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Sample records for suboxide cluster anions

  1. Insight into ethylene interactions with molybdenum suboxide cluster anions from photoelectron spectra of chemifragments

    Science.gov (United States)

    Schaugaard, Richard N.; Topolski, Josey E.; Ray, Manisha; Raghavachari, Krishnan; Jarrold, Caroline Chick

    2018-02-01

    Recent studies on reactions between MoxOy- cluster anions and H2O/C2H4 mixtures revealed a complex web of addition, hydrogen evolution, and chemifragmentation reactions, with chemifragments unambiguously connected to cluster reactions with C2H4. To gain insight into the molecular-scale interactions along the chemifragmentation pathways, the anion photoelectron (PE) spectra of MoC2H2-, MoC4H4-, MoOC2H2-, and MoO2C2H2- formed directly in MoxOy- + C2H4 (x > 1; y ≥ x) reactions, along with supporting CCSD(T) and density functional theory calculations, are presented and analyzed. The complexes have spectra that are all consistent with η2-acetylene complexes, though for all but MoC4H4-, the possibility that vinylidene complexes are also present cannot be definitively ruled out. Structures that are consistent with the PE spectrum of MoC2H2- differ from the lowest energy structure, suggesting that the fragment formation is under kinetic control. The PE spectrum of MoO2C2H2- additionally exhibits evidence that photodissociation to MoO2- + C2H2 may be occurring. The results suggest that oxidative dehydrogenation of ethylene is initiated by Lewis acid/base interactions between the Mo centers in larger clusters and the π orbitals in ethylene.

  2. The quantum structure of anionic hydrogen clusters

    Science.gov (United States)

    Calvo, F.; Yurtsever, E.

    2018-03-01

    A flexible and polarizable interatomic potential has been developed to model hydrogen clusters interacting with one hydrogen anion, (H2)nH-, in a broad range of sizes n = 1-54 and parametrized against coupled cluster quantum chemical calculations. Using path-integral molecular dynamics simulations at 1 K initiated from the putative classical global minima, the equilibrium structures are found to generally rely on icosahedral shells with the hydrogen molecules pointing toward the anion, producing geometric magic numbers at sizes n = 12, 32, and 44 that are in agreement with recent mass spectrometry measurements. The energetic stability of the clusters is also connected with the extent of vibrational delocalization, measured here by the fluctuations among inherent structures hidden in the vibrational wave function. As the clusters grow, the outer molecules become increasingly free to rotate, and strong finite size effects are also found between magic numbers, associated with more prominent vibrational delocalization. The effective icosahedral structure of the 44-molecule cluster is found to originate from quantum nuclear effects as well, the classical structure showing no particular symmetry.

  3. Structural evolution of small ruthenium cluster anions

    Energy Technology Data Exchange (ETDEWEB)

    Waldt, Eugen [Institut für Nanotechnologie, Karlsruher Institut für Technologie, Postfach 3640, 76021 Karlsruhe (Germany); Hehn, Anna-Sophia; Ahlrichs, Reinhart [Institute für Physikalische Chemie, Karlsruher Institut für Technologie, Kaiserstrasse 12, 76128 Karlsruhe (Germany); Kappes, Manfred M.; Schooss, Detlef, E-mail: detlef.schooss@kit.edu [Institut für Nanotechnologie, Karlsruher Institut für Technologie, Postfach 3640, 76021 Karlsruhe (Germany); Institute für Physikalische Chemie, Karlsruher Institut für Technologie, Kaiserstrasse 12, 76128 Karlsruhe (Germany)

    2015-01-14

    The structures of ruthenium cluster anions have been investigated using a combination of trapped ion electron diffraction and density functional theory computations in the size range from eight to twenty atoms. In this size range, three different structural motifs are found: Ru{sub 8}{sup −}–Ru{sub 12}{sup −} have simple cubic structures, Ru{sub 13}{sup −}–Ru{sub 16}{sup −} form double layered hexagonal structures, and larger clusters form close packed motifs. For Ru{sub 17}{sup −}, we find hexagonal close packed stacking, whereas octahedral structures occur for Ru{sub 18}{sup −}–Ru{sub 20}{sup −}. Our calculations also predict simple cubic structures for the smaller clusters Ru{sub 4}{sup −}–Ru{sub 7}{sup −}, which were not accessible to electron diffraction measurements.

  4. Percolation conductivity in hafnium sub-oxides

    Energy Technology Data Exchange (ETDEWEB)

    Islamov, D. R., E-mail: damir@isp.nsc.ru; Gritsenko, V. A., E-mail: grits@isp.nsc.ru [Rzhanov Institute of Semiconductor Physics, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090 (Russian Federation); Novosibirsk State University, Novosibirsk 630090 (Russian Federation); Cheng, C. H. [Department of Mechatronic Technology, National Taiwan Normal University, Taipei 106, Taiwan (China); Chin, A., E-mail: albert-achin@hotmail.com [National Chiao Tung University, Hsinchu 300, Taiwan (China)

    2014-12-29

    In this study, we demonstrated experimentally that formation of chains and islands of oxygen vacancies in hafnium sub-oxides (HfO{sub x}, x < 2) leads to percolation charge transport in such dielectrics. Basing on the model of Éfros-Shklovskii percolation theory, good quantitative agreement between the experimental and theoretical data of current-voltage characteristics was achieved. Based on the percolation theory suggested model shows that hafnium sub-oxides consist of mixtures of metallic Hf nanoscale clusters of 1–2 nm distributed onto non-stoichiometric HfO{sub x}. It was shown that reported approach might describe low resistance state current-voltage characteristics of resistive memory elements based on HfO{sub x}.

  5. Anion photoelectron spectroscopy of radicals and clusters

    Energy Technology Data Exchange (ETDEWEB)

    Travis, Taylor R. [Univ. of California, Berkeley, CA (United States)

    1999-12-01

    Anion photoelectron spectroscopy is used to study free radicals and clusters. The low-lying 2Σ and 2π states of C2nH (n = 1--4) have been studied. The anion photoelectron spectra yielded electron affinities, term values, and vibrational frequencies for these combustion and astrophysically relevant species. Photoelectron angular distributions allowed the author to correctly assign the electronic symmetry of the ground and first excited states and to assess the degree of vibronic coupling in C2H and C4H. Other radicals studied include NCN and I3. The author was able to observe the low-lying singlet and triplet states of NCN for the first time. Measurement of the electron affinity of I3 revealed that it has a bound ground state and attachment of an argon atom to this moiety enabled him to resolve the symmetric stretching progression.

  6. Activation of Molecular Oxygen by Anionic Gold Clusters

    NARCIS (Netherlands)

    Woodham, A. P.; Meijer, G.; Fielicke, A.

    2012-01-01

    A golden opportunity: Molecular oxygen is found to be converted into a superoxo (O2−) species upon complexation to gold-cluster anions containing an even number of Au atoms. Vibrational spectra (see scheme) reveal small variations in the extent of O[BOND]O bond activation dependent upon the electron

  7. Anionic clusters in dusty hydrocarbon and silane plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Hollenstein, C.; Schwarzenbach, W.; Howling, A.A.; Courteille, C.; Dorier, J.L.; Sansonnens, L. [Ecole Polytechnique Federale, Lausanne (Switzerland). Centre de Recherche en Physique des Plasma (CRPP)

    1995-10-01

    Measurements of anions and cations are reported for hydrocarbon and silane rf capacitive glow discharges. Series of anions were observed by quadrupole mass spectrometry using power-modulated plasmas and their structures are interpreted from the form of the mass spectra. Various experiments in silane plasmas show that anion confinement results in particles and conversely, anion de-trapping can inhibit particle formation. In contrast, the polymerized neutral flux magnitudes, mass spectra and dynamics are independent of the powder formation. Powder is known to form readily in deposition plasmas containing electronegative free radicals, and the general role of anions in particle formation is discussed in the light of these experiments. (author) 6 figs., 21 refs.

  8. The viability of aluminum Zintl anion moieties within magnesium-aluminum clusters

    Science.gov (United States)

    Wang, Haopeng; Jae Ko, Yeon; Zhang, Xinxing; Gantefoer, Gerd; Schnoeckel, Hansgeorg; Eichhorn, Bryan W.; Jena, Puru; Kiran, Boggavarapu; Kandalam, Anil K.; Bowen, Kit H.

    2014-03-01

    Through a synergetic combination of anion photoelectron spectroscopy and density functional theory based calculations, we have investigated the extent to which the aluminum moieties within selected magnesium-aluminum clusters are Zintl anions. Magnesium-aluminum cluster anions were generated in a pulsed arc discharge source. After mass selection, photoelectron spectra of MgmAln- (m, n = 1,6; 2,5; 2,12; and 3,11) were measured by a magnetic bottle, electron energy analyzer. Calculations on these four stoichiometries provided geometric structures and full charge analyses for the cluster anions and their neutral cluster counterparts, as well as photodetachment transition energies (stick spectra). Calculations revealed that, unlike the cases of recently reported sodium-aluminum clusters, the formation of aluminum Zintl anion moieties within magnesium-aluminum clusters was limited in most cases by weak charge transfer between the magnesium atoms and their aluminum cluster moieties. Only in cases of high magnesium content, e.g., in Mg3Al11 and Mg2Al12-, did the aluminum moieties exhibit Zintl anion-like characteristics.

  9. Anion-Templated Nanosized Silver Alkynyl Clusters: Cluster Engineering and Solution Behavior.

    Science.gov (United States)

    Zhang, Shan-Shan; Su, Hai-Feng; Wang, Zhi; Wang, Lina; Zhao, Quan-Qin; Tung, Chen-Ho; Sun, Di; Zheng, Lan-Sun

    2017-03-08

    Assembly of nanosized polynuclear metal clusters from simple building blocks usually involves complicated self-organization processes and thus is a long-standing challenge. Here, we demonstrate the controllable assembly, single-crystal structures and solution behaviors of four molecular assemblies based on nanosized silver alkynyl clusters, formulated as {[(CrO4 )2 Cl@Ag42 (PhC≡C)34 (CF3 COO)2 ]⋅CF3 COO} (1), {(NH4 )[(CrO4 )2 Cl@Ag42 (PhC≡C)34 (CrO4 )(H2 O)2 ]⋅2BF4 ⋅CH3 OH}n (2), [(CrO4 )@Ag22 (PhC≡C)16 (CF3 SO3 )4 ]n (3), and {[(CrO4 )2 @Ag31 (PhC≡C)22 (CF3 SO3 )4 ]⋅CF3 SO3 ⋅2CH3 OH⋅H2 O}n (4). In the presence of concomitant CrO42- and Cl- templates, we could isolate a discrete cluster 1 and a polymeric chain-like compound 2 by using different silver salts. Both 1 and 2 have a similar 42-metallic cage, which traps two CrO42- and one Cl- as anion templates. Using sole CrO42- template, 3 and 4 were simultaneously isolated in a one-pot reaction. Both of them are 1D chain structures based on single CrO42- templated Ag18 and double CrO42- templated Ag30 clusters, respectively. HR-ESI-MS was used to study the solution behaviors of 1-4. This work has the following purposes: i) it presents the cluster engineering concept used in the assembly of polynuclear silver alkynyl clusters; ii) it exemplifies template effects from hetero and homo anions; and iii) it provides a controllable way to achieve assembly of silver alkynyl clusters. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. The growth of ionic crystals based on the halogenation of copper cluster anions.

    Science.gov (United States)

    Luo, Zhixun; Smith, Jordan C; Woodward, W Hunter; Castleman, A W

    2012-03-08

    We investigated the halogenation reactivity of copper cluster anions produced via a magnetron-sputter source after introduction into a fast-flow tube reaction apparatus simultaneously with chlorine gas. Interesting cluster products corresponding to [Cu(n)Cl(n+1)](-) (n = 1-6) were observed with notable stability, and the mass distribution of these clusters exhibits an exponential decay with increasing values of n. Reaction kinetics analysis is provided on the gas-phase reactivity of copper cluster anions with chlorine. First-principle calculations suggest a series of cubic-like structures for these species similar to the structure of alkali halide clusters due to their similar electronic configurations. These structures act as a starting point in the formation of ionic crystals.

  11. Spermine Sepharose as a clustered-charge anion exchange adsorbent.

    Science.gov (United States)

    Dhamane, Sagar; Ruiz-Ruiz, Federico; Chen, Wen-hsiang; Kourentzi, Katerina; Benavides, Jorge; Rito-Palomares, Marco; Willson, Richard C

    2014-01-10

    We previously showed that the affinity and capacity of ion exchange adsorbents of a given total charge density are improved by immobilization of the charges in pre-ordered clusters, rather than individually in random locations. This previous work used pentalysinamide and pentaargininamide as clustered ligands. This approach allows close control of cluster size, but is uneconomically expensive for some research and most practical applications. In this work, we demonstrate that the inexpensive synthetic analog of the natural polyamine spermine (H2N-CH2-CH2-CH2-NH-CH2-CH2-CH2-CH2-NH-CH2-CH2-CH2-NH2) also can serve as the basis of effective clustered adsorbents. The calcium-depleted form of the protein α-lactalbumin, and RNA from baker's yeast, were adsorbed on a spermine Sepharose adsorbent. This adsorbent exhibited enhanced α-lactalbumin binding capacity (Qmax>1.6 and 1.3-fold higher than those for Qiagen DEAE and GE DEAE Sepharose adsorbents of much greater charge density) and higher initial binding affinity (Qmax/KD 2.4 and 2.1-fold higher, respectively). The new spermine-based matrix exhibited a higher value of the Z parameter, suggesting an increased number of apparent interaction sites between the protein and the resin, and functioned well in column mode. Copyright © 2013 Elsevier B.V. All rights reserved.

  12. Communication: Vibrational spectroscopy of atmospherically relevant acid cluster anions: Bisulfate versus nitrate core structures

    NARCIS (Netherlands)

    Yacovitch, T. I.; Heine, N.; Brieger, C.; Wende, T.; Hock, C.; Neumark, D. M.; Asmis, K. R.

    2012-01-01

    Infrared multiple photon dissociation spectra for the smallest atmospherically relevant anions of sulfuric and nitric acid allow us to characterize structures and distinguish between clusters with a bisulfate or a nitrate core. We find that bisulfate is the main charge carrier for HSO4−·H2SO4·HNO3

  13. Study of radicals, clusters and transition state species by anion photoelectron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Arnold, Don Wesley [Univ. of California, Berkeley, CA (United States)

    1994-08-01

    Free radicals, elemental and van der Waals clusters and transition state species for bimolecular chemical reactions are investigated using anion photoelectron spectroscopy. Several low-lying electronic states of ozone have been identified via photoelectron spectroscopy of O3-. A characterization of these states is important to models for atmospheric ozone reaction kinetics. The fluoroformyloxyl radical, FCO2, has been investigated, providing vibrational frequencies and energies for two electronic states. The technique has also been employed to make the first direct observation and characterization of the NNO2 molecule. Several electronic states are observed for this species which is believed to play a role as a reactive intermediate in the N + NO2 reaction. The experimental results for all three of these radicals are supplemented by ab initio investigations of their molecular properties. The clusters investigations include studies of elemental carbon clusters (C2- - C11-), and van der Waals clusters (X-(CO2)n, X = I, Br, Cl; n {le} 13 and I- (N2O)n=1--11). Primarily linear clusters are observed for the smaller carbon clusters, while the spectra of the larger clusters contain contribution from cyclic anion photodetachment. Very interesting ion-solvent interactions are observed in the X-(CO2)n clusters. The transition state regions for several bimolecular chemical reactions have also been investigated by photodetachment of a negative ion precursor possessing a geometry similar to that of the transition state species. These spectra show features which are assigned to motions of the unstable neutral complex existing between reactants and products.

  14. Observations on small anionic clusters in an electrostatic ion beam trap

    Energy Technology Data Exchange (ETDEWEB)

    Eritt, Markus

    2008-10-02

    The term atomic cluster relates to compounds of at least two or three atoms. Thereby the physical properties are size dependent and the property transitions between single atoms and bulk material are not always smooth. Ion traps allow it to observe internal cluster properties independent from the influence of external forces. In this work the electron induced decay of singly negatively charged atomic clusters was observed. The dissociation cross section of the clusters is dominated by detachment of the only weakly bound outer electrons. For simple atoms at low electron energies a simple scaling law can be obtained that includes only the binding energies of the valence electrons. Nevertheless for larger sizes theoretical calculations predict so called ''giant resonances'' as dominant decay process in metal clusters. Due to mass limitations in storage rings exist so far only cross section measurements for simple anions and small negative molecules. In this work the electron detachment cross sections of small negatively charged carbon (C{sub n}{sup -} n=2-12), aluminium (Al{sub n}{sup -} n=2-7) and silver clusters (Ag{sub n}{sup -} n=1-11) were measured in an electrostatic ion beam trap. The classical scaling law, including only the binding energies of the valence electrons, turned out to be not sufficient, especially for larger clusters. In order to improve the correlation between measured and predicted values it was proposed to involve the influence of the cluster volume and the specific polarisability induced by long range coulomb interaction. For silver clusters the best agreement was obtained using a combination of the projected area reduced by the polarisability. The existence of ''giant resonances'' could not be confirmed. According to theory for clusters with a broad internal energy distribution, a power-law decay close to 1/time is expected. For some clusters the lifetime behaviour would be strongly quenched by photon

  15. Kinetic energy spectra in thermionic emission from small tungsten cluster anions: evidence for nonclassical electron capture.

    Science.gov (United States)

    Concina, Bruno; Baguenard, Bruno; Calvo, Florent; Bordas, Christian

    2010-03-14

    The delayed electron emission from small mass-selected anionic tungsten clusters W(n)(-) has been studied for sizes in the range 9 < or = n < or = 21. Kinetic energy spectra have been measured for delays of about 100 ns after laser excitation by a velocity-map imaging spectrometer. They are analyzed in the framework of microreversible statistical theories. The low-energy behavior shows some significant deviations with respect to the classical Langevin capture model, which we interpret as possibly due to the influence of quantum dynamical effects such as tunneling through the centrifugal barrier, rather than shape effects. The cluster temperature has been extracted from both the experimental kinetic energy spectrum and the absolute decay rate. Discrepancies between the two approaches suggest that the sticking probability can be as low as a few percent for the smallest clusters.

  16. Cluster structure of imidazolium salts in methanol controlled by the balance of interactions: cation-anion, cation-solvent, and anion-solvent.

    Science.gov (United States)

    Kitaoka, Satoshi; Nobuoka, Kaoru; Ishikawa, Yuichi; Wakisaka, Akihiro

    2008-10-01

    We have studied the cluster structure of 1-butyl-3-methylimidazolium halide, bmimX (X = Cl, Br, I), in methanol solution by means of an electrospray mass spectrometer, which is specially designed for analysis of clusters isolated from solution. In positive ion mode experiments, the ratio of solvated bmim(+), bmim(+)(MeOH)(n) and ion-pair clusters, bmim(bmim(+)X(-))(m) was dependent on the counter anion. As for bmimCl solutions, few solvated bmim(+) clusters were observed, and the ion-pair clusters were clearly observed. On the other hand, bmimBr and bmimI with large anions, the solvated bmim(+) clusters increased obviously, and the ion-pair clusters were in turn remarkably decreased. In negative ion-mode experiments, the solvation for Br(-) by the methanol is found to be the most prominent among those for Cl(-), Br(-), and I(-). These results were reasonably explained in consideration of the balance between ion-solvent and ion-counterion interactions.

  17. C-H bond activation by aluminum oxide cluster anions, an experimental and theoretical study.

    Science.gov (United States)

    Tian, Li-Hua; Ma, Tong-Mei; Li, Xiao-Na; He, Sheng-Gui

    2013-08-21

    Aluminum oxide cluster anions are produced by laser ablation and reacted with n-butane in a fast flow reactor. A reflectron time-of-flight mass spectrometer is used to detect the cluster distribution before and after the reactions. Aluminum oxide clusters Al₂O4,6⁻ and Al₃O₇⁻ can react with n-C₄H₁₀ to produce Al₂O4,6H⁻ and Al₃O₇⁻, respectively, while cluster Al₃O₆⁻ reacts with n-C₄H₁₀ to produce both the Al₃O₆H⁻ and Al₃O₆H₂⁻. The theoretical calculations are performed to study the structures and bonding properties of clusters Al₂O4,6⁻ and Al₃O6,7⁻ as well as the reaction mechanism of Al₂O₄⁻ + n-C₄H₁₀. The calculated results show that the mononuclear oxygen-centred radicals (O⁻˙) on Al₂O4,6⁻ and Al₃O₇⁻, and oxygen-centred biradical on Al₃O₆⁻ are the active sites responsible for the observed hydrogen atom abstraction reactivity. Furthermore, mechanism investigation of the O⁻˙ generation in Al₃O₇⁻ upon O₂ molecule adsorption on un-reactive Al₃O₅⁻ is performed by theoretical calculations.

  18. Cluster-Continuum Calculations of Hydration Free Energies of Anions and Group 12 Divalent Cations

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Hao-Bo [ORNL; Liang, Liyuan [ORNL; Parks, Jerry M [ORNL; Smith, Jeremy C [ORNL; Riccardi, Demian M [ORNL; Gu, Baohua [ORNL

    2013-01-01

    Understanding aqueous phase processes involving group 12 metal cations is relevant to both environmental and biological sciences. Here, quantum chemical methods and polarizable continuum models are used to compute the hydration free energies of a series of divalent group 12 metal cations (Zn2+, Cd2+, and Hg2+) together with Cu2+ and the anions OH , SH , Cl , and F . A cluster-continuum method is employed, in which gas-phase clusters of the ion and explicit solvent molecules are immersed in a dielectric continuum. Two approaches to define the size of the solute-water cluster are compared, in which the number of explicit waters used is either held constant or determined variationally as that of the most favorable hydration free energy. Results obtained with various polarizable continuum models are also presented. Each leg of the relevant thermodynamic cycle is analyzed in detail to determine how different contributions yield the observed mean signed error (MSE) and the standard deviation of the error (STDEV) between theory and experiment. The use of a constant number of water molecules for each set of ions is found to lead to predicted relative trends that benefit from error cancellation. Overall, the best results are obtained with MP2 and the Solvent Model D polarizable continuum model (SMD), with eight explicit water molecules for anions and ten for the metal cations, yielding a STDEV of 2.3 kcal/mol and MSE of 0.9 kcal/mol between theoretical to experimental hydration free energies, which range from -72.4 kcal/mol for SH to -505.9 kcal/mol for Cu2+. Using B3PW91 with DFT-D3 dispersion corrections (B3PW91-D) and SMD yields a STDEV of 3.3 kcal mol 1 and MSE of 1.6 kcal/mol, to which adding MP2 corrections from smaller divalent metal ion water molecule clusters yields very good agreement with the full MP2 results. Using B3PW91-D and SMD, with two explicit water molecules for anions and six for divalent metal cations also yields reasonable agreement with experiment

  19. Comparison of adsorption probabilities of O2 and CO on copper cluster cations and anions.

    Science.gov (United States)

    Hirabayashi, Shinichi; Ichihashi, Masahiko; Kawazoe, Yoshiyuki; Kondow, Tamotsu

    2012-09-06

    Reactions of size-selected copper cluster cations and anions, Cu(n)(±), with O(2) and CO have been systematically investigated under single collision conditions by using a tandem-mass spectrometer. In the reactions of Cu(n)(±) (n = 3-25) with O(2), oxidation of the cluster is prominently observed with and without releasing Cu atoms at the collision energy of 0.2 eV. The reactivity of Cu(n)(+) is governed to some extent by the electronic shell structure; the relatively small reaction cross sections observed at n = 9 and 21 correspond to the electronic shell closings, and those at odd sizes in n ≤ 16 match with the clusters having no unpaired electron. On the other hand, the reactivity of Cu(n)(-) exhibits no remarkable decrease by the electronic shell closings and the even-numbered electrons. These behaviors may be due to an influence of the electron detachment of the reaction intermediate, Cu(n)O(2)(-). Both the cations and anions show the dominant formation of Cu(n-1)O(2)(±) in n ≤ 16 and Cu(n)O(2)(±) in n ≥ 17 in the experimental time window. By contrast, Cu(n)(-) (n = 3-11) do not react with CO at the collision energy of 0.2 eV, while Cu(n)(+) (n = 3-19) adsorb CO though the cross sections are relatively small. The difference in the reactivity between the charge states can be understood in terms of the frontier orbitals of the Cu cluster and O(2) or CO.

  20. Pb 4f photoelectron spectroscopy on mass-selected anionic lead clusters at FLASH

    Science.gov (United States)

    Bahn, J.; Oelßner, P.; Köther, M.; Braun, C.; Senz, V.; Palutke, S.; Martins, M.; Rühl, E.; Ganteför, G.; Möller, T.; von Issendorff, B.; Bauer, D.; Tiggesbäumker, J.; Meiwes-Broer, K.-H.

    2012-07-01

    4f core level photoelectron spectroscopy has been performed on negatively charged lead clusters, in the size range of 10-90 atoms. We deploy 4.7 nm radiation from the free-electron laser FLASH, yielding sufficiently high photon flux to investigate mass-selected systems in a beam. A new photoelectron detection system based on a hemispherical spectrometer and a time-resolving delayline detector makes it possible to assign electron signals to each micro-pulse of FLASH. The resulting 4f binding energies show good agreement with the metallic sphere model, giving evidence for a fast screening of the 4f core holes. By comparing the present work with previous 5d and valence region data, the paper presents a comprehensive overview of the energetics of lead clusters, from atoms to bulk. Special care is taken to discuss the differences of the valence- and core-level anion cluster photoionizations. Whereas in the valence case the escaping photoelectron interacts with a neutral system near its ground state, core-level ionization leads to transiently highly excited neutral clusters. Thus, the photoelectron signal might carry information on the relaxation dynamics.

  1. Effect of Carbon Doping on the Electronic Structure and Elastic Properties of Boron Suboxide

    Science.gov (United States)

    2015-06-01

    of Boron Suboxide by Amol B Rahane, Jennifer S Dunn, and Vijay Kumar Approved for public release; distribution unlimited...Laboratory Effect of Carbon Doping on the Electronic Structure and Elastic Properties of Boron Suboxide by Amol B Rahane and Vijay Kumar Dr...SUBTITLE Effect of Carbon Doping on the Electronic Structure and Elastic Properties of Boron Suboxide 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c

  2. anion dependence

    Indian Academy of Sciences (India)

    SUMAN Das

    the lifetime distributions show a pronounced anion dependence and suggest cluster stability time up to a few nanoseconds. Keywords. Amide deep eutectics; simulations; cluster size and lifetime distributions; anion dependence. 1. Introduction ... industrial applications.11–15 In chemical industry, they are used as ...

  3. The arsenic clusters Asn (n = 1-5) and their anions: structures, thermochemistry, and electron affinities.

    Science.gov (United States)

    Zhao, Yi; Xu, Wenguo; Li, Qianshu; Xie, Yaoming; Schaefer, Henry F

    2004-05-01

    The molecular structures, electron affinities, and dissociation energies of the As(n)/As(-) (n) (n = 1-5) species have been examined using six density functional theory (DFT) methods. The basis set used in this work is of double-zeta plus polarization quality with additional diffuse s- and p-type functions, denoted DZP++. These methods have been carefully calibrated (Chem Rev 2002, 102, 231) for the prediction of electron affinities. The geometries are fully optimized with each DFT method independently. Three different types of the neutral-anion energy separations reported in this work are the adiabatic electron affinity (EA(ad)), the vertical electron affinity (EA(vert)), and the vertical detachment energy (VDE). The first dissociation energies D(e)(As(n-1)-As) for the neutral As(n) species, as well as those D(e)(As(-) (n-1)-As) and D(e) (As(n-1)-As(-)) for the anionic As(-) (n) species, have also been reported. The most reliable adiabatic electron affinities, obtained at the DZP++ BLYP level of theory, are 0.90 (As), 0.74 (As(2)), 1.30 (As(3)), 0.49 (As(4)), and 3.03 eV (As(5)), respectively. These EA(ad) values for As, As(2), and As(4) are in good agreement with experiment (average absolute error 0.09 eV), but that for As(3) is a bit smaller than the experimental value (1.45 +/- 0.03 eV). The first dissociation energies for the neutral arsenic clusters predicted by the B3LYP method are 3.93 eV (As(2)), 2.04 eV (As(3)), 3.88 eV (As(4)), and 1.49 eV (As(5)). Compared with the available experimental dissociation energies for the neutral clusters, the theoretical predictions are excellent. Two dissociation limits are possible for the arsenic cluster anions. The atomic arsenic results are 3.91 eV (As(-) (2) --> As(-) + As), 2.46 eV (As(-) (3) --> As(-) (2) + As), 3.14 eV (As(-) (4) --> As(-) (3) + As), and 4.01 eV (As(-) (5) --> As(-) (4) + As). For dissociation to neutral arsenic clusters, the predicted dissociation energies are 2.43 eV (As(-) (3) --> As(2) + As

  4. 2D-3D Transition for Cationic and Anionic Gold Clusters: A Kinetic Energy Density Functional Study

    DEFF Research Database (Denmark)

    Ferrighi, Lara; Hammer, Bjørk; Madsen, Georg

    2009-01-01

    We present a density functional theory study of the energetics of isolated Aun+ (n = 5-10) and Aun- (n = 8-13) gold clusters. We compare our results to both theoretical and experimental values from the literature and find the use of meta-generalized gradient approximation (MGGA) functionals......, in particular the M06-L functional, to be of importance in order to match experiment. The M06-L values suggest crossovers between 2D and 3D structures at n = 8 and 12 for cationic and anionic clusters, respectively. We suggest that the MGGA's stronger tendency toward 3D structures arises from their smaller...

  5. Cobalt bis(dicarbollides)(1-) covalently attached to the calyx[4]arene platform: the first combination of organic bowl-shaped matrices and inorganic metallaborane cluster anions

    NARCIS (Netherlands)

    Grüner, Bohumír; Mikulasek, Libor; Baca, Jirí; Cisarova, Ivana; Böhmer, Volker; Danila, Crenguta; Reinoso garcia, M.M.; Verboom, Willem; Reinhoudt, David; Casnati, Alessandro; Ungaro, Rocco

    2005-01-01

    Various calix[4]arene and resorc[4]arene ionic compounds substituted by cobalt bis(dicarbollide) anions (1) have been prepared for the first time. From tBu-calix[4]arene (A) the complete series of mono-, di-, tri- and tetrasubstituted derivatives bearing one to four cluster anions on the lower rim

  6. Plasmonic properties of gold nanoparticles covered by silicon suboxide thin film

    Science.gov (United States)

    Baranov, Evgeniy; Zamchiy, Alexandr; Safonov, Aleksey; Starinskiy, Sergey; Khmel, Sergey

    2017-10-01

    The optical properties of nanocomposite material consisting of gold nanoparticles without/with silicon suboxide thin film were obtained. The gold film was deposited by thermal vacuum evaporation and then it was annealed in a vacuum chamber to form gold nanoparticles. The silicon suboxide thin films were deposited by the gas-jet electron beam plasma chemical vapor deposition method. The intensity of the localized surface plasmon resonance increased and the plasmon maximum peak shifted from 520 nm to 537 nm.

  7. Theoretical characterization of four distinct isomer types in hydrated-electron clusters, and proposed assignments for photoelectron spectra of water cluster anions.

    Science.gov (United States)

    Jacobson, Leif D; Herbert, John M

    2011-12-14

    Water cluster anions, (H(2)O)(N)(-), are examined using mixed quantum/classical molecular dynamics based on a one-electron pseudopotential model that incorporates many-body polarization and predicts vertical electron detachment energies (VDEs) with an accuracy of ~0.1 eV. By varying the initial conditions under which the clusters are formed, we are able to identify four distinct isomer types that exhibit different size-dependent VDEs. On the basis of a strong correlation between the electron's radius of gyration and its optical absorption maximum, and extrapolating to the bulk limit (N → ∞), our analysis supports the assignment of the "isomer Ib" data series, observed in photoelectron spectra of very cold clusters, as arising from cavity-bound (H(2)O)(N)(-) cluster isomers. The "isomer I" data reported in warmer experiments are assigned to surface-bound isomers in smaller clusters, transitioning to partially embedded isomers in larger clusters. The partially embedded isomers are characterized by a partially formed solvent cavity at the cluster surface, and they are spectroscopically quite similar to internalized cavity isomers. These assignments are consistent with various experimental data, and our theoretical characterization of these isomers sheds new light on a long-standing assignment problem. © 2011 American Chemical Society

  8. Photoelectron angular distributions for states of any mixed character: An experiment-friendly model for atomic, molecular, and cluster anions

    Energy Technology Data Exchange (ETDEWEB)

    Khuseynov, Dmitry; Blackstone, Christopher C.; Culberson, Lori M.; Sanov, Andrei, E-mail: sanov@u.arizona.edu [Department of Chemistry and Biochemistry, University of Arizona, Tucson, Arizona 85721 (United States)

    2014-09-28

    We present a model for laboratory-frame photoelectron angular distributions in direct photodetachment from (in principle) any molecular orbital using linearly polarized light. A transparent mathematical approach is used to generalize the Cooper-Zare central-potential model to anionic states of any mixed character. In the limit of atomic-anion photodetachment, the model reproduces the Cooper-Zare formula. In the case of an initial orbital described as a superposition of s and p-type functions, the model yields the previously obtained s-p mixing formula. The formalism is further advanced using the Hanstorp approximation, whereas the relative scaling of the partial-wave cross-sections is assumed to follow the Wigner threshold law. The resulting model describes the energy dependence of photoelectron anisotropy for any atomic, molecular, or cluster anions, usually without requiring a direct calculation of the transition dipole matrix elements. As a benchmark case, we apply the p-d variant of the model to the experimental results for NO{sup −} photodetachment and show that the observed anisotropy trend is described well using physically meaningful values of the model parameters. Overall, the presented formalism delivers insight into the photodetachment process and affords a new quantitative strategy for analyzing the photoelectron angular distributions and characterizing mixed-character molecular orbitals using photoelectron imaging spectroscopy of negative ions.

  9. Reaction mechanisms of CO oxidation on cationic, neutral, and anionic X-O-Cu (X = Au, Ag) clusters

    Science.gov (United States)

    Zhang, Yan; He, Xiao

    2017-10-01

    We performed extensive DFT calculations for the microscopic mechanism of CO oxidation on cationic, neutral and anionic X-O-Cu (X = Au, Ag) clusters. We obtained following findings. First, the reaction mechanism of neutral X-O-Cu (X = Au, Ag) to the CO follows the Eley-Rideal-like (ER) mechanism and Langmuir-Hinshelwood-like (LH) mechanism. Second, as compared to the pure Au clusters, new reaction pathways have been found via a Langmuir-Hinshelwood-like (LH) mechanism. The oxidation of CO on cationic Au-O-Cu in nature follows an Eley-Rideal-like (ER) mechanism. Third, comparing with their reaction profiles between cationic, neutral and anionic Au-O-Cu and CO, all the reactions on Ag-O-Cu can occur more easily. Furthermore, the selectivity of the oxidation of CO on Ag-O-Cu will be improved. On the basis of our calculations, we suggest that AgCu may also be a good catalyst due to its high oxidation performance.

  10. Thermochemistry and electronic structure of small boron clusters (B(n), n = 5-13) and their anions.

    Science.gov (United States)

    Truong, Ba Tai; Grant, Daniel J; Nguyen, Minh Tho; Dixon, David A

    2010-01-21

    Thermochemical parameters of a set of small-sized neutral (B(n)) and anionic (B(n)(-)) boron clusters, with n = 5-13, were determined using coupled-cluster theory CCSD(T) calculations with the aug-cc-pVnZ (n = D, T, and Q) basis sets extrapolated to the complete basis set limit (CBS) plus addition corrections and/or G3B3 calculations. Enthalpies of formation, adiabatic electron affinities (EA), vertical (VDE), and adiabatic (ADE) detachment energies were evaluated. Our calculated EAs are in good agreement with recent experiments (values in eV): B(5) (CBS, 2.29; G3B3, 2.48; exptl., 2.33 +/- 0.02), B(6) (CBS, 2.59; G3B3, 3.23; exptl., 3.01 +/- 0.04), B(7) (CBS, 2.62; G3B3, 2.67; exptl., 2.55 +/- 0.05), B(8) (CBS, 3.02; G3B3, 3.11; exptl., 3.02 +/- 0.02), B(9) (G3B3, 3.03; exptl., 3.39 +/- 0.06), B(10) (G3B3, 2.85; exptl., 2.88 +/- 0.09), B(11) (G3B4, 3.48;, exptl., 3.43 +/- 0.01), B(12) (G3B3, 2.33; exptl., 2.21 +/- 0.04), and B(13) (G3B3, 3.62; exptl., 3.78 +/- 0.02). The difference between the calculated adiabatic electron affinity and the adiabatic detachment energy for B(6) is due to the fact that the geometry of the anion is not that of the ground-state neutral. The calculated adiabatic detachment energies to the (3)A(u), C(2h) and (1)A(g), D(2h) excited states of B(6), which have geometries similar to the (1)A(g), D(2h) state of B(6)(-), are 2.93 and 3.06 eV, in excellent agreement with experiment. The VDEs were also well reproduced by the calculations. Partitioning of the electron localization functions into pi and sigma components allows probing of the partial and local delocalization in global nonaromatic systems. The larger clusters appear to exhibit multiple aromaticity. The binding energies per atom vary in a parallel manner for both neutral and anionic series and approach the experimental value for the heat of atomization of B. The resonance energies and the normalized resonance energies are convenient indices to quantify the stabilization of a cluster

  11. Theoretical study of the electronic states of Nb4, Nb5 clusters and their anions (Nb4?, Nb5?)

    Energy Technology Data Exchange (ETDEWEB)

    Balasubramanian, K; Majumdar, D

    2004-05-06

    Geometries and energy separations of the various low-lying electronic states of Nb{sub n} and Nb{sub n}{sup -} (n = 4, 5) clusters with various structural arrangements have been investigated. The complete active space multi-configuration self-consistent field (CASMCSCF) method followed by multi-reference singles and doubles configuration interaction (MRSDCI) calculations that included up to 52 million configuration spin functions have been used to compute several electronic states of these clusters. The ground states of both Nb{sub 4} ({sup 1}A', pyramidal) and Nb{sub 4}{sup -} ({sup 2}B{sub 3g}, rhombus) are low-spin states at the MRSDCI level. The ground state of Nb{sub 5} cluster is a doublet with a distorted trigonal bipyramid (DTB) structure. The anionic cluster of Nb{sub 5} has two competitive ground states with singlet and triplet multiplicities (DTB). The low-lying electronic states of these clusters have been found to be distorted due to Jahn-Teller effect. On the basis of the energy separations of our computed electronic states of Nb{sub 4} and Nb{sub 5}, we have assigned the observed photoelectron spectrum of Nb{sub n}{sup -}(n = 4, 5) clusters. We have also compared our MRSDCI results with density functional calculations. The electron affinity, ionization potential, dissociation and atomization energies of Nb{sub 4} and Nb{sub 5} have been calculated and the results have been found to be in excellent agreement with the experiment.

  12. Anomalous Behavior Observed upon Annealing and Photodetachment of Anionic Copper Carbonyl Clusters in Argon Matrices

    Science.gov (United States)

    Ludwig, Ryan M.; Moore, David T.

    2014-06-01

    Using matrix isolation FTIR, we have observed the formation of anionic copper carbonyl complexes [Cu(CO)n]- (n=1-3) following co-deposition of Cu- and counter-cations (Ar+ or Kr+) into argon matrices doped with CO. When the deposition is carried out at 20 K, weak bands corresponding to the neutral copper carbonyl complexes Cu(CO)n (n=1-3) are also observed, and these grow in steadily as the matrix is annealed up to 30 K. This is in contrast to what is observed at 10 K (c.f. ISMS 2014 abstract #P631), where no appreciable neutral bands are observed, and indicates that some neutralization occurs during the formation of the complexes in the 20 K matrix. In addition, sharp peaks not previously observed grow in around the anionic bands upon annealing to 30 K; this is somewhat odd, since annealing typically simplifies the spectra of matrix samples as kinetically trapped metastable species relax to more stable forms. In this case, higher-resolution (0.125 wn) spectra reveal considerable new fine structure, with 5 and 20 peaks appearing in the regions of the mono- and tricarbonyl anions, respectively, each of which nominally has but a single IR-active CO-stretching mode. These new features are tentatively assigned (at least in part) to electric-field-induced splitting arising from long-range interactions with cationic species in the matrix. A second anomalous feature of these spectra is that, upon photodetachment, several new bands are observed in the region of the neutral copper carbonyl species. Upon annealing these bands then disappear, with concomitant growth of the expected neutral bands. This behavior raises the exciting possibility that these transient bands represent metastable "vertical detachment products", where the neutral species has been kinetically trapped by the matrix in the geometry of the anion. Evidence supporting this interpretation will be presented. Funding support from NSF CAREER Award CHE-0955637 is gratefully acknowledged Ryan M. Ludwig and David

  13. Probing the magic numbers of aluminum-magnesium cluster anions and their reactivity toward oxygen.

    Science.gov (United States)

    Luo, Zhixun; Grover, Cameron J; Reber, Arthur C; Khanna, Shiv N; Castleman, A W

    2013-03-20

    We report a joint experimental and theoretical investigation into the geometry, stability, and reactivity with oxygen of alloy metal clusters Al(n)Mg(m)(-) (4 ≤ n+m ≤ 15; 0 ≤ m ≤ 3). Considering that Al and Mg possess three and two valence electrons, respectively, clusters with all possible valence electron counts from 11 to 46 are studied to probe the magic numbers predicted by the spherical jellium model, and to determine whether enhanced stability and reduced reactivity may be found for some Al(n)Mg(m)(-) at non-magic numbers. Al5Mg2(-) and Al11Mg3(-) exhibit enhanced stability corresponding to the expected magic numbers of 20 and 40 electrons, respectively; while Al7Mg3(-), Al11Mg(-), and Al11Mg2(-) turn out to be unexpectedly stable at electron counts of 28, 36, and 38, respectively. The enhanced stability at non-magic numbers is explained through a crystal-field-like splitting of degenerate shells by the geometrical distortions of the clusters. Al(n)Mg(m)(-) clusters appear to display higher oxidation than pure Al(n)(-) clusters, suggesting that the addition of Mg atoms enhances the combustion of pure aluminum clusters.

  14. Ab initio studies of O-2(-) (H2O)(n) and O-3(-) (H2O)(n) anionic molecular clusters, n

    DEFF Research Database (Denmark)

    Bork, Nicolai Christian; Kurten, T.; Enghoff, Martin Andreas Bødker

    2011-01-01

    An ab initio study of gaseous clusters of O-2(-) and O-3(-) with water is presented. Based on thorough scans of configurational space, we determine the thermodynamics of cluster growth. The results are in good agreement with benchmark computational methods and existing experimental data. We find...... that anionic O-2(-)(H2O)n and O-3(-)(H2O)n clusters are thermally stabilized at typical atmospheric conditions for at least n = 5. The first 4 water molecules are strongly bound to the anion due to delocalization of the excess charge while stabilization of more than 4 H2O is due to normal hydrogen bonding...... finally, the thermodynamics of a few relevant cluster reactions are considered....

  15. Chiral separability of hydrophobic boron cluster anions with native cyclodextrins in water-methanol background electrolytes

    Czech Academy of Sciences Publication Activity Database

    Horáková, Hana; Vespalec, Radim

    2007-01-01

    Roč. 28, č. 20 (2007), s. 3639-3649 ISSN 0173-0835 R&D Projects: GA AV ČR IAA400310613 Institutional research plan: CEZ:AV0Z40310501 Keywords : boron cluster compound * capillary electrophoresis * chiral separation Subject RIV: CB - Analytical Chemistry, Separation Impact factor: 3.609, year: 2007

  16. Ab initio studies of O2-(H2O)n and O3-(H2O)n anionic molecular clusters, n≤12

    DEFF Research Database (Denmark)

    Bork, Nicolai Christian; Kurtén, T.; Enghoff, Martin Andreas Bødker

    2011-01-01

    An ab initio study of gaseous clusters of O2− and O2− with water is presented. Based on thorough scans of configurational space, we determine the thermodynamics of cluster growth. The results are in good agreement with benchmark computational methods and existing experimental data. We find...... that anionic O2−(H2O)n and O3−(H2O)n clusters are thermally stabilized at typical atmospheric conditions for at least n = 5. The first 4 water molecules are strongly bound to the anion due to delocalization of the excess charge while stabilization of more than 4 H2O is due to normal hydrogen bonding. Although...... clustering up to 12 H2O, we find that the O2 and O3 anions retain at least ca. 80 % of the charge and are located at the surface of the cluster. The O2− and O3− speicies are thus accessible for further reactions. Finally, the thermodynamics of a few relevant cluster reactions are considered....

  17. Experimental and theoretical study of hydrogen atom abstraction from n-butane by lanthanum oxide cluster anions.

    Science.gov (United States)

    Xu, Bo; Zhao, Yan-Xia; Li, Xiao-Na; Ding, Xun-Lei; He, Sheng-Gui

    2011-09-22

    Lanthanum oxide cluster anions are prepared by laser ablation and reacted with n-C(4)H(10) in a fast flow reactor. A time-of-flight mass spectrometer is used to detect the cluster distribution before and after the reactions. (La(2)O(3))(m=1-3)OH(-) and La(3)O(7)H(-) are observed as products, which suggests the occurrence of hydrogen atom abstraction reactions: (La(2)O(3))(m=1-3)O(-) + n-C(4)H(10) → (La(2)O(3))(m=1-3)OH(-) + C(4)H(9) and La(3)O(7)(-) + n-C(4)H(10) → La(3)O(7)H(-) + C(4)H(9). Density functional theory (DFT) calculations are performed to study the structures and bonding properties of La(2)O(4)(-), La(3)O(7)(-), and La(4)O(7)(-) clusters. The calculated results show that each of La(2)O(4)(-) and La(4)O(7)(-) contains one oxygen-centered radical (O(-•)) which is responsible for the high reactivity toward n-C(4)H(10). La(3)O(7)(-) contains one oxygen-centered radical (O(-•)) and one superoxide unit (O(2)(-•)), and the O(-•) is responsible for its high reactivity toward n-C(4)H(10). The O(-•) and O(2)(-•) can be considered to be generated by the adsorption of an O(2) molecule onto the singlet La(3)O(5)(-) with electron transfer from a terminally bonded oxygen ion (O(2-)) to the O(2). This may help us understand the mechanism of the formation of O(-•) and O(2)(-•) radicals in lanthanum oxide systems. The reaction mechanisms of La(2)O(4)(-) + n-C(4)H(10) and La(3)O(7)(-) + n-C(4)H(10) are also studied by the DFT calculations, and the calculated results are in good agreement with the experimental observations. © 2011 American Chemical Society

  18. Octanuclear copper(I) clusters inscribed in a Se(12) icosahedron: anion-induced modulation of the core size and symmetry.

    Science.gov (United States)

    Liu, C W; Sarkar, Bijay; Huang, Yao-Jheng; Liao, Ping-Kuei; Wang, Ju-Chun; Saillard, Jean-Yves; Kahlal, Samia

    2009-08-12

    Synthesis and structural characterization of an octanuclear Cu(I) cluster [Cu(8){Se(2)P(O(i)Pr)(2)}(6)](PF(6))(2) (1) with an empty Cu(8) cubic core involving diisopropyl diselenophosphate (dsep) ligand has been demonstrated despite its high tendency to abstract anions even from the traces of impurities in the solvent. Reaction of 1 with anion sources (Bu(4)NF for F(-); NaBH(4) for H(-), and NaSH for S(2-)) in a 1:1 ratio produced anion-centered Cu(8) clusters with a formula [Cu(8)(X){Se(2)P(O(i)Pr)(2)}(6)](PF(6)) (X = F, 2a; H, 3a; D, 3a') and [Cu(8)(S){Se(2)P(O(i)Pr)(2)}(6)] (4) in high yields. In addition, fluoride- and hydride-centered Cu(8)(I) clusters [Cu(8)(X){Se(2)P(OEt)(2)}(6)](PF(6)) (X = F, 2b; H, 3b) could be generated in approximately 80% yield by direct reaction of [Cu(CH(3)CN)(4)](PF(6)), NH(4)Se(2)P(OEt)(2), and the anion sources (Bu(4)NF for F(-); NaBH(4) for H(-)) in 8:6:1 ratio. Whereas the structural elucidation of complexes 2 and 4 revealed an anion-centered cubic Cu(8) core surrounded by six dsep ligands, it was a tetracapped tetrahedral copper framework with a hydride in the center in compounds 3. All Cu...Cu distances along either the edge of the cube in 2 and 4 or the tetracapped tetrahedron in 3 are shorter than those identified in 1. Although the cubic (or spherical) contraction of the copper framework that was identified in a series of closed-shell anion-centered (except a hydride) Cu(8) cube having T(h) symmetry could be explained by the existence of strong anion-cation attractions, it was definitely a surprise that the hydride, which is the smallest closed-shell anion and spherical too, induced a tetrahedral contraction of four out of the eight Cu atoms in the empty cube 1, resulting in a tetracapped-tetrahedral geometry and reducing the symmetry to T from T(h). Furthermore the fact that the encapsulated anion induced modulation of the copper core size and symmetry was fully reproduced by DFT calculations on model compounds. To the

  19. Hydrogen bonded anion ribbons, networks and clusters and sulfur-anion interactions in novel radical cation salts of BEDT-TTF with sulfamate, pentaborate and bromide.

    Science.gov (United States)

    Brooks, Andrew C; Martin, Lee; Day, Peter; Lopes, Elsa B; Almeida, Manuel; Kikuchi, Koichi; Fujita, Wataru; Sasamori, Kota; Aktusu, Hiroki; Wallis, John D

    2013-05-14

    The novel radical cation salt (BEDT-TTF)3(sulfamate)2·2H2O (BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene) is semiconducting with donor stacks comprised of pairs of partially oxidized molecules and a single more highly oxidized molecule which is twisted out of the stack by ca. 30°. Hydrogen bonded pairs of sulfamate ions are linked into parallel ribbons by further hydrogen bonding between sulfamates and bridging water molecules. In contrast, the BEDT-TTF salt with pentaborate contains infinite layers formed of a network of hydrogen bonded pentaborate anions. Two new bromide salts of BEDT-TTF are reported, one is a semiconducting 1 : 1 salt in which the bromide is integrated among the BEDT-TTF donors, while the other contain a square of four bromide ions linked together by hydrogen bonding to a centrally located H5O2(+) cation for every five BEDT-TTF molecules.

  20. Anion Recognition and Induced Self-Assembly of an α,γ-Cyclic Peptide To Form Spherical Clusters.

    Science.gov (United States)

    Rodríguez-Vázquez, Nuria; Amorín, Manuel; Alfonso, Ignacio; Granja, Juan R

    2016-03-24

    A cyclic octapeptide composed of hydroxy-functionalized γ-amino acids folds in a "V-shaped" conformation that allows the selective recognition of anions such as chloride, nitrate, and carbonate. The process involves the simultaneous self-assembly of six peptide subunits and the recognition of four anions to form a tetrahedral structure, in which the anions are located at the corners of the resulting structure. Each anion is coordinated to three different peptides. The structure was fully characterized by several techniques, including NMR spectroscopy and X-ray diffraction, and the material was able to facilitate the transmembrane transport of chloride ions. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Three multi-nuclear clusters and one infinite chain induced by a pendant 4-butyl-1H-pyrazole ligand for modification of Keggin anions.

    Science.gov (United States)

    Tian, Ai-xiang; Ning, Ya-li; Ying, Jun; Hou, Xue; Li, Tian-jiao; Wang, Xiu-li

    2015-01-07

    By utilizing pendant 4-butyl-1H-pyrazole (Hbpz) with an alkyl "tail"--(CH2)3CH3, four Keggin-based complexes containing different transition metal multi-nuclear clusters and an infinite chain were hydrothermally synthesized and structurally characterized, [Cu(I)4(bpz)4(pz)2(H6PW11Cu(II)O39)2]·10H2O (1), [Cu(II)2(bpz)2(H2O)2(H3PCu0.5Mo11.5O40)]·3H2O (2), [Ag3(bpz)2(pz)(H4SiW12O40)]·4H2O (3) and [Ag5(bpz)4(H5/2PMo12O40)2]·6H2O (4) (pz = pyrazole). Compound 1 contains a tetra-nuclear cluster [Cu(I)4(bpz)4(pz)2](2-), in which four Cu(I) ions are fixed by four bpz and two pz ligands. These clusters are linked by Keggin anion dimers to form a 2D layer. In compound 2, the ptz ligands fuse the Cu(II) ions and an infinite 1D metal-organic chain is constructed with the Keggin anions hanging up and down covalently. Compound 3 has a planar triangle tri-nuclear cycle [Ag3(bpz)2(pz)] with three Ag(I) as cores. These cycles build a 3D framework of 3 through the further linkages of Keggin anions and Ag-Ag bonds. In compound 4, there exist discrete [Ag5(bpz)4](+) clusters with four bpz ligands fused by five Ag(I) cores, which are linked by Keggin anions alternately to form a 1D chain. Adjacent chains share the Ag-O bonds and a 2D layer is constructed. The bpz ligand is firstly introduced into the POM field and its successive two N donors are essential for the construction of multi-nuclear clusters and an infinite chain of 1-4. Additionally, the electrochemical and photocatalytic properties of the title compounds have been investigated.

  2. Bond Activation and Hydrogen Evolution from Water through Reactions with M3S4 (M = Mo, W) and W3S3 Anionic Clusters.

    Science.gov (United States)

    Kumar, Corrine A; Saha, Arjun; Raghavachari, Krishnan

    2017-03-02

    Transition metal sulfides (TMS) are being investigated with increased frequency because of their ability to efficiently catalyze the hydrogen evolution reaction. We have studied the trimetallic TMS cluster ions, Mo3S4-, W3S4-, and W3S3-, and probed their efficiency for bond activation and hydrogen evolution from water. These clusters have geometries that are related to the edge sites on bulk MoS2 surfaces that are known to play a role in hydrogen evolution. Using density functional theory, the electronic structures of these clusters and their chemical reactivity with water have been investigated. The reaction mechanism involves the initial formation of hydroxyl and thiol groups, hydrogen migration to form an intermediate with a metal hydride bond, and finally, combination of a hydride and a proton to eliminate H2. Using this mechanism, free energy profiles of the reactions of the three metal clusters with water have been constructed. Unlike previous reactivity studies of other related cluster systems, there is no overall energy barrier in the reactions involving the M3S4 systems. The energy required for the rate-determining step of the reaction (the initial addition of the cluster by water) is lower than the separated reactants (-0.8 kcal/mol for Mo and -5.1 kcal/mol for W). They confirm the M3S4- cluster's ability to efficiently activate the chemical bonds in water to release H2. Though the W3S3- cluster is not as efficient at bond activation, it provides insights into the factors that contribute to the success of the M3S4 anionic systems in hydrogen evolution.

  3. Quantum Features of Anionic Species He*⁻ and He₂*⁻ in Small He(N) Clusters.

    Science.gov (United States)

    Villarreal, Pablo; Rodríguez-Cantano, Rocío; González-Lezana, Tomás; Prosmiti, Rita; Delgado-Barrio, Gerardo; Gianturco, Franco A

    2015-11-25

    We present variational calculations on systems containing a few boson helium atoms attached to electronically excited atomic and molecular helium anions He*⁻ and He₂*⁻ and characterize their structures and energetics. Previously reported high-level ab initio results [Huber, S. E.; Mauracher, A. Mol. Phys. 2014, 112, 794] to describe the interactions between excited (metastable) anions and a neutral He atom have been employed. For the case of the atomic species He*⁻, the corresponding interaction with He suggests large anharmonicity effects due to the presence of a deep well of ∼17,500 cm⁻¹ at short distances, together with a more external shallow secondary well of ∼4 cm⁻¹, both supporting bound levels. Moreover, when a sum of pairwise interactions is assumed to describe the full PES corresponding to the presence of several neutral He atoms, geometrical constraints already predict the complete solvation of the anionic impurity by six helium atoms, giving rise to a bipyramidal structure. In turn, for the anisotropic weak interaction He-He₂*⁻, where the anionic dimer is considered as a rigid rotor, the obtained structures show the tendency of the helium atoms to pack themselves together and largely far away from the dopant, thereby confirming the heliophobic character of He₂*⁻.

  4. Ytterbium doped silicon clusters YbSi{sub n} (n = 4–10) and their anions: Structures, thermochemistry, and electron affinities

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Xiaohong [School of Chemical Engineering, Inner Mongolia University of Technology, Hohhot 010051 (China); Hao, Dongsheng [School of Chemical Engineering, Inner Mongolia University of Technology, Hohhot 010051 (China); School of Mining and Technology, Inner Mongolia University of Technology, Hohhot 010051 (China); Yang, Jucai, E-mail: yangjc@imut.edu.cn [School of Chemical Engineering, Inner Mongolia University of Technology, Hohhot 010051 (China); School of Energy and Power Engineering, Inner Mongolia University of Technology, Hohhot 010051 (China)

    2015-11-05

    Highlights: • The ground-state structure of YbSi{sub n} and its anion is substitutional structure. • The four DFT AEAs are in excellent agreement with the experimental data. • Theoretical AEA of 2.33 eV of YbSi{sub 9} is more reasonable than the experimental 2.60 eV. • Hardness analysis reveals that doping Yb to Si{sub n} raises photochemical sensitivity. • Relative stabilities of YbSi{sub n} and their anions are examined. - Abstract: The structures, electron affinities, dissociation energies, hardness, and dipole moments of YbSi{sub n} (n = 4–10) and their anions were examined using B3LYP, TPSSh, PBE and wB97X methods. The lowest-energy structures can be regarded as replacing a Si of the ground-state structure of Si{sub n+1} with a Yb atom. The theoretical adiabatic electron affinities (AEAs) of YbSi{sub n} are in excellent agreement with experimental data. The average absolute errors from experiment are by 0.08, 0.07, 0.05 and 0.08 eV at the B3LYP, the TPSSh, the PBE and the wB97X levels, respectively. Theoretical AEAs of 2.33 ± 0.05 eV for YbSi{sub 9} are more reliable than the experimental value of 2.60 ± 0.05 eV. The hardness analysis reveals that doping Yb atom to Si{sub n} (n = 4–10) clusters raises the photochemical sensitivity. The dissociation energies of Yb atom from YbSi{sub n} and their anions were calculated to examine relative stabilities.

  5. Ion distribution in quaternary-ammonium-functionalized aromatic polymers: effects on the ionic clustering and conductivity of anion-exchange membranes.

    Science.gov (United States)

    Weiber, E Annika; Jannasch, Patric

    2014-09-01

    A series of copoly(arylene ether sulfone)s that have precisely two, three, or four quaternary ammonium (QA) groups clustered directly on single phenylene rings along the backbone are studied as anion-exchange membranes. The copolymers are synthesized by condensation polymerizations that involve either di-, tri-, or tetramethylhydroquinone followed by virtually complete benzylic bromination using N-bromosuccinimide and quaternization with trimethylamine. This synthetic strategy allows excellent control and systematic variation of the local density and distribution of QA groups along the backbone. Small-angle X-ray scattering of these copolymers shows extensive ionic clustering, promoted by an increasing density of QA on the single phenylene rings. At an ion-exchange capacity (IEC) of 2.1 meq g(-1), the water uptake decreases with the increasing local density of QA groups. Moreover, at moderate IECs at 20 °C, the Br(-) conductivity of the densely functionalized copolymers is higher than a corresponding randomly functionalized polymer, despite the significantly higher water uptake of the latter. Thus, the location of multiple cations on single aromatic rings in the polymers facilitates the formation of a distinct percolating hydrophilic phase domain with a high ionic concentration to promote efficient anion transport, despite probable limitations by reduced ion dissociation. These findings imply a viable strategy to improve the performance of alkaline membrane fuel cells. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Spectroscopic Properties of Novel Aromatic Metal Clusters: NaM4 (M=Al, Ga, In) and their Cations and Anions

    Energy Technology Data Exchange (ETDEWEB)

    Balasubramanian, K; Zhao, C

    2004-03-17

    The ground and several excited states of metal aromatic clusters, namely NaM4 and NaM{sub 4}{sup {+-}} (M=Al, Ga, In) clusters have been investigated by employing complete activespace self-consistent-field (CASSCF) followed by Multi-reference singles and doubles configuration interaction (MRSDCI) computations that included up to 10 million configurations and other methods. The ground states NaM{sub 4}{sup -} of aromatic anions are found to be symmetric C{sub 4v} ({sup 1}A{sub 1}) electronic states with ideal square pyramid geometries. While the ground state of NaIn4 is also predicted to be a symmetric C{sub 4v} ({sup 2}A{sub 1}) square pyramid, the ground state of the NaAl4 cluster is found to have a C{sub 2v} ({sup 2}A{sub 1}) pyramid with a rhombus base and the ground state of NaGa{sub 4} possesses a C{sub 2v} ({sup 2}A{sub 1}) pyramid with a rectangle base. In general these structures exhibit 2 competing geometries, viz., an ideal C{sub 4v} structure and a distorted rhomboidal or rectangular pyramid structure (C{sub 2v}). All of the ground states of the NaM{sub 4}{sup +} (M= Al, Ga, In) cations are computed to be C{sub 2v} ({sup 3}A{sub 2}) pyramids with rhombus bases. The equilibrium geometries, vibrational frequencies, dissociation energies, adiabatic ionization potentials, adiabatic electron affinities for the electronic states of NaM{sub 4} (M=Al, Ga, In) and their ions are computed and compared with experimental results and other theoretical calculations. On the basis of our computed excited states energy separations, we have tentatively suggested assignments to the observed X and A states in the anion photoelectron spectra of Al{sub 4}Na{sup -} reported by Li et al. The X state can be assigned to a C{sub 2v} ({sup 2}A{sub 1}) rhomboidal pyramid. The A state observed in the anion spectrum is assigned to the first excited state ({sup 2}B{sub 1}) of the neutral NaAl{sub 4} with the C{sub 4v} symmetry. The assignments of the excited states are consistent with

  7. Variational and Path Integral Monte Carlo calculations on Helium Clusters Doped with Metastable Anions He^*- and He_2^*-

    OpenAIRE

    Villarreal, Pablo; Rodríguez-Cantano, Rocío; González-Lezana, Tomás; Prosmiti, Rita; Delgado Barrio, Gerardo; Gianturco, Franco A.

