Science.gov

Sample records for h2o-3h exchange reaction

  1. 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

    Polymers Generated from [Cu(2-methylpyrazine-5-carboxylate)2(H2O)],3H2O and Silver(I) Salts Yu-Bin Dong-carboxylate)2(H2O)],3H2O (1) was obtained as a molecular complex with two uncoor- dinated nitrogen donors by the reaction of 2-methylpyrazine-5-carboxylate sodium with CuCl2,2H2O in water. Compound 1 crystallized

  2. Multidimentional Normal Mode Calculations for the OH Vibrational Spectra of (H_2O)_3^+, (H_2O)_3^+Ar, H^+(H_2O)_3, and H^+(H_2O)_3Ar

    NASA Astrophysics Data System (ADS)

    Li, Ying-Cheng; Chuang, Hsiao-Han; Tan, Jake Acedera; Takahashi, Kaito; Kuo, Jer-Lai

    2014-06-01

    Recent experimental observations of (H_2O)_3^+, (H_2O)_3^+Ar, H^+(H_2O)_3, and H^+(H_2O)_3Ar clusters in the region 1400-3800 wn show that the OH stretching vibration has distinct characteristics. Multidimensional normal mode calculations were carried out for OH stretching vibrations in the 1200-4000 wn photon energy range. The potential energy and dipole surfaces were evaluated by using first-principles methods. By comparing the calculated frequencies and intensities of OH stretching vibration with experimental spectra, we found that the assignment of OH strecthing of H_3O^+ moiety and free OH strectching vibration have resonable agreement with experimental data. Jeffrey M. Headrick, Eric G. Diken, Richard S. Walters, Nathan I. Hammer, Richard A. Christie, Jun Cui, Evgeniy M. Myshakin, Michael A. Duncan, Mark A. Johnson, Kenneth D. Jordan, Science, 2005, 17, 1765. Kenta Mizuse, Jer-Lai Kuo and Asuka Fujii, Chem. Sci., 2011, 2, 868 Kenta Mizuse and Asuka Fujii, J. Phys. Chem. A, 2013, 117, 929.

  3. Extended networks, porous sheets, and chiral frameworks. Thorium materials containing mixed geometry anions: Structures and properties of Th(SeO 3)(SeO 4), Th(IO 3) 2(SeO 4)(H 2O) 3·H 2O, and Th(CrO 4)(IO 3) 2

    NASA Astrophysics Data System (ADS)

    Sullens, Tyler A.; Almond, Philip M.; Byrd, Jessica A.; Beitz, James V.; Bray, Travis H.; Albrecht-Schmitt, Thomas E.

    2006-04-01

    Three novel Th(IV) compounds containing heavy oxoanions, Th(SeO 3)(SeO 4) ( 1), Th(IO 3) 2(SeO 4)(H 2O) 3·H 2O ( 2), and Th(CrO 4)(IO 3) 2 ( 3), have been synthesized under mild hydrothermal conditions. Each of these three distinct structures contain trigonal pyramidal and tetrahedral oxoanions. Compound 1 adopts a three-dimensional structure formed from ThO 9 tricapped trigonal prisms, trigonal pyramidal selenite, SeO 32-, anions containing Se(IV), and tetrahedral selenate, SeO 42-, anions containing Se(VI). The structure of 2 contains two-dimensional porous sheets and occluded water molecules. The Th centers are found as isolated ThO 9 tricapped trigonal prisms and are bound by four trigonal pyramidal iodate anions, two tetrahedral selenate anions, and three coordinating water molecules. In the structure of 3, the Th(IV) cations are found as ThO 9 tricapped trigonal prisms. Each Th center is bound by six IO 31- anions and three CrO 42- anions forming a chiral three-dimensional structure. Second-harmonic generation of 532 nm light from 1064 nm radiation by a polycrystalline sample of 3 was observed. Crystallographic data (193 K, Mo K?, ?=0.71073): 1; monoclinic, P2 1/ c; a=7.0351(5) Å, b=9.5259(7) Å, c=9.0266(7) Å, ?=103.128(1), Z=4, R(F)=2.47% for 91 parameters with 1462 reflections with I>2?(I); 2, monoclinic, P2 1/ n, a=7.4889(9) Å, b=8.002(1) Å, c=20.165(3) Å, ?=100.142(2), Z=4, R(F)=4.71% for 158 parameters with 2934 reflections with I>2?(I); 3, orthorhombic, P2 12 12 1, a=7.3672(5) Å, b=9.3617(6) Å, c=11.9201(7) Å, Z=4, R(F)=2.04% for 129 parameters with 2035 reflections with I>2?(I).

  4. Charge-exchange reaction by Reggeon exchange and W{sup +}W{sup ?}-fusion

    SciTech Connect

    Schicker, R.

    2015-04-10

    Charge-exchange reactions at high energies are examined. The existing cross section data on the Reggeon induced reaction pp ? n + ?{sup ++} taken at the ZGS and ISR accelerators are extrapolated to the energies of the RHIC and LHC colliders. The interest in the charge-exchange reaction induced by W{sup ±}-fusion is presented, and the corresponding QCD-background is examined.

  5. Heterogeneous Catalysis: Deuterium Exchange Reactions of Hydrogen and Methane

    ERIC Educational Resources Information Center

    Mirich, Anne; Miller, Trisha Hoette; Klotz, Elsbeth; Mattson, Bruce

    2015-01-01

    Two gas phase deuterium/hydrogen exchange reactions are described utilizing a simple inexpensive glass catalyst tube containing 0.5% Pd on alumina through which gas mixtures can be passed and products collected for analysis. The first of these exchange reactions involves H[subscript 2] + D[subscript 2], which proceeds at temperatures as low as 77…

  6. Cu Vacancies Boost Cation Exchange Reactions in Copper Selenide Nanocrystals

    PubMed Central

    2015-01-01

    We have investigated cation exchange reactions in copper selenide nanocrystals using two different divalent ions as guest cations (Zn2+ and Cd2+) and comparing the reactivity of close to stoichiometric (that is, Cu2Se) nanocrystals with that of nonstoichiometric (Cu2–xSe) nanocrystals, to gain insights into the mechanism of cation exchange at the nanoscale. We have found that the presence of a large density of copper vacancies significantly accelerated the exchange process at room temperature and corroborated vacancy diffusion as one of the main drivers in these reactions. Partially exchanged samples exhibited Janus-like heterostructures made of immiscible domains sharing epitaxial interfaces. No alloy or core–shell structures were observed. The role of phosphines, like tri-n-octylphosphine, in these reactions, is multifaceted: besides acting as selective solvating ligands for Cu+ ions exiting the nanoparticles during exchange, they also enable anion diffusion, by extracting an appreciable amount of selenium to the solution phase, which may further promote the exchange process. In reactions run at a higher temperature (150 °C), copper vacancies were quickly eliminated from the nanocrystals and major differences in Cu stoichiometries, as well as in reactivities, between the initial Cu2Se and Cu2–xSe samples were rapidly smoothed out. These experiments indicate that cation exchange, under the specific conditions of this work, is more efficient at room temperature than at higher temperature. PMID:26140622

  7. Carbonyl-Olefin Exchange Reaction and Related Chemistry

    NASA Astrophysics Data System (ADS)

    Jossifov, Christo; Kalinova, Radostina

    A new carbon—carbon double bond forming reaction (carbonyl olefin exchange reaction) mediated by transition metal catalytic systems has been discovered. The catalytic systems used (transition metal halides or oxohalides alone or in combination with Lewis acids) are active only in the case when the two reacting groups are in one molecules and are conjugated. In addition these systems accelerate other reactions which run simultaneously with the carbonyl olefin metathesis rendering a detailed investigation of the process very complicated.

  8. Carbonyl-Olefin Exchange Reaction: Present State and Outlook

    NASA Astrophysics Data System (ADS)

    Kalinova, Radostina; Jossifov, Christo

    The carbonyl-olefin exchange reaction (COER) is a new reaction between carbonyl group and olefin double bond, which has a formal similarity with the olefin metathesis (OM) - one carbon atom in the latter is replaced with an oxygen atom. Till now the new reaction is performed successfully only when the two functional groups (carbonyl group and olefin double bond) are in one molecule and are conjugated. The ?, ?-unsaturated carbonyl compounds (substituted propenones) are the compounds with such a structure. They polymerize giving substituted polyacetylenes. The chain propagation step of this polymerization is in fact the COER. The question arises: is it possible the COER to take place when the two functional groups are not in one molecule and are not conjugated, and could this reaction became an alternative of the existing carbonyl olefination reactions?

  9. Separation of the isotopes of boron by chemical exchange reactions

    DOEpatents

    McCandless, Frank P. (Bozeman, MT); Herbst, Ronald S. (Idaho Falls, ID)

    1995-01-01

    The isotopes of boron, .sup.10 B and .sup.11 B, are separated by means of a gas-liquid chemical exchange reaction involving the isotopic equilibrium between gaseous BF.sub.3 and a liquid BF.sub.3 . donor molecular addition complex formed between BF.sub.3 gas and a donor chosen from the group consisting of: nitromethane, acetone, methyl isobutyl ketone, or diisobutyl ketone.

  10. Separation of the isotopes of boron by chemical exchange reactions

    DOEpatents

    McCandless, F.P.; Herbst, R.S.

    1995-05-30

    The isotopes of boron, {sup 10}B and {sup 11}B, are separated by means of a gas-liquid chemical exchange reaction involving the isotopic equilibrium between gaseous BF{sub 3} and a liquid BF{sub 3} donor molecular addition complex formed between BF{sub 3} gas and a donor chosen from the group consisting of: nitromethane, acetone, methyl isobutyl ketone, or diisobutyl ketone. 1 Fig.

  11. 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.

  12. Selenocysteine in Thiol/Disulfide-Like Exchange Reactions

    PubMed Central

    Marino, Stefano M.

    2013-01-01

    Abstract Significance: Among trace elements used as cofactors in enzymes, selenium is unique in that it is incorporated into proteins co-translationally in the form of an amino acid, selenocysteine (Sec). Sec differs from cysteine (Cys) by only one atom (selenium versus sulfur), yet this switch dramatically influences important aspects of enzyme reactivity. Recent Advances: The main focus of this review is an updated and critical discussion on how Sec might be used to accelerate thiol/disulfide-like exchange reactions in natural selenoenzymes, compared with their Cys-containing homologs. Critical Issues: We discuss in detail three major aspects associated with thiol/disulfide exchange reactions: (i) nucleophilicity of the attacking thiolate (or selenolate); (ii) electrophilicity of the center sulfur (or selenium) atom; and (iii) stability of the leaving group (sulfur or selenium). In all these cases, we analyze the benefits that selenium might provide in these types of reactions. Future Directions: It is the biological thiol oxidoreductase-like function that benefits from the use of Sec, since Sec functions to chemically accelerate the rate of these reactions. We review various hypotheses that could help explain why Sec is used in enzymes, particularly with regard to competitive chemical advantages provided by the presence of the selenium atom in enzymes. Ultimately, these chemical advantages must be connected to biological functions of Sec. Antioxid. Redox Signal. 18, 1675–1689. PMID:23121622

  13. EXFOR systems manual: Nuclear reaction data exchange format

    SciTech Connect

    McLane, V.

    1996-07-01

    This document describes EXFOR, the exchange format designed to allow transmission of nuclear reaction data between the members of the Nuclear Data Centers Network. In addition to storing the data and its bibliographic information, experimental information, including source of uncertainties, is also compiled. The status and history of the data set is also included, e.g., the source of the data, any updates which have been made, and correlations to other data sets. The exchange format, as outlined, is designed to allow a large variety of numerical data tables with explanatory and bibliographic information to be transmitted in an easily machine-readable format (for checking and indicating possible errors) and a format that can be read by personnel (for passing judgment on and correcting any errors indicated by the machine).

  14. Barrier Height for the Exchange Reaction F + HF ? FH + F

    PubMed Central

    O'Neil, Stephen V.; Schaefer, Henry F.; Bender, Charles F.

    1974-01-01

    There exists a body of conflicting data as to the existence or nonexistence of FHF, ClHCl, BrHBr, and IHI as chemically bound molecular species. Ab initio quantum mechanical electronic structure calculations are presented which predict linear symmetric FHF to be unstable. The barrier height for the F + HF exchange reaction is suggested to be no less than 18 kcal/mol, much larger than expected either intuitively or on the basis of certain experiments on related systems. The expected reliability of the calculations is based upon comparable results for diatomic molecules and the F + H2 and H + F2 potential energy surfaces. PMID:16592128

  15. Population of 13Be in a nucleon exchange reaction

    NASA Astrophysics Data System (ADS)

    Marks, B. R.; DeYoung, P. A.; Smith, J. K.; Baumann, T.; Brown, J.; Frank, N.; Hinnefeld, J.; Hoffman, M.; Jones, M. D.; Kohley, Z.; Kuchera, A. N.; Luther, B.; Spyrou, A.; Stephenson, S.; Sullivan, C.; Thoennessen, M.; Viscariello, N.; Williams, S. J.

    2015-11-01

    The neutron-unbound nucleus 13Be was populated with a nucleon exchange reaction from a 71 MeV/u secondary 13B beam. The decay-energy spectrum was reconstructed using invariant mass spectroscopy based on 12Be fragments in coincidence with neutrons. The data could be described with an s -wave resonance at Er=0.73 (9 ) MeV with a width of ?r=1.98 (34 ) MeV and a d -wave resonance at Er=2.56 (13 ) MeV with a width of ?r=2.29 (73 ) MeV . The observed spectral shape is consistent with previous one-proton removal reaction measurements from 14B .

  16. Population of 13Be in a Nucleon Exchange Reaction

    E-print Network

    B. R. Marks; P. A. DeYoung; J. K. Smith; T. Baumann; J. Brown; N. Frank; J. Hinnefeld; M. Hoffman; M. D. Jones; Z. Kohley; A. N. Kuchera; B. Luther; A. Spyrou; S. Stephenson; C. Sullivan; M. Thoennessen; N. Viscariello; S. J. Williams

    2015-12-02

    The neutron-unbound nucleus 13Be was populated with a nucleon-exchange reaction from a 71 MeV/u secondary 13B beam. The decay energy spectrum was reconstructed using invariant mass spectroscopy based on 12Be fragments in coincidence with neutrons. The data could be described with an s-wave resonance at E = 0.73(9) MeV with a width of Gamma = 1.98(34) MeV and a d-wave resonance at E = 2.56(13) MeV with a width of Gamma = 2.29(73) MeV. The observed spectral shape is consistent with previous one-proton removal reaction measurements from 14B.

  17. Charge-exchange reactions with a radioactive triton beam

    SciTech Connect

    Jaenecke, J.

    1998-12-21

    A high-resolution (t, {sup 3}He) test experiment has been performed recently by making use of a secondary triton beam produced by fragmentation of {alpha}-particles. The purpose of this charge-exchange experiment was to achieve good energy resolution in an (n,p)-type reaction at intermediate bombarding energies. The experiment was carried out with the K1200 cyclotron at the National Superconducting Cyclotron Laboratory using the A1200 beam-analysis system and the S800 magnetic spectrometer. The beam-analysis system was used to transport the energy-dispersed radioactive triton beam from the production target to the target position, and the magnetic spectrometer was used to focus the dispersion-matched {sup 3}He particles from the (t, {sup 3}He) reaction at 0 degree sign onto the focal plane of the spectrometer. An energy resolution of 200-250 keV was achieved.

  18. Population of 13Be in a Nucleon Exchange Reaction

    E-print Network

    Marks, B R; Smith, J K; Baumann, T; Brown, J; Frank, N; Hinnefeld, J; Hoffman, M; Jones, M D; Kohley, Z; Kuchera, A N; Luther, B; Spyrou, A; Stephenson, S; Sullivan, C; Thoennessen, M; Viscariello, N; Williams, S J

    2015-01-01

    The neutron-unbound nucleus 13Be was populated with a nucleon-exchange reaction from a 71 MeV/u secondary 13B beam. The decay energy spectrum was reconstructed using invariant mass spectroscopy based on 12Be fragments in coincidence with neutrons. The data could be described with an s-wave resonance at E = 0.73(9) MeV with a width of Gamma = 1.98(34) MeV and a d-wave resonance at E = 2.56(13) MeV with a width of Gamma = 2.29(73) MeV. The observed spectral shape is consistent with previous one-proton removal reaction measurements from 14B.

  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. Mechanism of the Exchange Reaction in HRAS from Multiscale Modeling

    PubMed Central

    Kapoor, Abhijeet; Travesset, Alex

    2014-01-01

    HRAS regulates cell growth promoting signaling processes by cycling between active (GTP-bound) and inactive (GDP-bound) states. Understanding the transition mechanism is central for the design of small molecules to inhibit the formation of RAS-driven tumors. Using a multiscale approach involving coarse-grained (CG) simulations, all-atom classical molecular dynamics (CMD; total of 3.02 µs), and steered molecular dynamics (SMD) in combination with Principal Component Analysis (PCA), we identified the structural features that determine the nucleotide (GDP) exchange reaction. We show that weakening the coupling between the SwitchI (residues 25–40) and SwitchII (residues 59–75) accelerates the opening of SwitchI; however, an open conformation of SwitchI is unstable in the absence of guanine nucleotide exchange factors (GEFs) and rises up towards the bound nucleotide to close the nucleotide pocket. Both I21 and Y32, play a crucial role in SwitchI transition. We show that an open SwitchI conformation is not necessary for GDP destabilization but is required for GDP/Mg escape from the HRAS. Further, we present the first simulation study showing displacement of GDP/Mg away from the nucleotide pocket. Both SwitchI and SwitchII, delays the escape of displaced GDP/Mg in the absence of GEF. Based on these results, a model for the mechanism of GEF in accelerating the exchange process is hypothesized. PMID:25272152

  1. Spin-Isospin responses via charge exchange reactions of RI beams at SHARAQ

    SciTech Connect

    Shimoura, Susumu

    2012-11-12

    Nuclear spectroscopy via direct reactions of RI beams is discussed focusing on characteristics of charge-exchange reactions of RI beams. Recent experiments using the SHARAQ spectrometer at the RIBF are presented, where isovector spin monopole and spin-non-flip monopole responses are studied by charge exchange reaction of RI beams. Some experimental plans and perspectives are also presented.

  2. Geometric Phase Appears in the Ultracold Hydrogen Exchange Reaction

    NASA Astrophysics Data System (ADS)

    Kendrick, B. K.; Hazra, Jisha; Balakrishnan, N.

    2015-10-01

    Quantum reactive scattering calculations for the hydrogen exchange reaction H +H2 (v =4 ,j =0 )?H +H2 (v', j') and its isotopic analogues are reported for ultracold collision energies. Because of 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 4 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.

  3. Kuiper-belt Binary Formation through Exchange Reactions

    E-print Network

    Yoko Funato; Junichiro Makino; Piet Hut; Eiichiro Kokubo; Daisuke Kinoshita

    2003-03-28

    Recent observations (Burnes et al 2002,Veillet et al 2002, Margot et al 2002a) have revealed an unexpectedly high binary fraction among the Trans-Neptunian Objects (TNOs) that populate the Kuiper Belt. The TNO binaries are strikingly different from asteroid binaries in four respects (Veillet et al 2002): their frequency is an order of magnitude larger, the mass ratio of their components is closer to unity, and their orbits are wider and highly eccentric. Two explanations have been proposed for their formation, one assuming large numbers of massive bodies (Weidenschilling 2002), and one assuming large numbers of light bodies (Goldreich et al 2002). We argue that both assumptions are unwarranted, and we show how TNO binaries can be produced from a modest number of intermediate-mass bodies of the type predicted by the gravitational instability theory for the formation of planetesimals (Goldreich and Ward 1973). We start with a TNO binary population similar to the asteroid binary population, but subsequently modified by three-body exchange reactions, a process that is far more efficient in the Kuiper belt, because of the much smaller tidal perturbations by the Sun. Our mechanism can naturally account for all four characteristics that distinguish TNO binaries from main-belt asteroid binaries.

  4. The formation of Kuiper-belt binaries through exchange reactions.

    PubMed

    Funato, Yoko; Makino, Junichiro; Hut, Piet; Kokubo, Eiichiro; Kinoshita, Daisuke

    2004-02-01

    Recent observations have revealed that an unexpectedly high fraction--a few per cent--of the trans-Neptunian objects (TNOs) that inhabit the Kuiper belt are binaries. The components have roughly equal masses, with very eccentric orbits that are wider than a hundred times the radius of the primary. Standard theories of binary asteroid formation tend to produce close binaries with circular orbits, so two models have been proposed to explain the unique characteristics of the TNOs. Both models, however, require extreme assumptions regarding the size distribution of the TNOs. Here we report a mechanism that is capable of producing binary TNOs with the observed properties during the early stages of their formation and growth. The only required assumption is that the TNOs were initially formed through gravitational instabilities in the protoplanetary dust disk. The basis of the mechanism is an exchange reaction in which a binary whose primary component is much more massive than the secondary interacts with a third body, whose mass is comparable to that of the primary. The low-mass secondary component is ejected and replaced by the third body in a wide but eccentric orbit. PMID:14765188

  5. Kinetics of the high temperature oxygen exchange reaction on 238PuO2 powder

    NASA Astrophysics Data System (ADS)

    Whiting, Christofer E.; Du, Miting; Felker, L. Kevin; Wham, Robert M.; Barklay, Chadwick D.; Kramer, Daniel P.

    2015-12-01

    Oxygen exchange reactions performed on PuO2 suggest the reaction is influenced by at least three mechanisms: an internal chemical reaction, surface mobility of active species/defects, and surface exchange of gaseous oxygen with lattice oxygen. Activation energies for the surface mobility and internal chemical reaction are presented. Determining which mechanism is dominant appears to be a complex function including at least specific surface area and temperature. Thermal exposure may also impact the oxygen exchange reaction by causing reductions in the specific surface area of PuO2. Previous CeO2 surrogate studies exhibit similar behavior, confirming that CeO2 is a good qualitative surrogate for PuO2, in regards to the oxygen exchange reaction. Comparison of results presented here with previous work on the PuO2 oxygen exchange reaction allows complexities in the previous work to be explained. These explanations allowed new conclusions to be drawn, many of which confirm the conclusions presented here.

  6. Multi-Nucleon Exchange in Quasi-Fission Reactions

    E-print Network

    Ayik, S; Yilmaz, O

    2015-01-01

    Nucleon exchange mechanism is investigated in the central collisions of ${}^{40}$Ca + ${}^{238}$U and ${}^{48}$Ca + ${}^{238}$U systems near the quasi-fission regime in the framework of the Stochastic Mean-Field (SMF) approach. Sufficiently below the fusion barrier, di-nuclear structure in the collisions is maintained to a large extend. Consequently, it is possible to describe nucleon exchange as a diffusion process familiar from deep-inelastic collisions. Diffusion coefficients for proton and neutron exchange are determined from the microscopic basis of the SMF approach in the semi-classical framework. Calculations show that after a fast charge equilibration the system drifts toward symmetry over a very long interaction time. Large dispersions of proton and neutron distributions of the produced fragments indicate that diffusion mechanism may help to populate heavy trans-uranium elements near the quasi-fission regime in these collisions.

  7. Comparison of meson-exchange and QCD calculations of. gamma. d. -->. np reaction

    SciTech Connect

    Lee, T.S.H.; Ohta, K.

    1989-01-01

    We report a calculation of ..gamma..d ..-->.. np reaction up to GeV energy region, based on a meson-exchange theory developed in the study of intermediate energy NN and ..pi..d reactions. The result is in a sharp disagreement with a QCD prediction by Brodsky and Hiller. 11 refs., 7 figs.

  8. 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

  9. $NN \\to NN ?$ reaction near threshold in a covariant one-boson-exchange model

    E-print Network

    R. Shyam; U. Mosel

    1996-11-07

    We calculate the cross sections for the $p(p,n\\pi^{+})p$ and $p(p,p\\pi^{0})p$ reactions for proton beam energies near threshold in a covariant one-boson-exchange model, which incorporates the exchange of $\\pi$, $\\rho$, $\\sigma$ and $\\omega$ mesons and treats both nucleon and delta isobar as intermediate states. The final state interaction effects have also been included. The $\\omega$ meson exchange is found to contribute significantly at these energies, which, along with other meson exchanges, provides an excellent agreement with the data. The cross sections at beam energies $\\leq$ 300 MeV are almost free from the contributions of the $\\Delta$ isobar excitation.

  10. New results on hypercharge exchange reactions from LASS

    SciTech Connect

    Aston, D.; Bienz, T.; Dunwoodie, W.; Johnson, W.B.; Kunz, P.; Kwon, Y.; Leigh, D.W.G.S.; Levinson, L.; Ratcliff, B.N.; Rensing, P.; Schultz, D.; Shapiro, S.; Sinervo, P.K.; Tarnopolsky, G.; Toge, N.; Waite, A.; Williams, S. ); Awaji, N.; Fujii, K.; Hayashii, H.; Iwata, S.; Kajikawa, R.; Matsui, T.; Miyamoto, A.; Ozaki, H.; Pak, C.O.; Shimomura, T.; Sugiyama, A.; Suzuk

    1990-11-01

    New results from a number of final states ({eta}{pi}{sup {minus}}{pi}{sup +},{bar K}*K*,{phi}{phi}) produced by hypercharge exchange in LASS by an 11 GeV/cK{sup {minus}} beam are described, and compared with results from other hadroproduction modes and from G/{psi} decay.

  11. Double FLP-Alkyne Exchange Reactions: A Facile Route to Te/B Heterocycles.

    PubMed

    Tsao, Fu An; Cao, Levy; Grimme, Stefan; Stephan, Douglas W

    2015-10-21

    1-Bora-4-tellurocyclohexa-2,5-diene undergoes sequential [4 + 2] cycloadditions/alkyne-elimination reactions to incorporate 2 equiv of terminal alkyne with the loss of diarylalkyne, affording access to a series of 11 new tellurium-boron heterocycles. These alkyne exchange reactions proceed regioselectively and can tolerate a variety of functional groups, thus providing the potential for further derivatization. The mechanism of the exchange reaction is confirmed by a DFT study to involve the interaction of the Te and B with the alkyne in a frustrated Lewis pair fashion in the transition states. PMID:26447492

  12. 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...

  13. Why Seemingly Trivial Events Sometimes Evoke Strong Emotional Reactions: The Role of Social Exchange Rule Violations

    PubMed Central

    Leary, Mark R.; Diebels, Kate J.; Jongman-Sereno, Katrina P.; Fernandez, Xuan Duong

    2015-01-01

    ABSTRACT People sometimes display strong emotional reactions to events that appear disproportionate to the tangible magnitude of the event. Although previous work has addressed the role that perceived disrespect and unfairness have on such reactions, this study examined the role of perceived social exchange rule violations more broadly. Participants (N = 179) rated the effects of another person’s behavior on important personal outcomes, the degree to which the other person had violated fundamental rules of social exchange, and their reactions to the event. Results showed that perceptions of social exchange rule violations accounted for more variance in participants’ reactions than the tangible consequences of the event. The findings support the hypothesis that responses that appear disproportionate to the seriousness of the eliciting event are often fueled by perceived rule violations that may not be obvious to others. PMID:26331429

  14. Why Seemingly Trivial Events Sometimes Evoke Strong Emotional Reactions: The Role of Social Exchange Rule Violations.

    PubMed

    Leary, Mark R; Diebels, Kate J; Jongman-Sereno, Katrina P; Fernandez, Xuan Duong

    2015-01-01

    People sometimes display strong emotional reactions to events that appear disproportionate to the tangible magnitude of the event. Although previous work has addressed the role that perceived disrespect and unfairness have on such reactions, this study examined the role of perceived social exchange rule violations more broadly. Participants (N = 179) rated the effects of another person's behavior on important personal outcomes, the degree to which the other person had violated fundamental rules of social exchange, and their reactions to the event. Results showed that perceptions of social exchange rule violations accounted for more variance in participants' reactions than the tangible consequences of the event. The findings support the hypothesis that responses that appear disproportionate to the seriousness of the eliciting event are often fueled by perceived rule violations that may not be obvious to others. PMID:26331429

  15. Selenium and sulfur in exchange reactions: a comparative study.

    PubMed

    Steinmann, Daniel; Nauser, Thomas; Koppenol, Willem H

    2010-10-01

    Cysteamine reduces selenocystamine to form hemiselenocystamine and then cystamine. The rate constants are k(1) = 1.3 × 10(5) M(-1) s(-1); k(-1) = 2.6 × 10(7) M(-1) s(-1); k(2) = 11 M(-1) s(-1); and k(-2) = 1.4 × 10(3) M(-1) s(-1), respectively. Rate constants for reactions of cysteine/selenocystine are similar. Reaction rates of selenium as a nucleophile and as an electrophile are 2-3 and 4 orders of magnitude higher, respectively, than those of sulfur. Sulfides and selenides are comparable as leaving groups. PMID:20806911

  16. 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.

  17. 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.

  18. 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.

  19. A molecular dynamics study of bond exchange reactions in covalent adaptable networks.

    PubMed

    Yang, Hua; Yu, Kai; Mu, Xiaoming; Shi, Xinghua; Wei, Yujie; Guo, Yafang; Qi, H Jerry

    2015-08-21

    Covalent adaptable networks are polymers that can alter the arrangement of network connections by bond exchange reactions where an active unit attaches to an existing bond then kicks off its pre-existing peer to form a new bond. When the polymer is stretched, bond exchange reactions lead to stress relaxation and plastic deformation, or the so-called reforming. In addition, two pieces of polymers can be rejoined together without introducing additional monomers or chemicals on the interface, enabling welding and reprocessing. Although covalent adaptable networks have been researched extensively in the past, knowledge about the macromolecular level network alternations is limited. In this study, molecular dynamics simulations are used to investigate the macromolecular details of bond exchange reactions in a recently reported epoxy system. An algorithm for bond exchange reactions is first developed and applied to study a crosslinking network formed by epoxy resin DGEBA with the crosslinking agent tricarballylic acid. The trace of the active units is tracked to show the migration of these units within the network. Network properties, such as the distance between two neighboring crosslink sites, the chain angle, and the initial modulus, are examined after each iteration of the bond exchange reactions to provide detailed information about how material behaviors and macromolecular structure evolve. Stress relaxation simulations are also conducted. It is found that even though bond exchange reactions change the macroscopic shape of the network, microscopic network characteristic features, such as the distance between two neighboring crosslink sites and the chain angle, relax back to the unstretched isotropic state. Comparison with a recent scaling theory also shows good agreement. PMID:26166382

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

    SciTech Connect

    Jiang, Bin; Guo, Hua

    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.

  1. Halogen Exchange Reaction of Aliphatic Fluorine Compounds with Organic Halides as Halogen Source.

    PubMed

    Mizukami, Yuki; Song, Zhiyi; Takahashi, Tamotsu

    2015-12-18

    The halogen exchange reaction of aliphatic fluorine compounds with organic halides as the halogen source was achieved. Treatment of alkyl fluorides (primary, secondary, or tertiary fluorides) with a catalytic amount of titanocene dihalides, trialkyl aluminum, and polyhalomethanes (chloro or bromo methanes) as the halogen source gave the corresponding alkyl halides in excellent yields under mild conditions. In the case of a fluorine/iodine exchange, no titanocene catalyst is needed. Only C-F bonds are selectively activated under these conditions, whereas alkyl chlorides, bromides, and iodides are tolerant to these reactions. PMID:26629792

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

    NASA Astrophysics Data System (ADS)

    Jiang, Bin; Guo, Hua

    2013-12-01

    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.

  3. Energy-loss cross sections for inclusive charge-exchange reactions at intermediate energies

    NASA Technical Reports Server (NTRS)

    Cucinotta, Francis A.; Townsend, Lawrence W.; Dubey, Rajendra R.

    1993-01-01

    Charge-exchange reactions for scattering to the continuum are considered in a high-energy multiple scattering model. Calculations for (p,n) and (He-3,H-3) reactions are made and compared with experimental results for C-12, O-16, and Al-27 targets. Coherent effects are shown to lead to an important role for inelastic multiple scattering terms when light projectiles are considered.

  4. Reaction chemistry and ligand exchange at cadmium selenide nanocrystal surfaces

    SciTech Connect

    Owen, Jonathan; Park, Jungwon; Trudeau, Paul-Emile; Alivisatos, A. Paul

    2008-12-02

    Chemical modification of nanocrystal surfaces is fundamentally important to their assembly, their implementation in biology and medicine, and greatly impacts their electrical and optical properties. However, it remains a major challenge owing to a lack of analytical tools to directly determine nanoparticle surface structure. Early nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS) studies of CdSe nanocrystals prepared in tri-n-octylphosphine oxide (1) and tri-n-octylphosphine (2), suggested these coordinating solvents are datively bound to the particle surface. However, assigning the broad NMR resonances of surface-bound ligands is complicated by significant concentrations of phosphorus-containing impurities in commercial sources of 1, and XPS provides only limited information about the nature of the phosphorus containing molecules in the sample. More recent reports have shown the surface ligands of CdSe nanocrystals prepared in technical grade 1, and in the presence of alkylphosphonic acids, include phosphonic and phosphinic acids. These studies do not, however, distinguish whether these ligands are bound datively, as neutral, L-type ligands, or by X-type interaction of an anionic phosphonate/phosphinate moiety with a surface Cd{sup 2+} ion. Answering this question would help clarify why ligand exchange with such particles does not proceed generally as expected based on a L-type ligand model. By using reagents with reactive silicon-chalcogen and silicon-chlorine bonds to cleave the ligands from the nanocrystal surface, we show that our CdSe and CdSe/ZnS core-shell nanocrystal surfaces are likely terminated by X-type binding of alkylphosphonate ligands to a layer of Cd{sup 2+}/Zn{sup 2+} ions, rather than by dative interactions. Further, we provide spectroscopic evidence that 1 and 2 are not coordinated to our purified nanocrystals.

  5. (4B-3H) NADH-H2O exchange reaction of the mitochondrial NADH dehydrogenase

    SciTech Connect

    Chen, S.; Guillory, R.J.

    1985-06-14

    The purified mitochondrial NADH dehydrogenase enzyme has been shown to catalyze a rapid (4B-/sup 3/H) NADH-H/sub 2/O exchange reaction. When the enzyme is subjected to a single freeze-thaw cycle there is a complete loss of NADH dehydrogenation without a measurable decrease in the (4B-/sup 3/H) NADH-H/sub 2/O exchange. Complete loss of the (4B-/sup 3/H) NADH-H/sub 2/O exchange follows brief exposure to ultraviolet photoirradiation. The differential sensitivity of the water exchange reaction and the dehydrogenase activity suggests a direct involvement of the enzymes flavin cofactor in the catalysis of the (4B-/sup 3/H) NADH-H/sub 2/O exchange. Arylazido-beta-alanyl NAD+ (A3'-0-(3-(N-4-azido-2-nitrophenyl)amino) propionyl)NAD+) is shown to be a potent photodependent inhibitor of the (4B-3H) NADH-H/sub 2/O exchange activity following photoirradiation with visible light. This is consistent with the observed photodependent inhibition of the dehydrogenase activity by this photoprobe.

  6. Analytical solutions for flow in porous media with multicomponent cation exchange reactions

    NASA Astrophysics Data System (ADS)

    Venkatraman, Ashwin; Hesse, Marc A.; Lake, Larry W.; Johns, Russell T.

    2014-07-01

    Multicomponent cation exchange reactions have important applications in groundwater remediation, disposal of nuclear wastes as well as enhanced oil recovery. The hyperbolic theory of conservation laws can be used to explain the nature of displacements observed during flow with cation exchange reactions between flowing aqueous phase and stationary solid phase. Analytical solutions have been developed to predict the effluent profiles for a particular case of heterovalent cations (Na+, Ca2+ and Mg2+) and an anion (Cl-) for any combination of constant injection and constant initial composition using this theory. We assume local equilibrium, neglect dispersion and model the displacement as a Riemann problem using mass action laws, the charge conservation equation and the cation exchange capacity equation. The theoretical predictions have been compared with experimental data available at two scales—the laboratory scale and the field scale. The theory agrees well with the experimental data at both scales. Analytical theory predictions show good agreement with numerical model, developed using finite differences.

  7. 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

  8. Competition between charge exchange and chemical reaction - The D2/+/ + H system

    NASA Technical Reports Server (NTRS)

    Preston, R. K.; Cross, R. J., Jr.

    1973-01-01

    Study of the special features of molecular charge exchange and its competition with chemical reaction in the case of the D2(+) + H system. The trajectory surface hopping (TSH) model proposed by Tully and Preston (1971) is used to study this competition for a number of reactions involving the above system. The diatomics-in-molecules zero-overlap approximation is used to calculate the three adiabatic surfaces - one triplet and two singlet - which are needed to describe this system. One of the significant results of this study is that the chemical reaction and charge exchange are strongly coupled. It is also found that the number of trajectories passing into the chemical regions of the three surfaces depends very strongly on the surface crossings.-

  9. Electron capture rates in stars studied with heavy ion charge exchange reactions

    E-print Network

    Bertulani, C A

    2015-01-01

    Indirect methods using nucleus-nucleus reactions at high energies (here, high energies mean $\\sim$ 50 MeV/nucleon and higher) are now routinely used to extract information of interest for nuclear astrophysics. This is of extreme relevance as many of the nuclei involved in stellar evolution are short-lived. Therefore, indirect methods became the focus of recent studies carried out in major nuclear physics facilities. Among such methods, heavy ion charge exchange is thought to be a useful tool to infer Gamow-Teller matrix elements needed to describe electron capture rates in stars and also double beta-decay experiments. In this short review, I provide a theoretical guidance based on a simple reaction model for charge exchange reactions.

  10. Electron capture rates in stars studied with heavy ion charge exchange reactions

    E-print Network

    C. A. Bertulani

    2015-10-02

    Indirect methods using nucleus-nucleus reactions at high energies (here, high energies mean $\\sim$ 50 MeV/nucleon and higher) are now routinely used to extract information of interest for nuclear astrophysics. This is of extreme relevance as many of the nuclei involved in stellar evolution are short-lived. Therefore, indirect methods became the focus of recent studies carried out in major nuclear physics facilities. Among such methods, heavy ion charge exchange is thought to be a useful tool to infer Gamow-Teller matrix elements needed to describe electron capture rates in stars and also double beta-decay experiments. In this short review, I provide a theoretical guidance based on a simple reaction model for charge exchange reactions.

  11. Oxidant-Free Au(I)-Catalyzed Halide Exchange and Csp2-O Bond Forming Reactions.

    PubMed

    Serra, Jordi; Whiteoak, Christopher J; Acuña-Parés, Ferran; Font, Marc; Luis, Josep M; Lloret-Fillol, Julio; Ribas, Xavi

    2015-10-21

    Au has been demonstrated to mediate a number of organic transformations through the utilization of its ? Lewis acid character, Au(I)/Au(III) redox properties or a combination of both. As a result of the high oxidation potential of the Au(I)/Au(III) couple, redox catalysis involving Au typically requires the use of a strong external oxidant. This study demonstrates unusual external oxidant-free Au(I)-catalyzed halide exchange (including fluorination) and Csp2-O bond formation reactions utilizing a model aryl halide macrocyclic substrate. Additionally, the halide exchange and Csp2-O coupling reactivity could also be extrapolated to substrates bearing a single chelating group, providing further insight into the reaction mechanism. This work provides the first examples of external oxidant-free Au(I)-catalyzed carbon-heteroatom cross-coupling reactions. PMID:26397959

  12. Aspartate aminotransferase isotope exchange reactions: implications for glutamate/glutamine shuttle hypothesis.

    PubMed

    Kimmich, George A; Roussie, James A; Randles, Joan

    2002-06-01

    Aspartate aminotransferase (AAT) catalyzes amino group transfer from glutamate (Glu) or aspartate (Asp) to a keto acid acceptor-oxaloacetate (OA) or alpha-ketoglutarate (KG), respectively. Data presented here show that AAT catalyzes two partial reactions resulting in isotope exchange between 3H-labeled Glu or 3H-labeled Asp and the cognate keto acid in the absence of the keto acid acceptor required for the net reaction. Tritiated keto acid product was detected by release of 3H2O from C-3 during base-induced enolization. Tritium released directly from C-2 (or C-3) by the enzyme was also evaluated and is a small fraction of that released because of exchange to the keto acid pool. Exchange is dependent on AAT concentration, time-dependent, proportional to the amino-to-keto acid ratio, and blocked by aminooxyacetate (AOA), an AAT inhibitor. Enzymatic conversion of [3H]KG to Glu by glutamic dehydrogenase (GDH) or of [3H]OA to malate by malic dehydrogenase (MDH) "protects" the label from release by base, showing that base-induced isotope release is from keto acid rather than a result of release during the exchange process. AAT isotope exchange is discussed in the context of the glutamate/glutamine shuttle hypothesis for astrocyte/neuron carbon cycling. PMID:11997255

  13. 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.

