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Sample records for ligand exchange reaction

  1. Development and Application of Ligand-Exchange Reaction Method ...

    African Journals Online (AJOL)

    Purpose: This paper presents an improved kinetic-spectrophotometric procedure for determining clonazepam (CZP) in pharmaceutical formulations and human serum. Methods: The method is based on ligand-exchange reaction. The reaction was followed spectrophotometrically by measuring the rate of change of ...

  2. Kinetic study on ligand exchange reaction between EC and 99mTc-GH

    International Nuclear Information System (INIS)

    Wu Chunying; Luo Shineng; Fang Ping; Huang Heyun; Xie Minhao; Meng Hong

    1995-01-01

    The ligand exchange reaction between EC and 99m Tc-GH and its influence factors such as concentrations of EC and pH were described. The concentration of EC has no influence on the exchange reaction rate constant, while pH is the most important influence factor. The rate constants of ligand exchange reaction at different pH values were determined. The results showed that in order to make the labelling yield of 99m Tc-EC higher than 90%, pH of the reaction must be higher than 8

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

    Energy Technology Data Exchange (ETDEWEB)

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

    1987-03-01

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

  4. Charge-Transfer Effects in Ligand Exchange Reactions of Au25 Monolayer-Protected Clusters.

    Science.gov (United States)

    Carducci, Tessa M; Blackwell, Raymond E; Murray, Royce W

    2015-04-16

    Reported here are second-order rate constants of associative ligand exchanges of Au25L18 nanoparticles (L = phenylethanethiolate) of various charge states, measured by proton nuclear magnetic resonance at room temperature and below. Differences in second-order rate constants (M(-1) s(-1)) of ligand exchange (positive clusters ∼1.9 × 10(-5) versus negative ones ∼1.2 × 10(-4)) show that electron depletion retards ligand exchange. The ordering of rate constants between the ligands benzeneselenol > 4-bromobenzene thiol > benzenethiol reveals that exchange is accelerated by higher acidity and/or electron donation capability of the incoming ligand. Together, these observations indicate that partial charge transfer occurs between the nanoparticle and ligand during the exchange and that this is a rate-determining effect in the process.

  5. Studies on ligand exchange reaction of functionalized mercaptothiadiazole compounds onto citrate capped gold nanoparticles

    International Nuclear Information System (INIS)

    Kalimuthu, Palraj; John, S. Abraham

    2010-01-01

    Mercaptothiadiazole ligands functionalized with thiol (2,5-dimercapto-1,3,4-thiadiazole (DMT)) and methyl (5-methyl-2-mercapto-1,3,4-thiadiazole (MMT)) groups capped onto citrate capped gold nanoparticles (C-AuNPs) by ligand exchange reaction was investigated by UV-vis spectroscopy, FT-IR spectroscopy and transmission electron microscopy (TEM) techniques. The surface plasmon resonance band at 522 nm for C-AuNPs was shifted to 530 nm after capping with DMT whereas an additional band was observed at 630 nm due to aggregation in addition to a shift in the band at 522 nm after capping of MMT onto C-AuNPs. Thus, capping of DMT onto C-AuNPs leads to the formation of stable AuNPs while capping of MMT leads to the formation of unstable AuNPs. FT-IR studies show that the citrate ions were completely replaced by both DMT and MMT ligands from the AuNPs. TEM images indicate that the size and shape of the AuNPs remain same after capping of these ligands.

  6. Ligand exchange reactions of the heme group in hemoglobin and myoglobin as studied by pulse radiolysis

    International Nuclear Information System (INIS)

    Raap, I.A.

    1978-01-01

    In this thesis, the kinetic aspects of the ligand exchange reactions of hemoglobin are studied using the pulse radiolysis technique, in particular, the reactions of hydrated electrons with methemoglobin. A hitherto unobserved transient state of the heme group is observed which appears immediately after the rapid reduction process. The absorption spectrum of this new species has the characteristics of a ferrous low-spin state and can therefore be ascribed to the formation of a hemochrome non-equilibrium state. The subsequent relaxation of this intermediate structure into a deoxy-conformation is dependent on the amount of proton activity in the solution and on the presence of organic and inorganic phosphate anions. The final absorption spectrum of the heme group is shown to correspond to a ferrous high-spin state in the relaxed quaternary conformation. This is in agreement with the kinetics observen the binding of carbon monoxide and oxygen to partially reduced methemoglobin. At reduction degrees of methemoglobin as well as of valncy 8ybrids where there is an important contribution from species with two reduced subunits, the binding of carbon monoxide to hemoglobin occurs with on-rate constants characteristic for the tensed quaternary conformation. It is argued that this conformational change of hemoglobin (the R-to-T transition) takes place very rapidly, which suggests the participation of an activated relaxed conformation. In addition, it is found that there is a distinct heterogeneity in the binding of oxygen to partially reduced methemoglobin even at low degrees of reduction

  7. In situ spectroscopy of ligand exchange reactions at the surface of colloidal gold and silver nanoparticles

    International Nuclear Information System (INIS)

    Dinkel, Rebecca; Peukert, Wolfgang; Braunschweig, Björn

    2017-01-01

    Gold and silver nanoparticles with their tunable optical and electronic properties are of great interest for a wide range of applications. Often the ligands at the surface of the nanoparticles have to be exchanged in a second step after particle formation in order to obtain a desired surface functionalization. For many techniques, this process is not accessible in situ . In this review, we present second-harmonic scattering (SHS) as an inherently surface sensitive and label-free optical technique to probe the ligand exchange at the surface of colloidal gold and silver nanoparticles in situ and in real time. First, a brief introduction to SHS and basic features of the SHS of nanoparticles are given. After that, we demonstrate how the SHS intensity decrease can be correlated to the thiol coverage which allows for the determination of the Gibbs free energy of adsorption and the surface coverage. (topical review)

  8. Amphiphilic ligand exchange reaction-induced supercapacitor electrodes with high volumetric and scalable areal capacitances

    Science.gov (United States)

    Nam, Donghyeon; Heo, Yeongbeom; Cheong, Sanghyuk; Ko, Yongmin; Cho, Jinhan

    2018-05-01

    We introduce high-performance supercapacitor electrodes with ternary components prepared from consecutive amphiphilic ligand-exchange-based layer-by-layer (LbL) assembly among amine-functionalized multi-walled carbon nanotubes (NH2-MWCNTs) in alcohol, oleic acid-stabilized Fe3O4 nanoparticles (OA-Fe3O4 NPs) in toluene, and semiconducting polymers (PEDOT:PSS) in water. The periodic insertion of semiconducting polymers within the (OA-Fe3O4 NP/NH2-MWCNT)n multilayer-coated indium tin oxide (ITO) electrode enhanced the volumetric and areal capacitances up to 408 ± 4 F cm-3 and 8.79 ± 0.06 mF cm-2 at 5 mV s-1, respectively, allowing excellent cycling stability (98.8% of the initial capacitance after 5000 cycles) and good rate capability. These values were higher than those of the OA-Fe3O4 NP/NH2-MWCNT multilayered electrode without semiconducting polymer linkers (volumetric capacitance ∼241 ± 4 F cm-3 and areal capacitance ∼1.95 ± 0.03 mF cm-2) at the same scan rate. Furthermore, when the asymmetric supercapacitor cells (ASCs) were prepared using OA-Fe3O4 NP- and OA-MnO NP-based ternary component electrodes, they displayed high volumetric energy (0.36 mW h cm-3) and power densities (820 mW cm-3).

  9. Kinetic study on ligand exchange reaction between ethylenedicysteine and 99mTc- glucoheptonate (99mTc-GH)

    International Nuclear Information System (INIS)

    Wu, C.Y.; Ji, S.R.; Lu, C.X.; Ding, S.Y.; Chen, Z.P.; Lin, X.T.

    2002-01-01

    Aim: 99m Tc-L,L-ethylenedicysteine( 99m Tc-EC)is a new type of renal imaging agent. It can be labeled very easily and efficiently at room temperature through direct labeling at pH 12. The need for direct labeling at pH 12 does not compromise the simplicity and ease of preparation of 99m Tc-EC and its practical usefulness in daily routine. On the basis of the labeling experiments, we developed a ligand exchange labeling method, in which the labeling EC with 99m Tc can be performed at pH 8. In order to provide a theoretic basis, a detailed kinetic study of ligand exchange reaction between 99m Tc- glucoheptonate( 99m Tc-GH) and EC was carried out. Materials and Methods: 99m Tc-EC is prepared as follows: 99m Tc-GH + EC → 99m Tc-EC + GH, labeling can be easily performed by adding 99m TcO 4 - (2∼6ml generator elute) to glucoheptonate solution containing SnCl 2 .2H 2 O solution to form 99m Tc-GH, then freshly prepared 99m Tc-GH is transferred to the aqueous solution of different concentrations of EC at different pH value, after being shaken, 99m Tc-EC was formed. Radiolabeling yield(RLY) and radiochemical purity(RCP) of 99m Tc-GH and 99m Tc-EC were measured by Xinhua No.1 paper with developing system of Me 2 CO/H 2 O/con.NH 3 .H 2 O=9/3/1(V/V). 99m Tc-GH(RCP must be over 98%, 80ul, 3.6∼7.4MBq) was added to 1ml of 0.5mol/L phosphate buffer(pH 12) containing different amount of EC(150, 75, 50 and 15ug), the sample was taken out at different time intervals and RCP was determined. The solution of EC(30ul, 5g/L) was added to 1ml of 0.5mol/L phosphate buffer at different pH value(pH11, 10, 9, 8, 7), after completely vortexed, 99m Tc-GH(RCP must be over 98%, 80ul, 3.6∼7.4MBq) was then added, the sample was taken out and RCP was determined as above. The rate constant(k) of ligand exchange reaction at different concentrations of EC and different reaction pH values were calculated out by integrating. Plot ln[1/(1-RLY)] vs t(time) showed a liner relationship, and the rate

  10. Ligand Exchange Kinetics of Environmentally Relevant Metals

    Energy Technology Data Exchange (ETDEWEB)

    Panasci, Adele Frances [Univ. of California, Davis, CA (United States)

    2014-07-15

    The interactions of ground water with minerals and contaminants are of broad interest for geochemists but are not well understood. Experiments on the molecular scale can determine reaction parameters (i.e. rates of ligand exchange, activation entropy, activation entropy, and activation volume) that can be used in computations to gain insight into reactions that occur in natural groundwaters. Experiments to determine the rate of isotopic ligand exchange for three environmentally relevant metals, rhodium (Rh), iron (Fe), and neptunium (Np), are described. Many environmental transformations of metals (e.g. reduction) in soil occur at trivalent centers, Fe(III) in particular. Contaminant ions absorb to mineral surfaces via ligand exchange, and the reversal of this reaction can be dangerous, releasing contaminants into the environment. Ferric iron is difficult to study spectroscopically because most of its complexes are paramagnetic and are generally reactive toward ligand exchange; therefore, Rh(III), which is diamagnetic and less reactive, was used to study substitution reactions that are analogous to those that occur on mineral oxide surfaces. Studies on both Np(V) and Np(VI) are important in their own right, as 237Np is a radioactive transuranic element with a half-life of 2 million years.

  11. Exchange Reactions. Proceedings of the Symposium on Exchange Reactions

    International Nuclear Information System (INIS)

    1965-01-01

    The mechanisms and kinetics of chemical reactions are of great interest to chemists. The study of exchange reactions in particular helps to shed light on the dynamics of chemical change, providing an insight into the structures and the reactivities of the chemical species involved. The main theme of this meeting was the subject of oxidation-reduction reactions in which the net result is the transfer of one or more electrons between the different oxidation states of the same element. Other studies reported included the transfer of protons, atoms, complex ligands or organic radicals between molecules. Heterogeneous exchange, which is of importance in many cases of catalytic action, was also considered. For a long time isotopic tracers have formed the most convenient means of studying exchange reactions and today a considerable amount of work continues to be done with their aid. Consequently, several papers presented at this Symposium reported on work carried out by purely radiochemical tracer methods. In recognition, however, of the important role which nuclear magnetic resonance and electron spin resonance play in this field, in particular in the study of fast reactions, a number of reports on investigations in which these techniques had been used was included in the programme. By kind invitation of the United States Government the Symposium on Exchange Reactions was held from 31 May to 4 June at the Brookhaven National Laboratory, Upton, Long Island, N.Y., USA. It was attended by 46 participants from nine countries and one inter-governmental organization. The publication of these Proceedings makes the contents of the papers and the discussion available to a wider audience

  12. Photodissociation dynamics of gaseous CpCo(CO)2 and ligand exchange reactions of CpCoH2 with C3H4, C3H6, and NH3.

    Science.gov (United States)

    Oana, Melania; Nakatsuka, Yumiko; Albert, Daniel R; Davis, H Floyd

    2012-05-31

    The photodissociation dynamics of CpCo(CO)(2) was studied in a molecular beam using photofragment translational energy spectroscopy with 157 nm photoionization detection of the metallic products. At 532 and 355 nm excitation, the dominant one-photon channel involved loss of a single CO ligand producing CpCoCO. The product angular distributions were isotropic, and a large fraction of excess energy appeared as product vibrational excitation. Production of CpCO + 2CO resulted from two-photon absorption processes. The two-photon dissociation of mixtures containing CpCo(CO)(2) and H(2) at the orifice of a pulsed nozzle was used to produce a novel 16-electron unsaturated species, CpCoH(2). Transition metal ligand exchange reactions, CpCoH(2) + L → CpCoL + H(2) (L = propyne, propene, or ammonia), were studied under single-collision conditions for the first time. In all cases, ligand exchange occurred via 18-electron association complexes with lifetimes comparable to their rotational periods. Although ligand exchange reactions were not detected from CpCoH(2) collisions with methane or propane (L = CH(4) or C(3)H(8)), a molecular beam containing CpCoCH(4) was produced by photolysis of mixtures containing CpCo(CO)(2) and CH(4).

  13. Multiscale simulations of ligand adsorption and exchange on gold nanoparticles.

    Science.gov (United States)

    Gao, Hui-Min; Liu, Hong; Qian, Hu-Jun; Jiao, Gui-Sheng; Lu, Zhong-Yuan

    2018-01-17

    We have developed a multiscale model that combines first-principles methods with atomistic and mesoscopic simulations to explore the molecular structures and packing density of the ligands present on the gold nanoparticle (AuNP) surface, as well as the adsorption/exchange reaction kinetics of cetyltrimethylammonium bromide (CTAB)/PEG-SH ligands on different facets of gold, namely, Au(111), Au(100), and Au(110). Our model predicts that on clean gold surfaces, CTAB adsorption is diffusion limited. Specifically, CTAB has the preferentially higher adsorption rate and coverage density on Au(100) and Au(110) surfaces, forming a more compact layer with respect to that on the Au(111) surface, which could result in greater growth of gold nanoparticles along the (111) direction. As opposed to CTAB adsorption, the exchange reaction between PEG-SH with CTAB shows no selectivity to different crystal faces, and the reaction process follows Langmuir diffusion kinetics. Kinetic analysis reveals that, in water, the exchange reaction is zeroth order with respect to the concentration of an incoming PEG-SH, indicative of a dissociative exchange mechanism. The observed rate constant decreases exponentially with the PEG-SH chain length, consistent with a diffusion process for the free PEG-SH in water. In particular, we show that the exchange efficiency increases as the chain rigidness and size of the incoming ligand and/or steric bulk of the initial protecting ligand shell are decreased. Our objectives are to provide a model to assess the kinetics and thermodynamics of the adsorption/exchange reaction process, and we expect that these findings will have important implications for routine surface characterization of AuNPs.

  14. Ligands Exchange Process on Gold Nanoparticles in Acetone Solution

    Science.gov (United States)

    Hu, C. L.; Mu, Y. Y.; Bian, Z. C.; Luo, Z. H.; Luo, K.; Huang, A. Z.

    2018-05-01

    The ligands exchange process on gold nanoparticles (GNPs) was proceeded by using hydrophobic group (PPh3) and hydrophilic group (THPO) in acetone solution. The FTIR and XPS results demonstrated that part of THPO was replaced by PPh3 which was dissolved in polar solution (acetone); the results were in accordance with the electrochemical analysis where the differential capacity decreased with increasing exchange time. After 12 h, the exchange process terminated and the final ratio of PPh3 and THPO was about 1.4: 1. This ratio remained unchanged although the PPh3 and THPO modified GNPs re-dispersed in the PPh3 acetone solution demonstrating the stable adsorption of both ligands after exchanging for 12 h. The TEM images showed that the gold nanoparticles were self-assembled from scattered to arranged morphology due to the existence of hydrophilic and hydrophobic ligands and led to Janus gold nanoparticles.

  15. Reversible Size Control of Silver Nanoclusters via Ligand-exchange

    KAUST Repository

    Bootharaju, Megalamane Siddaramappa

    2015-05-21

    The properties of atomically monodisperse noble metal nanoclusters (NCs) are intricately intertwined with their precise molecular formula. The vast majority of size-specific NC syntheses start from the reduction of the metal salt and thiol ligand mixture. Only in gold was it recently shown that ligand-exchange could induce the growth of NCs from one atomically precise species to another; a process of yet unknown reversibility. Here, we present a process for the ligand-exchange-induced growth of atomically precise silver NCs, in a biphasic liquid-liquid system, which is particularly of interest because of its complete reversibility and ability to occur at room temperature. We explore this phenomenon in-depth using Ag35(SG)18 [SG= glutathionate] and Ag44(4-FTP)30 [4-FTP= 4-fluorothiophenol] as model systems. We show that the ligand-exchange conversion of Ag35(SG)18 into Ag44(4-FTP)30 is rapid (< 5 min) and direct, while the reverse process proceeds slowly through intermediate cluster sizes. We adapt a recently developed theory of reverse Ostwald ripening to model the NCs’ interconvertibility. The model’s predictions are in good agreement with the experimental observations, and they highlight the importance of small changes in the ligand-metal binding energy in determining the final equilibrium NC size. Based on the insight provided by this model, we demonstrated experimentally that by varying the choice of ligands, ligand-exchange can be used to obtain different sized NCs. The findings in this work establish ligand-exchange as a versatile tool for tuning cluster sizes.

  16. Reversible Size Control of Silver Nanoclusters via Ligand-exchange

    KAUST Repository

    Bootharaju, Megalamane Siddaramappa; Burlakov, Victor M.; Besong, Tabot M.D.; Joshi, Chakra Prasad; AbdulHalim, L; Black, David; Whetten, Robert; Goriely, Alain; Bakr, Osman

    2015-01-01

    The properties of atomically monodisperse noble metal nanoclusters (NCs) are intricately intertwined with their precise molecular formula. The vast majority of size-specific NC syntheses start from the reduction of the metal salt and thiol ligand mixture. Only in gold was it recently shown that ligand-exchange could induce the growth of NCs from one atomically precise species to another; a process of yet unknown reversibility. Here, we present a process for the ligand-exchange-induced growth of atomically precise silver NCs, in a biphasic liquid-liquid system, which is particularly of interest because of its complete reversibility and ability to occur at room temperature. We explore this phenomenon in-depth using Ag35(SG)18 [SG= glutathionate] and Ag44(4-FTP)30 [4-FTP= 4-fluorothiophenol] as model systems. We show that the ligand-exchange conversion of Ag35(SG)18 into Ag44(4-FTP)30 is rapid (< 5 min) and direct, while the reverse process proceeds slowly through intermediate cluster sizes. We adapt a recently developed theory of reverse Ostwald ripening to model the NCs’ interconvertibility. The model’s predictions are in good agreement with the experimental observations, and they highlight the importance of small changes in the ligand-metal binding energy in determining the final equilibrium NC size. Based on the insight provided by this model, we demonstrated experimentally that by varying the choice of ligands, ligand-exchange can be used to obtain different sized NCs. The findings in this work establish ligand-exchange as a versatile tool for tuning cluster sizes.

  17. Organotellurium ligands – designing and complexation reactions

    Indian Academy of Sciences (India)

    Unknown

    membered rings it is negative and ~30 ppm only. Keywords. Organotellurium ligands; hybrid telluroether; platinum metal complexes; tellurium-125 NMR. 1. Introduction. Tellurium is the noblest metalloid which may act as a Lewis acid as well as Lewis base. The ligand chemistry of tellurium, which acts as a 'soft' donor, was ...

  18. Dynamics of ligand exchange and association processes in solutions of transition 3d-metal fluorides

    International Nuclear Information System (INIS)

    Nazmutdinova, G.A.; Shtyrlin, V.G.; Zakharov, A.V.; Sal'nikov, Yu.I.

    1993-01-01

    By 19 NMR in combination with ESR spectroscopy rate constants and activation parameters of fluoride-ion exchange reactions in solutions of VOF 5 3- and FeF 6 3- complexes were determined. Associative character of the studied reactions of ligand exchange is shown. Dependence of fluoride complex reactivity on the charge, electron structure of the central ion and formation of hydrogen bonds of coordinated F - ions with solvent molecules was demonstrated. Stability constants, rates of formation and dissociation of intercomplex associates in fluoride solutions were ascertained

  19. Nickel speciation and complexation kinetics in freshwater by ligand exchange and DPCSV

    NARCIS (Netherlands)

    Han Bin Xue,; Jansen, S.; Prasch, A.; Sigg, L.

    2001-01-01

    A technique of ligand exchange with DMG (dimethylglyoxime) and DPCSV was applied to determine Ni speciation in lake, river, and groundwater samples. The working conditions related to ligand-exchange equilibrium were optimized, and the ligand-exchange kinetics were examined. The observed

  20. Kinetics of hydrogen isotope exchange reactions

    International Nuclear Information System (INIS)

    Gold, V.; McAdam, M.E.

    1975-01-01

    Under the influence of tritium β-radiation, 1,4-dioxan undergoes hydrogen exchange with the solvent water. The inhibition of the reaction by known electron scavengers (Ag + , Cu 2+ , Ni 2+ , Co 2+ , Zn 2+ , H 3 + O) and also by species with high reactivity towards hydroxyl radicals but negligible reactivity towards solvated electrons (N 3 - , Br - , SCN - ) has been examined in detail. γ-irradiation similarly induces hydrogen exchange. The action of scavengers is interpreted as requiring the involvement of two separately scavengeable primary radiolysis products in the sequence of reactions leading to exchange. The presence of electron scavengers, even at high concentration, does not totally inhibit the exchange, and a secondary exchange route, involving a low vacancy state of inhibitor cations, is considered responsible for the 'unscavengeable' portion of the reaction, by providing an alternative exchange route. Analogies are drawn between the exchange reaction and other radiation-induced reactions that are thought to involve spur processes. Some implication of radiation-chemical studies in water-alcohol mixtures are indicated. (author)

  1. Ligand and proton exchange dynamics in recombinant human myoglobin mutants.

    Science.gov (United States)

    Lambright, D G; Balasubramanian, S; Boxer, S G

    1989-05-05

    Site-specific mutants of human myoglobin have been prepared in which lysine 45 is replaced by arginine (K45R) and aspartate 60 by glutamate (D60E), in order to examine the influence of these residues and their interaction on the dynamics of the protein. These proteins were studied by a variety of methods, including one and two-dimensional proton nuclear magnetic resonance spectroscopy, exchange kinetics for the distal and proximal histidine NH protons as a function of pH in the met cyano forms, flash photolysis of the CO forms, and ligand replacement kinetics. The electronic absorption and proton nuclear magnetic resonance spectra of the CO forms of these proteins are virtually identical, indicating that the structure of the heme pocket is unaltered by these mutations. There are, however, substantial changes in the dynamics of both CO binding and proton exchange for the mutant K45R, whereas the mutant D60E exhibits behavior indistinguishable from the reference human myoglobin. K45R has a faster CO bimolecular recombination rate and slower CO off-rate relative to the reference. The kinetics for CO binding are independent of pH (6.5 to 10) as well as ionic strength (0 to 1 M-NaCl). The exchange rate for the distal histidine NH is substantially lower for K45R than the reference, whereas the proximal histidine NH exchange rate is unaltered. The exchange behavior of the human proteins is similar to that reported for a comparison of the exchange rates for myoglobins having lysine at position 45 with sperm whale myoglobin, which has arginine at this position. This indicates that the differences in exchange rates reflects largely the Lys----Arg substitution. The lack of a simple correlation for the CO kinetics with this substitution means that these are sensitive to other factors as well. Specific kinetic models, whereby substitution of arginine for lysine at position 45 can affect ligand binding dynamics, are outlined. These experiments demonstrate that a relatively

  2. Experimental test of exchange degeneracy in hypercharge exchange reactions

    International Nuclear Information System (INIS)

    Moffeit, K.C.

    1978-10-01

    Two pairs of line-reversed reactions π + P → K + Σ + , K - p → π - Σ + and π + p → K + Y* + (1385), K - p → π - Y* + (1385) provide an experimental test of exchange degeneracy in hypercharge exchange reactions. From their study it is concluded that in contrast to the lower energy data, the 11.5 results for the two pairs of reactions are consistent with exchange degeneracy predictions for both helicity-flip and nonflip amplitudes. The Y(1385) decay angular distributions indicate that the quark model and Stodolsky--Sakurai predictions are in agreement with the main features of the data. However, small violations are observed at small momentum transfer. While the Y(1385) vertex is helicity-flip dominated, the nonvanishing of T/sub 3/2 - 1/2/ and T/sub -3/2 1/2/ suggests some finite helicity nonflip contribution in the forward direction. 23 references

  3. Exchange effects in direct reactions

    International Nuclear Information System (INIS)

    LeMere, M.; Kanellopoulos, E.J.; Suenkel, W.; Tang, Y.C.

    1979-01-01

    The effect of antisymmetrization in direct reactions is examined by studying the properties of the coupling-normalization kernel function occurring in a resonating-group formulation. From this study, one obtains useful information concerning the general behavior of direct-reactiion processes and some justification for the use of three-body models in phenomenological analyses

  4. Isotope exchange reaction on solid breeder materials

    International Nuclear Information System (INIS)

    Baba, A.; Nishikawa, M.; Eguchi, T.; Kawagoe, T.

    2000-01-01

    Lithium ceramic materials such as Li 2 O, LiAlO 2 , Li 2 ZrO 3 , Li 2 TiO 3 and Li 4 SiO 4 are considered to be as candidate for the tritium breeding material in a deuterium-tritium (D-T) fusion reactor. In the recent blanket designs, helium gas with hydrogen or deuterium is planned to be used as the blanket purge gas to reduce tritium inventory and promote tritium release from the breeding material. In addition, the rate of isotope exchange reaction between hydrogen isotopes in the purge gas and tritium on the surface of the breeding material is necessary to analyze the tritium release behavior from the breeding materials. However, the rate of isotope exchange reactions between hydrogen isotopes in the purge gas and tritium on the surface of those materials has not been quantified until recently. Recently, the present authors quantified the rate of isotope exchange reaction on Li 2 O and Li 2 ZrO 3 . The overall mass transfer coefficients representing the isotope exchange reaction between H 2 and D 2 O on breeding materials or the same between D 2 and H 2 O are experimentally obtained in this study. Comparison to isotope exchange reaction rates on various breeding materials is also performed in this study. Discussions about the effects of temperature, concentration of hydrogen in the purge gas or flow rate of the purge gas on the conversion of tritiated water to tritium gas are also performed

  5. The Ligand Substitution Reactions of Hydrophobic Vitamin B ...

    African Journals Online (AJOL)

    NJD

    Vitamin B. 12. Derivatives. Reaction of Cobyric Acid. Heptapropyl Ester with Heterocyclic N-donor Ligands. Mohamed S.A. .... RESEARCH ARTICLE. M.S.A. Hamza ..... neutralized with NaHCO3 and treated with excess KCN to give. DCCbs-Pr.

  6. : Recyclable, ligand free palladium(II) catalyst for Heck reaction

    Indian Academy of Sciences (India)

    well as heterogeneous palladium catalysts, generated from either palladium(0) compounds or palladium(II) acetate or chloride salts.6 Several ligands such as phosphines, phoshites, carbenes, thioethers have been successfully employed for this reaction.7 However, homogeneous catalysis results in problems of recovery.

  7. Isotopic studies on ligand exchange between complex and simple cyanides in water medium and in liquid hydrogen cyanide. Part 2. Radiocyanide ligand exchange study between hydrogen cyanide and octacyanotungstate(4) in water solutions of mineral acids

    International Nuclear Information System (INIS)

    Zielinski, M.

    1979-01-01

    Radiocyanide ligand exchange between potassium octacyanotungstate(4) and hydrogen cyanide in aqueous solutions of sulfuric acid and between octacyanotungstic(4) acid and hydrogen cyanide in aqueous solutions have been investigated experimentally. The observed enhancement of the rate of ligand exchange in acidic medium has been rationalized in terms of the proposed new general reaction scheme taking into account the reversible decomposition of complex cyanide at low pH, and irreversible one at high pH. The discussion on the results obtained has been carried out within the framework of derived formal kinetic equations. (author)

  8. Charge-exchange reactions on 36 S

    International Nuclear Information System (INIS)

    Fifield, L.K.; Catford, W.N.; Orr, N.A.; Ophel, T.R.; Etchegoyen, A.; Etchegoyen, M.C.

    1992-11-01

    A series of charge-exchange reactions on 36 S targets have been investigated at beam energies ∼7 MeV/A. Pronounced selectivities to different final states in 36 P are observed which depend on the projectile employed. An interpretation of the data in terms of one- and two-step pictures of the reaction mechanism is presented. At least two, and probably all, of the reactions have a significant 1-step contribution to the reaction mechanism at these energies. 22 refs., 5 tabs., 5 figs

  9. Catalytic process for tritium exchange reaction

    International Nuclear Information System (INIS)

    Hansoo Lee; Kang, H.S.; Paek, S.W.; Hongsuk Chung; Yang Geun Chung; Sook Kyung Lee

    2001-01-01

    The catalytic activities for a hydrogen isotope exchange were measured through the reaction of a vapor and gas mixture. The catalytic activity showed to be comparable with the published data. Since the gas velocity is relatively low, the deactivation was not found clearly during the 5-hour experiment. Hydrogen isotope transfer experiments were also conducted through the liquid phase catalytic exchange reaction column that consisted of a catalytic bed and a hydrophilic bed. The efficiencies of both the catalytic and hydrophilic beds were higher than 0.9, implying that the column performance was excellent. (author)

  10. A robust ligand exchange approach for preparing hydrophilic, biocompatible photoluminescent quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Sujuan; Zhou, Changhua [Key Laboratory for Special Functional Materials of the Ministry of Education, Henan University, Kaifeng 475004 (China); Yuan, Hang [Life Science Division, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055 (China); Shen, Huaibin [Key Laboratory for Special Functional Materials of the Ministry of Education, Henan University, Kaifeng 475004 (China); Zhao, Wenxiu [Life Science Division, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055 (China); Ma, Lan, E-mail: malan@sz.tsinghua.edu.cn [Life Science Division, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055 (China); Li, Lin Song, E-mail: lsli@henu.edu.cn [Key Laboratory for Special Functional Materials of the Ministry of Education, Henan University, Kaifeng 475004 (China)

    2013-08-01

    Graphical abstract: - Highlights: • Aqueous CdSe/ZnS QDs were prepared using polymaleic anhydrides as capping ligand. • Effect of reaction temperature and time were systematically studied in the synthesis process. • Water-soluble QDs exhibited a good stability in physiological relevant environment. • The aqueous QDs were applied as biological probe to detect human embryonic stem cell. - Abstract: This paper describes a robust ligand exchange approach for preparing biocompatible CdSe/ZnS quantum dots (QDs) to make bioprobe for effective cell imaging. In this method, polymaleic anhydride (PMA) ligand are first used to replace original hydrophobic ligand (oleic acid) and form a protection shell with multiple hydrophilic groups to coat and protect CdSe/ZnS QDs. The as-prepared aqueous QDs exhibit small particle size, good colloidal stability in aqueous solutions with a wide range of pH, salt concentrations and under thermal treatment, which are necessary for biological applications. The use of this new class of aqueous QDs for effective cell imaging shows strong fluorescence signal to human embryonic stem cell, which demonstrate that PMA coated QDs are fully satisfied with the requirements of preparing high quality biological probe.

  11. Rapid and Efficient Collection of Platinum from Karstedt's Catalyst Solution via Ligands-Exchange-Induced Assembly.

    Science.gov (United States)

    Yang, Gonghua; Wei, Yanlong; Huang, Zhenzhu; Hu, Jiwen; Liu, Guojun; Ou, Ming; Lin, Shudong; Tu, Yuanyuan

    2018-02-21

    Reported herein is a novel strategy for the rapid and efficient collection of platinum from Karstedt's catalyst solution. By taking advantage of a ligand-exchange reaction between alkynols and the 1,3-divinyltetramethyldisiloxane ligand (M Vi M Vi ) that coordinated with platinum (Pt(0)), the Karstedt's catalyst particles with a size of approximately 2.5 ± 0.7 nm could be reconstructed and assembled into larger particles with a size of 150 ± 35 nm due to the hydrogen bonding between the hydroxyl groups of the alkynol. In addition, because the silicone-soluble M Vi M Vi ligand of the Karstedt's catalyst was replaced by water-soluble alkynol ligands, the resultant large particles were readily dispersed in water, resulting in rapid, efficient, and complete collection of platinum from the Karstedt's catalyst solutions with platinum concentrations in the range from ∼20 000 to 0.05 ppm. Our current strategy not only was used for the rapid and efficient collection of platinum from the Karstedt's catalyst solutions, but it also enabled the precise evaluation of the platinum content in the Karstedt's catalysts, even if this platinum content was extremely low (i.e., 0.05 ppm). Moreover, these platinum specimens that were efficiently collected from the Karstedt's catalyst solutions could be directly used for the evaluation of platinum without the need for pretreatment processes, such as calcination and digestion with hydrofluoric acid, that were traditionally used prior to testing via inductively coupled plasma mass spectrometry in conventional methods.

  12. Forging Colloidal Nanostructures via Cation Exchange Reactions.

    Science.gov (United States)

    De Trizio, Luca; Manna, Liberato

    2016-09-28

    Among the various postsynthesis treatments of colloidal nanocrystals that have been developed to date, transformations by cation exchange have recently emerged as an extremely versatile tool that has given access to a wide variety of materials and nanostructures. One notable example in this direction is represented by partial cation exchange, by which preformed nanocrystals can be either transformed to alloy nanocrystals or to various types of nanoheterostructures possessing core/shell, segmented, or striped architectures. In this review, we provide an up to date overview of the complex colloidal nanostructures that could be prepared so far by cation exchange. At the same time, the review gives an account of the fundamental thermodynamic and kinetic parameters governing these types of reactions, as they are currently understood, and outlines the main open issues and possible future developments in the field.

  13. Forging Colloidal Nanostructures via Cation Exchange Reactions

    Science.gov (United States)

    2016-01-01

    Among the various postsynthesis treatments of colloidal nanocrystals that have been developed to date, transformations by cation exchange have recently emerged as an extremely versatile tool that has given access to a wide variety of materials and nanostructures. One notable example in this direction is represented by partial cation exchange, by which preformed nanocrystals can be either transformed to alloy nanocrystals or to various types of nanoheterostructures possessing core/shell, segmented, or striped architectures. In this review, we provide an up to date overview of the complex colloidal nanostructures that could be prepared so far by cation exchange. At the same time, the review gives an account of the fundamental thermodynamic and kinetic parameters governing these types of reactions, as they are currently understood, and outlines the main open issues and possible future developments in the field. PMID:26891471

  14. Ligand exchange chromatography for analysis and preparative separation of tritium-labelled amino acids

    International Nuclear Information System (INIS)

    Zolotarev, Yu.A.; Zaitsev, D.A.; Penkina, V.I.; Dostavalov, I.N.; Myasoedov, N.F.

    1988-01-01

    Racemic tritium-labelled amino acids were separated into optical isomers by chromatography on a chiral polyacrylamide sorbent filled with copper ions. The polyacrylamide sorbent is synthesized by Mannich's reaction through the action of formaldehyde and L-phenylalanine upon polyacrylamide Biogel P-4 in an alkali phosphate buffer. Tritium-labelled amino acids are eluted by a weak alkali solution of ammonium carbonate. Data are presented on the ligand exchange chromatography of amino acids depending on the degree to which the sorbent is filled with copper ions and on the eluent concentration. Amino acids are isolated from the eluent on short columns filled with sulfonated cation exchanger in the H + form. HPLC on modified silica gel sorbents is also used for the analysis of tritium-labelled optically active amino acids. Amino acids are eluted by a weakly acidic water-methanol solution containing ammonium acetate. UV and scintillation flow type detectors are used. (author) 7 refs.; 8 figs

  15. Reactions of diiron m-aminocarbyne complexes containing nitrile ligands

    Directory of Open Access Journals (Sweden)

    Busetto Luigi

    2003-01-01

    Full Text Available The acetonitrile ligand in the mu-aminocarbyne complexes [Fe2{mu-CN(MeR}(mu-CO(CO(NCMe(Cp2][SO 3CF3] (R = Me, 2a, CH2Ph, 2b, Xyl, 2c (Xyl = 2,6-Me2C6H3 is readily displaced by halides and cyanide anions affording the corresponding neutral species [Fe2{mu-CN(MeR}(mu-CO(CO(X(Cp2 ] (X = Br, I, CN. Complexes 2 undergo deprotonation and rearrangement of the coordinated MeCN upon treatment with organolithium reagents. Trimethylacetonitrile, that does not contain acidic alpha hydrogens has been used in place of MeCN to form the complexes [Fe2{mu-CN(MeR}(mu-CO(CO(NCCMe3 (Cp2][SO3CF3] (7a-c. Attempts to replace the nitrile ligand in 3 with carbon nucleophiles (by reaction with RLi failed, resulting in decomposition products. However the reaction of 7c with LiCºCTol (Tol = C6H4Me, followed by treatment with HSO3CF3, yielded the imino complex [Fe2{mu-CN(MeXyl}(mu-CO(CO {N(HC(CºCC6H4Me-4CMe3}(Cp 2][SO3CF3 ] (8, obtained via acetilyde addition at the coordinated NCCMe3.

  16. Asymmetric H-D exchange reactions of fluorinated aromatic ketones

    KAUST Repository

    Zhao, Yujun

    2012-01-01

    Chiral bicyclic guanidine catalyzes the asymmetric H-D exchange reactions. Up to 30% ee was achieved. DFT calculations were employed to elucidate and explain the origin of the reaction\\'s stereoselectivity. © 2012 The Royal Society of Chemistry.

  17. Characterization of Colloidal Quantum Dot Ligand Exchange by X-ray Photoelectron Spectroscopy

    Science.gov (United States)

    Atewologun, Ayomide; Ge, Wangyao; Stiff-Roberts, Adrienne D.

    2013-05-01

    Colloidal quantum dots (CQDs) are chemically synthesized semiconductor nanoparticles with size-dependent wavelength tunability. Chemical synthesis of CQDs involves the attachment of long organic surface ligands to prevent aggregation; however, these ligands also impede charge transport. Therefore, it is beneficial to exchange longer surface ligands for shorter ones for optoelectronic devices. Typical characterization techniques used to analyze surface ligand exchange include Fourier-transform infrared spectroscopy, x-ray diffraction, transmission electron microscopy, and nuclear magnetic resonance spectroscopy, yet these techniques do not provide a simultaneously direct, quantitative, and sensitive method for evaluating surface ligands on CQDs. In contrast, x-ray photoelectron spectroscopy (XPS) can provide nanoscale sensitivity for quantitative analysis of CQD surface ligand exchange. A unique aspect of this work is that a fingerprint is identified for shorter surface ligands by resolving the regional XPS spectrum corresponding to different types of carbon bonds. In addition, a deposition technique known as resonant infrared matrix-assisted pulsed laser evaporation is used to improve the CQD film uniformity such that stronger XPS signals are obtained, enabling more accurate analysis of the ligand exchange process.

  18. Tensor exchange amplitudes in K +- N charge exchange reactions

    International Nuclear Information System (INIS)

    Svec, M.

    1979-01-01

    Tensor (A 2 ) exchange amplitudes in K +- N charge exchange (CEX) are constructed from the K +- N CEX data supplemented by information on the vector (rho) exchange amplitudes from πN sca tering. We observed new features in the t-structure of A 2 exchange amplitudes which contradict the t-de pendence anticipated by most of the Regge models. The results also provide evidence for violation of weak exchange degeneracy

  19. New Ru(II) complexes for dual photoreactivity: ligand exchange and (1)O2 generation.

    Science.gov (United States)

    Knoll, Jessica D; Albani, Bryan A; Turro, Claudia

    2015-08-18

    Uncovering the factors that govern the electronic structure of Ru(II)-polypyridyl complexes is critical in designing new compounds for desired photochemical reactions, and strategies to tune excited states for ligand dissociation and (1)O2 production are discussed herein. The generally accepted mechanism for photoinduced ligand dissociation proposes that population of the dissociative triplet ligand field ((3)LF) state proceeds through thermal population from the vibrationally cooled triplet metal-to-ligand charge transfer ((3)MLCT) state; however, temperature-dependent emission spectroscopy provides varied activation energies using the emission and ligand exchange quantum yields for [Ru(bpy)2(L)2](2+) (bpy = 2,2'-bipyridine; L = CH3CN or py). This suggests that population of the (3)LF state proceeds from the vibrationally excited (3)MLCT state. Because the quantum yield of ligand dissociation for nitriles is much more efficient than that for py, steric bulk was introduced into the ligand set to distort the pseudo-octahedral geometry and lower the energy of the (3)LF state. The py dissociation quantum yield with 500 nm irradiation in a series of [Ru(tpy)(NN)(py)](2+) complexes (tpy = 2,2':6',2″-terpyridine; NN = bpy, 6,6'-dimethyl-2,2'-bipyridine (Me2bpy), 2,2'-biquinoline (biq)) increases by 2-3 orders of magnitude with the sterically bulky Me2bpy and biq ligands relative to bpy. Ultrafast transient absorption spectroscopy reveals population of the (3)LF state within 3-7 ps when NN is bulky, and density functional theory calculations support stabilized (3)LF states. Dual activity via ligand dissociation and (1)O2 production can be achieved by careful selection of the ligand set to tune the excited-state dynamics. Incorporation of an extended π system in Ru(II) complexes such as [Ru(bpy)(dppn)(CH3CN)2](2+) (dppn = benzo[i]dipyrido[3,2-a:2',3'-c]phenazine) and [Ru(tpy)(Me2dppn)(py)](2+) (Me2dppn = 3,6-dimethylbenzo[i]dipyrido[3,2-a:2',3'-c]phenazine) introduces

  20. New Ru(II) Complexes for Dual Photoreactivity: Ligand Exchange and 1O2 Generation

    Science.gov (United States)

    Knoll, Jessica D.; Albani, Bryan A.; Turro, Claudia

    2016-01-01

    CONSPECTUS Uncovering the factors that govern the electronic structure of Ru(II)–polypyridyl complexes is critical in designing new compounds for desired photochemical reactions, and strategies to tune excited states for ligand dissociation and 1O2 production are discussed herein. The generally accepted mechanism for photoinduced ligand dissociation proposes that population of the dissociative triplet ligand field (3LF) state proceeds through thermal population from the vibrationally cooled triplet metal-to-ligand charge transfer (3MLCT) state; however, temperature-dependent emission spectroscopy provides varied activation energies using the emission and ligand exchange quantum yields for [Ru(bpy)2(L)2]2+ (bpy = 2,2′-bipyridine; L = CH3CN or py). This suggests that population of the 3LF state proceeds from the vibrationally excited 3MLCT state. Because the quantum yield of ligand dissociation for nitriles is much more efficient than that for py, steric bulk was introduced into the ligand set to distort the pseudo-octahedral geometry and lower the energy of the 3LF state. The py dissociation quantum yield with 500 nm irradiation in a series of [Ru(tpy)(NN)(py)]2+ complexes (tpy = 2,2′:6′,2″-terpyridine; NN = bpy, 6,6′-dimethyl-2,2′-bipyridine (Me2bpy), 2,2′-biquinoline (biq)) increases by 2–3 orders of magnitude with the sterically bulky Me2bpy and biq ligands relative to bpy. Ultrafast transient absorption spectroscopy reveals population of the 3LF state within 3–7 ps when NN is bulky, and density functional theory calculations support stabilized 3LF states. Dual activity via ligand dissociation and 1O2 production can be achieved by careful selection of the ligand set to tune the excited-state dynamics. Incorporation of an extended π system in Ru(II) complexes such as [Ru(bpy)(dppn)(CH3CN)2]2+ (dppn = benzo[i]dipyrido[3,2-a:2′,3′-c]phenazine) and [Ru(tpy)(Me2dppn)(py)]2+ (Me2dppn = 3,6-dimethylbenzo[i]dipyrido[3,2-a:2′,3

  1. Design, Testing and Kinetic Analysis of Bulky Monodentate Phosphorus Ligands in the Mizoroki-Heck Reaction

    NARCIS (Netherlands)

    Dodds, Deborah L.; Boele, Maarten D. K.; van Strijdonck, Gino P. F.; de Vries, Johannes G.; van Leeuwen, Piet W. N. M.; Kamer, Paul C. J.

    A series of new monodentate phosphane ligands 2 have been evaluated in the MizorokiHeck arylation reaction of iodobenzene and styrene and compared with our previously reported ligands, 1, 3 and 4. The concept of rational ligand design is discussed, and we describe how the performance of this new

  2. Group IV nanocrystals with ion-exchangeable surface ligands and methods of making the same

    Science.gov (United States)

    Wheeler, Lance M.; Nichols, Asa W.; Chernomordik, Boris D.; Anderson, Nicholas C.; Beard, Matthew C.; Neale, Nathan R.

    2018-01-09

    Methods are described that include reacting a starting nanocrystal that includes a starting nanocrystal core and a covalently bound surface species to create an ion-exchangeable (IE) nanocrystal that includes a surface charge and a first ion-exchangeable (IE) surface ligand ionically bound to the surface charge, where the starting nanocrystal core includes a group IV element.

  3. New Ru(II) Complexes for Dual Photoreactivity: Ligand Exchange and 1O2 Generation

    OpenAIRE

    Knoll, Jessica D.; Albani, Bryan A.; Turro, Claudia

    2015-01-01

    Uncovering the factors that govern the electronic structure of Ru(II)–polypyridyl complexes is critical in designing new compounds for desired photochemical reactions, and strategies to tune excited states for ligand dissociation and 1O2 production are discussed herein. The generally accepted mechanism for photoinduced ligand dissociation proposes that population of the dissociative triplet ligand field (3LF) state proceeds through thermal population from the vibrationally cooled triplet meta...

  4. Deviation from the trans -Effect in Ligand-Exchange Reactions of Zeise’s Ions PtCl3(C2H4)- with Heavier Halides (Br, I- )

    Energy Technology Data Exchange (ETDEWEB)

    Hou, Gao-Lei [Physical; Govind, Niranjan [Environmental; Xantheas, Sotiris S. [Advanced; Department; Wang, Xue-Bin [Physical

    2018-01-16

    Four new Zeise’s family ions with mixed-halide ligands, i.e., PtClnX3-n(C2H4)- (X = Br, I; n = 1, 2), were synthesized via ligand-exchange reactions of KX salts with KPtCl3(C2H4) in aqueous solutions, and were detected in vacuum via electrospray ionization mass spectrometry. Their photoelectron spectra reveal a series of well-resolved spectral peaks with their electron binding energies (EBEs) decreasing with increasing halide size, with I having a much stronger effect than Br, i.e., 4.57 (–Cl3) > 4.56 (–Cl2Br) > 4.53 (–ClBr2) > 4.34 (–Cl2I) > 4.30 eV (–ClI2). Ab initio electronic structure calculations including spin-orbit coupling (SOC) predict that the cis- and trans-isomers are nearly isoenergetic with the cis-isomer for –Cl2X, and the trans-isomer for –ClX2 slightly favored, respectively. Excited-state spectra calculated with time-dependent density functional theory (TDDFT), and their comparison with the observed ones, suggest that for each species, both the cis- and trans-configurations coexist in the experiments and contribute to the observed spectra, a fact that clearly violates the prediction of the widely accepted trans-effect, which suggests that only one isomer would have formed.

  5. Asymmetric H-D exchange reactions of fluorinated aromatic ketones

    KAUST Repository

    Zhao, Yujun; Lim, XiaoZhi; Pan, Yuanhang; Zong, Lili; Feng, Wei; Tan, Choonhong; Huang, Kuo-Wei

    2012-01-01

    Chiral bicyclic guanidine catalyzes the asymmetric H-D exchange reactions. Up to 30% ee was achieved. DFT calculations were employed to elucidate and explain the origin of the reaction's stereoselectivity. © 2012 The Royal Society of Chemistry.

  6. Separation of uranium isotopes by accelerated isotope exchange reactions

    International Nuclear Information System (INIS)

    Seko, M.; Miyake, T.; Inada, K.; Ochi, K.; Sakamoto, T.

    1977-01-01

    A novel catalyst for isotope exchange reaction between uranium(IV) and uranium(VI) compounds enables acceleration of the reaction rate as much as 3000 times to make industrial separation of uranium isotopes economically possible

  7. New L-Serine Derivative Ligands as Cocatalysts for Diels-Alder Reaction

    Science.gov (United States)

    Sousa, Carlos A. D.; Rodríguez-Borges, José E.; Freire, Cristina

    2013-01-01

    New L-serine derivative ligands were prepared and tested as cocatalyst in the Diels-Alder reactions between cyclopentadiene (CPD) and methyl acrylate, in the presence of several Lewis acids. The catalytic potential of the in situ formed complexes was evaluated based on the reaction yield. Bidentate serine ligands showed good ability to coordinate medium strength Lewis acids, thus boosting their catalytic activity. The synthesis of the L-serine ligands proved to be highly efficient and straightforward. PMID:24383009

  8. Excitation of giant resonances via charge exchange reactions

    International Nuclear Information System (INIS)

    Goodman, C.D.

    1979-01-01

    Charge-exchange reactions can be useful for identifying isovector resonances. At present the most promising use of charge-exchange reactions with respect to giant resonances is to locate and study Gamow-Teller (GT) resonances. Detailed comparisons between GT and M1 strengths can yield further structure information. 7 figures

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

    Science.gov (United States)

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

    2015-01-01

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

  10. Functionalization of Cadmium Selenide Quantum Dots with Poly(ethylene glycol): Ligand Exchange, Surface Coverage, and Dispersion Stability.

    Science.gov (United States)

    Wenger, Whitney Nowak; Bates, Frank S; Aydil, Eray S

    2017-08-22

    Semiconductor quantum dots synthesized using rapid mixing of precursors by injection into a hot solution of solvents and surfactants have surface ligands that sterically stabilize the dispersions in nonpolar solvents. Often, these ligands are exchanged to disperse the quantum dots in polar solvents, but quantitative studies of quantum dot surfaces before and after ligand exchange are scarce. We studied exchanging trioctylphosphine (TOP) and trioctylphosphine oxide (TOPO) ligands on as-synthesized CdSe quantum dots dispersed in hexane with a 2000 g/mol thiolated poly(ethylene glycol) (PEG) polymer. Using infrared spectroscopy we quantify the absolute surface concentration of TOP/TOPO and PEG ligands per unit area before and after ligand exchange. While 50-85% of the TOP/TOPO ligands are removed upon ligand exchange, only a few are replaced with PEG. Surprisingly, the remaining TOP/TOPO ligands outnumber the PEG ligands, but these few PEG ligands are sufficient to disperse the quantum dots in polar solvents such as chloroform, tetrahydrofuran, and water. Moreover, as-synthesized quantum dots once easily dispersed in hexane are no longer dispersible in nonpolar solvents after ligand exchange. A subtle coverage-dependent balance between attractive PEG-solvent interactions and repulsive TOP/TOPO-solvent interactions determines the dispersion stability.

  11. Isotopic exchange reaction between barium ion and tri barium phosphate

    International Nuclear Information System (INIS)

    Bilgin, G.B.; Cetin, I.

    1982-01-01

    Heterogeneous exchange reaction of tri barium phosphate in barium chloride solution has been studied using 133 Ba as a tracer. The results show that the exchange fraction increases as barium chloride concentration increases for different mole ratio of the exchange ion on the solid surface and in the solution. The phenomenon was studied with respect to the previous treatment of the precipitate leading to different crystal sizes and the effect of reaction time. (author)

  12. Ion exchange and hydrolysis reactions in zeolites

    International Nuclear Information System (INIS)

    Harjula, Risto.

    1993-09-01

    Among other uses, zeolites are efficient cation exchangers for aquatic pollution control. At present they they are mainly used in nuclear waste effluent treatment and in detergency. In the thesis, several ion exchange equilibria, important in these main fields of zeolite applications, were studied, with special emphasis on the formulation and calculation of the equilibria. The main interest was the development of thermodynamic formulations for the calculation of zeolite ion exchange equilibria in solutions of low or very low (trace) ion concentration, which are relevant for the removal of trace pollutants, such as radionuclides, from waste waters. Two groups of zeolite-cation systems were studied. First, binary Ca 2+ /Na + exchange in zeolites X and Y, which are of interest for detergency applications. Second, binary Cs + /Na + and Cs + /K + exchanges, and ternary Cs + /Na + /K + exchange in mordenite, which are important in nuclear waste effluent treatment. The thesis is based on five previous publications by author. (100 refs., 7 figs.)

  13. Isotope exchange reactions in hydrogen mixtures

    International Nuclear Information System (INIS)

    Czaplinski, W.; Gula, A.; Kravtsov, A.; Mikhailov, A.; Popov, N.

    1990-12-01

    The rates of isotopic exchange for the excited states of muonic hydrogen are calculated as functions of collision energy. Ground state population q 1s for different collision energies, target densities and isotope concentrations is obtained. It is shown that for principal quantum numbers n > 5 the isotopic exchange still considerably influences the value of q 1s . (author)

  14. Ligand exchange chromatography of free amino acids and proteins on porous microparticulate zirconium oxide

    International Nuclear Information System (INIS)

    Blackwell, J.A.; Carr, P.W.

    1992-01-01

    The Lewis acid sites present on the underlying zirconium oxide particles are responsible for the unusual elution sequence for amino acids on copper loaded, phosphated zirconium oxide supports reported in an earlier study. To more thoroughly examine the effect of these strong Lewis acid sites in this paper. The authors have studied ligand exchange chromatography on copper loaded zirconium oxide particles. It is shown here that carboxylate functional groups on amino acid solutes strongly interact with surface Lewis acid sites. Addition of competing hard Lewis bases to the eluent attenuates these specific interactions. The result is a chromatographic system with high selectivity which is also suitable for ligand exchange chromatography of proteins

  15. Study of isotopic exchange reactions of azidothymidine with tritium

    International Nuclear Information System (INIS)

    Sidorov, G.V.; Zverkov, Yu.B.; Myasoedov, N.F.

    2003-01-01

    Different reactions of isotopic exchange of azidothymidine (3 - azido-3 - desoxythymidine) with tritium, such as solid- and liquid-phase catalytic isotopic exchange with gaseous tritium and isotopic exchange in solution with tritium water, are investigated. It is determined that catalytic reactions of azidothymidine with gaseous tritium in solution lead to practically full reduction of azido group up to amino group. In reactions of solid-phase catalytic hydrogenation this process takes place too and 3 - azido-3 - desoxythymidine yield is from 20 to 70 %. Molar radioactivity of labelled with tritium azidothymidine prepared in reactions of solid-phase catalytic isotopic exchange with gaseous tritium and so by isotopic exchange in solution with tritium water does not exceed 0.5 Cu/mmol [ru

  16. Fine-tuning the Wall Thickness of Ordered Mesoporous Graphene by Exploiting Ligand Exchange of Colloidal Nanocrystals

    Science.gov (United States)

    Han, Dandan; Yan, Yancui; Wei, Jishi; Wang, Biwei; Li, Tongtao; Guo, Guannan; Yang, Dong; Xie, Songhai; Dong, Angang

    2017-12-01

    Because of their unique physical properties, three-dimensional (3D) graphene has attracted enormous attention over the past years. However, it is still a challenge to precisely control the layer thickness of 3D graphene. Here, we report a novel strategy to rationally adjust the wall thickness of ordered mesoporous graphene (OMG). By taking advantage of ligand exchange capability of colloidal Fe3O4 nanocrystals, we are able to fine-tune the wall thickness of OMG from 2 to 6 layers of graphene by tailoring the hydrocarbon ligands attached to the nanocrystal surface. When evaluated as electrocatalyst for oxygen reduction reaction upon S and N doping, the 4-layer OMG is found to show better catalytic performance compared with its 2- and 6-layer counterparts, which we attribute to the enhanced exposure of active sites resulting from its ultrathin wall thickness and high surface area.

  17. Isotope exchange reaction in uranous-uranyl-sulphuric acid system

    International Nuclear Information System (INIS)

    Ling Daren; Yue Tingsheng; Mu Dehai; Wang Yani

    1990-01-01

    The kinetics of the isotope exchange reaction between U(IV) and U(VI) has been studied in low concentrations of sulphuric acid. A minimum exchange rate appears at 0.25 M H 2 SO 4 . From the rates at different temperatures ranging from 20deg to 35deg C, an apparent activation energy of 86 kcal/mole was calculated. The exchange rate was found to be accelerated by the addition of ferrous ions, and a half-life of less than 1 s, was obtained. Probable mechanisms for the acceleration of the uranium isotope exchange reactions by acidity and ferrous ions are proposed. (orig.)

  18. Kinetics and Mechanism of the Ligand Exchange Reaction Between ...

    African Journals Online (AJOL)

    NICO

    11 Y. Fan, W. You, W. Huang, J.L. Liu and Y.N. Wang, Salen-type nickel(II) ... 16 R. Vafazadeh, B. Khaledi and A.C. Willis, Synthesis and crystal struc- ture of a new ... 24 M.K. Taylor, J. Reglinski and D. Wallace, Coordination geometry.

  19. Determination of kinetic parameters of heterogeneous isotopic exchange reaction

    International Nuclear Information System (INIS)

    Huang, Ting-Chia; Tsai, Fuan-Nan

    1977-01-01

    A mathematical model has been proposed for a heterogeneous isotopic exchange reaction which involves film diffusion, surface chemical reaction and intraparticle diffusion. The exchange equation to predict the exchange fraction as a function of time for the spherical particles immersed in a solution of finite volume has been derived. The relations between the exchange fraction and dimensionless time are plotted with xi(=ak sub(f)/KD sub(e)), xi 1 (=K 1 a 2 /D sub(e)) and final fractional uptake as parameters. From the values of the kinetic parameters xi and xi 1 , the relative importance of each limiting step is discussed. Experimental results of the isotopic exchange reaction of calcium ion in both system CaCO 3 (s)/Ca 2+ (aq) and system calcium type resin Dowex 50W-X8/Ca 2+ (aq) are coincident with the theoretical equation proposed in this study. (auth.)

  20. Neat and complete: Thiolate-ligand exchange on a silver molecular nanoparticle

    KAUST Repository

    AbdulHalim, Lina G.

    2014-11-12

    Atomically precise thiolate-protected noble metal molecular nanoparticles are a promising class of model nanomaterials for catalysis, optoelectronics, and the bottom-up assembly of true molecular crystals. However, these applications have not fully materialized due to a lack of ligand exchange strategies that add functionality, but preserve the properties of these remarkable particles. Here we present a method for the rapid (<30 s) and complete thiolate-for-thiolate exchange of the highly sought after silver molecular nanoparticle [Ag44(SR)30]-4. Only by using this method were we able to preserve the precise nature of the particles and simultaneously replace the native ligands with ligands containing a variety of functional groups. Crucially, as a result of our method we were able to process the particles into smooth thin films, paving the way for their integration into solution-processed devices.

  1. Neat and complete: Thiolate-ligand exchange on a silver molecular nanoparticle

    KAUST Repository

    AbdulHalim, Lina G.; Kothalawala, Nuwan; Sinatra, Lutfan; Dass, Amala; Bakr, Osman

    2014-01-01

    Atomically precise thiolate-protected noble metal molecular nanoparticles are a promising class of model nanomaterials for catalysis, optoelectronics, and the bottom-up assembly of true molecular crystals. However, these applications have not fully materialized due to a lack of ligand exchange strategies that add functionality, but preserve the properties of these remarkable particles. Here we present a method for the rapid (<30 s) and complete thiolate-for-thiolate exchange of the highly sought after silver molecular nanoparticle [Ag44(SR)30]-4. Only by using this method were we able to preserve the precise nature of the particles and simultaneously replace the native ligands with ligands containing a variety of functional groups. Crucially, as a result of our method we were able to process the particles into smooth thin films, paving the way for their integration into solution-processed devices.

  2. Samarium ion exchanged montmorillonite for high temperature cumene cracking reaction

    International Nuclear Information System (INIS)

    Binitha, N.N.

    2009-01-01

    Full text: Nano material 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 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 Bronsted acidity is confirmed from high selectivity to benzene. (author)

  3. Thermo-Kinetic Investigation of Comparative Ligand Effect on Cysteine Iron Redox Reaction

    Directory of Open Access Journals (Sweden)

    Masood Ahmad Rizvi

    2015-03-01

    Full Text Available Transition metal ions in their free state bring unwanted biological oxidations generating oxidative stress. The ligand modulated redox potential can be indispensable in prevention of such oxidative stress by blocking the redundant bio-redox reactions. In this study we investigated the comparative ligand effect on the thermo-kinetic aspects of biologically important cysteine iron (III redox reaction using spectrophotometric and potentiometric methods. The results were corroborated with the complexation effect on redox potential of iron(III-iron(II redox couple. The selected ligands were found to increase the rate of cysteine iron (III redox reaction in proportion to their stability of iron (II complex (EDTA < terpy < bipy < phen. A kinetic profile and the catalytic role of copper (II ions by means of redox shuttle mechanism for the cysteine iron (III redox reaction in presence of 1,10-phenanthroline (phen ligand is also reported.

  4. Using reactive artificial muscles to determine water exchange during reactions

    International Nuclear Information System (INIS)

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

    2013-01-01

    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. (paper)

  5. Thermo-Kinetic Investigation of Comparative Ligand Effect on Cysteine Iron Redox Reaction

    OpenAIRE

    Rizvi, Masood Ahmad; Teshima, Norio; Maqsood, Syed Raashid; Akhoon, Showket Ahmad; Peerzada, Ghulam Mustafa

    2015-01-01

    Transition metal ions in their free state bring unwanted biological oxidations generating oxidative stress. The ligand modulated redox potential can be indispensable in prevention of such oxidative stress by blocking the redundant bio-redox reactions. In this study we investigated the comparative ligand effect on the thermo-kinetic aspects of biologically important cysteine iron (III) redox reaction using spectrophotometric and potentiometric methods. The results were corroborated...

  6. Forward pion-nucleon charge exchange reaction and Regge constraints

    International Nuclear Information System (INIS)

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

    2009-01-01

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

  7. On the treatment of exchange effects in direct reactions

    International Nuclear Information System (INIS)

    Bencze, G.; Chandler, C.; Argonne National Lab., IL; New Mexico Univ., Albuquerque

    1985-01-01

    Exchange effects in direct reactions are investigated in the framework of the general algebraic theory of identical particle scattering. It is shown that effects due to the permutation symmetry of the system can be separated from the treatment of reaction dynamics. Dynamical aspects of the problem are investigated within the framework of the channel coupling class of N-body theories. (orig.)

  8. Nucleon charge-exchange reactions at intermediate energy

    International Nuclear Information System (INIS)

    Alford, W.P.; Spicer, B.M.

    1997-01-01

    An historical review of the development of ideas pertaining to Gamow-Teller giant resonances is given, and a description of the emergence of techniques for the study of charge exchange reactions - particularly the technical advances which yielded the recent volume of new date. The present status of charge exchange reactions is reviewed and assessed. Evidence is presented from the 14 C(p,n) reaction for the dominance of the spin-isospin component of the nucleon-nucleon interaction in intermediate energy reactions. In (p,n) reactions the Gamow-Teller giant resonance dominates the spectra, with higher multipoles contributing. By contrast, in (n,p) reactions in the heavier nuclei, the Gamow-Teller transitions are substantially Pauli-blocked and the spin dipole resonance dominates, with contributions from higher multipoles. Discussions of the multipole decomposition process, used to obtain from the data the contributions of the different multipoles, and the contributions of the multipoles, are given

  9. Studies of nuclear structure in antinucleon charge-exchange reactions

    International Nuclear Information System (INIS)

    Auerbach, N.

    1986-01-01

    The antinucleon-nucleus charge exchange reaction is discussed an its use as a probe of isovector excitations in nuclei is described. Attention is drawn to the fact that the (anti p,anti n) reaction will predominantly excite ''pionic'' (i.e., longitudinal spin) modes in nuclei. Comparison between (anti p,anti n) and (n,p) reactions is made. Plans for (anti p,anti n) experiments in the near future are mentioned. 21 refs., 3 figs

  10. Quaternary Cu2ZnSnS4 quantum dot-sensitized solar cells: Synthesis, passivation and ligand exchange

    Science.gov (United States)

    Bai, Bing; Kou, Dongxing; Zhou, Wenhui; Zhou, Zhengji; Tian, Qingwen; Meng, Yuena; Wu, Sixin

    2016-06-01

    The quaternary Cu2ZnSnS4 (CZTS) QDs had been successfully introduced into quantum dot-sensitized solar cells (QDSC) via hydrolysis approach in our previous work [Green Chem. 2015, vol. 17, p. 4377], but the obtained cell efficiency was still limited by low open-circuit voltage and fill factor. Herein, we use 1-dodecanethiol (DDT) as capping ligand for fairly small-sized CZTS QDs synthesis to improve their intrinsic properties. Since this strong bonded capping ligand can not be replaced by 3-mercaptopropionic acid (MPA) directly, the nature cation (Cu, Zn or Sn)-DDT units of QDs are first exchanged by the preconjugated Cd-oleate via successive ionic layer adsorption and reaction (SILAR) procedure accompanied with the formation of a core/shell structure. The weak bonded oleic acid (OA) can be finally replaced by MPA and the constructed water soluble CZTS/CdSe QDSC achieves an impressive conversion efficiency of 4.70%. The electron transport and recombination dynamic processes are confirmed by intensity-modulated photocurrent spectroscopy (IMPS)/intensity-modulated photovoltage spectroscopy (IMVS) measurements. It is found that the removal of long alkyl chain is conducive to improve the electron transport process and the type-II core/shell structure is beneficial to accelerate electron transport and retard charge recombination. This effective ligand removal strategy is proved to be more convenient for the applying of quaternary QDs in QDSC and would boost a more powerful efficiency in the future work.

  11. Ligand isotopic exchange of tris(acetylacetonato)germanium(IV) perchlorate in organic solvents

    International Nuclear Information System (INIS)

    Nagasawa, Akira; Saito, Kazuo

    1978-01-01

    The ligand isotopic exchange between tris(acetylacetonato)germanium(IV) perchlorate and acetylacetone[ 14 C] has been studied in 1,1,2,2-tetrachloroethane (TCE), nitromethane (NM), and acetonitrile (AN), at 100 - 120 0 C. In these solvents, the rate formula was R = k[H 2 O][complex]; the concentrations of the complex, free ligand, and water in solution were in the ranges from 0.01 to 0.1 mol dm -3 . The activation enthalpies and entropies for the k's are 105, 98, and 90 kJ mol -1 ; and -25, -53, and -69 JK -1 mol -1 , in TCE, NM, and AN, respectively. Influence of acid and base concentrations, and deuterium isotope effect on the rate in AN suggest that the rate controlling step of the exchange is governed by the ease of the proton transfer between the leaving and the incoming acac - in an intermediate. (auth.)

