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Sample records for bond selective chemistry

  1. Bond selective chemistry beyond the adiabatic approximation

    Energy Technology Data Exchange (ETDEWEB)

    Butler, L.J. [Univ. of Chicago, IL (United States)

    1993-12-01

    One of the most important challenges in chemistry is to develop predictive ability for the branching between energetically allowed chemical reaction pathways. Such predictive capability, coupled with a fundamental understanding of the important molecular interactions, is essential to the development and utilization of new fuels and the design of efficient combustion processes. Existing transition state and exact quantum theories successfully predict the branching between available product channels for systems in which each reaction coordinate can be adequately described by different paths along a single adiabatic potential energy surface. In particular, unimolecular dissociation following thermal, infrared multiphoton, or overtone excitation in the ground state yields a branching between energetically allowed product channels which can be successfully predicted by the application of statistical theories, i.e. the weakest bond breaks. (The predictions are particularly good for competing reactions in which when there is no saddle point along the reaction coordinates, as in simple bond fission reactions.) The predicted lack of bond selectivity results from the assumption of rapid internal vibrational energy redistribution and the implicit use of a single adiabatic Born-Oppenheimer potential energy surface for the reaction. However, the adiabatic approximation is not valid for the reaction of a wide variety of energetic materials and organic fuels; coupling between the electronic states of the reacting species play a a key role in determining the selectivity of the chemical reactions induced. The work described below investigated the central role played by coupling between electronic states in polyatomic molecules in determining the selective branching between energetically allowed fragmentation pathways in two key systems.

  2. Computational Chemistry of Adhesive Bonds

    Science.gov (United States)

    Phillips, Donald H.

    1999-01-01

    This investigation is intended to determine the electrical mechanical, and chemical properties of adhesive bonds at the molecular level. The initial determinations will be followed by investigations of the effects of environmental effects on the chemistry and properties of the bond layer.

  3. The dissociative chemisorption of water on Ni(111): Mode- and bond-selective chemistry on metal surfaces

    International Nuclear Information System (INIS)

    A fully quantum approach based on an expansion in vibrationally adiabatic eigenstates is used to explore the dissociative chemisorption of H2O, HOD, and D2O on Ni(111). For this late barrier system, excitation of both the bending and stretching modes significantly enhances dissociative sticking. The vibrational efficacies vary somewhat from mode-to-mode but are all relatively close to one, in contrast to methane dissociation, where the behavior is less statistical. Similar to methane dissociation, the motion of lattice atoms near the dissociating molecule can significantly modify the height of the barrier to dissociation, leading to a strong variation in dissociative sticking with substrate temperature. Given a rescaling of the barrier height, our results are in reasonable agreement with measurements of the dissociative sticking of D2O on Ni(111), for both laser-excited molecules with one or two quanta of excitation in the antisymmetric stretch and in the absence of laser excitation. Even without laser excitation, the beam contains vibrationally excited molecules populated at the experimental source temperature, and these make significant contributions to the sticking probability. At high collision energies, above the adiabatic barrier heights, our results correlate with these barrier heights and mode softening effects. At lower energies, dissociative sticking occurs primarily via vibrationally nonadiabatic pathways. We find a preference for O–H over O–D bond cleavage for ground state HOD molecules at all but the highest collision energies, and excitation of the O–H stretch gives close to 100% O–H selectivity at lower energies. Excitation of the O–D stretch gives a lower O–D cleavage selectivity, as the interaction with the surface leads to energy transfer from the O–D stretch into the O–H bond, when mode softening makes these vibrations nearly degenerate

  4. The dissociative chemisorption of water on Ni(111): Mode- and bond-selective chemistry on metal surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Farjamnia, Azar; Jackson, Bret, E-mail: jackson@chem.umass.edu [Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003 (United States)

    2015-06-21

    A fully quantum approach based on an expansion in vibrationally adiabatic eigenstates is used to explore the dissociative chemisorption of H{sub 2}O, HOD, and D{sub 2}O on Ni(111). For this late barrier system, excitation of both the bending and stretching modes significantly enhances dissociative sticking. The vibrational efficacies vary somewhat from mode-to-mode but are all relatively close to one, in contrast to methane dissociation, where the behavior is less statistical. Similar to methane dissociation, the motion of lattice atoms near the dissociating molecule can significantly modify the height of the barrier to dissociation, leading to a strong variation in dissociative sticking with substrate temperature. Given a rescaling of the barrier height, our results are in reasonable agreement with measurements of the dissociative sticking of D{sub 2}O on Ni(111), for both laser-excited molecules with one or two quanta of excitation in the antisymmetric stretch and in the absence of laser excitation. Even without laser excitation, the beam contains vibrationally excited molecules populated at the experimental source temperature, and these make significant contributions to the sticking probability. At high collision energies, above the adiabatic barrier heights, our results correlate with these barrier heights and mode softening effects. At lower energies, dissociative sticking occurs primarily via vibrationally nonadiabatic pathways. We find a preference for O–H over O–D bond cleavage for ground state HOD molecules at all but the highest collision energies, and excitation of the O–H stretch gives close to 100% O–H selectivity at lower energies. Excitation of the O–D stretch gives a lower O–D cleavage selectivity, as the interaction with the surface leads to energy transfer from the O–D stretch into the O–H bond, when mode softening makes these vibrations nearly degenerate.

  5. Bonding, structure and solid-state chemistry

    CERN Document Server

    Ladd, Mark

    2016-01-01

    This book is aimed at undergraduate students in both chemistry and those degree subjects in which chemistry forms a significant part. It does not reflect any particular academic year, and so finds a place during the normal span of degree studies in the physical sciences. An A-level standard in science and mathematics is presumed; additional mathematical treatments are discussed in Appendices. An introductory first chapter leads into the main subject matter, which is treated through four chapters in terms of the principle bonding forces of cohesion in the solid state; a further chapter discusses nanosize materials. Important applications of the study topics are interspersed at appropriate points within the text. Each chapter is provided with a set of problems of varying degrees of difficulty, so as to assist the reader in gaining a facility with the subject matter and its applications. The problems are supplemented by detailed tutorial solutions, some of which present additional relevant material that indicate...

  6. Discovering Chemistry With Natural Bond Orbitals

    CERN Document Server

    Weinhold, Frank

    2012-01-01

    This book explores chemical bonds, their intrinsic energies, and the corresponding dissociation energies which are relevant in reactivity problems. It offers the first book on conceptual quantum chemistry, a key area for understanding chemical principles and predicting chemical properties. It presents NBO mathematical algorithms embedded in a well-tested and widely used computer program (currently, NBO 5.9). While encouraging a "look under the hood" (Appendix A), this book mainly enables students to gain proficiency in using the NBO program to re-express complex wavefunctions in terms of intui

  7. The CH/π hydrogen bond: Implication in chemistry

    Science.gov (United States)

    Nishio, M.

    2012-06-01

    The CH/π hydrogen bond is the weakest extreme of hydrogen bonds that occurs between a soft acid CH and a soft base π-system. Implication in chemistry of the CH/π hydrogen bond includes issues of conformation, crystal packing, and specificity in host/guest complexes. The result obtained by analyzing the Cambridge Structural Database is reviewed. The peculiar axial preference of isopropyl group in α-phellandrene and folded conformation of levopimaric acid have been explained in terms of the CH/π hydrogen bond, by high-level ab initio MO calculations. Implication of the CH/π hydrogen bond in structural biology is also discussed, briefly.

  8. Hydrogen Bond Basicity Prediction for Medicinal Chemistry Design.

    Science.gov (United States)

    Kenny, Peter W; Montanari, Carlos A; Prokopczyk, Igor M; Ribeiro, Jean F R; Sartori, Geraldo Rodrigues

    2016-05-12

    Hydrogen bonding is discussed in the context of medicinal chemistry design. Minimized molecular electrostatic potential (Vmin) is shown to be an effective predictor of hydrogen bond basicity (pKBHX), and predictive models are presented for a number of hydrogen bond acceptor types relevant to medicinal chemistry. The problems posed by the presence of nonequivalent hydrogen bond acceptor sites in molecular structures are addressed by using nonlinear regression to fit measured pKBHX to calculated Vmin. Predictions are made for hydrogen bond basicity of fluorine in situations where relevant experimental measurements are not available. It is shown how predicted pKBHX can be used to provide insight into the nature of bioisosterism and to profile heterocycles. Examples of pKBHX prediction for molecular structures with multiple, nonequivalent hydrogen bond acceptors are presented. PMID:26872049

  9. Computational Tools To Model Halogen Bonds in Medicinal Chemistry.

    Science.gov (United States)

    Ford, Melissa Coates; Ho, P Shing

    2016-03-10

    The use of halogens in therapeutics dates back to the earliest days of medicine when seaweed was used as a source of iodine to treat goiters. The incorporation of halogens to improve the potency of drugs is now fairly standard in medicinal chemistry. In the past decade, halogens have been recognized as direct participants in defining the affinity of inhibitors through a noncovalent interaction called the halogen bond or X-bond. Incorporating X-bonding into structure-based drug design requires computational models for the anisotropic distribution of charge and the nonspherical shape of halogens, which lead to their highly directional geometries and stabilizing energies. We review here current successes and challenges in developing computational methods to introduce X-bonding into lead compound discovery and optimization during drug development. This fast-growing field will push further development of more accurate and efficient computational tools to accelerate the exploitation of halogens in medicinal chemistry. PMID:26465079

  10. Teaching Chemical Bonding: A Resource Book for Senior Chemistry.

    Science.gov (United States)

    Lindsay, Margaret

    This document presents an instructional strategy for teaching chemical bonding using parables and music. Games, student interactions, and worksheets are included in the lesson plans. Topics include metallic bonding, covalent bonding including molecular and network structure, and ionic bonding. (JRH)

  11. New Research Center Will Free Chemistry from Earth's Bonds

    Science.gov (United States)

    2008-10-01

    A new research center combining the tools of chemistry and astronomy will use the unique laboratory of interstellar space to free the study of basic chemistry from the restrictive bonds of Earth. The Center for Chemistry of the Universe will allow scientists to explore new types of chemical reactions that occur under the extreme conditions of space. The center will combine laboratory experiments, theoretical studies, and radio-telescope observations to dramatically expand our understanding of the processes that build molecules that may "seed" young planets with the building blocks of life. Astrochemistry Graphic CREDIT: Bill Saxton, NRAO/AUI/NSF The Center forges a unique research collaboration among leading scientists in the field of astrochemistry from the University of Arizona, The Ohio State University, the Harvard-Smithsonian Center for Astrophysics, the National Institute of Standards and Technology, the National Radio Astronomy Observatory, and a group of chemists and physicists at the University of Virginia engaged in research to understand the fundamentals of chemical reactions. "We hope to answer some very basic questions, such as just how did the molecules that ultimately became us get their start?" said Brooks Pate, Professor of Chemistry at the University of Virginia (UVa) and leader of the team that will form the new center. The team received an initial grant of 1.5 million from the National Science Foundation (NSF) to form the center during the next two years. If the NSF then fully approves the initiative, the foundation will provide funding of 4 million per year for up to ten years. The new center will bring together laboratory researchers, theoreticians, and observers using radio telescopes of the National Radio Astronomy Observatory (NRAO) and the Arizona Radio Observatory (ARO). The group of chemists participating in the center have discovered more than half of the new interstellar molecules identified worldwide in the past 18 months. The NRAO

  12. Bonding and Structure. Independent Learning Project for Advanced Chemistry (ILPAC). Unit S4.

    Science.gov (United States)

    Inner London Education Authority (England).

    This unit on chemical bonding is one of 10 first year units produced by the Independent Learning Project for Advanced Chemistry (ILPAC). The unit, which consists of two levels, provides an introduction to the main types of chemical bonding and important aspects of structure. The main emphasis is placed on such topics as ionic and covalent bonding,…

  13. Consistent descriptions of metal–ligand bonds and spin-crossover in inorganic chemistry

    DEFF Research Database (Denmark)

    Kepp, Kasper Planeta

    2013-01-01

    -scale DFT studies of inorganic systems in catalysis and bioinorganic chemistry rely directly on the ability to balance correlation effects in the involved bonds across the s-, p-, and d-blocks. This review concerns recent efforts to describe such bonds accurately and consistently across the s-, p-, and d......-blocks. Physical effects and ingredients in functionals, their systematic errors, and approaches to deal with them are discussed, in order to identify broadly applicable methods for inorganic chemistry....

  14. Enhancing prospective chemistry teachers cognitive structures in the topics of bonding and hybridization by internet-assisted chemistry applications

    Directory of Open Access Journals (Sweden)

    Özge Özyalçın Oskay, Sinem Dinçol

    2011-08-01

    Full Text Available The purpose of this study is to determine the effects of internet-assisted chemistry applications on prospective chemistry teachers’ cognitive structures in the topics of bonding and hybridization. The sample of the study consisted of 36 prospective chemistry teachers attending Hacettepe University, Faculty of Education, the Department of Chemistry Education in 2010-2011 academic year and taking Basic Chemistry I lesson. In the study, students were separated into experimental and control groups according to their pre-cognitive structures. Students were requested to answer two open ended questions. Answers by each student were gathered and evaluated by flow map method. “Bonding and hybridization” topics were taught to control group with traditional teaching method and to experimental group besides traditional method internet-assisted applications were conducted. The same open-ended questions were given to both groups and their cognitive structures were examined once more. The differences between control and experimental groups’ cognitive structures were examined. A significant difference was identified in favour of experimental group (p<0, 05. The mean score of the Experimental group was X=19.94, and the mean score of the Control group was X=13.88. In addition, subsequent to internet assisted chemistry applications differences in terms of concepts and descriptions in prospective chemistry teachers’ in experimental and control group cognitive structure have been determined. When post flow maps of prospective chemistry teachers in experimental group, on whom internet assisted chemistry applications were made, are formed, it has been determined that there are more statements about hybridization, hybridization types, molecule geometry and bond angles compared to control grou

  15. Valence-Bond Concepts in Coordination Chemistry and the Nature of Metal-Metal Bonds.

    Science.gov (United States)

    Pauling, Linus; Herman, Zelek S.

    1984-01-01

    Discusses the valence-bond method, applying it to some coordination compounds of metals, especially those involving metal-metal bonds. Suggests that transition metals can form as many as nine covalent bonds, permitting valence-theory to be extended to transition metal compounds in a more effective way than has been possible before. (JN)

  16. Two-Center/Three-Electron Sigma Half-Bonds in Main Group and Transition Metal Chemistry.

    Science.gov (United States)

    Berry, John F

    2016-01-19

    First proposed in a classic Linus Pauling paper, the two-center/three-electron (2c/3e) σ half-bond challenges the extremes of what may or may not be considered a chemical bond. Two electrons occupying a σ bonding orbital and one electron occupying the antibonding σ* orbital results in bond orders of ∼0.5 that are characteristic of metastable and exotic species, epitomized in the fleetingly stable He2(+) ion. In this Account, I describe the use of coordination chemistry to stabilize such fugacious three-electron bonded species at disparate ends of the periodic table. A recent emphasis in the chemistry of metal-metal bonds has been to prepare compounds with extremely short metal-metal distances and high metal-metal bond orders. But similar chemistry can be used to explore metal-metal bond orders less than one, including 2c/3e half-bonds. Bimetallic compounds in the Ni2(II,III) and Pd2(II,III) oxidation states were originally examined in the 1980s, but the evidence collected at that time suggested that they did not contain 2c/3e σ bonds. Both classes of compounds have been re-examined using EPR spectroscopy and modern computational methods that show the unpaired electron of each compound to occupy a M-M σ* orbital, consistent with 2c/3e Ni-Ni and Pd-Pd σ half-bonds. Elsewhere on the periodic table, a seemingly unrelated compound containing a trigonal bipyramidal Cu3S2 core caused a stir, leaving prominent theorists at odds with one another as to whether the compound contains a S-S bond. Due to my previous experience with 2c/3e metal-metal bonds, I suggested that the Cu3S2 compound could contain a 2c/3e S-S σ half-bond in the previously unknown oxidation state of S2(3-). By use of the Cambridge Database, a number of other known compounds were identified as potentially containing S2(3-) ligands, including a noteworthy set of cyclopentadienyl-supported compounds possessing diamond-shaped Ni2E2 units with E = S, Se, and Te. These compounds were subjected to

  17. Selected new developments in computational chemistry.

    OpenAIRE

    Darden, T A; Bartolotti, L; Pedersen, L G

    1996-01-01

    Molecular dynamics is a general technique for simulating the time-dependent properties of molecules and their environments. Quantum mechanics, as applied to molecules or clusters of molecules, provides a prescription for predicting properties exactly (in principle). It is reasonable to expect that both will have a profound effect on our understanding of environmental chemistry in the future. In this review, we consider several recent advances and applications in computational chemistry. Image...

  18. Generalized Approach for Selecting Plasma Chemistries in Metal Etch

    OpenAIRE

    Chen, Kun-Chieh

    2016-01-01

    In this work, a generalized methodology, combining thermodynamic assessment of various etching chemistries and kinetic verification of etching efficacy, is proposed. To screen various chemistries, reactions between the dominant vapor phase/condensed species at various partial pressures of reactants are first considered. The volatility of etch product is determined to aid the selection of viable etch chemistry. Magnetic tunnel junction (MTJ) based magnetic random access memory (MRAM) was chose...

  19. A comparison of atmospheric composition using the Carbon Bond and Regional Atmospheric Chemistry Mechanisms

    OpenAIRE

    G. Sarwar; Godowitch, J.; B. H. Henderson; K. Fahey; Pouliot, G.; W. T. Hutzell; Mathur, R.; Kang, D.; W. S. Goliff; Stockwell, W. R.

    2013-01-01

    We incorporate the recently developed Regional Atmospheric Chemistry Mechanism (version 2, RACM2) into the Community Multiscale Air Quality modeling system for comparison with the existing 2005 Carbon Bond mechanism with updated toluene chemistry (CB05TU). Compared to CB05TU, RACM2 enhances the domain-wide monthly mean hydroxyl radical concentrations by 46% and nitric acid by 26%. However, it reduces hydrogen peroxide by 2%, peroxyacetic acid by 94%, methyl hydrogen peroxide...

  20. A comparison of atmospheric composition using the Carbon Bond and Regional Atmospheric Chemistry Mechanisms

    OpenAIRE

    Sarwar, G.; J. Godowitch; B. H. Henderson; K. Fahey; Pouliot, G.; W. T. Hutzell; Mathur, R.; Kang, D.; Goliff, W. S.; Stockwell, W. R.

    2013-01-01

    We incorporate the recently developed Regional Atmospheric Chemistry Mechanism (version 2, RACM2) into the Community Multiscale Air Quality modeling system for comparison with the existing 2005 Carbon Bond mechanism with updated toluene chemistry (CB05TU). Compared to CB05TU, RACM2 enhances the domain-wide monthly mean hydroxyl radical concentrations by 46% and nitric acid by 26%. However, it reduces hydrogen peroxide by 2%, peroxyacetic acid by 94%, methyl hydrogen peroxide by 19%, peroxyace...

  1. A comparison of atmospheric composition using the Carbon Bond and Regional Atmospheric Chemistry Mechanisms

    OpenAIRE

    Sarwar, G.; J. Godowitch; Henderson, B.; K. Fahey; Pouliot, G.; W. T. Hutzell; Mathur, R.; Kang, D.; Goliff, W. S.; Stockwell, W. R.

    2013-01-01

    We incorporate the recently developed Regional Atmospheric Chemistry Mechanism (version 2, RACM2) into the Community Multiscale Air Quality modeling system for comparison with the existing 2005 Carbon Bond mechanism with updated toluene chemistry (CB05TU). Compared to CB05TU, RACM2 enhances the domain-wide monthly mean hydroxyl radical concentrations by 46% and nitric acid by 26%. However, it reduces hydrogen peroxide by 2%, peroxyacetic acid by 94%, methyl hydrogen peroxide by 19%, pe...

  2. Spatially Selective Functionalization of Conducting Polymers by "Electroclick" Chemistry

    DEFF Research Database (Denmark)

    Hansen, Thomas Steen; Daugaard, Anders Egede; Hvilsted, Søren;

    2009-01-01

    Conducting polymer microelectrodes can electrochemically generate the catalyst required for their own functionalization by "click chemistry" with high spatial resolution. Interdigitated microelectrodes prepared from an azide-containing conducting polymer are selectively functionalized in sequence...

  3. Two-pulse laser control of bond-selective fragmentation

    DEFF Research Database (Denmark)

    Amstrup, Bjarne; Henriksen, Niels Engholm

    1996-01-01

    We elaborate on a two-pulse (pump-pump) laser control scheme for selective bond-breaking in molecules [Amstrup and Henriksen, J. Chem. Phys. 97, 8285 (1992)]. We show, in particular, that with this scheme one can overcome the obstacle of intramolecular vibrational relaxation. As an example, we...... consider an ozone molecule with isotopic substitution, that is, (OOO)-O-16-O-16-O-18. It is shown that asymmetric bond stretching can be created in simple (intense) laser fields. We predict that an alternating high selectivity between the channels O-16+(OO)-O-16-O-18 and (OO)-O-16-O-16+ O-18 can be...

  4. Site-selective and stereoselective functionalization of unactivated C-H bonds.

    Science.gov (United States)

    Liao, Kuangbiao; Negretti, Solymar; Musaev, Djamaladdin G; Bacsa, John; Davies, Huw M L

    2016-05-12

    The laboratory synthesis of complex organic molecules relies heavily on the introduction and manipulation of functional groups, such as carbon-oxygen or carbon-halogen bonds; carbon-hydrogen bonds are far less reactive and harder to functionalize selectively. The idea of C-H functionalization, in which C-H bonds are modified at will instead of the functional groups, represents a paradigm shift in the standard logic of organic synthesis. For this approach to be generally useful, effective strategies for site-selective C-H functionalization need to be developed. The most practical solutions to the site-selectivity problem rely on either intramolecular reactions or the use of directing groups within the substrate. A challenging, but potentially more flexible approach, would be to use catalyst control to determine which site in a particular substrate would be functionalized. Here we describe the use of dirhodium catalysts to achieve highly site-selective, diastereoselective and enantioselective C-H functionalization of n-alkanes and terminally substituted n-alkyl compounds. The reactions proceed in high yield, and functional groups such as halides, silanes and esters are compatible with this chemistry. These studies demonstrate that high site selectivity is possible in C-H functionalization reactions without the need for a directing or anchoring group present in the molecule. PMID:27172046

  5. Site-selective and stereoselective functionalization of unactivated C–H bonds

    Science.gov (United States)

    Liao, Kuangbiao; Negretti, Solymar; Musaev, Djamaladdin G.; Bacsa, John; Davies, Huw M. L.

    2016-05-01

    The laboratory synthesis of complex organic molecules relies heavily on the introduction and manipulation of functional groups, such as carbon–oxygen or carbon–halogen bonds; carbon–hydrogen bonds are far less reactive and harder to functionalize selectively. The idea of C–H functionalization, in which C–H bonds are modified at will instead of the functional groups, represents a paradigm shift in the standard logic of organic synthesis. For this approach to be generally useful, effective strategies for site-selective C–H functionalization need to be developed. The most practical solutions to the site-selectivity problem rely on either intramolecular reactions or the use of directing groups within the substrate. A challenging, but potentially more flexible approach, would be to use catalyst control to determine which site in a particular substrate would be functionalized. Here we describe the use of dirhodium catalysts to achieve highly site-selective, diastereoselective and enantioselective C–H functionalization of n-alkanes and terminally substituted n-alkyl compounds. The reactions proceed in high yield, and functional groups such as halides, silanes and esters are compatible with this chemistry. These studies demonstrate that high site selectivity is possible in C–H functionalization reactions without the need for a directing or anchoring group present in the molecule.

  6. Theoretical Chemistry Study of the Hydrogen-bonded Interaction between Acylamine and Chloromethane Compounds

    Institute of Scientific and Technical Information of China (English)

    GE Qing-Yu; WANG Hai-Jun; CHEN Jian-Hua

    2005-01-01

    The hydrogen-bonded interaction between acylamine and chloromethane was studied using theoretical calculation methods. Looking the interaction system as a hydrogen-bonded complex, the geometric optimization of the interaction system was performed with HF and B3LYP methods at 6-311++G** level. Stable structures of these complexes were obtained. Binding energies and some other physical chemistry parameters of them were computed and compared. According to the calculation results, it can be identified that DMA (DMF or DEF) can form stable complex with chloromethane by the hydrogen-bonded interaction between them. The stable orders of these hydrogen-bonded complexes were obtained and described as: DMF-CHCl3>DMF-CH2Cl2>DMF-CH3Cl, DEF-CHCl3>DEF-CH2Cl2>DEF-CH3Cl, DMA-CHCl3>DMA-CH2Cl2>DMA-CH3Cl, respectively.

  7. Two-dimensional gold nanostructures with high activity for selective oxidation of carbon–hydrogen bonds

    KAUST Repository

    Wang, Liang

    2015-04-22

    Efficient synthesis of stable two-dimensional (2D) noble metal catalysts is a challenging topic. Here we report the facile synthesis of 2D gold nanosheets via a wet chemistry method, by using layered double hydroxide as the template. Detailed characterization with electron microscopy and X-ray photoelectron spectroscopy demonstrates that the nanosheets are negatively charged and [001] oriented with thicknesses varying from single to a few atomic layers. X-ray absorption spectroscopy reveals unusually low gold–gold coordination numbers. These gold nanosheets exhibit high catalytic activity and stability in the solvent-free selective oxidation of carbon–hydrogen bonds with molecular oxygen.

