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1

[Cd[C2(COO)2](H2O)3].H2O, the first cadmium salt of acetylenedicarboxylic acid.  

PubMed

In catena-poly[[[triaquacadmium(II)]-micro-acetylenedicarboxylato-kappa(4)O,O':O",O"'] hydrate], [[Cd(C(4)O(4))(H(2)O)(3)].H(2)O](n), the Cd(II) atom is coordinated by two bidentate carboxylate groups and three water molecules, thus forming a sevenfold coordination polyhedron with all atoms located on general sites. These polyhedra are connected by the bifunctional acetylenedicarboxylate ligands, forming zigzag chains running parallel to [120]. Hydrogen bonds, which involve the non-coordinated water molecule, connect these chains to form a three-dimensional framework. PMID:12205378

Ruschewitz, Uwe; Pantenburg, Ingo

2002-09-01

2

[Cu[C2(COO)2](H2O)3].H2O, the first copper complex of acetylenedicarboxylic acid.  

PubMed

In the title compound, catena-poly[[[triaquacopper(II)]- micro -acetylenedicarboxylato-kappa(2)O:O"] hydrate], [[Cu(C(4)O(4))(H(2)O)(3)].H(2)O](n), the Cu(II) ion is coordinated by two monodentate carboxylate groups in trans positions and three water molecules, thus forming a fivefold coordination polyhedron that can be described as a distorted square pyramid. All atoms are located on general sites. The polyhedra are connected by bifunctional acetylenedicarboxylate ligands, to form almost linear chains parallel to [001]. Hydrogen bonds involving the non-coordinated water molecule connect these chains to form a three-dimensional framework. PMID:12682390

Billetter, Heinrich; Hohn, Frauke; Pantenburg, Ingo; Ruschewitz, Uwe

2003-04-01

3

The structure of {[Co(pht)(bpy)(H2O)]·3H2O}n (pht is phthalate and bpy is 4,4'-bipyridine) and the role of solvent water clusters in structure stability.  

PubMed

The Co(II) cation in poly[[aqua(?-benzene-1,2-dicarboxylato-?(3)O(1),O(2):O(1))(?-4,4'-bipyridine-?(2)N:N')cobalt(II)] trihydrate], {[Co(C8H4O4)(C10H8N2)(H2O)]·3H2O}n, is octahedrally coordinated by two N atoms of two 4,4'-bipyridine ligands, three O atoms from phthalate anions and a fourth O atom from a coordinated water molecule. The packing consists of planes of coordination polymers linked by hydrogen bonds mediated by three solvent water molecules; the linkage is achieved by the water molecules forming intricate oligomeric clusters which also involve the O atoms of the phthalate ligands. PMID:24816009

Harvey, Miguel Angel; Suarez, Sebastián; Doctorovich, Fabio; Cukiernik, Fabio D; Baggio, Ricardo

2014-05-01

4

Cation Exchange Reactions in Ionic Nanocrystals  

NASA Astrophysics Data System (ADS)

Cation exchange has been investigated in a wide range of nanocrystals of varying composition, size, and shape. Complete and fully reversible exchange occurs, and the rates of the reactions are much faster than in bulk cation exchange processes. A critical size has been identified below which the shapes of complex nanocrystals evolve toward the equilibrium shape with lowest energy during the exchange reaction. Above the critical size, the anion sublattice remains intact and the basic shapes of the initial nanocrystals are retained throughout the cation exchange. The size-dependent shape change can also be used to infer features of the microscopic mechanism.

Son, Dong Hee; Hughes, Steven M.; Yin, Yadong; Alivisatos, A. Paul

2004-11-01

5

Exchange reactions with Dick Dalitz  

NASA Astrophysics Data System (ADS)

An account is given of the close collaboration of Dick Dalitz with the European K Collaboration over many decades in many aspects of hypernuclear physics. In particular, emphasis is given to the topics of double hypernuclei and the discovery and resolution of p-wave ? strangeness exchange states. A brief review of early work on non-mesonic decays of hypernuclei is also given.

Davis, D. H.

2008-05-01

6

PEP Carboxykinase Exchange Reaction in Photosynthetic Bacteria 1  

PubMed Central

This paper describes some new characteristics of the phosphoenolpyruvate carboxykinase CO2-oxaloacetate exchange reaction in purified preparations of Rhodospirillum rubrum. The enzymatic activity has been purified 169-fold. Nucleotide diphosphates substitute for nucleotide triphosphates in the exchange reaction. Nucleotide diphosphates will not support the synthesis of phosphoenolpyruvate from oxaloacetate. This reaction differs significantly from the CO2-oxaloacetate exchange reaction in higher plants and animals. PMID:5661493

Cooper, T. G.; Benedict, C. R.

1968-01-01

7

Samarium Ion Exchanged Montmorillonite for High Temperature Cumene Cracking Reaction  

NASA Astrophysics Data System (ADS)

Montmorillonite clay is cation exchanged with samarium and its catalytic influence in cumene cracking reaction is investigated. Effect of exchange with sodium ions on further exchange with samarium ions is also noted. Acidity measurements are done using Temperature Programmed Desorption (TPD) of ammonia. The retention of basic structure is proved from FTIR spectra and XRD patterns. Elemental analysis result shows that samarium exchange has occurred, which is responsible for the higher catalytic activity. Surface area and pore volume remains more or less unaffected upon exchange. Thermogravimetric analysis indicates the enhanced thermal stability on exchanging. Cumene cracking reaction is carried out at atmospheric pressure in a fixed bed glass reactor at 673 K. The predominance of Brønsted acidity is confirmed from high selectivity to benzene.

Binitha, N. N.; Silija, P. P.; Suraj, V.; Yaakob, Z.; Sugunan, S.

2011-02-01

8

Hydrogen Isotope Exchange Reactions in an Electrical Discharge  

Microsoft Academic Search

Hydrogen isotope exchange reactions occurring in (H2O, D2)or (D2O, H2) reacting system under a DC electricaldischarge were investigated using spectroscopic methods such asFourier-transform infrared (FTIR) and plasma emission spectroscopy(PES). The progress of the reactions was determined by real-time measurementof the IR absorbance of HDO molecule, a major product of the reaction. Theprogress of the reaction was studied as a function

H. J. Kim; Y. D. Park; W. M. Lee

2000-01-01

9

Heat exchanger development at Reaction Engines Ltd.  

NASA Astrophysics Data System (ADS)

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

Varvill, Richard

2010-05-01

10

On the treatment of exchange effects in direct reactions  

NASA Astrophysics Data System (ADS)

Exchange effects in direct reactions are investigated in the framework of the general algebraic theory of identical particle scattering. It is shown that effects due to the permutation symmetry of the system can be separated from the treatment of reaction dynamics. Dynamical aspects of the problem are investigated within the framework of the channel coupling class of N-body theories. Department of Physics and Astronomy, University of New Mexico, Albuquerque, NM 87131, USA.

Bencze, Gy.; Chandler, C.

1985-05-01

11

Control of Cytochrome c Unfolding by Ligand Exchange Reactions  

NASA Astrophysics Data System (ADS)

The unfolding reaction of cytochrome c (cyt. c) was initiated by diluting the native protein with guanidine hydrochloride in a submillisecond solution mixer with a dead time of approximately 100 microseconds, and investigated by resonance Raman scattering. The heme ligation states, identified in the high frequency region of the spectra, exhibit large time dependent changes indicating that the unfolding of the polypeptide backbone is coupled with heme ligand exchange reactions. These ligand exchange reactions are strikingly similar to those observed during the folding of cyt. c, although with a reverse sequence. When unfolding under acidic conditions (pH 3.8), approximately 50form (HM) was converted to a His-water form (HW) within 1 millisecond. The population of HW reaches a maximum at about 50 milliseconds, at which point a five coordinated form (5C) starts to be populated at the expense of HW. At pH 5.8, the decay of the native HM coordinated form is much slower with a half-life of 10 milliseconds; in addition a bis-His form (HH) instead of the 5C form was observed. Combined with fluorescence data, a kinetic model is proposed in which a local structural rearrangement controlled by heme ligand exchange reactions appears prior to the global relaxation of the polypeptide chain.

Yeh, Syun-Ru; Rousseau, Denis

1998-03-01

12

EXFOR SYSTEMS MANUAL NUCLEAR REACTION DATA EXCHANGE FORMAT.  

SciTech Connect

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.

MCLANE,V.; NUCLEAR DATA CENTER NETWORK

2000-05-19

13

Separation of the isotopes of boron by chemical exchange reactions  

DOEpatents

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.

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

1995-05-30

14

Separation of the isotopes of boron by chemical exchange reactions  

DOEpatents

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.

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

1995-01-01

15

Internal reorganization effects on electron self-exchange reactions  

NASA Astrophysics Data System (ADS)

Adiabatic, outer-sphere electron transfer models are applied to the calculation of electron self-exchange rates in transition metal complexes and organic molecules. Large discrepancies between calculated and experimental values are found in the spin-allowed transfers of Fe(CN) 4-/3-6 and tetracyanoethylene -/0, and in the spin-forbidden transfers of Co(H 2O) 62+/3+, Co(NH 3) 62+/3+ and Co(phen) 32+/3+. The "diabatic path" of Evans and Polanyi (Trans. Faraday Soc., 31 (1935) 875) is utilized to define an alternative reaction profile which emphasizes the role of the changes occurring in the internal coordinate. The intersecting-state model (ISM) is employed to estimate the free-energy barriers for the self-exchange reactions along this path, and good agreement is found with the observed rate constants, provided the ?*-d electron transfers have appreciable non-adiabatic factors. Evidence for such non-adiabaticity is discussed. The electron self-exchange rate of cytochrome c calculated with this model is also in close agreement with the experimental value.

Formosinho, Sebastião J.; Arnaut, Luís G.

1994-07-01

16

EXFOR systems manual: Nuclear reaction data exchange format  

SciTech Connect

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).

McLane, V. [ed.

1996-07-01

17

Nuclear field shift effect in chemical exchange reactions  

NASA Astrophysics Data System (ADS)

The classic theory of stable isotope fractionation in chemical exchange reactions has been established by Bigeleisen, Mayer, and Urey in 1947. The theory was based on the difference of molecular vibrational energies of isotopomers that are proportional to the respective masses, and hence, results in mass-dependent isotope effect only. In 1996, this conventional mass-dependent theory has been expanded by Bigeleisen to include a mass-independent term named the nuclear field shift effect. The nuclear field shift is an isotope shift in orbital electrons, which results from the isotopic difference in nuclear size and shape. The new equation defined by Bigeleisen (at a constant temperature) can be simply expressed as, ln ? = ? A + (? m/mm') B, where ? is the isotope separation factor, ? isotopic difference in mean-square nuclear charge radius, ?m difference between isotopic masses m and m'. A and B are scaling factors of the nuclear field shift effect and the conventional mass effect, respectively. Since this new theory was presented, the mass-independent isotope fractionation of various elements, e.g, Ti, Cr, Ni, Zn, Sr, Zr, Mo, Ru, Cd, Te, Ba, Nd, Sm, Gd, Yb, and U, found in chemical exchange systems has been successfully explained as the nuclear field shift effect. In our most recent studies, the nuclear field shift effect of Cr, Mo, Ru, Cd, and Te isotopes has been found in laboratory scale experiments. The isotopes of these elements were fractionated by using a liquid-liquid extraction system (a ligand exchange system) at room temperature. The isotopic analysis was performed by the multiple-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) with a typical precision of <100 ppm (at ENS Lyon or UC Davis). Isotope enrichment factors did not show mass-dependent trend, but possessed a similar variation of their nuclear charge radii. For Cr, we tested a different chemical exchange system (a redox system): at high temperature (723-1023 K), an eutectic melt was contacted with a liquid metal. In this system, the nuclear field shift effect of Cr was also found. All these experimental results suggest that the nuclear field shift effect may occur in every chemical exchange reaction at various temperatures to various degrees. Therefore, isotopic anomalies found in a natural system might be partly or largely affected by the nuclear field shift effect via chemical reactions occurred in the nature. In order to clarify the degree and significance of its contribution, we may need to pay more attention to the nuclear field shift effect created chemically.

Fujii, T.; Moynier, F.; Yin, Q.; Albarède, F.

2007-12-01

18

Charge-exchange reactions with a radioactive triton beam  

SciTech Connect

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.

Jaenecke, J. [University of Michigan, Ann Arbor, Michigan 48109-1120 (United States)

1998-12-21

19

Reactive Resonances in N+N2 Exchange Reaction  

NASA Technical Reports Server (NTRS)

Rich reactive resonances are found in a 3D quantum dynamics study of the N + N2 exchange reaction using a recently developed ab initio potential energy surface. This surface is characterized by a feature in the interaction region called Lake Eyring , that is, two symmetric transition states with a shallow minimum between them. An L2 analysis of the quasibound states associated with the shallow minimum confirms that the quasibound states associated with oscillations in all three degrees of freedom in Lake Eyring are responsible for the reactive resonances in the state-to-state reaction probabilities. The quasibound states, mostly the bending motions, give rise to strong reasonance peaks, whereas other motions contribute to the bumps and shoulders in the resonance structure. The initial state reaction probability further proves that the bending motions are the dominating factors of the reaction probability and have longer life times than the stretching motions. This is the first observation of reactive resonances from a "Lake Eyring" feature in a potential energy surface.

Wang, Dunyou; Huo, Winifred M.; Dateo, Christopher E.; Schwenke, David W.; Stallcop, James R.

2003-01-01

20

Alloyed Copper Chalcogenide Nanoplatelets via Partial Cation Exchange Reactions  

PubMed Central

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

2014-01-01

21

Alloyed copper chalcogenide nanoplatelets via partial cation exchange reactions.  

PubMed

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

Lesnyak, Vladimir; George, Chandramohan; Genovese, Alessandro; Prato, Mirko; Casu, Alberto; Ayyappan, S; Scarpellini, Alice; Manna, Liberato

2014-08-26

22

Optical absorption assay for strand-exchange reactions in unlabeled nucleic acids  

Microsoft Academic Search

The nucleic acid exchange reaction is a common feature for genetic recombination, DNA replication and transcription. Due to the fact that in the strand- exchange reactions the reactant and product mole- cules have similar or identical nucleotide sequences, the reaction is undetectable. As a rule, the nucleic acids with radioactive or fluorescence labels are used in such studies. Besides the

Besik I. Kankia

2004-01-01

23

Postreplication repair in E. coli : Strand exchange reactions of gapped DNA by RecA protein  

Microsoft Academic Search

We have used a sensitive gel electrophoresis assay to detect the products of Escherichia coli RecA protein catalysed strand exchange reactions between gapped and duplex DNA molecules. We identify structures that correspond to joint molecules formed by homologous pairing, and show that joint molecules are converted by RecA protein into heteroduplex monomers by reciprocal strand exchanges. However, strand exchanges only

Stephen C. West; Era Cassuto; Paul Howard-Flanders

1982-01-01

24

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

E-print Network

&IBRARY A 4 N COLLEGE OF TEXAS THE EFFECT OF VARIOUS CROPPING SYSTEMS UPON ORGANIC MATTER, TOTAL NITROGEN, CATION EXCHANGE CAPACITY, EXCHANGEABLE CATIONS, CONDUCTIVITY AND REACTION. A Thesis By MOHAMMAD ABDUL MANNAN Submitted... to the Graduate School of the Agricultural and Mechanical College of Texas in . partial fulfilment of the requirements for the degree of : MASTER OF SCIENCE May 1958 Major Subject: Agronomy THE EFFECT OF VARIOUS CROPPING SYSTENS UPON ORGANIC NATTER& TOTAL...

Mannan, Mohammad Abdul

1958-01-01

25

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

NASA Technical Reports Server (NTRS)

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

Freihaut, B.; Raff, L. M.

1973-01-01

26

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

PubMed

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

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

2015-04-28

27

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

PubMed Central

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

Niemeyer, Emily D.; Brodbelt, Jennifer S.

2007-01-01

28

Substrate preferences for lipase-mediated acyl-exchange reactions with butteroil are concentration-dependent  

Microsoft Academic Search

Substrate preferences for pancreatic lipase-mediated acyl-exchange reactions with butteroil were concentration-dependent for\\u000a the series of acyl donors and alcohol acceptors evaluated. For acidolysis reactions, the initial reaction rates and percent\\u000a reaction yields after 18 h at 50 µmol acyl donor per gram substrate mixture were similar forn-fatty acids and their methyl and glycerol esters. At 400–500 µmol g?1 (and greater),

Shu-Jung Kuo; Kirk L. Parkin

1993-01-01

29

Reaction of Benzene with Cu(II)- and Fe(III)-Exchanged Hectorites  

Microsoft Academic Search

The reaction of benzene with exchangeable Cu(II) and Fe(III) in hectorite clay films was studied by electron paramagnetic resonance (EPR). The reaction when carried out in a sealed tube between 60* and 100*C produced a variety of organic radical products. The nature of these products depended on the concentration of water in the reaction medium and the reaction time. The

M. P. Eastman; D. E. PATTERSON; K. H. PANNELL

1984-01-01

30

Abstraction and exchange contributions to the rate constant of muonium+hydrogen chloride reaction  

NASA Astrophysics Data System (ADS)

Quantum collinear rate constants for the abstraction and the exchange channels of the Mu+HCl reaction have been calculated in order to have an estimate of the relative efficiency of the two processes in promoting reactivity for this system.

Laganà, A.; Ciccarelli, L.

1987-02-01

31

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

SciTech Connect

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

Baer, H.W.

1987-01-01

32

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

Microsoft Academic Search

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

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

2005-01-01

33

Anion selectivity in ion exchange reactions with surface functionalized ionosilicas.  

PubMed

Mesoporous imidazolium functionalized surface functionalized ionosilicas have been investigated as anion exchange materials for the adsorption of oxo-anions in aqueous media. We studied particularly pertechnetate adsorption and could show that solids bearing long chain substituted imidazolium groups are highly efficient anion exchange materials often displaying high distribution coefficients between solid and liquid phases. We observed that the distribution coefficient of pertechnetate is a function of the presence of competing anionic species. As a consequence, our experiments allowed reproducing experimentally Hofmeister's series. However, pertechnetate adsorption on the material can completely be inhibited in the presence of highly fluorinated anions such as bis(trifluoromethylsulfonyl)amide (NTf2). This behaviour indicates a particularly imidazophilic behaviour of these anions, which have a particular importance due to their use in water immiscible ionic liquids. Finally, the adsorption process has been shown to be reversible. This feature is of importance in view of the regeneration of the anion exchange material. PMID:25793553

Petrova, Maria; Guigue, Mireille; Venault, Laurent; Moisy, Philippe; Hesemann, Peter

2015-04-01

34

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

SciTech Connect

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.

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

1989-01-01

35

Anion-exchange synthesis of nanoporous FeP nanosheets as electrocatalysts for hydrogen evolution reaction.  

PubMed

Nanoporous FeP nanosheets are successfully synthesized via the anion-exchange reaction of inorganic-organic hybrid Fe18S25-TETAH (TETAH = protonated triethylenetetramine) nanosheets with P ions. The as-prepared nanoporous FeP nanosheets exhibit high electrochemical hydrogen evolution reaction activity in acidic medium. PMID:23771125

Xu, You; Wu, Rui; Zhang, Jingfang; Shi, Yanmei; Zhang, Bin

2013-07-28

36

Quantum resonance effects in exchange, photodissociation, and recombination reactions  

SciTech Connect

This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). This project studied quantum resonance effects on chemical reactions. The authors accurate reactive scattering calculations showed that quantum resonance phenomena dominate most chemical reactions and are essential to any real understanding of reactivity. It was found that, as long-lived metastable states of the colliding system, resonances can decay to reactants, products, or a mixture of both. Only the latter contribute to reaction. Conditions under which resonances can be neglected or treated statistically were studied. Important implications about the mechanism of recombination reactions were discovered, and some remarkable effects of geometric phases on the symmetries and energies of resonances were also discovered. Calculations were completed for the reaction H + O{sub 2} {yields} OH + O, which is the rate limiting step in the combustion of all hydrocarbons and the single most important reaction in all of combustion chemistry.

Pack, R.; Kendrick, B.; Kress, J.; Walker, R. [Los Alamos National Lab., NM (United States); Hayes, E. [Ohio State Univ., Columbus, OH (United States); Lagana, A. [Univ. of Perugia (Italy); Parker, G. [Univ. of Oklahoma, Norman, OK (United States); Butcher, E. [Auburn Univ., AL (United States)

1996-04-01

37

Extraterrestrial life detection based on oxygen isotope exchange reactions.  

PubMed

A method is described for detecting extraterrestrial life, based on catalysis of isotopic oxygen exchange between water and oxygen-containing anions such as phosphate, nitrate, or sulfate. This catalytic activity appears to be unique to living systems. Its applicability requires very few assumptions concerning the chemical nature of "life." Data obtained so far indicate that the experiment is sound and technically feasible. PMID:17812007

Kok, B; Varner, J E

1967-03-01

38

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

SciTech Connect

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.

MCLANE,V.; NUCLEAR DATA CENTER NETWORK

2000-05-19

39

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

SciTech Connect

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.

MCLANE,V.; NUCLEAR DATA CENTER NETWORK

2000-05-19

40

Perturbative QCD versus pion exchange and hadronic FSI effects in the ??? ? + ? ? reaction  

Microsoft Academic Search

The interplay of pQCD, pion exchange and FSI effects is studied for the ????+?? reaction in the region of 2 GeV exchange amplitudes up to W??? 4 GeV. We discuss to which extend the conventional hadronic FSI effects could cloud the pQCD effects. We study multiple soft and

A. Szczurek; J. Speth

2003-01-01

41

Probing the mechanisms and dynamics of gas phase hydrogen-deuterium exchange reactions of sodiated polyglycines.  

PubMed

The rate constants for H-D exchange reactions of sodiated polyglycines (GnNa(+), n = 2-8) and polyalanines (AnNa(+), n = 2, 3 and 5) with ND3 have been measured in the cell of an FT-ICR mass spectrometer. All peptides except G2Na(+) are found to undergo three exchange reactions, all of which are consecutive with no sign of multiple exchanges within a single collision event. This information has been used to construct full mechanistic scenarios with the help of detailed quantum chemical calculations of the possible reaction paths for H-D exchange. The first exchange is always located at the C terminus however with different mechanisms depending upon whether the peptide termini can (larger peptides) or cannot (smaller peptides) interact directly without strong energy penalty. The most favourable mechanisms for the second and third exchanges of the N terminus protons, are found to be different from those for the first for all peptide sizes. The peptide distortions that are necessary in order for some of these reactions to occur are made possible by the energy reservoir provided by the favorable interaction of the peptide ion with ND3. Their occurrence and variety preclude any general relationship between H-D exchange kinetics and the most stable ion structures. There is however a break at G7Na(+) in the kinetics trend, with a first exchange rate which is much smaller than for all other peptide sizes. This break can be directly related to a different structural type in which the C terminus is neither free nor close to the N terminus. PMID:25573245

McMahon, T B; Ohanessian, G

2015-01-28

42

New, unexpected, and dominant mechanisms in the hydrogen exchange reaction  

NASA Astrophysics Data System (ADS)

A quasiclassical trajectory study of the state specific H +D2(?=0,j=0)?HD(?'=0,j'=0)+D reaction at a collision energy of 1.85eV (total energy of 2.04eV) found that the scattering is governed by two unexpected and dominant new mechanisms, and not by direct recoil as is generally assumed. The new mechanisms involve strong interaction with the sloping potential around the conical intersection, an area of the potential energy surface not previously considered to have much effect upon reactive scattering. Initial investigations indicate that more than 50% of reactive scattering could be the result of these new mechanisms at this collision energy. Features in the corresponding quantum mechanical results can be attributed to these new (classical) reaction mechanisms.

Greaves, Stuart J.; Murdock, Daniel; Wrede, Eckart; Althorpe, Stuart C.

2008-04-01

43

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

NASA Technical Reports Server (NTRS)

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.

Tsuge, S.; Sagara, K.

1978-01-01

44

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

SciTech Connect

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.

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

2013-12-14

45

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

NASA Technical Reports Server (NTRS)

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.

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

1993-01-01

46

Charge exchange and chemical reactions with trapped thorium ions  

NASA Astrophysics Data System (ADS)

Most atomic nuclei have excitation energies ranging from keV to MeV. A unique exception is the ^229Th nucleus, which has an excited state just several eV above the nuclear ground state.ootnotetextB. R. Beck et al., Phys. Rev. Lett. 98, 142501 (2007). Th^3+ provides a convenient level structure for laser cooling in an rf Paul trap.ootnotetextC. J. Campbell et al., Phys. Rev. Lett 102, 233004 (2009). Unlike many ions commonly utilized in precision measurements, the trap lifetime of Th^3+ is limited to only several minutes. This is a severe limitation to experiments involving ^229Th as it is only available in minute quantities. Here we have studied the loss mechanisms by introduction of various contaminants and analyzed reaction products using trapped ion mass spectrometry techniques.ootnotetextL. R. Churchill et al., Phys. Rev. A 83, 012710 (2011).

Depalatis, Michael; Churchill, Layne; Chapman, Michael

2011-06-01

47

Reaction chemistry and ligand exchange at cadmium selenide nanocrystal surfaces  

SciTech Connect

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.

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

2008-12-02

48

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

SciTech Connect

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

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

2005-05-15

49

Charge-exchange reactions in metal clusters: Role of magic numbers  

SciTech Connect

Using total energies calculated from self-consistent theories, we show thatthe charge-exchange reactions of metal clusters tend to favor the production of''magic-number'' species in larger clusters. Implications of our results forone's ability to produce neutral-cluster beams of a given size are discussed.

Khanna, S. N.; Jena, P.; Rao, B. K.

1989-07-15

50

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

Microsoft Academic Search

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

J. A. Quinn; N. C. Otto

1971-01-01

51

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

NASA Astrophysics Data System (ADS)

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.

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

2014-07-01

52

Substituent exchange reactions of linear oligomeric aryloxyphosphazenes with sodium 2,2,2-trifluoroethoxide.  

PubMed

Side-group-exchange reactions have been studied for short-chain linear oligomeric phosphazenes, (RO)(4)P[N?P(OR(2))](n)OR (n = 6, 10, 20, and 40) as models for the corresponding linear high polymers (n ~ 15000). Specifically, the exchange behavior of oligomers where OR = OCH(2)CF(3), OC(6)H(5), OC(6)H(4)CHO-p, OC(6)H(4)CN-p, and OC(6)H(4)NO(2)-p with sodium trifluoroethoxide was examined. The ease of aryloxy group replacement by trifluoroethoxy increased with the electron-withdrawing character in the order OR = OC(6)H(5) ? OC(6)H(4)CHO-p < OC(6)H(4)CN-p < OC(6)H(4)NO(2)-p, but the reaction was efficient only if the phosphazene contained no more than 20 repeating units. However, attempts to force slower reactions by the use of excess sodium trifluoroethoxide induced secondary reactions at the trifluoroethoxy units already introduced to produce CF(3)CH(2)OCH(2)CF(3) and generate -O(-)Na(+) units in their place. The longest chain model underwent side-group-exchange reactions preferentially at the end units. These results are significant for the synthesis of phosphazene high polymers with fluoroalkoxy and aryloxy side groups. PMID:23039045

Liu, Xiao; Breon, Jonathan P; Chen, Chen; Allcock, Harry R

2012-11-01

53

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

E-print Network

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

Wang, Zhong L.

54

Helicity amplitudes and crossing relations for one-photon exchange antiproton proton reactions  

NASA Astrophysics Data System (ADS)

Antiproton proton annihilation reactions allow unique access to the moduli and phases of nucleon electromagnetic form factors in the time-like region. We present the helicity amplitudes for the unequal-mass single-photon reaction p¯ ? l + l - in the s channel including the lepton mass. The relative signs of these amplitudes are determined using simple invariance properties. Helicity amplitudes for one-photon exchange annihilation reaction p¯ ? B¯ are also given, where B is any spin-one-half particle with structure. Crossing relations between the ep ? ep scattering and the p¯ ? l + l - annihilation channels are discussed and the crossing matrix for the helicity amplitudes is given. This matrix may be used to verify known expressions for the space-like helicity amplitudes due to one-photon exchange.

Buttimore, N. H.; Jennings, E.

2007-07-01

55

HPLC characterization of Ag+ and Cu+ metal exchange reactions with Zn- and Cd-metallothioneins.  

PubMed

Anion exchange HPLC methods were developed to study the metal exchange reactions of ZnMT and CdMT with Ag+ and Cu+. The kinetics of these reactions revealed the existence of a slow interprotein metal redistribution process that follows initial rapid displacement of metal from Zn7MT or Cd7MT by Ag+ or Cu+. Kinetically-favored products of the reaction of Ag+ with Zn7MT in the presence of Chelex resin include Zn4Ag6MT and Ag12MT. Subsequent slow reaction between Zn7MT and Ag12MT leads to the thermodynamically-favored product, Zn4Ag6MT. Analogous behavior was observed for Cd7MT titrated with Ag+ and Zn7MT with Cu+. The use of Chelex resin to remove unbound metal ions was found to influence the reactions of Zn7MT and Cd7MT with Ag+. Upon addition of Ag+ to Zn7MT in the absence of Chelex, a Ag18MT species forms as the kinetically-favored product in addition to Zn4Ag6MT and Ag12MT. Subsequently, Ag18MT was found to donate Ag+ to Zn7MT and Zn4Ag6MT via slow interprotein metal exchange reactions. Chelex resin influences the titration reaction either by limiting formation of Ag18MT and/or by binding the positively charged Ag18MT species and removing it from solution. The formation of Ag18MT in the absence of Chelex explains why more than 12 equiv of Ag+ is required to displace all of the Zn2+ or Cd2+ from Zn7MT and Cd7MT. The HPLC methods developed in this study allow homogeneous preparations to be made of metal-hybrid MT species containing Ag+ in the beta-domain and Cd2+ or Zn2+ in the alpha-domain. PMID:8909291

Li, H; Otvos, J D

1996-11-01

56

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

E-print Network

of the requirements for the degree of MASTER OF SCIENCE January l964 Major Subject: Microbiology THE FUNCTION OF SUPPLEMENTS REQUIRED FOR THE FORMATE-PYRUVATE EXCHANGE REACTION I. N STREPTOCOCCUS FAECALIS A Thesis By GORDON MARSH SMITH Approved as to styie... necessary for tbe incorporation of formate-C into pyruvate by Streptococcus faeca'lis (Wood and O'Kane, 14 1960). Since cell extracts can exchange formate without an additional factor other than a required O-R potent:ial (Oster, 196'), t. he factor...

