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Sample records for cationic intermediate stabilization

  1. Planar Chiral, Ferrocene-Stabilized Silicon Cations.

    Science.gov (United States)

    Schmidt, Ruth K; Klare, Hendrik F T; Fröhlich, Roland; Oestreich, Martin

    2016-04-01

    The preparation of a series of planar chiral, ferrocenyl-substituted hydrosilanes as precursors of ferrocene-stabilized silicon cations is described. These molecules also feature stereogenicity at the silicon atom. The generation and (29) Si NMR spectroscopic characterization of the corresponding silicon cations is reported, and problems arising from interactions of the electron-deficient silicon atom and adjacent C(sp(3) )-H bonds or aromatic π donors are discussed. These issues are overcome by tethering another substituent at the silicon atom to the ferrocene backbone. The resulting annulation also imparts conformational rigidity and steric hindrance in such a way that the central chirality at the silicon atom is set with complete diastereocontrol. These chiral Lewis acid catalysts were then tested in difficult Diels-Alder reactions, but no enantioinduction was seen. PMID:26929105

  2. Cation-Cation Complexes of Pentavalent Uranyl: From Disproportionation Intermediates to Stable Clusters

    Energy Technology Data Exchange (ETDEWEB)

    Mougel, Victor; Horeglad, Pawel; Nocton, Gregory; Pecaut, Jacques; Mazzanti, Marinella [CEA, INAC, SCIB, Laboratoire de Reconnaissance Ionique et Chimie de Coordination, CEA-Grenoble, 38054 GRENOBLE, Cedex 09 (France)

    2010-07-01

    Three new cation cation complexes of pentavalent uranyl, stable with respect to the disproportionation reaction, have been prepared from the reaction of the precursor [(UO{sub 2}py{sub 5})-(KI{sub 2}py{sub 2})]{sub n} (1) with the Schiff base ligands salen{sup 2-}, acacen{sup 2-}, and salophen{sup 2-} (H{sub 2}salen N, N'-ethylene-bis(salicylidene-imine), H{sub 2}acacen=-N, N'-ethylenebis(acetylacetone-imine), H{sub 2}salophen=N, N'-phenylene-bis(salicylidene-imine)). The preparation of stable complexes requires a careful choice of counter ions and reaction conditions. Notably the reaction of 1 with salophen{sup 2-} in pyridine leads to immediate disproportionation, but in the presence of [18]crown-6 ([18]C-6) a stable complex forms. The solid-state structure of the four tetra-nuclear complexes ([UO{sub 2}-(acacen)]{sub 4}[{mu}{sub 8}-]{sub 2}[K([18]C-6)(py)]{sub 2}) (3) and ([UO{sub 2}(acacen)](4)[{mu}{sub 8}-]).2[K([222])(py)] (4) ([UO{sub 2}(salophen)](4)[{mu}{sub 8}-K]{sub 2}[mu(5)-KI]{sub 2}[(K([18]C-6)]).2 [K([18]C-6)-(thf){sub 2}].2I (5), and ([UO{sub 2}(salen)(4)][{mu}{sub 8}-Rb]{sub 2}[Rb([18]C-6)]{sub 2}) (9) ([222] = [222]cryptand, py =pyridine), presenting a T-shaped cation cation interaction has been determined by X-ray crystallographic studies. NMR spectroscopic and UV/Vis studies show that the tetra-nuclear structure is maintained in pyridine solution for the salen and acacen complexes. Stable mononuclear complexes of pentavalent uranyl are also obtained by reduction of the hexavalent uranyl Schiff base complexes with cobaltocene in pyridine in the absence of coordinating cations. The reactivity of the complex [U{sup V}O{sub 2}(salen)(py)][Cp*{sub 2}Co] with different alkali ions demonstrates the crucial effect of coordinating cations on the stability of cation cation complexes. The nature of the cation plays a key role in the preparation of stable cation cation complexes. Stable tetra-nuclear complexes form in the presence of K

  3. A sulfonium cation intermediate in the mechanism of methionine sulfoxide reductase B: a DFT study.

    Science.gov (United States)

    Robinet, Jesse J; Dokainish, Hisham M; Paterson, David J; Gauld, James W

    2011-07-28

    The hybrid density functional theory method B3LYP in combination with three systematically larger active site models has been used to investigate the substrate binding and catalytic mechanism by which Neisseria gonorrhoeae methionine sulfoxide reductase B (MsrB) reduces methionine-R-sulfoxide (Met-R-SO) to methionine. The first step in the overall mechanism is nucleophilic attack of an active site thiolate at the sulfur of Met-R-SO to form an enzyme-substrate sulfurane. This occurs with concomitant proton transfer from an active site histidine (His480) residue to the substrates oxygen center. The barrier for this step, calculated using our largest most complete active site model, is 17.2 kJ mol(-1). A subsequent conformational rearrangement and intramolecular -OH transfer to form an enzyme-derived sulfenic acid ((Cys495)S-OH) is not enzymatically feasible. Instead, transfer of a second proton from a second histidyl active site residue (His477) to the sulfurane's oxygen center to give water and a sulfonium cation intermediate is found to be greatly preferred, occurring with a quite low barrier of just 1.2 kJ mol(-1). Formation of the final product complex in which an intraprotein disulfide bond is formed with generation of methionine preferably occurs in one step via nucleophilic attack of the sulfur of a second enzyme thiolate ((Cys440)S(-)) at the S(Cys495) center of the sulfonium intermediate with a barrier of 23.8 kJ mol(-1). An alternate pathway for formation of the products via a sulfenic acid intermediate involves enzymatically feasible, but higher energy barriers. The role and impact of hydrogen bonding and active site residues on the properties and stability of substrate and mechanism intermediates and the affects of mutating His477 are also examined and discussed. PMID:21721538

  4. Nitrogen-doped zirconia: A comparison with cation stabilized zirconia

    International Nuclear Information System (INIS)

    The conductivity behavior of nitrogen-doped zirconia is compared with that of zirconia doped with lower-valent cations and discussed in the framework of defect-defect interactions. While nominally introducing the same number of vacancies as yttrium, nitrogen dopants introduced in the anion sublattice of zirconia lead to substantially different defect kinetics and energetics. Compared to the equivalent yttrium doping nitrogen doping in the Y-Zr-O-N system substantially increases the activation energy and correspondingly decreases the conductivity at temperatures below 500-bar C in the vacancy range below 4mol%. The comparison of N-doped zirconia and zirconia systems doped with size-matched cation stabilizers, such as Sc, Yb and Y, shows that elastically driven vacancy-vacancy ordering interactions can phenomenologically account for the temperature- and composition-dependence. It is striking that materials with superior high-temperature conductivities due to weak dopant-vacancy interactions undergo severe deterioration at low temperature due to the strong vacancy-ordering. The analysis also explains qualitatively similar effects of Y co-doping in Yb-, Sc-, and N-doped zirconia. Small amount of Y in N-doped zirconia as well as in Sc-doped zirconia appears to hinder the formation of the long-range ordered phase and thus enhance the conductivity substantially

  5. Intermediate-range chemical ordering of cations in molten RbCl-AgCl

    Energy Technology Data Exchange (ETDEWEB)

    Tahara, S. [Department of Physics and Earth Sciences, Faculty of Science, University of the Ryukyus, Okinawa 903-0213 (Japan); Research and Utilization Division, Japan Synchrotron Radiation Research Institute (JASRI, SPring-8), Hyogo 679-5198 (Japan); Kawakita, Y. [J-PARC Center, Japan Atomic Energy Agency (JAEA), Ibaraki 319-1195 (Japan); Shimakura, H. [Faculty of Pharmacy, Niigata University of Pharmacy and Applied Life Sciences, Niigata 956-8603 (Japan); Ohara, K. [Research and Utilization Division, Japan Synchrotron Radiation Research Institute (JASRI, SPring-8), Hyogo 679-5198 (Japan); Fukami, T. [Department of Physics and Earth Sciences, Faculty of Science, University of the Ryukyus, Okinawa 903-0213 (Japan); Takeda, S. [Department of Physics, Faculty of Sciences, Kyushu University, Fukuoka 812-8581 (Japan)

    2015-07-28

    A first sharp diffraction peak (FSDP) is observed in the X-ray total structure factor of a molten mixture of RbCl-AgCl, while both pure melts of RbCl and AgCl do not exhibit FSDP individually. Molecular dynamics simulations were performed to investigate the origin of the FSDP with the polarizable ion model (PIM). Coexistence of covalent Ag–Cl and ionic Rb–Cl bonds leads the system to evolve intermediate range ordering, which is simulated by introducing the induced polarization in different ways between Ag–Cl with fully polarizable treatment based on Vashishta-Raman potential and Rb–Cl with suppression over-polarization in the nearest neighbor contribution based on Born-Meyer potential. The partial structure factors for both the Ag–Ag and Rb–Rb correlations, S{sub AgAg}(Q) and S{sub RbRb}(Q), show a positive contribution to the FSDP, while S{sub AgRb}(Q) for the Ag–Rb correlation exhibits a negative contribution, indicating that Ag and Rb ions are distributed in an alternating manner within the intermediate-range length scale. The origin of the intermediate-range chemical ordering of cations can be ascribed to the preferred direction of the dipole moments of anions in the PIM.

  6. Intermediate-range chemical ordering of cations in molten RbCl-AgCl

    International Nuclear Information System (INIS)

    A first sharp diffraction peak (FSDP) is observed in the X-ray total structure factor of a molten mixture of RbCl-AgCl, while both pure melts of RbCl and AgCl do not exhibit FSDP individually. Molecular dynamics simulations were performed to investigate the origin of the FSDP with the polarizable ion model (PIM). Coexistence of covalent Ag–Cl and ionic Rb–Cl bonds leads the system to evolve intermediate range ordering, which is simulated by introducing the induced polarization in different ways between Ag–Cl with fully polarizable treatment based on Vashishta-Raman potential and Rb–Cl with suppression over-polarization in the nearest neighbor contribution based on Born-Meyer potential. The partial structure factors for both the Ag–Ag and Rb–Rb correlations, SAgAg(Q) and SRbRb(Q), show a positive contribution to the FSDP, while SAgRb(Q) for the Ag–Rb correlation exhibits a negative contribution, indicating that Ag and Rb ions are distributed in an alternating manner within the intermediate-range length scale. The origin of the intermediate-range chemical ordering of cations can be ascribed to the preferred direction of the dipole moments of anions in the PIM

  7. Stabilizing intermediate-term medium-range earthquake predictions

    International Nuclear Information System (INIS)

    A new scheme for the application of the intermediate-term medium-range earthquake prediction algorithm M8 is proposed. The scheme accounts for the natural distribution of seismic activity, eliminates the subjectivity in the positioning of the areas of investigation and provides additional stability of the predictions with respect to the original variant. According to the retroactive testing in Italy and adjacent regions, this improvement is achieved without any significant change of the alarm volume in comparison with the results published so far. (author)

  8. Electron exchange involving a sulfur-stabilized ruthenium radical cation.

    Science.gov (United States)

    Shaw, Anthony P; Ryland, Bradford L; Norton, Jack R; Buccella, Daniela; Moscatelli, Alberto

    2007-07-01

    Half-sandwich Ru(II) amine, thiol, and thiolate complexes were prepared and characterized by X-ray crystallography. The thiol and amine complexes react slowly with acetonitrile to give free thiol or amine and the acetonitrile complex. With the thiol complex, the reaction is dissociative. The thiolate complex has been oxidized to its Ru(III) radical cation and the solution EPR spectrum of that radical cation recorded. Cobaltocene reduces the thiol complex to the thiolate complex. The 1H and 31P NMR signals of the thiolate complex in acetonitrile become very broad whenever the thiolate and thiol complexes are present simultaneously. The line broadening is primarily due to electron exchange between the thiolate complex and its radical cation; the latter is generated by an unfavorable redox equilibrium between the thiol and thiolate complexes. Pyramidal inversion of sulfur in the thiol complex is fast at room temperature but slow at lower temperatures; major and minor conformers of the thiol complex were observed by 31P NMR at -98 degrees C in CD2Cl2. PMID:17569530

  9. A cation binding motif stabilizes the compound I radical of cytochrome c peroxidase.

    Science.gov (United States)

    Miller, M A; Han, G W; Kraut, J

    1994-11-01

    Cytochrome c peroxidase reacts with peroxide to form compound I, which contains an oxyferryl heme and an indolyl radical at Trp-191. The indolyl free radical has a half-life of several hours at room temperature, and this remarkable stability is essential for the catalytic function of cytochrome c peroxidase. To probe the protein environment that stabilizes the compound I radical, we used site-directed mutagenesis to replace Trp-191 with Gly or Gln. Crystal structures of these mutants revealed a monovalent cation binding site in the cavity formerly occupied by the side chain of Trp-191. Comparison of this site with those found in other known cation binding enzymes shows that the Trp-191 side chain resides in a consensus K+ binding site. Electrostatic potential calculations indicate that the cation binding site is created by partial negative charges at the backbone carbonyl oxygen atoms of residues 175 and 177, the carboxyl end of a long alpha-helix (residues 165-175), the heme propionates, and the carboxylate side chain of Asp-235. These features create a negative potential that envelops the side chain of Trp-191; the calculated free energy change for cation binding in this site is -27 kcal/mol (1 cal = 4.184J). This is more than sufficient to account for the stability of the Trp-191 radical, which our estimates suggest is stabilized by 7.8 kcal/mol relative to a Trp radical in solution. PMID:7972020

  10. Kinetic Monte Carlo Simulation of Oxygen and Cation Diffusion in Yttria-Stabilized Zirconia

    Science.gov (United States)

    Good, Brian

    2011-01-01

    Yttria-stabilized zirconia (YSZ) is of interest to the aerospace community, notably for its application as a thermal barrier coating for turbine engine components. In such an application, diffusion of both oxygen ions and cations is of concern. Oxygen diffusion can lead to deterioration of a coated part, and often necessitates an environmental barrier coating. Cation diffusion in YSZ is much slower than oxygen diffusion. However, such diffusion is a mechanism by which creep takes place, potentially affecting the mechanical integrity and phase stability of the coating. In other applications, the high oxygen diffusivity of YSZ is useful, and makes the material of interest for use as a solid-state electrolyte in fuel cells. The kinetic Monte Carlo (kMC) method offers a number of advantages compared with the more widely known molecular dynamics simulation method. In particular, kMC is much more efficient for the study of processes, such as diffusion, that involve infrequent events. We describe the results of kinetic Monte Carlo computer simulations of oxygen and cation diffusion in YSZ. Using diffusive energy barriers from ab initio calculations and from the literature, we present results on the temperature dependence of oxygen and cation diffusivity, and on the dependence of the diffusivities on yttria concentration and oxygen sublattice vacancy concentration. We also present results of the effect on diffusivity of oxygen vacancies in the vicinity of the barrier cations that determine the oxygen diffusion energy barriers.

  11. Synthesis of linear and cyclic peptide-PEG-lipids for stabilization and targeting of cationic liposome-DNA complexes.

    Science.gov (United States)

    Ewert, Kai K; Kotamraju, Venkata Ramana; Majzoub, Ramsey N; Steffes, Victoria M; Wonder, Emily A; Teesalu, Tambet; Ruoslahti, Erkki; Safinya, Cyrus R

    2016-03-15

    Because nucleic acids (NAs) have immense potential value as therapeutics, the development of safe and effective synthetic NA vectors continues to attract much attention. In vivo applications of NA vectors require stabilized, nanometer-scale particles, but the commonly used approaches of steric stabilization with a polymer coat (e.g., PEGylation; PEG=poly(ethylene glycol)) interfere with attachment to cells, uptake, and endosomal escape. Conjugation of peptides to PEG-lipids can improve cell attachment and uptake for cationic liposome-DNA (CL-DNA) complexes. We present several synthetic approaches to peptide-PEG-lipids and discuss their merits and drawbacks. A lipid-PEG-amine building block served as the common key intermediate in all synthetic routes. Assembling the entire peptide-PEG-lipid by manual solid phase peptide synthesis (employing a lipid-PEG-carboxylic acid) allowed gram-scale synthesis but is mostly applicable to linear peptides connected via their N-terminus. Conjugation via thiol-maleimide or strain-promoted (copper-free) azide-alkyne cycloaddition chemistry is highly amenable to on-demand preparation of peptide-PEG-lipids, and the appropriate PEG-lipid precursors are available in a single chemical step from the lipid-PEG-amine building block. Azide-alkyne cycloaddition is especially suitable for disulfide-bridged peptides such as iRGD (cyclic CRGDKGPDC). Added at 10 mol% of a cationic/neutral lipid mixture, the peptide-PEG-lipids stabilize the size of CL-DNA complexes. They also affect cell attachment and uptake of nanoparticles in a peptide-dependent manner, thereby providing a platform for preparing stabilized, affinity-targeted CL-DNA nanoparticles. PMID:26874401

  12. Storage Stability and Improvement of Intermediate Moisture Foods

    Science.gov (United States)

    Labuza, T. P.

    1976-01-01

    Shelf life tests are used to estimate the rate of nonenzymatic browning; however, controlling the reducing sugar levels below 23:1 molar ratio to amines, slows the rate. In addition, liquid glycols surpress browning. The protozoan Tetrahymena pyriformis W can be used to estimate nutrition losses during browning. At high temperatures (80 to 120 C) used in processing intermediate moisture foods (IMF), vitamin C destruction shifts to a zero order mechanism. BHA and BHT are the most effective antioxidants against rancidity. In shelf life testing however, 45 C should be the maximum temperature used. Water binding agents are studied. The five isotherms of thirteen humectants were determined. The results show that neither the method of addition nor sequence of addition affects the a sub u lowering ability of these humectants. Results were used to formulate shelf stable IMF processed cheese foods with at least four months shelf life.

  13. Improved chemical and electrochemical stability of perovskite oxides with less reducible cations at the surface.

    Science.gov (United States)

    Tsvetkov, Nikolai; Lu, Qiyang; Sun, Lixin; Crumlin, Ethan J; Yildiz, Bilge

    2016-09-01

    Segregation and phase separation of aliovalent dopants on perovskite oxide (ABO3) surfaces are detrimental to the performance of energy conversion systems such as solid oxide fuel/electrolysis cells and catalysts for thermochemical H2O and CO2 splitting. One key reason behind the instability of perovskite oxide surfaces is the electrostatic attraction of the negatively charged A-site dopants (for example, ) by the positively charged oxygen vacancies () enriched at the surface. Here we show that reducing the surface concentration improves the oxygen surface exchange kinetics and stability significantly, albeit contrary to the well-established understanding that surface oxygen vacancies facilitate reactions with O2 molecules. We take La0.8Sr0.2CoO3 (LSC) as a model perovskite oxide, and modify its surface with additive cations that are more and less reducible than Co on the B-site of LSC. By using ambient-pressure X-ray absorption and photoelectron spectroscopy, we proved that the dominant role of the less reducible cations is to suppress the enrichment and phase separation of Sr while reducing the concentration of and making the LSC more oxidized at its surface. Consequently, we found that these less reducible cations significantly improve stability, with up to 30 times faster oxygen exchange kinetics after 54 h in air at 530 °C achieved by Hf addition onto LSC. Finally, the results revealed a 'volcano' relation between the oxygen exchange kinetics and the oxygen vacancy formation enthalpy of the binary oxides of the additive cations. This volcano relation highlights the existence of an optimum surface oxygen vacancy concentration that balances the gain in oxygen exchange kinetics and the chemical stability loss. PMID:27295099

  14. MODIFICATION OF TRANSITION METAL CATIONS TO POLYMER- STABILIZED PLATINUM COLLOIDAL CLUSTERS IN ENANTIOSELECTIVE HYDROGENATION OF METHYL PYRUVATE

    Institute of Scientific and Technical Information of China (English)

    Xiao-ping Yan; Bao-lin He; Jie Zhang; Han-fan Liu

    2005-01-01

    Modification of transition metal cations to polymer-stabilized Pt colloidal clusters modified with cinchonidine was studied in enantioselective hydrogenation of methyl pyruvate. Compared to the enantiomeric excess (e.e.) value (71.4%)obtained without the presence of metal cations, obvious e.e. enhancement (up to 82.5%) was resulted from the addition of Zn2+ but with a certain decrease in activity. The reaction parameters in the presence of Zn2+ were also studied. It was found that the Pt colloidal catalysts in the presence of metal cations performed very differently from that in the absence of metal cations.

  15. Some investigations on the radiation stability of a strongly acidic cation exchange resin

    Science.gov (United States)

    Dessouki, A. M.; Zahran, A. H.; Rabie, A. M.; Amer, S. I.

    The radiation-chemical stability of Merck Cation Exchanger I, a strongly acidic sulphonated cation exchanger of the polymerization type based on styrene-divinylbenze (DVB) copolymers was investigated. The radiation stability of the resin was assessed from the change in exchange capacity, loss in weight, change in swelling behaviour and formation of new exchange groups. The loss in capacity was 44 and 32% for resin specimens in the H +-form irradiated to 1000 Mrad in air and in vacuum, respectively. The Na +-form of the exchanger showed high resistance to radiation and the loss in capacity did not exceed 7% at a dose of 1000 Mrad. The loss in capacity was accompanied by a loss in weight and a decrease in the degree of swelling of the irradiated resin. The formation of new functional groups of the carboxylic and phenolic types was confirmed. The amount of these group increases with the increase in the integral dose. The amount of sulphuric acid formed as a result of irradiating the resin in the dry and moist states was determined. An increase in the moisture content of the resin resulted in a marked decrease in its radiation stability.

  16. Graphene Oxide Nanofiltration Membranes Stabilized by Cationic Porphyrin for High Salt Rejection.

    Science.gov (United States)

    Xu, Xiao-Ling; Lin, Fu-Wen; Du, Yong; Zhang, Xi; Wu, Jian; Xu, Zhi-Kang

    2016-05-25

    Swelling has great influences on the structure stability and separation performance of graphene oxide laminate membranes (GOLMs) for water desalination and purification. Herein, we report cross-linked GOLMs from GO assembled with cationic tetrakis(1-methyl-pyridinium-4-yl)porphyrin (TMPyP) by a vacuum-assisted strategy. The concave nonoxide regions (G regions) of GO are used as cross-linking sites for the first time to precisely control the channel size for water permeation and salt ion retention. Channels around 1 nm are constructed by modulating the assembly ratio of TMPyP/GO, and these cross-linked GOLMs show high salt rejection. PMID:27158976

  17. Radiation stability of macro-porous and gel-type cation exchangers

    International Nuclear Information System (INIS)

    Macro-porous cation exchange resin Dianion CPK-08 and gel-type cation exchange resin Dowex 50WX8 were irradiated with γ-rays from 60Co, while soaked in distilled water, 0.5 M HNO3 or 4 M HNO3, and the ion-exchange properties, such as strong- and weak-acid capacities, moisture content and wet resin volume, were examined in relation to absorbed dose. There was no appreciable difference between the radiation stabilities of the two cation exchangers. Increase of HNO3 concentration reduced the loss of strong-acid capacity and increased the decross-linkage and the weak-acid capacity. Elution characteristics of 137Cs and 99Sr from columns packed with γ-irradiated resin were examined and the column distribution ratio of these radionuclides and the theoretical plate number were calculated. These values decreased with the increase of absorbed dose. Dianion CPK-08 was packed into a pressurized column and irradiated with γ-rays at a dose rate of 2x1O6 R/hr, while water was passed through the column at a constant flow rate. The greatest change in the resin properties was observed at an upper stream position from the position of the highest radiation dose of 2x106 R/hr. (T.G.)

  18. Stability Assessment of Injectable Castor Oil-Based Nano-sized Emulsion Containing Cationic Droplets Stabilized by Poloxamer–Chitosan Emulsifier Films

    OpenAIRE

    S Tamilvanan; Kumar, B. Ajith; Senthilkumar, S. R.; Baskar, Raj; Sekharan, T. Raja

    2010-01-01

    The objectives of the present work were to prepare castor oil-based nano-sized emulsion containing cationic droplets stabilized by poloxamer–chitosan emulgator film and to assess the kinetic stability of the prepared cationic emulsion after subjecting it to thermal processing and freeze–thaw cycling. Presence of cryoprotectants (5%, w/w, sucrose +5%, w/w, sorbitol) improved the stability of emulsions to droplet aggregation during freeze–thaw cycling. After storing the emulsion at 4°C, 25°C, a...

  19. The effect of multivalent cations and Tau on paclitaxel-stabilized microtubule assembly, disassembly, and structure.

    Science.gov (United States)

    Safinya, Cyrus R; Chung, Peter J; Song, Chaeyeon; Li, Youli; Ewert, Kai K; Choi, Myung Chul

    2016-06-01

    In this review we describe recent studies directed at understanding the formation of novel nanoscale assemblies in biological materials systems. In particular, we focus on the effects of multivalent cations, and separately, of microtubule-associated protein (MAP) Tau, on microtubule (MT) ordering (bundling), MT disassembly, and MT structure. Counter-ion directed bundling of paclitaxel-stabilized MTs is a model electrostatic system, which parallels efforts to understand MT bundling by intrinsically disordered proteins (typically biological polyampholytes) expressed in neurons. We describe studies, which reveal an unexpected transition from tightly spaced MT bundles to loose bundles consisting of strings of MTs as the valence of the cationic counter-ion decreases from Z=3 to Z=2. This transition is not predicted by any current theories of polyelectrolytes. Notably, studies of a larger series of divalent counter-ions reveal strong ion specific effects. Divalent counter-ions may either bundle or depolymerize paclitaxel-stabilized MTs. The ion concentration required for depolymerization decreases with increasing atomic number. In a more biologically related system we review synchrotron small angle x-ray scattering (SAXS) studies on the effect of the Tau on the structure of paclitaxel-stabilized MTs. The electrostatic binding of MAP Tau isoforms leads to an increase in the average radius of microtubules with increasing Tau coverage (i.e. a re-distribution of protofilament numbers in MTs). Finally, inspired by MTs as model nanotubes, we briefly describe other more robust lipid-based cylindrical nanostructures, which may have technological applications, for example, in drug encapsulation and delivery. PMID:26684364

  20. Stabilizing effect of divalent metallic cations on membranes against thermal and gamma-irradiation damages

    International Nuclear Information System (INIS)

    Heat treatment of 270C and onward modifies the beet root cell membranes, resulting in the efflux of betacyanin from the tissue slices. No further efflux of betacyanin is observed when tissue slices taken in different sets are heated at a temperature of 450C for different intervals of time, 30, 60 and 90 min each and then transferred to 250 +- 20C, showing thereby that the temperature damage of the membrane is reversible. But if tissue slices are heated for longer durations at 450C, it is noticed that the membranes undergo a plastic strain. Divalent cations, Ca2+, Mg2+, Zn2+ and Pb2+ have been observed to inhibit the heat induced efflux of betacyanin. Also γ-irradiation of these tissue slices altered the membrane permeability and it is seen that calcium ions have a stabilizing effect on membranes against γ-irradiation damage. (author)

  1. Mesityltellurenyl cations stabilized by triphenylpnictogens [MesTe(EPh(3))](+) (E = P, As, Sb).

    Science.gov (United States)

    Beckmann, Jens; Bolsinger, Jens; Duthie, Andrew; Finke, Pamela; Lork, Enno; Lüdtke, Carsten; Mallow, Ole; Mebs, Stefan

    2012-11-19

    The homoleptic 1:1 Lewis pair (LP) complex [MesTe(TeMes2)]O3SCF3 (1) featuring the cation [MesTe(TeMes2)](+) (1a) was obtained by the reaction of Mes2Te with HO3SCF3. The reaction of 1 with Ph3E (E = P, As, Sb, Bi) proceeded with substitution of Mes2Te and provided the heteroleptic 1:1 LP complexes [MesTe(EPh3)]O3SCF3 (2, E = P; 3, E = As) and [MesTe(SbPh3)][Ph2Sb(O3SCF3)2] (4) featuring the cations [MesTe(EPh3)](+) (2a, E = P; 3a, E = As; 4a, E = Sb) and the anion [Ph2Sb(O3SCF3)2](-) (4b). In the reaction with Ph3Bi, the crude product contained the cation [MesTe(BiPh3)](+) (5a) and the anion [Ph2Bi(O3SCF3)2](-) (5b); however, the heteroleptic 1:1 LP complex [MesTe(BiPh3)][Ph2Bi(O3SCF3)2] (5) could not be isolated because of its limited stability. Instead, fractional crystallization furnished a large amount of Ph2BiO3SCF3 (6), which was also obtained by the reaction of Ph3Bi with HO3SCF3. The formation of the anions 4b and 5b involves a phenyl group migration from Ph3E (E = Sb, Bi) to the MesTe(+) cation and afforded MesTePh as the byproduct, which was identified in the mother liquor. The heteroleptic 1:1 LP complexes 2-4 were also obtained by the one-pot reaction of Mes2Te, Ph3E (E = P, As, Sb) and HO3SCF3. Compounds 1-4 and 6 were investigated by single-crystal X-ray diffraction. The molecular structures of 1a-4a were used for density functional theory calculations at the B3PW91/TZ level of theory and studied using natural bond order (NBO) analyses as well as real-space bonding descriptors derived from an atoms-in-molecules (AIM) analysis of the theoretically obtained electron density. Additionally, the electron localizability indicator (ELI-D) and the delocalization index are derived from the corresponding pair density. PMID:23134409

  2. Organometallic Probe for the Electronics of Base-Stabilized Group 11 Metal Cations.

    Science.gov (United States)

    Braunschweig, Holger; Ewing, William C; Kramer, Thomas; Mattock, James D; Vargas, Alfredo; Werner, Christine

    2015-08-24

    A number of trimetalloborides have been synthesized through the reactions of base-stabilized coinage metal chlorides with a dimanganaborylene lithium salt in the hope of using this organometallic platform to compare and evaluate the electronics of these popular coinage metal fragments. The adducts of Cu(I), Ag(I), and Au(I) ions, stabilized by tricyclohexylphosphine (PCy3), N-1,3-bis(4-methylphenyl)imidazol-2-ylidene (ITol), or 1-(2,6-diisopropylphenyl)-3,3,5,5-tetramethylpyrrolidin-2-ylidene (CAAC), with [{Cp(CO)2Mn}2B](-) were studied spectroscopically, structurally, and computationally. The geometries of the adducts fall into two classes, one symmetric and one asymmetric, each relying on the combined characteristics of both the metal and ligand. The energetic factors proposed as the causes of the structural differences were investigated by ETS-NOCV (extended transition state-natural orbitals for chemical valence) analysis, which showed the final geometry to be controlled by the competition between the tendency of the coinage metal to adopt a higher or lower coordination number and the willingness of the cationic fragment to participate in back-bonding interactions. PMID:26178571

  3. Nanocomplexation of thrombin with cationic amylose derivative for improved stability and hemostatic efficacy

    Directory of Open Access Journals (Sweden)

    Zhuang B

    2015-01-01

    Full Text Available Baoxiong Zhuang,1,* Zhihua Li,1,* Jiadong Pang,2,* Wenbin Li,1 Pinbo Huang,1 Jie Wang,1 Yu Zhou,1 Qing Lin,1 Quanbo Zhou,1 Xiao Ye,1 Huilin Ye,1 Yimin Liu,1 Li-Ming Zhang,2 Rufu Chen1 1Department of Hepato-Pancreato-Billiary Surgery, Department of Medical Oncology, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, People’s Republic of China; 2DSAPM Lab and PCFM Lab, Institute of Polymer Science, Department of Polymer and Materials Science, School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou, People’s Republic of China *Authors share co-first authorship Abstract: As a topical hemostatic agent, thrombin has wide application for many surgical treatments. However, native thrombin always suffers from its physical and chemical instabilities. In this work, a nanocomplexation strategy was developed for modifying the stability and hemostatic efficacy of thrombin, in which a water-soluble cationic amylose derivative containing poly(l-lysine dendrons was prepared by a click reaction and then used to complex thrombin in an aqueous system. For resultant thrombin nanocomplexes, their morphology and particle size distribution were investigated. Their stabilities were studied in terms of activity retention percentages under different storage time, pH values, and illumination time. In addition, their ability to achieve in vitro fibrinogen and blood coagulation were evaluated. Via a rat hepatic hemorrhage model and a rat iliac artery hemorrhage model, these thrombin nanocomplexes were confirmed to have good tissue biocompatibility and in vivo hemostatic effectiveness. Keywords: thrombin, nanoparticles, amylose derivative, complexation, stability, hemostatic activity

  4. Cation-pi interactions stabilize the structure of the antimicrobial peptide indolicidin near membranes: molecular dynamics simulations

    DEFF Research Database (Denmark)

    Khandelia, Himanshu; Kaznessis, Yiannis N

    2007-01-01

    We implemented molecular dynamics simulations of the 13-residue antimicrobial peptide indolicidin (ILPWKWPWWPWRR-NH2) in dodecylphosphocholine (DPC) and sodium dodecyl sulfate (SDS) micelles. In DPC, a persistent cation-pi interaction between TRP11 and ARG13 defined the structure of the peptide...... residues to the sulfate groups leads to an extended peptide structure. To the best of our knowledge, this is the first time that a cation-pi interaction between peptide side chains has been shown to stabilize the structure of a small antimicrobial peptide. The simulations are in excellent agreement with...

  5. Formation of an intermediate radical cation in the nanosecond pulse radiolysis of malachite green leucocyanide in organic solvents

    International Nuclear Information System (INIS)

    The malachite green leucocyanide (MGCN) was irradiated in argon or oxygen saturated solutions of n-butyl chloride, 1.2-DCE, CCl4 and acetone with 13 ns electron pulses. Two species with absorption maxima at 620 and 480 nm were observed. The latter was attributed to the malachite green leucocyanide radical cation (MGCN+radical) and the former to the known carbonium ion of malachite green dye (MG+). Observation of the consecutive charge transfer via the schemes: DCE+radical → BPh+radical → MGCN+radical and DCE+radical → MGCN+radical → TMPD+radical, allowed to estimate the ionization potential of MGCN molecule in the range 6.9 eV MGCN +radical radical cation is located in the ''aniline'' part of the molecule. (author)

  6. Aggregation and Stability of Reduced Graphene Oxide: Complex Roles of Divalent Cations, pH, and Natural Organic Matter

    Science.gov (United States)

    The aggregation and stability of graphene oxide (GO) and three successively reduced GO (rGO) nanomaterials were investigated. Reduced GO species were partially reduced GO (rGO-1h), intermediately reduced GO (rGO-2h), and fully reduced GO (rGO-5h). Specifically, influence of pH, i...

  7. Stability of phenol and thiophenol radical cations - interpretation by comparative quantum chemical approaches

    Science.gov (United States)

    Hermann, R.; Naumov, S.; Mahalaxmi, G. R.; Brede, O.

    2000-07-01

    The deprotonation kinetics of phenol-type radical cations, formed via a very efficient electron transfer in the pulse radiolysis of non-polar solutions, for example n-chlorobutane, is governed mainly by electronic effects due to the nature of the phenol substituents, whereas steric effects are of minor importance; thiophenols, which are sulphur analogues of phenols, exhibit a similar behavior. Comparative quantum chemical calculations show that the calculated spin densities at the hetero atoms correlate well with the experimentally determined radical cation lifetimes. Not only the Density Functional Theory (DTF) B3LYP but also the semiempirical quantum chemical model PM3 can be applied for the open shell systems mentioned.

  8. Properties of cationic monosubstituted tetraalkylammonium cyclodextrin derivatives - their stability, complexation ability in solution or when deposited on solid anionic surface.

    Science.gov (United States)

    Popr, Martin; Filippov, Sergey K; Matushkin, Nikolai; Dian, Juraj; Jindřich, Jindřich

    2015-01-01

    The thermal stability of the monosubstituted cationic cyclodextrin (CD) derivatives PEMEDA-β-CD and PEMPDA-β-CD, which differ in their substituent linker length (ethylene and propylene, respectively), was studied via (1)H NMR experiments. PEMPDA-β-CD exhibited higher resistance towards the Hofmann degradation and was chosen as a more suitable host molecule for further studies. Inclusion properties of PEMPDA-β-CD in solution with a series of simple aromatic guests (salicylic acid, p-methoxyphenol and p-nitroaniline) were determined by isothermal titration calorimetry (ITC) and compared to the native β-CD. Permanently charged cationic CD derivatives were successfully deposited on the anionic solid surface of polymeric Nafion(®) 117 membrane via electrostatic interactions. Deposition kinetics and coverage of the surface were determined by ELSD. Finally, the ability of the CD derivatives bound to the solid surface to encapsulate aromatic compounds from aqueous solution was measured by UV-vis spectroscopy. The obtained results are promising for future industrial applications of the monosubstituted β-CD derivatives, because the preparation of cationic CD derivatives is applicable in large scale, without the need of chromatographic purification. Their ionic deposition on a solid surface is simple, yet robust and a straightforward process as well. PMID:25815069

  9. A dimeric DNA interface stabilized by stacked A.(G.G.G.G).A hexads and coordinated monovalent cations.

    Science.gov (United States)

    Kettani, A; Gorin, A; Majumdar, A; Hermann, T; Skripkin, E; Zhao, H; Jones, R; Patel, D J

    2000-03-31

    We report on the identification of an A.(G.G.G.G).A hexad pairing alignment which involves recognition of the exposed minor groove of opposing guanines within a G.G.G.G tetrad through sheared G.A mismatch formation. This unexpected hexad pairing alignment was identified for the d(G-G-A-G-G-A-G) sequence in 150 mM Na(+) (or K(+)) cation solution where four symmetry-related strands align into a novel dimeric motif. Each symmetric half of the dimeric "hexad" motif is composed of two strands and contains a stacked array of an A.(G.G.G.G).A hexad, a G.G.G.G tetrad, and an A.A mismatch. Each strand in the hexad motif contains two successive turns, that together define an S-shaped double chain reversal fold, which connects the two G-G steps aligned parallel to each other along adjacent edges of the quadruplex. Our studies also establish a novel structural transition for the d(G-G-A-G-G-A-N) sequence, N=T and G, from an "arrowhead" motif stabilized through cross-strand stacking and mismatch formation in 10 mM Na(+) solution (reported previously), to a dimeric hexad motif stabilized by extensive inter-subunit stacking of symmetry-related A.(G.G.G.G).A hexads in 150 mM Na(+) solution. Potential monovalent cation binding sites within the arrowhead and hexad motifs have been probed by a combination of Brownian dynamics and unconstrained molecular dynamics calculations. We could not identify stable monovalent cation-binding sites in the low salt arrowhead motif. By contrast, five electronegative pockets were identified in the moderate salt dimeric hexad motif. Three of these are involved in cation binding sites sandwiched between G.G.G. G tetrad planes and two others, are involved in water-mediated cation binding sites spanning the unoccupied grooves associated with the adjacent stacked A.(G.G.G.G).A hexads. Our demonstration of A.(G. G.G.G).A hexad formation opens opportunities for the design of adenine-rich G-quadruplex-interacting oligomers that could potentially target base

  10. Thermodynamic model of the stabilization of an intermediate state in the region of the metamagnetic phase transition in erbium orthoferrite

    International Nuclear Information System (INIS)

    The possible mechanisms of the thermodynamic stabilization of an intermediate state in the first-order metamagnetic phase transition in a magnetic field parallel to the Ising c axis of the Er3+ ions in erbium orthoferrite at T = 1.6 K have been analyzed. The model is chosen using the magneto-optical experimental data on the features of this state

  11. C---lH...O and O...H...O bonded intermediates in the dissociation of low energy methyl glycolate radical cations

    Science.gov (United States)

    Suh, Dennis; Kingsmill, Carol A.; Ruttink, Paul J. A.; Burgers, Peter C.; Terlouw, Johan K.

    1995-08-01

    Low energy methyl glycolate radical cations HOCH2C(=O)OCH3+, 1, abundantly lose HCO, yielding protonated methyl formate H---C(OH)OCH3+. Tandem mass spectrometry based experiments on 2H, 13C and 18O labelled isotopologues show that this loss is largely (about 75%) atom specific. Analysis of the atom connectivity in the product ions indicates that the reaction proceeds analogously to the loss of HCO and CH3CO from ionized acetol HOCH2C(=O)CH3+ and acetoin HOCH(CH3)C(=O)CH3+, respectively. The mechanism, it is proposed, involves isomerization of 1 to the key intermediate CH2=O... H---C(=O)OCH3+, an H-bridged ion-dipole complex of neutral formaldehyde and ionized methyl formate. Next, charge transfer takes place to produce CH3OC(H)=O...HC(H)=O+, an H-bridged ion-dipole complex of ionized formaldehyde and neutral methyl formate, followed by proton transfer to generate the products. Preliminary ab initio calculations executed at the UMP3/6-31G*//6-31G*+ZPVE level of theory are presented in support of this proposal. The non-specific loss of HCO from 1 (about 25%) is rationalized to occur via the same mechanism, but after communication with isomeric dimethyl carbonate ions CH3OC(=O)OCH3+, 2, via the O...H...O bonded intermediate [CH2=O...H...O=C---OCH3]+. The latter pathway is even more important in the formation of CH2OH+ ions from 1 which, it is shown, is not a simple bond cleavage reaction, but may involve consecutive or concerted losses of CH3 and CO2 from the above O...H...O bonded species. Ionized methyl lactate HOCH(CH3)C(=O)OCH3+, the higher homologue of 1, shows a unimolecular chemistry which is akin to that of 1.

  12. Synthesis of cationic hyperbranched multiarm copolymer and its application in self-reducing and stabilizing gold nanoparticles

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    A novel hyperbranched multiarm copolymer of HBPO-star-PDEAEMA with a hydrophobic poly(3-ethyl-3-(hydroxymethyl) oxetane)(HBPO) core and many cationic poly(2-(N,N-diethylamino) ethyl methacrylate)(PDEAEMA) arms has been synthesized through an atom transfer radical polymerization(ATRP) method,and been applied to spontaneously reduce and stabilize gold nanoparticles(AuNPs) in water without other additional agents.The size of the nanoparticles could be effectively controlled at about 4 nm,and the nanoparticles are extremely stable in solution without aggregation even for one year.It was found that solution pH and the molar ratio of N/Au have certain effects on the size and stability of AuNPs.This work provides a simple method for the synthesis of uniform and highly stable AuNPs.

  13. The Free Tricoordinated Silyl Cation Problem

    Directory of Open Access Journals (Sweden)

    Čičak, H.

    2010-03-01

    Full Text Available As the importance and abundance of silicon in our environment is large, it has been thought that silicon might take the place of carbon in forming a host of similar compounds and silicon-based life. However, until today there is no experimental evidence for such a hypothesis and carbon is still unique among the elements in the vast number and variety of compounds it can form. Also, the corresponding derivatives of the two elements show considerable differences in their chemical properties.The essential debate concerning organosilicon chemistry relates to the existence of the free planar tricoordinated silyl cations in condensed phase (R3Si+, in analogy to carbocations (R3C+ which have been known and characterized as free species. Although silyl cations are thermodynamically more stable than their carbon analogs, they are very reactive due to their high inherent electrophilicity and the ability of hypervalent coordination. On the other hand, stabilization by inductive and hyperconjugative effects and larger steric effects of carbocations make them less sensitive to solvation or other environmental effects than silyl cations. Hence, observation of free silyl cations in the condensed phase proved extremely difficult and the actual problem is the question of the degree of the (remaining silyl cation character.The first free silyl cation, trimesitylsilyl cation, and in analogy with it tridurylsilyl cation, were synthesized by Lambert et al. Free silyl cations based on analogy to aromatic ions (homocyclopropenylium and tropylium have also been prepared. However, in these silyl cations the cationic character is reduced by internal π -conjugation. Čičak et al. prepared some silyl-cationic intermediates (Me3Si--CH≡CR+in solid state. With the help of quantum-mechanical calculations it was concluded that these adducts have much more silyl cation than carbocation character.

  14. Cross-linked aromatic cationic polymer electrolytes with enhanced stability for high temperature fuel cell applications

    DEFF Research Database (Denmark)

    Ma, Wenjia; Zhao, Chengji; Yang, Jingshuai;

    2012-01-01

    anchoring of the molecule. Combining the excellent thermal stability, the addition of a small amount of diamines enhanced both the chemical and mechanical stability and the phosphoric acid doping (PA) ability of membranes. Fuel cell performance based on impregnated cross-linked membranes have been...

  15. Stabilization of Curcumin by Complexation with Divalent Cations in Glycerol/Water System

    Directory of Open Access Journals (Sweden)

    Bachar Zebib

    2010-01-01

    Full Text Available The purpose of present study was to stabilize curcumin food pigment by its complexation with divalent ions like (Zn2+,Cu2+,Mg2+,Se2+, in “green media” and evaluate its stability in vitro compared to curcumin alone. The curcumin complexes were prepared by mechanical mixture of curcumin and sulfate salts of each metal (metal : curcumin 1/1mol into unconventional and nontoxic glycerol/water solvent. Two stoichiometry of complex were obtained, 1 : 1 and 1 : 2 (metal/curcumin, respectively. On evaluation of in vitro stability, all complexes were found to provide a higher stability from curcumin alone.

  16. A cation binding motif stabilizes the compound I radical of cytochrome c peroxidase.

    OpenAIRE

    Miller, M.A.; Han, G W; Kraut, J

    1994-01-01

    Cytochrome c peroxidase reacts with peroxide to form compound I, which contains an oxyferryl heme and an indolyl radical at Trp-191. The indolyl free radical has a half-life of several hours at room temperature, and this remarkable stability is essential for the catalytic function of cytochrome c peroxidase. To probe the protein environment that stabilizes the compound I radical, we used site-directed mutagenesis to replace Trp-191 with Gly or Gln. Crystal structures of these mutants revealed...

  17. Heat-induced stabilization of the nuclear matrix is independent of divalent cations and high versus low salt extraction

    International Nuclear Information System (INIS)

    The authors devised a method to determine the structural integrity of the nuclear matrix. Nuclear matrices are prepared from exponentially growing cultures of control or heat shocked (450, 30') HeLa cells by DNase I digestion and high (3M) salt extraction of isolated nuclei. After staining with Fluorescein isothiocyanate for protein and Propidium Iodide for double stranded nuclei acids, these parameters and forward angle light scatter are quantitated simultaneously by a flow cytometer. PI quantitation indicates that matrices from heated cells are 2-4 fold more resistant to ribonuclease than those from control cells. This result suggests that the excess protein accumulated in the matrix due to heat shock may mask associated RNA from nucleolytic attack. In the absence of divalent cations (Mg/sup 2+/ and Ca/sup 2+/) matrices from heated cells remain RNase resistant but those from control cells lose all particulate integrity as a result of exposure to RNase. The RNase resistance of matrices from heat shocked cells is also evident when DNase I treated nuclei are extracted by a low salt procedure which has been shown to eliminate randomization of matrix associated DNA sequences due to high salt (Cell 39:223,1984). Thus the nuclease protection of double stranded RNA due to heat is not an artifact of salt-induced randomization of matrix associated DNA sequences. Heat also overcomes the divalent cation requirement for matrix stability after RNase treatment

  18. Frame Stability of Tunnel‐Structured Cryptomelane Nanofibers: The Role of Tunnel Cations

    DEFF Research Database (Denmark)

    Gao, Tao; Norby, Poul

    2013-01-01

    The role of tunnel K+ ions on the growth and stability of tunnel‐structured cryptomelane‐type MnO2 nanofibers (denoted as cryptomelane nanofibers hereafter) has been discussed by means of X‐ray diffraction and electron microscopy. Cryptomelane nanofibers with typical diameters of 20–80 nm and...... lengths of 1–6 μm have been synthesized by means of a simple hydrothermal reaction of KMnO4 and MnSO4 aqueous solutions at 140 °C. The growth of cryptomelane nanofibers under hydrothermal conditions follows a dissolution–recrystallization process and involves a morphological transformation from a layered...... precursor to the tunnel‐structured cryptomelane, in which the K+ ions play important roles in templating and stabilizing the tunneled framework. The presence of tunnel K+ ions also enhances the frame stability of the cryptomelane nanofibers at elevated temperatures. The formation of a layered KxMn2O4 (x ≈ 0...

  19. Fabrication, stability and efficacy of dual-component antimicrobial nanoemulsions: essential oil (thyme oil) and cationic surfactant (lauric arginate).

    Science.gov (United States)

    Chang, Yuhua; McLandsborough, Lynne; McClements, David Julian

    2015-04-01

    The influence of a cationic surfactant (lauric arginate, LAE) on the physical properties and antimicrobial efficacy of thyme oil nanoemulsions was investigated. Nanoemulsions prepared from pure thyme oil were highly unstable due to Ostwald ripening, but they could be stabilized by adding a ripening inhibitor (corn oil) to the oil phase prior to homogenisation. The loading capacity and antimicrobial efficacy of thyme oil nanoemulsions were significantly increased by adding LAE. In the absence of LAE, at least 60 wt% corn oil had to be added to the lipid phase to inhibit Ostwald ripening; but in the presence of 0.1 wt% LAE, only 30 wt% corn oil was needed. LAE addition substantially increased the antimicrobial efficacy of the thyme oil nanoemulsions: 200 μg/ml thyme oil was needed to inhibit growth of a spoilage yeast (Zygosaccharomyces bailii) if LAE was added, whereas ⩾ 400 μg/ml was needed in the absence of LAE. PMID:25442557

  20. Stabilization of Curcumin by Complexation with Divalent Cations in Glycerol/Water System

    OpenAIRE

    Bachar Zebib; Zéphirin Mouloungui; Virginie Noirot

    2010-01-01

    The purpose of present study was to stabilize curcumin food pigment by its complexation with divalent ions like ( Z n 2 + , C u 2 + , M g 2 + , S e 2 + ) , in “green media” and evaluate its stability in vitro compared to curcumin alone. The curcumin complexes were prepared by mechanical mixture of curcumin and sulfate salts of each metal (metal : curcumin 1/1mol) into unconventional and nontoxic glycerol/water solvent. Two stoichiometry of complex were obtained, 1 : 1 and 1 : 2 (metal/curcumi...

  1. The Influence of Salts with Different Cation Valency on Oil-in-Water Emulsion Stability

    OpenAIRE

    Nisja, Trine

    2015-01-01

    The effect of different emulsion preparation parameters on the stability of oil-in-water (o/w) emulsions has been studied by varying the preparation parameters and then observing the emulsion visually. Change in the turbidity of an emulsion indicated instability, and the formation of a dense layer on the top of the emulsion suggested that creaming had commenced. The creaming rate was diminishing with increasing mixing frequency, mixing time and oil phase density. The study was ...

  2. Effect of dietary cation-anion difference on performance of lactating dairy cows and stability of milk proteins.

    Science.gov (United States)

    Martins, C M M R; Arcari, M A; Welter, K C; Netto, A S; Oliveira, C A F; Santos, M V

    2015-04-01

    Casein micelle stability is negatively correlated with milk concentrations of ionic calcium, which may change according to the metabolic and nutritional status of dairy cows. The present study aimed to evaluate the effect of dietary cation-anion difference (DCAD) on concentrations of casein subunits, whey proteins, ionic calcium, and milk heat and ethanol stability. Sixteen Holstein cows were distributed in 4 contemporary 4 × 4 Latin square designs, which consisted of 4 periods of 21 d and 4 treatments according to DCAD: 290, 192, 98, and -71 mEq/kg of dry matter (DM). The milk concentrations of ionic calcium and κ-casein were reduced as DCAD increased, whereas the milk urea nitrogen and β-lactoglobulin concentrations were increased. As a result of these alterations, the milk ethanol stability and milk stability during heating at 140 °C were increased linearly with increasing DCAD [Y = 74.87 (standard error = 0.87) + 0.01174 (standard error = 0.0025) × DCAD (mEq/kg of DM) and Y = 3.95 (standard error = 1.02) + 0.01234 (standard error = 0.0032) × DCAD (mEq/kg of DM), respectively]. In addition, 3.5% fat-corrected milk and fat, lactose, and total milk solids contents were linearly increased by 13.52, 8.78, 2.5, and 2.6%, respectively, according to DCAD increases from -71 to 290 mEq/kg of DM, whereas crude protein and casein content were linearly reduced by 4.83 and 4.49%, respectively. In conclusion, control of metabolic changes in lactating dairy cows to maintain blood acid-base equilibrium plays an important role in keeping milk stable to ethanol and during heat treatments. PMID:25622868

  3. Electron spin resonance and intermediate neglect of differential overlap molecular orbital study of the π cations of (hydroxymethyl)uracil and (hydroxymethyl)cytosine. Evidence for internal hydrogen bonding

    International Nuclear Information System (INIS)

    The π-cation radicals of 5-(hydroxymethyl)uracil (HOMeU) and 5-(hydroxymethyl)cytosine (HOMeC) have been produced by Cl2- attack in γ-irradiated basic 12 M LiCl and photoionization in basic 8 M NaClO4 glasses at low temperatures. Analysis of the ESR spectra found for these radicals shows that each of the π-cation radicals converts to another species probably by a change in a nitrogen protonation state as the temperature is raised. For example, 5-(hydroxymethyl)uracil cation shows a 28.5-G average splitting for the two hydroxymethyl-group β protons which convert upon annealing to a 36-G splitting. The splittings and the narrowness of the line widths found after annealing are suggestive of a configuration which is intramolecularly rigid and stabilized by a intramolecular hydrogen bond from the hydroxyl proton to the 4-position oxygen. The π cation of 5-(hydroxymethyl)cytosine converts to a radical with substantial spin density on the exocyclic nitrogen which again shows strong evidence for intramolecular hydrogen bonding. Final radicals are found to be produced from the π-cation radicals of (hydroxymethyl)uracil and (hydroxymethyl)cytosine by deprotonation of a methylene proton. INDO calculations for the π cation of (hydroxymethyl)uracil as a function of orientation of the hydroxyl group show that the hydrogen bond to the 4-position oxygen increases in strength by a factor of 3 upon deprotonation at the 3-position nitrogen. The hydrogen bond is therefore predicted to substantially stabilize the π-cation radical

  4. High stability of electro-transport and magnetism against the A-site cation disorder in SrRuO3.

    Science.gov (United States)

    Wang, Y L; Liu, M F; Liu, R; Xie, Y L; Li, X; Yan, Z B; Liu, J-M

    2016-01-01

    It is known that the electro-transport and magnetism of perovskite alkaline-earth ruthenate oxides are sensitive to the lattice distortion associated with the A-site cation size. Orthorhombic CaRuO3 and cubic BaRuO3 exhibit distinctly different electro-transport and magnetic properties from orthorhombic SrRuO3. It has been suggested that SrRuO3 can be robust against some intrinsic/external perturbations but fragile against some others in terms of electro-transport and magnetism, and it is our motivation to explore such stability against the local site cation disorder. In this work, we prepare a set of SrRuO3-based samples with identical averaged A-site size but different A-site cation disorder (size mismatch) by Ca and Ba co-substitution of Sr. It is revealed that the electro-transport and magnetism of SrRuO3 demonstrate relatively high stability against this A-site cation disorder, characterized by the relatively invariable electrical and magnetic properties in comparison with those of SrRuO3 itself. A simple electro-transport network model is proposed to explain quantitatively the measured behaviors. The present work suggests that SrRuO3 as an itinerant electron ferromagnetic metal possesses relatively high robustness against local lattice distortion and cation occupation disorder. PMID:27297396

  5. High stability of electro-transport and magnetism against the A-site cation disorder in SrRuO3

    Science.gov (United States)

    Wang, Y. L.; Liu, M. F.; Liu, R.; Xie, Y. L.; Li, X.; Yan, Z. B.; Liu, J.-M.

    2016-06-01

    It is known that the electro-transport and magnetism of perovskite alkaline-earth ruthenate oxides are sensitive to the lattice distortion associated with the A-site cation size. Orthorhombic CaRuO3 and cubic BaRuO3 exhibit distinctly different electro-transport and magnetic properties from orthorhombic SrRuO3. It has been suggested that SrRuO3 can be robust against some intrinsic/external perturbations but fragile against some others in terms of electro-transport and magnetism, and it is our motivation to explore such stability against the local site cation disorder. In this work, we prepare a set of SrRuO3-based samples with identical averaged A-site size but different A-site cation disorder (size mismatch) by Ca and Ba co-substitution of Sr. It is revealed that the electro-transport and magnetism of SrRuO3 demonstrate relatively high stability against this A-site cation disorder, characterized by the relatively invariable electrical and magnetic properties in comparison with those of SrRuO3 itself. A simple electro-transport network model is proposed to explain quantitatively the measured behaviors. The present work suggests that SrRuO3 as an itinerant electron ferromagnetic metal possesses relatively high robustness against local lattice distortion and cation occupation disorder.

  6. Polaron Stabilization by Cooperative Lattice Distortion and Cation Rotations in Hybrid Perovskite Materials.

    Science.gov (United States)

    Neukirch, Amanda J; Nie, Wanyi; Blancon, Jean-Christophe; Appavoo, Kannatassen; Tsai, Hsinhan; Sfeir, Matthew Y; Katan, Claudine; Pedesseau, Laurent; Even, Jacky; Crochet, Jared J; Gupta, Gautam; Mohite, Aditya D; Tretiak, Sergei

    2016-06-01

    Solution-processed organometallic perovskites have rapidly developed into a top candidate for the active layer of photovoltaic devices. Despite the remarkable progress associated with perovskite materials, many questions about the fundamental photophysical processes taking place in these devices, remain open. High on the list of unexplained phenomena are very modest mobilities despite low charge carrier effective masses. Moreover, experiments elucidate unique degradation of photocurrent affecting stable operation of perovskite solar cells. These puzzles suggest that, while ionic hybrid perovskite devices may have efficiencies on par with conventional Si and GaAs devices, they exhibit more complicated charge transport phenomena. Here we report the results from an in-depth computational study of small polaron formation, electronic structure, charge density, and reorganization energies using both periodic boundary conditions and isolated structures. Using the hybrid density functional theory, we found that volumetric strain in a CsPbI3 cluster creates a polaron with binding energy of around 300 and 900 meV for holes and electrons, respectively. In the MAPbI3 (MA = CH3NH3) cluster, both volumetric strain and MA reorientation effects lead to larger binding energies at around 600 and 1300 meV for holes and electrons, respectively. Such large reorganization energies suggest appearance of small polarons in organometallic perovskite materials. The fact that both volumetric lattice strain and MA molecular rotational degrees of freedom can cooperate to create and stabilize polarons indicates that in order to mitigate this problem, formamidinium (FA = HC(NH2)2) and cesium (Cs) based crystals and alloys, are potentially better materials for solar cell and other optoelectronic applications. PMID:27224519

  7. Households credits and financial stability : A theoretical model of financial intermediation

    OpenAIRE

    Bastidon, Cécile

    2014-01-01

    This paper develops a theoretical model of financial intermediation with three original features: first, consideration of all sectors within total outstanding credits, including households; second, the possibility of a non monotic relationship between prices and funding supply volumes in periods of high financial strains; last, the link between interbank credit rationing and other sectors funding rationing. The central bank conducts an unconventional type monetary policy. We show that the int...

  8. Influence of Hydrocolloids (Dietary Fibers) on Lipid Digestion of Protein-Stabilized Emulsions: Comparison of Neutral, Anionic, and Cationic Polysaccharides.

    Science.gov (United States)

    Qin, Dingkui; Yang, Xiaojun; Gao, Songran; Yao, Junhu; McClements, David Julian

    2016-07-01

    The impact of dietary fibers on lipid digestion within the gastrointestinal tract depends on their molecular and physicochemical properties. In this study, the influence of the electrical characteristics of dietary fibers on their ability to interfere with the digestion of protein-coated lipid droplets was investigated using an in vitro small intestine model. Three dietary fibers were examined: cationic chitosan; anionic alginate; neutral locust bean gum (LBG). The particle size, ζ-potential, microstructure, and apparent viscosity of β-lactoglobulin stabilized oil-in-water emulsions containing different types and levels of dietary fiber were measured before and after lipid digestion. The rate and extent of lipid digestion depended on polysaccharide type and concentration. At relatively low dietary fiber levels (0.1 to 0.2 wt%), the initial lipid digestion rate was only reduced by chitosan, but the final extent of lipid digestion was unaffected by all 3 dietary fibers. At relatively high dietary fiber levels (0.4 wt%), alginate and chitosan significantly inhibited lipid hydrolysis, whereas LBG did not. The impact of chitosan on lipid digestion was attributed to its ability to promote fat droplet aggregation through bridging flocculation, thereby retarding access of the lipase to the droplet surfaces. The influence of alginate was mainly ascribed to its ability to sequester calcium ions and promote depletion flocculation. PMID:27300319

  9. Relative Stability of the Key Enamine,Oxazolidinone, and Imine Intermediates in Some Proline-catalyzed Asymmetric Reactions

    Institute of Scientific and Technical Information of China (English)

    HU Yi-Fan; LU Xin

    2008-01-01

    Many proline-catalyzed asymmetric addition reactions with ketones as substrates were assumed to involve a key intermediate, an enamine, produced by the condensation of proline and ketone. In this paper, the key intermediate enamines derived from L-proline and cyclohexanone (or acetone) as well as the corresponding oxazolidinone and imine tautomers have been investigated by means of density functional calculations at the B3LYP/6-311+G** level. The predicted order of stability for these tautomers is oxazolidinones > enamines > imines in gas phase and oxazolidinones > imines > enamines in aprotic THF solvent. This prediction explains why enamine intermediate can not be observed experimentally. The predicted energy/enthalpy difference between the formal oxazolidinone structure and the zwitterionic imine structures is very small in THF solvent, suggesting the oxazolidinone-to-imine tautomerization can be readily induced in solvent. 13C NMR chemical shifts of the oxazolidinone and imine structures have been computed and used to explain the experimental NMR spectra observed in oxazolidinone-to-imine tautomerization induced by protic solvent.

  10. Reaction of stabilized Criegee intermediates from ozonolysis of limonene with sulfur dioxide: ab initio and DFT study.

    Science.gov (United States)

    Jiang, Lei; Xu, Yi-sheng; Ding, Ai-zhong

    2010-12-01

    The mechanism of the reaction of the sulfur dioxide (SO(2)) with four stabilized Criegee intermediates (stabCI-CH(3)-OO, stabCI-OO, stabCIx-OO, and stabCH(2)OO) produced via the ozonolysis of limonene have been investigated using ab initio and DFT (density functional theory) methods. It has been shown that the intermediate adduct formed by the initiation of these reactions may be followed by two different reaction pathways such as H migration reaction to form carboxylic acids and rearrangement of oxygen to produce the sulfur trioxide (SO(3)) from the terminal oxygen of the COO group and SO(2). We found that the reaction of stabCI-OO and stabCH(2)OO with SO(2) can occur via both the aforementioned scenarios, whereas that of stabCI-CH(3)-OO and stabCIx-OO with SO(2) is limited to the second pathway only due to the absence of migrating H atoms. It has been shown that at the CCSD(T)/6-31G(d) + CF level of theory the activation energies of six reaction pathways are in the range of 14.18-22.59 kcal mol(-1), with the reaction between stabCIx-OO and SO(2) as the most favorable pathway of 14.18 kcal mol(-1) activation energy and that the reaction of stabCI-OO and stabCH(2)OO with SO(2) occurs mainly via the second reaction path. The thermochemical analysis of the reaction between SO(2) and stabilized Criegee intermediates indicates that the reaction of SO(2) and stabilized Criegee intermediates formed from the exocyclic primary ozonide decomposition is the main pathway of the SO(3) formation. This is likely to explain the large (~100%) difference in the production rate in the favor of the exocyclic compounds observed in recent experiments on the formation of H(2)SO(4) from exocyclic and endocyclic compounds. PMID:21053959

  11. Do Cation-π Interactions Exist in Bacteriorhodopsin

    Institute of Scientific and Technical Information of China (English)

    HU Kun-Sheng; WANG Guang-Yu; HE Jin-An

    2001-01-01

    Metal ions are essential to the structure and physiological functions of bacteriorhodopsin. Experimental evidence suggests the existence of specific cation binding to the negatively charged groups of Asp85 and Asp212 via an electrostatic interaction. However, only using electrostatic force is not enough to explain the role of the metal cations because the carboxylate of Asp85 is well known to be protonated in the M intermediate. Considering the presence of some aromatic amino acid residues in the vicinity of the retinal pocket, the existence of cation-π interactions between the metal cation and aromatic amino acid residues is suggested. Obviously, introduction of this kind of interaction is conducive to understanding the effects of the metal cations and aromatic amino acid residues inside the protein on the structural stability and proton pumping of bacteriorhodopsin.

