphinic acid (H 2pcp) with magnesium and calcium ions: Synthesis and characterization of [Mg(Hpcp) 2], [Mg(Hpcp) 2(H 2O) 4], [Mg(pcp)(H 2O) 3](H 2O), [Ca(Hpcp) 2] and [Ca(pcp)(H 2O)] complexes

    Microsoft Academic Search

    Stefano Midollini; Pablo Lorenzo-Luis; Annabella Orlandini

    2006-01-01

    The p,p?-diphenylmethylenediphosphinic acid (H2pcp) reacts with Mg(SO4) or CaCl2·6H2O to give the anhydrous hybrid material [Mg(Hpcp)2] or [Ca(Hpcp)2]. Both the Mg and Ca derivatives, which are isomorphous, present polymeric 1D structural arrays, where the metal ions are doubly bridged by two Hpcp? ligands. When the reaction is carried out with Mg(OH)2 (or Ca(OH)2), hydrate metal complexes of the aprotic form

  6. Cation exchange reactions in colloidal branched nanocrystals.

    PubMed

    Miszta, Karol; Dorfs, Dirk; Genovese, Alessandro; Kim, Mee Rahn; Manna, Liberato

    2011-09-27

    Octapod-shaped colloidal nanocrystals composed of a central "core" region of cubic sphalerite CdSe and pods of hexagonal wurtzite CdS are subject to a cation exchange reaction in which Cd(2+) ions are progressively exchanged by Cu(+) ions. The reaction starts from the tip regions of the CdS pods and proceeds toward the center of the nanocrystals. It preserves both the shape and the anionic lattices of the heterostructures. During the exchange, the hexagonal wurtzite CdS pods are converted gradually into pods of hexagonal Cu(2)S chalcocite. Therefore, the partial cation exchange reactions lead to the formation of a ternary nanostructure, consisting of an octapod in which the central core is still CdSe, while the pods have a segmented CdS/Cu(2)S composition. When the cation exchange reaches the core, the cubic sphalerite CdSe core is converted into a core of cubic Cu(2-x)Se berzelianite phase. Therefore fully exchanged octapods are composed of a core of Cu(2-x)Se and eight pods of Cu(2)S. All these structures are stable, and the epitaxial interfaces between the various domains are characterized by low lattice mismatch. The Cu(2-x)Se(core)/Cu(2)S(pods) octapod represents another example of a nanostructure in which branching is achieved by proper organization of cubic and hexagonal domains in a single nanocrystal. PMID:21809824

  7. Charge exchange reactions and applications to astrophysics

    SciTech Connect

    Cheoun, Myung-Ki; Ha, Eunja; Kajino, T. [Department of Physics, Soongsil University, Seoul, 156-743 (Korea, Republic of); National Astronomical Observatory, Mitaka, Tokyo 181-8589 (Japan) and Department of Astronomy, Graduate School of Science, University of Tokyo, 7-3-1 Hongo, Tokyo 113-0033 (Japan)

    2012-11-12

    Neutrino-induced reactions have been known to play important roles as the neutrino process on the nucleosynthesis in core collapsing supernovae (SNe) explosions because expected neutrino flux and energy are sufficiently high enough to excite many relevant nuclei in spite of small cross sections of the weak interaction. However, we do not have enough data for the neutrino reaction to be exploited in the network calculation. Only a sparse data in the relevant energy range is known, in specific, for {sup 12}C. Therefore we have to rely on theoretical estimation of the reaction, which has two different modes, charge current (CC) and neutral current (NC). In particular, CC reactions are closely related to charge exchange reactions (CEXRs) which are feasible in the experiment, such as, (p,n) or (n,p) reactions. These CEXRs are usually dominated by the Gamow-Teller (GT) transition in the lower energy region. In this respect, any theoretical approaches for the neutrino reaction should be investigated for the CEXR because we have and expect more useful experimental data. After confirming our models to the GT strength deduced from the CEXR, we calculated neutrino-induced reactions in the energy range below the quasielastic region for nuclei of astrophysical importance. Our calculations are carried out with the Quasi-particle Random Phase Approximation (QRPA), which successfully described the nuclear beta decays of relevant nuclei. To describe neutrino-nucleus reactions, general multipole transitions by the weak interaction are considered for CC and NC reactions. Both reactions are described in a theoretical framework. Our results are shown to well reproduce the data from CEXRs and the sparse experimental data related to the neutrino-induced reaction, and further extended for neutrino reactions on various nuclear targets. Parts of the results are reported in this talk.

  8. Propionate exchange reactions in methanogenic ecosystems.

    PubMed

    Boone, D R

    1984-10-01

    Propionate degradation was measured with [1-C]- and [2-C]propionate in an anaerobic digestor. When [1-C]propionate was used, label disappeared more rapidly from the propionate pool than when [2-C]propionate was used. This indicated that an exchange reaction involving the carboxyl group of propionate occurred. Labeled propionate added to digestor samples which were equilibrated with H(2) lost label from the carboxyl group but not from the methylene group. PMID:16346651

  9. Propionate exchange reactions in methanogenic ecosystems

    SciTech Connect

    Boone, D.R.

    1984-10-01

    Propionate degradation was measured with (1-/sup 14/C)- and (2-/sup 14/C)propionate in an anaerobic digestor. When (1-/sup 14/C)propionate was used, label disappeared more rapidly from the propionate pool than when (2-/sup 14/C)propionate was used. This indicated that an exchange reaction involving the carboxyl group of propionate occurred. Labeled propionate added to digestor samples which were equilibrated with H/sub 2/ lost label from the carboxyl group but not from the methylene group. 9 references 2 figures.

  10. Charge Exchange and Chemical Reactions with Trapped Th$^{3+}$

    E-print Network

    Churchill, L R; Chapman, M S

    2010-01-01

    We have measured the reaction rates of trapped, buffer gas cooled Th$^{3+}$ and various gases and have analyzed the reaction products using trapped ion mass spectrometry techniques. Ion trap lifetimes are usually limited by reactions with background molecules, and the high electron affinity of multiply charged ions such as Th$^{3+}$ make them more prone to loss. Our results show that reactions of Th$^{3+}$ with carbon dioxide, methane, and oxygen all occur near the classical Langevin rate, while reaction rates with argon, hydrogen, and nitrogen are orders of magnitude lower. Reactions of Th$^{3+}$ with oxygen and methane proceed primarily via charge exchange, while simultaneous charge exchange and chemical reaction occurs between Th$^{3+}$ and carbon dioxide. Loss rates of Th$^{3+}$ in helium are consistent with reaction with impurities in the gas. Reaction rates of Th$^{3+}$ with nitrogen and argon depend on the internal electronic configuration of the Th$^{3+}$.

  11. Heat exchanger development at Reaction Engines Ltd.

    NASA Astrophysics Data System (ADS)

    Varvill, Richard

    2010-05-01

    The SABRE engine for SKYLON has a sophisticated thermodynamic cycle with heat transfer between the fluid streams. The intake airflow is cooled in an efficient counterflow precooler, consisting of many thousand small bore thin wall tubes. Precooler manufacturing technology has been under investigation at REL for a number of years with the result that flightweight matrix modules can now be produced. A major difficulty with cooling the airflow to sub-zero temperatures at low altitude is the problem of frost formation. Frost control technology has been developed which enables steady state operation. The helium loop requires a top cycle heat exchanger (HX3) to deliver a constant inlet temperature to the main turbine. This is constructed in silicon carbide and the feasibility of manufacturing various matrix geometries has been investigated along with suitable joining techniques. A demonstration precooler will be made to run in front of a Viper jet engine at REL's B9 test facility in 2011. This precooler will incorporate full frost control and be built from full size SABRE engine modules. The facility will incorporate a high pressure helium loop that rejects the absorbed heat to a bath of liquid nitrogen.

  12. The formate-pyruvate exchange reaction by Streptococcus faecalis 

    E-print Network

    Yeager, Robert Lee

    1960-01-01

    of the fortrmts activating systen. . An apprca. =h t? study the formats exchange reaction was made by :hood (is. . s) with . faecalis. This organisrs requires lipoic acid for the oxidatio~ or tne dtsmutation of pyruve'. e. Du-;ing th&. investigation, Q... oscillation (IQkc Raytheon) for 10, 20, 50. 45, 50?90 and 120 minutes were Inacttve, liow?ver, as shown in Table 2, extracts of S. faecalis prepared by the French pressure call method were capable J of exchanging forr!ate-" 1" with the carboxyl group cf...

  13. Analysis of (3He,t) charge exchange reaction

    NASA Astrophysics Data System (ADS)

    Singh, Pardeep; Zegers, R. G. T.; Danielewicz, Pawel; Noji, Shumpei

    2014-03-01

    We have studied the (3He,t) charge-exchange reaction at 140 MeV/u on 12C, 18O, 26Mg, 58,62,64Ni, 68Zn and 118-120Sn targets, within distorted wave impulse approximation. In contrast to most previous calculations, exchange contributions to the reaction are treated exactly. The present work focuses on Gamow-Teller and Fermi transitions, for which a proportionality between the differential cross section at zero momentum transfer and transitions strength is known to exist. The goal of the study is to investigate the quality of the new reaction calculations. If successful, it will allow for more detailed investigation of charge-exchange reactions data obtained with composite particles including for transitions with non-zero ?L. This Work was supported by the India University Grants Commission under Indo-US 21st Century Knowledge Initiative and by the U.S. National Science Foundation under Grant Nos. PHY-1068571 and PHY-1102511.

  14. Cross-ligation and exchange reactions catalyzed by hairpin ribozymes.

    PubMed Central

    Komatsu, Y; Koizumi, M; Sekiguchi, A; Ohtsuka, E

    1993-01-01

    The negative strand of the satellite RNA of tobacco ringspot virus (sTobRV(-)) contains a hairpin catalytic domain that shows self-cleavage and self-ligation activities in the presence of magnesium ions. We describe here that the minimal catalytic domain can catalyze a cross-ligation reaction between two kinds of substrates in trans. The cross-ligated product increased when the reaction temperature was decreased during the reaction from 37 degrees C to 4 degrees C. A two-stranded hairpin ribozyme, divided into two fragments between G45 and U46 in a hairpin loop, showed higher ligation activity than the nondivided ribozyme. The two stranded ribozyme also catalyzed an exchange reaction of the 3'-portion of the cleavage site. Images PMID:8441626

  15. EXFOR SYSTEMS MANUAL NUCLEAR REACTION DATA EXCHANGE FORMAT.

    SciTech Connect

    MCLANE,V.; NUCLEAR DATA CENTER NETWORK

    2000-05-19

    EXFOR is an exchange format designed to allow transmission of nuclear reaction data between the members of the Nuclear Data Centers Network. This document has been written for use by the members of the Network and includes matters of procedure and protocol, as well as detailed rules for the compilation of data. Users may prefer to consult EXFOR Basics' for a brief description of the format.

  16. Synthesis of layered sodium lanthanum selenide through ion exchange reactions

    SciTech Connect

    Butts, Laura J.; Strickland, Nicholas [Department of Chemistry, Texas State University - San Marcos, 601 University Drive, San Marcos, TX 78666 (United States); Martin, Benjamin R. [Department of Chemistry, Texas State University - San Marcos, 601 University Drive, San Marcos, TX 78666 (United States)], E-mail: bmartin@txstate.edu

    2009-04-02

    Layered hexagonal KLaSe2 ({alpha}-NaFeO{sub 2}-type) was synthesized using the reactive flux method and analyzed by powder XRD to determine its lattice constants (space group R-3m, a = 4.40508(5) A, c = 22.7838(5) A). NaLaSe{sub 2}, which normally crystallizes as a disordered rock salt structure with mixed Na+/La + 3 sites, was synthesized through a solid state ion exchange reaction at 585 deg. C from a 1:3 molar ratio mixture of KLaSe{sub 2}:NaI. The product of this reaction was hexagonally layered NaLaSe{sub 2} (space group R-3m, a = 4.3497(3) A, c = 20.808(2) A) isostructural to KLaSe{sub 2}. This product was analyzed by comparison with members of the set of solid solutions Na{sub (1-x)}K{sub (x)}LaSe{sub 2} to confirm that the extent ion exchange in this reaction was complete. Cubic (disordered) NaLaSe{sub 2} was also reacted with KI to yield the poorly crystalline hexagonally layered product with the approximate formula Na{sub 0.79}K{sub 0.21}LaSe{sub 2}.

  17. Exotic low mass narrow baryons extracted from charge exchange reactions

    E-print Network

    B. Tatischeff; E. Tomasi-Gustafsson

    2010-02-12

    This paper aims to give further evidence for the existence of low mass exotic baryons. Narrow structures in baryonic missing mass or baryonic invariant mass were observed during the last twelve years. Since their evidence is still under debate, various data, measured with incident hadrons, by different collaborations, are reanalyzed to bring evidence on these narrow exotic baryonic resonances excited in charge-exchange reactions. These structures are clearly exotic as there is no room for them in the $qqq$ configurations: their width is smaller than the widths of "classical" baryonic resonances, moreover some of the masses lie below the pion threshold mass.

  18. Coherent pion production in heavy ion charge exchange reactions

    NASA Astrophysics Data System (ADS)

    Boyard, J.-L.; Augustyniak, W.; Dahl, R.; Drews, M.; Ellegaard, C.; Farhi, L.; Gaarde, C.; Hennino, T.; Jensen, J. A.; Jourdain, J.-C.; Kagarlis, M.; Kunne, R.; Larsen, J. S.; Radvanyi, P.; Ramstein, B.; Roy-Stephan, M.; Zupranski, P.

    2005-06-01

    We report the first observation of coherent pion production induced by a heavy ion charge exchange reaction. The ( 12C, 12N) reaction [D. Bachelier et al., Phys. Lett. B 172 (1986) 23; M. Roy-Stephan et al., Nucl. Phys. A 488 (1988) 178] at 1.1 GeV/nucleon has been used to shine negative (off-shell) pions on nuclei and observe (on-shell) pions, leaving the target nucleus in its ground state. The experiment was performed at the Laboratoire National Saturne with the SPES4- ? setup [Laurent Farhi PHD thesis IPNO-T97-12, Universite d'Orsay, 1997; Rasmus Dahl Ph.D., Niels Bohr Institutet, Copenhagen (1999)].

  19. Alloyed Copper Chalcogenide Nanoplatelets via Partial Cation Exchange Reactions

    PubMed Central

    2014-01-01

    We report the synthesis of alloyed quaternary and quinary nanocrystals based on copper chalcogenides, namely, copper zinc selenide–sulfide (CZSeS), copper tin selenide–sulfide (CTSeS), and copper zinc tin selenide–sulfide (CZTSeS) nanoplatelets (NPLs) (?20 nm wide) with tunable chemical composition. Our synthesis scheme consisted of two facile steps: i.e., the preparation of copper selenide–sulfide (Cu2–xSeyS1–y) platelet shaped nanocrystals via the colloidal route, followed by an in situ cation exchange reaction. During the latter step, the cation exchange proceeded through a partial replacement of copper ions by zinc or/and tin cations, yielding homogeneously alloyed nanocrystals with platelet shape. Overall, the chemical composition of the alloyed nanocrystals can easily be controlled by the amount of precursors that contain cations of interest (e.g., Zn, Sn) to be incorporated/alloyed. We have also optimized the reaction conditions that allow a complete preservation of the size, morphology, and crystal structure as that of the starting Cu2–xSeyS1–y NPLs. The alloyed NPLs were characterized by optical spectroscopy (UV–vis–NIR) and cyclic voltammetry (CV), which demonstrated tunability of their light absorption characteristics as well as their electrochemical band gaps. PMID:25050455

  20. The Geometric Phase Appears in the Ultracold Hydrogen Exchange Reaction

    E-print Network

    Kendrick, Brian K; Balakrishnan, Naduvalath

    2015-01-01

    Quantum reactive scattering calculations for the hydrogen exchange reaction H + H$_2$($v=4$, $j=0$) $\\to$ H + H$_2$($v'$, $j'$) and its isotopic analogues are reported for ultracold collision energies. Due to the unique properties associated with ultracold collisions, it is shown that the geometric phase effectively controls the reactivity. The rotationally resolved rate coefficients computed with and without the geometric phase are shown to differ by up to four orders of magnitude. The effect is also significant in the vibrationally resolved and total rate coefficients. The dynamical origin of the effect is discussed and the large geometric phase effect reported here might be exploited to control the reactivity through the application of external fields or by the selection of a particular nuclear spin state.

  1. Charge-exchange reactions with a secondary triton beam

    NASA Astrophysics Data System (ADS)

    Sherrill, B. M.; Akimune, H.; Austin, S. M.; Bazin, D.; van den Berg, A. M.; Berg, G. P. A.; Caggiano, J.; Daito, I.; Fujimura, H.; Fujita, Y.; Fujiwara, M.; Hara, K.; Harakeh, M. N.; Jänecke, J.; Kawabata, T.; Navin, A.; Roberts, D. A.; Steiner, M.

    1999-08-01

    A secondary triton beam from fragmentation of 560-MeV /?-particles has been used in a high-resolution (t,3He) charge-exchange experiment at intermediate bombarding energies. The experiment was carried out at the National Superconducting Cyclotron Laboratory using a 4He beam from the K1200 cyclotron. The radioactive triton beam of (0.5-1.0)×106 particles//s with a mean energy of 350 MeV was produced in a production target of the A1200 fragment separator and transported to the target position of the S800 magnetic spectrometer. Ray-tracing and dispersion-matching techniques were employed to detect 3He particles from the 12C(t,3He)12B reaction near 0/°. An energy resolution of /?E~160 keV or ?E/E~4.6×10-4 (FWHM) was achieved. This is an improvement over our previous results and opens the possibility for studying high-resolution (n,p)-type reactions at intermediate bombarding energies.

  2. Valence-bond study of the /H2, D2/ exchange reaction mechanism.

    NASA Technical Reports Server (NTRS)

    Freihaut, B.; Raff, L. M.

    1973-01-01

    The exchange reaction of H2 with D2 to form 2 HD is important in that it is fundamentally the simplest four-body exchange reaction and should therefore represent a model system on which various theories of reactions dynamics might be tested. A number of theoretical and experimental investigations carried out on this system are reviewed. It is concluded that a Y yields T yields Y mechanism for the (H2, D2) exchange is not a low energy pathway that would make theory compatible with the shock-tube experiments of Bauer and Ossa (1966) and of Burcat and Lifshits (1967).

  3. Thermodynamics of calcium-isotope-exchange reactions. 1. Exchange between isotopic calcium carbonates and aqueous calcium ions

    Microsoft Academic Search

    Rongsen Zhang; Charles P. Nash; Peter A. Rock

    1988-01-01

    This paper reports the authors results for the direct experimental determination of the equilibrium constant for the calcium-isotope-exchange reaction ⁴°CaCOâ(s) + ⁴⁴CaClâ(aq) reversible ⁴⁴CaCOâ(s) + ⁴°CaClâ(aq). The reaction was studied in electrochemical double cells without liquid junction of the type shown in eq 2. The experimental value of the equilibrium constant at 295 +\\/- 2 K is K = 1.08

  4. Theoretical investigation of isotope exchange reaction in tritium-contaminated mineral oil in vacuum pump.

    PubMed

    Dong, Liang; Xie, Yun; Du, Liang; Li, Weiyi; Tan, Zhaoyi

    2015-04-28

    The mechanism of the isotope exchange reaction between molecular tritium and several typical organic molecules in vacuum pump mineral oil has been investigated by density functional theory (DFT), and the reaction rates are determined by conventional transition state theory (TST). The tritium-hydrogen isotope exchange reaction can proceed with two different mechanisms, the direct T-H exchange mechanism and the hyrogenation-dehydrogenation exchange mechanism. In the direct exchange mechanism, the titrated product is obtained through one-step via a four-membered ring hydrogen migration transition state. In the hyrogenation-dehydrogenation exchange mechanism, the T-H exchange could be accomplished by the hydrogenation of the unsaturated bond with tritium followed by the dehydrogenation of HT. Isotope exchange between hydrogen and tritium is selective, and oil containing molecules with OH and COOH groups can more easily exchange hydrogen for tritium. For aldehydes and ketones, the ability of T-H isotope exchange can be determined by the hydrogenation of T2 or the dehydrogenation of HT. The molecules containing one type of hydrogen provide a single product, while the molecules containing different types of hydrogens provide competitive products. The rate constants are presented to quantitatively estimate the selectivity of the products. PMID:25625628

  5. Isomeric Differentiation of Green Tea Catechins using Gas-Phase Hydrogen/Deuterium Exchange Reactions

    PubMed Central

    Niemeyer, Emily D.; Brodbelt, Jennifer S.

    2007-01-01

    Hydrogen/deuterium exchange reactions in a quadrupole ion trap mass spectrometer are used to differentiate galloylated catechin stereoisomers (catechin gallate and epicatechin gallate; gallocatechin gallate and epigallocatechin gallate) and the non-galloylated analogs (catechin and epicatechin, gallocatechin and epigallocatechin). Significant differences in the hydrogen/deuterium exchange behavior of the four pairs of deprotonated catechin stereoisomers are observed upon reaction with D2O. Interestingly, the non-galloylated catechins undergo H/D exchange to a much greater extent than the galloylated species, incorporating deuterium at both aromatic/allylic and active phenolic sites. Non-galloylated catechin isomers are virtually indistinguishable by their H/D exchange kinetics over a wide range of reaction times (0.05 to 10 s). Our experimental results are explained using high-level ab initio calculations to elucidate the subtle structural variations in the catechin stereoisomers that lead to their differing H/D exchange kinetics. PMID:17702600

  6. The function of supplements required for the formate-pyruvate exchange reaction in Streptococcus faecalis 

    E-print Network

    Smith, Gordon Marsh

    1964-01-01

    THE FUNCTION OF SUPPLEMENTS REQUIRED FOR THE FORMATE-FYRUVATE EXCHANGE REACTION IN STREFTOCOCCUS FAECALIS A Thesis By GORDON MARSII SMITH Submitted to the Graduate College of the Texas AS' University in partial fulfillment... of the requirements for the degree of MASTER OF SCIENCE January l964 Major Subject: Microbiology THE FUNCTION OF SUPPLEMENTS REQUIRED FOR THE FORMATE-PYRUVATE EXCHANGE REACTION I. N STREPTOCOCCUS FAECALIS A Thesis By GORDON MARSH SMITH Approved as to styie...

  7. Measurement of positional isotope exchange rates in enzyme catalyzed reactions by fast atom bombardment mass spectrometry 

    E-print Network

    Hilscher, Larry Wayne

    1985-01-01

    of the requiremer ts for the degree of MASTEP. QF SCIENCE August 1985 Major Subject: Chemistry MEASUREMENT OF POSITIONAL ISOTOPE EXCHANGE RATES IN ENZYME CATALYZED REACTIONS BY FAST ATOM BOMBARDMENT MASS SPECTROMETRY A Thesis LARRY NAYNE HILSCHER Approved...MEASUREMENT OF POSITIONAL ISOTOPE EXCHANGE RATES IN ENZYME CATALYZED REACTIONS BY FAST ATOM BOMBARDMENT MASS SPECTROMETRY A Thesis by LARRY NAYNE HILSCHER Submitted to the Gradu te College of Texas A&M University in partial fulfil" mert...

  8. Pion single- and double-charge-exchange reactions at low energies

    SciTech Connect

    Baer, H.W.

    1987-01-01

    The general features of pion charge-exchange reactions at energies of 20 to 80 MeV leading to nuclear isobaric-analog states (IAS) and double-isobaric-analog states (DIAS) are reviewed. The recent progress achieved in understanding the role of short-range N-N correlations in the double-charge-exchange reactions is presented. 36 refs., 21 figs., 2 tabs.

  9. Fast Neutral Generation by Charge Exchange Reaction and Its Effect on Neutron Production Rate in Inertial Electrostatic Confinement Fusion Systems

    Microsoft Academic Search

    S. Yoshinaga; H. Matsuura; Y. Nakao; K. Kudo

    2005-01-01

    Fast neutral generation by charge exchange reaction in inertial electrostatic confinement plasmas is studied by solving the Poisson equation and the Boltzmann equation for fast neutrals. Fusion reactions carried by the charge exchange fast neutrals become appreciable compared with ion-background fusion reaction. It is shown that the fusion reaction between fast neutral and background gas is sensitively affected by experimental

  10. Two-pion-exchange effects in the $pp\\to pp?^0$ reaction

    E-print Network

    F. Myhrer

    2007-10-18

    We study the pp \\to pp\\pi^0 reaction near threshold based on heavy-baryon chiral perturbation theory. We show that the two-pion-exchange diagrams give much larger contribution than the one-pion-exchange diagram which is of lower chiral order in Weinberg's counting scheme. We also discuss the relation of our results to the momentum counting scheme.

  11. The formate-pyruvate exchange reaction by Streptococcus faecalis

    E-print Network

    Yeager, Robert Lee

    1960-01-01

    -free retreat FlGUBK lNDLX The effect oi time of LnruLetion of vulture and concentration of glucose on the formats-pyruvate exchange activity (basal med'um). . . , . . . . . . . , . . 16 The influence of time of incubation of culture and concentration... of glucose on ths amount cf growth (basal tnedium). . . . . . . . . . . . . . 18 A comparison of NSC and Difco hydrolyxed casein on the amount of growth and formats-pyruvats exchange activity (0. 1 psr cent glucose and basal medium) . . Ths effect...

  12. Invited Parallel Talk: Forward pion-nucleon charge exchange reaction and Regge constraints

    NASA Astrophysics Data System (ADS)

    Huang, Fei; Sibirtsev, A.; Krewald, S.; Hanhart, C.; Haidenbauer, J.; Meißner, U.-G.

    2009-12-01

    We present our recent study of pion-nucleon charge exchange amplitudes above 2 GeV. We analyze the forward pion-nucleon charge exchange reaction data in a Regge model and compare the resulting amplitudes with those from the Karlsruhe-Helsinki and George-Washington-University partial-wave analyses. We explore possible high-energy constraints for theoretical baryon resonance analyses in the energy region above 2 GeV. Our results show that for the pion-nucleon charge exchange reaction, the appropriate energy region for matching meson-nucleon dynamics to diffractive scattering should be around 3 GeV for the helicity flip amplitude.

  13. Interacting-boson-approximation study on the nuclear structural factor in double-charge-exchange reactions

    SciTech Connect

    Wu, H.; Wang, R.; Liu, Y.; Zhao, E. (World Laboratory (CCAST), P.O. Box 8730, Beijing (China) Physics Department, Suzhou University, Suzhou (China) Institute of High Energy Physics, Academia Sinica, Beijing (China) Institute of Theoretical Physics, Academia Sinica, Beijing (China))

    1992-04-01

    The double-charge-exchange (DCX) reaction with Ca isotopes as targets is studied by employing the interacting-boson approximation (IBA). A comparison between the IBA and the shell-model results shows that IBA is a good approximation of the shell model in describing the DCX reactions.

  14. The control of Phanerozoic atmosphere and seawater composition by basalt–seawater exchange reactions

    Microsoft Academic Search

    Rolf S. Arvidson; Michael Guidry; Fred T. Mackenzie

    2006-01-01

    We present results from a long term geochemical cycling model, with a focus on the sensitivity of atmospheric carbon dioxide, oxygen, and the major element composition of seawater to seafloor spreading rates. This model incorporates rock weathering, basalt–seawater exchange reactions, and the formation and destruction of chemical sediments and organic matter. Hydrothermal reactions between seafloor and seawater involving calcium, magnesium,

  15. Sequential Anion and Cation Exchange Reactions for Complete Material Transformations of Nanoparticles with Morphological Retention.

    PubMed

    Hodges, James M; Kletetschka, Karel; Fenton, Julie L; Read, Carlos G; Schaak, Raymond E

    2015-07-20

    Ion exchange reactions of colloidal nanocrystals provide access to complex products that are synthetically challenging using traditional hot-injection methods. However, such reactions typically achieve only partial material transformations by employing either cation or anion exchange processes. It is now shown that anion and cation exchange reactions can be coupled together and applied sequentially in one integrated pathway that leads to complete material transformations of nanocrystal templates. Although the product nanocrystals do not contain any of the original constituent elements, the original morphology is retained, thereby fully decoupling morphology and composition control. The sequential anion/cation exchange process was applied to pseudo-spherical CdO nanocrystals and ZnO tetrapods, producing fully transformed and shape-controlled nanocrystals of copper and silver sulfides and selenides. Furthermore, hollow core-shell tetrapod ZnS@CdS heterostructures were readily accessible. PMID:26110653

  16. Quantum dynamics of 16O + 36O2 and 18O + 32O2 exchange reactions

    NASA Astrophysics Data System (ADS)

    Rajagopala Rao, T.; Guillon, G.; Mahapatra, S.; Honvault, P.

    2015-05-01

    We present quantum dynamical investigations of 16O + 36O2 and 18O + 32O2 exchange reactions using a time-independent quantum mechanical method and an accurate global potential energy surface of ozone [Dawes et al., J. Chem. Phys. 135, 081102 (2011)]. Initial state-selected integral cross sections, rate constants, and Boltzmann averaged thermal rate constants are obtained and compared with earlier experimental and theoretical results. The computed thermal rate constants for the oxygen exchange reactions exhibit a negative temperature dependence, as found experimentally. They are in better agreement with the experiments than the previous studies on the same reactions.

  17. Addition reactions of thiophenol to ?,?-unsaturated carbonyl compounds using organic acid radical basic anion-exchange resins as catalysts

    Microsoft Academic Search

    Mingxia Li; Jinxia Huang; Wanxuan Zhang

    2001-01-01

    A series of organic acid radical basic anion-exchange resins were prepared from strongly basic quarternary ammonium I type anion-exchange resins, using as the catalysts in addition reactions of thiophenol to ?,?-unsaturated carbonyl compounds. The catalytic activity are influenced by exchange capacity, reaction temperature, solvent and molecular structure.

  18. Multistrange Baryon production from strangeness-exchange reactions 

    E-print Network

    Li, Changhui

    2002-01-01

    Using a gauged flavor SU(3) invariant hadronic Lagrangian, we study [] production from [ ] induced reactions on[] and [] in a coupled-channel approach. Including the four channels of [], and [], we solve the Bethe-Salpeter equation in the K...

  19. Multistrange Baryon production from strangeness-exchange reactions

    E-print Network

    Li, Changhui

    2002-01-01

    Using a gauged flavor SU(3) invariant hadronic Lagrangian, we study [] production from [ ] induced reactions on[] and [] in a coupled-channel approach. Including the four channels of [], and [], we solve the Bethe-Salpeter equation in the K...

  20. EXFOR BASICS A SHORT GUIDE TO THE NEUTRON REACTION DATA EXCHANGE FORMAT.

    SciTech Connect

    MCLANE,V.; NUCLEAR DATA CENTER NETWORK

    2000-05-19

    This manual is intended as a guide to users of nuclear reaction data compiled in the EXFOR format, and is not intended as a complete guide to the EXFOR System. EXFOR is the exchange format designed to allow transmission of nuclear reaction data between the Nuclear Reaction Data Centers. In addition to storing the data and its' bibliographic information, experimental information is also compiled. The status (e.g., the source of the data) and history (e.g., date of last update) of the data set is also included. EXFOR is designed for flexibility in order to meet the diverse needs of the nuclear reaction data centers. It was originally conceived for the exchange of neutron data and was developed through discussions among personnel from centers situated in Saclay, Vienna, Livermore and Brookhaven. It was accepted as the official exchange format of the neutron data centers at Saclay, Vienna, Brookhaven and Obninsk, at a meeting held in November 1969.3 As a result of two meetings held in 1975 and 1976 and attended by several charged-particle data centers, the format was further developed and adapted to cover all nuclear reaction data. The exchange format should not be confused with a center-to-user format. Although users may obtain data from the centers in the EXFOR format, other center-to-user formats have been developed to meet the needs of the users within each center's own sphere of responsibility. The EXFOR format, as outlined, allows a large variety of numerical data tables with explanatory and bibliographic information to be transmitted in a format: l that is machine-readable (for checking and indicating possible errors); l that can be read by personnel (for passing judgment on and correcting errors). The data presently included in the EXFOR exchange file include: a complete compilation of experimental neutron-induced reaction data, a selected compilation of charged-particle-induced reaction data, a selected compilation of photon-induced reaction data.

  1. EXFOR BASICS A SHORT GUIDE TO THE NEUTRON REACTION DATA EXCHANGE FORMAT.

    SciTech Connect

    MCLANE,V.; NUCLEAR DATA CENTER NETWORK

    2000-05-19

    This manual is intended as a guide to users of nuclear reaction data compiled in the EXFOR format, and is not intended as a complete guide to the EXFOR System. EXFOR is the exchange format designed to allow transmission of nuclear reaction data between the Nuclear Reaction Data Centers. In addition to storing the data and its' bibliographic information, experimental information is also compiled. The status (e.g., the source of the data) and history (e.g., date of last update) of the data set is also included. EXFOR is designed for flexibility in order to meet the diverse needs of the nuclear reaction data centers. It was originally conceived for the exchange of neutron data and was developed through discussions among personnel from centers situated in Saclay, Vienna, Livermore and Brookhaven. It was accepted as the official exchange format of the neutron data centers at Saclay, Vienna, Brookhaven and Obninsk, at a meeting held in November 1969. As a result of two meetings held in 1975 and 1976 and attended by several charged-particle data centers, the format was further developed and adapted to cover all nuclear reaction data. The exchange format should not be confused with a center-to-user format. Although users may obtain data from the centers in the EXFOR format, other center-to-user formats have been developed to meet the needs of the users within each center's own sphere of responsibility. The EXFOR format, as outlined, allows a large variety of numerical data tables with explanatory and bibliographic information to be transmitted in a format: that is machine-readable (for checking and indicating possible errors); that can be read by personnel (for passing judgment on and correcting errors). The data presently included in the EXFOR exchange file include: a complete compilation of experimental neutron-induced reaction data, a selected compilation of charged-particle-induced reaction data, a selected compilation of photon-induced reaction data.

  2. Copper ion-exchanged zeolite catalysts in deNO x reaction

    Microsoft Academic Search

    Hidenori Yahiro; Masakazu Iwamoto

    2001-01-01

    Copper ion-exchanged zeolites have widely been studied as the catalysts for NOx emission control. Cu-MFI zeolites, especially over-exchanged Cu-MFI, are very active for the catalytic decomposition of NO. The reaction mechanisms and the active sites suggested are summarized. The newly developed selective catalytic reduction of NO with hydrocarbons in the presence of excess oxygen is then introduced. The role of

  3. Reaction kinetics of ethylene conversion and hydrogen exchange on Pt by sup 2 H NMR

    SciTech Connect

    Zax, D.B.; Klug, C.A.; Slichter, C.P. (Univ. of Illinois, Urbana (USA)); Sinfelt, J.H. (Exxon Research and Engineering Co., Annandale, NJ (USA))

    1989-06-29

    The authors report the use of deuterium NMR to study two types of reactions involving ethylene adsorbed on small supported Pt metal particles typical of industrial catalysts. They utilized annealing experiments in which the reaction temperature was increased in steps, but all NMR measurements were made at 77 K. The first reaction is the structural rearrangement of ethylene adsorbed at low temperatures (200 K) to the stable room-temperature species (ethylidyne). The second reaction is the exchange between hydrogen atoms in ethylidyne and deuterium atoms adsorbed on the surface at low temperatures (77 K). From their observations they were able to determine the activation energies and preexponentials for these processes.

  4. Arrhenius' law in turbulent media and an equivalent tunnel effect. [in binary exchange chemical reactions

    NASA Technical Reports Server (NTRS)

    Tsuge, S.; Sagara, K.

    1978-01-01

    The indeterminacy inherent to the formal extension of Arrhenius' law to reactions in turbulent flows is shown to be surmountable in the case of a binary exchange reaction with a sufficiently high activation energy. A preliminary calculation predicts that the turbulent reaction rate is invariant in the Arrhenius form except for an equivalently lowered activation energy. This is a reflection of turbulence-augmented molecular vigor, and causes an appreciable increase in the reaction rate. A similarity to the tunnel effect in quantum mechanics is indicated. The anomaly associated with the mild ignition of oxy-hydrogen mixtures is discussed in this light.

  5. Pion double-charge-exchange reaction: Shell model formalism

    SciTech Connect

    Vergados, J.D. (Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (US) Department of Physics, University of Ioannina, Ioannina, Greece)

    1991-07-01

    A quite general formalism which allows one to compute the pion double-charge-exchange differential cross section in the context of the shell model has been developed. Compact formulas taking into account the full momentum and spin dependence of the elementary amplitude are given. These formulas hold for any nuclear angular momenta as well as any pion-nucleus partial waves. Thus the differential cross section depends on a quantity {ital B}{sub {ital l}1}{ital l2}{ital ifJ}({ital k}{sub 1},{ital k}{sub 2}) which is a function of the magnitude of the pion momenta {ital k}{sub 1},{ital k}{sub 2} and is composed of three factors: (1) the nuclear matrix element involving the states ({ital i}) and ({ital f}) expressed in terms of tensor operators {ital T}({ital a}{sup {dagger}}{ital a}); (2) the essentially geometric'' aspects of the elementary double-charge-exchange amplitude which are pretty independent of any specific model; (3) a radial integral which contains the ingredients of specific models as well as the distortion of the mesons involved.

  6. Competition between abstraction and exchange channels in H + HCN reaction: Full-dimensional quantum dynamics

    SciTech Connect

    Jiang, Bin; Guo, Hua, E-mail: hguo@unm.edu [Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131 (United States)] [Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131 (United States)

    2013-12-14

    Dynamics of the title reaction is investigated on an ab initio based potential energy surface using a full-dimensional quantum wave packet method within the centrifugal sudden approximation. It is shown that the reaction between H and HCN leads to both the hydrogen exchange and hydrogen abstraction channels. The exchange channel has a lower threshold and larger cross section than the abstraction channel. It also has more oscillations due apparently to quantum resonances. Both channels are affected by long-lived resonances supported by potential wells. Comparison with experimental cross sections indicates underestimation of the abstraction barrier height.

  7. New charge exchange model of GEANT4 for 9Be(p,n)9B reaction

    NASA Astrophysics Data System (ADS)

    Shin, Jae Won; Park, Tae-Sun

    2015-01-01

    A new data-based charge exchange model of GEANT4 dedicated to the 9Be(p,n)9B reaction is developed by taking the ENDF/B-VII.1 differential cross-section data as input. Our model yields results that are in good agreement with the experimental neutron yield spectrum data obtained for proton beams of energy (20-35) MeV. In particular, in contrast to all the considered GEANT4 hadronic models, the peak structure resulting from the discrete neutrons generated by the charge-exchange reaction is observed to be accurately reproduced in our model.

  8. Charge exchange and chemical reactions with trapped Th{sup 3+}

    SciTech Connect

    Churchill, L. R.; DePalatis, M. V.; Chapman, M. S. [School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332-0430 (United States)

    2011-01-15

    We have measured the reaction rates of trapped, buffer gas cooled Th{sup 3+} and various gases and have analyzed the reaction products using trapped ion mass spectrometry techniques. Ion trap lifetimes are usually limited by reactions with background molecules, and the high electron affinity of multiply charged ions such as Th{sup 3+} make them more prone to loss. Our results show that reactions of Th{sup 3+} with carbon dioxide, methane, and oxygen all occur near the classical Langevin rate, while reaction rates with argon, hydrogen, and nitrogen are orders of magnitude lower. Reactions of Th{sup 3+} with oxygen and methane proceed primarily via charge exchange, while simultaneous charge exchange and chemical reaction occurs between Th{sup 3+} and carbon dioxide. Loss rates of Th{sup 3+} in helium are consistent with reaction with impurities in the gas. Reaction rates of Th{sup 3+} with nitrogen and argon depend on the internal electronic configuration of the Th{sup 3+}.

  9. Energetics and control of ultracold isotope-exchange reactions between heteronuclear dimers in external fields

    E-print Network

    Tomza, Micha?

    2015-01-01

    We show that isotope-exchange reactions between ground-state alkali-metal, alkaline-earth-metal, and lanthanide heteronuclear dimers consisting of two isotopes of the same atom are exothermic with an energy change in the range of 1-8000$\\,$MHz thus resulting in cold or ultracold products. For these chemical reactions there are only one rovibrational and at most several hyperfine possible product states. The number and energetics of open and closed reactive channels can be controlled by the laser and magnetic fields. The exothermic isotope-exchange reactions can be tuned to become endothermic by employing a laser-induced state-selective Stark shift control thus providing a ground for testing models of the chemical reactivity. The present proposal opens the way for studying the state-to-state dynamics of ultracold chemical reactions beyond the universal limit with a meaningful control over quantum states of both reactants and products.

  10. Ester-exchange reaction between triglycerides with polyethylene glycol-modified lipase

    Microsoft Academic Search

    Ayako Matsushima; Yoh Kodera; Katsunobu Takahashi; Yuji Saito; Yuji Inada

    1986-01-01

    Summary Polyethylene glycol-modified lipase efficiently catalyzed esterexchange reaction between trilaurin and triolein in the straight hydrophobic substrates. Dilauroyl-monooleoyl-glycerol and monolauroyl-dioleoyl-glycerol were formed from two triglyceride-substrates, trilaurin and triolein, in the presence of the modified lipase at 58°C. Consequently, the melting temperature of the mixture of two substrates was decreased from 33–36°C to 11–13°C. Similar ester-exchange reaction took place between fat

  11. Fast Neutral Generation by Charge Exchange Reaction and Its Effect on Neutron Production Rate in Inertial Electrostatic Confinement Fusion Systems

    SciTech Connect

    Yoshinaga, S.; Matsuura, H.; Nakao, Y.; Kudo, K. [Kyushu University (Japan)

    2005-05-15

    Fast neutral generation by charge exchange reaction in inertial electrostatic confinement plasmas is studied by solving the Poisson equation and the Boltzmann equation for fast neutrals. Fusion reactions carried by the charge exchange fast neutrals become appreciable compared with ion-background fusion reaction. It is shown that the fusion reaction between fast neutral and background gas is sensitively affected by experimental parameters (grid voltage, background gas pressure) and ion distribution function.

  12. Carbon Dioxide Exchange at the Air–Sea Interface: Flux Augmentation by Chemical Reaction

    Microsoft Academic Search

    J. A. Quinn; N. C. Otto

    1971-01-01

    Numerical results for typical ocean conditions indicate that for film thicknesses less than, say, 400tz. oceanic exchange is not influenced by the hydration\\/dehydration reactions of dissolved carbon dioxide. This conclusion is in substantial agreement with the approximate analysis of Bolin [1960]. However, if suitable catalysts are present in the ocean (there is recent evidence to suggest that this may be

  13. Further studies on vinamidinium salt amine exchange reactions, borohydride reductions and subsequent transformations

    PubMed Central

    Gupton, John T.; Telang, Nakul; Jia, Xin; Giglio, Benjamin C.; Eaton, James E.; Barelli, Peter J.; Hovaizi, Mona; Hall, Kayleigh E.; Welden, R. Scott; Keough, Matthew J.; Worrall, Eric F.; Finzel, Kara L.; Kluball, Emily J.; Kanters, Rene P.F.; Smith, Timothy M.; Smith, Stanton Q.; Nunes, Shane R.; Wright, Mathew T.; Birnstihl, Jennifer M.

    2010-01-01

    Studies directed at the amine exchange reaction of vinamidinium salts followed by sodium borohydride reduction to secondary and tertiary allylic amines are described. The tertiary allylic amines were alkylated and subjected to base mediated rearrangement to yield a variety of highly functionalized tertiary homoallylic amines. PMID:21113324

  14. Superhydrophobic properties of silver-coated films on copper surface by galvanic exchange reaction

    Microsoft Academic Search

    A. Safaee; D. K. Sarkar; M. Farzaneh

    2008-01-01

    Hydrophobic properties of thin nanostructured silver films produced by galvanic exchange reaction on a copper surface were studied after passivation with stearic acid. The morphology of the silver films was controlled by varying the concentration of silver nitrate in the solution. Water contact angle as high as 156° and contact angle hysteresis as low as 5° were achieved for samples

  15. Synthesis of Single-Crystalline Niobate Nanorods via Ion-Exchange Based on Molten-Salt Reaction

    E-print Network

    Wang, Zhong L.

    Synthesis of Single-Crystalline Niobate Nanorods via Ion-Exchange Based on Molten-Salt Reaction by employing hydrothermal reaction2 or templates,3 molten-salt syn- thesis,4 and composite- exchange approach for the synthesis of single-crystal sodium and calcium niobates nanorods based on molten-salt

  16. Incorporation of monomethylethanolamine into phosphatidylcholine by way of an exchange reaction followed by methylation

    SciTech Connect

    Moore, T.S. Jr. (Louisiana State Univ., Baton Rouge (USA))

    1989-04-01

    Recent evidence by Datko and Mudd indicates that phosphatidylcholine (PC) may be synthesized by methylation of phosphatidylmonomethyl-ethanolamine (PMME), but perhaps not by utilization of phosphatidylethanolamine (PE) as a source of PMME. They provided evidence that a CDP derivative of monomethylethanolamine (MME) might be the source of the headgroup. Another possibility is incorporation of MME by an exchange reaction. We tested this by incubating MME with ER from castor bean endosperm and radiolabeled S- adenosylmethionine under conditions which would allow incorporation of the headgroup and methylation to PC. Under these conditions the reaction proceeded, with radiolabel appearing in both PC and phosphatidyldimethylethanolamine. Neither ethanolamine nor L-serine, both of which are known to undergo exchange reactions, yielded PC under the same conditions.

  17. Hydraulic controls of in-stream gravel bar hyporheic exchange and reactions

    NASA Astrophysics Data System (ADS)

    Trauth, Nico; Schmidt, Christian; Vieweg, Michael; Oswald, Sascha E.; Fleckenstein, Jan H.

    2015-04-01

    Hyporheic exchange transports solutes into the subsurface where they can undergo biogeochemical transformations, affecting fluvial water quality and ecology. A three-dimensional numerical model of a natural in-stream gravel bar (20 m × 6 m) is presented. Multiple steady state streamflow is simulated with a computational fluid dynamics code that is sequentially coupled to a reactive transport groundwater model via the hydraulic head distribution at the streambed. Ambient groundwater flow is considered by scenarios of neutral, gaining, and losing conditions. The transformation of oxygen, nitrate, and dissolved organic carbon by aerobic respiration and denitrification in the hyporheic zone are modeled, as is the denitrification of groundwater-borne nitrate when mixed with stream-sourced carbon. In contrast to fully submerged structures, hyporheic exchange flux decreases with increasing stream discharge, due to decreasing hydraulic head gradients across the partially submerged structure. Hyporheic residence time distributions are skewed in the log-space with medians of up to 8 h and shift to symmetric distributions with increasing level of submergence. Solute turnover is mainly controlled by residence times and the extent of the hyporheic exchange flow, which defines the potential reaction area. Although streamflow is the primary driver of hyporheic exchange, its impact on hyporheic exchange flux, residence times, and solute turnover is small, as these quantities exponentially decrease under losing and gaining conditions. Hence, highest reaction potential exists under neutral conditions, when the capacity for denitrification in the partially submerged structure can be orders of magnitude higher than in fully submerged structures.

  18. Charge Exchange Reaction: a powerful tool to study the ``Weak Response'' of nuclei

    NASA Astrophysics Data System (ADS)

    Fujita, Yoshitaka

    2014-09-01

    Weak-interaction processes, for example, Gamow-Teller (GT) transitions, play important roles in the stellar evolution and nucleosynthesis. ?-decay studies provide the most direct information on the transition strengths caused by these processes, but the accessible Ex range is limited by the decay Q values. On the other hand, Charge-Exchange (CE) reactions can access the transitions to higher excited states. Pioneering (p , n) reactions at intermediate incident energies (Ebeam > 100 MeV/nucleon) found the main part of the GT transition strength expected by the GT sum rule in GT resonances (GTRs) situated in the Ex = 10 - 15 MeV region, and detailed studies in combination with (n , p) studies provide further knowledge on the GT sum rule. Recent development of CE reactions toward higher resolution and sensitivity is impressive. The (p , n)-type (3He, t) reaction achieved a ?E ~ 30 keV and GTRs were resolved into individual states. The (d,2 He) reaction also provides much better resolution in the (n , p)-type study and recent (t,3 He) reaction in coincidence with ? decay could detect weakly excited states. We can also see future in the CE reactions using unstable incident beams. Weak-interaction processes, for example, Gamow-Teller (GT) transitions, play important roles in the stellar evolution and nucleosynthesis. ?-decay studies provide the most direct information on the transition strengths caused by these processes, but the accessible Ex range is limited by the decay Q values. On the other hand, Charge-Exchange (CE) reactions can access the transitions to higher excited states. Pioneering (p , n) reactions at intermediate incident energies (Ebeam > 100 MeV/nucleon) found the main part of the GT transition strength expected by the GT sum rule in GT resonances (GTRs) situated in the Ex = 10 - 15 MeV region, and detailed studies in combination with (n , p) studies provide further knowledge on the GT sum rule. Recent development of CE reactions toward higher resolution and sensitivity is impressive. The (p , n)-type (3He, t) reaction achieved a ?E ~ 30 keV and GTRs were resolved into individual states. The (d,2 He) reaction also provides much better resolution in the (n , p)-type study and recent (t,3 He) reaction in coincidence with ? decay could detect weakly excited states. We can also see future in the CE reactions using unstable incident beams. Partially supported by MEXT, Japan under Grant No. 22540310.

  19. Sn Cation Valency Dependence in Cation Exchange Reactions Involving Cu2-xSe Nanocrystals

    PubMed Central

    2014-01-01

    We studied cation exchange reactions in colloidal Cu2-xSe nanocrystals (NCs) involving the replacement of Cu+ cations with either Sn2+ or Sn4+ cations. This is a model system in several aspects: first, the +2 and +4 oxidation states for tin are relatively stable; in addition, the phase of the Cu2-xSe NCs remains cubic regardless of the degree of copper deficiency (that is, “x”) in the NC lattice. Also, Sn4+ ions are comparable in size to the Cu+ ions, while Sn2+ ones are much larger. We show here that the valency of the entering Sn ions dictates the structure and composition not only of the final products but also of the intermediate steps of the exchange. When Sn4+ cations are used, alloyed Cu2–4ySnySe NCs (with y ? 0.33) are formed as intermediates, with almost no distortion of the anion framework, apart from a small contraction. In this exchange reaction the final stoichiometry of the NCs cannot go beyond Cu0.66Sn0.33Se (that is Cu2SnSe3), as any further replacement of Cu+ cations with Sn4+ cations would require a drastic reorganization of the anion framework, which is not possible at the reaction conditions of the experiments. When instead Sn2+ cations are employed, SnSe NCs are formed, mostly in the orthorhombic phase, with significant, albeit not drastic, distortion of the anion framework. Intermediate steps in this exchange reaction are represented by Janus-type Cu2-xSe/SnSe heterostructures, with no Cu–Sn–Se alloys. PMID:25340627

  20. One-Step Deposition Process to Obtain Nanostructured Superhydrophobic Thin Films by Galvanic Exchange Reactions

    Microsoft Academic Search

    D. K. Sarkar; R. W. Paynter

    2010-01-01

    Superhydrophobic thin films of silver were fabricated on copper substrates by galvanic ion exchange reactions in a one-step process by immersing copper substrates in silver nitrate solution containing fluoroalkylsilane in different quantities. The X-ray diffraction (XRD) analyses confirmed the formation of silver films on copper substrates and the fractal-like morphological features of the silver films were confirmed using scanning electron

  1. Double pomeron exchange in the reaction ifpp --> pppi+pi- at ISR energies

    Microsoft Academic Search

    Daniel Drijard; H. G. Fischer; R. Gokieli; Pier Giorgio Innocenti; V. Korbel; Adolf G Minten; Alan Robert Norton; R. Sosnowski; S. Stein; H. D. Wahl; Michel Della Negra; G. Fontaine; P. Frenkiel; C. Ghesquiere; D. Linglin; G. Sajot; H. Frehse; E. E. Kluge; A. Putzer; J. Stiewe; P. Hanke; W. Hofmann; J. Spengler; D. Wegener

    1978-01-01

    Using the split field magnet (SFM) of the CERN ISR, we have investigated the main features of the reaction pp --> pppi+pi- in the kinematical region where double pomeron exchange (DPE) is supposed to play an important rôle. Using kinematically fitted events at the five standard ISR energies from &surd;s = 23.4 GeV to &surd;s = 63.4 GeV, we have

  2. Retention of the Cluster Core Structure during Ligand Exchange Reactions of Carboxylato-Substituted Metal Oxo Clusters

    PubMed Central

    Kreutzer, Johannes; Puchberger, Michael; Artner, Christine; Schubert, Ulrich

    2015-01-01

    The exchange of the carboxylato ligands of Zr4O2(methacrylato)12 in reactions with carboxylic acids proceeds with retention of the composition and structure of the cluster core. This was concluded from exchange/re-exchange experiments and from comparison of the IR bands of the cluster core of the original and ligand-exchanged clusters. The IR bands were assigned on the basis of DFT calculations. Scrambling reactions between two Zr4O2(OOCR)12 clusters with different carboxylato ligands are a new way to prepare mixed-ligand oxo clusters.

  3. Nitroxyl Radical plus Hydroxylamine Pseudo Self-Exchange Reactions: Tunneling in Hydrogen Atom Transfer

    PubMed Central

    Wu, Adam; Mader, Elizabeth A.; Datta, Ayan; Hrovat, David A.; Borden, Weston Thatcher; Mayer, James M.