Smith, Gordon Marsh

1964-01-01

57

Consecutive oxygen-for-sulfur exchange reactions between vanadium oxide cluster anions and hydrogen sulfide.  

PubMed

Vanadium oxide cluster anions Vm(16)On(-) and Vm(18)On(-) were prepared by laser ablation and reacted with hydrogen sulfide (H2S) in a fast flow reactor under thermal collision conditions. A time-of-flight mass spectrometer was used to detect the cluster distributions before and after the interactions with H2S. The experiments suggest that the oxygen-for-sulfur (O/S) exchange reaction to release water was evidenced in the reactor for most of the cluster anions: VmOn(-) + H2S ? VmOn-1S(-) + H2O. For reactions of clusters VO3(-) and VO4(-) with H2S, consecutive O/S exchange reactions led to the generation of sulfur containing vanadium oxide cluster anions VO3-kSk(-) (k = 1-3) and VO4-kSk(-) (k = 1-4). Density functional theory calculations were performed for the reactions of VO3-4(-) with H2S, and the results indicate that the O/S exchange reactions are both thermodynamically and kinetically favorable, which supports the experimental observations. The reactions of VmOn(+) cluster cations with H2S have been reported previously (Jia, M.-Y.; Xu, B.; Ding, X.-L.; Zhao, Y.-X.; He, S.-G.; Ge, M.-F. J. Phys. Chem. C 2012, 116, 9043), and this study of cluster anions provides further new insights into the transformations of H2S over vanadium oxides at the molecular level. PMID:24387129

Jia, Mei-Ye; Xu, Bo; Deng, Ke; He, Sheng-Gui; Ge, Mao-Fa

2014-09-18

58

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

E-print Network

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.

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

2004-05-11

59

Sn cation valency dependence in cation exchange reactions involving Cu(2-x)Se nanocrystals.  

PubMed

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

De Trizio, Luca; Li, Hongbo; Casu, Alberto; Genovese, Alessandro; Sathya, Ayyappan; Messina, Gabriele C; Manna, Liberato

2014-11-19

60

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

PubMed Central

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

2014-01-01

61

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

NASA Astrophysics Data System (ADS)

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.

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

2012-04-01

62

Synthesis of ordered mesoporous crystalline CuS and Ag2S materials via cation exchange reaction.  

PubMed

Cation exchange reaction is a strong tool for the synthesis of new ionic nanomaterials. Most of them are isolated nanoparticles with simple geometric features, such as nanodots, nanorods and nanospheres. In this work, we demonstrated that ordered mesoporous CdS with a complex cubic Ia3d gyroidal 3D bicontinuous porous structure and large particle size can be successfully converted to crystalline CuS and Ag2S materials via cation exchange reaction without destroying the well-defined nanostructure. The change in crystal structure is an important factor for a successful conversion when the reaction is carried out without the presence of a silica template. In addition, the cation exchange reaction is sufficient for a complete compositional conversion, even when the mesostructured CdS precursor is embedded inside a mesoporous silica matrix. Our results indicate that cation exchange reaction may be applied to highly complex nanostructures with extremely large particle sizes. PMID:25684647

Wang, Jun; Xu, Weiming; Bao, Haifeng; Shi, Yifeng

2015-02-26

63

Substituent exchange reactions of trimeric and tetrameric aryloxycyclophosphazenes with sodium 2,2,2-trifluoroethoxide.  

PubMed

Substituent exchange reactions of sodium 2,2,2-trifluoroethoxide with trimeric and tetrameric aryloxycyclophosphazenes with phenoxy, 4-formylphenoxy, 4-cyanophenoxy and 4-nitrophenoxy side groups were conducted at 66 °C in THF and monitored by (31)P NMR and mass spectrometry. These are model reactions for their counterparts with high polymeric linear organophosphazenes. The ease of displacement of OAr in cyclic trimeric and tetrameric molecules by CF(3)CH(2)O increased significantly with the presence of electron-withdrawing substituents in the polyphosphazene in the order, phenoxy ? 4-formylphenoxy < 4-cyanophenoxy ? 4-nitrophenoxy. Fully substituted 2,2,2-trifluoroethoxyphosphazene trimer and tetramer were formed by side group exchange, but these reactions were followed by an attack by the nucleophile on the ?-carbon of the 2,2,2-trifluoroethoxy groups linked to phosphorus to give a species in which one trifluoroethoxy group had been replaced by an ONa unit, and bis(trifluoroethyl) ether was formed as a side product. On the other hand, only partly exchanged species were formed when sodium phenoxide reacted with the trifluoroethoxy phosphazene trimer and tetramer, but again a product with an ONa side group was formed eventually together with phenyltrifluoroethyl ether generated via alpha-carbon attack. The relative sensitivity of 2,2,2-trifluoroethoxy and phenoxyphosphazene cyclic trimers and tetramers to the presence of trifluoroethoxide was established. PMID:22180860

Liu, Xiao; Breon, Jonathan P; Chen, Chen; Allcock, Harry R

2012-02-21

64

Enrichment factor, height of separation unit, and separation efficiency by ion exchange with chemical reaction  

SciTech Connect

The enrichment factor ({epsilon}{sub u}) in the separation unit of ion-exchange and chemical reactions is a function of the enrichment factor of the chemical reaction ({epsilon}{sub r,s}) and the {open_quotes}equilibrium coefficients{close_quotes} ({zeta}) which are determined only by the distribution of the ions in both the solution and ion-exchange phases. The factor can be simply expressed as {epsilon}{sub u}={zeta}{epsilon}{sub r,s}. The height of the separation unit is the sum of heights due to ion exchange, chemical reaction, and flow pattern. The height is also due to the {open_quotes}kinetics coefficient{close_quotes} {zeta}, which is a function of the distribution as well as the {open_quotes}equilibrium coefficient.{close_quotes} The separation efficiency is proportional to {zeta}/{radical}v, both of which depend on the concentration of ions in the unit. Several schemes for the separation units are also discussed.

Takeda, Kunihiko; Morita, Keiichiro [Shibaura Inst. of Technology, Tokyo (Japan)

1996-11-01

65

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

SciTech Connect

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.

McLane, V.

1996-07-01

66

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

PubMed Central

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

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

2009-01-01

67

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

SciTech Connect

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.

Vrakking, M.J.J.

1992-11-01

68

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

SciTech Connect

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.

Vrakking, M.J.J.

1992-11-01

69

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

SciTech Connect

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.'

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

2009-11-15

70

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

E-print Network

. The effect of the delay time on the ion partitioning efficiency. . 10 2. Temporal plot of the ligand exchange products of the ion-molecule reaction between Cr, (CO), ' and PMe, . 15 3. Temporal plot of the ligand exchange products of the ion... is increased". Data of Halpern and Phelan" for the associative reaction of 2Co(DH), L + PhCH, Br ? -& PhCH, Co(DH), L + BrCo(DH), L showed that larger ligands (L) inhibit the reaction. Poe and Twigg" " showed that the second- order rate term in the reaction...

Nguyen, Hanh Duc

1991-01-01

71

Double Regge exchange Limit for the $\\gamma p\\to K^+K^-p$ Reaction  

DOE PAGESBeta

We apply the generalized Veneziano model (B5 model) in the double-Regge exchange limit to the ?p?K+K?p reaction. Four different cases defined by the possible combinations of the signature factors of leading Regge exchanges ((K?,a2/f2), (K?,?/?), (K?2,a2/f2), and (K?2,?/?)) have been simulated through the Monte Carlo method. Suitable event candidates for the double-Regge exchange high-energy limit were selected employing \\textit{Van Hove} plots as a better alternative to kinematical cuts in the K+K?p Dalitz plot. In this way we predict and analyze the double-Regge contribution to the K+K?p Dalitz plot, which constitutes one of the major backgrounds in the search for strangeonia, 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.

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

2015-02-01

72

Double-Regge Exchange Limit for the $?p\\rightarrow K^+K^-p$ Reaction  

E-print Network

We apply the generalized Veneziano model ($B_5$ model) in the double-Regge exchange limit to the $\\gamma p \\to K^+ K^- p$ reaction. Four different cases defined by the possible combinations of the signature factors of leading Regge exchanges (($K^*,a_2/f_2$), ($K^*,\\rho/\\omega$), ($K_2^*,a_2/f_2$), and ($K_2^*,\\rho/\\omega$)) have been simulated through the Monte Carlo method. Suitable event candidates for the double-Regge exchange high-energy limit were selected employing \\textit{Van Hove} plots as a better alternative to kinematical cuts in the $K^+ K^- p$ Dalitz plot. In this way we predict and analyze the double-Regge contribution to the $K^+ K^- p$ Dalitz plot, which constitutes one of the major backgrounds in the search for strangeonia, hybrids and exotics using $\\gamma p\\rightarrow K^+K^-p$ 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.

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

2014-11-23

73

Double-Regge exchange limit for the ? p ?K+K-p reaction  

NASA Astrophysics Data System (ADS)

We apply the generalized Veneziano model (B5 model) in the double-Regge exchange limit to the ? p ?K+K-p reaction. Four different cases defined by the possible combinations of the signature factors of leading Regge exchanges [(K*,a2/f2 ) , (K*,? /? ) , (K2*,a2/f2) , and (K2*,? /? ) ] 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 those to come in the future, will allow verification of the double-Regge behavior and a better assessment of this component of the amplitude.

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

2015-02-01

74

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

SciTech Connect

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).

McLane, V. [ed.] [comp.

1997-07-01

75

Upper bounds to the impact parameter and cross section for atom-diatom exchange reactions  

NASA Astrophysics Data System (ADS)

We establish upper bounds to the impact parameter and cross section for any A+BC exchange reaction in which the reagents are in a given initial state. The approach we take is to use the centrifugal forces generated in a collision to place a bound on the values of the total angular momentum for which reaction can occur. The bounds on the impact parameter and cross section then follow directly from the restrictions imposed by energy and angular momentum conservation. Our approach is related to theories based on the properties of periodic trajectories in that the system configuration which determines the angular momentum bound is also that of a quasibound ABC rigid rotor periodic trajectory. The equation which defines the configuration of this trajectory is similar in form to a generating function recently derived by Child and Pollak. Furthermore, an analysis of the symmetric stretch periodic trajectories in the H+H2 reaction suggests that the rigid rotor trajectory is the maximum angular momentum member of a family of periodic trajectories which exist at energies below and above the dissociation threshold. Our approach is also related to variational transition state theory. However, rather than vary the location of a diving surface, we keep the surface fixed in the reagents' region of the system phase space and vary instead its boundary. We compare the bounds we place on the impact parameter and cross section to the quasiclassical trajectory data of Karplus, Porter, and Sharma for the H+H2 exchange reaction and to that of Persky for the reactions of Cl with H2, D2, and HD. The cross section ratios show a near-linear dependence on the fraction of the total system energy which is partitioned initially into relative translational energy of the reagents, whereas the impact parameter ratios smoothly increase from ˜0.2 near threshold to a maximum of ˜0.9.

Chesnavich, Walter J.

1982-09-01

76

Neutron Skin Thickness of 90Zr Determined By Charge Exchange Reactions  

E-print Network

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.

K. Yako; H. Sagawa; H. Sakai

2006-09-29

77

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

E-print Network

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.

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

2004-06-12

78

Identification of a critical intermediate in galvanic exchange reactions by single-nanoparticle-resolved kinetics.  

PubMed

The realization of common materials transformations in nanocrystalline systems is fostering the development of novel nanostructures and allowing a deep look into the atomistic mechanisms involved. Galvanic corrosion is one such transformation. We studied galvanic replacement within individual metal nanoparticles by using a combination of plasmonic spectroscopy and scanning transmission electron microscopy. Single-nanoparticle reaction trajectories showed that a Ag nanoparticle exposed to Au³? makes an abrupt transition into a nanocage structure. The transition is limited by a critical structural event, which we identified by electron microscopy to comprise the formation of a nanosized void. Trajectories also revealed a surprisingly strong nonlinearity of the reaction kinetics, which we explain by a model involving the critical coalescence of vacancies into a growing void. The critical void size for galvanic exchange to spontaneously proceed was found to be 20 atomic vacancies. PMID:24677345

Smith, Jeremy G; Yang, Qing; Jain, Prashant K

2014-03-10

79

Pt loaded carbon aerogel catalyst for catalytic exchange reactions between water and hydrogen gas  

NASA Astrophysics Data System (ADS)

We report development and characterization of platinum doped carbon aerogel catalyst for catalytic exchange reactions between water and hydrogen gas. The carbon aerogel with uniformly dispersed platinum nanoparticles was prepared by adding platinum precursor during the sol-gel process. Thereafter colloidal PTFE was mixed with the platinum doped carbon aerogel powder and coated on Dixon rings to obtain hydrophobic catalyst with required mechanical strength. Detailed studies have been carried out to observe the effect of physical characteristics of the catalyst powder (surface area and pore size of aerogels, Pt cluster size and its valence state etc) and the different coating parameters (PTFE to Pt-CA ratio and Pt loading on Dixon ring) on volume transfer rate (Ky.a) for H/D reaction. Ky.a values of ˜0.8 m3 (STP).s-1. m-3 were obtained for Pt loading of 7% and Pt cluster size of 3 nm at atmospheric pressure.

Singh, Rashmi; Singh, Ashish; Kohli, D. K.; Singh, M. K.; Gupta, P. K.

2013-06-01

80

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

SciTech Connect

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.

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

2009-07-06

81

Semi-relativistic meson exchange currents in (e,e') and (e,e'p) reactions  

E-print Network

Electron-induced one-nucleon knock-out observables are computed for moderate to high momentum transfer making use of semi-relativistic expressions for the one-body and two-body meson-exchange current matrix elements. Emphasis is placed on the semi-relativistic form of the $\\Delta$-isobar exchange current and several prescriptions for the dynamical-equivalent form of the $\\Delta$-propagator are analyzed. To this end, the inclusive transverse response function, evaluated within the context of the semi-relativistic approach and using different prescriptions for the $\\Delta$-propagator, is compared with the fully relativistic calculation performed within the scheme of the relativistic Fermi gas model. It is found that the best approximation corresponds to using the traditional static $\\Delta$-propagator. These semi-relativistic approaches, which contain important aspects of relativity, are implemented in a distorted wave analysis of quasielastic $(e,e'p)$ reactions. Final state interactions are incorporated through a phenomenological optical potential model and relativistic kinematics is assumed when calculating the energy of the ejected nucleon. The results indicate that meson exchange currents may modify substantially the $TL$ asymmetry for high missing momentum.

J. E. Amaro; M. B. Barbaro; J. A. Caballero; F. Kazemi Tabatabaei

2003-05-20

82

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

NASA Astrophysics Data System (ADS)

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.

Chen, Peng; Solomon, Edward I.

2004-09-01

83

Fe-Zn exchange reaction between tetrahedrite and sphalerite in natural environments  

NASA Astrophysics Data System (ADS)

Microprobe and fluid inclusion analyses of hydrothermal ore deposits containing the subassemblage sphalerite+ tetrahedrite-tennantite ˜[(Cu, Ag)10(Fe, Zn)2(As,Sb)4S13] reveal that the Gibbs energies of the reciprocal reaction Cu10Zn2Sb4S13 + Cu10Fe2As4S13 = Cu10Fe2Sb4S13 + Cu10Zn2As4S13 and the Fe-Zn exchange reaction 1/2Cu10Fe2Sb4S13 + ZnS = 1/2Cu10Zn2Sb4S13 + FeS are within the uncertainties of the values established by Sack and Loucks (1985) and Raabe and Sack (1984), 2.59±0.14 and 2.07±0.07 kcal/gfw. However, this study suggests that the Fe-Zn exchange reaction between sphalerite and Sb and Ag-rich tetrahedrites does not obey the simple systematics suggested by Sack and Loucks (1985) wherein tetrahedrite is assumed to behave as an “ideal” reciprocal solution. Instead these studies show that the configurational Gibbs energy of this exchange reaction, RTln[( X Fe/ X Zn)TET( X ZnS/ X FeS)SPH], corrected for sphalerite nonideality exhibits both a local maximum and minimum as a function of Ag/(Cu+Ag) ratio at a given X {FeS/SPH}and temperature. The local maximum for X {FeS/SPH}˜0.10 corresponds to the position of the cell edge maximum established for natural tetrahedrites by Riley (1974), Ag/(Ag+Cu)˜0.4. These studies and the results of structural refinements of Ag-bearing tetrahedrites suggest that in low silver tetrahedrites Ag is preferentially incorporated in trigonal-planar sites but that in tetrahedrites with intermediate and greater Ag/(Ag+Cu) ratio, Ag is preferentially incorporated in tetrahedral sites. A nonconvergent site ordering model for tetrahedrite is developed to quantify and extrapolate these predictions.

O'Leary, Michael J.; Sack, Richard O.

1987-12-01

84

Synthesis of PbS nanorods and other ionic nanocrystals of complex morphology by sequential cation exchange reactions.  

PubMed

We show that nanocrystals (NCs) with well-established synthetic protocols for high shape and size monodispersity can be used as templates to independently control the NC composition through successive cation exchange reactions. Chemical transformations like cation exchange reactions overcome a limitation in traditional colloidal synthesis, where the NC shape often reflects the inherent symmetry of the underlying lattice. Specifically we show that full or partial interconversion between wurtzite CdS, chalcocite Cu(2)S, and rock salt PbS NCs can occur while preserving anisotropic shapes unique to the as-synthesized materials. The exchange reactions are driven by disparate solubilites between the two cations by using ligands that preferentially coordinate to either monovalent or divalent transition metals. Starting with CdS, highly anisotropic PbS nanorods are created, which serve as an important material for studying strong two-dimensional quantum confinement, as well as for optoelectronic applications. In NC heterostructures containing segments of different materials, the exchange reaction can be made highly selective for just one of the components of the heterostructure. Thus, through precise control over ion insertion and removal, we can obtain interesting CdS|PbS heterostructure nanorods, where the spatial arrangement of materials is controlled through an intermediate exchange reaction. PMID:19863102

Luther, Joseph M; Zheng, Haimei; Sadtler, Bryce; Alivisatos, A Paul

2009-11-25

85

EXCHANGE  

SciTech Connect

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.

Boltz, J.C. (ed.)

1992-09-01

86

Synthesis of ordered mesoporous crystalline CuS and Ag2S materials via cation exchange reaction  

NASA Astrophysics Data System (ADS)

Cation exchange reaction is a strong tool for the synthesis of new ionic nanomaterials. Most of them are isolated nanoparticles with simple geometric features, such as nanodots, nanorods and nanospheres. In this work, we demonstrated that ordered mesoporous CdS with a complex cubic Ia3d gyroidal 3D bicontinuous porous structure and large particle size can be successfully converted to crystalline CuS and Ag2S materials via cation exchange reaction without destroying the well-defined nanostructure. The change in crystal structure is an important factor for a successful conversion when the reaction is carried out without the presence of a silica template. In addition, the cation exchange reaction is sufficient for a complete compositional conversion, even when the mesostructured CdS precursor is embedded inside a mesoporous silica matrix. Our results indicate that cation exchange reaction may be applied to highly complex nanostructures with extremely large particle sizes.Cation exchange reaction is a strong tool for the synthesis of new ionic nanomaterials. Most of them are isolated nanoparticles with simple geometric features, such as nanodots, nanorods and nanospheres. In this work, we demonstrated that ordered mesoporous CdS with a complex cubic Ia3d gyroidal 3D bicontinuous porous structure and large particle size can be successfully converted to crystalline CuS and Ag2S materials via cation exchange reaction without destroying the well-defined nanostructure. The change in crystal structure is an important factor for a successful conversion when the reaction is carried out without the presence of a silica template. In addition, the cation exchange reaction is sufficient for a complete compositional conversion, even when the mesostructured CdS precursor is embedded inside a mesoporous silica matrix. Our results indicate that cation exchange reaction may be applied to highly complex nanostructures with extremely large particle sizes. Electronic supplementary information (ESI) available: XRD patterns and nitrogen sorption data of the KIT-6 template, CdS precursor and Ag2S and CuS products. See DOI: 10.1039/c4nr07060g

Wang, Jun; Xu, Weiming; Bao, Haifeng; Shi, Yifeng

2015-02-01

87

The Gecko visual pigment: the dark exchange reaction and the effects of anions.  

PubMed

A dark reaction is known to occur in retinal extracts of the gecko (Gekko gekko), in which the natural 11-cis-chromophore of the 521-pigment is apparently replaced by adding 9-cis-retinal to form the 9-cis-photopigment. With chloride-deficient extracts the reaction involves some 70% of the 521-pigment. Anions like nitrate, azide, thiocyanate and cyanate that shift the spectrum toward the blue do not affect this 70% exchange. Anions like fluoride, iodide and sulfate likewise do not alter this magnitude of reaction. In contrast, chloride and bromide that induce a bathochromic spectral shift lead to a decrease in this dark replacement of the 11-cis chromophore. This protection is similar to the action of these two anions in antagonizing the pigment loss by NH2OH and by temperature, both occurring in the dark. Apparently, chloride and bromide alter the opsin conformation so as to stabilize and/or protect the Schiff's base linkage but nitrate, azide, thiocyanate and cyanate act at a different opsin site or by a different mechanism. PMID:2759190

Crescitelli, F; Karvaly, B

1989-07-01

88

A numerical modelling of gas exchange mechanisms between air and turbulent water with an aquarium chemical reaction  

NASA Astrophysics Data System (ADS)

This paper proposes a new numerical modelling to examine environmental chemodynamics of a gaseous material exchanged between the air and turbulent water phases across a gas-liquid interface, followed by an aquarium chemical reaction. This study uses an extended concept of a two-compartment model, and assumes two physicochemical substeps to approximate the gas exchange processes. The first substep is the gas-liquid equilibrium between the air and water phases, A(g)?A(aq), with Henry's law constant H. The second is a first-order irreversible chemical reaction in turbulent water, A(aq)+H2O?B(aq)+H+ with a chemical reaction rate ?A. A direct numerical simulation (DNS) technique has been employed to obtain details of the gas exchange mechanisms and the chemical reaction in the water compartment, while zero velocity and uniform concentration of A is considered in the air compartment. The study uses the different Schmidt numbers between 1 and 8, and six nondimensional chemical reaction rates between 10(?0) to 101 at a fixed Reynolds number. It focuses on the effects of the Schmidt number and the chemical reaction rate on fundamental mechanisms of the gas exchange processes across the interface.

Nagaosa, Ryuichi S.

2014-01-01

89

Reprint of: A numerical modelling of gas exchange mechanisms between air and turbulent water with an aquarium chemical reaction  

NASA Astrophysics Data System (ADS)

This paper proposes a new numerical modelling to examine environmental chemodynamics of a gaseous material exchanged between the air and turbulent water phases across a gas-liquid interface, followed by an aquarium chemical reaction. This study uses an extended concept of a two-compartment model, and assumes two physicochemical substeps to approximate the gas exchange processes. The first substep is the gas-liquid equilibrium between the air and water phases, A(g)?A(aq), with Henry's law constant H. The second is a first-order irreversible chemical reaction in turbulent water, A(aq)+H2O?B(aq)+H+ with a chemical reaction rate ?A. A direct numerical simulation (DNS) technique has been employed to obtain details of the gas exchange mechanisms and the chemical reaction in the water compartment, while zero velocity and uniform concentration of A is considered in the air compartment. The study uses the different Schmidt numbers between 1 and 8, and six nondimensional chemical reaction rates between 10(?0) to 101 at a fixed Reynolds number. It focuses on the effects of the Schmidt number and the chemical reaction rate on fundamental mechanisms of the gas exchange processes across the interface.

Nagaosa, Ryuichi S.

2014-08-01

90

Proton-3H scattering calculation: Elastic and charge-exchange reactions up to 30 MeV  

NASA Astrophysics Data System (ADS)

Proton-3H elastic scattering and charge-exchange reaction 3H(p ,n ) 3He in the energy regime above the four-nucleon breakup threshold are described in the momentum-space transition operator framework. Fully converged results are obtained by using realistic two-nucleon potentials and a two-proton Coulomb force as dynamic input. Differential cross section, proton analyzing power, outgoing neutron polarization, and proton-to-neutron polarization transfer coefficients are calculated between 6 and 30 MeV proton beam energy. Good agreement with the experimental data is found for the differential cross section both in elastic and charge-exchange reactions; the latter shows a complicated energy and angular dependence. The most sizable discrepancies between predictions and data are found for the proton analyzing power and outgoing neutron polarization in the charge-exchange reaction, while the respective proton-to-neutron polarization transfer coefficients are well described by the calculations.

Deltuva, A.; Fonseca, A. C.

2015-03-01

91

Proton-${}^3$H scattering calculation: Elastic and charge-exchange reactions up to 30 MeV  

E-print Network

Proton-${}^3$H elastic scattering and charge-exchange reaction ${}^3$H$(p,n){}^3$He in the energy regime above four-nucleon breakup threshold are described in the momentum-space transition operator framework. Fully converged results are obtained using realistic two-nucleon potentials and two-proton Coulomb force as dynamic input. Differential cross section, proton analyzing power, outgoing neutron polarization, and proton-to-neutron polarization transfer coefficients are calculated between 6 and 30 MeV proton beam energy. Good agreement with the experimental data is found for the differential cross section both in elastic and charge-exchange reactions; the latter shows a complicated energy and angular dependence. The most sizable discrepancies between predictions and data are found for the proton analyzing power and outgoing neutron polarization in the charge-exchange reaction, while the respective proton-to-neutron polarization transfer coefficients are well described by the calculations.

A. Deltuva; A. C. Fonseca

2015-03-12

92

Proton-${}^3$H scattering calculation: Elastic and charge-exchange reactions up to 30 MeV  

E-print Network

Proton-${}^3$H elastic scattering and charge-exchange reaction ${}^3$H$(p,n){}^3$He in the energy regime above four-nucleon breakup threshold are described in the momentum-space transition operator framework. Fully converged results are obtained using realistic two-nucleon potentials and two-proton Coulomb force as dynamic input. Differential cross section, proton analyzing power, outgoing neutron polarization, and proton-to-neutron polarization transfer coefficients are calculated between 6 and 30 MeV proton beam energy. Good agreement with the experimental data is found for the differential cross section both in elastic and charge-exchange reactions; the latter shows a complicated energy and angular dependence. The most sizable discrepancies between predictions and data are found for the proton analyzing power and outgoing neutron polarization in the charge-exchange reaction, while the respective proton-to-neutron polarization transfer coefficients are well described by the calculations.

Deltuva, A

2015-01-01

93

Pion induced double charge exchange reactions in the Delta resonance region  

E-print Network

We have applied the Giessen BUU (GiBUU) transport model to the description of the double charge exchange (DCX) reaction of pions with different nuclear targets at incident kinetic energies of 120-180 MeV . The DCX process is highly sensitive to details of the interactions of pions with the nuclear medium and, therefore, represents a major benchmark for any model of pion scattering off nuclei at low and intermediate energies. The impact of surface effects, such as the neutron skins of heavy nuclei, is investigated. The dependence of the total cross section on the nuclear mass number is also discussed. We achieve a good quantitative agreement with the extensive data set obtained at LAMPF. Furthermore, we compare the solutions of the transport equations obtained in the test-particle ansatz using two different schemes - the full and the parallel ensemble method.

O. Buss; L. Alvarez-Ruso; A. B. Larionov; U. Mosel

2006-07-10

94

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

SciTech Connect

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.

Rokni, S.H.

1987-06-01

95

Relativistic Effects in Electromagnetic Meson-Exchange Currents for One-Particle Emission Reactions  

E-print Network

Following recent studies of non-relativistic reductions of the single-nucleon electromagnetic current operator, here we extend the treatment to include meson exchange current operators. We focus on one-particle emission electronuclear reactions. In contrast to the traditional scheme where approximations are made for the transferred momentum, transferred energy and momenta of the initial-state struck nucleons, we treat the problem exactly for the transferred energy and momentum, thus obtaining new current operators which retain important aspects of relativity not taken into account in the traditional non-relativistic reductions. We calculate the matrix elements of our current operators between the Fermi sphere and a particle-hole state for several choices of kinematics. We present a comparison between our results using approximate current operators and those obtained using the fully-relativistic operators, as well as with results obtained using the traditional non-relativistic current operators.

J. E. Amaro; M. B. Barbaro; J. A. Caballero; T. W. Donnelly; A. Molinari

1998-10-26

96

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

NASA Astrophysics Data System (ADS)

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

Rustad, James R.; Casey, William H.

2012-03-01

97

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

SciTech Connect

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.

Maloszewski, P. (GSF-Inst. fuer Hydrologie, Neuherberg (West Germany)); Zuber, A. (Inst. of Nuclear Physics, Cracow (Poland))

1991-08-01

98

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

PubMed Central

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

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

2014-01-01

99

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

PubMed

Biogenic volatile organic compound (BVOC) emissions are widely modelled as inputs to atmospheric chemistry simulations. However, BVOC may interact with cellular structures and neighbouring 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 because of the 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 upon compound reactivity, physicochemical characteristics, as well as upon their participation in leaf metabolism. We argue that future models should be based upon the concept of bidirectional BVOC exchange and consider modification of BVOC sink/source strengths by within-leaf metabolism and storage. PMID:24635661

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

2014-08-01

100

Radiolysis of water vapor and a surface-catalyzed isotope-exchange reaction  

SciTech Connect

The steady-state radiolysis of deuterium oxide vapor has been examined using protium, perprotiopropane, or mixtures of these two as free-radical scavengers. Tritiated water was used as an internal radiation source, and glass irradiation vessels were employed. D atoms are produced in the radiolytic decomposition of D/sub 2/O, and HD is formed by reaction of this species with the added radical scavengers. It was assumed previously that the yield of HD molecules could be equated with the yield of radiolytically produced D atoms. However, the experimental results of the present investigation demonstrate conclusively that when H/sub 2/ is used as a radical scavenger there are two pathways for HD formation: (1) homogeneous scavenging of the radiolytically produced D atoms by H/sub 2/, as expected, and (2) heterogeneous combination of H atoms produced in the scavenging reaction (D + H/sub 2/ ..-->.. HD + H) with D atoms absorbed on the vessel surface, where the adsorbed D atoms are generated by a surface-catalyzed isotope-exchange reaction between H atoms adsorbed from the volume and D/sub 2/O. From the results of this investigation, it appears that the yield of D atoms produced in the radiolysis of D/sub 2/O is G/sub D/ = 7.0 atoms/100 eV absorbed energy, i.e., the G(HD) found in experiments using propane as the radical scavenger. G/sub D/sub 2// is shown to be 0.65 molecules/100 eV.