  14. Neutrino nuclear responses for double beta decays and astro neutrinos by charge exchange reactions

    NASA Astrophysics Data System (ADS)

    Ejiri, Hiroyasu

    2014-09-01

    Neutrino nuclear responses are crucial for neutrino studies in nuclei. Charge exchange reactions (CER) are shown to be used to study charged current neutrino nuclear responses associated with double beta decays(DBD)and astro neutrino interactions. CERs to be used are high energy-resolution (He3 ,t) reactions at RCNP, photonuclear reactions via IAR at NewSUBARU and muon capture reactions at MUSIC RCNP and MLF J-PARC. The Gamow Teller (GT) strengths studied by CERs reproduce the observed 2 neutrino DBD matrix elements. The GT and spin dipole (SD) matrix elements are found to be reduced much due to the nucleon spin isospin correlations and the non-nucleonic (delta isobar) nuclear medium effects. Impacts of the reductions on the DBD matrix elements and astro neutrino interactions are discussed.

  15. Tuning the Optical Properties of Cesium Lead Halide Perovskite Nanocrystals by Anion Exchange Reactions

    PubMed Central

    2015-01-01

    We demonstrate that, via controlled anion exchange reactions using a range of different halide precursors, we can finely tune the chemical composition and the optical properties of presynthesized colloidal cesium lead halide perovskite nanocrystals (NCs), from green emitting CsPbBr3 to bright emitters in any other region of the visible spectrum, and back, by displacement of Cl– or I– ions and reinsertion of Br– ions. This approach gives access to perovskite semiconductor NCs with both structural and optical qualities comparable to those of directly synthesized NCs. We also show that anion exchange is a dynamic process that takes place in solution between NCs. Therefore, by mixing solutions containing perovskite NCs emitting in different spectral ranges (due to different halide compositions) their mutual fast exchange dynamics leads to homogenization in their composition, resulting in NCs emitting in a narrow spectral region that is intermediate between those of the parent nanoparticles. PMID:26214734

  16. Tuning the Optical Properties of Cesium Lead Halide Perovskite Nanocrystals by Anion Exchange Reactions.

    PubMed

    Akkerman, Quinten A; D'Innocenzo, Valerio; Accornero, Sara; Scarpellini, Alice; Petrozza, Annamaria; Prato, Mirko; Manna, Liberato

    2015-08-19

    We demonstrate that, via controlled anion exchange reactions using a range of different halide precursors, we can finely tune the chemical composition and the optical properties of presynthesized colloidal cesium lead halide perovskite nanocrystals (NCs), from green emitting CsPbBr3 to bright emitters in any other region of the visible spectrum, and back, by displacement of Cl(-) or I(-) ions and reinsertion of Br(-) ions. This approach gives access to perovskite semiconductor NCs with both structural and optical qualities comparable to those of directly synthesized NCs. We also show that anion exchange is a dynamic process that takes place in solution between NCs. Therefore, by mixing solutions containing perovskite NCs emitting in different spectral ranges (due to different halide compositions) their mutual fast exchange dynamics leads to homogenization in their composition, resulting in NCs emitting in a narrow spectral region that is intermediate between those of the parent nanoparticles. PMID:26214734

  17. Induced Nucleon Polarization and Meson-Exchange Currents in (e,e'p) Reactions

    E-print Network

    F. Kazemi Tabatabaei; J. E. Amaro; J. A. Caballero

    2004-05-11

    Nucleon recoil polarization observables in $(e,e'\\vec{p})$ reactions are investigated using a semi-relativistic distorted-wave model which includes one- and two-body currents with relativistic corrections. Results for the induced polarization asymmetry are shown for closed-shell nuclei and a comparison with available experimental data for $^{12}$C is provided. A careful analysis of meson exchange currents shows that they may affect significantly the induced polarization for high missing momentum.

  18. Modeling dune-induced hyporheic exchange and nutrient reactions in stream sediments

    NASA Astrophysics Data System (ADS)

    Bardini, L.; Boano, F.; Cardenas, M. B.; Revelli, R.; Ridolfi, L.

    2012-04-01

    The exchange of water across the streambed plays an important role in the ecology of fluvial environments, since it assures the connections of surface and subsurface waters, which have very different peculiarities. Water-borne chemicals are also involved in the process: they enter the sediments with the water and they are transformed into oxidized or reduced substances by biogeochemical reactions, mediated by the hyporheic microbiota. In particular, organic substances can be used as electron donors in a series of redox reactions, with different electron acceptors, e.g., oxygen and nitrate. Nitrification and other secondary reactions also occur as soon as water enters the streambed. These pore-scale transformations concur to affect subsurface solute concentrations and, consequently, the chemistry of upwelling water and the quality of the stream environment. The exchange with the hyporheic zone occurs in response to variations in bed topography, with a very wide range of spatial and temporal scales. For instance, small-scale exchanges are mainly induced by river bed forms, like ripples and dunes, while large-scale exchanges depend on larger geomorphological features. In this work we focus on small-scale exchange induced by the presence of dunes on the streambed, investigating the interplay of hydrological and biogeochemical processes and their effects on solute spatial distribution in the sediments. We numerically simulate the turbulent water flow and the pressure distribution on the streambed and then we evaluate the coupled flow field and biogeochemical reactions in the hyporheic zone in steady-state conditions. Four representative reactive compounds are taken into account: dissolved organic carbon (DOC), oxygen (O2), nitrate (NO3-) and ammonium (NH4+). Sensitivity analyses are also performed to analyze the influence of hydrological and chemical properties of the system on solute reaction rates. The results demonstrate that the stream water quality can strongly affect the reactive behavior of the sediments. For instance, the DOC availability has shown to be a discriminating factor for determining a net nitrate production or consumption at the bed surface. Stream velocity and sediment permeability have also displayed a direct influence on the chemical zonation, by affecting the transport efficiency and the reaction rates. This study represents an initial step for a better understanding of the complex interactions between hydrodynamical and biogeochemical processes in the hyporheic zone.

  19. Hydrogen Isotope Exchange of Chlorinated Ethylenes in Aqueous Solution: Possibly a Termolecular Liquid Phase Reaction.

    PubMed

    Gabri?evi?, Mario; Lente, Gábor; Fábián, István

    2015-12-24

    This work reports an experimental study of the hydrogen/deuterium exchange in the basic aqueous solutions of trichloroethylene, trans-1,2-dichloroethylene, and cis-1,2-dichloroethylene using (1)H NMR as a monitoring method. 1,1-Dichlorethylene was also investigated but found not to exchange hydrogen isotopes with water. The kinetics of isotope exchange features two different pathways, the first is first order with respect to hydroxide ion, whereas the second is second order. The first pathway is interpreted as a straightforward bimolecular reaction between chloroethylene and hydroxide ion, which leads to the deprotonation of chloroethylene. The second pathway involves a transition state with the association of one molecule of the chloroethylene and two hydroxide ions. It is shown that the second pathway could involve the formation of a precursor complex composed of one chloroethylene molecule and one hydroxide ion, but a direct termolecular elementary reaction is also feasible, which is shown by deriving a theoretical highest limit for the rate constants of termolecular reactions in solution. PMID:26618984

  20. EXFOR basics: A short guide to the nuclear reaction data exchange format

    SciTech Connect

    McLane, V.

    1996-07-01

    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 data between the Nuclear Reaction Data Centers. In addition to storing the data and its` bibliographic information, experimental information, including source of uncertainties, is also compiled. The status and history of the data set is also included, e.g., the source of the data, any updates which have been made, and correlations to other data sets. EXFOR is designed for flexibility in order to meet the diverse needs of the nuclear data compilation centers. This 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 exchange format, as outlined, allows a large variety of numerical data tables with explanatory and bibliographic information to be transmitted in an easily machine-readable format (for checking and indicating possible errors) and a format that can be read by personnel (for passing judgment on and correcting any errors indicated by the machine). The data presently included in the EXFOR exchange 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. 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.

  2. 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.

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

    SciTech Connect

    Anisovich, V. V. Sarantsev, A. V.

    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.'

  4. Experimental and theoretical investigation of proton exchange reaction between protic ionic liquid diethylmethylammonium trifluoromethanesulfonate and H2O

    NASA Astrophysics Data System (ADS)

    Mori, Kazuki; Kobayashi, Takanori; Sakakibara, Kazuhisa; Ueda, Kazuyoshi

    2012-11-01

    We investigated the possibility of proton exchange reaction between protic ionic liquid of diethylmethylammonium trifluoromethanesulfonate ([dema][TfOH]) and H2O by using NMR spectroscopy and theoretical calculation. NMR spectroscopy experiment showed that the proton exchange between [dema][TfOH] and H2O in a 1:1 M ratio occurred at room temperature. From the theoretical calculation, we found two reaction pathways for proton exchange between [dema][TfOH] and H2O. Both pathways have stepwise reaction with two transition states. After finishing the reaction along these pathways, the same complex structures of [dema][TfOH] and H2O are again formed, respectively. But the proton is exchanged between [dema][TfOH] and H2O.

  5. 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 (B? 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*,a?/f?), (K*,?/?), (K*?,a?/f?), and (K*?,?/?)) have been simulated through the Monte Carlo method. Suitable event candidates for the double-Regge exchange high-energy limit were selected employing 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

  6. Double-regge exchange limit for the ?p? K?K?p reaction

    SciTech Connect

    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 (B? 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*,a?/f?), (K*,?/?), (K*?,a?/f?), and (K*?,?/?)) have been simulated through the Monte Carlo method. Suitable event candidates for the double-Regge exchange high-energy limit were selected employing 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, 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.

  7. EXFOR systems manual: Nuclear reaction data exchange format. Revision 97/1

    SciTech Connect

    McLane, V.

    1997-07-01

    This document describes EXFOR, the exchange format designed to allow transmission of nuclear reaction data between the members of the Nuclear Data Center Network. In addition to storing the data and its` bibliographic information, experimental information, including source of uncertainties, is also compiled. The status and history of the data set is also included, e.g., the source of the data, any updates which have been made, and correlations to other data sets. EXFOR is designed for flexibility rather than optimization of data processing in order to meet the diverse needs of the nuclear reaction data centers. 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 exchange format, as outlined, is designed to allow a large variety of numerical data tables with explanatory and bibliographic information to be transmitted in an easily machine-readable format (for checking and indicating possible errors) and a format that can be read by personnel (for passing judgment on and correcting any errors indicated by the machine).

  8. Controlling plasmonic "hot spots" in nanoparticle assemblies using ligand place-exchange reactions

    NASA Astrophysics Data System (ADS)

    Bao, Lanlan

    This thesis describes the 1) selective attachment of Au nanoparticles (NPs) to the edges of Au nanoplates via ligand place-exchange reactions, 2) preparation of coupled Au nanoplates via ligand place-exchange reactions, 3) attachment of Au NPs to Au nanorods via ligand place-exchange reactions, 4) study of the dynamics of ligand place-exchange reactions on Au nanoplates, 5) study of the changes in the optical properties of Au nanoplates upon attachment of Au NPs by observing the shift in the localized surface plasmon resonance (LSPR) band, and 6) study of the surface-enhanced Raman spectroscopy (SERS) enhancement of analyte molecules located in the "hot-spots" of coupled Au nanoplate-Au NP structures. We regio-selectively attached 20 nm Au NPs to Au nanoplates by first assembling hexanethiol (HT) onto Au nanoplates, then exchanging HT with 4-aminothiophenol (4-ATP) using different reaction times, and finally electrostatically attaching the negatively-charged Au NPs to the positively-charged 4-ATP ligands bound to the Au nanoplates. We prepared nanoplate-NP assemblies with 100% of the NPs attached to vertex sites or 100% attached to vertex and edge sites using 1 h and 2 h exchange times, respectively. The location and number of bound Au NPs to the nanoplates as a function of exchange time provided information about the mechanism of the ligand place-exchange reaction on the Au nanoplate surface. Ligand place-exchange starts from the vertex sites, then proceeds at the edge sites and finally occurs at smooth terrace sites for longer times. Direct exchange at terraces is possible but the data suggests it occurs mostly through lateral migration of the 4-ATP ligands from vertex/edge sites to the terrace. The data also suggests that phase segregation of 4-ATP ligands and HT ligands occurs on the terrace sites for longer times. The ligand place-exchange strategy also leads to interesting coupled Au nanoplate-Au nanoplate and Au nanorod-Au NP assemblies. The optical properties of the Au nanoplate-Au NP assemblies were studied by monitoring the shift in the LSPR band of the Au nanoplates upon attachment of Au NPs and by measuring the SERS enhancement of the 4-ATP linker. The LSPR band red shifted about 1 nm upon attachment of each Au NP at the vertex and edge sites. The estimated shift is about 0.1 to 0.6 nm per Au NP for those attached to the terraces sites, where the shift is larger for Au NPs attached to outer terrace sites close to the edge and smaller for the inner terrace sites. Au nanoplate-Au NP assemblies with 100% of the NPs attached on the vertex sites of the nanoplates showed the largest enhancement relative to the Au nanoplates. The intensity was similar to the assemblies with many more NPs, but relatively fewer at the vertex/edge sites, indicating that the "hottest spot" for enhancement is located in the interparticle junction between the vertex of the nanoplate and the attached NP. The relative enhancement of the Au nanoplate-Au NP couple relative to the Au nanoplate alone was about 11 on a per Au NP basis. Fundamentally, the results suggest that a small number of "hottest spots" in the laser beam area dominate the Raman enhancement signal and practically, the nanoplate-NP coupling approach controllably at the vertex/edge sites can be very useful for amplifying the detection of analyte down to the single molecule level. This research provides a simple approach for the preparation of various nanostructure assemblies with high accuracy and reproducibility. At the same time, it can potentially be used to control the location of analyte for LSPR and SERS sensing. Another important contribution of this study is the direct evidence for the mechanism and kinetics of the ligand place-exchange reaction on the nanoplate surfaces, which can be useful for controlling NP attachment to other structures as well.

  9. Neutron Skin Thickness of 90Zr Determined By Charge Exchange Reactions

    E-print Network

    K. Yako; H. Sagawa; H. Sakai

    2006-09-29

    Charge exchange spin-dipole (SD) excitations of 90Zr are studied by the 90Zr(p,n) and 90Zr(n,p) reactions at 300 MeV. A multipole decomposition technique is employed to obtain the SD strength distributions in the cross section spectra. For the first time, a model-independent SD sum rule value is obtained: 148+/-12 fm^2. The neutron skin thickness of 90Zr is determined to be 0.07+/-0.04 fm from the SD sum rule value.

  10. On the chemical equilibration of strangeness-exchange reaction in heavy-ion collisions

    E-print Network

    J. Cleymans; A. Foerster; H. Oeschler; K. Redlich; F. Uhlig

    2004-06-12

    The strangeness-exchange reaction pi + Y -> K- + N is shown to be the dynamical origin of chemical equilibration for K- production in heavy-ion collisions up to beam energies of 10 A GeV. The hyperons occurring in this process are produced associately with K+ in baryon-baryon and meson-baryon interactions. This connection is demonstrated by the ratio K-/K+ which does not vary with centrality and shows a linear correlation with the yield of pions per participant. At incident energies above AGS this correlation no longer holds due to the change in the production mechanism of kaons.

  11. NUMEN Project @ LNS : Heavy ions double charge exchange reactions towards the 0??? nuclear matrix element determination

    NASA Astrophysics Data System (ADS)

    Agodi, C.; Cappuzzello, F.; Bonanno, D. L.; Bongiovanni, D. G.; Branchina, V.; Calabretta, L.; Calanna, A.; Carbone, D.; Cavallaro, M.; Colonna, M.; Cuttone, G.; Foti, A.; Finocchiaro, P.; Greco, V.; Lanzalone, G.; Lo Presti, D.; Longhitano, F.; Muoio, A.; Pandola, L.; Rifuggiato, D.; Tudisco, S.

    2015-10-01

    In the NUMEN Project it is proposed an innovative technique to access the nuclear matrix elements entering in the expression of the life-time of the neutrinoless double beta decay, using relevant cross sections of double charge exchange reactions. A key aspect is the use of MAGNEX large acceptance magnetic spectrometer, for the detection of the ejectiles, and of the INFN Laboratori Nazionali del Sud (LNS) K800 Superconducting Cyclotron (CS), for the acceleration of the required high resolution and low emittance heavy-ion beams.

  12. 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.

  13. The neutron-proton charge-exchange amplitudes measured in the dp -> ppn reaction

    E-print Network

    D. Mchedlishvili; S. Barsov; J. Carbonell; D. Chiladze; S. Dymov; A. Dzyuba; R. Engels; R. Gebel; V. Glagolev; K. Grigoryev; P. Goslawski; M. Hartmann; A. Kacharava; V. Kamerdzhiev; I. Keshelashvili; A. Khoukaz; V. Komarov; P. Kulessa; A. Kulikov; A. Lehrach; N. Lomidze; B. Lorentz; G. Macharashvili; R. Maier; S. Merzliakov; M. Mielke; M. Mikirtychyants; S. Mikirtychyants; M. Nioradze; H. Ohm; M. Papenbrock; D. Prasuhn; F. Rathmann; V. Serdyuk; H. Seyfarth; H. J. Stein; E. Steffens; H. Stockhorst; H. Stroeher; M. Tabidze; S. Trusov; Yu. Uzikov; Yu. Valdau; C. Wilkin

    2012-12-11

    The unpolarised differential cross section and the two deuteron tensor analysing powers A_{xx} and A_{yy} of the pol{d}p -> (pp)n charge-exchange reaction have been measured with the ANKE spectrometer at the COSY storage ring. Using deuteron beams with energies 1.2, 1.6, 1.8, and 2.27 GeV, data were obtained for small momentum transfers to a (pp) system with low excitation energy. The results at the three lower energies are consistent with impulse approximation predictions based upon the current knowledge of the neutron-proton amplitudes. However, at 2.27GeV, where these amplitudes are far more uncertain, agreement requires a reduction in the overall double-spin-flip contribution, with an especially significant effect in the longitudinal direction. These conclusions are supported by measurements of the deuteron-proton spin-correlation parameters C_{x,x} and C_{y,y} that were carried out in the pol{d}pol{p} -> (pp)n reaction at 1.2 and 2.27GeV. The values obtained for the proton analysing power also suggest the need for a radical re-evaluation of the neutron-proton elastic scattering amplitudes at the higher energy. It is therefore clear that such measurements can provide a valuable addition to the neutron-proton database in the charge-exchange region.

  14. Phosphatidylinositol synthase of Tetrahymena: inositol isomers as substrates in phosphatidylinositol biosynthesis and headgroup exchange reactions.

    PubMed

    Riggs, Bridget M; Lansley, Tanya A; Ryals, Phillip E

    2007-01-01

    Phosphatidylinositol (PtdIns) synthase in microsomal fractions derived from Tetrahymena vorax was studied to determine its activity requirements. The suitability of inositol isomers as substrates for the synthase and in headgroup exchange reactions also was investigated. Tetrahymena PtdIn synthase activity was optimum in the presence of 2 mM MgCl2 plus 2 mM MnCl2, a pH of 7.8, and a temperature of 30 degrees C. The enzyme retained approximately 80% of its activity after incubation at 70 degrees C for 10 min. PtdIns headgroup exchange activity was maximal in the presence of cytidine monophosphate. By following either the accumulation of radiolabeled reaction products or the loss of radiolabel from precursors, each of the inositol isomers tested appeared to serve as substrates for both the PtdIns synthase and PtdIns:inositol phosphatidyl transferase activities. In each case, myo-inositol and scyllo-inositol were the preferred substrates. The data suggest two routes for the formation of phosphatidyl-non-myo-inositols in Tetrahymena and the potential for the production of novel, non-myo-inositol-containing second messengers. PMID:17403152

  15. O2 activation by binuclear Cu sites: Noncoupled versus exchange coupled reaction mechanisms

    NASA Astrophysics Data System (ADS)

    Chen, Peng; Solomon, Edward I.

    2004-09-01

    Binuclear Cu proteins play vital roles in O2 binding and activation in biology and can be classified into coupled and noncoupled binuclear sites based on the magnetic interaction between the two Cu centers. Coupled binuclear Cu proteins include hemocyanin, tyrosinase, and catechol oxidase. These proteins have two Cu centers strongly magnetically coupled through direct bridging ligands that provide a mechanism for the 2-electron reduction of O2 to a µ-2:2 side-on peroxide bridged species. This side-on bridged peroxo-CuII2 species is activated for electrophilic attack on the phenolic ring of substrates. Noncoupled binuclear Cu proteins include peptidylglycine -hydroxylating monooxygenase and dopamine -monooxygenase. These proteins have binuclear Cu active sites that are distant, that exhibit no exchange interaction, and that activate O2 at a single Cu center to generate a reactive CuII/O2 species for H-atom abstraction from the C-H bond of substrates. O2 intermediates in the coupled binuclear Cu enzymes can be trapped and studied spectroscopically. Possible intermediates in noncoupled binuclear Cu proteins can be defined through correlation to mononuclear CuII/O2 model complexes. The different intermediates in these two classes of binuclear Cu proteins exhibit different reactivities that correlate with their different electronic structures and exchange coupling interactions between the binuclear Cu centers. These studies provide insight into the role of exchange coupling between the Cu centers in their reaction mechanisms.

  16. Positional isotope exchange analysis of the uridine-diphosphoglucose pyrophosphorylase reaction

    SciTech Connect

    Hester, L.; Hilscher, L.; Raushel, F.M.

    1986-05-01

    The enzyme uridine-diphosphoglucose pyrophosphorylase catalyzes the reversible formation of pyrophosphate and UDP-glucose from UTP and glc-1P. The positional isotope exchange reaction was measured using oxygen-18 labelled UTP. The synthesis of (..beta..-/sup 18/O/sub 2/, ..beta gamma..-/sup 18/O, ..gamma..-/sup 18/O/sub 3/)UTP was accomplished by the coupled activities of carbamate kinase, nucleoside diphosphate kinase, and nucleoside monophosphate kinase. The exchange of an oxygen-18 from a ..beta..-nonbridge position of the labelled UTP to the ..cap alpha beta..-bridge position was measured with /sup 31/P NMR. The ratio of the rate of net substrate turnover and the positional isotope exchange rate was measured as a function of the initial glc-1P concentration. This ratio was found to increase with an increasing concentration of glc-1P. The intercept at low glc-1P was found to be 1.2 and the slope was 4.5 mM/sup -1/. These results have been interpreted to mean that this enzyme has an ordered addition of substrates. The lower limit for the release of pyrophosphate from E-UDPG-PP/sub i/ relative to V/sub 2/ is 1.2. The rate constant for the release of UTP from E-UTP relative to V/sub 1/ is 9.

  17. 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.

  18. Preparation of thin cation-exchange membranes using glow discharge plasma polymerization and its reactions

    SciTech Connect

    Uchimoto, Yoshiharu; Endo, Eishi; Yasuda, Kazuaki; Yamasaki, Yuki; Takehara, Zenichiro; Ogumi, Zempachi; Kitao, Osamu

    2000-01-01

    Thin cation-exchange films with fixed sulfonic acid groups were prepared by plasma polymerization followed by hydrolysis of sulfonyl halide groups using benzenesulfonyl fluoride and benzenesulfonyl chloride as starting materials. For benzenesulfonyl fluoride, sulfonyl fluoride groups were introduced into the plasma-formed polymers, whereas benzenesulfonyl chloride tended to decompose during plasma polymerization. The difference between the reaction in the glow discharge plasma of benzenesulfonyl fluoride and that of benzenesulfonyl chloride is discussed based on results obtained by in situ mass spectrometry and molecular orbital calculations. For benzenesulfonyl fluoride, the parent ion ([C{sub 6}H{sub 5}SO{sub 2}F]{sup +}{sm{underscore}bullet}) is the major species which introduces the sulfonic fluoride groups into the plasma polymer because S-F bond cleavage is difficult. However, the parent ion of benzenesulfonyl chloride is unstable in the glow discharge plasma, and cleavage of the S-Cl bond is facile and produces Cl radicals. The plasma polymer formed at 3.5 W using benzenesulfonyl fluoride exhibits a cation-exchange capacity of 1.3 mequiv/g after hydrolysis, which is comparable to the capacities of commercially available cation-exchange membranes.

  19. Lateral Intermolecular Self-Exchange Reactions for Hole and Energy Transport on Mesoporous Metal Oxide Thin Films.

    PubMed

    Hu, Ke; Meyer, Gerald J

    2015-10-20

    Intermolecular self-exchange energy and electron-transfer reactions occur without a loss of free energy. This behavior can be exploited for energy-transport applications when molecules that undergo self-exchange transfer reactions are immobilized on a solid support. This Article focuses upon lateral self-exchange reactions and the relevant interfacial chemistry that occurs on the mesoporous nanocrystalline (anatase) TiO2 thin films that are commonly used in dye-sensitized solar cells. It has been known for some time that all of the dye molecules (termed sensitizers) within such thin films can be reversibly oxidized and reduced by lateral self-exchange electron transfer provided that the sensitizer surface coverage exceeds a percolation threshold. Under conditions where excited-state electron injection into TiO2 is unfavored, lateral intermolecular energy-transfer reactions are also known to occur. The self-exchange rate constants have been quantified by electrochemical, absorption, and/or time-resolved anisotropy techniques and understood within the framework of Marcus theory. Such analysis reveals that the reorganization energy and the electronic coupling are sensitive to the identity of the molecular compound. Time-resolved anisotropy measurements have shown that lateral charge and energy-transfer reactions across the TiO2 surface occur in kinetic competition with charge recombination and excited-state relaxation, respectively. The extent to which lateral self-exchange reactions might be exploited for solar energy conversion applications is discussed, as are critical fundamental issues that remain unresolved. PMID:26223263

  20. 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).

  1. Pion nucleus single charge exchange reactions above the. delta. (1232) resonance

    SciTech Connect

    Rokni, S.H.

    1987-06-01

    Forward-angle differential cross sections for the (..pi../sup +/, ..pi../sup 0/) reaction leading to the Isobaric Analog State in the residual nuclei at 300, 425, 500 and 550 MeV have been measured. Targets ranged in mass from /sup 7/Li to /sup 208/Pb. A description of the experimental setup and the analysis is presented. The 0/sup 0/ cross sections are found to rise markedly between 300 and 425 MeV, contrary to the extrapolation from the lower energy data and to the behavior of the free pion-nucleon single charge exchange process. The angular distributions are sharply forward peaked. Systematics of the data indicate increased volume penetration with increasing pion beam energy. The cross sections are compared with the results of Glauber model calculations indicating the significance of higher order processes even at these energies. 67 refs., 40 figs., 22 tabs.

  2. EXCHANGE

    SciTech Connect

    Boltz, J.C.

    1992-09-01

    EXCHANGE is published monthly by the Idaho National Engineering Laboratory (INEL), a multidisciplinary facility operated for the US Department of Energy (DOE). The purpose of EXCHANGE is to inform computer users about about recent changes and innovations in both the mainframe and personal computer environments and how these changes can affect work being performed at DOE facilities.

  3. Prospects for ultracold carbon via charge exchange reactions and laser cooled carbides.

    PubMed

    Wells, Nathan; Lane, Ian C

    2011-11-14

    Strategies to produce an ultracold sample of carbon atoms are explored and assessed with the help of quantum chemistry. After a brief discussion of the experimental difficulties using conventional methods, two strategies are investigated. The first attempts to exploit charge exchange reactions between ultracold metal atoms and sympathetically cooled C(+) ions. Ab initio calculations including electron correlation have been conducted on the molecular ions [LiC](+) and [BeC](+) to determine whether alkali or alkaline earth metals are a suitable buffer gas for the formation of C atoms but strong spontaneous radiative charge exchange ensure they are not ideal. The second technique involves the stimulated production of ultracold C atoms from a gas of laser cooled carbides. Calculations on LiC suggest that the alkali carbides are not suitable but the CH radical is a possible laser cooling candidate thanks to very favourable Frank-Condon factors. A scheme based on a four pulse STIRAP excitation pathway to a Feshbach resonance is outlined for the production of atomic fragments with near zero centre of mass velocity. PMID:21971563

  4. 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.

  5. Influence of matrix diffusion and exchange reactions on radiocarbon ages in fissured carbonate aquifers

    SciTech Connect

    Maloszewski, P. ); Zuber, A. )

    1991-08-01

    The parallel fissure model coupled with the equation of diffusion into the matrix and with exchange reaction equations has been used to derive a simple formula for estimating the influence of matrix porosity and reaction parameters on the determination of radiocarbon ages in fissured carbonate rocks. Examples of evidently too great radiocarbon ages in carbonate formations, which are not explainable by models for the initial {sup 14}C corrections, can easily be explained by this formula. Parameters obtained for a chalk formation from a known multitracer experiment combined with a pumping test suggest a possibility of {sup 14}C ages more than three orders of magnitude greater than the ages which would be observed if the radiocarbon transport took place only in the mobile water in the fissures. It is shown that contrary to the solute movement on a small scale and with a variable input, the large-scale movement, characteristic for the {sup 14}C dating, does not necessarily require the knowledge of kinetic parameters, because they may be replaced by the distribution coefficient. Discordant tritium and {sup 14}C concentrations are commonly interpreted as a proof of mixing either in the aquifer or at the discharge site. For fissured carbonate formations, however, an alternative explanation is given by the derived model showing a considerable delay of {sup 14}C with respect to nonsorbable tracers.

  6. Bidirectional exchange of biogenic volatiles with vegetation: emission sources, reactions, breakdown and deposition

    PubMed Central

    Niinemets, Ülo; Fares, Silvano; Harley, Peter; Jardine, Kolby J.

    2014-01-01

    Biogenic volatile organic compound (BVOC) emissions are widely modeled as inputs to atmospheric chemistry simulations. However, BVOC may interact with cellular structures and neighboring leaves in a complex manner during volatile diffusion from the sites of release to leaf boundary layer and during turbulent transport to the atmospheric boundary layer. Furthermore, recent observations demonstrate that the BVOC emissions are bidirectional, and uptake and deposition of BVOC and their oxidation products are the rule rather than the exception. This review summarizes current knowledge of within-leaf reactions of synthesized volatiles with reactive oxygen species (ROS), uptake, deposition and storage of volatiles and their oxidation products as driven by adsorption on leaf surface and solubilization and enzymatic detoxification inside leaves. The available evidence indicates that due to reactions with ROS and enzymatic metabolism, the BVOC gross production rates are much larger than previously thought. The degree to which volatiles react within leaves and can be potentially taken up by vegetation depends on compound reactivity, physicochemical characteristics, as well as their participation in leaf metabolism. We argue that future models should be based on the concept of bidirectional BVOC exchange and consider modification of BVOC sink/source strengths by within-leaf metabolism and storage. PMID:24635661

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

    SciTech Connect

    Samana, A. R.; Krmpotic, F.; Paar, N.; Bertulani, C. A.

    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.

  8. 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

  9. Cation Exchange Reactions Controlling Desorption of 90Sr2+ From Coarse-Grained Contaminated Sediments at the Hanford Site, Washington

    NASA Astrophysics Data System (ADS)

    McKinley, J. P.; Zachara, J. M.; Smith, S. C.; Liu, C.

    2005-12-01

    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. We desorbed Sr2+, 90Sr2+, Mg2+, and Ca2+, and monitored total inorganic carbon concentration during the equilibration of this sediment with varying concentrations of Na+ and 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 produced an excellent prediction for desorption data. We also examined the contaminated sediment 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 a sediment that contained essentially no fine-grained material. The nature of this exchange component explains the relatively slow (scale of days) evolution of desorption solutions. The experimental and model results indicate that there is little risk of migration of 90Sr2+ to the water table.

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

    NASA Astrophysics Data System (ADS)

    McKinley, J. P.; Zachara, J. M.; Smith, S. C.; Liu, C.

    2007-01-01

    Nuclear waste that bore 90Sr 2+ 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. Sr 2+, 90Sr 2+, Mg 2+, and Ca 2+ was desorbed and total inorganic carbon concentration was monitored during the equilibration of this sediment with varying concentrations of Na +, Ca 2+. 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 90Sr 2+ to the water table.

  11. 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…

  12. 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.

  13. 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

  14. 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.

  15. Simulated Transport of Three Cations Through Porous Media: Effect of Different Approaches to Modeling Cation Exchange Reactions

    NASA Astrophysics Data System (ADS)

    Grant, S. A.; Mansell, R. S.; Bloom, S. A.; Rhue, R. D.

    1995-01-01

    Batch cation exchange and column experiments were conducted to evaluate selectivity coefficients which have been suggested for describing cation exchange reactions in solute transport models. Vanselow selectivity coefficients were calculated for cation exchange equilibria with a cation resin and for equilibria reported in the literature with a Yolo loam soil. Experimental column data were compared with data from simulations generated by a numerical solute transport model to evaluate Vanselow, Gaines-Thomas, and statistical thermodynamic selectivity coefficients. With the cation resin, the statistical thermodynamic selectivity coefficient gave the most reliable estimate of column effluent cation concentrations. In a column packed with the Yolo loam soil, the Vanselow selectivity coefficient gave the most accurate prediction of column response. Use of variable (as opposed to fixed) Vanselow selectivity coefficients gave more accurate predictions of column experiments. The use of ternary cation exchange data did not improve predictions of column response.

  16. Heavy-ion double charge exchange reactions: a tool towards 0v\\b{eta}\\b{eta} nuclear matrix elements

    E-print Network

    Cappuzzello, F; Agodi, C; Bond`?, M; Carbone, D; Cunsolo, A; Foti, A

    2015-01-01

    The knowledge of the nuclear matrix elements for the neutrinoless double beta decay is fundamental for neutrino physics. In this paper, an innovative technique to extract information on the nuclear matrix elements by measuring the cross section of a double charge exchange nuclear reaction is proposed. The basic point is that the initial and final state wave functions in the two processes are the same and the transition operators are similar. The double charge exchange cross sections can be factorized in a nuclear structure term containing the matrix elements and a nuclear reaction factor. First pioneering experimental results for the 40Ca(18O,18Ne)40Ar reaction at 270 MeV incident energy show that such cross section factorization reasonably holds for the crucial 0+ --> 0+ transition to 40Args, at least at very forward angles.

  17. Heavy-ion double charge exchange reactions: a tool towards 0v\\b{eta}\\b{eta} nuclear matrix elements

    E-print Network

    F. Cappuzzello; M. Cavallaro; C. Agodi; M. Bond`?; D. Carbone; A. Cunsolo; A. Foti

    2015-11-12

    The knowledge of the nuclear matrix elements for the neutrinoless double beta decay is fundamental for neutrino physics. In this paper, an innovative technique to extract information on the nuclear matrix elements by measuring the cross section of a double charge exchange nuclear reaction is proposed. The basic point is that the initial and final state wave functions in the two processes are the same and the transition operators are similar. The double charge exchange cross sections can be factorized in a nuclear structure term containing the matrix elements and a nuclear reaction factor. First pioneering experimental results for the 40Ca(18O,18Ne)40Ar reaction at 270 MeV incident energy show that such cross section factorization reasonably holds for the crucial 0+ --> 0+ transition to 40Args, at least at very forward angles.

  18. Presolvated Electron Reaction with Methylacetoacetate: Electron Localization, Proton-Deuteron Exchange, and H-atom Abstraction

    PubMed Central

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

    2015-01-01

    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 methylacetoacetate (MAA, CH3-CO-CH2-CO-OCH3) at 77 K and subsequent reactions of the anion radical (CH3-CO•?-CH2-CO-OCH3) in the temperature range (77 to ca. 170 K) 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-CO-OCH3. The ESR spectrum of CH3-C(•)OH-CH2-CO-OCH3 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-CO-OCH3 in D2O glass shows only the line components due to proton hyperfine couplings of CH3 group. This is expected since the methylen protons in MAA are readily exchangeable in D2O. On stepwise annealing to higher temperatures (ca. 150 to 170 K), CH3-C(•)OH-CH2-CO-OCH3 undergoes bimolecular H-atom abstraction from MAA to form the more stable radical, CH3-CO-CH•-CO-OCH3. Theoretical calculations using density functional theory (DFT) support the radical assignments. PMID:25255751

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

    SciTech Connect

    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.

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

    SciTech Connect

    Borysow, J.; Eckart, M.; Fink, M.

    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. Analysis of exchange terms in a projected ERPA Theory applied to the quasi-elastic (e,e') reaction

    E-print Network

    E. Bauer; A. Polls; A. Ramos

    1998-03-09

    A systematic study of the influence of exchange terms in the longitudinal and transverse nuclear response to quasi-elastic (e,e') reactions is presented. The study is performed within the framework of the extended random phase approximation (ERPA), which in conjuction with a projection method permits a separation of various contributions tied to different physical processes. The calculations are performed in nuclear matter up to second order in the residual interaction for which we take a (pi+rho)-model with the addition of the Landau-Migdal g'-parameter. Exchange terms are found to be important only for the RPA-type contributions around the quasielastic peak.

  2. A full dimensional time-dependent wave packet study for the H4 four-center, collision induced dissociation, and single exchange reactions: Reaction probabilities for J =0

    NASA Astrophysics Data System (ADS)

    Lu, Yunpeng; Lee, Soo-Y.; Zhang, Dong H.

    2006-01-01

    A time-dependent initial state selected wave packet method has been developed to study the H2(v1=10-11,j1=0)+H2'(v2=0,j2=0)?HH'+HH' four-center (4C) reaction, and two other competing reactions: the H2+H2'?H+H+H2' collision induced dissociation (CID) and the H2+H2'?H+HH'+H' single exchange (SE) reaction, in full six dimensions. Initial state-specific total reaction probabilities for these three competing reactions are presented for total angular momentum J =0 and the effects of reagent vibration on reactions are examined. It is found that (a) the CID process is the dominant process over the whole energy range considered in this study, but the 4C and SE processes also have non-negligible probabilities; (b) the SE process has a lower threshold energy than the 4C process, but the SE probability increases slower than the 4C probability as collision energy increases; (c) the vibrational excitation of H2(v1) is much more efficient than translational motion for promoting these processes, in particular to the CID process.

  3. The loss rates of O{sup +} in the inner magnetosphere caused by both magnetic field line curvature scattering and charge exchange reactions

    SciTech Connect

    Ji, Y.; Shen, C.

    2014-03-15

    With consideration of magnetic field line curvature (FLC) pitch angle scattering and charge exchange reactions, the O{sup +} (>300?keV) in the inner magnetosphere loss rates are investigated by using an eigenfunction analysis. The FLC scattering provides a mechanism for the ring current O{sup +} to enter the loss cone and influence the loss rates caused by charge exchange reactions. Assuming that the pitch angle change is small for each scattering event, the diffusion equation including a charge exchange term is constructed and solved; the eigenvalues of the equation are identified. The resultant loss rates of O{sup +} are approximately equal to the linear superposition of the loss rate without considering the charge exchange reactions and the loss rate associated with charge exchange reactions alone. The loss time is consistent with the observations from the early recovery phases of magnetic storms.

  4. Synthesis of N=127 isotones through (p,n) charge-exchange reactions induced by relativistic {sup 208}Pb projectiles

    SciTech Connect

    Morales, A. I.; Benlliure, J.; Alvarez-Pol, H.; Casarejos, E.; Dragosavac, D.; Perez-Loureiro, D.; Verma, S.; Agramunt, J.; Molina, F.; Rubio, B.; Algora, A.; Alkhomashi, N.; Farrelly, G.; Gelletly, W.; Pietri, S.; Podolyak, Z.; Regan, P. H.; Steer, S. J.; Boutachkov, P.; Caceres, L. S.