  12. One ligand capable of in situ reaction in a mixed-ligand system with two new different frameworks

    KAUST Repository

    Wang, Xiaofang

    2017-12-24

    The in situ ligand 2,3-pyrazinedicarboxylic acid (2,3-H2pzdc) mixed with 1,1′-(1,4-butanediyl)bis(benzimidazole) (bbbi) is used to form two coordination polymers ([Cd(2,3-pzdc)(bbbi)] (1) and [Cd2Cl3(2-pzc)(bbbi)2] (2)) under hydrothermal conditions. Complex 1 was obtained in the absence of in situ reaction and 2 was synthesized with 2,3-H2pzdc in situ generating 2-pyrazinecarboxylate (2-pzc−). The structural details reveal that 1 has a 3D framework with dia topology, and 2 is a 2D layer structure and develops a 3D supramolecular structure via strong π⋯π stacking interactions. The ligand effects were compared for the two frameworks. In addition, fluorescence properties and thermal stabilities of 1 and 2 in the solid were studied.

  13. Identification of individual protein-ligand NOEs in the limit of intermediate exchange

    International Nuclear Information System (INIS)

    Reibarkh, Mikhail; Malia, Thomas J.; Hopkins, Brian T.; Wagner, Gerhard

    2006-01-01

    Interactions of proteins with small molecules or other macromolecules play key roles in many biological processes and in drug action, and NMR is an excellent tool for their structural characterization. Frequently, however, line broadening due to intermediate exchange completely eliminates the signals needed for measuring specific intermolecular NOEs. This limits the use of NMR for detailed structural studies in such kinetic situations. Here we show that an optimally chosen excess of ligand over protein can reduce the extent of line broadening for both the ligand and the protein. This makes observation of ligand resonances possible but reduces the size of the measurable NOEs due to the residual line broadening and the non-stoichiometric concentrations. Because the solubility of small molecule drug leads are often limited to high micromolar concentrations, protein concentrations are restricted to even lower values in the low micromolar range. At these non-stoichiometric concentrations and in the presence of significant residual line broadening, conventional NOESY experiments very often are not sensitive enough to observe intermolecular NOEs since the signals inverted by the NOESY preparation pulse sequence relax prior to significant NOE build up. Thus, we employ methods related to driven NOE spectroscopy to investigate protein-ligand interactions in the intermediate exchange regime. In this approach, individual protein resonances are selectively irradiated for up to five seconds to build up measurable NOEs at the ligand resonances. To enable saturation of individual protein resonances we prepare deuterated protein samples selectively protonated at a few sites so that the 1D 1 H spectrum of the protein is resolved well enough to permit irradiation of individual protein signals, which do not overlap with the ligand spectrum. This approach is suitable for measuring a sufficiently large number of protein-ligand NOEs that allow calculation of initial complex structures

  14. Electron exchange reaction in anion exchangers as observed in uranium isotope separation

    International Nuclear Information System (INIS)

    Obanawa, Heiichiro; Takeda, Kunihiko; Seko, Maomi

    1991-01-01

    The mechanism of electron exchange in an ion exchanger, as occurring between U 4+ and UO 2 2+ in uranium isotope separation, was investigated. The height of the separation unit (H q ) in the presence of metal ion catalysts, as obtained from the separation experiments, was found to be almost coincident with the theoretical value of H q as calculated on the basis of the intrasolution acceleration mechanism of the metal ion, suggesting that the electron exchange mechanism in the ion-exchanger is essentially the same as that in the solution when metal ion catalysts are present. Separation experiments with no metal ion catalyst, on the other hand, showed the electron exchange reaction in the ion exchanger to be substantially higher than that in the solution, suggesting an acceleration of the electron exchange reaction by the ion-exchanger which is due to the close existence of higher order Cl - complexes of UO 2 2+ and U 4+ in the vicinity of the ion-exchange group. (author)

  15. On the mesonic-exchange currents in the photomesic reactions

    International Nuclear Information System (INIS)

    Lazard, C.; Maric, Z.; Zivanovic, D.

    1979-02-01

    The γd→π 0 d reaction is analysed in the framework of the relativistic many-body theory with mesonic degrees of freedom explicitly present. It is shown that the mesonic correlations can be grouped into transition operators containing vertices of some elementary reactions between photon, nucleons and pions. The wave function corrections due to meson exchange currents are included in the transition operators and the S-matrix is obtained with the non relativistic deuteron wave function

  16. Ultrafiltration technique in conjunction with competing ligand exchange method for Ni–humics speciation in aquatic environment

    Digital Repository Service at National Institute of Oceanography (India)

    Chakraborty, P.; Boissel, M.; Reuillon, A.; Babu, P.V.R.; Parthiban, G.

    The combination of ultrafiltration technique with competing ligand exchange method provides a better understanding of interactions between Ni and different molecular weight fractions of humic acid (HA) at varying pH in aquatic environment...

  17. Hydrogen/Chlorine exchange reactions of gaseous carbanions.

    Science.gov (United States)

    Chen, Hao; Cooks, R Graham; Meurer, Eduardo C; Eberlin, Marcos N

    2005-12-01

    Gas-phase reactions of three typical carbanions CH(2)NO(2)(-), CH(2)CN(-), and CH(2)S(O)CH(3)(-) with the chloromethanes CH(2)Cl(2), CHCl(3), and CCl(4), examined by tandem mass spectrometry, show a novel hydrogen/chlorine exchange reaction. For example, reaction between the nitromethyl anion CH(2)NO(2)(-) and carbon tetrachloride CCl(4) forms the ion CHClNO(2)(-). The suggested reaction mechanism involves nucleophilic attack by CH(2)NO(2)(-) at the chlorine of CCl(4) followed by proton transfer within the resulting complex [CH(2)ClNO(2) + CCl(3)(-)] to form CHClNO(2)(-) and CHCl(3). Two other carbanions CH(2)CN(-) and CH(2)S(O)CH(3)(-) also undergo the novel hydrogen/chlorine exchange reactions with CCl(4) but to a much smaller extent, their higher nucleophilicities favoring competitive nucleophilic attack reactions. Proton abstraction is the exclusive pathway in the reactions of these carbanions with CHCl(3). While CH(2)CN(-) and CH(2)S(O)CH(3)(-) promote mainly proton abstraction and nucleophilic displacement in reactions with CH(2)Cl(2), CH(2)NO(2)(-) does not react.

  18. The Ligand Substitution Reactions of Hydrophobic Vitamin B12 ...

    African Journals Online (AJOL)

    South African Journal of Chemistry ... The equilibrium constants, K, for the reaction of five-membered heterocyclic nitrogenous bases (the azoles imidazole, pyrazole and 1,2,4-triazole) with displacement of ... Keywords: Hydrophobic vitamin B12, cobalt corrinoids, equilibrium constants, solvent polarity, trans influence.

  19. Surface polyPEGylation of Eu3+ doped luminescent hydroxyapatite nanorods through the combination of ligand exchange and metal free surface initiated atom transfer radical polymerization

    Science.gov (United States)

    Zeng, Guangjian; Liu, Meiying; Heng, Chunning; Huang, Qiang; Mao, Liucheng; Huang, Hongye; Hui, Junfeng; Deng, Fengjie; Zhang, Xiaoyong; Wei, Yen

    2017-03-01

    The Eu3+ doped luminescent hydroxyapatite (HAp) nanorods with uniform size and morphology can be synthesized by hydrothermal route. However, these HAp nanorods are coated by hydrophobic oleylamine, which makes them difficult to be dispersed in aqueous solution and impede their biomedical applications. In this work, Eu3+ doped luminescent polymers functionalized HAp nanorods were prepared through the combination of ligand exchange reaction and metal free surface initiated atom transfer radical polymerization (ATRP) method. In this procedure, the amino group functionalized HAp nanorods were first prepared by ligand exchange reaction using adenosine monophosphate (AMP) as ligand. Then the Br-containing initiators (HAp-Br) were introduced onto the surface of HAp-AMP nanorods through the amidation reaction. Finally, polymers functionalized HAp nanorods were prepared by metal free ATRP method using poly(ethylene glycol) methacrylate (PEGMA) as monomer and 10-phenylphenothiazine (PTH) as organic photocatalyst. The properties of these obtained HAp nanocomposites (HAP-polyPEGMA nanorods) were characterized by means of transmission electron microscopy, Fourier transformed infrared spectroscopy, X-ray photoelectron spectroscopy and thermogravimetric analysis in detail. The cell imaging of these HAP-polyPEGMA nanorods was examined using laser scanning confocal microscope to evaluate their biomedical applications. We demonstrated for the first time that hydrophobic luminescent HAp nanorods can be functionalized with polyPEGMA through the combination of ligand exchange reaction and metal free surface initiated ATRP. As compared with the traditional ATRP, the metal free ATRP can overcome the toxic and fluorescence quenching effects of metal catalysts such as copper ions. More importantly, the strategy described in this work should also be utilized for fabrications of many other luminescent polymer nanocomposites due to its good monomer adoptability.

  20. Fine-Tuning the Wall Thickness of Ordered Mesoporous Graphene by Exploiting Ligand Exchange of Colloidal Nanocrystals

    Directory of Open Access Journals (Sweden)

    Dandan Han

    2017-12-01

    Full Text Available Because of their unique physical properties, three-dimensional (3D graphene has attracted enormous attention over the past years. However, it is still a challenge to precisely control the layer thickness of 3D graphene. Here, we report a novel strategy to rationally adjust the wall thickness of ordered mesoporous graphene (OMG. By taking advantage of ligand exchange capability of colloidal Fe3O4 nanocrystals, we are able to fine-tune the wall thickness of OMG from 2 to 6 layers of graphene. When evaluated as electrocatalyst for oxygen reduction reaction upon S and N doping, the 4-layer OMG is found to show better catalytic performance compared with their 2- and 6-layer counterparts, which we attribute to the enhanced exposure of active sites arising from the thin wall thickness and high surface area.

  1. Exchange reaction between tritiated hydrogen and water vapor

    International Nuclear Information System (INIS)

    Yamada, Koichi; Takano, Kenichi; Watanabe, Tamaki.

    1979-01-01

    Exchange reaction of tritiated hydrogen to water vapor under the condition of tritium gas concentration between 1 μCi/l and 1 mCi/l was studied. Tritium gas with hydrogen gas of 5 Torr and water of 20 mg were enclosed in a Pyrex glass ampule with volume of about 100 ml. The mixed gas with water vapor was heated with electric furnace. The heating time was between 2 and 100 hr, and the temperature was 776, 725, 675, 621, and 570.5 0 K. After heating, tritiated water was trapped with liquid nitrogen, and counted with a liquid scintillation counter. The radioactive concentration of initial tritiated hydrogen was measured with a calibrated ionization chamber. The main results obtained are as follows; 1) the concentration of produced tritiated water is well proportioned to that of initial tritiated hydrogen, 2) the activation energy of exchange reaction from tritiated hydrogen to tritiated water is 26.2 kcal/mol and that of inverse reaction is 27.4 kcal/mol, 3) the reaction rate at room temperature which calculated with activation energy is 1.04 x 10 -13 day -1 , and then exchange reaction at room temperature is negligible. (author)

  2. Study of substitution reactions of ligands in VO2+ complexes in toluene solutions by ESR method

    International Nuclear Information System (INIS)

    Lundkvist, R.; Panfilov, A.T.; Kalinichenko, N.B.; Marov, I.N.; AN SSSR, Moscow. Inst. Geokhimii i Analiticheskoj Khimii)

    1976-01-01

    Kinetics and equilibrium of stepwise substitution of ligands have been investigated at different temperatures for the complexes of oxovanadium (4) with salicylaldoxime, 8-oxyquinoline, acetylacetone, benzoylacetone, and tenoyltrifluoroacetone. The relative complexability of these ligands in toluene has been studied. The parameters of spin-Hamiltonian of EPR spectra of the VO 2+ complexes have been determined. The equilibrium constants, the rate constants, and activation energy have been found for the substitution reactions of ligands in the complexes VOA 2 : VOA 2 +HB=VOAB+HA; VOAB+HB=VOB 2 +HA, where HA and HB are the ligands with different donor atoms. The mixed complexes have been detected of the general formula VOAB, where HA is salicylaldoxime or 8-oxyquinoline and HB is β-diketone

  3. Comparative study on bromide and iodide ion-isotopic exchange reactions using strongly basic anion exchange resin Duolite A-113

    International Nuclear Information System (INIS)

    Lokhande, R.S.; Dole, M.H.; Singare, P.U.

    2006-01-01

    Kinetics of ion-isotopic exchange reaction was studied using industrial grade ion exchange resin Duolite A-113. The radioactive isotopes 131 I and 82 Br were used to trace the ion-isotopic exchange reaction. The experiments were performed in the temperature range of 26.0degC to 43.0degC and the concentration of external ionic solution varying from 0.005 M to 0.100 M. For bromide ion-isotopic exchange reaction, the calculated values of specific reaction rate, initial rate of bromide ion exchange, and amount of bromide ions exchanged were obtained higher than that for iodide ion-isotopic exchange reaction under identical experimental conditions. The observed variation in the results for two ion-isotopic exchange reactions was due to the difference in the ionic size of bromide and iodide ions. (author)

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

    Science.gov (United States)

    Kalinova, Radostina; Jossifov, Christo

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

  5. S,O-Ligand-Promoted Palladium-Catalyzed C-H Functionalization Reactions of Nondirected Arenes

    NARCIS (Netherlands)

    Naksomboon, K.; Valderas, C.; Gomez-Martinez, M.; Alvarez-Casao, Y.; Fernández Ibáñez, M.A.

    Pd(II)-catalyzed C-H functionalization of non directed arenes has been realized using an inexpensive and easily accessible type of bidentate S,O-ligand. The catalytic system shows high efficiency in the C-H olefination reaction of electron-rich and electron-poor arenes. This methodology is

  6. Surface polyPEGylation of Eu{sup 3+} doped luminescent hydroxyapatite nanorods through the combination of ligand exchange and metal free surface initiated atom transfer radical polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, Guangjian; Liu, Meiying [Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031 (China); Heng, Chunning [Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031 (China); Shaanxi Key Laboratory of Degradable Biomedical Materials, Shaanxi R& D Center of Biomaterials and Fermentation Engineering, School of Chemical and Engineering, Northwest University, Xi’an 710069 (China); Huang, Qiang; Mao, Liucheng; Huang, Hongye [Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031 (China); Hui, Junfeng [Shaanxi Key Laboratory of Degradable Biomedical Materials, Shaanxi R& D Center of Biomaterials and Fermentation Engineering, School of Chemical and Engineering, Northwest University, Xi’an 710069 (China); Deng, Fengjie, E-mail: fengjiedeng@aliyun.com [Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031 (China); Zhang, Xiaoyong, E-mail: xiaoyongzhang1980@gmail.com [Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031 (China); Wei, Yen, E-mail: weiyen@tsinghua.edu.cn [Department of Chemistry and The Tsinghua Center for Frontier Polymer Research, Tsinghua University, Beijing 100084 (China)

    2017-03-31

    Highlights: • Surface modification of HAp nanorods through the combination of ligand exchange reaction and metal free SI-ATRP. • HAp-polyPEGMA displayed high water dispersibility, good biocompatibility and biological imaging capability. • Metal free ATRP can overcome the toxic and fluorescence quenching effects of metal catalysts of conventional ATRP. - Abstract: The Eu{sup 3+} doped luminescent hydroxyapatite (HAp) nanorods with uniform size and morphology can be synthesized by hydrothermal route. However, these HAp nanorods are coated by hydrophobic oleylamine, which makes them difficult to be dispersed in aqueous solution and impede their biomedical applications. In this work, Eu{sup 3+} doped luminescent polymers functionalized HAp nanorods were prepared through the combination of ligand exchange reaction and metal free surface initiated atom transfer radical polymerization (ATRP) method. In this procedure, the amino group functionalized HAp nanorods were first prepared by ligand exchange reaction using adenosine monophosphate (AMP) as ligand. Then the Br-containing initiators (HAp-Br) were introduced onto the surface of HAp-AMP nanorods through the amidation reaction. Finally, polymers functionalized HAp nanorods were prepared by metal free ATRP method using poly(ethylene glycol) methacrylate (PEGMA) as monomer and 10-phenylphenothiazine (PTH) as organic photocatalyst. The properties of these obtained HAp nanocomposites (HAP-polyPEGMA nanorods) were characterized by means of transmission electron microscopy, Fourier transformed infrared spectroscopy, X-ray photoelectron spectroscopy and thermogravimetric analysis in detail. The cell imaging of these HAP-polyPEGMA nanorods was examined using laser scanning confocal microscope to evaluate their biomedical applications. We demonstrated for the first time that hydrophobic luminescent HAp nanorods can be functionalized with polyPEGMA through the combination of ligand exchange reaction and metal free surface

  7. Surface polyPEGylation of Eu"3"+ doped luminescent hydroxyapatite nanorods through the combination of ligand exchange and metal free surface initiated atom transfer radical polymerization

    International Nuclear Information System (INIS)

    Zeng, Guangjian; Liu, Meiying; Heng, Chunning; Huang, Qiang; Mao, Liucheng; Huang, Hongye; Hui, Junfeng; Deng, Fengjie; Zhang, Xiaoyong; Wei, Yen

    2017-01-01

    Highlights: • Surface modification of HAp nanorods through the combination of ligand exchange reaction and metal free SI-ATRP. • HAp-polyPEGMA displayed high water dispersibility, good biocompatibility and biological imaging capability. • Metal free ATRP can overcome the toxic and fluorescence quenching effects of metal catalysts of conventional ATRP. - Abstract: The Eu"3"+ doped luminescent hydroxyapatite (HAp) nanorods with uniform size and morphology can be synthesized by hydrothermal route. However, these HAp nanorods are coated by hydrophobic oleylamine, which makes them difficult to be dispersed in aqueous solution and impede their biomedical applications. In this work, Eu"3"+ doped luminescent polymers functionalized HAp nanorods were prepared through the combination of ligand exchange reaction and metal free surface initiated atom transfer radical polymerization (ATRP) method. In this procedure, the amino group functionalized HAp nanorods were first prepared by ligand exchange reaction using adenosine monophosphate (AMP) as ligand. Then the Br-containing initiators (HAp-Br) were introduced onto the surface of HAp-AMP nanorods through the amidation reaction. Finally, polymers functionalized HAp nanorods were prepared by metal free ATRP method using poly(ethylene glycol) methacrylate (PEGMA) as monomer and 10-phenylphenothiazine (PTH) as organic photocatalyst. The properties of these obtained HAp nanocomposites (HAP-polyPEGMA nanorods) were characterized by means of transmission electron microscopy, Fourier transformed infrared spectroscopy, X-ray photoelectron spectroscopy and thermogravimetric analysis in detail. The cell imaging of these HAP-polyPEGMA nanorods was examined using laser scanning confocal microscope to evaluate their biomedical applications. We demonstrated for the first time that hydrophobic luminescent HAp nanorods can be functionalized with polyPEGMA through the combination of ligand exchange reaction and metal free surface initiated

  8. Nucleon charge-exchange reactions at intermediate energy

    Energy Technology Data Exchange (ETDEWEB)

    Alford, W.P. [Western Ontario Univ., London, ON (Canada). Dept. of Physics]|[TRIUMF, Vancouver, BC (Canada); Spicer, B.M. [Melbourne Univ., Parkville, VIC (Australia). School of Physics

    1997-12-31

    An historical review of the development of ideas pertaining to Gamow-Teller giant resonances is given, and a description of the emergence of techniques for the study of charge exchange reactions - particularly the technical advances which yielded the recent volume of new date. The present status of charge exchange reactions is reviewed and assessed. Evidence is presented from the {sup 14}C(p,n) reaction for the dominance of the spin-isospin component of the nucleon-nucleon interaction in intermediate energy reactions. In (p,n) reactions the Gamow-Teller giant resonance dominates the spectra, with higher multipoles contributing. By contrast, in (n,p) reactions in the heavier nuclei, the Gamow-Teller transitions are substantially Pauli-blocked and the spin dipole resonance dominates, with contributions from higher multipoles. Discussions of the multipole decomposition process, used to obtain from the data the contributions of the different multipoles, and the contributions of the multipoles, are given. 226 refs., 19 figs.

  9. Charge exchange reactions and the efficiency of solar neutrino detectors

    International Nuclear Information System (INIS)

    Austin, S.M.; Anantaraman, N.; Love, W.G.

    1994-01-01

    The efficiencies of solar neutrino detectors are often based in part on weak interaction strengths determined by (p,n) and other charge exchange reactions. Although the (p,n) determinations are surprisingly good, it is shown that they may be inaccurate for important Gamow-Teller transitions whose strengths are a small fraction of the sum rule limit. This emphasizes the importance of direct calibration with ν sources for detectors such as 127 I and 115 In where direct β-decay information cannot be obtained. It may also bear on recent attempts to compare charge exchange and beta decay in the mass-37 system

  10. Investor Reaction to Mandatory Offers on the Warsaw Stock Exchange

    Directory of Open Access Journals (Sweden)

    Szymon Okoń

    2012-06-01

    Full Text Available The following paper aims to assess investor reaction to mandatory offers on the Warsaw Stock Exchange, which is important because knowledge about these reactions can be used to make better investment decisions. This paper highlights the importance of procedure in making a mandatory offer and its grounds in the Polish legal system. Additionally, it presents empirical research on the reactions of investors to mandatory offers on the Warsaw Stock Exchange. It has been provided that mandatory offers have a significant impact on the price of a company’s shares listed on the Warsaw Stock Exchange. Knowledge about the reactions of investors to a mandatory offer may be used when selecting securities for an investment portfolio. The findings may provide guidance in deciding whether to begin or end investment in the company, both for individual and institutional investors. The event study methodology approach used in the paper is regarded as valuable and can be the basis for further research in other areas of the capital market research, especially in the context of information efficiency.

  11. Ligand-tailored single-site silica supported titanium catalysts: Synthesis, characterization and towards cyanosilylation reaction

    International Nuclear Information System (INIS)

    Xu, Wei; Li, Yani; Yu, Bo; Yang, Jindou; Zhang, Ying; Chen, Xi; Zhang, Guofang; Gao, Ziwei

    2015-01-01

    A successive anchoring of Ti(NMe 2 ) 4 , cyclopentadiene and a O-donor ligand, 1-hydroxyethylbenzene (PEA), 1,1′-bi-2-naphthol (Binol) or 2,3-dihydroxybutanedioic acid diethyl ester (Tartrate), on silica was conducted by SOMC strategy in moderate conditions. The silica, monitored by in-situ Fourier transform infrared spectroscopy (in-situ FT-IR), was pretreated at different temperatures (200, 500 and 800 °C). The ligand tailored silica-supported titanium complexes were characterized by in-situ FT-IR, 13 C CP MAS-NMR, X-ray photoelectron spectroscopy (XPS), X-ray absorption near edge structure (XANES) and elemental analysis in detail, verifying that the surface titanium species are single sited. The catalytic activity of the ligand tailored single-site silica supported titanium complexes was evaluated by a cyanosilylation of benzaldehyde. The results showed that the catalytic activity is dependent strongly on the dehydroxylation temperatures of silica and the configuration of the ligands. - Graphical abstract: The ligand-tailored silica supported “single site” titanium complexes were synthesized by SOMC strategy and fully characterized. Their catalytic activity were evaluated by benzaldehyde silylcyanation. - Highlights: • Single-site silica supported Ti active species was prepared by SOMC technique. • O-donor ligand tailored Ti surface species was synthesized. • The surface species was characterized by XPS, 13 C CP-MAS NMR, XANES etc. • Catalytic activity of the Ti active species in silylcyanation reaction was evaluated

  12. A Ligand Structure-Activity Study of DNA-Based Catalytic Asymmetric Hydration and Diels-Alder Reactions

    NARCIS (Netherlands)

    Rosati, F.; Roelfes, J.G.

    A structure-activity relationship study of the first generation ligands for the DNA-based asymmetric hydration of enones and Diels-Alder reaction in water is reported. The design of the ligand was optimized resulting in a maximum ee of 83% in the hydration reaction and 75% in the Diels-Alder

  13. Anion exchange chromatography of 99mTc(Sn)-EHDP complexes: determination of the charge of the components and influence of pH and ligand concentration

    International Nuclear Information System (INIS)

    Huigen, Y.M.; Diender, M.; Gelsema, W.J.; De Ligny, C.L.

    1991-01-01

    The components of a 99m Tc(Sn)-EHDP complex mixture were separated by means of normal pressure and high-pressure anion exchange chromatography. Precautions were taken to prevent the dissociation of the complexes during chromatography. The charges of the components were determined according to the methods of Wilson and Pinkerton (1985) and Russell and Bischoff (1985). The values of the charges obtained with the two methods are not in agreement. Russell and Bischoff's method, in which a reference ion is used, must be preferred. However, even with this method the accuracy of the data obtained is probably limited, due to the difficulty of making corrections for activity coefficients of highly-charge ions at the rather high electrolyte concentrations that must be used in the ion exchange method. So, we think that it is only warranted to conclude that the mean charge of the components of 99m Tc(Sn)-EHDP is about -6 at pH 7, and that the charges of the individual components are in the range of -4 to -9. The influence of pH and ligand concentration in the reaction mixture was determined with high pressure anion exchange chromatography. It was found that a decrease in the pH of the reaction mixture favours the production of complexes with a long retention time, which leads to a slightly higher mean charge. The ligand concentration of the reaction mixture scarcely influenced the relative concentrations of the components. (author)

  14. On the treatment of exchange effects in direct reactions

    International Nuclear Information System (INIS)

    Bencze, Gy.

    1984-11-01

    In the theoretical description of direct nuclear reactions the dynamic effects are combined with 'kinematical' effects due to the quantum mechanical exchange interaction caused by the Pauli principle governing the mechanics of identical particles. In the present paper it is shown that in the frame of general algebraic theory of identical particle scattering the effects of the permutational symmetry of nucleons can be separated on an exact way from the treatment of reaction dynamics. Dynamical approximations may be used only after the separation of permutational effects. (D.Gy.)

  15. Metal- and Ligand-Accelerated Catalysis of the Baylis-Hillman Reaction.

    Science.gov (United States)

    Aggarwal, Varinder K.; Mereu, Andrea; Tarver, Gary J.; McCague, Ray

    1998-10-16

    The Baylis-Hillman reaction, the coupling of an unsaturated carbonyl compound/nitrile with aldehydes, is a valuable reaction but is limited in its practicality by poor reaction rates. We have endeavored to accelerate the reaction using Lewis acids and found that while conventional Lewis acids gave reduced rates group III, and lanthanide triflates (5 mol %) gave increased rates. The optimum metal salts were La(OTf)(3) and Sm(OTf)(3), which gave rate accelerations (k(rel)) of approximately 4.7 and 4.9, respectively, in reactions between tert-butyl acrylate and benzaldehyde when using stoichiometric amounts of DABCO. At low loadings of DABCO (up to 10 mol %), no reaction occurred due to association of DABCO with the metal. Use of additional ligands to displace the DABCO from the metal was studied, and the rate of reaction was found to increase further in most cases. Of the ligands tested, at 5 mol %, (+)-binol gave one of the largest rate accelerations (3.4-fold) and was studied in more detail. It was found that reactions occurred even at low DABCO concentration so that here the Lewis base and Lewis acid were able to promote the reaction without interference from each other. While the (+)-binol (and other chiral ligands) failed to provide any significant asymmetric induction, a substantial nonlinear effect was observed with binol. Thus, use of racemic binol gave no effect on the rate. In seeking to maximize the rate attainable, more soluble (liquid) ligands were studied. Diethyl tartrate and triethanolamine gave rate enhancements of 5.2x and 3.5x at 50 mol %, respectively, versus 1.5x and 2.3x at 5 mol %. The best protocol was to use 100 mol % DABCO, 50 mol % triethanolamine, and 5 mol % La(OTf)(3). This gave overall rate accelerations of between 23-fold and 40-fold depending on the acrylate and approximately 5-fold for acrylonitrile. A simple acid wash removed the reagents, leaving the product in the organic phase. While triethanolamine accelerated the reaction

  16. The gecko visual pigment: the chromophore dark exchange reaction.

    Science.gov (United States)

    Crescitelli, F

    1988-02-01

    This study confirms the occurrence of a dark-exchange reaction in the extracted 521-pigment of the Tokay gecko (G. gekko). The present study involved the exchange, in the dark, of the natural 11-cis-chromophore by the 9-cis-10-F-retinal analog. This analog is able to combine with the 521-opsin to regenerate a photopigment at 492 nm. In addition to this shift in absorbance from 521 to 492 nm, the analog photopigment has a photosensitivity some 2.4% that of the native 521-system in the chloride-sufficient state. These two properties of the regenerated analog pigment have simplified the demonstration of a dark exchange of chromophores. At 15 degrees C the 9-cis-10-F-analog replaces the 11-cis-chromophore by at least 30% (density-wise) in about 15 hr. This exchange occurs with the system in the chloride-deficient state. The presence of chloride during the period in the dark significantly reduces the magnitude of the exchange. Apparently, the protein has a more open structure at the chromophoric binding site, allowing this interchange of chromophores. The addition of chloride induces a conformational change at this site, 'burying' the Schiff base and reducing the exchange reaction. The biological implication of this mobile property of the gecko opsin is that it is similar to the behavior of the cone pigment iodopsin but is unlike that of rhodopsins. This supports the idea that the gecko visual cells, despite their appearance as rods, are phylogenetically related to ancestral photopic receptors.

  17. EXFOR Systems Manual Nuclear reaction Data Exchange Format

    International Nuclear Information System (INIS)

    McLane, V.

    2000-01-01

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

  18. EXFOR SYSTEMS MANUAL NUCLEAR REACTION DATA EXCHANGE FORMAT.

    Energy Technology Data Exchange (ETDEWEB)

    MCLANE,V.; NUCLEAR DATA CENTER NETWORK

    2000-05-19

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

  19. Momentum transfer in relativistic heavy ion charge-exchange reactions

    Science.gov (United States)

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

    1991-01-01

    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.

  20. Charge exchange reactions and solar neutrino detection in 81Br

    International Nuclear Information System (INIS)

    Liu, K.F.; Gabbard, F.

    1983-01-01

    The feasibility of 81 Br as the detector of the solar neutrino flux hinges upon the knowledge of the Gamow-Teller matrix element from the ground state of 81 Br to the (5/2) - state at 0.457 MeV in 81 Kr. The possibility of obtaining this matrix element is discussed in terms of the (p,n) and ( 3 He, t) charge exchange reactions. .ID CR2009 .PG 98 112

  1. Characterization and reaction studies of dimeric molybdenum(III) complexes with bridging dithiolate ligands. Catalytic reduction of acetylene to ethylene

    International Nuclear Information System (INIS)

    DuBois, M.R.; Haltiwanger, R.C.; Miller, D.J.; Glatzmaier, G.

    1979-01-01

    The complexes [C 5 H 5 MoSC/sub n/H/sub 2n/S] 2 (where n = 2 and 3) have been prepared by the reaction of ethylene sulfide and propylene sulfide, respectively, with C 5 H 5 MoH(CO) 3 or with [C 5 H 5 Mo(CO) 3 ] 2 . Cyclic voltammetry shows that each complex undergoes two reversible oxidations at 0.13 and 0.79 V vs. SCE (in acetonitrile with 0.1 M Bu 4 NBF 4 ). Both the one-electron and two-electron oxidation products have been synthesized and characterized by spectral and magnetic data. Electrochemical data for the oxidized complexes support the conclusion that the complexes have the same gross structural features in all three oxidation states. A single crystal of the monocation [C 5 H 5 MoSC 3 H 6 S] 2 BF 4 has been characterized by an x-ray diffraction study. The compound crystallizes in the space group C2/c with a = 18.266 (1) A, b = 9.206 (4) A, c = 12.911 (5) A, β = 100.83 (3) 0 , and V = 2128 A 3 . The metal ions of the cation are bridged by two 1,2-propanedithiolate ligands. The four sulfur atoms of these ligands form a plane which bisects the metal-metal distance. The neutral dimeric complexes undergo a unique reaction with alkenes and alkynes in which the hydrocarbon portion of the bridging dithiolate ligands is exchanged. The reaction has been characterized with olefinswith both electron-withdrawing and electron-donating substituents. When [C 5 H 5 MoSC 2 H 4 S] 2 (1) is reacted with acetylene at 25 0 C, ethene is produced and the complex [C 5 H 5 MoSC 2 H 2 S] 2 is isolated. The latter complex is reduced by hydrogen (2 atm) at 60 0 C to re-form 1. The utility of these reactions in the catalytic reduction of acetylene to ethylene has been investigated. The role of the sulfur ligands in this catalytic cycle is discussed. 50 references, 2 figures, 5 tables

  2. Kinetic and mechanism formation reaction of complex compound Cu with di-n-buthildithiocarbamate (dbdtc) ligand

    Science.gov (United States)

    Haryani, S.; Kurniawan, C.; Kasmui

    2018-04-01

    Synthesis of complex compound is one field of research which intensively studied. Metal-dithiocarbamate complexes find wide-ranging applications in nanomaterial and metal separation science, and have potential use as chemotherapeutic, pesticides, and as additives to lubricants. However, the information about is reaction kinetic and mechanism are very much lacking. The research and analyzes results show that reaction synthesis ligand DBDTC and complex compounds Cu-DBDTC. Optimum reaction condition of formation of complex compounds Cu with DBDTC at pH=3, [DBDTC] = 4.10-3 M, and the time of reaction 5 minutes. Based the analysis varian reaction of complex compounds at pH 3 and 4, diffrence significance at the other pH: 5; 5,5; 6; 6,5 ; 7; and 8. The various of mole with reactants comosition difference sigbificance, those the time reaction for 5 and 6 minutes diffrence by significance with the other time, it is 3,4,8, and 10 minutes. The great product to at condition pH 6, the time optimum at 5 minutes and molar ratio of logam: ligand = 1:2. The reaction kinetic equation of complex compound Cu with chelathing ligand DBDTC is V=0.917106 [Cu2+]0.87921 [DBDTC]2.03021. Based on the kinetic data, and formed complex compounds estimation, the mechanism explaining by 2 stages. In the first stage formation of [Cu(DBDTC)], and then [Cu(DBDTC)2] with the last structure geomethry planar rectangle. The result of this research will be more useful if an effort is being done in reaction mechanism by chemical computation method for obtain intermediate, and for constant “k” in same stage, k1.k2. and compound complex constanta (β).

  3. Comparative study on ion-isotopic exchange reaction kinetics by application of tracer technique

    International Nuclear Information System (INIS)

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

    2007-01-01

    The radioactive isotopes 131 I and 82 Br were used to trace the ion-isotopic exchange reactions using industrial grade ion exchange resins Amberlite IRA-400. The experiments were performed to understand the effect of temperature and concentration of ionic solution on kinetics of exchange reactions. Both the exchange reactions were greatly influenced by rise in temperature, which result in higher percentage of ions exchanged. For bromide ion-isotopic exchange reactions, the calculated values of specific reaction rate/min -1 , and amount of ions exchanged/mmol were obtained higher than that for iodide ion-isotopic exchange reactions under identical experimental conditions. The observed variation in the results for two ion-isotopic exchange reactions was due to the difference in the ionic size of bromide and iodide ions. (orig.)

  4. Selenocysteine in thiol/disulfide-like exchange reactions.

    Science.gov (United States)

    Hondal, Robert J; Marino, Stefano M; Gladyshev, Vadim N

    2013-05-01

    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. 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. 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. 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.

  5. Characterization of poly(allylamine) as a polymeric ligand for ion-exchange protein chromatography.

    Science.gov (United States)

    Li, Ming; Li, Yanying; Yu, Linling; Sun, Yan

    2017-02-24

    This work reports poly(allylamine) (PAA), as a polymeric ion-exchange ligand for protein chromatography. Sepharose FF was modified with PAA, and six anion exchangers with ionic capacities (ICs) from 165 to 618mmol/L were prepared. Inverse size exclusion chromatography, adsorption equilibrium, uptake kinetics and column elution were performed. It was found that both the adsorption capacity and effective diffusivity maintained low values in the IC range of 165-373mmol/L, but they started to increase beyond 373mmol/L, and increased by 80% and 23 times, respectively, when the IC reached 618mmol/L. Interestingly, a drastic decrease of pore size was observed around the IC of 373mmol/L. The results suggest that the PAA chains played an important role in protein adsorption by altering the inner pore structure of the gels. It is considered that, PAA chains turn from inextensible states with multipoint-grafting on the pore surface at low coupling densities (IC373mmol/L). These characters of the grafted chains at higher IC values benefit in protein adsorption by three-dimensional binding and encouraged the happening of "chain delivery" of bound proteins on the chains. Besides, the ion exchangers showed favorable adsorption and uptake properties in a wide ionic strength range, 0-500mmol/L NaCl, indicating much better salt tolerance feature than the so-far reported ion exchangers. Moreover, a mild condition of pH 5.0 offered effective recovery of bound proteins in elution chromatography. The results indicate that the PAA-based anion exchanger of a high IC value is promising for high-capacity protein chromatography dealing with feedstock of a wide range of ionic strengths. Copyright © 2016 Elsevier B.V. All rights reserved.

  6. Electron and ligand transfer reactions between cyclometallated platinum(II) compounds and thallium(III) carboxylates

    NARCIS (Netherlands)

    Koten, G. van; Ploeg, A.F.M.J. van der; Vrieze, K.

    1982-01-01

    Reaction of trans-[(2-Me{2}NCH{2}C{6}H{4}{2}Pt}I{}I{] with Tl}I{}I{}I{(O{2}CR){3} (R = Me, i-Pr) gave direct elimination of Tl}I{(O{2}CR) and formation of the oxidative addition product [(2-Me{2}NCH{2}C{6}H{4}){2}Pt}I{}V{ (O{2}CR){2}], in two isomeric forms. A structure with the carbon ligands in

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

    International Nuclear Information System (INIS)

    Butts, Laura J.; Strickland, Nicholas; Martin, Benjamin R.

    2009-01-01

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

  8. Thermoneutral isotope exchange reactions of cations in the gas phase

    International Nuclear Information System (INIS)

    Ausloos, P.; Lias, S.G.

    1981-01-01

    Rate constants have been measured for reactions of the type AD 2 + + MH → MD + ADH + , where AD 2 + is CD 3 CND + , CD 3 CDOD + , (CD 3 COCD 3 )D + , or (C 2 D 5 ) 2 OD + and the MH molecules are alcohols, acids, mercaptans, H 2 S, AsH 3 , PH 3 , or aromatic molecules. Rate constants are also presented for the reactions Ar/sub H/D + + D 2 O → Ar/sub d/D + + HDO, where Ar/sub H/D + is a deuteronated aromatic molecule and Ar/sub D/D + is the same species with a D atom incorporated on the ring. In all but two cases, the competing deuteron transfer is sufficiently endothermic that it cannot be observed under the conditions of the ICR experiments at 320 to 420 K. The efficiencies of the isotope exchange reactions are interpreted in terms of estimated potential surface cross sections for the reactions AD 2 + + MH → [AD 2 + MH] → [ADMHD + ] → [ADH + MD] → ADH + + MD. When the formation of the [ADMHD + ] complex is estimated to be thermoneutral or slightly endothermic, the isotope exchange process is inefficient (probability of a reactive collision 2 + MH] → [ADMHD + ] is exothermic. For most of the systems, trends in reaction efficiency appear to be related to factors such as dipole moments of reactant species (or for aromatic compounds, the electron-donating or -withdrawing properties of ring substituents) which influence the relative orientation of the two reactant species in the complex

  9. EXFOR systems manual: Nuclear reaction data exchange format

    International Nuclear Information System (INIS)

    McLane, V.

    1996-07-01

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

  10. Exchange reaction of acetylene-d2 with hydrogen chloride

    International Nuclear Information System (INIS)

    Bopp, A.F.; Kern, R.D.

    1975-01-01

    A mixture containing 3 percent each of the reactants C 2 D 2 and HCl in an Ne--Ar diluent was studied over the temperature range 1650 to 2600 0 K utilizing a shock tube coupled to a time-of-flight mass spectrometer. Plots of the mole fractions f of the exchange products, DCl and C 2 HD, revealed two distinct regions of growth: (a) an initial low conversion region characterized by an induction period t/sub i/; and (b) a region of accelerated exchange during which exchange products were formed with a quadratic dependence of the reaction time. These two regions labeled a and b were combined using two empirical equations, 1 - f/sub a//f/sub eq,a/ = exp [-k/sub a/[M]t], where t less than or equal to t/sub i/, and 1 - f/sub b//f/sub eq,b/ = exp [-k/sub b/[M](t - t/sub i/) 2 ], in order to represent the entire reaction profile at any given temperature within the interval investigated. The Arrhenius parameters for k/sub a/ and k/sub b/ were determined to be 10 11 . 15+-0 . 30 exp (-19990 +- 2850/RT) and 10 16 . 40+-0 . 41 exp (-31480 +- 4200/RT), respectively, for DCl and 10 11 . 69+-0 . 29 exp (-19150 +- 2740/RT) and 10 15 . 24+-0 . 34 exp (-17620 +- 3480/RT) for C 2 HD. The units for k/sub a/ are cm 3 mol -1 sec -1 and cm 3 mol -1 sec -2 for k/sub b/. Activation energies are reported in cal mol -1 . Comparison with the profiles obtained for acetylene pyrolysis strongly suggests that the mechanism for the exchange is atomic. Furthermore, the exchange experiments indicate that the initial step in the pyrolysis of acetylene is the disproportionation reaction, 2C 2 H 2 → C 2 H + C 2 H 3

  11. Bromine–lithium exchange: An efficient tool in the modular construction of biaryl ligands

    Directory of Open Access Journals (Sweden)

    Laurence Bonnafoux

    2011-09-01

    Full Text Available Regioselective bromine–lithium exchange reactions on polybrominated biaryls enable the modular synthesis of various polysubstituted biphenyls such as bis(dialkylphosphino-, bis(diarylphosphino- and dialkyl(diarylphosphinobiphenyls. All permutations of substituents at the ortho positions of the biphenyls are possible. In a similar manner, one can gain access to monophosphine analogues. So far, such a process, based on the effective discrimination between bromine atoms as a function of their chemical environment, has been observed only sporadically.

  12. Ligand-tailored single-site silica supported titanium catalysts: Synthesis, characterization and towards cyanosilylation reaction

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Wei; Li, Yani; Yu, Bo; Yang, Jindou; Zhang, Ying; Chen, Xi; Zhang, Guofang, E-mail: gfzhang@snnu.edu.cn; Gao, Ziwei, E-mail: zwgao@snnu.edu.cn

    2015-01-15

    A successive anchoring of Ti(NMe{sub 2}){sub 4}, cyclopentadiene and a O-donor ligand, 1-hydroxyethylbenzene (PEA), 1,1′-bi-2-naphthol (Binol) or 2,3-dihydroxybutanedioic acid diethyl ester (Tartrate), on silica was conducted by SOMC strategy in moderate conditions. The silica, monitored by in-situ Fourier transform infrared spectroscopy (in-situ FT-IR), was pretreated at different temperatures (200, 500 and 800 °C). The ligand tailored silica-supported titanium complexes were characterized by in-situ FT-IR, {sup 13}C CP MAS-NMR, X-ray photoelectron spectroscopy (XPS), X-ray absorption near edge structure (XANES) and elemental analysis in detail, verifying that the surface titanium species are single sited. The catalytic activity of the ligand tailored single-site silica supported titanium complexes was evaluated by a cyanosilylation of benzaldehyde. The results showed that the catalytic activity is dependent strongly on the dehydroxylation temperatures of silica and the configuration of the ligands. - Graphical abstract: The ligand-tailored silica supported “single site” titanium complexes were synthesized by SOMC strategy and fully characterized. Their catalytic activity were evaluated by benzaldehyde silylcyanation. - Highlights: • Single-site silica supported Ti active species was prepared by SOMC technique. • O-donor ligand tailored Ti surface species was synthesized. • The surface species was characterized by XPS, {sup 13}C CP-MAS NMR, XANES etc. • Catalytic activity of the Ti active species in silylcyanation reaction was evaluated.

  13. Inorganic-ligand exchanging time effect in PbS quantum dot solar cell

    International Nuclear Information System (INIS)

    Kim, Byung-Sung; Hong, John; Hou, Bo; Cho, Yuljae; Sohn, Jung Inn; Cha, SeungNam; Kim, Jong Min

    2016-01-01

    We investigate time-dependent inorganic ligand exchanging effect and photovoltaic performance of lead sulfide (PbS) nanocrystal films. With optimal processing time, volume shrinkage induced by residual oleic acid of the PbS colloidal quantum dot (CQD) was minimized and a crack-free film was obtained with improved flatness. Furthermore, sufficient surface passivation significantly increased the packing density by replacing from long oleic acid to a short iodide molecule. It thus facilities exciton dissociation via enhanced charge carrier transport in PbS CQD films, resulting in the improved power conversion efficiency from 3.39% to 6.62%. We also found that excess iodine ions on the PbS surface rather hinder high photovoltaic performance of the CQD solar cell.

  14. Inorganic-ligand exchanging time effect in PbS quantum dot solar cell

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Byung-Sung; Hong, John; Hou, Bo; Cho, Yuljae; Sohn, Jung Inn, E-mail: junginn.sohn@eng.ox.ac.uk, E-mail: seungnam.cha@eng.ox.ac.uk; Cha, SeungNam, E-mail: junginn.sohn@eng.ox.ac.uk, E-mail: seungnam.cha@eng.ox.ac.uk [Department of Engineering Science, University of Oxford, Parks Road, Oxford OX1 3PJ (United Kingdom); Kim, Jong Min [Department of Engineering, University of Cambridge, 9 JJ Thomson Avenue, Cambridge CB3 0FA (United Kingdom)

    2016-08-08

    We investigate time-dependent inorganic ligand exchanging effect and photovoltaic performance of lead sulfide (PbS) nanocrystal films. With optimal processing time, volume shrinkage induced by residual oleic acid of the PbS colloidal quantum dot (CQD) was minimized and a crack-free film was obtained with improved flatness. Furthermore, sufficient surface passivation significantly increased the packing density by replacing from long oleic acid to a short iodide molecule. It thus facilities exciton dissociation via enhanced charge carrier transport in PbS CQD films, resulting in the improved power conversion efficiency from 3.39% to 6.62%. We also found that excess iodine ions on the PbS surface rather hinder high photovoltaic performance of the CQD solar cell.

  15. Reaction of the diimine pyridine ligand with aluminum alkyls: An unexpectedly complex reaction

    NARCIS (Netherlands)

    Knijnenburg, Q.; Smits, J.M.M.; Budzelaar, P.H.M.

    2006-01-01

    The diimine pyridine ligand 2,6-{2,6-(Pr2C6H3N)-Pr-i=CMe}(2)C5H3N (1) was reacted with a series of aluminum alkyls (Me3Al, Et3Al, (Bu3Al)-Bu-i, (Bu2AlH)-Bu-i, Et2AlCl). Depending on the choice of alkyl, addition to the imine carbon and the pyridine C2 and C4 positions was observed. Addition to C2

  16. The reactivity of anion-exchange resins by applying OT-for-OH exchange reaction in the equilibrium state

    International Nuclear Information System (INIS)

    Kano, Naoki; Nihei, Makoto; Imaizumi, Hiroshi

    1996-01-01

    In order to reveal the behavior of hydroxyl group in isotope exchange reaction, OT-for-OH exchange reaction between each anion-exchange resin (OH - form) and tritiated water (abbreviated as HTO water below) was observed at 80degC under the equilibrium. Anion-exchange resins used were Amberlite IRA-400, IRA-410 (both strongly basic), and IRA-94S (weakly basic). It can be thought that an HTO molecule dissociates into H + +OT - (or T + +OH - ). The activity of each resin based on OT-for-OH exchange reaction was measured with a liquid scintillation counter. From the above-mentioned, the following five were found. Isotope exchange reaction as 'atomic group' occurred between the OH group in each anion-exchange resin and the OT group in HTO water. The reactivity of strongly basic anion-exchange resin is larger than that of weakly basic one. The ratio of the reactivity of these resins can roughly be expressed as follows: (IRA-410): (IRA-400): (IRA-94S)=42: 7: 1. The degree of OT-for-OH exchange reaction may be smaller than that of T-for-H exchange reaction. The method used and results obtained in this work may be helpful to obtain the data for the prevention of T-contamination, especially to obtain the data from certain atomic groups including T. (author)

  17. Molecular-weight-enlarged multiple-pincer ligands: synthesis and application in palladium-catalyzed allylic substitution reactions

    NARCIS (Netherlands)

    Ronde, N.J.; Totev, D.; Müller, Christian; Lutz, M.; Spek, A.L.; Vogt, D.

    2009-01-01

    Three different pincer ligand systems are synthesized via nucleophilic substitution reactions of polyaromatic benzyl bromides as support molecules and phenol derivatives as ligand precursors. Retention tests using a polymeric nanofiltration membrane show moderate to good retention in THF and CH2Cl2.

  18. Isotopic studies on ligand exchange between complex and simple cyanides in aqueous medium and in liquid hydrogen cyanide. Part 1. Rate law and temperature dependence study of the radiocyanide exchange between hydrogen cyanide and octacyanotungstate(4) in aque us medium

    International Nuclear Information System (INIS)

    Zielinski, M.

    1978-01-01

    Dark radiocyanide ligand exchange in the closed system consisting of K 4 W(CN) 8 , hydrogen cyanide and water have been investigated. It has been found that the reaction is first order in respect to the complex cyanide and zero order in respect to the free hydrogen cyanide. Arrhenius activation energy within the temperature interval of 20-100 0 C equals to 32.373 kcal/mole. Enthalpy and entropy of activation are correspondingly ΔH not equal to Λ31.716kcal/mole and ΔS not equal to =5.45 e.u. A preliminary discussion of the above findings is presented. (author)

  19. Speciation of Co(II) and Ni(II) in anaerobic bioreactors measured by competitive ligand exchange - adsorptive stripping voltammetry

    NARCIS (Netherlands)

    Jansen, S.; Steffen, F.; Threels, W.F.; Leeuwen, van H.P.

    2005-01-01

    Competitive ligand exchange-adsorptive stripping voltammetry is applied to speciation analysis of dissolved Ni(II) and Co(II) in an anaerobic bioreactor and similar batch media. Co and Ni speciation in these media can be measured down to concentration levels of ca. 1 nM. Sulfide interference is

  20. Phonon Raman spectra of colloidal CdTe nanocrystals: effect of size, non-stoichiometry and ligand exchange

    Directory of Open Access Journals (Sweden)

    Lokteva Irina

    2011-01-01

    Full Text Available Abstract Resonant Raman study reveals the noticeable effect of the ligand exchange on the nanocrystal (NC surface onto the phonon spectra of colloidal CdTe NC of different size and composition. The oleic acid ligand exchange for pyridine ones was found to change noticeably the position and width of the longitudinal optical (LO phonon mode, as well as its intensity ratio to overtones. The broad shoulder above the LO peak frequency was enhanced and sharpened after pyridine treatment, as well as with decreasing NC size. The low-frequency mode around 100 cm-1 which is commonly related with the disorder-activated acoustical phonons appears in smaller NCs but is not enhanced after pyridine treatment. Surprisingly, the feature at low-frequency shoulder of the LO peak, commonly assigned to the surface optical phonon mode, was not sensitive to ligand exchange and concomitant close packing of the NCs. An increased structural disorder on the NC surface, strain and modified electron-phonon coupling is discussed as the possible reason of the observed changes in the phonon spectrum of ligand-exchanged CdTe NCs. PACS: 63.20.-e, 78.30.-j, 78.67.-n, 78.67.Bf

  1. Time-dependent photoluminescence spectroscopy as a tool to measure the ligand exchange kinetics on a quantum dot surface

    NARCIS (Netherlands)

    Koole, R.; Schapotschnikow, P.Z.; de Mello Donega, C.; Vlugt, T.J.H.; Meijerink, A.

    2008-01-01

    The exchange kinetics of native ligands that passivate CdSe quantum dots (hexadecylamine (HDA), trioctylphosphine oxide (TOPO), and trioctylphosphine (TOP)) by thiols is followed in situ. This is realized by measuring, in real-time, the decrease in emission intensity of the QDs upon addition of

  2. Recoil implantation reactions in binary mixtures of catcher complexes and in mixed ligand catchers

    International Nuclear Information System (INIS)

    Sekine, Tsutomu; Sano, Masaaki; Yoshihara, Kenji

    1989-01-01

    Recoil implantation reactions were studied in binary mixtures of catcher complexes of tris(β-diketonato)metal(III) and in single-component catcher complexes of Cr(acac) n (dbm) 3-n where n=1 and 2. For the mixtures of M(acac) 3 and M(dbm) 3 , the products of 51 Cr(acac) 3 and 51 Cr(dbm) 3 were obtained as major components while 51 Cr(acac) 2 (dbm) and 51 Cr(acac)(dbm) 2 were seen as minor components. For the single component catcher complexes, predominant chemical species were parent retention type compounds. In addition to retentions there were product distributions which indicated a strong preference for acac pickup. The results were interpreted by a model which involves displacement reaction as a main process and ligand pickup reactions as side processes. (orig.)

  3. NMR study of ligand exchange and electron self-exchange between oxo-centered trinuclear clusters [Fe3(μ3-O)(μ-O2CR)6(4-R'py)3](+/0).

    Science.gov (United States)

    Novitchi, Ghenadie; Helm, Lothar; Anson, Christopher; Powell, Annie K; Merbach, André E

    2011-10-17

    The syntheses, single crystal X-ray structures, and magnetic properties of the homometallic μ₃-oxo trinuclear clusters [Fe₃(μ₃-O)(μ-O₂CCH₃)₆(4-Phpy)₃](ClO₄) (1) and [Fe₃(μ₃-O)(μ-O₂CAd)₆(4-Mepy)₃](NO₃) (2) are reported (Ad = adamantane). The persistence of the trinuclear structure within 1 and 2 in CD₂Cl₂ and C₂D₂Cl₄ solutions in the temperature range 190-390 K is demonstrated by ¹H NMR. An equilibrium between the mixed pyridine clusters [Fe₃(μ₃-O)(μ-O₂CAd)₆(4-Mepy)(3-x)(4-Phpy)(x)](NO₃) (x = 0, 1, 2, 3) with a close to statistical distribution of these species is observed in CD₂Cl₂ solutions. Variable-temperature NMR line-broadening made it possible to quantify the coordinated/free 4-Rpy exchanges at the iron centers of 1 and 2: k(ex)²⁹⁸ = 6.5 ± 1.3 × 10⁻¹ s⁻¹, ΔH(‡) = 89.47 ± 2 kJ mol⁻¹, and ΔS(‡) = +51.8 ± 6 J K⁻¹ mol⁻¹ for 1 and k(ex)²⁹⁸ = 3.4 ± 0.5 × 10⁻¹ s⁻¹, ΔH(‡) = 91.13 ± 2 kJ mol⁻¹, and ΔS(‡) = +51.9 ± 5 J K⁻¹ mol⁻¹ for 2. A limiting D mechanism is assigned for these ligand exchange reactions on the basis of first-order rate laws and positive and large entropies of activation. The exchange rates are 4 orders of magnitude slower than those observed for the ligand exchange on the reduced heterovalent cluster [Fe(III)₂Fe(II)(μ₃-O)(μ-O₂CCH₃)₆(4-Phpy)₃] (3). In 3, the intramolecular Fe(III)/Fe(II) electron exchange is too fast to be observed. At low temperatures, the 1/3 intermolecular second-order electron self-exchange reaction is faster than the 4-Phpy ligand exchange reactions on these two clusters, suggesting an outer-sphere mechanism: k₂²⁹⁸ = 72.4 ± 1.0 × 103 M⁻¹ s⁻¹, ΔH(‡) = 18.18 ± 0.3 kJ mol⁻¹, and ΔS(‡) = -90.88 ± 1.0 J K⁻¹ mol⁻¹. The [Fe₃(μ₃-O)(μ-O₂CCH₃)₆(4-Phpy)₃](+/0) electron self-exchange reaction is compared with the more than 3 orders of magnitude faster [Ru

  4. On quark model relations for hypercharge-exchange reactions

    International Nuclear Information System (INIS)

    Kluyver, J.C.; Blokzijl, R.; Massaro, G.G.G.; Wolters, G.F.; Grossmann, P.; Lamb, P.R.; Wells, J.

    1978-01-01

    Peripheral two-body reactions of the type K - p → M 0 + Λ, Σ 0 or Σ 0 (1385) are considered. Predictions based on the additive quark model and SU(6) baryon wave functions are tested against data on cross sections and polarisations for given momentum transfer. Data obtained in a high statistics experiment at 4.2 GeV/c K - momentum, as well as data from a large variety of other experiments are used. Highly significant violations of these predictions are observed in the data. These violations are shown to occur in a systematic fashion, according to which SU(6) must be relaxed, but the amplitude structure implied by additivity would remain valid. As an application an amplitude analysis for natural parity exchange reactions with M 0 = π, phi and rho respectively is performed, which determines a relative phase, which cannot be obtained in model-independent analysis. Also reactions with M 0 = delta or B are considered, and some implications for coupling constants are discussed. (Auth.)

  5. Ligand-Controlled Synthesis of Azoles via Ir-Catalyzed Reactions of Sulfoxonium Ylides with 2-Amino Heterocycles.

    Science.gov (United States)

    Phelps, Alicia M; Chan, Vincent S; Napolitano, José G; Krabbe, Scott W; Schomaker, Jennifer M; Shekhar, Shashank

    2016-05-20

    An iridium-catalyzed method was developed for the synthesis of imidazo-fused pyrrolopyrazines. The presence or absence of a nitrogenated ligand controlled the outcome of the reaction, leading to simple β-keto amine products in the absence of added ligand and the cyclized 7- and 8-substituted-imidazo[1,2-a]pyrrolo[2,3-e]pyrazine products in the presence of ligand. This catalyst control was conserved across a variety of ylide and amine coupling partners. The substrate was shown to act as a ligand for the iridium catalyst in the absence of other ligands via NMR spectroscopy. Kinetic studies indicated that formation of the Ir-carbene was reversible and the slow step of the reaction. These mechanistic investigations suggest that the β-keto amine products form via an intramolecular carbene N-H insertion, and the imidazopyrrolopyrazines form via an intermolecular carbene N-H insertion.

  6. Direct and quantitative characterization of dynamic ligand exchange between coordination-driven self-assembled supramolecular polygons.

    Science.gov (United States)

    Zheng, Yao-Rong; Stang, Peter J

    2009-03-18

    The direct observation of dynamic ligand exchange between Pt-N coordination-driven self-assembled supramolecular polygons (triangles and rectangles) has been achieved using stable (1)H/(2)D isotope labeling of the pyridyl donors and electrospray ionization mass spectrometry combined with NMR spectroscopy. Both the thermodynamic and kinetic aspects of such exchange processes have been established on the basis of quantitative mass spectral results. Further investigation has shown that the exchange is highly dependent on experimental conditions such as temperature, solvent, and the counteranions.

  7. Double Charge Exchange Reactions and Double Beta Decay

    Science.gov (United States)

    Auerbach, N.

    2018-05-01

    The subject of this presentation is at the forefront of nuclear physics, namely double beta decay. In particular one is most interested in the neutrinoless process of double beta decay, when the decay proceeds without the emission of two neutrinos. The observation of such decay would mean that the lepton conservation symmetry is violated and that the neutrinos are of Majorana type, meaning that they are their own anti-particles. The life time of this process has two unknowns, the mass of the neutrino and the nuclear matrix element. Determining the nuclear matrix element and knowing the cross-section well will set limits on the neutrino mass. There is a concentrated effort among the nuclear physics community to calculate this matrix element. Usually these matrix elements are a very small part of the total strength of the transition operators involved in the process. There is no simple way to “calibrate” the nuclear double beta decay matrix element. The double beta decay is a double charge exchange process, therefore it is proposed that double charge exchange reactions using ion projectiles on nuclei that are candidates for double beta decay, will provide additional necessary information about the nuclear matrix elements.

  8. Effect of Ligand Exchange on the Photoluminescence Properties of Cu-Doped Zn-In-Se Quantum Dots

    Science.gov (United States)

    Dong, Xiaofei; Xu, Jianping; Yang, Hui; Zhang, Xiaosong; Mo, Zhaojun; Shi, Shaobo; Li, Lan; Yin, Shougen

    2018-04-01

    The surface-bound ligands of a semiconductor nanocrystal can affect its electron transition behavior. We investigate the photoluminescence (PL) properties of Cu-doped Zn-In-Se quantum dots (QDs) through the exchange of oleylamine with 6-mercaptohexanol (MCH). Fourier transform infrared and 1H nuclear magnetic resonance spectroscopies, and mass spectrometry reveal that the short-chain MCH molecules are bound to the QD surface. The emission peaks remain unchanged after ligand exchange, and the PL quantum yield is reduced from 49% to 38%. The effects of particle size and defect type on the change in PL behavior upon ligand substitution are excluded through high-resolution transmission electron microscopy, UV-Vis absorption, and PL spectroscopies. The origin of the decreased PL intensity is associated with increased ligand density and the stronger ligand electron-donating abilities of MCH-capped QDs that induce an increase in the nonradiative transition probability. A lower PL quenching transition temperature is observed for MCH-capped QDs and is associated with increasing electron-acoustic phonon coupling due to the lower melting temperature of MCH.

  9. Analysis of ligand-protein exchange by Clustering of Ligand Diffusion Coefficient Pairs (CoLD-CoP)

    Science.gov (United States)

    Snyder, David A.; Chantova, Mihaela; Chaudhry, Saadia

    2015-06-01

    NMR spectroscopy is a powerful tool in describing protein structures and protein activity for pharmaceutical and biochemical development. This study describes a method to determine weak binding ligands in biological systems by using hierarchic diffusion coefficient clustering of multidimensional data obtained with a 400 MHz Bruker NMR. Comparison of DOSY spectrums of ligands of the chemical library in the presence and absence of target proteins show translational diffusion rates for small molecules upon interaction with macromolecules. For weak binders such as compounds found in fragment libraries, changes in diffusion rates upon macromolecular binding are on the order of the precision of DOSY diffusion measurements, and identifying such subtle shifts in diffusion requires careful statistical analysis. The "CoLD-CoP" (Clustering of Ligand Diffusion Coefficient Pairs) method presented here uses SAHN clustering to identify protein-binders in a chemical library or even a not fully characterized metabolite mixture. We will show how DOSY NMR and the "CoLD-CoP" method complement each other in identifying the most suitable candidates for lysozyme and wheat germ acid phosphatase.

  10. The dynamics of the Hg + Br2 reaction: elucidation of the reaction mechanism for the Br exchange reaction.

    Science.gov (United States)

    Jambrina, P G; Menéndez, M; Aoiz, F J

    2017-06-28

    In spite of its importance in the Hg atmospheric chemistry, the dynamics of the Hg + Br 2 → HgBr + Br reaction is poorly understood. In this article, we have carried out a comprehensive study of the reaction mechanism of this reaction by means of quasiclassical trajectories (QCTs) on an existing ab initio potential energy surface (PES). The reaction has a non trivial dynamics, as a consequence of its large endothermicity, the presence of a deep potential well, and the competition between the Br exchange and the collision induced dissociation processes. Our calculations demonstrate that insertion is only relevant at energies just above the reaction threshold and that, at energies above 2.3 eV, HgBr formation typically takes place via a sort of frustrated dissociation. In order to compare directly with the results obtained in extensive cross molecular beam experiments for the homologous reaction with I 2 , angular distributions in the laboratory frame for Hg + Br 2 have been simulated under similar experimental conditions. The lack of agreement at the highest energies considered suggests that either the two reactions have substantially different mechanisms or that calculations on a single PES cannot account for the dynamics at those energies.

  11. Enhancement of isotope exchange reactions over ceramic breeder material by deposition of catalyst metal

    International Nuclear Information System (INIS)

    Narisato, Y.; Munakata, K.; Koga, A.; Yokoyama, Y.; Takata, T.; Okabe, H.

    2004-01-01

    The deposition of catalyst metals in ceramic breeders could enhance the release rate of tritium due to the promotion of isotope exchange reactions taking place at the interface of the breeder surface and the sweep gas. In this work, the authors examined the effects of catalytic active metal deposited on lithium titanate on the isotope exchange reactions. With respect to the virgin lithium titanate, it was found that the rate of the isotope exchange reactions taking place on the surface is quite low. However, the deposition of palladium greatly increased the exchange reaction rate. The effect of the amounts of deposited palladium on the isotope exchange reaction rate was also investigated. The results indicate that the exchange reactions are still enhanced even if the amounts of deposited palladium are as low as 0.04%

  12. Isotope exchange reaction of tritium on precious metal catalyst based on cation-exchanged mordenite for blanket tritium recovery

    Energy Technology Data Exchange (ETDEWEB)

    Kawamura, Yoshinori, E-mail: kawamura.yoshinori@jaea.go.jp [Japan Atomic Energy Agency, 801-1 Mukoyama, Naka, Ibaraki 311-0193 (Japan); Hayashi, Takumi [Japan Atomic Energy Agency, 2-4 Shirane Shirakata, Tokai, Ibaraki 319-1195 (Japan); Yamanishi, Toshihiko [Japan Atomic Energy Agency, 2-166 Omotedate Obuchi, Rokkasho, Aomori 039-3212 (Japan)

    2016-11-01

    Highlights: • Precious metal catalyst based on cation-exchanged mordenite was prepared. • Isotope exchange reaction between H{sub 2} and HTO on the catalyst was investigated. • The order of entire reaction is not clear, but it is the first-order reaction as for HTO. • Effect of exchanged cation may appear as the difference of the surface area of catalyst. - Abstract: It is known that the chemical forms of tritium released from a ceramic breeder blanket are hydrogen form and water form. To recover tritiated water vapor, adoption of dryer that is packed column of synthetic zeolite has been proposed. On the other hand, synthetic zeolite is often used as a support of precious metal catalyst. Such catalysts usually have a capability of hydrogen isotope exchange between gas and water vapor. If this catalyst is used to dryer, the dryer may obtain a preferable function for tritium recovery by isotopic exchange reaction. To assess such functions, reaction rate should be estimated. The results of water adsorption experiment on cation-exchanged mordenite-type zeolite suggested the possibility that state of adsorbed water varied by exchanged cation. So, in this work, precious metal catalyst based on cation-exchanged mordenite was prepared, and the reaction rate of chemical exchange between hydrogen and tritiated water was investigated under temperature range between 30 °C and 80 °C by the steady-state approximation. In the case of platinum on Na-mordenite, the reaction between gaseous hydrogen and tritiated water vapor was almost expressed as first-order reaction concerning tritiated water vapor concentration.

  13. Complete relaxation and conformational exchange matrix (CORCEMA) analysis of intermolecular saturation transfer effects in reversibly forming ligand-receptor complexes.