  12. OMP decarboxylase: phosphodianion binding energy is used to stabilize a vinyl carbanion intermediate.

    Science.gov (United States)

    Goryanova, Bogdana; Amyes, Tina L; Gerlt, John A; Richard, John P

    2011-05-01

    Orotidine 5'-monophosphate decarboxylase (OMPDC) catalyzes the exchange for deuterium from solvent D(2)O of the C-6 proton of 1-(β-d-erythrofuranosyl)-5-fluorouracil (FEU), a phosphodianion truncated product analog. The deuterium exchange reaction of FEU is accelerated 1.8 × 10(4)-fold by 1 M phosphite dianion (HPO(3)(2-)). This corresponds to a 5.8 kcal/mol stabilization of the vinyl carbanion-like transition state, which is similar to the 7.8 kcal/mol stabilization of the transition state for OMPDC-catalyzed decarboxylation of a truncated substrate analog by bound HPO(3)(2-). These results show that the intrinsic binding energy of phosphite dianion is used in the stabilization of the vinyl carbanion-like transition state common to the decarboxylation and deuterium exchange reactions. PMID:21486036

  13. The role of alkali metal cations in the stabilization of guanine quadruplexes: why K(+) is the best.

    Science.gov (United States)

    Zaccaria, F; Paragi, G; Fonseca Guerra, C

    2016-08-21

    The alkali metal ion affinity of guanine quadruplexes has been studied using dispersion-corrected density functional theory (DFT-D). We have done computational investigations in aqueous solution that mimics artificial supramolecular conditions where guanine bases assemble into stacked quartets as well as biological environments in which telomeric quadruplexes are formed. In both cases, an alkali metal cation is needed to assist self-assembly. Our quantum chemical computations on these supramolecular systems are able to reproduce the experimental order of affinity of the guanine quadruplexes for the cations Li(+), Na(+), K(+), Rb(+), and Cs(+). The strongest binding is computed between the potassium cation and the quadruplex as it occurs in nature. The desolvation and the size of alkali metal cations are thought to be responsible for the order of affinity. Until now, the relative importance of these two factors has remained unclear and debated. By assessing the quantum chemical 'size' of the cation, determining the amount of deformation of the quadruplex needed to accommodate the cation and through the energy decomposition analysis (EDA) of the interaction energy between the cation and the guanines, we reveal that the desolvation and size of the alkali metal cation are both almost equally responsible for the order of affinity. PMID:27185388

  14. The Stabilized Cation Pool Method: Metal- and Oxidant-Free Benzylic C-H/Aromatic C-H Cross-Coupling.

    Science.gov (United States)

    Hayashi, Ryutaro; Shimizu, Akihiro; Yoshida, Jun-Ichi

    2016-07-13

    Electrochemical oxidation of toluene derivatives in the presence of a sulfilimine gave benzylaminosulfonium ions as stabilized benzyl cation pools, which reacted with subsequently added aromatic nucleophiles to give the corresponding cross-coupling products. The transformation serves as a powerful metal- and chemical-oxidant-free method for benzylic C-H/aromatic C-H cross-coupling. The method has been successfully applied to synthesis of TP27, an inhibitor of PTPase. PMID:27341676

  15. Effects of Land Use Practices on the Organic Carbon Content, Cation Exchange Capacity and Aggregate Stability of Soils in the Catchment Zones

    OpenAIRE

    Mosayeb Heshmati; Arifin Abdu; Shamshuddin Jusop; Nik M. Majid

    2011-01-01

    Problem statement: Land use practice leads to changes in the physico-chemical properties of soils, such as Soil Organic Carbon (SOC), Cation Exchange Capacity (CEC) and Soil Aggregate Stability (SAS) that cause soil erosion. Approach: Merek catchment, Iran suffers from land degradation due to poor land use practice. A study was carried out with the objectives: (i) to determine soil nutrient status in different agro-ecological zones in Merek catchment; and (ii) to evaluate the influence of lan...

  16. Reactive transport modelling of organic complexing agents in cement stabilized low and intermediate level waste

    Science.gov (United States)

    von Schenck, Henrik; Källström, Klas

    The Swedish final repository for short-lived radioactive waste (SFR 1) is located at Forsmark in Sweden. It holds low and intermediate-level operational waste from the Swedish nuclear power plants, as well as industrial, research-related, and medical waste. A variety of low molecular weight organic compounds are present in the waste or in its matrix. Such compounds can also be formed by chemical degradation of organic macromolecules. These organics can ligate to metal atoms forming stable complexes and also adsorb to the surface of cement, thereby influencing the net release of radionuclides from the repository. This motivates the study of the concentration distribution of complexing agents in the repository as a function of time. The following paper reports the results of mass transport modelling, describing the transport of complexing agents through the cementitous matrix in the rock vault for intermediate-level waste in the SFR 1 repository. Nitrilotriacetate (NTA) and isosaccharinate (ISA) have been investigated, where the former is considered to be non-sorbing and non-reacting, while the latter is produced from cellulose degradation and adsorbs strongly to cement. The 3D model considers advection, diffusion, and sorption of solvated species in cement pore water over a time period of 20,000 years. The model accounts for the spatial distribution of the flow field in the repository structure and also considers changing groundwater flow during the investigated time period. It is found that 99% of the NTA is removed after approximately 4000 years, while 90% of the ISA is retained in the rock vault after 20,000 years. The maximum pore water concentration of ISA is found to be 8.6 mol/m3 after approximately 2300 years, based on the degradation of the deposited amounts of cellulose. Over the investigated time scale, the ligands retained in the repository can redistribute across several waste compartments where the organic compounds were not originally deposited. In

  17. Aflatoxin M1 in the intermediate dairy products from Manchego cheese production: distribution and stability

    OpenAIRE

    Moya, V.J.; Rubio, R; Berruga, M. I.; Molina, M.P.; Molina, A. (Ángel)

    2011-01-01

    Aflatoxin M1 (AFM1) distribution in curd, whey, Manchego cheese, the traditional Spanish whey cheese Requesón and Requesón whey, and its stability during two different cold treatments, have been studied. Raw ewe’s milk was artificially contaminated with AFM1 in a final concentration of 50 and 100 ng kg-1, and was used to produce Manchego cheese. AFM1 determinations were carried out by HPLC with fluorimetric detection after immunoaffinity clean-up. The mean AFM1 concentrations in the produced ...

  18. Engineering of CH3 NH3 PbI3 Perovskite Crystals by Alloying Large Organic Cations for Enhanced Thermal Stability and Transport Properties.

    Science.gov (United States)

    Peng, Wei; Miao, Xiaohe; Adinolfi, Valerio; Alarousu, Erkki; El Tall, Omar; Emwas, Abdul-Hamid; Zhao, Chao; Walters, Grant; Liu, Jiakai; Ouellette, Olivier; Pan, Jun; Murali, Banavoth; Sargent, Edward H; Mohammed, Omar F; Bakr, Osman M

    2016-08-26

    The number of studies on organic-inorganic hybrid perovskites has soared in recent years. However, the majority of hybrid perovskites under investigation are based on a limited number of organic cations of suitable sizes, such as methylammonium and formamidinium. These small cations easily fit into the perovskite's three-dimensional (3D) lead halide framework to produce semiconductors with excellent charge transport properties. Until now, larger cations, such as ethylammonium, have been found to form 2D crystals with lead halide. Here we show for the first time that ethylammonium can in fact be incorporated coordinately with methylammonium in the lattice of a 3D perovskite thanks to a balance of opposite lattice distortion strains. This inclusion results in higher crystal symmetry, improved material stability, and markedly enhanced charge carrier lifetime. This crystal engineering strategy of balancing opposite lattice distortion effects vastly increases the number of potential choices of organic cations for 3D perovskites, opening up new degrees of freedom to tailor their optoelectronic and environmental properties. PMID:27468159

  19. Characterization of Y-Ba-Cu-O thin films and yttria-stabilized zirconia intermediate layers on metal alloys grown by pulsed laser deposition

    International Nuclear Information System (INIS)

    The use of an intermediate layer is necessary for the growth of YBaCuO thin films on polycrystalline metallic alloys for tape conductor applications. A pulsed laser deposition process to grow controlled-orientation yttria-stabilized zirconia (YSZ) films as intermediate layers on Haynes Alloy No. 230 was developed and characterized. YBaCuO films deposited on these YSZ-coated substrates are primarily c-axis oriented and superconducting as deposited. The best YBaCuO films grow on (001) oriented YSZ intermediate layers and have Tc (R=0) = 86.0 K and Jc ∼ 3x103 A/cm2 at 77 K

  20. Characterization of Y-Ba-Cu-O thin films and yttria-stabilized zirconia intermediate layers on metal alloys grown by pulsed laser deposition

    Science.gov (United States)

    Reade, R. P.; Mao, X. L.; Russo, R. E.

    1991-08-01

    The use of an intermediate layer is necessary for the growth of YBaCuO thin films on polycrystalline metallic alloys for tape conductor applications. A pulsed laser deposition process to grow controlled-orientation yttria-stabilized zirconia (YSZ) films as intermediate layers on Haynes Alloy No. 230 was developed and characterized. YBaCuO films deposited on these YSZ-coated substrates are primarily c-axis oriented and superconducting as deposited. The best YBaCuO films grow on (001)-oriented YSZ intermediate layers and have Tc (R = 0) = 86.0 K and Jc about 3000 A/sq cm at 77 K.

  1. Aflatoxin M1 in the intermediate dairy products from Manchego cheese production: distribution and stability

    Directory of Open Access Journals (Sweden)

    V.J. Moya

    2011-12-01

    Full Text Available Aflatoxin M1 (AFM1 distribution in curd, whey, Manchego cheese, the traditional Spanish whey cheese Requesón and Requesón whey, and its stability during two different cold treatments, have been studied. Raw ewe’s milk was artificially contaminated with AFM1 in a final concentration of 50 and 100 ng kg-1, and was used to produce Manchego cheese. AFM1 determinations were carried out by HPLC with fluorimetric detection after immunoaffinity clean-up. The mean AFM1 concentrations in the produced curd and Manchego cheese were approximately 2- and 3-fold higher than the initial milk they were made from, and the levels of this toxin remaining in whey were 42.3 % and 51.3 % of the initial concentrations. In the Requesón samples, the mean AFM1 values were 1.7 times higher than those in the corresponding whey, while 33.7 % and 44.4 % of the AFM1 concentration detected in milk also appeared in the Requesón whey. Short refrigeration and freezing periods did not affect the toxin levels in either curd or Requesón samples. When ewe’s milk destined for Manchego cheese-making is AFM1-contaminated at the EU limit level (50 ng kg-1 or double, a concentration of this toxin will appear in the manufactured products, but values will be considerably below the toxic doses (Tolerable Daily Intake = 2 ng kg-1 body weight per day, which poses a human health problem.

  2. Hydration, Ionic Valence and Cross-Linking Propensities of Cations Determine the Stability of Lipopolysaccharide (LPS) Membranes

    Energy Technology Data Exchange (ETDEWEB)

    Nascimento, Agrinaldo; Pontes, Frederico J.; Lins, Roberto D.; Soares, Thereza A.

    2013-10-29

    The supra-molecular structure of LPS aggregates governs outer membrane permeability and activation of the host immune response during Gram-negative bacterial infections. Molecular dynamics simulations unveil at atomic resolution 10 the subtle balance between cation hydration and cross-link ability in modulating phase transitions of LPS membranes.

  3. Acid decomposition and thiourea leaching of silver from hazardous jarosite residues: Effect of some cations on the stability of the thiourea system.

    Science.gov (United States)

    Calla-Choque, D; Nava-Alonso, F; Fuentes-Aceituno, J C

    2016-11-01

    The recovery of silver from hazardous jarosite residues was studied employing thiourea as leaching agent at acid pH and 90°C. The stability of the thiourea in synthetic solutions was evaluated in the presence of some cations that can be present in this leaching system: cupric and ferric ions as oxidant species, and zinc, lead and iron as divalent ions. Two silver leaching methods were studied: the simultaneous jarosite decomposition-silver leaching, and the jarosite decomposition followed by the silver leaching. The study with synthetic solutions demonstrated that cupric and ferric ions have a negative effect on thiourea stability due to their oxidant properties. The effect of cupric ions is more significant than the effect of ferric ions; other studied cations (Fe(2+), Zn(2+), Pb(2+)) had no effect on the stability of thiourea. When the decomposition of jarosite and the silver leaching are carried out simultaneously, 70% of the silver can be recovered. When the acid decomposition was performed at pH 0.5 followed by the leaching step at pH 1, total silver recovery increased up to 90%. The zinc is completely dissolved with any of these processes while the lead is practically insoluble with these systems producing a lead-rich residue. PMID:27322901

  4. Actinide cation-cation complexes

    International Nuclear Information System (INIS)

    The +5 oxidation state of U, Np, Pu, and Am is a linear dioxo cation (AnO2+) with a formal charge of +1. These cations form complexes with a variety of other cations, including actinide cations. Other oxidation states of actinides do not form these cation-cation complexes with any cation other than AnO2+; therefore, cation-cation complexes indicate something unique about AnO2+ cations compared to actinide cations in general. The first cation-cation complex, NpO2+·UO22+, was reported by Sullivan, Hindman, and Zielen in 1961. Of the four actinides that form AnO2+ species, the cation-cation complexes of NpO2+ have been studied most extensively while the other actinides have not. The only PuO2+ cation-cation complexes that have been studied are with Fe3+ and Cr3+ and neither one has had its equilibrium constant measured. Actinides have small molar absorptivities and cation-cation complexes have small equilibrium constants; therefore, to overcome these obstacles a sensitive technique is required. Spectroscopic techniques are used most often to study cation-cation complexes. Laser-Induced Photacoustic Spectroscopy equilibrium constants for the complexes NpO2+·UO22+, NpO2+·Th4+, PuO2+·UO22+, and PuO2+·Th4+ at an ionic strength of 6 M using LIPAS are 2.4 ± 0.2, 1.8 ± 0.9, 2.2 ± 1.5, and ∼0.8 M-1

  5. Intermediate-term medium-range earthquake prediction algorithm M8: A new spatially stabilized application in Italy

    International Nuclear Information System (INIS)

    A series of experiments, based on the intermediate-term earthquake prediction algorithm M8, has been performed for the retrospective simulation of forward predictions in the Italian territory, with the aim to design an experimental routine for real-time predictions. These experiments evidenced two main difficulties for the application of M8 in Italy. The first one is due to the fact that regional catalogues are usually limited in space. The second one concerns certain arbitrariness and instability, with respect to the positioning of the circles of investigation. Here we design a new scheme for the application of the algorithm M8, which is less subjective and less sensitive to the position of the circles of investigation. To perform this test, we consider a recent revision of the Italian catalogue, named UCI2001, composed by CCI1996, NEIC and ALPOR data for the period 1900-1985, and updated with the NEIC reduces the spatial heterogeneity of the data at the boundaries of Italy. The new variant of the M8 algorithm application reduces the number of spurious alarms and increases the reliability of predictions. As a result, three out of four earthquakes with magnitude Mmax larger than 6.0 are predicted in the retrospective simulation of the forward prediction, during the period 1972-2001, with a space-time volume of alarms comparable to that obtained with the non-stabilized variant of the M8 algorithm in Italy. (author)

  6. Role of stabilized Criegee Intermediate in secondary organic aerosol formation from the ozonolysis of α-cedrene

    Science.gov (United States)

    Yao, Lei; Ma, Yan; Wang, Lin; Zheng, Jun; Khalizov, Alexei; Chen, Mindong; Zhou, Yaoyao; Qi, Lu; Cui, Fenping

    2014-09-01

    Atmospheric ozonolysis of sesquiterpenes is an important source of secondary organic aerosols (SOA). The mechanisms by which Criegee Intermediates (CIs) react to form SOA precursors and the influence of environmental conditions, however, remain unclear. On the basis of environmental chamber experiments coupled with detailed characterization of gas-phase and particle-phase products, we present evidence that a significant fraction of CIs from ozonolysis of α-cedrene are stabilized and bimolecular reactions of these stabilized CIs (SCIs) play a key role in the formation of SOA precursors. Ozonolysis experiments were conducted in a 4.5 m3 collapsible fluoropolymer chamber under various conditions in the presence of the OH radical and SCI scavengers. The size and mass of SOA particles produced during ozonolysis were measured directly and used for calculation of particle effective density and mass yield. Gaseous and particulate products were analyzed by several mass spectrometry methods. A total of 14 compounds in gas phase and 17 compounds in particle phase were tentatively identified. The major gas-phase products are secondary ozonides (SOZ) from intramolecular reactions of SCIs. Multifunctional organic acids are dominant particle-phase products. The measured density of aerosol particles is 1.04 ± 0.03 to 1.38 ± 0.03 g/cm3, and the aerosol mass yield is (23.7 ± 0.4)% to (46.4 ± 6.5)%, depending on reaction conditions. The presence of acetic acid, an SCI scavenger, inhibits new particle formation, but leads to increased aerosol mass yield. In contrast, the addition of SO2 dramatically enhances new particle formation and total aerosol yield. The calculated OH formation yield decreases from (62.4 ± 4.9)% to (9.0 ± 1.6)% upon addition of SCI scavengers CH3COOH and SO2, indicating that a large fraction of excited CIs are collisionally stabilized and unimolecular decomposition of SCIs via the hydroperoxide channel can be suppressed by bimolecular reactions. The

  7. Review of the thermal stability and cation exchange properties of the zeolite minerals clinoptilolite, mordenite, and analcime; applications to radioactive waste isolation in silicic tuff

    International Nuclear Information System (INIS)

    Silicic tuffs of the southern Great Basin and basalts of the Columbia River Plateau are under investigation as potential host rocks for high- and intermediate-level radioactive wastes. Nonwelded and partially welded tuffs may contain major amounts (> 50%) of the zeolite minerals clinoptilolite, mordenite, and analcime. Densely welded tuffs and some basalt flows may contain clinoptilolite as fracture filling that limits the permeability of these rocks. The cation exchange properties of these zeolite minerals allow them to pose a formidable natural barrier to the migration of cationic species of various radionuclides in aqueous solutions. However, these minerals are unstable at elevated temperatures and at low water-vapor pressures and may break down either by reversible dehydration or by irreversible mineralogical reactions. All the breakdown reactions occurring at increased temperature involve a net volume reduction and evolution of fluids. Thus, they may provide a pathway (shrinkage fractures) and a driving force (fluid pressure) for release of radionuclides to the biosphere. These reactions may be avoided by keeping zeolite-bearing horizons saturated with water and below about 850C. This may restrict allowable gross thermal loadings in waste repositories in volcanic rocks

  8. Intermediates in monensin biosynthesis: A late step in biosynthesis of the polyether ionophore monensin is crucial for the integrity of cation binding

    Directory of Open Access Journals (Sweden)

    Wolfgang Hüttel

    2014-02-01

    Full Text Available Polyether antibiotics such as monensin are biosynthesised via a cascade of directed ring expansions operating on a putative polyepoxide precursor. The resulting structures containing fused cyclic ethers and a lipophilic backbone can form strong ionophoric complexes with certain metal cations. In this work, we demonstrate for monensin biosynthesis that, as well as ether formation, a late-stage hydroxylation step is crucial for the correct formation of the sodium monensin complex. We have investigated the last two steps in monensin biosynthesis, namely hydroxylation catalysed by the P450 monooxygenase MonD and O-methylation catalysed by the methyl-transferase MonE. The corresponding genes were deleted in-frame in a monensin-overproducing strain of Streptomyces cinnamonensis. The mutants produced the expected monensin derivatives in excellent yields (ΔmonD: 1.13 g L−1 dehydroxymonensin; ΔmonE: 0.50 g L−1 demethylmonensin; and double mutant ΔmonDΔmonE: 0.34 g L−1 dehydroxydemethylmonensin. Single crystals were obtained from purified fractions of dehydroxymonensin and demethylmonensin. X-ray structure analysis revealed that the conformation of sodium dimethylmonensin is very similar to that of sodium monensin. In contrast, the coordination of the sodium ion is significantly different in the sodium dehydroxymonensin complex. This shows that the final constitution of the sodium monensin complex requires this tailoring step as well as polyether formation.

  9. Intermediates in monensin biosynthesis: A late step in biosynthesis of the polyether ionophore monensin is crucial for the integrity of cation binding.

    Science.gov (United States)

    Hüttel, Wolfgang; Spencer, Jonathan B; Leadlay, Peter F

    2014-01-01

    Polyether antibiotics such as monensin are biosynthesised via a cascade of directed ring expansions operating on a putative polyepoxide precursor. The resulting structures containing fused cyclic ethers and a lipophilic backbone can form strong ionophoric complexes with certain metal cations. In this work, we demonstrate for monensin biosynthesis that, as well as ether formation, a late-stage hydroxylation step is crucial for the correct formation of the sodium monensin complex. We have investigated the last two steps in monensin biosynthesis, namely hydroxylation catalysed by the P450 monooxygenase MonD and O-methylation catalysed by the methyl-transferase MonE. The corresponding genes were deleted in-frame in a monensin-overproducing strain of Streptomyces cinnamonensis. The mutants produced the expected monensin derivatives in excellent yields (ΔmonD: 1.13 g L(-1) dehydroxymonensin; ΔmonE: 0.50 g L(-1) demethylmonensin; and double mutant ΔmonDΔmonE: 0.34 g L(-1) dehydroxydemethylmonensin). Single crystals were obtained from purified fractions of dehydroxymonensin and demethylmonensin. X-ray structure analysis revealed that the conformation of sodium dimethylmonensin is very similar to that of sodium monensin. In contrast, the coordination of the sodium ion is significantly different in the sodium dehydroxymonensin complex. This shows that the final constitution of the sodium monensin complex requires this tailoring step as well as polyether formation. PMID:24605157

  10. Salt-induced stabilization of apoflavodoxin at neutral pH is mediated through cation-specific effects

    OpenAIRE

    Maldonado, Susana; Irún, María Pilar; Campos, Luis Alberto; Rubio, José Antonio; Luquita, Alejandra; Lostao, Anabel; Wang, Renjie; García-Moreno E., Bertrand; Sancho, Javier

    2002-01-01

    Electrostatic contributions to the conformational stability of apoflavodoxin were studied by measurement of the proton and salt-linked stability of this highly acidic protein with urea and temperature denaturation. Structure-based calculations of electrostatic Gibbs free energy were performed in parallel over a range of pH values and salt concentrations with an empirical continuum method. The stability of apoflavodoxin was higher near the isoelectric point (pH 4) than at neutral pH. This beha...

  11. Cesium-containing triple cation perovskite solar cells: improved stability, reproducibility and high efficiency† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c5ee03874j Click here for additional data file.

    Science.gov (United States)

    Matsui, Taisuke; Seo, Ji-Youn; Domanski, Konrad; Correa-Baena, Juan-Pablo; Nazeeruddin, Mohammad Khaja; Zakeeruddin, Shaik M.; Tress, Wolfgang; Abate, Antonio; Hagfeldt, Anders; Grätzel, Michael

    2016-01-01

    Today's best perovskite solar cells use a mixture of formamidinium and methylammonium as the monovalent cations. With the addition of inorganic cesium, the resulting triple cation perovskite compositions are thermally more stable, contain less phase impurities and are less sensitive to processing conditions. This enables more reproducible device performances to reach a stabilized power output of 21.1% and ∼18% after 250 hours under operational conditions. These properties are key for the industrialization of perovskite photovoltaics.

  12. Structure and stability of hexa-aqua V(III) cations in vanadium redox flow battery electrolytes.

    Science.gov (United States)

    Vijayakumar, M; Li, Liyu; Nie, Zimin; Yang, Zhenguo; Hu, JianZhi

    2012-08-01

    The vanadium(III) cation structure in mixed acid based electrolyte solution from vanadium redox flow batteries is studied by (17)O and (35/37)Cl nuclear magnetic resonance (NMR) spectroscopy, electronic spectroscopy and density functional theory (DFT) based computational modelling. Both computational and experimental results reveal that the V(III) species can complex with counter anions (sulfate/chlorine) depending on the composition of its solvation sphere. By analyzing the powder precipitate it was found that the formation of sulfate complexed V(III) species is the crucial process in the precipitation reaction. The precipitation occurs through nucleation of neutral species formed through deprotonation and ion-pair formation process. However, the powder precipitate shows a multiphase nature which warrants multiple reaction pathways for precipitation reaction. PMID:22735894

  13. Water-soluble Ag:ZnSe nanocrystals with excellent stability via internal doping of donor-type cation impurity

    International Nuclear Information System (INIS)

    Aqueous internally doped ZnSe nanocrystals (NCs) are a recent promising Cd-free NC system. One major problem for this NC system is the intrinsic poor stability of NCs in aqueous environments due to the promoted oxidation of NC surface ligands by acceptor-type impurity. In this work, we successfully solve this problem by doping a donor-type Ag impurity instead of an acceptor-type impurity inside aqueous ZnSe NCs. Proper doping ratio and solution pH are keys for preparing high quality Ag:ZnSe NCs. Under similar synthesis conditions, as-prepared Ag:ZnSe NCs show quite different optical properties from acceptor-type impurity-doped ZnSe NCs, suggesting the donor nature of Ag impurity. In comparison to the weak stability of acceptor-type impurity-doped ZnSe NCs moreover, as-prepared Ag:ZnSe NCs show strong photochemical and luminescent stability, making this new type of NCs available for LED, optical coding, multicolor bio-imaging and so on. (papers)

  14. Reactivity of stabilized Criegee intermediates (sCIs) from isoprene and monoterpene ozonolysis toward SO2 and organic acids

    Science.gov (United States)

    Sipilä, M.; Jokinen, T.; Berndt, T.; Richters, S.; Makkonen, R.; Donahue, N. M.; Mauldin, R. L., III; Kurtén, T.; Paasonen, P.; Sarnela, N.; Ehn, M.; Junninen, H.; Rissanen, M. P.; Thornton, J.; Stratmann, F.; Herrmann, H.; Worsnop, D. R.; Kulmala, M.; Kerminen, V.-M.; Petäjä, T.

    2014-11-01

    Oxidation processes in Earth's atmosphere are tightly connected to many environmental and human health issues and are essential drivers for biogeochemistry. Until the recent discovery of the atmospheric relevance of the reaction of stabilized Criegee intermediates (sCIs) with SO2, atmospheric oxidation processes were thought to be dominated by a few main oxidants: ozone, hydroxyl radicals (OH), nitrate radicals and, e.g. over oceans, halogen atoms such as chlorine. Here, we report results from laboratory experiments at 293 K and atmospheric pressure focusing on sCI formation from the ozonolysis of isoprene and the most abundant monoterpenes (α-pinene and limonene), and subsequent reactions of the resulting sCIs with SO2 producing sulfuric acid (H2SO4). The measured total sCI yields were (0.15 ± 0.07), (0.27 ± 0.12) and (0.58 ± 0.26) for α-pinene, limonene and isoprene, respectively. The ratio between the rate coefficient for the sCI loss (including thermal decomposition and the reaction with water vapour) and the rate coefficient for the reaction of sCI with SO2, k(loss) /k(sCI + SO2), was determined at relative humidities of 10 and 50%. Observed values represent the average reactivity of all sCIs produced from the individual alkene used in the ozonolysis. For the monoterpene-derived sCIs, the relative rate coefficients k(loss) / k(sCI + SO2) were in the range (2.0-2.4) × 1012 molecules cm-3 and nearly independent of the relative humidity. This fact points to a minor importance of the sCI + H2O reaction in the case of the sCI arising from α-pinene and limonene. For the isoprene sCIs, however, the ratio k(loss) / k(sCI + SO2) was strongly dependent on the relative humidity. To explore whether sCIs could have a more general role in atmospheric oxidation, we investigated as an example the reactivity of acetone oxide (sCI from the ozonolysis of 2,3-dimethyl-2-butene) toward small organic acids, i.e. formic and acetic acid. Acetone oxide was found to react faster

  15. Reactivity of stabilized Criegee intermediates (sCI) from isoprene and monoterpene ozonolysis toward SO2 and organic acids

    Science.gov (United States)

    Sipilä, M.; Jokinen, T.; Berndt, T.; Richters, S.; Makkonen, R.; Donahue, N. M.; Mauldin, R. L., III; Kurten, T.; Paasonen, P.; Sarnela, N.; Ehn, M.; Junninen, H.; Rissanen, M. P.; Thornton, J.; Stratmann, F.; Herrmann, H.; Worsnop, D. R.; Kulmala, M.; Kerminen, V.-M.; Petäjä, T.

    2014-01-01

    Oxidation processes in Earth's atmosphere are tightly connected to many environmental and human health issues and are essential drivers for biogeochemistry. Until the recent discovery of the atmospheric relevance of stabilized Criegee intermediates (sCI), atmospheric oxidation processes were thought to be dominated by few main oxidants: ozone, hydroxyl radicals (OH), nitrate radicals and, e.g. over oceans, halogen atoms such as chlorine. Here, we report results from laboratory experiments at 293 K and atmospheric pressure focusing on sCI formation from the ozonolysis of isoprene and the most abundant monoterpenes (α-pinene and limonene), and subsequent reactions of the resulting sCIs with SO2 producing sulphuric acid (H2SO4). The measured sCI yields were (0.15 ± 0.07), (0.27 ± 0.12) and (0.58 ± 0.26) for the ozonolysis of α-pinene, limonene and isoprene, respectively. The ratio between the rate coefficient for the sCI loss (including thermal decomposition and the reaction with water vapour) and the rate coefficient for the reaction of sCI with SO2, k(loss) / k(sCI + SO2), was determined at relative humidities of 10% and 50%. Observed values represent the average reactivity of all sCIs produced from the individual alkene used in the ozonolysis. For the monoterpene derived sCIs, the relative rate coefficients k(loss) / k(sCI + SO2) were in the range (2.0-2.4) × 1012 molecule cm-3 and nearly independent on the relative humidity. This fact points to a minor importance of the sCI + H2O reaction in the case of the sCI arising from α-pinene and limonene. For the isoprene sCIs, however, the ratio k(loss) / k(sCI + SO2) was strongly dependent on the relative humidity. To explore whether sCIs could have a more general role in atmospheric oxidation, we investigated as an example the reactivity of acetone oxide (sCI from the ozonolysis of 2,3-dimethyl-2-butene) toward small organic acids, i.e. formic and acetic acid. Acetone oxide was found to react faster with the

  16. Implications of hydrogen/halogen-bond in the stabilization of confined water and anion-water clusters by a cationic receptor

    Science.gov (United States)

    Hoque, Md. Najbul; Das, Gopal

    2016-03-01

    Anion complexation of benzene capped flexible tripodal receptor and solid state stabilization of discrete hybrid anion-water or infinite water clusters by various supramolecular interactions are reported here. The crystal structure of the receptor in protonated states shows all the three arms projected in one direction. We structurally demonstrate discrete fluoride-water cluster [F2-H2O]2- and square shaped chloride-water cluster [Cl2-(H2O)2]2- inside the cationic channel of the receptor. Structural analysis also reveals that these clusters are stabilized inside the channel through active participation of N/C/Ow‧H⋯Ow, N/C/Ow‧H⋯X- (X- = F-, Cl- and I-) H-bonds and electrostatic interactions. Moreover, C-H⋯π and π⋯π types weak intermolecular interactions appear to play crucial role in supramolecular assembly of receptor. Additionally, on treatment with hydroiodic acid (HI) L resulted zwitterionic iodide complex. Crystal structure reveals the presence of S···I halogen bonded dimer, I2···I halogen bond, 1D infinite water chain and neutral iodine molecules. It is comprehensible that ligand basal structure (benzene capped and N-bridge head in two tripodal) play crucial roles in the formation of diverse halide-water cluster. All structures were well examined by different techniques such as NMR, IR, TGA, DSC, PXRD and XRD.

  17. Does Semi-Rigid Instrumentation Using Both Flexion and Extension Dampening Spacers Truly Provide an Intermediate Level of Stabilization?

    Directory of Open Access Journals (Sweden)

    Dilip Sengupta

    2013-01-01

    Full Text Available Conventional posterior dynamic stabilization devices demonstrated a tendency towards highly rigid stabilization approximating that of titanium rods in flexion. In extension, they excessively offload the index segment, making the device as the sole load-bearing structure, with concerns of device failure. The goal of this study was to compare the kinematics and intradiscal pressure of monosegmental stabilization utilizing a new device that incorporates both a flexion and extension dampening spacer to that of rigid internal fixation and a conventional posterior dynamic stabilization device. The hypothesis was the new device would minimize the overloading of adjacent levels compared to rigid and conventional devices which can only bend but not stretch. The biomechanics were compared following injury in a human cadaveric lumbosacral spine under simulated physiological loading conditions. The stabilization with the new posterior dynamic stabilization device significantly reduced motion uniformly in all loading directions, but less so than rigid fixation. The evaluation of adjacent level motion and pressure showed some benefit of the new device when compared to rigid fixation. Posterior dynamic stabilization designs which both bend and stretch showed improved kinematic and load-sharing properties when compared to rigid fixation and when indirectly compared to existing conventional devices without a bumper.

  18. Stopped Flow Kinetics of MnII Catalysed Periodate Oxidation of 2, 3- dimethylaniline - Evaluation of Stability Constant of the Ternary Intermediate Complex

    OpenAIRE

    Rajneesh Dutt Kaushik; Richa Agarwal; Priyanka Tyagi; Om Singh; Jaspal Singh

    2015-01-01

    The formation of ternary intermediate unstable complex during the oxidation of aromatic amines by periodate ion catalysed by MnII has been proposed in case of some anilines. This paper is the first report on stopped-flow kinetic study and evaluation of stability constant of ternary complex forming in the MnII - catalysed periodate oxidation of 2, 3-dimethylaniline (D) in acetone-water medium. Stop-flow spectrophotometric method was used to study the ternary complex formation and to determine ...

  19. Oxidation of SO2 by stabilized Criegee intermediate (sCI) radicals as a crucial source for atmospheric sulfuric acid concentrations

    OpenAIRE

    M. Boy; Mogensen, D.; Smolander, S.; Zhou, L; Nieminen, T.; Paasonen, P.; Plass-Dülmer, C.; Sipilä, M.; T. Petäjä; Mauldin, L.; Berresheim, H.; M. Kulmala

    2013-01-01

    The effect of increased reaction rates of stabilized Criegee intermediates (sCIs) with SO2 to produce sulfuric acid is investigated using data from two different locations, SMEAR II, Hyytiälä, Finland, and Hohenpeissenberg, Germany. Results from MALTE, a zero-dimensional model, show that using previous values for the rate coefficients of sCI + SO2, the model underestimates gas phase H2SO4 by up to a factor of two when compared to measurements. Using the rate coefficients recently calc...

  20. Characterization of iron hydroxide/oxide nanoparticles prepared in microemulsions stabilized with cationic/non-ionic surfactant mixtures.

    Science.gov (United States)

    Bumajdad, Ali; Ali, Sami; Mathew, Asha

    2011-03-15

    Iron oxide-hydroxide (α-Fe(2)O(3); Fe(OH)(3)) nanoparticles have been prepared by a microemulsion route using ammonia (NH(3)) solution or tetrabutylammonium hydroxide (TBAH) as precipitants. The iron oxide-hydroxide nanoparticles obtained were characterized by TGA, N(2) sorptiometry, XRD, IR, SEM, HR-TEM, and DLS techniques. Properties such as specific surface area (S(BET)), pore sizes and shapes, average particle size and distribution, crystallite structure, and thermal stability were determined. The properties of nanoparticles prepared using NH(3) and TBAH were compared after drying at 100°C and after being calcined in the temperature range 250-1100°C. It was found that the suspensions prepared using TBAH suffered immediate separation while those prepared using NH(3) resulted in very stable suspensions. Also, it was found that TBAH did not offer any advantage over NH(3) either in terms of specific surface area or in particle size of the prepared nanoparticles. Hence, the later part of the study was concentrated on the NH(3)-precipitated nanoparticles with particular emphasis on finding the most favorable, W (water-to-surfactant ratio) and/or surfactant concentration, S, to obtain the best conditions in terms of higher surface areas and narrower particle size distribution. It was found that the prepared suspension consisted of monodisperse nanoparticles (standard deviations <10%) and after separation and drying, high surface area powders were obtained. The highest surface area (315 m(2) g(-1)) was obtained when the smallest W (=20) and highest S (=0.20 mol L(-1)) were employed. PMID:21232750

  1. Stopped Flow Kinetics of MnII Catalysed Periodate Oxidation of 2, 3- dimethylaniline - Evaluation of Stability Constant of the Ternary Intermediate Complex

    Directory of Open Access Journals (Sweden)

    Rajneesh Dutt Kaushik

    2015-03-01

    Full Text Available The formation of ternary intermediate unstable complex during the oxidation of aromatic amines by periodate ion catalysed by MnII has been proposed in case of some anilines. This paper is the first report on stopped-flow kinetic study and evaluation of stability constant of ternary complex forming in the MnII - catalysed periodate oxidation of 2, 3-dimethylaniline (D in acetone-water medium. Stop-flow spectrophotometric method was used to study the ternary complex formation and to determine its stability constant. The stop-flow trace shows the reaction to occur in two steps. The first step, which is presumably the formation of ternary complex, is relatively fast while the second stage is relatively quite slow. The stability constant evaluated for D - MnII - IO4- ternary complex by determining  equilibrium absorbance is (2.2 ± 1.0 × 105. Kinetics of ternary complex formation was defined by the rate law(A  under pseudo first order conditions. ln{[C2]eq / ( [C2]eq -[C2]} = kobs . t (A where, kobs is the pseudo first order rate constant, [C2] is concentration of ternary complex at given time t, and [C2]eq is the equilibrium concentration of ternary complex. © 2015 BCREC UNDIP. All rights reservedReceived: 3rd October 2014; Revised: 4th December 2014; Accepted: 15th December 2014How to Cite: Kaushik, R.D., Agarwal, R., Tyagi, P., Singh, O., Singh, J. (2015. Stopped Flow Kinetics of MnII Catalysed Periodate Oxidation of 2,3-dimethylaniline - Evaluation of Stability Constant of the Ternary Intermediate Complex. Bulletin of Chemical Reaction Engineering & Catalysis, 10 (1: 78-87. (doi:10.9767/bcrec.10.1.7621.78-87Permalink/DOI: http://dx.doi.org/10.9767/bcrec.10.1.7621.78-87

  2. Optimization of the Asymmetric Intermediate Reflector Morphology for High Stabilized Efficiency Thin n-i-p Micromorph Solar Cells

    OpenAIRE

    Biron, Remi; Hanni, Simon; Boccard, Mathieu; Pahud, Celine; Bugnon, Gregory; Ding, Laura; NICOLAY, Sylvain; Parascandolo, Gaetano; Meillaud, Fanny; Despeisse, Matthieu; Haug, Franz-Josef; Ballif, Christophe

    2013-01-01

    This paper focuses on our latest progress in n-i-p thinmicromorph solar-cell fabrication using textured back reflectors and asymmetric intermediate reflectors, both deposited by lowpressure chemical vapor deposition of zinc oxide.We then present microcrystalline bottom cells with high crystallinity, which yield excellent long wavelength response for relatively thin absorber thickness. In a 1.5-μm-thick μc-Si:H single-junction n-i-p solar cell, we thus obtain a short-circuit current density of...

  3. The effects of monovalent and divalent cations on the stability of silver nanoparticles formed from direct reduction of silver ions by Suwannee River humic acid/natural organic matter

    International Nuclear Information System (INIS)

    The formation and characterization of AgNPs (silver nanoparticles) formed from the reduction of Ag+ by SRNOM (Suwannee River natural organic matter) is reported. The images of SRNOM-formed AgNPs and the selected area electron diffraction (SAED) were captured by high resolution transmission electron microscopy (HRTEM). The colloidal and chemical stability of SRNOM- and SRHA (Suwannee River humic acid)-formed AgNPs in different ionic strength solutions of NaCl, KCl, CaCl2 and MgCl2 was investigated in an effort to evaluate the key fate and transport processes of these nanoparticles in natural aqueous environments. The aggregation state, stability and sedimentation rate of the AgNPs were monitored by Dynamic Light Scattering (DLS), zeta potential, and UV–vis measurements. The results indicate that both types of AgNPs are very unstable in high ionic strength solutions. Interestingly, the nanoparticles appeared more unstable in divalent cation solutions than in monovalent cation solutions at similar concentrations. Furthermore, the presence of SRNOM and SRHA contributed to the nanoparticle instability at high ionic strength in divalent metallic cation solutions, most likely due to intermolecular bridging with the organic matter. The results clearly suggest that changes in solution chemistry greatly affect nanoparticle long term stability and transport in natural aqueous environments. Highlights: ► Formation of SRNOM-AgNPs under environmentally relevant conditions ► Influence of monovalent versus divalent cations on SRHA- and SRNOM-AgNP stability ► Effect of AgNPs on organic matter removal from water columns

  4. A new intermediate in the Prins reaction

    Directory of Open Access Journals (Sweden)

    Shinichi Yamabe

    2013-03-01

    Full Text Available Two Prins reactions were investigated by the use of DFT calculations. A model composed of R–CH=CH2 + H3O+(H2O13 + (H2C=O2, R = Me and Ph, was adopted to trace reaction paths. For both alkenes, the concerted path forming 1,3-diols was obtained as the rate determining step (TS1. TS stands for a transition state. From the 1,3-diol, a bimolecular elimination (TS2 leads to the allylic alcohol as the first channel. In the second channel, the 1,3-diol was converted via TS3 into an unprecedented hemiacetal intermediate, HO–CH2–O–CH(R–CH2–CH2–OH. This intermediate undergoes ring closure (TS4, affording the 1,3-dioxane product. The intermediate is of almost the same stability as the product, and two species were suggested to be in a state of equilibrium. While the geometry of TS1 appears to be forwarded to that of a carbocation intermediate, the cation disappeared through the enlargement of the water cluster. Dynamical calculations of a classical trajectory using the atom-centered density matrix propagation molecular dynamics model on the four TSs were carried out, and results of IRC calculations were confirmed by them.

  5. Oxidation of SO2 by stabilized Criegee intermediate (sCI radicals as a crucial source for atmospheric sulfuric acid concentrations

    Directory of Open Access Journals (Sweden)

    M. Boy

    2013-04-01

    Full Text Available The effect of increased reaction rates of stabilized Criegee intermediates (sCIs with SO2 to produce sulfuric acid is investigated using data from two different locations, SMEAR II, Hyytiälä, Finland, and Hohenpeissenberg, Germany. Results from MALTE, a zero-dimensional model, show that using previous values for the rate coefficients of sCI + SO2, the model underestimates gas phase H2SO4 by up to a factor of two when compared to measurements. Using the rate coefficients recently calculated by Mauldin et al. (2012 increases sulfuric acid by 30–40%. Increasing the rate coefficient for formaldehyde oxide (CH2OO with SO2 according to the values recommended by Welz et al. (2012 increases the H2SO4 yield by 3–6%. Taken together, these increases lead to the conclusion that, depending on their concentrations, the reaction of stabilized Criegee intermediates with SO2 could contribute as much as 33–46% to atmospheric sulfuric acid gas phase concentrations at ground level. Using the SMEAR II data, results from SOSA, a one-dimensional model, show that the contribution from sCI reactions to sulfuric acid production is most important in the canopy, where the concentrations of organic compounds are the highest, but can have significant effects on sulfuric acid concentrations up to 100 m. The recent findings that the reaction of sCI + SO2 is much faster than previously thought together with these results show that the inclusion of this new oxidation mechanism could be crucial in regional as well as global models.

  6. Atmospheric isoprene ozonolysis: impacts of stabilized Criegee intermediate reactions with SO2, H2O and dimethyl sulfide

    Directory of Open Access Journals (Sweden)

    M. J. Newland

    2015-03-01

    Full Text Available Isoprene is the dominant global biogenic volatile organic compound (VOC emission. Reactions of isoprene with ozone are known to form stabilised Criegee intermediates (SCIs, which have recently been shown to be potentially important oxidants for SO2 and NO2 in the atmosphere; however the significance of this chemistry for SO2 processing (affecting sulfate aerosol and NO2 processing (affecting NOx levels depends critically upon the fate of the SCI with respect to reaction with water and decomposition. Here, we have investigated the removal of SO2 in the presence of isoprene and ozone, as a function of humidity, under atmospheric boundary layer conditions. The SO2 removal displays a clear dependence on relative humidity, confirming a significant reaction for isoprene derived SCI with H2O. Under excess SO2 conditions, the total isoprene ozonolysis SCI yield was calculated to be 0.56 (±0.03. The observed SO2 removal kinetics are consistent with a relative rate constant, k(SCI + H2O/k(SCI + SO2, of 5.4 (±0.8 × 10−5 for isoprene derived SCI. The relative rate constant for k(SCI decomposition/k(SCI + SO2 is 8.4 (±5.0 × 1010 cm−3. Uncertainties are ±2σ and represent combined systematic and precision components. These kinetic parameters are based on the simplification that a single SCI species is formed in isoprene ozonolysis, an approximation which describes the results well across the full range of experimental conditions. Our data indicate that isoprene-derived SCIs are unlikely to make a substantial contribution to gas-phase SO2 oxidation in the troposphere. We also present results from an analogous set of experiments, which show a clear dependence of SO2 removal in the isoprene-ozone system as a function of dimethyl sulfide concentration. We propose that this behaviour arises from a rapid reaction between isoprene-derived SCI and DMS; the observed SO2 removal kinetics are consistent with a relative rate constant, k(SCI + DMS/k(SCI + SO2

  7. Effects of Land Use Practices on the Organic Carbon Content, Cation Exchange Capacity and Aggregate Stability of Soils in the Catchment Zones

    Directory of Open Access Journals (Sweden)

    Mosayeb Heshmati

    2011-01-01

    Full Text Available Problem statement: Land use practice leads to changes in the physico-chemical properties of soils, such as Soil Organic Carbon (SOC, Cation Exchange Capacity (CEC and Soil Aggregate Stability (SAS that cause soil erosion. Approach: Merek catchment, Iran suffers from land degradation due to poor land use practice. A study was carried out with the objectives: (i to determine soil nutrient status in different agro-ecological zones in Merek catchment; and (ii to evaluate the influence of land use practices on SOC, CEC and SAS. Results: It was found that soil texture was silty and clay, while soil reaction was alkaline (pH was 7.75. The respective amount of carbonates was 32 and 36% in the top-soil and sub-soil respectively, indicating high level of alkalinity in the soils of the study area. The mean SAS of the surface soil layer for agriculture, rangeland and forest was 53, 61 and 64%, respectively with its mean in the topsoil of agriculture is significantly lower (P≤0.05 than the other zones. SOC level in the agriculture, rangeland and forest were 1.35, 1.56, 2.14 % in the topsoil and 1.03, 1.33 and 1.45%, in the subsoil of the respective areas. The results of t-test and ANOVA analyses showed that SOC means are significantly different from each other within soil depth and among agro-ecological zones. The CEC in the agriculture, rangeland and forest areas were 25.8, 24.6 and 35.1 cmolckg-1 for the top-soil and 31.1, 26.8 and 26.9 cmolckg-1 in the sub-soil, respectively. All the above changes are due to the negative effects of agricultural activities. Conclusion: Improper tillage practice (up-down the slope, conversion of the rangeland and forest to rain-fed areas, crop residue burning, over grazing and forest clearance contribute to reduction in SOC and SAS in the Merek catchment, Iran.

  8. Advancements in Anion Exchange Membrane Cations

    Energy Technology Data Exchange (ETDEWEB)

    Sturgeon, Matthew R. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Long, Hai [National Renewable Energy Lab. (NREL), Golden, CO (United States); Park, Andrew M. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Pivovar, Bryan S. [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2015-10-15

    Anion-exchange membrane fuel cells (AME-FCs) are of increasingly popular interest as they enable the use of non-Pt fuel cell catalysts, the primary cost limitation of proton exchange membrane fuel cells. Benzyltrimethyl ammonium (BTMA) is the standard cation that has historically been utilized as the hydroxide conductor in AEMs. Herein we approach AEMs from two directions. First and foremost we study the stability of several different cations in a hydroxide solution at elevated temperatures. We specifically targeted BTMA and methoxy and nitro substituted BTMA. We've also studied the effects of adding an akyl spacer units between the ammonium cation and the phenyl group. In the second approach we use computational studies to predict stable ammonium cations, which are then synthesized and tested for stability. Our unique method to study cation stability in caustic conditions at elevated temperatures utilizes Teflon Parr reactors suitable for use under various temperatures and cation concentrations. NMR analysis was used to determine remaining cation concentrations at specific time points with GCMS analysis verifying product distribution. We then compare the experimental results with calculated modeling stabilities. Our studies show that the electron donating methoxy groups slightly increase stability (compared to that of BTMA), while the electron withdrawing nitro groups greatly decrease stability in base. These results give insight into possible linking strategies to be employed when tethering a BTMA like ammonium cation to a polymeric backbone; thus synthesizing an anion exchange membrane.

  9. Catching elusive glycosyl cations in a condensed phase with HF/SbF5 superacid

    Science.gov (United States)

    Martin, A.; Arda, A.; Désiré, J.; Martin-Mingot, A.; Probst, N.; Sinaÿ, P.; Jiménez-Barbero, J.; Thibaudeau, S.; Blériot, Y.

    2016-02-01

    Glycosyl cations are universally accepted key ionic intermediates in the mechanism of glycosylation, the reaction that covalently links carbohydrates to other molecules. These ions have remained hypothetical species so far because of their extremely short life in organic media as a consequence of their very high reactivity. Here, we report the use of liquid hydrofluoric acid-antimony pentafluoride (HF/SbF5) superacid to generate and stabilize the glycosyl cations derived from peracetylated 2-deoxy and 2-bromoglucopyranose in a condensed phase. Their persistence in this superacid medium allows their three-dimensional structure to be studied by NMR, aided by complementary computations. Their deuteration further confirms the impact of the structure of the glycosyl cation on the stereochemical outcome of its trapping.

  10. MD and NMR analyses of choline and TMA binding to duplex DNA: on the origins of aberrant sequence-dependent stability by alkyl cations in aqueous and water-free solvents.

    Science.gov (United States)

    Portella, Guillem; Germann, Markus W; Hud, Nicholas V; Orozco, Modesto

    2014-02-26

    It has been known for decades that alkylammonium ions, such as tetramethyl ammonium (TMA), alter the usual correlation between DNA GC-content and duplex stability. In some cases it is even possible for an AT-rich duplex to be more stable than a GC-rich duplex of the same length. There has been much speculation regarding the origin of this aberration in sequence-dependent DNA duplex stability, but no clear resolution. Using a combination of molecular dynamics simulations and NMR spectroscopy we demonstrate that choline (2-hydroxy-N,N,N-trimethylethanaminium) and TMA are preferentially localized in the minor groove of DNA duplexes at A·T base pairs and these same ions show less pronounced localization in the major groove compared to what has been demonstrated for alkali and alkali earth metal ions. Furthermore, free energy calculations show that single-stranded GC-rich sequences exhibit more favorable solvation by choline than single-stranded AT-rich sequences. The sequence-specific nature of choline and TMA binding provides a rationale for the enhanced stability of AT-rich sequences when alkyl-ammonium ions are used as the counterions of DNA. Our combined theoretical and experimental study provides one of the most detailed pictures to date of cations localized along DNA in the solution state, and provides insights that go beyond understanding alkyl-ammonium ion binding to DNA. In particular, because choline and TMA bind to DNA in a manner that is found to be distinct from that previously reported for Na(+), K(+), Mg(2+), and Ca(2+), our results reveal the important but underappreciated role that most other cations play in sequence-specific duplex stability. PMID:24490755

  11. Stability and instability of the isoelectronic UO22+ and PaO2+ actinyl oxo-cations in aqueous solution from density functional theory based molecular dynamics

    International Nuclear Information System (INIS)

    In this work, Pa(V) mono-cations have been studied in liquid water by means of density functional theory (DFT) based molecular dynamic simulations (CPMD) and compared with their U(VI) isoelectronic counterparts to understand the peculiar chemical behavior of Pa(V) in aqueous solution. Four different Pa(V) monocationic isomers appear to be stable in liquid water from our simulations: [PaO2(H2O)5]+(aq), [Pa(OH)4(H2O)2]+(aq), [PaO(OH)2(H2O)4]+(aq), and [Pa(OH)4(H2O)3]+(aq). On the other hand, in the case of U(VI) only the uranyl, [UO2(H2O)5]2+(aq), is stable. The other species containing hydroxyl groups replacing one or two oxo bonds are readily converted to uranyl. The Pa-OH bond is stable, while it is suddenly broken in U-OH. This makes possible the formation of a broad variety of Pa(V) species in water and participates to its unique chemical behavior in aqueous solution. Further, the two actinyl oxo-cations in water are different in the ability of the oxygen atoms to form stable and extended H-bond networks for Pa(V) contrary to U(VI). In particular, prot-actinyl is found to have between 2 and 3 hydrogen bonds per oxygen atom while uranyl has between zero and one. (authors)

  12. Construction of a novel cationic polymeric liposomes formed from PEGlated octadecyl-quaternized lysine modified chitosan/cholesterol for enhancing storage stability and cellular uptake efficiency.

    Science.gov (United States)

    Wang, Hanjie; Zhao, Peiqi; Liang, Xiaofei; Song, Tao; Gong, Xiaoqun; Niu, Ruifang; Chang, Jin

    2010-08-15

    The design and construction of delivery vectors with high stability and effective cellular uptake efficiency is very important. In this study, a novel polymeric liposomes (PLs) formed from PEGlated octadecyl-quaternized lysine modified chitosan (OQLCS) and cholesterol with higher size stability and cellular uptake efficiency has been synthesized successfully. Compared to conventional liposomes (CLs; phosphatidyl choline/cholesterol), the calcein-loaded PLs exhibited a multi-lamellar structure with homogenous size diameter (200 nm) and high calcein encapsulation efficiency (about 92%). PLs could be stored at different temperature (25, 4, and -20 degrees C) and different medium (deionized water, phosphate-buffered saline, and human plasma solution) for up to 4 weeks without significant size change. The spectrophotometer fluorometry analysis and the flow cytometry analysis indicated that in comparison with CL, PLs with positive zeta potential facilitates the uptake of calcein by MCF-7 tumor cells. The data suggests that PLs may provide a new method to overcome the stability and enhance the uptake efficiency of CLs. PMID:20506161

  13. Financial Intermediation

    OpenAIRE

    Gary Gorton; Andrew Winton

    2002-01-01

    The savings/investment process in capitalist economies is organized around financial intermediation, making them a central institution of economic growth. Financial intermediaries are firms that borrow from consumer/savers and lend to companies that need resources for investment. In contrast, in capital markets investors contract directly with firms, creating marketable securities. The prices of these securities are observable, while financial intermediaries are opaque. Why do financial inter...

  14. Intermediated Trade

    OpenAIRE

    Antras, Pol; Costinot, Arnaud

    2011-01-01

    This paper develops a simple model of international trade with intermediation. We consider an economy with two islands and two types of agents, farmers and traders. Farmers can produce two goods, but in order to sell these goods in centralized (Walrasian) markets, they need to be matched with a trader, and this entails costly search. In the absence of search frictions, our model reduces to a standard Ricardian model of trade. We use this simple model to contrast the implications of changes in...

  15. Stabilization

    Directory of Open Access Journals (Sweden)

    Muhammad H. Al-Malack

    2016-07-01

    Full Text Available Fuel oil flyash (FFA produced in power and water desalination plants firing crude oils in the Kingdom of Saudi Arabia is being disposed in landfills, which increases the burden on the environment, therefore, FFA utilization must be encouraged. In the current research, the effect of adding FFA on the engineering properties of two indigenous soils, namely sand and marl, was investigated. FFA was added at concentrations of 5%, 10% and 15% to both soils with and without the addition of Portland cement. Mixtures of the stabilized soils were thoroughly evaluated using compaction, California Bearing Ratio (CBR, unconfined compressive strength (USC and durability tests. Results of these tests indicated that stabilized sand mixtures could not attain the ACI strength requirements. However, marl was found to satisfy the ACI strength requirement when only 5% of FFA was added together with 5% of cement. When the FFA was increased to 10% and 15%, the mixture’s strength was found to decrease to values below the ACI requirements. Results of the Toxicity Characteristics Leaching Procedure (TCLP, which was performed on samples that passed the ACI requirements, indicated that FFA must be cautiously used in soil stabilization.

  16. Test procedure for cation exchange chromatography

    International Nuclear Information System (INIS)

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

  17. Silica-based cationic bilayers as immunoadjuvants

    OpenAIRE

    Carmona-Ribeiro Ana M; da Costa Maria; Faquim-Mauro Eliana; Santana Mariana RA; Lincopan Nilton

    2009-01-01

    Abstract Background Silica particles cationized by dioctadecyldimethylammonium bromide (DODAB) bilayer were previously described. This work shows the efficiency of these particulates for antigen adsorption and presentation to the immune system and proves the concept that silica-based cationic bilayers exhibit better performance than alum regarding colloid stability and cellular immune responses for vaccine design. Results Firstly, the silica/DODAB assembly was characterized at 1 mM NaCl, pH 6...

  18. Intermediate Images

    OpenAIRE

    Paech Joachim

    2014-01-01

    Starting from a definition of the word ‘picture’ as a real-world object that shows other objects on its surface as a representation of its image, I propose that the intermediality of pictures of all kinds is only possible through their images, after they have been separated from their material basis or foundation (for example, a painting in its physical reality can never be directly connected with a movie). In all technical reproductions of images, such as printing processes, an image is take...

  19. Intermediate Images

    Directory of Open Access Journals (Sweden)

    Paech Joachim

    2014-12-01

    Full Text Available Starting from a definition of the word ‘picture’ as a real-world object that shows other objects on its surface as a representation of its image, I propose that the intermediality of pictures of all kinds is only possible through their images, after they have been separated from their material basis or foundation (for example, a painting in its physical reality can never be directly connected with a movie. In all technical reproductions of images, such as printing processes, an image is taken from a negative matrix in order to realize multiple prints of the same representation. The most effective model of this procedure is photography: photographic images can easily be connected with their media forms to produce other, more complex forms, such as magazines, printed books, or films. Intermediate images in the form of matrices - sometimes transparent (e.g. in the light beam of a film projection, sometimes opaque - are required to transform one pictorial media form into another. Finally, for the digital matrix-image, there is no longer any difference between the matrix and the image: the matrix has become its own image, which can be linked to all other media forms.

  20. Intermediate uveitis

    Directory of Open Access Journals (Sweden)

    Babu B

    2010-01-01

    Full Text Available Intermediate uveitis (IU is described as inflammation in the anterior vitreous, ciliary body and the peripheral retina. In the Standardization of Uveitis Nomenclature (SUN working group′s international workshop for reporting clinical data the consensus reached was that the term IU should be used for that subset of uveitis where the vitreous is the major site of the inflammation and if there is an associated infection (for example, Lyme disease or systemic disease (for example, sarcoidosis. The diagnostic term pars planitis should be used only for that subset of IU where there is snow bank or snowball formation occurring in the absence of an associated infection or systemic disease (that is, "idiopathic". This article discusses the clinical features, etiology, pathogenesis, investigations and treatment of IU.

  1. Oxidation of SO2 by stabilized Criegee Intermediate (sCI) radicals as a crucial source for atmospheric sulphuric acid concentrations

    OpenAIRE

    Mauldin, L.; T. Petäjä; Plass-Dülmer, C.; Sipilä, M.; Paasonen, P.; Smolander, S.; Zhou, L; Nieminen, T.; Mogensen, D.; M. Boy; Berresheim, H.; M. Kulmala

    2012-01-01

    The effect of increased reaction rates of stabilised Criegee Intermediates (sCI) with SO2 to produce sulphuric acid is investigated using data from two different locations, SMEAR II, Hyytiälä, Finland and Hohenpeissenberg, Germany. Results from MALTE, a zero dimensional model, show that using previous values for the rate coefficients of sCI + SO2, the model underestimates gas phase H2SO4 by up to a factor of two when compared to measurements. Using the rate coefficients recently calcu...

  2. Cationic hetero diffusion and mechanical properties of yttria-stabilized zirconia: influence of irradiation; Heterodiffusion cationique et proprietes mecaniques de la zircone stabilisee a l'oxyde d'yttrium: influence de l'irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Menvie Bekale, V

    2007-12-15

    Cubic yttria-stabilized zirconia (YSZ) is a promising material as target for the transmutation of radioactive waste. In this context, the present work is dedicated to the study of the atomic transport and the mechanical properties of this ceramic, as well as the influence of irradiation on these properties. The preliminary step concerns the synthesis of YSZ cubic zirconia ceramic undoped and doped with rare earths to form homogeneous Ce-YSZ or Gd-YSZ solid solutions with the highest density. The diffusion experiments of Ce and Gd in YSZ or Ce-YSZ were performed in air from 900 to 1400 C, and the depth profiles were established by SIMS. The bulk diffusion decreases when the ionic radius of diffusing element increases. The comparison with literature data of activation energies for bulk diffusion suggests that the cationic diffusion occurs via a vacancy mechanism. The diffusion results of Ce in YSZ irradiated with 4 or 20 MeV Au ions show a bulk diffusion slowing-down at 1000 and 1100 C when the radiation damage becomes important (30 dpa). The mechanical properties of YSZ ceramics irradiated with 944 MeV Pb ions and non irradiated samples were studied by Vickers micro indentation and Berkovitch nano indentation techniques. The hardness of the material increases when the average grain size decreases. Furthermore, the hardness and the toughness increase with irradiation fluence owing to the occurrence of compressive residual stresses in the irradiated area. (author)

  3. Enhancement of YBCO thin film thermal stability under 1 ATM oxygen pressure by Intermediate Cu.sub.2./sub. O nanolayer

    Czech Academy of Sciences Publication Activity Database

    Cheng, L.; Wang, X.; Yao, X.; Wan, W.; Li, F.H.; Xiong, J.; Tao, B.W.; Jirsa, Miloš

    2010-01-01

    Roč. 114, č. 22 (2010), s. 7543-7547. ISSN 1520-6106 R&D Projects: GA MŠk(CZ) ME10069 Institutional research plan: CEZ:AV0Z10100520 Keywords : YBCO thin films * thermal stability * thin film growth orientation * temperature optical microscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.603, year: 2010

  4. Lithium-stabilized nucleophilic addition of thiamin to a ketone provides an efficient route to mandelylthiamin, a critical pre-decarboxylation intermediate.