    2011-07-15

    The production cross sections of four N=127 isotones ({sup 207}Hg, {sup 206}Au, {sup 205}Pt, and {sup 204}Ir) have been measured using (p,n) charge-exchange reactions, induced in collisions of a {sup 208}Pb primary beam at 1 A GeV with a Be target. These data allow one to investigate the use of a reaction mechanism to extend the limits of the chart of nuclides toward the important r-process nuclei in the region of the third peak of elemental abundance distribution.

  5. Reaction Engineering International and Pacific Northwest Laboratory staff exchange: Addressing computational fluid dynamics needs of the chemical process industry

    SciTech Connect

    Fort, J.A.

    1995-07-01

    Staff exchanges, such as the one described in this report, are intended to facilitate communications and collaboration among scientists and engineers at Department of Energy (DOE) laboratories, in US industry, and academia. Funding support for these exchanges is provided by the DOE, Office of Energy Research, Laboratory Technology Transfer Program. Funding levels for each exchange typically range from $20,000 to $40,000. The exchanges offer the opportunity for the laboratories to transfer technology and expertise to industry, gain a perspective to industry`s problems, and develop the basis for further cooperative efforts through Cooperative Research and Development Agreements (CRADAS) or other mechanisms. Information in this report on the staff exchange of the Pacific Northwest Laboratory (PNL) staff with Reaction Engineering International (REI) includes the significant accomplishments, significant problems, industry benefits realized, recommended follow-on work and potential benefit of that work. The objectives of this project were as follows: Work with REI to develop an understanding of the computational fluid dynamics (CFD) needs of the chemical process industry; assess the combined capabilities of the PNL and REI software analysis tools to address these needs; and establish a strategy for a future programmatically funded, joint effort to develop a new CFD tool for the chemical process industry.

  6. Kinetic and Mechanistic Studies of the Deuterium Exchange in Classical Keto-Enol Tautomeric Equilibrium Reactions

    ERIC Educational Resources Information Center

    Nichols, Michael A.; Waner, Mark J.

    2010-01-01

    An extension of the classic keto-enol tautomerization of beta-dicarbonyl compounds into a kinetic analysis of deuterium exchange is presented. It is shown that acetylacetone and ethyl acetoacetate undergo nearly complete deuterium exchange of the alpha-methylene carbon when dissolved in methanol-d[subscript 4]. The extent of deuteration may be…

  7. 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.

  8. Kinetics of Calcium-Magnesium Exchange on Soil Using a Stirred-Flow Reaction Chamber Mark S. Seyfried,* Donald L. Sparks, Asher Bar-Tal, and Sala Feigenbaum

    E-print Network

    Sparks, Donald L.

    . Seyfried,* Donald L. Sparks, Asher Bar-Tal, and Sala Feigenbaum ABSTRACT Ion exchange reaction kinetics may Orchard, Boise, ID 83705;D.L. Sparks, Dep. of Plant Science, Univ. of Delaware, DE 19717-1303; A. Bar-tal

  9. Formation of a Long-Lived P+ -State in Plant Pheophytin-Exchanged Reaction

    E-print Network

    van Stokkum, Ivo

    transient absorption spectroscopy in the range of 500-1040 nm was used to study electron transfer at 5 K that of P+BA -, which itself is below P*. Assuming that the pigment exchange does not affect the energy

  10. 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.

  11. 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

  12. 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

  13. 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.

  14. Reduced-Dimensionality Semiclassical Transition State Theory: Application to Hydrogen Atom Abstraction and Exchange Reactions of Hydrocarbons.

    PubMed

    Greene, Samuel M; Shan, Xiao; Clary, David C

    2015-12-17

    Quantum mechanical methods for calculating rate constants are often intractable for reactions involving many atoms. Semiclassical transition state theory (SCTST) offers computational advantages over these methods but nonetheless scales exponentially with the number of degrees of freedom (DOFs) of the system. Here we present a method with more favorable scaling, reduced-dimensionality SCTST (RD SCTST), that treats only a subset of DOFs of the system explicitly. We apply it to three H abstraction and exchange reactions for which two-dimensional potential energy surfaces (PESs) have previously been constructed and evaluated using RD quantum scattering calculations. We differentiated these PESs to calculate harmonic frequencies and anharmonic constants, which were then used to calculate cumulative reaction probabilities and rate constants by RD SCTST. This method yielded rate constants in good agreement with quantum scattering results. Notably, it performed well for a heavy-light-heavy reaction, even though it does not explicitly account for corner-cutting effects. Recent extensions to SCTST that improve its treatment of deep tunneling were also evaluated within the reduced-dimensionality framework. The success of RD SCTST in this study suggests its potential applicability to larger systems. PMID:26090556

  15. Chiral modification of copper exchanged zeolite-Y with cinchonidine and its application in the asymmetric Henry reaction.

    PubMed

    Deka, Jogesh; Satyanarayana, L; Karunakar, G V; Bhattacharyya, Pradip Kr; Bania, Kusum K

    2015-12-28

    Chirally modified Cu(2+) exchanged zeolite-Y was synthesized by direct adsorption of cinchonidine under ambient conditions. The chirally modified materials were characterized using various spectrochemical and physicochemical techniques viz. BET, FTIR, MAS ((1)H and (13)C NMR), XPS, SEM, cyclic voltammetry and PXRD. Characteristic peaks of cinchonidine observed in the supported materials confirmed the adsorption of cinchonidine and its coordination with the Cu(2+) active site on copper exchanged zeolite-Y. (13)C SSNMR and XPS analysis however confirmed for the half encapsulation process, only the quinoline ring of cinchonidine gets coordinated to the internal metal sites via the N atom while the quinuclidine moiety extends out of the host surface. Cinchonidine supported Cu(2+)-Y zeolites were found to exhibit good catalytic performance in the asymmetric Henry reaction. (1)H SSNMR studies also confirmed the protonation of the N atom of the quinuclidine ring during the course of the Henry reaction. Heterogeneous chiral catalysts were effective for up to two consecutive cycles. Leaching of cinchonidine after the second cycle was found to have a negative result in the catalytic performance. PMID:26579982

  16. Evidence for enhanced oxygen surface exchange reaction in nanostructured Gd2O3-doped CeO2 films.

    PubMed

    Develos-Bagarinao, Katherine; Kishimoto, Haruo; Yamaji, Katsuhiko; Horita, Teruhisa; Yokokawa, Harumi

    2015-05-29

    The effect of microstructure of Gd?O?-doped CeO? (GDC) films on oxygen surface exchange and diffusion is reported. Epitaxial GDC (10 mol% Gd) films up to 1 ?m in thickness are prepared using pulsed laser deposition on (100) yttria-stabilized zirconia single-crystal substrates and subjected to high-temperature annealing at 1300 °C in air to induce microstructural modifications. Characterization using atomic force microscopy and transmission electron microscopy reveals granular morphologies comprised of densely packed columnar nanostructures for the as-grown GDC films; however, significant microstructural reconstruction of the entire GDC layer occurs after high-temperature annealing. (18)O isotope exchange depth profiling with dynamic secondary ion mass spectroscopy is employed to evaluate the oxygen surface exchange coefficient k* and the diffusion coefficient D* at T = 600 °C. The as-grown GDC exhibits up to 10 times higher k* than the annealed film. The strong differences in oxygen surface reaction are correlated to the observed film properties including surface microstructure and cerium oxidation state as evaluated using electron energy loss spectroscopy in scanning transmission electron microscopy. PMID:25930178

  17. Remarkable nanoconfinement effects on chemical equilibrium manifested in nucleotide dimerization and H-D exchange reactions.

    PubMed

    Polak, Micha; Rubinovich, Leonid

    2011-10-01

    Nanoconfinement entropic effects on chemical equilibrium involving a small number of molecules, which we term NCECE, are revealed by two widely diverse types of reactions. Employing statistical-mechanical principles, we show how the NCECE effect stabilizes nucleotide dimerization observed within self-assembled molecular cages. Furthermore, the effect provides the basis for dimerization even under an aqueous environment inside the nanocage. Likewise, the NCECE effect is pertinent to a longstanding issue in astrochemistry, namely the extra deuteration commonly observed for molecules reacting on interstellar dust grain surfaces. The origin of the NCECE effect is elucidated by means of the probability distributions of the reaction extent and related variations in the reactant-product mixing entropy. Theoretical modelling beyond our previous preliminary work highlights the role of the nanospace size in addition to that of the nanosystem size, namely the limited amount of molecules in the reaction mixture. Furthermore, the NCECE effect can depend also on the reaction mechanism, and on deviations from stoichiometry. The NCECE effect, leading to enhanced, greatly variable equilibrium "constants", constitutes a unique physical-chemical phenomenon, distinguished from the usual thermodynamical properties of macroscopically large systems. Being significant particularly for weakly exothermic reactions, the effects should stabilize products in other closed nanoscale structures, and thus can have notable implications for the growing nanotechnological utilization of chemical syntheses conducted within confined nanoreactors. PMID:21858361

  18. Mechanisms by which reactions catalyzed by chloroplast coupling factor 1 are inhibited: ATP synthesis and ATP-H2O oxygen exchange

    SciTech Connect

    Spencer, J.G.; Wimmer, M.J.

    1985-07-16

    The ATP-H2O back-exchange reaction catalyzed by membrane-bound chloroplast coupling factor 1 (CF1) in the light is known to be extensive; each reacting ATP molecule nearly equilibrates its gamma-PO2 oxygens with H2O before it dissociates from the enzyme. Pi, ASi, ADP, and GDP, alternate substrates of photophosphorylation, each inhibit the exchange reaction. At all concentrations of these substrate/inhibitor molecules tested, the high extent of exchange per molecule of ATP that reacts remains the same, while the number of ATP molecules experiencing exchange decreases. Thus, these inhibitors appear to act in a competitive-type manner, decreasing ATP turnover, as opposed to modulating the rate constants responsible for the partitioning of E X ATP during the exchange reaction. This is consistent with the identity of CF1 catalytic sites for ATP-H2O back-exchange and ATP synthesis. The extent of ATP-H2O forward oxygen exchange, which occurs during net ATP synthesis prior to product dissociation, is unaffected by uncouplers, whether catalyzed by native CF1 (ATPase latent) or the dithiothreitol/light-activated ATPase form.

  19. The analysis of the pantothenate synthetase reaction by positional isotope exchange 

    E-print Network

    Williams, Lakenya Flatreese

    2003-01-01

    of ATP, D-pantoate and enzyme. In addition, these results require the complete torsional scrambling of the two phosphoryl groups of the labeled pyrophosphate product. The rate of the PIX reaction increased as the D-pantoate concentration was elevated...

  20. 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.

  1. One-pot approach to functional nucleosides possessing a fluorescent group using nucleobase-exchange reaction by thymidine phosphorylase.

    PubMed

    Hatano, Akihiko; Kurosu, Masayuki; Yonaha, Susumu; Okada, Munehiro; Uehara, Sanae

    2013-09-25

    Herein, we describe ?-selective coupling between a modified uracil and a deoxyribose to produce functionalized nucleosides catalyzed by thymidine phosphorylase derived from Escherichia coli. This enzyme mediates nucleobase-exchange reactions to convert unnatural nucleosides possessing a large functional group such as a fluorescent molecule, coumarin or pyrene, linked via an alkyl chain at the C5 position of uracil. 5-(Coumarin-7-oxyhex-5-yn)uracil (C4U) displayed 57.2% conversion at 40% DMSO concentration in 1.0 mM phosphate buffer pH 6.8 to transfer thymidine to an unnatural nucleoside with C4U as the base. In the case of using 5-(pyren-1-methyloxyhex-5-yn)uracil (P4U) as the substrate, TP also could catalyse the reaction to generate a product with a very large functional group at 50% DMSO concentration (21.6% conversion). We carried out docking simulations using MF myPrest for the modified uracil bound to the active site of TP. The uracil moiety of the substrate binds to the active site of TP, with the fluorescent moiety linked to the C5 position of the nucleobase located outside the surface of the enzyme. As a consequence, the bulky fluorescent moiety binding to uracil has little influence on the coupling reaction. PMID:24057401

  2. Positioning of Platinum Nanoparticles In Cation-exchange Membrane By Galvanic Reaction

    NASA Astrophysics Data System (ADS)

    Kumar, Rakesh; Pandey, A. K.; Ramagiri, S. V.; Bellare, J. R.; Goswami, A.

    2010-12-01

    Platinum nanoparticles were formed at the surface of the poly (perfluorosulfonic) acid membrane (Nafion-117) by the galvanic reaction of PtCl62- ions with Ag nanoparticles positioned near the surface of the membrane. The reduction with BH4- ions produced Ag nanoparticles (15±4 nm size) mostly positioned near the surface of membrane due to Donnan exclusion of co-ions (BH4-). Energy Dispersive X-ray Fluorescence (EDXRF) analysis of the membrane indicated that galvanic reaction proceeded quantitatively. Transmission Electron Microscopy (TEM) of the cross-sections of membrane samples indicated that the spherical Pt nanoparticles having size 2 to 8 nm were mostly located near the surface of the membrane. The positioning of Pt nanoparticles at surface of the membrane is important for using nano-composite in catalytical application.

  3. Polarized deuteron charge-exchange reaction $dp->{pp}_sN\\pi$ in the Delta-isobar region

    E-print Network

    Uzikov, Yu N; Wilkin, C

    2015-01-01

    Mechanisms of the charge exchange reaction $dp\\to \\{pp\\}_{\\!s} N\\pi$, where $\\{pp\\}_{\\!s}$ is a two-proton system at low excitation energy, are studied at beam energies 1 -- 2 GeV and for invariant masses $M_X$ of the final $N\\pi $ system that correspond to the formation of the $\\Delta(1232)$ isobar. The direct mechanism, where the initial proton is excited into the $\\Delta(1232)$, dominates and explains the existing data on the unpolarized differential cross section and spherical tensor analyzing power $T_{22}$ for $M_X> 1.2$ GeV/$c^2$. However, this model fails to describe $T_{20}.

  4. Polarized deuteron charge-exchange reaction $dp->{pp}_sN?$ in the Delta-isobar region

    E-print Network

    Yu. N. Uzikov; J. Haidenbauer; C. Wilkin

    2015-02-16

    Mechanisms of the charge exchange reaction $dp\\to \\{pp\\}_{\\!s} N\\pi$, where $\\{pp\\}_{\\!s}$ is a two-proton system at low excitation energy, are studied at beam energies 1 -- 2 GeV and for invariant masses $M_X$ of the final $N\\pi $ system that correspond to the formation of the $\\Delta(1232)$ isobar. The direct mechanism, where the initial proton is excited into the $\\Delta(1232)$, dominates and explains the existing data on the unpolarized differential cross section and spherical tensor analyzing power $T_{22}$ for $M_X> 1.2$ GeV/$c^2$. However, this model fails to describe $T_{20}.

  5. Exploring the limits of ultrafast polymerase chain reaction using liquid for thermal heat exchange: A proof of principle

    NASA Astrophysics Data System (ADS)

    Maltezos, George; Johnston, Matthew; Taganov, Konstantin; Srichantaratsamee, Chutatip; Gorman, John; Baltimore, David; Chantratita, Wasun; Scherer, Axel

    2010-12-01

    Thermal ramp rate is a major limiting factor in using real-time polymerase chain reaction (PCR) for routine diagnostics. We explored the limits of speed by using liquid for thermal exchange rather than metal as in traditional devices, and by testing different polymerases. In a clinical setting, our system equaled or surpassed state-of-the-art devices for accuracy in amplifying DNA/RNA of avian influenza, cytomegalovirus, and human immunodeficiency virus. Using Thermococcus kodakaraensis polymerase and optimizing both electrical and chemical systems, we obtained an accurate, 35 cycle amplification of an 85-base pair fragment of E. coli O157:H7 Shiga toxin gene in as little as 94.1 s, a significant improvement over a typical 1 h PCR amplification.

  6. Replica exchange reactive molecular dynamics simulations of initial reactions in zeolite synthesis.

    PubMed

    Jing, Zhifeng; Xin, Liang; Sun, Huai

    2015-10-14

    Molecular simulation is a promising tool for the study of zeolite formation. However, sufficient sampling remains a grand challenge for the practical use of molecular simulation for this purpose. Here, we investigate the initial stage of zeolite synthesis under realistic conditions by using the replica-exchange method and the ReaxFF reactive force field. After a total simulation time of 480 ns, both energetic and structural properties approach convergence. Analyses of data collected at 600 K show that the inorganic structure directing agent NaOH promotes the aggregation of silicate, the formation of branched Si atoms and the formation of 5-membered rings. With the trajectories collected simultaneously at different temperatures, the effect of temperature is discussed. PMID:26365615

  7. 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.

  8. Growth of ?-FeSi2 Layers on Si(100) Substrates by Exchange Reaction between Si and Molten Salts

    NASA Astrophysics Data System (ADS)

    Yoneyama, Tsuyoshi; Yoshikawa, Takeshi; Morita, Kazuki

    2007-08-01

    The growth of ?-FeSi2 layers on Si(100) substrates by a cation exchange reaction between Si and molten NaCl-KCl-FeCl2 salts, namely, 5Si(s)+2FeCl2(l)=2?-FeSi2(s)+SiCl4(g), has been investigated. A single-crystal Si(100) substrate was reacted with the molten salt at 1173 K for 1-64 h in Ar or He atmosphere. The grown layers were characterized by X-ray diffraction (XRD) measurement, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). When the FeCl2 concentration in molten salt was as low as 0.02 mol %, a ?-FeSi2 single layer was obtained, although the double layer of FeSi/?-FeSi2 formed with a higher FeCl2 concentration of 0.1-1.0 mol %. The ?-FeSi2 single layer grown at low FeCl2 concentration had a rough surface structure due to the decrease in driving force caused by the consumption of FeCl2 during the reaction. By annealing a flat double layer of FeSi/?-FeSi2 formed with a higher FeCl2 concentration where the driving force could be kept constant, a flat ?-FeSi2 single layer was obtained on the Si(100) substrate.

  9. 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.

  10. Investigation of Neutron--Deuteron Charge-Exchange Reaction at Small Transfer Momentum

    E-print Network

    N. B. Ladygina

    2007-04-20

    Analysis of the $nd\\to p(nn)$ reaction in a GeV-energy region is performed in the framework based on the multiple-scattering theory for the few-nucleon system. The special kinematic condition, when momentum transfer from neutron beam to final proton closes to zero, is considered. The possibility to extract the spin-dependent term of the elementary $np\\to pn $ amplitude from $nd$-breakup process is investigated. The energy dependence of the ratio $R=\\frac{d\\sigma_{nd}} {d\\Omega} / \\frac{d\\sigma_{np}}{d\\Omega}$ is obtained taking account of the final-state interaction of the two outgoing neutrons in $^1 S_0$-state.

  11. Final State Interaction in Neutron Deuteron Charge Exchange Reaction at Small Transfer Momentum

    E-print Network

    N. B. Ladygina

    2006-10-26

    Analysis of the $nd\\to p(nn)$ reaction in a Gev-energy region is performed in the framework based on the multiple-scattering theory for the few nucleon system. The special kinematic condition, when momentum transfer from neutron beam to final proton closes to zero, is considered. The possibility to extract the spin-flip term of the elementary $np\\to pn $ amplitude from nd-breakup process is investigated. The energy dependence of the ratio $R=\\frac{d\\sigma_{nd}} {d\\Omega} / \\frac{d\\sigma_{np}}{d\\Omega}$ is obtained taking account of the final state interaction two outgoing neutrons in $^1 S_0$-state.

  12. 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.

  13. Quasiclassical trajectory study of Li2 (v ? 100)-Na exchange reaction

    NASA Astrophysics Data System (ADS)

    Rubahn, H.-G.; Sathyamurthy, N.

    The effect of high initial vibrational (v = 0-25) and rotational (j = 0-100) excitation of the reactant molecule on the cross-section ?R for the reaction Li2 + Na ? LiNa + Li at a relative translational energy (Etrans) of 0·5 eV has been investigated using the three-dimensional quasiclassical trajectory method on the recently proposed Varandas-Morais-Pais (VMP) potential. ?R increases almost linearly with increase in v, but it remains unaltered, within the statistical error, with increase in j for j = 0-30. For the higher j states, there is an increase in ?R with increase in j, and the rotational enhancement gets larger with increase in v, becoming comparable to the vibrational enhancement at v = 20. The dependence of ?R on Etrans over the range 0·18 - 0·85 eV has been examined for v = 0, j = 0. For Etrans ? 0·25 eV, all trajectories get trapped. For higher Etrans, ?R rises to a maximum and then levels off. Comparison of our results with those on the Whitehead-Grice (WG) potential reveals that the reactivity is larger on the VMP potential than on the WG for the low v while the opposite is true for the higher v.

  14. Tunneling chemical exchange reaction $\\textrm{D}+\\textrm{HD}\\rightarrow\\textrm{D}_{2}+\\textrm{H}$ in solid HD at temperatures below 1$\\,$K

    E-print Network

    Sheludiakov, S; Järvinen, J; Zvezdov, D; Lehtonen, L; Vainio, O; Vasiliev, S; Khmelenko, V V; Lee, D M

    2015-01-01

    We report on a study of the exchange tunneling reaction D+HD$\\rightarrow$D$_{2}$+H in solid HD at temperatures between 130~mK and 1.5~K by electron spin resonance. The reaction proceeds at almost the same rate ($\\sim3\\times10^{-27}$cm$^{3}$s$^{-1}$) within this temperature range. This observation differs strongly with the recombination rate of H atoms in solid H$_{2}$ which was found substantially reduced upon lowering temperature below 1$\\,$K. These results suggest that the tunneling exchange reaction $\\textrm{H}+\\textrm{H}_{2}\\rightarrow\\textrm{H}_{2}+\\textrm{H}$ can take place in solid H$_{2}$ even though recombination is suppressed at ultra low temperatures in pure hydrogen.

  15. H/D exchange in reactions of OH(-) with D2 and of OD(-) with H2 at low temperatures.

    PubMed

    Mulin, Dmytro; Rou?ka, Št?pán; Jusko, Pavol; Zymak, Illia; Plašil, Radek; Gerlich, Dieter; Wester, Roland; Glosík, Juraj

    2015-04-14

    Using a cryogenic linear 22-pole rf ion trap, rate coefficients for H/D exchange reactions of OH(-) with D2 (1) and OD(-) with H2 (2) have been measured at temperatures between 11 K and 300 K with normal hydrogen. Below 60 K, we obtained k1 = 5.5 × 10(-10) cm(3) s(-1) for the exoergic . Upon increasing the temperature above 60 K, the data decrease with a power law, k1(T) ?T(-2.7), reaching ?1 × 10(-10) cm(3) s(-1) at 200 K. This observation is tentatively explained with a decrease of the lifetime of the intermediate complex as well as with the assumption that scrambling of the three hydrogen atoms is restricted by the topology of the potential energy surface. The rate coefficient for the endoergic increases with temperature from 12 K up to 300 K, following the Arrhenius equation, k2 = 7.5 × 10(-11) exp(-92 K/T) cm(3) s(-1) over two orders of magnitude. The fitted activation energy, EA-Exp = 7.9 meV, is in perfect accordance with the endothermicity of 24.0 meV, if one accounts for the thermal population of the rotational states of both reactants. The low mean activation energy in comparison with the enthalpy change in the reaction is mainly due to the rotational energy of 14.7 meV contributed by ortho-H2 (J = 1). Nonetheless, one should not ignore the reactivity of pure para-H2 because, according to our model, it already reaches 43% of that of ortho-H2 at 100 K. PMID:25738934

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

    USGS Publications Warehouse

    Miller, M.P.; McKnight, Diane 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.

  17. 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

    -exchange complex. Following elution with deionized water, the columns were sectioned and analyzed for residual Na. In all cases, the eluate exhibited approximate thermodynamic equilibrium with respect to calcite. Calcite dissolution and Na?/Ca²? ion exchange...

  18. Carbamoyl-phosphate synthetase II of the mammalian CAD protein: kinetic mechanism and elucidation of reaction intermediates by positional isotope exchange

    SciTech Connect

    Meek, T.D.; Karsten, W.E.; DeBrosse, C.W.

    1987-05-05

    The kinetic mechanism of carbamoyl-phosphate synthetase II from Syrian hamster kidney cells has been determined at pH 7.2 and 37 degrees C. Initial velocity, product inhibition, and dead-end inhibition studies of both the biosynthetic and bicarbonate-dependent adenosinetriphosphatase (ATPase) reactions are consistent with a partially random sequential mechanism in which the ordered addition of MgATP, HCO/sub 3/-, and glutamine is followed by the ordered release of glutamate and Pi. Subsequently, the binding of a second MgATP is followed by the release of MgADP, which precedes the random release of carbamoyl phosphate and a second MgADP. Carbamoyl-phosphate synthetase II catalyzes beta gamma-bridge:beta-nonbridge positional oxygen exchange of (gamma-/sup 18/O)ATP in both the ATPase and biosynthetic reactions. Negligible exchange is observed in the strict absence of HCO3- (and glutamine or NH/sub 4/+). The ratio of moles of MgATP exchanged to moles of MgATP hydrolyzed (nu ex/nu cat) is 0.62 for the ATPase reaction, and it is 0.39 and 0.16 for the biosynthetic reaction in the presence of high levels of glutamine and NH/sub 4/+, respectively. The observed positional isotope exchange is suppressed but not eliminated at nearly saturating concentrations of either glutamine or NH/sub 4/+, suggesting that this residual exchange results from either the facile reversal of an E-MgADP-carboxyphosphate-Gln(NH/sub 4/+) complex or exchange within an E-MgADP-carbamoyl phosphate-MgADP complex, or both. In the /sup 31/P NMR spectra of the exchanged (gamma-/sup 18/O)ATP, the distribution patterns of /sup 16/O in the gamma-phosphorus resonances in all samples reflect an exchange mechanism in which a rotationally unhindered molecule of (/sup 18/O, /sup 16/O)Pi does not readily participate.

  19. Ion-exchange reactions on clay minerals coupled with advection/dispersion processes. Application to Na+/Ca2+ exchange on vermiculite: Reactive-transport modeling, batch and stirred flow-through reactor experiments

    NASA Astrophysics Data System (ADS)

    Tertre, E.; Hubert, F.; Bruzac, S.; Pacreau, M.; Ferrage, E.; Prêt, D.

    2013-07-01

    The present study aims at testing the validity of using an Na+/Ca2+ ion-exchange model, derived from batch data to interpret experimental Ca2+-for-Na+ exchange breakthrough curves obtained on vermiculite (a common swelling clay mineral in surface environments). The ion-exchange model was constructed considering the multi-site nature of the vermiculite surface as well as the exchange of all aqueous species (Mg2+ derived from the dissolution of the solid and H+). The proposed ion-exchange model was then coupled with a transport model, and the predicted breakthrough curves were compared with the experimental ones obtained using a well stirred flow-through reactor. For a given solute residence time in the reactor (typically 50 min), our thermodynamic model based on instantaneous equilibrium was found to accurately reproduce several of the experimental breakthrough curves, depending on the Na+ and Ca2+ concentrations of the influents pumped through the reactor. However the model failed to reproduce experimental breakthrough curves obtained at high flow rates and low chemical gradient between the exchanger phase and the solution. An alternative model based on a hybrid equilibrium/kinetic approach was thus used and allowed predicting experimental data. Based on these results, we show that a simple parameter can be used to differentiate between thermodynamic and kinetic control of the exchange reaction with water flow. The results of this study are relevant for natural systems where two aquatic environments having contrasted chemistries interact. Indeed, the question regarding the attainment of a full equilibrium in such a system during the contact time of the aqueous phase with the particle/colloid remains most often open. In this context, we show that when a river (a flow of fresh water) encounters marine colloids, a systematic full equilibrium can be assumed (i.e., the absence of kinetic effects) when the residence time of the solute in 1 m3 of the system is ?6200 h.

  20. Conformal Cu2S-coated Cu2O nanostructures grown by ion exchange reaction and their photoelectrochemical properties

    NASA Astrophysics Data System (ADS)

    Minguez-Bacho, Ignacio; Courté, Marc; Fan, Hong Jin; Fichou, Denis

    2015-05-01

    Cuprous oxide Cu2O is a promising p-type semiconductor for photoelectrochemical (PEC) solar hydrogen generation because it has a suitable bandgap (Eg = 2.0-2.2 eV) and a band alignment adapted to water reduction. In addition, metallic Cu is earth-abundant thus making Cu2O a low-cost material. However, the reduction potential of Cu2O into metallic Cu (0.47 V versus RHE) is lower than that of water which induces a severe instability under irradiation in a PEC cell. Therefore, our recent efforts focused on the growth of a protective overlayer on top of Cu2O in order to stabilize Cu2O when used as a photocathode in an aqueous electrolyte. Among potential protective materials cuprous sulphide Cu2S is another p-type semiconductor with a 1.2 eV bandgap and an appropriate energy level alignment with Cu2O that would allow electrons flowing to the interface. We present here an original and simple method aimed at protecting a compact layer (CL) or nanowires (NWs) of Cu2O with a Cu2S coating. Our method is based on the ions exchange reaction (IER) of O2- into S2- at the surface of Cu2O itself in a solution-containing Na2S as the sulphur source. The local surface IER implies the formation of a conformal and uniform coating independently on the starting Cu2O morphology, CLs or NWs. As expected, coating Cu2O photocathodes by a conformal Cu2S layer improves their stability and PEC performances.

  1. Tuned synthesis of two coordination polymers of Cd(ii) using substituted bent 3-pyridyl linker and succinate: structures and their applications in anion exchange and sorption properties.

    PubMed

    Maity, Dilip Kumar; Bhattacharya, Biswajit; Halder, Arijit; Ghoshal, Debajyoti

    2015-12-28

    Two new Cd(ii) coordination polymers, namely [Cd(3-bpdh)2(ClO4)2]n (1) and {[Cd(3-bpdh)(suc)(H2O)]·3(H2O)}n (2), have been synthesized using a substituted bent N,N'-donor ligand 2,5-bis-(3-pyridyl)-3,4-diaza-2,4-hexadiene (3-bpdh) and aliphatic dicarboxylate disodium succinate (suc) with Cd(ii) perchlorate salts at room temperature by a slow diffusion technique for the exploration of our previous reported work. Both the structures were determined by single-crystal X-ray diffraction analysis and also by other physicochemical methods. Structure analysis revealed that complex 1 is a 1D chain structure containing coordinated perchlorate with a metal centre, and complex 2 shows a porous 3D framework with encapsulation of lattice water molecules into the void along the crystallographic a-axis. The PXRD study shows the bulk purity of both the complexes and TGA analysis of 2 exhibits that the structure is thermally stable up to 250 °C. Complex 1 shows a nice anion exchange property with replacement of weakly coordinated perchlorate with the inclusion of new anions; and the anion exchanged solids were characterised by FT-IR, PXRD and photoluminescence properties. The desolvated framework of 2 exhibits sorption of CO2 and water vapor and surface adsorption of N2 corroborating with the nature of the pore environment present in 2. The photoluminescence study has been also done for both complexes in the solid state which exhibits ligand based emissions at room temperature. PMID:26586233

  2. 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.

  3. Formation of gypsum and bassanite by cation exchange reactions in the absence of free-liquid H2O: Implications for Mars

    NASA Astrophysics Data System (ADS)

    Wilson, Siobhan A.; Bish, David L.

    2011-09-01

    Smectites and hydrated Mg sulfate minerals have been identified in close association at various locations on the Martian surface. The hydration states of sulfates and smectites are dependent on temperature and relative humidity (RH), and therefore these minerals have the potential to affect cycling and bioavailability of H2O on Mars. We have conducted X-ray powder diffraction experiments to investigate cycling of H2O within mixtures of Ca-bearing smectites and hydrated Mg sulfate minerals under conditions of varying RH similar to those that exist at or just beneath the Martian surface. Our experiments show that under conditions of varying RH, cation-exchange reactions occur between these two potential components of the Martian regolith, producing gypsum [CaSO4·2H2O] and bassanite [CaSO4·˜0.5H2O] in the absence of free-liquid H2O. Cation-exchange reactions were accompanied by significant loss of porosity, warping of the sample surface and, in some cases, volume expansion. The formation of Ca sulfate minerals in these experiments provides evidence for the development of thin films of H2O at mineral surfaces and suggests that similar processes may operate at the arid surface of Mars. Humidity-driven cation-exchange reactions between smectites and hydrated Mg sulfate minerals may therefore play a role in shaping the present-day Martian surface and could have provided a transient source of H2O and nutrients (e.g., major and trace elements and possibly organic micro/macronutrients) for putative microorganisms.

  4. Developing single-molecule TPM experiments for direct observation of successful RecA-mediated strand exchange reaction.

    PubMed

    Fan, Hsiu-Fang; Cox, Michael M; Li, Hung-Wen

    2011-01-01

    RecA recombinases play a central role in homologous recombination. Once assembled on single-stranded (ss) DNA, RecA nucleoprotein filaments mediate the pairing of homologous DNA sequences and strand exchange processes. We have designed two experiments based on tethered particle motion (TPM) to investigate the fates of the invading and the outgoing strands during E. coli RecA-mediated pairing and strand exchange at the single-molecule level in the absence of force. TPM experiments measure the tethered bead Brownian motion indicative of the DNA tether length change resulting from RecA binding and dissociation. Experiments with beads labeled on either the invading strand or the outgoing strand showed that DNA pairing and strand exchange occurs successfully in the presence of either ATP or its non-hydrolyzable analog, ATP?S. The strand exchange rates and efficiencies are similar under both ATP and ATP?S conditions. In addition, the Brownian motion time-courses suggest that the strand exchange process progresses uni-directionally in the 5'-to-3' fashion, using a synapse segment with a wide and continuous size distribution. PMID:21765895

  5. 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

  6. 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.

  7. MAX phase - Alumina composites via exchange reaction in the Mn+1AlCn systems (M=Ti, V, Cr, Nb, or Ta)

    NASA Astrophysics Data System (ADS)

    Cuskelly, Dylan T.; Kisi, Erich H.; Sugo, Heber O.

    2016-01-01

    MAX phases have been produced for the first time via an exchange reaction between the M-element oxide and Al leading to an M-Al-C-Al2O3 composite in the V-Al-C, Cr-Al-C, Nb-Al-C and Ta-Al-C systems in addition to the previously known Ti-Al-C system. The reduction reaction was first investigated by forming the binary M-X carbide and then proven to be generic across all M-Al-C systems with the production of the M2AlC phase in each case. The work was extended to the other M3AlC2 and M4AlC3 phases in the respective systems, and was successful in 4 of the 5 cases with moderate yield.

  8. PH dependence of deuterium isotope effects and tritium exchange in the bovine plasma amine oxidase reaction: a role for single-base catalysis in amine oxidation and imine exchange

    SciTech Connect

    Farnum, M.; Palcic, M.; Klinman, J.P.

    1986-04-22

    The pH dependence of steady-state parameters for (1,1-1H2)- and (1,1-2H2)benzylamine oxidation and of tritium exchange from (2-/sup 3/H)dopamine has been measured in the bovine plasma amine oxidase reaction. Deuterium isotope effects on kcat/Km for benzylamine are observed to be constant, near the intrinsic value of 13.5, over the experimental pH range, indicating that C-H bond cleavage is fully rate limiting for this parameter. As a consequence, pKa values derived from kcat/Km profiles, 8.0 +/- 0.1 (pK1) and 9.0 +/- 0.16 (pKs), can be ascribed to microscopic pKa values for the ionization of an essential active site residue (EB1) and substrate, respectively. Profiles for kcat and Dkcat show that EB1 undergoes a perturbation from 8.0 to 5.6 +/- 0.3 (pK1') in the presence of substrate; additionally, a second ionization, pK2 = 7.25 +/- 0.25, is observed to mediate but not be essential for enzyme reoxidation. The pH dependence of the ratio of tritium exchange to product formation for dopamine also indicates base catalysis with a pKexch = 5.5 +/- 0.01, which is within experimental error of pK1'. We conclude that the data presented herein support a single residue catalyzing both substrate oxidation and exchange, consistent with recent stereochemical results that implicate a syn relationship between these processes (Farnum, M., and Klinman, J.P. (1985) Fed. Proc., Fed. Am. Soc. Exp. Biol. 44, 1055). This conclusion contrasts with earlier kinetic data in support of a large rate differential for the exchange of hydrogen from C-1 vs. C-2 of phenethylamine derivatives.

  9. The Role of Ate Complexes in the Lithium-Sulfur, Lithium-Selenium and Lithium-Tellurium Exchange Reactions

    E-print Network

    Reich, Hans J.

    The Role of Ate Complexes in the Lithium-Sulfur, Lithium-Selenium and Lithium-Tellurium Exchange-shaped geometry of the hypervalent intermediates. For the selenium systems, ate complex intermediates (20-Se, 26 to many of the main-group third-, fourth-, and fifth-row elements. Tin [3a][4], selenium (first studied

  10. 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.

  11. 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.

  12. 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; Fang, Yi; Zhang, Wenjun; Zhang, Li; Chen, Yuhuan; Yu, Xiaoyan

    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.

  13. 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.

  14. Cumulative reaction probabilities and transition state properties: a study of the H+ + H2 and H+ + D2 proton exchange reactions.

    PubMed

    Jambrina, P G; Aoiz, F J; Eyles, C J; Herrero, V J; Sáez Rábanos, V

    2009-05-14

    Cumulative reaction probabilities (CRPs) have been calculated by accurate (converged, close coupling) quantum mechanical (QM), quasiclassical trajectory (QCT), and statistical QCT (SQCT) methods for the H(+) + H(2) and H(+) + D(2) reactions at collision energies up to 1.2 eV and total angular momentum J = 0-4. A marked resonance structure is found in the QM CRP, most especially for the H(3)(+) system and J = 0. When the CRPs are resolved in their ortho and para contributions, a clear steplike structure is found associated with the opening of internal states of reactants and products. The comparison of the QCT results with those of the other methods evinces the occurrence of two transition states, one at the entrance and one at the exit. At low J values, except for the quantal resonance structure and the lack of quantization in the product channel, the agreement between QM and QCT is very good. The SQCT model, that reflects the steplike structure associated with the opening of initial and final states accurately, clearly tends to overestimate the value of the CRP as the collision energy increases. This effect seems more marked for the H(+) + D(2) isotopic variant. For sufficiently high J values, the growth of the centrifugal barrier leads to an increase in the threshold of the CRP. At these high J values the discrepancy between SQCT and QCT becomes larger and is magnified with growing collision energy. The total CRPs calculated with the QCT and SQCT methods allowed the determination of the rate constant for the H(+) + D(2) reaction. It was found that the rate, in agreement with experiment, decreases with temperature as expected for an endothermic reaction. In the range of temperatures between 200 and 500 K the differences between SQCT and QCT rate results are relatively minor. Although exact QM calculations are formidable for an exact determination of the k(T), it can be reliably expected that their value will lie between those given by the dynamical and statistical trajectory methods. PMID:19449917

  15. Cumulative reaction probabilities and transition state properties: A study of the H++H2 and H++D2 proton exchange reactions

    NASA Astrophysics Data System (ADS)

    Jambrina, P. G.; Aoiz, F. J.; Eyles, C. J.; Herrero, V. J.; Sáez Rábanos, V.

    2009-05-01

    Cumulative reaction probabilities (CRPs) have been calculated by accurate (converged, close coupling) quantum mechanical (QM), quasiclassical trajectory (QCT), and statistical QCT (SQCT) methods for the H++H2 and H++D2 reactions at collision energies up to 1.2eV and total angular momentum J =0-4. A marked resonance structure is found in the QM CRP, most especially for the H3+ system and J =0. When the CRPs are resolved in their ortho and para contributions, a clear steplike structure is found associated with the opening of internal states of reactants and products. The comparison of the QCT results with those of the other methods evinces the occurrence of two transition states, one at the entrance and one at the exit. At low J values, except for the quantal resonance structure and the lack of quantization in the product channel, the agreement between QM and QCT is very good. The SQCT model, that reflects the steplike structure associated with the opening of initial and final states accurately, clearly tends to overestimate the value of the CRP as the collision energy increases. This effect seems more marked for the H++D2 isotopic variant. For sufficiently high J values, the growth of the centrifugal barrier leads to an increase in the threshold of the CRP. At these high J values the discrepancy between SQCT and QCT becomes larger and is magnified with growing collision energy. The total CRPs calculated with the QCT and SQCT methods allowed the determination of the rate constant for the H++D2 reaction. It was found that the rate, in agreement with experiment, decreases with temperature as expected for an endothermic reaction. In the range of temperatures between 200 and 500K the differences between SQCT and QCT rate results are relatively minor. Although exact QM calculations are formidable for an exact determination of the k(T ), it can be reliably expected that their value will lie between those given by the dynamical and statistical trajectory methods.