    2009-01-01

    Bimolecular rate constants have been measured for reactions that involve hydrogen atom transfer (HAT) from hydroxylamines to nitroxyl radicals, using the stable radicals TEMPO• (2,2,6,6-tetramethylpiperidine-1-oxyl radical), 4-oxo-TEMPO• (2,2,6,6-tetramethyl-4-oxo-piperidine-1-oxyl radical), di-tert-butylnitroxyl (tBu2NO•), and the hydroxylamines TEMPO-H, 4-oxo-TEMPO-H, 4-MeO-TEMPO-H (2,2,6,6-tetramethyl-N-hydroxy-4-methoxy-piperidine), and tBu2NOH. The reactions have been monitored by UV-vis stopped-flow methods, using the different optical spectra of nitroxyl radicals. The HAT reactions all have |?Go| ? 1.4 kcal mol?1 and therefore are close to self-exchange reactions. The reaction of 4-oxo-TEMPO• + TEMPO-H ? 4-oxo-TEMPO-H + TEMPO• occurs with k2H,MeCN = 10 ± 1 M?1 s?1 in MeCN at 298 K (K2H,MeCN = 4.5 ± 1.8). Surprisingly, the rate constant for the analogous deuterium atom transfer reaction is much slower: k2D,MeCN = 0.44 ± 0.05 M?1 s?1 with k2H,MeCN/k2D,MeCN = 23 ± 3 at 298 K. The same large kinetic isotope effect (KIE) is found in CH2Cl2, 23 ± 4, suggesting that the large KIE is not caused by solvent dynamics or hydrogen bonding to solvent. The related reaction of 4-oxo-TEMPO• with 4-MeO-TEMPO-H(D) also has a large KIE, k3H/k3D = 21 ± 3 in MeCN. For these three reactions, the EaD – EaH values, between 0.3 ± 0.6 and 1.3 ± 0.6 kcal mol?1, and the log(AH/AD) values, between 0.5 ± 0.7 and 1.1 ± 0.6, indicate that hydrogen tunneling plays an important role. The related reaction of tBu2NO• + TEMPO-H(D) in MeCN has a large KIE, 16 ± 3 in MeCN, and very unusual isotopic activation parameters, EaD – EaH = ?2.6 ± 0.4 and log(AH/AD) = 3.1 ± 0.6. Computational studies, using POLYRATE, also indicate substantial tunneling in the (CH3)2NO• + (CH3)2NOH model reaction for the experimental self-exchange processes. Additional calculations on TEMPO(•/H), tBu2NO(•/H), and Ph2NO(•/H) self-exchange reactions reveal why the phenyl groups make the last of these reactions several orders of magnitude faster than the first two. By inference, the calculations also suggest why tunneling appears to be more important in the self-exchange reactions of dialkylhydroxylamines than of arylhydroxylamines. PMID:19618933

  4. Charge-exchange reactions and nuclear matrix elements for {beta}{beta} decay

    SciTech Connect

    Frekers, D. [Institut fuer Kernphysik, Westfaelische Wilhelms-Universitaet, D-48149 Muenster (Germany)

    2009-11-09

    Charge-exchange reactions of (n, p) and (p, n) type at intermediate energies are a powerful tool for the study of nuclear matrix element in {beta}{beta} decay. The present paper reviews some of the most recent experiments in this context. Here, the (n, p) type reactions are realized through (d, {sup 2}He), where {sup 2}He refers to two protons in a singlet {sup 1}S{sub 0} state and where both of these are momentum analyzed and detected by the same spectrometer and detector. These reactions have been developed and performed exclusively at KVI, Groningen (NL), using an incident deuteron energy of 183 MeV. Final state resolutions of about 100 keV have routinely been available. On the other hand, the ({sup 3}He, t) reaction is of (p, n) type and was developed at the RCNP facility in Osaka (JP). Measurements with an unprecedented high resolution of 30 keV at incident energies of 420 MeV are now readily possible. Using both reaction types one can extract the Gamow-Teller transition strengths B(GT{sup +}) and B(GT{sup -}), which define the two ''legs'' of the {beta}{beta} decay matrix elements for the 2v{beta}{beta} decay The high resolution available in both reactions allows a detailed insight into the excitations of the intermediate odd-odd nuclei and, as will be shown, some unexpected features are being unveiled.

  5. Towards rotationally state-resolved differential cross sections for the hydrogen exchange reaction

    SciTech Connect

    Vrakking, M.J.J.

    1992-11-01

    The hydrogen exchange reaction H + H{sub 2} {yields} H{sub 2} + H (and its isotopic variants) plays a pivotal role in chemical reaction dynamics. It is the only chemical reaction for which fully converged quantum scattering calculations have been carried out using a potential energy surface which is considered to be chemically accurate. To improve our ability to test the theory, a `perfect experiment`, measuring differential cross sections with complete specification of the reactant and product states, is called for. In this thesis, the design of an experiment is described that aims at achieving this goal for the D + H{sub 2} reaction. A crossed molecular beam arrangement is used, in which a photolytic D atom beam is crossed by a pulsed beam of H{sub 2} molecules. DH molecules formed in the D + H{sub 2} reaction are state-specifically ionized using Doppler-free (2+1) Resonance-Enhanced Multi-Photon Ionization (REMPI) and detected using a Position-sensitive microchannel plate detector. This detection technique has an unprecedented single shot detection sensitivity of 6.8 10{sup 3} molecules/cc. This thesis does not contain experimental results for the D + H{sub 2} reaction yet, but progress that has been made towards achieving this goal is reported. In addition, results are reported for a study of the Rydberg spectroscopy of the water molecule.

  6. Towards rotationally state-resolved differential cross sections for the hydrogen exchange reaction

    SciTech Connect

    Vrakking, M.J.J.

    1992-11-01

    The hydrogen exchange reaction H + H[sub 2] [yields] H[sub 2] + H (and its isotopic variants) plays a pivotal role in chemical reaction dynamics. It is the only chemical reaction for which fully converged quantum scattering calculations have been carried out using a potential energy surface which is considered to be chemically accurate. To improve our ability to test the theory, a 'perfect experiment', measuring differential cross sections with complete specification of the reactant and product states, is called for. In this thesis, the design of an experiment is described that aims at achieving this goal for the D + H[sub 2] reaction. A crossed molecular beam arrangement is used, in which a photolytic D atom beam is crossed by a pulsed beam of H[sub 2] molecules. DH molecules formed in the D + H[sub 2] reaction are state-specifically ionized using Doppler-free (2+1) Resonance-Enhanced Multi-Photon Ionization (REMPI) and detected using a Position-sensitive microchannel plate detector. This detection technique has an unprecedented single shot detection sensitivity of 6.8 10[sup 3] molecules/cc. This thesis does not contain experimental results for the D + H[sub 2] reaction yet, but progress that has been made towards achieving this goal is reported. In addition, results are reported for a study of the Rydberg spectroscopy of the water molecule.

  7. The analysis of reactions {pi}N {yields} two mesons + N within reggeon exchanges. Basic formulas for fit

    SciTech Connect

    Anisovich, V. V., E-mail: anisovic@thd.pnpi.spb.ru; Sarantsev, A. V. [Russian Academy of Sciences, Petersburg Nuclear Physics Institute (Russian Federation)

    2009-11-15

    We present technical aspects of the fitting procedure given in the paper by V.V. Anisovich and A.V. Sarantsev 'The analysis of reactions {pi}N {yields} two mesons + N within reggeon exchanges. Fit and results.'

  8. Double Regge exchange Limit for the ?p? K?K?p Reaction

    DOE PAGESBeta

    Shi, M.; Danilkin, I. V.; Fernández-Ramírez, C.; Mathieu, V.; Pennington, M. R.; Schott, D.; Szczepaniak, A. P.

    2015-02-01

    We apply the generalized Veneziano model (B5 model) in the double-Regge exchange limit to the ?p?K+K?p reaction. Four different cases defined by the possible combinations of the signature factors of leading Regge exchanges ((K?,a2/f2), (K?,?/?), (K?2,a2/f2), and (K?2,?/?)) have been simulated through the Monte Carlo method. Suitable event candidates for the double-Regge exchange high-energy limit were selected employing \\textit{Van Hove} plots as a better alternative to kinematical cuts in the K+K?p Dalitz plot. In this way we predict and analyze the double-Regge contribution to the K+K?p Dalitz plot, which constitutes one of the major backgrounds in the search for strangeonia,more »hybrids and exotics using ?p?K+K?p reaction. We expect that data currently under analysis, and that to come in the future, will allow verification of the double-Regge behavior and a better assessment of this component of the amplitude.« less

  9. Charge-exchange reaction cross sections and the Gamow-Teller strength for double beta decay

    E-print Network

    K. Amos; Amand Faessler; V. Rodin

    2007-05-02

    The proportionality between single charge-exchange reaction cross sections in the forward direction as found, for example from $(p,n)$ and $(^3$He,$t)$ and from $(n,p)$ and $(d,^2$He) reactions, and the Gamow-Teller (GT) strength into the same final nuclear states has been studied and/or assumed often in the past. Using the most physically justified theory we have at our disposal and for the specific example of the ${}^{76}$Ge-${}^{76}$Se system that may undergo double beta-decay, we demonstrate that the proportionality is a relative good assumption for reactions changing a neutron into a proton, i.e. ${}^{76}$Ge$(p,n){}^{76}$As. In this channel, the main contribution to the GT strengths comes from the removal of a neutron from an occupied single-particle (SP) state and putting a proton into an unoccupied SP state having either the same state quantum numbers or those of the spin-orbit partner. In contrast to this, in the second leg of the double beta decay a single proton must be taken from an occupied SP state and a neutron placed in an unoccupied one. This second process often is Pauli forbidden in medium-heavy nuclei and only can be effected if the Fermi surface is smeared out. Such is the case for ${}^{76}$Se$(n,p){}^{76}$As. Our results suggest that one may not always assume a proportionality between the forward-angle cross sections of the charge-exchange reactions and the GT strength in any such medium-heavy nuclei. The discrepancy originates from a pronounced effect of the radial dependence of the nucleon-nucleon ($NN$) interaction in connection with the Pauli principle on the cross sections in the $(n,p)$ reaction channel. Such a radial dependence is completely absent in the GT transition operator.

  10. Low energy of activation for amide hydrogen exchange reactions in proteins supports a local unfolding model.

    PubMed

    Thomsen, N K; Poulsen, F M

    1993-11-01

    Hydrogen exchange reactions of amides in hen egg white lysozyme that are pH dependent and have a low energy of activation have been shown to be in accordance with a reaction mechanism in two steps, an equilibrium step and an exchange step. These results are not in agreement with the model, proposed by C.K. Woodward & B.D. Hilton, known as the penetration model. Therefore our results suggest that this model should be revised. The amide hydrogen/deuterium exchange rates in hen egg white lysozyme were measured at 4 degrees C, 10 degrees C, 15 degrees C and 25 degrees C at pH 7.0 by 1H nuclear magnetic resonance spectroscopy. Activation energies of the exchange reactions in the range from 20 kJ mol-1 to 333 kJ mol-1 were obtained for 32 of the 129 residues in the protein. The amides of lysozyme studied here could be divided into two groups, one group of amides are characterized by an observed amide exchange rate (ko) in the range 10(-4) to 10(-6) s-1, an equilibrium constant k1/k2 close to 10(-5), a low energy of activation (20 to 50 kJ mol-1) and a distance less than 6 A from solvent. The other group of amides are characterized by a ko less than 10(-6) s-1, a k1/k2 close to 10(-7), higher energies of activation (40 to 330 kJ mol-1) and a distance more than 4 A from solvent. In terms of structure the amides of the last group are from the core of the protein. They are typically involved in a hydrogen bond and form part of the secondary structure either as interior alpha-helices or central strands of beta-sheets. The first group consists of amides that are in the shell of the protein between the core and the surface. These amides are typically hydrogen bonded and involved in secondary structure such as external alpha-helices or outer strands of beta-sheets and turns. PMID:8230202

  11. Adverse tissue reactions in modular exchangeable neck implants: a report of two cases.

    PubMed

    Werner, S Douglas; Bono, James V; Nandi, Sumon; Ward, Daniel M; Talmo, Carl T

    2013-03-01

    Dual-modular femoral stems with exchangeable necks theoretically allow optimization of hip joint biomechanics via selective restoration of femoral anteversion, offset, and limb length. A potential disadvantage is the possible generation of metal ions and debris by fretting and crevice corrosion at the additional stem-neck interface. We present 2 cases of early-onset adverse inflammatory tissue reactions as a result of accelerated corrosion at the stem-neck interface of a dual-modular implant, requiring subsequent revision of well-fixed components. PMID:23141863

  12. Excitation of Nucleon Resonances in Heavy-Ion Charge-Exchange Reactions

    NASA Astrophysics Data System (ADS)

    Benlliure, J.; Vargas, J.; Alvarez-Pol, H.; Aumann, T.; Atkinson, J.; Ayyad, Y.; Beceiro, S.; Borezky, K.; Chatillon, A.; Cortina, D.; Diaz, P.; Estrade, A.; Geissel, H.; Lenske, H.; Litvinov, Y.; Mostazo, M.; Paradela, C.; Pietri, S.; Prochazka, A.; Taieb, J.; Takechi, M.; Vidaña, I.; Weick, H.; Winfield, J.

    Isobaric charge-exchange reactions induced by different tin isotopes have been investigated at GSI. The high-resolving power of the FRS spectrometer made it possible to separate elastic and inelastic components in the missing-energy spectra of the ejectiles. The inelastic component was associated to the in-medium excitation of nucleon resonances such as the Delta and Roper resonances. These data are expected to contribute to better understand the role of subnuclear degrees of freedom in three body forces or the missing strength in Gamow-Teller transitions but also to investigate the abundance of protons and neutrons at the nuclear periphery.

  13. Superhydrophobic properties of silver-coated films on copper surface by galvanic exchange reaction

    NASA Astrophysics Data System (ADS)

    Safaee, A.; Sarkar, D. K.; Farzaneh, M.

    2008-02-01

    Hydrophobic properties of thin nanostructured silver films produced by galvanic exchange reaction on a copper surface were studied after passivation with stearic acid. The morphology of the silver films was controlled by varying the concentration of silver nitrate in the solution. Water contact angle as high as 156° and contact angle hysteresis as low as 5° were achieved for samples obtained with initial silver ion concentration of 24.75 mM in the solution. However, a strong dependence of contact angle and contact angle hysteresis on the fractal-like morphology of the silver films was observed with the variation of silver ion concentration.

  14. Kinetics and mechanism of ligand-exchange reactions of Cd(II) chelates

    SciTech Connect

    Nivorozhkin, L.E.; Kalabin, G.A.; Nivorozhkin, A.L.; Valeev, R.B.; Minkin, V.I.

    1987-03-01

    Tetrahedral Cd(II) bis(5-thio(or seleno)pyrazole-4-carboxaldiminates) of types II and III have been synthesized for the first time. The kinetics of the degenerate ligand exchange and enantiomerization of the complexes obtained have been studied by dynamic /sup 111/Cd, /sup 77/Se, and /sup 1/H (s = 1/2) NMR. The rate of intramolecular enantiomerization (k = 1/tau) is more than an order of magnitude greater than the corresponding values for processes of degenerate ligand exchange (a second-order reaction) determined from the dynamics of the averaging of the /sup 111/Cd-/sup 77/Se and /sup 111/Cd-N=CH spin-spin coupling constants. The cleavage and formation processes of the Cd-Se and Cd-N bonds are isoenergetic (..delta.. G/sub 298//sup not equal to/ = 14.4 kcal/mole for chelate II with X = Se and R = CH/sub 2/C/sub 6/H/sub 5/). The free energies of activation of degenerate ligand exchange determined form the dynamics of the averaging of the /sup 111/Cd N=CH spin-spin coupling constant increase from 12.7 to 17.9 kcal/mole along the following series for R: C/sub 2/H/sub 5/ < Ar < CH/sub 2/C/sub 6/H/sub 5/ < t-C/sub 4/H/sub 9/ < cyclo-C/sub 6/H/sub 11/. Replacement of the sulfur atom in the chelate ring by selenium results in increases in the rates of ligand exchange. A mechanism of degenerate ligand exchange has been proposed.

  15. Dynamics of the molecular and atomic mechanisms for the hydrogen-iodine exchange reaction.

    NASA Technical Reports Server (NTRS)

    Raff, L. M.; Thompson, D. L.; Sims, L. B.; Porter, R. N.

    1972-01-01

    The molecular and atomic mechanisms for the hydrogen-iodine exchange reaction are treated theoretically by means of extensive classical trajectories calculated on a reasonable potential energy surface on which the single adjustable parameter is the iodine-core effective charge. The analysis shows the molecular mechanism to be dynamically forbidden, but gives an over-all rate constant for the atomic mechanism that is in agreement with the experimental values. It is indicated that the formation of a weak H2I complex plays an important dynamical role if the atomic mechanism is limited to reactions with collision complexes involving no more than two hydrogen atoms and two iodine atoms. Excellent agreement with experiment is obtained for the rate constant for the recombination I+I+H2 yields I2+H2 and its negative temperature coefficient.

  16. Weak interaction processes in supernovae: New probes using charge exchange reaction at intermediate energies

    NASA Astrophysics Data System (ADS)

    Frekers, Dieter

    2005-04-01

    Spin-isospin-flip excitations in nuclei at vanishing momentum transfer are generally referred to as Gamov-Teller (GT) transitions. They are being studied because the simplicity of the excitation makes them an ideal probe for testing nuclear structure models. In astrophysics, GT transitions provide an important input for model calculations and element formation during the explosive phase of a massive star at the end of its life-time. GT transitions in the ?- direction (also referred to as isospin lowering T< transitions) have extensively been studied through (p,n) and (3He,t) charge-exchange reactions [B.D. Anderson et al., Phys. Rev. C 36 (1987) 2195, B.D. Anderson et al., Phys. Rev. C 43 (1991) 50, J. Rapaport et al., Phys. Rev. C 24 (1981) 335, H. Akimune et al., Nucl. Phys. A 569 (1994) 245c, Y. Fujita et al., Phys. Lett. B 365 (1996) 29]. The generally good resolution allows easy extraction of the GT distribution and the total B(GT-) strength in the final nucleus. On the other hand, determination of B(GT+) strength through a charge-exchange reaction in the T> direction were mostly done with secondary neutron beams, and as such, they come with significant experimental difficulties. TRIUMF has pioneered this field in the late 80's and early 90's with a rich and highly successful (n,p) program using a several hundred MeV neutron beam from a 7Li(p,n)7Be reaction [R. Helmer, Can. J. Phys. 65 (1987) 588]. In this paper we present the (d,2He) reaction at intermediate energies as another and potentially even more powerful tool for charge-exchange reactions in the T>, resp. ?+ direction. The key issue here will be the high resolution of order 100 keV, which provides new and sometimes unexpected insight into nuclear structure phenomena. This program has been launched at the AGOR Superconducting Cyclotron Facility at the KVI Groningen. By now, it covers a wide field of physics questions ranging from few-body physics, the structure of halo-nuclei, to questions pertaining to the dynamics of supernova explosions and nuclear synthesis, and more recently to the measurements of (??) decay matrix elements and the determination of half-lives of (??) decaying nuclei.

  17. State-to-state quantum dynamics of O + O2 isotope exchange reactions reveals nonstatistical behavior at atmospheric conditions

    PubMed Central

    Sun, Zhigang; Liu, Lan; Lin, Shi Ying; Schinke, Reinhard; Guo, Hua; Zhang, Dong H.

    2010-01-01

    The O + O2 exchange reaction is a prerequisite for the formation of ozone in Earth’s atmosphere. We report here state-to-state differential and integral cross sections for several O + O2 isotope-exchange reactions obtained by dynamically exact quantum scattering calculations at collision energies relevant to atmospheric conditions. These reactions are shown to be highly nonstatistical, evidenced by dominant forward scattering and deviation of the integral cross section from the statistical limit. Mechanistic analyses revealed that the nonstatistical channel is facilitated by short-lived osculating resonances. The theoretical results provided an in-depth interpretation of a recent molecular beam experiment of the exchange reaction and shed light on the initial step of ozone recombination. PMID:20080718

  18. State-to-state quantum dynamics of O + O2 isotope exchange reactions reveals nonstatistical behavior at atmospheric conditions.

    PubMed

    Sun, Zhigang; Liu, Lan; Lin, Shi Ying; Schinke, Reinhard; Guo, Hua; Zhang, Dong H

    2010-01-12

    The O + O(2) exchange reaction is a prerequisite for the formation of ozone in Earth's atmosphere. We report here state-to-state differential and integral cross sections for several O + O(2) isotope-exchange reactions obtained by dynamically exact quantum scattering calculations at collision energies relevant to atmospheric conditions. These reactions are shown to be highly nonstatistical, evidenced by dominant forward scattering and deviation of the integral cross section from the statistical limit. Mechanistic analyses revealed that the nonstatistical channel is facilitated by short-lived osculating resonances. The theoretical results provided an in-depth interpretation of a recent molecular beam experiment of the exchange reaction and shed light on the initial step of ozone recombination. PMID:20080718

  19. Identification of a Critical Intermediate in Galvanic Exchange Reactions by Single-Nanoparticle Resolved Kinetics

    NASA Astrophysics Data System (ADS)

    Smith, Jeremy George; Jain, Prashant

    2014-06-01

    The realization of common materials transformations in nanocrystalline systems is fostering the development of novel nanostructures and allowing a deep look into the atomistic mechanisms involved. Galvanic corrosion is one such transformation. We studied galvanic replacement within individual metal nanoparticles by using plasmonic spectroscopy. This proved to be a powerful approach to studying materials transformations in the absence of ensemble averaging. Individual nanoscale units act as domains that can be interrogated optically in isolation, whereas the averaging of all such domains provides a bulk reaction trajectory. Single-nanoparticle reaction trajectories showed that a Ag nanoparticle exposed to Au3+ makes an abrupt transition into a nanocage structure. The transition is limited by a critical structural event, which we identified by electron microscopy to comprise the formation of a nanosized void, similar to the pitting process commonly observed in the corrosion of metals. Trajectories also revealed a surprisingly strong nonlinearity of the reaction kinetics, which we explain by a model involving the critical coalescence of vacancies into a growing void. The critical void size for galvanic exchange to spontaneously proceed was found to be 20 atomic vacancies. In the future we hope to extend this approach to examine a wide variety of materials transformations and chemical reactions.

  20. Structure and physical properties of lithium iron oxide, LiFeO 2, synthesized by ionic exchange reaction

    Microsoft Academic Search

    T. Shirane; R. Kanno; Y. Kawamoto; Y. Takeda; M. Takano; T. Kamiyama; F. Izumi

    1995-01-01

    Layered LiFeO2 was synthesized by ionic exchange reactions in molten salts from ?-NaFeO2; its structure was determined by X-ray and neutron diffraction measurements and the magnetic properties were characterized by magnetization measurements and Mössbauer spectroscopy. The reaction conditions were clarified using various molten salts containing lithium, and a “layered” sample was obtained by a reaction in LiCl\\/KCl molten salt at

  1. TraML--a standard format for exchange of selected reaction monitoring transition lists.

    PubMed

    Deutsch, Eric W; Chambers, Matthew; Neumann, Steffen; Levander, Fredrik; Binz, Pierre-Alain; Shofstahl, Jim; Campbell, David S; Mendoza, Luis; Ovelleiro, David; Helsens, Kenny; Martens, Lennart; Aebersold, Ruedi; Moritz, Robert L; Brusniak, Mi-Youn

    2012-04-01

    Targeted proteomics via selected reaction monitoring is a powerful mass spectrometric technique affording higher dynamic range, increased specificity and lower limits of detection than other shotgun mass spectrometry methods when applied to proteome analyses. However, it involves selective measurement of predetermined analytes, which requires more preparation in the form of selecting appropriate signatures for the proteins and peptides that are to be targeted. There is a growing number of software programs and resources for selecting optimal transitions and the instrument settings used for the detection and quantification of the targeted peptides, but the exchange of this information is hindered by a lack of a standard format. We have developed a new standardized format, called TraML, for encoding transition lists and associated metadata. In addition to introducing the TraML format, we demonstrate several implementations across the community, and provide semantic validators, extensive documentation, and multiple example instances to demonstrate correctly written documents. Widespread use of TraML will facilitate the exchange of transitions, reduce time spent handling incompatible list formats, increase the reusability of previously optimized transitions, and thus accelerate the widespread adoption of targeted proteomics via selected reaction monitoring. PMID:22159873

  2. Independent control of the shape and composition of ionic nanocrystals through sequential cation exchange reactions

    SciTech Connect

    Luther, Joseph Matthew; Zheng, Haimei; Sadtler, Bryce; Alivisatos, A. Paul

    2009-07-06

    Size- and shape-controlled nanocrystal growth is intensely researched for applications including electro-optic, catalytic, and medical devices. Chemical transformations such as cation exchange overcome the limitation of traditional colloidal synthesis, where the nanocrystal shape often reflects the inherent symmetry of the underlying lattice. Here we show that nanocrystals, with established synthetic protocols for high monodispersity, can be templates for independent composition control. Specifically, controlled interconversion between wurtzite CdS, chalcocite Cu2S, and rock salt PbS occurs while preserving the anisotropic dimensions unique to the as-synthesized materials. Sequential exchange reactions between the three sulfide compositions are driven by the disparate solubilites of the metal ion exchange pair in specific coordinating molecules. Starting with CdS, highly anisotropic PbS nanorods are created, which serve as an important material for studying strong 2-dimensional quantum confinement, as well as for optoelectronic applications. Furthermore, interesting nanoheterostructures of CdS|PbS are obtained by precise control over ion insertion and removal.

  3. Finding of Electronic-State Isotope Effects in Redox Chemical Exchange Reactions

    NASA Astrophysics Data System (ADS)

    Fujii, Y.

    2008-12-01

    Uranium isotope fractionation was extensively studied on the U(IV)-U(VI) exchange system. Experimental results were very interesting. In spite of the heavy element of uranium, relatively large isotope effects were observed at rather high temperature above 100 degree C. In addition, it was puzzling that light isotope U-235 was enriched not in U(IV), simple tetra-valence uranium ion, but in U(VI), which involves two strong bonds with oxygen atoms. These facts were not explained by the standard theory of isotope effects based on molecular vibration. To verify the applicability of the standard theory to uranium systems, experimental work was conducted on the measurements of isotope fractionation using different isotopes of U-232, U-233, U- 234, U-235, U-236 and U-238. The observed isotope fractionation was proportional to the mass difference among even mass number isotopes, while odd isotopes showed deviation from the relation observed for even mass isotopes. It was found the pattern of chemical isotope effects is very similar to that of isotope shifts in emission spectral lines of uranium. This phenomenon is called as odd-even staggering. This isotope effects arising from the electron-nucleus interaction is referred to as the nuclear volume effect. Although the chemical isotope effects resemble the isotope shift in emission lines, there was a question, why lighter isotope U-235 is fractionated in higher valence ionic species U(VI) in the U(IV)-U(VI) exchange system. This phenomenon was observed also in U(III)-U(IV) exchange system, where U-235 was enriched in higher valence U(IV). Recently the isotope fractionation of uranium in U(III)-U(IV) exchange system has been studied and the reason, why U-235 is enriched in U(IV), has been elucidated by theoretical calculation. It was confirmed that the chemical isotope effects of uranium is originated from nuclear-volume-effect. The experimental study has been extended to lanthanide chemical exchange systems. The nuclear volume effects were found to be dominant in the isotope fractionation of Gd complex formation systems. Further experiments were conducted on Fe(II)-Fe(III) exchange reactions. The nuclear-volume-effect was found not to be dominant in this case.

  4. Substituent effects on the vibronic coupling for the phenoxyl/phenol self-exchange reaction.

    PubMed

    Ludlow, Michelle K; Skone, Jonathan H; Hammes-Schiffer, Sharon

    2008-01-17

    The impact of substituents on the vibronic coupling for the phenoxyl/phenol self-exchange reaction, which occurs by a proton-coupled electron transfer mechanism, is investigated. The vibronic couplings are calculated with a grid-based nonadiabatic method and a nuclear-electronic orbital nonorthogonal configuration interaction method. The quantitative agreement between these two methods for the unsubstituted phenoxyl/phenol system and the qualitative agreement in the predicted trends for the substituted phenoxyl/phenol systems provides a level of validation for both methods. Analysis of the results indicates that electron-donating groups enhance the vibronic coupling, while electron-withdrawing groups attenuate the vibronic coupling. Thus, if all other aspects of the reaction are the same, then electron-donating groups will increase the rate, while electron-withdrawing groups will decrease the rate. Correlations between the vibronic coupling and physical properties of the phenol are also analyzed. Negative Hammett constants correspond to higher vibronic couplings, while positive Hammett constants correspond to similar or slightly lower vibronic couplings relative to the unsubstituted phenoxyl/phenol system. In addition, lower bond dissociation enthalpies, ionization potentials, and redox potentials, as well as higher pKa values, tend to correspond to higher vibronic couplings relative to the unsubstituted phenoxyl/phenol system. The observed trends enable the prediction of the impact of general substituents on the vibronic coupling, and hence the rate, for the phenoxyl/phenol self-exchange reaction. The fundamental physical insights obtained from these studies are applicable to other proton-coupled electron transfer systems. PMID:17939710

  5. Functional Integrity and Inflammatory Reactions of Exchange Vessels and Lymphatics in X-irradiated Tissues

    PubMed Central

    Van den Brenk, H. A. S.; Crowe, M. C.; Stone, M. G.

    1977-01-01

    Local pre-irradiation of the foot (LFI) with 500 to 20,000 rad X-rays and sublethal whole body irradiation (WBI) of rats did not significantly affect development, intensity or resolution of inflammatory oedema induced by subdermal injection of the foot with pharmacological mediators of inflammation or Compound 48/80. LFI and WBI both caused modest increases in swelling induced by carrageenan which are attributed to a combined (additive) effect of slight early oedema from increased vascular permeability induced by radiation and the inflammatory oedema induced by carrageenan. Age of rat did not significantly affect inflammatory oedema induced by various irritants in unirradiated or irradiated rats. The pattern of tissue swelling induced by irradiation was measured. It is concluded that the small exchange vessels (capillaries and venules) and lymphatics which largely regulate the amount and composition of interstitial fluids are highly radioresistant; they remain physiologically intact and react normally to vasoactive substances which mediate inflammatory reactions, even after exposure to doses of radiation which completely eliminate cell reproductive integrity. Inflammatory effects of X-rays (“roentgen reactions”) are largely attributed to the reactions mounted by the mature microvasculature to products of tissue damage, and the anti-inflammatory (“antiphlogistic”) effects to the suppression of regenerative growth of actively proliferating capillaries (angiogenesis) in the repair phase. PMID:588442

  6. Charge-exchange reactions and electron-capture rates for presupernova stellar evolution

    NASA Astrophysics Data System (ADS)

    Zegers, Remco

    2015-04-01

    Weak reaction rates such as electron captures and beta decays play major roles in a variety of astrophysical phenomena, such as core-collapse and thermonuclear supernovae and accreting neutron stars. Consequently, the use of accurate weak reaction rates in astrophysical simulations to understand these phenomena is important. Unfortunately, the number of relevant nuclei is typically very large, and, except for a few special cases, it is impossible to rely on experimental results only: theoretical models must be used to estimate the weak reaction rates. These models can then be benchmarked and improved on the basis of a limited number of experimental data. The most important nuclear structure input that is required for calculating weak reaction rates are Gamow-Teller transition strengths. Although these can be extracted from beta and electron-capture decay data, the energy window accessible by such experiments is limited, if accessible at all. However, at the high temperatures and densities that occur in massive stars prior to the cataclysmic demise, transitions to final states at high excitation energies are important. In addition, to properly test theory, full Gamow-Teller transition strength distributions are very valuable. Fortunately, nature is kind: charge-exchange experiments at intermediate energies can provide the relevant strength distributions over a wide energy window and a variety of charge-exchange probes, such as (p,n), (n,p), (d,2 He) and (t,3 He) have been used to extract strengths of relevance for astrophysics (and for other purposes). This presentation will focus on efforts to validate electron capture rates calculated based on nuclear structure models for nuclei with masses ranging from A ~ 40-65, and on studies aimed at testing astrophysical sensitivities to uncertainties/deviations in the theoretical rates. These efforts include experiments with unstable isotopes, and special gamma-ray coincidence techniques to localize very weak, but astrophysically important, low-lying Gamow-Teller transitions. Future efforts will focus on heavier nuclei (A>65) and nuclei further from stability. For the latter, opportunities provided at the Facility for Rare Isotope Beams (FRIB) will be critically important. In particular, experiments enables by the construction of a High Rigidity Spectrometer will strongly enhance the impact of the data for the validation and improvements of novel theoretical approaches. This work was supported by the US National Science Foundation (under Grants PHY-1102511 and PHY-0822648 [JINA]) and the US Department Of Energy under Grant DE- 334 AC02-05CH11231 (LBNL).

  7. Gaseous anion chemistry. Hydrogen-deuterium exchange in mono- and dialcohol alkoxide ions: ionization reactions in dialcohols

    SciTech Connect

    Lloyd, J.R.; Agosta, W.C.; Field, F.H.

    1980-08-15

    The subject of this work is H-D exchange in certain gaseous anions using D/sub 2/ as the exchanging agent. The anions involved are produced from ethylene glycol, 1,3-propanediol, 1,4-butanediol, ethanol, 1-propanol, and 1-butanol. Spectra and postulated ionization reactions for these mono- and dialcohols are given. Hydrogen-deuterium exchange occurs in the (M - 1)/sup -/ and (2M - 1)/sup -/ ions of ethylene glycol, 1,3-propanediol, and 1,4-butanediol. The amount of exchange occurring is 3-8 times greater in (2M - 1)/sup -/ than in (M - 1)/sup -/. The amount of H-D exchange occurring in ethanol, 1-propanol, and 1-butanol is small or zero in the (2M - 1)/sup -/ ions and in the (M - 1)/sup -/ ion for 1-butanol (the only (M - 1)/sup -/ ion which could be examined experimentally). The amount of exchange occurring in the (2M - 1)/sup -/ and (M - 1)/sup -/ ions from ethylene glycol is not affected by the total pressure or composition of the reaction mixture in the ionization chamber of the mass spectrometer. A novel hydrogen-bridging mechanism is suggested to account for the observed exchange occurring in the dialcohols.

  8. Metastable structures and isotope exchange reactions in polyoxometalate ions provide a molecular view of oxide dissolution

    NASA Astrophysics Data System (ADS)

    Rustad, James R.; Casey, William H.

    2012-03-01

    Reactions involving minerals and glasses in water are slow and difficult to probe spectroscopically but are fundamental to the performance of oxide materials in green technologies such as automotive thermoelectric power generation, CO2 capture and storage and water-oxidation catalysis; these must be made from geochemically common elements and operate in hydrous environments. Polyoxometalate ions (POMs) have structures similar to condensed oxide phases and can be used as molecular models of the oxide/water interface. Oxygen atoms in POM exchange isotopes at different rates, but, at present, there is no basis for predicting how the coordination environment and metal substitution influences rates and mechanisms. Here we identify low-energy metastable configurations that form from the breaking of weak bonds between metals and underlying highly coordinated oxygen atoms, followed by facile hydroxide, hydronium or water addition. The mediation of oxygen exchange by these stuffed structures suggests a new view of the relationship between structure and reactivity at the oxide/solution interface.

  9. Metastable structures and isotope exchange reactions in polyoxometalate ions provide a molecular view of oxide dissolution.

    PubMed

    Rustad, James R; Casey, William H

    2012-03-01

    Reactions involving minerals and glasses in water are slow and difficult to probe spectroscopically but are fundamental to the performance of oxide materials in green technologies such as automotive thermoelectric power generation, CO2 capture and storage and water-oxidation catalysis; these must be made from geochemically common elements and operate in hydrous environments. Polyoxometalate ions (POMs) have structures similar to condensed oxide phases and can be used as molecular models of the oxide/water interface. Oxygen atoms in POM exchange isotopes at different rates, but, at present, there is no basis for predicting how the coordination environment and metal substitution influences rates and mechanisms. Here we identify low-energy metastable configurations that form from the breaking of weak bonds between metals and underlying highly coordinated oxygen atoms, followed by facile hydroxide, hydronium or water addition. The mediation of oxygen exchange by these stuffed structures suggests a new view of the relationship between structure and reactivity at the oxide/solution interface. PMID:22231599

  10. Isotope exchange reaction between tritiated water and hydrogen on SiC

    NASA Astrophysics Data System (ADS)

    Katayama, K.; Nishikawa, M.; Takeishi, T.

    2003-11-01

    SiC has been considered as a primary candidate material for a first wall component in future fusion reactor because it has been claimed that SiC has excellent high-temperature properties, good chemical stability and low activation. However, the behavior of tritium on SiC has not been discussed yet. In this study, tritium trapping capacity on the surface of SiC was experimentally obtained at the temperature range of 25-800 °C in consideration of tritium trapping to the experimental system. The capacity, which was independent of the water vapor pressure in the gas phase and the temperature, was determined as about 10 6 Bq/cm 2. The isotope exchange reaction rate between tritiated water in a gas phase and hydrogen on the surface was quantified at the temperature of 25, 500 and 700 °C in consideration of the behavior of tritium trapping at change of experimental condition by the numerical curve fitting method applying the serial reactor model. The reaction rate was observed to be constant as 3.48 × 10 -5 m/s. Additionally tritium release behavior from the surface of SiC in water vapor atmosphere was predicted and compared with that for graphite and stainless steel.

  11. Reversible Dissociation and Ligand-Glutathione Exchange Reaction in Binuclear Cationic Tetranitrosyl Iron Complex with Penicillamine

    PubMed Central

    Syrtsova, Lidia; Sanina, Natalia; Lyssenko, Konstantin; Kabachkov, Evgeniy; Psikha, Boris; Shkondina, Natal'ja; Pokidova, Olesia; Kotelnikov, Alexander; Aldoshin, Sergey

    2014-01-01

    This paper describes a comparative study of the decomposition of two nitrosyl iron complexes (NICs) with penicillamine thiolic ligands [Fe2(SC5H11NO2)2(NO)4]SO4·5H2O (I) and glutathione- (GSH-) ligands [Fe2(SC10H17N3O6)2(NO)4]SO4·2H2O (II), which spontaneously evolve to NO in aqueous medium. NO formation was measured by a sensor electrode and by spectrophotometric methods by measuring the formation of a hemoglobin- (Hb-) NO complex. The NO evolution reaction rate from (I)??k1 = (4.6 ± 0.1)·10?3?s?1 and the elimination rate constant of the penicillamine ligand k2 = (1.8 ± 0.2)·10?3?s?1 at 25°C in 0.05?M phosphate buffer, ?pH 7.0, was calculated using kinetic modeling based on the experimental data. Both reactions are reversible. Spectrophotometry and mass-spectrometry methods have firmly shown that the penicillamine ligand is exchanged for GS? during decomposition of 1.5·10?4?M (I) in the presence of 10?3?M GSH, with 76% yield in 24?h. As has been established, such behaviour is caused by the resistance of (II) to decomposition due to the higher affinity of iron to GSH in the complex. The discovered reaction may impede S-glutathionylation of the essential enzyme systems in the presence of (I) and is important for metabolism of NIC, connected with its antitumor activity. PMID:24790592

  12. Neutrino and antineutrino charge-exchange reactions on {sup 12}C

    SciTech Connect

    Samana, A. R. [Department of Physics, Texas A and M University Commerce, P.O. Box 3011 Commerce, Texas 75429 (United States); Departamento de Ciencias Exactas e Tecnologicas, Universidade Estadual de Santa Cruz, CEP 45662-000, Ilheus, Bahia-BA (Brazil); Krmpotic, F. [Instituto de Fisica La Plata, CONICET, Facultad de Ciencias Astronomicas y Geofisicas, Universidad Nacional de La Plata, 1900 La Plata (Argentina); Paar, N. [Physics Department, Faculty of Science, University of Zagreb, Bijenicka 32, HR-10002 Zagreb (Croatia); Bertulani, C. A. [Department of Physics, Texas A and M University Commerce, P.O. Box 3011 Commerce, Texas 75429 (United States)

    2011-02-15

    We extend the formalism of weak interaction processes, obtaining new expressions for the transition rates, which greatly facilitate numerical calculations, for both neutrino-nucleus reactions and muon capture. Explicit violation of the conserved vector current hypothesis by the Coulomb field, as well as development of a sum-rule approach for inclusive cross sections, has been worked out. We have done a thorough study of exclusive (ground-state) properties of {sup 12}B and {sup 12}N within the projected quasiparticle random phase approximation (PQRPA). Good agreement with experimental data achieved in this way put into evidence the limitations of the standard RPA and QRPA models, which come from the inability of the RPA to open the p{sub 3/2} shell and from the nonconservation of the number of particles in the QRPA. The inclusive neutrino/antineutrino ({nu}/{nu}-tilde) reactions {sup 12}C({nu},e{sup -}){sup 12}N and {sup 12}C({nu}-tilde,e{sup +}){sup 12}B are calculated within both the PQRPA and the relativistic QRPA. It is found that (i) the magnitudes of the resulting cross sections are close to the sum-rule limit at low energy, but significantly smaller than this limit at high energies, for both {nu} and {nu}-tilde; (ii) they increase steadily when the size of the configuration space is augmented, particularly for {nu}/{nu}-tilde energies >200 MeV; and (iii) they converge for sufficiently large configuration space and final-state spin. The quasi-elastic {sup 12}C({nu},{mu}{sup -}){sup 12}N cross section recently measured in the MiniBooNE experiment is briefly discussed. We study the decomposition of the inclusive cross section based on the degree of forbiddenness of different multipoles. A few words are dedicated to the {nu}/{nu}-tilde-{sup 12}C charge-exchange reactions related to astrophysical applications.

  13. Photochemical Synthesis and Ligand Exchange Reactions of Ru(CO)[subscript 4] (Eta[superscript 2]-Alkene) Compounds

    ERIC Educational Resources Information Center

    Cooke, Jason; Berry, David E.; Fawkes, Kelli L.

    2007-01-01

    The photochemical synthesis and subsequent ligand exchange reactions of Ru(CO)[subscript 4] (eta[superscript2]-alkene) compounds has provided a novel experiment for upper-level inorganic chemistry laboratory courses. The experiment is designed to provide a system in which the changing electronic properties of the alkene ligands could be easily…

  14. DNA Strand Exchange Promoted by RecA K72R TWO REACTION PHASES WITH DIFFERENT Mg2

    E-print Network

    Cox, Michael M.

    that binds but does not hydrolyze ATP. The protein nevertheless promotes DNA strand exchange (Rehrauer, W. M-dependent ATPase, with a monomer kcat of 30 min 1 when bound to ssDNA.1 ATP is hydrolyzed uniformly throughout). The reaction is appar- ently quite inefficient, with about 100 ATPs hydrolyzed per base pair of hybrid DNA

  15. One- and two-dimensional chemical exchange nuclear magnetic resonance studies of the creatine kinase catalyzed reaction

    SciTech Connect

    Gober, J.R.

    1988-01-01

    The equilibrium chemical exchange dynamics of the creatine kinase enzyme system were studied by one- and two-dimensional {sup 31}P NMR techniques. Pseudo-first-order reaction rate constants were measured by the saturation transfer method under an array of experimental conditions of pH and temperature. Quantitative one-dimensional spectra were collected under the same conditions in order to calculate the forward and reverse reaction rates, the K{sub eq}, the hydrogen ion stoichiometry, and the standard thermodynamic functions. The pure absorption mode in four quadrant two-dimensional chemical exchange experiment was employed so that the complete kinetic matrix showing all of the chemical exchange process could be realized.

  16. Facile synthesis of magnetic metal (Mn, Fe, Co, and Ni) oxides nanocrystals via a cation-exchange reaction.

    PubMed

    Ning, Jiajia; Xiao, Guanjun; Wang, Li; Zou, Bo; Liu, Bingbing; Zou, Guangtian

    2011-02-01

    Magnetic metal (Mn, Fe, Co, and Ni) oxides nanocrystals with small size and uniform size distribution are synthesized via a cation-exchange reaction. Two experimental stages are included in the synthesis of metal oxides nanocrystals. Firstly, Cu(OH)2 decomposes to CuO nanocrystals, induced by free metal cations. Compared to CuO nanocrystals produced without any free metal cation, the free metal cation has an important influence on the shape and size of CuO. Secondly, free metal cations exchange with the Cu2+ cation in the CuO nanocrystals to get Mn3O4, Fe2O3, CoO and NiO nanocrystals by cation-exchange reactions. The magnetic properties of these metal oxides nanocrystals have been investigated, all the nanocrystals are superparamagnetic at room temperature. PMID:21109892

  17. Hydrogen and oxygen isotope exchange reactions between clay minerals and water

    USGS Publications Warehouse

    O'Neil, J.R.; Kharaka, Y.K.

    1976-01-01

    The extent of hydrogen and oxygen isotope exchange between clay minerals and water has been measured in the temperature range 100-350?? for bomb runs of up to almost 2 years. Hydrogen isotope exchange between water and the clays was demonstrable at 100??. Exchange rates were 3-5 times greater for montmorillonite than for kaolinite or illite and this is attributed to the presence of interlayer water in the montmorillonite structure. Negligible oxygen isotope exchange occurred at these low temperatures. The great disparity in D and O18 exchange rates observed in every experiment demonstrates that hydrogen isotope exchange occurred by a mechanism of proton exchange independent of the slower process of O18 exchange. At 350?? kaolinite reacted to form pyrophyllite and diaspore. This was accompanied by essentially complete D exchange but minor O18 exchange and implies that intact structural units in the pyrophyllite were inherited from the kaolinite precursor. ?? 1976.

  18. D/H Exchange Reactions in Salts Extracted from LEW 85320

    NASA Astrophysics Data System (ADS)

    Socki, R. A.; Romanek, C. S.; Gibson, E. K., Jr.

    1993-07-01

    Understanding the effects of terrestrial weathering on meteorites has been shown to be critical in distinguishing primary chemical and isotopic features from secondary alterations [1]. To further constrain weathering effects we report here the D/H composition of water thermally extracted from three distinct generations of efflorescence (,98, ,99, and ,102) occurring on the Antarctic H-5 chondrite LEW85320. To better understand the hydrogen isotope exchange systematics of these precipitates, an experiment was performed to characterize the rate of isotope exchange between a synthetic analog to the predominant weathering product, nesquehonite (Mg(HCO3)(OH).2H2O), found on the exterior of LEW85320 [2], and water. Synthetic nesquehonite, produced following the procedure of Ming and Franklin [3], a dehydrated CaSO4 standard, and deuterium-spiked water (deltaD = +701 permil SMOW) were placed together in a closed box and allowed to exchange hydrogen isotopes at constant temperature and humidity (30 degrees +- 2 degrees C and 75% +- 5%). Samples of each solid phase were taken initially and at 1, 3, 20, and 30 days. These samples along with three generations of efflorescence on LEW85320 (,98, ,99, and ,102) were weighed and loaded into separate high-purity, prebaked, 9-mm (O.D) quartz tubes. After degassing for two hours under high vacuum, samples were heated to 625 degrees C for 4 hr while all condensable gases were collected in a trap immersed in liquid nitrogen. CO2 was separated from water by exchanging the LN2 trap with a dry ice/alcohol mixture. All evolved water was frozen into a tube containing Zn turnings, which was then heated to 450 degrees C for 30 min, producing hydrogen gas for isotopic analysis. Results of our exchange experiment show that the CaSO4 standard quickly assumes the deltaD composition of the water (from -29 permil to +581 permil in 30 days). On the other hand, nesquehonite becomes only slightly enriched in deltaD (from -29 permil to +51 permil). Mass balance calculations reveal that absorption of the spiked water is stoichiometric with respect to the formation of CaSO4.2H2O, while within limits of sampling error no net change of weight was observed for the nesquehonite. Assuming that the change in deltaDnesq. is due entirely to exchange (i.e., no absorption), mass balance constraints dictate that less than 5 wt% of water exchanged. These data suggest that nesquehonite retains its original deltaD composition even under conditions of relatively high temperature and humidity. Hydrogen isotope data of water extracted from three generations of nesquehonite on LEW85320 are plotted as a function of the theoretical delta18O composition of water in equilibrium with the carbonate at 0 degrees C (where delta18Onesq. is derived by phosphoric acid digestion of the carbonate, assuming a calcite-CO2 fractionation factor of 1.01012). Our data plot very near the meteoric water line indicating formation from slightly enriched Antarctic meltwater. Water extracted from generations II (,99), salts consisting mostly of hydromagnesite (Mg5(CO3)4(OH)2.4H2O) (Gooding, 1993, personal communication), and III (,102), with mineralogy as yet unknown, is enriched in D (deltaD = -55 and -75 permil, respectively) and plot above the meteoric water line. Both generations precipitated in the Houston curatorial facility. Data suggest either that hydrogen isotopes have exchanged at least partially with local (i.e., Houston) water, or that the exchange reactions differ between structural sites within or among the various generations of efflorescent salts. Hydrogen isotopes extracted from hydrous weathering products can reveal information about the environment of crystal growth. However, hydrogen isotope exchange systematics could be complicated if water within the crystal structure of the mineral is located in multiple sites. Furthermore, these results could have profound implications for curation and long-term storage strategies in curatorial facilities. References: [1] Socki R. A. et al., (1991) Meteoritics, 26, 396-397. [2] Gooding J. L. e

  19. The effect of various cropping systems upon organic matter, total nitrogen, cation exchange capacity, exchangeable cations, conductivity and reaction 

    E-print Network

    Mannan, Mohammad Abdul

    1958-01-01

    Bxchan sable Sodium The concentration of exchangeable sodium ranged from 0. 82 to 1. 03 m. e. /100 gms in the surface layer, from 1. 08 to 2. 03 m. e. /100 gms in the second layer and from 1. 32 to 2. 56 m. e. /100 gms in the third layer (Table 7-'a...). The highest concentration of exchangeable sodium was found in the third layer under Treatment 1 and the lowest concen- tration was found in the same layer of Treatment 2. The second high- est concentration of sodium vas found in the third layer of Treatment...

  20. Surface enhanced exchange reactions of hydrogen isotopes with water and fomblin oil

    SciTech Connect

    Borysow, J. [Dept. of Physics, Michigan Technical Univ., Houghton, MI 49931 (United States); Eckart, M.; Fink, M. [Dept. of Physics, Univ. of Texas, Austin (United States)

    2008-07-15

    Maintaining isotopic purity of tritium is one of the major tasks in several new large facilities such as ITER (International Thermonuclear Experimental Reactor), KATRIN (Karlsruhe Tritium Experiment) and NEXTEX (Texas Neutrino Mass Experiment). Working with multiple isotopes and isotopomers is always accompanied by isotope exchanges, which are accelerated by catalysts. These are provided by surfaces of various materials, which are used in the recycling systems. Here new results are reported of the solubility of hydrogen in Fomblin oil and kinetics for reactions between D{sub 2}O, HDO, H{sub 2}O and D{sub 2}, HD and H{sub 2} taking place at the surface of a stainless steel (SS304) vessel at pressures of about 350 Pa. The kinetics of hydrogen isotopes were measured by Raman spectrometer. The water isotopomers were monitored by mass spectrometry. The solubility of hydrogen in Fomblin oil was determined at several H{sub 2} pressures using NMR spectroscopy. The results can be extended to lower pressures using Henry's law. (authors)

  1. Preparation of poly(aniline-co-o-anisidine)-intercalated mesostructured manganese oxide composites by exchange reaction

    SciTech Connect

    Wang Gengchao [Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China)], E-mail: gengchaow@ecust.edu.cn; Yang Zhenyu; Li Xingwei; Li Chunzhong [Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237 (China); Yuan Weikang [UNILAB, State Key Laboratory of Chemical Reaction Engineering, East China University of Science and Technology, Shanghai 200237 (China)

    2008-08-04

    Layered mesostructured manganese oxide (mesostructured MnO{sub 2}) was synthesized using manganese chloride and lithium hydroxide as the raw materials and cetyltrimethylammonium bromide (CTAB) as the structure-directing agent. Poly(aniline-co-o-anisidine)-intercalated mesostructured MnO{sub 2} composites (P(An-co-oAs)/MnO{sub 2}) were synthesized in an organic solvent through the exchange reaction between the CTAB in MnO{sub 2} gallery and the P(An-co-oAs). The interlayer spacing (I{sub c} values) of mesostructured MnO{sub 2} enlarged from 2.52 to 4.41 nm as the added amount of P(An-co-oAs) increased from 0 to 0.5 g per 0.5 g of mesostructured MnO{sub 2}. The regularity of the layered structure of the composites was firstly decreased due to intercalation of low amounts of P(An-co-oAs). However, with increasing the intercalated amount of P(An-co-oAs) the layered structure of the composites becomes more regular. The electrical conductivity of the composites is 10{sup 2} to 10{sup 3} times higher than that of the mesostructured MnO{sub 2}.

  2. Pd-Co-Mo electrocatalyst for the oxygen reduction reaction in proton exchange membrane fuel cells.

    PubMed

    Raghuveer, Vadari; Manthiram, Arumugam; Bard, Allen J

    2005-12-01

    The catalytic activity of carbon supported Pd-Co-Mo for the oxygen reduction reaction (ORR) in a single cell proton exchange membrane fuel cell (PEMFC) has been investigated at 60 degrees C and compared with data from commercial Pt catalyst and our previously reported Pd-Co-Au and Pd-Ti catalysts. The Pd-Co-Mo catalyst with a Pd:Co:Mo atomic ratio of 70:20:10 exhibits slightly higher catalytic activity like the Pd-Co-Au catalyst than the commercial Pt catalyst, but with excellent chemical stability unlike the Pd-Co-Au catalyst. The Pd-Co-Mo catalyst also exhibits better tolerance to methanol poisoning than Pt. Investigation of the catalytic activity of the Pd-Co-Mo system with varying composition and heat treatment temperature reveals that a Pd:Co:Mo atomic ratio of 70:20:10 with a heat treatment temperature of 500 degrees C exhibits the highest catalytic activity. Although the degree of alloying increases with increasing temperature from 500 to 900 degrees C as indicated by the X-ray diffraction data, the catalytic activity decreases due to an increase in particle size and a decrease in surface area. PMID:16853984

  3. Exchange repulsive potential adaptable for electronic structure changes during chemical reactions

    NASA Astrophysics Data System (ADS)

    Yokogawa, D.

    2015-04-01

    Hybrid methods combining quantum mechanical (QM) and classical calculations are becoming important tools in chemistry. The popular approach to calculate the interaction between QM and classical calculations employs interatomic potentials. In most cases, the interatomic potential is constructed of an electrostatic (ES) potential and a non-ES potential. Because QM treatment is employed in the calculation of the ES potential, the electronic change can be considered in this ES potential. However, QM treatment of the non-ES potential is difficult because of high computational cost. To overcome this difficulty of evaluating the non-ES potential, we proposed an exchange repulsive potential as the main part of the non-ES potential on the basis of a QM approach. This potential is independent of empirical parameters and adaptable for electronic structure. We combined this potential with the reference interaction site model self-consistent field explicitly including spatial electron density distribution and successfully applied it to the chemical reactions in aqueous phase.