    Science.gov (United States)

    Bielecki, Michael; Howe, Graeme W; Kluger, Ronald

    2015-10-01

    Mandelylthiamin (MTh) is an accurate model of the covalent intermediate derived from the condensation of thiamin diphosphate and benzoylformate in benzoylformate decarboxylase. The properties and catalytic susceptibilities of mandelylthiamin are the subjects of considerable interest. However, the existing synthesis gives only trace amounts of the precursor to MTh as it is conducted under reversible conditions. An improved approach derives from the unique ability of lithium ions to drive to completion the otherwise unfavorable condensation of the conjugate base of thiamin and methyl benzoylformate. The unique efficiency of the condensation reaction in the presence of lithium ions is established in contrast to the effects of other Lewis acids. Interpretation of the pattern of the results indicates that the condensation of the ketone and thiamin is thermodynamically controlled. It is proposed that the addition of lithium ions displaces the equilibrium toward the product through formation of a stable lithium-alkoxide. PMID:26333207

  5. Stabilization of the Simplest Criegee Intermediate from the Reaction between Ozone and Ethylene: A High-Level Quantum Chemical and Kinetic Analysis of Ozonolysis.

    Science.gov (United States)

    Nguyen, Thanh Lam; Lee, Hyunwoo; Matthews, Devin A; McCarthy, Michael C; Stanton, John F

    2015-06-01

    The fraction of the collisionally stabilized Criegee species CH2OO produced from the ozonolysis of ethylene is calculated using a two-dimensional (E, J)-grained master equation technique and semiclassical transition-state theory based on the potential energy surface obtained from high-accuracy quantum chemical calculations. Our calculated yield of 42 ± 6% for the stabilized CH2OO agrees well, within experimental error, with available (indirect) experimental results. Inclusion of angular momentum in the master equation is found to play an essential role in bringing the theoretical results into agreement with the experiment. Additionally, yields of HO and HO2 radical products are predicted to be 13 ± 6% and 17 ± 6%, respectively. In the kinetic simulation, the HO radical product is produced mostly from the stepwise decomposition mechanism of primary ozonide rather than from dissociation of hot CH2OO. PMID:25945650

  6. Identification of large channels in cationic PEGylated cubosome nanoparticles by synchrotron radiation SAXS and Cryo-TEM imaging.

    Science.gov (United States)

    Angelov, Borislav; Angelova, Angelina; Drechsler, Markus; Garamus, Vasil M; Mutafchieva, Rada; Lesieur, Sylviane

    2015-05-14

    Extra-large nanochannel formation in the internal structure of cationic cubosome nanoparticles results from the interplay between charge repulsion and steric stabilization of the lipid membrane interfaces and is evidenced by cryogenic transmission electron microscopy (Cryo-TEM) and synchrotron radiation small-angle X-ray scattering (SAXS). The swollen cubic symmetry of the lipid nanoparticles emerges through a shaping transition of onion bilayer vesicle intermediates containing a fusogenic nonlamellar lipid. Cationic amphiphile cubosome particles, thanks to the advantages of their liquid crystalline soft porous nanoarchitecture and capability for multi-drug nanoencapsulation, appear to be of interest for the design of mitochondrial targeting devices in anti-cancer therapies and as siRNA nanocarriers for gene silencing. PMID:25820228

  7. High performance of intermediate temperature solid oxide electrolysis cells using Nd2NiO4+δ impregnated scandia stabilized zirconia oxygen electrode

    Science.gov (United States)

    Chen, Ting; Liu, Minquan; Yuan, Chun; Zhou, Yucun; Ye, Xiaofeng; Zhan, Zhongliang; Xia, Changrong; Wang, Shaorong

    2015-02-01

    Nano-structured Nd2NiO4+δ(NNO) impregnated scandia stabilized zirconia (SSZ) is studied as the oxygen electrode of solid oxide electrolysis cells (SOECs). The hydrogen electrode-supported single cell with Ni-Zr0.92Y0.16O2.08 (YSZ) hydrogen electrode, SSZ electrolyte and impregnated NNO-SSZ composite oxygen electrode is prepared by a tape casting, co-firing and impregnation method. The electrochemical properties of the cell are investigated in the electrolysis mode. At the voltage of 1.3 V, current densities of 1.081, 0.677, 0.441 and 0.23 A cm-2 are obtained at 800, 750, 700 and 650 °C respectively. The cell also exhibits comparable performance with variation of the steam-to-hydrogen ratio (50/50 to 80/20) at 750 °C. Additionally, the short-term durability in the electrolysis mode of the cell is also studied.

  8. Ground state of naphthyl cation: Singlet or triplet?

    Energy Technology Data Exchange (ETDEWEB)

    Dutta, Achintya Kumar; Vaval, Nayana, E-mail: np.vaval@ncl.res.in; Pal, Sourav, E-mail: s.pal@ncl.res.in [Physical Chemistry Division, CSIR-National Chemical Laboratory, Pune 411008 (India); Manohar, Prashant U. [Department of Chemistry, BITS Pilani, Pilani Campus (India)

    2014-03-21

    We present a benchmark theoretical investigation on the electronic structure and singlet-triplet(S-T) gap of 1- and 2-naphthyl cations using the CCSD(T) method. Our calculations reveal that the ground states of both the naphthyl cations are singlet, contrary to the results obtained by DFT/B3LYP calculations reported in previous theoretical studies. However, the triplet states obtained in the two structural isomers of naphthyl cation are completely different. The triplet state in 1-naphthyl cation is (π,σ) type, whereas in 2-naphthyl cation it is (σ,σ{sup ′}) type. The S-T gaps in naphthyl cations and the relative stability ordering of the singlet and the triplet states are highly sensitive to the basis-set quality as well as level of correlation, and demand for inclusion of perturbative triples in the coupled-cluster ansatz.

  9. Cation-cation interaction in neptunyl(V) compounds

    International Nuclear Information System (INIS)

    The original manuscript was prepared by Professor N.N. Krot of Institute of Physical Chemistry, Russian Academy of Sciences, in 1997. Saeki tried to translate that into Japanese and to add some new data since 1997. The contents include the whole picture of cation-cation interactions mainly in 5-valence neptunium compounds. Firstly, characteristic structures of neptunium are summarized of the cation-cation bonding in compounds. Secondly, it is mentioned how the cation-cation bonding affects physical and chemical properties of the compounds. Then, characterization-methods for the cation-cation bonding in the compounds are discussed. Finally, the cation-cation interactions in compounds of other actinide-ions are shortly reviewed. (author)

  10. Multistep π dimerization of tetrakis(n-decyl)heptathienoacene radical cations: a combined experimental and theoretical study.

    Science.gov (United States)

    Ferrón, Cristina Capel; Capdevila-Cortada, Marçal; Balster, Russell; Hartl, František; Niu, Weijun; He, Mingqian; Novoa, Juan J; López Navarrete, Juan T; Hernández, Víctor; Ruiz Delgado, M Carmen

    2014-08-11

    Radical cations of a heptathienoacene α,β-substituted with four n-decyl side groups (D4T7(.) (+) ) form exceptionally stable π-dimer dications already at ambient temperature (Chem. Comm. 2011, 47, 12622). This extraordinary π-dimerization process is investigated here with a focus on the ultimate [D4T7(.) (+) ]2 π-dimer dication and yet-unreported transitory species formed during and after the oxidation. To this end, we use a joint experimental and theoretical approach that combines cyclic voltammetry, in situ spectrochemistry and spectroelectrochemistry, EPR spectroscopy, and DFT calculations. The impact of temperature, thienoacene concentration, and the nature and concentration of counteranions on the π-dimerization process is also investigated in detail. Two different transitory species were detected in the course of the one-electron oxidation: 1) a different transient conformation of the ultimate [D4T7(.) (+) ]2 π-dimer dications, the stability of which is strongly affected by the applied experimental conditions, and 2) intermediate [D4T7]2 (.) (+) π-dimer radical cations formed prior to the fully oxidized [D4T7]2 (.) (+) π-dimer dications. Thus, this comprehensive work demonstrates the formation of peculiar supramolecular species of heptathienoacene radical cations, the stability, nature, and structure of which have been successfully analyzed. We therefore believe that this study leads to a deeper fundamental understanding of the mechanism of dimer formation between conjugated aromatic systems. PMID:25043826

  11. Photochemical generation of a primary vinyl cation from (E)-bromostyrene: Mechanisms of formation and reaction

    NARCIS (Netherlands)

    Gronheid, R.; Zuilhof, H.; Hellings, M.G.

    2003-01-01

    The photochemistry of (E)-bromostyrene was investigated to determine the nature of the product-forming intermediates and to clarify the mechanism of formation of vinylic cations and vinylic radicals. Both a cation- and a radical-derived product are formed, and the ionic origin of the former product

  12. Molecular machines: stimulation of cation motion in molecular switches

    International Nuclear Information System (INIS)

    The theoretical aspects of the mechanism of the motion of cations and ligands in molecular machines referred to as redox switches are presented. The interrelated properties of cations - the energetic, electrochemical, spectral, and magnetic properties; their propensity to form either covalent or ionic bonds; and the relative softness and hardness of cations and ligands - stimulate molecular motion. These properties determine the thermal stability and stability to destruction caused by electrochemical processes and, eventually, the maximal number of transformation cycles. The maximal efficiency of redox switches is attained when the redox reaction involves a cation with a half-filled (d5, f7) or complete (d10, f14) electronic shell. The role of the Jahn-Teller effect is considered: it is responsible for geometry distortion, which stimulates cation motion. The properties of nd- and 4f-block cations are compared from the standpoint of their use for designing redox switches. In switches constructed on the basis of supramolecular compounds containing hard and soft moieties, softer cations (Fe2+, Co2+, Cu+, etc.) prefer to coordinate to soft ligands and harder cations (Fe3+, Co3+, Cu2+, etc.) prefer to coordinate to hard ligands. A cation moves due to the soft-hard change of its coordination sphere in the course of the redox reaction. Design of redox switches based on solid compounds with a cation in mixed oxidation state is shown to be promising. Cations can change their oxidation state with a change in temperature or pressure. The possibility of designing magnetic switches is considered

  13. Surface Intermediate Zone of Submerged Turbulent Buoyant Jet in Current

    DEFF Research Database (Denmark)

    Chen, H. B.; Larsen, Torben

    1995-01-01

    This paper deals with the intermediate zone between the jet and plume stages of a submerged buoyant discharge from sea outfall in current. The stability criteria, plume width and height after the intermediate zone and the dilution within the intermediate region have been studied theoretically...

  14. Degradation Mechanism of Cationic Red X-GRL by Ozonation

    Institute of Scientific and Technical Information of China (English)

    Wei Rong ZHAO; Xin Hua XU; Hui Xiang SHI; Da Hui WANG

    2003-01-01

    The degradation mechanism of Cationic Red X-GRL was investigated when the intermediates, the nitrate ion and the pH were analyzed in the ozonation. The degradation of the Cationic Red X-GRL includes the de-auxochrome stage, the decolour stage, and the decomposition of fragment stage. During the degradation process, among the six nitrogen atoms of Cationic Red X-GRL, one is transferred into a nitrate ion, one becomes the form of an amine compound, and the rest four are transformed into two molecules of nitrogen. In the course of the ozonation of Cationic Red X-GRL, the direct attack of ozone is the main decolour effect.

  15. Promotion of radiation-induced cationic polymerization by onium salts

    International Nuclear Information System (INIS)

    The radiation-induced cationic polymerization of styrene derivatives was studied in the presence of diphenyliodonium and triphenylsulfonium hexafluorophosphates in dichloromethane. A remarkable promotion of the polymerization was observed in the presence of the salts. The pulse radiolysis study revealed that the promotion of the polymerization is due to the ion-pair formation between the initiating cations and the nonnucleophilic complex metal halide anions of the salts resulting in the stabilization of the cations toward neutralization. An additional effect observed in the case of diphenyliodonium salt is the oxidation of free radical species to the cations responsible for the polymerization. An increase in molecular weight at low temperature suggested that the propagating cations are also paired with the counterions derived from the salts. (author)

  16. The measurement of financial intermediation in Japan

    OpenAIRE

    Gunther Capelle-Blancard; Jézabel Couppey-Soubeyran; Laurent Soulat

    2008-01-01

    In this paper, we examine the evolution of the Japanese financial structure, in order to challenge the expected incidences of the financial liberalization. We compute financial intermediation ratios for Japan (1979-2004) on a book value basis. According to our results, the intermediation ratio has remained quite stable, at around 85%. This stability is the result of two opposite trends: a decrease in credits and an increase in financial securities owned by financial (mostly, non-banking) inst...

  17. The measurement of financial intermediation in Japan

    OpenAIRE

    Gunther Capelle-Blancard; Jézabel Couppey-Soubeyran; Laurent Soulat

    2005-01-01

    In this paper, we compute financial intermediation ratios for Japan (1970-2003) on a book value basis. According to our results, the intermediation ratio has remained quite stable, at around 85%. However, this stability is the result of two opposing trends : a decrease in credits and an increase in financial securities owned by financial (mostly, non banking) institutions. These two opposing trends would not have appeared if we had used traditional indicators computed as a fraction on GDP, or...

  18. Study of radionuclides complexes formation by organic compounds in intermediate and low-level radioactive wastes

    International Nuclear Information System (INIS)

    In the general framework of the safety of nuclear wastes of low and intermediate activity, we have studied the effects of organic compounds on the solubilization of metallic cations. Organic compounds originate from the degradation of cellulose in concrete interstitial waters. Degradation reactions generate a number of products, among which carboxylic acids. These acids are known for their chelating properties. We have first analysed the degradation of cellulose in alkaline conditions: we have qualitatively and quantitatively determined the degradation products for various reaction progress indices, including a dozen of carboxylic acids. The principal goal of our work was the prediction of the behaviour of metallic cations in such cellulose degradation solutions. Owing the complexity of the system, a priori theoretical calculation are not possible. We have thus decided to choose tetra hydroxy pentanoic acid as a reference compound in order to simulate as accurately as possible the behaviour of more complex acids which contain similar functional groups. We have experimentally determined the complexing properties of this reference acid toward divalent cobalt and copper, and trivalent samarium and europium. Simple and mixed complex (hydroxyl) have been evidenced in alkaline medium. Their stability constants have been determined and extrapolated at zero ionic strength using the SIT theory. These results allowed us to theoretically predict the behaviour of our four reference cations in cellulose degradation products formed in concrete interstitial waters. In parallel, we have measured their solubility in real cellulose degradation solutions. Solubility predictions are correct for transition metals, but not for rare earth cations. In this case the complexes which have been identified with tetra hydroxy pentanoic acid are not stable enough to dissolve metallic hydroxides. In real degradation solutions, other compounds would account for the enhancement of rare earth

  19. Cationic Antimicrobial Peptide Cytotoxicity

    OpenAIRE

    Laverty, Garry; Gilmore, Brendan

    2014-01-01

    Fluorescence microscopy serves as a valuable tool for assessing the structural integrity and viability of eukaryotic cells. Through the use of calcein AM and the DNA stain 4,6-diamidino-2 phenylindole (DAPI), cell viability and membrane integrity can be qualified. Our group has previously shown the ultra-short cationic antimicrobial peptide H-OOWW-NH2; the amphibian derived 27-mer peptide Maximin-4and the ultra-short lipopeptide C12-OOWW-NH2 to be effective against a range of bacterial biofil...

  20. Polyenyl cations and radical cations – synthesis, spectroscopic properties and reactions

    OpenAIRE

    Kildahl-Andersen, Geir

    2007-01-01

    In the present work, polyene precursors for the formation of charged polyenyl species were synthesised. Their conversion to charge delocalised radical cations and diamagnetic mono- and dications was carried out by treatment with Brønsted and Lewis acids. Reaction conditions were optimised to achieve sufficient stability of the charged polyenes for characterisation by modern spectroscopic methods; in particular nearinfrared absorption spectroscopy (NIR), two-dimensional nuclear magnetic resona...

  1. Denaturation and intermediates study of two sturgeon hemoglobins by n-dodecyl trimethylammonium bromide

    Science.gov (United States)

    Ariaeenejad, Shohreh; Habibi-Rezaei, Mehran; Kavousi, Kaveh; Jamili, Shahla; Fatemi, Mohammad Reza; Hong, Jun; Poursasan, Najmeh; Sheibani, Nader; Moosavi-Movahedi, Ali. A.

    2013-01-01

    Varieties of hemoglobin (Hb) forms exist in fish, which are usually well adapted to the different ecological conditions or various habitats. In the current study, Hbs from two Sturgeon species of the Southern Caspian Sea Basin were purified and studied upon interaction with n-dodecyl trimethylammonium bromide (DTAB; as a cationic surfactant) by various methods including UV-visible absorption, dynamic light scattering (DLS), and ANS fluorescence spectrophotometry. The chemometric analysis of Hbs was investigated upon interaction with DTAB under titration, using UV-visible absorption spectra. The chemometric resolution techniques were used to determine the number of the components and mole fraction of the oxidized Hbs. These results provided the evidence for the existence of three different molecular components including native (N), intermediate (I) and denatured (D) in sturgeon Hbs. According to the distribution of intermediates, which were broadened in a range of DTAB concentration, the aggregation states, DLS experiments, and thermal stability (Tm obtained by differential scanning calorimetry (DSC)), the Acipenser stellatus Hb was more stable compared to Acipenser persicus Hb. These results demonstrate a significant relationship between the stability of fish Hbs and the habitat depth requirements. PMID:23142155

  2. Branching of keratin intermediate filaments.

    Science.gov (United States)

    Nafeey, Soufi; Martin, Ines; Felder, Tatiana; Walther, Paul; Felder, Edward

    2016-06-01

    Keratin intermediate filaments (IFs) are crucial to maintain mechanical stability in epithelial cells. Since little is known about the network architecture that provides this stiffness and especially about branching properties of filaments, we addressed this question with different electron microscopic (EM) methods. Using EM tomography of high pressure frozen keratinocytes, we investigated the course of several filaments in a branching of a filament bundle. Moreover we found several putative bifurcations in individual filaments. To verify our observation we also visualized the keratin network in detergent extracted keratinocytes with scanning EM. Here bifurcations of individual filaments could unambiguously be identified additionally to bundle branchings. Interestingly, identical filament bifurcations were also found in purified keratin 8/18 filaments expressed in Escherichia coli which were reassembled in vitro. This excludes that an accessory protein contributes to the branch formation. Measurements of the filament cross sectional areas showed various ratios between the three bifurcation arms. This demonstrates that intermediate filament furcation is very different from actin furcation where an entire new filament is attached to an existing filament. Instead, the architecture of intermediate filament bifurcations is less predetermined and hence consistent with the general concept of IF formation. PMID:27039023

  3. Radical Addition to Iminium Ions and Cationic Heterocycles

    Directory of Open Access Journals (Sweden)

    Johannes Tauber

    2014-10-01

    Full Text Available Carbon-centered radicals represent highly useful reactive intermediates in organic synthesis. Their nucleophilic character is reflected by fast additions to electron deficient C=X double bonds as present in iminium ions or cationic heterocycles. This review covers diverse reactions of preformed or in situ-generated cationic substrates with various types of C-radicals, including alkyl, alkoxyalkyl, trifluoromethyl, aryl, acyl, carbamoyl, and alkoxycarbonyl species. Despite its high reactivity, the strong interaction of the radical’s SOMO with the LUMO of the cation frequently results in a high regioselectivity. Intra- and intermolecular processes such as the Minisci reaction, the Porta reaction, and the Knabe rearrangement will be discussed along with transition metal and photoredox catalysis or electrochemical methods to generate the odd-electron species.

  4. Aggregate Formed by a Cationic Fluorescence Probe

    Institute of Scientific and Technical Information of China (English)

    TIAN, Juan; SANG, Da-Yong; JI, Guo-Zhen

    2007-01-01

    The aggregation behavior of a cationic fluorescence probe 10-(4,7,10,13,16-pentaoxa-1-azacyclooctadecyl-methyl)anthracen-9-ylmethyl dodecanoate (1) was observed and studied by a fluorescence methodology in acidic and neutral conditions. By using the Py scale, differences between simple aggregates and micelles have been discussed. The stability of simple aggregates was discussed in terms of hydrophobic interaction and electrostatic repulsion. The absence of excimer emission of the anthrancene moiety of probe 1 in neutral condition was attributed to the photoinduced electron transfer mechanism instead of photodimerization.

  5. Simplifying biochemical models with intermediate species

    DEFF Research Database (Denmark)

    Feliu, Elisenda; Wiuf, Carsten

    2013-01-01

    canonical model that characterizes crucial dynamical properties, such as mono- and multistationarity and stability of steady states, of all models in the class. We show that if the core model does not have conservation laws, then the introduction of intermediates does not change the steady...

  6. Looking for Intermediate-Mass Black Holes

    OpenAIRE

    Frampton, Paul H.

    2009-01-01

    A discussion of the entropy of the universe leads to the suggestion of very many intermediate-mass black holes between thirty and three hundred thousand solar masses in the halo. It is consistent with observations on wide binaries as well as microlensing and considerations of disk stability that such IMBHs constitute all cold dark matter

  7. Ion exchange behaviour of polymeric zirconium cations

    International Nuclear Information System (INIS)

    Polymeric zirconium cations formed in weakly acid solutions (pH2) are taken up strongly into macroporous cation exchange resins, while uptake into normal cation exchange resins (pore diameter about 1 nm) is low. Macroporous cation exchange resins loaded with polymeric Zr cations are shown to function as ligand exchange sorbents. (Authors)

  8. Intermediation under Trade Restrictions.

    OpenAIRE

    Winkler, G Michael

    1989-01-01

    Intermediation is the activity of buying and selling simultaneously in one market. In this paper, intermediation in the market for an arbitrary good is derived from trade restrictions in a general equilibrium exchange model. The trade restrictions are given by a trade feasibility relation defined on the set of households, and they necessitate dropping the one price assumption of standard general equilibrium theory. It is shown that, in this setting, equilibria need not exist in spite of well-...

  9. Intermediate algebra a textworkbook

    CERN Document Server

    McKeague, Charles P

    1985-01-01

    Intermediate Algebra: A Text/Workbook, Second Edition focuses on the principles, operations, and approaches involved in intermediate algebra. The publication first takes a look at basic properties and definitions, first-degree equations and inequalities, and exponents and polynomials. Discussions focus on properties of exponents, polynomials, sums, and differences, multiplication of polynomials, inequalities involving absolute value, word problems, first-degree inequalities, real numbers, opposites, reciprocals, and absolute value, and addition and subtraction of real numbers. The text then ex

  10. Intermediate algebra & analytic geometry

    CERN Document Server

    Gondin, William R

    1967-01-01

    Intermediate Algebra & Analytic Geometry Made Simple focuses on the principles, processes, calculations, and methodologies involved in intermediate algebra and analytic geometry. The publication first offers information on linear equations in two unknowns and variables, functions, and graphs. Discussions focus on graphic interpretations, explicit and implicit functions, first quadrant graphs, variables and functions, determinate and indeterminate systems, independent and dependent equations, and defective and redundant systems. The text then examines quadratic equations in one variable, system

  11. Complexation Between Cationic Diblock Copolymers and Plasmid DNA

    Science.gov (United States)

    Jung, Seyoung; Reineke, Theresa; Lodge, Timothy

    Deoxyribonucleic acids (DNA), as polyanions, can spontaneously bind with polycations to form polyelectrolyte complexes. When the polycation is a diblock copolymer with one cationic block and one uncharged hydrophilic block, the polyelectrolyte complexes formed with plasmid DNA (pDNA) are often colloidally stable, and show great promise in the field of polymeric gene therapy. While the resulting properties (size, stability, and toxicity to biological systems) of the complexes have been studied for numerous cationic diblocks, the fundamentals of the pDNA-diblock binding process have not been extensively investigated. Herein, we report how the cationic block content of a diblock influences the pDNA-diblock interactions. pDNA with 7164 base pairs and poly(2-deoxy-2-methacrylamido glucopyranose)-block-poly(N-(2-aminoethyl) methacrylamide) (PMAG-b-PAEMA) are used as the model pDNA and cationic diblock, respectively. To vary the cationic block content, two PMAG-b-PAEMA copolymers with similar PMAG block lengths but distinct PAEMA block lengths and a PAEMA homopolymer are utilized. We show that the enthalpy change from pDNA-diblock interactions is dependent on the cationic diblock composition, and is closely associated with both the binding strength and the pDNA tertiary structure.

  12. Circular dichroism and fluorescence spectroscopy of cysteinyl-tRNA synthetase from Halobacterium salinarum ssp. NRC-1 demonstrates that group I cations are particularly effective in providing structure and stability to this halophilic protein.

    Directory of Open Access Journals (Sweden)

    Christopher J Reed

    Full Text Available Proteins from extremophiles have the ability to fold and remain stable in their extreme environment. Here, we investigate the presence of this effect in the cysteinyl-tRNA synthetase from Halobacterium salinarum ssp. NRC-1 (NRC-1, which was used as a model halophilic protein. The effects of salt on the structure and stability of NRC-1 and of E. coli CysRS were investigated through far-UV circular dichroism (CD spectroscopy, fluorescence spectroscopy, and thermal denaturation melts. The CD of NRC-1 CysRS was examined in different group I and group II chloride salts to examine the effects of the metal ions. Potassium was observed to have the strongest effect on NRC-1 CysRS structure, with the other group I salts having reduced strength. The group II salts had little effect on the protein. This suggests that the halophilic adaptations in this protein are mediated by potassium. CD and fluorescence spectra showed structural changes taking place in NRC-1 CysRS over the concentration range of 0-3 M KCl, while the structure of E. coli CysRS was relatively unaffected. Salt was also shown to increase the thermal stability of NRC-1 CysRS since the melt temperature of the CysRS from NRC-1 was increased in the presence of high salt, whereas the E. coli enzyme showed a decrease. By characterizing these interactions, this study not only explains the stability of halophilic proteins in extremes of salt, but also helps us to understand why and how group I salts stabilize proteins in general.

  13. Intermediate-energy nuclear chemistry workshop

    International Nuclear Information System (INIS)

    This report contains the proceedings of the LAMPF Intermediate-Energy Nuclear Chemistry Workshop held in Los Alamos, New Mexico, June 23-27, 1980. The first two days of the Workshop were devoted to invited review talks highlighting current experimental and theoretical research activities in intermediate-energy nuclear chemistry and physics. Working panels representing major topic areas carried out indepth appraisals of present research and formulated recommendations for future research directions. The major topic areas were Pion-Nucleus Reactions, Nucleon-Nucleus Reactions and Nuclei Far from Stability, Mesonic Atoms, Exotic Interactions, New Theoretical Approaches, and New Experimental Techniques and New Nuclear Chemistry Facilities

  14. Intermediate-energy nuclear chemistry workshop

    Energy Technology Data Exchange (ETDEWEB)

    Butler, G.W.; Giesler, G.C.; Liu, L.C.; Dropesky, B.J.; Knight, J.D.; Lucero, F.; Orth, C.J.

    1981-05-01

    This report contains the proceedings of the LAMPF Intermediate-Energy Nuclear Chemistry Workshop held in Los Alamos, New Mexico, June 23-27, 1980. The first two days of the Workshop were devoted to invited review talks highlighting current experimental and theoretical research activities in intermediate-energy nuclear chemistry and physics. Working panels representing major topic areas carried out indepth appraisals of present research and formulated recommendations for future research directions. The major topic areas were Pion-Nucleus Reactions, Nucleon-Nucleus Reactions and Nuclei Far from Stability, Mesonic Atoms, Exotic Interactions, New Theoretical Approaches, and New Experimental Techniques and New Nuclear Chemistry Facilities.

  15. Analysis of intermediate wettability

    Energy Technology Data Exchange (ETDEWEB)

    Skauge, A.; Vik, B.; Spildo, K.; Ottesen, B. [Bergen Univ., Centre for Integrated Petroleum Research, Bergen (Norway)

    2003-09-01

    The fluid flow of porous media petroleum reservoirs is affected by wettability. In general, North Sea sandstone reservoirs fall into the large group of intermediate wet state reservoirs having end point saturation, capillary pressure, and relative permeability properties. This study examined intermediate the wet state by dividing the wet group into three sub-classes defined as fractionally-wet (FW), mixed-wet large (MWL), and mixed-wet small (MWS). Wettability indices were used to group reservoir data into reservoirs with FW, MWL and MWS behaviour. The analysis of wettability data from several North Sea fields showed that 13 reservoirs have sufficient wettability data to determine the state of intermediate wettability. Five of the reservoirs were classified as MWL, 4 as FW and 4 as MWS. Fractional-wet rock was found to have a more robust wettability and cleaned cores maintained a non-water state, suggesting that wetting sites can be coupled to mineralogy in addition to adsorption/deposition of oil components that change the surface properties of the rock. MWS was found to maintain wettability after cleaning, but MWL cores became water wet after solvent cleaning. This study indicates that the type of intermediate wettability has an impact on the data structure required to develop reservoir models. Wettability was found to influence the share of relative permeability curves and the capillary pressure relations in a variety of intermediate wettability classifications. 23 figs.

  16. Mobile communication and intermediality

    DEFF Research Database (Denmark)

    Helles, Rasmus

    2013-01-01

    The article argues the importance of intermediality as a concept for research in mobile communication and media. The constant availability of several, partially overlapping channels for communication (texting, calls, email, Facebook, etc.) requires that we adopt an integrated view of the various...... communicative affordances of mobile devices in order to understand how people choose between them for different purposes. It is argued that mobile communication makes intermediality especially central, as the choice of medium is detached from the location of stationary media and begins to follow the user across...

  17. Liquid-solid extraction of cationic metals by cationic amphiphiles

    International Nuclear Information System (INIS)

    In the field of selective separation for recycling of spent nuclear fuel, liquid-liquid extraction processes are widely used (PUREX, DIAMEX..) in industrial scale. In order to guarantee a sustainable nuclear energy for the forthcoming generations, alternative reprocessing techniques are under development. One of them bases on the studies from Heckmann et al in the 80's and consists in selectively precipitating actinides from aqueous waste solutions by cationic surfactants (liquid-solid extraction). This technique has some interesting advantages over liquid-liquid extraction techniques, because several steps are omitted like stripping or solvent washing. Moreover, the amount of waste is decreased considerably, since no contaminated organic solvent is produced. In this thesis, we have carried out a physico-chemical study to understand the specific interactions between the metallic cations with the cationic surfactant. First, we have analysed the specific effect of the different counter-ions (Cl-, NO3-, C2O42-) and then the effect of alkaline cations on the structural properties of the surfactant aggregation in varying thermodynamical conditions. Finally, different multivalent cations (Cu2+, Zn2+, UO22+, Fe3+, Nd3+, Eu3+, Th4+) were considered; we have concluded that depending on the anionic complex of these metals formed in acidic media, we can observe either an adsorption at the micellar interface or not. This adsorption has a large influence of the surfactant aggregation properties and determines the limits of the application in term of ionic strength, temperature and surfactant concentration. (author)

  18. Hispanic American Heritage, Intermediate.

    Science.gov (United States)

    Shepherd, Mike

    This resource book features the cultural heritage of Hispanics living within the United States and includes ideas, materials, and activities to be used with students in the intermediate grades and middle school. This book explores the definition of the term "Hispanic Americans" and suggests a multilayered population with a variety of cultural…

  19. Water oxidation: Intermediate identification

    Science.gov (United States)

    Cowan, Alexander J.

    2016-08-01

    The slow kinetics of light-driven water oxidation on haematite is an important factor limiting the material's efficiency. Now, an intermediate of the water-splitting reaction has been identified offering hope that the full mechanism will soon be resolved.

  20. GLOSSARY TO INTERMEDIATE HINDI.

    Science.gov (United States)

    Wisconsin Univ., Madison. Indian Language and Area Center.

    INCLUDED IN THIS GLOSSARY ARE THE VOCABULARY ITEMS FOR THE READINGS IN "INTERMEDIATE HINDI." THE ITEMS ARE ARRANGED BY SELECTION IN SERIAL ORDER. EACH ENTRY INCLUDES NAGARI (DEVANAGARI) SCRIPT SPELLING, A NOTATION OF THE FORM CLASS, AND A SHORT ENGLISH GLOSS. THESE TWO VOLUMES ARE ALSO AVAILABLE AS A SET FOR $7.00 FROM THE COLLEGE PRINTING…

  1. Photodissociation of Cerium Oxide Nanocluster Cations.

    Science.gov (United States)

    Akin, S T; Ard, S G; Dye, B E; Schaefer, H F; Duncan, M A

    2016-04-21

    Cerium oxide cluster cations, CexOy(+), are produced via laser vaporization in a pulsed nozzle source and detected with time-of-flight mass spectrometry. The mass spectrum displays a strongly preferred oxide stoichiometry for each cluster with a specific number of metal atoms x, with x ≤ y. Specifically, the most prominent clusters correspond to the formula CeO(CeO2)n(+). The cluster cations are mass selected and photodissociated with a Nd:YAG laser at either 532 or 355 nm. The prominent clusters dissociate to produce smaller species also having a similar CeO(CeO2)n(+) formula, always with apparent leaving groups of (CeO2). The production of CeO(CeO2)n(+) from the dissociation of many cluster sizes establishes the relative stability of these clusters. Furthermore, the consistent loss of neutral CeO2 shows that the smallest neutral clusters adopt the same oxidation state (IV) as the most common form of bulk cerium oxide. Clusters with higher oxygen content than the CeO(CeO2)n(+) masses are present with much lower abundance. These species dissociate by the loss of O2, leaving surviving clusters with the CeO(CeO2)n(+) formula. Density functional theory calculations on these clusters suggest structures composed of stable CeO(CeO2)n(+) cores with excess oxygen bound to the surface as a superoxide unit (O2(-)). PMID:27035210

  2. Cationic speciation in nonaqueous media

    International Nuclear Information System (INIS)

    Electronic spectra of solutions of d transition elements in the superacids HF, H2SO4, HSO3F, and CF3SO3H and in chloroaluminate melts indicate that in acidic monaqueous media the elements are present as solvated cations, whereas in basic media the speciation is anionic, the same situation as in aqueous solutions. Further, in very highly acidic media, cations in very low oxidation states are stable (e.g., Ti2+), but these disproportionate on addition of base to the system. In this paper spectra, where available, of U, Np, and Pu in oxidation states III and IV in aqueous media, in protonic superacids, and in chloroaluminates are presented to postulate cationic speciation of these early actinides in highly acidic media

  3. The Intermediate Neutrino Program

    CERN Document Server

    Adams, C; Ankowski, A M; Asaadi, J A; Ashenfelter, J; Axani, S N; Babu, K; Backhouse, C; Band, H R; Barbeau, P S; Barros, N; Bernstein, A; Betancourt, M; Bishai, M; Blucher, E; Bouffard, J; Bowden, N; Brice, S; Bryan, C; Camilleri, L; Cao, J; Carlson, J; Carr, R E; Chatterjee, A; Chen, M; Chen, S; Chiu, M; Church, E D; Collar, J I; Collin, G; Conrad, J M; Convery, M R; Cooper, R L; Cowen, D; Davoudiasl, H; De Gouvea, A; Dean, D J; Deichert, G; Descamps, F; DeYoung, T; Diwan, M V; Djurcic, Z; Dolinski, M J; Dolph, J; Donnelly, B; Dwyer, D A; Dytman, S; Efremenko, Y; Everett, L L; Fava, A; Figueroa-Feliciano, E; Fleming, B; Friedland, A; Fujikawa, B K; Gaisser, T K; Galeazzi, M; Galehouse, D C; Galindo-Uribarri, A; Garvey, G T; Gautam, S; Gilje, K E; Gonzalez-Garcia, M; Goodman, M C; Gordon, H; Gramellini, E; Green, M P; Guglielmi, A; Hackenburg, R W; Hackenburg, A; Halzen, F; Han, K; Hans, S; Harris, D; Heeger, K M; Herman, M; Hill, R; Holin, A; Huber, P; Jaffe, D E; Johnson, R A; Joshi, J; Karagiorgi, G; Kaufman, L J; Kayser, B; Kettell, S H; Kirby, B J; Klein, J R; Kolomensky, Yu G; Kriske, R M; Lane, C E; Langford, T J; Lankford, A; Lau, K; Learned, J G; Ling, J; Link, J M; Lissauer, D; Littenberg, L; Littlejohn, B R; Lockwitz, S; Lokajicek, M; Louis, W C; Luk, K; Lykken, J; Marciano, W J; Maricic, J; Markoff, D M; Caicedo, D A Martinez; Mauger, C; Mavrokoridis, K; McCluskey, E; McKeen, D; McKeown, R; Mills, G; Mocioiu, I; Monreal, B; Mooney, M R; Morfin, J G; Mumm, P; Napolitano, J; Neilson, R; Nelson, J K; Nessi, M; Norcini, D; Nova, F; Nygren, D R; Gann, G D Orebi; Palamara, O; Parsa, Z; Patterson, R; Paul, P; Pocar, A; Qian, X; Raaf, J L; Rameika, R; Ranucci, G; Ray, H; Reyna, D; Rich, G C; Rodrigues, P; Romero, E Romero; Rosero, R; Rountree, S D; Rybolt, B; Sanchez, M C; Santucci, G; Schmitz, D; Scholberg, K; Seckel, D; Shaevitz, M; Shrock, R; Smy, M B; Soderberg, M; Sonzogni, A; Sousa, A B; Spitz, J; John, J M St; Stewart, J; Strait, J B; Sullivan, G; Svoboda, R; Szelc, A M; Tayloe, R; Thomson, M A; Toups, M; Vacheret, A; Vagins, M; Van de Water, R G; Vogelaar, R B; Weber, M; Weng, W; Wetstein, M; White, C; White, B R; Whitehead, L; Whittington, D W; Wilking, M J; Wilson, R J; Wilson, P; Winklehner, D; Winn, D R; Worcester, E; Yang, L; Yeh, M; Yokley, Z W; Yoo, J; Yu, B; Yu, J; Zhang, C

    2015-01-01

    The US neutrino community gathered at the Workshop on the Intermediate Neutrino Program (WINP) at Brookhaven National Laboratory February 4-6, 2015 to explore opportunities in neutrino physics over the next five to ten years. Scientists from particle, astroparticle and nuclear physics participated in the workshop. The workshop examined promising opportunities for neutrino physics in the intermediate term, including possible new small to mid-scale experiments, US contributions to large experiments, upgrades to existing experiments, R&D plans and theory. The workshop was organized into two sets of parallel working group sessions, divided by physics topics and technology. Physics working groups covered topics on Sterile Neutrinos, Neutrino Mixing, Neutrino Interactions, Neutrino Properties and Astrophysical Neutrinos. Technology sessions were organized into Theory, Short-Baseline Accelerator Neutrinos, Reactor Neutrinos, Detector R&D and Source, Cyclotron and Meson Decay at Rest sessions.This report summ...

  4. Intermediate energy data

    International Nuclear Information System (INIS)

    Subgroup 13 (SG13) on Intermediate Energy Nuclear data was formed by NEA Nuclear Science Committee to solve common problems of these types of data for nuclear applications. An overview is presented in this final report of the present activities of SG13, including data needs, high-priority nuclear data request list (nuclides), compilation of experimental data, specialists meetings and benchmarks, data formats and data libraries. Some important accomplishments are summarized, and recommendations are presented. (R.P.)

  5. Volatility and Financial Intermediation

    OpenAIRE

    Joshua Aizenman; Andrew Powell

    1997-01-01

    Following the Tequila period, its after-effects in Latin America and recent events in South East Asia, the effect of volatility on emerging market economies has become an important topic of research with the domestic financial intermediation process being advanced as one of the most important transmission mechanisms. At the same time there has been continued interest in issues related to imperfect information and rationing in credit markets. In this paper, we consider an economy where risk ne...

  6. Stimulation of cation transport in mitochondria by gramicidin and truncated derivatives

    International Nuclear Information System (INIS)

    Gramicidin and the truncated derivatives desformylgramicidin (desfor) and des(formylvalyl)gramicidin (desval) stimulate monovalent cation transport in rat liver mitochondria. Cation fluxes were compared indirectly from the effect of cations on the membrane potential at steady state (state 4) or from the associated stimulation of electron transport. Rb+ transport was measured directly from the uptake of 86Rb. The truncated gramicidins show enhanced selectivity for K+ and Rb+ when compared to gramicidin. Moreover, the pattern of selectivity within the alkali cation series is altered. The cation fluxes through the truncated derivatives are more strongly dependent on the cation concentration. The presence of high concentrations of permeating cation enhances the transport of other cations through the truncated derivative channels, suggesting that cations are required for stabilizing the channel structure. In high concentrations of KCl, desfor and desval are nearly as effective as gramicidin in collapsing the mitochondrial membrane potential, and consequently, in the uncoupling of oxidative phosphorylation and enhancement of ATP hydrolysis. Preliminary experiments with liposomes show that 86Rb exchange is stimulated by desfor and desval almost to the same extend at gramicidin. These results strongly suggest that the truncated gramicidins form a novel conducting channel which differs from the gramicidin head-to-head, single-stranded β6.3-helical dimer (channel) in its conductance characteristic and its structure. On the basis of the secondary structure of the truncated derivatives, the authors suggest that the antiparallel double-stranded helix dimer (pore) is a likely alternative structure for this novel channel

  7. Research progress in cation-π interactions

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Cation-π interaction is a potent intermolecular interaction between a cation and an aromatic system,which has been viewed as a new kind of binding force,as being compared with the classical interactions(e.g. hydrogen bonding,electrostatic and hydrophobic interactions). Cation-π interactions have been observed in a wide range of biological contexts. In this paper,we present an overview of the typical cation-π interactions in biological systems,the experimental and theoretical investigations on cation-π interactions,as well as the research results on cation-π interactions in our group.

  8. Liquid-solid extraction of metallic cations by cationic amphiphiles

    International Nuclear Information System (INIS)

    In the field of selective metal ion separation, liquid-liquid extraction is usually conducted through an emulsion mixing of hydrophobic complexants dispersed in an organic phase and acidic water containing the ionic species. Recently, it has been shown that amphiphilic complexants could influence strongly extraction efficiency by enhancing the interfacial interaction between the metal ion in the aqueous and the complexant in the organic phase. Moreover, these amphiphiles can also substitute the organic phase if an appropriate aliphatic chain is chosen. The dispersion of such amphiphilic complexants in an aqueous solution of salt mixtures is not only attractive for studying specific interactions but also to better the understanding of complex formation in aqueous solution of multivalent metal ions, such as lanthanides and actinides. This understanding is of potential interest for a broad range of industries including purification of rare earth metals and pollute treatment e.g. of fission byproducts. This principle can also be applied to liquid-solid extraction, where the final state of the separation is a solid phase containing the selectively extracted ions. Indeed, a novel solid-liquid extraction method exploits the selective precipitation of metal ions from an aqueous salt mixture using a cationic surfactant, below its Krafft point (temperature below which the long aliphatic chains of surfactant crystallize). This technique has been proven to be highly efficient for the separation of actinides and heavy metal using long chain ammonium or pyridinium amphiphiles. The most important point in this process is the recognition of cationic metal ions by cationic surfactants. By computing the free energy of the polar head group per micelle as a function of the different counter-anions, we have demonstrated for the first time that different interactions exist between the micellar surface and the ions. These interactions depend on the nature of the cation but also on

  9. Carbocation Stability in H-ZSM5 at High Temperature

    Energy Technology Data Exchange (ETDEWEB)

    Ferguson, Glen A. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Cheng, Lei [Argonne National Lab. (ANL), Argonne, IL (United States); Bu, Lintao [National Renewable Energy Lab. (NREL), Golden, CO (United States); Kim, Seonah [National Renewable Energy Lab. (NREL), Golden, CO (United States); Robichaud, David J. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Nimlos, Mark R. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Curtiss, Larry A. [Argonne National Lab. (ANL), Argonne, IL (United States); Beckham, Gregg T. [National Renewable Energy Lab. (NREL), Golden, CO (United States)

    2015-10-26

    Zeolites are common catalysts for multiple industrial applications, including alcohol dehydration to produce olefins, and given their commercial importance, reaction mechanisms in zeolites have long been proposed and studied. Some proposed reaction mechanisms for alcohol dehydration exhibit noncyclic carbocation intermediates or transition states that resemble carbocations, and several previous studies suggest that the tert-butyl cation is the only noncyclic cation more stable than the corresponding chemisorbed species with the hydrocarbon bound to the framework oxygen (i.e., an alkoxide). To determine if carbocations can exist at high temperatures in zeolites, where these catalysts are finding new applications for biomass vapor-phase upgrading (~500 °C), the stability of carbocations and the corresponding alkoxides were calculated with two ONIOM embedding methods (M06-2X/6-311G(d,p):M06-2X/3-21G) and (PBE-D3/6-311G(d,p):PBE-D3/3-21G) and plane-wave density functional theory (DFT) using the PBE functional corrected with entropic and Tkatchenko–Scheffler van der Waals corrections. Additionally, the embedding methods tested are unreliable at finding minima for primary carbocations, and only secondary or higher carbocations can be described with embedding methods consistent with the periodic DFT results. The relative energy between the carbocations and alkoxides differs significantly between the embedding and the periodic DFT methods. The difference is between ~0.23 and 14.30 kcal/mol depending on the molecule, the model, and the functional chosen for the embedding method. At high temperatures, the pw-DFT calculations predict that the allyl, isopropyl, and sec-butyl cations exhibit negligible populations while acetyl and tert-butyl cations exhibit significant populations (>10%). Furthermore, the periodic DFT results indicate that mechanisms including secondary and tertiary carbocations intermediates or carbocations stabilized by adjacent oxygen or double bonds are

  10. Radiolytically generated cation radicals and their intramolecular transformations

    International Nuclear Information System (INIS)

    Recent theoretical and experimental results indicate that conventional cation radicals derived directly from their neutral precursors are often less stable than their nonconventional isomers with no stable counterparts. Many organic cation radicals may spontaneously isomerise, often by a single intramolecular hydrogen transfer, to more stable distonic forms characterised by spatially separated charge and radical side. Cation radicals radiolytically generated in Freon matrices were investigated using low temperature EPR spectroscopy and DFT quantum chemical calculations, which helped to assign the observed transients and to explain the underlying transformations. Different types of transformations of the cation radicals were comprehensively studied. The primary cation radicals of the 2,5-dihydrofuran (2,5-DHF) and 2,5-dihydropyrrol (2,5-DHP) are not stable and undergo irreversible transformation to 2,4-DHF.+ or 2,4-DHP.+, respectively, by intramolecular H-shift within the molecular ring to the former double bond. The 2,4-DHF.+ and 2,4-DHP.+ are stable only at a small temperature range and undergo further intramolecular rearrangements through 2→3 and 3→4 H-shifts, which can be induced by illumination with visible light. In case of lactone cation radicals intramolecular H-transfer occurs from the methylene group in α-position to the primary radical centre localized on carbonyl oxygen. The stability of the primary species depends on geometrical parameters of the lactones studied. The cation radicals of 5-membered ring lactones are most stable, due to the largest separation between the H-atom on the ring and the carbonyl oxygen and, as follows, the largest activation energy. The formation of two new cyclic species was observed in the case of the cation radical of ethyl acrylate (EA), in a reaction sequence of hydrogen transfer from the ester group to the carbonyl oxygen and subsequent intramolecular cycloaddition of the terminal radical to the vinyl double bond

  11. Mechanistic views on aromatic substitution reactions by gaseous cations.

    Science.gov (United States)

    Fornarini, S

    1996-01-01

    Recent advances in the understanding of the gas-phase reaction of aromatics with cationic electrophiles in a thermally equilibrated domain are described. The overall substitution reaction is analyzed in terms of its elementary steps. Their contribution to the overall reactivity pattern is dissected by the use of selected systems, which allowed one to highlight the kinetic role of single elementary events. Mechanistic studies have focused on the structure and reactivity of covalent and non-covalent ionic intermediates, which display a rich chemistry and provide benchmark reactivity models. Particular interest has been devoted to proton transfer reactions, which may occur in either an intra- or intermolecular fashion in arenium intermediates. A quantitative study of their rates and associated kinetic isotope effects is reported. © 1997 John Wiley & Sons, Inc. Mass Spectrom Rev 15(6), 365-389, 1997. PMID:27082944

  12. Blackbody-induced radiative dissociation of cationic SF 6 clusters

    DEFF Research Database (Denmark)

    Toker, Jonathan; Rahinov, I.; Schwalm, D.;

    2012-01-01

    The stability of cationic SF5+(SF6)n−1 clusters was investigated by measuring their blackbody-induced radiative dissociation (BIRD) rates. The clusters were produced in a supersonic expansion ion source and stored in an electrostatic ion-beam trap at room temperature, where their abundances and...... lifetimes were measured. Using the “master equation” approach, relative binding energies of an SF6 unit in the clusters could be extracted from the storage-time dependence of the survival probabilities. The results allow for a deeper insight into the effect of a localized charge on the structure and...... stability of SF6-based clusters....

  13. Stabilization of reactive species by supramolecular encapsulation.

    Science.gov (United States)

    Galan, Albano; Ballester, Pablo

    2016-03-14

    Molecular containers have attracted the interest of supramolecular chemists since the early beginnings of the field. Cavitands' inner cavities were quickly exploited by Cram and Warmuth to construct covalent containers able to stabilize and assist the characterization of short-lived reactive species such as cyclobutadiene or o-benzyne. Since then, more complex molecular architectures have been prepared able to store and isolate a myriad of fleeting species (i.e. organometallic compounds, cationic species, radical initiators…). In this review we cover selected examples of the stabilization of reactive species by encapsulation in molecular containers from the first reports of covalent containers described by Cram et al. to the most recent examples of containers with self-assembled structure (metal coordination cages and hydrogen bonded capsules). Finally, we briefly review examples reported by Rebek et al. in which elusive reaction intermediates could be detected in the inner cavities of self-folding resorcin[4]arene cavitands by the formation of covalent host-guest complexes. The utilization of encapsulated reactive species in catalysis or synthesis is not covered. PMID:26797259

  14. Effects of intermediate load on performance limitations in excitation control

    OpenAIRE

    Pichai Aree

    2008-01-01

    The stability of excitation control systems is of great concern in power system operations. In this paper, the effects of intermediate load on performance limitation in excitation control are studied. The results reveal that the open-loop characteristic of synchronous machines flux linkage can be changed from minimum to non-minimum phase at a high level of intermediate load. This change leads to instability of synchronous machines under manual excitation control. A particular emphasis is also...

  15. Supramolecular stabilization of N(2)H(7)(+).

    Science.gov (United States)

    Atwood, Jerry L; Barbour, Leonard J; Jerga, Agoston

    2002-03-13

    The cation N(2)H(7)(+) has been stabilized in a largely hydrophobic supramolecular environment and characterized in the solid state. The cation is situated in the bowl-shaped cavity of calix[4]arene. All of the hydrogen atoms are clearly discernible owing to high-quality X-ray data as well as lack of disorder and symmetry-imposed ambiguity. It appears that electrostatic interactions play a critical role in stabilizing the structure. PMID:11878959

  16. Polyelectrolyte Condensation Induced by Linear Cations

    OpenAIRE

    Guáqueta, Camilo; Luijten, Erik

    2007-01-01

    We examine the role of the condensing agent in the formation of polyelectrolyte bundles, via grand-canonical Monte Carlo simulations. Following recent experiments we use linear, rigid divalent cations of various lengths to induce condensation. Our results clarify and explain the experimental results for short cations. For longer cations we observe novel condensation behavior owing to alignment of the cations. We also study the role of the polyelectrolyte surface charge density, and find a non...

  17. Cationic electrodepositable coating composition comprising lignin

    Science.gov (United States)

    Fenn, David; Bowman, Mark P; Zawacky, Steven R; Van Buskirk, Ellor J; Kamarchik, Peter

    2013-07-30

    A cationic electrodepositable coating composition is disclosed. The present invention in directed to a cationic electrodepositable coating composition comprising a lignin-containing cationic salt resin, that comprises (A) the reaction product of: lignin, an amine, and a carbonyl compound; (B) the reaction product of lignin, epichlorohydrin, and an amine; or (C) combinations thereof.

  18. Organometallic cation-exchanged phyllosilicates

    OpenAIRE

    Fleming, Shay

    1991-01-01

    Organotin (IV) complexes formed between 0 01 M dimethyltin dichloride solutions prepared at pH 2 6 and 4 0, and trimethyltin chloride prepared at pH 3 4, with Na- 119 montmori 1lonite clay have been characterised using Sn Mflssbauer spectroscopy, X-ray diffraction, thermogravimetric analysis and water sorption isotherms Following cation exchange, Mttssbauer spectroscopy identified two tin species in the dimethyltin (IV)-exchanged clay prepared at pH 2 6 A cis specie...

  19. Calorimetric study of cationic photopolymerization

    International Nuclear Information System (INIS)

    The photopolymerization of penta-erythritol tetra-glycidyl ether (initiator Degacure KI-85) was studied by a du Pont 910 type DSC. From our experimental results the following conclusions can be drawn: (1) During the cationic polymerization reaction the lifetime of the initiating centers are long compared to the lifetime of free radicals in case of radical polymerization. (2) The rate of deactivation of the initiating centers increases with increasing temperature. (author)

  20. Radical cations of some water-soluble organoselenium compounds: Insights from pulse radiolysis studies

    Energy Technology Data Exchange (ETDEWEB)

    Priyadarsini, K. Indira [Radiation and Photochemistry Division, Bhabha Atomic Research Center, Trombay, Mumbai 400085 (India)], E-mail: kindira@barc.gov.in; Mishra, B. [Radiation and Photochemistry Division, Bhabha Atomic Research Center, Trombay, Mumbai 400085 (India)

    2008-10-15

    Radical cations of three water-soluble organoselenium compounds, viz., selenourea, selenomethionine, and selenocystine, were produced and their reactions in the pH range 1-7 were studied using nanosecond pulse radiolysis technique. The radical cations, centered on the selenium atom, were generated by one-electron oxidation using hydroxyl ({sup {center_dot}}OH) radicals and Cl{sub 2}{sup {center_dot}}{sup -} and Br{sub 2}{sup {center_dot}}{sup -} radicals. The radical cations of selenourea were converted to dimer radical cations in the entire pH range, which in presence of oxygen released elemental selenium as one of the products. The monomer radical cations of selenomethionine are stabilized at neutral pH by the lone pair of electrons on the N atom of the amino group and undergo partial decarboxylation to produce {alpha}-amino selenyl radicals, which are reducing in nature. At highly acidic conditions, when the lone pair is not available due to protonation, they were converted to dimer radical cations. Selenocystine, being a diselenide, produced monomer radical cations on one-electron oxidation in the entire pH range and acquires stability by sharing the electrons between the two adjacent selenium atoms.

  1. NMR investigation of cation distribution in HLW wasteform glass

    International Nuclear Information System (INIS)

    Magic-angle-spinning NMR has been used to establish the structural roles of various cations added to the borosilicate glass which is used for the vitrification of high-level nuclear waste (HLW). Representative surrogate oxides with nominal valencies of +1, +2 and +3 have been studied which span the range of oxides from modifier to intermediate and conditional glass former. NMR has been carried out on those nuclei which are accessible and the species observed have been correlated with the physical and chemical behaviour. The controlling factor is the manner in which the alkali cations partition between the various network groups, changing the distribution of silicon Qn species and the boron N4 ratio. Identifiable super-structural units are also present in these glasses. The aqueous corrosion rate increases with Q3 content, as does the weight loss due to evaporation from the melt. The activation energy for DC conduction scales with N4. Values of N4 obtained for these glasses deviate significantly from those predicted by the currently accepted model (Dell and Bray) and are strongly affected by the modifier or intermediate nature of the surrogate oxide and also by its effect on the distribution of non bridging oxygens between the silicate and borate polyhedra. (authors)

  2. Cationic Tungsten(VI) Penta-Methyl Complex: Synthesis, Characterization and its Application in Olefin Metathesis Reaction

    KAUST Repository

    Dey, Raju

    2016-04-13

    Tungsten-hexa-methyl readily reacts with B(C6F5)3 in dichloromethane and generates the corresponding well-defined cationic tungsten-penta-methyl complex which was identified precisely by 1H NMR, 13C NMR, 1H-13C NMR correlation spectroscopy. Unlike WMe6, this cationic complex has low energy barrier to form tungsten carbene intermediate, which was further supported by the fact that WMe6 alone has no activity in olefin metathesis reaction whereas the cationic complex shows catalytic activity for self-metathesis of 1-octene.

  3. Stability of antibiotics bound to polytetrafluoroethylene with cationic surfactants.

    OpenAIRE

    Donetz, A P; Harvey, R. A.; Greco, R S

    1984-01-01

    This study evaluated the effect of prolonged storage and sterilization on the noncovalent bonding of penicillin to polytetrafluoroethylene grafts. The surfactant tridodecylmethylammonium chloride was unaffected by prolonged storage or sterilization, and its ability to bind penicillin remained constant for as long as 3 months. Steam or ethylene oxide sterilization markedly diminished the antibacterial activity of bound penicillin. However, the antibacterial properties of penicillin remained co...

  4. Ozonation of Cationic Red X-GRL in aqueous solution: degradation and mechanism.

    Science.gov (United States)

    Zhao, Weirong; Shi, Huixiang; Wang, Dahui

    2004-12-01

    Ozonation of the azo dye Cationic Red X-GRL was investigated in a bubble column reactor at varying operating parameters such as oxygen flow rate, temperature, initial Cationic Red X-GRL concentration, and pH. The conversion of dye increased with the increasing of pH and oxygen flow rate. As the reaction rate constant and the volumetric mass transfer coefficient increase while the ozone equilibrium concentration decreases with the temperature, there is a minimum conversion of dye at 25 degrees C. The increasing of initial dye concentration leads to a decreasing conversion of dye while the ozonation rate increases. The formation of intermediates and the variation of pH, TOC, and nitrate ion during ozonation were investigated by the use of some analytical instruments such as GC/MS, GC, and IC. The intermediates of weak organic acids lower the pH value of the solution. The probable degradation mechanism of the Cationic Red X-GRL in aqueous solution was deliberated with the aid of Molecular Orbital calculations. The N(12)-C(13) site in Cationic Red X-GRL, instead of the N(6)-N(7) site, is found to be the principal site for ozone cycloaddition in the degradation processes. During the degradation process, among the six nitrogen atoms of Cationic Red X-GRL, one is transferred into a nitrate ion, one is converted into an amine compound, and the remaining four are transformed into two molecules of nitrogen. PMID:15504479

  5. A rapid method for decontamination of low and intermediate level liquid radioactive wastes by amalgamation

    International Nuclear Information System (INIS)

    The objective of this study is to develop an integrated workstation for rapid decontamination of low and intermediate level liquid radioactive wastes. The workstation comprises of an electrochemical amalgamator that allows the reduction of different radionuclides cations in the waste and eventually from amalgamate. The de-amalgamation results in purification of mercury and leftover a radioactive waste behind as secondary waste. (author)

  6. Solidification cracking in austenitic stainless steel welds

    Indian Academy of Sciences (India)

    V Shankar; T P S Gill; S L Mannan; S Sundaresan

    2003-06-01

    Solidification cracking is a significant problem during the welding of austenitic stainless steels, particularly in fully austenitic and stabilized compositions. Hot cracking in stainless steel welds is caused by low-melting eutectics containing impurities such as S, P and alloy elements such as Ti, Nb. The WRC-92 diagram can be used as a general guide to maintain a desirable solidification mode during welding. Nitrogen has complex effects on weld-metal microstructure and cracking. In stabilized stainless steels, Ti and Nb react with S, N and C to form low-melting eutectics. Nitrogen picked up during welding significantly enhances cracking, which is reduced by minimizing the ratio of Ti or Nb to that of C and N present. The metallurgical propensity to solidification cracking is determined by elemental segregation, which manifests itself as a brittleness temperature range or BTR, that can be determined using the varestraint test. Total crack length (TCL), used extensively in hot cracking assessment, exhibits greater variability due to extraneous factors as compared to BTR. In austenitic stainless steels, segregation plays an overwhelming role in determining cracking susceptibility.

  7. Financial Intermediation and Economic Growth

    OpenAIRE

    Dima, Bogdan; Petru-Eugen OPRIȘ

    2013-01-01

    The paper evaluates the relationship between financial intermediation and the economic growth in the developing economic systems. First, using dataset from 28 countries,between 2001 and 2010 we define a financial intermediation indicator applying EFA method. We use several dimensions of the financial intermediation: Domestic credit provided by banking sector (% of GDP); Domestic credit to private sector (% of GDP); Broad money (% of GDP); Market capitalization of listed companies (% of GDP). ...

  8. Financial Intermediation and Macroeconomic Analysis

    OpenAIRE

    Michael Woodford

    2010-01-01

    Understanding phenomena such as the recent financial crisis, and possible policy responses, requires the use of a macroeconomic framework in which financial intermediation matters for the allocation of resources. Neither standard macroeconomic models that abstract from financial intermediation nor traditional models of the "bank lending channel" are adequate as a basis for understanding the recent crisis. Instead we need models in which intermediation plays a crucial role, but in which interm...

  9. Cation coordination in oxychloride glasses

    Science.gov (United States)

    Johnson, J. A.; Holland, D.; Bland, J.; Johnson, C. E.; Thomas, M. F.

    2003-02-01

    Glasses containing mixtures of cations and anions of nominal compositions [Sb2O3]x - [ZnCl2]1-x where x = 0.25, 0.50, 0.75, and 1.00, have been studied by means of neutron diffraction and Raman and Mössbauer spectroscopy. There is preferential bonding within the system with the absence of Sb-Cl bonds. Antimony is found to be threefold coordinated to oxygen, and zinc fourfold coordinated. The main contributing species are of the form [Sb(OSb)2(OZn)] and [Zn(ClZn)2(OSb)2].

  10. Cation coordination in oxychloride glasses

    International Nuclear Information System (INIS)

    Glasses containing mixtures of cations and anions of nominal compositions [Sb2O3]x - [ZnCl2]1-x where x = 0.25, 0.50, 0.75, and 1.00, have been studied by means of neutron diffraction and Raman and Moessbauer spectroscopy. There is preferential bonding within the system with the absence of Sb-Cl bonds. Antimony is found to be threefold coordinated to oxygen, and zinc fourfold coordinated. The main contributing species are of the form [Sb(OSb)2(OZn)] and [Zn(ClZn)2(OSb)2

  11. Cation coordination in oxychloride glasses

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, J A [Energy Technology Division, Argonne National Laboratory, Argonne, IL (United States); Holland, D [Physics Department, Warwick University, Coventry (United Kingdom); Bland, J [Physics Department, University of Liverpool, PO Box 147, Liverpool (United Kingdom); Johnson, C E [Physics Department, Northern Illinois University, DeKalb, IL (United States); Thomas, M F [Physics Department, University of Liverpool, PO Box 147, Liverpool (United Kingdom)

    2003-02-19

    Glasses containing mixtures of cations and anions of nominal compositions [Sb{sub 2}O{sub 3}]{sub x} - [ZnCl{sub 2}]{sub 1-x} where x = 0.25, 0.50, 0.75, and 1.00, have been studied by means of neutron diffraction and Raman and Moessbauer spectroscopy. There is preferential bonding within the system with the absence of Sb-Cl bonds. Antimony is found to be threefold coordinated to oxygen, and zinc fourfold coordinated. The main contributing species are of the form [Sb(OSb){sub 2}(OZn)] and [Zn(ClZn){sub 2}(OSb){sub 2}].