  8. Selective breaking of bonds in water with intense, 2-cycle, infrared laser pulses

    Energy Technology Data Exchange (ETDEWEB)

    Mathur, D., E-mail: atmol1@tifr.res.in; Dharmadhikari, A. K. [Tata Institute of Fundamental Research, 1 Homi Bhabha Road, Mumbai 400 005 (India); Dota, K. [Tata Institute of Fundamental Research, 1 Homi Bhabha Road, Mumbai 400 005 (India); Centre for Atomic and Molecular Physics, Manipal University, Manipal 576 104 (India); Dey, D.; Tiwari, A. K. [Indian Institute of Science Education and Research Kolkata, Mohanpur 741 246 (India); Dharmadhikari, J. A. [Centre for Atomic and Molecular Physics, Manipal University, Manipal 576 104 (India); De, S. [Saha Institute of Nuclear Physics, Bidhan Nagar, Kolkata 700 064 (India); Vasa, P. [Department of Physics, Indian Institute of Technology Bombay, Mumbai 400 076 (India)

    2015-12-28

    One of the holy grails of contemporary science has been to establish the possibility of preferentially breaking one of several bonds in a molecule. For instance, the two O–H bonds in water are equivalent: given sufficient energy, either one of them is equally likely to break. We report bond-selective molecular fragmentation upon application of intense, 2-cycle pulses of 800 nm laser light: we demonstrate up to three-fold enhancement for preferential bond breaking in isotopically substituted water (HOD). Our experimental observations are rationalized by means of ab initio computations of the potential energy surfaces of HOD, HOD{sup +}, and HOD{sup 2+} and explorations of the dissociation limits resulting from either O–H or O–D bond rupture. The observations we report present a formidable theoretical challenge that need to be taken up in order to gain insights into molecular dynamics, strong field physics, chemical physics, non-adiabatic processes, mass spectrometry, and time-dependent quantum chemistry.

  9. Selective breaking of bonds in water with intense, 2-cycle, infrared laser pulses

    International Nuclear Information System (INIS)

    One of the holy grails of contemporary science has been to establish the possibility of preferentially breaking one of several bonds in a molecule. For instance, the two O–H bonds in water are equivalent: given sufficient energy, either one of them is equally likely to break. We report bond-selective molecular fragmentation upon application of intense, 2-cycle pulses of 800 nm laser light: we demonstrate up to three-fold enhancement for preferential bond breaking in isotopically substituted water (HOD). Our experimental observations are rationalized by means of ab initio computations of the potential energy surfaces of HOD, HOD+, and HOD2+ and explorations of the dissociation limits resulting from either O–H or O–D bond rupture. The observations we report present a formidable theoretical challenge that need to be taken up in order to gain insights into molecular dynamics, strong field physics, chemical physics, non-adiabatic processes, mass spectrometry, and time-dependent quantum chemistry

  10. Chemistry of zerumbone. 2. Regulation of ring bond cleavage and unique antibacterial activities of zerumbone derivatives.

    Science.gov (United States)

    Kitayama, T; Yamamoto, K; Utsumi, R; Takatani, M; Hill, R K; Kawai, Y; Sawada, S; Okamoto, T

    2001-10-01

    Further investigation of the chemistry of the eleven-membered cyclic sesquiterpene, zerumbone, the major component of the wild ginger, Zingiber zerumbet Smith, has revealed a new selective epoxidation process, a further example of a novel Favorskii-initiated double ring contraction, and a regiospecific fragmentation of zerumbone dibromide derivatives. Several zerumbone derivatives were found to be selective inhibitors of the growth of gram-positive bacteria. PMID:11758909

  11. Olfaction mediates the establishment of selective bonding in goats.

    Science.gov (United States)

    Romeyer, A; Poindron, P; Orgeur, P

    1994-10-01

    Nine pregnant goats of the Creole breed were rendered anosmic 3 weeks before parturition by irrigating their olfactory mucosa with zinc sulfate, and nine additional pregnant goats were left intact. At parturition, interactions between all females and their young were observed for 1 h. No differences were found in mother-young relationships between intact and anosmic mothers during this time, except that kids from anosmic females were slower to suck than controls. After 4 h of uninterrupted mother-young, mothers underwent three successive 5-min tests in a predetermined order to study selective bonding: with their own kid, an alien kid of similar coat color and pattern, and an alien kid of dissimilar coat color and pattern. Intact goats readily discriminated between kids, and rejected the two aliens while accepting their own. By contrast, anosmic mothers showed no signs of discrimination and accepted the three types of kids. It is concluded that during the first postpartum hours of contact, mother goats memorize individual olfactory characteristics of their kid that serve as a basis for selective suckling and exclusive bonding. Furthermore, at this early stage, visual characteristics of the young do not appear able to compensate for the loss of olfactory cues. PMID:7800735

  12. Undergraduate chemistry students' conceptions of atomic structure, molecular structure and chemical bonding

    Science.gov (United States)

    Campbell, Erin Roberts

    The process of chemical education should facilitate students' construction of meaningful conceptual structures about the concepts and processes of chemistry. It is evident, however, that students at all levels possess concepts that are inconsistent with currently accepted scientific views. The purpose of this study was to examine undergraduate chemistry students' conceptions of atomic structure, chemical bonding and molecular structure. A diagnostic instrument to evaluate students' conceptions of atomic and molecular structure was developed by the researcher. The instrument incorporated multiple-choice items and reasoned explanations based upon relevant literature and a categorical summarization of student responses (Treagust, 1988, 1995). A covalent bonding and molecular structure diagnostic instrument developed by Peterson and Treagust (1989) was also employed. The ex post facto portion of the study examined the conceptual understanding of undergraduate chemistry students using descriptive statistics to summarize the results obtained from the diagnostic instruments. In addition to the descriptive portion of the study, a total score for each student was calculated based on the combination of correct and incorrect choices made for each item. A comparison of scores obtained on the diagnostic instruments by the upper and lower classes of undergraduate students was made using a t-Test. This study also examined an axiomatic assumption that an understanding of atomic structure is important in understanding bonding and molecular structure. A Pearson Correlation Coefficient, ṟ, was calculated to provide a measure of the strength of this association. Additionally, this study gathered information regarding expectations of undergraduate chemistry students' understanding held by the chemical community. Two questionnaires were developed with items based upon the propositional knowledge statements used in the development of the diagnostic instruments. Subgroups of items from

  13. A HYDROGEN BONDING ASSISTED CATALYST SCREENED OUT VIA COMBINATORIAL CHEMISTRY STRATEGY

    Institute of Scientific and Technical Information of China (English)

    XUMancai; OUZhize; 等

    2000-01-01

    Possibilities for enhancement of catalytic reaction rate by combining phase transfer catalysis and hydrogen bonding of the catalyst with the substrate and reagent were studied.A phase transfer catalyst library with sixty polystyrene-supported quaternary ammonium salt catalysts was synthesized.The reduction of acetophenone by NaBH4 was used as the probing reaction to select out the ost active catalyst in the library by using iterative method.which was the gel-type triethanolamine aminsating strongly asic anion exchange resin with the crosslinking degeree of 2% A hydrogen bonding assisted catalytic mechanism was proposed to explain the high catalytic activity of the catalyst.

  14. Bond-selective photodissociation caused by vibrational excitation

    International Nuclear Information System (INIS)

    Ultraviolet photodissociations of partially deuterated water (HOD) and ammonia (NHD2/NH2D) molecules excited to the vibrationally excited states have been investigated by using a crossed laser and molecular beams method. Branching ratio between the H- and D-atom ejection channels has been determined by utilizing a (2+1) resonance enhanced multiphoton ionization scheme of H and D atoms. For 243 nm photolysis of HOD in the 5νOD state, the OD bond dissociation has been solely observed with the branching ratio ,,(D+OH)/ ,,(H+OD) >12, which has been determined by the detection limit for the H atom. For the photolysis of NHD2/NH2D in the vibrationally excited states, the branching ratio between the NH and ND dissociation channels has been largely altered by the vibrational state selection. (author)

  15. A Selection of Recent Advances in C1 Chemistry.

    Science.gov (United States)

    Mesters, Carl

    2016-06-01

    This review presents a selection of recent publications related to the chemistry and catalysis of C1 molecules, including methane, methanol, carbon monoxide, and carbon dioxide. These molecules play an important role in the current supply of energy and chemicals and will likely become even more relevant because of the need to decarbonize fuels (shift from coal to natural gas) in line with CO2 capture and use to mitigate global warming, as well as a gradual shift on the supply side from crude oil to natural gas. This review includes both recent industrial developments, such as the huge increase in methanol-to-olefins-capacity build in China and the demonstration of oxidative coupling of methane, and scientific developments in these chemistries facilitated by improved capabilities in, for example, analytical tools and computational modeling. PMID:27276549

  16. From ab initio quantum chemistry to molecular dynamics: The delicate case of hydrogen bonding in ammonia

    CERN Document Server

    Boese, A D; Martin, J M L; Marx, D; Chandra, Amalendu; Martin, Jan M.L.; Marx, Dominik

    2003-01-01

    The ammonia dimer (NH3)2 has been investigated using high--level ab initio quantum chemistry methods and density functional theory (DFT). The structure and energetics of important isomers is obtained to unprecedented accuracy without resorting to experiment. The global minimum of eclipsed C_s symmetry is characterized by a significantly bent hydrogen bond which deviates from linearity by about 20 degrees. In addition, the so-called cyclic C_{2h} structure is extremely close in energy on an overall flat potential energy surface. It is demonstrated that none of the currently available (GGA, meta--GGA, and hybrid) density functionals satisfactorily describe the structure and relative energies of this nonlinear hydrogen bond. We present a novel density functional, HCTH/407+, designed to describe this sort of hydrogen bond quantitatively on the level of the dimer, contrary to e.g. the widely used BLYP functional. This improved functional is employed in Car-Parrinello ab initio molecular dynamics simulations of liq...

  17. Role of the H bond network in the radiation chemistry of hydrated systems

    International Nuclear Information System (INIS)

    Introduction: In the present contribution, we want to address the influence of the H bond network on the observed reactivity of hydrated system. In radiation chemistry the primary species appear extremely simple and at the same time are very reactive. The comprehension of their dynamics is rather difficult since their reactivity involves the solvent molecules as reactant. Some of those species like the hydrated electron and the proton are highly hydrophilic, while others like the hydroxide radical and the H atom are rather hydrophobic. Both the hydrated electron and the H atom locate near a defect of the H bond network i.e. a cavity. As an example of the role of the environment in radical chemistry, when studying the radiation chemistry of porous media we noticed that the interface play a crucial role in the outcome of that chemistry. More particularly we observed that the silanol band of the silica/water interface was strongly affected by the irradiation even so no energy is directly absorbed by an interface. In this contribution, we will first review the recent work on the H bond dynamics, in absence of any reactant. We will then present recent results on the radiation chemistry of nanoporous media and its influence on the H bond network of an interface and will also present recent results obtained on the H bond dynamics at an alumina-water interface. All those results will be discussed in light of the H bonded nature of neat water. Radiation chemistry of an H bonded interface: A Fourier transformed infrared detection associated to an electron accelerator was developed so as to characterise in situ the effects of irradiation on various systems. The FT-IR spectrometer and the detector were moved out of the accelerator room to be protected against radiation. The infrared beam was guided on a distance of 6 meters by optical conduits and mirrors. The spectra were obtained from 100 scans accumulated with a Bruker Vertex 70 equipment operating with a 4 cm-1 resolution

  18. A comparison of atmospheric composition using the Carbon Bond and Regional Atmospheric Chemistry Mechanisms

    Directory of Open Access Journals (Sweden)

    G. Sarwar

    2013-03-01

    Full Text Available We incorporate the recently developed Regional Atmospheric Chemistry Mechanism (version 2, RACM2 into the Community Multiscale Air Quality modeling system for comparison with the existing 2005 Carbon Bond mechanism with updated toluene chemistry (CB05TU. Compared to CB05TU, RACM2 enhances the domain-wide monthly mean hydroxyl radical concentrations by 46% and nitric acid by 26%. However, it reduces hydrogen peroxide by 2%, peroxyacetic acid by 94%, methyl hydrogen peroxide by 19%, peroxyacetyl nitrate by 40%, and organic nitrate by 41%. RACM2 predictions generally agree better with the observed data than the CB05TU predictions. RACM2 enhances ozone for all ambient levels leading to higher bias at low (70 ppbv concentrations. The RACM2 ozone predictions are also supported by increased ozone production efficiency that agrees better with observations. Compared to CB05TU, RACM2 enhances the domain-wide monthly mean sulfate by 10%, nitrate by 6%, ammonium by 10%, anthropogenic secondary organic aerosols by 42%, biogenic secondary organic aerosols by 5%, and in-cloud secondary organic aerosols by 7%. Increased inorganic and organic aerosols with RACM2 agree better with observed data. While RACM2 enhances ozone and secondary aerosols by relatively large margins, control strategies developed for ozone or fine particles using the two mechanisms do not differ appreciably.

  19. A comparison of atmospheric composition using the Carbon Bond and Regional Atmospheric Chemistry Mechanisms

    Directory of Open Access Journals (Sweden)

    G. Sarwar

    2013-10-01

    Full Text Available We incorporate the recently developed Regional Atmospheric Chemistry Mechanism (version 2, RACM2 into the Community Multiscale Air Quality modeling system for comparison with the existing 2005 Carbon Bond mechanism with updated toluene chemistry (CB05TU. Compared to CB05TU, RACM2 enhances the domain-wide monthly mean hydroxyl radical concentrations by 46% and nitric acid by 26%. However, it reduces hydrogen peroxide by 2%, peroxyacetic acid by 94%, methyl hydrogen peroxide by 19%, peroxyacetyl nitrate by 40%, and organic nitrate by 41%. RACM2 enhances ozone compared to CB05TU at all ambient levels. Although it exhibited greater overestimates at lower observed concentrations, it displayed an improved performance at higher observed concentrations. The RACM2 ozone predictions are also supported by increased ozone production efficiency that agrees better with observations. Compared to CB05TU, RACM2 enhances the domain-wide monthly mean sulfate by 10%, nitrate by 6%, ammonium by 10%, anthropogenic secondary organic aerosols by 42%, biogenic secondary organic aerosols by 5%, and in-cloud secondary organic aerosols by 7%. Increased inorganic and organic aerosols with RACM2 agree better with observed data. Any air pollution control strategies developed using the two mechanisms do not differ appreciably.

  20. Wet-chemistry based selective coatings for concentrating solar power

    Science.gov (United States)

    Maimon, Eran; Kribus, Abraham; Flitsanov, Yuri; Shkolnik, Oleg; Feuermann, Daniel; Zwicker, Camille; Larush, Liraz; Mandler, Daniel; Magdassi, Shlomo

    2013-09-01

    Spectrally selective coatings are common in low and medium temperature solar applications from solar water heating collectors to parabolic trough absorber tubes. They are also an essential element for high efficiency in higher temperature Concentrating Solar Power (CSP) systems. Selective coatings for CSP are usually prepared using advanced expensive methods such as sputtering and vapor deposition. In this work, coatings were prepared using low-cost wet-chemistry methods. Solutions based on Alumina and Silica sol gel were prepared and then dispersed with black spinel pigments. The black dispersions were applied by spray/roll coating methods on stainless steel plates. The spectral emissivity of sample coatings was measured in the temperature range between 200 and 500°C, while the spectral absorptivity was measured at room temperature and 500°C. Emissivity at wavelengths of 0.4-1.7 μm was evaluated indirectly using multiple measurements of directional reflectivity. Emissivity at wavelengths 2-14 μm was measured directly using a broadband IR camera that acquires the radiation emitted from the sample, and a range of spectral filters. Emissivity measurement results for a range of coated samples will be presented, and the impact of coating thickness, pigment loading, and surface preparation will be discussed.

  1. Understanding Boron through Size-Selected Clusters: Structure, Chemical Bonding, and Fluxionality

    Energy Technology Data Exchange (ETDEWEB)

    Sergeeva, Alina P.; Popov, Ivan A.; Piazza, Zachary A.; Li, Wei-Li; Romanescu, Constantin; Wang, Lai S.; Boldyrev, Alexander I.

    2014-04-15

    /C analogy. It is believed that the electronic transmutation concept will be effective and valuable in aiding the design of new boride materials with predictable properties. The study of boron clusters with intermediate properties between those of individual atoms and bulk solids has given rise to a unique opportunity to broaden the frontier of boron chemistry. Understanding boron clusters has spurred experimentalists and theoreticians to find new boron-based nanomaterials, such as boron fullerenes, nanotubes, two-dimensional boron, and new compounds containing boron clusters as building blocks. Here, a brief and timely overview is presented addressing the recent progress made on boron clusters and the approaches used in the authors’ laboratories to determine the structure, stability, and chemical bonding of size-selected boron clusters by joint photoelectron spectroscopy and theoretical studies. Specifically, key findings on all-boron hydrocarbon analogues, metal-centered boron wheels, and electronic transmutation in boron clusters are summarized.

  2. Surface Chemistry at Size-Selected Nano-Aerosol Particles

    Science.gov (United States)

    Roberts, Jeffrey

    2005-03-01

    A method has been developed to conduct surface chemistry and extract surface kinetic rates from size-selected aerosol nanoparticles. The measurements encompass broad ranges of particle size, phase, and composition. Results will be presented on the uptake of water by aerosolized soot nanoparticles of radius between 10 and 40 nm. Water uptake was monitored by tandem differential mobility analysis (T-DMA), which is capable of measuring changes in particle diameter as little as 0.2 nm. Soot particles were produced in an ethene diffusion flame and extracted into an atmospheric pressure aerosol flow tube reactor. The particles were subjected to various thermal and oxidative treatments, and the effects of these treatments on the ability of soot to adsorb monolayer quantities of water was determined. The results are important because soot nucleates atmospheric cloud particles. More generally, the results represent one of the first kinetic and mechanistic studies of gas-phase nanoparticle reactivity. Co-author: Henry Ajo, University of Minnesota

  3. A consistent molecular hydrogen isotope chemistry scheme based on an independent bond approximation

    Directory of Open Access Journals (Sweden)

    M. C. Krol

    2009-11-01

    Full Text Available The isotopic composition of molecular hydrogen (H2 produced by photochemical oxidation of methane (CH4 and Volatile Organic Compounds (VOCs is a key quantity in the global isotope budget of (H2. The many individual reaction steps involved complicate its investigation. Here we present a simplified structure-activity approach to assign isotope effects to the individual elementary reaction steps in the oxidation sequence of CH4 and some other VOCs. The approach builds on and extends the work by Gerst and Quay (2001 and Feilberg et al. (2007b. The description is generalized and allows the application, in principle, also to other compounds. The idea is that the C-H and C-D bonds – seen as reactive sites – have similar relative reaction probabilities in isotopically substituted, but otherwise identical molecules. The limitations of this approach are discussed for the reaction CH4+Cl. The same approach is applied to VOCs, which are important precursors of H2 that need to be included into models. Unfortunately, quantitative information on VOC isotope effects and source isotope signatures is very limited and the isotope scheme at this time is limited to a strongly parameterized statistical approach, which neglects kinetic isotope effects. Using these concepts we implement a full hydrogen isotope scheme in a chemical box model and carry out a sensitivity study to identify those reaction steps and conditions that are most critical for the isotope composition of the final H2 product. The reaction scheme is directly applicable in global chemistry models, which can thus include the isotope pathway of H2 produced from CH4 and VOCs in a consistent way.

  4. A consistent molecular hydrogen isotope chemistry scheme based on an independent bond approximation

    Directory of Open Access Journals (Sweden)

    G. Pieterse

    2009-03-01

    Full Text Available The isotopic composition of molecular hydrogen (H2 produced by photochemical oxidation of methane (CH4 and Volatile Organic Compounds (VOCs is a key quantity in the global isotope budget of (H2. The many individual reaction steps involved complicate its investigation. Here we present a simplified structure-activity approach to assign isotope effects to the individual elementary reaction steps in the oxidation sequence of CH4 and some other VOCs. The approach builds on and extends the work by Gerst and Quay (2001 and Feilberg et al. (2007b. The description is generalized and allows the application, in principle, also to other compounds. The idea is that the C-H and C-D bonds – seen as reactive sites – have similar relative reaction probabilities in isotopically substituted, but otherwise identical molecules. The limitations of this approach are discussed for the reaction CH4+Cl. The same approach is applied to VOCs, which are important precursors of H2 that need to be included into models. Unfortunately, quantitative information on VOC isotope effects and source isotope signatures is very limited and the isotope scheme at this time is limited to a strongly parameterized statistical approach, which neglects kinetic isotope effects. Using these concepts we implement a full hydrogen isotope scheme in a chemical box model and carry out a sensitivity study to identify those reaction steps and conditions that are most critical for the isotope composition of the final H2 product. The reaction scheme is directly applicable in global chemistry models, which can thus include the isotope pathway of H2 produced from CH4 and VOCs in a consistent way.

  5. Application of the Covalent Bond Classification Method for the Teaching of Inorganic Chemistry

    Science.gov (United States)

    Green, Malcolm L. H.; Parkin, Gerard

    2014-01-01

    The Covalent Bond Classification (CBC) method provides a means to classify covalent molecules according to the number and types of bonds that surround an atom of interest. This approach is based on an elementary molecular orbital analysis of the bonding involving the central atom (M), with the various interactions being classified according to the…

  6. Analysing the chromium-chromium multiple bond using multiconfigurational quantum chemistry

    OpenAIRE

    Brynda, Marcin; Gagliardi, Laura; Roos, Björn O.

    2009-01-01

    This Letter discusses the nature of the chemical bond between two chromium atoms in different di-chromium complexes with the metal atoms in different oxidation states. Starting with the Cr diatom, with its formally sextuple bond and oxidation number zero, we proceed to analyse the bonding in some Cr(I)–Cr(I) XCrCrX complexes with X varying from F, to Phenyl, and Aryl. The bond distance in these complexes varies over a large range: 1.65–1.83 Å and we suggest explanations for these variations. ...

  7. Demystifying Introductory Chemistry. Part 2: Bonding and Molecular Geometry Without Orbitals--the Electron Domain Model.

    Science.gov (United States)

    Gillespie, Ronald J.; And Others

    1996-01-01

    Presents an alternative approach to bonding and geometry--the electron domain model--which avoids some of the problems with the conventional approach. Discusses difficulties with the orbital model at the introductory level, electron spin and the Pauli exclusion principle, electron pair domains, nonequivalent domains, multiple bonds, and origins…

  8. Exploring the uranyl organometallic chemistry: from single to double uranium carbon bonds

    International Nuclear Information System (INIS)

    Uranyl organometallic complexes featuring uranium(VI) carbon single and double bonds have been obtained from uranyl UO2X2 precursors by avoiding reduction of the metal center. X-ray diffraction and density functional theory analyses of these complexes showed that the UC and UdC bonds are polarized toward the nucleophilic carbon. (authors)

  9. Bonds Between Metal Atoms: A New Mode of Transition Metal Chemistry.

    Science.gov (United States)

    Cotton, F. Albert; Chisholm, Malcolm H.

    1982-01-01

    Discusses polynuclear metal clusters (containing two or more metal atoms bonded to one another as well as to nonmetallic elements), including their formation and applications. Studies of bonds between metal atoms reveal superconductors, organic-reaction catalysts, and photosensitive complexes that may play a role in solar energy. (JN)

  10. Investigating Hydrogen Bonding in Phenol Using Infrared Spectroscopy and Computational Chemistry

    Science.gov (United States)

    Fedor, Anna M.; Toda, Megan J.

    2014-01-01

    The hydrogen bonding of phenol can be used as an introductory model for biological systems because of its structural similarities to tyrosine, a para-substituted phenol that is an amino acid essential to the synthesis of proteins. Phenol is able to form hydrogen bonds readily in solution, which makes it a suitable model for biological…

  11. Selection of Authentic Modelling Practices as Contexts for Chemistry Education

    Science.gov (United States)

    Prins, Gjalt T.; Bulte, Astrid M. W.; van Driel, Jan H.; Pilot, Albert

    2008-01-01

    In science education, students should come to understand the nature and significance of models. In the case of chemistry education it is argued that the present use of models is often not meaningful from the students' perspective. A strategy to overcome this problem is to use an authentic chemical modelling practice as a context for a curriculum…

  12. Promote Chemistry Learning with Dynamic Visualizations: Generation, Selection, and Critique

    OpenAIRE

    Zhang, Zhihui

    2011-01-01

    Dynamic visualizations can strengthen chemistry instruction by illustrating atomic level phenomena. Visualizations can help students add ideas about unseen phenomena involving atomic particles. They allow students to interact with phenomena that cannot be investigated in hands-on laboratories. Connecting dynamic, atomic representations with associated observable phenomena and symbolic representations has the potential to increase the coherence and comprehensiveness of student understanding. C...

  13. Metabolic Engineering to Develop a Pathway for the Selective Cleavage of Carbon-Nitrogen Bonds

    Energy Technology Data Exchange (ETDEWEB)

    John J. Kilbane II

    2005-10-01

    The objective of the project is to develop a biochemical pathway for the selective cleavage of C-N bonds in molecules found in petroleum. Specifically a novel biochemical pathway will be developed for the selective cleavage of C-N bonds in carbazole. The cleavage of the first C-N bond in carbazole is accomplished by the enzyme carbazole dioxygenase, that catalyzes the conversion of carbazole to 2-aminobiphenyl-2,3-diol. The genes encoding carbazole dioxygenase were cloned from Sphingomonas sp. GTIN11 and from Pseudomonas resinovorans CA10. The selective cleavage of the second C-N bond has been challenging, and efforts to overcome that challenge have been the focus of recent research in this project. Enrichment culture experiments succeeded in isolating bacterial cultures that can metabolize 2-aminobiphenyl, but no enzyme capable of selectively cleaving the C-N bond in 2-aminobiphenyl has been identified. Aniline is very similar to the structure of 2-aminobiphenyl and aniline dioxygenase catalyzes the conversion of aniline to catechol and ammonia. For the remainder of the project the emphasis of research will be to simultaneously express the genes for carbazole dioxygenase and for aniline dioxygenase in the same bacterial host and then to select for derivative cultures capable of using carbazole as the sole source of nitrogen.