  4. Exchange repulsive potential adaptable for electronic structure changes during chemical reactions.

    PubMed

    Yokogawa, D

    2015-04-28

    Hybrid methods combining quantum mechanical (QM) and classical calculations are becoming important tools in chemistry. The popular approach to calculate the interaction between QM and classical calculations employs interatomic potentials. In most cases, the interatomic potential is constructed of an electrostatic (ES) potential and a non-ES potential. Because QM treatment is employed in the calculation of the ES potential, the electronic change can be considered in this ES potential. However, QM treatment of the non-ES potential is difficult because of high computational cost. To overcome this difficulty of evaluating the non-ES potential, we proposed an exchange repulsive potential as the main part of the non-ES potential on the basis of a QM approach. This potential is independent of empirical parameters and adaptable for electronic structure. We combined this potential with the reference interaction site model self-consistent field explicitly including spatial electron density distribution and successfully applied it to the chemical reactions in aqueous phase. PMID:25933754

  5. A Model of Exchange-Rate Determination with Policy Reaction: Evidence From Monthly Data

    Microsoft Academic Search

    William Branson

    1983-01-01

    During the 1970s an extensive theoretical literature has developed analyzing market determination of freely floating exchange rates. At the same time, there has been extensive and continuous intervention in the market by central banks. Exchange rates have not been floating freely; they have been managed, or manipulated, by central banks. However, most of the description of exchange rate policy, as

  6. A Model of Exchange-Rate Determination with Policy Reaction: Evidence from Monthly Data

    Microsoft Academic Search

    William H. Branson

    1983-01-01

    During the 1970s an extensive theoretical literature has developed analyzing market determination of freely floating exchange rates. At the same time, there has been extensive and continuous intervention in the market by central banks. Exchange rates have not been floating freely;they have been managed, or manipulated, by central banks. However, most of the description of exchange rate policy, as actually

  7. Metal-exchange reactions between the uranyl-18-crown-6 complex and Na/sup +/ ion in propylene carbonate

    SciTech Connect

    Fux, P.; Lagrange, J.; Lagrange, P.

    1988-01-13

    An intermediate complex, UO/sub 2/L/sup 2+/, is proposed to help explain the metal-exchange reaction between the uranyl-18-crown-6 and Na/sup +/ ion in propylene carbonate. This intermediate is thought to be an outer-sphere complex where the coordinating center UO/sub 2//sup 2+/ is partially enclosed in the ligand cavity and where the Na/sup +/ ion is completely desolvated. A total reaction scheme is proposed, and mathematical treatment of the data is presented. 20 refs., 2 figs.

  8. The effects of phosphorous ligands on the gas phase ligand exchange reactions of dichromium ionic cluster fragments 

    E-print Network

    Nguyen, Hanh Duc

    1991-01-01

    Table I. Cone angles and CO stretching frequencies of phosphorus ligands. , Page . . 11 II. The relative rate constants for disappearance of Cr, (CO), ' for ligand exchange reaction with phosphorusligands. 14 vu LIST OF FIGURES Figure Page 1... products of the ion-molecule reaction between Cr, (CO), ' and P(NMe, ), . 30 16. Plot of the M'/M, ' branching ratio versus the phosphorus ligand. . 34 17. Plot of the M'/M, ' branching ratio versus the CO stretching frequency(cm ') of the phosphorus...

  9. Facile synthesis of magnetic metal (Mn, Fe, Co, and Ni) oxides nanocrystals via a cation-exchange reaction

    NASA Astrophysics Data System (ADS)

    Ning, Jiajia; Xiao, Guanjun; Wang, Li; Zou, Bo; Liu, Bingbing; Zou, Guangtian

    2011-02-01

    Magnetic metal (Mn, Fe, Co, and Ni) oxides nanocrystals with small size and uniform size distribution are synthesized via a cation-exchange reaction. Two experimental stages are included in the synthesis of metal oxides nanocrystals. Firstly, Cu(OH)2 decomposes to CuO nanocrystals, induced by free metal cations. Compared to CuO nanocrystals produced without any free metal cation, the free metal cation has an important influence on the shape and size of CuO. Secondly, free metal cations exchange with the Cu2+ cation in the CuO nanocrystals to get Mn3O4, Fe2O3, CoO and NiO nanocrystals by cation-exchange reactions. The magnetic properties of these metal oxides nanocrystals have been investigated, all the nanocrystals are superparamagnetic at room temperature.Magnetic metal (Mn, Fe, Co, and Ni) oxides nanocrystals with small size and uniform size distribution are synthesized via a cation-exchange reaction. Two experimental stages are included in the synthesis of metal oxides nanocrystals. Firstly, Cu(OH)2 decomposes to CuO nanocrystals, induced by free metal cations. Compared to CuO nanocrystals produced without any free metal cation, the free metal cation has an important influence on the shape and size of CuO. Secondly, free metal cations exchange with the Cu2+ cation in the CuO nanocrystals to get Mn3O4, Fe2O3, CoO and NiO nanocrystals by cation-exchange reactions. The magnetic properties of these metal oxides nanocrystals have been investigated, all the nanocrystals are superparamagnetic at room temperature. Electronic supplementary information (ESI) available: XPS of Fe2O3 nanoparticles, TEM images of Fe2O3 and Mn3O4 nanocrystals produced with different molar ratios of precursors, TEM images and XRD patterns of CuO nanocrystals produced without any free cations and XRD patterns of the transformation from Cu(OH)2 to metal oxide nanocrystals, photographs of color change when reaction solution was exposed to air. See DOI: 10.1039/c0nr00684j

  10. Photodissociation Dynamics of Gaseous CpCo(CO)2 and Ligand Exchange Reactions of CpCoH2 with

    E-print Network

    Davis, H. Floyd

    1 Photodissociation Dynamics of Gaseous CpCo(CO)2 and Ligand Exchange Reactions of CpCoH2 with C3H6 correspondence should be addressed. Email: hfd1@cornell.edu. Abstract The photodissociation dynamics of CpCo(CO)2, the dominant one-photon channel involved loss of a single CO ligand producing CpCoCO. The product angular

  11. Highly enantioselective synthesis of 1,3-mercapto alcohols from ?,?-unsaturated ketones: asymmetric bifunctional group exchange reaction

    Microsoft Academic Search

    Hiroaki Shiraki; Kiyoharu Nishide; Manabu Node

    2000-01-01

    Optically active 1,3-mercapto alcohols were synthesized from ?,?-unsaturated ketones using a chiral reagent B and dimethylaluminum chloride in two steps. The transformation involved a tandem Michael addition–MPV reduction and a base-catalyzed elimination. The two newly created chiral carbons in trans-chalcone derivatives were enantioselectively controlled to a high degree. Using the above transformation, an asymmetric bifunctional group exchange reaction between the

  12. Meson-exchange calculation of the d(. gamma. ,p)n reaction in the GeV energy region

    SciTech Connect

    Lee, T.S.H.

    1991-01-01

    We show that a meson-exchange model of the d({gamma},p) reaction can be constructed to reproduce the energy-dependence of the existing data for the differential cross section at 90{degree}. The prediction of the model in the GeV energy region is found to be radically different from the QCD prediction by Brodsky and Hiller. The results will be compared with the new data presented in a companion paper. 12 refs., 4 figs.

  13. The effects of phosphorous ligands on the gas phase ligand exchange reactions of dichromium ionic cluster fragments

    E-print Network

    Nguyen, Hanh Duc

    1991-01-01

    on the steric effect. For Cr, (CO), ' the metal-metal bond cleavage depends on both steric and electronic effects. Also in this study, the rate constants for disappearance of Cr, (CO), ' are greater than those of Cr, (CO), '. Finally, Cr, (CO), ' tends... Table I. Cone angles and CO stretching frequencies of phosphorus ligands. , Page . . 11 II. The relative rate constants for disappearance of Cr, (CO), ' for ligand exchange reaction with phosphorusligands. 14 vu LIST OF FIGURES Figure Page 1...

  14. Quantal Study of the Exchange Reaction for N + N2 using an ab initio Potential Energy Surface

    NASA Technical Reports Server (NTRS)

    Wang, Dunyou; Stallcop, James R.; Huo, Winifred M.; Dateo, Christopher E.; Schwenke, David W.; Partridge, Harry; Kwak, Dochan (Technical Monitor)

    2002-01-01

    The N + N2 exchange rate is calculated using a time-dependent quantum dynamics method on a newly determined ab initio potential energy surface (PES) for the ground A" state. This ab initio PES shows a double barrier feature in the interaction region with the barrier height at 47.2 kcal/mol, and a shallow well between these two barriers, with the minimum at 43.7 kcal/mol. A quantum dynamics wave packet calculation has been carried out using the fitted PES to compute the cumulative reaction probability for the exchange reaction of N + N2(J=O). The J - K shift method is then employed to obtain the rate constant for this reaction. The calculated rate constant is compared with experimental data and a recent quasi-classical calculation using a LEPS PES. Significant differences are found between the present and quasiclassical results. The present rate calculation is the first accurate 3D quantal dynamics study for N + N2 reaction system and the ab initio PES reported here is the first such surface for N3.

  15. RecA Filament Dynamics during DNA Strand Exchange Reactions* (Received for publication, November 27, 1996)

    E-print Network

    Cox, Michael M.

    of the RecA redistribution idea. When ATP is hydrolyzed, DNA strand exchange is accompanied by a Rec is observed, and sig- nificant ATP is hydrolyzed, even though DNA strand exchange is entirely blocked bound to ssDNA (dATP is hydrolyzed at rates about 20% higher). ATP is hydrolyzed uniformly through- out

  16. A homogeneous quenching resonance energy transfer assay for the kinetic analysis of the GTPase nucleotide exchange reaction.

    PubMed

    Kopra, Kari; Ligabue, Alessio; Wang, Qi; Syrjänpää, Markku; Blaževitš, Olga; Veltel, Stefan; van Adrichem, Arjan J; Hänninen, Pekka; Abankwa, Daniel; Härmä, Harri

    2014-07-01

    A quenching resonance energy transfer (QRET) assay for small GTPase nucleotide exchange kinetic monitoring is demonstrated using nanomolar protein concentrations. Small GTPases are central signaling proteins in all eukaryotic cells acting as a "molecular switches" that are active in the GTP-state and inactive in the GDP-state. GTP-loading is highly regulated by guanine nucleotide exchange factors (GEFs). In several diseases, most prominently cancer, this process in misregulated. The kinetics of the nucleotide exchange reaction reports on the enzymatic activity of the GEF reaction system and is, therefore, of special interest. We determined the nucleotide exchange kinetics using europium-labeled GTP (Eu-GTP) in the QRET assay for small GTPases. After GEF catalyzed GTP-loading of a GTPase, a high time-resolved luminescence signal was found to be associated with GTPase bound Eu-GTP, whereas the non-bound Eu-GTP fraction was quenched by soluble quencher. The association kinetics of the Eu-GTP was measured after GEF addition, whereas the dissociation kinetics could be determined after addition of unlabeled GTP. The resulting association and dissociation rates were in agreement with previously published values for H-Ras(Wt), H-Ras(Q61G), and K-Ras(Wt), respectively. The broader applicability of the QRET assay for small GTPases was demonstrated by determining the kinetics of the Ect2 catalyzed RhoA(Wt) GTP-loading. The QRET assay allows the use of nanomolar protein concentrations, as more than 3-fold signal-to-background ratio was achieved with 50 nM GTPase and GEF proteins. Thus, small GTPase exchange kinetics can be efficiently determined in a HTS compatible 384-well plate format. PMID:24760397

  17. Theoretical studies of tunneling processes in three-body exchange reactions of van der Waals rare gas dimers

    SciTech Connect

    Turner, R.A.; Raff, L.M.; Thompson, D.L.

    1984-04-01

    Rare gas atom--diatom collisions of Ar+Ar/sub 2/, Xe+Ar/sub 2/, Kr+Xe/sub 2/, Kr+Ne/sub 2/, and Kr+NeAr have been investigated to determine the importance of tunneling processes in exchange and dissociation reactions involving van der Waals molecules. Reaction cross sections, angular distributions, and product-energy distributions have been computed using Monte Carlo quasiclassical trajectories. The effect of tunneling through the rotational barrier upon these quantities has been computed using WKB methods. The results show that metastable diatomic products with energies above the classical dissociation limit, but below the rotational barrier, play a significant role in the dynamics of both exchange and dissociation reactions. Lifetime distributions of such metastable dimers illustrate their importance in crossed molecular beam studies of rare gas systems. The WKB calculations indicate that a significant, and possibly measurable, number of the metastables dissociate by tunneling before they would reach the detector in a molecular beam experiment. Close agreement has been found between these calculations and statistical state-counting calculations of metastable product dimer lifetimes. Experiments are suggested that might permit the direct observation of tunneling in these systems.

  18. Inclusive measurement of (p,. pi. /sup -/xn) double charge exchange reactions on bismuth from threshold to 800 MeV

    SciTech Connect

    Dombsky, M.; D'Auria, J.M.; Kelson, I.; Yavin, A.I.; Ward, T.E.; Clark, J.L.; Ruth, T.; Sheffer, G.

    1985-07-01

    The energy dependence of the total angle-integrated cross section for the production of astatine isotopes from (p,..pi../sup -/xn) double charge exchange reactions on bismuth (/sup 209/Bi) was measured from 120 to 800 MeV using activation and radiochemical techniques. Chemical yields were estimated by direct radioassaying of /sup 211/At activity in thin (approx.1 mg/cm/sup 2/), irradiated bismuth targets. Calculations of the contributions of secondary (two-step) reactions to these measured astatine yields were performed, based partially upon the observed /sup 211/At activity although even at the highest energies, the contribution to products lighter than /sup 207/At was negligible. These data for products with as many as seven neutrons removed from the doubly coherent product (/sup 210/At) display nearly Gaussian shapes for the mass distributions of the astatine residues, with the maximum occurring for about /sup 204/At. The most probable momentum transfer deduced from these distributions for the initial ..pi../sup -/ production step was 335 MeV/c. The observed excitation functions display a behavior similar to that observed for the yield of /sup 210/Po from a (p,..pi../sup 0/) reaction on /sup 209/Bi, but radically different from that observed for inclusive ..pi../sup -/ reactions on a heavy nucleus. These data are discussed in terms of recent theoretical approaches to negative pion production from bismuth. In addition, a simple, schematic model is developed to treat the rapidly decreasing percentage of the total inclusive ..pi../sup -/ emission which is observed for this double charge exchange reaction. This model reflects the opacity of a nucleus to a source of internal energetic protons.

  19. Cu3-xP Nanocrystals as a Material Platform for Near-Infrared Plasmonics and Cation Exchange Reactions

    PubMed Central

    2015-01-01

    Synthesis approaches to colloidal Cu3P nanocrystals (NCs) have been recently developed, and their optical absorption features in the near-infrared (NIR) have been interpreted as arising from a localized surface plasmon resonance (LSPR). Our pump–probe measurements on platelet-shaped Cu3-xP NCs corroborate the plasmonic character of this absorption. In accordance with studies on crystal structure analysis of Cu3P dating back to the 1970s, our density functional calculations indicate that this material is substoichiometric in copper, since the energy of formation of Cu vacancies in certain crystallographic sites is negative, that is, they are thermodynamically favored. Also, thermoelectric measurements point to a p-type behavior of the majority carriers from films of Cu3-xP NCs. It is likely that both the LSPR and the p-type character of our Cu3-xP NCs arise from the presence of a large number of Cu vacancies in such NCs. Motivated by the presence of Cu vacancies that facilitate the ion diffusion, we have additionally exploited Cu3-xP NCs as a starting material on which to probe cation exchange reactions. We demonstrate here that Cu3-xP NCs can be easily cation-exchanged to hexagonal wurtzite InP NCs, with preservation of the anion framework (the anion framework in Cu3-xP is very close to that of wurtzite InP). Intermediate steps in this reaction are represented by Cu3-xP/InP heterostructures, as a consequence of the fact that the exchange between Cu+ and In3+ ions starts from the peripheral corners of each NC and gradually evolves toward the center. The feasibility of this transformation makes Cu3-xP NCs an interesting material platform from which to access other metal phosphides by cation exchange. PMID:25960605

  20. The (p, ? +) reaction on 9Be and 10B at intermediate energies and a coherent ?-exchange analysis

    NASA Astrophysics Data System (ADS)

    Dillig, M.; Couvert, P.; Bauer, Th. S.; Beurtey, R.; Boudard, A.; Bruge, G.; Catz, H.; Chaumeaux, A.; Duhm, H. H.; Escudie, J. L.; Garcon, M.; Garreta, D.; Igo, G. J.; Lugol, J. C.; Matoba, M.; Schecter, L.; Tabet, J. P.; Terrien, Y.; Aslanides, E.; Bertini, R.; Bing, O.; Brochard, F.; Hibou, F.; Gorodetzky, P.; Bimbot, L.; Brissaud, I.; Le Bornec, Y.; Tatischeff, B.

    1980-01-01

    Proton-induced pion production at intermediate energies, leaving the final nucleus in discrete, resolved states, has been measured at the Saclay Synchrotron Saturne I, using the high resolution spectrometer facility SPES I. The (p, ?+) reaction has been investigated on 9Be at proton energies of 410 and 605 MeV, and on 10B at incident energies of 320,410, 483 and 605 MeV. These data are presented and analysed in a coherent way, together with previous results at intermediate energies, by means of a pion exchange model. It is found that all the characteristic features of the data are reproduced satisfactorily.

  1. Exchange reactions catalyzed by group-transferring enzymes oppose the quantitation and the unravelling of the identify of the pentose pathway.

    PubMed

    Flanigan, I; Collins, J G; Arora, K K; MacLeod, J K; Williams, J F

    1993-04-01

    1. The distributions and rates of transfer of carbon isotopes from a selection of specifically labelled ketosugar-phosphate substrates by exchange reactions catalyzed by the pentose and photosynthetic carbon-reduction-pathway group-transferring enzymes transketolase, transaldolase and aldolase have been measured using 13C-NMR spectroscopy. 2. The rates of these exchange reactions were 5, 4 and 1.5 mumol min-1 mg-1 for transketolase exchange, transaldolase exchange and aldolase exchange, respectively. 3. A comparison of the exchange capacities contributed by the activities of these enzymes in three in vitro liver preparations with the maximum non-oxidative pentose pathway flux rates of the preparations shows that transketolase and aldolase exchanges exceeded flux by 9-19 times in liver cytosol and acetone powder enzyme preparations and by 5 times in hepatocytes. Transaldolase was less effective in the comparison of exchange versus flux rates: transaldolase exchange exceeded flux by 1.6 and 5 in catalysis by liver cytosol and acetone powder preparations, respectively, but was only 0.6 times the flux in hepatocytes. 4. Values of group enzyme exchange and pathway flux rates in the above three preparations are important because of the feature role of liver and of these particular preparations in the establishment, elucidation and measurement of a proposed reaction scheme for the fat-cell-type pentose pathway in biochemistry. 5. It is the claim of this paper that the excess of exchange rate activity (particularly transketolase exchange) over pathway flux will overturn attempts to unravel, using isotopically labelled sugar substrates, the identity, reaction sequence and quantitative contribution of the pentose pathway to glucose metabolism. 6. The transketolase exchange reactions relative to the pentose pathway flux rates in normal, regenerating and foetal liver, Morris hepatomas, mammary carcinoma, melanoma, colonic epithelium, spinach chloroplasts and epididymal fat tissue show that transketolase exchange may exceed flux in these tissues by factors ranging over 5-600 times. 7. The confusion of pentose pathway theory by the effects of transketolase exchange action is illustrated by the 13C-NMR spectrum of the hexose 6-phosphate products of ribose 5-phosphate dissimilation, formed after 30 min of liver enzyme action, and shows 13C-labelling in carbons 1 and 3 of glucose 6-phosphate with ratios which range over 2.1-6.4 rather than the mandatory value of 2 which is imposed by the theoretical mechanism of the pathway. PMID:8477719

  2. Charge-exchange and fusion reaction measurements during compression experiments with neutral beam heating in the Tokamak Fusion Test Reactor

    SciTech Connect

    Kaita, R.; Heidbrink, W.W.; Hammett, G.W.; Chan, A.A.; England, A.C.; Hendel, H.W.; Medley, S.S.; Nieschmidt, E.; Roquemore, A.L.; Scott, S.D.

    1986-04-01

    Adiabatic toroidal compression experiments were performed in conjunction with high power neutral beam injection in the Tokamak Fusion Test Reactor (TFTR). Acceleration of beam ions to energies nearly twice the injection energy was measured with a charge-exchange neutral particle analyzer. Measurements were also made of 2.5 MeV neutrons and 15 MeV protons produced in fusion reactions between the deuterium beam ions and the thermal deuterium and /sup 3/He ions, respectively. When the plasma was compressed, the d(d,n)/sup 3/He fusion reaction rate increased a factor of five, and the /sup 3/He(d,p)/sup 4/He rate by a factor of twenty. These data were simulated with a bounce-averaged Fokker-Planck program, which assumed conservation of angular momentum and magnetic moment during compression. The results indicate that the beam ion acceleration was consistent with adiabatic scaling.

  3. Analysis of the isotope effect in the hydrogen exchange reaction between pyridinium chloride and hydrogen chloride

    Microsoft Academic Search

    J. Szydlowski; M. Zielinski

    1979-01-01

    Hydrogen isotope exchange between pyridinium chloride and gaseous hydrogen chloride has been studied both experimentally and theoretically over the temperature range of 273 to 353 K. The experimental fractionation factor obtained shows some dependence on the composition of the substrates. This phenomenon can be accounted for by specific interactions in pyridinium chloride + hydrogen chloride system. The calculated fractionation factor

  4. Sequential chemical bath deposition of Cu(2-x)Se/CdS film by suppressing ion-exchange reaction.

    PubMed

    Cai, Gangri; Lim, Iseul; Lee, Deok Yeon; Shrestha, Nabeen K; Lee, Joong Kee; Nah, Yoon-Chae; Lee, Wonjoo; Han, Sung-Hwan

    2012-06-21

    Chemical bath deposition is an attractive technique to form single- and multilayered metal oxide/chalcogenide films on electrode surfaces. However, the occurrence of desorption and/or ion-exchange reaction during subsequent chemical bath deposition has so far limited preparation of multilayered metal oxide/chalcogenide films. In this paper, we report a method to prevent desorption and ion-exchange reaction of metal oxide/chalcogenide on electrode surfaces using a polyelectrolyte multilayer during sequential chemical bath deposition. By controlling the ion permeability of the polyelectrolyte multilayer, Cu(2-x)Se film was successfully deposited on the CdS film. The Cu(2-x)Se/CdS film is confirmed by UV-vis absorption spectroscopy, scanning electron microscopy, energy dispersive X-ray analysis, and X-ray powder diffractometer. Furthermore, the Cu(2-x)Se/CdS films were investigated as photoinduced charge transfer devices which showed photocurrents of 0.22 mA/cm(2) under illumination (I = 100 mW/cm(2)). PMID:22650229

  5. Imidazole C-2 Hydrogen/Deuterium Exchange Reaction at Histidine for Probing Protein Structure and Function with MALDI Mass Spectrometry

    PubMed Central

    Hayashi, Naoka; Kuyama, Hiroki; Nakajima, Chihiro; Kawahara, Kazuki; Miyagi, Masaru; Nishimura, Osamu; Matsuo, Hisayuki; Nakazawa, Takashi

    2015-01-01

    We present a mass spectrometric method for analyzing protein structure and function, based on the imidazole C-2 or histidine C?1 hydrogen/deuterium (H/D) exchange reaction, which is intrinsically second order with respect to the concentrations of the imidazolium cation and OD? in D2O. The second-order rate constant (k2) of this reaction was calculated from the pH-dependency of the pseudo-first-order rate constant (k?) obtained from the change of average mass ?Mr (0 ? ?Mr < 1) of a peptide fragment containing a defined histidine residue at incubation time (t) such that k? = ? [ln(1??Mr)]/t. We preferred using k2 rather than k? because k2max (maximal value of k2) was empirically related to pKa as illustrated with a Brønsted plot: logk2max=-0.7pKa+? (? is an arbitrary constant), so that we could analyze the effect of structure on the H/D-exchange rate in terms of log(k2max/k2) representing the deviation of k2 from k2max. In the catalytic site of bovine ribonuclease A, His12 showed much larger change in log(k2max/k2) compared with His119 upon binding with cytidine 3?-monophosphate, as anticipated from the X-ray structures and the possible change in solvent accessibility. However, there is a need of considering the hydrogen bonds of the imidazole group with non-dissociable groups to interpret an extremely slow H/D exchange rate of His48 in partially solvent-exposed situation. PMID:24606199

  6. Room Temperature Cation Exchange Reaction in Nanocrystals for Ultrasensitive Speciation Analysis of Silver Ions and Silver Nanoparticles.

    PubMed

    Huang, Ke; Xu, Kailai; Tang, Jie; Yang, Lu; Zhou, Jingrong; Hou, Xiandeng; Zheng, Chengbin

    2015-07-01

    To evaluate the toxicity of silver nanoparticles (AgNPs) and Ag(+) and gain deep insight into the transformation of AgNPs in the environment or organisms, ultrasensitive analytical methods are needed for their speciation analysis. About 40-fold of Cd(2+) in CdTe ionic nanocrystals can be "bombarded-and-exploded" (exchanged) in less than 1 min simply by mixing the nanocrystals with Ag(+) solution at room temperature, while this cation exchange reaction did not occur when only silver nanoparticles were present. On the basis of this striking difference, an ultrasensitive method was developed for speciation analysis of Ag(+) and AgNPs in complex matrices. The released Cd(2+) was reduced to its volatile species by sodium tetrahydroborate, which was separated and swept to an inductively coupled plasma mass spectrometer (ICPMS) or an atomic fluorescence spectrometer (AFS) for the indirect but ultrasensitive detection of Ag(+). Owing to the remarkable signal amplification via the cation exchange reaction and the advantages of chemical vapor generation for sampling, the limit of detection was 0.0003 ?g L(-1) for Ag(+) by ICPMS, which was improved by 100-fold compared to the conventional method. Relative standard deviations are better than 2.5% at a concentration of 0.5 ?g L(-1) Ag(+) or AgNPs regardless of the detector. The proposed method retains several unique advantages, including ultrahigh sensitivity, speciation analysis, simplicity and being organic reagent-free, and has been successfully utilized for speciation analysis of Ag(+) and AgNPs in environmental water samples and paramecium cells. PMID:26017198

  7. Hydrophobic Bimetallic Catalysts for H\\/D Exchange Reaction between Hydrogen and Water

    Microsoft Academic Search

    P. Mârginean; I. Hodor

    1994-01-01

    Hydrophobic bimetallic catalysts of Pt-M on styrenedivinylbenzene were prepared, where M represents successively: Ir, Rh, Pd, Cu and Ag. The total metal loading was 0.5 wt% and the weight fractions of the metal M were: 0.0,0.05,0.1,0.25,0.5,0.75 and 1.0. For each sample, the catalytic activity for H\\/D exchange between hydrogen and water vapor was measured. In case of monometallic catalysts, no

  8. Heavy-Ion Double-Charge Exchange Study via a 12C(18O,18Ne)12Be Reaction

    NASA Astrophysics Data System (ADS)

    Takaki, Motonobu; Matsubara, Hiroaki; Uesaka, Tomohiro; Aoi, Nori; Dozono, Masanori; Hashimoto, Takashi; Kawabata, Takahiro; Kawase, Shoichiro; Kisamori, Keiichi; Kubota, Yuki; Lee, Cheng Soo; Lee, Jenny; Maeda, Yukie; Michimasa, Shin'ichiro; Miki, Kenjiro; Ota, Shinsuke; Sasano, Masaki; Shimoura, Susumu; Suzuki, Tomokazu; Takahisa, Keiji; Tang, Tsz Leung; Tamii, Atsushi; Tokieda, Hiroshi; Yako, Kentaro; Yokoyama, Rin; Zenihiro, Juzo

    Heavy-ion double-charge exchange (HIDCX) reactions are a new promising spectroscopic tool for double spin-isospin flips excitation modes by taking an advantage of transferring isospin and/or spin quantum numbers by an amount of two to target nuclei. However, the data on HIDCX reactions is very scarce. A measurement of a (n,p)-type HIDCX reaction, 12C(18O,18Ne)12Be at 80 MeV/nucleon, was performed by employing the high-resolution spectrometer Grand Raiden at Research Center Nuclear Physics, Osaka University. The excitation energy spectrum of 12Be was obtained, and three clear peaks were observed at 0.0, 2.2, and 4.5 MeV, which are corresponding to ground and excited states of 12Be. The angular distributions of the cross sections for these peaks were obtained within the scattering angle range of 0.0°-4.0° in the center of mass system. We found that the angular distributions have characteristic shapes according to their mulpolarities.

  9. Thermodynamic clarification of the curious ferric/potassium ion exchange accompanying the electrochromic redox reactions of prussian blue, iron(III) hexacyanoferrate(II).

    PubMed

    Rosseinsky, David R; Glasser, Leslie; Jenkins, H Donald Brooke

    2004-08-25

    The recent Glasser-Jenkins method for lattice-energy prediction, applied to an examination of the solid-state thermodynamics of the cation exchanges that occur in electrochromic reactions of Prussian Blue, provides incisive thermodynamic clarification of an ill-understood ion exchange that accompanies particularly the early electrochromic cycles. A volume of 0.246 +/- 0.017 nm(3) formula unit(-1) for the ferrocyanide ion, Fe(II)[(CN)(6)],(4-) is first established and then used, together with other formula unit-volume data, to evaluate the changes of standard enthalpy, entropy, and Gibbs energy in those ion-exchange reactions. The results impressively show by how much the exchange of interstitial Fe(3+) ions by alkali metal ions, usually exemplified by K+, is thermodynamically favored. PMID:15315463

  10. Chemically modified reaction centers of photosystem II: Exchange of pheophytin a with 7-deformyl-7-hydroxymethyl-pheophytin b.

    PubMed

    Zabelin, Alexey A; Shkuropatova, Valentina A; Makhneva, Zoya K; Moskalenko, Andrey A; Shuvalov, Vladimir A; Shkuropatov, Anatoly Ya

    2014-11-01

    The native pheophytin a (Pheo a) in isolated reaction centers of photosystem II (PSII RCs) has been chemically exchanged with extraneous 7-deformyl-7-hydroxymethyl-Pheo b (7(1)-OH-Pheo b) which differs from Pheo a by the C-7 substituent (hydroxymethyl instead of methyl). The two pigments have similar reduction potentials in vitro [M. Meyer, Dissertation, Universität München, 1997], while their absorption spectra show small but distinct differences in the visible region. The resulting 7(1)-OH-Pheo b-modified reaction center preparations were characterized by high-performance liquid chromatography, electronic absorption and light-induced Fourier transform infra red absorption difference spectroscopies, together with photoaccumulation of the reduced pheophytin electron acceptor and NaBH4-treatment. About 70% of the total Pheo a molecules are found to be replaced by 7(1)-OH-Pheo b molecules in modified preparations, indicating that both the photochemically active (PheoD1) and inactive (PheoD2) binding sites were subjected to pigment exchange. The 7(1)-OH-Pheo b molecule located at the PheoD1 site is able to functionally replace the native Pheo a, participating in primary charge separation as an electron acceptor. The Qx absorption band of this modified pheophytin molecule is localized at ~546nm; its Qy band is blue-shifted with respect to the absorption of other reaction center core pigments, being located at ~665nm. The Qy and Qx optical transitions of the 7(1)-OH-Pheo b molecule exchanged into the PheoD2 site are identified at 677 and 543.5nm, respectively. The photochemically active double-modified PSII RCs additionally containing 7-deformyl-7-hydroxymethyl-13(1)-deoxo-13(1)-hydroxy-Pheo b at the PheoD2 site were obtained by treatment of the 7(1)-OH-Pheo b-modified RCs with NaBH4. PMID:25172518

  11. K*(890) Production in the Charge-Exchange Reaction K+n-->K+pi-p at 9 GeV\\/c

    Microsoft Academic Search

    D. Cords; D. D. Carmony; H. W. Clopp; A. F. Garfinkel; R. F. Holland; F. J. Loeffler; H. B. Mathis; L. K. Rangan; J. Erwin; R. L. Lander; D. E. Pellett; P. M. Yager; F. T. Meiere; W. L. Yen

    1971-01-01

    The energy dependence of the cross section for reactions K+n-->K*(890)p and K-p-->K*(890)n is compared over a wide range of incident momenta and found to be identical. This excludes odd C-parity exchanges in addition to the dominant pi exchange. The conventional absorption model does not reproduce the rapid decrease of rho00 as a function of the four-momentum transfer. The Reggeized pi-A2

  12. The Exchange Reaction Between Methane Hydrate and Carbon Dioxide: An Oceanic Feasibility Test

    Microsoft Academic Search

    R. M. Dunk; P. G. Brewer; E. T. Peltzer; P. M. Walz; K. C. Hester; E. D. Sloan

    2006-01-01

    The conversion of CH4 hydrate to CO2 hydrate offers, in principle, a way of sequestering CO2, with the additional recovery of CH4 gas as an energy source. We report results from the first in-situ oceanic experiment on this reaction, carried out in August 2006 at the massive thermogenic hydrate mounds in 850 m water depth, Barkley Canyon, offshore from Vancouver

  13. The T{sub z} = -1{yields}T{sub z} =0 beta decays and comparison with Charge Exchange reactions

    SciTech Connect

    Molina, F.; Rubio, B. [Instituto de Fisica Corpuscular, CSIC-Universidad de Valencia, E-46071 Valencia (Spain); Fujita, Y. [Department of Physics, Osaka University, Toyonaka, Osaka 560-0043 (Japan); Gelletly, W. [Department of Physics, University of Surrey, Guildford GU7XH, Surrey (United Kingdom); Collaboration: Santiago Collaboration

    2011-11-30

    Gamow-Teller (GT) transitions can be studied in both {beta} decay and charge exchange (CE) reactions. If isospin is a good quantum number, then the Tz = -1{yields}0 and Tz = +1{yields}0GT mirror transitions, are identical. Therefore, a comparison of the results from studies of {beta} decay and CE should shed light on this assumption. Accordingly we have studied the {beta} decay of the Tz = -1 fp-shell nuclei, {sup 54}Ni, {sup 50}Fe, {sup 46}Cr, and {sup 42}Ti, produced in fragmentation and we have compared our results with the spectra from ({sup 3}He, t) measurements on the mirror Tz = +1 target nuclei studied in high resolution at RCNP, Osaka. The {beta} decay experiments were performed as part of the STOPPED beam RISING campaign at GSI.

  14. Ion exchange kinetics of cesium for various reaction designs using crystalline silicotitanate, UOP IONSIV IE-911

    NASA Astrophysics Data System (ADS)

    Kim, Sung Hyun

    Through collaborative efforts at Texas A&M University and Sandia National Laboratories, a crystalline silicotitanate (CST), which shows extremely high selectivity for radioactive cesium removal in highly concentrated sodium solutions, was synthesized. The effect of hydrogen peroxide on a CST under cesium ion exchange conditions has been investigated. The experimental results with hydrogen peroxide showed that the distribution coefficient of cesium decreased and the tetragonal phase, the major component of CST, slowly dissolved at hydrogen peroxide concentrations greater than 1 M. A simple and novel experimental apparatus for a single-layer ion exchange column was developed to generate experimental data for estimation of the intraparticle effective diffusivity. A mathematical model is presented for estimation of effective diffusivities for a single-layer column of CST granules. The intraparticle effective diffusivity for Cs was estimated as a parameter in the analytical solution. By using the least square method, the effective diffusivities of 1.56 +/- 0.14 x 10-11 m2/s and 0.68 +/- 0.09 x 10-11 m2/s, respectively, were obtained. The difference in the two values was due to the different viscosities of the solutions. A good fit of the experimental data was obtained which supports the use of the homogeneous model for this system. A counter-current ion exchange (CCIX) process was designed to treat nuclear waste at the Savannah River Site. A numerical method based on the orthogonal collocation method was used to simulate the concentration profile of cesium in the CCIX loaded with CST granules. To maximize cesium loading onto the CST and minimize the volume of CST, two design cases of a moving bed, where the fresh CST is pulsed into the column at certain periods or at certain concentration of cesium, were investigated. Simulation results showed that cesium removal behavior in the pilot-scale test of CCIX experiment, where the column length is 22 ft and the CST is pulsed 1 ft in every 24 hours, was well predicted by using the values of the effective diffusivities of 1.0 to 6.0 x 10 -11 m2/s.

  15. Additional Evidence That Transaldolase Exchange, Isotope Discrimination During the Triose-Isomerase Reaction, or Both Occur in Humans

    PubMed Central

    Basu, Rita; Chandramouli, Visvanthan; Schumann, William; Basu, Ananda; Landau, Bernard R.; Rizza, Robert A.

    2009-01-01

    OBJECTIVE To determine whether deuterium enrichment on carbons 5 and 3 (C5/C3) in plasma glucose is influenced by processes other than gluconeogenesis and, if so, whether these processes are altered by type 2 diabetes. RESEARCH DESIGN AND METHODS In this study, 10 obese diabetic and 10 obese nondiabetic subjects were infused intravenously with [3,5-2H2] galactose enriched at a C5-to-C3 ratio of 1.0 as well as the enrichment of deuterium on C5 and C3 of plasma glucose, measured with nuclear magnetic resonance using the acetaminophen glucuronide method. RESULTS The ratio of deuterium enrichment on C5 and C3 of glucose was <1 (P < 0.001) in all of the diabetic and nondiabetic subjects, resulting in a means ± SE C5-to-C3 ratio that did not differ between groups (0.81 ± 0.01 vs. 0.79 ± 0.01, respectively). CONCLUSIONS That the C5-to-C3 glucose ratio is <1 indicates that transaldolase exchange, selective retention of deuterium at the level of the triose-isomerase reaction, or both occur in humans. This also indicates that the net effect of these processes on the C5-to-C3 ratio is the same in people with and without type 2 diabetes. The possible effects of transaldolase exchange or selective retention of deuterium (or tritium) at the level of the triose-isomerase reaction on tracee labeling and tracer metabolism should be considered when the deuterated water method is used to measure gluconeogenesis or [3-3H] glucose is used to measure glucose turnover in humans. PMID:19366865

  16. Kinematically complete measurement of the ?+d-->?0pp charge-exchange reaction

    NASA Astrophysics Data System (ADS)

    Tacik, R.; Boschitz, E. T.; Gyles, W.; Ottermann, C. R.; Wessler, M.; Wiedner, U.; Garcilazo, H.; Johnson, R. R.

    1990-11-01

    The triple differential cross section d3?/d?p1d?p2dpp1 was measured for the ?+d-->?0pp reaction as a function of proton momentum, in a kinematically complete experiment at T?=228 and 294 MeV. The two outgoing protons were detected in coincidence with plastic scintillator detectors, and their momenta determined by time-of-flight, at several angle pairs in regions of phase space far away from quasifree kinematics. The data are compared with predictions from the relativistic Faddeev calculation of Garcilazo.

  17. Determination of the Gamow-Teller Quenching Factor from Charge Exchange Reactions on 90Zr

    E-print Network

    K. Yako; H. Sakai; M. B. Greenfield; K. Hatanaka; M. Hatano; J. Kamiya; H. Kato; Y. Kitamura; Y. Maeda; C. L. Morris; H. Okamura; J. Rapaport; T. Saito; Y. Sakemi; K. Sekiguchi; Y. Shimizu; K. Suda; A. Tamii; N. Uchigashima; T. Wakasa

    2005-04-15

    Double differential cross sections between 0-12 degrees were measured for the 90Zr(n,p) reaction at 293 MeV over a wide excitation energy range of 0-70 MeV. A multipole decomposition technique was applied to the present data as well as the previously obtained 90Zr(p,n) data to extract the Gamow-Teller (GT) component from the continuum. The GT quenching factor Q was derived by using the obtained total GT strengths. The result is Q=0.88+/-0.06 not including an overall normalization uncertainty in the GT unit cross section of 16%.

  18. Gamow-Teller strengths from (t, 3He) charge-exchange reactions on light nuclei

    Microsoft Academic Search

    I. Daito; H. Akimune; Sam M Austin; D. Bazin; G. P. A Berg; J. A Brown; B. S Davids; Y. Fujita; H. Fujimura; M. Fujiwara; R. Hazama; T. Inomata; K. Ishibashi; J. Jänecke; S. Nakayama; K. Pham; D. A Roberts; B. M Sherrill; M. Steiner; A. Tamii; M. Tanaka; H. Toyokawa; M. Yosoi

    1998-01-01

    Zero-degree cross sections have been measured for (t,3He) reactions on the light target nuclei 9Be, 10B, 11B, 12C, and 13C at a bombarding energy of 127 MeV\\/A. The triton beam was produced by (4He,t+p) breakup on a Be production target using a 4He beam of 155 MeV\\/A. Dispersion matching was applied to obtain good energy resolution (?E\\/E=0.002, ?E=780 keV). The

  19. Time dependent three-dimensional body frame quantal wave packet treatment of the H + H2 exchange reaction on the Liu-Siegbahn-Truhlar-Horowitz (LSTH) surface

    NASA Technical Reports Server (NTRS)

    Neuhauser, Daniel; Baer, Michael; Judson, Richard S.; Kouri, Donald J.

    1989-01-01

    The first successful application of the three-dimensional quantum body frame wave packet approach to reactive scattering is reported for the H + H2 exchange reaction on the LSTH potential surface. The method used is based on a procedure for calculating total reaction probabilities from wave packets. It is found that converged, vibrationally resolved reactive probabilities can be calculated with a grid that is not much larger than required for the pure inelastic calculation. Tabular results are presented for several energies.

  20. Quantum mechanical study of the proton exchange in the ortho-para H2 conversion reaction at low temperature.

    PubMed

    Honvault, P; Jorfi, M; González-Lezana, T; Faure, A; Pagani, L

    2011-11-14

    Ortho-para H(2) conversion reactions mediated by the exchange of a H(+) proton have been investigated at very low energy for the first time by means of a time independent quantum mechanical (TIQM) approach. State-to-state probabilities and cross sections for H(+) + H(2) (v = 0, j = 0,1) processes have been calculated for a collision energy, E(c), ranging between 10(-6) eV and 0.1 eV. Differential cross sections (DCSs) for H(+) + H(2) (v = 0, j = 1) ? H(+) + H(2) (v' = 0, j' = 0) for very low energies only start to develop a proper global minimum around the sideways scattering direction (?? 90°) at E(c) = 10(-3) eV. Rate coefficients, a crucial information required for astrophysical models, are provided between 10 K and 100 K. The relaxation ortho-para process j = 1 ? j' = 0 is found to be more efficient than the j = 0 ? j' = 1 conversion at low temperatures, in line with the extremely small ratio between the ortho and para species of molecular hydrogen predicted at the temperature of interstellar cold molecular clouds. The results obtained by means of a statistical quantum mechanical (SQM) model, which has previously proved to provide an adequate description of the dynamics of the title reactions at a higher collision energy regime, have been compared with the TIQM results. A reasonable good agreement has been found with the only exception of the DCSs for the H(+) + H(2) (v = 0, j = 1) ? H(+) + H(2) (v' = 0, j' = 0) process at very low energy. SQM cross sections are also slightly below the quantum results. Estimates for the rate coefficients, in good accord with the TIQM values, are a clear improvement with respect to pioneering statistical studies on the reaction. PMID:21964447

  1. Does Size Really Matter? The Steric Isotope Effect in a Supramolecular Host?Guest Exchange Reaction

    SciTech Connect

    Mugridge, Jeffrey; Bergman, Robert; Raymond, Kenneth

    2010-01-29

    Isotope effects (IEs), which arise from differences in zero point energies (ZPEs) between a parent and isotopically substituted bond, have been used extensively by chemists to probe molecular interactions and reactivity. Due to the anharmonicity of the C-H/D vibrational potential energy function and the lower ZPE of a C-D bond, the average C-D bond length is typically {approx}0.005 {angstrom} shorter than an equivalent C-H bond. It is this difference in size that is often invoked to explain the observation of secondary, inverse kinetic isotope effects (KIEs) in chemical processes which proceed through a sterically strained transition state. This so-called 'steric isotope effect' (SIE) has been observed in processes such as the racemization of ortho-substituted biphenyls[6] and phenanthrenes, ring flipping of cyclophanes, and more recently in the deslipping of rotaxanes, where substitution of the sterically less demanding deuterium for protium results in rate accelerations for these processes. Herein, we use deuterium substitution in a cationic guest molecule to probe the sensitivity limits of the guest exchange process from a highly-charged supramolecular host.

  2. Sulfur(VI) fluoride exchange (SuFEx): another good reaction for click chemistry.

    PubMed

    Dong, Jiajia; Krasnova, Larissa; Finn, M G; Sharpless, K Barry

    2014-09-01

    Aryl sulfonyl chlorides (e.g. Ts-Cl) are beloved of organic chemists as the most commonly used S(VI) electrophiles, and the parent sulfuryl chloride, O2 S(VI) Cl2 , has also been relied on to create sulfates and sulfamides. However, the desired halide substitution event is often defeated by destruction of the sulfur electrophile because the S(VI) ?Cl bond is exceedingly sensitive to reductive collapse yielding S(IV) species and Cl(-) . Fortunately, the use of sulfur(VI) fluorides (e.g., R-SO2 -F and SO2 F2 ) leaves only the substitution pathway open. As with most of click chemistry, many essential features of sulfur(VI) fluoride reactivity were discovered long ago in Germany.6a Surprisingly, this extraordinary work faded from view rather abruptly in the mid-20th century. Here we seek to revive it, along with John Hyatt's unnoticed 1979 full paper exposition on CH2 ?CH-SO2 -F, the most perfect Michael acceptor ever found.98 To this history we add several new observations, including that the otherwise very stable gas SO2 F2 has excellent reactivity under the right circumstances. We also show that proton or silicon centers can activate the exchange of S?F bonds for S?O bonds to make functional products, and that the sulfate connector is surprisingly stable toward hydrolysis. Applications of this controllable ligation chemistry to small molecules, polymers, and biomolecules are discussed. PMID:25112519

  3. Cation exchange reactions controlling desorption of Sr-90(2+) from coarse-grained contaminated sediments at the Hanford site, Washington

    SciTech Connect

    McKinley, James P.; Zachara, John M.; Smith, Steven C.; Liu, Chongxuan

    2007-01-15

    Nuclear waste that bore 90Sr2+ was accidentally leaked into the vadose zone at the Hanford site, and was immobilized at relatively shallow depths in sediments containing little apparent clay or silt-sized components. Sr2+, 90Sr2+, Mg2+, and Ca2+ was desorbed and total inorganic carbon concentration was monitored during the equilibration of this sediment with varying concentrations of Na+, Ca2+. A cation exchange model previously developed for similar sediments was applied to these results as a predictor of final solution compositions. The model included binary exchange reactions for the four operant cations and an equilibrium dissolution/precipitation reaction for calcite. The model successfully predicted the desorption data. The contaminated sediment was also examined using digital autoradiography, a sensitive tool for imaging the distribution of radioactivity. The exchanger phase containing 90Sr was found to consist of smectite formed from weathering of mesostasis glass in basaltic lithic fragments. These clasts are a significant component of Hanford formation sands. The relatively small but significant cation exchange capacity of these sediments was thus a consequence of reaction with physically sequestered clays in sediment that contained essentially no fine-grained material. The nature of this exchange component explained the relatively slow (scale of days) evolution of desorption solutions. The experimental and model results indicated that there is little risk of migration of 90Sr2+ to the water table.

  4. Superhydrophobic pure silver surface with flower-like structures by a facile galvanic exchange reaction with [Ag(NH3)2]OH.

    PubMed

    Cao, Zongwei; Xiao, Debao; Kang, Longtian; Wang, Zhongliang; Zhang, Shuxiao; Ma, Ying; Fu, Hongbing; Yao, Jiannian

    2008-06-21

    Superhydrophobic pure silver film composed of flower-like microstructures built by interconnected silver nanoplates on a copper plate without any modification was prepared by a facile galvanic exchange reaction between the aqueous [Ag(NH3)2]OH and the copper plate, giving rise to a contact angle as high as 157 degrees . PMID:18535710

  5. Presolvated electron reactions with methyl acetoacetate: electron localization, proton-deuteron exchange, and H-atom abstraction.

    PubMed

    Petrovici, Alex; Adhikary, Amitava; Kumar, Anil; Sevilla, Michael D

    2014-01-01

    Radiation-produced electrons initiate various reaction processes that are important to radiation damage to biomolecules. In this work, the site of attachment of the prehydrated electrons with methyl acetoacetate (MAA, CH3-CO-CH2-COOCH3) at 77 K and subsequent reactions of the anion radical (CH3-CO•--CH2-COOCH3) in the 77 to ca. 170 K temperature range have been investigated in homogeneous H2O and D2O aqueous glasses by electron spin resonance (ESR) spectroscopy. At 77 K, the prehydrated electron attaches to MAA forming the anion radical in which the electron is delocalized over the two carbonyl groups. This species readily protonates to produce the protonated electron adduct radical CH3-C(•)OH-CH2-COOCH3. The ESR spectrum of CH3-C(•)OH-CH2-COOCH3 in H2O shows line components due to proton hyperfine couplings of the methyl and methylene groups. Whereas, the ESR spectrum of CH3-C(•)OH-CH2-COOCH3 in D2O glass shows only the line components due to proton hyperfine couplings of CH3 group. This is expected since the methylene protons in MAA are readily exchangeable in D2O. On stepwise annealing to higher temperatures (ca. 150 to 170 K), CH3-C(•)OH-CH2-COOCH3 undergoes bimolecular H-atom abstraction from MAA to form the more stable radical, CH3-CO-CH•-COOCH3. Theoretical calculations using density functional theory (DFT) support the radical assignments. PMID:25255751

  6. Hyporheic exchange and fulvic acid redox reactions in an alpine stream/wetland ecosystem, Colorado front range

    USGS Publications Warehouse

    Miller, M.P.; McKnight, D.M.; Cory, R.M.; Williams, M.W.; Runkel, R.L.

    2006-01-01

    The influence of hyporheic zone interactions on the redox state of fulvic acids and other redox active species was investigated in an alpine stream and adjacent wetland, which is a more reducing environment. A tracer injection experiment using bromide (Br-) was conducted in the stream system. Simulations with a transport model showed that rates of exchange between the stream and hyporheic zone were rapid (?? ??? 10-3 s -1). Parallel factor analysis of fluorescence spectra was used to quantify the redox state of dissolved fulvic acids. The rate coefficient for oxidation of reduced fulvic acids (?? = 6.5 ?? 10-3 s -1) in the stream indicates that electron-transfer reactions occur over short time scales. The rate coefficients for decay of ammonium (?? = 1.2 ?? 10-3 s-1) and production of nitrate (?? = -1.0 ?? 10-3 s-1) were opposite in sign but almost equal in magnitude. Our results suggest that fulvic acids are involved in rapid electron-transfer processes in and near the stream channel and may be important in determining ecological energy flow at the catchment scale. ?? 2006 American Chemical Society.

  7. Iridium-decorated palladium-platinum core-shell catalysts for oxygen reduction reaction in proton exchange membrane fuel cell.

    PubMed

    Wang, Chen-Hao; Hsu, Hsin-Cheng; Wang, Kai-Ching

    2014-08-01

    Carbon-supported Pt, Pd, Pd-Pt core-shell (Pt(shell)-Pd(core)/C) and Ir-decorated Pd-Pt core-shell (Ir-decorated Pt(shell)-Pd(core)/C) catalysts were synthesized, and their physical properties, electrochemical behaviors, oxygen reduction reaction (ORR) characteristics and proton exchange membrane fuel cell (PEMFC) performances were investigated herein. From the XRD patterns and TEM images, Ir-decorated Pt(shell)-Pd(core)/C has been confirmed that Pt was deposited on the Pd nanoparticle which had the core-shell structure. Ir-decorated Pt(shell)-Pd(core)/C has more positive OH reduction peak than Pt/C, which is beneficial to weaken the binding energy of Pt-OH during the ORR. Thus, Ir-decorated Pt(shell)-Pd(core)/C has higher ORR activity than Pt/C. The maximum power density of H2-O2 PEMFC using Ir-decorated Pt(shell)-Pd(core)/C is 792.2 mW cm(-2) at 70°C, which is 24% higher than that using Pt/C. The single-cell accelerated degradation test of PEMFC using Ir-decorated Pt(shell)-Pd(core)/C shows good durability by the potential cycling of 40,000 cycles. This study concludes that Ir-decorated Pt(shell)-Pd(core)/C has the low Pt content, but it can facilitate the low-cost and high-efficient PEMFC. PMID:24388448

  8. Fe2?Mg2 and TiAl2?MgSi2 exchange reactions between clinopyroxenes and silicate melts

    NASA Astrophysics Data System (ADS)

    Sack, R. O.; Carmichael, I. S. E.

    1984-02-01

    The interdependence of the Fe(Mg)-1 (e.g., FeO-MgO in silicate melt; CaFeSi2O6-CaMgSi2O6 in pyroxene) and TiAl2(MgSi2)-1 exchange reactions between silicate melts and coexisting Ca-pyroxene has been examined. High-calcium clinopyroxenes were grown in 1 atmosphere melting and crystallization experiments on rock powders spanning the composition range tholeiite to melilitite (1,092exchange and (X_{{text{Ti}}^{{text{4 + }}} }^{M1} )^{{text{CPX}}} suggest that at given values of ? _{{text{Fe(Mg)}}_{ - {text{1}}} } extent of Fe(Mg)-1 substitution is strongly coupled with the TiAl2(MgSi2)-1 substitution in pyroxenes near the five-component space CaMg(Si2O6-CaFe(Si)2O6-CaTi(Al)2O6-CaFe?(Al,Si)2O6-CaAl(Al,Si)2O6. The inferred stabilization of Ti in iron-rich relative to magnesium pyroxene is consistent with the operation of Fe2+?Ti4+ intervalence charge transfer interactions (e.g., Rossman 1980) and observations on zoning in natural titanaugites (e.g., Tracy and Robinson 1977). Although the rims of some pyroxenes grown in some melting experiments exhibit prominent zoning in TiAl2(MgSi2)-1, the average values of (X_{{text{Ti}}^{{text{4 + }}} }^{M1} /X_{{text{Mg}}^{{text{2 + }}} }^{M1} ) inferred from the compositions of these pyroxenes, together with those of the relatively homogeneous pyroxenes produced in crystallization experiments, exhibit a 1?1 correlation with values of ? _{{text{TiAl}}_{text{2}} ({text{MgSi}}_{text{2}} )_{ - 1} } derived from the solution model of Ghiorso et al. (1983) with a standard error of 750 calories. The Ti contents of Ca-rich pyroxenes crystallizing from a wide range of natural silicate liquids can therefore be predicted.