  12. Use of laser induced photoacoustic spectroscopy (LIPAS) to determine equilibrium constants of cation-cation complexes

    International Nuclear Information System (INIS)

    Laser Induced PhotoAcoustic Spectroscopy (LIPAS) is a relatively new, photothermal technique to examine solutions. Studies in the past have shown it to be more sensitive than conventional absorption spectroscopy, while, yielding the same information thus allowing lower concentrations to be used. This study is using LIPAS to examine solutions to determine the equilibrium constants of cation-cation complexes. It has been found that actinyl(V) cations form cation-cation complexes with a variety of cations, including actinyl(VI) cations. The radioactive nature of the actinide elements requires special handling techniques and also require limits be placed on the amount of material that can be used. The sensitivity of some oxidation states of the actinides to oxygen also presents a problem. Preliminary results will be presented for actinyl(V)-actinyl(VI) cation-cation complexes that were studied using a remote LIPAS system incorporating fiber optics for transmission of laser signals

  13. Optimal Auditing Under Intermediated Contracting

    OpenAIRE

    Wolfgang Gick

    2004-01-01

    This paper builds on Faure-Grimaud and Martimort’s [Economics Letters 71 (2001) 75-82] analysis of intermediated contracting. I argue that intermediated contracting permits one form of auditing, in which the sub-contract offered to the firm is examined, contingent on the intermediary’s report. Auditing reduces the intermediary’s rent and increases allocative efficiency.

  14. Recent results on intermediate polars

    OpenAIRE

    Hellier, Coel

    1999-01-01

    I review recent activity in the field of intermediate polars, concentrating on: the mode of accretion (disc-fed, disc-overflow or discless); accretion curtains (the transition region and the accretion footprint); X-ray pulse profiles (occultation and absorption effects); accretion columns (mass determinations, line-broadening, the soft X-ray component), and outbursts in intermediate polars.

  15. Masonry. Performance Objectives. Intermediate Course.

    Science.gov (United States)

    Thompson, Moses

    Several intermediate performance objectives and corresponding criterion measures are listed for each of 13 terminal objectives for an intermediate masonry course. These materials, developed for a two-semester (3 hours daily) course, are designed to provide the student with the skills and knowledge necessary for entry level employment in the field…

  16. Welding. Performance Objectives. Intermediate Course.

    Science.gov (United States)

    Vincent, Kenneth

    Several intermediate performance objectives and corresponding criterion measures are listed for each of nine terminal objectives for an intermediate welding course. The materials were developed for a 36-week (3 hours daily) course designed to prepare the student for employment in the field of welding. Electric welding and specialized (TIG & MIG)…

  17. Intermediate neutron spectrum problems and the intermediate neutron spectrum experiment

    International Nuclear Information System (INIS)

    Criticality benchmark data for intermediate energy spectrum systems does not exist. These systems are dominated by scattering and fission events induced by neutrons with energies between 1 eV and 1 MeV. Nuclear data uncertainties have been reported for such systems which can not be resolved without benchmark critical experiments. Intermediate energy spectrum systems have been proposed for the geological disposition of surplus fissile materials. Without the proper benchmarking of the nuclear data in the intermediate energy spectrum, adequate criticality safety margins can not be guaranteed. The Zeus critical experiment now under construction will provide this necessary benchmark data

  18. Anti-inflammatory activity of cationic lipids

    OpenAIRE

    Filion, Mario C; Phillips, Nigel C

    1997-01-01

    The effect of liposome phospholipid composition has been assumed to be relatively unimportant because of the presumed inert nature of phospholipids.We have previously shown that cationic liposome formulations used for gene therapy inhibit, through their cationic component, the synthesis by activated macrophages of the pro-inflammatory mediators nitric oxide (NO) and tumour necrosis factor-α (TNF-α).In this study, we have evaluated the ability of different cationic lipids to reduce footpad inf...

  19. Anti-inflammatory activity of cationic lipids.

    Science.gov (United States)

    Filion, M C; Phillips, N C

    1997-10-01

    1. The effect of liposome phospholipid composition has been assumed to be relatively unimportant because of the presumed inert nature of phospholipids. 2. We have previously shown that cationic liposome formulations used for gene therapy inhibit, through their cationic component, the synthesis by activated macrophages of the pro-inflammatory mediators nitric oxide (NO) and tumour necrosis factor-alpha (TNF-alpha). 3. In this study, we have evaluated the ability of different cationic lipids to reduce footpad inflammation induced by carrageenan and by sheep red blood cell challenge. 4. Parenteral (i.p. or s.c) or local injection of the positively charged lipids dimethyldioctadecylammomium bromide (DDAB), dioleyoltrimethylammonium propane (DOTAP), dimyristoyltrimethylammonium propane (DMTAP) or dimethylaminoethanecarbamoyl cholesterol (DC-Chol) significantly reduced the inflammation observed in both models in a dose-dependent manner (maximum inhibition: 70-95%). 5. Cationic lipids associated with dioleyol- or dipalmitoyl-phosphatidylethanolamine retained their anti-inflammatory activity while cationic lipids associated with dipalmitoylphosphatidylcholine (DPPC) or dimyristoylphosphatidylglycerol (DMPG) showed no anti-inflammatory activity, indicating that the release of cationic lipids into the macrophage cytoplasm is a necessary step for anti-inflammatory activity. The anti-inflammatory activity of cationic lipids was abrogated by the addition of dipalmitoylphosphatidylethanolamine-poly(ethylene)glycol-2000 (DPPE-PEG2000) which blocks the interaction of cationic lipids with macrophages. 6. Because of the significant role of protein kinase C (PKC) in the inflammatory process we have determined whether the cationic lipids used in this study inhibit PKC activity. The cationic lipids significantly inhibited the activity of PKC but not the activity of a non-related protein kinase, PKA. The synthesis of interleukin-6 (IL-6), which is not dependent on PKC activity for its

  20. Cation Intercalation in Manganese Oxide Nanosheets: Effects on Lithium and Sodium Storage.

    Science.gov (United States)

    Lu, Ke; Hu, Ziyu; Xiang, Zhonghua; Ma, Jizhen; Song, Bin; Zhang, Jintao; Ma, Houyi

    2016-08-22

    The rapid development of advanced energy-storage devices requires significant improvements of the electrode performance and a detailed understanding of the fundamental energy-storage processes. In this work, the self-assembly of two-dimensional manganese oxide nanosheets with various metal cations is introduced as a general and effective method for the incorporation of different guest cations and the formation of sandwich structures with tunable interlayer distances, leading to the formation of 3D Mx MnO2 (M=Li, Na, K, Co, and Mg) cathodes. For sodium and lithium storage, these electrode materials exhibited different capacities and cycling stabilities. The efficiency of the storage process is influenced not only by the interlayer spacing but also by the interaction between the host cations and shutter ions, confirming the crucial role of the cations. These results provide promising ideas for the rational design of advanced electrodes for Li and Na storage. PMID:27458045

  1. Exchangeable cations-mediated photodegradation of polycyclic aromatic hydrocarbons (PAHs) on smectite surface under visible light

    International Nuclear Information System (INIS)

    Graphical abstract: Roles of exchangeable cations in PAHs photodegradation on clay surafces under visible light. - Highlights: • Photolysis rate are strongly dependent on the type of cations on clay surface. • The strength of “cation–π” interactions governs the photodegradation rate of PAHs. • Several exchangeable cations could cause a shift in the absorption spectrum of PAHs. • Exchangeable cations influence the type and amount of reactive intermediates. - Abstract: Clay minerals saturated with different exchangeable cations are expected to play various roles in photodegradation of polycyclic aromatic hydrocarbons (PAHs) via direct and/or indirect pathways on clay surfaces. In the present study, anthracene and phenanthrene were selected as molecule probes to investigate the roles of exchangeable cations on their photodegradation under visible light irradiation. For five types of cation-modified smectite clays, the photodegradation rate of anthracene and phenanthrene follows the order: Fe3+ > Al3+ > Cu2+ >> Ca2+ > K+ > Na+, which is consistent with the binding energy of cation–π interactions between PAHs and exchangeable cations. The result suggests that PAHs photolysis rate depends on cation–π interactions on clay surfaces. Meanwhile, the deposition of anthracene at the Na+-smectite and K+-smectite surface favors solar light absorption, resulting in enhanced direct photodecomposition of PAHs. On the other hand, smectite clays saturated with Fe3+, Al3+, and Cu2+ are highly photoreactive and can act as potential catalysts giving rise to oxidative radicals such as O2−· , which initiate the transformation of PAHs. The present work provides valuable insights into understanding the transformation and fate of PAHs in the natural soil environment and sheds light on the development of technologies for contaminated land remediation

  2. Exchangeable cations-mediated photodegradation of polycyclic aromatic hydrocarbons (PAHs) on smectite surface under visible light

    Energy Technology Data Exchange (ETDEWEB)

    Jia, Hanzhong, E-mail: jiahz@ms.xjb.ac.cn [Laboratory of Environmental Sciences and Technology, Xinjiang Technical Institute of Physics & Chemistry, Key Laboratory of Functional Materials and Devices for Special Environments, Chinese Academy of Sciences, Urumqi 830011 (China); Li, Li [Laboratory of Environmental Sciences and Technology, Xinjiang Technical Institute of Physics & Chemistry, Key Laboratory of Functional Materials and Devices for Special Environments, Chinese Academy of Sciences, Urumqi 830011 (China); Chen, Hongxia; Zhao, Yue [Laboratory of Environmental Sciences and Technology, Xinjiang Technical Institute of Physics & Chemistry, Key Laboratory of Functional Materials and Devices for Special Environments, Chinese Academy of Sciences, Urumqi 830011 (China); School of Geology and Mining Engineering, Xinjiang University, Urumqi 830046 (China); Li, Xiyou [Laboratory of Environmental Sciences and Technology, Xinjiang Technical Institute of Physics & Chemistry, Key Laboratory of Functional Materials and Devices for Special Environments, Chinese Academy of Sciences, Urumqi 830011 (China); Wang, Chuanyi, E-mail: cywang@ms.xjb.ac.cn [Laboratory of Environmental Sciences and Technology, Xinjiang Technical Institute of Physics & Chemistry, Key Laboratory of Functional Materials and Devices for Special Environments, Chinese Academy of Sciences, Urumqi 830011 (China)

    2015-04-28

    Graphical abstract: Roles of exchangeable cations in PAHs photodegradation on clay surafces under visible light. - Highlights: • Photolysis rate are strongly dependent on the type of cations on clay surface. • The strength of “cation–π” interactions governs the photodegradation rate of PAHs. • Several exchangeable cations could cause a shift in the absorption spectrum of PAHs. • Exchangeable cations influence the type and amount of reactive intermediates. - Abstract: Clay minerals saturated with different exchangeable cations are expected to play various roles in photodegradation of polycyclic aromatic hydrocarbons (PAHs) via direct and/or indirect pathways on clay surfaces. In the present study, anthracene and phenanthrene were selected as molecule probes to investigate the roles of exchangeable cations on their photodegradation under visible light irradiation. For five types of cation-modified smectite clays, the photodegradation rate of anthracene and phenanthrene follows the order: Fe{sup 3+} > Al{sup 3+} > Cu{sup 2+} >> Ca{sup 2+} > K{sup +} > Na{sup +}, which is consistent with the binding energy of cation–π interactions between PAHs and exchangeable cations. The result suggests that PAHs photolysis rate depends on cation–π interactions on clay surfaces. Meanwhile, the deposition of anthracene at the Na{sup +}-smectite and K{sup +}-smectite surface favors solar light absorption, resulting in enhanced direct photodecomposition of PAHs. On the other hand, smectite clays saturated with Fe{sup 3+}, Al{sup 3+}, and Cu{sup 2+} are highly photoreactive and can act as potential catalysts giving rise to oxidative radicals such as O{sub 2}{sup −}· , which initiate the transformation of PAHs. The present work provides valuable insights into understanding the transformation and fate of PAHs in the natural soil environment and sheds light on the development of technologies for contaminated land remediation.

  3. Direct observation of hexamethylbenzenium radical cations generated during zeolite methanol-to-olefin catalysis: an ESR study.

    Science.gov (United States)

    Kim, Sun Jung; Jang, Hoi-Gu; Lee, Jun Kyu; Min, Hyung-Ki; Hong, Suk Bong; Seo, Gon

    2011-09-01

    The generation of hexamethylbenzenium radical cations as the key reaction intermediate in chabazite-type molecular sieve acids (i.e., H-SAPO-34 and H-SSZ-13) during the methanol-to-olefin process has been directly evidenced by ESR spectroscopy. PMID:21766115

  4. Afrikaans Syllabification Patterns

    Directory of Open Access Journals (Sweden)

    Tilla Fick

    2010-01-01

    Full Text Available In contrast to English, automatic hyphenation by computer of Afrikaans words is a problem that still needs to be addressed, since errors are still often encountered in printed text. An initial step in this task is the ability to automatically syllabify words. Since new words are created continuously by joining words, it is necessary to develop an “intelligent” technique for syllabification. As a first phase of the research, we consider only the orthographic information of words, and disregard both syntactic and morphological information. This approach allows us to use machine-learning techniques such as artificial neural networks and decision trees that are known for their pattern recognition abilities. Both these techniques are trained with isolated patterns consisting of input patterns and corresponding outputs (or targets that indicate whether the input pattern should be split at a certain position, or not. In the process of compiling a list of syllabified words from which to generate training data for the  syllabification problem, irregular patterns were identified. The same letter patterns are split differently in different words and complete words that are spelled identically are split differently due to meaning. We also identified irregularities in and between  the different dictionaries that we used. We examined the influence range of letters that are involved in irregularities. For example, for their in agter-ente and vaste-rente we have to consider three letters to the left of r to be certain where the hyphen should be inserted. The influence range of the k in verstek-waarde and kleinste-kwadrate is four to the left and three to the right. In an analysis of letter patterns in Afrikaans words we found that the letter e has the highest frequency overall (16,2% of all letters in the word list. The frequency of words starting with s is the highest, while the frequency of words ending with e is the highest. It is important to

  5. On the Nature of the Intermediates and the Role of Chloride Ions in Pd-Catalyzed Allylic Alkylations: Added Insight from Density Functional Theory

    DEFF Research Database (Denmark)

    Fristrup, Peter; Ahlquist, Mårten Sten Gösta; Tanner, David Ackland;

    2008-01-01

    The reactivity of intermediates in palladium-catalyzed allylic alkylation was investigated using DFT (B3LYP) calculations including a PB-SCRF solvation model. In the presence of both phosphine and chloride ligands, the allyl intermediate is in equilibrium between a cationic eta(3)-allylPd complex...... with two phosphine ligands, the corresponding neutral complex with one phosphine and one chloride ligand, and a neutral eta(1)-allylPd complex with one chloride and two phosphine ligands. The eta(1)-complex is unreactive toward nucleophiles. The cationic eta(3)-complex is the intermediate most...

  6. Naphthoxy Bounded Ferrocenium Salts as Cationic Photoinitiators for Epoxy Photopolymerization

    Directory of Open Access Journals (Sweden)

    Zh. Q. Li

    2009-01-01

    Full Text Available To improve the absorption and the bulk of arene ligands, two naphthoxy bounded ferrocenium salts as new cationic photoinitiators, (η6-α-naphthoxybenzene (η5-cyclopentadienyl iron hexafluorophosphate (NOFC-1 and (η6-β-naphthoxybenzene (η5-cyclopentadienyl iron hexafluorophosphate (NOFC-2, were synthesized, characterized, and studied. NOFC-1 and NOFC-2 were prepared by the reaction of nucleophilic substitution (SNAr with naphthol and chlorobenzene-cyclopentadienyliron salt. Their activity as cationic photoinitiators was studied using real-time infrared spectroscopy. The results obtained showed that NOFC-1 and NOFC-2 are capable of photoinitiating the cationic polymerization of epoxy monomer directly on irradiation with long-wavelength UV light (365 nm. Comparative studies also demonstrated that they exhibited better efficiency than cyclopentadienyl-Fe-cymene hexafluorophosphate (I-261. When NOFC-1 and NOFC-2 were used to efficiently initiate polymerization of epoxide, both rate of polymerization and final conversion increased using benzoyl peroxide (BPO as sensitizer. DSC studies showed that NOFC-1 and NOFC-2 photoinitiators in epoxides possess good thermal stability in the absence of light.

  7. Tripodal Receptors for Cation and Anion Sensors

    Directory of Open Access Journals (Sweden)

    David N. Reinhoudt

    2006-08-01

    Full Text Available This review discusses different types of artificial tripodal receptors for the selectiverecognition and sensing of cations and anions. Examples on the relationship between structure andselectivity towards cations and anions are described. Furthermore, their applications as potentiometricion sensing are emphasised, along with their potential applications in optical sensors or optodes.

  8. Intermediation Costs and Financial Fragility

    OpenAIRE

    Kaplan, Cafer; Salman, Ferhan

    2007-01-01

    This paper studies implications of intermediation costs in credit markets. The presence of intermediation costs increases the amount of risky projects therefore results in financial fragility. Moreover, for an open economy that has a perfectly liberal capital account, prudent firms finance their projects from foreign markets therefore shrinking the domestic credit markets. The theoretical predictions of our model gains support by Turkish data for the 1991 – 2004 period. Data suggests that an ...

  9. Intermediate uveitis and Lyme borreliosis.

    OpenAIRE

    Breeveld, J; Rothova, A.; Kuiper, H

    1992-01-01

    A case of chronic intermediate uveitis and associated classic snowbanking (pars planitis) with severe cystoid macular oedema probably due to Lyme borreliosis is reported. Despite a disease duration of 10 years the patient's ocular symptoms and visual acuity responded promptly to intravenous ceftriaxone treatment. This case demonstrates that periodic reevaluation of patients with intermediate uveitis is necessary to obtain a specific diagnosis which may include Lyme borreliosis.

  10. Wealth, Financial Intermediation and Growth

    OpenAIRE

    Gaytan, Alejandro; Ranci??re, Romain

    2005-01-01

    This paper presents empirical support for the existence of wealth effects in the contribution of financial intermediation to economic growth, and offers a theoretical explanation for these effects. Using GMM dynamic panel data techniques applied to study the growth-promoting effects of financial intermediation, we show that the exogenous contribution of financial development on economic growth has different effects for different levels of income per capita. We find that this contribution is g...

  11. Intermediate Filing in Household Taxation

    OpenAIRE

    Smith, Henry Edward

    1998-01-01

    This article explores an alternative filing system between joint and individual filing, here termed "intermediate filing." Under such a system, instead of allowing couples to "split" their income as joint filers or forcing them to file as individuals, intermediate filing presents couples with a choice of individual filing as a default or fractional splitting. The ratio of the split would govern both tax treatment and property division (broadly defined) on divorce. The article shows that such ...

  12. Freeze-quenched iron-oxo intermediates in cytochromes P450

    International Nuclear Information System (INIS)

    Since the discovery of cytochromes P450 and their assignment to heme proteins a reactive iron-oxo intermediate as the hydroxylating species has been discussed. It is believed that the electronic structure of this intermediate corresponds to an iron(IV)-porphyrin-π-cation radical system (Compound I). To trap this intermediate the reaction of P450 with oxidants (shunt pathway) has been used. The common approaches are stopped-flow experiments with UV-visible spectroscopic detection or rapid-mixing/freeze-quench studies with EPR and Moessbauer spectroscopic characterization of the trapped intermediate. Surprisingly, the two approaches seem to give conflicting results. While the stopped-flow data indicate the formation of a porphyrin-π-cation radical, no such species is seen by EPR spectroscopy, although the Moessbauer data indicate iron(IV) for P450cam (CYP101) and P450BMP (CYP102). Instead, radicals on tyrosine and tryptophan residues are observed. These findings are reviewed and discussed with respect to intramolecular electron transfer from aromatic amino acids to a presumably transiently formed porphyrin-π-cation radical

  13. Complexation of the cesium cation with lithium ionophore VIII: extraction and DFT study

    Czech Academy of Sciences Publication Activity Database

    Makrlík, E.; Novák, Vít; Vaňura, P.; Bouř, Petr

    2013-01-01

    Roč. 298, č. 3 (2013), s. 2065-2068. ISSN 0236-5731 Institutional support: RVO:61388963 Keywords : cesium cation * lithium ionophore VIII * complexation * extraction and stability constants * water-nitrobenzene system * DFT calculations * structures Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 1.415, year: 2013

  14. Lithium ionophore VIII as an extraordinarily effective receptor for the strontium cation: Experimental and theoretical study

    Czech Academy of Sciences Publication Activity Database

    Makrlík, E.; Novák, Vít; Vaňura, P.; Bouř, Petr

    2014-01-01

    Roč. 1061, Mar 5 (2014), s. 110-113. ISSN 0022-2860 Institutional support: RVO:61388963 Keywords : strontium cation * lithium ionophore VIII * complexation * extraction and stability constants * DFT calculations * structures Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.602, year: 2014

  15. Generation of pyridyl coordinated organosilicon cation pool by oxidative Si-Si bond dissociation

    Directory of Open Access Journals (Sweden)

    Itami Kenichiro

    2007-02-01

    Full Text Available Abstract An organosilicon cation stabilized by intramolecular pyridyl coordination was effectively generated and accumulated by oxidative Si-Si bond dissociation of the corresponding disilane using low temperature electrolysis, and was characterized by NMR and CSI-MS.

  16. Natural zeolite reactivity towards ozone: The role of compensating cations

    International Nuclear Information System (INIS)

    Highlights: ► Chemical and thermal treatment enhances catalytic activity of natural zeolite. ► Modified natural zeolite exhibits high stability after thermal treatment. ► Reducing the compensating cation content leads to an increase on ozone abatement. ► Surface active atomic oxygen was detected using the DRIFT technique. ► The highest reactivity toward ozone was performed by NH4Z3 zeolite sample. - Abstract: Among indoor pollutants, ozone is recognised to pose a threat to human health. Recently, low cost natural zeolites have been applied as alternative materials for ozone abatement. In this work, the effect of compensating cation content of natural zeolite on ozone removal is studied. A Chilean natural zeolite is used here as starting material. The amount of compensating cations in the zeolite framework was modified by ion exchange using an ammonium sulphate solution (0.1 mol L−1). Characterisation of natural and modified zeolites were performed by X-ray powder diffraction (XRD), nitrogen adsorption at 77 K, elemental analysis, X-ray fluorescence (XRF), thermogravimetric analysis coupled with mass spectroscopy (TGA-MS), and temperature-programmed desorption of ammonia (NH3-TPD). Ozone adsorption and/or decomposition on natural and modified zeolites were studied by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Results show that the zeolite compensating cation content affects ozone interaction with zeolite active sites. Ammonium ion-exchange treatments followed by thermal out-gassing at 823 K, reduces ozone diffusion resistance inside the zeolite framework, increasing ozone abatement on zeolite surface active sites. Weak and strong Lewis acid sites of zeolite surface are identified here as the main active sites responsible of ozone removal.

  17. Natural zeolite reactivity towards ozone: The role of compensating cations

    Energy Technology Data Exchange (ETDEWEB)

    Valdes, Hector, E-mail: hvaldes@ucsc.cl [Laboratorio de Tecnologias Limpias (F. Ingenieria), Universidad Catolica de la Santisima Concepcion, Alonso de Ribera 2850, Concepcion (Chile); Alejandro, Serguei; Zaror, Claudio A. [Departamento de Ingenieria Quimica (F. Ingenieria), Universidad de Concepcion, Concepcion (Chile)

    2012-08-15

    Highlights: Black-Right-Pointing-Pointer Chemical and thermal treatment enhances catalytic activity of natural zeolite. Black-Right-Pointing-Pointer Modified natural zeolite exhibits high stability after thermal treatment. Black-Right-Pointing-Pointer Reducing the compensating cation content leads to an increase on ozone abatement. Black-Right-Pointing-Pointer Surface active atomic oxygen was detected using the DRIFT technique. Black-Right-Pointing-Pointer The highest reactivity toward ozone was performed by NH4Z3 zeolite sample. - Abstract: Among indoor pollutants, ozone is recognised to pose a threat to human health. Recently, low cost natural zeolites have been applied as alternative materials for ozone abatement. In this work, the effect of compensating cation content of natural zeolite on ozone removal is studied. A Chilean natural zeolite is used here as starting material. The amount of compensating cations in the zeolite framework was modified by ion exchange using an ammonium sulphate solution (0.1 mol L{sup -1}). Characterisation of natural and modified zeolites were performed by X-ray powder diffraction (XRD), nitrogen adsorption at 77 K, elemental analysis, X-ray fluorescence (XRF), thermogravimetric analysis coupled with mass spectroscopy (TGA-MS), and temperature-programmed desorption of ammonia (NH{sub 3}-TPD). Ozone adsorption and/or decomposition on natural and modified zeolites were studied by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Results show that the zeolite compensating cation content affects ozone interaction with zeolite active sites. Ammonium ion-exchange treatments followed by thermal out-gassing at 823 K, reduces ozone diffusion resistance inside the zeolite framework, increasing ozone abatement on zeolite surface active sites. Weak and strong Lewis acid sites of zeolite surface are identified here as the main active sites responsible of ozone removal.

  18. Intermediate ions in the atmosphere

    Science.gov (United States)

    Tammet, Hannes; Komsaare, Kaupo; Hõrrak, Urmas

    2014-01-01

    Intermediate air ions are charged nanometer-sized aerosol particles with an electric mobility of about 0.03-0.5 cm2 V- 1 s- 1 and a diameter of about 1.5-7.5 nm. Intensive studies of new particle formation provided good knowledge about intermediate ions during burst events of atmospheric aerosol nucleation. Information about intermediate ions during quiet periods between the bursts remained poor. The new mobility analyzer SIGMA can detect air ions at concentrations of mobility fractions of about 1 cm- 3 and enables studying intermediate ions during quiet periods. It became evident that intermediate ions always exist in atmospheric air and should be considered an indicator and a mediator of aerosol nucleation. The annual average concentration of intermediate ions of one polarity in Tartu, Estonia, was about 40 cm- 3 while 5% of the measurements showed a concentration of less than 10 cm- 3. The fraction concentrations in logarithmic 1/8-decade mobility bins between 0.1 and 0.4 cm2 V- 1 s- 1 often dropped below 1 cm- 3. The bursts of intermediate ions at stations separated by around 100 km appeared to be correlated. The lifespan of intermediate ions in the atmosphere is a few minutes, and they cannot be carried by wind over long distances. Thus the observed long-range correlation of intermediate ions is explained by simultaneous changes in air composition in widely spaced stations. A certain amount of intermediate ion bursts, predominantly of negative polarity, are produced by the balloelectric effect at the splashing of water drops during rain. These bursts are usually excluded when speaking about new particle formation because the balloelectric particles are assumed not to grow to the size of the Aitken mode. The mobility distribution of balloelectric ions is uniform in shape in all measurements. The maximum is located at a mobility of about 0.2 cm2 V- 1 s- 1, which corresponds to the diameter of particles of about 2.5 nm.

  19. The lightest organic radical cation for charge storage in redox flow batteries

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Jinhua; Pan, Baofei; Duan, Wentao; Wei, Xiaoliang; Assary, Rajeev S.; Su, Liang; Brushett, Fikile; Cheng, Lei; Liao, Chen; Ferrandon, Magali S.; Wang, Wei; Zhang, Zhengcheng; Burrell, Anthony K.; Curtiss, Larry A.; Shkrob, Ilya A.; Moore, Jeffrey S.; Zhang, Lu

    2016-08-25

    Electrochemically reversible fluids of high energy density are promising materials for capturing the electrical energy generated from intermittent sources like solar and wind. To meet this technological challenge there is a need to understand the fundamental limits and interplay of electrochemical potential, stability and solubility in “lean” derivatives of redox-active molecules. Here we describe the process of molecular pruning, illustrated for 2,5-di-tert-butyl-1,4-bis(2-methoxyethoxy)benzene, a molecule known to produce a persistently stable, high-potential radical cation. By systematically shedding molecular fragments considered important for radical cation steric stabilization, we discovered a minimalistic structure that retains long-term stability in its oxidized form. Interestingly, we find the tert-butyl groups are unnecessary; high stability of the radical cation and high solubility are both realized in derivatives having appropriately positioned arene methyl groups. These stability trends are rationalized by mechanistic considerations of the postulated decomposition pathways. We suggest that the molecular pruning approach will uncover lean redox active derivatives for electrochemical energy storage leading to materials with long-term stability and high intrinsic capacity.

  20. Porphyrin Analogues of a Trityl Cation and Anion.

    Science.gov (United States)

    Kato, Kenichi; Kim, Woojae; Kim, Dongho; Yorimitsu, Hideki; Osuka, Atsuhiro

    2016-05-17

    Porphyrin-stabilized meso- or β-carbocations were generated upon treatment of the corresponding bis(4-tert-butylphenyl)porphyrinylcarbinols with trifluoroacetic acid (TFA). Bis(4-tert-butylphenyl)porphyrinylcarbinols were treated with TFA to generate the corresponding carbocations stabilized by a meso- or β-porphyrinyl group. The meso-porphyrinylmethyl carbocation displayed more effective charge delocalization with decreasing aromaticity compared with the β-porphyrinylmethyl carbocation. A propeller-like porphyrin trimer, tris(β-porphyrinyl)carbinol, was also synthesized and converted to the corresponding cation that displayed a more intensified absorption reaching over the NIR region. meso-Porphyrinylmethyl carbanion was generated as a stable species upon deprotonation of bis(4-tert-butylphenyl)(meso-porphyrinyl)methane with potassium bis(trimethylsilyl)amide (KHMDS) and [18]crown-6, whereas β-porphyrinylmethyl anions were highly unstable. PMID:26991021

  1. Preparation of cationic polyacrylamide by aqueous two-phase polymerization

    Directory of Open Access Journals (Sweden)

    2010-05-01

    Full Text Available Cationic polyacrylamide (CPAM was synthesized by aqueous two-phase polymerization technique using acrylamide (AM and dimethylaminoethyl methacrylate methyl chloride (DMC as raw materials, aqueous polyethylene glycol 20000 (PEG 20000 solution as dispersant, 2,2′-azobis(2-amidinopropane dihydrochloride (V-50 as initiator and poly(dimethylaminoethyl methacrylate methyl chloride (PDMC as stabilizer. The polymer was characterized by infrared (IR spectroscopy, 1H-NMR spectrum and transmission electron microscopy (TEM. The copolymer composition was analyzed. The effect of monomers concentration, PEG 20000 concentration and stabilizer concentration on copolymer were investigated, respectively. The optimum reaction conditions for obtaining a stable CPAM aqueous two-phase system were monomers concentration 8~15%, PEG 20000 concentration 15~25%, and PDMC concentration 0.5~1.5%. Finally, the formation process of copolymer particles was investigated by optical microscope.

  2. Cationic Bolaamphiphiles for Gene Delivery

    Science.gov (United States)

    Tan, Amelia Li Min; Lim, Alisa Xue Ling; Zhu, Yiting; Yang, Yi Yan; Khan, Majad

    2014-05-01

    Advances in medical research have shed light on the genetic cause of many human diseases. Gene therapy is a promising approach which can be used to deliver therapeutic genes to treat genetic diseases at its most fundamental level. In general, nonviral vectors are preferred due to reduced risk of immune response, but they are also commonly associated with low transfection efficiency and high cytotoxicity. In contrast to viral vectors, nonviral vectors do not have a natural mechanism to overcome extra- and intracellular barriers when delivering the therapeutic gene into cell. Hence, its design has been increasingly complex to meet challenges faced in targeting of, penetration of and expression in a specific host cell in achieving more satisfactory transfection efficiency. Flexibility in design of the vector is desirable, to enable a careful and controlled manipulation of its properties and functions. This can be met by the use of bolaamphiphile, a special class of lipid. Unlike conventional lipids, bolaamphiphiles can form asymmetric complexes with the therapeutic gene. The advantage of having an asymmetric complex lies in the different purposes served by the interior and exterior of the complex. More effective gene encapsulation within the interior of the complex can be achieved without triggering greater aggregation of serum proteins with the exterior, potentially overcoming one of the great hurdles faced by conventional single-head cationic lipids. In this review, we will look into the physiochemical considerations as well as the biological aspects of a bolaamphiphile-based gene delivery system.

  3. Association Mechanisms of Unsaturated C2 Hydrocarbons with Their Cations: Acetylene and Ethylene

    Science.gov (United States)

    Bera, Partha P.; Head-Gordon, Martin; Lee, Timothy J.

    2013-01-01

    The ion-molecule association mechanism of acetylene and ethylene with their cations is investigated by ab initio quantum chemical methods to understand the structures, association energies, and the vibrational and electronic spectra of the products. Stable puckered cyclic isomers are found as the result of first forming less stable linear and bridge isomers. The puckered cyclic complexes are calculated to be strongly bound, by 87, 35 and 56 kcal/mol for acetylene-acetylene cation, ethylene-ethylene cation and acetylene-ethylene cation, respectively. These stable complexes may be intermediates that participate in further association reactions. There are no association barriers, and no significant inter-conversion barriers, so the initial linear and bridge encounter complexes are unlikely to be observable. However, the energy gap between the bridged and cyclic puckered isomers greatly differs from complex to complex: it is 44 kcal/mol in C4H4 +, but only 6 kcal/mol in C4H8 +. The accurate CCSD(T) calculations summarized above are also compared against less computationally expensive MP2 and density functional theory (DFT) calculations for structures, relative energies, and vibrational spectra. Calculated vibrational spectra are compared against available experiments for cyclobutadiene cation. Electronic spectra are also calculated using time-dependent DFT.

  4. Radiation stability of selected ionic liquids: a pulse radiolysis study

    International Nuclear Information System (INIS)

    One important potential application of ionic liquids (IL) is as a medium for processing of spent nuclear fuel. It is therefore imperative to study the radiation chemistry of ILs, not only to determine their radiolytic products and degradation pathways, but also to describe how the radiolysis may affect or interfere in the separation processes. An understanding of Radiation Chemistry of ILs would also facilitate general chemical reactivity in this medium, which will aid in the development of energy production, chemical industry and environmental applications. We were interested in understanding how the specific physical properties of ionic liquids influence the dynamical processes that determine the stability and lifetimes of reactive intermediates and thereby affect the courses of chemical reactions and product distributions in this medium. In the pulse radiolysis experiments on Imidazolium based ILs (1-Ethyl-3-methylimidazolium) (Ethyl sulphate) or (Emim) (EtSO4) under oxidizing or reducing conditions, we observed a transient peak at 320 nm. This absorption may be due to the formation of a radical as electron reacts with the imidazolium cation of the ionic liquid. We have not observed hydrated electrons because the electron reacts with imidazolium cation very fast. Pulse radiolysis experiments have also been performed on FAP (Fluoro Alkyl Phosphates) ILs having imidazolium as cation e.g. (1-Ethyl-3-methylimidazolium) (tris(pentafluoroethyl) trifluorophosphate) or FAP-1 and (1-(2-HydroxyEthyl-3-methylimidazolium) (tris(pentafluoroethyl) trifluorophosphate) or FAP-2. FAP-ionic liquids show an excellent hydrolytic stability, low viscosity and high electrochemical and thermal stability that makes them attractive for use in electrochemical devices and as a new media for application in modern technologies and chemical synthesis. The time-resolved transient spectra of FAP ILs were recorded and characterized under different experimental conditions. The formation and decay

  5. Intermediate Temperature Solid Oxide Fuel Cell Development

    Energy Technology Data Exchange (ETDEWEB)

    S. Elangovan; Scott Barnett; Sossina Haile

    2008-06-30

    Solid oxide fuel cells (SOFCs) are high efficiency energy conversion devices. Present materials set, using yttria stabilized zirconia (YSZ) electrolyte, limit the cell operating temperatures to 800 C or higher. It has become increasingly evident however that lowering the operating temperature would provide a more expeditious route to commercialization. The advantages of intermediate temperature (600 to 800 C) operation are related to both economic and materials issues. Lower operating temperature allows the use of low cost materials for the balance of plant and limits degradation arising from materials interactions. When the SOFC operating temperature is in the range of 600 to 700 C, it is also possible to partially reform hydrocarbon fuels within the stack providing additional system cost savings by reducing the air preheat heat-exchanger and blower size. The promise of Sr and Mg doped lanthanum gallate (LSGM) electrolyte materials, based on their high ionic conductivity and oxygen transference number at the intermediate temperature is well recognized. The focus of the present project was two-fold: (a) Identify a cell fabrication technique to achieve the benefits of lanthanum gallate material, and (b) Investigate alternative cathode materials that demonstrate low cathode polarization losses at the intermediate temperature. A porous matrix supported, thin film cell configuration was fabricated. The electrode material precursor was infiltrated into the porous matrix and the counter electrode was screen printed. Both anode and cathode infiltration produced high performance cells. Comparison of the two approaches showed that an infiltrated cathode cells may have advantages in high fuel utilization operations. Two new cathode materials were evaluated. Northwestern University investigated LSGM-ceria composite cathode while Caltech evaluated Ba-Sr-Co-Fe (BSCF) based pervoskite cathode. Both cathode materials showed lower polarization losses at temperatures as low as 600

  6. Cationic ruthenium alkylidene catalysts bearing phosphine ligands

    OpenAIRE

    Endo, Koji; Grubbs, Robert H.

    2016-01-01

    The discovery of highly active catalysts and the success of ionic liquid immobilized systems have accelerated attention to a new class of cationic metathesis catalysts. We herein report the facile syntheses of cationic ruthenium catalysts bear-ing bulky phosphine ligands. Simple ligand exchange using silver(I) salts of non-coordinating or weakly coordinating anions pro-vided either PPh3 or chelating Ph2P(CH2)nPPh2 (n = 2 or 3) ligated cationic catalysts. The structures of these newly reported...

  7. Cation substitution in two coccolithophore species

    OpenAIRE

    Melteig, Hanna Elina

    2016-01-01

    Few things would be better than getting rid of CO2 while producing useful materials. Coccolithophores use CO2 in their photorespiration, in addition to using CO2 to produce coccoliths – small platelets made of calcite. Ca is a central cation in this process, and the goal of this project is to investigate to what extent other divalent cations can partially substitute for Ca and become part of the growing coccolith. The long term goal is to enable algae to harvest cations and produce mate...

  8. Nuclear Reactions at Intermediate Energies

    CERN Document Server

    Shyam, Radhey

    2015-01-01

    In the domain of Nuclear reactions at intermediate energies, the QCD coupling constant $\\alpha_s$ is large enough ($\\sim$ 0.3 - 0.5) to render the perturbative calculational techniques inapplicable. In this regime the quarks are confined into colorless hadrons and it is expected that effective field theories of hadron interactions via exchange of hadrons, provide useful tools to describe such reactions. In this contribution we discuss applications of one such theory, the effective Lagrangian model, in describing the hadronic reactions at intermediate energies whose measurements are the focus of a vast international experimental program.

  9. Brillouin spectroscopy with surface acoustic waves on intermediate valent, doped SmS

    International Nuclear Information System (INIS)

    Brillouin scattering on surface acoustic waves is a very powerful tool to determine the elastic constants of intermediate valent crystals, since the method is non-destructive and no mechanical contact is needed. A strong evidence for intermediate valence is a negative value of Poisson's ratio, which describes the behavior of the volume under uniaxial pressure. SmS by itself makes a semiconductor-metal transition at a pressure of more than 6.5 kbar. When substituting the divalent Sm by a trivalent cation, like Y, La or Tm, SmS can become - depending on the doping concentration - intermediate valent without any applied, external pressure. In this work, we will present measurements of the velocities of the surface acoustic waves and the calculation of the elastic constants of La- and Tm-doped SmS compounds. We found a clear dependence of Poisson's ratio on the doping concentration and on the valence of the materials. Furthermore, we will discuss the mechanism leading to intermediate valence when substituting Sm. Besides the internal, chemical pressure, which is produced by the built in trivalent cations with their smaller ionic radii, we have clear evidence, that the free electrons in the 5d band, induced by the substituting atoms, also play an important role in making doped SmS intermediate valent. (orig.)

  10. Perturbing peptide cation-radical electronic states by thioxoamide groups: formation, dissociations, and energetics of thioxopeptide cation-radicals.

    Science.gov (United States)

    Zimnicka, Magdalena; Chung, Thomas W; Moss, Christopher L; Tureček, František

    2013-02-14

    Thioxodipeptides Gly-thio-Lys (GtK), Ala-thio-Lys (AtK), and Ala-thio-Arg (AtR) in which the amide group has been modified to a thioxoamide were made into dications by electrospray ionization and converted to cation-radicals, (GtK + 2H)(+•), (AtK + 2H)(+•), and (AtR + 2H)(+•), by electron transfer dissociation (ETD) tandem mass spectrometry using fluoranthene anion-radical as an electron donor. The common and dominant dissociation of these cation-radicals was the loss of a hydrogen atom. The dissociation products were characterized by collision-induced dissociation (CID) multistage tandem mass spectrometry up to CID-MS(5). The ground electronic states of several (GtK + 2H)(+•), (AtK + 2H)(+•), and (AtR + 2H)(+•) conformers were explored by extensive ab initio and density functional theory calculations of the potential energy surface. In silico electron transfer to the precursor dications, (GtK + 2H)(2+), (AtK + 2H)(2+), and (AtR + 2H)(2+), formed zwitterionic intermediates containing thioenol anion-radical and ammonium cation groups that were local energy minima on the potential energy surface of the ground electronic state. The zwitterions underwent facile isomerization by N-terminal ammonium proton migration to the thioenol anion-radical group forming aminothioketyl intermediates. Combined potential energy mapping and RRKM calculations of dissociation rate constants identified N-C(α) bond cleavages as the most favorable dissociation pathways, in a stark contrast to the experimental results. This discrepancy is interpreted as being due to the population upon electron transfer of low-lying excited electronic states that promote loss of hydrogen atoms. For (GtK + 2H)(+•), these excited states were characterized by time-dependent density functional theory as A-C states that had large components of Rydberg-like 3s molecular orbitals at the N-terminal and lysine ammonium groups that are conducive to hydrogen atom loss. PMID:22765351

  11. Cationization of heparin for film applications

    Czech Academy of Sciences Publication Activity Database

    Šimkovic, I.; Mendichi, R.; Kelnar, Ivan; Filip, J.; Hricovíni, M.

    2015-01-01

    Roč. 115, 22 January (2015), s. 551-558. ISSN 0144-8617 Institutional support: RVO:61389013 Keywords : heparin * cationization * NMR Subject RIV: CD - Macromolecular Chemistry Impact factor: 4.074, year: 2014

  12. Cation locations and dislocations in zeolites

    Science.gov (United States)

    Smith, Luis James

    The focus of this dissertation is the extra-framework cation sites in a particular structural family of zeolites, chabazite. Cation sites play a particularly important role in the application of these sieves for ion exchange, gas separation, catalysis, and, when the cation is a proton, acid catalysis. Structural characterization is commonly performed through the use of powder diffraction and Rietveld analysis of powder diffraction data. Use of high-resolution nuclear magnetic resonance, in the study of the local order of the various constituent nuclei of zeolites, complements well the long-range order information produced by diffraction. Recent developments in solid state NMR techniques allow for increased study of disorder in zeolites particularly when such phenomena test the detection limits of diffraction. These two powerful characterization techniques, powder diffraction and NMR, offer many insights into the complex interaction of cations with the zeolite framework. The acids site locations in SSZ-13, a high silica chabazite, and SAPO-34, a silicoaluminophosphate with the chabazite structure, were determined. The structure of SAPO-34 upon selective hydration was also determined. The insensitivity of X-rays to hydrogen was avoided through deuteration of the acid zeolites and neutron powder diffraction methods. Protons at inequivalent positions were found to have different acid strengths in both SSZ-13 and SAPO-34. Other light elements are incorporated into zeolites in the form of extra-framework cations, among these are lithium, sodium, and calcium. Not amenable by X-ray powder diffraction methods, the positions of such light cations in fully ion-exchanged versions of synthetic chabazite were determined through neutron powder diffraction methods. The study of more complex binary cation systems were conducted. Powder diffraction and solid state NMR methods (MAS, MQMAS) were used to examine cation site preferences and dislocations in these mixed-akali chabazites

  13. Cycloaliphatic epoxide resins for cationic UV - cure

    International Nuclear Information System (INIS)

    This paper introduces the cyclo - aliphatic epoxide resins used for the various applications of radiation curing and their comparison with acrylate chemistry. Radiation curable coatings and inks are pre - dominantly based on acrylate chemistry but over the last few years, cationic chemistry has emerged successfully with the unique properties inherent with cyclo - aliphatic epoxide ring structures. Wide variety of cationic resins and diluents, the formulation techniques to achieve the desired properties greatly contributes to the advancement of UV - curing technology

  14. Cations and activated sludge floc structure

    OpenAIRE

    Park, Chul

    2002-01-01

    This research was designed to investigate the effect of cations on activated sludge characteristics and also to determine their influence on digestion performance. For this purpose, cations in solution and in floc were evaluated along with various activated sludge characteristics and the collected waste activated sludge underwent both anaerobic and aerobic digestion. It was found that large amounts of biopolymer (protein + polysaccharide) remained in the effluent of WWTP that received high in...

  15. Quantum-chemical analysis of lithium cation coordination with dimethylsulfoxide molecules

    International Nuclear Information System (INIS)

    Coordination of lithium cation by molecules of dimethylsulfoxide (DMSO) was studied in the framework of the HF and B3LYP methods, structural parameters of the complexes formed and charge distribution on them being identified. Thermal effects for each stage of the complexing process were calculated. It was ascertained that coordination number of Li+ cation in DMSO is 4, moreover, stability of Li+ · 4DMSO complex in gaseous phase is higher than that of Li+ · 4HO. Formation of the [Li+ · 4DMSO] · OH- · nH2O type associates is possible in superbasic environment of LiOH - H2O - DMSO

  16. Ion-radical intermediates of the radiation-chemical transformations of organic carbonates

    Science.gov (United States)

    Shiryaeva, Ekaterina S.; Sosulin, Ilya S.; Saenko, Elizaveta V.; Feldman, Vladimir I.

    2016-07-01

    The spectral features and reactions of ion-radical intermediates produced from organic carbonates in low-temperature matrices were investigated by EPR spectroscopy and quantum-chemical calculations. It was shown that radical cations of diethyl carbonate and dimethyl carbonate underwent intramolecular hydrogen transfer to yield alkyl-type species, as was suggested previously. Meanwhile, radical cation of EC demonstrates a ring cleavage even at 77 K, while radical cation of PC is probably intrinsically stable and undergo an ion-molecule reaction with a neighboring neutral molecule in dimers or associates. Radical anions were obtained in glassy matrices of diethyl ether or perdeuteroethanol. The radical anions of linear carbonates show photoinduced fragmentation to yield the corresponding alkyl radicals; such process may also occur directly under radiolysis. Radical anions of cyclic carbonates are relatively stable and yield only trace amounts of fragmentation products under similar conditions.

  17. Intermediality and the Child Performer

    Science.gov (United States)

    Budd, Natasha

    2016-01-01

    This report details examples of praxis in the creation and presentation of "Joy Fear and Poetry": an intermedial theatre performance in which children aged 7-12 years generated aesthetic gestures using a range of new media forms. The impetus for the work's development was a desire to make an intervention into habituated patterns of…

  18. Material Voices: Intermediality and Autism

    Science.gov (United States)

    Trimingham, Melissa; Shaughnessy, Nicola

    2016-01-01

    Autism continues to be regarded enigmatically; a community that is difficult to access due to perceived disruptions of interpersonal connectedness. Through detailed observations of two children participating in the Arts and Humanities Research Council funded project "Imagining Autism: Drama, Performance and Intermediality as Interventions for…

  19. Intermediate business programming with C++

    CERN Document Server

    Voils, Don

    2005-01-01

    Intermediate Business Programming with C++ 2005 offers a comprehensive approach to the topic with emphasis on the creation of object oriented programs for business and the use of data structures, this book deals with the writing of business programs using C++ from Microsoft Visual Studio .NET 2005.

  20. Divalent cation shrinks DNA but inhibits its compaction with trivalent cation

    Science.gov (United States)

    Tongu, Chika; Kenmotsu, Takahiro; Yoshikawa, Yuko; Zinchenko, Anatoly; Chen, Ning; Yoshikawa, Kenichi

    2016-05-01

    Our observation reveals the effects of divalent and trivalent cations on the higher-order structure of giant DNA (T4 DNA 166 kbp) by fluorescence microscopy. It was found that divalent cations, Mg(2+) and Ca(2+), inhibit DNA compaction induced by a trivalent cation, spermidine (SPD(3+)). On the other hand, in the absence of SPD(3+), divalent cations cause the shrinkage of DNA. As the control experiment, we have confirmed the minimum effect of monovalent cation, Na(+) on the DNA higher-order structure. We interpret the competition between 2+ and 3+ cations in terms of the change in the translational entropy of the counterions. For the compaction with SPD(3+), we consider the increase in translational entropy due to the ion-exchange of the intrinsic monovalent cations condensing on a highly charged polyelectrolyte, double-stranded DNA, by the 3+ cations. In contrast, the presence of 2+ cation decreases the gain of entropy contribution by the ion-exchange between monovalent and 3+ ions.

  1. Cationic bis-N-heterocyclic carbene (NHC) ruthenium complex: Structure and application as latent catalyst in olefin metathesis

    KAUST Repository

    Rouen, Mathieu

    2014-09-11

    An unexpected cationic bis-N-heterocyclic carbene (NHC) benzylidene ether based ruthenium complex (2 a) was prepared through the double incorporation of an unsymmetrical unsaturated N-heterocyclic carbene (U2-NHC) ligand that bore an N-substituted cyclododecyl side chain. The isolation and full characterization (including X-ray diffraction studies) of key synthetic intermediates along with theoretical calculations allowed us to understand the mechanism of the overall cationization process. Finally, the newly developed complex 2 a displayed interesting latent behavior during ring-closing metathesis, which could be "switched on" under acidic conditions.

  2. An overview of quantification methods in energy-dispersive X-ray fluorescence analysis

    Indian Academy of Sciences (India)

    A Markowicz

    2011-02-01

    This paper reviews the major factors influencing the accuracy of the energy-dispersive X-ray fluorescence (EDXRF) analysis including physical and chemical matrix effects (resulting from particle size, surface irregularity, mineralogy, moisture, absorption and enhancement) as well as the correction procedures with emphasis on the analysis of unprepared samples. Quantification methods for thin samples, samples with intermediate thickness and thick samples are presented including fundamental parameter methods, influence coefficient algorithms, empirical coefficient algorithms and quantification methods based on scattered primary radiation. Quality control procedures are also reviewed.

  3. Financial intermediation and the post-crisis financial system

    OpenAIRE

    Hyun Song Shin

    2010-01-01

    Securitization was meant to disperse credit risk to those who were better able to bear it. In practice, securitization appears to have concentrated the risks in the financial intermediary sector itself. This paper outlines an accounting framework for the financial system for assessing the impact of securitization on financial stability. If securitization leads to the lengthening of intermediation chains, then risks becomes concentrated in the intermediary sector with damaging consequences for...

  4. Quantum mechanical investigations on the role of neutral and negatively charged enamine intermediates in organocatalyzed reactions

    International Nuclear Information System (INIS)

    Highlights: • M06-2X functional is suitable to model key steps of proline-catalyzed reactions. • Investigation of the proline-catalyzed aldol reaction mechanism. • Influence of water molecules on the C–C bond formation step. • Mechanism for the reaction of proline-derived enamines with benzhydrylium cations. - Abstract: The proline-catalyzed aldol reaction is the seminal example of asymmetric organocatalysis. Previous theoretical and experimental studies aimed at identifying its mechanism in order to rationalize the outcome of this reaction. Here, we focus on key steps with modern first principle methods, i.e. the M06-2X hybrid exchange–correlation functional combined to the solvation density model to account for environmental effects. In particular, different pathways leading to the formation of neutral and negatively charged enamine intermediates are investigated, and their reactivity towards two electrophiles, i.e. an aldehyde and a benzhydrylium cation, are compared. Regarding the self-aldol reaction, our calculations confirm that the neutral enamine intermediate is more reactive than the negatively charged one. For the reaction with benzhydrylium cations however, the negatively charged enamine intermediate is more reactive

  5. Quantum mechanical investigations on the role of neutral and negatively charged enamine intermediates in organocatalyzed reactions

    Energy Technology Data Exchange (ETDEWEB)

    Hubin, Pierre O., E-mail: pierre.hubin@unamur.be [Laboratoire de Physico-Chimie Informatique (PCI), Unité de Chimie Physique Théorique et Structurale, University of Namur, 61 rue de Bruxelles, 5000 Namur (Belgium); Jacquemin, Denis [Laboratoire CEISAM – UMR CNRS 6230, Université de Nantes, 2 rue de la Houssinière, BP92208, 44322 Nantes Cedex 3 (France); Institut Universitaire de France 103, Boulevard St Michel, 75005 Paris Cedex 5 (France); Leherte, Laurence; Vercauteren, Daniel P. [Laboratoire de Physico-Chimie Informatique (PCI), Unité de Chimie Physique Théorique et Structurale, University of Namur, 61 rue de Bruxelles, 5000 Namur (Belgium)

    2014-04-15

    Highlights: • M06-2X functional is suitable to model key steps of proline-catalyzed reactions. • Investigation of the proline-catalyzed aldol reaction mechanism. • Influence of water molecules on the C–C bond formation step. • Mechanism for the reaction of proline-derived enamines with benzhydrylium cations. - Abstract: The proline-catalyzed aldol reaction is the seminal example of asymmetric organocatalysis. Previous theoretical and experimental studies aimed at identifying its mechanism in order to rationalize the outcome of this reaction. Here, we focus on key steps with modern first principle methods, i.e. the M06-2X hybrid exchange–correlation functional combined to the solvation density model to account for environmental effects. In particular, different pathways leading to the formation of neutral and negatively charged enamine intermediates are investigated, and their reactivity towards two electrophiles, i.e. an aldehyde and a benzhydrylium cation, are compared. Regarding the self-aldol reaction, our calculations confirm that the neutral enamine intermediate is more reactive than the negatively charged one. For the reaction with benzhydrylium cations however, the negatively charged enamine intermediate is more reactive.

  6. Accelerators for forming cationic technetium complexes useful as radiodiagnostic images

    International Nuclear Information System (INIS)

    This invention relates to compositions for making cationic radiodiagnostic agents and, in particular, to accelerator compounds for labelling such cationic radiodiagnostic agents, kits for preparing such 99mTc-labelled cationic radiodiagnostic agents with technetium, and methods for labelling such cationic radiodiagnostic agents with technetium

  7. Synthesis and Characterization of Zirconia Nanocrystallites by Cationic Surfactant and Anionic Surfactant

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Study on nanomaterials has attracted great interests in recent years. In this article,zirconia nanocrystallites of different structures have been successfully synthesized via hydrothermal methods with cationic surfactant (CTAB) and anionic surfactant (SDS), respectively. Differential Scanning Calorimeter (DSC-TG), X-ray Diffractometer (XRD), Transmission Electron Microscope (TEM), Ultraviolet-Visible (UV-vis) and N2 adsorption-desorption analyses are used for their structure characteristics. The results show that the cationic surfactant has a distinctive direction effect on the formation of zirconia nanocrystallites, while the anionic surfactant has a self-assembly synergistic effect on them. The sample synthesized with the cationic surfactant presents good dispersion with the main phase of tetragonal zirconia, and the average nanocryst al size is around 15nm after calcination at 500 ℃. While the sample synthesized with the anionic surfactant exhibits a worm-like mesoporous structure with pure tetragonal phase after calcination at 500 ℃ and with good thermal stability.

  8. The sequence to hydrogenate coronene cations: A journey guided by magic numbers

    CERN Document Server

    Cazaux, Stéphanie; Rougeau, Nathalie; Reitsma, Geert; Hoekstra, Ronnie; Teillet-Billy, Dominique; Morisset, Sabine; Spaans, Marco; Schlathölter, Thomas

    2016-01-01

    The understanding of hydrogen attachment to carbonaceous surfaces is essential to a wide variety of research fields and technologies such as hydrogen storage for transportation, precise localization of hydrogen in electronic devices and the formation of cosmic H2. For coronene cations as prototypical Polycyclic Aromatic Hydrocarbon (PAH) molecules, the existence of magic numbers upon hydrogenation was uncovered experimentally. Quantum chemistry calculations show that hydrogenation follows a site-specific sequence leading to the appearance of cations having 5, 11, or 17 hydrogen atoms attached, exactly the magic numbers found in the experiments. For these closed-shell cations, further hydrogenation requires appreciable structural changes associated with a high transition barrier. Controlling specific hydrogenation pathways would provide the possibility to tune the location of hydrogen attachment and the stability of the system. The sequence to hydrogenate PAHs, leading to PAHs with magic numbers of H atoms att...

  9. Larval helminths in intermediate hosts

    DEFF Research Database (Denmark)

    Fredensborg, Brian Lund; Poulin, R

    2005-01-01

    transmission to their bird definitive host by predation. In experimental infections, we found an intensity-dependent establishment success, with a decrease in the success rate of cercariae developing into infective metacercariae with an increasing dose of cercariae applied to each amphipod. In natural......Density-dependent effects on parasite fitness have been documented from adult helminths in their definitive hosts. There have, however, been no studies on the cost of sharing an intermediate host with other parasites in terms of reduced adult parasite fecundity. Even if larval parasites suffer a...... reduction in size, caused by crowding, virtually nothing is known about longer-lasting effects after transmission to the definitive host. This study is the first to use in vitro cultivation with feeding of adult trematodes to investigate how numbers of parasites in the intermediate host affect the size and...

  10. Evidence for Cation-Controlled Excited-State Localization in a Ruthenium Polypyridyl Compound.

    Science.gov (United States)

    Beauvilliers, Evan E; Meyer, Gerald J

    2016-08-01

    The visible absorption and photoluminescence (PL) properties of the four neutral ruthenium diimine compounds [Ru(bpy)2(dcb)] (B2B), [Ru(dtb)2(dcb)] (D2B), [Ru(bpy)2(dcbq)] (B2Q), and [Ru(dtb)2(dcbq)] (D2Q), where bpy is 2,2'-bipyridine, dcb is 4,4'-(CO2(-))2-bpy, dtb is 4,4'-(tert-butyl)2-bpy, and dcbq is 4,4'-(CO2(-))2-2,2'-biquinoline, are reported in the presence of Lewis acidic cations present in fluid solutions at room temperature. In methanol solutions, the measured spectra were insensitive to the presence of these cations, while in acetonitrile a significant red shift in the PL spectra (≤1400 cm(-1)) was observed consistent with stabilization of the metal-to-ligand charge transfer (MLCT) excited state through Lewis acid-base adduct formation. No significant spectral changes were observed in control experiments with the tetrabutylammonium cation. Titration data with Li(+), Na(+), Mg(2+), Ca(2+), Zn(2+), Al(3+), Y(3+), and La(3+) showed that the extent of stabilization saturated at high cation concentration with magnitudes that scaled roughly with the cation charge-to-size ratio. The visible absorption spectra of D2Q was particularly informative due to the presence of two well-resolved MLCT absorption bands: (1) Ru → bpy, λmax ≈ 450 nm; and (2) Ru → dcbq, λmax ≈ 540 nm. The higher-energy band blue-shifted and the lower-energy band red-shifted upon cation addition. The PL intensity and lifetime of the excited state of B2B first increased with cation addition without significant shifts in the measured spectra, behavior attributed to a cation-induced change in the localization of the emissive excited state from bpy to dcb. The importance of excited-state localization and stabilization for solar energy conversion is discussed. PMID:27391279

  11. Financial Intermediation with Risk Aversion

    OpenAIRE

    Hellwig, Martin

    1998-01-01

    The paper extends Diamond's (1984) analysis of financial intermediation to allow for risk aversion of the intermediary. It shows that, as in the case of risk neutrality, the agency costs of external funds provided to an intermediary are relatively small if the intermediary is financing many entrepreneurs with stochastically independent returns. Even though the intermediary is adding rather than subdividing risks, the underlying large-numbers argument is not invalidated by the presence of risk...

  12. Metal cations inserted in vanadium-oxide nanotubes

    International Nuclear Information System (INIS)

    Vanadium-oxide nanotubes (VO x-NTs) consist of nanosize cylinders of thin, easily bent vanadyl (VO x) wall chains, which are open at both ends. Surfactant molecules (e.g. C12H27N) can be easily trapped in the interior of the nanotube walls. The structure of as-synthesized VO x-NTs are observed to collapse to an amorphous vanadium oxide at temperatures greater than 250 deg, C. This happens, even under a protective atmosphere. This property makes the VO x-NTs unusable as a catalyst at temperatures between 400-500 deg, C, which is the temperature range where many applications would exist. In order to increase the thermal stability of VO x-NTs several exchange reactions have been used to modify the original nanotubes. In these reactions metallic cations (Cd2+, Co2+, Mn2+ or Zn2+) were introduced. It was observed that that the morphology of the nanotubes remained unchanged after the exchange reactions were performed. In order to characterize the exchanged VO x-NTs the following analytic techniques were used: scanning electron microscopy, X-ray powder diffraction, Fourier transform infrared, particle-induced X-ray emission and Rutherford backscattering spectrometry. The results showed that the VO x-NTs exchanged with metallic cations have preserved their tubular morphology. However, it has not been possible to fully perform a 100% efficient exchange reaction

  13. Dynamics of mobile ions in single- and mixed-cation glasses

    International Nuclear Information System (INIS)

    To study the ion dynamics of several inorganic glasses, including single- and mixed-cation glasses, we have determined conductivity spectra over wide ranges in frequency. In the case of the single-cation glasses, these spectra extend from a few hertz up to the terahertz regime. The spectra show a transition from their dc values to a dispersive regime where the conductivity increases continuously with frequency, tending towards a linear frequency dependence at sufficiently low temperatures. At high frequencies the dynamic conductivity is governed by vibrational contributions, whereas ionic hopping sequences determine the low-frequency part of the spectra. In an intermediate-frequency regime, both hopping and vibrational contributions contribute to the dynamic conductivity. The shape of the high-frequency conductivity spectra is discussed for various glasses. The low-frequency spectra are discussed in the framework of the concept of mismatch and relaxation. For the mixed-cation glasses where spectra have been taken by impedance spectroscopy, we report on a new kind of mixed-alkali effect. In contrast to conductivity spectra of single-cation glasses which follow the time-temperature superposition principle, featuring a temperature-invariant shape, the shapes of the conductivity spectra of the mixed-alkali glasses studied here are found to change with temperature. To explain this effect, we suggest differently activated mobilities of the two different ionic species

  14. Influence of the Ion Coordination Number on Cation Exchange Reactions with Copper Telluride Nanocrystals

    CERN Document Server

    Tu, Renyong; Bertoni, Giovanni; Lak, Aidin; Gaspari, Roberto; Rapallo, Arnaldo; Cavalli, Andrea; De Trizio, Luca; Manna, Liberato

    2016-01-01

    Cu2-xTe nanocubes were used as starting seeds to access metal telluride nanocrystals by cation exchanges at room temperature. The coordination number of the entering cations was found to play an important role in dictating the reaction pathways. The exchanges with tetrahedrally coordinated cations (i.e. with coordination number 4), such as Cd2+ or Hg2+, yielded monocrystalline CdTe or HgTe nanocrystals with Cu2-xTe/CdTe or Cu2-xTe/HgTe Janus-like heterostructures as intermediates. The formation of Janus-like architectures was attributed to the high diffusion rate of the relatively small tetrahedrally coordinated cations, which could rapidly diffuse in the Cu2-xTe NCs and nucleate the CdTe (or HgTe) phase in a preferred region of the host structure. Also, with both Cd2+ and Hg2+ ions the exchange led to wurtzite CdTe and HgTe phases rather than the more stable zinc-blende ones, indicating that the anion framework of the starting Cu2- xTe particles could be more easily deformed to match the anion framework of t...