  16. Anion-exchange reactions on a robust phosphonium photopolymer for the controlled deposition of ionic gold nanoclusters.

    PubMed

    Guterman, Ryan; Hesari, Mahdi; Ragogna, Paul J; Workentin, Mark S

    2013-05-28

    UV curing (photopolymerization) is ubiquitous in many facets of industry ranging from the application of paints, pigments, and barrier coatings all the way to fiber optic cable production. To date no reports have focused on polymerizable phosphonium salts under UV irradiation, and despite this dearth of examples, they potentially offer numerous substantial advantages to traditional UV formulation components. We have generated a highly novel coating based on UV-curable trialkylacryloylphosphonium salts that allow for the fast (seconds) and straightforward preparation of ion-exchange surfaces amenable to a roll-to-roll process. We have quantified the surface charges and exploited their accessibility by employing these surfaces in an anion exchange experiment by which [Au25L18](-) (L = SCH2CH2Ph) nanocrystals can be assembled into the solid state. This unprecedented application of such surfaces offers a paradigm shift in the emerging chemistry of Au25 research where the nanocrystals remain single and intact and where the integrity of the cluster and its solution photophysical properties are resilient in the solid state. The specific loading of [Au25L18](-) on the substrates has been determined and the completely reversible loading and unloading of intact nanocrystals to and from the surface has been established. In the solid state, the assembly has an incredible mechanical resiliency, where the surface remains undamaged even when subjected to repeated Scotch tests. PMID:23472738

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

    SciTech Connect

    Bhattacharya, M.; Goodman, C. D.; Garcia, A.

    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.

  18. 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.

  19. Precision evaluation of the 71Ga(?e,e- ) solar neutrino capture rate from the (3He,t ) charge-exchange reaction

    NASA Astrophysics Data System (ADS)

    Frekers, D.; Adachi, T.; Akimune, H.; Alanssari, M.; Brown, B. A.; Cleveland, B. T.; Ejiri, H.; Fujita, H.; Fujita, Y.; Fujiwara, M.; Gavrin, V. N.; Harakeh, M. N.; Hatanaka, K.; Holl, M.; Iwamoto, C.; Lennarz, A.; Okamoto, A.; Okamura, H.; Suzuki, T.; Tamii, A.

    2015-03-01

    A precision measurement of the 71Ga(3He,t ) 71Ge charge-exchange reaction was performed. By using a rather complete set of theoretical form factors to describe the cross-section angular distributions over a large angular range, the Gamow-Teller strength distribution up to the effective neutron-separation energy in 71Ge was extracted. The data and the analysis constrain the 71Ga(?e,e- ) solar neutrino rate in a neutrino nonoscillation scenario. For nonoscillating neutrinos we report a solar neutrino capture rate of 122.4 ±3.4 (stat ) ±1.1 (sys ) SNU, which is lower than the presently accepted value of 132 ±18 SNU, though not in disagreement given the quoted errors.

  20. Hydrogen bonding induced proton exchange reactions in dense D{sub 2}-NH{sub 3} and D{sub 2}-CH{sub 4} mixtures

    SciTech Connect

    Borstad, Gustav M.; Yoo, Choong-Shik

    2014-01-28

    We have investigated high-pressure behaviors of simple binary mixtures of NH{sub 3} and D{sub 2} to 50 GPa and CH{sub 4} and D{sub 2} to 30 GPa using confocal micro-Raman spectroscopy. The spectral data indicate strong proton exchange reactions occur in dense D{sub 2}-NH{sub 3} mixture, producing different isotopes of ammonia such as NH{sub 3}, NH{sub 2}D, NHD{sub 2}, and ND{sub 3}. In contrast, the proton exchange process in dense D{sub 2}-CH{sub 4} mixture is highly limited, and no vibration feature is apparent for deuterated methane. The vibrational modes of H{sub 2} isotopes in D{sub 2}-NH{sub 3} are blue shifted from those of pure H{sub 2} isotopes, whereas the modes of D{sub 2}-CH{sub 4} show overall agreement with those in pure D{sub 2} and CH{sub 4}. In turn, this result advocates the presence of strong repulsion and thereby internal pressure in D{sub 2}-NH{sub 3} mixture, which are absent in D{sub 2}-CH{sub 4}. In fact, the bond length of hydrogen molecules in D{sub 2}-NH{sub 3}, calculated from the present spectral data, is shorter than that observed in pure hydrogen – supporting the enhanced intermolecular interaction in the mixture. Comparing the present spectral results with those previously observed in D{sub 2}-H{sub 2}O mixtures further suggests that the strength of repulsive interaction or the magnitude of internal pressure in the mixtures is proportional to the strength of hydrogen bonding in H{sub 2}O, NH{sub 3}, and CH{sub 4} in decreasing order. Hence, we suggest that the proton exchange is assisted by hydrogen bonding in these molecules.

  1. 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.

  2. Hydrothermal alteration processes at midocean ridges: Experimental and theoretical constraints from Ca and Sr exchange reactions and Sr isotopic ratios

    NASA Astrophysics Data System (ADS)

    Berndt, Michael E.; Seyfried, William E., Jr.; Beck, J. Warren

    1988-05-01

    Diabase and basalt were reacted with Na-Ca-K-Cl fluids of seawater chlorinity at 375-425°C, 375-400 bars, and fluid/rock mass ratios of 0.5-1.0 to assess the role of basalt chemistry and texture on Sr and Ca mobility during high-temperature hydrothermal alteration. An additional experiment, utilizing an 84Sr spiked fluid, was performed to help quantify reaction rates of processes affecting Sr mobility. The experimental results help to constrain reaction processes responsible for the chemistry of hot spring fluids at midocean ridges. Alteration of basalt and diabase is characterized by formation of tremolite-actinolite-smectite-chlorite and clinozoisitic epidote-smectite-chlorite, respectively. Diabase alteration produced dissolved Sr/Ca ratios similar to those observed for ridge crest hot spring fluids, whereas alteration of a mostly crystalline basalt produced significantly lower ratios. This observation supports the premise that the Sr/Ca ratios observed in vent fluids may be produced during deep-seated reaction of the hydrothermal fluids with diabase dikes and/or gabbro at relatively low fluid/rock ratios and suggests that hydrothermal alteration of primary igneous minerals at relatively high temperatures (400°C) leads to formation of a mineral with low DSr/Ca, Possibly hydrothermal plagioclase. Results of the 84Sr spiked experiment indicated that only 4% of the Sr in basalt was mobilized after 800 hours of reaction despite the fact that B and Li were nearly quantitatively leached. It is thus suggested that B and Li are good indicators of the amount of fresh rock encountered by fluids, while Sr concentration and isotopic data can be used to estimate the degree of alteration that the Sr-bearing primary minerals have undergone. The degree of alteration of subsurface reservoirs may be estimated by dividing the fluid/rock ratio obtained for highly mobile elements by the fluid/rock ratio obtained from path-integrated Sr isotope and concentration data. Based on this method, for example, it can be estimated that only 5% of the primary Sr-bearing minerals encountered by fluids in the subsurface at EPR 21°N are actually converted to secondary phases.

  3. 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.

  4. A facile route to violet- to orange-emitting CdxZn1-xSe alloy nanocrystals via cation exchange reaction

    NASA Astrophysics Data System (ADS)

    Zhong, Xinhua; Feng, Yaoyu; Zhang, Yuliang; Gu, Zhenyu; Zou, Lei

    2007-09-01

    The most advanced CdSe-based binary semiconductor system does not work well for emission in the short wavelength spectral region from 420 to 500 nm, which is of special interest for the preparation of nanocrystal-based blue LEDs and white light generation. CdxZn1-xSe alloy nanocrystals are proven to be an attractive alternative as their emission color can be tuned from the UV spectral region (ZnSe) to the red region (CdSe) by changing the composition of the Zn/Cd ratio in the alloy. Herein we report a facile and 'green' alloying approach for the preparation of highly luminescent CdxZn1-xSe nanocrystals via cation exchange reaction of the pre-prepared ZnSe nanocrystals with Cd2+ at intermediate temperatures. Through this new synthetic strategy, high-quality alloy QDs with different desired emission wavelengths or colors (ranging from 370 to 600 nm) can be made reproducibly and precisely by varying the predetermined amounts of the reaction precursors.

  5. 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.

  6. 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.

  7. 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, Diane 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.

  8. Real-time monitoring of in situ gas-phase H/D exchange reactions of cations by atmospheric pressure helium plasma ionization mass spectrometry (HePI-MS).

    PubMed

    Attygalle, Athula B; Gangam, Rekha; Pavlov, Julius

    2014-01-01

    An enclosed atmospheric-pressure helium-plasma ionization (HePI-MS) source avoids, or minimizes, undesired back-exchange reactions usually encountered during deuterium incorporation experiments under ambient-pressure open-source conditions. A simple adaptation of an ESI source provides an economical way of conducting gas phase hydrogen/deuterium (H/D) exchange reactions (HDX) in real time without the need for complicated hardware modifications. For example, the spectrum of [(2)H8]toluene recorded under exposed ambient conditions showed the base peak at m/z 96 due to fast leaching of ring hydrogens because of interactions with H2O vapor present in the open source. Such D/H exchanges are rapidly reversed if the deuterium-depleted [(2)H8]toluene is exposed to D2O vapor. In addition to the enumeration of labile protons, our procedure enables the identification of protonation sites in molecules unambiguously, by the number of H/D exchanges observed in real time. For example, molecules such as tetrahydrofuran and pyridine protonate at the heteroatom and consequently undergo only one H/D exchange, whereas ethylbenzene, which protonates at a ring position of the aromatic ring, undergoes six H/D exchanges. In addition, carbocations generated in situ by in-source fragmentation of precursor protonated species, such as benzyl alcohol, do not undergo any rapid H/D exchanges. Because radical cations, second-generation cations (ions formed by losing a small molecule from a precursor ion), or those formed by hydride abstraction do not undergo rapid H/D exchanges, our technique provides a way to distinguish these ions from protonated molecules. PMID:24325360

  9. 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.

  10. Competing Noncovalent Host-guest Interactions and H/D Exchange: Reactions of Benzyloxycarbonyl-Proline Glycine Dipeptide Variants with ND3

    NASA Astrophysics Data System (ADS)

    Miladi, Mahsan; Olaitan, Abayomi D.; Zekavat, Behrooz; Solouki, Touradj

    2015-11-01

    A combination of density functional theory calculations, hydrogen/deuterium exchange (HDX) reactions, ion mobility-mass spectrometry, and isotope labeling tandem mass spectrometry was used to study gas-phase "host-guest" type interactions of a benzyloxycarbonyl (Z)-capped proline (P) glycine (G) model dipeptide (i.e., Z-PG) and its various structural analogues with ND3. It is shown that in a solvent-free environment, structural differences between protonated and alkali metal ion (Na+, K+, or Cs+)-complexed species of Z-PG affect ND3 adduct formation. Specifically, [Z-PG + H]+ and [Z-PG-OCH3 + H]+ formed gas-phase ND3 adducts ([Z-PG (or Z-PG-OCH3) + H + ND3]+) but no ND3 adducts were observed for [Z-PG + alkali metal]+ or [Z-PG + H - CO2]+. Experimentally measured and theoretically calculated collision cross sections (CCSs) of protonated and alkali metal ion-complexed Z-PG species showed similar trends that agreed with the observed structural differences from molecular modeling results. Moreover, results from theoretical ND3 affinity calculations were consistent with experimental HDX observations, indicating a more stable ND3 adduct for [Z-PG + H]+ compared to [Z-PG + alkali metal]+ species. Molecular modeling and experimental MS results for [Z-PG + H]+ and [Z-PG + alkali metal]+ suggest that optimized cation-? and hydrogen bonding interactions of carbonyl groups in final products are important for ND3 adduct formation.

  11. 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.

  12. Microfluidic chemical reaction circuits

    DOEpatents

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

    2012-06-26

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

  13. Competing Noncovalent Host-guest Interactions and H/D Exchange: Reactions of Benzyloxycarbonyl-Proline Glycine Dipeptide Variants with ND3.

    PubMed

    Miladi, Mahsan; Olaitan, Abayomi D; Zekavat, Behrooz; Solouki, Touradj

    2015-11-01

    A combination of density functional theory calculations, hydrogen/deuterium exchange (HDX) reactions, ion mobility-mass spectrometry, and isotope labeling tandem mass spectrometry was used to study gas-phase "host-guest" type interactions of a benzyloxycarbonyl (Z)-capped proline (P) glycine (G) model dipeptide (i.e., Z-PG) and its various structural analogues with ND3. It is shown that in a solvent-free environment, structural differences between protonated and alkali metal ion (Na(+), K(+), or Cs(+))-complexed species of Z-PG affect ND3 adduct formation. Specifically, [Z-PG + H](+) and [Z-PG-OCH3 + H](+) formed gas-phase ND3 adducts ([Z-PG (or Z-PG-OCH3) + H + ND3](+)) but no ND3 adducts were observed for [Z-PG + alkali metal](+) or [Z-PG + H - CO2](+). Experimentally measured and theoretically calculated collision cross sections (CCSs) of protonated and alkali metal ion-complexed Z-PG species showed similar trends that agreed with the observed structural differences from molecular modeling results. Moreover, results from theoretical ND3 affinity calculations were consistent with experimental HDX observations, indicating a more stable ND3 adduct for [Z-PG + H](+) compared to [Z-PG + alkali metal](+) species. Molecular modeling and experimental MS results for [Z-PG + H](+) and [Z-PG + alkali metal](+) suggest that optimized cation-? and hydrogen bonding interactions of carbonyl groups in final products are important for ND3 adduct formation. Graphical Abstract ?. PMID:26289383

  14. 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.

  15. 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.

  16. Optimum Temperature Difference and Pressure Drop in Heat Exchangers 

    E-print Network

    Steinmeyer, D.

    1991-01-01

    Most processing is thermal. Reaction systems and separation systems are typically dominated by their associated heat exchange. Optimization of this heat exchange has a tremendous leverage on the ultimate process efficiency. Heat exchangers use...

  17. Nucleophilic reactions at a vinylic center. XVI. Investigation of the nucleophilic exchange of fluorine in. beta. -fluoroacrylonitriles by the MINDO/3 method

    SciTech Connect

    Shainyan, B.A.

    1986-01-10

    The potential energy surfaces of the reactions of F/sup -/ with cis- and trans-..beta..-fluoroacrylonitriles were calculated by the MINDO/3 method. It was shown that three reaction paths can be realized in the system, i.e., attack by the nucleophile at the ..beta..-carbon atom, the elimination of a proton from the ..cap alpha.. position, and the elimination of a proton from the ..beta.. position. All three reaction paths are exothermic in the gas phase, and the elimination of the proton from the ..cap alpha.. position is 70 kJ/mole more favorable than from the ..beta.. position. Allowance for the effect of the medium in terms of an unconcerted solvation model modes not lead to the appearance of an activation barrier, in contrast to the reactions of anions with ethylene.

  18. 10 CFR Appendix E to Part 110 - Illustrative List of Chemical Exchange or Ion Exchange Enrichment Plant Equipment and Components...

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ...Part 110—Illustrative List of Chemical Exchange or Ion Exchange Enrichment...uranium causes small changes in chemical reaction equilibria that can be used as...successfully developed: liquid-liquid chemical exchange and solid-liquid...

  19. 10 CFR Appendix E to Part 110 - Illustrative List of Chemical Exchange or Ion Exchange Enrichment Plant Equipment and Components...

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ...Part 110—Illustrative List of Chemical Exchange or Ion Exchange Enrichment...uranium causes small changes in chemical reaction equilibria that can be used as...successfully developed: liquid-liquid chemical exchange and solid-liquid...

  20. 10 CFR Appendix E to Part 110 - Illustrative List of Chemical Exchange or Ion Exchange Enrichment Plant Equipment and Components...

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ...Part 110—Illustrative List of Chemical Exchange or Ion Exchange Enrichment...uranium causes small changes in chemical reaction equilibria that can be used as...successfully developed: liquid-liquid chemical exchange and solid-liquid...

  1. 10 CFR Appendix E to Part 110 - Illustrative List of Chemical Exchange or Ion Exchange Enrichment Plant Equipment and Components...

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ...Part 110—Illustrative List of Chemical Exchange or Ion Exchange Enrichment...uranium causes small changes in chemical reaction equilibria that can be used as...successfully developed: liquid-liquid chemical exchange and solid-liquid...

  2. 10 CFR Appendix E to Part 110 - Illustrative List of Chemical Exchange or Ion Exchange Enrichment Plant Equipment and Components...

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ...Part 110—Illustrative List of Chemical Exchange or Ion Exchange Enrichment...uranium causes small changes in chemical reaction equilibria that can be used as...successfully developed: liquid-liquid chemical exchange and solid-liquid...

  3. 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

  4. Role of ion exchange reactions in the in situ leaching of uraninite by NH{sub 4}HCO{sub 3} -- (NH{sub 4}){sub 2}CO{sub 3} -- H{sub 2}O{sub 2}

    SciTech Connect

    Brantner, J.; Liddell, K.

    1996-10-01

    Ion exchange on clay mineral surfaces can alter the concentrations of solution species, the solubility of other minerals that share a common cation, and the porosity and permeability of the host formation. Equilibrium cation exchange reactions involving NH{sub 4}{sup +}, Na{sup +}, K{sup +}, H{sup +}, Ca{sup 2+}, and Mg{sup 2+} were incorporated in a mathematical model for the in situ leaching of UO{sub 2} by solutions of NH{sub 4}HCO{sub 3}, (NH{sub 4}){sub 2}CO{sub 3}, and H{sub 2}O{sub 2}. The clay surface was assumed to be in equilibrium with ground water initially; contact with leach solution resulted in displacement of the Na{sup +}, K{sup +}, H{sup +}, Ca{sup 2+}, and Mg{sup 2+} cations from the clay, often accompanied by precipitation of calcite and magnesite. Development of the ion exchange model is described and implications for successful in situ uranium recovery and ground water restoration are discussed.

  5. Synthesis and crystal structure of Mg{sub 0.5}NbO{sub 2}: An ion-exchange reaction with Mg{sup 2+} between trigonal [NbO{sub 2}]{sup -} layers

    SciTech Connect

    Miura, Akira; Takei, Takahiro; Kumada, Nobuhiro

    2013-01-15

    A new layered niobate, Mg{sub 0.5}NbO{sub 2}, was synthesized from LiNbO{sub 2} through a cation-exchange reaction with Mg{sup 2+} at 450-550 Degree-Sign C. This is the first example of a topotactic reaction with an aliovalent cation between trigonal [NbO{sub 2}]{sup -} layers. It is proposed to be isostructural with LiNbO{sub 2} (space group; P6{sub 3}/mmc) with lattice parameters of a=2.9052(6) A, c=10.625(15) A. The lattice parameters and formation energy of Mg{sub 0.5}NbO{sub 2} crystallized in LiNbO{sub 2} form and other layered CaNb{sub 2}O{sub 4} one were calculated by density functional theory. - Graphical abstract: A new layered niobate, Mg{sub 0.5}NbO{sub 2}, was synthesized from LiNbO{sub 2} through a cation-exchange reaction with Mg{sup 2+} at 450-550 Degree-Sign C. It is isostructural with LiNbO{sub 2} with lattice parameters of a=2.9052(6) A, c=10.625(15) A. Mg{sup 2+} are described in spheres located between [NbO{sub 2}]{sup -} trigonal layers and its occupancy is 0.5. Highlights: Black-Right-Pointing-Pointer A new layered niobate, Mg{sub 0.5}NbO{sub 2}, was synthesized from LiNbO{sub 2}. Black-Right-Pointing-Pointer Cation-exchange reaction converted two monovalent Li{sup +} into one divalent Mg{sup 2+} at 450-550 Degree-Sign C. Black-Right-Pointing-Pointer Mg{sub 0.5}NbO{sub 2} was isostructural with LiNbO{sub 2} (space group; P6{sub 3}/mmc). Black-Right-Pointing-Pointer Its lattice parameters were a=2.9052(6) A and c=10.625(15) A. Black-Right-Pointing-Pointer Synthesized Mg{sub 0.5}NbO{sub 2} was calculated to be thermodynamically more favorable.

  6. 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)

  7. On the stability of metal-aminoacid complexes in water based on water-ligand exchange reactions and electronic properties: detailed study on iron-glycine hexacoordinated complexes.

    PubMed

    Mandado, Marcos; Cordeiro, M Natália D S

    2010-11-30

    Thermodynamic stability of metal-aminoacid complexes in water is discussed in terms of the Gibbs free energy of water-ligand exchange processes, and the electronic stabilizing factors thoroughly investigated by means of 1-electron and 2-electron density properties. Hexacoordinated complexes formed between iron cations and glycine molecules acting as monodentate or bidentate ligands have been chosen as targets for the current study. Results agree with experimental findings, and complexes formed with bidentate ligands are found to be more stable than those formed with monodentate ones. The larger the number of the coordinated glycine molecules the more stable is the complex. Fe(III) complexes are more stable than Fe(II) ones, but differences are small and the Fe(3+)/Fe(2+) exchange process appears to be energetically feasible for these complexes. Formation of the second glycine-iron interaction involving the amino nitrogen in the bidentate ligands is enthalpycally unfavorable but takes place due to the large entropy rise of the process. The larger stability of Fe(III) complexes is due however to the balance between energetic and solvation terms, which is favorable to these complexes. Electron density properties account satisfactorily for the electronic energy changes along the complex formation in terms of ligand-metal electron transfer and covalent bond orders. PMID:20839300

  8. Selective metal-ion extraction for multiple ion liquid-liquid exchange reactions. Progress report, March 1, 1980-February 28, 1981

    SciTech Connect

    Tavlarides, L.L.

    1981-03-01

    This research in hydrometallurgical solvent extraction is to develop a fundamental means to predict selectivity during simultaneous solvent extraction of multiple metal ions when the kinetic rates and thermodynamic equilibria both do not favor the desired metal. To this end the chemical kinetics and thermodynamic chemical equilibria models for the system copper-iron-acid sulfate solutions extracted by ..beta..-alkenyl - 8-hydroxy quinoline in xylene are being determined. These models can be employed with appropriate design equations to predict selectivity factors of the desired species for mixer settler or other two phase contactors. A thermodynamic equilibrium model was developed to describe the distribution of copper only between the aqueous and organic phases. The model considers the aqueous phase ionic equilibria and accounts for impurities in the extractant. The enthalpy of the reaction and the entropy change are -1275 cal/g-mol and 3.46 cal/g-mol, /sup 0/K respectively. The equation for the temperature dependent thermodynamic equilibrium coefficient is also determined. Kinetic data for the copper-sulfate-..beta..-alkenyl - 8-hydroxy quinoline were obtained using the liquid jet recycle reactor, and a kinetic model was developed. It was determined that the flux of copper is not diffusion controlled but either reaction controlled or mass transfer and reaction controlled. The mechanism which supports this model assumes an interfacial reaction in which the adsorbed organic chelation acid is undissociated and the rate limiting step is the formation of positive charged CuR/sup +/. Chemical equilibria and chemical kinetic studies for the iron-acid sulfate ..beta..-alkenyl - 8-hydroxy quinoline - xylene system are in progress.

  9. The inner-sphere reorganization energies for AH{sub 2} + AH{sub 2}{sup +(-)} (A = Al, Si, P, S) electron self-exchange reactions in electron-transfer processes from ab initio calculations

    SciTech Connect

    Yuxiang Bu; Zhaohua Cao; Zailun Yang

    1995-08-15

    This article presents an application of the accurate calculation scheme proposed recently for the inner-sphere reorganization energies of molecules of the type AH{sub 2} (A = Al, Si, P, and S). A reasonable extension has been made. The inner-sphere reorganization energies for the title thermal electron self-exchange reactions are calculated in terms of ab initio MO self-consistent field method (HFSCF) at different basis-set levels (6-31G**, 6-31 + G**, DZ, and DZP) and the involved parameters are also determined. These calculated results have been calibrated by comparing optimized molecular geometrical parameters and corresponding energy properties with the experimental findings or other theoretical values. An approximation, in which the contribution from the bond length-bond angle to the potential energy surface is neglected, is adopted in constructing the calculation formulas via the function model. Its adequacy is discussed. Agreement among different calculation schemes is analyzed. 32 refs., 2 tabs.

  10. Decay of {sup 6}Be populated in the {sup 6}Li({sup 3}He,{sup 3}H) charge-exchange reaction

    SciTech Connect

    Papka, P.; Nemulodi, F.; Bark, R. A.; Kheswa, N. Y.; Lawrie, E. A.; Lawrie, J. J.; Lieder, E. O.; Lieder, R. M.; Madiba, T. E.; Mullins, S. M.; Newman, R. T.; Shirinda, O.; Singo, T. D.; Alvarez-Rodriguez, R.; Fox, S. P.; Gal, J.; Kalinka, G.; Molnar, J.; Nyako, B. M.; Timar, J.

    2010-05-15

    A complete kinematic measurement of the {sup 6}Li({sup 3}He,{sup 3}H)alphapp reaction is performed at E{sub lab}=50 MeV, to investigate the cluster structure of {sup 6}Be. The energy and angular distributions of the breakup particles, emitted from the ground and first excited states of {sup 6}Be, are compared to three-body resonance and two-body sequential decay calculations. The results indicate a rather pure three-body configuration of the 2{sup +} state of {sup 6}Be but they are not conclusive regarding the decay mode of the 0{sup +} state. No branching ratio between sequential and three-body decay paths could be extracted. Excitations above the 2{sup +} state were populated at E{sub x}=1.67-23 MeV. Decay through {sup 5}Li-p and {sup 2}He-{sup 4}He channels is identified in the continuum of {sup 6}Be, and the reaction mechanism is discussed.

  11. Test procedure for cation exchange chromatography

    SciTech Connect

    Cooper, T.D.

    1994-08-24

    The purpose of this test plan is to demonstrate the synthesis of inorganic antimonate ion exchangers and compare their performance against the standard organic cation exchangers. Of particular interest is the degradation rate of both inorganic and organic cation exchangers. This degradation rate will be tracked by determining the ion exchange capacity and thermal stability as a function of time, radiation dose, and chemical reaction.

  12. Synthesis and characterization of alloy catalyst nanoparticles PtNi/C for oxygen reduction reaction in proton exchange membrane fuel cell

    NASA Astrophysics Data System (ADS)

    Linh Do, Chi; San Pham, Thy; Nguyen, Ngoc Phong; Tran, Viet Quan; Hanh Pham, Hong

    2015-01-01

    In this report, vulcan XC-72 supported PtNi alloy catalyst nanoparticles were synthesized by electroless deposition method using NaBH4 as a reduction agent. The properties of the synthesized Pt-Ni/C catalysts were investigated and evaluated. Transmission electron microscopy (TEM) results showed that PtNi alloy catalysts dispersed well on the carbon supports and their particle size was in the range of 4-8 nm. X-ray diffraction (XRD) analysis confirmed that the crystal lattice of Pt and PtNi alloy is face centered cubic. In the presence of Ni atom, an XRD pattern showed that structure of PtNi alloy crystal was contracted, which affected the catalyst’s properties. The activity of the catalyst was estimated by electrochemical methods including cyclic voltammetry (CV) and linear sweep voltammetry (LSV). The electrochemical results indicated that the activity of PtNi/C alloy catalysts toward oxygen reduction reaction on cathode of PEMFC was higher in comparison with Pt/C catalysts.

  13. The Dynamics of Multilateral Exchange

    NASA Astrophysics Data System (ADS)

    Hausken, Kjell; Moxnes, John F.

    The article formulates a dynamic mathematical model where arbitrarily many players produce, consume, exchange, loan, and deposit arbitrarily many goods over time to maximize utility. Consuming goods constitutes a benefit, and producing, exporting, and loaning away goods constitute a cost. Utilities are benefits minus costs, which depend on the exchange ratios and bargaining functions. Three-way exchange occurs when one player acquires, through exchange, one good from another player with the sole purpose of using this good to exchange against the desired good from a third player. Such a triple handshake is not merely a set of double handshakes since the player assigns no interest to the first good in his benefit function. Cognitive and organization costs increase dramatically for higher order exchanges. An exchange theory accounting for media of exchange follows from simple generalization of two-way exchange. The examples of r-way exchange are the triangle trade between Africa, the USA, and England in the 17th and 18th centuries, the hypothetical hypercycle involving RNAs as players and enzymes as goods, and reaction-diffusion processes. The emergence of exchange, and the role of trading agents are discussed. We simulate an example where two-way exchange gives zero production and zero utility, while three-way exchange causes considerable production and positive utility. Maximum utility for each player is reached when exchanges of the same order as the number of players in society are allowed. The article merges micro theory and macro theory within the social, natural, and physical sciences.

  14. Nano PtCu binary and PtCuAg ternary alloy catalysts for oxygen reduction reaction in proton exchange membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Zhou, Yanmei; Zhang, Dongming

    2015-03-01

    In order to decrease the cost and enhance the performance of the cathode catalyst for PEMFC, carbon supported PtCu and PtCuAg alloys with differential Ag content are synthesized by a borohydride chemical reduction. The oxygen reduction reaction (ORR) activity are tested by cyclic voltammetry (CV?and linear sweep voltammograms (LSV) in 0.5 M H2SO4. By comparison with the ORR activities of PtCu/C and a series of PtCuAg/C catalysts with differential metal atomic ratios of Pt:Cu:Ag, the PtCuAg/C catalyst with the atomic ratio on 3:10:1 (marked as PtCuAg/C(3:10:1)) shows the best catalytic activity. For the 200th cycles, the limited current reaches to 3.85 mA cm-2 for PtCuAg/C(3:10:1) with Pt-loading of 9.29 ?gPt cm-2. The CV curves of the PtCuAg/C catalysts show one more pair of redox peaks of Ag compared with PtCu/C catalyst, which is much different from Pt-M alloy catalysts reported in other literature. The TEM and XRD as well as XPS results indicate that the enhanced ORR activity is the result of the smaller particle size, the crystal distortion and the more exposure of Pt atoms with the introduction of Ag for PtCuAg/C(3:10:1) catalyst.

  15. Electron paramagnetic resonance investigation of photosynthetic reaction centers from Rhodobacter sphaeroides R-26 in which Fe2+ was replaced by Cu2+. Determination of hyperfine interactions and exchange and dipole-dipole interactions between Cu2+ and QA-.

    PubMed Central

    Calvo, R; Passeggi, M C; Isaacson, R A; Okamura, M Y; Feher, G

    1990-01-01

    We report electron paramagnetic resonance (EPR) experiments in frozen solutions of unreduced and reduced photosynthetic reaction centers (RCs) from Rhodobacter sphaeroides R-26 in which Fe2+ has been chemically replaced by the isotope 65Cu2+. Samples in which the primary quinone acceptor QA is unreduced (Cu2+QA:RCs) give a powder EPR spectrum typical for Cu2+ having axial symmetry, corresponding to a d(x2 - y2) ground state orbital, with g values g parallel = 2.314 +/- 0.001 and g perpendicular = 2.060 +/- 0.003. The spectrum shows a hyperfine structure for the nuclear spin of copper (65I = 3/2) with A parallel = (-167 +/- 1) x 10(-4) cm-1 and /A perpendicular/ = (16 +/- 2) x 10(-4) cm-1, and hyperfine couplings with three nitrogen ligands. This has been verified in samples containing the naturally occurring 14N isotope (l = 1), and in samples where the nitrogen ligands to copper were replaced by the isotope 15N (l = 1/2). We introduce a model for the electronic structure at the position of the metal ion which reflects the recently determined three-dimensional structure of the RCs of Rb. sphaeroides (Allen, J. P., G. Feher, T. O. Yeates, H. Komiya, and D. C. Rees. 1987. Proc. Natl. Acad. Sci. USA. 84:5730: Allen, J. P., G. Feher, T. O. Yeates, H. Komiya, and D. C. Rees. 1988. Proc. Natl. Acad. Sci. USA, 85:8487) as well as our EPR results. In this model the copper ion is octahedrally coordinated to three nitrogens from histidine residues and to one carboxylate oxygen from a glutamic acid, forming a distorted square in the plane of the d(x2 = y2) ground state orbital. It is also bound to a nitrogen of another histidine and to the other carboxylate oxygen of the same glutamic acid residue, in a direction approximately normal to this plane. The EPR spectrum changes drastically when the quinone acceptor QA is chemically reduced (Cu2+QA-:RCs); the change is due to the exchange and dipole-dipole interactions between the Cu2+ and QA- spins. A model spin Hamiltonian proposed for this exchange coupled cooper-quinone spin dimer accounts well for the observed spectra. From a comparison of the EPR spectra of the Cu2+QA:RC and CU2+QA-:RC complexes we obtain the values /J0/ = (0.30 +/- 0.02) K for the isotropic exchange coupling, and /d/ = (0.010 +/- 0.002) K for the projection of the dipole-dipole interaction tensor on the symmetry axis of the copper spin. From the EPR experiments only the relative signs of J0 and d can be deduced; it was determined that they have the same sign. The magnitude of the exchange coupling calculated for Cu2+QA-:RC is similar to that observed for the Fe2+QA-:RC complex (J0 = -0.43K). The exchange coupling is discussed in terms of the superexchange paths connecting the Cu2+ ion and the quinone radical using the structural data for the RCs of Rb. sphaeroides. From the value of the dipole-dipole interaction, d, we determined R approximately 8.4 A for the weighted distance between the metal ion and the quinone in reduced RCs, which is to be compared with 10 A obtained from x-ray analysis of unreduced RCs. This points to a shortening of the Cu2+ -QA- distance upon reduction of the quinone, as has been proposed by Allen et al. (1988). PMID:2166597

  16. 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.

  17. Structure and Properties of Precursor/Successor Complex and Transition State of the FeCl(2+)/Fe(2+) Electron Self-Exchange Reaction via the Inner-Sphere Pathway.

    PubMed

    Rotzinger, François P

    2015-11-01

    The electron self-exchange reaction FeCl(OH2)5(2+) + Fe(OH2)6(2+) ? Fe(OH2)6(2+) + FeCl(OH2)5(2+), proceeding via the inner-sphere pathway, was investigated with quantum chemical methods. Geometry and vibrational frequencies of the precursor/successor complex, (H2O)5Fe(III)ClFe(II)(OH2)5(4+)/(H2O)5Fe(II)ClFe(III)(OH2)5(4+) (P/S), and the transition state, (H2O)5FeClFe(OH2)5(4+?) (TS), were computed with the LC-BOP functional and CPCM hydration. Bent and linear structures were computed for the TS and P/S. The electronic coupling matrix element (Hab) and the electronic energies were calculated with multistate extended general multiconfiguration quasi-degenerate second-order perturbation theory (XGMC-QDPT2) and spin-orbit configuration interaction (SO-CI). Since the Fe···Fe distance changes considerably along the electron transfer step, the transformation P ? TS ? S, equations based on the hypothesis of a fixed donor-acceptor distance cannot be applied. Hence, the rate constant for the electron transfer step (ket) was calculated as described previously (Rotzinger, F. P. Inorg. Chem. 2014, 53, 9923). ket is very fast, ?9.4 × 10(8)-6.6 × 10(9) s(-1) at 0 °C. The experimental rate constant of the title reaction (k) is much slower and controlled by the formation of the precursor complex. The substitution of a water ligand by FeCl(OH2)5(2+) at Fe(OH2)6(2+) is rate-determining. PMID:26479082

  18. 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

  19. Exchangeable equilibria

    E-print Network

    Stein, Noah D. (Noah Daniel)

    2011-01-01

    The main contribution of this thesis is a new solution concept for symmetric games (of complete information in strategic form), the exchangeable equilibrium. This is an intermediate notion between symmetric Nash and symmetric ...

  20. 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

  1. Heat exchanger

    SciTech Connect

    Drury, C.R.

    1988-02-02

    A heat exchanger having primary and secondary conduits in heat-exchanging relationship is described comprising: at least one serpentine tube having parallel sections connected by reverse bends, the serpentine tube constituting one of the conduits; a group of open-ended tubes disposed adjacent to the parallel sections, the open-ended tubes constituting the other of the conduits, and forming a continuous mass of contacting tubes extending between and surrounding the serpentine tube sections; and means securing the mass of tubes together to form a predetermined cross-section of the entirety of the mass of open-ended tubes and tube sections.

  2. Manitoba Exchange.

    ERIC Educational Resources Information Center

    Coss, Maurice

    Planning ideas and follow-up activities are described for a reciprocal exchange program between groups of 5th and 6th grade students in Manitoba who are "twinned" with another school in the province. Emphasis is on providing learning experiences which help students become familiar with the economic activity in the area, with the local government…

  3. Kinetic isotope effect of the {sup 16}O + {sup 36}O{sub 2} and {sup 18}O + {sup 32}O{sub 2} isotope exchange reactions: Dominant role of reactive resonances revealed by an accurate time-dependent quantum wavepacket study

    SciTech Connect

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

    2015-05-07

    The O + O{sub 2} 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 {sup 18}O + {sup 32}O{sub 2} and {sup 16}O + {sup 36}O{sub 2} 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.

  4. Heat exchanger

    NASA Technical Reports Server (NTRS)

    Holmes, R. F.; Keller, E. E. (inventors)

    1976-01-01

    An improved lightweight heat exchanger particularly suited for use in systems having low volume flow, high longitudinal gradient and high effectiveness requirements is described. The heat exchanger is characterized by a shell of an annular configuration, an endless plate of minimal thickness and of a substantially uniformly convoluted configuration disposed within the annular shell for defining a plurality of endless, juxtaposed passages, each having a low Reynold's number and being of an annular configuration. A pair of manifolds disposed 180 deg apart is mounted on the shell in communication with the passages through which counterflowing fluids are simultaneously introduced and extracted from the passageways for achieving a continuous transfer of heat through the convoluted plate.

  5. Scraped surface heat exchangers.

    PubMed

    Rao, Chetan S; Hartel, Richard W

    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 food products. During operation, the product is brought in contact with a heat transfer surface that is rapidly and continuously scraped, thereby exposing the surface to the passage of untreated product. In addition to maintaining high and uniform heat exchange, the scraper blades also provide simultaneous mixing and agitation. Heat exchange for sticky and viscous foods such as heavy salad dressings, margarine, chocolate, peanut butter, fondant, ice cream, and shortenings is possible only by using SSHEs. High heat transfer coefficients are achieved because the boundary layer is continuously replaced by fresh material. Moreover, the product is in contact with the heating surface for only a few seconds and high temperature gradients can be used without the danger of causing undesirable reactions. SSHEs are versatile in the use of heat transfer medium and the various unit operations that can be carried out simultaneously. This article critically reviews the current understanding of the operations and applications of SSHEs. PMID:16527753

  6. Heat exchanger

    DOEpatents

    Brackenbury, Phillip J. (Richland, WA)

    1986-01-01

    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.

  7. Heat exchanger

    SciTech Connect

    Saperstein, Z.P.; Awe, R.C.; Costello, N.F.; Larrabee, S.R.

    1986-10-07

    A heat exchanger is described which consists of: spaced generally parallel header and tank constructions; each of the header and tank constructions having elongated, spaced, tube receiving holes in a header surface thereof; the holes in one header surface being aligned with and facing corresponding holes in the other header surface; and elongated open ended, flattened tubes extending between and into the header and tank constructions through aligned ones of the holes; the portions of each header surface between the holes including exteriorly convex domes defined by compound curves to thereby provide increased resistance to deformation as a result of force exerted by a pressurized fluid within the header and tank construction.

  8. Allelic Exchange.

    PubMed

    Lehman, McKenzie K; Bose, Jeffrey L; Bayles, Kenneth W

    2016-01-01

    Methods used to understand the function of a gene/protein are one of the hallmarks of modern molecular genetics. The ability to genetically manipulate bacteria has become a fundamental tool in studying these organisms and while basic cloning has become a routine task in molecular biology laboratories, generating directed mutations can be a daunting task. This chapter describes the method of allelic exchange in Staphylococcus aureus using temperature-sensitive plasmids that have successfully produced a variety of chromosomal mutations, including in-frame deletions, insertion of antibiotic-resistance cassettes, and even single-nucleotide point mutations. PMID:25646609

  9. 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.