    2015-01-01

    Variational calculations (T = 0 K) on small He_N...He^*- and He_N...He^2*- metastable clusters (N¿4), as well as Path Integral Monte Carlo (PIMC) simulations (T = 0.4 K) on larger species are presented and discussed.

  8. Computational Investigation of Cationic, Anionic and Neutral Ag2AuN (N = 1-7) Nanoalloy Clusters

    Science.gov (United States)

    Ranjan, Prabhat; Chakraborty, Tanmoy; Kumar, Ajay

    2017-08-01

    The study of bimetallic nanoalloy clusters is of immense importance due to their diverse applications in the field of science and engineering. A deep theoretical insight is required to explain the physico-chemical properties of such compounds. Among such nanoalloy clusters, the compound formed between Ag and Au has received a lot of attention because of their marked electronic, catalytic, optical and magnetic properties. Density Functional Theory (DFT) is one of the most successful approaches of quantum mechanics to study the electronic properties of materials. Conceptual DFT-based descriptors have turned to be indispensable tools for analysing and correlating the experimental properties of compounds. In this report, we have investigated the ground state configurations and physico-chemical properties of Ag2AuNλ (N = 1-7, λ=±1, 0) nanoalloy clusters invoking DFT methodology. Our computed data exhibits interesting odd-even oscillation behaviour. A close agreement between experimental and our computed bond length supports our theoretical analysis.

  9. Theoretical study of photodetachment spectroscopy of hydrogenated boron cluster anion H2B7- and its deuterated isotopomer

    Science.gov (United States)

    Sarkar, Rudraditya; Mahapatra, S.

    2017-11-01

    Photodetachment spectroscopy of H2B7- and its deuterated isotopomer probing the energetically low-lying electronic states of the respective neutral cluster is theoretically investigated in this paper. The theoretical methodology is based on detailed quantum chemistry calculations of electronic state energies, construction of a vibronic coupling model in the diabatic electronic basis, and nuclear dynamics calculations from first principles using time-dependent and time-independent quantum mechanical methods. The theoretical model consists of five coupled electronic states and fifteen vibrational modes. Several reduced dimensional calculations are performed to identify the relevant vibrational modes contributing to the vibronic structure of electronic bands and the impact of non-adiabatic coupling on them. The low-energy part of the spectrum of both H2B7 and its deuterated analogue is assigned by examining the vibronic wavefunctions and the results are compared with the experimental findings. The nonadiabatic decay dynamics of the electronic excited states of the neutral clusters is examined at length.

  10. Physical properties and electronic structure of a new barium titanate suboxide Ba{sub 1+δ}Ti{sub 13−δ}O{sub 12} (δ = 0.11)

    Energy Technology Data Exchange (ETDEWEB)

    Rotundu, Costel R.; Jiang, Shan; Ni, Ni [Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, California 90095 (United States); CNSI, University of California Los Angeles, Los Angeles, California 90095 (United States); Deng, Xiaoyu; Kotliar, Gabriel [Department of Physics, Rutgers University, Piscataway, New Jersey 08854 (United States); Qian, Yiting; Hawthorn, David G. [Department of Physics and Astronomy, University of Waterloo, Waterloo N2L 3G1 (Canada); Khan, Saeed [UCLA Molecular Instrumentation Center, University of California Los Angeles, Los Angeles, California 90095 (United States)

    2015-04-01

    The structure, transport, thermodynamic properties, x-ray absorption spectra (XAS), and electronic structure of a new barium titanate suboxide, Ba{sub 1+δ}Ti{sub 13−δ}O{sub 12} (δ = 0.11), are reported. It is a paramagnetic poor metal with hole carriers dominating the transport. Fermi liquid behavior appears at low temperature. The oxidization state of Ti obtained by the XAS is consistent with the metallic Ti{sup 2+} state. Local density approximation band structure calculations reveal the material is near the Van Hove singularity. The pseudogap behavior in the Ti-d band and the strong hybridization between the Ti-d and O-p orbitals reflect the characteristics of the building blocks of the Ti{sub 13} semi-cluster and the TiO{sub 4} quasi-squares, respectively.

  11. Excellent Silicon Surface Passivation Achieved by Industrial Inductively Coupled Plasma Deposited Hydrogenated Intrinsic Amorphous Silicon Suboxide

    Directory of Open Access Journals (Sweden)

    Jia Ge

    2014-01-01

    Full Text Available We present an alternative method of depositing a high-quality passivation film for heterojunction silicon wafer solar cells, in this paper. The deposition of hydrogenated intrinsic amorphous silicon suboxide is accomplished by decomposing hydrogen, silane, and carbon dioxide in an industrial remote inductively coupled plasma platform. Through the investigation on CO2 partial pressure and process temperature, excellent surface passivation quality and optical properties are achieved. It is found that the hydrogen content in the film is much higher than what is commonly reported in intrinsic amorphous silicon due to oxygen incorporation. The observed slow depletion of hydrogen with increasing temperature greatly enhances its process window as well. The effective lifetime of symmetrically passivated samples under the optimal condition exceeds 4.7 ms on planar n-type Czochralski silicon wafers with a resistivity of 1 Ωcm, which is equivalent to an effective surface recombination velocity of less than 1.7 cms−1 and an implied open-circuit voltage (Voc of 741 mV. A comparison with several high quality passivation schemes for solar cells reveals that the developed inductively coupled plasma deposited films show excellent passivation quality. The excellent optical property and resistance to degradation make it an excellent substitute for industrial heterojunction silicon solar cell production.

  12. Atmospheric chemistry, sources and sinks of carbon suboxide, C3O2

    Science.gov (United States)

    Keßel, Stephan; Cabrera-Perez, David; Horowitz, Abraham; Veres, Patrick R.; Sander, Rolf; Taraborrelli, Domenico; Tucceri, Maria; Crowley, John N.; Pozzer, Andrea; Stönner, Christof; Vereecken, Luc; Lelieveld, Jos; Williams, Jonathan

    2017-07-01

    Carbon suboxide, O = C = C = C = O, has been detected in ambient air samples and has the potential to be a noxious pollutant and oxidant precursor; however, its lifetime and fate in the atmosphere are largely unknown. In this work, we collect an extensive set of studies on the atmospheric chemistry of C3O2. Rate coefficients for the reactions of C3O2 with OH radicals and ozone were determined as kOH = (2.6 ± 0.5) × 10-12 cm3 molecule-1 s-1 at 295 K (independent of pressure between ˜ 25 and 1000 mbar) and kO3 Henry's law solubility and hydrolysis rate constant) were also investigated, enabling its photodissociation lifetime and hydrolysis rates, respectively, to be assessed. The role of C3O2 in the atmosphere was examined using in situ measurements, an analysis of the atmospheric sources and sinks and simulation with the EMAC atmospheric chemistry-general circulation model. The results indicate sub-pptv levels at the Earth's surface, up to about 10 pptv in regions with relatively strong sources, e.g. influenced by biomass burning, and a mean lifetime of ˜ 3.2 days. These predictions carry considerable uncertainty, as more measurement data are needed to determine ambient concentrations and constrain the source strengths.

  13. Non-iterative triple excitations in equation-of-motion coupled-cluster theory for electron attachment with applications to bound and temporary anions.

    Science.gov (United States)

    Jagau, Thomas-C

    2018-01-14

    The impact of residual electron correlation beyond the equation-of-motion coupled-cluster singles and doubles (EOM-CCSD) approximation on positions and widths of electronic resonances is investigated. To establish a method that accomplishes this task in an economical manner, several approaches proposed for the approximate treatment of triple excitations are reviewed with respect to their performance in the electron attachment (EA) variant of EOM-CC theory. The recently introduced EOM-CCSD(T)(a)* method [D. A. Matthews and J. F. Stanton, J. Chem. Phys. 145, 124102 (2016)], which includes non-iterative corrections to the reference and the target states, reliably reproduces vertical attachment energies from EOM-EA-CC calculations with single, double, and full triple excitations in contrast to schemes in which non-iterative corrections are applied only to the target states. Applications of EOM-EA-CCSD(T)(a)* augmented by a complex absorbing potential (CAP) to several temporary anions illustrate that shape resonances are well described by EOM-EA-CCSD, but that residual electron correlation often makes a non-negligible impact on their positions and widths. The positions of Feshbach resonances, on the other hand, are significantly improved when going from CAP-EOM-EA-CCSD to CAP-EOM-EA-CCSD(T)(a)*, but the correct energetic order of the relevant electronic states is still not achieved.

  14. Small copper-doped silicon clusters CuSin (n = 4-10) and their anions: structures, thermochemistry, and electron affinities.

    Science.gov (United States)

    Lin, Lin; Yang, Jucai

    2015-06-01

    The structures and energies of copper-doped small silicon clusters CuSi n (n = 4-10) and their anions were investigated systematically using CCSD(T)/aug-cc-pVTZ-DK//MP2/6-31G(2df,p), G4//MP2/6-31G(2df,p), and the B3LYP/6-311+G* basis set. The performance of the methods used for the prediction of energetic and thermodynamic properties was evaluated. Comparing experimental [Xu et al. (2012) J Chem Phys 136:104308] and theoretical calculations, it was concluded that the CCSD(T) results are very accurate and exhibit the best performance; the mean absolute deviation from experimental data was 0.043 eV. The excellent agreement of vertical detachment energy (VDE) between experimental results and CCSD(T) calculations indicates that the ground state structures of CuSi n (-) (n = 4-10) presented in this paper are reliable. For CuSi10, assigning 2.90±0.08 eV to the experimental adiabatic electron affinity (AEA) and 3.90±0.08 eV to the VDE is more reasonable than to 3.46±0.08 eV and 3.62±0.08 eV, respectively, based on the CCSD(T) calculations and the previous photoelectron spectrum of CuSi10 (-) (Xu et al., op. cit.). The AEAs of CuSi n (n = 4-10), excluding CuSi7, are in excellent agreement with experimental data, showing that the ground state structures of CuSi n (n = 4-6, 8-10) reported in this paper are reliable. CuSi10 is suggested to be the smallest endohedral ground state structure. However, adding an additional electron to CuSi10 pulls out the Cu atom from the center location, forming an exohedral ground state structure of CuSi10 (-). The charge transfer and dissociation energy of Cu from CuSi n and their anions determined to examine the nature of bonding and their relative stabilities.

  15. cluster

    Indian Academy of Sciences (India)

    electron transfer chains involved in a number of biologi- cal systems including respiration and photosynthesis.1. The most common iron–sulphur clusters found as active centres in iron–sulphur proteins are [Fe2S2], [Fe3S4] and [Fe4S4], in which Fe(III) ions are coordinated to cysteines from the peptide and are linked to each ...

  16. A first-principles study on the effect of oxygen content on the structural and electronic properties of silicon suboxide as anode material for lithium ion batteries

    Science.gov (United States)

    Rahaman, Obaidur; Mortazavi, Bohayra; Rabczuk, Timon

    2016-03-01

    Silicon suboxide is currently considered as a unique candidate for lithium ion batteries anode materials due to its considerable capacity. However, no adequate information exists about the role of oxygen content on its performance. To this aim, we used density functional theory to create silicon suboxide matrices of various Si:O ratios and investigated the role of oxygen content on the structural, dynamic, electronic properties and lithiation behavior of the matrices. Our study demonstrates that the O atoms interact strongly with the inserted Li atoms resulting in a disintegration of the host matrix. We found that higher concentration of oxygen atoms in the mixture reduces its relative expansion upon lithiation, which is a desirable quality for anode materials. It helps in preventing crack formation and pulverization due to large fluctuations in volume. Our study also demonstrates that a higher oxygen content increases the lithium storage capacity of the anode. However, it can also cause the formation of stable complexes like lithium silicates that might result into reversible capacity loss as indicated by the voltage-composition curves. The study provides valuable insights into the role of oxygen in moderating the interaction of lithium in silicon suboxide mixture in microscopic details.

  17. FT-ICR-MS studies on the reactivity of coinage metal clusters and on the electronic stability of fullerene anions; FT-ICR-MS Studien zur Reaktivitaet kationischer Muenzmetallcluster und zur elektronischen Stabilitaet von Fullerenanionen

    Energy Technology Data Exchange (ETDEWEB)

    Neumaier, M.

    2008-01-15

    In the context of this work the chemical reactivity of cationic coinage metal clusters towards carbon monoxide (CO) as well as the electronic stability of fullerene anions have been studied. In order to generate metal clusters a home-built laser vaporization source was adapted to the existing Fourier transform mass spectrometer and has been optimized. Further the reactivity of cationic gold clusters Au{sup +}{sub n} (n = 1 - 65) and of mixed silver-gold clusters Ag{sub m}Au{sup +}{sub n} (m + n = 1 - 6) towards CO has been examined. Rate constants of CO adsorption has been determined which were found to depend strongly on the cluster size (gold clusters) and on the composition (silver-gold clusters). By applying the kinetic model of radiative association to the measured rate constants binding energies of CO to the clusters could be derived. In order to determine ground state structures and CO binding energies DFT calculations were accomplished. A good agreement between the computed binding energies and the data from the kinetic modelling has been found. In principle a strong decrease of the CO-binding energy (approx. 1,03 eV for Au{sub 5}(CO){sup +} to 0,65 eV for Au{sub 41}(CO){sup +}) with increasing cluster size could be observed. This behavior can be attributed to an increasing delocalization of the positive charge and shows that electrostatic forces constitute a majority of the CO binding energy especially for smaller gold cluster carbonyl cations. For the mixed silver-gold clusters a reduction of the CO binding energy with increasing number of silver atoms for a given cluster size was observed. This could be explained with an increase of the energy of the lowest unoccupied molecular orbital (LUMO) in the Ag{sub m}Au{sup +}{sub n} clusters. As fullerenes (C{sub 60}, C{sub 70} - C{sub 86},..) form a homologous row they are (besides metal clusters) suitable to study size-dependent characteristics. Furthermore the fullerene cage possesses a high stability. Within

  18. Atomically Thin Interfacial Suboxide Key to Hydrogen Storage Performance Enhancements of Magnesium Nanoparticles Encapsulated in Reduced Graphene Oxide.

    Science.gov (United States)

    Wan, Liwen F; Liu, Yi-Sheng; Cho, Eun Seon; Forster, Jason D; Jeong, Sohee; Wang, Hsiao-Tsu; Urban, Jeffrey J; Guo, Jinghua; Prendergast, David

    2017-09-13

    As a model system for hydrogen storage, magnesium hydride exhibits high hydrogen storage density, yet its practical usage is hindered by necessarily high temperatures and slow kinetics for hydrogenation-dehydrogenation cycling. Decreasing particle size has been proposed to simultaneously improve the kinetics and decrease the sorption enthalpies. However, the associated increase in surface reactivity due to increased active surface area makes the material more susceptible to surface oxidation or other side reactions, which would hinder the overall hydrogenation-dehydrogenation process and diminish the capacity. Previous work has shown that the chemical stability of Mg nanoparticles can be greatly enhanced by using reduced graphene oxide as a protecting agent. Although no bulklike crystalline MgO layer has been clearly identified in this graphene-encapsulated/Mg nanocomposite, we propose that an atomically thin layer of honeycomb suboxide exists, based on first-principles interpretation of Mg K-edge X-ray absorption spectra. Density functional theory calculations reveal that in contrast to conventional expectations for thick oxides this interfacial oxidation layer permits H2 dissociation to the same degree as pristine Mg metal with the added benefit of enhancing the binding between reduced graphene oxide and the Mg nanoparticle, contributing to improved mechanical and chemical stability of the functioning nanocomposite.

  19. Electron transfer from alpha-keggin anions to dioxygen

    Science.gov (United States)

    Yurii V. Geletii; Rajai H. Atalla; Craig L. Hill; Ira A. Weinstock

    2004-01-01

    Polyoxometalates (POMs), of which alpha-Keggin anions are representative, are a diverse and rapidly growing class of water-soluble cluster-anion structures with applications ranging from molecular catalysis to materials. [1] POMs are inexpensive, minimally or non-toxic, negatively charged clusters comprised of early transition-metals, usually in their do electronic...

  20. Structure of phosphorus clusters using simulated annealing. II. P9, P10, P11, anions P2-4, P2-10, P3-11, and cations P+n to n=11

    Science.gov (United States)

    Jones, R. O.; Seifert, G.

    1992-05-01

    Previous calculations on the structures of isomers of phosphorus clusters P2 to P8 [density functional calculations with simulated annealing (SA), J. Chem. Phys. 92, 6710 (1990)] have been extended to P9, P10, and P11. The tendency of phosphorus to form tubular structures is already evident in clusters of this size. We have also performed calculations on additional isomers of the hexamer P6, positive ions up to P+11, and the P2-4, P2-10, and P3-11 anions. Ionization energies agree well with available measurements [P1 to P4] and show trends that can be correlated with the structures and the measured relative abundances of the ions. The calculated structure of P3-11 agrees very well with x-ray diffraction data, and we observe isomerization in P9 resulting from charge transfer. A simplified SA scheme using a linear combination of atomic orbitals (LCAO) has been used to aid the analysis of the results.

  1. Combining research in physical chemistry and chemical education: Part A. The femtosecond molecular dynamics of small gas-phase anion clusters. Part B. Surveying student beliefs about chemistry and the development of physical chemistry learning tutorials

    Science.gov (United States)

    Barbera, Jack

    2007-12-01

    This dissertation combines work in the areas of experimental physical chemistry and chemical education. In the area of physical chemistry, femtosecond pump-probe spectroscopy is used to interrogate the time-dependence for energy redistribution, solvent reorientation, and dissociation dynamics in small gas-phase anion clusters. The chemical education research addressed in this manuscript include the development and validation of a survey to measure students' beliefs about chemistry and the learning of chemistry and the development and testing of learning tutorials for use in undergraduate physical chemistry courses in thermodynamics and kinetics. In the first part of this dissertation, the Cu(CD3OD) dynamics are investigated using a combination of femtosecond pump-probe experiments and ab initio calculations. Dissociation of this complex into Cu and CD3OD occurs on two distinct time scales: 3 and 30 ps, which arise, respectively, from the coupling of intermolecular solvent rotations and excited methyl rotor rotation into the Cu-O dissociation component upon electron photodetachment of the precursor anion. In the second part of this dissertation, the time-resolved recombination of photodissociated IBr-(CO2)n (n = 5 - 10) cluster anions is investigated. Upon excitation to the A' 2pi 1/2 state of the chromophore, the bare anion results in I- and Br products, upon solvation with CO2, the IBr- chromophore regains near-IR absorption after recombination and vibrational relaxation on the ground electronic state. The recombination times vary with the number of solvent molecules from 12 ps for n = 5 to 900 ps for n = 10. Extensive electronic structure and non-adiabatic molecular dynamic simulations provide a framework to understand this behavior. In the third part of this dissertation, the modification and validation of the Colorado Learning Attitudes about Science Survey (CLASS) for use in chemistry is presented in detail. The CLASS survey is designed to measure student

  2. Complex absorbing potential based equation-of-motion coupled cluster method for the potential energy curve of CO{sub 2}{sup −} anion

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, Aryya; Vaval, Nayana; Pal, Sourav [Physical Chemistry Division, CSIR-National Chemical Laboratory, Pune 411008 (India); Bartlett, Rodney J. [Quantum Theory Project, University of Florida, Gainesville, Florida 32611 (United States)

    2014-10-28

    The equation-of-motion coupled cluster method employing the complex absorbing potential has been used to investigate the low energy electron scattering by CO{sub 2}. We have studied the potential energy curve for the {sup 2}Π{sub u} resonance states of CO{sub 2}{sup −} upon bending as well as symmetric and asymmetric stretching of the molecule. Specifically, we have stretched the C−O bond length from 1.1 Å to 1.5 Å and the bending angles are changed between 180° and 132°. Upon bending, the low energy {sup 2}Π{sub u} resonance state is split into two components, i.e., {sup 2}A{sub 1}, {sup 2}B{sub 1} due to the Renner-Teller effect, which behave differently as the molecule is bent.

  3. clusters: density functional theory (DFT)

    Indian Academy of Sciences (India)

    contain contributions from the central atom by symmetry at the anion ground state geometry. The resulting RuF. −. 3 anion, thus, has a closed-shell structure and should be thermo- dynamically and electronically very stable. Table 1 shows energy difference for different multiplicities of neutral and anionic RuFn clusters.

  4. Anion exchange membrane

    Science.gov (United States)

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

    2013-05-07

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

  5. Diffuse neutron scattering from anion-excess strontium chloride

    DEFF Research Database (Denmark)

    Goff, J.P.; Clausen, K.N.; Fåk, B.

    1992-01-01

    The defect structure and diffusional processes have been studied in the anion-excess fluorite (Sr, Y)Cl2.03 by diffuse neutron scattering techniques. Static cuboctahedral clusters found at ambient temperature break up at temperatures below 1050 K, where the anion disorder is highly dynamic. The a...

  6. Receptors for anions

    Energy Technology Data Exchange (ETDEWEB)

    Itsikson, N A; Chupakhin, O N [I. Ya. Postovsky Institute of Organic Synthesis, Urals Branch of the Russian Academy of Sciences, Ekaterinburg (Russian Federation); Morzherin, Yu Yu; Matern, A I [B N Yeltsin Urals State Technical University - UPI (Russian Federation)

    2008-09-30

    The published data on receptors for anions with different geometry are generalised. Special attention is given to the analysis of binding abilities of organic ligands. Structural features of complex-forming agents and their properties are considered.

  7. Anion exchange polymer electrolytes

    Science.gov (United States)

    Kim, Yu Seung; Kim, Dae Sik

    2015-06-02

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

  8. Anion-π catalysis.

    Science.gov (United States)

    Zhao, Yingjie; Beuchat, César; Domoto, Yuya; Gajewy, Jadwiga; Wilson, Adam; Mareda, Jiri; Sakai, Naomi; Matile, Stefan

    2014-02-05

    The introduction of new noncovalent interactions to build functional systems is of fundamental importance. We here report experimental and theoretical evidence that anion-π interactions can contribute to catalysis. The Kemp elimination is used as a classical tool to discover conceptually innovative catalysts for reactions with anionic transition states. For anion-π catalysis, a carboxylate base and a solubilizer are covalently attached to the π-acidic surface of naphthalenediimides. On these π-acidic surfaces, transition-state stabilizations up to ΔΔGTS = 31.8 ± 0.4 kJ mol(-1) are found. This value corresponds to a transition-state recognition of KTS = 2.7 ± 0.5 μM and a catalytic proficiency of 3.8 × 10(5) M(-1). Significantly increasing transition-state stabilization with increasing π-acidity of the catalyst, observed for two separate series, demonstrates the existence of "anion-π catalysis." In sharp contrast, increasing π-acidity of the best naphthalenediimide catalysts does not influence the more than 12 000-times weaker substrate recognition (KM = 34.5 ± 1.6 μM). Together with the disappearance of Michaelis-Menten kinetics on the expanded π-surfaces of perylenediimides, this finding supports that contributions from π-π interactions are not very important for anion-π catalysis. The linker between the π-acidic surface and the carboxylate base strongly influences activity. Insufficient length and flexibility cause incompatibility with saturation kinetics. Moreover, preorganizing linkers do not improve catalysis much, suggesting that the ideal positioning of the carboxylate base on the π-acidic surface is achieved by intramolecular anion-π interactions rather than by an optimized structure of the linker. Computational simulations are in excellent agreement with experimental results. They confirm, inter alia, that the stabilization of the anionic transition states (but not the neutral ground states) increases with the π-acidity of the

  9. Potentiometric anion selective sensors

    NARCIS (Netherlands)

    Antonisse, M.M.G.; Reinhoudt, David

    1999-01-01

    In comparison with selective receptors (and sensors) for cationic species, work on the selective complexation and detection of anions is of more recent date. There are three important components for a sensor, a transducer element, a membrane material that separates the transducer element and the

  10. Complex anion inclusion compounds: flexible anion-exchange materials.

    Science.gov (United States)

    Williams, Edward R; Leithall, Rebecca M; Raja, Robert; Weller, Mark T

    2013-01-11

    Copper chloropyrophosphate frameworks have been synthesised with a wide variety of complex inorganic anions trapped in a large, flexible, one-dimensional pore, with anions including chloride, bromide, phosphate and the complex metal halo-anions PtCl(4)(2-), PdBr(4)(2-), CuCl(4)(2-) and AuCl(4)(-).

  11. Unprecedented connection mode of [V{sub 16}Sb{sub 4}O{sub 42}(H{sub 2}O)]{sup 8-} cluster anions by Mn{sup 2+} centered complexes. Solvothermal synthesis and properties of {[Mn(teta)]_4V_1_6Sb_4O_4_2(H_2O)}{sub n}.[(H{sub 2}O){sub 12}]{sub n}

    Energy Technology Data Exchange (ETDEWEB)

    Rasmussen, Maren; Naether, Christian; Bensch, Wolfgang [Institute of Inorganic Chemistry, Christian-Albrechts-University of Kiel (Germany); Leusen, Jan van; Koegerler, Paul [Institute of Inorganic Chemistry, RWTH Aachen University, Aachen (Germany)

    2017-11-17

    The new compound {[Mn(teta)]_4V_1_6Sb_4O_4_2}{sub n}.[(H{sub 2}O){sub 12}]{sub n} (teta = triethylenetetraamine) was synthesized under solvothermal conditions. The crystal structure features the high nuclearity [V{sub 16}{sup IV}Sb{sub 4}{sup III}O{sub 42}(H{sub 2}O)]{sup 8-} cluster anion, which consists of two rings composed of 8 edge-sharing VO{sub 5} polyhedra. The rings are perpendicular to each other generating four niches, which are occupied by two VO{sub 5} pyramids and two handle-like Sb{sub 2}O{sub 5} units. The two unique anions are each surrounded by eight Mn{sup 2+} centered complexes via Mn-O{sub term}-V bonds. Such an expansion has never been observed in heterometal polyoxovanadate chemistry. The connection mode between cluster anions and complex cations generates two individual layers stacked onto each other. Between the layers weak Sb..O contacts are observed. The crystal water molecules are mainly located in the empty space between the layers. Upon heating H{sub 2}O molecules are removed, while the crystal structure remains intact. The magnetic behavior is dominated by strong antiferromagnetic exchange interactions between the central V{sup 4+} ions, while the interaction between the cluster anion and central Mn{sup 2+} ions is significantly less pronounced. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  12. Empirical correlation methods for temporary anions.

    Science.gov (United States)

    Sommerfeld, Thomas; Weber, Rebecca J

    2011-06-23

    A temporary anion is a short-lived radical anion that decays through electron autodetachment into a neutral molecule and a free electron. The energies of these metastable species are often predicted using empirical correlation methods because ab initio predictions are computationally very expensive. Empirical correlation methods can be justified in the framework of Weisskopf-Fano-Feshbach theory but tend to work well only within closely related families of molecules or within a restricted energy range. The reason for this behavior can be understood using an alternative theoretical justification in the framework of the Hazi-Taylor stabilization method, which suggests that the empirical parameters do not so much correct for the coupling of the computed state to the continuum but for electron correlation effects and that therefore empirical correlation methods can be improved by using more accurate electronic structure methods to compute the energy of the confined electron. This idea is tested by choosing a heterogeneous reference set of temporary states and comparing empirical correlation schemes based on Hartree-Fock orbital energies, Kohn-Sham orbital energies, and attachment energies computed with the equation-of-motion coupled-cluster method. The results show that using more reliable energies for the confined electron indeed enhances the predictive power of empirical correlation schemes and that useful correlations can be established beyond closely related families of molecules. Certain types of σ* states are still problematic, and the reasons for this behavior are analyzed. On the other hand, preliminary results suggest that the new scheme can even be useful for predicting energies of bound anions at a fraction of the computational cost of reliable ab initio calculations. It is then used to make predictions for bound and temporary states of the furantrione and croconic acid radical anions.

  13. Hydrogen bonding in two ionic complexes built from octahedral rhenium(III) chalcocyanohydroxo cluster anions and tris(ethylenediamine)nickel(II) cations, [Ni(en)3]2[Re6S8(CN)4(OH)2]·5.5H2O and [Ni(en)3]2[Re6Se8(CN)4(OH)2]·10H2O

    Science.gov (United States)

    Smolentsev, Anton I.; Ermolaev, Andrey V.; Mironov, Yuri V.

    2012-04-01

    Two novel octahedral rhenium(III) chalcocyanohydroxo cluster complexes [Ni(en)3]2[Re6S8(CN)4(OH)2]·5.5H2O (1) and [Ni(en)3]2[Re6Se8(CN)4(OH)2]·10H2O (2) have been prepared by reaction of cluster complexes Cs1.68K2.32[Re6S8(CN)4(OH)2]·2H2O and Cs2.75K1.25[Re6Se8(CN)4(OH)2]·H2O with NiCl2 and en (en = ethylenediamine) in aqueous ammonia solutions. Both compounds were characterized by IR-spectra, elemental analysis, EDS, DTA and single-crystal X-ray analysis. Compound 1 crystallizes in the monoclinic space group C2/c, while compound 2 refers to the triclinic space group P-1. The structures of both compounds consist of discrete ions [Ni(en)3]2+, [Re6Q8(CN)4(OH)2]4- and water molecules of crystallization that are bonded by a network of hydrogen bonds. In the structure of 1 the [Re6S8(CN)4(OH)2]4- anions are bound to each other via Osbnd H⋯Nsbnd C hydrogen interactions (O⋯N distance is 2.950(10) Å), thus forming a linear chains running along the c axis.

  14. Anionic forensic signatures for sample matching of potassium cyanide using high performance ion chromatography and chemometrics.

    Science.gov (United States)

    Fraga, Carlos G; Farmer, Orville T; Carman, April J

    2011-01-30

    Potassium cyanide was used as a model toxicant to determine the feasibility of using anionic impurities as a forensic signature for matching cyanide salts back to their source. In this study, portions of eight KCN stocks originating from four countries were separately dissolved in water and analyzed by high performance ion chromatography (HPIC) using an anion exchange column and conductivity detection. Sixty KCN aqueous samples were produced from the eight stocks and analyzed for 11 anionic impurities. Hierarchal cluster analysis and principal component analysis were used to demonstrate that KCN samples cluster according to source based on the concentrations of their anionic impurities. The Fisher-ratio method and degree-of-class separation (DCS) were used for feature selection on a training set of KCN samples in order to optimize sample clustering. The optimal subset of anions needed for sample classification was determined to be sulfate, oxalate, phosphate, and an unknown anion named unk5. Using K-nearest neighbors (KNN) and the optimal subset of anions, KCN test samples from different KCN stocks were correctly determined to be manufactured in the United States. In addition, KCN samples from stocks manufactured in Belgium, Germany, and the Czech Republic were all correctly matched back to their original stocks because each stock had a unique anionic impurity profile. The application of the Fisher-ratio method and DCS for feature selection improved the accuracy and confidence of sample classification by KNN. Copyright © 2010 Elsevier B.V. All rights reserved.

  15. The many ways of making anionic clays

    Indian Academy of Sciences (India)

    Unknown

    trivalent metal hydroxides and their hydroxy salts are actually anionic clays consisting of positively charged hydroxide layers with anions intercalated in the interlayer region. The anionic clays exhibit anion sorption, anion diffusion and exchange properties together with surface basicity making them materials of importance ...

  16. The many ways of making anionic clays

    Indian Academy of Sciences (India)

    Together with hydrotalcite-like layered double hydroxides, bivalent and trivalent metal hydroxides and their hydroxy salts are actually anionic clays consisting of positively charged hydroxide layers with anions intercalated in the interlayer region. The anionic clays exhibit anion sorption, anion diffusion and exchange ...

  17. Anion-responsive supramolecular gels.

    Science.gov (United States)

    Maeda, Hiromitsu

    2008-01-01

    Supramolecular gels that change their state or structure in response to anion stimuli have been highlighted. Only a few examples exist of such supramolecular gels, the structures and properties of which can be controlled and modulated by interactions with anions. To form anion-responsive dimensionally-controlled organized structures, the constituent low-molecular-weight gelator molecules must act as anion receptors by possessing one or more of van der Waals interaction units (aliphatic chains), stacking pi planes, hydrogen-bonding sites, and metal-coordination units. This Concept focuses on the gelation and transition behaviors of amide- and urea-based anion-stimulated systems, metal-coordinated systems, and novel acyclic pi-conjugated oligopyrroles that act as "molecular flippers."

  18. Phosphazene-promoted anionic polymerization

    KAUST Repository

    Zhao, Junpeng

    2014-01-01

    In the recent surge of metal-free polymerization techniques, phosphazene bases have shown their remarkable potential as organic promoters/catalysts for the anionic polymerization of various types of monomers. By complexation with the counterion (e.g. proton or lithium cation), phosphazene base significantly improve the nucleophilicity of the initiator/chain-end resulting in rapid and usually controlled anionic/quasi-anionic polymerization. In this review, we will introduce the general mechanism, i.e. in situ activation (of initiating sites) and polymerization, and summarize the applications of such a mechanism on macromolecular engineering toward functionalized polymers, block copolymers and complex macromolecular architectures.

  19. Pentaarylfullerenes as noncoordinating cyclopentadienyl anions

    NARCIS (Netherlands)

    Bouwkamp, Marco W.; Meetsma, Auke

    2009-01-01

    The first example of an early-transition-metal complex involving a pentaarylfullerene was prepared. Instead of half-sandwich complexes, solvent separated ion pairs were obtained in which the pentaarylfullerene moiety acts as noncoordinating cyclopentadienyl anion.

  20. Bound anionic states of adenine

    Energy Technology Data Exchange (ETDEWEB)

    Haranczyk, Maciej; Gutowski, Maciej S; Li, Xiang; Bowen, Kit H

    2007-03-20

    Anionic states of nucleic acid bases are involved in DNA damage by low-energy electrons and in charge transfer through DNA. Previous gas phase studies of free, unsolvated nucleic acid base parent anions probed only dipole-bound states, which are not present in condensed phase environments, but did not observe valence anionic states, which for purine bases, are thought to be adiabatically unbound. Contrary to this expectation, we have demonstrated that some thus far ignored tautomers of adenine, which result from enamine-imine transformations, support valence anionic states with electron vertical detachment energies as large as 2.2 eV, and at least one of these anionic tautomers is adiabatically bound. Moreover, we predict that the new anionic tautomers should also dominate in solutions and should be characterized by larger values of electron vertical detachment energy than the canonical valence anion. All of the new-found anionic tautomers might be formed in the course of dissociative electron attachment followed by a hydrogen atom attachment to a carbon atom, and they might affect the structure and properties of DNA and RNA exposed to low-energy electrons. The discovery of these valence anionic states of adenine was facilitated by the development of: (i) a new experimental method for preparing parent anions of nucleic acid bases for photoelectron experiments, and (ii) a new combinatorial/ quantum chemical approach for identification of the most stable tautomers of organic molecules. The computational portion of this work was supported by the: (i) Polish State Committee for Scientific Research (KBN) Grants: DS/8000-4-0140-7 (M.G.) and N204 127 31/2963 (M.H.), (ii) European Social Funds (EFS) ZPORR/2.22/II/2.6/ARP/U/2/05 (M.H.), and (iii) US DOE Office of Biological and Environmental Research, Low Dose Radiation Research Program (M.G.). M.H. holds the Foundation for Polish Science (FNP) award for young scientists. The calculations were performed at the Academic

  1. The Oxidation Products of Aluminum Hydride and Boron Aluminum Hydride Clusters

    Science.gov (United States)

    2016-01-04

    AFRL-AFOSR-VA-TR-2016-0075 The Oxidation Products of Aluminum Hydride and Boron Aluminum Hydride Clusters KIT BOWEN JOHNS HOPKINS UNIV BALTIMORE MD...Hydride and Boron Aluminum Hydride Clusters 5a.  CONTRACT NUMBER 5b.  GRANT NUMBER FA9550-14-1-0324 5c.  PROGRAM ELEMENT NUMBER 61102F 6. AUTHOR(S) KIT...of both Aluminum Hydride Cluster Anions and Boron Aluminum Hydride Cluster Anions with Oxygen: Anionic Products The anionic products of reactions

  2. Photoelectron spectra and structure of the Mn{sub n}{sup −} anions (n = 2–16)

    Energy Technology Data Exchange (ETDEWEB)

    Gutsev, G. L., E-mail: gennady.gutsev@famu.edu; Weatherford, C. A. [Department of Physics, Florida A& M University, Tallahassee, Florida 32307 (United States); Ramachandran, B. R. [College of Engineering and Science, Louisiana Tech University, Ruston, Louisiana 71272 (United States); Gutsev, L. G. [Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306 (United States); Zheng, W.-J.; Thomas, O. C.; Bowen, Kit H., E-mail: kbowen@jhu.edu [Departments of Chemistry and Materials Science, Johns Hopkins University, Baltimore, Maryland 21218 (United States)

    2015-07-28

    Photoelectron spectra of the Mn{sub n}{sup −} anion clusters (n = 2–16) are obtained by anion photoelectron spectroscopy. The electronic and geometrical structures of the anions are computed using density functional theory with generalized gradient approximation and a basis set of triple-ζ quality. The electronic and geometrical structures of the neutral Mn{sub n} clusters have also been computed to estimate the adiabatic electron affinities. The average absolute difference between the computed and experimental vertical detachment energies of an extra electron is about 0.2 eV. Beginning with n = 6, all lowest total energy states of the Mn{sub n}{sup −} anions are ferrimagnetic with the spin multiplicities which do not exceed 8. The computed ionization energies of the neutral Mn{sub n} clusters are in good agreement with previously obtained experimental data. According to the results of our computations, the binding energies of Mn atoms are nearly independent on the cluster charge for n > 6 and possess prominent peaks at Mn{sub 13} and Mn{sub 13}{sup −} in the neutral and anionic series, respectively. The density of states obtained from the results of our computations for the Mn{sub n}{sup −} anion clusters show the metallic character of the anion electronic structures.

  3. Pu Anion Exchange Process Intensification

    Energy Technology Data Exchange (ETDEWEB)

    Taylor-Pashow, K. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2015-10-08

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

  4. Anion order in perovskite oxynitrides.

    Science.gov (United States)

    Yang, Minghui; Oró-Solé, Judith; Rodgers, Jennifer A; Jorge, Ana Belén; Fuertes, Amparo; Attfield, J Paul

    2011-01-01

    Transition-metal oxynitrides with perovskite-type structures are an emerging class of materials with optical, photocatalytic, dielectric and magnetoresistive properties that may be sensitive to oxide-nitride order, but the anion-ordering principles were unclear. Here we report an investigation of the representative compounds SrMO(2)N (M = Nb, Ta) using neutron and electron diffraction. This revealed a robust 1O/2(O(0.5)N(0.5)) partial anion order (up to at least 750 °C in the apparently cubic high-temperature phases) that directs the rotations of MO(4)N(2) octahedra in the room-temperature superstructure. The anion distribution is consistent with local cis-ordering of the two nitrides in each octahedron driven by covalency, which results in disordered zigzag M-N chains in planes within the perovskite lattice. Local structures for the full range of oxynitride perovskites are predicted and a future challenge is to tune properties by controlling the order and dimensionality of the anion chains and networks.

  5. Pu Anion Exchange Process Intensification

    Energy Technology Data Exchange (ETDEWEB)

    Taylor-Pashow, Kathryn M. L. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2017-10-06

    This research is focused on improving the efficiency of the anion exchange process for purifying plutonium. While initially focused on plutonium, the technology could also be applied to other ion-exchange processes. Work in FY17 focused on the improvement and optimization of porous foam columns that were initially developed in FY16. These foam columns were surface functionalized with poly(4-vinylpyridine) (PVP) to provide the Pu specific anion-exchange sites. Two different polymerization methods were explored for maximizing the surface functionalization with the PVP. The open-celled polymeric foams have large open pores and large surface areas available for sorption. The fluid passes through the large open pores of this material, allowing convection to be the dominant mechanism by which mass transport takes place. These materials generally have very low densities, open-celled structures with high cell interconnectivity, small cell sizes, uniform cell size distributions, and high structural integrity. These porous foam columns provide advantages over the typical porous resin beads by eliminating the slow diffusion through resin beads, making the anion-exchange sites easily accessible on the foam surfaces. The best performing samples exceeded the Pu capacity of the commercially available resin, and also offered the advantage of sharper elution profiles, resulting in a more concentrated product, with less loss of material to the dilute heads and tails cuts. An alternate approach to improving the efficiency of this process was also explored through the development of a microchannel array system for performing the anion exchange.

  6. THERMODYNAMIC ASSESSMENT OF ANIONIC LIGANDS ...

    African Journals Online (AJOL)

    DJFLEX

    2010-06-30

    Jun 30, 2010 ... ion. This brings about repulsion between the adsorbent and positively charged ion and consequently a reduction in the amount of heavy metal adsorbed at lower pH. (Lee, 1999). The effectiveness of the anionic ligands in the removal of heavy metal ions from aqueous solution seems to be low for the EDTA.

  7. Anion binding in biological systems

    Science.gov (United States)

    Feiters, Martin C.; Meyer-Klaucke, Wolfram; Kostenko, Alexander V.; Soldatov, Alexander V.; Leblanc, Catherine; Michel, Gurvan; Potin, Philippe; Küpper, Frithjof C.; Hollenstein, Kaspar; Locher, Kaspar P.; Bevers, Loes E.; Hagedoorn, Peter-Leon; Hagen, Wilfred R.

    2009-11-01

    We compare aspects of biological X-ray absorption spectroscopy (XAS) studies of cations and anions, and report on some examples of anion binding in biological systems. Brown algae such as Laminaria digitata (oarweed) are effective accumulators of I from seawater, with tissue concentrations exceeding 50 mM, and the vanadate-containing enzyme haloperoxidase is implicated in halide accumulation. We have studied the chemical state of iodine and its biological role in Laminaria at the I K edge, and bromoperoxidase from Ascophyllum nodosum (knotted wrack) at the Br K edge. Mo is essential for many forms of life; W only for certain archaea, such as Archaeoglobus fulgidus and the hyperthermophilic archaeon Pyrococcus furiosus, and some bacteria. The metals are bound and transported as their oxo-anions, molybdate and tungstate, which are similar in size. The transport protein WtpA from P. furiosus binds tungstate more strongly than molybdate, and is related in sequence to Archaeoglobus fulgidus ModA, of which a crystal structure is known. We have measured A. fulgidus ModA with tungstate at the W L3 (2p3/2) edge, and compared the results with the refined crystal structure. XAS studies of anion binding are feasible even if only weak interactions are present, are biologically relevant, and give new insights in the spectroscopy.

  8. Anion binding in biological systems

    Energy Technology Data Exchange (ETDEWEB)

    Feiters, Martin C [Department of Organic Chemistry, Institute for Molecules and Materials, Faculty of Science, Radboud University Nijmegen, Heyendaalseweg 135, 6525 AJ Nijmegen (Netherlands); Meyer-Klaucke, Wolfram [EMBL Hamburg Outstation at DESY, Notkestrasse 85, D-22607 Hamburg (Germany); Kostenko, Alexander V; Soldatov, Alexander V [Faculty of Physics, Southern Federal University, Sorge 5, Rostov-na-Donu, 344090 (Russian Federation); Leblanc, Catherine; Michel, Gurvan; Potin, Philippe [Centre National de la Recherche Scientifique and Universite Pierre et Marie Curie Paris-VI, Station Biologique de Roscoff, Place Georges Teissier, BP 74, F-29682 Roscoff cedex, Bretagne (France); Kuepper, Frithjof C [Scottish Association for Marine Science, Dunstaffnage Marine Laboratory, Oban, Argyll PA37 1QA, Scotland (United Kingdom); Hollenstein, Kaspar; Locher, Kaspar P [Institute of Molecular Biology and Biophysics, ETH Zuerich, Schafmattstrasse 20, Zuerich, 8093 (Switzerland); Bevers, Loes E; Hagedoorn, Peter-Leon; Hagen, Wilfred R, E-mail: m.feiters@science.ru.n [Department of Biotechnology, Delft University of Technology, Julianalaan 67, 2628 BC Delft (Netherlands)

    2009-11-15

    We compare aspects of biological X-ray absorption spectroscopy (XAS) studies of cations and anions, and report on some examples of anion binding in biological systems. Brown algae such as Laminaria digitata (oarweed) are effective accumulators of I from seawater, with tissue concentrations exceeding 50 mM, and the vanadate-containing enzyme haloperoxidase is implicated in halide accumulation. We have studied the chemical state of iodine and its biological role in Laminaria at the I K edge, and bromoperoxidase from Ascophyllum nodosum (knotted wrack) at the Br K edge. Mo is essential for many forms of life; W only for certain archaea, such as Archaeoglobus fulgidus and the hyperthermophilic archaeon Pyrococcus furiosus, and some bacteria. The metals are bound and transported as their oxo-anions, molybdate and tungstate, which are similar in size. The transport protein WtpA from P. furiosus binds tungstate more strongly than molybdate, and is related in sequence to Archaeoglobus fulgidus ModA, of which a crystal structure is known. We have measured A. fulgidus ModA with tungstate at the W L{sub 3} (2p{sub 3/2}) edge, and compared the results with the refined crystal structure. XAS studies of anion binding are feasible even if only weak interactions are present, are biologically relevant, and give new insights in the spectroscopy.

  9. The anionic biosurfactant rhamnolipid does not denature industrial enzymes

    Directory of Open Access Journals (Sweden)

    Jens Kvist Madsen

    2015-04-01

    Full Text Available Biosurfactants (BS are surface-active molecules produced by microorganisms. Their combination of useful properties and sustainable production make them promising industrial alternatives to petrochemical and oleochemical surfactants. Here we compare the impact of the anionic BS rhamnolipid (RL and the conventional/synthetic anionic surfactant sodium dodecyl sulfate (SDS on the structure and stability of three different commercially used enzymes, namely the cellulase Carezyme® (CZ, the phospholipase Lecitase Ultra® (LT and the α-amylase Stainzyme® (SZ. Our data reveal a fundamental difference in their mode of interaction. SDS shows great diversity of interaction towards the different enzymes. It efficiently unfolds both LT and CZ, but LT is unfolded by SDS through formation of SDS clusters on the protein well below the cmc, while CZ is only unfolded by bulk micelles and on average binds significantly less SDS than LT. SDS binds with even lower stoichiometry to SZ and leads to an increase in thermal stability. In contrast, RL does not affect the tertiary or secondary structure of any enzyme at room temperature, has little impact on thermal stability and only binds detectably (but at low stoichiometries to SZ. Furthermore all enzymes maintain activity at both monomeric and micellar concentrations of RL. We conclude that RL, despite its anionic charge, is a surfactant that does not compromise the structural integrity of industrially relevant proteins. This makes RL a promising alternative to current synthetic anionic surfactants in a wide range of commercial applications.

  10. Tripodal receptors for cation and anion sensors

    NARCIS (Netherlands)

    Kuswandi, Bambang; Nuriman, [Unknown; Verboom, Willem; Reinhoudt, David

    2006-01-01

    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

  11. Triiodide and mixed tri-halide anions from negative ion electrospray ionization of alkali halide solutions

    Science.gov (United States)

    Shukla, Anil

    2017-10-01

    Electrospray ionization of alkali halide solutions in the negative ion mode results in the formation of cluster ions of the general formula, (MX)nX-. However, alkali iodides form triiodide anion, I3-, in high abundance in addition to cluster ions. Br3- ions are observed in low abundance. Also, mixed tri-halide anions, I2Y-, are observed in high abundance when a small amount (<1%) of KI is added to other alkali halide solutions. These results are explained by the uniquely different physical characteristics of lithium and the iodide ions compared with others in the series.

  12. Recognition, Sensing and Separation of Anions

    Indian Academy of Sciences (India)

    Dr Pradyut Ghosh

    2016-11-05

    Nov 5, 2016 ... Anion Recognition. Basic Science: Coordination chemistry of anions. Potential Applications: Development of Selective. Anion Receptor towards. • Chemical Separation. • Clean Environment. • Safe Water. • Chemical Sensing. Inorg. Chem. 2011, 50, 4229. Ion Sensing. Inorg. Chem. 2010, 49, 4447. Chem.

  13. Methods and systems for measuring anions

    KAUST Repository

    Masih, Dilshad

    2016-08-18

    Embodiments of the present disclosure provide for methods for detecting the presence and/or concentration of anions in a solution, systems for detecting the presence and/or concentration of anions in a solution, anion sensor systems, and the like.

  14. Cancer Clusters

    Science.gov (United States)

    ... Genetics Services Directory Cancer Prevention Overview Research Cancer Clusters On This Page What is a cancer cluster? ... the number of cancer cases in the suspected cluster Many reported clusters include too few cancer cases ...

  15. The chemical activities of the Viking biology experiments and the arguments for the presence of superoxides, peroxides, gamma-Fe2O3 and carbon suboxide polymer in the Martian soil

    Science.gov (United States)

    Oyama, V. I.; Berdahl, B. J.; Woeller, F.; Lehwalt, M.

    1978-01-01

    The evolution of N2, Ar, O2, and CO2 from Martian soil as a function of humidity in the Gas Exchange Experiment are correlated with the mean level of water vapor in the Martian atmosphere. All but O2 are associated with desorption. The evolution of oxygen is consistent with the presence of alkaline earth and alkali metal superoxides; and their peroxides and the gamma-Fe2O3 in the soil can account for the generation of radioactive gas in the Labeled Release Experiment. The slower evolution of CO2 from both the Gas Exchange Experiment and the Labeled Release Experiment are associated with the direct oxidation of organics by gamma-Fe2O3. The Pyrolytic Release Experiment's second peak may be carbon suboxide as demonstrated by laboratory experiments. A necessary condition is that the polymer exists in the Martian soil. We ascribe the activity of the surface samples to the reaction of Martian particulates with an anhydrous CO2 atmosphere activated by uv and ionizing radiations. The surface particles are ultimately altered by exposure to small but significant amounts of water at the sites. From the working model, we have predicted the peculiar nature of the chemical entities and demonstrated that the model is justified by laboratory data. The final confirmation of this model will entail a return to Mars, but the nature and implications of this chemistry for the Martian surface is predicted to reveal even more about Mars with further simulations in the laboratory.

  16. Polymerization of anionic wormlike micelles.

    Science.gov (United States)

    Zhu, Zhiyuan; González, Yamaira I; Xu, Hangxun; Kaler, Eric W; Liu, Shiyong

    2006-01-31

    Polymerizable anionic wormlike micelles are obtained upon mixing the hydrotropic salt p-toluidine hydrochloride (PTHC) with the reactive anionic surfactant sodium 4-(8-methacryloyloxyoctyl)oxybenzene sulfonate (MOBS). Polymerization captures the cross-sectional radius of the micelles (approximately 2 nm), induces micellar growth, and leads to the formation of a stable single-phase dispersion of wormlike micellar polymers. The unpolymerized and polymerized micelles were characterized using static and dynamic laser light scattering, small-angle neutron scattering, 1H NMR, and stopped-flow light scattering. Stopped-flow light scattering was also used to measure the average lifetime of the unpolymerized wormlike micelles. A comparison of the average lifetime of unpolymerized wormlike micelles with the surfactant monomer propagation rate was used to elucidate the mechanism of polymerization. There is a significant correlation between the ratio of the average lifetime to the monomer propagation rate and the average aggregation number of the polymerized wormlike micelles.

  17. Laser Cooling of Molecular Anions

    CERN Document Server

    Yzombard, Pauline; Gerber, Sebastian; Doser, Michael; Comparat, Daniel

    2015-01-01

    We propose a scheme for laser cooling of negatively charged molecules. We briefly summarise the requirements for such laser cooling and we identify a number of potential candidates. A detailed computation study with C$\\_2^-$, the most studied molecular anion, is carried out. Simulations of 3D laser cooling in a gas phase show that this molecule could be cooled down to below 1 mK in only a few tens of milliseconds, using standard lasers. Sisyphus cooling, where no photo-detachment process is present, as well as Doppler laser cooling of trapped C$\\_2^-$, are also simulated. This cooling scheme has an impact on the study of cold molecules, molecular anions, charged particle sources and antimatter physics.

  18. 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...... and the expulsion of anions; a broad anodic peak centered at ca. - 0.5 V representing the expulsion of cations; and a second broad peak at +0.2 to +0.5 V corresponding to anions being inserted. Although the motion of cations is the most important, as expected, there is a significant anion contribution, thereby...... complicating reproducibility when employing PPy(DBS) polymers as actuators. When the cation is doubly charged, it enters the film less readily, and anions dominate the mobility. Using a large and bulky cation switches the mechanism to apparently total anion motion. The changes in area of the three peaks...

  19. From anion receptors to transporters.

    Science.gov (United States)

    Gale, Philip A

    2011-03-15

    Cystic fibrosis is the most well-known of a variety of diseases termed channelopathies, in which the regulation of ion transport across cell membranes is so disrupted that the threshold of a pathology is passed. The human toll exacted by these diseases has led a number of research groups, including our own, to create compounds that mediate ion transport across lipid bilayers. In this Account, we discuss three classes of synthetic compounds that were refined to bind and transport anions across lipid bilayer membranes. All of the compounds were originally designed as anion receptors, that is, species that would simply create stable complexes with anions, but were then further developed as transporters. By studying structurally simple systems and varying their properties to change the degree of preorganization, the affinity for anions, or the lipophilicity, we have begun to rationalize why particular anion transport mechanisms (cotransport or antiport processes) occur in particular cases. For example, we have studied the chloride transport properties of receptors based on the closely related structures of isophthalamide and pyridine-2,6-dicarboxamide: the central ring in each case was augmented with pendant methylimidazole groups designed to cotransport H(+) and Cl(-). We observed that the more preorganized pyridine-based receptor was the more efficient transporter, a finding replicated with a series of isophthalamides in which one contained hydroxyl groups designed to preorganize the receptor. This latter class of compound, together with the natural product prodigiosin, can transport bicarbonate (as part of a chloride/bicarbonate antiport process) across lipid bilayer membranes. We have also studied the membrane transport properties of calix[4]pyrroles. Although the parent meso-octamethylcalix[4]pyrrole functions solely as a Cs(+)/Cl(-) cotransporter, other compounds with increased anion affinities can function through an antiport process. One example is octafluoro

  20. Anion

    Directory of Open Access Journals (Sweden)

    A. Vadivel Murugan

    2003-01-01

    . Its characterization is investigated by Fourier Transform Infrared Spectroscopy (FT-IR and Scanning Electron Microscopy (SEM. The hybrid material presents predominantly high electronic conductivities of around 2.0 and 7.0 S cm-1 at 300 and 400K respectively.

  1. Interstellar Anions: The Role of Quantum Chemistry.

    Science.gov (United States)

    Fortenberry, Ryan C

    2015-10-01

    Six anions have been conclusively detected in the interstellar medium (ISM). They all arrived within a five-year window ending five years ago. Why have no new anions been detected? It is likely a lack of laboratory data for novel anions. This work reviews the role that valence and dipole-bound excited states may play in the formation, detection, and lifetime of anions that may yet be observed in the ISM and how quantum chemistry enhances this understanding. The list of interstellar anions has certainly not been exhausted by any means, but electronic, spectroscopic, and structural data must be provided to aid in any future detections. Quantum chemistry has the flexibility and completeness to provide a full picture of these systems and has shown exceptional accuracies of late. The work reviewed herein gives an overview of what quantum chemical computations have produced and will continue to provide related to anions and how this will enhance both laboratory experiment and astronomical observation.

  2. Polyelectrolytes with sterically hindered anionic charges

    Energy Technology Data Exchange (ETDEWEB)

    Yeh, T.F.; Liu, H.; Okamoto, Y.; Lee, H.S.; Skotheim, T.A. (Polytechnic Inst. of Brooklyn, NY (USA); Brookhaven National Lab., Upton, NY (USA))

    1989-01-01

    The central problem in the development of single phase polymer electrolytes with exclusive cation conduction has been inadequate ion mobility due to extensive ion pairing between the mobile cation and the covalently attached anion. We have developed a new class of single ion conducting polymers, or polyelectrolytes, based on highly flexible polysiloxane backbones and attached sterically hindered phenolate anions. The combination of a highly delocalized and sterically enclosed anionic charged separation and consequently enhanced cation mobility. 10 refs., 2 figs.

  3. Schlenk Techniques for Anionic Polymerization

    KAUST Repository

    Ratkanthwar, Kedar

    2015-09-01

    Anionic polymerization-high vacuum techniques (HVTs) are doubtlessly the most prominent and reliable experimental tools to prepare polymer samples with well-defined and, in many cases, complex macromolecular architectures. Due to the high demands for time and skilled technical personnel, HVTs are currently used in only a few research laboratories worldwide. Instead, most researchers in this filed are attracted to more facile Schlenk techniques. The basic principle of this technique followed in all laboratories is substantially the same, i.e. the use of alternate vacuum and inert gas atmosphere in glass apparatus for the purification/charging of monomer, solvents, additives, and for the manipulation of air-sensitive compounds such as alkyl metal initiators, organometallic or organic catalysts. However, it is executed quite differently in each research group in terms of the structure of Schlenk apparatus (manifolds, connections, purification/storage flasks, reactors, etc.), the use of small supplementary devices (soft tubing, cannulas, stopcocks, etc.) and experimental procedures. The operational methods are partly purpose-oriented while also featured by a high flexibility, which makes it impossible to describe in detail each specific one. In this chapter we will briefly exemplify the application of Schlenk techniques for anionic polymerization by describing the performance of a few experiments from our own work.

  4. Anion exchange: a novel way of preparing hierarchical porous structure in poly(ionic liquid)s.

    Science.gov (United States)

    Qin, Li; Wang, Binshen; Zhang, Yongya; Chen, Li; Gao, Guohua

    2017-03-28

    Hierarchical porous poly(ionic liquid)s (PILs) with high specific surface area were firstly synthesized via anion exchange. The exchange of bulky salicylate and its dimers/clusters in PILs by other smaller anions increased the specific surface area and fabricated a hierarchical porous structure. The high specific surface area and hierarchical porous structure prompted a high degree of exposure of the active sites and made the heterogeneous PIL catalysts contact with substrates sufficiently, enhancing their catalytic activity.

  5. Application of Multivariate Analysis in Understanding Anions in Soils Close to an Abandoned Manganese Oxide Ore Mine

    Science.gov (United States)

    Ekosse, Georges-Ivo E.

    Multivariate Analysis (MVA) was used in elucidating on the relationships and environmental implications of anions (particularly chloride, sulphate and carbonate which generally affect bioavailability of soil nutrients) in soils within the proximity of an abandoned Mn oxide ore mine in Southeastern Botswana. Four hundred soil samples were obtained from a 4 km2 area close to the abandoned mine and analysed for their anionic contents and pH. The Statistical Package for Social Sciences (SPSS) software was used for data processing. Anion concentrations in the soil samples were: chloride = 0.2 to 11.9 mg kg-1, with a mean of 7.63 mg kg-1, sulphate = 2.1 to 47.5 mg kg-1, with a mean of 19.36 mg kg-1 and carbonate = 5.1 g kg-1 to 59.1 g kg-1, with a mean of 40.98 g kg-1. Correlation coefficients depicted strong positive associations. Two clusters were produced: cluster one had the three anions with SO42¯ being the most important; and cluster two equally had all three anions but with negative t-statistic values. The anions have been continuously displaced as result of their very high mobility as reflected in lower concentrations than those from the control site.

  6. Star clusters

    NARCIS (Netherlands)

    Gieles, M.

    2006-01-01

    Star clusters are observed in almost every galaxy. In this thesis we address several fundamental problems concerning the formation, evolution and disruption of star clusters. From observations of (young) star clusters in the interacting galaxy M51, we found that clusters are formed in complexes of

  7. Dissolution of anionic surfactant mesophases.

    Science.gov (United States)

    Poulos, Andreas S; Jones, Christopher S; Cabral, João T

    2017-08-09

    Linear and circular solvent penetration experiments are used to study the dissolution of anionic SLE3S surfactant mesophases in water. We show that a lamellar (Lα) phase in contact with water will transit through a series of cubic, hexagonal, and micellar phase bands with sharp interfaces identified from their optical textures. In both linear and circular geometries, the kinetics of front propagation and eventual dissolution are well described by diffusive penetration of water, and a simple model applies to both geometries, with a different effective diffusion coefficient for water Df as the only fitting parameter. Finally, we show a surprising variation of dissolution rates with initial surfactant concentration that can be well explained by assuming that the driving force for solvent penetration is the osmotic pressure difference between neat water and the aqueous fraction of the mesophase that is highly concentrated in surfactant counterions.

  8. 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.

  9. Neutral anion receptors: design and application

    NARCIS (Netherlands)

    Antonisse, M.M.G.; Reinhoudt, David

    1998-01-01

    After the development of synthetic cation receptors in the late 1960s, only in the past decade has work started on the development of synthetic neutral anion receptors. Combination and preorganization of different anion binding groups, like amides, urea moieties, or Lewis acidic metal centers lead

  10. Weighted Clustering

    DEFF Research Database (Denmark)

    Ackerman, Margareta; Ben-David, Shai; Branzei, Simina

    2012-01-01

    We investigate a natural generalization of the classical clustering problem, considering clustering tasks in which different instances may have different weights.We conduct the first extensive theoretical analysis on the influence of weighted data on standard clustering algorithms in both...... the partitional and hierarchical settings, characterizing the conditions under which algorithms react to weights. Extending a recent framework for clustering algorithm selection, we propose intuitive properties that would allow users to choose between clustering algorithms in the weighted setting and classify...

  11. Gels based on anion recognition between triurea receptor and phosphate anion.

    Science.gov (United States)

    Yang, Cuiling; Wu, Biao; Chen, Yongming; Zhang, Ke

    2015-04-01

    Anion recognition between the triurea receptor and phosphate anion is demonstrated as the cross-linkage to build supramolecular polymer gels for the first time. A novel multi-block copolymer (3) is designed to have functional triurea groups as cross-linking units along the polymer main chain. By virtue of anion coordination between the triurea receptor and phosphate anion with a binding mode of 2:1, supramolecular polymer gels are then prepared based on anion recognition using 3 as the building block. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Creating molecular macrocycles for anion recognition

    Directory of Open Access Journals (Sweden)

    Amar H. Flood

    2016-03-01

    Full Text Available The creation and functionality of new classes of macrocycles that are shape persistent and can bind anions is described. The genesis of triazolophane macrocycles emerges out of activity surrounding 1,2,3-triazoles made using click chemistry; and the same triazoles are responsible for anion capture. Mistakes made and lessons learnt in anion recognition provide deeper understanding that, together with theory, now provides for computer-aided receptor design. The lessons are acted upon in the creation of two new macrocycles. First, cyanostars are larger and like to capture large anions. Second is tricarb, which also favors large anions but shows a propensity to self-assemble in an orderly and stable manner, laying a foundation for future designs of hierarchical nanostructures.