Richter, H.W.; Firestone, R.F.

1981-08-26

101

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

PubMed Central

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

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

2014-01-01

102

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

NASA Astrophysics Data System (ADS)

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.

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

2007-01-01

103

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

NASA Astrophysics Data System (ADS)

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.

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

2005-12-01

104

Hydrogen and oxygen isotope exchange reactions between clay minerals and water  

USGS Publications Warehouse

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.

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

1976-01-01

105

Pictet-spengler reaction using ion-exchange resin as a catalyst and support for 'catch and release' purification.  

PubMed

The Pictet-Spengler reaction between tryptamine and aldehydes was catalyzed by Dowex 50W-X4 acidic ion-exchange resin. The products were obtained from the resin in high purity by 'catch and release' without the need for separate chromatographic purification. PMID:21307579

Izumi, Minoru; Kido, Takeshi; Murakami, Miyu; Nakajima, Shuhei; Ganesan, A

2011-01-01

106

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

ERIC Educational Resources Information Center

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…

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

2007-01-01

107

Modelling of geochemical reactions and experimental cation exchange in MX 80 bentonite.  

PubMed

Bentonites are widely used for waste repository systems because of their hydrodynamic, surface and chemical-retention properties. MX 80 bentonite (bentonite of Wyoming) contains approximately 85% Na/Ca-montmorillonite and 15% accessory minerals. The dominant presence of Na/Ca-montmorillonite in this clay mineral could cause it to perform exceptionally well as an engineered barrier for a radioactive waste repository because this buffer material is expected to fill up by swelling the void between canisters containing waste and the surrounding ground. However, the Na/Ca-montmorillonite could be transformed to other clay minerals as a function of time under repository conditions. Previous modelling studies based on the hydrolysis reactions have shown that the Na/Ca-montmorillonite-to-Ca-montmorillonite conversion is the most significant chemical transformation. In fact, this chemical process appears to be a simple cation exchange into the engineered barrier. The purpose of the present study was two-fold. Firstly, it was hoped to predict the newly formed products of bentonite-fluid reactions under repository conditions by applying a thermokinetic hydrochemical code (KIRMAT: Kinetic Reactions and Mass Transport). The system modelled herein was considered to consist of a 1-m thick zone of water-saturated engineered barrier. This non-equilibrated system was placed in contact with a geological fluid on one side, which was then allowed to diffuse into the barrier, while the other side was kept in contact with iron-charged water. Reducing initial conditions ( [P(O)2 approximately equals 0] ; Eh=-200 mV) and a constant reaction temperature (100 degrees C) were considered. Secondly, it was hoped to estimate the influence of inter-layer cations (Ca and Na) on the swelling behaviour of the MX 80 bentonite by using an isothermal system of water vapour adsorption and an environmental scanning electron microscope (ESEM) coupled with a digital image analysis (DIA) program. Here, the MX 80 bentonite was previously treated with concentrated solutions (1N) of calcium and sodium chlorides. The results confirmed that the Na/Ca-montmorillonite-to-Ca-montmorillonite conversion was the main chemical transformation in the bentonite barrier under repository conditions. A simplified method (based on volume balance) has shown that the swelling capacity of the engineered barrier would be slightly affected after 1000 years of diffusion-reaction because the volume of neo-formed swelling clays is almost directly proportional to the volume of transformed initial-montmorillonite. Minimal neo-formation of saponites, vermiculites and chlorites was also observed. In addition, an isothermal system of water adsorption and ESEM-DIA methods showed that in the raw-bentonite-to-Ca-bentonite exchange there is a small decrease in the amount of adsorbed water and the swelling potential. PMID:15946786

Montes-H, G; Fritz, B; Clement, A; Michau, N

2005-10-01

108

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

E-print Network

Proton and light ion induced charge exchange reactions in nuclei This article has been downloaded Scripta. Vol. 48, 101-104, 1993 Proton and Light Ion Induced Charge Exchange Reactions in Nuclei E. Oset of strength from the proton to the deu- teron targets and an even more remarkable shift of the strength

Fernández de Córdoba, Pedro

109

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

PubMed

The surface chemistry of cadmium selenide nanocrystals, prepared from tri-n-octylphosphine selenide and cadmium octadecylphosphonate in tri-n-octylphosphine oxide, was studied with 1H and {1H}31P NMR spectroscopy as well as ESI-MS and XPS. The identity of the surface ligands was inferred from reaction of nanocrystals with Me3Si-X (X = -S-SiMe3, -Se-SiMe3, -Cl and -S-(CH2CH2O)4OCH3)) and unambiguous assignment of the organic byproducts, O,O'-bis(trimethylsilyl)octadecylphosphonic acid ester and O,O'-bis(trimethylsilyl)ocatdecylphosphonic acid anhydride ester. Nanocrystals isolated from these reactions have undergone exchange of the octadecylphosphonate ligands for -X as was shown by 1H NMR (X = -S-(CH2CH2O)4OCH3) and XPS (X = -Cl). Addition of free thiols to as prepared nanocrystals results in binding of the thiol to the particle surface and quenching of the nanocrystal fluorescence. Isolation of the thiol-ligated nanocrystals shows this chemisorption proceeds without displacement of the octadecylphosphonate ligands, suggesting the presence of unoccupied Lewis-acidic sites on the particle surface. In the presence of added triethylamine, however, the octadecylphosphonate ligands are readily displaced from the particle surface as was shown with 1H and {1H}31P NMR. These results, in conjunction with previous literature reports, indicate that as-prepared nanocrystal surfaces are terminated by X-type binding of octadecylphosphonate moieties to a layer of excess cadmium ions. PMID:18722426

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

2008-09-17

110

Supportless silver nanowires as oxygen reduction reaction catalysts for hydroxide-exchange membrane fuel cells.  

PubMed

Silver nanowires (AgNWs) and nanoparticles (AgNPs) have been synthesized to facilitate hydroxide-exchange membrane fuel cell development and commercialization. AgNWs and AgNPs with variable diameters (25-60 nm AgNWs, 2.4-30 nm AgNPs) have been studied with rotating-disk electrode experiments to examine the impact of size and morphology on the oxygen reduction reaction (ORR). Although a detrimental particle size effect is observed, AgNWs exceed the specific activity of bulk polycrystalline Ag. AgNWs with a diameter of 25 nm further exceed the ORR specific and mass activity of 2.4 nm AgNPs 5.3 times and by 16 %, respectively. Rotating ring-disk electrode testing demonstrates minimal peroxide formation on AgNWs; peroxide production increases with the use of AgNPs by as much as an order of magnitude and further increases with particle size reduction. Silver catalysts demonstrate alcohol tolerance for ORR, illustrating the benefit of silver and AgNWs as catalysts in hydroxide and alcohol hydroxide-based fuel cells. PMID:22887923

Alia, Shaun M; Duong, Kathlynne; Liu, Toby; Jensen, Kurt; Yan, Yushan

2012-08-01

111

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

SciTech Connect

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

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

2008-08-04

112

13C NMR Characterization of an Exchange Reaction between CO and CO2 Catalyzed by Carbon Monoxide Dehydrogenase†  

PubMed Central

Carbon monoxide dehydrogenase (CODH) catalyzes the reversible oxidation of CO to CO2 at a nickel?iron?sulfur cluster (the C-cluster). CO oxidation follows a ping-pong mechanism involving two-electron reduction of the C-cluster followed by electron transfer through an internal electron transfer chain to external electron acceptors. We describe 13C NMR studies demonstrating a CODH-catalyzed steady-state exchange reaction between CO and CO2 in the absence of external electron acceptors. This reaction is characterized by a CODH-dependent broadening of the 13CO NMR resonance; however, the chemical shift of the 13CO resonance is unchanged, indicating that the broadening is in the slow exchange limit of the NMR experiment. The 13CO line broadening occurs with a rate constant (1080 s?1 at 20 °C) that is approximately equal to that of CO oxidation. It is concluded that the observed exchange reaction is between 13CO and CODH-bound 13CO2 because 13CO line broadening is pH-independent (unlike steady-state CO oxidation), because it requires a functional C-cluster (but not a functional B-cluster) and because the 13CO2 line width does not broaden. Furthermore, a steady-state isotopic exchange reaction between 12CO and 13CO2 in solution was shown to occur at the same rate as that of CO2 reduction, which is approximately 750-fold slower than the rate of 13CO exchange broadening. The interaction between CODH and the inhibitor cyanide (CN?) was also probed by 13C NMR. A functional C-cluster is not required for 13CN? broadening (unlike for 13CO), and its exchange rate constant is 30-fold faster than that for 13CO. The combined results indicate that the 13CO exchange includes migration of CO to the C-cluster, and CO oxidation to CO2, but not release of CO2 or protons into the solvent. They also provide strong evidence of a CO2 binding site and of an internal proton transfer network in CODH. 13CN? exchange appears to monitor only movement of CN? between solution and its binding to and release from CODH. PMID:18589895

2008-01-01

113

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

SciTech Connect

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.

Ji, Y., E-mail: yji@spaceweather.ac.cn [State Key Laboratory of Space Weather, Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing 100190 (China); College of Earth Science, University of Chinese Academy of Sciences, Beijing 100049 (China); Shen, C. [State Key Laboratory of Space Weather, Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing 100190 (China)] [State Key Laboratory of Space Weather, Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing 100190 (China)

2014-03-15

114

Robust strand exchange reactions for the sequence-specific, real-time detection of nucleic Acid amplicons.  

PubMed

Loop-mediated isothermal amplification (LAMP) of DNA is a powerful isothermal nucleic acid amplification method that can generate upward of 10(9) copies from less than 100 copies of template DNA within an hour. Unfortunately, although the amplification reactions are extremely powerful, real-time and specific detection of LAMP products remains analytically challenging. In order to both improve the specificity of LAMP detection and to make readout simpler and more reliable, we have replaced the intercalating dye typically used for monitoring in real-time fluorescence with a toehold-mediated strand exchange reaction termed one-step strand displacement (OSD). Due to the inherent sequence specificity of toehold-mediated strand exchange, the OSD reporter could successfully distinguish side products from true amplicons arising from templates corresponding to the biomedically relevant M. tuberculosis RNA polymerase (rpoB) and the melanoma-related biomarker BRAF. OSD allowed the Yes/No detection of rpoB in a complex mixture such as synthetic sputum and also demonstrated single nucleotide specificity in Yes/No detection of a mutant BRAF allele (V600E) in the presence of 20-fold more of the wild-type gene. Real-time detection of different genes in multiplex LAMP reactions also proved possible. The development of simple, readily designed, modular equivalents of TaqMan probes for isothermal amplification reactions should generally improve the applicability of these reactions and may eventually assist with the development of point-of-care tests. PMID:25708458

Jiang, Yu Sherry; Bhadra, Sanchita; Li, Bingling; Wu, Yuefeng Rose; Milligan, John N; Ellington, Andrew D

2015-03-17

115

Mechanism of the anion exchange reactions of the layered double hydroxides (LDHs) of Ca and Mg with Al  

NASA Astrophysics Data System (ADS)

The nitrate containing layered double hydroxide (LDH) of Ca with Al on reaction with aqueous solutions of Na 2CO 3 and Na 3PO 4 yields CaCO 3 and Ca 5(PO 4) 3OH respectively rather than the carbonate/phosphate containing LDHs. The LDH of Mg with Al on reacting with dissolved phosphate ions also leads to the formation of unitary phosphates. This shows that the anion exchange reactions of layered double hydroxides take place by the dissolution-reprecipitation mechanism rather than by the topotactic mechanism.

Radha, A. V.; Vishnu Kamath, P.; Shivakumara, C.

2005-10-01

116

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

SciTech Connect

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.

Morales, A. I.; Benlliure, J.; Alvarez-Pol, H.; Casarejos, E.; Dragosavac, D.; Perez-Loureiro, D.; Verma, S. [Universidade de Santiago de Compostela, 15782 Santiago de Compostela (Spain); Agramunt, J.; Molina, F.; Rubio, B. [IFIC, CSIC-Universidad de Valencia, E-46071 Valencia (Spain); Algora, A. [IFIC, CSIC-Universidad de Valencia, E-46071 Valencia (Spain); Institute of Nuclear Research of the Hungarian Academy of Sciences, H-4001 Debrecen (Hungary); Alkhomashi, N.; Farrelly, G.; Gelletly, W.; Pietri, S.; Podolyak, Z.; Regan, P. H.; Steer, S. J. [Department of Physics, University of Surrey, Guildford GU2 7XH (United Kingdom); Boutachkov, P.; Caceres, L. S. [GSI, Planckstrasse 1, D-64291 Darmstadt (Germany)

2011-07-15

117

The Nuclear Responses for Double Beta Neutrinos and Double Spin Isospin Resonances by Using of Double Charge Exchange Heavey Ion Reaction  

NASA Astrophysics Data System (ADS)

To study double spin-isospin responses in view of the ??? decays, double charge-exchange nuclear reactions have measured at RCNP. We have succeeded to measure the double charge exchange reaction by means of heavy ion reaction. From these experiments, we conclude that the (11B,11Li) reaction at 70 MeV/nucleon is a good spectroscopic tool. We believe that the reaction can be well applied to the study of pure spin-flip nuclear responses in higher-excited regions including DGT and higher ?L excitations.

Takahisa, K.; Akimune, H.; Ejiri, H.; Fujimura, H.; Fujiwara, M.; Hara, K.; Hasimoto, H.; Hatanaka, K.; Itahasi, T.; Kawabata, T.; Kawase, K.; Koreeda, Y.; Maehara, N.; Mordechai, S.; Nagai, Y.; Nakanishi, K.; Ninomiya, S.; Shima, T.; Tanaka, M.; Umehara, S.; Umisedo, S.; Yoshida, H. P.; Yoshida, S.; Yoshimura, M.; Yosoi, M.

2005-12-01

118

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

ERIC Educational Resources Information Center

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…

Nichols, Michael A.; Waner, Mark J.

2010-01-01

119

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

NASA Technical Reports Server (NTRS)

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.

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

2002-01-01

120

Stereo-dynamics of the exchange reaction Ha+LiHb?LiHa+Hb and its isotopic variants  

NASA Astrophysics Data System (ADS)

The quasi-classical trajectory (QCT) method is used to calculate the stereo-dynamics of the exchange reaction Ha+LiHb?LiHa+Hb and its isotopic variants based on an accurate potential energy surface reported by Prudente et al. [Prudente F V, Marques J M C and Maniero A M 2009 Chem. Phys. Lett. 474 18]. The reactive probability of the title reaction is computed. The vector correlations and four polarization-dependent generalized differential cross sections (PDDCSs) at different collision energies are presented. The influences of the collision energy and the reagent rotation on the product polarization are studied in the present work. The results indicate that the product rotational angular momentum j' is not only aligned, but also oriented along the direction perpendicular to the scattering plane. The product polarization distributions of the title reaction and its isotopic variants exhibit distinct differences which may arise from different mass combinations.

Zhai, Hong-Sheng; Yin, Shu-Hui

2012-12-01

121

The Reaction of Exchange Rates and Interest Rates to News Releases  

Microsoft Academic Search

This paper examines the response of exchange rates and interest rates--US and foreign--to economic news. The news is associated with the surprise component of the monthly release of six US macroeconomic variables. The results suggest that dollar exchange rates systematically react to news about real economic activity--a surprise of 100,000 on non-farm payroll employment leads to a 0.2% appreciation of

Hali J. Edison

1997-01-01

122

The reaction of exchange rates and interest rates to news releases  

Microsoft Academic Search

This paper examines the response of exchange rates and interest rates--U.S. and foreign--to economic news. The news is associated with the surprise component of the monthly release of six U.S. macroeconomic variables. The results suggest that dollar exchange rates systematically react to news about real economic activity--a surprise of 100,000 on nonfarm payroll employment leads to a 0.2 percent appreciation

Hali J. Edison

1996-01-01

123

A Computational Study of a Recreated G Protein-GEF Reaction Intermediate Competent for Nucleotide Exchange: Fate of the Mg Ion  

PubMed Central

Small G-proteins of the superfamily Ras function as molecular switches, interacting with different cellular partners according to their activation state. G-protein activation involves the dissociation of bound GDP and its replacement by GTP, in an exchange reaction that is accelerated and regulated in the cell by guanine-nucleotide exchange factors (GEFs). Large conformational changes accompany the exchange reaction, and our understanding of the mechanism is correspondingly incomplete. However, much knowledge has been derived from structural studies of blocked or inactive mutant GEFs, which presumably closely represent intermediates in the exchange reaction and yet which are by design incompetent for carrying out the nucleotide exchange reaction. In this study we have used comparative modelling to recreate an exchange-competent form of a late, pre-GDP-ejection intermediate species in Arf1, a well-characterized small G-protein. We extensively characterized three distinct models of this intermediate using molecular dynamics simulations, allowing us to address ambiguities related to the mutant structural studies. We observed in particular the unfavorable nature of Mg associated forms of the complex and the establishment of closer Arf1-GEF contacts in its absence. The results of this study shed light on GEF-mediated activation of this small G protein and on predicting the fate of the Mg ion at a critical point in the exchange reaction. The structural models themselves furnish additional targets for interfacial inhibitor design, a promising direction for exploring potentially druggable targets with high biological specificity. PMID:20174625

Ben Hamida-Rebaï, Mériam; Robert, Charles H.

2010-01-01

124

Studies in the reaction-separation method for the preparation of barium chloride from barite using ion exchange  

SciTech Connect

The authors report the application of an ion-exchange process as a reaction-separation strategy for the preparation of barium chloride from barite ore and sodium chloride. Experimental studies were carried out to evaluate the process efficiency and purity/yield of barium chloride using a strong acid cation-exchange resin, Tulsion T-42. The effects of various process parameters such as concentration of barium sulfide and concentration of sodium chloride were investigated, and optimization of the experimental variables was attempted. The results indicate the developed strategy to be attractive and an alternative route to existing processes. The methodology developed has large potential for the inorganic chemical process industry in general.

Gokarn, A.N.; Gaikwad, A.G.; Phalak, C.A.; Bhandari, V.M. [National Chemical Lab., Pune (India). Chemical Engineering Div.] [National Chemical Lab., Pune (India). Chemical Engineering Div.

1999-06-01

125

Aggregation-induced chemical reactions: acid dissociation in growing water clusters.  

PubMed

Understanding chemical reactivity at ultracold conditions, thus enabling molecular syntheses via interstellar and atmospheric processes, is a key issue in cryochemistry. In particular, acid dissociation and proton transfer reactions are ubiquitous in aqueous microsolvation environments. Here, the full dissociation of a HCl molecule upon stepwise solvation by a small number of water molecules at low temperatures, as relevant to helium nanodroplet isolation (HENDI) spectroscopy, is analyzed in mechanistic detail. It is found that upon successive aggregation of HCl with H(2)O molecules, a series of cyclic heteromolecular structures, up to and including HCl(H(2)O)(3), are initially obtained before a precursor state for dissociation, HCl(H(2)O)(3)···H(2)O, is observed upon addition of a fourth water molecule. The latter partially aggregated structure can be viewed as an "activated species", which readily leads to dissociation of HCl and to the formation of a solvent-shared ion pair, H(3)O(+)(H(2)O)(3)Cl(-). Overall, the process is mostly downhill in potential energy, and, in addition, small remaining barriers are overcome by using kinetic energy released as a result of forming hydrogen bonds due to aggregation. The associated barrier is not ruled by thermal equilibrium but is generated by athermal non-equilibrium dynamics. These "aggregation-induced chemical reactions" are expected to be of broad relevance to chemistry at ultralow temperature much beyond HENDI spectroscopy. PMID:21351796

Forbert, Harald; Masia, Marco; Kaczmarek-Kedziera, Anna; Nair, Nisanth N; Marx, Dominik

2011-03-23

126

Investigation of alkali ion exchange processes in waste glasses using Rutherford backscattering spectrometry and nuclear reaction analysis  

NASA Astrophysics Data System (ADS)

A series of dissolution experiments using isotopic labeled (D2 18O) aqueous solution were carried out to investigate the ion exchange mechanism in Na2O-Al2O3-SiO2 glasses with fixed Na2O and variable Al2O3 concentrations. The sodium removal and the deuterium and oxygen uptake in the glass coupons were measured using ion beam methods such as Rutherford backscattering spectrometry (RBS) and nuclear reaction analysis (NRA). Both RBS and NRA experimental spectra were simulated using the SIMNRA simulation code with a thin layer approximation. Na, D, and 18O concentrations as a function of depth in reacted and non-reacted glasses were determined using simulated spectra. On the basis of the depth distributions of these elements, three different zones (reaction, transition, and diffusion zones) were identified in both samples.

Shutthanandan, V.; Thevuthasan, S.; Baer, D. R.; Adams, E. M.; Maheswaran, S.; Engelhard, M. H.; Icenhower, J. P.; McGrail, B. P.

2001-07-01

127

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

SciTech Connect

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.

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

128

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

PubMed

Single-molecule fluorescence microscopy provided information about the real-time distribution of chemical reactivity on silicon oxide supports at the solution-surface interface, at a level of detail which would be unavailable from a traditional ensemble technique or from a technique that imaged the static physical properties of the surface. Chemical reactions on the surface were found to be uncorrelated; that is, the chemical reaction of one metal complex did not influence the location of a future chemical reaction of another metal complex. PMID:20731349

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

2010-11-01

129

Clusters [Ma(GaCp*)b(CNR)c] (M = Ni, Pd, Pt): synthesis, structure, and Ga/Zn exchange reactions.  

PubMed

Reactions of homoleptic isonitrile ligated complexes or clusters of d(10)-metals with the potent carbenoid donor ligand GaCp* are presented (Cp* = pentamethylcyclopentadienyl). Treatment of [Ni4(CNt-Bu)7], [{M(CNR)2}3] (M = Pd, Pt) and [Pd(CNR)2Me2] (R = t-Bu, Ph) with suitable amounts of GaCp* lead to the formation of the heteroleptic, tri- and tetranuclear clusters [Ni4(CNt-Bu)7(GaCp*)3] (1), [{M(CNt-Bu)}3(GaCp*)4] (M = Pd: 2a, Pt: 2b), and [{Pd(CNR)}4(GaCp*)4] (R = t-Bu: 3a, Ph: 3b). The reactions involve isonitrile substitution reactions, GaCp* addition reactions, and cluster formation reactions. The new compounds were investigated for their ability to undergo Ga/Zn exchange reactions when treated with ZnMe2. The novel tetranuclear Zn-rich clusters [Ni4GaZn7(Cp*)2Me7(CNt-Bu)6] (4) and [{Pd(CNR)}4(ZnCp*)4(ZnMe)4] (R = t-Bu: 5a, Ph: 5b) were obtained and isolated. The electronic situation and geometrical arrangement of atoms of all compounds will be presented and discussed. All new compounds are characterized by solution (1)H, (13)C NMR and IR spectroscopy, elemental analysis (EA), liquid injection field desorption ionization mass spectrometry (LIFDI-MS) as well as single crystal X-ray crystallography. PMID:24283457

Molon, Mariusz; Dilchert, Katharina; Gemel, Christian; Seidel, Rüdiger W; Schaumann, Julian; Fischer, Roland A

2013-12-16

130

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

PubMed

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

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

2012-06-21

131

Theoretical investigation of the thermodynamic structures and kinetic water-exchange reactions of aqueous Al(III)-salicylate complexes  

NASA Astrophysics Data System (ADS)

Density functional theory (DFT) calculations were performed on the structures and water-exchange reactions of aqueous Al(III)-salicylate complexes. Based on the four models (gas phase (GP); polarizable continuum model (PCM), which estimates the bulk solvent effect; supermolecule model (SM), which considers the explicit solvent effect, and supermolecule-polarizable continuum model (SM-PCM), which accounts for both types of solvent effects), we systematically conducted this study by examining three different properties of the complexes. (1) The microscopic properties of the aqueous Al(III)-salicylate complexes were studied by optimizing their various structures (including the possible 1:1 mono- and bidentate complexes, cis and trans isomers of the 1:2 bidentate complexes and 1:3 bidentate complexes) at the B3LYP/6-311+G(d, p) level. (2) The 27Al and 13C NMR chemical shifts were calculated using the GIAO method at the HF/6-311+G(d, p) level. The calculation results show that the values obtained with the SM-PCM models are in good agreement with the experimental data available in the literature, indicating that the models we employed are appropriate for Al(III)-salicylate complexes. (3) The water-exchange reactions of 1:1 mono- and bidentate Al(III)-salicylate complexes were simulated using supermolecule models at the B3LYP/6-311+G(d, p) level. The logarithm of the water-exchange rate constant (log kex) of the 1:1 bidentate complex predicted using the “log kex-dAl-OH2” correlation is 4.0, which is in good agreement with the experimental value of 3.7, whereas the calculated range of log kex of the 1:1 monodentate complexes is 1.3-1.9. By effectively combining the results for the thermodynamic static structures with the simulations of the kinetic water-exchange reactions, this work promotes further understanding of the configurations and formation mechanism of Al(III)-salicylate complexes.

Shi, Wenjing; Jin, Xiaoyan; Dong, Shaonan; Bi, Shuping

2013-11-01

132

Analysis of Meson Exchange and Isobar Currents in (e,e'p) Reactions from O-16  

E-print Network

An analysis of the effects of meson exchange and isobar currents in exclusive (e,e'p) processes from O-16 under quasi-free kinematics is presented. A model that has probed its feasibility for inclusive quasi-elastic (e,e') processes is considered. Sensitivity to final state interactions between the outgoing proton and the residual nucleus is discussed by comparing the results obtained with phenomenological optical potentials and a continuum nuclear shell-model calculation. The contribution of the meson-exchange and isobar currents to the response functions is evaluated and compared to previous calculations, which differ notably from our results. These two-body contributions cannot solve the puzzle of the simultaneous description of the different responses experimentally separated. Copyright 1999 by The American Physical Society

J. E. Amaro; A. M. Lallena; J. A. Caballero

1999-04-13

133

Quasiclassical dynamics for the H + HS abstraction and exchange reactions on the 3A? and the 3A' states  

NASA Astrophysics Data System (ADS)

A detailed quasiclassical trajectory study of the H + HS reaction yielding an exchange (H + HS) and an abstraction (H2 + S) channel has been performed by employing the new triplet 3A? and 3A' surfaces developed by our group. The cross sections for both channels are presented and found to be in good agreement with previous quantum wave packet results. The thermal rate coe?cients for abstraction channel at the temperature between 200 and 1000 K have been evaluated by averaging over a Boltzmann distribution of rotational states and compared with the available experimental values. It is found that the thermal rate coe?cients exhibit a conventional Arrhenius-type dependence on temperature, which agrees well with the experimental data. Average fractions, vibration and rotation distributions of the products H2 and HS at different collision energies have been also fully investigated. Furthermore, influence of the collision energy on the total and product-state-resolved differential cross sections (DCSs) for both channels are calculated and discussed. Some observations on the mechanism of the title reaction have been made; in particular it was discovered that reactive collisions along the collinear pathway cause the H2 product to scatter backward, while the reactive collisions with large impact parameters b, which are favored deviating from the minimum energy path, produced mainly forward scattering. For the exchange channel, the discrepancies in the DCS are also distinguished through an analysis of individual trajectories and found a double microscopic mechanism, migration or non-migration. The state-to-state DCSs provide a global perspective of the reaction mechanisms and their contribution to the final product internal energy states. The theoretical findings are discussed and compared with a kinematic constraint model.

Duan, Zhi Xin; Li, Wen Liang; Xu, Wen Wu; Lv, Shuang Jiang

2013-09-01

134

The analysis of the pantothenate synthetase reaction by positional isotope exchange  

E-print Network

the ?- and ?-nonbridge positions. The rates of these two PIX reactions were followed by ³¹P NMR spectroscopy and found to be identical. These results are consistent with the formation of enzyme-bound pantoyl-adenylate and pyrophosphate upon the mixing...

Williams, Lakenya Flatreese

2003-01-01

135

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

PubMed

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

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

2013-09-25

136

Charge exchange (p,n) reactions to the isobaric analog states of high Z nuclei: 73<=Z<=92  

NASA Astrophysics Data System (ADS)

Differential cross sections have been measured for the (p,n) reaction to the isobaric analog states of 181Ta, 197Au, 209Bi, 232Th, and 238U at an incident energy of 27 MeV. Because of the importance of collective effects in this mass region, coupled-channel calculations have been carried out in the analysis of the data. Optical potentials obtained from the Lane model for the charge exchange reaction have been used in the simultaneous analysis of coupled proton and neutron channels. The sensitivity of the calculations to the different couplings between the levels and to the magnitude of the isovector potentials, V1 and W1, is discussed. The good agreement obtained between the measured and calculated (p,n) angular distributions to the analog state confirms the validity of the Lane formalism for high-Z nuclei (Z>=50). Elastic neutron differential cross sections inferred from the coupled-channel analysis are compared with measurements available in the literature in the energy range 7-8 MeV. The results of these calculations agree with the measured values as well as the results of calculations made using global neutron optical potential parameters optimized to fit neutron data. NUCLEAR REACTIONS 181Ta, 197Au, 209Bi, 232Th, 238U(p,n)IAS; E=27 MeV; Measured ?(?) for ground-state analog transition; deduced (n,n)?(?), E=7-8 MeV; coupled-channel analysis.

Hansen, L. F.; Grimes, S. M.; Poppe, C. H.; Wong, C.

1983-11-01

137

Further links between the maximum hardness principle and the hard/soft acid/base principle: insights from hard/soft exchange reactions.  