  14. Selection of authentic modelling practices as contexts for chemistry education

    OpenAIRE

    Prins, Gjalt; Bulte, Astrid M.W.; Pilot, Albert; Driel, Jan van

    2008-01-01

    Abstract In science education, students should come to understand the nature and significance of models. In case of chemistry education it is argued that the present use of models is often not meaningful from the students? perspective. A strategy to overcome this problem is to use an authentic chemical modelling practice as a context for a curriculum unit. The theoretical framework for this strategy is activity theory rooted in sociocultural theories on learning. An authentic chemi...

  15. Extending Stannyl Anion Chemistry to the Actinides: Synthesis and Characterization of a Uranium-Tin Bond.

    Science.gov (United States)

    Winston, Matthew S; Batista, Enrique R; Yang, Ping; Tondreau, Aaron M; Boncella, James M

    2016-06-01

    We have synthesized a rare example of a uranium(IV) stannyl (κ(4)-N(CH2CH2NSi((i)Pr)3)3U(SnMe3), 1) via transmetalation with LiSnMe3. This complex has been characterized crystallographically and shown to have a U-Sn bond length of 3.3130(3) Å, substantially longer than the only other crystallographically observed U-Sn bond (3.166 Å). Computational studies suggest that the U-Sn bond in 1 is highly polarized, with significant charge transfer to the stannylate ligand. We briefly discuss plausible mechanistic scenarios for the formation of 1, which may be relevant to other transmetalation processes involving heavy main group atoms. Furthermore, we demonstrate the reducing ability of [SnMe3](-) in the absence of strongly donating ligands on U(IV). PMID:27219499

  16. Selective molecular recognition, C-H bond activation, and catalysis in nanoscale reaction vessels

    Energy Technology Data Exchange (ETDEWEB)

    Fiedler, Dorothea; Leung, Dennis H.; Raymond, Kenneth N.; Bergman, Robert G.

    2004-11-27

    Supramolecular chemistry represents a way to mimic enzyme reactivity by using specially designed container molecules. We have shown that a chiral self-assembled M{sub 4}L{sub 6} supramolecular tetrahedron can encapsulate a variety of cationic guests, with varying degrees of stereoselectivity. Reactive iridium guests can be encapsulated and the C-H bond activation of aldehydes occurs, with the host cavity controlling the ability of substrates to interact with the metal center based upon size and shape. In addition, the host container can act as a catalyst by itself. By restricting reaction space and preorganizing the substrates into reactive conformations, it accelerates the sigmatropic rearrangement of enammonium cations.

  17. Selective C–H bond activation of alkanes by gas-phase metal ions

    Czech Academy of Sciences Publication Activity Database

    Roithová, J.; Schröder, Detlef

    2010-01-01

    Roč. 110, č. 2 (2010), s. 1170-1211. ISSN 0009-2665 R&D Projects: GA AV ČR KJB400550704; GA ČR GA203/08/1487 Grant ostatní: European Research Council(XE) AdG HORIZOMS Institutional research plan: CEZ:AV0Z40550506 Keywords : alkanes * C-H bond activation * density functional theory * mass spectrometry * matrix isolation Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 33.033, year: 2010

  18. Localized removal of the Au-Si eutectic bonding layer for the selective release of microstructures

    Science.gov (United States)

    Gradin, Henrik; Braun, Stefan; Stemme, Göran; van der Wijngaart, Wouter

    2009-10-01

    This paper presents and investigates a novel technique for the footprint and thickness-independent selective release of Au-Si eutectically bonded microstructures through the localized removal of their eutectic bond interface. The technique is based on the electrochemical removal of the gold in the eutectic layer and the selectivity is provided by patterning the eutectic layer and by proper electrical connection or isolation of the areas to be etched or removed, respectively. The gold removal results in a porous silicon layer, acting similar to standard etch holes in a subsequent sacrificial release etching. The paper presents the principle and the design requirements of the technique. First test devices were fabricated and the method successfully demonstrated. Furthermore, the paper investigates the release mechanism and the effects of different gold layouts on both the eutectic bonding and the release procedure.

  19. Localized removal of the Au–Si eutectic bonding layer for the selective release of microstructures

    International Nuclear Information System (INIS)

    This paper presents and investigates a novel technique for the footprint and thickness-independent selective release of Au–Si eutectically bonded microstructures through the localized removal of their eutectic bond interface. The technique is based on the electrochemical removal of the gold in the eutectic layer and the selectivity is provided by patterning the eutectic layer and by proper electrical connection or isolation of the areas to be etched or removed, respectively. The gold removal results in a porous silicon layer, acting similar to standard etch holes in a subsequent sacrificial release etching. The paper presents the principle and the design requirements of the technique. First test devices were fabricated and the method successfully demonstrated. Furthermore, the paper investigates the release mechanism and the effects of different gold layouts on both the eutectic bonding and the release procedure

  20. NMR Determination of Hydrogen Bond Thermodynamics in a Simple Diamide: A Physical Chemistry Experiment

    Science.gov (United States)

    Morton, Janine G.; Joe, Candice L.; Stolla, Massiel C.; Koshland, Sophia R.; Londergan, Casey H.; Schofield, Mark H.

    2015-01-01

    Variable temperature NMR spectroscopy is used to determine the ?H° and ?S° of hydrogen bond formation in a simple diamide. In this two- or three-day experiment, students synthesize N,N'-dimethylmalonamide, dimethylsuccinamide, dimethylglutaramide, or dimethyladipamide from methylamine and the corresponding diester (typically in 50% recrystallized…

  1. Organometallic complex chemistry of plutonium and selected lanthanides

    International Nuclear Information System (INIS)

    This study deals with the metallo-organic chemistry of plutonium and also with that of some lanthanides. For plutonium, the conversion of Cs2PuCl6 with four equivalents KCp is investigated. In the series Sm, Gd, Dy and Er, compounds of the type Cp2LnX and the base adducts with acetonitrile are analysed. The ligand X passes the series Cl, N3, NCS and NCO. Both, the thermal and the vibrational spectroscopic behaviour is investigated. In addition, the effect of a changed ligand sphere on the optical spectrum is discussed. The adduct-free compounds are described by a ternary reaction not yet known from literature. For the first time, force constant calculations are carried out on metallo-organic compounds of lanthanides. With the exception of Cp2LnCl compounds, all compouds are presented for the first time in the framework of this study. (orig.)

  2. Selective loss of cysteine residues and disulphide bonds in a potato proteinase inhibitor II family.

    Directory of Open Access Journals (Sweden)

    Xiu-Qing Li

    Full Text Available Disulphide bonds between cysteine residues in proteins play a key role in protein folding, stability, and function. Loss of a disulphide bond is often associated with functional differentiation of the protein. The evolution of disulphide bonds is still actively debated; analysis of naturally occurring variants can promote understanding of the protein evolutionary process. One of the disulphide bond-containing protein families is the potato proteinase inhibitor II (PI-II, or Pin2, for short superfamily, which is found in most solanaceous plants and participates in plant development, stress response, and defence. Each PI-II domain contains eight cysteine residues (8C, and two similar PI-II domains form a functional protein that has eight disulphide bonds and two non-identical reaction centres. It is still unclear which patterns and processes affect cysteine residue loss in PI-II. Through cDNA sequencing and data mining, we found six natural variants missing cysteine residues involved in one or two disulphide bonds at the first reaction centre. We named these variants Pi7C and Pi6C for the proteins missing one or two pairs of cysteine residues, respectively. This PI-II-7C/6C family was found exclusively in potato. The missing cysteine residues were in bonding pairs but distant from one another at the nucleotide/protein sequence level. The non-synonymous/synonymous substitution (Ka/Ks ratio analysis suggested a positive evolutionary gene selection for Pi6C and various Pi7C. The selective deletion of the first reaction centre cysteine residues that are structure-level-paired but sequence-level-distant in PI-II illustrates the flexibility of PI-II domains and suggests the functionality of their transient gene versions during evolution.

  3. Aluminum germanides of the divalent lanthanoides Eu and Yb. Synthesis, structural chemistry and chemical bonding

    International Nuclear Information System (INIS)

    In the course of attempts to substitute Ca by Yb and Sr by Eu in known alkaline earth Al-germanides, the four new ternary compounds Eu3Al1.8Ge2.2, Eu3Al2Ge4, Yb2AlGe3, and Yb17Al8Ge19 have been synthesized from mixtures of the elements and their crystal structures determined by means of single-crystal X-ray data. The two europium compounds Eu3Al1.8Ge2.2 (Ta3B4 structure type, orthorhombic, space group Immm, a = 417.68(3), b = 470.70(3), c = 1897.2(2) pm, Z = 2, R1 = 0.0439) and Eu3Al2Ge4 (Sr3Al2Ge4 structure type, monoclinic, space group C2/m, a = 1235.9(6), b = 416.8(2), c = 878.4(4) pm, β = 110.615(13) , Z = 2, R1 = 0.0978) are isotypic with the corresponding strontium phases. After ionic decomposition, the layers [Al-2Ge-4]6- in Eu3Al2Ge4 with four-bonded Al and three-bonded Ge atoms can be interpreted as electron-precise Zintl anions. In contrast, the planar ribbons 1∞[Al2/2Ge2Al2/2] of condensed six-membered rings in Eu3Al1.8Ge2.2 exhibit considerably shorter Al-Ge bonds and an Al-Al bond length of only 251 pm. Yb2AlGe3 (orthorhombic, space group Pnma, a = 682.20(10), b = 417.87(9), c = 1813.9(3) pm, Z = 4, R1 = 0.0415) crystallizes with the Y2AlGe3 structure type. Folded [Al2Ge2] ladders, also found in Eu3Al2Ge4 and the known compound Yb7Al5Ge8, are connected by planar cis/trans chains of Ge atoms. The total density of states calculated within the FP-LAPW DFT band structure approach shows a distinct minimum at the Fermi level for the electron precise Zintl compound Eu3Al2Ge4, whereas π-bonding contributions are evident from the band structures of Eu3Al2Ge2 and Yb2AlGe3. In full accordance, the tDOS of both compounds exhibits no minimum at EF, small phase widths are possible for Eu3Al2Ge2 and related alkaline earth compounds, and Yb2AlGe3 is isotypic with several other more electron-rich LnIII compounds. The complicated structure of the new compound Yb17Al8Ge19 (tetragonal, space group P4/nmm, a = 1542.50(2), c = 788.285(8) pm, Z = 2, R1 = 0.0282) contains

  4. Catalytic C-H bond functionalisation chemistry: the case for quasi-heterogeneous catalysis.

    Science.gov (United States)

    Reay, Alan J; Fairlamb, Ian J S

    2015-11-25

    This feature article examines the potential of heterogeneous Pd species to mediate catalytic C-H bond functionalisation processes employing suitable substrates (e.g. aromatic/heteroaromatic compounds). A focus is placed on the reactivity of supported and non-supported Pd nanoparticle (PdNPs) catalysts, in addition to the re-appropriation of well-established heterogeneous Pd catalysts such as Pd/C. Where possible, reasonable comparisons are made between PdNPs and traditional 'homogeneous' Pd precatalyst sources (which form PdNPs). The involvement of higher order Pd species in traditional cross-coupling processes, such as Mizoroki-Heck, Sonogashira and Suzuki-Miyaura reactions, allows the exemplification of potential future topics for study in the area of catalytic C-H bond functionalisation processes. PMID:26439875

  5. METABOLIC ENGINEERING TO DEVELOP A PATHWAY FOR THE SELECTIVE CLEAVAGE OF CARBON-NITROGEN BONDS

    Energy Technology Data Exchange (ETDEWEB)

    John J. Kilbane II

    2004-10-01

    The objective of the project is to develop biochemical pathways for the selective cleavage of C-N bonds in molecules found in petroleum. The initial phase of the project was focused on the isolation or development of an enzyme capable of cleaving the C-N bond in aromatic amides, specifically 2-aminobiphenyl. The objective of the second phase of the research will be to construct a biochemical pathway for the selective removal of nitrogen from carbazole by combining the carA genes from Sphingomonas sp. GTIN11 with the gene(s) encoding an appropriate deaminase. The objective of the final phase of the project will be to develop derivative C-N bond cleaving enzymes that have broader substrate ranges and to demonstrate the use of such strains to selectively remove nitrogen from petroleum. During the first year of the project (October, 2002-September, 2003) enrichment culture experiments resulted in the isolation of microbial cultures that utilize aromatic amides as sole nitrogen sources, several amidase genes were cloned and were included in directed evolution experiments to obtain derivatives that can cleave C-N bonds in aromatic amides, and the carA genes from Sphingomonas sp. GTIN11, and Pseudomonas resinovorans CA10 were cloned in vectors capable of replicating in Escherichia coli. During the second year of the project (October, 2003-September, 2004) enrichment culture experiments succeeded in isolating a mixed bacterial culture that can utilize 2-aminobiphenyl as a sole nitrogen source, directed evolution experiments were focused on the aniline dioxygenase enzyme that is capable of deaminating aniline, and expression vectors were constructed to enable the expression of genes encoding C-N bond cleaving enzymes in Rhodococcus hosts. The construction of a new metabolic pathway to selectively remove nitrogen from carbazole and other molecules typically found in petroleum should lead to the development of a process to improve oil refinery efficiency by reducing the

  6. Strong Coupling between Nanofluidic Transport and Interfacial Chemistry: How Defect Reactivity Controls Liquid-Solid Friction through Hydrogen Bonding.

    Science.gov (United States)

    Joly, Laurent; Tocci, Gabriele; Merabia, Samy; Michaelides, Angelos

    2016-04-01

    Defects are inevitably present in nanofluidic systems, yet the role they play in nanofluidic transport remains poorly understood. Here, we report ab initio molecular dynamics (AIMD) simulations of the friction of liquid water on defective graphene and boron nitride sheets. We show that water dissociates at certain defects and that these "reactive" defects lead to much larger friction than the "nonreactive" defects at which water molecules remain intact. Furthermore, we find that friction is extremely sensitive to the chemical structure of reactive defects and to the number of hydrogen bonds they can partake in with the liquid. Finally, we discuss how the insight obtained from AIMD can be used to quantify the influence of defects on friction in nanofluidic devices for water treatment and sustainable energy harvesting. Overall, we provide new insight into the role of interfacial chemistry on nanofluidic transport in real, defective systems. PMID:27012818

  7. METABOLIC ENGINEERING TO DEVELOP A PATHWAY FOR THE SELECTIVE CLEAVAGE OF CARBON-NITROGEN BONDS

    Energy Technology Data Exchange (ETDEWEB)

    John J. Kilbane III

    2003-12-01

    The objective of the project is to develop biochemical pathways for the selective cleavage of C-N bonds in molecules found in petroleum. The initial phase of the project will focus on the isolation or development of an enzyme capable of cleaving the C-N bond in aromatic amides, specifically 2-aminobiphenyl. The objective of the second phase of the research will be to construct a biochemical pathway for the selective removal of nitrogen from carbazole by combining the carA genes from Sphingomonas sp. GTIN11 with the gene(s) encoding an appropriate amidase. The objective of the final phase of the project will be to develop derivative CN bond cleaving enzymes that have broader substrate ranges and to demonstrate the use of such strains to selectively remove nitrogen from petroleum. The project is on schedule and no major difficulties have been encountered. During the first year of the project (October, 2002-September, 2003) enrichment culture experiments have resulted in the isolation of promising cultures that may be capable of cleaving C-N bonds in aromatic amides, several amidase genes have been cloned and are currently undergoing directed evolution to obtain derivatives that can cleave C-N bonds in aromatic amides, and the carA genes from Sphingomonas sp. GTIN11, and Pseudomonas resinovorans CA10 were cloned in vectors capable of replicating in Escherichia coli. Future research will address expression of these genes in Rhodococcus erythropolis. Enrichment culture experiments and directed evolution experiments continue to be a main focus of research activity and further work is required to obtain an appropriate amidase that will selectively cleave C-N bonds in aromatic substrates. Once an appropriate amidase gene is obtained it must be combined with genes encoding an enzyme capable of converting carbazole to 2'aminobiphenyl-2,3-diol: specifically carA genes. The carA genes from two sources have been cloned and are ready for construction of C-N bond cleavage

  8. Site selective syntheses of [(3)H]omeprazole using hydrogen isotope exchange chemistry.

    Science.gov (United States)

    Pollack, Scott R; Schenk, David J

    2015-01-01

    Omeprazole (Prilosec®) is a selective and irreversible proton pump inhibitor used to treat various medical conditions related to the production of excess stomach acids. It functions by suppressing secretion of those acids. Radiolabeled compounds are commonly employed in the drug discovery and development process to support efforts including library screening, target identification, receptor binding, assay development and validation and safety assessment. Herein, we describe synthetic approaches to the controlled and selective labeling of omeprazole with tritium via hydrogen isotope exchange chemistry. The chemistry may also be used to prepare tritium labeled esomeprazole (Nexium®), the active pure (S)-enantiomer of omeprazole. PMID:26380956

  9. Engineering novel cell surface chemistry for selective tumor cell targeting

    Energy Technology Data Exchange (ETDEWEB)

    Bertozzi, C.R. [Univ. of California, Berkeley, CA (United States)]|[Lawrence Berkeley National Lab., CA (United States)

    1997-12-31

    A common feature of many different cancers is the high expression level of the two monosaccharides sialic acid and fucose within the context of cell-surface associated glycoconjugates. A correlation has been made between hypersialylation and/or hyperfucosylation and the highly metastatic phenotype. Thus, a targeting strategy based on sialic acid or fucose expression would be a powerful tool for the development of new cancer cell-selective therapies and diagnostic agents. We have discovered that ketone groups can be incorporated metabolically into cell-surface associated sialic acids. The ketone is can be covalently ligated with hydrazide functionalized proteins or small molecules under physiological conditions. Thus, we have discovered a mechanism to selectively target hydrazide conjugates to highly sialylated cells such as cancer cells. Applications of this technology to the generation of novel cancer cell-selective toxins and MRI contrast reagents will be discussed, in addition to progress towards the use of cell surface fucose residues as vehicles for ketone expression.

  10. Implementation and Evaluation of Web-Based Learning Activities on Bonding and the Structure of Matter for 10-th Grade Chemistry

    Science.gov (United States)

    Frailich, Marcel

    This study deals with the development, implementation, and evaluation of web-based activities associated with the topic of chemical bonding , as taught in 10th grade chemistry. A website was developed entitled: "Chemistry and the Chemical Industry in the Service of Mankind", its URL is: http://stwww.weizmann.ac.il/g-chem/learnchem (Kesner, Frailich, & Hofstein, 2003). The main goal of this study was to assess the educational effectiveness of website activities dealing with the chemical bonding concept. These activities include visualization tools, as well as topics relevant to daily life and industrial applications. The study investigated the effectiveness of a web-based learning environment regarding the understanding of chemical bonding concepts, students' perceptions of the classroom learning environment, their attitudes regarding the relevance of learning chemistry to everyday life, and their interest in chemistry studies. As mentioned before, in the present study we focused on activities (from the website), all of which deal with chemical bonding concept. The following are the reasons for the decision to focus on this topic: (1) Chemical bonding is a key concept that is taught in 10th grade chemistry in high school. It provides the basis for many other chemistry topics that are taught later, and (2) Chemical bonding is a difficult for students using existing tools (e. g., static models in books, ball-and- stick models), which are insufficient to demonstrate the abstract nature phenomena associated with this topic. The four activities developed for this study are (1) models of the atomic structure, (2) metals -- structure and properties, (3) ionic substances in everyday life and in industry, and (4) molecular substances -- structure, properties, and uses. The study analyzed both quantitative and qualitative research. The quantitative tools of the study included: A Semantic Differential questionnaire and a Chemistry Classroom Web-Based Learning Environment

  11. Bioinformatics in crosslinking chemistry of collagen with selective cross linkers

    Directory of Open Access Journals (Sweden)

    Gopal Ramesh

    2011-10-01

    Full Text Available Abstract Background Identifying the molecular interactions using bioinformatics tools before venturing into wet lab studies saves the energy and time considerably. The present study summarizes, molecular interactions and binding energy calculations made for major structural protein, collagen of Type I and Type III with the chosen cross-linkers, namely, coenzyme Q10, dopaquinone, embelin, embelin complex-1 & 2, idebenone, 5-O-methyl embelin, potassium embelate and vilangin. Results Molecular descriptive analyses suggest, dopaquinone, embelin, idebenone, 5-O-methyl embelin, and potassium embelate display nil violations. And results of docking analyses revealed, best affinity for Type I (- 4.74 kcal/mol and type III (-4.94 kcal/mol collagen was with dopaquinone. Conclusions Among the selected cross-linkers, dopaquinone, embelin, potassium embelate and 5-O-methyl embelin were the suitable cross-linkers for both Type I and Type III collagen and stabilizes the collagen at the expected level.

  12. GREEN CHEMISTRY. Shape-selective zeolite catalysis for bioplastics production.

    Science.gov (United States)

    Dusselier, Michiel; Van Wouwe, Pieter; Dewaele, Annelies; Jacobs, Pierre A; Sels, Bert F

    2015-07-01

    Biodegradable and renewable polymers, such as polylactic acid, are benign alternatives for petrochemical-based plastics. Current production of polylactic acid via its key building block lactide, the cyclic dimer of lactic acid, is inefficient in terms of energy, time, and feedstock use. We present a direct zeolite-based catalytic process, which converts lactic acid into lactide. The shape-selective properties of zeolites are essential to attain record lactide yields, outperforming those of the current multistep process by avoiding both racemization and side-product formation. The highly productive process is strengthened by facile recovery and practical reactivation of the catalyst, which remains structurally fit during at least six consecutive reactions, and by the ease of solvent and side-product recycling. PMID:26138977

  13. Is There a Need to Discuss Atomic Orbital Overlap When Teaching Hydrogen-Halide Bond Strength and Acidity Trends in Organic Chemistry?

    Science.gov (United States)

    Devarajan, Deepa; Gustafson, Samantha J.; Bickelhaupt, F. Matthias; Ess, Daniel H.

    2015-01-01

    Undergraduate organic chemistry textbooks and Internet websites use a variety of approaches for presenting and explaining the impact of halogen atom size on trends in bond strengths and/or acidity of hydrogen halides. In particular, several textbooks and Internet websites explain these trends by invoking decreasing orbital overlap between the…

  14. Driving Forces for Covalent Assembly of Porphyrins by Selective C-H Bond Activation and Intermolecular Coupling on a Copper Surface.