  13. Fungal growth on anion surfactant medium.

    Science.gov (United States)

    Hamada, Nobuo; Abe, Niichiro

    2009-12-01

    Before the present study, no fungi using anion surfactant as a nutrient had been identified, although some fungi were known to use nonion surfactant. Washing water collected from 63 washing machines was inoculated onto 0.1% LAS (Sodium dodecyl benzenesulfonate) anion surfactant media to identify fungi that can feed on anion-surfactant. Small dark colonies of fungi were found on several of the Petri-dishes from 12 days after inoculation. These were identified as Cladophialophora boppii and Exophiala spinifera using morphological features and rDNA data. A number of the isolates of C. boppii specifically were recognized as using anion surfactant as a nutrient. The growth characteristics of the two fungal species were examined on surfactant media of three kinds. Apart from anion surfactant, the fungi were also able to grow on nonion surfactant and on soap. The application of these fungi for environmental cleansing after detergent pollution is also discussed.

  14. Anion stripping as a general method to create cationic porous framework with mobile anions.

    Science.gov (United States)

    Mao, Chengyu; Kudla, Ryan A; Zuo, Fan; Zhao, Xiang; Mueller, Leonard J; Bu, Xianhui; Feng, Pingyun

    2014-05-28

    Metal-organic frameworks (MOFs) with cationic frameworks and mobile anions have many applications from sensing, anion exchange and separation, to fast ion conductivity. Despite recent progress, the vast majority of MOFs have neutral frameworks. A common mechanism for the formation of neutral frameworks is the attachment of anionic species such as F(-) or OH(-) to the framework metal sites, neutralizing an otherwise cationic scaffolding. Here, we report a general method capable of converting such neutral frameworks directly into cationic ones with concurrent generation of mobile anions. Our method is based on the differential affinity between distinct metal ions with framework anionic species. Specifically, Al(3+) is used to strip F(-) anions away from framework Cr(3+) sites, leading to cationic frameworks with mobile Cl(-) anions. The subsequent anion exchange with OH(-) further leads to a porous network with mobile OH(-) anions. New materials prepared by anion stripping can undergo ion exchange with anionic organic dyes and also exhibit much improved ionic conductivity compared to the original unmodified MOFs.

  15. Cluster management.

    Science.gov (United States)

    Katz, R

    1992-11-01

    Cluster management is a management model that fosters decentralization of management, develops leadership potential of staff, and creates ownership of unit-based goals. Unlike shared governance models, there is no formal structure created by committees and it is less threatening for managers. There are two parts to the cluster management model. One is the formation of cluster groups, consisting of all staff and facilitated by a cluster leader. The cluster groups function for communication and problem-solving. The second part of the cluster management model is the creation of task forces. These task forces are designed to work on short-term goals, usually in response to solving one of the unit's goals. Sometimes the task forces are used for quality improvement or system problems. Clusters are groups of not more than five or six staff members, facilitated by a cluster leader. A cluster is made up of individuals who work the same shift. For example, people with job titles who work days would be in a cluster. There would be registered nurses, licensed practical nurses, nursing assistants, and unit clerks in the cluster. The cluster leader is chosen by the manager based on certain criteria and is trained for this specialized role. The concept of cluster management, criteria for choosing leaders, training for leaders, using cluster groups to solve quality improvement issues, and the learning process necessary for manager support are described.

  16. Cluster Headache

    Science.gov (United States)

    ... re at risk of cluster headache. A family history. Having a parent or sibling who has had cluster headache might increase your risk. By Mayo Clinic Staff . Mayo Clinic Footer Legal Conditions and Terms ...

  17. Molecular uranates - laser synthesis of uranium oxide anions in the gas phase

    Energy Technology Data Exchange (ETDEWEB)

    Marcalo, Joaquim; Santos, Marta; Pires de Matos, Antonio; Gibson, John K

    2009-12-14

    Laser ablation of solid UO{sub 3} or (NH{sub 4}){sub 2}U{sub 2}O{sub 7} yielded in the gas phase molecular uranium oxide anions with compositions ranging from [UO{sub n}]{sup -} (n = 2-4) to [U{sub 14}O{sub n}]{sup -} (n = 32-35), as detected by Fourier transform ion cyclotron resonance mass spectrometry. The cluster series [U{sub x}O{sub 3x}]{sup -} for x {le} 6 and various [U{sub x}O{sub 3x-y}]{sup -}, in which y increased with increasing x, could be identified. A few anions with H atoms were also present, and their abundance increased when hydrated UO{sub 3} was used in place of anhydrous UO{sub 3}. Collision-induced dissociation experiments with some of the lower m/z cluster anions supported extended structures in which neutral UO{sub 3} constitutes the building block. Cationic uranium oxide clusters [U{sub x}O{sub n}]{sup +} (x = 2-9; n = 3-24) could also be produced and are briefly discussed. Common trends in the O/U ratios for both negative and positive clusters could be unveiled.

  18. Molecular anions sputtered from fluorides

    CERN Document Server

    Gnaser, H

    2002-01-01

    The emission of negatively charged ions from different fluoride samples (LiF, CaF sub 2 , LaF sub 3 and HfF sub 4) induced by sputtering with a 14.5-keV Cs sup + ion beam was studied. Sputtered ions were detected in a high-sensitivity double-focusing mass spectrometer. In particular, the possible existence of small doubly charged negative molecular ions was investigated. But whereas singly charged species of the general type MF sub n sup - (where M represents a metal atom) were detected with high abundances, stable dianions were observed in an unambiguous way only for one molecule: HfF sub 6 sup 2 sup -. The flight time through the mass spectrometer of approx 35 mu s establishes a lower limit with respect to the intrinsic lifetime of this doubly charged ion. For singly charged anions abundance distributions and, in selected cases, emission-energy spectra were recorded. For two ion species (Ca sup - and HfF sub 5 sup -) isotopic fractionation effects caused by the (velocity dependent) ionization process were d...

  19. Cluster Headache

    OpenAIRE

    Bergseng, Marta Næss

    1985-01-01

    Cluster headache is the most severe primary headache with recurrent pain attacks described as worse than giving birth. The aim of this paper was to make an overview of current knowledge on cluster headache with a focus on pathophysiology and treatment. This paper presents hypotheses of cluster headache pathophysiology, current treatment options and possible future therapy approaches. For years, the hypothalamus was regarded as the key structure in cluster headache, but is now thought to be pa...

  20. Cation effects on rotational dynamics of anions and water molecules in alkali (Li+, Na+, K+, Cs+) thiocyanate (SCN-) aqueous solutions.

    Science.gov (United States)

    Bian, Hongtao; Chen, Hailong; Zhang, Qiang; Li, Jiebo; Wen, Xiewen; Zhuang, Wei; Zheng, Junrong

    2013-07-03

    Waiting time dependent rotational anisotropies of SCN(-) anions and water molecules in alkali thiocyanate (XSCN, X = Li, Na, K, Cs) aqueous solutions at various concentrations were measured with ultrafast infrared spectroscopy. It was found that cations can significantly affect the reorientational motions of both water molecules and SCN(-) anions. The dynamics are slower in a solution with a smaller cation. The reorientational time constants follow the order of Li(+) > Na(+) > K(+) ~/= Cs(+). The changes of rotational time constants of SCN(-) at various concentrations scale almost linearly with the changes of solution viscosity, but those of water molecules do not. In addition, the concentration-dependent amplitudes of dynamical changes are much more significant in the Li(+) and Na(+) solutions than those in the K(+) and Cs(+) solutions. Further investigations on the systems with the ultrafast vibrational energy exchange method and molecular dynamics simulations provide an explanation for the observations: the observed rotational dynamics are the balanced results of ion clustering and cation/anion/water direct interactions. In all the solutions at high concentrations (>5 M), substantial amounts of ions form clusters. The structural inhomogeneity in the solutions leads to distinct rotational dynamics of water and anions. The strong interactions of Li(+) and Na(+) because of their relatively large charge densities with water molecules and SCN(-) anions, in addition to the likely geometric confinements because of ion clustering, substantially slow down the rotations of SCN(-) anions and water molecules inside the ion clusters. The interactions of K(+) and Cs(+) with water or SCN(-) are much weaker. The rotations of water molecules inside ion clusters of K(+) and Cs(+) solutions are not significantly different from those of other water species so that the experimentally observed rotational relaxation dynamics are only slightly affected by the ion concentrations.

  1. Meaningful Clusters

    Energy Technology Data Exchange (ETDEWEB)

    Sanfilippo, Antonio P.; Calapristi, Augustin J.; Crow, Vernon L.; Hetzler, Elizabeth G.; Turner, Alan E.

    2004-05-26

    We present an approach to the disambiguation of cluster labels that capitalizes on the notion of semantic similarity to assign WordNet senses to cluster labels. The approach provides interesting insights on how document clustering can provide the basis for developing a novel approach to word sense disambiguation.

  2. Source Attribution of Cyanides using Anionic Impurity Profiling, Stable Isotope Ratios, Trace Elemental Analysis and Chemometrics

    Energy Technology Data Exchange (ETDEWEB)

    Mirjankar, Nikhil S.; Fraga, Carlos G.; Carman, April J.; Moran, James J.

    2016-01-08

    Chemical attribution signatures (CAS) for chemical threat agents (CTAs) are being investigated to provide an evidentiary link between CTAs and specific sources to support criminal investigations and prosecutions. In a previous study, anionic impurity profiles developed using high performance ion chromatography (HPIC) were demonstrated as CAS for matching samples from eight potassium cyanide (KCN) stocks to their reported countries of origin. Herein, a larger number of solid KCN stocks (n = 13) and, for the first time, solid sodium cyanide (NaCN) stocks (n = 15) were examined to determine what additional sourcing information can be obtained through anion, carbon stable isotope, and elemental analyses of cyanide stocks by HPIC, isotope ratio mass spectrometry (IRMS), and inductively coupled plasma optical emission spectroscopy (ICP-OES), respectively. The HPIC anion data was evaluated using the variable selection methods of Fisher-ratio (F-ratio), interval partial least squares (iPLS), and genetic algorithm-based partial least squares (GAPLS) and the classification methods of partial least squares discriminate analysis (PLSDA), K nearest neighbors (KNN), and support vector machines discriminate analysis (SVMDA). In summary, hierarchical cluster analysis (HCA) of anion impurity profiles from multiple cyanide stocks from six reported country of origins resulted in cyanide samples clustering into three groups: Czech Republic, Germany, and United States, independent of the associated alkali metal (K or Na). The three country groups were independently corroborated by HCA of cyanide elemental profiles and corresponded to countries with known solid cyanide factories. Both the anion and elemental CAS are believed to originate from the aqueous alkali hydroxides used in cyanide manufacture. Carbon stable isotope measurements resulted in two clusters: Germany and United States (the single Czech stock grouped with United States stocks). The carbon isotope CAS is believed to

  3. Multiply-negatively charged aluminium clusters and fullerenes

    Energy Technology Data Exchange (ETDEWEB)

    Walsh, Noelle

    2008-07-15

    Multiply negatively charged aluminium clusters and fullerenes were generated in a Penning trap using the 'electron-bath' technique. Aluminium monoanions were generated using a laser vaporisation source. After this, two-, three- and four-times negatively charged aluminium clusters were generated for the first time. This research marks the first observation of tetra-anionic metal clusters in the gas phase. Additionally, doubly-negatively charged fullerenes were generated. The smallest fullerene dianion observed contained 70 atoms. (orig.)

  4. About the Clusters Program

    Science.gov (United States)

    The Environmental Technology Innovation Clusters Program advises cluster organizations, encourages collaboration between clusters, tracks U.S. environmental technology clusters, and connects EPA programs to cluster needs.

  5. On the Structure of the SF6^- Anion

    Science.gov (United States)

    Steill, Jeffrey; Compton, Robert; Bowen, K.; Stokes, Sarah

    2006-05-01

    Negative ions of Sulfur hexafluoride have been studied in detail for decades; however, there remains much to be understood about this subject. The geometry of SF6^- in its ground state is either of Oh symmetry like the parent molecule, or of a distorted C4v symmetry. The lower symmetry form with an elongated axial S-F bond is predicted by Coupled-Cluster computational methods to be lower in energy by about 0.1 eV. The calculated frequencies for the two different geometries are significantly different, providing a possible means for a definitive structure determination. Photoelectron spectra of vibrationally relaxed SF6^- give an EA of 1.0 (+/- 0.1) eV with a very broad energy spectrum, implying a significant geometry change from the neutral to the anion. This suggests the C4v form may be the likely geometry. Quasi-equilibrium theory calculations of the lifetime of SF6^- using the calculated frequencies for the anion combined with the known electron attachment rates gives a mean lifetime on the order of one millisecond. This lifetime is much larger than the lifetime derived from TOFMS methods, which is on the order of microseconds. The vibrational structure in the PES spectra is compared to the calculated frequencies for both of the possible geometries, but does not provide a completely unambiguous assignment. Therefore, we will also describe our recent attempts to measure the vibrational spectrum of gas-phase SF6^- .

  6. Data Clustering

    Science.gov (United States)

    Wagstaff, Kiri L.

    2012-03-01

    On obtaining a new data set, the researcher is immediately faced with the challenge of obtaining a high-level understanding from the observations. What does a typical item look like? What are the dominant trends? How many distinct groups are included in the data set, and how is each one characterized? Which observable values are common, and which rarely occur? Which items stand out as anomalies or outliers from the rest of the data? This challenge is exacerbated by the steady growth in data set size [11] as new instruments push into new frontiers of parameter space, via improvements in temporal, spatial, and spectral resolution, or by the desire to "fuse" observations from different modalities and instruments into a larger-picture understanding of the same underlying phenomenon. Data clustering algorithms provide a variety of solutions for this task. They can generate summaries, locate outliers, compress data, identify dense or sparse regions of feature space, and build data models. It is useful to note up front that "clusters" in this context refer to groups of items within some descriptive feature space, not (necessarily) to "galaxy clusters" which are dense regions in physical space. The goal of this chapter is to survey a variety of data clustering methods, with an eye toward their applicability to astronomical data analysis. In addition to improving the individual researcher’s understanding of a given data set, clustering has led directly to scientific advances, such as the discovery of new subclasses of stars [14] and gamma-ray bursts (GRBs) [38]. All clustering algorithms seek to identify groups within a data set that reflect some observed, quantifiable structure. Clustering is traditionally an unsupervised approach to data analysis, in the sense that it operates without any direct guidance about which items should be assigned to which clusters. There has been a recent trend in the clustering literature toward supporting semisupervised or constrained

  7. Studies of anions sorption on natural zeolites.

    Science.gov (United States)

    Barczyk, K; Mozgawa, W; Król, M

    2014-12-10

    This work presents results of FT-IR spectroscopic studies of anions-chromate, phosphate and arsenate - sorbed from aqueous solutions (different concentrations of anions) on zeolites. The sorption has been conducted on natural zeolites from different structural groups, i.e. chabazite, mordenite, ferrierite and clinoptilolite. The Na-forms of sorbents were exchanged with hexadecyltrimethylammonium cations (HDTMA(+)) and organo-zeolites were obtained. External cation exchange capacities (ECEC) of organo-zeolites were measured. Their values are 17mmol/100g for chabazite, 4mmol/100g for mordenite and ferrierite and 10mmol/100g for clinoptilolite. The used initial inputs of HDTMA correspond to 100% and 200% ECEC of the minerals. Organo-modificated sorbents were subsequently used for immobilization of mentioned anions. It was proven that aforementioned anions' sorption causes changes in IR spectra of the HDTMA-zeolites. These alterations are dependent on the kind of anions that were sorbed. In all cases, variations are due to bands corresponding to the characteristic Si-O(Si,Al) vibrations (occurring in alumino- and silicooxygen tetrahedra building spatial framework of zeolites). Alkylammonium surfactant vibrations have also been observed. Systematic changes in the spectra connected with the anion concentration in the initial solution have been revealed. The amounts of sorbed CrO4(2-), AsO4(3-) and PO4(3-) ions were calculated from the difference between their concentrations in solutions before (initial concentration) and after (equilibrium concentration) sorption experiments. Concentrations of anions were determined by spectrophotometric method. Copyright © 2014 Elsevier B.V. All rights reserved.

  8. Structures and energetics of small lead cluster ions.

    Science.gov (United States)

    Kelting, Rebecca; Otterstätter, Robin; Weis, Patrick; Drebov, Nedko; Ahlrichs, Reinhart; Kappes, Manfred M

    2011-01-14

    By a combination of gas phase ion mobility measurements and relativistic density functional theory calculations with inclusion of spin-orbit coupling, we assign structures of lead cluster cations and anions in the range between 4 and 15 atoms. We find a planar rhombus for the tetramer, a trigonal bipyramid for the pentamer, and a pentagonal bipyramid for the heptamer, independent of charge state. For the hexamer, the cation and anion structures differ: we find an octahedron for the anion while the cation consists of fused tetrahedra. For the octamer, we find in both cases structures based on the pentagonal bipyramid motif plus adatom. For the larger clusters investigated we always find different structures for cations and anions. For example, Pb(12)(-) is confirmed to be a hollow icosahedron while Pb(12)(+) is a truncated filled icosahedron. Pb(13)(+) is a filled icosahedron but Pb(13)(-) is a hollow icosahedron with the additional atom capping a face. In order to get experimental information on the relative stabilities, we investigated the collision induced dissociation mass spectra for the different cluster sizes and charge states, and observe a strong correlation with the calculated fragmentation energies. Up to n = 13 the main fragmentation channel is atom loss; for the larger cluster sizes we observe fission into two large fragments. This channel is dominant for larger anions, less pronounced but clearly present for the cations.

  9. Supramolecular Chemistry of Selective Anion Recognition for Anions of Environmental Relevance

    Energy Technology Data Exchange (ETDEWEB)

    Bowman-James, Kristen

    2004-12-01

    This project have focuses on the basic chemical aspects of anion receptor design of functional pH independent systems, with the ultimate goal of targeting the selective binding of sulfate, as well as design of separations strategies for selective and efficient removal of targeted anions. Key findings include: (1) the first synthetic sulfate-selective anion-binding agents; (2) simple, structure-based methods for modifying the intrinsic anion selectivity of a given class of anion receptors; and (3) the first system capable of extracting sulfate anion from acidic, nitrate-containing aqueous media. Areas probed during the last funding period include: the design, synthesis, and physical and structural characterization of receptors and investigation of anion and dual ion pair extraction using lipophilic amide receptors for anion binding. A new collaboration has been added to the project in addition to the one with Dr. Bruce Moyer at Oak Ridge National Laboratory, with Professor Jonathan Sessler at the University of Texas at Austin.

  10. Anion Recognition by Aliphatic Helical Oligoureas.

    Science.gov (United States)

    Diemer, Vincent; Fischer, Lucile; Kauffmann, Brice; Guichard, Gilles

    2016-10-24

    Anion binding properties of neutral helical foldamers consisting of urea type units in their backbone have been investigated. (1) H NMR titration studies in various organic solvents including DMSO suggest that the interaction between aliphatic oligoureas and anions (CH3 COO(-) , H2 PO4(-) , Cl(-) ) is site-specific, as it largely involves the urea NHs located at the terminal end of the helix (positive pole of the helix), which do not participate to the helical intramolecular hydrogen-bonding network. This mode of binding parallels that found in proteins in which anion-binding sites are frequently found at the N-terminus of an α-helix. (1) H NMR studies suggest that the helix of oligoureas remains largely folded upon anion binding, even in the presence of a large excess of the anion. This study points to potentially useful applications of oligourea helices for the selective recognition of small guest molecules. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Anion exchange in ionic liquid mixtures.

    Science.gov (United States)

    Cha, Seoncheol; Kim, Doseok

    2015-11-28

    Advantage of ionic liquids as designer solvents can be maximized by mixing different ionic liquids (ILs) for a possibility of continuous tunability of material properties. The property of these mixed ILs would be determined by their microscopic conformation between cations and anions. The mixtures of two ILs having 1-butyl-3-methylimidaolium cations and different anions were investigated by IR and NMR spectroscopy, utilizing that the vibrational frequencies of the C-H stretching and bending modes of the most acidic proton in the imidazolium ring of the cation and the NMR chemical shift for the corresponding proton were clearly distinct between the ILs having different anions. The IR absorption spectra of the IL mixtures at different concentrations were well-matched to weighted sums of the two spectra of the pure ILs. In contrast, the two distinct peaks in the NMR spectra of the pure ILs coalesced into a single peak, which shifted continuously following the relative portion of two different ILs in the mixture. IR spectroscopy in the optical frequency range seems to take the instantaneous snapshot of the cation-anion interaction, while NMR spectroscopy in the radio-frequency (∼500 MHz) range samples over a much longer timescale, enough for the cation to interact with different anion species in the mixture.

  12. Approximation Clustering

    Indian Academy of Sciences (India)

    First page Back Continue Last page Overview Graphics. Approximation Clustering. Clustering within (1+ ε) of the optimum cost. ε is user defined tolerance. For metric spaces even approximating is. hard (below, say 30%). Euclidean k-median in fixed dimension can. be approximated in polynomial time.

  13. Cluster Matters

    DEFF Research Database (Denmark)

    Gulati, Mukesh; Lund-Thomsen, Peter; Suresh, Sangeetha

    2018-01-01

    In this chapter, we investigate corporate social responsibility (CSR) in industrial clusters in the Indian context. We use the definition of CSR as given in the Indian Ministry of Corporate Affairs’ National Voluntary Guidelines (NVGs) for Business Responsibility: ‘the commitment of an enterprise...... sell their products successfully in international markets, but there is also an increasingly large consumer base within India. Indeed, Indian industrial clusters have contributed to a substantial part of this growth process, and there are several hundred registered clusters within the country....... At the same time, several attempts have been made at promoting the adoption of CSR in MSMEs in Indian industrial clusters. In fact, India has proved to be a kind of laboratory for experimenting with different types of cluster-based CSR and is thus an interesting location in relation to the broader aim...

  14. High Vacuum Techniques for Anionic Polymerization

    KAUST Repository

    Ratkanthwar, Kedar

    2015-09-01

    Anionic polymerization high vacuum techniques (HVTs) are the most suitable for the preparation of polymer samples with well-defined complex macromolecular architectures. Though HVTs require glassblowing skill for designing and making polymerization reactor, it is the best way to avoid any termination of living polymers during the number of steps for the synthesis of polymers with complex structure. In this chapter, we describe the different polymerization reactors and HVTs for the purification of monomers, solvents, and other reagents for anionic polymerization as well as few model reactions for the synthesis of polymers with simple to complex structure.

  15. Clustering Dycom

    KAUST Repository

    Minku, Leandro L.

    2017-10-06

    Background: Software Effort Estimation (SEE) can be formulated as an online learning problem, where new projects are completed over time and may become available for training. In this scenario, a Cross-Company (CC) SEE approach called Dycom can drastically reduce the number of Within-Company (WC) projects needed for training, saving the high cost of collecting such training projects. However, Dycom relies on splitting CC projects into different subsets in order to create its CC models. Such splitting can have a significant impact on Dycom\\'s predictive performance. Aims: This paper investigates whether clustering methods can be used to help finding good CC splits for Dycom. Method: Dycom is extended to use clustering methods for creating the CC subsets. Three different clustering methods are investigated, namely Hierarchical Clustering, K-Means, and Expectation-Maximisation. Clustering Dycom is compared against the original Dycom with CC subsets of different sizes, based on four SEE databases. A baseline WC model is also included in the analysis. Results: Clustering Dycom with K-Means can potentially help to split the CC projects, managing to achieve similar or better predictive performance than Dycom. However, K-Means still requires the number of CC subsets to be pre-defined, and a poor choice can negatively affect predictive performance. EM enables Dycom to automatically set the number of CC subsets while still maintaining or improving predictive performance with respect to the baseline WC model. Clustering Dycom with Hierarchical Clustering did not offer significant advantage in terms of predictive performance. Conclusion: Clustering methods can be an effective way to automatically generate Dycom\\'s CC subsets.

  16. Cluster analysis

    CERN Document Server

    Everitt, Brian S; Leese, Morven; Stahl, Daniel

    2011-01-01

    Cluster analysis comprises a range of methods for classifying multivariate data into subgroups. By organizing multivariate data into such subgroups, clustering can help reveal the characteristics of any structure or patterns present. These techniques have proven useful in a wide range of areas such as medicine, psychology, market research and bioinformatics.This fifth edition of the highly successful Cluster Analysis includes coverage of the latest developments in the field and a new chapter dealing with finite mixture models for structured data.Real life examples are used throughout to demons

  17. Anion conductance of the human red cell is carried by a maxi-anion channel

    DEFF Research Database (Denmark)

    Glogowska, Edyta; Dyrda, Agnieszka; Cueff, Anne

    2010-01-01

    Historically, the anion transport through the human red cell membrane has been perceived to be mediated by Band 3, in the two-component concept with the large electroneutral anion exchange accompanied by the conductance proper, which dominated the total membrane conductance. The status of anion...... to the red cell than the ground leak mediated by Band 3....... channels proper has never been clarified, and the informations obtained by different groups of electrophysiologists are rather badly matched. This study, using the cell-attached configuration of the patch-clamp technique, rationalizes and explains earlier confusing results by demonstrating...

  18. Ab Initio Computational Study of Chromate Molecular Anion Adsorption on the Surfaces of Pristine and B- or N-Doped Carbon Nanotubes and Graphene.

    Science.gov (United States)

    Hizhnyi, Yuriy; Nedilko, Sergii; Borysiuk, Viktor; Shyichuk, Andrii

    2017-12-01

    Density functional theory (DFT) computations of the electronic structures of undoped, B- and N-doped CNT(3,3), CNT(5,5) carbon nanotubes, and graphene with adsorbed chromate anions CrO42- were performed within molecular cluster approach. Relaxed geometries, binding energies, charge differences of the adsorbed CrO42- anions, and electronic wave function contour plots were calculated using B3LYP hybrid exchange-correlation functional. Oscillator strengths of electronic transitions of CrO42- anions adsorbed on the surfaces of studied carbon nanostructures were calculated by the TD-DFT method. Calculations reveal covalent bonding between the anion and the adsorbents in all studied adsorption configurations. For all studied types of adsorbent structures, doping with N strengthens chemical bonding with CrO42- anions, providing a ~2-eV increase in binding energies comparatively to adsorption of the anion on undoped adsorbents. Additional electronic transitions of CrO42- anions appear in the orange-green spectral region when the anions are adsorbed on the N-doped low-diameter carbon nanotubes CNT(3,3) and CNT(5,5).

  19. Ab Initio Computational Study of Chromate Molecular Anion Adsorption on the Surfaces of Pristine and B- or N-Doped Carbon Nanotubes and Graphene

    Science.gov (United States)

    Hizhnyi, Yuriy; Nedilko, Sergii; Borysiuk, Viktor; Shyichuk, Andrii

    2017-01-01

    Density functional theory (DFT) computations of the electronic structures of undoped, B- and N-doped CNT(3,3), CNT(5,5) carbon nanotubes, and graphene with adsorbed chromate anions CrO4 2- were performed within molecular cluster approach. Relaxed geometries, binding energies, charge differences of the adsorbed CrO4 2- anions, and electronic wave function contour plots were calculated using B3LYP hybrid exchange-correlation functional. Oscillator strengths of electronic transitions of CrO4 2- anions adsorbed on the surfaces of studied carbon nanostructures were calculated by the TD-DFT method. Calculations reveal covalent bonding between the anion and the adsorbents in all studied adsorption configurations. For all studied types of adsorbent structures, doping with N strengthens chemical bonding with CrO4 2- anions, providing a 2-eV increase in binding energies comparatively to adsorption of the anion on undoped adsorbents. Additional electronic transitions of CrO4 2- anions appear in the orange-green spectral region when the anions are adsorbed on the N-doped low-diameter carbon nanotubes CNT(3,3) and CNT(5,5).

  20. Cluster editing

    DEFF Research Database (Denmark)

    Böcker, S.; Baumbach, Jan

    2013-01-01

    The Cluster Editing problem asks to transform a graph into a disjoint union of cliques using a minimum number of edge modifications. Although the problem has been proven NP-complete several times, it has nevertheless attracted much research both from the theoretical and the applied side. The prob......The Cluster Editing problem asks to transform a graph into a disjoint union of cliques using a minimum number of edge modifications. Although the problem has been proven NP-complete several times, it has nevertheless attracted much research both from the theoretical and the applied side....... The problem has been the inspiration for numerous algorithms in bioinformatics, aiming at clustering entities such as genes, proteins, phenotypes, or patients. In this paper, we review exact and heuristic methods that have been proposed for the Cluster Editing problem, and also applications...

  1. Donnan Membrane Technique (DMT) for Anion Measurement

    NARCIS (Netherlands)

    Alonso Vega, M.F.; Weng, L.P.; Temminghoff, E.J.M.; Riemsdijk, van W.H.

    2010-01-01

    Donnan membrane technique (DMT) is developed and tested for determination of free anion concentrations. Time needed to reach the Donnan membrane equilibrium depends on type of ions and the background. The Donnan membrane equilibrium is reached in 1 day for Cl-, 1-2 days for NO3-, 1-4 days for SO42-

  2. Mechanisms of renal anionic drug transport.

    NARCIS (Netherlands)

    El-Sheikh, A.A.K.; Masereeuw, R.; Russel, F.G.M.

    2008-01-01

    By utilizing filtration, active secretion and reabsorption processes, the kidney can conserve essential nutrients, and eliminate drugs and potentially toxic compounds. Active uptake of organic anions and cations across the basolateral membrane, and their extrusion into the urine across the brush

  3. Stoichiometry of uranyl salophene anion complexes

    NARCIS (Netherlands)

    Antonisse, M.M.G.; Ruel, Bianca H.M.; Engbersen, Johannes F.J.; Reinhoudt, David

    1998-01-01

    In PVC/NPOE ion-selective membranes of potentiometric sensors, the guest-host stoichiometry of the anion complex of H2PO4 - and F- selective uranyl salophene derivatives is 2:1. This stoichiometry is different from the stoichiometry observed in DMSO solution (1H NMR) or solid state (X-ray crystal

  4. Anion exchange membrane design for reverse electrodialysis

    NARCIS (Netherlands)

    Güler, E.

    2014-01-01

    Reverse electrodialysis (RED) is a clean, sustainable technology for the generation of energy from the mixing of solutions with different salinity. The ion exchange membranes are key elements in RED. Especially the study of anion exchange membranes is crucial since limited research has been done

  5. Anion-Conducting Polymer, Composition, and Membrane

    Science.gov (United States)

    Pivovar, Bryan S.; Thorn, David L.

    2008-10-21

    Anion-conducing polymers and membranes with enhanced stability to aqueous alkali include a polymer backbone with attached sulfonium, phosphazenium, phosphazene, and guanidinium residues. Compositions also with enhanced stability to aqueous alkali include a support embedded with sulfonium, phosphazenium, and guanidinium salts.

  6. Structural, electronic, vibrational and optical properties of Bin clusters

    Science.gov (United States)

    Liang, Dan; Shen, Wanting; Zhang, Chunfang; Lu, Pengfei; Wang, Shumin

    2017-10-01

    The neutral, anionic and cationic bismuth clusters with the size n up to 14 are investigated by using B3LYP functional within the regime of density functional theory and the LAN2DZ basis set. By analysis of the geometries of the Bin (n = 2-14) clusters, where cationic and anionic bismuth clusters are largely similar to those of neutral ones, a periodic effect by adding units with one to four atoms into smaller cluster to form larger cluster is drawn for the stable structures of bismuth clusters. An even-odd alteration is shown for the properties of the clusters, such as the calculated binding energies and dissociation energies, as well as frontier orbital energies, electron affinities, ionization energies. All the properties indicate that the Bi4 cluster is the most possible existence in bismuth-containing materials, which supports the most recent experiment. The orbital compositions, infrared and Raman activities and the ultraviolet absorption of the most possible tetramer bismuth cluster are given in detail to reveal the periodic tendency of adding bismuth atoms and the stability of tetramer bismuth cluster.

  7. Synthesis and anion-exchange reactions of a new anionic clay, α-magnesium hydroxide.

    Science.gov (United States)

    Nethravathi, C; Rajamathi, Jacqueline T; George, Preeta; Rajamathi, Michael

    2011-02-15

    A new anionic clay, α-magnesium hydroxide, was synthesized by hydrolysis of magnesium acetate in propylene glycol. The structure of this α-hydroxide is similar to that of hydrotalcites. It consists of positively charged magnesium hydroxide layers arising out of partial protonation of the hydroxyl groups of the [Mg(OH)(2)] layers and loosely held anions in the interlayer region. As expected it ages readily in water to give β-magnesium hydroxide, brucite. While anion-exchange reactions of α-magnesium hydroxide could not be carried out in aqueous medium a number of anion-exchange reactions could be carried out successfully in ethanol medium. Copyright © 2010 Elsevier Inc. All rights reserved.

  8. Benzodipyrrole derivates as new ionophores for anion-selective electrodes: improving potentiometric selectivity towards divalent anions.

    Science.gov (United States)

    Cuartero, M; Ortuño, J A; García, M S; Sánchez, G; Más-Montoya, M; Curiel, D

    2011-09-30

    Two open substituted benzodipyrroles were tested as hydrogen-bond-forming anion ionophores for the development of anion-selective electrodes. These compounds were incorporated in plasticized polymeric membranes with different plasticizers, using different membrane compositions to explore their response towards several anions. The electrodes constructed with membranes containing 2-nitrophenyl octyl ether and a 0.5 molar ratio ionic additive/ionophore showed pronounced anti-Hofmeister behaviour, providing a significantly enhanced response towards the divalent anions sulfate, sulfite, thiosulfate and oxalate. The selected electrodes were also evaluated in terms of detection limits and selectivity. (1)H NMR experiments were carried out in an attempt to explain some aspects of the behaviour observed. Copyright © 2011 Elsevier B.V. All rights reserved.

  9. Advances in anion supramolecular chemistry: from recognition to chemical applications.

    Science.gov (United States)

    Evans, Nicholas H; Beer, Paul D

    2014-10-27

    Since the start of this millennium, remarkable progress in the binding and sensing of anions has been taking place, driven in part by discoveries in the use of hydrogen bonding, as well as the previously under-exploited anion-π interactions and halogen bonding. However, anion supramolecular chemistry has developed substantially beyond anion recognition, and now encompasses a diverse range of disciplines. Dramatic advance has been made in the anion-templated synthesis of macrocycles and interlocked molecular architectures, while the study of transmembrane anion transporters has flourished from almost nothing into a rapidly maturing field of research. The supramolecular chemistry of anions has also found real practical use in a variety of applications such as catalysis, ion extraction, and the use of anions as stimuli for responsive chemical systems. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Bussines Clusters

    Directory of Open Access Journals (Sweden)

    Sarmiza Pencea

    2010-10-01

    Full Text Available Clusters are complex economic structures in which similar companies, their up-stream and down-stream business partners, universities, research institutes, educational units, various service providers, diverse private and public institutions concentrate geografically, striving to get economies of agglomeration and scale, to capitalize on the resulting spill over effects, to cut costs, to better harness resources, to exchange information and experience, to improve quality, innovation, skills and productivity. By somehow unexpectedly combining competition and cooperation, they form a new, sophisticated stage in the evolution of production structures in quest of higher efficiency. This paper forays into the world of clusters and clusterization, which seem to increasingly capture the interest of businesses, scholars and policy makers. It looks at what clusters are, how they arise, what are their specific features, what benefits and challenges they can generate for companies and for the regions in which they locate and if and how they should be fostered by industrial policy interventions. The conclusion is that clusters can be very important development triggers and therefore they should be encouraged and nurtured by adequate policy measures. They should not only be used as a regular policy tool, but be placed at the very center of the development strategies of emerging economies.

  11. Cluster forcing

    DEFF Research Database (Denmark)

    Christensen, Thomas Budde

    The cluster theory attributed to Michael Porter has significantly influenced industrial policies in countries across Europe and North America since the beginning of the 1990s. Institutions such as the EU, OECD and the World Bank and governments in countries such as the UK, France, The Netherlands......, Portugal and New Zealand have adopted the concept. Public sector interventions that aim to support cluster development in industries most often focus upon economic policy goals such as enhanced employment and improved productivity, but rarely emphasise broader societal policy goals relating to e.......g. sustainability or quality of life. The purpose of this paper is to explore how and to what extent public sector interventions that aim at forcing cluster development in industries can support sustainable development as defined in the Brundtland tradition and more recently elaborated in such concepts as eco-industrialism...

  12. Effect of morphology of thin DNA films on the electron stimulated desorption of anions

    Science.gov (United States)

    Mirsaleh-Kohan, Nasrin; Bass, Andrew D.; Sanche, Léon

    2011-01-01

    We present a comparison between the electron stimulated desorption (ESD) of anions from DNA samples prepared by lyophilization (an example of poorly organized or nonuniform films) and molecular self-assembly (well-ordered films). The lyophilization (or freeze- drying) method is perhaps the most frequently employed technique for forming DNA films for studies of low-energy electron (LEE) interactions leading to DNA damage; however, this technique usually produces nonuniform films with considerable clustering which may affect DNA configuration and enhance sample charging when the film is irradiated. Our results confirm the general validity of ESD measurements obtained with lyophilized samples, but also reveal limitations of lyophilization for LEE studies on DNA films. Specifically we observe some modulation of structures, associated with dissociative electron attachment, in the anion yield functions from different types of DNA film, confirming that conformational factors play a role in the LEE induced damage to DNA.

  13. Heavy atom vibrational modes and low-energy vibrational autodetachment in nitromethane anions

    Energy Technology Data Exchange (ETDEWEB)

    Thompson, Michael C.; Weber, J. Mathias, E-mail: weberjm@jila.colorado.edu [JILA, University of Colorado at Boulder, 440 UCB, Boulder, Colorado 80309-0440 (United States); Department of Chemistry and Biochemistry, University of Colorado at Boulder, 215UCB, Boulder, Colorado 80309-0215 (United States); Baraban, Joshua H. [Department of Chemistry and Biochemistry, University of Colorado at Boulder, 215UCB, Boulder, Colorado 80309-0215 (United States); Matthews, Devin A. [Institute for Computational Engineering and Science, University of Texas at Austin, 201 E. 24th St., Austin, Texas 78712 (United States); Stanton, John F. [Department of Chemistry and Biochemistry, University of Texas at Austin, 1 University Station A5300, Austin, Texas 78712-0165 (United States)

    2015-06-21

    We report infrared spectra of nitromethane anion, CH{sub 3}NO{sub 2}{sup −}, in the region 700–2150 cm{sup −1}, obtained by Ar predissociation spectroscopy and electron detachment spectroscopy. The data are interpreted in the framework of second-order vibrational perturbation theory based on coupled-cluster electronic structure calculations. The modes in the spectroscopic region studied here are mainly based on vibrations involving the heavier atoms; this work complements earlier studies on nitromethane anion that focused on the CH stretching region of the spectrum. Electron detachment begins at photon energies far below the adiabatic electron affinity due to thermal population of excited vibrational states.

  14. Anion Binding of One-, Two-, and Three-Armed Thiourea Receptors Examined via Photoelectron Spectroscopy and Quantum Computations.

    Science.gov (United States)

    Beletskiy, Evgeny V; Wang, Xue-Bin; Kass, Steven Robert

    2016-10-05

    A benzene ring substituted with 1-3 thiourea containing arms (1-3) were examined by photoelectron spectroscopy and density functional theory computations. Their conjugate bases and chloride, acetate and dihydrogen phosphate anion clusters are reported. The resulting vertical and adiabatic detachment energies span from 3.93 - 5.82 eV (VDE) and 3.65 - 5.10 (ADE) for the deprotonated species and 4.88 - 5.97 eV (VDE) and 4.45 - 5.60 eV (ADE) for the anion complexes. These results reveal the stabilizing effects of multiple hydrogen bonds and anionic host-guest interactions in the gas phase. Previously measured equilibrium binding constants in aqueous dimethyl sulfoxide for all three thioureas are compared to the present results and cooperative binding is uniformly observed in the gas phase but only for one case (i.e., 3 • H2PO4-) in solution.

  15. Studies on cluster, salt and molecular complex of zinc-quinolinate

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 127; Issue 2. Studies on cluster ... Keywords. Zinc-clusters; molecular complex; hydrolytic equilibrium; zinc oxide; porous material. ... Complex 5 is formed from a hydrolytic equilibrium of water with zinc chloride yielding tetrachloro zinc anion and zinc hydroxide. Taking ...

  16. Electron attachment and electron ionization of acetic acid clusters embedded in helium nanodroplets

    NARCIS (Netherlands)

    da Silva, F. Ferreira; Jaksch, S.; Martins, G.; Dang, H. M.; Dampc, M.; Denifl, S.; Maerk, T. D.; Limao-Vieira, P.; Liu, J.; Yang, S.; Ellis, A. M.; Scheier, P.

    2009-01-01

    The effect of incident electrons on acetic acid clusters is explored for the first time. The acetic acid clusters are formed inside liquid helium nanodroplets and both cationic and anionic products ejected into the gas phase are detected by mass spectrometry. The cation chemistry (induced by

  17. Several hemicyanine dyes as fluorescence chemosensors for cyanide anions

    Science.gov (United States)

    Liang, Muhan; Wang, Kangnan; Guan, Ruifang; Liu, Zhiqiang; Cao, Duxia; Wu, Qianqian; Shan, Yanyan; Xu, Yongxiao

    2016-05-01

    Four hemicyanine dyes as chemosensors for cyanide anions were synthesized easily. Their photophysical properties and recognition properties for cyanide anions were investigated. The results indicate that all the dyes can recognize cyanide anions with obvious color, absorption and fluorescence change. The recognition mechanism analysis basing on in situ 1H NMR and Job plot data indicates that to the compounds with hydroxyl group, the recognition mechanism is intramolecular hydrogen bonding interaction. However, to the compounds without hydroxyl group, cyanide anion is bonded to carbon-carbon double bond in conjugated bridge and induces N+ CH3 to neutral NCH3. Fluorescence of the compounds is almost quenched upon the addition of cyanide anions.

  18. Femtosecond photoelectron spectroscopy: a new tool for the study of anion dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Greenblatt, Benjamin J. [Univ. of California, Berkeley, CA (United States)

    1999-02-01

    A new experimental technique for the time-resolved study of anion reactions is presented. Using femtosecond laser pulses, which provide extremely fast (~100 fs) time resolution, in conjunction with photoelectron spectroscopy, which reveals differences between anion and neutral potential energy surfaces, a complex anion reaction can be followed from its inception through the formation of asymptotic products. Experimental data can be modeled quantitatively using established theoretical approaches, allowing for the refinement of potential energy surfaces as well as dynamical models. After a brief overview, a detailed account of the construction of the experimental apparatus is presented. Documentation of the data acquisition program is contained in the Appendix. The first experimental demonstration of the technique is then presented for I2- photodissociation, modeled using a simulation program which is also detailed in the Appendix. The investigation of I2- photodissociation in several size-selected I2-(Ar)n (n = 6-20) and I2-(CO2)n (n = 4-16) clusters forms the heart of the dissertation. In a series of chapters, the numerous effects of solvation on this fundamental bond-breaking reaction are explored, the most notable of which is the recombination of I2- on the ground $\\tilde{X}$(2Σu+) state in sufficiently large clusters. Recombination and trapping of I2- on the excited $\\tilde{A}$(2π3/2,g) state is also observed in both types of clusters. The studies have revealed electronic state transitions, the first step in recombination, on a ~500 fs to ~10 ps timescale. Accompanying the changes in electronic state is solvent reorganization, which occurs on a similar timescale. Over longer periods (~1 ps to >200 ps), energy is transferred from vibrationally

  19. Politseiuuringud kooskõlastamisele / Liivia Anion

    Index Scriptorium Estoniae

    Anion, Liivia

    2003-01-01

    1. aprillil 2003. a. moodustatud uurimistööde kooskõlastamise komisjoni tegevuse eesmärk on saada ülevaade kõrgkoolides õppivate töötajate poolt politseis korraldatavatest uurimustest, kasutada saadud infot politsei kasuks ja vältida teenistujate tööd segavate uurimuste tegemist. Komisjoni liige Liivia Anion teeb ülevaate komisjoni otsustuspädevuse valdkondadest ja töökorraldusest

  20. Metal-organic framework supported ionic liquid membranes for CO2 capture: anion effects.

    Science.gov (United States)

    Gupta, Krishna M; Chen, Yifei; Hu, Zhongqiao; Jiang, Jianwen

    2012-04-28

    IRMOF-1 supported ionic liquid (IL) membranes are investigated for CO(2) capture by atomistic simulation. The ILs consist of identical cation 1-n-butyl-3-methylimidazolium [BMIM](+), but four different anions, namely hexafluorophosphate [PF(6)](-), tetrafluoroborate [BF(4)](-), bis(trifluoromethylsulfonyl)imide [Tf(2)N](-), and thiocyanate [SCN](-). As compared with the cation, the anion has a stronger interaction with IRMOF-1 and a more ordered structure in IRMOF-1. The small anions [PF(6)](-), [BF(4)](-), and [SCN](-) prefer to locate near to the metal-cluster, particularly the quasi-spherical [PF(6)](-) and [BF(4)](-). In contrast, the bulky and chain-like [BMIM](+) and [Tf(2)N](-) reside near the phenyl ring. Among the four anions, [Tf(2)N](-) has the weakest interaction with IRMOF-1 and thus the strongest interaction with [BMIM](+). With increasing the weight ratio of IL to IRMOF-1 (W(IL/IRMOF-1)), the selectivity of CO(2)/N(2) at infinite dilution is enhanced. At a given W(IL/IRMOF-1), the selectivity increases as [Tf(2)N](-) calculation. In the [BMIM][SCN]/IRMOF-1 membrane with W(IL/IRMOF-1) = 1, [SCN](-) is identified to be the most favorable site for CO(2) adsorption. [BMIM][SCN]/IRMOF-1 outperforms polymer membranes and polymer-supported ILs in CO(2) permeability, and its performance surpasses Robeson's upper bound. This simulation study reveals that the anion has strong effects on the microscopic properties of ILs and suggests that MOF-supported ILs are potentially intriguing for CO(2) capture. This journal is © the Owner Societies 2012

  1. Photoelectron imaging of cyanovinylidene and cyanoacetylene anions.

    Science.gov (United States)

    Goebbert, Daniel J; Khuseynov, Dmitry; Sanov, Andrei

    2010-02-18

    Negative ions of cyanoacetylene and cyanovinylidene are generated simultaneously via the competing 1,1-H(2)(+) and 1,2-H(2)(+) abstraction channels of O(-) reaction with acrylonitrile. The two stable isomeric forms of the anion, CCHCN(-) and HCCCN(-), are separated by a large (approximately 2 eV) potential energy barrier. Their photodetachment provides access to both the reactant and the product sides of the neutral cyanovinylidene --> cyanoacetylene rearrangement reaction, predicted to involve only a very small barrier. Using photoelectron imaging spectroscopy at 532 and 355 nm, the adiabatic electron affinity of the reactive intermediate :C horizontal lineCHCN (X(1)A'), is determined to be 1.84 +/- 0.01 eV. The photoelectron spectrum of CCHCN(-) exhibits a vibrational progression attributed to the excitation of the CCH bending mode. The observed spectral features are reproduced reasonably well using a Franck-Condon simulation under the parallel-mode approximation. In contrast to unsubstituted acetylene, cyanoacetylene has a stable anionic state, which is adiabatically weakly bound, but has an experimentally determined vertical detachment energy of 1.04 +/- 0.05 eV. This measurement, along with the broad, structureless photoelectron spectrum of HCCCN(-) (with no identifiable origin), reflects the large geometry difference between the w-shaped structure of the anion and the linear equilibrium geometry of HCCCN.

  2. Water permeation through anion exchange membranes

    Science.gov (United States)

    Luo, Xiaoyan; Wright, Andrew; Weissbach, Thomas; Holdcroft, Steven

    2018-01-01

    An understanding of water permeation through solid polymer electrolyte (SPE) membranes is crucial to offset the unbalanced water activity within SPE fuel cells. We examine water permeation through an emerging class of anion exchange membranes, hexamethyl-p-terphenyl poly (dimethylbenzimidazolium) (HMT-PMBI), and compare it against series of membrane thickness for a commercial anion exchange membrane (AEM), Fumapem® FAA-3, and a series of proton exchange membranes, Nafion®. The HMT-PMBI membrane is found to possess higher water permeabilities than Fumapem® FAA-3 and comparable permeability than Nafion (H+). By measuring water permeation through membranes of different thicknesses, we are able to decouple, for the first time, internal and interfacial water permeation resistances through anion exchange membranes. Permeation resistances on liquid/membrane interface is found to be negligible compared to that for vapor/membrane for both series of AEMs. Correspondingly, the resistance of liquid water permeation is found to be one order of magnitude smaller compared to that of vapor water permeation. HMT-PMBI possesses larger effective internal water permeation coefficient than both Fumapem® FAA-3 and Nafion® membranes (60 and 18% larger, respectively). In contrast, the effective interfacial permeation coefficient of HMT-PMBI is found to be similar to Fumapem® (±5%) but smaller than Nafion®(H+) (by 14%).

  3. Revisiting the Anionic Polymerization of Methyl Ethacrylate

    Energy Technology Data Exchange (ETDEWEB)

    Kennemur, Justin G. [Department of Chemistry and Biochemistry, Florida State University, Tallahassee FL 32306-4390 USA; Bates, Frank S. [Department of Chemical Engineering and Materials Science, University of Minnesota, Minneapolis MN 55455-0431 USA; Hillmyer, Marc A. [Department of Chemistry, University of Minnesota, Minneapolis MN 55455-0431 USA

    2017-09-26

    Synthesis of poly(methyl ethacrylate), (PMEA), in tetrahydrofuran at -78 °C using anionic polymerization techniques results in high molar mass (>30 kg mol-1), low dispersity (1.3), and high conversion (>81%). The molar masses of a series of samples are consistent with values anticipated by the monomer-to-initiator ratio and conversion. These results represent a significant improvement to earlier reported attempts to prepare PMEA using anionic methods. Successful diblock polymerization of polystyrene-block-PMEA, (PS-PMEA), and poly(4-tert-butylstyrene)-block-PMEA, (PtBS-PMEA), is achieved through sequential anionic polymerization techniques with dispersities as low as 1.06 and segment molar fractions close to those targeted. Broad principal scattering peaks observed by small-angle X-ray scattering (SAXS) for symmetric PS-PMEA at relatively high molar mass (39 kg mol-1) suggests an effective interaction parameter (χeff) that is smaller than for PS-block-poly(methyl methacrylate). On the other hand, PtBS-PMEA block polymers form a well-ordered morphology based on SAXS measurements and is attributable to the more hydrophobic PtBS segment. These results confirm the viability of PMEA as a new constituent in the expanding suite of polymers suitable for preparing nanostructured block polymers.

  4. Fuzzy Clustering

    DEFF Research Database (Denmark)

    Berks, G.; Keyserlingk, Diedrich Graf von; Jantzen, Jan

    2000-01-01

    and clustering are the basic concerns in medicine. Classification depends on definitions of the classes and their required degree of participant of the elements in the cases' symptoms. In medicine imprecise conditions are the rule and therefore fuzzy methods are much more suitable than crisp ones. Fuzzy c...

  5. CH-anion versus anion-π interactions in the crystal and in solution of pentafluorobenzyl phosphonium salts.

    Science.gov (United States)

    Müller, Michael; Albrecht, Markus; Sackmann, Johannes; Hoffmann, Andreas; Dierkes, Fiete; Valkonen, Arto; Rissanen, Kari

    2010-12-21

    A series of phosphonium salts with pentafluorobenzyl substituents have been synthesized and were investigated in the crystal as well as in solution. The solid state structures of 1a, 1b and 2d reveal the presence of anion-π as well as CH-anion interactions. The two attractive, yet competitive forces seem to act in concert and a directing effect of the CH interaction on the relative position between anion and π-system is observed. The search for anion-π interactions in solution failed. Only CH-anion interactions proved to be important in solution.

  6. Microsolvation of anions by molecules forming CH··X{sup −} hydrogen bonds

    Energy Technology Data Exchange (ETDEWEB)

    Nepal, Binod; Scheiner, Steve, E-mail: steve.scheiner@usu.edu

    2015-12-16

    Highlights: • n CF{sub 3}H + anion forms clusters with n CH···X{sup −} H-bonds. • F{sup −}, Cl{sup −}, Br{sup −}, I{sup −}, CN{sup −}, NO{sub 3}{sup −}, HCOO{sup −}, CH{sub 3}COO{sup −}, HSO{sub 4}{sup −}, H{sub 2}PO{sub 4}{sup −}, SO{sub 4}{sup 2−}, HPO{sub 4}{sup 2−}, PO{sub 4}{sup 3−}. • Average H-bond energy decreases steadily with n as average R increases. • Total binding energies proportional to the magnitude of the anionic charge. - Abstract: Various anions were surrounded by n molecules of CF{sub 3}H, which was used as a prototype CH donor solvent, and the structures and energies studied by M06-2X calculations with a 6-31+G∗∗ basis set. Anions considered included the halides F{sup −}, Cl{sup −}, Br{sup −} and I{sup −}, as well as those with multiple proton acceptor sites: CN{sup −}, NO{sub 3}{sup −}, HCOO{sup −}, CH{sub 3}COO{sup −}, HSO{sub 4}{sup −}, H{sub 2}PO{sub 4}{sup −}, and anions with higher charges SO{sub 4}{sup 2−}, HPO{sub 4}{sup 2−} and PO{sub 4}{sup 3−}. Well structured cages were formed and the average H-bond energy decreases steadily as the number of surrounding solvent molecules rises, even when n exceeds 6 and the CF{sub 3}H molecules begin to interact with one another rather than with the central anion. Total binding energies are very nearly proportional to the magnitude of the negative charge on the anion. The free energy of complexation becomes more negative for larger n initially, but then reaches a minimum and begins to rise for larger values of n.

  7. Graphene-coated polymeric anion exchangers for ion chromatography

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Kai; Cao, Minyi; Lou, Chaoyan [Department of Chemistry, Xixi Campus, Zhejiang University, Hangzhou 310028 (China); Wu, Shuchao, E-mail: wushch2002@163.com [Zhejiang Institute of Geology and Mineral Resources, Hangzhou 310007 (China); Zhang, Peimin [Department of Chemistry, Xixi Campus, Zhejiang University, Hangzhou 310028 (China); Zhi, Mingyu [Hangzhou Vocational & Technical College, Hangzhou, 310018 (China); Zhu, Yan, E-mail: zhuyan@zju.edu.cn [Department of Chemistry, Xixi Campus, Zhejiang University, Hangzhou 310028 (China)

    2017-06-01

    Carbonaceous stationary phases have gained much attention for their peculiar selectivity and robustness. Herein we report the fabrication and application of a graphene-coated polymeric stationary phase for anion exchange chromatography. The graphene-coated particles were fabricated by a facile evaporation-reduction method. These hydrophilic particles were proven appropriate substrates for grafting of hyperbranched condensation polymers (HBCPs) to make pellicular anion exchangers. The new phase was characterized by zeta potentials, Fourier transform infrared spectroscopy, thermogravimetry and scanning electron microscope. Frontal displacement chromatography showed that the capacities of the anion exchangers were tuned by both graphene amount and HBCPs layer count. The chromatographic performance of graphene-coated anion exchangers was demonstrated with separation of inorganic anions, organic acids, carbohydrates and amino acids. Good reproducibility was obtained by consecutive injections, indicating high chemical stability of the coating. - Highlights: • Graphene-coated polymeric particles were fabricated by a facile method. • Hyperbranched condensation polymers (HBCPs) were grafted from graphene-coated particles to make anion exchangers. • Graphene amount and HBCPs layer count had significant effects on the anion exchange capacities. • Separation of diverse anionic analytes on the anion exchangers was demonstrated. • The prepared anion exchangers exhibited high stability.

  8. Cluster Headache.

    Science.gov (United States)

    Salvesen

    1999-11-01

    The care of patients with cluster headache has at least two goals: 1) immediately abolishing an ongoing attack and 2) stopping or shortening a bout (a cluster period). The fierceness and the relative brevity of the attacks dictate the use of a fast-acting agent. There are probably three agents fulfilling these criteria: sumatriptan (by subcutaneous injection), oxygen (inhaled through a face mask), and ergotamines (by injection or, perhaps, sublingual tablets). An abundance of data from controlled studies as well as recent clinical experience probably favors sumatriptan as the most effective alternative, the most significant drawback being its high cost. Oxygen inhalation is free of side effects and may be effective but is inconvenient to use. Ergotamines in tablet form act less rapidly, and there are more contraindications to their use. In short-term prophylaxis, however, ergotamine may still be a drug of choice if the timing of the attacks allows planned use of the drug shortly before the attack. If the timing is more irregular, steroids may at least temporarily break a cycle (eg, prednisolone, 60 or 80 mg/d, gradually tapered to zero in 3 to 4 weeks). If more long-lasting prophylaxis is needed or expected, lithium carbonate, 900 mg/d, or verapamil, 360 mg/d, both have reasonable response rates. As for chronic cluster headache, lithium probably will still be the drug of choice. For a very limited group of patients with chronic cluster headache, surgery may be a last resort. The best surgical options are probably radiofrequency rhizotomy or microvascular decompression of the trigeminal nerve.

  9. Regional Innovation Clusters

    Data.gov (United States)

    Small Business Administration — The Regional Innovation Clusters serve a diverse group of sectors and geographies. Three of the initial pilot clusters, termed Advanced Defense Technology clusters,...

  10. Organic superconductors with an incommensurate anion structure

    Directory of Open Access Journals (Sweden)

    Tadashi Kawamoto and Kazuo Takimiya

    2009-01-01

    Full Text Available Superconducting incommensurate organic composite crystals based on the methylenedithio-tetraselenafulvalene (MDT-TSF series donors, where the energy band filling deviates from the usual 3/4-filled, are reviewed. The incommensurate anion potential reconstructs the Fermi surface for both (MDT-TSF(AuI20.436 and (MDT-ST(I30.417 neither by the fundamental anion periodicity q nor by 2q, but by 3q, where MDT-ST is 5H-2-(1,3-dithiol-2-ylidene-1,3-diselena-4,6-dithiapentalene, and q is the reciprocal lattice vector of the anion lattice. The selection rule of the reconstructing vectors is associated with the magnitude of the incommensurate potential. The considerably large interlayer transfer integral and three-dimensional superconducting properties are due to the direct donor–donor interactions coming from the characteristic corrugated conducting sheet structure. The materials with high superconducting transition temperature, Tc, have large ratios of the observed cyclotron masses to the bare ones, which indicates that the strength of the many-body effect is the major determinant of Tc. (MDT-TS(AuI20.441 shows a metal–insulator transition at TMI=50 K, where MDT-TS is 5H-2-(1,3-diselenol-2-ylidene-1,3,4,6-tetrathiapentalene, and the insulating phase is an antiferromagnet with a high Néel temperature (TN=50 K and a high spin–flop field (Bsf=6.9 T. There is a possibility that this material is an incommensurate Mott insulator. Hydrostatic pressure suppresses the insulating state and induces superconductivity at Tc=3.2 K above 1.05 GPa, where Tc rises to the maximum, Tcmax=4.9 K at 1.27 GPa. This compound shows a usual temperature–pressure phase diagram, in which the superconducting phase borders on the antiferromagnetic insulating phase, despite the unusual band filling.

  11. Gas-Phase Reactivity of Microsolvated Anions

    DEFF Research Database (Denmark)

    Thomsen, Ditte Linde

    the gas-phase α-effect. The experimental studies are performed by means of the flowing after glow selected ion flow tube technique, and these are supplemented by electronic structure calculations. The α-nucleophile employed is the microsolvated hydrogen peroxide anion whose reactivity is compared...... for the microsolvated α-nucleophile, and a significant α-effect was observed in this channel. Quantum chemical calculations reveal that the structure of the microsolvated hydrogen peroxide adduct is distinctly different from the structure of the microsolvated alkoxy nucleophiles, in that it involves transfer a proton...... cannot be expected to catalyze hydrogen abstraction reactions by the hydroxyl radical under atmospherically relevant conditions....

  12. Probes for anionic cell surface detection

    Science.gov (United States)

    Smith, Bradley D.

    2013-03-05

    Embodiments of the present invention are generally directed to compositions comprising a class of molecular probes for detecting the presence of anionic cell surfaces. Embodiments include compositions that are enriched for these compositions and preparations, particularly preparations suitable for use as laboratory/clinical reagents and diagnostic indicators, either alone or as part of a kit. An embodiment of the invention provides for a highly selective agent useful in the discernment and identification of dead or dying cells, such as apoptotic cells, in a relatively calcium-free environment. An embodiment of the invention provides a selective agent for the identification of bacteria in a mixed population of bacterial cells and nonbacterial cells.

  13. Analysis of anions in beer using ion chromatography

    OpenAIRE

    Bruce, Jonathan

    2002-01-01

    The majority of anions found in beer are a consequence of impurities derived from the water used during the brewing process. The process of beer manufacture consists of malting, brewing and fermentation followed by maturation before filtration and finally storage. Strict quality control is required because the presence of certain anions outside strictly defined tolerance limits can affect the flavour characteristics of the finished product. The anions present were quantified using the techniq...

  14. Unexpectedly strong anion-π interactions on the graphene flakes.

    Science.gov (United States)

    Shi, Guosheng; Ding, Yihong; Fang, Haiping

    2012-05-30

    Interactions of anions with simple aromatic compounds have received growing attention due to their relevancy in various fields. Yet, the anion-π interactions are generally very weak, for example, there is no favorable anion-π interaction for the halide anion F(-) on the simplest benzene surface unless the H-atoms are substituted by the highly negatively charged F. In this article, we report a type of particularly strong anion-π interactions by investigating the adsorptions of three halide anions, that is, F(-), Cl(-), and Br(-), on the hydrogenated-graphene flake using the density functional theory. The anion-π interactions on the graphene flake are shown to be unexpectedly strong compared to those on simple aromatic compounds, for example, the F(-)-adsorption energy is as large as 17.5 kcal/mol on a graphene flake (C(84) H(24)) and 23.5 kcal/mol in the periodic boundary condition model calculations on a graphene flake C(113) (the supercell containing a F(-) ion and 113 carbon atoms). The unexpectedly large adsorption energies of the halide anions on the graphene flake are ascribed to the effective donor-acceptor interactions between the halide anions and the graphene flake. These findings on the presence of very strong anion-π interactions between halide ions and the graphene flake, which are disclosed for the first time, are hoped to strengthen scientific understanding of the chemical and physical characteristics of the graphene in an electrolyte solution. These favorable interactions of anions with electron-deficient graphene flakes may be applicable to the design of a new family of neutral anion receptors and detectors. Copyright © 2012 Wiley Periodicals, Inc.