  10. 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.

  11. 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.

  12. Allergic Reactions

    MedlinePLUS

    ... allergic reaction is actually a result of a chain reaction that begins in your genes and is expressed ... Tips • Allergy symptoms are the result of a chain reaction that starts in your immune system. • If you ...

  13. Thiol-disulfide exchange yields multivalent dendrimers of melamine.

    PubMed

    Umali, Alona P; Simanek, Eric E

    2003-04-17

    [reaction: see text] Thiol-disulfide exchange can be used to prepare multivalent conjugates of a small molecule or octapeptide displayed on dendrimers based on melamine. Exchange of four or eight thiopyridyl groups by captopril occurs at room temperature in methanol almost quantitatively. Exchange using the peptide requires higher temperatures and guanidinium chloride in DMF. While exchange on the tetravalent scaffold with four peptides is almost quantitative, sterics retard formation of the octavalent conjugate: the hexavalent conjugate forms readily. PMID:12688730

  14. Segmented heat exchanger

    DOEpatents

    Baldwin, Darryl Dean (Lafayette, IN); Willi, Martin Leo (Dunlap, IL); Fiveland, Scott Byron (Metamara, IL); Timmons, Kristine Ann (Chillicothe, IL)

    2010-12-14

    A segmented heat exchanger system for transferring heat energy from an exhaust fluid to a working fluid. The heat exchanger system may include a first heat exchanger for receiving incoming working fluid and the exhaust fluid. The working fluid and exhaust fluid may travel through at least a portion of the first heat exchanger in a parallel flow configuration. In addition, the heat exchanger system may include a second heat exchanger for receiving working fluid from the first heat exchanger and exhaust fluid from a third heat exchanger. The working fluid and exhaust fluid may travel through at least a portion of the second heat exchanger in a counter flow configuration. Furthermore, the heat exchanger system may include a third heat exchanger for receiving working fluid from the second heat exchanger and exhaust fluid from the first heat exchanger. The working fluid and exhaust fluid may travel through at least a portion of the third heat exchanger in a parallel flow configuration.

  15. Charge exchange in the Io torus and exosphere

    NASA Technical Reports Server (NTRS)

    Johnson, R. E.; Strobel, D. F.

    1982-01-01

    Charge-exchange cross sections and their velocity dependence have been estimated for the most important reactions in the Io torus and exosphere. The methods used for calculating the cross sections are given and discussed in some detail. For symmetric-resonant single and double charge exchange, the cross sections are slowly varying functions of velocity. For inelastic charge-exchange collisions, the transition probabilities into a given final state can depend critically on velocity. Models are described which can be used to estimate both the most rapid charge-exchange processes and those states which play an important role. Calculated cross sections are used to obtain reaction rates as a function of radial position, demonstrating the importance of charge exchange in the inner torus. Charge-exchange reactions of torus ions with molecular species in Io's exosphere may yield a net supply of neutrals and plasma to the torus.

  16. Heat exchanger

    SciTech Connect

    Niggemann, R.E.

    1987-01-20

    A heat exchanger is described comprising: a liquid impingement plate having a liquid carrying channel therein; means for spraying a liquid carrying channel; a liquid containment plate disposed in spaced relation to the liquid carrying channel, the liquid containment plate and the liquid impingement plate defining a liquid flow chamber therebetween; liquid inlet means in communication with the liquid spraying means to permit the liquid to flow through the liquid spraying means into the liquid carrying channel; liquid outlet means in communication with the liquid flow chamber to permit liquid to be removed from the liquid flow chamber; and means for cooling the liquid impingement plate on the side thereof opposite the liquid flow chamber to a temperature at or below the freezing point of the liquid; the liquid carrying channel including means for retaining a portion of the liquid in a frozen state there-within, the retaining means comprising a narrowed channel opening facing the liquid spraying means in spaced relation to cooling means.

  17. Corrosive resistant heat exchanger

    DOEpatents

    Richlen, Scott L. (Annandale, VA)

    1989-01-01

    A corrosive and errosive resistant heat exchanger which recovers heat from a contaminated heat stream. The heat exchanger utilizes a boundary layer of innocuous gas, which is continuously replenished, to protect the heat exchanger surface from the hot contaminated gas. The innocuous gas is conveyed through ducts or perforations in the heat exchanger wall. Heat from the heat stream is transferred by radiation to the heat exchanger wall. Heat is removed from the outer heat exchanger wall by a heat recovery medium.

  18. Ion-exchange selectivity of anion exchange resin modified with polystyrenesulfonic acid.

    PubMed

    Endo, Nobutaka; Ikuta, Rei; Higa, Mitsuru; Matsusaki, Koji

    2004-07-01

    In order to change the ion-exchange selectivity of anion-exchange resin, the surface of a gel-type anion exchange resin was modified with anionic polyelectrolyte, polystyrenesulfonic acid. Using this modified resin, the ion-exchange rate of nitrate was little decreased, but that of sulfate was evidently decreased. It is considered that the ion-exchange reaction of the multivalent anion is suppressed by the greater electrostatic repulsive force against the modification layer than that against the monovalent anion. Thus, this modified resin may be suitable for the selective separation of monovalent anions. The influence of the modified condition on the ion-exchange rate was examined. Furthermore, this modified resin was used to separate nitrate ions from sulfate ions in the aqueous solution. PMID:15293411

  19. Woven heat exchanger

    DOEpatents

    Piscitella, Roger R. (Idaho Falls, ID)

    1987-01-01

    In a woven ceramic heat exchanger using the basic tube-in-shell design, each heat exchanger consisting of tube sheets and tube, is woven separately. Individual heat exchangers are assembled in cross-flow configuration. Each heat exchanger is woven from high temperature ceramic fiber, the warp is continuous from tube to tube sheet providing a smooth transition and unitized construction.

  20. Woven heat exchanger

    DOEpatents

    Piscitella, R.R.

    1984-07-16

    This invention relates to a heat exchanger for waste heat recovery from high temperature industrial exhaust streams. In a woven ceramic heat exchanger using the basic tube-in-shell design, each heat exchanger consisting of tube sheets and tube, is woven separately. Individual heat exchangers are assembled in cross-flow configuration. Each heat exchanger is woven from high temperature ceramic fiber, the warp is continuous from tube to tube sheet providing a smooth transition and unitized construction.

  1. Are Ate Complexes True Intermediates in LithiumMetalloid Exchange? Subtle Effects

    E-print Network

    Reich, Hans J.

    -Pair Structure in Lithium±Tellurium and Lithium±Selenium Exchange Reactions** Hans J. Reich,* Martin J. Bevan inter- mediates in these reactions [Eq. (1)]. Ate complexes of iodine,[1a,b,4] tellurium,[1b,5] selenium

  2. Mechanism of Ligand Exchange Studied Using Transition Path Sampling

    E-print Network

    Harris, Charles B.

    Mechanism of Ligand Exchange Studied Using Transition Path Sampling Preston T. Snee, Jennifer@socrates.berkeley.edu Abstract: The mechanism of intermolecular ligand exchange has been studied using transition path sampling that there are multiple steps in the reaction mechanism. The first involves partial dissociation of the coordinated

  3. Bifunctional anion-exchange resins with improved selectivity and exchange kinetics

    DOEpatents

    Alexandratos, Spiro D. (Knoxville, TN); Brown, Gilbert M. (Knoxville, TN); Bonnesen, Peter V. (Knoxville, TN); Moyer, Bruce A. (Oak Ridge, TN)

    2000-01-01

    Disclosed herein are a class of anion exchange resins containing two different exchange sites with improved selectivity and sorptive capability for chemical species in solution, such as heptavalent technetium (as pertechnetate anion, TcO.sub.4.sup.-). The resins are prepared by first reacting haloalkylated crosslinked copolymer beads with a large tertiary amine in a solvent in which the resin beads can swell, followed by reaction with a second, smaller, tertiary amine to more fully complete the functionalization of the resin. The resins have enhanced selectivity, capacity, and exchange kinetics.

  4. Reaction product imaging

    SciTech Connect

    Chandler, D.W.

    1993-12-01

    Over the past few years the author has investigated the photochemistry of small molecules using the photofragment imaging technique. Bond energies, spectroscopy of radicals, dissociation dynamics and branching ratios are examples of information obtained by this technique. Along with extending the technique to the study of bimolecular reactions, efforts to make the technique as quantitative as possible have been the focus of the research effort. To this end, the author has measured the bond energy of the C-H bond in acetylene, branching ratios in the dissociation of HI, the energetics of CH{sub 3}Br, CD{sub 3}Br, C{sub 2}H{sub 5}Br and C{sub 2}H{sub 5}OBr dissociation, and the alignment of the CD{sub 3} fragment from CD{sub 3}I photolysis. In an effort to extend the technique to bimolecular reactions the author has studied the reaction of H with HI and the isotopic exchange reaction between H and D{sub 2}.

  5. Indiana Health Information Exchange

    Cancer.gov

    The Indiana Health Information Exchange is comprised of various Indiana health care institutions, established to help improve patient safety and is recognized as a best practice for health information exchange.

  6. Ion Exchange Formation via Sulfonated Bicomponent Nonwovens

    NASA Astrophysics Data System (ADS)

    Stoughton, Hannah L.

    For many years ion exchange resins were used to: remove heavy metals from water, recover materials from wastewater, and eliminate harmful gases from the air. While use of these resin beads dominates the ion exchange industry, the beads have limitations that should be considered when decisions are made to employ them. For instance, officials must balance the inherent zero sum surface area and porosity of the materials. This series of studies investigates the use of bicomponent nonwovens as a base substrate for producing high surface area ion exchange materials for the removal of heavy metal ions. Functionalized materials were produced in a two-step process: (1) PET/PE spunbond bicomponent fibers were fractured completely, producing the high surface area nonwoven to be used as the base ion exchange material, and (2) the conditions for functionalizing the PET fibers of the nonwoven webs were investigated where an epoxy containing monomer was grafted to the surface followed by sulfonation of the monomer. The functionalization reactions of the PET fibers were monitored based on: weight gain, FTIR, TOF-SIMS, and SEM. Ion exchange properties were evaluated using titration and copper ion removal capacity from test solutions. The relationship between web structure and removal efficiency of the metal ions was defined through a comparison of the bicomponent and homocomponent nonwovens for copper ion removal efficiency. The investigation revealed that utilizing the high surface area, fractured bicomponent nonwoven ion exchange materials with capacities comparable to commercially available ion exchange resins could be produced.

  7. ZEOLITE PERFORMANCE AS AN ANION EXCHANGER FOR ARSENIC SEQUESTRATION IN WATER

    EPA Science Inventory

    Zeolites are well known for their use in ion exchange and acid catalysis reactions. The use of zeolites in anion or ligand exchange reactions is less studied. The NH4+ form of zeolite Y (NY6, Faujasite) has been tested in this work to evaluate its performance for arsenic removal...

  8. 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.

  9. 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.

  10. Developing an exchange mindset.

    PubMed

    Thackeray, Rosemary

    2010-09-01

    Exchange is a fundamental concept that underlies all social marketing efforts. In a successful exchange, both parties receive something of value and the benefits that they desire in return for a price. The purpose of this article is to describe how practitioners can develop an "exchange mindset." A practitioner's answer to five basic questions will enable him or her to see the exchange through the eyes of the customer and increase the likelihood of creating a successful exchange that will benefit both parties involved and result in positive behavior change. PMID:20817631

  11. Electrical and magnetic properties of ion-exchangeable layered ruthenates

    SciTech Connect

    Sugimoto, Wataru . E-mail: wsugi@shinshu-u.ac.jp; Omoto, Masashi; Yokoshima, Katsunori; Murakami, Yasushi; Takasu, Yoshio

    2004-12-01

    An ion-exchangeable ruthenate with a layered structure, K{sub 0.2}RuO{sub 2.1}, was prepared by solid-state reactions. The interlayer cation was exchanged with H{sup +}, C{sub 2}H{sub 5}NH{sub 3}{sup +}, and ((C{sub 4}H{sub 9}){sub 4}N{sup +}) through proton-exchange, ion-exchange, and guest-exchange reactions. The electrical and magnetic properties of the products were characterized by DC resistivity and susceptibility measurements. Layered K{sub 0.2}RuO{sub 2.1} exhibited metallic conduction between 300 and 13K. The products exhibited similar magnetic behavior despite the differences in the type of interlayer cation, suggesting that the ruthenate sheet in the protonated form and the intercalation compounds possesses metallic nature.

  12. Proton exchange in group VIII metal-oxide films

    NASA Astrophysics Data System (ADS)

    Lodi, G.; Zucchini, G. L.; De Battisti, A.; Giatti, A.; Battaglin, G.; Della Mea, G.

    1991-07-01

    In the present work a comparison has been tried between the proton-exchange properties of thermally prepared films of ruthenium oxide and iridium oxide, by means of nuclear reaction analysis and a radiometric method based on exchange of tritium-labelled species. Hydrogen concentration depth-profiles have been determined before and after anodic polarization. Results indicated that a thickness of about 50 nm below the surface is involved in the exchange process. Larger amounts of hydrogenated species were found in iridium oxide samples. Tritium-exchange experiments confirmed these data. Comparison with electrochemical results has also been carried out.

  13. Controlled optical properties of water-soluble CdTe nanocrystals via anion exchange.

    PubMed

    Li, Jing; Jia, Jianguang; Lin, Yuan; Zhou, Xiaowen

    2016-02-01

    We report a study on anion exchange reaction of CdTe nanocrystals with S(2-) in aqueous solution under ambient condition. We found that the optical properties of CdTe nanocrystals can be well tuned by controlling the reaction conditions, in which the reaction temperature is crucially important. At low reaction temperature, the product nanocrystals showed blue-shifts in both absorption and PL spectra, while the photoluminescence quantum yield (PLQY) was significantly enhanced. When anion exchanges were carried out at higher reaction temperature, on the other hand, obvious red shifts in absorption and PL spectra accompanied by a fast increase followed by gradual decrease in PLQY were observed. On variation of S(2-) concentration, it was found that the overall kinetics of Te(2-) for S(2-) exchanges depends also on [S(2-)] when anion exchanges were performed at higher temperature. A possible mechanism for anion exchanges in CdTe NCs was proposed. PMID:26520812

  14. Chem 115Lithium-Halogen ExchangeMyers RLi + R'X RX + R'Li

    E-print Network

    Chem 115Lithium-Halogen ExchangeMyers RLi + R'X RX + R'Li Lithium-halogen exchange reactions are essentially inert. 2 t-BuLi t-BuI + RLi t-BuLi isobutene + isobutane + LiI Lithium-halogen exchange reactions, and lithium iodide. H OEtBr H H OEtLi H1.1 eq n-BuLi Et2O, !80 °C Lau, K. S.; Schlosser, M. J. Org. Chem. 1978

  15. Process for operating equilibrium controlled reactions

    DOEpatents

    Nataraj, Shankar (Allentown, PA); Carvill, Brian Thomas (Orefield, PA); Hufton, Jeffrey Raymond (Fogelsville, PA); Mayorga, Steven Gerard (Allentown, PA); Gaffney, Thomas Richard (Allentown, PA); Brzozowski, Jeffrey Richard (Bethlehem, PA)

    2001-01-01

    A cyclic process for operating an equilibrium controlled reaction in a plurality of reactors containing an admixture of an adsorbent and a reaction catalyst suitable for performing the desired reaction which is operated in a predetermined timed sequence wherein the heating and cooling requirements in a moving reaction mass transfer zone within each reactor are provided by indirect heat exchange with a fluid capable of phase change at temperatures maintained in each reactor during sorpreaction, depressurization, purging and pressurization steps during each process cycle.

  16. 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.

  17. Chemical Reactions in DSMC

    SciTech Connect

    Bird, G. A.

    2011-05-20

    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.

  18. Systematics of pion double charge exchange

    SciTech Connect

    Gilman, R.A.

    1985-10-01

    Differential cross sections have been measured for pion-induced double-charge-exchange (DCX) reactions leading to double-isobaric-analog states (DIAS) and low-lying nonanalog states in the residual nuclei. A description of the experimental details and data analysis is presented. The experimentally observed systematics of reactions leading to DIAS, to nonanalog ground states, and to low-lying 2 states are described. Lowest-order optical-model calculations of DIAS DCX are compared to the data. Efforts to understand the anomalies by invoking additional reaction-mechanism amplitudes and a higher-order optical potential are described. Calculations of nonanalog DCX reactions leading to J/sup / = 0 states were performed within a distorted-wave impulse-approximation framework. The sensitivities of these calculations to input parameters are discussed. 58 refs., 41 figs., 16 tabs.

  19. Nonsurvivable momentum exchange system

    NASA Technical Reports Server (NTRS)

    Roder, Russell (Inventor); Ahronovich, Eliezer (Inventor); Davis, III, Milton C. (Inventor)

    2007-01-01

    A demiseable momentum exchange system includes a base and a flywheel rotatably supported on the base. The flywheel includes a web portion defining a plurality of web openings and a rim portion. The momentum exchange system further includes a motor for driving the flywheel and a cover for engaging the base to substantially enclose the flywheel. The system may also include components having a melting temperature below 1500 degrees Celsius. The momentum exchange system is configured to demise on reentry.

  20. Emittance exchange results

    SciTech Connect

    Fliller, R.P., III; Koeth, T.; /Rutgers U., Piscataway

    2009-09-01

    The promise of next-generation light sources depends on the availability of ultra-low emittance electron sources. One method of producing low transverse emittance beams is to generate a low longitudinal emittance beam and exchange it with a large transverse emittance. Experiments are underway at Fermilab's A0 Photoinjector and ANL's Argonne Wakefield Accelerator using the exchange scheme of Kim and Sessler. The experiment at the A0 Photoinjector exchanges a large longitudinal emittance with a small transverse emittance. AWA expects to exchange a large transverse emittance with a small longitudinal emittance. In this paper we discuss recent results at A0 and AWA and future plans for these experiments.

  1. Setup Exchange 2010 on an Android Device Exchange 2010

    E-print Network

    Calgary, University of

    an email app that can use ActiveSync to identify Exchange settings. Add an Exchange Account to an AndroidSetup Exchange 2010 on an Android Device Exchange 2010 The following instructions are for setting up an Exchange 2010 account on an Android device such as a Samsung Galaxy III or tablet

  2. Direct fired heat exchanger

    DOEpatents

    Reimann, Robert C. (Lafayette, NY); Root, Richard A. (Spokane, WA)

    1986-01-01

    A gas-to-liquid heat exchanger system which transfers heat from a gas, generally the combustion gas of a direct-fired generator of an absorption machine, to a liquid, generally an absorbent solution. The heat exchanger system is in a counterflow fluid arrangement which creates a more efficient heat transfer.

  3. 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.…

  4. Handicapping Social Exchange Theory.

    ERIC Educational Resources Information Center

    Mishler, Barbara

    The economic theory of social exchange has some serious shortcomings when applied to minorities--especially the disabled. First, it assumes dyads comprise the basic unit where exchange occurs and that rewards and costs must occur at that level. Second, the model standardizes the experience of white, Western European and American males. The model…

  5. exchange? Part Universiteit

    E-print Network

    Lange, Tanja

    that it takes at least 15 years. ECC­encrypted long­term­confidential documents (e.g. health records, stateWhat is a use case for quantum key exchange? Part I Tanja Lange Technische Universiteit Eindhoven. . DH key exchange is dead. . DSA is dead. . XTR is dead. . ECDSA is dead. . ECC is dead. . HECC is dead

  6. 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.

  7. Higher Education Exchange, 2005

    ERIC Educational Resources Information Center

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

    2005-01-01

    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…

  8. Building Relationships through Exchange

    ERIC Educational Resources Information Center

    Primavera, Angi; Hall, Ellen

    2011-01-01

    From the moment of birth, children form and develop relationships with others in their world based on exchange. Children recognize that engaging in such encounters offers them the opportunity to enter into a relationship with another individual and to nurture that relationship through the exchange of messages and gifts, items and ideas. At Boulder…

  9. 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"…

  10. 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…

  11. 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.

  12. Proton channels and exchangers in cancer.

    PubMed

    Spugnini, Enrico Pierluigi; Sonveaux, Pierre; Stock, Christian; Perez-Sayans, Mario; De Milito, Angelo; Avnet, Sofia; Garcìa, Abel Garcìa; Harguindey, Salvador; Fais, Stefano

    2015-10-01

    Although cancer is characterized by an intratumoral genetic heterogeneity, a totally deranged pH control is a common feature of most cancer histotypes. Major determinants of aberrant pH gradient in cancer are proton exchangers and transporters, including V-ATPase, Na+/H+ exchanger (NHE), monocarboxylate transporters (MCTs) and carbonic anhydrases (CAs). Thanks to the activity of these proton transporters and exchangers, cancer becomes isolated and/or protected not only from the body reaction against the growing tumor, but also from the vast majority of drugs that when protonated into the acidic tumor microenvironment do not enter into cancer cells. Proton transporters and exchangers represent a key feature tumor cells use to survive in the very hostile microenvironmental conditions that they create and maintain. Detoxifying mechanisms may thus represent both a key survival option and a selection outcome for cells that behave as unicellular microorganisms rather than belonging to an organ, compartment or body. It is, in fact, typical of malignant tumors that, after a clinically measurable yet transient initial response to a therapy, resistant tumor clones emerge and proliferate, thus bursting a more malignant behavior and rapid tumor progression. This review critically presents the background of a novel and efficient approach that aims to fight cancer through blocking or inhibiting well characterized proton exchangers and transporters active in human cancer cells. This article is part of a Special Issue entitled: Membrane channels and transporters in cancers. PMID:25449995

  13. Heat and mass exchanger

    DOEpatents

    Lowenstein, Andrew (Princeton, NJ); Sibilia, Marc J. (Princeton, NJ); Miller, Jeffrey A. (Hopewell, NJ); Tonon, Thomas (Princeton, NJ)

    2011-06-28

    A mass and heat exchanger includes at least one first substrate with a surface for supporting a continuous flow of a liquid thereon that either absorbs, desorbs, evaporates or condenses one or more gaseous species from or to a surrounding gas; and at least one second substrate operatively associated with the first substrate. The second substrate includes a surface for supporting the continuous flow of the liquid thereon and is adapted to carry a heat exchange fluid therethrough, wherein heat transfer occurs between the liquid and the heat exchange fluid.

  14. Heat and mass exchanger

    DOEpatents

    Lowenstein, Andrew (Princeton, NJ); Sibilia, Marc J. (Princeton, NJ); Miller, Jeffrey A. (Hopewell, NJ); Tonon, Thomas (Princeton, NJ)

    2007-09-18

    A mass and heat exchanger includes at least one first substrate with a surface for supporting a continuous flow of a liquid thereon that either absorbs, desorbs, evaporates or condenses one or more gaseous species from or to a surrounding gas; and at least one second substrate operatively associated with the first substrate. The second substrate includes a surface for supporting the continuous flow of the liquid thereon and is adapted to carry a heat exchange fluid therethrough, wherein heat transfer occurs between the liquid and the heat exchange fluid.

  15. Wound tube heat exchanger

    DOEpatents

    Ecker, Amir L. (Duncanville, TX)

    1983-01-01

    What is disclosed is a wound tube heat exchanger in which a plurality of tubes having flattened areas are held contiguous adjacent flattened areas of tubes by a plurality of windings to give a double walled heat exchanger. The plurality of windings serve as a plurality of effective force vectors holding the conduits contiguous heat conducting walls of another conduit and result in highly efficient heat transfer. The resulting heat exchange bundle is economical and can be coiled into the desired shape. Also disclosed are specific embodiments such as the one in which the tubes are expanded against their windings after being coiled to insure highly efficient heat transfer.

  16. Microtube strip heat exchanger

    SciTech Connect

    Doty, F.D.

    1991-10-16

    This progress report is for the September--October 1991 quarter. We have demonstrated feasibility of higher specific conductance by a factor of five than any other work in high-temperature gas-to-gas exchangers. These laminar-flow, microtube exchangers exhibit extremely low pressure drop compared to alternative compact designs under similar conditions because of their much shorter flow length and larger total flow area for lower flow velocities. The design appears to be amenable to mass production techniques, but considerable process development remains. The reduction in materials usage and the improved heat exchanger performance promise to be of enormous significance in advanced engine designs and in cryogenics.

  17. Anion exchange membrane

    DOEpatents

    Verkade, John G; Wadhwa, Kuldeep; Kong, Xueqian; Schmidt-Rohr, Klaus

    2013-05-07

    An anion exchange membrane and fuel cell incorporating the anion exchange membrane are detailed in which proazaphosphatrane and azaphosphatrane cations are covalently bonded to a sulfonated fluoropolymer support along with anionic counterions. A positive charge is dispersed in the aforementioned cations which are buried in the support to reduce the cation-anion interactions and increase the mobility of hydroxide ions, for example, across the membrane. The anion exchange membrane has the ability to operate at high temperatures and in highly alkaline environments with high conductivity and low resistance.

  18. Heat exchanger for fuel cell power plant reformer

    DOEpatents

    Misage, Robert (Manchester, CT); Scheffler, Glenn W. (Tolland, CT); Setzer, Herbert J. (Ellington, CT); Margiott, Paul R. (Manchester, CT); Parenti, Jr., Edmund K. (Manchester, CT)

    1988-01-01

    A heat exchanger uses the heat from processed fuel gas from a reformer for a fuel cell to superheat steam, to preheat raw fuel prior to entering the reformer and to heat a water-steam coolant mixture from the fuel cells. The processed fuel gas temperature is thus lowered to a level useful in the fuel cell reaction. The four temperature adjustments are accomplished in a single heat exchanger with only three heat transfer cores. The heat exchanger is preheated by circulating coolant and purge steam from the power section during startup of the latter.

  19. Microscopic theory of cation exchange in CdSe nanocrystals.

    PubMed

    Ott, Florian D; Spiegel, Leo L; Norris, David J; Erwin, Steven C

    2014-10-10

    Although poorly understood, cation-exchange reactions are increasingly used to dope or transform colloidal semiconductor nanocrystals (quantum dots). We use density-functional theory and kinetic Monte Carlo simulations to develop a microscopic theory that explains structural, optical, and electronic changes observed experimentally in Ag-cation-exchanged CdSe nanocrystals. We find that Coulomb interactions, both between ionized impurities and with the polarized nanocrystal surface, play a key role in cation exchange. Our theory also resolves several experimental puzzles related to photoluminescence and electrical behavior in CdSe nanocrystals doped with Ag. PMID:25375732

  20. Anion exchange polymer electrolytes

    DOEpatents

    Kim, Yu Seung; Kim, Dae Sik

    2015-06-02

    Anion exchange polymer electrolytes that include guanidinium functionalized polymers may be used as membranes and binders for electrocatalysts in preparation of anodes for electrochemical cells such as solid alkaline fuel cells.

  1. Munich, Germany Exchange Program

    E-print Network

    Fernandez, Eduardo

    Munich, Germany Exchange Program Ludwig-Maximilians-Universitat Founded in 1472, Ludwig talented scholars and students from all over the world. As one of Germany's most dynamic universities, LMU, psychology, physics, biology, chemistry, social sciences, economics, business administration, and geosciences

  2. Place of exchange

    E-print Network

    Hollander, Adi

    2015-01-01

    The thesis is written as a theoretical presentation of the research I conducted at MIT between 2013 and 2015. I will discuss what I consider to be an important aspect of my artistic practice; creating places of exchange, ...

  3. 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+}.

  4. Microtube strip heat exchanger

    SciTech Connect

    Doty, F.D.

    1992-07-09

    The purpose of this contract has been to explore the limits of miniaturization of heat exchangers with the goals of (1) improving the theoretical understanding of laminar heat exchangers, (2) evaluating various manufacturing difficulties, and (3) identifying major applications for the technology. A low-cost, ultra-compact heat exchanger could have an enormous impact on industry in the areas of cryocoolers and energy conversion. Compact cryocoolers based on the reverse Brayton cycle (RBC) would become practical with the availability of compact heat exchangers. Many experts believe that hardware advances in personal computer technology will rapidly slow down in four to six years unless lowcost, portable cryocoolers suitable for the desktop supercomputer can be developed. Compact refrigeration systems would permit dramatic advances in high-performance computer work stations with conventional'' microprocessors operating at 150 K, and especially with low-cost cryocoolers below 77 K. NASA has also expressed strong interest in our MTS exchanger for space-based RBC cryocoolers for sensor cooling. We have demonstrated feasibility of higher specific conductance by a factor of five than any other work in high-temperature gas-to-gas exchangers. These laminar-flow, microtube exchangers exhibit extremely low pressure drop compared to alternative compact designs under similar conditions because of their much shorter flow length and larger total flow area for lower flow velocities. The design appears to be amenable to mass production techniques, but considerable process development remains. The reduction in materials usage and the improved heat exchanger performance promise to be of enormous significance in advanced engine designs and in cryogenics.

  5. Microtube strip heat exchanger

    NASA Astrophysics Data System (ADS)

    Doty, F. D.

    1992-07-01

    The purpose of this contract has been to explore the limits of miniaturization of heat exchangers with the goals of (1) improving the theoretical understanding of laminar heat exchangers, (2) evaluating various manufacturing difficulties, and (3) identifying major applications for the technology. A low-cost, ultra-compact heat exchanger could have an enormous impact on industry in the areas of cryocoolers and energy conversion. Compact cryocoolers based on the reverse Brayton cycle (RBC) would become practical with the availability of compact heat exchangers. Many experts believe that hardware advances in personal computer technology will rapidly slow down in four to six years unless lowcost, portable cryocoolers suitable for the desktop supercomputer can be developed. Compact refrigeration systems would permit dramatic advances in high-performance computer work stations with 'conventional' microprocessors operating at 150 K, and especially with low-cost cryocoolers below 77 K. NASA has also expressed strong interest in our MTS exchanger for space-based RBC cryocoolers for sensor cooling. We have demonstrated feasibility of higher specific conductance by a factor of five than any other work in high-temperature gas-to-gas exchangers. These laminar-flow, microtube exchangers exhibit extremely low pressure drop compared to alternative compact designs under similar conditions because of their much shorter flow length and larger total flow area for lower flow velocities. The design appears to be amenable to mass production techniques, but considerable process development remains. The reduction in materials usage and the improved heat exchanger performance promise to be of enormous significance in advanced engine designs and in cryogenics.

  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. Radial flow heat exchanger

    DOEpatents

    Valenzuela, Javier (Hanover, NH)

    2001-01-01

    A radial flow heat exchanger (20) having a plurality of first passages (24) for transporting a first fluid (25) and a plurality of second passages (26) for transporting a second fluid (27). The first and second passages are arranged in stacked, alternating relationship, are separated from one another by relatively thin plates (30) and (32), and surround a central axis (22). The thickness of the first and second passages are selected so that the first and second fluids, respectively, are transported with laminar flow through the passages. To enhance thermal energy transfer between first and second passages, the latter are arranged so each first passage is in thermal communication with an associated second passage along substantially its entire length, and vice versa with respect to the second passages. The heat exchangers may be stacked to achieve a modular heat exchange assembly (300). Certain heat exchangers in the assembly may be designed slightly differently than other heat exchangers to address changes in fluid properties during transport through the heat exchanger, so as to enhance overall thermal effectiveness of the assembly.

  8. 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.

  9. Electron self-exchange in hemoglobins revealed by deutero-hemin substitution.

    PubMed

    Athwal, Navjot Singh; Alagurajan, Jagannathan; Sturms, Ryan; Fulton, D Bruce; Andreotti, Amy H; Hargrove, Mark S

    2015-09-01

    Hemoglobins (phytoglobins) from rice plants (nsHb1) and from the cyanobacterium Synechocystis (PCC 6803) (SynHb) can reduce hydroxylamine with two electrons to form ammonium. The reaction requires intermolecular electron transfer between protein molecules, and rapid electron self-exchange might play a role in distinguishing these hemoglobins from others with slower reaction rates, such as myoglobin. A relatively rapid electron self-exchange rate constant has been measured for SynHb by NMR, but the rate constant for myoglobin is equivocal and a value for nsHb1 has not yet been measured. Here we report electron self-exchange rate constants for nsHb1 and Mb as a test of their role in hydroxylamine reduction. These proteins are not suitable for analysis by NMR ZZ exchange, so a method was developed that uses cross-reactions between each hemoglobin and its deutero-hemin substituted counterpart. The resulting electron transfer is between identical proteins with low driving forces and thus closely approximates true electron self-exchange. The reactions can be monitored spectrally due to the distinct spectra of the prosthetic groups, and from this electron self-exchange rate constants of 880 (SynHb), 2900 (nsHb1), and 0.05M(-1)s(-1) (Mb) have been measured for each hemoglobin. Calculations of cross-reactions using these values accurately predict hydroxylamine reduction rates for each protein, suggesting that electron self-exchange plays an important role in the reaction. PMID:26141377

  10. A degradable polydopamine coating based on disulfide-exchange reaction.

    PubMed

    Hong, Daewha; Lee, Hojae; Kim, Beom Jin; Park, Taegyun; Choi, Ji Yu; Park, Matthew; Lee, Juno; Cho, Hyeoncheol; Hong, Seok-Pyo; Yang, Sung Ho; Jung, Sun Ho; Ko, Sung-Bo; Choi, Insung S

    2015-12-21

    Although the programmed degradation of biocompatible films finds applications in various fields including biomedical and bionanotechnological areas, coating methods have generally been limited to be substrate-specific, not applicable to any kinds of substrates. In this paper, we report a dopamine derivative, which allows for both universal coating of various substrates and stimuli-responsive film degradation, inspired by mussel-adhesive proteins. Two dopamine moieties are linked together by the disulfide bond, the cleavage of which enables the programmed film degradation. Mechanistic analysis of the degradable films indicates that the initial cleavage of the disulfide linkage causes rapid uptake of water molecules, hydrating the films, which leads to rapid degradation. Our substrate-independent coating of degradable films provides an advanced tool for drug delivery systems, tissue engineering, and anti-fouling strategies. PMID:26572596

  11. 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.

  12. Gas exchange measurements in natural systems

    SciTech Connect

    Broecker, W.S.; Peng, T.H.

    1983-01-01

    Direct knowledge of the rates of gas exchange in lakes and the ocean is based almost entirely on measurements of the isotopes /sup 14/C, /sup 222/Rn and /sup 3/He. The distribution of natural radiocarbon has yielded the average rate of CO/sub 2/ exchange for the ocean and for several closed basin lakes. That of bomb produced radiocarbon has been used in the same systems. The /sup 222/Rn to /sup 226/Ra ratio in open ocean surface water has been used to give local short term gas exchange rates. The radon method generally cannot be used in lakes, rivers, estuaries or shelf areas because of the input of radon from sediments. A few attempts have been made to use the excess /sup 3/He produced by decay of bomb produced tritium in lakes to give gas transfer rates. The uncertainty in the molecular diffusivity of helium and in the diffusivity dependence of the rate of gas transfer holds back the application of this method. A few attempts have been made to enrich the surface waters of small lakes with /sup 226/Ra and /sup 3/H in order to allow the use of the /sup 222/Rn and /sup 3/He methods. While these studies give broadly concordant results, many questions remain unanswered. The wind velocity dependence of gas exchange rate has yet to be established in field studies. The dependence of gas exchange rate on molecular diffusivity also remains in limbo. Finally, the degree of enhancement of CO/sub 2/ exchange through chemical reactions has been only partially explored. 49 references, 2 figures, 2 tables.

  13. Anion-exchange mechanisms in bacteria.

    PubMed Central

    Maloney, P C; Ambudkar, S V; Anatharam, V; Sonna, L A; Varadhachary, A

    1990-01-01

    This article discusses the physiological, biochemical, and molecular properties of bacterial anion-exchange reactions, with a particular focus on a family of phosphate (Pi)-linked antiporters that accept as their primary substrates sugar phosphates such as glucose 6-phosphate (G6P), mannose 6-phosphate, or glycerol 3-phosphate. Pi-linked antiporters may be found in both gram-positive and gram-negative cells. As their name suggests, these exchange proteins accept both inorganic and organic phosphates, but the two classes of substrate interact very differently with the protein. Thus, Pi is always accepted with a relatively low affinity, and when it participates in exchange, it is always taken as the monovalent anion. By contrast, when the high-affinity organic phosphates are used, these same systems fail to discriminate between monovalent and divalent forms. Tests of heterologous exchange (e.g., Pi: G6P) indicate that these proteins have a bifunctional active site that accepts a pair of negative charges, whether as two monovalent anions or as a single divalent anion. For this reason, exchange stoichiometry moves between limits of 2:1 and 2:2, according to the ratio of mono- and divalent substrates at either membrane surface. Since G6P has a pK2 within the physiological range (pK of 6.1), this predicts a novel reaction sequence in vivo because internal pH is more alkaline than external pH. Accordingly, one expects an asymmetric exchange as two monovalent G6P anions from the relatively acidic exterior move against a single divalent G6P from the alkaline interior. In this way an otherwise futile self-exchange of G6P can be biased towards a net inward flux driven (indirectly) by the pH gradient. Despite the biochemical complexity exhibited by Pi-linked antiporters, they resemble all other secondary carriers at a molecular level and show a likely topology in which two sets of six transmembrane alpha-helices are connected by a central hydrophilic loop. Speculations on the derivation of this common form suggest a limited number of structural models to accommodate such proteins. Three such models are presented. PMID:2181257

  14. Understand spiral heat exchangers

    SciTech Connect

    Bailey, K.M.

    1994-05-01

    Shell-and-tube heat exchangers are standard in most chemical process industries (CPI) applications. However, they do have limitations related to thermal efficiency, mechanical design, and maintenance requirements that will not allow the standard straight-tube fixed-tubesheet shell-and-tube (S and T) heat exchanger to work properly in certain applications. It is in these problem areas that spiral heat exchangers (SHEs) have been used successfully worldwide for over 60 years. The SHE can be a viable alternative to the complex and often expensive shell-and-tube heat exchanger. The SHEs' unique spiral countercurrent monochannel design gives them exceptionally high heat-transfer rates and low fouling tendencies. The mechanical configuration of the SHE also allows full access to all heat-transfer surfaces for simplified inspection, maintenance, and cleaning. This article describes how SHEs operate, discusses their advantages in terms of thermal efficiency, fouling, mechanical design, and maintenance characteristics, and provides guidance on choosing between spiral and tubular exchangers.

  15. Downhole heat exchangers

    SciTech Connect

    Culver, G.; Lund, J.W.

    1999-09-01

    The downhole heat exchanger (DHE) eliminates the problem of disposal of geothermal fluid, since only heat is taken from the well. The exchanger consists of a system of pipes or tubes suspended in the well through which clean secondary water is pumped or allowed to circulate by natural convection. These systems offer substantial economic savings over surface heat exchangers where a single-well system is adequate (typically less than 0.8 MWt, with well depths up to about 500 ft) and may be economical under certain conditions at well depths to 1500 ft. Several designs have proven successful; but, the most popular are a simple hairpin loop or multiple loops of iron pipe (similar to the tubes in a U-tube and shell exchanger) extending to near the well bottom. An experimental design consisting of multiple small tubes with headers at each end suspended just below the water surface appears to offer economic and heating capacity advantages. The paper describes design and construction details and New Zealand`s experience with downhole heat exchangers.

  16. Dynamic Covalent Chemistry of Nucleophilic Substitution Component Exchange of Quaternary Ammonium Salts.

    PubMed

    Kulchat, Sirinan; Lehn, Jean-Marie

    2015-11-01

    Dynamic covalent libraries (DCLs) of quaternary ammonium cations were set up by reversible nucleophilic substitution (SN 2' and SN 2) exchange reactions of ammonium salts and tertiary amines. The reactions were conducted at 60?°C to generate thermodynamically and kinetically controlled mixtures of quaternary ammonium compounds and tertiary amines, and were accelerated by using iodide as a nucleophilic catalyst. Microwave irradiation was used to assist the exchange reaction between the pyridinium salts and pyridine derivatives. Finally, experiments towards the generation of dynamic ionic liquids were performed. The results of this study pave the way for the extension of dynamic combinatorial chemistry to nucleophilic substitution reactions. PMID:26213320

  17. FOCUS: HYDROGEN EXCHANGE AND COVALENT MODIFICATION Solvent Accessibility of Protein Surfaces

    E-print Network

    Komives, Elizabeth A.