PubMed

Ayers, Parr, and Pearson recently showed that insight into the hard/soft acid/base (HSAB) principle could be obtained by analyzing the energy of reactions in hard/soft exchange reactions, i.e., reactions in which a soft acid replaces a hard acid or a soft base replaces a hard base [J. Chem. Phys., 2006, 124, 194107]. We show, in accord with the maximum hardness principle, that the hardness increases for favorable hard/soft exchange reactions and decreases when the HSAB principle indicates that hard/soft exchange reactions are unfavorable. This extends the previous work of the authors, which treated only the "double hard/soft exchange" reaction [P. K. Chattaraj and P. W. Ayers, J. Chem. Phys., 2005, 123, 086101]. We also discuss two different approaches to computing the hardness of molecules from the hardness of the composing fragments, and explain how the results differ. In the present context, it seems that the arithmetic mean of fragment softnesses is the preferable definition. PMID:17637976

Chattaraj, Pratim K; Ayers, Paul W; Melin, Junia

2007-08-01

138

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

PubMed

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

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

2014-11-01

139

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

PubMed

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

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

2004-08-25

140

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

NASA Astrophysics Data System (ADS)

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.

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

2010-12-01

141

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

E-print Network

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}.

Uzikov, Yu N; Wilkin, C

2015-01-01

142

Determination of alkanolamines in cattails (Typha latifolia) utilizing electrospray ionization with selected reaction monitoring and ion-exchange chromatography.  

PubMed

Selected reaction monitoring (SRM) with electrospray ionization was used as a specific detection technique for the analysis of alkanolamines in plant tissue extracts. Ion-exchange chromatography was used as the method of separation. Quantification was based on monitoring the loss of either H2O or 2(H2O) from the protonated molecule [M+H]+. The method provided increased selectivity for all analytes and better detection limits for three of the six analytes investigated compared with an earlier method using selected ion monitoring with liquid chromatography. Instrumental detection limits ranged from 6-300 pg injected for monoethanolamine (MEA), monoisopropanolamine (MIPA), diethanolamine (DEA), methyldiethanolamine (MDEA), diisopropanolamine (DIPA), and triethanolamine (TEA). Method robustness and selectivity were demonstrated by the determination of DIPA and a known transformation product MIPA in over 35 plant extract samples derived from a laboratory study of plant uptake mechanisms. PMID:15282789

Peru, Kerry M; Headley, John V; Doucette, William J

2004-01-01

143

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

NASA Astrophysics Data System (ADS)

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.

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

2010-12-01

144

Investigation of Isovector Giant Resonances Using the (LITHIUM-7, BERYLLIUM-7) Charge-Exchange Reaction at 50 Mev/u.  

NASA Astrophysics Data System (ADS)

Isovector giant resonances have been investigated using the (^7Li, ^7 Be) charge-exchange reaction in neutron-rich nuclei. The (^7Li,^7Be) reaction has characteristics similar to the (n,p) reaction, since ^7Li and ^7 Be are mirror nuclei with identical intrinsic configurations. The ^7Be has only one particle-stable excited state at 430 keV. The spins and parities of the ^7Li and ^7Be ground states and the ^7Be first excited state are 3/2^-, 3/2 ^-, and 1/2^-, respectively. Therefore, the transition to the ^7Be ground state has both spin-flip and non-spin-flip components, while the transition to the ^7Be excited first excited state is a pure spin-flip transition. The spin-flip or non-spin-flip characteristics of giant resonances can be determined by separately detecting the transitions to the ^7 Be_{gs} and ^7 Be_{ex }. Target nuclei of ^1H, ^6Li, ^{12} C, ^{90}Zr, ^{120}Sn and ^{208 }Pb were investigated in the present work. The ^7 Li^{+3 } beam of energy 50 MeV/u was produced by the K1200 Cyclotron at the National Superconducting Cyclotron Laboratory. The outgoing ^7Be particles were analyzed with the S320 QQDMS magnetic spectrograph for the finite-angle measurements, and with the A1200 magnetic analysis system for the zero degree measurements. The gamma-rays were measured with an array of BGO (Bismuth Germanate) detectors located very close to the target. They were detected in singles mode and in coincidence with 430 keV Doppler-shifted gamma-rays from the decay in flight of the excited ^7 Be_{ex} . About 20 giant resonances were observed in the residual nuclei. Of these, only about 13 resonances have been observed before in other charge-exchange reactions. About half of the observed resonances correspond to theoretically predicted resonances. The new resonance observed in ^6He at 5.6 MeV was predicted earlier to be a "soft giant dipole" resonance. However, the present work indicates a spin-flip transition to this resonance which contradicts such an interpretation. Angular distributions for the transitions to states in ^6He and ^{12}B were measured and compared with theoretical predictions using the fully microscopic, finite-range, di storted-wave-Born-approximation code FOLD. Excellent agreement was observed for the ground state of ^6He and ^ {12}B.

Annakkage, Thilina Nilasiya

1995-01-01

145

Viking gas exchange reaction - Simulation on UV-irradiated manganese dioxide substrate  

NASA Technical Reports Server (NTRS)

The exchange of O2 for H2O, analogous to that recorded on Mars by the Viking GEX experiment, has been observed on humidifying powdered beta-MnO2 (pyrolusite) which had been irradiated by UV in a humidified analog of the Martian atmosphere. Pyrolusite irradiated in a dry atmosphere did not release O2 on humidification. The XPS spectra of Mn and O of the reactive pyrolusite were shifted toward higher binding energies during UV irradiation. These shifts are consistent with the creation of a surface layer of a Mn(V) or Mn(VI) compound. The destruction of such a layer on humidification could account for the observed O2 release. Although manganese has not been identified in the Martian regolith, the upper limit of the Mn concentration is sufficiently high that O2 release from pyrolusite could have been responsible for the results of the Viking GEX experiment.

Blackburn, T. R.; Holland, H. D.; Ceasar, G. P.

1979-01-01

146

Studies on the reaction of the 5'-phosphorimidazolide of adenosine with Cu(II)-exchanged hectorite  

NASA Astrophysics Data System (ADS)

The role of clay minerals in the prebiotic synthesis of nucleotide oligomers has received considerable attention in recent years. Scanning force microscopy and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry are used to identify oligomers of adenylic acid formed on the clay mineral Cu(II)-exchanged hectorite in simulated prebiotic cycling experiments. Electron-spin resonance and x-ray diffraction data indicate that the monomer (5'-phosphorimidazolide of adenosine, or ImpA) penetrates into the intergallery regions of the mineral substrate, and complexes the gallery Cu(II) cations. It is postulated that polymerization of the monomer is initiated in the clay intergallery regions, producing oligomers of adenylic acid up to 8 units in length or more.

Porter, T. L.; Whitehorse, R.; Eastman, M. P.; Bain, E. D.

1999-10-01

147

Simple ligand exchange reactions enabling excellent dispersibility and stability of magnetic nanoparticles in polar organic, aromatic, and protic solvents.  

PubMed

The use of magnetic nanoparticles (MNPs) in real-world applications is often limited by the lack of stable solutions of monodisperse NPs in appropriate solvents. We report a facile one-pot ligand exchange reaction that is fast, efficient, and thorough for the synthesis of hydrophilic MNPs that are readily dispersed in polar organic and protic solvents (polarity index = 3.9-7.2) including alcohols, THF, DMF, and DMSO for years without precipitation. We emphasize the rational selection of small-molecule ligands such as 4-hydroxybenzoic acid (HBA), 3-(4-hydroxyphenyl)propionic acid (HPP), and gallic acid (GAL) that provide strong bonding with the MNP (FePt and FeOx) surfaces, hydrophilic termini to match the polarity of target solvents, and offer the potential for hydrogen-bonding interactions to facilitate incorporation into polymers and other media. Areal ligand densities (?) calculated based on the NP core size from transmission electron microscopy (TEM) images, and the inorganic fractions of NPs derived from thermogravimetric analysis (TGA) indicated a significant (2-4 times) increase in the ligand coverage after the exchange reactions. Fourier transform infrared spectrometry (FTIR) and (1)H nuclear magnetic resonance (NMR) studies also confirmed anchoring of carboxyl groups on NP surfaces. In addition, we demonstrate a facile one-step in situ synthesis of FePt NPs with aromatic ligands for better dispersibility in solvents of intermediate polarity (polarity index = 1.0-3.5) such as toluene, chlorobenzene, and dichloromethane. The creation of stable dispersions of NPs in solvents across the polarity spectrum opens up new applications and new processing widows for creating NP composites in a variety of host materials. PMID:24460074

Wang, Xinyu; Tilley, Richard D; Watkins, James J

2014-02-18

148

Heat and mass exchange in films of a reacting mixture and a cooling liquid under exothermic-reaction conditions  

NASA Astrophysics Data System (ADS)

Conjugate turbulent heat and mass exchange in fast exothermic reactions in thin films has been investigated with allowance for the change in the pressure. A modification of the equal-flow-rate method, the most natural for problems of such a kind, has been constructed. Its distinctive feature is that it is constructed on formal passage to a rectangular domain of variation in variables. The modification obtained has been tested on the problem solved earlier by the well-known equal-flow-rate method. Despite the fact that the proposed mathematical model and the procedure of its investigation enjoy rather wide application, in the present work, it is oriented toward the cationic liquid-phase polymerization of isobutylene. The local concentration distributions of the monomer and the catalyst and the temperature distributions have been obtained in numerical investigations. The reaction and cooling zones have been singled out; it has been recorded that the process of the most active chemical transformation is localized by the narrow zone of entry into the film.

Kholpanov, L. P.; Zakiev, S. E.

2008-05-01

149

Oxide acid-base reaction relating to the inhibition of vandium attack on REY zeolite catalysts. [Rare earth-exchanged yttrium  

Microsoft Academic Search

Certain materials, especially Sn, passivate the rare earth-exchanged Y zeolite (REY) used in petrochemical fluid-cracking catalysts against vanadium degradation caused by V impurities in the feed oil. The mechanism of passivation was investigated here from the standpoint of high-temperature oxide acid-base reaction; i.e., where the controlling factors were considered to be Lewis acid-base reactions between VâOâ, the RE oxides, SnOâ,

1991-01-01

150

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)

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.

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

1989-01-01

151

Methane to Acetic Acid over Cu-Exchanged Zeolites: Mechanistic Insights from a Site-Specific Carbonylation Reaction.  

PubMed

The selective low temperature oxidation of methane is an attractive yet challenging pathway to convert abundant natural gas into value added chemicals. Copper-exchanged ZSM-5 and mordenite (MOR) zeolites have received attention due to their ability to oxidize methane into methanol using molecular oxygen. In this work, the conversion of methane into acetic acid is demonstrated using Cu-MOR by coupling oxidation with carbonylation reactions. The carbonylation reaction, known to occur predominantly in the 8-membered ring (8MR) pockets of MOR, is used as a site-specific probe to gain insight into important mechanistic differences existing between Cu-MOR and Cu-ZSM-5 during methane oxidation. For the tandem reaction sequence, Cu-MOR generated drastically higher amounts of acetic acid when compared to Cu-ZSM-5 (22 vs 4 ?mol/g). Preferential titration with sodium showed a direct correlation between the number of acid sites in the 8MR pockets in MOR and acetic acid yield, indicating that methoxy species present in the MOR side pockets undergo carbonylation. Coupled spectroscopic and reactivity measurements were used to identify the genesis of the oxidation sites and to validate the migration of methoxy species from the oxidation site to the carbonylation site. Our results indicate that the Cu(II)-O-Cu(II) sites previously associated with methane oxidation in both Cu-MOR and Cu-ZSM-5 are oxidation active but carbonylation inactive. In turn, combined UV-vis and EPR spectroscopic studies showed that a novel Cu(2+) site is formed at Cu/Al <0.2 in MOR. These sites oxidize methane and promote the migration of the product to a Brønsted acid site in the 8MR to undergo carbonylation. PMID:25562431

Narsimhan, Karthik; Michaelis, Vladimir K; Mathies, Guinevere; Gunther, William R; Griffin, Robert G; Román-Leshkov, Yuriy

2015-02-11

152

Grafting of polymers onto vapor grown carbon fiber surface by ligand-exchange reaction of ferrocene moieties of polymer with polycondensed aromatic rings of the wall-surface  

Microsoft Academic Search

To improve the dispersibility of vapor grown carbon fiber (VGCF) in solvents, the grafting of copolymer containing vinyl ferrocene (VFE) onto the surface by ligand-exchange reaction between ferrocene moieties of the copolymer and polycondensed aromatic rings of VGCF was investigated. The copolymer containing VFE was prepared by the radical copolymerization of VFE with methyl methacrylate (MMA) using 2, 2?-azobisisobutyronitrole as

Gang Wei; Satoshi Saitoh; Hiroshi Saitoh; Kazuhiro Fujiki; Takeshi Yamauchi; Norio Tsubokawa

2004-01-01

153

Tuning the Optical Properties of Nanoscale Materials on Surfaces Through Controlled Exchange Reactions on Cadmium Selenide Quantum Dots and Patterning of Gold and QD Nanoparticle Arrays  

E-print Network

their surface and optical properties to study their fundamental chemical and physical processes as well as their applications. First, the cation exchange reactions between CdSe QDs and Ag+ cations were explored as the surface properties of the QDs were...

Pravitasari, Arika

2013-11-11

154

Computational modeling of transport and electrochemical reactions in proton-exchange membrane fuel cells  

NASA Astrophysics Data System (ADS)

A comprehensive, multi-physics computational fuel cell dynamics (CFCD) model integrating electrochemical kinetics, charge transport, mass transport (particularly water transport), and flow dynamics is developed in this thesis. The numerical model is validated against published experimental data and utilized to generate results that reveal the internal operation of a PEM fuel cell. A number of model applications are demonstrated in the present work. First, the CFCD model is applied to explore hydrogen dilution effects in the anode feed. Detailed two-dimensional electrochemical and flow/transport simulations are provided to examine substantial anode concentration polarization due to hydrogen depletion at the reaction sites. A transient simulation of the cell current response to a step change in cell voltage is also attempted to elucidate characteristics of the dynamic response of a fuel cell for the first time. After the two-dimensional computational study, the CFCD model is applied to illustrate three-dimensional interactions between mass transfer and electrochemical kinetics. Emphasis is placed on obtaining a fundamental understanding of fully three-dimensional flow in the air cathode with interdigitated flowfield design and how it impacts the transport and electrochemical reaction processes. The innovative design concept for enhanced oxygen transport to, and effective water removal from the cathode, is explored numerically. Next, an analytical study of water transport is performed to investigate various water transport regimes of practical interest. The axial locations characteristic of anode water loss and cathode flooding are predicted theoretically and compared with numerical results. A continuous stirred fuel cell reactor (CSFCR) model is also proposed for the limiting situation where the anode and cathode sides reach equilibrium in water concentration with a thin ionomer membrane in between. In addition to the analytical solutions, a detailed water transport model extending the CFCD framework is developed in which a unified water equation is arrived at using the equilibrium water uptake curve between the gas and membrane phases. Various modes of water transport, i.e. diffusion, convection, and electro-osmotic drag, are incorporated in the unified water transport equation. This water transport model is then applied to elucidate water management in three-dimensional fuel cells with dry to low humidified inlet gases after its validation against available experimental data with dry oxidant and fuel streams. An internal circulation of water with the aid of counter-flow design is found to be essential for low-humidity operation, for example, in portable application of a PEM fuel cell without external humidifier. Finally, to handle the most important issue associated with PEM fuel cells using reformate gas, namely the CO poisoning anode Pt catalysts, a major modification of the present CFCD model is made to include CO oxidation processes. A four-step CO poisoning mechanism is implemented here and anode species equation for CO is added to model the electro- and chemical-oxidation processes on the anode. Numerical results of CO poisoning effects using a commercial package, STAR-CD, are presented. Basic features of CO poisoning are delineated and discussed. Future research areas of the fuel cell modeling are also indicated. As an example, preliminary results of extending the CFCD model to include heat transfer using a commercial package, FLUENTRTM, are given to demonstrate the need for careful thermal management in a multi-cell stack design.

Um, Sukkee

155

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

PubMed

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

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

2015-04-14

156

Nanosized IrxRu1?xO2 electrocatalysts for oxygen evolution reaction in proton exchange membrane water electrolyzer  

NASA Astrophysics Data System (ADS)

Normally in proton exchange membrane water electrolysis (PEMWE), the anode has the largest overpotential at typical operating current densities. By development of the electrocatalytic material used for the oxygen evolving electrode, great improvements in efficiency can be performed. In electrochemistry, rare metallic oxides RuO2 and IrO2 exhibit the best catalytic properties for the oxygen evolution reaction (OER) in acid electrolytes compared to other noble metals. RuO2 is the most active catalyst and IrO2 is the most stable catalyst. An oxide containing both elements is therefore expected to be a good catalyst for the OER. In this study IrxRu1?xO2 nanosized powder electrocatalysts for oxygen evolution reaction is synthesized by hydrolysis method. Cyclic voltammetry, anodic polarization and galvanostatic measurements were conducted in solution of 0.5 M H2SO4 to investigate electrocatalytic behavior and stability of the electrocatalyst. The mechanisms of the thermal decomposition process of RuCl3.nH2O and IrCl3.mH2O precursors to form oxide powders were studied by means of thermal gravity analysis (TGA). X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used analysis for determination of the crystallographic structure, morphology and catalysts particle size. Based on the given results, the IrxRu1?xO2 (x = 0.5 0.7) compounds were found to be more active than pure IrO2 and more stable than pure RuO2.

Hanh Pham, Hong; Nguyen, Ngoc Phong; Linh Do, Chi; Thang Le, Ba

2015-01-01

157

Vibrational analysis of pyruvate ion molecules and estimation of equilibrium constants for their hydrogen isotopic exchange reactions  

SciTech Connect

The infrared spectra (4000 to 200 cm/sup -1/) of CH/sub 3/COCOONa and its four isotopic substitutions including /sup 13/C- and /sup 18/O-labeled modifications suspended in KBr disks were measured. Complete vibrational assignments were established on the basis of the isotope shifts of the fundamentals and a normal-coordinate analysis. From the normal-coordinate analysis a general valence force field involving 40 force constants, 7 of them being transferred from pyruvic acid, has been determined, which reproduced 90 experimental frequencies with a root-mean-squares deviation of 2.1 cm/sup -1/. The valence force field was used to estimate fundamental frequencies which were not obtained from direct observation, and the reduced partition function ratios of the pyruvate ion molecules were evaluated by using the spectroscopic data including the predicted values of the fundamentals. The calculated equilibrium constants of some hydrogen isotopic exchange reactions between the pyruvate ion molecules were reported.

Kakihana, M.; Okamoto, M.

1984-04-26

158

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

PubMed

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

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

2014-08-01

159

Attenuated total reflection infrared studies of oleate and trioctylphosphine oxide ligand adsorption and exchange reactions on CdS quantum dot films.  

PubMed

Ligand exchange reactions at the surface of oleate- and trioctylphosphine oxide (TOPO)-capped CdS quantum dots have been studied with attenuated total reflection infrared (ATR-IR) spectroscopy, using thin films deposited from organic solvent suspensions. The oleate and trioctylphosphine capping ligands were found to form highly ordered and densely packed monolayers on the CdS surface. Adsorbed oleate is coordinated to CdS in a chelating bidentate manner through the carboxylate functional group, while adsorbed trioctylphosphine oxide is coordinated though the P=O functional group and appears to have numerous adsorption environments on the CdS surface. Exposure of such films to aqueous solution was found to cause partial delamination of the films from the ATR prism interface which was reversible upon redrying. Ligand exchange reactions on the oleate- and trioctylphosphine-capped CdS films were studied in situ at room temperature by allowing the films to be exposed to dilute aqueous solutions of thiol-containing ligands. Oleate and trioctylphosphine oxide are both strongly adsorbed to the CdS surface, and ligand exchange with monothiol-containing ligands has been found to be highly dependent upon experimental conditions, in particular pH, where exchange is only observed at solution pH where the exchanging ligand is uncharged. This is attributed to the inability of a charged ligand to penetrate the hydrophobic polymethylene layer on the CdS surface. PMID:18312011

Young, Aidan G; Al-Salim, Najeh; Green, David P; McQuillan, A James

2008-04-15

160

reactions  

Microsoft Academic Search

Gene regulatory, signal transduction and metabolic networks are major areas of interest in the newly emerging field of systems biology. In living cells, stochastic dynamics play an important role; however, the kinetic parameters of biochemical reactions necessary for modelling these processes are often not accessible directly through experiments. The problem of estimating stochastic reaction constants from molecule count data measured,

S. Reinker; R. M. Altman; J. Timmer

161

Amine exchange reactions of 3- tert -butyl-6-(methylsulfanyl)-1,2,3,4-tetrahydro-1,3,5-triazine hydroiodide with amino acids  

Microsoft Academic Search

3-tert-Butyl-6-(methylsulfanyl)-1,2,3,4-tetrahydro-1,3,5-triazine hydroiodide enters into the amine exchange reaction with glycine\\u000a and ?-alanine in aqueous solution. The final exchange products are [4-(methylsulfanyl)-5,6-dihydro-1,3,5-triazin-3-ium-1(2H)-yl] acetate and 3-[4-(methylsulfanyl)-5, 6-dihydro-1,3,5-triazin-3-ium-1(2H)-yl] propanoate, respectively, crystallizing together with t-butylamine hydroiodide from aqueous or aqueous alcoholic solutions as ion associates, which also can be detected in solution\\u000a in DMSO-d\\u000a 6. [4-(Methylsulfanyl)-5,6-dihydro-1,3,5-triazin-3-ium-1(2H)-yl] acetate can be extracted directly from the reaction

Sun Min’yan’; S. M. Ramsh; V. S. Fundamenskii; S. Yu. Solov’eva; V. I. Zakharov

2010-01-01

162

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

PubMed

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 O(2-) into S(2-) 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. PMID:25865464

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

2015-05-01

163

Characterization of the dynamic oxygen migration over Pt\\/CeO 2-ZrO 2 catalysts by 18 O\\/ 16 O isotopic exchange reaction  

Microsoft Academic Search

To characterize the oxygen mobility over metal supported catalysts on a dynamic and in situ base, 18O\\/16O isotopic exchange reaction combined with CO oxidation was designed and exemplified on three kinds of three way catalysts of Pt\\/CeO2-ZrO2 (CZ-O, CZ-D and CZ-R). The obtained oxygen diffusion coefficients, oxygen release rate, and oxygen storage capacity were discussed and correlated with XRD spectra

F Dong; A Suda; T Tanabe; Y Nagai; H Sobukawa; H Shinjoh; M Sugiura; C Descorme; D Duprez

2004-01-01

164

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

Microsoft Academic Search

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

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

1995-01-01

165

Gas phase hydrogen deuterium exchange reactions of a model peptide: FT-ICR and computational analyses of metal induced conformational mutations  

Microsoft Academic Search

We utilized gas phase hydrogen\\/deuterium (H\\/D) exchange reactions and ab initio calculations to investigate the complexation\\u000a between a model peptide (Arg-Gly-Asp?RGD) with various alkali metal ions. The peptide conformation is drastically altered\\u000a upon alkali metal ion complexation. The associated conformational changes depend on both the number and type of complexing\\u000a alkali metal ions. Sodium has a smaller ionic diameter and

T. Solouki; R. C. Fort; A. Alomary; A. Fattahi

2001-01-01

166

Stability Order of Caffeine Co-crystals Determined by Co-crystal Former Exchange Reaction and Its Application for the Validation of in Silico Models.  

PubMed

The purpose of the present study was to determine the thermodynamic stability orders of co-crystals by co-crystal former (CCF) exchange reactions. Caffeine (CA) was employed as a model drug. The CCF exchange reaction was performed by liquid-assisted grinding using ethanol. When oxalic acid (OX) was added to CA-citric acid co-crystal (CA-CI), CA-CI converted to CA-OX, suggesting that CA-OX is more stable than CA-CI. The stability orders of other co-crystals were determined in the same manner. The stability order of CA co-crystals was determined as CA-OX?CA-p-hydroxybenzoic acid (HY)>CA-CI>CA-malonic acid>CA-maleic acid. The stability order correlated with the difference in hydrogen bond energy estimated in silico, except for CA-HY. The ?-? stacking in CA-HY was suggested as a reason for this discrepancy. The CCF exchange reaction was demonstrated as a useful method to determine the stability order of co-crystals, which can be used for the validation of in silico parameters to predict co-crystal formation. PMID:25743190

Mukaida, Makoto; Sugano, Kiyohiko; Terada, Katsuhide

2015-01-01

167

Metal chalcogenide nanoparticle gel networks: Their formation mechanism and application for novel material generation and heavy metal water remediation via cation exchange reactions  

NASA Astrophysics Data System (ADS)

The dissertation research is focused on (1) uncovering the mechanism of metal chalcogenide nanoparticle gel formation; (2) extending the cation exchange reaction protocol to zinc sulfide gel networks, with the goal of accessing new aerogel chemistries and understanding the factors that drive the process; and (3) conducting a quantitative analysis of the ability of ZnS aerogels to remove heavy metal ions from aqueous solutions. The mechanism of metal chalcogenide nanoparticle gel formation was investigated using Raman spectroscopy and X-ray Photoelectron Spectroscopy to probe the chemical changes that occur during the gelation process. These techniques suggest that the bonding between the particles in the CdSe nanoparticle gels is due to the oxidation of surface selenide species, forming covalent Se--Se bonds. Treating the gel networks with a suitable reducing agent, such as a thiol, breaks the covalent bond and disperses the gel network. The addition of sodium borohydride, a "pure" reducing agent, also breaks down the gel network, strengthening the hypothesis that the reducing character of the thiols, not their ligation ability, is responsible for the gel network breakdown. UV-Vis spectroscopy, Transmission Electron Microscopy and Powder X-ray Diffraction were used to analyze the particles after successive gelation-dispersion cycles. The primary particle size decreases after repeated oxidation-reduction cycles, due to nanoparticle surface etching. This trend is observed for CdSe and CdS gel networks, allowing for the proposition that the oxidative-reductive mechanism responsible for the formation-dispersion of the gels is general, applying to other metal chalcogenide nanocrystals as well. The cation exchange reaction previously demonstrated for CdSe gels was extended to ZnS gel networks. The exchange occurs under mild reaction conditions (room temperature, methanol solvent) with exchanging ions of different size, charge and mobility (Ag+, Pb2+, Cd2+ , Cu2+). The overall reaction is kinetically controlled, since systems with similar solubility, and thus similar thermodynamic driving force (e.g. PbS and CdS) exchange at very different rates. A correlation exists between the speed of the reaction and the difference between the reduction potential of the incoming cation and that of Zn2+; the larger the difference, the faster the exchange. At the same time, the porosity of the aerogels and the surfactant-free surfaces hold great importance for the exchange reactions, allowing for exchange between cations of similar size and charge (i.e. Pb2+ for Zn2+), a phenomenon that was previously reported as impossible in ligand-capped metal chalcogenide nanoparticles. These observations allowed for a better understanding of the factors governing the cation exchange reaction in nanoscale metal chalcogenides. Quaternary ZnS-CuInS2 gels were obtained by cation exchange with Cu+ and In3+, but the pure CuInS2 phase was not obtained under the mild reaction conditions used, probably due to the very different mobility of the two exchanging cations. The kinetically fast cation exchange process and the propensity of the soft chalcogenide gel networks to bind heavy metal ions selectively, suggest that these materials could also be suitable for the removal of heavy metal ions from the environment. The dissertation research studied the capacity of ZnS aerogels to sequester heavy metal ions such as Pb2+ and Hg2+ from water. The materials are efficient in removing the heavy metal ions from aqueous solutions with a wide range of initial concentrations. For initial concentrations that mimic an environmental spill (i.e. 100 ppb Pb2+), the treatment with the aerogel affords a final concentration lower than the 15 ppm action level recommended by the EPA. Under thermodynamically forcing conditions, the water remediation capacity of the ZnS nanoparticle aerogels was determined to be 14.2 mmol Pb2+ / g ZnS aerogel, which is the highest value reported to date.

Palhares, Leticia F.

168

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

NASA Astrophysics Data System (ADS)

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

Woensdregt, Cornelis F.; Glikin, Arkady E.

2005-10-01

169

Occurrence and characteristics of ¹⁸O exchange reactions catalyzed by sodium- and potassium-dependent adenosine triphosphates  

Microsoft Academic Search

Microsomal preparations of the Na\\/sup +\\/, K\\/sup +\\/-ATPase from the porcine kidney outer medulla and the Electrophorus electroplax catalyzed a rapid Mg\\/sup 2 +\\/- and K\\/sup +\\/-dependent exchange of water oxygens with inorganic phosphate in the absence of ATP or ADP. Exchange activity was unaffected by uncouplers and inhibitors of oxidative phosphorylation but was inhibited by Na\\/sup +\\/, ouabain, N,N'-dicyclohexylcarbodiimide,

A. S. Dahms; P. D. Boyer

1973-01-01

170

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

NASA Astrophysics Data System (ADS)

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

Noji, Shumpei; Sakai, Hideyuki

2009-10-01

171

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

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

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

2003-10-31

172

Effect of grossular on garnet-biotite, Fe–Mg exchange reactions: evidence from garnet with mixed growth and diffusion zoning  

Microsoft Academic Search

Garnets that exhibit mixed growth and diffusion zoning are used to evaluate the effect of grossular content on garnet Fe–Mg\\u000a exchange reactions. These garnets from the uppermost amphibolite-facies to granulite-facies gneiss of the Wissahickon Group,\\u000a southeastern Pennsylvania, show variation in grossular content (0.035X\\u000a CaX\\u000a Mg\\/(X\\u000a Mg+X\\u000a Fe) and X\\u000a Mn through the interior indicating re-equilibration of garnet and matrix minerals

J. Alcock

1996-01-01

173

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

E-print Network

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

Navarre, Audrey

1999-01-01

174

Human immunodeficiency virus-1 protease. 1. Initial velocity studies and kinetic characterization of reaction intermediates by sup 18 O isotope exchange  

SciTech Connect

The peptidolytic reaction HIV-1 protease has been investigated by using four oligopeptide substrates, Ac-Ser-Gln-Asn-Pro-Val-Val-NH{sub 2}, Ac-Arg-Ala-Ser-Gln-Asn-Tyr-Pro-Val-Val-NH{sub 2}, Ac-Ser-Gln-Ser-Tyr-Pro-Val-Val-NH{sub 2}, and Ac-Arg-Lys-Ile-Leu-Phe-Leu-Asp-Gly-NH{sub 2} that resemble two cleavage sites found within the naturally occurring polyprotein substrates Pr55{sup gag} and Pr160{sup gag-pol}. By use of a variety of inorganic salts, it was concluded that the peptidolytic reaction is nonspecifically activated by increasing ionic strength. V/K increased in an apparently parabolic fashion with increasing ionic strength, while V was either increased or decreased slightly. From product inhibition studies, the kinetic mechanism of the protease is either random or ordered uni-bi, depending on the substrate studied. The protease-catalyzed exchange of an atom of {sup 18}O from H{sub 2}{sup 18}O into the re-formed substrates occurred at a rate which was 0.01-0.12 times that the forward peptidolytic reaction. The results of these studies are in accord with the formation of a kinetically competent enzyme-bound amide hydrate intermediate, the collapse of which is the rate-limiting chemical step in the reaction pathway.