    Science.gov (United States)

    Floris, Andrea; Haq, Sam; In't Veld, Mendel; Amabilino, David B; Raval, Rasmita; Kantorovich, Lev

    2016-05-11

    Recent synthesis of covalent organic assemblies at surfaces has opened the promise of producing robust nanostructures for functional interfaces. To uncover how this new chemistry works at surfaces and understand the underlying mechanisms that control bond-breaking and bond-making processes at specific positions of the participating molecules, we study here the coupling reaction of tetra(mesityl)porphyrin molecules, which creates covalently connected networks on the Cu(110) surface by utilizing the 4-methyl groups as unique connection points. Using scanning tunneling microscopy (STM), state-of-the-art density functional theory (DFT), and Nudged Elastic Band (NEB) calculations, we show that the unique directionality of the covalent bonding is found to stem from a chain of highly selective C-H activation and dehydrogenation processes, followed by specific intermolecular C-C coupling reactions that are facilitated by the surface, by steric constraints, and by anisotropic molecular diffusion. These insights provide the first steps toward developing synthetic rules for complex two-dimensional covalent organic chemistry that can be enacted directly at a surface to deliver specific macromolecular structures designed for specific functions. PMID:27097295

  15. Chemistry

    International Nuclear Information System (INIS)

    The chemical research and development efforts related to the design and ultimate operation of molten-salt breeder reactor systems are concentrated on fuel- and coolant-salt chemistry, including the development of analytical methods for use in these systems. The chemistry of tellurium in fuel salt is being studied to help elucidate the role of this element in the intergranular cracking of Hastelloy N. Studies were continued of the effect of oxygen-containing species on the equilibrium between dissolved UF3 and dissolved UF4, and, in some cases, between the dissolved uranium fluorides and graphite, and the UC2. Several aspects of coolant-salt chemistry are under investigation. Hydroxy and oxy compounds that could be formed in molten NaBF4 are being synthesized and characterized. Studies of the chemistry of chromium (III) compounds in fluoroborate melts were continued as part of a systematic investigation of the corrosion of structural alloys by coolant salt. An in-line voltammetric method for determining U4+/U3+ ratios in fuel salt was tested in a forced-convection loop over a six-month period. (LK)

  16. Chemistry in microtime selected writings on flash photolysis, free radicals, and the excited state

    CERN Document Server

    Porter, Sir George

    1997-01-01

    This volume contains a selection of the pioneering papers by Nobel Laureate George Porter. It outlines his work on fast reactions, occurring in times from milliseconds to femtoseconds, in photochemistry, photosynthesis and solar energy, and includes the papers which led to the award of the Nobel Prize in Chemistry in 1967 for his work on flash photolysis. Lord Porter, President of the Royal Society from 1985 to 1990, is Chairman of the Centre for Photomolecular Sciences, Imperial College, and Emeritus Professor of Chemistry of the Royal Institution of Great Britain.This book is divided into 11

  17. Americium(3) coordination chemistry: An unexplored diversity of structure and bonding

    Energy Technology Data Exchange (ETDEWEB)

    Fedosseev, A.M.; Grigoriev, M.S.; Budantseva, N.A. [A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Moscow (Russian Federation); Guillaumont, D.; Den Auwer, Ch.; Moisy, Ph. [CEA Marcoule, Nuclear Energy Division, RadioChemistry and Processes Department, 30 (France); Le Naour, C.; Simoni, E. [CNRS, University Paris-11 Orsay, IPN, 91 - Orsay (France)

    2010-06-15

    The comparison of the physicochemical behavior of the actinides with that of the lanthanides can be justified by the analogy of their electronic structure, as each of the series is made up of elements corresponding to the filling of a given (n)f atomic shell. However relatively few points of comparison are available, given the lack of available structure for trans-plutonium(III) elements and the additional difficulty of stabilizing coordination complexes of uranium(III) to plutonium(III). This contribution is a focal point of trans-plutonium(III) chemistry and, more specifically, of some americium compounds that have been recently synthesized, all related with hard acid oxygen donor ligands that may be involved in the reprocessing chain of nuclear fuel. After a brief review of the solid hydrates and aquo species for the lanthanide and actinide families, we discuss two types of ligands that have in common three carboxylic groups, namely the amino-tri-acetic acid and the citric acid anions. The additional roles of the nitrogen atom for the first one and of the hydroxy function for the second one are discussed. Accordingly, five new complexes with either americium or lanthanides elements are described: [Co(NH{sub 3}){sub 6}][M(NTA){sub 2}(H{sub 2}O)].8H{sub 2}O with M Nd, Yb and Am, and [Co(NH{sub 3}){sub 6}]{sub 2}K[M{sub 3}(Cit){sub 4}(H{sub 2}O){sub 3}].18H{sub 2}O with Nd and Am cations. In all cases the americium complexes are isostructural with their lanthanide equivalents. (authors)

  18. Americium(3) coordination chemistry: An unexplored diversity of structure and bonding

    International Nuclear Information System (INIS)

    The comparison of the physicochemical behavior of the actinides with that of the lanthanides can be justified by the analogy of their electronic structure, as each of the series is made up of elements corresponding to the filling of a given (n)f atomic shell. However relatively few points of comparison are available, given the lack of available structure for trans-plutonium(III) elements and the additional difficulty of stabilizing coordination complexes of uranium(III) to plutonium(III). This contribution is a focal point of trans-plutonium(III) chemistry and, more specifically, of some americium compounds that have been recently synthesized, all related with hard acid oxygen donor ligands that may be involved in the reprocessing chain of nuclear fuel. After a brief review of the solid hydrates and aquo species for the lanthanide and actinide families, we discuss two types of ligands that have in common three carboxylic groups, namely the amino-tri-acetic acid and the citric acid anions. The additional roles of the nitrogen atom for the first one and of the hydroxy function for the second one are discussed. Accordingly, five new complexes with either americium or lanthanides elements are described: [Co(NH3)6][M(NTA)2(H2O)].8H2O with M Nd, Yb and Am, and [Co(NH3)6]2K[M3(Cit)4(H2O)3].18H2O with Nd and Am cations. In all cases the americium complexes are isostructural with their lanthanide equivalents. (authors)

  19. A permanently porous single molecule H-bonded organic framework for selective CO2 capture.

    Science.gov (United States)

    Nandi, Shyamapada; Chakraborty, Debanjan; Vaidhyanathan, Ramanathan

    2016-05-26

    Permanent porosity has been realized in a hydrogen bonded framework formed by a single tripodal tricarboxylic acid molecule. The presence of three phenyl rings linked to a flexible sp(3) nitrogen centre renders a near-propeller shape to the molecule generating an unusual 'non-planar' 3-D framework formed by highly directional planar -COOHHOOC- hydrogen bonds, propagating in all three directions. The material shows exceptional hydrolytic, acidic and thermal stability and has a surface area of 1025 m(2) g(-1). Importantly, it shows preferential adsorption of CO2 over N2 with very high selectivities (350 : 1@1 bar, 303 K). DFT modeling shows the presence of stable T-shaped CO2CO2 dimers within the channels suggesting favorable co-operativity between them. PMID:27174692

  20. Controllable synthesis of silver and silver sulfide nanocrystals via selective cleavage of chemical bonds

    International Nuclear Information System (INIS)

    A one-step colloidal process has been adopted to prepare silver (Ag) and silver sulfide (Ag2S) nanocrystals, thus avoiding presynthesis of an organometallic precursor and the injection of a toxic phosphine agent. During the reaction, a layered intermediate compound is first formed, which then acts as a precursor, decomposing into the nanocrystals. The composition of the as-obtained products can be controlled by selective cleavage of S–C bonds or Ag–S bonds. Pure Ag2S nanocrystals can be obtained by directly heating silver acetate (Ag(OAc)) and n-dodecanethiol (DDT) at 200 ° C without any surfactant, and pure Ag nanocrystals can be synthesized successfully if the reaction temperature is reduced to 190 ° C and the amount of DDT is decreased to 1 ml in the presence of a non-coordinating organic solvent (1-octadecene, ODE). Otherwise, the mixture of Ag and Ag2S is obtained by directly heating Ag(OAc) in DDT by increasing the reaction temperature or in a mixture of DDT and ODE at 200 ° C. The formation mechanism has been discussed in detail in terms of selective S–C and Ag–S bond dissociation due to the nucleophilic attack of DDT and the lower bonding energy of Ag–S. Interestingly, some products can easily self-assemble into two- or three-dimensional (2D or 3D) highly ordered superlattice structures on a copper grid without any additional steps. The excess DDT plays a key role in the superlattice structure due to the bundling and interdigitation of the thiolate molecules adsorbed on the as-obtained nanocrystals. (paper)

  1. Copper(I)-catalyzed carbon-halogen bond-selective boryl substitution of alkyl halides bearing terminal alkene moieties

    OpenAIRE

    Iwamoto, Hiroaki; Kubota, Koji; Yamamoto, Eiji; Ito, Hajime

    2015-01-01

    The selective boryl substitution of alkyl halides bearing terminal C=C double bonds has been achieved using a copper(I)/tricyclohexylphosphine or copper(I)/o-diphenylphosphinophenol catalyst. This reaction represents a useful complementary approach to conventional procedures for the hydroboration of C=C double bonds or the borylative cyclization of alkyl halides bearing terminal alkenes.

  2. Chemistry

    International Nuclear Information System (INIS)

    Research progress is reported in programs on fuel-salt chemistry, properties of compounds in the Li--Te system, Te spectroscopy UF4--H equilibria, porous electrode studies of molten salts, fuel salt-coolant salt reactions, thermodynamic properties of transition-metal fluorides, and properties of sodium fluoroborate. Developmental work on analytical methods is summarized including in-line analysis of molten MSBR fuel, analysis of coolant-salts for tritium, analysis of molten LiF--BeF2--ThF4 for Fe and analysis of LiF--BeF--ThF4 for Te

  3. Bond and fracture strength of metal-ceramic restorations formed by selective laser sintering

    OpenAIRE

    Bae, Eun-Jeong; Kim, Ji-Hwan; Kim, Woong-Chul; Kim, Hae-Young

    2014-01-01

    PURPOSE The purpose of this study was to compare the fracture strength of the metal and the bond strength in metal-ceramic restorations produced by selective laser sintering (SLS) and by conventional casting (CAST). MATERIALS AND METHODS Non-precious alloy (StarLoy C, DeguDent, Hanau, Germany) was used in CAST group and metal powder (SP2, EOS GmbH, Munich, Germany) in SLS group. Metal specimens in the form of sheets (25.0 × 3.0 × 0.5 mm) were produced in accordance with ISO 9693:1999 standard...

  4. Design and synthesis of multidentate ligands via metal promoted C-N bond formation processes and their coordination chemistry

    Indian Academy of Sciences (India)

    Kunal K Kamar; Amrita Saha; Sreebrata Goswami

    2002-08-01

    This presentation reports some novel examples of organic ring amination reactions via metal mediation. The organic transformations are highly regioselective and can be controlled by the proper selection of the mediator complex. The two isomeric organic ligands viz. HL1 and HL2 were isolated in their pure states by the removal of the metal ions. These were fully characterized. The ligand HL1 has low , 8.5. Upon deprotonation, it behaves as a potential bis chelating N,N,N-donors. The coordination chemistry of the HL1 ligand involving some 3-metal ions is described. Two unusual low-spin complexes of manganese(II) and iron(III) are reported. The ferric complex displayed a rhombic EPR while, the corresponding manganese compound showed a complex pattern due to hyperfine coupling. All the complexes displayed large number of redox responses. A brief mention about the future projection of this work is noted.

  5. Complex chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Bong Gon; Kim, Jae Sang; Kim, Jin Eun; Lee, Boo Yeon

    2006-06-15

    This book introduces complex chemistry with ten chapters, which include development of complex chemistry on history coordination theory and Warner's coordination theory and new development of complex chemistry, nomenclature on complex with conception and define, chemical formula on coordination compound, symbol of stereochemistry, stereo structure and isomerism, electron structure and bond theory on complex, structure of complex like NMR and XAFS, balance and reaction on solution, an organo-metallic chemistry, biology inorganic chemistry, material chemistry of complex, design of complex and calculation chemistry.

  6. Complex chemistry

    International Nuclear Information System (INIS)

    This book introduces complex chemistry with ten chapters, which include development of complex chemistry on history coordination theory and Warner's coordination theory and new development of complex chemistry, nomenclature on complex with conception and define, chemical formula on coordination compound, symbol of stereochemistry, stereo structure and isomerism, electron structure and bond theory on complex, structure of complex like NMR and XAFS, balance and reaction on solution, an organo-metallic chemistry, biology inorganic chemistry, material chemistry of complex, design of complex and calculation chemistry.

  7. Chemistry of selected cyclic P(III) compounds possessing a P-Cl bond

    Indian Academy of Sciences (India)

    K C Kumara Swamy; Sudha Kumaraswamy; Praveen Kommana; N Satish Kumar; K Senthil Kumar

    2002-08-01

    The compounds [CH2(6--Bu-4-Me-C6H2O)2]PCl (1), (OCH2CMe2CH2O)-PCl (2), and [ClPN(-Bu)]2 (3) have been utilized as precursors in the synthesis of (i) new pentacoordinate phosphorus compounds [e.g. CH2(6--Bu-4-Me-C6H2O)2 P(NRR')(O2C6Cl4), CH2(6--Bu-4-Me-C6H2O)2PX[OC(O--Pr)N=N(C(O)O--Pr)], (ii) cyclic phosphates and their complexes [e.g. {imidazolium}+{CH2(6--Bu-4-Me-C6H2O)2PO2}-.MeOH], (iii) new cycloaddition products [e.g. {CH2(6--Bu-4-Me-C6H2O)2}P{C(CO2Me)C(CO2Me)C(O)N}, (iv) macrocyclic compounds [e.g. {[(-BuN)P]2[-OCH2CMe2CH2O-]}2] and (v) phosphonates [e.g. (OCH2CMe2CH2O)P (O)CH2C(CN)=CHC5H4FeC5H5]. The synthetic and structural aspects of these new products are discussed.

  8. Spectators Control Selectivity in Surface Chemistry: Acrolein Partial Hydrogenation Over Pd.

    Science.gov (United States)

    Dostert, Karl-Heinz; O'Brien, Casey P; Ivars-Barceló, Francisco; Schauermann, Swetlana; Freund, Hans-Joachim

    2015-10-28

    We present a mechanistic study on selective hydrogenation of acrolein over model Pd surfaces--both single crystal Pd(111) and Pd nanoparticles supported on a model oxide support. We show for the first time that selective hydrogenation of the C═O bond in acrolein to form an unsaturated alcohol is possible over Pd(111) with nearly 100% selectivity. However, this process requires a very distinct modification of the Pd(111) surface with an overlayer of oxopropyl spectator species that are formed from acrolein during the initial stages of reaction and turn the metal surface selective toward propenol formation. By applying pulsed multimolecular beam experiments and in situ infrared reflection-absorption spectroscopy, we identified the chemical nature of the spectator and the reactive surface intermediate (propenoxy species) and experimentally followed the simultaneous evolution of the reactive intermediate on the surface and formation of the product in the gas phase. PMID:26481220

  9. Chemistry

    International Nuclear Information System (INIS)

    Research and development activities dealing with the chemical problems related to design and ultimate operation of molten-salt reactor systems are described. An experimental test stand was constructed to expose metallurgical test specimens to Te2 vapor at defined temperatures and deposition rates. To better define the chemistry of fluoroborate coolant, several aspects are being investigated. The behavior of hydroxy and oxy compounds in molten NaBF4 is being investigated to define reactions and compounds that may be involved in corrosion and/or could be involved in methods for trapping tritium. Two corrosion products of Hastelloy N, Na3CrF6 and Na5Cr3F14, were identified from fluoroborate systems. The evaluation of fluoroborate and alternate coolants continued. Research on the behavior of hydrogen and its isotopes is summarized. The solubilities of hydrogen, deuterium, and helium in Li2BeF4 are very low. The sorption of tritium on graphite was found to be significant (a few milligrams of tritium per kilogram of graphite), possibly providing a means of sequestering a portion of the tritium produced. Development of analytical methods continued with emphasis on voltammetric and spectrophotometric techniques for the in-line analysis of corrosion products such as Fe2+ and Cr3+ and the determination of the U3+/U4+ ratio in MSBR fuel salt. Similar studies were conducted with the NaBF4--NaF coolant salt. Information developed during the previous operation of the CSTF has been assessed and used to formulate plans for evaluation of in-line analytical methods in future CSTF operations. Electroanalytical and spectrophotometric research suggests that an electroactive protonic species is present in molten NaBF4--NaF, and that this species rapidly equilibrates with a volatile proton-containing species. Data obtained from the CSTF indicated that tritium was concentrated in the volatile species. (JGB)

  10. Photoisomerization selectivity in conjugated π-bond systems through local microenvironment

    Science.gov (United States)

    Virshup, Aaron; Martinez, Todd

    2007-03-01

    Photoisomerization represents one of the simplest means to convert light energy into mechanical motion on the molecular scale. Theoretical models of photobiology often require description of not only a small photochemically active chromophore, but also the effects of the much larger solvent or protein environment containing the chromophore. We have recently developed a program for carrying out excited state QM/MM studies of photodynamics using ab initio quantum chemistry techniques for the QM region, and modeling the time evolution of the system with the Full Multiple Spawning method for molecular dynamics. With this method, we show how local charge environments can be used to manipulate and enhance the photoisomer selectivity of small conjugated molecules.

  11. Metal Nanoparticles Catalyzed Selective Carbon-Carbon Bond Activation in the Liquid Phase.

    Science.gov (United States)

    Ye, Rong; Yuan, Bing; Zhao, Jie; Ralston, Walter T; Wu, Chung-Yeh; Unel Barin, Ebru; Toste, F Dean; Somorjai, Gabor A

    2016-07-13

    Understanding the C-C bond activation mechanism is essential for developing the selective production of hydrocarbons in the petroleum industry and for selective polymer decomposition. In this work, ring-opening reactions of cyclopropane derivatives under hydrogen catalyzed by metal nanoparticles (NPs) in the liquid phase were studied. 40-atom rhodium (Rh) NPs, encapsulated by dendrimer molecules and supported in mesoporous silica, catalyzed the ring opening of cyclopropylbenzene at room temperature under hydrogen in benzene, and the turnover frequency (TOF) was higher than other metals or the Rh homogeneous catalyst counterparts. Comparison of reactants with various substitution groups showed that electron donation on the three-membered ring boosted the TOF of ring opening. The linear products formed with 100% selectivity for ring opening of all reactants catalyzed by the Rh NP. Surface Rh(0) acted as the active site in the NP. The capping agent played an important role in the ring-opening reaction kinetics. Larger particle size tended to show higher TOF and smaller reaction activation energy for Rh NPs encapsulated in either dendrimer or poly(vinylpyrrolidone). The generation/size of dendrimer and surface group also affected the reaction rate and activation energy. PMID:27322570

  12. Size-selective fractionation and visual mapping of allergen protein chemistry in Arachis hypogaea.

    Science.gov (United States)

    Hebling, Christine M; Ross, Mark M; Callahan, John H; McFarland, Melinda A

    2012-11-01

    Peanuts (Arachis hypogaea) in addition to milk, eggs, fish, crustaceans, wheat, tree nuts, and soybean are commonly referred to as the "big eight" foods that contribute to the majority of food allergies worldwide. Despite the severity of allergic reactions and growing prevalence in children and adults, there is no cure for peanut allergy, leaving avoidance as the primary mode of treatment. To improve analytical methods for peanut allergen detection, researchers must overcome obstacles involved in handling complex food matrices while attempting to decipher the chemistry that underlies allergen protein interactions. To address such challenges, we conducted a global proteome characterization of raw peanuts using a sophisticated GELFrEE-PAGE-LC-MS/MS platform consisting of gel-based protein fractionation followed by mass spectrometric identification. The in-solution mass-selective protein fractionation: (1) enhances the number of unique peptide identifications, (2) provides a visual map of protein isoforms, and (3) aids in the identification of disulfide-linked protein complexes. GELFrEE-PAGE-LC-MS/MS not only overcomes many of the challenges involved in the study of plant proteomics, but enriches the understanding of peanut protein chemistry, which is typically unattainable in a traditional bottom-up proteomic analysis. A global understanding of protein chemistry in Arachis hypogaea ultimately will aid the development of improved methods for allergen detection in food. PMID:23020697

  13. The Novel Selective Reduction of the C-C Triple Bond

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    A novel reduction system is reported here in which the compounds with terminal C-C triple bond and disubstituted C-C triple bond react with NaBH4/Pd(PPh3)4 in a base condition and only terminal C-C triple bond is reduced.

  14. Conceptual chemistry approach towards the support effect in supported vanadium oxides : Valence bond calculations on the ionicity of vanadium catalysts

    NARCIS (Netherlands)

    Fievez, Tim; De Proft, Frank; Geerlings, Paul; Weckhuysen, Bert M.; Havenith, Remco W. A.

    2011-01-01

    The concept of bond ionicity, obtained via a valence bond analysis, is invoked in the interpretation of the catalytic activity of supported vanadium oxides, in analogy with previous work conducted within the framework of conceptual DFT. For a set of model clusters representing the vanadium oxide sup

  15. ASSESSMENT OF SELECTED PHYSICAL AND MECHANICAL PROPERTIES OF CEMENT BONDED BOARD PRODUCED FROM Gliricidia sepium (AGUNMANIYE

    Directory of Open Access Journals (Sweden)

    John Tosin ALADEJANA

    2016-03-01

    Full Text Available Selected physical and mechanical properties of cement bonded board produced from Gliricidia sepium were assessed. The following board properties were evaluated, water absorption, thickness swelling, water absorption and thickness swelling following accelerated aging, modulus of rupture and modulus of elasticity. The Board formation was based on cement: wood ratio 1:1, 2:1 and 3:1, board densities of 800, 900 and 1000kg/m3 on dry weight basis. The quantity of cement, particles, and water for the production of each board was weighed, mixed separately and very well in order to prevent the formation of particles lumps. Blended mixture was transferred and formed inside a nominal mould dimension of 650mm in length, 650mm in width and 13mm thickness on a caul plate that was covered with polythene sheet before plywood was laid at the top of the mat. The mean value for water absorption and thickness swelling ranged from 3.06 to 6.99% and 1.40 to 7.51%, respectively. Following accelerated aging test, water absorption and thickness swelling ranged from 3.41 to 8.12% and 3.46 to 15.58%, respectively. The mean values for Modulus of rupture (MOR ranged from 0.76 to 10.22N/mm2 while the mean values for Modulus of Elasticity (MOE of the experimental boards produced ranged from 1800.77 to 5220.60N/mm2 . Water absorption and thickness swelling decreased with increase in board density and cement: wood ratio. After the board had been subjected to accelerated aging, water absorption and thickness swelling of the boards decreased with increase in density and cement: wood ratio. Modulus of rupture and modulus of elasticity increased with increase in board density and cement: wood ratio. Gliricidia sepium was found suitable for the production of cement bonded board.

  16. Enhanced Control of PWR Primary Coolant Water Chemistry Using Selective Separation Systems for Recovery and Recycle of Enriched Boric Acid

    Energy Technology Data Exchange (ETDEWEB)

    Ken Czerwinski; Charels Yeamans; Don Olander; Kenneth Raymond; Norman Schroeder; Thomas Robison; Bryan Carlson; Barbara Smit; Pat Robinson

    2006-02-28

    The objective of this project is to develop systems that will allow for increased nuclear energy production through the use of enriched fuels. The developed systems will allow for the efficient and selective recover of selected isotopes that are additives to power water reactors' primary coolant chemistry for suppression of corrosion attack on reactor materials.

  17. The mechanical bond on carbon nanotubes: diameter-selective functionalization and effects on physical properties

    Science.gov (United States)

    Martínez-Periñán, Emiliano; de Juan, Alberto; Pouillon, Yann; Schierl, Christoph; Strauss, Volker; Martín, Nazario; Rubio, Ángel; Guldi, Dirk M.; Lorenzo, Encarnación; Pérez, Emilio M.

    2016-04-01

    We describe the functionalization of SWNTs enriched in (6,5) chirality with electron donating macrocycles to yield rotaxane-type mechanically interlocked carbon nanotubes (MINTs). Investigations by means of electron microscopy and control experiments corroborated the interlocked nature of the MINTs. A comprehensive characterization of the MINTs through UV-vis-NIR, Raman, fluorescence, transient absorption spectroscopy, cyclic voltammetry, and chronoamperometry was carried out. Analyses of the spectroscopic data reveal that the MINT-forming reaction proceeds with diameter selectivity, favoring functionalization of (6,5) SWNTs rather than larger (7,6) SWNTs. In the ground state, we found a lack of significant charge-transfer interactions between the electron donor exTTF and the SWNTs. Upon photoexcitation, efficient charge-transfer between the electron donating exTTF macrocycles and SWNTs was demonstrated. As a complement, we established significantly different charge-transfer rate constants and diffusion coefficients for MINTs and the supramolecular models, which confirms the fundamentally different type of interactions between exTTF and SWNTs in the presence or absence of the mechanical bond. Molecular mechanics and DFT calculations support the experimental findings.We describe the functionalization of SWNTs enriched in (6,5) chirality with electron donating macrocycles to yield rotaxane-type mechanically interlocked carbon nanotubes (MINTs). Investigations by means of electron microscopy and control experiments corroborated the interlocked nature of the MINTs. A comprehensive characterization of the MINTs through UV-vis-NIR, Raman, fluorescence, transient absorption spectroscopy, cyclic voltammetry, and chronoamperometry was carried out. Analyses of the spectroscopic data reveal that the MINT-forming reaction proceeds with diameter selectivity, favoring functionalization of (6,5) SWNTs rather than larger (7,6) SWNTs. In the ground state, we found a lack of

  18. Metal free and selective activation of one C-F bond in a bound CF3 group.

    OpenAIRE

    Azhakar, Ramachandran; Roesky, Herbert W.; Wolf, Hilke; Stalke, Dietmar

    2013-01-01

    The first metal free selective C-F bond activation of a CF(3) group was observed with N-heterocyclic silylenes [PhC(NtBu)(2)SiCl] (1) and [CH{(C=CH(2))(CMe)(2,6-iPr(2)C(6)H(3)N)(2)}Si] (2) with PhN=C(CF(3))(2). The reaction proceeds in a 1 : 1 molar ratio to yield the mono C-F bond activated products 3 and 4 with each containing a CF(2) group. Both the reactions proceed through an unprecedented selective activation of one of the C-F bonds rather than forming the [1+2] cycloaddition product co...

  19. Selected legal aspects of mortgage bonds in European law, with emphasis on German legislation

    OpenAIRE

    Sieradzki, Jakub

    2011-01-01

    The article discusses the German legislation in relation to mortgage bonds, and also briefly describes the state of European legislation in this regard. There are also themes from other countries in which such mortgage bonds are used. The publication consists of 5 sections, where the first is the introduction and the last contains the conclusions. The main part of the article is part 4, where the author briefly discusses the German Law on Mortgage Bonds. Parts 2 and 3 are the legal background...

  20. Quantum dynamics of polyatomic dissociative chemisorption on transition metal surfaces: mode specificity and bond selectivity.