  15. Trapping five-coordinate platinum(iv) intermediates.

    Science.gov (United States)

    Shaw, Paul A; Phillips, Jessica M; Clarkson, Guy J; Rourke, Jonathan P

    2016-07-28

    The oxidation of three different complexes of the doubly cycloplatinated 2,6-di(4-fluorophenyl)pyridine ligand (namely DMSO, PPh3 and PPr3 derivatives, 1a, 1b and 1c, respectively) with the electrophilic oxidant iodobenzenedichloride was studied. In each case oxidation can yield a simple trans-dichloro platinum(iv) complex (2(t)), which subsequently isomerises to the cis isomer (2(c)). However, by changing the solvent, or performing the reaction in the presence of an additional ligating species, a five-coordinate intermediate can be trapped out and isolated. Thus, cationic species with additional DMSO or pyridine coordinated could be collected for the DMSO and PPh3 derivatives. The PPr3 derivative traps out the reactive five-coordinate species with an agostic interaction that subsequently induces a transcyclometallation reaction to give a complex with a singly cyclometallated pyridine and a cyclometallated phosphine, which was characterised crystallographically, (6c PMID:27335216

  16. Cationically polymerizable monomers derived from renewable sources

    Energy Technology Data Exchange (ETDEWEB)

    Crivello, J.V.

    1991-10-01

    The objective of this project is to make use of products obtained from renewable plant sources as monomers for the direct production of polymers which can be used for a wide range of plastic applications. In this report is described progress in the synthesis and polymerization of cationically polymerizable monomers and oligomers derived from botanical oils, terpenes, natural rubber, and lignin. Nine different botanical oils were obtained from various sources, characterized and then epoxidized. Their photopolymerization was carried out using cationic photoinitiators and the mechanical properties of the resulting polymers characterized. Preliminary biodegradation studies are being conducted on the photopolymerized films from several of these oils. Limonene was cationically polymerized to give dimers and the dimers epoxidized to yield highly reactive monomers suitable for coatings, inks and adhesives. The direct phase transfer epoxidation of squalene and natural rubber was carried out. The modified rubbers undergo facile photocrosslinking in the presence of onium salts to give crosslinked elastomers. 12 refs., 3 figs., 10 tabs.

  17. A spectroscopic study of interaction of cationic dyes with heparin

    Directory of Open Access Journals (Sweden)

    R. Nandini

    2010-01-01

    Full Text Available The interaction of two cationic dyes namely, acridine orange and pinacyanol chloride with an anionic polyelectrolyte, heparin, has been investigated by spectrophotometric method.The polymer induced metachromasy in the dyes resulting in the shift of the absorption maxima of the dyes towards shorter wavelengths. The stability of the complexes formed between acridine orange and heparin was found to be lesser than that formed between pinacyanol chloride and heparin. This fact was further confirmed by reversal studies using alcohols, urea and surfactants. The interaction of acridine orange with heparin has also been investigated fluorimetrically.The interaction parameters revealed that binding between acridine orange and heparin arises due to electrostatic interaction while that between pinacyanol chloride and heparin is found to involve both electrostatic and hydrophobic forces. The effect of the structure of the dye in inducing metachromasy has also been discussed.

  18. Efficient scavenging of β-carotene radical cations by antiinflammatory salicylates

    DEFF Research Database (Denmark)

    Cheng, Hong; Liang, Ran; Han, Rui-Min;

    2014-01-01

    by the anion of salicylic acid with 2.2 × 10 L mol s, but still of possible importance for light-exposed tissue. Surprisingly, acetylsalicylate, the aspirin anion, reacts with an intermediate rate in a reaction assigned to the anion of the mixed acetic-salicylic acid anhydride formed through base induced......The radical cation generated during photobleaching of β-carotene is scavenged efficiently by the anion of methyl salicylate from wintergreen oil in a second-order reaction approaching the diffusion limit with k = 3.2 × 10 L mol s in 9:1 v/v chloroform-methanol at 23 °C, less efficiently...... rearrangements. The relative scavenging rate of the β-carotene radical cation by the three salicylates is supported by DFT-calculations. © 2014 The Royal Society of Chemistry....

  19. Living cationic polymerization and polyhomologation: an ideal combination to synthesize functionalized polyethylene–polyisobutylene block copolymers

    KAUST Repository

    Zhang, Hefeng

    2015-12-17

    A series of hydroxyl-terminated polyisobutylene-b-polyethylene (PIB-b-PE-OH) copolymers were synthesized by combining living cationic polymerization and polyhomologation. Allyl-terminated PIBs, synthesized by living cationic polymerization, were hydroborated with BH3·THF to produce 3-arm boron-linked stars, PIB3B, which served as macroinitiators for the in situ polyhomologation of dimethylsulfoxonium methylide. The resulting 3-arm star block copolymers, (PIB-b-PE)3B, were oxidized/hydrolysed to afford PIB-b-PE-OH. Characterization of all intermediates and final products by high temperature gel permeation chromatography (HT-GPC) and proton nuclear magnetic resonance spectroscopy (1H NMR) revealed the well-defined character of the copolymers. The thermal properties of the copolymers were studied by differential scanning calorimetry (DSC).

  20. Cation Effect on Copper Chemical Mechanical Polishing

    Institute of Scientific and Technical Information of China (English)

    WANG Liang-Yong; LIU Bo; SONG Zhi-Tang; FENG Song-Lin

    2009-01-01

    We examine the effect of cations in solutions containing benzotriazole (BTA) and H2O2 on copper chemical mechanical polishing (CMP). On the base of atomic force microscopy (AFM) and material removal rate (MRR) results, it is found that ammonia shows the highest MRR as well as good surface after CMP, while KOH demon-strates the worst performance. These results reveal a mechanism that sma//molecules with lone-pairs rather than molecules with steric effect and common inorganic cations are better for copper CMP process, which is indirectly confirmed by open circuit potential (OCP).

  1. Role of Intermediate Filaments in Vesicular Traffic

    Directory of Open Access Journals (Sweden)

    Azzurra Margiotta

    2016-04-01

    Full Text Available Intermediate filaments are an important component of the cellular cytoskeleton. The first established role attributed to intermediate filaments was the mechanical support to cells. However, it is now clear that intermediate filaments have many different roles affecting a variety of other biological functions, such as the organization of microtubules and microfilaments, the regulation of nuclear structure and activity, the control of cell cycle and the regulation of signal transduction pathways. Furthermore, a number of intermediate filament proteins have been involved in the acquisition of tumorigenic properties. Over the last years, a strong involvement of intermediate filament proteins in the regulation of several aspects of intracellular trafficking has strongly emerged. Here, we review the functions of intermediate filaments proteins focusing mainly on the recent knowledge gained from the discovery that intermediate filaments associate with key proteins of the vesicular membrane transport machinery. In particular, we analyze the current understanding of the contribution of intermediate filaments to the endocytic pathway.

  2. Binding of Divalent Cations to Polygalacturonate: A Mechanism Driven by the Hydration Water.

    Science.gov (United States)

    Huynh, Uyen T D; Lerbret, Adrien; Neiers, Fabrice; Chambin, Odile; Assifaoui, Ali

    2016-02-11

    We have investigated the interactions between polygalacturonate (polyGal) and four divalent cations (M(2+) = Ba(2+), Ca(2+), Mg(2+), Zn(2+)) that differ in size and affinity for water. Our results evidence that M(2+)-polyGal interactions are intimately linked to the affinity of M(2+) for water. Mg(2+) interacts so strongly with water that it remains weakly bound to polyGal (polycondensation) by sharing water molecules from its first coordination shell with the carboxylate groups of polyGal. In contrast, the other cations form transient ionic pairs with polyGal by releasing preferentially one water molecule (for Zn(2+)) or two (for Ca(2+) and Ba(2+)), which corresponds to monodentate and bidentate binding modes with carboxylates, respectively. The mechanism for the binding of these three divalent cations to polyGal can be described by two steps: (i) monocomplexation and formation of point-like cross-links between polyGal chains (at low M(2+)/Gal molar ratios, R) and (ii) dimerization (at higher R). The threshold molar ratio, R*, between these two steps depends on the nature of divalent cations and is lower for calcium ions (R* barium ions (R* > 0.3). This difference may be explained by the intermediate affinity of Ca(2+) for water with respect to those of Zn(2+) and Ba(2+), which may induce the formation of cross-links of intermediate flexibility. By comparison, the lower and higher flexibilities of the cross-links formed by Zn(2+) and Ba(2+), respectively, may shift the formation of dimers to higher molar ratios (R*). PMID:26771109

  3. Cable Stability

    CERN Document Server

    Bottura, L

    2014-01-01

    Superconductor stability is at the core of the design of any successful cable and magnet application. This chapter reviews the initial understanding of the stability mechanism, and reviews matters of importance for stability such as the nature and magnitude of the perturbation spectrum and the cooling mechanisms. Various stability strategies are studied, providing criteria that depend on the desired design and operating conditions.

  4. THE FUNCTIONS OF FINANCIAL INTERMEDIATION - A SURVEY

    OpenAIRE

    Andries Marius Alin

    2009-01-01

    Traditional theories of intermediation are based on transaction costs and asymmetric information. In recent decades although transaction costs and asymmetric information have declined, intermediation has increased. New markets for financial futures and options are mainly markets for intermediaries rather than individuals or firms. In this paper we survey the last theoretical and empirical research on financial intermediation and functions of financial intermediation. We discuss the functions ...

  5. How Should Financial Intermediation Services be Taxed?

    OpenAIRE

    Lockwood, Ben

    2010-01-01

    This paper considers the optimal taxation of two types of financial intermediation services (savings intermediation, and payment services) in a dynamic general equilibrium setting, when the government can also use consumption and income taxes. When payment services are used in strict proportion to final consumption, and the cost of intermediation services is the same across firms, the optimal taxes on financial intermediation are generally indeterminate. But, when firms differ in the cost of ...

  6. ESL intermediate/advanced writing

    CERN Document Server

    Munoz Page, Mary Ellen; Jaskiewicz, Mary

    2011-01-01

    Master ESL (English as a Second Language) Writing with the study guide designed for non-native speakers of English. Skill-building lessons relevant to today's topics help ESL students write complete sentences, paragraphs, and even multi-paragraph essays. It's perfect for classroom use or self-guided writing preparation.DETAILS- Intermediate drills for improving skills with parallel structure, mood, correct shifting errors & dangling participles- Advanced essay drills focusing on narrative, descriptive, process, reaction, comparison and contrast- Superb preparation for students taking the TOEFL

  7. Thermal stability of phosphate coatings on steel

    Directory of Open Access Journals (Sweden)

    P. Pokorny

    2015-07-01

    Full Text Available The work was validated thermal stability of zinc, manganese and tri-cations phosphate coatings on steel, made from commercial phosphating bath type Pragofos. Thermogravimetric data dehydration of scholzite, phosphophylite and hureaulite coatings in the temperature range 160 °C – 400 °C define the conditions for applying paints with higher firing temperature or thermal spraying ceramic coatings.

  8. Method for encapsulating and isolating hazardous cations, medium for encapsulating and isolating hazardous cations

    Energy Technology Data Exchange (ETDEWEB)

    Wasserman, S.R.; Anderson, K.B.; Song, K.; Yuchs, S.E.; Marshall, C.L.

    1996-12-31

    The problems associated with the disposal of toxic metals in an environmentally acceptable manner continues to plague industry. Such metals as nickel, vanadium, molybdenum, cobalt, iron, and antimony present physiological and ecological challenges that are best addressed through minimization of exposure and dispersion. A method for encapsulating hazardous cations is provided comprising supplying a pretreated substrate containing the cations; contacting the substrate with an organo-silane compound to form a coating on the substrate; and allowing the coating to cure. A medium for containing hazardous cations is also provided, comprising a substrate having ion-exchange capacity and a silane-containing coating on the substrate.

  9. Microsecond molecular dynamics simulations of Mg²⁺- and K⁺-bound E1 intermediate states of the calcium pump.

    Directory of Open Access Journals (Sweden)

    L Michel Espinoza-Fonseca

    Full Text Available We have performed microsecond molecular dynamics (MD simulations to characterize the structural dynamics of cation-bound E1 intermediate states of the calcium pump (sarcoendoplasmic reticulum Ca²⁺-ATPase, SERCA in atomic detail, including a lipid bilayer with aqueous solution on both sides. X-ray crystallography with 40 mM Mg²⁺ in the absence of Ca²⁺ has shown that SERCA adopts an E1 structure with transmembrane Ca²⁺-binding sites I and II exposed to the cytosol, stabilized by a single Mg²⁺ bound to a hybrid binding site I'. This Mg²⁺-bound E1 intermediate state, designated E1•Mg²⁺, is proposed to constitute a functional SERCA intermediate that catalyzes the transition from E2 to E1•2Ca²⁺ by facilitating H⁺/Ca²⁺ exchange. To test this hypothesis, we performed two independent MD simulations based on the E1•Mg²⁺ crystal structure, starting in the presence or absence of initially-bound Mg²⁺. Both simulations were performed for 1 µs in a solution containing 100 mM K⁺ and 5 mM Mg²⁺ in the absence of Ca²⁺, mimicking muscle cytosol during relaxation. In the presence of initially-bound Mg²⁺, SERCA site I' maintained Mg²⁺ binding during the entire MD trajectory, and the cytosolic headpiece maintained a semi-open structure. In the absence of initially-bound Mg²⁺, two K⁺ ions rapidly bound to sites I and I' and stayed loosely bound during most of the simulation, while the cytosolic headpiece shifted gradually to a more open structure. Thus MD simulations predict that both E1•Mg²⁺ and E•2K+ intermediate states of SERCA are populated in solution in the absence of Ca²⁺, with the more open 2K+-bound state being more abundant at physiological ion concentrations. We propose that the E1•2K⁺ state acts as a functional intermediate that facilitates the E2 to E1•2Ca²⁺ transition through two mechanisms: by pre-organizing transport sites for Ca²⁺ binding, and by partially opening the

  10. Mixed cation effect in sodium aluminosilicate glasses

    DEFF Research Database (Denmark)

    Kjeldsen, Jonas; Smedskjær, Morten Mattrup; Mauro, John C.;

    , network structure, and the resistances associated with the deformation processes in mixed cation glasses by partially substituting magnesium for calcium and calcium for lithium in sodium aluminosilicate glasses. We use Raman and 27Al NMR spectroscopies to obtain insights into the structural and...

  11. Sorption of alkylammonium cations on montmorillonite

    Czech Academy of Sciences Publication Activity Database

    Navrátilová, Z.; Wojtowicz, P.; Vaculíková, Lenka; Šugárková, Věra

    2007-01-01

    Roč. 4, 3/147/ (2007), s. 59-65. ISSN 1214-9705 R&D Projects: GA ČR GA205/05/0871 Institutional research plan: CEZ:AV0Z30860518 Keywords : montmorillonite * adsorption * alkylammonium cations Subject RIV: CB - Analytical Chemistry, Separation

  12. Cationic flotation of some lithium ores

    International Nuclear Information System (INIS)

    The cationic flotation of some lithium ores (spodumene, amblygonite, petalite, lepidolite) is studied by the measure of zeta potential and micro-flotation tests in Hallimond tube. The effect of some modifier agents (corn starch, meta sodium silicate) on the lithium flotation is studied. (M.A.C.)

  13. Simultaneous anion and cation mobility in polypyrrole

    DEFF Research Database (Denmark)

    Skaarup, Steen; Bay, Lasse; Vidanapathirana, K.;

    2003-01-01

    Polypyrrole (PPy) polymer films permanently doped with large, immobile anion dodecyl benzene sulfonate (DBS) have been characterized by cyclic voltammetry in order to clarify the roles of cations and anions in the aqueous electrolyte as mobile ions in the film. Aqueous solutions of 0.05-0.1 M alk...

  14. A CATIONIC POLYACRYLAMIDE DISPERSION SYNTHESIS BY DISPERSION POLYMERIZATION IN AQUEOUS SOLUTION

    OpenAIRE

    Yufeng Wang; Kefu Chen; Lihuan Mo; Huiren Hu,

    2011-01-01

    A cationic polyacrylamide (CPAM) dispersion, the copolymer of acrylamide (AM) and acryloyloxyethyltrimethyl ammonium chloride (DAC), has been synthesized through dispersion polymerization in aqueous ammonium sulfate ((NH4)2SO4) solution. The polymerization was initiated by tert-butyl hydroperoxide (TBHP) and ferrisulfas (FeSO4) using poly(dimethyl diallyl ammonium chloride) (PDMDAAC) as the stabilizer. At the optimal reaction conditions, the relative molecular weight of the CPAM dispersion wa...

  15. Three-body scattering at intermediate energies

    International Nuclear Information System (INIS)

    The Faddeev equation for three-body scattering at arbitrary energies is formulated in momentum space and directly solved in terms of momentum vectors without employing a partial-wave decomposition. In its simplest form, the Faddeev equation for identical bosons, which we are using, is a three-dimensional integral equation in five variables, magnitudes of relative momenta and angles. This equation is solved through Pade summation. Based on a Malfliet-Tjon-type potential, the numerical feasibility and stability of the algorithm for solving the Faddeev equation is demonstrated. Special attention is given to the selection of independent variables and the treatment of three-body breakup singularities with a spline-based method. The elastic differential cross section, semiexclusive d(N,N') cross sections, and total cross sections of both elastic and breakup processes in the intermediate-energy range up to about 1 GeV are calculated and the convergence of the multiple-scattering series is investigated in every case. In general, a truncation in the first or second order in the two-body t matrix is quite insufficient

  16. Three-Body Scattering at Intermediate Energies

    CERN Document Server

    Liu, H; Glöckle, W; Elster, Ch.

    2004-01-01

    The Faddeev equation for three-body scattering at arbitrary energies is formulated in momentum space and directly solved in terms of momentum vectors without employing a partial wave decomposition. In its simplest form the Faddeev equation for identical bosons, which we are using, is a three-dimensional integral equation in five variables, magnitudes of relative momenta and angles. This equation is solved through Pade summation. Based on a Malfliet-Tjon-type potential, the numerical feasibility and stability of the algorithm for solving the Faddeev equation is demonstrated. Special attention is given to the selection of independent variables and the treatment of three-body break-up singularities with a spline based method. The elastic differential cross section, semi-exclusive d(N,N') cross sections and total cross sections of both elastic and breakup processes in the intermediate energy range up to about 1 GeV are calculated and the convergence of the multiple scattering series is investigated in every case....

  17. Intermediate view synthesis from stereoscopic images

    Institute of Scientific and Technical Information of China (English)

    Lü Chaohui; An Ping; Zhang Zhaoyang

    2005-01-01

    A new method is proposed for synthesizing intermediate views from a pair of stereoscopic images. In order to synthesize high-quality intermediate views, the block matching method together with a simplified multi-window technique and dynamic programming is used in the process of disparity estimation. Then occlusion detection is performed to locate occluded regions and their disparities are compensated. After the projecton of the left-to-right and right-to-left disparities onto the intermediate image, intermediate view is synthesized considering occluded regions. Experimental results show that our synthesis method can obtain intermediate views with higher quality.

  18. Theory of Square-Wave Voltammetry of Two-Electron Reduction with the Adsorption of Intermediate

    OpenAIRE

    Milivoj Lovrić; Šebojka Komorsky-Lovrić

    2012-01-01

    Thermodynamically unstable intermediate of fast and reversible two-electron electrode reaction can be stabilized by the adsorption to the electrode surface. In square-wave voltammetry of this reaction mechanism, the split response may appear if the electrode surface is not completely covered by the adsorbed intermediate. The dependence of the difference between the net peak potentials of the prepeak and postpeak on the square-wave frequency is analyzed theoretically. This relationship can be ...

  19. Vizualization of intermediate state near metamagnetic phase transition in ErFeO3

    International Nuclear Information System (INIS)

    Visualization of intermediate magnetic state in ErFeO3 plates during 1 order metamagnetic phase transition in magnetic field parallel to Er3+ ion Ising axis is first carried out at T=1.6 K. The range of intermediate state exsistence and domain sizes are determined. Possible mechanisms of intermediatestate thermodynamical stabilization and its visualization conditions in ErFeO3 plates are analysed

  20. Beyond interfacial anion/cation pairing: The role of Cu(I) coordination chemistry in additive-controlled copper plating

    International Nuclear Information System (INIS)

    Highlights: ► We study synergistic and antagonistic ensemble effects of various polymeric suppressor additives and MPS relevant for copper electroplating. ► Type-I suppressors (e.g. PEGs) show a purely antagonistic interaction with MPS. ► Type-II suppressors (e.g. PEIs) show a purely synergistic interaction with MPS. ► Hybrid suppressors (e.g. Imep) reveal both synergistic and antagonistic effects depending on the MPS concentration. ► We identify a combination of Cu(I) coordination chemistry and an inner salt formation as key to the understanding of the suppressing mode of polymeric leveler additives. - Abstract: This study reinvestigates the electrochemical characteristics of three different suppressor additives that are used in context of industrial copper plating (Damascene, Through-Silicon-Via). It is the particular aim of this contribution to further substantiate our recently introduced classification scheme of suppressor chemistries that relies on their antagonistic and synergistic interplay with MPS (mercaptopropane sulfonic acid/sulfonate). The latter appears as intermediate species in the course of copper electrodeposition in the presence of SPS (bis-(sodium-sulfopropyl)-disulfide). Both the linear sweep voltammetry and potential transient experiments reveal a purely antagonistic interaction between PAG (polyalkylene glycol) based suppressor ensembles and the SPS (MPS precursor) which is rationalized in terms of the coordinative dissolution of a hyper-branched PAG-Cu(I)-Cl coordination network by the MPS. Such purely antagonistic suppressor/MPS interplay is our criterion for a so-called type-I suppressor. A purely synergistic suppressor/MPS interaction is observed for the PEI (polyethylene-imine) which can be considered as a prototypical type-II suppressor. Beyond classical interfacial anion/cation pairing the partly protonated, poly-cationic PEI is capable to form MPS-stabilized Cu(I) adducts. Their suppressing effect relies on an in situ hyper

  1. Experimental and theoretical study on interaction of the potassium cation with antamanide

    International Nuclear Information System (INIS)

    Graphical abstract: - Highlights: • Stability of the antamanide – K+ complex was determined. • Quantum mechanical DFT calculations were applied. • The structure of the resulting complex was predicted. - Abstract: On the basis of extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium K+ (aq) + 1·Na+ (nb) ⇄1·K+ (nb) + Na+ (aq) taking part in the two-phase water–nitrobenzene system (1 = antamanide; aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log Kex (K+, 1 · Na+) = 0.2 ± 0.1. Further, the stability constant of the 1 · K+ complex in nitrobenzene saturated with water was calculated for a temperature of 25 °C: log βnb (1 · K+) = 4.7 ± 0.2. Finally, by using quantum mechanical DFT calculations, the most probable structure of the cationic complex species 1 · K+ was derived. In the resulting complex, the “central” cation K+ is bound by four bond interactions to the corresponding four carbonyl oxygen atoms of the parent ligand 1. Besides, the whole 1 · K+ complex structure is stabilized by two intramolecular hydrogen bonds. The interaction energy of the considered 1 · K+ complex was found to be −346.6 kJ/mol, confirming also the formation of this cationic species

  2. Triplet State of the Semiquinone–Rieske Cluster as an Intermediate of Electronic Bifurcation Catalyzed by Cytochrome bc 1

    OpenAIRE

    Sarewicz, Marcin; Dutka, Małgorzata; Pintscher, Sebastian; Osyczka, Artur

    2013-01-01

    Efficient energy conversion often requires stabilization of one-electron intermediates within catalytic sites of redox enzymes. While quinol oxidoreductases are known to stabilize semiquinones, one of the famous exceptions includes the quinol oxidation site of cytochrome bc 1 (Qo), for which detection of any intermediate states is extremely difficult. Here we discover a semiquinone at the Qo site (SQo) that is coupled to the reduced Rieske cluster (FeS) via spin–spin exchange interaction. Thi...

  3. Stability Scores: Measuring Coalitional Stability

    OpenAIRE

    Feldman, Michal; Meir, Reshef; Tennenholtz, Moshe

    2011-01-01

    We introduce a measure for the level of stability against coalitional deviations, called \\emph{stability scores}, which generalizes widely used notions of stability in non-cooperative games. We use the proposed measure to compare various Nash equilibria in congestion games, and to quantify the effect of game parameters on coalitional stability. For our main results, we apply stability scores to analyze and compare the Generalized Second Price (GSP) and Vickrey-Clarke-Groves (VCG) ad auctions....

  4. Cationic modified nucleic acids for use in DNA hairpins and parallel triplexes

    DEFF Research Database (Denmark)

    Bomholt, Niels; Filichev, Vyacheslav V; Pedersen, Erik Bjerregaard

    2011-01-01

    Non-nucleosidic DNA monomers comprising partially protonated amines at low pH have been designed and synthesized. The modifications were incorporated into DNA oligonucleotides via standard DNA phosphoramidite synthesis. The ability of cationic modifications to stabilize palindromic DNA hairpins and...... parallel triplexes were evaluated using gel electrophoresis, circular dichroism and thermal denaturation measurements. The non-nucleosidic modifications were found to increase the thermal stability of palindromic hairpins at pH 8.0 as compared with a nucleosidic tetraloop (TCTC). Incorporation of...

  5. Cation-cation interactions, magnetic communication and reactivity of the pentavalent uraniumion [U(NR)2]+

    Energy Technology Data Exchange (ETDEWEB)

    Spencer, Liam P [Los Alamos National Laboratory; Schelter, Eric J [Los Alamos National Laboratory; Boncella, James M [Los Alamos National Laboratory; Yang, Ping [Los Alamos National Laboratory; Gsula, Robyn L [NON LANL; Scott, Brian L [Los Alamos National Laboratory; Thompson, Joe D [Los Alamos National Laboratory; Kiplinger, Jacqueline L [Los Alamos National Laboratory; Batista, Enrique R [Los Alamos National Laboratory

    2009-01-01

    The dimeric bis(imido) uranium complex [{l_brace}U(NtBu)2(I)(tBu2bpy){r_brace}2] (see picture; U green, N blue, I red) has cation-cation interactions between [U(NR)2]+ ions. This f1-f1 system also displays f orbital communication between uranium(V) centers at low temperatures, and can be oxidized to generate uranium(VI) bis(imido) complexes.

  6. Dipicolinate complexes of main group metals with hydrazinium cation

    Indian Academy of Sciences (India)

    K Saravanan; S Govindarajan

    2002-02-01

    Some new coordination complexes of hydrazinium main group metal dipicolinate hydrates of formulae (N2H5)2M(dip)2.H2O (where, M =Ca, Sr, Ba or Pb and = 0, 2, 4 and 3 respectively and dip = dipicolinate), N2H5Bi(dip)2.3H2O and (N2H5)3Bi(dip)3.4H2O have been prepared and characterized by physico-chemical techniques. The infrared spectra of the complexes reveal the presence of tridentate dipicolinate dianions and non-coordinating hydrazinium cations. Conductance measurements show that the mono, di and trihydrazinium complexes behave as 1:1, 2:1 and 3:1 electrolytes respectively, in aqueous solution. Thermal decomposition studies show that these compounds lose water followed by endothermic decomposition of hydrazine to give respective metal hydrogendipicolinate intermediates, which further decompose exothermically to the final product of either metal carbonates (Ca, Sr, Ba and Pb) or metal oxycarbonates (Bi). The coordination numbers around the metal ions differ from compound to compound. The various coordination numbers exhibited by these metals are six (Ca), seven (Ba), eight (Sr) and nine (Pb and Bi). In all the complexes the above coordination number is attained by tridentate dipicolinate dianions and water molecules. The X-ray diffraction patterns of these compounds differ from one another suggesting that they are not isomorphous.

  7. Intermediate inflation from rainbow gravity

    CERN Document Server

    Barrow, John D

    2013-01-01

    It is possible to dualize theories based on deformed dispersion relations and Einstein gravity so as to map them into theories with trivial dispersion relations and rainbow gravity. This often leads to "dual inflation" without the usual breaking of the strong energy condition. We identify the dispersion relations in the original frame which map into "intermediate" inflationary models. These turn out to be particularly simple: power-laws modulated by powers of a logarithm. The fluctuations predicted by these scenarios are near, but not exactly scale-invariant, with a red running spectral index. These dispersion relations deserve further study within the context of quantum gravity and the phenomenon of dimensional reduction in the ultraviolet.

  8. Intermediate Jacobians of moduli spaces

    CERN Document Server

    Arapura, D; Arapura, Donu; Sastry, Pramathanath

    1996-01-01

    Let $SU_X(n,L)$ be the moduli space of rank n semistable vector bundles with fixed determinant L on a smooth projective genus g curve X. Let $SU_X^s(n,L)$ denote the open subset parametrizing stable bundles. We show that if g>3 and n > 1, then the mixed Hodge structure on $H^3(SU_X^s(n, L))$ is pure of type ${(1,2),(2,1)}$ and it carries a natural polarization such that the associated polarized intermediate Jacobian is isomorphic J(X). This is new when deg L and n are not coprime. As a corollary, we obtain a Torelli theorem that says roughly that $SU_X^s(n,L)$ (or $SU_X(n,L)$) determines X. This complements or refines earlier results of Balaji, Kouvidakis-Pantev, Mumford-Newstead, Narasimhan-Ramanan, and Tyurin.

  9. Preparation and Characterization of Cationic PLA-PEG Nanoparticles for Delivery of Plasmid DNA

    Science.gov (United States)

    Zou, Weiwei; Liu, Chunxi; Chen, Zhijin; Zhang, Na

    2009-09-01

    The purpose of the present work was to formulate and evaluate cationic poly(lactic acid)-poly(ethylene glycol) (PLA-PEG) nanoparticles as novel non-viral gene delivery nano-device. Cationic PLA-PEG nanoparticles were prepared by nanoprecipitation method. The gene loaded nanoparticles were obtained by incubating the report gene pEGFP with cationic PLA-PEG nanoparticles. The physicochemical properties (e.g., morphology, particle size, surface charge, DNA binding efficiency) and biological properties (e.g., integrity of the released DNA, protection from nuclease degradation, plasma stability, in vitro cytotoxicity, and in vitro transfection ability in Hela cells) of the gene loaded PLA-PEG nanoparticles were evaluated, respectively. The obtained cationic PLA-PEG nanoparticles and gene loaded nanoparticles were both spherical in shape with average particle size of 89.7 and 128.9 nm, polydispersity index of 0.185 and 0.161, zeta potentials of +28.9 and +16.8 mV, respectively. The obtained cationic PLA-PEG nanoparticles with high binding efficiency (>95%) could protect the loaded DNA from the degradation by nuclease and plasma. The nanoparticles displayed sustained-release properties in vitro and the released DNA maintained its structural and functional integrity. It also showed lower cytotoxicity than Lipofectamine 2000 and could successfully transfect gene into Hela cells even in presence of serum. It could be concluded that the established gene loaded cationic PLA-PEG nanoparticles with excellent properties were promising non-viral nano-device, which had potential to make cancer gene therapy achievable.

  10. Preparation and Characterization of Cationic PLA-PEG Nanoparticles for Delivery of Plasmid DNA

    Directory of Open Access Journals (Sweden)

    Zou Weiwei

    2009-01-01

    Full Text Available Abstract The purpose of the present work was to formulate and evaluate cationic poly(lactic acid-poly(ethylene glycol (PLA-PEG nanoparticles as novel non-viral gene delivery nano-device. Cationic PLA-PEG nanoparticles were prepared by nanoprecipitation method. The gene loaded nanoparticles were obtained by incubating the report gene pEGFP with cationic PLA-PEG nanoparticles. The physicochemical properties (e.g., morphology, particle size, surface charge, DNA binding efficiency and biological properties (e.g., integrity of the released DNA, protection from nuclease degradation, plasma stability, in vitro cytotoxicity, and in vitro transfection ability in Hela cells of the gene loaded PLA-PEG nanoparticles were evaluated, respectively. The obtained cationic PLA-PEG nanoparticles and gene loaded nanoparticles were both spherical in shape with average particle size of 89.7 and 128.9 nm, polydispersity index of 0.185 and 0.161, zeta potentials of +28.9 and +16.8 mV, respectively. The obtained cationic PLA-PEG nanoparticles with high binding efficiency (>95% could protect the loaded DNA from the degradation by nuclease and plasma. The nanoparticles displayed sustained-release properties in vitro and the released DNA maintained its structural and functional integrity. It also showed lower cytotoxicity than Lipofectamine 2000 and could successfully transfect gene into Hela cells even in presence of serum. It could be concluded that the established gene loaded cationic PLA-PEG nanoparticles with excellent properties were promising non-viral nano-device, which had potential to make cancer gene therapy achievable.

  11. Intermediate processes in nuclear reactions

    International Nuclear Information System (INIS)

    The main results presented here cannot be interpreted in terms of the direct reaction model or the statistical models and one can more or less explicitely use some nuclear configurations for their interpretation. The first chapter deals with the so-called second order intermediate structures observed in the elastic and inelastic proton scattering on 66Zn and 70Ge targets in the energetic regions of some isobaric analog resonances. A formal theory for their interpretation is developed and the comparison with the experimental data is presented. New experimental results on the resonant structures observed in the elastic and inelastic scattering of 12C on 24Mg are presented in the second chapter. Detailed statistical analysis and their interpretation is presented too. Charge equilibration in deep inelastic collisions is the main subject of the third chapter. The experimental results obtained by the 98Mo + 154Sm collision at 12 MeV/n, a quantum treatment of a damped harmonic oscillator and the comparison with the experimental data are given. In the last chapter, some results on the existence of two other processes which could candidate to be involved in the main topic are presented. Those processes are: the fast fragmentation and preequilibrium charged particles emission. All these processes originate in the excitation of some simple configurations which can be seen on ''doorway'' states (''Hallway'' in the case of the second intermediate structures). The coupling of these states to other more complicated excitation modes of the nuclei and to outgoing channel=gives the possibility to study the nuclear dynamics. This justifies the interest for their detailed theoretical and experimental investigations. (author)

  12. Cu2Se and Cu Nanocrystals as Local Sources of Copper in Thermally Activated In Situ Cation Exchange

    KAUST Repository

    Casu, Alberto

    2016-01-27

    Among the different synthesis approaches to colloidal nanocrystals a recently developed toolkit is represented by cation exchange reactions, where the use of template nanocrystals gives access to materials that would be hardly attainable via direct synthesis. Besides, post-synthetic treatments, such as thermally activated solid state reactions, represent a further flourishing route to promote finely controlled cation exchange. Here, we report that, upon in situ heating in a transmission electron microscope, Cu2Se nanocrystals deposited on an amorphous solid substrate undergo partial loss of Cu atoms, which are then engaged in local cation exchange reactions with Cu “acceptors” phases represented by rod- and wire- shaped CdSe nanocrystals. This thermal treatment slowly transforms the initial CdSe nanocrystals into Cu2-xSe nanocrystals, through the complete sublimation of Cd and the partial sublimation of Se atoms. Both Cu “donor” and “acceptor” particles were not always in direct contact with each other, hence the gradual transfer of Cu species from Cu2Se or metallic Cu to CdSe nanocrystals was mediated by the substrate and depended on the distance between the donor and acceptor nanostructures. Differently from what happens in the comparably faster cation exchange reactions performed in liquid solution, this study shows that slow cation exchange reactions can be performed at the solid state, and helps to shed light on the intermediate steps involved in such reactions.

  13. Cd/Hg cationic substitution in magic-sized CdSe clusters: Optical characterization and theoretical studies

    International Nuclear Information System (INIS)

    Highlights: • HgSe magic-sized clusters were prepared via Cd/Hg cationic exchange in pyridine. • Upon cationic exchange CdSe clusters behave differently from quantum dots or rods. • Theoretical calculations of magic-sized clusters agree well with experimental data. - Abstract: We examine conversion of magic-sized CdSe clusters (MSCs) into HgSe ones by means of Cd/Hg cation exchange. With this procedure Cd8Cd17– and Cd32–selenide clusters can be converted into corresponding Hg8–, Hg17– and Hg32–selenide ones. Upon cationic exchange MSCs behavior differs from that of bulkier counterparts – larger (2–3 nm) quantum dots. Unlike CdSe colloidal quantum dots, magic-sized clusters are converted in fast and complete manner without a formation of intermediate mixed CdxHg1−x compounds that was established on the basis of optical absorption spectroscopy and chemical composition analysis. These assumptions were supported by DFT quantum chemical calculations performed for Cd8–, Cd17– and Hg8–, Hg17–selenide model clusters. Energies of experimental and calculated optical transitions were compared in order to prove the isostructural character of cationic substitution in magic-sized clusters

  14. Cation distribution and mixing thermodynamics in Fe/Ni thiospinels

    Science.gov (United States)

    Haider, Saima; Grau-Crespo, Ricardo; Devey, Antony J.; de Leeuw, Nora H.

    2012-07-01

    The structural analogy between Ni-doped greigite minerals (Fe3S4) and the (Fe, Ni)S clusters present in biological enzymes has led to suggestions that these minerals could have acted as catalysts for the origin of life. However, little is known about the distribution and stability of Ni dopants in the greigite structure. We present here a theoretical investigation of mixed thiospinels (Fe1-xNix)3S4, using a combination of density functional theory (DFT) calculations and Monte Carlo simulations. We find that the equilibrium distribution of the cations deviates significantly from a random distribution: at low Ni concentrations, Ni dopants are preferably located in octahedral sites, while at higher Ni concentrations the tetrahedral sites become much more favourable. The thermodynamic mixing behaviour between greigite and polydymite (Ni3S4) is dominated by the stability field of violarite (FeNi2S4), for which the mixing enthalpy exhibits a deep negative minimum. The analysis of the free energy of mixing shows that Ni doping of greigite is very unstable with respect to the formation of a separate violarite phase. The calculated variation of the cubic cell parameter with composition is found to be non-linear, exhibiting significant deviation from Vegard’s law, but in agreement with experiment.

  15. Ideal Stabilization

    CERN Document Server

    Nesterenko, Mikhail

    2009-01-01

    We define and explore the concept of ideal stabilization. The program is ideally stabilizing if its every state is legitimate. Ideal stabilization allows the specification designer to prescribe with arbitrary degree of precision not only the fault-free program behavior but also its recovery operation. Specifications may or may not mention all possible states. We identify approaches to designing ideal stabilization to both kinds of specifications. For the first kind, we state the necessary condition for an ideally stabilizing solution. On the basis of this condition we prove that there is no ideally stabilizing solution to the leader election problem. We illustrate the utility of the concept by providing examples of well-known programs and proving them ideally stabilizing. Specifically, we prove ideal stabilization of the conflict manager, the alternator, the propagation of information with feedback and the alternating bit protocol.

  16. Effects of intermediate load on performance limitations in excitation control

    Directory of Open Access Journals (Sweden)

    Pichai Aree

    2008-05-01

    Full Text Available The stability of excitation control systems is of great concern in power system operations. In this paper, the effects of intermediate load on performance limitation in excitation control are studied. The results reveal that the open-loop characteristic of synchronous machine’s flux linkage can be changed from minimum to non-minimum phase at a high level of intermediate load. This change leads to instability of synchronous machines under manual excitation control. A particular emphasis is also given to investigate the fundamental limitations in excitation control, imposed by non-minimum phases with regard to the open-loop right-half-plane (ORHP pole. The study demonstrates the difficulties of excitation control tuning to achieve the desired performance and robustness under the ORHP pole occurrence. Moreover, this paper shows the conditional stability in excitation control loop, where either an increase or decrease of the exciter gain causes a destabilization of the system’s stability. Frequency response techniques are used for these investigations.

  17. Structurally Distinct Cation Channelrhodopsins from Cryptophyte Algae.

    Science.gov (United States)

    Govorunova, Elena G; Sineshchekov, Oleg A; Spudich, John L

    2016-06-01

    Microbial rhodopsins are remarkable for the diversity of their functional mechanisms based on the same protein scaffold. A class of rhodopsins from cryptophyte algae show close sequence homology with haloarchaeal rhodopsin proton pumps rather than with previously known channelrhodopsins from chlorophyte (green) algae. In particular, both aspartate residues that occupy the positions of the chromophore Schiff base proton acceptor and donor, a hallmark of rhodopsin proton pumps, are conserved in these cryptophyte proteins. We expressed the corresponding polynucleotides in human embryonic kidney (HEK293) cells and studied electrogenic properties of the encoded proteins with whole-cell patch-clamp recording. Despite their lack of residues characteristic of the chlorophyte cation channels, these proteins are cation-conducting channelrhodopsins that carry out light-gated passive transport of Na(+) and H(+). These findings show that channel function in rhodopsins has evolved via multiple routes. PMID:27233115

  18. Radiation chemistry of aromatic dimer radical cations

    International Nuclear Information System (INIS)

    π-π Interactions of aromatic molecules are paid attention much in many fields, especially biology, chemistry, and applied physics, represented as protein, DNA, electron donor-accepter complexes, charge transfers, and self assembly molecules. Aromatic molecules including benzene rings are the simplest case to study the π-π interactions. To interpret the charge resonance (CR) structure in the dimer radical cations, spectroscopic and ESR methods have been carried out. The spectroscopic study on the dimer radical ion of molecules with two chromophores would be profitable to identify the electronic and configurational properties. In this article, dynamics of the dimer radical cation of benzenes, polystyrenes, and resist polymers is described on the basis of direct observation of CR band by the nanosecond pulse radiolysis and low temperature γ-radiolysis methods. (author)

  19. Mechanism of adsorption of cations onto rocks

    International Nuclear Information System (INIS)

    Adsorption behavior of cations onto granite was investigated. The distribution coefficient (Kd) of Sr2+ and Ba2+ onto granite was determined in the solution of which pH was ranged from 3.5 to 11.3 and ionic strength was set at 10-2 and 10-1. The Kd values were found to increase with increasing pH and with deceasing ionic strength. The obtained data were successfully analyzed by applying an electrical double layer model. The optimum parameter values of the double layer electrostatics and adsorption reactions were obtained, and the mechanism of adsorption of cations onto granite was discussed. Feldspar was found to play an important role in their adsorption. (author)

  20. Ultrafast dynamics of water in cationic micelles.

    Science.gov (United States)

    Dokter, Adriaan M; Woutersen, Sander; Bakker, Huib J

    2007-03-28

    The effect of confinement on the dynamical properties of liquid water is investigated for water enclosed in cationic reverse micelles. The authors performed mid-infrared ultrafast pump-probe spectroscopy on the OH-stretch vibration of isotopically diluted HDO in D(2)O in cetyltrimethylammonium bromide (CTAB) reverse micelles of various sizes. The authors observe that the surfactant counterions are inhomogeneously distributed throughout the reverse micelle, and that regions of extreme salinity occur near the interfacial Stern layer. The authors find that the water molecules in the core of the micelles show similar orientational dynamics as bulk water, and that water molecules in the counterion-rich interfacial region are much less mobile. An explicit comparison is made with the dynamics of water confined in anionic sodium bis(2-ethythexyl) sulfosuccinate (AOT) reverse micelles. The authors find that interfacial water in cationic CTAB reverse micelles has a higher orientational mobility than water in anionic AOT reverse micelles. PMID:17411144

  1. Ultrafast dynamics of water in cationic micelles

    Science.gov (United States)

    Dokter, Adriaan M.; Woutersen, Sander; Bakker, Huib J.

    2007-03-01

    The effect of confinement on the dynamical properties of liquid water is investigated for water enclosed in cationic reverse micelles. The authors performed mid-infrared ultrafast pump-probe spectroscopy on the OH-stretch vibration of isotopically diluted HDO in D2O in cetyltrimethylammonium bromide (CTAB) reverse micelles of various sizes. The authors observe that the surfactant counterions are inhomogeneously distributed throughout the reverse micelle, and that regions of extreme salinity occur near the interfacial Stern layer. The authors find that the water molecules in the core of the micelles show similar orientational dynamics as bulk water, and that water molecules in the counterion-rich interfacial region are much less mobile. An explicit comparison is made with the dynamics of water confined in anionic sodium bis(2-ethythexyl) sulfosuccinate (AOT) reverse micelles. The authors find that interfacial water in cationic CTAB reverse micelles has a higher orientational mobility than water in anionic AOT reverse micelles.

  2. Proton dynamics investigation for dimethyl ammonium cation

    International Nuclear Information System (INIS)

    Proton dynamics in dimethyl ammonium cation has been investigated by means of NMR and spin echo methods in polycrystalline salts [NH2(CH3)2]+Bi2J9- and [NH2(CH3)2]+SbJ9-. Spin-lattice relaxation time as well as second moment of NMR line have been measured for influence study of crystal structure changes on proton dynamics

  3. Alkaline earth cation extraction from acid solution

    Science.gov (United States)

    Dietz, Mark; Horwitz, E. Philip

    2003-01-01

    An extractant medium for extracting alkaline earth cations from an aqueous acidic sample solution is described as are a method and apparatus for using the same. The separation medium is free of diluent, free-flowing and particulate, and comprises a Crown ether that is a 4,4'(5')[C.sub.4 -C.sub.8 -alkylcyclohexano]18-Crown-6 dispersed on an inert substrate material.

  4. Rabbit cationic protein enhances leukocyte adhesiveness.

    OpenAIRE

    Oseas, R S; Allen, J; Yang, H. H.; Baehner, R. L.; Boxer, L A

    1981-01-01

    Cationic protein purified from rabbit peritoneal polymorphonuclear leukocytes (PMN) was demonstrated to incite autoaggregation of the rabbit PMN and promote adhesiveness of human PMN to endothelial cells. PMN aggregation induced by supernatants derived from secretory PMN was blocked by a specific anticationic protein antibody. These studies reveal that a positively charged protein derived from the PMN can alter surface properties of the PMN itself and imply a role for this protein in PMN immo...

  5. Limited data speaker identification

    Indian Academy of Sciences (India)

    H S Jayanna; S R Mahadeva Prasanna

    2010-10-01

    In this paper, the task of identifying the speaker using limited training and testing data is addressed. Speaker identification system is viewed as four stages namely, analysis, feature extraction, modelling and testing. The speaker identification performance depends on the techniques employed in these stages. As demonstrated by different experiments, in case of limited training and testing data condition, owing to less data, existing techniques in each stage will not provide good performance. This work demonstrates the following: multiple frame size and rate (MFSR) analysis provides improvement in the analysis stage, combination of mel frequency cepstral coefficients (MFCC), its temporal derivatives $(\\Delta,\\Delta \\Delta)$, linear prediction residual (LPR) and linear prediction residual phase (LPRP) features provides improvement in the feature extraction stage and combination of learning vector quantization (LVQ) and gaussian mixture model – universal background model (GMM–UBM) provides improvement in the modelling stage. The performance is further improved by integrating the proposed techniques at the respective stages and combining the evidences from them at the testing stage. To achieve this, we propose strength voting (SV), weighted borda count (WBC) and supporting systems (SS) as combining methods at the abstract, rank and measurement levels, respectively. Finally, the proposed hierarchical combination (HC) method integrating these three methods provides significant improvement in the performance. Based on these explorations, this work proposes a scheme for speaker identification under limited training and testing data.

  6. Low cation coordination in oxide melts

    Energy Technology Data Exchange (ETDEWEB)

    Skinner, Lawrie [State University of New York, Stony Brook; Benmore, Chris J [Argonne National Laboratory (ANL); Du, Jincheng [University of North Texas; Weber, Richard [Argonne National Laboratory (ANL); Neuefeind, Joerg C [ORNL; Tumber, Sonia [Materials Development, Inc., Evanston, IL; Parise, John B [Stony Brook University (SUNY)

    2014-01-01

    The complete set of Faber-Ziman partial pair distribution functions for a rare earth oxide liquid were measured for the first time by combining aerodynamic levitation, neutron diffraction, high energy x-ray diffraction and isomorphic substitution using Y2 O3 and Ho2 O3 melts. The average Y- O coordination is measured to be 5.5(2), which is significantly less than the octahedral coordination of crystalline Y2 O3 (or Ho2 O3 ). Investigation of high temperature La2 O3 , ZrO2 , SiO2 , and Al2 O3 melts by x-ray diffraction and molecular dynamics simulations also show lower-than-crystal cation- oxygen coordination. These measurements suggest a general trend towards lower M-O coordination compared to their crystalline counterparts. It is found that this coordination number drop is larger for lower field strength, larger radius cations and is negligible for high field strength (network forming) cations. These findings have broad implications for predicting the local structure and related physical properties of metal-oxide melts and oxide glasses.

  7. Cation-Exchange Equilibria with Fused Salts

    International Nuclear Information System (INIS)

    Solute distributions of alkali metal, alkaline- earth, transition metal, and actinide ions have been studied in fused salt-cation exchanger systems. The fused salts employed were alkali halides and nitrates. The cation exchangers used were natural zeolites, synthetic zeolites, high-porosity glasses, and molten oxide mixtures. The molten exchangers were composed of Na2O and B2O3 in various proportions. The relative quantities not only determined the exchanger capacity and electrolyte penetration but also produced distribution coefficients for a given solute which varied over several orders of magnitude. Moreover, they produced marked reversals in the selectivity series. Additional studies on the anion distributions, miscibility diagrams, vapour pressures and diffusion rates in these systems have elucidated the mechanisms involved and the relation of selectivity to solute properties, system thermodynamics, exchanger structure and available functional groups. In the region of high Na2O composition, the distribution coefficients for mono-, di- and trivalent cations in NaCl have not only the same order of selectivity found in Dowex 50-HCl systems but also similar values for the distribution coefficients. The results are summarized qualitatively and compared to behaviour in aqueous systems (Table VII). (author)

  8. Switching between dynamic states in intermediate-length Josephson junctions

    OpenAIRE

    S. Pagano; Sørensen, Mads Peter; Parmentier, R. D.; Christiansen, Peter Leth; Skovgaard, Ove; Mygind, Jesper; Pedersen, Niels Falsig; Samuelsen, Mogens Rugholm

    1986-01-01

    The appearance of zero-field steps (ZFS’s) in the current-voltage characteristics of intermediate-length overlap-geometry Josephson tunnel junctions described by a perturbed sine-Gordon equation (PSGE) is associated with the growth of parametrically excited instabilities of the McCumber background curve (MCB). A linear stability analysis of a McCumber solution of the PSGE in the asymptotic linear region of the MCB and in the absence of magnetic field yields a Hill’s equation which predicts ho...

  9. On financial equilibrium with intermediation costs

    DEFF Research Database (Denmark)

    Markeprand, Tobias Ejnar

    2008-01-01

    This paper studies the set of competitive equilibria in financial economies with intermediation costs. We consider an arbitrary dividend structure, which includes options and equity with limited liabilities.We show a general existence result and upper-hemi continuity of the equilibrium...... correspondence. Finally, we prove that when intermediation costs approach zero, unbounded volume of asset trades is a necessary and sufficient condition, provided that, there is no financial equilibrium without intermediation costs....

  10. FINANCIAL INTERMEDIATION, ENTREPRENEURSHIP AND ECONOMIC GROWTH

    OpenAIRE

    Wenli Cheng

    2007-01-01

    This paper presents a simple general equilibrium model of financial intermediation, entrepreneurship and economic growth. In this model, the role of financial intermediation is to pool savings and to lend the pooled funds to an entrepreneur, who in turn invests the funds in a new production technology. The adoption of the new production technology improves individual real income. Thus financial intermediation promotes economic growth through affecting individuals’ saving behaviour and enabl...

  11. How should Financial Intermediation Services be Taxed?

    OpenAIRE

    Lockwood, Ben

    2010-01-01

    This paper considers the optimal taxation of savings intermediation and payment services in a dynamic general equilibrium setting, when the government can also use consumption and income taxes. When payment services are used in strict proportion to final consumption, and the cost of intermediation services is fixed and the same across firms, the optimal taxes are generally indeterminate. But, when firms differ exogenously in the cost of intermediation services, the tax on savings intermediati...

  12. Effect of Extra-Framework Cations of LTL Nanozeolites to Inhibit Oil Oxidation

    Science.gov (United States)

    Tan, Kok-Hou; Cham, Hooi-Ying; Awala, Hussein; Ling, Tau Chuan; Mukti, Rino R.; Wong, Ka-Lun; Mintova, Svetlana; Ng, Eng-Poh

    2015-06-01

    Lubricant oils take significant part in current health and environmental considerations since they are an integral and indispensable component of modern technology. Antioxidants are probably the most important additives used in oils because oxidative deterioration plays a major role in oil degradation. Zeolite nanoparticles (NPs) have been proven as another option as green antioxidants in oil formulation. The anti-oxidative behavior of zeolite NPs is obvious; however, the phenomenon is still under investigation. Herein, a study of the effect of extra-framework cations stabilized on Linde Type L (LTL) zeolite NPs (ca. 20 nm) on inhibition of oxidation in palm oil-based lubricant oil is reported. Hydrophilic LTL zeolites with a Si/Al ratio of 3.2 containing four different inorganic cations (Li+, Na+, K+, Ca2+) were applied. The oxidation of the lubricant oil was followed by visual observation, colorimetry, fourier transform infrared (FTIR) spectroscopy, 1H NMR spectroscopy, total acid number (TAN), and rheology analyses. The effect of extra-framework cations to slow down the rate of oil oxidation and to control the viscosity of oil is demonstrated. The degradation rate of the lubricant oil samples is decreased considerably as the polarizability of cation is increased with the presence of zeolite NPs. More importantly, the microporous zeolite NPs have a great influence in halting the steps that lead to the polymerization of the oils and thus increasing the lifetime of oils.

  13. Effect of Sulfuric and Triflic Acids on the Hydration of Vanadium Cations: An ab Initio Study.

    Science.gov (United States)

    Sepehr, Fatemeh; Paddison, Stephen J

    2015-06-01

    Vanadium redox flow batteries (VRFBs) may be a promising solution for large-scale energy storage applications, but the crossover of any of the redox active species V(2+), V(3+), VO(2+), and VO2(+) through the ion exchange membrane will result in self-discharge of the battery. Hence, a molecular level understanding of the states of vanadium cations in the highly acidic environment of a VRFB is needed. We examine the effects of sulfuric and triflic (CF3SO3H) acids on the hydration of vanadium species as they mimic the electrolyte and functional group of perfluorosulfonic acid (PFSA) membranes. Hybrid density functional theory in conjunction with a continuum solvation model was utilized to obtain the local structures of the hydrated vanadium cations in proximity to H2SO4, CF3SO3H, and their conjugate anions. The results indicate that none of these species covalently bond to the vanadium cations. The hydration structure of V(3+) is more distorted than that of V(2+) in an acidic medium. The oxo-group of VO2(+) is protonated by either acid, in contrast to VO(2+) which is not protonated. The atomic partial charge of the four oxidation states of vanadium varies from +1.7 to +2.0. These results provide the local solvation structures of vanadium cations in the VRFBs environment that are directly related to the electrolytes stability and diffusion of vanadium ions into the membrane. PMID:25954916

  14. Formation of Stable Cationic Lipid/DNA Complexes for Gene Transfer

    Science.gov (United States)

    Hofland, Hans E. J.; Shephard, Lee; Sullivan, Sean M.

    1996-07-01

    Stable cationic lipid/DNA complexes were formed by solubilizing cationic liposomes with 1% octylglucoside and complexing a DNA plasmid with the lipid in the presence of detergent. Removal of the detergent by dialysis yielded a lipid/DNA suspension that was able to transfect tissue culture cells up to 90 days after formation with no loss in activity. Similar levels of gene transfer were obtained by mixing the cationic lipid in a liposome form with DNA just prior to cell addition. However, expression was completely lost 24 hr after mixing. The transfection efficiency of the stable complex in 15% fetal calf serum was 30% of that obtained in the absence of serum, whereas the transient complex was completely inactivated with 2% fetal calf serum. A 90-day stability study comparing various storage conditions showed that the stable complex could be stored frozen or as a suspension at 4 degrees C with no loss in transfection efficiency. Centrifugation of the stable complex produced a pellet that contained approximately 90% of the DNA and 10% of the lipid. Transfection of cells with the resuspended pellet and the supernatant showed that the majority of the transfection activity was in the pellet and all the toxicity was in the supernatant. Formation of a stable cationic lipid/DNA complex has produced a transfection vehicle that can be stored indefinitely, can be concentrated with no loss in transfection efficiency, and the toxicity levels can be greatly reduced when the active complex is isolated from the uncomplexed lipid.

  15. Misfit strain driven cation inter-diffusion across an epitaxial multiferroic thin film interface

    Energy Technology Data Exchange (ETDEWEB)

    Sankara Rama Krishnan, P. S.; Munroe, Paul; Nagarajan, V. [School of Materials Science and Engineering, The University of New South Wales, Sydney, New South Wales 2052 (Australia); Morozovska, Anna N.; Eliseev, Eugene A. [Institute of Physics, Institute of Material Sciences, NAS of Ukraine, 03028 Kiev (Ukraine); Ramasse, Quentin M.; Kepaptsoglou, Demie [SuperSTEM laboratory, SciTech Daresbury, Daresbury WA4 4AD (United Kingdom); Liang, Wen-I.; Chu, Ying-Hao [Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu 30010, Taiwan (China)

    2014-02-07

    Cation intermixing at functional oxide interfaces remains a highly controversial area directly relevant to interface-driven nanoelectronic device properties. Here, we systematically explore the cation intermixing in epitaxial (001) oriented multiferroic bismuth ferrite (BFO) grown on a (001) lanthanum aluminate (LAO) substrate. Aberration corrected dedicated scanning transmission electron microscopy and electron energy loss spectroscopy reveal that the interface is not chemically sharp, but with an intermixing of ∼2 nm. The driving force for this process is identified as misfit-driven elastic strain. Landau-Ginzburg-Devonshire-based phenomenological theory was combined with the Sheldon and Shenoy formula in order to understand the influence of boundary conditions and depolarizing fields arising from misfit strain between the LAO substrate and BFO film. The theory predicts the presence of a strong potential gradient at the interface, which decays on moving into the bulk of the film. This potential gradient is significant enough to drive the cation migration across the interface, thereby mitigating the misfit strain. Our results offer new insights on how chemical roughening at oxide interfaces can be effective in stabilizing the structural integrity of the interface without the need for misfit dislocations. These findings offer a general formalism for understanding cation intermixing at highly strained oxide interfaces that are used in nanoelectronic devices.

  16. Interaction of cationic dye/surfactants with Klebsiella K18 capsular polysaccharides: Physico-chemical studies

    Energy Technology Data Exchange (ETDEWEB)

    Nath, Ranendu Kumar, E-mail: rknath1959@gmail.com [Department of Chemistry, Tripura University, Suryamaninagar, Tripura-799130 (India); Singh, Th. Charanjit [Department of Chemistry, D.D.M. College, Khowai, Tripura-799 202 (India); Dasgupta, Satwati [Department of Chemistry, Tripura University, Suryamaninagar, Tripura-799130 (India); Mitra, Asish [Department of Chemistry, MBB College, Agartala, Tripura-799001 (India); Panda, Amiya Kumar [Department of Chemistry, University of North Bengal, P.O. North Bengal University, Dt: Darjeeling, West Bengal-734013 (India)

    2010-05-10

    Physico-chemical studies on the interaction of capsular polysaccharide (SPS) isolated from Klebsiella K18, with cationic dyes and surfactants have been reported. SPS is an integral component of gram-negative bacteria and having glucuronic acid as the potential anionic site, induced strong metachromasy (blue shift {approx} 110 nm) in the cationic dye pinacyanol chloride (PCYN). Reversal of metachromasy was observed upon addition of co-solvents which provides a qualitative measurement of stability and nature of metachromatic compound associated with PCYN-SPS interaction. Thermodynamic parameters such as association constant, changes in free energy, enthalpy and entropy of dye-polymer interaction, were evaluated which revealed the nature of interaction. Studies on fluorescence quenching of acridine orange (AO) was also performed. The interaction of SPS with cationic and cationic-non-ionic mixed surfactant systems have been studied by turbidimetry, spectrophotometry, spectrofluorometry and viscosity measurements. The studies could provide an understanding on the effects of the surfactants on binding with the polymer. The binding was found to be electrostatic in origin and also hydrophobic in nature to a certain extent.

  17. Interaction of cationic dye/surfactants with Klebsiella K18 capsular polysaccharides: Physico-chemical studies

    International Nuclear Information System (INIS)

    Physico-chemical studies on the interaction of capsular polysaccharide (SPS) isolated from Klebsiella K18, with cationic dyes and surfactants have been reported. SPS is an integral component of gram-negative bacteria and having glucuronic acid as the potential anionic site, induced strong metachromasy (blue shift ∼ 110 nm) in the cationic dye pinacyanol chloride (PCYN). Reversal of metachromasy was observed upon addition of co-solvents which provides a qualitative measurement of stability and nature of metachromatic compound associated with PCYN-SPS interaction. Thermodynamic parameters such as association constant, changes in free energy, enthalpy and entropy of dye-polymer interaction, were evaluated which revealed the nature of interaction. Studies on fluorescence quenching of acridine orange (AO) was also performed. The interaction of SPS with cationic and cationic-non-ionic mixed surfactant systems have been studied by turbidimetry, spectrophotometry, spectrofluorometry and viscosity measurements. The studies could provide an understanding on the effects of the surfactants on binding with the polymer. The binding was found to be electrostatic in origin and also hydrophobic in nature to a certain extent.

  18. Cationic Covalent Organic Frameworks: A Simple Platform of Anionic Exchange for Porosity Tuning and Proton Conduction.

    Science.gov (United States)

    Ma, Heping; Liu, Bailing; Li, Bin; Zhang, Liming; Li, Yang-Guang; Tan, Hua-Qiao; Zang, Hong-Ying; Zhu, Guangshan

    2016-05-11

    Mimicking proton conduction mechanism of Nafion to construct novel proton-conducting materials with low cost and high proton conductivity is of wide interest. Herein, we have designed and synthesized a cationic covalent organic framework with high thermal and chemical stability by combining a cationic monomer, ethidium bromide (EB) (3,8-diamino-5-ethyl-6-phenylphenanthridinium bromide), with 1,3,5-triformylphloroglucinol (TFP) in Schiff base reactions. This is the first time that the stable cationic crystalline frameworks allowed for the fabrication of a series of charged COFs (EB-COF:X, X = F, Cl, Br, I) through ion exchange processes. Exchange of the extra framework ions can finely modulate the COFs' porosity and pore sizes at nanoscale. More importantly, by introducing PW12O40(3-) into this porous cationic framework, we can greatly enhance the proton conductivity of ionic COF-based material. To the best of our knowledge, EB-COF:PW12 shows the best proton conductivity at room temperature among ever reported porous organic materials. PMID:27094048

  19. [Antioxidant activity of cationic whey protein isolate].