    , then the exchange reaction is quenched, the protein is digested under quench condi- tions by pepsin, and finally the pepsin digest is ana- lyzed by mass spectrometry [1]. The main disadvantage of most current mass

  18. J/psi absorption by nucleons in the meson-exchange model 

    E-print Network

    Oh, Yongseok; Liu, Wei; Ko, Che Ming.

    2007-01-01

    We reinvestigate the J/Psi dissociation processes induced by the reactions with nucleons, J/Psi + N -> D-(*) + Lambda(c), in the meson- exchange model. Main constraints used in this work are vector- meson dominance and charm vector...

  19. 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 ...

  20. Microgravity condensing heat exchanger

    NASA Technical Reports Server (NTRS)

    Thomas, Christopher M. (Inventor); Ma, Yonghui (Inventor); North, Andrew (Inventor); Weislogel, Mark M. (Inventor)

    2011-01-01

    A heat exchanger having a plurality of heat exchanging aluminum fins with hydrophilic condensing surfaces which are stacked and clamped between two cold plates. The cold plates are aligned radially along a plane extending through the axis of a cylindrical duct and hold the stacked and clamped portions of the heat exchanging fins along the axis of the cylindrical duct. The fins extend outwardly from the clamped portions along approximately radial planes. The spacing between fins is symmetric about the cold plates, and are somewhat more closely spaced as the angle they make with the cold plates approaches 90.degree.. Passageways extend through the fins between vertex spaces which provide capillary storage and communicate with passageways formed in the stacked and clamped portions of the fins, which communicate with water drains connected to a pump externally to the duct. Water with no entrained air is drawn from the capillary spaces.

  1. Ion exchange phenomena

    SciTech Connect

    Bourg, I.C.; Sposito, G.

    2011-05-01

    Ion exchange phenomena involve the population of readily exchangeable ions, the subset of adsorbed solutes that balance the intrinsic surface charge and can be readily replaced by major background electrolyte ions (Sposito, 2008). These phenomena have occupied a central place in soil chemistry research since Way (1850) first showed that potassium uptake by soils resulted in the release of an equal quantity of moles of charge of calcium and magnesium. Ion exchange phenomena are now routinely modeled in studies of soil formation (White et al., 2005), soil reclamation (Kopittke et al., 2006), soil fertilitization (Agbenin and Yakubu, 2006), colloidal dispersion/flocculation (Charlet and Tournassat, 2005), the mechanics of argillaceous media (Gajo and Loret, 2007), aquitard pore water chemistry (Tournassat et al., 2008), and groundwater (Timms and Hendry, 2007; McNab et al., 2009) and contaminant hydrology (Chatterjee et al., 2008; van Oploo et al., 2008; Serrano et al., 2009).

  2. Microscale Regenerative Heat Exchanger

    NASA Technical Reports Server (NTRS)

    Moran, Matthew E.; Stelter, Stephan; Stelter, Manfred

    2006-01-01

    The device described herein is designed primarily for use as a regenerative heat exchanger in a miniature Stirling engine or Stirling-cycle heat pump. A regenerative heat exchanger (sometimes called, simply, a "regenerator" in the Stirling-engine art) is basically a thermal capacitor: Its role in the Stirling cycle is to alternately accept heat from, then deliver heat to, an oscillating flow of a working fluid between compression and expansion volumes, without introducing an excessive pressure drop. These volumes are at different temperatures, and conduction of heat between these volumes is undesirable because it reduces the energy-conversion efficiency of the Stirling cycle.

  3. Heat exchanger panel

    NASA Technical Reports Server (NTRS)

    Warburton, Robert E. (Inventor); Cuva, William J. (Inventor)

    2005-01-01

    The present invention relates to a heat exchanger panel which has broad utility in high temperature environments. The heat exchanger panel has a first panel, a second panel, and at least one fluid containment device positioned intermediate the first and second panels. At least one of the first panel and the second panel have at least one feature on an interior surface to accommodate the at least one fluid containment device. In a preferred embodiment, each of the first and second panels is formed from a high conductivity, high temperature composite material. Also, in a preferred embodiment, the first and second panels are joined together by one or more composite fasteners.

  4. Heat exchanger support

    SciTech Connect

    McDonald, D.K.; Weitzel, P.S.

    1988-09-13

    This patent describes a support structure for in-bed heat exchanger tubes of a fluidzed bed boiler having wall means defining a fluidized bed region and a freeboard region above the fluidized bed region, the wall means including tubular means disposed near a transition zone between the fluidized bed and freeboard regions, the structure comprising support tubes having opposite ends extending respectively through the wall means and over the tubular means for support thereby, each support tube having at least one upright portion disposed in the fluidized bed region, and at least one heat exchanger tube being supportingly secured to the upright portion.

  5. Nuclear reactor exchanger

    SciTech Connect

    Doublet, P.; Jullien, G.

    1983-03-22

    Nuclear reactor exchanger which assures the transfer of heat between two streams of coolant sodium. It includes an outlet connector which channels coolant sodium leaving a bundle of exchanger tubes traversed on the inside by the sodium and immersed externally in coolant sodium, and an inner tubular jacket forming a surface of revolution about a vertical axis and an outer tubular jacket. The wall of the inner jacket has a folded portion distinguished by at least one flank in the form of a crown.

  6. 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.

  7. ION-EXCHANGE PROCESSES AND MECHANISMS IN GLASSES

    EPA Science Inventory

    Recent performance assessment calculations of a disposal system at Hanford, Washington for low activity waste glass show that a Na ion-exchange reaction can effectively increase the radionuclide release rate by over a factor of 1000 and so is a major factor that currently limits ...

  8. Rapid biologically mediated oxygen isotope exchange between water and phosphate

    E-print Network

    Yehoshua, Kolodny

    Rapid biologically mediated oxygen isotope exchange between water and phosphate Adina Paytan,1 between water and phosphate via biochemical reactions a set of controlled experiments were conducted composition (d18 Ow) were monitored. The oxygen isotopic composition of phosphate (d18 Op) in the organisms

  9. Mechanism of ligand exchange studied using transition path sampling.

    PubMed

    Snee, Preston T; Shanoski, Jennifer; Harris, Charles B

    2005-02-01

    The mechanism of intermolecular ligand exchange has been studied using transition path sampling (TPS) based molecular dynamics (MD) simulations. Specifically, the exchange of solvent molecules bound to unsaturated Cr(CO)5 in methanol solution has been investigated. The results of the TPS simulations have shown that there are multiple steps in the reaction mechanism. The first involves partial dissociation of the coordinated solvent from the Cr metal center followed by association with a new methanol molecule between the normally void first and second solvent layers. After diffusive motion of the exchanging ligands, the last step involves the originally bound methanol molecule moving into the bath continuum followed by solvation of the Cr metal fragment by the exchanging ligand. It has been found that the reaction center (defined as the organometallic fragment and two exchanging ligands only) and the solvent bath have favorable interactions. This is likely due to the adiabatic nature of the ligand exchange transition. The ability to understand the microscopic molecular dynamics of a chemical process based on a free energy analysis is also discussed. PMID:15669868

  10. 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

  11. 10 CFR Appendix E to Part 110 - Illustrative List of Chemical Exchange or Ion Exchange Enrichment Plant Equipment and Components...

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... between the isotopes of uranium causes small changes in chemical reaction equilibria that can be used as a basis for separation of the isotopes. Two processes have been successfully developed: liquid-liquid... producing high-purity uranium chloride feed solutions for chemical exchange uranium isotope...

  12. 10 CFR Appendix E to Part 110 - Illustrative List of Chemical Exchange or Ion Exchange Enrichment Plant Equipment and Components...

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... between the isotopes of uranium causes small changes in chemical reaction equilibria that can be used as a basis for separation of the isotopes. Two processes have been successfully developed: liquid-liquid... producing high-purity uranium chloride feed solutions for chemical exchange uranium isotope...

  13. 10 CFR Appendix E to Part 110 - Illustrative List of Chemical Exchange or Ion Exchange Enrichment Plant Equipment and Components...

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... between the isotopes of uranium causes small changes in chemical reaction equilibria that can be used as a basis for separation of the isotopes. Two processes have been successfully developed: liquid-liquid... producing high-purity uranium chloride feed solutions for chemical exchange uranium isotope...

  14. 10 CFR Appendix E to Part 110 - Illustrative List of Chemical Exchange or Ion Exchange Enrichment Plant Equipment and Components...

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... between the isotopes of uranium causes small changes in chemical reaction equilibria that can be used as a basis for separation of the isotopes. Two processes have been successfully developed: liquid-liquid... producing high-purity uranium chloride feed solutions for chemical exchange uranium isotope...

  15. 10 CFR Appendix E to Part 110 - Illustrative List of Chemical Exchange or Ion Exchange Enrichment Plant Equipment and Components...

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... between the isotopes of uranium causes small changes in chemical reaction equilibria that can be used as a basis for separation of the isotopes. Two processes have been successfully developed: liquid-liquid... producing high-purity uranium chloride feed solutions for chemical exchange uranium isotope...

  16. Higher Education Exchange

    ERIC Educational Resources Information Center

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

    2009-01-01

    This volume begins with an essay by Noelle McAfee, a contributor who is familiar to readers of Higher Education Exchange (HEX). She reiterates Mathews' argument regarding the disconnect between higher education's sense of engagement and the public's sense of engagement, and suggests a way around the epistemological conundrum of "knowledge produced…

  17. Ankara, Turkey Exchange Program

    E-print Network

    Fernandez, Eduardo

    Ankara, Turkey Exchange Program Bilkent University Bilkent University (BU) was founded in 1984 as Turkey's first private, non-profit institution of higher education. BU is recognized and ranked internationally as the premier institution of higher education in Turkey. Its lively campus with its cultural

  18. Microtube strip heat exchanger

    SciTech Connect

    Doty, F.D.

    1991-04-02

    During the last quarter, Doty Scientific, Inc. (DSI) continued to make progress on the microtube strip (MTS) heat exchangers. The team has begun a heat exchanger stress analysis, however they have been concentrating the bulk of their analytical energies on a CFD model to determine the location and magnitude of shell-side flow maldistribution which decreases heat exchanger effectiveness. DSI received 120 fineblanked tubestrips from Southern Fineblanking (SFB) for manufacturing process development. Both SFB and NIST provided inspection reports of the tubestrips. DSI completed the tooling required to encapsulate a tube array and press tubestrips on the array. Pressing the tubestrips on tube arrays showed design deficiencies both in the tubestrip design and the tooling design. DSI has a number of revisions in process to correct these deficiencies. The research effort has identified a more economical fusible alloy for encapsulating the tube array, and determined the parameters required to successfully encapsulate the tube array with the new alloy. A more compact MTS heat exchanger bank was designed. 1 ref., 4 figs.

  19. Higher Education Exchange 2006

    ERIC Educational Resources Information Center

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

    2006-01-01

    Contributors to this issue of the Higher Education Exchange debate the issues around knowledge production, discuss the acquisition of deliberative skills for democracy, and examine how higher education prepares, or does not prepare, students for citizenship roles. Articles include: (1) "Foreword" (Deborah Witte); (2) "Knowledge, Judgment and…

  20. Technology Performance Exchange

    SciTech Connect

    2015-09-01

    To address the need for accessible, high-quality data, the Department of Energy has developed the Technology Performance Exchange (TPEx). TPEx enables technology suppliers, third-party testing laboratories, and other entities to share product performance data. These data are automatically transformed into a format that technology evaluators can easily use in their energy modeling assessments to inform procurement decisions.

  1. Visiting Scholar Exchange Reports.

    ERIC Educational Resources Information Center

    Rubin, Kyna, Ed.

    1986-01-01

    Provides reports of four United States scholars who visited China as part of the Visiting Scholar Exchange Program. The titles of the reports are (1) "China Journey: A Political Scientist's Look at Yan'an," (2) "The Social Consequences of Land Reclamation in Chinese Coastal Ecosystems," (3) "Anthropology Lectures in South China," and (4) "The Use…

  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. 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

  4. 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.

  5. Currency Exchange Rates.

    ERIC Educational Resources Information Center

    Siler, Carl R.

    This curriculum unit of the Muncie (Indiana) Southside High School is to simulate the dynamics of foreign currency exchange rates from the perspectives of: (1) a major U.S. corporation, ABB Power T & D Company, Inc., of Muncie, Indiana, a manufacturer of large power transformers for the domestic and foreign markets; and (2) individual consumers…

  6. A corrosive resistant heat exchanger

    DOEpatents

    Richlen, S.L.

    1987-08-10

    A corrosive and erosive resistant heat exchanger which recovers heat from a contaminated heat stream. The heat exchanger utilizes a boundary layer of innocuous gas, which is continuously replenished, to protect the heat exchanger surface from the hot contaminated gas. The innocuous gas is pumped through ducts or perforations in the heat exchanger wall. Heat from the heat stream is transferred by radiation to the heat exchanger wall. Heat is removed from the outer heat exchanger wall by a heat recovery medium. 3 figs., 3 tabs.

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

    SciTech Connect

    Kodama, Tatsuya; Komarneni, Sridhar

    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.

  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. Counterflow Regolith Heat Exchanger

    NASA Technical Reports Server (NTRS)

    Zubrin, Robert; Jonscher, Peter

    2013-01-01

    A problem exists in reducing the total heating power required to extract oxygen from lunar regolith. All such processes require heating a great deal of soil, and the heat energy is wasted if it cannot be recycled from processed material back into new material. The counterflow regolith heat exchanger (CoRHE) is a device that transfers heat from hot regolith to cold regolith. The CoRHE is essentially a tube-in-tube heat exchanger with internal and external augers attached to the inner rotating tube to move the regolith. Hot regolith in the outer tube is moved in one direction by a right-hand - ed auger, and the cool regolith in the inner tube is moved in the opposite direction by a left-handed auger attached to the inside of the rotating tube. In this counterflow arrangement, a large fraction of the heat from the expended regolith is transferred to the new regolith. The spent regolith leaves the heat exchanger close to the temperature of the cold new regolith, and the new regolith is pre-heated close to the initial temperature of the spent regolith. Using the CoRHE can reduce the heating requirement of a lunar ISRU system by 80%, reducing the total power consumption by a factor of two. The unique feature of this system is that it allows for counterflow heat exchange to occur between solids, instead of liquids or gases, as is commonly done. In addition, in variants of this concept, the hydrogen reduction can be made to occur within the counterflow heat exchanger itself, enabling a simplified lunar ISRU (in situ resource utilization) system with excellent energy economy and continuous nonbatch mode operation.

  10. Exam Question Exchange.

    ERIC Educational Resources Information Center

    Alexander, John J.

    1980-01-01

    Provides exam questions and solutions for a problem in amplification sequence of reactions, and a problem in applying group theory techniques and making spectral assignments and structural determination by qualitative arguments in the bonding in metal complexes. (CS)

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

    USGS Publications Warehouse

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

    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 of mass equation. The simultaneous solutions to these equations generate curved exchange trajectories on ??-?? 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. ?? 1987.

  12. 0022-3530/90 $3.00 Reaction Between Ultramafic Rock and Fractionating

    E-print Network

    reaction between peridotite and fractionating tholeiitic basalt in simple and complex silicate systems, the result of reactions between 'basalt' and 'peridotite' may be treated as a combination of Fe-Mg exchange with peridotite, and crystal products of such reactions will be dunite. Liquids saturated in clinopyroxene

  13. Clearing Algorithms for Barter Exchange Markets: Enabling Nationwide Kidney Exchanges

    E-print Network

    Clearing Algorithms for Barter Exchange Markets: Enabling Nationwide Kidney Exchanges David J national kidney-exchange mar- ket, where patients with kidney disease can obtain compat- ible donors kidney in the US, this market is seen as the only ethical way to significantly reduce the 4,000 deaths

  14. Origins of Linear Partitioning in Binary Solutions: the Exchange Coefficient

    NASA Astrophysics Data System (ADS)

    Morse, S. A.

    2006-05-01

    Linear partitioning occurs when, as often in petrologic systems and perhaps always in azeotropes, a straight- line relationship occurs when the partition coefficient D = X1S/X1L is plotted against the solid composition X2S and runs from an intercept value KD at pure (2) to 1.0 at pure (1). The equation is then D = KD*X2S + X1S (Morse 1997, JGeol 105:471; 2000 GCA, 64:2309). The notation KD was taken from its long-standing familiarity in binary solutions (Roeder & Emslie 1970, CMP 29:275) and described as the exchange coefficient (Beattie et al. 1993 GCA 57:1605). But the binary loop is not in itself an exchange equilibrium; it is a transfer equilibrium marching to a different drummer, and that causes a problem (Kretz 2005, CanMin 43:1349). In at least three ways, the binary loop qualifies as an exchange reaction and justifies calling the intercept KD. To the experimentalist this issue never arises. In a perfect liquidus experiment, an infinitesimal mass of liquid is indeed transferred to the crystal. A second bulk composition is then made, and at the new liquidus a second mass transfer occurs. The ensemble of all such perfect partitioning experiments in sufficient number then completely delineates the binary loop without any continuous transfer at changing T having taken place. The partitionings are therefore truly independent of the path. Moreover, each equilibrium pair defines a common tangent in G-X space whose intercept at pure (2) unarguably gives the value of the common chemical potential, a partial Gibbs energy. But where is the exchange reaction? The real experimentalist makes no perfect experiments, and neither does nature. In reality, the barrier to nucleation (particularly formidable in the case of plagioclase) dictates that the crystals nucleate only at some supercooling. They therefore have some composition between the initial solidus and the liquid lying at the bulk composition (BC). Over time the two phases may drift apart by diffusion, the crystal going to the solidus and the liquid going to the liquidus, with evolution of latent heat and a gain in T. The parting of the two compositions is a true exchange reaction, revealed by kinetics. An isothermal exchange reaction occurs in the petrologically important adcumulus growth (Wager et al. 1960, JPet. 1:73; Walker et al. 1985, EOS 66:362). In this process, a porous cumulate becomes solidified by the expulsion of low-melting components in the pore liquid to an infinite reservoir (the main magma) with the concomitant return of refractory components to the crystals, a perfect open-system exchange process involving the complete transit of the local bulk composition from that of the liquid to that of the crystals. Ideally, the exchange operates on a constant G-X tangent and constant chemical potential with constant D and T but with extraction of latent heat to the surroundings. Here again the Gibbs function is described by KD. In metamorphic systems, for a bulk composition between biotite and garnet in the AFM projection, the two phases are in true Fe-Mg exchange as a function of T, following the usual association of KD with T. But when the BC encounters the 3-phase triangle Bi-Gt-Sill, the reaction becomes a transfer reaction, still, however, responding to the linear partitioning principle (Morse 2000). Here the transfer reaction is a limiting case of an exchange reaction. In linear partitioning, the exchange coefficient is a constant anchor for all T, and only D tracks the temperature. The big surprise, of course, is that KD is, in this limiting case, an isothermal function, with consequences explored elsewhere (Morse, 2000).

  15. 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.

  16. Phosphonic acid based exchange resins

    DOEpatents

    Horwitz, E. Philip (Naperville, IL); Alexandratos, Spiro D. (Knoxville, TN); Gatrone, Ralph C. (Naperville, IL); Chiarizia, Ronato (Oak Park, IL)

    1995-01-01

    An ion exchange resin for extracting metal ions from a liquid waste stream. An ion exchange resin is prepared by copolymerizing a vinylidene diphosphonic acid with styrene, acrylonitrile and divinylbenzene.

  17. Parallelization for reaction

    E-print Network

    Louvet, Violaine

    Parallelization for reaction waves with complex chemistry Context Application Background Numerical Results Conclusions and Perspectives Parallelization strategies for multi-scale reaction waves for Engineering - Paraguay 2010 #12;Parallelization for reaction waves with complex chemistry Context Application

  18. 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)

  19. Ion Exchange Chromatography Using Fractogel

    E-print Network

    Lebendiker, Mario

    . Fig.1 X-ray structure of a protein. All charged amino acids involved in binding to the ion exchanger Chromatography Ion exchange chromatography is commonly used for nearly all purifications of proteins. This widely can be used as well as cation exchangers. With a strongly acidic pH value all amino acids are present

  20. Exchange Program University of Castilla

    E-print Network

    Fernandez, Eduardo

    , public local transportation (1-2.10 per trip), and spending money. Exchange rates fluctuate daily, visitSPAIN Exchange Program University of Castilla ­ La Mancha UCLM is located in the historic La Mancha www.oanda.com for the latest exchange rate. Deadlines for Applying: May 30 (fall); November 14 (spring

  1. GAS EXCHANGE Respiration: An Introduction

    E-print Network

    Wood, Spencer

    in Respiratory Ventilation and Gas-Exchange Organs Physiology Gas Transport and Exchange Further Reading Glossary part of the space between the lamellae of fish gills. Lamellae Also known as secondary lamellae, these are attached in rows to the gill filaments. They are the primary sites for gas exchange in fish gills. Each

  2. 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...

  3. Serpentine heat exchanger

    SciTech Connect

    Tomlinson, R.S.

    1991-01-08

    This patent describes a furnace having a burner means for providing hot products of combustion, and an air flow means for circulating conditioned air, a heat exchanger for transferring heat from products of combustion to conditioned air. The heat exchanger comprises first and second matched clamshell plates assembled together. The plates connected at their respective edges by a sealing means for providing a seal thereat, each the plate having an internal surface defining a depression. The depressions together defining a serpentine passageway, an entrance and exhaust ported formed in the passageway. The surfaces including elongated ribs for obstructing fluid flow adjacent the exhaust portal and for directing fluid flow to under-utilized portions in the passageway.

  4. Generalized replica exchange method.

    PubMed

    Kim, Jaegil; Keyes, Thomas; Straub, John E

    2010-06-14

    We present a powerful replica exchange method, particularly suited to first-order phase transitions associated with the backbending in the statistical temperature, by merging an optimally designed generalized ensemble sampling with replica exchanges. The key ingredients of our method are parametrized effective sampling weights, smoothly joining ordered and disordered phases with a succession of unimodal energy distributions by transforming unstable or metastable energy states of canonical ensembles into stable ones. The inverse mapping between the sampling weight and the effective temperature provides a systematic way to design the effective sampling weights and determine a dynamic range of relevant parameters. Illustrative simulations on Potts spins with varying system size and simulation conditions demonstrate a comprehensive sampling for phase-coexistent states with a dramatic acceleration of tunneling transitions. A significant improvement over the power-law slowing down of mean tunneling times with increasing system size is obtained, and the underlying mechanism for accelerated tunneling is discussed. PMID:20550390

  5. Sorption and binary exchange of nitrate, sulfate, and uranium on an anion-exchange resin.

    PubMed

    Gu, Baohua; Ku, Yee-Kyoung; Jardine, Philip M

    2004-06-01

    Competitive ion-exchange reactions were studied on a strong-base anion-exchange resin to remove NO3- and uranium from a contaminated groundwater containing high levels of NO3- (approximately 140 mM), SO4(2-) (approximately 10 mM), and U(VI) (approximately 0.2 mM). Results indicate that although SO4(2-) carries divalent negative charges, it showed the least selectivity for sorption by the Purolite A-520E resin, which is functionalized with triethylamine exchange sites. Nitrate was the most strongly sorbed. Sorption selectivity followed the order of NO3- > Cl- > SO4(2-) under the experimental conditions. Nitrate competitively sorbed and displaced previously sorbed SO4(2-) in a column flow-through experiment and resulted in a high elution front of SO4(2-) in the effluent. Although the concentration of uranium in groundwater is orders of magnitude lower than that of NO3- or SO4(2-), it was found to be strongly sorbed by the anion-exchange resin. Because the most stable uranium species in oxic and suboxic environments is the UO2(2+) cation, its strong sorption by anion-exchange resins is hypothesized to be the result of the co-ion effect of NO3- by forming anionic UO2(NO3)3- complexes in the resin matrix. These observations point out a potential alternative remediation strategy that uses strong-base anion-exchange resins to remove uranium from this site-specific groundwater, which has a low pH and a relatively high NO3- concentration. PMID:15224753

  6. Anion Exchange Chemistry of Middle Atlantic Soils: Charge Properties and Nitrate Retention Kinetics

    E-print Network

    Sparks, Donald L.

    Anion Exchange Chemistry of Middle Atlantic Soils: Charge Properties and Nitrate Retention Kinetics C. V. Toner, IV,* D. L. Sparks, and T. H. Carski ABSTRACT The negativeimpactof nitrate(NO3-flow reaction chamber and a first-order reaction best described the data. Nitrate adsorption was found

  7. 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…

  8. 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.

  9. Emittance and Phase Space Exchange

    SciTech Connect

    Xiang, Dao; Chao, Alex; /SLAC

    2011-08-19

    Alternative chicane-type beam lines are proposed for exact emittance exchange between horizontal phase space (x; x{prime}) and longitudinal phase space (z; {delta}). Methods to achieve exact phase space exchanges, i.e. mapping x to z, x{prime} to {delta}, z to x and {delta} to x{prime} are suggested. Methods to mitigate the thick-lens effect of the transverse cavity on emittance exchange are discussed. Some applications of the phase space exchanger and the feasibility of an emittance exchange experiment with the proposed chicane-type beam line at SLAC are discussed.

  10. Advanced Chemical Heat Pumps Using Liquid-Vapor Reactions 

    E-print Network

    Kirol, L.

    1987-01-01

    have significant potential advantage over conventional tech nology. An electric drive reactive heat pump can use smaller heat exchangers and compressor than a vapor-compression machine, and have more flexible operating 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 tures...

  11. Molecular recognition in cation-exchanged zeolites

    NASA Astrophysics Data System (ADS)

    Pidko, Evgeny A.; van Santen, Rutger A.

    The concepts of confinement- and molecular recognition-driven chemical reactivity of cation-exchanged zeolites is illustrated by our recent results from periodic and cluster density functional theory (DFT) calculations. The reactivity of alkali-earth- and alkaline-exchanged low-silica zeolites for selective photo-oxidation of alkenes with molecular oxygen and for N2O4 disproportionation is shown to be mainly due to the specific arrangement and the size of the cations in the zeolite cage. An attempt is made to separate the effects of basicity of the framework, the Lewis acidity of the extra-framework cations and the electrostatic field in the zeolite cage as well as its geometrical properties for the respective reactions. The importance of the favorable adsorption fashion of the reagents controlled by noncovalent interactions with the microporous matrix is shown. The role of the weak interactions with the zeolite walls and the factors, which determine the preference for a particular adsorption mode, are discussed by the example of light alkanes adsorption to Mg- and Ca-exchanged faujasites.

  12. 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.

  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. Preserving local gauge invariance with t -channel Regge exchange

    NASA Astrophysics Data System (ADS)

    Haberzettl, Helmut; Wang, Xiao-Yun; He, Jun

    2015-11-01

    Considering single-meson photo- and electroproduction off a baryon, it is shown how to restore local gauge invariance that was broken by replacing standard Feynman-type meson exchange in the t channel by exchange of a Regge trajectory. This is achieved by constructing a contact current whose four-divergence cancels the gauge-invariance-violating contributions resulting from all states above the base state on the Regge trajectory. To illustrate the procedure, modifications necessary for the process ? +p ?K++?*0 are discussed in some detail. We also provide the general expression for the contact current for an arbitrary reaction.

  15. Analysis of titanium/carbon steel heat exchanger fire

    SciTech Connect

    Prine, B.A. )

    1992-04-01

    In the past fifteen years two serious titanium fires have occurred at scrap dealer facilities. Both incidents involved the cutting of titanium/carbon steel heat exchangers by scrap metal dealers. This paper reviews the properties of titanium and carbon steel under extreme conditions and the oxy-acetylene cutting process relevant to its potential for initiating titanium fires. The probable modes of propagation involved in these specific incidents are considered. The formation of low melting eutectic mixtures and the Thermite reaction are both felt to contribute to the incident once initiated. Alternate methods of cutting titanium/carbon steel exchangers are discussed.

  16. 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)

  17. The Glyoxal Clock Reaction

    ERIC Educational Resources Information Center

    Ealy, Julie B.; Negron, Alexandra Rodriguez; Stephens, Jessica; Stauffer, Rebecca; Furrow, Stanley D.

    2007-01-01

    Research on the glyoxal clock reaction has led to adaptation of the clock reaction to a general chemistry experiment. This particular reaction is just one of many that used formaldehyde in the past. The kinetics of the glyoxal clock makes the reaction suitable as a general chemistry lab using a Calculator Based Laboratory (CBL) or a LabPro. The…

  18. Compact heat exchangers

    SciTech Connect

    1999-11-01

    This report aims to increase the market penetration of compact heat exchangers (CHEs) in industry by detailing current experience of their use. CHEs are characterized by having a comparatively large amount of surface area in a given volume, compared to traditional heat exchangers, in particular the shell-and-tube type. The most basic CHEs have volumes of less than 50% of that of a comparable shell-and-tube heat exchanger, for a given duty. Some new designs can, under appropriate process conditions, have only 5% of the volume of traditional equivalents. An essential component of many of these compact concepts is heat (and mass) transfer enhancement. This report also details some of the main enhancement methods which are used in the implementation of compact systems. CHEs are of interest for a number of reasons. As well as being, in general, highly efficient, allowing greater amounts of energy to be recovered between process streams, they are more versatile in terms of the number of process streams that can be handled. Some CHEs can handle only two streams. Others can handle four or more with ease. That, coupled with the availability of units to cater for most operating temperatures and pressures, makes them of interest to operators of complex thermal processing plants. Of even greater long-term importance to the process industries is the ability to use CHE manufacturing technology to integrate effective heat transfer with other unit operations, such as reactors, in one unit. This radical approach to process plant design has fostered many exciting concepts for combined unit operations, some of which are discussed in this report. Topics covered are: types of CHE; (2) the role of heat transfer enhancement; (3) benefits and perceived limitations of CHEs; (4) costs; (5) fouling; (6) specification, installation and operating procedures; (7) the new opportunities; and (8) conclusions.

  19. Blocked exchanges revisited.

    PubMed

    Machan, T R

    1997-01-01

    This paper reconsiders the topic of blocked exchanges. It has been argued by some philosophers and social theorists that in order to encourage people to make donations of, e.g., blood, the sale of such items should be banned by law or public policy. In this paper I argue that (a) donations made without the option of selling are morally diminished and (2) selling such items isn't morally wrong or even insignificant in all cases since prudence (which is a moral virtue, pace Kant) may require that one sell them. PMID:12474848

  20. The Gift Exchange Problem

    E-print Network

    Applegate, David

    2009-01-01

    The aim of this paper is to solve the "gift exchange" problem: you are one of n players, and there are n wrapped gifts on display; when your turn comes, you can either choose any of the remaining wrapped gifts, or you can "steal" a gift from someone who has already unwrapped it, subject to the restriction that no gift can be stolen more than a total of S times. The problem is to determine the number of ways that the game can be played out, for given values of S and n. Several recurrences and explicit formulas are given for these numbers, although some open questions remain.

  1. Classes of Chemical Reactions Reactions in aqueous media

    E-print Network

    Zakarian, Armen

    Classes of Chemical Reactions Reactions in aqueous media · Precipitation reactions · Acid-Base reactions · Oxidation-Reduction reactions · Reversible reactions Classes of Chemical Reactions Water (H2O;Classes of Chemical Reactions The solubility of ionic compounds: dissociation O H H + NaCl Cl- Cl- Cl- Na

  2. Divergent layer topologies in divalent metal aliphatic dicarboxylate coordination polymers containing 3-pyridylmethylnicotinamide

    NASA Astrophysics Data System (ADS)

    White, Charmaine L.; Torres Salgado, Maria D.; Mizzi, Jessica E.; LaDuca, Robert L.

    2015-12-01

    Hydrothermal reaction of the requisite metal salt, an aliphatic dicarboxylic acid, and the hydrogen-bonding capable dipyridylamide ligand 3-pyridylmethylnicotinamide (3-pmna) resulted in four coordination polymers whose connectedness and layer topology depend on the metal coordination environment and dicarboxylate binding mode. These new crystalline phases were characterized by single crystal X-ray diffraction. [Cu(ox)(3-pmna)]n (1, ox = oxalate) manifests stacked 3-connected (6,3) herringbone layer motifs. {[Cd(mal)(3-pmna)(H2O)]·3H2O}n (2, mal = malonate) shows a 4-connected (4,4) grid topology with entrained water molecule trimeric chains in the interlamellar regions. {[Cd2(suc)2(3-pmna)(H2O)2]·3H2O}n (3, suc = succinate) possesses {Cd2O2} dimer-based [Cd(suc)]n layers pillared by 3-pmna ligands into a 5-connected sandwich motif with 4862 topology. {[Cd(glu)(3-pmna)(H2O)]·3H2O}n (4, glu = glutarate) manifests a rippled (4,4) grid topology. Luminescent behavior in the cadmium complexes is ascribed to intra-ligand molecular orbital transitions. Thermal decomposition behavior is also discussed herein.

  3. Myristate exchange on the Trypanosoma brucei variant surface glycoprotein.

    PubMed Central

    Buxbaum, L U; Milne, K G; Werbovetz, K A; Englund, P T

    1996-01-01

    The glycosyl-phosphatidylinositol (GPI) anchor of the Trypanosoma brucei variant surface glycoprotein (VSG) is unique in having exclusively myristate as its fatty acid component. We previously demonstrated that the myristate specificity is the result of two independent pathways. First, the newly synthesized free GPI, which is not myristoylated, undergoes fatty acid remodeling to replace both its fatty acids with myristate. Second, the myristoylated precursor, glycolipid A, undergoes a myristate exchange reaction, detected by the replacement of unlabeled myristate by [3H]myristate. Remodeling and exchange have different enzymatic properties and apparently occur in different subcellular compartments. We now demonstrate that the GPI anchor linked to VSG is the major substrate for myristate exchange. VSG can be efficiently labeled with [3H]myristate by exchange in the presence of cycloheximide, an inhibitor that prevents new VSG synthesis and thus anchor addition to protein. Not only is newly synthesized VSG subject to exchange, but mature VSG, possibly recycling from the cell surface, also undergoes myristate exchange. Images Fig. 1 Fig. 4 PMID:8577736

  4. Size Influence on the Oxygen Reduction Reaction Activity and Instability of Supported Pt Nanoparticles

    E-print Network

    Sheng, Wenchao

    Size-dependent oxygen reduction reaction activity (ORR) and instability of Pt nanoparticles is of great importance in proton exchange membrane fuel cell applications. In this study, the size-dependence of ORR activity on ...

  5. Heat exchanger-accumulator

    DOEpatents

    Ecker, Amir L. (Dallas, TX)

    1980-01-01

    What is disclosed is a heat exchanger-accumulator for vaporizing a refrigerant or the like, characterized by an upright pressure vessel having a top, bottom and side walls; an inlet conduit eccentrically and sealingly penetrating through the top; a tubular overflow chamber disposed within the vessel and sealingly connected with the bottom so as to define an annular outer volumetric chamber for receiving refrigerant; a heat transfer coil disposed in the outer volumetric chamber for vaporizing the liquid refrigerant that accumulates there; the heat transfer coil defining a passageway for circulating an externally supplied heat exchange fluid; transferring heat efficiently from the fluid; and freely allowing vaporized refrigerant to escape upwardly from the liquid refrigerant; and a refrigerant discharge conduit penetrating sealingly through the top and traversing substantially the length of the pressurized vessel downwardly and upwardly such that its inlet is near the top of the pressurized vessel so as to provide a means for transporting refrigerant vapor from the vessel. The refrigerant discharge conduit has metering orifices, or passageways, penetrating laterally through its walls near the bottom, communicating respectively interiorly and exteriorly of the overflow chamber for controllably carrying small amounts of liquid refrigerant and oil to the effluent stream of refrigerant gas.

  6. 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.

  7. 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.

  8. Alkaline earth metal cation exchange: effect of mobile counterion and dissolved organic matter.

    PubMed

    Indarawis, Katrina; Boyer, Treavor H

    2012-04-17

    The goal of this research was to provide an improved understanding of the interactions between alkaline earth metals and DOM under conditions that are encountered during drinking water treatment with particular focus on cation exchange. Both magnetically enhanced and nonmagnetic cation exchange resins were converted to Na, Mg, Ca, Sr, and Ba mobile counterion forms as a novel approach to investigate the exchange behavior between the cations and the interactions between the cations and DOM. The results show that cation exchange is a robust process for removal of Ca(2+) and Mg(2+) considering competition with cations on the resin surface and presence of DOM. DOM was actively involved during the cation exchange process through complexation, adsorption, and coprecipitation reactions. In addition to advancing the understanding of ion exchange processes for water treatment, the results of this work are applicable to membrane pretreatment to minimize fouling, treatment of membrane concentrate, and precipitative softening. PMID:22424449

  9. Production of Radioactive Nuclides in Inverse Reaction Kinematics

    E-print Network

    E. Traykov; A. Rogachevskiy; U. Dammalapati; P. Dendooven; O. C. Dermois; K. Jungmann; C. J. G. Onderwater; M. Sohani; L. Willmann; H. W. Wilschut; A. R. Young

    2006-08-08

    Efficient production of short-lived radioactive isotopes in inverse reaction kinematics is an important technique for various applications. It is particularly interesting when the isotope of interest is only a few nucleons away from a stable isotope. In this article production via charge exchange and stripping reactions in combination with a magnetic separator is explored. The relation between the separator transmission efficiency, the production yield, and the choice of beam energy is discussed. The results of some exploratory experiments will be presented.

  10. Optimization of Heat Exchanger Cleaning 

    E-print Network

    Siegell, J. H.

    1986-01-01

    EXCHANGER CLEANING Jeffrey H. Siegell Exxon Research and Engineering Company Florham Park, New Jersey ABSTRACT 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, economic incentives for heat exchanger cleaning are evaluated using linear, exponential, and exponential finite decrease models of the heat...

  11. Ion-exchange hollow fibers

    NASA Technical Reports Server (NTRS)

    Rembaum, A.; Yen, S. P. S.; Klein, E. (inventors)

    1976-01-01

    An ion-exchange hollow fiber is prepared by introducing into the wall of the fiber polymerizable liquid monomers, and polymerizing the monomers therein to form solid, insoluble, crosslinked, ion-exchange resin particles which embed in the wall of the fiber. Excess particles blocking the central passage or bore of the fiber are removed by forcing liquid through the fiber. The fibers have high ion-exchange capacity, a practical wall permeability and good mechanical strength even with very thin wall dimensions. Experimental investigation of bundles of ion-exchange hollow fibers attached to a header assembly have shown the fiber to be very efficient in removing counterions from solution.

  12. Ion-exchange hollow fibers

    NASA Technical Reports Server (NTRS)

    Rembaum, Alan (Inventor); Yen, Shiao-Ping S. (Inventor); Klein, Elias (Inventor)

    1977-01-01

    An ion-exchange hollow fiber is prepared by introducing into the wall of the fiber polymerizable liquid monomers, and polymerizing the monomers therein to form solid, insoluble, cross-linked, ion-exchange resin particles which embed in the wall of the fiber. Excess particles blocking the central passage or bore of the fiber are removed by forcing liquid through the fiber. The fibers have high ion-exchange capacity, a practical wall permeability and good mechanical strength even with very thin wall dimensions. Experimental investigation of bundles of ion-exchange hollow fibers attached to a header assembly have shown the fiber to be very efficient in removing counterions from solution.

  13. Ion-exchange hollow fibers

    NASA Technical Reports Server (NTRS)

    Rembaum, Alan (Inventor); Yen, Shiao-Ping S. (Inventor); Klein, Elias (Inventor)

    1980-01-01

    An ion-exchange hollow fiber is prepared by introducing into the wall of the fiber polymerizable liquid monomers, and polymerizing the monomers therein to form solid, insoluble, cross-linked, ion-exchange resin particles which embed in the wall of the fiber. Excess particles blocking the central passage or bore of the fiber are removed by forcing liquid through the fiber. The fibers have high ion-exchange capacity, a practical wall permeability and good mechanical strength even with very thin wall dimensions. Experimental investigation of bundles of ion-exchange hollow fibers attached to a header assembly have shown the fiber to be very efficient in removing counterions from solution.

