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1

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

Microsoft Academic Search

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

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

2005-01-01

2

{[Dy 2(bpdc) 3(H 2O) 3] · H 2O} n (bpdc = 2,2?-bipyridine-4,4?-dicarboxylate): A highly-thermostable 3D coordination polymer with unusual mixed-connected network topology  

Microsoft Academic Search

A novel 3D coordination polymer {[Dy2(bpdc)3(H2O)3H2O}n (bpdc=2,2?-bipyridine-4,4?- dicarboxylate) based on inorganic rod-shaped infinite secondary building unit is presented, which possesses unusual mixed-connected network topology and shows high thermal stability and strong photoluminescence at room temperature.

Feng Fu; Dong-Sheng Li; Cui-Qiao Zhang; Ji-Jiang Wang; Ya-Pan Wu; Miao Du; Ji-Wu Wang

2008-01-01

3

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

Microsoft Academic Search

Three novel Th(IV) compounds containing heavy oxoanions, Th(SeO3)(SeO4) (1), Th(IO3)2(SeO4)(H2O)3·H2O (2), and Th(CrO4)(IO3)2 (3), have been synthesized under mild hydrothermal conditions. Each of these three distinct structures contain trigonal pyramidal and tetrahedral oxoanions. Compound 1 adopts a three-dimensional structure formed from ThO9 tricapped trigonal prisms, trigonal pyramidal selenite, SeO32–, anions containing Se(IV), and tetrahedral selenate, SeO42–, anions containing Se(VI). The

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

2006-01-01

4

Extended networks, porous sheets, and chiral frameworks. Thorium materials containing mixed geometry anions: Structures and properties of Th(SeO3)(SeO4), Th(IO3)2(SeO4)(H2O)3·H2O, and Th(CrO4)(IO3)2  

Microsoft Academic Search

Three novel Th(IV) compounds containing heavy oxoanions, Th(SeO3)(SeO4) (1), Th(IO3)2(SeO4)(H2O)3·H2O (2), and Th(CrO4)(IO3)2 (3), have been synthesized under mild hydrothermal conditions. Each of these three distinct structures contain trigonal pyramidal and tetrahedral oxoanions. Compound 1 adopts a three-dimensional structure formed from ThO9 tricapped trigonal prisms, trigonal pyramidal selenite, SeO32 , anions containing Se(IV), and tetrahedral selenate, SeO42 , anions containing

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

2006-01-01

5

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

Microsoft Academic Search

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

Stefano Midollini; Pablo Lorenzo-Luis; Annabella Orlandini

2006-01-01

6

Charge exchange reactions and applications to astrophysics  

SciTech Connect

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

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

2012-11-12

7

Charge exchange reaction by Reggeon exchange and W$^{+}$W$^{-}$-fusion  

E-print Network

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

Schicker, R

2014-01-01

8

Water dissociation reaction generated in an ion exchange membrane  

Microsoft Academic Search

Based on pH measurement in water dissociation experiments, the mechanism of a water dissociation (water splitting) reaction is discussed assuming that the reaction is generated in a reaction layer formed in an ion exchange membrane and the reaction layer extends throughout the space in the membrane. The process is established to estimate the current efficiency for H+ and OH? ions

Yoshinobu Tanaka

2010-01-01

9

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

10

Using reactive artificial muscles to determine water exchange during reactions  

NASA Astrophysics Data System (ADS)

Artificial muscles based on films of conducting polymers translate film volume variations, driven by electrochemical reactions (Faradaic motors), into macroscopic movements with generation of mechanical energy. The reaction promotes exchange of counterions (anions here) and solvent molecules with the electrolyte. Attributing here both the film volume variation and the movement originated by these exchanges of ions and solvent, the described angles can be used to quantify the exchanged solvent. Different angles described by bending muscles consuming equal driving charges in electrolytes having the same cation and different anions were measured. The number of exchanged counterions is given by the consumed charge and the ion valence: this is a Faradaic reaction. The described angle fraction due to the exchanged anions is given by the number of anions and the crystallographic radius. Taking as reference the anion giving the shorter angle, whatever the consumed charge, the relative number of solvent molecules exchanged by the polymeric membrane during a reversible reaction was determined. Actuators and artificial muscles can be used as useful tools for, at least, an initial study of the solvent exchange during reactions in reactive gels.

Otero, T. F.; Martínez, J. G.; Zaifoglu, B.

2013-10-01

11

Phospholipid exchange reactions within the liver cell  

PubMed Central

1. Isolated rat liver mitochondria do not synthesize labelled phosphatidylcholine from CDP-[14C]choline or any phospholipid other than phosphatidic acid from [32P]phosphate. The minimal labelling of phosphatidylcholine and other phosphoglycerides can be attributed to microsomal contamination. However, when mitochondria and microsomes are incubated together with [32P]phosphate, the phosphatidylcholine, phosphatidylinositol and phosphatidylethanolamine of the reisolated mitochondria become labelled, suggesting a transfer of phospholipids between the two fractions. 2. When liver microsomes or mitochondria containing labelled phosphatidylcholine are independently incubated with the opposite un-labelled fraction, there is a substantial and rapid exchange of the phospholipid between the two membranes. Exchange of phosphatidylinositol also occurs rapidly, whereas phosphatidylethanolamine and phosphatidic acid exchange only slowly. There is no corresponding transfer of marker enzymes. The transfer of phosphatidylcholine does not occur at 0°, and there is no requirement for added substrate, ATP or Mg2+, but the omission of a heat-labile supernatant fraction markedly decreases the exchange. 3. After intravenous injection of [32P]phosphate, short-period labelling experiments of the individual phospholipids of rat liver microsomes and mitochondria in vivo give no evidence for a similar exchange process. However, the incubation of isolated microsomes and mitochondria with [32P]phosphate also fails on reisolation of the fractions to demonstrate a precursor–product relationship between the individual phospholipids of the two membranes. 4. The intraperitoneal injection of [32P]phosphate results in a far greater proportion of the dose entering the liver than does intravenous administration. After intraperitoneal administration of [32P]phosphate the specific radioactivities of the individual phospholipids are in the order microsomes > outer mitochondrial membrane > inner mitochondrial membrane. 5. The incorporation of 32P into cardiolipin is very slow both in vivo and in vitro. After labelling in vivo the radioactivity in the cardiolipin persists compared with that of the other phospholipids, whose specific radioactivities in the microsomes and mitochondrial fragments decay at a similar rate to that of the acid-soluble phosphate pool. 6. The possibility of phospholipid exchange processes occurring in the liver cell in vivo is discussed, and it is suggested that only a small but highly labelled part of the endoplasmic-reticulum lipoprotein pool is involved in the transfer. PMID:4304512

McMurray, W. C.; Dawson, R. M. C.

1969-01-01

12

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

13

Lock-exchange experiments with an autocatalytic reaction front.  

PubMed

A viscous lock-exchange gravity current corresponds to the reciprocal exchange of two fluids of different densities in a horizontal channel. The resulting front between the two fluids spreads as the square root of time, with a diffusion coefficient reflecting the buoyancy, viscosity, and geometrical configuration of the current. On the other hand, an autocatalytic reaction front between a reactant and a product may propagate as a solitary wave, namely, at a constant velocity and with a stationary concentration profile, resulting from the balance between molecular diffusion and chemical reaction. In most systems, the fluid left behind the front has a different density leading to a lock-exchange configuration. We revisit, with a chemical reaction, the classical situation of lock-exchange. We present an experimental analysis of buoyancy effects on the shape and the velocity of the iodate arsenous acid autocatalytic reaction fronts, propagating in horizontal rectangular channels and for a wide range of aspect ratios (1/3 to 20) and cylindrical tubes. We do observe stationary-shaped fronts, spanning the height of the cell and propagating along the cell axis. Our data support the contention that the front velocity and its extension are linked to each other and that their variations scale with a single variable involving the diffusion coefficient of the lock-exchange in the absence of chemical reaction. This analysis is supported by results obtained with lattice Bathnagar-Gross-Krook (BGK) simulations Jarrige et al. [Phys. Rev. E 81, 06631 (2010)], in other geometries (like in 2D simulations by Rongy et al. [J. Chem. Phys. 127, 114710 (2007)] and experiments in cylindrical tubes by Pojman et al. [J. Phys. Chem. 95, 1299 (1991)]), and for another chemical reaction Schuszter et al. [Phys. Rev. E 79, 016216 (2009)]. PMID:21198000

Bou Malham, I; Jarrige, N; Martin, J; Rakotomalala, N; Talon, L; Salin, D

2010-12-28

14

Momentum transfer in relativistic heavy ion charge-exchange reactions  

NASA Astrophysics Data System (ADS)

Relativistic heavy ion charge-exchange reactions yield fragments (Delta-Z = + 1) whose longitudinal momentum distributions are downshifted by larger values than those associated with the remaining fragments (Delta-Z = 1, -2,...). Kinematics alone cannot account for the observed downshifts; therefore, an additional contribution from collision dynamics must be included. In this work, an optical model description of collision momentum transfer is used to estimate the additional dynamical momentum downshift. Good agreement between theoretical estimates and experimental data is obtained.

Townsend, L. W.; Wilson, J. W.; Khan, F.; Khandelwal, G. S.

1991-07-01

15

Momentum transfer in relativistic heavy ion charge-exchange reactions.  

PubMed

Relativistic heavy ion charge-exchange reactions yield fragments (delta Z = +1) whose longitudinal momentum distributions are downshifted by larger values than those associated with the remaining fragments (delta Z = -1, -2, ...). Kinematics alone cannot account for the observed downshifts; therefore, an additional contribution from collision dynamics must be included. In this work, an optical model description of collision momentum transfer is used to estimate the additional dynamical momentum downshift. Good agreement between theoretical estimates and experimental data is obtained. PMID:9967432

Townsend, L W; Wilson, J W; Khan, F; Khandelwal, G S

1991-07-01

16

Selenocysteine in Thiol/Disulfide-Like Exchange Reactions  

PubMed Central

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

Marino, Stefano M.

2013-01-01

17

Charge-exchange reactions and nuclear matrix elements for ?? decay  

NASA Astrophysics Data System (ADS)

Charge-exchange reactions of (n, p) and (p, n) type at intermediate energies are a powerful tool for the study of nuclear matrix element in ?? decay. The present paper reviews some of the most recent experiments in this context. Here, the (n, p) type reactions are realized through (d, 2He), where 2He refers to two protons in a singlet 1S0 state and where both of these are momentum analyzed and detected by the same spectrometer and detector. These reactions have been developed and performed exclusively at KVI, Groningen (NL), using an incident deuteron energy of 183 MeV. Final state resolutions of about 100 keV have routinely been available. On the other hand, the (3He, t) reaction is of (p, n) type and was developed at the RCNP facility in Osaka (JP). Measurements with an unprecedented high resolution of 30 keV at incident energies of 420 MeV are now readily possible. Using both reaction types one can extract the Gamow-Teller transition strengths B(GT+) and B(GT-), which define the two "legs" of the ?? decay matrix elements for the 2v?? decay The high resolution available in both reactions allows a detailed insight into the excitations of the intermediate odd-odd nuclei and, as will be shown, some unexpected features are being unveiled.

Frekers, D.

2009-11-01

18

Surface mediated isotope exchange reactions between water and gaseous deuterium  

NASA Astrophysics Data System (ADS)

Maintaining isotopic purity of hydrogen is one of the major tasks in tritium processing systems. The work with multiple isotopes and isotopomers is accompanied by isotope exchanges which is often accelerated by catalysts e.g. surfaces of various materials. In this work, densities of D 2O, HDO produced via isotope exchange reactions in the mixture of D 2, H 2, D 2O, H 2O, HD and HDO contained in a stainless steel (type SS304) vessel were measured as a function of time (40-36 000 s) and pressures near 3.5 × 10 2 Pa, using mass spectrometry. The derived rates of change of the isotopomers densities are described accurately by a postulated kinetic model.

Roland, Teboh F.; Borysow, Jacek; Fink, Manfred

2006-07-01

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

Mechanism of the Exchange Reaction in HRAS from Multiscale Modeling  

PubMed Central

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

Kapoor, Abhijeet; Travesset, Alex

2014-01-01

21

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

22

The formation of Kuiper-belt binaries through exchange reactions.  

PubMed

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

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

2004-02-01

23

Reversible Thiazolidine Exchange: A New Reaction Suitable for Dynamic Combinatorial Chemistry  

PubMed Central

New dynamic combinatorial libraries (DCLs) were generated using the reversible aminothiol exchange reaction of thiazolidines and aromatic aldehydes. The reaction proceeded in aqueous buffered media at pH 4 and room temperature to generate thermodynamically controlled mixtures of heterocycles. The synthesis of an enantiomerically pure thiazolidinyloxazolidine is also reported. The oxazolidine moiety could be exchanged in CH2Cl2 in the presence of catalytic p-TsOH. PMID:19585999

Saiz, Cecilia; Wipf, Peter; Manta, Eduardo; Mahler, Graciela

2009-01-01

24

Reversible thiazolidine exchange: a new reaction suitable for dynamic combinatorial chemistry.  

PubMed

New dynamic combinatorial libraries (DCLs) were generated using the reversible aminothiol exchange reaction of thiazolidines and aromatic aldehydes. The reaction proceeded in aqueous buffered media at pH 4 and room temperature to generate thermodynamically controlled mixtures of heterocycles. The synthesis of an enantiomerically pure thiazolidinyloxazolidine is also reported. The oxazolidine moiety could be exchanged in CH(2)Cl(2) in the presence of catalytic p-TsOH. PMID:19585999

Saiz, Cecilia; Wipf, Peter; Manta, Eduardo; Mahler, Graciela

2009-08-01

25

The kinetics and mechanism of bromide ion isotope exchange reaction in strongly basic anion-exchange resin duolite A-162 determined by the radioactive tracer technique  

Microsoft Academic Search

In the present investigation, 82Br radioactive isotope was used as a tracer to study the kinetics and mechanism of exchange reaction between an ion exchange\\u000a resin and an external bromide ion solution. In an attempt to study the reversible bromide ion isotopic exchange reaction kinetics,\\u000a it was expected that whether the initial step was the exchange of radioactive bromide ions

R. S. Lokhande; P. U. Singare; P. Karthikeyan

2007-01-01

26

Oxygen exchange reaction kinetics for cerium(IV) oxide at 1000 °C  

NASA Astrophysics Data System (ADS)

Bulk oxygen exchange rate kinetics on CeO2 at 1000 °C were observed to have a first order dependence on the fraction of reaction remaining and to be independent of oxygen partial pressure, total pressure, particle size, and specific surface area. This suggests that the exchange reaction is dominated by an internal chemical reaction that is occurring throughout the bulk of the material, and not at the material surface. Oxygen exchange rates were limited by this internal chemical reaction for all CeO2 powders studied (15 nm to -325 mesh), and had a rate constant of 1.19×10-2 s-1 with a time to completion of 617 s. These results are similar to the exchange rates observed previously on PuO2, suggesting that oxygen exchange on PuO2 may also be dominated by an internal chemical reaction under similar conditions. This work will help guide future experiments on 238PuO2 oxygen exchange reactions.

Whiting, Christofer E.; Douglas, John M.; Cremeans, Bethany M.; Barklay, Chadwick D.; Kramer, Daniel P.

2014-10-01

27

Dynamic diselenide bonds: exchange reaction induced by visible light without catalysis.  

PubMed

Dynamic covalent bonds are extensively employed in dynamic combinatorial chemistry. The metathesis reaction of disulfide bonds is widely used, but requires catalysis or irradiation with ultraviolet (UV) light. It was found that diselenide bonds are dynamic covalent bonds and undergo dynamic exchange reactions under mild conditions for diselenide metathesis. This reaction is induced by irradiation with visible light and stops in the dark. The exchange is assumed to proceed through a radical mechanism, and experiments with 2,2,6,6-tetramethylpiperidin-1-yloxyl (TEMPO) support this assumption. Furthermore, the reaction can be conducted in different solvents, including protic solvents. Diselenide metathesis can also be used to synthesize diselenide-containing asymmetric block copolymers. This work thus entails the use of diselenide bonds as dynamic covalent bonds, the development of a dynamic exchange reaction under mild conditions, and an extension of selenium-related dynamic chemistry. PMID:24842614

Ji, Shaobo; Cao, Wei; Yu, Ying; Xu, Huaping

2014-06-23

28

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

29

Public announcement induced market reactions on Baltic stock exchanges  

Microsoft Academic Search

Purpose – The purpose of this paper is to determine to what extent economically significant stock return and volume changes on Tallinn, Riga and Vilnius Stock Exchanges (TSE, RSE, VSE) are contributable to public announcements disclosures and which types of announcements drive these. Design\\/methodology\\/approach – Event-study methodology was used to determine economically significant return and volume events. Findings – It

Laivi Laidroo

2008-01-01

30

Sulfo cation-exchange resins as heterogeneous catalysts for the reaction of styrene with formaldehyde  

SciTech Connect

Macroporous and gel sulfo cation-exchange resins are active catalysts for the condensation of styrene with formaldehyde. The product, 4-phenyl-1,3-dioxane was obtained in up to 97% yield. The activity of macroporous sulfo cation-exchange resins increases with decreasing particle diameter but in the case of the gel samples, granule size has only a slight effect on the reaction rate. The enhanced activity of sulfo cation-exchange resins is presumably a result of the high value of the acidity function H/sub 0/ of the sulfonic acid groups of the cation-exchange resin.

Kasymova, K.A.; Sharf, V.Z.; Litvin, E.F.; Grigor'eva, E.N.

1987-07-20

31

A convenient imino aldol reaction in ethyl alcohol catalyzed by a cation-exchange resin.  

PubMed

Imino aldol reaction of ketene silyl acetals with imines proceeds smoothly to give beta-amino esters in good yields under the influence of a cation-exchange resin in ethanol, and the work-up of the reaction consists only of a simple filtration followed by concentration of the crude mixture and purification. PMID:12240054

Shimizu, M; Itohara, S; Hase, E

2001-11-21

32

Transition into non-monotonic approach to equilibrium in geminate exchange reaction  

E-print Network

þ B) [18,19], electron transfer, or atom transfer (A þ BC $ AB þ C) in solution (e.g., SN2 reacTransition into non-monotonic approach to equilibrium in geminate exchange reaction Alexander V� diffusion equations describing the survival and reaction probabilities. Investigating its long

Agmon, Noam

33

Determination of the energetics of the UDP-glucose pyrophosphorylase reaction by positional isotope exchange inhibition  

SciTech Connect

A method has been developed for obtaining qualitative information about enzyme-catalyzed reactions by measuring the inhibitory effects of added substrates on positional isotope exchange rates. It has been demonstrated for ordered kinetic mechanisms that an increase in the concentration of the second substrate to add to the enzyme will result in a linear increase in the ratio of the chemical and positional isotope exchange rates. The slopes and intercepts from these plots can be used to determine the partitioning ratios of binary and ternary enzyme complexes. The method has been applied to the reaction catalyzed by UDP-glucose pyrophosphorylase. A positional isotope exchange reaction was measured within oxygen-18-labeled UTP as a function of variable glucose 1-phosphate concentration in the forward reaction. In the reverse reaction, a positional isotope exchange reaction was measured within oxygen-18-labeled UDP-glucose as a function of increasing pyrophosphate concentration. The results have been interpreted to indicate that the interconversion of the ternary central complexes is fast relative to product dissociation in either direction. In the forward direction, the release of UDP-glucose is slower than the release of pyrophosphate. The release of glucose 1-phosphate is slower than the release of UTP in the reverse reaction.

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

1987-10-06

34

Some H/D exchange reactions involved in the deuteration of interstellar molecules  

NASA Astrophysics Data System (ADS)

Deuterium is commonly observed in interstellar molecules which vary in complexity from HD to CH3OD. Quantitative estimates of deuteration rates have been hampered by the lack of appropriate kinetic data and thermodynamic data. Experimental investigations have, therefore, been initiated of ion-molecule reactions in which isotope exchange occurs, including reactions involving H/D exchange. A major objective of such studies is to determine the temperature variation of reaction rate coefficients. The present investigation is mainly concerned with studies of the reaction D(+) + H2 yields reversibly H(+) + HD, which generates the interstellar HD, and with the reactions H3(+) + HD yields reversibly H2D(+) + H2, and CH3(+) + HD yields reversibly CH2D(+) + H2, which are both probably important first steps in the synthesis of deuterated molecules.

Smith, D.; Adams, N. G.; Alge, E.

1982-12-01

35

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

36

Ion exchange and redox reactions in metal-ion exchanger nanocomposites  

NASA Astrophysics Data System (ADS)

The reducing sorption of oxygen dissolved in water with the use of metal-containing nanocomposites is considered taking into account the bifunctional nature of sorbents possessing both redox and ion exchange properties. A physicochemical model of the process including metal particle dispersity, their distribution over a grain, and the special features of the chemical oxidation of metals was used. Based on this model, a mathematical formulation of the problem including the stage of the interdiffusion of metal ions (metal oxidation products) and hydrogen ions (matrix counterions) is given.

Kipriyanova, E. S.; Konev, D. V.; Kravchenko, T. A.; Khorol'skaya, S. V.

2012-07-01

37

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

38

Integrated heat exchange and heat storage system using low-temperature reactions  

Microsoft Academic Search

An integrated heat exchange and heat storage system using thermochemical reactions which comprises a first plurality of parallel adjacent tubes containing an element for storing and yielding heat; and a second plurality of tubes parallel to said first plurality of tubes and interposed therebetween and containing a fluid heat vehicle, the first and second plurality of tubes being disposed in

U. Buzzi; F. Farfaletti-casali; L. Nobel; F. Reiter

1982-01-01

39

CATALYSTS ON THE ENRICHMENT OF HEAVY WATER BY MEANS OF EXCHANGE REACTION  

Microsoft Academic Search

As a screening test for finding a practical catalyst for the dual ; exchange process of heavy water production, the catalytic activities of about 50 ; metal-metal, metal-oxide, oxide-oxide type catalyst were compared. The rate of ; the reaction, HâO + HD in equilibrium HDO + Hâ, was measured in the ; presence of these catalysts at 80 and 300

S. Enomoto; H. Ugajin

1961-01-01

40

A Social Exchange Model of Employee Reactions to Electronic Performance Monitoring  

Microsoft Academic Search

The primary goal of this study was to develop and test a social exchange model of employee reactions to electronic performance monitoring (EPM) to help managers use EPM more effectively. This study proposed that certain EPM practices are related to perceptions of interpersonal and informational justice, which in turn build trust in the manager, along with other important attitudes and

Laurel A. McNall; Sylvia G. Roch

2009-01-01

41

Stock price reaction to M&A announcements: Evidence from the London Stock Exchange  

Microsoft Academic Search

We investigate short-tem investor reaction to initial press releases regarding mergers and acquisitions in the London Stock Exchange. Announcements are sorted by whether the firm is a bidder or a target, by whether the announcement refers to an acquisition or a merger, by investor sophistication, by the level of information disclosure, by whether the announcements generate a positive or negative

Spyros I. Spyrou; Georgia Siougle

42

A catalytic heat-exchanging tubular reactor for combining of high temperature exothermic and endothermic reactions  

Microsoft Academic Search

A multifunctional catalytic heat-exchanging (HEX) tubular reactor for combining exothermic and endothermic reactions has been developed and tested for catalytic methane oxidation and methane steam reforming. The methane combustion and steam reforming catalysts were synthesized on the heat-conducting metal foam support materials by application of preliminary plasma spraying of alumina in order to increase adhesive properties of the active layer.

Z. R Ismagilov; V. V Pushkarev; O. Yu Podyacheva; N. A Koryabkina; H Veringa

2001-01-01

43

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

44

Kinetic study on the reaction between CO2-CO and wustite using the isotope exchange method  

NASA Astrophysics Data System (ADS)

To investigate the reaction between CO2-CO and wustite using the isotope exchange method at 1073, 1173, 1273, and 1373 K, the experiment apparatus was designed to simulate the fluidized bed. The chemical rate constant was estimated by considering the effect of gas phase mass transfer on the reaction. It is found that the chemical rate constant is inversely decreased with the increase in the ratio of CO2/CO by volume. The activation energy of reaction is in a linear relationship with the ratio of CO2/CO by volume, and the average activation energy is 155.37 kJ/mol.

Zhang, Teng; Hu, Xiao-jun; Chou, Kuo-Chih

2013-02-01

45

The pyruvate-proton exchange reaction of malic enzyme from pigeon liver.  

PubMed

Malic enzyme (L-malate:NADP+ oxidoreductase (decarboxylating) EC 1.1.1.40) catalyzes the incorporation of proton from medium water into pyruvate present either as the initial substrate or as the enzyme-bound product of malate decarboxylation. In the later reaction a single proton is incorporated into the methyl group of pyruvate. The pyruvate-medium proton exchange reaction requires Mg2+, NADPH and CO2-HCO3- as cofactors. The apparent Michaelis constants of pyruvate, NADPH and CO2-HCO3- are 4.8 mM, 2 microM and approx. 9 microM, respectively. The experimentally determined incorporation of 2.5 tritium atoms from tritiated water into pyruvate indicates that all three methyl protons of this compound are stereochemically equivalent in the exchange reaction. These results are consistent with the postulated kinetic mechanism for the malate reaction (Hsu, R.Y., Lardy, H.A. and Cleland, W.W. (1967) J. Biol. Chem. 242, 5315--5322), which predicts the formation of an enolpyruvate intermediate during the reaction. The rate of malic enzyme-catalyzed detritiation of beta-tritiated pyruvate is unaffected by modification of an essential protein thiol group with 5,5'-dithiobis(2-nitrobenzoic acid) or KCN. Moreover, the native- and thiol-modified enzymes also catalyze the detritiation of beta-tritiated bromopyruvate at slower rates. PMID:7066344

Bratcher, S C; Hsu, R Y

1982-03-18

46

Experimental determination of reaction rates of water. Hydrogen exchange of tritium with hydrophobic catalysts  

Microsoft Academic Search

This study was undertaken to obtain data needed for further development of a process for the enrichment and removal of tritium from the water associated with light-water reactors, fuel-reprocessing plants, and tritium-handling laboratories. The approach is based on the use of antiwetting, hydrophobic catalysts which permit the chemical exchange reactions between liquid water and gaseous hydrogen in direct contact, thus

J. C. Bixel; B. W. Hartzell; W. K. Park

1976-01-01

47

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

48

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

2004-02-02

49

New magnetic materials obtained by ion-exchange reactions from non-magnetic layered perovskites  

Microsoft Academic Search

New layered magnetic materials, (MCl)Ca2Ta3O10 (M = Cu, Fe), have been prepared by ion-exchange reactions of non-magnetic perovskite derivatives, ACa2Ta3O10 (A = Rb, Li), in corresponding anhydrous molten salts. Powder x-ray diffraction patterns of the products are successfully indexed assuming tetragonal symmetry with cell dimensions a = 3.829 Å and c = 15.533 Å for Cu, and a = 3.822

H. Kageyama; L. Viciu; G. Caruntu; Y. Ueda; J. B. Wiley

2004-01-01

50

Reaction of 5-ethylidene-2-norbomene with formic acid: cation exchange resins as catalysts  

Microsoft Academic Search

The esterification of formic acid with ethylidene norbornene (ENB), i.e. 5-ethylidene bicyclo[2.2.1]hept 2-ene was carried out with and without cation exchange resins as catalysts. The effect of various parameters e.g. speed of agitation, catalyst loading, mole ratio of the reactants, temperature, concentration of formic acid in aqueous solutions were studied to optimise the reaction conditions; the reusability of catalysts was

Basudeb Saha

1998-01-01

51

The Influence of Stereochemical Structure on the Kinetics and Mechanism of Ester-Ester Exchange Reactions by Mass Spectrometry. II  

Microsoft Academic Search

Exter-ester exchange reactions in polyesters, formulated from adipic acid and various linear and branched glycols, were studied by mass spectrometry employing the Dimer Analysis Method (DAM). Activation energies (E) and frequency factors (A) were obtained for the reaction systems at temperatures of 572–585 K. The kinetic behavior of these reactions was influenced by the stereochemical structures of carbonyl oxygens along

H. G. Ramjit

1983-01-01

52

Theoretical study of acetonitrile-exchange reactions on hexasolvated divalent cations in the first transition series elements  

NASA Astrophysics Data System (ADS)

Penta-, hexa-, and heptaacetonitrile complexes of divalent cations of the first transition series are studied by ab initio molecular orbital calculations. The factors that determine the structural stability and the reaction mechanism of solvent-exchange reactions are discussed. All the penta- and hexaacetonitrile species are at local minima, whereas the geometrical stability of the heptacoordinated species depends on the 3d electron configurations. The structural stability of heptaacetonitrile species is intermediate between those of hydrogen cyanide complexes and hydrates. Acetonitrile exchange reactions have more dissociative character than hydrogen cyanide exchange reactions because the inductive effect of the methyl group in CH3CN destabilizes the heptacoordinated structures. The successive binding energies show that associative mechanisms are favorable for acetonitrile exchange with earlier members of the first transition series, whereas dissociative mechanisms become favorable for later members.