  9. Thermal behavior of Belousov-Zhabotinskii reactions with Ce(IV) salts measured by heat exchange calorimetry of flow type involving simultaneous observation of potentiometric oscillations

    Microsoft Academic Search

    Shuko Fujieda; Wei Zhang

    1995-01-01

    Thermal and potentiometric oscillations of Belousov-Zhabotinskii reactions catalyzed by Ce(IV) salt were simultaneously observed in a continuously stirred tank reactor. A heat exchange calorimeter of flow type was assembled. An Ag-AgBr electrode and one end of salt bridge were incorporated in the sample and reference vessels. Three kinds of stock solutions in 0.200 M sulfuric acid were used in typical

  10. Fragmentation and splitting of Gamow-Teller resonances in Sn(3He,t)Sb charge-exchange reactions, A=112-124

    Microsoft Academic Search

    K. Pham; J. Jänecke; D. A. Roberts; M. N. Harakeh; G. P. A. Berg; S. Chang; J. Liu; E. J. Stephenson; B. F. Davis; H. Akimune; M. Fujiwara

    1995-01-01

    Fragmentation and splitting of the Gamow-Teller (GT) strength has been observed in a systematic study of the (3He,t) charge-exchange reaction at E(3He)=200 MeV over the entire range of stable Sn isotopes. Triton energy spectra were observed with a high-resolution magnetic spectrometer at angles near theta=0° where DeltaL=0 transitions are enhanced. Excitation energies, widths, 0° cross sections, and strengths B(GT) were

  11. 218 Inorg. Chem. 1993, 32, 218-222 Synthesis, X-ray CrystalStructure, and Phosphine-Exchange Reactions of the

    E-print Network

    Girolami, Gregory S.

    -Exchange Reactions of the Hafnium(III)-Hafnium(II1)Dimer HfiCb(PEt& Matthew E.Riehl, Scott R. Wilson, and Gregory S of PEt3 yields the dark green hafnium(II1)- hafnium(II1) dimer HfiC&(PEt,)d. The X-ray crystal structure shows that moleculesof Hf2C&(PEt3)4consistof two octahedral hafnium centers that are connected

  12. Growth of nanocrystalline CuIn 3Se 5 (OVC) thin films by ion exchange reactions at room temperature and their characterization as photo-absorbing layers

    Microsoft Academic Search

    Ramphal Sharma; Anil Ghule; Vidya Taur; R. Joshi; Rajaram Mane; J. C. Vyas; Gangri Cai; T. Ganesh; Sun-Ki Min; Wonjoo Lee; Sung-Hwan Han

    2009-01-01

    Nanocrystalline CuIn3Se5 thin films have been grown on ITO glass substrates using chemical ion exchange reactions with CdS, in alkaline medium at pH 11. The as-deposited films were annealed in air at 200°C for 30min and characterized using X-ray diffraction (XRD), transmission electron microscopy, energy dispersive X-ray analysis, X-ray photoelectron spectroscopy, and scanning electron microscopy to study the structural, compositional

  13. XPS analysis of ?-AlF 3 phases with Al successively substituted by Mg to be used for heterogeneously catalyzed Cl\\/F exchange reactions

    Microsoft Academic Search

    O. Böse; E. Kemnitz; A. Lippitz; W. E. S. Unger

    1997-01-01

    A new method of static charge referencing was applied in a XPS study of ?-AlF3 phases with aluminum successively substituted by magnesium. This class of compounds is characterized by strong Lewis acid sites, which are assumed to be the catalytically active sites for Cl\\/F exchange reactions. In order to adjust their strengths Mg was introduced into the ?-AlF3 lattice. At

  14. Photochemical C-H activation and ligand exchange reactions of CpRe(PPh{sub 3}){sub 2}H{sub 2}. Phosphine dissociation is not involved

    SciTech Connect

    Jones, W.D.; Rosini, G.P.; Maguire, J.A. [Univ. of Rochester, NY (United States). Dept. of Chemistry] [Univ. of Rochester, NY (United States). Dept. of Chemistry

    1999-04-26

    The dihydride CpRe(PPh{sub 3}){sub 2}H{sub 2} (1) catalyzes H/D exchange between C{sub 6}D{sub 6} and other arenes or alkanes. Compound 1 also undergoes photochemical phosphine substitution with PMe{sub 3} to give CpRe(PPh{sub 3})(PMe{sub 3})H{sub 2} and then CpRe(PMe{sub 2}){sub 2}H{sub 2}. Mechanistic studies of these reactions are inconsistent with [CpRe(PPh{sub 3})H{sub 2}] as an intermediate. An alternative mechanism is presented proposing that the active species for H/D exchange is the 14-electron cyclic allyl intermediate [({eta}{sup 3}-C{sub 5}H{sub 7})Re(PPh{sub 3}){sub 2}] (E), in which both hydrides have migrated from the rhenium to the cyclopentadienyl ligand. This intermediate accounts for the fact that (1) deuterium does not exchange into the hydride ligands of complex 1 during the H/D exchange catalysis and (2) phosphine substitution occurs by an associative pathway. The precursor to intermediate E, [({eta}{sup 4}-C{sub 5}H{sub 6})Re(PPh{sub 3}){sub 2}H] (D), can undergo reversible orthometalation, allowing H/D exchange between the hydride ligands and the ortho phosphine positions. Evidence is presented to support this new mechanism as well as to rule out other feasible mechanisms.

  15. The zinc-64(t, helium-3) charge-exchange reaction at 115 MeV per nucleon and application to zinc-64 stellar electron-capture

    NASA Astrophysics Data System (ADS)

    Hitt, George Wesley

    2009-09-01

    A secondary, 115 MeV per nucleon triton beam has been reinstituted at the National Superconducting Cyclotron Laboratory for use in ( t, 3 He) charge- exchange reaction studies. This ( n,p )-type charge-exchange reaction is useful for extracting the full Gamow-Teller (GT) response of the nucleus, overcoming Q-value restrictions present in conventional decay studies. The GT + -strength in the pf -shell nucleus 64 Cu has been determined from the absolute cross section measurement of 64 Zn( t, 3 He) near zero-degrees, exploiting an empirical proportionality between the differential angular cross section and the GT-strength. The detailed features of the GT + -strength distribution in a nucleus has an important impact on electron-capture rates in Type 1a and core- collapse supernovae. The measured GT + -strength in 64 Cu is directly compared with the results of modern pf -shell effective interactions GXPF1a and KB3G which can be used to calculate the GT + contribution to electron-capture on nuclei in supernova simulations. The ( t, 3 He) charge-exchange program at the National Superconducting Cyclotron Laboratory provides stringent tests and can aid the development of such nuclear shell-model calculations.

  16. Ex situ scanning force microscopic observation of growth and dissolution phenomena on {0 1 0} surfaces of potassium hydrogen phthalate crystals (KAP) caused by isomorphic exchange reactions

    NASA Astrophysics Data System (ADS)

    Woensdregt, Cornelis F.; Glikin, Arkady E.

    2005-10-01

    Ex situ scanning force microscopic observations reveal characteristic phenomena of growth and dissolution on {0 1 0} surfaces of potassium hydrogen phthalate crystals (KHC 8H 4O 4 or KAP) in contact with a saturated solution of rubidium hydrogen phthalate (RbHC 8H 4O 4 or RbAP) due to an isomorphic exchange reaction. An array of small torpedo-shaped inclusions elongated parallel to the crystallographic c-axis covers the initially smooth cleaved surfaces in less than 1 s. Even in such a short time, almost simultaneous very tiny acicular crystals crystallize parallel to the borders of the elongated etch pits. Moreover, protuberances on the step edges of these etch pits and isometric crystals on the surface are formed as well. When KAP {0 1 0} surfaces are wetted during 10 s with a saturated solution of RbAP, these phenomena are much better visible. After 15 s of wetting numerous elongated crystals cover the surface and the channels. After 30 s, the {0 1 0} surface becomes almost too rough for SFM observations since the etch pits are overgrown by precipitates. These phenomena of nearly simultaneous dissolution and consequent crystallization are the initial stages of the monocrystalline isomorphic exchange process on nanometric scale. It is a very fast process, which unfortunately could not be followed in situ. Our observations corroborate the importance of the volume effect on the isomorphic exchange reactions.

  17. Radiochemical study of the medium energy pion double charge exchange reactions: /sup 209/Bi(pi/sup +/pi/sup -/)/sup 209-x/At

    SciTech Connect

    Clark, J.L.

    1980-01-01

    Carrier-free radiochemical techniques have been used to measure cross sections for the double charge exchange reactions of the type /sup 209/Bi(pi/sup +/, pi/sup -/xn)/sup 209-x/At for 100, 180, and 300 MeV incident pions. The observed formation of astatine products with mass numbers ranging from 208 to 205 is interpreted as evidence of processes in which energy deposited in the initial double charge exchange interaction is subsequently dissipated through neutron evaporation. The excitation functions for these reactions are seen to rise rapidly with decreasing incident pion energy with the maximum results for this study at 100 MeV. The astatine production cross secions measured for these positive pion irradiations of thick bismuth targets must be corrected for secondary processes, particularly the pion induced production of fast alpha particles which can contribute to the total cross sections through reactions like /sup 209/Bi(alpha,xn)/sup 213-x/At. The importance of these secondary contributions was studied through a series of negative pion irradiations of bismuth in which secondary pathways furnish the only means of producing astatine. The failure of evaporation calculations to reproduce the astatine product mass yields observed in these secondary studies suggests that direct mechanisms for energetic complex particle formation are quite important. Values for the alpha decay branches of /sup 207/At, /sup 208/At, and /sup 209/At were determined through a study of the electron capture and alpha decay characteristics of chemically purified astatine fractions.

  18. Proposed experiment for the observation of the isovector spin monopole resonance via the exothermic charge-exchange reaction using the SHARAQ spectrometer

    NASA Astrophysics Data System (ADS)

    Noji, Shumpei; Sakai, Hideyuki

    2009-10-01

    We are developing the exothermic charge-exchange reaction induced by the ?-unstable beam, (^12N,^12C), as a new probe for the study of spin-isospin modes in nuclei. Good features of this reaction include the large mass difference of ^12N and ^12C, the spin-isospin selection of ?S = ?T = 1, and the surface-sensitivity due to the strong absorption. They are suited for the study of spin-isospin modes such as the isovector spin monopole resonance (IVSMR). We have proposed, at the RI Beam Factory (RIBF) at RIKEN, a measurement of the ^90Zr(^12N,^12C) reaction at 200 A , at 0 degrees to observe the IVSMR in ^90Nb. The ^12N beam is produced via the projectile fragmentation of the ^14N primary beam at 250 A , and separated in the BigRIPS, and transported through the dispersion-matched beam line to the reaction target of ^90Zr. The reaction product of ^12C is momentum analyzed by the newly constructed SHARAQ spectrometer. We performed commissioning experiments in March and May, 2009, to study the production of the ^12N secondary beam and the ion optical properties of the beam line and the SHARAQ spectrometer. We report the results from the commissioning experiments together with the present situation of this project.

  19. Ab initio calculation of transition state normal mode properties and rate constants for the H(T)+CH4(CD4) abstraction and exchange reactions

    NASA Astrophysics Data System (ADS)

    Schatz, George C.; Walch, Stephen P.; Wagner, Albert F.

    1980-11-01

    We present ab initio (GVB-POL-CI) calculations for enough of the region about the abstraction and exchange saddle points for H(T)+CH4(CD4) to perform a full normal mode analysis of the transition states. The resulting normal mode frequencies are compared to four other published surfaces: an ab initio UHF-SCF calculation by Carsky and Zahradnik, a semiempirical surface by Raff, and two semiempirical surfaces by Kurylo, Hollinden, and Timmons. Significant quantitative and qualitative differences exist between the POL-CI results and those of the other surfaces. Transition state theory rate constants and vibrationally adiabatic reaction threshold energies were computed for all surfaces and compared to available experimental values. For abstraction, the POL-CI rates are in good agreement with experimental rates and in better agreement than are the rates of any of the other surfaces. For exchange, uncertainties in the experimental values and in the importance of vibrationally nonadiabatic effects cloud the comparison of theory to experiment. Tentative conclusions are that the POL-CI barrier is too low by several kcal. Unless vibrationaly nonadiabatic effects are severe, the POL-CI surface is still in better agreement with experiment than are the other surfaces. The rates for a simple 3-atom transition state theory model (where CH3 is treated as an atom) are compared to the rates for the full 6-atom model. The kinetic energy coupling of reaction coordinate modes to methyl group modes is identified as being of primary importance in determining the accuracy of the 3-atom model for this system. Substantial coupling in abstraction, but not exchange, causes the model to fail for abstraction but succeed for exchange.

  20. Modeling and experiment reveal an unexpected stereoelectronic effect on conformation and scalar couplings of alpha-aminoorganostannanes, with possible relevance to the tin-lithium exchange reaction.

    PubMed

    Santiago, Marcelina; Low, Eddy; Chambournier, Gilles; Gawley, Robert E

    2003-10-31

    The solution conformation of N-methyl-2-(tributylstannyl)piperidines has been determined through the use of vicinal 119Sn-13C coupling constants, revealing a conformational distortion caused by an unexpected stereoelectronic effect in some cases. Specifically, the "equatorial" conformer is distorted into a half-chair, in which the nitrogen lone pair eclipses the C-Sn bond. This distortion, which "costs" approximately 1 kcal/mol, correlates with a conformational dependence of geminal 119Sn-15N couplings and a possible correlation with reactivity in the tin-lithium exchange reaction. PMID:14575474

  1. Modification of Malonamide Ion-Exchange\\/Chelating Resins Using the Fields–Kabatschnik Reaction and Their Application to Metal Ion Removal from Aqueous Solutions

    Microsoft Academic Search

    Andrzej W. Trochimczuk; Julia Jezierska

    2000-01-01

    A resin containing 2-aminoethyl-substituted amides of malonic acid was modified in the Fields–Kabatschnik reaction using diethyl phosphite. The resultant ion-exchange\\/chelating resins have aminomethylphosphonate groups. Modification proceeds almost quantitatively, giving a resin with P=1.97 mmol\\/g, N=4.20 mmol\\/g, and water regain of 0.44 g\\/g. It can be selectively hydrolyzed by treatment with trimethylchlorosilane\\/potassium bromide in dry acetonitrile. Both acidic and ester forms

  2. Calcite dissolution and Ca/Na ion-exchange reactions in columns with different flow rates through high ESR soil

    E-print Network

    Navarre, Audrey

    1999-01-01

    of stability was used to calculate rate constants which were then compared for the influence of flow rate on overall reaction rate. The rate constant approximately doubled as the flow rate was doubled, which implied flow rate control of the reactions...

  3. Impact of transient stream flow on water exchange and reactions in the hyporheic zone of an in-stream gravel bar

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    Groundwater-surface water exchange is an important process that can facilitate the degradation of critical substances like nitrogen-species and contaminants, supporting a healthy status of the aquatic ecosystem. In our study, we simulate water exchange, solute transport and reactions within a natural in-stream gravel bar using a coupled surface and subsurface numerical model. Stream water flow is simulated by computational fluid dynamics software that provides hydraulic head distributions at the streambed, which are used as an upper boundary condition for a groundwater model. In the groundwater model water exchange, solute transport, aerobic respiration and denitrification in the subsurface are simulated. Ambient groundwater flow is introduced by lateral upstream and downstream hydraulic head boundaries that generate neutral, losing or gaining stream conditions. Stream water transports dissolved oxygen, organic carbon (as the dominant electron donor) and nitrate into the subsurface, whereas an additional nitrate source exists in the ambient groundwater. Scenarios of stream flow events varying in duration and stream stage are simulated and compared with steady state scenarios with respect to water fluxes, residence times and the solute turn-over rates. Results show, that water exchange and solute turn-over rates highly depend on the interplay between event characteristics and ambient groundwater levels. For scenarios, where the stream flow event shifts the hydraulic system to a net-neutral hydraulic gradient between the average stream stage and the ambient groundwater level (minimal exchange between ground- and surface water), solute consumption is higher, compared to the steady losing or gaining case. In contrast, events that induce strong losing conditions lead to a lower potential of solute consumption.

  4. Invited paper: Composition-dependent electrical properties of ternary AgxSb1-xTey thin films synthesized by cationic exchange reaction

    NASA Astrophysics Data System (ADS)

    Jung, Hyunsung; Park, Hosik; Choa, Yongho; Myung, Nosang V.

    2012-04-01

    Ternary silver antimony telluride (AgxSb1-xTey) thin films with tailored compositions were synthesized by a cationic exchange reaction of thermally evaporated antimony telluride thin films, as a simple and costeffective approach. The composition of AgxSb1-xTey thin films was controlled by the reaction time. Temperaturedependent electrical properties of the AgxSb1-xTey thin films demonstrated phase transition behavior from 323 K to 343 K. The composition-dependent thermoelectric properties (i.e., electrical resistivity (?), Seebeck coefficient (S) and power factor (S2?)) of the as-deposited Sb54Te46, the transformed AgxSb1-xTey and the annealed AgxSb1-xTey thin films were investigated as a function of temperature.

  5. Two-dimensional free-energy surface on the exchange reaction of alkyl chloride/chloride using the QM/MM-MC method

    SciTech Connect

    Ohisa, M.; Yamataka, H.; Dupuis, Michel; Aida, Misako

    2007-12-05

    Two-dimensional free-energy surfaces are calculated for alkyl chloride/chloride exchange/inversion reactions: Cl- + RCl (R = Me and t-Bu) surrounded by one hundred H2O molecules as a model of solvent. The methodology of free-energy calculation by perturbation theory based on a mixed-Hamiltonian model (QM/MM) combined with Monte Carlo sampling of the solvent configurations was used to obtain the changes in solvation free energy. We devised a special procedure to analyze the two-dimensional free-energy surfaces to gain unique insight into the differences in the reaction mechanisms between the two systems. The inversion reaction path for R = t-Bu on the free-energy surface is found to proceed in an asynchronous way within a concerted framework via the ion-pair region. This is in contrast to the R = Me system that proceeds as a typical SN2 reaction. This work was supported by the U.S. Department of Energy's (DOE) Office of Basic Energy Sciences, Chemical Sciences program. The Pacific Northwest National Laboratory is operated by Battelle for DOE.

  6. Dimension reduction for extracting geometrical structure of multidimensional phase space: Application to fast energy exchange in the reaction O(D1)+N2O?NO+NO

    NASA Astrophysics Data System (ADS)

    Kawai, Shinnosuke; Fujimura, Yo; Kajimoto, Okitsugu; Yamashita, Takefumi; Li, Chun-Biu; Komatsuzaki, Tamiki; Toda, Mikito

    2007-02-01

    One of the most fundamental problems in studying general Hamiltonian systems with many degrees of freedom is to extract a low-dimensional subsystem including the essential dynamics. In this paper, a new partial normal form (PNF) method is developed to reduce the number of coupling terms in the Hamiltonian and to simplify the dynamics analyses. The PNF method allows one to decouple many unimportant bath modes as well as the reactive mode from the system by assessing the significance of the coupling terms. The method is applied to the chemical reaction O(D1)+N2O?NO+NO , which was found to exhibit efficient energy exchange between the two NO stretching modes despite the short lifetime of the reaction intermediate [S. Kawai , J. Chem. Phys. 124, 184315 (2006)]. Through the analysis of the two-dimensional PNF Hamiltonian subsystem, it is found that the motion of the subsystem preserves the “normal mode picture” of the symmetric and antisymmetric NO stretching modes despite its high energy. Then the vibrational energy, initially localized in the newly formed NO bond, is transferred to the reactants’ NO bond through the beating between the symmetric and antisymmetric stretching modes. The preservation of the normal mode picture and the short period of the beating explain the fast energy exchange between the two NO bonds. This successful application proves that the PNF method can extract the essential small subspace from many-degrees-of-freedom Hamiltonian systems.

  7. Indoor transient SOA formation from ozone + ?-pinene reactions: Impacts of air exchange and initial product concentrations, and comparison to limonene ozonolysis

    NASA Astrophysics Data System (ADS)

    Youssefi, Somayeh; Waring, Michael S.

    2015-07-01

    The ozonolysis of reactive organic gases (ROG), e.g. terpenes, generates secondary organic aerosol (SOA) indoors. The SOA formation strength of such reactions is parameterized by the aerosol mass fraction (AMF), a.k.a. SOA yield, which is the mass ratio of generated SOA to oxidized ROG. AMFs vary in magnitude both among and for individual ROGs. Here, we quantified dynamic SOA formation from the ozonolysis of ?-pinene with 'transient AMFs,' which describe SOA formation due to pulse emission of a ROG in an indoor space with air exchange, as is common when consumer products are intermittently used in ventilated buildings. We performed 19 experiments at low, moderate, and high (0.30, 0.52, and 0.94 h-1, respectively) air exchange rates (AER) at varying concentrations of initial reactants. Transient AMFs as a function of peak SOA concentrations ranged from 0.071 to 0.25, and they tended to increase as the AER and product of the initial reactant concentrations increased. Compared to our similar research on limonene ozonolysis (Youssefi and Waring, 2014), for which formation strength was driven by secondary ozone reactions, the AER impact for ?-pinene was opposite in direction and weaker, while the initial reactant product impact was in the same direction but stronger for ?-pinene than for limonene. Linear fits of AMFs for ?-pinene ozonolysis as a function of the AER and initial reactant concentrations are provided so that future indoor models can predict SOA formation strength.

  8. Hg(ii) bacterial biouptake: the role of anthropogenic and biogenic ligands present in solution and spectroscopic evidence of ligand exchange reactions at the cell surface.

    PubMed

    Thomas, Sara Anne; Tong, Tiezheng; Gaillard, Jean-François

    2014-12-01

    We have used a whole cell biosensor to investigate how the chemical speciation of aqueous Hg(ii) affects its biouptake. The reporter system consists of a model gram-negative bacterium (Escherichia coli) with a chromosomally inserted merR::luxCDABE fusion. Synthetic aminopolycarboxylate organic ligands (EDTA, DTPA, EDDS, and NTA) as well as naturally-occurring thiol-containing ligands (cysteine, penicillamine, and glutathione) were used to control Hg(ii) speciation in solution. We observed that all aminopolycarboxylate ligands promote the biouptake of Hg(ii), following trends unexplained by Hg(ii) speciation. Hg(ii) biouptake was greatly enhanced in the presence of cysteine whereas it was inhibited in the presence of penicillamine and glutathione. Bioreporter exposure to increasing concentrations of Hg(ii) quantitatively complexed by EDTA, DTPA, EDDS and cysteine showed that the extent of uptake is dose-dependent until a plateau is reached. Additionally, Hg LIII-edge X-ray absorption near edge structure (XANES) spectra of Hg(ii) associated with the bioreporter membrane under the conditions used to perform the biouptake experiments suggest that a ligand exchange reaction occurs between the Hg(ii)-aminopolycarboxylate complex and thiol moieties at the cell membrane. We conclude that ligand-exchange reactions at the cell surface play a critical role in the bacterial biouptake of Hg(ii). PMID:25322360

  9. Uniformly microsized luminescent materials obtained through a solid state reaction of WO{sub 3} with Ln{sup 3+}-exchanged zeolite L at 700 °C

    SciTech Connect

    Wang, Yige, E-mail: wangyige@hebut.edu.cn [School of Chemical Engineering and Technology, Hebei University of Technology, Tianjin 300130 (China); Fang, Yi; Zhang, Wenjun; Zhang, Li; Chen, Yuhuan; Yu, Xiaoyan [School of Chemical Engineering and Technology, Hebei University of Technology, Tianjin 300130 (China)

    2013-06-01

    Graphical abstract: We have reported the modification of Ln3+/ZL microcrystals by the tungstate-oxygen species via a solid state reaction of WO{sub 3} and Ln{sup 3+}-exchanged zeolite L at 700 °C. Highlights: ? Luminescent materials were obtained from zeolite L crystals. ? The materials show characteristic luminescence of Eu{sup 3+} and Tb{sup 3+} ions. ? The framework of zeolite L crystals has been kept during the annealing process. ? Energy transfer from tungstate-oxygen species to lanthanide was confirmed. - Abstract: In this work, we report the uniformly microsized luminescent materials prepared by a solid state reaction of WO{sub 3} and Ln{sup 3+}-exchanged zeolite L at 700 °C. The obtained materials were investigated by SEM, XRD and photoluminescence spectroscopy. The influence of tungstate-oxygen species on the morphology and luminescence of the materials were discussed in detail. Energy transfer from the tungstate-oxygen species to Eu{sup 3+} and Tb{sup 3+} ions have been demonstrated by the photoluminescence spectra, implying the loading of tungstate-oxygen species into the nanochannels of the crystals and the close proximity of which to Eu{sup 3+} ions.

  10. Isotope effects in the transient phases of the reaction catalyzed by ethanolamine ammonia-lyase: determination of the number of exchangeable hydrogens in the enzyme-cofactor complex.

    PubMed

    Bandarian, V; Reed, G H

    2000-10-01

    Transient phases of the reaction catalyzed by ethanolamine ammonia-lyase (EAL) from Salmonella typhimurium have been investigated by stopped-flow visible spectrophotometry and deuterium kinetic isotope effects. The cleavage of adenosylcobalamin (coenzyme B(12)) to form cob(II)alamin (B(12r)) with ethanolamine as the substrate occurred within the dead time of the instrument whenever coenzyme B(12) was preincubated with enzyme prior to mixing with substrate. The rate was, however, slowed sufficiently to be measured with perdeutero ethanolamine as the substrate. Optical spectra indicate that, during the steady states of the reactions with ethanolamine and with S-2-aminopropanol as substrates, approximately 90% of the active sites contain B(12r). Reformation of the carbon-cobalt bond of the cofactor occurs following depletion of substrate in the reaction mixtures, and the rate constant for this process reflects k(cat) of the respective substrates. This late phase of the reaction also exhibits (2)H isotope effects similar to those measured for the overall reaction with (2)H-labeled substrates. With unlabeled substrates, the rate of cofactor reassembly is independent of the number of substrate molecules turned over in the steady-state phase. However, with (2)H-labeled substrates, kinetic isotope effects appear in the reassembly phase, and these isotope effects are maximal after only approximately 2 equiv of substrate/active site are processed. With 5'-deuterated coenzyme B(12) and deuterated substrate, the isotope effect on reassembly is independent of the number of substrate molecules that are turned over. These results indicate that the pool of exchangeable hydrogens in the enzyme-cofactor complex is two-a finding consistent with the hydrogens in the C5' methylene of coenzyme B(12). PMID:11009622

  11. Two-pion-exchange and other higher-order contributions to the pp{yields}pp{pi}{sup 0} reaction

    SciTech Connect

    Kim, Y. [Department of Physics and Astronomy, University of South Carolina, Columbia, South Carolina 29208 (United States); School of Physics, Korea Institute for Advanced Study, Seoul 130-012 (Korea, Republic of); Sato, T. [Department of Physics, Osaka University, Toyonaka, Osaka 560-0043 (Japan); Myhrer, F.; Kubodera, K. [Department of Physics and Astronomy, University of South Carolina, Columbia, South Carolina 29208 (United States)

    2009-07-15

    Much effort has been invested on effective-field-theoretical studies of the near-threshold NN{yields}NN{pi} reactions and, in order to deal with the somewhat large three-momentum transfers involved, the momentum counting scheme (MCS) was proposed as an alternative to the usual Weinberg counting scheme. Given the fact that a quantitative explanation of the existing high-precision NN{yields}NN{pi} data requires a careful examination of higher chiral order contributions to the transition operator, we make a detailed numerical investigation of the convergence property of MCS for a pilot case of the pp{yields}pp{pi}{sup 0} reaction. Our study indicates that MCS is superior to the Weinberg scheme in identifying dominant higher order contributions to the NN{yields}NN{pi} reactions.

  12. Weak-interaction strength from charge-exchange reactions versus {beta} decay in the A=40 isoquintet

    SciTech Connect

    Bhattacharya, M. [Brookhaven National Laboratory, P.O. Box 5000, Upton, New York 11973-5000 (United States); Indiana University Cyclotron Facility, 2401 Milo B. Sampson Lane, Bloomington, Indiana 47408 (United States); Goodman, C. D. [Indiana University Cyclotron Facility, 2401 Milo B. Sampson Lane, Bloomington, Indiana 47408 (United States); Garcia, A. [Physics Department, University of Washington, Seattle, Washington 98195-1560 (United States)

    2009-11-15

    We report a measurement of the Gamow-Teller (GT) strength distribution for {sup 40}Ar{yields}{sup 40}K using the 0 deg. (p,n) reaction. The measurement extends observed GT strength distribution in the A=40 system up to an excitation energy of {approx}8 MeV. In comparing our results with those from the {beta} decay of the isospin mirror nucleus {sup 40}Ti, we find that, within the excitation energy region probed by the {beta}-decay experiment, we observe a total GT strength that is in fair agreement with the {beta}-decay measurement. However, we find that the relative strength of the two strongest transitions differs by a factor of {approx}1.8 in comparing our results from (p,n) reactions with the {beta} decay of {sup 40}Ti. Using our results we present the neutrino-capture cross section for {sup 40}Ar.

  13. Preparation of carrier-free 7Be by ion-exchange following charged particle and photonuclear reactions.

    PubMed

    Ohtsuki, T; Fujikawa, S-I; Yuki, H

    2003-10-01

    Carrier-free 7Be has been produced by 7Li(p,n)7Be and 10B(gamma,p2n)7Be (as well as 11B(gamma,p3n)7Be) reactions using a cyclotron and electron linear accelerator, respectively. Radiochemical methods for purification of the carrier-free radioactive 7Be isotope from the irradiated lithium and boron compounds have been investigated. A simple separation scheme is proposed. PMID:14522228

  14. Heterogeneous reactions of Cl2 with sea salts at ambient temperature: Implications for halogen exchange in the atmosphere

    NASA Astrophysics Data System (ADS)

    Mochida, M.; Hirokawa, J.; Kajii, Y.; Akimoto, H.

    Laboratory measurements of heterogeneous reactions of Cl2(g) on solid sea salts at ambient temperature and low relative humidity have been carried out using a Knudsen cell reactor. Synthetic sea salt and commercial natural sea salt are used to represent sea salt particles. The uptake probabilities for synthetic sea salt (? = (2.2 ± 0.3) × 10-2) and for natural salt (? = (3.1 ± 1.1) × 10-2) have been obtained and Br2 is observed as the predominant product. The heterogeneous reactions of Cl2 with solid pure NaBr and KBr: 1/2Cl2(g) + MBr(s) ? MCl(s) + 1/2Br2(g) (M = Na, K), have been investigated. These results show that synthetic and natural salts have a similar extent of reactivity compared with solid pure bromides in spite of their small Br fraction. These reactions are expected to be an important Cl2 sink and Br2 source in the marine boundary layer.

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  16. Quasiclassical trajectory studies of 18O(3P) + NO2 isotope exchange and reaction to O2 + NO on D0 and D1 potentials.

    PubMed

    Fu, Bina; Zhang, Dong H; Bowman, Joel M

    2013-07-14

    We report quasiclassical trajectory calculations for the bimolecular reaction (18)O((3)P) + NO2 on the recent potential energy surfaces of the ground (D0) and first excited (D1) states of NO3 [B. Fu, J. M. Bowman, H. Xiao, S. Maeda, and K. Morokuma, J. Chem. Theory. Comput. 9, 893 (2013)]. The branching ratio of isotope exchange versus O2 + NO formation, as well as the product angular distributions and energy and rovibrational state distributions are presented. The calculations are done at the collision energy of relevance to recent crossed beam experiments [K. A. Mar, A. L. Van Wyngarden, C.-W. Liang, Y. T. Lee, J. J. Lin, and K. A. Boering, J. Chem. Phys. 137, 044302 (2012)]. Very good agreement is achieved between the current calculations and these experiments for the branching ratio and final translational energy and angular distributions of isotope exchange products (16)O((3)P) + NO2 and O2 + NO formation products. The reactant (18)O atom results in (18)O(16)O but not N(18)O for the O2 + NO formation product channel, consistent with the experiment. In addition, the detailed vibrational and rotational state information of diatomic molecules calculated currently for the (34)O2 + NO formation channel on D0 and D1 states are in qualitative agreement with the previous experimental and theoretical results of the photodissociation of NO3 and are consistent with older thermal bimolecular kinetics measurements. PMID:23862939

  17. Quasiclassical trajectory studies of 18O(3P) + NO2 isotope exchange and reaction to O2 + NO on D0 and D1 potentials

    NASA Astrophysics Data System (ADS)

    Fu, Bina; Zhang, Dong H.; Bowman, Joel M.

    2013-07-01

    We report quasiclassical trajectory calculations for the bimolecular reaction 18O(3P) + NO2 on the recent potential energy surfaces of the ground (D0) and first excited (D1) states of NO3 [B. Fu, J. M. Bowman, H. Xiao, S. Maeda, and K. Morokuma, J. Chem. Theory. Comput. 9, 893 (2013)], 10.1021/ct3009792. The branching ratio of isotope exchange versus O2 + NO formation, as well as the product angular distributions and energy and rovibrational state distributions are presented. The calculations are done at the collision energy of relevance to recent crossed beam experiments [K. A. Mar, A. L. Van Wyngarden, C.-W. Liang, Y. T. Lee, J. J. Lin, and K. A. Boering, J. Chem. Phys. 137, 044302 (2012)], 10.1063/1.4736567. Very good agreement is achieved between the current calculations and these experiments for the branching ratio and final translational energy and angular distributions of isotope exchange products 16O(3P) + NO2 and O2 + NO formation products. The reactant 18O atom results in 18O16O but not N18O for the O2 + NO formation product channel, consistent with the experiment. In addition, the detailed vibrational and rotational state information of diatomic molecules calculated currently for the 34O2 + NO formation channel on D0 and D1 states are in qualitative agreement with the previous experimental and theoretical results of the photodissociation of NO3 and are consistent with older thermal bimolecular kinetics measurements.

  18. A Structure-Function Study of RecA: The Structural Basis for ATP Specificity in the Strand Exchange Reaction

    NASA Astrophysics Data System (ADS)

    Gegner, Julie; Spruill, Natalie; Plesniak, Leigh A.

    1999-11-01

    The terms "structure" and "function" can assume a variety of meanings. In biochemistry, the "structure" of a protein can refer to its sequence of amino acids, the three-dimensional arrangement of atoms within a subunit, or the arrangement of subunits into a larger oligomeric or filamentous state. Likewise, the function of biological macromolecules can be examined at many levels. The function of a protein can be described by its role in an organism's survival or by a chemical reaction that it promotes. We have designed a three-part biochemical laboratory experiment that characterizes the structure and function of the Escherichia coli RecA protein. The first part examines the importance of RecA in the survival of bacteria that have been exposed to UV light. This is the broadest view of function of the enzyme. Second, the students use an in vitro assay of RecA whereby the protein promotes homologous recombination. Because RecA functions not catalytically, but rather stoichiometrically, in this recombination reaction, the oligomeric state of RecA in complex with DNA must also be discussed. Finally, through molecular modeling of X-ray crystallographic structures, students identify functionally important features of the ATP cofactor binding site of RecA.

  19. Rapid direct conversion of Cu2-xSe to CuAgSe nanoplatelets via ion exchange reactions at room temperature.

    PubMed

    Moroz, N A; Olvera, A; Willis, G M; Poudeu, P F P

    2015-06-01

    The use of template nanostructures for the creation of photovoltaic and thermoelectric semiconductors is becoming a quickly expanding synthesis strategy. In this work we report a simple two-step process enabling the formation of ternary CuAgSe nanoplatelets with a great degree of control over the composition and shape. Starting with hexagonal nanoplatelets of cubic Cu2-xSe, ternary CuAgSe nanoplatelets were generated through a rapid ion exchange reaction at 300 K using AgNO3 solution. The Cu2-xSe nanoplatelet template and the final CuAgSe nanoplatelets were analyzed by electron microscopy and X-ray diffraction (XRD). It was found that both the low temperature pseudotetragonal and the high temperature cubic forms of CuAgSe phase were created while maintaining the morphology of the Cu2-xSe nanoplatelet template. Thermal and electronic transport measurements of hot-pressed pellets of the synthesized CuAgSe nanoplatelets showed a drastic reduction in the thermal conductivity and a sharp transition from n-type (S = -45 ?V K(-1)) to p-type (S = +200 ?V K(-1)) semiconducting behavior upon heating above the structural transition from the low temperature orthorhombic to the high temperature super-ionic cubic phase. This simple reaction process utilizing a template nanostructure matrix represents an energy efficient, cost-efficient, and versatile strategy to create interesting materials with lower defect density and superior thermoelectric performance. PMID:25965176

  20. The orbital-based view on reaction dynamics: ligand exchange of Fe(CO)5 in solution

    NASA Astrophysics Data System (ADS)

    Föhlisch, Alexander

    2015-03-01

    Time resolved soft X-ray spectroscopy has proven recently, that it can beat the complexity of dynamics in materials and chemical processes by its high selectivity towards elemental, chemical, and magnetic properties. Changes in chemical bonding, in particular bond breaking and bond creation seem conceptually simple, but as a result of coherent wave packet motion it is difficult to catch the dynamic pathways in a multidimensional potential energy landscape. In this contribution we exploit the unique approach of femtosecond time resolved resonant inelastic X-ray scattering at LCLS to derive how ultrafast spin-crossover and ligation determines the pathways of ligand exchange of Ironpentacarbonyl (Fe(CO)5) in solution. As an outlook, it will be discussed, how non-linear X-ray processes can push time resolved soft X-ray spectroscopy in a new phase. In particular, stimulated Raman scattering and amplified spontaneous emission can overcome the weak scattering cross-sections of spontaneous processes, help to suppress sample damage and increase spectral resolution and excited state selectivity through the exploitation of Anti-Stokes Raman Scattering.

  1. A "uniform" heterogeneous photocatalyst: integrated p-n type CuInS2/NaInS2 nanosheets by partial ion exchange reaction for efficient H2 evolution.

    PubMed

    Hu, Peng; Ngaw, Chee Keong; Tay, Yee Yan; Cao, Shaowen; Barber, James; Tan, Timothy Thatt Yang; Loo, Say Chye Joachim

    2015-05-21

    Single-crystalline-like P-N type CuInS2/NaInS2 heterogeneous nanosheets were synthesized by partial cation exchange reaction and show highly improved photocatalytic H2 evolution activity attributed to the increased efficiency of interfacial charge transfer. PMID:25959829

  2. Active microchannel heat exchanger

    DOEpatents

    Tonkovich, Anna Lee Y. (Pasco, WA) [Pasco, WA; Roberts, Gary L. (West Richland, WA) [West Richland, WA; Call, Charles J. (Pasco, WA) [Pasco, WA; Wegeng, Robert S. (Richland, WA) [Richland, WA; Wang, Yong (Richland, WA) [Richland, WA

    2001-01-01

    The present invention is an active microchannel heat exchanger with an active heat source and with microchannel architecture. The microchannel heat exchanger has (a) an exothermic reaction chamber; (b) an exhaust chamber; and (c) a heat exchanger chamber in thermal contact with the exhaust chamber, wherein (d) heat from the exothermic reaction chamber is convected by an exothermic reaction exhaust through the exhaust chamber and by conduction through a containment wall to the working fluid in the heat exchanger chamber thereby raising a temperature of the working fluid. The invention is particularly useful as a liquid fuel vaporizer and/or a steam generator for fuel cell power systems, and as a heat source for sustaining endothermic chemical reactions and initiating exothermic reactions.

  3. Toward a protecting-group-free halogen-metal exchange reaction: practical, chemoselective metalation of functionalized aromatic halides using dianion-type zincate, tBu4ZnLi2.

    PubMed

    Uchiyama, Masanobu; Furuyama, Taniyuki; Kobayashi, Minoru; Matsumoto, Yotaro; Tanaka, Kentaro

    2006-07-01

    A versatile preparation method for aromatic zincate compounds through a halogen-zinc exchange reaction using dilithium tetra-tert-butylzincate (tBu4ZnLi2) has been developed. This reagent permits efficient preparation of highly functionalized aromatic zincates, particularly, those with electrophilic functional groups, such as ester, amide, alcohol, and phenol. Halogen-zinc exchange reactions followed by electrophilic trapping (with allyl bromide or benzaldehyde) proved to be a powerful tool for C-C bond formation on functionalized aromatic rings. The functionalized aromatic zincate intermediate was also found to undergo copper- and palladium-catalyzed C-C bond-forming reactions with good yields and high chemoselectivity. PMID:16802798

  4. Weathering reactions and hyporheic exchange controls on stream water chemistry in a glacial meltwater stream in the McMurdo Dry Valleys

    USGS Publications Warehouse

    Gooseff, M.N.; McKnight, D.M.; Lyons, W.B.; Blum, A.E.

    2002-01-01

    In the McMurdo Dry Valleys, Antarctica, dilute glacial meltwater flows down well-established streambeds to closed basin lakes during the austral summer. During the 6-12 week flow season, a hyporheic zone develops in the saturated sediment adjacent to the streams. Longer Dry Valley streams have higher concentrations of major ions than shorter streams. The longitudinal increases in Si and K suggest that primary weathering contributes to the downstream solute increase. The hypothesis that weathering reactions in the hyporheic zone control stream chemistry was tested by modeling the downstream increase in solute concentration in von Guerard Stream in Taylor Valley. The average rates of solute supplied from these sources over the 5.2 km length of the stream were 6.1 ?? 10-9 mol Si L-1 m-1 and 3.7 ?? 10-9 mol K L-1 m-1, yielding annual dissolved Si loads of 0.02-1.30 tool Si m-2 of watershed land surface. Silicate minerals in streambed sediment were analyzed to determine the representative surface area of minerals in the hyporheic zone subject to primary weathering. Two strategies were evaluated to compute sediment surface area normalized weathering rates. The first applies a best linear fit to synoptic data in order to calculate a constant downstream solute concentration gradient, dC/dx (constant weathering rate contribution, CRC method); the second uses a transient storage model to simulate dC/dx, representing both hyporheic exchange and chemical weathering (hydrologic exchange, HE method). Geometric surface area normalized dissolution rates of the silicate minerals in the stream ranged from 0.6 ?? 10-12 mol Si m-2 s-1 to 4.5 ?? 10-12 mol Si m-2 s-1 and 0.4 ?? 10-12 mol K m-2 s-1 to 1.9 ?? 10-12 mol K m-2 s-1. These values are an order of magnitude lower than geometric surface area normalized weathering rates determined in laboratory studies and are an order of magnitude greater than geometric surface area normalized weathering rates determined in a warmer, wetter setting in temperate basins, despite the cold temperatures, lack of precipitation and lack of organic material. These results suggest that the continuous saturation and rapid flushing of the sediment due to hyporheic exchange facilitates weathering in Dry Valley streams.

  5. Rapid direct conversion of Cu2-xSe to CuAgSe nanoplatelets via ion exchange reactions at room temperature

    NASA Astrophysics Data System (ADS)

    Moroz, N. A.; Olvera, A.; Willis, G. M.; Poudeu, P. F. P.

    2015-05-01

    The use of template nanostructures for the creation of photovoltaic and thermoelectric semiconductors is becoming a quickly expanding synthesis strategy. In this work we report a simple two-step process enabling the formation of ternary CuAgSe nanoplatelets with a great degree of control over the composition and shape. Starting with hexagonal nanoplatelets of cubic Cu2-xSe, ternary CuAgSe nanoplatelets were generated through a rapid ion exchange reaction at 300 K using AgNO3 solution. The Cu2-xSe nanoplatelet template and the final CuAgSe nanoplatelets were analyzed by electron microscopy and X-ray diffraction (XRD). It was found that both the low temperature pseudotetragonal and the high temperature cubic forms of CuAgSe phase were created while maintaining the morphology of the Cu2-xSe nanoplatelet template. Thermal and electronic transport measurements of hot-pressed pellets of the synthesized CuAgSe nanoplatelets showed a drastic reduction in the thermal conductivity and a sharp transition from n-type (S = -45 ?V K-1) to p-type (S = +200 ?V K-1) semiconducting behavior upon heating above the structural transition from the low temperature orthorhombic to the high temperature super-ionic cubic phase. This simple reaction process utilizing a template nanostructure matrix represents an energy efficient, cost-efficient, and versatile strategy to create interesting materials with lower defect density and superior thermoelectric performance.The use of template nanostructures for the creation of photovoltaic and thermoelectric semiconductors is becoming a quickly expanding synthesis strategy. In this work we report a simple two-step process enabling the formation of ternary CuAgSe nanoplatelets with a great degree of control over the composition and shape. Starting with hexagonal nanoplatelets of cubic Cu2-xSe, ternary CuAgSe nanoplatelets were generated through a rapid ion exchange reaction at 300 K using AgNO3 solution. The Cu2-xSe nanoplatelet template and the final CuAgSe nanoplatelets were analyzed by electron microscopy and X-ray diffraction (XRD). It was found that both the low temperature pseudotetragonal and the high temperature cubic forms of CuAgSe phase were created while maintaining the morphology of the Cu2-xSe nanoplatelet template. Thermal and electronic transport measurements of hot-pressed pellets of the synthesized CuAgSe nanoplatelets showed a drastic reduction in the thermal conductivity and a sharp transition from n-type (S = -45 ?V K-1) to p-type (S = +200 ?V K-1) semiconducting behavior upon heating above the structural transition from the low temperature orthorhombic to the high temperature super-ionic cubic phase. This simple reaction process utilizing a template nanostructure matrix represents an energy efficient, cost-efficient, and versatile strategy to create interesting materials with lower defect density and superior thermoelectric performance. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr01451d

  6. Reaction mechanisms of Li(0.30)La(0.57)TiO3 powder with ambient air: H+/Li+ exchange with water and Li2CO3 formation.

    PubMed

    Boulant, Anthony; Bardeau, Jean Francois; Jouanneaux, Alain; Emery, Joël; Buzare, Jean-Yves; Bohnke, Odile

    2010-04-28

    The proton/lithium exchange property of the lithium lanthanum titanate Li(0.30)La(0.57)TiO(3) (named LLTO) is shown to occur at room temperature under ambient air. The (1)H and (7)Li MAS NMR, TGA analysis and IR spectroscopy techniques are used to probe reaction mechanisms. XRPD analysis gives evidence of the topotactic character of this exchange reaction. As for exchange in aqueous solution, it is shown that Li(0.30)La(0.57)TiO(3) is able to dissociate water on the grain surface and then to exchange H(+) for Li(+) into the perovskite structure. Lithium hydroxide is then formed on the grain surface and afterwards reacts with CO(2) contained in air to form Li(2)CO(3). It is shown that this mechanism is reversible. When the aged sample (aging in air for 5 months at room temperature) is annealed at 400 degrees C for two hours, the initial LLTO sample is totally recovered, a mass loss is observed and the carbonate signal in IR spectra disappears, demonstrating the reversibility of the carbonation reaction process. PMID:20372722

  7. Gram-level synthesis of core-shell structured catalysts for the oxygen reduction reaction in proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Luo, Mingchuan; Wei, Lingli; Wang, Fanghui; Han, Kefei; Zhu, Hong

    2014-12-01

    Over the past decade, Pt based core-shell structured alloys have been studied extensively as oxygen reduction reaction (ORR) catalysts for proton exchange membrane fuel cells (PEMFCs) because of their distinctive electrochemical performance and low Pt loading. In this paper, a facile route based on microwave-assisted polyol method and chemical dealloying process is proposed to synthesize carbon supported core-shell structured nanoparticles (NPs) in gram-level for ORR electrocatalysis in PEMFCs. The obtained samples are characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), inductively coupled plasma atomic emission spectroscopy (ICP-AES), and X-ray photoelectron spectroscopy (XPS). These physical characterization indicate that the final synthesized NPs are highly dispersed on the carbon support, and in a core-shell structure with CuPt alloy as the core and Pt as the shell. Electrochemical measurements, conducted by cyclic voltammetry (CV) and rotating disk electrode (RDE) tests, show the core-shell structured catalyst exhibit a 3× increase in mass activity and a 2× increase in specific activity over the commercial Pt/C catalyst, respectively. These results demonstrate that this route can be a reliable way to synthesize low-Pt catalyst in large-scale for PEMFCs.

  8. A review of the stability and durability of non-precious metal catalysts for the oxygen reduction reaction in proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Banham, Dustin; Ye, Siyu; Pei, Katie; Ozaki, Jun-ichi; Kishimoto, Takeaki; Imashiro, Yasuo

    2015-07-01

    A major hurdle to the widespread commercialization of proton exchange membrane fuel cells (PEMFCs) is the high loading of noble metal (Pt/Pt-alloy) catalyst at the cathode, which is necessary to facilitate the inherently sluggish oxygen reduction reaction (ORR). To eliminate the use of Pt/Pt-alloy catalysts at the cathode of PEMFCs and thus significantly reduce the cost, extensive research on non-precious metal catalysts (NPMCs) has been carried out over the past decade. Major advances in improving the ORR activity of NPMCs, particularly Fe- and Co-based NPMCs, have elevated these materials to a level at which they can start to be considered as potential alternatives to Pt/Pt-alloy catalysts. Unfortunately, the stability (performance loss following galvanostatic experiments) of these materials is currently unacceptably low and the durability (performance loss following voltage cycling) remains uncertain. The three primary mechanisms of instability are: (a) Leaching of the metal site, (b) Oxidative attack by H2O2, and (c) Protonation followed by possible anion adsorption of the active site. While (a) has largely been solved, further work is required to understand and prevent losses from (b) and/or (c). Thus, this review is focused on historical progress in (and possible future strategies for) improving the stability/durability of NPMCs.

  9. Kinetic isotope effect of the (16)O + (36)O2 and (18)O + (32)O2 isotope exchange reactions: Dominant role of reactive resonances revealed by an accurate time-dependent quantum wavepacket study.

    PubMed

    Sun, Zhigang; Yu, Dequan; Xie, Wenbo; Hou, Jiayi; Dawes, Richard; Guo, Hua

    2015-05-01

    The O + O2 isotope exchange reactions play an important role in determining the oxygen isotopic composition of a number of trace gases in the atmosphere, and their temperature dependence and kinetic isotope effects (KIEs) provide important constraints on our understanding of the origin and mechanism of these and other unusual oxygen KIEs important in the atmosphere. This work reports a quantum dynamics study of the title reactions on the newly constructed Dawes-Lolur-Li-Jiang-Guo (DLLJG) potential energy surface (PES). The thermal reaction rate coefficients of both the (18)O + (32)O2 and (16)O + (36)O2 reactions obtained using the DLLJG PES exhibit a clear negative temperature dependence, in sharp contrast with the positive temperature dependence obtained using the earlier modified Siebert-Schinke-Bittererova (mSSB) PES. In addition, the calculated KIE shows an improved agreement with the experiment. These results strongly support the absence of the "reef" structure in the entrance/exit channels of the DLLJG PES, which is present in the mSSB PES. The quantum dynamics results on both PESs attribute the marked KIE to strong near-threshold reactive resonances, presumably stemming from the mass differences and/or zero point energy difference between the diatomic reactant and product. The accurate characterization of the reactivity for these near-thermoneutral reactions immediately above the reaction threshold is important for correct characterization of the thermal reaction rate coefficients. PMID:25956105

  10. Kinetic isotope effect of the 16O + 36O2 and 18O + 32O2 isotope exchange reactions: Dominant role of reactive resonances revealed by an accurate time-dependent quantum wavepacket study

    NASA Astrophysics Data System (ADS)

    Sun, Zhigang; Yu, Dequan; Xie, Wenbo; Hou, Jiayi; Dawes, Richard; Guo, Hua

    2015-05-01

    The O + O2 isotope exchange reactions play an important role in determining the oxygen isotopic composition of a number of trace gases in the atmosphere, and their temperature dependence and kinetic isotope effects (KIEs) provide important constraints on our understanding of the origin and mechanism of these and other unusual oxygen KIEs important in the atmosphere. This work reports a quantum dynamics study of the title reactions on the newly constructed Dawes-Lolur-Li-Jiang-Guo (DLLJG) potential energy surface (PES). The thermal reaction rate coefficients of both the 18O + 32O2 and 16O + 36O2 reactions obtained using the DLLJG PES exhibit a clear negative temperature dependence, in sharp contrast with the positive temperature dependence obtained using the earlier modified Siebert-Schinke-Bittererova (mSSB) PES. In addition, the calculated KIE shows an improved agreement with the experiment. These results strongly support the absence of the "reef" structure in the entrance/exit channels of the DLLJG PES, which is present in the mSSB PES. The quantum dynamics results on both PESs attribute the marked KIE to strong near-threshold reactive resonances, presumably stemming from the mass differences and/or zero point energy difference between the diatomic reactant and product. The accurate characterization of the reactivity for these near-thermoneutral reactions immediately above the reaction threshold is important for correct characterization of the thermal reaction rate coefficients.