    Science.gov (United States)

    Jayalakshmi, V; Krishna, N Rama

    2002-03-01

    A couple of recent applications of intermolecular NOE (INOE) experiments as applied to biomolecular systems involve the (i) saturation transfer difference NMR (STD-NMR) method and (ii) the intermolecular cross-saturation NMR (ICS-NMR) experiment. STD-NMR is a promising tool for rapid screening of a large library of compounds to identify bioactive ligands binding to a target protein. Additionally, it is also useful in mapping the binding epitopes presented by a bioactive ligand to its target protein. In this latter application, the STD-NMR technique is essentially similar to the ICS-NMR experiment, which is used to map protein-protein or protein-nucleic acid contact surfaces in complexes. In this work, we present a complete relaxation and conformational exchange matrix (CORCEMA) theory (H. N. B. Moseley et al., J. Magn. Reson. B 108, 243-261 (1995)) applicable for these two closely related experiments. As in our previous work, we show that when exchange is fast on the relaxation rate scale, a simplified CORCEMA theory can be formulated using a generalized average relaxation rate matrix. Its range of validity is established by comparing its predictions with those of the exact CORCEMA theory which is valid for all exchange rates. Using some ideal model systems we have analyzed the factors that influence the ligand proton intensity changes when the resonances from some protons on the receptor protein are saturated. The results show that the intensity changes in the ligand signals in an intermolecular NOE experiment are very much dependent upon: (1) the saturation time, (2) the location of the saturated receptor protons with respect to the ligand protons, (3) the conformation of the ligand-receptor interface, (4) the rotational correlation times for the molecular species, (5) the kinetics of the reversibly forming complex, and (6) the ligand/receptor ratio. As an example of a typical application of the STD-NMR experiment we have also simulated the STD effects for a

  14. Neutrino and antineutrino charge-exchange reactions on 12C

    International Nuclear Information System (INIS)

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

    2011-01-01

    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 12 B and 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 3/2 shell and from the nonconservation of the number of particles in the QRPA. The inclusive neutrino/antineutrino (ν/ν-tilde) reactions 12 C(ν,e - ) 12 N and 12 C(ν-tilde,e + ) 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 ν and ν-tilde; (ii) they increase steadily when the size of the configuration space is augmented, particularly for ν/ν-tilde energies >200 MeV; and (iii) they converge for sufficiently large configuration space and final-state spin. The quasi-elastic 12 C(ν,μ - ) 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 ν/ν-tilde- 12 C charge-exchange reactions related to astrophysical applications.

  15. Mechanistic study of the isotopic-exchange reaction between gaseous hydrogen and palladium hydride powder

    International Nuclear Information System (INIS)

    Outka, D.A.; Foltz, G.W.

    1991-01-01

    A detailed mechanism for the isotopic-exchange reaction between gaseous hydrogen and solid palladium hydride is developed which extends previous model for this reaction by specifically including surface reactions. The modeling indicates that there are two surface-related processes that contribute to the overall rate of exchange: the desorption of hydrogen from the surface and the exchange between surface hydrogen and bulk hydrogen. This conclusion is based upon measurements examining the effect of small concentrations of carbon monoxide were helpful in elucidating the mechanism. Carbon monoxide reversibly inhibits certain steps in the exchange; this slows the overall rate of exchange and changes the distribution of products from the reactor

  16. Hexacationic Dendriphos ligands in the Pd-catalyzed Suzuki-Miyaura cross-coupling reaction: scope and mechanistic studies

    NARCIS (Netherlands)

    Snelders, D.J.M.; van Koten, G.; Klein Gebbink, R.J.M.

    2009-01-01

    The combination of Pd2dba3·CHCl3and hexacationic triarylphosphine-based Dendriphos ligands (1-3) leads to a highly active catalytic system in the Suzuki-Miyaura cross-coupling reaction. Under relatively mild reaction conditions, nonactivated aryl bromides and activated aryl chlorides can be coupled

  17. Ion-Isotopic Exchange Reaction Kinetics using Anion Exchange Resins Dowex 550A LC and Indion-930A

    Directory of Open Access Journals (Sweden)

    P.U. Singare

    2014-06-01

    Full Text Available The present paper deals with the characterization of ion exchange resins Dowex 550A LC and Indion-930A based on kinetics of ion-isotopic exchange reactions for which the short lived radioactive isotopes 131I and 82Br were used as a tracers. The study was performed for different concentration of ionic solution varying from 0.001 mol/L to 0.004 mol/L and temperature in the range of 30.0 °C to 45.0 °C. The results indicate that as compared to bromide ion-isotopic exchange reaction, iodide exchange reaction take place at the faster rate. For both the ion-isotopic exchange reactions, under identical experimental conditions, the values of specific reaction rate increases with increase in the ionic concentration and decreases with rise in temperature. It was observed that at 35.00C, 1.000 g of ion exchange resins and 0.002 mol/L labeled iodide ion solution for iodide ion-isotopic exchange reaction, the values of specific reaction rate (min-1, amount of ion exchanged (mmol, initial rate of ion exchange (mmol/min and log Kd were 0.270, 0.342, 0.092 and 11.8 respectively for Dowex 550A LC resin, which was higher than the respective values of 0.156, 0.241, 0.038 and 7.4 as that obtained for Indion-930A resins. From the results, it appears that Dowex 550A LC resins show superior performance over Indion-930A resins under identical experimental conditions.

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

    Science.gov (United States)

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

    2014-05-19

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

  19. Enhanced Open-Circuit Voltage in Colloidal Quantum Dot Photovoltaics via Reactivity-Controlled Solution-Phase Ligand Exchange

    KAUST Repository

    Jo, Jea Woong; Kim, Younghoon; Choi, Jongmin; de Arquer, F. Pelayo Garcí a; Walters, Grant; Sun, Bin; Ouellette, Olivier; Kim, Junghwan; Proppe, Andrew H.; Quintero-Bermudez, Rafael; Fan, James; Xu, Jixian; Tan, Chih Shan; Voznyy, Oleksandr; Sargent, Edward H.

    2017-01-01

    The energy disorder that arises from colloidal quantum dot (CQD) polydispersity limits the open-circuit voltage (VOC) and efficiency of CQD photovoltaics. This energy broadening is significantly deteriorated today during CQD ligand exchange and film assembly. Here, a new solution-phase ligand exchange that, via judicious incorporation of reactivity-engineered additives, provides improved monodispersity in final CQD films is reported. It has been found that increasing the concentration of the less reactive species prevents CQD fusion and etching. As a result, CQD solar cells with a VOC of 0.7 V (vs 0.61 V for the control) for CQD films with exciton peak at 1.28 eV and a power conversion efficiency of 10.9% (vs 10.1% for the control) is achieved.

  20. Enhanced Open-Circuit Voltage in Colloidal Quantum Dot Photovoltaics via Reactivity-Controlled Solution-Phase Ligand Exchange

    KAUST Repository

    Jo, Jea Woong

    2017-10-09

    The energy disorder that arises from colloidal quantum dot (CQD) polydispersity limits the open-circuit voltage (VOC) and efficiency of CQD photovoltaics. This energy broadening is significantly deteriorated today during CQD ligand exchange and film assembly. Here, a new solution-phase ligand exchange that, via judicious incorporation of reactivity-engineered additives, provides improved monodispersity in final CQD films is reported. It has been found that increasing the concentration of the less reactive species prevents CQD fusion and etching. As a result, CQD solar cells with a VOC of 0.7 V (vs 0.61 V for the control) for CQD films with exciton peak at 1.28 eV and a power conversion efficiency of 10.9% (vs 10.1% for the control) is achieved.

  1. Kinetics of isotope exchange reactions involving intra- and intermolecular reactions: 1. Rate law for a system with two chemical compounds and three exchangeable atoms

    International Nuclear Information System (INIS)

    Xuelei Chu; Ohmoto, Hiroshi

    1991-01-01

    For an isotopic exchange reaction between two compounds (X and AB) in a homogeneous system, such as a gaseous or aqueous system, where one (AB) of them possesses two exchangeable atoms in non-equivalent positions and where one intramolecular isotope exchange (A ↔ B) and two intermolecular isotope exchange reactions (X ↔ A and X ↔ B) may occur, its rate law no longer obeys a pseudo-first order rate equation described for simple two-component systems by many previous investigators. The change with time of the δ value of each of the three components (X, A, and B) in a closed and homogeneous system is a complicated function of the initial δ values of the three components, the chemical concentrations of the two compounds, and the overall rate constants of the forward and reverse reactions involving the two intermolecular and one intramolecular reactions of isotope exchanges. Also, for some one of the three components, the change of its δ value with time may not be monotonic, and the relationship of 1n (1 - F) with time may be non-linear in a plot of 1n (1 - F) vs. t. In addition, the rate law of the isotope exchange reaction in this system also provides a quantitative method to estimate the overall rate constants for the one-intra-and two intermolecular isotope exchanges and the equilibrium isotopic fractionation factors among the three components

  2. Mass-independent isotope effects in chemical exchange reaction

    International Nuclear Information System (INIS)

    Nishizawa, Kazushige

    2000-01-01

    Isotope effects of some elements in chemical exchange reaction were investigated by use of liquid-liquid extraction, liquid membrane or chromatographic separation. Cyclic polyether was used for every method. All polyethers used in a series of the studies were made clear that they distinguished the isotopes not only by their nuclear masses but also by their nuclear sizes and shapes. Chromium isotopes, for example, were recognized to have enrichment factors being proportional to δ 2 > which is a parameter to show field shift or the nuclear size and shape of the isotope. It follows that the chromium isotopes are separated not by their masses but by their field shift effects. Nuclear spin also played a great role to separate odd mass number isotopes from even mass number isotopes in even atomic number elements. Contribution of the nuclear spin (I=3/2) of 53 Cr to total enrichment factor, ε 53/52 = -0.00028, for 53 Cr to 52 Cr was observed to be, ε spin = -0.0025. (author)

  3. One ligand capable of in situ reaction in a mixed-ligand system with two new different frameworks

    KAUST Repository

    Wang, Xiaofang; Wang, Runwei; Liu, Xiaofang; Zhu, Pinwen; Qiu, Shilun

    2017-01-01

    The in situ ligand 2,3-pyrazinedicarboxylic acid (2,3-H2pzdc) mixed with 1,1′-(1,4-butanediyl)bis(benzimidazole) (bbbi) is used to form two coordination polymers ([Cd(2,3-pzdc)(bbbi)] (1) and [Cd2Cl3(2-pzc)(bbbi)2] (2)) under hydrothermal conditions

  4. Synthesis and Optical Properties of Thiol Functionalized CdSe/ZnS (Core/Shell Quantum Dots by Ligand Exchange

    Directory of Open Access Journals (Sweden)

    Huaping Zhu

    2014-01-01

    Full Text Available The colloidal photoluminescent quantum dots (QDs of CdSe (core and CdSe/ZnS (core/shell were synthesized at different temperatures with different growth periods. Optical properties (i.e., UV/Vis spectra and photoluminescent emission spectra of the resulting QDs were investigated. The shell-protected CdSe/ZnS QDs exhibited higher photoluminescent (PL efficiency and stability than their corresponding CdSe core QDs. Ligand exchange with various thiol molecules was performed to replace the initial surface passivation ligands, that is, trioctylphosphine oxide (TOPO and trioctylphosphine (TOP, and the optical properties of the surface-modified QDs were studied. The thiol ligand molecules in this study included 1,4-benzenedimethanethiol, 1,16-hexadecanedithiol, 1,11-undecanedithiol, biphenyl-4,4′-dithiol, 11-mercapto-1-undecanol, and 1,8-octanedithiol. After the thiol functionalization, the CdSe/ZnS QDs exhibited significantly enhanced PL efficiency and storage stability. Besides surface passivation effect, such enhanced performance of thiol-functionalized QDs could be due to cross-linked assembly formation of dimer/trimer clusters, in which QDs are linked by dithiol molecules. Furthermore, effects of ligand concentration, type of ligand, and heating on the thiol stabilization of QDs were also discussed.

  5. OXYGEN 18 EXCHANGE REACTIONS OF ALDEHYDES AND KETONES

    Energy Technology Data Exchange (ETDEWEB)

    Byrn, Marianne; Calvin, Melvin

    1965-12-01

    Using infra-red spectroscopy, the equilibrium exchange times have been determined for a series of ketones, aromatic aldehydes, and {beta}-ketoesters reacting with oxygen 18 enriched water. These exchange times have been evaluated in terms of steric and electronic considerations, and applied to a discussion of the exchange times of chlorophylls a and b and chlorophyll derivatives.

  6. H/D exchange in the reaction of D2 with Bis(triphenyl phosphite)(acetylacetonato)rhodium(I), Rh(P(OPh)3)2(acac)

    International Nuclear Information System (INIS)

    Whitmore, B.C.; Eisenberg, R.

    1984-01-01

    The reaction of Rh(P)OPh) 3 ) 2 (acac) (1) with D 2 benzene has been studied by 1 H NMR spectroscopy, and complex 1 has been found to undergo H/D exchange at the ortho positions of the coordinated phosphite ligands and at the central methine position of the acetylacetonate ligand. At 75 0 C, the exchange reaction proceeds with the extent of deuterium incorporation into P(OPh) 3 being the same as that into acac at all stages of the H/D exchange process. At 60 0 C, deuterium incorporation into P(OPh) 3 is initially more rapid than that into the acac ligand. The initial rate of deuterium incorporation into P(OPh) 3 by 1 in benzene-d 6 under D 2 at 60 0 C proceeds with a first-order rate constant of 9.6 x 10 -5 s -1 . A mechanism for this exchange process is proposed. 13 references, 3 figures, 2 tables

  7. Stability Investigation of Ligand-Exchanged CdSe/ZnS-Y (Y = 3-Mercaptopropionic Acid or Mercaptosuccinic Acid through Zeta Potential Measurements

    Directory of Open Access Journals (Sweden)

    Ngoc Thuy Vo

    2016-01-01

    Full Text Available Quantum dots have been considered to be promising candidates for bioapplications because of their high sensitivity, rapid response, and reliability. The synthesis of high-quality quantum dots that can be dissolved in water and other biological media is a crucial step toward their further application in biology. Starting with a one-pot reaction and the successive ionic layer adsorption and reaction (SILAR method, we produced the CdSe/ZnS core/shell structure. Through a ligand-exchange mechanism, we coated the as-made CdSe/ZnS structure with 3-mercaptopropionic acid (MPA or mercaptosuccinic acid (MSA. Various techniques, including photoluminescence (PL, ultraviolet-visible (UV-Vis spectroscopy, transmission electron microscopy (TEM, X-ray diffraction (XRD, and Fourier transform infrared (FTIR spectroscopy, were utilized to characterize the ligand-coated CdSe/ZnS structure. The results show enhanced luminescence intensity, CdSe surface passivation by ZnS, and successful coating with MPA and MSA. The stability of quantum dots in solutions with different pH values was investigated by performing zeta potential measurements. The results revealed that the quantum dots shifted from displaying hydrophobic to hydrophilic behavior and could be connected with bioagents.

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

    International Nuclear Information System (INIS)

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

    2015-01-01

    Oxygen exchange reactions performed on PuO 2 suggest the reaction is influenced by at least three mechanisms: an internal chemical reaction, surface mobility of active species/defects, and surface exchange of gaseous oxygen with lattice oxygen. Activation energies for the surface mobility and internal chemical reaction are presented. Determining which mechanism is dominant appears to be a complex function including at least specific surface area and temperature. Thermal exposure may also impact the oxygen exchange reaction by causing reductions in the specific surface area of PuO 2 . Previous CeO 2 surrogate studies exhibit similar behavior, confirming that CeO 2 is a good qualitative surrogate for PuO 2 , in regards to the oxygen exchange reaction. Comparison of results presented here with previous work on the PuO 2 oxygen exchange reaction allows complexities in the previous work to be explained. These explanations allowed new conclusions to be drawn, many of which confirm the conclusions presented here. - Highlights: • PuO 2 Oxygen exchange kinetics can be influenced by at least 3 different mechanisms. • An internal chemical reaction controls the rate at high temperature and large SSA. • Surface mobility and surface exchange influence rate at lower temperatures and SSA. • Exchange temperatures may alter SSA and make data difficult to interpret.

  9. Synthesis of freestanding water-soluble indium oxide nanocrystals capped by alanine nitric acid via ligand exchange for thin film transistors and effects of ligands on the electrical properties

    International Nuclear Information System (INIS)

    Choi, Jin-Kyu; Koh, Ye-Seul; Jeong, Hyun-Dam

    2015-01-01

    We demonstrate synthesis of freestanding water-soluble indium oxide nanocrystals (In 2 O 3 NCs) by ligand exchange to β-alanine nitric acid (Ala·HNO 3 ) and its application for active channel layer in thin film transistors (TFTs), with investigation of the effect of curing temperatures on the TFT properties in terms of thermal behaviour of the ligand molecules at 150, 300, and 350 °C. After ligand exchange from long alkyl ligand (myristic acid, MA) to short Ala·HNO 3 , the mobility of NC TFTs cured at 150 °C increased by over 1 order of magnitude, from 1.3 × 10 −4 cm 2 V -1 s −1 to 4.5 × 10 −3 cm 2 V -1 s −1 , due to enhanced tunnelling rate (Γ) between adjective NCs. Higher curing temperatures such as 300 and 350 °C, inducing thermal decomposition of the organic ligands, led to further enhancement of the mobility, particularly up to 2.2 cm 2 V -1 s −1 for the In 2 O 3 NC-Ala·HNO 3 TFT cured at 350 °C. It is also found that the ligand exchange of In 2 O 3 NC in acidic condition (e.g. HNO 3 ) would be simple and effective to reduce the surface defects by surface etching, which may lead to better device performances. - Graphical abstract: Display Omitted - Highlights: • Freestanding water-soluble In 2 O 3 nanocrystals (NCs) were synthesized by ligand exchange. • Thin film transistors (TFTs) of colloidal NCs were fabricated by spin-coating method. • Water-soluble In 2 O 3 NC TFTs showed higher mobilities due to shorter ligand length. • Surface defects of NCs were notably reduced by surface etching during ligand exchange

  10. Reaction of Tris(cyclopentadienyl)uranium compounds with amines, azides, and related ligands

    International Nuclear Information System (INIS)

    Rosen, R.K.

    1989-12-01

    The trivalent uranium compound, (MeC 5 H 4 ) 3 U(thf), serves as a one- or two-electron reducing agent towards azides, RN 3 . These reactions produce either the uranium(IV) azide, (MeC 5 H 4 ) 3 UN 3 , or uranium(V) imides, (MeC 5 H 4 ) 3 UNR. The role of steric and electronic effects upon this reaction has been investigated using several series of azides. For Me 3 XN 3 , the imides are produced when X = C or Si, both products are formed when X = Ge, and the azide is produced when X = Sn. For Ph 3 XN 3 , the azide is produced when X = C or Sn. For Ph 3-x CH 3 N 3 , the imide is produced when x = 2 and both compounds are produced when x = 1. For substituted phenylazides, RC 6 H 4 N 3 , only the imides are produced. The magnetic properties of uranium diimides, [(MeC 5 H 4 ) 3 U] 2 (μ-NRN), were investigated. Several uranium(III) amines, (MeC 5 H 4 ) 3 U(NH 2 R), were produced from (MeC 5 H 4 ) 3 U(thf) and RNH 2 , and NH 3 was found to be a better ligand towards (MeC 5 H 4 ) 3 U than is PMe 3

  11. Reduction reactions of water soluble cyano-cobalt(III)-porphyrins: Metal versus ligand centered processes

    International Nuclear Information System (INIS)

    Mosseri, S.; Neta, P.; Harriman, A.; Hambright, P.

    1990-01-01

    Reduction reactions of dicyano-cobalt(III)-porphyrins [potential in vivo cyanide scavenger drugs] were studied by radiolytic and electrochemical methods using the water soluble tetrakis(4-sulfonatophenyl)porphyrin (TPPS) and tetrakis(N-methyl-4-pyridyl)porphyrin (TMPyP). For [(CN)2CoIIITPPS]-, reduction occurs stepwise to the CoII, CoI, and finally to the phlorin anion. This behavior is similar to that of the cobalt porphyrins in the absence of cyanide, except that the cyanide ligand shifts the reduction potentials to much more negative values. On the other hand, under radiolytic conditions, [(CN)2CoIIITMPyP]- is reduced on the porphyrin macrocycle by one electron to give the CoIII pi-radical anion, which disproportionates into the initial complex and the two-electron ring reduced CoIII phlorin. The radical anion is also formed by intramolecular electron transfer subsequent to the reaction of CoIITMPyP and cyanide. The results are compared with the chemistry of Vitamin B-12

  12. Dynamics of ligand exchange mechanism at Cu(II) in water: An ab initio quantum mechanical charge field molecular dynamics study with extended quantum mechanical region

    International Nuclear Information System (INIS)

    Moin, Syed Tarique; Hofer, Thomas S.; Weiss, Alexander K. H.; Rode, Bernd M.

    2013-01-01

    Ab initio quantum mechanical charge field molecular dynamics (QMCF-MD) were successfully applied to Cu(II) embedded in water to elucidate structure and to understand dynamics of ligand exchange mechanism. From the simulation studies, it was found that using an extended large quantum mechanical region including two shells of hydration is required for a better description of the dynamics of exchanging water molecules. The structural features characterized by radial distribution function, angular distribution function and other analytical parameters were consistent with experimental data. The major outcome of this study was the dynamics of exchange mechanism and reactions in the first hydration shell that could not be studied so far. The dynamical data such as mean residence time of the first shell water molecules and other relevant data from the simulations are close to the results determined experimentally. Another major characteristic of hydrated Cu(II) is the Jahn-Teller distortion which was also successfully reproduced, leading to the final conclusion that the dominating aqua complex is a 6-coordinated species. The ab initio QMCF-MD formalism proved again its capabilities of unraveling even ambiguous properties of hydrated species that are far difficult to explore by any conventional quantum mechanics/molecular mechanics (QM/MM) approach or experiment

  13. Dynamics of ligand exchange mechanism at Cu(II) in water: an ab initio quantum mechanical charge field molecular dynamics study with extended quantum mechanical region.

    Science.gov (United States)

    Moin, Syed Tarique; Hofer, Thomas S; Weiss, Alexander K H; Rode, Bernd M

    2013-07-07

    Ab initio quantum mechanical charge field molecular dynamics (QMCF-MD) were successfully applied to Cu(II) embedded in water to elucidate structure and to understand dynamics of ligand exchange mechanism. From the simulation studies, it was found that using an extended large quantum mechanical region including two shells of hydration is required for a better description of the dynamics of exchanging water molecules. The structural features characterized by radial distribution function, angular distribution function and other analytical parameters were consistent with experimental data. The major outcome of this study was the dynamics of exchange mechanism and reactions in the first hydration shell that could not be studied so far. The dynamical data such as mean residence time of the first shell water molecules and other relevant data from the simulations are close to the results determined experimentally. Another major characteristic of hydrated Cu(II) is the Jahn-Teller distortion which was also successfully reproduced, leading to the final conclusion that the dominating aqua complex is a 6-coordinated species. The ab initio QMCF-MD formalism proved again its capabilities of unraveling even ambiguous properties of hydrated species that are far difficult to explore by any conventional quantum mechanics/molecular mechanics (QM/MM) approach or experiment.

  14. Exchange reaction between hydrogen and deuterium. I. Importance of surface reactions in the steady-state mechanism

    Energy Technology Data Exchange (ETDEWEB)

    Marteau, C; Gaillard-Cusin, F; James, H [Centre National de la Recherche Scientifique, 45 - Orleans-la-Source (France). Centre de Recherches sur la Chimie de Combustion et des Hautes Temperatures

    1978-05-01

    Investigation of heterogeneous initiation process of gas phase linear chain reactions is carried out through the study of H/sub 2/-D/sub 2/ exchange reaction. Experimental data under study concern mainly the stationary rate of HD formation and the prestationary proceeding. Steady-state method accounts for the first one of these data; it allows to clearly compare the wall process part to the part played by the homogeneous chain reaction towards HD formation. Activation energy of exchange elementary step between chemisorbed hydrogen (on silica) and gaseous deuterium has been evaluated: Esub(e1)=52+-1 Kcal/mole.

  15. Redox non-innocent ligands: versatile new tools to control catalytic reactions

    NARCIS (Netherlands)

    Lyaskovskyy, V.; de Bruin, B.

    2012-01-01

    In this (tutorial overview) perspective we highlight the use of "redox non-innocent" ligands in catalysis. Two main types of reactivity in which the redox non-innocent ligand is involved can be specified: (A) The redox active ligand participates in the catalytic cycle only by accepting/donating

  16. Mechanism of redox reactions induced by light and electron pulse in solutions of mixed ligand iron(II) complex cyanides

    International Nuclear Information System (INIS)

    Horvath, A.; Szoeke, J.; Wojnarovits, L.

    1991-01-01

    Redox reactions induced by light and electron pulse have been studied in aqueous solutions of mixed ligand iron(II) complex cyanides. The short lived intermediates have been identified by time resolved specroscopy, the results of detailed kinetic analysis have been discussed. (author) 6 refs.; 3 figs.; 2 tabs

  17. Exchange reactions in the systems of alkali metal, silver and thallium, sulfates, niobates and tantalates

    International Nuclear Information System (INIS)

    Belyaev, I.N.; Lupejko, T.G.; Nalbandyan, V.B.; Abanina, E.V.

    1978-01-01

    Investigated are exchange interactions in diagonal cross sections of twenty triple mutual systems with A and A' cations and SO 4 and MO 3 anions where A and A'-Li, Na, K, Ag, Tl, M-Nb, Ta using the methods of X-ray phase, chemical and differential thermal analyses. Exchange reaction between crystal complex oxide and melted salt are effective synthesis method. These reactions in particular permitted to obtain pure AgNbO 3 , AgTaO 3 and their solid solutions at temperatures hundreds degrees lower than in displacement reactions. Equilibrium samples of AMO 3 -A'MO 3 systems, continuous or discontinuous solid solutions, compounds (except NaMO 3 -KMO 3 , and also LiTaO 3 -KTaO 3 ) are formed in exchange reactions when there is sulfate shortage. Thus, exchange reactions can be applied for solid solution synthesis, and also for phase diagram study

  18. Organic-inorganic hybrid perovskite quantum dots with high PLQY and enhanced carrier mobility through crystallinity control by solvent engineering and solid-state ligand exchange.

    Science.gov (United States)

    Woo Choi, Jin; Woo, Hee Chul; Huang, Xiaoguang; Jung, Wan-Gil; Kim, Bong-Joong; Jeon, Sie-Wook; Yim, Sang-Youp; Lee, Jae-Suk; Lee, Chang-Lyoul

    2018-05-22

    The photoluminescence quantum yield (PLQY) and charge carrier mobility of organic-inorganic perovskite QDs were enhanced by the optimization of crystallinity and surface passivation as well as solid-state ligand exchange. The crystallinity of perovskite QDs was determined by the Effective solvent field (Esol) of various solvents for precipitation. The solvent with high Esol could more quickly countervail the localized field generated by the polar solvent, and it causes fast crystallization of the dissolved precursor, which results in poor crystallinity. The post-ligand adding process (PLAP) and post-ligand exchange process (PLEP) increase the PLQY of perovskite QDs by reducing non-radiative recombination and the density of surface defect states through surface passivation. Particularly, the post ligand exchange process (PLEP) in the solid-state improved the charge carrier mobility of perovskite QDs in addition to the PLQY enhancement. The ligand exchange with short alkyl chain length ligands could improve the packing density of perovskite QDs in films by reducing the inter-particle distance between perovskite QDs. The maximum hole mobility of 6.2 × 10-3 cm2 V-1 s-1, one order higher than that of pristine QDs without the PLEP, is obtained at perovskite QDs with hexyl ligands. By using PLEP treatment, compared to the pristine device, a 2.5 times higher current efficiency in perovskite QD-LEDs was achieved due to the improved charge carrier mobility and PLQY.

  19. Isotope exchange reaction in Li2ZrO3 packed bed

    International Nuclear Information System (INIS)

    Kawamura, Y.; Enoeda, M.; Okuno, K.

    1998-01-01

    To understand the release behavior of bred tritium in a solid breeder blanket, the tritium transfer rate and tritium inventory for various mass transfer processes should be investigated. The contribution of the surface reactions (adsorption, desorption and two kinds of isotope exchange reactions) to the release process cannot be ignored. It is believed that two kinds of isotope exchange reactions (gaseous hydrogen-tritiated water and water vapor-tritiated water) occur on the surface of the solid breeder materials when hydrogen is added to the sweep gas to enhance the tritium release rate. The isotope exchange reaction study in H-D systems was carried out using a Li 2 ZrO 3 packed bed. The exchange reaction between gaseous hydrogen and water was the rate controlling step among the two kinds of exchange reactions. The reaction rate constants were quantified, and experimental equations were proposed. The equilibrium constant of the isotope exchange reaction in the H-D system was obtained from experimental data and was found to be 1.17. (orig.)

  20. Relative mobility of 1-H atoms of carbohydrates in heterogeneous isotope exchange reactions

    International Nuclear Information System (INIS)

    Akulov, G.P.; Snetkova, E.V.; Kayumov, V.G.; Kaminskii, Yu.L.

    1988-01-01

    The method of competitive reactions was used to determine the relative mobilities of the 1-H atoms of carbohydrates in reactions of heterogeneous isotope exchange, using various reference standards, catalysts, and buffer systems. On the basis of the results obtained, the investigated carbohydrates are ranged in a series of decreasing mobility of the hydrogen atoms exchanged in heterogeneous isotope exchange reactions. It was demonstrated that the mobility of the 1-H atoms is related to the concentration of the acyclic forms of the carbohydrates

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

    International Nuclear Information System (INIS)

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

    1987-01-01

    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

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

    Science.gov (United States)

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

    2015-04-28

    The mechanism of the isotope exchange reaction between molecular tritium and several typical organic molecules in vacuum pump mineral oil has been investigated by density functional theory (DFT), and the reaction rates are determined by conventional transition state theory (TST). The tritium-hydrogen isotope exchange reaction can proceed with two different mechanisms, the direct T-H exchange mechanism and the hyrogenation-dehydrogenation exchange mechanism. In the direct exchange mechanism, the titrated product is obtained through one-step via a four-membered ring hydrogen migration transition state. In the hyrogenation-dehydrogenation exchange mechanism, the T-H exchange could be accomplished by the hydrogenation of the unsaturated bond with tritium followed by the dehydrogenation of HT. Isotope exchange between hydrogen and tritium is selective, and oil containing molecules with OH and COOH groups can more easily exchange hydrogen for tritium. For aldehydes and ketones, the ability of T-H isotope exchange can be determined by the hydrogenation of T2 or the dehydrogenation of HT. The molecules containing one type of hydrogen provide a single product, while the molecules containing different types of hydrogens provide competitive products. The rate constants are presented to quantitatively estimate the selectivity of the products. Copyright © 2015 Elsevier B.V. All rights reserved.

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

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Liang; Xie, Yun [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China); Du, Liang [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China); School of Radiation Medicine and Protection (SRMP), School for Radiological and Interdisciplinary Sciences (RAD-X), Suzhou 215000 (China); Li, Weiyi [School of Physics and Chemistry, Xihua University, Chengdu 610065 (China); Tan, Zhaoyi, E-mail: zhyitan@126.com [Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621900 (China)

    2015-04-28

    Highlights: • This is the first theoretical investigation about T–H exchange in vacuum oil. • T–H isotope exchange is accomplished through two different change mechanisms. • Isotope exchange is selective, molecules with −OH and −COOH exchange more easily. • The methyl and methylene radicals in waste oil were observed by {sup 1}HNMR. - Abstract: The mechanism of the isotope exchange reaction between molecular tritium and several typical organic molecules in vacuum pump mineral oil has been investigated by density functional theory (DFT), and the reaction rates are determined by conventional transition state theory (TST). The tritium–hydrogen isotope exchange reaction can proceed with two different mechanisms, the direct T–H exchange mechanism and the hyrogenation–dehydrogenation exchange mechanism. In the direct exchange mechanism, the titrated product is obtained through one-step via a four-membered ring hydrogen migration transition state. In the hyrogenation–dehydrogenation exchange mechanism, the T–H exchange could be accomplished by the hydrogenation of the unsaturated bond with tritium followed by the dehydrogenation of HT. Isotope exchange between hydrogen and tritium is selective, and oil containing molecules with −OH and −COOH groups can more easily exchange hydrogen for tritium. For aldehydes and ketones, the ability of T–H isotope exchange can be determined by the hydrogenation of T{sub 2} or the dehydrogenation of HT. The molecules containing one type of hydrogen provide a single product, while the molecules containing different types of hydrogens provide competitive products. The rate constants are presented to quantitatively estimate the selectivity of the products.

  4. Reaction of Tris(cyclopentadienyl)uranium compounds with amines, azides, and related ligands

    Energy Technology Data Exchange (ETDEWEB)

    Rosen, R.K.

    1989-12-01

    The trivalent uranium compound, (MeC{sub 5}H{sub 4}){sub 3}U(thf), serves as a one- or two-electron reducing agent towards azides, RN{sub 3}. These reactions produce either the uranium(IV) azide, (MeC{sub 5}H{sub 4}){sub 3}UN{sub 3}, or uranium(V) imides, (MeC{sub 5}H{sub 4}){sub 3}UNR. The role of steric and electronic effects upon this reaction has been investigated using several series of azides. For Me{sub 3}XN{sub 3}, the imides are produced when X = C or Si, both products are formed when X = Ge, and the azide is produced when X = Sn. For Ph{sub 3}XN{sub 3}, the azide is produced when X = C or Sn. For Ph{sub 3-x}CH{sub 3}N{sub 3}, the imide is produced when x = 2 and both compounds are produced when x = 1. For substituted phenylazides, RC{sub 6}H{sub 4}N{sub 3}, only the imides are produced. The magnetic properties of uranium diimides, ((MeC{sub 5}H{sub 4}){sub 3}U){sub 2}({mu}-NRN), were investigated. Several uranium(III) amines, (MeC{sub 5}H{sub 4}){sub 3}U(NH{sub 2}R), were produced from (MeC{sub 5}H{sub 4}){sub 3}U(thf) and RNH{sub 2}, and NH{sub 3} was found to be a better ligand towards (MeC{sub 5}H{sub 4}){sub 3}U than is PMe{sub 3}.

  5. Hydrogen and oxygen isotope exchange reactions over illuminated and nonilluminated TiO2

    International Nuclear Information System (INIS)

    Sato, S.

    1987-01-01

    Hydrogen isotope exchange between H 2 , gaseous H 2 O, and the surface hydroxyls of TiO 2 , and oxygen isotope exchange between O 2 , CO 2 , CO, H 2 O vapor, and the hydroxyls over TiO 3 were studied at room temperature in the dark and under illumination. Hydrogen isotope exchange between H 2 O and the hydroxyls occurred rapidly in the dark, but the exchange involving H 2 did not occur at all even under illumination. Oxygen isotope exchange among H 2 O vapor, CO 2 , and the hydroxyls easily took place in the dark, but the exchange involving O 2 required band-gap illumination. Dioxygen isotope equilibration was much faster than the other photoexchange reactions. Although the oxygen exchange between O 2 and illuminated TiO 2 has been considered to involve lattice-oxygen exchange, the present experiments revealed that the hydroxyls of TiO 2 mainly participate in the exchange reaction. The oxygen exchange between O 2 and H 2 O vapor was strongly inhibited by H 2 O vapor itself probably because oxygen adsorption was retarded by adsorbed water. Oxygen in CO was not exchanged with the other substrates under any conditions tested

  6. Hydrogen isotopic exchange reaction in a trickle-bed

    International Nuclear Information System (INIS)

    Paek, Seung Woo; Ahn, Do Hee; Kim, Kwang Rag; Lee, Min Soo; Yim, Sung Paal; Chung, Hong Suk

    2005-01-01

    The CECE (Combined Electrolysis Catalytic Exchange) with a hydrophobic catalyst is ideally suited for extracting tritium from water because of its high separation factor and mild operating conditions. This process for different hydrogen isotope applications has been developed by AECL. A laboratory scale CECE was built and operated at Mound Laboratory. Belgium and Japan have also developed independently similar processes which are based on a hydrophobic catalyst. The CECE column is composed of an electrolysis cell and a liquid phase catalytic exchange column. The liquid phase catalytic exchange columns having various structures were developed; and it has been recognized that a multistage type and a trickle-bed type are promising. The multistage type gave more successful results than the trickle-bed type. However, the structure of the column is complicated. The trickle-bed type has a significant advantage in that the structure of the column is quite simple: the hydrophobic catalysts or the catalysts and packings are packed within the column. This structure would lead us to a smaller column height than the multistage type. This paper deals with the experiment for the hydrogen isotope exchange in a trickle-bed reactor packed with a hydrophobic catalyst and the design of the catalytic column for the CECE to tritium recovery from light water

  7. Hydrogen isotopic exchange reaction in a trickle-bed

    Energy Technology Data Exchange (ETDEWEB)

    Paek, Seung Woo; Ahn, Do Hee; Kim, Kwang Rag; Lee, Min Soo; Yim, Sung Paal; Chung, Hong Suk [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    2005-07-01

    The CECE (Combined Electrolysis Catalytic Exchange) with a hydrophobic catalyst is ideally suited for extracting tritium from water because of its high separation factor and mild operating conditions. This process for different hydrogen isotope applications has been developed by AECL. A laboratory scale CECE was built and operated at Mound Laboratory. Belgium and Japan have also developed independently similar processes which are based on a hydrophobic catalyst. The CECE column is composed of an electrolysis cell and a liquid phase catalytic exchange column. The liquid phase catalytic exchange columns having various structures were developed; and it has been recognized that a multistage type and a trickle-bed type are promising. The multistage type gave more successful results than the trickle-bed type. However, the structure of the column is complicated. The trickle-bed type has a significant advantage in that the structure of the column is quite simple: the hydrophobic catalysts or the catalysts and packings are packed within the column. This structure would lead us to a smaller column height than the multistage type. This paper deals with the experiment for the hydrogen isotope exchange in a trickle-bed reactor packed with a hydrophobic catalyst and the design of the catalytic column for the CECE to tritium recovery from light water.

  8. Gamow Teller strength from charge exchange reactions at intermediate energies

    International Nuclear Information System (INIS)

    Haeusser, O.

    1989-07-01

    Detailed studies of the spin-isospin structure of nuclear excitations are possible at TRIUMF's medium resolution spectrometer using the (n,p), ( p → , p →/ ) and (p,n) reactions. We discuss here results on isospin symmetry of inelastic nucleon scattering reactions populating isospin triads in A=6 and A=12 nuclei. The β + Gamow Teller strength function from (n,p) reactions on (sd) and (fp) shell targets is found to be substantially quenched compared to current nuclear structure models using the free-nucleon axial-vector coupling constant. (Author) 22 refs., 3 figs

  9. Roles of Bridging Ligand Topology and Conformation in Controlling Exchange Interactions between Paramagnetic Molybdenum Fragments in Dinuclear and Trinuclear Complexes.

    Science.gov (United States)

    Ung VÂ, V&acaron;n Ân; Cargill Thompson, Alexander M. W.; Bardwell, David A.; Gatteschi, Dante; Jeffery, John C.; McCleverty, Jon A.; Totti, Federico; Ward, Michael D.

    1997-07-30

    The magnetic properties of two series of dinuclear complexes, and one trinuclear complex, have been examined as a function of the bridging pathway between the metal centers. The first series of dinuclear complexes is [{Mo(V)(O)(Tp)Cl}(2)(&mgr;-OO)], where "OO" is [1,4-O(C(6)H(4))(n)O](2)(-) (n = 1, 1; n = 2, 3), [4,4'-O(C(6)H(3)-2-Me)(2)O](2)(-) (4), or [1,3-OC(6)H(4)O](2)(-) (2) [Tp = tris(3,5-dimethylpyrazolyl)hydroborate]. The second series of dinuclear complexes is [{Mo(I)(NO)(Tp)Cl}(2)(&mgr;-NN)], where "NN" is 4,4'-bipyridyl (5), 3,3'-dimethyl-4,4'-bipyridine (6), 3,8-phenanthroline (7), or 2,7-diazapyrene (8). The trinuclear complex is [{Mo(V)(O)(Tp)Cl}(3)(1,3,5-C(6)H(3)O(3))] (9), whose crystal structure was determined [9.5CH(2)Cl(2): C(56)H(81)B(3)Cl(13)Mo(3)N(18)O(6); monoclinic, P2(1)/n; a = 13.443, b = 41.46(2), c = 14.314(6) Å; beta = 93.21(3) degrees; V = 7995(5) Å(3); Z = 4; R(1) = 0.106]. In these complexes, the sign and magnitude of the exchange coupling constant J is clearly related to both the topology and the conformation of the bridging ligand [where J is derived from H = -JS(1)().S(2)() for 1-8 and H = -J(S(1)().S(2)() + S(2)().S(3)() + S(1)().S(3)()) for 9]. The values are as follows: 1, -80 cm(-)(1); 2, +9.8 cm(-)(1); 3, -13.2 cm(-)(1); 4, -2.8 cm(-)(1); 5, -33 cm(-)(1); 6, -3.5 cm(-)(1); 7, -35.6 cm(-)(1); 8, -35.0 cm(-)(1); 9, +14.4 cm(-)(1). In particular the following holds: (1) J is negative (antiferromagnetic exchange) across the para-substituted bridges ligands of 1 and 3-8 but positive (ferromagnetic exchange) across the meta-substituted bridging ligands of 2 and 9. (2) J decreases in magnitude dramatically as the bridging ligand conformation changes from planar to twisted (compare 3 and 4, or 6 and 8). These observations are consistent with a spin-polarization mechanism for the exchange interaction, propagated across the pi-system of the bridging ligand by via overlap of bridging ligand p(pi) orbitals with the d(pi) magnetic

  10. Cross sections and rate coefficients for charge exchange reactions of protons with hydrocarbon molecules

    International Nuclear Information System (INIS)

    Janev, R.K.; Kato, T.; Wang, J.G.

    2001-05-01

    The available experimental and theoretical cross section data on charge exchange processes in collisions of protons with hydrocarbon molecules have been collected and critically assessed. Using well established scaling relationships for the charge exchange cross sections at low and high collision energies, as well as the known rate coefficients for these reactions in the thermal energy region, a complete cross section database is constructed for proton-C x H y charge exchange reactions from thermal energies up to several hundreds keV for all C x H y molecules with x=1, 2, 3 and 1 ≤ y ≤ 2x + 2. Rate coefficients for these charge exchange reactions have also been calculated in the temperature range from 0.1 eV to 20 keV. (author)

  11. Cross sections and rate coefficients for charge exchange reactions of protons with hydrocarbon molecules

    Energy Technology Data Exchange (ETDEWEB)

    Janev, R.K.; Kato, T. [National Inst. for Fusion Science, Toki, Gifu (Japan); Wang, J.G. [Department of Physics and Astronomy, University of Georgia, Athens (United States)

    2001-05-01

    The available experimental and theoretical cross section data on charge exchange processes in collisions of protons with hydrocarbon molecules have been collected and critically assessed. Using well established scaling relationships for the charge exchange cross sections at low and high collision energies, as well as the known rate coefficients for these reactions in the thermal energy region, a complete cross section database is constructed for proton-C{sub x}H{sub y} charge exchange reactions from thermal energies up to several hundreds keV for all C{sub x}H{sub y} molecules with x=1, 2, 3 and 1 {<=} y {<=} 2x + 2. Rate coefficients for these charge exchange reactions have also been calculated in the temperature range from 0.1 eV to 20 keV. (author)

  12. High-affinity multivalent wheat germ agglutinin ligands by one-pot click reaction

    Directory of Open Access Journals (Sweden)

    Henning S. G. Beckmann

    2012-06-01

    Full Text Available A series of six mono-, di-, and trivalent N,N’-diacetylchitobiose derivatives was conveniently prepared by employing a one-pot procedure for Cu(II-catalyzed diazo transfer and Cu(I-catalyzed azide–alkyne cycloaddition (CuAAC starting from commercially available amines. These glycoclusters were probed for their binding potencies to the plant lectin wheat germ agglutinin (WGA from Triticum vulgaris by an enzyme-linked lectin assay (ELLA employing covalently immobilized N-acetylglucosamine (GlcNAc as a reference ligand. IC50 values were in the low micromolar/high nanomolar range, depending on the linker between the two disaccharides. Binding enhancements β up to 1000 for the divalent ligands and 2800 for a trivalent WGA ligand, compared to N,N’-diacetylchitobiose as the corresponding monovalent ligand, were observed. Molecular modeling studies, in which the chitobiose moieties were fitted into crystallographically determined binding sites of WGA, correlate the binding enhancements of the multivalent ligands with their ability to bind to the protein in a chelating mode. The best WGA ligand is a trivalent cluster with an IC50 value of 220 nM. Calculated per mol of contained chitobiose, this is the best WGA ligand known so far.

  13. Experimental evaluation of improved dual temperature hydrogen isotopic exchange reaction system

    International Nuclear Information System (INIS)

    Asakura, Yamato; Uchida, Shunsuke

    1984-01-01

    A proposed dual temperature hydrogen isotopic exchange reaction system between water and hydrogen gas is evaluated experimentally. The proposed system is composed of low temperature co-current reactors for reaction between water mists and hydrogen gas and high temperature co-current reactors for reaction between water vapor and hydrogen gas. Thus, operation is possible under atmospheric pressure with high reaction efficiency. Using the pilot test system which is composed of ten low temperature (30 0 C) reaction units and ten high temperature (200 0 C) reaction units, an experimental separation of deuterium from light water is carried out. The enrichment factor under steady state conditions, its dependency on operating time, and the reaction period necessary to obtain the steady state enrichment factor are determined experimentally and compared with calculations. It is shown that separation ability in a multistage reaction system can be estimated by numerical calculation using actual reaction efficiency in a unit reactor. (author)

  14. Proton exchange in acid–base complexes induced by reaction coordinates with heavy atom motions

    International Nuclear Information System (INIS)

    Alavi, Saman; Taghikhani, Mahdi

    2012-01-01

    Highlights: ► Proton exchange in acid–base complexes is studied. ► The structures, binding energies, and normal mode vibrations are calculated. ► Transition state structures of proton exchange mechanism are determined. ► In the complexes studied, the reaction coordinate involves heavy atom rocking. ► The reaction coordinate is not simply localized in the proton movements. - Abstract: We extend previous work on nitric acid–ammonia and nitric acid–alkylamine complexes to illustrate that proton exchange reaction coordinates involve the rocking motion of the base moiety in many double hydrogen-bonded gas phase strong acid–strong base complexes. The complexes studied involve the biologically and atmospherically relevant glycine, formic, acetic, propionic, and sulfuric acids with ammonia/alkylamine bases. In these complexes, the magnitude of the imaginary frequencies associated with the proton exchange transition states are −1 . This contrasts with widely studied proton exchange reactions between symmetric carboxylic acid dimers or asymmetric DNA base pair and their analogs where the reaction coordinate is localized in proton motions and the magnitude of the imaginary frequencies for the transition states are >1100 cm −1 . Calculations on complexes of these acids with water are performed for comparison. Variations of normal vibration modes along the reaction coordinate in the complexes are described.

  15. Quantum theory of exchange reactions: Use of nonorthogonal bases and coordinates

    International Nuclear Information System (INIS)

    Stechel, E.B.; Schmalz, T.G.; Light, J.C.

    1979-01-01

    A general approach to quantum scattering theory of exchange reactions utilizing nonorthogonal (''over-complete'') basis sets and nonorthogonal coordinates is presented. The method is shown to resolve many of the formal and practical difficulties attending earlier theories. Although the inspiration came from the early and accurate work on the collinear H+H 2 reaction by Diestler possible applications include electron transfer processes as well as chemical exchange reactions. The mathematics is formulated in detail and the solution is presented in terms of the R-matrix propagation method preserving all the symmetries of the physical process, i.e., conservation of flux and microscopic reversibility

  16. Synthesis of freestanding water-soluble indium oxide nanocrystals capped by alanine nitric acid via ligand exchange for thin film transistors and effects of ligands on the electrical properties

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Jin-Kyu; Koh, Ye-Seul; Jeong, Hyun-Dam, E-mail: hdjeong@chonnam.ac.kr

    2015-07-15

    We demonstrate synthesis of freestanding water-soluble indium oxide nanocrystals (In{sub 2}O{sub 3} NCs) by ligand exchange to β-alanine nitric acid (Ala·HNO{sub 3}) and its application for active channel layer in thin film transistors (TFTs), with investigation of the effect of curing temperatures on the TFT properties in terms of thermal behaviour of the ligand molecules at 150, 300, and 350 °C. After ligand exchange from long alkyl ligand (myristic acid, MA) to short Ala·HNO{sub 3}, the mobility of NC TFTs cured at 150 °C increased by over 1 order of magnitude, from 1.3 × 10{sup −4} cm{sup 2}V{sup -1}s{sup −1} to 4.5 × 10{sup −3} cm{sup 2}V{sup -1}s{sup −1}, due to enhanced tunnelling rate (Γ) between adjective NCs. Higher curing temperatures such as 300 and 350 °C, inducing thermal decomposition of the organic ligands, led to further enhancement of the mobility, particularly up to 2.2 cm{sup 2}V{sup -1}s{sup −1} for the In{sub 2}O{sub 3} NC-Ala·HNO{sub 3} TFT cured at 350 °C. It is also found that the ligand exchange of In{sub 2}O{sub 3} NC in acidic condition (e.g. HNO{sub 3}) would be simple and effective to reduce the surface defects by surface etching, which may lead to better device performances. - Graphical abstract: Display Omitted - Highlights: • Freestanding water-soluble In{sub 2}O{sub 3} nanocrystals (NCs) were synthesized by ligand exchange. • Thin film transistors (TFTs) of colloidal NCs were fabricated by spin-coating method. • Water-soluble In{sub 2}O{sub 3} NC TFTs showed higher mobilities due to shorter ligand length. • Surface defects of NCs were notably reduced by surface etching during ligand exchange.

  17. Field-effect measurements of mobility and carrier concentration of Cu2S colloidal quantum dot thin films after ligand exchange

    International Nuclear Information System (INIS)

    Brewer, Adam S.; Arnold, Michael S.

    2014-01-01

    Colloidal quantum dots (CQDs) of copper sulfide (Cu 2 S), an earth-abundant semiconductor, have a number of intriguing applications that require knowledge of their electrical properties. Depending on stoichiometry, mobility, and surface treatment, applications include photoabsorbers for solar cells, tunable plasmonics, and counter-electrodes for polysulfate electrolytes. However, there have not been any direct measurements of electrical properties in Cu 2 S CQD thin films. Here, we exchange as synthesized dodecanethiol ligands with short ethanedithiol or ethylenediamine ligands to form thin films of coupled Cu 2 S CQDs. The mobility and carrier concentration were found to vary by ligand treatment from 10 −5 cm 2 /Vs and 10 19 holes/cm 3 for ethanedithiol ligands to 10 −3 cm 2 /Vs and 10 20 holes/cm 3 for ethylenediamine. These results are consistent with the carrier concentrations inferred from sub-bandgap surface-plasmon-resonances measured by infrared spectroscopy. These results will be useful when designing Cu 2 S materials for future applications. - Highlights: • Colloidal Cu2S quantum dots were synthesized and characterized. • Ligand exchange was performed to alter the Cu2S nanocrystal properties. • Ligand exchange was studied using photoluminescence and infrared spectroscopy. • Field effect mobility and carrier concentration were directly measured. • Carrier concentration was compared to estimates from surface plasmon resonances

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

    Science.gov (United States)

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

    2015-01-01

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

  19. Density functional theory studies on the structures and water-exchange reactions of aqueous Al(III)-oxalate complexes.

    Science.gov (United States)

    Jin, Xiaoyan; Yan, Yu; Shi, Wenjing; Bi, Shuping

    2011-12-01

    The structures and water-exchange reactions of aqueous aluminum-oxalate complexes are investigated using density functional theory. The present work includes (1) The structures of Al(C(2)O(4))(H(2)O)(4)(+) and Al(C(2)O(4))(2)(H(2)O)(2)(-) were optimized at the level of B3LYP/6-311+G(d,p). The geometries obtained suggest that the Al-OH(2) bond lengths trans to C(2)O(4)(2-) ligand in Al(C(2)O(4))(H(2)O)(4)(+) are much longer than the Al-OH(2) bond lengths cis to C(2)O(4)(2-). For Al(C(2)O(4))(2)(H(2)O)(2)(-), the close energies between cis and trans isomers imply the coexistence in aqueous solution. The (27)Al NMR and (13)C NMR chemical shifts computed with the consideration of sufficient solvent effect using HF GIAO method and 6-311+G(d,p) basis set are in agreement with the experimental values available, indicating the appropriateness of the applied models; (2) The water-exchange reactions of Al(III)-oxalate complexes were simulated at the same computational level. The results show that water exchange proceeds via dissociative pathway and the activation energy barriers are sensitive to the solvent effect. The energy barriers obtained indicate that the coordinated H(2)O cis to C(2)O(4)(2-) in Al(C(2)O(4))(H(2)O)(4)(+) is more labile than trans H(2)O. The water-exchange rate constants (k(ex)) of trans- and cis-Al(C(2)O(4))(2)(H(2)O)(2)(-) were estimated by four methods and their respective characteristics were explored; (3) The significance of the study on the aqueous aluminum-oxalate complexes to environmental chemistry is discussed. The influences of ubiquitous organic ligands in environment on aluminum chemistry behavior can be elucidated by extending this study to a series of Al(III)-organic system.

  20. Syntheses, crystal structures and properties of novel copper(II) complexes obtained by reactions of copper(II) sulfate pentahydrate with tripodal ligands.

    Science.gov (United States)

    Zhao, Wei; Fan, Jian; Song, You; Kawaguchi, Hiroyuki; Okamura, Taka-aki; Sun, Wei-Yin; Ueyama, Norikazu

    2005-04-21

    Three novel metal-organic frameworks (MOFs), [Cu(1)SO4].H2O (4), [Cu2(2)2(SO4)2].4H2O (5) and [Cu(3)(H2O)]SO4.5.5H2O (6), were obtained by hydrothermal reactions of CuSO4.5H2O with the corresponding ligands, which have different flexibility. The structures of the synthesized complexes were determined by single-crystal X-ray diffraction analyses. Complex 4 has a 2D network structure with two types of metallacycles. Complex 5 also has a 2D network structure in which each independent 2D sheet contains two sub-layers bridged by oxygen atoms of the sulfate anions. Complex 6 has a 2D puckered structure in which the sulfate anions serve as counter anions, which are different from those in complexes 4 (terminators) and 5 (bridges). The different structures of complexes 4, 5 and 6 indicate that the nature of organic ligands affected the structures of the assemblies greatly. The magnetic behavior of complex 5 and anion-exchange properties of complex 6 were investigated.

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

    International Nuclear Information System (INIS)

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

    1987-01-01

    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

  2. Exchange interactions in a dinuclear manganese (II) complex with cyanopyridine-N-oxide bridging ligands

    Energy Technology Data Exchange (ETDEWEB)

    Markosyan, A.S. [Faculty of Physics, M.V. Lomonosov Moscow State University, 119992 Moscow (Russian Federation); Department of Applied Physics, Stanford University (United States); Gaidukova, I.Yu.; Ruchkin, A.V. [Faculty of Physics, M.V. Lomonosov Moscow State University, 119992 Moscow (Russian Federation); Anokhin, A.O. [Institute of Metal Physics, Ural Division of the Russian, Ekaterinburg (Russian Federation); Irkhin, V.Yu., E-mail: valentin.irkhin@imp.uran.ru [Institute of Metal Physics, Ural Division of the Russian, Ekaterinburg (Russian Federation); Ryazanov, M.V.; Kuz’mina, N.P. [Faculty of Chemistry, M.V. Lomonosov Moscow State University, 119992 Moscow (Russian Federation); Nikiforov, V.N. [Faculty of Physics, M.V. Lomonosov Moscow State University, 119992 Moscow (Russian Federation)

    2014-01-01

    The magnetic properties of dinuclear manganese(II) complex [Mn(hfa){sub 2}cpo]{sub 2} (where hfa is hexafluoroacetylacetonate anion and cpo is 4-cyanopyridine-N-oxide) are presented. The non-monotonous dependence of magnetic susceptibility is explained in terms of the hierarchy of exchange parameters by using exact diagonalization. The thermodynamic behavior of pure cpo and [Mn(hfa){sub 2}(cpo)]{sub 2} is simulated numerically by an extrapolation to spin S=5/2. The Mn–Mn exchange integral is evaluated.

  3. The exchange reaction between deuterium and water vapour on platinum deposited over a hydrophobic support

    International Nuclear Information System (INIS)

    Itsuo, Iida; Junko, Kato; Kenzi, Tamuru

    1977-01-01

    Isotope exchange reaction between deuterium gas and water vapour at room temperature and below on platinum deposited on hydrophobic supports such as polytetrafluoroethylene (PTFE) or Porapak Q (copolymer of styrene and divinylbenzene) was studied and the results were compared with those of the exchange reaction on platinum over hydrophilic support such as alumina. It was demonstrated that the exchange reaction at temperatures below the boiling point of water is markedly retarded by the multilayer adsorption of water over the platinum catalyst deposited on hydrophilic support, whereas the platinum catalyst on hydrophobic support exhibited a high catalytic activity, being not retarded by the water, forming no multilayer of adsorbed water over platinum surface. Therefore in the case of the hydrogen isotope exchange reaction on platinum over hydrophobic support, the chemical exchange rate can be measured even under a saturated vapour pressure of water. The surface area of platinum was estimated by hydrogen chemisorption and hydrogen titration and specific activities of the catalyst were calculated at both room temperature and freezing point of water, which revealed that the specific rate of this reaction does not differ so much over various supports. (orig.) [de

  4. Examining the reaction of monetary policy to exchange rate changes: A nonlinear ARDL approach

    Science.gov (United States)

    Manogaran, Lavaneesvari; Sek, Siok Kun

    2017-04-01

    Previous studies showed the exchange rate changes can have significant impacts on macroeconomic performance. Over fluctuation of exchange rate may lead to economic instability. Hence, monetary policy rule tends to react to exchange rate changes. Especially, in emerging economies where the policy-maker tends to limit the exchange rate movement through interventions. In this study, we seek to investigate how the monetary policy rule reacts to exchange rate changes. The nonlinear autoregressive distributed lag (NARDL) model is applied to capture the asymmetric effect of exchange rate changes on monetary policy reaction function (interest rate). We focus the study in ASEAN5 countries (Indonesia, Malaysia, Philippines, Thailand and Singapore). The results indicated the existence of asymmetric effect of exchange rates changes on the monetary reaction function for all ASEAN5 countries in the long-run. Where, in majority of the cases the monetary policy is reacting to the appreciation and depreciation of exchange rate by raising the policy rate. This affirms the intervention of policymakers with the `fear of floating' behavior.

  5. Gaseous exchange reaction of deuterium between hydrogen and water on hydrophobic catalyst supporting platinum

    International Nuclear Information System (INIS)

    Izawa, Hirozumi; Isomura, Shohei; Nakane, Ryohei.

    1979-01-01

    The deuterium exchange reaction between hydrogen and water in the gas phase where the fed hydrogen gas is saturated with water vapor is studied experimentally by use of the proper hydrophobic catalysts supporting platinum. It is found that the activities of those catalysts for this reaction system are very high compared with the other known ones for the systems in which gas and liquid should coexist on catalyst surfaces, and that the apparent catalytic activity becomes larger as the amount of platinum supported on a catalyst particle increases. By analyses of the data the following informations are obtained. The exchange reaction can be expressed by a first order reversible reaction kinetics. The pore diffusion in the catalyst particles has significant effect on the overall reaction mechanisms. (author)

  6. The influence of ligand field effects on the magnetic exchange of high-spin Co(II)-semiquinonate complexes.

    Science.gov (United States)

    Bencini, Alessandro; Beni, Alessandra; Costantino, Ferdinando; Dei, Andrea; Gatteschi, Dante; Sorace, Lorenzo

    2006-02-07

    [Co(Me(4)cyclam)(tropolonate)](PF(6)) was synthesised and structurally characterised. Its electronic and W-band EPR spectra have been analysed by means of the angular overlap calculation of the Spin Hamiltonian parameters that provided also a satisfactory reproduction of the temperature dependence of the magnetic susceptibility. The present results can be interpreted assuming a pseudo-octahedral character for the Co(II) center. This prompted us to reconsider the model formerly used for the analysis of the magnetic coupling between hs-Co(II) and the paramagnetic o-semiquinonate ligand in the corresponding derivatives [Co(Me(4)cyclam)(PhenSQ)](PF(6)) and [Co(Me(4)cyclam)(DTBSQ)](PF(6)). These results indicate that the effect of the magnetic coupling is active only below 50 K and that a more refined model of exchange coupling between Co(II) and semiquinonato ligands is needed to quantitatively analyze the magnetic behaviour of this class of systems.

  7. N-Decyl-S-trityl-(R)-cysteine, a new chiral selector for "green" ligand-exchange chromatography applications.

    Science.gov (United States)

    Carotti, Andrea; Ianni, Federica; Camaioni, Emidio; Pucciarini, Lucia; Marinozzi, Maura; Sardella, Roccaldo; Natalini, Benedetto

    2017-09-10

    In search for new enantioselectivity profiles, the N-decyl-S-trityl-(R)-cysteine [C 10 -(R)-STC] was synthesized through a one-step procedure and then hydrophobically adsorbed onto an octadecylsilica surface to generate a stable chiral stationary phase for ligand-exchange chromatography (CLEC-CSP) applications. The CLEC analysis was carried out on underivatized amino acids, by using a Cu(II) sulphate (1.0mM) containing aqueous eluent system. Most of the analysed compounds (34 out of 45) were enantiodiscriminated by the C 10 -(R)-STC-based CSP, with resolution factor (R S ) values up to 8.86. Conformationally rigid and hydrophobic ligands often experienced the largest enantioselectivity effects. A high loadability emerged from the analysis of rac-NorVal (selected as prototype test compound): up to 20mg/mL were efficiently enantioseparated with the CLEC-CSP. Two in-line hand-made cartridges filled with a strong cation-exchange resin allowed the effective catching of Cu(II) ions after the semi-preparative enantioseparation. The quantitative recovery of the rac-NorVal enantiomers was made possible by flowing through the cartridge a 5% (v) ammonia solution. The CLEC phase proved successful in the enantioselective analysis of a commercially available (S)-Leu containing tablet. Furthermore, in order to understand the molecular basis for a successful use of the C 10 -(R)-STC-based CLEC system, a descriptive structure-separation relationship study was performed. As a result, all compounds with a MEAN-QPlogS (a hydrophilicity descriptor) value lower than 0.373 can be most likely enantioseparated with the CLEC system under investigation. In the work, the numerous aspects complying with the principles of green chromatography are highlighted and discussed. Copyright © 2017 Elsevier B.V. All rights reserved.

  8. Hydrogen isotope exchange reaction rates in tritium, hydrogen and deuterium mixed gases

    International Nuclear Information System (INIS)

    Uda, Tatsuhiko

    1992-01-01

    Hydrogen isotope exchange reaction rates in H 2 +T 2 , D 2 +T 2 and H 2 +D 2 +T 2 mixed gases, as induced by tritium decay and beta radiation, were experimentally measured by laser Raman spectrometry. Initially a glass cell was filled with T 2 gas to a pressure of 30-40 kPa, and an equivalent partial pressure of H 2 and/or D 2 was added. The first-order hydrogen isotope exchange reaction rates were 5.54x10 -2 h -1 for H 2 +T 2 mixed gas and 4.76x10 -2 h -1 for D 2 +T 2 . The actual HT producing rate was nearly equivalent to the rate of DT, but the reverse reaction rate of HT was faster than that of DT. The exchange reaction rates between H, D and T showed the isotope effect, HD>HT>DT. The hydrogen isotope exchange reaction rates observed were about twenty times larger than ion formation rates by beta radiation. This result suggests that a free radical chain reaction in hydrogen isotopes is occurring. (orig.)

  9. Study of reactions of isotopic exchange of trans-zeatin with tritium

    International Nuclear Information System (INIS)

    Sidorov, G.V.; Myasoedov, N.F.

    2006-01-01

    Reactions of isotopic exchange of trans-zeatin with high-radioactive tritium water, with gaseous tritium in solution and solid-phase catalytic hydrogenation are studied to prepare trans-zeatin and dihydrozeatin labelled with tritium. It is shown that reaction of isotopic exchange of trans-zeatin with gaseous tritium both in solutions and without solvents at 160 Deg C and above leads to practically total hydrogenation of initial compound with formation of dihydrozeatin labelled with tritium. Isotopic exchange with tritium water permits to prepare zeatin labelled with tritium with 67 % yield and specific radioactivity 0.68 PBq/mol. It is determined that in the case of solid-phase isotopic exchange within 150-155 Deg C temperature interval both dihydrozeatin and trans-zeatin labelled with tritium are formed [ru

  10. EXFOR Basics. A short guide to the neutron reaction data exchange format

    International Nuclear Information System (INIS)

    McLane, V.; NUCLEAR DATA CENTER NETWORK

    2000-01-01

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

  11. Application of tracer isotope in kinetic study of first order ion exchange reaction

    International Nuclear Information System (INIS)

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

    1998-01-01

    Analysis of first order ion exchange reaction rates at different temperatures (27 deg- 48 degC) and particularly at low concentration of potassium iodide solution (electrolyte) ranging from 0.005 M to 0.040 M is carried out by application of radioactive tracer isotope 131 I. With increase in concentration of electrolyte, amount of iodide ion exchanged in millimoles increases. Specific reaction rates of ion exchange reaction are calculated for different temperatures and for different amount of ion exchange resins. It is observed that with increase in temperature, reaction rate increases but the increase is more pronounced for increase in amount of ion exchange resins. For 0.005 M solution of electrolyte, the reaction rate increases from 0.121 min -1 at 27 degC to 0.178 min -1 at 48 degC. For 0.005 M solution of electrolyte the reaction rate increases from 0.121 min -1 at 27 degC to 0.178 min 1 at 48 degC. For 0.005 M solution of electrolyte at 27 degC the reaction rate increases from 0.121 min -1 for 1.0 g of resin to 0.368 min -1 for 5.0 g of resin. From the reaction rates calculated at different temperatures, energy of activation in kJ/mole is calculated. It is observed that for 0.005 M solution of electrolyte, energy of activation is 4.62 kJ/mole which decreases to 2.87 kJ/mole for increase in concentration of electrolyte to 0.100 M. (author)

  12. Rates of nickel(II) capture from complexes with NTA, EDDA, and related tetradentate chelating agents by the hexadentate chelating agents EDTA and CDTA: Evidence of a "semijunctive" ligand exchange pathway

    Science.gov (United States)

    Boland, Nathan E.; Stone, Alan T.