Wasada, Hiroaki; Wasada-Tsutsui, Yuko; Hashimoto, Tomohiro; Funahashi, Shigenobu

53

Intermediates in the Guanine Nucleotide Exchange Reaction of Rab8 Protein Catalyzed by Guanine Nucleotide Exchange Factors Rabin8 and GRAB*  

PubMed Central

Small G-proteins of the Ras superfamily control the temporal and spatial coordination of intracellular signaling networks by acting as molecular on/off switches. Guanine nucleotide exchange factors (GEFs) regulate the activation of these G-proteins through catalytic replacement of GDP by GTP. During nucleotide exchange, three distinct substrate·enzyme complexes occur: a ternary complex with GDP at the start of the reaction (G-protein·GEF·GDP), an intermediary nucleotide-free binary complex (G-protein·GEF), and a ternary GTP complex after productive G-protein activation (G-protein·GEF·GTP). Here, we show structural snapshots of the full nucleotide exchange reaction sequence together with the G-protein substrates and products using Rabin8/GRAB (GEF) and Rab8 (G-protein) as a model system. Together with a thorough enzymatic characterization, our data provide a detailed view into the mechanism of Rabin8/GRAB-mediated nucleotide exchange. PMID:24072714

Guo, Zhong; Hou, Xiaomin; Goody, Roger S.; Itzen, Aymelt

2013-01-01

54

Detection of the strand exchange reaction using DNAzyme and Thermotoga maritima recombinase A.  

PubMed

We have designed multiple detection systems for the DNA strand exchange process. Thermostable Thermotoga maritima recombinase A (TmRecA), a core protein in homologous recombination, and DNAzyme, a catalytic DNA that can cleave a specific DNA sequence, are introduced in this work. In a colorimetric method, gold nanoparticles (AuNPs) modified with complementary DNAs (cDNAs) were assembled by annealing. Aggregated AuNPs were then separated irreversibly by TmRecA and DNAzyme, leading to a distinct color change in the particles from purple to red. For the case of fluorometric detection, fluorescein isothiocyanate (FITC)-labeled DNA as a fluorophore and black hole quencher 1 (BHQ1)-labeled DNA as a quencher were used; successful strand exchange was clearly detected by variations in fluorescence intensity. In addition, alterations in the impedance of a gold electrode with immobilized DNA were employed to monitor the regular exchange of DNA strands. All three methods provided sufficient evidence of efficient strand exchange reactions and have great potential for applications in the monitoring of recombination, discovery of new DNAzymes, detection of DNAzymes, and measurement of other protein activities. PMID:22178915

Jo, Hunho; Lee, Seonghwan; Min, Kyoungin; Ban, Changill

2012-02-01

55

Interfacial energy exchange and reaction dynamics in collisions of gases on model organic surfaces  

NASA Astrophysics Data System (ADS)

Molecular beam scattering experiments and molecular dynamics simulations have been combined to develop an atomic-level understanding of energy transfer, accommodation, and reactions during collisions between gases and model organic surfaces. The work highlighted in this progress report has been motivated by the scientific importance of understanding fundamental interfacial chemical reactions and the relevance of reactions on organic surfaces to many areas of environmental chemistry. The experimental investigations have been accomplished by molecular beam scattering from ?-functionalized self-assembled monolayers (SAMs) on gold. Molecular beams provide a source of reactant molecules with precisely characterized collision energy and flux; SAMs afford control over the order, structure, and chemical nature of the surface. The details of molecular motion that affect energy exchange and scattering have been elucidated through classical-trajectory simulations of the experimental data using potential energy surfaces derived from ab initio calculations. Our investigations began by employing rare-gas scattering to explore how alkanethiol chain length and packing density, terminal group relative mass, orientation, and chemical functionality influence energy transfer and accommodation at organic surfaces. Subsequent studies of small molecule scattering dynamics provided insight into the influence of internal energy, molecular orientation, and gas-surface attractive forces in interfacial energy exchange. Building on the understanding of scattering dynamics in non-reactive systems, our work has recently explored the reaction probabilities and mechanisms for O3 and atomic fluorine in collisions with a variety of functionalized SAM surfaces. Together, this body of work has helped construct a more comprehensive understanding of reaction dynamics at organic surfaces.

Lu, Jessica W.; Day, B. Scott; Fiegland, Larry R.; Davis, Erin Durke; Alexander, William A.; Troya, Diego; Morris, John R.

2012-09-01

56

Theoretical investigation of exchange and recombination reactions in O(3P)+NO(2?) collisions  

NASA Astrophysics Data System (ADS)

We present a detailed dynamical study of the kinetics of O(P3)+NO(?2) collisions including O atom exchange reactions and the recombination of NO2. The classical trajectory calculations are performed on the lowest A'2 and A?2 potential energy surfaces, which were calculated by ab initio methods. The calculated room temperature exchange reaction rate coefficient, kex, is in very good agreement with the measured one. The high-pressure recombination rate coefficient, which is given by the formation rate coefficient and to a good approximation equals 2kex, overestimates the experimental data by merely 20%. The pressure dependence of the recombination rate, kr, is described within the strong-collision model by assigning a stabilization probability to each individual trajectory. The measured falloff curve is well reproduced over five orders of magnitude by a single parameter, i.e., the strong-collision stabilization frequency. The calculations also yield the correct temperature dependence, kr?T-1.5, of the low-pressure recombination rate coefficient. The dependence of the rate coefficients on the oxygen isotopes are investigated by incorporating the difference of the zero-point energies between the reactant and product NO radicals, ?ZPE, into the potential energy surface. Similar isotope effects as for ozone are predicted for both the exchange reaction and the recombination. Finally, we estimate that the chaperon mechanism is not important for the recombination of NO2, which is in accord with the overall T-1.4 dependence of the measured recombination rate even in the low temperature range.

Ivanov, M. V.; Zhu, H.; Schinke, R.

2007-02-01

57

Oxygen isotope evolution in the protosolar disk induced by isotopic exchange reactions  

NASA Astrophysics Data System (ADS)

Oxygen isotopic heterogeneity is one of the most extensively studied and debated topics in planetary science, though no consensus has been achieved yet. We quantitatively examine the role of exchange reactions in mass-dependent oxygen isotope fractionation during evaporation and recondensation of silicate melts in gas with isotopically identical and distinct gases. The results are applied to the CCAM line, mass-dependent oxygen isotopic fractionation of FUN inclusions, and oxygen isotopic variations of Allende chondrules. We examine the role of oxygen isotopic exchange for silicate melt and ambient gas during evaporation and recondensation in a closed system that monotonically cools from high temperature. Silicate dust aggregates are assumed to be instantaneously heated to an above liquidus temperature. There are three free parameters; one is the efficiency of the isotope ex-change, the second is the cooling rate of the system, and the third is the amount of initial oxygen in the ambient gas. We found following results : (1) Evolution of oxygen isotopic fractionation is decoupled with chemical fractionation of silicate melt; oxygen isotopic fractionation goes more rapidly than chemical fractionation, of which timing depends on the isotopic exchange efficiency. (2) Mass-dependent oxygen isotopic fractionation of silicate melt is suppressed by isotopic exchange during evaporation/recondensation. If isotopic exchange does not work, oxygen isotopic composition of silicate melt spheres after evaporation / recondensation becomes lighter than the initial one if the silicate and gas have identical oxygen isotopic composition due to more abundance of 16O in the gas. Isotopic exchange homogenizes the compositions effectively to result in the same composition between silicate and gas. (3) Cooling rate of the system affects the evolution time of oxygen isotopic mass fractionation, but the final composition is not affected. In a system with initially different oxygen isotopic compositions between silicate melt and gas, deviation from a straight mixing line to the ?18O-rich side on a three-oxygen isotope plot is inevitable through evaporation/recondensation and isotope exchange. (4) Abundance of oxygen in the initial gas largely affects the degree of deviation from a simple mixing line during the cooling process. The average oxygen abundance in gas of protosolar disk relative to that in silicate (~10), and silicate melt gets oxygen isotopic composition very close to the gas. (5) Isotopic exchange efficiency plays an important role on evolution and final oxygen isotopic composition of silicate melt heated in gas. Effective isotopic exchange largely suppresses mass dependent isotopoic fractionation, which tends to result in forming a straight "mixing line", whereas, smaller efficiency causes larger degree of mass-dependent isotopic fractionation, and deviation from a straight "mixing line" becomes larger. (6) A straight mixing line such as CCAM line requires the presence of oxygen in the ambient gas more than the average protosolar disk. (7) The mass-dependent oxygen isotope fractionation of FUN inclusions by ~40‰ or more is not achieved by evaporation in a closed system, and almost vacuum condition is required, which was possible by almost complete continuous separation of gas and silicate melt during evaporation. If FUN inclusions were formed from oxygen isotopically light solid, they have suffered a reaction between isotopically heavy gas after vacuum evaporation, where the gas abundance must have been more than 10 times of the average protosolar gas. In summary, a series of oxygen isotopic composition of CAIs and chondrules reflects the ambient physical conditions such as dust/gas ratio and dust/gas separation of a protosolar disk.

Nagahara, H.

2012-04-01

58

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

59

Positional isotope exchange analysis of the uridine-diphosphoglucose pyrophosphorylase reaction  

SciTech Connect

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

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

1986-05-01

60

Dianion formation from anion-alkali metal charge exchange reactions: TCNQ^- + Na -> TCNQ^-- + Na^+  

NASA Astrophysics Data System (ADS)

The interaction of an electron with an anion is characterized by a long-range coulomb repulsion and a short range polarizability attraction giving rise to a coulomb barrier. The permanent addition of an extra electron to a negatively charged anion requires tunneling through the barrier or attachment of the electron over the top of this coulomb barrier followed by disposal of the excess energy. Charge-exchange collisions of an anion with an alkali atom utilize the latter channel to produce permanent dianions with cross sections of ˜1 å^2. We have previously examined the reaction TCNQ-F4^- + Xe -> TCNQ-F4^-- + Xe^+ and reported a delayed threshold and quantum phase interference effects in the charge exchange cross section.ootnotetextS. Yu. Ovchinnikov, et al. Phys. Rev. A, 73, 64704(2006) Employing sodium as the collision partner, the cross section is seen to increase with decreasing energy with a threshold below 180 eV (com). A new apparatus has been constructed to allow measurements down to energies below the expected threshold (˜41 eV, laboratory energy based upon a 1 eV second electron affinity). This method has been used to study the reaction TCNQ^- + NA -> TCNQ^-- + Na^+ and will provide one of the first measurements of second electron affinities for molecular anions.

Smith, Byron; Compton, Robert; Ovchinnikov, Serge; Holm, Anne; Nielsen, Steen

2011-10-01

61

A survey of place-exchange reaction for the preparation of water-soluble gold nanoparticles.  

PubMed

Water-soluble gold nanoparticles (AuNPs) have gained considerable attention because they offer a myriad of potential applications, especially in the fields of biology and medicine. One method to prepare such gold nanoparticles is through the well-known Murray place-exchange reaction. In this method, precursor gold nanoparticles, bearing labile ligands and with very good size distribution, are synthesized first, and then reacted with a large excess of the desired ligand. We report a comparison of the reactivity of several known precursor gold nanoparticles (citrate-stabilized, pentanethiol-stabilized, tetraoctylammonium bromide-stabilized, and 4-dimethylaminopyridine-stabilized) to several biologically relevant ligands, including amino acids, peptides, and carbohydrates. We found that citrate-stabilized and 4-dimethylaminopyridine-stabilized gold nanoparticles have broader reactivities than the other precursors studied. Citrate-stabilized gold nanoparticles are more versatile precursors because they can be prepared in a wide range of sizes and are very stable. The hydrophobic pentane-stabilized gold nanoparticles made them "inert" toward highly water-soluble ligands. Tetraoctylammonium bromide-stabilized gold nanoparticles exhibited selective reactivity, especially for small, unhindered and amphiphilic ligands. Depending on the desired ligand and size of AuNPs, a judicious selection of the available precursors can be made for use in place-exchange reactions. In preparing water-soluble AuNPs with biologically relevant ligands, the nature of the incoming ligand and the size of the AuNP should be taken into account in order to choose the most suitable place-exchange procedure. PMID:23149107

Briñas, Raymond P; Maetani, Micah; Barchi, Joseph J

2013-02-15

62

Reactivity of alcohols of normal structure in reactions with isobutene in presence of KU-23 cation-exchange resin  

SciTech Connect

Reactions of alcohols with isobutene and isopentenes are used for the synthesis of ethers as high-octane additives to automotive fuels. In this paper, the reactions of several alcohols with isobutene were studied in the presence of the KU-23 cation exchange resin to determine the etherification reaction orders and rate constants and the nature of the ether yields, and also to determine the catalytic behavior of the resin in enhancing the rate and yield of the reaction. Structural analysis of the reaction mixtures is conducted.

Sharonov, K.G.; Rozhnov, A.M.; Barkov, V.I.; Cherkasova, R.I.

1987-08-10

63

Green condensation reaction of aromatic aldehydes with active methylene compounds catalyzed by anion-exchange resin under ultrasound irradiation.  

PubMed

To realize a practical and green chemistry, two important challenges need to be addressed, namely the effective process for the activation of reaction and efficient, eco-friendly and robust chemical methods for the reaction conversion to target products via highly selective catalytic and reactions. Ultrasonic energy promotes the conversion process through its special cavitational effects. Combined with anion-exchange resin as a heterogeneous, reusable and efficient catalyst, Ultrasonic energy enhances the Knoevenagel condensation and leads to reduced reaction time at lower reaction temperature with less amounts of solvent and catalyst. PMID:25112685

Ammar, Hafedh Belhadj; Chtourou, Manef; Frikha, Mohamed Hédi; Trabelsi, Mahmoud

2015-01-01

64

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

65

Deuterium-hydrogen exchange and scrambling reactions in the pyrolysis of labeled cyclopentene. A radical mechanism  

SciTech Connect

Inter- and intraradical mechanisms that promote deuterium-hydrogen scrambling in labeled cyclopentene-d/sub 1/ are investigated at 800 and 1200 K. Rate constants are estimated for each step and for possible competing side reactions. The fast radical bimolecular exchange at 800 K and unimolecular scrambling at 1200 K of labeled cyclopentene are shown to be faster than the Woodward-Hoffman allowed 1,4 concerted molecular elimination of hydrogen. The low-energy estimate of 8.0 kcal/mol by Lewis of the difference between the allowed 1,4 and disallowed 1,2 channels can thus be explained. No conclusions can be drawn concerning the 1,2 channel. The estimated rates of radical reactions are in agreement with experiments on the addition of D/sub 2/ to cyclopentadiene at 300/sup 0/C which shows only cis, 3 to 5 addition and with pyrolysis experiments at 500 +- 20/sup 0/C which show about 5% contribution of a higher than first-order radical reaction. The mechanism of this radical decomposition is given and its steps are explicitly evaluated. 2 tables.

Kosnik, K.G.; Benson, S.W.

1983-07-21

66

Exchange and Complementation of Genes Coding for Photosynthetic Reaction Center Core Subunits among Purple Bacteria.  

PubMed

A mutant of the phototrophic species belonging to the ?-proteobacteria, Rubrivivax gelatinosus, lacking the photosynthetic growth ability was constructed by the removal of genes coding for the L, M, and cytochrome subunits of the photosynthetic reaction center complex. The L, M, and cytochrome genes derived from five other species of proteobacteria, Acidiphilium rubrum, Allochromatium vinosum, Blastochloris viridis, Pheospirillum molischianum, and Roseateles depolymerans, and the L and M subunits from two other species, Rhodobacter sphaeroides and Rhodopseudomonas palustris, respectively, have been introduced into this mutant. Introduction of the genes from three of these seven species, Rte. depolymerans, Ach. vinosum, and Psp. molischianum, restored the photosynthetic growth ability of the mutant of Rvi. gelatinosus, although the growth rates were 1.5, 9.4, and 10.7 times slower, respectively, than that of the parent strain. Flash-induced kinetic measurements for the intact cells of these three mutants showed that the photo-oxidized cytochrome c bound to the introduced reaction center complex could be rereduced by electron donor proteins of Rvi. gelatinosus with a t1/2 of less than 10 ms. The reaction center core subunits of photosynthetic proteobacteria appear to be exchangeable if the sequence identities of the LM core subunits between donor and acceptor species are high enough, i.e., 70 % or more. PMID:25080366

Nagashima, Kenji V P; Verméglio, André; Fusada, Naoki; Nagashima, Sakiko; Shimada, Keizo; Inoue, Kazuhito

2014-08-01

67

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

68

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 reactions of the type ('He, t) (p, n) etc., in the region of excitation of the delta resonance. We show

Fernández de Córdoba, Pedro

69

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

70

Transient homodimer interactions studied using the electron self-exchange reaction.  

PubMed

Transient homodimer protein interactions have been investigated by analyzing the influence of ionic strength (NaCl) on the electron self-exchange (the bimolecular reaction whereby the two oxidation states of a redox protein interconvert) rate constant (k(ese)) of four plastocyanins. The k(ese) values for the plastocyanins from spinach, Dryopteris crassirhizoma (a fern), and the green alga Ulva pertusa, which possess acidic patches of varying size and locations, increase 190-, 29-, and 21-fold, respectively, at elevated ionic strength (I = 2.03 M). In contrast, the k(ese) for the almost neutral cyanobacterial plastocyanin from Anabaena variabilis exhibits very little dependence on ionic strength. The temperature dependence of the k(ese) for spinach plastocyanin (I = 0.28 M) provides evidence for poor packing at the homodimer interface. Representative structures of the transient homodimers involved in electron self-exchange, which are consistent with fits of the ionic strength dependence of k(ese) to van Leeuwen theory, have been obtained from protein modeling and docking simulations. The Coulombic energy of the docked homodimers follows the order spinach > D. crassirhizoma > U. pertusa > A. variabilis, which matches that of the overall influence of ionic strength on k(ese). Analysis of the homodimer structures indicates that poor packing and high planarity are features of the interface that favor transient interactions. The physiologically relevant Mg2+ ion has a much more pronounced influence on the k(ese) of spinach plastocyanin, which along with the known properties of the thylakoid lumen suggests a biological role for electron self-exchange. PMID:15743773

Sato, Katsuko; Crowley, Peter B; Dennison, Christopher

2005-05-13

71

Full-dimensional quantum dynamics study of exchange processes for the D + H2O and D + HOD reactions  

NASA Astrophysics Data System (ADS)

The exchange processes of D + H2O and D + HOD reactions are studied using initial state-selected time-dependent wave packet approach in full dimension. The total reaction probabilities for different partial waves, together with the integral cross sections, are obtained both by the centrifugal sudden (CS) approximation and exact coupled-channel (CC) calculations, for the H2O(HOD) reactant initially in the ground rovibrational state. In the CC calculations, small resonance peaks in the reaction probabilities and quick diminishing of the resonance peaks with the increase of total angular momenta J do not lead to clear step-like features just above the threshold in the cross sections for the title reactions, which are different in other isotopically substituted reactions where the hydrogen atom was included as the reactant instead of the deuterium atom [B. Fu, Y. Zhou, and D. H. Zhang, Chem. Sci. 3, 270 (2012); B. Fu and D. H. Zhang, J. Phys. Chem. A 116, 820 (2012)]. It is interesting that the shape resonance-induced features resulting from the reaction tunneling are significantly diminished accordingly in the reactions of the deuterium atom and H2O or HOD, owing to the weaker tunneling capability of the reagent deuterium atom in the title reactions than the reagent hydrogen atom in other reactions. In the CS calculations, the resonance peaks persist in many partial waves but cannot survive the partial-wave summations. The cross sections for the D' + H2O --> D'OH + H and D' + HOD --> D'OD + H reactions are substantially larger than those for the D' + HOD --> HOD' + D reaction, indicating that the D'/H exchange reactions are much more favored than the D'/D exchange.

Fu, Bina; Zhang, Dong H.

2012-05-01

72

Characteristics of low energy atom and molecule beams generated by the charge exchange reaction  

SciTech Connect

A low energy NB source, which consisted of a surface wave plasma (SWP) source and two large diameter carbon electrodes, was developed for damageless etching of ultralarge-scale integrated devices. Ion beams were extracted from the SWP using two carbon electrodes, accelerated and injected to the process chamber, and then neutralized without energy loss by a charge exchange reaction. The energy distribution functions of an Ar ion beam and an Ar atom beam was observed using a quadrupole mass spectroscope equipped with an energy analyzer. The energy of the Ar ion beam and the Ar atom beam was controlled by the acceleration voltage. N{sub 2} ion and N ion beams were also extracted from a nitrogen plasma source. The intensity ratio of the N ion beam to the N{sub 2} ion beam was 5:9, indicating that N ions were efficiently generated in the nitrogen SWP. The N{sub 2} ion and N ion beams were changed to N{sub 2} molecule and N atom beams, respectively, through a charge exchange reaction without energy loss. The energy of these beams was controlled by the acceleration voltage and was in the region less of than 100 eV. When the acceleration voltage is higher than 40 V, not only the primary peaks due to the N{sub 2} ion beam or N ion beam were observed but also a low energy second peak was observed in the energy distribution. The energy of the low energy second peak was controlled by the acceleration voltage. It was concluded that the low energy second peak corresponds to the N{sub 2} molecule ion beam and the N ion beam, which is extracted from the second plasma generated in the space between the two carbon electrodes.

Hara, Yasuhiro; Takashima, Seigo; Toyoda, Hirotaka; Sekine, Makoto; Hori, Masaru [Department of Electrical Engineering and Computer Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Yamakawa, Koji; Den, Shoji [Katagiri Engineering Co., Ltd., Tsurumi-ku, Yokohama 230-0003 (Japan)

2008-03-01

73

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

E-print Network

CALCITE DISSOLUTION AND Ca/Na ION-EXCHANGE REACTIONS IN COLUMNS WITH DIFFERENT FLOW RATES THROUGH HIGH ESR SOIL A Thesis by AUDREY NAVARRE Submitted to the Office of Graduate Studies of Texas A&:M University in partial fulfillment... of the requirements for the degree of MASTER OF SCIENCE August 1999 Major Subject: Soil Science CALCITE DISSOLUTION AND Ca/Na ION-EXCHANGE REACTIONS IN COLUMNS WITH DIFFERENT FLOW RATES THROUGH HIGH ESR SOIL A Thesis by AUDREY NAVARRE Submitted to Texas A...

Navarre, Audrey

2012-06-07

74

Estimation of the outer-sphere contribution to the activation volume for electron exchange reactions using the mean spherical approximation  

NASA Astrophysics Data System (ADS)

The outer-sphere contribution to the volume of activation of homogeneous electron exchange reactions is estimated for selected solvents on the basis of the mean spherical approximation (MSA), and the calculated values are compared with those estimated by the Strank-Hush-Marcus (SHM) theory and with activation volumes obtained experimentally for the electron exchange reaction between tris(hexafluoroacetylacetonato)ruthenium(III) and -(II) in acetone, acetonitrile, methanol and chloroform. The MSA treatment, which recognizes the molecular nature of the solvent, does not improve significantly upon the continuous-dielectric SHM theory, which represents the experimental data adequately for the more polar solvents.

Takagi, Hideo D.; Swaddle, Thomas W.

1996-01-01

75

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

76

Isotope dependence of the O+O2 exchange reaction: Experiment and theory  

NASA Astrophysics Data System (ADS)

The isotope dependence of the O+O2 exchange reaction is investigated by means of kinetic experiments and classical trajectory calculations on an accurate potential energy surface. The measurements confirm the previously reported negative temperature dependence and yield the rate coefficients for both the exothermic 18O+16O2?18O16O+16O and the endothermic 16O+18O2?16O18O+18O reaction between 233 and 353 K: k8=(3.4±0.6)×10-12 (300 K/T)1.1±0.5 cm3 s-1 and k6=(2.7±0.4)×10-12 (300 K/T)0.9±0.5 cm3 s-1. In addition, the ratio of these two rates, R, has been measured with comparatively higher precision. It is 1.27±0.04 at 300 K and also shows a distinct negative temperature dependence. Four types of classical trajectory calculations are performed in order to interpret the experimental result. They differ by the way in which the quantum mechanical zero-point energy of the reactants and the differences of zero-point energies between reactants and products, ?EZPE?±22 cm-1, are phenomenologically incorporated. Only calculations which account for ?EZPE are successful in reproducing the temperature dependence of R. This emphasizes that ?EZPE is an important factor in low-temperature ozone kinetics. At energies slightly above threshold a dynamical effect is found which additionally favors the exothermic over the endothermic reaction.

Fleurat-Lessard, Paul; Grebenshchikov, S. Yu.; Schinke, Reinhard; Janssen, Christof; Krankowsky, Dieter

2003-09-01

77

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

SciTech Connect

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

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

2011-02-15

78

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

Microsoft Academic Search

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

L. P. Kholpanov; S. E. Zakiev

2008-01-01

79

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

80

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

SciTech Connect

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

Gober, J.R.

1988-01-01

81

Hydrogen-exchange reaction of alkyl halides with formic and acetic acids  

Microsoft Academic Search

1.An investigation was made of the hydrogen exchange of alkyl halides in media differing in dielectric constant, namely formic and acetic acids.2.Tertiary halides (chloride, bromides, and iodides) undergo hydrogen exchange with formic acid-d, whereas secondary alkyl halides do not undergo hydrogen exchange under the same conditions. Tertiary chlorides do not undergo hydrogen exchange with acetic acid-d, whereas under the same

D. N. Kursanov; E. V. Bykova; V. N. Setkina

1959-01-01

82

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

83

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

SciTech Connect

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

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

2008-07-15

84

Energy deposition accompanying pion double charge exchange: Radiochemical study of the 209Bi(?+, ?-xn)209-xAt reactions  

NASA Astrophysics Data System (ADS)

The pion double charge exchange reactions, 209Bi(?+, ?-xn)209-xAt, have been studied by radiochemical techniques for incident pion energies of 100, 180, and 300 MeV. Cross sections for the chemically separated At isotopes A=205-209 were determined by alpha-particle and gamma-ray spectroscopy. The contribution of secondary processes, such as 209Bi(?+, 3,4He)X followed by 209Bi(4He, xn)213-xAt and 209Bi(3He, xn)212-xAt, which mimic the double charge exchange process, was evaluated through a study of the 209Bi(?-, X)At reactions, since double charge exchange channels cannot contribute to At production in such ?- interactions. Such secondary reactions were further characterized through target thickness studies employing 100-300 MeV ?- beams. An upper limit of the cross sections for 209At production via elastic or inelastic double charge exchange below particle emission thresholds was determined to be 6 ?b-a result which is roughly consistent with independent spectrometer measurements. Double charge exchange processes in which 8-50 MeV of excitation energy remains in 209At (to be later dissipated by neutron evaporation) are found to be much more probable as evidenced by the 209Bi(?+, ?-xn)209-xAt, x=2-4 excitation functions which are seen to be strongly and inversely dependent on the incident pion energy. NUCLEAR REACTIONS 209Bi(?+, ?-xn)209-xAt, E?+=100-300 MeV; 209Bi(?-, X)207-211At, E?-=100-300 MeV; measured ?(E), deduced secondary contributions; alpha particle and ?-ray spectroscopy, Si and Ge(Li) detectors, high purity targets, carrier-free radiochemistry.

Clark, J. L.; Haustein, P. E.; Ruth, T. J.; Hudis, J.; Caretto, A. A., Jr.

1983-03-01

85

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

E-print Network

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

E. Bauer; A. Polls; A. Ramos

1998-03-09

86

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

87

Momentum dependence of spin polarization for beta emitting nuclei produced through charge exchange reaction at intermediate energy  

NASA Astrophysics Data System (ADS)

In order to investigate the polarization process in charge exchange reactions, we observed the momentum and angular distribution as well as the nuclear polarization of a proton-rich beta-emitting nucleus, 28P ( I ? = 3 + , T 1/2 = 270 msec), produced through the reaction 28Si+ 9Be at E = 100 MeV/u, by selecting the momentum and the ejection angle. An analysis by using double Gaussian functions resolved the observed momentum distribution into two reaction components, nucleon knockout and pick-up abrasion reactions, as suggested in a previous study. The behavior of the observed angular distribution and nuclear polarization implies the influence of those two components. The momentum dependence of the observed nuclear polarization of 28P could be consistently reproduced by a simple model, in which two reaction components are considered. The present study also shows that the charge exchange reaction at intermediate energy is a useful method to produce polarized beta-emitting nuclei, especially for proton-rich nuclei.