  15. 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.

  16. Fluorescence quenching of etilefrine by acetate anion

    Science.gov (United States)

    Quintero Osso, B.; Carazo Rodríguez, F. M.; Morales Domingo, J. J.; Cabeza González, M. C.; Thomas Gómez, J.

    1999-02-01

    Acid dissociation in the excited state of antihypotensor drug etilefrine [2-(ethylamino1-3-hydroxyphenyl)ethanol] is studied. Fluorescence of etilefrine decreases at pH7. Analyses of the absorption and fluorescence spectra of aqueous solutions of etilefrine in the presence of acetate anions have been made. Considering the existence of an equilibrium in the excited state the values of 3.47×10 -9 and 0.216×10 -9 M -1 s -1 have been obtained for the rate constants for direct and inverse reactions, respectively. Moreover, the lifetime ( τ0'=0.58×10 -9 s) and quantum yield (0.01) of non-protonated etilefrine have been determined. Our results seem to support the existence of a dynamic quenching process based on a proton transfer mechanism induced by acetate anions. This process could represent a serious inconvenience in analytical fluorimetric techniques taking into account that the acetic acid/acetate pair is commonly used as a buffer. Additional fluorescence quenching by H + ions could be involved in acid aqueous mediums. At high concentrations of acetic acid, a value of 2.98×10 -9 M -1 s -1 for the bimolecular constant for the quenching by H + has been calculated.

  17. Anion-Directed Metallocages: A Study on the Tendency of Anion Templation.

    Science.gov (United States)

    Wu, Jing-Yun; Zhong, Ming-Shiou; Chiang, Ming-Hsi

    2017-11-13

    Self-assembly of Cu(NO3 )2 ⋅3 H2 O and di(3-pyridylmethyl)amine (dpma) with addition of different acids (HNO3 , HOAc, HCl, HClO4 , HOTf, HPF6 , HBF4 , and H2 SO4 ) afforded a family of anion-templated tetragonal metallocages with a cationic prismatic structure of [(G(n-) )⊂{Cu2 (Hdpma)4 }]((8-n)+) (G(n-) =NO3(-) , PF6(-) , SiF6(2-) ) with different ligating anions/solvents (NO3(-) , Cl(-) , ClO4(-) , OTf(-) , H2 O) outside the cage. Systematic competitive experiments have rationalized the tendency of anion templation towards the formation of metallocages [(G(n-) )⊂{Cu2 (Hdpma)4 }]((8-n)+) as occurring in the order SiF6(2-) ≈PF6(-) >NO3(-) >SO4(2-) ≈ClO4(-) ≈BF4(-) . This sequence is mostly elucidated by shape control over size selectivity and electrostatic attraction between the cationic {Cu2 (Hdpma)4 }(8+) host and the anionic guests. In addition, these results have also roughly ranked the anion coordination ability in the order Cl(-) , ClO4(-) , OTf(-) >NO3(-) >BF4(-) , CH3 SO4(-) . Magnetic studies of metallocages 1 t and 2-4 suggest that the fitted magnetic interaction, being weakly magnetically coupled overall, is interpreted as a result of the combination of intracage ferromagnetic coupling integrals and intercage antiferromagnetic exchange; both contributions are very weak and comparable in strength. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. A colorimetric tetrathiafulvalene-calix 4 pyrrole anion sensor

    DEFF Research Database (Denmark)

    Nielsen, K. A.

    2012-01-01

    The interaction and colorimetric sensing properties of a tetrathiafulvalene substituted calix[4]pyrrole sensor with anions were investigated using H-1 NMR and absorption spectroscopic techniques. Visual color changes were observed upon addition of different anions (Cl-, Br-, CN-, and AcO-) to a s......The interaction and colorimetric sensing properties of a tetrathiafulvalene substituted calix[4]pyrrole sensor with anions were investigated using H-1 NMR and absorption spectroscopic techniques. Visual color changes were observed upon addition of different anions (Cl-, Br-, CN-, and Ac......O-) to a solution of the sensor. (C) 2012 Elsevier Ltd. All rights reserved....

  19. A nanosized {Ag@Ag12} "molecular windmill" templated by polyoxometalates anions.

    Science.gov (United States)

    Wang, Lei; Yang, Weiting; Zhu, Wei; Guan, Xingang; Xie, Zhigang; Sun, Zhong-Ming

    2014-11-03

    Reaction of multidentate 5-(4-imidazol-1-yl-phenyl)-2H-tetrazole (L) ligand with Ag(I) ions in the existence of H3PW12O40 as anionic template under hydrothermal conditions results in tridecanuclear silver cluster-polyoxometalates hybrid: {Ag13L12}{PW12O40}4·30H2O (1). X-ray single crystal diffraction analysis indicates that the main structural feature of 1 is a nanosized molecular windmill-shaped polynuclear Ag cluster with intriguing {M@M12}-type cuboctahedral topology. The as-synthesized compound exhibits effective photocatalytic activity in the photodegradation of Rhodamine-B (RhB) and antibacterial activity against Escherichia coli, respectively.

  20. Series of SHG Materials Based on Lanthanide Borate-Acetate Mixed Anion Compounds.

    Science.gov (United States)

    Yang, Hui; Hu, Chun-Li; Xu, Xiang; Mao, Jiang-Gao

    2015-08-03

    The first examples of lanthanide borate-acetate mixed anion compounds, namely, Ln2(CH3CO2)2[B5O9(OH)]·H2O (Ln = La 1; Ce 2; Pr 3), were synthesized under hydrothermal conditions. These compounds are isostructural and crystallize in polar space group Cc. They display a unique three-dimensional (3D) framework built by a 3D network of lanthanide borate further decorated by acetate anions. The borate anion exhibits a 2D layer in the ac plane with large 9-member rings (MRs) which are filled by lanthanide(III) ions into a {Ln[B5O9(OH)]}(-) 2D layer. Adjacent {Ln[B5O9(OH)]}(-) layers are bridged by remaining lanthanide (III) ions to form a 3D network of lanthanide borate. It is noteworthy that Ln2(CH3CO2)2[B5O9(OH)]·H2O (Ln = La 1; Ce 2; Pr 3) can be changed into Ln2(CH3CO2)2[B5O9(OH)] (Ln = La 4; Ce 5; Pr 6) under heating at 500 K. Compounds 1-4 display moderate SHG signals of about 2.0, 1.0, 1.4, and 2.5 times that of KH2PO4, respectively, and they are phase matchable. Their SHG responses mainly arise from the synergistic polarization effects of both asymmetric borate clusters and π-conjugated CH3COO(-) anions.

  1. Spectrophotometric Determination of Selenium Through Triiodide Anion.

    Science.gov (United States)

    Bizerea-Spiridon, Otilia; Nartita, Radu; Rogobete, Alexandru F; Negrea, Adina; Stroescu, Ramona; Bizerea, Teofana O; Ilie, Constantin; Marginean, Otilia

    2017-05-01

    Selenium is a chemical element found in the human body that plays a crucial role in its regulation. Depending on the concentration, it may have beneficial or have toxic effects. Selenium is incorporated as selenocysteine amino acid residue in selenoproteins which play an important role in many biological functions: anti-oxidant defense, regulation of the immune function and of the inflammatory response, metabolism of thyroid hormones, functioning of the central nervous system, biosynthesis of DNA and RNA, fertility, and reproduction. Excess selenium, altough less common than selenium deficiency, has equally important negative effects. Given the importance of selenium quantification in various samples, the study proposes a simple and direct spectrophotometric determination of selenium using triiodide anions. The method is based on the oxidation of iodide in acidic medium by selenium (IV) contained in the sample, to form elemental iodine which, in turn, reacts with the excess iodide to form the triiodide anions, the most stable soluble species in aqueous solution. Triiodide is colored from yellow to brown, depending on the concentration. The coloured compound has maximum absorbance at specific wavelengths and thus, the stage of interaction with a chromogenic agent is eliminated. Due to the sensitivity of the reaction, the detection limit of triiodide, and therefore selenium, is extended toward lower values. The optimal conditions for the measurements were established: λ = 290 nm, pH = 1.0 - 1.5, reaction time = 15 minutes. Two areas of selenium detection were determined from the samples: 0.025 - 0.100 ppm, and 0.1 - 4.0 ppm. The detection limit of selenium was lowered at 0.100 ppm and even at 0.025 ppm, which significantly improves the sensitivity of the determination. Types of samples were specified which are suitable for analysis using the proposed method and explained why, in case of biological fluids, it must be used only accompanied by an adequate digestion

  2. Nitric oxide is involved in phosphorus deficiency-induced cluster root development and citrate exudation in white lupin

    Science.gov (United States)

    White lupin (Lupinus albus) forms specialized cluster roots characterized by exudation of organic anions under phosphorus (P) deficiency. Here, we evaluated the role of nitric oxide (NO) in P deficiency-induced cluster-root formation and citrate exudation in white lupin. Plants were treated with NO ...

  3. Scavenging of superoxide anion radical by chaparral.

    Science.gov (United States)

    Zang, L Y; Cosma, G; Gardner, H; Starks, K; Shi, X; Vallyathan, V

    1999-06-01

    Chaparral is considered to act as an antioxidant. However, the inhibitory effects of chaparral on specific radical species are not well understood. Using electron paramagnetic resonance (EPR) spectroscopy in combination with spin trapping techniques, we have found that chaparral scavenges superoxide anion radical (O2*-) in a dose-dependent manner. 5,5-dimethyl-lpyrroline-N-oxide (DMPO) was used as a spin trapping agent and the reaction of xanthine and xanthine oxidase as a source of O2*-. The kinetic parameters, IC50 and Vmax, for chaparral scavenging of O2*- were found to be 0.899 microg/mL and 8.4 ng/mL/sec, respectively. The rate constant for chaparral scavenging O2*- was found to be 1.22 x 10(6) g(-1) s(-1). Our studies suggest that the antioxidant properties of chaparral may involve a direct scavenging effect of the primary oxygen radical, O2*-.

  4. Anion permselective membrane. [For redox fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Alexander, S.S.; Hodgdon, R.B.

    1978-01-01

    Experimental anion permeselective membranes were improved and characterized for use as separators in a chemical redox, power storage cell being developed at the NASA Lewis Research Center. The goal of minimal Fe/sup +3/ ion transfer was achieved for each candidate membrane system. Minimal membrane resistivity was demonstrated by reduction of film thickness using synthetic backing materials but usefulness of thin membranes was limited by the scarcity of compatible fabrics. The most durable and useful backing fabrics were modacrylics. One membrane, a copolymer of 4 vinylpyridine and vinyl benzylchloride was outstanding in overall electrochemical and physical properties. Long term (1000 hrs) membrane chemical and thermal durability in redox environment was shown by three candidate polymers and two membranes. The remainder had good durability at ambient temperature. Manufacturing capability was demonstrated for large scale production of membrane sheets 5.5 ft/sup 2/ in area for two candidate systems.

  5. Nanospectroscopy of thiacyanine dye molecules adsorbed on silver nanoparticle clusters

    Science.gov (United States)

    Ralević, Uroš; Isić, Goran; Anicijević, Dragana Vasić; Laban, Bojana; Bogdanović, Una; Lazović, Vladimir M.; Vodnik, Vesna; Gajić, Radoš

    2018-03-01

    The adsorption of thiacyanine dye molecules on citrate-stabilized silver nanoparticle clusters drop-cast onto freshly cleaved mica or highly oriented pyrolytic graphite surfaces is examined using colocalized surface-enhanced Raman spectroscopy and atomic force microscopy. The incidence of dye Raman signatures in photoluminescence hotspots identified around nanoparticle clusters is considered for both citrate- and borate-capped silver nanoparticles and found to be substantially lower in the former case, suggesting that the citrate anions impede the efficient dye adsorption. Rigorous numerical simulations of light scattering on random nanoparticle clusters are used for estimating the electromagnetic enhancement and elucidating the hotspot formation mechanism. The majority of the enhanced Raman signal, estimated to be more than 90%, is found to originate from the nanogaps between adjacent nanoparticles in the cluster, regardless of the cluster size and geometry.

  6. Protonation Reaction of Benzonitrile Radical Anion and Absorption of Product

    DEFF Research Database (Denmark)

    Holcman, Jerzy; Sehested, Knud

    1975-01-01

    The rate constant for the protonation of benzonitrile radical anions formed in pulse radiolysis of aqueous benzonitrile solutions is (3.5 ± 0.5)× 1010 dm3 mol–1 s–1. A new 270 nm absorption band is attributed to the protonated benzonitrile anion. The pK of the protonation reaction is determined...

  7. Water-induced quenching of salicylic anion fluorescence

    NARCIS (Netherlands)

    Joshi, H.C.; Gooijer, C.; van der Zwan, G.

    2002-01-01

    Salicylic anion absorption and emission are studied in a variety of solvents and solvent mixtures. The large Stokes shift observed for this anion is taken to be indicative of a rapid excited state proton transfer reaction to its keto form. The changes in the Stokes shift in the various solvents can

  8. Anion binding by biotin[6]uril in water

    DEFF Research Database (Denmark)

    Lisbjerg, Micke; Nielsen, Bjarne Enrico; Milhøj, Birgitte Olai

    2015-01-01

    In this contribution we show that the newly discovered 6 + 6 biotin-formaldehyde macrocycle Biotin[6]uril binds a variety of anionic guest molecules in water. We discuss how and why the anions are bound based on data obtained using NMR spectroscopy, mass spectrometry, isothermal titration...

  9. Superoxide anion production by human neutrophils activated by Trichomonas vaginalis.

    Science.gov (United States)

    Song, Hyun-Ouk; Ryu, Jae-Sook

    2013-08-01

    Neutrophils are the predominant inflammatory cells found in vaginal discharges of patients infected with Trichomonas vaginalis. In this study, we examined superoxide anion (O2 (.-)) production by neutrophils activated by T. vaginalis. Human neutrophils produced superoxide anions when stimulated with either a lysate of T. vaginalis, its membrane component (MC), or excretory-secretory product (ESP). To assess the role of trichomonad protease in production of superoxide anions by neutrophils, T. vaginalis lysate, ESP, and MC were each pretreated with a protease inhibitor cocktail before incubation with neutrophils. Superoxide anion production was significantly decreased by this treatment. Trichomonad growth was inhibited by preincubation with supernatants of neutrophils incubated for 3 hr with T. vaginalis lysate. Furthermore, myeloperoxidase (MPO) production by neutrophils was stimulated by live trichomonads. These results indicate that the production of superoxide anions and MPO by neutrophils stimulated with T. vaginalis may be a part of defense mechanisms of neutrophils in trichomoniasis.

  10. Heavy hitters via cluster-preserving clustering

    DEFF Research Database (Denmark)

    Larsen, Kasper Green; Nelson, Jelani; Nguyen, Huy L.

    2016-01-01

    , providing correctness whp. In fact, a simpler version of our algorithm for p = 1 in the strict turnstile model answers queries even faster than the "dyadic trick" by roughly a log n factor, dominating it in all regards. Our main innovation is an efficient reduction from the heavy hitters to a clustering...... problem in which each heavy hitter is encoded as some form of noisy spectral cluster in a much bigger graph, and the goal is to identify every cluster. Since every heavy hitter must be found, correctness requires that every cluster be found. We thus need a "cluster-preserving clustering" algorithm......, that partitions the graph into clusters with the promise of not destroying any original cluster. To do this we first apply standard spectral graph partitioning, and then we use some novel combinatorial techniques to modify the cuts obtained so as to make sure that the original clusters are sufficiently preserved...

  11. Supramolecular Chemistry of Selective Anion Recognition for Anions of Environmental Relevance

    Energy Technology Data Exchange (ETDEWEB)

    Moyer, Bruce a.; Bostick, Debra A.; Fowler, Christopher J.; Kang, Hyun-Ah; Ruas, Alexandre; Delmau, Laetitia H.; Haverlock, Tamara J.; Llinares, Jose M.; Hossain, Alamgir; Kang, S. O.; Bowman-James, Kristin; Shriver, James A.; Marquez, Manuel; Sessler, Jonathan L.

    2005-09-22

    The major thrust of this project led by the University of Kansas (Prof. Kristin Bowman-Jones) entails the exploration of the principles of recognition and separation of sulfate by the design, synthesis, and testing of novel sulfate extractants. A key science need for the cleanup of tank wastes at Hanford has been identified in developing methods to separate those bulk waste components that have low solubilities in borosilicate glass. Sulfate has been identified as a particularly difficult and expensive problem in that its concentration in the waste is relatively high, its solubility in glass is especially low, and it interferes with the performance of both vitrification equipment and the glass waste form. The new extractants will be synthesized by the University of Kansas and the University of Texas, Austin. Oak Ridge National Laboratory (ORNL) is subjecting the new extractants to experiments that will determine their properties and effectiveness in separating sulfate from the major competing anions in the waste, especially nitrate. Such experiments will entail primarily liquid-liquid extraction. Current efforts focus on exciting new systems in which the anion receptors act as synergists for anion exchange.

  12. AT Base Pair Anions vs. (9-methyl-A)(1-methyl-T) Base Pair Anions

    Energy Technology Data Exchange (ETDEWEB)

    Radisic, Dunja; Bowen, Kit H.; Dabkowska, Iwona; Storoniak, Piotr; Rak, Janusz; Gutowski, Maciej S.

    2005-05-04

    The anionic base pairs of adenine and thymine, (AT)-, and 9-methyladenine and 1-methylthymine, (MAMT)-, have been investigated both theoretically and experimentally in a complementary, synergistic study. Calculations on (AT)- found that it had undergone a barrier-free proton transfer (BFPT) similar to that seen in other dimer anion systems and that its structural configuration that was neither Watson-Crick (WC) nor Hoogsteen (HS). The vertical detachment energy (VDE) of (AT)- was determined by anion photoelectron spectroscopy and found to be in agreement with the VDE value predicted by theory for the BFPT mechanism. An AT pair in DNA is structurally immobilized into the WC configuration, in part, by being bonded to the sugars of the double helix. This circumstance was mimicked by methylating the sites on both A and T where these sugars would have been tied, viz., 9-methyladenine and 1-methylthymine. Calculations found no BFPT in (MAMT)- and a resulting (MAMT)- configuration that wa s either HS or WC, with the configurations differing in stability by ca. 2 kcal/mol. The photoelectron spectrum of (MAMT)- occurred at a completely different electron binding energy than had (AT)-. Moreover, the VDE value of (MAMT)- was in agreement with that predicted by theory. The configuration of (MAMT)- and its lack of electron-induced proton transfer are inter-related. While there may be other pathways for electron-induced damage, BFPT in the WC/HS configurations of (AT)- is not feasible.

  13. Selectivity control in synergistic liquid-liquid anion exchange of univalent anions via structure-specific cooperativity between quaternary ammonium cations and anion receptors.

    Science.gov (United States)

    Borman, Christopher J; Bonnesen, Peter V; Moyer, Bruce A

    2012-10-02

    Two anion receptors enhance liquid-liquid anion exchange when added to quaternary alkylammonium chloride anion exchangers, but with a striking dependence on the structure of the alkylammonium cation that suggests a supramolecular cooperative effect. Two anion receptors were investigated, meso-octamethylcalix[4]pyrrole (C4P) and the bisthiourea tweezer 1,1'-(propane-1,3-diyl)bis(3-(4-sec-butylphenyl)thiourea (BTU). Whereas synergism is comparatively weak when either methyltri(C(8,10))alkylammonium chloride (Aliquat 336) or tetraheptylammonium chloride is used with the BTU receptor, synergism between C4P and Aliquat 336 is so pronounced that anion exchange prefers chloride over more extractable nitrate and trifluoroacetate, effectively overcoming the ubiquitous Hofmeister bias. A thermochemical analysis of synergistic anion exchange has been provided for the first time, resulting in the estimation of binding constants for C4P with the ion pairs of A336(+) with Cl(-), Br(-), OAc(F3)(-), NO(3)(-), and I(-).

  14. Cluster headache

    Directory of Open Access Journals (Sweden)

    Ducros Anne

    2008-07-01

    Full Text Available Abstract Cluster headache (CH is a primary headache disease characterized by recurrent short-lasting attacks (15 to 180 minutes of excruciating unilateral periorbital pain accompanied by ipsilateral autonomic signs (lacrimation, nasal congestion, ptosis, miosis, lid edema, redness of the eye. It affects young adults, predominantly males. Prevalence is estimated at 0.5–1.0/1,000. CH has a circannual and circadian periodicity, attacks being clustered (hence the name in bouts that can occur during specific months of the year. Alcohol is the only dietary trigger of CH, strong odors (mainly solvents and cigarette smoke and napping may also trigger CH attacks. During bouts, attacks may happen at precise hours, especially during the night. During the attacks, patients tend to be restless. CH may be episodic or chronic, depending on the presence of remission periods. CH is associated with trigeminovascular activation and neuroendocrine and vegetative disturbances, however, the precise cautive mechanisms remain unknown. Involvement of the hypothalamus (a structure regulating endocrine function and sleep-wake rhythms has been confirmed, explaining, at least in part, the cyclic aspects of CH. The disease is familial in about 10% of cases. Genetic factors play a role in CH susceptibility, and a causative role has been suggested for the hypocretin receptor gene. Diagnosis is clinical. Differential diagnoses include other primary headache diseases such as migraine, paroxysmal hemicrania and SUNCT syndrome. At present, there is no curative treatment. There are efficient treatments to shorten the painful attacks (acute treatments and to reduce the number of daily attacks (prophylactic treatments. Acute treatment is based on subcutaneous administration of sumatriptan and high-flow oxygen. Verapamil, lithium, methysergide, prednisone, greater occipital nerve blocks and topiramate may be used for prophylaxis. In refractory cases, deep-brain stimulation of the

  15. Designation and Exploration of Halide-Anion Recognition Based on Cooperative Noncovalent Interactions Including Hydrogen Bonds and Anion-π.

    Science.gov (United States)

    Liu, Yan-Zhi; Yuan, Kun; Lv, Ling-Ling; Zhu, Yuan-Cheng; Yuan, Zhao

    2015-06-04

    A novel urea-based anion receptor with an electron-deficient aromatic structural unit, N-p-nitrophenyl-N-(4-vinyl-2-five-fluoro-benzoic acid benzyl ester)-phenyl-urea (FUR), was designed to probe the potential for halide-anion recognition through the cooperation of two distinct noncovalent interactions including hydrogen bonds and anion-π in this work. The nature of the recognition interactions between halide-anion and the designed receptor was theoretically investigated at the molecular level. The geometric features of the hydrogen bond and anion-π of the FUR@X(-) (X = F, Cl, Br, and I) systems were thoroughly investigated. The binding energies and thermodynamic information on the halide-anion recognitions show that the presently designed FUR might selectively recognize anion F(-) based on the cooperation of the N-H···F(-) hydrogen bond and anion-π interactions both in vacuum and in solvents. IR and UV-visible spectra of free FUR and FUR@F(-) have been simulated and discussed qualitatively, which may be helpful for further experimental investigations in the future. Additionally, the electronic properties and behaviors of the FUR@X(-) systems were discussed according to the calculations on the natural bond orbital (NBO) data, molecular electrostatic potential (MEP), and weak interaction regions.

  16. Iodide and triiodide anion complexes involving anion-π interactions with a tetrazine-based receptor.

    Science.gov (United States)

    Savastano, Matteo; Bazzicalupi, Carla; García, Celeste; Gellini, Cristina; López de la Torre, María Dolores; Mariani, Palma; Pichierri, Fabio; Bianchi, Antonio; Melguizo, Manuel

    2017-04-05

    Protonated forms of the tetrazine ligand L2 (3,6-bis(morpholin-4-ylethyl)-1,2,4,5-tetrazine) interact with iodide in aqueous solution forming relatively stable complexes (ΔG° = -11.6(4) kJ mol(-1) for HL2(+) + I(-) = (HL2)I and ΔG° = -13.4(2) kJ mol(-1) for H2L2(2+) + I(-) = [(H2L2)I](+)). When solutions of [(H2L2)I](+) are left in contact with air, crystals of the oxidation product (H2L2)2(I3)3I·4H2O are formed. Unfortunately, the low solubility of I3(-) complexes prevents the determination of their stability constants. The crystal structures of H2L2I2·H2O (1), H2L2(I3)2·2H2O (2) and (H2L2)2(I3)3I·4H2O (3) were determined by means of X-ray diffraction analyses. In all crystal structures, it was found that the interaction between I(-) and I3(-) with H2L2(2+) is dominated by anion interactions with the π electron density of the receptor. Only in the case of 1, the iodide anions involved in close anion-π interactions with the ligand tetrazine ring form an additional H-bond with the protonated morpholine nitrogen of an adjacent ligand molecule. Conversely, in crystals of 2 and 3 there are alternate segregated planes which contain only protonated ligands hydrogen-bonded to cocrystallized water molecules or I3(-) and I(-) forming infinite two-dimensional networks established through short interhalogen contacts, making these crystalline products good candidates to behave as solid conductors. In the solid complexes, the triiodide anion displays both end-on and side-on interaction modes with the tetrazine ring, in agreement with density functional theory calculations indicating a preference for the alignment of the I3(-) molecular axis with the molecular axis of the ligand. Further information about geometries and structures of triiodide anions in 2 and 3 was acquired by the analysis of their Raman spectra.

  17. Gallium based low-interaction anions

    Science.gov (United States)

    King, Wayne A.; Kubas, Gregory J.

    2000-01-01

    The present invention provides: a composition of the formula M.sup.+x (Ga(Y).sub.4.sup.-).sub.x where M is a metal selected from the group consisting of lithium, sodium, potassium, cesium, calcium, strontium, thallium, and silver, x is an integer selected from the group consisting of 1 or 2, each Y is a ligand selected from the group consisting of aryl, alkyl, hydride and halide with the proviso that at least one Y is a ligand selected from the group consisting of aryl, alkyl and halide; a composition of the formula (R).sub.x Q.sup.+ Ga(Y).sub.4.sup.- where Q is selected from the group consisting of carbon, nitrogen, sulfur, phosphorus and oxygen, each R is a ligand selected from the group consisting of alkyl, aryl, and hydrogen, x is an integer selected from the group consisting of 3 and 4 depending upon Q, and each Y is a ligand selected from the group consisting of aryl, alkyl, hydride and halide with the proviso that at least one Y is a ligand selected from the group consisting of aryl, alkyl and halide; an ionic polymerization catalyst composition including an active cationic portion and a gallium based weakly coordinating anion; and bridged anion species of the formula M.sup.+x.sub.y [X(Ga(Y.sub.3).sub.z ].sup.-y.sub.x where M is a metal selected from the group consisting of lithium, sodium, potassium, magnesium, cesium, calcium, strontium, thallium, and silver, x is an integer selected from the group consisting of 1 or 2, X is a bridging group between two gallium atoms, y is an integer selected from the group consisting 1 and 2, z is an integer of at least 2, each Y is a ligand selected from the group consisting of aryl, alkyl, hydride and halide with the proviso that at least one Y is a ligand selected from the group consisting of aryl, alkyl and halide.

  18. Partitional clustering algorithms

    CERN Document Server

    2015-01-01

    This book summarizes the state-of-the-art in partitional clustering. Clustering, the unsupervised classification of patterns into groups, is one of the most important tasks in exploratory data analysis. Primary goals of clustering include gaining insight into, classifying, and compressing data. Clustering has a long and rich history that spans a variety of scientific disciplines including anthropology, biology, medicine, psychology, statistics, mathematics, engineering, and computer science. As a result, numerous clustering algorithms have been proposed since the early 1950s. Among these algorithms, partitional (nonhierarchical) ones have found many applications, especially in engineering and computer science. This book provides coverage of consensus clustering, constrained clustering, large scale and/or high dimensional clustering, cluster validity, cluster visualization, and applications of clustering. Examines clustering as it applies to large and/or high-dimensional data sets commonly encountered in reali...

  19. Study of clusters using negative ion photodetachment spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Yuexing [Univ. of California, Berkeley, CA (United States)

    1995-12-01

    The weak van der Waals interaction between an open-shell halogen atom and a closed-shell atom or molecule has been investigated using zero electron kinetic energy (ZEKE) spectroscopy. This technique is also applied to study the low-lying electronic states in GaAs and GaAs-. In addition, the spectroscopy and electron detachment dynamics of several small carbon cluster anions are studied using resonant multiphoton detachment spectroscopy.

  20. Mixture model modal clustering

    OpenAIRE

    Chacón, José E.

    2016-01-01

    The two most extended density-based approaches to clustering are surely mixture model clustering and modal clustering. In the mixture model approach, the density is represented as a mixture and clusters are associated to the different mixture components. In modal clustering, clusters are understood as regions of high density separated from each other by zones of lower density, so that they are closely related to certain regions around the density modes. If the true density is indeed in the as...

  1. Unsupervised ensemble minority clustering

    OpenAIRE

    Gonzàlez Pellicer, Edgar; Turmo Borras, Jorge

    2012-01-01

    Cluster analysis lies at the core of most unsupervised learning tasks. However, the majority of clustering algorithms depend on the all-in assumption, in which all objects belong to some cluster, and perform poorly on minority clustering tasks, in which a small fraction of signal data stands against a majority of noise. The approaches proposed so far for minority clustering are supervised: they require the number and distribution of the foreground and background clusters. In supervised learni...

  2. Simultaneous determination of inorganic and organic anions by ion chromatography

    Energy Technology Data Exchange (ETDEWEB)

    Park, Yang Soon; Joe, Ki Soo; Han, Sun Ho; Park, Soon Dal; Choi, Kwang Soon

    1999-06-01

    Four methods were investigated for the simultaneous determination of several inorganic and organic anions in aqueous solution by ion chromatography. The first is two columns coupled system. The second is the gradient elution system with an anion exchange column. The third is the system with a mixed-mode stationary phase. The fourth is the system with an anion exchange column and the eluant of low conductivity without ion suppressor. The advantages and disadvantages of individual systems were discussed. The suitable methods were proposed for the application to the samples of the nuclear power industry and the environment. (author)

  3. A Quick Reference on High Anion Gap Metabolic Acidosis.

    Science.gov (United States)

    Funes, Silvia; de Morais, Helio Autran

    2017-03-01

    High anion gap (AG) metabolic acidoses can be identified by a decrease in pH, decrease in HCO3- or base excess, and an increased AG. The AG represents the difference between unmeasured cations and unmeasured anions; it increases secondary to the accumulation of anions other than bicarbonate and chloride. The most common causes of high AG acidosis are renal failure, diabetic ketoacidosis, and lactic acidosis. Severe increases in concentration of phosphorus can cause hyperphosphatemic acidosis. Copyright © 2016 Elsevier Inc. All rights reserved.

  4. Anion, cation, and zwitterion selectivity of phospholemman channel molecules.

    Science.gov (United States)

    Kowdley, G C; Ackerman, S J; Chen, Z; Szabo, G; Jones, L R; Moorman, J R

    1997-01-01

    Phospholemman (PLM), a 72-amino acid membrane protein with a single transmembrane domain, forms taurine-selective ion channels in lipid bilayers. Because taurine forms zwitterions, a taurine-selective channel might have binding sites for both anions and cations. Here we show that PLM channels indeed allow fluxes of both cations and anions, making instantaneous and voltage-dependent transitions among conformations with drastically different ion selectivity characteristics. This surprising and novel ion channel behavior offers a molecular explanation for selective taurine flux across cell membranes and may explain why molecules in the phospholemman family can induce cation- or anion-selective conductances when expressed in Xenopus oocytes. PMID:8994599

  5. Superoxide anion radical scavenging property of catecholamines.

    Science.gov (United States)

    Kładna, Aleksandra; Berczyński, Paweł; Kruk, Irena; Michalska, Teresa; Aboul-Enein, Hassan Y

    2013-01-01

    The direct effect of the four catecholamines (adrenaline, noradrenaline, dopamine and isoproterenol) on superoxide anion radicals (O2•) was investigated. The reaction between 18-crown-6-ether and potassium superoxide in dimethylsulfoxide was used as a source of O2•. The reactivity of catecholamines with O2• was examined using chemiluminescence, reduction of nitroblue tetrazolium and electron paramagnetic resonance spin-trapping techniques. 5,5-Dimethyl-1-pyrroline-N-oxide was included as the spin trap. The results showed that the four catecholamines were effective and efficient in inhibiting chemiluminescence accompanying the potassium superoxide/18-crown-6-ether system in a dose-dependent manner over the range 0.05-2 mM in the following order: adrenaline > noradrenaline > dopamine > isoproterenol, with, IC50 = 0.15 ± 0.02 mM 0.21 ± 0.03 mM, 0.27 ± 0.03 mM and 0.50 ± 0.04 mM, respectively. The catecholamines examined also exhibited a strong scavenging effect towards O2• when evaluated this property by the inhibition of nitroblue tetrazolium reduction (56-73% at 1 M concentration). A very similar capacity of O2• scavenging was monitored in the 5,5-dimethyl-1-pyrroline-N-oxide spin-trapping assay. The results suggest that catecholamines tested may involve a direct effect on scavenging O2- radicals. Copyright © 2013 John Wiley & Sons, Ltd.

  6. Renal transport of organic anions and cations.

    Science.gov (United States)

    Pelis, Ryan M; Wright, Stephen H

    2011-10-01

    Organic anions and cations (OAs and OCs, respectively) comprise an extraordinarily diverse array of compounds of physiological, pharmacological, and toxicological importance. The kidney, primarily the renal proximal tubule, plays a critical role in regulating the plasma concentrations of these organic electrolytes and in clearing the body of potentially toxic xenobiotics agents, a process that involves active, transepithelial secretion. This transepithelial transport involves separate entry and exit steps at the basolateral and luminal aspects of renal tubular cells. Basolateral and luminal OA and OC transport reflects the concerted activity of a suite of separate proteins arranged in parallel in each pole of proximal tubule cells. The cloning of multiple members of several distinct transport families, the subsequent characterization of their activity, and their subcellular localization within distinct regions of the kidney, now allows the development of models describing the molecular basis of the renal secretion of OAs and OCs. New information on naturally occurring genetic variation of many of these processes provides insight into the basis of observed variability of drug efficacy and unwanted drug-drug interactions in human populations. The present review examines recent work on these issues. 2011 American Physiological Society

  7. The role of anions, solvent molecules and solvated electrons in layer formation processes on anode materials for rechargeable lithium batteries

    Energy Technology Data Exchange (ETDEWEB)

    Rahner, D. [Technische Univ. Dresden (Germany). Inst. fuer Physikalische Chemie und Elektrochemie

    1999-09-01

    The reactivity of anions, solvent molecules and solvated electrons against anode materials are coupled in a given electrolyte solution. The ratio between anion and solvent decomposition depends on the potential and the electrolyte composition. The life time of trapped solvated electrons within the growing SEI layer depends on the donor-acceptor properties of the incorporated solvent molecules and is in the range among 3-10 s. The places of the trapped electrons are the origin of 'metallic' lithium clusters within the forming layer. Their growth will lead to the well-known lithium dendrites on lithium-metal or the progressive irreversible capacity loss on lithium-carbons and therefore causes a lot of problems. Suggestions will be made how to solve these problems in order to achieve a homogeneous SEI with a reduced dendrite growth or decreased irreversible capacity loss. (orig.)

  8. Structures of building blocks in clusters of sweetpotato amylopectin.

    Science.gov (United States)

    Zhu, Fan; Corke, Harold; Åman, Per; Bertoft, Eric

    2011-12-27

    φ,β-Limit dextrins of domains and clusters of sweetpotato amylopectin were subjected to extensive hydrolysis by Bacillus amyloliquefaciens α-amylase to release building blocks and reveal the internal structures of clusters. The composition of building blocks was analyzed by size-fractionation, gel permeation chromatography, and high performance anion exchange chromatography. Different domains and clusters had structurally similar building blocks with around three chains per building block and internal chain length around 2.9. Singly branched and doubly branched building blocks were the largest and second largest groups in the clusters. Type A clusters had more large building blocks and contained 5-6 blocks per cluster with an inter-block chain length (IB-CL) of 7.0, whereas type B clusters had less large building blocks and contained 3-4 blocks per cluster with IB-CL 7.9. Models on how the building blocks could be organized into type A and type B clusters are discussed. Copyright © 2011 Elsevier Ltd. All rights reserved.

  9. Structural and optical properties of Si-doped Ag clusters

    KAUST Repository

    Mokkath, Junais Habeeb

    2014-03-06

    The structural and optical properties of AgN and Ag N-1Si1 (neutral, cationic, and anionic) clusters (N = 5 to 12) are systematically investigated using the density functional based tight binding method and time-dependent density functional theory, providing insight into recent experiments. The gap between the highest occupied and lowest unoccupied molecular orbitals and therefore the optical spectrum vary significantly under Si doping, which enables flexible tuning of the chemical and optical properties of Ag clusters. © 2014 American Chemical Society.

  10. Fast determination of anions on a short coated column.

    Science.gov (United States)

    Li, Jing; Zhu, Yan; Guo, Yingying

    2006-06-16

    In this paper, a simple method for the separation and determination of common inorganic anions by fast ion-exchange chromatography, using a modified short (25 mm x 4.6 mm) monolithic column, is reported. Coating the column with a cationic surfactant, cetylpyridinium chloride (CPC), the isocratic separation of some inorganic anions in minutes was possible, by direct or indirect UV detection. The coated column demonstrated excellent stability over time, even at a high flow-rate, giving retention times with an average relative standard deviation of 1.3% for over 10 consecutive runs. The developed column exhibited unusual selectivity for common anions, was successfully applied to the rapid analysis of inorganic anions of food samples, river water and factory waste water samples.

  11. Adsorption of inorganic anionic contaminants on surfactant modified minerals

    Directory of Open Access Journals (Sweden)

    MAGDALENA TOMASEVIC-CANOVIC

    2003-11-01

    Full Text Available Organo-mineral complexes were obtained by treatment of aluminosilicate minerals (zeolite, bentonite and diatomaceous earth with a primary amine (oleylamine and an alkyl ammonium salt (stearyldimethylbenzyl ammonium chloride. The modification of the zeolite surface was carried out in two steps. The first step was treatment of the zeolite with 2 M HCl. This acid treatment of the zeolite increased its affinity for neutral molecules such as surface-active amines. The second step of the modification was the adsorption of oleylamine on the acid treated zeolite. Four types of organo-mineral complexes were prepared and their anion adsorption properties were compared to those of organo-zeolite. The adsorption of sulphate, bichromate and dihydrogenphosphate anions on the organo-mineral complexes was investigated. The anion adsorption measurements showed that the most efficient adsorbent for anion water pollutants was the primary amine modified H+-form zeolite.

  12. Detection of cyanide anion by zinc porphyrin-spiropyran dyad

    Energy Technology Data Exchange (ETDEWEB)

    Kho, Young Min; Hur, Dae Young; Shin, Eun Ju [Dept. of Chemistry, Sunchon National University, Suncheon (Korea, Republic of)

    2016-10-15

    Versatile methods of the sensitive and selective detection for cyanide anion to monitor toxic cyanide have been developed. These include colorimetric, colorimetric, chromatographic, and electrochemical analyses. Among those methods for cyanide detection, optical methods based on absorption and fluorescence spectroscopy are relatively simple, inexpensive, and sensitive. A number of organic sensors for cyanide anion have been designed and synthesized. Absorption and/or fluorescence spectra of these sensors are changed by forming coordination complex or bonding covalently with cyanide. Compared with other anions, cyanide anion has some characteristic properties, such as its strong nucleophilicity and high binding affinity toward metal ions, and is superior and useful for the development of the sensors. Both covalent bond-based sensors and coordination complex-based sensors have been developed for cyanide detection. The results indicate that ZnP-SP plays a role as a CN{sup -} selective, colorimetric sensor either without or with UV irradiation.

  13. New anion-exchange polymers for improved separations

    Energy Technology Data Exchange (ETDEWEB)

    Jarvinen, G.D.; Barr, M.E.; Marsh, S.F.

    1997-08-01

    Objective is to improve the understanding of how the structure of a new class of anion-exchange polymers controls the binding of anionic actinide complexes from solution. This is needed to develop practical separation systems that will reduce the cost of actinide processing operations within the DOE complex. In addition anion exchange is widely used in industry. Several new series of bifunctional anion- exchange polymers have been designed, synthesized, and tested for removing Pu(IV), Am(III), and U(VI) from nitric acid. The polymers contain a pyridinium site derived from the host poly(4-vinylpyridine) and a second cationic site attached through a chain of 2 to 6 methylene groups. The new polymers removed Pu four to ten times more efficiently than the best commercial materials.

  14. Photoinduced Dynamics of Neutral, Cationic, and Anionic Species

    DEFF Research Database (Denmark)

    Stephansen, Anne Boutrup

    -puckering of the nucleobases. In certain cases specific ring-puckering can stabilize the valence-anions to prolong their lifetimes significantly, even when formed in the scattering continuum. The study of cation dynamics aims at understanding peculiar isotope effects in the decomposition of ionized dihaloalkanes. Br...... electrons and subsequently transition from dipole to valence-bound anions in different energy regimes. The investigations indicate that dipole-bound anion formation depends strongly on the magnitude of the molecular dipole moment, while the formation and stability of valence-bound anions depends on ring......-C-Br bending is activated by pump-induced ionization, which shows up as oscillating ion transitions arising from probe-induced fragmentation. The source of the isotopic preference is analyzed by tracking temporal changes in the contribution from each isotopomer to the total fragment-ion signal. Preliminary...

  15. Two benzoyl coumarin amide fluorescence chemosensors for cyanide anions

    Science.gov (United States)

    Wang, Zian; Wu, Qianqian; Li, Jiale; Qiu, Shuang; Cao, Duxia; Xu, Yongxiao; Liu, Zhiqiang; Yu, Xueying; Sun, Yatong

    2017-08-01

    Two new benzoyl coumarin amide derivatives with ortho hydroxyl benzoyl as terminal group have been synthesized. Their photophysical properties and recognition properties for cyanide anions in acetonitrile have also been examined. The influence of electron donating diethylamino group in coumarin ring and hydroxyl in benzoyl group on recognition properties was explored. The results indicate that the compounds can recognize cyanide anions with obvious absorption and fluorescence spectral change and high sensitivity. The import of diethylamine group increases smartly the absorption ability and fluorescence intensity of the compound, which allows the recognition for cyanide anions can be observed by naked eyes. The in situ hydrogen nuclear magnetic resonance spectra combining photophysical properties change and job's plot data confirm that Michael addition between the chemosensors and cyanide anions occurs. Molecular conjugation is interrupted, which leads to fluorescence quenching. At the same time, there is a certain extent hydrogen bond reaction between cyanide and hydroxyl group in the compounds, which is beneficial to the recognition.

  16. Two independent anion transport systems in rabbit mandibular salivary glands

    DEFF Research Database (Denmark)

    Novak, I; Young, J A

    1986-01-01

    Cholinergically stimulated Cl and HCO3 transport in perfused rabbit mandibular glands has been studied with extracellular anion substitution and administration of transport inhibitors. In glands perfused with HCO3-free solutions, replacement of Cl with other anions supported secretion in the foll......Cholinergically stimulated Cl and HCO3 transport in perfused rabbit mandibular glands has been studied with extracellular anion substitution and administration of transport inhibitors. In glands perfused with HCO3-free solutions, replacement of Cl with other anions supported secretion...... stimulated secretion by about 30%, but when infused in addition to furosemide (0.1 mmol/l), it inhibited by about 20%. Amiloride (1.0 mmol/l) caused no inhibition. The results suggest that there are at least three distinct carriers in the rabbit mandibular gland. One is a furosemide-sensitive Na-coupled Cl...

  17. Anionic solid lipid nanoparticles supported on protamine/DNA complexes

    Science.gov (United States)

    Ye, Jiesheng; Wang, Aihua; Liu, Chunxi; Chen, Zhijin; Zhang, Na

    2008-07-01

    The objective of this study was to design novel anionic ternary nanoparticles for gene delivery. These ternary nanoparticles were equipped with protamine/DNA binary complexes (150-200 nm) as the support, and the anionic formation was achieved by absorption of anionic solid lipid nanoparticles (lipofectamine. The transfection efficiency of the ternary nanoparticles was better than that of naked DNA and the binary complexes, and almost equal to that of lipofectamine/DNA complexes, as revealed by inversion fluorescence microscope observation. These results indicated that the anionic ternary nanoparticles could facilitate gene transfer in cultured cells, and might alleviate the drawbacks of the conventional cationic vector/DNA complexes for gene delivery in vivo.

  18. Ion-exchange concentration of inorganic anions from aqueous solution

    Directory of Open Access Journals (Sweden)

    L. P. Bondareva

    2016-01-01

    Full Text Available Monitoring of natural waters in the present time - consuming process, the accuracy of which is influenced by many factors: the composition of water, the presence of impurities and "interfering" components. The water sample preparation process includes the step of concentration and separation of ions determined. The most versatile, efficient, and frequently used method is the concentration of inorganic anions from aqueous solutions by ion exchanger, which can optimize the composition of water to the optimal for identification and quantitative determination of anions. The characteristics of sorption chloride, nitrate and sulfate ions of basic anion exchange resin AВ-17 and Purolite A430 were compared in the article. The constants of protolysis of ion exchangers both AB 17 and Purolite A430 are the same and equal 0.037 ± 0,002. The value of total capacity (POE Purolite A430 was 4.3 mmol/g, AB 17 – 3.4 mmol/g. The studied ion exchangers have the same type of ionic groups – quaternary ammonium, but their number and denotes differ. The number of quaternary ammonium groups is higher in Purolite A430, respectively the number of absorbed anions of these ion exchanger is higher. The values of dynamic exchange capacity (DOE of ion exchanger Purolite A430 is higher than these values of AB-17 and equal to 1.48 ± 0.03 mmol / dm3 for chloride ion, 1.50 ± 0.03 mmol / dm3 for nitrate ion, 1.62 ± 0.03 mmol / dm3 for sulfate ion. The values of the POE and DOE of anion-exchange resins Purolite A430 and AV-17 and the characteristics of the individual sorption of chloride, nitrate, sulfate ions showed an advantage of the Purolite for the concentrationing of anions. It is found that times of anions sorption from triple-anion solutions by Purolite A430 are significantly different for different anions, and these times are close for anion-exchanger AV-17. It proves the possibility of quantitative separation and concentration by anion-exchanger Purolite A430.

  19. Intestinal transporters for endogenic and pharmaceutical organic anions

    DEFF Research Database (Denmark)

    Grandvuinet, Anne Sophie; Vestergaard, Henrik Tang; Rapin, Nicolas

    2012-01-01

    This review provides an overview of intestinal human transporters for organic anions and stresses the need for standardization of the various in-vitro methods presently employed in drug-drug interaction (DDI) investigations.......This review provides an overview of intestinal human transporters for organic anions and stresses the need for standardization of the various in-vitro methods presently employed in drug-drug interaction (DDI) investigations....

  20. Gas-Grain Models for Interstellar Anion Chemistry

    Science.gov (United States)

    Cordiner, M. A.; Charnely, S. B.

    2012-01-01

    Long-chain hydrocarbon anions C(sub n) H(-) (n = 4, 6, 8) have recently been found to be abundant in a variety of interstellar clouds. In order to explain their large abundances in the denser (prestellar/protostellar) environments, new chemical models are constructed that include gas-grain interactions. Models including accretion of gas-phase species onto dust grains and cosmic-ray-induced desorption of atoms are able to reproduce the observed anion-to-neutral ratios, as well as the absolute abundances of anionic and neutral carbon chains, with a reasonable degree of accuracy. Due to their destructive effects, the depletion of oxygen atoms onto dust results in substantially greater polyyne and anion abundances in high-density gas (with n(sub H2) approx > / cubic cm). The large abundances of carbon-chain-bearing species observed in the envelopes of protostars such as L1527 can thus be explained without the need for warm carbon-chain chemistry. The C6H(-) anion-to-neutral ratio is found to be most sensitive to the atomic O and H abundances and the electron density. Therefore, as a core evolves, falling atomic abundances and rising electron densities are found to result in increasing anion-to-neutral ratios. Inclusion of cosmic-ray desorption of atoms in high-density models delays freeze-out, which results in a more temporally stable anion-to-neutral ratio, in better agreement with observations. Our models include reactions between oxygen atoms and carbon-chain anions to produce carbon-chain-oxide species C6O, C7O, HC6O, and HC7O, the abundances of which depend on the assumed branching ratios for associative electron detachment

  1. Thin Robust Anion Exchange Membranes for Fuel Cell Applications

    Science.gov (United States)

    2014-01-01

    provide inexpensive compact power from a wider variety of fuels than is possible with a proton exchange membrane ( PEM ) fuel cell , has continued to...complexity and carbonate formation. Anion exchange membrane (AEMs) fuel cells have a number of advantages over both PEM fuel cells and traditional AFCs...release; distribution is unlimited. (Invited) Thin Robust Anion Exchange Membranes for Fuel Cell Applications The views, opinions and/or findings

  2. Neutral and negatively-charged formamide, N-methylformamide and dimethylformamide clusters

    Energy Technology Data Exchange (ETDEWEB)

    Desfrancois, C.; Periquet, V.; Carles, S.; Schermann, J.P. [Laboratoire de Physique des Lasers, Universite Paris-Nord, 93430 Villetaneuse (France); Adamowicz, L. [Chemistry Department, University of Arizona, Tucson, AZ 85721 (United States)

    1998-12-15

    The structure and low energy electron attachment properties of small clusters of formamide, N-methylformamide and dimethylformamide have been studied. The experimental technique used is Rydberg electron transfer (RET) between laser-excited atoms and the molecular systems. The richness of hydrogen bonding possibilities of these three highly polar molecules leads to very different structures and resultant dipoles or quadrupoles which we determine by means of an empirical model. A corresponding wide variety of cluster anions is observed and interpreted, ranging from dipole-bound or quadrupole-bound anions in their ground state or first excited state to valence-type anions. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

  3. Molecular dynamics simulations of the surface tension and structure of salt solutions and clusters.

    Science.gov (United States)

    Sun, Lu; Li, Xin; Hede, Thomas; Tu, Yaoquan; Leck, Caroline; Ågren, Hans

    2012-03-15

    Sodium halides, which are abundant in sea salt aerosols, affect the optical properties of aerosols and are active in heterogeneous reactions that cause ozone depletion and acid rain problems. Interfacial properties, including surface tension and halide anion distributions, are crucial issues in the study of the aerosols. We present results from molecular dynamics simulations of water solutions and clusters containing sodium halides with the interatomic interactions described by a conventional force field. The simulations reproduce experimental observations that sodium halides increase the surface tension with respect to pure water and that iodide anions reach the outermost layer of water clusters or solutions. It is found that the van der Waals interactions have an impact on the distribution of the halide anions and that a conventional force field with optimized parameters can model the surface tension of the salt solutions with reasonable accuracy. © 2012 American Chemical Society

  4. Grain boundary mobility in anion doped MgO

    Science.gov (United States)

    Kapadia, C. M.; Leipold, M. H.

    1973-01-01

    Certain anions OH(-), F(-) and Gl(-) are shown to enhance grain growth in MgO. The magnitude of their effect decreases in the order in which the anions are listed and depends on their location (solid-solution, second phase) in the MgO lattice. As most anions exhibit relatively high vapor pressures at sintering temperatures, they retard densification and invariably promote residual porosity. The role of anions on grain growth rates was studied in relation to their effect on pore mobility and pore removal; the atomic process controlling the actual rates was determined from observed kinetics in conjunction with the microstructural features. With respect to controlling mechanisms, the effects of all anions are not the same. OH(-) and F(-) control behavior through creation of a defect structure and a grain boundary liquid phase while Cl(-) promotes matter transport within pores by evaporation-condensation. Studies on an additional anion, S to the minus 2nd power gave results which were no different from undoped MgO, possibly because of evaporative losses during hot pressing. Hence, the effect of sulphur is negligible or undetermined.

  5. Management of cluster headache

    DEFF Research Database (Denmark)

    Tfelt-Hansen, Peer C; Jensen, Rigmor H

    2012-01-01

    and agitation. Patients may have up to eight attacks per day. Episodic cluster headache (ECH) occurs in clusters of weeks to months duration, whereas chronic cluster headache (CCH) attacks occur for more than 1 year without remissions. Management of cluster headache is divided into acute attack treatment...

  6. Clustering of correlated networks

    OpenAIRE

    Dorogovtsev, S. N.

    2003-01-01

    We obtain the clustering coefficient, the degree-dependent local clustering, and the mean clustering of networks with arbitrary correlations between the degrees of the nearest-neighbor vertices. The resulting formulas allow one to determine the nature of the clustering of a network.

  7. Cluster knockout reactions

    Indian Academy of Sciences (India)

    2014-04-07

    Apr 7, 2014 ... 2 fm) N–N interaction enhances clustering in the low density surface region of the nuclei. Therefore, to study the clustering aspect of the nuclei, one has to have high projectile energies but has to choose kinematics which probes the low momentum component of the bound clusters. While the cluster pickup ...

  8. Cluster knockout reactions

    Indian Academy of Sciences (India)

    2014-04-07

    Apr 7, 2014 ... Cluster knockout reactions are expected to reveal the amount of clustering (such as that of , d and even of heavier clusters such as 12C, 16O etc.) in the target nucleus. In simple terms, incident medium high-energy nuclear projectile interacts strongly with the cluster (present in the target nucleus) as if it ...

  9. Anion-cation charge-transfer properties and spectral studies of [M(phen)3][Cd4(SPh)10] (M = Ru, Fe, and Ni).

    Science.gov (United States)

    Jiang, Jian-Bing; Bian, Guo-Qing; Zhang, Ya-Ping; Luo, Wen; Zhu, Qin-Yu; Dai, Jie

    2011-10-07

    Three anion-cation compounds 1-3 with formula [M(phen)(3)][Cd(4)(SPh)(10)]·Sol (M = Ru(2+), Fe(2+), and Ni(2+), Sol = MeCN and H(2)O) have been synthesized and characterized by single-crystal analysis. Both the cations and anion are well-known ions, but the properties of the co-assembled compounds are interesting. Molecular structures and charge-transfer between the cations and anions in crystal and even in solution are discussed. These compounds are isomorphous and short inter-ion interactions are found in these crystals, such as π···π stacking and C-H···π contacts. Both spectroscopic and theoretical calculated results indicate that there is anion-cation charge-transfer (ACCT) between the Ru-phen complex dye and the Cd-SPh cluster, which plays an important role in their photophysical properties. The intensity of the fluorescent emission of the [Ru(phen)(3)](2+) is enhanced when the cation interacts with the [Cd(4)(SPh)(10)](2-) anion. The mechanism for the enhancement of photoluminescence has been proposed.

  10. Synthesis and Structure-Property Relationships of Poly(sulfone)s for Anion Exchange Membranes

    Energy Technology Data Exchange (ETDEWEB)

    Yan, JL; Moore, HD; Hibbs, MR; Hickner, MA

    2013-10-05

    Membranes based on cationic polymers that conduct anions are important for enabling alkaline membrane fuel cells and other solid-state electrochemical devices that operate at high pH. Anion exchange membranes with poly(arylene ether sulfone) backbones are demonstrated by two routes: chloromethylation of commercially available poly(sulfone)s or radical bromination of benzylmethyl moieties in poly(sulfone)s containing tetramethylbisphenol A monomer residues. Polymers with tethered trimethylbenzyl ammonium moieties resulted from conversion of the halomethyl groups by quaternization with trimethyl amine. The water uptake of the chloromethylated polymers was dependent on the type of poly(sulfone) backbone for a given IEC. Bisphenol A-based Udel (R) poly(sulfone) membranes swelled in water to a large extent while membranes from biphenol-based Radel (R) poly(sulfone), a stiffer backbone than Udel, only showed moderate water uptake. The water uptake of cationic poly(sulfone)s was further reduced by synthesizing tetramethylbisphenol A and 4,4-biphenol-containing poly(sulfone) copolymers where the ionic groups were clustered on the tetramethylbisphenol A residues. The conductivity of all samples scaled with the bulk water uptake. The hydration number of the membranes could be increased by casting membranes from the ionic form polymers versus converting the halomethyl form cast polymers to ionic form in the solid state. (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1790-1798, 2013

  11. Anion-macrodipole interactions: self-assembling oligourea/amide macrocycles as anion transporters that respond to membrane polarization.

    OpenAIRE

    Hennig Andreas; Fischer Lucile; Guichard Gilles; Matile Stefan

    2009-01-01

    Macrocyclic urea/amide hybrids are introduced as functional anion selective membrane transporters in lipid bilayer membranes. Six derivatives with varying side chains (aliphatic and aromatic) and conformations (parallel and antiparallel carbonyl dipoles) are investigated by fluorescence methods among which the more active aromatic derivatives were selected for an in depth study. Strong response of transport activity toward anion exchange and weak response toward cation exchange establish anio...

  12. Clustering in analytical chemistry.

    Science.gov (United States)

    Drab, Klaudia; Daszykowski, Michal

    2014-01-01

    Data clustering plays an important role in the exploratory analysis of analytical data, and the use of clustering methods has been acknowledged in different fields of science. In this paper, principles of data clustering are presented with a direct focus on clustering of analytical data. The role of the clustering process in the analytical workflow is underlined, and its potential impact on the analytical workflow is emphasized.

  13. Citrate-Permeable Channels in the Plasma Membrane of Cluster Roots from White Lupin1

    Science.gov (United States)

    Zhang, Wen-Hao; Ryan, Peter R.; Tyerman, Stephen D.

    2004-01-01

    White lupin (Lupinus albus) is well adapted to phosphorus deficiency by developing cluster roots that release large amounts of citrate into the rhizosphere to mobilize the sparingly soluble phosphorus. To determine the mechanism underlying citrate release from cluster roots, we isolated protoplasts from different types of roots of white lupin plants grown in phosphorus-replete (+P) and phosphorus-deficient (−P) conditions and used the patch-clamp technique to measure the whole-cell currents flowing across plasma membrane of these protoplasts. Two main types of anion conductance were observed in protoplasts prepared from cluster root tissue: (1) an inwardly rectifying anion conductance (IRAC) activated by membrane hyperpolarization, and (2) an outwardly rectifying anion conductance (ORAC) that became more activated with membrane depolarization. Although ORAC was an outward rectifier, it did allow substantial inward current (anion efflux) to occur. Both conductances showed citrate permeability, with IRAC being more selective for citrate3− than Cl− (PCit/PCl = 26.3), while ORAC was selective for Cl− over citrate (PCl/PCit = 3.7). Both IRAC and ORAC were sensitive to the anion channel blocker anthracene-9-carboxylic acid. These currents were also detected in protoplasts derived from noncluster roots of −P plants, as well as from normal (noncluster) roots of plants grown with 25 μm phosphorus (+P). No differences were observed in the magnitude or frequency of IRAC and ORAC currents between the cluster roots and noncluster roots of −P plants. However, the IRAC current from +P plants occurred less frequently than in the −P plants. IRAC was unaffected by external phosphate, but ORAC had reduced inward current (anion efflux) when phosphate was present in the external medium. Our data suggest that IRAC is the main pathway for citrate efflux from white lupin roots, but ORAC may also contribute to citrate efflux. PMID:15516510

  14. Positron Spur Reactions with Excess Electrons and Anions in Liquid Organic Mixtures of Electron Acceptors

    DEFF Research Database (Denmark)

    Lévay, B.; Mogensen, O. E.

    1980-01-01

    By means of the positron lifetime technique we have measured positronium (Ps) yields in mixtures of nonpolar liquids with various electron scavengers which bind the electron fairly weakly (1–2 eV) in stable anions. The results are discussed with reference to recent excess electron works, and new...... curve. Alcohol clusters did not show antiinhibition in 0.05 M CCl4/neopentane system. Weak electron scavengers (C6F6, naphthalene, biphenyl, benzene) which generally act as antiinhibitors were added to pure non-polar solvents (hexane, isooctane, cyclohexane) and caused Ps enhancement. This can...... to the system, indicating that antirecombination and antiinhibition took place simultaneously. On addition of hexane, isooctane, CS2 or 0.8 M CS2/hexane to pure C6F6 the Ps yield drastically decreased. This correlates well with the drastic decrease of the electron mobility by adding similar additives to C6F6...

  15. Water oxidation by electrodeposited cobalt oxides--role of anions and redox-inert cations in structure and function of the amorphous catalyst.

    Science.gov (United States)

    Risch, Marcel; Klingan, Katharina; Ringleb, Franziska; Chernev, Petko; Zaharieva, Ivelina; Fischer, Anna; Dau, Holger

    2012-03-12

    For the production of nonfossil fuels, water oxidation by inexpensive cobalt-based catalysts is of high interest. Films for the electrocatalysis of water oxidation were obtained by oxidative self-assembly (electrodeposition) from aqueous solutions containing, apart from Co, either K, Li or Ca with either a phosphate, acetate or chloride anion. X-ray absorption spectroscopy (XAS) at the Co K-edge revealed clusters of edge-sharing CoO(6) octahedra in all films, but the size or structural disorder of the Co-oxido clusters differed. Whereas potassium binding is largely unspecific, CaCo(3) O(4) cubanes, which resemble the CaMn(3) O(4) cubane of the biological catalyst in oxygenic photosynthesis, may form, as suggested by XAS at the Ca K-edge. Cyclic voltammograms in a potassium phosphate buffer at pH 7 revealed that no specific combination of anions and redox-inactive cations is required for catalytic water oxidation. However, the anion type modulates not only the size (or order) of the Co-oxido clusters, but also electrodeposition rates, redox potentials, the capacity for oxidative charging, and catalytic currents. On these grounds, structure-activity relations are discussed. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. What Makes Clusters Decline?

    DEFF Research Database (Denmark)

    Østergaard, Christian Richter; Park, Eun Kyung

    2015-01-01

    Most studies on regional clusters focus on identifying factors and processes that make clusters grow. However, sometimes technologies and market conditions suddenly shift, and clusters decline. This paper analyses the process of decline of the wireless communication cluster in Denmark....... The longitudinal study on the high-tech cluster reveals that technological lock-in and exit of key firms have contributed to decline. Entrepreneurship has a positive effect on the cluster’s adaptive capabilities, while multinational companies have contradicting effects by bringing in new resources to the cluster...