    Science.gov (United States)

    Jiang, Bin; Yang, Minghui; Xie, Daiqian; Guo, Hua

    2016-06-27

    Dissociative chemisorption is the initial and often rate-limiting step in many heterogeneous processes. As a result, an in-depth understanding of the reaction dynamics of such processes is of great importance for the establishment of a predictive model of heterogeneous catalysis. Overwhelming experimental evidence has suggested that these processes have a non-statistical nature and excitations in various reactant modes have a significant impact on reactivity. A comprehensive characterization of the reaction dynamics requires a quantum mechanical treatment on a global potential energy surface. In this review, we summarize recent progress in constructing high-dimensional potential energy surfaces for polyatomic molecules interacting with transition metal surfaces based on the plane-wave density functional theory and in quantum dynamical studies of dissociative chemisorption on these potential energy surfaces. A special focus is placed on the mode specificity and bond selectivity in these gas-surface collisional processes, and their rationalization in terms of the recently proposed Sudden Vector Projection model. PMID:26100606

  1. Selectively bonded polymeric glaucoma drainage device for reliable regulation of intraocular pressure.

    Science.gov (United States)

    Moon, Seunghwan; Im, Seongmin; An, Jaeyong; Park, Chang Ju; Kim, Hwang Gyun; Park, Sang Woo; Kim, Hyoung Ihl; Lee, Jong-Hyun

    2012-04-01

    A novel glaucoma drainage device (GDD) using a polymeric micro check valve with no reverse flow is presented for the effective regulation of intraocular pressure (IOP). A significant functional improvement was achieved by reducing the possible incidence of hypotony, as the proposed GDD only drains aqueous humor at a certain cracking pressure or higher. The device consists of three biocompatible polymer layers: a top layer (cover), an intermediate layer (membrane), and a bottom layer (base plate with a cannula). All three layers, made of soft polydimethylsiloxane (PDMS), were bonded together to realize the thin GDDs. The bottom layer was selectively coated with chromium (Cr)/gold (Au) to prevent stiction between the valve seat and the valve orifice so that the device could show enhanced reliability in operation and high yield in production. Two types of polymeric devices were fabricated; one was a glaucoma drainage device for humans (GDDH) and the other was a glaucoma drainage device for animals (GDDA). From subsequent in vitro tests, the cracking pressures were 18.33 ± 0.66 mmHg (mean ± standard deviation) for GDDH and 12.42 mmHg for GDDA, both of which were very close to the corresponding normal IOPs. From in vivo tests of GDDA, the IOP of all implanted devices was properly regulated within the target pressure (10-15 mmHg). The experimental results showed that the proposed polymeric GDD has high potential for use in the treatment of glaucoma disease in terms of its repeatability of the cracking pressure and patients' relief from post-operative discomfort. PMID:22094823

  2. A Rational Reconstruction of the Origin of the Covalent Bond and Its Implications for General Chemistry Textbooks.

    Science.gov (United States)

    Niaz, Mansoor

    2001-01-01

    Develops a perspective based on the history and philosophy of science considerations (rational reconstruction) in order to understand the postulation of the covalent bond by Lewis. Formulates four criteria based on the perspective and evaluates of 27 textbooks based on the four criteria. Shows that most textbooks lacked a history and philosophy of…

  3. MICROWAVE-ASSISTED CHEMISTRY: SYNTHESIS OF AMINES AND HETEROCYCLES VIA CARBON-NITROGEN BOND FORMATION IN AQUEOUS MEDIA

    Science.gov (United States)

    Improved C-N bond formation under MW influence is demonstrated by a) solventless three-component coupling reaction to generate propargyl amines that uses only Cu (I); b) aqueous N-alkylation of amines by alkyl halides that proceeds expeditiously in the presence of NaOH to deliver...

  4. Application of Radiation Chemistry to Some Selected Technological Issues Related to the Development of Nuclear Energy.

    Science.gov (United States)

    Bobrowski, Krzysztof; Skotnicki, Konrad; Szreder, Tomasz

    2016-10-01

    The most important contributions of radiation chemistry to some selected technological issues related to water-cooled reactors, reprocessing of spent nuclear fuel and high-level radioactive wastes, and fuel evolution during final radioactive waste disposal are highlighted. Chemical reactions occurring at the operating temperatures and pressures of reactors and involving primary transients and stable products from water radiolysis are presented and discussed in terms of the kinetic parameters and radiation chemical yields. The knowledge of these parameters is essential since they serve as input data to the models of water radiolysis in the primary loop of light water reactors and super critical water reactors. Selected features of water radiolysis in heterogeneous systems, such as aqueous nanoparticle suspensions and slurries, ceramic oxides surfaces, nanoporous, and cement-based materials, are discussed. They are of particular concern in the primary cooling loops in nuclear reactors and long-term storage of nuclear waste in geological repositories. This also includes radiation-induced processes related to corrosion of cladding materials and copper-coated iron canisters, dissolution of spent nuclear fuel, and changes of bentonite clays properties. Radiation-induced processes affecting stability of solvents and solvent extraction ligands as well oxidation states of actinide metal ions during recycling of the spent nuclear fuel are also briefly summarized. PMID:27573502

  5. Environmental carbonate chemistry selects for phenotype of recently isolated strains of Emiliania huxleyi

    Science.gov (United States)

    Rickaby, Rosalind E. M.; Hermoso, Michaël; Lee, Renee B. Y.; Rae, Benjamin D.; Heureux, Ana M. C.; Balestreri, Cecilia; Chakravarti, Leela; Schroeder, Declan C.; Brownlee, Colin

    2016-05-01

    Coccolithophorid algae, particularly Emiliania huxleyi, are prolific biomineralisers that, under many conditions, dominate communities of marine eukaryotic plankton. Their ability to photosynthesise and form calcified scales (coccoliths) has placed them in a unique position in the global carbon cycle. Contrasting reports have been made with regards to the response of E. huxleyi to ocean acidification. Therefore, there is a pressing need to further determine the fate of this key organism in a rising CO2 world. In this paper, we investigate the phenotype of newly isolated, genetically diverse, strains of E. huxleyi from UK Ocean Acidification Research Programme (UKOA) cruises around the British Isles, the Arctic, and the Southern Ocean. We find a continuum of diversity amongst the physiological and photosynthetic parameters of different strains of E. huxleyi morphotype A under uniform, ambient conditions imposed in the laboratory. This physiology is best explained by adaptation to carbonate chemistry in the former habitat rather than being prescribed by genetic fingerprints such as the coccolithophore morphology motif (CMM). To a first order, the photosynthetic capacity of each strain is a function of both aqueous CO2 availability, and calcification rate, suggestive of a link between carbon concentrating ability and calcification. The calcification rate of each strain is related linearly to the natural environmental [CO32-] at the site of isolation, but a few exceptional strains display low calcification rates at the highest [CO32-] when calcification is limited by low CO2 availability and/or a lack of a carbon concentrating mechanism. We present O2-electrode measurements alongside coccolith oxygen isotopic composition and the uronic acid content (UAC) of the coccolith associated polysaccharide (CAP), that act as indirect tools to show the differing carbon concentrating ability of the strains. The environmental selection revealed amongst our recently isolated strain

  6. Chemistry {ampersand} Materials Science progress report summary of selected research and development topics, FY97

    Energy Technology Data Exchange (ETDEWEB)

    Newkirk, L.

    1997-12-01

    This report contains summaries of research performed in the Chemistry and Materials Science division. Topics include Metals and Ceramics, High Explosives, Organic Synthesis, Instrument Development, and other topics.

  7. Crystal chemistry of sartorite homologues and related sulfosalts

    DEFF Research Database (Denmark)

    Berlepsch, Peter; Makovicky, Emil; Balic-Zunic, Tonci

    2001-01-01

    sartorite homologues, sulfosalt, crystal chemistry, coordination polyhedra, bond-pairs, crankshaft chains......sartorite homologues, sulfosalt, crystal chemistry, coordination polyhedra, bond-pairs, crankshaft chains...

  8. Frontiers in Gold Chemistry

    OpenAIRE

    Mohamed, Ahmed A.

    2015-01-01

    Basic chemistry of gold tells us that it can bond to sulfur, phosphorous, nitrogen, and oxygen donor ligands. The Frontiers in Gold Chemistry Special Issue covers gold complexes bonded to the different donors and their fascinating applications. This issue covers both basic chemistry studies of gold complexes and their contemporary applications in medicine, materials chemistry, and optical sensors. There is a strong belief that aurophilicity plays a major role in the unending applications of g...

  9. Reductive cleavage of dichalcogenide bonds. Communication 3. Selectivity of electron exchange in diaryldichalcogenide-bispyridinium systems

    International Nuclear Information System (INIS)

    The kinetics of reductive cleavage of the dichalcogenide bond in dimeric Schiff's bases ArEEAr (E = S, Te) induced by indirect electron transfer by the in situ generated bridged bispyridinium radical cations and biradicals was studied by cyclic voltammetry. It is found that the dependence between the apparent rate constants of intermolecular electron transfer and the electron-withdrawing properties of diaryldichalcogenides is violated. The mechanisms of homogeneous (chemical) and heterogeneous (electrochemical) reductive cleavage of diaryldichalcogenides are discussed

  10. Organometallic chemistry

    OpenAIRE

    Bashkin, James K.; M.L.H. Green; Dr. M. L. H. Green

    1982-01-01

    Transition metal organometallic chemistry is a rapidly expanding field, which has an important relationship to industrial problems of petrochemical catalysis. This thesis describes studies of fundamental organometallic reaction processes, such as C-H and C-C bond formation and cleavage, and investigations of the structure and bonding of organometallic compounds. A number of techniques were used to pursue these studies, including synthesis, X-ray crystallography, and semi-em...

  11. A Systematic Study of Structure and E-H Bond Activation Chemistry by Sterically Encumbered Germylene Complexes.

    Science.gov (United States)

    Usher, Matthew; Protchenko, Andrey V; Rit, Arnab; Campos, Jesús; Kolychev, Eugene L; Tirfoin, Rémi; Aldridge, Simon

    2016-08-01

    A series of new germylene compounds has been synthesized offering systematic variation in the σ- and π-capabilities of the α-substituent and differing levels of reactivity towards E-H bond activation (E=H, B, C, N, Si, Ge). Chloride metathesis utilizing [(terphenyl)GeCl] proves to be an effective synthetic route to complexes of the type [(terphenyl)Ge(ERn )] (1-6: ERn =NHDipp, CH(SiMe3 )2 , P(SiMe3 )2 , Si(SiMe3 )3 or B(NDippCH)2 ; terphenyl=C6 H3 Mes2 -2,6=Ar(Mes) or C6 H3 Dipp2 -2,6=Ar(Dipp) ; Dipp=C6 H3 iPr2 -2,6, Mes=C6 H2 Me3 -2,4,6), while the related complex [{(Me3 Si)2 N}Ge{B(NDippCH)2 }] (8) can be accessed by an amide/boryl exchange route. Metrical parameters have been probed by X-ray crystallography, and are consistent with widening angles at the metal centre as more bulky and/or more electropositive substituents are employed. Thus, the widest germylene units (θ>110°) are found to be associated with strongly σ-donating boryl or silyl ancillary donors. HOMO-LUMO gaps for the new germylene complexes have been appraised by DFT calculations. The aryl(boryl)-germylene system [Ar(Mes) Ge{B(NDippCH)2 }] (6-Mes), which features a wide C-Ge-B angle (110.4(1)°) and (albeit relatively weak) ancillary π-acceptor capabilities, has the smallest HOMO-LUMO gap (119 kJ mol(-1) ). These features result in 6-Mes being remarkably reactive, undergoing facile intramolecular C-H activation involving one of the mesityl ortho-methyl groups. The related aryl(silyl)-germylene system, [Ar(Mes) Ge{Si(SiMe3 )3 }] (5-Mes) has a marginally wider HOMO-LUMO gap (134 kJ mol(-1) ), rendering it less labile towards decomposition, yet reactive enough to oxidatively cleave H2 and NH3 to give the corresponding dihydride and (amido)hydride. Mixed aryl/alkyl, aryl/amido and aryl/phosphido complexes are unreactive, but amido/boryl complex 8 is competent for the activation of E-H bonds (E=H, B, Si) to give hydrido, boryl and silyl products. The results of these reactivity studies

  12. Combining Chemistry and Music to Engage Student Interest: Using Songs to Accompany Selected Chemical Topics

    Science.gov (United States)

    Last, Arthur M.

    2009-01-01

    The use of recorded music to add interest to a variety of lecture topics is described. Topics include the periodic table, the formation of ionic compounds, thermodynamics, carbohydrates, nuclear chemistry, and qualitative analysis. (Contains 1 note.)

  13. Direct Construction of 4-Hydroxybenzils via Para-Selective C-C Bond Coupling of Phenols and Aryl Methyl Ketones.

    Science.gov (United States)

    Xiang, Jia-Chen; Cheng, Yan; Wang, Miao; Wu, Yan-Dong; Wu, An-Xin

    2016-09-01

    A highly para-selective C-C bond coupling is presented between phenols C(sp(2)) and aryl methyl ketones C(sp(3)), which enables the direct construction of 4-hydroxybenzil derivatives. This practical method exhibits a broad substrate scope and large-scale applicability and represents a general gateway to the hydroxybenzil natural product family. Mechanistic investigations indicated that the combination of HI with DMSO realized the oxidative carbonylation of aryl methyl ketones, while boric acid acted as a dual-functional relay reagent to promote this transformation. PMID:27513164

  14. Solvent-Free Selective Condensations Based on the Formation of the Olefinic (C=C Bond Catalyzed by Organocatalyst

    Directory of Open Access Journals (Sweden)

    Heyuan Song

    2016-07-01

    Full Text Available Pyrrolidine and its derivatives were used to catalyze aldol and Knoevenagel condensations for the formation of the olefinic (C=C bond under solvent-free conditions. The 3-pyrrolidinamine showed high activity and afforded excellent yields of α,β-unsaturated compounds. The aldol condensation of aromatic/heterocyclic aldehydes with ketones affords enones in high conversion (99.5% and selectivity (92.7%. Good to excellent yields of α,β-unsaturated compounds were obtained in the Knoevenagel condensation of aldehydes with methylene-activated substrates.

  15. Selective Oxidative Decarbonylative Cleavage of Unstrained C(sp(3))-C(sp(2)) Bond: Synthesis of Substituted Benzoxazinones.

    Science.gov (United States)

    Verma, Ajay; Kumar, Sangit

    2016-09-01

    A transition metal (TM)-free practical synthesis of biologically relevant benzoxazinones has been established via a selective oxidative decarbonylative cleavage of an unstrained C(sp(3))-C(sp(2)) bond employing iodine, sodium bicarbonate, and (t)butyl hydroperoxide in DMSO at 95 °C. Control experiments and Density Functional Theory (DFT) calculations suggest that the reaction involves a [1,5]H shift and extrusion of CO gas as the key steps. The extrusion of CO has also been established using PMA-PdCl2. PMID:27549986

  16. Students' Visualization of Metallic Bonding and the Malleability of Metals

    Science.gov (United States)

    Cheng, Maurice M. W.; Gilbert, John K.

    2014-01-01

    This study investigated the mental representations of metallic bonding and the malleability of metals held by three male students aged 14-15 (Year 10) who were attending a Hong Kong school. One student was selected by their chemistry teacher as representing each of the highest, the medium, and the lowest level of attainment in chemistry in a…

  17. Surface chemistry of Ti6Al4V components fabricated using selective laser melting for biomedical applications.

    Science.gov (United States)

    Vaithilingam, Jayasheelan; Prina, Elisabetta; Goodridge, Ruth D; Hague, Richard J M; Edmondson, Steve; Rose, Felicity R A J; Christie, Steven D R

    2016-10-01

    Selective laser melting (SLM) has previously been shown to be a viable method for fabricating biomedical implants; however, the surface chemistry of SLM fabricated parts is poorly understood. In this study, X-ray photoelectron spectroscopy (XPS) was used to determine the surface chemistries of (a) SLM as-fabricated (SLM-AF) Ti6Al4V and (b) SLM fabricated and mechanically polished (SLM-MP) Ti6Al4V samples and compared with (c) traditionally manufactured (forged) and mechanically polished Ti6Al4V samples. The SLM-AF surface was observed to be porous with an average surface roughness (Ra) of 17.6±3.7μm. The surface chemistry of the SLM-AF was significantly different to the FGD-MP surface with respect to elemental distribution and their existence on the outermost surface. Sintered particles on the SLM-AF surface were observed to affect depth profiling of the sample due to a shadowing effect during argon ion sputtering. Surface heterogeneity was observed for all three surfaces; however, vanadium was witnessed only on the mechanically polished (SLM-MP and FGD-MP) surfaces. The direct and indirect 3T3 cell cytotoxicity studies revealed that the cells were viable on the SLM fabricated Ti6Al4V parts. The varied surface chemistry of the SLM-AF and SLM-MP did not influence the cell behaviour. PMID:27287125

  18. Fluorine in medicinal chemistry: a century of progress and a 60-year retrospective of selected highlights.

    Science.gov (United States)

    Filler, Robert; Saha, Rituparna

    2009-08-01

    This perspective explores the origins of both fluorine and medicinal chemistry a century ago and traces the early history of the intersection of these areas and the subsequent roles that fluorine has played in advancing medicinal innovations and diagnoses during the past 60 years. The overview highlights remarkable breakthroughs in many diverse areas of medicinal chemistry, including inter alia, anesthetics, steroidal and nonsteroidal anti-inflammatory drugs, anticancer and antiviral agents, CNS medications, antibacterials and cholesterol biosynthesis inhibitors. The increasing use of fluorine-18-labeled radiotracers in PET for diagnostic imaging of the brain, heart and in oncology is briefly presented. The signature roles of fluorine in medicinal chemistry are now firmly established. The presence of fluorine in pharmaceuticals has had a major impact on a plethora of important medical applications, such as those cited above. Fluorine will very likely continue to contribute significantly by playing multifaceted roles in enhancing future medical advances. PMID:21426080

  19. Film/chemistry selection for the earth resources technology satellite /ERTS/ ground data handling system

    Science.gov (United States)

    Shaffer, R. M.

    1973-01-01

    A detailed description is given of the methods of choose the duplication film and chemistry currently used in the NASA-ERTS Ground Data Handling System. The major ERTS photographic duplication goals are given as background information to justify the specifications for the desirable film/chemistry combination. Once these specifications were defined, a quantitative evaluation program was designed and implemented to determine if any recommended combinations could meet the ERTS laboratory specifications. The specifications include tone reproduction, granularity, MTF and cosmetic effects. A complete description of the techniques used to measure the test response variables is given. It is anticipated that similar quantitative techniques could be used on other programs to determine the optimum film/chemistry consistent with the engineering goals of the program.

  20. Bond-selective fragmentation of water molecules with intense, ultrafast, carrier envelope phase stabilized laser pulses

    CERN Document Server

    Mathur, D; Dharmadhikari, J A; Dharmadhikari, A K

    2013-01-01

    Carrier envelope phase (CEP) stabilized pulses of intense 800 nm light of 5 fs duration are used to probe the dissociation dynamics of dications of isotopically-substituted water, HOD. HOD$^{2+}$ dissociates into either H$^+$ + OD$^+$ or D$^+$ + OH$^+$. The branching ratio for these two channels is CEP-dependent; the OD$^+$/OH$^+$ ratio (relative to that measured with CEP-unstabilized pulses) varies from 150% to over 300% at different CEP values, opening prospects of isotope-dependent control over molecular bond breakage. The kinetic energy released as HOD$^{2+}$ Coulomb explodes is also CEP-dependent. Formidable theoretical challenges are identified for proper insights into the overall dynamics which involve non-adiabatic field ionization from HOD to HOD$^+$ and, thence, to HOD$^{2+}$ via electron rescattering.

  1. Continuously operated falling film microreactor for selective hydrogenation of carbon-carbon triple bonds

    OpenAIRE

    Rehm, Thomas H.; Berguerand, Charline; Ek, Satu; Zapf, Ralf; Löb, Patrick; Nikoshvili, Linda; Kiwi-Minsker, Lioubov

    2016-01-01

    Despite significant advances in the fabrication and applications of microreactors for production of chemicals, their use for catalytic reactions remains a challenge, especially in fine chemical synthesis where the selectivity towards the desired product is an issue. A falling film microstructured reactor (FFMR) was tested in the selective hydrogenation of 2-butyne-1,4-diol (1) to its olefinic derivative (2). The FFMR plates were coated with Al2O3 or ZnO followed by the deposition of Pd nanopa...

  2. An evaluation of the performance of chemistry transport models, Part 2: detailed comparison with two selected campaigns

    Directory of Open Access Journals (Sweden)

    D. Brunner

    2004-11-01

    Full Text Available This is the second part of a rigorous model evaluation study involving five global Chemistry-Transport and two Chemistry-Climate Models operated by different groups in Europe. Simulated trace gas fields were interpolated to the exact times and positions of the observations to account for the actual weather conditions and hence for the specific histories of the sampled air masses. In this part of the study we focus on a detailed comparison with two selected campaigns, PEM-Tropics A and SONEX, contrasting the clean environment of the tropical Pacific with the more polluted North Atlantic region. The study highlights the different strengths and weaknesses of the models in accurately simulating key processes in the UT/LS region including stratosphere-troposphere-exchange, rapid convective transport, lightning emissions, radical chemistry and ozone production. Model simulated Radon, which was used as an idealized tracer for continental influence, was occasionally much better correlated with measured CO than simulated CO pointing towards deficiencies in the used biomass burning emission fields. The abundance and variability of HOx radicals is in general well represented in the models as inferred directly from the comparison with measured OH and HO2 and indirectly from the comparison with hydrogen peroxide concentrations. Components of the NOy family such as PAN, HNO3 and NO were found to compare less favorably. Interestingly, models showing good agreement with observations in the case of PEM-Tropics A often failed in the case of SONEX and vice versa. A better description of NOx and NOy emissions, chemistry and sinks is thought to be key to future model improvements with respect to the representation of chemistry in the UT/LS region.

  3. Gender and High School Chemistry: Student Perceptions on Achievement in a Selective Setting

    Science.gov (United States)

    Cousins, Andrew; Mills, Martin

    2015-01-01

    This paper reports on research undertaken in a middle-class Australian school. The focus of the research was on the relationship between gender and students' engagement with high school chemistry. Achievement data from many OECD [Organisation for Economic Co-operation and Development] countries suggest that middle-class girls are achieving equally…

  4. Selected scientific articles. (Investigations in the field of hydrides chemistry and mineral raw materials processing)

    International Nuclear Information System (INIS)

    Articles, included in the present book are covering period 1977-2013 y. The main scientific articles in the field of power-consuming substances, mineral raw-materials and wastes reprocessing, including uranium industry wastes are collected. Scientific works on hydrogen chemistry which carried out basically bu U.M. Mirsaidov without co-authors are considered. These works are on aluminium hydrides and borohydrides lanthanides. Besides, author's popular-science articles on research carried out by Academy of Sciences during the period when he was the President of Academy of Sciences of the Republic of Tajikistan (1995-2005) are included. Mineral raw materials and wastes reprocessing results are given as well. The book is intended for engineer and technical staff, those working in the field of hydrogen chemistry, hydrometallurgy workers, engineering chemists as well as for PhD, post graduate students and students of appropriate profiles.

  5. Regulating Biocompatibility of Carbon Spheres via Defined Nanoscale Chemistry and a Careful Selection of Surface Functionalities

    Science.gov (United States)

    Misra, Santosh K.; Chang, Huei-Huei; Mukherjee, Prabuddha; Tiwari, Saumya; Ohoka, Ayako; Pan, Dipanjan

    2015-10-01

    A plethora of nanoarchitectures have been evaluated preclincially for applications in early detection and treatment of diseases at molecular and cellular levels resulted in limited success of their clinical translation. It is important to identify the factors that directly or indirectly affect their use in human. We bring a fundamental understanding of how to adjust the biocompatibility of carbon based spherical nanoparticles (CNPs) through defined chemistry and a vigilant choice of surface functionalities. CNPs of various size are designed by tweaking size (2-250 nm), surface chemistries (positive, or negatively charged), molecular chemistries (linear, dendritic, hyperbranched) and the molecular weight of the coating agents (MW 400-20 kDa). A combination of in vitro assays as tools were performed to determine the critical parameters that may trigger toxicity. Results indicated that hydrodynamic sizes are potentially not a risk factor for triggering cellular and systemic toxicity, whereas the presence of a highly positive surface charge and increasing molecular weight enhance the chance of inducing complement activation. Bare and carboxyl-terminated CNPs did present some toxicity at the cellular level which, however, is not comparable to those caused by positively charged CNPs. Similarly, negatively charged CNPs with hydroxyl and carboxylic functionalities did not cause any hemolysis.

  6. Water chemistry in 179 randomly selected Swedish headwater streams related to forest production, clear-felling and climate.

    Science.gov (United States)

    Löfgren, Stefan; Fröberg, Mats; Yu, Jun; Nisell, Jakob; Ranneby, Bo

    2014-12-01

    From a policy perspective, it is important to understand forestry effects on surface waters from a landscape perspective. The EU Water Framework Directive demands remedial actions if not achieving good ecological status. In Sweden, 44 % of the surface water bodies have moderate ecological status or worse. Many of these drain catchments with a mosaic of managed forests. It is important for the forestry sector and water authorities to be able to identify where, in the forested landscape, special precautions are necessary. The aim of this study was to quantify the relations between forestry parameters and headwater stream concentrations of nutrients, organic matter and acid-base chemistry. The results are put into the context of regional climate, sulphur and nitrogen deposition, as well as marine influences. Water chemistry was measured in 179 randomly selected headwater streams from two regions in southwest and central Sweden, corresponding to 10 % of the Swedish land area. Forest status was determined from satellite images and Swedish National Forest Inventory data using the probabilistic classifier method, which was used to model stream water chemistry with Bayesian model averaging. The results indicate that concentrations of e.g. nitrogen, phosphorus and organic matter are related to factors associated with forest production but that it is not forestry per se that causes the excess losses. Instead, factors simultaneously affecting forest production and stream water chemistry, such as climate, extensive soil pools and nitrogen deposition, are the most likely candidates The relationships with clear-felled and wetland areas are likely to be direct effects. PMID:25260924

  7. Trends in chemistry of materials selected research papers of C. N. R. Rao

    CERN Document Server

    Rao, C N R

    2008-01-01

    In this collection, the author has compiled a set of his papers representing some of the highlights of materials chemistry. It features a section on oxidic materials, which includes high-temperature superconductivity, colossal magnetoresistance, electronic phase separation and multiferroics. The author has also included novel methods for making gallium nitride, boron nitride and such materials, by using precursors and the urea decomposition route. Moreover, there is a section dealing with open-framework and hybrid materials of which the latter has a great future since one can make use of the r

  8. Highly efficient and selective enrichment of peptide subsets combining fluorous chemistry with reversed-phase chromatography

    OpenAIRE

    Ying, Wantao; Perlman, David H.; Li, Lei(Beijing Institute of Petrochemical Technology, Beijing, 102617, People's Republic of China); Théberge, Roger; Costello, Catherine E; McComb, Mark E.