Hyland, L.J.; Tomaszek, T.A. Jr.; Roberts, G.D.; Carr, S.A.; Magaard, V.W.; Bryan, H.L.; Fakhoury, S.A.; Moore, M.L.; Minnich, M.D.; Culp, J.S.; DesJarlais, R.L.; Meek, T.D. (Smline Beecham Pharmaceuticals, King of Prussia, PA (United States))

1991-08-27

175

Study of the $\\vec{p}d \\to n\\{pp\\}_{s}$ charge-exchange reaction using a polarised deuterium target  

E-print Network

The vector and tensor analysing powers, $A_y$ and $A_{yy}$, of the $\\vec{p}d \\to n\\{pp\\}_{s}$ charge-exchange reaction have been measured at a beam energy of 600 MeV at the COSY-ANKE facility by using an unpolarised proton beam incident on an internal storage cell target filled with polarised deuterium gas. The low energy recoiling protons were measured in a pair of silicon tracking telescopes placed on either side of the target. Putting a cut of 3 MeV on the diproton excitation energy ensured that the two protons were dominantly in the $^{1}S_{0}$ state, here denoted by $\\{pp\\}_{s}$. The polarisation of the deuterium gas was established through measurements in parallel of proton-deuteron elastic scattering. By analysing events where both protons entered the same telescope, the charge-exchange reaction was measured for momentum transfers $q\\geq 160$ MeV/$c$. These data provide a good continuation of the earlier results at $q\\leq 140$ MeV/$c$ obtained with a polarised deuteron beam. They are also consistent with impulse approximation predictions with little sign evident for any modifications due to multiple scatterings.

B. Gou; D. Mchedlishvili; Z. Bagdasarian; S. Barsov; D. Chiladze; S. Dymov; R. Engels; M. Gaisser; R. Gebel; K. Grigoryev; M. Hartmann; A. Kacharava; A. Khoukaz; P. Kulessa; A. Kulikov; A. Lehrach; Z. Li; N. Lomidze; B. Lorentz; G. Macharashvili; S. Merzliakov; M. Mielke; M. Mikirtychyants; S. Mikirtychyants; M. Nioradze; H. Ohm; D. Prasuhn; F. Rathmann; V. Serdyuk; H. Seyfarth; V. Shmakova; H. Ströher; M. Tabidze; S. Trusov; D. Tsirkov; Yu. Uzikov; Yu. Valdau; T. Wang; C. Weidemann; C. Wilkin; X. Yuan

2014-08-08

176

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

PubMed

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

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

2014-12-01

177

Absolute level-to-level rate constants for inelastic collisions and exchange reactions in lithium + gaseous lithium(v,j) going to gaseous lithium(v',j') + lithium  

NASA Astrophysics Data System (ADS)

We report 644 absolute level-to-level inelastic and reactive constants for the L7i*2 A1S+u (nui, ji) + 7Li ? L7i*2 A1S+u (nu', j') + 7Li system with initial molecular quantum numbers nui = 2 and ji = 3, 11, and 19. We collected 87 rate constants for rotationally inelastic and vibrationally elastic collisions, 281 rate constants for vibrationally inelastic collisions, and 276 constants for exchange reactions with final vibrational levels from nu f = 0 to nuf = 3. Inelastic collisions are characterized by even changes in rotational quantum number, j , and exchange reactions are identified by odd Deltaj. Level-to-level rate constants for even Deltaj inelastic collisions show distributions similar to those in rare gas collisions with the excited Li2 molecule. The ECS (energy corrected sudden) scaling law of DePristo, et al., fit the vibrationally elastic data well. Reactive rate constant results are characterized by a statistical distribution for Deltanu of 0, -1, and -2 at a substantially reduced effective temperature consistent with a kinematic model proposed by Picconatto et al. Fitting quasiclassical trajectory studies to the data using a modified LEPS potential surface provide first insights into the parameters of the excited-state Li3* three-body potential.

Coppage, Steven Danforth

178

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)

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.

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

2007-02-01

179

Fully converged integral cross sections of collision induced dissociation, four-center, and single exchange reactions, and accuracy of the centrifugal sudden approximation in H2 + D2 reaction  

NASA Astrophysics Data System (ADS)

The initial state selected time-dependent wave packet method was employed to calculate the integral cross sections for the H2 + D2 reaction with and without the centrifugal sudden (CS) approximation by including all important K (the projection of the total angular momentum on the body-fixed axis) blocks. With a full-dimensional model, the first fully converged coupled-channel (CC) cross sections for different competitive processes from the ground rotational state were obtained: collision induced dissociation (CID), four-center (4C) reaction and single exchange (SE) reaction. The effect of the total angular momentum J on the reaction dynamics of H2 + D2 and the accuracy of the CS approximation have also been studied. It was found that the CID and SE processes occur in a wide range of J values while the 4C process can only take place in a narrow window of J values. For this reason, the CC cross section for the 4C channel is merely comparable to the SE channel. A comparison of the integral cross sections from CC and CS calculations showed that the CS approximation works well for the CID process but not for the 4C and SE processes, and the discrepancy between the CC and CS cross sections grows larger as the translational energy and/or the vibrational energy increase(s).

Song, Hongwei; Lu, Yunpeng; Lee, Soo-Y.

2012-03-01

180

New reactions and theory in organic photochemistry: The 1,3-vinyl migration and its relevance to exchange integral control*  

PubMed Central

The photochemistry of 1,1,4-triphenyl-1,4-pentadiene was investigated. Sensitized irradiation of this compound labeled at carbon 3 with 2H led to a degenerate rearrangement wherein the diphenylvinyl moiety migrated 1,3, thus affording diene with 2H substitution at carbon 5. In contrast, direct irradiation of the triphenyl pentadiene led to 1,3,3-triphenylbicyclo[2.1.0]pentane by a [2 + 2] cycloaddition. This multiplicity dependence of the photochemistry is understood on the basis of triplet reactants preferring a linearly conjugated diradical mechanism with a large exchange integral (K) and singlet reactants preferring an electrocyclic mechanism with a small exchange integral. PMID:16593003

Zimmerman, Howard E.; Penn, John H.; Johnson, Mark R.

1981-01-01

181

Theoretical studies of the alteration of spodumene, petalite, eucryptite and pollucite in granitic pegmatites: exchange reactions with alkali feldspars  

Microsoft Academic Search

The ratios Na\\/Li, K\\/Li, Na\\/Cs and K\\/Cs have been calculated for exchange equilibria among the Li and Cs silicates spodumene, petalite, eucryptite, and pollucite, and the alkali feldspars albite and K-feldspar plus quartz, in pure water and in chloride solutions at temperatures from 100° to 700°C and pressures from 0.5 to 4 kbar, using available thermodynamic data for minerals and

Scott A. Wood; Anthony E. Williams-Jones

1993-01-01

182

/sup 31/P NMR saturation-transfer measurements in Saccharomyces cerevisiae: characterization of phosphate exchange reactions by iodoacetate and antimycin A inhibition  

SciTech Connect

/sup 31/P nuclear magnetic resonance (NMR) saturation-transfer (ST) techniques have been used to measure steady-state flows through phosphate-adenosine 5'-triphosphate (ATP) exchange reactions in glucose-grown derepressed yeast. The results have revealed that the reactions catalyzed by glyceraldehyde-3-phosphate dehydrogenase/phosphoglycerate kinase (GAPDH/PGK) and by the mitochondrial ATPase contribute to the observed ST. Contributions from these reactions were evaluated by performing ST studies under various metabolic conditions in the presence and absence of either iodoacetate, a specific inhibitor of GAPDH, or the respiratory chain inhibitor antimycin A. Intracellular phosphate (P/sub i/) longitudinal relaxation times were determined by performing inversion recovery experiments during steady-state ATP/sub lambda/ saturation and were used in combination with ST data to determine P/sub i/ consumption rates. /sup 13/C NMR and O/sub 2/ electrode measurements were also conducted to monitor changes in rates of glucose consumption and O/sub 2/ consumption, respectively, under the various metabolic conditions examined. The results suggest that GAPDH/PGK-catalyzed P/sub i/-ATP exchange is responsible for antimycin-resistant saturation transfer observed in anaerobic and aerobic glucose-fed yeast. Kinetics through GAPDH/PGK were found to depend on metabolic conditions. The coupled system appears to operate in a unidirectional manner during anaerobic glucose metabolism and bidirectionally when the cells are respiring on exogenously supplied ethanol. Additionally, mitochondrial ATPase activity appears to be responsible for the transfer observed in iodoacetate-treated aerobic cells supplied with either glucose or ethanol, with synthesis of ATP occurring unidirectionally.

Campbell-Burk, S.L.; Jones, K.A.; Shulman, R.G.

1987-11-17

183

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

SciTech Connect

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

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

2009-07-15

184

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

NASA Astrophysics Data System (ADS)

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.

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

2009-05-01

185

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

NASA Astrophysics Data System (ADS)

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.

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

186

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

SciTech Connect

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.

Borstad, Gustav M.; Yoo, Choong-Shik, E-mail: csyoo@wsu.edu [Institute for Shock Physics, Department of Physics and Department of Chemistry, Washington State University, Pullman, Washington 99164 (United States)] [Institute for Shock Physics, Department of Physics and Department of Chemistry, Washington State University, Pullman, Washington 99164 (United States)

2014-01-28

187

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

NASA Astrophysics Data System (ADS)

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.

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

2013-07-01

188

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)

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.

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

1988-05-01

189

3-D agricultural air quality modeling: Impacts of NH3/H2S gas-phase reactions and bi-directional exchange of NH3  

NASA Astrophysics Data System (ADS)

Accurately simulating the transport and fate of reduced nitrogen (NHx = ammonia (NH3) + ammonium (NH4+))- and sulfur-containing compounds emitted from agricultural activities represents a major challenge in agricultural air quality modeling. In this study, the Community Multiscale Air Quality (CMAQ) modeling system is further developed and improved by implementing 22 ammonia (NH3)/hydrogen sulfide (H2S) related gas-phase reactions and adjusting a few key parameters (e.g., emission potential) for bi-directional exchange of NH3 fluxes. Several simulations are conducted over the eastern U.S. domain at a 12-km horizontal resolution for January and July 2002 to examine the impacts of those improved treatments on air quality. The 5th generation mesoscale model (MM5) and CMAQ predict an overall satisfactory and consistent performance with previous modeling studies, especially for 2-m temperature, 2-m relative humidity, ozone (O3), and fine particulate matter (PM2.5). High model biases exist for precipitation in July and also dry/wet depositions. The updated model treatments contribute to O3, NHx, and PM2.5 by up to 0.4 ppb, 1.0 ?g m-3, and 1.0 ?g m-3 in January, respectively, and reduce O3 by up to 0.8 ppb and contribute to NHx and PM2.5 by up to 1.2 and 1.1 ?g m-3 in July, respectively. The spatial distributions of O3 in both months and sulfur dioxide (SO2) in January are mainly affected by inline dry deposition velocity calculation. The spatial distributions of SO2 and sulfate (SO42-) in July are affected by both inline dry deposition velocity and NH3/H2S reactions. The variation trends of NH3, NHx, ammonium nitrate (NH4NO3), PM2.5 and total nitrogen (TN) are predominated by bi-directional exchange of NH3 fluxes. Uncertainties of NH3 emission potentials and empirical constants used in the bi-directional exchange scheme may significantly affect the concentrations of NHx and PM2.5, indicating that a more accurate and explicit treatment for those parameters should be considered in the future work.

Wang, Kai; Zhang, Yang

2014-12-01

190

Implications of weak Donnan potential in ion-exchange reactions. An alternate strategy for modeling sorption processes  

SciTech Connect

Donnan potential generated during an ion-exchange process is conventionally believed to play an important role in partitioning co-ions in the resin and solution phases; most earlier studies implied near total exclusion of co-ions from the resin pores. The present work attempts to investigate implications of weak Donnan potential with specific reference to the sorption of acids on weak base resins. An alternate mathematical treatment has been proposed to describe the sorption behavior of any type of acid by assuming diffusion and sorption of single species, the composite acid molecule, in the resin pores. Fick`s law is then used to characterize the diffusion process. The proposed model is validated using data reported in the literature for the sorption of a strong monobasic acid (HCl) and also for a weak monobasic acid (HCOOH). The fit of the model is excellent, and the regressed values of the effective diffusion coefficient are shown to be reasonable and correct to the order of magnitude. The model is expected to offer a simpler and unified approach for modeling sorption behavior of different types of acids and will be more useful in problems of acid separation from mixtures.

Bhandari, V.M. [National Chemical Lab., Pune (India). Chemical Engineering Div.

1998-09-01

191

Active microchannel heat exchanger  

DOEpatents

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.

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

192

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

USGS Publications Warehouse

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.

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

2002-01-01

193

Speciation analysis of ultratrace chromium in water by on-line reaction/concentration/separation method using a cation-exchange column.  

PubMed

A cation-exchange column (TSK IC-Cation, 4.6 mm i.d., 10 mm) was used as a reaction/concentration/separation medium in an HPLC system. Cr(VI) and 1,5-diphenylcarbazide (DPC) were on-line mixed and reacted in a flow tube. When the reagents flowed into the column, both DPC and the complex were concentrated on the column, and the higher DPC concentration accelerated the remaining Cr(VI) to quickly complete the reaction with the DPC on the column. After the complexation and preconcentration, the complex and the extra DPC were eluted by a mixed solution containing lanthanum chloride and 1-propanol. The absorbance of the Cr(III)-DPCO complex at 540 nm was continuously monitored. In addition, the dissolved Cr(III) could be oxidized to Cr(VI) by 185-nm irradiation using a low pressure ultraviolet (UV) lamp for 8 min, and then analyzed by the present method as total chromium, thus the quantitative speciation analysis of Cr(III) and Cr(VI) was realized. In the range of 1 ng dm?³ - 100 ?g dm?³ Cr(VI) concentration, the calibration curve was linear. The analytical time was 8 min for Cr(VI) and 24 min for total Cr. The detection limit (3?) of the method was 0.6 ng dm?³ for Cr(VI) and 0.8 ng dm?³ for total chromium when using a 3.9-cm³ water sample. The present method could be successfully applied to the speciation analysis of dissolved chromium in natural water, and the leaching test of Cr(III) and Cr(VI) from stainless steel. PMID:23934564

Sarenqiqige; Ashitomi, Masaki; Yoshimura, Kazuhisa

2013-01-01

194

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

NASA Astrophysics Data System (ADS)

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.

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

2014-12-01

195

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

PubMed

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

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

2010-04-28

196

Microfluidic chemical reaction circuits  

DOEpatents

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.

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

197

Nuclear Reaction Data Centers  

SciTech Connect

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.

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

1988-01-01

198

Reactions of M 3Te 7 4+ (M = Mo, W) clusters with electrophilic reagents: Chalcogen exchange in the Te 2 ligand and the first complexes of (TeS) 2?  

Microsoft Academic Search

Reactions of triangular telluride-bridged Mo and W clusters [M3(?3-Te)(?2-Te2)3(dtp)3]+ (M=Mo, W; dtp=(EtO)2PS2) with S2Cl2 or Br2 lead to Te\\/S exchange in the Te2 ligands, with the formation of complexes with a novel TeS2? ligand. Reaction of [W3(?3-Te)(?2-Te2)3(dtp)3]+ with Br2 or S2Cl2 gives a mixture of complexes formulated as [W3Te4.25S2.75(dtp)3]+ and [W3Te4.30S2.70(dtp)3]+, respectively, on the basis of X-ray structural analysis. Reaction

Artem L. Gushchin; Maxim N. Sokolov; Cristian Vicent; Alexander V. Virovets; Eugenia V. Peresypkina; Vladimir P. Fedin

2009-01-01

199

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

...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...

2012-01-01

200

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

Microsoft Academic Search

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

K. Akilimali; B. Lumu; W. Mwamba

1979-01-01

201

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

Microsoft Academic Search

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

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

2004-01-01

202

Nonadiabatic effects in the H+H2 exchange reaction: Accurate quantum dynamics calculations at a state-to-state level  

Microsoft Academic Search

Real wave packet propagations were carried out on both a single ground electronic state and two-coupled-electronic states of the title reaction to investigate the extent of nonadiabatic effects on the distinguishable-atom reaction cross sections. The latest diabatic potential matrix of Abrol and Kuppermann [J. Chem. Phys. 116, 1035 (2002)] was employed in the present nonadiabatic quantum state-to-state scattering calculations over

Tian-Shu Chu; Ke-Li Han; Marlies Hankel; Gabriel G. Balint-Kurti; Aron Kuppermann; Ravinder Abrol

2009-01-01

203

Differential cross sections of the charge-exchange reaction pip>pi0n in the momentum range from 103 to 178 MeV\\/c  

Microsoft Academic Search

Measured values of the differential cross sections for pion-nucleon charge exchange, pi-p-->pi0n, are presented for pi- momenta of 103,112,120,130,139,152, and 178 MeV\\/c. Complete angular distributions were obtained by using the Crystal Ball detector at the Alternating Gradient Synchrotron at Brookhaven National Laboratory. Statistical uncertainties of the differential cross sections vary from 3 to 6% in the backward angle region and

D. Mekterovic; I. Supek; V. Abaev; V. Bekrenev; C. Bircher; W. J. Briscoe; R. V. Cadman; M. Clajus; J. R. Comfort; K. Craig; D. Grosnick; D. Isenhover; M. Jerkins; M. Joy; N. Knecht; D. D. Koetke; N. Kozlenko; A. Kulbardis; S. Kruglov; G. Lolos; I. Lopatin; D. M. Manley; R. Manweiler; A. Marusic; S. McDonald; B. M. K. Nefkens; J. Olmsted; Z. Papandreou; D. Peaslee; J. Peterson; N. Phaisangittisakul; S. N. Prakhov; J. W. Price; A. Ramirez; M. E. Sadler; A. Shafi; H. Spinka; S. Stanislaus; A. Starostin; H. M. Staudenmaier; I. Strakovsky; W. B. Tippens; S. Watson

2009-01-01

204

Nanoparticle conversion chemistry: Kirkendall effect, galvanic exchange, and anion exchange  

NASA Astrophysics Data System (ADS)

Conversion chemistry is a rapidly maturing field, where chemical conversion of template nanoparticles (NPs) into new compositions is often accompanied by morphological changes, such as void formation. The principles and examples of three major classes of conversion chemical reactions are reviewed: the Kirkendall effect for metal NPs, galvanic exchange, and anion exchange, each of which can result in void formation in NPs. These reactions can be used to obtain complex structures that may not be attainable by other methods. During each kind of conversion chemical reaction, NPs undergo distinct chemical and morphological changes, and insights into the mechanisms of these reactions will allow for improved fine control and prediction of the structures of intermediates and products. Conversion of metal NPs into oxides, phosphides, sulphides, and selenides often occurs through the Kirkendall effect, where outward diffusion of metal atoms from the core is faster than inward diffusion of reactive species, resulting in void formation. In galvanic exchange reactions, metal NPs react with noble metal salts, where a redox reaction favours reduction and deposition of the noble metal (alloying) and oxidation and dissolution of the template metal (dealloying). In anion exchange reactions, addition of certain kinds of anions to solutions containing metal compound NPs drives anion exchange, which often results in significant morphological changes due to the large size of anions compared to cations. Conversion chemistry thus allows for the formation of NPs with complex compositions and structures, for which numerous applications are anticipated arising from their novel catalytic, electronic, optical, magnetic, and electrochemical properties.

Anderson, Bryan D.; Tracy, Joseph B.

2014-10-01

205

Human immunodeficiency virus-1 protease. 1. Initial velocity studies and kinetic characterization of reaction intermediates by sup 18 O isotope exchange  

Microsoft Academic Search

The peptidolytic reaction HIV-1 protease has been investigated by using four oligopeptide substrates, Ac-Ser-Gln-Asn-Pro-Val-Val-NHâ, Ac-Arg-Ala-Ser-Gln-Asn-Tyr-Pro-Val-Val-NHâ, Ac-Ser-Gln-Ser-Tyr-Pro-Val-Val-NHâ, and Ac-Arg-Lys-Ile-Leu-Phe-Leu-Asp-Gly-NHâ that resemble two cleavage sites found within the naturally occurring polyprotein substrates Pr55{sup gag} and Pr160{sup gag-pol}. By use of a variety of inorganic salts, it was concluded that the peptidolytic reaction is nonspecifically activated by increasing ionic strength. V\\/K increased in

Lawrence J. Hyland; Thaddeus A. Tomaszek; Gerald D. Roberts; Steven A. Carr; Victoria W. Magaard; Heidi L. Bryan; Stephen A. Fakhoury; Michael L. Moore; Michael D. Minnich; J. S. Culp; R. L. DesJarlais; T. D. Meek

1991-01-01

206

ION EXCHANGE  

EPA Science Inventory

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

207

Science exchanges  

Microsoft Academic Search

Dwindling scientific and technical exchange between the United States and the Soviet Union and prospects for enhancing such exchanges were discussed at an August 2 hearing by the Foreign Affairs Committee of the U.S. House of Representatives. The committee also heard overviews on the United States' approach to international exchange of science and technology. The hearing was the first in

Barbara T. Richman

1983-01-01

208

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

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)

Delmas, Michael; And Others

1982-01-01

209

Discrete and infinite 1D, 2D/3D cage frameworks with inclusion of anionic species and anion-exchange reactions of Ag3L2 type receptor with tetrahedral and octahedral anions.  

PubMed

Complexes [PF6 subset(Ag3(titmb)2](PF6)2 (8) and {SbF6 subset[Ag3(titmb)2](SbF6)2}.H2O.1.5 CH3OH (9) are obtained by reaction of titmb and Ag+ salts with different anions (PF6(-) and SbF6(-)), and crystal structures reveal that they are both M3L2 cage complexes with short Ag...F interactions between the silver atoms and the fluorine atoms of the anions. In complex 8, a novel cage dimer is formed by weak Ag...F contacts; an unique cage tetramer formed via Ag...pi interactions (Ag...eta5-imidazole) between dimers and an infinite 1D cage chain is presented. However, each of the external non-disordered SbF6(-) anions connect with six cage 9s via Ag...F contacts, and each cage 9 in turn connects with three SbF6(-) anions to form a 2D network cage layer; and the layers are connected by pi-pi interactions to form a 3D network. The anion-exchange reactions of four Ag3L2 type complexes ([BF4 subset(Ag3(titmb)2](BF4)2 (6), [ClO4 subset(Ag3(titmb)2](ClO4)2 (7b), [PF6 subset(Ag3(titmb)2](PF6)2 (8) and [SbF6 subset(Ag3(titmb)2](SbF6)2.1.5CH3OH (9)) with tetrahedral and octahedral anions (ClO4(-), BF4(-), PF6(-) and SbF6(-)) are also reported. The anion-exchange experiments demonstrate that the anion selective order is SbF6(-) > PF6(-) > BF4(-), ClO4(-), and this anion receptor is preferred to trap octahedral and tetrahedral anions rather than linear or triangle anions; SbF6(-) is the biggest and most preferable one, so far. The dimensions of cage complexes with or without internal anions, anion-exchange reactions, cage assembly and anion inclusions, silver(I) coordination environments, Ag-F and Ag-pi interactions of Ag3L2 complexes 1-9 are discussed. PMID:18688416

Liu, Hong-Ke; Huang, Xiaohua; Lu, Tianhong; Wang, Xiujian; Sun, Wei-Yin; Kang, Bei-Sheng

2008-06-28

210

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

E-print Network

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

Zhao, Tianshou

211

High-resolution 100Mo(3He,t)100Tc charge-exchange experiment and the impact on double-? decays and neutrino charged-current reactions  

NASA Astrophysics Data System (ADS)

The Gamow-Teller (GT) strength distribution has been investigated in a high-resolution (3He,t) charge-exchange experiment on the double-beta (??) decaying nucleus 100Mo. The experiment was carried out at the Osaka University Research Center for Nuclear Physics (RCNP) with a 420 MeV incident 3He beam and the Grand Raiden magnetic spectrometer. A final-state energy resolution of 33 keV was achieved. It was found that nearly the entire low-energy (up to ?4 MeV) GT- strength is concentrated in the ground-state transition to 100Tc, which is interpreted as a result of the particular neutron and proton sub-shell occupancies. The impact on the matrix elements for the two-neutrino double-beta (2???) decay and the use of 100Mo as a neutrino detection material is discussed.

Thies, J. H.; Adachi, T.; Dozono, M.; Ejiri, H.; Frekers, D.; Fujita, H.; Fujita, Y.; Fujiwara, M.; Grewe, E.-W.; Hatanaka, K.; Heinrichs, P.; Ishikawa, D.; Khai, N. T.; Lennarz, A.; Matsubara, H.; Okamura, H.; Oo, Y. Y.; Puppe, P.; Ruhe, T.; Suda, K.; Tamii, A.; Yoshida, H. P.; Zegers, R. G. T.

2012-10-01

212

Test procedure for cation exchange chromatography  

SciTech Connect

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.

Cooper, T.D.

1994-08-24

213

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

PubMed Central

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

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

2012-01-01

214

The Dynamics of Multilateral Exchange  

NASA Astrophysics Data System (ADS)

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.

Hausken, Kjell; Moxnes, John F.

215

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

NASA Astrophysics Data System (ADS)

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.

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

2015-01-01

216

Thermostability of endo-1,4-beta-xylanase II from Trichoderma reesei studied by electrospray ionization Fourier-transform ion cyclotron resonance MS, hydrogen/deuterium-exchange reactions and dynamic light scattering.  

PubMed Central

Endo-1,4-beta-xylanase II (XYNII) from Trichoderma reesei is a 21 kDa enzyme that catalyses the hydrolysis of xylan, the major plant hemicellulose. It has various applications in the paper, food and feed industries. Previous thermostability studies have revealed a significant decrease in enzymic activity of the protein at elevated temperatures in citrate buffer [Tenkanen, Puls and Poutanen (1992) Enzyme Microb. Technol. 14, 566-574]. Here, thermostability of XYNII was investigated using both conventional and nanoelectrospray ionization Fourier-transform ion cyclotron resonance MS and hydrogen/deuterium (H/D)-exchange reactions. In addition, dynamic light scattering (DLS) was used as a comparative method to observe possible changes in both tertiary and quaternary structures of the protein. We observed a significant irreversible conformational change and dimerization when the protein was exposed to heat. H/D exchange revealed two distinct monomeric protein populations in a narrow transition temperature region. The conformational change in both the water and buffered solutions occurred in the same temperature region where enzymic-activity loss had previously been observed. Approx. 10-30% of the protein was specifically dimerized when exposed to the heat treatment. However, adding methanol to the solution markedly lowered the transition temperature of conformational change as well as increased the dimerization up to 90%. DLS studies in water confirmed the change in conformation observed by electrospray ionization MS. We propose that the conformational change is responsible for the loss of enzymic activity at temperatures over 50 degrees C and that the functioning of the active site in the enzyme is unfeasible in a new, more labile solution conformation. PMID:11368772

Jänis, J; Rouvinen, J; Leisola, M; Turunen, O; Vainiotalo, P

2001-01-01

217

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

E-print Network

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

Sparks, Donald L.

218

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

NASA Technical Reports Server (NTRS)

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.

Liechty, Derek S.; Lewis, Mark J.

2010-01-01

219

Closed cycle ion exchange method for regenerating acids, bases, and salts  

Microsoft Academic Search

A method is described for conducting a chemical reaction in acidic, basic, or neutral solution as required and then regenerating the acid, base, or salt by means of ion exchange in a closed cycle reaction sequence which comprises contacting the spent acid, base, or salt with an ion exchanger. The ion exchanger is preferably a synthetic organic ion-exchange resin so

Dreyfuss

1976-01-01

220

Heat exchanger  

SciTech Connect

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.

Drury, C.R.

1988-02-02

221

Structure and properties of the precursor/successor complex and transition state of the CrCl²?/Cr²? electron self-exchange reaction via the inner-sphere pathway.  

PubMed

The electron self-exchange reaction CrCl(OH2)5(2+) + Cr(OH2)6(2+) ? Cr(OH2)6(2+) + CrCl(OH2)5(2+), proceeding via the inner-sphere pathway, was investigated with quantum-chemical methods. Geometry and vibrational frequencies of the precursor/successor (P/S) complex, (H2O)5Cr(III)ClCr(II)(OH2)5(4+)/(H2O)5Cr(II)ClCr(III)(OH2)5(4+), and the transition state (TS), (H2O)5CrClCr(OH2)5(4+‡), were computed with density functional theory (DFT) and conductor polarizable continuum model hydration. Consistent data were obtained solely with long-range-corrected functionals, whereby in this study, LC-BOP was used. Bent and linear structures were computed for the TS and P/S. The electronic coupling matrix element (H(ab)) and the reorganizational energy (?) were calculated with multistate extended general multiconfiguration quasi-degenerate second-order perturbation theory. The nuclear tunneling factor (?(n)), the nuclear frequency factor (?(n)), the electronic frequency factor (?(el)), the electron transmission coefficient (?(el)), and the first-order rate constant (k(et)) for the electron-transfer step (the conversion of the precursor complex into the successor complex) were calculated based on the imaginary frequency (?(‡)) of the TS, the Gibbs activation energy (?G(‡)), H(ab), and ?. The formation of the precursor complex via water substitution at Cr(OH2)6(2+) was also investigated with DFT and found to be very fast. Thus, the electron-transfer step is rate-determining. For the substitution reaction, only a bent TS structure could be obtained. The overall rate constant (k) was estimated as the product K(A)k(et), whereby K(A) is the equilibrium constant for the formation of the ion aggregate of the reactants Cr(OH2)6(2+) and CrCl(OH2)5(2+), Cr(H2O)6·CrCl(OH2)5(4+) (IAR). k calculated for the bent and linear isomers agrees with the experimental value. PMID:25162781

Rotzinger, François P

2014-09-15

222

Law on Exchange InternationalExchangeProgram  

E-print Network

Law on Exchange InternationalExchangeProgram Law students have a range of exchange options available both at the faculty level and through University- wide exchange partners. Law students can spend a maximum of one semester on exchange in the last year of their Bachelor of Law or Juris Doctor course. Law

Viglas, Anastasios

223

Media Exchange.  