  17. Treatment of acute non-anion gap metabolic acidosis

    Science.gov (United States)

    Kraut, Jeffrey A.; Kurtz, Ira

    2015-01-01

    Acute non-anion gap metabolic acidosis, also termed hyperchloremic acidosis, is frequently detected in seriously ill patients. The most common mechanisms leading to this acid–base disorder include loss of large quantities of base secondary to diarrhea and administration of large quantities of chloride-containing solutions in the treatment of hypovolemia and various shock states. The resultant acidic milieu can cause cellular dysfunction and contribute to poor clinical outcomes. The associated change in the chloride concentration in the distal tubule lumen might also play a role in reducing the glomerular filtration rate. Administration of base is often recommended for the treatment of acute non-anion gap acidosis. Importantly, the blood pH and/or serum bicarbonate concentration to guide the initiation of treatment has not been established for this type of metabolic acidosis; and most clinicians use guidelines derived from studies of high anion gap metabolic acidosis. Therapeutic complications resulting from base administration such as volume overload, exacerbation of hypertension and reduction in ionized calcium are likely to be as common as with high anion gap metabolic acidosis. On the other hand, exacerbation of intracellular acidosis due to the excessive generation of carbon dioxide might be less frequent than in high anion gap metabolic acidosis because of better tissue perfusion and the ability to eliminate carbon dioxide. Further basic and clinical research is needed to facilitate development of evidence-based guidelines for therapy of this important and increasingly common acid–base disorder. PMID:25852932

  18. Metal-Oxide Film Conversions Involving Large Anions

    Energy Technology Data Exchange (ETDEWEB)

    Pretty, S.; Zhang, X.; Shoesmith, D.W.; Wren, J.C. [The University of Western Ontario, Chemistry Department, 1151 Richmond St., N6A 5B7, London, Ontario (Canada)

    2008-07-01

    The main objective of my research is to establish the mechanism and kinetics of metal-oxide film conversions involving large anions (I{sup -}, Br{sup -}, S{sup 2-}). Within a given group, the anions will provide insight on the effect of anion size on the film conversion, while comparison of Group 6 and Group 7 anions will provide insight on the effect of anion charge. This research has a range of industrial applications, for example, hazardous radioiodine can be immobilized by reaction with Ag to yield AgI. From the perspective of public safety, radioiodine is one of the most important fission products from the uranium fuel because of its large fuel inventory, high volatility, and radiological hazard. Additionally, because of its mobility, the gaseous iodine concentration is a critical parameter for safety assessment and post-accident management. A full kinetic analysis using electrochemical techniques has been performed on the conversion of Ag{sub 2}O to (1) AgI and (2) AgBr. (authors)

  19. Effect of anionic macromolecules on intestinal permeability of furosemide.

    Science.gov (United States)

    Valizadeh, Hadi; Fahimfar, Hadi; Ghanbarzadeh, Saeed; Islambulchilar, Ziba; Zakeri-Milani, Parvin

    2015-02-01

    Furosemide is an anionic molecule and has very low absorption in gastro intestinal tract. The aim of this study was to investigate the effect of anionic macromolecules on the intestinal permeability of Furosemide. The intestinal permeability of Furosemide was determined using single-pass intestinal perfusion technique in rats. Briefly a jejunal segment of ∼10 cm was isolated and cannulated in both ends for inlet and outlet solution. The perfusate was collected every 10 min and samples were analyzed using the RP-HPLC method. Test samples containing furosemide and two anionic macromolecules, sodium carboxy methyl cellulose and sodium alginate, at different concentrations were used. The obtained data showed that existence of Sodium carboxy methyl cellulose significantly increased the Peff values in all three investigated concentrations (p < 0.05) but sodium alginate only in concentrations <0.1% increased drug permeability. It is concluded that the anionic macromolecules at specific concentrations could alter the permeability of anionic drugs across the biological membranes. Donnan phenomenon and chelating property of macromolecules could be attributed to the observed effect.

  20. Cellular uptake mechanisms of novel anionic siRNA lipoplexes.

    Science.gov (United States)

    Kapoor, Mamta; Burgess, Diane J

    2013-04-01

    To investigate cellular uptake pathways of novel anionic siRNA-lipoplexes as a function of formulation composition. Anionic formulations with anionic lipid/Ca(2+)/siRNA ratio of 1.3/2.5/1 (AF1) and 1.3/0.3/1 (AF2) were utilized. Uptake mechanisms were investigated using uptake inhibition and co-localization approaches in breast cancer cells. Actin-mediated uptake was investigated using actin polymerization and rearrangement assays. Silencing efficiency and endosomal escaping capability of lipoplexes were evaluated. The cationic formulation Lipofectamine-2000 was used as a control. Anionic lipoplexes entered the breast cancer cells via endocytosis specifically via macropinocytosis or via both macropinocytosis and HSPG (heparin sulfate proteoglycans) pathways, depending on the Ca(2+)/siRNA ratio. Additionally, uptake of these lipoplexes was both microtubule and actin dependent. The control cationic lipid-siRNA complexes (Lipofectamine-2000) were internalized via both endocytic (phagocytosis, HSPG) and non-endocytic (membrane fusion) pathways. Their uptake was microtubule independent but actin dependent. Silencing efficiency of the AF2 formulation was negligible mainly due to poor endosomal release (rate-limiting step). Formulation composition significantly influences the internalization mechanism of anionic lipoplexes. Uptake mechanism together with formulation bioactivity helped in identification of the rate-limiting steps to efficient siRNA delivery. Such studies are extremely useful for formulation optimization to achieve enhanced intracellular delivery of nucleic acids.

  1. REACTIVITY OF ANIONS IN INTERSTELLAR MEDIA: DETECTABILITY AND APPLICATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Senent, M. L. [Departamento de Quimica y Fisica Teoricas, Instituto de Estructura de la Materia, IEM-C.S.I.C., Serrano 121, Madrid E-28006 (Spain); Hochlaf, M., E-mail: senent@iem.cfmac.csic.es, E-mail: hochlaf@univ-mlv.fr [Laboratoire de Modelisation et Simulation Multi Echelle, Universite Paris-Est, MSME UMR 8208 CNRS, 5 boulevard Descartes, F-77454 Marne-la-Vallee (France)

    2013-05-01

    We propose a general rule to distinguish between detectable and undetectable astronomical anions. We believe that only few anions live long enough in the interstellar medium and thus can be detected. Our method is based on quantum mechanical calculations capable of describing accurately the evolution of electronic states during chemical processes. The still not fully understood reactivity at low temperatures is discussed considering non-adiabatic effects. The role of excited states has usually been neglected in previous works which basically focused on the ground electronic state for interpretations of experimental observations. Here, we deal with unsaturated carbon chains (e.g., C{sub n} H{sup -}), which show a high density of electronic states close to their corresponding ground electronic states, complex molecular dynamics, and non-adiabatic phenomena. Our general rule shows that it is not sufficient that anions exist in the gas phase (in the laboratory) to be present in media such as astrophysical media, since formation and decomposition reactions of these anions may allow the population of anionic electronic states to autodetach, forming neutrals. For C{sub n} H, reactivity depends strongly on n, where long and short chains behave differently. Formation of linear chains is relevant.

  2. Comprehensive cluster analysis with Transitivity Clustering.

    Science.gov (United States)

    Wittkop, Tobias; Emig, Dorothea; Truss, Anke; Albrecht, Mario; Böcker, Sebastian; Baumbach, Jan

    2011-03-01

    Transitivity Clustering is a method for the partitioning of biological data into groups of similar objects, such as genes, for instance. It provides integrated access to various functions addressing each step of a typical cluster analysis. To facilitate this, Transitivity Clustering is accessible online and offers three user-friendly interfaces: a powerful stand-alone version, a web interface, and a collection of Cytoscape plug-ins. In this paper, we describe three major workflows: (i) protein (super)family detection with Cytoscape, (ii) protein homology detection with incomplete gold standards and (iii) clustering of gene expression data. This protocol guides the user through the most important features of Transitivity Clustering and takes ∼1 h to complete.

  3. Anion Binding of One-, Two-, and Three-Armed Thiourea Receptors Examined via Photoelectron Spectroscopy and Quantum Computations

    Energy Technology Data Exchange (ETDEWEB)

    Beletskiy, Evgeny V.; Wang, Xue-Bin; Kass, Steven R.

    2016-10-27

    A benzene ring substituted with 1–3 thiourea containing arms (1–3) were examined by photoelectron spectroscopy and density functional theory computations. Their conjugate bases and chloride, acetate and dihydrogen phosphate anion clusters are reported. The resulting vertical and adiabatic detachment energies span from 3.93 – 5.82 eV (VDE) and 3.65 – 5.10 (ADE) for the deprotonated species and 4.88 – 5.97 eV (VDE) and 4.45 – 5.60 eV (ADE) for the anion complexes. These results reveal the stabilizing effects of multiple hydrogen bonds and anionic host-guest interactions in the gas phase. Previously measured equilibrium binding constants in aqueous dimethyl sulfoxide for all three thioureas (Org. Biolmol. Chem. 2015, 13, 2170-2176) are compared to the present results and cooperative binding is uniformly observed in the gas phase but only for one case (i.e., 3 • H2PO4–) in solution.

  4. Effect of the chemical structure of anion exchange resin on the adsorption of humic acid: behavior and mechanism.

    Science.gov (United States)

    Shuang, Chendong; Wang, Jun; Li, Haibo; Li, Aimin; Zhou, Qing

    2015-01-01

    Polystyrenic (PS) anion-exchange resin and polyacrylic (PA) anion-exchange resin were used to investigate the effect of resin chemical structure on the adsorption of humic acid (HA). Due to the rearrangement of HA to form layers that function as barricades to further HA diffusion, PS resin exhibited 12.4 times slower kinetics for the initial adsorption rate and 8.4 times for the diffusion constant in comparison to that of the PA resin. An HA layer and a spherical cluster of HA can be observed on the surface of the PS and PA resins after adsorption, respectively. The considerable difference in HA adsorption between the PS and PA resins was due to the difference in molecule shape for interaction with different resin structures, which can essentially be explained by the hydrophobicity and various interactions of the PS resin. A given amount of HA occupies more positively charged sites and hydrophobic sites on the PS resin than were occupied by the same amount of HA on the PA resin. Increased pH resulted in an increase of HA adsorption onto the PA resin but a decrease in adsorption onto PS resin, as the non-electrostatic adsorption led to electrostatic repulsion between the HA attached to the resin and the HA dissolved in solution. These results suggest higher rates of adsorption and higher regeneration efficiency for interaction of HA with more hydrophilic anion exchange materials. Copyright © 2014 Elsevier Inc. All rights reserved.

  5. Fast Constrained Spectral Clustering and Cluster Ensemble with Random Projection

    National Research Council Canada - National Science Library

    Wenfen Liu; Mao Ye; Jianghong Wei; Xuexian Hu

    2017-01-01

    Constrained spectral clustering (CSC) method can greatly improve the clustering accuracy with the incorporation of constraint information into spectral clustering and thus has been paid academic attention widely...

  6. Clustering high dimensional data

    DEFF Research Database (Denmark)

    Assent, Ira

    2012-01-01

    High-dimensional data, i.e., data described by a large number of attributes, pose specific challenges to clustering. The so-called ‘curse of dimensionality’, coined originally to describe the general increase in complexity of various computational problems as dimensionality increases, is known...... for clustering are required. Consequently, recent research has focused on developing techniques and clustering algorithms specifically for high-dimensional data. Still, open research issues remain. Clustering is a data mining task devoted to the automatic grouping of data based on mutual similarity. Each cluster...... groups objects that are similar to one another, whereas dissimilar objects are assigned to different clusters, possibly separating out noise. In this manner, clusters describe the data structure in an unsupervised manner, i.e., without the need for class labels. A number of clustering paradigms exist...

  7. Synthesis and anion binding properties of porphyrins and related compounds

    KAUST Repository

    Figueira, Flávio

    2016-12-02

    Over the last two decades the preparation of pyrrole-based receptors for anion recognition has attracted considerable attention. In this regard porphyrins, phthalocyanines and expanded porphyrins have been used as strong and selective receptors while the combination of those with different techniques and materials can boost their applicability in different applications as chemosensors and extracting systems. Improvements in the field, including the synthesis of this kind of compounds, can contribute to the development of efficient, cheap, and easy-to-prepare anion receptors. Extensive efforts have been made to improve the affinity and selectivity of these compounds and the continuous expansion of related research makes this chemistry even more promising. In this review, we summarize the most recent developments in anion binding studies while outlining the strategies that may be used to synthesize and functionalize these type of macrocycles. © 2016 World Scientific Publishing Company.

  8. Solubility and transport of cationic and anionic patterned nanoparticles

    Science.gov (United States)

    Su, Jiaye; Guo, Hongxia; Olvera de La Cruz, Monica

    2012-02-01

    Diffusion and transport of nanoparticles (NPs) though nanochannels is important for desalination, drug delivery, and biomedicine. Their surface composition dictate their efficiency separating them by reverse osmosis, delivering into into cells, as well as their toxicity. We analyze bulk diffusion and transport through nanochannels of NPs with different hydrophobic-hydrophilic patterns achieved by coating a fraction of the NP sites with positive or negative charges via explicit solvent molecular dynamics simulations. The cationic NPs are more affected by the patterns, less water soluble, and have higher diffusion constants and fluxes than their anionic NPs counterparts. The NP-water interaction dependence on surface pattern and field strength explains these observations. For equivalent patterns, anionic NPs solubilize more than cationic NPs since the Coulomb interaction of free anionic NPs, which are much stronger than hydrophobic NP-water interactions, are about twice that of cationic NPs.

  9. Differential stabilization of adenine quartets by anions and cations.

    Science.gov (United States)

    van der Wijst, Tushar; Lippert, Bernhard; Swart, Marcel; Guerra, Célia Fonseca; Bickelhaupt, F Matthias

    2010-03-01

    We have investigated the structures and stabilities of four different adenine quartets with alkali and halide ions in the gas phase and in water, using dispersion-corrected density functional theory at the BLYP-D/TZ2P level. First, we examine the empty quartets and how they interact with alkali cations and halide anions with formation of adenine quartet-ion complexes. Second, we examine the interaction in a stack, in which a planar adenine quartet interacts with a cation or anion in the periphery as well as in the center of the quartet. Interestingly, for the latter situation, we find that both cations and anions can stabilize a planar adenine quartet in a stack.

  10. Anion-macrodipole interactions: self-assembling oligourea/amide macrocycles as anion transporters that respond to membrane polarization.

    Science.gov (United States)

    Hennig, Andreas; Fischer, Lucile; Guichard, Gilles; Matile, Stefan

    2009-11-25

    Macrocyclic urea/amide hybrids are introduced as functional, anion-selective membrane transporters in lipid bilayer membranes. Six derivatives with varying side chains (aliphatic and aromatic) and conformations (parallel and antiparallel carbonyl dipoles) are investigated by fluorescence methods, among which the more active aromatic derivatives were selected for an in-depth study. Strong response of transport activity toward anion exchange and weak response toward cation exchange establish anion selectivity for all macrocycles. "Antiparallel" macrocycles that self-assemble into "antiparallel" nanotubes without macrodipole exhibit Hofmeister selectivity. Parallel macrocycles that self-assemble into parallel nanotubes with strong macrodipole are capable of overcoming the dehydration penalty of the Hofmeister bias. Both systems show additional chloride selectivity. The activity of antiparallel and parallel nanotubes in binary mixtures of bromide/perchlorate and chloride/thiocyanate is over- and underadditive, respectively (positive and negative AMFE). The activity of antiparallel nanotubes decreases rapidly with increasing membrane polarization, whereas parallel nanotubes are inactivated at high and activated by membrane potentials at low concentration. Hill coefficients of parallel nanotubes decrease significantly with membrane polarization, whereas those of antiparallel nanotubes increase slightly. The overall unusual characteristics of parallel nanotubes call for a new transport mechanism, where macrodipole-potential interactions account for voltage sensitivity and anion-macrodipole interactions account for anion selectivity.

  11. Pulsars in Globular Clusters

    OpenAIRE

    Camilo, Fernando; Rasio, Frederic A.

    2005-01-01

    More than 100 radio pulsars have been detected in 24 globular clusters. The largest observed samples are in Terzan 5 and 47 Tucanae, which together contain 45 pulsars. Accurate timing solutions, including positions in the cluster, are known for many of these pulsars. Here we provide an observational overview of some properties of pulsars in globular clusters, as well as properties of the globular clusters with detected pulsars. The many recent detections also provide a new opportunity to re-e...

  12. Cluster Physics with Merging Galaxy Clusters

    Directory of Open Access Journals (Sweden)

    Sandor M. Molnar

    2016-02-01

    Full Text Available Collisions between galaxy clusters provide a unique opportunity to study matter in a parameter space which cannot be explored in our laboratories on Earth. In the standard LCDM model, where the total density is dominated by the cosmological constant ($Lambda$ and the matter density by cold dark matter (CDM, structure formation is hierarchical, and clusters grow mostly by merging.Mergers of two massive clusters are the most energetic events in the universe after the Big Bang,hence they provide a unique laboratory to study cluster physics.The two main mass components in clusters behave differently during collisions:the dark matter is nearly collisionless, responding only to gravity, while the gas is subject to pressure forces and dissipation, and shocks and turbulenceare developed during collisions. In the present contribution we review the different methods used to derive the physical properties of merging clusters. Different physical processes leave their signatures on different wavelengths, thusour review is based on a multifrequency analysis. In principle, the best way to analyze multifrequency observations of merging clustersis to model them using N-body/HYDRO numerical simulations. We discuss the results of such detailed analyses.New high spatial and spectral resolution ground and space based telescopeswill come online in the near future. Motivated by these new opportunities,we briefly discuss methods which will be feasible in the near future in studying merging clusters.

  13. Mesolysis of radical anions of tetra-, penta-, and hexaphenylethanes.

    Science.gov (United States)

    Tojo, Sachiko; Fujitsuka, Mamoru; Majima, Tetsuro

    2013-03-01

    A central carbon–carbon (C–C) σ bond dissociation of polyphenylethane radical anions (Ph(n)E•-, n = 3–6), mesolysis, was investigated by the transient absorption measurement during pulse radiolysis of Ph(n)E in 2-methyltetrahydrofuran. The charge resonance (CR) band of 1,1,2,2-tetraphenylethane radical anion (1,1,2,2-Ph4E•-) was observed in the near-infrared region immediately after an electron pulse to be attributed to the intramolecular dimer radical anion. The CR band disappeared with simultaneous formation of two absorption bands at 330 and 460 nm corresponding to diphenylmethyl radical and diphenylmethyl anion, respectively, indicating the occurrence of the mesolysis in 1,1,2,2-Ph4E•-. During pulse radiolysis of 1,1,1,2,2,2-hexaphenylethane (Ph6E), an absorption band of triphenylmethyl radical was observed at 340 nm immediately after an electron pulse. It is suggested that one electron attachment to Ph6E is followed by the subsequent rapid C–C σ bond dissociation. Formation of intramolecular dimer radical anions in Ph(n)E•- such as 1,1,2-triphenylethane (Ph3E), 1,1,1,2-tetraphenylethane (1,1,1,2-Ph4E), and 1,1,1,2,2-pentaphenylethane (Ph5E) was also studied together with the subsequent mesolysis. The mesolysis of Ph(n)E•- is discussed in terms of charge delocalization in the intramolecular dimer radical anions and the central C–C σ bond as well as bond dissociation energy of the central C–C σ bond of Ph(n)E•-.

  14. Anionic solid lipid nanoparticles supported on protamine/DNA complexes

    Energy Technology Data Exchange (ETDEWEB)

    Ye Jiesheng; Liu Chunxi; Chen Zhijin; Zhang Na [School of Pharmaceutical Science, Shandong University, 44 Wenhua Xi Road, Ji' nan (China); Wang Aihua [Department of Respiratory Medicine, Affiliated Qilu Hospital, Shandong University, 44 Wenhua Xi Road, Ji' nan (China)], E-mail: zhangnancy9@sdu.edu.cn

    2008-07-16

    The objective of this study was to design novel anionic ternary nanoparticles for gene delivery. These ternary nanoparticles were equipped with protamine/DNA binary complexes (150-200 nm) as the support, and the anionic formation was achieved by absorption of anionic solid lipid nanoparticles ({<=}20 nm) onto the surface of the binary complexes. The small solid lipid nanoparticles (SLNs) were prepared by a modified film dispersion-ultrasonication method, and adsorption of the anionic SLNs onto the binary complexes was typically carried out in water via electrostatic interaction. The formulated ternary nanoparticles were found to be relatively uniform in size (257.7 {+-} 10.6 nm) with a 'bumpy' surface, and the surface charge inversion from 19.28 {+-} 1.14 mV to -17.16 {+-} 1.92 mV could be considered as evidence of the formation of the ternary nanoparticles. The fluorescence intensity measurements from three batches of the ternary nanoparticles gave a mean adsorption efficiency of 96.75 {+-} 1.13%. Circular dichroism spectra analysis showed that the protamine/DNA complexes had been coated by small SLNs, and that the anionic ternary nanoparticles formed did not disturb the construction of the binary complexes. SYBR Green I analysis suggested that the ternary nanoparticles could protect the DNA from nuclease degradation, and cell viability assay results showed that they exhibit lower cytotoxicity to A549 cells compared with the binary complexes and lipofectamine. The transfection efficiency of the ternary nanoparticles was better than that of naked DNA and the binary complexes, and almost equal to that of lipofectamine/DNA complexes, as revealed by inversion fluorescence microscope observation. These results indicated that the anionic ternary nanoparticles could facilitate gene transfer in cultured cells, and might alleviate the drawbacks of the conventional cationic vector/DNA complexes for gene delivery in vivo.

  15. Clustering of Galaxy Clusters at Intermediate Redshifts

    Science.gov (United States)

    Postman, Marc; Lauer, Tod R.; Oegerle, William

    2001-02-01

    We propose to continue a redshift survey of 141 objectively selected galaxy clusters to measure their clustering properties and constrain models of the formation of structure in the universe. This is the first redshift survey to probe cluster correlations on comoving scales of ~ 50h_75^-1 Mpc at z ~ 0.5 and will thus provide an original and important constraint on the evolution of large-scale structure. The cluster sample comes from our deep (I_AB ≤ 24), contiguous 16 deg^2 I-band KPNO 4-m survey. The proposed observations distinguish themselves from other ongoing distant cluster redshift work in that this survey will be able to provide meaningful constraints on the large-scale spatial distribution of moderate redshift clusters owing to the large angular area and contiguous geometry of the parent survey. The availability of the HET/LRS provides a highly efficient solution to the acquisition of redshifts for the 80 cluster candidates with 0.6 ≤ z_est ≤ 0.7. The systems with z_est > 0.6 are needed to assure complete sampling of the cluster population at z_obs ~ 0.5. The survey declination (52+/-2°) and observational strategy are extremely well-suited to the initial capabilities and queue observing mode of the HET. The 4m/RCSP is well suited to completing the survey of the z_est data. This survey began using the KPNO 4m to obtain redshifts for the 0.3 ≤ z_est < 0.6 sample. So far, we have observed 31 clusters and we're presently ~25% complete with the z_est < 0.6 observations (75% complete for z_est < 0.4). We have discovered at least 2 superclusters at z=0.23 and z=0.50.

  16. Marketing research cluster analysis

    Directory of Open Access Journals (Sweden)

    Marić Nebojša

    2002-01-01

    Full Text Available One area of applications of cluster analysis in marketing is identification of groups of cities and towns with similar demographic profiles. This paper considers main aspects of cluster analysis by an example of clustering 12 cities with the use of Minitab software.

  17. The Durban Auto Cluster

    DEFF Research Database (Denmark)

    Lorentzen, Jochen; Robbins, Glen; Barnes, Justin

    2004-01-01

    The paper describes the formation of the Durban Auto Cluster in the context of trade liberalization. It argues that the improvement of operational competitiveness of firms in the cluster is prominently due to joint action. It tests this proposition by comparing the gains from cluster activities...

  18. Cosmology with cluster surveys

    Indian Academy of Sciences (India)

    Surveys of clusters of galaxies provide us with a powerful probe of the density and nature of the dark energy. The red-shift distribution of detected clusters is highly sensitive to the dark energy equation of state parameter . Upcoming Sunyaev–Zel'dovich (SZ) surveys would provide us large yields of clusters to very high ...

  19. Cosmology with cluster surveys

    Indian Academy of Sciences (India)

    Cosmology with cluster surveys. SUBHABRATA MAJUMDAR. CITA, University of Toronto, Toronto, ON, M5S 3H8, Canada. E-mail: subha@cita.utoronto.ca. Abstract. Surveys of clusters of galaxies provide us with a powerful probe of the den- sity and nature of the dark energy. The red-shift distribution of detected clusters is.

  20. Formation of stellar clusters

    Science.gov (United States)

    Smilgys, Romas; Bonnell, Ian A.

    2017-12-01

    We investigate the triggering of star formation and the formation of stellar clusters in molecular clouds which form as the interstellar medium passes through spiral shocks. The spiral shock compresses gas into an ∼100 pc long main star formation ridge, where clusters form every 5-10 pc along the merger ridge. We use a gravitational potential-based cluster finding algorithm, which extracts individual clusters, calculates their physical properties and traces cluster evolution over multiple time-steps. Final cluster masses at the end of simulation range between 1000 and 30 000 M⊙ with their characteristic half-mass radii between 0.1 and 2 pc. These clusters form by gathering material from 10-20 pc size scales. Clusters also show a mass-specific angular momentum relation, where more massive clusters have larger specific angular momentum due to the larger size scales, and hence angular momentum from which they gather their mass. The evolution shows that more massive clusters experience hierarchical merging process, which increases stellar age spreads up to 2-3 Myr. Less massive clusters appear to grow by gathering nearby recently formed sinks, while more massive clusters with their large global gravitational potentials are increasing their mass growth from gas accretion.

  1. Relational aspects of clusters

    DEFF Research Database (Denmark)

    Gjerding, Allan Næs

    The present paper is the first preliminary account of a project being planned for 2013, focussing on the development of the biomedico cluster in North Denmark. The project focusses on the relational capabilities of the cluster in terms of a number of organizational roles which are argued...... to be necessary for the development and growth of the upcoming cluster in question....

  2. Structures of Mn clusters

    Indian Academy of Sciences (India)

    Abstract. The geometries of several Mn clusters in the size range Mn13–Mn23 are studied via the generalized gradient approximation to density functional theory. For the 13- and 19-atom clusters, the icosahedral structures are found to be most stable, while for the 15-atom cluster, the bcc structure is more favoured.

  3. Structures of Mn clusters

    Indian Academy of Sciences (India)

    Unknown

    Abstract. The geometries of several Mn clusters in the size range Mn13–Mn23 are studied via the generalized gradient approximation to density functional theory. For the 13- and 19-atom clusters, the icosahedral struc- tures are found to be most stable, while for the 15-atom cluster, the bcc structure is more favoured.

  4. Samarium Doped Cerium Oxide Clusters: a Study on the Modulation of Electronic Structure

    Science.gov (United States)

    Topolski, Josey E.; Kafader, Jared O.; Marrero-Colon, Vicmarie; Chick Jarrold, Caroline

    2017-06-01

    Cerium oxide is known for its use in solid oxide fuel cells due to its high ionic conductivity. The doping of trivalent samarium atoms into cerium oxide is known to enhance the ionic conductivity through the generation of additional oxygen vacancies. This study probes the electronic structure of Sm_{x}Ce_{y}O_{z} (x+y=3, z=2-4) anion and neutral clusters. Anion photoelectron spectra of these mixed metal clusters exhibit additional spectral features not present in the previously studied cerium oxide clusters. Density functional theory calculations have been used to aid interpretation of collected spectra. The results of this work can be used to inform the design of materials used for solid oxide fuel cells.

  5. Time-dependent Anion Chemistry in the CSE IRC+10216

    Science.gov (United States)

    Guelin, M.; Agundez, M.; Cernicharo, J.; Gottlieb, C.; McCarthy, M.; Thaddeus, P.

    2011-05-01

    Following the spectral characterization of C-chain anions, in the Harvard microwave laboratory, we have discovered 6 anions in the envelope of the C-rich star IRC+10216 and set limits to the abundance of two others. The anions we studied in this source range from CCH- to C8H- and from CN- to C5N- [1,2,3]. Anion abundances are low and the rotational lines weak, even in favorable cases. Two years ago, we have been able to map C6H- in IRC+10216, with the PdB interferometer, and to show that it is located, like the C6H radical, in a hollow shell. The angular resolution of the observations (5) and the S/N ratio were however insufficient to spatially differentiate the anion from the radical. Taking advantage of the recent installation of a wide-band correlator on PdBI, we have re-observed with a twice higher resolution the 83 GHz line of C6H- , as well as nearby lines of C5N-, C4H-, C2H- and of several C-chain molecules and radicals. Except for CCH-, all those species are detected and we are currently analyzing their distributions and abundances. Chemistry models, based on the electron radiative attachment theory developed by Herbst and collaborators, predict that anions and parent radicals peak at different radii in the expanding CSE[4]. Predicted radial shifts range from a few arcsec, for C6H-, to more than 10 (500 yr) for C4H- and CN-. We know, from previous single-dish observations, that the actual abundances of C4H- and CN- , relative to C4H and CN, differ by orders of magnitude from radiative attachment model predictions, while those of the long anions, C6H- and C8H agree well with predictions. The new interferometric observations, allied to single-dish data, allow us to measure the formation/destruction time of the different species and to set constraints on the rates of electron radiative attachment, rates which, so far, are only crudely evaluated through the statistical theory. The relatively high abundances of CN-, C3N - and C5N - , compared to CCH-, C4H - and

  6. Photocatalytic degradation of anionic surfactant using zinc oxide nanoparticles

    Science.gov (United States)

    Giahi, M.; Habibi, S.; Toutounchi, S.; Khavei, M.

    2012-04-01

    In this paper the photocatalytic degradation of anionic surfactant LABS was studied by a batch process using ZnO nanoparticles with diameter size of 20 nm catalyst on irradiation with UV light and their behavior comparatively examined with respect to ZnO commercial powder. The effect of parameters such as initial surfactant concentration, initial solution pH has been studied. Also degradation at LABS in the presence of an electron acceptor like potassium peroxydisulfate and effect of anion presence on surfactant degradation has been systematically investigated. The obtained result demonstrated a high photocatalytic activity of nanosize semiconducting particles.

  7. A theoretical study of ternary indole-cation-anion complexes.

    Science.gov (United States)

    Carrazana-García, Jorge A; Cabaleiro-Lago, Enrique M; Campo-Cacharrón, Alba; Rodríguez-Otero, Jesús

    2014-12-07

    The simultaneous interactions of an anion and a cation with a π system were investigated by MP2 and M06-2X theoretical calculations. Indole was chosen as a model π system for its relevance in biological environments. Two different orientations of the anion, interacting with the N-H and with the C-H groups of indole, were considered. The four cations (Na(+), NH4(+), C(NH2)3(+) and N(CH3)4(+)) and the four anions (Cl(-), NO3(-), HCOO(-) and BF4(-)) included in the study are of biological interest. The total interaction energy of the ternary complexes was calculated and separated into its two- and three-body components and all of them are further divided into their electrostatic, exchange, repulsion, polarization and dispersion contributions using the local molecular orbital-energy decomposition analysis (LMO-EDA) methodology. The binding energy of the indole-cation-anion complexes depends on both ions, with the cation having the strongest effect. The intense cation-anion attraction determines the geometric and energetic features in all ternary complexes. These structures, with both ions on the same side of the π system, show an anti-cooperative interaction. However, the interaction is not only determined by electrostatics, but also the polarization contribution is important. Specific interactions like the one established between the anion and the N-H group of indole or the proton transfer between an acidic cation and a basic anion play a significant role in the energetics and the structure of particular complexes. The presence of the polar solvent as modelled with the polarizable continuum model (PCM) does not seem to have a significant effect on the geometry of the ternary complexes, but drastically weakens the interaction energy. Also, the strength of the interaction is reduced at a faster rate when the anion is pushed away, compared to the results obtained in the gas phase. The combination of PCM with the addition of one water molecule indicates that the PCM

  8. Anion Conduction in Solid Electrolytes Probed by Water Transport Measurement

    OpenAIRE

    Takahashi, Hiroki; Takeguchi, Tatsuya; Yamanaka, Toshiro; Ueda, Wataru

    2010-01-01

    The application of inorganic materials as electrolyte of alkaline fuel cell is an important task to achieve noble-metal-free and high-temperature-resistant fuel cells. In the present study, water transport during ion conduction through solid electrolyte was measured to seek inorganic materials with anion conduction. We discovered the anion conduction in layered oxide NaCo2O4. Although LiCoO2 has the similar layered structure to NaCo2O4, this oxide showed cation conduction.

  9. Preparation of Cationic MOFs with Mobile Anions by Anion Stripping to Remove 2,4-D from Water

    Directory of Open Access Journals (Sweden)

    Tao Chen

    2017-07-01

    Full Text Available A cationic porous framework with mobile anions (MIL-101(Cr-Cl was easily and successfully synthesized by utilizing the stronger affinity of F− to Al3+ than Cr3+ in the charge-balanced framework of MIL-101(Cr. The structure, morphology and porosity of MIL-101(Cr-Cl were characterized. The obtained new materials retain the high surface area, good thermostability, and structure topology of MIL-101(Cr. With the mobile Cl− anion, MIL-101(Cr-Cl can be used as an ion-exchange material for anionic organic pollutions. In this work, 2,4-dichlorophenoxyacetic acid (2,4-D was used as a model to test the absorption performance of this new material. This new material exhibited improved adsorbability compared to that of the original metal-organic frameworks (MOFs. At the same time, this material also shows high anti-interference performance with changing solution pH.

  10. Tetrabutylammonium Salts of Aluminum(III) and Gallium(III) Phthalocyanine Radical Anions Bonded with Fluoren-9-olato(-) Anions and Indium(III) Phthalocyanine Bromide Radical Anions.

    OpenAIRE

    Konarev, Dmitri V; Khasanov, Salavat S; Ishikawa, Manabu; Nakano, Yoshiaki; Otsuka, Akihiro; Yamochi, Hideki; Saito, Gunzi; Lyubovskaya, Rimma N

    2017-01-01

    Reduction of aluminum(III), gallium(III), and indium(III) phthalocyanine chlorides by sodium fluorenone ketyl in the presence of tetrabutylammonium cations yielded crystalline salts of the type (Bu4 N(+) )2 [M(III) (HFl-O(-) )(Pc(.3-) )](.-) (Br(-) )⋅1.5 C6 H4 Cl2 [M=Al (1), Ga (2); HFl-O(-) =fluoren-9-olato(-) anion; Pc=phthalocyanine] and (Bu4 N(+) ) [In(III) Br(Pc(.3-) )](.-) ⋅0.875 C6 H4 Cl2 ⋅0.125 C6 H14 (3). The salts were found to contain Pc(.3-) radical anions with negatively charged ...

  11. Tuning the electronic environment of the anion by using binary ionic liquid mixtures

    Science.gov (United States)

    Men, Shuang; Licence, Peter

    2017-08-01

    The electronic environment of the anion is tuned by using binary ionic liquid mixtures employing a common anion and two cations with large difference in acidity. X-ray photoelectron spectroscopy is used to monitor the change of the electronic environment of the anion by measuring the binding energy of elements present in the anion. It is found that due to the large difference in acidity of the two cations, noticeable shifts can be observed for all anion-based components, no matter how basic the anion is.

  12. Selective anion exchange and tunable luminescent behaviors of metal-organic framework based supramolecular isomers.

    Science.gov (United States)

    Manna, Biplab; Singh, Shweta; Karmakar, Avishek; Desai, Aamod V; Ghosh, Sujit K

    2015-01-05

    Owing to the conformational (cis or trans) flexibility of a N-donor ligand, the combinations of the same and Cd(ClO4)2 under variable solvent templates afforded two supramolecular isomers based on two-dimensional metal-organic frameworks. Both compounds contain weakly coordinating ClO4(-) anions attached to the metal centers. Both frameworks showed facile anion exchange behaviors with various kinds of foreign anions. Moreover, both frameworks showed anion-driven structural dynamism and exhibited the preferential uptake of strongly coordinating anions over others. Anion-regulated modulation in luminescent behaviors was also observed in both cases.

  13. Electronic properties of polyoxometalates: electron and proton affinity of mixed-addenda Keggin and Wells-Dawson anions.

    Science.gov (United States)

    López, Xavier; Bo, Carles; Poblet, Josep M

    2002-10-23

    A series of systematic DFT calculations were conducted on Keggin [SiW(9)M(3)O(40)](n-), M = Mo, V, and Nb; and Wells-Dawson anions [P(2)M(18)O(62)],(6-) M = W and Mo; [P(2)M(15)M(3)'O(62)](m-), M = W and Mo, M' = W, Mo, and V to analyze the redox properties and the basicity of the external oxygen sites in polyoxometalates with nonequivalent addenda metals. The energy and composition of the lowest unoccupied orbitals, formally delocalized over the addenda atoms, determine the redox properties of a polyoxometalate. When a Mo(6+) substitutes one W(6+) in the 1:12 tungstate, the energy of the LUMO decreases and the cluster is more easily reduced. The tungstoniobates behave differently because the niobium orbitals insert into the tungsten band and the reduction of [SiW(9)Nb(3)O(40)](7-) yields the blue species SiW(9)Nb(3) 1e and not the cluster SiW(9)Nb(2)Nb(IV). In Wells-Dawson structures, the polar and equatorial sites have different electron affinities and the reduction preferentially occurs in the equatorial sites. Inserting ions with larger electron affinities into the polar sites can modify this traditional conduct. Hence, the trisubstituted [P(2)W(15)V(3)O(62)](9-) anion is reduced in the vanadium polar sites. By means of molecular electrostatic potential maps and the relative energy of the various protonated forms of [SiW(9)V(3)O(40)](7-) and [SiW(9)Mo(3)O(40)](4-), we established the basicity scale: OV(2) > OMo(2) > OW(2) > OV > OW > OMo. Finally, a continuum model for the solvent enabled us to compare anions with different total charges.

  14. Cluster analysis for applications

    CERN Document Server

    Anderberg, Michael R

    1973-01-01

    Cluster Analysis for Applications deals with methods and various applications of cluster analysis. Topics covered range from variables and scales to measures of association among variables and among data units. Conceptual problems in cluster analysis are discussed, along with hierarchical and non-hierarchical clustering methods. The necessary elements of data analysis, statistics, cluster analysis, and computer implementation are integrated vertically to cover the complete path from raw data to a finished analysis.Comprised of 10 chapters, this book begins with an introduction to the subject o

  15. Ion-pair dissociation of highly excited carbon clusters: Size and charge effects

    OpenAIRE

    Launoy, Thibaut; Béroff, Karine; Chabot, Marin; Martinet, Guillaume; Le Padellec, A.; Pino, Thomas; Bouneau, S.; Vaeck, Nathalie; Liévin, Jacques; Féraud, Géraldine G.; Loreau, Jérôme; Mahajan, Thejus T. M

    2017-01-01

    We present measurements of ion-pair dissociation (IPD) of highly excited neutral and ionized carbon clusters Cn=2-5(q=0-3)+. The tool for producing these species was a high-velocity collision between Cn+ projectiles (v=2.25 a.u.) and helium atoms. The setup allowed us to detect in coincidence anionic and cationic fragments, event by event, leading to a direct and unambiguous identification of the IPD process. Compared with dissociation without anion emission, we found typical 10-4 IPD rates, ...

  16. Convergence of coupled cluster perturbation theory

    CERN Document Server

    Eriksen, Janus Juul; Matthews, Devin A; Jørgensen, Poul; Olsen, Jeppe

    2016-01-01

    The convergence of a recently proposed coupled cluster (CC) family of perturbation series [Eriksen et al., J. Chem. Phys. 140, 064108 (2014)], in which the energetic difference between a parent and a target CC model is expanded in orders of the M{\\o}ller-Plesset (MP) fluctuation potential, is investigated for four prototypical closed-shell systems (Ne, singlet methylene, distorted HF, and the fluoride anion) in standard and augmented basis sets. In these investigations, energy corrections of the various series have been calculated to high orders and their convergence radii determined by probing for possible front- and back-door intruder states. In summary, we conclude how it is primarily the choice of target state, and not the choice of parent state, which ultimately governs the convergence behavior of a given series. For example, restricting the target state to, say, triple or quadruple excitations might remove intruders present in series that target the full configuration interaction (FCI) limit, such as th...

  17. Spatial cluster modelling

    CERN Document Server

    Lawson, Andrew B

    2002-01-01

    Research has generated a number of advances in methods for spatial cluster modelling in recent years, particularly in the area of Bayesian cluster modelling. Along with these advances has come an explosion of interest in the potential applications of this work, especially in epidemiology and genome research. In one integrated volume, this book reviews the state-of-the-art in spatial clustering and spatial cluster modelling, bringing together research and applications previously scattered throughout the literature. It begins with an overview of the field, then presents a series of chapters that illuminate the nature and purpose of cluster modelling within different application areas, including astrophysics, epidemiology, ecology, and imaging. The focus then shifts to methods, with discussions on point and object process modelling, perfect sampling of cluster processes, partitioning in space and space-time, spatial and spatio-temporal process modelling, nonparametric methods for clustering, and spatio-temporal ...

  18. Modeling Clustered Data with Very Few Clusters.

    Science.gov (United States)

    McNeish, Daniel; Stapleton, Laura M

    2016-01-01

    Small-sample inference with clustered data has received increased attention recently in the methodological literature, with several simulation studies being presented on the small-sample behavior of many methods. However, nearly all previous studies focus on a single class of methods (e.g., only multilevel models, only corrections to sandwich estimators), and the differential performance of various methods that can be implemented to accommodate clustered data with very few clusters is largely unknown, potentially due to the rigid disciplinary preferences. Furthermore, a majority of these studies focus on scenarios with 15 or more clusters and feature unrealistically simple data-generation models with very few predictors. This article, motivated by an applied educational psychology cluster randomized trial, presents a simulation study that simultaneously addresses the extreme small sample and differential performance (estimation bias, Type I error rates, and relative power) of 12 methods to account for clustered data with a model that features a more realistic number of predictors. The motivating data are then modeled with each method, and results are compared. Results show that generalized estimating equations perform poorly; the choice of Bayesian prior distributions affects performance; and fixed effect models perform quite well. Limitations and implications for applications are also discussed.

  19. Clusters and how to make it work : Cluster strategy toolkit

    NARCIS (Netherlands)

    Anu Manickam; Karel van Berkel

    2014-01-01

    Clusters are the magic answer to regional economic development. Firms in clusters are more innovative; cluster policy dominates EU policy; ‘top-sectors’ and excellence are the choice of national policy makers; clusters are ‘in’. But, clusters are complex, clusters are ‘messy’; there is no clear

  20. Electronic and structural investigations of gold clusters doped with copper: Aun-1Cu- (n=13-19).

    Science.gov (United States)

    Zorriasatein, Shahab; Joshi, Kavita; Kanhere, D G

    2008-05-14

    We have obtained the ground state and the equilibrium geometries of Au(n) (-) and Au(n-1)Cu(-) in the size range of n=13-19. We have used first principles density functional theory within plane wave and Gaussian basis set methods. For each of the cluster we have obtained at least 100 distinct isomers. The anions of gold clusters undergo two structural transformations, the first one from flat cage to hollow cage and the second one from hollow cage to pyramidal structure. The Cu doped clusters do not show any flat cage structures as the ground state. The copper doped systems evolve from a general 3D structure to hollow cage with Cu trapped inside the cage at n=16 and then to pyramidal structure at n=19. The introduction of copper atom enhances the binding energy per atom as compared to gold cluster anions.

  1. Beneficiation of Nigerian Clay with Poly Anionic Cellulose-Regular ...

    African Journals Online (AJOL)

    ... concentrations and the effect of different concentration of Poly Anionic Cellulose-Regular (PAC-R) on the Emede clay was investigated. The experiment centred on the determination of its suitability for use in drilling mud formulation. Preliminary investigation suggests that Emede clay has a good potential for use in drilling ...

  2. Dietary cation anion difference: Impact on productive and ...

    African Journals Online (AJOL)

    Various nutritional tools have been used to improve the productive and reproductive performance of animals, among which difference between certain minerals, called dietary cation anion difference (DCAD) plays a pivotal role. Low or negative DCAD diets reduce blood pH and HCO3- and animal becomes acidotic.

  3. Retention Behavior of Inorganic Anions in Hydrophilic Interaction Chromatography.

    Science.gov (United States)

    Takayama, Nobuyuki; Lim, Lee Wah; Takeuchi, Toyohide

    2017-01-01

    The retention behavior of inorganic anions was studied in hydrophilic interaction chromatography (HILIC). In this study, five kinds of HILIC stationary phases (amino, imidazole, amide, pyridine and zwitterionic) were investigated. It was found that only amino and imidazole columns exhibited the separation of inorganic anions under HILIC conditions. The retention mechanism was further investigated under both columns. A reversed elution order of inorganic anions was observed under the HILIC condition compared with those observed under the ion-exchange chromatography mode (IEC). The effect of salt species and their concentration in the eluent were investigated under constant acetonitrile (ACN) content. Sodium chloride and sodium perchlorate were chosen as the salt, and the salt (sodium perchlorate) concentration was varied from 10 to 40 mM to confirm the effect of the electrostatic interaction. The slope values of the plots of the log retention factor (k) versus the log eluent concentration were calculated to be between -0.43 and -0.45 for the amino column, while those obtained on the imidazole column were between -0.68 and -0.73. Various concentrations of ACN were also examined with 20 mM sodium perchlorate, and the typical HILIC retention behavior was observed on both amino and imidazole columns. Due to the obtained results, it is considered that the separation of inorganic anions under the HILIC condition was achieved by both electrostatic interaction and partition.

  4. Contribution of attendant anions on cadmium toxicity to soil enzymes.

    Science.gov (United States)

    Tian, Haixia; Kong, Long; Megharaj, Mallavarapu; He, Wenxiang

    2017-11-01

    Sorption and desorption are critical processes to control the mobility and biotoxicity of cadmium (Cd) in soils. It is known that attendant anion species of heavy metals could affect metal adsorption on soils and might further alter their biotoxicity. However, for Cd, the influence of attendant anions on its sorption in soils and subsequent toxicity on soil enzymes are still unknown. In this work, four Cd compounds with different salt anions (SO42-, NO3-, Cl-, and Ac-) were selected to investigate their impact of on the sorption, soil dehydrogenase activity (DHA) and alkaline phosphatase activity (ALP). Thus, a series of simulated Cd pollution batch experiments including measuring adsorption-desorption behavior of Cd on soils and soil enzyme activities were carried out. Results showed that CdSO4 exhibited highest sorption capacity among the tested soils except in Hunan soil. The Cd sorption with NO3- displayed a similar behavior with Cl- on all tested soils. Compared with soil properties, all four kinds of anions on Cd sorption played a more significant role affecting Cd ecological toxicity to soil DHA and ALP. Cd in acetate or nitrate form appears more sensitive towards DHA than sulphate and chloride, while the later pair is more toxic towards ALP than the former. These results have important implications for evaluation of Cd contamination using soil enzyme as bioindicator. Copyright © 2017 Elsevier Ltd. All rights reserved.

  5. An anionic two-dimensional indium carboxylate framework derived ...

    Indian Academy of Sciences (India)

    1385–1391. c Indian Academy of Sciences. An anionic two-dimensional indium carboxylate framework derived from a pseudo C3-symmetric semi-flexible tricarboxylic acid. PRATAP VISHNOI, ALOK CH KALITA and RAMASWAMY MURUGAVEL. ∗. Department of Chemistry, Indian Institute of Technology Bombay, Powai, ...

  6. Adsorption and intercalation of anionic surfactants onto layered ...

    Indian Academy of Sciences (India)

    Unknown

    Abstract. Layered double hydroxides (LDH) with brucite like structure was modified with various anionic surfactants containing sulfonate, carboxyl, phosphonate and sulfate end group through ion-exchange method. XRD reports indicated that the sulfonate group containing surfactants led to an adsorption process whereas.

  7. Changing certain dietary cationic and anionic minerals: Impact on ...

    African Journals Online (AJOL)

    This study was conducted to examine the influence of varying dietary cation anion difference (DCAD) on acid base status, mineral dynamics, occurrence of milk fever and udder edema in Nili Ravi buffaloes in a randomized complete block design. Four iso-nitrogenous and iso-caloric diets having -22, -11, +11 and +22 ...

  8. Electronic spectra of anions intercalated in layered double hydroxides

    Indian Academy of Sciences (India)

    Transition metal complexes intercalated in layered double hydroxides have a different electronic structure as compared to their free state owing to their confinement within the interlayer gallery. UV–Vis absorptions of the intercalated complex anions show a significant shift as compared to their free state. The ligand to metal ...

  9. Evaluation of some anionic exchange resins as potential tablet ...

    African Journals Online (AJOL)

    Purpose: To determine the potential of some anionic exchange resins as tablet disintegrants. Methods: Dowex1® x2, x4 and x8 resins (crosslinked copolymers of styrene and divinylbenzene with quaternary methyl amine functionality) were evaluated as disintegrant for dibasic calcium phosphate dihydrate tablets. The best ...

  10. Anion effects on the cyclobis(paraquat-p-phenylene) host

    DEFF Research Database (Denmark)

    Andersen, Sissel Stenbæk; Jensen, Morten; Sørensen, Anne

    2012-01-01

    Binding studies between the electron accepting host cyclobis(paraquat-p-phenylene) and a series of electron donors in the presence of differently sized counteranions reveal that both the nature and the concentration of the anion have a large impact on the association strength of the resulting host...

  11. Mechanism of protection of adenosine from sulphate radical anion ...

    Indian Academy of Sciences (India)

    The photooxidation of adenosine in presence of peroxydisulphate (PDS) has been studied by spectrophotometrically measuring the absorbance of adenosine at 260 nm. The rates of oxidation of adenosine by sulphate radical anion have been determined in the presence of different concentrations of caffeic acid. Increase in ...

  12. Anionic Redox Chemistry in Polysulfide Electrode Materials for Rechargeable Batteries.

    Science.gov (United States)

    Grayfer, Ekaterina D; Pazhetnov, Egor M; Kozlova, Mariia N; Artemkina, Sofya B; Fedorov, Vladimir E

    2017-12-22

    Classical Li-ion battery technology is based on the insertion of lithium ions into cathode materials involving metal (cationic) redox reactions. However, this vision is now being reconsidered, as many new-generation electrode materials with enhanced reversible capacities operate through combined cationic and anionic (non-metal) reversible redox processes or even exclusively through anionic redox transformations. Anionic participation in the redox reactions is observed in materials with more pronounced covalency, which is less typical for oxides, but quite common for phosphides or chalcogenides. In this Concept, we would like to draw the reader's attention to this new idea, especially, as it applies to transition-metal polychalcogenides, such as FeS 2 , VS 4 , TiS 3 , NbS 3 , TiS 4 , MoS 3 , etc., in which the key role is played by the (S-S) 2- /2 S 2- redox reaction. The exploration and better understanding of the anion-driven chemistry is important for designing advanced materials for battery and other energy-related applications. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Adsorption and intercalation of anionic surfactants onto layered ...

    Indian Academy of Sciences (India)

    Layered double hydroxides (LDH) with brucite like structure was modified with various anionic surfactants containing sulfonate, carboxyl, phosphonate and sulfate end group through ion-exchange method. XRD reports indicated that the sulfonate group containing surfactants led to an adsorption process whereas the sulfate ...

  14. On the Adsorption of Some Anionic Collectors on Fluoride Minerals

    DEFF Research Database (Denmark)

    Sørensen, Emil

    1973-01-01

    Test flotations have been carried out in a small apparatus under standardized conditions in order to determine the dependence of the flotation yield on the reagent concentration for certain minerals and anionic collectors. The results suggest that a special adsorption mechanism is operating...

  15. Anion-π Catalysis of Diels-Alder Reactions.

    Science.gov (United States)

    Liu, Le; Cotelle, Yoann; Bornhof, Anna-Bea; Besnard, Céline; Sakai, Naomi; Matile, Stefan

    2017-10-09

    Among concerted cycloadditions, the Diels-Alder reaction is the grand old classic, which is usually achieved with acid catalysis. In this report, hydroxypyrones, oxa-, and thiazolones are explored because they provide access to anionic dienes. Their [4+2] cycloaddition with cyclic and acyclic dienophiles, such as maleimides and fumarates, affords bicyclic products with four new stereogenic centers. Bifunctional anion-π catalysts composed of amine bases next to the π surface of naphthalenediimides (NDIs) are shown to selectively stabilize the "open", fully accessible anionic exo transition state on the π-acidic aromatic surface. Our results also include reactivities that are hard to access with conventional organocatalysts, such as the exo-specific and highly enantioselective Diels-Alder reaction of thiazolones and maleimides with complete suppression of the otherwise dominant Michael addition. With increasing π acidity of the anion-π catalysts, the rates, chemo-, diastereo-, and enantioselectivities increase consistently. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Effect of Anionic Polymers on Drug Loading and Release from ...

    African Journals Online (AJOL)

    or sodium alginate as anionic polymers for the delivery of clindamycin phosphate as a model hydrophilic cationic ... Controlled drug delivery, enhanced bioavailability of entrapped drugs [5], and/or improved tissue distribution, good tolerability, and drug targeting have been ... certain types of bacterial infections, including.

  17. Effect of biocides and anionic homopolymeric inhibitors on the ...

    African Journals Online (AJOL)

    This paper describes the effect of biocides and of the anionic homopolymeric inhibitors on the precipitation behavior of calcium fluoride (CaF2).The efficiency of inhibitors in the presence and absence of biocides was calculated using the half-life (t1/2) approach, where 50% of the concentration has been precipitated.

  18. The effect of membrane diffusion potential change on anionic drugs ...

    African Journals Online (AJOL)

    The effect of membrane potential change on anionic drugs Indomethacin and barbitone induced human erythrocyte shape change and red cell uptake of drug has been studied using microscopy and spectrophotometry techniques respectively. The membrane potential was changed by reducing the extracellular chloride ...

  19. Cation and anion sequences in dark-adapted Balanus photoreceptor

    Science.gov (United States)

    1977-01-01

    Anion and cation permeabilities in dark-adapted Balanus photoreceptors were determined by comparing changes in the membrane potential in response to replacement of the dominant anion (Cl-) or cation (Na+) by test anions or cations in the superfusing solution. The anion permeability sequence obtained was PI greater than PSO4 greater than PBr greater than PCl greater than Pisethionate greater than Pmethanesulfonate. Gluconate, glucuronate, and glutamate generally appeared more permeable and propionate less permeable than Cl-. The alkali-metal cation permeability sequence obtained was PK greater than PRb greater than PCx greater than PNa approximately PLi. This corresponds to Eisenman's IV which is the same sequencethat has been obtained for other classes of nerve cells in the resting state. The values obtained for the permeability ratios of the alkali-metal cations are considered to be minimal. The membrane conductance measured by passing inward current pulses in the different test cations followed the sequence, GK greater than GRb greater than GCs greater than GNa greater than GLi. The conductance ratios obtained for a full substitution of the test cation agreed quite well with permeability ratios for all the alkali-metal cations except K+ which was generally higher. PMID:199688

  20. Cations but not anions regulate the responsiveness of kainate receptors.

    Science.gov (United States)

    Maclean, David M; Wong, Adrian Y C; Fay, Anne-Marie; Bowie, Derek

    2011-02-09

    Kainate-selective ionotropic glutamate receptors are unique among ligand-gated ion channels in their obligate requirement of external anions and cations for activation. Although it is established that the degree of kainate receptor (KAR) activation is shaped by the chemical nature of the agonist molecule, the possible complementary role of external ions has yet to be examined. Here we show that external cations but not anions regulate the responsiveness to a range of full and partial agonists acting on rat GluK2 receptors. This observation is unexpected as previous work has assumed anions and cations affect KARs in an identical manner through functionally coupled binding sites. However, our data demonstrate that anion- and cation-binding pockets behave discretely. We suggest cations uniquely regulate a pregating or flipping step that impacts the closed-cleft stability of the agonist-binding domain (ABD). This model departs from a previous proposal that KAR agonist efficacy is governed by the degree of closure elicited in the ABD by ligand binding. Our findings are, however, in line with recent studies on Cys-loop ligand-gated ion channels suggesting that the "flipping" mechanism has been conserved by structurally diverse ligand-gated ion channel families as a common means of regulating neurotransmitter behavior.

  1. Trinuclear Metal Chalcogenide Clusters as Precursors for Superatomic Solids and Cluster Organic Frameworks

    Science.gov (United States)

    Shott, Jessica Lauren

    Inorganic molecular clusters Ni3(mu3-I) 2(mu2-dppm)3 (1), Ni3(mu 3-Te)2(mu2-dppm)3 (2), Ni3(mu3-Se)2(mu2-dppm) 3 (3), Ni3(mu3-S)2(mu 2-dppm)3 (4), Co4(mu3-S) 4(PPri3)4 (5), and Mo3(mu3-S)2(mu2-S)3(PMe 3)6 (6) have been used as building block precursors in the formation of binary superatomic solids with fullerenes (1-6•C 60). These solids are crystallized from solution and charge transfer from the electron-rich molecular cluster precursors to fullerene was confirmed using infrared (IR) spectroscopy. Structural data for these superatomic solids was obtained using single-crystal X-ray diffraction (XRD) experiments and suggests that their assembly is directed by noncovalent interactions. Close-contacts, reminiscent of halogen bonds, between cluster capping ligands and fulleride anions are observed in the solid state. Superconducting quantum interference device (SQUID) magnetometry and two-probe conductivity measurements indicate that compounds 1•C60 and 2•C 60 are paramagnetic and one hundred times more conductive than the constituent cluster precursors. Additionally, derivatives of molecular clusters 5 and 6 have been synthesized and investigated for use as superatomic secondary building units for 2D and 3D cluster organic frameworks. Characterization of these novel building blocks was accomplished using NMR spectroscopy as well as matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) and XRD analysis.

  2. RF Reactive Magnetron Sputter Deposition of Silicon Sub-Oxides

    NARCIS (Netherlands)

    Hattum, E.D. van

    2007-01-01

    RF reactive magnetron plasma sputter deposition of silicon sub oxide E.D. van Hattum Department of Physics and Astronomy, Faculty of Sciences, Utrecht University The work described in the thesis has been inspired and stimulated by the use of SiOx layers in the direct inductive printing technology,

  3. First Principles Atomistic Model for Carbon-Doped Boron Suboxide

    Science.gov (United States)

    2014-09-01

    chemically distinct B sites within an individual icosahedron (polar Bp and equatorial Be). The Bp sites occupy 2 opposing 3-atom planes of the... icosahedron and create Bp- Bp linkages between the icosahedra. The Be sites bond along the equatorial axis of the icosahedron , forming a hexagonal Be-Be chair

  4. Raman spectra of hot-pressed boron suboxide

    CSIR Research Space (South Africa)

    Machaka, R

    2011-01-01

    Full Text Available -64 Copyright ? 2011 VBRI press. (d) The relatively sharp feature at 500 cm-1 corresponds to the symmetric stretching of the B?O?B triatomic chain, (e) The narrow line just above 500 cm-1, has been attributed to the motion of the entire B12 icosahedron...

  5. Open source clustering software.

    Science.gov (United States)

    de Hoon, M J L; Imoto, S; Nolan, J; Miyano, S

    2004-06-12

    We have implemented k-means clustering, hierarchical clustering and self-organizing maps in a single multipurpose open-source library of C routines, callable from other C and C++ programs. Using this library, we have created an improved version of Michael Eisen's well-known Cluster program for Windows, Mac OS X and Linux/Unix. In addition, we generated a Python and a Perl interface to the C Clustering Library, thereby combining the flexibility of a scripting language with the speed of C. The C Clustering Library and the corresponding Python C extension module Pycluster were released under the Python License, while the Perl module Algorithm::Cluster was released under the Artistic License. The GUI code Cluster 3.0 for Windows, Macintosh and Linux/Unix, as well as the corresponding command-line program, were released under the same license as the original Cluster code. The complete source code is available at http://bonsai.ims.u-tokyo.ac.jp/mdehoon/software/cluster. Alternatively, Algorithm::Cluster can be downloaded from CPAN, while Pycluster is also available as part of the Biopython distribution.

  6. Agricultural Clusters in the Netherlands

    NARCIS (Netherlands)

    Schouten, M.A.; Heijman, W.J.M.

    2012-01-01

    Michael Porter was the first to use the term cluster in an economic context. He introduced the term in The Competitive Advantage of Nations (1990). The term cluster is also known as business cluster, industry cluster, competitive cluster or Porterian cluster. This article aims at determining and

  7. Imidazolium-based anion exchange membranes for alkaline anion fuel cells: (2) elucidation of the ionic structure and its impact on conducting properties.

    Science.gov (United States)

    Yoshimura, Kimio; Zhao, Yue; Hasegawa, Shin; Hiroki, Akihiro; Kishiyama, Yoshihiro; Shishitani, Hideyuki; Yamaguchi, Susumu; Tanaka, Hirohisa; Koizumi, Satoshi; Appavou, Marie-Sousai; Radulescu, Aurel; Richter, Dieter; Maekawa, Yasunari

    2017-11-22

    In our previous study (Soft Matter, 2016, 12, 1567), the relationship between the morphology and properties of graft-type imidazolium-based anion exchange membranes (AEMs) was revealed, in that the semi-crystalline features of the polymer matrix maintain its mechanical properties and the formation of interconnected hydrophilic domains promotes the membrane conductivity. Here, we report a novel ionic structure of the same graft-type AEMs with different grafting degrees, analyzed using a small-angle X-ray scattering method under different relative humidity (RH) conditions. The characteristic "ionomer peak" with a corresponding correlation distance of approximately 1.0 nm was observed at RH ionic clusters, but close to the Bjerrum length of water. Since the representative number of water molecules per cation, nw, was small, we proposed that dissociated ion-pairs are distributed in the hydrophilic domains (ion-channels). At RH < 80%, ion-channels are disconnected, however in liquid water, they are well-connected as evidenced by the sharp increase in nw. The disconnected ion-channels even under relatively high RH conditions should be a substantial factor for the low power generation efficiency of AEM-type fuel cells.

  8. Simultaneous separation of inorganic anions and cations by using anion-exchange and cation-exchange columns connected in tandem in ion chromatography.