    2009-01-01

    The selective capture of target peptides poses a great challenge to modern chemists and biologists, especially when enriching them from proteome samples possessing extremes in concentration dynamic range and sequence diversity. While approaches based on traditional techniques such as biotin-avidin pairing offer versatile tools to design strategies for selective enrichment, problems are still encountered due to sample loss or poor selectivity of enrichment. Here we show that the recently intro...

  9. Chemistry principles for thermoplastic polymer binder formula selection for powder injection molding

    Institute of Scientific and Technical Information of China (English)

    梁叔全; 唐艳; 黄伯云; 李少强

    2004-01-01

    The polymer binder selection is one of the very important aspects for the powder injection molding.However, even nowadays the binder selection is still mainly performed by try and error method. Six commercial or intensive studied binder formulas were analyzed according to state diagram and chemical characteristics of ingredients in each binder formula. In addition, the interactions between the binder components and additives were also taken into account. Based on the analysis, the optimum binder formula was selected and some selection criterions were put forward for the binder and additives.

  10. Two-Dimensional Micro-TLC Phenolic Fingerprints of Selected Mentha sp. on Cyano-Bonded Polar Stationary Phase.

    Science.gov (United States)

    Hawrył, Mirosław A; Niemiec, Małgorzata A; Słomka, Kamil; Waksmundzka-Hajnos, Monika; Szymczak, Grażyna

    2016-01-01

    Micro-thin-layer chromatography in two-dimensional (2D-mTLC) mode in normal- (NP) and reversed-phase (RP) systems by use of cyanopropyl-bonded stationary phases was applied to make fingerprints of 11 species of Mentha genus and two finished pharmaceutical products. Non-aqueous eluents were used in the NP systems. Mixtures of acetonitrile with water and methanol with water were used in the RP chromatographic systems. Optimization of one-dimensional systems was performed by determining RM vs. composition of mobile phase dependencies for standards occurring in various Mentha sp. On the basis of these dependencies, the most selective chromatographic systems for each run were chosen. Then most selective eluents were applied to optimize two-dimensional systems by creating RF in NP systems vs. RF in RP systems correlations. The best two-dimensional systems were chosen on the basis of R(2) values for RF vs. RF correlations (the lowest values of R(2) coefficients). The 2D-mTLC optimized systems were applied to separate phenolic compounds and make fingerprints of the examined plant materials. PMID:26673190

  11. Theoretical chemistry periodicities in chemistry and biology

    CERN Document Server

    Eyring, Henry

    1978-01-01

    Theoretical Chemistry: Periodicities in Chemistry and Biology, Volume 4 covers the aspects of theoretical chemistry. The book discusses the stably rotating patterns of reaction and diffusion; the chemistry of inorganic systems exhibiting nonmonotonic behavior; and population cycles. The text also describes the mathematical modeling of excitable media in neurobiology and chemistry; oscillating enzyme reactions; and oscillatory properties and excitability of the heart cell membrane. Selected topics from the theory of physico-chemical instabilities are also encompassed. Chemists, mechanical engin

  12. Public perception of chemistry

    OpenAIRE

    Stražar, Alenka

    2015-01-01

    The thesis deals with the perception of chemistry among the public, which reflects the stereotypes that people have about chemistry. It presents the existing classification of stereotypes about chemistry and their upgrade. An analysis of movies that reflect the existing perception of chemistry in the public is written. Literature on selected aspects of the application of chemistry in movies is collected and analyzed. A qualification of perception of chemistry in the movies is presented based ...

  13. Cooperativity and Site-Selectivity of Intramolecular Hydrogen Bonds on the Fluorescence Quenching of Modified GFP Chromophores.

    Science.gov (United States)

    Chang, Deng-Hsiang; Ou, Chun-Lin; Hsu, Hung-Yu; Huang, Guan-Jhih; Kao, Chen-Yi; Liu, Yi-Hung; Peng, Shie-Ming; Diau, Eric Wei-Guang; Yang, Jye-Shane

    2015-12-18

    This paper provides the first example of experimentally characterized hydrogen-bond cooperativity on fluorescence quenching with a modified green fluorescence protein (GFP) chromophore that contains a 6-membered C═N···H-O and a 7-membered C═O···H-O intramolecular H-bonds. Variable-temperature (1)H NMR and electronic absorption and emission spectroscopies were used to elucidate the preference of intra- vs intermolecular H-bonding at different concentrations (1 mM and 10 μM), and X-ray crystal structures provide clues of possible intermolecular H-bonding modes. In the ground state, the 6-membered H-bond is significant but the 7-membered one is rather weak. However, fluorescence quenching is dominated by the 7-membered H-bond, indicating a strengthening of the H-bond in the excited state. The H-bonding effect is more pronounced in more polar solvents, and no intermediates were observed from femtosecond fluorescence decays. The fluorescence quenching is attributed to the occurrence of diabatic excited-state proton transfer. Cooperativity of the two intramolecular H-bonds on spectral shifts and fluorescence quenching is evidenced by comparing with both the single H-bonded and the non-H-bonded counterparts. The H-bond cooperativity does not belong to the conventional patterns of σ- and π-cooperativity but a new type of polarization interactions, which demonstrates the significant interplay of H-bonds for multiple H-bonding systems in the electronically excited states. PMID:26583964

  14. Selected constants oxydo-reduction potentials tables of constants and numerical data affiliated to the International Union of Pure and Applied Chemistry, v.8

    CERN Document Server

    Charlot, G

    1958-01-01

    Selected Constants: Oxydo-Reduction Potentials contains Tables of the most probable value of the normal oxidation-reduction potential, or of the formal or apparent potential, of a given oxidation-reduction system. This book is prepared under the sponsorship of the Commission on Electrochemical Data of the Section of Analytical Chemistry of the International Union of Pure and Applied Chemistry. It is included in a general program of the Section of Analytical Chemistry. Entry items are classified in alphabetical order. This book will be of value to specialized and non-specialized chemists, teach

  15. Gas-phase chemistry of Sc(CH{sub 3}){sub 2}{sup +} with alkenes: Activation of allylic C-H bonds by a d{sup 0} system and the migratory insertion of C=C bonds into Sc{sup +}-CH{sub 3} bonds

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Yongqing; Hill, Y.D.; Freiser, B.S. [Purdue Univ., West Lafayette, IN (United States)] [and others

    1992-11-04

    The gas-phase chemistry of Sc(CH{sub 3}){sub 2}{sup +} with alkenes was studied by Fourier transform mass spectrometry. The metal center on Sc(CH{sub 3}){sub 2}{sup +} is d{sup 0}, providing an opportunity to study alternative mechanisms of C-C or C-H activation other than the most common one involving oxidative addition. The elimination of H{sub 2} is observed in the reaction of Sc(CH{sub 3}){sub 2}{sup +} with ethylene, and the product ScC{sub 4}H{sub 8}{sup +} and ScC{sub 6}H{sub 10}{sup +} ions have a metal(methyl)(allyl) and metal-bisallyl structure, respectively, consistent with a proposed reaction mechanism involving the consecutive migratory insertion of ethylenes into the scandium-methyl bonds. In addition, theoretical calculations indicate that the metal(methyl)(allyl) structure is between 10 and 20 kcal/mol more stable than the metal(1-butene) isomer. Sc(CH{sub 3}){sub 2}{sup +} reacts with propene to form predominantly ScC{sub 4}H{sub 8}{sup +} by loss of CH{sub 4}, with minor amounts of ScC{sub 3}H{sub 4}{sup +} and ScC{sub 4}H{sub 6}{sup +} also observed. ScC{sub 4}H{sub 6}{sup +} is formed as either the exclusive or the predominant product ion in the reactions of Sc(CH{sub 3}){sub 2}{sup +} with butenes. Sc(CH{sub 3}){sub 2} reacts with cyclopentene to form predominantly ScC{sub 6}H{sub 8}{sup +} by losing CH{sub 4} and H{sub 2}. Isotope labeling studies with Sc(CD{sub 3}){sub 2}{sup +} and other structure studies indicate that all of the alkenes studied, with the exception of ethylene, react with Sc(CH{sub 3}){sub 2}{sup +} via a multicentered {sigma}-bond metathesis mechanism to activate allylic C-H bonds. Finally, the dehydrogenation reactions of Sc{sup +} with n-butane and neopentane were revisited, and a new mechanism is proposed for such chemistry in light of the new results from this study. 34 refs., 5 figs., 2 tabs.

  16. Solution chemistry of a water-soluble eta2-H2 ruthenium complex: evidence for coordinated H2 acting as a hydrogen bond donor.

    Science.gov (United States)

    Szymczak, Nathaniel K; Zakharov, Lev N; Tyler, David R

    2006-12-13

    The ability of an eta2-H2 ligand to participate in intermolecular hydrogen bonding in solution has long been an unresolved issue. Such species are proposed to be key intermediates in numerous important reactions such as the proton-transfer pathway of H2 production by hydrogenase enzymes. We present the synthesis of several new water-soluble ruthenium coordination complexes including an eta2-H2 complex that is surprisingly inert to substitution by water. The existence of dihydrogen hydrogen bonding (DHHB) was experimentally probed by monitoring the chemical shift of H-bonded Ru-(H2) complexes using NMR spectroscopy, by UV-visible spectroscopy, and by monitoring the rotational dynamics of a hydrogen-bonding probe molecule. The results provide strong evidence that coordinated H2 can indeed participate in intermolecular hydrogen bonding to bulk solvent and other H-bond acceptors. PMID:17147394

  17. Supramolecular chemistry of selective anion recognition for anions of environmental relevance. 1998 annual progress report

    Energy Technology Data Exchange (ETDEWEB)

    Bowman-James, K.; Wilson, G.S.; Kuczera, K. [Univ. of Kansas, Lawrence, KS (US); Moyer, B. [Oak Ridge National Lab., TN (US)

    1998-06-01

    'This project has as its focus the design and synthesis of polyammonium macrocyclic receptors for oxoanions of environmental importance. The basic research aspects of this project involve: (1) synthesis (and the search for improved synthetic methods); (2) solid state structure determination and thermodynamics studies (to ascertain structural criteria for and strength of anion binding); and (3) molecular dynamics simulations (to assess solution characteristics of the interactions between anions and their receptors). Applications-oriented goals include the fabrication of more selective anion-selective electrodes and the use of these compounds in liquid-liquid separations. The latter goal comprises the subcontract with Dr. Bruce Moyer at Oak Ridge National Laboratory. This report summarizes work after 1 year and 7 months of a 3-year project. To date, the authors have focussed on the design and synthesis of selective receptors for nitrate and phosphate.'

  18. A rod-packing microporous hydrogen-bonded organic framework for highly selective separation of C2H2/CO2at room temperature

    KAUST Repository

    Li, Peng

    2014-11-13

    Self-assembly of a trigonal building subunit with diaminotriazines (DAT) functional groups leads to a unique rod-packing 3D microporous hydrogen-bonded organic framework (HOF-3). This material shows permanent porosity and demonstrates highly selective separation of C2H2/CO2 at ambient temperature and pressure.

  19. Chemistry of Secondary Polyphenols Produced during Processing of Tea and Selected Foods

    Directory of Open Access Journals (Sweden)

    Takashi Tanaka

    2009-12-01

    Full Text Available This review will discuss recent progress in the chemistry of secondary polyphenols produced during food processing. The production mechanism of the secondary polyphenols in black tea, whisky, cinnamon, and persimmon fruits will be introduced. In the process of black tea production, tea leaf catechins are enzymatically oxidized to yield a complex mixture of oxidation products, including theaflavins and thearubigins. Despite the importance of the beverage, most of the chemical constituents have not yet been confirmed due to the complexity of the mixture. However, the reaction mechanisms at the initial stages of catechin oxidation are explained by simple quinone–phenol coupling reactions. In vitro model experiments indicated the presence of interesting regio- and stereoselective reactions. Recent results on the reaction mechanisms will be introduced. During the aging of whisky in oak wood barrels, ellagitannins originating from oak wood are oxidized and react with ethanol to give characteristic secondary ellagitannins. The major part of the cinnamon procyanidins is polymerized by copolymerization with cinnamaldehyde. In addition, anthocyanidin structural units are generated in the polymer molecules by oxidation which accounts for the reddish coloration of the cinnamon extract. This reaction is related to the insolubilization of proanthocyanidins in persimmon fruits by condensation with acetaldehyde. In addition to oxidation, the reaction of polyphenols with aldehydes may be important in food processing.

  20. Controlling orbital-selective Kondo effects in a single molecule through coordination chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Tsukahara, Noriyuki; Kawai, Maki; Takagi, Noriaki, E-mail: n-takagi@k.u-tokyo.ac.jp [Department of Advanced Materials Science, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561 (Japan); Minamitani, Emi; Kim, Yousoo [RIKEN, 2-1 Hirosawa, Saitama 351-0198 (Japan)

    2014-08-07

    Iron(II) phthalocyanine (FePc) molecule causes novel Kondo effects derived from the unique electronic structure of multi-spins and multi-orbitals when attached to Au(111). Two unpaired electrons in the d{sub z}{sup 2} and the degenerate dπ orbitals are screened stepwise, resulting in spin and spin+orbital Kondo effects, respectively. We investigated the impact on the Kondo effects of the coordination of CO and NO molecules to the Fe{sup 2+} ion as chemical stimuli by using scanning tunneling microscopy (STM) and density functional theory calculations. The impacts of the two diatomic molecules are different from each other as a result of the different electronic configurations. The coordination of CO converts the spin state from triplet to singlet, and then the Kondo effects completely disappear. In contrast, an unpaired electron survives in the molecular orbital composed of Fe d{sub z}{sup 2} and NO 5σ and 2π* orbitals for the coordination of NO, causing a sharp Kondo resonance. The isotropic magnetic response of the peak indicates the origin is the spin Kondo effect. The diatomic molecules attached to the Fe{sup 2+} ion were easily detached by applying a pulsed voltage at the STM junction. These results demonstrate that the single molecule chemistry enables us to switch and control the spin and the many-body quantum states reversibly.

  1. One-Step "Click Chemistry"-Synthesized Cross-Linked Prodrug Nanogel for Highly Selective Intracellular Drug Delivery and Upregulated Antitumor Efficacy.

    Science.gov (United States)

    Zhang, Yu; Ding, Jianxun; Li, Mingqiang; Chen, Xin; Xiao, Chunsheng; Zhuang, Xiuli; Huang, Yubin; Chen, Xuesi

    2016-05-01

    Polymeric prodrugs formed by the conjugation of drugs onto polymers have shown great promise in cancer therapy because of the enhancement of water solubility, elimination of premature drug release, and the improvement of pharmacokinetics. To integrate the two advantages of upregulated stability during circulation and selective release of drug in cancer cells, a pH and reduction dual-sensitive prodrug nanogel (CLP) was synthesized via a simple one step "click chemistry". CLP was spherically shaped with a uniform diameter of 60.6 ± 13.7 nm and exhibited great stability in size against large volume dilution, high salt concentration, and long-time incubation in phosphate-buffered saline. Owing to the presence of hydrazone-bonded doxorubicin (DOX) and disulfide cross-linker, CLP released minimal amount (7.8%) of drug under normal physiological pH (i.e., 7.4) condition. But it released 85.5% of the loaded DOX at endosomal pH (i.e., 5.5) plus the presence of 5.0 mM GSH in 120 h. CLP could be effectively internalized by tumor cells and subsequently release DOX in the intracellular environment, resulting in effective proliferation inhibition of HeLa and MCF-7 cells. Furthermore, compared with free DOX and non-cross-linked prodrug micelle (NCLP), CLP accumulated more in tumor site but less in the normal organs, so that CLP performed the enhanced antitumor efficiency and reduced side-toxicities toward the MCF-7 human breast cancer xenograft nude mouse model. With convenient fabrication, favorable stability, controlled release properties, optimized biodistribution, and enhanced suppression of tumor growth, CLP held great potential for optimal antitumor therapy. PMID:27077549

  2. Modifying the chemistry of graphene with substrate selection: A study of gold nanoparticle formation

    International Nuclear Information System (INIS)

    Graphene and metal nanoparticle composites are a promising class of materials with unique electronic, optical, and chemical properties. In this work, graphene is used as a reducing surface to grow gold nanoparticles out of solution-based metal precursors. The nanoparticle formation is found to strongly depend upon the graphene substrate selection. The studied substrates include diamond, p-type silicon, aluminum oxide, lithium niobate, and copper. Our results indicate that the chemical properties of graphene depend upon this selection. For example, for the same reaction times and concentration, the reduction of gold chloride to gold nanoparticles on graphene/lithium niobate results in 3% nanoparticle coverage compared to 20% coverage on graphene/silicon and 60% on graphene/copper. On insulators, nanoparticles preferentially form on folds and edges. Energy dispersive X-ray analysis is used to confirm the nanoparticle elemental makeup

  3. Modifying the chemistry of graphene with substrate selection: A study of gold nanoparticle formation

    Energy Technology Data Exchange (ETDEWEB)

    Zaniewski, Anna M.; Trimble, Christie J.; Nemanich, Robert J. [Department of Physics, Arizona State University, Tempe, Arizona 85281 (United States)

    2015-03-23

    Graphene and metal nanoparticle composites are a promising class of materials with unique electronic, optical, and chemical properties. In this work, graphene is used as a reducing surface to grow gold nanoparticles out of solution-based metal precursors. The nanoparticle formation is found to strongly depend upon the graphene substrate selection. The studied substrates include diamond, p-type silicon, aluminum oxide, lithium niobate, and copper. Our results indicate that the chemical properties of graphene depend upon this selection. For example, for the same reaction times and concentration, the reduction of gold chloride to gold nanoparticles on graphene/lithium niobate results in 3% nanoparticle coverage compared to 20% coverage on graphene/silicon and 60% on graphene/copper. On insulators, nanoparticles preferentially form on folds and edges. Energy dispersive X-ray analysis is used to confirm the nanoparticle elemental makeup.

  4. The geology, botany and chemistry of selected peat-forming environments from temperate and tropical latitudes

    Energy Technology Data Exchange (ETDEWEB)

    Cameron, C.C.; Esterle, J.S.; Palmer, C.A. (US Geological Survey, Reston, VA (USA))

    1989-06-01

    Several peat forming deposits typical of temperate and tropical latitudes that were selected as representing principles of stratigraphic development are described. Their organic and inorganic contents are related to their geomorphology. The general nature of commercial-quality peat and its formation are briefly outlined. The stratigraphy of each peat deposit reflects a succession of peat-forming environments that can be identified with their modern-equivalent bogs, swamps and marshes. Types of peat in each deposit reflect the kind of peat-forming vegetation and degree of decomposition. Models and processes of peat accumulation are described to provide a frame of reference for understanding the geomorphology of the selected deposits. 64 refs., 15 figs., 5 tabs.

  5. Toward Cell Selective Surfaces: Cell Adhesion and Proliferation on Breath Figures with Antifouling Surface Chemistry.

    Science.gov (United States)

    Martínez-Campos, Enrique; Elzein, Tamara; Bejjani, Alice; García-Granda, Maria Jesús; Santos-Coquillat, Ana; Ramos, Viviana; Muñoz-Bonilla, Alexandra; Rodríguez-Hernández, Juan

    2016-03-16

    We report the preparation of microporous functional polymer surfaces that have been proven to be selective surfaces toward eukaryotic cells while maintaining antifouling properties against bacteria. The fabrication of functional porous films has been carried out by the breath figures approach that allowed us to create porous interfaces with either poly(ethylene glycol) methyl ether methacrylate (PEGMA) or 2,3,4,5,6-pentafluorostyrene (5FS). For this purpose, blends of block copolymers in a polystyrene homopolymer matrix have been employed. In contrast to the case of single functional polymer, using blends enables us to vary the chemical distribution of the functional groups inside and outside the formed pores. In particular, fluorinated groups were positioned at the edges while the hydrophilic PEGMA groups were selectively located inside the pores, as demonstrated by TOF-SIMS. More interestingly, studies of cell adhesion, growth, and proliferation on these surfaces confirmed that PEGMA functionalized interfaces are excellent candidates to selectively allow cell growth and proliferation while maintaining antifouling properties. PMID:26909529

  6. Directing Group in Decarboxylative Cross-Coupling: Copper-Catalyzed Site-Selective C-N Bond Formation from Nonactivated Aliphatic Carboxylic Acids.

    Science.gov (United States)

    Liu, Zhao-Jing; Lu, Xi; Wang, Guan; Li, Lei; Jiang, Wei-Tao; Wang, Yu-Dong; Xiao, Bin; Fu, Yao

    2016-08-01

    Copper-catalyzed directed decarboxylative amination of nonactivated aliphatic carboxylic acids is described. This intramolecular C-N bond formation reaction provides efficient access to the synthesis of pyrrolidine and piperidine derivatives as well as the modification of complex natural products. Moreover, this reaction presents excellent site-selectivity in the C-N bond formation step through the use of directing group. Our work can be considered as a big step toward controllable radical decarboxylative carbon-heteroatom cross-coupling. PMID:27439145

  7. Effect of Electronic Factor in Ru-phosphine-diamine Complexes on Selective Hydrogenation of C=C and C-O Bonds

    Institute of Scientific and Technical Information of China (English)

    ZHANG,Yu; Yu,Xiaojun; YU,Changbin; XIA,Yuqing; LI,Ruixiang; CHEN,Hua; LI,Xianjun

    2009-01-01

    A series of ruthenium complexes bearing different phosphines and diamines were synthesized and their compo-nents and structures were characterized by NMR spectra and elemental analyses. The catalytic properties of these complexes for the hydrogenation of benzylideneacetone and the mixture of acetophenone and styrene were investi-gated. The results showed that the basicity increase of phosphine or diamine dramatically facilitates the hydrogena-tion activity and selectivity to C=O double bond. On the contrary, the basicity decrease of phosphine or diamine not only slows down the catalytic activity, but also significantly suppresses the hydrogenation selectivity to C=O double bond. Based on the effect of electron factors of these complexes on the hydrogenation activity and selectiv-ity of benzylideneacetone and the mixture of styrene and acetophenone, the activation mechanism of dihydrogen in ruthenium-phosphine-diamine system was proposed.

  8. Non-selective chemical sensors in analytical chemistry: from ''electronic nose'' to ''electronic tongue''

    International Nuclear Information System (INIS)

    Development, recent historical background and analytical applications of promising sensor instruments based on sensor arrays with data processing by pattern recognition methods have been described. Attention is paid to the ''electronic tongue'' based on an array of original non-specific (non-selective) potentiometric chemical sensors. Application results for integral qualitative analysis of beverages and for quantitative analysis of biological liquids and solutions, containing heavy metals are reported. Discriminating abilities and precision obtained allow to consider ''electronic tongue'' as a perspective analytical tool. (orig.)

  9. [Highly selective analysis of biogenic-related compounds utilizing fluorous chemistry].

    Science.gov (United States)

    Hayama, Tadashi

    2015-01-01

    Perfluoroalkyl-containing compounds are highly fluorous, meaning that they have a remarkable affinity for one another and effectively exclude non-fluorous species. Utilizing this unique property, we have developed a fluorous derivatization with a liquid chromatographic analysis method for highly selective analysis of target analytes. Although most previous methods focused on extremely sensitive detection-oriented derivatization, the fluorous derivatization method involves highly specific separation for analytes. This method includes perfluoroalkylation of analytes with a fluorous reagent, and separation of the derivatives using a perfluoroalkyl-modified stationary phase LC column. The derivatives can be selectively retained on the fluorous-phase LC column, whereas the non-fluorous derivatives are poorly retained under the same separation conditions. The combination of this method with LC-tandem mass spectrometry (MS/MS) is very useful for complex biological sample analysis, because matrix-induced suppression effects, which are a common problem in LC-MS/MS analysis arising from components of a biological endogenous matrix, have not been observed. We have successfully applied this method to precise and accurate LC-MS/MS analysis of some biogenic compounds, such as sialic acids and biogenic amines, in complex biological samples. PMID:25747214

  10. Site-selective protein-modification chemistry for basic biology and drug development

    Science.gov (United States)

    Krall, Nikolaus; da Cruz, Filipa P.; Boutureira, Omar; Bernardes, Gonçalo J. L.

    2016-02-01

    Nature has produced intricate machinery to covalently diversify the structure of proteins after their synthesis in the ribosome. In an attempt to mimic nature, chemists have developed a large set of reactions that enable post-expression modification of proteins at pre-determined sites. These reactions are now used to selectively install particular modifications on proteins for many biological and therapeutic applications. For example, they provide an opportunity to install post-translational modifications on proteins to determine their exact biological roles. Labelling of proteins in live cells with fluorescent dyes allows protein uptake and intracellular trafficking to be tracked and also enables physiological parameters to be measured optically. Through the conjugation of potent cytotoxicants to antibodies, novel anti-cancer drugs with improved efficacy and reduced side effects may be obtained. In this Perspective, we highlight the most exciting current and future applications of chemical site-selective protein modification and consider which hurdles still need to be overcome for more widespread use.