    2017-09-01

    Many siderophores and metallophores produced by soil organisms, as well as anthropogenic chelating agent soil amendments, rely upon amine and carboxylate Lewis base groups for metal ion binding. UV-visible spectra of metal ion-chelating agent complexes are often similar and, as a consequence, whole-sample absorbance measurements are an unreliable means of monitoring the progress of exchange reactions. In the present work, we employ capillary electrophoresis to physically separate Ni(II)-tetradentate chelating agent complexes (NiL) from Ni(II)-hexadentate chelating agent complexes (NiY) prior to UV detection, such that progress of the reaction NiL + Y → NiY + L can be conveniently monitored. Rates of ligand exchange for Ni(II) are lower than for other +II transition metal ions. Ni(II) speciation in environmental media is often under kinetic rather than equilibrium control. Nitrilotriacetic acid (NTA), with three carboxylate groups all tethered to a central amine Lewis base group, ethylenediamine-N,N‧-diacetic acid (EDDA), with carboxylate-amine-amine-carboxylate groups arranged linearly, plus four structurally related compounds, are used as tetradentate chelating agents. Ethylenediaminetetraacetic acid (EDTA) and the structurally more rigid analog trans-cyclohexaneethylenediaminetetraacetic acid (CDTA) are used as hexadentate chelating agents. Effects of pH and reactant concentration are explored. Ni(II) capture by EDTA was consistently more than an order of magnitude faster than capture by CDTA, and too fast to quantify using our capillary electrophoresis-based technique. Using NiNTA as a reactant, Ni(II) capture by CDTA is independent of CDTA concentration and greatly enhanced by a proton-catalyzed pathway at low pH. Using NiEDDA as reactant, Ni(II) capture by CDTA is first order with respect to CDTA concentration, and the contribution from the proton-catalyzed pathway diminished by CDTA protonation. While the convention is to assign either a disjunctive

  13. Analysis of (3He, t) charge exchange reactions at 140 AMeV

    International Nuclear Information System (INIS)

    Singh, Pardeep; Zegers, R.G.T.; Danielewicz, Pawel; Noji, S.; Kim, B.T.; Sakai, H.

    2014-01-01

    The spin-isospin response in nuclei has been studied widely through ( 3 He, t) and (t, 3 He) charge-exchange reactions wherein a proton (neutron) transforms into a neutron (proton), which in turn changes the isospin, ΔT=1, of the nuclei participating in the reaction, either with or without spin transfer. The Gamow-Teller transitions are used to obtain the weak transition strength in the excitation-energy regions inaccessible through β-decay. The strengths deduced using charge exchange experiments provide stringent tests for nuclear structure calculations and serve as inputs for variety of applications in which weak transition strengths play a role. In this context, we explore here the ( 3 He,t) charge-exchange reaction at 140 MeV/u on 18 O, 26 Mg, 58,60,62, 64 Ni, 90 Zr, 118,120 Sn and 208 Pb targets, within the theoretical framework of distorted wave impulse approximation

  14. Role of protein-glutathione contacts in defining glutaredoxin-3 [2Fe-2S] cluster chirality, ligand exchange and transfer chemistry.

    Science.gov (United States)

    Sen, Sambuddha; Cowan, J A

    2017-10-01

    Monothiol glutaredoxins (Grx) serve as intermediate cluster carriers in iron-sulfur cluster trafficking. The [2Fe-2S]-bound holo forms of Grx proteins display cysteinyl coordination from exogenous glutathione (GSH), in addition to contact from protein-derived Cys. Herein, we report mechanistic studies that investigate the role of exogenous glutathione in defining cluster chirality, ligand exchange, and the cluster transfer chemistry of Saccharomyces cerevisiae Grx3. Systematic perturbations were introduced to the glutathione-binding site by substitution of conserved charged amino acids that form crucial electrostatic contacts with the glutathione molecule. Native Grx3 could also be reconstituted in the absence of glutathione, with either DTT, BME or free L-cysteine as the source of the exogenous Fe-S ligand contact, while retaining full functional reactivity. The delivery of the [2Fe-2S] cluster to Grx3 from cluster donor proteins such as Isa, Nfu, and a [2Fe-2S](GS) 4 complex, revealed that electrostatic contacts are of key importance for positioning the exogenous glutathione that in turn influences the chiral environment of the cluster. All Grx3 derivatives were reconstituted by standard chemical reconstitution protocols and found to transfer cluster to apo ferredoxin 1 (Fdx1) at rates comparable to native protein, even when using DTT, BME or free L-cysteine as a thiol source in place of GSH during reconstitution. Kinetic analysis of cluster transfer from holo derivatives to apo Fdx1 has led to a mechanistic model for cluster transfer chemistry of native holo Grx3, and identification of the likely rate-limiting step for the reaction.

  15. Conformational change of adenosine deaminase during ligand-exchange in a crystal.

    Science.gov (United States)

    Kinoshita, Takayoshi; Tada, Toshiji; Nakanishi, Isao

    2008-08-15

    Adenosine deaminase (ADA) perpetuates chronic inflammation by degrading extracellular adenosine which is toxic for lymphocytes. ADA has two distinct conformations: open form and closed form. From the crystal structures with various ligands, the non-nucleoside type inhibitors bind to the active site occupying the critical water-binding-position and sustain the open form of apo-ADA. In contrast, substrate mimics do not occupy the critical position, and induce the large conformational change to the closed form. However, it is difficult to predict the binding of (+)-erythro-9-(2-hydroxy-3-nonyl)adenine (EHNA), as it possesses characteristic parts of both the substrate and the non-nucleoside inhibitors. The crystal structure shows that EHNA binds to the open form through a novel recognition of the adenine base accompanying conformational change from the closed form of the PR-ADA complex in crystalline state.

  16. Design of Ion-Exchange Resins Through EDTA and DTPA Modified Ligands

    Directory of Open Access Journals (Sweden)

    2014-07-01

    Catechol, resorcinol, and their admixtures with EDTA and DTPA moieties were converted into polymeric resins by alkaline polycondensation with formaldehyde. The resins were characterized by FTIR spectroscopy, elemental analysis, ion-exchange capacity, and distribution coefficient (D for heavy metal and radionuclide such as Cs and Sr. 137Cs and 90Sr constitutes a major source of heat in nuclear waste streams and in regards to recent nuclear event their remediation in complex solution – sea water - represent an important issue.

  17. Inhibition of ligand exchange kinetics via active-site trapping with an antibody fragment.

    Science.gov (United States)

    Oyen, David; Steyaert, Jan; Barlow, John N

    2014-04-01

    We describe the first example of an inhibitory antibody fragment (nanobody ca1697) that binds simultaneously to an enzyme (the enzyme dihydrofolate reductase from Escherichia coli) and its bound substrate (folate). Binding of the antibody to the substrate causes a 20-fold reduction in the rate of folate exchange kinetics. This work opens up the prospect of designing new types of antibody-based inhibitors of enzymes and receptors through suitable design of immunogens.

  18. Reactions of Cp2MCl2 (M=Ti or Zr with Imine-Oxime Ligands. Formation of Metallacycles

    Directory of Open Access Journals (Sweden)

    C. Tripathi

    2005-07-01

    Full Text Available The reactions of bis(cyclopentadienyltitanium(IV/zirconium(IV dichloridewith a series of imine-oxime ligands (LH2, derived by condensing benzil-α-monoxime and2-phenylenediamine, 4-phenylenediamine, 4-methyl-2-phenylenediamine, 2,6-diamino-pyridine, have been studied in anhydrous tetrahydrofuran in the presence of base andmetallocycles of the [Cp2M(L] (M=Ti or Zr type have been isolated. Tentative structureshave been proposed for the products based on elemental analysis, electrical conductance andspectral (electronic, IR and 1H-NMR data. Proton NMR spectra indicate that on the NMRtime scale there is rapid rotation of the cyclopentadienyl ring around the metal-ring axis at25oC. Studies were conducted to assess the growth inhibiting potential of the complexessynthesized and the ligands against various bacterial strains.

  19. Scaling Hydrologic Exchange Flows and Biogeochemical Reactions from Bedforms to Basins

    Science.gov (United States)

    Harvey, J. W.; Gomez-Velez, J. D.

    2015-12-01

    River water moves in and out of the main channel along pathways that are perpendicular to the channel's main axis that flow across or beneath the ground surface. These hydrologic exchange flows (HEFs) are difficult to measure, yet no less important than a river's downstream flow, or exchanges with the atmosphere and deeper groundwater (Harvey and Gooseff, 2015, WRR). There are very few comprehensive investigations of exchange fluxes to understand patterns with river size and relative importance of specific types of exchanges. We used the physically based model NEXSS to simulate multiple scales of hyporheic flow and their cumulative effects on solute reaction in large basins (on the order of Chesapeake Bay basin or larger). Our goal was to explain where and when particular types of hyporheic flow are important in enhancing key biogeochemical reactions, such as organic carbon respiration and denitrification. Results demonstrate that hyporheic flux (expressed per unit area of streambed) varies surprisingly little across the continuum of first-order streams to eighth-order rivers, and vertical exchange beneath small bedforms dominates in comparison with lateral flow beneath gravel bars and meanders. Also, the river's entire volume is exchanged many times with hyporheic flow within a basin, and the turnover length (after one entire river volume is exchanged) is strongly influenced by hydrogeomorphic differences between physiographic regions as well as by river size. The cumulative effects on biogeochemical reactions were assessed using a the reaction significance factor, RSF, which computes the cumulative potential for hyporheic reactions using a dimensionless index that balances reaction progress in a single hyporheic flow path against overall processing efficiency of river turnover through hyporheic flow paths of that type. Reaction significance appears to be strongly dominated by hydrologic factors rather than biogeochemical factors, and seems to be dominated by

  20. Oxygen Atom Exchange between H2O and Non-Heme Oxoiron(IV) Complexes: Ligand Dependence and Mechanism.

    Science.gov (United States)

    Puri, Mayank; Company, Anna; Sabenya, Gerard; Costas, Miquel; Que, Lawrence

    2016-06-20

    Detailed studies of oxygen atom exchange (OAE) between H2(18)O and synthetic non-heme oxoiron(IV) complexes supported by tetradentate and pentadentate ligands provide evidence that they proceed by a common mechanism but within two different kinetic regimes, with OAE rates that span 2 orders of magnitude. The first kinetic regime involves initial reversible water association to the Fe(IV) complex, which is evidenced by OAE rates that are linearly dependent on [H2(18)O] and H2O/D2O KIEs of 1.6, while the second kinetic regime involves a subsequent rate determining proton-transfer step between the bound aqua and oxo ligands that is associated with saturation behavior with [H2(18)O] and much larger H2O/D2O KIEs of 5-6. [Fe(IV)(O)(TMC)(MeCN)](2+) (1) and [Fe(IV)(O)(MePy2TACN)](2+) (9) are examples of complexes that exhibit kinetic behavior in the first regime, while [Fe(IV)(O)(N4Py)](2+) (3), [Fe(IV)(O)(BnTPEN)](2+) (4), [Fe(IV)(O)(1Py-BnTPEN)](2+) (5), [Fe(IV)(O)(3Py-BnTPEN)](2+) (6), and [Fe(IV)(O)(Me2Py2TACN)](2+) (8) represent complexes that fall in the second kinetic regime. Interestingly, [Fe(IV)(O)(PyTACN)(MeCN)](2+) (7) exhibits a linear [H2(18)O] dependence below 0.6 M and saturation above 0.6 M. Analysis of the temperature dependence of the OAE rates shows that most of these complexes exhibit large and negative activation entropies, consistent with the proposed mechanism. One exception is complex 9, which has a near-zero activation entropy and is proposed to undergo ligand-arm dissociation during the RDS to accommodate H2(18)O binding. These results show that the observed OAE kinetic behavior is highly dependent on the nature of the supporting ligand and are of relevance to studies of non-heme oxoiron(IV) complexes in water or acetonitrile/water mixtures for applications in photocatalysis and water oxidation chemistry.

  1. Kinetics of a redox reaction in the system Ce(IV) β-diketonate - additional ligand

    International Nuclear Information System (INIS)

    Anufrieva, S.I.; Snezhko, N.I.; Pechurova, N.I.; Martynenko, L.N.; Spitsyn, V.I.

    1982-01-01

    Preparation of solutions containing stable compounds of Ce(IV) with organic ligands is difficult, because even strong Ce(IV) complexes undergo intramolecular reduction and have a tendency to hydrolysis. It is known that Ce(IV) β-diketonates have different resistances to reduction inorganic solvents, depending on the structure. Using spectrophotometric analysis we have investigated the oxidation-reduction characteristics of solutions of certain Ce(IV) β-diketonates in benzene in the absence and presence of neutral ligands containing donor O or N atoms

  2. Current status of uranium enrichment by way of chemical exchange reactions

    International Nuclear Information System (INIS)

    El Basyouny, A.; Bechthold, H.C.; Knoechel, A.; Vollmer, H.J.

    1985-04-01

    For this report, conference proceedings, patents and other types of literature have been collected to present an account of the current status of uranium enrichment by way of chemical exchange reactions. The report further presents a new concept along with the relevant process strategy developed by the authors. The principal process of the new concept is a chemical exchange process with crown ethers, complexed or free, playing an important part in the reactions. The authors also describe their experiments carried out for establishing suitable chemical systems. (orig./PW) [de

  3. The 10B (7Li, 7Be)10Be charge-exchange reaction

    International Nuclear Information System (INIS)

    Etchegoyen, A.

    1987-01-01

    It is analysed the mechanisms: direct charge-exchange through the two-body residual force (Q opt ∼ 0.2 MeV, which is close to the reaction Q-value of - 1,42 MeV); and single-Nucleon Knock-on exchange (SNKE) due to the intereacting nucleons being undistinguishable. These mechanisms are analysed in detail for producing 10 B ( 7 Li, 7 Be) 10 Be reaction. The experience was carried out at the Tandar Laboratory using conventional electronics. The elastic scattering was simultaneously measured in order to obtain an optical model parameter set. (M.C.K.) [pt

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

    Energy Technology Data Exchange (ETDEWEB)

    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)

    2013-12-14

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

  5. P-chiral 1-phosphanorbornenes: from asymmetric phospha-Diels-Alder reactions towards ligand design and functionalisation.

    Science.gov (United States)

    Möller, Tobias; Wonneberger, Peter; Sárosi, Menyhárt B; Coburger, Peter; Hey-Hawkins, Evamarie

    2016-02-07

    The principle of stereotopic face differentiation was successfully applied to 2H-phospholes which undergo a very efficient and highly stereoselective Diels-Alder reaction giving phosphorus-chiral 1-phosphanorbornenes with up to 87% yield. The observed reaction pathway has been supported by theoretical calculations showing that the cycloaddition reaction between 2H-phosphole 3a and the dienophile (5R)-(-)-menthyloxy-2(5H)-furanone (8) is of normal electron demand. Optically pure phosphanes were obtained by separation of the single diastereomers and subsequent desulfurisation of the sulfur-protected phosphorus atom. Finally, divergent ligand synthesis is feasible by reduction of the chiral auxiliary, subsequent stereospecific intramolecular Michael addition, and various functionalisations of the obtained key compound 13a. Furthermore, the unique structural properties of phospanorbornenes are presented and compared to those of phosphanorbornanes.

  6. Ligand-tailored single-site silica supported titanium catalysts: Synthesis, characterization and towards cyanosilylation reaction

    Science.gov (United States)

    Xu, Wei; Li, Yani; Yu, Bo; Yang, Jindou; Zhang, Ying; Chen, Xi; Zhang, Guofang; Gao, Ziwei

    2015-01-01

    A successive anchoring of Ti(NMe2)4, cyclopentadiene and a O-donor ligand, 1-hydroxyethylbenzene (PEA), 1,1‧-bi-2-naphthol (Binol) or 2,3-dihydroxybutanedioic acid diethyl ester (Tartrate), on silica was conducted by SOMC strategy in moderate conditions. The silica, monitored by in-situ Fourier transform infrared spectroscopy (in-situ FT-IR), was pretreated at different temperatures (200, 500 and 800 °C). The ligand tailored silica-supported titanium complexes were characterized by in-situ FT-IR, 13C CP MAS-NMR, X-ray photoelectron spectroscopy (XPS), X-ray absorption near edge structure (XANES) and elemental analysis in detail, verifying that the surface titanium species are single sited. The catalytic activity of the ligand tailored single-site silica supported titanium complexes was evaluated by a cyanosilylation of benzaldehyde. The results showed that the catalytic activity is dependent strongly on the dehydroxylation temperatures of silica and the configuration of the ligands.

  7. 1,2- and 1,3-dihydroxylated and hydroxynitrogenated monoterpenes as chiral ligands in the asymmetric reformatsky reaction

    International Nuclear Information System (INIS)

    Ribeiro, Carlos Magno R.; Morita, Cristina M.; Maia, Monica P.

    2008-01-01

    This study describes the use of three (-)-α-pinene derivatives, one diol-1,2 [(-)- (1R, 2R, 3S, 5R)-2,6,6-trimethylbicyclo[3.1.1]heptane-2,3-diol 4] and two pyridine-hydroxy derivatives [(+)-(1R,2S,3R,5S)-2,6,6- trimethyl-3-(2-pyridinylmethyl)bicyclo[3.1.1]heptane-3-ol 7 and (-)-(1R,2S,3R,5S)-2,6,6-trimethyl-3-[2-(2-pyridinyl) ethyl]bicyclo[3.1.1]heptane-3-ol 8]; one diol-1,3 [(-)-(1S,2R,5S)-2-(1-hydroxy-1-methylethyl)-5-methylcyclohexanol 5] derived from (+)-isopulegol 2 and one diol-1,3 [(+)-(1R,2R,5R)-2-(1-hydroxy-1-methylethyl)-5-methylcyclohexanol 6] derived from (+)-neoisopulegol 3, as ligands in the asymmetric Reformatsky reaction. The best enantiomeric excess of β-hydroxy ester obtained in the Reformatsky asymmetric reaction was 18% using ligand 6, and the chemical yield of the reactions was 65% on average. (author)

  8. Nucleophilic radioiodination of 6-bromocholesterol via non-isotopic exchange reaction in molten state

    International Nuclear Information System (INIS)

    El-Shaboury, G.; Farah, K.; El-Tawoosy, M.

    2001-01-01

    A synthetic method for preparing radioiodinated 6-[ 125 I]iodocholesterol [CL-6- 125 I] for adrenal evaluation is described. The radioiodine atom was incorporated onto the cholesterol molecule via non-isotopic exchange between 6-bromocholesterol [CL-6-Br] and radioiodine as iodide ion [ 125 I - ] in a molten state. The different parameters affecting the yield of exchange were investigated using 125 I (T 1/2 ≅ 60 d) to centralize the different physical and chemical reaction conditions and purification of the final product as pure as 6-[ 125 I]iodocholesterol. The method was suitable to either 131 I (T 1/2 ≅ 8 d) nucleophilic radioiodination which facilitates the scanning of the adrenal for a few days after administration or the use of 124 I (T 1/2 ≅ 4.16 d) nucleophilic radioiodination for PET evaluation of the adrenal. TLC as well as HPLC chromatographic analysis is used to determine the efficiency of the exchange reactions under different chemical reaction conditions and to monitor the stability of the final product as pure as CL-6- 125 I with radiochemical purity of ≅99%. This no-carrier-added method improved the speed of the reaction and affords high radiochemical yield of 90% and suitable specific activity due to the use of CL-6-Br rather than CL-6-I as substrate. Kinetic studies revealed second order iodine-bromine exchange reaction. The activation energy for the exchange reaction in ammonium acetate (m.p. 114 deg C) was calculated to be 4.576 kcal/mole. (author)

  9. A Biphasic Ligand Exchange Reaction on Cdse Nanoparticles: Introducing Undergraduates to Functionalizing Nanoparticles for Solar Cells

    Science.gov (United States)

    Zemke, Jennifer M.; Franz, Justin

    2016-01-01

    Semiconductor nanoparticles, including cadmium selenide (CdSe) particles, are attractive as light harvesting materials for solar cells. In the undergraduate laboratory, the size-tunable optical and electronic properties can be easily investigated; however, these nanoparticles (NPs) offer another platform for application-based tunability--the NP…

  10. One-step ligand exchange reaction as an efficient way for functionalization of magnetic nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Mrowczynski, Radoslaw [Humboldt-University Berlin, Department of Chemistry (Germany); Rednic, Lidia; Turcu, Rodica [National Institute of Research and Development for Isotopic and Molecular Technologies (Romania); Liebscher, Juergen, E-mail: liebscher@chemie.hu-berlin.de [Humboldt-University Berlin, Department of Chemistry (Germany)

    2012-07-15

    Novel magnetic Fe{sub 3}O{sub 4} nanoparticles (NPs) covered by one layer of functionalized fatty acids, bearing entities (Hayashi catalyst, biotin, quinine, proline, and galactose) of high interest for practical application in nanomedicine or organocatalysis, were synthesized. The functionalized fatty acids were obtained by Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) of azido fatty acids with alkynes. All the magnetic NPs show superparamagnetic behavior with high values of magnetization and high colloidal stability in DCM solution.

  11. One-step ligand exchange reaction as an efficient way for functionalization of magnetic nanoparticles

    International Nuclear Information System (INIS)

    Mrówczyński, Radosław; Rednic, Lidia; Turcu, Rodica; Liebscher, Jürgen

    2012-01-01

    Novel magnetic Fe 3 O 4 nanoparticles (NPs) covered by one layer of functionalized fatty acids, bearing entities (Hayashi catalyst, biotin, quinine, proline, and galactose) of high interest for practical application in nanomedicine or organocatalysis, were synthesized. The functionalized fatty acids were obtained by Cu(I)-catalyzed azide–alkyne cycloaddition (CuAAC) of azido fatty acids with alkynes. All the magnetic NPs show superparamagnetic behavior with high values of magnetization and high colloidal stability in DCM solution.

  12. On-column ligand exchange for structure-based drug design: a case study with human 11β-hydroxysteroid dehydrogenase type 1

    International Nuclear Information System (INIS)

    Qin, Wenying; Judge, Russell A.; Longenecker, Kenton L.; Solomon, Larry R.; Harlan, John E.

    2012-01-01

    An on-column ligand- and detergent-exchange method was developed to obtain ligand–protein complexes for an adamantane series of compounds with 11β-HSD1 after a variety of other complexation methods had failed. An interesting byproduct of the method was the observation of artificial trimers in the crystal structures. Successfully forming ligand–protein complexes with specific compounds can be a significant challenge in supporting structure-based drug design for a given protein target. In this respect, an on-column ligand- and detergent-exchange method was developed to obtain ligand–protein complexes of an adamantane series of compounds with 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) after a variety of other complexation methods had failed. This report describes the on-column exchange method and an unexpected byproduct of the method in which artificial trimers were observed in the structures

  13. Reaction of Non-Symmetric Schiff Base Metallo-Ligand Complexes Possessing an Oxime Function with Ln Ions

    Directory of Open Access Journals (Sweden)

    Jean-Pierre Costes

    2018-03-01

    Full Text Available The preparation of non-symmetric Schiff base ligands possessing one oxime function that is associated to a second function such as pyrrole or phenol function is first described. These ligands, which possess inner N4 or N3O coordination sites, allow formation of cationic or neutral non-symmetric CuII or NiII metallo-ligand complexes under their mono- or di-deprotonated forms. In presence of Lanthanide ions the neutral complexes do not coordinate to the LnIII ions, the oxygen atom of the oxime function being only hydrogen-bonded to a water molecule that is linked to the LnIII ion. This surprising behavior allows for the isolation of LnIII ions by non-interacting metal complexes. Reaction of cationic NiII complexes possessing a protonated oxime function with LnIII ions leads to the formation of original and dianionic (Gd(NO352− entities that are well separated from each other. This work highlights the preparation of well isolated mononuclear LnIII entities into a matrix of diamagnetic metal complexes. These new complexes complete our previous work dealing with the complexing ability of the oxime function toward Lanthanide ions. It could open the way to the synthesis of new entities with interesting properties, such as single-ion magnets for example.

  14. Study of iodine-iodate isotopic exchange reaction in neutral aqueous solutions by radiotracer technique

    International Nuclear Information System (INIS)

    Tripathi, R.; Ram, K.D.

    1993-01-01

    The isotopic exchange of iodine atoms in neutral aqueous solutions of iodate ions and iodine (in KI) is found to obey the rate law R = k [IO 3 - ] 0.4 [I 2 ] 1.2 at 175 o C. The addition of neutral ionic salts, e.g. KCl and KNO 3 , in the reaction mixture showed a slight catalytic effect on the exchange rate. Further, the kinetic salt effect indicated the involvement of at least one neutral species on the rate-determining step. The activation energy in neutral aqueous solutions of iodate ions and iodine is found to be 86 ± 3 kJ mol -1 , which decreases in the presence of KCl (79 ± 3 kJ mol -1 and KNO 3 (82 + 3 kJ mol -1 ). The activation parameters, viz. free energy of activation, enthalpy of activation and entropy of activation, were also calculated. Based on these results, an association-dissociation type of reaction mechanism is proposed for this exchange reaction in neutral aqueous medium, similar to that proposed earlier for iodide-iodate isotopic exchange reaction in neutral aqueous solutions, nitrate eutectic melts and iodide-iodate melts. (author)

  15. Ligand intermediates in metal-catalyzed reactions; Annual technical report, August 1, 1992--August 1, 1993

    Energy Technology Data Exchange (ETDEWEB)

    Gladysz, J.A.

    1993-08-10

    Achievements are reported for the following 4 areas: {pi}/{sigma} equillibria in aldehyde and ketone complexes; thermodynamic ligand binding affinities ({alpha},{beta} unsaturated organic carbonyl compounds); (a new form of coordinated carbon) an unsupported C{sub 3} chain that spans two different transition metals; and (a new form of coordinated carbon) an C{sub 3} chain that is anchored by a metal on each end and spanned by a third.

  16. Chiral ligand exchange high-speed countercurrent chromatography: mechanism, application and comparison with conventional liquid chromatography in enantioseparation of aromatic α-hydroxyl acids

    Science.gov (United States)

    Tong, Shengqiang; Shen, Mangmang; Cheng, Dongping; Ito, Yoichiro; Yan, Jizhong

    2014-01-01

    This work concentrates on the separation mechanism and application of chiral ligand exchange high-speed countercurrent chromatography (HSCCC) in enantioseparations, and comparison with traditional chiral ligand exchange high performance liquid chromatography (HPLC). The enantioseparation of ten aromatic α-hydroxyl acids were performed by these two chromatographic methods. Results showed that five of the racemates were successfully enantioseparated by HSCCC while only three of the racemates could be enantioseparated by HPLC using a suitable chiral ligand mobile phase additive. For HSCCC, the two-phase solvent system was composed of butanol-water (1:1, v/v), to which N-n-dodecyl-L-proline was added in the organic phase as chiral ligand and cupric acetate was added in the aqueous phase as a transition metal ion. Various operation parameters in HSCCC were optimized by enantioselective liquid-liquid extraction. Based on the results of the present studies the separation mechanism for HSCCC was proposed. For HPLC, the optimized mobile phase composed of aqueous solution containing 6 mmol L−1 L-phenylalanine and 3 mmol L−1 cupric sulfate and methanol was used for enantioseparation. Among three ligands tested on a conventional reverse stationary phase column, only one was found to be effective. In the present studies HSCCC presented unique advantages due to its high versatility of two-phase solvent systems and it could be used as an alternative method for enantioseparations. PMID:25087742

  17. Conferring specificity in redox pathways by enzymatic thiol/disulfide exchange reactions.

    Science.gov (United States)

    Netto, Luis Eduardo S; de Oliveira, Marcos Antonio; Tairum, Carlos A; da Silva Neto, José Freire

    2016-01-01

    Thiol-disulfide exchange reactions are highly reversible, displaying nucleophilic substitutions mechanism (S(N)2 type). For aliphatic, low molecular thiols, these reactions are slow, but can attain million times faster rates in enzymatic processes. Thioredoxin (Trx) proteins were the first enzymes described to accelerate thiol-disulfide exchange reactions and their high reactivity is related to the high nucleophilicity of the attacking thiol. Substrate specificity in Trx is achieved by several factors, including polar, hydrophobic, and topological interactions through a groove in the active site. Glutaredoxin (Grx) enzymes also contain the Trx fold, but they do not share amino acid sequence similarity with Trx. A conserved glutathione binding site is a typical feature of Grx that can reduce substrates by two mechanisms (mono and dithiol). The high reactivity of Grx enzymes is related to the very acid pK(a) values of reactive Cys that plays roles as good leaving groups. Therefore, although distinct oxidoreductases catalyze similar thiol–disulfide exchange reactions, their enzymatic mechanisms vary. PDI and DsbA are two other oxidoreductases, but they are involved in disulfide bond formation, instead of disulfide reduction, which is related to the oxidative environment where they are found. PDI enzymes and DsbC are endowed with disulfide isomerase activity, which is related with their tetra-domain architecture. As illustrative description of specificity in thiol-disulfide exchange, redox aspects of transcription activation in bacteria, yeast, and mammals are presented in an evolutionary perspective. Therefore, thiol-disulfide exchange reactions play important roles in conferring specificity to pathways, a required feature for signaling.

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

    Science.gov (United States)

    Bertulani, C. A.

    2018-01-01

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

  19. Kinetics of the high temperature oxygen exchange reaction on {sup 238}PuO{sub 2} powder

    Energy Technology Data Exchange (ETDEWEB)

    Whiting, Christofer E., E-mail: chris.whiting@udri.udayton.edu [University of Dayton – Research Institute, 300 College Park, Dayton, OH 45469-0172 (United States); Du, Miting; Felker, L. Kevin; Wham, Robert M. [Oak Ridge National Laboratory, P.O. Box 2008, Oak Ridge, TN 37831 (United States); Barklay, Chadwick D.; Kramer, Daniel P. [University of Dayton – Research Institute, 300 College Park, Dayton, OH 45469-0172 (United States)

    2015-12-15

    Oxygen exchange reactions performed on PuO{sub 2} suggest the reaction is influenced by at least three mechanisms: an internal chemical reaction, surface mobility of active species/defects, and surface exchange of gaseous oxygen with lattice oxygen. Activation energies for the surface mobility and internal chemical reaction are presented. Determining which mechanism is dominant appears to be a complex function including at least specific surface area and temperature. Thermal exposure may also impact the oxygen exchange reaction by causing reductions in the specific surface area of PuO{sub 2}. Previous CeO{sub 2} surrogate studies exhibit similar behavior, confirming that CeO{sub 2} is a good qualitative surrogate for PuO{sub 2}, in regards to the oxygen exchange reaction. Comparison of results presented here with previous work on the PuO{sub 2} oxygen exchange reaction allows complexities in the previous work to be explained. These explanations allowed new conclusions to be drawn, many of which confirm the conclusions presented here. - Highlights: • PuO{sub 2} Oxygen exchange kinetics can be influenced by at least 3 different mechanisms. • An internal chemical reaction controls the rate at high temperature and large SSA. • Surface mobility and surface exchange influence rate at lower temperatures and SSA. • Exchange temperatures may alter SSA and make data difficult to interpret.

  20. Multidentate Di-N-heterocyclic carbene ligands for transition metal catalyzed hydrogenation reactions

    NARCIS (Netherlands)

    Sluijter, S.N.

    2015-01-01

    Synthetic catalysts play an important role in creating a more sustainable society. The use of catalysts has environmental as well as economic advantages. They speed up reactions without being consumed in the reaction itself. Moreover, they reduce the amount of byproducts and waste significantly.

  1. New Oxime Ligand with Potential for Proton-Coupled Electron-Transfer Reactions

    DEFF Research Database (Denmark)

    Deville, Claire; Sundberg, Jonas; McKenzie, Christine Joy

    Proton-coupled electron-transfer (PCET) is found in a range of oxidation-reduction reactions in biology.1 This mechanism is of interest for applications in energy conversion processes. The PCET reaction has been shown to be facilitated when the proton is transferred to an intramolecular basic sit...

  2. Transforming single domain magnetic CoFe_2O_4 nanoparticles from hydrophobic to hydrophilic by novel mechanochemical ligand exchange

    International Nuclear Information System (INIS)

    Munjal, Sandeep; Khare, Neeraj

    2017-01-01

    Single-phase uniform-sized (~9 nm) cobalt ferrite (CFO) nanoparticles have been synthesized by hydrothermal synthesis using oleic acid as a surfactant. The as-synthesized oleic acid-coated CFO (OA-CFO) nanoparticles were well dispersible in nonpolar solvents but not dispersible in water. The OA-CFO nanoparticles have been successfully transformed to highly water-dispersible citric acid-coated CFO (CA-CFO) nanoparticles using a novel single-step ligand exchange process by mechanochemical milling, in which small chain citric acid molecules replace the original large chain oleic acid molecules available on CFO nanoparticles. The OA-CFO nanoparticle’s hexane solution and CA-CFO nanoparticle’s water solution remain stable even after 6 months and show no agglomeration and their dispersion stability was confirmed by zeta-potential measurements. The contact angle measurement shows that OA-CFO nanoparticles are hydrophobic whereas CA-CFO nanoparticles are superhydrophilic in nature. The potentiality of as-synthesized OA-CFO and mechanochemically transformed CA-CFO nanoparticles for the demulsification of highly stabilized water-in-oil and oil-in-water emulsions has been demonstrated.

  3. Beneficial phosphate recovery from reverse osmosis (RO) concentrate of an integrated membrane system using polymeric ligand exchanger (PLE).

    Science.gov (United States)

    Kumar, Manish; Badruzzaman, Mohammad; Adham, Samer; Oppenheimer, Joan

    2007-05-01

    Phosphorus (P) discharge to surface water is a major environmental problem. Wastewater treatment is targeted towards removal of this nutrient to prevent degradation of surface water. Integrated membrane systems (IMS) are increasingly being considered for wastewater reclamation, and provide excellent removal of P compounds. However, reverse osmosis (RO), which forms an integral part of these IMSs, concentrates most dissolved substances including P-species such as phosphates in the RO waste stream. In this study, removal of phosphate from this stream using polymeric ligand exchange (PLE) resins was investigated. Further, the possibility of phosphate recovery through struvite (MgNH(4)PO(4).6H(2)O) precipitation was tested. Struvite has been promoted as a slow release fertilizer in recent years. This study demonstrates that PLEs can be successfully used to remove phosphate from RO-concentrate, and to recover more than 85% of the adsorbed phosphorus from the exhausted media and precipitated as a beneficial product (struvite). The approach, presented in this study, suggests advantages of providing economic benefit from a waste product (RO) while avoiding phosphorus discharge to the environment.

  4. Effect of competing ions and causticization on the ammonia adsorption by a novel poly ligand exchanger (PLE) ammonia adsorption reagent.

    Science.gov (United States)

    Chen, Quanzhou; Zhou, Kanggen; Hu, Yuanjuan; Liu, Fang; Wang, Aihe

    2017-03-01

    In this paper, a poly ligand exchanger, Cu(II)-loaded chelating resin named ammonia adsorption reagent (AMAR), bearing the functional group of weak iminodiacetate acid, was prepared to efficiently remove ammonia from solutions. Batch adsorption equilibrium experiments were conducted under a range of conditions. The effects of pH on the removal of ammonia by AMAR were investigated at 25 °C. The copper loaded on the resin forms a complex with NH 3 in solution under alkaline condition. The effect of alkaline dosage (AD) on the ammonia adsorption was investigated. The maximum breakthrough bed volumes were obtained when the AD was set as 0.75 mmol OH - /mL. The higher AD did not guarantee the better ammonia removal efficiency due to the forming of Cu(OH) 2 precipitate between OH - in solutions and Cu(II) on the resin. The effect of competing ions on the adsorption breakthrough curve of virgin AMAR and causticized AMAR was also investigated. The results demonstrated that the existence of competing ions had a negative impact on the adsorption capacity for both virgin AMAR and causticized AMAR. After causticization, the AMAR was more resistant to the competing ions comparing with virgin AMAR. The bivalent Ca 2+ affects the ammonia adsorption more than does the monovalent Na + .

  5. Preparation of radioactive acetyl-l-carnitine by an enzymatic exchange reaction

    International Nuclear Information System (INIS)

    Emaus, R.; Bieber, L.L.

    1982-01-01

    A rapid method for the preparation of [1- 14 C]acetyl-L-carnitine is described. The method involves exchange of [1- 14 C]acetic acid into a pool of unlabeled acetyl-L-carnitine using the enzymes acetyl-CoA synthetase and carnitine acetyltransferase. After isotopic equilibrium is attained, radioactive acetylcarnitine is separated from the other reaction components by chromatography on Dowex 1 (C1 - ) anion exchange resin. One of the procedures used to verify the product [1- 14 C]acetyl-L-carnitine can be used to synthesize (3S)-[5- 14 C]citric acid

  6. On line determination of deuterium in hydrogen water exchange reaction by mass spectrometry. IRP-10

    International Nuclear Information System (INIS)

    Sharma, J.D.; Alphonse, K.P.; Mishra, Sushama; Prabhu, S.A.; Mohan, Sadhana; Tangri, V.K.

    2007-01-01

    The Deuterium (D)/Hydrogen (H) analysis at low Concentration is generally carried out by Mass Spectrometry. Mass Spectrometer is specially designed for the measurement of Mass 2 and 3 ratio. The Deuterium analysis of water and hydrogen in concentration range of a few ppm to about 1% plays an important role in the Heavy Water Production Plants. For the enrichment of the Deuterium concentration in H 2 O by H 2 - H 2 O exchange a catalyst is essential as reaction is relatively slow. Heavy Water Division has developed in house Platinum based catalyst for the isotopic exchange of Hydrogen and Water

  7. Kinetics of H-D exchange in olefins with complicating reactions

    International Nuclear Information System (INIS)

    Trokhimets, A.I.

    1979-01-01

    The kinetics of H-D-exchange is considered for olefins under conditions when simple and complicated exchange occur together with hydrogenation. If hydrogenation takes place in the system, it is theoretically impossible to derive the integrated rate equation for the accumulation of deuterium in the olefin. The variation of the concentration of different deuteroolefins during the process can be calculated numerically. A method is proposed for evaluating the contribution of individual steps to the overall process and determining the rate constants of the most important reactions. (author)

  8. New method for the hydrogen isotope exchange reaction in a hydrophobic catalyst bed

    International Nuclear Information System (INIS)

    Asakura, Y.; Kikuchi, M.; Yusa, H.

    1982-01-01

    To improve the isotope exchange reaction efficiency between water and hydrogen, a new reactor in which water mists and hydrogen gas react cocurrently was studied. To apply this to the enrichment of tritium in heavy water, a dual temperature isotope exchange reactor which is composed of cocurrent low temperature reactors and the usual countercurrent high temperature reactor was proposed and analyzed using a McCabe-Thiele diagram. By utilizing cocurrent reactors, in combination, the necessary catalyst volume can be reduced to one-tenth as compared with the usual countercurrent low temperature reactor. 17 refs

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

    International Nuclear Information System (INIS)

    Zhang, R.S.; Nash, C.P.; Rock, P.A.

    1988-01-01

    This paper reports the authors results for the direct experimental determination of the equilibrium constant for the calcium-isotope-exchange reaction 40 CaCO 3 (s) + 44 CaCl 2 (aq) reversible 44 CaCO 2 (s) + 40 CaCl 2 (aq). The reaction was studied in electrochemical double cells without liquid junction of the type shown in eq 2. The experimental value of the equilibrium constant at 295 +/- 2 K is K = 1.08 +/- 0.02. The experimental value for K is compared with the values of K calculated for various model reactions according to the statistical thermodynamic theory of isotope effects. The isotopic solid carbonates were modeled according to both the Debye and Kieffer theories. No structured models of solvated isotopic aqueous calcium ions yield calculated equilibrium constants in agreement with their experimental results. This conclusion is in agreement with published molecular dynamics calculations which show that the aqueous solvation of Ca 2 =(aq) is essentially unstructured

  10. Pd-bound functionalized mesoporous silica as active catalyst for Suzuki coupling reaction: Effect of OAcˉ, PPh3 and Clˉ ligands on catalytic activity

    Science.gov (United States)

    Das, Trisha; Uyama, Hiroshi; Nandi, Mahasweta

    2018-04-01

    Three new palladium catalysts, PdCat-I, PdCat-II and PdCat-III, immobilized over heterogeneous silica support have been synthesized using different ligands attached to the palladium precursor. The ligands that have been used in this study are acetate, triphenylphosphine and chloride in PdCat-I, PdCat-II and PdCat-III, respectively. The ligands have different effect on stability of the compounds and impart different oxidation states to the metal center. The materials have been characterized by powder X-ray diffraction, nitrogen adsorption-desorption studies, transmission electron microscopy, thermal analysis, and different spectroscopic techniques. The Pd-content of the samples have been determined by ICP-AES analysis. The materials have been used as catalysts for Suzuki coupling reaction of aryl halides with phenylboronic acid under mild conditions. A comparative study has been carried out to ascertain the effect of the nature of different ligands on the outcome of the catalytic reactions. Products have been identified and estimated by 1H NMR and gas chromatography. The results show that the best yields are obtained with the catalyst containing triphenylphosphine as the ligand in methanol. Such type of work to study the effect of ligand on Suzuki coupling reaction over functionalized mesoporous silica heterogeneous catalysts have not been carried out so far.

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

    Science.gov (United States)

    Ejiri, Hiroyasu

    2014-09-01

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

  12. Empirical potentials for recombination reactions of photo-dissociated ligands. Final report

    International Nuclear Information System (INIS)

    Elber, R.

    1998-01-01

    The aim of this research was to design an appropriate potential and simulation methodology to describe the effect of radiation on ligands bound to metal-proteins. As model systems the authors investigated myoglobin, hemoglobin and their mutants. The great advantage of the globins as a target for theoretical studies is the wealth of experimental data available for them. They focused on studies that combine fast spectroscopy with mutation experiments. The mutations make it possible to examine detailed changes in the kinetic curves with atomically detailed information. The first spectroscopy, which is in the same time scale as of ordinary molecular dynamics (sub nanoseconds), makes it possible to compare the results of the computations to raw experimental data

  13. General Tritium Labelling of Gentamicin C by catalytic hydrogen exchange Reaction with Tritiated Water

    International Nuclear Information System (INIS)

    Suarez, C.; Diaz, D.; Paz, D.

    1991-01-01

    Gentamicin C was labelled with tritium by means of a PtO2 catalyzed hydrogen exchange reaction. Under the conditions of the exchange (100 mg of gentamicin, basic form, 0,3 ml H2O-3H, and 50 mg of prereduced PtO2) the radiochemical yield was 0,24, 0,38 and 0,48 % at 120 degree celsius, for 8, 16 and 24 hours respectively. Chemical yield for purified gentamicin was about 60 %. Purification was accomplished with a cellulose column eluted with the lower phase of chloroform-methanol 17 % ammonium hydroxide (2:1:1, v/v) . Chemical purity, determined by HPLC, was 96,5 % and radiochemical one was 95. Main exchange degradation products show biological activity. (Author) 12 refs

  14. General Tritium labelling of gentamicin C by catalytic hydrogen exchange reaction with tritiated water

    International Nuclear Information System (INIS)

    Suarez, C.; Diaz, D.

    1991-01-01

    Gentamicin C was labelled with tritium by means of a PtO 2 catalized hydrogen exchange reaction. Under the conditions of the exchange (100 mg of gentamicin, basic form, 0,3 ml H 2 O- 3 H, and 50 mg of prereduced PtO 2 ) the radiochemical yield was 0,24, 0,38 and 0,48 % at 120 o C, for 8, 16 and 24 hours respectively. Chemical yield for purified gentamicin was about 60 %. Purification was accoumplished with a cellulose column eluted with the lower phase of chloroform-methanol 17 % ammonium hydroxide (2:1:1, v/v). Chemical purity, determined by HPLC, was 96,5 % and radiochemical one was 95 % . Main exchange degradation products show biological activity. (Author). 12 refs

  15. Reaction mechanism and nuclear correlations study by low energy pion double charge exchange

    International Nuclear Information System (INIS)

    Weinfeld, Z.

    1993-06-01

    In pion double-charge-exchange (DCX) reactions, a positive (negative) pion is incident on a nucleus and a negative (positive) pion emerges. These reactions are of fundamental interest since the process must involve at least two nucleons in order to conserve charge. Although two nucleon processes are present in many reactions they are usually masked by the dominant single nucleon processes. DCX is unique in that respect since it is a two nucleon process in lowest order and thus may be sensitive to two-nucleon correlations. Measurements of low energy pion double-charge-exchange reactions to the double-isobaric-analog-state (DIAS) and ground-state (GS) of the residual nucleus provide new means for studying nucleon-nucleon correlations in nuclei. At low energies (T π 7/2 shell at energies ranging from 25 to 65 MeV. Cross sections were measured on 42,44,48 Ca, 46,50 Ti and 54 Fe. The calcium isotopes make a good set of nuclei on which to study the effects of correlations in DCX reactions

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

    International Nuclear Information System (INIS)

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

    1976-01-01

    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 eliminating problems of catalyst deactivation and the complexity of reactor design normally associated with current catalytic-detritiation techniques involving gas-phase catalysis. An apparatus and procedure were developed for measuring reaction rates of water-hydrogen chemical exchange with hydrophobic catalysts. Preliminary economic evaluations of the process were made as it might apply to the AGNS fuel reprocessing plant

  17. 13C(α,n)16O reaction as the knock-out exchange process

    International Nuclear Information System (INIS)

    Kim, G.; Khajdarov, R.R.; Zaparov, Eh.A.

    2000-01-01

    S-factor for the 13 C(α,n) 16 O reaction is studied. In the framework of the simple phenomenological model this reaction is analysed as neutron knocked-out by α-particle exchange process. The analysis demonstrates the importance of taking into account 2p-state in 13 C. The 13 C(α,n) 16 O cross section is considered both as the knock-out exchange process and as it's combination with process through a compound nucleus. It was shown that for E α s value extrapolated to low energies is found to be noticeably larger that of R-matrix analysis. Different ways of improving the proposed model are discussed. (author)

  18. Charge Exchange Reaction in Dopant-Assisted Atmospheric Pressure Chemical Ionization and Atmospheric Pressure Photoionization.

    Science.gov (United States)

    Vaikkinen, Anu; Kauppila, Tiina J; Kostiainen, Risto

    2016-08-01

    The efficiencies of charge exchange reaction in dopant-assisted atmospheric pressure chemical ionization (DA-APCI) and dopant-assisted atmospheric pressure photoionization (DA-APPI) mass spectrometry (MS) were compared by flow injection analysis. Fourteen individual compounds and a commercial mixture of 16 polycyclic aromatic hydrocarbons were chosen as model analytes to cover a wide range of polarities, gas-phase ionization energies, and proton affinities. Chlorobenzene was used as the dopant, and methanol/water (80/20) as the solvent. In both techniques, analytes formed the same ions (radical cations, protonated molecules, and/or fragments). However, in DA-APCI, the relative efficiency of charge exchange versus proton transfer was lower than in DA-APPI. This is suggested to be because in DA-APCI both dopant and solvent clusters can be ionized, and the formed reagent ions can react with the analytes via competing charge exchange and proton transfer reactions. In DA-APPI, on the other hand, the main reagents are dopant-derived radical cations, which favor ionization of analytes via charge exchange. The efficiency of charge exchange in both DA-APPI and DA-APCI was shown to depend heavily on the solvent flow rate, with best efficiency seen at lowest flow rates studied (0.05 and 0.1 mL/min). Both DA-APCI and DA-APPI showed the radical cation of chlorobenzene at 0.05-0.1 mL/min flow rate, but at increasing flow rate, the abundance of chlorobenzene M(+.) decreased and reagent ion populations deriving from different gas-phase chemistry were recorded. The formation of these reagent ions explains the decreasing ionization efficiency and the differences in charge exchange between the techniques. Graphical Abstract ᅟ.

  19. Elastic scattering and charge exchange reaction studies with {sup 6}He, {sup 10,11}Be

    Energy Technology Data Exchange (ETDEWEB)

    Roussel-Chomaz, P; Cortina-Gil, M D; Mittig, W; Casandjian, J M; Chartier, M [Grand Accelerateur National d` Ions Lourds (GANIL), 14 - Caen (France); Alamanos, N; Auger, F; Fekou-Youmbi, V [CEA Centre d` Etudes de Saclay, 91 - Gif-sur-Yvette (France). Dept. d` Astrophysique, de la Physique des Particules, de la Physique Nucleaire et de l` Instrumentation Associee; Barrette, J [McGill Univ., Montreal, PQ (Canada); Blumenfeld, Y [Paris-11 Univ., 91 - Orsay (France). Inst. de Physique Nucleaire; and others

    1996-12-31

    The elastic scattering and charge exchange reaction of {sup 6}He, {sup 10,11}Be secondary beams on proton and {sup 12}C targets have been measured. The combined use of SISSI and SPEG allowed to obtain very good quality data in terms of energy and angular resolution. Preliminary analyses of the angular distributions using global parameter set for the optical model potentials, as well as more microscopic approaches are presented. (author). 14 refs.

  20. Hydrophobic catalyst mixture for the isotopic exchange reaction between hydrogen and water

    Energy Technology Data Exchange (ETDEWEB)

    Paek, S.; Ahn, D. H.; Choi, H. J.; Kim, K. R.; Lee, M.; Yim, S. P.; Chung, H. [KAERI, Taejon (Korea, Republic of)

    2005-11-15

    Pt/SDBC catalyst, which is used for the hydrogen-water isotopic exchange reaction, was prepared. The various properties of the catalyst, such as the thermal stability, pore structure and the platinum dispersion, were investigated. A hydrophobic Pt/SDBC catalyst which has been developed for the LPCE column of the WTRF (Wolsong Tritium Removal Facility) was tested in a trickle bed reactor. An experimental apparatus was built for the test of the catalyst at various temperatures and gas velocities.

  1. Hydrophobic catalyst mixture for the isotopic exchange reaction between hydrogen and water

    International Nuclear Information System (INIS)

    Paek, S.; Ahn, D. H.; Choi, H. J.; Kim, K. R.; Lee, M.; Yim, S. P.; Chung, H.

    2005-01-01

    Pt/SDBC catalyst, which is used for the hydrogen-water isotopic exchange reaction, was prepared. The various properties of the catalyst, such as the thermal stability, pore structure and the platinum dispersion, were investigated. A hydrophobic Pt/SDBC catalyst which has been developed for the LPCE column of the WTRF (Wolsong Tritium Removal Facility) was tested in a trickle bed reactor. An experimental apparatus was built for the test of the catalyst at various temperatures and gas velocities

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

    International Nuclear Information System (INIS)

    McLane, Victoria

    2000-01-01

    EXFOR is the agreed exchange format for the transmission of experimental nuclear reaction data between national and international nuclear data centers for the benefit of nuclear data users in all countries. This report is intended as a guide to data users. For a complete guide to the EXFOR system see: EXFOR Systems Manual, IAEA-NDS-207 (BNL-NCS-63330-00/04-Rev.) (author)

  3. Isotope exchange reactions on ceramic breeder materials and their effect on tritium inventory

    Energy Technology Data Exchange (ETDEWEB)

    Nishikawa, M; Baba, A [Kyushu Univ., Fukuoka (Japan). Faculty of Engineering; Kawamura, Y; Nishi, M

    1998-03-01

    Though lithium ceramic materials such as Li{sub 2}O, LiAlO{sub 2}, Li{sub 2}ZrO{sub 3}, Li{sub 2}TiO{sub 3} and Li{sub 4}SiO{sub 4} are considered as breeding materials in the blanket of a D-T fusion reactor, the release behavior of the bred tritium in these solid breeder materials has not been fully understood. The isotope exchange reaction rate between hydrogen isotopes in the purge gas and tritium on the surface of breeding materials have not been quantified yet, although helium gas with hydrogen or deuterium is planned to be used as the blanket purge gas in the recent blanket designs. The mass transfer coefficient representing the isotope exchange reaction between H{sub 2} and D{sub 2}O or that between D{sub 2} and H{sub 2}O in the ceramic breeding materials bed is experimentally obtained in this study. Effects of isotope exchange reactions on the tritium inventory in the bleeding blanket is discussed based on data obtained in this study where effects of diffusion of tritium in the grain, absorption of water in the bulk of grain, and adsorption of water on the surface of grain, together with two types of isotope exchange reactions are considered. The way to estimate the tritium inventory in a Li{sub 2}ZrO{sub 3} blanket used in this study shows a good agreement with data obtained in such in-situ experiments as MOZART, EXOTIC-5, 6 and TRINE experiments. (author)

  4. Catalytic isotope exchange reaction between deuterium gas and water pre-adsorbed on platinum/alumina

    International Nuclear Information System (INIS)

    Iida, Itsuo; Kato, Junko; Tamaru, Kenzi.

    1976-01-01

    The catalytic isotope exchange reaction between deuterium gas and the water pre-adsorbed on Pt/Al 2 O 3 was studied. At reaction temperatures above 273 K, the exchange rate was proportional to the deuterium pressure and independent of the amount of adsorbed water, which suggests that the rate determining step is the supply of deuterium from the gas phase. Its apparent activation energy was 38 kJ mol -1 . Below freezing point of water, the kinetic behaviour was different from that above freezing point. At higher deuterium pressures the rate dropped abruptly at 273 K. Below the temperature the apparent activation energy was 54 kJ mol -1 and the exchange rate depended not on the deuterium pressure but on the amount of the pre-adsorbed water. At lower pressures, however, the kinetic behaviour was the same as the above 273 K, till the rate of the supply of deuterium from the gas phase exceeded the supply of hydrogen from adsorbed water to platinum surface. These results suggest that below 273 K the supply of hydrogen is markedly retarded, the state of the adsorbed water differing from that above 273 K. It was also demonstrated that when the adsorbed water is in the state of capillary condensation, the exchange rate becomes very small. (auth.)

  5. Development of styrene divinyl benzene catalyst in isotopic exchange reaction of water and hydrogen

    International Nuclear Information System (INIS)

    Morishita, Teizo; Noda, Shigeyuki; Tan, Tsutomu; Noguchi, Hiroshi

    1982-01-01

    Styrene divinyl benzene copolymer (SDBC) is hydrophobic, and porous with large specific surface area. Utilizing these properties, the SDBC was used for the carrier of catalyst in water-hydrogen exchange reaction process, and the hydrophobic platinum catalyst with very high performance was able to be developed. However, the SDBC is usually fine particles smaller than 1 mm, and is not suitable as the filling catalyst for exchange reaction towers. Therefore, in this study, using only platinum as a catalyst metal, the improvement of the property of carriers was emphatically examined, and platinum bearing was proved with an optical or electron microscope. As the result, it was found that the SDBC catalyst showed high activity practically usable as the hydrophobic catalyst for heavy water or tritium exchange reaction. The characteristics of SDBC are explained. The manufacturing processes of the catalyst by making SDBC carriers with fine particles and letting them bear platinum are described. The results of the trial manufacture of spherical, extrusion-formed and honeycomb carrier catalysts are reported. Platinum must be dispersed over the large specific surface area of SDBC carriers. (Kako, I.)

  6. Moving Towards a State of the Art Charge-Exchange Reaction Code

    Science.gov (United States)

    Poxon-Pearson, Terri; Nunes, Filomena; Potel, Gregory

    2017-09-01

    Charge-exchange reactions have a wide range of applications, including late stellar evolution, constraining the matrix elements for neutrinoless double β-decay, and exploring symmetry energy and other aspects of exotic nuclear matter. Still, much of the reaction theory needed to describe these transitions is underdeveloped and relies on assumptions and simplifications that are often extended outside of their region of validity. In this work, we have begun to move towards a state of the art charge-exchange reaction code. As a first step, we focus on Fermi transitions using a Lane potential in a few body, Distorted Wave Born Approximation (DWBA) framework. We have focused on maintaining a modular structure for the code so we can later incorporate complications such as nonlocality, breakup, and microscopic inputs. Results using this new charge-exchange code will be shown compared to the analysis in for the case of 48Ca(p,n)48Sc. This work was supported in part by the National Nuclear Security Administration under the Stewardship Science Academic Alliances program through the U.S. DOE Cooperative Agreement No. DE- FG52-08NA2855.

  7. Uniform thin film electrode made of low-temperature-sinterable silver nanoparticles: optimized extent of ligand exchange from oleylamine to acrylic acid

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Yung Jong; Kim, Na Rae; Lee, Changsoo; Lee, Hyuck Mo, E-mail: hmlee@kaist.ac.kr [Department of Materials Science and Engineering (Korea, Republic of)

    2017-02-15

    Lowering the sintering temperature of nanoparticles in the electrode deposition process holds both academic and industrial interest because of the potential applications of such electrodes in polymer devices and flexible electronics. In addition, achieving uniform electrode formation after ligand exchange is equally important as lowering the sintering temperature. Here, we report a simple chemical treatment by the addition of ligand-exchanging interfaces to lower the sintering temperature; we also determine the optimum extent of ligand exchange for crack-free electrode formation. First, we investigated the structural change of Ag thin films with respect to the concentration of acrylic acid (AA) solutions. Second, we used thermal analysis to evaluate the effects of changes in the sintering temperature. We observed that the resulting conductivity of the Ag patterns was only one order of magnitude lower than that of bulk Ag when the patterns were sintered at 150 °C. The simple chemical treatment developed in this work for solution-processed Ag electrode formation can be adopted for flexible electronics, which would eliminate the need for vacuum and high-temperature processes.

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

    International Nuclear Information System (INIS)

    McLane, V.

    1996-07-01

    This manual is intended as a guide to users of nuclear reaction data compiled in the EXFOR format, and is not intended as a complete guide to the EXFOR System. EXFOR is the exchange format designed to allow transmission of nuclear data between the Nuclear Reaction Data Centers. In addition to storing the data and its' bibliographic information, experimental information, including source of uncertainties, is also compiled. The status and history of the data set is also included, e.g., the source of the data, any updates which have been made, and correlations to other data sets. EXFOR is designed for flexibility in order to meet the diverse needs of the nuclear data compilation centers. This format should not be confused with a center-to-user format. Although users may obtain data from the centers in the EXFOR format, other center-to-user formats have been developed to meet the needs of the users within each center's own sphere of responsibility. The exchange format, as outlined, allows a large variety of numerical data tables with explanatory and bibliographic information to be transmitted in an easily machine-readable format (for checking and indicating possible errors) and a format that can be read by personnel (for passing judgment on and correcting any errors indicated by the machine). The data presently included in the EXFOR exchange include: a complete compilation of experimental neutron-induced reaction data, a selected compilation of charged-particle induced reaction data, a selected compilation of photon-induced reaction data

  9. Site-specific chemical conjugation of human Fas ligand extracellular domain using trans-cyclooctene - methyltetrazine reactions.

    Science.gov (United States)

    Muraki, Michiro; Hirota, Kiyonori

    2017-07-03

    Fas ligand plays a key role in the human immune system as a major cell death inducing protein. The extracellular domain of human Fas ligand (hFasLECD) triggers apoptosis of malignant cells, and therefore is expected to have substantial potentials in medical biotechnology. However, the current application of this protein to clinical medicine is hampered by a shortage of the benefits relative to the drawbacks including the side-effects in systemic administration. Effective procedures for the engineering of the protein by attaching useful additional functions are required to overcome the problem. A procedure for the site-specific chemical conjugation of hFasLECD with a fluorochrome and functional proteins was devised using an inverse-electron-demand Diels-Alder reaction between trans-cyclooctene group and methyltetrazine group. The conjugations in the present study were attained by using much less molar excess amounts of the compounds to be attached as compared with the conventional chemical modification reactions using maleimide derivatives in the previous study. The isolated conjugates of hFasLECD with sulfo-Cy3, avidin and rabbit IgG Fab' domain presented the functional and the structural integrities of the attached molecules without impairing the specific binding activity toward human Fas receptor extracellular domain. The present study provided a new fundamental strategy for the production of the engineered hFasLECDs with additional beneficial functions, which will lead to the developments of the improved diagnostic systems and the effective treatment methods of serious diseases by using this protein as a component of novel molecular tools.

  10. Oxygen Reduction Reaction on Pt Overlayers Deposited onto a Gold Film: Ligand, Strain, and Ensemble Effect

    DEFF Research Database (Denmark)

    Deng, Yu-Jia; Tripkovic, Vladimir; Rossmeisl, Jan

    2016-01-01

    We study the oxygen reduction reaction (ORR), the catalytic process occurring at the cathode in fuel cells, on Pt layers prepared by electrodeposition onto an Au substrate. Using a nominal Pt layer by layer deposition method previously proposed, imperfect layers of Pt on Au are obtained. The ORR...

  11. Ion exchange equilibrium for some uni-univalent and uni-divalent reaction systems using strongly basic anion exchange resin Duolite A-102 D

    Directory of Open Access Journals (Sweden)

    R.S. Lokhande

    2008-04-01

    Full Text Available The study on thermodynamics of ion exchange equilibrium for uni-univalent Cl-/I-, Cl-/Br-, and uni-divalent Cl-/SO42-, Cl-/C2O42- reaction systems was carried out using ion exchange resin Duolite A-102 D. The equilibrium constant K was calculated by taking into account the activity coefficient of ions both in solution as well as in the resin phase. The K values calculated for uni-univalent and uni-divalent anion exchange reaction systems was observed to increase with rise in temperature, indicating the endothermic exchange reactions having enthalpy values of 13.7, 38.0, 23.9, 22.9 kJ/mol, respectively.

  12. Use of deuterium n. m. r. spectroscopy in mechanistic studies of exchange reactions of ethers on supported metal catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Campbell, J.A.; Kemball, Charles; McDougall, G.S.

    1987-10-01

    Exchange reactions of diethyl ether (DEE) and tetrahydrofuran (THF) with deuterium have been studied over supported nickel, palladium, platinum, and rhodium catalysts. Products from most of the systems were analysed by deuterium n.m.r. spectroscopy (55.28 MHz) which gave quantitative results about the distribution of deuterium in the exchanged ethers. The results confirm earlier conclusions about the mechanism of the exchange of DEE and provide new evidence about the reactions of THF. Some hydrogenolysis occurred simultaneously with exchange of THF over both nickel and platinum.

  13. Exchange reaction between hydrogen and deuterium. II - Proposal for an heterogeneous initiation mechanism of gaseous phase reactions

    Energy Technology Data Exchange (ETDEWEB)

    Marteau, Chantal; Gaillard-Cusin, Francoise; James, Henri [Centre National de la Recherche Scientifique, 45 - Orleans-la-Source (France). Centre de Recherches sur la Chimie de Combustion et des Hautes Temperatures

    1978-05-01

    Investigation of experimental data related to evolution period exhibited by H/sub 2/-D/sub 2/ exchange process requires to take into account the variation against time of every atomic species -adsorbed or not- implied in the reaction mechanism. The formation of first chain carriers involves: - chemisorption of either gaseous reactant on the surface active centres (..sigma..), e.g.: ..sigma.. + 1/2 H/sub 2/ reversible ..sigma..H; - consecutive generation of atomic species through hetero-homogeneous transfer between chemisorbed species (..sigma..H) and gaseous molecules: ..sigma..H+H/sub 2/..--> sigma..+H/sub 2/+H/sup 0/, ..sigma..H+D/sub 2/..--> sigma..+HD+D/sup 0/. Therefore, it can be shown that the heterogeneous initiation process of a gas phase reaction identifies to a chain linear mechanism. Such an heterogeneous sequence conditions the further proceeding of the homogeneous chain reaction; both evolutions being kinematically connected. Rate constant of hydrogen adsorption on silica glass: ksub(a1) approximately 10/sup 14/ exp(-47/RT)Isup(0,5).molesup(-0,5).S/sup -1/ has been evaluated.

  14. Addition and spin exchange rate constants by longitudinal field μSR: the Mu + NO reaction

    International Nuclear Information System (INIS)

    Senba, Masayoshi; Gonzalez, A.C.; Kempton, J.R.; Arseneau, D.J.; Pan, J.J.; Tempelmann, A.; Fleming, D.G.

    1991-01-01

    The addition reaction Mu + NO + M → MuNO + M and the spin exchange reaction Mu(↑) + NO(↓)→Mu(↓)+NO(↑) have been measured by longitudinal field μSR at room temperature in the presence of up to 58 atm of N 2 as inert collider. The pressure dependence of the longitudinal relaxation rate due to the addition reaction (λ c ) demonstrates that the system is still in the low pressure regime in this pressure range. The corresponding termolecular rate constant has been determined as k 0.Mu =(1.10±0.25)x10 -32 cm 6 molecules -2 s -1 , almost 4 times smaller than the corresponding H atom reaction k 0,H =3.90x10 -32 cm 6 molecules -2 s -1 . The average value of the spin exchange rate constants in the 2.5-58 atm pressure range, k SE = (3.16±0.06)x10 -10 cm 3 molecule -1 s -1 , is in good agreement with previous values obtained by transverse field μSR. (orig.)

  15. Hydrogen-deuterium exchange reaction of 2-methylpyridine catalyzed by several fatty acids

    International Nuclear Information System (INIS)

    Hirata, Hirohumi; Fukuzumi, Kazuo.

    1976-01-01

    Hydrogen-deuterium exchange reaction of 2-methylpyridine has been studied by using several fatty acids as catalysts. The reaction was carried out in a sealed pyrex tube at 120 0 C, and the contents of the products were determined by mass spectrometry. Reaction of 2-methylpyridine with monodeuteroacetic acid (1 : 1, mol/mol) arrived at a equilibrium (d 0 reversible d 1 reversible d 2 reversible d 3 ) in 2 hr (d 0 41%, d 1 42%, d 2 15%, d 3 2%). No exchange was observed for the reaction of pyridine with monodeuteroacetic acid. The conversion-time curves of typical series reactions (d 0 → d 1 → d 2 → d 3 ) were obtained for the fatty acid catalyzed exchange in deuterium oxide. The effect of the fatty acid RCO 2 H (substrate : fatty acid : D 2 O=1 : 0.86 : 27.6, mol/mol/mol) on the conversion was in the order of R; C 1 --C 3 4 --C 10 , where the reaction mixtures were homogeneous in the case of C 1 --C 3 and were heterogeneous in the case of C 4 --C 10 . The effects of the initial concentration of the substrates and the catalysts (RCO 2 H) on the total conversion were studied by using some fatty acids (R; C 2 , C 4 and C 9 ) in deuterium oxide (for 2 hr). The total conversion of the substrate increases with increasing the concentration of the acids. The total conversion decreases in the case of R=C 9 , but, increases in the case of R=C 2 with increasing the concentration of the substrate. In the case of reactions with low concentrations of the substrate, the reactivity was in the order of C 9 >C 4 >C 2 , while with high concentrations, the reactivity was in the order of C 4 >C 2 >C 9 and C 9 >C 4 >C 2 with high and low concentrations of the acids, respectively. A possible reaction mechanism was proposed and discussed. (auth.)

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

    KAUST Repository

    Fornander, Louise H; Renodon-Corniè re, Axelle; Kuwabara, Naoyuki; Ito, Kentaro; Tsutsui, Yasuhiro; Shimizu, Toshiyuki; Iwasaki, Hiroshi; Nordé n, Bengt; Takahashi, Masayuki

    2013-01-01

    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

  17. Thermochemical study of deuterium exchange reactions in water-alcohol and alcohol-alcohol systems

    International Nuclear Information System (INIS)

    Khurma, J.R.; Fenby, D.V.