    Science.gov (United States)

    Karim, Khairil Juhanni Binti Abd; Jin, Ji-Ye; Takeuchi, Toyohide

    2003-05-02

    Inorganic anions and cations in environmental waters were determined by ion chromatography. Stationary and mobile phases were examined for the simultaneous separation of both anions and cations. Cations detection by UV detection requires a mobile phase with a UV absorbing additive, which indirectly visualizes cations as negative peaks. Simultaneous separation of anions and cations were achieved when using an eluent that consists of inorganic acid with weak basic amino acid as additives. It was convenient to separate both anions and cations by coupling anion-exchange and cation-exchange columns in tandem. The order of the separation columns connected affected the elution profiles. When the eluent comprises of multiple anions and a single cation, the anion-exchange column should be connected in the upper stream, whereas when the eluent comprises multiple cations and a single anion, the cation-exchange column should be connected in the upper stream. Use of switching valves also allowed simultaneous separation of anions and cations in a single chromatographic run. In the present work, operating conditions were optimized for the simultaneous separation of anions and cations.

  9. Plane-wave Density Functional Theory Study of the Electronic and Structural Properties of Ionized and Neutral Small Gold Clusters

    OpenAIRE

    Min, Byeong June; Shin, Won Chul; Park, Jae Ik

    2016-01-01

    We studied the structural and the electronic properties of ionized and neutral small Au clusters via plane wave pseudopotential calculations. All except the anionic heptamer favor one-dimensional zigzag structures or two-dimensional arrangements of triangles. The HOMO-LUMO (highest occupied molecular orbital - lowest unoccupied molecular orbital) gap, the ionization energy, and the electronic affinity exhibit even-odd variation as a function of the cluster size.

  10. 76 FR 2130 - Prospective Grant of Exclusive License: Inhibitors of the Plasmodial Surface Anion Channel as...

    Science.gov (United States)

    2011-01-12

    ... Plasmodial Surface Anion Channel as Antimalarials AGENCY: National Institutes of Health, Public Health... January 28, 2010, both applications entitled ``Inhibitors of the Plasmodial Surface Anion Channel As... channel (PSAC), an essential nutrient acquisition ion channel expressed on human erythrocytes infected...

  11. Stable G-quadruplex structure in a hydrated ion pair: cholinium cation and dihydrogen phosphate anion.

    Science.gov (United States)

    Fujita, Kyoko; Ohno, Hiroyuki

    2012-06-11

    A combination of cholinium cations and dihydrogen phosphate anions is indispensable for the G-quadruplex structure regardless of water content. No G-quadruplex structure was observed in most salts even containing either cholinium cations or dihydrogen phosphate anions.

  12. Reducing nitrogen crossover in microbial reverse-electrodialysis cells by using adjacent anion exchange membranes and anion exchange resin

    KAUST Repository

    Wallack, Maxwell J.

    2015-01-01

    Microbial reverse electrodialysis cells (MRECs) combine power generation from salinity gradient energy using reverse electrodialysis (RED), with power generation from organic matter using a microbial fuel cell. Waste heat can be used to distill ammonium bicarbonate into high (HC) and low salt concentration (LC) solutions for use in the RED stack, but nitrogen crossover into the anode chamber must be minimized to avoid ammonia loses, and foster a healthy microbial community. To reduce nitrogen crossover, an additional low concentration (LC) chamber was inserted before the anode using an additional anion exchange membrane (AEM) next to another AEM, and filled with different amounts of anion or cation ion exchange resins. Addition of the extra AEM increased the ohmic resistance of the test RED stack from 103 Ω cm2 (1 AEM) to 295 Ω cm2 (2 AEMs). However, the use of the anion exchange resin decreased the solution resistance of the LC chamber by 74% (637 Ω cm2, no resin; 166 Ω cm2 with resin). Nitrogen crossover into the anode chamber was reduced by up to 97% using 50% of the chamber filled with an anion exchange resin compared to the control (no additional chamber). The added resistance contributed by the use of the additional LC chamber could be compensated for by using additional LC and HC membrane pairs in the RED stack.

  13. Simultaneous separation and detection of anions and thiophilic cations using capillary-size anion exchange chromatography with suppressed conductivity detection.

    Science.gov (United States)

    Sötz, Veronika Anna; Kochmann, Sven

    2015-05-01

    In this fundamental study, the simultaneous separation and detection of anions and thiophilic cations in anion exchange chromatography with suppressed conductivity detection is investigated. Mercury(II) and cadmium(II) served as model analytes. Separation and detection was performed by introducing 2-mercaptoethanesulfonate, which forms complexes with both mercury and cadmium with a strong metal-sulfur bond, into the KOH eluent. Additional to the separation on the column, these complexes were able to pass the suppressor. Subsequently, they could be detected as negative peaks. A simple model for the separation mechanism was developed based on these results. Furthermore, the effect of the eluent concentration on the retention factors of both cation complexes and standard anions was examined and quantified. It revealed that the concentration of 2-mercaptoethanesulfonate has more influence on the cations than the KOH concentration. Also, 2.0 mM of 2-mercaptoethanesulfonate had about the same effect on the anion separation as 60 mM KOH. Finally, selectivity and detection limits were investigated. The detection limits were 4.9 μM for mercury and 2.2 μM for cadmium. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. A microporous anionic metal-organic framework for sensing luminescence of lanthanide(III) ions and selective absorption of dyes by ionic exchange.

    Science.gov (United States)

    Qin, Jun-Sheng; Zhang, Shu-Ran; Du, Dong-Ying; Shen, Ping; Bao, Shao-Juan; Lan, Ya-Qian; Su, Zhong-Min

    2014-05-05

    Herein, a novel anionic framework with primitive centered cubic (pcu) topology, [(CH3 )2 NH2 ]4 [(Zn4 dttz6 )Zn3 ]⋅15 DMF⋅4.5 H2 O, (IFMC-2; H3 dttz=4,5-di(1H-tetrazol-5-yl)-2H-1,2,3-triazole) was solvothermally isolated. A new example of a tetranuclear zinc cluster {Zn4 dttz6 } served as a secondary building unit in IFMC-2. Furthermore, the metal cluster was connected by Zn(II) ions to give rise to a 3D open microporous structure. The lanthanide(III)-loaded metal-organic framework (MOF) materials Ln(3+) @IFMC-2, were successfully prepared by using ion-exchange experiments owing to the anionic framework of IFMC-2. Moreover, the emission spectra of the as-prepared Ln(3+) @IFMC-2 were investigated, and the results suggested that IFMC-2 could be utilized as a potential luminescent probe toward different Ln(3+) ions. Additionally, the absorption ability of IFMC-2 toward ionic dyes was also performed. Cationic dyes can be absorbed, but not neutral and anionic dyes, thus indicating that IFMC-2 exhibits selective absorption toward cationic dyes. Furthermore, the cationic dyes can be gradually released in the presence of NaCl. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Disentangling Porterian Clusters

    DEFF Research Database (Denmark)

    Jagtfelt, Tue

    This dissertation investigates the contemporary phenomenon of industrial clusters based on the work of Michael E. Porter, the central progenitor and promoter of the cluster notion. The dissertation pursues two central questions: 1) What is a cluster? and 2) How could Porter’s seemingly fuzzy...... to his membership on the Commission on Industrial Competitiveness, and that the cluster notion found in his influential book, Nations, represents a significant shift in his conception of cluster compared with his early conceptions. This shift, it is argued, is a deliberate attempt by Porter to create......, contested theory become so widely disseminated and applied as a normative and prescriptive strategy for economic development? The dissertation traces the introduction of the cluster notion into the EU’s Lisbon Strategy and demonstrates how its inclusion originates from Porter’s colleagues: Professor Örjan...

  16. From collisions to clusters

    DEFF Research Database (Denmark)

    Loukonen, Ville; Bork, Nicolai; Vehkamaki, Hanna

    2014-01-01

    The clustering of sulphuric acid with base molecules is one of the main pathways of new-particle formation in the Earth's atmosphere. First step in the clustering process is likely the formation of a (sulphuric acid)1(base)1(water)n cluster. Here, we present results from direct first......-principles molecular dynamics collision simulations of (sulphuric acid)1(water)0, 1 + (dimethylamine) → (sulphuric acid)1(dimethylamine)1(water)0, 1 cluster formation processes. The simulations indicate that the sticking factor in the collisions is unity: the interaction between the molecules is strong enough...... to overcome the possible initial non-optimal collision orientations. No post-collisional cluster break up is observed. The reasons for the efficient clustering are (i) the proton transfer reaction which takes place in each of the collision simulations and (ii) the subsequent competition over the proton...

  17. Clustering by Local Gravitation.

    Science.gov (United States)

    Wang, Zhiqiang; Yu, Zhiwen; Chen, C L Philip; You, Jane; Gu, Tianlong; Wong, Hau-San; Zhang, Jun

    2017-05-02

    The objective of cluster analysis is to partition a set of data points into several groups based on a suitable distance measure. We first propose a model called local gravitation among data points. In this model, each data point is viewed as an object with mass, and associated with a local resultant force (LRF) generated by its neighbors. The motivation of this paper is that there exist distinct differences between the LRFs (including magnitudes and directions) of the data points close to the cluster centers and at the boundary of the clusters. To capture these differences efficiently, two new local measures named centrality and coordination are further investigated. Based on empirical observations, two new clustering methods called local gravitation clustering and communication with local agents are designed, and several test cases are conducted to verify their effectiveness. The experiments on synthetic data sets and real-world data sets indicate that both clustering approaches achieve good performance on most of the data sets.

  18. Convex Discriminative Multitask Clustering.

    Science.gov (United States)

    Zhang, Xiao-Lei

    2015-01-01

    Multitask clustering tries to improve the clustering performance of multiple tasks simultaneously by taking their relationship into account. Most existing multitask clustering algorithms fall into the type of generative clustering, and none are formulated as convex optimization problems. In this paper, we propose two convex Discriminative Multitask Clustering (DMTC) objectives to address the problems. The first one aims to learn a shared feature representation, which can be seen as a technical combination of the convex multitask feature learning and the convex Multiclass Maximum Margin Clustering (M3C). The second one aims to learn the task relationship, which can be seen as a combination of the convex multitask relationship learning and M3C. The objectives of the two algorithms are solved in a uniform procedure by the efficient cutting-plane algorithm and further unified in the Bayesian framework. Experimental results on a toy problem and two benchmark data sets demonstrate the effectiveness of the proposed algorithms.

  19. Cluster Management Institutionalization

    DEFF Research Database (Denmark)

    Normann, Leo; Agger Nielsen, Jeppe

    2015-01-01

    This article explores a new management form – cluster management – in Danish public sector day care. Although cluster management has been widely adopted in Danish day care at the municipality level, it has attracted only sparse research attention. We use theoretical insights from Scandinavian...... institutionalism together with a longitudinal case-based inquiry into how cluster management has entered and penetrated the management practices of day care in Denmark. We demonstrate how cluster management became widely adopted in the day care field not only because of its intrinsic properties but also because...... of how it was legitimized as a “ready-to-use” management model. Further, our account reveals how cluster management translated into considerably different local variants as it travelled into specific organizations. However, these processes have not occurred sequentially with cluster management first...

  20. A combined experimental and computational study of the molecular interactions between anionic ibuprofen and water

    Energy Technology Data Exchange (ETDEWEB)

    Zapata-Escobar, Andy; Manrique-Moreno, Marcela; Guerra, Doris; Hadad, C. Z.; Restrepo, Albeiro, E-mail: albeiro@exactas.udea.edu.co [Instituto de Química, Universidad de Antioquia UdeA, Calle 70 No. 52–21, Medellín (Colombia)

    2014-05-14

    In this work, we report a detailed study of the microsolvation of anionic ibuprofen, Ibu{sup −}. Stochastic explorations of the configurational spaces for the interactions of Ibu{sup −} with up to three water molecules at the DFT level lead to very rich and complex potential energy surfaces. Our results suggest that instead of only one preponderant structure, a collection of isomers with very similar energies would have significant contributions to the properties of the solvated drug. One of these properties is the shift on the vibrational frequencies of the asymmetric stretching band of the carboxylate group in hydrated Ibu{sup −} with respect to the anhydrous drug, whose experimental values are nicely reproduced using the weighted contribution of the structures. We found at least three types of stabilizing interactions, including conventional CO {sub 2}{sup −}⋯H{sub 2}O, H{sub 2}O⋯H{sub 2}O charge assisted hydrogen bonds (HBs), and less common H{sub 2}O⋯H–C and H{sub 2}O⋯π interactions. Biological water molecules, those in direct contact with Ibu{sup −}, prefer to cluster around the carboxylate oxygen atoms via cyclic or bridged charge assisted hydrogen bonds. Many of those interactions are strongly affected by the formal carboxylate charge, resulting in “enhanced” HBs with increased strengths and degree of covalency. We found striking similarities between this case and the microsolvation of dymethylphosphate, which lead us to hypothesize that since microsolvation of phosphatidylcholine depends mainly on the formal charge of its ionic PO {sub 2}{sup −} group in the polar head, then microsolvation of anionic ibuprofen and interactions of water molecules with eukaryotic cell membranes are governed by the same types of physical interactions.

  1. Ultrahigh and Selective SO2 Uptake in Inorganic Anion-Pillared Hybrid Porous Materials.

    Science.gov (United States)

    Cui, Xili; Yang, Qiwei; Yang, Lifeng; Krishna, Rajamani; Zhang, Zhiguo; Bao, Zongbi; Wu, Hui; Ren, Qilong; Zhou, Wei; Chen, Banglin; Xing, Huabin

    2017-07-01

    The efficient capture of SO2 is of great significance in gas-purification processes including flue-gas desulfurization and natural-gas purification, but the design of porous materials with high adsorption capacity and selectivity of SO2 remains very challenging. Herein, the selective recognition and dense packing of SO2 clusters through multiple synergistic host-guest and guest-guest interactions by controlling the pore chemistry and size in inorganic anion (SiF6(2-) , SIFSIX) pillared metal-organic frameworks is reported. The binding sites of anions and aromatic rings in SIFSIX materials grasp every atom of SO2 firmly via S(δ+) ···F(δ-) electrostatic interactions and O(δ-) ···H(δ+) dipole-dipole interactions, while the guest-guest interactions between SO2 molecules further promote gas trapping within the pore space, which is elucidated by first-principles density functional theory calculations and powder X-ray diffraction experiments. These interactions afford new benchmarks for the highly efficient removal of SO2 from other gases, even if at a very low SO2 concentration. Exceptionally high SO2 capacity of 11.01 mmol g(-1) is achieved at atmosphere pressure by SIFSIX-1-Cu, and unprecedented low-pressure SO2 capacity is obtained in SIFSIX-2-Cu-i (4.16 mmol g(-1) SO2 at 0.01 bar and 2.31 mmol g(-1) at 0.002 bar). More importantly, record SO2 /CO2 selectivity (86-89) and excellent SO2 /N2 selectivity (1285-3145) are also achieved. Experimental breakthrough curves further demonstrate the excellent performance of these hybrid porous materials in removing low-concentration SO2 . © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Active cluster crystals

    Science.gov (United States)

    Delfau, Jean-Baptiste; López, Cristóbal; Hernández-García, Emilio

    2017-09-01

    We study the appearance and properties of cluster crystals (solids in which the unit cell is occupied by a cluster of particles) in a two-dimensional system of self-propelled active Brownian particles with repulsive interactions. Self-propulsion deforms the clusters by depleting particle density inside, and for large speeds it melts the crystal. Continuous field descriptions at several levels of approximation allow us to identify the relevant physical mechanisms.

  3. Percolation in clustered networks

    OpenAIRE

    Miller, Joel C

    2009-01-01

    The social networks that infectious diseases spread along are typically clustered. Because of the close relation between percolation and epidemic spread, the behavior of percolation in such networks gives insight into infectious disease dynamics. A number of authors have studied clustered networks, but the networks often contain preferential mixing between high degree nodes. We introduce a class of random clustered networks and another class of random unclustered networks with the same prefer...

  4. Cluster Symmetries and Dynamics

    Directory of Open Access Journals (Sweden)

    Freer Martin

    2016-01-01

    Full Text Available Many light nuclei display behaviour that indicates that rather than behaving as an A-body systems, the protons and neutrons condense into clusters. The α-particle is the most obvious example of such clustering. This contribution examines the role of such α-clustering on the structure, symmetries and dynamics of the nuclei 8Be, 12C and 16O, recent experimental measurements and future perspectives.

  5. Data Mining with Clustering

    OpenAIRE

    Klímek, Petr

    2008-01-01

    One of the oppotunities in data mining is a use of clustering analysis. Clustering analysis belongs to unsupervised methods of data mining. We put here a focus on this method. Some basic principles are described in the second part of this paper. This method is examined on two examples from the marketing field. In the first example is used software Statgraphics 5.0Plus to solve clustering problem (nearest neighbour algorithm and Eucleidian distance); and in the second example is used Statistic...

  6. Spatial Scan Statistic: Selecting clusters and generating elliptic clusters

    OpenAIRE

    Christiansen, Lasse Engbo; Andersen, Jens Strodl

    2004-01-01

    The spatial scan statistic is widely used to search for clusters. This paper shows that the usually applied elimination of overlapping clusters to find secondary clusters is sensitive to smooth changes in the shape of the clusters. We present an algorithm for generation of set of confocal elliptic clusters. In addition, we propose a new way to present the information in a given set of clusters based on the significance of the clusters.

  7. Spatial Scan Statistic: Selecting clusters and generating elliptic clusters

    DEFF Research Database (Denmark)

    Christiansen, Lasse Engbo; Andersen, Jens Strodl

    2004-01-01

    The spatial scan statistic is widely used to search for clusters. This paper shows that the usually applied elimination of overlapping clusters to find secondary clusters is sensitive to smooth changes in the shape of the clusters. We present an algorithm for generation of set of confocal elliptic...... clusters. In addition, we propose a new way to present the information in a given set of clusters based on the significance of the clusters....

  8. Synthesis and anion exchange reactions of a layered copper-zinc ...

    Indian Academy of Sciences (India)

    A mixed-metal hydroxysalt of formula Cu1.6Zn0.4(OH)3(OAc) ⋅ H2O has been synthesized by an acetate hydrolysis route. Acetate ions can be exchanged with simple inorganic anions such as chloride and nitrate, and organic anions such as benzoate and large surfactant anions such as dodecyl sulphate. Structures of ...

  9. Use of weak ion association in the separation of inorganic anions by ...

    African Journals Online (AJOL)

    In this work weak ion association was used to effect selectivity and detection of inorganic anions with environmental or health significance by capillary electropheresis, CE. Tetrabutylammonium ion was used as a pairing anion to separate mixtures containing closely or co-migrating inorganic anions at pHs 3.8 and pH 7.

  10. Synthesis and anion exchange reactions of a layered copper–zinc ...

    Indian Academy of Sciences (India)

    Unknown

    Abstract. A mixed-metal hydroxysalt of formula Cu1⋅6Zn0⋅4(OH)3(OAc)⋅H2O has been synthesized by an acetate hydrolysis route. Acetate ions can be exchanged with simple inorganic anions such as chloride and nitrate, and organic anions such as benzoate and large surfactant anions such as dodecyl sulphate. Struc-.

  11. Polyspecific organic anion transporting polypeptides mediate hepatic uptake of amphipathic type II organic cations

    NARCIS (Netherlands)

    van Montfoort, J.E; Hagenbuch, B; Fattinger, K.E; Muller, M; Groothuis, Geny; Meijer, D.K F; Meier, P.J

    1999-01-01

    Hepatic uptake of albumin-bound amphipathic organic cations has been suggested to be mediated by multispecific bile salt and organic anion transport systems. Therefore, we investigated whether the recently cloned rat organic anion transporting polypeptides 1 and 2 as well as the human organic anion

  12. Contribution of various metabolites to the "unmeasured" anions in critically ill patients with metabolic acidosis.

    NARCIS (Netherlands)

    Moviat, M.; Terpstra, A.M.; Ruitenbeek, W.; Kluijtmans, L.A.J.; Pickkers, P.; Hoeven, J.G. van der

    2008-01-01

    OBJECTIVE: The physicochemical approach, described by Stewart to investigate the acid-base balance, includes the strong ion gap (SIG), a quantitative measure of "unmeasured" anions, which strongly correlates to the corrected anion gap. The chemical nature of these anions is for the most part

  13. Charge inversion via concurrent cation and anion transfer: application to corticosteroids.

    Science.gov (United States)

    Hassell, Kerry M; LeBlanc, Yves; McLuckey, Scott A

    2011-02-28

    A novel charge inversion process that involves the removal of an excess cation from an analyte ion and the transfer of an anion to the neutral analyte in a single ion/ion encounter is described. Polyamidoamine (PAMAM) half-generation dendrimer anions that contain small anions, such as the chloride ion, were used as charge inversion reagents. Several competing processes can occur that include removal of the cation to neutralize the analyte, the removal of the excess cation and an additional proton to yield the deprotonated molecule, or removal of the excess cation and transfer of a small anion to the analyte. For the latter process to dominate, several requirements for both the reagent anion and the analyte cation must be met. The reagent anion must form multiply charged anions and must be able to incorporate one or more small anions for transfer. The analyte must have no strongly acidic sites as well as a relatively high affinity for small anion attachment. The PAMAM dendrimer anions must meet the conditions for the reagent anions and the cations of the corticosteroids meet the conditions for the analyte. The estrogenic steroid estrone, on the other hand, does not meet the requirements and, as a result, is largely neutralized when reacted with the reagent anions. This reaction, therefore, is highly selective and might serve as a useful reaction for the screening of appropriate analytes. Copyright © 2011 John Wiley & Sons, Ltd.

  14. Performance analysis of cation and anion exchangers in water treatment plant: an industrial case study

    National Research Council Canada - National Science Library

    Ramzan, Naveed; Feroze, Nadeem; Kazmi, Mohsin; Ashraf, Muhammad Arsalan; Hasan, Sajid

    2012-01-01

    ...% for cation, primary and secondary anion exchangers respectively. The operating time of the water treatment train was significantly increased by achieving adequate capacity utilization of secondary anion exchanger. The low capacity utilization of secondary anion resin due to early silica slippage, has been discussed in the paper.

  15. 15th Cluster workshop

    CERN Document Server

    Laakso, Harri; Escoubet, C. Philippe; The Cluster Active Archive : Studying the Earth’s Space Plasma Environment

    2010-01-01

    Since the year 2000 the ESA Cluster mission has been investigating the small-scale structures and processes of the Earth's plasma environment, such as those involved in the interaction between the solar wind and the magnetospheric plasma, in global magnetotail dynamics, in cross-tail currents, and in the formation and dynamics of the neutral line and of plasmoids. This book contains presentations made at the 15th Cluster workshop held in March 2008. It also presents several articles about the Cluster Active Archive and its datasets, a few overview papers on the Cluster mission, and articles reporting on scientific findings on the solar wind, the magnetosheath, the magnetopause and the magnetotail.

  16. Metal Cluster Topology. 1. Osmium Carbonyl Clusters.

    Science.gov (United States)

    1986-01-29

    AD-A164 372 NETAL CLUSTER TOPOLOGY I OSNIUM CARDONYI. CLUSTERS(U) i ’ GEORGIA IiNIY ATHENS DEPT OF CHENISTRY R 8 KING UCr S 29 JAN 86 TR-15 NSSSI4-S5...to distinguish between globally delocalized (D) and edge-localized (L) polyhedra. Treatment of globally delocalized polyhedra leads clearly to the same...of five internal orbitals for two of the six vertex atoms will make the pair of edge-fused tetrahedra unfavorable except for some of the heavy

  17. A "light-on" colorimetric assay for anion detection using the inhibitory effect of anions on the catalytic activity of metal nanoparticles for the degradation of methyl orange.

    Science.gov (United States)

    Lu, Lixia; Yang, Fan; Yang, Xiurong

    2014-12-07

    In this communication, we studied the inhibitory effects of anions on the catalytic activity of metal nanoparticles for the degradation of methyl orange (MO). Some anions have great affinity with specific metal nanoparticles, thus resulting in the change of surface state and inhibition of catalytic activity, which can be observed with the naked eye or manifested in the UV spectrum of MO for anion detection.

  18. Tetrabutylammonium Salts of Aluminum(III) and Gallium(III) Phthalocyanine Radical Anions Bonded with Fluoren-9-olato-Anions and Indium(III) Phthalocyanine Bromide Radical Anions.

    Science.gov (United States)

    Konarev, Dmitri V; Khasanov, Salavat S; Ishikawa, Manabu; Nakano, Yoshiaki; Otsuka, Akihiro; Yamochi, Hideki; Saito, Gunzi; Lyubovskaya, Rimma N

    2017-04-18

    Reduction of aluminum(III), gallium(III), and indium(III) phthalocyanine chlorides by sodium fluorenone ketyl in the presence of tetrabutylammonium cations yielded crystalline salts of the type (Bu 4 N + ) 2 [M III (HFl-O - )(Pc .3- )] .- (Br - )⋅1.5 C 6 H 4 Cl 2 [M=Al (1), Ga (2); HFl-O - =fluoren-9-olato - anion; Pc=phthalocyanine] and (Bu 4 N + ) [In III Br(Pc .3- )] .- ⋅0.875 C 6 H 4 Cl 2 ⋅0.125 C 6 H 14 (3). The salts were found to contain Pc .3- radical anions with negatively charged phthalocyanine macrocycles, as evidenced by the presence of intense bands of Pc .3- in the near-IR region and a noticeable blueshift in both the Q and Soret bands of phthalocyanine. The metal(III) atoms coordinate HFl-O - anions in 1 and 2 with short Al-O and Ga-O bond lengths of 1.749(2) and 1.836(6) Å, respectively. The C-O bonds [1.402(3) and 1.391(11) Å in 1 and 2, respectively] in the HFl-O - anions are longer than the same bond in the fluorenone ketyl (1.27-1.31 Å). Salts 1-3 show effective magnetic moments of 1.72, 1.66, and 1.79 μ B at 300 K, respectively, owing to the presence of unpaired S=1/2 spins on Pc .3- . These spins are coupled antiferromagnetically with Weiss temperatures of -22, -14, and -30 K for 1-3, respectively. Coupling can occur in the corrugated two-dimensional phthalocyanine layers of 1 and 2 with an exchange interaction of J/k B =-0.9 and -1.1 K, respectively, and in the π-stacking {[In III Br(Pc .3- )] .- } 2 dimers of 3 with an exchange interaction of J/k B =-10.8 K. The salts show intense electron paramagnetic resonance (EPR) signals attributed to Pc .3- . It was found that increasing the size of the central metal atom strongly broadened these EPR signals. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Super Star Clusters

    Science.gov (United States)

    O'Connell, R. W.

    1994-05-01

    Super star clusters represent an extreme in the star formation process. They are very luminous, compact objects with L_V > 10(6) L_{V,sun} and diameters = 100 times higher than normal OB associations and clusters in ``giant H II regions''. Prior to HST about a dozen such objects had been identified in nearby galaxies, but at ground-based resolution they are nearly point sources. We review recent HST observations of individual super star clusters in NGC 1140, 1569, and 1705. They have half-light radii of only 2--3.5 pc, and some show evidence of substructure which should be resolvable with the repaired HST. After allowing for age differences, the surface brightness of NGC 1569-A is over 65 times higher than the core of 30 Doradus in the LMC and 1200 times higher than the mean rich LMC star cluster. In some cases, the energy released by the clusters into their surroundings is sufficient to drive galaxy-wide winds. Their properties make super star clusters good analogues of young globular clusters. In some, though not all, cases super star clusters appear to form in the aftermath of a merger or accretion event. The most impressive examples are the clusters detected by HST in NGC 1275 and 7252, one of which has the extraordinary luminosity ~ 6 times 10(8) L_{V,sun}. M82 affords a nearby view of a post-interaction system. HST imaging has identified over 80 super star clusters in its central regions with mean luminosities of ~ 3 times 10(6) L_{V,sun}. Their close packing and signs of interaction with the well-known supernova-driven wind suggest that they do not evolve independently. Super cluster evolution in starbursts is probably a collective phenomenon.

  20. Statistical properties of convex clustering

    OpenAIRE

    Tan, Kean Ming; Witten, Daniela

    2015-01-01

    In this manuscript, we study the statistical properties of convex clustering. We establish that convex clustering is closely related to single linkage hierarchical clustering and $k$-means clustering. In addition, we derive the range of the tuning parameter for convex clustering that yields a non-trivial solution. We also provide an unbiased estimator of the degrees of freedom, and provide a finite sample bound for the prediction error for convex clustering. We compare convex clustering to so...

  1. Nonlocalized clustering and evolution of cluster structure in nuclei

    Science.gov (United States)

    Horiuchi, H.

    2017-06-01

    It is shown that the THSR (Tohsaki-Horiuchi-Schuck-Roepke) wave function describe well not only cluster-gas like structures but also ordinary cluster structures with spatial localization of clusters. Based on this fact, the container model has been proposed as a new model of cluster dynamics. For better description of cluster dynamics, extended version of container model has been introduced. The container model of cluster dynamics teaches us how is the evolution of cluster structure which starts from the ground state having shell-model structure to many kinds of cluster states up to the cluster-gas states.

  2. Synthetic ion transporters that work with anion-π interactions, halogen bonds, and anion-macrodipole interactions.

    Science.gov (United States)

    Vargas Jentzsch, Andreas; Hennig, Andreas; Mareda, Jiri; Matile, Stefan

    2013-12-17

    The transport of ions and molecules across lipid bilayer membranes connects cells and cellular compartments with their environment. This biological process is central to a host of functions including signal transduction in neurons and the olfactory and gustatory sensing systems, the translocation of biosynthetic intermediates and products, and the uptake of nutrients, drugs, and probes. Biological transport systems are highly regulated and selectively respond to a broad range of physical and chemical stimulation. A large percentage of today's drugs and many antimicrobial or antifungal agents take advantage of these systems. Other biological transport systems are highly toxic, such as the anthrax toxin or melittin from bee venom. For more than three decades, organic and supramolecular chemists have been interested in developing new transport systems. Over time, curiosity about the basic design has evolved toward developing of responsive systems with applications in materials sciences and medicine. Our early contributions to this field focused on the introduction of new structural motifs with emphasis on rigid-rod scaffolds, artificial β-barrels, or π-stacks. Using these scaffolds, we have constructed selective systems that respond to voltage, pH, ligands, inhibitors, or light (multifunctional photosystems). We have described sensing applications that cover the three primary principles of sensor development: immunosensors that use aptamers, biosensors (an "artificial" tongue), and differential sensors (an "artificial" nose). In this Account, we focus on our recent interest in applying synthetic transport systems as analytical tools to identify the functional relevance of less common noncovalent interactions, anion-π interactions, halogen bonds, and anion-macrodipole interactions. Anion-π interactions, the poorly explored counterpart of cation-π interactions, occur in aromatic systems with a positive quadrupole moment, such as TNT or hexafluorobenzene. To observe

  3. Thermal Properties of Anionic Polyurethane Composition for Leather Finishing

    Directory of Open Access Journals (Sweden)

    Olga KOVTUNENKO

    2016-09-01

    Full Text Available Thermal properties of anionic polyurethane composition mixed with collagen product and hydrophilic sodium form of montmorillonite for use in the finishing of leather were studied by thermogravimetric method. The thermal indices of processes of thermal and thermo-oxidative destruction depending on the polyurethane composition were determined. The influence of anionic polyurethane composition on thermal behavior of chromium tanned gelatin films that imitate the leather were studied. APU composition with natural compounds increases their thermal stability both in air and in nitrogen atmosphere due to the formation of additional bonds between active groups of APU, protein and chrome tanning agent as the result of chemical reactions between organic and inorganic parts with the new structure formation.DOI: http://dx.doi.org/10.5755/j01.ms.22.3.10043

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

    Science.gov (United States)

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

    2015-07-01

    For anion exchange membranes (AEMs), achieving efficient hydroxide conductivity without excessive hydrophilicity presents a challenge. Hence, new strategies for constructing mechanically strengthened and hydroxide conductive (especially at controlled humidity) membranes are critical for developing better AEMs. Macromolecular modification involving ylide chemistry (Wittig reaction) for the fabrication of novel AEMs with an interpenetrating polymer network structure is reported. The macromolecular modification is cost effective, facile, and based on a one-pot synthesis. AEM water uptake is reduced to 3.6 wt% and a high hydroxide conductivity (69.7 mS cm(-1) , 90 °C) is achieved simultaneously. More importantly, the membrane exhibits similar tensile strength (>35 MPa) and comparable flexibility in both dry and wet states. These AEMs could find further applications within anion exchange membrane fuel cells with low humidity or photoelectric assemblies. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Anionic lipids and the maintenance of membrane electrostatics in eukaryotes.

    Science.gov (United States)

    Platre, Matthieu Pierre; Jaillais, Yvon

    2017-02-01

    A wide range of signaling processes occurs at the cell surface through the reversible association of proteins from the cytosol to the plasma membrane. Some low abundant lipids are enriched at the membrane of specific compartments and thereby contribute to the identity of cell organelles by acting as biochemical landmarks. Lipids also influence membrane biophysical properties, which emerge as an important feature in specifying cellular territories. Such parameters are crucial for signal transduction and include lipid packing, membrane curvature and electrostatics. In particular, membrane electrostatics specifies the identity of the plasma membrane inner leaflet. Membrane surface charges are carried by anionic phospholipids, however the exact nature of the lipid(s) that powers the plasma membrane electrostatic field varies among eukaryotes and has been hotly debated during the last decade. Herein, we discuss the role of anionic lipids in setting up plasma membrane electrostatics and we compare similarities and differences that were found in different eukaryotic cells.

  6. Anion-switchable supramolecular gels for controlling pharmaceutical crystal growth

    Science.gov (United States)

    Foster, Jonathan A.; Piepenbrock, Marc-Oliver M.; Lloyd, Gareth O.; Clarke, Nigel; Howard, Judith A. K.; Steed, Jonathan W.

    2010-12-01

    We describe the use of low-molecular-weight supramolecular gels as media for the growth of molecular crystals. Growth of a range of crystals of organic compounds, including pharmaceuticals, was achieved in bis(urea) gels. Low-molecular-weight supramolecular gelators allow access to an unlimited range of solvent systems, in contrast to conventional aqueous gels such as gelatin and agarose. A detailed study of carbamazepine crystal growth in four different bis(urea) gelators, including a metallogelator, is reported. The crystallization of a range of other drug substances, namely sparfloxacin, piroxicam, theophylline, caffeine, ibuprofen, acetaminophen (paracetamol), sulindac and indomethacin, was also achieved in supramolecular gel media without co-crystal formation. In many cases, crystals can be conveniently recovered from the gels by using supramolecular anion-triggered gel dissolution; however, crystals of substances that themselves bind to anions are dissolved by them. Overall, supramolecular gel-phase crystallization offers an extremely versatile new tool in pharmaceutical polymorph screening.

  7. Securing Personal Network Clusters

    NARCIS (Netherlands)

    Jehangir, A.; Heemstra de Groot, S.M.

    2007-01-01

    A Personal Network is a self-organizing, secure and private network of a user’s devices notwithstanding their geographic location. It aims to utilize pervasive computing to provide users with new and improved services. In this paper we propose a model for securing Personal Network clusters. Clusters

  8. Neurostimulation in cluster headache

    DEFF Research Database (Denmark)

    Pedersen, Jeppe L; Barloese, Mads; Jensen, Rigmor H

    2013-01-01

    PURPOSE OF REVIEW: Neurostimulation has emerged as a viable treatment for intractable chronic cluster headache. Several therapeutic strategies are being investigated including stimulation of the hypothalamus, occipital nerves and sphenopalatine ganglion. The aim of this review is to provide...... effective strategy must be preferred as first-line therapy for intractable chronic cluster headache....

  9. Cauchy cluster process

    DEFF Research Database (Denmark)

    Ghorbani, Mohammad

    2013-01-01

    In this paper we introduce an instance of the well-know Neyman–Scott cluster process model with clusters having a long tail behaviour. In our model the offspring points are distributed around the parent points according to a circular Cauchy distribution. Using a modified Cramér-von Misses test...

  10. Cluster Synchronization Algorithms

    NARCIS (Netherlands)

    Xia, Weiguo; Cao, Ming

    2010-01-01

    This paper presents two approaches to achieving cluster synchronization in dynamical multi-agent systems. In contrast to the widely studied synchronization behavior, where all the coupled agents converge to the same value asymptotically, in the cluster synchronization problem studied in this paper,

  11. Mixed-Initiative Clustering

    Science.gov (United States)

    Huang, Yifen

    2010-01-01

    Mixed-initiative clustering is a task where a user and a machine work collaboratively to analyze a large set of documents. We hypothesize that a user and a machine can both learn better clustering models through enriched communication and interactive learning from each other. The first contribution or this thesis is providing a framework of…

  12. Reflections on cluster policies

    NARCIS (Netherlands)

    Brakman, Steven; van Marrewijk, Charles

    Economic activity tends to cluster. This results in productivity gains. For policy makers this offers an opportunity to formulate and promote policies that foster clustering of economic activity. Paradoxically, although agglomeration rents are often found in empirical research, a rationale for

  13. Calixarene-supported clusters

    DEFF Research Database (Denmark)

    Taylor, Stephanie M.; McIntosh, Ruaraidh D.; Piligkos, Stergios

    2012-01-01

    A combination of complementary cluster ligands results in the formation of a new calixarene-supported ferromagnetic [Mn(5)] cage that displays the characteristic bonding modes of each support.......A combination of complementary cluster ligands results in the formation of a new calixarene-supported ferromagnetic [Mn(5)] cage that displays the characteristic bonding modes of each support....

  14. Detecting clusters of mutations.

    Directory of Open Access Journals (Sweden)

    Tong Zhou

    Full Text Available Positive selection for protein function can lead to multiple mutations within a small stretch of DNA, i.e., to a cluster of mutations. Recently, Wagner proposed a method to detect such mutation clusters. His method, however, did not take into account that residues with high solvent accessibility are inherently more variable than residues with low solvent accessibility. Here, we propose a new algorithm to detect clustered evolution. Our algorithm controls for different substitution probabilities at buried and exposed sites in the tertiary protein structure, and uses random permutations to calculate accurate P values for inferred clusters. We apply the algorithm to genomes of bacteria, fly, and mammals, and find several clusters of mutations in functionally important regions of proteins. Surprisingly, clustered evolution is a relatively rare phenomenon. Only between 2% and 10% of the genes we analyze contain a statistically significant mutation cluster. We also find that not controlling for solvent accessibility leads to an excess of clusters in terminal and solvent-exposed regions of proteins. Our algorithm provides a novel method to identify functionally relevant divergence between groups of species. Moreover, it could also be useful to detect artifacts in automatically assembled genomes.

  15. Anion Exchange Membranes: Current Status and Moving Forward

    Energy Technology Data Exchange (ETDEWEB)

    Hickner, MA; Herring, AM; Coughlin, EB

    2013-10-29

    This short review is meant to provide the reader with highlights in anion exchange membrane research, describe current needs in the field, and point out promising directions for future work. Anion exchange membranes (AEMs) provide one possible route to low platinum or platinum-free fuel cells with the potential for facile oxidation of complex fuels beyond hydrogen and methanol. AEMs and related stable cationic polymers also have applications in energy storage and other electrochemical technologies such as water electrolyzers and redox flow batteries. While anion exchange membranes have been known for a long time in water treatment applications, materials for electrochemical technology with robust mechanical properties in thin film format have only recently become more widely available. High hydroxide and bicarbonate anion conductivity have been demonstrated in a range of AEM formats, but intrinsic stability of the polymers and demonstration of long device lifetime remain major roadblocks. Novel approaches to stable materials have focused on new types of cations that employ delocalization and steric shielding of the positive center to mitigate nucleophilic attack by hydroxide. A number of promising polymer backbones and membrane architectures have been identified, but limited device testing and a lack of understanding of the degradation mechanisms in operating devices is slowing progress on engineered systems with alkaline fuel cell technology. Our objective is to spur more research in this area to develop fuel cell systems that approach the costs of inexpensive batteries for large-scale applications. (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 51, 1727-1735, 2013

  16. Closing anion gap without insulin in euglycaemic diabetic ketoacidosis

    Directory of Open Access Journals (Sweden)

    Resham Raj Poudel

    2017-01-01

    Full Text Available Euglycaemic diabetic ketoacidosis (euDKA occurs in patients with poor carbohydrate intake who continue to take insulin. For these patients are not truly in the insulin-deficient state, intravenous fluid resuscitation alone can correct the ketoacidosis without any risk of hypoglycaemia. Diagnosis of euDKA can be missed in inexperienced settings; therefore, calculating anion gap and measuring ketone levels should be practiced in every sick diabetic patient regardless of glucose levels.

  17. Micromachined Amperometric Nitrate Sensor with an Anion Permeable Membrane

    OpenAIRE

    Kim, Dohyun; Goldberg, Ira; Judy, J W

    2004-01-01

    A nitrate-sensing system that consists of a micromachined sensor substrate, anion-permeable membrane, integrated microfluidic channels, and standard fluidic connectors has been designed, fabricated, assembled, and tested. Our microsensor was designed for in-situ monitoring of nitrate concentrations in ground water. A silver electrode was patterned for amperometric nitrate detection. An electrochemically oxidized silver electrode was used as a reference electrode. Microfluidic channels were fa...

  18. Multicolor expressible ECD materials consisted of polyaniline and anionic quinone

    Energy Technology Data Exchange (ETDEWEB)

    Yano, Jun [Department of Food Science, Faculty of Engineering, University of East Asia, Ichinomiya-Gakuencho 2-1, Shimonoseki, Yamaguchi 751 (Japan); Kitani, Akira [Department of Applied Chemistry, Faculty of Engineering, Hiroshima University, Kagamiyama 1-4-1, Higashihiroshima, Hiroshima 724 (Japan)

    1995-03-01

    An anionic quinone, 1-amino-4-bromoanthraquinone-2-sulfonic acid, in 0.1 M (1M=1moldm{sup -3}) H{sub 2}SO{sub 4} looked bright red in the oxidized state and colorless in the reduced state. Polyaniline film on an ITO electrode not only electrocatalyzed the redox reaction of the quinone markedly but also incorporated the quinone inside. The polyaniline film incorporated the quinone showed colorless-green-bluish purple color change by applied potentials. (orig.)

  19. Polypropylene based anion exchange fiber for enrichment and ...

    African Journals Online (AJOL)

    Indium was enriched and separated by a new polypropylene based anion exchange fiber before determined by graphite furnace atomic absorption spectrometry (GFAAS). Indium can be enriched quantitatively by 0.1 g of fiber at the flow rate within 6 mL·min-1 in the pH 4 and can be desorbed quantitatively with 10 mL of 1.0 ...

  20. Local impermeant anions establish the neuronal chloride concentration

    DEFF Research Database (Denmark)

    Glykys, J; Dzhala, V; Egawa, K

    2014-01-01

    Neuronal intracellular chloride concentration [Cl(-)](i) is an important determinant of γ-aminobutyric acid type A (GABA(A)) receptor (GABA(A)R)-mediated inhibition and cytoplasmic volume regulation. Equilibrative cation-chloride cotransporters (CCCs) move Cl(-) across the membrane, but accumulat...... anions determine the homeostatic set point for [Cl(-)], and hence, neuronal volume and the polarity of local GABA(A)R signaling....

  1. Negotiating Cluster Boundaries

    DEFF Research Database (Denmark)

    Giacomin, Valeria

    2017-01-01

    Palm oil was introduced to Malay(si)a as an alternative to natural rubber, inheriting its cluster organizational structure. In the late 1960s, Malaysia became the world’s largest palm oil exporter. Based on archival material from British colonial institutions and agency houses, this paper focuses...... on the governance dynamics that drove institutional change within this cluster during decolonization. The analysis presents three main findings: (i) cluster boundaries are defined by continuous tug-of-war style negotiations between public and private actors; (ii) this interaction produces institutional change...... within the cluster, in the form of cumulative ‘institutional rounds’ – the correction or disruption of existing institutions or the creation of new ones; and (iii) this process leads to a broader inclusion of local actors in the original cluster configuration. The paper challenges the prevalent argument...

  2. Mathematical classification and clustering

    CERN Document Server

    Mirkin, Boris

    1996-01-01

    I am very happy to have this opportunity to present the work of Boris Mirkin, a distinguished Russian scholar in the areas of data analysis and decision making methodologies. The monograph is devoted entirely to clustering, a discipline dispersed through many theoretical and application areas, from mathematical statistics and combina­ torial optimization to biology, sociology and organizational structures. It compiles an immense amount of research done to date, including many original Russian de­ velopments never presented to the international community before (for instance, cluster-by-cluster versions of the K-Means method in Chapter 4 or uniform par­ titioning in Chapter 5). The author's approach, approximation clustering, allows him both to systematize a great part of the discipline and to develop many in­ novative methods in the framework of optimization problems. The optimization methods considered are proved to be meaningful in the contexts of data analysis and clustering. The material presented in ...

  3. Cool Cluster Correctly Correlated

    Energy Technology Data Exchange (ETDEWEB)

    Varganov, Sergey Aleksandrovich [Iowa State Univ., Ames, IA (United States)

    2005-01-01

    Atomic clusters are unique objects, which occupy an intermediate position between atoms and condensed matter systems. For a long time it was thought that physical and chemical properties of atomic dusters monotonically change with increasing size of the cluster from a single atom to a condensed matter system. However, recently it has become clear that many properties of atomic clusters can change drastically with the size of the clusters. Because physical and chemical properties of clusters can be adjusted simply by changing the cluster's size, different applications of atomic clusters were proposed. One example is the catalytic activity of clusters of specific sizes in different chemical reactions. Another example is a potential application of atomic clusters in microelectronics, where their band gaps can be adjusted by simply changing cluster sizes. In recent years significant advances in experimental techniques allow one to synthesize and study atomic clusters of specified sizes. However, the interpretation of the results is often difficult. The theoretical methods are frequently used to help in interpretation of complex experimental data. Most of the theoretical approaches have been based on empirical or semiempirical methods. These methods allow one to study large and small dusters using the same approximations. However, since empirical and semiempirical methods rely on simple models with many parameters, it is often difficult to estimate the quantitative and even qualitative accuracy of the results. On the other hand, because of significant advances in quantum chemical methods and computer capabilities, it is now possible to do high quality ab-initio calculations not only on systems of few atoms but on clusters of practical interest as well. In addition to accurate results for specific clusters, such methods can be used for benchmarking of different empirical and semiempirical approaches. The atomic clusters studied in this work contain from a few atoms

  4. Fusing N-heterocyclic carbenes with carborane anions.

    Science.gov (United States)

    El-Hellani, Ahmad; Lavallo, Vincent

    2014-04-22

    Here we describe the fusion of two families of unusual carbon-containing molecules that readily disregard the tendency of carbon to form four chemical bonds, namely N-heterocyclic carbenes (NHCs) and carborane anions. Deprotonation of an anionic imidazolium salt with lithium diisopropylamide at room temperature leads to a mixture of lithium complexes of C-2 and C-5 dianionic NHC constitutional isomers as well as a trianionic (C-2, C-5) adduct. Judicious choice of the base and reaction conditions allows the selective formation of all three stable polyanionic carbenes. In solution, the so-called abnormal C-5 NHC lithium complex slowly isomerizes to the normal C-2 NHC, and the process can be proton-catalyzed by the addition of the anionic imidazolium salt. These results indicate that the combination of two unusual forms of carbon atoms can lead to unexpected chemical behavior, and that this strategy paves the way for the development of a broad new generation of NHC ligands for catalysis. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Molecular modeling of penicilloate anions: an RHF-SCF analysis.

    Science.gov (United States)

    Weltman, Joel K; Loriot, George B

    2003-08-01

    An ab initio restricted Hartree-Fock self-consistent field (RHF-SCF) analysis of penicilloate anions was performed at the TZV level with GAMESS. Geometry optimization was initialized by the semi-empirical AM1 method followed by optimization at the 6-31++G** level. The total energy obtained was -1116.0997 a.u. for the penicilloate amine, -1115.3164 a.u. for the imine, -1115.2969 a.u. for the enamine and -1115.2017 a.u. for the amine that was deprotonated at the thiazolidine nitrogen. Formation of the free thiolate in the imine and enamine anions by deprotonation of the penicilloate amine is associated with: (1) an increase in total energy (2) an increase in the energy of the highest occupied molecular orbital (HOMO) to that of anti-bonding (3) a decrease in chemical hardness (4) an increase in the chemical potential (5) a more negative Mulliken net charge on the sulfur atom and (6) an increase in the Mulliken atomic population on the former thiazolidine sulfur atom in the HOMO. The RHF-SCF analysis presented here suggests a potential role for the thiolate sulfur of penicilloate anions, especially of the imine, as a chemically reactive soft nucleophile.

  6. Galaxy cluster's rotation

    Science.gov (United States)

    Manolopoulou, M.; Plionis, M.

    2017-03-01

    We study the possible rotation of cluster galaxies, developing, testing, and applying a novel algorithm which identifies rotation, if such does exist, as well as its rotational centre, its axis orientation, rotational velocity amplitude, and, finally, the clockwise or counterclockwise direction of rotation on the plane of the sky. To validate our algorithms we construct realistic Monte Carlo mock rotating clusters and confirm that our method provides robust indications of rotation. We then apply our methodology on a sample of Abell clusters with z ≲ 0.1 with member galaxies selected from the Sloan Digital Sky Survey DR10 spectroscopic data base. After excluding a number of substructured clusters, which could provide erroneous indications of rotation, and taking into account the expected fraction of misidentified coherent substructure velocities for rotation, provided by our Monte Carlo simulation analysis, we find that ∼23 per cent of our clusters are rotating under a set of strict criteria. Loosening the strictness of the criteria, on the expense of introducing spurious rotation indications, we find this fraction increasing to ∼28 per cent. We correlate our rotation indicators with the cluster dynamical state, provided either by their Bautz-Morgan type or by their X-ray isophotal shape and find for those clusters showing rotation within 1.5 h^{-1}_{70} Mpc that the significance of their rotation is related to the dynamically younger phases of cluster formation but after the initial anisotropic accretion and merging has been completed. Finally, finding rotational modes in galaxy clusters could lead to the necessity of correcting the dynamical cluster mass calculations.

  7. Anion induced conformational preference of CαNN motif residues in functional proteins.

    Science.gov (United States)

    Patra, Piya; Ghosh, Mahua; Banerjee, Raja; Chakrabarti, Jaydeb

    2017-12-01

    Among different ligand binding motifs, anion binding C α NN motif consisting of peptide backbone atoms of three consecutive residues are observed to be important for recognition of free anions, like sulphate or biphosphate and participate in different key functions. Here we study the interaction of sulphate and biphosphate with C α NN motif present in different proteins. Instead of total protein, a peptide fragment has been studied keeping C α NN motif flanked in between other residues. We use classical force field based molecular dynamics simulations to understand the stability of this motif. Our data indicate fluctuations in conformational preferences of the motif residues in absence of the anion. The anion gives stability to one of these conformations. However, the anion induced conformational preferences are highly sequence dependent and specific to the type of anion. In particular, the polar residues are more favourable compared to the other residues for recognising the anion. © 2017 Wiley Periodicals, Inc.

  8. A simple halide-to-anion exchange method for heteroaromatic salts and ionic liquids.

    Science.gov (United States)

    Alcalde, Ermitas; Dinarès, Immaculada; Ibáñez, Anna; Mesquida, Neus

    2012-04-02

    A broad and simple method permitted halide ions in quaternary heteroaromatic and ammonium salts to be exchanged for a variety of anions using an anion exchange resin (A(-) form) in non-aqueous media. The anion loading of the AER (OH(-) form) was examined using two different anion sources, acids or ammonium salts, and changing the polarity of the solvents. The AER (A(-) form) method in organic solvents was then applied to several quaternary heteroaromatic salts and ILs, and the anion exchange proceeded in excellent to quantitative yields, concomitantly removing halide impurities. Relying on the hydrophobicity of the targeted ion pair for the counteranion swap, organic solvents with variable polarity were used, such as CH(3)OH, CH(3)CN and the dipolar nonhydroxylic solvent mixture CH(3)CN:CH(2)Cl(2) (3:7) and the anion exchange was equally successful with both lipophilic cations and anions.

  9. A Simple Halide-to-Anion Exchange Method for Heteroaromatic Salts and Ionic Liquids

    Directory of Open Access Journals (Sweden)

    Neus Mesquida

    2012-04-01

    Full Text Available A broad and simple method permitted halide ions in quaternary heteroaromatic and ammonium salts to be exchanged for a variety of anions using an anion exchange resin (A− form in non-aqueous media. The anion loading of the AER (OH− form was examined using two different anion sources, acids or ammonium salts, and changing the polarity of the solvents. The AER (A− form method in organic solvents was then applied to several quaternary heteroaromatic salts and ILs, and the anion exchange proceeded in excellent to quantitative yields, concomitantly removing halide impurities. Relying on the hydrophobicity of the targeted ion pair for the counteranion swap, organic solvents with variable polarity were used, such as CH3OH, CH3CN and the dipolar nonhydroxylic solvent mixture CH3CN:CH2Cl2 (3:7 and the anion exchange was equally successful with both lipophilic cations and anions.

  10. Polyoxometal cations within polyoxometalate anions. Seven-coordinate uranium and zirconium heteroatom groups in [(UO2)12(μ3-O)4(μ2-H2O)12(P2W15O56)4]32- and [Zr4(μ3-O)2(μ2-OH)2(H2O)4 (P2W16O59)2]14-

    Science.gov (United States)

    Gaunt, Andrew J.; May, Iain; Collison, David; Travis Holman, K.; Pope, Michael T.

    2003-08-01

    Two new composite polyoxotungstate anions with unprecedented structural features, [(UO2)12(μ3-O)4(μ2-H2O)12(P2W15O56)4]32- (1) and [Zr4(μ3-O)2(μ2-OH)2(H2O)4 (P2W16O59)2]14- (2) contain polyoxo-uranium and -zirconium clusters as bridging units. The anions are synthesized by reaction of Na12[P2W15O56] with solutions of UO2(NO3)2 and ZrCl4. The structure of 1 in the sodium salt contains four [P2W15O56]12- anions assembled into an overall tetrahedral cluster by means of trigonal bridging groups formed by three equatorial-edge-shared UO7 pentagonal bipyramids. The structure of anion 2 consists of a centrosymmetric assembly of two [P2W16O59]12- anions linked by a {Zr4O2(OH)2(H2O)4}10+ cluster. Both complexes in solution yield the expected two-line 31P-NMR spectra with chemical shifts of -2.95, -13.58 and -6.45, -13.69 ppm, respectively.

  11. Anion Transport in a Chemically Stable, Sterically Bulky alpha-C Modified Imidazolium Functionalized Anion Exchange Membrane

    Science.gov (United States)

    2014-06-24

    AEM is often inconvenient, as ambient carbon dioxide (at publication time, 400 ppm) will react with the OH− to form a mixture of CO3 2− and HCO3 − in...T. In and Ex Situ Characterization of an Anion-Exchange Membrane for Alkaline Direct Methanol Fuel Cell (Admfc). J. Power Sources 2011, 196, 6153...exchange membranes (AEMs) have the potential to enable new electrochemical devices based on catalysis in alkaline media such as fuel cells or electrolyzers.2

  12. Studies in clustering theory

    Science.gov (United States)

    Stell, George

    In recent years the properties of percolation models have been studied intensively. The purpose of our project was to develop a general theory of percolation and clustering between particles of arbitrary size and shape, with arbitrary correlations between them. The goal of such a theory includes the treatment of continuum percolation as well as a novel treatment of lattice percolation. We made substantial progress toward this goal. The quantities basic to a description of clustering, the mean cluster size, mean number of clusters, etc., were developed. Concise formulas were given for the terms in such series, and proved, at least for sufficiently low densities, that the series are absolutely convergent. These series can now be used to construct Pade approximants that will allow one to probe the percolation transition. A scaled-particle theory of percolation was developed which gives analytic approximants for the mean number of clusters in a large class of two and three dimensional percolation models. Although this quantity is essential in many applications, e.g., explaining colligative properties, and interpreting low-angle light-scattering data, no systematic studies of it have been done before this work. Recently carried out detailed computer simulations show that the mean number of clusters is given to high accuracy by several of there approximations. Extensions of this work will allow calculation of the complete cluster size distribution.

  13. An anionic metal-organic framework with ternary building units for rapid and selective adsorption of dyes.

    Science.gov (United States)

    Yao, Shuo; Xu, Tong; Zhao, Nian; Zhang, Lirong; Huo, Qisheng; Liu, Yunling

    2017-03-07

    A novel metal-organic framework, [(CH3)2NH2]2[Cu3O(SO4)3Cu2L2(DMF)(H2O)]·9DMF (JLU-Liu39) H2L = pyridine-3,5-bis(phenyl-4-carboxylic acid), has been successfully synthesized under solvothermal conditions. Structure analysis indicates that the framework of JLU-Liu39 is constructed by ternary building units which include a rare hexa-nuclear [Cu6O2(SO4)6] cluster, a classical [Cu2(CO2)4] paddlewheel, and a 3-connected hetero-N, O donor ligand. The whole 3D framework possesses a (3,4,4)-connected fjh topology and a large window size of 25.3 Å with high solvent-accessible volume accounting for approximately 75.8% of the cell volume. On the basis of the anionic framework and large pore volume, JLU-Liu39 can efficiently adsorb cationic dyes such as MLB, MV, RhB and neutral dye NR but exclude anionic dyes such as MO and Orange II. Moreover, JLU-Liu39 also exhibits size-exclusion performance for dyes of different sizes, and the dye adsorption amounts decrease with the increase of dye size. With respect to the proportional mixture dyes with different charges for MO & MLB and Orange II & MLB, JLU-Liu39 can be able to selectively adsorb the cationic dye MLB efficiently. Based on the aforementioned considerations, JLU-Liu39 is a good anionic-skeleton MOF material for the adsorption and separation of organic dyes.

  14. Mimicking the cell membrane: bio-inspired simultaneous functions with monovalent anion selectivity and antifouling properties of anion exchange membrane

    Science.gov (United States)

    Zhao, Yan; Liu, Huimin; Tang, Kaini; Jin, Yali; Pan, Jiefeng; der Bruggen, Bart Van; Shen, Jiangnan; Gao, Congjie

    2016-11-01

    A new bio-inspired method was applied in this study to simultaneously improve the monovalent anion selectivity and antifouling properties of anion exchange membranes (AEMs). Three-layer architecture was developed by deposition of polydopamine (PDA) and electro-deposition of N-O-sulfonic acid benzyl chitosan (NSBC). The innermost and outermost layers were PDA with different deposition time. The middle layer was prepared by NSBC. Fourier transform infrared spectroscopy and scanning electron microscopy confirmed that PDA and NSBC were successfully modified on the surfaces of AEMs. The contact angle of the membranes indicated an improved hydrophilicity of the modified membranes. A series of electrodialysis experiments in which Cl-/SO42- separation was studied, demonstrating the monovalent anion selectivity of the samples. The Cl-/SO42- permselectivity of the modified membranes can reach up to 2.20, higher than that of the commercial membrane (only 0.78) during 90 minutes in electrodialysis (ED). The increase value of the resistance of the membranes was also measured to evaluate the antifouling properties. Sodium dodecyl benzene sulfonate (SDBS) was used as the fouling material in the ED process and the membrane area resistance of modified membrane increase value of was only 0.08 Ωcm2 30 minutes later.

  15. Document clustering methods, document cluster label disambiguation methods, document clustering apparatuses, and articles of manufacture

    Science.gov (United States)

    Sanfilippo, Antonio [Richland, WA; Calapristi, Augustin J [West Richland, WA; Crow, Vernon L [Richland, WA; Hetzler, Elizabeth G [Kennewick, WA; Turner, Alan E [Kennewick, WA

    2009-12-22

    Document clustering methods, document cluster label disambiguation methods, document clustering apparatuses, and articles of manufacture are described. In one aspect, a document clustering method includes providing a document set comprising a plurality of documents, providing a cluster comprising a subset of the documents of the document set, using a plurality of terms of the documents, providing a cluster label indicative of subject matter content of the documents of the cluster, wherein the cluster label comprises a plurality of word senses, and selecting one of the word senses of the cluster label.

  16. Introduction to cluster dynamics

    CERN Document Server

    Reinhard, Paul-Gerhard

    2008-01-01

    Clusters as mesoscopic particles represent an intermediate state of matter between single atoms and solid material. The tendency to miniaturise technical objects requires knowledge about systems which contain a ""small"" number of atoms or molecules only. This is all the more true for dynamical aspects, particularly in relation to the qick development of laser technology and femtosecond spectroscopy. Here, for the first time is a highly qualitative introduction to cluster physics. With its emphasis on cluster dynamics, this will be vital to everyone involved in this interdisciplinary subje

  17. The concept of cluster

    DEFF Research Database (Denmark)

    Laursen, Lea Louise Holst; Møller, Jørgen

    2013-01-01

    villages in order to secure their future. This paper will address the concept of cluster-villages as a possible approach to strengthen the conditions of contemporary Danish villages. Cluster-villages is a concept that gather a number of villages in a network-structure where the villages both work together...... to forskellige positioner ser vi en ny mulighed for landsbyudvikling, som vi kalder Clustervillages. In order to investigate the potentials and possibilities of the cluster-village concept the paper will seek to unfold the concept strategically; looking into the benefits of such concept. Further, the paper seeks...

  18. Partially supervised speaker clustering.

    Science.gov (United States)

    Tang, Hao; Chu, Stephen Mingyu; Hasegawa-Johnson, Mark; Huang, Thomas S

    2012-05-01

    Content-based multimedia indexing, retrieval, and processing as well as multimedia databases demand the structuring of the media content (image, audio, video, text, etc.), one significant goal being to associate the identity of the content to the individual segments of the signals. In this paper, we specifically address the problem of speaker clustering, the task of assigning every speech utterance in an audio stream to its speaker. We offer a complete treatment to the idea of partially supervised speaker clustering, which refers to the use of our prior knowledge of speakers in general to assist the unsupervised speaker clustering process. By means of an independent training data set, we encode the prior knowledge at the various stages of the speaker clustering pipeline via 1) learning a speaker-discriminative acoustic feature transformation, 2) learning a universal speaker prior model, and 3) learning a discriminative speaker subspace, or equivalently, a speaker-discriminative distance metric. We study the directional scattering property of the Gaussian mixture model (GMM) mean supervector representation of utterances in the high-dimensional space, and advocate exploiting this property by using the cosine distance metric instead of the euclidean distance metric for speaker clustering in the GMM mean supervector space. We propose to perform discriminant analysis based on the cosine distance metric, which leads to a novel distance metric learning algorithm—linear spherical discriminant analysis (LSDA). We show that the proposed LSDA formulation can be systematically solved within the elegant graph embedding general dimensionality reduction framework. Our speaker clustering experiments on the GALE database clearly indicate that 1) our speaker clustering methods based on the GMM mean supervector representation and vector-based distance metrics outperform traditional speaker clustering methods based on the “bag of acoustic features” representation and statistical

  19. Raspberry Pi super cluster

    CERN Document Server

    Dennis, Andrew K

    2013-01-01

    This book follows a step-by-step, tutorial-based approach which will teach you how to develop your own super cluster using Raspberry Pi computers quickly and efficiently.Raspberry Pi Super Cluster is an introductory guide for those interested in experimenting with parallel computing at home. Aimed at Raspberry Pi enthusiasts, this book is a primer for getting your first cluster up and running.Basic knowledge of C or Java would be helpful but no prior knowledge of parallel computing is necessary.