Momota, S.; Mihara, M.; Nishimura, D.; Fukuda, M.; Kamisho, Y.; Wakabayashi, M.; Matsuta, K.; Suzuki, S.; Nagashima, M.; Zhu, Shengyun; Yuan, Daqing; Zheng, Yongnan; Yi, Zuo; Fan, Ping; Izumikawa, T.; Kitagawa, A.; Sato, S.; Kanazawa, M.; Torikoshi, M.; Minamisono, T.; Nakamura, Y.; Tashiro, K.; Honma, A.; Yoshida, N.; Shirai, H.; Ohtsubo, T.; Nagatomo, T.; Uenishi, H.; Iwamoto, K.; Yaguchi, M.; Ogura, T.; Ito, T.; Yamamura, K.; Ichikawa, Y.; Nojiri, Y.; Alonso, J. R.; Symons, T. J. M.

2013-05-01

88

Electrocatalytic reduction of acetone in a proton-exchange-membrane reactor: a model reaction for the electrocatalytic reduction of biomass.  

PubMed

Acetone was electrocatalytically reduced to isopropanol in a proton-exchange-membrane (PEM) reactor on an unsupported platinum cathode. Protons needed for the reduction were produced on the unsupported Pt-Ru anode from either hydrogen gas or electrolysis of water. The current efficiency (the ratio of current contributing to the desired chemical reaction to the overall current) and reaction rate for acetone conversion increased with increasing temperature or applied voltage for the electrocatalytic acetone/water system. The reaction rate and current efficiency went through a maximum with respect to acetone concentration. The reaction rate for acetone conversion increased with increasing temperature for the electrocatalytic acetone/hydrogen system. Increasing the applied voltage for the electrocatalytic acetone/hydrogen system decreased the current efficiency due to production of hydrogen gas. Results from this study demonstrate the commercial feasibility of using PEM reactors to electrocatalytically reduce biomass-derived oxygenates into renewable fuels and chemicals. PMID:22961747

Green, Sara K; Tompsett, Geoffrey A; Kim, Hyung Ju; Bae Kim, Won; Huber, George W

2012-12-01

89

Synthesis of free-standing metal sulfide nanoarrays via anion exchange reaction and their electrochemical energy storage application.  

PubMed

Metal sulfides are an emerging class of high-performance electrode materials for solar cells and electrochemical energy storage devices. Here, a facile and powerful method based on anion exchange reactions is reported to achieve metal sulfide nanoarrays through a topotactical transformation from their metal oxide and hydroxide preforms. Demonstrations are made to CoS and NiS nanowires, nanowalls, and core-branch nanotrees on carbon cloth and nickel foam substrates. The sulfide nanoarrays exhibit superior redox reactivity for electrochemical energy storage. The self-supported CoS nanowire arrays are tested as the pseudo-capacitor cathode, which demonstrate enhanced high-rate specific capacities and better cycle life as compared to the powder counterparts. The outstanding electrochemical properties of the sulfide nanoarrays are a consequence of the preservation of the nanoarray architecture and rigid connection with the current collector after the anion exchange reactions. PMID:24809111

Xia, Xinhui; Zhu, Changrong; Luo, Jingshan; Zeng, Zhiyuan; Guan, Cao; Ng, Chin Fan; Zhang, Hua; Fan, Hong Jin

2014-02-26

90

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

Microsoft Academic Search

Conjugate turbulent heat and mass exchange in fast exothermic reactions in thin films has been investigated with allowance\\u000a for the change in the pressure. A modification of the equal-flow-rate method, the most natural for problems of such a kind,\\u000a has been constructed. Its distinctive feature is that it is constructed on formal passage to a rectangular domain of variation\\u000a in

L. P. Kholpanov; S. E. Zakiev

2008-01-01

91

Reaction of dicyclopentadiene with formic acid and chloroacetic acid with and without cation-exchange resins as catalysts  

Microsoft Academic Search

The uncatalysed and catalysed (with cation-exchange resin) esterification of formic acid and chloroacetic acid, with dicyclopentadiene (DCPD), i.e. 4,7-methano-3a,4,7,7a-tetrahydroindene, was carried out. The effect of various parameters, e.g. speed of agitation, catalyst loading, mole ratio of the reactants, temperature, concentration of formic acid in aqueous solutions were studied to optimise the reaction conditions. DCPD cam be quantitatively converted to the

Basudeb Saha; Man Mohan Sharma

1997-01-01

92

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

E-print Network

to rotation of the DNA substrates to drive branch movement unidirectionally. Here, we test key predictions a central prediction of the model. The RecA pro- tomer exchange is not required for, and does not occur is observed, and sig- nificant ATP is hydrolyzed, even though DNA strand exchange is entirely blocked

Cox, Michael M.

93

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

94

Influence of montmorillonite tactoid size on Na-Ca cation exchange reactions.  

PubMed

The spatial organisation of swelling clay platelets in a suspension depends on the chemical composition of the equilibration solution. Individual clay platelets can be well dispersed, with surfaces entirely in contact with the external solution, or be stacked in tactoids, where part of the surfaces forms parallel alignments embedding interlayer water and cations. External and interlayer surfaces do not exhibit similar affinities for cations having different hydration and charge properties and the clay platelet stacking arrangement influences the clay affinity for these cations. This paper aims to establish the link between exchange properties and clay tactoid size and organisation for Na-Ca exchange on montmorillonite. Different montmorillonite samples behave differently with regards to Na-Ca exchange, from ideal to non-ideal exchange behaviour. A simple model coupling the tactoid stacking size to different Na/Ca relative affinities of the external and interlayer clay surfaces enables these differences to be reproduced. PMID:21920529

Tournassat, Christophe; Bizi, Mohamed; Braibant, Gilles; Crouzet, Catherine

2011-12-15

95

Declines in Soil pH due to Anthropogenic Nitrogen Inputs Alter Buffering and Exchange Reactions in Tropical Forest Soils  

NASA Astrophysics Data System (ADS)

Anthropogenic nitrogen (N) inputs may alter tropical soil buffering and exchange reactions that have important implications for nutrient cycling, forest productivity, and downstream ecosystems. In contrast to relatively young temperate soils that are typically buffered from N inputs by base cation reactions, aluminum reactions may serve to buffer highly weathered tropical soils and result in immediate increases in aluminum mobility and toxicity. Increased nitrate losses due to chronic N inputs may also deplete residual base cations in already weathered base cation-poor soils, further acidify soils, and thereby reduce nitrate mobility through pH-dependent anion exchange reactions. To test these hypotheses, I determined soil pH and cation and anion exchange capacity (CEC and AEC) and measured base cation and aluminum soil solution losses following first-time and long-term experimental N additions from two Hawaiian tropical forest soils, a 300 year old Andisol and a 4.1 million year old Oxisol. I found that elevated base cation losses accompanied increased nitrate losses after first time N additions to the young Andisol whereas immediate and large aluminum losses were associated with increased nitrate losses from the Oxisol. In the long-term, base cation and aluminum losses increased in proportion to nitrate losses. Long-term N additions at both sites resulted in significant declines in soil pH, decreased CEC and increased AEC. These results suggest that even chronic N inputs resulting in small but elevated nitrate losses may deplete residual base cations, increase mobility and toxicity of aluminum, and potentially lead to declines in forest productivity and acidification of downstream ecosystems. These findings also suggest that AEC may provide a long-term mechanism to delay nitrate losses in tropical forests with significant variable charge that are experiencing chronic anthropogenic N inputs.

Lohse, K. A.

2003-12-01

96

Analysis of ping-pong reaction mechanisms by positional isotope exchange. Application to galactose-1-phosphate uridyltransferase  

SciTech Connect

A new positional isotope exchange method has been developed that can be used for the analysis of enzyme-catalyzed reactions which have ping-pong kinetic mechanisms. The technique can be used to measure the relative rates of ligand dissociation from enzyme-product complexes. Enzyme is incubated with the labeled substrate and an excess of the corresponding unlabeled product. The partitioning of the enzyme-product complex back toward free enzyme is determined from the rate of positional isotope exchange within the original labeled substrate. The partitioning of the enzyme-product complex forward toward free enzyme is determined from the rate of formation of totally unlabeled substrate. It has been shown that the ratio of the two rates provides a lower limit for the release of product from the enzyme-product complex. The technique has been applied to the reaction catalyzed by galactose-1-phosphate uridyltransferase. The lower limit for the release of glucose 1-phosphate from the uridyl-enzyme relative to the maximal velocity of the reverse reaction was determined to be 3.4 +/- 0.5.

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

1987-09-05

97

Inclusive measurement of (p,?-xn) double charge exchange reactions on bismuth from threshold to 800 MeV  

NASA Astrophysics Data System (ADS)

The energy dependence of the total angle-integrated cross section for the production of astatine isotopes from (p,?-xn) double charge exchange reactions on bismuth (209Bi) was measured from 120 to 800 MeV using activation and radiochemical techniques. Chemical yields were estimated by direct radioassaying of 211At activity in thin (~1 mg/cm2), irradiated bismuth targets. Calculations of the contributions of secondary (two-step) reactions to these measured astatine yields were performed, based partially upon the observed 211At activity although even at the highest energies, the contribution to products lighter than 207At was negligible. These data for products with as many as seven neutrons removed from the doubly coherent product (210At) display nearly Gaussian shapes for the mass distributions of the astatine residues, with the maximum occurring for about 204At. The most probable momentum transfer deduced from these distributions for the initial ?- production step was 335 MeV/c. The observed excitation functions display a behavior similar to that observed for the yield of 210Po from a (p,?0) reaction on 209Bi, but radically different from that observed for inclusive ?- reactions on a heavy nucleus. These data are discussed in terms of recent theoretical approaches to negative pion production from bismuth. In addition, a simple, schematic model is developed to treat the rapidly decreasing percentage of the total inclusive ?- emission which is observed for this double charge exchange reaction. This model reflects the opacity of a nucleus to a source of internal energetic protons.

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

1985-07-01

98

Membrane integrity and phospholipid movement influence the base exchange reaction in rat liver microsomesý  

Microsoft Academic Search

Properties of Ca2+-stimulated incorporation of amincalcohols, serine and ethanolamine, into phospholipids, and factors regulating the reaction were studied in endoplasmic reticulum membranes isolated from rat liver. In contrast to apparent Km values for either aminoalcohol, maximal velocities of the reaction were significantly affected by Ca2+ concentration. No competition between these two soluble substrates used at equimolar concentrations close to their

Mariola Rakowska; Renata Jasiäska; Jacek Lenart; Izabela Komaäska; Piotr Makowski; Anna Dygas; Sêawomir Pikuêa

1997-01-01

99

Calculated formation and reaction energies of 3d transition metal oxides using a hierachy of exchange-correlation functionals  

NASA Astrophysics Data System (ADS)

The formation and oxidation reaction energies of 16 transition metal oxides (TMOs) are benchmarked against experiments with an increasing complexity of the exchange-correlation (xc) functionals: PBE, PBE + U with a single U for each transition metal element, PBE0 (25% exact exchange included), EXX (100% exact exchange), and EXX + RPA (random phase approximation for the correlation energy). Although rather challenging on standard CPU computing facilities, the RPA calculations were performed efficiently on graphic processing units (GPUs). For the formation energies, the PBE + U, PBE0, EXX + RPA improves significantly over PBE with mean absolute errors (MAE) of 0.83 (PBE), 0.39 (PBE + U), 0.34 (PBE0), and 0.39 (EXX + RPA) eV per oxygen. In addition, EXX + RPA improves over the other xc functionals on the oxidation reaction energies, with MAE of 0.27 (PBE), 0.28 (PBE + U), 0.30 (PBE0), to 0.13 (EXX + RPA) eV per oxygen. The distinct trend observed for the calculated oxidation reaction energies compared to the formation energies is due to that the errors in formation energies for PBE and EXX + RPA are systematic; while for PBE + U and PBE0 the deviations have both signs, so that the error cancellations between different valence states work better for PBE and EXX + RPA. Finally, we compared the performance of the EXX + RPA for total energies and G0W0, which uses the random phase approximation in constructing the W kernel, for band gaps, and discuss a few challenges for the EXX + RPA method on TMOs.

Yan, Jun; Nørskov, Jens K.

2013-12-01

100

Theoretical investigation of exchange and recombination reactions in O({sup 3}P)+NO({sup 2}{pi}) collisions  

SciTech Connect

We present a detailed dynamical study of the kinetics of O({sup 3}P)+NO({sup 2}{pi}) collisions including O atom exchange reactions and the recombination of NO{sub 2}. The classical trajectory calculations are performed on the lowest {sup 2}A{sup '} and {sup 2}A{sup ''} potential energy surfaces, which were calculated by ab initio methods. The calculated room temperature exchange reaction rate coefficient, k{sup ex}, is in very good agreement with the measured one. The high-pressure recombination rate coefficient, which is given by the formation rate coefficient and to a good approximation equals 2k{sup ex}, overestimates the experimental data by merely 20%. The pressure dependence of the recombination rate, k{sup r}, is described within the strong-collision model by assigning a stabilization probability to each individual trajectory. The measured falloff curve is well reproduced over five orders of magnitude by a single parameter, i.e., the strong-collision stabilization frequency. The calculations also yield the correct temperature dependence, k{sup r}{proportional_to}T{sup -1.5}, of the low-pressure recombination rate coefficient. The dependence of the rate coefficients on the oxygen isotopes are investigated by incorporating the difference of the zero-point energies between the reactant and product NO radicals, {delta}{sub ZPE}, into the potential energy surface. Similar isotope effects as for ozone are predicted for both the exchange reaction and the recombination. Finally, we estimate that the chaperon mechanism is not important for the recombination of NO{sub 2}, which is in accord with the overall T{sup -1.4} dependence of the measured recombination rate even in the low temperature range.

Ivanov, M. V.; Zhu, H.; Schinke, R. [Max-Planck-Institut fuer Dynamik und Selbstorganisation, D-37073 Goettingen (Germany)

2007-02-07

101

Fe 2 ?Mg 2 and TiAl 2 ?MgSi 2 exchange reactions between clinopyroxenes and silicate melts  

Microsoft Academic Search

The interdependence of the Fe(Mg)?1 (e.g., FeO-MgO in silicate melt; CaFeSi2O6-CaMgSi2O6 in pyroxene) and TiAl2(MgSi2)?1 exchange reactions between silicate melts and coexisting Ca-pyroxene has been examined. High-calcium clinopyroxenes were grown in 1 atmosphere melting and crystallization experiments on rock powders spanning the composition range tholeiite to melilitite (1,092

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

1984-01-01

102

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

103

Isotope exchange and collisional association in the reactions of CH3/+/ and its deuterated analogs with H2, HD, and D2.  

NASA Astrophysics Data System (ADS)

Two types of reaction, characterized by isotope (H/D) exchange and by ion-molecule collisionally stabilized association, are distinguished by a selected ion flow tube apparatus which determined the rate coefficients and product ion distributions at 80, 205, and 295 K for the reactions of CH3(+), CH2D(+), CHD2(+), and CD3(+) with H2, HD, and D2. Both exoergic and endoergic isotope exchange occurred, and more than one product was often observed. From the endoergic and exoergic rate coefficients of some of the reactions, van't Hoff plots are constructed for the derivation of enthalpy and entropy changes. It is noted that association channels occur in parallel with endoergic, but not exoergic, isotope exchange channels. It is suggested that this is due to internal rearrangement of the H and D atoms in the excited intermediate complexes, resulting in adiabatic cooling of the complex when endoergic isotope exchange channels are available.

Smith, D.; Adams, N. G.; Alge, E.

1982-08-01

104

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

105

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

PubMed

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

Polak, Micha; Rubinovich, Leonid

2011-10-01

106

Strong geometric-phase effects in the hydrogen-exchange reaction at high collision energies  

Microsoft Academic Search

We report quantum wave packet calculations of state-to-state reaction probabilities and cross sections for the reaction H+H2(v0=0,j0=0)?H2(v,j)+H, at total energies up to 4.5 eV above the ground state potential minimum. The calculations are repeated using (i) the ground electronic state only, (ii) the ground state plus the diagonal non-Born–Oppenheimer correction, (iii) the ground state, diagonal non-Born–Oppenheimer correction and geometric phase

Foudhil Bouakline; Stuart C. Althorpe; Daniel Pela´ez Ruiz

2008-01-01

107

Strong geometric-phase effects in the hydrogen-exchange reaction at high collision energies  

Microsoft Academic Search

We report quantum wave packet calculations of state-to-state reaction probabilities and cross sections for the reaction H+H2(v0=0,j0=0)-->H2(v,j)+H, at total energies up to 4.5 eV above the ground state potential minimum. The calculations are repeated using (i) the ground electronic state only, (ii) the ground state plus the diagonal non-Born-Oppenheimer correction, (iii) the ground state, diagonal non-Born-Oppenheimer correction and geometric phase

Foudhil Bouakline; Stuart C. Althorpe; Daniel Peláez Ruiz

2008-01-01

108

Dipole and spin-dipole resonances in charge-exchange reactions on 12C  

NASA Astrophysics Data System (ADS)

The 12C(n,p)12B reaction was studied using the white neutron source at the Los Alamos Meson Physics Facility/Weapon Neutron Research Center with a continuous incident neutron energy from 60 to 260 MeV. Double differential cross sections were measured in the angular range 11°<=?lab<=37°. Using the neutron time-of-flight facility at the Indiana University Cyclotron Facility, we also studied the 12C(p,n)12N reaction at Ep=186 MeV and the 12C(p-->,n-->)12N reaction at Ep-->=160 and 186 MeV. Double differential cross sections were measured between ?lab=0° and ?lab=50° in 5° steps. Spin observables DNN, AY, and P were measured at ?lab=5°,9°,13° with Ep-->=160 MeV and ?lab=15°,20° with Ep-->=186 MeV. Angular distributions of differential cross section and spin observables for low-lying transitions in the residual nuclei are compared with disorted-wave impulse approximation (DWIA) calculations. A multipole decomposition analysis was performed to study the giant dipole and giant spin-dipole resonances. The contributions of the quasifree reaction in the giant resonance region was subtracted. The empirical results of energy distributions for dipole (?L=1) transition are compared with DWIA calculations using nuclear structure information obtained with a conventional shell model and also with a random phase approximation.

Yang, X.; Wang, L.; Rapaport, J.; Goodman, C. D.; Foster, C.; Wang, Y.; Unkelbach, W.; Sugarbaker, E.; Marchlenski, D.; de Lucia, S.; Luther, B.; Ullmann, J. L.; Ling, A. G.; Park, B. K.; Sorenson, D. S.; Rybarcyk, L.; Taddeucci, T. N.; Howell, C. R.; Tornow, W.

1993-09-01

109

The analysis of the pantothenate synthetase reaction by positional isotope exchange  

E-print Network

and then decreased to zero at saturating levels of D-pantoate. These inhibition results support the ordered binding of ATP and D-pantoate to the enzyme active site. The PIX reaction was abolished with the addition of inorganic pyrophosphatase and thus PP[i] must...

Williams, Lakenya Flatreese

2012-06-07

110

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

111

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

NASA Astrophysics Data System (ADS)

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

Kim, Sung Hyun

112

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

113

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

114

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

NASA Astrophysics Data System (ADS)

The conversion of CH4 hydrate to CO2 hydrate offers, in principle, a way of sequestering CO2, with the additional recovery of CH4 gas as an energy source. We report results from the first in-situ oceanic experiment on this reaction, carried out in August 2006 at the massive thermogenic hydrate mounds in 850 m water depth, Barkley Canyon, offshore from Vancouver Island (48° 18.642' N, 126° 3.903' W), using MBARI's ROV Tiburon deployed from the R/V Western Flyer. Two small cores (10 cm length, 4 cm diameter) of white hydrate were collected from exposed outcrops using an ROV operated tool and hydraulically ejected into a glass walled, closed top, reaction chamber. Approximately 2 L of liquid CO2 were dispensed into the chamber, and the chamber transferred to an aluminium base plate to seal the system. Under ambient conditions (P = 870 dbar, T = 4.0 °C, S = 34.2), the densities of natural gas hydrate and liquid CO2 are closely matched and less than that of seawater, where the hydrate cores floated at the top of the chamber fully immersed within the buoyant liquid CO2. Over the following ~48 hours, the system was inspected periodically with the ROV HDTV camera prior to examination with the sea-going laser Raman spectrometer, DORISS II. For this, the chamber was transferred to a Precision Underwater Positioner (PUP) that enabled focusing of the laser beam with sub- mm precision. Our choice of where to focus the laser was based upon the need to explore all phases the cored natural gas hydrate, liquid CO2, any created CO2 hydrate, and any liberated CH4 gas. The natural gas hydrate was composed primarily of CH4, with minor amounts of C2H6 and C3H8, indicating the presence of Structure II hydrate. To date, laboratory experiments have focused on the reaction between pure Structure I CH4 hydrate and CO2 vapour, where the difference in free energy between the CH4 and CO2 hydrate states provides a thermodynamic argument in favour of conversion. However for a Structure II hydrate with a complex guest gas composition immersed in liquid CO2 there are multiple pathways for the reaction to proceed. If the hydrate cage occupancy is 100% then we suspect on thermodynamic grounds that the reaction may proceed slowly; nevertheless if cage occupancy is <100%, and/or a mixture of Structure I and II is present, then substitution could occur rapidly. In addition, dissolution of the natural gas hydrate in the unsaturated liquid CO2 will liberate water molecules that are then available to form CO2 hydrate. Obviously, grain size and porosity (surface area) will have profound effects on reaction rate and extent. We also note that the solubility of CH4 in CO2 is significant, and we may not expect liberation of a free CH4 gas phase until the saturation condition has been met. Given the complexity of this system, the only way to know what will occur is to do the experiment. Indeed, spectra were obtained of a commingled CO2 and CH4 hydrate. The CO2 fermi-diad peaks in the hydrate phase are distinguishable from the liquid, and are shifted to lower wavenumbers by ~~3 cm-1. We also observed the presence of dissolved CH4 within the liquid CO2, and free CH4 gas in a small but visually identifiable bubble layer at the top of the chamber. The initial success of this pilot study bodes well for future investigations both in the laboratory and in ROV based experiments.

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

2006-12-01

115

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

116

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

E-print Network

al, 1954), After 1 ml of the reaction mix- ture was added to 0, 2 ml of 5 N H2S04, the solution was placed in the outer well of a Conway diffusion unit containing I ml of saturated K2005. The inner well contained 1 ml of 2'/o boric acid solution... with brom cresol green indicator ( 2 ml of 0. 1% brom cresol green in alcohol per liter of boric acid solution). After the diffusion, which was per- f ormed at room temperature f or 75 min, the boric acid was titrated with standard H2SO4. A standard...

Smith, Gordon Marsh

2012-06-07

117

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

E-print Network

by the ordered release of arginino- succinate, PP. , and AiMP. Ghose and Raushel (1985) then proved the existence of the citrulline-adenylate intermediate in this reaction through static and dynamic quench experiments. This involved the quantitation of acid... to incubate in a 30 0 water bath with the pH bei~g adjusted to pH 6. 5 with acetic acid. at 5 minute intervals. After 25 minutes the remaining 0. 5 mL of KCNO solution was Scheme 8. Strategy for synthesis of ( - 08)ATP 18 (Cohn and Hu, 1980) ado- -0 + ado...

Hilscher, Larry Wayne

2012-06-07

118

Swi5-Sfr1 protein stimulates Rad51-mediated DNA strand exchange reaction through organization of DNA bases in the presynaptic filament  

PubMed Central

The Swi5-Sfr1 heterodimer protein stimulates the Rad51-promoted DNA strand exchange reaction, a crucial step in homologous recombination. To clarify how this accessory protein acts on the strand exchange reaction, we have analyzed how the structure of the primary reaction intermediate, the Rad51/single-stranded DNA (ssDNA) complex filament formed in the presence of ATP, is affected by Swi5-Sfr1. Using flow linear dichroism spectroscopy, we observe that the nucleobases of the ssDNA are more perpendicularly aligned to the filament axis in the presence of Swi5-Sfr1, whereas the bases are more randomly oriented in the absence of Swi5-Sfr1. When using a modified version of the natural protein where the N-terminal part of Sfr1 is deleted, which has no affinity for DNA but maintained ability to stimulate the strand exchange reaction, we still observe the improved perpendicular DNA base orientation. This indicates that Swi5-Sfr1 exerts its activating effect through interaction with the Rad51 filament mainly and not with the DNA. We propose that the role of a coplanar alignment of nucleobases induced by Swi5-Sfr1 in the presynaptic Rad51/ssDNA complex is to facilitate the critical matching with an invading double-stranded DNA, hence stimulating the strand exchange reaction. PMID:24304898

Fornander, Louise H.; Renodon-Corniere, Axelle; Kuwabara, Naoyuki; Ito, Kentaro; Tsutsui, Yasuhiro; Shimizu, Toshiyuki; Iwasaki, Hiroshi; Norden, Bengt; Takahashi, Masayuki

2014-01-01

119

Theoretical calculation of reorganization energy for electron self-exchange reaction by constrained density functional theory and constrained equilibrium thermodynamics.  

PubMed

Within the framework of constrained density functional theory (CDFT), the diabatic or charge localized states of electron transfer (ET) have been constructed. Based on the diabatic states, inner reorganization energy ?in has been directly calculated. For solvent reorganization energy ?s, a novel and reasonable nonequilibrium solvation model is established by introducing a constrained equilibrium manipulation, and a new expression of ?s has been formulated. It is found that ?s is actually the cost of maintaining the residual polarization, which equilibrates with the extra electric field. On the basis of diabatic states constructed by CDFT, a numerical algorithm using the new formulations with the dielectric polarizable continuum model (D-PCM) has been implemented. As typical test cases, self-exchange ET reactions between tetracyanoethylene (TCNE) and tetrathiafulvalene (TTF) and their corresponding ionic radicals in acetonitrile are investigated. The calculated reorganization energies ? are 7293 cm(-1) for TCNE/TCNE(-) and 5939 cm(-1) for TTF/TTF(+) reactions, agreeing well with available experimental results of 7250 cm(-1) and 5810 cm(-1), respectively. PMID:23895675

Ren, Hai-Sheng; Ming, Mei-Jun; Ma, Jian-Yi; Li, Xiang-Yuan

2013-08-22

120

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

121

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

122

Ion exchange reactions of NaSbO 3 and morphotropic series MSbO 3  

NASA Astrophysics Data System (ADS)

By reactions of ilmenite-type NaSbO 3 with molten nitrates at ca. 300 °C, ilmenite forms of AgSbO 3 and TlSbO 3 have been obtained and characterized by chemical analysis and X-ray diffraction (rhombohedral, a=5.3272(9) and 5.3149(7) Å, c=16.6923(2) and 21.5136(4) Å, respectively). Unexpectedly, a new form of LiSbO 3, prepared in a similar way, is not rhombohedral. Its XRD pattern has been indexed on a monoclinic C-centred pseudo-orthorhombic cell with a=5.2948(7), b=9.0082(7), c=5.2923(6) Å, ?=113.790(5). This cell may be derived from the ilmenite structure by gliding SbO 6/2 layers. Diffuse nature of the XRD pattern is due to stacking faults. TlSbO 3 also contains faults, which have been modelled by ˜10% 2H stacking analogous to known P-31c polytype. On heating, layered AgSbO 3 and LiSbO 3 transform to stable phases (pyrochlore and Pncn, respectively), but TlSbO 3 remains unchanged at least to 850 °C. Attempts to substitute Cs for Na have been unsuccessful. Previously reported X-ray data for ilmenite-type CsSbO 3 are discredited. Volume relations in the MSbO 3 series are discussed.

Nalbandyan, Vladimir Babkenovich; Avdeev, Maxim; Pospelov, Andrey Aleksandrovich

2006-12-01

123

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

PubMed

We utilized gas phase hydrogen/deuterium (H/D) exchange reactions and ab initio calculations to investigate the complexation between a model peptide (Arg-Gly-Asp[triple bond]RGD) with various alkali metal ions. The peptide conformation is drastically altered upon alkali metal ion complexation. The associated conformational changes depend on both the number and type of complexing alkali metal ions. Sodium has a smaller ionic diameter and prefers a multidentate interaction that involves all three amino acids of the peptide. Conversely, potassium and cesium form different types of complexes with the RGD. The [RGD + 2Cs - H]+ species exhibit the slowest H/D exchange reactivity (reaction rate constant of approximately 6 x 10(-13) cm3molecule(-1)s(-1) for the fastest exchanging labile hydrogen with ND3). The reaction rate constant of the protonated RGD is two orders of magnitude faster than that of the [RGD + 2Cs - H]+. Addition of the first cesium to the RGD reduces the H/D exchange reaction rate constant (i.e., D0) by a factor of seven whereas sodium reduces this value by a factor of thirty. Conversely, addition of the second alkali metal ions has the opposite effect; the rate of D0 disappearance for all [RGD + 2Met - H]+ species (Met[triple bond]Na, K, and Cs) decreases with the alkali metal ion size. PMID:11766754

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

2001-12-01

124

Measurement of spin transfer parameters in the p-bar p yields n-bar n charge-exchange reaction at LEAR.  