    1979-01-01

    Molar excess enthalpies of water-alcohol systems have been analyzed to give equilibrium constants and enthalpies of the reactions 2ROH + D 2 O = 2ROD + H 2 O (R = CH 3 , C 2 H 5 , n-C 3 H 7 ). The equilibrium constants are significantly greater than the ''random'' value. Molar excess enthalpies of alcohol-alcohol systems have been analyzed to give enthalpies of reactions ROH + R'OD = ROD + R'OH. The enthalpies of water-alcohol and alcohol-alcohol exchange reactions form a self-consistent set and are in good agreement with values from earlier studies. Molar excess enthalpies at 298.15 K are reported for n-C 3 H 7 OH and n-C 3 H 7 OD with H 2 O, D 2 O, CH 3 OH, CH 3 OD, C 2 H 5 OH, and C 2 H 5 OD

  18. Measurement of exclusive hypercharge-exchange reactions at 35 to 140 GeV/c

    International Nuclear Information System (INIS)

    Arenton, M. W.; Ayres, D.S.; Cohen, D.

    1978-07-01

    Data on the reactions π + p → K + Σ + and π + p → K + Y* + were obtained using the Fermilab Single Arm Spectrometer Facility at incident π + momenta of 35, 70, and 140 GeV/c for momentum transfers vertical bar t vertical bar less than or approximately equal to 1 GeV 2 . The line-reversed reactions K - p → π - Σ + and K - p → π - Y* + were also studied at 70 GeV/c with the same apparatus in order to test exchange degeneracy of the K*(890) and K**(1420) trajectories. Preliminary results on the first set of reactions at 70 GeV/c are presented and found to be in qualitative agreement with the model of Navelet and Stevens

  19. Effect of the competition of Cu(II) and Ni(II) on the kinetic and thermodynamic stabilities of Cr(III)-organic ligand complexes using competitive ligand exchange (EDTA).

    Science.gov (United States)

    Cunha, Graziele da Costa; Goveia, Danielle; Romão, Luciane Pimenta Cruz; de Oliveira, Luciana Camargo

    2015-05-01

    The effect of competition of Cu(II) and Ni(II) on the kinetic stability of Cr(III) complexed with natural organic matter (NOM) was characterized using EDTA exchange with single-stage tangential-flow ultrafiltration. For a water sample from Serra de Itabaiana, 3% of spiked Cr(III) was exchanged, while for a sample from the Itapanhaú River, 7, 10, 10, and 21% was exchanged in experiments using Cr(III) alone and in combination with Cu(II), Ni(II), or Cu(II) + Ni(II), respectively. Times required to reach exchange equilibrium with EDTA were less than 360 min. The influence of competition from Ni(II) and Cu(II) on the availability of complexed Cr(III) was low, demonstrating preference of the ligand sites for Cr(III). This was correlated with sample humification, as confirmed by EPR and (13)C NMR analyses. Exchange efficiency was in the order Cu > Ni > Cr, and the process could be readily described by first order kinetics, with average rate constants of 0.35-0.37 h(-1). Copyright © 2015 Elsevier Ltd. All rights reserved.

  20. Probing Ligand Exchange in the P450 Enzyme CYP121 from Mycobacterium tuberculosis: Dynamic Equilibrium of the Distal Heme Ligand as a Function of pH and Temperature.

    Science.gov (United States)

    Fielding, Andrew J; Dornevil, Kednerlin; Ma, Li; Davis, Ian; Liu, Aimin

    2017-12-06

    CYP121 is a cytochrome P450 enzyme from Mycobacterium tuberculosis that catalyzes the formation of a C-C bond between the aromatic groups of its cyclodityrosine substrate (cYY). The crystal structure of CYP121 in complex with cYY reveals that the solvent-derived ligand remains bound to the ferric ion in the enzyme-substrate complex. Whereas in the generally accepted P450 mechanism, binding of the primary substrate in the active-site triggers the release of the solvent-derived ligand, priming the metal center for reduction and subsequent O 2 binding. Here we employed sodium cyanide to probe the metal-ligand exchange of the enzyme and the enzyme-substrate complex. The cyano adducts were characterized by UV-vis, EPR, and ENDOR spectroscopies and X-ray crystallography. A 100-fold increase in the affinity of cyanide binding to the enzyme-substrate complex over the ligand-free enzyme was observed. The crystal structure of the [CYP121(cYY)CN] ternary complex showed a rearrangement of the substrate in the active-site, when compared to the structure of the binary [CYP121(cYY)] complex. Transient kinetic studies showed that cYY binding resulted in a lower second-order rate constant (k on (CN) ) but a much more stable cyanide adduct with 3 orders of magnitude slower k off (CN) rate. A dynamic equilibrium between multiple high- and low-spin species for both the enzyme and enzyme-substrate complex was also observed, which is sensitive to changes in both pH and temperature. Our data reveal the chemical and physical properties of the solvent-derived ligand of the enzyme, which will help to understand the initial steps of the catalytic mechanism.

  1. Reactivity of the functional groups in functional polymers. Use of T-for-H exchange reaction

    International Nuclear Information System (INIS)

    Imaizumi, Hiroshi; Hasegawa, Shinobu.

    1997-01-01

    In order to reveal the reactivity of several functional polymers, the following two experiments were carried out: observing the hydrogen-isotope exchange reaction (T-for-H exchange reaction) between one of T-labeled functional polymers and 0.500 mol·l -1 aniline dissolved in p-xylene, observing the degree of the T dispersed from the surface area of the polymer under the several conditions. Consequently, the following six matters have been quantitatively obtained. The T-for-H exchange reaction occurred between each T-labeled polymer and aniline, and is more predominant than other chemical reactions within the range of 50-90degC. The reactivity of the polymers are strongly affected by their matrix structures. The degree of the T dispersed from the surface area of each T-labeled polymer is hardly affected by humidity. The higher the temperature is, the larger is the degree of the T dispersed from the surface area. At the same temperature, the degree of the T dispersed from the surface area of each polymer is strongly affected by the physical form of the polymer even if the polymer has the same functional group as the others, and the T existing in the surface area of a T-labeled glassy polymer is less dispersed than that of a porous one. The degree of the T dispersed from the surface area of a T-labeled polymer is small when the degree of the polymerization of the polymer is high. (author)

  2. Structure, equilibrium and ligand exchange dynamics in the binary and ternary dioxouranium(VI)-ethylenediamine-N,N'-diacetic acid-fluoride system: A potentiometric, NMR and X-ray crystallographic study.

    Science.gov (United States)

    Palladino, Giuseppe; Szabó, Zoltán; Fischer, Andreas; Grenthe, Ingmar

    2006-11-21

    The structure, thermodynamics and kinetics of the binary and ternary uranium(VI)-ethylenediamine-N,N'-diacetate (in the following denoted EDDA) fluoride systems have been studied using potentiometry, 1H, 19F NMR spectroscopy and X-ray diffraction. The UO2(2+)-EDDA system could be studied up to -log[H3O+] = 3.4 where the formation of two binary complexes UO2(EDDA)(aq) and UO2(H3EDDA)3+ were identified, with equilibrium constants logbeta(UO2EDDA) = 11.63 +/- 0.02 and logbeta(UO2H3EDDA3+) = 1.77 +/- 0.04, respectively. In the ternary system the complexes UO2(EDDA)F-, UO2(EDDA)(OH)- and (UO2)2(mu-OH)2(HEDDA)2F2(aq) were identified; the latter through 19F NMR. 1H NMR spectra indicate that the EDDA ligand is chelate bonded in UO2(EDDA)(aq), UO2(EDDA)F- and UO2(EDDA)(OH)- while only one carboxylate group is coordinated in UO2(H3EDDA)3+. The rate and mechanism of the fluoride exchange between UO2(EDDA)F- and free fluoride was studied by 19F NMR spectroscopy. Three reactions contribute to the exchange; (i) site exchange between UO2(EDDA)F- and free fluoride without any net chemical exchange, (ii) replacement of the coordinated fluoride with OH- and (iii) the self dissociation of the coordinated fluoride forming UO2(EDDA)(aq); these reactions seem to follow associative mechanisms. (1)H NMR spectra show that the exchange between the free and chelate bonded EDDA is slow and consists of several steps, protonation/deprotonation and chelate ring opening/ring closure, the mechanism cannot be elucidated from the available data. The structure (UO2)2(EDDA)2(mu-H2EDDA) was determined by single crystal X-ray diffraction and contains two UO2(EDDA) units with tetracoordinated EDDA linked by H2EDDA in the "zwitterion" form, coordinated through a single carboxylate oxygen from each end to the two uranium atoms. The geometry of the complexes indicates that there is no geometric constraint for an associative ligand substitution mechanism.

  3. Exchanged cations and water during reactions in polypyrrole macroions from artificial muscles.

    Science.gov (United States)

    Valero, Laura; Otero, Toribio F; Martínez, José G

    2014-02-03

    The movement of the bilayer (polypyrrole-dodecylbenzenesulfonate/tape) during artificial muscle bending under flow of current square waves was studied in aqueous solutions of chloride salts. During current flow, polypyrrole redox reactions result in variations in the volumes of the films and macroscopic bending: swelling by reduction with expulsion of cations and shrinking by oxidation with the insertion of cations. The described angles follow a linear function, different in each of the studied salts, of the consumed charge: they are faradaic polymeric muscles. The linearity indicates that cations are the only exchanged ions in the studied potential range. By flow of the same specific charge in every electrolyte, different angles were described by the muscle. The charge and the angle allow the number and volume of both the exchanged cations and the water molecules (related to a reference) between the film to be determined, in addition to the electrolyte per unit of charge during the driving reaction. The attained apparent solvation numbers for the exchanged cations were: 0.8, 0.7, 0.6, 0.5, 0.5, 0.4, 0.25, and 0.0 for Na(+), Mg(2+), La(3+), Li(+), Ca(2+), K(+), Rb(+), and Cs(+), respectively. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

    International Nuclear Information System (INIS)

    McLane, V.

    1997-07-01

    This document describes EXFOR, the exchange format designed to allow transmission of nuclear reaction data between the members of the Nuclear Data Center Network. In addition to storing the data and its' bibliographic information, experimental information, including source of uncertainties, is also compiled. The status and history of the data set is also included, e.g., the source of the data, any updates which have been made, and correlations to other data sets. EXFOR is designed for flexibility rather than optimization of data processing in order to meet the diverse needs of the nuclear reaction data centers. The exchange format should not be confused with a center-to-user format. Although users may obtain data from the centers in the EXFOR format, other center-to-user formats have been developed to meet the needs of the users within each center's own sphere of responsibility. The exchange format, as outlined, is designed to allow a large variety of numerical data tables with explanatory and bibliographic information to be transmitted in an easily machine-readable format (for checking and indicating possible errors) and a format that can be read by personnel (for passing judgment on and correcting any errors indicated by the machine)

  5. Complex ion kinetics. Reaction rates on ion-exchange resins compared to those in water

    International Nuclear Information System (INIS)

    Liss, I.B.; Murmann, R.K.

    1975-01-01

    A comparison has been made between the rates in water and on an ion-exchange resin for the aquation of [(NH 3 ) 5 CoOReO 3 ] 2+ and [(H 2 O) 5 CrCl] 2+ and for the 18 O isotopic exchange of water with [(NH 3 ) 5 Co(OH 2 )] 3+ and ReO 4 - . The rate of water exchange on [(NH 3 ) 5 Co(OH 2 )] 3+ was not changed by association with Dowex 50W resins. Aquation of [(NH 3 ) 5 CoOReO 3 ] 2+ and water exchange on ReO 4 - had modified pH dependencies when associated with a resin. With the cobalt complex the rates were faster on the resin in the acidic region and slower on the resin in the basic region. A new term in the rate equation was observed when ReO 4 - was on the resin, first order in H + , while the other terms appear to be unchanged. Aquation of [(H 2 O) 5 CrCl] 2+ was much slower when it was absorbed on the resin. This was related to the known ionic strength effect of the reaction. (auth)

  6. Controlled growth of gold nanoparticles in zeolite L via ion-exchange reactions and thermal reduction processes

    KAUST Repository

    Zeng, Shangjing; Ding, Shuang; Li, Shangyu; Wang, Runwei; Zhang, Zongtao

    2014-01-01

    The growth of gold nanoparticles in zeolite can be controlled using ion-exchange reactions and thermal reduction processes. We produce a number of different sizes of the gold nanoparticles with the particle size increasing with increased temperature

  7. A Monte Carlo simulation of the exchange reaction between gaseous molecules and the atoms on a heterogeneous solid surface

    International Nuclear Information System (INIS)

    Imai, Hisao

    1980-01-01

    A method of the Monte Carlo simulation of the isotopic exchange reaction between gaseous molecules and the atoms on an arbitrarily heterogeneous solid surface is described by employing hydrogen as an example. (author)

  8. Photochemical exchange reactions of thymine, uracil and their nucleosides with selected amino acids

    International Nuclear Information System (INIS)

    Shetlar, M.D.; Taylor, J.A.; Hom, K.

    1984-01-01

    The photoinduced exchange reactions of thymine with lysine at basic pH, using 254 nm light, have been studied. Three products have been isolated, namely, 6-amino-2-(1-thyminyl)hexanoic acid (Ia), 2-amino-6-(1-thyminyl)hexanoic acid (IIa) and 1-amino-5-(1-thyminyl)pentane (IIIa). Compound IIIa was shown to be a secondary product, produced by photochemical decarboxylation of Ia. Photochemical reaction of thymine with glycine and alanine at basic pH led, respectively, to formation of 2-(1-thyminyl)acetic acid (Ic) and 2-(1-thyminyl)propionic acid (Id). Compounds Ic and Id underwent photolysis to produce the decarboxylated secondary products 1-methylthymine and 1-ethylthymine, respectively. Thymidine reacts photochemically with glycine and alanine to produce the same products. Irradiation of DNA in the presence of lysine at basic pH led to the formation of the same products formed in the thymine-lysine system, namely Ia, IIa and IIIa. Uracil was found to undergo analogous photochemical exchange reactions with lysine to form 6-amino-2-(1-uracilyl)hexanoic acid (Ib), and 2-amino-6-(1-uracilyl)hexanoic acid (IIb). Compound Ib was found to undergo photodecarboxylation to form 1-amino-5-(1-uracilyl)pentane (IIIb), analogous to the secondary photoreaction of Ia. Photoreaction of uracil with 1,5-diaminopentane (cadaverine) likewise led to formation of IIIb. (author)

  9. Effects of the anion salt nature on the rate constants of the aqueous proton exchange reactions.

    Science.gov (United States)

    Paredes, Jose M; Garzon, Andres; Crovetto, Luis; Orte, Angel; Lopez, Sergio G; Alvarez-Pez, Jose M

    2012-04-28

    The proton-transfer ground-state rate constants of the xanthenic dye 9-[1-(2-methyl-4-methoxyphenyl)]-6-hydroxy-3H-xanthen-3-one (TG-II), recovered by Fluorescence Lifetime Correlation Spectroscopy (FLCS), have proven to be useful to quantitatively reflect specific cation effects in aqueous solutions (J. M. Paredes, L. Crovetto, A. Orte, J. M. Alvarez-Pez and E. M. Talavera, Phys. Chem. Chem. Phys., 2011, 13, 1685-1694). Since these phenomena are more sensitive to anions than to cations, in this paper we have accounted for the influence of salts with the sodium cation in common, and the anion classified according to the empirical Hofmeister series, on the proton transfer rate constants of TG-II. We demonstrate that the presence of ions accelerates the rate of the ground-state proton-exchange reaction in the same order than ions that affect ion solvation in water. The combination of FLCS with a fluorophore undergoing proton transfer reactions in the ground state, along with the desirable feature of a pseudo-dark state when the dye is protonated, allows one unique direct determination of kinetic rate constants of the proton exchange chemical reaction. This journal is © the Owner Societies 2012

  10. A Generalizable Top-Down Nanostructuring Method of Bulk Oxides: Sequential Oxygen-Nitrogen Exchange Reaction.

    Science.gov (United States)

    Lee, Lanlee; Kang, Byungwuk; Han, Suyoung; Kim, Hee-Eun; Lee, Moo Dong; Bang, Jin Ho

    2018-05-27

    A thermal reaction route that induces grain fracture instead of grain growth is devised and developed as a top-down approach to prepare nanostructured oxides from bulk solids. This novel synthesis approach, referred to as the sequential oxygen-nitrogen exchange (SONE) reaction, exploits the reversible anion exchange between oxygen and nitrogen in oxides that is driven by a simple two-step thermal treatment in ammonia and air. Internal stress developed by significant structural rearrangement via the formation of (oxy)nitride and the creation of oxygen vacancies and their subsequent combination into nanopores transforms bulk solid oxides into nanostructured oxides. The SONE reaction can be applicable to most transition metal oxides, and when utilized in a lithium-ion battery, the produced nanostructured materials are superior to their bulk counterparts and even comparable to those produced by conventional bottom-up approaches. Given its simplicity and scalability, this synthesis method could open a new avenue to the development of high-performance nanostructured electrode materials that can meet the industrial demand of cost-effectiveness for mass production. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Influence of ligand-bridged substitution on the exchange coupling constant of chromium-wheels host complexes: a density functional theory study

    Science.gov (United States)

    Sadeghi Googheri, Motahare; Abolhassani, Mohammad Reza; Mirzaei, Mahmoud

    2018-05-01

    Designing and introducing novel wheel-shaped supramolecular as host complexes with new magnetic properties is the theme of the day. So in this study, new eight binuclear chromium (III) complexes, as models of real chromium-wheel host complexes, were designed based on changing of bridged-ligands and exchange coupling constants (J) of them were calculated using the broken symmetry density functional theory approach. Substitution of fluorine ligand in fluoro-bridged model [Cr2F(tBuCO2)2(H2O)2(OH)4]-1 by halogen anions (Cl-, Br- and I- ) decreased the antiferromagnetic exchange coupling between Cr(III) centres such that by going from F- to I- the J values became more positive. In the case of hydroxo-bridged model [Cr2OH(tBuCO2)2(H2O)2(OH)4]-1, replacement of hydroxyl by methoxy anion (OMe-) strengthened the antiferromagnetic property of the complex but substitution by sulfanide (SH-) and amide (NH2-) anions weakened it and changed the nature of complexes to ferromagnetic. Because of their different magnetic properties, these new investigated complexes can be suggested as interesting synthetic targets. Also, the J value changes due to ligand substitution were evaluated and it was found that the Cr-X bond strength and partial charges of involved atoms were the most effective factors on it.

  12. Nucleon charge exchange reaction and antiproton elastic scattering at intermediate energies

    International Nuclear Information System (INIS)

    Kronenfeld, J.

    1985-02-01

    This work treats the medium energy nuclear (p,n) charge exchange reaction to analog states and the low energy elastic scattering of antiprotons and investigates the central aspects of a microscopic theory based on multiple-scattering series which are pertinent to these reactions. A two-step term of the Distorted Wave Impulse Approximation (DWIA) in treating the (p,n) reaction, was included. For the very absorptive p-bar interaction with nuclei we conjecture that a partial infinite summation, constituing a renormalization of the single scattering term of the optical potential series provides the dominant feature of this interaction. In this work the excitation of analog states is calculated and it was found that the (p,n) reaction is described fairly well by the DWIA. In the first part of the work the (p,n) reaction in the energy range 100-200 MeV was treated. The DWIA calculations were based on eikonalization. In the second part of the work the p-barA interaction with the selfconsistent scheme mentioned above, for scattering energies 30-120 MeV, was examined. (author)

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

    International Nuclear Information System (INIS)

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

    2007-01-01

    We present a detailed dynamical study of the kinetics of O( 3 P)+NO( 2 Π) collisions including O atom exchange reactions and the recombination of NO 2 . The classical trajectory calculations are performed on the lowest 2 A ' and 2 A '' potential energy surfaces, which were calculated by ab initio methods. The calculated room temperature exchange reaction rate coefficient, k 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 ex , overestimates the experimental data by merely 20%. The pressure dependence of the recombination rate, k 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 r ∝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, Δ 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 2 , which is in accord with the overall T -1.4 dependence of the measured recombination rate even in the low temperature range

  14. Rate of Isotope Exchange Reaction Between Tritiated Water in a Gas Phase and Water on the Surface of Piping Materials

    International Nuclear Information System (INIS)

    Nakashio, Nobuyuki; Yamaguchi, Junya; Kobayashi, Ryusuke; Nishikawa, Masabumi

    2001-01-01

    The system effect of tritium arises from the interaction of tritium in the gas phase with water on the surface of piping materials. It has been reported that the system effect can be quantified by applying the serial reactor model to the piping system and that adsorption and isotope exchange reactions play the main roles in the trapping of tritium. The isotope exchange reaction that occurs when the chemical form of tritium in the gas phase is in the molecular form, i.e., HT or T 2 , has been named isotope exchange reaction 1, and that which occurs when tritium in the gas phase is in water form, i.e., HTO or T 2 O, has been named isotope exchange reaction 2.The rate of isotope exchange reaction 2 is experimentally quantified, and the rate is observed to be about one-third of the rate of adsorption. The trapping and release behavior of tritium from the piping surface due to isotope exchange reaction 2 is also discussed. It is certified that swamping of water vapor to process gas is effective to release tritium from the surface contaminated with tritium

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

    International Nuclear Information System (INIS)

    Gober, J.R.

    1988-01-01

    The equilibrium chemical exchange dynamics of the creatine kinase enzyme system were studied by one- and two-dimensional 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 eq , the hydrogen ion stoichiometry, and the standard thermodynamic functions. The pure absorption mode in four quadrant two-dimensional chemical exchange experiment was employed so that the complete kinetic matrix showing all of the chemical exchange process could be realized

  16. Mineral carbonation of gaseous carbon dioxide using a clay-hosted cation exchange reaction.

    Science.gov (United States)

    Kang, Il-Mo; Roh, Ki-Min

    2013-01-01

    The mineral carbonation method is still a challenge in practical application owing to: (1) slow reaction kinetics, (2) high reaction temperature, and (3) continuous mineral consumption. These constraints stem from the mode of supplying alkaline earth metals through mineral acidification and dissolution. Here, we attempt to mineralize gaseous carbon dioxide into calcium carbonate, using a cation exchange reaction of vermiculite (a species of expandable clay minerals). The mineralization is operated by draining NaCI solution through vermiculite powders and continuously dropping into the pool of NaOH solution with CO2 gas injected. The mineralization temperature is regulated here at 293 and 333 K for 15 min. As a result of characterization, using an X-ray powder diffractometer and a scanning electron microscopy, two types of pure CaCO3 polymorphs (vaterite and calcite) are identified as main reaction products. Their abundance and morphology are heavily dependent on the mineralization temperature. Noticeably, spindle-shaped vaterite, which is quite different from a typical vaterite morphology (polycrystalline spherulite), forms predominantly at 333 K (approximately 98 wt%).

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2009-07-06

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

  18. Aprotic solvent systems provide mechanistic windows for biomolecular reactions: nucleic acid proton exchange

    International Nuclear Information System (INIS)

    McConnell, B.; Tan, A.

    1986-01-01

    Detection of general acid-base catalysis of proton transfer reactions in aqueous cytidine (or adenosine) is completely obscured by the highly reactive endocyclic protonated species of the nucleobase, whose amino proton lifetime is much shorter than that of the neutral form. In aqueous solution, protonation of the nucleobase always accompanies protonation of the buffer catalyzing exchange. However, in DMSO/water mixtures this is not the case; aqueous protonated acetate or chloroacetate can be added to cytidine in DMSO solutions without further dissociation of the buffer or significant protonation of cytidine N-3. Under these conditions general acid catalysis is observed, which involves an H-bonded complex between cytidine (N-3) and the buffer acid. Increased amino proton exchange in response to H-bond donation to C(N-3) is further suggested by increased 1 H NMR saturation-recovery rates with the formation of G-C base-pairs in DMSO and by the inverse dependence of amino proton exchange on nucleoside concentration

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

    International Nuclear Information System (INIS)

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

    1986-01-01

    The enzyme uridine-diphosphoglucose pyrophosphorylase catalyzes the reversible formation of pyrophosphate and UDP-glucose from UTP and glc-1P. The positional isotope exchange reaction was measured using oxygen-18 labelled UTP. The synthesis of [β- 18 O 2 , βγ- 18 O, γ- 18 O 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 β-nonbridge position of the labelled UTP to the αβ-bridge position was measured with 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 -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 2 is 1.2. The rate constant for the release of UTP from E-UTP relative to V 1 is 9

  20. Tritons for the study of the charge-exchange reactions with the LHE streamer chamber: status and some possibilities

    International Nuclear Information System (INIS)

    Avramenko, S.A.; Belikov, Yu.A.; Golokhvastov, A.I.; Kirillov, A.D.; Khorozov, S.A.; Komolov, L.N.; Lukstin'sh, Yu.; Rukoyatkin, P.A.

    1997-01-01

    The 6 and 9 GeV/c secondary tritons, produced in the 4 He+A→ 3 H+X reaction, were used to study the charge-exchange reactions using a streamer chamber in magnetic field. The triton formation schemes, the beam parameters achieved as well as a way to reduce the beam momentum spread are given in the paper

  1. The deuterium-exchange reaction between water and hydrogen with the thin-film hydrophobic catalyst

    International Nuclear Information System (INIS)

    Yamashita, Hisao; Mizumoto, Mamoru; Matsuda, Shimpei

    1985-01-01

    The deuterium-exchange reaction between water and hydrogen with a hydrophobic catalyst was studied. The hydrophobic catalyst was composed of platinum as an active component and porous poly(tetrafluoroethylene) (PTFE) as a support. The PTFE support was in two forms, i.e., (a) a pellet and (b) a thin-film with the thickness of 50 μm. The primary purpose of the thin film hydrophobic catalyst was to reduce the platinum usage in the reactor. The activity of the catalyst was measured in a trickle bed reactor at atmospheric pressure and temperature of 20 ∼ 70 deg C. It has been found that the employment of the thin-film catalyst reduced the platinum usage to 1/5 of the reactor in the case of using a conventional catalyst. Platinum particles on the thin-film catalyst work efficiently because the reactants were easily diffused to the active sites. It has also been found that the isotopic exchange rate with the thin-film catalyst increased with the increase in the ratio of liquid/gas and increased with the rise of the reaction temperature. It was found from an endurance test that the activity of the thin-film catalyst decreased gradually due to the condensation of water vapor in the catalyst, but was regenarated by heating the catalyst to remove the condensed water. (author)

  2. 1H NMR studies of substrate hydrogen exchange reactions catalyzed by L-methionine gamma-lyase

    International Nuclear Information System (INIS)

    Esaki, N.; Nakayama, T.; Sawada, S.; Tanaka, H.; Soda, K.

    1985-01-01

    Hydrogen exchange reactions of various L-amino acids catalyzed by L-methionine gamma-lyase (EC 4.4.1.11) have been studied. The enzyme catalyzes the rapid exchange of the alpha- and beta-hydrogens of L-methionine and S-methyl-L-cysteine with deuterium from the solvent. The rate of alpha-hydrogen exchange was about 40 times faster than that of the enzymatic elimination reaction of the sulfur-containing amino acids. The enzyme also catalyzes the exchange reaction of alpha- and beta-hydrogens of the straight-chain L-amino acids which are not susceptible to elimination. The exchange rates of the alpha-hydrogen and the total beta-hydrogens of L-alanine and L-alpha-aminobutyrate with deuterium followed first-order kinetics. For L-norvaline, L-norleucine, S-methyl-L-cysteine, and L-methionine, the rate of alpha-hydrogen exchange followed first-order kinetics, but the rate of total beta-hydrogen exchange decreased due to a primary isotope effect at the alpha-position. L-Phenylalanine and L-tryptophan slowly underwent alpha-hydrogen exchange. The pro-R hydrogen of glycine was deuterated stereospecifically

  3. Studies on Pd/NiFe2O4 catalyzed ligand-free Suzuki reaction in aqueous phase: synthesis of biaryls, terphenyls and polyaryls

    Directory of Open Access Journals (Sweden)

    Suresh B. Waghmode

    2011-03-01

    Full Text Available Palladium supported on nickel ferrite (Pd/NiF2O4 was found to be a highly active catalyst for the Suzuki coupling reaction between various aryl halides and arylboronic acids. The reaction gave excellent yields (70–98% under ligand free conditions in a 1:1 DMF/H2O solvent mixture, in short reaction times (10–60 min. The catalyst could be recovered easily by applying an external magnetic field. The polyaryls were similarly synthesized.

  4. Chemistry of sustainability-Part I: Carbon dioxide as an organic synthon and Part II: Study of thermodynamics of cation exchange reactions in semiconductor nanocrystals

    Science.gov (United States)

    Sathe, Ajay A.

    chapter introduces the role of nanomaterials in sustainable solar energy conversion and storage. The use of cation exchange reactions in nanocrystals to access novel materials is highlighted. Despite having shown tremendous promise in the synthetic applications, the fundamental measurements of the thermodynamic and kinetic parameters of a cation exchange reaction are largely non-existent. This impedes the future growth of this powerful methodology. The technique of isothermal titration calorimetry is introduced, and its importance to studying the thermochemical changes occurring during cation exchange is outlined. The final chapter presents results obtained from the isothermal titration calorimetry on the prototypical cation exchange reaction between cadmium selenide and silver ions. The role of nanoparticle size, identity of the silver salt, solvent, surface ligands and temperature is studied. Recommendations for future investigations using ITC as well as other characterization techniques for discerning the kinetics of cation exchange are presented. I believe that a more unified mechanistic understanding of the cation exchange process in nanomaterials will aid the development of more efficient and robust materials for applications in a wide variety of fields.

  5. Stock Price Reaction to Announcements of Right Issues and Debenture Issues: Evidence from Colombo Stock Exchange

    Directory of Open Access Journals (Sweden)

    Udani Chathurika Edirisinghe

    2015-02-01

    Full Text Available This study investigates the stock market reaction for right issues and debenture issues of Colombo Stock Exchange (CSE during the period of 2005 to 2011 while providing evidence for the research question “how do stock prices react to the debt and equity issue announcements of listed companies in CSE?” In investigating the ex-ante and ex-post market reactions the study employees event study methodology, while predicting abnormal returns, based on three alternative normal/expected returns modeling methods, namely Mean Adjusted Model, Market Adjusted Model, and Capital Asset Pricing Model. When testing the alternative hypothesis, whether stock prices significantly reacts to the announcement of right & debenture issues, results of all models show positive market reaction during the 30 days prior to the announcement and react negatively from 2 days after the announcements for right issues, but for debenture issues market reacted negatively during the period prior to debenture issues and continue to do the same during the post event period. Although the magnitude and significance of abnormal return generated through three alternatives methods differ, the pattern of the CAAR of all models are similar. Thus, as far as the speed of the price adjustment is concerned it seems that the CSE is not efficient.

  6. Carboxylate ligands drastically enhance the rates of oxo exchange and hydrogen peroxide disproportionation by oxo manganese compounds of potential biological significance.

    Science.gov (United States)

    Dubois, Lionel; Pécaut, Jacques; Charlot, Marie-France; Baffert, Carole; Collomb, Marie-Noëlle; Deronzier, Alain; Latour, Jean-Marc

    2008-01-01

    To mimic the carboxylate-rich active site of the manganese catalases more closely we introduced carboxylate groups into dimanganese complexes in place of nitrogen ligands. The series of dimanganese(III,IV) complexes of tripodal ligands [Mn(2)(L)(2)(O)(2)](3+/+/-/3-) was extended from those of tpa (1) and H(bpg) (2) to those of H(2)(pda) (3) and H(3)(nta) (4) (tpa=tris-picolylamine, H(bpg)=bis-picolylglycylamine, H(2)(pda)=picolyldiglycylamine, H(3)(nta)=nitrilotriacetic acid). While 3 [Mn(2)(pda)(2)(O)(2)][Na(H(2)O)(3)] could be synthesized at -20 degrees C and characterized in the solid state, 4 [Mn(2)(nta)(2)(O)(2)](3-) could be obtained and studied only in solution at -60 degrees C. A new synthetic procedure for the dimanganese(III,III) complexes was devised, using stoichiometric reduction of the dimanganese(III,IV) precursor by the benzil radical with EPR monitoring. This enabled the preparation of the parent dimanganese(III,III) complex 5 [Mn(2)(tpa)(2)(O)(2)](ClO(4))(2), which was structurally characterized. The UV/visible, IR, EPR, magnetic, and electrochemical properties of complexes 1-3 and 5 were analyzed to assess the electronic changes brought about by the carboxylate replacement of pyridine ligands. The kinetics of the oxo ligand exchanges with labeled water was examined in acetonitrile solution. A dramatic effect of the number of carboxylates was evidenced. Interestingly, the influence of the second carboxylate substitution differs from that of the first one probably because this substitution occurs on an out-of-plane coordination while the former occurs in the plane of the [Mn(2)O(2)] core. Indeed, on going from 1 to 3 the exchange rate was increased by a factor of 50. Addition of triethylamine caused a rate increase for 1, but not for 3. The abilities of 1-3 to disproportionate H(2)O(2) were assessed volumetrically. The disproportionation exhibited a sensitivity corresponding to the carboxylate substitution. These observations strongly suggest that

  7. Theoretical study on platinum-catalyzed isotope exchange reaction mechanism of hydrogen and liquid water

    International Nuclear Information System (INIS)

    Hu Sheng; Wang Heyi; Luo Shunzhong

    2009-04-01

    Based on electron and vibration approximate means and the density function theory B3LYP, the ΔG degree and equilibrium pressures of adsorption and dissociation reactions of H 2 and water vapor on Pt surface have been calculated. The adsorption, dissociation and coadsorption actions of H 2 and water were analyzed. According to the ΔG degree, hydrogen molecule combines with metal atoms in single atom, and water vapor molecule has no tendency to dissociate on Pt surface. The dissociation of hydrogen molecule would hold back the direct adsorption of water vapor molecules on Pt surface. The structures of Pt-H (OH 2 ) n + (n=1, 2, 3) hydroniums were optimized. According to the mulliken overlap populations, Pt-H (OH 2 ) + is not stable or produced. Hydrogen isotope exchange occurs between hydration layer and D atoms which adsorb on Pt surface via intermediates (H 2 O) n D + (ads) (n≥2). (authors)

  8. Non-coherent contributions in charge-exchange reactions and η-η{sup '} mixing

    Energy Technology Data Exchange (ETDEWEB)

    Nekrasov, M.L. [NRC ' ' Kurchatov Institute' ' , Institute for High Energy Physics, Protvino (Russian Federation)

    2017-05-15

    We analyse K{sup -}p → (η,η{sup '},π{sup 0})Λ on the basis of the fit of data in a wide region of energies, and π{sup -}p → (η,η{sup '})n at the energies of GAMS-4π. We show that disagreements between the data and the predictions of Regge theory may be explained by the mode change of summation of intermediate contributions at increasing energy, from coherent to non-coherent. A method of experimental measurement of the non-coherent contributions is proposed. On the basis of available data on the charge-exchange reactions the η-η{sup '} mixing is estimated. (orig.)

  9. Absorption of carbon dioxide and isotope exchange rate of carbon in a reaction system between carbon dioxide and carbamic acid

    International Nuclear Information System (INIS)

    Takeshita, Kenji; Kitamoto, Asashi

    1985-01-01

    The performance of isotope separation of carbon-13 by chemical exchange between carbon dioxide and carbamic acid was studied. The working fluid used in the study was a solution of DNBA, (C 4 H 9 ) 2 NH and n-octane mixture. Factors related to the isotope exchange rate were measured, such as the absorption rate of carbon dioxide into the solution of DNBA and n-octane, the isotope exchange rate and the separation factor in the reaction between CO 2 and carbamic acid. The absorption of CO 2 into the working fluid was the sum of chemical absorption by DNBA and physical absorption by n-octane. The absorption of carbon dioxide into the working fluid was negligible at temperatures over 90 0 C, but increased gradually at lower temperatures. Carbon dioxide was absorbed into DNBA by chemical absorption, and DNBA was converted to carbamic acid by the reaction. The reaction for synthesis and decomposition of carbamic acid was reversible. The separation factor in equilibrium reached a large value at lower temperatures. The isotope exchange rate between gas and liquid was proportional to the product of the concentration of carbamic acid and the concentration of CO 2 by physical absorption. The isotope separation of carbon by chemical exchange reaction is better operated under the conditions of lower temperature and higher pressure. (author)

  10. Bifluoride-catalysed sulfur(VI) fluoride exchange reaction for the synthesis of polysulfates and polysulfonates

    Science.gov (United States)

    Gao, Bing; Zhang, Linda; Zheng, Qinheng; Zhou, Feng; Klivansky, Liana M.; Lu, Jianmei; Liu, Yi; Dong, Jiajia; Wu, Peng; Sharpless, K. Barry

    2017-11-01

    Polysulfates and polysulfonates possess exceptional mechanical properties making them potentially valuable engineering polymers. However, they have been little explored due to a lack of reliable synthetic access. Here we report bifluoride salts (Q+[FHF]-, where Q+ represents a wide range of cations) as powerful catalysts for the sulfur(VI) fluoride exchange (SuFEx) reaction between aryl silyl ethers and aryl fluorosulfates (or alkyl sulfonyl fluorides). The bifluoride salts are significantly more active in catalysing the SuFEx reaction compared to organosuperbases, therefore enabling much lower catalyst-loading (down to 0.05 mol%). Using this chemistry, we are able to prepare polysulfates and polysulfonates with high molecular weight, narrow polydispersity and excellent functional group tolerance. The process is practical with regard to the reduced cost of catalyst, polymer purification and by-product recycling. We have also observed that the process is not sensitive to scale-up, which is essential for its future translation from laboratory research to industrial applications.

  11. PRICE REACTION TO CORPORATE GOVERNANCE RATING ANNOUNCEMENTS AT THE ISTANBUL STOCK EXCHANGE

    Directory of Open Access Journals (Sweden)

    Aslıhan BOZCUK

    2010-01-01

    Full Text Available The purpose of this paper is to investigate the price reaction to corporate governance rating announcements at the Istanbul Stock Exchange and to identify the factors which could be driving the results. Using an event study analysis framework, the cumulative abnormal returns (AR are calculated for various event windows surrounding the announcement day for each firm. The average AR is 0.5% on announcement day, followed by all positive average cumulative ARs for the next 18 days following the announcement. In the multivariate regression analysis, a number of variables are used to proxy for factors suggested as relevant by the agency theory and the corporate governance literature; such as the size of the Audit Committee, the size of the Board of Directors, Corporate Governance Rating of each firm, number of non-executive members on the board, percentage of firm’s stock traded on the market, number of blockholders, family ownership, the price-earnings ratio, the market-to-book ratio and firm size. Audit committee size (P: 0.012 and board size (P: 0.043 together explained 32% of the variation in announcement day returns (F: 5.215, P: 0.018. Surprisingly, the corporate governance rating per se was not found to be significant. Overall, the price reaction on announcement day tends to be higher for firms with larger boards and smaller audit committees.

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

    Science.gov (United States)

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

    2014-01-01

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

  13. A mathematical analysis of Prx2-STAT3 disulfide exchange rate constants for a bimolecular reaction mechanism.

    Science.gov (United States)

    Langford, Troy F; Deen, William M; Sikes, Hadley D

    2018-03-22

    Appreciation of peroxiredoxins as the major regulators of H 2 O 2 concentrations in human cells has led to a new understanding of redox signaling. In addition to their status as the primary reducers of H 2 O 2 to water, the oxidized peroxiredoxin byproduct of this reaction has recently been shown capable of participation in H 2 O 2 -mediated signaling pathways through disulfide exchange reactions with the transcription factor STAT3. The dynamics of peroxidase-transcription factor disulfide exchange reactions have not yet been considered in detail with respect to how these reactions fit into the larger network of competing reactions in human cells. In this study, we used a kinetic model of oxidation and reduction reactions related to H 2 O 2 metabolism in the cytosol of human cells to study the dynamics of peroxiredoxin-2 mediated oxidation of the redox-regulated transcription factor STAT3. In combination with previously reported experimental data, the model was used to estimate the rate coefficient of a biomolecular reaction between Prx2 and STAT3 for two sets of assumptions that constitute lower and upper bound cases. Using these estimates, we calculated the relative rates of the reaction of oxidized peroxiredoxin-2 and STAT3 and other competing reactions in the cytosol. These calculations revealed that peroxiredoxin-2-mediated oxidation of STAT3 likely occurs at a much slower rate than competing reactions in the cytosol. This analysis suggests the existence of more complex mechanisms, potentially involving currently unknown protein-protein recognition partners, which facilitate disulfide exchange reactions between peroxiredoxin-2 and STAT3. Copyright © 2018 Elsevier Inc. All rights reserved.

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

    International Nuclear Information System (INIS)

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

    1980-01-01

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

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

    Science.gov (United States)

    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...

  16. Quasiclassical trajectory study of the molecular beam kinetics of the deuterium atom--hydrogen halide exchange reactions

    International Nuclear Information System (INIS)

    Raff, L.M.; Suzukawa, H.H. Jr.; Thompson, D.L.

    1975-01-01

    Unadjusted quasiclassical trajectory computations have been carried out to simulate the molecular beam scattering of thermal D atom beams at 2800 degreeK crossed with beams of HCl and HI at 250 degreeK. Total reaction cross sections, energy partitioning distributions, and differential scattering cross sections have been computed for the exchange reactions D+HCl → DCl+H and D+HI → DI+H while total reaction cross sections are reported for the corresponding abstractions, i.e., D+HCl → HD+Cl and D+HI → HD+I. For the exchange reactions, the computed reaction cross sections are within the range estimated from the crossed beam experiments. The calculated average energy partitioned into relative translational motion of products is in near quantitative agreement with the beam results, and the predicted differential scattering cross sections appear to be in qualitative accord with the beam experiments. The over-all agreement between theory and experiment indicates that previously computed values for the thermal rate coefficients for the exchange reactions are of the right order and that a systematic error exists in the interpretation of photolysis data in the hydrogen--hydrogen halide systems

  17. Removal of phosphate using copper-loaded polymeric ligand exchanger prepared by radiation grafting of polypropylene/polyethylene (PP/PE) nonwoven fabric

    Science.gov (United States)

    Barsbay, Murat; Kavaklı, Pınar Akkaş; Güven, Olgun

    2010-03-01

    A novel polymeric ligand exchanger (PLE) was prepared for the removal of phosphate ions from water. 2,2'-dipyridylamine (DPA), a bidentate ligand forming compound with high coordination capacity with a variety of metal ions was bound to glycidyl methacrylate (GMA) grafted polypropylene/polyethylene (PP/PE) nonwoven fabric synthesized by radiation-induced grafting technique. DPA attachment on epoxy ring of GMA units was tested in different solvents, i.e. methanol, ethanol, dioxane and dimethylsulfoxide (DMSO). The highest amount of modification was achieved in dioxane. In order to prepare the corresponding PLE for the removal of phosphate, DPA-immobilized fabric was loaded with Cu(II) ions. Phosphate adsorption experiments were performed in batch mode at different pH (5-9) and phosphate concentrations. The fabric was found to be effective for the removal of phosphate ions. At every stage of preparation and use, the nonwoven fabric was characterized by thermal (i.e. DSC and TGA) and spectroscopic (FTIR) methods. Competitive adsorption experiments were also carried out using two solutions with different concentration levels at pH 7 to see the effect of competing ions. Phosphate adsorption was found to be effective and selective from solutions having trace amounts of competitive anions. It is expected that the novel PLE synthesized can be used for the removal of phosphate ions in low concentrations over a large range of pH.

  18. Chiral ligand-exchange high-performance liquid chromatography with copper (II)-L-phenylalanine complexes for separation of 3,4-dimethoxy-α-methylphenylalanine racemes.

    Science.gov (United States)

    Jia, Dong-Xu; Ai, Zheng-Gui; Xue, Ya-Ping; Zheng, Yu-Guo

    2014-11-01

    L-3, 4-dimethoxy-α-methylphenylalanine (L-DMMD) is an important intermediate for the synthesis of 3-hydroxy-α-methyl-L-tyrosine (L-methyldopa). This paper describes an efficient, accurate, and low-priced method of high-performance liquid chromatography (HPLC) using chiral mobile phase and conventional C18 column to separate L-DMMD from its enantiomers. The effects of ligands, copper salts, organic modifiers, pHs of mobile phase, and temperatures on the retention factors (k') and selectivity (α) were evaluated to achieve optimal separation performance. Then, thermal analysis of the optimal separation conditions was investigated as well. It was confirmed that the optimal mobile phase was composed of 20 % (v/v) methanol, 8 mM L-phenylalanine (L-Phe), and 4 mM cupric sulfate in water of pH 3.2, and the column temperature was set at 20 °C. Baseline separation of two enantiomers could be obtained through the conventional C18 column with a resolution (R) of 3.18 in less than 18 min. Thermodynamic data (∆∆H and ∆∆S) obtained by Van't Hoff plots revealed the chiral separation was an enthalpy-controlled process. To the best of our knowledge, this is the first report regarding the enantioseparation of DMMD by chiral ligand-exchange HPLC.

  19. Enantioseparation of dansyl amino acids and dipeptides by chiral ligand exchange capillary electrophoresis based on Zn(II)-L-hydroxyproline complexes coordinating with γ-cyclodextrins.

    Science.gov (United States)

    Mu, Xiaoyu; Qi, Li; Qiao, Juan; Yang, Xinzheng; Ma, Huimin

    2014-10-10

    A chiral ligand exchange capillary electrophoresis (CLE-CE) method using Zn(II) as the central ion and L-4-hydroxyproline as the chiral ligand coordinating with γ-cyclodextrin (γ-CD) was developed for the enantioseparation of amino acids (AAs) and dipeptides. The effects of various separation parameters, including the pH of the running buffer, the ratio of Zn(II) to L-4-hydroxyproline, the concentration of complexes and cyclodextrins (CDs) were systematically investigated. After optimization, it has been found that eight pairs of labeled AAs and six pairs of labeled dipeptides could be baseline-separated with a running electrolyte of 100.0mM boric acid, 5.0mM ammonium acetate, 3.0mM Zn(II), 6.0mM L-hydroxyproline and 4.0mM γ-CD at pH 8.2. The quantitation of AAs and dipeptides was conducted and good linearity (r(2)≥0.997) and favorable repeatability (RSD≤3.6%) were obtained. Furthermore, the proposed method was applied in determining the enantiomeric purity of AAs and dipeptides. Meanwhile, the possible enantiorecognition mechanism based on the synergistic effect of chiral metal complexes and γ-CD was explored and discussed briefly. Copyright © 2014 Elsevier B.V. All rights reserved.

  20. A phenomenological study of the π- p → π0 n charge exchange reaction at high energy

    International Nuclear Information System (INIS)

    Michaud, Y.

    1995-01-01

    The aim of the study was to examine the behaviour of the proton-proton elastic scattering, for mass center energies around 10 GeV, and more especially to study the charge exchange reaction π - p → π 0 n for mass center energies between 3 and 20 GeV. A formalism based on the Glauber model has been used, and a Regge trajectory exchange term was introduced in the model in order to enable the description of the lower energy domain (inferior to 10 GeV) that is characterized by a large contribution of meson exchanges at the scattering amplitude. The Glauber model is then applied to the charge exchange reaction and the differential cross section is analyzed for a center mass energy comprised between 3 and 20 GeV, together with the polarization at 40 GeV/c. The approach is then validated through the study of the π - p → η n reaction. The size of the kernel of proton and pion components implied in the π - p → π 0 n reaction, is also investigated. 90 refs., 48 figs., 4 tabs., 5 appends

  1. Controlled growth of gold nanoparticles in zeolite L via ion-exchange reactions and thermal reduction processes

    KAUST Repository

    Zeng, Shangjing

    2014-09-01

    The growth of gold nanoparticles in zeolite can be controlled using ion-exchange reactions and thermal reduction processes. We produce a number of different sizes of the gold nanoparticles with the particle size increasing with increased temperature of the final heat treatment. © 2014 Elsevier B.V.

  2. Dendrimer ligands-capped CH3NH3PbBr3 perovskite nanocrystals with delayed halide exchange and record stability against both moisture and water

    Science.gov (United States)

    Xu, Yiren; Xu, Shuhong; Shao, Haibao; Jiang, Han; Cui, Yiping; Wang, Chunlei

    2018-06-01

    CH3NH3PbBr3 perovskite nanocrystals (NCs) suffer from poor stability because of their high sensitivity to environmental moisture and water. To solve this problem, previous works mainly focus on embedding perovskite NCs into water-resistant matrix to form large composites (size of microns or larger). As an alternative solution without serious changing of NC size, enhancing the stability of perovskite NCs themselves by ligand engineering is rarely reported. In this work, we used hyperbranched polyamidoamine (PAMAM) dendrimers with two different generations (G0 and G4) to synthesize CH3NH3PbBr3 perovskite NCs with high photoluminescence (PL) quantum yields (QY) above 70% and a new record stability. A novel dendrimers generation-dependent stability of perovskite NCs was observed. The water-resistance time is 18 h (27 h) for perovskite NCs capped by G0 (G4) generation of PAMAM, which is 7 times (11 times) longer than that of traditional oleic acid-capped NCs. Similar PAMAM generation-related stability is also observed in moisture-resistance tests. The stability time against moisture is 500 h (800 h) for G0 (G4) generation of PAMAM-capped perovskite NCs, which is a new record stability time against moisture for CH3NH3PbBr3 perovskite NCs. In addition, our results also indicate that PAMAM ligands outside perovskite NCs can dramatically slow down the speed of halide exchange. Even for the mixture of perovskite NCs with two different halide composition, the original luminescence properties of PAMAM-capped perovskite NCs can retain after mixing. In view of slow halide exchange speed, excellent water and moisture stability, PAMAM dendrimers-capped perovskite NCs and their mixture are available as color conversion single layer in fabrication of light-emitting diodes (LED).

  3. Dendrimer ligands-capped CH3NH3PbBr3 perovskite nanocrystals with delayed halide exchange and record stability against both moisture and water.

    Science.gov (United States)

    Xu, Yiren; Xu, Shuhong; Shao, Haibao; Jiang, Han; Cui, Yiping; Wang, Chunlei

    2018-06-08

    CH 3 NH 3 PbBr 3 perovskite nanocrystals (NCs) suffer from poor stability because of their high sensitivity to environmental moisture and water. To solve this problem, previous works mainly focus on embedding perovskite NCs into water-resistant matrix to form large composites (size of microns or larger). As an alternative solution without serious changing of NC size, enhancing the stability of perovskite NCs themselves by ligand engineering is rarely reported. In this work, we used hyperbranched polyamidoamine (PAMAM) dendrimers with two different generations (G0 and G4) to synthesize CH 3 NH 3 PbBr 3 perovskite NCs with high photoluminescence (PL) quantum yields (QY) above 70% and a new record stability. A novel dendrimers generation-dependent stability of perovskite NCs was observed. The water-resistance time is 18 h (27 h) for perovskite NCs capped by G0 (G4) generation of PAMAM, which is 7 times (11 times) longer than that of traditional oleic acid-capped NCs. Similar PAMAM generation-related stability is also observed in moisture-resistance tests. The stability time against moisture is 500 h (800 h) for G0 (G4) generation of PAMAM-capped perovskite NCs, which is a new record stability time against moisture for CH 3 NH 3 PbBr 3 perovskite NCs. In addition, our results also indicate that PAMAM ligands outside perovskite NCs can dramatically slow down the speed of halide exchange. Even for the mixture of perovskite NCs with two different halide composition, the original luminescence properties of PAMAM-capped perovskite NCs can retain after mixing. In view of slow halide exchange speed, excellent water and moisture stability, PAMAM dendrimers-capped perovskite NCs and their mixture are available as color conversion single layer in fabrication of light-emitting diodes (LED).

  4. Synthesis and characterization of divalent metal complexes with ligand derived from the reaction of 3-aminopyridine and biacetyl

    Directory of Open Access Journals (Sweden)

    RAMESH KUMAR

    2006-09-01

    Full Text Available Divalent cobalt, nickel and copper salts reacted in situ with 3-aminopyridine and biacetyl to form complexes of the type: [M(Ap2biac2X2], where Ap2biac is the ligand and X=Cl, Br, NO3 or NCS. The complexes were analysed and characterized as distorted octahedral by conductance, molecular weight, magnetic, electronic and IR spectral studies. The electronic spectra were interpreted and tentative aassignments made. The infrared spectral studies revealed that two molecules of 3-aminopyridine were joined by molecules of biacetyl through a two carbon atom bridge and that the ligand coordinated through azomethine nitrogen atoms, whereas the pyridine nitrogen does not participate in the coordination. In the far infrared spectra, various metal–ligand vibrations were observed and are discussed.

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

    Science.gov (United States)

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

    2015-01-01

    Radiation-produced electrons initiate various reaction processes that are important to radiation damage to biomolecules. In this work, the site of attachment of the prehydrated electrons with methylacetoacetate (MAA, CH3-CO-CH2-CO-OCH3) at 77 K and subsequent reactions of the anion radical (CH3-CO•−-CH2-CO-OCH3) in the temperature range (77 to ca. 170 K) have been investigated in homogeneous H2O and D2O aqueous glasses by electron spin resonance (ESR) spectroscopy. At 77 K, the prehydrated electron attaches to MAA forming the anion radical in which the electron is delocalized over the two carbonyl groups. This species readily protonates to produce the protonated electron adduct radical CH3-C(•)OH-CH2-CO-OCH3. The ESR spectrum of CH3-C(•)OH-CH2-CO-OCH3 in H2O shows line components due to proton hyperfine couplings of the methyl and methylene groups. Whereas, the ESR spectrum of CH3-C(•)OH-CH2-CO-OCH3 in D2O glass shows only the line components due to proton hyperfine couplings of CH3 group. This is expected since the methylen protons in MAA are readily exchangeable in D2O. On stepwise annealing to higher temperatures (ca. 150 to 170 K), CH3-C(•)OH-CH2-CO-OCH3 undergoes bimolecular H-atom abstraction from MAA to form the more stable radical, CH3-CO-CH•-CO-OCH3. Theoretical calculations using density functional theory (DFT) support the radical assignments. PMID:25255751

  6. Aziridine- and Azetidine-Pd Catalytic Combinations. Synthesis and Evaluation of the Ligand Ring Size Impact on Suzuki-Miyaura Reaction Issues

    Directory of Open Access Journals (Sweden)

    Hamza Boufroura

    2017-01-01

    Full Text Available The synthesis of new vicinal diamines based on aziridine and azetidine cores as well as the comparison of their catalytic activities as ligand in the Suzuki-Miyaura coupling reaction are described in this communication. The synthesis of three- and four-membered ring heterocycles substituted by a methylamine pendant arm is detailed from the parent nitrile derivatives. Complexation to palladium under various conditions has been examined affording vicinal diamines or amine-imidate complexes. The efficiency of four new catalytic systems is compared in the preparation of variously substituted biaryls. Aziridine- and azetidine-based catalytic systems allowed Suzuki-Miyaura reactions from aryl halides including chlorides with catalytic loadings until 0.001% at temperatures ranging from 100 °C to r.t. The evolution of the Pd-metallacycle ring strain moving from azetidine to aziridine in combination with a methylamine or an imidate pendant arm impacted the Suzuki-Miyaura reaction issue.

  7. Kinetics of the radiation-induced exchange reactions of H2, D2, and T2: a review

    International Nuclear Information System (INIS)

    Pyper, J.W.; Briggs, C.K.

    1978-01-01

    Mixtures of H 2 --T 2 or D 2 --T 2 will exchange to produce HT or DT due to catalysis by the tritium β particle. The kinetics of the reaction D 2 + T 2 = 2DT may play an important role in designing liquid or solid targets of D 2 --DT--T 2 for implosion fusion, and distillation schemes for tritium cleanup systems in fusion reactors. Accordingly, we have critically reviewed the literature for information on the kinetics and mechanism of radiation-induced self-exchange reactions among the hydrogens. We found data for the reaction H 2 + T 2 = 2HT in the gas phase and developed a scheme based on these data to predict the halftime to equilibrium for any gaseous H 2 + T 2 mixture at ambient temperature with an accuracy of +-10 percent. The overall order of the H 2 + T 2 = 2HT reaction is 1.6 based on an initial rate treatment of the data. The most probable mechanism for radiation-induced self-exchange reaction is an ion-molecule chain mechanism

  8. Adaptable liquid crystal elastomers with transesterification-based bond exchange reactions.

    Science.gov (United States)

    Hanzon, Drew W; Traugutt, Nicholas A; McBride, Matthew K; Bowman, Christopher N; Yakacki, Christopher M; Yu, Kai

    2018-02-14

    Adaptable liquid crystal elastomers (LCEs) have recently emerged to provide a new and robust method to program monodomain LCE samples. When a constant stress is applied with active bond exchange reactions (BERs), polymer chains and mesogens gradually align in the strain direction. Mesogen alignment is maintained after removing the BER stimulus (e.g. by lowering the temperature) and the programmed LCE samples exhibit free-standing two-way shape switching behavior. Here, a new adaptable main-chain LCE system was developed with thermally induced transesterification BERs. The network combines the conventional properties of LCEs, such as an isotropic phase transition and soft elasticity, with the dynamic features of adaptable network polymers, which are malleable to stress relaxation due to the BERs. Polarized Fourier transform infrared measurements confirmed the alignment of polymer chains and mesogens after strain-induced programming. The influence of the creep stress, temperature, and time on the strain amplitude of two-way shape switching was examined. The LCE network demonstrates an innovative feature of reprogrammability, where the reversible shape-switching memory of programmed LCEs is readily deleted by free-standing heating as random BERs disrupt the mesogen alignment, so LCEs are reprogrammed after returning to the polydomain state. Due to the dynamic nature of the LCE network, it also exhibits a surface welding effect and can be fully dissolved in the organic solvent, which might be utilized for green and sustainable recycling of LCEs.

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

    International Nuclear Information System (INIS)

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

    2004-01-01

    New layered magnetic materials (MCl)Ca 2 Ta 3 O 10 (M = Cu, Fe), have been prepared by ion-exchange reactions of non-magnetic perovskite derivatives, ACa 2 Ta 3 O 10 (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 A and c = 15.533 A for Cu, and a = 3.822 A and c = 15.672 A for Fe. Being separated by the Ca 2 Ta 3 O 10 triple-layer perovskite slabs, the transition-metal chloride (MCl) network provides a two-dimensional magnetic lattice. Magnetic susceptibility measurements show that (CuCl)Ca 2 Ta 3 O 10 is in an antiferromagnetic state below 8 K, while (FeCl)Ca 2 Ta 3 O 10 has two anomalies at 91 and 125 K, suggesting successive phase transitions due to geometrical spin frustration

  10. In Silico Generation of Peptides by Replica Exchange Monte Carlo: Docking-Based Optimization of Maltose-Binding-Protein Ligands.

    Directory of Open Access Journals (Sweden)

    Anna Russo

    Full Text Available Short peptides can be designed in silico and synthesized through automated techniques, making them advantageous and versatile protein binders. A number of docking-based algorithms allow for a computational screening of peptides as binders. Here we developed ex-novo peptides targeting the maltose site of the Maltose Binding Protein, the prototypical system for the study of protein ligand recognition. We used a Monte Carlo based protocol, to computationally evolve a set of octapeptides starting from a polialanine sequence. We screened in silico the candidate peptides and characterized their binding abilities by surface plasmon resonance, fluorescence and electrospray ionization mass spectrometry assays. These experiments showed the designed binders to recognize their target with micromolar affinity. We finally discuss the obtained results in the light of further improvement in the ex-novo optimization of peptide based binders.

  11. An investigation of one- versus two-dimensional semiclassical transition state theory for H atom abstraction and exchange reactions.

    Science.gov (United States)

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

    2016-02-28

    We investigate which terms in Reduced-Dimensionality Semiclassical Transition State Theory (RD SCTST) contribute most significantly in rate constant calculations of hydrogen extraction and exchange reactions of hydrocarbons. We also investigate the importance of deep tunneling corrections to the theory. In addition, we introduce a novel formulation of the theory in Jacobi coordinates. For the reactions of H atoms with methane, ethane, and cyclopropane, we find that a one-dimensional (1-D) version of the theory without deep tunneling corrections compares well with 2-D SCTST results and accurate quantum scattering results. For the "heavy-light-heavy" H atom exchange reaction between CH3 and CH4, deep tunneling corrections are needed to yield 1-D results that compare well with 2-D results. The finding that accurate rate constants can be obtained from derivatives of the potential along only one dimension further validates RD SCTST as a computationally efficient yet accurate rate constant theory.

  12. Pulse radiolysis of porphyrin and ferriporphyrin solutions in 2-propanol-carbon tetrachloride systems. Protonation and ligand exchange kinetics

    International Nuclear Information System (INIS)

    Brault, D.; Neta, P.

    1983-01-01

    Pulse radiolysis of aqueous and nonaqueous 2-propanol-acetone-carbon tetrachloride mixtures has been investigated by means of conductivity measurements and spectrophotometry. In these solvent mixtures, a pulse of hydrochloric acid originating from either primary events of solvent radiolysis or from further reactions of carbon tetrachloride with radicals derived from 2-propanol and acetone, is produced within ca 100 nanoseconds. Further production of hydrochloric acid occurs as a result of chain reactions involving hydrogen abstraction by CCl 3 or CCl 3 O 2 radicals. These latter radicals appear to be much more reactive and are likely to be involved in the reaction unless the solutions have been thoroughly deoxygenated. Protonation Reactions of porphyrins and ferriporphyrins, which do not react rapidly with the above radicals, were followed by means of spectrophotometric measurements. In turn, these reactions may be used to monitor hydrochloric acid formation. Spectrophotometric measurements on porphyrins corroborate conductivity results, although a quantitative comparison is not feasible because of differences in solvent properties. 6 figures

  13. Experimental Investigation of Gaseous Reaction Products from Na-CO{sub 2} Reaction in Na/CO{sub 2} Heat Exchanger leakage scenario

    Energy Technology Data Exchange (ETDEWEB)

    Go, A-Reum; Jung, Hwa-Young; Kim, Min Seok; Lee, Jeong Ik [KAIST, Daejeon (Korea, Republic of); Min, Jaehong; Wi, Myung-Hwan [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2015-10-15

    The SFRs have operated with the steam Rankine cycle as a power conversion system. However, the potential sodium-water reaction (SWR) whose chemical reactivity is vigorous and instantaneous has been one of the major issues concerning the safety and integrity of the SFRs. In order to avoid SWR, supercritical CO{sub 2}(S-CO{sub 2}) Brayton cycles have been investigated recently. Compared to conventional steam Rankine cycles, S-CO{sub 2} Brayton cycle features higher thermal efficiency and potential compactness of its required equipment. In spite of the superiority of S-CO{sub 2} Brayton cycle, there is a potential reactive process between sodium and CO{sub 2} if the pressure boundary fails in the sodium-CO{sub 2} heat exchanger. The leakage scenario which could lead to mechanical and thermal problems should be evaluated. Previous studies have reported the following major reaction formulas. Each reaction occurs competitively. In this paper, the experimental setup to observe the pressure variation and CO concentration in Na-CO{sub 2} heat exchanger during the CO{sub 2} leak is explained. Before the experiment is carried out, water-CO{sub 2} mock-up test will be performed. In order to evaluate the leakage scenario in Na-CO{sub 2} heat exchanger more accurately, this study will be important for guaranteeing the system of SFR coupled with S-CO{sub 2} cycle.

  14. A Recyclable Cu-MOF-74 Catalyst for the Ligand-Free O-Arylation Reaction of 4-Nitrobenzaldehyde and Phenol.

    Science.gov (United States)

    Leo, Pedro; Orcajo, Gisela; Briones, David; Calleja, Guillermo; Sánchez-Sánchez, Manuel; Martínez, Fernando

    2017-06-16

    The activity and recyclability of Cu-MOF-74 as a catalyst was studied for the ligand-free C-O cross-coupling reaction of 4-nitrobenzaldehyde (NB) with phenol (Ph) to form 4-formyldiphenyl ether (FDE). Cu-MOF-74 is characterized by having unsaturated copper sites in a highly porous metal-organic framework. The influence of solvent, reaction temperature, NB/Ph ratio, catalyst concentration, and basic agent (type and concentration) were evaluated. High conversions were achieved at 120 °C, 5 mol % of catalyst, NB/Ph ratio of 1:2, DMF as solvent, and 1 equivalent of K₂CO₃ base. The activity of Cu-MOF-74 material was higher than other ligand-free copper catalytic systems tested in this study. This catalyst was easily separated and reused in five successive runs, achieving a remarkable performance without significant porous framework degradation. The leaching of copper species in the reaction medium was negligible. The O-arylation between NB and Ph took place only in the presence of Cu-MOF-74 material, being negligible without the solid catalyst. The catalytic advantages of using nanostructured Cu-MOF-74 catalyst were also proven.

  15. Magnetic isotope effect and theory of atomic orbital hybridization to predict a mechanism of chemical exchange reactions.

    Science.gov (United States)

    Epov, Vladimir N

    2011-08-07

    A novel approach is suggested to investigate the mechanisms of chemical complexation reactions based on the results of Fujii with co-workers; they have experimentally observed that several metals and metalloids demonstrate mass-independent isotope fractionation during the reactions with the DC18C6 crown ether using solvent-solvent extraction. In this manuscript, the isotope fractionation caused by the magnetic isotope effect is used to understand the mechanisms of chemical exchange reactions. Due to the rule that reactions are allowed for certain electron spin states, and forbidden for others, magnetic isotopes show chemical anomalies during these reactions. Mass-independent fractionation is suggested to take place due to the hyperfine interaction of the nuclear spin with the electron spin of the intermediate product. Moreover, the sign of the mass-independent fractionation is found to be dependent on the element and its species, which is also explained by the magnetic isotope effect. For example, highly negative mass-independent isotope fractionation of magnetic isotopes was observed for reactions of DC18C6 with SnCl(2) species and with several Ru(III) chloro-species, and highly positive for reactions of this ether with TeCl(6)(2-), and with several Cd(II) and Pd(II) species. The atomic radius of an element is also a critical parameter for the reaction with crown ether, particularly the element ions with [Kr]4d(n)5s(m) electron shell fits the best with the DC18C6 crown ring. It is demonstrated that the magnetic isotope effect in combination with the theory of orbital hybridization can help to understand the mechanism of complexation reactions. The suggested approach is also applied to explain previously published mass-independent fractionation of Hg isotopes in other types of chemical exchange reactions. This journal is © the Owner Societies 2011

  16. Direct versus ligand-exchange synthesis of [PtAg28(BDT)12(TPP)4]4− nanoclusters: effect of a single-atom dopant on the optoelectronic and chemical properties

    KAUST Repository

    Bootharaju, Megalamane Siddaramappa; Kozlov, Sergey M.; Cao, Zhen; Harb, Moussab; Parida, Manas R.; Hedhili, Mohamed N.; Mohammed, Omar F.; Bakr, Osman; Cavallo, Luigi; Basset, Jean-Marie

    2017-01-01

    to offer monodisperse doped NCs. For instance, the direct synthesis of PtAg28 NCs produces a mixture of [Ag29(BDT)12(TPP)4]3- and [PtAg28(BDT)12(TPP)4]4- NCs (TPP: triphenylphosphine; BDT: 1,3-benzenedithiolate). Here, we designed a ligand-exchange (LE

  17. Magnetic Pd-Fe{sub 3}O{sub 4} heterodimer nanocrystals as recoverable catalysts for ligand-free hiyama cross-coupling reactions

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Woong Sup; Byun, Sang Moon; Kwon, Jung Min; Kim, B. Moon [Dept. of Chemistry, College of Natural Sciences, Seoul National University, Seoul (Korea, Republic of)

    2016-12-15

    Ligand-free Hiyama cross-coupling reaction was achieved through the use of Pd-Fe{sub 3}O{sub 4} heterodimeric nanocrystals (1 mol% in Pd) as recyclable catalysts. The nanocrystal catalysts exhibited good activities accommodating a variety of substrates including aryl bromides and iodides with substituents of varying electronic and steric properties. Furthermore, the nanocrystal catalyst could be conveniently recovered with the aid of an external magnet and recycled five times without the loss of catalytic activity to a considerable degree.