    Science.gov (United States)

    titova, M E; Komolov, S A; Tikhomirova, N A

    2012-01-01

    The process of lipid peroxidation (LPO) in biological membranes of cells is carried out by free radical mechanism, a feature of which is the interaction of radicals with other molecules. In this work we investigated the antioxidant activity of cationic whey protein isolate, obtained by the cation-exchange chromatography on KM-cellulose from raw cow's milk, in vitro and in vivo. In biological liquids, which are milk, blood serum, fetal fluids, contains a complex of biologically active substances with a unique multifunctional properties, and which are carrying out a protective, antimicrobial, regenerating, antioxidant, immunomodulatory, regulatory and others functions. Contents of the isolate were determined electrophoretically and by its biological activity. Cationic whey protein isolate included lactoperoxidase, lactoferrin, pancreatic RNase, lysozyme and angeogenin. The given isolate significantly has an antioxidant effect in model experimental systems in vitro and therefore may be considered as a factor that can adjust the intensity of lipid oxidation. In model solutions products of lipid oxidation were obtained by oxidation of phosphatidylcholine by hydrogen peroxide in the presence of a source of iron. The composition of the reaction mixture: 0,4 mM H2O2; 50 mcM of hemin; 2 mg/ml L-alpha-phosphatidylcholine from soybean (Sigma, German). Lipid peroxidation products were formed during the incubation of the reaction mixture for two hours at 37 degrees C. In our studies rats in the adaptation period immediately after isolation from the nest obtained from food given orally native cationic whey protein isolate at the concentration three times higher than in fresh cow's milk. On the manifestation of the antioxidant activity of cationic whey protein isolate in vivo evidence decrease of lipid peroxidation products concentration in the blood of rats from the experimental group receipt whey protein isolate in dos 0,6 mg/g for more than 20% (pwhey protein isolate has an

  20. Nanoscale cation motion in TaOx, HfOx and TiOx memristive systems

    Science.gov (United States)

    Wedig, Anja; Luebben, Michael; Cho, Deok-Yong; Moors, Marco; Skaja, Katharina; Rana, Vikas; Hasegawa, Tsuyoshi; Adepalli, Kiran K.; Yildiz, Bilge; Waser, Rainer; Valov, Ilia

    2016-01-01

    A detailed understanding of the resistive switching mechanisms that operate in redox-based resistive random-access memories (ReRAM) is key to controlling these memristive devices and formulating appropriate design rules. Based on distinct fundamental switching mechanisms, two types of ReRAM have emerged: electrochemical metallization memories, in which the mobile species is thought to be metal cations, and valence change memories, in which the mobile species is thought to be oxygen anions (or positively charged oxygen vacancies). Here we show, using scanning tunnelling microscopy and supported by potentiodynamic current-voltage measurements, that in three typical valence change memory materials (TaOx, HfOx and TiOx) the host metal cations are mobile in films of 2 nm thickness. The cations can form metallic filaments and participate in the resistive switching process, illustrating that there is a bridge between the electrochemical metallization mechanism and the valence change mechanism. Reset/Set operations are, we suggest, driven by oxidation (passivation) and reduction reactions. For the Ta/Ta2O5 system, a rutile-type TaO2 film is believed to mediate switching, and we show that devices can be switched from a valence change mode to an electrochemical metallization mode by introducing an intermediate layer of amorphous carbon.

  1. Experiments in intermediate energy physics

    Energy Technology Data Exchange (ETDEWEB)

    Dehnhard, D.

    2003-02-28

    Research in experimental nuclear physics was done from 1979 to 2002 primarily at intermediate energy facilities that provide pion, proton, and kaon beams. Particularly successful has been the work at the Los Alamos Meson Physics Facility (LAMPF) on unraveling the neutron and proton contributions to nuclear ground state and transition densities. This work was done on a wide variety of nuclei and with great detail on the carbon, oxygen, and helium isotopes. Some of the investigations involved the use of polarized targets which allowed the extraction of information on the spin-dependent part of the triangle-nucleon interaction. At the Indiana University Cyclotron Facility (IUCF) we studied proton-induced charge exchange reactions with results of importance to astrophysics and the nuclear few-body problem. During the first few years, the analysis of heavy-ion nucleus scattering data that had been taken prior to 1979 was completed. During the last few years we created hypernuclei by use of a kaon beam at Brookhaven National Laboratory (BNL) and an electron beam at Jefferson Laboratory (JLab). The data taken at BNL for a study of the non-mesonic weak decay of the A particle in a nucleus are still under analysis by our collaborators. The work at JLab resulted in the best resolution hypernuclear spectra measured thus far with magnetic spectrometers.

  2. Electron transfer-induced four-membered cyclic intermediate formation: Olefin cross-coupling vs. olefin cross-metathesis

    International Nuclear Information System (INIS)

    An electron transfer-induced four-membered cyclic intermediate, formed between a radical cation of an enol ether and an unactivated olefin, played a key role in the pathway toward either cross-coupling or cross-metathesis. The presence of an alkoxy group on the phenyl ring of the olefin entirely determined the synthetic outcome of the reaction, which mirrored the efficiency of the intramolecular electron transfer.

  3. Interaction between cationic and conventional nonionic surfactants in the mixed micelle and monolayer formed in aqueous medium

    Directory of Open Access Journals (Sweden)

    Nabel A. Negm

    2011-01-01

    Full Text Available Mixed micellization and surface properties of cationic and nonionic surfactants dimethyl decyl-, tetradecyl- and hexadecyl phosphineoxide mixtures are studied using conductivity and surface tension measurements. The models of Rubingh, Rosen, and Clint, are used to obtain the interaction parameter, minimum area per molecule, mixed micelle composition, free energies of mixing and activity coefficients. The micellar mole fractions were always higher than ideal values indicating high contributions of cationics in mixed micelles. Activity coefficients were less than unity indicating synergism in micelles. The negative free energies of mixing showed the stability of the surfactants in the mixed micelles.

  4. Complexation of the sodium cation with sodium ionophore III: Experimental and theoretical study

    Science.gov (United States)

    Makrlík, Emanuel; Kvíčala, Jaroslav; Vaňura, Petr

    2014-06-01

    By using extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium Na+(aq) + A-(aq) + 1(nb) ⇄ 1·Na+(nb) + A-(nb) occurring in the two-phase water - nitrobenzene system (A- = picrate, 1 = sodium ionophore III; aq = aqueous phase, nb = nitrobenzene phase) was determined as log Kex (1·Na+, A-) = 1.5 ± 0.1. Further, the stability constant of the 1·Na+ complex in nitrobenzene saturated with water was calculated for a temperature of 25 °C: log βnb (1·Na+) = 6.7 ± 0.1. Finally, applying quantum mechanical DFT calculations, the most probable structure of the nonhydrated 1·Na+ and hydrated 1·Na+·2H2O cationic complex species were derived. In both of these complexes, the “central” cation Na+ is bound by four bonding interactions to the corresponding four oxygen atoms of the parent ligand 1. Besides, in the case of 1·Na+·2H2O complex, the considered hydrated structure is stabilized by two water molecules bound to the “central” sodium cation.

  5. Tuning light emission of PbS nanocrystals from infrared to visible range by cation exchange

    Science.gov (United States)

    Binetti, Enrico; Striccoli, Marinella; Sibillano, Teresa; Giannini, Cinzia; Brescia, Rosaria; Falqui, Andrea; Comparelli, Roberto; Corricelli, Michela; Tommasi, Raffaele; Agostiano, Angela; Curri, M. Lucia

    2015-10-01

    Colloidal semiconductor nanocrystals, with intense and sharp-line emission between red and near-infrared spectral regions, are of great interest for optoelectronic and bio-imaging applications. The growth of an inorganic passivation layer on nanocrystal surfaces is a common strategy to improve their chemical and optical stability and their photoluminescence quantum yield. In particular, cation exchange is a suitable approach for shell growth at the expense of the nanocrystal core size. Here, the cation exchange process is used to promote the formation of a CdS passivation layer on the surface of very small PbS nanocrystals (2.3 nm in diameter), blue shifting their optical spectra and yielding luminescent and stable nanostructures emitting in the range of 700-850 nm. Structural, morphological and compositional investigation confirms the nanocrystal size contraction after the cation-exchange process, while the PbS rock-salt crystalline phase is retained. Absorption and photoluminescence spectroscopy demonstrate the growth of a passivation layer with a decrease of the PbS core size, as inferred by the blue-shift of the excitonic peaks. The surface passivation strongly increases the photoluminescence intensity and the excited state lifetime. In addition, the nanocrystals reveal increased stability against oxidation over time. Thanks to their absorption and emission spectral range and the slow recombination dynamics, such highly luminescent nano-objects can find interesting applications in sensitized photovoltaic cells and light-emitting devices.

  6. Tuning light emission of PbS nanocrystals from infrared to visible range by cation exchange

    KAUST Repository

    Binetti, Enrico

    2015-10-27

    Colloidal semiconductor nanocrystals, with intense and sharp-line emission between red and near-infrared spectral regions, are of great interest for optoelectronic and bio-imaging applications. The growth of an inorganic passivation layer on nanocrystal surfaces is a common strategy to improve their chemical and optical stability and their photoluminescence quantum yield. In particular, cation exchange is a suitable approach for shell growth at the expense of the nanocrystal core size. Here, the cation exchange process is used to promote the formation of a CdS passivation layer on the surface of very small PbS nanocrystals (2.3 nm in diameter), blue shifting their optical spectra and yielding luminescent and stable nanostructures emitting in the range of 700–850 nm. Structural, morphological and compositional investigation confirms the nanocrystal size contraction after the cation-exchange process, while the PbS rock-salt crystalline phase is retained. Absorption and photoluminescence spectroscopy demonstrate the growth of a passivation layer with a decrease of the PbS core size, as inferred by the blue-shift of the excitonic peaks. The surface passivation strongly increases the photoluminescence intensity and the excited state lifetime. In addition, the nanocrystals reveal increased stability against oxidation over time. Thanks to their absorption and emission spectral range and the slow recombination dynamics, such highly luminescent nano-objects can find interesting applications in sensitized photovoltaic cells and light-emitting devices.

  7. Electrolytes For Intermediate Temperature Solid Oxide Fuel Cells

    Directory of Open Access Journals (Sweden)

    Rękas M.

    2015-06-01

    Full Text Available Solid electrolytes for construction of the intermediate-temperature solid oxide fuel cells, IT-SOFC, have been reviewed. Yttrium stabilized tetragonal zirconia polycrystals, YTZP, as a potential electrolyte of IT-SOFC have been highlighted. The experimental results involving structural, microstructural, electrical properties based on our own studies were presented. In order to study aluminum diffusion in YTZP, aluminum oxide was deposited on the surface of 3 mol.% yttria stabilized tetragonal zirconia polycrystals (3Y-TZP. The samples were annealed at temperatures from 1523 to 1773 K. Diffusion profiles of Al in the form of mean concentration vs. depth in B-type kinetic region were investigated by secondary ion mass spectroscopy (SIMS. Both the lattice (DB and grain boundary (DGB diffusion were determined.

  8. Intramolecular Halogen Transfer via Halonium Ion Intermediates in the Gas Phase.

    Science.gov (United States)

    Chai, Yunfeng; Xiong, Xingchuang; Yue, Lei; Jiang, You; Pan, Yuanjiang; Fang, Xiang

    2016-01-01

    The fragmentation of halogen-substituted protonated amines and quaternary ammonium ions (R(1)R(2)R(3)N(+)CH2(CH2)nX, where X = F, Cl, Br, I, n = 1, 2, 3, 4) was studied by electrospray ionization tandem mass spectrometry. A characteristic fragment ion (R(1)R(2)R(3)N(+)X) resulting from halogen transfer was observed in collision-induced dissociation. A new mechanism for the intramolecular halogen transfer was proposed that involves a reactive intermediate, [amine/halonium ion]. A potential energy surface scan using DFT calculation for CH2-N bond cleavage process of protonated 2-bromo-N,N-dimethylethanamine supports the formation of this intermediate. The bromonium ion intermediate-involved halogen transfer mechanism is supported by an examination of the ion/molecule reaction between isolated ethylenebromonium ion and triethylamine, which generates the N-bromo-N,N,N-triethylammonium cation. For other halogens, Cl and I also can be involved in similar intramolecular halogen transfer, but F cannot be involved. With the elongation of the carbon chain between the halogen (bromine as a representative example) and amine, the migration ability of halogen decreases. When the carbon chain contains two or three CH2 units (n = 1, 2), formal bromine cation transfer can take place, and the transfer is easier when n = 1. When the carbon chain contains four or five CH2 units (n = 3, 4), formal bromine cation transfer does not occur, probably because the five- and six-membered cyclic bromonium ions are very stable and do not donate the bromine to the amine. PMID:26383734

  9. Digital low-level RF control system using multi-intermediate frequencies

    International Nuclear Information System (INIS)

    In a superconducting accelerator, an FPGA-based low-level rf system is adopted and a digital feedback control system is utilized to satisfy the requirement of stability in the accelerating field. A digital low-level rf system using multi-intermediate frequencies (IF-Mixture technique) has been developed at STF (Superconducting rf Test Facility) in KEK. A superconducting cavity was operated using this IF-mixture technique and the stability under the feedback operation was measured. (author)

  10. Nuclear structure at intermediate energies

    Energy Technology Data Exchange (ETDEWEB)

    Bonner, B.E.; Mutchler, G.S.

    1991-09-30

    The theme that unites the sometimes seemingly disparate experiments undertaken by the Bonner Lab Medium Energy Group is a determination to understand in detail the many facets and manifestations of the strong interaction, that which is now referred to as nonperturbative QCD. Whether we are investigating the question of just what does carry the spin of baryons, or the extent of the validity of the SU(6) wavefunctions for the excited hyperons (as will be measured in their radiative decays in our CEBAF experiment), or questions associated with the formation of a new state of matter predicted by QCD (the subject of our BNL experiments E810, E854, as well as our approved experiment at RHIC), -- all these projects share this common goal. Our other experiments represent different approaches to the same broad undertaking. LAMPF E1097 will provide definitive answers to the question of the spin dependence of the inelastic channel of pion production in the n-p interaction. FNAL E683 may well open a new field of investigation in nuclear physics: that of just how quarks and gluons interact with nuclear matter as they transverse nuclei of different sizes. In most all of the experiments mentioned above, the Bonner Lab Group is playing major leadership roles as well as doing a big fraction of the hard work that such experiments require. We use many of the facilities that are unavailable to the intermediate energy physics community and we use our expertise to design and fabricate the detectors and instrumentation that are required to perform the measurements which we decide to do.

  11. Retention of intermediate polarization states in ferroelectric materials enabling memories for multi-bit data storage

    Science.gov (United States)

    Zhao, Dong; Katsouras, Ilias; Asadi, Kamal; Groen, Wilhelm A.; Blom, Paul W. M.; de Leeuw, Dago M.

    2016-06-01

    A homogeneous ferroelectric single crystal exhibits only two remanent polarization states that are stable over time, whereas intermediate, or unsaturated, polarization states are thermodynamically instable. Commonly used ferroelectric materials however, are inhomogeneous polycrystalline thin films or ceramics. To investigate the stability of intermediate polarization states, formed upon incomplete, or partial, switching, we have systematically studied their retention in capacitors comprising two classic ferroelectric materials, viz. random copolymer of vinylidene fluoride with trifluoroethylene, P(VDF-TrFE), and Pb(Zr,Ti)O3. Each experiment started from a discharged and electrically depolarized ferroelectric capacitor. Voltage pulses were applied to set the given polarization states. The retention was measured as a function of time at various temperatures. The intermediate polarization states are stable over time, up to the Curie temperature. We argue that the remarkable stability originates from the coexistence of effectively independent domains, with different values of polarization and coercive field. A domain growth model is derived quantitatively describing deterministic switching between the intermediate polarization states. We show that by using well-defined voltage pulses, the polarization can be set to any arbitrary value, allowing arithmetic programming. The feasibility of arithmetic programming along with the inherent stability of intermediate polarization states makes ferroelectric materials ideal candidates for multibit data storage.

  12. Dehydration and Stabilization of a Reactive Tertiary Hydroxyl Group in Solid Oral Dosage Forms of BMS-779788.

    Science.gov (United States)

    Adams, Monica L; Sharma, Vijayata; Gokhale, Madhushree; Huang, Yande; Stefanski, Kevin; Su, Ching; Hussain, Munir A

    2016-04-01

    BMS-779788 contains a reactive tertiary hydroxyl attached to a weakly basic imidazole ring. Propensity of the carbinol toward dehydration to yield the corresponding alkene, BMS-779788-ALK, was evaluated. Elevated levels of BMS-779788-ALK were observed in excipient compatibility samples. Stability studies revealed that BMS-779788 degrades to BMS-779788-ALK in capsules and tablets prepared by both dry and wet granulation processes. An acid-catalyzed dehydration mechanism, in which the heterocyclic core contributes resonance stability to the cationic intermediate via charge transfer to the imidazole ring, was proposed. Therefore, neutralization via a buffered (pH 7.0) granulating solution was used to mitigate dehydration. Solution studies revealed degradation of BMS-779788 to BMS-779788-ALK over the pH range of 1-7.5. Reversibility was confirmed by initiating reactions with BMS-779788-ALK over the same pH range. Accordingly, a simple reversible scheme can be used to describe reactions initiated with either BMS-779788 or BMS-779788-ALK. To eliminate potential for charge delocalization across the heterocycle and probe the degradation mechanism, the imidazole ring of BMS-779788 was methylated (BMS-779788-Me). The propensity for acid-catalyzed dehydration was then evaluated. The acid stability of BMS-779788-Me confirmed that the heterocyclic core contributes to reactivity liability of the tertiary hydroxyl. PMID:26921118

  13. Liver resection for intermediate hepatocellular carcinoma.

    Science.gov (United States)

    Yi, Peng-Sheng; Zhang, Ming; Zhao, Ji-Tong; Xu, Ming-Qing

    2016-05-18

    Hepatocellular carcinoma (HCC) is one of the most common malignant tumors in China. The Barcelona Clinic Liver Cancer (BCLC) staging system is regarded as the gold standard staging system for HCC, classifying HCC as early, intermediate, or advanced. For intermediate HCC, trans-catheter arterial chemoembolization (TACE) is recommended as the optimal strategy by the BCLC guideline. This review investigates whether liver resection is better than TACE for intermediate HCC. Based on published studies, we compare the survival benefits and complications of liver resection and TACE for intermediate HCC. We also compare the survival benefits of liver resection in early and intermediate HCC. We find that liver resection can achieve better or at least comparable survival outcomes compared with TACE for intermediate HCC; however, we do not observe a significant difference between liver resection and TACE in terms of safety and morbidity. We conclude that liver resection may improve the short- and long-term survival of carefully selected intermediate HCC patients, and the procedure may be safely performed in the management of intermediate HCC. PMID:27190577

  14. Intermediate energy nuclear data for applications

    International Nuclear Information System (INIS)

    A comprehensive review of the data needs for various applications was performed by the participants of the meeting. The status of compilation and evaluation of the needed data in the intermediate energy range of incident particles was discussed. The following broad application areas were identified and considered by the participants: intermediate energy nuclear data needed for accelerators; intermediate energy nuclear data needed for space applications; intermediate energy nuclear data for medical applications. The role of nuclear model calculations in data evaluations in this energy range was considered. The possibilities of existing model codes were considered from the point of view of reliability, accuracy, cost of computer time, availability to specialists in the Member States. The Meeting presentations were divided into the following three sessions: Nuclear data needs in the intermediate energy range (6 papers), Progress of nuclear data computations and evaluations in the intermediate energy range (6 papers) and Progress of experimental data measurements in the intermediate energy range. A separate abstract was prepared for each paper. The ways of further improvement of the status of nuclear data in the intermediate energy range were discussed and the results of these discussions can be found in the conclusions and recommendations of this meeting. Refs, figs and tabs

  15. Gasoline Engine Mechanics. Performance Objectives. Intermediate Course.

    Science.gov (United States)

    Jones, Marion

    Several intermediate performance objectives and corresponding criterion measures are listed for each of six terminal objectives presented in this curriculum guide for an intermediate gasoline engine mechanics course at the secondary level. (For the beginning course guide see CE 010 947.) The materials were developed for a two-semester (2 hour…

  16. Air Conditioning. Performance Objectives. Intermediate Course.

    Science.gov (United States)

    Long, William

    Several intermediate performance objectives and corresponding criterion measures are listed for each of seven terminal objectives for an intermediate air conditioning course. The titles of the seven terminal objectives are Refrigeration Cycle, Job Requirement Skills, Air Conditioning, Trouble Shooting, Performance Test, Shop Management, and S.I.E.…

  17. 39 CFR 3001.39 - Intermediate decisions.

    Science.gov (United States)

    2010-07-01

    ... 39 Postal Service 1 2010-07-01 2010-07-01 false Intermediate decisions. 3001.39 Section 3001.39... Applicability § 3001.39 Intermediate decisions. (a) Initial decision by presiding officer. In any proceedings in... certify and file with the Secretary, a copy of the record of the hearing and his/her initial decision...

  18. Inorganic magnetic support for sodium cation scavenging

    International Nuclear Information System (INIS)

    Three different magnetic iron oxide-silica matrices with polyoxaalkyl units have been obtained in a multi-step synthesis. The structures of the matrices were confirmed by Fourier transform infrared spectroscopy, while their surface morphology was analyzed by scanning electron microscopy. The scavenging ability was studied by ultraviolet-visible measurements. The results demonstrate very good scavenging efficiency of compounds studied against sodium cations (Na+). The complexing abilities of the magnetic iron oxide-silica surfaces were compared with those of the previously studied analogously modified non-magnetic silica surfaces.

  19. Mobility of cations in magnesium aluminate spinel

    Energy Technology Data Exchange (ETDEWEB)

    Martinelli, J.R.; Sonder, E.; Weeks, R.A.; Zuhr, R.A.

    1986-04-15

    Transport of cations in magnesium aluminate spinel due to an applied electric field at approximately 1000 /sup 0/C has been measured by observing changes in elemental concentrations near the cathode and anode surfaces using ion backscattering techniques. The results indicate that magnesium ions are the mobile species at 1000 /sup 0/C and that these ions combine with ambient oxygen at the cathode surface to form a MgO layer. Quantitative interpretation of the data leads to the conclusion that the ionic transference number of spinel becomes approximately 0.5 after treatment in an electric field.

  20. Mobility of cations in magnesium aluminate spinel

    International Nuclear Information System (INIS)

    Transport of cations in magnesium aluminate spinel due to an applied electric field at approximately 1000 0C has been measured by observing changes in elemental concentrations near the cathode and anode surfaces using ion backscattering techniques. The results indicate that magnesium ions are the mobile species at 1000 0C and that these ions combine with ambient oxygen at the cathode surface to form a MgO layer. Quantitative interpretation of the data leads to the conclusion that the ionic transference number of spinel becomes approximately 0.5 after treatment in an electric field

  1. Mobility of cations in magnesium aluminate spinel

    Science.gov (United States)

    Martinelli, J. R.; Sonder, E.; Weeks, R. A.; Zuhr, R. A.

    1986-04-01

    Transport of cations in magnesium aluminate spinel due to an applied electric field at approximately 1000 °C has been measured by observing changes in elemental concentrations near the cathode and anode surfaces using ion backscattering techniques. The results indicate that magnesium ions are the mobile species at 1000 °C and that these ions combine with ambient oxygen at the cathode surface to form a MgO layer. Quantitative interpretation of the data leads to the conclusion that the ionic transference number of spinel becomes approximately 0.5 after treatment in an electric field.

  2. Complex Macromolecular Architectures by Living Cationic Polymerization

    KAUST Repository

    Alghamdi, Reem D.

    2015-05-01

    Poly (vinyl ether)-based graft polymers have been synthesized by the combination of living cationic polymerization of vinyl ethers with other living or controlled/ living polymerization techniques (anionic and ATRP). The process involves the synthesis of well-defined homopolymers (PnBVE) and co/terpolymers [PnBVE-b-PCEVE-b-PSiDEGVE (ABC type) and PSiDEGVE-b-PnBVE-b-PSiDEGVE (CAC type)] by sequential living cationic polymerization of n-butyl vinyl ether (nBVE), 2-chloroethyl vinyl ether (CEVE) and tert-butyldimethylsilyl ethylene glycol vinyl ether (SiDEGVE), using mono-functional {[n-butoxyethyl acetate (nBEA)], [1-(2-chloroethoxy) ethyl acetate (CEEA)], [1-(2-(2-(t-butyldimethylsilyloxy)ethoxy) ethoxy) ethyl acetate (SiDEGEA)]} or di-functional [1,4-cyclohexanedimethanol di(1-ethyl acetate) (cHMDEA), (VEMOA)] initiators. The living cationic polymerizations of those monomers were conducted in hexane at -20 0C using Et3Al2Cl3 (catalyst) in the presence of 1 M AcOEt base.[1] The PCEVE segments of the synthesized block terpolymers were then used to react with living macroanions (PS-DPE-Li; poly styrene diphenyl ethylene lithium) to afford graft polymers. The quantitative desilylation of PSiDEGVE segments by n-Bu4N+F- in THF at 0 °C led to graft co- and terpolymers in which the polyalcohol is the outer block. These co-/terpolymers were subsequently subjected to “grafting-from” reactions by atom transfer radical polymerization (ATRP) of styrene to afford more complex macromolecular architectures. The base assisted living cationic polymerization of vinyl ethers were also used to synthesize well-defined α-hydroxyl polyvinylether (PnBVE-OH). The resulting polymers were then modified into an ATRP macro-initiator for the synthesis of well-defined block copolymers (PnBVE-b-PS). Bifunctional PnBVE with terminal malonate groups was also synthesized and used as a precursor for more complex architectures such as H-shaped block copolymer by “grafting-from” or

  3. Flocculation performance of a cationic biopolymer derived from a cellulosic source in mild aqueous solution.

    Science.gov (United States)

    Liimatainen, Henrikki; Sirviö, Juho; Sundman, Ola; Visanko, Miikka; Hormi, Osmo; Niinimäki, Jouko

    2011-10-01

    The flocculation behavior of cationic, quaternary ammonium groups containing cellulosic biopolymers, CDACs, synthesized by cationizing dialdehyde cellulose in mild aqueous solution was studied in a kaolin suspension. In particular, the role of CDAC dosage and solution pH, NaCl concentration, and temperature were clarified. In addition, the initial apparent charge densities (CDs), particle sizes, ζ-potential, and stability of CDs were determined. CDACs possessed a high flocculation activity in neutral and acidic solutions, but a significant decrease was observed in alkaline solutions (pH >9). This was also seen as a decline in the apparent CD and particle size of the CDACs in alkaline conditions. The measurements also indicated that the apparent CD decreased to a constant level of 3 mmol/g in aqueous solutions. However, no notable decrease in flocculation performance was obtained after several days of storage. Moreover, the variation of NaCl concentration and temperature did not affect the flocculation activity. PMID:21862324

  4. Effect of electrolytes on wettability of glass surface using anionic and cationic surfactant solutions.

    Science.gov (United States)

    Chaudhuri, Rajib Ghosh; Paria, Santanu

    2014-01-01

    Wetting behavior of a flat glass surface using pure nonionic, anionic, and cationic surfactants solutions has been studied by the dynamic contact angle (Wilhelmy plate) measurement technique. The advancing contact angle increases with the increasing concentration of surfactant and the value is maximum in the presence of cationic surfactant CTAB. The effect of different electrolytes in the presence of ionic surfactants was also studied to see the wetting behavior in the presence of electrolytes. The presence of electrolytes on ionic surfactant solutions significantly enhance the contact angle at very low concentration, which in turn lead to reduction in ionic surfactant requirement by more than 90% to achieve a particular contact angle. The effectiveness of electrolyte highly depends on the valance of counter ion. The reduction of ionic surfactant requirement is mostly useful for different applications such as flotation, and colloidal stability to reduce the production cost as well as environmental pollution. PMID:24183426

  5. Cation-π interactions: accurate intermolecular potential from symmetry-adapted perturbation theory.

    Science.gov (United States)

    Ansorg, Kay; Tafipolsky, Maxim; Engels, Bernd

    2013-09-01

    Symmetry-adapted perturbation theory (SAPT) is used to decompose the total intermolecular interaction energy between the ammonium cation and a benzene molecule into four physically motivated individual contributions: electrostatics, exchange, dispersion, and induction. Based on this rigorous decomposition, it is shown unambiguously that both the electrostatic and the induction energy components contribute almost equally to the attractive forces stabilizing the dimer with a nonnegligible contribution coming from the dispersion term. A polarizable potential model for the interaction of ammonium cation with benzene is parametrized by fitting these four energy components separately using the functional forms of the AMOEBA force field augmented with the missing charge penetration energy term calculated as a sum over pairwise electrostatic energies between spherical atoms. It is shown that the proposed model is able to produce accurate intermolecular interaction energies as compared to ab initio results, thus avoiding error compensation to a large extent. PMID:23924321

  6. CHARACTERISTICS OF AKD EMULSION PREPARED BY CATIONIC STARCH WITH WELL-DEFINED STRUCTURES

    Institute of Scientific and Technical Information of China (English)

    Y.S. Chew; H. Xiao; G. Peng; J. C. Roberts; K. Nurmi; K. Sundberg

    2004-01-01

    Alkyl ketene dimers (AKD) have been used in the papermaking industry as reactive internal sizing agents for more than 30 years. AKD emulsions are normally stabilised by cationic starch. The advantages and disadvantages of the emulsions prepared in this way have been well documented. However, the influence of factors such as electrolytes, polyelectrolytes oligomers and pH on AKD emulsion stability has not been addressed. Polyelectrolyte oligomers often arise as impurities in cationic starch or as by-products during the cationisation of starches. The key objectives of this work have been to use starches purified by dialysis and precipitation to study (a)emulsion stabilising properties, (b) factor affecting emulsion characterisation and (c) the adsorption behaviour on AKD particles.Size exclusion chromatography (SEC) and intrinsic viscosity measurements were performed to evaluate molecular weight and MW distribution of cationic starches. NMR and Elemental analysis were conducted to characterise the degree of substitution (DS), and electrophoresis mobility was used to measure the surface charge characteristics of the emulsion particles.Within the experimental concentration ranges, the amount of the cationic starch adsorbed on the AKD particle surfaces has been shown to increase proportionally with the addition level but a high proportion remained unabsorbed. Molecular weight and charge density of cationic starch have also been observed and shown to be important. The zeta-potential of the emulsion particles was strongly dependent on the concentrations of the electrolytes added as well as pH. Excessive electrolytes and extreme pH conditions tended to reduce the zeta potential of the AKD particles.

  7. Interactions of cationic trimeric, gemini and monomeric surfactants with trianionic curcumin in aqueous solution.

    Science.gov (United States)

    Wang, Meina; Wu, Chunxian; Tang, Yongqiang; Fan, Yaxun; Han, Yuchun; Wang, Yilin

    2014-05-21

    Interactions of trianionic curcumin (Cur(3-)) with a series of cationic surfactants, monomeric surfactant dodecyl trimethylammonium bromide (DTAB), dimeric surfactant hexamethylene-1,6-bis(dodecyldimethylammonium bromide) (12-6-12) and trimeric surfactant tri(dodecyldimethylammonioacetoxy)diethyltriamine trichloride (DTAD), have been investigated in aqueous solution of pH 13.0. Surface tension and spectral measurements indicate that the cationic surfactants display a similar surfactant concentration dependent interaction process with Cur(3-), involving three interaction stages. At first the three cationic surfactants electrostatically bind on Cur(3-) to form the surfactant-Cur(3-) complex. Then the bound and unbound cationic surfactants with Cur(3-) aggregate into surfactant-Cur(3-) mixed micelles through hydrophobic interactions above the critical micelle concentration of the surfactants (CMCC) in the presence of Cur(3-). Finally excess unbound surfactants self-assemble into micelles like those without Cur(3-). For all the three surfactants, the addition of Cur(3-) only decreases the critical micelle concentration of 12-6-12 but does not affect the critical micelle concentration of DTAB and DTAD. As the oligomeric degree of surfactants increases, the intermolecular interaction of the cationic surfactants with Cur(3-) increases and the surfactant amount needed for Cur(3-) encapsulation decreases. Compared with 12-6-12, either the weaker interaction of DTAB with Cur(3-) or stronger interaction of DTAD with Cur(3-) limits the stability or solubility of Cur(3-) in surfactant micelles. Therefore, gemini surfactant 12-6-12 is the best choice to effectively suppress Cur(3-) degradation at very low concentrations. Isothermal titration microcalorimetry, surface tension and (1)H NMR results reveal that 12-6-12 and Cur(3-) form a (12-6-12)2-Cur(3-) complex and start to form micelles at extremely decreased concentrations, where either 12-6-12 or Cur(3-) works as a bridge

  8. Identification and Structural Characterization of an Intermediate in the Folding of the Measles Virus X Domain.

    Science.gov (United States)

    Bonetti, Daniela; Camilloni, Carlo; Visconti, Lorenzo; Longhi, Sonia; Brunori, Maurizio; Vendruscolo, Michele; Gianni, Stefano

    2016-05-13

    Although most proteins fold by populating intermediates, the transient nature of such states makes it difficult to characterize their structures. In this work we identified and characterized the structure of an intermediate of the X domain of phosphoprotein (P) of measles virus. We obtained this result by a combination of equilibrium and kinetic measurements and NMR chemical shifts used as structural restraints in replica-averaged metadynamics simulations. The structure of the intermediate was then validated by rationally designing four mutational variants predicted to affect the stability of this state. These results provide a detailed view of an intermediate state and illustrate the opportunities offered by a synergistic use of experimental and computational methods to describe non-native states at atomic resolution. PMID:27002146

  9. Structure of a low-population binding intermediate in protein-RNA recognition

    Science.gov (United States)

    Bardaro, Michael F.; Aprile, Francesco A.; Varani, Gabriele; Vendruscolo, Michele

    2016-01-01

    The interaction of the HIV-1 protein transactivator of transcription (Tat) and its cognate transactivation response element (TAR) RNA transactivates viral transcription and represents a paradigm for the widespread occurrence of conformational rearrangements in protein-RNA recognition. Although the structures of free and bound forms of TAR are well characterized, the conformations of the intermediates in the binding process are still unknown. By determining the free energy landscape of the complex using NMR residual dipolar couplings in replica-averaged metadynamics simulations, we observe two low-population intermediates. We then rationally design two mutants, one in the protein and another in the RNA, that weaken specific nonnative interactions that stabilize one of the intermediates. By using surface plasmon resonance, we show that these mutations lower the release rate of Tat, as predicted. These results identify the structure of an intermediate for RNA-protein binding and illustrate a general strategy to achieve this goal with high resolution. PMID:27286828

  10. Influence of 3‧-3‧ inversion of polarity site within d(TGGGGT) on inter quartet cation binding

    Science.gov (United States)

    Šket, Primož; Korbar, Tjaša; Plavec, Janez

    2014-10-01

    Stability, dynamics and function of nucleic acids are affected by nature of cations that are involved in interaction with specific functionalities. Introduction of inversion of polarity sites represents a very useful and chemically accessible backbone modification, which can alter the binding affinity of cations. NMR study on cation binding between G-quartets in tetramolecular G-quadruplex adopted by d(5‧TGG3‧-3‧GGT5‧) with 3‧-3‧ inversion of polarity sites in the middle of G-tract showed existence of two different G-quadruplex forms with all strands in parallel orientation, where all guanine residues adopt anti conformation around glycosidic bonds in the presence of 15NH4+ ions. In one of the forms all three binding sites are equally populated, while in the second form the binding site next to the inversion of polarity site is not fully populated by 15NH4+ ions.

  11. Ionothermal synthesis and electrochemical properties of a selenidostannate containing the mixed cations of Na+ and enH+

    Science.gov (United States)

    Du, Cheng-Feng; Li, Jian-Rong; Shen, Nan-Nan; Huang, Xiao-Ying

    2016-06-01

    In this report, by taking advantages of the competitive and synergistic effects of mixed-cations under the ionothermal conditions, a novel selenidostannate compound containing the mixed cations, namely (enH)3Na[Sn3Se7]2·1.5Me2NH·1.5H2O (1, en=ethylenediamine, Me2NH=dimethylamine) was obtained in the presence of the ionic liquid (IL) [DAMS]I (4-N,N-Dimethylamino-4‧-N‧-methylstilbazolium iodide) with a bulky and more structurally rigid organic cation as the main solvent and en as the auxiliary solvent. The compound features anionic [Sn3Se7]n2n- layers that are interconnected by sodium ions to form a three-dimensional (3D) structure. The syntheses, structure, thermal, optical and electrochemical properties of 1 were investigated. 1 showed good thermal stability and a Na+ ion storage property without capacity fading over 150 cycles.

  12. PREAPARATION OF CATIONIC LATEXES OF POLY(STYRENE-CO-BUTYL ACRYLATE) AND THEIR PROPERTIES EVOLUTION IN LATEX DILUTION

    Institute of Scientific and Technical Information of China (English)

    Dong Zou; Xiu-fen Li; Xiao-li Zhu; Xiang-zheng Kong

    2012-01-01

    Cationic latexes were prepared through emulsion copolymerization of styrene (St) and butyl acrylate (BA) with a cationic surfactant,cetyl trimethyl ammonium bromide (CTAB).Latex properties,including particle size,size distribution,ζ potential,surface tension and monomer conversion,were determined for latexes prepared with different CTAB amounts.Evolution of these properties during emulsion polymerization was followed in order to understand the mechanism of the particles formation.Results showed that both particle size and ζpotential were function of polymerization time and latex solids.Parallel emulsion polymerizations with cationic,anionic charged initiator and charge-free initiators were also carried out,the latex properties were determined at different polymerization time.All these results were attentively interpreted based on the mechanisms of emulsion polymerization,surfactant adsorption and latex particle stabilization.

  13. Simultaneous Determination of Anions and Cations in Natural Water by Ion-exclusion/Cation-exchange Chromatography with a Weakly Acidic Cation-exchange Resin Column

    International Nuclear Information System (INIS)

    The simultaneous determination of anions (SO4 2-, Cl-, and NO3 -) and cations (Na+, NH4+, K+, Mg2+, and Ca2+) in natural water obtained by Nakdong River waters system in Korea were performed by ion-exclusion/cation exchange chromatography with conductimetric detection. The stationary phase was a polymethacrylate-based weakly acidic cation-exchange resin column in the H+-form and a weak-acid eluent. When using only a 1.4 mM sulfosalicylic acid/6 mM 18-crown-6 ether as an eluent, good resolution of both anions and cations, minimum time required for the separation, and satisfactory detection sensitivity were obtained in a reasonable time. The method was successfully applied to the simultaneous determination of anions and cations in natural waters

  14. Simultaneous Determination of Anions and Cations in Natural Water by Ion-exclusion/Cation-exchange Chromatography with a Weakly Acidic Cation-exchange Resin Column

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Kwang Pill; Choi, Seong Ho; Park, Yu Chul; Bae, Zun Ung; Lee, Mu Sang; Lee, Sang Hak; Chang, Hye Yong [Graduate School, Kyungpook National University, Daegu (Korea, Republic of); Kwon, Se Mok [Ulsan City Health and Environmental Research Institute, Ulsan (Korea, Republic of); Tanaka, Kazuhiko [National Industrial Research Institute of Nagoya, Nagoya (Japan)

    2003-09-15

    The simultaneous determination of anions (SO{sub 4} {sup 2-}, Cl{sup -}, and NO{sub 3} {sup -}) and cations (Na{sup +}, NH{sup 4+}, K{sup +}, Mg{sup 2+}, and Ca{sup 2+}) in natural water obtained by Nakdong River waters system in Korea were performed by ion-exclusion/cation exchange chromatography with conductimetric detection. The stationary phase was a polymethacrylate-based weakly acidic cation-exchange resin column in the H{sup +}-form and a weak-acid eluent. When using only a 1.4 mM sulfosalicylic acid/6 mM 18-crown-6 ether as an eluent, good resolution of both anions and cations, minimum time required for the separation, and satisfactory detection sensitivity were obtained in a reasonable time. The method was successfully applied to the simultaneous determination of anions and cations in natural waters.

  15. Cationic polymers in water treatment: Part 1: Treatability of water with cationic polymers

    Czech Academy of Sciences Publication Activity Database

    Polasek, P.; Mutl, Silvestr

    2002-01-01

    Roč. 28, č. 1 (2002), s. 69-82. ISSN 0378-4738 R&D Projects: GA AV ČR KSK2067107 Keywords : cationic polymers * treatability * water quality Subject RIV: BK - Fluid Dynamics Impact factor: 0.481, year: 2002

  16. Cobalt 60 cation exchange with mexican clays

    International Nuclear Information System (INIS)

    Mexican clays can be used to remove radioactive elements from contaminated aqueous solutions. Cation exchange experiments were performed with 60 Co radioactive solution. In the present work the effect of contact time on the sorption of Co 2+ was studied. The contact time in hydrated montmorillonite was from 5 to 120 minutes and in dehydrated montmorillonite 5 to 1400 minutes. The Co 2+ uptake value was, in hydrated montmorillonite, between 0.3 to 0.85 m eq/g and in dehydrated montmorillonite, between 0.6 to 1.40 m eq/g. The experiments were done in a pH 5.1 to 5.7 and normal conditions. XRD patterns were used to characterize the samples. The crystallinity was determined by X-ray Diffraction and it was maintained before and after the cation exchange. DTA thermo grams showed the temperatures of the lost humidity and crystallization water. Finally, was observed that dehydrated montmorillonite adsorb more cobalt than hydrated montmorillonite. (Author)

  17. Cationic Antimicrobial Polymers and Their Assemblies

    Directory of Open Access Journals (Sweden)

    Ana Maria Carmona-Ribeiro

    2013-05-01

    Full Text Available Cationic compounds are promising candidates for development of antimicrobial agents. Positive charges attached to surfaces, particles, polymers, peptides or bilayers have been used as antimicrobial agents by themselves or in sophisticated formulations. The main positively charged moieties in these natural or synthetic structures are quaternary ammonium groups, resulting in quaternary ammonium compounds (QACs. The advantage of amphiphilic cationic polymers when compared to small amphiphilic molecules is their enhanced microbicidal activity. Besides, many of these polymeric structures also show low toxicity to human cells; a major requirement for biomedical applications. Determination of the specific elements in polymers, which affect their antimicrobial activity, has been previously difficult due to broad molecular weight distributions and random sequences characteristic of radical polymerization. With the advances in polymerization control, selection of well defined polymers and structures are allowing greater insight into their structure-antimicrobial activity relationship. On the other hand, antimicrobial polymers grafted or self-assembled to inert or non inert vehicles can yield hybrid antimicrobial nanostructures or films, which can act as antimicrobials by themselves or deliver bioactive molecules for a variety of applications, such as wound dressing, photodynamic antimicrobial therapy, food packing and preservation and antifouling applications.

  18. Cation control of energetics on dye-sensitized nanocrystalline TiO2 for solar cells

    Science.gov (United States)

    Stux, Arnold M.

    Regenerative solar cells based on nanocrystalline TiO2 (anatase) and the dye Ru(deeb)(bpy)2(PF6)2, where deeb is 4,4'-(CO2CH2CH3)2-2,2 '-bipyridine and bpy is 2,2'-bipyridine, have increased efficiency when in the presence of a high concentration of cations with a large charge-to-radius ratio. Concentration-dependent photoluminescence (PL) quenching and increased quantum yield for interfacial charge separation have been explored for mono- and divalent cations by absorbance, time-resolved and steady-state PL. Cation adsorption stabilizes TiO2 acceptor states resulting in energetically favorable electron transfer from the dye into the semiconductor conduction band. Quenching of the PL of excited states is reversible. A new luminescence approach for sensing alkali and alkaline earth metal cations utilizes the surface-adsorption/desorption induced energetic shifts of a semiconductor conduction band to alter the electron transfer quenching efficiency of a photoluminescent dye such as Ru(deeb)(bpy)2(PF 6)2 anchored to TiO2 nanoparticles. This approach yields intensity, lifetime, and wavelength-ratiometric calcium ion sensors that are sensitive to 5 x 10-4 M concentrations. In situ photoluminescence of a regenerative solar cell has been demonstrated as a probe of injection and efficiencies. The smaller the alkali cation, the higher the photocurrent and the more quenched the photoluminescence. The extent of quenching in 0.1 M iodide/0.01 M iodine electrolytes was 10-fold with LiI and 3-fold with NaI. A millimolar threshold concentration is observed for Li+ at which point a red shift in absorbance and photoluminescence spectra concomitant with significant static and dynamic quenching occurs. For Na+, the threshold concentration for observable red shift is more than an order of magnitude higher than for Li+. Cation adsorption was also observed on planar TiO2 surfaces in the absence of dye. The flat band potentials of single crystal TiO 2 (rutile) with cations in propylene

  19. Aging of Cations of Ionic Liquids Monitored by Ion Chromatography hyphenated to an Electrospray Ionization Mass Spectrometer

    International Nuclear Information System (INIS)

    Highlights: • Proposed decomposition mechanisms for the cations. • No influence of the electrolyte salts on the decomposition behavior of the IL cation was observed. • A new method for the identification of decomposition products in ILs. - ABSTRACT: The stability of 1-methyl-1-propylpyrrolidinium bis(trifluoromethanesulfonyl) imide (PYR13TFSI), 1-methyl-1-propylpyrrolidinium bis(fluorosulfonyl) imide (PYR13FSI), 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl) imide (PYR14TFSI) and 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl) imide (EMIM TFSI) ionic liquids (ILs) at different temperatures (room temperature and 95 °C) was investigated by ion chromatography (IC) hyphenated to a mass spectrometer. The degradation of the cations can be summarized in the following way: The side chain of the main molecule cleaves and reacts subsequently with the main cation molecule to new decomposition products. In addition, the results show that at elevated temperatures more decomposition products are formed. The influence of Li+ cation based electrolyte salts, lithium hexafluorophosphate (LiPF6), lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) and lithium perchlorate (LiClO4), on the decomposition of the ionic liquids was analyzed over a long term stability study at room temperature and 60 °C. It was found out that in the mixtures of ILs and electrolyte salt, the same decomposition products were formed like in the pure ILs at the same temperature. Accordingly, there is no influence of the electrolyte salts on the decomposition behavior of the IL cation. The influence of the counter anion on the decomposition of PYR13+ was analyzed as well. It was observed that different decomposition products were detected for PYR13TFSI and PYR13FSI

  20. Docetaxel in cationic lipid nanocapsules for enhanced in vivo activity.

    Science.gov (United States)

    Jain, Ankitkumar S; Makhija, Dinesh T; Goel, Peeyush N; Shah, Sanket M; Nikam, Yuvraj; Gude, Rajiv P; Jagtap, Aarti G; Nagarsenker, Mangal S

    2016-01-01

    The usefulness of Docetaxel (DT) as an anti-cancer agent is limited to parenteral route owing to its very poor oral bioavailability. Thus, to improve its oral efficacy, DT was loaded in novel cationic lipid nanocapsules (DT CLNC). The DT CLNC possessed size of 130-150 nm, zeta potential of +72mV, adequate DT loading and over 95% encapsulation efficiency. TEM revealed capsular structure of DT CLNC. Lipolysis study indicated improved solubilization of DT by nanocapsules in comparison to DT solution. DT CLNC exhibited significantly higher release of DT in comparison to DT solution during in vitro permeation studies employing non-reverted rat-intestinal sac. Superior uptake of DT in zebra fishes exposed to DT CLNC resulted in greater apoptosis-based cell death as compared to those exposed to DT solution. This correlated well with the significantly superior (p zebra fish model. DT CLNC also inhibited tumor growth in melanoma cell line induced tumors in C57BL/6 mice significantly, as compared to DT solution (p < 0.05). The DT CLNC system demonstrated adequate stability, with tremendous potential to improve oral efficacy of DT and can serve as an alternative to existing DT formulations available commercially for parenteral use. PMID:25329444

  1. Intermedial Strategies of Memory in Contemporary Novels

    DEFF Research Database (Denmark)

    Tanderup, Sara

    2014-01-01

    Judd Morrissey and drawing on the theoretical perspectives of N. Katherine Hayles (media studies) and Andreas Huyssen (cultural memory studies), Tanderup argues that recent intermedial novels reflect a certain nostalgia celebrating and remembering the book as a visual and material object in the age of......In her article "Intermedial Strategies and Memory in Contemporary Novels" Sara Tanderup discusses a tendency in contemporary literature towards combining intermedial experiments with a thematic preoccupation with memory and trauma. Analyzing selected works by Steven Hall, Jonathan Safran Foer, and...... digital media while also highlighting the influence of new media on our cultural understanding and representation of memory and the past....

  2. Bespoke cationic nano-objects via RAFT aqueous dispersion polymerisation

    OpenAIRE

    Williams, M.; Penfold, NJW; Lovett, JR; Warren, NJ; Douglas, CWI; Doroshenko, N; Verstraete, P; Smets, J; Armes, SP

    2016-01-01

    A range of cationic diblock copolymer nanoparticles are synthesised via polymerisation-induced self-assembly (PISA) using a RAFT aqueous dispersion polymerisation formulation. The cationic character of these nanoparticles can be systematically varied by utilising a binary mixture of two macro-CTAs, namely non-ionic poly(glycerol monomethacrylate) (PGMA) and cationic poly[2-(methacryloyloxy)ethyl]trimethylammonium chloride (PQDMA), with poly(2-hydroxypropyl methacrylate) (PHPMA) being selected...

  3. Development of Recombinant Cationic Polymers for Gene Therapy Research

    OpenAIRE

    Canine, Brenda F.; Hatefi, Arash

    2010-01-01

    Cationic polymers created through recombinant DNA technology have the potential to fill a void in the area of gene delivery. The recombinant cationic polymers to be discussed here are amino acid based polymers synthesized in E.coli with the purpose to not only address the major barriers to efficient gene delivery but offer safety, biodegradability, targetability and cost-effectiveness. This review helps the readers to get a better understanding about the evolution of recombinant cationic poly...

  4. Effect of Headgroup on DNA−Cationic Surfactant Interactions

    OpenAIRE

    Dasgupta, Antara; Das, Prasanta Kumar; Dias, Rita S.; Miguel, Maria G.; Lindman, Björn; Jadhav, Vaibhav M.; Gnanamani, Muthaiah; Maiti, Souvik

    2007-01-01

    The interaction behavior of DNA with different types of hydroxylated cationic surfactants has been studied. Attention was directed to how the introduction of hydroxyl substituents at the headgroup of the cationic surfactants affects the compaction of DNA. The DNA−cationic surfactant interaction was investigated at different charge ratios by several methods like UV melting, ethidium bromide exclusion, and gel electrophoresis. Studies show that there is a discrete transition in the DNA chain fr...

  5. MHD stability analysis of diagnostic optimized configuration shots in JET

    Energy Technology Data Exchange (ETDEWEB)

    Saarelma, S [Helsinki University of Technology, Euratom-TEKES Association, FIN-02015 HUT (Finland); Parail, V [EURATOM/UKAEA Fusion Association, Culham Science Centre, Abingdon, Oxfordshire OX14 3DB (United Kingdom); Andrew, Y [EURATOM/UKAEA Fusion Association, Culham Science Centre, Abingdon, Oxfordshire OX14 3DB (United Kingdom); Luna, E de la [Associacion EURATOM-CIEMAT para Fusion, Avenida Complutense 22, E-28040 Madrid (Spain); Kallenbach, A [MPI fuer Plasmaphysik, EURATOM Association, D-85748 Garching (Germany); Kempenaars, M [FOM-Rijnhuizen, Ass. Euratom-FOM, TEC, PO Box 1207, 3430 BE Nieuwegein (Netherlands); Korotkov, A [EURATOM/UKAEA Fusion Association, Culham Science Centre, Abingdon, Oxfordshire OX14 3DB (United Kingdom); Loarte, A [EFDA, CSU-Garching, Garching (Germany); Loennroth, J [Helsinki University of Technology, Euratom-TEKES Association, FIN-02015 HUT (Finland); Monier-Garbet, P [Association EURATOM-CEA, CEA Cadarache, DRFC, 13108, Saint-Paul-Lez-Durance (France); Stober, J [MPI fuer Plasmaphysik, EURATOM Association, D-85748 Garching (Germany); Suttrop, W [MPI fuer Plasmaphysik, EURATOM Association, D-85748 Garching (Germany)

    2005-05-01

    The plasma edge MHD stability is analysed for several JET discharges in the diagnostic optimized configuration. The stability analysis of Type I ELMy plasmas shows how after an edge localized mode (ELM) crash the plasma edge is deep in the stable region against low- to intermediate-n peeling-ballooning modes. As the pressure gradient steepens and the edge current builds up, the plasma reaches the low- to intermediate-n peeling-ballooning mode stability boundary just before the ELM crash. Increasing the plasma fuelling by gas puffing makes the second stability access against high-n ballooning modes narrower until it closes completely and the ELMs change from Type I to Type III. Reducing the plasma heating has a similar effect. Increasing the safety factor at the plasma edge improves the stability against low- to intermediate-n modes allowing steeper pressure gradients to develop before an ELM crash.

  6. Against Stabilization

    Directory of Open Access Journals (Sweden)

    Roger Mac Ginty

    2012-11-01

    Full Text Available This is a polemic against the concept and practice of stabilization as practiced by leading states from the global north in peace support interventions. It is not an argument against stability. Instead, it depicts stabilization as an essentially conservative doctrine that runs counter to its stated aims of enhancing local participation and legitimacy. It is an agenda of control that privileges notions of assimilation with international (western standards and mainstreams the military into peace-support operations. As a result, the value of peace is undercut.

  7. Non-bonding interactions and non-covalent delocalization effects play a critical role in the relative stability of group 12 complexes arising from interaction of diethanoldithiocarbamate with the cations of transition metals Zn(II), Cd(II), and Hg(II): a theoretical study.

    Science.gov (United States)

    Bahrami, Homayoon; Farhadi, Saeed; Siadatnasab, Firouzeh

    2016-07-01

    The chelating properties of diethanoldithiocarbamate (DEDC) and π-electron flow from the nitrogen atom to the sulfur atom via a plane-delocalized π-orbital system (quasi ring) was studied using a density functional theory method. The molecular structure of DEDC and its complexes with Zn(II), Cd(II), and Hg(II) were also considered. First, the geometries of this ligand and DEDC-Zn(II), DEDC-Cd(II), and DEDC-Hg(II) were optimized, and the formation energies of these complexes were then calculated based on the electronic energy, or sum of electronic energies, with the zero point energy of each species. Formation energies indicated the DEDC-Zn(II) complex as the most stable complex, and DEDC-Cd(II) as the least stable. Structural data showed that the N1-C2 π-bond was localized in the complexes rather than the ligand, and a delocalized π-bond over S7-C2-S8 was also present. The stability of DEDC-Zn(II), DEDC-Cd(II), and DEDC-Hg(II) complexes increased in the presence of the non-specific effects of the solvent (PCM model), and their relative stability did not change. There was π-electron flow or resonance along N1-C2-S7 and along S7-C2-S8 in the ligand. The π-electron flow or resonance along N1-C2-S7 was abolished when the metal interacted with sulfur atoms. Energy belonging to van der Waals interactions and non-covalent delocalization effects between the metal and sulfur atoms of the ligand was calculated for each complex. The results of nucleus-independent chemical shift (NICS) indicated a decreasing trend as Zn(II) electronic cloud localized on Hg(II) in the Hg(II)-DEDC complex. PMID:27299888

  8. Bithiophene radical cation: Resonance Raman spectroscopy and molecular orbital calculations

    DEFF Research Database (Denmark)

    Grage, M.M.-L.; Keszthelyi, T.; Offersgaard, J.F.; Wilbrandt, R.

    1998-01-01

    The resonance Raman spectrum of the photogenerated radical cation of bithiophene is reported. The bithiophene radical cation was produced via a photoinduced electron transfer reaction between excited bithiophene and the electron acceptor fumaronitrile in a room temperature acetonitrile solution a...... the Raman spectrum excited in resonance with the absorption band at 425 nm. The spectrum was interpreted with the help of density functional theory calculations. (C) 1998 Elsevier Science B.V.......The resonance Raman spectrum of the photogenerated radical cation of bithiophene is reported. The bithiophene radical cation was produced via a photoinduced electron transfer reaction between excited bithiophene and the electron acceptor fumaronitrile in a room temperature acetonitrile solution and...

  9. Cationic and PEGylated Amphiphilic Cyclodextrins: Co-Formulation Opportunities for Neuronal Sirna Delivery.

    Science.gov (United States)

    O'Mahony, Aoife M; Ogier, Julien; Darcy, Raphael; Cryan, John F; O'Driscoll, Caitriona M

    2013-01-01

    Optimising non-viral vectors for neuronal siRNA delivery presents a significant challenge. Here, we investigate a co-formulation, consisting of two amphiphilic cyclodextrins (CDs), one cationic and the other PEGylated, which were blended together for siRNA delivery to a neuronal cell culture model. Co-formulated CD-siRNA complexes were characterised in terms of size, charge and morphology. Stability in salt and serum was also examined. Uptake was determined by flow cytometry and toxicity was measured by MTT assay. Knockdown of a luciferase reporter gene was used as a measure of gene silencing efficiency. Incorporation of a PEGylated CD in the formulation had significant effects on the physical and biological properties of CD.siRNA complexes. Co-formulated complexes exhibited a lower surface charge and greater stability in a high salt environment. However, the inclusion of the PEGylated CD also dramatically reduced gene silencing efficiency due to its effects on neuronal uptake. The co-formulation strategy for cationic and PEGylated CDs improved the stability of the CD.siRNA delivery systems, although knockdown efficiency was impaired. Future work will focus on the addition of targeting ligands to the co-formulated complexes to restore transfection capabilities. PMID:23805220

  10. Investigations on the liquid crystalline phases of cation-induced condensed DNA

    Indian Academy of Sciences (India)

    C K S Pillai; Neethu Sundaresan; M Radhakrishnan Pillai; T Thomas; T J Thomas

    2005-10-01

    Viral and nonviral condensing agents are used in gene therapy to compact oligonucleotides and plasmid DNA into nanostructures for their efficient transport through the cell membranes. Whereas viral vectors are best by the toxic effects on the immune system, most of the nonviral delivery vehicles are not effective for use in clinical system. Recent investigations indicate that the supramolecular organization of DNA in the condensed state is liquid crystalline. The present level of understanding of the liquid crystalline phase of DNA is inadequate and a thorough investigation is required to understand the nature, stability, texture and the influence of various environmental conditions on the structure of the phase. The present study is mainly concerned with the physicochemical investigations on the liquid crystalline transitions during compaction of DNA by cationic species such as polyamines and metallic cations. As a preliminary to the above investigation, studies were conducted on the evolution of mesophase transitions of DNA with various cationic counterion species using polarized light microscopy. These studies indicated significant variations in the phase behaviour of DNA in the presence of Li and other ions. Apart from the neutralization of the charges on the DNA molecule, these ions are found to influence selectively the hydration sphere of DNA that in turn influences the induction and stabilization of the LC phases. The higher stability observed with the liquid crystalline phases of Li-DNA system could be useful in the production of nanostructured DNA. In the case of the polyamine, a structural specificity effect depending on the nature, charge and structure of the polyamine used has been found to be favoured in the crystallization of DNA.

  11. Investigations on the liquid crystalline phases of cation-induced condensed DNA

    Science.gov (United States)

    Pillai, C. K. S.; Sundaresan, Neethu; Radhakrishnan Pillai, M.; Thomas, T.; Thomas, T. J.

    2005-10-01

    Viral and nonviral condensing agents are used in gene therapy to compact oligonucleotides and plasmid DNA into nanostructures for their efficient transport through the cell membranes. Whereas viral vectors are best by the toxic effects on the immune system, most of the nonviral delivery vehicles are not effective for use in clinical system. Recent investigations indicate that the supramolecular organization of DNA in the condensed state is liquid crystalline. The present level of understanding of the liquid crystalline phase of DNA is inadequate and a thorough investigation is required to understand the nature, stability, texture and the influence of various environmental conditions on the structure of the phase. The present study is mainly concerned with the physico-chemical investigations on the liquid crystalline transitions during compaction of DNA by cationic species such as polyamines and metallic cations. As a preliminary to the above investigation, studies were conducted on the evolution of mesophase transitions of DNA with various cationic counterion species using polarized light microscopy. These studies indicated significant variations in the phase behaviour of DNA in the presence of Li and other ions. Apart from the neutralization of the charges on the DNA molecule, these ions are found to influence selectively the hydration sphere of DNA that in turn influences the induction and stabilization of the LC phases. The higher stability observed with the liquid crystalline phases of Li--DNA system could be useful in the production of nanostructured DNA. In the case of the polyamine, a structural specificity effect depending on the nature, charge and structure of the polyamine used has been found to be favoured in the crystallization of DNA.

  12. Foams Stabilized by Tricationic Amphiphilic Surfactants

    OpenAIRE

    Heerschap, Seth; Marafino, John N.; McKenna, Kristin; Caran, Kevin L.; Feitosa, Klebert

    2015-01-01

    The unique surface properties of amphiphilic molecules have made them widely used in applications where foaming, emulsifying or coating processes are needed. Novel surfactant architectures with multi-cephalic and multi-tailed molecules have reportedly enhanced their anti-bacterial activity in connection with tail length and the nature of the head group, but their ability to produce and stabilize foam is mostly unknown. Here we report on experiments with tris-cationic, triple-headed, double- a...

  13. Intermediate/Advanced Research Design and Statistics

    Science.gov (United States)

    Ploutz-Snyder, Robert

    2009-01-01

    The purpose of this module is To provide Institutional Researchers (IRs) with an understanding of the principles of advanced research design and the intermediate/advanced statistical procedures consistent with such designs

  14. Bursts of intermediate ions in atmospheric air

    Science.gov (United States)

    Hõrrak, U.; Salm, J.; Tammet, H.

    1998-06-01

    The mobility spectrum of air ions has been measured at Tahkuse Observatory in Estonia for several years. The average concentration of intermediate ions with mobilities of 0.05-0.5 cm2 V-1 s-1 in atmospheric air is about 50 cm-3. On the level of this low background, high concentration bursts of intermediate air ions occur occasionally. A burst can be followed by subsequent evolution of intermediate ions into larger ones. To explain the bursts of intermediate air ions, two hypotheses can be advanced: (1)A burst of neutral particles occurs due to homogeneous nucleation, and the particles are charged by the attachment of cluster ions. (2) The cluster ions grow by ion-induced nucleation in proper environmental conditions.

  15. Preparation of poly(glycidylmethacrylate-divinylbenzene) weak acid cation exchange stationary phases with succinic anhydride, phthalic anhydride, and maleic anhydride for ion chromatography.

    Science.gov (United States)

    Liu, Junwei; Wang, Yong; Wu, Shuchao; Zhang, Peimin; Zhu, Yan

    2016-08-01

    In this work, poly(glycidylmethacrylate-divinylbenzene) microspheres were prepared and applied for the preparation of weak acid cation exchange stationary phases. Succinic anhydride, phthalic anhydride, and maleic anhydride were selected as carboxylation reagents to prepare three weak acid cation exchangers by direct chemical derivatization reaction without solvent or catalyst. The diameters and dispersity of the microspheres were characterized by scanning electron microscopy; the amount of accessible epoxy groups and mechanical stability were also measured. The weak acid cation exchangers were characterized by Fourier transform infrared spectroscopy; the content of carboxyl groups was measured by traditional acid base titration method. The chromatographic properties were characterized and compared by separating alkali, alkaline earth metal ions and ammonium and polar amines. The separation properties enhanced in the order of succinic anhydride, phthalic anhydride, and maleic anhydride modified poly(glycidylmethacrylate-divinylbenzene) cation exchangers. PMID:27288092

  16. Current stabilizer

    International Nuclear Information System (INIS)

    A current stabilizer for supplying magnetic lens of β-monochromator at the electron energy up to 1 MeV is described. Stabilization method with use of reference high-stabilized source of direct voltage with switching-in loading (monochromator coil) to circuit of negative feedback of direct-current amplifier with high gain is chosen for stabilization of direct current. The range of current regulation is 0.5 A at available power up to 15 W. Current instability during 10 hour continuous work does not exceed 10-4% that makes it possible to provide instability of electron energy at the monochromator exit using 90Sr+90Y β-nucleide of not more than 10 -4% and number of electrons 2.5x10-4% respectively

  17. Some Aspects of Intermediate mass black holes

    OpenAIRE

    Sivaram, C; Arun, Kenath

    2007-01-01

    There is a lot of current astrophysical evidence and interest in intermediate mass black holes, ranging from a few hundred to several thousand solar masses. The active galaxy M82 and the globular cluster in M31, for example, are known to host such objects. Here we discuss several aspects of intermediate mass black holes such as their expected luminosity, spectral nature of radiation, associated jets, etc. We also discuss possible scenarios for their formation including the effects of dynamica...