National Technical Information Service (NTIS)

The experiment PS199 at LEAR investigates the spin structure of the charge-exchange reaction p-bar p yields n-bar n. Data for the measurement of the spin transfer parameters for both neutron and antineutron were collected during 1990 and preliminary resul...

J. Arvieux, M. Agnello, A. Ahmidouch, M. Lamanna

1991-01-01

125

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

PubMed

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

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

2014-01-01

126

Glutathione peroxidase (GPx)-like antioxidant activity of the organoselenium drug ebselen: unexpected complications with thiol exchange reactions.  

PubMed

The factors that are responsible for the relatively low glutathione peroxidase (GPx)-like antioxidant activity of organoselenium compounds such as ebselen (1, 2-phenyl-1,2-benzisoselenazol-3(2H)-one) in the reduction of hydroperoxides with aromatic thiols such as benzenethiol and 4-methylbenzenethiol as cosubstrates are described. Experimental and theoretical investigations reveal that the relatively poor GPx-like catalytic activity of organoselenium compounds is due to the undesired thiol exchange reactions that take place at the selenium center in the selenenyl sulfide intermediate. This study suggests that any substituent that is capable of enhancing the nucleophilic attack of thiol at sulfur in the selenenyl sulfide state would enhance the antioxidant potency of organoselenium compounds such as ebselen. It is proved that the use of thiol having an intramolecularly coordinating group would enhance the biological activity of ebselen and other organoselenium compounds. The presence of strong S...N or S...O interactions in the selenenyl sulfide state can modulate the attack of an incoming nucleophile (thiol) at the sulfur atom of the -Se-S- bridge and enhance the GPx activity by reducing the barrier for the formation of the active species selenol. PMID:16089478

Sarma, Bani Kanta; Mugesh, G

2005-08-17

127

Active microchannel heat exchanger  

Microsoft Academic Search

The present invention is an active microchannel heat exchanger with an active heat source and with microchannel architecture. The active 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

Anna Lee Y. Tonkovich; Gary L. Roberts; Charles J. Call; Robert S. Wegeng; Yong Wang

2001-01-01

128

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

Microsoft Academic Search

METAL CHALCOGENIDE NANOPARTICLE GEL NETWORKS: THEIR FROMATION MECHANISM AND APPLICATION FOR NOVEL MATERIAL GENERATION AND HEAVY METAL REMEDIATION VIA CATION EXCHANGE REACTIONS\\u000aby\\u000aIRINA R. PALA\\u000aFebruary 2012\\u000aAdvisor: Dr. Stephanie L. Brock\\u000aMajor: Chemistry\\u000aDegree: Doctor of Philosophy\\u000aThe dissertation research is focused on (1) uncovering the mechanism of metal chalcogenide nanoparticle gel formation; (2) extending the cation exchange

Irina Ramona Pala

2012-01-01

129

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

130

The isotope exchange reactions H + +D2 ? HD+D + and D + +H2?HD+H + in the temperature range 200-300 K  

NASA Astrophysics Data System (ADS)

Forward and reverse rate coefficients have been measured in the temperature range 200-300 K for the two reactions H++D2?HD+D+ and D++H2?HD+H+. Equilibrium constants derived therefrom agree with theoretical van't Hoff plots calculated from statistical mechanics and confirm the temperature calibration of the SIFT apparatus used. It is suggested that these reactions can be used as kinetic thermometers to measure independently the temperature of ion-molecule reaction cells. The system provides a particularly clear example of the role of statistical factors in chemical kinetics, 1 for the forward reactions and 1/2 for their reverse reactions; and the system illustrates further the relationship between statistical factors in kinetics, symmetry numbers in statistical mechanics, and the corresponding thermodynamic entropy changes. Constraints upon the temperature dependence of the rate coefficients are derived from consideration of thermodynamics and collision dynamics, and the data are seen to conform to these over a limited temperature range. A further trend is suggested by the data, supporting previous observations of isotope-exchange reactions—the rate coefficients of the exoergic reactions decrease with increasing temperature—and may be described in terms of the partitioning of the system according to the number of states available to the products and the original reactants. It is suggested that this should be a general result for reactions where the exoergicity is comparable to the temperature of measurement.

Henchman, M. J.; Adams, N. G.; Smith, D.

1981-08-01

131

Oxygen isotope biogeochemistry of pore water sulfate in the deep biosphere: Dominance of isotope exchange reactions with ambient water during microbial sulfate reduction (ODP Site 1130)  

Microsoft Academic Search

Microbially mediated sulfate reduction affects the isotopic composition of dissolved and solid sulfur species in marine sediments. Experiments and field data show that the ?18OSO42- composition is also modified in the presence of sulfate-reducing microorganisms. This has been attributed either to a kinetic isotope effect during the reduction of sulfate to sulfite, cell-internal exchange reactions between enzymatically-activated sulfate (APS), and\\/or

Ulrich G. Wortmann; Boris Chernyavsky; Stefano M. Bernasconi; Benjamin Brunner; Michael E. Böttcher; Peter K. Swart

2007-01-01

132

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

133

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

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 A Dissertation by ARIKA PRAVITASARI Submitted... Jaime Grunlan Head of Department, David H. Russell December 2013 Major Subject: Chemistry Copyright 2013 Arika Pravitasari ii ABSTRACT This work focused on the integration of CdSe quantum dots (QDs) and Au nanoparticles (NPs...

Pravitasari, Arika

2013-11-11

134

Spin structure of the "Forward" nucleon charge-exchange reaction n + p ? p + n and the deuteron charge-exchange breakup  

NASA Astrophysics Data System (ADS)

The structure of the nucleon charge-exchange process n + p ? p + n is investigated basing on the isotopic invariance of the nucleon-nucleon scattering. Using the operator of permutation of the spin projections of the neutron and proton, the connection between the spin matrices, describing the amplitude of the nucleon charge-exchange process at zero angle and the amplitude of the elastic scattering of the neutron on the proton in the "backward" direction, has been considered. Due to the optical theorem, the spin-independent part of the differential cross section of the process n + p ? p + n at zero angle for unpolarized particles is expressed through the difference of total cross sections of unpolarized proton-proton and neutron-proton scattering. Meantime, the spin-dependent part of this cross section is proportional to the differential cross section of the deuteron charge-exchange breakup d + p ? ( pp) + n at zero angle at the deuteron momentum k d = 2 k n ( k n is the initial neutron momentum). Analysis shows that, assuming the real part of the spin-independent term of the "forward" amplitude of the process n + p ? p + n to be smaller or of the same order as compared with the imaginary part, in the wide range of neutron laboratory momenta k n > 700 MeV/ c the main contribution into the differential cross section of the process n + p ? p + n at zero angle is provided namely by the spin-dependent term.

Lyuboshitz, V. L.; Lyuboshitz, V. V.

2011-02-01

135

/sup 1/H NMR study of the base-pairing reactions of d(GGAATTCC): salt and polyamine effects on the imino proton exchange  

SciTech Connect

Salts and polyamines have a variety of effects on the physical properties of DNA, including stabilization against thermal melting. The authors wished to gain greater insight into the mechanism of this stabilization by ascertaining its effect on the dynamics of base opening and closing reactions, as measured by NMR. Since the binding of spermidine (3+) is influenced by salt, and since spermidine may act as a base catalyst in proton exchange reactions, they have undertaken a study of salt and base catalyst effects on the imino proton exchange kinetics of a model oligomeric DNA. The selective longitudinal NMR relaxation rates of the hydrogen-bonded imino protons of the self-complementary octadeoxyribonucleotide d(GGAATTCC) monitor the rate of the base-catalyzed chemical exchange of these protons with solvent water. The exchange rates thus obtained provide a sensitive measure of the base-pair opening reactions of the DNA duplex. Under conditions of low pH and no added base catalyst, the NMR relaxation rates allow the determination of k/sub d/, the rate constant for the dissociation of the octameric duplex into single strands. Titration with the base catalyst tris(hydroxymethyl) aminomethane allows the determination of k/sub op/, the rate constant for the localized opening of individual base pairs, prior to dissociation. The activation energy for helix dissociation is not dependent on the sodium ion concentration. In agreement with previous results, no measurable salt dependence is found for k/sub op/. Under low-salt conditions, the trivalent cation spermidine decreases the rate of helix dissociation, again without affecting the activation energy for this process.

Braunlin, W.H.; Bloomfield, V.A.

1988-02-23

136

Measurement of the depolarization parameter and the spin transfer parameter in the charge-exchange reaction [bar p]p[yields][bar n]n at LEAR  

SciTech Connect

Experiment PS199 at LEAR studied the charge-exchange [bar p]p[yields][bar n]n reaction and, in particular, its spin structure. Data for the measurement of the depolarization parameter for a polarized target (D[sub 0n0n]) and the polarization-transfer parameter from the target to the scattered particle (K[sub 0n0n]) have been collected during 1990. The determination of these parameters requires n and [bar n] polarimetry. Polarimeters are described, and their performances are given. 10 refs., 7 figs.

Birsa, R.; Bradamante, F.; Dalla Torre-Colautti, S.; Giorgi, M.; Lamanna, M.; Martin, A.; Penzo, A.; Schiavon, P.; Tessarotto, F. (INFN Trieste and Univ. of Trieste, Trieste (Italy)); Macciotta, M.P. (and others)

1992-05-01

137

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

Microsoft Academic Search

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

Andrzej W. Trochimczuk; Julia Jezierska

2000-01-01

138

Share Price Reactions to Sporty Performances of Soccer Clubs listed on the London Stock Exchange and the AIM  

Microsoft Academic Search

This paper investigates whether or not the share prices of soccer clubs listed on the London Stock Exchange and the Alternative Investment Market are influenced by the soccer teams' weekly sporty performances. Event studies corrected for thin trading and with Baysian updating reveal that at the first day of trading after a game, positive abnormal returns almost 1% were realised

L. D. R. Renneboog; P. Vanbrabant

2000-01-01

139

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

SciTech Connect

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

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

2007-12-05

140

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

2014-12-20

141

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 wi...

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

2014-01-01

142

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

143

The isolation of an unidentified factor from yeast extract for the formate-pyruvate exchange reaction in streptococcus faecalis  

E-print Network

added to the reaction mimture containing- yeast emtraot only a 2N riduotion of activity. was TAMIL 1, Bigratii-n ni' tho factor on loper in s pyridinc butcnol-i. ztsr solvent system. . Band Boo Color of bands hy u+ve Activity Fold apmspmols... added to the reaction mimture containing- yeast emtraot only a 2N riduotion of activity. was TAMIL 1, Bigratii-n ni' tho factor on loper in s pyridinc butcnol-i. ztsr solvent system. . Band Boo Color of bands hy u+ve Activity Fold apmspmols...

Chen, Chi-sin

2012-06-07

144

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

PubMed

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

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

2013-05-28

145

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

SciTech Connect

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 V{sub 2}O{sub 5}, the RE oxides, SnO{sub 2}, etc. Molten salt tests at 680{degree}C showed SnO{sub 2}, presumably because of its acidic nature, to be essentially nonreactive with V{sub 2}O{sub 5} or Na{sub 2}O-V{sub 2}O{sub 5} compounds. A hypothesis was developed to explain how the passivation effect by Sn might result from the unique resistivity of SnO{sub 2} to reaction with V{sub 2}O{sub 5}.

Jones, R.L. (Naval Research Lab., Washington, D.C. (USA))

1991-05-01

146

Non-innocent electrolyte effects on bimolecular pseudo-self-exchange reactions of ruthenium ammine complexes: Evidence for electron-transfer catalysis in H-bonded ternary assemblies  

Microsoft Academic Search

The kinetics of bimolecular pseudo-self-exchange reactions such as that between pentaammine(pyridine)ruthenium(II) and pentaammine(3-fluoropyridine)ruthenium(III) shown below,(NH3)5RuII(py)2++(NH3)5RuIII(3-Fpy)3+?kex(NH3)5RuIII(py)3++(NH3)5RuII(3-Fpy)2+reveal a novel form of non-covalently mediated electron transfer over distance when salts of non-innocent electrolytes such as the conjugated dicarboxylic acid anions trans,trans-muconate2? or terephthalate2? are added to the solution. The kinetic accelerations are distinct from those seen with simple electrolytes such as KCl or

Jeff Christian Curtis; Mayuko Inagaki; Sam J. Chun; Vahid Eskandari; Xining Luo; Zheng N. Pan; Uma Sankararaman; Gina E. Pengra; Jiahua Zhou; Philip Hailey; Jeanny Laurent; Daniel Utalan

2006-01-01

147

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

148

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

E-print Network

. 1972, 94, 1881. 14. Poe, A. J. ; Twigg, M. V. J. Organomet. Chem. 1973, 50, C 39. 15. Poe, A. J4 Twigg, M. V. J. Chem. Soc. Dalton Trans. 1974, 1860. Atwood, J. D. Inorganic and Organomettalic Reactions Mechanisms; Brooks/Cole: Monterey, CA, 1985.... 17. Basolo, F. Inotg. Chim. Acta 1981, 50, 65. 18. Basolo, F. Inorg. Chim. Acta 1981, 100, 33. 19. Howell, J. A. S4 Burkinshaw, P. M. Chem. Rev. 1983, 83, 557. 20. Darensbourg, D. J. Adv. Organomet. Chem. 1982, 21, 113. 21 Fredeen, D. A4 Russell...

Nguyen, Hanh Duc

2012-06-07

149

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

150

Deactivation of hydrophobic Pt/SDBC-catalyst for H{sub 2}/HTO-exchange reaction destined for tritium removal in reprocessing plant  

SciTech Connect

Deactivation of a hydrophobic Pt/SDBC catalyst for the H{sub 2}/HTO isotopic exchange reaction used to remove tritium from the waste water generated in a nuclear-fuel reprocessing plant has been studied experimentally. The catalyst was poisoned reversibly by a small amount of HNO{sub 3} and could be regenerated by washing with water followed by drying in an inert gas. As a countermeasure against this poisoning, the neutralization of the waste water was found to be effective. The presence of I{sub 2} in the waste water caused a sharp decrease in the activity of the catalyst, due to the irreversible adsorption of I{sub 2} onto the catalyst surface. The I{sub 2} poisoning could be prevented by the conversion of I{sub 2} into I{sup -} or IO{sub 3}{sup -} by neutralization or redox reaction. TBP and the neutral nitrate salts of fission products such as Sr(NO{sub 3}){sub 2} showed negligible poisoning effects on the catalyst. 10 refs., 8 figs., 1 tab.

Wei, Y.Z.; Takeshita, K.; Kumagai, M.; Takashima, Y. [Inst. of Research and Innovation, Chiba (Japan); Matsumoto, S. [Saitama Univ. (Japan); Shimizu, M. [Isotope Science Lab., Kanagawa (Japan)

1995-10-01

151

Evidence for sequence scrambling and divergent H/D exchange reactions of doubly-charged isobaric b-type fragment ions.  

PubMed

To date, only a limited number of reports are available on structural variants of multiply-charged b-fragment ions. We report on observed bimodal gas-phase hydrogen/deuterium exchange (HDX) reaction kinetics and patterns for substance P b10(2+) that point to presence of isomeric structures. We also compare HDX reactions, post-ion mobility/collision-induced dissociation (post-IM/CID), and sustained off-resonance irradiation-collision induced dissociation (SORI-CID) of substance P b10(2+) and a cyclic peptide with an identical amino acid (AA) sequence order to substance P b10. The observed HDX patterns and reaction kinetics and SORI-CID pattern for the doubly charged head-to-tail cyclized peptide were different from either of the presumed isomers of substance P b10(2+), suggesting that b10(2+) may not exist exclusively as a head-to-tail cyclized structure. Ultra-high mass measurement accuracy was used to assign identities of the observed SORI-CID fragment ions of substance P b10(2+); over 30% of the observed SORI-CID fragment ions from substance P b10(2+) had rearranged (scrambled) AA sequences. Moreover, post-IM/CID experiments revealed the presence of two conformer types for substance P b10(2+), whereas only one conformer type was observed for the head-to-tail cyclized peptide. We also show that AA sequence scrambling from CID of doubly-charged b-fragment ions is not unique to substance P b10(2+). PMID:24346960

Zekavat, Behrooz; Miladi, Mahsan; Al-Fdeilat, Abdullah H; Somogyi, Arpad; Solouki, Touradj

2014-02-01

152

Evidence for Sequence Scrambling and Divergent H/D Exchange Reactions of Doubly-Charged Isobaric b-Type Fragment Ions  

NASA Astrophysics Data System (ADS)

To date, only a limited number of reports are available on structural variants of multiply-charged b-fragment ions. We report on observed bimodal gas-phase hydrogen/deuterium exchange (HDX) reaction kinetics and patterns for substance P b10 2+ that point to presence of isomeric structures. We also compare HDX reactions, post-ion mobility/collision-induced dissociation (post-IM/CID), and sustained off-resonance irradiation-collision induced dissociation (SORI-CID) of substance P b10 2+ and a cyclic peptide with an identical amino acid (AA) sequence order to substance P b10. The observed HDX patterns and reaction kinetics and SORI-CID pattern for the doubly charged head-to-tail cyclized peptide were different from either of the presumed isomers of substance P b10 2+, suggesting that b10 2+ may not exist exclusively as a head-to-tail cyclized structure. Ultra-high mass measurement accuracy was used to assign identities of the observed SORI-CID fragment ions of substance P b10 2+; over 30 % of the observed SORI-CID fragment ions from substance P b10 2+ had rearranged (scrambled) AA sequences. Moreover, post-IM/CID experiments revealed the presence of two conformer types for substance P b10 2+, whereas only one conformer type was observed for the head-to-tail cyclized peptide. We also show that AA sequence scrambling from CID of doubly-charged b-fragment ions is not unique to substance P b10 2+.

Zekavat, Behrooz; Miladi, Mahsan; Al-Fdeilat, Abdullah H.; Somogyi, Arpad; Solouki, Touradj

2013-12-01

153

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

154

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

155

Hydrothermal synthesis of ?-NaYF4 nanotubes by in situ ion exchange reaction using Y(OH)3 nanotubes as templates  

NASA Astrophysics Data System (ADS)

In this article, we reported the synthesis of uniform hexagonal NaYF4 (?-NaYF4) nanotubes through in situ ion exchange reaction using Y(OH)3 nanotubes as templates via a facile hydrothermal route. The structure and morphology of the products were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that the as-prepared ?-NaYF4 with a length of about 4 ?m, an external diameter of about 160 nm, and a thickness of about 50 nm preserved the basic morphology of the initial Y(OH)3 nanotubes. The influence of pH value of the precursor on the morphology and structure of the products was also studied, and the results indicated that ?-NaYF4 nanotubes could only be obtained at proper pH value. The strength of acids adjusting the pH value of the precursor had no influence on the morphology and structure of the products. Additionally, the upconversion luminescence properties of Yb3+/Er3+ codoped ?-NaYF4 were investigated. Yb3+/Er3+ codoped NaYF4 emitted bright green and red light, both of which were two-photon processes.

Liu, Lina; Zang, Chunhe; Zhang, Yongsheng

2012-06-01

156

Non-innocent electrolyte effects on bimolecular pseudo-self-exchange reactions of ruthenium ammine complexes: Evidence for electron-transfer catalysis in H-bonded ternary assemblies  

NASA Astrophysics Data System (ADS)

The kinetics of bimolecular pseudo-self-exchange reactions such as that between pentaammine(pyridine)ruthenium(II) and pentaammine(3-fluoropyridine)ruthenium(III) shown below, (NH3)5RuII(py)+(NH3)5RuIII(3-Fpy)?kex(NH3)5RuIII(py)+(NH3)5RuII(3-Fpy) reveal a novel form of non-covalently mediated electron transfer over distance when salts of non-innocent electrolytes such as the conjugated dicarboxylic acid anions trans, trans-muconate 2- or terephthalate 2- are added to the solution. The kinetic accelerations are distinct from those seen with simple electrolytes such as KCl or CaCl 2, and are thus outside the realm of classical electrolyte effects described by the Debye-Huckel theory of ion atmospheres. Kinetic simulations are presented, and the rate acceleration is interpreted in the context of possible superexchange-type interactions taking place in hydrogen-bonded ternary (or higher) association complexes which create new kinetic pathways for electron transfer over distance in aqueous solution.

Curtis, Jeff Christian; Inagaki, Mayuko; Chun, Sam J.; Eskandari, Vahid; Luo, Xining; Pan, Zheng N.; Sankararaman, Uma; Pengra, Gina E.; Zhou, Jiahua; Hailey, Philip; Laurent, Jeanny; Utalan, Daniel

2006-07-01

157

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

158

Novel protonated and hydrated n=1 Ruddlesden-Popper phases, H{sub x}Na{sub 1-x}LaTiO{sub 4}.yH{sub 2}O, formed by ion-exchange/intercalation reaction  

SciTech Connect

New derivatives of layered perovskite compounds with H{sub 3}O{sup +} ions, H{sup +} ions and water molecules in the interlayer, H{sub x}Na{sub 1-x}LaTiO{sub 4}.yH{sub 2}O, were successfully synthesized by an ion-exchange/intercalation reaction with dilute HCl solution, using an n=1 member of Ruddlesden-Popper phase, NaLaTiO{sub 4}. Powder X-ray diffraction revealed that the layered structure changed from space group P4/nmm with a=3.776(1) and c=13.028(5)A to I4/mmm with a=3.7533(3) and c=28.103(4)A after the ion-exchange/intercalation reaction at pH 5. The change of space group indicates that the perovskite layers are transformed from staggered to an eclipsed configuration through the ion-exchange/intercalation reaction. Thermogravimetric analysis and high-temperature powder X-ray diffraction suggested the existence of the secondary hydrated phase by dehydrating H{sub x}Na{sub 1-x}LaTiO{sub 4}.yH{sub 2}O at 100{sup o}C.

Nishimoto, Shunsuke [Faculty of Environmental Science and Technology, Department of Environmental Chemistry and Materials, Okayama University, Tsushima-Naka, Okayama 700-8530 (Japan); Matsuda, Motohide [Faculty of Environmental Science and Technology, Department of Environmental Chemistry and Materials, Okayama University, Tsushima-Naka, Okayama 700-8530 (Japan); Miyake, Michihiro [Faculty of Environmental Science and Technology, Department of Environmental Chemistry and Materials, Okayama University, Tsushima-Naka, Okayama 700-8530 (Japan)]. E-mail: mmiyake@cc.okayama-u.ac.jp

2005-03-15

159

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

E-print Network

the ORR reaction pathway is highly dependent on electrode materials and reaction media.4­6 Pt of the prepared catalysts for the oxygen reduction reaction (ORR) in alkaline media are investigated. We show.7­9 Electrode kinetics particularly for the ORR is faster in alkaline media than that in acid media

Zhao, Tianshou

160

Evaluation of the partitioning of bound inorganic phosphate during medium and intermediate phosphate in equilibrium water oxygen exchange reactions of yeast inorganic pyrophosphatase.  

PubMed Central

During the rapid exchange of oxygens of Pi with water catalyzed by yeast inorganic pyrophosphatase, Pi at the catalytic site may either dissociate or undergo reversible loss of an oxygen to water. The effective partitioning of bound Pi during exchange starting with medium Pi containing 18O in all four oxygens has been evaluated by mass spectral analysis of the change in the distribution of Pi species containing zero to four 18O oxygens per Pi. This analysis indicates that the rate of Pi release from the enzyme is only 1.4 times faster than the rate of reformation of the anhydrous intermediate. A similar partitioning of bound Pi is observed during PPi hydrolysis, indicating that hydrolysis and medium exchange have common intermediates. The approach should be applicable to study of related phosphate oxygen exchanges. PMID:356047

Hackney, D D; Boyer, P D

1978-01-01

161

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

162

Degradation of salicylic acid by photo-assisted Fenton reaction using Fe ions on strongly acidic ion exchange resin as catalyst  

Microsoft Academic Search

The photo-assisted Fenton degradation of salicylic acid (SA) was studied by using strongly acidic ion exchange resin (SAIER) exchanged with Fe ions as catalyst in the presence of UV light (254nm) and H2O2. The X-ray photoelectron spectroscopy (XPS) results revealed that the Fe ions are indeed anchored by the sulfonate groups on the surface of the SAIER and are Fe3+.

Jiyun Feng; Xijun Hu; Po Lock Yue

2004-01-01

163

Effect of the salt melt composition, temperature, and interaction time on the contact exchange reaction in the MCl-PbCl 2 MeN systems  

Microsoft Academic Search

The interaction of titanium, zirconium, and aluminum nitrides with a mixture of fused alkali-metal chlorides with lead chloride\\u000a at 870–1070 K is studied. It is shown that as a result of the contact exchange interaction, which occurs in no more than 5\\u000a h, a large fraction of the powdered nitrides transforms into a soluble state, and lead precipitates in a

L. A. Elshina; V. Ya. Kudyakov; N. G. Molchanova

2008-01-01

164

Determination of D/H ratios of nonexchangeable hydrogen in cellulose: A method based on the cellulose-water exchange reaction  

SciTech Connect

The authors have established a simple technique for the determination of D/H ratios of nonexchangeable hydrogen in cellulose. This technique is based on equilibrating cellulose prepared from raw wood or cotton with water of known isotopic composition. A temperature of 0[degrees]C was selected for the exchange experiments. This allowed the rapid freezing and subsequent sublimation of the ice without affecting the isotopic composition of the equilibrated hydroxyl hydrogen. A sodium hydroxide treatment of the cellulose is necessary to achieve equilibrium between cellulose and water within 24 hours. The best sodium hydroxide treatment procedure was found to be overnight soaking of cellulose in a 17% NaOH solution at near 0[degrees]C, following by rinsing and transferring the cellulose to the exchange vessels without drying. The authors have obtained a very good reproducibility of the [sigma]D analysis of the equilibrated cellulose treated with this procedure (1[sigma] < 2[per thousand]). The resulting [sigma]D values of nonexchangeable hydrogen, using the equilibration technique, were compared with those obtained using the nitration technique. The agreement between the two techniques is [+-]3.3[per thousand] (1[sigma]), and the analytical accuracy of the equilibration method is [+-]2.5[per thousand] (1[sigma]). This method may be useful in dealing with the nitration of ancient plant materials, which is sometimes not possible. In addition, the technique may be extended to the isotopic analysis of other organic compounds that contain exchangeable hydrogen.

Feng, X.; Krishnamurthy, R.V.; Epstein, S. (California Institute of Technology, Pasadena, CA (United States))

1993-09-01

165

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

Microsoft Academic Search

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

Derek S. Liechty; Mark J. Lewis

2011-01-01

166

Effects which will not blur the message of the 1H (11Li, 9Li) 3H reaction: observation of phonon-exchange pairing correlations in nuclei  

NASA Astrophysics Data System (ADS)

The results of the 1H (11Li, 9Li) 3H experiment carried out recently at TRIUMF have given detailed information concerning the structure and the reaction mechanism at work in the case of halo, exotic nuclei, providing important stepping stones for an eventual quantitative description of superfluidity in finite nuclei. In fact, the central role played by renormalization processes as testified by the excitation of the 1/2- (2.69 MeV) member of the 9Li (2+ otimesp3/2(?))j- multiplet (nuclear structure) together with the post-prior symmetry (reaction), testify to the fact that a detailed knowledge of the "bare" quantities, like e.g. the NN-interaction is likely to be less important, in a unified Nuclear Field Theory description of the structure and the reaction aspects of the experiment, than previously thought.

Vigezzi, E.; Potel, G.; Barranco, F.; Broglia, R. A.

2011-09-01

167

Monetary policy, foreign exchange intervention, and the exchange rate in a unifying framework  

Microsoft Academic Search

The structural VAR model is developed to jointly analyze the effects of foreign exchange intervention and (money or interest rate setting) conventional monetary policy on the exchange rate, the two types of policy reactions to the exchange rate, and interactions between the two types of policies. First, many interactions among the two types of policies and the exchange rate are

Soyoung Kim

2003-01-01

168

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

169

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

170

Water dissociation in ion-exchange membrane electrodialysis  

Microsoft Academic Search

When an electrical current larger than the limiting current density passes across an ion-exchange membrane, H+ ions and OH? ions are generated and transported in a water dissociation layer formed between the ion-exchange membrane and the boundary layer. Water dissociation reactions consist of a forward reaction and a reverse reaction. The forward reaction rate increases along with the increase of

Yoshinobu Tanaka

2002-01-01

171

Isotope effects in peptide group hydrogen exchange  

Microsoft Academic Search

Kinetic and equilibrium iso- tope effects in peptide group hydrogen ex- change reactions were evaluated. Unlike many other reactions, kinetic isotope effects in amide hydrogen exchange are small because ex- change pathways are not limited by bond- breaking steps. Rate constants for the acid-cat- alyzed exchange of peptide group NH, ND, and NT in H,O are essentially identical, but a

Gregory P. Connelly; Yawen Bai; Mei-Fen Jeng; S. Walter Englander

1993-01-01

172

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

173

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.