ERIC Educational Resources Information Center

Reviews filmstrip/cassette recording materials titled "Reaction Rates: Molecules in Motion." Also reviews six college-level textbooks, addressing major strengths/weaknesses of texts under consideration with regard to their specific usefulness to high school chemistry teachers. (JN)

Friedstein, Harriet G., Ed.

1983-01-01

224

Composite ion exchange materials  

SciTech Connect

Composite ion exchange materials can be formed by sorbing ion exchange polymers on inert, high surface area substrates. In general, the flux of ions and molecules through these composites, as measured electrochemically, increases as the ratio of the surface area of the substrate increases relative to the volume of the ion exchanger. This suggests that fields and gradients established at the interface between the ion exchanger and substrate are important in determining the transport characteristics of the composites. Here, the authors will focus on composites formed with a cation exchange polymer, Nafion, and two different types of microbeads: polystyrene microspheres and polystyrene coated magnetic microbeads. For the polystyrene microbeads, scanning electron micrographs suggest the beads cluster in a self-similar manner, independent of the bead diameter. Flux of Ru(NH3)63+ through the composites was studied as a function of bead fraction, bead radii, and fixed surface area with mixed bead sizes. Flux was well modeled by surface diffusion along a fractal interface. Magnetic composites were formed with columns of magnetic microbeads normal to the electrode surface. Flux of Ru(NH3)63+ through these composites increased exponentially with bead fraction. For electrolyses, the difference in the molar magnetic susceptibility of the products and reactants, Dcm, tends to be non-zero. For seven redox reactions, the ratio of the flux through the magnetic composites to the flux through a Nafion film increases monotonically with {vert_bar}Dcm{vert_bar}, with enhancements as large as thirty-fold. For reversible species, the electrolysis potential through the magnetic composites is 35 mV positive of that for the Nafion films.

Amarasinghe, S.; Zook, L.; Leddy, J. [Univ. of Iowa, Iowa City, IA (United States)

1994-12-31

225

Mass Exchange Processes with Input  

E-print Network

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

P. L. Krapivsky

2015-03-07

226

Job Exchange  

NSDL National Science Digital Library

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

1998-01-01

227

Pairwise kidney exchange  

Microsoft Academic Search

The literature on exchange of indivisible goods finds natural application in the exchange of live donor kidneys for transplant. However, in kidney exchange, there are constraints on the size of exchanges. Initially, kidney exchanges are likely to be between just two patient–donor pairs. We show that, although this constraint eliminates some potential exchanges, there is a wide class of constrained-efficient

Alvin E. Roth; Tayfun Sönmez; M. Utku Ünver

2005-01-01

228

Heat exchanger  

NASA Astrophysics Data System (ADS)

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

Brackenbury, P. J.

1983-12-01

229

Heat exchanger  

DOEpatents

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.

Brackenbury, Phillip J. (Richland, WA)

1986-01-01

230

Heat exchanger  

DOEpatents

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.

Brackenbury, P.J.

1983-12-08

231

Agriculture on Exchange InternationalExchangeProgram  

E-print Network

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

Viglas, Anastasios

232

Music on Exchange InternationalExchangeProgram  

E-print Network

agreements in Austria, Germany, South Korea, the United Kingdom and the USA. These programs are administeredMusic on Exchange InternationalExchangeProgram Music students enrolled at the Sydney Conservatorium of Music have the option of considering exchange at a faculty-specific exchange partner university

Viglas, Anastasios

233

Field Based Constraints on Reaction Rates in the Crust  

Microsoft Academic Search

Modern research in plate boundary processes involving metamorphism frequently employs complex physical models. Such models require some quantification (or assumption) of the rate at which metamorphic reactions, or chemical exchange, proceed in natural systems. Here, a compilation of available quantitative field-based constraints on high temperature reaction rates will be presented. These include quantifications based on isotopic exchange, porphyroblast and reaction

E. F. Baxter

2004-01-01

234

Segmented heat exchanger  

SciTech Connect

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.

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

2010-12-14

235

Closed cycle ion exchange method for regenerating acids, bases and salts  

Microsoft Academic Search

A method for conducting a chemical reaction in acidic, basic, or neutral solution as required and then regenerating the acid, base, or salt by means of ion exchange in a closed cycle reaction sequence which comprises contacting the spent acid, base, or salt with an ion exchanger, preferably a synthetic organic ion-exchange resin, so selected that the counter ions thereof

Dreyfuss; Robert M

1976-01-01

236

High temperature heat exchangers  

Microsoft Academic Search

This book contains the proceedings from the XVII Symposium of the International Center for Heat and Mass Transfer on High Temperature Heat Exchangers, held August 1985 in Yugoslavia. Papers were presented under the following topics: High Temperature Heat Exchangers Development; Basic Problem in High Temperature Heat Exchangers; Heat Exchangers for High Temperature Recovery; and High Temperature Heat Exchangers for Future

Y. Mori; A. E. Sheindlin; N. Afgan

1986-01-01

237

Educator Exchange Resource Guide.  

ERIC Educational Resources Information Center

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

Garza, Cris; Rodriguez, Victor

238

Reactor for exothermic reactions  

DOEpatents

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.

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

1993-03-02

239

Reactor for exothermic reactions  

DOEpatents

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.

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

1993-01-01

240

Charge exchange in the Io torus and exosphere  

NASA Technical Reports Server (NTRS)

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.

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

1982-01-01

241

Corrosive resistant heat exchanger  

DOEpatents

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.

Richlen, Scott L. (Annandale, VA)

1989-01-01

242

Psychology on Exchange InternationalExchangeProgram  

E-print Network

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

Viglas, Anastasios

243

New [LNiII2]+ complexes incorporating 2-formyl or 2,6-diformyl-4-methyl phenol as inhibitors of the hydrolysis of the ligand L3-: Ni...Ni ferromagnetic coupling and S=2 ground states.  

PubMed

Reaction of the dinucleating ligand H3L (2-(2'-hydroxyphenyl)-1,3-bis[4-(2-hydroxyphenyl)-3-azabut-3-enyl]-1,3-imidazolidine) with Ni(NO3)(2).6H2O produces the dimer of monomers [Ni(HL1)]2(NO3)(2).4H2O (1.4H2O) following the hydrolysis of H3L. If the reaction occurs in the presence of 2-formylphenol (Hfp) or 2,6-diformyl-4-methylphenol (Hdfp), this hydrolysis is prevented by incorporation of these co-ligands into the structure and stabilization of the new complexes [Ni2L(fp)(H2O)].3H2O (2.3H2O) and [Ni2L(dfp)].4.5H2O (3.4.5H2O), respectively. Complexes 2 and 3 may be considered to be structural models of the active site of urease, where coordination of the carbonyl ligand mimics binding of urea. In complex 2, coordination of terminal water reproduces the binding of this substrate of the enzyme to the active site. In both dinuclear complexes, the NiII ions are coupled ferromagnetically to yield S=2 ground states, whereas complex 1 exhibits weak intradimer antiferromagnetic exchange through hydrogen bonds. The magnetic data can be modeled by using the Van Vleck equation, incorporating intermolecular interactions, or by diagonalization of a spin Hamiltonian that includes single-ion anisotropy. PMID:17569529

Paital, Alok Ranjan; Wong, Wing Tak; Aromí, Guillem; Ray, Debashis

2007-07-01

244

Concerted hydrogen atom exchange between three HF molecules  

NASA Technical Reports Server (NTRS)

The termolecular reaction involving concerted hydrogen-atom exchange between three HF molecules was investigated with particular attention given to the effects of correlation at the various stationary points along the reaction. Using large segmented Gaussian basis sets to locate the (HF)3 stationary points at the SCF level, the geometries of the stable hydrogen-bonded trimer, which is of C(3h) symmetry, were located, together with the transition state for hydrogen exchange, which is of D(3h) symmetry. Then, using a large atomic natural orbital basis and correlating all valence electrons, the energetics of the exchange reaction were evaluated at the correlated level.

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

1992-01-01

245

Altruistically Unbalanced Kidney Exchange  

Microsoft Academic Search

Although a pilot national live-donor kidney exchange program was recently launched in the US, the kidney shortage is increasing faster than ever. A new solution paradigm is able to incorporate compatible pairs in exchange. In this paper, we consider an exchange framework that has both compatible and in- compatible pairs, and patients are indifferent over compatible pairs. Only two-way exchanges

Tayfun Sönmez; M. Utku Ünver

2011-01-01

246

Corrosive resistant heat exchanger  

Microsoft Academic Search

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

Richlen; Scott L

1989-01-01

247

Industrial heat exchangers  

Microsoft Academic Search

This book presents the papers given at a symposium on the use of heat exchangers in the industrial plants. Topics considered include the US DOE and GRI research programs, advanced fixed boundary heat exchanger technology, commercial heat exchanger applications, thermo-hydraulic performance of heat-transfer equipment, field tests, the corrosion of heat exchanger materials, economics, cost benefit analysis, payback, and advanced assembly

A. J. Hayes; W. W. Liang; S. L. Richlen; E. S. Tabb

1985-01-01

248

Woven heat exchanger  

DOEpatents

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.

Piscitella, Roger R. (Idaho Falls, ID)

1987-01-01

249

Woven heat exchanger  

DOEpatents

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.

Piscitella, R.R.

1984-07-16

250

Allergic reactions  

MedlinePLUS

... more often in people who have a family history of allergies . Substances that don't bother most people ( ... reaction is getting worse. The person has a history of severe allergic reactions (check for a medical ID ...

251

PROTEINS Structure, Function, and Genetics 17:87-92 (1993) Isotope Effects in Peptide Group Hydrogen Exchange  

E-print Network

reactions were evaluated. Unlike many other reactions,kinetic isotope effects in amide hydrogen exchange in this issue]. 0 1993 Wiley-Liss,Inc. Key words: hydrogen exchange, equilibrium isotope effects, kinetic isotope ef- fects, protein structure, ply-DL- alanine INTRODUCTION Hydrogen exchange (HX) rates

Englander, S. Walter

252

Business School Exchanges InternationalExchangeProgram  

E-print Network

units on exchange so should keep a minimum of one semester's worth of elective study (24 credit points units per the exchange period, which is insufficient for a full semester study load of 24 credit points. Most partners cannot guarantee courses so you will not be assured of obtaining credit towards your

Viglas, Anastasios

253

Enzyme Reactions  

NSDL National Science Digital Library

This video shows an enzyme reaction lab. The teacher demonstrates how the enzyme, catalase, reacts with hydrogen peroxide (a substrate found in cells). The teacher first demonstrates a normal enzyme reaction. He or she then goes on to show how manipulating temperature and pH will affect the reaction of an enzyme.

Minerva Deland School

2011-10-03

254

Special Reactions  

NSDL National Science Digital Library

The basics of chemical reactions were covered in the first chemistry book, including how to write and balance chemical equations that represent those reactions. There is also a quick review of chemical reactions in Chapter 1 of this book. We're going to d

William C. Robertson, Ph.D.

2010-03-01

255

Chemical Reactions  

NSDL National Science Digital Library

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

National Science Teachers Association (NSTA)

2009-05-01

256

Bifunctional anion-exchange resins with improved selectivity and exchange kinetics  

DOEpatents

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.

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

2000-01-01

257

Ion Exchange Formation via Sulfonated Bicomponent Nonwovens  

NASA Astrophysics Data System (ADS)

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.

Stoughton, Hannah L.

258

Electrical and magnetic properties of ion-exchangeable layered ruthenates  

SciTech Connect

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.

Sugimoto, Wataru [Faculty of Textile Science and Technology, Department of Fine Materials Engineering, Shinshu University, 3-15-1 Tokida, Ueda 386-8567 (Japan)]. E-mail: wsugi@shinshu-u.ac.jp; Omoto, Masashi [Faculty of Textile Science and Technology, Department of Fine Materials Engineering, Shinshu University, 3-15-1 Tokida, Ueda 386-8567 (Japan); Yokoshima, Katsunori [Faculty of Textile Science and Technology, Department of Fine Materials Engineering, Shinshu University, 3-15-1 Tokida, Ueda 386-8567 (Japan); Murakami, Yasushi [Faculty of Textile Science and Technology, Department of Fine Materials Engineering, Shinshu University, 3-15-1 Tokida, Ueda 386-8567 (Japan); Takasu, Yoshio [Faculty of Textile Science and Technology, Department of Fine Materials Engineering, Shinshu University, 3-15-1 Tokida, Ueda 386-8567 (Japan)

2004-12-01

259

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

Microsoft Academic Search

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

Ingmar M. Schoegl; Janet L. Ellzey

2010-01-01

260

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...

261

Reaction Time  

NSDL National Science Digital Library

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

2012-06-26

262

Named Reactions  

NSDL National Science Digital Library

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

263

Reaction product imaging  

SciTech Connect

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}.

Chandler, D.W. [Sandia National Laboratories, Livermore, CA (United States)

1993-12-01

264

Chemical Reactions  

NSDL National Science Digital Library

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

Mrs. Hicken

2009-05-04

265

Determinants of protein hydrogen exchange studied in equine cytochrome c.  

PubMed Central

The exchange of a large number of amide hydrogens in oxidized equine cytochrome c was measured by NMR and compared with structural parameters. Hydrogens known to exchange through local structural fluctuations and through larger unfolding reactions were separately considered. All hydrogens protected from exchange by factors greater than 10(3) are in defined H-bonds, and almost all H-bonded hydrogens including those at the protein surface were measured to exchange slowly. H-exchange rates do not correlate with H-bond strength (length) or crystallographic B factors. It appears that the transient structural fluctuation necessary to bring an exchangeable hydrogen into H-bonding contact with the H-exchange catalyst (OH(-)-ion) involves a fairly large separation of the H-bond donor and acceptor, several angstroms at least, and therefore depends on the relative resistance to distortion of immediately neighboring structure. Accordingly, H-exchange by way of local fluctuational pathways tends to be very slow for hydrogens that are neighbored by tightly anchored structure and for hydrogens that are well buried. The slowing of buried hydrogens may also reflect the need for additional motions that allow solvent access once the protecting H-bond is separated, although it is noteworthy that burial in a protein like cytochrome c does not exceed 4 angstroms. When local fluctuational pathways are very slow, exchange can become dominated by a different category of larger, cooperative, segmental unfolding reactions reaching up to global unfolding. PMID:9541406

Milne, J. S.; Mayne, L.; Roder, H.; Wand, A. J.; Englander, S. W.

1998-01-01

266

Neopentane and solid acids: direct hydron exchange before cracking.  

PubMed

The hydrogen/deuterium exchange reaction of 2,2-dimethylpropane (neopentane) over D(2)O-exchanged zeolites (MOR, FAU, BEA, MFI) using a batch recirculation reactor was studied by means of gas chromatography coupled with mass spectrometer. In the temperature range 473-573 K, H/D exchange proceeds without side reaction such as cracking at short contact times. Indeed the C-H bond has appeared favorably involved in the activation of neopentane compared to the less accessible C-C bond. The transition state allowing hydron exchange is most likely a carbonium species (pentacoordinated carbon) as in the case of the H/D exchange between methane and solid acid. The activation energies of the H/D exchange between neopentane and zeolites are the same for all zeolites indicating a common carbonium ion type transition state. On the basis of previous results in the case of the exchange between methane and liquid superacids, the deuterium exchange rates in neopentane were tentatively related to the acidity of the solids. However the order of activity MOR > MFI > BEA > FAU seems to be related to the size of the pores, which may suggest the involvement of a confinement effect in the zeolites cavities. Moreover we found that H/D exchange takes also place between neopentane and deuterated sulfated zirconia (SZ) emphasizing its strong acidity. PMID:16970460

Walspurger, Stéphane; Sun, Yinyong; Souna Sido, Abdelkarim Sani; Sommer, Jean

2006-09-21

267

Chicago Climate Exchange, Inc. 2010 Chicago Climate Exchange 1 The Role of Exchanges and Standardization  

E-print Network

Chicago Climate Exchange®, Inc.© 2010 Chicago Climate Exchange 1 The Role of Exchanges and Standardization in Reducing Emissions at Scale Michael J. Walsh, Ph.D. Executive Vice President Chicago Climate Exchange, Inc. #12;Chicago Climate Exchange®, Inc.© 2010 Chicago Climate Exchange Pacala-Socolow GHG

268

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

269

Theorization on ion-exchange equilibria: activity of species in 2-D phases  

Microsoft Academic Search

Ion-exchange reactions are naturally occurring at soil and sediment\\/water interphases, determining soil fertility and water quality. These ion-exchange reactions with inorganic and organic exchangers are applied to chemical analysis, recovery of useful ions from low-grade ores (potentially from sea water), water purification including the preparation of “ultrapure” water, production of foods and medicines, therapy, and other uses. It is important

Hiroki Tamura

2004-01-01

270

Conquer heat exchanger fouling  

Microsoft Academic Search

Fouling plays a dominant role in heat exchanger performance. It is extremely important to choose the most appropriate type of heat exchanger for a particular application and adopt proper values for fouling resistance. A design practice for shell-and-tube heat exchangers that will limit fouling to a minimum and thus ensure trouble-free operation is essential. Due to the availability of specialized

1996-01-01

271

Fundamental aspects of electrocatalysis of the hydrogen electrode reaction and oxygen electrode reaction on platinum  

Microsoft Academic Search

This dissertation work studies the fundamental aspects of the electrocatalysis of the hydrogen electrode reaction (HER) and oxygen electrode reaction (OER) on platinum over a wide temperature range from ambient up to 220°C. Previously, the majority of the work reported was restricted to temperatures below 70°C due to apparatus constraints, whereas the current operation temperature for proton exchange membrane fuel

Jianer Bao

2007-01-01

272

Text Exchange System  

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

273

Microtube strip heat exchanger  

SciTech Connect

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

Doty, F.D.

1991-07-08

274

Emittance Exchange Results  

SciTech Connect

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.

Fliller III,R.; Koeth, T.

2009-05-04

275

Emittance exchange results  

SciTech Connect

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.

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

2009-09-01

276

Method for conducting exothermic reactions  

DOEpatents

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.

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

1993-01-05

277

Method for conducting exothermic reactions  

DOEpatents

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.

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

1993-01-01

278

Chemical properties of anion-exchangers prepared from waste natural materials  

Microsoft Academic Search

Waste natural materials (WNM) were converted into anion-exchangers through consecutive chemical reactions with thionylchloride, N,N-Dimethylformamide (DMF), dimethylamine and formaldehyde as crosslinking agents. The final products obtained were weak-base anion-exchangers with tertiary amines as major functional exchange groups. WNM containing small amounts of extractives gave higher yields. Also, anion-exchangers produced from WNM with higher lignin content gave higher maximum nitrate adsorption

T. Okuda; A. U. Baes; W. Nishijima; M. Okada

2003-01-01

279

Drug Reactions  

MedlinePLUS

Most of the time, medicines make our lives better. They reduce aches and pains, fight infections, and control problems such as high blood pressure or diabetes. But medicines can also cause unwanted reactions. One problem is ...

280

Enzyme Reactions  

NSDL National Science Digital Library

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

Maryland Virtual High School

281

ERASMUS EXCHANGE General Information  

E-print Network

exchange agreements with partner regions in the US, Canada, Australia and Mexico. Some of the exchange for courses from the International Master of Science programs Advanced Materials, Communication Technology by the university but by the Studentenwerk (Student Service Agency). This fee is only a nominal contribution

Petriu, Emil M.

282

How to Exchange Items  

Microsoft Academic Search

This paper looks at a system where agents exchange items for mutual beneflt in the absence of money. Each agent has one item and a preference list (without ties) of items it would be willing to exchange its item for. Each agent gives its item and reveals its list to a central authority, which then re-allocates the items - one

Sujay Sanghavi

283

Higher Education Exchange, 2012  

ERIC Educational Resources Information Center

"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.…

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

2012-01-01

284

Biological Ion Exchanger Resins  

PubMed Central

Utilizing Escherichia coli as the prototype of an ion-accumulating cell, the ion exchange isotherm is introduced as a concise method of characterizing biological ion exchange events. The ion exchange isotherm for the alkali cation exchange, K ? Na, is described. The total charge profile of this bacterium is compiled and compared for bacteria in the Na form and in the K form. Macromolecule fixed charge was found to provide 80% of the counter ions that pair with potassium. Therefore, in its physiological state, 80% of the cell potassium in E. coli is associated with an ion exchange site on a macromolecule. The primary cation exchange sites are found to be about equally divided between carboxylate and phosphate sites indicating that E. coli is a bifunctional resin with respect to cation exchange. During substrate-dependent cation accumulation (“active transport”), phosphate esters and organic acids were shown to accumulate. One may conclude that the role of intermediate metabolism in “active transport” is to increase the ion exchange capacity of the biological resin by the production of charged metabolites that sorb to the framework of the resin. PMID:4943652

Damadian, Raymond

1971-01-01

285

STUDENT EXCHANGE HANDBOOK.  

ERIC Educational Resources Information Center

THIS HANDBOOK IS TO GUIDE SCHOOL PERSONNEL IN DEVELOPING OR EVALUATING STUDENT EXCHANGE PROGRAMS IN HIGH SCHOOLS, ESPECIALLY IN MICHIGAN. CHAPTER 1 CONSISTS OF A DISCUSSION OF THE EDUCATIONAL, CULTURAL, AND SOCIAL OBJECTIVES FOR EXCHANGE PROGRAMS. CHAPTER 2 LISTS THE PROGRAMS SUCCESSFULLY OPERATING IN MICHIGAN, AND DISCUSSES THE RESPONSIBILITIES…

FRIEDRICHS, DONALD E.

286

Direct fired heat exchanger  

DOEpatents

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.

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

1986-01-01

287

Higher Education Exchange, 2011  

ERIC Educational Resources Information Center

"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.…

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

2011-01-01

288

Building Relationships through Exchange  

ERIC Educational Resources Information Center

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…

Primavera, Angi; Hall, Ellen

2011-01-01

289

Living donor kidney exchange.  

PubMed

Living donor kidney exchange, also referred to as kidney paired donation (KPD), is a relatively new transplant modality that is growing by leaps and bounds in the U.S. From its first realization as an exchange of kidneys between two incompatible donor/recipient pairs, KPD has expanded to include compatible pairs, nondirected donors, three-way and larger exchanges, and living/deceased donor exchanges. Innovations both clinical (transporting organs instead of donors, and improved HLA screening) and mathematical (simulation to test policies, optimization to find better and more matches) have made this modality even more useful and accessible. There are several independent multi-center paired donation registries and many more single-center registries operating in the U.S., but incompatible pairs are most likely to match when they participate in the largest possible paired exchange pool; a single, unified KPD program in the United States would likely best serve patients in search of matches. PMID:22755420

Gentry, Sommer; Segev, Dorry L

2011-01-01

290

Process for operating equilibrium controlled reactions  

DOEpatents

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.

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

291

Chemical Reactions in DSMC  

SciTech Connect

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.

Bird, G. A. [GAB Consulting Pty Ltd, 144/110 Sussex Street, Sydney NSW 2000 (Australia)

2011-05-20

292

Heat and mass exchanger  

DOEpatents

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.

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

2011-06-28

293

Heat and mass exchanger  

DOEpatents

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.

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

2007-09-18

294

Microtube strip heat exchanger  

SciTech Connect

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.

Doty, F.D.

1991-10-16

295

Anion exchange membrane  

DOEpatents

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.

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

2013-05-07

296

Wound tube heat exchanger  

DOEpatents

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.

Ecker, Amir L. (Duncanville, TX)

1983-01-01

297

Reaction Time  

NSDL National Science Digital Library

This lab is not an inquiry activity. There are some students whose reaction times will not allow them to catch a 12 inch ruler. They may use a dowel, stick, strip of cardboard, etc. Although the students are led to believe that the point of the lab is to

Michael Horton

2009-05-30

298

Reaction Time  

NSDL National Science Digital Library

In this activity, learners conduct an experiment to test how fast they can react. Learners try to catch a piece of paper with a ruler printed on it (or a ruler) as quickly as they can. Learners collect data and compare the reaction times of friends and family.

WGBH Boston

2003-01-01

299

Study Abroad & Exchange Students  

E-print Network

Study Abroad & Exchange Students Essential Guide 2011 #12;Study Abroad Office, The University of Western Australia CRICOS Provider Code: 00126G Page 2 CONTENTS THE STUDY ABROAD OFFICE ...................................................................................................................... 3 Study Abroad Office Staff

Petriu, Emil M.

300

Microtube strip heat exchanger  

NASA Astrophysics Data System (ADS)

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.

Doty, F. D.

1990-12-01

301

The Tacoma Syringe Exchange.  

PubMed

For over a year, the Tacoma Syringe Exchange has been operating in spite of existing drug paraphernalia laws. One hundred fifty-four subjects have been interviewed regarding drug injection practices for the month prior to first use of the exchange and for the most recent month since using the exchange. Statistically significant reductions in mean frequency of obtaining used syringes, and in mean rate of passing on used syringes, have been reported. Mean number of times bleach was used to disinfect contaminated syringes has risen. The exchange continues to attract mainly men, median age 35, with a long history of injection. No differences have been observed in mean number of injections per month. In order to increase utilization, new sites are planned, but expansion has been hampered by a series of legal problems. Since the exchange draws many difficult to reach individuals, it is an important location for STD screening and drug treatment recruitment. Documentation of participation patterns and barriers to exchange use, and effects upon HIV serological status are recommended. PMID:1777501

Hagan, H; Des Jarlais, D C; Purchase, D; Reid, T; Friedman, S R

1991-01-01

302

Radial flow heat exchanger  

DOEpatents

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.

Valenzuela, Javier (Hanover, NH)

2001-01-01

303

Heat exchanger for fuel cell power plant reformer  

DOEpatents

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.

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

304

The Exchange Rate - A Shock-Absorber or Source of Shocks? A Study of Four Open Economies  

Microsoft Academic Search

The paper provides SVAR estimates for four open economies: the UK, Canada, Sweden and Denmark, making explicit a monetary policy reaction function and taking account of exchange rate targeting practices. The object of the analysis is to examine the idea that an independent money and exchange rate should allow for effective shock-absorption. A polar extreme would be that exchange markets

Michael J Artis; Michael Ehrmann

2000-01-01

305

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

Microsoft Academic Search

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

Sandro Brandenberger; Oliver Kröcher; Arno Tissler; Roderik Althoff

2008-01-01

306

Ceramic Spheres From Cation Exchange Beads  

NASA Technical Reports Server (NTRS)

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.

Dynys, F. W.

2003-01-01

307

Downhole heat exchangers  

SciTech Connect

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.

Culver, G.; Lund, J.W. [Oregon Inst. of Tech., Klamath Falls, OR (United States). Geo-Heat Center

1999-09-01

308

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

309

Extraction and ion-exchange behavior of mendelevium (II)  

Microsoft Academic Search

Medelevium-256 was obtained via multinucleon transfer reactions upon irradiation of ²⁴⁹Bk by ²²Ne 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.

L. I. Guseva; G. S. Tikhomirova; G. V. Buklanov; Z. Z. Pkhar; I. A. Lebedev; N. V. Katargin; B. F. Myasoedov

1988-01-01

310

Deacidification of a synthetic oil with an anion exchange resin  

Microsoft Academic Search

Esters of trimethylolpropane were prepared by reaction of trimethylolpropane with erucic acid. Unreacted erucic acid was eliminated\\u000a by fixation on an anion exchange resin to produce an oil with a low free fatty acid content. The authors describe the deacidification\\u000a of the reaction product by Lewatit MP500A and MP600 resins in a fixed-bed reactor or in a stirred reactor. The

Valérie Eychenne; Zéphirin Mouloungui

1998-01-01

311

Search for R-parity breaking sneutrino exchange at LEP  

Microsoft Academic Search

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

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

1997-01-01

312

Multistrange Baryon production from strangeness-exchange reactions  

E-print Network

-matrix approximation by neglecting the off-shell contribution in the intermediate states. For the transition potential which drives the higher-order contribution, we consider all allowed Born diagrams in the s, t, and u channels. With coupling constants determined from...

Li, Changhui

2002-01-01

313

The formate-pyruvate exchange reaction by Streptococcus faecalis  

E-print Network

of these inter. . onversions kn . '. ; metabokksm are kinked ivkth derivatives of tetrehydrofolic acid. '}uennekens et al. (1958), emphasi'. ed the role of reduced folic acid as the co?nzyme or carrier of Ci groups. t, " right et al. (1958) showed, in a... bacterial system. that folic acid may be reduced to dihydrofolic acid by pyruvic ox}des?. Pine and Guthrie (1959) studied the influence of folic acid in the lncorporatlon of formats-C14 into the pyrimidine ring of thiagdne. ", 'hiteley et al. (1959) have...

Yeager, Robert Lee

1960-01-01

314

Calculation of Equilibrium Constants for Isotopic Exchange Reactions  

Microsoft Academic Search

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

Jacob Bigeleisen; Maria Goeppert Mayer

1947-01-01

315

Phosphine-initiated cation exchange for precisely tailoring composition and properties of semiconductor nanostructures: old concept, new applications.  

PubMed

Phosphine-initiated cation exchange is a well-known inorganic chemistry reaction. In this work, different phosphines have been used to modulate the thermodynamic and kinetic parameters of the cation exchange reaction to synthesize complex semiconductor nanostructures. Besides preserving the original shape and size, phosphine-initiated cation exchange reactions show potential to precisely tune the crystallinity and composition of metal/semiconductor core-shell and doped nanocrystals. Furthermore, systematic studies on different phosphines and on the elementary reaction mechanisms have been performed. PMID:25655404

Gui, Jing; Ji, Muwei; Liu, Jiajia; Xu, Meng; Zhang, Jiatao; Zhu, Hesun

2015-03-16

316

Ion exchange phenomena  

SciTech Connect

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).