  18. Has Banks’ Financial Intermediation Improved in Russia?

    OpenAIRE

    Fungachova, Z.; Solanko, L.

    2010-01-01

    The aim of this paper is to analyze the increasing importance of banks in the Russian economy over the period following the financial crisis of 1998. We use several measures to assess the role of banks in domestic financial intermediation in Russia. The traditional macro-level view is complemented by the analysis of sectoral financial flows as well as by insights from micro-level studies. All of these confirm that banks are becoming increasingly important in financial intermediation. We find ...

  19. Financial intermediation and occupational choice in development

    OpenAIRE

    Erosa, Andrés

    2000-01-01

    This paper presents evidence that the spread between the marginal product of capital and the return on financial assets is mich higher in poor than in rich countries. A model with costly intermediation is developed. In this economy, individuals choose at each instant whether to work or to operate a technology. Entrepreneurs finance their business with their own savings and, if necessary, by borrowing from banks. I find that in this framework intermediation costs are not equivalent to a tax on...

  20. Firm. An intermediate language for compiler research

    OpenAIRE

    Beck, Michael; Boesler, Boris; Geiß, Rubino; Lindenmaier, Götz

    2005-01-01

    State of the art compiler intermediate representations incorporate SSA data dependencies in a graph based manner. We present the intermediate representation Firm, which extends the functional stores of Steensgard and introduces a novel representation of exceptions. Firm offers a high-level representation of the type hierarchy and object-oriented features, which makes it exceptional suitable for analysing and optimizing of strongly typed languages. The co...

  1. Financial Intermediation in the United States

    OpenAIRE

    Benjamin M. Friedman

    1984-01-01

    The principal rationales that give rise to financial intermediation are benefits of size and specialization, the diversification of specific asset risks, and the pooling of even broader classes of risk. Each is a significant factor in accounting for the U.S. economy's reliance on intermediation. In addition, since World War II a further important factor has been the economy's continual shift away from government debt toward the debt of private nonfinancial entities including individuals and b...

  2. Interaction of actinide cations with synthetic polyelectrolytes

    International Nuclear Information System (INIS)

    The binding of Am+3, Th+4 and UO2+2 to polymaleic acid, polyethylenemaleic acid and polymethylvinylethermaleic acid has been measured by a solvent extraction technique at 250C and either 0.02 or 0.10 M ionic strength. The solutions were buffered over a pH range such that the percent of carboxylate groups ionized ranged from 25 to 74%. The binding was described by two constants, β1 and β2, which were evaluated after correction for complexation of the actinide cations by acetate and hydrolysis. For comparable degrees of ionization, all three polyelectrolytes showed similar binding strengths. In general, these results indicated that the binding of actinides to these synthetic polyelectrolytes is basically similar to that of natural polyelectrolytes such as humic and fulvic acids. (orig.)

  3. Hydration Structure of the Quaternary Ammonium Cations

    KAUST Repository

    Babiaczyk, Wojtek Iwo

    2010-11-25

    Two indicators of the hydropathicity of small solutes are introduced and tested by molecular dynamics simulations. These indicators are defined as probabilities of the orientation of water molecules\\' dipoles and hydrogen bond vectors, conditional on a generalized distance from the solute suitable for arbitrarily shaped molecules. Using conditional probabilities, it is possible to distinguish features of the distributions in close proximity of the solute. These regions contain the most significant information on the hydration structure but cannot be adequately represented by using, as is usually done, joint distance-angle probability densities. Our calculations show that using our indicators a relative hydropathicity scale for the interesting test set of the quaternary ammonium cations can be roughly determined. © 2010 American Chemical Society.

  4. Univalent-cation-elicited acidification by yeasts.

    Science.gov (United States)

    Kotyk, A; Georghiou, G

    1994-08-01

    Addition of univalent cations to sugar-metabolizing Saccharomyces cerevisiae, Schizosaccharomyces pombe and Lodderomyces elongisporus brought about a powerful acidification of the external medium with rates up to nearly 20 nmol H+ per min per mg dry wt. in S. cerevisiae, over 15 nmol in S. pombe, and 4.7 nmol in L. elongisporus. These rates were as much as 20 times, 5.5 times and 10.3 times, respectively. higher than in the absence of K+. Use of galactose-induced cells, of H(+)-ATPase-deficient mutants and observations over the entire growth curve indicated that the K+ effect on H+ extrusion is not connected with the H(+)-ATPase function as such but rather depends on metabolic reactions producing ATP. The effect has apparently nothing to do with the electrical potential across the plasma membrane. PMID:7804140

  5. Cationic nanofibrillar cellulose with high antibacterial properties.

    Science.gov (United States)

    Chaker, Achraf; Boufi, Sami

    2015-10-20

    Cationic nanofibrillar cellulose (C-NFC) has been prepared via a high pressure homogenization using quaternized cellulose fibers with glycidyltrimethylammonium chloride. It has been shown that the quaternization of dried softwood pulp facilitated the defibrillation processes and prevented clogging of the homogenizer. The effects of the trimethylammonium chloride content on the fibrillation yield, the transparency degree of the gel, the rheological behavior of the NFC suspension and their electrokinetic properties were investigated. AFM observation showed that the NFC suspension consisted of individualized cellulose I nanofibrils 4-5nm in width and length in the micronic scale. In addition to their strong reinforcing potential, the inclusion of C-NFC into a polymer matrix was shown to efficiently enhance the antibacterial activity. The reinforcing potential of C-NFC, studied by dynamic mechanical analysis (DMA), was compared to anionic NFC and the difference was explained in terms of the nanofibrils capacities to build up a strong networks held by hydrogen bonding. PMID:26256179

  6. Electronic structure near cationic defects in magnetite

    International Nuclear Information System (INIS)

    We used the DFT + U method to describe the modification of the physical properties induced by cationic point defects in cubic magnetite Fe3O4. We considered the case of Fe vacancies and interstitial atoms in non-stoichiometric magnetite, and of Frenkel defects in a stoichiometric crystal. For each of these defects, we give results on the modification of the magnetic moment of atoms near the defect. We describe the local reorganization of the electric charge which is responsible for changes in the average oxidation degree of Fe atoms. We show that gap states, when they exist, do not destroy the half-metallic character of magnetite. Fe defects, however, change the filling of bands crossing the Fermi level and must be mostly responsible for a decrease in the magnetization. (paper)

  7. Higher order antibunching in intermediate states

    International Nuclear Information System (INIS)

    Since the introduction of binomial state as an intermediate state, different intermediate states have been proposed. Different nonclassical effects have also been reported in these intermediate states. But till now higher order antibunching is predicted in only one type of intermediate state, which is known as shadowed negative binomial state. Recently we have shown that the higher order antibunching is not a rare phenomenon [P. Gupta, P. Pandey, A. Pathak, J. Phys. B 39 (2006) 1137]. To establish our earlier claim further, here we have shown that the higher order antibunching can be seen in different intermediate states, such as binomial state, reciprocal binomial state, hypergeometric state, generalized binomial state, negative binomial state and photon added coherent state. We have studied the possibility of observing the higher order subpoissonian photon statistics in different limits of intermediate states. The effects of different control parameters on the depth of non classicality have also been studied in this connection and it has been shown that the depth of nonclassicality can be tuned by controlling various physical parameters

  8. Refolding of Denatured/Reduced Lysozyme Using Weak-Cation Exchange Chromatography

    Institute of Scientific and Technical Information of China (English)

    Yan WANG; Bo Lin GONG; Xin Du GENG

    2003-01-01

    Oxidative refolding of the denatured/reduced lysozyme was investigated by using weak-cation exchange chromatography (WCX). The stationary phase of WCX binds to the reduced lysozyme and prevented it from forming intermolecular aggregates. At the same time urea and ammonium sulfate were added to the mobile phase to increase the elution strength for lysozyme. Ammonium sulfate can more stabilize the native protein than a common eluting agent, sodium chloride. Refolding of lysozyme by using this WCX is successfully. It was simply carried out to obtain a completely and correctly refolding of the denatured lysozyme at high concentration of 20.0 mg/mL.

  9. Synthesis and Characterization of Yttrium Doped Nano-zirconia by a Cationic Surfactant-assisted Route

    Institute of Scientific and Technical Information of China (English)

    YU Jian-Chang; HU Shen-Wei

    2006-01-01

    Recently, more and more interest has been focused on zirconia for its unique characteristics. In this paper, via the preceding preparation technique, yttrium can be successfully incorporated into nano-zirconia by a cationic surfactant-assisted route. The methods of XRD, TEM, EDS, Uv-vis and N2 adsorption-desorption are adopted to characterize the synthesized samples. The results show that the yttrium has been successfully incorporated into the zirconia lattice, and the thermal stability of yttrium doped zirconia has been enhanced remarkably.

  10. Elaboration of ammonio methacrylate copolymer based spongy cationic particles via double emulsion solvent evaporation process.

    Science.gov (United States)

    Zafar, Nadiah; Bitar, Ahmad; Valour, Jean Pierre; Fessi, Hatem; Elaissari, Abdelhamid

    2016-04-01

    The aim of present work is to investigate systematic study of the preparation of biodegradable particles via double emulsion solvent evaporation technique. The used formation is based on cationic ammonium methacrylate copolymer Eudragit® RS 100, without the use of any stabilizer. The effect of process parameters like ultra turrax® stirring speed and stirring time, ultrasonication time, polymer amount, and volume of outer aqueous phases on the colloidal properties of particles was investigated. All prepared dispersions were characterized in terms of size, size distribution, and electrokinetic properties, and surface morphology was investigated. PMID:26838828

  11. A review of modelling the interaction between natural organic matter and metal cations

    International Nuclear Information System (INIS)

    This report reviews techniques available to model the interaction between natural organic matter (mainly fulvic and humic acids) and metal cations and protons. A comprehensive overview over the properties of natural organic matter is given and experimental techniques are presented briefly. Two major concepts of modelling have been identified: discrete ligand models and continuous distribution model. Different modelling approaches like Discrete Ligand Models (s.s.), Random-Structure Model, Affinity Spectra, Statistical Distribution Models, Continuous Stability Function Models and surface sorption models and their advantages/disadvantages are discussed. (author)

  12. Understanding the fate of the oxyallyl cation following Nazarov electrocyclization: sequential Wagner-Meerwein migrations and the synthesis of spirocyclic cyclopentenones

    OpenAIRE

    Huang, Jie; Lebœuf, David; Frontier, Alison J.

    2011-01-01

    A general reaction sequence is described that involves Nazarov cyclization followed by two sequential Wagner Meerwein migrations, to afford spirocyclic compounds from divinyl ketones in the presence of one equivalent of copper(II) complexes. A detailed investigation of this sequence is described including a study of substrate scope and limitations. It was found that after 4π electrocyclization, two different pathways are available to the oxyallyl cation intermediate: elimination of a proton c...

  13. Unexpected tautomeric equilibria of the carbanion-enamine intermediate in pyruvate oxidase highlight unrecognized chemical versatility of thiamin

    OpenAIRE

    Meyer, Danilo; Neumann, Piotr; Koers, Eline; Sjuts, Hanno; Lüdtke, Stefan; Sheldrick, George M.; Ficner, Ralf; Tittmann, Kai

    2012-01-01

    Thiamin diphosphate, the vitamin B1 coenzyme, plays critical roles in fundamental metabolic pathways that require acyl carbanion equivalents. Studies on chemical models and enzymes had suggested that these carbanions are resonance-stabilized as enamines. A crystal structure of this intermediate in pyruvate oxidase at 1.1 Å resolution now challenges this paradigm by revealing that the enamine does not accumulate. Instead, the intermediate samples between the ketone and the carbanion both inter...

  14. Lithium ionophore VIII as an extraordinarily strong receptor for the trivalent europium cation

    Science.gov (United States)

    Makrlík, Emanuel; Novák, Vít; Vaňura, Petr

    2015-01-01

    On the basis of extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium Eu3+(aq) + 3A-(aq) + 1(nb) ⇆ 1.Eu3+(nb) + 3A‑(nb) occurring in the two-phase water-nitrobenzene system (A- = CF3SO-3; 1 = lithium ionophore VIII; aq = aqueous phase, nb = nitrobenzene phase) was determined as log Kex (1.Eu3+, 3A‑) = 2.5 ± 0.1. Furthermore, the extremely high stability constant of the 1.Eu3+ complex in nitrobenzene saturated with water was calculated: log βnb (1.Eu3+) = 15.6 ± 0.1. Finally, by using DFT calculations, the most probable structure of the cationic complex species 1.Eu3+ was derived. In the resulting complex, the 'central' cation Eu3+ is bound by six very strong bond interactions to the corresponding six oxygen atoms of the parent ligand 1. It is evident that this exceptionally effective receptor 1 for the Eu3+ cation could be considered as a potential extraction agent for nuclear waste treatment.

  15. Cation Exchange in Dynamic 3D Porous Magnets: Improvement of the Physical Properties.

    Science.gov (United States)

    Grancha, Thais; Acosta, Alvaro; Cano, Joan; Ferrando-Soria, Jesús; Seoane, Beatriz; Gascon, Jorge; Pasán, Jorge; Armentano, Donatella; Pardo, Emilio

    2015-11-16

    We report two novel three-dimensional porous coordination polymers (PCPs) of formulas Li4{Mn4[Cu2(Me3mpba)2]3}·68H2O (2) and K4{Mn4[Cu2(Me3mpba)2]3}·69H2O (3) obtained-via alkali cation exchange in a single-crystal to single-crystal process-from the earlier reported anionic manganese(II)-copper(II) PCP of formula Na4{Mn4[Cu2(Me3mpba)2]3}·60H2O (1) [Me3mpba(4-) = N,N'-2,4,6-trimethyl-1,3-phenylenebis(oxamate)]. This postsynthetic process succeeds where the direct synthesis in solution from the corresponding building blocks fails and affords significantly more robust PCPs with enhanced magnetic properties [long-range 3D magnetic ordering temperatures for the dehydrated phases (1'-3') of 2.0 (1'), 12.0 (2'), and 20.0 K (3')]. Changes in the adsorptive properties upon postsynthetic exchange suggest that the nature, electrostatic properties, mobility, and location of the cations within the framework are crucial for the enhanced structural stability. Overall, these results further confirm the potential of postsynthetic methods (including cation exchange) to obtain PCPs with novel or enhanced physical properties while maintaining unaltered their open-framework structures. PMID:26492551

  16. Cationic lioposomes with folic acid as targeting ligand for gene delivery.

    Science.gov (United States)

    Cui, Shao-Hui; Zhi, De-Fu; Zhao, Yi-Nan; Chen, Hui-Ying; Meng, Yao; Zhang, Chuan-Min; Zhang, Shu-Biao

    2016-08-15

    In our previous Letter, we have carried out the synthesis of a novel DDCTMA cationic lipid which was formulated with DOPE for gene delivery. Herein, we used folic acid (FA) as targeting ligand and cholesterol (Chol) as helper lipid instead of DOPE for enhancing the stability of the liposomes. These liposomes were characterized by dynamic laser scattering (DLS), transmission electron microscopy (TEM) and agarose gel electrophoresis assays of pDNA binding affinity. The lipoplexes were prepared by using different weight ratios of DDCTMA/Chol (1:1, 2:1, 3:1, 4:1) liposomes and different concentrations of FA (50-200μg/mL) combining with pDNA. The transfection efficiencies of the lipoplexes were evaluated using pGFP-N2 and pGL3 plasmid DNA against NCI-H460 cells in vitro. Among them, the optimum gene transfection efficiency with DDCTMA/Chol (3:1)/FA (100μg/mL) was obtained. The results showed that FA could improve the gene transfection efficiencies of DDCTMA/Chol cationic liposome. Our results also convincingly demonstrated FA (100μg/mL)-coated DDCTMA/Chol (3:1) cationic liposome could serve as a promising candidate for the gene delivery. PMID:27426864

  17. The sequence to hydrogenate coronene cations: A journey guided by magic numbers.

    Science.gov (United States)

    Cazaux, Stéphanie; Boschman, Leon; Rougeau, Nathalie; Reitsma, Geert; Hoekstra, Ronnie; Teillet-Billy, Dominique; Morisset, Sabine; Spaans, Marco; Schlathölter, Thomas

    2016-01-01

    The understanding of hydrogen attachment to carbonaceous surfaces is essential to a wide variety of research fields and technologies such as hydrogen storage for transportation, precise localization of hydrogen in electronic devices and the formation of cosmic H2. For coronene cations as prototypical Polycyclic Aromatic Hydrocarbon (PAH) molecules, the existence of magic numbers upon hydrogenation was uncovered experimentally. Quantum chemistry calculations show that hydrogenation follows a site-specific sequence leading to the appearance of cations having 5, 11, or 17 hydrogen atoms attached, exactly the magic numbers found in the experiments. For these closed-shell cations, further hydrogenation requires appreciable structural changes associated with a high transition barrier. Controlling specific hydrogenation pathways would provide the possibility to tune the location of hydrogen attachment and the stability of the system. The sequence to hydrogenate PAHs, leading to PAHs with magic numbers of H atoms attached, provides clues to understand that carbon in space is mostly aromatic and partially aliphatic in PAHs. PAH hydrogenation is fundamental to assess the contribution of PAHs to the formation of cosmic H2. PMID:26821925

  18. Experimental and theoretical study on interaction of the silver cation with nonactin

    Science.gov (United States)

    Makrlík, Emanuel; Vaňura, Petr

    2015-12-01

    From extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium ? occurring in the two-phase water-nitrobenzene system (1 = nonactin, aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log Kex (Ag+, 1 ṡ Na+) = 0.6 ± 0.1. Furthermore, the stability constant of the 1 ṡ Ag+ complex in nitrobenzene saturated with water was calculated for a temperature of 25 °C: log βnb(1 ṡ Ag+) = 6.6 ± 0.2. Finally, employing quantum mechanical calculations, the most probable structure of the cationic complex species 1 ṡ Ag+ was derived. In the resulting complex, having a tennis-ball-seam conformation with the C2 symmetry, the 'central' cation Ag+ is bound by eight relatively strong bonding interactions to eight oxygen atoms of the parent nonactin ligand. The interaction energy of the considered 1 ṡ Ag+ complex was found to be -468.5 kJ/mol, confirming also the formation of this cationic species.

  19. Uranium adsorption from the sulphuric acid leach liquor containing more chlorides with cation-exchange resin SL-406

    International Nuclear Information System (INIS)

    The feasibility of uranium adsorption was studied from the sulphuric acid leach liquor of a uranium ore containing more chlorides with cation-exchange resin SL-406. The influence of some factors on uranium adsorption was investigated. It was shown that the resin possesses better selectivity, stability and higher capacity. It can be effectively used to recovery uranium from leach liquors of uranium ores containing more chlorides

  20. Effects of cationic hydroxyethyl cellulose on glucose tolerance and obesity

    Science.gov (United States)

    Cholestyramine is a cationic polymer prescribed to lower cholesterol in humans. We investigated the effects of cationic hydroxyethyl cellulose (cHEC) on weight loss and metabolic disorders associated with obesity using both hamster and diet-induced obese mouse models. Golden Syrian hamsters and ob...

  1. Photodynamic Inactivation of Bacteria and Biofilms Using Cationic Bacteriochlorins

    Science.gov (United States)

    Meerovich, G. A.; Tiganova, I. G.; Makarova, E. A.; Meerovich, I. G.; Romanova Ju., M.; Tolordova, E. R.; Alekseeva, N. V.; Stepanova, T. V.; Yu, Koloskova; Luk'anets, E. A.; Krivospitskaya, N. V.; Sipailo, I. P.; Baikova, T. V.; Loschenov, V. B.; Gonchukov, S. A.

    2016-02-01

    This work is devoted to the study of two new synthetic bacteriochlorins with four and eight cationic substitutes as the photosensitizers in the photodynamic process. The spectral and antibacterial properties of these photosensitizers in saline solution were investigated. It is shown, that the aggregation ability decreases and the antibacterial efficiency grows as the cationic substitute number increases.

  2. Decomplexing metallic cations from metallo-organic compounds

    OpenAIRE

    Melian, C.I.; Kapteijn F.; Moulijn, J.A.

    2006-01-01

    The invention is directed to a process for liberating metallic cations from metallo-organic compounds, said process comprising contacting an aqueous solution of the metallo-organic compound with an oxidising agent, thereby oxidising the organic component and obtaining the free cation

  3. Effects of metallic cations in the beryl flotation

    International Nuclear Information System (INIS)

    The beryl zeta potential in microelectrophoretic cell is studied in the presence of neutral electrolyte, cations of calcium, magnesium and iron. The petroleum sulfonate is used how collector in Hallimond tube. Hydroxy complex of metallic cations seems activate the ore and precipitates of colloidal metallic hidroxies seems lower him when added to the mixture. (M.A.C.)

  4. Stable polyfluorinated cycloalkenyl cations and their NMR spectra

    International Nuclear Information System (INIS)

    New stable 1-methoxyperfluoro-2-ethylcyclobutenyl, 1-methoxyperfluoro-2-methylcyclo-pentenyl, and 1-methoxyperfluoro-2-ethylcyclohexenyl cations were obtained by the action of antimony pentafluoride on the corresponding olefins. The distribution of the charges in the investigated polyfluorinated cycloalkenyl cations was investigated by 13C NMR method

  5. In vivo toxicity of cationic micelles and liposomes

    DEFF Research Database (Denmark)

    Knudsen, Kristina Bram; Northeved, Helle; Ek, Pramod Kumar;

    2015-01-01

    This study investigated toxicity of nanocarriers comprised of cationic polymer and lipid components often used in gene and drug delivery, formulated as cationic micelles and liposomes. Rats were injected intravenously with 10, 25 or 100 mg/kg and sacrificed after 24 or 48 h, or 24 h after the las...

  6. Application of remote sensing technique to site selection for low and intermediate level radioactive waste

    International Nuclear Information System (INIS)

    Based on the relative criteria of selection of disposal site for low and intermediate level radioactive waste, the social-economic conditions, landform, morphologic properties, regional geological stability, hydrogeological and engineering geological characters of adjacent area of Anhui, Zhejiang and Jiangsu provinces were investigated. The geological interpretation of thematic mapper images, field reconnaissance and data analysis were conducted during the research work. The results show that three areas in the west part of Zhejiang Province were recommended as potential site for disposal of low and intermediate level radioactive waste. They are Bajiaotang area, Tiebanchong area and Changxing-Guangde-Anji nabes

  7. Theory of Square-Wave Voltammetry of Two-Electron Reduction with the Adsorption of Intermediate

    Directory of Open Access Journals (Sweden)

    Milivoj Lovric

    2012-01-01

    Full Text Available Thermodynamically unstable intermediate of fast and reversible two-electron electrode reaction can be stabilized by the adsorption to the electrode surface. In square-wave voltammetry of this reaction mechanism, the split response may appear if the electrode surface is not completely covered by the adsorbed intermediate. The dependence of the difference between the net peak potentials of the prepeak and postpeak on the square-wave frequency is analyzed theoretically. This relationship can be used for the estimation of adsorption constant.

  8. Observing a late folding intermediate of Ubiquitin at atomic resolution by NMR.

    Science.gov (United States)

    Surana, Parag; Das, Ranabir

    2016-08-01

    The study of intermediates in the protein folding pathway provides a wealth of information about the energy landscape. The intermediates also frequently initiate pathogenic fibril formations. While observing the intermediates is difficult due to their transient nature, extreme conditions can partially unfold the proteins and provide a glimpse of the intermediate states. Here, we observe the high resolution structure of a hydrophobic core mutant of Ubiquitin at an extreme acidic pH by nuclear magnetic resonance (NMR) spectroscopy. In the structure, the native secondary and tertiary structure is conserved for a major part of the protein. However, a long loop between the beta strands β3 and β5 is partially unfolded. The altered structure is supported by fluorescence data and the difference in free energies between the native state and the intermediate is reflected in the denaturant induced melting curves. The unfolded region includes amino acids that are critical for interaction with cofactors as well as for assembly of poly-Ubiquitin chains. The structure at acidic pH resembles a late folding intermediate of Ubiquitin and indicates that upon stabilization of the protein's core, the long loop converges on the core in the final step of the folding process. PMID:27111887

  9. Theoretical study of partial oxidation of ethylene by vanadium trioxide cluster cation

    Institute of Scientific and Technical Information of China (English)

    WANG ZheChen; DING XunLei; MA YanPing; CAO Hai; WU XiaoNan; ZHAO YanXia; HE ShengGui

    2009-01-01

    Density functional theory (DFT) study of reaction between vanadium trioxide cluster cation (VO+3) and ethylene (C2H4) to yield VO+2 + CH3CHO (acetaldehyde) and VO2CH+2 + HCHO (formaldehyde) is carried out.Structures of all reactants,products,intermediates,and transition state in the reaction have been optimized and characterized.The results show unexpected barriers in the reaction due to the existence of a η2-O2 moiety in the ground state structure of VO+3.The initial reaction steps combining ethylene adsorption,C=C activation and O-O cleavage are proposed as rate limiting processes.Comparison of reactions of VO+3 + C2H4 with VO3 + C2H4 and VO+2 + C2H4 in the previous studies is made in detail.The results of this work may shed light on the understanding of C=C bond cleavage in related heterogeneous catalysis.

  10. A useful methoxyvinyl cation equivalent: α-t-butyldimethylsilyl-α-methoxyacetaldehyde

    Science.gov (United States)

    McCune, Christopher D.; Beio, Matthew L.; Friest, Jacob A.; Ginotra, Sandeep; Berkowitz, David B.

    2015-01-01

    Described are the synthesis and application of α-t-butyldimethylsilyl-α-methoxyacetaldehyde as a formal methoxyvinyl cation equivalent. Addition of Grignard reagents to the title aldehyde, followed by treatment of the intermediate β-hydroxysilanes with KH, gives good yields of large Z-methoxyvinylated products. Assuming a Peterson-like elimination mechanism, one can infer that the Grignard addition proceeds with high syn selectivity. These results are consistent with a chelation control model involving coordination to the α-methoxy group in the title aldehyde rather than an alternative stereoelectronic Felkin-Anh-type model. It must be noted that a steric Felkin-Anh model also accounts for the observed stereochemistry. All told, the title reagent can be employed to efficiently append a Z-configured methoxyvinyl group to an appropriate R-M species, in two steps. PMID:26028786

  11. Aqueous oxidation of sulfonamide antibiotics: aromatic nucleophilic substitution of an aniline radical cation.

    Science.gov (United States)

    Tentscher, Peter R; Eustis, Soren N; McNeill, Kristopher; Arey, J Samuel

    2013-08-19

    Sulfonamide antibiotics are an important class of organic micropollutants in the aquatic environment. For several, sulfur dioxide extrusion products have been previously reported upon photochemical or dark oxidation. Using quantum chemical modeling calculations and transient absorption spectroscopy, it is shown that single-electron oxidation from sulfadiazine produces the corresponding aniline radical cation. Density functional theory calculations indicate that this intermediate can exist in four protonation states. One species exhibits a low barrier for an intramolecular nucleophilic attack at the para position of the oxidized aniline ring, in which a pyrimidine nitrogen acts as a nucleophile. This attack can lead to a rearranged structure, which exhibits the same connectivity as the SO2 -extruded oxidation product that was previously observed in the aquatic environment and characterized by NMR spectroscopy. We report a detailed reaction mechanism for this intramolecular aromatic nucleophilic substitution, and we discuss the possibility of this reaction pathway for other sulfonamide drugs. PMID:23828254

  12. Anaerobic Toxicity of Cationic Silver Nanoparticles

    Science.gov (United States)

    The microbial toxicity of silver nanoparticles (AgNPs) stabilized with different capping agents was compared to that of Ag+ under anaerobic conditions. Three AgNPs were investigated: (1) negatively charged citrate-coated AgNPs (citrate-AgNPs), (2) minimally charged p...

  13. PARALLEL STABILIZATION

    Institute of Scientific and Technical Information of China (English)

    J.L.LIONS

    1999-01-01

    A new algorithm for the stabilization of (possibly turbulent, chaotic) distributed systems, governed by linear or non linear systems of equations is presented. The SPA (Stabilization Parallel Algorithm) is based on a systematic parallel decomposition of the problem (related to arbitrarily overlapping decomposition of domains) and on a penalty argument. SPA is presented here for the case of linear parabolic equations: with distrjbuted or boundary control. It extends to practically all linear and non linear evolution equations, as it will be presented in several other publications.

  14. Partially folded intermediates during trypsinogen denaturation

    Directory of Open Access Journals (Sweden)

    Martins N.F.

    1999-01-01

    Full Text Available The equilibrium unfolding of bovine trypsinogen was studied by circular dichroism, differential spectra and size exclusion HPLC. The change in free energy of denaturation was = 6.99 ± 1.40 kcal/mol for guanidine hydrochloride and = 6.37 ± 0.57 kcal/mol for urea. Satisfactory fits of equilibrium unfolding transitions required a three-state model involving an intermediate in addition to the native and unfolded forms. Size exclusion HPLC allowed the detection of an intermediate population of trypsinogen whose Stokes radii varied from 24.1 ± 0.4 Å to 26.0 ± 0.3 Å for 1.5 M and 2.5 M guanidine hydrochloride, respectively. During urea denaturation, the range of Stokes radii varied from 23.9 ± 0.3 Å to 25.7 ± 0.6 Å for 4.0 M and 6.0 M urea, respectively. Maximal intrinsic fluorescence was observed at about 3.8 M urea with 8-aniline-1-naphthalene sulfonate (ANS binding. These experimental data indicate that the unfolding of bovine trypsinogen is not a simple transition and suggest that the equilibrium intermediate population comprises one intermediate that may be characterized as a molten globule. To obtain further insight by studying intermediates representing different stages of unfolding, we hope to gain a better understanding of the complex interrelations between protein conformation and energetics.

  15. Preparation, characterization, and evaluation of antitumor effect of Brucea javanica oil cationic nanoemulsions.

    Science.gov (United States)

    Liu, Ting-Ting; Mu, Li-Qiu; Dai, Wei; Wang, Chuan-Bang; Liu, Xin-Yi; Xiang, Da-Xiong

    2016-01-01

    The purpose of this study was to prepare Brucea javanica oil cationic nanoemulsions (BJO-CN) with BJO as drug as well as oil phase and chitosan as cationic inducer, to explore the practical suitability of using cationic nanoemulsions for oral delivery of mixed oil, and to test its bioavailability and antitumor effect. BJO-CN was prepared by chitosan solution stirring method and then characterized physicochemically. The obtained BJO-CN had a spherical morphology with a positive zeta potential of 18.9 mV and an average particle size of 42.36 nm, showing high colloidal stability. The drug loading of BJO-CN was 91.83 mg·mL(-1), determined by high-performance liquid chromatography with precolumn derivatization. Pharmacokinetic studies revealed that, compared with BJO emulsion (BJO-E) (the dosage of BJO-CN and BJO-E was equal to 505 mg·kg(-1), calculated by oleic acid), BJO-CN exhibited a significant increase in the area under the plasma drug concentration-time curve over the period of 24 hours and relative bioavailability was 1.6-fold. Furthermore, the antitumor effect of BJO-CN in the orthotopic mouse model of lung cancer was evaluated by recording the median survival time and the weight of lung tissue with tumor, hematoxylin and eosin staining, and immunohistochemical technique. Results of anticancer experiments illustrated that, even though the administrated dosage in the BJO-CN group was half of that in the BJO-E group, BJO-CN exhibited similar antitumor effect to BJO-E. Moreover, BJO-CN had good synergistic effect in combination therapy with vinorelbine. These results suggested that cationic nanoemulsions are an effective and promising delivery system to enhance the oral bioavailability and anticancer effect of BJO. PMID:27330293

  16. Gramicidin tryptophans mediate formamidinium-induced channel stabilization.

    OpenAIRE

    Seoh, S A; Busath, D

    1995-01-01

    Compared with alkali metal cations, formamidinium ions stabilize the gramicidin A channel molecule in monoolein bilayers (Seoh and Busath, 1993a). A similar effect is observed with N-acetyl gramicidin channel molecules in spite of the modified forces at the dimeric junction (Seoh and Busath, 1993b). Here we use electrophysiological measurements with tryptophan-to-phenylalanine-substituted gramicidin analogs to show that the formamidinium-induced channel molecule stabilization is eliminated wh...

  17. Automated dual capillary electrophoresis system with hydrodynamic injection for the concurrent determination of cations and anions

    International Nuclear Information System (INIS)

    Highlights: • Concurrent determination of cations and anions was carried out by electrophoretic separation. • Optimized conditions for each class of analystes was possible by using separate capillaries. • Simultaneous hydrodynamic injection was carried out. • Pneumatic actuation was used for flushing and sample handling. • The denitrification of drinking water was successfully demonstrated. - Abstract: The capillary electrophoresis instrument developed for the concurrent determination of cations and anions features two separate capillaries and individual detectors to allow independent optimization for each group of ions. The capillaries are joined in a common injector block. The sample is drawn into the injector with a small membrane pump and automated simultaneous injection into both capillaries is achieved by pressurization of the fluid with compressed air. Flushing of the injector and of the capillaries with the background electrolyte is also carried out automatically by the same means. The buffer consisted of 12 mM histidine and 2 mM 18-crown-6 adjusted to pH 4 with acetic acid and was suitable for the contactless conductivity detection employed. The system was optimized for the determination of cationic NH4+ and anionic NO3− and NO2−, and linear calibration curves from about 20 μM up to about 1.5 mM were obtained for these ions. In a test run over 8 h, the reproducibility for the peak areas was within ±7%. For demonstration, the instrument was successfully applied to the concurrent monitoring of the concentrations of the three ions during the biological removal of ammonium from contaminated groundwater in a sequencing batch reactor, where NO3− and NO2− are formed as intermediate products

  18. Automated dual capillary electrophoresis system with hydrodynamic injection for the concurrent determination of cations and anions

    Energy Technology Data Exchange (ETDEWEB)

    Pham, Thi Thanh Thuy; Mai, Thanh Duc [University of Basel, Department of Chemistry, Spitalstrasse 51, Basel 4056 (Switzerland); Centre for Environmental Technology and Sustainable Development (CETASD), Hanoi University of Science, Nguyen Trai Street 334, Hanoi (Viet Nam); Nguyen, Thanh Dam [Centre for Environmental Technology and Sustainable Development (CETASD), Hanoi University of Science, Nguyen Trai Street 334, Hanoi (Viet Nam); Sáiz, Jorge [Department of Analytical Chemistry, Physical Chemistry and Chemical Engineering – University of Alcalá, Ctra. Madrid-Barcelona km 33.6, Alcalá de Henares, Madrid 28871 (Spain); Pham, Hung Viet, E-mail: phamhungviet@hus.edu.vn [Centre for Environmental Technology and Sustainable Development (CETASD), Hanoi University of Science, Nguyen Trai Street 334, Hanoi (Viet Nam); Hauser, Peter C., E-mail: Peter.Hauser@unibas.ch [University of Basel, Department of Chemistry, Spitalstrasse 51, Basel 4056 (Switzerland)

    2014-09-02

    Highlights: • Concurrent determination of cations and anions was carried out by electrophoretic separation. • Optimized conditions for each class of analystes was possible by using separate capillaries. • Simultaneous hydrodynamic injection was carried out. • Pneumatic actuation was used for flushing and sample handling. • The denitrification of drinking water was successfully demonstrated. - Abstract: The capillary electrophoresis instrument developed for the concurrent determination of cations and anions features two separate capillaries and individual detectors to allow independent optimization for each group of ions. The capillaries are joined in a common injector block. The sample is drawn into the injector with a small membrane pump and automated simultaneous injection into both capillaries is achieved by pressurization of the fluid with compressed air. Flushing of the injector and of the capillaries with the background electrolyte is also carried out automatically by the same means. The buffer consisted of 12 mM histidine and 2 mM 18-crown-6 adjusted to pH 4 with acetic acid and was suitable for the contactless conductivity detection employed. The system was optimized for the determination of cationic NH{sub 4}{sup +} and anionic NO{sub 3}{sup −} and NO{sub 2}{sup −}, and linear calibration curves from about 20 μM up to about 1.5 mM were obtained for these ions. In a test run over 8 h, the reproducibility for the peak areas was within ±7%. For demonstration, the instrument was successfully applied to the concurrent monitoring of the concentrations of the three ions during the biological removal of ammonium from contaminated groundwater in a sequencing batch reactor, where NO{sub 3}{sup −} and NO{sub 2}{sup −} are formed as intermediate products.

  19. Towards a molecular description of intermediate filament structure and assembly

    International Nuclear Information System (INIS)

    Intermediate filaments (IFs) represent one of the prominent cytoskeletal elements of metazoan cells. Their constituent proteins are coded by a multigene family, whose members are expressed in complex patterns that are controlled by developmental programs of differentiation. Hence, IF proteins found in epidermis differ significantly from those in muscle or neuronal tissues. Due to their fibrous nature, which stems from a fairly conserved central α-helical coiled-coil rod domain, IF proteins have long resisted crystallization and thus determination of their atomic structure. Since they represent the primary structural elements that determine the shape of the nucleus and the cell more generally, a major challenge is to arrive at a more rational understanding of how their nanomechanical properties effect the stability and plasticity of cells and tissues. Here, we review recent structural results of the coiled-coil dimer, assembly intermediates and growing filaments that have been obtained by a hybrid methods approach involving a rigorous combination of X-ray crystallography, small angle X-ray scattering, cryo-electron tomography, computational analysis and molecular modeling

  20. Intermediate Coupling For Core-Level Excited States: Consequences For X-Ray Absorption Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Bagus, Paul S.; Sassi, Michel JPC; Rosso, Kevin M.

    2015-04-15

    The origin of the complex NEXAFS features of X-Ray Absorption, XAS, spectra in transition metal complexes is analyzed and interpreted in terms of the angular momentum coupling of the open shell electrons. Especially for excited configurations where a core-electron is promoted to an open valence shell, the angular momentum coupling is intermediate between the two limits of Russell- Saunders, RS, coupling where spin-orbit splitting of the electron shells is neglected and j-j coupling where this splitting is taken as dominant. The XAS intensities can be understood in terms of two factors: (1) The dipole selection rules that give the allowed excited RS multiplets and (2) The contributions of these allowed multiplets to the wavefunctions of the intermediate coupled levels. It is shown that the origin of the complex XAS spectra is due to the distribution of the RS allowed multiplets over several different intermediate coupled excited levels. The specific case that is analyzed is the L2,3 edge XAS of an Fe3+ cation, because this cation allows a focus on the angular momentum coupling to the exclusion of other effects; e.g., chemical bonding. Arguments are made that the properties identified for this atomic case are relevant for more complex materials. The analysis is based on the properties of fully relativistic, ab initio, many-body wavefunctions for the initial and final states of the XAS process. The wavefunction properties considered include the composition of the wavefunctions in terms of RS multiplets and the occupations of the spin-orbit split open shells; the latter vividly show whether the coupling is j-j or not.

  1. A CATIONIC POLYACRYLAMIDE DISPERSION SYNTHESIS BY DISPERSION POLYMERIZATION IN AQUEOUS SOLUTION

    Directory of Open Access Journals (Sweden)

    Yufeng Wang

    2011-07-01

    Full Text Available A cationic polyacrylamide (CPAM dispersion, the copolymer of acrylamide (AM and acryloyloxyethyltrimethyl ammonium chloride (DAC, has been synthesized through dispersion polymerization in aqueous ammonium sulfate ((NH42SO4 solution. The polymerization was initiated by tert-butyl hydroperoxide (TBHP and ferrisulfas (FeSO4 using poly(dimethyl diallyl ammonium chloride (PDMDAAC as the stabilizer. At the optimal reaction conditions, the relative molecular weight of the CPAM dispersion was 4.2×106, its charge density was 2.2 mmol•g-1, its average particle size was 6.01 μm, and its stability and dissolvability were both excellent. The CPAM dispersion was characterized using Fourier-transform infrared (FTIR spectroscopy, nuclear magnetic resonance (NMR spectroscopy, and differential scanning calorimeter (DSC. Results indicated that the copolymerization was successful.

  2. Combining oxygen plasma treatment with anchorage of cationized gelatin for enhancing cell affinity of poly(lactide-co-glycolide).

    Science.gov (United States)

    Shen, Hong; Hu, Xixue; Yang, Fei; Bei, Jianzhong; Wang, Shenguo

    2007-10-01

    Surface characteristics greatly influence attachment and growth of cells on biomaterials. Although polylactone-type biodegradable polymers have been widely used as scaffold materials for tissue engineering, lack of cell recognition sites, poor hydrophilicity and low surface energy lead to a bad cell affinity of the polymers, which limit the usage of polymers as scaffolds in tissue engineering. In the present study, surface of poly (L-lactide-co-glycolide) (PLGA) was modified by a method of combining oxygen plasma treatment with anchorage of cationized gelatin. Modification effect of the method was compared with other methods of oxygen plasma treatment, cationized gelatin or gelatin coating and combining oxygen plasma treatment with anchorage of gelatin. The change of surface property was compared by contact angles, surface energy, X-ray photoelectron spectra (XPS), attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) and scanning electron microscopy (SEM) measurement. The optimum oxygen pretreatment time determined by surface energy was 10 min when the power was 50 W and the oxygen pressure was 20 Pa. Analysis of the stability of gelatin and cationized gelatin anchored on PLGA by XPS, ATR-FTIR, contact angles and surface energy measurement indicated the cationized gelatin was more stable than gelatin. The result using mouse NIH 3T3 fibroblasts as model cells to evaluate cell affinity in vitro showed the cationized gelatin-anchored PLGA (OCG-PLGA) was more favorable for cell attachment and growth than oxygen plasma treated PLGA (O-PLGA) and gelatin-anchored PLGA (OG-PLGA). Moreover cell affinity of OCG-PLGA could match that of collagen-anchored PLGA (AC-PLGA). So the surface modification method combining oxygen plasma treatment with anchorage of cationized gelatin provides a universally effective way to enhance cell affinity of polylactone-type biodegradable polymers. PMID:17618682

  3. Therapeutic potential of cationic steroid antibacterials.

    Science.gov (United States)

    Salmi, Chanaz; Brunel, Jean M

    2007-08-01

    Antibiotics were one of the great health successes of the 20th century. Antibiotics, both naturally derived and synthetic, have resulted in huge decreases in both morbidity and mortality from bacterial infections. As a consequence, the 'antibiotic age' has changed public expectations about the results of infectious disease. However, this has led to high levels of inappropriate prescribing, where antibiotics may be administered to fulfil patient expectations rather than for clinical benefit. Along with unwise uses in agriculture and elsewhere, this has contributed to recent rises in numbers of antibiotic-resistant bacteria. As a result, many commentators have described this as the end of the antibiotic age and the term 'superbug' has entered the common vocabulary for multi-drug-resistant bacteria such as vancomycin-resistant Enterococcus, multi-drug-resistant Staphylococcus aureus and multi-drug-resistant Pseudomonas aeruginosa. In this context, an attractive approach for the development of antibacterial agents is the use of a new class of cationic steroidal compounds mimicking polymyxin activities. The permeabilization properties of these agents of the outer membranes of Gram-negative bacteria are reported in this review, as well as a discussion of literature results. PMID:17685865

  4. INTERACTIONS BETWEEN CATIONIC POLYELECTROLYTE AND PULP FINES

    Directory of Open Access Journals (Sweden)

    Elina Orblin

    2011-05-01

    Full Text Available Papermaking pulps are a mixture of fibres, fibre fragments, and small cells (parenchyma or ray cells, usually called pulp fines. The interactions between pulp fines and a cationic copolymer of acrylamide and acryloxyethyltrimethyl ammonium chloride were investigated based on solid-liquid isotherms prepared under different turbulence, and subsequent advanced surface characterization using X-ray photoelectron spectroscopy (XPS and time-of-flight secondary ion mass spectrometry (ToF-SIMS. The surface charge and surface area of pulp fine substrates were measured by methylene blue sorption-XPS analysis and nitrogen adsorption combined with mercury porosimetry, respectively. The driving force behind polyelectrolyte adsorption was the amount of the surface anionic charge, whereas surface area appeared to be of less importance. Based on a comparison of solid-liquid and XPS sorption isotherms, different polyelectrolyte conformations were suggested, depending on the types of fines: A flatter conformation and partial cell-wall penetration of polyelectrolytes on kraft fines from freshly prepared pulp, and a more free conformation with extended loops and tails on lignocellulosic fines from recycled pulp. Additionally, ToF-SIMS imaging proved that recycled pulp fines contained residual de-inking chemicals (primarily palmitic acid salts that possibly hinder the electrostatic interactions with polyelectrolytes.

  5. Repurposing Cationic Amphiphilic Antihistamines for Cancer Treatment.

    Science.gov (United States)

    Ellegaard, Anne-Marie; Dehlendorff, Christian; Vind, Anna C; Anand, Atul; Cederkvist, Luise; Petersen, Nikolaj H T; Nylandsted, Jesper; Stenvang, Jan; Mellemgaard, Anders; Østerlind, Kell; Friis, Søren; Jäättelä, Marja

    2016-07-01

    Non-small cell lung cancer (NSCLC) is one of the deadliest cancers worldwide. In search for new NSCLC treatment options, we screened a cationic amphiphilic drug (CAD) library for cytotoxicity against NSCLC cells and identified several CAD antihistamines as inducers of lysosomal cell death. We then performed a cohort study on the effect of CAD antihistamine use on mortality of patients diagnosed with non-localized cancer in Denmark between 1995 and 2011. The use of the most commonly prescribed CAD antihistamine, loratadine, was associated with significantly reduced all-cause mortality among patients with non-localized NSCLC or any non-localized cancer when compared with use of non-CAD antihistamines and adjusted for potential confounders. Of the less frequently described CAD antihistamines, astemizole showed a similar significant association with reduced mortality as loratadine among patients with any non-localized cancer, and ebastine use showed a similar tendency. The association between CAD antihistamine use and reduced mortality was stronger among patients with records of concurrent chemotherapy than among those without such records. In line with this, sub-micromolar concentrations of loratadine, astemizole and ebastine sensitized NSCLC cells to chemotherapy and reverted multidrug resistance in NSCLC, breast and prostate cancer cells. Thus, CAD antihistamines may improve the efficacy of cancer chemotherapy. PMID:27333030

  6. Riparian zone controls on base cation concentrations in boreal streams

    Directory of Open Access Journals (Sweden)

    J. L. J. Ledesma

    2013-01-01

    Full Text Available Forest riparian zones are a major in control of surface water quality. Base cation (BC concentrations, fluxes, and cycling in the riparian zone merit attention because of increasing concern of negative consequences for re-acidification of surface waters from future climate and forest harvesting scenarios. We present a two-year study of BC and silica (Si flow-weighted concentrations from 13 riparian zones and 14 streams in a boreal catchment in northern Sweden. The Riparian Flow-Concentration Integration Model (RIM was used to estimate riparian zone flow-weighted concentrations and tested to predict the stream flow-weighted concentrations. Spatial variation in BC and Si concentrations as well as in flow-weighted concentrations was related to differences in Quaternary deposits, with the largest contribution from lower lying silty sediments and the lowest contribution from wetland areas higher up in the catchment. Temporal stability in the concentrations of most elements, a remarkably stable Mg / Ca ratio in the soil water and a homogeneous mineralogy suggest that the stable patterns found in the riparian zones are a result of distinct mineralogical upslope groundwater signals integrating the chemical signals of biological and chemical weathering. Stream water Mg / Ca ratio indicates that the signal is subsequently maintained in the streams. RIM gave good predictions of Ca, Mg, and Na flow-weighted concentrations in headwater streams. The difficulty in modelling K and Si suggests a stronger biogeochemical influence on these elements. The observed chemical dilution effect with flow in the streams was related to variation in groundwater levels and element concentration profiles in the riparian zones. This study provides a first step toward specific investigations of the vulnerability of riparian zones to changes induced by forest management or climate change, with focus on BC or other compounds.

  7. Macroeconomic stability

    DEFF Research Database (Denmark)

    Jespersen, Jesper

    2004-01-01

    It is demonstrated that full employment and sustainable development not necessarily are conflicting goals. On the other hand macroeconomic stability cannot be obtained without a deliberate labour sharing policy and a shift in the composition of private consumption away from traditional material...

  8. Novel polymer electrolytes based on cationic polyurethane with different alkyl chain length

    Science.gov (United States)

    Liu, Libin; Wu, Xiwen; Li, Tianduo

    2014-03-01

    A series of comb-like cationic polyurethanes (PUs) were synthesized by quaternizing different bromoalkane (C2H5Br, C8H17Br, and C14H29Br) with polyurethane. Solid polymer electrolytes were prepared by complexes cationic PUs with different content of LiClO4. All the solid polymer electrolytes had sufficient thermal stability as confirmed by TGA and exhibited a single-phase behavior evidenced by DSC results. For these electrolytes, FT-IR spectra indicated the formation of polymer-ion complexes. The ac impedance spectra show that the conductivity of the electrolytes follow the Arrhenius behavior, and ionic conductivity is associated with both the charge migration of ions between coordination sites and transmission between aggregates, as confirmed by FT-IR and SEM. Alkyl quaternary ammonium salts in the polymer backbone are recognized as inherent plasticizers, which make the electrolytes exhibit liquid-like behavior. The plasticizing effect of PU-C8 and PU-C14 electrolytes are more effective than that of PU-C2 electrolyte. Maximum ionic conductivity at room temperature for PU-C8 electrolytes containing 50 wt% LiClO4 reached 1.1 × 10-4 S cm-1. This work provides a new research clue that alkyl quaternary ammonium salts could be used as inherent plasticizers and hence make the system behave like a liquid with high ionic conductivity, while preserving the dimensional stability of the solids.

  9. Strain Manipulated Magnetic Properties in ZnO and GaN Induced by Cation Vacancy

    Science.gov (United States)

    Gai, Yanqin; Jiang, Jiaping; Wu, Yuxi; Tang, Gang

    2016-07-01

    The effects of isotropic strains on the magnetic properties in ZnO and GaN induced by cation vacancies are comparatively investigated by density functional theory calculations. The magnetic moments and the couplings between vacancies in different charged states are calculated as a function of strains. The modulation of strain on the magnetic properties relies on the materials and the charge states of cation vacancies in them. As the occurrence of charge transfer in ZnO: V Zn under compression, the coupling between V_{{Zn}}0 is antiferromagnetic (AFM) and it could be stabilized by strains. Tensions can strengthen the ferromagnetic (FM) coupling between V_{{Zn}}0 but weaken that of V_{{Ga}}^{ - } . The neutral V Ga are always AFM coupling under strains from -6 to +6% and could be stabilized by compressions. The interactions between V_{{Ga}}^{ - } are always FM with ignorable variations under strains; however, the FM couplings between V_{{Ga}}^{2 - } could be strengthened by compressions. These varying trends of magnetic coupling under strains are interpreted by the band coupling models. Therefore, strain-engineering provides a route to manipulate and design high Curie temperature ferromagnetism derived and mediated by intrinsic defect for spintronic applications.

  10. Increased mineral oil bioavailability in slurries by monovalent cation-induced dispersion

    International Nuclear Information System (INIS)

    Bioavailability of apolar contaminants is an important limiting factor for microbial reclamation of polluted soils. This paper describes a laboratory study of the relation between microaggregate stability and bioavailability of mineral oil in soil-water slurries. The stability of microaggregates in slurries is regulated by the valence and surface affinity of the cations in the system, and by the complexing anion P2O74- (metaphosphate). A silt loam, contaminated with a weathered gas oil, was collected from an oil refinery site. Degradation rates were monitored in small-scale incubations at solid:liquid ratios of 1:5 (w/w). The solution contained Ca, Na, or K as the dominant cation. The levels of nutrients and metaphosphate were varied. Biodegradation rates increased with the sequence Ca 2 treatment. Measurements of the particle size distribution the slurry showed that an increase in the finer fractions qualitatively correlated with enhanced biodegradation. This is a strong indication that dispersion of the microaggregates increased bioavailability of the contaminant

  11. Stearylamine-Containing Cationic Nanoemulsion as a Promising Carrier for Gene Delivery.

    Science.gov (United States)

    Silva, André L; Marcelino, Henrique R; Verissimo, Lourena M; Araujo, Ivonete B; Agnez-Lima, Lucymara F; do Egito, Eryvaldo S T

    2016-02-01

    The drawbacks related to the use of viral vectors in gene therapy have been stimulated the research in non-viral strategies such as cationic nanoemulsions. The aim of this work was to develop a stearylamine-containing nanoemulsion for gene therapy purpose. The formulation was chosen from a Pseudo-Ternary Phase Diagram and had its long-term stability assessed by Dynamic Light Scattering and Phase Analysis Light Scattering during 180 days at 4 degrees C, 25 degrees C and 40 degrees C. Besides, studies of sterilization and scale up of the product were conducted. It was demonstrated that the proposed system was stable up to 180 days when stored at 4 degrees C and could be sterilized by a 0.22 microm filter pore without changes on its characteristics. The scale up was possible by adjusting the volume to the sonication time. Because the nanoemulsion presented a droplet size smaller than 200 nm and a zeta potential higher than 30 mV, this system was able to correctly complex the plasmid model PIRES2-EGFP, as confirmed by the agarosis gel electrophoresis assay. The nanoemulsion toxicity evaluated over lung fetus human cells (MRC-5) was dose-dependent. However, it does not appear to be a limiting factor for further experiments aiming gene transfection. As a conclusion, stearylamine-containing cationic nanoemulsions can be used for gene therapy, since it presents suitable characteristics, stability and possibility of sterilization. PMID:27433584

  12. Extraction and DFT study on the complexation of the strontium cation with enniatin B

    International Nuclear Information System (INIS)

    Highlights: • Stability of the enniatin B–Sr2+ complex was determined. • Quantum mechanical DFT calculations were applied. • Structure of the resulting complex was predicted. - Abstract: By using extraction experiments and γ-activity measurements, the extraction constant corresponding to the equilibrium Sr2+(aq) + 2A−(aq) + 1(nb) ⇄ 1 · Sr2+(nb) + 2A−(nb) occurring in the two-phase water–nitrobenzene system (A− = picrate, 1 = enniatin B; aq = aqueous phase, nb = nitrobenzene phase) was evaluated as log Kex (1 · Sr2+,2A−) = 3.4 ± 0.1. Further, the stability constant of the 1 · Sr2+ complex in nitrobenzene saturated with water was calculated for a temperature of 25 °C: log βnb (1 · Sr2+) = 12.5 ± 0.1. Finally, applying quantum mechanical DFT calculations, the most probable structure of the proved 1 · Sr2+ cationic complex was derived. In the resulting complex, which is most energetically favored, the “central” cation Sr2+ is bound by nine bonding interactions to the corresponding nine oxygen atoms of the parent enniatin B ligand. The interaction energy of the considered 1 · Sr2+ complex was found to be −877.4 kJ/mol, confirming also the formation of this complex

  13. Strain Manipulated Magnetic Properties in ZnO and GaN Induced by Cation Vacancy

    Science.gov (United States)

    Gai, Yanqin; Jiang, Jiaping; Wu, Yuxi; Tang, Gang

    2016-04-01

    The effects of isotropic strains on the magnetic properties in ZnO and GaN induced by cation vacancies are comparatively investigated by density functional theory calculations. The magnetic moments and the couplings between vacancies in different charged states are calculated as a function of strains. The modulation of strain on the magnetic properties relies on the materials and the charge states of cation vacancies in them. As the occurrence of charge transfer in ZnO:V Zn under compression, the coupling between V_{{Zn}}0 is antiferromagnetic (AFM) and it could be stabilized by strains. Tensions can strengthen the ferromagnetic (FM) coupling between V_{{Zn}}0 but weaken that of V_{{Ga}}^{ - } . The neutral V Ga are always AFM coupling under strains from -6 to +6% and could be stabilized by compressions. The interactions between V_{{Ga}}^{ - } are always FM with ignorable variations under strains; however, the FM couplings between V_{{Ga}}^{2 - } could be strengthened by compressions. These varying trends of magnetic coupling under strains are interpreted by the band coupling models. Therefore, strain-engineering provides a route to manipulate and design high Curie temperature ferromagnetism derived and mediated by intrinsic defect for spintronic applications.

  14. Competitive Effects of 2+ and 3+ Cations on DNA Compaction

    CERN Document Server

    Tongu, C; Yoshikawa, Y; Zinchenko, A A; Chen, N; Yoshikawa, K

    2016-01-01

    By using single-DNA observation with fluorescence microscopy, we observed the effects of divalent and trivalent cations on the higher-order structure of giant DNA (T4 DNA with 166 kbp). It was found that divalent cations, such as Mg(2+) and Ca(2+), inhibit DNA compaction induced by a trivalent cation, spermidine (SPD(3+)). On the other hand, in the absence of SPD(3+), divalent cations cause the shrinkage of DNA. These experimental observations are inconsistent with the well-established Debye-Huckel scheme regarding the shielding effect of counter ions, which is given as the additivity of contributions of cations with different valences. We interpreted the competition between 2+ and 3+ cations in terms of the change in the translational entropy of the counter ions before and after the folding transition of DNA. For the compaction with SPD(3+), we considered the increase in translational entropy due to the ion-exchange of the intrinsic monovalent cations condensing on a highly-charged polyelectrolyte, double-st...

  15. Effect of cations on activated sludge dewatering

    OpenAIRE

    Raynaud, M.; Vaxelaire, J.; Héritier, P.; Baudez, J.C.

    2010-01-01

    Even after mechanical dewatering, the residual water within activated sludge remains high. Due to its complex structure, this material is usually extremely compressible and known to be difficult to dewater. The ability of sludge to dewater depends on its biological nature, its composition and also the type of treatment it comes from. Indeed, changes in ionic strength and in ionic composition of sludge affect the stability of structural properties of activated sludge and thus the dewatering...

  16. Electrostatic charge confinement using bulky tetraoctylammonium cation and four anions

    Science.gov (United States)

    Andreeva, Nadezhda A.; Chaban, Vitaly V.

    2016-04-01

    Thanks to large opposite electrostatic charges, cations and anions establish strong ionic bonds. However, applications of ionic systems - electrolytes, gas capture, solubilization, etc. - benefit from weaker non-covalent bonds. The common approaches are addition of cosolvents and delocalization of electron charge density via functionalization of ions. We report fine tuning of closest-approach distances, effective radii, and cation geometry by different anions using the semi-empirical molecular dynamics simulations. We found that long fatty acid chains employed in the tetraalkylammonium cation are largely inefficient and new substituents must be developed. The reported results foster progress of task-specific ionic liquids.

  17. Cationic Nanoparticles Induce Nanoscale Disruption in Living Cell Plasma Membranes

    OpenAIRE

    Chen, Jiumei; Hessler, Jessica A.; Putchakayala, Krishna; Panama, Brian K.; Khan, Damian P.; Hong, Seungpyo; Mullen, Douglas G.; DiMaggio, Stassi C.; Som, Abhigyan; Tew, Gregory N.; Lopatin, Anatoli N.; Baker, James R.; Banaszak Holl, Mark M.; Orr, Bradford G

    2009-01-01

    It has long been recognized that cationic nanoparticles induce cell membrane permeability. Recently, it has been found that cationic nanoparticles induce the formation and/or growth of nanoscale holes in supported lipid bilayers. In this paper we show that non-cytotoxic concentrations of cationic nanoparticles induce 30–2000 pA currents in 293A and KB cells, consistent with a nanoscale defect such as a single hole or group of holes in the cell membrane ranging from 1 to 350 nm2 in total area....

  18. Competitive Solvation of the Imidazolium Cation by Water and Methanol

    CERN Document Server

    Chaban, Vitaly

    2014-01-01

    Imidazolium-based ionic liquids are widely used in conjunction with molecular liquids for various applications. Solvation, miscibility and similar properties are of fundamental importance for successful implementation of theoretical schemes. This work reports competitive solvation of the 1,3-dimethylimidazolium cation by water and methanol. Employing molecular dynamics simulations powered by semiempirical Hamiltonian (electronic structure level of description), the local structure nearly imidazolium cation is described in terms of radial distribution functions. Although water and methanol are chemically similar, water appears systematically more successful in solvating the 1,3-dimethylimidazolium cation. This result fosters construction of future applications of the ternary ion-molecular systems.

  19. Evaluation of phenomena affecting diffusion of cations in compacted bentonite

    International Nuclear Information System (INIS)

    In a number of diffusion studies, contradictions between the apparent diffusivities of cations and their distribution coefficients in bentonite have been found. Two principal reasons have been offered as explanations for this discrepancy; diffusion of the sorbed cations, often called surface diffusion, and the decrease of sorption in compacted clay compared to a sorption value obtained from a batch experiment. In the study the information available from the literature on sorption-diffusion mechanisms of cations in bentonite has been compiled and re-interpreted in order to improve the understanding of the diffusion process. (103 refs., 23 figs., 8 tabs.)

  20. The Newtonian limit at intermediate energies

    International Nuclear Information System (INIS)

    We study the metric solutions for the gravitational equations in Modified Gravity Models (MGMs). In models with negative powers of the scalar curvature, we show that the Newtonian Limit (NL) is well defined as a limit at intermediate energies, in contrast with the usual low energy interpretation. Indeed, we show that the gravitational interaction is modified at low densities or low curvatures

  1. The Newtonian limit at intermediate energies

    OpenAIRE

    Cembranos, J. A. R.

    2005-01-01

    We study the metric solutions for the gravitational equations in Modified Gravity Models (MGMs). In models with negative powers of the scalar curvature, we show that the Newtonian Limit (NL) is well defined as a limit at intermediate energies, in contrast with the usual low energy interpretation. Indeed, we show that the gravitational interaction is modified at low densities or low curvatures.

  2. What Should be Taught in Intermediate Macroeconomics?

    Science.gov (United States)

    de Araujo, Pedro; O'Sullivan, Roisin; Simpson, Nicole B.

    2013-01-01

    A lack of consensus remains on what should form the theoretical core of the undergraduate intermediate macroeconomic course. In determining how to deal with the Keynesian/classical divide, instructors must decide whether to follow the modern approach of building macroeconomic relationships from micro foundations, or to use the traditional approach…

  3. Software Testing An ISEB Intermediate Certificate

    CERN Document Server

    Hambling, Brian

    2009-01-01

    Covering testing fundamentals, reviews, testing and risk, test management and test analysis, this book helps newly qualified software testers to learn the skills and techniques to take them to the next level. Written by leading authors in the field, this is the only official textbook of the ISEB Intermediate Certificate in Software Testing.

  4. Trusted intermediating agents in electronic trade networks

    NARCIS (Netherlands)

    Klos, T.B.; Alkemade, F.

    2005-01-01

    Electronic commerce and trading of information goods significantly impact the role of intermediaries: consumers can bypass intermediating agents by forming direct links to producers. One reason that traditional intermediaries can still make a profit, is that they have more knowledge of the market, s

  5. Changes to the Intermediate Accounting Course Sequence

    Science.gov (United States)

    Davidson, Lesley H.; Francisco, William H.

    2009-01-01

    There is an ever-growing amount of information that must be covered in Intermediate Accounting courses. Due to recent accounting standards and the implementation of IFRS this trend is likely to continue. This report incorporates the results of a recent survey to examine the trend of spending more course time to cover this additional material.…

  6. Teaching Vocabulary and Morphology in Intermediate Grades

    Science.gov (United States)

    Palumbo, Anthony; Kramer-Vida, Louisa; Hunt, Carolyn V.