  11. Full paper / Mmoire Self-assembly of hybrid solids consisting of 2D supramolecular

    E-print Network

    Paik Suh, Myunghyun

    (cyclam)][Ni(cyclam)(H2O)2]·8 H2O (1) and [NaCr(ox)3][Cu(tren)(H2O)]·3 H2O (2) are assembled in MeCN/H2O from the reaction(cyclam)][Ni(cyclam)(H2O)2]·8 H2O (1) et [NaCr(ox)3][Cu(tren)(H2O)]·3 H2O (2) sont assemblés dans une mixture de MeCN/H2O­9] (MII = Mn, Fe, Co, Ni, Cu and Zn; ox = oxalate) or [MI MIII (ox)3]n 2n­ [10­12] (MI = Li, Na, K; MIII

  12. Nuclear Reaction Data Centers

    SciTech Connect

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

    1988-01-01

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

  13. Inorganic ion exchangers for the removal of scandium and rare earth elements in neutron activation analysis of geological samples. [Neutron reactions

    Microsoft Academic Search

    K. Akilimali; B. Lumu; W. Mwamba

    1979-01-01

    Sorption properties of inorganic ion exchangers have been investigated for use in radiochemical separation of elements in geological samples subjected to neutron activation analysis. Samples were allowed to decay for two weeks, dissolved in hydrofluoric acid, and saturated boric acid was added to dissolve any fluoride complexes. Samples were placed onto the COX column and eluted with nitric acid. Retained

  14. Differential cross section of the charge-exchange reaction pi- p--> pi0 n in the momentum range from 148 to 323 MeV\\/c

    Microsoft Academic Search

    M. E. Sadler; A. Kulbardis; V. Abaev; C. Allgower; A. Barker; V. Bekrenev; C. Bircher; W. J. Briscoe; R. Cadman; C. Carter; M. Clajus; J. R. Comfort; K. Craig; M. Daugherity; B. Draper; D. Grosnic; S. Hayden; J. Huddleston; D. Isenhower; M. Jerkins; M. Joy; N. Knecht; D. D. Koetke; N. Kozlenko; S. Kruglov; T. Kycia; G. Lolos; I. Lopatin; D. M. Manley; R. Manweiler; A. Marusic; S. McDonald; B. M. Nefkens; J. Olmsted; Z. Papandreou; D. Peaslee; J. Peterson; N. Phaisangittisakul; S. N. Prakhov; J. W. Price; A. Ramirez; C. Robinson; A. Shafi; H. Spinka; S. Stanislaus; A. Starostin; H. M. Staudenmaier; I. Strakovsky; I. Supek; W. B. Tippens; S. Watson

    2004-01-01

    Measured values of the differential cross section for pion-nucleon charge exchange, pi- p--> pi0 n , are presented at pi- momenta of 148, 174, 188, 212, 238, 271, 298, and 323 MeV\\/c , a region dominated by the Delta ( 1232 ) resonance. Complete angular distributions were obtained using the Crystal Ball detector at the Alternating Gradient Synchrotron (AGS) at

  15. Dimension reduction for extracting geometrical structure of multidimensional phase space: Application to fast energy exchange in the reaction O({sup 1}D)+N{sub 2}O{yields}NO+NO

    SciTech Connect

    Kawai, Shinnosuke; Fujimura, Yo; Kajimoto, Okitsugu; Yamashita, Takefumi; Li, Chun-Biu; Komatsuzaki, Tamiki; Toda, Mikito [Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa-Oiwakecho, Sakyo-ku, Kyoto 606-8502 (Japan); Department of Basic Science, Graduate School of Arts and Sciences, University of Tokyo, Komaba, Tokyo 153-8902 (Japan); Nonlinear Science Laboratory, Department of Earth and Planetary Sciences, Faculty of Science, Kobe University, Nada, Kobe 657-8501 (Japan); Nonlinear Science Laboratory, Department of Earth and Planetary Sciences, Faculty of Science, Kobe University, Nada, Kobe 657-8501, Japan and Department of Theoretical Studies, Institute for Molecular Science, Myodaiji, Okazaki 444-8585 (Japan); Department of Physics, Faculty of Science, Nara Women's University, Nara 630-8506 (Japan)

    2007-02-15

    One of the most fundamental problems in studying general Hamiltonian systems with many degrees of freedom is to extract a low-dimensional subsystem including the essential dynamics. In this paper, a new partial normal form (PNF) method is developed to reduce the number of coupling terms in the Hamiltonian and to simplify the dynamics analyses. The PNF method allows one to decouple many unimportant bath modes as well as the reactive mode from the system by assessing the significance of the coupling terms. The method is applied to the chemical reaction O({sup 1}D)+N{sub 2}O{yields}NO+NO, which was found to exhibit efficient energy exchange between the two NO stretching modes despite the short lifetime of the reaction intermediate [S. Kawai et al., J. Chem. Phys. 124, 184315 (2006)]. Through the analysis of the two-dimensional PNF Hamiltonian subsystem, it is found that the motion of the subsystem preserves the 'normal mode picture' of the symmetric and antisymmetric NO stretching modes despite its high energy. Then the vibrational energy, initially localized in the newly formed NO bond, is transferred to the reactants' NO bond through the beating between the symmetric and antisymmetric stretching modes. The preservation of the normal mode picture and the short period of the beating explain the fast energy exchange between the two NO bonds. This successful application proves that the PNF method can extract the essential small subspace from many-degrees-of-freedom Hamiltonian systems.

  16. Oxidation of CO by N/sub 2/O between 1076 and 1228 K: determination of the rate constant of the exchange reaction

    SciTech Connect

    Loirat, H.; Caralp, F.; Destriau, M.; Lesclaux, R.

    1987-12-17

    New measurements of the rate constant of the direct reaction of CO with N/sub 2/O are reported with the principal purpose of removing some of the remaining discrepancies on its value. Experiments were performed at lower temperatures (1076-1228 K) and lower pressure (approx. 15 Torr) than those prevailing in most of previous works, by using a static reactor. It is shown that, under these experimental conditions, the reaction proceeds essentially according to the direct reaction CO + N/sub 2/O ..-->.. CO/sub 2/ + N/sub 2/ (1). The previously proposed wet mechanism is not significant under our experimental conditions. It has to be taken into account, however, to describe the observed production and consumption of molecular oxygen. The Arrhenius expression derived from these experiments is k/sub 1/ = 10/sup 14.4 +/- 0.3 exp(-(46 +- 2) kcal mol/sup -1/RT) cm/sup 3/ mol/sup -1/ s/sup -1/. A detailed analysis of the results shows that the uncertainties in side reactions do not greatly influence the value of k/sub 1/. A critical discussion of the data reported in the literature is presented. In spite of remaining uncertainties in the reaction mechanism, the present results, obtained in a low-temperature range, show that the low activation energy values of reaction 1, reported in several works performed at higher temperatures, are highly unlikely

  17. An Easy Student Synthesis of a Substituted 1,3-Dioxane by Use of an Ion-Exchange Resin as Catalyst: Clean Illustration of the Prins Reaction.

    ERIC Educational Resources Information Center

    Delmas, Michael; And Others

    1982-01-01

    Background information and experimental procedures are provided for a Prins reaction (condensation of an aldehyde with an alkene). The preparation of 4-(4-hydroxy, 3-methoxy-phenyl) 5-methyl, 1,3-dioxane realized from isoeugenol (natural plant product, commercially available) can be completed in a three-hour laboratory period. (Author/JN)

  18. Proton and light ion induced charge exchange reactions in nuclei This article has been downloaded from IOPscience. Please scroll down to see the full text article.

    E-print Network

    Fernández de Córdoba, Pedro

    of strength from the proton to the deu- teron targets and an even more remarkable shift of the strength) reaction on the neutron target is different to the one with the proton target and has its strength shifted)Delta excitation in the target; (b) Delta excitation in the project- ile necessarily has some strength below

  19. Differential cross section of the pion-nucleon charge-exchange reaction in the momentum range from 148 to 323 MeV/c

    E-print Network

    Sadler, M E; Abaev, V V; Allgower, C; Barker, A; Bekrenev, V; Bircher, C; Briscoe, W J; Cadman, R; Carter, C; Clajus, M; Comfort, J R; Craig, K; Daugherity, M; Draper, B; Grosnick, D P; Hayden, S; Huddleston, J; Isenhower, D; Jerkins, M; Joy, M; Knecht, N; Koetke, D D; Kozlenko, N; Kruglov, S; Kycia, T; Lolos, G J; Lopatin, I; Manley, D M; Manweiler, R; Marusic, A; McDonald, S; Nefkens, B M K; Olmsted, J; Papandreou, Z; Peaslee, D; Peterson, J; Phaisangittisakul, N; Prakhov, S N; Price, J W; Ramírez, A; Robinson, C; Shafi, A; Spinka, H; Stanislaus, S; Starostin, A; Staudenmaier, H M; Strakovsky, I I; Supek, I; Tippens, W B; Watson, S

    2004-01-01

    Measured values of the differential cross section for pion-nucleon charge exchange are presented at momenta 148, 174, 188, 212, 238, 271, 298, and 323 MeV/c, a region dominated by the Delta resonance. Complete angular distributions were obtained using the Crystal Ball detector at the Alternating Gradient Synchrotron (AGS) at Brookhaven National Laboratory (BNL). Statistical uncertainties of the differential cross sections are typically 2-6%, exceptions being the results at the lowest momentum and at the most forward measurements of the five lowest momenta. We estimate the systematic uncertainties to be 3-6%.

  20. ION EXCHANGE

    EPA Science Inventory

    The IONEX program's name is a contraction of "ion exchange." The IONEX program performs calculations related to removing radium and/or uranium from water with the ion exchange process. IONEX provides a quick method of calculating whether a proposed ion exchange process will m...

  1. Non-precious Co3O4 nano-rod electrocatalyst for oxygen reduction reaction in anion-exchange membrane fuel cells

    E-print Network

    Zhao, Tianshou

    Non-precious Co3O4 nano-rod electrocatalyst for oxygen reduction reaction in anion 2011 DOI: 10.1039/c1ee01431e We report preparation of carbon-supported Co3O4 electrocatalysts with nano that the non-precious Co3O4 electrocatalyst with the nano-rod structure ($12 nm in length and $5.1 nm

  2. C-H bond activation during and after the reactions of a metallacyclic amide with silanes: formation of a ?-alkylidene hydride complex, its H-D exchange, and ?-H abstraction by a hydride ligand.

    PubMed

    Wang, Li; Hunter, Seth C; Song, Zhimin; Steren, Carlos A; Chen, Tianniu; Wei, Zhenhong; Cai, Hu; Xue, Zi-Ling

    2014-05-12

    Metallacyclic complex [(Me2N)3Ta(?(2)-CH2SiMe2NSiMe3)] (3) undergoes C-H activation in its reaction with H3SiPh to afford a Ta/?-alkylidene/hydride complex, [(Me2N)2{(Me3Si)2N}Ta(?-H)2(?-C-?(2)-CHSiMe2NSiMe3)Ta(NMe2)2] (4). Deuterium-labeling studies with [D3]SiPh show H-D exchange between the Ta-D-Ta unit and all methyl groups in [(Me2N)2{(Me3Si)2N}Ta(?-D)2(?-C-?(2)-CHSiMe2NSiMe3)Ta(NMe2)2] ([D2]-4) to give the partially deuterated complex [Dn]-4. In addition, 4 undergoes ?-H abstraction between a hydride and an NMe2 ligand and forms a new complex [(Me2N){(Me3 Si)2N}Ta(?-H)(?-N-?(2)-C,N-CH2NMe)(?-C-?(2)-C,N-CHSiMe2NSiMe3)Ta(NMe2)2] (5) with a cyclometalated, ?(2)-imine ligand. These results indicate that there are two simultaneous processes in [Dn]-4:1)?H-D exchange through ?-bond metathesis, and 2)?H-D elimination through ?-H abstraction (to give [Dn]-5). Both 4 and 5 have been characterized by single-crystal X-ray diffraction studies. PMID:24682935

  3. ESR-spectroscopy in ionic liquids: Dynamic linebroadening effects caused by electron-self exchange reactions within the methylviologene redox couple

    NASA Astrophysics Data System (ADS)

    Grampp, Günter; Kattnig, Daniel; Mladenova, Boryana

    2006-03-01

    Well-resolved ESR-spectra of the methylviologene radical cation ( MV) are recorded in room-temperature liquid ions as solvents. The temperature dependences of the ESR-coupling constants are similar to those measured in classical organic solvents. Electron-self exchange rates are reported for the methylviologene redox couple ( MV/MV) in 1-butyl-3-methylimidazolium hexafluorophosphate (bmim +PF 6-), 1-butlyl-3-methylimidazolium fluoroborate (bmim +BF 4-) and 1-ethyl-3-imidazolium ethylsulfate (emim +O 3SOEt -) within a temperature range of 350 K ? T ? 460 K. The diffusion controlled rate constants observed vary between 8.2 × 10 7 M -1 s -1 and 1.2 × 10 9 M -1 s -1. From temperature-dependent measurements the activation energies obtained range from 27.4 kJ/mol in emim +O 3SOEt - to 42.1 kJ/mol in bmim +PF 6-, respectively.

  4. ESR-spectroscopy in ionic liquids: Dynamic linebroadening effects caused by electron-self exchange reactions within the methylviologene redox couple.

    PubMed

    Grampp, Günter; Kattnig, Daniel; Mladenova, Boryana

    2006-03-13

    Well-resolved ESR-spectra of the methylviologene radical cation (MV*+) are recorded in room-temperature liquid ions as solvents. The temperature dependences of the ESR-coupling constants are similar to those measured in classical organic solvents. Electron-self exchange rates are reported for the methylviologene redox couple (MV++/MV*+) in 1-butyl-3-methylimidazolium hexafluorophosphate (bmim+ PF6-), 1-butlyl-3-methylimidazolium fluoroborate (bmim+ BF4-) and 1-ethyl-3-imidazolium ethylsulfate (emim+ O3SOEt-) within a temperature range of 350 K < or = T < or = 460 K. The diffusion controlled rate constants observed vary between 8.2 x 10(7) M(-1) s(-1) and 1.2 x 10(9) M(-1) s(-1). From temperature-dependent measurements the activation energies obtained range from 27.4 kJ/mol in emim+ O3SOEt- to 42.1 kJ/mol in bmim+ PF6-, respectively. PMID:16500142

  5. Ligand exchange reactions starting from [Re(CO) 3Br 3] 2?. Synthesis, characterization and structures of rhenium(I) tricarbonyl complexes with thiourea and thiourea derivatives

    Microsoft Academic Search

    Ulrich Abram; Sonja Abram; Roger Alberto; Roger Schibli

    1996-01-01

    The anionic rhenium(I) complex fac-[Re(CO)3Br3]2? has been reacted with thiourea (tu), N,N-dialkylbenzoylthioureas (HR2btu) and N,N-dialkylthiocarbamoylbenzamidines (HR12tcbR2) to give novel mono- and binuclear rhenium(I) complexes. All new compounds are air-stable and non-sensitive against aqueous media. Fac-[Re(CO)3(tu)3] (NO3) is formed from the bromo complex by precipitation of AgBr after addition of AgNO3 and subsequent reaction with thiourea. The compound co-crystallizes with one

  6. The Third Dimension of a More O’Ferrall-Jencks Diagram for Hydrogen Atom Transfer in the Isoelectronic Hydrogen Exchange Reactions of (PhX)2H• with X = O, NH, and CH2

    PubMed Central

    Cembran, Alessandro; Provorse, Makenzie R.; Wang, Changwei

    2012-01-01

    A critical element in theoretical characterization of the mechanism of proton-coupled electron transfer (PCET) reactions, including hydrogen atom transfer (HAT), is the formulation of the electron and proton localized diabatic states, based on which a More O’Ferrall-Jencks diagram can be represented to determine the step-wise and concerted nature of the reaction. Although the More O’Ferrall-Jencks diabatic states have often been used empirically to develop theoretical models for PCET reactions, the potential energy surfaces for these states have never been determined directly based on first principles calculations using electronic structure theory. The difficulty is due to a lack of practical method to constrain electron and proton localized diabatic states in wave function or density functional theory calculations. Employing a multistate density functional theory (MSDFT), in which the electron and proton localized diabatic configurations are constructed through block-localization of Kohn-Sham orbitals, we show that distinction between concerted proton-electron transfer (CPET) and HAT, which are not distinguishable experimentally from phenomenological kinetic data, can be made by examining the third dimension of a More O’Ferrall-Jencks diagram that includes both the ground and excited state potential surfaces. In addition, we formulate a pair of effective two-state valence bond models to represent the CPET and HAT mechanisms. We found that the lower energy of the CPET and HAT effective diabatic states at the intersection point can be used as an energetic criterion to distinguish the two mechanisms. In the isoelectronic series of hydrogen exchange reaction in (PhX)2H•, where X = O, NH, and CH2, there is a continuous transition from a CPET mechanism for the phenoxy radical-phenol pair to a HAT process for benzyl radical and toluene, while the reaction between PhNH2 and PhNH• has a mechanism intermediate of CPET and HAT. The electronically nonadiabatic nature of the CPET mechanism in the phenol system can be attributed to the overlap interactions between the ground and excited state surfaces, resulting in roughly orthogonal minimum energy paths on the adiabatic ground and excited state potential energy surfaces. On the other hand, the minimum energy path on the adiabatic ground state for the HAT mechanism coincides with that on the excited state, producing a large electronic coupling that separates the two surfaces by more than 120 kcal/mol. PMID:23226989

  7. The Third Dimension of a More O'Ferrall-Jencks Diagram for Hydrogen Atom Transfer in the Isoelectronic Hydrogen Exchange Reactions of (PhX)(2)H(•) with X = O, NH, and CH(2).

    PubMed

    Cembran, Alessandro; Provorse, Makenzie R; Wang, Changwei; Wu, Wei; Gao, Jiali

    2012-11-13

    A critical element in theoretical characterization of the mechanism of proton-coupled electron transfer (PCET) reactions, including hydrogen atom transfer (HAT), is the formulation of the electron and proton localized diabatic states, based on which a More O'Ferrall-Jencks diagram can be represented to determine the step-wise and concerted nature of the reaction. Although the More O'Ferrall-Jencks diabatic states have often been used empirically to develop theoretical models for PCET reactions, the potential energy surfaces for these states have never been determined directly based on first principles calculations using electronic structure theory. The difficulty is due to a lack of practical method to constrain electron and proton localized diabatic states in wave function or density functional theory calculations. Employing a multistate density functional theory (MSDFT), in which the electron and proton localized diabatic configurations are constructed through block-localization of Kohn-Sham orbitals, we show that distinction between concerted proton-electron transfer (CPET) and HAT, which are not distinguishable experimentally from phenomenological kinetic data, can be made by examining the third dimension of a More O'Ferrall-Jencks diagram that includes both the ground and excited state potential surfaces. In addition, we formulate a pair of effective two-state valence bond models to represent the CPET and HAT mechanisms. We found that the lower energy of the CPET and HAT effective diabatic states at the intersection point can be used as an energetic criterion to distinguish the two mechanisms. In the isoelectronic series of hydrogen exchange reaction in (PhX)(2)H(•), where X = O, NH, and CH(2), there is a continuous transition from a CPET mechanism for the phenoxy radical-phenol pair to a HAT process for benzyl radical and toluene, while the reaction between PhNH(2) and PhNH(•) has a mechanism intermediate of CPET and HAT. The electronically nonadiabatic nature of the CPET mechanism in the phenol system can be attributed to the overlap interactions between the ground and excited state surfaces, resulting in roughly orthogonal minimum energy paths on the adiabatic ground and excited state potential energy surfaces. On the other hand, the minimum energy path on the adiabatic ground state for the HAT mechanism coincides with that on the excited state, producing a large electronic coupling that separates the two surfaces by more than 120 kcal/mol. PMID:23226989

  8. High performance fluorine doped (Sn,Ru)O2 oxygen evolution reaction electro-catalysts for proton exchange membrane based water electrolysis

    NASA Astrophysics Data System (ADS)

    Kadakia, Karan; Datta, Moni Kanchan; Velikokhatnyi, Oleg I.; Jampani, Prashanth; Park, Sung Kyoo; Chung, Sung Jae; Kumta, Prashant N.

    2014-01-01

    Identification of electro-catalysts containing non-noble metal or significantly reduced amounts of expensive noble metals (e.g. RuO2) is highly desirable. Development of such a catalyst with comparable electrochemical performance to the standard noble metal oxide for proton exchange membrane (PEM) based water electrolysis would constitute a pioneering breakthrough in hydrogen generation by water electrolysis. In line with these goals, by exploiting a two-pronged theoretical first principles and experimental approach herein we demonstrate that a nano-structured solid solution of SnO2:10 wt% F containing only 20 at.% RuO2 [e.g. (Sn0.80Ru0.20)O2:10F] displays a remarkably similar electrochemical activity and moreover, comparable or even much improved electrochemical stability and durability compared to pure the noble metal counterpart, RuO2. Density functional theory calculations have demonstrated direct dependence of the catalytic activity on the electronic structure peculiarities of the F-doped (Ru,Sn)O2 which corresponds well with the experimental results.

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

    NASA Technical Reports Server (NTRS)

    Liechty, Derek S.; Lewis, Mark J.

    2010-01-01

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

  10. Sodium-Copper Exchange on Wyoming Montmorillonite in Chloride, Perchlorate, Nitrate, and Sulfate Solutions

    E-print Network

    Sparks, Donald L.

    Sodium-Copper Exchange on Wyoming Montmorillonite in Chloride, Perchlorate, Nitrate, and Sulfate. The copper exchange capacity (CuEC) and Na-Cu exchange reactions on Wyoming montmo- rillonite were studied

  11. COMMUNICATIONS On Neglecting Chemical Exchange Effects When Correcting

    E-print Network

    Ouwerkerk, Ronald

    , such as the creatine- kinase reaction involving phosphocreatine (PCr) and -ATP in human skeletal and cardiac muscle exchange; saturation factors; longitudinal relaxation; dual angle method; progressive saturation; creatine

  12. Metal implants and surface reactions

    Microsoft Academic Search

    S. G. Steinemann

    1996-01-01

    A metal in living tissue is prone to corrosion. The interaction of the foreign body with the tissue involves the redox reaction (an electron exchange) at the interface, the hydrolysis (a proton exchange) of oxidehydrates as products of corrosion, and the formation of metal-organic complexes in the electrolyte. Denatured tissue in contact with the foreign body is the consequence. But

  13. exchange membranes

    Microsoft Academic Search

    W. Michaels; J. Vermeulen; R. D. Sanderson; D. G. Bessarabov

    The chemical modification of the surface of ion-exchange membranes (SPE, solid polymer electrolytes) provides new possibilities for applications of SPE-based membrane catalytic systems (1). Surface modification can considerably influence the surface properties of the membrane. In the case of catalyst deposition on the modified membrane, the profile of the catalyst particles within the membrane and their size can be alternated

  14. Mass Exchange Processes with Input

    E-print Network

    P. L. Krapivsky

    2015-03-07

    We investigate a system of interacting clusters evolving through mass exchange and supplemented by input of small clusters. Three possibilities depending on the rate of exchange generically occur when input is homogeneous: continuous growth, gelation, and instantaneous gelation. We mostly study the growth regime using scaling methods. An exchange process with reaction rates equal to the product of reactant masses admits an exact solution which allows us to justify the validity of scaling approaches in this special case. We also investigate exchange processes with a localized input. We show that if the diffusion coefficients are mass-independent, the cluster mass distribution becomes stationary and develops an algebraic tail far away from the source.

  15. Weathering Reactions and Soil-Groundwater Reactions

    NSDL National Science Digital Library

    David M. Sherman

    This 11-page PDF document is part of an environmental geochemistry course taught by Dr. David Sherman at the University of Bristol. The lecture explores the weathering reactions that convert primary minerals into quartz or phyllosilicate clays and iron oxide hydroxides, and the mineral-water reactions that buffer pH and the dissolved ion concentration of groundwater. Also discussed is the manner in which phyllosilicate clays, iron oxides and hydroxides sorb pollutants via ion exchange and adsorption. Helpful diagrams and illustrations accompany the text.

  16. Attitude control of spacecraft using internal momentum exchange devices

    Microsoft Academic Search

    Shriram Krishnan

    1997-01-01

    This dissertation addresses some of the important problems related to spacecraft attitude control using internal momentum exchange devices such as Control Moment Gyros (CMGs), reaction wheels and robot manipulators. The use of momentum exchange devices for attitude control is an attractive alternative to reaction type devices such as thrusters due to the fact that they do not require any expendable

  17. Job Exchange

    NSDL National Science Digital Library

    1998-01-01

    Job Exchange, provided by BioMedNet (discussed in the February 14, 1997 Scout Report) is a searchable database of jobs in molecular biology, genetics, general biology, and the biomedical sciences. Employment opportunities are updated frequently and may be searched or browsed by position type (Academic/Research Institution, Government/Private Research, Hospital/Medical Institution, Industry/Other), international region, or specialty. Typical returns include full job details, including summary of duties, salary range, duration of position, and contact information.

  18. Heat exchanger

    DOEpatents

    Brackenbury, P.J.

    1983-12-08

    A heat exchanger comparising a shell attached at its open end to one side of a tube sheet and a detachable head connected to the other side of said tube sheet. The head is divided into a first and second chamber in fluid communication with a nozzle inlet and nozzle outlet, respectively, formed in said tube sheet. A tube bundle is mounted within said shell and is provided with inlets and outlets formed in said tube sheet in communication with said first and second chambers, respectively.

  19. Agriculture on Exchange InternationalExchangeProgram

    E-print Network

    Viglas, Anastasios

    Agriculture on Exchange InternationalExchangeProgram Students enrolled in courses offered through the Faculty of Agriculture and Environment are welcome to apply for exchange. However, to ensure that you Academic Adviser before submitting an exchange application. Undergraduate Agriculture students normally go

  20. Reactor for exothermic reactions

    DOEpatents

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

    1993-03-02

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

  1. Reactor for exothermic reactions

    DOEpatents

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

    1993-01-01

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

  2. Textile Exchange

    NSDL National Science Digital Library

    From crochet machines to the uses of acrylic yarn, the Textile Exchange website has rather fine comprehensive coverage across the nooks and crannies of the textile industry. Visitors to the homepage will find a search engine and a very thorough products directory which includes topical headings like "Textile Products", "Fibers, Yarns & Threads", and "Textile Chemicals". After looking over a few of these areas, visitors will definitely want to peruse the "Knowledge Center". Here they can learn more about fiber and textile history, and the types of weaves. One section that should not be missed is the "Textile Personalities" area. For those individuals who've been pining to learn about giants of the textile industry such as John Mercer, John Kay (who patented the flying shuttle), and Richard Roberts, this area will be quite the eye-opener.

  3. Exchange hub.

    PubMed

    2015-07-01

    The Expert in the Room is a series of web seminars hosted by the Edge, NHS Improving Quality's virtual information exchange hub. The free online sessions will feature leaders in health and social care with up-to-date knowledge and practice in the field of transformational change, and viewers will have an opportunity to interact with them live. The monthly, 90-minute sessions take place at 9.30am on Fridays and the next seminars are on the following dates: September 4, October 2, November 4, and January 22 next year. Joining instructions for each session are posted on the related links, which you can find at theedge.nhsiq.nhs.uk/expert. PMID:26135190

  4. Educator Exchange Resource Guide.

    ERIC Educational Resources Information Center

    Garza, Cris; Rodriguez, Victor

    This resource guide was developed for teachers and administrators interested in participating in intercultural and international exchange programs or starting an exchange program. An analysis of an exchange program's critical elements discusses exchange activities; orientation sessions; duration of exchange; criteria for participation; travel,…

  5. Separation of Gallium and Indium Isotopes by Cation and Anion Exchange Chromatography

    Microsoft Academic Search

    I. Herdzik; W. Dembi?ski; J. Narbutt; S. Siekierski

    2012-01-01

    Ion exchange chromatography was applied to study chemical isotope effects of gallium and indium in ligand exchange reactions. Strongly acidic cation and strongly basic anion exchange resin were used as a solid phase, and aqueous HCl as a liquid phase. On the cation exchanger, the light isotope Ga was enriched at the front part of the elution band and the

  6. Psychology on Exchange InternationalExchangeProgram

    E-print Network

    Viglas, Anastasios

    Psychology on Exchange InternationalExchangeProgram Psychology majors are welcome to apply Honours, you need to take into account the advice from the Department of Psychology (http://sydney.edu.au/ current_students/student_exchange/forms_downloads.shtml). Timing To meet Australian Psychology

  7. Crystal structure of the external aldimine of Citrobacter freundii methionine ?-lyase with glycine provides insight in mechanisms of two stages of physiological reaction and isotope exchange of ?- and ?-protons of competitive inhibitors.

    PubMed

    Revtovich, Svetlana V; Faleev, Nicolai G; Morozova, Elena A; Anufrieva, Natalya V; Nikulin, Alexey D; Demidkina, Tatyana V

    2014-06-01

    The three-dimensional structure of the external aldimine of Citrobacter freundii methionine ?-lyase with competitive inhibitor glycine has been determined at 2.45 ? resolution. It revealed subtle conformational changes providing effective binding of the inhibitor and facilitating labilization of C?-protons of the external aldimine. The structure shows that 1, 3-prototropic shift of C?-proton to C4'-atom of the cofactor may proceed with participation of active site Lys210 residue whose location is favorable for performing this transformation by a concerted mechanism. The observed stereoselectivity of isotopic exchange of enantiotopic C?-protons of glycine may be explained on the basis of external aldimine structure. The exchange of C?-pro-(R)-proton of the external aldimine might proceed in the course of the concerted transfer of the proton from C?-atom of glycine to C4'-atom of the cofactor. The exchange of C?-pro-(S)-proton may be performed with participation of Tyr113 residue which should be present in its basic form. The isotopic exchange of ?-protons, which is observed for amino acids bearing longer side groups, may be effected by two catalytic groups: Lys210 in its basic form, and Tyr113 acting as a general acid. PMID:24463191

  8. Reactions on ZSM-5-type zeolite catalysts

    Microsoft Academic Search

    J. R. Anderson; K. Foger; T. Mole; R. A. Rajadhyaksha; J. V. Sanders

    1979-01-01

    Catalytic reactions and sorption measurements have been carried out with ZSM-5 and silicalite catalysts which are distinguished by variation in skeletal heteroatom concentration. The catalysts were used in both the hydrogen-exchanged and sodium-exchanged forms. Sorption measurements were made with the hydrocarbons n-hexane, 3-methylpentane, and 2,2-dimethyl-butane, and with the bases ammonia, n-butylamine, t-butylamine, and 4-methylquinoline. Catalytic reactions were carried out on

  9. Formaldehyde reactions in dark clouds

    NASA Technical Reports Server (NTRS)

    Sen, A. D.; Anicich, V. G.; Federman, S. R.

    1992-01-01

    The low-pressure reactions of formaldehyde (H2CO) with D(+), D2(+), D3(+), and He(+) are studied by the ion-cyclotron resonance technique. These reactions are potential loss processes for formaldehyde in cores of dark interstellar clouds. The deuterated reactants represent direct analogs for protons. Rate coefficients and branching ratios of product channels have been measured. Charge transfer is observed to be the dominant reaction of H2CO with D(+), D2(+), and He(+) ions. Only the D3(+) reaction exhibits a proton-transfer channel. All reactions proceed at rate coefficients near the collision limit. Proton-deuteron exchange reactions are found to be inefficient processes in the formaldehyde system.

  10. Chemical Reactions

    NSDL National Science Digital Library

    National Science Teachers Association (NSTA)

    2009-05-01

    We don't often stop to think about it, but underlying many of our everyday activities are chemical reactions. From the cooking of an egg to the growth of a child, chemical reactions make things happen. Although many of the reactions that support our lives

  11. Synthetic and mechanistic aspects of the reactions between bromodifluoromethyltriphenylphosphonium bromide and dibromofluoromethyltriphenylphosphonium bromide and trialkylphosphites

    Microsoft Academic Search

    Richard M. Flynn; Donald J. Burton; Denise M. Wiemers

    2008-01-01

    Bromofluoromethyltriphenylphosphonium bromides react with trialkylphosphites in two distinct ways. Bromodifluoromethyltriphenylphosphonium bromide undergoes a rapid exchange reaction with trialkylphosphites to give the corresponding bromodifluoromethylphosphonates in good to excellent yields. A similar exchange reaction also occurred with an analogous diethoxyphenylphosphonite to give the corresponding ethoxyphenylphosphinate. Mechanistically, the exchange process involves the formation of difluorocarbene via dissociation of the intermediate difluoromethylene ylide, capture

  12. Precision of diffusion coefficients by the isotope exchange technique

    Microsoft Academic Search

    Masao Nanba; Y. Oishi; Ken Ando

    1981-01-01

    The precision of diffusion coefficients determined by the gas–solid isotope exchange technique was analyzed for planar sheet diffusion, rate controlled by the isotope exhange reaction. An objective function was employed to estimate the degree of fit of a theoretical calculation to the experimental diffusion profile as a function of the sample size (l), the diffusion coefficient (D), the surface exchange

  13. Dividend Signalling Equilibria: Quantitative Evidence from the Brussels Stock Exchange

    Microsoft Academic Search

    Francisca M. Beer

    1993-01-01

    The objective of this research is to document the market reaction to dividend changes on the Brussels Stock Exchange and to relate it to information releases by the firms. The results show important differences between Belgian investors' behavior and U.S. investors' behavior. On the Brussels Stock Exchange, when companies use dividends as the usual way to remunerate stockholders, the market

  14. Kinetic theory of oxygen isotopic exchange between minerals and water

    Microsoft Academic Search

    R. E. Criss; R. T. Gregory; H TAYLORJR

    1987-01-01

    Kinetic and mass conservation equations are used to describe oxygen isotopic exchange between minerals and water in ''closed'' and open hydrothermal systems. In cases where n coexisting mineral phases having different reaction rates are present, the exchange process is described by a system of n + 1 simultaneous differential equations consisting of n pseudo first-order rate equations and a conservation

  15. Parisian exchange options

    Microsoft Academic Search

    An Chen; Michael Suchanecki

    2010-01-01

    The option to exchange one asset for another is one of the oldest and one of the most popular exotic options. In the present article, we extend the existing literature on options to Parisian exchange options, i.e. the option to exchange one asset for the other contingent on the occurrence of the Parisian time. Thus, these options are a special

  16. EXCHANGE VISITOR PROGRAM GUIDE

    E-print Network

    Bieber, Michael

    process should be ad- dressed to the Department of Re- search and Development If visitor qualifies for J-1 For complete and comprehensive J-1 guidance please refer to: http://www.state.gov/ J-1 Exchange Visitor Prospective 2 J-1 Exchange Visitor Categories 2 Flow chart 3 SECTION 1. The NJIT Exchange Visitor J-1 Program

  17. AN OLD QUALITY LESSON FROM FAILURE OF A NEW HEAT EXCHANGER

    Microsoft Academic Search

    Scott J. Whitlow

    A Gulf Coast manufacturing unit has three heat exchangers in its reaction overhead off-gas system. All the heat exchangers are once-through condensers with carbon steel shells, zirconium tubes and double tube sheets. There are four reaction trains in the manufacturing unit for a total of 12 condensers. All have many years of satisfactory service except the newest condenser which failed

  18. Numerical Investigation of Ultra-Rich Combustion in Counter Flow Heat Exchangers

    Microsoft Academic Search

    Ingmar M. Schoegl; Janet L. Ellzey

    2010-01-01

    Recirculation of heat has been used for decades to react mixtures beyond the conventional flammability limits. One means of obtaining this recirculation is through counter-flow heat exchange. In contrast to filtration combustion in which a reaction front propagates through a packed bed, counter-flow heat exchange results in stationary reactions zones. The objective of this study is the numerical investigation of

  19. Named Reactions

    NSDL National Science Digital Library

    This Web site lists 95 of the most important named reactions in organic chemistry. Each is linked to a Web page that gives the primary reference and equations for one or more recent literature examples that illustrate the use of the reaction.

  20. Reaction Time

    NSDL National Science Digital Library

    New York Hall of Science

    1999-01-01

    In this activity, learners explore reaction time and challenge themselves to improve their coordination. Do you want to move faster? Catch that ball that you never seem to see in time? Use a simple test to help you improve your reaction (or response) time.

  1. Chemical Reactions

    NSDL National Science Digital Library

    Mrs. Hicken

    2009-05-04

    We are going go over a general view of reactions to prepare us for our unit on Chemical Reactions! Have fun learning! WARNING: If you are caught looking at ANY other site, without permission, you will be sent to the ALC, and you will not participate in any other computer activities for the rest of the year. Get your worksheet and begin! Overview Take this quiz and have me come over and sign off on your worksheet when you have completed the quiz! Overview Quiz Next let's take a look at what effect the rate of a chemical reaction. Rates of Reactions Another quiz, another check off by me! Rates of Reactions Quiz Now how do we measure how fast a ...

  2. Method for conducting exothermic reactions

    DOEpatents

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

    1993-01-05

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

  3. Method for conducting exothermic reactions

    DOEpatents

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

    1993-01-01

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

  4. Direct Reactions of Borromean Nuclei

    SciTech Connect

    Shimoura, S. [Center for Nuclear Study (CNS), University of Tokyo, Wako branch at RIKEN, Wako, Saitama 351-0198 (Japan)

    2008-04-29

    There are so-called Borromean nuclei on the drip-line in the nuclear chart, where any two-body subsystem has no bound state. The exotic structure and responses of Borromean nuclei have been studied by measurements of three-body (final-state) channels produced via direct reactions. Measurement of the three-body decay of the isospin partner of light drip-line nuclei populated by the charge exchange reaction is discussed as a means for studying the neutron halo structure. Experimental efforts to study nuclei beyond the drip-line, where many-body resonances may appear, are also presented.

  5. Enzyme Reactions

    NSDL National Science Digital Library

    Maryland Virtual High School

    The enzyme reaction rate activity allows students to simulate the effects of variables such as temperature and pH on the reaction rate of the enzyme catalase. This computer simulation is best used after the students have done a wet lab experiment. The value of the simulation is that it requires the students to interpret and analyze the graphical representation of data and it enables the running of mutiple experiments in a short amount of time.

  6. Preparation of Pt-Co nanoparticles by galvanostatic pulse electrochemical codeposition on in situ electrochemical reduced graphene nanoplates based carbon paper electrode for oxygen reduction reaction in proton exchange membrane fuel cell

    NASA Astrophysics Data System (ADS)

    Yaldagard, Maryam; Seghatoleslami, Naser; Jahanshahi, Mohsen

    2014-10-01

    Nanocomposite films of Pt-Co nanoparticles deposited on graphene nanoplate based gas diffusion layer electrode are fabricated via an electrochemical route involving a series of electrochemical process. Pt-Co nanoparticles of 11.37 nm in average size are prepared by galvanostatic codeposition in 0.5 M NaCl at PH of 2.5 at 300 mA cm-2 on the surface of in situ reduced graphene nanoplates on carbon paper. The topographical features, structure, morphology and composition of the prepared film samples are characterized by Atomic Force microscopy, Raman Spectroscopy, FTIR analysis, X-ray Diffraction, FESEM and EDS. At the same time, the catalytic activities of prepared electrodes for the oxygen reduction reaction are evaluated through cyclic voltammetry, linear sweep voltammetry and chronoamperometry and electrochemical impedance spectroscopy measurements. Raman spectroscopy measurements confirmed the graphitic structure of the produced graphene nanoplates. The nanoparticles in the film were observed to be uniform spherical objects and well distributed. Catalytic properties of Pt-Co/GNP/GDL electrode were compared with Pt/C/GDL using half cell polarization measurements based on both mass activity and specific activity. The as prepared Pt-Co/GNP/GDL electrode exhibits high catalytic activity for the ORR, which may be attributed to structural changes caused by alloying and the high specific surface area of graphene nanoplates catalyst support. The mass activity peak current is found to be as high as 728.25 mA mgPt-1.

  7. Text Exchange System

    NASA Technical Reports Server (NTRS)

    Snyder, W. V.; Hanson, R. J.

    1986-01-01

    Text Exchange System (TES) exchanges and maintains organized textual information including source code, documentation, data, and listings. System consists of two computer programs and definition of format for information storage. Comprehensive program used to create, read, and maintain TES files. TES developed to meet three goals: First, easy and efficient exchange of programs and other textual data between similar and dissimilar computer systems via magnetic tape. Second, provide transportable management system for textual information. Third, provide common user interface, over wide variety of computing systems, for all activities associated with text exchange.

  8. Microtube strip heat exchanger

    SciTech Connect

    Doty, F.D.

    1991-07-08

    During the last quarter, Doty Scientific, Inc. (DSI) continued to make progress on the microtube strip (MTS) heat exchanger. DSI completed a heat exchanger stress analysis of the ten-module heat exchanger bank; and, performed a shell-side flow inhomogeneity analysis of the three-module heat exchanger bank. The company produced 50 tubestrips using an in-house CNC milling machine and began pressing them onto tube arrays. DSI revised some of the tooling required to encapsulate a tube array and press tubestrips into the array to improve some of the prototype tooling. 2 refs., 4 figs.

  9. Chemical Reactions in DSMC

    NASA Astrophysics Data System (ADS)

    Bird, G. A.

    2011-05-01

    DSMC simulations of chemically reacting gas flows have generally employed procedures that convert the macroscopic chemical rate equations to reaction cross-sections at the microscopic level. They therefore depend on the availability of experimental data that has been fitted to equations of the Arrhenius form. This paper presents a physical model for dissociation and recombination reactions and a phenomenological model for exchange and chain reactions. These are based on the vibrational states of the colliding molecules and do not require any experimentally-based data. The simplicity of the models allows the corresponding rate equations to be written down and, while these are not required for the implementation of the models, they facilitate their validation. The model is applied to a typical hypersonic atmospheric entry problem and the results are compared with the corresponding results from the traditional method. It is also used to investigate both spontaneous and forced ignition as well as the structure of a deflagration wave in an oxygen-hydrogen mixture.

  10. Optimization of Heat Exchangers

    SciTech Connect

    Ivan Catton

    2010-10-01

    The objective of this research is to develop tools to design and optimize heat exchangers (HE) and compact heat exchangers (CHE) for intermediate loop heat transport systems found in the very high temperature reator (VHTR) and other Generation IV designs by addressing heat transfer surface augmentation and conjugate modeling. To optimize heat exchanger, a fast running model must be created that will allow for multiple designs to be compared quickly. To model a heat exchanger, volume averaging theory, VAT, is used. VAT allows for the conservation of mass, momentum and energy to be solved for point by point in a 3 dimensional computer model of a heat exchanger. The end product of this project is a computer code that can predict an optimal configuration for a heat exchanger given only a few constraints (input fluids, size, cost, etc.). As VAT computer code can be used to model characteristics )pumping power, temperatures, and cost) of heat exchangers more quickly than traditional CFD or experiment, optimization of every geometric parameter simultaneously can be made. Using design of experiment, DOE and genetric algorithms, GE, to optimize the results of the computer code will improve heat exchanger disign.

  11. Higher Education Exchange, 2004

    ERIC Educational Resources Information Center

    Brown, David W., Ed; Witte, Deborah, Ed.

    2004-01-01

    The Higher Education Exchange is part of a movement to strengthen higher education's democratic mission and foster a more democratic culture throughout American society. Working in this tradition, the Higher Education Exchange publishes case studies, analyses, news, and ideas about efforts within higher education to develop more democratic…

  12. Higher Education Exchange, 2007

    ERIC Educational Resources Information Center

    Brown, David W., Ed.; Witte, Deborah, Ed.

    2007-01-01

    "Higher Education Exchange" publishes case studies, analyses, news, and ideas about efforts within higher education to develop more democratic societies. Contributors to this issue of the "Higher Education Exchange" discuss the concept of growing public scholars; each contribution incorporates a student component. Articles include: (1) "Foreword"…

  13. Higher Education Exchange, 2010

    ERIC Educational Resources Information Center

    Brown, David W., Ed.; Witte, Deborah, Ed.

    2010-01-01

    "Higher Education Exchange" publishes case studies, analyses, news, and ideas about efforts within higher education to develop more democratic societies. Contributors to this issue of the "Higher Education Exchange" examine whether institutions of higher learning are doing anything to increase the capacity of citizens to shape their future.…

  14. Higher Education Exchange, 2012

    ERIC Educational Resources Information Center

    Brown, David W., Ed.; Witte, Deborah, Ed.

    2012-01-01

    "Higher Education Exchange" publishes case studies, analyses, news, and ideas about efforts within higher education to develop more democratic societies. Contributors to this issue of the "Higher Education Exchange" examine whether institutions of higher learning are doing anything to increase the capacity of citizens to shape their future.…

  15. International Exchange Formats.

    ERIC Educational Resources Information Center

    Hopkinson, Alan

    This paper focuses on the establishment of three standard international formats for the exchange of bibliographic data--UNIMARC, CCF, and the UNISIST Reference Manual--and outlines their common and differing features. The development of the UNIMARC manual as the standard international MARC network exchange format is traced, and its salient…

  16. Higher Education Exchange, 2011

    ERIC Educational Resources Information Center

    Brown, David W., Ed.; Witte, Deborah, Ed.

    2011-01-01

    "Higher Education Exchange" publishes case studies, analyses, news, and ideas about efforts within higher education to develop more democratic societies. Contributors to this issue of the "Higher Education Exchange" examine whether institutions of higher learning are doing anything to increase the capacity of citizens to shape their future.…

  17. Aberration Corrected Emittance Exchange

    E-print Network

    Nanni, Emilio A

    2015-01-01

    Full exploitation of emittance exchange (EEX) requires aberration-free performance of a complex imaging system including active radio-frequency (RF) elements which can add temporal distortions. We investigate the performance of an EEX line where the exchange occurs between two dimensions with normalized emittances which differ by orders of magnitude. The transverse emittance is exchanged into the longitudinal dimension using a double dog-leg emittance exchange setup with a 5 cell RF deflector cavity. Aberration correction is performed on the four most dominant aberrations. These include temporal aberrations that are corrected with higher order magnetic optical elements located where longitudinal and transverse emittance are coupled. We demonstrate aberration-free performance of emittances differing by 4 orders of magnitude, i.e. an initial transverse emittance of $\\epsilon_x=1$ pm-rad is exchanged with a longitudinal emittance of $\\epsilon_z=10$ nm-rad.

  18. Nonlocal exchange correlation in screened-exchange density functional methods

    E-print Network

    Lee, Byounghak; Wang, Lin-Wang; Spataru, Catalin D.; Louie, Steven G.

    2007-01-01

    of bulk silicon in the screened-exchange method (black solidof bulk silicon in the screened-exchange method (black solidblack solid line) and Hartree-Fock (red dashed line) exchange hole of bulk silicon

  19. Kinetics and thermodynamics studies of copper exchange on Na–montmorillonite clay mineral

    Microsoft Academic Search

    Mervette El-Batouti; Olfat M. Sadek; Fayez F. Assaad

    2003-01-01

    The kinetics of Cu ion exchange on Na–montmorillonite clay has been investigated at 20, 30, and 40°C in water, methanol, and ethanol. The reaction is endothermic in nature. Solvent effects on the reaction rate have been discussed. The thermodynamic activation parameters were calculated and discussed in terms of solvation effects. A multiple reaction rate order equation was used to describe

  20. Deuterium Exchange in the Systems of H2O+/H2O and H3O+/H2O

    NASA Technical Reports Server (NTRS)

    Anicich, V. G.; Sen, A. D.

    1995-01-01

    Using tandem mass spectrometry various water ion interactions were observed. These reactions consisted of a series of charge transfer, proton transfer, and isotopic exchange steps. The experimental data sets consist of variations of ion abundances over a neutral pressure range. An expected sequence of isotopic exchange reactions is given along with differential equation solutions & reaction rate data.

  1. [(CH3)2NH(CH2)2NH(CH3)2][(UO2)2F2(HPO4)2]: a new organically templated layered uranium phosphate fluoride--synthesis, structure, characterization, and ion-exchange reactions.

    PubMed

    Min Ok, Kang; Doran, Michael B; O'Hare, Dermot

    2007-08-14

    A new organically templated layered uranium phosphate fluoride, [(CH(3))(2)NH(CH(2))(2)NH(CH(3))(2)][(UO(2))(2)F(2)(HPO(4))(2)] has been synthesized by hydrothermal reaction of UO(3), H(3)PO(4), HF, and (CH(3))(2)NCH(2)CH(2)N(CH(3))(2) at 140 degrees C. [(CH(3))(2)NH(CH(2))(2)NH(CH(3))(2)][(UO(2))(2)F(2)(HPO(4))(2)] has a layered crystal structure consisting of seven-coordinated UO(5)F(2) pentagonal bipyramids and four-coordinated HPO(4) tetrahedra. Each anionic layer containing three-, four-, and six-membered rings is separated by [(CH(3))(2)NH(CH(2))(2)NH(CH(3))(2)](2+) cations. The [(CH(3))(2)NH(CH(2))(2)NH(CH(3))(2)](2+) cations may be readily exchanged with the M(2+) ions (M = Ba, Sr and Ca) in water to give high crystalline AE(UO(2))(2)(PO(4))(2).6H(2)O (AE = Ca, Sr, Ba). PMID:17893779

  2. Controlling chemical reactions of a single particle

    E-print Network

    Ratschbacher, Lothar; Sias, Carlo; Köhl, Michael

    2012-01-01

    The control of chemical reactions is a recurring theme in physics and chemistry. Traditionally, chemical reactions have been investigated by tuning thermodynamic parameters, such as temperature or pressure. More recently, physical methods such as laser or magnetic field control have emerged to provide completely new experimental possibilities, in particular in the realm of cold collisions. The control of reaction pathways is also a critical component to implement molecular quantum information processing. For these undertakings, single particles provide a clean and well-controlled experimental system. Here, we report on the experimental tuning of the exchange reaction rates of a single trapped ion with ultracold neutral atoms by exerting control over both their quantum states. We observe the influence of the hyperfine interaction on chemical reaction rates and branching ratios, and monitor the kinematics of the reaction products. These investigations advance chemistry with single trapped particles towards achi...

  3. Probing nuclear correlations with pion-nucleus double charge exchange

    SciTech Connect

    Ginocchio, J.N.

    1988-01-01

    In this paper we have calculated the lowest order pion double charge reaction mechanism using shell model wavefunctions of medium weight nuclei. We have the sequential reaction mechanism in which the pion undergoes two single-charge exchange scatterings on the valence neutrons. The distortion of the incoming, intermediate, and outgoing pion are included. The closure approximation is made for the intermediate states with an average excitation energy used in the pion propagator. The double-charge exchange is assumed to take place on the valence nucleons which are assumed to be in one spherical shell model orbital. 34 refs., 5 figs., 3 tabs.

  4. Equilibrious Strand Exchange Promoted by DNA Conformational Switching

    PubMed Central

    Wu, Zhiguo; Xie, Xiao; Li, Puzhen; Zhao, Jiayi; Huang, Lili; Zhou, Xiang

    2013-01-01

    Most of DNA strand exchange reactions in vitro are based on toehold strategy which is generally nonequilibrium, and intracellular strand exchange mediated by proteins shows little sequence specificity. Herein, a new strand exchange promoted by equilibrious DNA conformational switching is verified. Duplexes containing c-myc sequence which is potentially converted into G-quadruplex are designed in this strategy. The dynamic equilibrium between duplex and G4-DNA is response to the specific exchange of homologous single-stranded DNA (ssDNA). The SER is enzyme free and sequence specific. No ATP is needed and the displaced ssDNAs are identical to the homologous ssDNAs. The SER products and exchange kenetics are analyzed by PAGE and the RecA mediated SER is performed as the contrast. This SER is a new feature of G4-DNAs and a novel strategy to utilize the dynamic equilibrium of DNA conformations. PMID:23350029

  5. Determination of the cation-exchange capacity of muscovite mica

    SciTech Connect

    Osman, M.A.; Suter, U.W.

    2000-04-01

    High cation-exchange capacity (CEC) muscovite mica with a homoionic surface was prepared by replacing the Li{sup +} surface ions of partially delaminated Li-mica with K{sup +}. The CEC of this K-mica was determined by exchanging its surface cations with Cs{sup +}, NH{sub 4}{sup +}, methylene blue (MB{sup +}), and copper triethylenetetramine [Cu(trien){sup 2+}]. The kinetics of these exchange reactions were studied and showed large differences depending on their relative affinities to mica. The NH{sub 4}{sup +}/K{sup +} exchange was slow, while the Cs{sup +} and Cu(trien){sup 2+}/K{sup +} exchange was fast. The MB{sup +}/K{sup +} exchange was quite slow and was not completed even after 99 h. Insufficient reaction time is one of the main reasons for the contradictory results reported in the literature for the CEC of aluminosilicates obtained by different methods. The CEC of mica can be photometrically measured by exchanging its surface cations with Cu(trien){sup 2+}.

  6. Microtube strip heat exchanger

    NASA Astrophysics Data System (ADS)

    Doty, F. D.

    1990-12-01

    Doty Scientific (DSI) believes their microtube-strip heat exchanger will contribute significantly to the following: (1) the closed Brayton cycles being pursued at MIT, NASA, and elsewhere; (2) reverse Brayton cycle cryocoolers, currently being investigated by NASA for space missions, being applied to MRI superconducting magnets; and (3) high-efficiency cryogenic gas separation schemes for CO2 removal from exhaust stacks. The goal of this current study is to show the potential for substantial progress in high-effectiveness, low-cost, gas-to-gas heat exchangers for diverse applications at temperatures from below 100 K to above 1000 K. To date, the highest effectiveness measured is about 98 percent and relative pressure drops below 0.1 percent with a specific conductance of about 45 W/kgK are reported. During the pre-award period DSI built and tested a 3-module heat exchanger bank using 103-tube microtube strip (MTS) modules. To add to their analytical capabilities, DSI has acquired computational fluid dynamics (CFD) software. This report describes the pre-award work and the status of the ten tasks of the current project, which are: analyze flow distribution and thermal stresses within individual modules; design a heat exchanger bank of ten modules with 400 microtube per module; obtain production quality tubestrip die and AISI 304 tubestrips; obtain production quality microtubing; construct revised MTS heat exchanger; construct dies and fixtures for prototype heat exchanger; construct 100 MTS modules; assemble 8 to 10 prototype MTS heat exchangers; test prototype MTS heat exchanger; and verify test through independent means.

  7. Microtube Strip Heat Exchanger

    SciTech Connect

    Doty, F.D.

    1990-12-27

    Doty Scientific (DSI) believes their Microtube-Strip Heat Exchanger will contribute significantly to (a) the closed Brayton cycles being pursued at MIT, NASA, and elsewhere; (b) reverse Brayton cycle cryocoolers, currently being investigated by NASA for space missions, being applied to MRI superconducting magnets; and (c) high-efficiency cryogenic gas separation schemes for CO{sub 2} removal from exhaust stacks. The goal of this current study is to show the potential for substantial progress in high-effectiveness, low-cost, gas-to-gas heat exchangers for diverse applications at temperatures from below 100 K to above 1000 K. To date, the highest effectiveness measured is about 98%, and relative pressure drops below 0.1% with a specific conductance of about 45 W/kgK are reported. During the pre-award period DSI built and tested a 3-module heat exchanger bank using 103-tube microtube strip (MTS) modules. To add to their analytical capabilities, DSI has acquired computational fluid dynamics (CFD) software. This report describes the pre-award work and the status of the ten tasks of the current project, which are: analyze flow distribution and thermal stresses within individual modules; design a heat exchanger bank of ten modules with 400 microtube per module; obtain production quality tubestrip die and AISI 304 tubestrips; obtain production quality microtubing; construct revised MTS heat exchanger; construct dies and fixtures for prototype heat exchanger; construct 100 MTS modules; assemble 8-10 prototype MTS heat exchangers; test prototype MTS heat exchanger; and verify test through independent means. 7 refs., 9 figs. 1 tab. (CK)

  8. WMS International Exchange Scholarships WMS International Exchange Scholarships Regulations

    E-print Network

    Waikato, University of

    WMS International Exchange Scholarships WMS International Exchange Scholarships Regulations I N T R. The WMS International Exchange Scholarships are awarded twice a year for exchanges in A Semester and B programme Reasons for choosing particular institution/country 2. To be eligible to apply for a WMS

  9. Vacuum powered heat exchanger

    SciTech Connect

    Ruffolo, R.F.