Bourg, I.C.; Sposito, G.

2011-05-01

317

Laser Assisted Emittance Exchange  

SciTech Connect

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

Xiang, Dao; /SLAC

2012-06-11

318

IEL Policy Exchange  

NSDL National Science Digital Library

The Institute for Educational Leadership (IEL) Policy Exchange is a "hands-on" think tank that attempts to make "the connection between ideas and leaders in all domestic policy arenas" at all levels of government in the areas of education, vocational training, health, social services, welfare, juvenile justice, and housing. The IEL Policy exchange unites leaders with ideas through policy research, published reports, and hands-on workshops for policy makers. Two of the 1998 special reports issued by the IEL Policy Exchange are "Mixed Results: Lessons Learned from a Case Study of Interagency Collaboration" by Margaret C. Dunkle and Stephanie A. Surles, and "The Measure of Success: What are the Policy Implications of the New National Indicators of Child Well-Being?" by Jeanne Jehl (both available in .pdf and WordPerfect formats).

319

Reactions of ultracold alkali-metal dimers  

SciTech Connect

We investigate the energetics of reactions involving pairs of alkali-metal dimers. Atom exchange reactions to form homonuclear dimers are energetically allowed for some but not all of the heteronuclear dimers. We carry out high-level electronic structure calculations on the potential energy surfaces of all the heteronuclear alkali-metal trimers and show that trimer formation reactions are always energetically forbidden for low-lying singlet states of the dimers. The results have important implications for the stability of quantum gases of alkali-metal dimers.

Zuchowski, Piotr S.; Hutson, Jeremy M. [Department of Chemistry, Durham University, South Road, Durham, DH1 3LE (United Kingdom)

2010-06-15

320

Metal Reactions  

NSDL National Science Digital Library

This is written as a static display, but can easily be adapted to a hands-on experiment for learners to conduct. Sodium phosphate, a clear colorless solution, is combined with six different metal ion solutions. Each metal (copper, nickel, iron, silver, cobalt, and barium) forms a different color and texture precipitate. Learners discover that a chemical reaction can be identified by a color change, and formation of a precipitate. They also learn that metals can be identified by their precipitates. For safety reasons, this activity should be conducted as a demonstration for younger audiences.

Oregon Museum of Science and Industry

1997-01-01

321

Thermonuclear reaction rates. II  

Microsoft Academic Search

A revision and updating of charged particle reactions involving nuclei ; with A less than or approximately equal to 30, except for the $sup ; 2$H(d,$gamma$)⁴He reaction whose reaction rate is very uncertain, is ; presented. Reactions involving neutrons are treated as neutron-producing ; reactions but factors for calculating the reverse reaction rate are provided for ; all reactions. The

W. A. Fowler; G. R. Caughlan; B. A. Zimmerman

1975-01-01

322

Heat exchanger panel  

NASA Technical Reports Server (NTRS)

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.

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

2005-01-01

323

Microscale Regenerative Heat Exchanger  

NASA Technical Reports Server (NTRS)

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.

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

2006-01-01

324

Metal implants and surface reactions.  

PubMed

A metal in living tissue is prone to corrosion. The interaction of the foreign body with the tissue involves the redox reaction (an electron exchange) at the interface, the hydrolysis (a proton exchange) of oxide-hydrates as products of corrosion, and the formation of metal-organic complexes in the electrolyte. Denatured tissue in contact with the foreign body is the consequence. But behaviour of metals is variable; gold, stainless steel and most other metals react as described while few others like titanium and tantalum do not. The absence of a foreign body effect of a chemical kind is, without doubt, favorable in terms of tissue susceptibility to infection in the presence of titanium. PMID:9039349

Steinemann, S G

1996-01-01

325

Fe atom exchange between aqueous Fe2+ and magnetite.  

PubMed

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

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

2012-11-20

326

Measurement of product alignment in beam-gas chemiluminescent reactions  

E-print Network

Measurement of product alignment in beam-gas chemiluminescent reactions Michael G. Prisant, Charles of the chemiluminescent atom-diatom exchange reaction A + BC-.AB* + C under beam-gas conditions. The degree of product momentum appears as product rotational angular momentum. For beam-gas chemiluminescence, this implies

Zare, Richard N.

327

Is the simplest chemical reaction really so simple?  

PubMed Central

Modern computational methods have become so powerful for predicting the outcome for the H + H2 ? H2 + H bimolecular exchange reaction that it might seem further experiments are not needed. Nevertheless, experiments have led the way to cause theorists to look more deeply into this simplest of all chemical reactions. The findings are less simple. PMID:24367084

Jankunas, Justin; Sneha, Mahima; Zare, Richard N.; Bouakline, Foudhil; Althorpe, Stuart C.; Herráez-Aguilar, Diego; Aoiz, F. Javier

2014-01-01

328

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

Federal Register 2010, 2011, 2012, 2013, 2014

...Exchange, Inc.; Financial Industry Regulatory Authority, Inc.; International Securities Exchange LLC; NASDAQ OMX...Exchange, Inc., Financial Industry Regulatory Authority, Inc., International Securities Exchange, LLC, The...

2010-08-18

329

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

Federal Register 2010, 2011, 2012, 2013, 2014

...Exchange, Inc.; Financial Industry Regulatory Authority, Inc.; International Securities Exchange LLC; NASDAQ OMX...Exchange, Inc., Financial Industry Regulatory Authority, Inc., International Securities Exchange, LLC, The...

2010-08-31

330

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

E-print Network

, 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

Komives, Elizabeth A.

331

Ion-exchange equilibrium of N-acetyl-d-neuraminic acid on a strong anionic exchanger.  

PubMed

N-acetyl-d-neuraminic acid (Neu5Ac) is a high value-added product widely applied in the food industry. A suitable equilibrium model is required for purification of Neu5Ac based on ion-exchange chromatography. Hence, the equilibrium uptake of Neu5Ac on a strong anion exchanger, AD-1 was investigated experimentally and theoretically. The uptake of Neu5Ac by the hydroxyl form of the resin occurred primarily by a stoichiometric exchange of Neu5Ac(-) and OH(-). The experimental data showed that the selectivity coefficient for the exchange of Neu5Ac(-) with OH(-) was a non-constant quantity. Subsequently, the Saunders' model, which took into account the dissociation reactions of Neu5Ac and the condition of electroneutrality, was used to correlate the Neu5Ac sorption isotherms at various solution pHs and Neu5Ac concentrations. The model provided an excellent fit to the binary exchange data for Cl(-)/OH(-) and Neu5Ac(-)/OH(-), and an approximate prediction of equilibrium in the ternary system Cl(-)/Neu5Ac(-)/OH(-). This basic information combined with the general mass transfer model could lay the foundation for the prediction of dynamic behavior of fixed bed separation process afterwards. PMID:25863634

Wu, Jinglan; Ke, Xu; Zhang, Xudong; Zhuang, Wei; Zhou, Jingwei; Ying, Hanjie

2015-09-15

332

OXALOACETATE DECARBOXYLATION AND OXALOACETATE-CARBON DIOXIDE EXCHANGE IN ACETOBACTER XYLINUM  

PubMed Central

Benziman, Moshe (The Hebrew University of Jerusalem, Jerusalem, Israel), and N. Heller. Oxaloacetate decarboxylation and oxaloacetate-carbon dioxide exchange in Acetobacter xylinum. J. Bacteriol. 88:1678–1687. 1964.—Extracts of Acetobacter xylinum, prepared by sonic treatment, were shown to catalyze the decarboxylation of oxaloacetate (OAA) to pyruvate and CO2, and the exchange of C14-carbon dioxide into the ?-carboxyl of OAA. Fractionation of the extracts with ammonium sulfate resulted in a 10-fold increase of the specific activity of the enzyme system catalyzing the CO2 exchange and OAA decarboxylation reactions. The purified preparation catalyzed the exchange of pyruvate-3-C14 into OAA. Similar pH curves with a pH optimum of 5.6 were obtained for the CO2 exchange and OAA decarboxylation reactions. Both reactions require the presence of Mn2+ or Mg2+ ions. OAA decarboxylation was more strongly inhibited than the exchange of CO2 by dialysis or metal-chelating agents. Avidin did not inhibit either reaction. Adenosine triphosphate (ATP), adenosine diphosphate (ADP), guanosine triphosphate (GTP), guanosine diphosphate (GDP), pyrophosphate, or inorganic phosphate did not promote OAA decarboxylation and the CO2-exchange reaction catalyzed by the purified preparation. The purified preparation failed to catalyze the carboxylation of phosphoenolpyruvate in the presence of GDP, ADP, or inorganic phosphate, and that of pyruvate in the presence of ATP or GTP, even when supplemented with an OAA-trapping system. A scheme for OAA decarboxylation which could account for the observed exchange reactions and for the failure to obtain net fixation of CO2 is proposed. The relation between the exchange reaction and the synthesis of cellulose from pyruvate by A. xylinum is discussed. PMID:14240957

Benziman, Moshe; Heller, N.

1964-01-01

333

The Sodium-Potassium Exchange Pump  

PubMed Central

A model for the Na-K exchange pump was applied to data on Na+-loaded frog sartorius muscle, and was used to relate the rate of adenosine triphosphate (ATP) hydrolysis to the electrical properties of the cell membrane. Membrane hyperpolarization was considered to arise from an electrical current which was produced by the hydrolysis reaction coupled to ion movements, and which flowed across the membrane. The reaction rate, as calculated from hyperpolarization, agreed with direct measurements of ATP hydrolysis and with the rate estimated from Na+ tracer efflux studies. Although Na+ is actively extruded, the model showed that K+ is inwardly transported if the potassium permeability of the membrane is less than about 6.6 × 10-6 cm/sec, as is suggested by resistance data. Calculations indicated that the reaction conductance Lrr was relatively constant when compared with the reaction rate and reaction free energy for large changes in internal and external ionic concentrations. Its value agreed with the value obtained from the dependence of Na+ tracer efflux on external K+. A set of experiments was suggested which would provide a more complete interpretation of the data. PMID:5116580

Rapoport, Stanley I.

1971-01-01

334

Hydrogen Isotope Exchange Properties of Porous Solids Containing Hydrogen  

SciTech Connect

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

HEUNG, LEUNGK.

2004-08-18

335

Visiting Scholar Exchange Reports.  

ERIC Educational Resources Information Center

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…

Rubin, Kyna, Ed.

1986-01-01

336

Currency Exchange Rates.  

ERIC Educational Resources Information Center

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…

Siler, Carl R.

337

Higher Education Exchange, 2009  

ERIC Educational Resources Information Center

This volume begins with an essay by Noelle McAfee, a contributor who is familiar to readers of Higher Education Exchange (HEX). She reiterates Kettering's president David 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…

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

2009-01-01

338

Higher Education Exchange  

ERIC Educational Resources Information Center

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…

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

2009-01-01

339

The Creative Learning Exchange  

NSDL National Science Digital Library

This site is the homepage of The Creative Learning Exchange. CLE encourages a view of education for primary and secondary schools based on discovery as the essence of the learning process and advocates systems education implemented through learner-centered learning. Links to a downloadable introductory packet and models and lesson plans are also included.

The Creative Learning Exchange

340

Chimney heat exchanger  

SciTech Connect

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.

Whiteley, I.C.

1981-09-01

341

The Pizza Exchange  

NSDL National Science Digital Library

The students will receive paper pizzas that are divided into different fractional parts. They will decorate their pizza, and then make equal trades with classmates to explore equivalence of fractions. The students will be able to explain equivalence of fractions based on their pizza exchanges and will be able to compare and order the fractional parts by their size.

Elizabeth Gehron

2012-07-20

342

Higher Education Exchange 2006  

ERIC Educational Resources Information Center

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…

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

2006-01-01

343

KIDNEY EXCHANGE PROBLEM  

Microsoft Academic Search

To overcome the shortage of kidneys available for transplantation, several countries have started various programmes of kidney exchanges between incompatible patient-donor pairs. This situation can be modelled as a cooperative game in which the players are the patient-donor pairs and their preferences are derived in the first step from the suitability of the donated kidney and in the second step

Peter Biro; Katar ´ ina Cechlarova

344

Exchanging Faces in Images  

Microsoft Academic Search

Pasting somebody's face into an existing image with traditional photo retouching and digital image processing tools has only been possible if both images show the face from the same viewpoint and with the same illumination. However, this is rarely the case for given pairs of images. We present a system that exchanges faces across large differences in viewpoint and illumination.

Volker Blanz; Kristina Scherbaum; Thomas Vetter; Hans-peter Seidel

2004-01-01

345

Dublin, Ireland Exchange Program  

E-print Network

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

Fernandez, Eduardo

346

Charge and Exchange  

NASA Technical Reports Server (NTRS)

Even though comets are basically giant dirty snowballs, a few years ago they surprised astronomers by emitting X-radiation. These X-rays are not produced by multi-million degree gas (as is often the case) but rather by a process called 'charge exchange'. In this process, ionized atoms (which have lost one or more electrons) which are carried within the solar wind collide with neutral atoms in the comet's coma. The solar wind ion can collide with and capture an electron from the neutral comet atom, and in doing so some of the energy of the collision is observed in the form of X-rays. This produces a glow of X-rays on the sunward side of the comet's atmosphere. Charge exchange can occur in a variety of astrophysical settings, and cometary charge exchange provides astronomers a means to study this process up close. The image above is a pretty picture of comet 73P/Schwassmann-Wachmann 3 passing by the Ring Nebula. This image was obtained by the ultraviolet and optical telescope (UVOT) on the Swift gamma-ray burst hunter. The UVOT observations help astronomers to study the structure and chemistry of the comet, while Swift's X-ray Telescope (XRT) simultaneously monitors the charge exchange process. Comet 73P/Schwassmann-Wachmann 3 is currently in the process of breaking up, and the UVOT observations show important details of how this breakup is occurring.

2008-01-01

347

Nature's Heat Exchangers.  

ERIC Educational Resources Information Center

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)

Barnes, George

1991-01-01

348

Exchange bias theory  

Microsoft Academic Search

Research on the exchange bias (EB) phenomenon has witnessed a flurry of activity during recent years, which stems from its use in magnetic sensors and as stabilizers in magnetic reading heads. EB was discovered in 1956 but it attracted only limited attention until these applications, closely related to giant magnetoresistance, were developed during the last decade. In this review, I

Miguel Kiwi

2001-01-01

349

Cultural Exchange Through BD.  

ERIC Educational Resources Information Center

Discusses the development of and the popularity of comic strips (the BD or "bande dessinee" in French) in both France and the United States. Argues that comic strips play a major role in French-American cultural exchange because they express each culture and convey their message both visually and linguistically. (SED)

Lawlor, Patricia M.

1985-01-01

350

A corrosive resistant heat exchanger  

DOEpatents

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.

Richlen, S.L.

1987-08-10

351

Reaction steps for the water-gas shift reaction and NOx storage\\/reduction catalysts studied by FTIR methods  

Microsoft Academic Search

Proton exchange membrane (PEM) fuel cells are an environmentally friendly source of energy since they are roughly twice as fuel efficient as internal combustion engines. The source of H2 is generally from hydrocarbons through the catalytic reforming and water-gas shift (WGS) reactions. The challenge on the WGS reaction is to find a catalyst that is more stable but has the

Joshua Lynn Ratts

2008-01-01

352

y scaling in quasifree pion-single-charge exchange  

Microsoft Academic Search

Data for pion-single-charge exchange reactions at 750 MeV\\/c on complex nuclei are analyzed for y -scaling, or single scattering quasifree, responses. The angular dependence of the data is used to separate the spin and nonspin isovector responses, with comparisons to electron scattering results.

R. J. Peterson; C. E. Allgower; V. Bekrenev; W. J. Briscoe; J. R. Comfort; K. Craig; D. Grosnick; D. Isenhower; N. Knecht; D. Koetke; A. A. Kulbardis; G. Lolos; V. Lopatin; D. M. Manley; R. Manweiler; A. Marusic; S. McDonald; B. M. Nefkens; J. Olmsted; Z. Papandreou; D. C. Peaslee; N. Phaisangittisakul; J. Price; D. E. Prull; A. F. Ramirez; M. Sadler; A. Shafi; H. Spinka; T. D. Stanislaus; A. Starostin; H. M. Staudenmaier; I. Strakovsky; I. Supek

2004-01-01

353

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 ...

354

Chemical exchange program analysis.  

SciTech Connect

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.

Waffelaert, Pascale

2007-09-01

355

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

SciTech Connect

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.

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

1986-12-20

356

Oxygen isotopic exchange: A useful tool for characterizing oxygen conducting oxides  

E-print Network

Oxygen isotopic exchange: A useful tool for characterizing oxygen conducting oxides Bassat J we obtain in both cases data concerning the oxygen diffusion in the bulk and the oxygen exchange with regards to the oxygen reduction reaction. Detailed experimental and analytical processes are given

Paris-Sud XI, Université de

357

Evaporation heat transfer and pressure drop of refrigerant R-134a in a plate heat exchanger  

Microsoft Academic Search

Plate heat exchangers (PHE) have been widely used in food processing, chemical reaction processes, and other industrial applications for many years. Particularly, in the last 20 years plate heat exchangers have been introduced to the refrigeration and air conditioning systems as evaporators or condensers for their high efficiency and compactness. Here, the evaporation heat transfer coefficient and pressure drop for

Y.-Y. Yan; T.-F. Lin

1999-01-01

358

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

E-print Network

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

Raschke, Tanya M.

359

Counterflow Regolith Heat Exchanger  

NASA Technical Reports Server (NTRS)

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.

Zubrin, Robert; Jonscher, Peter

2013-01-01

360

Reciprocal Exchange: A Self-Sustaining System  

Microsoft Academic Search

Reciprocal exchange, or gift exchange, remains a widespread means of obtaining goods and services. This paper examines the persistence of reciprocal exchange by formalizing the interaction between self-enforcing exchange agreements and monetary market exchange. When more people engage in reciprocal exchange, market search costs increase, reciprocity is easier to enforce and yields higher utility. Thus, personalized exchange can persist even

Rachel E Kranton

1996-01-01

361

WMS International Exchange Scholarships WMS International Exchange Scholarships Regulations  

E-print Network

WMS International Exchange Scholarships WMS International Exchange Scholarships Regulations I N T R O D U C T I O N These scholarships have been established to enhance awareness and foster interest in exchange programmes offered by the University of Waikato. The scholarships are offered: To encourage

Waikato, University of

362

The heat pipe exchanger with controllable heat exchanging area  

Microsoft Academic Search

The heat transfer rate through the heat exchanger in an industrial boiler that burns heavy oils must be controlled so as not to decrease the exhaust gas temperature below the dew point of sulfuric acid. Two systems of heat pipe exchangers are examined: one controls the heat exchange area of the condenser section of the heat pipes and the other

M. Oshiro; S. Takasu; M. Kurihara; K. Taneda; T. Nakamoto; H. Nakayama

1984-01-01

363

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

Blum, Avrim

364

Phosphonic acid based exchange resins  

DOEpatents

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. 10 figs.

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

1995-09-12

365

Ecosystem Restoration through Interdisciplinary Exchange  

E-print Network

Ecosystem Restoration through Interdisciplinary Exchange David M. Blersch dblersch Shade of Blue and You 21 September 2010 #12;National Science Foundation Ecosystem Restoration through;National Science Foundation Ecosystem Restoration through Interdisciplinary Exchange UB's ERIE Program www

Sachs, Frederick

366

Phosphonic acid based exchange resins  

DOEpatents

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.

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

1995-01-01

367

The Dynamics of Multilateral Exchange  

Microsoft Academic Search

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

Kjell Hausken; John F. Moxnes

2005-01-01

368

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...

369

Exchange Rates and Financial Fragility  

Microsoft Academic Search

In this paper we analyze three views of the relationship between the exchange rate and financial fragility: (1) the moral hazard hypothesis, according to which pegged exchange rates offer implicit insurance against exchange risk and thereby encourage reckless borrowing and lending; (2) the original sin hypothesis, which emphasizes an incompleteness in financial markets which prevents the domestic currency from being

Barry Eichengreen; Ricardo Hausmann

1999-01-01

370

Resource Exchange | BASBE  

NSDL National Science Digital Library

The Biotechnology Alliance for Suncoast Biology Educators (BASBE) is a community of science educators and support partners. They are K-12 teachers, college professors, curriculum specialists, scientists, entrepreneurs, and business people who seek to improve the overall quality of science education in local secondary schools and to better prepare high school graduates to succeed in college science courses. They provide a forum where K12 teachers collaborate with college professors to form ongoing partnerships that enable continuity of instruction for science students as they transition from high school to college. The Resource Exchange allows members to share educational materials. Educators freely exchange lesson plans, protocols, technique tips, teaching strategies, and other materials that they have developed and used in their classrooms. BASBE site users provide direct feed back on materials leading to ongoing improvements in site content.

371

Serpentine heat exchanger  

SciTech Connect

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.

Tomlinson, R.S.

1991-01-08

372

Energy exchange between subject and belt during treadmill walking.  

PubMed

Treadmill walking aims to simulate overground walking, but intra-stride belt speed variations of treadmills result in some interaction between treadmill and subject, possibly obstructing this aim. Especially in self-paced treadmill walking, in which the belt speed constantly adjusts to the subject, these interactions might affect the gait pattern significantly. The aim of this study was to quantify the energy exchange between subject and treadmill, during the fixed speed (FS) and self-paced (SP) modes of treadmill walking. Eighteen subjects walked on a dual-belt instrumented treadmill at both modes. The energy exchange was calculated as the integration of the product of the belt speed deviation and the fore-aft ground reaction force over the stride cycle. The total positive energy exchange was 0.44 J/stride and the negative exchange was 0.11 J/stride, which was both less than 1.6% of the performed work on the center of mass. Energy was mainly exchanged from subject to treadmill during both the braking and propulsive phase of gait. The two treadmill modes showed a similar pattern of energy exchange, with a slightly increased energy exchange during the braking phase of SP walking. It is concluded that treadmill walking is only mildly disturbed by subject-belt interactions when using instrumented treadmills with adequate belt control. PMID:24589022

Sloot, L H; van der Krogt, M M; Harlaar, J

2014-04-11

373

Repeated Reasoning: Valentine Exchange  

NSDL National Science Digital Library

This professional development video clip shows students engaged in Common Core Practice Standard #8-Look for and express regularity in repeated reasoning. In this video clip fourth grade students are developing their algebraic thinking skills by problem solving the question: "How many cards would be needed if all 24 students in the class were to exchange cards with each other?" Additional resources include a video transcript, teaching tips, and a link to a professional development reflection activity based upon the video.

WGHB Boston

2013-01-01

374

Thermoelectric heat exchange element  

DOEpatents

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

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

2007-08-14

375

The kidney exchange game  

Microsoft Academic Search

Abstract. The most efiective treatment for kidney failure that is currently known,is transplantation. As the number of cadaveric donors is not su?cient and kidneys from living donors are often not suitable for immunological reasons, there are attempts to organize exchanges between patient-donor pairs. In this paper we model this situation as a cooperative game and propose some algorithms for flnding

Katarna Cechlarova; Tamas Fleiner; David Manlove

376

Microtube strip heat exchanger  

Microsoft Academic Search

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

F. D. Doty

1990-01-01

377

The exchangeability of shape  

PubMed Central

Background Landmark based geometric morphometrics (GM) allows the quantitative comparison of organismal shapes. When applied to systematics, it is able to score shape changes which often are undetectable by traditional morphological studies and even by classical morphometric approaches. It has thus become a fast and low cost candidate to identify cryptic species. Due to inherent mathematical properties, shape variables derived from one set of coordinates cannot be compared with shape variables derived from another set. Raw coordinates which produce these shape variables could be used for data exchange, however they contain measurement error. The latter may represent a significant obstacle when the objective is to distinguish very similar species. Results We show here that a single user derived dataset produces much less classification error than a multiple one. The question then becomes how to circumvent the lack of exchangeability of shape variables while preserving a single user dataset. A solution to this question could lead to the creation of a relatively fast and inexpensive systematic tool adapted for the recognition of cryptic species. Conclusions To preserve both exchangeability of shape and a single user derived dataset, our suggestion is to create a free access bank of reference images from which one can produce raw coordinates and use them for comparison with external specimens. Thus, we propose an alternative geometric descriptive system that separates 2-D data gathering and analyzes. PMID:20964872

2010-01-01

378

Soviets seek scientific exchange  

NASA Astrophysics Data System (ADS)

GEOS-A, associated with the Soviet Union's Institute of Earth Physics, is seeking to promote exchange between Soviet and Western geophysicists. GEOS-A is a nonprofit, private organization formed by specialists from the U.S.S.R. Academy of Scientists.GEOS-A aims to promote the transfer of academic research results to industry and education. It also seeks to stimulate international scientific exchange and to support independent nongovernmental programs and expertise in geophysics and ecology. The organization would like to cooperate with Western universities in exchanging students and young scientists and in building scientific relationships between the two countries. This would include inviting students and young specialists for collaborative scientific research, consultations, language practice, and graduate study in any institute of the U.S.S.R. Academy of Sciences. Participants would live in rented private apartments in downtown Moscow for approximately one week to several months. All living expenses would be covered at a rate higher than the academy's standard one (unfortunately travel to and from the Soviet Union cannot be covered).

379

Kinetics of tritium removal from heavy water by exchange with deuterochloroform  

SciTech Connect

A technique was developed to determine the rate and equilibrium constants for the base-catalyzed exchange of tritium from ehavy water to deuterochloroform. An activation energy and entropy were also calculated. These quantities are comparable with those reported in the literature for a similar reaction involving the exchange of deuterium from deuterochloroform to water. It was found that the exchange reaction occurred predominately between the dissolved reactants in the D/sub 2/O and CDCl/sub 3/ phases. The rate constant is a strong direct function of temperature while the equilibrium constant is a weak inverse function.

Hsiao, P.

1983-03-14

380

Lightweight Long Life Heat Exchanger  

NASA Technical Reports Server (NTRS)

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.

Moore, E. K.

1976-01-01

381

Emittance and Phase Space Exchange  

SciTech Connect

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.

Xiang, Dao; Chao, Alex; /SLAC

2011-08-19

382

Charge Transfer Reactions  

NASA Astrophysics Data System (ADS)

Charge transfer, or charge exchange, describes a process in which an ion takes one or more electrons from another atom. Investigations of this fundamental process have accompanied atomic physics from its very beginning, and have been extended to astrophysical scenarios already many decades ago. Yet one important aspect of this process, i.e. its high efficiency in generating X-rays, was only revealed in 1996, when comets were discovered as a new class of X-ray sources. This finding has opened up an entirely new field of X-ray studies, with great impact due to the richness of the underlying atomic physics, as the X-rays are not generated by hot electrons, but by ions picking up electrons from cold gas. While comets still represent the best astrophysical laboratory for investigating the physics of charge transfer, various studies have already spotted a variety of other astrophysical locations, within and beyond our solar system, where X-rays may be generated by this process. They range from planetary atmospheres, the heliosphere, the interstellar medium and stars to galaxies and clusters of galaxies, where charge transfer may even be observationally linked to dark matter. This review attempts to put the various aspects of the study of charge transfer reactions into a broader historical context, with special emphasis on X-ray astrophysics, where the discovery of cometary X-ray emission may have stimulated a novel look at our universe.

Dennerl, Konrad

2010-12-01

383

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

384

Four-Angle Saturation Transfer (FAST) Method for Measuring Creatine Kinase Reaction Rates In Vivo  

E-print Network

Four-Angle Saturation Transfer (FAST) Method for Measuring Creatine Kinase Reaction Rates In Vivo of measuring kinetic reaction rates for two-site chemical exchange is described. The method employs saturation different flip angles, and the equilibrium magnetization, relaxation times, and reaction rates

Ouwerkerk, Ronald

385

Diffusion of Weak Acids across Lipid Bilayer Membranes: Effects of Chemical Reactions in the Unstirred Layers  

Microsoft Academic Search

Chemical reactions in the aqueous unstirred layers of solution adjacent to a membrane can have dramatic effects on the diffusion of solutes across that membrane. This is demonstrated by the diffusion of labeled salicylate and salicylic acid across a phospholipid bilayer membrane. Two types of chemical reactions are considered. The first is an isotopic exchange reaction between the ionic and

John Gutknecht; D. C. Tosteson

1973-01-01

386

Selective facet reactivity during cation exchange in cadmium sulfide nanorods.  

PubMed

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 (Cu(2)S) grows inward 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 nonselective nucleation of silver sulfide (Ag(2)S) occurs (Robinson, R. D.; Sadtler, B.; Demchenko, D. O.; Erdonmez, C. K.; Wang, L.-W.; Alivisatos, A. P. Science 2007, 317, 355-358). From interface formation energies calculated for several models of epitaxial connections between CdS and Cu(2)S or Ag(2)S, we infer the relative stability of each interface during the nucleation and growth of Cu(2)S or Ag(2)S within the CdS nanorods. The epitaxial attachments of Cu(2)S to the end facets of CdS nanorods minimize the formation energy, making these interfaces stable throughout the exchange reaction. Additionally, as the two end facets of wurtzite CdS nanorods are crystallographically nonequivalent, asymmetric heterostructures can be produced. PMID:19351206

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

2009-04-15

387

Selective Facet Reactivity During Cation Exchange in Cadmium Sulfide Nanorods  

SciTech Connect

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.

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

2008-12-18

388

Concerted hydrogen atom exchange between three HF molecules  

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

389

StatetoState Quantum Dynamics of O + O2 Isotope Exchange  

E-print Network

is a prototypical complexforming reaction via the metastable ozone ( ) intermediate. The importance body (M). An in depth understanding of the bimolecular isotope exchange reactions will shed light fractionation of oxygen: A novel isotope effect and its possible cosmochemical implications. Science 1983, 219

Maccabe, Barney

390

The reaction 3 cordierite = 2 garnet + 4 sillimanite + 5 quartz as a geological thermometer in the Opinicon Lake region, Ontario  

Microsoft Academic Search

In equilibrated metamorphic rocks containing coexisting garnet, cordierite, quartz and sillimanite, the exchange of iron and magnesium between cordierite and garnet offers a highly favourable geological thermometer and barometer, because this exchange reaction is insensitive to pressure. Thermodynamic analysis shows that this thermometer may be calibrated from knowledge of the breakdown reactions for iron and magnesian cordierite end members to

K. L. Currie

1971-01-01

391

Stochastic thermodynamics of chemical reaction networks  

E-print Network

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.