174

Exchangeable equilibria  

E-print Network

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

Stein, Noah D. (Noah Daniel)

2011-01-01

175

Real exchange rate stabilisation and managed floating: exchange rate policy in India, 1993–2001  

Microsoft Academic Search

The paper examines the exchange rate management objectives of the Indian central bank after the shift to a floating exchange rate regime in 1993. It argues that three empirical features of the post-float period, viz. nominal and real exchange rate stability and increase in reserves’ volatility are inter-related. A policy reaction function relates these features and finds that central bank

Renu Kohli

2003-01-01

176

Heat exchanger development at Reaction Engines Ltd  

Microsoft Academic Search

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

Richard Varvill

2010-01-01

177

Chemical exchange magnetic resonance imaging (CHEMI)  

SciTech Connect

Systems investigated with NMR spectroscopy are sometimes heterogeneous with respect to chemical composition, rates of chemical exchange, and other properties influencing magnetic resonance parameters. A method was developed to spatially encode reaction kinetic information and produce NMR images sensitive to chemical exchange. A modified spin-echo pulse sequence was used to allow chemical shift-selective imaging and chemical exchange encoding. /sup 1/H and /sup 31/P images with microscopic resolution were obtained which yielded chemical exchange as a function of position. Chemical exchange images of the base-catalyzed proton exchange of acetylacetone and of the enzyme-catalyzed /sup 31/P transfer between PCr and ATP were obtained at 8.4 T in phantoms at 360 and 146 MHz, respectively. These images demonstrate a means of investigating kinetic heterogeneity and compartmentalization of reactions that are important in the study of both living and non-living systems.

McFarland, E.W.; Neuringer, L.J.; Kushmerick, M.J.

1988-09-01

178

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

179

PROTEIN ANALYSIS BY HYDROGEN EXCHANGE MASS SPECTROMETRY  

Microsoft Academic Search

? Abstract Mass spectrometry has provided a powerful method for monitoring hydrogen exchange of protein backbone amides with deuterium from solvent. In com- parison to popular NMR approaches, mass spectrometry has the advantages of higher sensitivity, wider coverage of sequence, and the ability to analyze larger proteins. Pro- teolytic fragmentation of proteins following the exchange reaction provides moderate structural resolution,

Andrew N. Hoofnagle; Katheryn A. Resing; Natalie G. Ahn

2003-01-01

180

Weathering Reactions and Soil-Groundwater Reactions  

NSDL National Science Digital Library

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

Sherman, David M.; Bristol, University O.

181

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

182

Textile Exchange  

NSDL National Science Digital Library

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

183

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

184

Reactions & Rates  

NSDL National Science Digital Library

Explore what makes a reaction happen by colliding atoms and molecules. Design experiments with different reactions, concentrations, and temperatures. When are reactions reversible? What affects the rate of a reaction?

Simulations, Phet I.; Koch, Linda; Lemaster, Ron; Loeblein, Trish; Perkins, Kathy; Gratny, Mindy

2006-12-01

185

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

186

Exchange-Rate Regimes: \\  

Microsoft Academic Search

Traditionally the IMF's Annual Report on Exchange Arrangements and Exchange Restrictions has been the main source of information about the exchange-rate policies pursued by member countries. The classification contained therein has been used to document the evolution of exchange rate regimes over time as well as to study the relationship between economic performance and the choice of exchange rate system.

Hans Genberg; Alexander K. Swoboda

2004-01-01

187

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

188

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

189

A new reactor concept for endothermic high-temperature reactions  

Microsoft Academic Search

A new reactor concept for the autothermal operation of endothermic high-temperature reactions is presented. An endothermic synthesis reaction is coupled with a combustion reaction in such a way that both reactions take place in adjacent channels of a countercurrent fixed-bed reactor. Due to the countercurrent heat exchange the feed and the exit of both reactions have low temperatures while a

J. Frauhammer; G. Eigenberger; L. v. Hippel; D. Arntz

1999-01-01

190

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

191

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

192

A combined experimental, theoretical, and Van't Hoff model study for identity methyl, proton, hydrogen atom, and hydride exchange reactions. Correlation with three-center four-, three-, and two-electron systems  

NASA Astrophysics Data System (ADS)

We have studied carbon transfer reactions following an SN2 reaction profile. With ab initio calculations and experimental geometries concerning the nature of the various complexes indicated as stable, intermediate, and transition state we were able to show the additional value of van't Hoff's tetrahedral configuration by changing its geometry via a trigonal pyramid into a trigonal bipyramid. The ratio of the apical bond and corresponding tetrahedral bond distances is then nearly 1.333. The relevance of this approach has also been shown for identity proton-(hydrogen atom-, and hydride-) in-line reactions. The use of this geometrical transmission will be demonstrated for the hydrogen bonding distances in e.g., DNA duplexes and other biological (supra) molecular systems.

Buck, Henk M.

193

Formaldehyde reactions in dark clouds  

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

194

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.

School, Minerva D.

2011-10-03

195

Reversible Reactions  

NSDL National Science Digital Library

Watch a reaction proceed over time. How does total energy affect a reaction rate? Vary temperature, barrier height, and potential energies. Record concentrations and time in order to extract rate coefficients. Do temperature dependent studies to extract Arrhenius parameters. This simulation is best used with teacher guidance because it presents an analogy of chemical reactions.

Simulations, Phet I.; Barbera, Jack; Koch, Linda; Lemaster, Ron; Adams, Wendy

2005-09-01

196

Nuclear Reactions  

Microsoft Academic Search

Nuclear reactions generate energy in nuclear reactors, in stars, and are responsible for the existence of all elements heavier than hydrogen in the universe. Nuclear reactions denote reactions between nuclei, and between nuclei and other fundamental particles, such as electrons and photons. A short description of the conservation laws and the definition of basic physical quantities is presented, followed by

C. A. Bertulani

2009-01-01

197

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

198

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

Robertson, William C.

2010-03-01

199

GE Healthcare Ion exchange  

E-print Network

GE Healthcare Ion exchange columns and media Selection Guide imagination at work #12;Principle. Chromatography media selection Select the ion exchange medium according to the objective of the purification step

Lebendiker, Mario

200

Real-time monitoring of intermediates reveals the reaction pathway in the thiol-disulfide exchange between disulfide bond formation protein A (DsbA) and B (DsbB) on a membrane-immobilized quartz crystal microbalance (QCM) system.  

PubMed

Disulfide bond formation protein B (DsbBS-S,S-S) is an inner membrane protein in Escherichia coli that has two disulfide bonds (S-S, S-S) that play a role in oxidization of a pair of cysteine residues (SH, SH) in disulfide bond formation protein A (DsbASH,SH). The oxidized DsbAS-S, with one disulfide bond (S-S), can oxidize proteins with SH groups for maturation of a folding preprotein. Here, we have described the transient kinetics of the oxidation reaction between DsbASH,SH and DsbBS-S,S-S. We immobilized DsbBS-S,S-S embedded in lipid bilayers on the surface of a 27-MHz quartz crystal microbalance (QCM) device to detect both formation and degradation of the reaction intermediate (DsbA-DsbB), formed via intermolecular disulfide bonds, as a mass change in real time. The obtained kinetic parameters (intermediate formation, reverse, and oxidation rate constants (kf, kr, and kcat, respectively) indicated that the two pairs of cysteine residues in DsbBS-S,S-S were more important for the stability of the DsbA-DsbB intermediate than ubiquinone, an electron acceptor for DsbBS-S,S-S. Our data suggested that the reaction pathway of almost all DsbASH,SH oxidation processes would proceed through this stable intermediate, avoiding the requirement for ubiquinone. PMID:24145032

Yazawa, Kenjiro; Furusawa, Hiroyuki; Okahata, Yoshio

2013-12-13

201

Mechanism of Ligand Exchange Studied Using Transition Path Sampling  

E-print Network

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

Harris, Charles B.

202

Exchange rate exposure  

Microsoft Academic Search

In this paper we examine the relationship between exchange rate movements and firm value. We estimate the exchange rate exposure of publicly listed firms in a sample of eight (non-US) industrialized and emerging markets. We find that exchange rate movements do matter for a significant fraction of firms, though which firms are affected and the direction of exposure depends on

Kathryn M. E. Dominguez; Linda L. Tesar

2006-01-01

203

Internally consistent representation of binary ion exchange equilibria  

Microsoft Academic Search

A model has been developed to obtain the thermodynamic parameters, i.e., the equilibrium constant and solid-phase activity coefficients, that describe binary ion exchange reactions. The model is based on the thermodynamic framework for adsorption exchange reactions developed by Gaines and Thomas (1953. Journal of Chemical Physics, 21, 714–718). The Wilson activity coefficient model is used for the adsorbed phase and

Socrates Ioannidis; Andrzej Anderko; Stephen J Sanders

2000-01-01

204

Nuclear Reactions  

Microsoft Academic Search

Nuclear reactions generate energy in nuclear reactors, in stars, and are\\u000aresponsible for the existence of all elements heavier than hydrogen in the\\u000auniverse. Nuclear reactions denote reactions between nuclei, and between nuclei\\u000aand other fundamental particles, such as electrons and photons. A short\\u000adescription of the conservation laws and the definition of basic physical\\u000aquantities is presented, followed by

C. A. Bertulani; B. Kinematics

2009-01-01

205

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.

Science, New Y.

1999-01-01

206

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

207

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

208

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 ...

Hicken, Mrs.

2009-05-04

209

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

210

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

211

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

212

Azoxy rearrangement reactions  

NASA Astrophysics Data System (ADS)

The mechanisms of several types of azoxy compound (XN(O)NY) rearrangement reactions have been studied using density functional theory (DFT) with the B3LYP exchange-correlation potential. The substituents X and Y are taken from the set H, CH , F, C H , Cl and CN. The 6-311 + G(d,p) basis set was used to optimize up to ten equilibrium and transition state structures for a given pair of X and Y substituents; except for azoxybenzene where a 6- 311(+)G(d) basis set was used. All geometric structures were characterized by a frequency calculation. The reaction path for converting XN (O)N Y to XN N (O)Y via a concerted intramolecular shift of the oxygen atom from N to N involves three equilibrium and two saddle-point structures. The relatively high (about 70-80 kcalmol1) calculated barrier height to reaction and its independence of the nature of the X and Y substituents is attributed to characteristic orbital, atomic charge and structural factors along the reaction path. Cis trans isomerization across N-- N in the NH(O)NH azoxy compound and across N-N in the ring XNONY oxadiaziridine intermediate is found to have a barrier height of at least - 1 about 30 kcalmol . Single-point CCSD(T)/DFT energy differences are found to be somewhat smaller than the DFT calculated values. 3 6 5

Basch, Harold; Hoz, Tova

213

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

214

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

215

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...

216

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

NASA Astrophysics Data System (ADS)

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

Yaldagard, Maryam; Seghatoleslami, Naser; Jahanshahi, Mohsen

2014-10-01

217

Oxygen isotope exchange rate between dissolved sulfate and water at hydrothermal temperatures  

Microsoft Academic Search

Oxygen isotope exchange rate between dissolved sulfate and water was experimentally determined at 100, 200 and 300°C. The isotope exchange rate is strongly dependent on temperature and pH of the solution. Combining the temperature and pH dependence of the reaction rate, the exchange reaction was estimated to be first-order with respect to sulfate. The logarithm of apparent rate constant of

Hitoshi Chiba; Hitoshi Sakai

1985-01-01

218

Computational Science - Stack Exchange  

NSDL National Science Digital Library

This is a free, community driven Q&A for scientists using computers to solve scientific problems. It is a part of the Stack Exchange network of Q&A websites, and it was created through the open democratic process defined at Stack Exchange Area 51.

219

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

220

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

221

Higher Education Exchange, 2005  

ERIC Educational Resources Information Center

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

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

2005-01-01

222

Higher Education Exchange, 2008  

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.

2008-01-01

223

Higher Education Exchange, 2007  

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" discuss the concept of growing public scholars; each contribution incorporates a student component. Articles include: (1) "Foreword"…

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

2007-01-01

224

Higher Education Exchange, 2010  

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.

2010-01-01

225

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.

226

Motivation for International Exchange.  

ERIC Educational Resources Information Center

An objective analysis of students' initial motivation for studying overseas was attempted by surveying students before they embarked on their exchange programs. Eighty-eight students who were planning to study in France, Great Britain, Germany, and the People's Republic of China were surveyed. The exchange program was sponsored by the University…

Brewer, Elizabeth

227

Foreign Exchange Markets  

Microsoft Academic Search

market touched about 175 billion US dollars. Compare this with the monthly trading volume of about 120 billion US dollars for all cash, derivatives and debt instruments put together in the country, and the sheer size of the foreign exchange market becomes evident. Since then, the foreign exchange market activity has more than doubled with the average monthly turnover reaching

Rajesh Chakrabarti

228

Handicapping Social Exchange Theory.  

ERIC Educational Resources Information Center

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

Mishler, Barbara

229

Money and Exchange.  

ERIC Educational Resources Information Center

This teaching guide begins with an explanation of the role of money in the economy, focusing on its circulation or exchange. The use of money as a unit of account, a store of value, and a medium of exchange are explained. Three brief teaching units are included. The grade K-2 unit, "Money Counts," provides games and activities which develop the…

Walstad, William B.; And Others

1982-01-01

230

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

231

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 ...

232

Allergic Reactions  

MedlinePLUS

... For instance, if you have an allergy to pollen, your immune system identifies pollen as an invader or allergen . Your immune system ... it can affect a child's speech and language development. Diagnosing and Treating Allergic Reactions An allergist / immunologist, ...

233

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.

School, Maryland V.

234

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

235

Wittig Reaction 33 Reaction: Synthesis of Alkenes  

E-print Network

elimination reactions (E1 or E2 reactions from alcohols or alkyl halides, for example), in eliminationWittig Reaction 33 The Wittig Reaction: Synthesis of Alkenes Intro The "Wittig Reaction" is one reactions the carbon skeleton is already pre-assembled. In the Wittig reaction, however, two smaller carbon

Jasperse, Craig P.

236

Taxol reactions.  

PubMed

Paclitaxel (Taxol) a taxane antineoplastic agent causing irreversible microtubule aggregation with activity against breast, ovarian, lung, head and neck, bladder, testicular, esophageal, endometrial and other less common tumors was derived from the bark of the Pacific yew (Taxus brevifolia). Phase I trials conducted in the late 1980s were almost halted because of the high frequency of hypersensitivity-like reactions. Respiratory distress (dyspnea and/or bronchospasm), hypotension, and angioedema were the major manifestations, but flushing, urticaria, chest, abdomen, and extremity pains were described also. Reactions occurred on first exposure in the majority of cases raising etiologic questions. The vehicle for paclitaxel Cremophor EL (polyoxyethylated castor oil in 50% ethanol) was strongly suspect as a direct (non-immunoglobulin E dependent) histamine releaser. Premedication regimens and longer infusion times lowered the incidence of reactivity allowing phase II and III trials to progress through the early 1990s. The mechanism(s) underlying paclitaxel hypersensitivity-like reactions is still unknown, and clinical data on probable complement and mast cell activation are lacking. The original clinical trial protocols for paclitaxel required discontinuation of therapy for patients who experienced hypersensitivity-like reactions. Here, we review the current etiologic knowledge of these reactions and describe our clinical approach to allow completion of chemotherapy with this powerful plant-derived agent. PMID:12125509

Price, Kursteen S; Castells, Mariana C

2002-01-01

237

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

238

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

239

Cryptographic Securities Exchanges  

NASA Astrophysics Data System (ADS)

While transparency in financial markets should enhance liquidity, its exploitation by unethical and parasitic traders discourages others from fully embracing disclosure of their own information. Traders exploit both the private information in upstairs markets used to trade large orders outside traditional exchanges and the public information present in exchanges' quoted limit order books. Using homomorphic cryptographic protocols, market designers can create "partially transparent" markets in which every matched trade is provably correct and only beneficial information is revealed. In a cryptographic securities exchange, market operators can hide information to prevent its exploitation, and still prove facts about the hidden information such as bid/ask spread or market depth.

Thorpe, Christopher; Parkes, David C.

240

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

241

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

242

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

243

Single event kinetic modeling of solid acid alkylation of isobutane with butenes over proton-exchanged Y-Zeolites  

E-print Network

Complex reaction kinetics of the solid acid alkylation of isobutane with butenes over a proton-exchanged Y-zeolite has been modeled at the elementary step level. Starting with a computer algorithm that generated the reaction network based...

Martinis Coll, Jorge Maximiliano

2006-04-12

244

EXCHANGE VISITOR PROGRAM GUIDE  

E-print Network

Program. J-1 EXCHANGE VISITOR CATEGORIES DEFINITION OF CATEGORIES: Student: an individual who will pursue in the U.S. DS-2019 issuance is handled in accordance with current immigration status regulations

Bieber, Michael

245

Greywater heat exchanger  

SciTech Connect

A kilowatt meter and water meter were installed to monitor pregreywater usage. The design considerations, the heat exchanger construction and installation, and the monitoring of usage levels are described.

Holmberg, D.

1983-11-21

246

Exchange transfusion - series (image)  

MedlinePLUS

... the infant's blood and replacement with fresh donor blood or plasma. Guidelines for an exchange transfusion include: Hemolytic disease of the newborn (Rh disease) Life-threatening infection Severe disturbances in body chemistry Toxic effects of ...

247

Exchanging Graphs with GXL  

Microsoft Academic Search

GXL (Graph eXchange Language) is designed to be a standard dataexchange format for graph-based tools. GXL is defined as an XML sublanguage,which offers support for exchanging instance graphs together with their appropriateschema information in a uniform format. Formally, GXL is based on typed,attributed, directed, ordered graphs which are extended by concepts to representhypergraphs and hierarchical graphs. Using this general graph

Andreas Winter

2001-01-01

248

Exchange Rate Economics  

Microsoft Academic Search

The paper summarizes the current theory of how a floating exchange rate is determined, dividing the subject into what determines\\u000a the steady state and what determines the transition to steady state. The inadequacies of this model are examined, and an alternative\\u000a “behavioral” model, which recognizes that the foreign exchange market is populated by both fundamentalists and chartists is\\u000a presented. It

John Williamson

2009-01-01

249

Contact Heat Exchanger  

NASA Technical Reports Server (NTRS)

Fluid pressure controls contact between heat pipe and heat exchanger. Heat exchanger system in cross section provides contact interface between fluid system and heat pipe with easy assembly/disassembly of heat-pipe/ pumped-liquid system. Originally developed for use in space, new device applicable on Earth where fluid system is linked with heat pipe, where rapid assembly/disassembly required, or where high pressures or corrosive fluids used.

Fleming, M. L.; Stalmach, D. D.; Cox, R. L.

1985-01-01

250

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

Horton, Michael

2009-05-30

251

Cryptographic Combinatorial Securities Exchanges  

NASA Astrophysics Data System (ADS)

We present a useful new mechanism that facilitates the atomic exchange of many large baskets of securities in a combinatorial exchange. Cryptography prevents information about the securities in the baskets from being exploited, enhancing trust. Our exchange offers institutions who wish to trade large positions a new alternative to existing methods of block trading: they can reduce transaction costs by taking advantage of other institutions’ available liquidity, while third party liquidity providers guarantee execution—preserving their desired portfolio composition at all times. In our exchange, institutions submit encrypted orders which are crossed, leaving a “remainder”. The exchange proves facts about the portfolio risk of this remainder to third party liquidity providers without revealing the securities in the remainder, the knowledge of which could also be exploited. The third parties learn either (depending on the setting) the portfolio risk parameters of the remainder itself, or how their own portfolio risk would change if they were to incorporate the remainder into a portfolio they submit. In one setting, these third parties submit bids on the commission, and the winner supplies necessary liquidity for the entire exchange to clear. This guaranteed clearing, coupled with external price discovery from the primary markets for the securities, sidesteps difficult combinatorial optimization problems. This latter method of proving how taking on the remainder would change risk parameters of one’s own portfolio, without revealing the remainder’s contents or its own risk parameters, is a useful protocol of independent interest.

Thorpe, Christopher; Parkes, David C.

252

Ion exchange equilibrium between ion exchange membrane and electrolyte solutions  

Microsoft Academic Search

The ion exchange equilibrium between an ion exchange membrane and solutions of different electrolytes was studied. The matrix of the ion exchange membrane used consists of a vinyl polychloride network reinforced by a polyester screen; with quaternary and tertiary ammonium as functional groups. The data, provided by manufacturer, were completed by the experimental determinations of humidity percentage and ion exchange

Ch. Hannachi; S. Bouguecha; B. Hamrouni; M. Dhahbi

2008-01-01

253

Steric Effects in Peptide and Protein Exchange with Activated Disulfides  

PubMed Central

Disulfide exchange is an important bioconjugation tool, enabling chemical modification of peptides and proteins containing free cysteines. We previously reported the synthesis of a macromer bearing an activated disulfide and its incorporation into hydrogels. Despite their ability to diffuse freely into hydrogels, larger proteins were unable to undergo in-gel disulfide exchange. In order to understand this phenomenon, we synthesized four different activated disulfide-bearing model compounds (Mn = 300 Da-10 kDa) and quantified their rate of disulfide exchange with a small peptide (glutathione), a moderate-sized protein (?-lactoglobulin), and a large protein (bovine serum albumin) in four different pH solutions (6.0, 7.0, 7.4, and 8.0) to mimic biological systems. Rate constants of exchange depend significantly on the size and accessibility of the thiolate. pH also significantly affects the rate of reaction, with the faster reactions occurring at higher pH. Surprisingly, little difference in exchange rates is seen between macromolecular disulfides of varying size (Mn = 2 kDa – 10kDa), although all undergo exchange more slowly than their small molecule analogue (MW = 300 g/mol). The maximum exchange efficiencies (% disulfides exchanged after 24 h) are not siginificantly affected by thiol size or pH, but somewhat affected by disulfide size. Therefore, while all three factors investigated (pH, disulfide size and thiolate size) can influence the exchange kinetics and extent of reaction, the size of the thiolate and its accessibility plays the most significant role. PMID:23865598

Kerr, Jason; Schlosser, Jessica L.; Griffin, Donald R.; Wong, Darice Y.; Kasko, Andrea M.

2014-01-01

254

Nucleophilic substitution at the halogen atom (halogenophilic reactions)  

NASA Astrophysics Data System (ADS)

The key features of halogenophilic reactions defining their role in organic chemistry are considered. The results of studies of mechanisms involving a nucleophilic attack at the halogen atom (SN2Hal) are summarized. The main mechanistic evidence comes from the studies of halogen-metal exchange reactions. Primary attention is paid to the role of halogenophilic reaction as a competing process or a concealed mechanism in ordinary nucleophilic substitution reaction at carbon atoms. The bibliography includes 249 references.

Sazonov, Petr K.; Artamkina, Galina A.; Beletskaya, Irina P.

2012-04-01

255

Empirical tests for ecological exchangeability  

Microsoft Academic Search

The concept of ecological exchangeability, together with genetic exchangeability, is central to both the Cohesion Species Concept as well as to some definitions of Evolutionarily Significant Units. While there are well- established criteria for measuring genetic exchangeability, the concept of ecological exchangeability has generated considerable confusion. We describe a procedure that uses the complementary strengths, while recognising the limitations, of

Russell B. Rader; Mark C. Belk; Dennis K. Shiozawa; Keith A. Crandall

2005-01-01

256

Microscopic Theory of Cation Exchange in CdSe Nanocrystals  

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

257

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

258

Recuperative coupling of exothermic and endothermic reactions  

Microsoft Academic Search

Coupling energy intensive endothermic reaction systems with suitable exothermic reactions improves the thermal efficiency of processes and reduces the size of the reactors. One type of reactor suitable for such a type of coupling is the heat exchanger reactor. In this work, a one-dimensional pseudo-homogeneous plug flow model is used to analyze and compare the performance of co-current and counter-current

R. C. Ramaswamy; P. A. Ramachandran; M. P. Dudukovi?

2006-01-01

259

Fluid exchange flows  

NASA Astrophysics Data System (ADS)

Flow flows from one container to another play important roles in many natural and industrial situations. The talk will describe the latest work on some of these. 1. The exchange flow of relatively dense, viscous fluid in a container connected by a vertical pipe to a container beneath it, initially full of relatively light fluid, will be discussed. This mimics the important exchange flow between a volcanic crater and a deep magma reservoir. A quantitative analysis of the flow will be presented. For the volcanic situation this allows the conduit radius to be evaluated from observations of the sulphur dioxide flux from the crater to the atmosphere. 2. A closed container initially full of liquid, which can drain into the atmosphere through a very long tube, displays different phenomena, which are associated with the compressibility of the air that exchanges space with the liquid. Three distinct regimes are observed, which we term: `popping'; `glugging'; and `slugging'. During each of these the container drains at a quite different rate. 3. Hot air in a house can be exchanged through doors and windows with the cooler air outside. The form and rate of exchange and its dependence on window geometry is of considerable architectural interest at the moment, if only to make our working environment as green as possible. New experiments and the associated concepts for this problem will be discussed.

Huppert, Herbert

2006-11-01

260

Stoichiometry of removal of natural organic matter by ion exchange.  

PubMed

Five anion exchange resins, including a magnetic ion exchange (MIEX) resin, were evaluated for removal of Suwannee River Fulvic Acid (SRFA) in the presence of bicarbonate and chloride. The charge density of SRFA, obtained by potentiometric titration, was used to perform charge balances for ion exchange reactions involving SRFA, bicarbonate, and chloride under different solution conditions. The results clearly show the equivalence of SRFA uptake and chloride release by ion exchange. Although the structure of the anion exchange resins did not affect the stoichiometry of the reaction, the polyacrylic resins did exhibit greater removal of SRFA than the polystyrene resins. The hindered removal of SRFA by the polystyrene resins was hypothesized to be a result of size exclusion. The MIEX resin, which has a polyacrylic structure, performed similarly to the other polyacrylic resins. For the MIEX resin, the separation factor for SRFA over chloride was approximately 8 times greater than for bicarbonate over chloride. This work provides an improved understanding of the interactions between natural organic matter (NOM), inorganic anions, and anion exchange resins, and should result in more effective applications of ion exchange for the removal of NOM in the treatment of drinking water. PMID:18284170

Boyer, Treavor H; Singer, Philip C

2008-01-15

261

Two-photon exchange in electron deuteron scattering  

E-print Network

It is shown that the amplitude of elastic ed scattering beyond Born approximation contains six generalized form factors, but only three linearly independent combinations of them (generalized charge, quadrupole and magnetic form factors) contribute to the reaction cross section in the second order perturbation theory. We examine two-photon exchange and find that it includes two types of diagrams, when two virtual photons interact with the same nucleon and when the photons interact with different nucleons.We discuss contribution of the two-photon exchange in reaction observables, generalized \\mathcal A and \\mathcal B structure functions and tensor polarization of the deuteron.

A. P. Kobushkin; Ya. D. Krivenko-Emetov

2011-01-10

262

Interdiffusion of exchanging counterions in poly(perfluorosulfonic acid) membrane.  

PubMed

The kinetics of forward (Li+/Na+mem <=> Mn+aq) and reverse (Mn+mem <=> Li+/Na+aq) exchanges of metal ions(Mn+ ) Ag+, Cs+, Ba2+, and Eu3+) in the poly(perfluorosulfonic acid) membrane (Nafion-117) equilibrated with a well-stirred aqueous salt solution were experimentally measured using radioactivity tagged counterions. A numerical solution of the Nernst-Planck (N-P) equation for interdiffusion was used to interpret the kinetics of these exchanges. The experimentally measured kinetics of forward and reverse Na+ ion exchanges with Mn+ ions between the membrane and the equilibrating solution were found to be close to that predicted by the N-P equation. The minor differences between the experimental and predicted exchange rate profiles were attributed to change in water content of the poly(perfluorosulfonic acid) membrane in different ionic forms. The kinetics of Li+ ion exchanges with Na+ and Cs+ ions was found to be unusual as the self-diffusion coefficient D(ion)(m) of Li+ ions in the membrane were quite different in the forward and reverse exchanges. The values of D(ion)(m) for Li+ ion, obtained by the N-P equation, were found to be 2 x 10-6 and 0.2 x 10-6 cm2 s-1in Li+mem <=> Na+/Cs+aq and Na+/Cs+mem <=> Li+aq exchanges, respectively. The drastic differences in diffusion mobility of Li+ ions during forward and reverse exchanges was attributed to weak electrostatic interactions of Li+ ions with the fixed exchange sites as indicated by the reported equilibrium constant Kex of the Li+-exchange reaction in Nafion membrane. D(ion)(m) is high in the forward exchange due to minimum retardation in diffusion mobility of Li+ ions by the electrostatic forces in the membrane. In reverse exchange, Li+ diffusion mobility is retarded due to its slow replacement of counterions from the membrane. PMID:19705822

Sodaye, Suparna; Suresh, G; Pandey, Ashok K; Goswami, A

2009-09-17

263

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

2012-06-07

264

Multistrange Baryon production from strangeness-exchange reactions  

E-print Network

) 2 ' cos tb'6, I) 2+m~e2imsg'6 tn?? me) (C. 9) Inserting the above equation into Eq. (C. S) and comparing with Eq. (C. 7), we obtain Using 1 g(&') = ? P[Tj+ ? Ti ] sin 8'Pi'(cos 0'). 4' ( o . p'cr p = cos 0' y io ~ p' x p, (C. 1O) (C. 11) we...(ID((((mp ? i2&s g p (m, 'm', ] jm) (jmlmi'm, ") (mi"m", 1 jm) Umlmim*) fm, impIDV'mp I I P ?/* (8', 0')Y/-((8 4) ? i2Vs p p (m/7n', ]jm)(jm]m(m, )Y/* (6f, @')Y/, (8, (t))Vf(Tf/. fm /m(m', (D. 4) The Bethe-Salpeter equation can thus be written as 8' +s...