    1986-06-24

    In an internal combustion engine including an oil lubrication system, a liquid cooling system, and an improved air intake system is described. The improved air intake system comprises: a housing including a first opening in one end, which opening is open to the atmosphere and a second opening comprising an air outlet opening in the other end open to the air intake manifold of the engine, a heat exchanger positioned in the first opening. The heat exchanger consists of a series of coils positioned in the flow path of the atmospheric air as it enters the housing, the heat exchanger being fluidly connected to either the engine lubrication system or the cooling system to provide a warm heat source for the incoming air to the housing, acceleration means positioned in the housing downstream of the heat exchanger, the acceleration means comprising a honeycomb structure positioned across the air intake flow path. The honey-comb structure includes a multitude of honey combed mini-venturi cells through which the heated air flows in an accelerated mode, a removable air filter positioned between the heat exchanger and the acceleration means and a single opening provided in the housing through which the air filter can be passed and removed, and additional openings in the housing positioned downstream of the heat exchanger and upstream of the air filter, the additional openings including removable flaps for opening and closing the openings to control the temperature of the air flowing through the housing.

  10. The State of the Art in Selective Catalytic Reduction of NOx by Ammonia Using Metal?Exchanged Zeolite Catalysts

    Microsoft Academic Search

    Sandro Brandenberger; Oliver Kröcher; Arno Tissler; Roderik Althoff

    2008-01-01

    An overview is given of the selective catalytic reduction of NOx by ammonia (NH3?SCR) over metal?exchanged zeolites. The review gives a comprehensive overview of NH3?SCR chemistry, including undesired side?reactions and aspects of the reaction mechanism over zeolites and the active sites involved. The review attempts to correlate catalyst activity and stability with the preparation method, the exchange metal, the exchange

  11. (18O,18Ne) double charge-exchange with MAGNEX

    NASA Astrophysics Data System (ADS)

    Bondí, M.; Cappuzzello, F.; Agodi, C.; Carbone, D.; Cavallaro, M.; Cunsolo, A.; De Napoli, M.; Foti, A.; Nicolosi, D.; Tropea, S.

    2014-05-01

    An experimental study concerning Double Gamow-Teller (DGT) modes in (18O,18Ne) Double Charge-Exchange reactions has been very recently performed at INFN-LNS laboratory in Catania. The experiment was performed using a 40Ca solid target and a 18O Cyclotron beam at 270 MeV incident energy. Charged ejectiles produced in the reaction were momentum analyzed and identified by MAGNEX spectrometer at very forward angles. Preliminary results are presented in the present paper.

  12. Search for R-parity breaking sneutrino exchange at LEP

    Microsoft Academic Search

    M. Acciarri; O Adriani; M. Aguilar-Benitez; S P Ahlen; J Alcaraz; G. Alemanni; James V Allaby; A Aloisio; G. Alverson; M. G. Alviggi; G. Ambrosi; H Anderhub; V. P Andreev; T Angelescu; F Anselmo; A Arefiev; T Azemoon; T Aziz; P Bagnaia; L Baksay; S Banerjee; K Banicz; A Barczyk; R Barillère; L Barone; P Bartalini; A Baschirotto; M Basile; R Battiston; A Bay; F Becattini; U Becker; F Behner; J Berdugo; P Berges; B Bertucci; B. L Betev; S Bhattacharya; M Biasini; A Biland; G. M Bilei; J. J Blaising; S. C Blyth; Gerjan J Bobbink; R K Böck; A Böhm; L Boldizsar; B Borgia; D Bourilkov; Maurice Bourquin; S Braccini; J. G Branson; V Brigljevic; I. C Brock; A Buffini; A Buijs; J. D Burger; W. J Burger; J K Busenitz; A M Button; X. D Cai; M Campanelli; M Capell; G Cara Romeo; G Carlino; A. M Cartacci; J Casaus; G Castellini; F Cavallari; N Cavallo; C Cecchi; M Cerrada-Canales; F Cesaroni; M Chamizo-Llatas; Y. H Chang; U. K Chaturvedi; S. V Chekanov; M Chemarin; A Chen; G Chen; H. F Chen; H. S Chen; X J Chéreau; G Chiefari; C. Y Chien; Luisa Cifarelli; F Cindolo; C Civinini; I Clare; R Clare; H. O Cohn; G Coignet; A. P Colijn; N Colino; V Commichau; S Costantini; F Cotorobai; B de la Cruz; Akos Csilling; T. S Dai; R D'Alessandro; R de Asmundis; A Degré; K Deiters; D della Volpe; P Denes; F DeNotaristefani; Daryl DiBitonto; M Diemoz; D N Van Dierendonck; F Di Lodovico; C Dionisi; Michael Dittmar; A Dominguez; A Doria; M. T Dova; D Duchesneau; P Duinker; I Duran; S Dutta; S Easo; Yu V Efremenko; H El Mamouni; A Engler; F. J Eppling; F. C Erné; J. P Ernenwein; Pierre Extermann; M Fabre; R Faccini; S Falciano; A Favara; J Fay; O Fedin; Marta Felcini; B Fenyi; T Ferguson; F Ferroni; H S Fesefeldt; E Fiandrini; J. H Field; Frank Filthaut; P. H Fisher; I Fish; G Forconi; L Fredj; Klaus Freudenreich; C Furetta; Yu Galaktionov; S. N Ganguli; P Garcia-Abia; S. S Gau; S Gentile; N Gheordanescu; S Giagu; S Goldfarb; J Goldstein; Z. F Gong; Andreas Gougas; Giorgio Gratta; M. W Gruenewald; V. K Gupta; A Gurtu; L. J Gutay; B Hartmann; A Hasan; D Hatzifotiadou; T Hebbeker; A Hervé; W. C van Hoek; H Hofer; S. J Hong; H Hoorani; S. R Hou; G Hu; Vincenzo Innocente; K Jenkes; B. N Jin; L. W Jones; P de Jong; I Josa-Mutuberria; A Kasser; R. A Khan; D Kamrad; Yu A Kamyshkov; J. S Kapustinsky; Yu Karyotakis; M Kaur; M. N Kienzle-Focacci; D Kim; J. K Kim; S. C Kim; Y. G Kim; W. W Kinnison; A Kirkby; D Kirkby; Jasper Kirkby; D Kiss; W Kittel; A Klimentov; A. C König; A Kopp; I Korolko; V F Koutsenko; R. W Kraemer; W Krenz; A Kunin; P Ladron de Guevara; I Laktineh; G Landi; C Lapoint; K M Lassila-Perini; P Laurikainen; M Lebeau; A Lebedev; P Lebrun; P Lecomte; P Lecoq; P Le Coultre; H. J Lee; J. M Le Goff; R Leiste; E Leonardi; P Levtchenko; Li Chuan; C. H Lin; W. T Lin; Frank L Linde; L Lista; Z. A Liu; W Lohmann; E Longo; W Lu; Y. S Lu; K Lübelsmeyer; C Luci; D Luckey; L Luminari; W Lustermann; W. G Ma; M Maity; G Majumder; L Malgeri; A Malinin; C Maña; D J J Mangeol; S Mangla; P A Marchesini; A Marin; J. P Martin; F Marzano; G. G. G Massaro; D McNally; R. R McNeil; S Mele; L Merola; M Meschini; W. J Metzger; M von der Mey; Y Mi; A Mihul; A. J. W van Mil; H Milcent; G Mirabelli; J Mnich; P Molnar; B Monteleoni; R Moore; S Morganti; T Moulik; R Mount; S Müller; F Muheim; A. J. M Muijs; S Nahn; M Napolitano; F Nessi-Tedaldi; H Newman; T Niessen; A Nippe; A Nisati; H Nowak; Yu D Oh; H Opitz; G Organtini; R Ostonen; C Palomares; D Pandoulas; S Paoletti; P Paolucci; H. K Park; I. H Park; G Pascale; G Passaleva; S Patricelli; T Paul; M Pauluzzi; C Paus; Felicitas Pauss; D Peach; Y. J Pei; S Pensotti; D Perret-Gallix; B Petersen; S Petrak; A Pevsner; D Piccolo; M Pieri; P. A Piroué; E Pistolesi; V Plyaskin; M Pohl; V Pozhidaev; H Postema; N Produit; D Prokofiev; G Rahal-Callot; N Raja; P. G Rancoita; M Rattaggi; P Razis; K Read; D Ren; M Rescigno; S Reucroft; T van Rhee; S Riemann; K Riles; A Robohm; J Rodin; B. P Roe; L Romero; S Rosier-Lees; Ph Rosselet; W van Rossum; S Roth; J. A Rubio; D Ruschmeier; H Rykaczewski; J Salicio; E Sanchez; M. P Sanders; M. E Sarakinos; S Sarkar; M Sassowsky; C Schäfer; V Schegelsky; S Schmidt-Kaerst; D Schmitz; P Schmitz; N Scholz; H Schopper; D. J Schotanus; J Schwenke; G Schwering; C Sciacca; D Sciarrino; L Servoli; S Shevchenko; N Shivarov; V Shoutko; J Shukla; E Shumilov; A Shvorob; T Siedenburg; D Son; A Sopczak; B Smith; P Spillantini; M Steuer; D. P Stickland; A Stone; H Stone; B Stoyanov; A Straessner; K Strauch; K Sudhakar; G Sultanov; L. Z Sun; G. F Susinno; H Suter; J. D Swain; X. W Tang; L Tauscher; L Taylor; Samuel C. C Ting; S. M Ting; M Tonutti; S. C Tonwar; J Tóth; C Tully; H Tuchscherer; K. L Tung; Y Uchida; J Ulbricht; U Uwer; E Valente; R. T Van de Walle; G Vesztergombi; I Vetlitsky; G Viertel; M Vivargent; R Völkert; H Vogel; H Vogel; I Vorobiev; A. A Vorobyov; A Vorvolakos; M Wadhwa; W Wallraff

    1997-01-01

    We report on a search for R-parity breaking effects due to supersymmetric tau-sneutrino exchange in the reactions e+e? ? e+e? and e+e? ? ?+?? at centre-of-mass energies from 91 GeV to 172 GeV, using the L3 detector at LEP. No evidence for deviations from the Standard Model expectations of the measured cross sections and forward-backward asymmetries for these reactions is

  13. Ceramic Spheres From Cation Exchange Beads

    NASA Technical Reports Server (NTRS)

    Dynys, F. W.

    2003-01-01

    Porous ZrO2 and hollow TiO2 spheres were synthesized from a strong acid cation exchange resin. Spherical cation exchange beads, polystyrene based polymer, were used as a morphological-directing template. Aqueous ion exchange reaction was used to chemically bind (ZrO)(2+) ions to the polystyrene structure. The pyrolysis of the polystyrene at 600 C produces porous ZrO2 spheres with a surface area of 24 sq m/g with a mean sphere size of 42 microns. Hollow TiO2 spheres were synthesized by using the beads as a micro-reactor. A direct surface reaction - between titanium isopropoxide and the resin beads forms a hydrous TiO2 shell around the polystyrene core. The pyrolysis of the polystyrene core at 600 C produces hollow anatase spheres with a surface area of 42 sq m/g with a mean sphere size of 38 microns. The formation of ceramic spheres was studied by XRD, SEM and B.E.T. nitrogen adsorption measurements.

  14. Formamidine Reactions

    E-print Network

    Griffin, E. L.

    1913-05-15

    of Hantzsch. (1), and the method of Uhlenhuth (2) was found to be not very much more satisfactory owing to the fact that the methyl lsoxazolon broKe down too much on heating Better results were obtained when the oxime of acetoacetic ester was obtained...,C ~ CH RNrOM-SHR = CH.C - C::CHHKR * li , II I H-0- CO U-0- CO * E2sTHx since methyl lsoxazolon is made by the reaction of hydroxylamine hydrochlorid on acetoacetic ester, it was thought that it might be possible to maKe the amldo methylene...

  15. Potential reactions among indoor pollutants

    NASA Astrophysics Data System (ADS)

    Weschler, Charles J.; Shields, Helen C.

    Reactions among indoor pollutants can produce products that, otherwise, might not be present in an indoor environment. To be relevant in an indoor setting, a chemical reaction must occur within a time interval shorter than or comparable to the residence time for a packet of indoor air. At typical air exchange rates, the reactions that meet this criterion include those of ozone with nitric oxide, nitrogen dioxide, and selected unsaturated hydrocarbons; thermal decomposition of peroxyacyl nitrates; numerous free radical reactions; and selected heterogeneous processes. Stable products include aldehydes, ketones, carboxylic acids and various organic nitrates. These reactions also generate free radicals, starting with the nitrate radical, Criegree biradicals, and peroxyacyl radicals, and leading to the hydroxyl, alkyl, alkylperoxy, hydroperoxy, and alkoxy radicals. Such radicals can react with other indoor species yielding additional aldehydes, ketones, carboxylic acids, dinitrates and peroxyacyl nitrates. Some of the potential products are known or suspected to be irritating (e.g. methacrolein, nonanoic acid, 1,2-propanediol dinitrate, peroxybenzoyl nitrate, and radical anions of the type [Cl… NO 2] -) However, some of these same products are difficult to detect using the sampling and analysis techniques currently applied to indoor air.

  16. Record activity and stability of dealloyed bimetallic catalysts for proton exchange membrane fuel cells

    E-print Network

    Han, Binghong

    We demonstrate the unprecedented proton exchange membrane fuel cell (PEMFC) performance durability of a family of dealloyed Pt–Ni nanoparticle catalysts for the oxygen reduction reaction (ORR), exceeding scientific and ...

  17. Calculation of Equilibrium Constants for Isotopic Exchange Reactions

    Microsoft Academic Search

    Jacob Bigeleisen; Maria Goeppert Mayer

    1947-01-01

    It is pointed out that the possibility of chemical separation of isotopes is a quantum effect. This permits a direct calculation of the difference in the free energies of two isotopic molecules. Tables and approximation methods are given which permit a rapid calculation of equilibrium constants if the frequency shifts on isotopic substitution are known. Several applications are discussed.

  18. Exam Question Exchange: A Popular Approach to Reaction Kinetics.

    ERIC Educational Resources Information Center

    Collins, Michael P. S.; Alexander, John J., Ed.

    1979-01-01

    Presents an undergraduate physical chemistry question and its acceptable solution. This question, presented to share exam questions with other teachers, shows the analogy between molecular kinetics and population dynamics. (HM)

  19. Protein hydrogen exchange: testing current models.

    PubMed

    Skinner, John J; Lim, Woon K; Bédard, Sabrina; Black, Ben E; Englander, S Walter

    2012-07-01

    To investigate the determinants of protein hydrogen exchange (HX), HX rates of most of the backbone amide hydrogens of Staphylococcal nuclease were measured by NMR methods. A modified analysis was used to improve accuracy for the faster hydrogens. HX rates of both near surface and well buried hydrogens are spread over more than 7 orders of magnitude. These results were compared with previous hypotheses for HX rate determination. Contrary to a common assumption, proximity to the surface of the native protein does not usually produce fast exchange. The slow HX rates for unprotected surface hydrogens are not well explained by local electrostatic field. The ability of buried hydrogens to exchange is not explained by a solvent penetration mechanism. The exchange rates of structurally protected hydrogens are not well predicted by algorithms that depend only on local interactions or only on transient unfolding reactions. These observations identify some of the present difficulties of HX rate prediction and suggest the need for returning to a detailed hydrogen by hydrogen analysis to examine the bases of structure-rate relationships, as described in the companion paper (Skinner et al., Protein Sci 2012;21:996-1005). PMID:22544567

  20. Fe atom exchange between aqueous Fe2+ and magnetite.

    PubMed

    Gorski, Christopher A; Handler, Robert M; Beard, Brian L; Pasakarnis, Timothy; Johnson, Clark M; Scherer, Michelle M

    2012-11-20

    The reaction between magnetite and aqueous Fe(2+) has been extensively studied due to its role in contaminant reduction, trace-metal sequestration, and microbial respiration. Previous work has demonstrated that the reaction of Fe(2+) with magnetite (Fe(3)O(4)) results in the structural incorporation of Fe(2+) and an increase in the bulk Fe(2+) content of magnetite. It is unclear, however, whether significant Fe atom exchange occurs between magnetite and aqueous Fe(2+), as has been observed for other Fe oxides. Here, we measured the extent of Fe atom exchange between aqueous Fe(2+) and magnetite by reacting isotopically "normal" magnetite with (57)Fe-enriched aqueous Fe(2+). The extent of Fe atom exchange between magnetite and aqueous Fe(2+) was significant (54-71%), and went well beyond the amount of Fe atoms found at the near surface. Mössbauer spectroscopy of magnetite reacted with (56)Fe(2+) indicate that no preferential exchange of octahedral or tetrahedral sites occurred. Exchange experiments conducted with Co-ferrite (Co(2+)Fe(2)(3+)O(4)) showed little impact of Co substitution on the rate or extent of atom exchange. Bulk electron conduction, as previously invoked to explain Fe atom exchange in goethite, is a possible mechanism, but if it is occurring, conduction does not appear to be the rate-limiting step. The lack of significant impact of Co substitution on the kinetics of Fe atom exchange, and the relatively high diffusion coefficients reported for magnetite suggest that for magnetite, unlike goethite, Fe atom diffusion is a plausible mechanism to explain the rapid rates of Fe atom exchange in magnetite. PMID:22577839

  1. Laser Assisted Emittance Exchange

    SciTech Connect

    Xiang, Dao; /SLAC

    2012-06-11

    We describe here the laser assisted emittance exchange (LAEE) technique. A laser operating in the transverse mode (TEM10 or TEM01) is used to interact with the electron beam in a dispersive region and to initiate the transverse-to-longitudinal emittance exchange. It is shown that with the LAEE one can generate an electron beam with ultralow transverse emittance, which allows one to significantly bring down the size of an X-ray free electron laser (FEL) and greatly extend the availability of these light sources. The technique can also be used to enhance the performances of X-ray FELs in storage rings. The timing and energy jitter problems for the standard emittance exchange and LAEE techniques are also discussed.

  2. Sorption of iron(III) from chromate solution by the aminocarboxylic ion exchanger ANKB-2

    SciTech Connect

    Stoyanova, O.F.; Izmailova, D.R.; Kurolap, N.S.; Uglyanskaya, V.A.

    1986-12-20

    The possibility of iron(III) sorption by the amphoteric ion exchanger ANKB-2 from chromate solution and its superiority over the cation exchanger KU-23 (10/60) have been demonstrated. By means of IR spectroscopy it has been shown that iron(III) sorption from chromate solution by ANKB-2 proceeds via both ionic and coordination reactions. The proportion of these kinds of reaction does not depend on the Cr(VI) content of the initial solution.

  3. Advanced Chemical Heat Pumps Using Liquid-Vapor Reactions

    E-print Network

    Kirol, L.

    ADVANCED CHEMICAL HEAT PUMPS USING LIQUID-VAPOR REACTIONS LANCE KIROL Senior Program Specialist Idaho National Engineering Laboratory Idaho Falls, Idaho . ABSTRACT Chemical heat pumps utilizing liquid-vapor reactions can be configured... characteristics. A waste heat driven heat pump (temperature amplifier) using liquid-vapor chem1cal reactions- can oper ate with higher coefficient of performance and smaller heat exchangers than an absorption temp erature amplifying heat pump. Higher tempera...

  4. Calcium Isotope Effect in Calcium Ion Exchange with a Fluid Phase Containing a Macrocyclic Compound

    Microsoft Academic Search

    B. E. Jepson; W. F. Evans

    1987-01-01

    The separation coefficient for calcium isotope exchange with a macrocyclic polyether was measured by ion exchange chromatography. The isotopic enrichment proceeds according to the chemical exchange reaction:where L represents the macrocyclic polyether 18-crown-6. The observed -separation coefficient for the calcium 40\\/44 isotope pair, ?(40\\/44), was 4.9×10 (±1.3×10, 95% C.L.) with calcium-40 enriched in the fluid phase. A sulfonic acid resin

  5. DOI: 10.1002/cphc.200700485 Monomer Exchange Dynamics of

    E-print Network

    Richmond, Geraldine L.

    reflection spectroscopy (IR-ATR) has been used[4,5] to study exchange reactions of aggregates at interfa- ces--including mole- cules far beyond the monolayer. Higher interfacial specificity is obtained with nonlinear optical.[8,9] The related but more powerful vibrational sum-frequency spectroscopy (VSFS) exploits resonant

  6. Proton exchange membrane fuel cell conductivity and system analysis

    Microsoft Academic Search

    Qian Han

    2003-01-01

    A fuel cell converts chemical energy to electrical energy. It is a device that uses the electrochemical reaction of hydrogen and an oxidant, to produce electrical energy silently, without combustion. The role of the electrolyte in a PEM fuel cell is played by a proton exchange membrane. NafionRTM and its derivatives are the most widely used and studied polymers. Percolation

  7. 21 CFR 173.20 - Ion-exchange membranes.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...reaction with chloromethyl methyl ether, and by subsequent amination with tri-methyl-amine, di-methyl-amine, di-ethyl-ene-triamine, or di-methyl-ethanol-amine. (b) The ion-exchange membrane is manufactured so as to comply...

  8. Hydrogen exchange studies of protein structure Tanya M Raschke and Susan Marqusee*

    E-print Network

    Raschke, Tanya M.

    80 Hydrogen exchange studies of protein structure Tanya M Raschke and Susan Marqusee* Hydrogen partially folded ensembles present at equilibrium. Analysis of hydrogen exchange mechanisms has revealed intrinsicexchangerate kobs observedexchangerate NH amide hydrogen AGHx free energy of the opening reaction Introduction

  9. Structure Revealing H/D Exchange with Co-Adsorbed Hydrogen and Water on Gold

    E-print Network

    Henkelman, Graeme

    of gold. Deuterium isotopic labeling shows H/D exchange in H-D2O and D-H2O systems, indicating water an isotopically labeled reaction system, such as D2O + H or H2O + D, we have discovered the production the dissociation of water on a Au(111) sample. Pt surfaces have also shown hydrogenic isotopic exchange via

  10. Hydrogen Isotope Exchange Properties of Porous Solids Containing Hydrogen

    SciTech Connect

    HEUNG, LEUNGK.

    2004-08-18

    Porous solids such as activated alumina, silica and molecular sieves generally contain significant amounts of hydrogen atoms in the form of H2O or OH even at high temperature and low humidity environment. A significant amount of this hydrogen is available for reversible isotopic exchange. This exchange reaction is slow under normal conditions and does not render itself to practical applications. But if the exchange kinetics is improved this reaction has the potential to be used for tritium removal from gas streams or for hydrogen isotopic separation.The use of catalysts to improve the exchange kinetics between hydrogen isotope in the gas phase and that in the solid phase was investigated. Granules of alumina, silica and molecular sieve were coated with platinum or palladium as the catalyst. The granules were packed in a 2-cm diameter column for isotope exchange tests. Gas streams containing different concentrations of deuterium in nitrogen or argon were fed through the protium saturated column. Isotope concentration in column effluent was monitored to generate isotope break-through curves. The curves were analyzed to produce information on the kinetics and capacity of the material. The results showed that all materials tested provided some extent of isotope exchange but some were superior both in kinetics and capacity. This paper will present the test results.

  11. 75 FR 52558 - Self-Regulatory Organizations; BATS Exchange, Inc.; Chicago Board Options Exchange, Incorporated...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-26

    ...Inc.; Chicago Board Options Exchange, Incorporated...EDGX Exchange, Inc.; Financial Industry Regulatory Authority...Inc.; Chicago Board Options Exchange, Incorporated...EDGX Exchange, Inc.; Financial Industry Regulatory...

  12. 75 FR 51138 - Self-Regulatory Organizations; BATS Exchange, Inc.; Chicago Board Options Exchange, Incorporated...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-18

    ...Inc.; Chicago Board Options Exchange, Incorporated...EDGX Exchange, Inc.; Financial Industry Regulatory Authority...Inc., Chicago Board Options Exchange, Incorporated...EDGX Exchange, Inc., Financial Industry Regulatory...

  13. 75 FR 53366 - Self-Regulatory Organizations; BATS Exchange, Inc.; Chicago Board Options Exchange, Incorporated...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-31

    ...Inc.; Chicago Board Options Exchange, Incorporated...EDGX Exchange, Inc.; Financial Industry Regulatory Authority...Inc., Chicago Board Options Exchange, Incorporated...EDGX Exchange, Inc., Financial Industry Regulatory...

  14. Polymethylmethacrylate open tubular ion exchange columns: nondestructive measurement of very small ion exchange capacities.

    PubMed

    Zhang, Min; Yang, Bingcheng; Dasgupta, Purnendu K

    2013-08-20

    We describe an approach to prepare an open tubular ion exchange (OTIE) column by coating a monolayer of anion exchange nanoparticle to a 16-20 ?m bore polymethylmethacrylate (PMMA) capillary. The latex nanoparticle was electrostatically attached to carboxylate groups on the inner wall of capillary, pretreated with strong base for hydrolyzing the ester. Several approaches to nondestructively measure ion exchange capacities (IEC) of the columns were examined: (a) adsorption-desorption of an intensely fluorescent ion, e.g. fluorescein, and off-line fluorometry, (b) loading a weakly retained ion (e.g., IO3(-)), frontal displacement by a strongly bound ion (e.g., Cl(-)), and online optical or conductometric boundary detection, and (c) similar to the above except displacement being accompanied by reaction (e.g., acid-base titration). To our knowledge, this is the first time on-column titration has been used to measure capacities. By using different pH displacer solutions, we demonstrate for the first time the possibility of pKa-differentiated ion exchange capacity measurements. The cation exchange capacity of bare PMMA capillaries was on the order of 1 pequiv/mm(2) with little dependence on time and temperature of hydrolysis conditions. After AS18 latex coating, the strong base anion exchange capacity was on the order of 10 pequiv/mm(2), very close to what would be estimated on the basis of monolayer coverage of the surface by individual latex particles. The latex used contained a significant, additional amount of weak base character, about the same as the strong base ion exchange capacity. PMID:23875750

  15. General Biology 1, Reactions 1 CHEMICAL REACTIONS *

    E-print Network

    Prestwich, Ken

    General Biology 1, Reactions 1 CHEMICAL REACTIONS * Note: This is the first of a two-part set of notes. This set will review chemical reactions and the next will overview enzymes. What you learn and ribozymes. At their heart, organisms are complex chemical engines. However, many of the chemical reactions

  16. Intro Biology, Reactions 1 CHEMICAL REACTIONS *

    E-print Network

    Prestwich, Ken

    Intro Biology, Reactions 1 CHEMICAL REACTIONS * Note: This is the first of a two-part set of notes. This set will review chemical reactions and the next will overview enzymes. What you learn in these two and ribozymes. At their heart, organisms are complex chemical engines. However, many of the chemical reactions

  17. THE EXCHANGE OF DEUTERIUM WITH METHANOL OVER RANEY NICKEL CATALYST AND THE EFFECT OF CERTAIN NITRO COMPOUNDS UPON THE EXCHANGE

    Microsoft Academic Search

    H. A. Smith; B. B. Stewart

    1960-01-01

    Deuterium gas exchanges slowly with liquid methanol over Raney nickel ; catalyst at 35 deg . The reaction is zero order with respect to deuterium ; pressure and has a low activation energy. The influences of catalyst weight, ; catalyst treatment, and of the presence of certain nitro compounds were studied. ; Since active Raney nickel can liberate hydrogen directly,

  18. Selective Cu{sup 2+} and Pb{sup 2+} exchange with highly charged cation exchanger of Na-4-mica

    SciTech Connect

    Kodama, Tatsuya; Komarneni, Sridhar [Pennsylvania State Univ., University Park, PA (United States)] [Pennsylvania State Univ., University Park, PA (United States)

    1999-09-01

    Selective cation exchange for Cu and Pb has been demonstrated with the high-charge-density sodium fluorophlogopite mica, Na-4-mica. The 2Na{sup +} {yields} M{sup 2+} exchange reaction (M = Cu or Pb) was investigated with Na-4-micas prepared by two different synthetic processes. One was easily and economically prepared by crystallization from a mixture of NaF, MgO, and metakaolin, the latter serves as an inexpensive aluminosilicate source. Another was prepared by solution-sol-gel processing. Ion-exchange isotherms for Cu{sup 2+} and Pb{sup 2+} were obtained at room temperature. The thermodynamic functions for the initial ion-exchange reactions were calculated because the isotherms were not completed., High selectivities for both copper and lead exchange were found on the highly crystallized Na-4-mica prepared from metakaolin. Their ion-exchange capacities were 225 and 257 milliequivalents per 100 g of dry clay for Cu{sup 2+} and Pb{sup 2+}, respectively. This high level decontamination of copper and lead with the highly crystallized Na-4-mica from metakaolin will be a very important separation required for purification of drinking water as well as for wastewater treatment and disposal.

  19. Exchangeable PV shingle

    Microsoft Academic Search

    T. Yagiura; M. Morizane; K. Murata; K. Uchihashi; S. Tsuda; S. Nakano; T. Ito; S. Omoto; Y. Yamashita; H. Yamakawa; T. Fujiwara

    1997-01-01

    An “exchangeable photovoltaic (PV) shingle” which is a new type of PV module integrated with a shingle tile has been developed. The new PV shingle tile offers many attractive features, such as a lower total cost, simple construction and maintenance, good design, and fire resistance, compared with previous PV modules. The PV shingles were trial tested and evaluated as PV

  20. Chicago Mercantile Exchange

    NSDL National Science Digital Library

    The Chicago Mercantile Exchange, the World's Largest Marketplace, trading approximately $200 trillion annually in underlying value of financial and agricultural futures and options, now has a Web page. Accessible from the CME Home Page are background and product information, volume and membership-price information and charts, and the CME Model for Federal Financial Regulation, a proposal for streamlining government oversight of financial institutions.

  1. DHE (Downhole Heat Exchangers)

    Microsoft Academic Search

    G. Culver

    1990-01-01

    The use of downhole heat exchangers (DHE) for residential or commercial space and domestic water heating and other applications has several desirable features. Systems are nearly or completely passive -- that is, no or very little geothermal water or steam is produced from the well either reducing or completely eliminating surface environmental concerns and the need for disposal systems or

  2. Nature's Heat Exchangers.

    ERIC Educational Resources Information Center

    Barnes, George

    1991-01-01

    Discusses the heat-transfer systems of different animals. Systems include heat conduction into the ground, heat transferred by convection, heat exchange in lizards, fish and polar animals, the carotid rete system, electromagnetic radiation from animals and people, and plant and animal fiber optics. (MDH)

  3. Chimney heat exchanger

    SciTech Connect

    Whiteley, I.C.

    1981-09-01

    A heat exchanger for installation on the top of a chimney of a building includes a housing having a lower end receiving the top of the chimney and an upper end with openings permitting the escape of effluent from the chimney and a heat exchanger assembly disposed in the housing including a central chamber and a spirally arranged duct network defining an effluent spiral path between the top of the chimney and the central chamber and a fresh air spiral path between an inlet disposed at the lower end of the housing and the central chamber, the effluent and fresh air spiral paths being in heat exchange relationship such that air passing through the fresh air spiral path is heated by hot effluent gases passing upward through the chimney and the effluent spiral path for use in heating the building. A pollution trap can be disposed in the central chamber of the heat exchanger assembly for removing pollutants from the effluent, the pollution trap including a rotating cage carrying pumice stones for absorbing pollutants from the effluent with the surface of the pumice gradually ground off to reveal fresh stone as the cage rotates.

  4. Scraped Surface Heat Exchangers

    Microsoft Academic Search

    Chetan S. Rao; Richard W. Hartel

    2006-01-01

    Scraped surface heat exchangers (SSHEs) are commonly used in the food, chemical, and pharmaceutical industries for heat transfer, crystallization, and other continuous processes. They are ideally suited for products that are viscous, sticky, that contain particulate matter, or that need some degree of crystallization. Since these characteristics describe a vast majority of processed foods, SSHEs are especially suited for pumpable

  5. Dublin, Ireland Exchange Program

    E-print Network

    Fernandez, Eduardo

    Dublin, Ireland Exchange Program Dublin Institute of Technology Dublin, the capital of Ireland of the European University Association and is Ireland's largest higher educational institution with over 22 business school in Ireland and the Faculty of Business is the largest business faculty in Ireland

  6. Systems of social exchange

    Microsoft Academic Search

    James S. Coleman

    1972-01-01

    This paper develops a formal model for exchange within a system of action. The system of action is defined by actors, events, control of actors over events, and interests of actors in the outcomes of events. The system is designed to deal with divisible events (best exemplified by private goods) or indivisible events (such as a bill on which a

  7. Exchange Bank Position Description

    E-print Network

    Ravikumar, B.

    Exchange Bank Position Description Position Title: Web Technical Administrator FLSA Status: Non applications to support Bank operations · Administer existing vendor supplied web based applications. · Work with vendors and consultants that provide web applications or content. · Work with LAN Administrator to develop

  8. Chemical exchange program analysis.

    SciTech Connect

    Waffelaert, Pascale

    2007-09-01

    As part of its EMS, Sandia performs an annual environmental aspects/impacts analysis. The purpose of this analysis is to identify the environmental aspects associated with Sandia's activities, products, and services and the potential environmental impacts associated with those aspects. Division and environmental programs established objectives and targets based on the environmental aspects associated with their operations. In 2007 the most significant aspect identified was Hazardous Materials (Use and Storage). The objective for Hazardous Materials (Use and Storage) was to improve chemical handling, storage, and on-site movement of hazardous materials. One of the targets supporting this objective was to develop an effective chemical exchange program, making a business case for it in FY07, and fully implementing a comprehensive chemical exchange program in FY08. A Chemical Exchange Program (CEP) team was formed to implement this target. The team consists of representatives from the Chemical Information System (CIS), Pollution Prevention (P2), the HWMF, Procurement and the Environmental Management System (EMS). The CEP Team performed benchmarking and conducted a life-cycle analysis of the current management of chemicals at SNL/NM and compared it to Chemical Exchange alternatives. Those alternatives are as follows: (1) Revive the 'Virtual' Chemical Exchange Program; (2) Re-implement a 'Physical' Chemical Exchange Program using a Chemical Information System; and (3) Transition to a Chemical Management Services System. The analysis and benchmarking study shows that the present management of chemicals at SNL/NM is significantly disjointed and a life-cycle or 'Cradle-to-Grave' approach to chemical management is needed. This approach must consider the purchasing and maintenance costs as well as the cost of ultimate disposal of the chemicals and materials. A chemical exchange is needed as a mechanism to re-apply chemicals on site. This will not only reduce the quantity of unneeded chemicals and the amount spent on new purchases, but will also avoid disposal costs. If SNL/NM were to realize a 5 percent reduction in chemical inventory and a 10 percent reduction in disposal of unused chemicals the total savings would be $189, 200 per year.

  9. DNA strand exchange and RecA homologs in meiosis.

    PubMed

    Brown, M Scott; Bishop, Douglas K

    2015-01-01

    Homology search and DNA strand-exchange reactions are central to homologous recombination in meiosis. During meiosis, these processes are regulated such that the probability of choosing a homolog chromatid as recombination partner is enhanced relative to that of choosing a sister chromatid. This regulatory process occurs as homologous chromosomes pair in preparation for assembly of the synaptonemal complex. Two strand-exchange proteins, Rad51 and Dmc1, cooperate in regulated homology search and strand exchange in most organisms. Here, we summarize studies on the properties of these two proteins and their accessory factors. In addition, we review current models for the assembly of meiotic strand-exchange complexes and the possible mechanisms through which the interhomolog bias of recombination partner choice is achieved. PMID:25475089

  10. Kinetic theory of oxygen isotopic exchange between minerals and water

    SciTech Connect

    Criss, R.E.; Gregory, R.T.; Taylor, H.P.

    1987-05-01

    Kinetic and mass conservation equations are used to describe oxygen isotopic exchange between minerals and water in ''closed'' and open hydrothermal systems. In cases where n coexisting mineral phases having different reaction rates are present, the exchange process is described by a system of n + 1 simultaneous differential equations consisting of n pseudo first-order rate equations and a conservation of mass equation. The simultaneous solutions to these equations generate curved exchange trajectories on delta-delta plots. Families of such trajectories generated under conditions allowing for different fluid mole fractions, different fluid isotopic compositions, or different fluid flow rates are connected by positive-sloped isochronous lines. These isochrons reproduce the effects observed in hydrothermally exchanged mineral pairs including 1) steep positive slopes, 2) common reversals in the measured fractionation factors ( ), and 3) measured fractionations that are highly variable over short distances where no thermal gradient can be geologically demonstrated.

  11. Quantum Theory of Fast Chemical Reactions

    SciTech Connect

    Light, John C

    2007-07-30

    The aims of the research under this grant were to develop a theoretical understanding and predictive abiility for a variety of processes occurring in the gas phase. These included bimolecular chemical exchange reactions, photodissociation, predissociation resonances, unimolecular reactions and recombination reactions. In general we assumed a knowledge, from quantum chemistry, of the interactions of the atoms and molecular fragments involved. Our focus was primarily on the accurate (quantum) dynamics of small molecular systems. This has been important for many reactions related to combustion and atmospheric chemistry involving light atom transfer reactions and, for example, resonances in dissociation and recombination reactions. The rates of such reactions, as functions of temperature, internal states, and radiation (light), are fundamental for generating models of overall combustion processes. A number of new approaches to these problems were developed inclluding the use of discrete variable representations (DVR's) for evaluating rate constants with the flux-flux correlation approach, finite range approaches to exact quantum scattering calculations, energy selected basis representations, transition state wave packet approaches and improved semiclassical approaches. These (and others) were applied to a number of reactive systems and molecular systems of interest including (many years ago) the isotopic H + H2 exchange reactions, the H2 + OH (and H + H2O) systems, Ozone resonances, van der Waals molecule reactions, etc. A total of 7 graduate students, and 5 post-doctoral Research Associates were supported, at least in part, under this grant and seven papers were published with a total of 10 external collaborators. The majority of the 36 publications under this grant were supported entirely by DOE.

  12. Kinetics of reactions between aqueous sulfates and sulfides in hydrothermal systems

    Microsoft Academic Search

    Hiroshi Ohmoto; Antonio C. Lasaga

    1982-01-01

    The rates of chemical reactions between aqueous sulfates and sulfides are essentially identical to sulfur isotopic exchange rates between them, because both the chemical and isotopic reactions involve simultaneous oxidation of sulfide-sulfur atoms and reduction of sulfate-sulfur. The rate of reaction can be expressed as a second order rate law: R = k ·[ SO 4 2- ]·[ S 2-

  13. A coupled chemical burster: The chlorine dioxide-iodide reaction in two flow reactors

    E-print Network

    Epstein, Irving R.

    A coupled chemical burster: The chlorine dioxide-iodide reaction in two flow reactors Miles Dolnika-iodide reaction has been studied in a system consisting of two continuous flow stirred tank reactors (CSTRs triggered, exponentially decreasing stimulation, and alternating mass exchange. The reaction, which exhibits

  14. Exchange Rate Regimes: Middling Through

    Microsoft Academic Search

    Ashima Goyal

    2006-01-01

    The appropriate exchange rate regime, in the context of integration of currency markets with financial markets and of large international capital flows, continues to be a policy dilemma. It is found that the majority of countries are moving towards somewhat higher exchange and lower interest rate volatility. Features of foreign exchange (forex) markets could be partly motivating these choices. A

  15. COMPACT EXCHANGERS FOR PHASE CHANGE

    Microsoft Academic Search

    Vishwas V. Wadekar

    Compact heat exchangers are being increasingly considered for duties involving phase change processes of boiling and condensation. In many cases such applications are completely new and no previous experience or information on exchanger performance is available. Understanding the thermal-hydraulic characteristics of flow passages of compact heat exchangers for phase change duties is therefore vitally important. Even for those compact heat

  16. SNOWPACK ENERGY EXCHANGE: BASIC THEORY

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The exchange of energy between the snowpack and its environment ultimately determines the rate of snowpack water losses due to melting and evaporation/sublimation. Energy exchange primarily occurs at the snowpack surface through exchange of shortwave and longwave radiation and turbulent or convect...

  17. AGRICULTURAL EXCHANGE RATE DATA SHEET

    EPA Science Inventory

    The ERS data set contains annual and monthly data for exchange rates important to U.S. agriculture. It includes both nominal and real exchange rates for 80 countries (plus the European Union) as well as real trade-weighted exchange rate indexes for many commodities and aggregatio...

  18. Stochastic thermodynamics of chemical reaction networks

    E-print Network

    Tim Schmiedl; Udo Seifert

    2006-12-19

    For chemical reaction networks described by a master equation, we define energy and entropy on a stochastic trajectory and develop a consistent nonequilibrium thermodynamic description along a single stochastic trajectory of reaction events. A first-law like energy balance relates internal energy, applied (chemical) work and dissipated heat for every single reaction. Entropy production along a single trajectory involves a sum over changes in the entropy of the network itself and the entropy of the medium. The latter is given by the exchanged heat identified through the first law. Total entropy production is constrained by an integral fluctuation theorem for networks arbitrarily driven by time-dependent rates and a detailed fluctuation theorem for networks in the steady state. Further exact relations like a generalized Jarzynski relation and a generalized Clausius inequality are discussed. We illustrate these results for a three-species cyclic reaction network which exhibits nonequilibrium steady states as well as transitions between different steady states.

  19. Serial Replica Exchange

    PubMed Central

    Hagen, Morten; Kim, Byungchan; Liu, Pu; Friesner, Richard A.; Berne, B. J.

    2009-01-01

    Parallel tempering (or the replica exchange method (REM)) is a powerful method for speeding up the sampling of conformational states of systems with rough energy landscapes, like proteins, where stable conformational states can be separated by large energy barriers. The usual implementation of the REM is performed on local computer clusters (or parallel processors) where the different replicas must be run synchronously. Here, we present serial replica exchange (SREM), a method that is equivalent to the standard REM in terms of efficiency yet runs asynchronously on a distributed network of computers. A second advantage is the method’s greatly enhanced fault tolerance, which enables the study of biological systems on worldwide distributed computing environments, such as Folding@Home.1 For proof of concept, we apply the SREM to a single alanine dipeptide molecule in explicit water. We show that the SREM reproduces the thermodynamic and structural properties determined by the REM. PMID:17249714

  20. Preparation of an Ester-Containing Grignard Reagent by Halogen-Metal Exchange

    ERIC Educational Resources Information Center

    Snider, Barry B.

    2015-01-01

    In this experiment, students carry out a halogen-metal exchange reaction of methyl 2-iodobenzoate with isopropylmagnesium chloride in THF at 0°C to afford 2-carbomethoxyphenylmagnesium chloride, which is treated with "p"-methoxybenzaldehyde to give a lactone (phthalide) product. This reaction introduces students to the modern method of…

  1. Reach-Scale Cation Exchange Controls on Major Ion Chemistry of an Antarctic Glacial Meltwater Stream

    Microsoft Academic Search

    Michael N. Gooseff; Diane M. Mcknight; Robert L. Runkel

    2004-01-01

    McMurdo dry valleys of Antarctica represent the largest of the ice-free areas on the Antarctic continent, containing glaciers, meltwater streams, and closed basin lakes. Previous geochemical studies of dry valley streams and lakes have addressed chemical weathering reactions of hyporheic substrate and geochemical evolution of dry valley surface waters. We examine cation transport and exchange reactions during a stream tracer

  2. Thermoelectric heat exchange element

    DOEpatents

    Callas, James J. (Peoria, IL); Taher, Mahmoud A. (Peoria, IL)

    2007-08-14

    A thermoelectric heat exchange module includes a first substrate including a heat receptive side and a heat donative side and a series of undulatory pleats. The module may also include a thermoelectric material layer having a ZT value of 1.0 or more disposed on at least one of the heat receptive side and the heat donative side, and an electrical contact may be in electrical communication with the thermoelectric material layer.

  3. Exchange and evolution

    Microsoft Academic Search

    Jason Potts

    2007-01-01

    This paper offers an extension of the distinction of [Kohn, Cato Journal, 24:303–339 (2004)] between the two paradigms of modern economic theory—value and exchange—as derived from the generic–operant framework\\u000a of [Dopfer and Potts, The general theory of economic evolution, Routledge, London, (2007)]. I argue that Austrian and evolutionary economics can be analytically unified about a general framework of rule coordination

  4. Lightweight Long Life Heat Exchanger

    NASA Technical Reports Server (NTRS)

    Moore, E. K.

    1976-01-01

    A shuttle orbiter flight configuration aluminum heat exchanger was designed, fabricated, and tested. The heat exchanger utilized aluminum clad titanium composite parting sheets for protection against parting sheet pin hole corrosion. The heat exchanger, which is fully interchangeable with the shuttle condensing heat exchanger, includes slurpers (a means for removing condensed water from the downstream face of the heat exchanger), and both the core air passes and slurpers were hydrophilic coated to enhance wettability. The test program included performance tests which demonstrated the adequacy of the design and confirmed the predicted weight savings.

  5. Selective Facet Reactivity During Cation Exchange in Cadmium Sulfide Nanorods

    SciTech Connect

    Sadtler, Bryce; Demchenko, Denis; Zheng, Haimei; Hughes, Steven; Merkle, Maxwell; Dahmen, Ulrich; Wang, Lin-Wang; Alivisatos, A. Paul

    2008-12-18

    The partial transformation of ionic nanocrystals through cation exchange has been used to synthesize nanocrystal heterostructures. We demonstrate that the selectivity for cation exchange to take place at different facets of the nanocrystal plays an important role in determining the resulting morphology of the binary heterostructure. In the case of copper I (Cu+) cation exchange in cadmium sulfide (CdS) nanorods, the reaction starts preferentially at the ends of the nanorods such that copper sulfide (Cu2S) grows inwards from either end. The resulting morphology is very different from the striped pattern obtained in our previous studies of silver I (Ag+) exchange in CdS nanorods where non-selective nucleation of silver sulfide (Ag2S) occurs. From interface formation energies calculated for several models of epitaxialconnections between CdS and Cu2S or Ag2S, we infer the relative stability of each interface during the nucleation and growth of Cu2S or Ag2S within the CdS nanorods. The epitaxial connections of Cu2S to the end facets of CdS nanorods minimize the formation energy, making these interfaces stable throughout the exchange reaction. However, as the two end facets of wurtzite CdS nanorods are crystallographically nonequivalent, asymmetric heterostructures can be produced.

  6. Concerted hydrogen atom exchange between three HF molecules

    NASA Technical Reports Server (NTRS)

    Komornicki, Andrew; Dixon, David A.; Taylor, Peter R.

    1992-01-01

    We have investigated the termolecular reaction involving concerted hydrogen exchange between three HF molecules, with particular emphasis on the effects of correlation at the various stationary points along the reaction. Using an extended basis, we have located the geometries of the stable hydrogen-bonded trimer, which is of C(sub 3h) symmetry, and the transition state for hydrogen exchange, which is of D(sub 3h) symmetry. The energies of the exchange reation were then evaluated at the correlated level, using a large atomic natural orbital basis and correlating all valence electrons. Several correlation treatments were used, namely, configration interaction with single and double excitations, coupled-pair functional, and coupled-cluster methods. We are thus able to measure the effect of accounting for size-extensivity. Zero-point corrections to the correlated level energetics were determined using analytic second derivative techniques at the SCF level. Our best calculations, which include the effects of connected triple excitations in the coupled-cluster procedure, indicate that the trimer is bound by 9 +/- 1 kcal/mol relative to three separate monomers, in excellent agreement with previous estimates. The barrier to concerted hydrogen exchange is 15 kcal/mol above the trimer, or only 4.7 kcal/mol above three separated monomers. Thus the barrier to hydrogen exchange between HF molecules via this termolecular process is very low.

  7. Quantum Theory of Fast Chemical Reactions

    Microsoft Academic Search

    John C. Light

    2007-01-01

    The aims of the research under this grant were to develop a;\\u000atheoretical understanding and;\\u000apredictive abiility for a variety of processes occurring in the;\\u000agas phase.;\\u000aThese included bimolecular chemical exchange reactions,;\\u000aphotodissociation,;\\u000apredissociation resonances, unimolecular reactions and recombination;\\u000areactions. In general we assumed a knowledge, from quantum chemistry,;\\u000aof the interactions of the atoms and molecular fragments involved.;

  8. Catalysis of Photochemical Reactions.

    ERIC Educational Resources Information Center

    Albini, A.

    1986-01-01

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

  9. Exam Question Exchange.

    ERIC Educational Resources Information Center

    Alexander, John J., Ed.

    1978-01-01

    Two exam questions are presented. One suitable for advanced undergraduate or beginning graduate courses in organic chemistry, is on equivalent expressions for the description of several pericyclic reactions. The second, for general chemistry students, asks for an estimation of the rate of decay of a million-year-old Uranium-238 sample. (BB)

  10. Exchange functional by a range-separated exchange hole

    SciTech Connect

    Toyoda, Masayuki; Ozaki, Taisuke [Research Center for Integrated Science (RCIS), Japan Advanced Institute of Science and Technology (JAIST), 1-1 Asahidai, Nomi, Ishikawa 923-1292 (Japan)

    2011-03-15

    An approximation to the exchange-hole density is proposed for the evaluation of the exact exchange energy in electronic structure calculations within the density-functional theory and the Kohn-Sham scheme. Based on the localized nature of density matrix, the exchange hole is divided into the short-range (SR) and long-range (LR) parts by using an adequate filter function, where the LR part is deduced by matching of moments with the exactly calculated SR counterpart, ensuring the correct asymptotic -1/r behavior of the exchange potential. With this division, the time-consuming integration is truncated at a certain interaction range, largely reducing the computation cost. The total energies, exchange energies, exchange potentials, and eigenvalues of the highest-occupied orbitals are calculated for the noble-gas atoms. The close agreement of the results with the exact values suggests the validity of the approximation.

  11. [Univerity students' exchange experience].

    PubMed

    De Caro, Walter; Maddalena, Claudio; Badolamenti, Sondra

    2004-01-01

    We report the experience of three University "La Sapienza" of Rome students (two of the Advanced Nursing master science course and one of the 3rd year of Nursing Degree) that participated to the FIPSE programme between European and Transatlantic Universities. The leader of the programme in our Country is Prof J. Sansoni. Web courses have been offered and students participated in a short period exchange at the Capital University with prof Kerr. The experience has been very positive and exciting. We really hope that this programme could be an example to other Italians Colleagues to have a look outside our Country. PMID:15134593

  12. The Quantum Exchange

    NSDL National Science Digital Library

    The Quantum Exchange is a collection of information and resources for teachers of quantum physics. To get started, visitors can look over areas such as Featured Materials, Quantum Pictures, and Resource Categories. The Featured Materials area contains helpful items like Paradigms in Physics: Quantum Activities and a rather exciting quantum mechanics visualization project from the University of St. Andrews. Moving on, visitors can browse Quantum Topics that include bound state systems, multi-particle systems, and spin and finite dimensional systems. The site also has a great search engine for those with a specific topic in mind.

  13. Controlling chemical reactions of a single particle

    E-print Network

    Lothar Ratschbacher; Christoph Zipkes; Carlo Sias; Michael Köhl

    2012-09-26

    The control of chemical reactions is a recurring theme in physics and chemistry. Traditionally, chemical reactions have been investigated by tuning thermodynamic parameters, such as temperature or pressure. More recently, physical methods such as laser or magnetic field control have emerged to provide completely new experimental possibilities, in particular in the realm of cold collisions. The control of reaction pathways is also a critical component to implement molecular quantum information processing. For these undertakings, single particles provide a clean and well-controlled experimental system. Here, we report on the experimental tuning of the exchange reaction rates of a single trapped ion with ultracold neutral atoms by exerting control over both their quantum states. We observe the influence of the hyperfine interaction on chemical reaction rates and branching ratios, and monitor the kinematics of the reaction products. These investigations advance chemistry with single trapped particles towards achieving quantum-limited control of chemical reactions and indicate limits for buffer gas cooling of single ion clocks.

  14. Catalytic behavior of Group VIII transition metals in the deuterium-acrolein reaction

    SciTech Connect

    Touroude, R.

    1980-09-01

    The catalytic reactions between acrolein and deuterium over all the Group VIII transition metals were studied by microwave spectrometry. A high catalyst selectivity in the exchange reaction, in which hydrogen is replaced by deuterium in acrolein, was found. Over Rh, Pd, Ir, Ru, and Ni, hydrogens situated on the ..beta.. carbon were quasi-selectively exchanged while over Pt, Os, and especially Co, an additional exchange of the aldehydic hydrogen took place. Over Fe, the hydrogen situated on the ..cap alpha.. carbon and the aldehydic hydrogen were exchanged equally. An attempt is made to relate the nature of the exchange to hydrogenation, decarbonylation, and hydrogenolysis and several reaction mechanisms are proposed in addition to the classical Horiuti-Polanyi mechanism, which is restricted to hydrogenation of the C-C double bond.

  15. Vector and tensor analysing powers in deuteron-proton breakup reactions at intermediate energies

    E-print Network

    D. Chiladze; J. Carbonell; S. Dymov; V. Glagolev; M. Hartmann; V. Hejny; A. Kacharava; I. Keshelashvili; A. Khoukaz; H. R. Koch; V. Komarov; P. Kulessa; A. Kulikov; G. Macharashvili; Y. Maeda; T. Mersmann; S. Merzliakov; S. Mikirtytchiants; A. Mussgiller; M. Nioradze; H. Ohm; F. Rathmann; R. Schleichert; H. J. Stein; H. Stroeher; Yu. Uzikov; S. Yaschenko; C. Wilkin

    2006-03-15

    Vector and tensor analysing powers of the d(pol)p->(pp)n (charge-exchange) and d(pol)p->(pn)p (non-charge-exchange) breakup reactions have been measured with the ANKE spectrometer at the COSY ring at a deuteron beam energy of 1170 MeV for small momentum transfers to the low excitation energy (pp) or (pn) systems. A quantitative understanding of the values of A_xx and A_yy for the charge-exchange reaction is provided by impulse approximation calculations. The data suggest that spin-flip isospin-flip transitions, which dominate the charge-exchange breakup of the deuteron, are also important in the non-charge-exchange reaction.

  16. Oil-absorbent cellulosic derivatives. [Cellulose-containing substance having cationic exchange properties and a quaternary ammonium salt

    SciTech Connect

    Fanta, G.F.; Doane, W.M.

    1986-08-12

    A composition is described for absorbing oil from oil-in-water emulsions comprising the reaction product of a cellulose-containing substance having cationic exchange properties and a fatty quaternary ammonium salt.

  17. Enzymatic fragmentation of cation exchange membrane bound immunoglobulin G.

    PubMed

    Yu, Deqiang; Ghosh, Raja

    2011-01-01

    Immunoglobulin G (IgG) was immobilized on a stack of microporous cation-exchange membranes and pulsed with pepsin solution. Fc fragment and its sub-fragments thus produced were removed along with the reaction flow-through, whereas F(ab')(2) which remained membrane bound could subsequently be eluted in a pure form using salt. The extent of IgG fragmentation and the apparent reaction rate constant were both significantly higher than in equivalent liquid phase reaction, presumably due to a combination of mass transport, steric, and substrate concentration effects. This approach of using a membrane surface as molecule cutting board could be attractive in niche applications such as integrated enzymatic reaction and purification processes involving macromolecular substrates. PMID:20949445

  18. Ion exchange technology assessment report

    SciTech Connect

    Duhn, E.F.