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

    International Nuclear Information System (INIS)

    This project focused on identifying selective binding agents for the removal of negative ions that hamper vitrification efforts. The project was led by Professor Kristin Bowman-James at the University of Kansas (KU) and consisted of a collaborative effort between the KU group, the group of Professor Jonathan Sessler at the University of Texas Austin (UT), and Dr. Bruce Moyer at Oak Ridge National Laboratory (ORNL). Research efforts during this funding period have focused on a particularly difficult target species, sulfate ion, which is highly insoluble in borosilicate glass. The project is unique in that it combines the synthetic expertise of the Bowman-James and Sessler groups with the analytical/extraction expertise of the Moyer group at ORNL, with a synergy that can bridge disciplines. Sulfate ion is a relatively small ionic species that, because of its solubility characteristics as well as its caustic nature, are a hindrance to the vitrification process. Not only is it relatively insoluble in the medium that has been chosen to store the wastes, but it also has the potential for accelerating the corrosion of the furnaces used to vitrify the borosilicate in a liquid to allow for waste incorporation. The goal of the Bowman-James group has been to design sequestering agents for sulfate that are selective for that ion over nitrate, for example, to allow for a liquid-liquid extraction step that can remove most of the sulfate prior to vitrification. The collaborative design efforts between the Bowman-James and Sessler groups helped to accelerate progress in the design process. In particular the Bowman-James group has been probing the influence of dimensionality and charge on sulfate binding, i.e., progressing from circular to spherical extractants, while at the same time adding positive charges to the agents so that when sulfate is bound, the resulting species is neutral. Not only does this project serve to benefit the remediation process, but it also provides an

  12. Nobel Prize in Chemistry

    Science.gov (United States)

    2000-01-01

    The Royal Swedish Academy has awarded the 1999 Nobel Prize in Chemistry to Ahmed H. Zewail (California Institute of Technology, Pasadena, CA) "for his studies of the transition states of chemical reactions using femtosecond spectroscopy". Zewail's work has taken the study of the rates and mechanisms of chemical reactions to the ultimate degree of detail - the time scale of bond making and bond breaking.

  13. Environmental Role of Rime Chemistry at Selected Mountain Sites in Poland

    Science.gov (United States)

    Godek, Michał; Błaś, Marek; Sobik, Mieczysław; Polkowska, Żaneta; Cichała-Kamrowska, Katarzyna; Namieśnik, Jacek

    2012-05-01

    The results of field experiments on fog pollutant deposition enhanced by local mountain climate, completed by the dendrochronological analysis of the forest response, are presented in this paper. In spite of their low absolute altitude (1,000-1,600 m a.s.l), the Sudetes and the Silesian Beskid form a noticeable orographic barrier for the airflow of the humid Atlantic air masses. This results in the increase of cloudiness and fog frequency as well as both atmospheric precipitation and horizontal precipitation volume. Between January and December 2009 the daily samples of atmospheric precipitation and rime were collected on three selected mountain tops of similar height. The selected measurement sites were situated along a 300 km WNW-ESE profile parallel to the direction of the prevailing atmospheric circulation. High day-to-day variability of rime water volume, the total ionic content and chemical composition of the individual samples were typical of each measurement site and depended on the emission patterns, synoptic situation and the local climatic conditions influenced chiefly by terrain relief. Significantly larger rime efficiency and pollution deposition via fog were observed at the westernmost Szrenica Mt site rather than more to the southeast at Śnieżnik Mt and Skrzyczne Mt. This difference should be explained by more intense orographic deformation of predominant airflow from the western sector as well as the higher liquid water content of fog in the vicinity of Szrenica. Both temporal and spatial variability of fog deposition correlates closely with the health status of the drilled trees of Norway Spruce ( Picea Abies) in the Śnieżnik Massif. The averaged annual tree rings width near the local tree line (1,350 m a.s.l.) on the summit dome of Śnieżnik decreased by 71% between 1950 and the early 1980s. This is also the area of the highest rate of atmospheric pollutant deposition due to particularly important role of fog. At an altitude of 1,200 m a

  14. Groundwater age and chemistry, and future nutrient loads for selected Rotorua Lakes catchments

    International Nuclear Information System (INIS)

    Hydrochemical analysis and age dating of groundwater and groundwater-fed streams were carried out in the Lake Rotorua and Okareka catchments to assess the past and current states, and future trends in groundwater chemistry. The study was undertaken because of declining lake water quality due to observed increases in nutrient loads entering these lakes. THe hydrogeology of the Rotorua Lakes area can be described as a permeable pumiceous surface tephra layer that allows easy penetration of rainwater recharge to deeper rhyolite and ignimbrite aquifers. These aquifers are essentially unconfined and yield high volumes of groundwater that discharges to spring-fed streams or directly to the lake. The hydrochemistry of groundwaters is characterised by much lower concentrations of Ca, Mg and SO4 and much higher concentrations of PO4-P and SiO2 than other groundwaters in New Zealand. This chemical signature reflects the volcanic origin of the aquifer lithology. Because the aquifers in the Rotorua area have large water storage capacity there is a long residence time for nutrient-laden groundwater. It takes decades for the water after being recharged to reach the spring-fed streams and the lakes. The large groundwater bodies have therefore 'silently' been contaminated over decades, with the old pristine groundwater being progressively replaced by younger nutrient-laden water that will discharge to the spring-fed streams and finally to the lakes. This study involved age dating of springs, wells, and groundwater-fed streams to assess how long it takes for nutrient-enriched groundwater to travel from pastoral land to springs and streams, and to the lakes. Most of the springs and wells in the Lake Rotorua and Okareka catchments contained relatively old groundwaters, with mean residence times between 40 and >170 years (only two wells have younger water of 26 and 31 years mean residence time). This corresponds to young water fractions (water recharged within the last 55 years since

  15. Synthesis of 1,2,4-Triazoles via Oxidative Heterocyclization: Selective C-N Bond Over C-S Bond Formation.

    Science.gov (United States)

    Gogoi, Anupal; Guin, Srimanta; Rajamanickam, Suresh; Rout, Saroj Kumar; Patel, Bhisma K

    2015-09-18

    The higher propensity of C-N over C-S bond forming ability was demonstrated, through formal C-H functionalization during the construction of 4,5-disubstituted 1,2,4-triazole-3-thiones from arylidenearylthiosemicarbazides catalyzed by Cu(II). However, steric factors imparted by the o-disubstituted substrates tend to change the reaction path giving thiodiazole as the major or an exclusive product. Upon prolonging the reaction time, the in situ generated thiones are transformed to 4,5-disubstituted 1,2,4-triazoles via a desulfurization process. Two classes of heterocycles viz. 4,5-disubstituted 1,2,4-triazole-3-thiones and 4,5-disubstituted 1,2,4-triazoles can be synthesized from arylidenearylthiosemicarbazides by simply adjusting the reaction time. Desulfurization of 1,2,4-triazole-3-thiones is assisted by thiophilic Cu to provide 1,2,4-triazoles with concomitant formation of CuS and polynuclear sulfur anions as confirmed from scanning electron microscope and energy dispersive X-ray spectroscopy measurements. A one-pot synthesis of an antimicrobial compound has been successfully achieved following this strategy. PMID:26332253

  16. Effect of nonthermal plasma treatment on surface chemistry of commercially-pure titanium and shear bond strength to autopolymerizing acrylic resin.

    Science.gov (United States)

    Vechiato-Filho, Aljomar José; da Silva Vieira Marques, Isabella; dos Santos, Daniela Micheline; Matos, Adaias Oliveira; Rangel, Elidiane Cipriano; da Cruz, Nilson Cristino; Barão, Valentim Adelino Ricardo

    2016-03-01

    The effect of nonthermal plasma on the surface characteristics of commercially pure titanium (cp-Ti), and on the shear bond strength between an autopolymerizing acrylic resin and cp-Ti was investigated. A total of 96 discs of cp-Ti were distributed into four groups (n=24): Po (no surface treatment), SB (sandblasting), Po+NTP and SB+NTP (methane plasma). Surface characterization was performed through surface energy, surface roughness, scanning microscopy, energy dispersive spectroscopy, and X-ray diffraction tests. Shear bond strength test was conducted immediately and after thermocycling. Surface treatment affected the surface energy and roughness of cp-Ti discs (P<.001). SEM-EDS showed the presence of the carbide thin film. XRD spectra revealed no crystalline phase changes. The SB+NTP group showed the highest bond strength values (6.76±0.70 MPa). Thermocycling reduced the bond strength of the acrylic resin/cp-Ti interface (P<.05), except for Po group. NTP is an effective treatment option for improving the shear bond strength between both materials. PMID:26706504

  17. Amphoteric Aqueous Hafnium Cluster Chemistry.

    Science.gov (United States)

    Goberna-Ferrón, Sara; Park, Deok-Hie; Amador, Jenn M; Keszler, Douglas A; Nyman, May

    2016-05-17

    Selective dissolution of hafnium-peroxo-sulfate films in aqueous tetramethylammonium hydroxide enables extreme UV lithographic patterning of sub-10 nm HfO2 structures. Hafnium speciation under these basic conditions (pH>10), however, is unknown, as studies of hafnium aqueous chemistry have been limited to acid. Here, we report synthesis, crystal growth, and structural characterization of the first polynuclear hydroxo hafnium cluster isolated from base, [TMA]6 [Hf6 (μ-O2 )6 (μ-OH)6 (OH)12 ]⋅38 H2 O. The solution behavior of the cluster, including supramolecular assembly via hydrogen bonding is detailed via small-angle X-ray scattering (SAXS) and electrospray ionization mass spectrometry (ESI-MS). The study opens a new chapter in the aqueous chemistry of hafnium, exemplifying the concept of amphoteric clusters and informing a critical process in single-digit-nm lithography. PMID:27094575

  18. Hypercarbon chemistry

    International Nuclear Information System (INIS)

    This text points out the emerging significance of higher-valent carbon compounds. It describes the compounds of carbon with coordination numbers greater than four and explores the delocalized bonds of π aromatic molecules as a basis for rational description of orbitals; localized multicentered orbitals; the interactions of metallic ions with other atoms and molecules; the skeletal electron counts as a guide for synthesis; and the isolobal concept. Illustrated are the ways in which these subjects bring together structure and reactivity in the great diversity of novel carbon chemistry and its relationship to that of boron, lithium, hydrogen, the metals, and others

  19. Polarized infrared spectroscopy and quantum chemistry calculations studies on structure and orientation of C-H---O=C hydrogen bondings in biodegradable poly(3-hydroxybutyrate)

    Czech Academy of Sciences Publication Activity Database

    Sato, H.; Dybal, Jiří; Iwata, T.; Zhang, J.; Tashiro, K.; Noda, I.; Ozaki, Y.

    Delavan : International Steering Committee, 2005. s. 274. [International Conference on Advanced Vibrational Spectroscopy /3./. 14.8.2005-19.8.2005, Delavan] Institutional research plan: CEZ:AV0Z40500505 Keywords : UHMW- PHB * IR spectra Subject RIV: CD - Macromolecular Chemistry

  20. The influence of four dual-cure resin cements and surface treatment selection to bond strength of fiber post

    Institute of Scientific and Technical Information of China (English)

    Chang Liu; Hong Liu; Yue-Tong Qian; Song Zhu; Su-Qian Zhao

    2014-01-01

    In this study, we evaluate the influence of post surface pre-treatments on the bond strength of four different cements to glass fiber posts. Eighty extracted human maxillary central incisors and canines were endodontically treated and standardized post spaces were prepared. Four post pre-treatments were tested:(i) no pre-treatment (NS, control), (ii) sandblasting (SA), (iii) silanization (SI) and (iv) sandblasting followed by silanization (SS). Per pre-treatment, four dual-cure resin cements were used for luting posts:DMG LUXACORE Smartmix Dual, Multilink Automix, RelyX Unicem and Panavia F2.0. All the specimens were subjected to micro push-out test. Two-way analysis of variance and Tukey post hoc tests were performed (a50.05) to analyze the data. Bond strength was significantly affected by the type of resin cement, and bond strengths of RelyX Unicem and Panavia F2.0 to the fiber posts were significantly higher than the other cement groups. Sandblasting significantly increased the bond strength of DMG group to the fiber posts.

  1. Quantum chemistry

    CERN Document Server

    Lowe, John P

    2006-01-01

    Lowe's new edition assumes little mathematical or physical sophistication and emphasizes an understanding of the techniques and results of quantum chemistry. It can serve as a primary text in quantum chemistry courses, and enables students and researchers to comprehend the current literature. This third edition has been thoroughly updated and includes numerous new exercises to facilitate self-study and solutions to selected exercises.* Assumes little initial mathematical or physical sophistication, developing insights and abilities in the context of actual problems* Provides thorough treatment

  2. Bonds Between Atoms.

    Science.gov (United States)

    Holden, Alan

    The field of inquiry into how atoms are bonded together to form molecules and solids crosses the borderlines between physics and chemistry encompassing methods characteristic of both sciences. At one extreme, the inquiry is pursued with care and rigor into the simplest cases; at the other extreme, suggestions derived from the more careful inquiry…

  3. The influence of four dual-cure resin cements and surface treatment selection to bond strength of fiber post

    OpenAIRE

    Liu, Chang; Liu, Hong; Qian, Yue-Tong; Zhu, Song; Zhao, Su-Qian

    2013-01-01

    In this study, we evaluate the influence of post surface pre-treatments on the bond strength of four different cements to glass fiber posts. Eighty extracted human maxillary central incisors and canines were endodontically treated and standardized post spaces were prepared. Four post pre-treatments were tested: (i) no pre-treatment (NS, control), (ii) sandblasting (SA), (iii) silanization (SI) and (iv) sandblasting followed by silanization (SS). Per pre-treatment, four dual-cure resin cements...

  4. Mechanisms of Selective Cleavage of C-O Bonds in Di-aryl Ethers in Aqueous Phase

    Energy Technology Data Exchange (ETDEWEB)

    He, Jiayue; Zhao, Chen; Mei, Donghai; Lercher, Johannes A.

    2014-01-02

    A novel route for cleaving the C-O aryl ether bonds of p-substituted H-, CH3-, and OH- diphenyl ethers has been explored over Ni/SiO2 catalysts at very mild conditions. The C-O bond of diphenyl ether is cleaved by parallel hydrogenolysis and hydrolysis (hydrogenolysis combined with HO* addition) on Ni. The rates as a function of H2 pressure from 0 to 10 MPa indicate that the rate-determining step is the C-O bond cleavage on Ni. H* atoms compete with the organic reactant for adsorption leading to a maximum in the rate with increasing H2 pressure. In contrast to diphenyl ether, hydrogenolysis is the exclusive route for cleaving an ether C-O bond of di-p-tolyl ether to form p-cresol and toluene. 4,4'-dihydroxydiphenyl ether undergoes sequential surface hydrogenolysis, first to phenol and HOC6H4O* (adsorbed), which is then cleaved to phenol (C6H5O* with added H*) and H2O (O* with two added H*) in a second step. Density function theory supports the operation of this pathway. Notably, addition of H* to HOC6H4O* is less favorable than a further hydrogenolytic C-O bond cleavage. The TOFs of three aryl ethers with Ni/SiO2 in water followed the order 4,4'-dihydroxydiphenyl ether (69 h-1) > diphenyl ether (26 h-1) > di-p-tolyl ether (1.3 h-1), in line with the increasing apparent activation energies, ranging from 93 kJ∙mol-1 (4,4'-dihydroxydiphenyl ether) < diphenyl ether (98 kJ∙mol-1) to di-p-tolyl ether (105 kJ∙mol-1). D.M. thanks the support from the US Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. Pacific Northwest National Laboratory (PNNL) is a multiprogram national laboratory operated for DOE by Battelle. Computing time was granted by the grand challenge of computational catalysis of the

  5. Computational chemistry

    Science.gov (United States)

    Arnold, J. O.

    1987-01-01

    With the advent of supercomputers, modern computational chemistry algorithms and codes, a powerful tool was created to help fill NASA's continuing need for information on the properties of matter in hostile or unusual environments. Computational resources provided under the National Aerodynamics Simulator (NAS) program were a cornerstone for recent advancements in this field. Properties of gases, materials, and their interactions can be determined from solutions of the governing equations. In the case of gases, for example, radiative transition probabilites per particle, bond-dissociation energies, and rates of simple chemical reactions can be determined computationally as reliably as from experiment. The data are proving to be quite valuable in providing inputs to real-gas flow simulation codes used to compute aerothermodynamic loads on NASA's aeroassist orbital transfer vehicles and a host of problems related to the National Aerospace Plane Program. Although more approximate, similar solutions can be obtained for ensembles of atoms simulating small particles of materials with and without the presence of gases. Computational chemistry has application in studying catalysis, properties of polymers, all of interest to various NASA missions, including those previously mentioned. In addition to discussing these applications of computational chemistry within NASA, the governing equations and the need for supercomputers for their solution is outlined.

  6. Hydrogen Bonds Involving Metal Centers

    OpenAIRE

    Pavlović, G.; N. Raos

    2006-01-01

    Hydrogen bonds involving metal center as a hydrogen donor or hydrogen acceptor are only a specific type of metal-hydrogen interactions; it is therefore not easy to differentiate hydrogen bond from other metal-hydrogen interactions, especially agostic ones. The first part of the review is therefore devoted to the results of structural chemistry and molecular spectroscopy (NMR, IR), as a tool for differentiating hydrogen bondings from other hydrogen interactions. The classical examples of Pt···...

  7. Novel mononuclear vanadium complexes having pentalene ligands η8-bonded to a single metal atom - a new type of coordination in organometallic chemistry

    International Nuclear Information System (INIS)

    The pronounced folding of the η8-coordinated pentalene ligand along the bond between the two bridgehead carbon atoms is the most prominent structural feature of the vanadium complex 2. This compound and further 18e complexes of this type are readily prepared by the reaction of vanadocene monohalides 1 or their derivatives with dilithium pentalenediide. Although these mononuclear complexes are air-sensitive, they are thermally so stable that they can be sublimed in high vacuum at 80-100 C without decomposition. (orig.)

  8. Novel mononuclear vanadium complexes having pentalene ligands {eta}{sup 8}-bonded to a single metal atom - a new type of coordination in organometallic chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Jonas, K.; Gabor, B.; Mynott, R.; Angermund, K.; Heinemann, O.; Krueger, C. [Max-Planck-Institut fuer Kohlenforschung, Muelheim an der Ruhr (Germany)

    1997-09-01

    The pronounced folding of the {eta}{sup 8}-coordinated pentalene ligand along the bond between the two bridgehead carbon atoms is the most prominent structural feature of the vanadium complex 2. This compound and further 18e complexes of this type are readily prepared by the reaction of vanadocene monohalides 1 or their derivatives with dilithium pentalenediide. Although these mononuclear complexes are air-sensitive, they are thermally so stable that they can be sublimed in high vacuum at 80-100 C without decomposition. (orig.)

  9. Comparative analysis of a nontraditional general chemistry textbook and selected traditional textbooks used in Texas community colleges

    Science.gov (United States)

    Salvato, Steven Walter

    The purpose of this study was to analyze questions within the chapters of a nontraditional general chemistry textbook and the four general chemistry textbooks most widely used by Texas community colleges in order to determine if the questions require higher- or lower-order thinking according to Bloom's taxonomy. The study employed quantitative methods. Bloom's taxonomy (Bloom, Engelhart, Furst, Hill, & Krathwohl, 1956) was utilized as the main instrument in the study. Additional tools were used to help classify the questions into the proper category of the taxonomy (McBeath, 1992; Metfessel, Michael, & Kirsner, 1969). The top four general chemistry textbooks used in Texas community colleges and Chemistry: A Project of the American Chemical Society (Bell et al., 2005) were analyzed during the fall semester of 2010 in order to categorize the questions within the chapters into one of the six levels of Bloom's taxonomy. Two coders were used to assess reliability. The data were analyzed using descriptive and inferential methods. The descriptive method involved calculation of the frequencies and percentages of coded questions from the books as belonging to the six categories of the taxonomy. Questions were dichotomized into higher- and lower-order thinking questions. The inferential methods involved chi-square tests of association to determine if there were statistically significant differences among the four traditional college general chemistry textbooks in the proportions of higher- and lower-order questions and if there were statistically significant differences between the nontraditional chemistry textbook and the four traditional general chemistry textbooks. Findings indicated statistically significant differences among the four textbooks frequently used in Texas community colleges in the number of higher- and lower-level questions. Statistically significant differences were also found among the four textbooks and the nontraditional textbook. After the analysis of

  10. Surface-Controlled Mono/Diselective ortho C-H Bond Activation.

    Science.gov (United States)

    Li, Qing; Yang, Biao; Lin, Haiping; Aghdassi, Nabi; Miao, Kangjian; Zhang, Junjie; Zhang, Haiming; Li, Youyong; Duhm, Steffen; Fan, Jian; Chi, Lifeng

    2016-03-01

    One of the most charming and challenging topics in organic chemistry is the selective C-H bond activation. The difficulty arises not only from the relatively large bond-dissociation enthalpy, but also from the poor reaction selectivity. In this work, Au(111) and Ag(111) surfaces were used to address ortho C-H functionalization and ortho-ortho couplings of phenol derivatives. More importantly, the competition between dehydrogenation and deoxygenation drove the diversity of reaction pathways of phenols on surfaces, that is, diselective ortho C-H bond activation on Au(111) surfaces and monoselective ortho C-H bond activation on Ag(111) surfaces. The mechanism of this unprecedented phenomenon was extensively explored by scanning tunneling microscopy, density function theory, and X-ray photoelectron spectroscopy. Our findings provide new pathways for surface-assisted organic synthesis via the mono/diselective C-H bond activation. PMID:26853936

  11. Comparison of select hematology and serum chemistry analtyes between wild-caught and aquarium-housed lake sturgeon (Acipenser fulvescens)

    Science.gov (United States)

    DiVincenti, Louis, Jr.; Priest, Heather; Walker, Kyle J.; Wyatt, Jeffrey D.; Dittman, Dawn

    2013-01-01

    Hematology and serum chemistry analytes were compared between wild-caught and aquarium-housed lake sturgeon (Acipenser fulvescens) to potentially improve understanding of medical issues in lake sturgeon. Blood samples were taken from 30 lake sturgeon exhibited in 11 institutions in the United States and from 23 experimentally stocked lake sturgeon caught in gill nets in the lower Genesee River in Rochester, New York, USA. For hematology, only segmented neutrophil count was significantly different, with wild-caught fish having a higher number of circulating neutrophils. For clinical chemistry analytes, chloride, uric acid, calcium, phosphate, glucose, aspartate aminotransferase, triglycerides, and creatine kinase were significantly different between the two cohorts. These differences are likely not clinically significant and are attributable to handling stress, variability in environmental parameters, or differences in nutritional status. This is the first report of hematology and serum chemistry values in aquarium-housed lake sturgeon and provides useful reference intervals for clinicians.

  12. Exercises in Computational Chemistry

    DEFF Research Database (Denmark)

    Spanget-Larsen, Jens

    2016-01-01

    A selection of HyperChem© PC-exercises in computational chemistry. Answers to most questions are appended (Roskilde University 2014-16).......A selection of HyperChem© PC-exercises in computational chemistry. Answers to most questions are appended (Roskilde University 2014-16)....

  13. C-H bond activation by f-block complexes.

    Science.gov (United States)

    Arnold, Polly L; McMullon, Max W; Rieb, Julia; Kühn, Fritz E

    2015-01-01

    Most homogeneous catalysis relies on the design of metal complexes to trap and convert substrates or small molecules to value-added products. Organometallic lanthanide compounds first gave a tantalizing glimpse of their potential for catalytic C-H bond transformations with the selective cleavage of one C-H bond in methane by bis(permethylcyclopentadienyl)lanthanide methyl [(η(5) -C5 Me5 )2 Ln(CH3 )] complexes some 25 years ago. Since then, numerous metal complexes from across the periodic table have been shown to selectively activate hydrocarbon C-H bonds, but the challenges of closing catalytic cycles still remain; many f-block complexes show great potential in this important area of chemistry. PMID:25384554

  14. Probing the structures and chemical bonding of boron-boronyl clusters using photoelectron spectroscopy and computational chemistry: B4(BO)(n)- (n = 1-3).

    Science.gov (United States)

    Chen, Qiang; Zhai, Hua-Jin; Li, Si-Dian; Wang, Lai-Sheng

    2012-07-28

    The electronic and structural properties of a series of boron oxide clusters, B(5)O(-), B(6)O(2)(-), and B(7)O(3)(-), are studied using photoelectron spectroscopy and density functional calculations. Vibrationally resolved photoelectron spectra are obtained, yielding electron affinities of 3.45, 3.54, and 4.94 eV for the corresponding neutrals, B(5)O, B(6)O(2), and B(7)O(3), respectively. Structural optimizations show that these oxide clusters can be formulated as B(4)(BO)(n)(-) (n = 1-3), which involve boronyls coordinated to a planar rhombic B(4) cluster. Chemical bonding analyses indicate that the B(4)(BO)(n)(-) clusters are all aromatic species with two π electrons. PMID:22852618

  15. Mechanistic aspects of dinitrogen cleavage and hydrogenation to produce ammonia in catalysis and organometallic chemistry: relevance of metal hydride bonds and dihydrogen.