  18. Chemical kinetics: on the heterogeneous catalysis processes leading to an exchange between two phases. Example: isotopic exchange reactions; Cinetique chimique: sur les processus de catalyse 'heterogene' conduisant a un echange entre deux phases. Exemple: reactions d'echange isotopique

    Energy Technology Data Exchange (ETDEWEB)

    Dirian, G; Grandcollot, P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1961-07-01

    For an exchange reaction between a gaseous and a liquid phase proceeding by 'heterogeneous' catalysis in the liquid phase, diffusion in the liquid and the chemical reaction are two simultaneous and indivisible processes. We have nevertheless been able to establish criteria making it possible to distinguish between a really homogeneous kinetic process and a pseudo-homogeneous one. (author) [French] Pour une reaction d'echange entre une phase gazeuse et une phase liquide procedant par catalyse 'heterogene' en phase liquide, la diffusion dans le liquide et la reaction chimique sont deux etapes simultanees et indissociables. Nous avons pu neanmoins etablir des criteres permettant de distinguer entre une cinetique homogene vraie et une cinetique pseudo-homogene. (auteur)

  19. Bis-Indole Derivatives for Polysaccharide Compositional Analysis and Chiral Resolution of D-, L-Monosaccharides by Ligand Exchange Capillary Electrophoresis Using Borate-Cyclodextrin as a Chiral Selector

    Directory of Open Access Journals (Sweden)

    Wen-Bin Yang

    2011-02-01

    Full Text Available A series of aldo-bis-indole derivatives (aldo-BINs was prepared by aromatic C-alkylation reactions of aldoses and indole in acetic acid solution. Common monosaccharides such as glucose, mannose, galactose, fucose, xylose, rhamnose, ribose, arabinose and N-acetylglucosamine were smoothly derivatized to form the UV absorbing aldo-BINs. The use of a capillary electrophoretic method to separate these novel aldo-BIN derivatives was established. The capillary electrophoresis conditions were set by using borate buffer (100 mM at high pH (pH 9.0. The limit of determination was assessed to be 25 nM. The enantioseparation of D, L-pairs of aldo-BINs based on chiral ligand-exchange capillary electrophoresis technology was also achieved by using modified hydroxypropyl-β-cyclodextrin as the chiral selector in the presence of borate buffer. This aldose labeling method was applied successfully to the compositional and configurational analysis of saccharides, exemplified by a rapid and efficient method to simultaneously analyze the composition and configuration of saccharides from the medicinal herbs Cordyceps sinensis and Dendrobium huoshanense.

  20. Kinetic analysis of the reactivity of aromatic amino acids in the T-for-H exchange reaction

    International Nuclear Information System (INIS)

    Yoshida, Akira; Imaizumi, Hiroshi; Sato, Takayuki; Kano, Naoki

    2009-01-01

    To quantitatively evaluate the influence of tritium ( 3 H or T) on ecosystem, the hydrogen isotope exchange reaction (T-for-H exchange reaction) between each aromatic amino acid (L-tyrosine, L-phenylalanine, or L-2-phenylglycine) and HTO vapor was observed at 50-70degC in the gas-solid system. Applying the A''-McKay plot method to data (obtained in the exchange reaction), the rate constants (k) of functional groups of each aromatic amino acid in this reaction was obtained. Comparing the rate constants, following six matters have been found in the T-for-H exchange reaction. (1) The reactivity of the functional groups in each amino acid increases with increasing temperature. (2) The reactivity of the functional groups of the amino acids (used) increases in the order of L-tyrosine, L-phenylalanine, and L-2-phenylglycine. (3) As to l-tyrosine, 1) the temperature dependence of each functional group increases in the order of COOH group, OH one, and NH 2 one, 2) the reactivity of OH group is 3.8 times greater than that of NH 2 one, and 3) the reactivity of COOH group is 2.0 times greater than NH 2 one. (4) As to the influence of the substituent, the reactivity of NH 2 group is larger than that of the COOH one. (5) Using the A''-McKay plot method, the reactivity of each functional group in an amino acid can be nondestructively and simultaneously clarified without using masking reagent. (6) The results obtained in this work is useful for preventing T contamination and for evaluating the influence of T on environment. (author)

  1. Ligand sphere conversions in terminal carbide complexes

    DEFF Research Database (Denmark)

    Morsing, Thorbjørn Juul; Reinholdt, Anders; Sauer, Stephan P. A.

    2016-01-01

    Metathesis is introduced as a preparative route to terminal carbide complexes. The chloride ligands of the terminal carbide complex [RuC(Cl)2(PCy3)2] (RuC) can be exchanged, paving the way for a systematic variation of the ligand sphere. A series of substituted complexes, including the first...... example of a cationic terminal carbide complex, [RuC(Cl)(CH3CN)(PCy3)2]+, is described and characterized by NMR, MS, X-ray crystallography, and computational studies. The experimentally observed irregular variation of the carbide 13C chemical shift is shown to be accurately reproduced by DFT, which also...... demonstrates that details of the coordination geometry affect the carbide chemical shift equally as much as variations in the nature of the auxiliary ligands. Furthermore, the kinetics of formation of the sqaure pyramidal dicyano complex, trans-[RuC(CN)2(PCy3)2], from RuC has been examined and the reaction...

  2. Synthesis of imine bond containing insoluble polymeric ligand and its transition metal complexes, structural characterization and catalytic activity on esterification reaction.

    Science.gov (United States)

    Gönül, İlyas; Ay, Burak; Karaca, Serkan; Saribiyik, Oguz Yunus; Yildiz, Emel; Serin, Selahattin

    2017-01-01

    In this study, synthesis of insoluble polymeric ligand (L) and its transition metal complexes [Cu(L)Cl 2 ]·2H 2 O (1) , [Co(L)Cl 2 (H 2 O) 2 ] (2) and [Ni(L)Cl 2 (H 2 O) 2 ] (3) , having the azomethine groups, were synthesized by the condensation reactions of the diamines and dialdehydes. The structural properties were characterized by the analytical and spectroscopic methods using by elemental analysis, Fourier Transform Infrared, Thermo Gravimetric Analysis, Powder X-ray Diffraction, magnetic susceptibility and Inductively Coupled Plasma. The solubilities of the synthesized polymeric materials were also investigated and found as insoluble some organic and inorganic solvents. Additionally, their catalytic performance was carried out for the esterification reaction of acetic acid and butyl acetate. The highest conversion rate is 75.75% by using catalyst 1 . The esterification of butanol gave butyl acetate with 100% selectivity.

  3. Synthesis and Ligand-Exchange Reactions of a Tri-Tungsten Cluster with Applications in Biomedical Imaging

    Science.gov (United States)

    Noey, Elizabeth; Curtis, Jeff C.; Tam, Sylvia; Pham, David M.; Jones, Ella F.

    2011-01-01

    In this experiment students are exposed to concepts in inorganic synthesis and various spectroscopies as applied to a tri-tungsten cluster with applications in biomedical imaging. The tungsten-acetate cluster, Na[W[superscript 3](mu-O)[subscript 2](CH[superscript 3]COO)[superscript 9

  4. Schiff base ligand

    Indian Academy of Sciences (India)

    Unknown

    Low-temperature stoichiometric Schiff base reaction in air in 3 : 1 mole ratio between benz- aldehyde and triethylenetetramine (trien) in methanol yields a novel tetraaza µ-bis(bidentate) acyclic ligand L. It was .... electrochemical work was performed as reported in ..... change in ligand shape through change in oxidation.

  5. Specific ability of sulfur-ligands on removal of 203Hg-labeled organomercury from hemoglobin in comparison with nitrogen-ligands

    International Nuclear Information System (INIS)

    Hojo, Yasuji; Sugiura, Yukio; Tanaka, Hisashi

    1975-01-01

    Removal of 203 Hg-labeled organomercurials, bound to sulfhydryl groups of hemoglobin, by various chelating agents was investigated by the use of equilibrium dialysis. Organomercurials employed were chlormerodrin, methylmercury, ethylmercury and phenylmercury compounds. Higher and more specific effects of the sulfur-ligands, such as penicillamine and glutathione, on removal of organomercurial were found as compared with those of the nitrogen-ligands such as EDTA, glycine and polymethylenediamines. Linear correlation was observed between the degree of organomercury elimination from hemoglobin and the stability constant (log K 1 ) of 1:1 organomercury complex in both the sulfur- and nitrogen-ligand systems and at the same value of log K 1 , the elimination-effect of sulfur-ligands was extremely greater than that of the nitrogen-ligands. The relationship between the average percentage of removal and the Taft's polar substituent constant of organic moiety of the metal was also linear among the organomercury compounds other than chlormerodrin. The average removal percentage by sulfur-ligands increased in the order, ethylmercury>methylmercury>phenylmercury, while that of the nitrogen-ligands was not different among the organomercurials investigated. In addition, direct ligand-exchange reaction between hemoglobin-SH and the ligand coordinating-atom (S or N) against organomercurials rather than Ssub(N2) reaction via the ternary complex, hemoglobin-S-RHg-ligand, is postulated. (auth.)

  6. Bombarding energy dependence of nucleon exchange and energy dissipation in the strongly damped reaction 209Bi + 136Xe

    International Nuclear Information System (INIS)

    Wilcke, W.W.; Schroeder, W.U.; Huizenga, J.R.; Birkelund, J.R.; Randrup, J.

    1980-01-01

    Although considerable progress has been achieved in the understanding of strongly damped reactions at energies several MeV/u above the Coulomb barrier, some important experimental results are not yet clearly understood. Among these is the degree of correlation between the nucleon exchange and the large energy losses observed. Experimental evidence suggesting nucleon exchange as described by a one-body model to be the major component of the dissipation mechanism is discussed. It is concluded that the previously unexplained bombarding energy dependence between energy loss and fragment charge dispersion can be understood on the basis of a nucleon exchange model, provided the Pauli exclusion principle is taken into account. No necessity is seen to invoke further energy dissipation mechanisms. 7 figures

  7. Catalytic activity in reactions of isotopic exchange of carbon monoxide and adsorption properties of catalysts on zinc oxide base

    International Nuclear Information System (INIS)

    Mikheeva, T.M.; Kasatkina, L.A.; Volynkina, A.Ya.

    1987-01-01

    Activity of different zinc oxide samples in reaction of CO homomolecular isotopic exchnge (HMIE) ( 13 C 18 O+ 12 C 16 O= 13 C 16 O+ 12 C 18 O), CO adsorption on ZnO and isotopic exchange between adsorbed and gaseous CO are investigated. The most active is ZnO sample prepared from ZnCO 3 . Quantitative ratio between different with respect to surface strength molecules of adsorbed CO are experimentally determined. It is shown that by increase of ZnO time contact with CO the quantity of adsorbed CO(N σ/0 ), capable of fast exchange with a gaseous phase, is reduced and the quantity of slowly exchanged adsorbed CO is increased. Correlation between decrease of N σ/0 and decrease of CO HMIE with the catalyst holding time in CO medium is stated

  8. Nucleon exchange properties of the E/A=8.5 MeV 74Ge+165Ho reaction

    International Nuclear Information System (INIS)

    Planeta, R.; Kwiatkowski, K.; Zhou, S.H.; Viola, V.E.; Breuer, H.; McMahan, M.A.; Kehoe, W.; Mignerey, A.C.

    1990-01-01

    Mass and charge distributions have been measured for damped projectile-like fragments in the reaction 74 Ge+ 165 Ho at 8.5 MeV per nucleon bombarding energy. Coincidences were measured between Z- and A-identified projectile-like fragments and angle-correlated heavy reaction partners in order to derive the primary mass distribution for projectile-like fragments. Centroids and variances of the primary and post-evaporative Z, N, and A distributions are presented. The evolution of the primary N and Z distributions as a function of energy loss is found to deviate from predictions of the nucleon exchange transport model

  9. A meson-exchange isobar model for the {pi}{sup +}d {r_reversible} pp reaction

    Energy Technology Data Exchange (ETDEWEB)

    Canton, L.; Cattapan, G.; Dortmans, P.J.; Pisent, G. [Istituto Nazionale di Fisica Nucleare, Padua (Italy); Svenne, J.P. [Manitoba Univ., Winnipeg, MB (Canada). Dept. of Physics]|[Winnipeg Inst. for Theoretical Physics, Winnipeg, MB (Canada)

    1994-10-10

    A broad set of observables are calculated for the {pi}{sup +} d {r_reversible} pp reaction with a relatively simple meson-exchange isobar model. The comparison between the calculated results and experimental data (including spin observables), shows that the model gives an overall phenomenologically acceptable description of the reaction around the {Delta} resonance. The effects due to the inclusion of Galilei invariant (pseudovector) recoil term in the {pi}NN vertex, of relativistic corrections to the {rho}-exchange component of the {Delta}N transition potential, and of NN final state interaction in the {pi}{sup +}d {yields} p+p process are also discussed. It is estimated that the model is sufficiently simple to be extended to the case of pion absorption on other light nuclei, in particular {sup 3}He (or tritium). 32 refs., 13 figs.

  10. Haptoglobin preferentially binds β but not α subunits cross-linked hemoglobin tetramers with minimal effects on ligand and redox reactions.

    Science.gov (United States)

    Jia, Yiping; Wood, Francine; Buehler, Paul W; Alayash, Abdu I

    2013-01-01

    Human hemoglobin (Hb) and haptoglobin (Hp) exhibit an extremely high affinity for each other, and the dissociation of Hb tetramers into dimers is generally believed to be a prerequisite for complex formation. We have investigated Hp interactions with native Hb, αα, and ββ cross-linked Hb (ααXLHb and ββXLHb, respectively), and rapid kinetics of Hb ligand binding as well as the redox reactivity in the presence of and absence of Hp. The quaternary conformation of ββ subunit cross-linking results in a higher binding affinity than that of αα subunit cross-linked Hb. However, ββ cross-linked Hb exhibits a four fold slower association rate constant than the reaction rate of unmodified Hb with Hp. The Hp contact regions in the Hb dimer interfaces appear to be more readily exposed in ββXLHb than ααXLHb. In addition, apart from the functional changes caused by chemical modifications, Hp binding does not induce appreciable effects on the ligand binding and redox reactions of ββXLHb. Our findings may therefore be relevant to the design of safer Hb-based oxygen therapeutics by utilizing this preferential binding of ββXLHb to Hp. This may ultimately provide a safe oxidative inactivation and clearance pathway for chemically modified Hbs in circulation.

  11. Coherent production of pions in nuclei with ({sup 3}He,t) charge exchange reaction at 2. GeV

    Energy Technology Data Exchange (ETDEWEB)

    Farhi, L.; Roy-Stephan, M.; Boyard, J.L. [Paris-11 Univ., 91 - Orsay (France). Inst. de Physique Nucleaire; Hennino, T.; Kagarlis, M.; Radvanyi, P. [Laboratoire National Saturne - Centre d`Etudes Nucleaires de Saclay, 91 - Gif-sur-Yvette (France); Dahl, R.; Ellegaard, C. [Niels Bohr Inst., Copenhagen (Denmark); Augustiniak, W.; Zupranski, P. [Soltan Inst. for Nuclear Studies, Otwock-Swierk (Poland)] [and others

    1996-12-31

    The ({sup 3}He,t) charge exchange reaction at 2. GeV incident energy with the new setup SPES IV-{pi} has been realized in order to study the coherent production process of pions. This setup allows to isolate the ground state of the target nucleus, and to sign this process without ambiguity. Some preliminary results in target excitation energy and transferred energy are given. (author). 8 refs.

  12. Synthesis and characterization of an octaimidazolium-based polyhedral oligomeric silsesquioxanes ionic liquid by an ion-exchange reaction.

    Science.gov (United States)

    Tan, Jinglin; Ma, Depeng; Sun, Xingrong; Feng, Shengyu; Zhang, Changqiao

    2013-04-07

    Preparation of POSS-min-DS, an octaimidazolium-based polyhedral oligomeric silsesquioxanes (POSS) room temperature ionic liquid, by an ion-exchange reaction between POSS and sodium dodecyl sulfate was reported. Octaimidazolium-based POSS was synthesized with more than 98% yield within 3 h. POSS-min-DS and octaimidazolium-based POSS were confirmed by (1)H, (13)C, and (29)Si NMR, FT-IR and elemental analysis.

  13. Ab initio R1 mechanism of photostimulated oxygen isotope exchange reaction on a defect TiO{sub 2} surface: The case of terminal oxygen atom exchange

    Energy Technology Data Exchange (ETDEWEB)

    Kevorkyants, Ruslan, E-mail: ruslan.kevorkyants@gmail.com; Sboev, Mikhail N.; Chizhov, Yuri V.

    2017-05-01

    Highlights: • DFT R1 mechanism of photostimulated oxygen isotope exchange between {sup 16}O{sup 18}O and terminal oxygen atom of a defect surface of nanocrystalline TiO{sub 2} is proposed. • The mechanism involves four adsorption intermediates and five transition states. • Activation energy of the reaction is 0.24 eV. • G-tensors of O{sub 3}{sup −} intermediates match EPR data on O{sub 2} adsorbed on UV-irradiated TiO{sub 2} surface. - Abstract: Based on density functional theory we propose R1 mechanism of photostimulated oxygen isotope exchange (POIEx) reaction between {sup 16}O{sup 18}O and terminal oxygen atom of a defect TiO{sub 2} surface, which is modeled by amorphous Ti{sub 8}O{sub 16} nanocluster in excited S{sup 1} electronic state. The proposed mechanism involves four adsorption intermediates and five transition states. The computed activation energy of the POIEx equals 0.24 eV. The computed g-tensors of the predicted ozonide O{sub 3}{sup −} chemisorption species match well EPR data on O{sub 2} adsorption on UV-irradiated nanocrystalline TiO{sub 2}. This match serves a mean of justification of the proposed R1 mechanism of the POIEx reaction. In addition, it is found that the proposed R1 POIEx reaction’s mechanism differs from R1 mechanism of thermo-assisted OIEx reaction on a surface of supported vanadium oxide catalyst VO{sub x}/TiO{sub 2} reported earlier.

  14. Kinetic Isotope Effect Determination Probes the Spin of the Transition State, Its Stereochemistry, and Its Ligand Sphere in Hydrogen Abstraction Reactions of Oxoiron(IV) Complexes.

    Science.gov (United States)

    Mandal, Debasish; Mallick, Dibyendu; Shaik, Sason

    2018-01-16

    This Account outlines interplay of theory and experiment in the quest to identify the reactive-spin-state in chemical reactions that possess a few spin-dependent routes. Metalloenzymes and synthetic models have forged in recent decades an area of increasing appeal, in which oxometal species bring about functionalization of hydrocarbons under mild conditions and via intriguing mechanisms that provide a glimpse of Nature's designs to harness these reactions. Prominent among these are oxoiron(IV) complexes, which are potent H-abstractors. One of the key properties of oxoirons is the presence of close-lying spin-states, which can mediate H-abstractions. As such, these complexes form a fascinating chapter of spin-state chemistry, in which chemical reactivity involves spin-state interchange, so-called two-state reactivity (TSR) and multistate reactivity (MSR). TSR and MSR pose mechanistic challenges. How can one determine the structure of the reactive transition state (TS) and its spin state for these mechanisms? Calculations can do it for us, but the challenge is to find experimental probes. There are, however, no clear kinetic signatures for the reactive-spin-state in such reactions. This is the paucity that our group has been trying to fill for sometime. Hence, it is timely to demonstrate how theory joins experiment in realizing this quest. This Account uses a set of the H-abstraction reactions of 24 synthetic oxoiron(IV) complexes and 11 hydrocarbons, together undergoing H-abstraction reactions with TSR/MSR options, which provide experimentally determined kinetic isotope effect (KIE exp ) data. For this set, we demonstrate that comparing KIE exp results with calculated tunneling-augmented KIE (KIE TC ) data leads to a clear identification of the reactive spin-state during H-abstraction reactions. In addition, generating KIE exp data for a reaction of interest, and comparing these to KIE TC values, provides the mechanistic chemist with a powerful capability to

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

    Science.gov (United States)

    Ji, Y.; Shen, C.

    2014-03-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-03-15

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

  17. Nonheme Fe(IV) Oxo Complexes of Two New Pentadentate Ligands and Their Hydrogen-Atom and Oxygen-Atom Transfer Reactions.

    Science.gov (United States)

    Mitra, Mainak; Nimir, Hassan; Demeshko, Serhiy; Bhat, Satish S; Malinkin, Sergey O; Haukka, Matti; Lloret-Fillol, Julio; Lisensky, George C; Meyer, Franc; Shteinman, Albert A; Browne, Wesley R; Hrovat, David A; Richmond, Michael G; Costas, Miquel; Nordlander, Ebbe

    2015-08-03

    Two new pentadentate {N5} donor ligands based on the N4Py (N4Py = N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl)methylamine) framework have been synthesized, viz. [N-(1-methyl-2-benzimidazolyl)methyl-N-(2-pyridyl)methyl-N-(bis-2-pyridyl methyl)amine] (L(1)) and [N-bis(1-methyl-2-benzimidazolyl)methyl-N-(bis-2-pyridylmethyl)amine] (L(2)), where one or two pyridyl arms of N4Py have been replaced by corresponding (N-methyl)benzimidazolyl-containing arms. The complexes [Fe(II)(CH3CN)(L)](2+) (L = L(1) (1); L(2) (2)) were synthesized, and reaction of these ferrous complexes with iodosylbenzene led to the formation of the ferryl complexes [Fe(IV)(O)(L)](2+) (L = L(1) (3); L(2) (4)), which were characterized by UV-vis spectroscopy, high resolution mass spectrometry, and Mössbauer spectroscopy. Complexes 3 and 4 are relatively stable with half-lives at room temperature of 40 h (L = L(1)) and 2.5 h (L = L(2)). The redox potentials of 1 and 2, as well as the visible spectra of 3 and 4, indicate that the ligand field weakens as ligand pyridyl substituents are progressively substituted by (N-methyl)benzimidazolyl moieties. The reactivities of 3 and 4 in hydrogen-atom transfer (HAT) and oxygen-atom transfer (OAT) reactions show that both complexes exhibit enhanced reactivities when compared to the analogous N4Py complex ([Fe(IV)(O)(N4Py)](2+)), and that the normalized HAT rates increase by approximately 1 order of magnitude for each replacement of a pyridyl moiety; i.e., [Fe(IV)(O)(L(2))](2+) exhibits the highest rates. The second-order HAT rate constants can be directly related to the substrate C-H bond dissociation energies. Computational modeling of the HAT reactions indicates that the reaction proceeds via a high spin transition state.

  18. Rare events via multiple reaction channels sampled by path replica exchange

    NARCIS (Netherlands)

    Bolhuis, P.G.

    2008-01-01

    Transition path sampling (TPS) was developed for studying activated processes in complex systems with unknown reaction coordinate. Transition interface sampling (TIS) allows efficient evaluation of the rate constants. However, when the transition can occur via more than one reaction channel

  19. Encaging palladium(0 in layered double hydroxide: A sustainable catalyst for solvent-free and ligand-free Heck reaction in a ball mill

    Directory of Open Access Journals (Sweden)

    Wei Shi

    2017-08-01

    Full Text Available In this paper, the synthesis of a cheap, reusable and ligand-free Pd catalyst supported on MgAl layered double hydroxides (Pd/MgAl-LDHs by co-precipitation and reduction methods is described. The catalyst was used in Heck reactions under high-speed ball milling (HSBM conditions at room temperature. The effects of milling-ball size, milling-ball filling degree, reaction time, rotation speed and grinding auxiliary category, which would influence the yields of mechanochemical Heck reactions, were investigated in detail. The characterization results of XRD, ICP–MS and XPS suggest that Pd/MgAl-LDHs have excellent textural properties with zero-valence Pd on its layers. The reaction results indicate that the catalyst could be utilized in HSBM systems to afford a wide range of Heck coupling products in satisfactory yields. Furthermore, this catalyst could be easily recovered and reused for at least five times without significant loss of catalytic activity.

  20. The use of deuterium n.m.r. spectroscopy in mechanistic studies of exchange reactions of ethers on supported metal catalysts

    International Nuclear Information System (INIS)

    Campbell, J.A.; Kemball, Charles; McDougall, G.S.

    1987-01-01

    Exchange reactions of diethyl ether (DEE) and tetrahydrofuran (THF) with deuterium have been studied over supported nickel, palladium, platinum, and rhodium catalysts. Products from most of the systems were analysed by deuterium n.m.r. spectroscopy (55.28 MHz) which gave quantitative results about the distribution of deuterium in the exchanged ethers. The results confirm earlier conclusions about the mechanism of the exchange of DEE and provide new evidence about the reactions of THF. Some hydrogenolysis occurred simultaneously with exchange of THF over both nickel and platinum. (author)

  1. A paradox: The thermal rate coefficient for the H+DCl → HCl+D exchange reaction

    International Nuclear Information System (INIS)

    Thompson, D.L.; Suzukawa, H.H. Jr.; Raff, L.M.

    1975-01-01

    Previously reported photolysis experiments indicate that the frequency factors associated with the hydrogen-exchange reactions H+DCl → HCl+D and D+HCl → DCl+H are on the order of 10 10 cm 3 /molcenter-dotsec. A series of unadjusted, quasiclassical trajectory calculations were been carried out to compute the thermal rate coefficients and activation parameters for a series of 13 thermal processes of the type A+BC → AB+C, where A=H, D, or Cl and BC=H 2 , D 2 , HCl, DCl, or Cl 2 . In addition, hot-atom yield ratios have been computed from the IRP equation for the reactions D*+DCl → D 2 +Cl, D*+Cl 2 → DCl + Cl as a function of the initial D* laboratory energy. The computations yield (1) hot-atom DCl/D 2 yield ratios within a factor of 2 of the experimental values; (2) thermal activation energies in satisfactory agreement with experiment for all processes investigated; and (3) frequency factors in reasonable accord with experiment for all the reactions except the hydrogen exchange reactions

  2. Equilibrium dialysis-ligand exchange: adaptation of the method for determination of conditional stability constants of radionuclide-fulvic acid complexes

    International Nuclear Information System (INIS)

    Glaus, M.A.; Hummel, W.; Van Loon, L.R.

    1995-01-01

    The equilibrium dialysis-ligand exchange technique (EDLE) is used to determine conditional stability constants for the complexation of metal ions with humic acid, particularly in high pH solutions. Here, this technique has been adapted to measure conditional stability constants with fulvic acid. Fulvic acid permeates across all membranes during the experiment. The quantities involved therefore have to be determined analytically and taken into account when calculating the conditional stability constants. Co(II) and Laurentian Soil fulvic (LFA) acid were selected as a test system in order to investigate the time scale required to establish chemical and diffusion equilibria. After an incubation time of approximately two days, the conditional stability constants measured for the formation of Co-LFA-complexes are not time dependent, although across the whole time period investigated, LFA was still diffusing in increasing amounts across the dialysis membrane. This work demonstrates that the modified EDLE technique can be used in the determination of conditional metal stability constants of fulvic acid. (authors)

  3. Transforming single domain magnetic CoFe{sub 2}O{sub 4} nanoparticles from hydrophobic to hydrophilic by novel mechanochemical ligand exchange

    Energy Technology Data Exchange (ETDEWEB)

    Munjal, Sandeep; Khare, Neeraj, E-mail: nkhare@physics.iitd.ernet.in [Indian Institute of Technology Delhi, Department of Physics (India)

    2017-01-15

    Single-phase uniform-sized (~9 nm) cobalt ferrite (CFO) nanoparticles have been synthesized by hydrothermal synthesis using oleic acid as a surfactant. The as-synthesized oleic acid-coated CFO (OA-CFO) nanoparticles were well dispersible in nonpolar solvents but not dispersible in water. The OA-CFO nanoparticles have been successfully transformed to highly water-dispersible citric acid-coated CFO (CA-CFO) nanoparticles using a novel single-step ligand exchange process by mechanochemical milling, in which small chain citric acid molecules replace the original large chain oleic acid molecules available on CFO nanoparticles. The OA-CFO nanoparticle’s hexane solution and CA-CFO nanoparticle’s water solution remain stable even after 6 months and show no agglomeration and their dispersion stability was confirmed by zeta-potential measurements. The contact angle measurement shows that OA-CFO nanoparticles are hydrophobic whereas CA-CFO nanoparticles are superhydrophilic in nature. The potentiality of as-synthesized OA-CFO and mechanochemically transformed CA-CFO nanoparticles for the demulsification of highly stabilized water-in-oil and oil-in-water emulsions has been demonstrated.

  4. Simultaneous measurement of proline and related compounds in oak leaves by high-performance ligand-exchange chromatography and electrospray ionization mass spectrometry for environmental stress studies.

    Science.gov (United States)

    Oufir, Mouhssin; Schulz, Nadine; Sha Vallikhan, Patan Shaik; Wilhelm, Eva; Burg, Kornel; Hausman, Jean-Francois; Hoffmann, Lucien; Guignard, Cedric

    2009-02-13

    A mass spectrometer was coupled to high-performance ligand-exchange liquid chromatography (HPLEC) for simultaneous analysis of stress associated solutes such as proline, hydroxyproline, methylproline, glycine betaine and trigonelline extracted from leaves of drought stressed oaks and an internal standard namely N-acetylproline. Methanol/chloroform/water extracts were analyzed using an Aminex HPX-87C column and specifically quantified by the positive ion mode of an electrospray ionisation-mass spectrometry (ESI-MS) in single ion monitoring (SIM) mode. The recovery of N-acetyl proline added to oak leaf extracts ranged from 85.2 to 122.1% for an intra-day study. Standard calibration curves showed good linearity in the measured range from 0.3125 to 10micromolL(-1) with the lowest correlation coefficient of 0.99961 for trigonelline. The advantages of this alternative procedure, compared to previously published methods using fluorescence or amperometric detections, are the simultaneous and direct detection of osmoprotectants in a single chromatographic run, a minimal sample preparation, a good specificity and reduced limits of quantification, ranging from 0.1 to 0.6micromolL(-1). Fifty-six days of water deficit exposure resulted in increased foliar free proline levels (2.4-fold, P<0.001, 155micromolg(-1) FW) and glycine betaine contents (2.5-fold, P<0.05, 175micromolg(-1) FW) of drought stressed oak compared to control.

  5. Self-Assembled Fluorescent Nanoprobe Based on Forster Resonance Energy Transfer for Carbon Monoxide in Living Cells and Animals via Ligand Exchange.

    Science.gov (United States)

    Jia, Ruizhen; Song, Pengfei; Wang, Jingjing; Mai, Hengtang; Li, Sixian; Cheng, Yu; Wu, Song

    2018-05-29

    Carbon monoxide (CO) is recognized as a biologically essential gaseous neurotransmitter that modulates many physiological processes in living subjects. Currently reported fluorescent probes for CO imaging in cells basically utilize palladium related chemistry which requires complicated synthetic work. Herein we provide a new strategy to construct a fluorescent nanoprobe, NanoCO-1, based on the Forster resonance energy transfer (FRET) mechanism by entrapping the existing dirhodium complex as the energy acceptor and the CO recognition part, and a commonly used nitrobenzoxadiazole (NBD) dye as energy donor into a micelle formed by self-assembly. The exchange of ligands in the dirhodium complex by CO in the nanoprobe disrupts the FRET and leads to the turn-on of fluorescence. The merits of NanoCO-1 including good biocompatibility, selectivity, photostability, and low cytotoxity, render this nanoprobe ability to track CO in living cells, zebrafish embryo, and larvae. Our straightforward approach can be extended to establish the CO fluorescent probes based on adsorption of CO on a variety of metal derivatives.

  6. Mechanism of pyridine-ligand exchanges at the different labile sites of 3d heterometallic and mixed valence mu3-oxo trinuclear clusters.

    Science.gov (United States)

    Novitchi, Ghenadie; Riblet, Fabrice; Scopelliti, Rosario; Helm, Lothar; Gulea, Aurelian; Merbach, André E

    2008-11-17

    The syntheses and single crystal X-ray structural analysis of five novel hetero- and homometallic mu 3-oxo trinuclear cluster with the formula [Fe (III) 2M (II)(mu 3-O)(mu-O 2CCH 3) 6(4-Rpy) 3]. x(4-Rpy). y(CH 3CN) where R = Ph for 1(Fe 2Mn), 2(Fe 2Fe), 3(Fe 2Co), 4(Fe 2Ni) and R = CF 3 for 5(Fe 2Co), are reported. The persistence of the structure for compounds 2- 5 in dichloromethane solution in the temperature range 190-320 K is demonstrated by (1)H and (19)F NMR spectroscopy. Even at the lowest temperature, the electron exchange in the homometallic mixed-valence compound 2(Fe 2Fe) is in the fast regime at the NMR time scale. Variable temperature and pressure NMR line broadening allowed quantifying the fast coordinated/free 4-Rpy exchanges at the two labile metal centers in these clusters: 2: Fe (III)( k (298)/10 (3) s (-1) = 16.6; Delta H (++) = 60.32 kJ mol (-1); Delta S (++) = + 34.8 J K (-1) mol (-1); Delta V (++) = + 12.5 cm (3) mol (-1)); 3: Fe (11.9; 58.92; +30.7; +10.6) and Co (2.8; 68.24; +49.8; +13.9); 4: Fe(12.2; 67.91; +61.0; -) and Ni (0.37; 78.62; +67.8; +12.3); 5: Fe (46; 58.21; +39.3; +14.2) and Co (4.7; 55.37; +11.2; +10.9). A limiting D mechanism is assigned to these exchange reactions. This assignment is based on a first-order rate law, the detection of intermediates, the positive and large entropies and volumes of activation. The order of reactivity k (Co) > k (Ni) is expected for a D mechanism at these metal centers: their low exchange rates are due to their strong binding with the 4-Rpy donor. Surrounded by oxygen donors the d (5) iron(III) usually reacts associatively; however, here due to low affinity of this ion for nitrogen the mechanism is D and the rate of exchange is very fast, even faster than on the divalent ions. There is no significant effect of the divalent ion in cluster 2, 3, and 5 on the exchange rates of 4-Phpy at the iron center, which seems to indicate that the specific electronic interactions between the three ions making

  7. Palladium-Catalyzed Heck Coupling Reaction of Aryl Bromides in Aqueous Media Using Tetrahydropyrimidinium Salts as Carbene Ligands

    Directory of Open Access Journals (Sweden)

    İsmail Özdemir

    2010-01-01

    Full Text Available An efficient and stereoselective catalytic system for the Heck cross coupling reaction using novel 1,3-dialkyl-3,4,5,6-tetrahydropyrimidinium salts (1, LHX and Pd(OAc2 loading has been reported. The palladium complexes derived from the salts 1a-f prepared in situ exhibit good catalytic activity in the Heck coupling reaction of aryl bromides under mild conditions.

  8. Deuterium exchange reaction between hydrogen and water in a trickle-bed column packed with novel catalysts

    International Nuclear Information System (INIS)

    Ahn, D. H.; Baek, S. W.; Lee, H. S.; Kim, K. R.; Kang, H. S.; Lee, S. H.; Jeong, H. S.

    1998-01-01

    The activity of a novel catalyst (Pt/SDBC) for deuterium exchange reaction between water and hydrogen streams in a trickle bed was measured. The performance of the catalyst was compared with a commercial catalyst with same metal content. The catalytic activity for the bed of wet-proofed catalyst diluted with hydrophillic packing material also measured. The Pt/SDBC catalyst shows higher activity in the liquid phase reaction than the commercial catalyst as measured in the vapor phase reaction. The performance for 50% dilution of the Pt/SDBC catalyst bed with hydrophillic packing material is better than that of the 100% bed due to more liquid holdup and better water distribution

  9. ESI-MS studies of the reactions of novel platinum(II) complexes containing O,O'-chelated acetylacetonate and sulfur ligands with selected model proteins.

    Science.gov (United States)

    Marzo, Tiziano; De Pascali, Sandra A; Gabbiani, Chiara; Fanizzi, Francesco P; Messori, Luigi; Pratesi, Alessandro

    2017-08-01

    A group of mixed-ligand Pt(II) complexes bearing acetylacetonate and sulphur ligands were recently developed in the University of Lecce as a new class of prospective anticancer agents that manifested promising pharma-cological properties in preliminary in vitro and in vivo tests. Though modelled on the basis of cisplatin, these Pt(II) complexes turned out to exhibit a profoundly distinct mode of action as they were found to act mainly on non-genomic targets rather than on DNA. Accordingly, we have explored here their reactions with two representative model proteins through an established ESI-MS procedure with the aim to describe their general interaction mechanism with protein targets. A pronounced reactivity with the tested proteins was indeed documented; the nature of the resulting metallodrug-protein interactions could be characterised in depth in the various cases. Preferential binding to protein targets compared to DNA is supported by independent ICP-OES measurements. The implications of these findings are discussed.

  10. Solvent- and ligand-induced switch of selectivity in gold(I-catalyzed tandem reactions of 3-propargylindoles

    Directory of Open Access Journals (Sweden)

    Roberto Sanz

    2011-06-01

    Full Text Available The selectivity of our previously described gold-catalyzed tandem reaction, 1,2-indole migration followed by aura-iso-Nazarov cyclization, of 3-propargylindoles bearing (heteroaromatic substituents at both the propargylic and terminal positions, was reversed by the proper choice of the catalyst and the reaction conditions. Thus, 3-(inden-2-ylindoles, derived from an aura-Nazarov cyclization (instead of an aura-iso-Nazarov cyclization, were obtained in moderate to good yields from a variety of 3-propargylindoles.

  11. Theoretical study of the Cs isotope exchange reaction of CsI + Cs' → Cs + ICs' (Contract research)

    International Nuclear Information System (INIS)

    Kobayashi, Takanori; Hashimoto, Masashi; Yokoyama, Keiichi

    2015-12-01

    To discuss the exchange reaction of Cs isotope by CsI + Cs' → Cs + ICs', the structure and chemical properties of Cs 2 I intermediate and potential energy surface of the entrance reaction are calculated using M06/def2-TZVPPD density functional calculation. The calculation shows that the reaction to the intermediate has no barrier and the two Cs-I bonds of Cs 2 I are chemically equivalent. These results suggest that the rate of the Cs exchange reaction of CsI + Cs' → Cs + ICs' is as high as the collision rate. (author)

  12. Note on some charge exchange cross sections of inelastic pn and pp reactions in terms of the quark interchange concept

    International Nuclear Information System (INIS)

    Bakken, V.; Jacobsen, T.

    The charge exchange cross sections observed for pN interactions at 19 GeV/c in terms of the quark-quark interchange concept are discussed. If one uu-pair and one dd-pair of sea-quarks are assigned to each initial nucleon in pn and pp inelastic reactions, and if these quarks are assumed to participate on equal footing with the valence quarks in a quark-quark interchange mechanism between the two initial nucleons, the ratios between some observed charge exchange cross sections are well reproduced. This indicates that in this model the sea-quarks contribute significantly to the particle production in low p(subT) hadronic processes. (Auth.)

  13. Influence of Ligand Architecture in Tuning Reaction Bifurcation Pathways for Chlorite Oxidation by Non-Heme Iron Complexes

    NARCIS (Netherlands)

    Barman, Prasenjit; Faponle, Abayomi S; Vardhaman, Anil Kumar; Angelone, Davide; Löhr, Anna-Maria; Browne, Wesley R; Comba, Peter; Sastri, Chivukula V; de Visser, Sam P

    2016-01-01

    Reaction bifurcation processes are often encountered in the oxidation of substrates by enzymes and generally lead to a mixture of products. One particular bifurcation process that is common in biology relates to electron transfer versus oxygen atom transfer by high-valent iron(IV)-oxo complexes,

  14. Pair natural orbital and canonical coupled cluster reaction enthalpies involving light to heavy alkali and alkaline earth metals: the importance of sub-valence correlation

    KAUST Repository

    Minenkov, Yury; Bistoni, Giovanni; Riplinger, Christoph; Auer, Alexander A.; Neese, Frank; Cavallo, Luigi

    2017-01-01

    In this work, we tested canonical and domain based pair natural orbital coupled cluster methods (CCSD(T) and DLPNO-CCSD(T), respectively) for a set of 32 ligand exchange and association/dissociation reaction enthalpies involving ionic complexes

  15. A computational study of a recreated G protein-GEF reaction intermediate competent for nucleotide exchange: fate of the Mg ion.

    Directory of Open Access Journals (Sweden)

    Mériam Ben Hamida-Rebaï

    Full Text Available Small G-proteins of the superfamily Ras function as molecular switches, interacting with different cellular partners according to their activation state. G-protein activation involves the dissociation of bound GDP and its replacement by GTP, in an exchange reaction that is accelerated and regulated in the cell by guanine-nucleotide exchange factors (GEFs. Large conformational changes accompany the exchange reaction, and our understanding of the mechanism is correspondingly incomplete. However, much knowledge has been derived from structural studies of blocked or inactive mutant GEFs, which presumably closely represent intermediates in the exchange reaction and yet which are by design incompetent for carrying out the nucleotide exchange reaction. In this study we have used comparative modelling to recreate an exchange-competent form of a late, pre-GDP-ejection intermediate species in Arf1, a well-characterized small G-protein. We extensively characterized three distinct models of this intermediate using molecular dynamics simulations, allowing us to address ambiguities related to the mutant structural studies. We observed in particular the unfavorable nature of Mg2+ associated forms of the complex and the establishment of closer Arf1-GEF contacts in its absence. The results of this study shed light on GEF-mediated activation of this small G protein and on predicting the fate of the Mg ion at a critical point in the exchange reaction. The structural models themselves furnish additional targets for interfacial inhibitor design, a promising direction for exploring potentially druggable targets with high biological specificity.

  16. Deuterium labelling of tryptamine, serotonin and their N-methylated metabolites using solvent exchange reactions

    Energy Technology Data Exchange (ETDEWEB)

    Raeisaenen, M; Kaerkkaeinen, J [Helsinki Univ. (Finland). Dept. of Medical Chemistry

    1979-01-01

    Technically uncomplicated methods based on catalytic isotope exchange in deuterated solvents are described for the deuteration of tryptamine, serotonin and their N-methylated metabolites. Heterogeneous platinum catalysis, homogeneous acid catalysis and their combination have been employed. The properties of the labelled derivatives prepared with each technique as well as their use in mass spectrometric work are discussed.

  17. Deuterium labelling of tryptamine, serotonin and their N-methylated metabolites using solvent exchange reactions

    International Nuclear Information System (INIS)

    Raeisaenen, M.; Kaerkkaeinen, J.

    1979-01-01

    Technically uncomplicated methods based on catalytic isotope exchange in deuterated solvents are described for the deuteration of tryptamine, serotonin and their N-methylated metabolites. Heterogeneous platinum catalysis, homogeneous acid catalysis and their combination have been employed. The properties of the labelled derivatives prepared with each technique as well as their use in mass spectrometric work are discussed. (author)

  18. Synthesis and anion exchange reactions of a layered copper–zinc ...

    Indian Academy of Sciences (India)

    Unknown

    replaced by Zn2+. Keywords. Copper–zinc hydroxides; Cu–Zn hydroxysalts; anion exchange. ... be broadly separated into two structural types, based on the structure of ... thermogravimetry (a lab-built system, heating rate. 5°C per minute) and ...

  19. Working-state Morphologies of Ion Exchange Catalysts and Their Influence on Reaction Kinetics

    Czech Academy of Sciences Publication Activity Database

    Jeřábek, Karel; Hanková, Libuše; Holub, Ladislav

    2010-01-01

    Roč. 333, 1-2 (2010), s. 109-113 ISSN 1381-1169 Grant - others:DCH(US) BD20 Institutional research plan: CEZ:AV0Z40720504 Keywords : ion exchanger catalyst * morphology * esterification Subject RIV: CC - Organic Chemistry Impact factor: 2.872, year: 2010

  20. Corrections to the one-pion exchange amplitudes for the reaction np→pΔsub(33)sup(deg)

    International Nuclear Information System (INIS)

    Ferraz De Camargo, A.; Laville, J.L.

    1978-01-01

    A simple modified one-pion exchange model is applied to the analysis of the reaction np→pΔsub(33)sup(deg) from 1.39 to 1.90GeV/c. It is shown that important corrections to the evasive amplitudes can account for the turnover observed in the differential cross-section and rather good fits are obtained. Such corrections do not agree with the prescription known as ''poor man's absorption''. The results for the density matrix elements are briefly discussed

  1. Preparation of Pt-SDB hydrophobic catalyst used in H2-H2O isotope exchange reaction

    International Nuclear Information System (INIS)

    Li Junhua; Kang Yi; Ruan Hao; Dou Qincheng; Han Yande; Hu Shilin

    2001-01-01

    The preparation of Pt-SDB hydrophobic catalyst is studied, in which platinum as active metal and polystyrene divinylbenzene (SDB) as the carrier. Hydrogen isotope exchange reaction is carried out with Pt-SDB catalyst in counter-current in the trickle bed. The effect of preparing condition on the activity of catalyst is discussed. The results show that the excellent catalyst is obtained by reduced at the temperature of 200 degree C over 8 hours. Hydrophobic catalyst is high activity and stability as the amount of platinum content is 3%, the platinum can reach the economic use with the content of (1-2)%

  2. Negative pion topography by observation of γ-quanta after the charge exchange reaction π- p → π0 n

    International Nuclear Information System (INIS)

    Bueche, G.

    It is shown that the gamma quanta from the π 0 decay after the charge exchange reaction π - p → nπ 0 can be used to map the capture region of a π - beam in hydrogen-containing substances. In view of the applications in radiotherapy, the detectors have to be placed laterally from the absorber volume. For such a geometry the probability distribution of γ-γ coincidences were calculated. The results show that the range of the beam and its lateral position can be determined to the order of one millimeter within a time short compared with irradiation times usual in radiotherapy

  3. A high-statistics measurement of the pp→nn charge-exchange reaction at 875 MeV/c

    International Nuclear Information System (INIS)

    Lamanna, M.; Ahmidouch, A.; Birsa, R.; Bradamante, F.; Bressan, A.; Bressani, T.; Dalla Torre-Colautti, S.; Giorgi, M.; Heer, E.; Hess, R.; Kunne, R.A.; Lechanoine-Le Luc, C.; Martin, A.; Mascarini, C.; Masoni, A.; Penzo, A.; Rapin, D.; Schiavon, P.; Tessarotto, F.

    1995-01-01

    A new measurement of the differential cross section and of the analysing power A 0n of the charge-exchange reaction pp→nn at 875 MeV/c is presented. The A 0n data cover the entire angular range and constitute a considerable improvement over previously published data, both in the forward and in the backward hemisphere. The cross-section data cover only the backward region, but are unique at this energy. A careful study of the long-term drifts of the apparatus has allowed to fully exploit the good statistics of the data. ((orig.))

  4. Dynamic separation of Szilard-Chalmers reaction products applied to the trioxalatochromium ion adsorbed on anionic exchange resin

    International Nuclear Information System (INIS)

    Silva, J.B.S.

    1979-01-01

    A method of dynamic elution of recoiled 51 Cr +3 , formed by the Szilard-Chalmers reaction during the irradiation of trioxalatochromium ion adsorbed on anionic exchange resin is presented. The influence of some factors on the separation yield of chromium-51, such as: composition, concentration and flow rate of eluent, mesh size of the resin and irradiation time are studied. The results are compardd with those obtained by the static method, in which the recoiled atom is separated from the target after irradiation. Because of the high separation yield of chromium-51, the method of dynamic separation is proposed for routine production of this elemnt, with high specific activities. (author) [pt

  5. Chiral speciation and determination of selenomethionine enantiomers in selenized yeast by ligand-exchange micellar electrokinetic capillary chromatography after solid phase extraction.

    Science.gov (United States)

    Duan, Jiankun; He, Man; Hu, Bin

    2012-12-14

    A new phenylalanine derivative (L-N-(2-hydroxy-propyl)-phenylalanine, L-HP-Phe) was synthesized and its chelate with Cu(II) (Cu(II)-(L-HP-Phe)(2)) was used as the chiral selector for the ligand-exchange (LE) chiral separation of D,L-selenomethionine (SeMet) in selenized yeast samples by micelle electrokinetic capillary chromatography (MEKC). In order to improve the sensitivity of MEKC-UV, two-step preconcentration strategy was employed, off-line solid phase extraction (SPE) and on-line large volume sample stacking (LVSS). D,L-SeMet was first retained on the Cu(II) loaded mesoporous TiO(2), then eluted by 0.1 mL of 5 mol L(-1) ammonia, and finally introduced for MEKC-UV analysis by LVSS injection after evaporation of NH(3). With the enrichment factors of 1400 and 1378, the LODs of 0.44 and 0.60 ng mL(-1) for L-SeMet and D-SeMet was obtained, respectively. The developed method was applied to the analysis of D,L-SeMet in a certified reference material of SELM-1 and a commercial nutrition yeast, and the results showed that most of SeMet in the SELM-1 selenized yeast was l isomer and the recovery for L and D isomers in the spiked commercial nutrition yeast was 96.3% and 103%, respectively. This method is featured with low running cost, high sensitivity and selectivity, and exhibits application potential in chiral analysis of seleno amino acids in real world samples. Copyright © 2012 Elsevier B.V. All rights reserved.

  6. Intermediate energy charge-exchange reactions induced by polarized 3He

    International Nuclear Information System (INIS)

    Kim, B.T.

    1998-01-01

    Spin polarization transfer is proven to be very useful in obtaining detailed information of the continuum nuclear responses. The data, taken for the (vector p,vector n) reactions, have enabled us to separate the response into the spin longitudinal and transverse components. These partial nuclear responses have been successfully used to make critical tests of nuclear structure models. In the present paper, we first summarize the results of the data and the theoretical analyses made so far. We then discuss information obtainable from the ( 3 vector He,vector t) reaction, emphasizing on the differences and similarities in comparison with the (vector p,vector n) reaction. The results of numerical calculations made for ( 3 vector He,vector t) reactions based on the microscopic distorted wave impulse approximation will also be reported. (orig.)

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

    International Nuclear Information System (INIS)

    Kaita, R.; Heidbrink, W.W.; Hammett, G.W.

    1986-04-01

    Adiabatic toroidal compression experiments were performed in conjunction with high power neutral beam injection in the Tokamak Fusion Test Reactor (TFTR). Acceleration of beam ions to energies nearly twice the injection energy was measured with a charge-exchange neutral particle analyzer. Measurements were also made of 2.5 MeV neutrons and 15 MeV protons produced in fusion reactions between the deuterium beam ions and the thermal deuterium and 3 He ions, respectively. When the plasma was compressed, the d(d,n) 3 He fusion reaction rate increased a factor of five, and the 3 He(d,p) 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

  8. Expansive failure reactions and their prevention in the encapsulation of phenol formaldehyde type ion exchange resins in cement based systems

    Energy Technology Data Exchange (ETDEWEB)

    Constable, M.; Howard, C.G.; Johnson, M.A.; Jolliffe, C.B. (AEA Decommissioning and Waste Management, Winfrith (United Kingdom)); Sellers, R.M. (Nuclear Electric plc, Barnwood (United Kingdom))

    1992-01-01

    Lewatit DN is a phenol formaldehyde based ion exchange resin used to remove radioactive caesium from liquid waste streams such as fuel cooling ponds and effluents. This paper presents the results of a study of the encapsulation of the bead form of the resin in cement with particular reference to the mechanisms of its interaction with the encapsulant. When incorporated in pure ordinary Portland cement (OPC) at loadings in excess of 15 wt % an unstable product results due to expansion of the systems and at higher waste loadings failure results after only a few days. Evidence from differential scanning calorimetry, X-ray diffraction and scanning electron microscopy all indicate the cause of the expansive reaction to be the formation of crystals of calcium salts around and within the resin beads. Addition of BFS and sodium hydroxide prevent the formation of these salts by removal of calcium hydroxide from the system in other reactions. (author).

  9. Reactive trajectories of the Ru2+/3+ self-exchange reaction and the connection to Marcus' theory.

    Science.gov (United States)

    Tiwari, Ambuj; Ensing, Bernd

    2016-12-22

    Outer sphere electron transfer between two ions in aqueous solution is a rare event on the time scale of first principles molecular dynamics simulations. We have used transition path sampling to generate an ensemble of reactive trajectories of the self-exchange reaction between a pair of Ru 2+ and Ru 3+ ions in water. To distinguish between the reactant and product states, we use as an order parameter the position of the maximally localised Wannier center associated with the transferring electron. This allows us to align the trajectories with respect to the moment of barrier crossing and compute statistical averages over the path ensemble. We compare our order parameter with two typical reaction coordinates used in applications of Marcus theory of electron transfer: the vertical gap energy and the solvent electrostatic potential at the ions.

  10. First-Principles Computed Rate Constant for the O + O2 Isotopic Exchange Reaction Now Matches Experiment.

    Science.gov (United States)

    Guillon, Grégoire; Honvault, Pascal; Kochanov, Roman; Tyuterev, Vladimir

    2018-04-19

    We show, by performing exact time-independent quantum molecular scattering calculations, that the quality of the ground electronic state global potential energy surface appears to be of utmost importance in accurately obtaining even as strongly averaged quantities as kinetic rate constants. The oxygen isotope exchange reaction, 18 O + 32 O 2 , motivated by the understanding of a complex long-standing problem of isotopic ozone anomalies in the stratosphere and laboratory experiments, is explored in this context. The thermal rate constant for this key reaction is now in quantitative agreement with all experimental data available to date. A significant recent progress at the frontier of three research domains, advanced electronic structure calculations, ultrasensitive spectroscopy, and quantum scattering calculations, has therefore permitted a breakthrough in the theoretical modeling of this crucial collision process from first principles.

  11. Quasi-elastic transfer and charge-exchange reactions in collisions of 48Ti on 42Ca and 26Mg

    International Nuclear Information System (INIS)

    Brendel, C.

    1985-01-01

    At the GSI magnetic spectrometer quasi-elastic transfer and charge-exchange reactions of the system 48 Ti + 42 Ca at incident energies E lab = 240, 300, and 385 MeV and additionally at the higher projectile energy the system 48 Ti + 26 Mg were studied each in the excitation energy range up to E x ≅ 80 MeV. The transition strength was for each particle-hole configuration of the final system calculated by means of the DWBA and subsequently folded with a Breit-Wigner distribution. The localization of the strength of the cross section and the specific structure of the energy spectra were at incident energies between 6 and 8 MeV/amu for all angles well reproduced. By an extension of the core-excitation model to many-stage reactions the charge-exchange reaction 48 Ti + 42 Ca → 48 Sc + 42 Sc could be described as sequential two-stage process. In the two-neutron stripping reaction 48 Ti + 42 Ca → 46 Ti + 44 Ca a surprisingly narrow line with a width of the experimental resolution and an excitation energy of E x = 17.8 MeV was measured at angles smaller than the grazing angle. In the 48 Ti + 26 Mg system the corresponding 46 Ti spectra show also under forward angles structures at excitation energies between 8 and 16 MeV. These lines can be explained as two-neutron states with high spin. (orig./HSI) [de

  12. Excitation of the Δ resonance in heavy ion charge exchange reactions

    International Nuclear Information System (INIS)

    Roy-Stephan, M.

    1987-06-01

    Results on the Δ excitation by heavy ion charge exchange are presented. 900 MeV per nucleon 12 C, 16 0, 20 Ne and 1100 MeV per nucleon 12 C have been used. The Δ excitation strength depends on the projectile - ejectile nature and on the incident energy. The role of the target mass is also discussed. The peak for the Δ in nuclei is energy shifted from the free Δ peak

  13. Agmatine, an endogenous ligand at imidazoline binding sites, does not antagonize the clonidine-mediated blood pressure reaction

    Science.gov (United States)

    Raasch, Walter; Schäfer, Ulrich; Qadri, Fatimunnisa; Dominiak, Peter

    2002-01-01

    Since agmatine has been identified as a clonidine displacing substance (CDS), the aim of this study was to investigate whether agmatine can mimic CDS-induced cardiovascular reactions in organ bath experiments, pithed spontaneously hypertensive rats (SHR) and anaesthetized SHR.Intravenously-administered agmatine significantly reduced the blood pressure and heart rate of anaesthetized SHR at doses higher than 1 and 3 mg kg−1, respectively. These effects are probably mediated via central mechanisms, since there was an approximate 8 fold rightward shift of the dose-response curve in the pithed SHR (indicating a weakened cardiovascular effect). Moreover, in organ bath experiments, agmatine failed to alter the contractility of intact or endothelium-denuded aortal rings. When agmatine was administered i.c.v. to anaesthetized SHR, blood pressure was increased without any alteration of heart rate, whereas blood pressure was unchanged and heart rate was increased after injection into the 4th brain ventricle. This suggests that haemodynamic reaction patterns after central application are related to distinct influences on central cardiovascular mechanisms.Agmatine reduces noradrenaline release in pithed SHR while α2-adrenoceptors are irreversibly blocked with phenoxybenzamine, but not while I1-binding sites are selectively blocked with AGN192403. This suggests that agmatine may modulate noradrenaline release in the same way that clonidine does, i.e. via imidazoline binding sites; this involves a reduction in sympathetic tone which in turn reduces blood pressure and heart rate.Finally, CDS-like cardiovascular activity appears not to be due to agmatine, since (i) blood pressure in anaesthetized SHR is decreased by agmatine and clonidine, and (ii) agmatine did not antagonize the blood pressure reaction to clonidine in pithed or anaesthetized SHR. PMID:11834614

  14. Exchange Rate and Interest Rate in the Monetary Policy Reaction Function

    Directory of Open Access Journals (Sweden)

    Krušković Borivoje D.

    2017-01-01

    Full Text Available In recent years there has been a particular interest in the relation between exchange rates and interest rates both in developed countries and emerging countries. This is understandable given the important role that these variables have in determining the movement of nominal and real economic variables, including the movement of domestic inflation, real output, exports and imports, foreign exchange reserves, etc. To realized the importance of the given instruments selected macroeconomic indicators, data analysis (monthly data relating to Serbia was made on the basis of the Transfer Function Model, a data analysis (annual data relating to emerging countries was done on the basis of the Stepvise Multiple Regression model. In the transfer function model we used the Maximum Likelihood method for assessing unknown coefficients. In the gradual multiple regression model we used the Least Square method for the evaluation of unknown coefficients. All indicator values were used in the original unmodified form, i.e. there was no need for a variety of transformations. Empirical analysis showed that the exchange rate is a more significant transmission mechanism than the interest rate both in emerging markets and Serbia.

  15. Meson exchange calculation of the p-barp→Lambda-barΛ reaction

    International Nuclear Information System (INIS)

    Tabakin, F.; Eisenstein, R.A.

    1985-01-01

    The process p-barp→Lambda-barΛ is studied using a one-boson t-channel strangeness exchange mechanism incorporating pseudoscalar, vector, and tensor mesons. Particular attention is paid to the spin degrees of freedom in the calculation. Initial and final state interactions, including the spin-orbit interaction and absorption, are taken into account using simple phenomenological models. The calculations are performed using density matrix ideas in the helicity basis, and the most important contributing amplitudes are identified. A reasonable fit to existing data can be obtained by allowing a smooth variation of the final state parameters with laboratory momentum. The effect of each of the exchanged mesons, and of the initial- and final-state baryon-baryon interactions on the cross sections and spin observables, is discussed. It is found that the tensor meson exchange plays an essential role even near threshold, which indicates the need for a detailed understanding of the short-range spin dynamics, perhaps as provided by future quark model studies

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

    Science.gov (United States)

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

    2015-12-17

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

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

    Science.gov (United States)

    Polak, Micha; Rubinovich, Leonid

    2011-10-06

    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.

  18. Chemical Exchange Saturation Transfer in Chemical Reactions: A Mechanistic Tool for NMR Detection and Characterization of Transient Intermediates.

    Science.gov (United States)

    Lokesh, N; Seegerer, Andreas; Hioe, Johnny; Gschwind, Ruth M

    2018-02-07

    The low sensitivity of NMR and transient key intermediates below detection limit are the central problems studying reaction mechanisms by NMR. Sensitivity can be enhanced by hyperpolarization techniques such as dynamic nuclear polarization or the incorporation/interaction of special hyperpolarized molecules. However, all of these techniques require special equipment, are restricted to selective reactions, or undesirably influence the reaction pathways. Here, we apply the chemical exchange saturation transfer (CEST) technique for the first time to NMR detect and characterize previously unobserved transient reaction intermediates in organocatalysis. The higher sensitivity of CEST and chemical equilibria present in the reaction pathway are exploited to access population and kinetics information on low populated intermediates. The potential of the method is demonstrated on the proline-catalyzed enamine formation for unprecedented in situ detection of a DPU stabilized zwitterionic iminium species, the elusive key intermediate between enamine and oxazolidinones. The quantitative analysis of CEST data at 250 K revealed the population ratio of [Z-iminium]/[exo-oxazolidinone] 0.02, relative free energy +8.1 kJ/mol (calculated +7.3 kJ/mol), and free energy barrier of +45.9 kJ/mol (ΔG ⧧ calc. (268 K) = +42.2 kJ/mol) for Z-iminium → exo-oxazolidinone. The findings underpin the iminium ion participation in enamine formation pathway corroborating our earlier theoretical prediction and help in better understanding. The reliability of CEST is validated using 1D EXSY-build-up techniques at low temperature (213 K). The CEST method thus serves as a new tool for mechanistic investigations in organocatalysis to access key information, such as chemical shifts, populations, and reaction kinetics of intermediates below the standard NMR detection limit.

  19. Strong Metal Support Interaction of Pt and Ru Nanoparticles Deposited on HOPG Probed by the H-D Exchange Reaction

    DEFF Research Database (Denmark)

    Fiordaliso, Elisabetta M.; Dahl, Søren; Chorkendorff, Ib

    2012-01-01

    The interaction between metals and support is investigated in the case of 50 Å Pt and 50 Å Ru films deposited on a HOPG substrate. The films are prepared by electron beam physical vapor deposition and annealed in UHV to temperatures up to 700 °C. The equilibrium hydrogen exchange rate between...... adsorbed and gas phase at 1 bar is measured before and after annealing. The rate is measured in the temperature range of 40–200 °C at 1 bar, by utilization of the H-D exchange reaction. Experiments are performed on fresh cleaved and sputtered HOPG, which give similar results. We find that annealing...... the films from 150 up to 700 °C increases the amount of carbon present in the films up to 95%, as derived by surface analysis, indicating the formation of a carbon layer on top of the metal films. The exchange rate decreases dramatically with increasing carbon content on the films for both metals, pointing...

  20. Gas-phase ion/molecule isotope-exchange reactions: methodology for counting hydrogen atoms in specific organic structural environments by chemical ionization mass spectrometry

    International Nuclear Information System (INIS)

    Hunt, D.F.; Sethi, S.K.

    1980-01-01

    Ion/molecule reactions are described which facilitate exchange of hydrogens for deuteriums in a variety of different chemical environments. Aromatic hydrogens in alkylbenzenes, oxygenated benzenes, m-toluidine, m-phenylenediamine, thiophene, and several polycyclic aromatic hydrocarbons and metallocenes are exchanged under positive ion CI conditions by using either D 2 O, EtOD, or ND 3 as the reagent gas. Aromatic hydrogens, benzylic hydrogens, and hydrogens on carbon adjacent to carbonyl groups suffer exchange under negative ion CI conditions in ND 3 , D 2 O, and EtOD, respectively. A possible mechanism for the exchange process is discussed. 1 figure, 2 tables

  1. An alternative preparation method for ion exchanged catalysts: Solid state redox reaction

    DEFF Research Database (Denmark)

    Schneider, E.; Hagen, A.; Grunwaldt, J.-D.

    2004-01-01

    A new method for modifying zeolites with zinc is proposed. The solid state redox reaction between metallic zinc and ZSM-5 zeolites with different Si/Al ratios was investigated by temperature programmed hydrogen evolution (TPHE), X-ray absorption near edge structure (XANES) and diffuse reflectance...... infrared Fourier transform spectroscopy (DRIFTS). The evolution of hydrogen was detected at temperatures above 620 K. The source of hydrogen was the solid state redox reaction of the metal with protons of the support. The samples exhibit catalytic activity in ethane aromatization indicating that zinc...... should be located at the same sites as in catalysts prepared by conventional methods. Combination of XANES and catalytic activity point to zinc being mainly present in tetrahedral geometry under reaction conditions....

  2. Isovector couplings for nucleon charge-exchange reactions at intermediate energies

    International Nuclear Information System (INIS)

    Love, W.G.; Nakayama, K.; Franey, M.A.

    1987-01-01

    The isovector parts of the effective nucleon-nucleon interaction are studied by examination of the reaction /sup 14/C(p,n) at intermediate energies near zero momentum transfer with use of recently developed G-matrix and free--t-matrix interactions. The spin-independent coupling (V/sub tau/) exhibits a strong energy and density dependence which, in the case of the G matrix based on the Bonn potential, significantly improves the agreement between calculated values of chemical bondV/sub σ//sub tau//V/sub tau/chemical bond 2 at q = 0 and those recently extracted from the reaction /sup 14/C

  3. Kinetic analysis of the reactivity of aliphatic cyclic alcohols and carboxylic acids in the T-for-H exchange reaction

    International Nuclear Information System (INIS)

    Tamura, Kiyoshi; Imaizumi, Hiroshi; Kano, Naoki

    2007-01-01

    In order to quantitatively evaluate the influence of tritium ( 3 He or T) on various functional groups in environment, the hydrogen isotope exchange reaction (T-for-H exchange reaction) between tritium-labeled poly-(vinyl alcohol) and each aliphatic cyclic alcohol (or carboxylic acid) has been dynamically observed in the range of 50 to 90degC. Consequently, the activities of the aliphatic cyclic alcohol and carboxylic acid increased with increasing reaction time. Applying in A''-McKay plot method to the observed data, the rate constants (k) for these materials were obtained. Using the k, the relation between the number of carbon atoms in the ring in each alcohol and the reactivity of the alcohol was quantitatively compared. Then, to clarify the effect of relative atomic charge of O atom (connected with the H atom in the hydroxy (or carboxy) group in the material) on the reactivity of the material, the MOPAC method was used. From both the above-mentioned and the obtained previously, the following nine items were found as to aliphatic cyclic alcohols (and carboxylic acids) in the T-for-H exchange reaction. (1) The reactivity of aliphatic cyclic alcohols (and carboxylic acids) depends on the temperature. (2) The reactivity of the cyclic materials decreases with increasing number of carbon atoms in the ring. (3) The reactivity of the aliphatic cyclic carboxylic acid seems to be smaller than that of aliphatic cyclic alcohol, and be larger than that of aliphatic cyclic amine. (4) For aliphatic cyclic alcohols, correlation exists between k and relative atomic charges of O atom obtained by the MOPAC method, but the tendency for aliphatic cyclic carboxylic acid is not clear. (5) As to having the same number of carbon atoms in each ring, the reactivity of the aliphatic cyclic carboxylic acid including the side chain is smaller than of the aliphatic cyclic carboxylic acid including no side chain. (6) The reactivity of aliphatic cyclic carboxylic acid is larger than that of

  4. Influence of exchange reactions in salt melts on cathodic reduction of nitrate ion

    International Nuclear Information System (INIS)

    Prisyazhnyj, V.D.; Chernukhin, S.I.; Kirillov, S.A.; Safronova, I.M.; Zayats, A.D.