    1992-01-01

    In the execution of its charter, the SRS Ion Exchange Technology Assessment Team has determined that ion exchange (IX) technology has evolved to the point where it should now be considered as a viable alternative to the SRS reference ITP/LW/PH process. The ion exchange media available today offer the ability to design ion exchange processing systems tailored to the unique physical and chemical properties of SRS soluble HLW's. The technical assessment of IX technology and its applicability to the processing of SRS soluble HLW has demonstrated that IX is unquestionably a viable technology. A task team was chartered to evaluate the technology of ion exchange and its potential for replacing the present In-Tank Precipitation and proposed Late Wash processes to remove Cs, Sr, and Pu from soluble salt solutions at the Savannah River Site. This report documents the ion exchange technology assessment and conclusions of the task team.

  19. Ion exchange technology assessment report

    SciTech Connect

    Duhn, E.F.

    1992-12-31

    In the execution of its charter, the SRS Ion Exchange Technology Assessment Team has determined that ion exchange (IX) technology has evolved to the point where it should now be considered as a viable alternative to the SRS reference ITP/LW/PH process. The ion exchange media available today offer the ability to design ion exchange processing systems tailored to the unique physical and chemical properties of SRS soluble HLW`s. The technical assessment of IX technology and its applicability to the processing of SRS soluble HLW has demonstrated that IX is unquestionably a viable technology. A task team was chartered to evaluate the technology of ion exchange and its potential for replacing the present In-Tank Precipitation and proposed Late Wash processes to remove Cs, Sr, and Pu from soluble salt solutions at the Savannah River Site. This report documents the ion exchange technology assessment and conclusions of the task team.

  20. Kinetics of elementary atom and radical reactions. Progress report, December 1, 1981-November 30, 1982

    SciTech Connect

    Gordon, R J

    1982-08-02

    Research projects discussed include: the branching ratio for abstraction vs. exchange in the reaction D + HCl; kinetics of O + H/sub 2/; energy storage in polyatomic molecules; and optoacoustic measurements of ir absorption and relaxation in large molecules. (GHT)

  1. Iodine Clock Reaction

    NSDL National Science Digital Library

    This site allows the user to vary initial solution concentration and temperature for the iodine clock reaction. A simulation of the reaction lets reaction times be measured. The data can then be used to determine the order of reaction for the various components.

  2. Coupled acoustic-gravity field for dynamic evaluation of ion exchange with a single resin bead.

    PubMed

    Kanazaki, Takahiro; Hirawa, Shungo; Harada, Makoto; Okada, Tetsuo

    2010-06-01

    A coupled acoustic-gravity field is efficient for entrapping a particle at the position determined by its acoustic properties rather than its size. This field has been applied to the dynamic observation of ion-exchange reactions occurring in a single resin bead. The replacement of counterions in an ion-exchange resin induces changes in its acoustic properties, such as density and compressibility. Therefore, we can visually trace the advancement of an ion-exchange reaction as a time change in the levitation position of a resin bead entrapped in the field. Cation-exchange reactions occurring in resin beads with diameters of 40-120 microm are typically completed within 100-200 s. Ion-exchange equilibrium or kinetics is often evaluated with off-line chemical analyses, which require a batch amount of ion exchangers. Measurements with a single resin particle allow us to evaluate ion-exchange dynamics and kinetics of ions including those that are difficult to measure by usual off-line analyses. The diffusion properties of ions in resins have been successfully evaluated from the time change in the levitation positions of resin beads. PMID:20462180

  3. Improve heat exchanger leak detection

    SciTech Connect

    Pugh, T. (Amoco Production Co., Houston, TX (United States)); York, B.; Laxton, G.; Simpson, G.D. (Unichem International, Inc., The Woodlands, TX (United States))

    1993-11-01

    A quick and easy method identifies exchangers that leak hydrocarbons into cooling water. A portable, explosion-proof flame ionization detector (FID) measures volatile hydrocarbons off-gassing from an exchanger's cooling water. Now, a hydrocarbon processing industry (HPI) facility can perform a leak detection survey on heat exchangers on a routine schedule. Suspected leakers are identified earlier than with conventional leak-detection methods such as chlorine consumption and cooling water turbidity. Greater sensitivity to hydrocarbons enables a facility to be proactive -- not reactive -- on exchanger maintenance.

  4. ABC's of pion charge exchange. [Absorption, blocking, and correlations

    SciTech Connect

    Gibbs, W.R.; Kaufmann, W.B.; Siegel, P.B.

    1985-01-01

    Calculations of pion single charge exchange using the PWIA and DWIA are presented. Emphasis is given to the effects of absorbtion and blocking. A microscopic calculation of the 0/sup 0/ excitation and low energy angular distribution is in excellent agreement with the data. A fixed nucleon multiple scattering calculation of the pion double charge exchange reaction is presented. Various valence neutron wave functions are used, and the contributions of different spatial orientations of the last two neutrons to the reaction are examined. The DCX cross section is found to be very sensitive to the inclusion of correlations in the two-neutron wave function. Satisfactory agreement with DCX data on /sup 14/C can be obtained using a nucleonic picture of the nucleus.

  5. Disease Exchanges 20-365 Chapter 20. DISEASE EXCHANGES

    E-print Network

    Richerson, Peter J.

    Disease Exchanges 20-365 Chapter 20. DISEASE EXCHANGES Soldiers have rarely won wars. They more of history. Hans Zinsser (1935) I. Introduction A. Disease as an Example of Links Between Environment, Technology, & Biology We might say that disease is part of an "environment core," defined by analogy

  6. MIDDLE EAST TECHNICAL UNIVERSITY EXCHANGE PROGRAM A Semester Exchange Program

    E-print Network

    Suzuki, Masatsugu

    MIDDLE EAST TECHNICAL UNIVERSITY EXCHANGE PROGRAM A Semester Exchange Program All Courses or national origin. Revised 12/11 MIDDLE EAST TECHNICAL UNIVERSITY Middle East Technical University (METU.7 million. Long an important center of trade between the east and west because it lay along ancient caravan

  7. Direct measurements of the energy flux due to chemical reactions at the surface of a silicon sample interacting with a SF6 plasma

    E-print Network

    Boyer, Edmond

    1 Direct measurements of the energy flux due to chemical reactions at the surface of a silicon, France Abstract Energy exchanges due to chemical reactions between a silicon surface and a SF6 plasma obtained when only few reactions occur at the surface to show the part of chemical reactions. At 800 W

  8. The Engineering Exchange

    NSDL National Science Digital Library

    Matheson, Marshall

    2013-01-01

    Under the banner of "developed by engineers for engineers," the Engineering Exchange functions as a global educational networking community for engineers. The materials on the site are divided into eight primary areas, which include Groups, Videos, Images, Events, Blogs, and Resources. Sections such as the Top Blog Posts showcase some of the most popular insights, which include updates like Manufacturing Productivity Through Design Efficiency and technical pieces on engineering software. Moving on, the Groups area is a great way for visitors to learn from other professionals with sub-sections that include Green Engineering, Water & Wastewater, and Solar Power Development. The Videos section is another gem that features over 1400 items such as Additive Manufacturing: When will it arrive? and The Safest Key-Smart Key. Additionally, visitors can search all of the videos and create their own playlists.

  9. Biofuels Information Exchange

    NSDL National Science Digital Library

    Holmes, Tim

    As biofuels grow in importance, there is more interest in finding places where professionals, scientists, and policymakers with a passion for the subject can come together and exchange ideas. CABI, a non-profit science-based development and information organization, has created this website to allow just that to happen. What can you do on the site? Well, for starters you can peruse the "What's in the News" area to learn about timely reports from different news outlets and scholarly sources regarding biofuels technology. Dedicated users should sign up on the site so that they can create their own group to discuss shared interests with other colleagues on the site and so that they may create a profile. The site also has a blog, a section dedicated to relevant publications, and a RSS feed of activities from registered users.

  10. Monogroove liquid heat exchanger

    NASA Technical Reports Server (NTRS)

    Brown, Richard F. (Inventor); Edelstein, Fred (Inventor)

    1990-01-01

    A liquid supply control is disclosed for a heat transfer system which transports heat by liquid-vapor phase change of a working fluid. An assembly (10) of monogroove heat pipe legs (15) can be operated automatically as either heat acquisition devices or heat discharge sources. The liquid channels (27) of the heat pipe legs (15) are connected to a reservoir (35) which is filled and drained by respective filling and draining valves (30, 32). Information from liquid level sensors (50, 51) on the reservoir (35) is combined (60) with temperature information (55) from the liquid heat exchanger (12) and temperature information (56) from the assembly vapor conduit (42) to regulate filling and draining of the reservoir (35), so that the reservoir (35) in turn serves the liquid supply/drain needs of the heat pipe legs (15), on demand, by passive capillary action (20, 28).

  11. Origin of strong acidity in lanthanum-exchanged zeolites 

    E-print Network

    Carvajal Freese, Ralf R.

    1989-01-01

    compositions for the hydrocarbon process include Czo-C4o molecules comprised of single and fused aromatic rings, naphthene rings, and paraffins (3). These molecules are converted mainly by acid-catalyzed reactions, such as isomerization, polymerization...ORIGIN OF STRONG ACIDITY IN LANTHANUM- EXCHANGED ZEOLITES A Thesis by RALF R. CARVAJAL FREESE Submitted to the Office of Graduate Studies of Texas A&M University in the partial fulfillment of the requirements for the degree of MASTER...

  12. Microscopic calculations of charge-exchange nuclear modes

    SciTech Connect

    Fracasso, S., E-mail: Sara.Fracasso@mi.infn.it; Colo, G. [Dipartimento di Fisica dell'Universita degli Studi di Milano and INFN (Italy)

    2007-08-15

    Microscopic calculations of nuclear states excited by means of charge-exchange reactions and involving spin and isospin degrees of freedom, in particular, of the Gamow-Teller and the spin-dipole resonances, are discussed. The framework is a fully self-consistent nonrelativistic spherical quasiparticle random-phase approximation constructed on top of the Hartree-Fock-Bardeen-Cooper-Schrieffer approach. Our results are compared with available experimental data, and a critical discussion is attempted.

  13. Gas Exchange of Algae

    PubMed Central

    Ammann, Elizabeth C. B.; Lynch, Victoria H.

    1966-01-01

    Changes in the oxygen partial pressure of air over the range of 8 to 258 mm of Hg did not adversely affect the photosynthetic capacity of Chlorella pyrenoidosa. Gas exchange and growth measurements remained constant for 3-week periods and were similar to air controls (oxygen pressure of 160 mm of Hg). Oxygen partial pressures of 532 and 745 mm of Hg had an adverse effect on algal metabolism. Carbon dioxide consumption was 24% lower in the gas mixture containing oxygen at a pressure 532 mm of Hg than in the air control, and the growth rate was slightly reduced. Oxygen at a partial pressure of 745 mm of Hg decreased the photosynthetic rate 39% and the growth rate 37% over the corresponding rates in air. The lowered metabolic rates remained constant during 14 days of measurements, and the effect was reversible after this time. Substitution of helium or argon for the nitrogen in air had no effect on oxygen production, carbon dioxide consumption, or growth rate for 3-week periods. All measurements were made at a total pressure of 760 mm of Hg, and all gas mixtures were enriched with 2% carbon dioxide. Thus, the physiological functioning and reliability of a photosynthetic gas exchanger should not be adversely affected by: (i) oxygen partial pressures ranging from 8 to 258 mm of Hg; (ii) the use of pure oxygen at reduced total pressure (155 to 258 mm of Hg) unless pressure per se affects photosynthesis, or (iii) the inclusion of helium or argon in the gas environment (up to a partial pressure of 595 mm of Hg). PMID:5927028

  14. Reaction cycle and thermodynamics in bacteriorhodopsin

    NASA Technical Reports Server (NTRS)

    Lanyi, J. K.

    1992-01-01

    Light causes the all-trans to 13-cis isomerization of the retinal in bacteriorhodopsin; the thermal relaxation leading back to the initial state drives proton transport first via proton transfer between the retinal Schiff base and D85 and then between the Schiff base and D96. The reaction sequence and thermodynamics of this photocycle are described by measuring time-resolved absorption changes with a gated multichannel analyzer between 100 ns and 100 ms, at six temperatures between 5 degrees C and 30 degrees C. Analysis of the energetics of the chromophore reaction sequence is on the basis of a recently proposed model (Varo & Lanyi, Biochemistry 30, 5016-5022, 1991) which consists of a single cycle and many reversible reactions: BR -hv-->K<==>L<==>M1-->M2<==>N<==>O-->BR. The existence of the M1-->M2 reaction, which functions as the switch in the proton transfer, is confirmed by spectroscopic evidence. The calculated thermodynamic parameters indicate that the exchange of free energy between the protein and the protons is at the switch step. Further, a large entropy decrease at this reaction suggests a protein conformation change which will conserve delta G for driving the completion of the reaction cycle. The results provide insights to mechanism and energy coupling in this system, with possible relevance to the general question of how ion pumps function.

  15. Plate heat exchanger design theory

    Microsoft Academic Search

    R. K. Shah; A. S. Wanniarachchi

    1991-01-01

    Plate heat exchangers are commonly used in hygienic applications as well as in chemical processing and other industrial applications. Pertinent information on plate exchangers from a designer's point of view is summarized to provide a basic insight into performance behavior of chevron plates. Basic design methods are presented and a method of coupling between heat transfer and pressure drop is

  16. Exchange currents in nuclear physics

    Microsoft Academic Search

    E. A. Ivanov; E. Truhlik

    1981-01-01

    The low-energy theorems for ''soft'' currents and pions are used to construct single-nucleon pion production amplitudes and, on their basis, two-particle operators of exchange currents. The connection between the exchange currents and the structure of the nuclear potential is analyzed. A critical comparison of the theory with the experimental data is made.

  17. Mirage of Floating Exchange Rates

    Microsoft Academic Search

    Carmen M. Reinhart

    2000-01-01

    This note summarizes some of the highlights of my longer paper with Guillermo Calvo”Fear of Floating.” Many emerging market countries have suffered financial crises. One view blames soft pegs for these crises. Adherents to that view suggest that countries move to corner solutions--hard pegs or floating exchange rates. We analyze the behavior of exchange rates, reserves, and interest rates to

  18. PHOSPHORUS EXCHANGE IN MARINE PHYTOPLANKTON

    E-print Network

    PHOSPHORUS EXCHANGE IN MARINE PHYTOPLANKTON BY THEODORE R. RICE FISHERY BULLETIN 80 UNITED STATES;ABSTRACT Phosphorus exchange in Nitzschia· clostai'iu.In, isoiated and grown in pure culture, was demunstrated by using rudioactive phosphorus find was ~h()\\\\"n to "IlI'Y with changes in the phosphorus

  19. Heusler alloys: Tuning exchange bias

    NASA Astrophysics Data System (ADS)

    Nordblad, Per

    2015-07-01

    Exchange bias is a magnetic phenomenon that has facilitated the ever-increasing storage density of magnetic recording systems. The finding of high tunable exchange bias in certain Heusler alloys indicates new routes for the design of rare-earth-free hard magnetic materials.

  20. The liquid droplet heat exchanger

    Microsoft Academic Search

    A. P. Bruckner

    1982-01-01

    Direct contact heat exchange between a gas and a molten metal dispersed into droplets offers an attractive new approach to increasing the efficiency and decreasing the specific weight of thermal power cycles for space applications. The ability of a droplet heat exchanger to transfer heat directly from a liquid metal to a working gas over a wide temperature range circumvents

  1. Inside this issue: Ogmius Exchange

    E-print Network

    Colorado at Boulder, University of

    Inside this issue: Ogmius Exchange The Cherry Pick By Roger Pielke, Jr. 1 Center News · Bob.edu/ogmius. Ogmius Exchange The Cherry Pick By Roger Pielke, Jr. L awyers get paid considerable sums to do it be OK, right? "It" refers to the cherry pick -- the careful selection of information to buttress

  2. GXL: Toward a Standard Exchange Format

    Microsoft Academic Search

    Richard C. Holt; Andreas Winter; Andy Schiirr

    2000-01-01

    This paper describes ongoing work toward the devel- opment of a standard software exchange format (SEF), for exchanging information among tools that analyze com- puter programs. A particular exchange format called GXL (Graph Exchange Language) is proposed. GXL can be viewed as a merger of well known formats (e. g. GraX, PRO- GRES, RPA, RSF, and TA) for exchanging typed,

  3. Surface Exchange and Bulk Diffusivity of LSCF as SOFC Cathode: Electrical Conductivity Relaxation and Isotope Exchange Characterizations

    SciTech Connect

    Li, Yihong; Gerdes, Kirk; Horita, Teruhisa; Liu, Xingbo

    2013-05-05

    The oxygen diffusion coefficient (D) and surface exchange coefficient (k) of a typical SOFC cathode material, La{sub 0.6}Sr{sub 0.4}Co{sub 0.2}Fe{sub 0.8}O{sub 3-?} (LSCF) were characterized by both electrical conductivity relaxation (ECR) and oxygen isotope exchange (IE) methods. Conductivity relaxation experiments were conducted at 800°C for small step changes in partial pressure of oxygen (P{sub O{sub 2}} ), both decreasing and increasing, from 0.02 atm to 0.20 atm. The results revealed P{sub O{sub 2}} dependent hysteresis with the reduction process requiring more equilibration time than oxidation. Analysis of the experimental data indicated that the surface exchange coefficient is a function of the final oxygen partial pressure in an isothermal system. In addition, both forward and backward oxygen reduction reaction constants, which are vital for the fundamental understanding of SOFC cathode reaction mechanisms, are investigated based on the relationship between surface exchange coefficient and P{sub O{sub 2}} . The direct comparisons between the results from both ECR and IE were presented and the possible experimental errors in both methods were discussed.

  4. High Temperature Heat Exchanger Project

    SciTech Connect

    Anthony E. Hechanova, Ph.D.

    2008-09-30

    The UNLV Research Foundation assembled a research consortium for high temperature heat exchanger design and materials compatibility and performance comprised of university and private industry partners under the auspices of the US DOE-NE Nuclear Hydrogen Initiative in October 2003. The objectives of the consortium were to conduct investigations of candidate materials for high temperature heat exchanger componets in hydrogen production processes and design and perform prototypical testing of heat exchangers. The initial research of the consortium focused on the intermediate heat exchanger (located between the nuclear reactor and hydrogen production plan) and the components for the hydrogen iodine decomposition process and sulfuric acid decomposition process. These heat exchanger components were deemed the most challenging from a materials performance and compatibility perspective

  5. Structural Insight into the Ion-Exchange Mechanism of the Sodium/Calcium Exchanger

    SciTech Connect

    Liao, Jun; Li, Hua; Zeng, Weizhong; Sauer, David B.; Belmares, Ricardo; Jiang, Youxing (UTSMC)

    2012-06-19

    Sodium/calcium (Na{sup +}/Ca{sup 2+}) exchangers (NCX) are membrane transporters that play an essential role in maintaining the homeostasis of cytosolic Ca{sup 2+} for cell signaling. We demonstrated the Na{sup +}/Ca{sup 2+}-exchange function of an NCX from Methanococcus jannaschii (NCX{_}Mj) and report its 1.9 angstrom crystal structure in an outward-facing conformation. Containing 10 transmembrane helices, the two halves of NCX{_}Mj share a similar structure with opposite orientation. Four ion-binding sites cluster at the center of the protein: one specific for Ca{sup 2+} and three that likely bind Na{sup +}. Two passageways allow for Na{sup +} and Ca{sup 2+} access to the central ion-binding sites from the extracellular side. Based on the symmetry of NCX{_}Mj and its ability to catalyze bidirectional ion-exchange reactions, we propose a structure model for the inward-facing NCX{_}Mj.

  6. Role of Cu in the deuterium addition and exchange of propene over Pd-Cu and Pt-Cu alloy catalysts

    Microsoft Academic Search

    Shuichi Naito; Mitsutoshi Tanimoto

    1989-01-01

    The reaction intermediate and the reaction mechanism of deuterium addition and exchange of propene over a bimetallic alloy have been studied by microwave spectroscopy as well as by kinetic measurements. The isotopic distribution pattern of monodeuteropropene formed during the reaction changed considerably by alloying Pd or Pt with Cu and resembled that over Cu metal. However, the turnover frequency and

  7. Fractal Reaction Kinetics

    NASA Astrophysics Data System (ADS)

    Kopelman, Raoul

    1988-09-01

    Classical reaction kinetics has been found to be unsatisfactory when the reactants are spatially constrained on the microscopic level by either walls, phase boundaries, or force fields. Recently discovered theories of heterogeneous reaction kinetics have dramatic consequences, such as fractal orders for elementary reactions, self-ordering and self-unmixing of reactants, and rate coefficients with temporal ``memories.'' The new theories were needed to explain the results of experiments and supercomputer simulations of reactions that were confined to low dimensions or fractal dimensions or both. Among the practical examples of ``fractal-like kinetics'' are chemical reactions in pores of membranes, excitation trapping in molecular aggregates, exciton fusion in composite materials, and charge recombination in colloids and clouds. Diffusion-controlled reactions with geometrical constraints, as found in heterogeneous kinetics, may be described by reactions on fractal domains. The hallmarks of ``fractal-like'' reactions are anomalous reaction orders and time-dependent reaction rate ``constants.'' These anomalies stem from the nonrandomness of the reactant distributions in low dimensions. For homo-bimolecular reactions (A + A --> Pr) the distribution is partially ordered, for example, quasi-periodic. However, for hetero-bimolecular reactions (A + B --> Pr) the reactants segregate. Theory, simulations, and experiments are interrelated through the formalism of fractal reaction kinetics (42).

  8. Conversion of ion exchange resin to various functional resins and the application in the field of pharmaceutical sciences

    NASA Astrophysics Data System (ADS)

    Nakayama, Morio

    Ion exchange resins are widely used for separating ions in the solution, desalination, removal of impurities, and etc. Giving a new function to these ion exchange resins enables the application in more various fields. Until now, we carried out the research work about the following 5 project.: (1) Conversion of ion exchange resins into selective adsorbents by using low molecular reagents, which possess capabilities of a selective reaction with target ions, ion exchange reaction with the ion exchange resin and strong physical adsorption to the ion exchange resin. (2) Synthesis of resins for ion exchange high performance liquid chromatography (IEHPLC) and the analysis of biomaterials. (3) Development of insoluble macromolecular Sn(II) complex based on the aminophosphonic acid type ion exchange resin and its application to the 99mTc labeling of proteins. (4) Development of a new 68Ge-68Ga generator using N-methylglucamine type organic polymer as the adsorbent for 68Ge and production of 68Ga for PET. (5) Preparation of an ion-exchangeable polymer bead wrapped with bilayer membrane structures. In this paper, the application of various functional resins prepared based on ion exchange resin in the field of pharmaceutical sciences has been summarized.

  9. Oxacycle Synthesis via Intramolecular Reaction of Carbanions and Peroxides

    PubMed Central

    2015-01-01

    The intramolecular reaction of dialkyl peroxides with carbanions, generated via chemoselective metal-heteroatom exchange or deprotonation, provides a new approach to cyclic ethers. Applied in tandem with C–C bond formation, the strategy enables a one-step annelation to form oxaospirocycles. PMID:24702123

  10. Redox reactions with empirical potentials: atomistic battery discharge simulations

    E-print Network

    Mueser, Martin

    Redox reactions with empirical potentials: atomistic battery discharge simulations Wolf B. Dapp1, a ionization state to each atom. Along with exchanging partial charges across bonds, atoms can swap integer charges. With redoxSQE we study the discharge behavior of a nano-battery, and demonstrate

  11. Ion exchange equilibria of heavy metals in aqueous solution on new chelating resins of sporopollenin

    Microsoft Academic Search

    M. Ersoz; E. Pehlivan; H. J. Duncan; S. Yildiz; M. Pehlivan

    1995-01-01

    Studies have been conducted on the sorption of several heavy metal ions Cu(II), Ni(II), Zn(II), Cd(II) and Al(III) from aqueous solutions on the new chelating exchangers of sporopollenin (Lycopodium clavatum) as a function of pH at several temperatures between 20 and 50°C. The novel metal-ligand exchange resins possessing oxime and carboxylic acid side arm functionality were prepared through the reaction

  12. Surface Exchange and Shape Transitions of PbSe Quantum Dots during Overgrowth

    SciTech Connect

    Abtin, L.; Springholz, G. [Institut fuer Halbleiter- und Festkoerperphysik, Johannes Kepler Universitaet, A-4040 Linz (Austria); Holy, V. [Charles University, Faculty of Mathematics and Physics, Prague (Czech Republic)

    2006-12-31

    Epitaxial overgrowth of PbSe quantum dots is shown to drastically affect their shape and composition due to anion exchange reactions. As shown by scanning tunneling microscopy, for PbTe capping layers this results in a complete truncation of the dots. Introduction of EuTe into the cap layer leads to an effective suppression of the anion exchange process. This preserves the original dot pyramids and induces a large stress concentration on the surface which further alters the overgrowth process.

  13. Quantitative evaluation of the nucleophilicity of some ethers and metal halides in radical exchange between phenyllithium and bromobenzene

    SciTech Connect

    Batalov, A.P.

    1987-05-01

    The authors discuss the results of a study of the effect of alkali metal and tetramethylammonium halides (MX) on the rate of radical exchange between phenyllithium and bromobenzene in diethyl ether. The phenyllithium was synthesized by an exchange reaction, from ethyllithium and triphenylantimony. The MX concentration (0.15 mole/liter) in all cases was an excess as compared with the phenyllithium concentration (0.1 mole/liter). In the present work, /sup 14/C-bromobenzene was used. The rate of exchange was followed from the rise in radioactivity of the benzoic acid isolated after carbonation of the reaction mixture.

  14. Microscale Thermite Reactions.

    ERIC Educational Resources Information Center

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

    1998-01-01

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

  15. Anaphylaxis-Like Reactions

    MedlinePLUS

    ... antibody) is involved. These reactions are called anaphylactoid (meaning anaphylaxis-like) reactions. While the immune system must ... Find Programs & Services Make a Donation Find a Location Connect With Us View Events Calendar Read the ...

  16. Electrically switched ion exchange

    SciTech Connect

    Lilga, M.A. [Pacific Northwest National Lab., Richland, WA (United States); Schwartz, D.T.; Genders, D.

    1997-10-01

    A variety of waste types containing radioactive {sup 137}Cs are found throughout the DOE complex. These waste types include water in reactor cooling basins, radioactive high-level waste (HLW) in underground storage tanks, and groundwater. Safety and regulatory requirements and economics require the removal of radiocesium before these wastes can be permanently disposed of. Electrically Switched Ion Exchange (ESIX) is an approach for radioactive cesium separation that combines IX and electrochemistry to provide a selective, reversible, and economic separation method that also produces little or no secondary waste. In the ESIX process, an electroactive IX film is deposited electrochemically onto a high-surface area electrode, and ion uptake and elution are controlled directly by modulating the potential of the film. For cesium, the electroactive films under investigation are ferrocyanides, which are well known to have high selectivities for cesium in concentrated sodium solutions. When a cathode potential is applied to the film, Fe{sup +3} is reduced to the Fe{sup +2} state, and a cation must be intercalated into the film to maintain charge neutrality (i.e., Cs{sup +} is loaded). Conversely, if an anodic potential is applied, a cation must be released from the film (i.e., Cs{sup +} is unloaded). Therefore, to load the film with cesium, the film is simply reduced; to unload cesium, the film is oxidized.

  17. Energy-Exchange Project

    SciTech Connect

    Not Available

    1982-04-01

    The purpose of the study was to determine what energy savings can be achieved by coordinating the resources and requirements of two facilities, the 26th Ward Water Pollution Control Plant (WPCP) and a housing development named Starrett City with its own total energy system. It was determined that three energy exchange options were economically and technically feasible. These include: the transfer of digester gas produced at the 26th Ward to the boilers at the Starrett City's total energy plant (TEP); the transfer of hot water heated at the TEP to the 26th Ward for space and process heating; and the transfer of coal effluent waste water from the 26th Ward to the condenser cooling systems at the TEP. Technical information is presented to support the findings. The report addresses those tasks of the statement of work dedicated to data acquisition, analysis, and energy conservation strategies internal to the Starrett City TEP and the community it supplies as well as to the 26th Ward WPCP. (MCW)

  18. Chemical Reactions and Stoichiometry

    NSDL National Science Digital Library

    2012-07-31

    In this activity, students explore reactions in which chemical bonds are formed and broken. Students experiment with changing the temperature and the concentration of the atoms in order to see how these affect reaction rates. They also learn how to communicate what happens during a chemical reaction by writing the ratios of reactants and products, known as stoichiometry.

  19. Explaining competitive reaction effects

    Microsoft Academic Search

    Peter S. H. Leeflang; Dick R. Wittink

    2001-01-01

    Changes in promotional expenditure decisions for a brand, as in other marketing decisions, should be based on the expected impact on purchase and consumption behavior as well as on the likely reactions by competitors. Purchase behavior may be predicted from estimated demand functions. Competitive reactions can be anticipated based on estimated reaction functions, which show how changes in an instrument

  20. Custom, contract, and kidney exchange.

    PubMed

    Healy, Kieran; Krawiec, Kimberly D

    2012-01-01

    In this Essay, we examine a case in which the organizational and logistical demands of a novel form of organ exchange (the nonsimultaneous, extended, altruistic donor (NEAD) chain) do not map cleanly onto standard cultural schemas for either market or gift exchange, resulting in sociological ambiguity and legal uncertainty. In some ways, a NEAD chain resembles a form of generalized exchange, an ancient and widespread instance of the norm of reciprocity that can be thought of simply as the obligation to “pay it forward” rather than the obligation to reciprocate directly with the original giver. At the same time, a NEAD chain resembles a string of promises and commitments to deliver something in exchange for some valuable consideration--that is, a series of contracts. Neither of these salient "social imaginaries" of exchange--gift giving or formal contract--perfectly meets the practical demands of the NEAD system. As a result, neither contract nor generalized exchange drives the practice of NEAD chains. Rather, the majority of actual exchanges still resemble a simpler form of exchange: direct, simultaneous exchange between parties with no time delay or opportunity to back out. If NEAD chains are to reach their full promise for large-scale, nonsimultaneous organ transfer, legal uncertainties and sociological ambiguities must be finessed, both in the practices of the coordinating agencies and in the minds of NEAD-chain participants. This might happen either through the further elaboration of gift-like language and practices, or through a creative use of the cultural form and motivational vocabulary, but not necessarily the legal and institutional machinery, of contract. PMID:23461002

  1. Entanglement Exchange and Bohmian Mechanics

    E-print Network

    Nick Huggett; Tiziana Vistarini

    2009-05-25

    This paper analyses the phenomenon of entanglement exchange in Bohm's pilot wave interpretation of quantum mechanics. The interesting feature of the phenomenon is that systems become entangled without causal interaction; hence it is a useful situation for investigating the unique nature of interaction in Bohmian mechanics. The first two sections introduce, respectively, entanglement exchange in the standard interpretation of quantum mechanics, and the basic principles of Bohmian mechanics. The next section shows that the Bohmian interpretation makes the same experimental predictions about entanglement exchange as the standard one. The final section draws some conclusions about interactions and entanglement in Bohmian mechanics.

  2. 76 FR 72492 - Self-Regulatory Organizations; BATS Exchange, Inc.; BATS Y-Exchange, Inc.; NASDAQ OMX BX, Inc...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-11-23

    ...Chicago Board Options Exchange, Incorporated; C2 Options Exchange, Incorporated...Exchange, Inc.; Financial Industry Regulatory...CBOE''), C2 Options Exchange, Incorporated...EDGX''), Financial Industry...

  3. 77 FR 20451 - Self-Regulatory Organizations; BATS Exchange, Inc.; BATS Y-Exchange, Inc.; NASDAQ OMX BX, Inc...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-04-04

    ...Chicago Board Options Exchange, Incorporated; C2 Options Exchange, Incorporated...Exchange, Inc.; Financial Industry Regulatory...CBOE''), C2 Options Exchange, Incorporated...EDGX''), Financial Industry...

  4. Reaction coordinates for electron transfer reactions

    SciTech Connect

    Rasaiah, Jayendran C. [Department of Chemistry, University of Maine, Orono, Maine 04469 (United States); Zhu Jianjun [Department of Chemistry, State University of New York, Stonybrook, New York 11790 (United States) and Department of Chemistry, Henan Normal University, Xinxiang, Henan (China)

    2008-12-07

    The polarization fluctuation and energy gap formulations of the reaction coordinate for outer sphere electron transfer are linearly related to the constant energy constraint Lagrangian multiplier m in Marcus' theory of electron transfer. The quadratic dependence of the free energies of the reactant and product intermediates on m and m+1, respectively, leads to similar dependence of the free energies on the reaction coordinates and to the same dependence of the activation energy on the reorganization energy and the standard reaction free energy. Within the approximations of a continuum model of the solvent and linear response of the longitudinal polarization to the electric field in Marcus' theory, both formulations of the reaction coordinate are expected to lead to the same results.

  5. Marriage exchanges, seed exchanges, and the dynamics of manioc diversity

    PubMed Central

    Delêtre, Marc; McKey, Doyle B.; Hodkinson, Trevor R.

    2011-01-01

    The conservation of crop genetic resources requires understanding the different variables—cultural, social, and economic—that impinge on crop diversity. In small-scale farming systems, seed exchanges represent a key mechanism in the dynamics of crop genetic diversity, and analyzing the rules that structure social networks of seed exchange between farmer communities can help decipher patterns of crop genetic diversity. Using a combination of ethnobotanical and molecular genetic approaches, we investigated the relationships between regional patterns of manioc genetic diversity in Gabon and local networks of seed exchange. Spatially explicit Bayesian clustering methods showed that geographical discontinuities of manioc genetic diversity mirror major ethnolinguistic boundaries, with a southern matrilineal domain characterized by high levels of varietal diversity and a northern patrilineal domain characterized by low varietal diversity. Borrowing concepts from anthropology—kinship, bridewealth, and filiation—we analyzed the relationships between marriage exchanges and seed exchange networks in patrilineal and matrilineal societies. We demonstrate that, by defining marriage prohibitions, kinship systems structure social networks of exchange between farmer communities and influence the movement of seeds in metapopulations, shaping crop diversity at local and regional levels. PMID:22042843

  6. Nonlocal exchange correlation in screened-exchange densityfunctional methods

    SciTech Connect

    Lee, Byounghak; Wang, Lin-Wang; Spataru, Catalin D.; Louie,Steven G.

    2007-04-22

    We present a systematic study on the exchange-correlationeffects in screened-exchange local density functional method. Toinvestigate the effects of the screened-exchange potential in the bandgap correction, we have compared the exchange-correlation potential termin the sX-LDA formalism with the self-energy term in the GWapproximation. It is found that the band gap correction of the sX-LDAmethod primarily comes from the downshift of valence band states,resulting from the enhancement of bonding and the increase of ionizationenergy. The band gap correction in the GW method, on the contrary, comesin large part from the increase of theconduction band energies. We alsostudied the effects of the screened-exchange potential in the totalenergy by investigating the exchange-correlation hole in comparison withquantum Monte Carlo calculations. When the Thomas-Fermi screening isused, the sX-LDA method overestimates (underestimates) theexchange-correlation hole in short (long) range. From theexchange-correlation energy analysis we found that the LDA method yieldsbetter absolute total energy than sX-LDA method.

  7. Unraveling the chemical dynamics of bimolecular reactions of ground state boron atoms, B(2

    E-print Network

    Kaiser, Ralf I.

    Unraveling the chemical dynamics of bimolecular reactions of ground state boron atoms, B(2 PjArticle on the web 8th March 2004 The reaction dynamics of atomic boron, B(2 P), with acetylene, C2H2(X 1 Sg þ molecular beams technique. Only the atomic boron versus hydrogen atom exchange pathway was observed. Forward

  8. What prompts Japan to intervene in the Forex market? A new approach to a reaction function

    Microsoft Academic Search

    Takatoshi Ito; Tomoyoshi Yabu

    2007-01-01

    This paper estimates and analyzes the reaction function of Japanese intervention in the foreign exchange (Forex) markets, using daily Japanese intervention data from April 1, 1991 to December 31, 2002. A theoretical friction model is adopted to describe the intervention as cost-minimizing behavior. An ordered probit model, consistent with the theoretical model, is employed to estimate authorities' reaction function. A

  9. Design criteria for extraction with chemical reaction and liquid membrane permeation

    NASA Technical Reports Server (NTRS)

    Bart, H. J.; Bauer, A.; Lorbach, D.; Marr, R.

    1988-01-01

    The design criteria for heterogeneous chemical reactions in liquid/liquid systems formally correspond to those of classical physical extraction. More complex models are presented which describe the material exchange at the individual droplets in an extraction with chemical reaction and in liquid membrane permeation.

  10. O-atom exchange in O( 3P) + H 2O( 1A 1) collisions

    NASA Astrophysics Data System (ADS)

    Braunstein, Matthew; Conforti, Patrick F.

    2012-01-01

    Global potential energy surfaces for the three lowest electronic triplet states of O(3P) + H2O(1A1) are used to explore two unusual reaction pathways, not previously identified. Both pathways go through a D2h rhombus geometry, with zero potential gradient and two imaginary frequencies. Motion along one imaginary frequency leads to O + H2O, while motion along the other leads to OH + OH. In each case, an O-atom is exchanged. Classical trajectory methods are used to compute exchange cross sections up to 11 km s-1. Transition state theory rate constants for O-atom exchange processes are also computed.

  11. Reaction efficiency effects on binary chemical reactions.

    PubMed

    Lazaridis, Filippos; Savara, Aditya; Argyrakis, Panos

    2014-09-14

    We study the effect of the variation of reaction efficiency in binary reactions. We use the well-known A + B ? 0 model, which has been extensively studied in the past. We perform simulations on this model where we vary the efficiency of reaction, i.e., when two particles meet they do not instantly react, as has been assumed in previous studies, but they react with a probability ?, where ? is in the range 0 < ? < 1. Our results show that at small ? values the system is reaction limited, but as ? increases it crosses over to a diffusion limited behavior. At early times, for small ? values, the particle density falls slower than for larger ? values. This fall-off goes over a crossover point, around the value of ? = 0.50 for high initial densities. Under a variety of conditions simulated, we find that the crossover point was dependent on the initial concentration but not on the lattice size. For intermediate and long times simulations, all ? values (in the depleted reciprocal density versus time plot) converge to the same behavior. These theoretical results are useful in models of epidemic reactions and epidemic spreading, where a contagion from one neighbor to the next is not always successful but proceeds with a certain probability, an analogous effect with the reaction probability examined in the current work. PMID:25217900

  12. Encouragement Exchange: Avoiding Therapist Burnout.

    ERIC Educational Resources Information Center

    Evans, Timothy D.; Villavisanis, Robert

    1997-01-01

    States that therapists need to take care of their own mental health in order to avoid burnout. Discusses the encouragement exchange, a group setting where therapists help each other deal with stress. Provides a case example. (MKA)

  13. Optimization of Heat Exchanger Cleaning 

    E-print Network

    Siegell, J. H.

    1986-01-01

    The performance of heat integration systems is quantified in terms of the amount of heat that is recovered. This decreases with time due to increased fouling of the heat exchange surface. Using the "Total Fouling Related Expenses (TFRE)" approach...

  14. NTU Incoming Exchange/Visiting

    E-print Network

    Wu, Yih-Min

    Admin. Building) · Fee payment for the 2nd Semester of your exchange period · General Service Division"+MMDD.) NTU webmail (300MB) Internet space (300MB) Wireless service login #12;NTU Wireless Login Page #12

  15. Interference-Resilient Information Exchange

    E-print Network

    Newport, Calvin Charles

    This paper presents an efficient protocol for reliably exchanging information in a single-hop, multi-channel radio network subject to unpredictable interference. We model the interference by an adversary that can simultaneously ...

  16. Vitrification of ion exchange resins

    DOEpatents

    Cicero-Herman, Connie A. (Aiken, SC); Workman, Rhonda Jackson (North Augusta, SC)

    2001-01-01

    The present invention relates to vitrification of ion exchange resins that have become loaded with hazardous or radioactive wastes, in a way that produces a homogenous and durable waste form and reduces the disposal volume of the resin. The methods of the present invention involve directly adding borosilicate glass formers and an oxidizer to the ion exchange resin and heating the mixture at sufficient temperature to produce homogeneous glass.

  17. Anion exchange polymer electrolytes

    DOEpatents

    Kim, Yu Seung; Kim, Dae Sik; Lee, Kwan-Soo

    2013-07-23

    Solid anion exchange polymer electrolytes and compositions comprising chemical compounds comprising a polymeric core, a spacer A, and a guanidine base, wherein said chemical compound is uniformly dispersed in a suitable solvent and has the structure: ##STR00001## wherein: i) A is a spacer having the structure O, S, SO.sub.2, --NH--, --N(CH.sub.2).sub.n, wherein n=1-10, --(CH.sub.2).sub.n--CH.sub.3--, wherein n=1-10, SO.sub.2-Ph, CO-Ph, ##STR00002## wherein R.sub.5, R.sub.6, R.sub.7 and R.sub.8 each are independently --H, --NH.sub.2, F, Cl, Br, CN, or a C.sub.1-C.sub.6 alkyl group, or any combination of thereof; ii) R.sub.9, R.sub.10, R.sub.11, R.sub.12, or R.sub.13 each independently are --H, --CH.sub.3, --NH.sub.2, --NO, --CH.sub.nCH.sub.3 where n=1-6, HC.dbd.O--, NH.sub.2C.dbd.O--, --CH.sub.nCOOH where n=1-6, --(CH.sub.2).sub.n--C(NH.sub.2)--COOH where n=1-6, --CH--(COOH)--CH.sub.2--COOH, --CH.sub.2--CH(O--CH.sub.2CH.sub.3).sub.2, --(C.dbd.S)--NH.sub.2, --(C.dbd.NH)--N--(CH.sub.2).sub.nCH.sub.3, where n=0-6, --NH--(C.dbd.S)--SH, --CH.sub.2--(C.dbd.O)--O--C(CH.sub.3).sub.3, --O--(CH.sub.2).sub.n--CH--(NH.sub.2)--COOH, where n=1-6, --(CH.sub.2).sub.n--CH.dbd.CH wherein n=1-6, --(CH.sub.2).sub.n--CH--CN wherein n=1-6, an aromatic group such as a phenyl, benzyl, phenoxy, methylbenzyl, nitrogen-substituted benzyl or phenyl groups, a halide, or halide-substituted methyl groups; and iii) wherein the composition is suitable for use in a membrane electrode assembly.

  18. Individual radiosensitivity and its daily variations. [leukocyte reaction to epinephrine load

    NASA Technical Reports Server (NTRS)

    Druzhinin, Y. N.; Grigoryev, Y. G.; Podluzhnaya, G. N.; Pospishil, M.

    1974-01-01

    The effectiveness of determining individual radiosensitivity of rats by total gas exchange measurements, studies of Na/K content in urine, and the reaction of leukocytes to intra-abdominal administration of epinephrine, was studied. The most indicative results of predicting individual reaction to radiation were obtained by the leukocyte reaction to epinephrine load; however, changes in the leukocyte content of peripheral blood after epinephrine administration depended on the initial level during the day.

  19. Recovery of propylene glycol from dilute aqueous solutions via reversible reaction with aldehydes

    Microsoft Academic Search

    R. R. Broekhuis; S. Lynn; C. J. King

    1993-01-01

    A means is proposed for separating propylene glycol and other compounds bearing multiple hydroxyl groups by reversible chemical reaction. Glycols react with aldehydes in cyclic acetalization reactions to form substituted dioxolanes. Propylene glycol reacts with formaldehyde and acetaldehyde to form 4-methyl-1,3-dioxolane and 2,4-dimethyl-1,3-dioxolane. The reaction is catalyzed homogeneously by strong mineral acids or heterogeneously by cation exchange resins in the

  20. R-matrix analysis of the /sup 7/Li system with peripheral channel overlap exchange effects

    SciTech Connect

    Hale, G.M.

    1985-01-01

    The parameters of an R-matrix analysis that includes data for all reactions open in the /sup 7/Li system at E/sub x/ less than or equal to 10 MeV suggest that deuteron exchange contributes to the low-energy /sup 6/Li(n,t) reaction. A method for including this mechanism directly in the theory is discussed and preliminary results are given.

  1. Microwave-assisted aliphatic fluorine–chlorine exchange using triethylamine trihydrofluoride (TREAT-HF)

    Microsoft Academic Search

    Jennifer M. Kremsner; Michael Rack; Christian Pilger; C. Oliver Kappe

    2009-01-01

    Aliphatic fluorine–chlorine exchange reactions can be performed under microwave conditions using TREAT-HF as a mild and selective fluorination reagent. The highly polar TREAT-HF couples efficiently with microwave irradiation and reaction temperatures of 250°C can be reached within 30s. Under these conditions dichloromethyl- and trichloromethyl substrates can be converted into the corresponding fluoro analogs within 5min. In order to prevent corrosion

  2. Inverse Modeling of Tracer Tests in Streams Undergoing Hyporheic Exchange

    NASA Astrophysics Data System (ADS)

    Liao, Zijie; Arie Cirpka, Olaf

    2010-05-01

    Hyporheic exchange has been identified as a key process in solute transport, biogeochemical cycling, and ecosystem functioning of streams. Physical solute transport through the hyporheic zone may be characterized by the total flux of water exchange and the distribution of hyporheic travel times. The classical method of obtaining travel-time distributions is an artificial-tracer experiment, in which an easy to detect compound is injected into the river, and the breakthrough curve (BTC) is measured at an observation point further downstream in the river. This BTC is affected by in-stream transport and hyporheic exchange as expressed in the transient storage model for linear solute transport in rivers undergoing hyporheic exchange: (? ) ?c+ v-?c- D ?2c-= q tp(?)c(t- ?)exp(- ??)d? - c(t) + q (c - c(t)) ?t ?x ?x2 he 0 in in (1) in which v and D are the velocity and dispersion coefficient, respectively, qhe is the hyporheic exchange flux, ? is the travel-time coordinate in the hyporheic zone, p(?) is the probability density function of ?, ? is a first-order rate coefficient quantifying potential decay within the hyporheic zone, qin expresses lateral inflow, and cin is the corresponding concentration within that inflow. The target quantities are the exchange flux qhe and the nonnegative travel time distribution p(?) in the hyporheic zone. Common transient storage models use parametric distribution functions, such as the exponential, power-law, or log-normal distributions. By predefining the functional form of p(?), however, important features such as multimodality may remain unnoticed. We present a nonparametric approach of obtaining p(?) jointly with the other transport parameters by fitting BTCs of conservative and reactive solutes. For regularization p(?) is assumed autocorrelated, and nonnegativity is enforced by the method of Lagrange multipliers. The method extends a nonparametric deconvolution approach for the determination of transfer functions. It requires successive linearization (Gauss-Newton scheme), stabilized by a line-search, and forward simulation in the Laplace domain with numerical back-transformation. Once the hyporheic travel-time distribution p(?) has been identified, the transport model can be extended to include nonlinear reactions of river-borne compound within the hyporheic zone thus facilitating the simulation of biogeochemical cycling in streams undergoing hyporheic exchange. This method has been tested by virtual conservative and reactive tracer experiments undergoing hyporheic exchange. Joint inversion of conservative and reactive tracer BTCs is essential for distinguishing the effects of in-stream dispersion from hyporheic exchange. Applications to field data are on the way.

  3. Krypton charge exchange cross sections for Hall effect thruster models

    NASA Astrophysics Data System (ADS)

    Hause, Michael L.; Prince, Benjamin D.; Bemish, Raymond J.

    2013-04-01

    Following discharge from a Hall effect thruster, charge exchange occurs between ions and un-ionized propellant atoms. The low-energy cations produced can disturb operation of onboard instrumentation or the thruster itself. Charge-exchange cross sections for both singly and doubly charged propellant atoms are required to model these interactions. While xenon is the most common propellant currently used in Hall effect thrusters, other propellants are being considered, in particular, krypton. We present here guided-ion beam measurements and comparisons to semiclassical calculations for Kr+ + Kr and Kr2+ + Kr cross sections. The measurements of symmetric Kr+ + Kr charge exchange are in good agreement with both the calculations including spin-orbit effects and previous measurements. For the symmetric Kr2+ + Kr reaction, we present cross section measurements for center-of-mass energies between 1 eV and 300 eV, which spans energies not previously examined experimentally. These cross section measurements compare well with a simple one-electron transfer model. Finally, cross sections for the asymmetric Kr2+ + Kr ? Kr+ + Kr+ reaction show an onset near 12 eV, reaching cross sections near constant value of 1.6 Å2 with an exception near 70-80 eV.

  4. Original article Spontaneous sister chromatid exchanges

    E-print Network

    Paris-Sud XI, Université de

    Original article Spontaneous sister chromatid exchanges in mitotic chromosomes of cattle (Bos chromatid exchanges were counted on 50 s cycle metaphase spreads, randomly scored, for each donor at each exchanges/cell and that of chromosomes showing various numbers of exchanges followed the Poisson probability

  5. FACULTY EXCHANGE AGREEMENT I. PROGRAM OBJECTIVES

    E-print Network

    Rosen, Jay

    of the Host Institution. H. Exchange Faculty will be proficient in the predominant language of the HostFACULTY EXCHANGE AGREEMENT I. PROGRAM OBJECTIVES A. In recognition of the mutual benefits") for the purpose of exchanging faculty ("Exchange Faculty"). B. For the purposes of this Agreement, the party

  6. Demutualization and Public Offerings of Financial Exchanges

    Microsoft Academic Search

    Reena Aggarwal; Sandeep Dahiya

    2006-01-01

    The recent merger of the New York Stock Exchange with Archipelago, a publicly listed electronic exchange, can be viewed as the final phase of a wave of organizational transformation that has swept across most of the world's major financial exchanges in the last ten years. Until the early 1990s, almost all stock and derivatives exchanges were organized as non-profit, mutual

  7. Anaphylactic reactions to cinoxacin.

    PubMed

    Stricker, B H; Slagboom, G; Demaeseneer, R; Slootmaekers, V; Thijs, I; Olsson, S

    1988-12-01

    During 1981 to mid-1988 three cases of anaphylactic shock after treatment with the quinolone derivative cinoxacin were reviewed by the Netherlands Centre for Monitoring of Adverse Reactions to Drugs and 17 cases of an anaphylactic type of reaction notified to the World Health Organisation Collaborating Centre for International Drug Monitoring. In five out of six patients for whom data were available the reaction began shortly after taking a single capsule of a second or next course of treatment. Cinoxacin is related to nalidixic acid, and one patient previously treated with that agent subsequently had an anaphylactoid reaction to cinoxacin and later developed a skin reaction to nalidixic acid. There were no deaths, and patients treated as an emergency with plasma expanders or with adrenaline and corticosteroids generally recovered promptly and uneventfully. In view of the potentially fatal consequences of anaphylactic reactions to cinoxacin and other quinolones doctors should take care when prescribing these drugs. PMID:3147004

  8. External control of reactions in microdroplets

    PubMed Central

    Mashaghi, Samaneh; van Oijen, Antoine M.

    2015-01-01

    Scale reduction of chemical reactions enables novel screening and synthesis approaches that facilitate a highly parallelized and combinatorial exploration of chemical space. Droplet-based microfluidics have evolved as a powerful platform to allow many chemical reactions within small volumes that each can be controlled and manipulated. A significant technical challenge is the ability to change the concentration of reactants inside a droplet. Here we describe a strategy that relies on the use of reactants that are soluble in both oil and water and allow a passive, diffusive exchange of reactants between the oil and aqueous phases to externally control composition of the droplets. We demonstrate the applicability of our approach by externally changing the pH inside microdroplets without the need for physical manipulation or droplet merging. PMID:26135837

  9. External control of reactions in microdroplets.

    PubMed

    Mashaghi, Samaneh; van Oijen, Antoine M

    2015-01-01

    Scale reduction of chemical reactions enables novel screening and synthesis approaches that facilitate a highly parallelized and combinatorial exploration of chemical space. Droplet-based microfluidics have evolved as a powerful platform to allow many chemical reactions within small volumes that each can be controlled and manipulated. A significant technical challenge is the ability to change the concentration of reactants inside a droplet. Here we describe a strategy that relies on the use of reactants that are soluble in both oil and water and allow a passive, diffusive exchange of reactants between the oil and aqueous phases to externally control composition of the droplets. We demonstrate the applicability of our approach by externally changing the pH inside microdroplets without the need for physical manipulation or droplet merging. PMID:26135837

  10. Reaction-diffusion textures

    Microsoft Academic Search

    Andrew P. Witkin; Michael Kass

    1991-01-01

    We present a method for texture synthesis based on the simulation of a process of local nonlinear interaction, called reaction-diffusion, which has been proposed as a model of biological pattern formation. We extend traditional reaction-diffusion systems by allowing anisotropic and spatially non-uniform diffusion, as well as multiple competing directions of diffusion. We adapt reaction-diffusion system to the needs of computer

  11. Immediate Contact Reactions

    Microsoft Academic Search

    David Basketter; Arto Lahti

    \\u000a Immediate contact reactions comprise a diverse spectrum of inflammatory skin reactions of both immune and nonimmune origin\\u000a and involving several often poorly characterized mechanisms and which can be caused by an enormous variety of chemicals and\\u000a proteins. Reactions range from sensory effects through local weal and flare to a more generalized response, but all generally\\u000a characterized by a rapid onset

  12. 77 FR 3590 - Covered Securities of Bats Exchange, Inc.

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-01-25

    ...3235-AL20 Covered Securities of Bats Exchange, Inc. AGENCY: Securities and Exchange Commission...authorized for listing, on BATS Exchange, Inc. (``BATS'' or ``Exchange'') as...Tier 1 of the Pacific Exchange, Inc. (``PCX'') (now known as NYSE...

  13. Desosamine in multicomponent reactions.

    PubMed

    Achatz, Sepp; Dömling, Alexander

    2006-12-15

    Desosamine occurring ubiquitously in natural products is introduced into isocyanide based multicomponent reaction chemistry. Corresponding products are of potential interest for the design of novel antibiotics. PMID:17070045

  14. Radical reactions of borohydrides.

    PubMed

    Kawamoto, Takuji; Ryu, Ilhyong

    2014-12-28

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

  15. Sleeve reaction chamber system

    DOEpatents

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

    2009-08-25

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

  16. Implementation of a vibrationally linked chemical reaction model for DSMC

    NASA Technical Reports Server (NTRS)

    Carlson, A. B.; Bird, Graeme A.