  14. Bifurcations of dividing surfaces in chemical reactions

    NASA Astrophysics Data System (ADS)

    Iñarrea, Manuel; Palacián, Jesús F.; Pascual, Ana Isabel; Salas, J. Pablo

    2011-07-01

    We study the dynamical behavior of the unstable periodic orbit (NHIM) associated to the non-return transition state (TS) of the H2 + H collinear exchange reaction and their effects on the reaction probability. By means of the normal form of the Hamiltonian in the vicinity of the phase space saddle point, we obtain explicit expressions of the dynamical structures that rule the reaction. Taking advantage of the straightforward identification of the TS in normal form coordinates, we calculate the reaction probability as a function of the system energy in a more efficient way than the standard Monte Carlo method. The reaction probability values computed by both methods are not in agreement for high energies. We study by numerical continuation the bifurcations experienced by the NHIM as the energy increases. We find that the occurrence of new periodic orbits emanated from these bifurcations prevents the existence of a unique non-return TS, so that for high energies, the transition state theory cannot be longer applied to calculate the reaction probability.

  15. 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.

  16. 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

  17. Hybrid Heat Exchangers

    NASA Technical Reports Server (NTRS)

    Tu, Jianping Gene; Shih, Wei

    2010-01-01

    A hybrid light-weight heat exchanger concept has been developed that uses high-conductivity carbon-carbon (C-C) composites as the heat-transfer fins and uses conventional high-temperature metals, such as Inconel, nickel, and titanium as the parting sheets to meet leakage and structural requirements. In order to maximize thermal conductivity, the majority of carbon fiber is aligned in the fin direction resulting in 300 W/m.K or higher conductivity in the fin directions. As a result of this fiber orientation, the coefficient of thermal expansion (CTE) of the C-C composite in both non-fiber directions matches well with the CTE of various high-temperature metal alloys. This allows the joining of fins and parting sheets by using high-temperature braze alloys.

  18. South Atlantic interbasin exchange

    NASA Technical Reports Server (NTRS)

    Rintoul, Stephen Rich

    1991-01-01

    The exchange of mass and heat between the South Atlantic and the neighboring ocean basins was estimated using hydrographic data and inverse methods, in order to gain information on the links between the deep-water formation processes occurring within the Atlantic and the global thermohaline circulation. Results demonstrate that the global thermohaline cell associated with the formation and export of North Atlantic deep water (NADW) is closed primarily by a 'cold water path' in which deep water leaving the Atlantic ultimately returns as intermediate water entering the basin through Drake Passage. This conclusion conflicts with the suggestion by Gordon (1986) that the global thermohaline circulation associated with the formation of NADW is closed primarily by a 'warm water path', in which the export of NADW is compensated by an inflow of warm Indian Ocean thermocline water south of Africa.

  19. 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).

  20. Meson-baryon interaction in the meson exchange picture

    SciTech Connect

    Doering, M.

    2011-10-24

    Elastic {pi}N scattering and the reaction {pi}{sup +}p{yields}K{sup +}{Sigma}{sup +} 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.

  1. Insoluble polyelectrolyte and ion-exchange hollow fiber impregnated therewith

    NASA Technical Reports Server (NTRS)

    Rembaum, A. (inventor)

    1977-01-01

    The number of quaternary sites and ion exchange capacity of a polyquaternary, cross linked, insoluble copolymer of a vinyl pyridine and a dihalo organic compound is increased by about 15-35% by reaction of the polymer with an amine followed by quaternization, if required. The polymer forms spontaneously in the presence of a substrate such as within the pores of a hollow fiber. The improved resin impregnated fiber may be utilized to remove ions from waste or process steams.

  2. Simultaneous Disulfide and Boronic Acid Ester Exchange in Dynamic Combinatorial Libraries.

    PubMed

    Diemer, Sanna L; Kristensen, Morten; Rasmussen, Brian; Beeren, Sophie R; Pittelkow, Michael

    2015-01-01

    Dynamic combinatorial chemistry has emerged as a promising tool for the discovery of complex receptors in supramolecular chemistry. At the heart of dynamic combinatorial chemistry are the reversible reactions that enable the exchange of building blocks between library members in dynamic combinatorial libraries (DCLs) ensuring thermodynamic control over the system. If more than one reversible reaction operates in a single dynamic combinatorial library, the complexity of the system increases dramatically, and so does its possible applications. One can imagine two reversible reactions that operate simultaneously or two reversible reactions that operate independently. Both these scenarios have advantages and disadvantages. In this contribution, we show how disulfide exchange and boronic ester transesterification can function simultaneous in dynamic combinatorial libraries under appropriate conditions. We describe the detailed studies necessary to establish suitable reaction conditions and highlight the analytical techniques appropriate to study this type of system. PMID:26378519

  3. Simultaneous Disulfide and Boronic Acid Ester Exchange in Dynamic Combinatorial Libraries

    PubMed Central

    Diemer, Sanna L.; Kristensen, Morten; Rasmussen, Brian; Beeren, Sophie R.; Pittelkow, Michael

    2015-01-01

    Dynamic combinatorial chemistry has emerged as a promising tool for the discovery of complex receptors in supramolecular chemistry. At the heart of dynamic combinatorial chemistry are the reversible reactions that enable the exchange of building blocks between library members in dynamic combinatorial libraries (DCLs) ensuring thermodynamic control over the system. If more than one reversible reaction operates in a single dynamic combinatorial library, the complexity of the system increases dramatically, and so does its possible applications. One can imagine two reversible reactions that operate simultaneously or two reversible reactions that operate independently. Both these scenarios have advantages and disadvantages. In this contribution, we show how disulfide exchange and boronic ester transesterification can function simultaneous in dynamic combinatorial libraries under appropriate conditions. We describe the detailed studies necessary to establish suitable reaction conditions and highlight the analytical techniques appropriate to study this type of system. PMID:26378519

  4. Allergic reactions (image)

    MedlinePLUS

    Allergic reaction is a sensitivity to a specific substance, called an allergen, that is contacted through the skin, inhaled into the lungs, swallowed or injected. The body's reaction to an allergen can be mild, such as ...

  5. Allergic reactions (image)

    MedlinePLUS

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

  6. 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)

  7. Deuterium isotopic exchangeability of resin and amber at low thermal stress under hydrous conditions

    NASA Astrophysics Data System (ADS)

    Gonzalez, G.; Tappert, R.; Wolfe, A. P.; Muehlenbachs, K.

    2012-04-01

    Hydrous deuterium-exchange experiments have shown that a significant fraction of the original D/H composition of bulk kerogens, bitumens and expelled oils may participate in isotopic exchange reactions during burial diagenesis. However, it is unknown to what extent plant-derived secondary metabolites, namely resins and their fossil counterpart amber, exchange hydrogen isotopes following their biosynthesis. This situation hinders the application of resin D/H measurements in paleoenvironmental reconstruction. Here, we assess explicitly hydrogen exchange in resins and ambers using a series of immersion experiments in deuterated (D-enriched) waters over a period of several months at several temperatures. We are especially interested in assessing whether significant H-isotopic exchange occurs between resins and meteoric waters during early thermal maturation and polymerization. At 90°C, equivalent to ~3km of burial in most diagenetic regimes, modern conifer and angiosperm resins have an average post-metabolic H exchange of 4.6%, compared to only 1.1% for mature, polymerized ambers. At 55°C the degree of exchange is considerably lower: 1.9% for resins and 0.6% for ambers. These results indicate that most D/H isotopic exchange occurs prior to polymerization reactions, thereby confirming that D/H measurements from amber constitute a potentially sensitive proxy for environmental change.

  8. University of Haifa Exchange Program

    E-print Network

    Fernandez, Eduardo

    Israel University of Haifa Exchange Program The University of Haifa International School is located, and North America. For more information about the University, visit: http://overseas2.haifa.ac.il/ Program, 2016 Academic Program: Students on the exchange program will be enrolled as full-time students at FAU

  9. Exchange Rates and Old People.

    ERIC Educational Resources Information Center

    Dowd, James J.

    1980-01-01

    Extends earlier work on aging as a process of exchange by focusing on the issue of exchange rates and how they are negotiated. Access to power resources declines with age, placing the old person in the position of negotiating from weakness. (Author)

  10. EXCHANGE. Volume 9-92

    SciTech Connect

    Boltz, J.C.

    1992-09-01

    EXCHANGE is published monthly by the Idaho National Engineering Laboratory (INEL), a multidisciplinary facility operated for the US Department of Energy (DOE). The purpose of EXCHANGE is to inform computer users about about recent changes and innovations in both the mainframe and personal computer environments and how these changes can affect work being performed at DOE facilities.

  11. 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

  12. The NESACS Exchange with Germany

    ERIC Educational Resources Information Center

    Hoffman, Morton Z.; Tanner, Ruth; Strem, Michael

    2007-01-01

    The Northeastern Section of the American Chemical Society (NESACS) is going to host visit to the representatives of the German Chemical Society (GDCh) at their annual exchange program this year. The delegation is expected to spotlight the ACS international effects, in addition to the advantages of the exchange between the two organizations.

  13. Technology Performance Exchange (Fact Sheet)

    SciTech Connect

    Not Available

    2012-10-01

    This fact sheet, 'The Technology Performance Exchange' will be presented at the ET Summit, held at the Pasadena Convention Center on October 15-17, 2012. The Technology Performance Exchange will be a centralized, Web-based portal for finding and sharing energy performance data for commercial building technologies.

  14. The microtube strip heat exchanger

    SciTech Connect

    Doty, F.D.; Hosford, G.; Spitzmesser, J.B. ); Jones, J.D. . School of Engineering Science)

    1991-01-01

    The advantages of designing heat exchangers in the laminar-flow regime are discussed from a theoretical standpoint. It is argued that laminar-flow designs have the advantages of reducing thermodynamic and hydrodynamic irreversibilities, and hence increasing system efficiency. More concretely, laminar-flow heat exchangers are free from the turbulence-induced vibration common in conventional heat exchangers, and can thus offer longer life and greater reliability. The problems of manufacturing heat exchangers suited to laminar flow are discussed. A method of manufacture is outlined that allows compact, modular design. Experience with this method of manufacture is described. Experimental results with a prototype heat exchanger bank are presented: these results show good agreement with theory at moderate levels of effectiveness (75--85%), but fall below predicted values at higher levels. It is argued that this discrepancy results from flow maldistribution. The problem of fouling and flow maldistribution are briefly discussed, and some possible applications are mentioned.

  15. 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

  16. Microdroplet fusion mass spectrometry for fast reaction kinetics

    E-print Network

    Zare, Richard N.

    Microdroplet fusion mass spectrometry for fast reaction kinetics Jae Kyoo Leea,b , Samuel Kima,b,1 94305; b Center for Plant Aging Research, Institute for Basic Science, Daegu 711-873, Republic of Korea the existence of two distinct popula- tions with fast and slow exchange rates. These studies demon- strated

  17. 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

    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.

  18. Fault-Tolerant Heat Exchanger

    NASA Technical Reports Server (NTRS)

    Izenson, Michael G.; Crowley, Christopher J.

    2005-01-01

    A compact, lightweight heat exchanger has been designed to be fault-tolerant in the sense that a single-point leak would not cause mixing of heat-transfer fluids. This particular heat exchanger is intended to be part of the temperature-regulation system for habitable modules of the International Space Station and to function with water and ammonia as the heat-transfer fluids. The basic fault-tolerant design is adaptable to other heat-transfer fluids and heat exchangers for applications in which mixing of heat-transfer fluids would pose toxic, explosive, or other hazards: Examples could include fuel/air heat exchangers for thermal management on aircraft, process heat exchangers in the cryogenic industry, and heat exchangers used in chemical processing. The reason this heat exchanger can tolerate a single-point leak is that the heat-transfer fluids are everywhere separated by a vented volume and at least two seals. The combination of fault tolerance, compactness, and light weight is implemented in a unique heat-exchanger core configuration: Each fluid passage is entirely surrounded by a vented region bridged by solid structures through which heat is conducted between the fluids. Precise, proprietary fabrication techniques make it possible to manufacture the vented regions and heat-conducting structures with very small dimensions to obtain a very large coefficient of heat transfer between the two fluids. A large heat-transfer coefficient favors compact design by making it possible to use a relatively small core for a given heat-transfer rate. Calculations and experiments have shown that in most respects, the fault-tolerant heat exchanger can be expected to equal or exceed the performance of the non-fault-tolerant heat exchanger that it is intended to supplant (see table). The only significant disadvantages are a slight weight penalty and a small decrease in the mass-specific heat transfer.

  19. Mechanism and Dynamics of Molecular Exchange at the Silica/Binary Solvent Mixtures Interface.

    PubMed

    Karnes, John J; Benjamin, Ilan

    2015-12-17

    Nonequilibrium molecular dynamics simulations of acetonitrile/methanol mixtures in contact with a hydroxylated silica surface are used to elucidate the mechanism of molecular exchange at a hydrophilic liquid/solid interface. The different hydrogen-bonding ability of the two solvents provides a driving force for the adsorption/desorption process, which is followed by examining several structural and energetic properties of the system. Two different reaction coordinates for the hydrogen bonding exchange are defined and are used to identify transition states in which the methanol attains a well-defined orientation. The reaction coordinates are used to examine the mechanism and dynamics of the exchange. We find that the exchange process involves multiple recrossing of the transition state and can progress via two different mechanisms, depending whether the methanol first acts as a hydrogen bond donor or acceptor at the silica surface. PMID:26186086

  20. The many faces of ion-exchange resins

    SciTech Connect

    McNutty, J.T.

    1997-06-01

    Ion-exchange resins have been used commercially for over 60 years. Softening and demineralization of water for boiler feed and process use were then, and continue to be, the most familiar and widespread applications of ion-exchange resins throughout the chemical process industries (CPI). Several types of membrane-based technologies, such as electrodialysis, reverse osmosis and, more recently, electrodeionization are recognized as alternative methods for water treatment. Yet, modern versions of ion-exchange resins remain a major player in water treatment. In addition, these versatile materials can be found performing a wide range of tasks in both aqueous and nonaqueous environments. Some of these diverse applications include: acid or base catalysis; manufacture of high-purity solvents and reagent chemicals; separation of by-products of fermentation processes; deacidification of organic solvents; high-purity water production for semiconductor manufacture; recovery of valuable waste from dilute process effluents; controlled release of pharmaceutical products; and chromatography, both on the analytical and the industrial scale. The key to understanding the potential of ion-exchange resins is to look beyond their exchange and adsorptive characteristics, and to see their fundamental nature. In other words, it`s necessary to first consider them as spherical, particulate reactive polymers that perform chemical reactions.

  1. Solar system X-rays from charge exchange processes

    NASA Astrophysics Data System (ADS)

    Dennerl, K.; Lisse, C. M.; Bhardwaj, A.; Christian, D. J.; Wolk, S. J.; Bodewits, D.; Zurbuchen, T. H.; Combi, M.; Lepri, S.

    2012-04-01

    While X-ray astronomy began in 1962 and has made fast progress since then in expanding our knowledge about where in the Universe X-rays are generated by which processes, it took one generation before the importance of a fundamentally different process was recognized. This happened in our immediate neighborhood, when in 1996 comets were discovered as a new class of X-ray sources, directing our attention to charge exchange reactions. Charge exchange is fundamentally different from other processes which lead to the generation of X-rays, because the X-rays are not produced by hot electrons, but by ions picking up electrons from cold gas. Thus it opens up a new window, making it possible to detect cool gas in X-rays (like in comets), while all the other processes require extremely high temperatures or otherwise extreme conditions. After having been overlooked for a long time, the astrophysical importance of charge exchange for the generation of X-rays is now receiving increased general attention. In our solar system, charge exchange induced X-rays have now been established to originate in comets, in all the planets from Venus to Jupiter, and even in the heliosphere itself. In addition to that, evidence for this X-ray emission mechanism has been found at various locations across the Universe. Here we summarize the current knowledge about solar system X-rays resulting from charge exchange processes.

  2. Refractive lens exchange.

    PubMed

    Alio, Jorge L; Grzybowski, Andrzej; El Aswad, Amr; Romaniuk, Dorota

    2014-01-01

    Advances in small incision surgery have enabled cataract surgery to evolve from being concerned primarily with the safe removal of the opaque crystalline lens to a procedure refined to yield the best possible postoperative refractive result. As the outcomes of cataract surgery have improved, the use of lens surgery as a refractive modality in patients without cataracts (clear lens extraction) has increased in popularity. The removal of the crystalline lens for refractive purposes, or so-called refractive lens exchange (RLE), offers distinct advantages over corneal refractive surgery in selected cases. Nevertheless, in some middle-aged patients with high refractive errors, corneal refractive surgery can be a safe and effective treatment. In addition, the use of multifocal lenses offers an alternative for the correction of presbyopia. A further advantage of RLE is that it simultaneously eliminates the need for cataract surgery in the future. The keys for success in RLE are effectiveness and consistency in the refractive outcome, providing at the same time surgical and postoperative safety. To achieve these goals, adequate indications following strict risk/benefit criteria and refractive precision based on accurate preoperative protocols for IOL calculation and selection are mandatory, together with an appropriate choice of surgical procedure based on the surgeon's skills, minimizing complications. PMID:25127929

  3. 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)

  4. Modular heat exchanger

    DOEpatents

    Giardina, Angelo R. [Marple Township, Delaware County, PA

    1981-03-03

    A shell and tube heat exchanger having a plurality of individually removable tube bundle modules. A lattice of structural steel forming rectangular openings therein is placed at each end of a cylindrical shell. Longitudinal structural members are placed in the shell between corners of the rectangular openings situated on opposite ends of the shell. Intermediate support members interconnect the longitudinal supports so as to increase the longitudinal supports rigidity. Rectangular parallelpiped tube bundle moldules occupy the space defined by the longitudinal supports and end supports and each include a rectangular tube sheet situated on each end of a plurality of tubes extending therethrough, a plurality of rectangular tube supports located between the tube sheets, and a tube bundle module stiffening structure disposed about the bundle's periphery and being attached to the tube sheets and tube supports. The corners of each tube bundle module have longitudinal framework members which are mateable with and supported by the longitudinal support members. Intermediate support members constitute several lattice, each of which is situate d in a plane between the end support members. The intermediate support members constituting the several lattice extend horizontally and vertically between longitudinal supports of adjacent tube module voids. An alternative embodiment for intermediate support members constitute a series of structural plates situated at the corners of the module voids and having recesses therein for receiving the respective longitudinal support members adjacent thereto, protrusions separating the recesses, and a plurality of struts situated between protrusions of adjacent structural plates.

  5. Modular heat exchanger

    DOEpatents

    Giardina, A.R.

    1981-03-03

    A shell and tube heat exchanger is described having a plurality of individually removable tube bundle modules. A lattice of structural steel forming rectangular openings therein is placed at each end of a cylindrical shell. Longitudinal structural members are placed in the shell between corners of the rectangular openings situated on opposite ends of the shell. Intermediate support members interconnect the longitudinal supports so as to increase the longitudinal supports rigidity. Rectangular parallelepiped tube bundle modules occupy the space defined by the longitudinal supports and end supports and each include a rectangular tube sheet situated on each end of a plurality of tubes extending there through, a plurality of rectangular tube supports located between the tube sheets, and a tube bundle module stiffening structure disposed about the bundle's periphery and being attached to the tube sheets and tube supports. The corners of each tube bundle module have longitudinal framework members which are mateable with and supported by the longitudinal support members. Intermediate support members constitute several lattices, each of which is situated in a plane between the end support members. The intermediate support members constituting the several lattices extend horizontally and vertically between longitudinal supports of adjacent tube module voids. An alternative embodiment for intermediate support members constitute a series of structural plates situated at the corners of the module voids and having recesses therein for receiving the respective longitudinal support members adjacent thereto, protrusions separating the recesses, and a plurality of struts situated between protrusions of adjacent structural plates. 12 figs.

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

    SciTech Connect

    Abtin, L.; Springholz, G.; Holy, V.

    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.

  7. 75 FR 51138 - Self-Regulatory Organizations; BATS Exchange, Inc.; Chicago Board Options Exchange, Incorporated...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-18

    ... Exchange Act Release Nos. 62251 (June 10, 2010), 75 FR 34183 (June 16, 2010); 62252 (June 10, 2010), 75 FR...; BATS Exchange, Inc.; Chicago Board Options Exchange, Incorporated; Chicago Stock Exchange, Inc.; EDGA... Securities Exchange LLC; NASDAQ OMX BX, Inc.; The NASDAQ Stock Market LLC; National Stock Exchange, Inc.;...

  8. Semilocal density functional obeying a strongly tightened bound for exchange

    PubMed Central

    Sun, Jianwei; Perdew, John P.; Ruzsinszky, Adrienn

    2015-01-01

    Because of its useful accuracy and efficiency, density functional theory (DFT) is one of the most widely used electronic structure theories in physics, materials science, and chemistry. Only the exchange-correlation energy is unknown, and needs to be approximated in practice. Exact constraints provide useful information about this functional. The local spin-density approximation (LSDA) was the first constraint-based density functional. The Lieb–Oxford lower bound on the exchange-correlation energy for any density is another constraint that plays an important role in the development of generalized gradient approximations (GGAs) and meta-GGAs. Recently, a strongly and optimally tightened lower bound on the exchange energy was proved for one- and two-electron densities, and conjectured for all densities. In this article, we present a realistic “meta-GGA made very simple” (MGGA-MVS) for exchange that respects this optimal bound, which no previous beyond-LSDA approximation satisfies. This constraint might have been expected to worsen predicted thermochemical properties, but in fact they are improved over those of the Perdew–Burke–Ernzerhof GGA, which has nearly the same correlation part. MVS exchange is however radically different from that of other GGAs and meta-GGAs. Its exchange enhancement factor has a very strong dependence upon the orbital kinetic energy density, which permits accurate energies even with the drastically tightened bound. When this nonempirical MVS meta-GGA is hybridized with 25% of exact exchange, the resulting global hybrid gives excellent predictions for atomization energies, reaction barriers, and weak interactions of molecules. PMID:25561554

  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. Heat exchanger with ceramic elements

    DOEpatents

    Corey, John A. (North Troy, NY)

    1986-01-01

    An annular heat exchanger assembly includes a plurality of low thermal growth ceramic heat exchange members with inlet and exit flow ports on distinct faces. A mounting member locates each ceramic member in a near-annular array and seals the flow ports on the distinct faces into the separate flow paths of the heat exchanger. The mounting member adjusts for the temperature gradient in the assembly and the different coefficients of thermal expansion of the members of the assembly during all operating temperatures.

  11. Charge exchange molecular ion source

    DOEpatents

    Vella, Michael C.

    2003-06-03

    Ions, particularly molecular ions with multiple dopant nucleons per ion, are produced by charge exchange. An ion source contains a minimum of two regions separated by a physical barrier and utilizes charge exchange to enhance production of a desired ion species. The essential elements are a plasma chamber for production of ions of a first species, a physical separator, and a charge transfer chamber where ions of the first species from the plasma chamber undergo charge exchange or transfer with the reactant atom or molecules to produce ions of a second species. Molecular ions may be produced which are useful for ion implantation.

  12. Heat exchanger using graphite foam

    DOEpatents

    Campagna, Michael Joseph; Callas, James John

    2012-09-25

    A heat exchanger is disclosed. The heat exchanger may have an inlet configured to receive a first fluid and an outlet configured to discharge the first fluid. The heat exchanger may further have at least one passageway configured to conduct the first fluid from the inlet to the outlet. The at least one passageway may be composed of a graphite foam and a layer of graphite material on the exterior of the graphite foam. The layer of graphite material may form at least a partial barrier between the first fluid and a second fluid external to the at least one passageway.

  13. 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.

  14. Heat exchanger for electrothermal devices

    NASA Technical Reports Server (NTRS)

    Zavesky, Ralph J. (inventor); Sovey, James S. (inventor); Mirtich, Michael J. (inventor); Marinos, Charalampus (inventor); Penko, Paul F. (inventor)

    1986-01-01

    An improved electrothermal device is disclosed. An electrothermal thruster utilizes a generally cylindrical heat exchanger chamber to convert electricity to heat which raises the propellant temperature. A textured, high emissivity heat element radiatively transfers heat to the inner wall of this chamber that is ion beam morphologically controlled for high absorptivity. This, in turn, raises the temperature of a porous heat exchanger material in an annular chamber surrounding the cylindrical chamber. Propellant gas flows through the annular chamber and is heated by the heat exchanger material.

  15. Preparation of Cd/Pb Chalcogenide Heterostructured Janus Particles via Controllable Cation Exchange.

    PubMed

    Zhang, Jianbing; Chernomordik, Boris D; Crisp, Ryan W; Kroupa, Daniel M; Luther, Joseph M; Miller, Elisa M; Gao, Jianbo; Beard, Matthew C

    2015-07-28

    We developed a strategy for producing quasi-spherical nanocrystals of anisotropic heterostructures of Cd/Pb chalcogenides. The nanostructures are fabricated via a controlled cation exchange reaction where the Cd(2+) cation is exchanged for the Pb(2+) cation. The cation exchange reaction is thermally activated and can be controlled by adjusting the reaction temperature or time. We characterized the particles using TEM, XPS, PL, and absorption spectroscopy. With complete exchange, high quality Pb-chalcogenide quantum dots are produced. In addition to Cd(2+), we also find suitable conditions for the exchange of Zn(2+) cations for Pb(2+) cations. The cation exchange is anisotropic starting at one edge of the nanocrystals and proceeds along the ?111? direction producing a sharp interface at a (111) crystallographic plane. Instead of spherical core/shell structures, we produced and studied quasi-spherical CdS/PbS and CdSe/PbSe Janus-type heterostructures. Nontrivial PL behavior was observed from the CdS(e)/PbS(e) heterostructures as the Pb:Cd ratio is increased. PMID:26161785

  16. Synthesis, structural characterization, and catalytic properties of tungsten-exchanged H-ZSM5

    SciTech Connect

    Ding, Weiping; Meitzner, George D.; Marler, David O.; Iglesia, Enrique

    2001-01-18

    W-exchanged H-ZSM5 was prepared by sublimation of WCl6 at 673 K followed by hydrolysis of exchanged WClx species at 523 K. D2 exchange with residual OH groups showed that each W initially replaced about two zeolitic protons for W/Al ratios of 0.29 and 0.44, consistent with the formation of (WO2)2+ containing W6+ species bridging two cation exchange sites. As temperatures reached973 K during D2-OH exchange, these species reduced to (WO2)+ with the concurrent formation of one OD group. CH4 conversion turnover rates (per W) and C2-C1 2 selectivities are very similar to those observed on a Mo/H-ZSM5 sample with similar cation exchange level. As in the case of Mo/H-ZSM5, WOx/H-ZSM5 precursors are initially inactive in CH4 reactions, but they activate during induction with the concurrent evolution of CO, H2O, and an excess amount of H2. The reduction and carburization processes occurring during CH4 reactions and the structure of the exchanged WOx precursors was probed using in situ X-ray absorption spectroscopy (XAS). XAS studies confirmed the isolated initial nature of the exchanged WOx precursors after hydrolysis and dehydration and the formation of WCx clusters 0.6 nm in diameter during CH4 reactions at 973 K. The structural and catalytic resemblance between W- and Mo-exchanged H-ZSM5 is not unexpected, in view of chemical similarities between oxides or carbides of Mo and W. The synthesis of exchanged WOx precursors and their subsequent carburization during CH4 reactions, however, are more difficult than the corresponding processes for the MoOx counterparts. This may account for previous reports of lower CH4 reaction rates and aromatics selectivities on W/H-ZSM5 compared with those observed on Mo/H-ZSM5 and with those reported here for rigorously exchanged W/H-ZSM5.

  17. 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.

  18. Heat exchange assembly

    DOEpatents

    Lowenstein, Andrew; Sibilia, Marc; Miller, Jeffrey; Tonon, Thomas S.

    2004-06-08

    A heat exchange assembly comprises a plurality of plates disposed in a spaced-apart arrangement, each of the plurality of plates includes a plurality of passages extending internally from a first end to a second end for directing flow of a heat transfer fluid in a first plane, a plurality of first end-piece members equaling the number of plates and a plurality of second end-piece members also equaling the number of plates, each of the first and second end-piece members including a recessed region adapted to fluidly connect and couple with the first and second ends of the plate, respectively, and further adapted to be affixed to respective adjacent first and second end-piece members in a stacked formation, and each of the first and second end-piece members further including at least one cavity for enabling entry of the heat transfer fluid into the plate, exit of the heat transfer fluid from the plate, or 180.degree. turning of the fluid within the plate to create a serpentine-like fluid flow path between points of entry and exit of the fluid, and at least two fluid conduits extending through the stacked plurality of first and second end-piece members for providing first fluid connections between the parallel fluid entry points of adjacent plates and a fluid supply inlet, and second fluid connections between the parallel fluid exit points of adjacent plates and a fluid discharge outlet so that the heat transfer fluid travels in parallel paths through each respective plate.

  19. Hear Exchange Assembly

    DOEpatents

    Lowenstein, Andrew (Princeton, NJ); Sibilia, Marc (Princeton, NJ); Miller, Jeffrey (Rocky Hill, NJ); Tonon, Thomas S. (Princeton, NJ)

    2003-05-27

    A heat exchange assembly comprises a plurality of plates disposed in a spaced-apart arrangement, each of the plurality of plates includes a plurality of passages extending internally from a first end to a second end for directing flow of a heat transfer fluid in a first plane, a plurality of first end-piece members equaling the number of plates and a plurality of second end-piece members also equaling the number of plates, each of the first and second end-piece members including a recessed region adapted to fluidly connect and couple with the first and second ends of the plate, respectively, and further adapted to be affixed to respective adjacent first and second end-piece members in a stacked formation, and each of the first and second end-piece members further including at least one cavity for enabling entry of the heat transfer fluid into the plate, exit of the heat transfer fluid from the plate, or 180.degree. turning of the fluid within the plate to create a serpentine-like fluid flow path between points of entry and exit of the fluid, and at least two fluid conduits extending through the stacked plurality of first and second end-piece members for providing first fluid connections between the parallel fluid entry points of adjacent plates and a fluid supply inlet, and second fluid connections between the parallel fluid exit points of adjacent plates and a fluid discharge outlet so that the heat transfer fluid travels in parallel paths through each respective plate.

  20. Collective Resonances in Pion Charge Exchange

    NASA Astrophysics Data System (ADS)

    Smith, Douglas A.

    This dissertation presents new data for the pion single (SCX) and double (DCX) charge exchange reactions. The data measured were from the reactions (pi ^-,pi^0) on ^ {56}Fe and (pi^+, pi^-) on ^{55} Mn, ^{75}As, ^{89}Y, ^{139 }La, ^{165}Ho, and ^{181}Ta. The SCX data were angular distributions measured at beam energies of 120, 164, and 230 MeV. The observations were performed to determine the strengths of the giant resonances: the giant dipole resonance (GDR), the isovector monopole resonance (IVM), and the spin-flip giant dipole resonance (SDR). Calculations of the energy dependence of these resonances are compared to the measured data. The DCX data were measured at a beam energy of 292 MeV and a scattering angle of 5 ^circ. The strength of the double isobaric analog state (DIAS) was determined for each measurement. The observations fill out the set of measurements of the DIAS in odd-A nuclei. The mass dependence of the data is determined and is compared to all known mass dependences for the even -A DIAS data. In addition a table of all previously measured DCX cross sections is included in the appendix.

  1. Charge exchange spectroscopy by Fabry-Perot spectrometer in W7-AS

    SciTech Connect

    Yoshinuma, M.; Ida, K.; Baldzuhn, J.

    2004-10-01

    Charge exchange spectroscopy using a Fabry-Perot spectrometer has been developed to study the dynamic of ion temperature and radial electric field in plasmas. A charge coupled device detecter with 80x80 pixels was used to gain the spectral resolution of the charge exchange spectroscopy system. This Fabry-Perot charge exchange spectroscopy system has been applied to measure the ion temperature using the charge exchange line of carbon impurity with a time resolution of 5 ms for high density quasisteady discharges in W7-AS. The cold component due to the charge exchange reaction between the carbon impurity and thermal neutrals is subtracted from the change emission with the beam modulation technique.

  2. Isotope exchange of indoles with D/sub 2/O over group VIII metals

    SciTech Connect

    Karakhanov, E.A.; Dedov, A.G.; Kurts, A.L.; Luzikov, Yu.N.

    1981-08-01

    Results of H - D exchange between indole and its methyl derivatives and D/sub 2/O over metallic Pt, Rh, and Pd are reported. The composition of the reaction mixture after the isotopic exchange was determined by mass spectrometry. The order of reactivity of the metals was Pt>Pd>Rh. It was determined that it was only the heterocycle ..pi..-electron system that interacts with the surface and mainly the hydrogens at C/sub 2/ and C/sub 3/ that undergo exchange and not those bonded to the N. (BLM)

  3. Ag and Cu doped colloidal CdSe nanocrystals: partial cation exchange and luminescence

    NASA Astrophysics Data System (ADS)

    Bala Gopal, M.

    2015-08-01

    Partial cation exchange was employed to dope pre-formed colloidal CdSe nanocrystals with Ag+ and Cu2+ ions. Unusual photoluminescence (PL) properties were observed after these partial cation exchange reactions. Intensity of excitonic PL increases by ?4 times at low level of doping (1.3 dopant per nanocrystal). However, systematic study shows that the dopant ions do not enhance the excitonic emission. Instead, better surface passivation by trioctylphosphine used during the cation exchange is responsible for enhancement of excitonic PL. As doping concentration increases, intensity of excitonic PL decreases, and a new dopant-related emission emerges.

  4. Heat pipe array heat exchanger

    DOEpatents

    Reimann, Robert C. (Lafayette, NY)

    1987-08-25

    A heat pipe arrangement for exchanging heat between two different temperature fluids. The heat pipe arrangement is in a ounterflow relationship to increase the efficiency of the coupling of the heat from a heat source to a heat sink.

  5. Molecular spintronics: A warm exchange

    NASA Astrophysics Data System (ADS)

    Heutz, Sandrine

    2015-10-01

    Molecular layers show antiferromagnetic ordering up to room temperature and are able to exchange bias a ferromagnetic electrode, demonstrating that molecules could be much more than a simple vehicle for transporting spin.

  6. Pu Anion Exchange Process Intensification

    SciTech Connect

    Taylor-Pashow, K.

    2015-10-08

    This project seeks to improve the efficiency of the plutonium anion-exchange process for purifying Pu through the development of alternate ion-exchange media. The objective of the project in FY15 was to develop and test a porous foam monolith material that could serve as a replacement for the current anion-exchange resin, Reillex® HPQ, used at the Savannah River Site (SRS) for purifying Pu. The new material provides advantages in efficiency over the current resin by the elimination of diffusive mass transport through large granular resin beads. By replacing the large resin beads with a porous foam there is much more efficient contact between the Pu solution and the anion-exchange sites present on the material. Several samples of a polystyrene based foam grafted with poly(4-vinylpyridine) were prepared and the Pu sorption was tested in batch contact tests.

  7. Definition of Magnetic Exchange Length

    SciTech Connect

    Abo, GS; Hong, YK; Park, J; Lee, J; Lee, W; Choi, BC

    2013-08-01

    The magnetostatic exchange length is an important parameter in magnetics as it measures the relative strength of exchange and self-magnetostatic energies. Its use can be found in areas of magnetics including micromagnetics, soft and hard magnetic materials, and information storage. The exchange length is of primary importance because it governs the width of the transition between magnetic domains. Unfortunately, there is some confusion in the literature between the magnetostatic exchange length and a similar distance concerning magnetization reversal mechanisms in particles known as the characteristic length. This confusion is aggravated by the common usage of two different systems of units, SI and cgs. This paper attempts to clarify the situation and recommends equations in both systems of units.

  8. Reaction spreading on graphs

    NASA Astrophysics Data System (ADS)

    Burioni, Raffaella; Chibbaro, Sergio; Vergni, Davide; Vulpiani, Angelo

    2012-11-01

    We study reaction-diffusion processes on graphs through an extension of the standard reaction-diffusion equation starting from first principles. We focus on reaction spreading, i.e., on the time evolution of the reaction product M(t). At variance with pure diffusive processes, characterized by the spectral dimension ds, the important quantity for reaction spreading is found to be the connectivity dimension dl. Numerical data, in agreement with analytical estimates based on the features of n independent random walkers on the graph, show that M(t)˜tdl. In the case of Erdös-Renyi random graphs, the reaction product is characterized by an exponential growth M(t)˜e?t with ? proportional to ln, where is the average degree of the graph.

  9. The polymorphic phototest reaction

    SciTech Connect

    Jansen, C.

    1982-09-01

    One hundred tem patients with polymorphic light eruption (PMLE) and 58 control subjects were tested with an overdose of erythemogenic radiation. A morphologically abnormal phototest reaction was demonstrable in 72% of the patients with PMLE and in 9% of the control subjects. On the average, a dose of 3.8 times the patient's minimal erythemal dose was needed to produce the reaction. The most common findings in positive phototest reaction sites were edema and itching. A medium-pressure mercury lamp was shown to be as effective as a xenon arc lamp in producing the phototest reaction. The time of the reaction varied considerably in different patients, and frequent inspections of test sites were necessary to detect positive phototest reactions. When properly performed and interpreted, phototesting is a valuable diagnostic procedure for PMLE.

  10. Reactions of tetraphenyltitanium with organic acids

    SciTech Connect

    Razuvaev, G.A.; Vyshinskaya, L.I.; Vasil'eva, G.A.

    1987-12-10

    As a result of the reactions of tetraphenyltitanium with dibasic organic acids high yields were obtained of new thermally stable titanium(III) complexes: phenyltitanium(III)carboxylates. Under the action of proton-active reagents (hydrochloric acid, cyclopentadiene, methanol) the latter break down with the breakage of titanium-phenyl bond. The proposed structure was based on IR- and ESR-spectral data. The dinuclear structure of the complexes was established on the basis of a study of the triplet structure of the ESR spectra, which showed the existence of intermolecular titanium-titanium exchange through methylene groups of the dicarboxylate bridges.

  11. 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.

  12. 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.

  13. 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

  14. 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.

  15. 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.

  16. 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

  17. External control of reactions in microdroplets

    NASA Astrophysics Data System (ADS)

    Mashaghi, Samaneh; van Oijen, Antoine M.

    2015-07-01

    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.

  18. Reaction Energies of Oxides using Random Phase Approximation

    NASA Astrophysics Data System (ADS)

    Yan, Jun; Hummelshoej, Jens; Nørskov, Jens

    2013-03-01

    Oxides are widely used in industrial heterogeneous catalysis, photo catalysis, electrochemistry and in making batteries and fuel cells. To facilitate the computational engineer and design of novel materials in these fields, it is vital important to quantitatively predict the formation and reactions energies of the oxides. LDA/GGA, the success of which has largely relied on the mysterious error cancellation in the exchange-correlation term, generally failed for these oxides, showing systematic and non-canceling errors. Recently, the use of exact exchange (EXX), plus correlation energy from Random Phase Approximation (RPA) emerges as a promising approach to obtain non-empirical exchange-correlation terms. Exact exchange energy is free of self-interaction error, while RPA correlation energy takes into account dynamic electronic screening and is fully non-local. EXX +RPA has shown to systematically improve lattice constants, atomization energies, adsorption energies, reaction barriers for a wide range of systems that have ironic, covalent and van der Waals interactions. In this talk I will present our results comparing RPA and GGA functional for the formation and reaction energies of oxides.

  19. Charge exchange probes of nuclear structure and interactions with emphasis on (p,n)

    SciTech Connect

    Goodman, C.D.

    1980-01-01

    New results from (p,n) studies at IUCF show that it is possible to observe Gamow-Teller (GT) strength and extract GT matrix elements from (p,n) measurements. The charge exchange reactions (/sup 6/Li,/sup 6/He) and (..pi../sup +/,..pi../sup 0/) involve different projectile quantum numbers, and the relationships of these reactions to (p,n) is discussed.