    1981-01-01

    Potentiodynamical method has been used to investigate the process of cathodic reduction of nitrate ion in the melts of ternary mutual systems K + , Li + /NO 3- , Dsup(n-) and K + , B 2 + /NO 3 , Dsup(n-) (where B 2 + -Ba 2 + , Sr 2 + , Ca 2 + , and Dsup(n-)-Fsup(-), Cl - , Br - , SO 4- ). The investigations show, that the anion reduction depends on nitrate ion centration of two-charge metals. Influence of the composition of the first and second spheres of the nitrate ion ionic environment on electrode process parameters according to the value of free exchange energy is shown

  5. Isotopic exchange reactions. Kinetics and efficiency of the reactors using them in isotopic separation

    International Nuclear Information System (INIS)

    Ravoire, Jean

    1979-11-01

    In the first part, some definitions and the thermodynamic and kinetic isotopic effect concepts are recalled. In the second part the kinetic laws are established, in homogeneous and heterogeneous medium (one component being on occasions present in both phases), without and with isotopic effects. Emphasis is put on application to separation of isotopes, the separation factor α being close to 1, one isotope being in large excess with respect to the other one. Isotopic transfer is then given by: J = Ka (x - y/α) where x and y are the (isotopic) mole fractions in both phases, Ka may be either the rate of exchange or a transfer coefficient which can be considered as the 'same in both ways' if α-1 is small compared to the relative error on the measure of Ka. The third part is devoted to isotopic exchange reactors. Relationships between their efficiency and kinetics are established in some simple cases: plug cocurrent flow reactors, perfectly mixed reactors, countercurrent reactors without axial mixing. We treat only cases where α and the up flow to down flow ratio is close to 1 so that Murphee efficiency approximately overall efficiency (discrete stage contactors). HTU (phase 1) approximately HTU (phase 2) approximately HETP (columns). In a fourth part, an expression of the isotopic separative power of reactors is proposed and discussed [fr

  6. Ligand modeling and design

    Energy Technology Data Exchange (ETDEWEB)

    Hay, B.P. [Pacific Northwest National Lab., Richland, WA (United States)

    1997-10-01

    The purpose of this work is to develop and implement a molecular design basis for selecting organic ligands that would be used in the cost-effective removal of specific radionuclides from nuclear waste streams. Organic ligands with metal ion specificity are critical components in the development of solvent extraction and ion exchange processes that are highly selective for targeted radionuclides. The traditional approach to the development of such ligands involves lengthy programs of organic synthesis and testing, which in the absence of reliable methods for screening compounds before synthesis, results in wasted research effort. The author`s approach breaks down and simplifies this costly process with the aid of computer-based molecular modeling techniques. Commercial software for organic molecular modeling is being configured to examine the interactions between organic ligands and metal ions, yielding an inexpensive, commercially or readily available computational tool that can be used to predict the structures and energies of ligand-metal complexes. Users will be able to correlate the large body of existing experimental data on structure, solution binding affinity, and metal ion selectivity to develop structural design criteria. These criteria will provide a basis for selecting ligands that can be implemented in separations technologies through collaboration with other DOE national laboratories and private industry. The initial focus will be to select ether-based ligands that can be applied to the recovery and concentration of the alkali and alkaline earth metal ions including cesium, strontium, and radium.

  7. Rate coefficients of exchange reactions accounting for vibrational excitation of reagents and products

    Science.gov (United States)

    Kustova, E. V.; Savelev, A. S.; Kunova, O. V.

    2018-05-01

    Theoretical models for the vibrational state-resolved Zeldovich reaction are assessed by comparison with the results of quasi-classical trajectory (QCT) calculations. An error in the model of Aliat is corrected; the model is generalized taking into account NO vibrational states. The proposed model is fairly simple and can be easily implemented to the software for non-equilibrium flow modeling. It provides a good agreement with the QCT rate coefficients in the whole range of temperatures and reagent/product vibrational states. The developed models are tested in simulations of vibrational and chemical relaxation of air mixture behind a shock wave. The importance of accounting for excitated NO vibrational states and accurate prediction of Zeldovich reactions rates is shown.

  8. Gamow-Teller Strengths from (3He,t) Charge-Exchange Reaction

    International Nuclear Information System (INIS)

    Fujita, Yoshitaka

    2006-01-01

    Gamow-Teller (GT) transition is the most popular nuclear weak process with the nature of spin-isospin excitation. GT transitions in pf-shell nuclei, including those starting from unstable nuclei, are of interest, due to their importance in astrophysical processes. Weak processes, however, gives us rather limited information on the GT response of nuclei. We introduce high-resolution ( 3 He, t) reaction at 0 0 and at an intermediate beam energy as a new spectroscopic tool for studying GT excitations. Owing to the high energy-resolution of the reaction (∼ 30 keV), individual transitions can be observed up to the region of GT giant resonance. Assuming isospin symmetry for the T z = ±1 → 0 isobaric analogous transitions in isobars with mass number A, we present a new method to deduce GT transition strengths starting from proton rich exotic nuclei

  9. Novel support effects on the mechanism of propene-deuterium: Addition and exchange reactions over dispersed ZrO2

    International Nuclear Information System (INIS)

    Naito, Shuichi; Tanimoto, Mitsutoshi

    1995-01-01

    The effect on the rate and mechanisms of propene-deuterium reactions of dispersing ZrO 2 on various supports such as silica, alumina, and titanium dioxide has been studied by microwave spectroscopic analysis of monodeuteropropene as well as by kinetic investigation. By dispersal of ZrO 2 on these supports, the rate of the C 3 H 6 -D 2 reactions is increased considerbly compared to that over unsupported ZrO 2 , with the decrease of activation energy. Hydrogen exchange in propene proceeds simultaneously with addition via the associative mechanism through n-propyl and s-propyl intermediates. Through XPS analysis of ZrO 2 /SiO 2 , it was found that a monolayer of ZrO 2 is formed over the silica support. The monolayer catalyst exhibits catalytic behavior quite different from that of unsupported ZrO 2 . On the other hand, alumina surfaces modified by ZrO 2 layers may be the main active sites in the case of ZrO 2 /Al 2 O 3 . The marked enhancement of the reaction rate in the lower loading region of ZrO 2 /TiO 2 may be explained by the strong interaction of atomically dispersed zirconium ions with active centers on TiO 2 . 28 refs., 10 figs., 1 tab

  10. Development of Functional Inorganic Materials by Soft Chemical Process Using Ion-Exchange Reactions

    Science.gov (United States)

    Feng, Qi

    Our study on soft chemical process using the metal oxide and metal hydroxide nanosheets obtained by exfoliation their layered compounds were reviewed. Ni(OH)2⁄MnO2 sandwich layered nanostructure can be prepared by layer by-layer stacking of exfoliated manganese oxide nanosheets and nickel hydroxide layers. Manganese oxide nanotubes can be obtained by curling the manganese oxide nanosheets using the cationic surfactants as the template. The layered titanate oriented thin film can be prepared by restacking the titanate nanosheets on a polycrystalline substrate, and transformed to the oriented BaTiO3 and TiO2 thin films by the topotactic structural transformation reactions, respectively. The titanate nanosheets can be transformed anatase-type TiO2 nanocrystals under hydrothermal conditions. The TiO2 nanocrystals are formed by a topotactic structural transformation reaction. The TiO2 nanocrystals prepared by this method expose specific crystal plane on their surfaces, and show high photocatalytic activity and high dye adsorption capacity for high performance dye-sensitized solar cell. A series of layered basic metal salt (LBMS) compounds were prepared by hydrothermal reactions of transition metal hydroxides and organic acids. We succeeded in the exfoliation of these LBMS compounds in alcohol solvents, and obtained the transition metal hydroxide nanosheets for the first time.

  11. Deuterium exchange reaction in a trickle bed packed with a mixture of hydrophobic catalyst and hydrophilic packings

    International Nuclear Information System (INIS)

    Seungwoo Paek; Heui-Joo Choi; DO-Hee Ahn; Kwang-Rag Kim; Minsoo Lee; Sung-Paal Yim; Hongsuk Chung

    2006-01-01

    Full text of publication follows: The isotopic exchange reaction between hydrogen and water on the platinum supported catalysts provides a useful step for separating hydrogen isotopes such as deuterium and tritium. The CECE (Combined Electrolysis Catalytic Exchange) with a hydrophobic catalyst is a very effective method to remove small quantities of tritium from light or heavy waste water streams because of its high separation factor and mild operating conditions. The CECE column is composed of an electrolysis cell and a liquid phase catalytic exchange column. This paper deals with the experiments for the hydrogen isotopic exchange reaction in a trickle bed reactor packed with a hydrophobic catalyst in order to develop the catalytic column of the CECE. Hydrophobic Pt/SDBC catalyst which has been developed for the LPCE column of WTRF (Wolsong Tritium Removal Facility) was tested in a trickle bed reactor. The catalyst column was packed with a mixture of hydrophobic catalyst and hydrophilic packing (Dixon gauze ring) to improve liquid distribution and vapor/liquid transfer area. An experimental apparatus was built for the test of the catalyst at various temperatures and gas velocities. The catalyst was packed wet into the column and water was injected at the top through a liquid distributor and trickled through a catalyst mixture. Hydrogen gas passed up the column and deuterium was transferred to water stream flowing counter currently. The temperature of the column was controlled to maintain at 60 deg. C using water jackets around the reactor and equilibrator, a feed waster heater, and a circulation water heater. A metal bellows pump was used to circulate the hydrogen gas at the typical flow rate of 60 LPM.The reactor pressure was controlled to maintain at 135 kPa (abs) by a water column. Gas samples were drawn off from the top and bottom of the column. The difference in deuterium concentration between the inlet and outlet gas samples was analyzed using Gas

  12. Deuterium exchange reaction in a trickle bed packed with a mixture of hydrophobic catalyst and hydrophilic packings

    Energy Technology Data Exchange (ETDEWEB)

    Seungwoo Paek [KAERI (Korea, Republic of); Heui-Joo Choi; DO-Hee Ahn; Kwang-Rag Kim; Minsoo Lee; Sung-Paal Yim; Hongsuk Chung

    2006-07-01

    Full text of publication follows: The isotopic exchange reaction between hydrogen and water on the platinum supported catalysts provides a useful step for separating hydrogen isotopes such as deuterium and tritium. The CECE (Combined Electrolysis Catalytic Exchange) with a hydrophobic catalyst is a very effective method to remove small quantities of tritium from light or heavy waste water streams because of its high separation factor and mild operating conditions. The CECE column is composed of an electrolysis cell and a liquid phase catalytic exchange column. This paper deals with the experiments for the hydrogen isotopic exchange reaction in a trickle bed reactor packed with a hydrophobic catalyst in order to develop the catalytic column of the CECE. Hydrophobic Pt/SDBC catalyst which has been developed for the LPCE column of WTRF (Wolsong Tritium Removal Facility) was tested in a trickle bed reactor. The catalyst column was packed with a mixture of hydrophobic catalyst and hydrophilic packing (Dixon gauze ring) to improve liquid distribution and vapor/liquid transfer area. An experimental apparatus was built for the test of the catalyst at various temperatures and gas velocities. The catalyst was packed wet into the column and water was injected at the top through a liquid distributor and trickled through a catalyst mixture. Hydrogen gas passed up the column and deuterium was transferred to water stream flowing counter currently. The temperature of the column was controlled to maintain at 60 deg. C using water jackets around the reactor and equilibrator, a feed waster heater, and a circulation water heater. A metal bellows pump was used to circulate the hydrogen gas at the typical flow rate of 60 LPM.The reactor pressure was controlled to maintain at 135 kPa (abs) by a water column. Gas samples were drawn off from the top and bottom of the column. The difference in deuterium concentration between the inlet and outlet gas samples was analyzed using Gas

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

    Science.gov (United States)

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

    2006-12-01

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

  14. Solvent effects on the kinetics of the chlorine isotopic exchange reaction between chloride ion and O,O-diphenyl phosphorochloridate or O,O-diphenyl phosphorchloridothioate

    International Nuclear Information System (INIS)

    Mikolajczyk, M.; Slebocka-Tilk, H.; Reimschussel, W.

    1982-01-01

    The effect of solvent on the kinetics of the chlorine isotopic exchange reaction between 36 Cl- ions and O,O-diphenyl phosphorochloridate or O,O-diphenyl phosphorochloridothioate has been investigated in nitromethane, acetonitrile, propylene carbonate, benzonitrile, nitrobenzene, and hexamethyl-phosphoric triamide. The rate constants decrease with increasing electrophilicity of the solvent. A good correlation between the logarithm of the rate constants and acceptor number (AN) of the solvent was obtained with identical slopes for reactions with phosphoryl and thiophosporyl compounds. The slopes for the dependence of ΔH or TΔS vs. AN for chlorine isotopic exchange in (PHO) 2 pace are opposite those for the exchange reaction in (PHO) 2 PSCl, so a constant ratio of k/sub p=O//k/sub p=s/ is observed, resulting from compensation of ΔH by ΔS. The effect of solvent on the initial state (from solubility measurements) and the transition state of the reaction between (PhO) 2 PSCl and the Cl- ion was evaluated. Changes of solvation of (PHO) 2 PSCE have practically no effect on the kinetics of the reactions. Changes of solvation of the chloride ion and of the transition state primarily influence the rate constants and activation parameters of the investigated isotopic-exchange reaction

  15. Reaction of BH4- with [Mo2Cp2(mu-SMe)n] species to give tetrahydroborato, hydrido or dimetallaborane compounds: control of product by ancillary ligands.

    Science.gov (United States)

    Cabon, Nolwenn; Petillon, Francois Y; Schollhammer, Philippe; Talarmin, Jean; Muir, Kenneth W

    2004-09-07

    The reaction of mono- or dichloro-dimolybdenum(III) complexes [Mo2Cp2(mu-SMe)2(mu-Cl)(mu-Y)] (Cp=eta5-C5H5; 1, Y=SMe; 2, Y=PPh2; 3, Y=Cl) with NaBH4 at room temperature gave in high yields tetrahydroborato (8), hydrido (9) or metallaborane (12) complexes depending on the ancillary ligands. The correct formulation of derivatives and has been unambigously determined by X-ray diffraction methods. That of the hydrido compound 9 has been established in solution by NMR analysis and confirmed by an X-ray study of the mu-azavinylidene derivative [Mo2Cp2(mu-SMe)2(mu-PPh2)(mu-N=CHMe)] (10) obtained from the insertion of acetonitrile into the Mo-H bond of 9. Reaction of NaBH4 with nitrile derivatives, [Mo2Cp2(mu-SMe)4-n(CH3CN)2n]n+(5, n=1; 6 n=2), afforded the tetrahydroborato compound 8, together with a mu-azavinylidene species [Mo2Cp2(mu-SMe)3(mu-N=CHMe)](14), when n=1, and the metallaborane complex 12, together with a mixed borohydrato-azavinylidene derivative [Mo2Cp2(mu-SMe)2(mu-BH4)(mu-N=CHMe)] (13), when n=2. The molecular structures of these complexes have been confirmed by X-ray analysis. Preparations of some of the starting complexes (3 and 4) are also described, as are the molecular structures of the precursors [Mo2Cp2(mu-SMe)2(mu-X)(mu-Y)] (1, X/Y=Cl/SMe; 2, X/Y=Cl/PPh2; 4, X/Y=SMe/PPh2).

  16. Growing Platinum-Ruthenium-Tin ternary alloy nanoparticles on reduced graphene oxide for strong ligand effect toward enhanced ethanol oxidation reaction.

    Science.gov (United States)

    Xia, Qing Qing; Zhang, Lian Ying; Zhao, Zhi Liang; Li, Chang Ming

    2017-11-15

    Uniform Pt 1 Ru 0.5 Sn 0.5 ternary alloy nanoparticles are in situ deposited on reduced graphene oxide (Pt 1 Ru 0.5 Sn 0.5 -RGO) through its functional groups and defects as nucleation sites to greatly electrocatalyze ethanol oxidation reaction for much higher mass current densities, larger apparent specific current densities and better stability than commercial Pt-C catalyst (Pt-C(commer)). Mechanistic studies indicate that the excellent electrocatalytic activity and anti-poisoning are resulted from a strong ligand effect of the ternary alloy components, in which the charge transfer is boosted while decreasing the density of states close to the Fermi level of Pt to reduce bond energy between Pt and CO-like adsorbates for greatly improved anti-poisoning ability. This work holds a great promise to fabricate a high performance anode catalyst with a low Pt loading for direct ethanol fuel cells. Copyright © 2017. Published by Elsevier Inc.

  17. Coordination polymers of Fe(iii) and Al(iii) ions with TCA ligand: distinctive fluorescence, CO2 uptake, redox-activity and oxygen evolution reaction.

    Science.gov (United States)

    Dhara, Barun; Sappati, Subrahmanyam; Singh, Santosh K; Kurungot, Sreekumar; Ghosh, Prasenjit; Ballav, Nirmalya

    2016-04-28

    Fe and Al belong to different groups in the periodic table, one from the p-block and the other from the d-block. In spite of their different groups, they have the similarity of exhibiting a stable 3+ oxidation state. Here we have prepared Fe(iii) and Al(iii) based coordination polymers in the form of metal-organic gels with the 4,4',4''-tricarboxyltriphenylamine (TCA) ligand, namely Fe-TCA and Al-TCA, and evaluated some important physicochemical properties. Specifically, the electrical conductivity, redox-activity, porosity, and electrocatalytic activity (oxygen evolution reaction) of the Fe-TCA system were noted to be remarkably higher than those of the Al-TCA system. As for the photophysical properties, almost complete quenching of the fluorescence originating from TCA was observed in case of the Fe-TCA system, whereas for the Al-TCA system a significant retention of fluorescence with red-shifted emission was observed. Quantum mechanical calculations based on density functional theory (DFT) were performed to unravel the origin of such discriminative behaviour of these coordination polymer systems.

  18. Plasma Deposited Thin Iron Oxide Films as Electrocatalyst for Oxygen Reduction Reaction in Proton Exchange Membrane Fuel Cells

    Directory of Open Access Journals (Sweden)

    Lukasz JOZWIAK

    2017-02-01

    Full Text Available The possibility of using plasma deposited thin films of iron oxides as electrocatalyst for oxygen reduction reaction (ORR in proton exchange membrane fuel cells (PEMFC was examined. Results of energy-dispersive X-ray spectroscopy (EDX and X-ray photoelectron spectroscopy (XPS analysis indicated that the plasma deposit consisted mainly of FeOX structures with the X parameter close to 1.5. For as deposited material iron atoms are almost exclusively in the Fe3+ oxidation state without annealing in oxygen containing atmosphere. However, the annealing procedure can be used to remove the remains of carbon deposit from surface. The single cell test (SCT was performed to determine the suitability of the produced material for ORR. Preliminary results showed that power density of 0.23 mW/cm2 could be reached in the tested cell.DOI: http://dx.doi.org/10.5755/j01.ms.23.1.14406

  19. Quantum-tunneling isotope-exchange reaction H2+D-→HD +H-

    Science.gov (United States)

    Yuen, Chi Hong; Ayouz, Mehdi; Endres, Eric S.; Lakhamanskaya, Olga; Wester, Roland; Kokoouline, Viatcheslav

    2018-02-01

    The tunneling reaction H2+D-→HD +H- was studied in a recent experimental work at low temperatures (10, 19, and 23 K) by Endres et al. [Phys. Rev. A 95, 022706 (2017), 10.1103/PhysRevA.95.022706]. An upper limit of the rate coefficient was found to be about 10-18cm3 /s. In the present study, reaction probabilities are determined using the ABC program developed by Skouteris et al. [Comput. Phys. Commun. 133, 128 (2000), 10.1016/S0010-4655(00)00167-3]. The probabilities for ortho-H2 and para-H2 in their ground rovibrational states are obtained numerically at collision energies above 50 meV with the total angular momentum J =0 -15 and extrapolated below 50 meV using a WKB approach. Thermally averaged rate coefficients for ortho- and para-H2 are obtained; the largest one, for ortho-H2, is about 3.1 ×10-20cm3 /s, which agrees with the experimental results.

  20. Mechano-chemical synthesis K2MF6 (M = Mn, Ni) by cation-exchange reaction at room temperature

    Science.gov (United States)

    Rawat, Pooja; Nagarajan, Rajamani

    2018-02-01

    In order to establish the power of mechanochemistry to produce industrially important phosphors, synthesis of K2MnF6 has been attempted by the successive grinding reactions of manganese (II) acetate with ammonium fluoride and potassium fluoride. The progress of reaction was followed by ex-situ characterization after periodic intervals of time. Cubic symmetry of K2MnF6 was evident from its powder X-ray diffraction pattern which was refined successfully in cubic space group (Fm-3m) with a = 8.4658 (20) Å. Stretching and bending vibration modes of MnF62- octahedral units appeared at 740 and 482 cm-1 in the fourier transformed infrared spectrum. Bands at 405 and 652 cm-1 appeared in the Raman spectrum and they were finger-print positions of cubic K2MnF6. Other than the ligand to metal charge transfer transition at 242 nm, transitions from 4A2g to 4T1g, 4T2g and 2T2g of Mn4+-ion appeared at 352, 429, 474 and 569 nm in the UV-visible diffuse reflectance spectrum of the sample. Red emission due to Mn4+ was observed in the photoluminescence spectrum with a decay time of 0.22 ms. Following the success in forming cubic K2MnF6, this approach has been extended to synthesize cubic K2NiF6 at room temperature. All these results confirmed the susceptibility of acetate salts of transition metals belonging to first-row of the periodic table to facile fluorination at room temperature aided by mechanical forces.

  1. Two-body hypercharge-exchange reactions in K-p and π+p interactions at 10 and 16 GeV/c

    International Nuclear Information System (INIS)

    Girtler, P.; Otter, G.; Sliwa, K.; Barnham, K.W.J.; Eason, R.M.; Newham, P.; Pollock, B.; Wells, J.; Mandl, F.; Markytan, M.

    1979-01-01

    Cross section values or upper limits are presented for twenty-five two-body hypercharge-exchange reactions in K - p and π + p interactions at 10 and 16 GeV/c. The 16 GeV/c results are compared with some predictions of line-reversal plus exchange-degenerate Regge poles, of SU(3) and of the additive quark model. Agreement is found in all cases. (author)

  2. Kinetics of exchange reaction between neodymium(3) transcyclohexanediaminetetraacetate and europium(3)- and holmium(3) aquo-ions in the H2O and D2O solutions

    International Nuclear Information System (INIS)

    Nikitenko, S.I.; Martynenko, L.I.; Pechurova, N.I.; Spitsyn, V.I.

    1983-01-01

    The exchange reaction between central ions in the NdD - Ln' 3+ systems, where Ln' 3+ is a substituting cation (Eu 3+ and Ho 3+ , D 4 =cyclohexanediaminetetraacetate) is studied and the electrophilic suhstitution mechanism is considered. To study the kinetic isotope effects, the reagents have been solVed in heavy water containing 99.9% D 2 O. The electrophilic substitution in the indicated systems proceeds through the dissociative mechanism catalyzed by protons and via the spontaneous dissociation mechanism. The exchange via the acid-catalyzed mechanism is limited by the intermediate protonated complex decay. The associative mechanism of the electrophilic exchange in the studied systems is not realized

  3. Enhanced bimolecular exchange reaction through programmed coordination of a five-coordinate oxovanadium complex for efficient redox mediation in dye-sensitized solar cells.

    Science.gov (United States)

    Oyaizu, Kenichi; Hayo, Noriko; Sasada, Yoshito; Kato, Fumiaki; Nishide, Hiroyuki

    2013-12-07

    Electrochemical reversibility and fast bimolecular exchange reaction found for VO(salen) gave rise to a highly efficient redox mediation to enhance the photocurrent of a dye-sensitized solar cell, leading to an excellent photovoltaic performance with a conversion efficiency of 5.4%. A heterogeneous electron-transfer rate constant at an electrode (k0) and a second-order rate constant for an electron self-exchange reaction (k(ex)) were proposed as key parameters that dominate the charge transport property, which afforded a novel design concept for the mediators based on their kinetic aspects.

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

    International Nuclear Information System (INIS)

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

    1983-01-01

    Differential cross sections have been measured for the (p,n) reaction to the isobaric analog states of 181 Ta, 197 Au, 209 Bi, 232 Th, and 238 U at an incident energy of 27 MeV. Because of the importance of collective effects in this mass region, coupled-channel calculations have been carried out in the analysis of the data. Optical potentials obtained from the Lane model for the charge exchange reaction have been used in the simultaneous analysis of coupled proton and neutron channels. The sensitivity of the calculations to the different couplings between the levels and to the magnitude of the isovector potentials, V 1 and W 1 , is discussed. The good agreement obtained between the measured and calculated (p,n) angular distributions to the analog state confirms the validity of the Lane formalism for high-Z nuclei (Z> or =50). Elastic neutron differential cross sections inferred from the coupled-channel analysis are compared with measurements available in the literature in the energy range 7--8 MeV. The results of these calculations agree with the measured values as well as the results of calculations made using global neutron optical potential parameters optimized to fit neutron data

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

    Science.gov (United States)

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

    2013-08-22

    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 λin has been directly calculated. For solvent reorganization energy λs, a novel and reasonable nonequilibrium solvation model is established by introducing a constrained equilibrium manipulation, and a new expression of λs has been formulated. It is found that λs 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 λ 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.

  6. Self-assembled monolayer exchange reactions as a tool for channel interface engineering in low-voltage organic thin-film transistors.

    Science.gov (United States)

    Lenz, Thomas; Schmaltz, Thomas; Novak, Michael; Halik, Marcus

    2012-10-02

    In this work, we compared the kinetics of monolayer self-assembly long-chained carboxylic acids and phosphonic acids on thin aluminum oxide surfaces and investigated their dielectric properties in capacitors and low-voltage organic thin-film transistors. Phosphonic acid anchor groups tend to substitute carboxylic acid molecules on aluminum oxide surfaces and thus allow the formation of mixed or fully exchanged monolayers. With different alkyl chain substituents (n-alkyl or fluorinated alkyl chains), the exchange reaction can be monitored as a function of time by static contact angle measurements. The threshold voltage in α,α'-dihexyl-sexithiophene thin-film transistors composed of such mixed layer dielectrics correlates with the exchange progress and can be tuned from negative to positive values or vice versa depending on the dipole moment of the alkyl chain substituents. The change in the dipole moment with increasing exchange time also shifts the capacitance of these devices. The rate constants for exchange reactions determined by the time-dependent shift of static contact angle, threshold voltage, and capacitance exhibit virtually the same value thus proving the exchange kinetics to be highly controllable. In general, the exchange approach is a powerful tool in interface engineering, displaying a great potential for tailoring of device characteristics.

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

    KAUST Repository

    Fornander, Louise H

    2013-12-03

    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.

  8. Demonstration of Synaptic Behaviors and Resistive Switching Characterizations by Proton Exchange Reactions in Silicon Oxide

    Science.gov (United States)

    Chang, Yao-Feng; Fowler, Burt; Chen, Ying-Chen; Zhou, Fei; Pan, Chih-Hung; Chang, Ting-Chang; Lee, Jack C.

    2016-02-01

    We realize a device with biological synaptic behaviors by integrating silicon oxide (SiOx) resistive switching memory with Si diodes. Minimal synaptic power consumption due to sneak-path current is achieved and the capability for spike-induced synaptic behaviors is demonstrated, representing critical milestones for the use of SiO2-based materials in future neuromorphic computing applications. Biological synaptic behaviors such as long-term potentiation (LTP), long-term depression (LTD) and spike-timing dependent plasticity (STDP) are demonstrated systematically using a comprehensive analysis of spike-induced waveforms, and represent interesting potential applications for SiOx-based resistive switching materials. The resistive switching SET transition is modeled as hydrogen (proton) release from (SiH)2 to generate the hydrogen bridge defect, and the RESET transition is modeled as an electrochemical reaction (proton capture) that re-forms (SiH)2. The experimental results suggest a simple, robust approach to realize programmable neuromorphic chips compatible with large-scale CMOS manufacturing technology.

  9. Optimization of the Pd-Fe-Mo Catalysts for Oxygen Reduction Reaction in Proton-Exchange Membrane Fuel Cells

    International Nuclear Information System (INIS)

    Lee, Yeayeon; Jang, Jeongseok; Lee, Jin Goo; Jeon, Ok Sung; Kim, Hyeong Su; Hwang, Ho Jung; Shul, Yong Gun

    2016-01-01

    Highlights: • Pd-Mo-Fe catalysts show high catalytic activity and stability for oxygen-reduction reactions in acid media. • The optimum compositions were 7.5:1.5:1.0 for Pd-Fe-Mo, and the optimum temperatures were 500 °C. • The Pd-Fe-Mo catalysts were successfully applied to the PEMFC cathode, showing ∼500 mA cm −1 at 0.6 V. • The lattice constant was strongly related to the activity and stability of the catalysts for oxygen-reduction reactions. - Abstract: Highly active and durable non-platinum catalysts for oxygen-reduction reaction (ORR) have been developed for energy conversion devices such as proton-exchange membrane fuel cells (PEMFCs). In this study, Pd-Fe-Mo catalyst is reported as a non-platinum catalyst for ORR. The atomic ratio and annealing temperatures are controlled on the catalysts to understand interplay between their physical and chemical properties and electrochemical activities. The Pd-Fe-Mo catalyst optimized with 7.5:1.5:1.0 of the atomic ratio and 500 °C of the annealing temperature shows 32.18 mA mg −1 PGM (PGM: platinum group metal) of the kinetic current density at 0.9 V for ORR, which is comparable to that of commercial Pt/C catalyst. The current density is degraded to 6.20 mA mg −1 PGM after 3000 cycling of cyclic voltammetry, but it is greatly enhanced value compared to other non-platinum catalysts. In actual application to PEMFCs, the 20% Pd-Fe-Mo catalyst supported on carbons exhibits a high performance of 506 mA cm −2 at 0.6 V. The results suggest that the Pd-Fe-Mo catalyst can be a good candidate for non-platinum ORR catalysts.

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

    Science.gov (United States)

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

    2011-11-14

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

  11. Time resolved investigations on biogenic trace gases exchanges using proton-transfer-reaction mass spectrometry

    International Nuclear Information System (INIS)

    Karl, T.

    2000-02-01

    Volatile organic compounds (VOCs) released from vegetation, including wound-induced VOCs, can have important effects on atmospheric chemistry. The analytical methods for measuring wound-induced VOCs, especially the hexenal family of VOCs (hexenals, hexenols and hexenyl esters) but also compounds like acetaldehyde, are complicated by their chemical instability and the transient nature of their formation after leaf and stem wounding. The goal of this thesis was to assess, quantify and complement our understanding on the origin of tropospheric VOCs. This thesis demonstrates that formation and emission of hexenal family compounds can be monitored on-line using proton-transfer-reaction mass spectrometry (PTR-MS), avoiding the need for preconcentration or chromatography. These measurements revealed the rapid emission of the parent compound, (Z)-3-hexenal, within 1-2 seconds of wounding of leaves from various woody and nonwoody plants, and its metabolites including (E)-2-hexenal, hexenols and hexenyl acetates. Emission of (Z)-3-hexenal from detached, drying leaves averaged 500 μg (gram dry weight)-1. PTR-MS showed to be a useful tool for the analysis of VOC emissions resulting from grazing, herbivory, harvesting and senescing leaves. The release of reactive VOCs during lawn mowing was observed in on-line ambient air measurements in July and August 1998 in the outskirts of Innsbruck. Also obtained were data on emission rates of reactive aldehydes (hexenyl compounds) and other abundant VOCs such as methanol, acetaldehyde and acetone from drying grass in various chamber experiments. Fluxes were measured after cutting of grass using eddy covariance measurements and the micrometeorological gradient method (Obhukov-Similarity-Method). Comparison of data obtained by these different methods showed satisfactory agreement. The highest fluxes for methanol during drying were 5 mg/m2h, for (Z)-3-hexenal 1.5 mg/m2h. Experiments conducted on the Sonnblick Observatory in Fall and Winter

  12. Ion exchange equilibrium constants

    CERN Document Server

    Marcus, Y

    2013-01-01

    Ion Exchange Equilibrium Constants focuses on the test-compilation of equilibrium constants for ion exchange reactions. The book first underscores the scope of the compilation, equilibrium constants, symbols used, and arrangement of the table. The manuscript then presents the table of equilibrium constants, including polystyrene sulfonate cation exchanger, polyacrylate cation exchanger, polymethacrylate cation exchanger, polysterene phosphate cation exchanger, and zirconium phosphate cation exchanger. The text highlights zirconium oxide anion exchanger, zeolite type 13Y cation exchanger, and

  13. Production of 13C by chemical exchange reaction between amine carbamate and carbon dioxide in a solvent-carrier system

    International Nuclear Information System (INIS)

    Ghate, M.R.; Taylor, T.I.

    1975-01-01

    The chemical exchange reaction between amine carbamate and CO 2 has been investigated for the purpose of using it as a practical method to concentrate 13 C. The effects of solvent, concentration of amines, catalysts, flow rate, and diameter of the column have been studied for a number of amines. Of the solutions studied, di-n-butylamine (DNBA) in triethylamine (TEA) as a solvent proved to be the most favorable for use in the preparation of highly enriched 13 C. The overall separations obtained as a function of the concentration of DNBA using 2.5 cm i.d. x 100 cm column ranged from 2.05 at 1 M to 1.69 at 2.84 M. For 2 M DNBA the maximum separation was 1.94. At this concentration of DNBA the overall separation as a function of flow rate ranged from 1.94 at 0.845 ml/cm 2 -min to 1.31 at 2.9 ml/cm 2 -min. Neither the rate of exchange nor the overall separations were improved by use of catalysts. Increasing the diameter twofold resulted in little or no loss in overall separations. On the basis of the properties of the system and the data obtained with respect to the above variables, design calculations were made for a six-stage tapered cascade. These calculations were based on a flow of 40 ml/min of 2 M DNBA in TEA, giving a maximum transport of 7.1 x 10 -3 mmole/min or a maximum production rate of 130 mg 13 C/day. The cascade was operated for about 5 months during which period gram quantities of 67 percent 13 C were produced

  14. Correcting ligands, metabolites, and pathways

    NARCIS (Netherlands)

    Ott, M.A.; Vriend, G.

    2006-01-01

    BACKGROUND: A wide range of research areas in bioinformatics, molecular biology and medicinal chemistry require precise chemical structure information about molecules and reactions, e.g. drug design, ligand docking, metabolic network reconstruction, and systems biology. Most available databases,

  15. Presolvated Electron Reactions with Methyl Acetoacetate: Electron Localization, Proton-Deuteron Exchange, and H-Atom Abstraction

    Directory of Open Access Journals (Sweden)

    Alex Petrovici

    2014-09-01

    Full Text Available 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.

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

    Science.gov (United States)

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

    2014-09-01

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

  17. Two approaches to the clinical dilemma of treating TTP with therapeutic plasma exchange in patients with a history of anaphylactic reactions to plasma.

    Science.gov (United States)

    Sidhu, Davinder; Snyder, Edward L; Tormey, Christopher A

    2017-06-01

    Thrombotic thrombocytopenic purpura (TTP) is a rare but serious disease caused by autoantibody-mediated deficiency in von Willebrand factor (VWF) cleaving protease, ADAMTS-13. The primary acute treatment is therapeutic plasma exchange (TPE). However, some patients can develop allergic/anaphylactic reactions to the replacement (i.e., donor) plasma over time. Two potential treatment strategies for patients with TTP who demonstrate severe allergic reactions to plasma used for exchange were examined. Two patients with TTP exacerbations who developed severe allergic reactions to donor plasma were identified. One patient's TPE was re-initiated with Octaplas, a lot-batched solvent and detergent treated, type-specific, pooled donor plasma product. The other patient was exchanged with primarily albumin, followed by slow incremental exposures to donor plasma to mitigate exposures and allergic risks. Both patients were assessed for anaphylaxis. Both treatment strategies were successful in preventing any further clinically significant allergic/anaphylactic reactions and facilitated both patients' TTP remissions. Based on our experience with two similar patients with TTP exacerbations and history of anaphylactic reactions to plasma during TPE, we have identified two possible treatment protocols to achieve remission in this clinical dilemma. Substituting Octaplas for standard plasma or, alternatively, using albumin with slowly increasing amounts of standard plasma may help to mitigate the risk of further anaphylactic adverse events. J. Clin. Apheresis 32:158-162, 2017. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  18. Reaction

    African Journals Online (AJOL)

    abp

    19 oct. 2017 ... Reaction to Mohamed Said Nakhli et al. concerning the article: "When the axillary block remains the only alternative in a 5 year old child". .... Bertini L1, Savoia G, De Nicola A, Ivani G, Gravino E, Albani A et al ... 2010;7(2):101-.

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

    Science.gov (United States)

    Miller, Matthew P.; McKnight, Diane M.; Cory, R.M.; Williams, Mark W.; Runkel, Robert L.

    2006-01-01

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

  20. Synthesis and characterization of the Bis- Cyclometalating Ligand 3,3',5,5'-tetrakis[(dimethylamino)methyl]biphenyl and its use in the preparation of bimetallic M(II), M(IV) (M = Pt, Pd) and mixed-valence Pt(II)-Pt(IV) complexes via a dilithio-derivative. Crystal structure of the Pd dimer [ClPd{2,6-(Me2NCH2)2C6H2}]2,

    NARCIS (Netherlands)

    Koten, G. van; Lagunas, M.C.; Gossage, R.A.; Spek, A.L.

    1998-01-01

    The potentially bis-cyclometalating ligand 3,3',5,5'-tetrakis[(dimethylamino)methyl]biphenyl, was prepared from 3,5-(Me2NCH2)2C6H3Br in a one-pot synthesis involving lithium-halogen exchange, transmetalation, and reductive-elimination reactions. This ligand undergoes selective dilithiation in the 4

  1. Gamma irradiation effects of 51Cr(III) isotope exchange in doped magnesium chromate - zinc chromate mixtures

    International Nuclear Information System (INIS)

    Mahfouz, R.M.

    1984-01-01

    Gamma irradiation effects of 51 Cr(III) isotope exchange in magnesium chromate - zinc chromate mixtures doped with 51 Cr(III) were investigated. It was found that γ irradiation has an oxidation effect and the percentage of exchanged 51 Cr(VI) increases with the increasing γ-ray dose. The data are explained in terms of mechanistic model involving metal and ligand vacancies exchange and substitution reactions. (author)

  2. Coupled transport/reaction modelling with ion-exchange: Study of the long-term properties of bentonite buffer in a final repository

    International Nuclear Information System (INIS)

    Liu Jinsong; Neretnieks, I.

    1997-05-01

    Possible transformation of Na-montmorillonite to Ca-montmorillonite, by ion exchange, in the bentonite buffer in a final repository for spent nuclear fuel can lead to a drastic decrease in the swelling capacity and a significant increase in the permeability of the bentonite. The ion exchange mechanism has been studied, by using the coupled transport/reaction model. In most typical sites of the granite bedrock where there are no large fractures, groundwater flow is limited. The results of this study show that the ion-exchange process will be very slow in this case. Only a few percent of the total Na-montmorillonite is exchanged within 1 to 10 thousand years. When the groundwater flow in the bedrock is assumed to be unlimited, an upper bound of the conditions of the water flow, a sharp ion-exchange front can be formed and propagate within the bentonite buffer. When the groundwater is assumed to be the Aespoe water, with a high Ca concentration, the break-through time of the ion-exchange front can be a few thousand years. When the water is assumed to be Allard water with low Ca concentration, the break-through time can be as long as 10 5 to 10 6 years. When a canister has manufacturing defects, both the pyrite oxidation and the ion-exchange processes can occur simultaneously. A redox front and an ion-exchange front develop from both sides of the bentonite buffer. before the two fronts meet, they travel relatively independently in the bentonite. After they have met, they interact only marginally. Even if a large scale ion-exchange happens, the release of the dissolved uranium species from the bentonite to the rock can still be extremely small. The release is mainly controlled by the redox potential of pyrite oxidation

  3. Slow Histidine H/D Exchange Protocol for Thermodynamic Analysis of Protein Folding and Stability using Mass Spectrometry

    OpenAIRE

    Tran, Duc T.; Banerjee, Sambuddha; Alayash, Abdu I.; Crumbliss, Alvin L.; Fitzgerald, Michael C.

    2012-01-01

    Described here is a mass spectrometry based protocol to study the thermodynamic stability of proteins and protein-ligand complexes using the slow H/D exchange reaction of the imidazole C2 proton in histidine side chains. The protocol, which involves evaluating the denaturant dependence of this slow H/D exchange reaction in proteins, allows the global and/or subglobal unfolding/refolding properties of proteins and protein-ligand complexes to be probed. The protocol is developed using several m...

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

    Science.gov (United States)

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

    2014-08-01

    Carbon-supported Pt, Pd, Pd-Pt core-shell (Pt(shell)-Pd(core)/C) and Ir-decorated Pd-Pt core-shell (Ir-decorated Pt(shell)-Pd(core)/C) catalysts were synthesized, and their physical properties, electrochemical behaviors, oxygen reduction reaction (ORR) characteristics and proton exchange membrane fuel cell (PEMFC) performances were investigated herein. From the XRD patterns and TEM images, Ir-decorated Pt(shell)-Pd(core)/C has been confirmed that Pt was deposited on the Pd nanoparticle which had the core-shell structure. Ir-decorated Pt(shell)-Pd(core)/C has more positive OH reduction peak than Pt/C, which is beneficial to weaken the binding energy of Pt-OH during the ORR. Thus, Ir-decorated Pt(shell)-Pd(core)/C has higher ORR activity than Pt/C. The maximum power density of H2-O2 PEMFC using Ir-decorated Pt(shell)-Pd(core)/C is 792.2 mW cm(-2) at 70°C, which is 24% higher than that using Pt/C. The single-cell accelerated degradation test of PEMFC using Ir-decorated Pt(shell)-Pd(core)/C shows good durability by the potential cycling of 40,000 cycles. This study concludes that Ir-decorated Pt(shell)-Pd(core)/C has the low Pt content, but it can facilitate the low-cost and high-efficient PEMFC. Copyright © 2013 Elsevier Inc. All rights reserved.

  5. Effects of Surfactants on the Rate of Chemical Reactions

    Directory of Open Access Journals (Sweden)

    B. Samiey

    2014-01-01

    Full Text Available Surfactants are self-assembled compounds that depend on their structure and electric charge can interact as monomer or micelle with other compounds (substrates. These interactions which may catalyze or inhibit the reaction rates are studied with pseudophase, cooperativity, and stoichiometric (classical models. In this review, we discuss applying these models to study surfactant-substrate interactions and their effects on Diels-Alder, redox, photochemical, decomposition, enzymatic, isomerization, ligand exchange, radical, and nucleophilic reactions.

  6. General Tritium Labelling of Gentamicin C by catalytic hydrogen exchange Reaction with Tritiated Water; Marcado general con tritio de la Gentamicina C por intercambio catalitico con agua triatiada

    Energy Technology Data Exchange (ETDEWEB)

    Suarez, C; Diaz, D; Paz, D

    1991-07-01

    Gentamicin C was labelled with tritium by means of a PtO2 catalyzed hydrogen exchange reaction. Under the conditions of the exchange (100 mg of gentamicin, basic form, 0,3 ml H2O-3H, and 50 mg of prereduced PtO2) the radiochemical yield was 0,24, 0,38 and 0,48 % at 120 degree celsius, for 8, 16 and 24 hours respectively. Chemical yield for purified gentamicin was about 60 %. Purification was accomplished with a cellulose column eluted with the lower phase of chloroform-methanol 17 % ammonium hydroxide (2:1:1, v/v) . Chemical purity, determined by HPLC, was 96,5 % and radiochemical one was 95. Main exchange degradation products show biological activity. (Author) 12 refs.

  7. The influence of the charge-exchange reactions of carbon in the photoionization models for spectrum-line emitting region in the quasi-stellar objects

    International Nuclear Information System (INIS)

    Souza Pellegrini, P.S. de.

    1976-08-01

    The charge exchange reactions: C +2 + H sub(e) 0 → H +1 + C +1 and C +2 + H 0 → H +1 + C +1 were taken into account in the ionization equilibrium of Carbon in photoionization models for line emitting regions of quasi-stellar objects. The new ionization structure of Carbon was obtained and the intensities of the most important emission lines of this element usually observed in QSO's with large redshifts were calculated. The charge exchange with Hidrogen produces negligible effects while the importance of taking into account the charge exchange with Helium can be seen from the change of the ionization structure of Carbon in all considered models. The homogeneous optically thin model is shown not to be consistent with the observations. For non homogeneous optically thick models observable changes in line intensities occur when in the region where charge exhange is dominant the electron density is high enough to produce collisional excitation and consequent line emission. (Author)

  8. Light-Induced Copper(II) Coordination by a Bicyclic Tetraaza Chelator through a Ligand-to-Metal Charge-Transfer Reaction

    DEFF Research Database (Denmark)

    Holm-Jørgensen, Jacob Rørdam; Jensen, Mikael; Bjerrum, Morten J.

    2011-01-01

    coordinated amine groups) at pH above 6. These findings are supported by pH titrations of mixtures of Cu2+ and [24.31]adz in water. Irradiation of this complex in the ligand-to-metal charge-transfer (LMCT) band by a diode-array spectrophotometer leads to photodeprotonation and subsequently to formation...

  9. Iminobisphosphines to (non-)symmetrical diphosphinoamine ligands : Metal-induced synthesis of diphosphorus nickel complexes and application in ethylene oligomerisation reactions

    NARCIS (Netherlands)

    Boulens, Pierre; Lutz, Martin|info:eu-repo/dai/nl/304828971; Jeanneau, Erwann; Olivier-Bourbigou, Hélène; Reek, Joost N H; Breuil, Pierre Alain R

    2014-01-01

    We describe the synthesis of a range of novel iminobisphosphine ligands based on a sulfonamido moiety [R1SO2N=P(R 2)2-P(R3)2]. These molecules rearrange in the presence of nickel by metal-induced breakage of the P-P bond to yield symmetrical and nonsymmetrical diphosphinoamine nickel complexes of

  10. Deprotonation induced ligand-to-metal electron transfer: Synthesis of a mixed-valence Rh(-I,I) dinuclear compound and its reaction with dioxygen

    NARCIS (Netherlands)

    Tejel, C.; Ciriano, M.A.; del Río, M.P.; van den Bruele, F.J.; Hetterscheid, D.G.H.; Tsichlis i Spithas, N.; de Bruin, B.

    2008-01-01

    Treatment of bis(2-picolyl)amine (bpa) with [{Rh(nbd)(mu-OMe))(2)] leads to unexpected and unique redox asymmetric dinuclear Rh-I, Rh+I complex [{Rh(ndb)}(2)(bpa-2H)] (2) with a pi-coordinating imine bound to a tetrahedral low valent rhodate(-I). Mono-oxygenation of the deprotonated bpa ligand in 2

  11. Interference effects in inclusive charge-exchange p+p→n+X and n+p→p+X reactions at intermediate energies

    International Nuclear Information System (INIS)

    Gareev, F.A.; Ratis, Yu.L.; Korovin, P.P.; Strokovskij, E.A.; Vaagen, J.S.

    1992-01-01

    The formalism of Feynman diagrams to describe charge-exchange reactions p+p→n+X and n+p→p+X on a free proton target taking into account spectator and decay modes in the π+ρ+g'-model have used. It is shown that the interference between these modes depends on the set of vertex function parameters used. It is also shown that the constructive interference of the Δ + and Δ 0 -isobars is important. 22 refs.; 10 figs

  12. Line-emission cross sections for the charge-exchange reaction between fully stripped carbon and atomic hydrogen in tokamak plasma

    International Nuclear Information System (INIS)

    Ida, K.; Kato, T.

    1992-01-01

    Line-emission cross sections of the charge-exchange reaction between fully stripped carbon and atomic hydrogen are measured in the energy range of 18 - 38 keV/amu in tokamak plasmas. The energy dependence of the emission cross sections for the transition of Δn = 8 - 7 and Δn = 7 - 6 and their ratios are compared with theoretical calculations. (author)

  13. Molecular beam scattering experiments on the abstraction and exchange reactions of deuterium atoms with the hydrogen halides HCl, HBr, and HI

    International Nuclear Information System (INIS)

    Bauer, W.; Rusin, L.Y.; Toennies, J.P.

    1978-01-01

    Molecular beam scattering experiments have been carried out on the abstraction and exchange reactions of deuterium atoms (T=2600 K) with the hydrogen halides HX(T=300 K) in the range of scattering angles: 0 0 0 (theta/sub cm/=0 0 is the direction of the incident D-atom beam). The apparatus employed a very sensitive electron bombardment detector with a sufficiently low H 2 background to make possible the measurement of differential cross sections of about 0.1 A 2 /sr for reactively scattered HD and H and nonreactively scattered D-atoms. The measured HD signal can be largely attributed to various background sources and only serves to establish a rough upper limit on the abstraction cross section in the angular range investigated. The H-atom signal was more intense. The observed angular distribution was forward peaked, and is attributed to the exchange reaction. The nonreactively scattered D-atom signal was used in conjunction with a recently reported effective spherically symmetric potential to provide an absolute calibration of the detector sensitivity. The measured integral cross sections for the exchange reactions are 2.3 A 2 (D+HCl), 1.3 A 2 (D+HBr) and 1.6 A 2 (D+HI) with an estimated error of about +- 30%. The absolute cross sections and the H-atom angular distributions are consistent with the DX distributions measured by McDonald and Herschbach. Both experimental angular distributions are considerably narrower than those predicted by the recent classical trajectory calculations of Raff, Suzukawa, and Thompson. The implications of the new data for the activation energies for the exchange reactions are discussed

  14. Polarization observables of the d-vector p-vector → p-vector d reaction and one-neutron-exchange approximation

    International Nuclear Information System (INIS)

    Kobushkin, A.P.; Syamtomov, A.I.; Perdrisat, C.F.; Punjabi, V.

    1994-01-01

    The polarization observables in the elastic scattering of polarized deuterons on a polarized hydrogen target, with measurement of the recoil proton polarization, are considered. The observables are calculated in the one-neutron exchange approximation, for the special case of backward scattering (Θ c.m = 180 degree). Several new relations between polarization observables of the reaction are derived within the framework of this approximation. (author). 20 refs., 3 figs

  15. Iron-platinum multilayer thin film reactions to form L1(0) iron-platinum and exchange spring magnets

    Science.gov (United States)

    Yao, Bo

    FePt films with the L10 phase have potential applications for magnetic recording and permanent magnets due to its high magnetocrystalline anisotropy energy density. Heat treatment of [Fe/Pt] n multilayer films is one approach to form the L10 FePt phase through a solid state reaction. This thesis has studied the diffusion and reaction of [Fe/Pt]n multilayer films to form the L10 FePt phase and has used this understanding to construct exchange spring magnets. The process-structure-property relations of [Fe/Pt] n multilayer films were systematically examined. The transmission electron microscopy (TEM) study of the annealed multilayers indicates that the Pt layer grows at the expense of Fe during annealing, forming a disordered fcc FePt phase by the interdiffusion of Fe into Pt. This thickening of the fcc Pt layer can be attributed to the higher solubilities of Fe into fcc Pt, as compared to the converse. For the range of film thickness studied, a continuous L10 FePt product layer that then thickens with further annealing is not found. Instead, the initial L10 FePt grains are distributed mainly on the grain boundaries within the fcc FePt layer and at the Fe/Pt interfaces and further transformation of the sample to the ordered L10 FePt phase proceeds coupled with the growth of the initial L10 FePt grains. A comprehensive study of annealed [Fe/Pt]n films is provided concerning the phase fraction, grain size, nucleation/grain density, interdiffusivity, long-range order parameter, and texture, as well as magnetic properties. A method based on hollow cone dark field TEM is introduced to measure the volume fraction, grain size, and density of ordered L10 FePt phase grains in the annealed films, and low-angle X-ray diffraction is used to measure the effective Fe-Pt interdiffusivity. The process-structure-properties relations of two groups of samples with varying substrate temperature and periodicity are reported. The results demonstrate that the processing parameters

  16. $\\beta$- decay of $^{58}$Zn. A critical test for the charge-exchange reaction as a probe for the $\\beta$- decay strength distribution

    CERN Multimedia

    2002-01-01

    % IS353 \\\\ \\\\ Due to its importance in fundamental physics and astrophysics, a great effort both theoretically and experimentally is devoted to study Gamow Teller (GT)-strength. The GT-strength and its distribution play a key role in late stellar evolution. During the pre-supernova core-collapse of massive stars, the electron capture and nuclear $\\beta$ -decay determine the electron-to-baryon ratio, which influences the infall dynamics and the mass of the final core. The cross-section of the charge-exchange reaction at forward angles with energies above 100~MeV is expected to be proportional to the squares of Fermi and GT matrix elements. This proportionality should provide a Q-value free method to probe the weak interaction strength and renormalization effects in nuclei. Thus charge-exchange reactions are often used to determine the experimental GT-strength. However, the connection between the GT-strength and the cross-section of the charge-exchange reaction is partially model-dependent and the question aris...

  17. Improved Oxygen Reduction Activity and Durability of Dealloyed PtCox Catalysts for Proton Exchange Membrane Fuel Cells: Strain, Ligand, and Particle Size Effects

    Science.gov (United States)

    Jia, Qingying; Caldwell, Keegan; Strickland, Kara; Ziegelbauer, Joseph M.; Liu, Zhongyi; Yu, Zhiqiang; Ramaker, David E.; Mukerjee, Sanjeev

    2015-01-01

    The development of active and durable catalysts with reduced platinum content is essential for fuel cell commercialization. Herein we report that the dealloyed PtCo/HSC and PtCo3/HSC nanoparticle (NP) catalysts exhibit the same levels of enhancement in oxygen reduction activity (~4-fold) and durability over pure Pt/C NPs. Surprisingly, ex situ high-angle annular dark field scanning transmission electron microscopy (HAADF STEM) shows that the bulk morphologies of the two catalysts are distinctly different: D-PtCo/HSC catalyst is dominated by NPs with solid Pt shells surrounding a single ordered PtCo core; however, the D-PtCo3/HSC catalyst is dominated by NPs with porous Pt shells surrounding multiple disordered PtCo cores with local concentration of Co. In situ X-ray absorption spectroscopy (XAS) reveals that these two catalysts possess similar Pt–Pt and Pt–Co bond distances and Pt coordination numbers (CNs), despite their dissimilar morphologies. The similar activity of the two catalysts is thus ascribed to their comparable strain, ligand, and particle size effects. Ex situ XAS performed on D-PtCo3/HSC under different voltage cycling stage shows that the continuous dissolution of Co leaves behind the NPs with a Pt-like structure after 30k cycles. The attenuated strain and/or ligand effects caused by Co dissolution are presumably counterbalanced by the particle size effects with particle growth, which likely accounts for the constant specific activity of the catalysts along with voltage cycling. PMID:26413384

  18. Effect of degree of polymerization and of temperature on the reactivity of poly(vinyl alcohol) by applying T-for-H exchange reaction

    International Nuclear Information System (INIS)

    Imaizumi, Hiroshi; Imai, Kazunari

    1999-01-01

    In order to reveal the effect of the degree of polymerization and of temperature on the reactivity of functional polymers, the hydrogen-isotope exchange reaction between poly(vinyl alcohol) (PVA) having each degree of polymerization and tritiated water vapor (HTO vapor) was dynamically observed at 35-80 deg C in a gas-solid system. The reason of the observation at 35 deg C is to clarify the possibility of the T-for-H exchange reaction at a temperature near the environment. The degree of polymerization of PVA used in this work was 500, 1000, 2000, 2800, or 3500. Applying the A''-McKay plot method to the data obtained in each observation, the rate constant (k) for each PVA in the reaction was calculated. Moreover, the Arrhenius plot for each PVA was made by using the k values. Comparing the k values and the results obtained previously, the following six matters have been clarified. In the temperature range of 35-80 deg C, the T-for-H exchange reaction between HTO vapor and each PVA occurred, and in this case, the atoms participating in the reaction are the H atoms in the OH groups in PVA and T atoms in HTO vapor. The reactivity of each PVA increases with rising temperature, and decreases with increasing the degree of polymerization. The rate of the decreasing of k with increasing the degree of polymerization changes at near the degree of polymerization of 1000, and the rate is fairly large under the degree of 1000. Under the degree of polymerization of 1000, the reactivity of PVA is more affected by the effect of the degree of polymerization than by the effect of temperature, and the reactivity is large when the degree of polymerization is small. Over the degree of polymerization of 1000, the reactivity of PVA is affected by both the degree of polymerization and temperature, and the reactivity is large when temperature is high. For the T-for-H exchange reaction in a gas-solid system, the reaction form is unchanged in the range of 35-80 deg C, and the reactivity at 35

  19. Poisoning by carbon monoxide in the hydrogen exchange reaction between deuterium gas and water preadsorbed on a platinum--alumina catalyst

    International Nuclear Information System (INIS)

    Iida, I.; Tamaru, K.

    1979-01-01

    Poisoning by carbon monoxide in the exchange reaction between deuterium and the water preadsorbed on a platinum--alumina catalyst was studied, by measuring not only the rate of reaction but also its kinetic behavior and the adsorption of reactants on the catalyst surface. The shape of the poisoning curve is closely associated with the kinetic behavior and exhibited an abrupt change on freezing the adsorbed water below 273 0 K. When the rate is proportional to deuterium pressure and independent of the amount of water adsorbed, the exchange rate dropped sharply by carbon monoxide adsorbed of a few percent coverage without any marked changes in the amount and the rate of hydrogen adsorption on the platinum surface. However, at temperatures lower than 273 0 K and at higher deuterium pressures, the rate depends not on the deuterium pressure but on the amount of water adsorbed. The migration of hydrogen in or through the adsorbed water is seemingly sufficiently suppressed by freezing to control the overall reaction rate. In this case, a small amount of adsorption of carbon monoxide did not show any toxicity, but then a steep poisoning started accompanying a change in the kinetic behavior. It was accordingly demonstrated that the mechanism of the reaction may be better understood by studying poisoning and measuring adsorption, overall rate, and kinetic behavior

  20. Investigation into reaction of heterogenous isotopic exchange with gaseoUs tritium in solution for preparation labelled lipid compounds

    International Nuclear Information System (INIS)

    Shevchenko, V.P.; Myasoedov, N.F.

    1983-01-01

    The applicability of the method of heterogeneous catalytic isotopic exchange with gaseous tritium in the solution for the production of labelled lipide preparations is studied. Labelled saturated and unsaturated aliphatic acids, prostaglandins, phospholipides and sphingolipides are prepared

  1. Study of hypercharge exchange reactions of the type K/sup -/p to 1/sup -3///sub 2//sup +or-/ at 42 GeV/c

    CERN Document Server

    Aguilar-Benítez, M; Hemingway, Richard J; Holmgren, S O; Losty, Michael J; Toet, D Z; Worden, R P; Zatz, J; Kluyver, J C; Massaro, G G G; Wolters, G F; Engelen, J J; Tiecke, H G; Vergeest, J S M; Van de Walle, R T

    1977-01-01

    Results are presented for the quasi two-body hypercharge exchange reactions of the type 0/sup -1///sub 2//sup +/ to 1/sup -3///sub 2 //sup +/, i.e. K/sup -/p to rho /sup -/ Sigma /sup +/(1385) or K/sup - /p to phi Sigma /sup 0/(1385), and 0/sup -1///sub 2//sup +/ to 1/sup -3///sub 2//sup -/, i.e. K/sup -/p to omega Lambda (1520) or K/sup -/p to phi Lambda (1520), using data from a high statistics bubble chamber experiment. Total and differential cross sections and the momentum transfer dependence of the meson and hyperon resonance single density matrix elements are discussed. Amplitude analyses are performed for the first two reactions. The results are compared with quark model and duality predictions and with those from other related reactions. (7 refs).

  2. Effect of the number of phenyl groups per molecule on the reactivity of hydroxyl or carboxyl group in hydrogen-isotope exchange reaction

    International Nuclear Information System (INIS)

    Okada, Minoru; Imaizumi, Hiroshi; Oguma, Shuichi

    1989-01-01

    Hydrogen-exchange reactions in solid alcohols (or solid carboxylic acids) which contain phenyl group(s) in each molecule have been observed in a gas-solid system or liquid-solid system at 40 ≅ 80deg C. The data thus obtained have been analyzed by using the A''-McKay plot method, and 'the acidities based on kinetic logic' have been obtained for those compounds. From the acidities the following four characteristics have been determined. (1) The acidity increases with increases of temperature. (2) The reactivities of carboxylic acids are larger than those of alcohols at any temperature. (3) The effect of the number of phenyl groups on the reactivity of the functional group in the molecule in question is fairly large. (4) Acidity based on kinetic logic can be applied not only to gas-solid reactions, but also to liquid-solid reactions. (orig.)

  3. Silver nanoclusters-assisted ion-exchange reaction with CdTe quantum dots for photoelectrochemical detection of adenosine by target-triggering multiple-cycle amplification strategy.

    Science.gov (United States)

    Zhao, Yang; Tan, Lu; Gao, Xiaoshan; Jie, Guifen; Huang, Tingyu

    2018-07-01

    Herein, we successfully devised a novel photoelectrochemical (PEC) platform for ultrasensitive detection of adenosine by target-triggering cascade multiple cycle amplification based on the silver nanoparticles-assisted ion-exchange reaction with CdTe quantum dots (QDs). In the presence of target adenosine, DNA s1 is released from the aptamer and then hybridizes with hairpin DNA (HP1), which could initiate the cycling cleavage process under the reaction of nicking endonuclease. Then the product (DNA b) of cycle I could act as the "DNA trigger" of cycle II to further generate a large number of DNA s1, which again go back to cycle I, thus a cascade multiple DNA cycle amplification was carried out to produce abundant DNA c. These DNA c fragments with the cytosine (C)-rich loop were captured by magnetic beads, and numerous silver nanoclusters (Ag NCs) were synthesized by AgNO 3 and sodium borohydride. The dissolved AgNCs released numerous silver ions which could induce ion exchange reaction with the CdTe QDs, thus resulting in greatly amplified change of photocurrent for target detection. The detection linear range for adenosine was 1.0 fM ~10 nM with the detection limit of 0.5 fM. The present PEC strategy combining cascade multiple DNA cycle amplification and AgNCs-induced ion-exchange reaction with QDs provides new insight into rapid, and ultrasensitive PEC detection of different biomolecules, which showed great potential for detecting trace amounts in bioanalysis and clinical biomedicine. Copyright © 2018 Elsevier B.V. All rights reserved.

  4. Structures, equilibria and ligand exchange dynamics in the binary and ternary dioxouranium(VI)-ethylenediamine-N-N'-diacetic acid - fluoride system; a potentiometric, NMR and X-ray study

    International Nuclear Information System (INIS)

    Palladino, G.; Szabo, Z.; Fischer, A.; Grenthe, I.

    2005-01-01

    Full text of publication follows: The structure, thermodynamics and kinetics of the binary and ternary Uranyl(VI)- ethylenediamine- N-N'-di-acetate (in the following denoted EDDA) fluoride system have been studied using potentiometry, 1 H, 19 F NMR and a single-crystal X-ray determination. The potentiometric data were obtained using measurements of the free hydrogen ion and fluoride concentrations with glass and fluoride electrodes, respectively. The experimental data were used to deduce stoichiometry and equilibrium constants using a least square refinements programme. The UO 2 2+ - EDDA system could be studied up to -log[H 3 O + ] 3.4, after which a precipitate was formed. The test solutions contained two binary complexes, the uncharged UO 2 (EDDA)(aq) and UO 2 (H 3 EDDA) 3+ , with equilibrium constants log β(UO 2 EDDA) = 11.63 ± 0.02 and log β(UO 2 H 3 EDDA 3+ ) = 1.77 ± 0.04, respectively. By using fluoride as additional ligand the solubility increases because of the formation of very stable ternary complexes that allowed an experimental study over a larger pH range. The structure of the complexes in the ternary system was deduced using a combination of 1 H and 19 F NMR spectroscopy. The 19 F NMR spectra at lower pH, had peaks from the binary fluoride complexes (UO 2 F + , UO 2 F 2 (aq) and UO 2 F 3 - ) that could be used to obtain information on the equilibrium constants in the ternary system; at -log[H 3 O + ] > 4.7 new signals for the complexes (UO 2 ) 2 (EDDA) 2 F 2 2- , and UO 2 (EDDA)F - were observed. The analyses of 1 H NMR spectra indicate clearly that the EDDA ligand is chelate bonded in UO 2 (EDDA)F-. The fluorine exchange between UO 2 (EDDA)F- and UO 2 F 3 - was studied using 19 F NMR line-broadening technique. The experimental rate constant is k obs = k 0 + k 1 [UO 2 F 3 - ], with k 0 (3.24 ± 0.06) 10 2 s -1 and k 1 = (71.2 ± 2.3) 10 3 M -1 s -1 .The rate and the activation parameters for the exchange between UO 2 (EDDA)F - complex and free

  5. Charge-exchange breakup of the deuteron with the production of two protons and spin structure of the amplitude of the nucleon charge transfer reaction

    International Nuclear Information System (INIS)

    Glagolev, V.V.; Lyuboshits, V.L.; Lyuboshits, V.V.; Piskunov, N.M.

    1999-01-01

    In the framework of the impulse approximation, the relation between the effective cross section of the charge-exchange breakup of a fast deuteron d + a → (pp) + b and the effective cross section of the charge transfer process n + a → p + b is discussed. In doing so, the effects of the proton identity (Fermi-statistics) and of the Coulomb and strong interactions of protons in the final state are taken into account. The distribution over relative momenta of the protons, produced in the charge-exchange process d + p → (pp) + n in the forward direction, is investigated. At the transfer momenta being close to zero the effective cross section of the charge-exchange breakup of a fast deuteron, colliding with the proton target, is determined only by the spin-flip part of the amplitude of the charge transfer reaction n + p → p + n at the zero angle. It is shown that the study of the process d + p → (pp) + n in a beam of the polarized (aligned) deuterons allows one, in principle, to separate two spin-dependent terms in the amplitude of the charge transfer reaction n + p → p + n, one of which does not conserve and the other one conserves the projection of the nucleon spin onto the direction of momentum at the transition of the neutron into the proton

  6. Tritium Labeled Gentamicin C: II.- Bioradiactive Degradation Products of Gentamicin by Catalytic H2O-3H Exchange Reaction

    International Nuclear Information System (INIS)

    Suarez, C.; Diaz, A.; Paz, D.; Jimeno, M. L.