  20. Between Localization and Delocalization: Ru(cod)(2+) Units in the Zintl Clusters [Bi9 {Ru(cod)}2 ](3-) and [Tl2 Bi6 {Ru(cod)}](2).

    Science.gov (United States)

    Lichtenberger, Niels; Spang, Nils; Eichhöfer, Andreas; Dehnen, Stefanie

    2017-10-16

    Reactions of [K(crypt-222)]2 (TlBi3 )⋅0.5 en (1 b) with [Ru(cod)(H2 CC(Me)CH2 )2 ] (A) in 1,2-diaminoethane (en) led to the formation of two compounds with new bismuth-rich cluster anions, [K(crypt-222)]3 [Bi9 {Ru(cod)}2 ]⋅1.5 en (2) and [K(crypt-222)]2 [Tl2 Bi6 {Ru(cod)}]⋅2 tol (3), alongside the salt of a binary nido cluster, [K(crypt-222)]3 (Tl4 Bi5 )⋅2 en (4). The anions in 2 and 3 are two further examples of rare heterometallic clusters containing Ru atoms. As one cod ligand is retained on each Ru atom in both clusters, the anions may be viewed as intermediates on the way towards larger, ligand-free intermetalloid clusters. Quantum-chemical studies provided insight into the bonding situation in these clusters. According to these studies, the anion of 2 features both electron-precise and electron-deficient parts. Electrospray ionization mass spectrometry analysis indicated that the clusters undergo stepwise fragmentation. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Spanning Tree Based Attribute Clustering

    DEFF Research Database (Denmark)

    Zeng, Yifeng; Jorge, Cordero Hernandez

    2009-01-01

    inconsistent edges from a maximum spanning tree by starting appropriate initial modes, therefore generating stable clusters. It discovers sound clusters through simple graph operations and achieves significant computational savings. We compare the Star Discovery algorithm against earlier attribute clustering...

  2. Tune Your Brown Clustering, Please

    DEFF Research Database (Denmark)

    Derczynski, Leon; Chester, Sean; Bøgh, Kenneth Sejdenfaden

    2015-01-01

    Brown clustering, an unsupervised hierarchical clustering technique based on ngram mutual information, has proven useful in many NLP applications. However, most uses of Brown clustering employ the same default configuration; the appropriateness of this configuration has gone predominantly...

  3. A general halide-to-anion switch for imidazolium-based ionic liquids and oligocationic systems using anion exchange resins (A- form).

    Science.gov (United States)

    Alcalde, Ermitas; Dinarès, Immaculada; Ibáñez, Anna; Mesquida, Neus

    2011-03-21

    Further studies on the application of an AER (A(-) form) method broadened the anion exchange scope of representative ionic liquids and bis(imidazolium) systems. Depending on the hydrophobicity nature of the targeted imidazolium species and counteranions, different organic solvents were used to swap halides for assorted anions, proceeding in excellent to quantitative yields.

  4. Hydrogen binding effect on charged P2n (n = 1–7) clusters

    Indian Academy of Sciences (India)

    of P5, P7, P9 and their cations and anions which exhibit intensities of significance on the mass spectra had been acquired by means of the B3LYP, DFT method.10 A cationic cluster prefers to adopt structures with an atom which is four-fold coordinated. The planar pentagon structure is a frequent sub-unit in the phosphorus ...

  5. Probing microhydration effect on the electronic structure of the GFP chromophore anion: Photoelectron spectroscopy and theoretical investigations

    Energy Technology Data Exchange (ETDEWEB)

    Bhaskaran-Nair, Kiran; Shelton, William A. [Cain Department of Chemical Engineering, Louisiana State University, Baton Rouge, Louisiana 70803 (United States); Center for Computation and Technology, Louisiana State University, Baton Rouge, Louisiana 70803 (United States); Valiev, Marat; Kowalski, Karol, E-mail: karol.kowalski@pnnl.gov [William R. Wiley Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, K8-91, P.O. Box 999, Richland, Washington 99352 (United States); Deng, S. H. M.; Wang, Xue-Bin, E-mail: xuebin.wang@pnnl.gov [Physical Sciences Division, Pacific Northwest National Laboratory, K8-88, P.O. Box 999, Richland, Washington 99352 (United States)

    2015-12-14

    The photophysics of the Green Fluorescent Protein (GFP) chromophore is critically dependent on its local structure and on its environment. Despite extensive experimental and computational studies, there remain many open questions regarding the key fundamental variables that govern this process. One outstanding problem is the role of autoionization as a possible relaxation pathway of the excited state under different environmental conditions. This issue is considered in our work through combined experimental and theoretical studies of microsolvated clusters of the deprotonated p-hydroxybenzylidene-2,3-dimethylimidazolinone anion (HBDI{sup −}), an analog of the GFP chromophore. Through selective generation of microsolvated structures of predetermined size and subsequent analysis of experimental photoelectron spectra by high level ab initio methods, we are able to precisely identify the structure of the system, establish the accuracy of theoretical data, and provide reliable description of auto-ionization process as a function of hydrogen-bonding environment. Our study clearly illustrates the first few water molecules progressively stabilize the excited state of the chromophore anion against the autodetached neutral state, which should be an important trait for crystallographic water molecules in GFPs that has not been fully explored to date.

  6. Probing microhydration effect on the electronic structure of the GFP chromophore anion. Photoelectron spectroscopy and theoretical investigations

    Energy Technology Data Exchange (ETDEWEB)

    Bhaskaran-Nair, Kiran; Valiev, Marat; Deng, Shihu; Shelton, William A.; Kowalski, Karol; Wang, Xue B.

    2015-12-14

    The photophysics of Green Fluorescent Protein (GFP) chromophore is critically dependent on its local structure and on its environment. Despite extensive experimental and computational studies, there remain many open questions regarding the key fundamental variables that govern this process. One outstanding problem is the role of autoionization as a possible relaxation pathway of the excited state under different environmental conditions. This issue is considered in our work through combined experimental and theoretical studies of microsolvated clusters of the deprotonated p-hydroxybenzylidene-2,3-dimethylimidazolinone anion (HBDI⁻), an analog of GFP chromophore. Through selective generation of microsolvated structures of predetermined size and subsequent analysis of experimental photoelectron spectra by high level ab-initio methods we are able to precisely identify the structure of the system, establish the accuracy of theoretical data, and provide reliable description of auto-ionization process as a function of hydrogen-bonding environment. Our study clearly illustrates the first few water molecules progressively stabilize the excited state of the chromophore anion against the autodetached neutral state, which should be an important trait for crystallographic water molecules in GFPs that has not been fully explored to date.

  7. Probing microhydration effect on the electronic structure of the GFP chromophore anion: Photoelectron spectroscopy and theoretical investigations

    Science.gov (United States)

    Bhaskaran-Nair, Kiran; Valiev, Marat; Deng, S. H. M.; Shelton, William A.; Kowalski, Karol; Wang, Xue-Bin

    2015-12-01

    The photophysics of the Green Fluorescent Protein (GFP) chromophore is critically dependent on its local structure and on its environment. Despite extensive experimental and computational studies, there remain many open questions regarding the key fundamental variables that govern this process. One outstanding problem is the role of autoionization as a possible relaxation pathway of the excited state under different environmental conditions. This issue is considered in our work through combined experimental and theoretical studies of microsolvated clusters of the deprotonated p-hydroxybenzylidene-2,3-dimethylimidazolinone anion (HBDI-), an analog of the GFP chromophore. Through selective generation of microsolvated structures of predetermined size and subsequent analysis of experimental photoelectron spectra by high level ab initio methods, we are able to precisely identify the structure of the system, establish the accuracy of theoretical data, and provide reliable description of auto-ionization process as a function of hydrogen-bonding environment. Our study clearly illustrates the first few water molecules progressively stabilize the excited state of the chromophore anion against the autodetached neutral state, which should be an important trait for crystallographic water molecules in GFPs that has not been fully explored to date.

  8. N-acetylglyoxylic amide bearing a nitrophenyl group as anion receptors: NMR and X-ray investigations on anion binding and selectivity

    Science.gov (United States)

    Suryanti, Venty; Bhadbhade, Mohan; Black, David StC; Kumar, Naresh

    2017-10-01

    N-Nitrophenylglyoxylic amides 1 and 2 in presence of tetrabutylammonium cation (TBA) act as receptors for anions HSO4-, Cl-, Br- and NO3- as investigated by NMR studies. The receptors formed 1:1 host-guest complexes in solution. X-ray structure of 1 along with TBA that bind a chloride anion is reported. Molecule 1 showed the highest selectivity for HSO4- anion over others measured. X-ray structure of the bound Cl- revealed a pocket containing the anion making strong (Nsbnd H⋯Cl) and weak hydrogen bonds (Csbnd H⋯Cl) that contribute to the recognition of the chloride anion. Nsbnd H and Csbnd H hydrogen bonds resulted in a relatively strong binding for chloride ions.

  9. Galaxy clusters and cosmology

    CERN Document Server

    White, S

    1994-01-01

    Galaxy clusters are the largest coherent objects in Universe. It has been known since 1933 that their dynamical properties require either a modification of the theory of gravity, or the presence of a dominant component of unseen material of unknown nature. Clusters still provide the best laboratories for studying the amount and distribution of this dark matter relative to the material which can be observed directly -- the galaxies themselves and the hot,X-ray-emitting gas which lies between them.Imaging and spectroscopy of clusters by satellite-borne X -ray telescopes has greatly improved our knowledge of the structure and composition of this intergalactic medium. The results permit a number of new approaches to some fundamental cosmological questions,but current indications from the data are contradictory. The observed irregularity of real clusters seems to imply recent formation epochs which would require a universe with approximately the critical density. On the other hand, the large baryon fraction observ...

  10. CSR in Industrial Clusters

    DEFF Research Database (Denmark)

    Lund-Thomsen, Peter; Pillay, Renginee G.

    2012-01-01

    Purpose – The paper seeks to review the literature on CSR in industrial clusters in developing countries, identifying the main strengths, weaknesses, and gaps in this literature, pointing to future research directions and policy implications in the area of CSR and industrial cluster development....... Design/methodology/approach – A literature review is conducted of both academic and policy-oriented writings that contain the keywords “industrial clusters” and “developing countries” in combination with one or more of the following terms: corporate social responsibility, environmental management, labor...... in this field and their comments incorporated in the final version submitted to Corporate Governance. Findings – The article traces the origins of the debate on industrial clusters and CSR in developing countries back to the early 1990s when clusters began to be seen as an important vehicle for local economic...

  11. Evolution of clustered storage

    CERN Multimedia

    CERN. Geneva; Van de Vyvre, Pierre

    2007-01-01

    The session actually featured two presentations: * Evolution of clustered storage by Lance Hukill, Quantum Corporation * ALICE DAQ - Usage of a Cluster-File System: Quantum StorNext by Pierre Vande Vyvre, CERN-PH the second one prepared at short notice by Pierre (thanks!) to present how the Quantum technologies are being used in the ALICE experiment. The abstract to Mr Hukill's follows. Clustered Storage is a technology that is driven by business and mission applications. The evolution of Clustered Storage solutions starts first at the alignment between End-users needs and Industry trends: * Push-and-Pull between managing for today versus planning for tomorrow * Breaking down the real business problems to the core applications * Commoditization of clients, servers, and target devices * Interchangeability, Interoperability, Remote Access, Centralized control * Oh, and yes, there is a budget and the "real world" to deal with This presentation will talk through these needs and trends, and then ask the question, ...

  12. How Clusters Work

    Science.gov (United States)

    Technology innovation clusters are geographic concentrations of interconnected companies, universities, and other organizations with a focus on environmental technology. They play a key role in addressing the nation’s pressing environmental problems.

  13. Air void clustering.

    Science.gov (United States)

    2015-06-01

    Air void clustering around coarse aggregate in concrete has been identified as a potential source of : low strengths in concrete mixes by several Departments of Transportation around the country. Research was : carried out to (1) develop a quantitati...

  14. Clustering of Emerging Flux

    Science.gov (United States)

    Ruzmaikin, A.

    1997-01-01

    Observations show that newly emerging flux tends to appear on the Solar surface at sites where there is flux already. This results in clustering of solar activity. Standard dynamo theories do not predict this effect.

  15. Effects of Te(IV) Oxo-Anion Incorporation into Thorium Molybdates and Tungstates.

    Science.gov (United States)

    Xiao, Bin; Klinkenberg, Martina; Bosbach, Dirk; Suleimanov, Evgeny V; Alekseev, Evgeny V

    2015-06-15

    The exploration of phase formation in the Th-Mo/W-Te systems has resulted in four mixed oxo-anion compounds from high-temperature solid-state reactions: ThWTe2O9, Th(WO4)(TeO3), ThMoTe2O9, and Th2(MoO4)(TeO3)3. All four compounds contain edge-sharing thorium polyhedra linked by MoO4/WO6 and different tellurium oxo-groups to form three-dimensional frameworks. In ThWTe2O9, each helical Th based chain is connected by four tungstotellurite clusters resulting in a building fragment which has a cross-section of four-leafed clovers. The structure of Th(WO4)(TeO3) exhibits a multilayer-sandwich framework composed of thorium tellurite layers with tungsten chains in between. In the case of the molybdate family, ThMoTe2O9 and Th2(MoO4)(TeO3)3 are built from puckered Th-Te sheets which are further interconnected by MoO4 tetrahedral linkers. The DSC-TG technique was performed to gain insight into the thermal behavior of the synthesized compounds. Raman spectra of as-prepared phases were obtained and analyzed for signature peaks.

  16. Photo-Cross-Linked Anion Exchange Membranes with Improved Water Management and Conductivity

    Energy Technology Data Exchange (ETDEWEB)

    Ertem, S. Piril; Tsai, Tsung-Han; Donahue, Melissa M.; Zhang, Wenxu; Sarode, Himanshu; Liu, Ye; Seifert, Soenke; Herring, Andrew M.; Coughlin, E. Bryan

    2016-01-12

    Robust, cross-linked anion exchange membranes (AEMs) were prepared from solvent-processable polyisoprene- ran -poly(vinylbenzyltrimethylammonium chloride) (PI- ran -P- [VBTMA][Cl]) ionomers via photoinitiated thiol - ene chem- istry. Two series of membranes were prepared choosing two dithiol cross-linkers, 1,10-decanedithiol and 2,2 ' - (ethylenedioxy)diethanethiol, selected for their di ff erent hydro- phobicities. A strong correlation was found between the choice of dithiol cross-linker, water uptake, morphology, and the ion conductivity of the membranes. Results were compared with previous fi ndings of thermally cross-linked AEMs from analogous random copolymers. Comparably high chloride ion conductivities were obtained at low to moderate ion exchange capacities (IECs) with signi fi cantly low water uptake values. It was shown that by choosing a hydrophilic cross-linker ion cluster formation may be suppressed and ion conduction improved. This study highlights that it is possible to promote ion conductivities for low IEC membranes (<1 mmol/g) by forming well- connected, ion conducting network morphology. This observation paves the way for mechanically robust ion conducting membranes with enhanced conductivities and better water management.

  17. Adsorption of water molecules on selected charged sodium-chloride clusters.

    Science.gov (United States)

    Bradshaw, James A; Gordon, Sidney L; Leavitt, Andrew J; Whetten, Robert L

    2012-01-12

    The adsorption of water molecules (H(2)O) on sodium chloride cluster cations and anions was studied at 298 K over a mass range of 100-1200 amu using a custom-built laser desorption ionization reactor and mass spectrometer. Under the conditions used, the cations Na(3)Cl(2)(+) and Na(4)Cl(3)(+) bind up to three water molecules, whereas the larger cations, Na(5)Cl(4)(+) to Na(19)Cl(18)(+), formed hydrates with one or two only. The overall trend is a decrease in hydration with increasing cluster size, with an abrupt drop occurring at the closed-shell Na(14)Cl(13)(+). As compared to the cluster cations, the cluster anions showed almost no adsorption. Among smaller clusters, a weak adsorption of one water molecule was observed for the cluster anions Na(6)Cl(7)(-) and Na(7)Cl(8)(-). In the higher mass region, a substantial adsorption of one water molecule was observed for Na(14)Cl(15)(-). Density functional theory (DFT) computations were carried out for the adsorption of one molecule of H(2)O on the cations Na(n)Cl(n-1)(+), for n = 2-8, and the anions Na(n)Cl(n+1)(-), for n = 1-7. For each ion, the structure of the hydrate, the hydration energy, and the standard-state enthalpy, entropy, and Gibbs energy of hydration at 298 K were computed. In addition, it was useful to compute the distortion energy, defined as the electronic energy lost due to weakening of the Na-Cl bonds upon adsorption of H(2)O. The results show that strong adsorption of a H(2)O molecule occurs for the linear cations only at an end Na ion and for the nonlinear cations only at a corner Na ion bonded to two Cl ions. An unexpected result of the theoretical investigation for the anions is that certain low-energy isomers of Na(6)Cl(7)(-) and Na(7)Cl(8)(-) bind H(2)O strongly enough to produce the observed weak adsorption. The possible implications of these results for the initial hydration of extended NaCl surfaces are discussed.

  18. Globular clusters with Gaia

    Science.gov (United States)

    Pancino, E.; Bellazzini, M.; Giuffrida, G.; Marinoni, S.

    2017-05-01

    The treatment of crowded fields in Gaia data will only be a reality in a few years from now. In particular, for globular clusters, only the end-of-mission data (public in 2022-2023) will have the necessary full crowding treatment and will reach sufficient quality for the faintest stars. As a consequence, the work on the deblending and decontamination pipelines is still ongoing. We describe the present status of the pipelines for different Gaia instruments, and we model the end-of-mission crowding errors on the basis of available information. We then apply the nominal post-launch Gaia performances, appropriately worsened by the estimated crowding errors, to a set of 18 simulated globular clusters with different concentration, distance and field contamination. We conclude that there will be 103-104 stars with astrometric performances virtually untouched by crowding (contaminated by <1 mmag) in the majority of clusters. The most limiting factor will be field crowding, not cluster crowding: the most contaminated clusters will only contain 10-100 clean stars. We also conclude that (i) the systemic proper motions and parallaxes will be determined to 1 per cent or better up to ≃15 kpc, and the nearby clusters will have radial velocities to a few km s-1; (ii) internal kinematics will be of unprecedented quality, cluster masses will be determined to ≃10 per cent up to 15 kpc and beyond, and it will be possible to identify differences of a few km s-1 or less in the kinematics (if any) of cluster sub-populations up to 10 kpc and beyond; (iii) the brightest stars (V ≃ 17 mag) will have space-quality, wide-field photometry (mmag errors), and all Gaia photometry will have 1-3 per cent errors on the absolute photometric calibration.

  19. Structure of Silicon Clusters

    OpenAIRE

    Pan, Jun; Bahel, Atul; Ramakrishna, Mushti V.

    1995-01-01

    We determined the structures of silicon clusters in the 11-14 atom size range using the tight-binding molecular dynamics method. These calculations reveal that \\Si{11} is an icosahedron with one missing cap, \\Si{12} is a complete icosahedron, \\Si{13} is a surface capped icosahedron, and \\Si{14} is a 4-4-4 layer structure with two caps. The characteristic feature of these clusters is that they are all surface.

  20. Simultaneous determination of NH4+, NO2(-) and NO3(-) by ion-exclusion/anion-exchange chromatography on a strongly basic anion-exchange resin with basic eluent.

    Science.gov (United States)

    Mori, Masanobu; Hironaga, Takahiro; Itabashi, Hideyuki; Nakatani, Nobutake; Kozaki, Daisuke; Tanaka, Kazuhiko

    2012-04-01

    Ion-exclusion/anion-exchange chromatography (IEC/AEC) on a combination of a strongly basic anion-exchange resin in the OH(-)-form with basic eluent has been developed. The separation mechanism is based on the ion-exclusion/penetration effect for cations and the anion-exchange effect for anions to anion-exchange resin phase. This system is useful for simultaneous separation and determination of ammonium ion (NH4+), nitrite ion (NO2(-)), and nitrate ion (NO3(-)) in water samples. The resolution of analyte ions can be manipulated by changing the concentration of base in eluent on a polystyrene-divinylbenzene based strongly basic anion-exchange resin column. In this study, several separation columns, which consisted of different particle sizes, different functional groups and different anion-exchange capacities, were compared. As the results, the separation column with the smaller anion-exchange capacity (TSKgel Super IC-Anion) showed well-resolved separation of cations and anions. In the optimization of the basic eluent, lithium hydroxide (LiOH) was used as the eluent and the optimal concentration was concluded to be 2 mmol/L, considering the resolution of analyte ions and the whole retention times. In the optimal conditions, the relative standard deviations of the peak areas and the retention times of NH4+, NO2(-), and NO3(-) ranged 1.28% - 3.57% and 0.54% - 1.55%, respectively. The limits of detection at signal-to-noise of 3 were 4.10 micromol/L for NH4+, 1.87 micromol/L for NO2(-) and 2.83 micromol/L for NO3(-).

  1. The impact of dietary cation anion difference (DCAD) on the acid-base balance and calcium metabolism of non-lactating, non-pregnant dairy cows fed equal amounts of different anionic salts.

    Science.gov (United States)

    Gelfert, Carl-Christian; Leonie Loeffler, S; Frömer, Sven; Engel, Maike; Hartmann, Helmut; Männer, Klaus; Baumgartner, Walter; Staufenbiel, Rudolf

    2007-08-01

    We evaluated the impact of the dietary cation-anion difference (DCAD) on the influence of anionic salts (AS) on the metabolism of dairy cows using a study-design that included control of feed intake. Ten mature, non-lactating, non-pregnant, Holstein-Friesian-crossbreed cows received 2000 mEq of either one of the seven anionic salts tested, two combinations of the anionic salts or water as control via a rumen cannula. Salts and controls were assigned in a 10x10 Latin square design. Whole blood, serum and urine samples were taken during treatment (TP) and washout period. Samples of whole blood were tested for pH, base-excess and bicarbonate concentrations. In urine, pH and net acid-base excretion (NABE) were analysed. Calcium was measured in serum and urine. According to the different batches of hay, five groups of DCAD were created regarding cluster analysis. Changes in urine and blood parameters were statistically analysed for each DCAD group separately. The different DCAD had an impact on the amount of change in acid-base balance (ABB) and calcium metabolism and for how long these changes lasted. In the DCAD group receiving the highest amount of AS (239 mEq/kg dry matter with AS), changes of ABB were only noticeable in urine and these changes only differed from day zero in the first week of TP (Pdiffer significantly (Pdiffered clearly from day zero (Pdifferences were very small and only differed from day zero on a few TP days. We conclude that the DCAD of a dairy cow's diet has an important impact on the effect of AS on ABB and calcium metabolism with respect to the duration and amount of change. The target regions of DCAD should be clearly below 100 mEq/kg dry matter to ensure the desired effect on ABB and calcium metabolism. Extremely negative DCAD should be avoided to minimize the risk of clinical acidosis induced by AS.

  2. Chemistry of nitrile anions in the interstellar medium

    Energy Technology Data Exchange (ETDEWEB)

    Carles, S.; Le Garrec, J.-L.; Biennier, L. [Institut de Physique de Rennes, Département de Physique Moléculaire, Astrophysique de Laboratoire, UMR CNRS 6251, Université de Rennes 1, Campus de Beaulieu, 35042 Rennes Cedex (France); Guillemin, J.-C. [Institut des Sciences Chimiques de Rennes, Ecole Nationale Supérieure de Chimie de Rennes, CNRS, UMR 6226, 11 Allée de Beaulieu, CS 50837,35708 Rennes Cedex 7 (France)

    2015-12-31

    Despite the extreme conditions of temperature (down to 10K) and density (down to 100 molecules/cm{sup 3}), the giant molecular clouds and the circumstellar envelopes present a rich and complex chemistry. To date, more than 180 molecules have been detected in the InterStellar Medium (ISM) with a large abundance of nitriles (RC≡N). In addition, several anions have been recently observed in this medium: C{sub 4}H{sup ¯}, C{sub 6}H{sup ¯}, C{sub 8}H{sup ¯}, CN{sup ¯}, C{sub 3}N{sup ¯} and C{sub 5}N{sup ¯}. These last species should play a key role in the molecular growth towards complexity. To explore this hypothesis, their reactivity must be studied in the laboratory. The FALP-MS and the CRESU experimental apparatuses of the Rennes University are able to measure absolute rate coefficient of various chemical reactions, including the ion – molecule reactions, in gas phase at low temperature (from 300K for the FALP-MS down to 15K for the CRESU). Therefore, these experimental tools are particularly adapted to the kinetic studies of reactions potentially involved in the Interstellar Medium. One of the difficulties encountered in experiments with anions is their generation. We describe here the formation of the CN{sup ¯} and C{sub 3}N{sup ¯} anions by dissociative electron attachment on the molecular precursors BrCN and BrC{sub 3}N.

  3. Natural minerals and synthetic materials for sorption of radioactive anions

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Mun Ja; Chun, Kwan Sik; Kim, Seung Soo

    1998-07-01

    Technetium-99 and iodine-129 are fission products with long half-lives, and exist as highly soluble anionic species. Studies on natural and synthetic materials sorbing TcO{sub 4} and/or I have been performed by several researchers. The application of these materials as an additive in the high-level waste disposal has been considered. The iron- or sulfide-containing minerals such as metal iron, iron powder, stibnite and pyrrhotite show a high capacity for TcO{sub 4} sorption. And the small amounts of activated carbon are reported to have high distribution coefficients recently. In the iodine sorption studies, sulfide-, copper-, lead- or mercury-containing minerals can be a candidate. Pyrite, chalcopyrite, galena, Cu{sub 2}S and CuS reveal a high capacity for I sorption. The synthetic materials were found to have high sorption capacity and compensate the defects of natural minerals, which contain hydrous oxides such as zirconium oxide, aluminium oxide and mercarbide. The mercarbide has the high distribution coefficients for the sorption of TcO{sub 4} and I. Recently it was proposed that the synthetic clay, hydrotalcite, could be useful for the fixation of anion. However, to determine the applicability of those natural and synthetic materials as an additive to a buffer or backfill material for sorption of TcO{sub 4} and/or I, the sorption behavior of the anions on those materials under the repository conditions should be identified. (author). 32 refs., 21 tabs., 10 figs

  4. REMOVAL OF ANIONIC SURFACTANTS FROM WASTEWATER BY MAGNETIC MINERAL SORBENTS

    Directory of Open Access Journals (Sweden)

    Oksana Vladimirova Makarchuk

    2016-07-01

    Full Text Available The simplest and most effective method of removing low concentrations of anionic surfactants such as sodium dodecyl benzenesulfonate (SDBS and sodium lauryl sulfate (SLS is adsorption. Among adsorbents the natural clays are cheap and promising for these purposes. However, there are significant difficulties in removal of spent sorbent after the adsorption process. So, the creation of magnetic sorbents that can be effectively removed from water after sorption by magnetic separation will be a successful decision. The aim of this investigation is the creation of cheap and efficient magnetic sorbents based on natural clays and magnetite for anionic surfactant removal from wastewater. We have synthesized a series of magnetic sorbents from different natural clays with a content of magnetite from 2 to 10 wt%. The ability of magnetic sorbents to remove SDBS and SLS from aqueous solutions has been studied for different adsorbate concentrations by varying the amount of adsorbent, temperature and shaking time. Thermodynamic parameters were calculated from the slope and intercept of the linear plots of ln K against 1/T. Analysis of adsorption results obtained at different temperatures showed that the adsorption pattern on magnetic sorbents correspond to the Langmuir isotherm. It is shown that with increasing the content of magnetite in the magnetic sorbents improves not only their separation from water by magnetic separation, but adsorption capacity to SDBS and SLS. Thus, we obtained of cheap magnetic sorbents based on natural clays and magnetite by the easy way, which not only quickly separated from the solution by magnetic separation, but effectively remove anionic surfactants.

  5. Adsorption and desorption dynamics of citric acid anions in soil

    KAUST Repository

    Oburger, E.

    2011-07-26

    The functional role of organic acid anions in soil has been intensively investigated, with special focus on (i) microbial respiration and soil carbon dynamics, (ii) nutrient solubilization or (iii) metal detoxification and reduction of plant metal uptake. Little is known about the interaction dynamics of organic acid anions with the soil matrix and the potential impact of adsorption and desorption processes on the functional significance of these effects. The aim of this study was to characterize experimentally the adsorption and desorption dynamics of organic acid anions in five agricultural soils differing in iron and aluminium oxide contents and using citrate as a model carboxylate. Results showed that both adsorption and desorption processes were fast in all soils, reaching a steady state within approximately 1 hour. However, for a given total soil citrate concentration (ct) the steady state was critically dependent on the starting conditions of the experiment, whether most of the citrate was initially present in solution (cl) or held on the solid phase (cs). Specifically, desorption-led processes resulted in significantly smaller steady-state solution concentrations than adsorption-led processes, indicating that hysteresis occurred. As it is not possible to distinguish between different adsorption and desorption pools in soil experimentally, a new dynamic hysteresis model that relies only on measured soil solution concentrations was developed. The model satisfactorily explained experimental data and was able to predict dynamic adsorption and desorption behaviour. To demonstrate its use, we applied the model to two relevant situations involving exudation and microbial degradation. The study highlighted the complex nature of citrate adsorption and desorption dynamics in soil. We conclude that existing models need to incorporate both temporal and hysteresis components to describe realistically the role and fate of organic acids in soil processes. © 2011 The

  6. Interaction of Organic Cations with Organic Anion Transporters*

    Science.gov (United States)

    Ahn, Sun-Young; Eraly, Satish A.; Tsigelny, Igor; Nigam, Sanjay K.

    2009-01-01

    Studies of the organic anion transporters (Oats) have focused mainly on their interactions with organic anionic substrates. However, as suggested when Oat1 was originally identified as NKT (Lopez-Nieto, C. E., You, G., Bush, K. T., Barros, E. J., Beier, D. R., and Nigam, S. K. (1997) J. Biol. Chem. 272, 6471–6478), since the Oats share close homology with organic cation transporters (Octs), it is possible that Oats interact with cations as well. We now show that mouse Oat1 (mOat1) and mOat3 and, to a lesser degree, mOat6 bind a number of “prototypical” Oct substrates, including 1-methyl-4-phenylpyridinium. In addition to oocyte expression assays, we have tested binding of organic cations to Oat1 and Oat3 in ex vivo assays by analyzing interactions in kidney organ cultures deficient in Oat1 and Oat3. We also demonstrate that mOat3 transports organic cations such as 1-methyl-4-phenylpyridinium and cimetidine. A pharmacophore based on the binding affinities of the tested organic cations for Oat3 was generated. Using this pharmacophore, we screened a chemical library and were able to identify novel cationic compounds that bound to Oat1 and Oat3. These compounds bound Oat3 with an affinity higher than the highest affinity compounds in the original set of prototypical Oct substrates. Thus, whereas Oat1, Oat3, and Oat6 appear to function largely in organic anion transport, they also bind and transport some organic cations. These findings could be of clinical significance, since drugs and metabolites that under normal physiological conditions do not bind to the Oats may undergo changes in charge and become Oat substrates during pathologic conditions wherein significant variations in body fluid pH occur. PMID:19737926

  7. Interaction of organic cations with organic anion transporters.

    Science.gov (United States)

    Ahn, Sun-Young; Eraly, Satish A; Tsigelny, Igor; Nigam, Sanjay K

    2009-11-06

    Studies of the organic anion transporters (Oats) have focused mainly on their interactions with organic anionic substrates. However, as suggested when Oat1 was originally identified as NKT (Lopez-Nieto, C. E., You, G., Bush, K. T., Barros, E. J., Beier, D. R., and Nigam, S. K. (1997) J. Biol. Chem. 272, 6471-6478), since the Oats share close homology with organic cation transporters (Octs), it is possible that Oats interact with cations as well. We now show that mouse Oat1 (mOat1) and mOat3 and, to a lesser degree, mOat6 bind a number of "prototypical" Oct substrates, including 1-methyl-4-phenylpyridinium. In addition to oocyte expression assays, we have tested binding of organic cations to Oat1 and Oat3 in ex vivo assays by analyzing interactions in kidney organ cultures deficient in Oat1 and Oat3. We also demonstrate that mOat3 transports organic cations such as 1-methyl-4-phenylpyridinium and cimetidine. A pharmacophore based on the binding affinities of the tested organic cations for Oat3 was generated. Using this pharmacophore, we screened a chemical library and were able to identify novel cationic compounds that bound to Oat1 and Oat3. These compounds bound Oat3 with an affinity higher than the highest affinity compounds in the original set of prototypical Oct substrates. Thus, whereas Oat1, Oat3, and Oat6 appear to function largely in organic anion transport, they also bind and transport some organic cations. These findings could be of clinical significance, since drugs and metabolites that under normal physiological conditions do not bind to the Oats may undergo changes in charge and become Oat substrates during pathologic conditions wherein significant variations in body fluid pH occur.

  8. Determination of atomic cluster structure with cluster fusion algorithm

    DEFF Research Database (Denmark)

    Obolensky, Oleg I.; Solov'yov, Ilia; Solov'yov, Andrey V.

    2005-01-01

    We report an efficient scheme of global optimization, called cluster fusion algorithm, which has proved its reliability and high efficiency in determination of the structure of various atomic clusters.......We report an efficient scheme of global optimization, called cluster fusion algorithm, which has proved its reliability and high efficiency in determination of the structure of various atomic clusters....

  9. Review: equipment for anionic surfactant manufacture from oil palm

    Directory of Open Access Journals (Sweden)

    Jesús Alfonso Torres Ortega

    2010-05-01

    Full Text Available In the present study is performed a review of the current processes of sulfonation of various raw materials for determine the process conditions in order to present the state of the art of sulfonation processes for the manufacture of anionic surfactants. There has been a scientific literature with emphasis on several aspects: Technology, sulfonation reactors and operating conditions in the process, analytical techniques for monitoring the reaction degree, the mathematical models proposed in the literature for the sulfonation/sulfation in tubular absorbers, patenting and specialized industry publications in this area.

  10. Minority anion substitution by Ni in ZnO

    CERN Document Server

    Pereira, Lino Miguel da Costa; Correia, João Guilherme; Amorim, Lígia Marina; Silva, Daniel José; David-Bosne, Eric; Decoster, Stefan; da Silva, Manuel Ribeiro; Temst, Kristiaan; Vantomme, André

    2013-01-01

    We report on the lattice location of implanted Ni in ZnO using the $\\beta$− emission channeling technique. In addition to the majority substituting for the cation (Zn), a significant fraction of the Ni atoms occupy anion (O) sites. Since Ni is chemically more similar to Zn than it is to O, the observed O substitution is rather puzzling. We discuss these findings with respect to the general understanding of lattice location of dopants in compound semiconductors. In particular, we discuss potential implications on the magnetic behavior of transition metal doped dilute magnetic semiconductors.

  11. Interaction of dodecaborate cluster compounds on hydrophilic column materials in water.

    Science.gov (United States)

    Fan, Ping; Neumann, Jennifer; Stolte, Stefan; Arning, Jürgen; Ferreira, Denise; Edwards, Katarina; Gabel, Detlef

    2012-09-21

    The interaction of a series of dodecaborate cluster compounds B(12)X(12)(2-) and B(12)X(11)Y(2-) (X=H, Cl, Br, I and Y=SH, OH, NR(3)) with hydrophilic column materials (Superdex 200, Sepharose 4B, Sephadex G-50, Sephadex G-100, alumina, silica gel and anion exchange material) was studied. Almost all the dodecaborate cluster compounds were retained strongly on Superdex 200. The halogenated cluster compounds interacted with Sepharose 4B, Sephadex G-50, Sephadex G-100 and alumina; on alumina, also the non-halogenated clusters were retained. Silica gel showed the least interaction with all compounds. The thermodynamic parameters were investigated for a selection of compounds on Superdex 200 and Sephadex G-100. Values for ΔH° were found to be negative on both gels. As the change in entropy ΔS° was also negative, it compensated ΔH° to a large extent. The clusters interacted also strongly with anion exchange material in ion chromatography; the interaction decreased with increasing acetonitrile concentration, implying a large contribution from solvent effects. Copyright © 2012 Elsevier B.V. All rights reserved.

  12. Cluster fusion algorithm: application to Lennard-Jones clusters

    DEFF Research Database (Denmark)

    Solov'yov, Ilia; Solov'yov, Andrey V.; Greiner, Walter

    2006-01-01

    We present a new general theoretical framework for modelling the cluster structure and apply it to description of the Lennard-Jones clusters. Starting from the initial tetrahedral cluster configuration, adding new atoms to the system and absorbing its energy at each step, we find cluster growing...... paths up to the cluster size of 150 atoms. We demonstrate that in this way all known global minima structures of the Lennard-Jones clusters can be found. Our method provides an efficient tool for the calculation and analysis of atomic cluster structure. With its use we justify the magic number sequence...... for the clusters of noble gas atoms and compare it with experimental observations. We report the striking correspondence of the peaks in the dependence of the second derivative of the binding energy per atom on cluster size calculated for the chain of the Lennard-Jones clusters based on the icosahedral symmetry...

  13. Origin of Magic Species in Al_nX^- (X=C,N) Clusters

    Science.gov (United States)

    Khanna, S. N.; Ashman, C.; Pederson, M. R.

    2000-03-01

    Castleman and co-workers have recently experimented with the reactivity of anionic Al_mN and Al_mC clusters when exposed to oxygen. They have identified several clusters which are far less reactive than others and appear as magic numbers in the mass spectrum. In particular, the experiments identify sets of clusters which have closed electronic shells and comprable electronic affinity and yet exhibit extremely different reactivity. Ab initio theoretical electronic structure calculations have been carried out to elucidate the origin of these magic species. It is shown that the primary product of the reaction with oxygen are the AlO_2^- fragments. The studies enable us to identify factors determining the reactivity and show that the electronic shell closure is not sufficient to determine cluster stability in reactions with oxygen.

  14. Chloride-Anion-Templated Synthesis of a Strapped-Porphyrin-Containing Catenane Host System

    Science.gov (United States)

    Brown, Asha; Langton, Matthew J; Kilah, Nathan L; Thompson, Amber L; Beer, Paul D

    2015-01-01

    The synthesis, structure and anion-recognition properties of a new strapped-porphyrin-containing [2]catenane anion host system are described. The assembly of the catenane is directed by discrete chloride anion templation acting in synergy with secondary aromatic donor–acceptor and coordinative pyridine–zinc interactions. The [2]catenane incorporates a three-dimensional, hydrogen-bond-donating anion-binding pocket; solid-state structural analysis of the catenane⋅chloride complex reveals that the chloride anion is encapsulated within the catenane’s interlocked binding cavity through six convergent CH⋅⋅⋅⋅Cl and NH⋅⋅⋅Cl hydrogen-bonding interactions and solution-phase 1H NMR titration experiments demonstrate that this complementary hydrogen-bonding arrangement facilitates the selective recognition of chloride over larger halide anions in DMSO solution. PMID:26508679

  15. Zn-Al LAYERED DOUBLE HYDROXIDE PILLARED BY DIFFERENT DICARBOXYLATE ANIONS

    Directory of Open Access Journals (Sweden)

    S. Gago

    2004-12-01

    Full Text Available Zn-Al layered double hydroxides (LDHs intercalated by terephthalate (TPH and biphenyl-4,4'-dicarboxylate (BPH anions have been synthesized by direct co-precipitation from aqueous solution. The Zn/Al ratio in the final materials was 1.8. The products were characterized by powder X-ray diffraction, thermogravimetric analysis, FTIR and FT Raman spectroscopy, and MAS NMR spectroscopy. The basal spacing for the TPH-LDH intercalate was 14.62 Å, indicating that the guest anions stack to form a monolayer with the aromatic rings perpendicular to the host layers. For the LDH intercalate containing BPH anions, a basal spacing of at least 19.2 Å would be expected if the anions adopted an arrangement similar to that for the TPH anions. The observed spacing was 18.24 Å, suggesting that the anions are tilted slightly with respect to the host layers.

  16. A new anion-exchange/hydrophobic monolith as stationary phase for nano liquid chromatography of small organic molecules and inorganic anions.

    Science.gov (United States)

    Aydoğan, Cemil

    2015-05-01

    In this study, an anion-exchange/hydrophobic polymethacrylate-based stationary phase was prepared for nano-liquid chromatography of small organic molecules and inorganic anions. The stationary phase was synthesized by in situ polymerization of 3-chloro-2-hydroxypropylmethacrylate and ethylene dimethacrylate inside silanized 100 μm i.d. fused silica capillary. The porogen mixture consisted of toluene and dodecanol. The pore size distrubution profiles of the resulting monolith were determined by mercury intrusion porosimetry and the morphology of the prepared monolith was investigated by scanning electron microscope. Good permeability, stability and column efficiency were observed on the monolithic column with nano flow. The produced monolithic column, which contains reactive chloro groups, was then modified by reaction with N,N-dimethyl-N-dodecylamine to obtain an anion-exchange/hydrophobic monolithic stationary phase. The functionalized monolith contained ionizable amine groups and hydrophobic groups that are useful of anion-exchange/hydrophobic mixed-mode chromatography. The final monolithic column performance with respect to anion-exchange and hydrophobic interactions was assesed by the separation of alkylbenzene derivatives, phenolic compounds and inorganic anions, respectively. Theoretical plate numbers up to 23,000 plates/m were successfully achieved in the separation of inorganic anions. Copyright © 2015 Elsevier B.V. All rights reserved.

  17. Investigation of thermally induced anion disorder in fluorites using neutron scattering techniques

    DEFF Research Database (Denmark)

    Hutchings, M T; Clausen, Kurt Nørgaard; Dickens, M H

    1984-01-01

    the coherent diffuse quasielastic neutron scattering from single crystals of three such fluorite compounds PbF2, SrCl2 and CaF2, was investigated. The diffuse scattering intensity, and its energy width, increases with temperature into the fast-ion phase, and when integrated over energy transfer the intensity...... anion Frenkel interstitials, anion vacancies and relaxed anions has been developed which satisfactorily accounts for the distribution of intensity....

  18. Dissociation dynamics of transient anion formed via electron attachment to sulfur dioxide

    OpenAIRE

    Gope, K.; Prabhudesai, V. S.; Mason, N. J.; Krishnakumar, E.

    2017-01-01

    We report the molecular dynamics of dissociative electron attachment to sulfur dioxide (SO2) by measuring the momentum distribution of fragment anions using the velocity slice imaging technique in the electron energy range of 2–10 eV. The S- channel results from symmetric dissociation which exhibits competition between the stretch mode and bending mode of vibration in the excited parent anion. The asymmetric dissociation of parent anions leads to the production of O- and SO- channels where th...

  19. Nitrite-Templated Synthesis of Lanthanide-Containing [2]Rotaxanes for Anion Sensing**

    Science.gov (United States)

    Langton, Matthew J; Blackburn, Octavia A; Lang, Thomas; Faulkner, Stephen; Beer, Paul D

    2014-01-01

    The first anion-templated synthesis of a lanthanide-containing interlocked molecule is demonstrated by utilizing a nitrite anion to template initial pseudorotaxane formation. Subsequent stoppering of the interpenetrated assembly allows for the preparation of a lanthanide-functionalized [2]rotaxane in high yield. Following removal of the nitrite anion template, the europium [2]rotaxane host is demonstrated to recognize and sense fluoride selectively. PMID:24989322

  20. Dithranol-Anion: UV/Vis-Spektrum und chemische Reaktivität

    OpenAIRE

    Retzow, A.; Wiegrebe, Wolfgang

    1985-01-01

    Dithranol and its monoacetate as well as aloin and 9-hydroxyanthracen show a bathochromically shifted band in their electronexcitation spectra, when they are taken in alkaline solutions. The spectrum of aloin-anion was correlated with the isomerisation of aloin B into aloin A. These results and the Diels-Alder-reactivity of dithranol-anion indicate that R a a b' s biochemically highly active species, derived from dithranol, is its anion.

  1. Preparation, Characterization and Adsorption Performance of a Novel Anionic Starch Microsphere

    OpenAIRE

    De, Yang; De, Wei; Sun; Wan

    2010-01-01

    Neutral starch microspheres (NSMs) were synthesized by an inverse microemulsion technology with epichlorohydrin as a crosslinker and soluble starch as starting material. Anionic starch microspheres (ASMs) were prepared from NSMs by the secondary polymerization with chloroacetic acid as the anionic etherifying agent. Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and laser diffraction particle size analyzer were used to characterize the anionic starch micro...

  2. Hofmeister Effect on PNIPAM in Bulk and at an Interface: Surface Partitioning of Weakly Hydrated Anions

    DEFF Research Database (Denmark)

    Moghaddam, Saeed Zajforoushan; Thormann, Esben

    2017-01-01

    microbalance, and atomic force microscopy. The results indicate a surface partitioning of the weakly hydrated anions, i.e., thiocyanate and trichloroacetate, and the findings are discussed in terms of anion-induced electrostatic stabilization. Although attractive polymer-ion interactions are suggested...... for thiocyanate and trichloroacetate, a salting-out effect is found for sodium trichloroacetate. This apparent contradiction is explained by a combination of previously suggested mechanisms for the salting-out effect by weakly hydrated anions....

  3. Two three-dimensional coordination polymers of lead(II) with iminodiacetate and naphthalene-dicarboxylate anions: Synthesis, characterization and luminescence behavior

    Energy Technology Data Exchange (ETDEWEB)

    Hazari, Debdoot; Jana, Swapan Kumar [Department of Chemistry and Chemical Technology, Vidyasagar University, Midnapore 721 102, West Bengal (India); Fleck, Michel [Institute of Mineralogy and Crystallography, University of Vienna, Geozentrum, Althanstr. 9, A-1090 Vienna (Austria); Zangrando, Ennio [Department of Chemical and Pharmaceutical Sciences, University of Trieste, 34127 Trieste (Italy); Dalai, Sudipta, E-mail: sudipta@mail.vidyasagar.ac.in [Department of Chemistry and Chemical Technology, Vidyasagar University, Midnapore 721 102, West Bengal (India)

    2014-11-15

    Two lead(II) compounds [Pb{sub 3}(idiac){sub 3}(phen){sub 2}(H{sub 2}O)]·2(H{sub 2}O) (1) and [Pb(ndc)]{sub n} (2), where H{sub 2}idiac=iminodiacetic acid, phen=1,10-phenanthroline and H{sub 2}ndc=naphthalene-2,6-dicarboxylic acid, have been synthesized and structurally characterized. Single crystal X-ray diffraction analysis showed that compound 1 is a discrete trinuclear complex (of two-fold symmetry) which evolves to a supramolecular 3D network via π–π interactions, while in compound 2 the naphthalene dicarboxylate anion act as a linker to form a three dimensional architecture, where the anion adopts a bis-(bidentate bridging) coordination mode connecting four Pb(II) centers. The photoluminescence property of the two complexes has been studied. - graphical abstract: Two new topologically different 1D coordination polymers formed by Pb{sub 4} clusters have been synthesized and characterized by x-ray analysis. The luminescence and thermal properties have been studied. - Highlights: • 1 is a trinuclear complex of Pb(II) growing to 3D network via weak interactions. • In 1, layers of (4,4) rhomboidal topology are identified. • In 2, the ndc anion adopts interesting bis-(bidentate bridging) coordination. • In 2, network is reinforced by C–H…π-ring interactions between the ndc rings.

  4. Subspace K-means clustering

    NARCIS (Netherlands)

    Timmerman, Marieke E.; Ceulemans, Eva; De Roover, Kim; Van Leeuwen, Karla

    2013-01-01

    To achieve an insightful clustering of multivariate data, we propose subspace K-means. Its central idea is to model the centroids and cluster residuals in reduced spaces, which allows for dealing with a wide range of cluster types and yields rich interpretations of the clusters. We review the

  5. FINDCLUS : Fuzzy INdividual Differences CLUStering

    NARCIS (Netherlands)

    Giordani, Paolo; Kiers, Henk A. L.

    ADditive CLUStering (ADCLUS) is a tool for overlapping clustering of two-way proximity matrices (objects x objects). In Simple Additive Fuzzy Clustering (SAFC), a variant of ADCLUS is introduced providing a fuzzy partition of the objects, that is the objects belong to the clusters with the so-called

  6. Concerted rearrangement versus heterolytic cleavage in anionic [2,3]- and [3,3]-sigmatropic shifts. A DFT study of relationships among anion stabilities, mechanisms, and rates.

    Science.gov (United States)

    Haeffner, Fredrik; Houk, K N; Schulze, Suzanne M; Lee, Jeehiun K

    2003-03-21

    The anionic [2,3] sigmatropic Wittig rearrangements of deprotonated 4-hetera-1-pentenes and the anionic [3,3] sigmatropic Cope rearrangements of 3-substituted-1,5-hexadienes were explored by using density functional theory calculations. While the deprotonated anionic 3-hydroxy-1,5 hexadiene (2a), 3-thiohydroxy-1,5-hexadiene (2c), and 3-formamidyl-1,5-hexadiene (2d) Cope substrates undergo concerted rearrangements, the deprotonated anionic 3-amino-1,5-hexadiene (2b) and 3-methyl-1,5-hexadiene (2e) Cope substrates follow nonconcerted cleavage/recombination pathways. We have also found that the gas-phase Wittig (1a), aza-Wittig (1b), and carba-Wittig (1c) reactions proceed via nonconcerted cleavage/recombination pathways. These results are compared with previous results on the Cope rearrangements of deprotonated anionic 3-hydroxy-1,5-hexadiene and 3-amino-1,5-hexadiene anions. A previously established model that heterolytic and homolytic bond dissociation energies can be used to predict how anionic amino- and oxy-Cope substrates will react is generalized to account for the reactivity of other Cope substrates as well as for the Wittig rearrangements. There is also a relationship between the basicity of the anionic substituent in the Cope rearrangement and the reaction pathway: the more basic the substituent anion, the less stable it is, and the more likely it is that cleavage will occur. A first step toward studying these reactions in solution was also taken by calculating energetics for some of the rearrangements with a lithium counterion present.

  7. Effect of different forms of anionic nanoclays on cytotoxicity.

    Science.gov (United States)

    Baek, Miri; Kim, In-Sun; Yu, Jin; Chung, Hae Eun; Choy, Jin-Ho; Choi, Soo-Jin

    2011-02-01

    Anionic nanoclays, so-called layered double hydroxide (LDH) nanoparticles, have been extensively applied as drug delivery systems, since they efficiently enter cells via endocytosis pathway and possess controlled release property. However, the stability of LDHs varies, depending on the type of interlayer anions, which can also affect their toxicity. In this study, we investigated the effects of two different forms of LDH, carbonate form (MgAl-LDH-CO3) and chloride form (MgAl-LDH-Cl), on cytotoxicity in human lung epithelial cells. The result showed that MgAl-LDH-Cl was more easily dissolved into metal ions under simulated lysosomal (pH 4.5) and body fluid (pH 7.4) conditions than did MgAl-LDH-CO3. According to cytotoxicity evaluation, MgAl-LDH-CO3 exhibited high toxicity compared with MgAl-LDH-Cl in terms of induction of oxidative stress, apoptosis and membrane damage. These results suggest that easily dissoluble MgAl-LDH-Cl has low cytotoxicity, while high stability of MgAl-LDH-CO3 is correlated to elevated cytotoxicity.

  8. Review of cell performance in anion exchange membrane fuel cells

    Science.gov (United States)

    Dekel, Dario R.

    2018-01-01

    Anion exchange membrane fuel cells (AEMFCs) have recently received increasing attention since in principle they allow for the use of non-precious metal catalysts, which dramatically reduces the cost per kilowatt of power in fuel cell devices. Until not long ago, the main barrier in the development of AEMFCs was the availability of highly conductive anion exchange membranes (AEMs); however, improvements on this front in the past decade show that newly developed AEMs have already reached high levels of conductivity, leading to satisfactory cell performance. In recent years, a growing number of research studies have reported AEMFC performance results. In the last three years, new records in performance were achieved. Most of the literature reporting cell performance is based on hydrogen-AEMFCs, although an increasing number of studies have also reported the use of fuels others than hydrogen - such as alcohols, non-alcohol C-based fuels, as well as N-based fuels. This article reviews the cell performance and performance stability achieved in AEMFCs through the years since the first reports in the early 2000s.

  9. Dynamics of anion-molecule reactions at low energy

    Energy Technology Data Exchange (ETDEWEB)

    Mikosch, J.

    2007-11-15

    Anion-molecule reactions must find their way through deeply bound entrance and exit channel complexes separated by a central barrier. This results in low reaction rates and rich dynamics since direct pathways compete with the formation of transient intermediates. In this thesis we examine the probability of proton transfer to a small anion and transient lifetimes of a thermoneutral bimolecular nucleophilic substitution (S{sub N}2) reaction at well defined variable temperature down to 8 Kelvin in a multipole trap. The observed strong inverse temperature dependence is attributed to the deficit of available quantum states in the entrance channel at decreasing temperature. Furthermore we investigate scattering dynamics of S{sub N}2 reactions at defined relative energy between 0.4 and 10 eV by crossed beam slice imaging. A weakly exothermic reaction with high central barrier proceeds via an indirect, complex-mediated mechanism at low relative energies featuring high internal product excitation in excellent quantitative agreement with a statistical model. In contrast, direct backward scattering prevails for higher energies with product velocities close to the kinematical cutoff. For a strongly exothermic reaction, competing S{sub N}2-, dihalide- and proton transfer-channels are explored which proceed by complex mediation for low energy and various rebound-, grazing- and collision induced bond rupture-mechanisms at higher energy. From our data and a collaboration with theory we identify a new indirect roundabout S{sub N}2 mechanism involving CH{sub 3}-rotation. (orig.)

  10. Anionic and cationic Hofmeister effects on hydrophobic and hydrophilic surfaces.

    Science.gov (United States)

    Schwierz, Nadine; Horinek, Dominik; Netz, Roland R

    2013-02-26

    Using a two-step modeling approach, we address the full spectrum of direct, reversed, and altered ionic sequences as the charge of the ion, the charge of the surface, and the surface polarity are varied. From solvent-explicit molecular dynamics simulations, we extract single-ion surface interaction potentials for halide and alkali ions at hydrophilic and hydrophobic surfaces. These are used within Poisson-Boltzmann theory to calculate ion density and electrostatic potential distributions at mixed polar/unpolar surfaces for varying surface charge. The resulting interfacial tension increments agree quantitatively with experimental data and capture the Hofmeister series, especially the anomaly of lithium, which is difficult to obtain using continuum theory. Phase diagrams that feature different Hofmeister series as a function of surface charge, salt concentration, and surface polarity are constructed from the long-range force between two surfaces interacting across electrolyte solutions. Large anions such as iodide have a high hydrophobic surface affinity and increase the effective charge magnitude on negatively charged unpolar surfaces. Large cations such as cesium also have a large hydrophobic surface affinity and thereby compensate an external negative charge surface charge most efficiently, which explains the well-known asymmetry between cations and anions. On the hydrophilic surface, the size-dependence of the ion surface affinity is reversed, explaining the Hofmeister series reversal when comparing hydrophobic with hydrophilic surfaces.

  11. Perpendicularly Aligned, Anion Conducting Nanochannels in Block Copolymer Electrolyte Films

    Energy Technology Data Exchange (ETDEWEB)

    Arges, Christopher G.; Kambe, Yu; Suh, Hyo Seon; Ocola, Leonidas E.; Nealey, Paul F.

    2016-03-08

    Connecting structure and morphology to bulk transport properties, such as ionic conductivity, in nanostructured polymer electrolyte materials is a difficult proposition because of the challenge to precisely and accurately control order and the orientation of the ionic domains in such polymeric films. In this work, poly(styrene-block-2-vinylpyridine) (PSbP2VP) block copolymers were assembled perpendicularly to a substrate surface over large areas through chemical surface modification at the substrate and utilizing a versatile solvent vapor annealing (SVA) technique. After block copolymer assembly, a novel chemical vapor infiltration reaction (CVIR) technique selectively converted the 2-vinylpyridine block to 2-vinyl n-methylpyridinium (NMP+ X-) groups, which are anion charge carriers. The prepared block copolymer electrolytes maintained their orientation and ordered nanostructure upon the selective introduction of ion moieties into the P2VP block and post ion-exchange to other counterion forms (X- = chloride, hydroxide, etc.). The prepared block copolymer electrolyte films demonstrated high chloride ion conductivities, 45 mS cm(-1) at 20 degrees C in deionized water, the highest chloride ion conductivity for anion conducting polymer electrolyte films. Additionally, straight-line lamellae of block copolymer electrolytes were realized using chemoepitaxy and density multiplication. The devised scheme allowed for precise and accurate control of orientation of ionic domains in nanostructured polymer electrolyte films and enables a platform for future studies that examines the relationship between polymer electrolyte structure and ion transport.

  12. Destabilization of Surfactant-Dispersed Carbon Nanotubes by Anions.

    Science.gov (United States)

    Hirano, Atsushi; Gao, Weilu; He, Xiaowei; Kono, Junichiro

    2017-12-01

    The colloidal stability of surfactant-dispersed single-wall carbon nanotubes (SWCNTs) is determined by microscopic physicochemical processes, such as association, partitioning, and adsorption propensities. These processes can be controlled by the addition of solutes. While the effects of cations on the colloidal stability of SWCNTs are relatively well understood, little is known about the effects of anions. In this study, we examined the effects of anions on the stability of SWCNTs dispersed by sodium dodecyl sulfate (SDS) using sodium salts, such as NaCl and NaSCN. We observed that the intensity of the radial breathing mode Raman peaks rapidly decreased as the salts were added, even at concentrations less than 25 mM, indicating the association of SWCNTs. The effect was stronger with NaSCN than NaCl. We propose that the association of SWCNTs was caused by thermodynamic destabilization of SDS assemblies on SWCNT surfaces by these salts, which was confirmed through SWCNT separation experiments using aqueous two-phase extraction and gel chromatography. These results demonstrate that neutral salts can be used to control the colloidal stability of surfactant-dispersed SWCNTs.

  13. Anion exchange fractionation of serum proteins versus albumin elimination.

    Science.gov (United States)

    Sahab, Ziad J; Iczkowski, Kenneth A; Sang, Qing-Xiang Amy

    2007-09-01

    Elimination of albumin, constituting more than 50% of total serum proteins, allows increased protein loads on immobilized pH gradient (IPG) gels and better visualization of low-abundance proteins; however, it may result in the loss of albumin-bound low-abundance proteins. In this study, we report the prefractionation of serum proteins by batch anion exchange chromatography into three fractions: one containing proteins with isoelectric points (pI values) higher than the pI of albumin, a second fraction containing proteins with pI values in the same range as the pI of albumin, and a third fraction containing proteins with pI values lower than the pI of albumin. This procedure uses common instrumentation, is carried out under denaturing conditions, and takes less than 30min. We also report the loss of a clinically established prostate cancer serum biomarker, prostate-specific antigen (PSA), after albumin is eliminated using two commercially available albumin elimination kits: one that uses Cibacron Blue F3GA, which achieves albumin depletion through dye-ligand binding, and one that uses specific albumin antibody. The loss of PSA secondary to albumin elimination exceeded that after batch anion exchange serum sample prefractionation.

  14. Cation-enhanced capillary electrophoresis separation of atropoisomer anions.

    Science.gov (United States)

    Na, Yun-Cheol; Berthod, Alain; Armstrong, Daniel W

    2015-12-01

    CE was used to study the separation of the atropoisomers of four phosphoric acids and two sulfonic acids and the enantiomers of two phosphoric acids. All solutes are in their anionic forms in aqueous electrolytes. The chiral additives were two hydroxypropyl cyclodextrins (CDs) and cyclofructan 6 (CF6). The CDs were able to separate four solutes and the CF6 additive could separate only one: 1,1'-binaphthyl-2,2'-diyl hydrogenphosphate (BHP). Since CF6 is able to bind with cations, nitrate of alkaline metals, Ba(2+) , and Pb(2+) were added, greatly improving the BHP separation at the expense of longer migration times. There seems to be a link between CF6-cation-binding constants and BHP resolution factors. Cation additions were also performed with CD selectors that are less prone to form complexes with cations. Significant improvements of enantiomer or atropoisomer separations were observed also associated with longer migration times. It is speculated that the anionic solutes associate with the added cations forming larger entities better differentiated by CDs. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Synthetic cation-selective nanotube: permeant cations chaperoned by anions.

    Science.gov (United States)

    Hilder, Tamsyn A; Gordon, Dan; Chung, Shin-Ho

    2011-01-28

    The ability to design ion-selective, synthetic nanotubes which mimic biological ion channels may have significant implications for the future treatment of bacteria, diseases, and as ultrasensitive biosensors. We present the design of a synthetic nanotube made from carbon atoms that selectively allows monovalent cations to move across and rejects all anions. The cation-selective nanotube mimics some of the salient properties of biological ion channels. Before practical nanodevices are successfully fabricated it is vital that proof-of-concept computational studies are performed. With this in mind we use molecular and stochastic dynamics simulations to characterize the dynamics of ion permeation across a single-walled (10, 10), 36 Å long, carbon nanotube terminated with carboxylic acid with an effective radius of 5.08 Å. Although cations encounter a high energy barrier of 7 kT, its height is drastically reduced by a chloride ion in the nanotube. The presence of a chloride ion near the pore entrance thus enables a cation to enter the pore and, once in the pore, it is chaperoned by the resident counterion across the narrow pore. The moment the chaperoned cation transits the pore, the counterion moves back to the entrance to ferry another ion. The synthetic nanotube has a high sodium conductance of 124 pS and shows linear current-voltage and current-concentration profiles. The cation-anion selectivity ratio ranges from 8 to 25, depending on the ionic concentrations in the reservoirs.