Li, Changhui

2012-06-07

265

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

266

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.

Dao Xiang [SLAC National Accelerator Laboratory, Menlo Park, CA, 94025 (United States)

2010-11-04

267

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).

268

Microgravity condensing heat exchanger  

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

269

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

270

Gaseous Nitrogen Heat Exchanger  

SciTech Connect

A heat exchanger is necessary to warm the gaseous nitrogen from the nitrogen dewar from 77 K to ambient temperature for use in the D-Zero Building. The original proposal would use an ambient air vaporizer, but further investigation led to the consideration and evaluation of other possibilities and a different final system. The vaporizer must be able to handle a flow rate of 1200 scfh at 30 psig on a continuous basis subject to local weather conditions. Upon consulting with a representative from Thermax Incorporated, So. Dartmouth, Massachusetts, four different heat exchanging systems were proposed. Their advantages and disadvantages are stated.

Kurita, C.H.; /Fermilab

1988-08-19

271

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

272

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

273

Formamidine Reactions  

E-print Network

.36$, 8.44$ Calculated for C ^ O ^ B r , nitrogen = 3.16$. METHYL IS0XAZ0L0N DERIVATIVES. The amido methylene derivatives of methyl lsoxazolon should be obtainable by the same methods as those of phenyl lsoxazolon. There are however, two practical... hydrochloid is neutralized. If it is neutralized with pyirldene the following reaction takes place. CH3 0 -==-C 'COHHR H«C - 0 * COINHR ' 1 II /I 0 CH v " " 1 - = N-O-O-OH, + H,0 f-R UH- H * flTO 3 HO- JT/Ha I t This gives the aMde of 5-methyl...

Griffin, E. L.

1913-05-15

274

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

275

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.

276

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.

Gehron, Elizabeth

2012-07-20

277

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

278

Idea Exchange: Volunteerism.  

ERIC Educational Resources Information Center

This issue of "Idea Exchange" which focuses on the volunteer in education programs includes a variety of materials related to volunteer experiences and viewpoints: (1) a handbook for volunteer coordinators which discusses the coordinator's role, the recruiting and interviewing of volunteers, and the essentials of volunteer placement and…

Ryan, Jamice, Ed.

1974-01-01

279

Interpersonal Exchange in Isolation.  

National Technical Information Service (NTIS)

The study explored interpersonal exchange in isolated and non-isolated groups. Nine dyads formed at different levels on need achievement, need dominance, need affiliation and dogmatism worked out lived in a small room for ten days, with no outside contact...

I. Altman, W. W. Haythorn

1965-01-01

280

Dublin, Ireland Exchange Program  

E-print Network

Dublin, Ireland Exchange Program Dublin Institute of Technology Dublin, the capital of Ireland, is one of Europe's top urban hotspots. This youthful city pulsates with a compelling mix of history, and a fascinating heritage just waiting to be discovered. The Dublin Institute of Technology (DIT) is a member

Fernandez, Eduardo

281

China's exchange rate policy  

Microsoft Academic Search

Should or will the yuan depreciate? This is an important question widely speculated in world financial markets and intensively debated in China in the wake of the East Asian financial crisis in 1997. The present paper examines in detail the fundamentals that determine the exchange rate in China and concludes with two important findings. One is that the past two

Yingfeng Xu

2000-01-01

282

KNOWLEDGE EXCHANGE SEMINAR SERIES  

E-print Network

1 KNOWLEDGE EXCHANGE SEMINAR SERIES Institutional stigma and the delivery of methadone maintenance Belfast (k.mcelrath@qub.ac.uk) 1. The early vision of methadone maintenance Although methadone was first increased. Their review of the medical literature suggested that methadone was suitable for stabilising

Paxton, Anthony T.

283

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.

Exchange, The C.

284

Heat exchanger support system  

Microsoft Academic Search

A mounting system to interconnect a gas turbine heat exchanger with a gas turbine includes three interconnecting gas manifolds: one to receive cool compressed air from the engine, one to receive hot exhaust gas from the engine, and one to communicate heated intake air to the engine. The manifolds, acting in cooperation with a jointed support arm, allow the heat

Young

1978-01-01

285

Chicago Mercantile Exchange  

NSDL National Science Digital Library

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

1994-01-01

286

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

287

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

288

Nonstandard Exchange Economies.  

National Technical Information Service (NTIS)

Edgeworth's conjecture that as the number of traders in an exchange economy increases the core approaches that set of competitive equilibria has been formalized both as a theorem about a sequence of finite economies, and as a theorem about an economy havi...

D. J. Brown, A. Robinson

1971-01-01

289

KNOWLEDGE EXCHANGE SEMINAR SERIES  

E-print Network

1 KNOWLEDGE EXCHANGE SEMINAR SERIES Improving court work skills in child care proceedings. Dr in child welfare and criminal justice proceedings. The programme aims to develop student skills in advocacy, giving evidence and dealing with cross-examination in cases involving child protection and welfare issues

Paxton, Anthony T.

290

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

291

Effects of viscosity variation on an exothermic reaction in a flow system  

Microsoft Academic Search

The glass unit was used for visual observation of the hydrodynamic features; the internal diameter was 0.4 cm, while the outside diameter was 0.8 cm and the length was 160 cm. The reaction tube lay along the axis of the heat exchanger; the annular air gap between the surface of the reaction tube and the heat exchanger was of width

A. A. Butakov; A. M. Zanin

1978-01-01

292

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

293

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

294

Reactions of alkenes on lanthana  

SciTech Connect

Reactions of ethene, propene, butenes, 2-methylpropene, cyclopentene, 2,3-dimethylbut-1-ene, and 3,3-dimethylbut-1-ene have been studied with hydrogen, and sometimes deuterium, on lanthana catalysts. Many alkene/lanthana systems show evidence of self-poisoning which is more marked with straight-chain hydrocarbons than with branched hydrocarbons and at higher temperatures; the catalysts are also highly sensitive to impurities. The temperature required to attain a fixed rate of hydrogenation (10/sup 16/ molecules s/sup -1/ m/sup -2/) varied from 220 K for ethene to over 373 K for the 2,3-dimethylbutenes. Fast hydrogenation without accompanying deuterium exchange was observed with alkenes which cannot form allylic species. The ability to form such species led to rapid isomerization of the butenes below 273 K and of 2-3-dimethylbut-1-ene at 373 K, and to exchange rates with deuterium which were comparable to (propene) or faster than (2-methylpropene) addition reactions at 380 K. Deuterium NMR spectroscopy was used for analysis of the products from the reactions with deuterium. Although the hydrogenation of 3,3-dimethylbut-1-ene occurred readily at 245 K, no isomerization was detected even at 510 K.

Bird, R.; Kemball, C.; Leach, H.F.

1987-05-01

295

Lysine uptake and exchange in Corynebacterium glutamicum.  

PubMed Central

Resting cells of Corynebacterium glutamicum (ATCC 13032) accumulate [14C]lysine by a transport system with a relatively high affinity (10 microMs) and a low maximum velocity (0.15 nmol/min per mg [dry weight]). Uptake of lysine was not inhibited by uncouplers or by ionophores affecting the ion gradients and the energetic state of the cell. Analysis of intracellular amino acid concentrations during the transport reaction as well as kinetic studies revealed that the observed uptake of lysine in fact represents a homologous antiport between extracellular [14C]lysine and intracellular unlabeled lysine. Intracellular [14C]lysine could only be released by the addition of unlabeled lysine to the bacterial suspension. In contrast to this homologous antiport reaction, we observed net uptake of lysine in lysine-depleted cells of a lysine auxotrophic strain. This net uptake was found to be electrogenic and could also be observed as a heterologous antiport reaction in wild-type cells under particular conditions. In this case exchange was mediated between internal lysine and external alanine, isoleucine, or valine. This antiport was electrogenic, since the substrates differ in charge. The cells can switch between electroneutral homologous exchange and electrogenic heterologous antiport mode during fermentation because of changing metabolic conditions. PMID:2123868

Bröer, S; Krämer, R

1990-01-01

296

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

297

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

298

Reaction energetics on long-range corrected density functional theory: Diels-Alder reactions.  

PubMed

The possibility of quantitative reaction analysis on the orbital energies of long-range corrected density functional theory (LC-DFT) is presented. First, we calculated the Diels-Alder reaction enthalpies that have been poorly given by conventional functionals including B3LYP functional. As a result, it is found that the long-range correction drastically improves the reaction enthalpies. The barrier height energies were also computed for these reactions. Consequently, we found that dispersion correlation correction is also crucial to give accurate barrier height energies. It is, therefore, concluded that both long-range exchange interactions and dispersion correlations are essentially required in conventional functionals to investigate Diels-Alder reactions quantitatively. After confirming that LC-DFT accurately reproduces the orbital energies of the reactant and product molecules of the Diels-Alder reactions, the global hardness responses, the halves of highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energy gaps, along the intrinsic reaction coordinates of two Diels-Alder reactions were computed. We noticed that LC-DFT results satisfy the maximum hardness rule for overall reaction paths while conventional functionals violate this rule on the reaction pathways. Furthermore, our results also show that the HOMO-LUMO gap variations are close to the reaction enthalpies for these Diels-Alder reactions. Based on these results, we foresee quantitative reaction analysis on the orbital energies. PMID:23037888

Singh, Raman K; Tsuneda, Takao

2013-02-15

299

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

300

Home bias, exchange rate disconnect, and optimal exchange rate policy  

Microsoft Academic Search

This paper examines how much the central bank should adjust the interest rate in response to real exchange rate fluctuations. The paper first demonstrates, in a two-country Dynamic Stochastic General Equilibrium (DSGE) model, that home bias in consumption is important to replicate the exchange rate volatility and exchange rate disconnect documented in the data. When home bias is high, the

Jian Wang

2010-01-01

301

Equilibrium exchange rate theories under flexible exchange rate regimes  

Microsoft Academic Search

Economic theory refers to several notions of the exchange rate equilibrium value in a flexible exchange rate regime. It has been defined as that consistent with : a) the equilibrium of trade balance; b)the equilibrium of current account; c) the overall equilibrium of the balance of payments; d) the absence of speculative attacks on foreign exchange markets; e) the absence

Rosaria Rita Canale

2002-01-01

302

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

303

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

E-print Network

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

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

2007-01-01

304

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

305

PREPARATION AND UTILIZATION OF CARBOXYL-CONTAINING CATION EXCHANGE CELLULOSE  

Microsoft Academic Search

A cation-exchange resin was synthesized by esterification of cellulose fibers, with ?-hydroxy polycarboxylic acids (citric acid (CA), malic acid, or tartaric acid) in presence of sodium hypophosphite (SHP) as an esterification catalyst, followed by curing at high temperature. Factors affecting the reaction such as CA concentration, CA\\/SHP molar ratio, curing conditions (temperature and time), type of polycarboxylic acid, and type

M. H. Abo-Shosha; N. A. Ibrahim; E. I. Elnagdy; M. A. Gaffar

2002-01-01

306

Carbon monoxide poisoning of proton-exchange membrane fuel cells  

Microsoft Academic Search

The platinum-alloy catalyst used in proton-exchange membrane (PEM) fuel cell anodes is highly susceptible to carbon monoxide (CO) poisoning. CO reduces the catalyst activity by blocking active catalyst sites normally available for hydrogen chemisorption and dissociation. The reaction kinetics at the anode catalyst surface can be used to estimate the decrease in cell voltage due to various levels of CO

Aida Rodrigues; John C. Amphlett; Ronald F. Mann; Brant A. Peppley; Pierre R. Roberge

1997-01-01

307

The market reaction to international cross-listings  

Microsoft Academic Search

This paper examines the stock price impact of international dual listings. The sample consists of 181 firms from 35 countries that instituted their first Depositary Receipt program over the period 1985–1995. The market reaction to a Depositary Receipt program is larger in magnitude and more pervasive than previously reported. The stock price reaction is related to choice of exchange, geographical

Darius P. Miller

1999-01-01

308

Electrochemical and spectroscopic studies of fuel cell reactions  

Microsoft Academic Search

Fuel cells, especially proton exchange membrane fuel cells (PEMFCs) are expected soon to become a major source of clean energy. However, the sluggish kinetics of the fuel cell reactions, i.e., the fuel oxidation and oxygen reduction, hinders the wide-spread application of PEMFCs. These problems prompted our studies to focus on elucidating the nature of the reaction intermediates during the oxidation

Minhua Shao

2006-01-01

309

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.

2012-07-10

310

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

SciTech Connect

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

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

1999-09-01

311

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.

Boston, Wghb

2013-01-01

312

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

313

Asset Exchange Model Package  

NSDL National Science Digital Library

The EjsS Asset Exchange Model Package contains JavaScript models to investigate the the transfer of wealth in a simple economic model consisting of N buyers and sellers, known as agents, who spend their time buying and selling goods at a yard sale. In this economic model, two agents A and B are chosen at random and goods are exchanged. If the price of the item is correct, neither agent gains or looses wealth but this is uninteresting and unrealistic. In a realistic transaction an agent can either pay too much or get a bargain so that one agent becomes slightly richer while the other agent becomes poorer. What happens to the wealth of agent wA if this process is repeated many times and if we assume that the agent receiving the bargain is chosen at random so that sometimes agent A gains and sometimes agent A looses in the transaction. In other words, neither agent is always shrewd or always gullible so that all agents have an equal chance of getting rich. Does this model produce an equitable distribution of wealth? The EjsS Asset Exchange Model Package was developed using the Easy Java/JavaScript Simulations (EjsS) version 5 authoring tool. Although EjsS is a Java program, it can create stand alone JavaScript programs that run in almost any PC or tablet.

Christian, Wolfgang; Tobochnik, Jan; Gould, Harvey

2014-08-28

314

Kinetic theory of oxygen isotopic exchange between minerals and water  

USGS Publications Warehouse

Kinetic and mass conservation equations are used to describe oxygen isotopic exchange between minerals and water in "closed" and open hydrothermal systems. In cases where n coexisting mineral phases having different reaction rates are present, the exchange process is described by a system of n + 1 simultaneous differential equations consisting of n pseudo first-order rate equations and a conservation of mass equation. The simultaneous solutions to these equations generate curved exchange trajectories on ??-?? plots. Families of such trajectories generated under conditions allowing for different fluid mole fractions, different fluid isotopic compositions, or different fluid flow rates are connected by positive-sloped isochronous lines. These isochrons reproduce the effects observed in hydrothermally exchanged mineral pairs including 1) steep positive slopes, 2) common reversals in the measured fractionation factors (??), and 3) measured fractionations that are highly variable over short distances where no thermal gradient can be geologically demonstrated. ?? 1987.

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

1987-01-01

315

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

316

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

317

Diverse secondary interactions between ions exchanged into the resin phase and their analytical applications.  

PubMed

The research activities by the author's group to elucidate the chemical states of ions within the ion exchange resin phase are summarized. The resin with the higher exchange capacity has the smaller space available for ion exchange, and the higher cross linking degree interferes more with swelling of the resin. As a result, diverse secondary interactions between exchanged ions are observed on the resins of high exchange capacities and high cross linking degrees: the van der Waals contact results in incomplete exchange or enhanced dehydration of ions, hydrogen bond formation between acidic anions, and coadsorption of anions with metal ions. Contribution of the simple ion exchange mechanism to the reactions of iminodiactate-type chelating resins with metal ions in the acidic media is quantitatively discussed. The resulting complexes were successfully applied to preconcentration and separation of anions. PMID:24420244

Yuchi, Akio

2014-01-01

318

A novel (3,4,8)-connected 3D topology framework based on [Gd 2(bpdc) 3(H 2O) 3] second building units  

Microsoft Academic Search

A new 3D coordination polymer {[Gd2(bpdc)3(H2O)3H2O}n(1) has been isolated from the reaction of 2,2?-bipyridine-4,4?-dicarboxylic acid (H2bpdc) and Gd(III) salts under hydrothermal conditions. Single-crystal X-ray diffraction study shows that compound 1 is constructed from Gd2-based second building units (SBUs) [Gd2(bpdc)3(H2O)3] and displays a 3D (3,4,8)-connected net with (42·6)(32·42·52)(32·45·54·611·76) topology. A thermogravimetric analysis of 1 shows a high thermal stability. The magnetic

Rui-ping Liu; Jun Li; Gui-ping Yao; Yun Luo; Dario Braga; Feng-Xing Zhang

2011-01-01

319

A New Rare-Earth Metal Coordination Polymer Constructed from N -hetero Aromatic Multicarboxylate Ligand  

Microsoft Academic Search

\\u000a Abstract  The hydrothermal reaction of Gd(NO3)3·6H2O with 2,2?-bipyridyl-4,4?-dicarboxylic acid(H2BPDC) ligand results in the formation of a new Gd(III) polymer: {[Gd2(BPDC)3(H2O)3H2O}\\u000a n..(1). The central gadolinium ion is coordinated by eight oxygen atoms to give a dicapped triangular prism geometry. Based on\\u000a the versatile coordination modes of BPDC2? ligand, together with hydrogen bonds and ?···? stacking interactions, a 3-D network is presented. DFT

Hai-Jun DongMin; Min Wang; Shu-Wei Huang; Yan-Ling Wu; Hao-Hong Li; Zhi-Rong Chen

2010-01-01

320

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

321

The Gift Exchange Problem  

E-print Network

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

Applegate, David

2009-01-01

322

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.

323

Strat-trop exchange  

NASA Astrophysics Data System (ADS)

Exchange between the stratosphere and troposphere is important to the chemical composition of both regions. The export of ozone from the stratosphere provides the troposphere with a means of initiating photochemistry. The precursor molecules originating from the planetary surface provide the stratosphere with its chemical feedstock from which the ozone-controlling HO(x), NO(x), and Cl(x) photochemistries are driven. The tropopause is defined both statistically and in a local, synoptic sense by the value P(sub theta) = .000016 K sq m/kg/s, taken from an objective analysis of 8 years of zonal, temporal mean cross sections of potential temperature, wind and potential vorticity.

Tuck, A. F.; Browell, E. V.; Danielsen, E. F.; Holton, J. R.; Kley, D.; Krueger, A. J.; Megie, G.; Newell, R. E.; Vaughan, G.; Hoskins, B. J.

324

6.RP Currency Exchange  

NSDL National Science Digital Library

This is a task from the Illustrative Mathematics website that is one part of a complete illustration of the standard to which it is aligned. Each task has at least one solution and some commentary that addresses important asects of the task and its potential use. Here are the first few lines of the commentary for this task: Joe was planning a business trip to Canada, so he went to the bank to exchange \\$200 U.S. dollars for Canadian (CDN) dollars (at a rate of \\$1.02 CDN p...

325

Strat-trop exchange  

NASA Technical Reports Server (NTRS)

Exchange between the stratosphere and troposphere is important to the chemical composition of both regions. The export of ozone from the stratosphere provides the troposphere with a means of initiating photochemistry. The precursor molecules originating from the planetary surface provide the stratosphere with its chemical feedstock from which the ozone-controlling HO(x), NO(x), and Cl(x) photochemistries are driven. The tropopause is defined both statistically and in a local, synoptic sense by the value P(sub theta) = .000016 K sq m/kg/s, taken from an objective analysis of 8 years of zonal, temporal mean cross sections of potential temperature, wind and potential vorticity.

Tuck, A. F.; Browell, E. V.; Danielsen, E. F.; Holton, J. R.; Kley, D.; Krueger, A. J.; Megie, G.; Newell, R. E.; Vaughan, G.; Hoskins, B. J.

1985-01-01

326

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

327

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

328

Quantum Theory of Fast Chemical Reactions  

SciTech Connect

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

John C. Light

2007-07-30

329

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

330

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

331

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

332

Biodiesel production using anionic ion-exchange resin as heterogeneous catalyst.  

PubMed

The transesterification reactions of triolein with ethanol using various ion-exchange resin catalysts were conducted to produce ethyl oleate as a biodiesel. The anion-exchange resins exhibited much higher catalytic activities than the cation-exchange resin. The anion-exchange resin with a lower cross-linking density and a smaller particle size gave a high reaction rate as well as a high conversion. By combining the three-step regeneration method, the resin could be repeatedly used for the batch transesterification without any loss in the catalytic activity. A continuous transesterification reaction was carried out using an expanded bed reactor packed with the most active resin. The reactor system permitted the continuous production of ethyl oleate with a high conversion. PMID:16455240

Shibasaki-Kitakawa, Naomi; Honda, Hiroki; Kuribayashi, Homare; Toda, Takuji; Fukumura, Takuya; Yonemoto, Toshikuni

2007-01-01

333

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

E-print Network

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

Sparks, Donald L.

334

Atomistic Evidence of How Force Dynamically Regulates Thiol/Disulfide Exchange  

E-print Network

, while an associate SN2 mechanism prevails, force causes a move of the transition state to a longer on the thiol/disulfide exchange reaction. We here aimed at elucidating the underlying dynamic effects of force on the reaction center for the case of disulfide bond reduction by dithiothreitol at forces of 200-2000 p

Gräter, Frauke

335

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.

336

High performance of a carbon supported ternary PdIrNi catalyst for ethanol electro-oxidation in anion-exchange membrane direct ethanol fuel cells  

E-print Network

-oxidation in anion-exchange membrane direct ethanol fuel cells Shuiyun Shen, T. S. Zhao,* Jianbo Xu and Yinshi Li-exchange membrane direct ethanol fuel cells (AEM DEFCs). We demonstrate that the use of the ternary PdIrNi catalyst for the ethanol oxidation reaction (EOR) in anion-exchange membrane direct ethanol fuel cells (AEM DEFCs) offers

Zhao, Tianshou

337

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

338

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

339

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

340

Catalytic gasification: Isotopic labeling and transient reaction  

SciTech Connect

Temperature-programmed reaction was used with labeled isotopes (/sup 13/C and /sup 18/O) to study interactions between carbon black and potassium carbonate in pure He and 10% CO/sub 2//90% He atmospheres. Catalytic gasification precursor complexes were observed. Carbon and oxygen-bearing carbon surface groups interacted with the carbonate above 500 K to form surface complexes. Between 500 K and 950 K, and in the presence of gaseous carbon dioxide, the complexes promoted carbon and oxygen exchange between the gas-phase CO/sub 2/ and the surface. Oxygen exchanged between the surface complexes; but carbon did not exchange between the carbonate and the carbon black. As the temperature rose, the complexes decomposed to produce carbon dioxide, and catalytic gasification then began. Elemental potassium formed, and the active catalyst appears to alternate between potassium metal and a potassium-oxygen-carbon complex.

Saber, J.M.; Falconer, J.L.; Brown, L.F.

1985-01-01

341

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

342

Biological Ion Exchanger Resins  

PubMed Central

Biological selectivity is shown to vary with medium osmotic strength and temperature. Selectivity reversals occur at 4°C and at an external osmolality of 0.800 indicating that intracellular hydration and endosolvent (intracellular water) structure are important determinants in selectivity. Magnetic resonance measurements of line width by steady-state nuclear magnetic resonance (NMR) indicate a difference in the intracellular water signal of 16 Hz between the K form and Na form of Escherichia coli, providing additional evidence that changes in the ionic composition of cells are accompanied by changes in endosolvent structure. The changes were found to be consistent with the thermodynamic and magnetic resonance properties of aqueous electrolyte solutions. Calculation of the dependence of ion-pairing forces on medium dielectric reinforces the role of endosolvent structure in determining ion exchange selectivity. PMID:4943653

Damadian, Raymond; Goldsmith, Michael; Zaner, K. S.

1971-01-01

343

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

344

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

345

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!

346

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

347

Viscous exchange flows  

NASA Astrophysics Data System (ADS)

Gravitationally driven exchange flows of viscous fluids with different densities are analysed theoretically and investigated experimentally within a horizontal channel. Following initiation from rest when there is a vertical boundary dividing the two fluids, the denser fluid slumps under the less dense along the underlying boundary, while the less dense fluid intrudes along the upper boundary. The motion is driven by the pressure gradients associated with the density differences between the two fluids, resisted by viscous stresses, and mathematically modelled by a similarity solution that depends on the ratio of the viscosities of the two fluids. When the viscosity of the less dense fluid is much smaller than the viscosity of the denser fluid, the shape of the interface between the fluids varies rapidly close to the upper boundary and depends weakly on the viscosity ratio within the interior of the flow. Matched asymptotic expansions are employed in this regime to determine the shape of the interface and the rates of its propagation along the boundaries. The similarity solutions are shown to be linearly stable and thus are expected to represent the intermediate asymptotics of the flow. Experiments confirm the similarity form of solutions and demonstrate close agreement with the theoretical predictions when the viscosities of the fluids are comparable, but exhibit some discrepancies when the viscosities differ more substantially. It is suggested that these discrepancies may be due to mixing between the fluids close to the boundaries, which is induced by the no-slip boundary condition. Exchange flows within porous domains are also investigated to determine the shape of the interface as a function of the ratio of the viscosities of the two fluids and using asymptotic analysis, this shape is determined when this ratio is much larger, or smaller, than unity.

Matson, Gary P.; Hogg, Andrew J.

2012-02-01

348

Health Science on Exchange InternationalExchangeProgram  

E-print Network

Perspective; Solving Health Disasters in an International Approach · Mental Health Sciences Track - Research and is worth 60 ECTS Oregon State University, College of Health and Human Sciences, USA (http://healthHealth Science on Exchange InternationalExchangeProgram Students enrolled in Health Sciences

Viglas, Anastasios

349

Neutrino Capture Reactions on $^{40}$Ar  

E-print Network

Gamow-Teller (GT) strength in $^{40}$Ar is studied by shell-model calculations with monopole-based universal intearction, which has tensor components of $\\pi$\\rho$-meson exchanges. Calculated GT strength is found to be consistent with the experimental data obtained by recent ($p, n$) reactions. Neutrino capture cross sections on $^{40}$Ar for solar neutrinos from $^{8}$B are found to be enhanced compared with previous calculations. The reaction cross sections for multipoles other than $0^{+}$ and $1^{+}$ are obtained by random-phase approximation (RPA). Their contributions become important for neutrino energies larger than 50 MeV.

Toshio Suzuki; Michio Honma

2012-11-17

350

Do ?-conjugative effects facilitate SN2 reactions?  

PubMed

Rigorous quantum chemical investigations of the SN2 identity exchange reactions of methyl, ethyl, propyl, allyl, benzyl, propargyl, and acetonitrile halides (X = F(-), Cl(-)) refute the traditional view that the acceleration of SN2 reactions for substrates with a multiple bond at C? (carbon adjacent to the reacting C? center) is primarily due to ?-conjugation in the SN2 transition state (TS). Instead, substrate-nucleophile electrostatic interactions dictate SN2 reaction rate trends. Regardless of the presence or absence of a C? multiple bond in the SN2 reactant in a series of analogues, attractive C?(?(+))···X(?(-)) interactions in the SN2 TS lower net activation barriers (E(b)) and enhance reaction rates, whereas repulsive C?(?(-))···X(?(-)) interactions increase E(b) barriers and retard SN2 rates. Block-localized wave function (BLW) computations confirm that ?-conjugation lowers the net activation barriers of SN2 allyl (1t, coplanar), benzyl, propargyl, and acetonitrile halide identity exchange reactions, but does so to nearly the same extent. Therefore, such orbital interactions cannot account for the large range of E(b) values in these systems. PMID:24450965

Wu, Chia-Hua; Galabov, Boris; Wu, Judy I-Chia; Ilieva, Sonia; Schleyer, Paul von R; Allen, Wesley D

2014-02-26

351

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

352

Catalysis of oxygen-18 exchange between inorganic phosphate and water by the gastric H,K-ATPase.  