    1992-01-01

    The main bio radioactive degradation products from catalytic hydrogen exchange of gentamicin C, (C1 + C2 + Cla) in basic form, are generated by N-demethylation in 3 - N and 6-N positions. Their structures were confirmed by 1HNMR and 13CNMR. These derivatives were fractionated by chromatography on silica gel. Antibacterial activities were similar to those of the parent antibiotics. Tritium exchange, under vacuum or nitrogen, is highly increased (4:1) when gentamicin are in basic form. In contrast with gentamicin sulfate, hydrolytic sub products as gramine, genta mines, garosamine and purpurosamines are practically absent. To properly optimize the exchange process, the composition of the gentamicin C complex must be taken into account. The exchange decreases in the order C2 > C1> Cla. Because of 6'-N-demethyl gentamicin C1 is C2, the radiochemical yield of C2 appears enhanced in the H2O-3H exchange of a mixture of them. Radioactivity distribution among the components and subunits of these three gentamicin were studied by strong and mild hydrolysis, and by methanolysis. (Author) 18 refs

  7. Tritium labeled Gentamicin C : II.- Bioradioactive products of Gentamicin by Catalytic H2O-3H exchange reaction

    International Nuclear Information System (INIS)

    Suarez, C.; Diaz, A.; Paz, D.; Jimeno, M.L.

    1992-01-01

    The main bioradioactive degradation products from catalytic hydrogen exchange of gentamicin C, (C1 + C2 + C1a) in basic form, are generated by N-dimethylations in 3 - N and 6'-N positions. Their structures were confirmed by HNMR and 13 CNMR. These derivatives were fractionated by chromatography on silica gel. Antibacterial activities were similar to those of the parent antibiotics. Tritium exchange, under vacuum or nitrogen, is highly increased (4:1) when gentamicina are in basic form. In contrast with gentamicin sulfate, hydrolytic subproducts as garamine, gentamicine, garosamine and purpurosamines are practically absent. To properly optimize the exchange process, the composition of the gentamicin C complex must be taken into account. The exchange decreases in the order C2 > C1 > C1a. Because of 6' -N-dimenthyl gentamicin C1 is C2, the radiochemical yield of C2 appears enhanced in the H 2 O- 3 H exchange of a mixture of them. Radioactivity distribution among the components and subunits of these three gentamicins were studied by stron and mild hydrolysis, and by methanolysis. (author)

  8. Ligand-Free Suzuki-Miyaura Coupling Reactions Using an Inexpensive Aqueous Palladium Source: A Synthetic and Computational Exercise for the Undergraduate Organic Chemistry Laboratory

    Science.gov (United States)

    Hill, Nicholas J.; Bowman, Matthew D.; Esselman, Brian J.; Byron, Stephen D.; Kreitinger, Jordan; Leadbeater, Nicholas E.

    2014-01-01

    An inexpensive procedure for introducing the Suzuki-Miyaura coupling reaction into a high-enrollment undergraduate organic chemistry laboratory course is described. The procedure employs an aqueous palladium solution as the catalyst and a range of para-substituted aryl bromides and arylboronic acids as substrates. The coupling reactions proceed…

  9. Evaluation of the isotope separation rate of deuterium exchange reaction between H2 and H2O with platinum catalyst

    International Nuclear Information System (INIS)

    Kitamoto, Asashi; Takashima, Yoichi; Shimizu, Masami.

    1983-01-01

    The high performance catalysts of hydrophobic carrier with fully dispersed platinum were used to measure the isotope separation performance of hydrogen by the chemical exchange method. The continuous injection of oxygen on the order of 10 3 ppm was effective in regenerating catalyst activity and in maintaining high performance for a long time. The separation performance in a trickle bed column should be evaluated by using two parameters, ksub(g) and ksub(l). These two parameters were unified to the overall transfer coefficient ksub(fg), which may be sufficient in the estimation of overall performance or the design of a separation plant by the chemical exchange method. When one wants to increase the transfer rate in a chemical exchange column, the improvement of ksub(l) rather than ksub(g) may be more effective in increasing the overall transfer rate (its coefficient is expressed by ksub(fg) in this paper). (author)

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

    International Nuclear Information System (INIS)

    Schatz, G.C.; Walch, S.P.; Wagner, A.F.

    1980-01-01

    We present ab initio (GVB--POL--CI) calculations for enough of the region about the abstraction and exchange saddle points for H(T)+CH 4 (CD 4 ) to perform a full normal mode analysis of the transition states. The resulting normal mode frequencies are compared to four other published surfaces: an ab initio UHF--SCF calculation by Carsky and Zahradnik, a semiempirical surface by Raff, and two semiempirical surfaces by Kurylo, Hollinden, and Timmons. Significant quantitative and qualitative differences exist between the POL--CI results and those of the other surfaces. Transition state theory rate constants and vibrationally adiabatic reaction threshold energies were computed for all surfaces and compared to available experimental values. For abstraction, the POL--CI rates are in good agreement with experimental rates and in better agreement than are the rates of any of the other surfaces. For exchange, uncertainties in the experimental values and in the importance of vibrationally nonadiabatic effects cloud the comparison of theory to experiment. Tentative conclusions are that the POL--CI barrier is too low by several kcal. Unless vibrationaly nonadiabatic effects are severe, the POL--CI surface is still in better agreement with experiment than are the other surfaces. The rates for a simple 3-atom transition state theory model (where CH 3 is treated as an atom) are compared to the rates for the full 6-atom model. The kinetic energy coupling of reaction coordinate modes to methyl group modes is identified as being of primary importance in determining the accuracy of the 3-atom model for this system. Substantial coupling in abstraction, but not exchange, causes the model to fail for abstraction but succeed for exchange

  11. Carbon isotope exchange between gaseous CO2 and thin solution films: Artificial cave experiments and a complete diffusion-reaction model

    Science.gov (United States)

    Hansen, Maximilian; Scholz, Denis; Froeschmann, Marie-Louise; Schöne, Bernd R.; Spötl, Christoph

    2017-08-01

    Speleothem stable carbon isotope (δ13C) records provide important paleoclimate and paleo-environmental information. However, the interpretation of these records in terms of past climate or environmental change remains challenging because of various processes affecting the δ13C signals. A process that has only been sparsely discussed so far is carbon isotope exchange between the gaseous CO2 of the cave atmosphere and the dissolved inorganic carbon (DIC) contained in the thin solution film on the speleothem, which may be particularly important for strongly ventilated caves. Here we present a novel, complete reaction diffusion model describing carbon isotope exchange between gaseous CO2 and the DIC in thin solution films. The model considers all parameters affecting carbon isotope exchange, such as diffusion into, out of and within the film, the chemical reactions occurring within the film as well as the dependence of diffusion and the reaction rates on isotopic mass and temperature. To verify the model, we conducted laboratory experiments under completely controlled, cave-analogue conditions at three different temperatures (10, 20, 30 °C). We exposed thin (≈0.1 mm) films of a NaHCO3 solution with four different concentrations (1, 2, 5 and 10 mmol/l, respectively) to a nitrogen atmosphere containing a specific amount of CO2 (1000 and 3000 ppmV). The experimentally observed temporal evolution of the pH and δ13C values of the DIC is in good agreement with the model predictions. The carbon isotope exchange times in our experiments range from ca. 200 to ca. 16,000 s and strongly depend on temperature, film thickness, atmospheric pCO2 and the concentration of DIC. For low pCO2 (between 500 and 1000 ppmV, as for strongly ventilated caves), our time constants are substantially lower than those derived in a previous study, suggesting a potentially stronger influence of carbon isotope exchange on speleothem δ13C values. However, this process should only have an

  12. Ratiometric analysis in hyperpolarized NMR (I): test of the two-site exchange model and the quantification of reaction rate constants.

    Science.gov (United States)

    Li, Lin Z; Kadlececk, Stephen; Xu, He N; Daye, Dania; Pullinger, Benjamin; Profka, Harrilla; Chodosh, Lewis; Rizi, Rahim

    2013-10-01

    Conventional methods for the analysis of in vivo hyperpolarized (13) C NMR data from the lactate dehydrogenase (LDH) reaction usually make assumptions on the stability of rate constants and/or the validity of the two-site exchange model. In this study, we developed a framework to test the validity of the assumption of stable reaction rate constants and the two-site exchange model in vivo via ratiometric fitting of the time courses of the signal ratio L(t)/P(t). Our analysis provided evidence that the LDH enzymatic kinetics observed by hyperpolarized NMR are in near-equilibrium and satisfy the two-site exchange model for only a specific time window. In addition, we quantified both the forward and reverse exchange rate constants of the LDH reaction for the transgenic and mouse xenograft models of breast cancer using the ratio fitting method developed, which includes only two modeling parameters and is less sensitive to the influence of instrument settings/protocols, such as flip angles, degree of polarization and tracer dosage. We further compared the ratio fitting method with a conventional two-site exchange modeling method, i.e. the differential equation fitting method, using both the experimental and simulated hyperpolarized NMR data. The ratio fitting method appeared to fit better than the differential equation fitting method for the reverse rate constant on the mouse tumor data, with less relative errors on average, whereas the differential equation fitting method also resulted in a negative reverse rate constant for one tumor. The simulation results indicated that the accuracy of both methods depends on the width of the transport function, noise level and rate constant ratio; one method may be more accurate than the other based on the experimental/biological conditions aforementioned. We were able to categorize our tumor models into specific conditions of the computer simulation and to estimate the errors of rate quantification. We also discussed possible

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

    NARCIS (Netherlands)

    Renneboog, L.D.R.; Vanbrabant, P.

    2000-01-01

    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

  14. Intermediate energy nuclear physics (Task C) and charge exchange reactions (Task W). Technical progress report, October 1, 1985-October 1, 1986

    International Nuclear Information System (INIS)

    Kraushaar, J.J.

    1986-10-01

    This report describes the experimental work in intermediate energy research carried out over the past year at the University of Colorado. The experimental program is very broad in nature, ranging from investigations in pion-nucleus interactions, nucleon charge exchange, inelastic electron scattering, and nucleon transfer reactions. The experiments were largely carried out at the Los Alamos Meson Physics Facility, but important programs were conducted at the Tri-University Meson Facility at the University of British Columbia, the Indiana University Cyclotron Facility and Netherlands Institute for Nuclear Physics Research (NIKHEF-K)

  15. Invariant mass spectroscopy of {sup 19,17}C and {sup 14}B using proton inelastic and charge-exchange reactions

    Energy Technology Data Exchange (ETDEWEB)

    Satou, Y., E-mail: satou@phya.snu.ac.k [Department of Physics and Astronomy, Seoul National University, Seoul (Korea, Republic of); Nakamura, T. [Department of Physics, Tokyo Institute of Technology, Tokyo (Japan); Fukuda, N. [Institute of Physical and Chemical Research (RIKEN), Saitama (Japan); Sugimoto, T.; Kondo, Y.; Matsui, N.; Hashimoto, Y.; Nakabayashi, T.; Okumura, Y.; Shinohara, M. [Department of Physics, Tokyo Institute of Technology, Tokyo (Japan); Motobayashi, T.; Yanagisawa, Y.; Aoi, N.; Takeuchi, S.; Gomi, T.; Togano, Y. [Institute of Physical and Chemical Research (RIKEN), Saitama (Japan); Kawai, S. [Department of Physics, Rikkyo University, Tokyo (Japan); Sakurai, H. [Institute of Physical and Chemical Research (RIKEN), Saitama (Japan); Ong, H.J.; Onishi, T.K. [Department of Physics, University of Tokyo, Tokyo (Japan)

    2010-03-01

    The neutron-rich carbon isotopes {sup 19,17}C and the boron isotope {sup 14}B have been investigated, respectively, by the proton inelastic and charge-exchange reactions on a liquid hydrogen target at around 70 MeV/nucleon. The invariant mass method in inverse kinematics was employed to map the energy spectrum above the neutron decay threshold of the residual nuclei. New states on carbon isotopes are reported. An experimental capability of extracting beta-decay strengths via forward angle (p,n) cross sections on unstable nuclei is shown.

  16. Synthesis and crystal structure of Mg0.5NbO2: An ion-exchange reaction with Mg2+ between trigonal [NbO2]- layers

    Science.gov (United States)

    Miura, Akira; Takei, Takahiro; Kumada, Nobuhiro

    2013-01-01

    A new layered niobate, Mg0.5NbO2, was synthesized from LiNbO2 through a cation-exchange reaction with Mg2+ at 450-550 °C. This is the first example of a topotactic reaction with an aliovalent cation between trigonal [NbO2]- layers. It is proposed to be isostructural with LiNbO2 (space group; P63/mmc) with lattice parameters of a=2.9052(6) Å, c=10.625(15) Å. The lattice parameters and formation energy of Mg0.5NbO2 crystallized in LiNbO2 form and other layered CaNb2O4 one were calculated by density functional theory.

  17. Direct versus ligand-exchange synthesis of [PtAg28(BDT)12(TPP)4]4− nanoclusters: effect of a single-atom dopant on the optoelectronic and chemical properties

    KAUST Repository

    Bootharaju, Megalamane Siddaramappa

    2017-06-07

    Heteroatom doping of atomically precise nanoclusters (NCs) often yields a mixture of doped and undoped products of single-atom difference, whose separation is extremely difficult. To overcome this challenge, novel synthesis methods are required to offer monodisperse doped NCs. For instance, the direct synthesis of PtAg28 NCs produces a mixture of [Ag29(BDT)12(TPP)4]3- and [PtAg28(BDT)12(TPP)4]4- NCs (TPP: triphenylphosphine; BDT: 1,3-benzenedithiolate). Here, we designed a ligand-exchange (LE) strategy to synthesize single-sized, Pt-doped, superatomic Ag NCs [PtAg28(BDT)12(TPP)4]4- by LE of [Pt2Ag23Cl7(TPP)10] NCs with BDTH2 (1,3-benzenedithiol). The doped NCs were thoroughly characterized by optical and photoelectron spectroscopy, mass spectrometry, total electron count, and time-dependent density functional theory (TDDFT). We show that the Pt dopant occupies the center of the PtAg28 cluster, modulates its electronic structure and enhances its photoluminescence intensity and excited-state lifetime, and also enables solvent interactions with the NC surface. Furthermore, doped NCs showed unique reactivity with metal ions - the central Pt atom of PtAg28 could not be replaced by Au, unlike the central Ag of Ag29 NCs. The achieved synthesis of single-sized PtAg28 clusters will facilitate further applications of the LE strategy for the exploration of novel multimetallic NCs.

  18. Ion-Exchange Reaction Of A-Site In A2Ta2O6 Pyrochlore Crystal Structure

    Directory of Open Access Journals (Sweden)

    Matsunami M.

    2015-06-01

    Full Text Available Na+ or K+ ion rechargeable battery is started to garner attention recently in Place of Li+ ion cell. It is important that A+ site ion can move in and out the positive-electrode materials. When K2Ta2O6 powder had a pyrochlore structure was only dipped into NaOH aqueous solution at room temperature, Na2Ta2O6 was obtained. K2Ta2O6 was fabricated from a tantalum sheet by a hydrothermal synthesize with KOH aqueous solution. When Na2Ta2O6 was dipped into KOH aqueous solution, K2Ta2O6 was obtained again. If KTaO3 had a perovskite structure was dipped, Ion-exchange was not observed by XRD. Because a lattice constant of pyrochlore structure of K-Ta-O system is bigger than perovskite, K+ or Na+ ion could shinny through and exchange between Ta5+ and O2− ion site in a pyrochlore structure. K+ or Na+ ion exchange of A2Ta2O6 pyrochlore had reversibility. Therefore, A2Ta2O6 had a pyrochlore structure can be expected such as Na+ ion rechargeable battery element.

  19. Heat transfer characteristics evaluation of heat exchangers of mock-up test facility with full-scale reaction tube for HTTR hydrogen production system (Contract research)

    International Nuclear Information System (INIS)

    Shimizu, Akira; Ohashi, Hirofumi; Kato, Michio; Hayashi, Koji; Aita, Hideki; Nishihara, Tetsuo; Inaba, Yoshitomo; Takada, Shoji; Morisaki, Norihiro; Sakaki, Akihiro; Maeda, Yukimasa; Sato, Hiroyuki; Inagaki, Yoshiyuki; Hanawa, Hiromi; Fujisaki, Katsuo; Yonekawa, Hideo

    2005-06-01

    Connection of hydrogen production system by steam reforming of methane to the High Temperature Engineering Test Reactor (HTTR) of the Japan Atomic Energy Research Institute (JAERI) has been surveyed until now. Mock-up test facility of this steam reforming system with full-scale reaction tube was constructed in FY 2001 and hydrogen of 120 Nm 3 /h was successfully produced in overall performance test. Totally 7 times operational tests were performed from March 2002 to December 2004. A lot of operational test data on heat exchanges were obtained in these tests. In this report specifications and structures of steam reformer, steam superheater, steam generator, condenser, helium gas cooler, feed gas heater and feed gas superheater were described. Heat transfer correlation equations for inside and outside tube were chosen from references. Spreadsheet programs were newly made to evaluate heat transfer characteristics from measured test data such as inlet and outlet temperature pressure and flow-rate. Overall heat-transfer coefficients obtained from the experimental data were compared and evaluated with the calculated values with heat transfer correlation equation. As a result, actual measurement values of all heat exchangers gave close agreement with the calculated values with correlation equations. Thermal efficiencies of the heat exchangers were adequate as they were well accorded with design value. (author)

  20. Synthesis of Isotactic-block-Syndiotactic Poly(methyl Methacrylate via Stereospecific Living Anionic Polymerizations in Combination with Metal-Halogen Exchange, Halogenation, and Click Reactions

    Directory of Open Access Journals (Sweden)

    Naoya Usuki

    2017-12-01

    Full Text Available Isotactic (it- and syndiotactic (st- poly(methyl methacrylates (PMMAs form unique crystalline stereocomplexes, which are attractive from both fundamental and application viewpoints. This study is directed at the efficient synthesis of it- and st-stereoblock (it-b-st- PMMAs via stereospecific living anionic polymerizations in combination with metal-halogen exchange, halogenation, and click reactions. The azide-capped it-PMMA was prepared by living anionic polymerization of MMA, which was initiated with t-BuMgBr in toluene at –78 °C, and was followed by termination using CCl4 as the halogenating agent in the presence of a strong Lewis base and subsequent azidation with NaN3. The alkyne-capped st-PMMA was obtained by living anionic polymerization of MMA, which was initiated via an in situ metal-halogen exchange reaction between 1,1-diphenylhexyl lithium and an α-bromoester bearing a pendent silyl-protected alkyne group. Finally, copper-catalyzed alkyne-azide cycloaddition (CuAAC between these complimentary pairs of polymers resulted in a high yield of it-b-st-PMMAs, with controlled molecular weights and narrow molecular weight distributions. The stereocomplexation was evaluated in CH3CN and was affected by the block lengths and ratios.

  1. Calculating constants of the rates of the reactions of excitation, ionization, and atomic exchange: A model of a shock oscillator with a change of the Hamiltonian of the system

    Science.gov (United States)

    Tsyganov, D. L.

    2017-11-01

    A new model for calculating the rates of reactions of excitation, ionization, and atomic exchange is proposed. Diatomic molecule AB is an unstructured particle M upon the exchange of elastic-vibrational (VT) energy, i.e., a model of a shock forceful oscillator with a change in Hamiltonian (SFOH). The SFOH model is based on the quantum theory of strong perturbations. The SFOH model allows generalization in simulating the rates of the reactions of excitation, ionization, and atomic exchange in the vibrational-vibrational (VV) energy exchange of diatomic molecules, and the exchange of VV- and VT-energy of polyatomic molecules. The rate constants of the excitation of metastables A 3Σ u +, B 3Π g , W 3Δ u , B'3Σ u -, a'3Σ u -, and the ionization of a nitrogen molecules from ground state X2Σ g + upon a collision with a heavy structureless particle (a nitrogen molecule), are found as examples.

  2. The K/sup -/p charge exchange and elastic scattering reactions at 42 GeV/c

    CERN Document Server

    Marzano, F; Gavillet, P; Gay, J B; Grossmann, P; Heinen, P M; Hemingway, R J; Jongejans, B; Kluyver, J C; Maréchal, B; Schotanus, D J; Toet, D Z; Wells, J; Wolters, G F

    1977-01-01

    Results are presented on the reactions K/sup -/p to K/sup 0/n and K /sup -/p to K/sup -/p from a high statistics CERN 2-metre hydrogen bubble chamber exposure at 4.15 GeV/c. The behaviour of the differential cross section as a function of four-momentum transfer shows remarkable similarities between the two reactions studied. From a comparison of their data with K/sup +/p elastic scattering at 4.27 GeV/c the authors draw some conclusions concerning the magnitude of the contributing amplitudes. (10 refs).

  3. The K-p charge exchange and elastic scattering reactions at 4.2 GeV/c

    International Nuclear Information System (INIS)

    Marzano, F.; Toet, D.Z.; Gavillet, Ph.; Gay, J.B.; Hemingway, R.J.; Marechal, B.; Blokzijl, R.; Jongejans, B.; Kluyver, J.C.; Wolters, G.F.; Grossmann, P.; Wells, J.

    1977-01-01

    In this letter results are presented on the reactions K - p→anti K 0 n and K - p→K - p from a high statistics CERN 2 m etre hydrogen bubble chamber exposure a t 4.15 GeV/c. The behaviour of the differential cross section as a function of four-momentum transfer shows remarkable similarities between the two reactions studied. From a comparison of the data with K + p elastic scattering at 4.27 GeV/c some conclusions are drawn concerning the magnitude of the contributing amplitudes. (Auth.)

  4. 31P NMR saturation-transfer measurements in Saccharomyces cerevisiae: characterization of phosphate exchange reactions by iodoacetate and antimycin A inhibition

    International Nuclear Information System (INIS)

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

    1987-01-01

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

  5. Natural Deposition Strategy for Interfacial, Self-Assembled, Large-Scale, Densely Packed, Monolayer Film with Ligand-Exchanged Gold Nanorods for In Situ Surface-Enhanced Raman Scattering Drug Detection.

    Science.gov (United States)

    Mao, Mei; Zhou, Binbin; Tang, Xianghu; Chen, Cheng; Ge, Meihong; Li, Pan; Huang, Xingjiu; Yang, Liangbao; Liu, Jinhuai

    2018-03-15

    Liquid interfacial self-assembly of metal nanoparticles holds great promise for its various applications, such as in tunable optical devices, plasmonics, sensors, and catalysis. However, the construction of large-area, ordered, anisotropic, nanoparticle monolayers and the acquisition of self-assembled interface films are still significant challenges. Herein, a rapid, validated method to fabricate large-scale, close-packed nanomaterials at the cyclohexane/water interface, in which hydrophilic cetyltrimethylammonium bromide coated nanoparticles and gold nanorods (AuNRs) self-assemble into densely packed 2D arrays by regulating the surface ligand and suitable inducer, is reported. Decorating AuNRs with polyvinylpyrrolidone not only extensively decreases the charge of AuNRs, but also diminishes repulsive forces. More importantly, a general, facile, novel technique to transfer an interfacial monolayer through a designed in situ reaction cell linked to a microfluidic chip is revealed. The self-assembled nanofilm can then automatically settle on the substrate and be directly detected in the reaction cell in situ by means of a portable Raman spectrometer. Moreover, a close-packed monolayer of self-assembled AuNRs provides massive, efficient hotspots to create great surface-enhanced Raman scattering (SERS) enhancement, which provides high sensitivity and reproducibility as the SERS-active substrate. Furthermore, this strategy was exploited to detect drug molecules in human urine for cyclohexane-extracted targets acting as the oil phase to form an oil/water interface. A portable Raman spectrometer was employed to detect methamphetamine down to 100 ppb levels in human urine, exhibiting excellent practicability. As a universal platform, handy tool, and fast pretreatment method with a good capability for drug detection in biological systems, this technique shows great promise for rapid, credible, and on-spot drug detection. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. The concept of mixed organic ligands in metal-organic frameworks: design, tuning and functions.

    Science.gov (United States)

    Yin, Zheng; Zhou, Yan-Ling; Zeng, Ming-Hua; Kurmoo, Mohamedally

    2015-03-28

    The research on metal-organic frameworks (MOFs) has been developing at an extraordinary pace in its two decades of existence, as judged by the exponential growth of novel structures and the constant expansion of its applicability and research scope. A major part of the research and its success are due to the vital role of the concept of mixed organic ligands in the design, tuning and functions. This perspective, therefore, reviews the recent advances in MOFs based on this concept, which is generally based on employing a small polydentate ligand (here labelled as "nodal ligand") to form either clusters, rods or layers, which are then connected by a second ditopic linker ligand to form the framework. The structures of the materials can be grouped into the following three categories: layer-spacer (usually known as pillared-layer), rod-spacer, and cluster-spacer based MOFs. Depending on the size and geometry of the spacer ligands, interpenetrations of frameworks are occasionally found. These MOFs show a wide range of properties such as (a) crystal-to-crystal transformations upon solvent modifications, post-synthetic metal exchange or ligand reactions, (b) gas sorption, solvent selectivity and purification, (c) specific catalysis, (d) optical properties including colour change, luminescence, non-linear optic, (e) short- and long range magnetic ordering, metamagnetism and reversible ground-state modifications and (f) drug and iodine carriers with controlled release. In the following, we will highlight the importance of the above concept in the design, tuning, and functions of a selection of existing MOFs having mixed organic ligands and their associated structures and properties. The results obtained so far using this concept look very promising for fine-tuning the pore size and shape for selective adsorption and specificity in catalytic reactions, which appears to be one way to propel the advances in the application and commercialization of MOFs.

  7. Search for $\\Sigma$ Hypernuclear States using the Strangeness Exchange Reactions $(K^{-},\\pi^{-})$ and $(K^{-},\\pi^{+})$

    CERN Multimedia

    2002-01-01

    In previous $\\Lambda$ hypernuclei experiments details of the $\\Lambda$ nucleus interaction have been deduced, the most outstanding being a very small spin orbit interaction in p$^{-}$ and sd shell $\\Lambda$ hypernuclei. This kind of information is decisive in the understanding of the baryon interaction and will contribute to distinguish between the boson exchange and the QCD motivated picture of the baryon baryon interaction. To further exploit the hyperon nucleus interaction one has to investigate hypernuclei with hyperons of different quark configuration, i.e. $\\Sigma$ hypernuclei. Since the $\\Sigma\\$ particle can, in contrast to the $\\Lambda$, decay by strong interaction in the nucleus, the existence of narrow states was not obvious. A small momentum transfer guarantees that the spectra are dominated by a few strong transitions to narrow hypernuclear states with the same spin and space quantum numbers as the target nucleus. Therefore a new kaon beamline was built with a lower momentum of 400~MeV/c and a co...

  8. An Active Alkali-Exchanged Faujasite Catalyst for p-Xylene Production via the One-Pot Diels-Alder Cycloaddition/Dehydration Reaction of 2,5-Dimethylfuran with Ethylene.

    Science.gov (United States)

    Rohling, Roderigh Y; Uslamin, Evgeny; Zijlstra, Bart; Tranca, Ionut C; Filot, Ivo A W; Hensen, Emiel J M; Pidko, Evgeny A

    2018-02-02

    The one-pot Diels-Alder cycloaddition (DAC)/dehydration (D) tandem reaction between 2,5-dimethylfuran and ethylene is a potent pathway toward biomass-derived p -xylene. In this work, we present a cheap and active low-silica potassium-exchanged faujasite (KY, Si/Al = 2.6) catalyst. Catalyst optimization was guided by a computational study of the DAC/D reaction mechanism over different alkali-exchanged faujasites using periodic density functional theory calculations complemented by microkinetic modeling. Two types of faujasite models were compared, i.e., a high-silica alkali-exchanged faujasite model representing isolated active cation sites and a low-silica alkali-exchanged faujasite in which the reaction involves several cations in the proximity. The mechanistic study points to a significant synergetic cooperative effect of the ensemble of cations in the faujasite supercage on the DAC/D reaction. Alignment of the reactants by their interactions with the cationic sites and stabilization of reaction intermediates contribute to the high catalytic performance. Experiments confirmed the prediction that KY is the most active catalyst among low-silica alkali-exchanged faujasites. This work is an example of how the catalytic reactivity of zeolites depends on multiple interactions between the zeolite and reagents.

  9. Transition metal complexes with pyrazole-based ligands.Part 29. Reactions of zinc(II and mercury(II thiocyanate with 4-acetyl-3-amino-5-methylpyrazole

    Directory of Open Access Journals (Sweden)

    KATALIN MÉSZÁROS SZÉCSÉNYI

    2009-11-01

    Full Text Available The work is concerned with the crystal and molecular structures of zinc(II and mercury(II complexes with 4-acetyl-3-amino-5-methyl-pyrazole (aamp of the coordination formulae [Zn(NCS2(aamp2] and (Haamp2[Hg(SCN4]. The zinc(II complex was obtained by the reaction of a warm methanolic solution of aamp with a mixture of zinc(II nitrate and ammonium thiocyanate, whereas the mercury(II complex was prepared by the reaction of a warm ethanolic solution of aamp and a warm, slightly acidified aqueous solution of [Hg(SCN4]2-. Both complexes have a tetrahedral geometry, which in the case of zinc complex is formed by monodentate coordination of two aamp molecules and two isothiocyanate groups. The Zn(II and Hg(II atoms have significantly deformed coordination geometry. In both crystal structures the pyrazole derivative has a planar form, probably stabilized by an intramolecular N–H···O hydrogen bond. Apart from the X-ray structural analysis, the isolated complexes were characterized by elemental analysis, IR spectroscopy, conductometric measurements and thermal analysis.

  10. Isotopic Exchange Reaction Assisted with Cu (I) generated ''in situ'' For Synthesis of Ready-to-Use for on-the-spot Formulation of [131 I] Iodobenzyl Derivatives

    International Nuclear Information System (INIS)

    Abudaia, J.A.; Suliman, M.O.

    2007-01-01

    It has been examined that meta-Iodobenzylguanidine (m-IBG), para-Iodoamphetamine (p-IPA) and orth-Iodohippuric acid (o-IHA) are three commonly used Iodobenzyl derivative compounds, and can be formulated as Ready-to-Use Kits for on-the-spot labeling catalyzed with copper ion Cu+ (I) generated ''In Situ''. The labeling procedure efficiently has been established within 30 min of heating using an autoclave, 20 min. and 90 min. using dry heating block respectively. Isotopic exchange reaction with Iodine-131 radioactive of those three Ready-to-Use Kits has led to Radiochemical Purity ''RCP'' equals to 98%, > 98%, and almost 99%, and Radiochemical Yield ''RCY'' > 97%, >93% and > 98% respectively. Attention was paid to the Radiochemical Stability of those three Iodobenzyl derivatives for a period time of preservation at low temperature. As a result, this gave evidence that such Radiopharmaceuticals could be used as Ready-to-Use products at different times of preservations.

  11. Comparison of the reactivity of the materials having two different kinds of functional groups by applying hydrogen-isotope exchange reaction

    International Nuclear Information System (INIS)

    Imaizumi, H.; Yumoto, Y.

    1995-01-01

    The hydrogen-isotope exchange reaction between m- (or p-) aminobenzoic acid and HTO vapor has been observed in order to estimate the scale of the reactivity of the material. Each rate constant has been obtained by the A''-McKay plot method. Comparing the rate constants, the following three items have been confirmed: (1) the reactivity of both COOH and NH 2 groups increases with temperature; (2) the degree of the effect of the COOH (or NH 2 ) group on the reactivity in m-aminobenzoic acid is larger than that in p-aminobenzoic acid; (3) the A''-McKay plot method is useful in studying the reactivity of the materials not only with one (or the same kinds of) functional group(s), but also with two different kinds of functional groups. (orig.)

  12. Comparison of hydrogen isotope exchange reactions between HTO vapor and the sodium salts of o-, m-, and p-aminobenzoic acid

    International Nuclear Information System (INIS)

    Okada, Minoru; Imaizumi, Hiroshi; Itoh, Tomoko

    1991-01-01

    Hydrogen isotope exchange reaction between HTO vapor and one of the sodium salts of o-, m-, and p-aminobenzoic acid (solid) was observed at 50 ∼ 80 degC. The acidity (acidity based on kinetic logic) for the materials at each temperature has been obtained with the A''-McKay plots based on the respective data obtained. The followings have been clarified by comparing these acidities (and the acidities obtained previously). 1) The acidity of aromatic amines can be expressed in terms of the acidity based on kinetic logic. 2) The reactivity of aromatic amine is strongly affected by both I-effect and R-effect. 3) It can be deduced that aromatic amines are more reactive than aliphatic amines. (author)

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

    Science.gov (United States)

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

    1999-11-01

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

  14. Sterochemical consequences of hydrogen exchange as a result of tritium atom reactions on solid aliphatic amino acids

    International Nuclear Information System (INIS)

    Ehrenkaufer, R.L.E.; Hembree, W.C.; Lieberman, S.; Wolf, A.P.

    1977-01-01

    The products of stereochemistry resulting from radicals generated by the interaction of tritium atoms with L-isoleucine and L-alloisoleucine in the solid phase were determined. Among the four possible tritiated stereoisomers for each amino acid the major product was the parent L-amino acid (approximately 70 percent in each case) with the major fraction of the labeling being in positions other than the α position. Approximately 30 percent of the labeling resulted in the diastereomeric product by reaction at either the α or β position, with the major pathway being β-inversion. The yield of products from α-carbon attack of L-isoleucine was minor (7.9 percent) and occurred with net retention. Labeling at the α-carbon of alloisoleucine was less than 1 percent. Tritiated glycine was formed from both amino acids by cleavage of the alkyl side chain. This may result from the excitation decomposition of the intermediates formed from recombination of α (or β) amino acid radicals with tritium. Determination of the stereochemical and chemical consequences of radical formation at chiral centers provides a sensitive probe for studying the consequences of tritium (hydrogen or deuterium) atom reactions

  15. Using positive-ion electrospray ionization mass spectrometry and H/D exchange study phosphoryl group transfer reactions involved in amino acid ester isopropyl phosphoramidates of Brefeldin A

    International Nuclear Information System (INIS)

    Fang, Mei-Juan; Zhang, He; Liao, Chao; Qiu, Ying-Kun; Fang, Hua; Zheng, Zhen-Yu; Gao, Xiang; Zhao, Yu-Fen; Wu, Zhen

    2015-01-01

    Highlights: • ESI-MS n , HRMS and H/D exchange were used. • The fragmentation pathways of NPAAE-BFA in ESI-MS n were described. • Fragment ions involved in phosphorus group’s rearrangement reactions were observed. • Two rearrangement mechanisms about phosphorylation–dephosphorylation were proposed. - Abstract: As mini-chemical models, amino acid ester isopropyl phosphoramidates of Brefeldin A (compounds 2a–2d) were synthesized and investigated by electrospray ionization tandem mass spectrometry in combination with H/D exchange. To further confirm the fragments’s structures, off-line Fourier transform resonance tandem mass spectrometry (FT-ICR-MS/MS) was also performed. The fragmentation rules of compounds 2a–2d have been summarized and the plausible schemes for the fragmentation pathways were proposed. In this study, one dephosphorylated ion and two phosphorylated ions were observed in ESI-MS 2 spectra of [M + Na] + ions for compounds 2a–2d. The possible mechanisms about phosphorylation and dephosphorylation were proposed and confirmed by H/D exchange. For the “dephosphorylation” rearrangement, a nitrogen atom was migrated from the phosphoryl group to the carbon atom of Brefeldin A’s backbone with losing a molecule of C 3 H 7 PO 3 (122 Da). For the “phosphorylation” rearrangement, an oxygen atom of one phosphoryl group attacked the sideward phosphorus atom to form a nine-member ring intermediate, then two steps of C-H covalent bond cleavage with consecutive migration of hydrogen atom to lose a molecule of C 16 H 20 O 2 (244 Da). The two proposed rearrangement mechanisms about phosphoryl group transfer might be valuable for the structure analysis of other analogs and provide insights into elucidating the dynamic process of the phosphorylation–dephosphorylation of proteins

  16. Using positive-ion electrospray ionization mass spectrometry and H/D exchange study phosphoryl group transfer reactions involved in amino acid ester isopropyl phosphoramidates of Brefeldin A

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Mei-Juan; Zhang, He; Liao, Chao; Qiu, Ying-Kun [School of Pharmaceutical Sciences and the Key Laboratory for Chemical Biology of Fujian Province, Xiamen University, Xiang-An South Road, Xiamen 361102 (China); Fang, Hua [The Third Institute of Oceanography of the State Oceanic Administration, Xiamen 361005 (China); Zheng, Zhen-Yu [College of Chemistry and Chemical Engineering, Department of Chemistry, Xiamen University, Xiamen 361005 (China); Gao, Xiang [School of Pharmaceutical Sciences and the Key Laboratory for Chemical Biology of Fujian Province, Xiamen University, Xiang-An South Road, Xiamen 361102 (China); Zhao, Yu-Fen [School of Pharmaceutical Sciences and the Key Laboratory for Chemical Biology of Fujian Province, Xiamen University, Xiang-An South Road, Xiamen 361102 (China); College of Chemistry and Chemical Engineering, Department of Chemistry, Xiamen University, Xiamen 361005 (China); Wu, Zhen, E-mail: wuzhen@xmu.edu.cn [School of Pharmaceutical Sciences and the Key Laboratory for Chemical Biology of Fujian Province, Xiamen University, Xiang-An South Road, Xiamen 361102 (China)

    2015-01-01

    Highlights: • ESI-MS{sup n}, HRMS and H/D exchange were used. • The fragmentation pathways of NPAAE-BFA in ESI-MS{sup n} were described. • Fragment ions involved in phosphorus group’s rearrangement reactions were observed. • Two rearrangement mechanisms about phosphorylation–dephosphorylation were proposed. - Abstract: As mini-chemical models, amino acid ester isopropyl phosphoramidates of Brefeldin A (compounds 2a–2d) were synthesized and investigated by electrospray ionization tandem mass spectrometry in combination with H/D exchange. To further confirm the fragments’s structures, off-line Fourier transform resonance tandem mass spectrometry (FT-ICR-MS/MS) was also performed. The fragmentation rules of compounds 2a–2d have been summarized and the plausible schemes for the fragmentation pathways were proposed. In this study, one dephosphorylated ion and two phosphorylated ions were observed in ESI-MS{sup 2} spectra of [M + Na]{sup +} ions for compounds 2a–2d. The possible mechanisms about phosphorylation and dephosphorylation were proposed and confirmed by H/D exchange. For the “dephosphorylation” rearrangement, a nitrogen atom was migrated from the phosphoryl group to the carbon atom of Brefeldin A’s backbone with losing a molecule of C{sub 3}H{sub 7}PO{sub 3} (122 Da). For the “phosphorylation” rearrangement, an oxygen atom of one phosphoryl group attacked the sideward phosphorus atom to form a nine-member ring intermediate, then two steps of C-H covalent bond cleavage with consecutive migration of hydrogen atom to lose a molecule of C{sub 16}H{sub 20}O{sub 2} (244 Da). The two proposed rearrangement mechanisms about phosphoryl group transfer might be valuable for the structure analysis of other analogs and provide insights into elucidating the dynamic process of the phosphorylation–dephosphorylation of proteins.

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

    Science.gov (United States)

    Youssefi, Somayeh; Waring, Michael S.

    2015-07-01

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

  18. A new potential of π-nucleus scattering and its application to nuclear structure study using elastic scattering and charge exchange reactions

    International Nuclear Information System (INIS)

    Durand, Gerard.

    1974-01-01

    First the different theories used for studying pion-nucleus scattering and especially Glauber microscopic model and Kisslinger optical model are summarized. From the comparison of these two theories it was concluded that Kisslinger's was better for studying pion-nucleus scattering near the (3/2-3/2) resonance. The potential was developed, with a local corrective term, proposed by this author. This new term arises from taking into account correctly the Lorentz transformation from the pion-nucleon center of mass to the pion nucleus center of mass system. A coupled-channel formalism was developed allowing the study of pion-nucleus elastic scattering and also the study of single and double charge exchange reactions on nucleus with N>Z. The influence of the new term and the shape of nucleon densities on π- 12 C scattering was studied near 200MeV. It was found that at the nucleus surface the neutron density was larger than the proton density. On the other hand, a maximum of sensibility to the different nuclear parameters was found near 180MeV and for elastic scattering angles greater than 100 deg. The calculations of the total cross section for simple and double charge exchange for 13 C and 63 Cu yielded results simular to those of previous theories and showed the same discrepancy between theory and experiment in the resonance region [fr

  19. Hexacoordinate Ru-based olefin metathesis catalysts with pH-responsive N-heterocyclic carbene (NHC and N-donor ligands for ROMP reactions in non-aqueous, aqueous and emulsion conditions

    Directory of Open Access Journals (Sweden)

    Shawna L. Balof

    2015-10-01

    Full Text Available Three new ruthenium alkylidene complexes (PCy3Cl2(H2ITapRu=CHSPh (9, (DMAP2Cl2(H2ITapRu=CHPh (11 and (DMAP2Cl2(H2ITapRu=CHSPh (12 have been synthesized bearing the pH-responsive H2ITap ligand (H2ITap = 1,3-bis(2’,6’-dimethyl-4’-dimethylaminophenyl-4,5-dihydroimidazol-2-ylidene. Catalysts 11 and 12 are additionally ligated by two pH-responsive DMAP ligands. The crystal structure was solved for complex 12 by X-ray diffraction. In organic, neutral solution, the catalysts are capable of performing standard ring-opening metathesis polymerization (ROMP and ring closing metathesis (RCM reactions with standard substrates. The ROMP with complex 11 is accelerated in the presence of two equiv of H3PO4, but is reduced as soon as the acid amount increased. The metathesis of phenylthiomethylidene catalysts 9 and 12 is sluggish at room temperature, but their ROMP can be dramatically accelerated at 60 °C. Complexes 11 and 12 are soluble in aqueous acid. They display the ability to perform RCM of diallylmalonic acid (DAMA, however, their conversions are very low amounting only to few turnovers before decomposition. However, both catalysts exhibit outstanding performance in the ROMP of dicyclopentadiene (DCPD and mixtures of DCPD with cyclooctene (COE in acidic aqueous microemulsion. With loadings as low as 180 ppm, the catalysts afforded mostly quantitative conversions of these monomers while maintaining the size and shape of the droplets throughout the polymerization process. Furthermore, the coagulate content for all experiments stayed <2%. This represents an unprecedented efficiency in emulsion ROMP based on hydrophilic ruthenium alkylidene complexes.

  20. Heme-bound nitroxyl, hydroxylamine, and ammonia ligands as intermediates in the reaction cycle of cytochrome c nitrite reductase: a theoretical study.

    Science.gov (United States)

    Bykov, Dmytro; Plog, Matthias; Neese, Frank

    2014-01-01

    In this article, we consider, in detail, the second half-cycle of the six-electron nitrite reduction mechanism catalyzed by cytochrome c nitrite reductase. In total, three electrons and four protons must be provided to reach the final product, ammonia, starting from the HNO intermediate. According to our results, the first event in this half-cycle is the reduction of the HNO intermediate, which is accomplished by two PCET reactions. Two isomeric radical intermediates, HNOH(•) and H2NO(•), are formed. Both intermediates are readily transformed into hydroxylamine, most likely through intramolecular proton transfer from either Arg114 or His277. An extra proton must enter the active site of the enzyme to initiate heterolytic cleavage of the N-O bond. As a result of N-O bond cleavage, the H2N(+) intermediate is formed. The latter readily picks up an electron, forming H2N(+•), which in turn reacts with Tyr218. Interestingly, evidence for Tyr218 activity was provided by the mutational studies of Lukat (Biochemistry 47:2080, 2008), but this has never been observed in the initial stages of the overall reduction process. According to our results, an intramolecular reaction with Tyr218 in the final step of the nitrite reduction process leads directly to the final product, ammonia. Dissociation of the final product proceeds concomitantly with a change in spin state, which was also observed in the resonance Raman investigations of Martins et al. (J Phys Chem B 114:5563, 2010).

  1. Arene-mercury complexes stabilized by gallium chloride: relative rates of H/D and arene exchange.

    Science.gov (United States)

    Branch, Catherine S; Barron, Andrew R

    2002-11-27

    We have previously proposed that the Hg(arene)(2)(GaCl(4))(2) catalyzed H/D exchange reaction of C(6)D(6) with arenes occurs via an electrophilic aromatic substitution reaction in which the coordinated arene protonates the C(6)D(6). To investigate this mechanism, the kinetics of the Hg(C(6)H(5)Me)(2)(GaCl(4))(2) catalyzed H/D exchange reaction of C(6)D(6) with naphthalene has been studied. Separate second-order rate constants were determined for the 1- and 2-positions on naphthalene; that is, the initial rate of H/D exchange = k(1i)[Hg][C-H(1)] + k(2i)[Hg][C-H(2)]. The ratio of k(1i)/k(2i) ranges from 11 to 2.5 over the temperature range studied, commensurate with the proposed electrophilic aromatic substitution reaction. Observation of the reactions over an extended time period shows that the rates change with time, until they again reach a new and constant second-order kinetics regime. The overall form of the rate equation is unchanged: final rate = k(1f)[Hg][C-H(1)] + k(2f)[Hg][C-H(2)]. This change in the H/D exchange is accompanied by ligand exchange between Hg(C(6)D(6))(2)(GaCl(4))(2) and naphthalene to give Hg(C(10)H(8))(2)(GaCl(4))(2,) that has been characterized by (13)C CPMAS NMR and UV-visible spectroscopy. The activation parameters for the ligand exchange may be determined and are indicative of a dissociative reaction and are consistent with our previously calculated bond dissociation for Hg(C(6)H(6))(2)(AlCl(4))(2). The initial Hg(arene)(2)(GaCl(4))(2) catalyzed reaction of naphthalene with C(6)D(6) involves the deuteration of naphthalene by coordinated C(6)D(6); however, as ligand exchange progresses, the pathway for H/D exchange changes to where the protonation of C(6)D(6) by coordinated naphthalene dominates. The site selectivity for the H/D exchange is initially due to the electrophilic aromatic substitution of naphthalene. As ligand exchange occurs, this selectivity is controlled by the activation of the naphthalene C-H bonds by mercury.

  2. Study on the optical properties of CdSe QDs with different ligands in specific matrix

    International Nuclear Information System (INIS)

    Lin Wei; Zou Wei; Du Zhongjie; Li Hangquan; Zhang Chen

    2013-01-01

    Different ligand structures of CdSe quantum dots were designed and synthesized for the specific matrix and the effect of the ligands on the photoluminescence and optical properties were further investigated. Ligand exchange reaction was used to synthesize thioglycolic acid-capped CdSe QDs and the process was characterized by FT-IR and titration. The influence of environmental pH value and storing time on the properties of thioglycolic acid-capped CdSe QDs in aqueous solution were studied by absorption and photoluminescence spectra. It was found that alkaline environment was more beneficial for the application of CdSe QDs. Therefore, the amino ligands with different molecular weight were grafted onto CdSe QDs for improving the compatibility with epoxy matrix and then amino-capped CdSe QDs/epoxy nanocomposites were fabricated. The morphologies and properties of the nanocomposites were characterized by DLS, HR-TEM, UV–Vis spectra, and photoluminescence spectra. As a result, amino ligands with short-molecular chain-capped CdSe QDs/epoxy nanocomposites exhibited good dispersion, high transparency and photoluminescence, and would be suitable for potential application in light-emitting diode device.

  3. MAX phase – Alumina composites via elemental and exchange reactions in the Ti{sub n+1}AC{sub n} systems (A=Al, Si, Ga, Ge, In and Sn)

    Energy Technology Data Exchange (ETDEWEB)

    Cuskelly, Dylan, E-mail: dylan.cuskelly@uon.edu.au; Richards, Erin; Kisi, Erich, E-mail: Erich.Kisi@newcastle.edu.au

    2016-05-15

    Extension of the aluminothermal exchange reaction synthesis of M{sub n+1}AX{sub n} phases to systems where the element ‘A’ is not the reducing agent was investigated in systems TiO{sub 2}–A–Al–C for A=Al, Si, Ga, Ge, In and Sn as well as Cr{sub 2}O{sub 3}–Ga–Al–C. MAX phase-Al{sub 2}O{sub 3} composites were made in all systems except those with A=Ga or In. The effectiveness of conversion to MAX phases was generally in the range 63–96% without optimisation of starting ratios. Optimisation in the Ti–Si–C system gave a MAX phase component with >98% Ti{sub 3}SiC{sub 2}. - Graphical abstract: A range of Ti{sub n+1}AX{sub n} phases with different A elements were synthesised directly from the M oxide via exchange reactions. The process has now been shown to be general in all the systems marked in green in the table. - Highlights: • Ti{sub n+1}AC{sub n} phases were produced via a single step exchange reaction. • 3 MAX phase systems were successful via this method for the first time. • Cr{sub 2}GeC was also able to be produced via an exchange reaction. • The interconversion reaction in MAX phases is more general than previously thought.

  4. Submolecular regulation of cell transformation by deuterium depleting water exchange reactions in the tricarboxylic acid substrate cycle.

    Science.gov (United States)

    Boros, László G; D'Agostino, Dominic P; Katz, Howard E; Roth, Justine P; Meuillet, Emmanuelle J; Somlyai, Gábor

    2016-02-01

    The naturally occurring isotope of hydrogen ((1)H), deuterium ((2)H), could have an important biological role. Deuterium depleted water delays tumor progression in mice, dogs, cats and humans. Hydratase enzymes of the tricarboxylic acid (TCA) cycle control cell growth and deplete deuterium from redox cofactors, fatty acids and DNA, which undergo hydride ion and hydrogen atom transfer reactions. A model is proposed that emphasizes the terminal complex of mitochondrial electron transport chain reducing molecular oxygen to deuterium depleted water (DDW); this affects gluconeogenesis as well as fatty acid oxidation. In the former, the DDW is thought to diminish the deuteration of sugar-phosphates in the DNA backbone, helping to preserve stability of hydrogen bond networks, possibly protecting against aneuploidy and resisting strand breaks, occurring upon exposure to radiation and certain anticancer chemotherapeutics. DDW is proposed here to link cancer prevention and treatment using natural ketogenic diets, low deuterium drinking water, as well as DDW production as the mitochondrial downstream mechanism of targeted anti-cancer drugs such as Avastin and Glivec. The role of (2)H in biology is a potential missing link to the elusive cancer puzzle seemingly correlated with cancer epidemiology in western populations as a result of excessive (2)H loading from processed carbohydrate intake in place of natural fat consumption. Published by Elsevier Ltd.

  5. Isobaric analog states in rare-earth nuclei studied with the (3He,t) charge-exchange reaction at thetasub(L)=00

    International Nuclear Information System (INIS)

    Jaenecke, J.

    1983-01-01

    The ( 3 He, t) charge-exchange reaction leading to the ground-state isobaric analog states (IAS) of sup(152, 154, 156, 158, 160)Gd, sup(160, 162)Dy, sup(162, 164, 166, 168, 170)Er, sup(170, 172, 174, 176)Yb and sup(176, 178, 180)Hf has been studied at thetasub(L) = 0 0 and E( 3 He) = 60.5 MeV. The reaction 28 Si( 3 He, t) 28 P was used for energy calibration. The centroid energies of most IAS were determined to +- 6 keV. Coulomb displacement energies have been extracted from the measured Q-values. They display the influence of non-spherical nuclear shapes which increase the rms radii and lower the Coulomb displacement energies. The dependence on both quadrupole and hexadecapole deformations is apparent with deformation parameters in good agreement with results from other measurements. The total widths GAMMA of the IAS are in the range 30 to 110 keV. They increase more strongly with neutron excess than is known for the IAS of the Sn and Te isotopes. The width of the IAS of 176 Yb is anomalously low. The zero-degree ( 3 He, t) cross sections are in the range 5 to 20 μb/sr. They generally increase with neutron excess except for the sequence of Yb isotopes. No systematic dependence on (N - Z) appears to exist. Excitation energies and zero-degree cross sections for the reactions 28 Si( 3 He, t) 28 P, 16 O( 3 He, t) 16 F and 12 C( 3 He,t) 12 N are reported. (orig.)

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

    Science.gov (United States)

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

    2014-02-01

    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+.

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

    Science.gov (United States)

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

    2014-02-01

    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+).

  8. Investor Reaction to Market Surprises on the Istanbul Stock Exchange Investor Reaction to Market Surprises on the Istanbul Stock Exchange = İstanbul Menkul Kıymetler Borsasında Piyasa Sürprizlerine Yatırımcı Tepkisi

    Directory of Open Access Journals (Sweden)

    Yaman Ömer ERZURUMLU

    2011-08-01

    Full Text Available This paper examines the reaction of investors to the arrival of unexpected information on the Istanbul Stock Exchange. The empirical results suggest that the investor reaction following unexpected news on the ISE100 is consistent with Overreaction Hypothesis especially after unfavorable market surprises. Interestingly such pattern does not exist for ISE30 index which includes more liquid and informationally efficient securities. A possible implication of this study for investors is that employing a semi contrarian investment strategy of buying losers in ISE100 may generate superior returns. Moreover, results are supportive of the last regulation change of Capital Market Board of Turkey which mandates more disclosure regarding the trading of less liquid stocks with lower market capitalization.

  9. Metal-ligand interactions

    Science.gov (United States)

    Ervin, Kent M.

    Experimental studies of the interactions of small transition-metal cluster anions with carbonyl ligands are reviewed and compared with neutral and cationic clusters. Under thermal conditions, the reaction rates of transition-metal clusters with carbon monoxide are measured as a function of cluster size. Saturation limits for carbon monoxide addition can be related to the geometric structures of the clusters. Both energy-resolved threshold collision-induced dissociation experiments and time-resolved photodissociation experiments are used to measure metal-carbonyl binding energies. For platinum and palladium trimer anions, the carbonyl binding energies are assigned to different geometric binding sites. Platinum and palladium cluster anions catalyse the oxidation of carbon monoxide to carbon dioxide in a full catalytic cycle at thermal energies.

  10. The value of molecular expression of KIT and KIT ligand analysed using real-time polymerase chain reaction and immunohistochemistry as a prognostic indicator for canine cutaneous mast cell tumours.

    Science.gov (United States)

    Costa Casagrande, T A; de Oliveira Barros, L M; Fukumasu, H; Cogliati, B; Chaible, L M; Dagli, M L Z; Matera, J M

    2015-03-01

    This study investigated the correlation between KIT gene expression determined by immunohistochemistry and real-time polymerase chain reaction (RT-PCR) and the rate of tumour recurrence and tumour-related deaths in dogs affected with mast cell tumour (MCT). Kaplan-Meier curves were constructed to compare tumour recurrence and tumour-related death between patients. The log-rank test was used to check for significant differences between curves. KIT-I, KIT-II and KIT-III staining patterns were observed in 9 (11.11%), 50 (61.73%) and 22 (27.16%) tumours, respectively. Tumour recurrence rates and tumour-related deaths were not associated with KIT staining patterns (P = 0278, P > 0.05), KIT (P = 0.289, P > 0.05) or KIT ligand (P = 0.106, P > 0.05) gene expression. Despite the lack of association between KIT staining pattern and patient survival time, the results suggest a correlation between aberrant KIT localization and increased proliferative activity of MCTs. RT-PCR seems to be a sensible method for quantitative detection of KIT gene expression in canine MCT, although expressions levels are not correlated with prognosis. © 2013 Blackwell Publishing Ltd.

  11. Bexarotene ligand pharmaceuticals.

    Science.gov (United States)

    Hurst, R E

    2000-12-01

    target rates; side effects were primarily limited to local skin reactions [349982]. Ligand has worldwide rights to market bexarotene capsules, and will market the drug in the US, Canada and selected European markets. In Spain, Portugal, Greece and Central and South America, Ferrer Internacional will market and distribute the drug. As of December 1999, Ligand was seeking additional distribution partners for select European and Asian markets [351604]. In January 2000, Alfa Wassermann signed an agreement with Ligand to exclusively market and distribute Targretin gel and capsules in Italy. Alfa paid US $0.75 million on signing with additional amounts up to an aggregate total of US $1.0 million on achievement of certain registration milestones, which are expected to be met in 2000 [351882].

  12. Relationship Between Equilibrium Hydrogen Pressure and Exchange Current for the Hydrogen Electrode-Reaction at Mmni(3.9-X)Mn(0.4)A1(X)Co(0.7) Alloy Electrodes

    NARCIS (Netherlands)

    Senoh, H.; Morimoto, K.; Inoue, H.; Iwakura, C.; Notten, P.H.L.

    2000-01-01

    We present a theoretical relationship between equilibrium hydrogen pressure and exchange current for the hydrogen electrode reaction which considers the degree of hydrogen coverage at the electrode surface. Electrochemical measurements at MmNi3.9–xMn0.4AlxCo0.7 (0 x 0.8) electrodes were performed to

  13. The isotope separation by ion exchange chromatography. Application to the lithium isotopes separation

    International Nuclear Information System (INIS)

    Albert, M.G.; Barre, Y.; Neige, R.

    1993-01-01

    In this work is described the used study step to demonstrate the industrial feasibility of a lithium isotopes separation process by ion exchange chromatography. After having recalled how is carried out the exchange reaction between the lithium isotopes bound on the cations exchanger resin and those which are in solution and gave the ion exchange chromatography principle, the authors establish a model which takes into account the cascade theory already used for enriched uranium production. The size parameters of this model are: the isotopic separation factor (which depends for lithium of the ligands nature and of the coordination factor), the isotopic exchange kinetics and the mass flow (which depends of the temperature, the lithium concentration, the resins diameter and the front advance). The way they have to be optimized and the implementation of the industrial process are given. (O.M.)

  14. Stability of a Cu0.7Co2.3O4 electrode during the oxygen evolution reaction for alkaline anion-exchange membrane water electrolysis

    Science.gov (United States)

    Kang, Kyoung Eun; Kim, Chi Ho; Lee, Myung Sup; Jung, Chang Wook; Kim, Yang Do; Lee, Jae Ho

    2018-01-01

    The electrode materials for oxygen evolution, especially non-platinum group metal oxides, have attracted increasing attention. Among the spinel-type transition metal oxides, Cu0.7Co2.3O4 powders were evaluated as a potential replacement for expensive dimensionally stabilized anode materials. Cu0.7Co2.3O4 powder for use as an electrode material for oxygen evolution in an alkaline anion-exchange membrane water electrolyzer was prepared using a thermal decomposition method. The Cu0.7Co2.3O4 powders heat-treated at 250 °C exhibited the same X-ray diffraction patterns without any secondary phases as the Co3O4 spinel structure did. The Cu0.7Co2.3O4 powders heat-treated at 250 °C for 30 minutes showed the smallest mean particle size of approximately 376 nm with the powders having a homogeneous shape and size distribution. The fine powders with a relatively homogeneous size distribution showed a higher current density during the oxygen evolution reaction. The lifetime of the Cu0.7Co2.3O4 electrode was relatively long at a low current density, but was quickly shortened due to physical detachment of the Cu0.7Co2.3O4 powders as the current density was increased. This study showed that the efficiency and the stability of Cu0.7Co2.3O4 powders during the oxygen evolution reaction were related directly to the active electrode area.

  15. Ion-exchange separation of radioiodine and its application to production of {sup 124}I by alpha particle induced reactions on antimony

    Energy Technology Data Exchange (ETDEWEB)

    Shuza Uddin, Md. [Forschungszentrum Juelich (Germany). Inst. fuer Neurowissenschaften und Medizin, INM-5: Nuklearchemie; Atomic Energy Research Establishment, Inst. of Nuclear Science and Technology, Dhaka (Bangladesh); Qaim, Seyed M.; Spahn, Ingo; Spellerberg, Stefan; Scholten, Bernhard; Coenen, Heinz H. [Forschungszentrum Juelich (Germany). Inst. fuer Neurowissenschaften und Medizin, INM-5: Nuklearchemie; Hermanne, Alex [Vrije Univ. Brussel (Belgium). Cyclotron Lab.; Hossain, Syed Mohammod [Atomic Energy Research Establishment, Inst. of Nuclear Science and Technology, Dhaka (Bangladesh)

    2015-07-01

    The basic parameters related to radiochemical separation of iodine from tellurium and antimony by anion-exchange chromatography using the resin Amberlyst A26 were studied. The separation yield of {sup 124}I amounted to 96% and the decontamination factor from {sup 121}Te and {sup 122}Sb was > 10{sup 4}. The method was applied to the production of {sup 124}I via the {sup 123}Sb(α, 3n) reaction. In an irradiation of 110 mg of {sup nat}Sb{sub 2}O{sub 3} (thickness ∝0.08 g/cm{sup 2}) with 38 MeV α-particles at 1.2 μA beam current for 4 h, corresponding to the beam energy range of E{sub α} = 37 → 27 MeV, the batch yield of {sup 124}I obtained was 12.42 MBq and the {sup 125}I and {sup 126}I impurities amounted to 3.8% and 0.7%, respectively. The experimental batch yield of {sup 124}I amounted to 80% of the theoretically calculated value but the level of the radionuclidic impurities were in agreement with the theoretical values. About 96% of the radioiodine was in the form of iodide and the inactive impurities (Te, Sb, Sn) were below the permissible level. Due to the relatively high level of radionuclidic impurity the {sup 124}I produced would possibly be useful only for restricted local consumption or for animal experiments.

  16. Ion exchange and trace element surface complexation reactions associated with applied recharge of low-TDS water in the San Joaquin Valley, California

    International Nuclear Information System (INIS)

    McNab, Walt W.; Singleton, Michael J.; Moran, Jean E.; Esser, Bradley K.

    2009-01-01

    Stable isotope data, a dissolved gas tracer study, groundwater age dating, and geochemical modeling were used to identify and characterize the effects of introducing low-TDS recharge water in a shallow aerobic aquifer affected by a managed aquifer recharge project in California's San Joaquin Valley. The data all consistently point to a substantial degree of mixing of recharge water from surface ponds with ambient groundwater in a number of nearby wells screened at depths above 60 m below ground surface. Groundwater age data indicate that the wells near the recharge ponds sample recently recharged water, as delineated by stable O and C isotope data as well as total dissolved solids, in addition to much older groundwater in various mixing proportions. Where the recharge water signature is present, the specific geochemical interactions between the recharge water and the aquifer material appear to include ion exchange reactions (comparative enrichment of affected groundwater with Na and K at the expense of Ca and Mg) and the desorption of oxyanion-forming trace elements (As, V, and Mo), possibly in response to the elevated pH of the recharge water

  17. Genetic polymorphisms of tumour necrosis factor receptor superfamily 1b and fas ligand are associated with clinical efficacy and/or acute severe infusion reactions to infliximab in Crohn's disease

    DEFF Research Database (Denmark)

    Steenholdt, C; Enevold, C; Ainsworth, M A

    2012-01-01

    Single nucleotide polymorphisms (SNPs) in TNF receptor superfamily (TNFRSF) 1A and 1B, and Fas ligand (FASLG) genes, have been associated with responsiveness to infliximab (IFX) in Crohn's disease.......Single nucleotide polymorphisms (SNPs) in TNF receptor superfamily (TNFRSF) 1A and 1B, and Fas ligand (FASLG) genes, have been associated with responsiveness to infliximab (IFX) in Crohn's disease....

  18. Reduction of dinitrogen ligands

    International Nuclear Information System (INIS)

    Richards, R.L.

    1983-01-01

    Processes of dinitrogen ligand reduction in complexes of transition metals are considered. The basic character of the dinitrogen ligand is underlined. Data on X-ray photoelectronic spectroscopy and intensities of bands ν (N 2 ) in IR-spectra of nitrogen complexes are given. The mechanism of protonation of an edge dinitrogen ligand is discussed. Model systems and mechanism of nitrogenogenase are compared

  19. Reactions of [WI2(CO)(NCMe)(η2-RC2R)2] (R = Me, Ph) with pyridines and related ligands, X-ray crystal structure of [WI(CO)(bpy)(η2-MeC2Me)2][BPh4

    International Nuclear Information System (INIS)

    Baker, P.K.; Armstrong, E.M.; Drew, M.G.B.

    1988-01-01

    The reactions of the highly versatile bis(alkyne) compounds [WI 2 (CO)(NCMe)(η 2 -RC 2 R) 2 ] (R = Me, Ph) with pyridine and related ligands to give neutral and cationic alkyne complexes are reported. The x-ray structure of [WI 2 (CO)(bpy)(η 2 -MeC 2 Me) 2 ][BPh 4 ] was also measured and is reported. 10 references, 1 figure, 6 tables

  20. Photo-Induced Electron-Exchange Reactions Exhibiting Chain Characteristics; Echanges d'Electrons Photoinduits Presentant les Caracteristiques d'une Reaction en Chaine; Vyzvannye fotonami reaktsii ehlektronnogo obmena, proyavlyayushchie kharakteristiki tsepochki; Intercambio de Electrones Fotoinducido del Tipo de Cadena

    Energy Technology Data Exchange (ETDEWEB)

    Stranks, D. R.; Yandell, J. R. [University of Adelaide, Adelaide (Australia)

    1965-10-15

    The absorption of light of an appropriate wavelength can markedly accelerate the rate of a two-electron exchange reaction. Charge-transfer absorption generates an intermediate oxidation state which is responsible for propagating a chain reaction between the two stable oxidation states. The general kinetic equations for exchange systems involving chain propagation and either linear or quadratic termination are derived. It is shown that the dependence of the observed quantum yield on reactant concentrations and the absorbed light intensity is more complex than has been hitherto assumed. In principle, a kinetic investigation of such an exchange system should evaluate the primary quantum yield for the initial charge-transfer absorption process, the rates of electron transfer between each of the two stable oxidation states and the intermediate state, and the rate of disproportionation of the intermediate oxidation state. These general considerations are illustrated with the results of an experimental study of the thallium(I)- thallium(III) system. Selective charge-transfer absorption at 2537 A by the Tl{sup 3+}. OH{sup -} ion-pair is used to generate Tl{sup II}. The ensuing exchange reaction with Tl{sup +} exhibits marked induction periods and is sensitive to micromolar concentrations of oxidants and reductants. At millimolar concentrations of Tl{sup +} and Tl{sup 3+}, the observed quantum yields are directly proportional to the Tl{sup +} and Tl{sup 3+} concentrations. At higher concentrations, the quantum yields level oui to ''plateau'' values which range from 6 to 30, depending on the absorbed light intensity. The plateau quantum yield is a direct measure of the relative rates of the propagation reactions Tl{sup +} + Tl{sup 2+} -> Tl{sup 2+} + T1+ and Tl{sup 2+} + Tl{sup 3+} -> Tl{sup 3+} + Tl{sup 2+} compared to the termination reaction 2 Tl{sup 2+} -> Tl{sup +} + Tl{sup 3+}. This disproportionation reaction is consistent with a light intensity exponent of 0. 50