    2015-01-01

    Direct vocabulary instruction of Tier 2 and Tier 3 words in intermediate-grade curricula is an important tool of literacy instruction because English is a language grafted from many roots and has not developed a one-to-one phoneme-grapheme correspondence. In addition to knowing graphemes and phonemes, students must formally learn words that cross…

  7. Moroccan Arabic Intermediate Reader, Part II.

    Science.gov (United States)

    Alami, Wali A.; Hodge, Carlton T., Ed.

    The first section of this companion volume to "Moroccan Arabic Intermediate Reader, Part I" (AL 002 041) presents the Arabic script version of the pre-drills in Lessons IA-IIB in that volume. The second and major section comprises 20 lessons consisting of pre-drills, texts, notes, and questions. All material in this volume appears in Arabic script…

  8. Frequency stability

    Czech Academy of Sciences Publication Activity Database

    Kroupa, Věnceslav František

    Bratislava: Department of Radio and Electronics, FEI STU, 2006 - (Píš, P.; Krajčušková, Z.), I.1-I.9 ISBN 80-227-2388-6. [ Radio elektronika 2006. Conference proceedings. Bratislava (SK), 25.04.2006-26.04.2006] R&D Projects: GA ČR(CZ) GA102/05/0852 Institutional research plan: CEZ:AV0Z20670512 Keywords : noise * frequency stability * frequency control Subject RIV: JW - Navigation, Links, Detection ; Counter-Measures

  9. stability of a layer of viscous magnetic fluid-flow down an inclined plane

    OpenAIRE

    Renardy, Y.; Sun, S. M.

    1994-01-01

    This paper concerns the linear stability of a layer of viscous magnetic fluid flow down an inclined plane under the influence of gravity and a tangential magnetic field. The stability of a magnetic fluid in a three-dimensional space is first reduced to the stability of the flow in a two-dimensional space by using Squire's transformation. The stability of long waves and short waves is analyzed asymptotically. The stability of waves with intermediate length is obtained numerically. It is found ...

  10. Isomerization of propargyl cation to cyclopropenyl cation: Mechanistic elucidations and effects of lone pair donors

    Indian Academy of Sciences (India)

    Zodinpuia Pachuau; Kiew S Kharnaior; R H Duncan Lyngdoh

    2013-03-01

    This ab initio study examines two pathways (one concerted and the other two-step) for isomerization of the linear propargyl cation to the aromatic cyclopropenyl cation, also probing the phenomenon of solvation of this reaction by simple lone pair donors (NH3, H2O, H2S and HF) which bind to the substrate at two sites. Fully optimized geometries at the B3LYP/6-31G(d) level were used, along with single point QCISD(T)/6-311+G(d,p) and accurate G3 level calculations upon the DFT optimized geometries. For the unsolvated reaction, the two-step second pathway is energetically favoured over the one-step first pathway. Lone pair donor affinity for the various C3H$^{+}_{3}$ species follows the uniform order NH3 > H2S>H2O>HF. The activation barriers for the solvated isomerizations decrease in the order HF>H2O>H2S>NH3 for both pathways. The number of lone pairs on the donor heteroatom as well as the heteroatom electronegativity are factors related to both these trends. Compared to the unsolvated cases, the solvated reactions have transition states which are usually ‘later’ in position along the reaction coordinate, validating the Hammond postulate.

  11. Nanoscale cation motion in TaO(x), HfO(x) and TiO(x) memristive systems.

    Science.gov (United States)

    Wedig, Anja; Luebben, Michael; Cho, Deok-Yong; Moors, Marco; Skaja, Katharina; Rana, Vikas; Hasegawa, Tsuyoshi; Adepalli, Kiran K; Yildiz, Bilge; Waser, Rainer; Valov, Ilia

    2016-01-01

    A detailed understanding of the resistive switching mechanisms that operate in redox-based resistive random-access memories (ReRAM) is key to controlling these memristive devices and formulating appropriate design rules. Based on distinct fundamental switching mechanisms, two types of ReRAM have emerged: electrochemical metallization memories, in which the mobile species is thought to be metal cations, and valence change memories, in which the mobile species is thought to be oxygen anions (or positively charged oxygen vacancies). Here we show, using scanning tunnelling microscopy and supported by potentiodynamic current-voltage measurements, that in three typical valence change memory materials (TaO(x), HfO(x) and TiO(x)) the host metal cations are mobile in films of 2 nm thickness. The cations can form metallic filaments and participate in the resistive switching process, illustrating that there is a bridge between the electrochemical metallization mechanism and the valence change mechanism. Reset/Set operations are, we suggest, driven by oxidation (passivation) and reduction reactions. For the Ta/Ta2O5 system, a rutile-type TaO2 film is believed to mediate switching, and we show that devices can be switched from a valence change mode to an electrochemical metallization mode by introducing an intermediate layer of amorphous carbon. PMID:26414197

  12. Chemical bonding and structural ordering of cations in silicate glasses

    International Nuclear Information System (INIS)

    The specific surrounding of cations in multicomponent silicate glasses is briefly presented. Information about interatomic distances and site geometry may be gained by using spectroscopic methods among which x-ray absorption spectroscopy may be used for the largest number of glass components. Scattering of x-rays and neutrons may also be used to determine the importance of medium range order around specific cations. All the existing data show that cations occur in sites with a well-defined geometry, which are in most cases connected to the silicate polymeric network. Medium range order has been detected around cations such as Ti, Ca and Ni, indicating that these elements have an heterogeneous distribution within the glassy matrix. (authors)

  13. SITING OF LITHIUM CATIONS IN FERRIERITE. MULTINUCLEAR NMR CRYSTALLOGRAPHY STUDY

    Czech Academy of Sciences Publication Activity Database

    Klein, Petr; Dědeček, Jiří; Sklenák, Štěpán; Thomas, Haunani M.

    Segovia: CIS-5, 2013. s. 1. [Czech-Italian- Spanish Conference on Molecular Sieves and Catalysis /5./. 16.06.2013-19.06.2013, Segovia] Institutional support: RVO:61388955 Keywords : lithium cations * crystallography Subject RIV: CF - Physical ; Theoretical Chemistry

  14. Infrared spectroscopy of mass-selected metal carbonyl cations

    Science.gov (United States)

    Ricks, A. M.; Reed, Z. E.; Duncan, M. A.

    2011-04-01

    Metal carbonyl cations of the form M(CO)n+ are produced in a molecular beam by laser vaporization in a pulsed nozzle source. These ions, and their corresponding rare gas atom "tagged" analogs, M(CO)n(RG)m+, are studied with mass-selected infrared photodissociation spectroscopy in the carbonyl stretching region and with density functional theory computations. The number of infrared-active bands, their frequency positions, and their relative intensities provide distinctive patterns allowing determination of the geometries and electronic structures of these complexes. Cobalt penta carbonyl and manganese hexacarbonyl cations are compared to isoelectronic iron pentacarbonyl and chromium hexacarbonyl neutrals. Gold and copper provide examples of "non-classical" carbonyls. Seven-coordinate carbonyls are explored for the vanadium group metal cations (V +, Nb + and Ta +), while uranium cations provide an example of an eight-coordinate carbonyl.

  15. Study on cationic photopolymerization reaction of epoxy polysiloxane

    Science.gov (United States)

    Sun, F.; Jiang, S. L.; Liu, J.

    2007-11-01

    The effects of epoxy monomers, concentration of photoinitiator and radical photoinitiators on the photosensitive properties of cationic phopolymerization system with a novel epoxy polysiloxane oligomer (CEPS) were investigated via a gel yield method. The results showed that among the tested epoxy monomers, the reactivity of ERL-4221 with cycloaliphatic epoxy groups was the highest. The optimum concentration of diaryldiodonium salt (SR-1012) was determined as 4-5 wt.%. Increasing the amounts of ERL-4221 in the CEPS cationic photopolymerization system, UV-curing rate increased. Radical photoinitiators with ArC dbnd O structure possessed sensitization capacity to the cationic photoinitiator SR-1012. The photosensitivity of the CEPS system could be up to 165 mJ/cm 2. Adding a small amount of IPA and BP could greatly improve the photosensitivity of CEPS cationic photosensitive system. The optimal quantity of isopropanol added to the system was not more than 2 wt.%.

  16. Cation antisite disorder in uranium-doped gadolinium zirconate pyrochlores

    International Nuclear Information System (INIS)

    The incorporation of uranium into gadolinium zirconate (Gd2Zr2O7) is investigated by synchrotron X-ray powder diffraction and X-ray absorption near-edge structure (XANES) spectroscopy. The results suggest that the uranium cation is largely located on the pyrochlore B-site instead of the targeted A-site. Cation disorder in Gd2Zr2O7 and U-doped Gd2Zr2O7 is investigated by positron annihilation lifetime spectroscopy (PALS) which demonstrates the absence of cation vacancies in these systems. This work provides direct evidence for cation antisite (A- and B-site mixing) disorder in U-doped and off-stoichiometric Gd2Zr2O7 pyrochlore

  17. Study on cationic photopolymerization reaction of epoxy polysiloxane

    International Nuclear Information System (INIS)

    The effects of epoxy monomers, concentration of photoinitiator and radical photoinitiators on the photosensitive properties of cationic phopolymerization system with a novel epoxy polysiloxane oligomer (CEPS) were investigated via a gel yield method. The results showed that among the tested epoxy monomers, the reactivity of ERL-4221 with cycloaliphatic epoxy groups was the highest. The optimum concentration of diaryldiodonium salt (SR-1012) was determined as 4-5 wt.%. Increasing the amounts of ERL-4221 in the CEPS cationic photopolymerization system, UV-curing rate increased. Radical photoinitiators with ArC=O structure possessed sensitization capacity to the cationic photoinitiator SR-1012. The photosensitivity of the CEPS system could be up to 165 mJ/cm2. Adding a small amount of IPA and BP could greatly improve the photosensitivity of CEPS cationic photosensitive system. The optimal quantity of isopropanol added to the system was not more than 2 wt.%

  18. Investigation of Fragmentation of Tryptophan Nitrogen Radical Cation

    Science.gov (United States)

    Piatkivskyi, Andrii; Happ, Marshall; Lau, Justin Kai-Chi; Siu, K. W. Michael; Hopkinson, Alan C.; Ryzhov, Victor

    2015-08-01

    This work describes investigation of the fragmentation mechanism of tryptophan N-indolyl radical cation, H3N+-TrpN• ( m/ z 204) studied via DFT calculations and several gas-phase experimental techniques. The main fragment ion at m/ z 131, shown to be a mixture of up to four isomers including 3-methylindole (3MI) π-radical cation, was found to undergo further loss of an H atom to yield one of the two isomeric m/ z 130 ions. 3-Methylindole radical cation generated independently (via CID of [CuII(terpy)3MI]•2+) displayed gas-phase reactivity partially similar to that of the m/ z 131 fragment, further confirming our proposed mechanism. CID of deuterated tryptophan N-indolyl radical cation ( m/ z 208) suggested that up to six H atoms are involved in the pathway to formation of the m/ z 131 ion, consistent with hydrogen atom scrambling during CID of protonated Trp.

  19. Effect of substrates and intermediate compounds on foaming in manure digestion systems

    DEFF Research Database (Denmark)

    Boe, Kanokwan; Kougias, Panagiotis; Pacheco, F.;

    2012-01-01

    effect of physicochemical properties of substrates and intermediate compounds on liquid properties such as surface tension, surfactant property, and hydrophobicity were investigated and compared with the effect on foaming tendency and foam stability. The results showed that there was no consistent...... correlation between foaming potential and hydrophobicity, oil displacement area (ODA) or surface tension of the tested solutions, and the best way to determine the foaming property of the solution was to directly measure foaming tendency and foam stability. Na-oleate and acetic acid showed the highest...

  20. Recent Advances in Lipase-Mediated Preparation of Pharmaceuticals and Their Intermediates

    OpenAIRE

    Ana Caroline Lustosa de Melo Carvalho; Thiago de Sousa Fonseca; Marcos Carlos de Mattos; Maria da Conceição Ferreira de Oliveira; Telma Leda Gomes de Lemos; Francesco Molinari; Diego Romano; Immacolata Serra

    2015-01-01

    Biocatalysis offers an alternative approach to conventional chemical processes for the production of single-isomer chiral drugs. Lipases are one of the most used enzymes in the synthesis of enantiomerically pure intermediates. The use of this type of enzyme is mainly due to the characteristics of their regio-, chemo- and enantioselectivity in the resolution process of racemates, without the use of cofactors. Moreover, this class of enzymes has generally excellent stability in the presence of ...

  1. Asymmetric intermediate reflector for tandem micromorph thin film silicon solar cells

    OpenAIRE

    Söderström, T; Haug, F.-J.; Niquille, X.; Terrazzoni, V; Ballif, C.

    2009-01-01

    The micromorph solar cell (stack of amorphous and microcrystalline cells) concept is the key for achieving high efficiency stabilized thin film silicon solar cells. We introduce a device structure that allows a better control of the light in-coupling into the two subcell components. It is based on an asymmetric intermediate reflector, which increases the effective thickness of the a-Si:H by a factor of more than three. Hence, the a- Si:H thickness reduction dimi...

  2. Micromorph n-i-p tandem cells with asymmetric intermediate reflectors

    OpenAIRE

    Haug, Franz-Josef; Söderström, Thomas; Terrazzoni-Daudrix, Vanessa; Ballif, Christophe; Sai, Hitoshi; Kondo, Michio

    2010-01-01

    We present tandem thin film silicon solar cells in n-i-p configuration with 12% initial efficiency. The stabilized efficiency of these devices is 10%. The result has become possible by the combination of a microcrystalline bottom cell with high current density and an asymmetric intermediate reflector that establishes a well adapted surface texture for the amorphous top cell. After successfully integrating these two steps, we obtain micromorph tandems cells with size of typically 0.25 cm2. The...

  3. Atmospheric fates of Criegee intermediates in the ozonolysis of isoprene.

    Science.gov (United States)

    Nguyen, Tran B; Tyndall, Geoffrey S; Crounse, John D; Teng, Alexander P; Bates, Kelvin H; Schwantes, Rebecca H; Coggon, Matthew M; Zhang, Li; Feiner, Philip; Milller, David O; Skog, Kate M; Rivera-Rios, Jean C; Dorris, Matthew; Olson, Kevin F; Koss, Abigail; Wild, Robert J; Brown, Steven S; Goldstein, Allen H; de Gouw, Joost A; Brune, William H; Keutsch, Frank N; Seinfeld, John H; Wennberg, Paul O

    2016-04-21

    We use a large laboratory, modeling, and field dataset to investigate the isoprene + O3 reaction, with the goal of better understanding the fates of the C1 and C4 Criegee intermediates in the atmosphere. Although ozonolysis can produce several distinct Criegee intermediates, the C1 stabilized Criegee (CH2OO, 61 ± 9%) is the only one observed to react bimolecularly. We suggest that the C4 Criegees have a low stabilization fraction and propose pathways for their decomposition. Both prompt and non-prompt reactions are important in the production of OH (28% ± 5%) and formaldehyde (81% ± 16%). The yields of unimolecular products (OH, formaldehyde, methacrolein (42 ± 6%) and methyl vinyl ketone (18 ± 6%)) are fairly insensitive to water, i.e., changes in yields in response to water vapor (≤4% absolute) are within the error of the analysis. We propose a comprehensive reaction mechanism that can be incorporated into atmospheric models, which reproduces laboratory data over a wide range of relative humidities. The mechanism proposes that CH2OO + H2O (k(H2O)∼ 1 × 10(-15) cm(3) molec(-1) s(-1)) yields 73% hydroxymethyl hydroperoxide (HMHP), 6% formaldehyde + H2O2, and 21% formic acid + H2O; and CH2OO + (H2O)2 (k(H2O)2∼ 1 × 10(-12) cm(3) molec(-1) s(-1)) yields 40% HMHP, 6% formaldehyde + H2O2, and 54% formic acid + H2O. Competitive rate determinations (kSO2/k(H2O)n=1,2∼ 2.2 (±0.3) × 10(4)) and field observations suggest that water vapor is a sink for greater than 98% of CH2OO in a Southeastern US forest, even during pollution episodes ([SO2] ∼ 10 ppb). The importance of the CH2OO + (H2O)n reaction is demonstrated by high HMHP mixing ratios observed over the forest canopy. We find that CH2OO does not substantially affect the lifetime of SO2 or HCOOH in the Southeast US, e.g., CH2OO + SO2 reaction is a minor contribution (production by stabilized Criegees is likely unimportant in regions dominated by the reactivity of ozone with isoprene. In contrast

  4. Interconnects for intermediate temperature solid oxide fuel cells

    Science.gov (United States)

    Huang, Wenhua

    Presently, one of the principal goals of solid oxide fuel cells (SOFCs) research is to reduce the stack operating temperature to between 600 and 800°C. However, one of the principal technological barriers is the non-availability of a suitable material satisfying all of the stability requirements for the interconnect. In this work two approaches for intermediate temperature SOFC interconnects have been explored. The first approach comprises an interconnect consisting of a bi-layer structure, a p-type oxide (La0.96Sr0.08MnO 2.001/LSM) layer exposed to a cathodic environment, and an n-type oxide (Y0.08Sr0.88Ti0.95Al0.05O 3-delta/YSTA) layer exposed to anodic conditions. Theoretical analysis based on the bi-layer structure has established design criteria to implement this approach. The analysis shows that the interfacial oxygen partial pressure, which determines the interconnect stability, is independent of the electronic conductivities of both layers but dependent on the oxygen ion layer interconnects, the oxygen ion conductivities of LSM and YSTA were measured as a function of temperature and oxygen partial pressure. Based on the measured data, it has been determined that if the thickness of YSTA layer is around 0.1cm, the thickness of LSM layer should be around 0.6 mum in order to maintain the stability of LSM. In a second approach, a less expensive stainless steel interconnect has been studied. However, one of the major concerns associated with the use of metallic interconnects is the development of a semi-conducting or insulating oxide scale and chromium volatility during extended exposure to the SOFC operating environment. Dense and well adhered Mn-Cu spinet oxide coatings were successfully deposited on stainless steel by an electrophoretic deposition (EPD) technique. It was found that the Mn-Cu-O coating significantly reduced the oxidation rate of the stainless steel and the volatility of chromium. The area specific resistance (ASR) of coated Crofer 22 APU is

  5. Sulfometuron incorporation in cationic micelles adsorbed on montmorillonite

    OpenAIRE

    Mishael, Y. G.; Undabeytia López, Tomás; Rytwo, Giora; Papahadjopoulos Sternberg, B.; Rubin, Baruch; Nir, Shlomo

    2002-01-01

    The aim of this study was to understand the interactions between alkylammonium cations present as monomers and micelles and a clay mineral, montmorillonite, to develop slow release formulations of anionic herbicides, such as sulfometuron (SFM) whose leaching in soils is an environmental and economic problem. In the proposed formulation the herbicide is incorporated in positively charged micelles of quaternary amine cations, which in turn adsorb on the negatively charged clay. The adsorption o...

  6. Microscopic Theory of Cation Exchange in CdSe Nanocrystals

    OpenAIRE

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

    2014-01-01

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

  7. Bithiophene radical cation: Resonance Raman spectroscopy and molecular orbital calculations

    DEFF Research Database (Denmark)

    Grage, M.M.-L.; Keszthelyi, T.; Offersgaard, J.F.;

    1998-01-01

    The resonance Raman spectrum of the photogenerated radical cation of bithiophene is reported. The bithiophene radical cation was produced via a photoinduced electron transfer reaction between excited bithiophene and the electron acceptor fumaronitrile in a room temperature acetonitrile solution a...... the Raman spectrum excited in resonance with the absorption band at 425 nm. The spectrum was interpreted with the help of density functional theory calculations. (C) 1998 Elsevier Science B.V....

  8. Migration of Cations and Anions in Amorphous Polymer Electrolytes

    Institute of Scientific and Technical Information of China (English)

    N.A.Stolwijk; S.H.Obeidi; M.Wiencierz

    2007-01-01

    1 Results Polymer electrolytes are used as ion conductors in batteries and fuel cells.Simple systems consist of a polymer matrix complexing an inorganic salt and are fully amorphous at the temperatures of interest.Both cations and anions are mobile and contribute to charge transport.Most studies on polymer electrolytes use the electrical conductivity to characterize the ion mobility.However,conductivity measurements cannot discriminate between cations and anions.This paper reports some recent results fr...

  9. Mercury release from deforested soils triggered by base cation enrichment.

    Science.gov (United States)

    Farella, N; Lucotte, M; Davidson, R; Daigle, S

    2006-09-01

    The Brazilian Amazon has experienced considerable colonization in the last few decades. Family agriculture based on slash-and-burn enables millions of people to live in that region. However, the poor nutrient content of most Amazonian soils requires cation-rich ashes from the burning of the vegetation biomass for cultivation to be successful, which leads to forest ecosystem degradation, soil erosion and mercury contamination. While recent studies have suggested that mercury present in soils was transferred towards rivers upon deforestation, little is known about the dynamics between agricultural land-use and mercury leaching. In this context, the present study proposes an explanation that illustrates how agricultural land-use triggers mercury loss from soils. This explanation lies in the competition between base cations and mercury in soils which are characterized by a low adsorption capacity. Since these soils are naturally very poor in base cations, the burning of the forest biomass suddenly brings high quantities of base cations to soils, destabilizing the previous equilibrium amongst cations. Base cation enrichment triggers mobility in soil cations, rapidly dislocating mercury atoms. This conclusion comes from principal component analyses illustrating that agricultural land-use was associated with base cation enrichment and mercury depletion. The overall conclusions highlight a pernicious cycle: while soil nutrient enrichment actually occurs through biomass burning, although on a temporary basis, there is a loss in Hg content, which is leached to rivers, entering the aquatic chain, and posing a potential health threat to local populations. Data presented here reflects three decades of deforestation activities, but little is known about the long-term impact of such a disequilibrium. These findings may have repercussions on our understanding of the complex dynamics of deforestation and agriculture worldwide. PMID:16781764

  10. Suppression of the two-dimensional electron gas in LaGaO 3 /SrTiO 3 by cation intermixing

    KAUST Repository

    Nazir, S.

    2013-12-03

    Cation intermixing at the n-type polar LaGaO 3 /SrTiO 3 (001) interface is investigated by first principles calculations. Ti"Ga, Sr"La, and SrTi"LaGa intermixing are studied in comparison to each other, with a focus on the interface stability. We demonstrate in which cases intermixing is energetically favorable as compared to a clean interface. A depopulation of the Ti 3d xy orbitals under cation intermixing is found, reflecting a complete suppression of the two-dimensional electron gas present at the clean interface.

  11. Electronic structures, vibrational spectra, and revised assignment of aniline and its radical cation: Theoretical study

    Science.gov (United States)

    Wojciechowski, Piotr M.; Zierkiewicz, Wiktor; Michalska, Danuta; Hobza, Pavel

    2003-06-01

    Comprehensive studies of the molecular and electronic structures, vibrational frequencies, and infrared and Raman intensities of the aniline radical cation, C6H5NH2+ have been performed by using the unrestricted density functional (UB3LYP) and second-order Møller-Plesset (UMP2) methods with the extended 6-311++G(df,pd) basis set. For comparison, analogous calculations were carried out for the closed-shell neutral aniline. The studies provided detailed insight into the bonding changes that take place in aniline upon ionization. The natural bond orbital (NBO) analysis has revealed that the pπ-radical conjugative interactions are of prime importance in stabilizing the planar, quinoid-type structure of the aniline radical cation. It is shown that the natural charges calculated for aniline are consistent with the chemical properties of this molecule (an ortho- and para-directing power of the NH2 group in electrophilic substitutions), whereas Mulliken charges are not reliable. The theoretical vibrational frequencies of aniline, calculated by the B3LYP method, show excellent agreement with the available experimental data. In contrast, the MP2 method is deficient in predicting the frequencies of several modes in aniline, despite the use of the extended basis set in calculations. The frequencies of aniline radical cation, calculated at the UB3LYP/6-311++G(df,pd) level, are in very good agreement with the recently reported experimental data from zero kinetic energy photoelectron and infrared depletion spectroscopic studies. The clear- cut assignment of the IR and Raman spectra of the investigated molecules has been made on the basis of the calculated potential energy distributions. Several bands in the spectra have been reassigned. It is shown that ionization of aniline can be easily identified by the appearance of the very strong band at about 1490 cm-1, in the Raman spectrum. The redshift of the N-H stretching frequencies and the blueshift of the C-H stretching

  12. A Ferric-Peroxo Intermediate in the Oxidation of Heme by IsdI.

    Science.gov (United States)

    Takayama, Shin-Ichi J; Loutet, Slade A; Mauk, A Grant; Murphy, Michael E P

    2015-04-28

    The canonical heme oxygenases (HOs) catalyze heme oxidation via a heme-bound hydroperoxo intermediate that is stabilized by a water cluster at the active site of the enzyme. In contrast, the hydrophobic active site of IsdI, a heme-degrading enzyme from Staphylococcus aureus, lacks a water cluster and is expected to oxidize heme by an alternative mechanism. Reaction of the IsdI-heme complex with either H2O2 or m-chloroperoxybenzoic acid fails to produce a specific oxidized heme iron intermediate, suggesting that ferric-hydroperoxo or ferryl derivatives of IsdI are not involved in the catalytic mechanism of this enzyme. IsdI lacks a proton-donating group in the distal heme pocket, so the possible involvement of a ferric-peroxo intermediate has been evaluated. Density functional theory (DFT) calculations indicate that heme oxidation involving a ferric-peroxo intermediate is energetically accessible, whereas the energy barrier for a reaction involving a ferric-hydroperoxo intermediate is too great in the absence of a proton donor. We propose that IsdI catalyzes heme oxidation through nucleophilic attack by the heme-bound peroxo species. This proposal is consistent with our previous demonstration by nuclear magnetic resonance spectroscopy that heme ruffling increases the susceptibility of the meso-carbon of heme to nucleophilic attack. PMID:25853501

  13. Density functional theory study of interaction, bonding and affinity of group IIb transition metal cations with nucleic acid bases

    Science.gov (United States)

    Bagchi, Sabyasachi; Mandal, Debasish; Ghosh, Deepanwita; Das, Abhijit K.

    2012-05-01

    The structure, bonding, and energetics of the complexes obtained from the interaction between the most stable tautomeric forms of free DNA and RNA bases and Zn2+, Cd2+ and Hg2+ cations have been studied using density functional B3LYP method. The 6-311+G (2df, 2p) basis set along with LANL2DZ pseudopotentials for the cations are used in the calculations. The tautomerization paths of the nucleobases are investigated and transition states between the tautomeric forms of the free bases are located. The relative stability of the complexes and the tautomers of the free nucleobases are discussed referring to MIA and relative energy values. For uracil, thymine and adenine, interaction of the metal cations with the most stable tautomers form the least stable molecular complexes. For cytosine and guanine, the stability of the metalated complexes differs significantly. The enthalpy (ΔH), entropy (TΔS) and free energy (ΔG) of the complexes at 298 K have also been calculated.

  14. Effect of Lyophilization and Freeze-thawing on the Stability of siRNA-liposome Complexes

    OpenAIRE

    Yadava, Preeti; Gibbs, Melissa; de Castro, Carlos; Hughes, Jeffrey A.

    2007-01-01

    The purpose of this research was to describe the application of lyophilization in the delivery of siRNA using cationic lipids by addressing the long-term formulation/stability issues associated with cationic lipids and to understand the mechanism of lyoprotection. siRNA liposomes complexes were formed in different potential cyro/lyoprotectants and subjected to either lyophilization or freeze thaw cycles. siRNA, liposomes and/or lipoplexes were tested for activity, SYBR Green I binding, cellul...

  15. Enhancing Intrinsic Stability of Hybrid Perovskite Solar Cell by Strong, yet Balanced, Electronic Coupling

    OpenAIRE

    El-Mellouhi, fedwa; Bentria, El Tayeb; Rashkeev, Sergey N.; Kais, Sabre; Alharbi, Fahhad H.

    2016-01-01

    In the past few years, the meteoric development of hybrid organic--inorganic perovskite solar cells (PSC) astonished the community. The efficiency has already reached the level needed for commercialization; however, the instability hinders its deployment on the market. Here, we report a mechanism to chemically stabilize PSC absorbers. We propose to replace the widely used methylammonium cation (\\ce{CH3NH3+}) by alternative molecular cations allowing an enhanced electronic coupling between the...

  16. Financial Intermediation, Monetary Uncertainty, and Bank Interest Margins Financial Intermediation, Monetary Uncertainty, and Bank Interest Margins

    OpenAIRE

    Leonardo Hernández

    1992-01-01

    Financial Intermediation, Monetary Uncertainty, and Bank Interest Margins This paper studies a simple model of financial intermediation in order to understand how the lending-borrowing spread or interest margin) charged by financial intermediaries is determined in equilibrium in a monetary economy. The main conclusion of the paper concerns the effect on the spread of changes in the distribution of monetary innovations. Thus, changes in the monetary-policy-rule followed by the Central Bank whi...

  17. A comparison between three methods for the determination of cation exchange capacity and exchangeable cations in soils

    OpenAIRE

    Ciesielski, H.; Sterckeman, T.

    1997-01-01

    The object of this study is to compare the results obtained with three standardized methods of determination of cationic exchange capacity (CEC) and exchangeable cations (Ca, Mg, K) in soils. The three methods are based on different exchange reagents: cobalt hexamine (Cohex) trichloride, barium chloride and ammonium acetate. Exchange procedures are different as well; they are, respectively, single extraction, successive extractions and percolation. Values measured with barium and Cohex as ind...

  18. Evolutionary Characteristics of China's Intermediate Manufactures

    Institute of Scientific and Technical Information of China (English)

    Minsung Kang; Jeong-Dong Lee

    2007-01-01

    China's economic development is characterized by progressive integration with international production chains as an assembly producer. Japan and South Korea are the major partners providing intermediate products to China. The present paper analyzes the Chinese intermediate sector's present condition and evolutionary characteristics revealed in bilateral trade with Japan and South Korea. The analysis uses the framework of new trade theory represented by "intra-industry trade". Trade statistics from 1997 to 2004 are analyzed using the database published by the OECD. Results show that China's inter-industrial evolution is characterized by its expanding positioning in the manner of the flying geese development paradigm of Asian countries. Furthermore, intra-industrial evolution is characterized by a concentration on price competitiveness. The framework and results of the industrial analysis presented in this paper assist in the understanding of China's manufacturing evolution and of the policy-making decisions taken in the process.

  19. Being back home after intermediate care

    DEFF Research Database (Denmark)

    Martinsen, Bente; Harder, Ingegerd; Norlyk, Annelise

    2015-01-01

    Older people may face many challenges and experience insecurity after discharge from hospital to home. To bridge the potential gap between general hospital and home, the concept ‘Intermediate Care’ (IC) was developed at the beginning of 2000. IC aims to safeguard older people from being discharged...... interviews. Transcripts were analysed using a phenomenological approach. The essential meaning of being back home after a stay in an IC unit was characterised by ‘uncertainty’. Four constituents emerged: ‘in a state of shock about coming home’, ‘dependence on informal helpers’, ‘a sense of isolation’, and...... ‘fear of losing functional ability permanently’. Key words: intermediate care, older people, discharge, interview, phenomenology...

  20. Comments on intermediate-scale models

    International Nuclear Information System (INIS)

    Some superstring-inspired models employ intermediate scales mI of gauge symmetry breaking. Such scales should exceed 1016 GeV in order to avoid prima facie problems with baryon decay through heavy particles and non-perturbative behaviour of the gauge couplings above mI. However, the intermediate-scale phase transition does not occur until the temperature of the Universe falls below O(mW), after which an enormous excess of entropy is generated. Moreover, gauge symmetry breaking by renormalization group-improved radiative corrections is inapplicable because the symmetry-breaking field has not renormalizable interactions at scales below mI. We also comment on the danger of baryon and lepton number violation in the effective low-energy theory. (orig.)

  1. Intermediate filaments in small configuration spaces.

    Science.gov (United States)

    Nöding, Bernd; Köster, Sarah

    2012-02-24

    Intermediate filaments play a key role in cell mechanics. Apart from their great importance from a biomedical point of view, they also act as a very suitable micrometer-sized model system for semiflexible polymers. We perform a statistical analysis of the thermal fluctuations of individual filaments confined in microchannels. The small channel width and the resulting deflections at the walls give rise to a reduction of the configuration space by about 2 orders of magnitude. This circumstance enables us to precisely measure the intrinsic persistence length of vimentin intermediate filaments and to show that they behave as ideal wormlike chains; we observe that small fluctuations in perpendicular planes decouple. Furthermore, the inclusion of results for confined actin filaments demonstrates that the Odijk confinement regime is valid over at least 1 order of magnitude in persistence length. PMID:22463576

  2. Is TW Pictoris really an intermediate polar?

    CERN Document Server

    Norton, A J

    1998-01-01

    We present the results of a long ROSAT HRI observation of the candidate intermediate polar TW Pic. The power spectrum shows no sign of either the previously proposed white dwarf spin period or the proposed binary orbital period (1.996 hr and 6.06 hr respectively). The limits to the X-ray modulation are less than 0.3% in each case. In the absence of a coherent X-ray pulsation, the credentials of TW Pic for membership of the intermediate polar subclass must be suspect. We further suggest that the true orbital period of the binary may be the shorter of the two previously suggested, and that the longer period may represent a quasi-periodic phenomenon associated with the accretion disc.

  3. Entropy of Intermediate-Mass Black Holes

    OpenAIRE

    Frampton, Paul H.

    2009-01-01

    Observational searches for Intermediate-Mass Black Holes (IMBHs), defined to have masses between 30 and 300,000 solar masses, provide limits which allow up to ten percent of what is presently identified as halo dark matter to be in the form of IMBHs. These concentrate entropy so efficiently that the halo contribution can be bigger than the core supermassive black hole. Formation of IMBHs is briefly discussed.

  4. Desperately Seeking Intermediate-Mass Black Holes

    OpenAIRE

    Frampton, Paul H.

    2009-01-01

    Observational searches for Intermediate Mass Black Holes (IMBHs), defined to have masses between 30 and 300,000 solar masses, provide limits which allow up to ten percent of what is presently identified as halo dark matter to be in the form of IMBHs. These concentrate entropy so efficiently that the halo contribution can be bigger than the core supermassive black hole. Formation of IMBHs is briefly discussed.

  5. Financial Reforms in Sudan; Streamlining Bank Intermediation

    OpenAIRE

    Alexei Kireyev

    2001-01-01

    The paper reviews the experience of financial reforms in Sudan with a view to assessing their macroeconomic impact and to shedding light on the question why such reforms have not yet brought about visible improvements in financial intermediation. The paper concludes that regardless of the progress achieved in recent years, deficiencies in the reform design, institutional weaknesses, shallow financial markets, shortcomings of the Islamic mode of finance, and strong seasonality remain key facto...

  6. Ruthenium Vinyl Carbene Intermediates in Enyne Metathesis

    OpenAIRE

    Diver, Steven T.

    2007-01-01

    This review provides an overview of ruthenium vinyl carbene reactivity as it relates to enyne metathesis. Methods for the synthesis of metathesis-active and metathesis-inactive complexes are also summarized. Some of the early hypotheses about vinyl carbene intermediates in enyne metatheses were tested in the arena of synthetic chemistry and subsequently led to mechanistic studies. In these two areas, studies from the author's labs are described. There are still many unresolved questions in en...

  7. Deuteron Stripping on Nuclei at Intermediate Energies

    CERN Document Server

    Kovalchuk, V I

    2016-01-01

    A general analytical expression for the double differential cross section of inclusive deuteron stripping reaction on nuclei at intermediate energies of incident particles was obtained in the diffraction approximation. Nucleon-nucleus phases were calculated in the framework of Glauber formalism and making use of the double-folding potential. The exact wave function of deuteron with correct asymptotics at short and long distances between nucleons was used. The calculated angular dependencies of cross sections are in good agreement with corresponding experimental data.

  8. Far from the intermediate nuclear field

    International Nuclear Information System (INIS)

    Pairing correlations in nuclear physics; the BCS state and quasi-particles; the layer model; collision effects on nuclear dynamics; the theory of cluster formation (application to nucleus fragmentation); short range correlations (few-particle systems); deuterium electron scattering; dibaryonic resonances; traditional and exotic hadron probes of nuclear structure; spectral fluctuations and chaotic motion; corrections to the intermediate nuclear field (nonrelativistic and other effects); and heavy nuclei splitting and nuclear superfluidity are introduced

  9. Mobile phones in conflicts of financial intermediation

    OpenAIRE

    Asongu, Simplice A; Tchamyou, Vanessa S.

    2015-01-01

    To the best our knowledge, in the first empirical macroeconomic examination of the nexus between financial intermediation and mobile phones, Asongu employs two conflicting financial system definitions in the assessment of how mobile phones have stimulated financial development in Africa. Within the framework of the dominant International Monetary Fund's International Financial Statistics (2008) definition, mobile phones are established to be negatively associated with financial intermediary d...

  10. Mobile Phones in Conflicts of Financial Intermediation

    OpenAIRE

    Asongu, Simplice; Tchamyou, Vanessa

    2015-01-01

    To the best our knowledge, in the first empirical macroeconomic examination of the nexus between financial intermediation and mobile phones, Asongu employs two conflicting financial system definitions in the assessment of how mobile phones have stimulated financial development in Africa. Within the framework of the dominant International Monetary Fund’s International Financial Statistics (2008) definition, mobile phones are established to be negatively associated with financial intermediary d...

  11. Leveraging Efforts on Remittances and Financial Intermediation

    OpenAIRE

    Manuel Orozco; Rachel Fedewa

    2006-01-01

    This report seeks to analyze the efforts among financial institutions to leverage the relationship between financial intermediation and remittance transfers. The impact of family remittances has been highlighted in the literature as an important one for development. A development impact is one that addresses issues relating to the distribution of wealth and overall improvements in the quality of people's lives. More recently, policy recommendations have stressed the importance of linking remi...

  12. An Idealized View of Financial Intermediation

    OpenAIRE

    Sissoko, Carolyn

    2007-01-01

    Using the monetary model developed in Sissoko (2007), where the general equilibrium assumption that every agent buys and sells simultaneously is relaxed, we observe that in this environment fiat money can implement a Pareto optimum only if taxes are type-specific. We then consider intermediated money by assuming that financial intermediaries whose liabilities circulate as money have an important identifying characteristic: they are widely viewed as default-free. The paper demonstrates that de...

  13. Discovery of the intermediate W boson

    CERN Multimedia

    1983-01-01

    Press conference on 25 January 1983 when the announcement was made of the discovery of the intermediate W boson at CERN. From right to left: Carlo Rubbia, spokesman of the UA1 experiment; Simon van der Meer, responsible for developing the stochastic cooling technique; Herwig Schopper, Director- General of CERN; Erwin Gabathuler, Research Director at CERN, and Pierre Darriulat, spokesman of the UA2 experiment, whose results confirmed those from Carlo Rubbia's experiment.

  14. Interest Based Financial Intermediation: Analysis and Solutions

    OpenAIRE

    Shaikh, Salman

    2012-01-01

    Interest is prohibited in all monotheist religions. Apart from religion, interest is also regarded as unjust price of money capital by pioneer secular philosophers as well as some renowned economists. However, it is argued by some economists that modern day, market driven interest rate in a competitive financial market is different from usury and that the interest based financial intermediation has served a useful purpose in allocation of resources as well as in allocation of risk, given the ...

  15. Sedimentation of dilute suspension in intermediate region

    Czech Academy of Sciences Publication Activity Database

    Vlasák, Pavel; Chára, Zdeněk

    Prague : ITAM AS CR, v. v. i., 2012 - (Náprstek, J.; Fischer, C.), s. 1517-1524 ISBN 978-80-86246-40-6. [Engineering Mechanics 2012 /18./. Svratka (CZ), 14.05.2012-17.05.2012] R&D Projects: GA ČR GAP105/10/1574 Institutional research plan: CEZ:AV0Z20600510 Keywords : sedimentation * intermediate settlement * particle size * concentration * vessel inclination Subject RIV: BK - Fluid Dynamics

  16. FIRM - A Graph-Based Intermediate Representation

    OpenAIRE

    Braun, Matthias; Buchwald, Sebastian; Zwinkau, Andreas

    2011-01-01

    We present our compiler intermediate representation Firm. Programs are always in SSA-form enabling a representation as graphs. We argue that this naturally encodes context information simplifying many analyses and optimizations. Instructions are connected by dependency edges relaxing the total to a partial order inside a basic block. For example alias analysis results can be directly encoded in the graph structure. The paper gives an overview of the representation and focuses on its construct...

  17. Intermediation and matching in insurance markets

    OpenAIRE

    Focht, Uwe; Richter, Andreas; Schiller, Jörg

    2009-01-01

    This paper addresses the role of independent insurance intermediaries in markets where matching is important. A controversial matter in the discussion concerning insurance intermediation is the issue of compensation customs and how the latter affect prices, rents and advice quality in insurance markets. This work compares a fee-based with a commission-based system. We show that in a situation with a non-strategic intermediary both remuneration systems are payoff-equivalent. In a second step, ...

  18. Intermediate Trainee Perspectives of Family Therapy Skills

    OpenAIRE

    Benson, Margo

    2004-01-01

    Marriage and family therapy training involves the development of therapy skills that lead to effective treatment, and the family therapy literature recognizes the importance of skill development in training. The training literature dealing with specific skills most often refers to beginning-level skills and obtains data largely from supervisors and trainers. Intermediate-level skills appear to be overlooked and no apparent attention is given from the perspective of trainees. This research ...

  19. Households Credits, Financial Intermediation and Monetary Policies

    OpenAIRE

    Cécile Bastidon

    2014-01-01

    This paper develops a theoretical model of financial intermediation with three original characteristics. Firstly, all sectors are taken into account within total outstanding credits, including households. Secondly, in periods of high financial strains, the relationship between prices and funding supply volumes may be non-monotonic. Finally, the occurrence of interbank credit rationing results in other sectors’ funding rationing in credit and securities markets. The central b...

  20. Intermedial Representations in Asian Macbeth-s

    OpenAIRE

    Wang, I-Chun

    2011-01-01

    In her article "Intermedial representations in Asian Macbeth-s" I-Chun Wang discusses three Asian versions of Macbeths that exemplify the cultural meanings through the interaction of landscape, body, and spectacles of power. Shakespeare remains one of the most popular playwrights in the Eastern world, and playwrights in the Asian world find Shakespearean plays attractive to the Asian audience. Among Shakespearean plays, Macbeth fascinates its Asian audience with its theme on kingship, territo...

  1. Intermediate inflation with modified kinetic term

    Science.gov (United States)

    Mohammadi, A.; Ossoulian, Z.; Golanbari, T.; Saaidi, K.

    2015-09-01

    Intermediate inflation is considered in a non-canonical scalar field model, in which the kinetic term of scalar field is taken as a power-law function. The free parameters of the model are constrained by using the most recent observational data related to scalar spectra index, tensor-to-scalar ratio, and scalar perturbation amplitude. The results are used to depict the potential behavior of the model and estimate the initial and final time of inflation.

  2. UEP LT Codes with Intermediate Feedback

    DEFF Research Database (Denmark)

    Sørensen, Jesper Hemming; Popovski, Petar; Østergaard, Jan

    2013-01-01

    We analyze a class of rateless codes, called Luby transform (LT) codes with unequal error protection (UEP). We show that while these codes successfully provide UEP, there is a significant price in terms of redundancy in the lower prioritized segments. We propose a modification with a single inter...... intermediate feedback message. Our analysis shows a dramatic improvement on the decoding performance of the lower prioritized segment....

  3. Financial intermediation and the rights offer paradox

    OpenAIRE

    Koenig-Matsoukis, Laure

    2010-01-01

    In this study, we investigate the trading dynamics around rights issues. We employ signed and unsigned trading activity measures in order to provide evidence of costly financial intermediation. We, first, document short selling activity by underwriters and shareholders during rights issues leading to significant negative abnormal returns during the offer. Further, we provide evidence that rights tend to be sold below their fair value. Our results, therefore, suggest that the lack of use of ri...

  4. Intermediate Temperature Water Heat Pipe Tests

    Science.gov (United States)

    Devarakonda, Angirasa; Xiong, Da-Xi; Beach, Duane E.

    2005-01-01

    Heat pipes are among the most promising technologies for space radiator systems. Water heat pipes are explored in the intermediate temperature range of 400 to above 500 K. The thermodynamic and thermo-physical properties of water are reviewed in this temperature range. Test data are reported for a copper-water heat pipe. The heat pipe was tested under different orientations. Water heat pipes show promise in this temperature range. Fabrication and testing issues are being addressed.

  5. Cation Uptake and Allocation by Red Pine Seedlings under Cation-Nutrient Stress in a Column Growth Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Shi, Zhenqing; Balogh-Brunstad, Zsuzsanna; Grant, Michael R.; Harsh, James B.; Gill, Richard; Thomashow, Linda; Dohnalkova, Alice; Stacks, Daryl; Letourneau, Melissa; Keller, Chester K.

    2014-01-10

    Background and Aims Plant nutrient uptake is affected by environmental stress, but how plants respond to cation-nutrient stress is poorly understood. We assessed the impact of varying degrees of cation-nutrient limitation on cation uptake in an experimental plant-mineral system. Methods Column experiments, with red pine (Pinus resinosa Ait.) seedlings growing in sand/mineral mixtures, were conducted for up to nine months under a range of Ca- and K-limited conditions. The Ca and K were supplied from both minerals and nutrient solutions with varying Ca and K concentrations. Results Cation nutrient stress had little impact on carbon allocation after nine months of plant growth and K was the limiting nutrient for biomass production. The Ca/Sr and K/Rb ratio results allowed independent estimation of dissolution incongruency and discrimination against Sr and Rb during cation uptake processes. The fraction of K in biomass from biotite increased with decreasing K supply from nutrient solutions. The mineral anorthite was consistently the major source of Ca, regardless of nutrient treatment. Conclusions Red pine seedlings exploited more mineral K in response to more severe K deficiency. This did not occur for Ca. Plant discrimination factors must be carefully considered to accurately identify nutrient sources using cation tracers.

  6. The birthline for intermediate-mass stars

    International Nuclear Information System (INIS)

    The protostar mass-radius relation is combined with standard premain-sequence evolutionary tracks to construct the birthline for stars of intermediate mass. This theoretical birthline is in good agreement with the observed upper envelope of the distribution of Herbig Ae and Be stars in the H-R diagram. From the intersection of the birthline with the ZAMS, it is predicted that stars with more than 10 solar masses should never exhibit an optical premain-sequence phase; this prediction also agrees with existing observations. These findings show that stars of intermediate mass are first optically visible quite close to the main sequence. Hence, their contraction ages are less than the traditional ones derived assuming large initial radii. The birthline is also well delineated by the locus in the diagram of optically visible stars with associated molecular outflows. The underlying protostar theory predicts that newly formed stars of intermediate mass burn deuterium in a subsurface shell. An outer convection zone maintained by this shell burning is proposed to be the cause of the winds and surface activity commonly observed in these stars. 23 refs

  7. Controlling DNA compaction with cationic amphiphiles for efficient delivery systems A step forward towards non-viral Gene Therapy

    Science.gov (United States)

    Savarala, Sushma

    The synthesis of pyridinium cationic lipids, their counter-ion exchange, and the transfection of lipoplexes consisting of these lipids with firefly luciferase plasmid DNA (6.7 KDa), into lung, prostate and breast cancer cell lines was investigated. The transfection ability of these newly synthesized compounds was found to be twice as high as DOTAP/cholesterol and Lipofectamine TM (two commercially available successful transfection agents). The compaction of the DNA onto silica (SiO2) nanoparticles was also investigated. For this purpose, it was necessary to study the stability and fusion studies of colloidal systems composed of DMPC (1,2-dimyristoyl-sn-glycero-3-phosphocholine), a zwitterionic lipid, and mixtures of DMPC with cationic DMTAP (1,2-dimyristoyl-3-trimethylammonium-propane).

  8. Solvent-Free Selective Oxidation of Toluene with O2 Catalyzed by Metal Cation Modified LDHs and Mixed Oxides

    Directory of Open Access Journals (Sweden)

    Xiaoli Wang

    2016-01-01

    Full Text Available A series of metal cation modified layered-double hydroxides (LDHs and mixed oxides were prepared and used to be the selective oxidation of toluene with O2. The results revealed that the modified LDHs exhibited much higher catalytic performance than their parent LDH and the modified mixed oxides. Moreover, the metal cations were also found to play important roles in the catalytic performance and stabilities of modified catalysts. Under the optimal reaction conditions, the highest toluene conversion reached 8.7% with 97.5% of the selectivity to benzyldehyde; moreover, the catalytic performance remained after nine catalytic runs. In addition, the reaction probably involved a free-radical mechanism.

  9. Transformation of Vesicles in Aqueous Two-Phase System of an Anionic Gemini Surfactant and a Cationic Conventional Surfactant Mixture

    Institute of Scientific and Technical Information of China (English)

    JIANG Rong; HUANG Yi-Xiong; ZHAO Jian-Xi; HUANG Chang-Cang

    2008-01-01

    Transformation of vesicles formed in DTAB/C11-p-PhCNa aqueous surfactant two-phase (ASTP) was observed by the transmission electron microscopy (TEM). The trans-conformation of the gemini surfactant in the aggregates was considered to be the important factor for constructing the multi-lamellar structure of the vesicle wall. The cation-π interaction between the quaternary ammonium cation and the aromatic ring in the spacer was determined by the UV-Vis spectrum analysis, which, as well as the general electrostatic attraction and hydrophobic force, contributes to the stability of the multi-lamellar structure. The concentrations of the surface-active ions were measured for understanding the mechanism of vesicle transformation. The results show that isoelectric mixing of the two components benefits the growth of vesicles both in size and wall thickness.

  10. Thermal treatment effects imposed on solid DNA cationic lipid complex with hexadecyltrimethylammonium chloride, observed by variable angle spectroscopic ellipsometry

    Energy Technology Data Exchange (ETDEWEB)

    Nizioł, Jacek, E-mail: niziol@agh.edu.pl [Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, al. Mickiewicza 30, 30-059 Kraków (Poland)

    2014-12-21

    DNA cationic lipid complexes are materials of properties required for applications in organic electronics and optoelectronics. Often, their thermal stability demonstrated by thermogravimetry is cited in the literature as important issue. However, little is known about processes occurring in heated solid DNA cationic lipid complexes. In frame of this work, thin films of Deoxyribonucleic acid-hexadecyltrimethylammonium chloride (DNA-CTMA) were deposited on silicon wafers. Samples were thermally annealed, and simultaneously, their optical functions were measured by spectroscopic ellipsometry. At lower temperatures, thermal expansion coefficient of solid DNA-CTMA was negative, but at higher temperatures positive. Thermally induced modification of absorption spectrum in UV-vis was observed. It occurred at a range of temperatures higher than this of DNA denaturation in solution. The observed phenomenon was irreversible, at least in time scale of the experiment (one day)

  11. Stability and efficacy of synthetic cationic antimicrobial peptides nebulized using high frequency acoustic waves.

    Science.gov (United States)

    Wang, Ying; Rezk, Amgad R; Khara, Jasmeet Singh; Yeo, Leslie Y; Ee, Pui Lai Rachel

    2016-05-01

    Surface acoustic wave (SAW), a nanometer amplitude electroelastic wave generated and propagated on low-loss piezoelectric substrates (such as LiNbO3), is an extremely efficient solid-fluid energy transfer mechanism. The present study explores the use of SAW nebulization as a solution for effective pulmonary peptide delivery. In vitro deposition characteristics of the nebulized peptides were determined using a Next Generation Cascade Impactor. 70% of the peptide-laden aerosols generated were within a size distribution favorable for deep lung distribution. The integrity of the nebulized peptides was found to be retained, as shown via mass spectrometry. The anti-mycobacterial activity of the nebulized peptides was found to be uncompromised compared with their non-nebulized counterparts, as demonstrated by the minimum inhibition concentration and the colony forming inhibition activity. The peptide concentration and volume recoveries for the SAW nebulizer were significantly higher than 90% and found to be insensitive to variation in the peptide sequences. These results demonstrate the potential of the SAW nebulization platform as an effective delivery system of therapeutic peptides through the respiratory tract to the deep lung. PMID:27375820

  12. Stabilized borata-alkene formation: structural features, reactions and the role of the counter cation.

    Science.gov (United States)

    Kohrt, Sonja; Dachwitz, Steffen; Daniliuc, Constantin G; Kehr, Gerald; Erker, Gerhard

    2015-12-28

    Dimethylbenzofulvene adds Piers' borane [HB(C6F5)2] at the indene double bond to give a mixture of regioisomeric boranes 8a,b. Subsequent isomerization under equilibrium conditions gives the isopropyl substituted 1H and 3H borylindenes 10a,b. Their treatment with the bulky LiTMP base under frustrated Lewis pair conditions resulted in a clean deprotonation reaction to give the borata-alkene 14. Its X-ray crystal structure analysis indicated a pronounced B[double bond, length as m-dash]C double bond character and thus a borata-benzofulvene description. The borata-alkene underwent (probably stepwise) [4 + 2] cycloaddition reactions with chalcone derivatives and a formal [6 + 2] cycloaddition with phenylmethylketene. Many products and derivatives were characterized by X-ray diffraction. PMID:26584629

  13. Montmorillonite stability - experimental results

    International Nuclear Information System (INIS)

    repository. High concentration of silica in the bentonite pore-water may buffer the reaction. Consequently, the flux of potassium into the pore-water, and the flux of silica from the pore-water are of interest from an alteration rate limiting perspective. The present work includes one year laboratory experiments, mainly to study silica release and fixation of potassium. Wyoming bentonite, as delivered, and after purification and ion-exchange to sodium form were used. Test samples were compacted to repository density and a thickness of 5 mm and placed in titanium/PEEK test cells. Each sample was contacted, through filters at both sides, to 250 mL, 50 mM chloride solutions with Na, K, Mg and Ca as cations, respectively. The test solutions were slowly circulated outside the samples, and repeatedly changed in order to provide a complete ion exchange. The temperature was successively increased to 90 deg. C, and the water solutions were less frequently changed, and intermittently analyzed with respect to Na, K, Mg, Ca, Si, Al, Fe and pH. Swelling pressure was measured before and after the heating period. The silica release rate was similar in all tests, and the silica concentration repeatedly stabilized at around 2 mM in all the test solutions. At test termination, each sample was analyzed with respect to cation exchange capacity and chemical composition, and a slight decrease in CEC was noticed in the sample exposed to the potassium solution. (authors)

  14. X-ray absorption study of intermediate valence in Sm1-xGdxS alloys

    International Nuclear Information System (INIS)

    X-ray absorption near edge structure (XANES) measurements above LH edge of Sm are employed to study the intermediate valence in Sm1-xGdxS(0.05 ≤ x ≤ 0.30) alloys. The split white lines at the LH edge of Sm are used to determine the average valence of SM in these alloys. The internal chemical pressure generated by substitution of smaller trivalent cation, Gd, for Sm drives the latter to a higher valence. Sm valence increases smoothly first and then undergoes an abrupt increment at a critical concentration of 16 at.% of Gd. At concentration of Gd higher than 16 at. % the increase in Sm valence is smooth and small. The data for Sm average valence for Sm1-xGdxS alloys obtained by LH absorption edges shows fair agreement with other techniques

  15. Geo-polymers as Candidates for the Immobilisation of Low- and Intermediate-Level Waste

    International Nuclear Information System (INIS)

    Geo-polymers should be serious waste form candidates for intermediate level waste (ILW), insofar as they are more durable than Portland cement and can pass the PCT-B test for high-level waste. Thus an alkaline ILW could be considered to be satisfactorily immobilised in a geo-polymer formulation. However a simulated Hanford tank waste was found to fail the PCT-B criterion even for a waste loading as low as 5 wt%, very probably due to the formation of a soluble sodium phosphate compound(s). This suggests that it could be worth developing a 'mixed' GP waste form in which the amorphous material can immobilize cations and a zeolitic component to immobilize anions. The PCT-B test is demonstrably subject to significant saturation effects, especially for relatively soluble waste forms. (authors)

  16. Effects of humic acid-based buffer + cation on chemical characteristics of saline soils and maize growth

    Directory of Open Access Journals (Sweden)

    W. Mindari

    2014-10-01

    Full Text Available Humic acid is believed to maintain the stability of the soil reaction, adsorption / fixation / chelate of cation, thereby increasing the availability of water and plant nutrients. On the other hand, the dynamics of saline soil cation is strongly influenced by the change of seasons that disrupt water and plant nutrients uptake. This experiment was aimed to examine the characteristics of the humic acid from compost, coal, and peat and its function in the adsorption of K+ and NH4+ cations, thus increasing the availability of nutrients and of maize growth. Eighteen treatments consisted of three humic acid sources (compost, peat and coal, two cation additives (K+ and NH4+, and three doses of humic acid-based buffer (10, 20, and 30 g / 3kg, were arranged in a factorial completely randomized with three replicates. The treatments were evaluated against changes in pH, electric conductivity (EC, cation exchange capacity (CEC, chlorophyll content, plant dry weight and plant height. The results showed that the addition of K+ and NH4+ affected pH, CEC, K+, NH4+, and water content of the buffer. Application of humic acid-based buffer significantly decreased soil pH from > 7 to about 6.3, decreased soil EC to 0.9 mS / cm, and increased exchangeable Na from 0.40 to 0.56 me / 100g soil, Ca from 15.57 to 20.21 me/100 g soil, Mg from 1.76 to 6.52 me/100 g soil, and K from 0.05-0.51 me / 100g soil. Plant growth (plant height, chlorophyll content, leaf area, and stem weight at 35 days after planting increased with increasing dose of humic acid. The dose of 2.0g peat humic acid + NH4+ / 3 kg of soil or 30g peat humic acid + K+ / 3 kg of oil gave the best results of maize growth.

  17. Cation ordering and effect of biaxial strain in double perovskite CsRbCaZnCl6

    International Nuclear Information System (INIS)

    Here, we investigate the electronic structure, energetics of cation ordering, and effect of biaxial strain on double perovskite CsRbCaZnCl6 using first-principles calculations based on density functional theory. The two constituents (i.e., CsCaCl3 and RbZnCl3) forming the double perovskite exhibit a stark contrast. While CsCaCl3 is known to exist in a cubic perovskite structure and does not show any epitaxial strain induced phase transitions within an experimentally accessible range of compressive strains, RbZnCl3 is thermodynamically unstable in the perovskite phase and exhibits ultra-sensitive response at small epitaxial strains if constrained in the perovskite phase. We show that combining the two compositions in a double perovskite structure not only improves overall stability but also the strain-polarization coupling of the material. Our calculations predict a ground state with P4/nmm space group for the double perovskite, where A-site cations (i.e., Cs and Rb) are layer-ordered and B-site cations (i.e., Ca and Zn) prefer a rocksalt type ordering. The electronic structure and bandgap in this system are shown to be quite sensitive to the B-site cation ordering and is minimally affected by the ordering of A-site cations. We find that at experimentally accessible compressive strains CsRbCaZnCl6 can be phase transformed from its paraelectric ground state to an antiferroelectric state, where Zn atoms contribute predominantly to the polarization. Furthermore, both energy difference and activation barrier for a transformation between this antiferroelectric state and the corresponding ferroelectric configuration are predicted to be small. The computational approach presented here opens a new pathway towards a rational design of novel double perovskites with improved strain response and functionalities

  18. Intermediate order in tetrahedrally coordinated silicon: evidence for chainlike objects

    Energy Technology Data Exchange (ETDEWEB)

    Tsu, D.V.; Chao, B.S.; Jones, S.J. [Energy Conversion Devices, Rochester Hills, MI (United States)

    2003-07-01

    In this report, we describe the nature of intermediate order in silicon as determined by recent measurements on thin films using transmission electron microscopy (TEM) and Raman scattering. The TEM images show in addition to the expected continuous random network (CRN), the presence of highly ordered quasi-one-dimensional ''chain-like objects'' (CLOs) that are 1-2 nm wide and tens of nm long that meander and show some evidence of cross-linking with each other. The presence of these objects correlate to a Raman feature centered at 490 cm{sup -1} whose width is 35-40 cm{sup -1}, and is used to quantify the heterogeneity in terms of the CLO and CRN (=475 cm{sup -1} scattering) concentrations. The 490 and 35 cm{sup -1} values are consistent with bond angle deviations approaching 0{sup o}, and thus reinforces an association with the CLOs. We find that in reference quality a-Si:H (made using pure SiH{sub 4}), the CLO concentration is about 5 vol%, while in state-of-the-art material using high H{sub 2} levels of dilution during processing, it increases to about 15%. Increased stability of such material to light-soaking is thus not mediated by a direct volumetric replacement of poor with high-quality components. Rather, an important characteristic of intermediate order in silicon is the low-dimensional aspect of its order, which allows it to influence more total volume than which it is itself composed. Consistent with these and other recent findings, we propose a tensegrity model of amorphous silicon. (author)

  19. Understanding selectivity of hard and soft metal cations within biological systems using the subvalence concept. I. Application to blood coagulation: direct cation-protein electronic effects vs. indirect interactions through water networks

    Science.gov (United States)

    de Courcy, B.; Pedersen, L. G.; Parisel, O.; Gresh, N.; Silvi, B.; Pilmé, J.; Piquemal, J.-P.

    2010-01-01

    transfer network, external sites are better stabilised by Mg(II), rather than Ca(II), in agreement with experiment. The central role of discrete water molecules is also discussed in order to understand the stabilities of the observed X-rays structures of the Gla domain. Indeed, the presence of explicit water molecules generating indirect cation-protein interactions through water networks is shown to be able to reverse the observed electronic selectivity occuring when cations directly interact with the Gla domain without the need of water. PMID:20419068

  20. Intermediates in Isotopic Exchange Reactions Involving Diborane

    International Nuclear Information System (INIS)

    By conventional mass spectrometric analysis, the self-exchange reaction of diborane was studied by using boron and hydrogen isotopes as tracers. The ratio of deuterium to boron exchange was found to be 2.8. This suggests that the reaction is not completely proceeding by exchange of BH3's as an entity, and that the mechanism is more complicated than simply a stripping reaction between diborane and a borane. It was therefore decided to attempt to get some knowledge of the intermediates that are present in diborane dissociation since they may shed light on the mechanism of the exchange. Using a specially constructed mass spectrometer of high sensitivity coupled with a flow reactor, it was possible to make a direct detection of the intermediate involved in the diborane equilibria. The intermediates BH3 and BH2 were found to be present and their ionization potentials were measured. In addition, a small amount of B3Hn was observed but the value of n could not be determined because of the weak peaks obtained. An attempt is made to interpret the self-exchange reaction of diborane in terms of these intermediates. The results suggest that diborane is in rapid equilibrium with borane (BH3). In addition, apparently diborane can also dissociate in BH2 which was about twice as abundant as BH3. The B3Hn intermediate that was observed is believed to arise from the reaction. BH3 + B2H6 -> B3H9. In applying this information to the isotopic self-exchange in diborane, it appears that the exchange cannot be going by a stripping mechanism such as BD3 + BH3 - BH3 - BD3 - BH3 + BH3, since the deuterium-to-boron isotopic ratio then should be 3. Another possible mechanism of exchange is BD3 + B2H6 ⇌ B3D3H6; the B3 complex can be pictured as a symmetrical one. If the bonds were all exactly equivalent the D/ 10B ratio would statistically become 3; however, some isotope effect may be present in the fragmentation of the complex and the ratio could deviate from 3. Another possible way in which