PubMed

The gastric H,K-ATPase is shown to catalyze 18O exchange between Pi and HOH. Mg2+ is the only ion required for the reaction. K+ increases the rate of isotope exchange, which is directly proportional to specific ATPase activity. Ouabain, which potently inhibits the Na,K-ATPase, has no effect on the exchange reaction. Conversely, omeprazole, which is specific for the H,K-ATPase, completely inhibits 18O exchange. Vanadate inhibition of exchange can be explained by competitive binding with Pi. The rate of 18O exchange is faster than the hydrolytic rate and about equal to the dephosphorylation rate. Thus, the ionic requirements for exchange, inhibition of exchange, and the rate of exchange are all compatible with catalysis occurring via the same phosphoenzyme intermediate formed during hydrolysis of ATP. The distribution of 18O-labeled Pi species formed with time indicates that Pi loss is only about twice as fast as covalent bond formation. This kinetic pattern is unaffected by K+, temperature, or the specific activity of the enzyme preparation. Invariance of the kinetic pattern could mean isotope exchange is always catalyzed by the same form of the enzyme, and K+ and higher temperature accelerate the reaction by increasing the relative amount of the active conformer. Independence of the kinetic pattern from specific activity implies that the catalytic mechanism of active enzyme molecules is unaffected by inactive proteins in gastric microsomal membranes. PMID:6099142

Faller, L D; Elgavish, G A

1984-12-18

353

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

354

On the Exchange Magnetic Moments  

Microsoft Academic Search

The exchange magnetic moment operators for the two nucleon system are obtained in terms of photopion production matrix elements. This photopion production part is closely related with the pion-nucleon scattering part, thus enabling us to use pi -N scattering experimental values in the expressions of the exchange magnetic moment operators. These formulae are applied to cases of triton magnetic moment

Eiichi Kuroboshi; Yasuo Hara

1958-01-01

355

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

356

How to exchange (secret) keys  

Microsoft Academic Search

A protocol is presented whereby two adversaries may exchange secrets, although neither trusts the other. The secrets are the prime factors of their publicly announced composite numbers. The two adversaries can exchange their secrets bit by bit, but each fears the other will cheat by sending \\

Manuel Blum

1983-01-01

357

Inside this issue: Ogmius Exchange  

E-print Network

Inside this issue: Ogmius Exchange Science, Genetically Modified Foods, and the Rumsfeld Doctrine.colorado.edu/ogmius. Ogmius Exchange Science, Genetically Modified Foods, and the Rumsfeld Doctrine A s they have for the last ten years, next spring U.S. farmers will plant more genetically- modified (GM) corn, cotton

Colorado at Boulder, University of

358

Asset Prices and Exchange Rates  

Microsoft Academic Search

This paper develops a simple two-country, two-good model, in which the real exchange rate, stock and bond prices are jointly determined. The model predicts that stock market prices are correlated internationally even though their dividend processes are independent, providing a theoretical argument in favor of financial contagion. The foreign exchange market serves as a propagation channel from one stock market

Anna Pavlova; Roberto Rigobon

2003-01-01

359

Asset Prices and Exchange Rates  

Microsoft Academic Search

This paper develops a simple two-country, two-good model, in which the real exchange rate, stock and bond prices are jointly determined. The model predicts that stock market prices are correlated internationally even though their dividend processes are independent, providing a theoretical argument in favor of financial markets contagion. The foreign exchange market serves as a propagation channel from one stock

Roberto Rigobon; Anna Pavlova

2004-01-01

360

Asset Prices and Exchange Rates  

Microsoft Academic Search

This paper develops a simple two-country, two-good model, in which the real exchange rate, stock and bond prices are jointly determined. The model predicts that stock market prices are correlated internationally even though their dividend processes are independent, providing a theoretical argument in favor of financial contagion. The foreign exchange market serves as a propagation channel from one stock market

Anna Pavlova; Roberto Rigobon

2004-01-01

361

Compact heat exchanger design progress  

Microsoft Academic Search

Development of compact plate type heat exchangers for OTEC plants is reviewed. The heat exchangers have horizontal, single pass water flow, vertical downflow condenser, and vertical upflow boiler passages. The design lends itself to many variations in type of water side configuration, and in boiling and condensing surface design. It makes high heat transfer coefficients possible, along with low pressure

J. H. Anderson Jr.; P. B. Pribis

1979-01-01

362

Two-stage heat exchanger  

Microsoft Academic Search

Improved furnaces are described in which secondary and tertiary heat exchanges are incorporated into new and existing hot-air furnace systems for controlled cooling of hot combustion products by co-current and countercurrent heat exchanges. Hot combustion products are cooled to a temperature at which latent heat of water vapor contained in combustion gases are substantially recovered. In one embodiment of our

J. C. Overall; O. O. Schaus

1981-01-01

363

Knowledge exchange, matching, and agglomeration  

Microsoft Academic Search

Despite wide recognition of their significant role in explaining sustained growth and economic development, uncompensated knowledge spillovers have not yet been fully modeled with a microeconomic foundation. This paper illustrates the exchange of knowledge as well as its consequences for agglomerative activity in a general-equilibrium search-theoretic framework. Agents, possessing differentiated types of knowledge, search for partners to exchange ideas in

Marcus Berliant; Robert R. Reed III; Ping Wang

2006-01-01

364

Knowledge Exchange, Matching, and Agglomeration  

Microsoft Academic Search

Despite wide recognition of their significant role in explaining sustained growth and economic development, uncompensated knowledge spillovers have not yet been fully modeled with a microeconomic foundation. This paper illustrates the exchange of knowledge as well as its consequences for agglomerative activity in a general-equilibrium search-theoretic framework. Agents, possessing differentiated types of knowledge, search for partners to exchange ideas in

Marcus Berliant; Robert R. Reed III; Ping Wang

2005-01-01

365

Knowledge Exchange, Matching, and Agglomeration  

Microsoft Academic Search

Despite wide recognition of their significant role in explaining sustained growth and economic development, uncompensated knowledge spillovers have not yet been fully modeled with a microeconomic foundation. This paper illustrates the exchange of knowledge as well as its consequences for agglomerative activity in a general-equilibrium search-theoretic framework. Agents, possessing differentiated types of knowledge, search for partners to exchange ideas in

Marcus Berliant; Robert R. Reed III; Ping Wang

2004-01-01

366

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

367

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

368

Enzymatic fragmentation of cation exchange membrane bound immunoglobulin G.  

PubMed

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

Yu, Deqiang; Ghosh, Raja

2011-01-01

369

Plasma exchange in Canada. The Canadian Apheresis Study Group.  

PubMed Central

Since 1982 the Canadian Apheresis Study Group (CASG) has collected data on plasma exchange activities in Canada. In 1987, 5907 such procedures were carried out on 700 patients for more than 22 different diseases; this represented an increase of 28% over the figure for 1982. A shift in activity has occurred over the years; originally hematologic disorders accounted for most of the procedures; however, in 1987, 60% of the exchanges were done to treat neurologic disorders, mainly myasthenia gravis and acute and chronic Guillain-Barré syndrome. Several prospective randomized clinical trials have recently been completed by the CASG in the hope of determining the optimal application of plasma exchange. These studies, currently under review, include 168 patients with multiple sclerosis, 100 with thrombotic thrombocytopenic purpura and 43 with rapidly progressive glomerulonephritis. Reactions occur in 12% of cases; they are usually minor and are limited to circumoral paresthesia, mild hypertension or hypotension and hives. PMID:2178759

Rock, G A; Tricklebank, G W; Kasaboski, C A

1990-01-01

370

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

371

Preequilibrium reactions with complex particle channels  

SciTech Connect

Investigations of nucleon induced reactions at incident energies of 14-90 MeV resulting in the emission of complex particles (A=2-4) have provided insights which complement those previously obtained from (N,xN) reactions. The description of the preequilibrium energy spectra required modifications to an earlier phenomenological model for direct pickup reactions. This model supplements the usual exciton preequilibrium model. Work on complex particle induced reactions confirms some of these results, extends them to include stripping and exchange reactions, and provides evidence for a projectile dependence of the average effective matrix elements for the residual interactions in the exciton model. A full description of reactions with complex projectiles will require the inclusion of a realistic breakup component and the resulting reduction of the cross section available for the exciton model calculations. Reactions with complex particles in the entrance and/or exit channels have provided indirect evidence for the amount of surface peaking of the initial target-projectile interaction. A summary of additional data needed to help resolve remaining questions is presented.

Kalbach, C. [Physics Department, Duke University, Durham, North Carolina 27708-0305 (United States)

2005-03-01

372

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

373

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

374

Multiple Gluon Exchange Webs  

E-print Network

Webs are weighted sets of Feynman diagrams which build up the logarithms of correlators of Wilson lines, and provide the ingredients for the computation of the soft anomalous dimension. We present a general analysis of multiple gluon exchange webs (MGEWs) in correlators of semi-infinite non-lightlike Wilson lines, as functions of the exponentials of the Minkowski cusp angles, $\\alpha_{ij}$, formed between lines $i$ and $j$. We compute a range of webs in this class, connecting up to five Wilson lines through four loops, we give an all-loop result for a special class of diagrams, and we discover a new kind of relation between webs connecting different numbers of Wilson lines, based on taking collinear limits. Our results support recent conjectures, stating that the contribution of any MGEW to the soft anomalous dimension is a sum of products of polylogarithms, each depending on a single cusp angle, and such that their symbol alphabet is restricted to $\\alpha_{i j}$ and $1 - \\alpha_{i j}^2$. Finally, we construc...

Falcioni, Giulio; Harley, Mark; Magnea, Lorenzo; White, Chris D

2014-01-01

375

Multiple Gluon Exchange Webs  

E-print Network

Webs are weighted sets of Feynman diagrams which build up the logarithms of correlators of Wilson lines, and provide the ingredients for the computation of the soft anomalous dimension. We present a general analysis of multiple gluon exchange webs (MGEWs) in correlators of semi-infinite non-lightlike Wilson lines, as functions of the exponentials of the Minkowski cusp angles, $\\alpha_{ij}$, formed between lines $i$ and $j$. We compute a range of webs in this class, connecting up to five Wilson lines through four loops, we give an all-loop result for a special class of diagrams, and we discover a new kind of relation between webs connecting different numbers of Wilson lines, based on taking collinear limits. Our results support recent conjectures, stating that the contribution of any MGEW to the soft anomalous dimension is a sum of products of polylogarithms, each depending on a single cusp angle, and such that their symbol alphabet is restricted to $\\alpha_{i j}$ and $1 - \\alpha_{i j}^2$. Finally, we construct a simple basis of functions, defined through a one-dimensional integral representation in terms of powers of logarithms, which has all the expected analytic properties. This basis allows us to compactly express the results of all MGEWs computed so far, and we conjecture that it is sufficient for expressing all MGEWs at any loop order.

Giulio Falcioni; Einan Gardi; Mark Harley; Lorenzo Magnea; Chris D. White

2014-07-13

376

Multiple gluon exchange webs  

NASA Astrophysics Data System (ADS)

Webs are weighted sets of Feynman diagrams which build up the logarithms of correlators of Wilson lines, and provide the ingredients for the computation of the soft anomalous dimension. We present a general analysis of multiple gluon exchange webs (MGEWs) in correlators of semi-infinite non-lightlike Wilson lines, as functions of the exponentials of the Minkowski cusp angles, $\\alpha_{ij}$, formed between lines $i$ and $j$. We compute a range of webs in this class, connecting up to five Wilson lines through four loops, we give an all-loop result for a special class of diagrams, and we discover a new kind of relation between webs connecting different numbers of Wilson lines, based on taking collinear limits. Our results support recent conjectures, stating that the contribution of any MGEW to the soft anomalous dimension is a sum of products of polylogarithms, each depending on a single cusp angle, and such that their symbol alphabet is restricted to $\\alpha_{i j}$ and $1 - \\alpha_{i j}^2$. Finally, we construct a simple basis of functions, defined through a one-dimensional integral representation in terms of powers of logarithms, which has all the expected analytic properties. This basis allows us to compactly express the results of all MGEWs computed so far, and we conjecture that it is sufficient for expressing all MGEWs at any loop order.

Falcioni, Giulio; Gardi, Einan; Harley, Mark; Magnea, Lorenzo; White, Chris D.

2014-10-01

377

IC ................................... ... Reaction Product Imaging  

E-print Network

offers two modes of operation. One mode involves imaging of the atomic fragment or reaction productIC ................................... ... Reaction Product Imaging: The H + D2 Reaction Theofanis reaction product imaging. In this experiment, a photolytically produced beam of hydrogen (H) atoms crossed

Zare, Richard N.

378

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.

379

Reaction electronic flux: a new concept to get insights into reaction mechanisms. Study of model symmetric nucleophilic substitutions.  

PubMed

The present work is focused on studying chlorine and fluorine identity SN2 substitutions on a methyl center, within the framework of the newly introduced reaction electronic flux J(xi), that allows one to identify charge transfer and polarization mechanisms that take place along the reaction coordinate. The main results concern the discovery of different charge transfer mechanism, despite both reactions have the same energetic pattern with simultaneous bond breaking and formation. It turns out that the chlorine substitution is mainly driven by polarization effects and characterized by through bond interactions while intermolecular charge transfer dominates the fluorine exchange reaction, that is characterized by through space interactions. PMID:18942822

Echegaray, Eleonora; Toro-Labbé, Alejandro

2008-11-20

380

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

Federal Register 2010, 2011, 2012, 2013

...Topaz Exchange, LLC for Registration as a National Securities Exchange; Findings...an Application for Registration as a National Securities Exchange (``Form 1...Application.\\6\\ Topaz Exchange submitted a detailed response to comments on July...

2013-08-01

381

40 CFR 63.104 - Heat exchange system requirements.  

...exchanger or any combination of heat exchangers. (i) For samples taken at...exchanger or any combination of heat exchangers in chemical manufacturing process...individual heat exchanger or group of heat exchangers and the exit is the point...

2014-07-01

382

40 CFR 63.104 - Heat exchange system requirements.  

Code of Federal Regulations, 2013 CFR

...exchanger or any combination of heat exchangers. (i) For samples taken at...exchanger or any combination of heat exchangers in chemical manufacturing process...individual heat exchanger or group of heat exchangers and the exit is the point...

2013-07-01

383

In situ coating on cation exchange resin catalyst, Amberlyst-15, and its impact on the hydration of dicyclopentadiene  

Microsoft Academic Search

New phenomenon of in situ coating by the reactant\\/product on ion exchange resin catalyst, Amberlyst-15, that helps to improve the reaction kinetics of dicyclopentadiene (DCPD) hydration has been reported.

Sandip Talwalkar; Pramod Kumbhar; Sanjay Mahajani

2006-01-01

384

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

E-print Network

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

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

2006-01-27

385

77 FR 62177 - Retail Foreign Exchange Transactions  

Federal Register 2010, 2011, 2012, 2013

...ID OCC-2012-0014] RIN 1557-AD42 Retail Foreign Exchange Transactions AGENCY...Currency (OCC) is proposing to amend its retail foreign exchange rule for transactions...if possible. Please use the title ``Retail Foreign Exchange Transactions'' to...

2012-10-12

386

Post-Quantum Key Exchange Protocols  

E-print Network

If an eavesdropper Eve is equipped with quantum computers, she can easily break the public key exchange protocols used today. In this paper we will discuss the post-quantum Diffie-Hellman key exchange and private key exchange protocols.

Xiangdong Li; Lin Leung; Andis Chi-Tung Kwan; Xiaowen Zhang; Dammika Kahanda; Michael Anshel

2006-03-25

387

Effect of Electron Donors on the Isotopic Exchange between Aluminium (III), Gallium (III) and Indium (III) Iodides and Alkyl Iodides  

Microsoft Academic Search

VERY few investigations have been devoted to the isotopic exchange reactions of halogens in AlX3-RX solutions1, where X is a halogen atom and R is an alkyl radical. No work on analogous systems with gallium and indium halides has hitherto been published. In the work recorded here, the isotopic exchange reactions of iodine between aluminium, gallium and indium triiodides and

A. Polaczek; A. Halpern

1963-01-01

388

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

389

Entanglement Exchange and Bohmian Mechanics  

E-print Network

This paper analyses the phenomenon of entanglement exchange in Bohm's pilot wave interpretation of quantum mechanics. The interesting feature of the phenomenon is that systems become entangled without causal interaction; hence it is a useful situation for investigating the unique nature of interaction in Bohmian mechanics. The first two sections introduce, respectively, entanglement exchange in the standard interpretation of quantum mechanics, and the basic principles of Bohmian mechanics. The next section shows that the Bohmian interpretation makes the same experimental predictions about entanglement exchange as the standard one. The final section draws some conclusions about interactions and entanglement in Bohmian mechanics.

Nick Huggett; Tiziana Vistarini

2009-05-25

390

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

391

MINIMIZING BACK EXCHANGE IN THE HYDROGEN EXCHANGE - MASS SPECTROMETRY EXPERIMENT  

PubMed Central

The addition of mass spectrometry (MS) analysis to the hydrogen exchange (HX) proteolytic fragmentation experiment extends powerful HX methodology to the study of large biologically important proteins. A persistent problem is the degradation of HX information due to back exchange of deuterium label during the fragmentation-separation process needed to prepare samples for MS measurement. This paper reports a systematic analysis of the factors that influence back exchange (solution pH, ionic strength, desolvation temperature, LC column interaction, flow rates, system volume). The many peptides exhibit a range of back exchange due to intrinsic amino acid HX rate differences. Accordingly, large back exchange leads to large variability in D-recovery from one residue to another as well as one peptide to another that cannot be corrected for by reference to any single peptide-level measurement. The usual effort to limit back exchange by limiting LC time provides little gain. Shortening the LC elution gradient by two-fold only reduced back-exchange by ~2 % (from ~30% to 28%), while sacrificing S/N and peptide count. An unexpected dependence of back exchange on ionic strength as well as pH suggests a strategy in which solution conditions are changed during sample preparation. Higher salt should be used in the first stage of sample preparation (proteolysis and trapping) and lower salt (< 20 mM) and pH in the second stage before electrospray injection. Adjustment of these and other factors together with recent advances in peptide fragment detection yields hundreds of peptide fragments with D-label recovery of 90 ± 5%. PMID:22965280

Walters, Benjamin T.; Ricciuti, Alec; Mayne, Leland; Englander, S. Walter

2012-01-01

392

Hear Exchange Assembly  

DOEpatents

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

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

2003-05-27

393

Field of Vision and Simple Reaction Time During Recreation Exercises at Work.  

National Technical Information Service (NTIS)

Measurements were made of the simple reaction time to sound and light stimuli and of the field of vision with respect to different colors in female telephone exchange operators performing and not performing recreation exercises during break periods. After...

T. Mieczkowski, S. Rotenberg

1974-01-01

394

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

E-print Network

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

Sheng, Wenchao

395

[Ca2+/H(+)-exchange in myometrium mitochondria].  

PubMed

Using the fluorescent probe Fluo-4 AM the authors have identified Na(+)-independent Ca2+H(+)-exchange in isolated mitochondria of rat myometrium and studied its individual properties. Formation of directional protons gradient in the matrix of mitochondria causes antyporte release of Ca2+, which has been previously accumulated in energetic processes (in the presence of Mg-ATP and succinate). The functioning of Ca2+/H(+)-exchange depends on the proton gradient and is characterized by reversibility, in case of extramitochondria environment alkalization the additional accumulation of Ca2+ by organelles is recorded. Monovalent cations gradients (Na+, K+, Li+) do not cause the release of Ca2+ from mitochondria. Rate of Ca2+/H(+)-exchange is growing in terms of increasing deltapH on the mitochondria membrane and kinetics of deltapH-induced Ca2+ release from the matrix corresponds to the laws of first order reaction. Research of Ca2+/H(+)-exchange some properties in the myometrium mitochondria showed that the above transport process is of electrogenic nature, perhaps it is done in a 1: 1 stechiometry (Hill coefficient on H+ close to 1) and is able to adjust matrix Ca2+ concentration under physiological conditions (pH activation of about 6.9). Thus, in the inner membrane of the myometrium mitochondria the available system of the secondary active Ca(2+)-transport from the matrix of these organelles to myoplasm and the functioning of Ca2+/H(+)-exchanger may underlie this process. PMID:25033553

Kolomiiets', O V; Danylovych, Iu V; Danylovych, H V; Kosterin, S O

2014-01-01

396

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

397

Basic Exchangeable Cations in Soils.  

National Technical Information Service (NTIS)

Several possible solutions for displacing basic exchangeable cations have been tested on some agricultural soils. The quantities of cations which the solutions could displace varied according to the nature of the displacing ion. This behaviour is comparab...

B. M. Tucker

1971-01-01

398

Asset Prices and Exchange Rates  

E-print Network

This paper develops a simple two-country, two-good model, in which the real exchange rate, stock and bond prices are jointly determined. The model predicts that stock market prices are correlated ...

Pavlova, Anna

2004-11-30

399

Exchange couplings in magnetic films  

NASA Astrophysics Data System (ADS)

Recent advances in the study of exchange couplings in magnetic films are introduced. To provide a comprehensive understanding of exchange coupling, we have designed different bilayers, trilayers and multilayers, such as anisotropic hard-/soft-magnetic multilayer films, ferromagnetic/antiferromagnetic/ferromagnetic trilayers, [Pt/Co]/NiFe/NiO heterostructures, Co/NiO and Co/NiO/Fe trilayers on an anodic aluminum oxide (AAO) template. The exchange-coupling interaction between soft- and hard-magnetic phases, interlayer and interfacial exchange couplings and magnetic and magnetotransport properties in these magnetic films have been investigated in detail by adjusting the magnetic anisotropy of ferromagnetic layers and by changing the thickness of the spacer layer, ferromagnetic layer, and antiferromagnetic layer. Some particular physical phenomena have been observed and explained.

Liu, Wei; Liu, Xiong-Hua; Cui, Wei-Bin; Gong, Wen-Jie; Zhang, Zhi-Dong

2013-02-01

400

Designing Flexible Heat Exchanger Networks  

E-print Network

Procedures and methods used for designing flexible heat exchanger networks are described. The general approach consists of defining the flexibility problem as a set of cases. Pinch Technology is then used to develop an initial network design...

Gautam, R.; Chen, H. S.; Wareck, J. S.

401

Heat pipe array heat exchanger  

DOEpatents

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

Reimann, Robert C. (Lafayette, NY)

1987-08-25

402

Leader–Member Exchange Theory  

Microsoft Academic Search

\\u000a The Leader–Member Exchange (LMX) theory first emerged in the 1970s. It conceptualizes leadership as a process of interaction\\u000a between leader and follower and centers on the dyadic exchange relationships between both. The leader–follower relationships\\u000a within work groups are split up into a set of working relationships between a leader and the various members of the work team\\u000a (Van Breukelen et

Ingo Winkler

403

Approximate calculations for heat exchangers  

Microsoft Academic Search

Estimates were developed for the total heat transfer coefficient for various types of heat exchangers. These estimates were not meant to replace more accurate calculations for individual heat exchangers, but to provide quick approximations for situations in which great accuracy was not required. The heat transfer coefficients k (in kcal\\/m²\\/hr\\/°C) were calculated based on assumed average values for input and

Matz

2008-01-01

404

Ion exchange - Simulation and experiment  

NASA Technical Reports Server (NTRS)

A FORTRAN program for simulating multicomponent adsorption by ion-exchange resins was adapted for use as both an ASPEN-callable module and as a free-standing simulator of the ion-exchange bed. Four polystyrene-divinylbenzene sulfonic acid resins have been characterized for three principal ions. It is concluded that a chelating resin appears appropriate as a heavy-metal trap. The same ASPEN-callable module is used to model this resin when Wilson parameters can be obtained.

Herrmann, Cal C.; Finn, John E.

1991-01-01

405

Electrically switched cesium ion exchange  

SciTech Connect

Electrically Switched Ion Exchange (ESIX) is a separation technology being developed as an alternative to conventional ion exchange for removing radionuclides from high-level waste. The ESIX technology, which combines ion exchange and electrochemistry, is geared toward producing electroactive films that are highly selective, regenerable, and long lasting. During the process, ion uptake and elution are controlled directly by modulating the potential of an ion exchange film that has been electrochemically deposited onto a high surface area electrode. This method adds little sodium to the waste stream and minimizes the secondary wastes associated with traditional ion exchange techniques. Development of the ESIX process is well underway for cesium removal using ferrocyanides as the electroactive films. Films having selectivity for perrhenate (a pertechnetate surrogate) over nitrate also have been deposited and tested. A case study for the KE Basin on the Hanford Site was conducted based on the results of the development testing. Engineering design baseline parameters for film deposition, film regeneration, cesium loading, and cesium elution were used for developing a conceptual system. Order of magnitude cost estimates were developed to compare with conventional ion exchange. This case study demonstrated that KE Basin wastewater could be processed continuously with minimal secondary waste and reduced associated disposal costs, as well as lower capital and labor expenditures.

Lilga, M.A.; Orth, R.J.; Sukamto, J.P.H. [Pacific Northwest National Lab., Richland, WA (United States); Schwartz, D.T.; Haight, S.M. [Univ. of Washington, Seattle, WA (United States); Genders, J.D. [Electrosynthesis Co., Inc. (United States)

1997-04-01

406

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

407

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

NASA Astrophysics Data System (ADS)

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

Nakayama, Morio

408

Isotope exchange as a probe of the kinetic mechanism of pyrophosphate-dependent phosphofructokinase  

SciTech Connect

Data obtained from isotope exchange at equilibrium, exchange of inorganic phosphate against forward reaction flux, and positional isotope exchange of /sup 18/O from the bridge position of pyrophosphate to a nonbridge position all indicate that the pyrophosphate-dependent phosphofructokinase fromPropionibacterium freudenreichii has a rapid equilibrium random kinetic mechanism. The maximum rates of isotope exchange at equilibrium for the (/sup 14/C)fructose 1,6-bisphosphate in equilibrium fructose 6-phosphate, (/sup 32/P)P/sub i/ in equilibrium MgPP/sub i/, and Mg(/sup 32/P)PP/sub i/ in equilibrium fructose, 1,6-bisphosphate exchange reactions increasing all four possible substrate-product pairs in constant ratio are identical, consistent with a rapid equilibrium mechanism. All exchange reactions are strongly inhibited at high concentrations of the fructose 6-phosphate (F6P)P/sub i/ and MgPP/sub i/P/sub i/ substrate-product pairs and weakly inhibited at high concentrations of the MgPP/sub i/fructose 1,6-bisphosphate (FBP) pair suggesting three dead-end complexes, E:F6P:P/sub i/, E:MgPP/sub i/:P/sub i/, and E:FBP:MgPP/sub i/, in agreement with initial velocity studies. Neither back-exchange by (/sup 32/P)P/sub i/ nor positional isotope exchange of /sup 18/O-bridge-labeled pyrophosphate was observed under any conditions, suggesting that either the chemical interconversion step or a step prior to it limits the overall rate of the reaction.

Cho, Y.K.; Matsunaga, T.O.; Kenyon, G.I.; Bertagnolli, B.L.; Cook, P.F.

1988-05-03

409

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

Microsoft Academic Search

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

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

1995-01-01

410

Optical waveguides Me:LiTaO3 prepared by nonisovalent ion exchange  

Microsoft Academic Search

A new method to form optical waveguides in lithium tantalate crystals, the nonisovalent ion exchange in the salt melts, is proposed. We found that the waveguides can be formed by ion exchange reactions Zn ? 2Li, Ni ? 2Li, Mn ? 2Li, Fe ? 2Li, Co ? 2Li, Ca ? 2Li, Mg ? 2Li in the melts of mixtures K2SO4—Na2SO4—Li2SO4—MeSO4

V. A. Fedorov; V. A. Ganshin; Yu. N. Korkishko; T. V. Morozova

1993-01-01

411

Microscale Thermite Reactions.  

ERIC Educational Resources Information Center

Describes the adaptation of thermite (aluminum with metal oxides) reactions from whole-class demonstrations to student-run micro-reactions. Lists detailed directions and possible variations of the experiment. (WRM)

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

1998-01-01

412

Treatment and Managing Reactions  

MedlinePLUS

Treatment & Managing Reactions Currently, the only way to prevent a food-allergic reaction is to avoid the problem food. ... treatment plan includes all of the following: Strict avoidance of problem foods Working with your doctor to ...

413

Passivation of Anodic Reactions.  

National Technical Information Service (NTIS)

Extending the Wagner definition of passivity to anodic reactions of chemical species on inert electrodes, passivation of a Pt electrode for the hydrogen oxidation reaction can be explained as being caused by small amounts (fraction of a monolayer) of adso...