  16. Cluster Implantation and Deposition Apparatus

    DEFF Research Database (Denmark)

    Hanif, Muhammad; Popok, Vladimir

    2015-01-01

    In the current report, a design and capabilities of a cluster implantation and deposition apparatus (CIDA) involving two different cluster sources are described. The clusters produced from gas precursors (Ar, N etc.) by PuCluS-2 can be used to study cluster ion implantation in order to develop...... contributions to the theory of cluster stopping in matter as well as for practical applications requiring ultra-shallow implantation and modification of surfaces on the nanoscale. Metal clusters from the magnetron cluster source are of interest for the production of optical sensors to detect specific biological...

  17. Transformation of layered polyoxometallate cluster salts into mesoporous materials

    Energy Technology Data Exchange (ETDEWEB)

    Holland, B.T.; Isbester, P.K.; Munson, E.J.; Stein, A. (Univ. of Minnesota, Minneapolis, MN (United States). Dept. of Chemistry)

    1999-02-01

    A new approach to the formation of mesoporous materials has been developed, based on a two-step salt-gel'' synthesis, in which mesoporous aluminophosphates, galloaluminophosphates, and aluminosilicates have been created. The first step involves pre-organizing charged inorganic clusters (MO[sub 4]Al[sub 12](OH)[sub 24](H[sub 2]O)[sub 12][sup 7+], M = Al or Ga) into a layered mesoscopic material with oppositely charged organic surfactant molecules. In the second step, phosphate or silicate linker molecules are added, which diffuse through the cluster/surfactant salt, react with the clusters, and transform the layered precursor into a non-lamellar mesostructured material. Removal of the surfactant from the alumino- and galloaluminophosphates by anion-exchange and from the aluminosilicates by calcination results in mesoporous materials with BET surface areas up to 630, 455, and 431 m[sup 2]/g, respectively. Direct condensation by calcination of polyoxoaluminate cluster salts without additional linkers produces nanometer-sized one-dimensional strings.

  18. Globular Clusters - Guides to Galaxies

    CERN Document Server

    Richtler, Tom; Joint ESO-FONDAP Workshop on Globular Clusters

    2009-01-01

    The principal question of whether and how globular clusters can contribute to a better understanding of galaxy formation and evolution is perhaps the main driving force behind the overall endeavour of studying globular cluster systems. Naturally, this splits up into many individual problems. The objective of the Joint ESO-FONDAP Workshop on Globular Clusters - Guides to Galaxies was to bring together researchers, both observational and theoretical, to present and discuss the most recent results. Topics covered in these proceedings are: internal dynamics of globular clusters and interaction with host galaxies (tidal tails, evolution of cluster masses), accretion of globular clusters, detailed descriptions of nearby cluster systems, ultracompact dwarfs, formations of massive clusters in mergers and elsewhere, the ACS Virgo survey, galaxy formation and globular clusters, dynamics and kinematics of globular cluster systems and dark matter-related problems. With its wide coverage of the topic, this book constitute...

  19. Procedure to reduce sulphite in wine with anion-exchange resin

    Directory of Open Access Journals (Sweden)

    Miroslav Horák

    2012-01-01

    Full Text Available The aim of this experiment was to eliminate SO2 ions present in wine using the anion-exchanger resins. To compare the effectiveness, 2 following strongly basic anion-exchange resin were used. When activated, the sodium bicarbonate solution (activation solution I is used to prevent parallel reduction of sulphites, tartates and malates, so the anion-exchange resins were activated in two-step activation. In the second step, it was immersed into a mixture of malic acid and tartaric acid (1:1. After the application of anex into wine, the content of total SO2 was reduced to 97–201 mg.L−1 (depending on the amount of anex added into the wine sample. According to our expectations, the variants with anion-exchange resin activated only with bicarbonate solution, the tartrates and malates were significantly reduced. If the anion-exchange resin was activated with a two-steps activation, the tartaric acid and malic acid were reduced in the range of ± 0.13 g.L−1. This phenomenon was strongly reflected at the anion-exchanger Aqua Osmotic 02. The changes in antioxidant content were not affected by the type of anion-exchange resin, the method of activation, or an amount of used anion-exchanger. The color parameters of wine, expressed by the L * a * b *, were not significantly affected by the effects of anion-exchange resin use.

  20. Model-based analysis of anion-exchanger positioning in direct methanol fuel cell systems

    Science.gov (United States)

    Kraus, Maik; Schröder, Daniel; Krewer, Ulrike

    2014-09-01

    In this work we present a model based study to investigate the presence of anion exchangers in direct methanol fuel cell (DMFC) systems. It is well known that environmental or fuel impurities lead to accumulation of harmful anions, such as chloride, in the system. However, due to DMFC anodic reaction, a carbonate system is present. These corbanate anions have to be taken into account for the anion exchanger design and placement as well as for the system operation strategy with and without anion exchanger, which is the objective of this study. For this purpose, the expected amount of harmful chloride ions in a DMFC system is estimated, and that of carbonate ions is calculated with a model of the carbonate system in a DMFC system. The predicition of durability and dimensions of an anion exchanger is based on a monovalent anion exchange model. The design of gas liquid separators in the DMFC system has a major influence on the amount of dissolved carbon dioxide, which is crucial for durability and dimension of a system integrated anion exchanger. Finally, feasible positions of anion exchanger in a DMFC system are elaborated to fulfill the needs for long term and stable DMFC operation.

  1. Gas-Phase Anionic ?-Adduct (Trans)formations in Heteroaromatic Systems1

    OpenAIRE

    Zimnicka, Magdalena; Danikiewicz, Witold

    2015-01-01

    Anions of nitroderivatives of thiophene and furan were subjected to the reactions with selected C-H acids in the gas phase. Various structures and reaction pathways were proposed for the observed ionic products. In general, the reactions of heteroaromatic anions with C-H acids may be divided into three groups, depending on the proton affinity difference between C-H acid?s conjugate base and heteroaromatic anion (?PA). The proton transfer from C-H acid to heteroaromatic anion is a dominant pro...

  2. Evaluation of a new, macroporous polyvinylpyridine resin for processing plutonium using nitrate anion exchange

    Energy Technology Data Exchange (ETDEWEB)

    Marsh, S.F.

    1989-04-01

    Anion exchange in nitric acid is the major aqueous process used to recover and purify plutonium from impure scrap materials. Most strong-base anion exchange resins incorporate a styrene-divinylbenzene copolymer. A newly available, macroporous anion exchange resin based on a copolymer of 1-methyl-4-vinylpyridine and divinylbenzene has been evaluated. Comparative data for Pu(IV) sorption kinetics and capacity are presented for this new resin and two other commonly used anion exchange resins. The new resin offers high capacity and rapid sorption kinetics for Pu(IV) from nitric acid, as well as greatly stability to chemical and radiolytic degradation. 8 refs., 14 figs.

  3. Anion-tunable control of thermal Z→E isomerisation in basic azobenzene receptors.

    Science.gov (United States)

    Dąbrowa, Kajetan; Niedbała, Patryk; Jurczak, Janusz

    2014-12-25

    Herein, we report that thermal Z→E isomerisation of simple azobenzene urea derivatives is selectively and predictably controlled by anion binding. The rate of this process depends strictly on the anion concentration and its binding affinity to the Z-isomer of the azobenzene host, i.e. increased rate constants are observed for higher anion concentration as well as for more strongly bound guests. The origin of this phenomenon is attributed to the electron density transfer from the anion to the host π-system, resulting in increased repulsion between the lone electron pairs in the N=N bond.

  4. Radiation induced redox reactions and fragmentation of constituent ions in ionic liquids. I. Anions.

    Energy Technology Data Exchange (ETDEWEB)

    Shkrob, I. A.; Marin, T.; Chemerisov, S.; Wishart, J. (Chemical Sciences and Engineering Division); (BNL); (Benedictine Univ.)

    2011-04-14

    Room temperature ionic liquids (IL) find increasing use for the replacement of organic solvents in practical applications, including their use in solar cells and electrolytes for metal deposition, and as extraction solvents for the reprocessing of spent nuclear fuel. The radiation stability of ILs is an important concern for some of these applications, as previous studies suggested extensive fragmentation of the constituent ions upon irradiation. In the present study, electron paramagnetic resonance (EPR) spectroscopy has been used to identify fragmentation pathways for constituent anions in ammonium, phosphonium, and imidazolium ILs. Many of these detrimental reactions are initiated by radiation-induced redox processes involving these anions. Scission of the oxidized anions is the main fragmentation pathway for the majority of the practically important anions; (internal) proton transfer involving the aliphatic arms of these anions is a competing reaction. For perfluorinated anions, fluoride loss following dissociative electron attachment to the anion can be even more prominent than this oxidative fragmentation. Bond scission in the anion was also observed for NO{sub 3}{sup -} and B(CN){sub 4}{sup -} anions and indirectly implicated for BF{sub 4}{sup -} and PF{sub 6}{sup -} anions. Among small anions, CF{sub 3}SO{sub 3}{sup -} and N(CN){sub 2}{sup -} are the most stable. Among larger anions, the derivatives of benzoate and imide anions were found to be relatively stable. This stability is due to suppression of the oxidative fragmentation. For benzoates, this is a consequence of the extensive sharing of unpaired electron density by the {pi}-system in the corresponding neutral radical; for the imides, this stability could be the consequence of N-N {sigma}{sup 2}{sigma}*{sup 1} bond formation involving the parent anion. While fragmentation does not occur for these 'exceptional' anions, H atom addition and electron attachment are prominent. Among the

  5. Cation-Anion Balance during Potassium and Sodium Absorption by Barley Roots

    Science.gov (United States)

    Jackson, P. C.; Adams, H. R.

    1963-01-01

    Steady-state rates of potassium ion and sodium ion absorption by excised barley roots accompanied by various anions were compared with the rates of anion absorption and the concomitant H+ and base release by the roots. The cation absorption rates were found to be independent of the identities, concentrations, and rates of absorption of the anions of the external solution, including bicarbonate. Absorption of the anion of the salt plus bicarbonate could not account for the cation absorption. H+ is released during cation absorption and base during anion absorption. The magnitude by which one or the other predominates depends on the relative rates of anion and cation absorption under various conditions of pH, cation and anion concentration, and inhibitor concentrations. The conclusion is that potassium and sodium ions are absorbed independently of the anions of the absorption solution in exchange for H+, while anions are exchanged for a base. The H+ release reflects a specificity between K+ and Na+ absorption such that it appears to be H+ exchanged in the specific rate-limiting reactions of the cation absorption. PMID:13964256

  6. A computational study of anion-modulated cation-π interactions.

    Science.gov (United States)

    Carrazana-García, Jorge A; Rodríguez-Otero, Jesús; Cabaleiro-Lago, Enrique M

    2012-05-24

    The interaction of anions with cation-π complexes formed by the guanidinium cation and benzene was thoroughly studied by means of computational methods. Potential energy surface scans were performed in order to evaluate the effect of the anion coming closer to the cation-π pair. Several structures of guanidinium-benzene complexes and anion approaching directions were examined. Supermolecule calculations were performed on ternary complexes formed by guanidinium, benzene, and one anion and the interaction energy was decomposed into its different two- and three-body contributions. The interaction energies were further dissected into their electrostatic, exchange, repulsion, polarization and dispersion contributions by means of local molecular orbital energy decomposition analysis. The results confirm that, besides the electrostatic cation-anion attraction, the effect of the anion over the cation-π interaction is mainly due to polarization and can be rationalized following the changes in the anion-π and the nonadditive (three-body) terms of the interaction. When the cation and the anion are on the same side of the π system, the three-body interaction is anticooperative, but when the anion and the cation are on opposite sides of the π system, the three-body interaction is cooperative. As far as we know, this is the first study where this kind of analysis is carried out with a structured cation as guanidinium with a significant biological interest.

  7. Determination of common inorganic anions and cations by non-suppressed ion chromatography with column switching.

    Science.gov (United States)

    Amin, Muhammad; Lim, Lee Wah; Takeuchi, Toyohide

    2008-02-29

    An ion chromatography (IC) method has been proposed for the determination of seven common inorganic anions (F(-), H(2)PO(4)(-), NO(2)(-), Cl(-), Br(-), NO(3)(-), and SO(4)(2-)) and/or five common inorganic cations (Na(+), NH(4)(+), K(+), Mg(2+), and Ca(2+)) using a single pump, a single eluent and a single detector. The present system used cation-exchange and anion-exchange columns connected in series via a single 10-port switching valve. The 10-port valve was switched for the separation of either cations or anions in a single chromatographic run. When 1.0mM trimellitic acid (pH 2.94) was used as the eluent, the seven anions and the five cations could be separated on the anion-exchange column and the cation-exchange column, respectively. The elution order was found to be F(-)anions and Na(+)cations. Complete separation of the above anions or cations was demonstrated within 35min each. Detection limits calculated at S/N=3 were 0.05-0.58ppm (mg/l) for the anions and 0.05-0.38ppm for the cations, whereas repeatability values were below 2.26, 2.76, and 2.90% for peak height, peak area and retention time, respectively. The method was successfully applied to the determination of inorganic anions and cations in river water samples.

  8. Explaining ionic liquid water solubility in terms of cation and anion hydrophobicity

    National Research Council Canada - National Science Library

    Ranke, Johannes; Othman, Alaa; Fan, Ping; Müller, Anja

    2009-01-01

    .... In this contribution, the activity coefficients of ionic liquids in water are split into cation and anion contributions by regression against cation hydrophobicity parameters that are experimentally...

  9. Enhancement of anion binding in lanthanide optical sensors.

    Science.gov (United States)

    Cable, Morgan L; Kirby, James P; Gray, Harry B; Ponce, Adrian

    2013-11-19

    In the design of molecular sensors, researchers exploit binding interactions that are usually defined in terms of topology and charge complementarity. The formation of complementary arrays of highly cooperative, noncovalent bonding networks facilitates protein-ligand binding, leading to motifs such as the "lock-and-key". Synthetic molecular sensors often employ metal complexes as key design elements as a way to construct a binding site with the desired shape and charge to achieve target selectivity. In transition metal complexes, coordination number, structure and ligand dynamics are governed primarily by a combination of inner-sphere covalent and outer-sphere noncovalent interactions. These interactions provide a rich variable space that researchers can use to tune structure, stability, and dynamics. In contrast, lanthanide(III)-ligand complex formation and ligand-exchange dynamics are dominated by reversible electrostatic and steric interactions, because the unfilled f shell is shielded by the larger, filled d shell. Luminescent lanthanides such as terbium, europium, dysprosium, and samarium display many photophysical properties that make them excellent candidates for molecular sensor applications. Complexes of lanthanide ions act as receptors that exhibit a detectable change in metal-based luminescence upon binding of an anion. In our work on sensors for detection of dipicolinate, the unique biomarker of bacterial spores, we discovered that the incorporation of an ancillary ligand (AL) can enhance binding constants of target anions to lanthanide ions by as much as two orders of magnitude. In this Account, we show that selected ALs in lanthanide/anion systems greatly improve sensor performance for medical, planetary science, and biodefense applications. We suggest that the observed anion binding enhancement could result from an AL-induced increase in positive charge at the lanthanide ion binding site. This effect depends on lanthanide polarizability, which can be

  10. Clustering Game Behavior Data

    DEFF Research Database (Denmark)

    Bauckhage, C.; Drachen, Anders; Sifa, Rafet

    2015-01-01

    Recent years have seen a deluge of behavioral data from players hitting the game industry. Reasons for this data surge are many and include the introduction of new business models, technical innovations, the popularity of online games, and the increasing persistence of games. Irrespective...... of the causes, the proliferation of behavioral data poses the problem of how to derive insights therefrom. Behavioral data sets can be large, time-dependent and high-dimensional. Clustering offers a way to explore such data and to discover patterns that can reduce the overall complexity of the data. Clustering...... and other techniques for player profiling and play style analysis have, therefore, become popular in the nascent field of game analytics. However, the proper use of clustering techniques requires expertise and an understanding of games is essential to evaluate results. With this paper, we address game data...

  11. Exotic cluster structures on

    CERN Document Server

    Gekhtman, M; Vainshtein, A

    2017-01-01

    This is the second paper in the series of papers dedicated to the study of natural cluster structures in the rings of regular functions on simple complex Lie groups and Poisson-Lie structures compatible with these cluster structures. According to our main conjecture, each class in the Belavin-Drinfeld classification of Poisson-Lie structures on \\mathcal{G} corresponds to a cluster structure in \\mathcal{O}(\\mathcal{G}). The authors have shown before that this conjecture holds for any \\mathcal{G} in the case of the standard Poisson-Lie structure and for all Belavin-Drinfeld classes in SL_n, n<5. In this paper the authors establish it for the Cremmer-Gervais Poisson-Lie structure on SL_n, which is the least similar to the standard one.

  12. Architecture, electronic structure and stability of TM@Ge(n) (TM = Ti, Zr and Hf; n = 1-20) clusters: a density functional modeling.

    Science.gov (United States)

    Kumar, Manish; Bhattacharyya, Nilanjana; Bandyopadhyay, Debashis

    2012-01-01

    The present study reports the geometry, electronic structure and properties of neutral and anionic transition metal (TM = Ti, Zr and Hf)) doped germanium clusters containing 1 to 20 germanium atoms within the framework of linear combination of atomic orbitals density functional theory under spin polarized generalized gradient approximation. Different parameters, like, binding energy (BE), embedding energy (EE), energy gap between the highest occupied and lowest unoccupied molecular orbitals (HOMO-LUMO), ionization energy (IP), electron affinity (EA), chemical potential etc. of the energetically stable clusters (ground state cluster) in each size are calculated. From the variation of these parameters with the size of the clusters the most stable cluster within the range of calculation is identified. It is found that the clusters having 20 valence electrons turn out to be relatively more stable in both the neutral and the anionic series. The sharp drop in IP as the valence electron count increases from 20 to 21 in neutral cluster is in agreement with predictions of shell models. To study the vibrational nature of the clusters, IR and Raman spectrum of some selected TM@Ge(n) (n = 15,16,17) clusters are also calculated and compared. In the end, relevance of calculated results to the design of Ge-based super-atoms is discussed.

  13. Refractory chronic cluster headache

    DEFF Research Database (Denmark)

    Mitsikostas, Dimos D; Edvinsson, Lars; Jensen, Rigmor H

    2014-01-01

    Chronic cluster headache (CCH) often resists to prophylactic pharmaceutical treatments resulting in patients' life damage. In this rare but pragmatic situation escalation to invasive management is needed but framing criteria are lacking. We aimed to reach a consensus for refractory CCH definition...... for clinical and research use. The preparation of the final consensus followed three stages. Internal between authors, a larger between all European Headache Federation members and finally an international one among all investigators that have published clinical studies on cluster headache the last five years...

  14. Clustering via Kernel Decomposition

    DEFF Research Database (Denmark)

    Have, Anna Szynkowiak; Girolami, Mark A.; Larsen, Jan

    2006-01-01

    Methods for spectral clustering have been proposed recently which rely on the eigenvalue decomposition of an affinity matrix. In this work it is proposed that the affinity matrix is created based on the elements of a non-parametric density estimator. This matrix is then decomposed to obtain...... posterior probabilities of class membership using an appropriate form of nonnegative matrix factorization. The troublesome selection of hyperparameters such as kernel width and number of clusters can be obtained using standard cross-validation methods as is demonstrated on a number of diverse data sets....

  15. Emergence of regional clusters

    DEFF Research Database (Denmark)

    Dahl, Michael S.; Østergaard, Christian Richter; Dalum, Bent

    2010-01-01

    The literature on regional clusters has increased considerably during the last decade. The emergence and growth patterns are usually explained by such factors as unique local culture, regional capabilities, tacit knowledge or the existence of location-specific externalities (knowledge spillovers......, networks, labour market pooling and specialised suppliers). However, these factors are not sufficient to explain the early formation of clusters. The dominant theories focus more on explaining ex-post dynamics than their early development. This chapter focuses on the early phase and uses an alternative...

  16. South Asian Cluster

    Directory of Open Access Journals (Sweden)

    Ionel Sergiu Pirju

    2014-12-01

    Full Text Available This article aims at presenting the South Asian cluster composed of India, Indonesia, Iran and Malaysia, the intercultural values that characterizes it, the supported leadership style and tracing the main macroeconomic considerations which characterizes them. The research is synchronic, analysing the contemporary situation of these countries without reference to their evolution in time, by using the positivist paradigm that explains the reality at one point. It will be analysed the overall cluster with the existing interactions between the countries that composes it, while the article being one of information will avoid building recommendation, or new theories.

  17. Crystal structure and mutational analysis of the Saccharomyces cerevisiae cell cycle regulatory protein Cks1: implications for domain swapping, anion binding and protein interactions.

    Science.gov (United States)

    Bourne, Y; Watson, M H; Arvai, A S; Bernstein, S L; Reed, S I; Tainer, J A

    2000-08-15

    The Saccharomyces cerevisiae protein Cks1 (cyclin-dependent kinase subunit 1) is essential for cell-cycle progression. The biological function of Cks1 can be modulated by a switch between two distinct molecular assemblies: the single domain fold, which results from the closing of a beta-hinge motif, and the intersubunit beta-strand interchanged dimer, which arises from the opening of the beta-hinge motif. The crystal structure of a cyclin-dependent kinase (Cdk) in complex with the human Cks homolog CksHs1 single-domain fold revealed the importance of conserved hydrophobic residues and charged residues within the beta-hinge motif. The 3.0 A resolution Cks1 structure reveals the strict structural conservation of the Cks alpha/beta-core fold and the beta-hinge motif. The beta hinge identified in the Cks1 structure includes a novel pivot and exposes a cluster of conserved tyrosine residues that are involved in Cdk binding but are sequestered in the beta-interchanged Cks homolog suc1 dimer structure. This Cks1 structure confirms the conservation of the Cks anion-binding site, which interacts with sidechain residues from the C-terminal alpha helix of another subunit in the crystal. The Cks1 structure exemplifies the conservation of the beta-interchanged dimer and the anion-binding site in evolutionarily distant yeast and human Cks homologs. Mutational analyses including in vivo rescue of CKS1 disruption support the dual functional roles of the beta-hinge residue Glu94, which participates in Cdk binding, and of the anion-binding pocket that is located 22 A away and on an opposite face to Glu94. The Cks1 structure suggests a biological role for the beta-interchanged dimer and the anion-binding site in targeting Cdks to specific phosphoproteins during cell-cycle progression.

  18. Anionic and zwitterionic copper(I) complexes incorporating an anionic N-heterocyclic carbene decorated with a malonate backbone: synthesis, structure and catalytic applications.

    Science.gov (United States)

    César, Vincent; Barthes, Cécile; Farré, Yoann C; Cuisiat, Stéphane V; Vacher, Bernard Y; Brousses, Rémy; Lugan, Noël; Lavigne, Guy

    2013-05-28

    The anionic malonate-derived N-heterocyclic carbenes (maloNHCs) react cleanly and rapidly with copper chloride to generate the anionic complexes of type [(maloNHC)CuCl]·Li, which crystallize in the solid state either in an oligomeric trimer arrangement or in polymeric helixes depending on the substitution pattern and the solvent. Ten zwitterionic heteroleptic Cu(I) complexes combining the anionic maloNHC and a neutral imidazol-2-ylidene are also obtained in a very selective manner and fully characterized. Whereas the anionic complexes are relatively active catalysts for the hydrosilylation of carbonyl compounds, the zwitterionic complexes reveal to be efficient and extremely robust pre-catalysts for the intramolecular cyclopropanation reaction of a diazo ester and outperform the corresponding cationic Cu(i) complexes with classical imidazol-2-ylidenes.

  19. Dual transport properties of anion exchanger 1: the same transmembrane segment is involved in anion exchange and in a cation leak.

    Science.gov (United States)

    Barneaud-Rocca, Damien; Borgese, Franck; Guizouarn, Hélène

    2011-03-18

    Previous results suggested that specific point mutations in human anion exchanger 1 (AE1) convert the electroneutral anion exchanger into a monovalent cation conductance. In the present study, the transport site for anion exchange and for the cation leak has been studied by cysteine scanning mutagenesis and sulfhydryl reagent chemistry. Moreover, the role of some highly conserved amino acids within members of the SLC4 family to which AE1 belongs has been assessed in AE1 transport properties. The results suggest that the same transport site within the AE1 spanning domain is involved in anion exchange or in cation transport. A functioning mechanism for this transport site is proposed according to transport properties of the different studied point mutations of AE1.

  20. Large Crater Clustering tool

    Science.gov (United States)

    Laura, Jason; Skinner, James A.; Hunter, Marc A.

    2017-08-01

    In this paper we present the Large Crater Clustering (LCC) tool set, an ArcGIS plugin that supports the quantitative approximation of a primary impact location from user-identified locations of possible secondary impact craters or the long-axes of clustered secondary craters. The identification of primary impact craters directly supports planetary geologic mapping and topical science studies where the chronostratigraphic age of some geologic units may be known, but more distant features have questionable geologic ages. Previous works (e.g., McEwen et al., 2005; Dundas and McEwen, 2007) have shown that the source of secondary impact craters can be estimated from secondary impact craters. This work adapts those methods into a statistically robust tool set. We describe the four individual tools within the LCC tool set to support: (1) processing individually digitized point observations (craters), (2) estimating the directional distribution of a clustered set of craters, back projecting the potential flight paths (crater clusters or linearly approximated catenae or lineaments), (3) intersecting projected paths, and (4) intersecting back-projected trajectories to approximate the local of potential source primary craters. We present two case studies using secondary impact features mapped in two regions of Mars. We demonstrate that the tool is able to quantitatively identify primary impacts and supports the improved qualitative interpretation of potential secondary crater flight trajectories.

  1. doped stable clusters a

    Indian Academy of Sciences (India)

    ABHIJIT DUTTA

    2018-01-30

    ., showed that Ru-doped. Rh6 cluster is a better catalyst for the activation of methanol compared to pure Rh6. It may be noted that methanol activation occurs via O–H bond dissociation rather than C–H bond.25 Rhodium nano ...

  2. Greedy subspace clustering.

    Science.gov (United States)

    2016-09-01

    We consider the problem of subspace clustering: given points that lie on or near the union of many low-dimensional linear subspaces, recover the subspaces. To this end, one first identifies sets of points close to the same subspace and uses the sets ...

  3. Cluster - Smart Specialization Relationship

    Directory of Open Access Journals (Sweden)

    Florina Popa

    2016-01-01

    The paper refers to the relationship that is created in the regional economic space, between thecluster phenomenon and that of the strategy of smart specialization; in the process oftransformation of the regional economy, the smart specialization strategies take over clusters’policies and clusters integrate activities specific to areas of technological knowledge.

  4. Detecting alternative graph clusterings.

    Science.gov (United States)

    Mandala, Supreet; Kumara, Soundar; Yao, Tao

    2012-07-01

    The problem of graph clustering or community detection has enjoyed a lot of attention in complex networks literature. A quality function, modularity, quantifies the strength of clustering and on maximization yields sensible partitions. However, in most real world networks, there are an exponentially large number of near-optimal partitions with some being very different from each other. Therefore, picking an optimal clustering among the alternatives does not provide complete information about network topology. To tackle this problem, we propose a graph perturbation scheme which can be used to identify an ensemble of near-optimal and diverse clusterings. We establish analytical properties of modularity function under the perturbation which ensures diversity. Our approach is algorithm independent and therefore can leverage any of the existing modularity maximizing algorithms. We numerically show that our methodology can systematically identify very different partitions on several existing data sets. The knowledge of diverse partitions sheds more light into the topological organization and helps gain a more complete understanding of the underlying complex network.

  5. Cluster Decline and Resilience

    DEFF Research Database (Denmark)

    Østergaard, Christian Richter; Park, Eun Kyung

    -2011. Our longitudinal study reveals that technological lock-in and exit of key firms have contributed to impairment of the cluster’s resilience in adapting to disruptions. Entrepreneurship has a positive effect on cluster resilience, while multinational companies have contradicting effects by bringing...

  6. Clustering of resting state networks.

    Directory of Open Access Journals (Sweden)

    Megan H Lee

    Full Text Available The goal of the study was to demonstrate a hierarchical structure of resting state activity in the healthy brain using a data-driven clustering algorithm.The fuzzy-c-means clustering algorithm was applied to resting state fMRI data in cortical and subcortical gray matter from two groups acquired separately, one of 17 healthy individuals and the second of 21 healthy individuals. Different numbers of clusters and different starting conditions were used. A cluster dispersion measure determined the optimal numbers of clusters. An inner product metric provided a measure of similarity between different clusters. The two cluster result found the task-negative and task-positive systems. The cluster dispersion measure was minimized with seven and eleven clusters. Each of the clusters in the seven and eleven cluster result was associated with either the task-negative or task-positive system. Applying the algorithm to find seven clusters recovered previously described resting state networks, including the default mode network, frontoparietal control network, ventral and dorsal attention networks, somatomotor, visual, and language networks. The language and ventral attention networks had significant subcortical involvement. This parcellation was consistently found in a large majority of algorithm runs under different conditions and was robust to different methods of initialization.The clustering of resting state activity using different optimal numbers of clusters identified resting state networks comparable to previously obtained results. This work reinforces the observation that resting state networks are hierarchically organized.

  7. Clustering: a neural network approach.

    Science.gov (United States)

    Du, K-L

    2010-01-01

    Clustering is a fundamental data analysis method. It is widely used for pattern recognition, feature extraction, vector quantization (VQ), image segmentation, function approximation, and data mining. As an unsupervised classification technique, clustering identifies some inherent structures present in a set of objects based on a similarity measure. Clustering methods can be based on statistical model identification (McLachlan & Basford, 1988) or competitive learning. In this paper, we give a comprehensive overview of competitive learning based clustering methods. Importance is attached to a number of competitive learning based clustering neural networks such as the self-organizing map (SOM), the learning vector quantization (LVQ), the neural gas, and the ART model, and clustering algorithms such as the C-means, mountain/subtractive clustering, and fuzzy C-means (FCM) algorithms. Associated topics such as the under-utilization problem, fuzzy clustering, robust clustering, clustering based on non-Euclidean distance measures, supervised clustering, hierarchical clustering as well as cluster validity are also described. Two examples are given to demonstrate the use of the clustering methods.

  8. On the structural and electronic properties of hexanuclear vanadium oxide clusters V6On(-/0) (n=12-15): is V6O12 cluster planar or cage-like?

    Science.gov (United States)

    Wang, Ling-Fei; Xie, Lu; Fang, Hong-Ling; Li, Yun-Fei; Zhang, Xiao-Bin; Wang, Bin; Zhang, Yong-Fan; Huang, Xin

    2014-10-15

    Density functional theory (DFT) calculations are carried out to investigate the structural and electronic properties of a series of hexanuclear vanadium oxide clusters V6On(-/0) (n=12-15). Generalized Koopmans' theorem is applied to predict the vertical detachment energies (VDEs) and simulate the photoelectron spectra (PES) for V6On(-) (n=12-15) clusters. Extensive DFT calculations are performed in search of the lowest-energy structures for both the anions and neutrals. All of these clusters appear to prefer the polyhedral cage structures, in contrast to the planar star-like structures observed in prior model surface studies for the V6O12 cluster. Molecular orbitals are performed to analyze the chemical bonding in the hexanuclear vanadium oxide clusters and provide insights into the sequential oxidation of V6On(-) (n=12-15) clusters. The V6On(-) (n=12-15) clusters possess well-defined V(5+) and V(3+) sites, and may serve as molecular models for surface defects. Electron spin density analyses show that the unpaired electrons in V6On(-) (n=12-14) clusters are primarily localized on the V(3+) sites rather than on the V(5+) sites. The difference gas phase versus model surface structures of V6O12 hints the critical roles of cluster-substrate interactions in stabilizing the planar V6O12 cluster on model surfaces. Copyright © 2014 Elsevier B.V. All rights reserved.

  9. Optimization of anion separation by nonsuppressed ion chromatography

    Energy Technology Data Exchange (ETDEWEB)

    Jenke, D.R.; Pagenkopf, G.K.

    1984-01-01

    The effect of eluent pH and eluent species concentration on the nonsuppressed ion chromatographic separation of anions has been studied. The retention times of Cl/sup -/, Br/sup -/, NO/sub 3//sup -/, SO/sub 4//sup 2 -/, and S/sub 2/O/sub 3//sup 2 -/ were determined over a large range of eluent compositions and the data were utilized to construct window diagrams. These window diagrams were used to optimize eluent composition for the separation of two or more analytes. In virtually every case resolution is limited by the separation of the NO/sub 3//sup -//Br/sup -/ pair. 10 references, 5 figures, 2 tables.

  10. Reproducible surface-enhanced Raman spectroscopy of small molecular anions

    Science.gov (United States)

    Owens, F. J.

    2011-03-01

    A gold-coated silicon substrate having an array of pyramidal shaped holes is shown to provide a reproducible surface-enhanced Raman spectra (SERS) in a number of inorganic ions such as ? , ? , ? , and ? deposited on the substrate as 10-3 to10-4 molar aqueous solutions of their salts. Of particular interest is the observation of a SERS effect in ? , the anion of ammonium nitrate, a commonly used terrorist explosive, suggesting the potential for sensitive detection of this material. An unusual increase in the frequency of the ? bending mode frequency is observed in the SERS spectra of KNO2. Density Functional Theory calculations of the frequencies of the normal modes of vibration of ? bonded to gold predict an upward shift of the frequencies compared with the calculated results for a free ? , suggesting a possible explanation for the shifts.

  11. Anionic Palladium(0) and Palladium(II) Ate Complexes.

    Science.gov (United States)

    Kolter, Marlene; Böck, Katharina; Karaghiosoff, Konstantin; Koszinowski, Konrad

    2017-10-16

    Palladium ate complexes are frequently invoked as important intermediates in Heck and cross-coupling reactions, but so far have largely eluded characterization at the molecular level. Here, we use electrospray-ionization mass spectrometry, electrical conductivity measurements, and NMR spectroscopy to show that the electron-poor catalyst [L3 Pd] (L=tris[3,5-bis(trifluoromethyl)phenyl]phosphine) readily reacts with Br(-) ions to afford the anionic, zero-valent ate complex [L3 PdBr](-) . In contrast, more-electron-rich Pd catalysts display lower tendencies toward the formation of ate complexes. Combining [L3 Pd] with LiI and an aryl iodide substrate (ArI) results in the observation of the Pd(II) ate complex [L2 Pd(Ar)I2 ](-) . © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Reactivity of amino acid anions with nitrogen and oxygen atoms.

    Science.gov (United States)

    Wang, Zhe-Chen; Li, Ya-Ke; He, Sheng-Gui; Bierbaum, Veronica M

    2018-02-14

    For many decades, astronomers have searched for biological molecules, including amino acids, in the interstellar medium; this endeavor is important for investigating the hypothesis of the origin of life from space. The space environment is complex and atomic species, such as nitrogen and oxygen atoms, are widely distributed. In this work, the reactions of eight typical deprotonated amino acids (glycine, alanine, cysteine, proline, aspartic acid, histidine, tyrosine, and tryptophan) with ground state nitrogen and oxygen atoms are studied by experiment and theory. These amino acid anions do not react with nitrogen atoms. However, the reactions of these ions with oxygen atoms show an intriguing variety of ionic products and the reaction rate constants are of the order of 10 -10 cm 3 s -1 . Density functional calculations provide detailed mechanisms of the reactions, and demonstrate that spin conversion is essential for some processes. Our study provides important data and insights for understanding the kinetic and dynamic behavior of amino acids in space environments.

  13. The thiomethyl anion: Formation, reactivity, and thermodynamic properties.

    Science.gov (United States)

    Kass, S R; Guo, H; Dahlke, G D

    1990-09-01

    The thiomethyl anion (1) has been generated by fluorodesilylation of trimethylsilylmethanethiol in a variable-temperature flowing afterglow device. The proton affinity (1649 ± 12 kJ mol(-1)) and electron affinity (0.67 ± .13 eV) were determined and compared to a previously reported molecular orbital calculation. Isomerization via a 1,2-proton shift does not take place between -40° and 100°C despite a 156 kJ mol(-1) driving force. Ion-molecule reactions of 1 were examined with a number of reagents including N20, O2, CS2, COS, and CO2, Hydride ion transfer was observed in every case, along with other products, and thermodynamic information has been derived.

  14. Photoinduced Dynamics of Neutral, Cationic, and Anionic Species

    DEFF Research Database (Denmark)

    Stephansen, Anne Boutrup

    than those predicted by statistical models, but also a more critical dependence between molecular structure and (photo)-reactivity. This thesis presents a collection of studies of various types of photoinduced processes in neutral, anionic, or cationic molecular species as introduced below....... The investigations have primarily employed femtosecond time-resolved photoionization or photodetachment techniques. Intersystem crossing (ISC) in neutral organic species is conventionally assumed to be slow due to the spin-forbidden nature of the process; this assumption has been challenged during the past decade...... studies indicate that this approach can provide new insight into the origin of the isotope effect; the investigation thereby constitutes a novel way of investigating isotope effects. Common for all reactions discussed in this thesis is that the early-time dynamics initiated by photon-absorption have large...

  15. Highly durable direct hydrazine hydrate anion exchange membrane fuel cell

    Science.gov (United States)

    Sakamoto, Tomokazu; Serov, Alexey; Masuda, Teruyuki; Kamakura, Masaki; Yoshimoto, Koji; Omata, Takuya; Kishi, Hirofumi; Yamaguchi, Susumu; Hori, Akihiro; Horiuchi, Yousuke; Terada, Tomoaki; Artyushkova, Kateryna; Atanassov, Plamen; Tanaka, Hirohisa

    2018-01-01

    The factors influenced on degradation of direct hydrazine hydrate fuel cells (DHFCs) under operation conditions are analyzed by in situ soft X-ray radiography. A durability of DHFCs is significantly improved by multi-step reaction DHFCs (MSR-DHFCs) approach designed to decrease the crossover of liquid fuel. An open circuit voltage (OCV) as well as cell voltage at 5 mA cm-2 of MSR-DHFC construct with commercial anion exchange membrane (AEM) maintained for over of 3500 h at 60 °C. Furthermore, the commercial proton exchange membrane (PEM) is integrated into AEM of MSR-DHFCs resulting in stable power output of MSR-DHFCs for over than 2800 h at 80 °C.

  16. Preliminary Testing For Anionic, Cationic and Non-ionic

    Directory of Open Access Journals (Sweden)

    Bokic, Lj.

    2007-11-01

    Full Text Available Detergents present a major environmental problem due to large quantities of surfactants released from laundries. For this reason, it is important to apply an appropriate analytical method for their determination. In this work, we propose two simple, fast and inexpensive analytical methods for anionic, cationic and non-ionic surfactant determination: thin layer chromatography (TLC separation for qualitative screening and quantitative potentiometric determination with ion-selective electrodes. These methods have been chosen because of their many advantages: rapidity, ease of operation, low cost of analysis and a wide variety of TLC application possibilities. The advantage of potentiometric titration is its very high degree of automation and very low detection limits obtained with different ion-selective electrodes applied for different surfactants.

  17. IR spectroscopy of gaseous fluorocarbon ions: The perfluoroethyl anion

    Energy Technology Data Exchange (ETDEWEB)

    Crestoni, Maria Elisa; Chiavarino, Barbara [Dipartimento di Chimica e Tecnologie del Farmaco, Universita di Roma ' La Sapienza' , P. le A. Moro 5, I-00185 Roma (Italy); Lemaire, Joel; Maitre, Philippe [Universite Paris Sud, Laboratoire de Chimie Physique - UMR8000 CNRS, Faculte des Sciences - Batiment 350, 91405 Orsay Cedex (France); Fornarini, Simonetta, E-mail: simonetta.fornarini@uniroma1.it [Dipartimento di Chimica e Tecnologie del Farmaco, Universita di Roma ' La Sapienza' , P. le A. Moro 5, I-00185 Roma (Italy)

    2012-04-04

    Highlights: Black-Right-Pointing-Pointer C{sub 2}F{sub 5}{sup -} ions are formed by dissociative electron capture in perfluoropropane. Black-Right-Pointing-Pointer Both their reactivity towards neutrals and IRMPD spectroscopy are investigated. Black-Right-Pointing-Pointer The sampled C{sub 2}F{sub 5}{sup -} ions are best described as covalently bound pentafluoroethyl anions. - Abstract: The first IR spectrum of a perfluorinated carbanion has been obtained in the gas phase by IRMPD spectroscopy. Quantum chemical calculations at the MP2/cc-pVTZ level were performed yielding the optimized geometries and IR spectra for a covalently bound C{sub 2}F{sub 5}{sup -} species and for conceivable loosely bound F{sup -}(C{sub 2}F{sub 4}) complexes. Both the computational results and the IR characterization point to a covalent structure for the assayed species in agreement with the reactivity pattern displayed with selected neutrals.

  18. Common, yet elusive: a case of severe anion gap acidosis.

    Science.gov (United States)

    Agrawal, Akanksha; Kishlyansky, Marina; Biso, Sylvia; Patnaik, Soumya; Punjabi, Chitra

    2017-09-01

    Acid-base disturbances are common occurrence in hospitalized patients with life threatening complications. 5-oxoproline has been increasingly recognized as cause of high anion gap metabolic acidosis (AGMA) in association with chronic acetaminophen use. However, laboratory workup for it are not widely available. We report case of 56-year-old female with severe AGMA not attributable to ketoacidosis, lactic acidosis or toxic ingestion. History was significant for chronic acetaminophen use, and laboratory workup negative for all frequent causes of AGMA. Given history and clinical presentation, our suspicion for 5-oxoproline toxicity was high. Our patient required emergent hemodialysis and subsequently improved clinically. With an increasing awareness of the uncommon causes of high AGMA, tests should be more readily available to detect their presence. Physicians should be more vigilant of underdiagnosed causes of AGMA if the presentation and laboratory values do not reflect a common cause, as definitive treatment may vary based on the offending agent.

  19. Probing phosphoric acid redistribution and anion migration in polybenzimidazole membranes

    DEFF Research Database (Denmark)

    Becker, Hans; Cleemann, Lars Nilausen; Aili, David

    2017-01-01

    Micro platinum electrodes embedded in a laminated phosphoric acid doped polybenzimidazole membrane are employed to monitor the acid migration during hydrogen pump mode operation. Upon application of a constant current, an immediate ohmic resistance decrease of the membrane near the anode is obser......Micro platinum electrodes embedded in a laminated phosphoric acid doped polybenzimidazole membrane are employed to monitor the acid migration during hydrogen pump mode operation. Upon application of a constant current, an immediate ohmic resistance decrease of the membrane near the anode...... is observed, accompanied by a corresponding increase near the cathode side. This is a direct evidence of migration of the acid anions via the vehicle conducting mechanism, resulting in an accumulation of acid at the anode side and depletion at the cathode side. Both resistances reach a steady state value...

  20. Nonvalence Correlation-Bound Anion States of Polycyclic Aromatic Hydrocarbons.

    Science.gov (United States)

    Voora, Vamsee K; Jordan, Kenneth D

    2015-10-15

    In this work, we characterize the nonvalence correlation-bound anion states of several polycyclic aromatic hydrocarbon (PAH) molecules. Unlike the analogous image potential states of graphene that localize the charge density of the excess electron above and below the plane of the sheet, we find that for PAHs, much of the charge distribution of the excess electron is localized around the periphery of the molecule. This is a consequence of the electrostatic interaction of the electron with the polar CH groups. By replacing the H atoms by F atoms or the CH groups by N atoms, the charge density of the excess electron shifts from the periphery to above and below the plane of the ring systems.

  1. Data clustering algorithms and applications

    CERN Document Server

    Aggarwal, Charu C

    2013-01-01

    Research on the problem of clustering tends to be fragmented across the pattern recognition, database, data mining, and machine learning communities. Addressing this problem in a unified way, Data Clustering: Algorithms and Applications provides complete coverage of the entire area of clustering, from basic methods to more refined and complex data clustering approaches. It pays special attention to recent issues in graphs, social networks, and other domains.The book focuses on three primary aspects of data clustering: Methods, describing key techniques commonly used for clustering, such as fea

  2. Enhancing the basicity of ionic liquids by tuning the cation-anion interaction strength and via the anion-tethered strategy.

    Science.gov (United States)

    Xu, Dan; Yang, Qiwei; Su, Baogen; Bao, Zongbi; Ren, Qilong; Xing, Huabin

    2014-01-30

    Ionic liquids (ILs) with relatively strong basicity often show impressive performance in chemical processes, so it is important to enhance the basicity of ILs by molecular design. Here, we proposed two effective ways to enhance the basicity of ILs: by weakening the cation-anion interaction strength and by employing the anion-tethered strategy. Notably, two quantum-chemical parameters, the most negative surface electrostatic potential and the lowest surface average local ionization energy, were adopted as powerful tools to demonstrate the electrostatic and covalent aspects of basicity, respectively, at the microscopic level. It was shown that, for the ILs with the same anion (acetate or trifluoroacetate), the basicity of the ILs could be enhanced when the cation-anion interaction strength was weakened. For the acetate anion-based ILs, the hydrogen-bonding basicity scale (β) increased by 29% when the cation changed from 1-butyl-3-methylimidazolium ([Bmim]) to tetrabutylphosphonium ([P4444]), achieving one of the highest reported β values for ILs. Moreover, it was also demonstrated that, when an amine group was tethered to the anion of the IL, its basicity was stronger than when it was tethered to the cation. These results are highly instructive for designing ILs with strong basicity and for improving the efficiency of IL-based processes, such as CO2 capture, SO2 and acetylene absorption, dissolution of cellulose, extraction of bioactive compounds, and so on.

  3. Probing electron density of H-bonding between cation-anion of imidazolium-based ionic liquids with different anions by vibrational spectroscopy.

    Science.gov (United States)

    Gao, Yan; Zhang, Liqun; Wang, Yong; Li, Haoran

    2010-03-04

    Attenuated total reflection infrared spectroscopy and density functional theory calculation have been employed to study the spectral properties of imidazolium-based ionic liquids (ILs) with different anions. ILs based on 1-butyl-3-methylimidazolium cation with different anions, OH(-), CF(3)CO(2)(-), HSO(4)(-), H(2)PO(4)(-), Cl(-), PF(6)(-), and BF(4)(-), are investigated in the present work. It has been shown that the C(2)-H stretching vibration of the imidazolium ring is closely related to the electron density of H-bonding between the two closest cations and anions for pure ILs. The electron density of H-bonding between cation and anion with different anions decreases in the order [OH](-) > [H(2)PO(4)](-) > [HSO(4)](-) > [CF(3)CO(2)](-) > [Cl](-) > [BF(4)](-) > [PF(6)](-). For aqueous ILs, with increasing water content, the aromatic C-H stretching vibration of the imidazolium cation showed systematic blue-shifts. Especially for BmimOH, the nu(C(2))(-H) undergoes a drastic blue-shift by 58 cm(-1), suggesting that the formation of the strong hydrogen bonds O-H...O may greatly weaken the electron density of H-bonding between the cation and anion of ILs.

  4. Engineered pendrin protein, an anion transporter and molecular motor.

    Science.gov (United States)

    Tang, Jie; Pecka, Jason L; Tan, Xiaodong; Beisel, Kirk W; He, David Z Z

    2011-09-02

    Pendrin and prestin both belong to a distinct anion transporter family called solute carrier protein 26A, or SLC26A. Pendrin (SLC26A4) is a chloride-iodide transporter that is found at the luminal membrane of follicular cells in the thyroid gland as well as in the endolymphatic duct and sac of the inner ear, whereas prestin (SLC26A5) is expressed in the plasma membrane of cochlear outer hair cells and functions as a unique voltage-dependent motor. We recently identified a motif that is critical for the motor function of prestin. We questioned whether it was possible to create a chimeric pendrin protein with motor capability by integrating this motility motif from prestin. The chimeric pendrin was constructed by substituting residues 160-179 in human pendrin with residues 156-169 from gerbil prestin. Non-linear capacitance and somatic motility, two hallmarks representing prestin function, were measured from chimeric pendrin-transfected human embryonic kidney 293 cells using the voltage clamp technique and photodiode-based displacement measurement system. We showed that this 14-amino acid substitution from prestin was able to confer pendrin with voltage-dependent motor capability despite the amino acid sequence disparity between pendrin and prestin. The molecular mechanism that facilitates motor function appeared to be the same as prestin because the motor activity depended on the concentration of intracellular chloride and was blocked by salicylate treatment. Radioisotope-labeled formate uptake measurements showed that the chimeric pendrin protein retained the capability to transport formate, suggesting that the gain of motor function was not at the expense of its inherent transport capability. Thus, the engineered pendrin was capable of both transporting anions and generating force.

  5. Theoretical characterization of the SiC3H- anion.

    Science.gov (United States)

    Inostroza, N; Senent, M L

    2010-11-14

    Highly correlated ab initio methods are used to predict the equilibrium structures and spectroscopic parameters of the SiC(3)H(-) anion. The total energies and physical properties are reported using CASSCF/MRCI, RCCSD(T), and RCCSD(T)-F12 approaches and extended basis sets. The search of stable geometries leads to a total of 12 isomers (4 linear and 8 cyclic), for which electronic ground states have close-shell configurations. The stability of the linear form, l-SiC(3)H(-), is prominent. For the most stable linear isomer, the B(e) equilibrium rotational constant has been calculated with RCCSD(T) and a complete basis set. Core-correlation and vibrational effects have been taken into account to predict a B(0) of 2621.68 MHz for l-SiC(3)H(-) and 2460.48 MHz for l-SiC(3)D(-). The dipole moment of l-SiC(3)H(-) was found to be 2.9707 D with CASSCF/aug-cc-pV5Z and the electron affinity to be 2.7 eV with RCCSD(T)-F12A/aug-cc-pVTZ. Anharmonic spectroscopic parameters are derived from a quadratic, cubic, and quartic RCCSD(T)-F12A force field and second order perturbation theory. CASSCF/MRCI vertical excitations supply three metastable electronic states, (1)Σ(+) (3)Σ(+) and (3)Δ. Electron affinities calculated for a series of chains type SiC(n)H and SiC(n) (n=1-5) allow us to discuss the anion formation probabilities.

  6. The structure of deprotonated tri-alanine and its a(3)(-) fragment anion by IR spectroscopy

    NARCIS (Netherlands)

    Oomens, J.; Steill, J.D.

    2010-01-01

    We present the first infrared spectra of a mass-selected deprotonated peptide anion (AlaAlaAla) and its decarboxylated fragment anion formed by collision induced dissociation. Spectra are obtained by IRMPD spectroscopy using an FTICR mass spectrometer in combination with the free electron laser

  7. The Structure of Deprotonated Tri-Alanine and Its a(3)(-) Fragment Anion by IR Spectroscopy

    NARCIS (Netherlands)

    Oomens, J.; Steill, J. D.

    2010-01-01

    We present the first infrared spectra of a mass-selected deprotonated peptide anion (AlaAlaAla) and its decarboxylated fragment anion formed by collision induced dissociation. Spectra are obtained by IRMPD spectroscopy using an FTICR mass spectrometer in combination with the free electron laser

  8. Anionic polymerization and polyhomologation: An ideal combination to synthesize polyethylene-based block copolymers

    KAUST Repository

    Zhang, H.

    2013-08-07

    A novel one-pot methodology combining anionic polymerization and polyhomologation, through a "bridge" molecule (BF3OEt 2), was developed for the synthesis of polyethylene (PE)-based block copolymers. The anionically synthesized macroanion reacts with the "bridge" molecule to afford a 3-arm star (trimacromolecular borane) which serves as an initiator for the polyhomologation. 2013 The Royal Society of Chemistry.

  9. Specificity of anion-binding in the substrate-pocket ofbacteriorhodopsin

    Energy Technology Data Exchange (ETDEWEB)

    Facciotti, Marc T.; Cheung, Vincent S.; Lunde, Christopher S.; Rouhani, Shahab; Baliga, Nitin S.; Glaeser, Robert M.

    2003-08-30

    The structure of the D85S mutant of bacteriorhodopsin with a nitrate anion bound in the Schiff-base binding site, and the structure of the anion-free protein have been obtained in the same crystal form. Together with the previously solved structures of this anion pump, in both the anion-free state and bromide-bound state, these new structures provide insight into how this mutant of bacteriorhodopsin is able to bind a variety of different anions in the same binding pocket. The structural analysis reveals that the main structural change that accommodates different anions is the repositioning of the polar side-chain of S85. On the basis of these x-ray crystal structures, the prediction is then made that the D85S/D212N double mutant might bind similar anions and do so over a broader pH range than does the single mutant. Experimental comparison of the dissociation constants, K{sub d}, for a variety of anions confirms this prediction and demonstrates, in addition, that the binding affinity is dramatically improved by the D212N substitution.

  10. Theoretical considerations on the indirect determination of anions : Determination of sulphate with barium chloranilate

    NARCIS (Netherlands)

    Agterdenbos, J.; Martinius, N.

    Some anions (sulphate) may be determined by their reaction with a slightly dissociated or slightly soluble compound (barium chloranilate), another anion (chloranilate ion) being liberated and its extinction measured. An equation is given in this paper for the relationship between the concentration

  11. Superoxide anion-induced pain and inflammation depends on TNFα/TNFR1 signaling in mice.

    Science.gov (United States)

    Yamacita-Borin, Fabiane Y; Zarpelon, Ana C; Pinho-Ribeiro, Felipe A; Fattori, Victor; Alves-Filho, Jose C; Cunha, Fernando Q; Cunha, Thiago M; Casagrande, Rubia; Verri, Waldiceu A

    2015-09-25

    Inhibition of tumor necrosis factor-alpha (TNFα) and superoxide anion production reduces inflammation and pain. The present study investigated whether superoxide anion-induced pain depends on TNFα signaling and the role of superoxide anion in TNFα-induced hyperalgesia to clarify the interrelation between these two mediators in the context of pain. Intraplantar injection of a superoxide anion donor (potassium superoxide) induced mechanical hyperalgesia (0.5-5h after injection), neutrophil recruitment (myeloperoxidase activity), and overt pain-like behaviors (paw flinching, paw licking, and abdominal writhings) in wild-type mice. Tumor necrosis factor receptor 1 deficiency (TNFR1-/-) and treatment of wild-type mice with etanercept (a soluble TNFR2 receptor that inhibits TNFα actions) inhibited superoxide anion-induced pain-like behaviors. TNFR1(-/-) mice were also protected from superoxide anion donor-induced oxidative stress, suggesting the role of this pathway in the maintenance of oxidative stress. Finally, we demonstrated that Apocynin (an NADPH oxidase inhibitor) or Tempol (a superoxide dismutase mimetic) treatment inhibited TNFα-induced paw mechanical hyperalgesia and neutrophil recruitment (myeloperoxidase activity). These results demonstrate that TNFα/TNFR1 signaling is important in superoxide anion-triggered pain and that TNFα/TNFR1 signaling amplifies the oxidative stress triggered by superoxide anion, which contributes to sustaining pain and inflammation. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  12. CO2 binding in the (quinoline-CO2)- anionic complex

    Science.gov (United States)

    Graham, Jacob D.; Buytendyk, Allyson M.; Wang, Yi; Kim, Seong K.; Bowen, Kit H.

    2015-06-01

    We have studied the (quinoline-CO2)- anionic complex by a combination of mass spectrometry, anion photoelectron spectroscopy, and density functional theory calculations. The (quinoline-CO2)- anionic complex has much in common with previously studied (N-heterocycle-CO2)- anionic complexes both in terms of geometric structure and covalent bonding character. Unlike the previously studied N-heterocycles, however, quinoline has a positive electron affinity, and this provided a pathway for determining the binding energy of CO2 in the (quinoline-CO2)- anionic complex. From the theoretical calculations, we found CO2 to be bound within the (quinoline-CO2)- anionic complex by 0.6 eV. We also showed that the excess electron is delocalized over the entire molecular framework. It is likely that the CO2 binding energies and excess electron delocalization profiles of the previously studied (N-heterocycle-CO2)- anionic complexes are quite similar to that of the (quinoline-CO2)- anionic complex. This class of complexes may have a role to play in CO2 activation and/or sequestration.

  13. LEVELS OF SOME ANIONS IN SOKOTO-RIMA RIVER SYSTEM IN ...

    African Journals Online (AJOL)

    user

    ABSTRACT. The level of some anions in Sokoto-Rima River system at the fishing site of the Argungu. International Fishing and Cultural Festival (AIFCF) were analyzed. Water samples were collected for twelve months and analyzed for anions. Data generated was analyzed using. ANOVA. Statistical analysis of the data was ...

  14. Determining the Structure of Oxalate Anion Using Infrared and Raman Spectroscopy Coupled with Gaussian Calculations

    Science.gov (United States)

    Peterson, Karen I.; Pullman, David P.

    2016-01-01

    A laboratory project for the upper-division physical chemistry laboratory is described, and it combines IR and Raman spectroscopies with Gaussian electronic structure calculations to determine the structure of the oxalate anion in solid alkali oxalates and in aqueous solution. The oxalate anion has two limiting structures whose vibrational spectra…

  15. Neutral anion receptors; synthesis and evaluation as sensing molecules in chemically modified field effect transistors (CHEMFETs)

    NARCIS (Netherlands)

    Antonisse, M.M.G.; Ruel, Bianca H.M.; Yigit, Isteyfo; Engbersen, Johannes F.J.; Reinhoudt, David

    1997-01-01

    new class of anion selective receptors is based on the neutral uranylsalophene building block as Lewis acidic binding site. Additional hydrogen bond accepting or donating moieties near the anion binding site offer the possibility of varying the binding selectivity. Field effect transistors

  16. Anion recognition by azophenol thiourea-based chromogenic sensors: a combined DFT and molecular dynamics investigation.

    Science.gov (United States)

    Wong, Ming Wah; Xie, Huifang; Kwa, Soo Tin

    2013-01-01

    The relative binding affinities of several anions towards 2-nitroazophenol thiourea-based receptors were studied using density functional theory (DFT) in the gas phase and in chloroform solvent via PCM calculations. Both receptors have five distinctive NH and OH hydrogen donor atoms. All receptor-anion complexes are characterized by five intermolecular hydrogen bonds. The binding free energies are strongly influenced by a dielectric medium, and the solvation effect alters the trend of anion binding to the receptor. The calculated order of anion binding affinity for the receptor in chloroform, H2PO4->AcO->F->Cl->HSO4->NO3-, is in excellent accord with experimental findings. The overall order of binding affinity is attributed to the basicity of the anion, the effect of solvation, and the number of proton acceptors available. Calculations of the NMR and UV-vis spectra strongly support the experimental characterization of the receptor-anion complexes. Explicit solvent molecular dynamics simulations of selected receptor-anion complexes were also carried out. Analysis of the structural descriptors revealed that the anions were strongly bound within the binding pocket via hydrogen-bonding interactions to the five receptor protons throughout the simulation.

  17. Improvement of Anion Transport Systems by Modulation of Chalcogen Interactions: The influence of solvent.

    Science.gov (United States)

    Sánchez-Sanz, Goar; Trujillo, Cristina

    2018-02-08

    A series of potential anion transporters, dithieno[3,2-b;2',3'-d]thiophenes (DTT), involving anion-chalcogen interactions have been studied by analyzing the interaction energy, geometry, and charge transfer. It was found that gas phase calculations show very negative interaction energies with short anion-chalcogen distances, but when solvent effects are considered, the interaction energy values decreased drastically concomitantly with an elongation on the interatomic distances. To enhance the chalcogen interaction between the DTT derivatives and the anion, increasing the anion transporter capacity, bisisothioazole moiety was considered; i.e., the σ-hole of the chalcogen atom was modulated by substitution of the adjacent carbon by a nitrogen atom in the S-C axis, increasing the depth of the σ-hole and therefore the interaction between the chalcogen and anion. Finally, different anions were analyzed within the complexes, finding that F - and NO 3 - would be the best candidates to form complexes and possibly displace other anions such as Cl - or Br - .

  18. Evaluation of Serum Anion gap in the three trimesters of pregnancy ...

    African Journals Online (AJOL)

    Evaluation of Serum Anion gap in the three trimesters of pregnancy in a Christian Religious Hospital in Benin City, Nigeria. ... Results were compared using the student's t-test and p < 0.05 were considered statistically significant. The anion gap for the first trimester of pregnancy (11.01 ± 0.13 mmol/L) was significantly lower ...

  19. Facilitated transport of hydrophilic salts by mixtures of anion and cation carriers and by ditopic carriers

    NARCIS (Netherlands)

    Chrisstoffels, L.A.J.; de Jong, Feike; Reinhoudt, David; Sivelli, Stefano; Gazzola, Licia; Casnati, Alessandro; Ungaro, Rocco

    1999-01-01

    Anion transfer to the membrane phase affects the extraction efficiency of salt transport by cation carriers 1 and 3. Addition of anion receptors 5 or 6 to cation carriers 1, 3, or 4 in the membrane phase enhances the transport of salts under conditions in which the cation carriers alone do not

  20. Study of small carbon and semiconductor clusters using negative ion threshold photodetachment spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Arnold, Caroline Chick [Univ. of California, Berkeley, CA (United States)

    1994-08-01

    The bonding and electronics of several small carbon and semiconductor clusters containing less than ten atoms are probed using negative ion threshold photodetachment (zero electron kinetic energy, or ZEKE) spectroscopy. ZEKE spectroscopy is a particularly advantageous technique for small cluster study, as it combines mass selection with good spectroscopic resolution. The ground and low-lying electronic states of small clusters in general can be accessed by detaching an electron from the ground anion state. The clusters studied using this technique and described in this work are C6-/C6, Sin-/Sin (n = 2, 3, 4), Ge2-/Ge2, In2P-/In2P,InP2-/InP2, and Ga2As-. The total photodetachment cross sections of several other small carbon clusters and the ZEKE spectrum of the I-•CH3I SN2 reaction complex are also presented to illustrate the versatility of the experimental apparatus. Clusters with so few atoms do not exhibit bulk properties. However, each specie exhibits bonding properties that relate to the type of bonding found in the bulk. C6, as has been predicted, exhibits a linear cumulenic structure, where double bonds connect all six carbon atoms. This double bonding reflects how important π bonding is in certain phases of pure carbon (graphite and fullerenes). The symmetric stretch frequencies observed in the C6- spectra, however, are in poor agreement with the calculated values. Also observed as sharp structure in total photodetachment cross section scans was an excited anion state bound by only ~40 cm-1 relative to the detachment continuum. This excited anion state appears to be a valence bound state, possible because of the high electron affinity of C6, and the open shell of the anion.