    1994-01-01

    A new procedure closely linking dissociation and exchange reactions in air to the vibrational levels of the diatomic molecules has been implemented in both one- and two-dimensional versions of Direct Simulation Monte Carlo (DSMC) programs. The previous modeling of chemical reactions with DSMC was based on the continuum reaction rates for the various possible reactions. The new method is more closely related to the actual physics of dissociation and is more appropriate to the particle nature of DSMC. Two cases are presented: the relaxation to equilibrium of undissociated air initially at 10,000 K, and the axisymmetric calculation of shuttle forebody heating during reentry at 92.35 km and 7500 m/s. Although reaction rates are not used in determining the dissociations or exchange reactions, the new method produces rates which agree astonishingly well with the published rates derived from experiment. The results for gas properties and surface properties also agree well with the results produced by earlier DSMC models, equilibrium air calculations, and experiment.

  17. Electrically Switched Cesium Ion Exchange

    SciTech Connect

    JPH Sukamto; ML Lilga; RK Orth

    1998-10-23

    This report discusses the results of work to develop Electrically Switched Ion Exchange (ESIX) for separations of ions from waste streams relevant to DOE site clean-up. ESIX combines ion exchange and electrochemistry to provide a selective, reversible method for radionuclide separation that lowers costs and minimizes secondary waste generation typically associated with conventional ion exchange. In the ESIX process, an electroactive ion exchange film is deposited onto. a high surface area electrode, and ion uptake and elution are controlled directly by modulating the potential of the film. As a result, the production of secondary waste is minimized, since the large volumes of solution associated with elution, wash, and regeneration cycles typical of standard ion exchange are not needed for the ESIX process. The document is presented in two parts: Part I, the Summary Report, discusses the objectives of the project, describes the ESIX concept and the approach taken, and summarizes the major results; Part II, the Technology Description, provides a technical description of the experimental procedures and in-depth discussions on modeling, case studies, and cost comparisons between ESIX and currently used technologies.

  18. Structure of the Hsp110:Hsc70 Nucleotide Exchange Machine

    PubMed Central

    Schuermann, Jonathan P.; Jiang, Jianwen; Cuellar, Jorge; Llorca, Oscar; Wang, Liping; Gimenez, Luis E.; Jin, Suping; Taylor, Alexander B.; Demeler, Borries; Morano, Kevin A.; Hart, P. John; Valpuesta, Jose M.; Lafer, Eileen M.; Sousa, Rui

    2010-01-01

    Summary Hsp70s mediate protein folding, translocation, and macromolecular complex remodeling reactions. Their activities are regulated by proteins that exchange ADP for ATP from the nucleotide-binding domain (NBD) of the Hsp70. These nucleotide exchange factors (NEFs) include the Hsp110s, which are themselves members of the Hsp70 family. We report the structure of an Hsp110:Hsc70 nucleotide exchange complex. The complex is characterized by extensive protein:protein interactions and symmetric bridging interactions between the nucleotides bound in each partner protein's NBD. An electropositive pore allows nucleotides to enter and exit the complex. The role of nucleotides in complex formation and dissociation, and the effects of the protein:protein interactions on nucleotide exchange, can be understood in terms of the coupled effects of the nucleotides and protein:protein interactions on the open-closed isomerization of the NBDs. The symmetrical interactions in the complex may model other Hsp70 family heterodimers in which two Hsp70s reciprocally act as NEFs. PMID:18550409

  19. The control of hyperhomocysteinemia through thiol exchange mechanisms by mesna.

    PubMed

    Di Giuseppe, Danila; Priora, Raffaella; Coppo, Lucia; Ulivelli, Monica; Bartalini, Sabina; Summa, Domenico; Margaritis, Antonios; Frosali, Simona; Di Simplicio, Paolo

    2014-02-01

    In hyperhomocysteinemic patients, after reaction with homocysteine-albumin mixed disulfides (HSS-ALB), mesna (MSH) forms the mixed disulfide with Hcy (HSSM) which can be removed by renal clearance, thus reducing the plasma concentration of total homocysteine (tHcy). In order to assess the HSS-ALB dethiolation via thiol exchange reactions, the distribution of redox species of cysteine, cysteinylglycine, homocysteine and glutathione was investigated in the plasma of healthy subjects: (i) in vitro, after addition of 35 ?M reduced homocysteine (HSH) to plasma for 72 h, followed by MSH addition (at the concentration range 10-600 ?M) for 25 min; (ii) in vivo, after oral treatment with methionine (methionine, 200 mg/kg body weight, observation time 2-6 h). In both experiments the distribution of redox species, but not the total amount of each thiol, was modified by thiol exchange reactions of albumin and cystine, with changes thermodynamically related to the pKa values of thiols in the corresponding mixed disulfides. MSH provoked a dose-response reversal of the redox state of aged plasma, and the thiol action was confirmed by in vivo experiments. Since it was observed that the dimesna production could be detrimental for the in vivo optimization of HSSM formation, we assume that the best plasma tHcy lowering can be obtained at MSH doses producing the minimum dimesna concentration in each individual. PMID:24337902

  20. New data on Cu-exchanged phillipsite: a multi-methodological study

    NASA Astrophysics Data System (ADS)

    Gatta, G. Diego; Cappelletti, Piergiulio; de'Gennaro, Bruno; Rotiroti, Nicola; Langella, Alessio

    2015-05-01

    The cation exchange capacity of a natural phillipsite-rich sample from the Neapolitan Yellow Tuff, Southern Italy (treated in order to obtain a 95 wt% zeolite-rich sample composed mainly of phillipsite and minor chabazite) for Cu was evaluated using the batch exchange method. The sample had previously been exchanged into its monocationic form (Na), and then used for the equilibrium studies of the exchange reaction 2Na+ ? Cu2+. Reversibility ion exchange tests were performed. The isotherm displays an evident hysteresis loop. Interestingly, the final Cu-exchanged polycrystalline material was green-bluish. Natural, Na- and Cu-exchanged forms were analyzed by X-ray powder diffraction, and the Cu-phillipsite was also investigated by transmission electron microscopy (TEM). Structure refinement of Cu-phillipsite was performed by the Rietveld method using synchrotron data, and it indicates a small, but significant, fraction of Cu sharing with Na two-three independent extra-framework sites. The TEM experiment shows sub-spherical nano-clusters of crystalline species (with average size of 5 nm) lying on the surfaces of zeolite crystals or dispersed in the amorphous fraction, with electron diffraction patterns corresponding to those of CuO (tenorite-like structure) and Cu(OH)2 (spertiniite-like structure). X-ray and TEM investigations show that Cu is mainly concentrated in different species (crystalline or amorphous) within the sample, not only in phillipsite. The experimental findings based on X-ray and TEM investigations, along with the hysteresis loop of the ion exchange tests, are discussed and some general considerations about the mechanisms of exchange reactions involving divalent cations with high hydration energy are provided.

  1. 77 FR 33531 - Self-Regulatory Organizations; BATS Exchange, Inc.; BATS Y-Exchange, Inc.; NASDAQ OMX BX, Inc...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-06

    ...Chicago Board Options Exchange, Incorporated; C2 Options Exchange, Incorporated...Exchange, Inc.; Financial Industry Regulatory...CBOE''), C2 Options Exchange, Incorporated...Exchanges'') and the Financial Regulatory...

  2. 76 FR 38243 - Self-Regulatory Organizations; BATS Exchange, Inc.; BATS Y-Exchange, Inc.; NASDAQ OMX BX, Inc...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-29

    ...Chicago Board Options Exchange, Incorporated...Exchange, Inc.; Financial Industry Regulatory...Chicago Board Options Exchange, Incorporated...EDGX''), Financial Industry Regulatory...Chicago Board Options Exchange, Incorporated...Exchange, Inc., Financial Industry...

  3. Exchange interaction between J multiplets

    NASA Astrophysics Data System (ADS)

    Iwahara, Naoya; Chibotaru, Liviu F.

    2015-05-01

    Analytical expressions for the exchange interaction between J multiplets of interacting metallic centers are derived on the basis of a complete electronic model which includes the intrasite relativistic effects. A common belief that this interaction can be approximated by an isotropic form ?J1.J2 (or ?J1.S2 in the case of interaction with an isotropic spin) is found to be ungrounded. It is also shown that the often used "1 /U approximation" for the description of the kinetic contribution of the exchange interaction is not valid in the case of J multiplets. The developed theory can be used for microscopic description of exchange interaction in materials containing lanthanides, actinides, and some transition-metal ions.

  4. Gamow-Teller strength extraction from (3He, t) reactions

    NASA Astrophysics Data System (ADS)

    Frekers, D.; Puppe, P.; Thies, J. H.; Ejiri, H.

    2013-10-01

    Details of Gamow-Teller (GT) and Fermi (F) strength extraction from charge-exchange reactions at intermediate energies, as well as the concept of using the phenomenological effective interaction for the description of the reactions are reviewed. The focus lies on high-resolution (3He, t) data, yet new data on (d, 2He) charge-exchange reactions are presented as well to indicate the connection and the similarity of both probes to the elementary (p,n), resp. (n,p) reactions. We show that for the extraction of B(GT) and B(F) strength a proper extrapolation of the charge-exchange cross section to the zero momentum transfer point, q=0, gets to be increasingly important for medium to high-mass target nuclei and at moderate excitation energies of a few MeV. Numerous (3He, t) and (p,n) spectra are being compared, and, once adjusted for the different momentum transfers, they reveal a remarkable similarity up to the highest measured excitation energies of ?25 MeV. Further, we remark that the precision, with which GT and F transition strengths can be extracted, is limited by the relatively poor knowledge of the absorption processes, and a more thorough theoretical understanding of the nuclear structure leading to absorption in charge-exchange reactions, especially in the restricted kinematic region of low-momentum transfers, is warranted. Finally, B(GT) values for the 136Xe(3He, t) are being re-evaluated in the light of the present discussion.

  5. Anaphylactic reactions to cinoxacin

    Microsoft Academic Search

    B. H. Stricker; G. Slagboom; R. Demaeseneer; V. Slootmaekers; I. Thijs; S. Olsson

    1988-01-01

    During 1981 to mid-1988 three cases of anaphylactic shock after treatment with the quinolone derivative cinoxacin were reviewed by the Netherlands Centre for Monitoring of Adverse Reactions to Drugs and 17 cases of an anaphylactic type of reaction notified to the World Health Organisation Collaborating Centre for International Drug Monitoring. In five out of six patients for whom data were

  6. Analysis of Layer Charge, Cation and Anion Exchange Capacities, and Synthesis of Reduced Charge Clays

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Surface charge is one of the most important properties of clay minerals. Surface charge is used in classification of 2:1 phyllosilicates and has a strong influence on properties of clays such as hydration, swelling, cation exchange, and reactions with organic molecules. In this chapter, analytical m...

  7. Effects of Exchange Energy and Spin-Orbit Coupling on Bond Energies

    ERIC Educational Resources Information Center

    Smith, Derek W.

    2004-01-01

    Since chemical reactions involve the breaking and making of bonds, understanding the relative strengths of bonds is of paramount importance in the study, teaching, and practice of chemistry. Further, it is showed that free atoms having p(super n) configuration with n = 2,3, or 4 are stabilized by exchange energy, and by spin-orbit coupling for n =…

  8. Relationship Between Cation Exchange Selectivity and Crystalline Swelling in Expanding 2:1 Phyllosilicates

    Microsoft Academic Search

    DAVID A. LAIRD

    1997-01-01

    Abstraet--A theoretical model describing the interaction between crystalline swelling and cation ex- change selectivity is proposed for expanding 2:1 phyllosilicates. The model is based on the assumption that changes in basal spacing of a clay are phase changes, and that each phase of a clay has a different selectivity constant for a particular cation exchange reaction. Energy barriers stabilize the

  9. Pion-nucleon charge exchange amplitudes above 2 GeV

    NASA Astrophysics Data System (ADS)

    Huang, F.; Sibirtsev, A.; Krewald, S.; Hanhart, C.; Haidenbauer, J.; Meißner, U.-G.

    2009-04-01

    The amplitudes for the pion-nucleon charge exchange reaction of the Karlsruhe-Helsinki and the George-Washington-University partial-wave analyses are compared with those of a Regge-cut model with the aim to explore the possibility to provide high-energy constraints for theoretical baryon resonance analyses in the energy region above 2GeV.

  10. Water uptake, ionic conductivity and swelling properties of anion-exchange membrane

    E-print Network

    . Introduction With the advantages of using non-precious electrocatalysts and reduced corrosion problems, anion to be an alternative to proton exchange membrane fuel cells (PEMFCs). The chemical reactions in hydrogen fueled a substantial improvement. Nevertheless, it is still far below current PEMFC performance. Similar to Nafion

  11. New sulfonic acid ion-exchange resins for the preesterification of different oils and fats with high content of free fatty acids

    Microsoft Academic Search

    Bernhard M. E. Russbueldt; Wolfgang F. Hoelderich

    2009-01-01

    The preesterification of free fatty acid (FFA) containing vegetable oils by strong acid ion-exchange resins was studied. The catalysts were characterized by scanning electron microscopy (SEM) and ion-exchange capacity. Based on a simple kinetic model the rate constants were determined. The effect of the catalyst structure, particle size, stirring speed, oil properties and water removal method on the reaction rate

  12. Oxygen isotope exchange and disequilibrium between calcite and tremolite in the absence and presence of an experimental C–O–H fluid

    Microsoft Academic Search

    Y.-F. Zheng; M. Satir; P. Metz

    2004-01-01

    Oxygen isotope exchange between minerals during metamorphism can occur in either the presence or the absence of aqueous fluids. Oxygen isotope partitioning among minerals and fluid is governed by both chemical and isotopic equilibria during these processes, which progress by intragranular and intergranular diffusion as well as by surface reactions. We have carried out isotope exchange experiments in two- and

  13. Grafted methylenediphosphonate ion exchange resins

    DOEpatents

    Trochimcznk, A.W.; Gatrone, R.C.; Alexandratos, S.; Horwitz, E.P.

    1997-04-08

    An ion exchange resin is disclosed that is comprised of an insoluble copolymer onto which are grafted pendent groups that provide 1.0 to about 10 mmol/g dry weight phosphorus. The pendent groups have the formula as shown in the patent wherein R is hydrogen, a cation or mixtures thereof; and R{sup 1} is hydrogen or an C{sub 1}-C{sub 2} alkyl group. The resin also contains zero to about 5 mmol/g dry weight of pendent aromatic sulfonate groups. Processes for making and using an ion exchange resin are also disclosed.

  14. DHE (downhole heat exchangers). [Downhole Heat Exchangers (DHE)

    Microsoft Academic Search

    Culver

    1990-01-01

    The use of downhole heat exchangers (DHE) for residential or commercial space and domestic water heating and other applications has several desirable features. Systems are nearly or completely passive -- that is, no or very little geothermal water or steam is produced from the well either reducing or completely eliminating surface environmental concerns and the need for disposal systems or

  15. Softhard exchange-coupled layered structures with modulated exchange coupling

    E-print Network

    Garmestani, Hamid

    , Tuscaloosa, Alabama 35487-0209 Received 8 April 2003; accepted 28 June 2003 Magnetically soft/hard exchange permanent mag- netic properties. A figure of merit of permanent magnetic materials is the maximum magnetic of this material system. Therefore, it seems that there is little room left for improving the magnetic energy

  16. Desalination by electrodialysis with the ion-exchange membrane prepared by radiation-induced graft polymerization

    NASA Astrophysics Data System (ADS)

    Choi, Seong-Ho; Han Jeong, Young; Jeong Ryoo, Jae; Lee, Kwang-Pill

    2001-01-01

    Ion-exchange membranes modified with the triethylamine [-N(CH 2CH 3) 3] and phosphoric acid (-PO 3 H) groups were prepared by radiation-induced grafting of glycidyl methacrylate (GMA) onto the polyolefin nonwavon fabric (PNF) and subsequent chemical modification of poly(GMA) graft chains. The physical and chemical properties of the GMA-grafted PNF and the PNF modified with ion-exchange groups were investigated by SEM, XPS, TGA, and DSC. Furthermore, electrochemical properties such as specific electric resistance, transport number of K +, and desalination were examined. The grafting yield increased with increasing reaction time and reaction temperature. The maximum grafting yield was obtained with 40% (vol.%) monomer concentration in dioxane at 60°C. The content of the cation- and anion-exchange group increased with increasing grafting yield. Electrical resistance of the PNF modified with TEA and -PO 3 H group decreased, while the water uptake (%) increased with increasing ion-exchange group capacities. Transport number of the PNF modified with ion-exchange group were the range of ca. 0.82-0.92. The graft-type ion-exchange membranes prepared by radiation-induced graft copolymerization were successfully applied as separators for electrodialysis.

  17. Fractal reaction kinetics.

    PubMed

    Kopelman, R

    1988-09-23

    Classical reaction kinetics has been found to be unsatisfactory when the reactants are spatially constrained on the microscopic level by either walls, phase boundaries, or force fields. Recently discovered theories of heterogeneous reaction kinetics have dramatic consequences, such as fractal orders for elementary reactions, self-ordering and self-unmixing of reactants, and rate coefficients with temporal "memories." The new theories were needed to explain the results of experiments and supercomputer simulations of reactions that were confined to low dimensions or fractal dimensions or both. Among the practical examples of "fractal-like kinetics" are chemical reactions in pores of membranes, excitation trapping in molecular aggregates, exciton fusion in composite materials, and charge recombination in colloids and clouds. PMID:17820893

  18. Reversible Control of Nanoparticle Functionalization and Physicochemical Properties by Dynamic Covalent Exchange**

    PubMed Central

    della?Sala, Flavio; Kay, Euan R

    2015-01-01

    Existing methods for the covalent functionalization of nanoparticles rely on kinetically controlled reactions, and largely lack the sophistication of the preeminent oligonucleotide-based noncovalent strategies. Here we report the application of dynamic covalent chemistry for the reversible modification of nanoparticle (NP) surface functionality, combining the benefits of non-biomolecular covalent chemistry with the favorable features of equilibrium processes. A homogeneous monolayer of nanoparticle-bound hydrazones can undergo quantitative dynamic covalent exchange. The pseudomolecular nature of the NP system allows for the in?situ characterization of surface-bound species, and real-time tracking of the exchange reactions. Furthermore, dynamic covalent exchange offers a simple approach for reversibly switching—and subtly tuning—NP properties such as solvophilicity. PMID:25973468

  19. Reversible control of nanoparticle functionalization and physicochemical properties by dynamic covalent exchange.

    PubMed

    della Sala, Flavio; Kay, Euan R

    2015-03-27

    Existing methods for the covalent functionalization of nanoparticles rely on kinetically controlled reactions, and largely lack the sophistication of the preeminent oligonucleotide-based noncovalent strategies. Here we report the application of dynamic covalent chemistry for the reversible modification of nanoparticle (NP) surface functionality, combining the benefits of non-biomolecular covalent chemistry with the favorable features of equilibrium processes. A homogeneous monolayer of nanoparticle-bound hydrazones can undergo quantitative dynamic covalent exchange. The pseudomolecular nature of the NP system allows for the in?situ characterization of surface-bound species, and real-time tracking of the exchange reactions. Furthermore, dynamic covalent exchange offers a simple approach for reversibly switching—and subtly tuning—NP properties such as solvophilicity. PMID:25973468

  20. Competition, Liquidity and Volatility - A Comparative Study of Bombay Stock Exchange and National Stock Exchange

    Microsoft Academic Search

    Chandrasekhar Krishnamurti; Eugene Lim

    2000-01-01

    India currently has two major stock exchanges: The Bombay Stock Exchange and theNational Stock Exchange. There are important differences in ownership structure,geographic reach, internal control systems and institutionalised risk managementfacilities between the Bombay Stock Exchange and the National Stock Exchange.The purpose of this study is to examine if these significant structural differencesbetween these stock exchanges contribute to variations in observed

  1. The load and release characteristics on a strong cationic ion-exchange fiber: kinetics, thermodynamics, and influences

    PubMed Central

    Yuan, Jing; Gao, Yanan; Wang, Xinyu; Liu, Hongzhuo; Che, Xin; Xu, Lu; Yang, Yang; Wang, Qifang; Wang, Yan; Li, Sanming

    2014-01-01

    Ion-exchange fibers were different from conventional ion-exchange resins in their non-cross-linked structure. The exchange was located on the surface of the framework, and the transport resistance reduced significantly, which might mean that the exchange is controlled by an ionic reaction instead of diffusion. Therefore, this work aimed to investigate the load and release characteristics of five model drugs with the strong cationic ion-exchange fiber ZB-1. Drugs were loaded using a batch process and released in United States Pharmacopoeia (USP) dissolution apparatus 2. Opposing exchange kinetics, suitable for the special structure of the fiber, were developed for describing the exchange process with the help of thermodynamics, which illustrated that the load was controlled by an ionic reaction. The molecular weight was the most important factor to influence the drug load and release rate. Strong alkalinity and rings in the molecular structures made the affinity between the drug and fiber strong, while logP did not cause any profound differences. The drug–fiber complexes exhibited sustained release. Different kinds and concentrations of counter ions or different amounts of drug–fiber complexes in the release medium affected the release behavior, while the pH value was independent of it. The groundwork for in-depth exploration and further application of ion-exchange fibers has been laid. PMID:25114504

  2. Meson-baryon interaction in the meson exchange picture

    E-print Network

    M. Döring

    2010-09-29

    This is the contribution to the proceedings of the MENU 2010 conference. The recent work of Ref. [7] is summarized. Elastic piN scattering and the reaction pi^+ p --> K^+ Sigma^+ are described simultaneously in a unitary coupled-channels approach which respects analyticity. SU(3) flavor symmetry is used to relate the t- and u- channel exchanges that drive the meson-baryon interaction in the different channels. Angular distributions, polarizations, and spin-rotation parameters are compared with available experimental data. The pole structure of the amplitudes is extracted from the analytic continuation.

  3. UCI Equipment Management Peter's Exchange

    E-print Network

    Rose, Michael R.

    UCI Equipment Management Peter's Exchange (UCI Surplus Sales) SURPLUS PICK-UP REQUEST Department) Phone: (949) 824-6111, 6447, 6519, 6100 Fax this form to (949) 824-4115, or e-mail Equipment-Management&S approval for moving laboratory equipment visit EH&S at: http

  4. An exchange model of antiferromagnetism

    Microsoft Academic Search

    H. K. Charles Jr.

    1972-01-01

    A nearest-neighbor two sublattice model of antiferromagnetism has been constructed for arbitrary spin using the Schrodinger exchange operator. By use of diagrammatic and cluster expansion technique, eight terms in the high temperature series for the low-field staggered susceptibility are obtained for the open lattices. Critical parameters such as the Neel temperature, T sub n and critical point exponent, gamma sub

  5. Protocol emulation simplifies data exchange

    Microsoft Academic Search

    C. Gignac

    1988-01-01

    The author compares the protocols of two major manufacturers, Allen Bradley and Gould, with respect to their capabilities for data exchange and explores the minimum functionality that a protocol emulator should provide. He also discusses what protocol emulation cannot achieve. The OPTO-22 Optomux protocol is also briefly covered. It is concluded that protocol emulation can be used as a simple,

  6. The Picture Exchange Communication System

    Microsoft Academic Search

    Andrew S. Bondy; Lori A. Frost

    1994-01-01

    A variety of strategies have been used to help children with autism acquire functional communication skills. The Picture Exchange Communication System (PECS) is a unique communication training program that was developed as a means of circumventing some shortcomings associatd with these strategies. A description of the steps within PECS is provided. Long-term group data have indicated that a large proportion

  7. The Picture Exchange Communication System

    Microsoft Academic Search

    Andy Bondy; Lori Frost

    2001-01-01

    The Picture Exchange Communication System (PECS) is an alternative\\/augmentative communication system that was developed to teach functional communication to children with limited speech. The approach is unique in that it teaches children to initiate communicative interactions within a social framework. This article describes the advantages to implementing PECS over traditional approaches. The PECS training protocol is described wherein children are

  8. Exchange Program University of Technology

    E-print Network

    Fernandez, Eduardo

    Australia Exchange Program University of Technology Sydney (UTS) UTS, one of Australia's leading. With a total enrollment of over 37,000, UTS is one of the largest universities in Australia; it is also ranked Eligibility: Undergraduate and graduate students with a 2.50 GPA or higher. Courses: Comprehensive course

  9. Lightweight long life heat exchanger

    NASA Technical Reports Server (NTRS)

    Moore, E. K.

    1975-01-01

    The design, fabrication, and evaluation of a full scale shuttle-type condensing heat exchanger constructed of aluminum and utilizing aluminum clad titanium parting sheets is described. A long term salt spray test of candidate parting sheet specimens is described. The results of an investigation into an alternate method of making composite sheet material are discussed.

  10. Electron gas exchange for atoms

    Microsoft Academic Search

    José Luis Gázquez; Jaime Keller

    1977-01-01

    Current use of electron gas theory for exchange allows calculations of Hartree-Fock (HF) energies through the use of local potentials. A recent proposal of Gopinathan, Whitehead, and Bogdanovic to use a realistic pair correlation function f??(1, 2) that incorporates the boundary conditions of Kutzelnigg, Del Re, and Berthier, which consider the finite number of electrons of a given spin, showed

  11. Geothermal direct contact heat exchange

    Microsoft Academic Search

    A. V. Sims

    1977-01-01

    A glass direct contact heat exchange column was operated in the laboratory. The column was operated at atmospheric pressure using hot water and normal hexane. Column internals testing included an empty column, sieve trays, disk-and-doughnut trays, and two types of packing. Operation was very smooth in all cases and the minimum temperature approaches varied from less than 1 C for

  12. Extended area ceramic heat exchanger

    Microsoft Academic Search

    R. A. Clyde

    1978-01-01

    A ceramic sponge heat exchanger with an extended area can now be made. It consists of a ceramic with random holes, holding rods of silicon carbide. The method of manufacture results in the SiC being held firmly so the brittleness factor is overcome. The ceramic will withstand high temperatures and can be coated with metals. It can be used in

  13. Kinetic approach to evaluate the energy and entropy of activation for the exchange of alkaline earth metal ions on tin(IV) tungstate cation exchanger

    SciTech Connect

    Varshney, K.G.; Khan, A.A.; Varshney, K.; Agrawal, S.

    1984-01-01

    A new approach based on the Nernst-Planck equations has been applied to study the reaction kinetics on the surface of tin(IV) tungstate for the Mg(II)-H(I), Ca(II)-H(I), Sr(II)-H(I) and Ba(II)-H(I) exchanges under the conditions favouring a particle diffusion phenomenon. On the basis of these studies the various physical parameters such as the effective diffusion coefficients, activation energies and entropies of activation have been evaluated which give some informations regarding the mechanism of ion-exchange on the surface of inorganic materials. 25 references, 3 figures, 3 tables.

  14. PROTON-COUPLED ELECTRON TRANSFER: A Reaction Chemist's View

    NASA Astrophysics Data System (ADS)

    Mayer, James M.

    2004-01-01

    Proton-coupled electron transfer (PCET) reactions involve the concerted transfer of an electron and a proton. Such reactions play an important role in many areas of chemistry and biology. Concerted PCET is thermochemically more favorable than the first step in competing consecutive processes involving stepwise electron transfer (ET) and proton transfer (PT), often by >=1 eV. PCET reactions of the form X-H + Y X + H-Y can be termed hydrogen atom transfer (HAT). Another PCET class involves outersphere electron transfer concerted with deprotonation by another reagent, Y+ + XH-B Y + X-HB+ . Many PCET/HAT rate constants are predicted well by the Marcus cross relation. The cross-relation calculation uses rate constants for self-exchange reactions to provide information on intrinsic barriers. Intrinsic barriers for PCET can be comparable to or larger than those for ET. These properties are discussed in light of recent theoretical treatments of PCET.

  15. N-Heterocyclic Carbene Complexes in Reactions Involving Carbon Monoxide

    NASA Astrophysics Data System (ADS)

    Jeletic, Matthew; Veige, Adam

    This chapter focuses on carbon monoxide as a reagent in M-NHC catalysed reactions. The most important and popular of these reactions is hydroformylation. Unfortunately, uncertainty exists as to the identity of the active catalyst and whether the NHC is bound to the catalyst in a number of the reported reactions. Mixed bidentate NHC complexes and cobalt-based complexes provide for better stability of the catalyst. Catalysts used for hydroaminomethylation and carbonylation reactions show promise to rival traditional phosphine-based catalysts. Reports of decarbonylation are scarce, but the potential strength of the M-NHC bond is conducive to the harsh conditions required. This report will highlight, where appropriate, the potential benefits of exchanging traditional phosphorous ligands with N-heterocyclic carbenes as well as cases where the role of the NHC might need re-evaluation. A review by the author on this topic has recently appeared [1].

  16. Nuclear Reactions and Reactor Safety

    E-print Network

    Onuchic, José

    Nuclear Reactions and Reactor Safety DO NOT LICK We haven't entirely nailed down what element nuclear chain reaction, 1938 #12;Nuclear Chain Reactions Do nuclear chain reactions lead to runaway explosions? or ? -Controlled nuclear chain reactions possible: control energy release/sec -> More

  17. Comparative Study of Some Layered Hydroxide Salts Containing Exchangeable Interlayer Anions

    NASA Astrophysics Data System (ADS)

    Newman, Steven P.; Jones, William

    1999-11-01

    Anion-exchange reactions of layered Zn, Cu, Ni, or La hydroxide nitrates with the organic anions acetate, terephthalate, and benzoate are compared. Powder X-ray diffraction (PXRD), Fourier-transform infrared spectroscopy (FTIR), and thermogravimetry combined with mass spectrometry (TG-MS) are used to characterize the materials. Exchange of the interlayer nitrate anions for these organic anions is generally possible, although no exchange is observed for the parent nickel hydroxide material. The organo derivatives obtained may be considered inorganic-organic hybrids, consisting of alternating hydroxide and A- layers, where A is the incorporated organic anion. The materials are structurally similar to the layered double hydroxide family of materials, which also exhibit an anion-exchange capacity.

  18. Fundamental characteristics study of anion-exchange PVDF-SiO(2) membranes.

    PubMed

    Zuo, Xingtao; Shi, Wenxin; Yu, Shuili; He, Jiajie

    2012-01-01

    A new type of poly(vinylidene fluoride)(PVDF)-SiO(2) hybrid anion-exchange membrane was prepared by blending method. The anion-exchange groups were introduced by the reaction of epoxy groups with trimethylamine (TMA). Contact angle between water and the membrane surface was measured to characterize the hydrophilicity change of the membrane surface. The effects of nano-sized SiO(2) particles in the membrane-forming materials on the membrane mechanical properties and conductivity were also investigated. The experimental results indicated that PVDF-SiO(2) anion-exchange membranes exhibited better water content, ion-exchange capacity, conductivity and mechanic properties, and so may find potential applications in alkaline membrane fuel cells and water treatment processes. PMID:23032763

  19. Some Reactions of Formamidines

    E-print Network

    Malleis, Otto Oscar

    1913-05-15

    trichloride on a mixture of a formanilide and amine. 3,- The reaction of orthoformic-ester on a primary amine. OCsHs / HalOeHs . ICdHs HC- OOaHs • = 3C«HsOH + HC^ \\ HEHCeHs MOeHs OOaHs The substituted product in case of aniline is diphenyl- formamidine... as hydrochloride b.- Piorates o.- Chloroplatinates. 2.- Reaction with compounds containing methylene hydrogen. a.- Reaction of oyanacetio ethyl ester with a substi­ tuted formamidine. OH OH I R I CHa * HO = 0 * HCHH R ^ R M a I * HER I COOCaHs COOCa...

  20. Extraction and ion-exchange behavior of mendelevium (II)

    SciTech Connect

    Guseva, L.I.; Tikhomirova, G.S.; Buklanov, G.V.; Pkhar, Z.Z.; Lebedev, I.A.; Katargin, N.V.; Myasoedov, B.F.

    1988-09-01

    Medelevium-256 was obtained via multinucleon transfer reactions upon irradiation of /sup 249/Bk by /sup 22/Ne ions from the extracted beam of a U-300 cyclotron. In order to extract mendelevium and separate it from the products of nuclear reactions, an express ion-exchange method using one column with cationite and zinc amalgam in a solution of 1 mole/liter HCl as the eluent was developed. It was shown that under these conditions mendelevium is reduced and washes out as an alkaline earth element. On the basis of the location of the peaks of the elution curves of Sr/sup 2+/, Eu/sup 2+/, and Md/sup 2+/, the value of the ionic radium of Md/sup 2+/ is estimated and is used to estimate the heat of hydration.

  1. Reaction Studies and Astrophysics with In-flight Beams

    NASA Astrophysics Data System (ADS)

    Zegers, Remco

    2004-10-01

    The availability of rare isotope beams of significant intensities provides many exciting possibilities to study nuclear reactions and their applications towards astrophysics. A good example is charge-exchange reactions, which provide, amongst others, ways to measure weak interaction rates important for stellar evolution studies, neutron-skin thicknesses and the neutrino process. Whereas with stable beams, such studies are relatively straightforward, working with radioactive beams in inverse kinematics provides many experimental challenges. For example, simply measuring the heavy ejectile after a reaction will generally speaking not suffice to obtain sufficiently high resolutions and to separate various channels that lead to the same product. Therefore, alternative techniques have to be developed and tested. Using the (p,n) (for the ? T_z=-1 direction ) and (d,^2He) (for the ? Tz = +1 direction) reactions in inverse kinematics, where the reactions are tagged by the light recoil, are interesting options. At present, these and other possibilities (like heavy-ion charge exchange) are being investigated at the NSCL by means of Monte Carlo simulations and, in the future, in real experiments. The presentation will focus on the experimental methods and challenges and the physics opportunities.

  2. Quantification of transthyretin kinetic stability in human plasma using subunit exchange.

    PubMed

    Rappley, Irit; Monteiro, Cecília; Novais, Marta; Baranczak, Aleksandra; Solis, Gregory; Wiseman, R Luke; Helmke, Stephen; Maurer, Mathew S; Coelho, Teresa; Powers, Evan T; Kelly, Jeffery W

    2014-04-01

    The transthyretin (TTR) amyloidoses are a group of degenerative diseases caused by TTR aggregation, requiring rate-limiting tetramer dissociation. Kinetic stabilization of TTR, by preferential binding of a drug to the native tetramer over the dissociative transition state, dramatically slows the progression of familial amyloid polyneuropathy. An established method for quantifying the kinetic stability of recombinant TTR tetramers in buffer is subunit exchange, in which tagged TTR homotetramers are added to untagged homotetramers at equal concentrations to measure the rate at which the subunits exchange. Herein, we report a subunit exchange method for quantifying the kinetic stability of endogenous TTR in human plasma. The subunit exchange reaction is initiated by the addition of a substoichiometric quantity of FLAG-tagged TTR homotetramers to endogenous TTR in plasma. Aliquots of the subunit exchange reaction, taken as a function of time, are then added to an excess of a fluorogenic small molecule, which immediately arrests further subunit exchange. After binding, the small molecule reacts with the TTR tetramers, rendering them fluorescent and detectable in human plasma after subsequent ion exchange chromatography. The ability to report on the extent of TTR kinetic stabilization resulting from treatment with oral tafamidis is important, especially for selection of the appropriate dose for patients carrying rare mutations. This method could also serve as a surrogate biomarker for the prediction of the clinical outcome. Subunit exchange was used to quantify the stabilization of WT TTR from senile systemic amyloidosis patients currently being treated with tafamidis (20 mg orally, once daily). TTR kinetic stability correlated with the tafamidis plasma concentration. PMID:24661308

  3. Modelling charge transfer reactions with the frozen density embedding formalism

    SciTech Connect

    Pavanello, Michele [Gorlaeus Laboratories, Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden (Netherlands); Neugebauer, Johannes [Institute for Physical and Theoretical Chemistry, Technische Universitaet Braunschweig, Hans-Sommer-Strasse 10, 38106 Braunschweig (Germany)

    2011-12-21

    The frozen density embedding (FDE) subsystem formulation of density-functional theory is a useful tool for studying charge transfer reactions. In this work charge-localized, diabatic states are generated directly with FDE and used to calculate electronic couplings of hole transfer reactions in two {pi}-stacked nucleobase dimers of B-DNA: 5{sup '}-GG-3{sup '} and 5{sup '}-GT-3{sup '}. The calculations rely on two assumptions: the two-state model, and a small differential overlap between donor and acceptor subsystem densities. The resulting electronic couplings agree well with benchmark values for those exchange-correlation functionals that contain a high percentage of exact exchange. Instead, when semilocal GGA functionals are used the electronic couplings are grossly overestimated.

  4. Untoward penicillin reactions

    PubMed Central

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

    1958-01-01

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

  5. Iodine Clock Reaction.

    ERIC Educational Resources Information Center

    Mitchell, Richard S.

    1996-01-01

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

  6. Polymerase Chain Reaction

    NSDL National Science Digital Library

    2009-09-08

    This interactive activity adapted from the University of Nebraska's Library of Crop Technologies depicts steps in the polymerase chain reaction (PCR) technique and explains how it is used to efficiently copy sections of DNA for analysis.

  7. Bad Reaction to Cosmetics?

    MedlinePLUS

    ... Cosmetics Dietary Supplements Drugs Food Medical Devices Nutrition Radiation-Emitting Products Tobacco Products Vaccines, Blood & Biologics Articulos en Espanol Bad Reaction to Cosmetics? Tell FDA Search the Consumer Updates ...

  8. Chemisorption And Precipitation Reactions

    EPA Science Inventory

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

  9. Second Law Optimization of Heat Exchangers 

    E-print Network

    Witte, L. C.

    1985-01-01

    A new method for optimizing heat exchangers is developed in this paper. It is based on second law efficiency relationships rather than on the traditional heat exchanger effectiveness concept. The cost of energy is based on its availability level...

  10. 47 CFR 27.70 - Information exchange.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ...2010-10-01 false Information exchange. 27.70 Section...COMMUNICATIONS SERVICES Technical Standards § 27.70 Information exchange. (a) Prior...must provide the following information to the public safety...

  11. 47 CFR 27.70 - Information exchange.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ...2011-10-01 false Information exchange. 27.70 Section...COMMUNICATIONS SERVICES Technical Standards § 27.70 Information exchange. (a) Prior...must provide the following information to the public safety...

  12. 47 CFR 27.70 - Information exchange.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ...2012-10-01 false Information exchange. 27.70 Section...COMMUNICATIONS SERVICES Technical Standards § 27.70 Information exchange. (a) Prior...must provide the following information to the public safety...

  13. Magnetic Orbitals and Mechanisms of Exchange I. Direct Exchange

    Microsoft Academic Search

    Jacques Curély

    2005-01-01

    Summary.  The problem of direct exchange is examined in the simplest cases (formal coupling of two electrons initially isolated and hydrogen molecule). Then we consider the general case of a solid characterized by weak overlaps between the atomic orbitals of first-nearest neighbours so that the involved electrons are quasi-localized. We recall the physical origin of spin-orbit coupling. Its influence on direct

  14. Phototoxic and Photoallergic Reactions

    Microsoft Academic Search

    Margarida Gonçalo

    \\u000a Phototoxic and photoallergic reactions represent skin reactions to the sun, in the presence of photoactive chemicals applied\\u000a on the skin or taken systemically. They have a highly polymorphic clinical presentation – photocontact urticaria, eczema on\\u000a sun-exposed areas sometimes with erythema multiforme, exaggerated sunburn, linear phytophotodermatitis, pseudoporphyria, photoonycholysis,\\u000a dyschromia, and lupus erythematosus. Also, skin cancers are increasingly associated with exposure to

  15. Glucose reversion reaction kinetics.

    PubMed

    Pilath, Heidi M; Nimlos, Mark R; Mittal, Ashutosh; Himmel, Michael E; Johnson, David K

    2010-05-26

    The reversion reactions of glucose in mildly acidic aqueous solutions have been studied, and the kinetics of conversion to disaccharides has been modeled. The experiments demonstrate that, at high sugar loadings, up to 12 wt % of the glucose can be converted into reversion products. The reversion products observed are primarily disaccharides; no larger oligosaccharides were observed. Only disaccharides linked to the C1 carbon of one of the glucose residues were observed. The formation of 1,6-linked disaccharides was favored, and alpha-linked disaccharides were formed at higher concentrations than beta-linked disaccharides. This observation can be rationalized on the basis of steric effects. At temperatures >140 degrees C, the disaccharides reach equilibrium with glucose and the reversion reaction competes with dehydration reactions to form 5-hydroxymethylfurfural. As a result, disaccharide formation reaches a maximum at reaction times <10 min and decreases with time. At temperatures <130 degrees C, disaccharide formation reaches a maximum at reaction times >30 min. As expected, disaccharide formation exhibits a second-order dependence upon glucose concentration. Levoglucosan formation is also observed; because it shows a first-order dependence upon glucose concentration, its formation is more significant at low concentrations (10 mg mL(-1)), whereas disaccharide formation dominates at high concentrations (200 mg mL(-1)). Experiments conducted using glucose and its disaccharides were calibrated with readily available standards. The kinetic parameters for hydrolysis of some glucodisaccharides could be compared to published literature values. From these experiments, the kinetics and activation energies for the reversion reactions have been calculated. The rate parameters can be used to model the formation of the disaccharides as a function of reaction time and temperature. A new and detailed picture of the molecular mechanism of these industrially important reversion reactions has been developed. PMID:20429509

  16. The Bílik Reaction

    Microsoft Academic Search

    Ladislav Petruš; Mária Petrušová; Zuzana Hricovíniová

    The introduction of the Bílik reaction, the molybdic acid catalyzed interconversion of epimeric aldoses, is an important milestone\\u000a in carbohydrate chemistry. The essentials of this unique, stereospecific carbon-skeleton rearrangement of epialdoses are presented.\\u000a Emphasis is laid on the latest developments in the area, namely the mutual interconversion of 2-ketoses and 2-C-(hydroxymethyl)aldoses, a reaction that is exploited for the preparation of

  17. Ligase Chain Reaction

    Microsoft Academic Search

    Carla Osiowy

    \\u000a Nucleic acid amplification technologies have greatly facilitated medical diagnostics for genetic and infectious diseases through\\u000a the exquisite sensitivity and specificity associated with these methods. Polymerase chain reaction (PCR) (see\\u000a Chapter 6) ushered in these technologies and was soon accompanied by numerous newly developed amplification techniques, including\\u000a ligase chain reaction (LCR). These nucleic acid amplification techniques result in the exponential increase

  18. Acceptance criteria for heat exchanger head staybolts

    Microsoft Academic Search

    R. L. Sindelar; P. S. Lam; D. M. Barnes; A. Placr; J. M. Morrison

    1991-01-01

    Each of the six primary coolant loop systems of the Savannah River Site production reactors contains two parallel single-pass heat exchangers to transfer heat from the primary coolant (DâO) to the secondary cooling water (HâO). The configuration of the heat exchangers includes a plenary space defined by the heat exchanger tubesheet and the heat exchanger head at both the heat

  19. SPES4- ?: installation for exclusive study of nuclear reactions

    NASA Astrophysics Data System (ADS)

    Alkhazov, G. D.; Astashin, V. V.; Atamanchuk, A. G.; Augustyniak, W.; Bachelier, D.; Baublis, V. V.; Boivin, M.; Boyard, J.-L.; Clavelin, J.-F.; Courtat, P.; Denoit, M.; Douet, R.; Ellegaard, C.; Farhi, L.; Gaarde, C.; Gacougnolle, R.; Gerzenstein, V. Ya.; Golovtsov, V. L.; Golubev, V. V.; Hennino, T.; Jourdain, J.-C.; Khanzadeev, A. V.; Komkov, B. G.; Kravtsov, A. V.; Kudin, L. G.; Kunne, R.; Larsen, J.; Lebon, S.; Malinina, L. V.; Maroni, A.; Martin, J.-M.; Morsch, H.-P.; Mylnikov, V. A.; Orischin, E. M.; Osterlund, M.; Poux, V.; Prokofiev, A. N.; Radvanyi, P.; Ramstein, B.; Razmyslovich, B. V.; Roy-Stephan, M.; Samsonov, V. M.; Skowron, R.; Smirnov, I. B.; Strokovsky, E. A.; Tkach, I. I.; Vikhrov, V. V.; Volkov, S. S.; Vorobyov, An. A.; Zhdanov, A. A.; Zupranski, P.

    2005-10-01

    The paper describes the spectrometric system "SPES4- ?" used at the National Laboratory Saturne (CE Saclay, France) for the exclusive study of the baryon resonance excitation in inelastic ? and d scattering on the proton, as well as coherent pion production in charge exchange reactions. The system consists of the magnetic spectrometer SPES4 and two wide-aperture position-sensitive detector arrays, equipped with wire chambers and scintillator hodoscopes, installed around a large-gap C-shape dipole magnet.

  20. FEM analysis of multifluid heat exchangers

    Microsoft Academic Search

    K. N. Seetharamu; G. A. Quadir; Z. A. Zainal; G. M. Krishnan

    2004-01-01

    Heat exchangers are devices for exchanging energy between two or more fluids. They find applications in various industries like power, process, electronics, refining, cryogenics, chemicals, metals and manufacturing sector. Even though heat exchanger designs have been reported quite extensively, they are generally limited to steady-state performance, single phase fluids, a few of the many possible flow arrangements and only two

  1. Optimum design of double pipe heat exchanger

    Microsoft Academic Search

    Prabhata K. Swamee; Nitin Aggarwal; Vijay Aggarwal

    2008-01-01

    Heat exchangers are used in industrial processes to recover heat between two process fluids. Although the necessary equations for heat transfer and the pressure drop in a double pipe heat exchanger are available, using these equations the optimization of the system cost is laborious. In this paper the optimal design of the exchanger has been formulated as a geometric programming

  2. Answering aggregate queries in data exchange

    Microsoft Academic Search

    Foto N. Afrati; Phokion G. Kolaitis

    2008-01-01

    Data exchange, also known as data translation, has been extensively investigated in recent years. One main direction of research has focused on the semantics and the complexity of answering first-order queries in the context of data exchange between relational schemas. In this paper, we initiate a systematic investigation of the semantics and the complexity of aggregate queries in data exchange,

  3. 36 CFR 254.14 - Exchange agreement.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...proposed exchange may enter into an exchange...equalization, and all other terms and conditions necessary...consent or upon such terms as may be provided in...or to comply with the terms of an exchange agreement...timber cruises, title searches, title curative...

  4. 36 CFR 254.14 - Exchange agreement.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...proposed exchange may enter into an exchange...equalization, and all other terms and conditions necessary...consent or upon such terms as may be provided in...or to comply with the terms of an exchange agreement...timber cruises, title searches, title curative...

  5. 36 CFR 254.14 - Exchange agreement.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...proposed exchange may enter into an exchange...equalization, and all other terms and conditions necessary...consent or upon such terms as may be provided in...or to comply with the terms of an exchange agreement...timber cruises, title searches, title curative...

  6. 36 CFR 254.14 - Exchange agreement.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...proposed exchange may enter into an exchange...equalization, and all other terms and conditions necessary...consent or upon such terms as may be provided in...or to comply with the terms of an exchange agreement...timber cruises, title searches, title curative...

  7. 36 CFR 254.14 - Exchange agreement.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...proposed exchange may enter into an exchange...equalization, and all other terms and conditions necessary...consent or upon such terms as may be provided in...or to comply with the terms of an exchange agreement...timber cruises, title searches, title curative...

  8. Towards a new generation heat exchanger models

    Microsoft Academic Search

    Geert W. Haarlemmer; Jérôme Pigourier

    2008-01-01

    In the quest for more dependable process models, attending to small detail and integrating increasing their internal complexity will improve dynamic behavior and simulation accuracy. Although detailed heat exchanger models in dedicated steady state design programs are common, steady state process models and dynamic simulations have been based largely on shorteut heat exchanger calculations. However, detailed heat exchanger models can

  9. Handleiding Exchange mail/agendaop Mac OS

    E-print Network

    Galis, Frietson

    Handleiding Exchange mail/agendaop Mac OS Versie: 1.0 Exchange mail & agenda Datum: 03-04-2013 #12;2 Met behulp van onderstaande handleiding kunt u uw Facultaire e-mail en agenda op uw Mac configureren;4 5) U krijgt een overzicht te zien van uw aangemaakte Exchange profiel op uw Mac, selecteer "Continue

  10. Salary Exchange Car Policy FEBRUARY 2010

    E-print Network

    Bearhop, Stuart

    Salary Exchange Car Policy FEBRUARY 2010 1. Preamble 1.1 This policy forms part of the terms and conditions of the agreement between the employee and the University in relation to the Salary Exchange Car Policy. 1.2 The Salary Exchange Car Scheme is based upon a leasing agreement between the University

  11. Exchange trading rules and stock market liquidity

    Microsoft Academic Search

    Douglas Cumming; Sofia Johan; Dan Li

    2011-01-01

    We examine stock exchange trading rules for market manipulation, insider trading, and broker–agency conflict, across countries and over time, in 42 stock exchanges around the world. Some stock exchanges have extremely detailed rules that explicitly prohibit specific manipulative practices, but others use less precise and broadly framed rules. We create new indices for market manipulation, insider trading, and broker–agency conflict

  12. Pharmaceutical Applications of Ion-Exchange Resins

    ERIC Educational Resources Information Center

    Elder, David

    2005-01-01

    The historical uses of ion-exchanged resins and a summary of the basic chemical principles involved in the ion-exchanged process are discussed. Specific applications of ion-exchange are provided that include drug stabilization, pharmaceutical excipients, taste-masking agents, oral sustained-release products, topical products for local application…

  13. Fiat Money as a Medium of Exchange

    Microsoft Academic Search

    Scott J Freeman

    1989-01-01

    This paper presents a completely explicit exchange environment in which agents wishing to exchange one type of good for another choose to trade for fiat money, which is then traded for the desired goods. This exchange pattern is chosen over barter because specified properties of fiat money make this pattern less expensive than the search for a double coincidence of

  14. Heat exchangers: Selection, rating, and thermal design

    SciTech Connect

    Kakac, S.; Liu, H.

    1998-01-01

    This book takes a systematic approach to the subject, focusing on the selection, design, rating, and operational challenges of various types of heat exchangers. Written by well-known authors in the field of heat transfer, this book covers all the most commonly used types of heat exchangers, including condensers and evaporators. The text begins with the classification of the different types of heat exchangers and discusses methods for their sizing and rating. Single phase forced convection correlations in ducts and pressure drop and pumping power analysis are also covered. A chapter is devoted to the special problem of fouling. Thermal design methods and processes, including designs for condensers and evaporators, complete this thorough introduction to the subject. The appendix provides information on the thermophysical properties of fluids, including the new refrigerants. Every topic features worked examples to illustrate the methods and procedures presented, and additional problems are included at the end of each chapter, with examples to be used as a student design project. An instructor's manual is available, including complete solutions to selected problems in the text. The contents include: classification of heat exchangers; basic design methods of heat exchangers; forced convection correlations for single-phase side of heat exchangers; heat exchanger pressure drop and pumping power; fouling of heat exchangers; double-pipe heat exchangers; design correlations for condensers and evaporators; shell-and-tube heat exchangers; compact heat exchangers; gasketed-plate heat exchangers; and condensers and evaporators.

  15. Power and Dependence in Intimate Exchange

    ERIC Educational Resources Information Center

    van de Rijt, Arnout; Macy, Michael W.

    2006-01-01

    A division of labor is mediated by exchange of valued goods and services. We use social exchange theory to extend this principal to "labors of love." Sexual activity in a close personal relationship seems outside the domain of bargaining and exchange. Nevertheless, we explore the possibility that this most intimate of human relations is influenced…

  16. Pressurized bellows flat contact heat exchanger interface

    NASA Technical Reports Server (NTRS)

    Voss, Fred E. (inventor); Howell, Harold R. (inventor); Winkler, Roger V. (inventor)

    1990-01-01

    Disclosed is an interdigitated plate-type heat exchanger interface. The interface includes a modular interconnect to thermally connect a pair or pairs of plate-type heat exchangers to a second single or multiple plate-type heat exchanger. The modular interconnect comprises a series of parallel, plate-type heat exchangers arranged in pairs to form a slot therebetween. The plate-type heat exchangers of the second heat exchanger insert into the slots of the modular interconnect. Bellows are provided between the pairs of fins of the modular interconnect so that when the bellows are pressurized, they drive the plate-type heat exchangers of the modular interconnect toward one another, thus closing upon the second heat exchanger plates. Each end of the bellows has a part thereof a thin, membrane diaphragm which readily conforms to the contours of the heat exchanger plates of the modular interconnect when the bellows is pressurized. This ensures an even distribution of pressure on the heat exchangers of the modular interconnect thus creating substantially planar contact between the two heat exchangers. The effect of the interface of the present invention is to provide a dry connection between two heat exchangers whereby the rate of heat transfer can be varied by varying the pressure within the bellows.

  17. Data exchange: semantics and query answering

    Microsoft Academic Search

    Ronald Fagin; Phokion G. Kolaitis; Renée J. Miller; Lucian Popa

    2003-01-01

    Data exchange is the problem of taking data structured under a source schema and creating an instance of a target schema that reflects the source data as accurately as possible. In this paper, we address foundational and algorithmic issues related to the semantics of data exchange and to the query answering problem in the context of data exchange. These issues

  18. The Revised Exchange-Orientation Scale.

    ERIC Educational Resources Information Center

    Murstein, Bernard I.; And Others

    1987-01-01

    Reviews literature on exchange-orientation in relationship to marital adjustment and cohabitation and friendship compatibility. Presents revised exchange-orientation scale consisting of items which were judged relevant to exchange and which passed internal consistency tests and differentiated between high and low scorers. Includes various versions…

  19. Self-disclosure as an exchange process

    Microsoft Academic Search

    Morgan Worthy; Albert L. Gary; Gay M. Kahn

    1969-01-01

    Found the exchange of self-disclosures in a laboratory setting to function in a manner consistent with social exchange theory. The intimacy of disclosures exchanged tended to follow the norm of reciprocity. More intimate initial disclosures were made to those who were initially better liked. In turn, final liking was higher for those who made more intimate disclosures. The authoritarianism of

  20. Cryogenic Heat Exchanger with Turbulent Flows

    ERIC Educational Resources Information Center

    Amrit, Jay; Douay, Christelle; Dubois, Francis; Defresne, Gerard

    2012-01-01

    An evaporator-type cryogenic heat exchanger is designed and built for introducing fluid-solid heat exchange phenomena to undergraduates in a practical and efficient way. The heat exchanger functions at liquid nitrogen temperature and enables cooling of N[subscript 2] and He gases from room temperatures. We present first the experimental results of…