S. Schuldiner

1968-01-01

414

Microscale Thermite Reactions  

NASA Astrophysics Data System (ADS)

The reaction of aluminum with the oxides of a variety of elements (aluminothermy, or the Goldschmidt process) illustrates exothermic reactions that require a high activation energy. It is also an appropriate experiment with regard to the discussion of Ellingham diagrams. Because it is spectacular, this reaction is a favorite for demonstrations. When drama is not the main objective, conducting these reactions at microscale level offers numerous advantages over the usual scale.

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

1998-12-01

415

Inhibition and activation of Na/sup +/-Ca/sup 2 +/ exchange activity by quinacrine  

SciTech Connect

Quinacrine either inhibited or stimulated Na-Ca exchange in cardiac sarcolemmal vesicles, depending on the experimental conditions. When present in the assay medium for Na-Ca exchange, quinacrine inhibited both Na/sub i/-dependent Ca/sup 2 +/ uptake (K/sub i/ = 50 ..mu..M) and Na/sub 0/-dependent Ca/sup 2 +/ efflux. Quinacrine's inhibition of Ca/sub 2//sup +/ efflux was attenuated by high concentrations of Na/sup +/. Quinacrine also blocked Na-Na and Ca-Ca exchange activities in the vesicles. The inhibitory effects of quinacrine on Na-Ca exchange activity are qualitatively similar to those reported previously for amiloride derivatives. When Na-loaded vesicles were preincubated with quinacrine and then assayed for Na-Ca exchange in a quinacrine-free medium, stimulation of exchange activity was observed. This stimulation was reversible on the removal of bound quinacrine and involved a reduction in the apparent K/sub m/ for extravesicular Ca/sup 2 +/. Stimulation of exchange activity under these conditions was also observed with the lipophilic cations tetraphenylphosphonium. Since Ca/sup 2 +/, quinacrine and tetraphenylphosphonium all bind strongly to sarcolemmal membranes it is suggested that the observed stimulation of exchange activity involves a local electrostatic effect of the bound cations in accelerating a rate-limiting step in the reaction mechanism for Na-Ca exchange.

de la Pena, P.; Reeves, J.P.

1987-01-01

416

found in Exhibit J to Topaz Exchange’s Form 1 application.  

E-print Network

electronically by its registered brokerdealer members, as well as from quotes submitted electronically by market makers. A more detailed description of the manner of operation of Topaz Exchange’s proposed system can be found in Exhibit E to Topaz Exchange’s Form 1 application. The proposed rulebook for the proposed exchange can be found in Exhibit B to Topaz Exchange’s Form 1 application, and the governing documents for both Topaz

unknown authors

417

Nuclear Reactions Some Basics  

E-print Network

Q in a reaction ­ Definition: Q = masses BEFORE the reaction ­ masses AFTER the reaction ­ Example: e + 3He e + p + d: Q = (Me + M3He) - (Me + Mp + Md) ­ Q may be >0 (exothermic) or ?) measurements made in a nuclear physics lab experiment. #12;Formal Definition of Cross Section · Consider a beam

Gilfoyle, Jerry

418

Chemical Reactions at Surfaces  

Microsoft Academic Search

Chemical reactions at surfaces underlie some of the most important processes of today, including catalysis, energy conversion, microelectronics, human health and the environment. Understanding surface chemical reactions at a fundamental level is at the core of the field of surface science. The Gordon Research Conference on Chemical Reactions at Surfaces is one of the premiere meetings in the field. The

Nancy Ryan Gray Michael Henderson

2010-01-01

419

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

SciTech Connect

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

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

2001-01-18

420

Mechanism of thiolate-disulfide interchange reactions in biochemistry.  

PubMed

Both density functional theory (DFT) (B3LYP) and CCSD ab initio calculations were employed in a theoretical investigation of the mechanism of thiolate-disulfide exchange reactions. The reaction pathway for degenerate thiolate-disulfide exchange reactions with dimethyl disulfide has been shown to proceed through a SN2-like transition structure that is very close in energy to the corresponding trisulfur anionic intermediate ([delta-S-S-Sdelta(-)]). When relatively small substituents are involved, the level of theory must be increased to CCSD to make this rather subtle mechanistic distinction. With the more sterically hindered exchange reaction involving t-butyl mercaptide and di-t-butyl disulfide, the potential energy surface exhibits a distinct preference for the S(N)2 displacement pathway with an activation barrier of 9.8 kcal/mol. When corrections for solvent polarity are included (COSMO), an S(N)2 mechanism is also implicated in both polar and nonpolar solvents. DFT studies on thiolate-disulfide exchange, when the substituent is a model peptide, strongly support the intermediacy of a trisulfur intermediate that lies 10.7 kcal/mol below isolated reactants. A well depth of this magnitude should provide a sufficient lifetime of the intermediate to accommodate the requisite conformational adjustments that accompanies formation of the new disulfide bond. PMID:18052192

Bach, Robert D; Dmitrenko, Olga; Thorpe, Colin

2008-01-01

421

The Microstructure Approach to Exchange Rates  

Microsoft Academic Search

Historically, the fields of exchange-rate economics and microstructure finance have progressed independently of each other. Recent interaction, however, has given rise to a microstructure approach to exchange rates. This book focuses on the economics of financial information and how microstructure tools help to clarify the types of information most relevant to exchange rates. The microstructure approach views exchange rates from

Richard K. Lyons

2001-01-01

422

Integral stabilization policy and flexible exchange rates  

Microsoft Academic Search

Summary Under a floating exchange rate system, exchange rates influence economic activity through their effect on the trade balance. Nevertheless, exchange rate movementsper se do not prevent integral fiscal and monetary policies from achieving a target for domestic economic activity24. At the same time, since the exchange rate continuously moves to preserve asset market equilibrium, the (potential) balance of payments

Jay H. Levin

1982-01-01

423

Conflict and Fairness in Social Exchange  

ERIC Educational Resources Information Center

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

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

2006-01-01

424

Existence of Positive Steady States for Mass Conserving and Mass-Action Chemical Reaction Networks with a Single Terminal-Linkage Class  

Microsoft Academic Search

We establish that mass conserving single terminal-linkage networks of chemical reactions admit positive steady states regardless of network deficiency and the choice of reaction rate constants. This result holds for closed systems without material exchange across the boundary, as well as for open systems with material exchange at rates that satisfy a simple sufficient and necessary condition. Our proof uses

Santiago Akle; Onkar Dalal; Ronan M. T. Fleming; Michael Saunders; Nicole Taheri; Yinyu Ye

2011-01-01

425

A Colorful Ion Exchange Experiment  

NASA Astrophysics Data System (ADS)

A colorful ion-exchange experiment is described. The use of a resin with an adsorbed acid-base indicator allows students to follow the progress of the ion-exchange front along the column. In parallel, students can follow the ion-exchange breakthrough curve using a continuous conductometric cell at the column outlet. In the present example, K+ (KCl) exchanges with H+ (HCl) in a strong cationic resin (Amberlite IR 120). The adsorbed indicator is methyl violet. Sorption equilibrium is favorable to the K+ ions. Monovalent ions, used in this experiment, have the disadvantage of usually being colorless (except perhaps permanganate, but this is an extremely strong oxidant which attacks the resin). On the other hand, many divalent ions are colorful but the shape of the concentration front is hard to explain qualitatively as well as quantitatively. That is because the shape of the front depends on the total ionic concentration. However, color can be introduced in a monovalent ion-exchange system by adding an appropriate acid-base indicator to the resin. The text describes this experiment qualitatively. A simplified quantitative description, using the solute movement theory, can be found online.

Mendes, Adélio

1999-11-01

426

Electrically Switched Cesium Ion Exchange  

SciTech Connect

This report discusses the results of work to develop Electrically Switched Ion Exchange (ESIX) for separations of ions from waste streams relevant to DOE site clean-up. ESIX combines ion exchange and electrochemistry to provide a selective, reversible method for radionuclide separation that lowers costs and minimizes secondary waste generation typically associated with conventional ion exchange. In the ESIX process, an electroactive ion exchange film is deposited onto. a high surface area electrode, and ion uptake and elution are controlled directly by modulating the potential of the film. As a result, the production of secondary waste is minimized, since the large volumes of solution associated with elution, wash, and regeneration cycles typical of standard ion exchange are not needed for the ESIX process. The document is presented in two parts: Part I, the Summary Report, discusses the objectives of the project, describes the ESIX concept and the approach taken, and summarizes the major results; Part II, the Technology Description, provides a technical description of the experimental procedures and in-depth discussions on modeling, case studies, and cost comparisons between ESIX and currently used technologies.

JPH Sukamto; ML Lilga; RK Orth

1998-10-23

427

Removal of catalyst in polybutene production by treatment with ion exchange resin  

SciTech Connect

The development of process technology for removal of AlCl/sub 3/ from the reaction mass obtained in the polymerization of butenes by treatment with ion exchange resins is reported. This work also investigated certain reactions that take place in this treatment. It is proposed that the polymerized product should be treated with KU-2-8 cation exchange resin in the H form. The study demonstrates that by the use of resin treatment of the polymerized product that has been prehomogenized with alcohols, it becomes possible to produce low molecular weight polybutenes in a low waste process.

Vlasov, A.V.; Prokof'ev, K.V.; Sangalov, Yu.A.; Kotov, S.V.

1988-09-01

428

NASA data exchange standards for computational fluid dynamics  

NASA Technical Reports Server (NTRS)

This paper covers the following topics in viewgraph format: purpose of data exchange standards; data exchange in engineering analysis/CFD; geometry data exchange through existing product data exchange standards, NASA Data Exchange Committee, and NASA-IGES (Initial Graphics Exchange Specification); CFD grid and solution data exchange; and data exchange for multi-disciplinary engineering.

Blake, Matthew

1993-01-01

429

Mechanisms in knockout reactions  

E-print Network

We report on the first detailed study of the mechanisms involved in knockout reactions, via a coincidence measurement of the residue and fast proton in one-proton knockout reactions, using the S800 spectrograph in combination with the HiRA detector array at the NSCL. Results on the reactions $^9$Be($^9$C,$^8$B+X)Y and $^9$Be($^8$B,$^7$Be+X)Y are presented. They are compared with theoretical predictions for both the diffraction and stripping reaction mechanisms, as calculated in the eikonal model. The data shows a clear distinction between the two reaction mechanisms, and the observed respective proportions are very well reproduced by the reaction theory. This agreement supports the results of knockout reaction analyses and their applications to the spectroscopy of rare isotopes.

D. Bazin; R. J. Charity; R. T. de Souza; M. A. Famiano; A. Gade; V. Henzl; D. Henzlova; S. Hudan; J. Lee; S. Lukyanov; W. G. Lynch; S. McDaniel; M. Mocko; A. Obertelli; A. M. Rogers; L. G. Sobotka; J. R. Terry; J. A. Tostevin; M. B. Tsang; M. S. Wallace

2009-02-16

430

Thermodynamics of Potassium Exchange in Soil Using a Kinetics Approach1 D. L. SPARKS AND P. M. JARDINEZ  

E-print Network

were determined using Gibbs' and Eyring's reaction rate theories. The free energy for K exchange (AG Gibbs' theory and from Eyr- ing's reaction rate theory indicated that pure thermodynamic parameters could be calculated using a chemical kinetics approach. The enthalpy (A//°) values were exothermic

Sparks, Donald L.

431

Krypton charge exchange cross sections for Hall effect thruster models  

NASA Astrophysics Data System (ADS)

Following discharge from a Hall effect thruster, charge exchange occurs between ions and un-ionized propellant atoms. The low-energy cations produced can disturb operation of onboard instrumentation or the thruster itself. Charge-exchange cross sections for both singly and doubly charged propellant atoms are required to model these interactions. While xenon is the most common propellant currently used in Hall effect thrusters, other propellants are being considered, in particular, krypton. We present here guided-ion beam measurements and comparisons to semiclassical calculations for Kr+ + Kr and Kr2+ + Kr cross sections. The measurements of symmetric Kr+ + Kr charge exchange are in good agreement with both the calculations including spin-orbit effects and previous measurements. For the symmetric Kr2+ + Kr reaction, we present cross section measurements for center-of-mass energies between 1 eV and 300 eV, which spans energies not previously examined experimentally. These cross section measurements compare well with a simple one-electron transfer model. Finally, cross sections for the asymmetric Kr2+ + Kr ? Kr+ + Kr+ reaction show an onset near 12 eV, reaching cross sections near constant value of 1.6 Å2 with an exception near 70-80 eV.

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

2013-04-01

432

Krypton charge exchange cross sections for Hall effect thruster models  

SciTech Connect

Following discharge from a Hall effect thruster, charge exchange occurs between ions and un-ionized propellant atoms. The low-energy cations produced can disturb operation of onboard instrumentation or the thruster itself. Charge-exchange cross sections for both singly and doubly charged propellant atoms are required to model these interactions. While xenon is the most common propellant currently used in Hall effect thrusters, other propellants are being considered, in particular, krypton. We present here guided-ion beam measurements and comparisons to semiclassical calculations for Kr{sup +} + Kr and Kr{sup 2+} + Kr cross sections. The measurements of symmetric Kr{sup +} + Kr charge exchange are in good agreement with both the calculations including spin-orbit effects and previous measurements. For the symmetric Kr{sup 2+} + Kr reaction, we present cross section measurements for center-of-mass energies between 1 eV and 300 eV, which spans energies not previously examined experimentally. These cross section measurements compare well with a simple one-electron transfer model. Finally, cross sections for the asymmetric Kr{sup 2+} + Kr {yields} Kr{sup +} + Kr{sup +} reaction show an onset near 12 eV, reaching cross sections near constant value of 1.6 A{sup 2} with an exception near 70-80 eV.

Hause, Michael L. [Institute for Scientific Research, Boston College, Chestnut Hill, Massachusetts 02159 (United States); Prince, Benjamin D.; Bemish, Raymond J. [Air Force Research Laboratory, Space Vehicles Directorate, Kirtland AFB, New Mexico 87117 (United States)

2013-04-28

433

Grafted methylenediphosphonate ion exchange resins  

DOEpatents

An ion exchange resin is disclosed that is comprised of an insoluble copolymer onto which are grafted pendent groups that provide 1.0 to about 10 mmol/g dry weight phosphorous. The pendent groups have the formula ##STR1## wherein R is hydrogen, a cation or mixtures thereof; and R.sup.1 is hydrogen or an C.sub.1 -C.sub.2 alkyl group. The resin also contains zero to about 5 mmol/g dry weight of pendent aromatic sulfonate groups. Processes for making and using an ion exchange-resin are also disclosed.

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

1998-01-27

434

Grafted methylenediphosphonate ion exchange resins  

DOEpatents

An ion exchange resin is disclosed that is comprised of an insoluble copolymer onto which are grafted pendent groups that provide 1.0 to about 10 mmol/g dry weight phosphorous. The pendent groups have the formula ##STR1## wherein R is hydrogen, a cation or mixtures thereof; and R.sup.1 is hydrogen or an C.sub.1 -C.sub.2 alkyl group. The resin also contains zero to about 5 mmol/g dry weight of pendent aromatic sulfonate groups. Processes for making and using an ion exchange resin are also disclosed.

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

1997-01-01

435

Oscillating-Coolant Heat Exchanger  

NASA Technical Reports Server (NTRS)

Devices useful in situations in which heat pipes inadequate. Conceptual oscillating-coolant heat exchanger (OCHEX) transports heat from its hotter portions to cooler portions. Heat transported by oscillation of single-phase fluid, called primary coolant, in coolant passages. No time-averaged flow in tubes, so either heat removed from end reservoirs on every cycle or heat removed indirectly by cooling sides of channels with another coolant. Devices include leading-edge cooling devices in hypersonic aircraft and "frost-free" heat exchangers. Also used in any situation in which heat pipe used and in other situations in which heat pipes not usable.

Scotti, Stephen J.; Blosser, Max L.; Camarda, Charles J.

1992-01-01

436

Theta^+ baryon production in kn and nn reactions  

SciTech Connect

We study ?+(1540) productions in kaon-nucleon (KN) and nucleon-nucleon (NN) interactionsby assuming that the ?+ is an isosinglet with JP = 1/2+. Possible t-channel diagrams with K?exchange are considered in both reactions as well as K exchange in NN reaction. The crosssection for np ! ?0?+, which has not been considered in previous calculations, is found to beabout a factor of 5 larger than that for np ! ?0?+ due to the large coupling of KN? interaction.The cross sections are obtained by setting gKN002 = 1 and varying the ratio of gK*N THETA/gKN THETA so that future experimental data can be used to estimate these couplings. We also ?nd that the isospin relations hold for these reactions.

Oh, Yongseok; Houng Lee, Su

2004-04-01

437

Design criteria for extraction with chemical reaction and liquid membrane permeation  

NASA Technical Reports Server (NTRS)

The design criteria for heterogeneous chemical reactions in liquid/liquid systems formally correspond to those of classical physical extraction. More complex models are presented which describe the material exchange at the individual droplets in an extraction with chemical reaction and in liquid membrane permeation.

Bart, H. J.; Bauer, A.; Lorbach, D.; Marr, R.

1988-01-01

438

What prompts Japan to intervene in the Forex market? A new approach to a reaction function  

Microsoft Academic Search

This paper estimates and analyzes the reaction function of Japanese intervention in the foreign exchange (Forex) markets, using daily Japanese intervention data from April 1, 1991 to December 31, 2002. A theoretical friction model is adopted to describe the intervention as cost-minimizing behavior. An ordered probit model, consistent with the theoretical model, is employed to estimate authorities' reaction function. A

Takatoshi Ito; Tomoyoshi Yabu

2007-01-01

439

Structure of the Hsp110:Hsc70 Nucleotide Exchange Machine  

PubMed Central

Summary Hsp70s mediate protein folding, translocation, and macromolecular complex remodeling reactions. Their activities are regulated by proteins that exchange ADP for ATP from the nucleotide-binding domain (NBD) of the Hsp70. These nucleotide exchange factors (NEFs) include the Hsp110s, which are themselves members of the Hsp70 family. We report the structure of an Hsp110:Hsc70 nucleotide exchange complex. The complex is characterized by extensive protein:protein interactions and symmetric bridging interactions between the nucleotides bound in each partner protein's NBD. An electropositive pore allows nucleotides to enter and exit the complex. The role of nucleotides in complex formation and dissociation, and the effects of the protein:protein interactions on nucleotide exchange, can be understood in terms of the coupled effects of the nucleotides and protein:protein interactions on the open-closed isomerization of the NBDs. The symmetrical interactions in the complex may model other Hsp70 family heterodimers in which two Hsp70s reciprocally act as NEFs. PMID:18550409

Schuermann, Jonathan P.; Jiang, Jianwen; Cuellar, Jorge; Llorca, Oscar; Wang, Liping; Gimenez, Luis E.; Jin, Suping; Taylor, Alexander B.; Demeler, Borries; Morano, Kevin A.; Hart, P. John; Valpuesta, Jose M.; Lafer, Eileen M.; Sousa, Rui

2010-01-01

440

Reactions of tetraphenyltitanium with organic acids  

SciTech Connect

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

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

1987-12-10

441

Pion-induced reactions for charmed baryons  

NASA Astrophysics Data System (ADS)

We study pion-induced binary reactions for charmed baryons, ? +N to D^{ast } +B, where B is a charmed baryon of ground or excited state. First we estimate charm production rates in comparison with strangeness production using a Regge model, which is dominated by vector (D^{ast } or K^{ast }) Reggeon exchange. Then we examine the production rates of various charmed baryons B in a quark-diquark model. We find that the production of excited states is not necessarily suppressed, a sharp contrast to strangeness production, which is a unique feature of the charm production with a large momentum transfer.

Kim, Sang-Ho; Hosaka, Atsushi; Kim, Hyun-Chul; Noumi, Hiroyuki; Shirotori, Kotaro

2014-10-01

442

76 FR 25774 - Determination of Foreign Exchange Swaps and Foreign Exchange Forwards Under the Commodity...  

Federal Register 2010, 2011, 2012, 2013

...strengthened business-conduct standards...of a global foreign exchange trade...regulators and the market more broadly...with clearing foreign exchange swaps...impact their business activities...requirements on the foreign exchange market would...

2011-05-05

443

Noncanonical Reactions of Flavoenzymes  

PubMed Central

Enzymes containing flavin cofactors are predominantly involved in redox reactions in numerous cellular processes where the protein environment modulates the chemical reactivity of the flavin to either transfer one or two electrons. Some flavoenzymes catalyze reactions with no net redox change. In these reactions, the protein environment modulates the reactivity of the flavin to perform novel chemistries. Recent mechanistic and structural data supporting novel flavin functionalities in reactions catalyzed by chorismate synthase, type II isopentenyl diphosphate isomerase, UDP-galactopyranose mutase, and alkyl-dihydroxyacetonephosphate synthase are presented in this review. In these enzymes, the flavin plays either a direct role in acid/base reactions or as a nucleophile or electrophile. In addition, the flavin cofactor is proposed to function as a “molecular scaffold” in the formation of UDP-galactofuranose and alkyl-dihydroxyacetonephosphate by forming a covalent adduct with reaction intermediates. PMID:23203060

Sobrado, Pablo

2012-01-01

444

Free energies for acid attack reactions of lithium cobaltate.  

SciTech Connect

The attack of lithium-ion battery cathodes by stray aqueous HF, with resultant dissolution, protonation, and possibly other unintended reactions, can be a significant source of capacity fade. We explore the calculation of reaction free energies of lithium cobaltate in acid by a 'hybrid' method, in which solid-phase free energies are calculated from first principles at the generalized gradient approximation + intrasite coulomb interaction (GGA+U) level and tabulated values of ionization potentials and hydration energies are employed for the aqueous species. Analysis of the dissolution of the binary oxides Li{sub 2}O and CoO suggests that the atomic energies for Co and Li should be shifted from values calculated by first principles to yield accurate reaction free energies within the hybrid method. With the shifted atomic energies, the hybrid method was applied to analyze proton-promoted dissolution and protonation reactions of LiCoO{sub 2} in aqueous acid. Reaction free energies for the dissolution reaction, the reaction to form Co{sub 3}O{sub 4} spinel, and the proton-for-lithium exchange reaction are obtained and compared to empirical values. An extension of the present treatment to consider partial reactions is proposed, with a view to investigating interfacial and environmental effects on the dissolution reaction.

Benedek, R.; van de Walle, A.; Chemical Sciences and Engineering Division; California Inst. of Tech.

2008-01-01

445

Pion-nucleus double charge exchange and the nuclear shell model  

Microsoft Academic Search

The pion-nucleus double charge exchange reaction is studied with special emphasis on nuclear structure. The reaction mechanism and nuclear structure aspects of the process are separated using both the plane-wave and distorted-wave impulse approximations. Predictions are made employing both the seniority model and a full shell model (with a single active orbit). Transitions to the double analog state and to

N. Auerbach; W. R. Gibbs; Joseph Ginocchio; W. B. Kaufmann

1988-01-01

446

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

SciTech Connect

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

Goodman, C.D.

1980-01-01

447

The Interactions and Exchanges of Metal-bound Sulfur Containing Ligands with Various Transition Metals  

E-print Network

....... 26 Figure 4-1 The zinc-platinum adduct (a) and the metal exchange product (b) ... 29 Figure 4-2 Previously studied reactions of zinc and nickel biomimetic pathways 31 Figure 4-3 The ligand cannibalism of Zn-1?-Ac to form the diacetate... species and the starting dimer ........................................................................ 32 Figure 4-4 Reaction pathways to address the mechanism for ligand cannibalism and reformulation...

Foley, William

2011-02-22

448

Separation of the lanthanides on high-efficiency bonded phases and conventional ion-exchange resins  

Microsoft Academic Search

High-performance liquid chromatographic separations (< 20 min) of the lanthanides are illustrated for both 5- and 10-..mu..m bonded-phase strong-acid ion exchangers. The performance of these bonded phase packings is compared with that obtained with a 13-..mu..m styrene-divinylbenzene resin. The eluted metal ions are detected with a variable-wavelength detector after a post-column complexation reaction. The requirements and characteristics of post-column reaction

S. Elchuk; R. M. Cassidy

1979-01-01

449

The Picture Exchange Communication System  

Microsoft Academic Search

A variety of strategies have been used to help children with autism acquire functional communication skills. The Picture Exchange Communication System (PECS) is a unique communication training program that was developed as a means of circumventing some shortcomings associatd with these strategies. A description of the steps within PECS is provided. Long-term group data have indicated that a large proportion

Andrew S. Bondy; Lori A. Frost

1994-01-01

450

NTU Incoming Exchange/Visiting  

E-print Network

Admin. Building) · Fee payment for the 2nd Semester of your exchange period · General Service Division Networking Center #12;Health Center · Opening hours: 9:10~11:30 2:10~4:30 Registration Fee: NTD 50 · Reservation #12;Global Lounge #12;Campus Tour Meeting Point: the Main Gate Chinese · 2/17(Thu.) 10:00, 14

Wu, Yih-Min

451

Does Foreign Exchange Intervention Work?  

Microsoft Academic Search

Following the Versailles G-7 summit of 1982, most government officials and academic analysts downplayed the potential impact of exchange market intervention unless such intervention was permitted to affect national monetary policies. This study challenges the conventional wisdom. Using previously unavailable data on daily intervention by the US Federal Reserve and the German Bundesbank, the authors find to the contrary that

Kathryn Dominguez; Jeffrey A. Frankel

1993-01-01

452

Brain Drain or Brain Exchange?  

Microsoft Academic Search

This paper explores the “brain drain” hypothesis – the idea that New Zealand is losing many of its most talented citizens to other countries. We conclude that we are experiencing more of a brain exchange than a brain drain. There have been net outflows of New Zealand citizens for forty years, and we have been replacing those leaving with non-New

Hayden Glass; Wai Kin Choy

2001-01-01

453

Knowledge Exchange with Sistema Scotland  

ERIC Educational Resources Information Center

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

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

2010-01-01

454

CATION EXCHANGE WITH MOLTEN SALTS  

Microsoft Academic Search

The applicability of cation exchange between synthetic zeolites, such as ; Linde Molecular Sieve 4A, and molten salts, such as monovalent nitrates, was ; studied. It was found that sodium and silver nitrate were occluded in the ; cavities of the zeolite framework, wfth approximately nine to ten molecules ; occuluded per unit cell of the zeolite. No occlusion was

M. Liquornik; Y. Marcus

1963-01-01

455

Educational Telecomputing Projects: Interpersonal Exchanges.  

ERIC Educational Resources Information Center

Six different types of interpersonal exchanges, or educational telecomputing activities that incorporate the use of interpersonal skills are presented: (1) "keypals"; (2) global classrooms; (3) electronic "appearances"; (4) electronic monitoring; (5) question-and-answer services; and (6) impersonations. From this presentation, it is hoped that…

Harris, Judi

1995-01-01

456

Forecast in foreign exchange markets  

NASA Astrophysics Data System (ADS)

We perform a statistical study of weak efficiency in Deutschemark/US dollar exchange rates using high frequency data. The presence of correlations in the returns sequence implies the possibility of a statistical forecast of market behavior. We show the existence of correlations and how information theory can be relevant in this context.

Baviera, R.; Pasquini, M.; Serva, M.; Vergni, D.; Vulpiani, A.

2001-04-01

457

Heat pipe array heat exchanger  

Microsoft Academic Search

A heat exchanger is described for transferring heat between a first fluid and a second fluid in an absorption refrigeration system comprising: a first shell having an inlet for receiving the first fluid at a first elevated temperature and an outlet for discharging the first fluid at a first reduced temperature with the shell defining a free flow path for

Reimann

1987-01-01

458

Primer on nuclear exchange models  

NASA Astrophysics Data System (ADS)

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

Hafemeister, David

2014-05-01

459

Lightweight long life heat exchanger  

NASA Technical Reports Server (NTRS)

The design, fabrication, and evaluation of a full scale shuttle-type condensing heat exchanger constructed of aluminum and utilizing aluminum clad titanium parting sheets is described. A long term salt spray test of candidate parting sheet specimens is described. The results of an investigation into an alternate method of making composite sheet material are discussed.

Moore, E. K.

1975-01-01

460

Non-EU Exchange Orientation  

E-print Network

students taking level 3 English modules Theatre R, Newman Building 19.00 Movie Screening The Best Exotic students Theatre 1 Roebuck Castle 18.00 Orientation BBQ Food and refreshments served. 5 per person. UCD-EU exchange students' orientation (students outside of Business & Law)** Theatre N, Newman Building 16

461

Reaction-diffusion textures  

Microsoft Academic Search

We present a method for texture synthesis based on the simulation of a process of local nonlinear interaction, called reaction-diffusion, which has been proposed as a model of biological pattern formation. We extend traditional reaction-diffusion systems by allowing anisotropic and spatially non-uniform diffusion, as well as multiple competing directions of diffusion. We adapt reaction-diffusion system to the needs of computer

Andrew P. Witkin; Michael Kass

1991-01-01