Tim Schmiedl; Udo Seifert

2006-12-19

392

Exam Question Exchange.  

ERIC Educational Resources Information Center

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)

Alexander, John J., Ed.

1978-01-01

393

Exchange functional by a range-separated exchange hole  

SciTech Connect

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

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

2011-03-15

394

The Quantum Exchange  

NSDL National Science Digital Library

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

395

California Data Exchange Center  

NSDL National Science Digital Library

At the California Data Exchange Center website, the California Department of Water Resources provides access to an array of operational hydrologic data. Within the River Stages and Flow Data link, visitors will find river stage maps, river schematics, information on various rivers, and daily hydrologic summaries. The website provides snow information including snow sensor plots, water supply conditions, reservoir data, and reports. Individuals can view numerous satellite images and water- and weather-related forecasts. The data query tools offer an easy way to search historical and current data, data plots and graphs, and station information.

396

Analysis of titanium/carbon steel heat exchanger fire  

SciTech Connect

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.

Prine, B.A. (Dow Chemical Canada Inc., Sarnia, Ontario (Canada))

1992-04-01

397

The rate of oxygen isotope exchange between nitrate and water  

NASA Astrophysics Data System (ADS)

The oxygen isotope exchange rate between nitrate and water was measured at a temperature of 50-80 °C and pH -0.6 to 1.1. Oxygen isotope exchange is a first-order reaction, with the exchange rate being strongly affected by both reaction temperature and pH, with increased rates of isotope exchange at higher temperatures and lower pH values. The rate of oxygen isotope exchange under natural conditions is extremely slow, with an estimated half-life for isotope exchange of 5.5 × 109 years at 25 °C and pH 7. The extremely slow rate of oxygen isotope exchange between nitrate and water under typical environmental conditions illustrates that nitrate-?18O signatures (and also nitrate ?17O and ?17O signatures) associated with various nitrate sources, as well as isotope compositions produced by biogeochemical processes, will be preserved. Hence, it is valid to use the value of nitrate-?18O to investigate the sources and biogeochemical behavior of nitrate, in a similar manner to the use of sulfate-?18O signatures to study the sources and biogeochemical behavior of sulfate. Equilibrium oxygen isotope fractionation factors have been determined, although quantification of the nitrate-water equilibrium fractionation factor is not possible due to the presence of nitrate as both protonated (i.e. HNO3) and unprotonated forms (i.e. NO3-) under the experimental conditions, and the difficulty in accurately calculating nitrate speciation in low pH, high ionic strength solutions.

Kaneko, Masanori; Poulson, Simon R.

2013-10-01

398

Tagged hypervalent iodine reagents: a new purification concept based on ion exchange through SN2 substitution.  

PubMed

The preparation of phenylsulfonate-tagged iodine(III) reagents as well as their use in a novel purification strategy for iodine(III)-promoted reactions is described. The concept is based on ion exchange and is initiated by an azide-promoted SN2-reaction at the alkyl sulfonate followed by trapping of the resulting aryl sulfonate anion with an ion-exchange resin. The concept is successfully proven for Ru-catalyzed oxidations of alcohols, the activation and glycosidation of thioglycosides, and the SuArez reaction of pyranoses. PMID:17999512

Kunst, Eike; Gallier, Florian; Dujardin, Gilles; Yusubov, Mekhman S; Kirschning, Andreas

2007-12-01

399

Heat exchanger mat  

SciTech Connect

An improved heat exchanger mat and a method of dislodging and retrieving the mat from the bottom of a solar pond without disturbing an established thermal gradient. The mat is separated from the pond bottom by the injection of a dislodging medium between the mat and the bottom of the pond. When the pond contains a liner, the dislodging medium is injected between the mat and the pond liner. The mat utilizes a dual conduit network of one integral conduit for the flow of heat exchanger fluid and a second integral conduit for the flow of dislodging medium. The dislodging medium enters the dislodging conduit via an inlet and exits through a plurality of outlets located on the underside of the mat. The medium, as it exits, forces the mat upward and frees it from the bottom of the pond. Once the dislodging medium has separated the mat from the pond bottom, attached retrieval cords are used to remove the mat by drawing it up the side of the pond.

Walmet, G. E.

1985-04-16

400

Catalysis of Photochemical Reactions.  

ERIC Educational Resources Information Center

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)

Albini, A.

1986-01-01

401

Investigation of Alkali Ion Exchange Processes in Na-Al-Si Glass Using Ion beam Techniques  

NASA Astrophysics Data System (ADS)

Glass and ceramic waste forms are proposed for the stabilization and immobilization of high level wastes. Recent findings show that Na ion exchange reaction can effectively increase the release of radionuclides from the glass matrix. We investigated the Na ion exchange processes and mechanisms using Rutherford backscattering spectrometry (RBS) and nuclear reaction analysis (NRA). The glass samples with fixed Na_2O and variable Al_2O3 concentrations were exposed to different times at 23^oC in a single pass flow-through apparatus, which contained aqueous D2 ^18O solution, supersaturated with respect to amorphous silica. The results show that the Na exchange rate is much higher than the matrix dissolution rate. On the basis of the depth distributions of Na, D, and ^18O, three different zones (reaction, transition and diffusion zones) were identified. The samples with higher amounts of Al content have a significantly narrower reaction zone than the low Al content glass samples.

Shutthanandan, V.; Thevuthasan, S.; Baer, D. R.; Icenhower, J. P.; Engelhard, M. H.; McGrail, B. P.

2001-03-01

402

Reaction-diffusion equations for interacting particle systems  

NASA Astrophysics Data System (ADS)

We study interacting spin (particle) systems on a lattice under the combined influence of spin flip (Glauber) and simple exchange (Kawasaki) dynamics. We prove that when the particle-conserving exchanges (stirrings) occur on a fast time scale of order ?-2 the macroscopic density, defined on spatial scale ?-1, evolves according to an autonomous nonlinear diffusion-reaction equation. Microscopic fluctuations about the deterministic macroscopic evolution are found explicitly. They grow, with time, to become infinite when the deterministic solution is unstable.

de Masi, A.; Ferrari, P. A.; Lebowitz, J. L.

1986-08-01

403

Ion exchange technology assessment report  

SciTech Connect

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.

Duhn, E.F.

1992-01-01

404

Ion exchange technology assessment report  

SciTech Connect

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.

Duhn, E.F.

1992-12-31

405

On Thermonuclear Reaction Rates  

E-print Network

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

H. J. Haubold; A. M. Mathai

1996-12-02

406

The Microtube Strip Heat Exchanger  

Microsoft Academic Search

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

F. DAVID DOTY; GREG HOSFORD; J. B. SPITZMESSER; I JOHN DEWEY JONES

1991-01-01

407

Optimistic protocols for fair exchange  

Microsoft Academic Search

We describe a generic protocol for fair exchange of electronic goods with non-repudiation. Goods can be signatures (i.e., non-repudiation tokens of public data), confidential data, or payments. The protocol does not involve a third party in the exchange in the fault-less case but only for recovery. Many commercial transactions can be modelled as a sequence of exchanges of electronic goods

N. Asokan; Matthias Schunter; Michael Waidner

1997-01-01

408

Optimization of Heat Exchanger Cleaning  

E-print Network

decrease models of the heat recovery decay. A mathematical comparison of mechanical and chemical cleaning of heat exchangers has identified the most significant parameters which affect the choice between the two methods. INTRODUCTION In most... can be somewhat mitigated by periodic chemical or mechanical cleaning of the exchanger surface, and by the addition of antifoul ants. The typical decay in heat recovery capabil ity due to fou 1i ng and restoration afte r heat exchanger cleaning...

Siegell, J. H.

409

Ion-exchange hollow fibers  

NASA Technical Reports Server (NTRS)

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.

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

1977-01-01

410

Ion-exchange hollow fibers  

NASA Technical Reports Server (NTRS)

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.

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

1980-01-01

411

Ion-exchange hollow fibers  

NASA Technical Reports Server (NTRS)

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.

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

1976-01-01

412

A classical but new kinetic equation for hydride transfer reactions.  

PubMed

A classical but new kinetic equation to estimate activation energies of various hydride transfer reactions was developed according to transition state theory using the Morse-type free energy curves of hydride donors to release a hydride anion and hydride acceptors to capture a hydride anion and by which the activation energies of 187 typical hydride self-exchange reactions and more than thirty thousand hydride cross transfer reactions in acetonitrile were safely estimated in this work. Since the development of the kinetic equation is only on the basis of the related chemical bond changes of the hydride transfer reactants, the kinetic equation should be also suitable for proton transfer reactions, hydrogen atom transfer reactions and all the other chemical reactions involved with breaking and formation of chemical bonds. One of the most important contributions of this work is to have achieved the perfect unity of the kinetic equation and thermodynamic equation for hydride transfer reactions. PMID:23917398

Zhu, Xiao-Qing; Deng, Fei-Huang; Yang, Jin-Dong; Li, Xiu-Tao; Chen, Qiang; Lei, Nan-Ping; Meng, Fan-Kun; Zhao, Xiao-Peng; Han, Su-Hui; Hao, Er-Jun; Mu, Yuan-Yuan

2013-09-28

413

Disease Exchanges 20-365 Chapter 20. DISEASE EXCHANGES  

E-print Network

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

Richerson, Peter J.

414

Design of heat exchange element for plastic film heat exchanger  

Microsoft Academic Search

This report presents the results of an effort to design a plastic film heat exchanger element (PFHX) suitable for use in an industrial heat pump evaporator. This report addresses the selection of materials, the expected flow and heat transfer behavior, and the mechanical design features of a parallel plate type exchanger that uses thin plastic films as the boundary between

E. C. Guyer; D. L. Brownell

1984-01-01

415

Biomass heat exchanger furnace  

SciTech Connect

A hot air heat exchanger furnace that uses crop residue as a fuel source is provided for producing the heat required for various purposes, such as the drying of grains, peanuts, soybeans and other materials and for the heating of buildings. The furnace includes a combustion chamber, an upper manifold, a lower manifold, a plenum and a number of exhaust tubes. The exhaust tubes direct the flow of combustion gases from the combustion chamber in a serpentine path in the plenum between the upper and lower manifolds and into a stack. Meanwhile, ambient air passes into the plenum, past the heat transfer surfaces of the combustion chamber and the exhaust tubes as heat transfers to it. Then it passes out of the furnace.

Sukup, E.G.

1984-05-22

416

Monogroove liquid heat exchanger  

NASA Technical Reports Server (NTRS)

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).

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

1990-01-01

417

The International Power Exchange  

SciTech Connect

The International Power Exchange (IPEX) is an on-line bulletin board enabling utilities and other subscibers to advertise Wholesale Power. Bulk Transmission and Emission Allowances for sale or purchase. IPEX was created in response of the electric utility industry for a 24-hour per day, 7-day per week, computer-based communication system. The system provides instant access to market prices allowing a subscriber to increase their span of of knowledge when needing to buy or sell energy. The IPEX database provides information for trend analysis and other market research activities. IPEX was designed for investor-owned utilities, generation and transmission cooperatives, municipal organizations, and independent power producers. Capabilities and procedures for using the IPEX are discussion in some detail.

NONE

1994-12-31

418

The Engineering Exchange  

NSDL National Science Digital Library

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

Matheson, Marshall

2013-01-01

419

Environmental Research Information Exchange  

NSDL National Science Digital Library

The National Library for the Environment has launched its new Environmental Research Information Exchange (ERIE) service, to provide "a forum for researchers, educators, resource managers, agency decision-makers, foundation representatives, journalists and others in all environmental fields to share information and discuss issues." The site will include postings of research needs (identified by researchers and managers), research opportunities (for students and established researchers), funding opportunities, and a wealth of scientific information about the environment. In addition, a bulletin board will be available for posting messages, questions, and answers. This site aims to fill an important and much-needed role in facilitating communication between researchers, managers, journalists, and funding agencies; skeptics and interested participants should check out the examples of how ERIE might be useful ... and take it from there!

420

South Atlantic interbasin exchange  

NASA Technical Reports Server (NTRS)

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.

Rintoul, Stephen Rich

1991-01-01

421

Hybrid Heat Exchangers  

NASA Technical Reports Server (NTRS)

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.

Tu, Jianping Gene; Shih, Wei

2010-01-01

422

Biofuels Information Exchange  

NSDL National Science Digital Library

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

Holmes, Tim

423

Chiral analyses of peptides by ion/molecule reactions  

NASA Astrophysics Data System (ADS)

Protonated complexes comprised of guest peptides with permethylated hosts ([beta]-cyclodextrin and maltoheptaose) were produced in the gas phase by electrospray ionization and reacted with a gaseous amine in a Fourier transform ion cyclotron resonance mass spectrometer. An exchange reaction was observed whereby the guest peptide was replaced by the gaseous alkyl amine. The exchange reaction was enantioselective and was used to determine enantiomeric excess in mixtures of enantiomers. The nature of the recognition is probed by the selection of the peptides and the use of molecular dynamics calculations.

Grigorean, Gabriela; Cong, Xin; Lebrilla, Carlito B.

2004-05-01

424

Controlling chemical reactions of a single particle  

E-print Network

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.

Lothar Ratschbacher; Christoph Zipkes; Carlo Sias; Michael Köhl

2012-09-26

425

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

PubMed

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

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

2010-06-01

426

CADCAM data exchange pilot project  

Microsoft Academic Search

CAD-CAM data were exchanged between dissimilar CAD systems and the information was used to fabricate three parts. Problems were identified and solutions were proposed or implemented in the area of translation methods, data verification, CAD drawing conventions, and data handling. Additional software needed for productive data exchange has been identified.

J. Hintz; D. Williams

1986-01-01

427

Rare Disasters and Exchange Rates  

Microsoft Academic Search

We propose a new model of exchange rates, which yields a theory of the forward premium puzzle. Our explanation combines two ingredients: the possibility of rare economic disasters, and an asset view of the exchange rate. Our model is frictionless, has complete markets, and works for an arbitrary number of countries. In the model, rare worldwide disasters can occur and

Emmanuel Farhi; Xavier Gabaix

2008-01-01

428

StarBright Learning Exchange  

ERIC Educational Resources Information Center

This article features StarBright Learning Exchange, a program that provides a cross-cultural exchange between Australian and South African early childhood educators. The program was originated when its president, Carol Allen, and her colleague, Karen Williams, decided that they could no longer sit by and watch the unfolding social catastrophe that…

Kalinowski, Michael

2007-01-01

429

Heat exchanger wrap-up  

Microsoft Academic Search

Heat exchangers are used between the collector fluid and the storage tank in active solar energy systems. The thermal performance of heat exchangers can be predicted if the two parameters are known: the number of transfer units, which is the ratio of characteristic size for heat transfer to the smaller of the heat capacity flow rates, and the ratio of

Lunde

1983-01-01

430

4, 125164, 2007 Methanol exchange  

E-print Network

BGD 4, 125­164, 2007 Methanol exchange between grassland and the atmosphere A. Brunner et al. Title Discussions Biogeosciences Discussions is the access reviewed discussion forum of Biogeosciences Methanol (albrecht.neftel@art.admin.ch) 125 #12;BGD 4, 125­164, 2007 Methanol exchange between grassland

Paris-Sud XI, Université de

431

Technology Performance Exchange (Fact Sheet)  

SciTech Connect

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.

Not Available

2012-10-01

432

Designing heat exchangers by computer  

Microsoft Academic Search

The design of heat exchangers by computer has come a long way in a short time due to the explosive development of computer hardware and the ingenuity of the software developers. It is already possible to design by computer a reasonably-sized heat exchanger for most services. However, the future potential is great for the computer to simulate performance for troubleshooting,

Palen

1986-01-01

433

Gas Exchange, Partial Pressure Gradients,  

E-print Network

Gas Exchange, Partial Pressure Gradients, and the Oxygen Window Johnny E. Brian, Jr., M affect the precise gas exchange occurring in individual areas of the lungs and body tissues. To make of circulatory and gas transport physiology, and the best place to start is with normobaric physiology. LIFE

Riba Sagarra, Jaume

434

EXCHANGE. Volume 9-92  

SciTech Connect

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.

Boltz, J.C. [ed.] [ed.

1992-09-01

435

Risk, Uncertainty and Exchange Rates  

Microsoft Academic Search

This paper explores a new direction for empirical models of exchange rate determination. The motivation arises from two well documented facts, the failure of log-linear empirical exchange rate models of the 1970's and the variability of risk premiums in the forward market. Rational maximizing models of economic behavior imply that changes in the conditional variances of exogenous processes, such as

Robert J. Hodrick

1989-01-01

436

Flow maldistribution in heat exchangers  

Microsoft Academic Search

Based on the study of gross flow maldistribution in an experimental electrical heater, this paper presents the effect of flow nonuniformity on the performance of heat exchangers. First, it is shown that it is much more important to understand maldistributions for electrical heaters than for two-fluid heat exchangers. The study of the flow distribution in a particular heater shows that

S. Lalot; P. Florent; S. K. Lang; A. E. Bergles

1999-01-01

437

Educators Exchange: A Program Evaluation.  

ERIC Educational Resources Information Center

The Educators Exchange Program (EEP) was established under a training and educational exchange agreement reached by California's San Diego Community College District (SDCCD) and the republic of Mexico. In the program, the District provided a 4-week technological training program to faculty at Centros de Capacitacion Tecnologica Industrial…

Armstrong, William B.

438

Iodine Clock Reaction  

NSDL National Science Digital Library

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

439

The Glyoxal Clock Reaction  

ERIC Educational Resources Information Center

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…

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

2007-01-01

440

The exchange rate – A shock-absorber or source of shocks? A study of four open economies  

Microsoft Academic Search

The paper provides SVAR estimates for the UK, Canada, Sweden and Denmark, making explicit a monetary policy reaction function and taking account of exchange rate targeting practices. It examines the role of the exchange rate as shock-absorber as opposed to a source of its own, and destabilizing, shocks. We find that in all countries but the UK, real shocks are

Michael Artis; Michael Ehrmann

2006-01-01

441

NUCLEAR POLARIZATION OF He³ GAS BY METASTABILITY EXCHANGE WITH OPTICALLY PUMPED METASTABLE He³ATOMS  

Microsoft Academic Search

A small fraction of metastable He³ is maintained, by means of a r-; f discharge, in He³ in a magnetic field. The metastable atoms are ; partially polarized by optical pumping using a 1- mu V circularly polarized ; pumping light. Further, however, the stable and metastable atoms are capable of ; exchanging excitations; in the exchange reactions, the outgoing

G. K. Walters; F. D. Colegrove; L. D. Schearer

1962-01-01

442

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

SciTech Connect

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

Gordon, R J

1982-08-02

443

High Temperature Heat Exchanger Project  

SciTech Connect

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

Anthony E. Hechanova, Ph.D.

2008-09-30

444

Insoluble polyelectrolyte and ion-exchange hollow fiber impregnated therewith  

NASA Technical Reports Server (NTRS)

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.

Rembaum, A. (inventor)

1977-01-01

445

Plasma ion temperature measurements via charge-exchange recombination radiation  

SciTech Connect

Spatially and temporally resolved plasma ion temperatures can be determined by measuring the Doppler-broadened line profiles of transitions excited by charge-exchange recombination reactions between fast hydrogen atoms and fully ionized low-Z ions. Plasma rotation velocity profiles can also be obtained. A sample result from the PDX tokamak using He/sup +/ radiation is presented, and expected line intensities for model cases for PDX and TFTR are calculated.

Fonck, R.J.; Goldston, R.J.; Kaita, R.; Post, D.E.

1982-11-01

446

Natural Zeolites: Cation Exchange, Cation Arrangement and Dehydration Behavior  

Microsoft Academic Search

Still 50 years ago natural zeolites mainly from vugs and fissures of volcanic rocks were considered a rare curiosity of nature.\\u000a About 100 years ago chemists recognized that these minerals with a tetrahedral framework structure, characterized by internal\\u000a porous space in form of cavities and connecting channels, can be used for ion exchange, molecular sieving, and catalytic reactions.\\u000a Thus in

Thomas Armbruster

447

Isolation and ion exchanging behaviour of mendelevium\\/II  

Microsoft Academic Search

Mendelevium-256 was obtained by irradiating of Bk-249 with Ne-22 ions in the external beam of U-300 cyclotron. An efficient ionexchanging method of medelevium isolation and separation from nuclear reaction products have been developed in which a column with cation exchanger and zinc amalgam and 1M HCl solutions as eluents were used. Under these conditions mendelevium has been shown to be

L. I. Guseva; G. S. Tikhomirova; G. V. Buklanov; Zen Zin Phar; I. A. Lebedev; N. V. Katargin; B. F. Myasoedov

1987-01-01

448

High-resolution spectroscopy using direct reactions of RI beams  

NASA Astrophysics Data System (ADS)

Nuclear spectroscopy via direct reactions of RI beams is discussed especially for focusing on charge exchange reactions of unstable nuclei. As an example, study of isospin multiplets of drip-line nuclei is presented discussing neutron halo phenomena studied by proton decay of isobaric analog states populated by the (p,n) reaction around 70 A MeV. The SHARAQ project is presented along high-resolution nuclear spectroscopy using RI beams at 150-350 A MeV, where the characteristics of exothemic charge exchange reactions are discussed. The present status of construction of the SHARAQ spectrometer and the high-resolution beam line in the RIBF at RIKEN are presented.

Shimoura, Susumu

2009-05-01

449

Fault-Tolerant Heat Exchanger  

NASA Technical Reports Server (NTRS)

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.

Izenson, Michael G.; Crowley, Christopher J.

2005-01-01

450

40 CFR 63.654 - Heat exchange systems.  

Code of Federal Regulations, 2014 CFR

...c) through (g) of this section if all heat exchangers within the heat exchange system either...heat exchange system. (ii) Selected heat exchanger exit line(s) so that each heat exchanger or group of heat exchangers within a...

2014-07-01

451

40 CFR 63.654 - Heat exchange systems.  

Code of Federal Regulations, 2013 CFR

...c) through (g) of this section if all heat exchangers within the heat exchange system either...heat exchange system. (ii) Selected heat exchanger exit line(s) so that each heat exchanger or group of heat exchangers within a...

2013-07-01

452

Particle production in antiproton induced nuclear reactions  

E-print Network

The quantum molecular dynamics model has been improved to investigate the reaction dynamics induced by antiprotons. The reaction channels of elastic scattering, annihilation, charge exchange and inelastic collisions have been included in the model. Dynamics on particle production, in particular pions, kaons, antikaons and hyperons, is investigated in collisions of $\\overline{p}$ on $^{12}$C, $^{20}$Ne, $^{40}$Ca, $^{112}$Sn, $^{181}$Ta, $^{197}$Au and $^{238}$U from a low to high incident momentum. The rapidity and momentum distributions of $\\pi^{+}$ and protons from the LEAR measurements can be well reproduced. The impacts of system size and incident momentum on particle emissions are investigated from the inclusive spectra, transverse momentum and rapidity distributions. It is found that the annihilations of $\\overline{p}$ on nucleons are of importance on the particle production. Hyperons are mainly produced via meson induced reactions on nucleons and strangeness exchange collisions when the incident momentum is below the threshold value of annihilation reaction. A higher nuclear temperature is obtained from the kaon emission, but it has a lower value for hyperon production.

Zhao-Qing Feng; Horst Lenske

2014-05-07

453

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

Federal Register 2010, 2011, 2012, 2013, 2014

...34-70050; File No. 10-209] Application of Topaz Exchange, LLC for Registration as a National Securities...July 26, 2013. I. Introduction On July 3, 2012, Topaz Exchange, LLC (``Topaz Exchange'' or ``Exchange'') submitted to...

2013-08-01

454

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

SciTech Connect

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.

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

2012-06-19

455

Production of Radioactive Nuclides in Inverse Reaction Kinematics  

E-print Network

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.

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

456

Excitation of giant resonances via direct reactions  

SciTech Connect

Experimental measurements of electric giant multipole resonances are discussed. The parameters of the giant quadrupole resonance are now firmly established by an extensive set of measurements. The GQR is providing a significant influence in other areas of nuclear physics. The monopole resonance has now been established and its observation has provided the first direct measure of the nuclear compressibility. A strong case for the existence of a giant octupole resonance is now being made through a variety of hadron reactions. However, the supply of giant multipole resonances has not been exhausted. The newer techniques such as higher energy proton scattering, charge exchange reactions, heavy-ion scattering and pion reactions offer considerable hope for identifying new resonances during the next few years.

Bertrand, F.E.

1982-01-01

457

Energy-Exchange Project  

SciTech Connect

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)

Not Available

1982-04-01

458

Modular heat exchanger  

DOEpatents

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.

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

1981-03-03

459

Modular heat exchanger  

DOEpatents

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.

Giardina, A.R.

1981-03-03

460

Vapor-phase catalytic oxidesulfurization (ODS) of organosulfur compounds over supported metal oxide catalysts  

NASA Astrophysics Data System (ADS)

Sulfur in transportation fuels remains a leading source of SOx emissions from vehicle engines and is a major source of air pollution. The very low levels of sulfur globally mandated for transportation fuels in the near future cannot be achieved by current practices of hydrodesulfurization (HDS) for sulfur removal, which operate under severe conditions (high T, P) and use valuable H2. Novel vapor-phase catalytic oxidesulfurization (ODS) processes of selectively oxidizing various organosulfur compounds (carbonyl sulfide, carbon disulfide, methanethiol, dimethyl sulfide (DMS), dimethyl disulfide (DMDS), thiophene, 2,5-dimenthylthiophene) typically found in various industrial streams (e.g., petroleum refining, pulp and paper) into valuable chemical intermediates (H 2CO, CO, H2, maleic anhydride and concentrated SO2) has been extensively studied. This research has primarily focused on establishing the fundamental kinetics and mechanisms of these selective oxidation reactions over well-defined supported metal oxide catalysts. The selective oxidation reactions of COS + O2 ? CO + SO2; 2CS2 + 5O2 ? 2CO + 4SO2; CH3SH + 2O 2 ? H2CO + SO2 + H2O; C4 H4S + 3O2 ? C4H2O 3 + H2O + SO2; were studied. Raman spectroscopy revealed that the supported metal oxide phases were 100% dispersed on the oxide substrate. All the catalysts were highly active and selective for the oxidesulfurization of carbonyl sulfide, carbon disulfide, methanethiol, and thiophene between 290--330°C, 230--270°C, 350--400°C, and 250--400°C, respectively and did not deactivate. The TOFs (turnover frequency, normalized activity per active catalytic site) for all ODS reactions over supported vanadia catalysts, only containing molecularly dispersed surface vanadia species, varied within one order of magnitude and revealed the V-O-Support bridging bond was involved in the critical rate-determining kinetic steps. The surface reaction mechanism for each reaction was revealed by in situ IR (infrared) and temperature programmed surface reaction-mass spectroscopy (TPSR-MS). The systematic investigation of vapor-phase oxidesulfurization (ODS) reactions of organosulfur compounds over catalytic supported metal oxides revealed the facile S-O exchange mechanisms allow for the efficient removal of sulfur while producing value-added chemicals and represents the discovery of a new series of catalytic reactions.

Choi, Sukwon

461

Grafted megaporous materials as ion-exchangers for bioproduct adsorption.  

PubMed

Megaporous chromatographic materials were manufactured by a three-step procedure, including backbone synthesis, chemical grafting, and introduction of ion-exchange functionality. The backbone of the adsorbent cylindrical bodies was prepared by polymerization of methacrylic acid and poly(ethylene glycol) diacrylate at sub-zero temperatures. Grafting was performed employing glycidyl methacrylate and a chemical initiator, cerium ammonium nitrate. The degree of grafting was adjusted by modifying the concentration of the initiator in the reaction mixture to a range of values (23, 39, 62, 89, and 105%). Further, the pendant epoxy-groups generated by the previous step were reacted to cation- and anion-exchanging moieties utilizing known chemical routes. Infrared spectroscopy studies confirmed the incorporation of epoxy and ion-exchanger groups to the backbone material. Optimized materials were tested for chromatography applications with model proteins; the dynamic binding capacity, as recorded at 10% breakthrough and 2.0 × 10(-4) m/s superficial velocity, were 350 and 58 mg/g for the cation-exchanger and the anion-exchanger material, respectively. These results may indicate that long tentacle-type polymer brushes were formed during grafting therefore increasing the ability of the megaporous body to efficiently capture macromolecules. PMID:23401432

Bibi, Noor Shad; Fernández-Lahore, Marcelo

2013-01-01

462

The many faces of ion-exchange resins  

SciTech Connect

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.

McNutty, J.T. [Rohm and Haas Co., Philadelphia, PA (United States)

1997-06-01

463

Reaction cycle and thermodynamics in bacteriorhodopsin  

NASA Technical Reports Server (NTRS)

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.

Lanyi, J. K.

1992-01-01

464

Charge exchange molecular ion source  

DOEpatents

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.

Vella, Michael C.

2003-06-03

465

Heat exchanger for electrothermal devices  

NASA Technical Reports Server (NTRS)

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.

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

1986-01-01

466

IAESTE Exchange Development and Participation  

NASA Astrophysics Data System (ADS)

The International Association for the Exchange of Students for Technical Experience is an Association of National Committees representing academic, industrial and students interests. Participation in the IAESTE exchange is open to bona fide students attending courses at Universities, Institutes of Technology and similar Institutions of Higher Education. This Report contains the Activities of IAESTE with its history and the detail on the bilateral exchanges, study fields, training periods and other useful information. We also look to the future as we continue our journey to improve our Association in partnership with our Academics, Employers and Students.

Ishita, Yusuke

467

Heat exchanger with ceramic elements  

DOEpatents

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.

Corey, John A. (North Troy, NY)

1986-01-01

468

Heat exchanger using graphite foam  

SciTech Connect

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.

Campagna, Michael Joseph; Callas, James John

2012-09-25

469