  20. 4. Heat exchangers; Steam, steam processes

    E-print Network

    Zevenhoven, Ron

    1/74 4. Heat exchangers; Steam, steam processes Ron Zevenhoven Åbo Akademi University Thermal Engineering | 20500 Turku | Finland 2/74 4.1 Heat exchangers Åbo Akademi University | Thermal and Flow Engineering | 20500 Turku | Finland #12;3/74 Heat exchangers: General /1 In a heat exchanger heat

  1. Building Cohesion in Positively Connected Exchange Networks

    ERIC Educational Resources Information Center

    Schaefer, David R.; Kornienko, Olga

    2009-01-01

    This research investigates the process through which individuals build cohesive relationships in positively connected exchange relations. Positive connections exist any time exchange in one relation must precede exchange in another. Such situations arise through gatekeeping, in generalized exchange contexts, and when resources diffuse across a…

  2. Conflict and Fairness in Social Exchange

    ERIC Educational Resources Information Center

    Molm, Linda D.; Collett, Jessica L.; Schaefer, David R.

    2006-01-01

    Inherent to all social exchange relations are elements of both cooperation and competition. We develop and test a theoretical model which proposes that the relative salience of the competitive, conflictual elements of exchange mediate and explain the negative effects of negotiated exchange, as compared with reciprocal exchange, on actors'…

  3. 22 CFR 41.62 - Exchange visitors.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 22 Foreign Relations 1 2010-04-01 2010-04-01 false Exchange visitors. 41.62 Section 41.62 Foreign... NATIONALITY ACT, AS AMENDED Students and Exchange Visitors § 41.62 Exchange visitors. (a) J-1 classification. An alien is classifiable as an exchange visitor if qualified under the provisions of INA 101(a)...

  4. Electron assisted neutron exchange process in solid state environment

    E-print Network

    Péter Kálmán; Tamás Keszthelyi

    2013-12-19

    Electron assisted neutron exchange process in solid state environment is investigated. It is shown that if a metal is irradiated with free electrons then the $e+$ $_{Z}^{A_{1}}X+$ $_{Z}^{A_{2}}X\\rightarrow e^{\\prime }+$ $% _{Z}^{A_{1}-1}X+$ $_{Z}^{A_{2}+1}X+\\Delta $ electron assisted neutron exchange process has measurable probability even in the case of slow electrons of energy much less than the reaction energy $\\Delta $. The transition probability per unit time, the cross section of the process and the yield in an irradiated sample are determined in the Weisskopf and long wavelength approximations and in the single particle shell model. Numerical data for the $e+$ $_{28}^{A_{1}}Ni+$ $_{28}^{A_{2}}Ni\\rightarrow e^{\\prime }+ $ $_{28}^{A_{1}+1}Ni+$ $_{28}^{A_{2}-1}Ni+\\Delta $ and the $e+$ $% _{46}^{A_{1}}Pd+$ $_{46}^{A_{2}}Pd\\rightarrow e^{\\prime }+$ $% _{46}^{A_{1}+1}Pd+$ $_{46}^{A_{2}-1}Pd+\\Delta $ electron assisted neutron exchange reactions are also presented.

  5. Krypton charge exchange cross sections for Hall effect thruster models

    SciTech Connect

    Hause, Michael L.; Prince, Benjamin D.; Bemish, Raymond J.

    2013-04-28

    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{sup +} + Kr and Kr{sup 2+} + Kr cross sections. The measurements of symmetric Kr{sup +} + Kr charge exchange are in good agreement with both the calculations including spin-orbit effects and previous measurements. For the symmetric Kr{sup 2+} + 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 Kr{sup 2+} + Kr {yields} Kr{sup +} + Kr{sup +} reaction show an onset near 12 eV, reaching cross sections near constant value of 1.6 A{sup 2} with an exception near 70-80 eV.

  6. 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.

  7. Exchange flow with geological heterogeneity

    NASA Astrophysics Data System (ADS)

    Chang, K.; Hesse, M. A.

    2013-12-01

    Two aquifers can be hydraulically connected by a fault cutting across the intermediate aquitard. If the upper aquifer contains denser fluid, an exchange flow across the fault will develop. The unstable density stratification leads to fingering pattern with localized zones of upwelling and downwelling along the fault. Due to the small volume of the fault relative to the aquifers the exchange-flow will quickly approach a quasi steady state. If the permeability of the fault plane is homogeneous, the average number of the quasi-steady plume fingers, , follows a power law function of the Rayleigh number Ra (? Ra1/2) and the exchange rate measured by dimensionless convective flux, the Sherwood number Sh, is a linear function of Ra (Sh? Ra). The presence of flow barriers along the fault triggers unsteady exchange flow and subsequently controls the growth of the plume fingers. If the barriers are sufficiently wide to dominate the flow system, they creates preferential pathways for exchange flow that determines the distribution of the quasi-steady fingers, and converges to a constant value. In addition, wider barriers induce substantial lateral spreading and enhance the efficiency of structural trapping, and reduce the exchange rate that follows a power law Sh? Ran, where n<1 and decreases with increasing barrier length. This study is motivated by geological carbon dioxide (CO2) storage in brine-saturated aquifer, but the unstable exchange of multiphase fluids through conductive faults is also important in many other geological and engineering applications, in particular the migration of hydrocarbons in tectonic-driven faulting system or hydraulically developed fractures in unconventional reservoirs. Better understanding of the density-driven flow in a faulted system will allow more precise estimate of the reservoir capacity as well as more efficient operation of injection or production wells.

  8. Degradations and Rearrangement Reactions

    NASA Astrophysics Data System (ADS)

    Zhang, Jianbo

    This section deals with recent reports concerning degradation and rearrangement reactions of free sugars as well as some glycosides. The transformations are classified in chemical and enzymatic ways. In addition, the Maillard reaction will be discussed as an example of degradation and rearrangement transformation and its application in current research in the fields of chemistry and biology.

  9. Oscillating Reactions: Two Analogies

    ERIC Educational Resources Information Center

    Petruševski, Vladimir M.; Stojanovska, Marina I.; Šoptrajanov, Bojan T.

    2007-01-01

    Oscillating chemical reactions are truly spectacular phenomena, and demonstrations are always appreciated by the class. However, explaining such reactions to high school or first-year university students is problematic, because it may seem that no acceptable explanation is possible unless the students have profound knowledge of both physical…

  10. Applications of Reaction Rate

    ERIC Educational Resources Information Center

    Cunningham, Kevin

    2007-01-01

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

  11. Chemical Reaction Problem Solving.

    ERIC Educational Resources Information Center

    Veal, William

    1999-01-01

    Discusses the role of chemical-equation problem solving in helping students predict reaction products. Methods for helping students learn this process must be taught to students and future teachers by using pedagogical skills within the content of chemistry. Emphasizes that solving chemical reactions should involve creative cognition where…

  12. THE CUTANEOUS TRICHOPHYTIN REACTION

    PubMed Central

    Amberg, Samuel

    1910-01-01

    There exists a far-reaching analogy between the cutaneous trichophytin reaction and the cutaneous tuberculin reaction. Both indicate that the organism is the seat of a definite infection or that it has passed through such an infection. Both may persist for a long time after the active disease has come to rest, indicating that the infection has left the organism in a state of altered reactivity—allergy. Under certain conditions both may be of diagnostic value, but since the reaction persists for a long time after the infection has passed, the negative reaction may be of greater value, excluding the existence of a specific infection. The analogy of the trichophytin reaction with the tuberculin reaction is not only limited to the obvious clinical manifestations, but, as in the tuberculin reaction, it can be shown that with uniform concentration of antibody, the intensity of the reaction is dependent on the concentration of the trichophytin. A tentative explanation of the halo formation is offered, based on a rapidly renewed formation of antibody stimulated probably by the entrance of a small amount of allergen into the general circulation. PMID:19867336

  13. Clock Reaction: Outreach Attraction

    ERIC Educational Resources Information Center

    Carpenter, Yuen-ying; Phillips, Heather A.; Jakubinek, Michael B.

    2010-01-01

    Chemistry students are often introduced to the concept of reaction rates through demonstrations or laboratory activities involving the well-known iodine clock reaction. For example, a laboratory experiment involving thiosulfate as an iodine scavenger is part of the first-year general chemistry laboratory curriculum at Dalhousie University. With…

  14. Quantum dynamics of fast chemical reactions

    SciTech Connect

    Light, J.C.

    1993-12-01

    The aims of this research are to explore, develop, and apply theoretical methods for the evaluation of the dynamics of gas phase collision processes, primarily chemical reactions. The primary theoretical tools developed for this work have been quantum scattering theory, both in time dependent and time independent forms. Over the past several years, the authors have developed and applied methods for the direct quantum evaluation of thermal rate constants, applying these to the evaluation of the hydrogen isotopic exchange reactions, applied wave packet propagation techniques to the dissociation of Rydberg H{sub 3}, incorporated optical potentials into the evaluation of thermal rate constants, evaluated the use of optical potentials for state-to-state reaction probability evaluations, and, most recently, have developed quantum approaches for electronically non-adiabatic reactions which may be applied to simplify calculations of reactive, but electronically adiabatic systems. Evaluation of the thermal rate constants and the dissociation of H{sub 3} were reported last year, and have now been published.

  15. Alternative Anode Reaction for Copper Electrowinning

    SciTech Connect

    Not Available

    2005-07-01

    This report describes a project funded by the Department of Energy, with additional funding from Bechtel National, to develop a copper electrowinning process with lower costs and lower emissions than the current process. This new process also includes more energy efficient production by using catalytic-surfaced anodes and a different electrochemical couple in the electrolyte, providing an alternative oxidation reaction that requires up to 50% less energy than is currently required to electrowin the same quantity of copper. This alternative anode reaction, which oxidizes ferric ions to ferrous, with subsequent reduction back to ferric using sulfur dioxide, was demonstrated to be technically and operationally feasible. However, pure sulfur dioxide was determined to be prohibitively expensive and use of a sulfur burner, producing 12% SO{sub 2}, was deemed a viable alternative. This alternate, sulfur-burning process requires a sulfur burner, waste heat boiler, quench tower, and reaction towers. The electrolyte containing absorbed SO{sub 2} passes through activated carbon to regenerate the ferrous ion. Because this reaction produces sulfuric acid, excess acid removal by ion exchange is necessary and produces a low concentration acid suitable for leaching oxide copper minerals. If sulfide minerals are to be leached or the acid unneeded on site, hydrogen was demonstrated to be a potential reductant. Preliminary economics indicate that the process would only be viable if significant credits could be realized for electrical power produced by the sulfur burner and for acid if used for leaching of oxidized copper minerals on site.

  16. Synthetic inorganic ion exchange materials XLIV: Synthesis and ion exchange properties of cubic niobic acid (HNbO{sub 3})

    SciTech Connect

    Ohsaka, Tohru; Abe, Mitsuo; Kanzaki, Yasushi; Kotani, Takashi; Awano, Sachio

    1999-07-01

    A cubic niobic acid (C-NbA) was synthesized by Li{sup +}/H{sup +} ion exchange reaction with an 8 M (mol dm{sup {minus}3}) nitric acid solution from LiNbO{sub 3}. The LiNbO{sub 3} was obtained by heating a mixture of Li{sub 2}CO{sub 3} and Nb{sub 2}O{sub 5} with molar ratio of 1:1 at 900 C for 24 h. X-ray diffraction pattern of C-NbA was indexed to a cubic structure (space group Im3), with the lattice constant a{sub o} = 7.6445 {angstrom} ({angstrom} = 100 pm). The C-NbA product showed an exchange reaction equivalent to one proton per one Li{sup +} in a mixed solution of lithium nitrate and lithium hydroxide. The pH titration curves of C-NbA on the Li{sup +}/H{sup +} exchange system indicated a weak monobasic acid. C-NbA showed high uptake for lithium ions, whereas no appreciable amount of uptake was observed for other alkali metal ions in the pH range 4--12. An extremely high selectivity was found for lithium ions, and the separation factor ({alpha}) of lithium ions to other alkali metal ions was higher than 10{sup 3}.

  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. 78 FR 46622 - Application of Topaz Exchange, LLC for Registration as a National Securities Exchange; Findings...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-08-01

    .... See Securities Exchange Act Release No. 69011, 78 FR 14844 (March 7, 2013). Because Topaz Exchange's... Exchange. \\5\\ See Securities Exchange Act Release No. 69012 (March 1, 2013), 78 FR 14847 (``Notice''). \\6... Exchange Act Release No. 56955 (December 13, 2007), 72 FR 71979 (December 19, 2007) (File No....

  19. Data on Bitcoin-Exchange Closures Survival Analysis of Exchange Closure

    E-print Network

    Thornton, Mitchell

    Data on Bitcoin-Exchange Closures Survival Analysis of Exchange Closure Regression Analysis of Exchange Breaches Beware the Middleman: Empirical Analysis of Bitcoin-Exchange Risk Tyler Moore1 Nicolas Moore & Nicolas Christin Empirical Analysis of Bitcoin-Exchange Risk #12

  20. 75 FR 52558 - Self-Regulatory Organizations; BATS Exchange, Inc.; Chicago Board Options Exchange, Incorporated...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-08-26

    ... contained a typographical error in the signature block. In the Federal Register of August 18, 2010, in FR...; BATS Exchange, Inc.; Chicago Board Options Exchange, Incorporated; Chicago Stock Exchange, Inc.; EDGA... Securities Exchange LLC; NASDAQ OMX BX, Inc.; The NASDAQ Stock Market LLC; National Stock Exchange, Inc.;...

  1. Heat exchangers and solar heating

    SciTech Connect

    Fuller, D.L.

    1980-01-22

    A heat exchanger and a solar heating unit incorporating the heat exchanger and described. The heat exchanger is constructed with an outer tubular member closed at its ends and provided with a fluid inlet at one end and a fluid outlet at the other end, and an inner tubular member of different cross-sectional shape to the cross-sectional shape of the outer tubular member but positioned and dimensioned so as to provide a plurality of longitudinal points of contact between the outer member inner surface and the inner member outer surface and a plurality of fluid ducts defined by the longitudinal wall portions of the outer and inner tubular members between said points of contact.

  2. 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.

  3. 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

    2015-10-01

    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.

  4. 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.

  5. Na+/H+ Exchange Activity in the Plasma Membrane of Arabidopsis1

    PubMed Central

    Qiu, Quan-Sheng; Barkla, Bronwyn J.; Vera-Estrella, Rosario; Zhu, Jian-Kang; Schumaker, Karen S.

    2003-01-01

    In plants, Na+/H+ exchangers in the plasma membrane are critical for growth in high levels of salt, removing toxic Na+ from the cytoplasm by transport out of the cell. The molecular identity of a plasma membrane Na+/H+ exchanger in Arabidopsis (SOS1) has recently been determined. In this study, immunological analysis provided evidence that SOS1 localizes to the plasma membrane of leaves and roots. To characterize the transport activity of this protein, purified plasma membrane vesicles were isolated from leaves of Arabidopsis. Na+/H+ exchange activity, monitored as the ability of Na to dissipate an established pH gradient, was absent in plants grown without salt. However, exchange activity was induced when plants were grown in 250 mm NaCl and increased with prolonged salt exposure up to 8 d. H+-coupled exchange was specific for Na, because chloride salts of other monovalent cations did not dissipate the pH gradient. Na+/H+ exchange activity was dependent on Na (substrate) concentration, and kinetic analysis indicated that the affinity (apparent Km) of the transporter for Na+ is 22.8 mm. Data from two experimental approaches supports electroneutral exchange (one Na+ exchanged for one proton): (a) no change in membrane potential was measured during the exchange reaction, and (b) Na+/H+ exchange was unaffected by the presence or absence of a membrane potential. Results from this research provide a framework for future studies into the regulation of the plant plasma membrane Na+/H+ exchanger and its relative contribution to the maintenance of cellular Na+ homeostasis during plant growth in salt. PMID:12805632

  6. Highly Water Resistant Anion Exchange Membrane for Fuel Cells.

    PubMed

    Yang, Zhengjin; Hou, Jianqiu; Wang, Xinyu; Wu, Liang; Xu, Tongwen

    2015-07-01

    For anion exchange membranes (AEMs), achieving efficient hydroxide conductivity without excessive hydrophilicity presents a challenge. Hence, new strategies for constructing mechanically strengthened and hydroxide conductive (especially at controlled humidity) membranes are critical for developing better AEMs. Macromolecular modification involving ylide chemistry (Wittig reaction) for the fabrication of novel AEMs with an interpenetrating polymer network structure is reported. The macromolecular modification is cost effective, facile, and based on a one-pot synthesis. AEM water uptake is reduced to 3.6 wt% and a high hydroxide conductivity (69.7 mS cm(-1) , 90 °C) is achieved simultaneously. More importantly, the membrane exhibits similar tensile strength (>35 MPa) and comparable flexibility in both dry and wet states. These AEMs could find further applications within anion exchange membrane fuel cells with low humidity or photoelectric assemblies. PMID:25962480

  7. Evaluation of anion exchange resins Tulsion A-30 and Indion-930A by application of radioanalytical technique

    NASA Astrophysics Data System (ADS)

    Singare, P. U.

    2014-07-01

    Radioanalytical technique using 131I and 82Br was employed to evaluate organic based anion exchange resins Tulsion A-30 and Indion-930A. The evaluation was based on performance of these resins during iodide and bromide ion-isotopic exchange reactions. It was observed that for iodide ion-isotopic exchange reaction by using Tulsion A-30 resin, the values of specific reaction rate (min-1), amount of iodide ion exchanged (mmol), initial rate of iodide ion exchange (mmol/min) and log K d were 0.238, 0.477, 0.114, and 11.0, respectively, which was higher than 0.155, 0.360, 0.056, and 7.3, respectively as that obtained by using Indion-930A resins under identical experimental conditions of 40.0°C, 1.000 g of ion exchange resins and 0.003 M labeled iodide ion solution. Also at a constant temperature of 40.0°C, as the concentration of labeled iodide ion solution increases 0.001 to 0.004 M, for Tulsion A-30 resins the percentage of iodide ions exchanged increases from 59.0 to 65.1%, and from 46.4 to 48.8% for Indion-930A resins under identical experimental conditions. The identical trend was observed for both the resins during bromide ion-isotopic exchange reactions. The overall results indicate that under identical experimental conditions, Tulsion A-30 show superior performance over Indion-930A resins. The results of present experimental work have demonstrated that the radioanalytical technique used here can be successfully applied for characterization of different ion exchange resins so as to evaluate their performance under various process parameters.

  8. 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.

  9. Grafted methylenediphosphonate ion exchange resins

    DOEpatents

    Trochimcznk, Andrzej W. (Knoxbille, TN); Gatrone, Ralph C. (Plymouth, PA); Alexandratos, Spiro (Knoxville, TN); Horwitz, E. Philip (Naperville, IL)

    1997-01-01

    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 phosphorous. The pendent groups have the formula ##STR1## 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.

  10. Grafted methylenediphosphonate ion exchange resins

    DOEpatents

    Trochimcznk, Andrzej W. (Knoxville, TN); Gatrone, Ralph C. (Plymouth, PA); Alexandratos, Spiro (Knoxville, TN); Horwitz, E. Philip (Naperville, IL)

    1998-01-27

    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 phosphorous. The pendent groups have the formula ##STR1## 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.

  11. Inorganic Chemistry, "01. 13,No. 7, 1974 exchange resin using acetonitrile as eluent. The acetonitrile was

    E-print Network

    Bodner, George M.

    Inorganic Chemistry, "01. 13,No. 7, 1974 exchange resin using acetonitrile as eluent-28-6. Contribution No. 2359 from the Department of Chemistry, Indiana University, Bloomington, Indiana 47401 esonance reactions is proposed. AIC309100 Introduction Exciusive of the carboranes, the chemistry of nine

  12. Perchlorate Degradation Using Partially Oxidized Titanium Ions and Ion Exchange Membrane Hybrid System 

    E-print Network

    Park, Sung Hyuk

    2011-08-08

    + and Ti3+) in solutions and as part of an ion exchange membrane reactor system. Aqueous titanium ions (Ti2+ and Ti3+) were applied to remove perchlorate ions and its destructive mechanism, reaction kinetics, and the effect of environmental factors were...

  13. 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 =…

  14. An analytical approach to transient homovalent cation exchange problems Xavier Sanchez-Vila, Diogo Bolster *

    E-print Network

    Bolster, Diogo

    Cation exchange in groundwater is one of the dominant surface reactions that occurs in nature and it car. Introduction Many natural and artificial substances are characterized as being electrically unbalanced. Thus pollution problems (Appelo et al., 1993), saltwater intrusion problems (Carlyle et al., 2004; Bolster et al

  15. Interactions among K+-Ca2+ Exchange, Sorption of m-Dinitrobenzene, and Smectite Quasicrystal Dynamics

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The fate of organic compounds in soils and sediments is influenced by sorption of the compounds on surfaces of soil materials. We investigated the interaction among sorption of an organic compound, cation exchange reactions, and both the size and swelling of smectite quasicrystals. Two reference sme...

  16. Patterned ion exchange membranes for improved power production in microbial reverse-electrodialysis cells

    E-print Network

    lists available at ScienceDirect Journal of Power Sources journal homepage: www. Journal of Power Sources 271 (2014) 437e443 #12;pair [3,4]), which can drive redox reactionsPatterned ion exchange membranes for improved power production in microbial reverse

  17. 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.

  18. Kinetics of Ion Exchange on Clay Minerals and Soil: II. Elucidation of Rate-limiting Steps1 R. A. OGWADA ANDD. L. SPARKS2

    E-print Network

    Sparks, Donald L.

    Kinetics of Ion Exchange on Clay Minerals and Soil: II. Elucidation of Rate-limiting Steps1 R. A, diffusion, reaction kinetics, K-ion selective electrode, energies of activation. Ogwada, R.A., and D.L. Sparks. 1986. Kinetics of ion exchange on clay minerals and soil: II. Elucidation of rate-limiting steps

  19. Synthesis, Structural Characterization, and Catalytic Properties of Tungsten-Exchanged Weiping Ding, George D. Meitzner, David O. Marler,| and Enrique Iglesia*

    E-print Network

    Iglesia, Enrique

    Synthesis, Structural Characterization, and Catalytic Properties of Tungsten-Exchanged H-ZSM5 and dehydration and the formation of WCx clusters 0.6 nm in diameter during CH4 reactions at 973 K. The structural between oxides or carbides of Mo and W. The synthesis of exchanged WOx precursors and their subsequent

  20. 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].

  1. Entropy effects in hydrocarbon conversion reactions: free-energy integrations and transition-path sampling

    NASA Astrophysics Data System (ADS)

    Bucko, T.; Hafner, J.

    2010-09-01

    The standard approach to ab initio simulations of activated chemical processes is based on the harmonic-oscillator/rigid-rotor approximation to transition state theory. However, there is increasing evidence that these approximations fail for reactions involving loosely bound reactant and/or transitions states where entropy makes a significant contribution to the free-energy reaction barrier. Examples are provided by the conversion (proton exchange, dehydrogenation, monomolecular cracking) of short alkanes over acidic zeolites. For proton exchange and monomolecular cracking the reaction path may be described reasonably well by simple vectorial reaction coordinates and the free energy of activation may be derived by free-energy integration schemes such as the Blue-Moon ensemble technique in combination with constrained ab initio molecular dynamics simulations. For alkane dehydrogenation, however, several reaction scenarios are in competition and techniques such as transition-path sampling must be used to determine the dominant reaction mechanism. In our paper we describe the fundamental aspects of these techniques and discuss their application to compute free-energy barriers for proton exchange between isobutane and acidic chabazite and for monomolecular cracking of propane. Dehydrogenation of propane has been studied using transition-path sampling. In this case the static approach based on harmonic transition state theory not only fails in producing accurate reaction barriers but even leads to incorrect predictions of reaction intermediates and products.

  2. 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

  3. An Illuminating Reaction.

    ERIC Educational Resources Information Center

    Matthews, Catherine E.

    1996-01-01

    Describes the use of carbide lights as an excellent mechanism for introducing or reviewing many basic chemistry concepts including elements and compounds, endothermic and exothermic reactions, physical and chemical changes, and balancing chemical equations. (JRH)

  4. Reaction wheel assembly

    NASA Technical Reports Server (NTRS)

    1976-01-01

    The fabrication and testing of three reaction wheels with associated drive and system monitoring electronics and brushless dc spin motors are discussed; the wheels are intended for use in a teleoperator simulator. Test results are included as graphs.

  5. Vaccine Reaction Images

    MedlinePLUS

    ... Methyl bromide Methyl isocyanate Nicotine Nitrogen mustard Opioids Organic solvents Osmium tetroxide Paraquat Phosgene Phosgene oxime Phosphine ... Doing What You Can Do Blog: Public Health Matters What's New A - Z Index Vaccine Reaction Images* ...

  6. Bad Reaction to Cosmetics?

    MedlinePLUS

    ... Home For Consumers Consumer Updates Bad Reaction to Cosmetics? Tell FDA Share Tweet Linkedin Pin it More ... M.D., director of the agency’s Office of Cosmetics and Colors. “So, consumers are one of FDA’s ...

  7. 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)

  8. ULTRAFAST REACTION Martin Gruebele

    E-print Network

    Zewail, Ahmed

    ULTRAFAST REACTION DYNAMICS Martin Gruebele and Ahmed H. Zewail With new lasertechniques andwith fellowand the dynamics. We use the term "transition state" in its Ahmed Zewail is LinusPauling Professorof

  9. 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...

  10. 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

  11. Primer on nuclear exchange models

    SciTech Connect

    Hafemeister, David

    2014-05-09

    Basic physics is applied to nuclear force exchange models between two nations. Ultimately, this scenario approach can be used to try and answer the age old question of 'how much is enough?' This work is based on Chapter 2 of Physics of Societal Issues: Calculations on National Security, Environment and Energy (Springer, 2007 and 2014)

  12. Export bill and scientific exchanges

    NASA Astrophysics Data System (ADS)

    President Ronald Reagan has signed into law the reauthorization of the Export Administration Act (EAA), first passed in 1979. The amended version of the law, signed July 12, includes a policy statement in support of “vigorous scientific enterprise. . .in accordance with applicable provisions of law. . .by means of publication, teaching, conferences, and other forms of scholarly exchange.”

  13. BRAZIL, Belo Horizonte Exchange Program

    E-print Network

    Fernandez, Eduardo

    BRAZIL, Belo Horizonte Exchange Program Universidade Federal de Minas Gerais (UFMG) Brazil, one and Carnival. Belo Horizonte is the 1st planned city in Brazil and is the capital of Minas Gerais. It has transportation, and spending money. These fees are paid in Brazil and are estimated at R$1,800 Real per month

  14. Student Exchange Advisor Regula Steiner

    E-print Network

    Fischlin, Andreas

    Student Exchange Advisor Regula Steiner UMNW - LEARNING AGREEMENT Family name Student no. First at ETH ECTS Course at receiving institution ECTS Approved: Advisor for Environm. System Date Module Course unit code Course at ETH ECTS Course at receiving institution ECTS Approved: Advisor

  15. Exchange Program Kansai Gaidai University

    E-print Network

    Fernandez, Eduardo

    JAPAN Exchange Program Kansai Gaidai University Japan, a country of over three thousand islands sights and beautiful forests, mountains and sea coasts. The Kansai Gaidai University is located in Hirakata City, the capital heart of Japan. Kansai Gaidai is accessible, within a one-hour train ride

  16. Knowledge Exchange with Sistema Scotland

    ERIC Educational Resources Information Center

    Allan, Julie; Moran, Nikki; Duffy, Celia; Loening, Gica

    2010-01-01

    This paper reports on a knowledge exchange project, funded by the Scottish Funding Council and undertaken by a group of researchers from three higher education institutions in Scotland and the project partner, Sistema Scotland. This newly established charity is attempting to implement a major programme of social change, developed in Venezuela,…

  17. UCI Equipment Management Peter's Exchange

    E-print Network

    Wood, Marcelo A.

    UCI Equipment Management Peter's Exchange (UCI Surplus Sales) SURPLUS PICK-UP REQUEST Department&S approval for moving laboratory equipment visit EH&S at: http) Phone: (949) 824-6111, 6447, 6519, 6100 Fax this form to (949) 824-4115, or e-mail Equipment

  18. 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.

  19. Clay-catalyzed reactions of coagulant polymers during water chlorination

    USGS Publications Warehouse

    Lee, J.-F.; Liao, P.-M.; Lee, C.-K.; Chao, H.-P.; Peng, C.-L.; Chiou, C.T.

    2004-01-01

    The influence of suspended clay/solid particles on organic-coagulant reactions during water chlorination was investigated by analyses of total product formation potential (TPFP) and disinfection by-product (DBP) distribution as a function of exchanged clay cation, coagulant organic polymer, and reaction time. Montmorillonite clays appeared to act as a catalytic center where the reaction between adsorbed polymer and disinfectant (chlorine) was mediated closely by the exchanged clay cation. The transition-metal cations in clays catalyzed more effectively than other cations the reactions between a coagulant polymer and chlorine, forming a large number of volatile DBPs. The relative catalytic effects of clays/solids followed the order Ti-Mont > Fe-Mont > Cu-Mont > Mn-Mont > Ca-Mont > Na-Mont > quartz > talc. The effects of coagulant polymers on TPFP follow the order nonionic polymer > anionic polymer > cationic polymer. The catalytic role of the clay cation was further confirmed by the observed inhibition in DBP formation when strong chelating agents (o-phenanthroline and ethylenediamine) were added to the clay suspension. Moreover, in the presence of clays, total DBPs increased appreciably when either the reaction time or the amount of the added clay or coagulant polymer increased. For volatile DBPs, the formation of halogenated methanes was usually time-dependent, with chloroform and dichloromethane showing the greatest dependence. ?? 2003 Elsevier Inc. All rights reserved.

  20. Chemistry in interstellar space. [environment characteristics influencing reaction dynamics

    NASA Technical Reports Server (NTRS)

    Donn, B.

    1973-01-01

    The particular characteristics of chemistry in interstellar space are determined by the unique environmental conditions involved. Interstellar matter is present at extremely low densities. Large deviations from thermodynamic equilibrium are, therefore, to be expected. A relatively intense ultraviolet radiation is present in many regions. The temperatures are in the range from 5 to 200 K. Data concerning the inhibiting effect of small activation energies in interstellar clouds are presented in a table. A summary of measured activation energies or barrier heights for exothermic exchange reactions is also provided. Problems of molecule formation are discussed, taking into account gas phase reactions and surface catalyzed processes.

  1. Solute transport with equilibrium aqueous complexation and either sorption or ion exchange: Simulation methodology and applications

    USGS Publications Warehouse

    Lewis, F.M.; Voss, C.I.; Rubin, J.

    1987-01-01

    Methodologies that account for specific types of chemical reactions in the simulation of solute transport can be developed so they are compatible with solution algorithms employed in existing transport codes. This enables the simulation of reactive transport in complex multidimensional flow regimes, and provides a means for existing codes to account for some of the fundamental chemical processes that occur among transported solutes. Two equilibrium-controlled reaction systems demonstrate a methodology for accommodating chemical interaction into models of solute transport. One system involves the sorption of a given chemical species, as well as two aqueous complexations in which the sorbing species is a participant. The other reaction set involves binary ion exchange coupled with aqueous complexation involving one of the exchanging species. The methodology accommodates these reaction systems through the addition of nonlinear terms to the transport equations for the sorbing species. Example simulation results show (1) the effect equilibrium chemical parameters have on the spatial distributions of concentration for complexing solutes; (2) that an interrelationship exists between mechanical dispersion and the various reaction processes; (3) that dispersive parameters of the porous media cannot be determined from reactive concentration distributions unless the reaction is accounted for or the influence of the reaction is negligible; (4) how the concentration of a chemical species may be significantly affected by its participation in an aqueous complex with a second species which also sorbs; and (5) that these coupled chemical processes influencing reactive transport can be demonstrated in two-dimensional flow regimes. ?? 1987.

  2. Helium escape from the Earth's atmosphere - The charge exchange mechanism revisited

    NASA Technical Reports Server (NTRS)

    Lie-Svendsen, O.; Rees, M. H.; Stamnes, K.

    1992-01-01

    We have studied the escape of neutral helium from the terrestrial atmosphere through exothermic charge exchange reactions between He(+) ions and the major atmospheric constituents N2, O2 and O. Elastic collisions with the neutral background particles were treated quantitatively using a recently developed kinetic theory approach. An interhemispheric plasma transport model was employed to provide a global distribution of He(+) ions as a function of altitude, latitude and local solar time and for different levels of solar ionization. Combining these ion densities with neutral densities from an MSIS model and best estimates for the reaction rate coefficients of the charge exchange reactions, we computed the global distribution of the neutral He escape flux. The escape rates show large diurnal and latitudinal variations, while the global average does not vary by more than a factor of three over a solar cycle. We find that this escape mechanism is potentially important for the overall balance of helium in the Earth's atmosphere. However, more accurate values for the reaction rate coefficients of the charge exchange reactions are required to make a definitive assessment of its importance.

  3. Microporous titanosilicate AM-2: Rb-exchange and thermal behaviour

    SciTech Connect

    Doebelin, Nicola . E-mail: nicola@doebelin.org; Armbruster, Thomas

    2007-01-18

    Rb-exchange and thermal stability of the microporous titanosilicate AM-2 were analysed by powder X-ray diffraction, thermo-gravimetric analysis, and chemical analysis of the mother liquid after exchange. The dehydration and thermal stability of the exchanged structure were monitored with in situ high temperature powder X-ray diffraction. Crystal structures were refined with Rietveld methods at 25 and 400 deg. C. The AM-2 structure was found to incorporate Rb{sup +} by replacing K{sup +}. After four exchange cycles and 166 h reaction time at 90 deg. C, the chemical composition was refined to K{sub 0.18}Rb{sub 1.82}TiSi{sub 3}O{sub 9}.H{sub 2}O. Extrapolation suggests that higher exchange ratios may be obtained after further cycles. H{sub 2}O was expelled by heating, leading to a dehydrated structure at 360 deg. C. Dehydration was associated with a change of space group symmetry from orthorhombic P2{sub 1}2{sub 1}2{sub 1} to monoclinic P2{sub 1}, which proved to be reversible after rehydration. This change of symmetry leaves the AM-2 characteristic structural topology uninfluenced and causes only minor distortions. The monoclinic AM-2 structure breaks down above 600 deg. C to become X-ray amorphous, and at 750 deg. C a wadeite-type phase (K {sub x}Rb{sub 2-x}TiSi{sub 3}O{sub 9}) crystallises. This transformation is irreversible and leads to immobilisation of Rb{sup +}.

  4. Structural Basis for Rab GTPase Activation by VPS9 Domain Exchange Factors

    SciTech Connect

    Delprato,A.; Lambright, D.

    2007-01-01

    RABEX-5 and other exchange factors with VPS9 domains regulate endocytic trafficking through activation of the Rab family GTPases RAB5, RAB21 and RAB22. Here we report the crystal structure of the RABEX-5 catalytic core in complex with nucleotide-free RAB21, a key intermediate in the exchange reaction pathway. The structure reveals how VPS9 domain exchange factors recognize Rab GTPase substrates, accelerate GDP release and stabilize the nucleotide-free conformation. We further identify an autoinhibitory element in a predicted amphipathic helix located near the C terminus of the VPS9 domain. The autoinhibitory element overlaps with the binding site for the multivalent effector RABAPTIN-5 and potently suppresses the exchange activity of RABEX-5. Autoinhibition can be partially reversed by mutation of conserved residues on the nonpolar face of the predicted amphipathic helix or by assembly of the complex with RABAPTIN-5.

  5. Biodiesel production using cation-exchange resin as heterogeneous catalyst.

    PubMed

    Feng, Yaohui; He, Benqiao; Cao, Yuhe; Li, Jianxin; Liu, Meng; Yan, Feng; Liang, Xiaoping

    2010-03-01

    Three types of cation-exchange resins (NKC-9, 001 x 7 and D61) as solid acid catalysts were employed to prepare biodiesel from acidified oils generated from waste frying oils. The results show that the catalytic activity of NKC-9 was higher than that of 001 x 7 and D61. The conversion of the esterification by NKC-9 increased with increasing in the amount of catalyst, reaction temperature and time and methanol/oil molar ratio. The maximal conversion of reaction is approximately 90.0%. Furthermore, NKC-9 resin exhibits good reusability. Gas chromatography-mass spectrometry analysis reveals that the production is simplex and mainly composed of C16:0 (palmitic), C18:2 (linoleic), and C18:1 (oleic) acids of methyl ester, respectively. PMID:19699089

  6. 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.

  7. Prediction of the Dependence of the Fuel Cell Oxygen Reduction Reactions on Operating Voltage from DFT Calculations

    E-print Network

    Goddard III, William A.

    Prediction of the Dependence of the Fuel Cell Oxygen Reduction Reactions on Operating Voltage from reduction reaction (ORR) in a proton exchange membrane fuel cell, we developed a sys- tematic way to handle on the operating electrochemical potential for the Pt-catalyzed fuel cell. This method is used to estimate

  8. Modular Heat Exchanger With Integral Heat Pipe

    NASA Technical Reports Server (NTRS)

    Schreiber, Jeffrey G.

    1992-01-01

    Modular heat exchanger with integral heat pipe transports heat from source to Stirling engine. Alternative to heat exchangers depending on integrities of thousands of brazed joints, contains only 40 brazed tubes.

  9. Phosphonic acid based ion exchange resins

    DOEpatents

    Horwitz, E.P.; Alexandratos, S.D.; Gatrone, R.C.; Chiarizia, R.

    1994-01-25

    An ion exchange resin is described for extracting metal ions from a liquid waste stream. An ion exchange resin is prepared by copolymerizing a vinylidene diphosphonic acid with styrene, acrylonitrile and divinylbenzene. 9 figures.

  10. 12 CFR 614.4900 - Foreign exchange.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Cooperatives and Agricultural Credit Banks Financing International Trade § 614.4900 Foreign exchange. (a... international financial activities. The bank's policies should include established guidelines for: (1) Net... Department of the Treasury pertaining to currency exchange activities and international transfers of...

  11. 12 CFR 614.4900 - Foreign exchange.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ...normally reduce risks in the conduct and management of international...activities. The bank's policies should...not apply if a bank purchases or sells...exchange through a commercial bank and has no foreign exchange risk exposure....

  12. 12 CFR 614.4900 - Foreign exchange.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ...normally reduce risks in the conduct and management of international...activities. The bank's policies should...not apply if a bank purchases or sells...exchange through a commercial bank and has no foreign exchange risk exposure....

  13. 12 CFR 614.4900 - Foreign exchange.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ...normally reduce risks in the conduct and management of international...activities. The bank's policies should...not apply if a bank purchases or sells...exchange through a commercial bank and has no foreign exchange risk exposure....

  14. 12 CFR 614.4900 - Foreign exchange.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ...normally reduce risks in the conduct and management of international...activities. The bank's policies should...not apply if a bank purchases or sells...exchange through a commercial bank and has no foreign exchange risk exposure....

  15. 12 CFR 614.4900 - Foreign exchange.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ...normally reduce risks in the conduct and management of international...activities. The bank's policies should...not apply if a bank purchases or sells...exchange through a commercial bank and has no foreign exchange risk exposure....

  16. Integrated Approach to Revamping Heat Exchangers Networks 

    E-print Network

    Glass, K. E.; Dhole, V.; Wang, Y.

    2002-01-01

    A heat exchanger network constitutes the core of the plant energy systems interlinking the core process operation and the utility systems. This paper will illustrate an integrated approach for the revamp of a heat exchanger network by bringing...

  17. 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...

  18. Heat Exchanger Fouling- Prediction, Measurement and Mitigation 

    E-print Network

    Peterson, G. R.

    1989-01-01

    The U. S. Department of Energy (DOE), Office of Industrial Programs (OIP) sponsors the development of innovative heat exchange systems. Fouling is a major and persistent cost associated with most industrial heat exchangers and nationally wastes...

  19. New Challenges in Multihospital Kidney Exchange

    E-print Network

    Ashlagi, Itai

    The growth of kidney exchange presents new challenges for the design of kidney exchange clearinghouses. The players now include directors of transplant centers, who see sets of patient-donor pairs, and can choose to reveal ...

  20. Phosphonic acid based ion exchange resins

    DOEpatents

    Horwitz, E. Philip (Naperville, IL); Alexandratos, Spiro D. (Knoxville, TN); Gatrone, Ralph C. (Naperville, IL); Chiarizia, Ronato (Oak Park, IL)

    1996-01-01

    An ion exchange resin for extracting metal ions from a liquid waste stream. An ion exchange resin is prepared by copolymerizing a vinylidene diphosphonic acid with styrene, acrylonitrile and divinylbenzene.