    Science.gov (United States)

    Jia, Hong-Peng; Quadrelli, Elsje Alessandra

    2014-01-21

    Dinitrogen cleavage and hydrogenation by transition-metal centers to produce ammonia is central in industry and in Nature. After an introductory section on the thermodynamic and kinetic challenges linked to N2 splitting, this tutorial review discusses three major classes of transition-metal systems (homogeneous, heterogeneous and biological) capable of achieving dissociation and hydrogenation of dinitrogen. Molecular complexes, solid-state Haber-Bosch catalytic systems, silica-supported tantalum hydrides and nitrogenase will be discussed. Emphasis is focused on the reaction mechanisms operating in the process of dissociation and hydrogenation of dinitrogen, and in particular on the key role played by metal hydride bonds and by dihydrogen in such reactions. PMID:24108246

  16. Application of mixed-mode, solid-phase extraction in environmental and clinical chemistry. Combining hydrogen-bonding, cation-exchange and Van der Waals interactions

    Science.gov (United States)

    Mills, M.S.; Thurman, E.M.; Pedersen, M.J.

    1993-01-01

    Silica- and styrene-divinylbenzene-based mixed-mode resins that contain C8, C18 and sulphonated cation-exchange groups were compared for their efficiency in isolation of neutral triazine compounds from water and of the basic drug, benzoylecgonine, from urine. The triazine compounds were isolated by a combination of Van der Waals and hydrogen-bonding interactions, and benzoylecgonine was isolated by Van der Waals interactions and cation exchange. All analytes were eluted with a polar organic solvent contaning 2% ammonium hydroxide. Larger recoveries (95%) were achieved on copolymerized mixed-mode resins where C18 and sulfonic acid are in closer proximity than on 'blended' mixed-mode resins (60-70% recovery).

  17. Radicals and Transition-Metal Catalysis: An Alliance Par Excellence to Increase Reactivity and Selectivity in Organic Chemistry

    Czech Academy of Sciences Publication Activity Database

    Ford, Leigh Robert; Jahn, Ullrich

    2009-01-01

    Roč. 48, č. 35 (2009), s. 6386-6389. ISSN 1433-7851 Institutional research plan: CEZ:AV0Z40550506 Keywords : cross-coupling * elimination * homogeneous catalysis * hydrogen transfer * radicals Subject RIV: CC - Organic Chemistry Impact factor: 11.829, year: 2009

  18. The Application of SCC-DV-Xα Computational Method of Quantum Chemistry in Cement Chemistry

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    It has been explored why quantum chemistry is applied to the research field of cement chemistry. The fundamental theory of SCC-DV-Xα computational method of quantum chemistry is synopsized. The results obtained by computational quantum chemistry method in recent years of valence-bond structures and hydration activity of some cement clinker minerals, mechanical strength and stabilization of some hydrates are summarized and evaluated. Finally the prospects of the future application of quantum chemistry to cement chemistry are depicted.

  19. Velocity Map Imaging Study of Ion-Radical Chemistry: Charge Transfer and Carbon-Carbon Bond Formation in the Reactions of Allyl Radicals with C(.).

    Science.gov (United States)

    Pei, Linsen; Farrar, James M

    2016-08-11

    We present an experimental and computational study of the dynamics of collisions of ground state carbon cations with allyl radicals, C3H5, at a collision energy of 2.2 eV. Charge transfer to produce the allyl cation, C3H5(+), is exoergic by 3.08 eV and proceeds via energy resonance such that the electron transfer occurs without a significant change in nuclear velocities. The products have sufficient energy to undergo the dissociation process C3H5(+) → C3H4(+) + H. Approximately 80% of the reaction products are ascribed to charge transfer, with ∼40% of those products decaying via loss of a hydrogen atom. We also observe products arising from the formation of new carbon-carbon bonds. The experimental velocity space flux distributions for the four-carbon products are symmetric about the centroid of the reactants, providing direct evidence that the products are mediated by formation of a C4H5(+) complex living at least a few rotational periods. The primary four-carbon reaction products are formed by elimination of molecular hydrogen from the C4H5(+) complex. More than 75% of the nascent C4H3(+) products decay by C-H bond cleavage to yield a C4H2(+) species. Quantum chemical calculations at the MP2/6-311+g(d,p) level of theory support the formation of a nonplanar cyclic C4H5(+) adduct that is produced when the p-orbital containing the unpaired electron on C(+) overlaps with the unpaired spin density on the terminal carbon atoms in allyl. Product formation then occurs by 1,2-elimination of molecular hydrogen from the cyclic intermediate to form a planar cyclic C4H3(+) product. The large rearrangement in geometry as the C4H3(+) products are formed is consistent with high vibrational excitation in that product and supports the observation that the majority of those products decay to form the C4H2(+) species. PMID:27434380

  20. DOE fundamentals handbook: Chemistry

    International Nuclear Information System (INIS)

    The Chemistry Handbook was developed to assist nuclear facility operating contractors in providing operators, maintenance personnel, and the technical staff with the necessary fundamentals training to ensure a basic understanding of chemistry. The handbook includes information on the atomic structure of matter; chemical bonding; chemical equations; chemical interactions involved with corrosion processes; water chemistry control, including the principles of water treatment; the hazards of chemicals and gases, and basic gaseous diffusion processes. This information will provide personnel with a foundation for understanding the chemical properties of materials and the way these properties can impose limitations on the operation of equipment and systems

  1. An investigation on the chemistry of the R2P[double bond, length as m-dash]P ligand: reactions of a phosphanylphosphinidene complex of tungsten(vi) with electrophilic reagents.

    Science.gov (United States)

    Grubba, Rafał; Ordyszewska, Anna; Ponikiewski, Łukasz; Gudat, Dietrich; Pikies, Jerzy

    2016-02-01

    The nucleophilic properties of the title compound [(2,6-i-Pr2C6H3N)2(Cl)W(η(2)-t-Bu2P[double bond, length as m-dash]P)]Li·3DME (1) were investigated in reactions with selected electrophilic reagents such as MeI, M(CO)5THF (M = Cr, Mo, W), AlCl3, and GaCl3. Methylation of 1 by MeI yields phosphanylphosphido complexes [(2,6-i-Pr2C6H3N)2W(X)(1,2-η-t-Bu2P[double bond, length as m-dash]P-CH3)] (X = Cl, I) (2-Cl/2-I) with the formation of a new P-C bond. Moreover, 1 reacts with electrophilic compounds [(OC)5M·THF] (M = Cr, Mo, W) to yield a series of novel dinuclear phosphanylphosphinidene complexes [(2,6-i-Pr2C6H3N)2(Cl)W(1,2-η-t-Bu2P[double bond, length as m-dash]P-M(CO)5)]Li·3DME (3, 4, 5) with very long P-M distances. Adducts [(2,6-i-Pr2C6H3N)2(Cl)W(1,2-η-t-Bu2P[double bond, length as m-dash]P-MCl3)]Li·3DME (6, 7) formed by reaction of 1 with GaCl3 and AlCl3 are labile and dissociate into 1 and MCl3 (M = Ga, Al). The outcomes of reactions were monitored by (31)P-NMR spectroscopy. Furthermore, the structures of the isolated complexes 2-Cl/2-I, 3, 4, and [(2,6-i-Pr2C6H3N)2(Cl)W(1,2-η-t-Bu2P[double bond, length as m-dash]P-W(t-Bu2PH)(CO)3COLi·2DME] (5-P) were confirmed unambiguously by X-ray diffraction studies. PMID:26556527

  2. Metalloradical-Catalyzed Selective 1,2-Rh-H Insertion into the Aliphatic Carbon-Carbon Bond of Cyclooctane

    NARCIS (Netherlands)

    Y.W. Chan; B. de Bruin; K.S. Chan

    2015-01-01

    The selective aliphatic carboncarbon activation of cyclo-octane (c-octane) was achieved via the Rh-II(ttp)-catalyzed 1,2-addition of Rh(ttp)H to give Rh(ttp)(n-octyl) (ttp = tetratolylporphyrinato dianion) in good yield under mild reaction conditions. This mechanism is further supported by DFT calcu

  3. A crystal chemistry approach for high-power ytterbium doped solid-state lasers: diffusion-bonded crystals and new crystalline hosts

    International Nuclear Information System (INIS)

    This work deals with ytterbium based crystals for high-power laser applications. In particular, we focus our interest in reducing crystal heating and its consequences during laser operation following two different ways. First, we review the specific properties of ytterbium doped solid-state lasers in order to define a figure-of-merit which gives the evaluation of laser performances, thermo-mechanical and thermo-optical properties. Bearing in mind this analysis, we propose a set of theoretical tools, based on the crystallographic structure of the crystal and its chemical composition, to predict thermo-mechanical and optical potentials. This approach, used for the seek of new Yb3+-doped materials for high-power laser applications, shows that simple oxides containing rare-earths are favorable. Therefore, the spectroscopic properties of six new materials Yb3+:GdVO4, Yb3+:GdAlO3, Yb3+:Gd2O3, Yb3+:Sc2SiO5, Yb3+:CaSc2O4 and Yb3+:SrSc2O4 are described. The second aspect developed in this work deals with thermal properties enhancement of already well characterized laser materials. Two different ways are explored: a) elaboration by diffusion bonding of end-caps lasers with undoped crystals (composite crystals). Thus, different composites were obtained and a fairly lowering of thermal lensing effect was observed during laser operation. b) strengthening of crystalline structures by ionic substitution of one of its constituents. We demonstrate how crystal growth ability can be improved by a cationic substitution in the case of Yb3+:BOYS, a largely-tunable laser material which is of great interest for femtosecond pulses generation. (author)

  4. Fine chemistry

    International Nuclear Information System (INIS)

    The 1988 progress report of the Fine Chemistry laboratory (Polytechnic School, France) is presented. The research programs are centered on the renewal of the organic chemistry most important reactions and on the invention of new, highly efficient and highly selective reactions, by applying low cost reagents and solvents. An important research domain concerns the study and fabrication of new catalysts. They are obtained by means of the reactive sputtering of the metals and metal oxydes thin films. The Monte Carlo simulations of the long-range electrostatic interaction in a clay and the obtention of acrylamides from anhydrous or acrylic ester are summarized. Moreover, the results obtained in the field of catalysis are also given. The published papers and the congress communications are included

  5. An in vitro compartmentalization-based method for the selection of bond-forming enzymes from large libraries.

    Science.gov (United States)

    Gianella, Paul; Snapp, Erik L; Levy, Matthew

    2016-08-01

    We have developed a generalized in vitro compartmentalization-based bead display selection strategy that allows for the identification of enzymes that can perform ligation reactions. Although a number of methods have been developed to evolve such enzymes, many of them are limited in library size (10(6) -10(7) ), do not select for enzymes using a scheme that allows for multiple turnover, or only work on enzymes specific to nucleic acids. This approach is amenable to screening libraries of up to 10(12) protein variants by allowing beads to be overloaded with up to 10(4) unique mutants. Using this approach we isolated a variant of sortase A from Staphylococcus aureus that shows a 114-fold enhancement in kcat /KM in the absence of calcium compared to the wild-type and improved resistance to the inhibitory effects of cell lysates. Unlike the wild-type protein, the newly selected variant shows intracellular activity in the cytoplasm of eukaryotic cells where it may prove useful for intracellular labeling or synthetic biological applications. Biotechnol. Bioeng. 2016;113: 1647-1657. © 2016 Wiley Periodicals, Inc. PMID:26806853

  6. Unwilling bonding in U2@C80: Endohedral fullerene with U-U bond

    Czech Academy of Sciences Publication Activity Database

    Foroutan-Nejad, C.; Patzschke, M.; Straka, Michal

    Edinburgh : Royal Society of Chemistry, 2014. [Dalton Discussion 14. Advancing the chemistry of the f-elements. 28.07.2014-30.07.2014, Edinburgh] R&D Projects: GA ČR(CZ) GA14-03564S Grant ostatní: European Social Fund(XE) CZ.1.07/2.3.00/30.009 Institutional support: RVO:61388963 Keywords : endohedral actinide fullerene * U-U bonding * actinide-actinide bonding Subject RIV: CF - Physical ; Theoretical Chemistry

  7. Aggregation-resistant VHs selected by in vitro evolution tend to have disulfide-bonded loops and acidic isoelectric points.

    Science.gov (United States)

    Arbabi-Ghahroudi, M; To, R; Gaudette, N; Hirama, T; Ding, W; MacKenzie, R; Tanha, J

    2009-02-01

    When panned with a transient heat denaturation approach against target enzymes, a human V(H) (antibody heavy chain variable domain) phage display library yielded V(H)s with composite characteristics of binding, non-aggregation and reversible thermal unfolding. Moreover, selection was characterized by enrichment for V(H)s with (i) an even number of disulfide forming Cys residues in complementarity-determining region (CDR) 1 and CDR3 and (ii) acidic isoelectric points. This parallels naturally occurring camelid and shark single-domain antibodies (sdAbs) which are also characterized by (i) solubility and reversible unfolding, (ii) a high occurrence of disulfide forming Cys in their CDRs, particularly, in CDR1 and CDR3 and (iii) acidic V(H)s as inferred here by a pI distribution analysis, reported here, of pools of human and camelid V(H) and V(H)H (camelid heavy chain antibody V(H)) sequences. Our results, reinforced by previous observations by others, suggest that protein acidification may yet be another mechanism nature has devised to create functional sdAbs and that this concept along with the inclusion of inter-CDR disulfide linkages may be applied to human V(H) domains/libraries for non-aggregation optimization. In addition, calculation of theoretical pIs of V(H)s selected by panning may be used for rapid and precise identification of non-aggregating V(H)s. PMID:19033278

  8. Outer-Sphere Coordination Chemistry: Amido-Ammonium Ligands as Highly Selective Tetrachloridozinc(II)ate Extractants

    OpenAIRE

    Turkington, Jennifer R; Cocalia, Violina; Kendall, Katrina; Morrison, Carole A.; Richardson, Patricia; Sassi, Thomas; Tasker, Peter A.; Bailey, Philip J.; Sole, Kathryn C.

    2012-01-01

    Eight new amido functionalized reagents, L-1-L-8, have been synthesized containing the sequence of atoms R2N-CH2-NR'-CO-R '', which upon protonation forms a six-membered chelate with a hydrogen bond between the tertiary ammonium N-H+ group and the amido oxygen atom. The monocationic ligands, LH+, extract tetrachloridometal(II)ates from acidic solutions containing high concentrations of chloride ions via a mechanism in which two ligands address the "outer sphere" of the [MCl4](2-) unit using b...

  9. Selecting ethanol as a model organic solvent in radiation chemistry--3. Radiolysis of glycyrrhetinic acid (GL)-ethanol system and structure modification of GL by γ radiation method

    International Nuclear Information System (INIS)

    CH3CHOH, H·, esolv- are the main active radicals in the ethanol system irradiated by γ-ray without the presence of oxygen. In this study, GL ethanolic solution saturated with nitrogen was γ-irradiated, the radiolytic products were isolated by HPLC and the molecular structure was determined with UV, IR, MS spectra and elementary analysis methods. In this system GL reacts with H· and CH3CHOH radicals. CH3CHOH adds to the C-C double bond of GL, then the formed radicals disproportionate to the final products RP1 (olean 29-oic acid,3-hydroxy-11-oxo-12-ethoxyl-13-hydro-,(3β, 20β)-) and RP3. H· reacts with GL in the similar way. The rate constant of H· reacting with GL was obtained as kGL+H·=2.0x1010 dm3 mol-1 s-1. The rate constant of CH3CHOH reacting with GL was calculated as result of (1.2±0.1)x104 dm3 mol-1 s-1 by using steady state method and by using the numerical quadrature method with computer. G(-GL), G(H2 ), G(2,3-butanediol), G(CH3CHO) and G values of the radiolytic products of ethanolic solution with different GL concentration were measured. A material balance was obtained. Results show that the active site of a GL molecule is the C-C double bond. The radiation chemistry technique can be used to modify the structure of glycyrrhetinic acid

  10. A Phenomenographic Study on Chemical Bonding

    Directory of Open Access Journals (Sweden)

    Şenol Şen

    2013-12-01

    Full Text Available This study aims to reveal how students perceive and identify the concept of chemical bonding, and to identify and explain the misconceptions of students on this subject through phenomenographic research method, as well. The present study included 17 2nd grade students who enrolled to Inorganic Chemistry course in the Faculty of Education. Concept maps and lotus blossom technique were used as data collection tools in order to determine the perceptions and definitions of students about chemical bonding. Data analysis results determined the misconceptions of students about chemical bonding classified misconceptions under seven categories, which are, according to the results of the study, physical changes and bonding, ionic bond, formation of chemical bonding, the existence of chemical bonding, covalent bonds, metallic bonds and intermolecular bonding.

  11. Bad chemistry

    OpenAIRE

    Petsko, Gregory A

    2004-01-01

    General chemistry courses haven't changed significantly in forty years. Because most basic chemistry students are premedical students, medical schools have enormous influence and could help us start all over again to create undergraduate chemistry education that works.

  12. Aza-Quaternary Scaffolds from Selective Bond Cleavage of Bridgehead-Substituted 7-Azabicyclo[2.2.1]heptane: Total Synthesis of (+)-Cylindricines C-E and (-)-Lepadiformine A.

    Science.gov (United States)

    Pandey, Ganesh; Janakiram, Vaitla

    2015-09-01

    A novel bridgehead-substituted aza-bicyclic framework has been designed and developed in both enantiomeric forms through an asymmetric desymmetrization reaction. Strategic exploitation of the ring strain in the aza-bicyclic framework has been utilized for the construction of the chiral aza-quaterenary scaffolds by selective bond fragmentation processes. Furthermore, a strategically designed precursor is employed for selective bond cleavage to initiate a cascade rearrangement for the total synthesis of the 1-azaspirotricyclic marine alkaloids (+)-cylindricines C, D, and E, as well as (-)-lepadiformine A. An oxidation/retro-aldol/aza-Michael sequence generated three new chiral centers with the required configuration in one pot. PMID:26220441

  13. Hydrodenitrogenation chemistry. I. Cleavage of alkylcarbon-nitrogen bonds, methane and ammonia formation in the HDN reaction of 1,2,3,4-tetrahydroquinoline with a nickel oxide catalyst supported on silica/alumina

    Energy Technology Data Exchange (ETDEWEB)

    Fish, R.H.; Thormodsen, A.D.; Moore, R.S.; Perry, D.L.; Heinemann, H.

    1986-11-01

    The hydrodenitrogenation reaction (HDN) is one of the most important industrial processes used in the refining of petroleum feedstocks and involves the removal of the nitrogen atom, as ammonia, from polynuclear heteroaromatic nitrogen compounds at high temperatures and high pressures of hydrogen gas (350-500/sup 0/C and 2000 psi). It is interesting to note that most of the reported heterogeneous catalysts require the complete hydrogenation of both the nitrogen heterocyclic ring and the aromatic ring before carbon-nitrogen bond cleavage can occur. A major breakthrough in the technical and economic aspects of the HDN reaction would take place if, in fact a catalyst could be found that would selectively cleave the C-N bond din the saturated nitrogen ring and subsequently produce ammonia, without substantial reduction of the aromatic rings, at lower temperatures as well as lower pressures of hydrogen gas. In this note, the authors report on a highly loaded nickel oxide catalyst (50% by weight Ni), supported on silica/alumina, that will effectively provide some of the criteria for an ideal HDN catalyst. 8 references.

  14. Facile Isolation of Adsorbent-Free Long and Highly-Pure Chirality-Selected Semiconducting Single-Walled Carbon Nanotubes Using A Hydrogen-bonding Supramolecular Polymer

    Science.gov (United States)

    Toshimitsu, Fumiyuki; Nakashima, Naotoshi

    2015-12-01

    The ideal form of semiconducting-single-walled carbon nanotubes (sem-SWNTs) for science and technology is long, defect-free, chirality pure and chemically pure isolated narrow diameter tubes. While various techniques to solubilize and purify sem-SWNTs have been developed, many of them targeted only the chiral- or chemically-purity while sacrificing the sem-SWNT intrinsic structural identities by applying strong ultra-sonication and/or chemical modifications. Toward the ultimate purification of the sem-SWNTs, here we report a mild-conditioned extraction of the sem-SWNTs using removable supramolecular hydrogen-bonding polymers (HBPs) that are composed of dicarboxylic- or diaminopyridyl-fluorenes with ~70%-(8,6)SWNT selective extraction. Replacing conventional strong sonication techniques by a simple shaking using HPBs was found to provide long sem-SWNTs (>2.0 μm) with a very high D/G ratio, which was determined by atomic force microscopy observations. The HBPs were readily removed from the nanotube surfaces by an outer stimulus, such as a change in the solvent polarities, to provide chemically pure (8,6)-enriched sem-SWNTs. We also describe molecular mechanics calculations to propose possible structures for the HBP-wrapped sem-SWNTs, furthermore, the mechanism of the chiral selectivity for the sorted sem-SWNTs is well explained by the relationship between the molecular surface area and mass of the HBP/SWNT composites.

  15. Selective Catalytic Synthesis Using the Combination of Carbon Dioxide and Hydrogen: Catalytic Chess at the Interface of Energy and Chemistry.

    Science.gov (United States)

    Klankermayer, Jürgen; Wesselbaum, Sebastian; Beydoun, Kassem; Leitner, Walter

    2016-06-20

    The present Review highlights the challenges and opportunities when using the combination CO2 /H2 as a C1 synthon in catalytic reactions and processes. The transformations are classified according to the reduction level and the bond-forming processes, covering the value chain from high volume basic chemicals to complex molecules, including biologically active substances. Whereas some of these concepts can facilitate the transition of the energy system by harvesting renewable energy into chemical products, others provide options to reduce the environmental impact of chemical production already in today's petrochemical-based industry. Interdisciplinary fundamental research from chemists and chemical engineers can make important contributions to sustainable development at the interface of the energetic and chemical value chain. The present Review invites the reader to enjoy this exciting area of "catalytic chess" and maybe even to start playing some games in her or his laboratory. PMID:27237963

  16. Cyclodextrin chemistry

    International Nuclear Information System (INIS)

    The chemistry of cyclodextrins was studied. This study included synthesising some cyclodextrin derivatives, preparing selected inclusion complexes with cyclodextrin and investigating the effects of gamma irradiation on cyclodextrins and certain linear oligosaccharides. This report presents a brief review of the structure and properties of cyclodextrins, the synthesis of cyclodextrin derivatives, their complexation and applications. This is followed by a description of the synthesis of some cyclodextrin derivatives and the preparation of inclusion complexes of cyclodextrin with some organic compounds. Finally, the effects of gamma irradiation on cyclodextrins, some of their derivatives and certain structurally related carbohydrates are discussed. The gamma irradiation studies were carried out for two reasons: to study the effects of gamma irradiation on cyclodextrins and their derivatives; and to investigate selectivity during the gamma irradiation of cyclodextrin derivatives

  17. Beauty in chemistry

    Directory of Open Access Journals (Sweden)

    Peter Atkins

    2006-03-01

    Full Text Available Though hard going for the general reader and highly personal in its selectivity, Elegant Solutions: Ten Beautiful Experiments in Chemistry provides reflections of a thoughtful author that will delight chemists

  18. Beauty in chemistry

    OpenAIRE

    Peter Atkins

    2006-01-01

    Though hard going for the general reader and highly personal in its selectivity, Elegant Solutions: Ten Beautiful Experiments in Chemistry provides reflections of a thoughtful author that will delight chemists

  19. Mathematical Chemistry

    OpenAIRE

    Trinajstić, Nenad; Gutman, Ivan

    2002-01-01

    A brief description is given of the historical development of mathematics and chemistry. A path leading to the meeting of these two sciences is described. An attempt is made to define mathematical chemistry, and journals containing the term mathematical chemistry in their titles are noted. In conclusion, the statement is made that although chemistry is an experimental science aimed at preparing new compounds and materials, mathematics is very useful in chemistry, among other things, to produc...

  20. Principles of quantum chemistry

    CERN Document Server

    George, David V

    2013-01-01

    Principles of Quantum Chemistry focuses on the application of quantum mechanics in physical models and experiments of chemical systems.This book describes chemical bonding and its two specific problems - bonding in complexes and in conjugated organic molecules. The very basic theory of spectroscopy is also considered. Other topics include the early development of quantum theory; particle-in-a-box; general formulation of the theory of quantum mechanics; and treatment of angular momentum in quantum mechanics. The examples of solutions of Schroedinger equations; approximation methods in quantum c

  1. Mild and Selective Catalytic Hydrogenation of the C=C Bond in α,β-Unsaturated Carbonyl Compounds Using Supported Palladium Nanoparticles.

    Science.gov (United States)

    Nagendiran, Anuja; Pascanu, Vlad; Bermejo Gómez, Antonio; González Miera, Greco; Tai, Cheuk-Wai; Verho, Oscar; Martín-Matute, Belén; Bäckvall, Jan-E

    2016-05-17

    Chemoselective reduction of the C=C bond in a variety of α,β-unsaturated carbonyl compounds using supported palladium nanoparticles is reported. Three different heterogeneous catalysts were compared using 1 atm of H2 : 1) nano-Pd on a metal-organic framework (MOF: Pd(0) -MIL-101-NH2 (Cr)), 2) nano-Pd on a siliceous mesocellular foam (MCF: Pd(0) -AmP-MCF), and 3) commercially available palladium on carbon (Pd/C). Initial studies showed that the Pd@MOF and Pd@MCF nanocatalysts were superior in activity and selectivity compared to commercial Pd/C. Both Pd(0) -MIL-101-NH2 (Cr) and Pd(0) -AmP-MCF were capable of delivering the desired products in very short reaction times (10-90 min) with low loadings of Pd (0.5-1 mol %). Additionally, the two catalytic systems exhibited high recyclability and very low levels of metal leaching. PMID:27111403

  2. Photoinduced hydrogen-bonding dynamics.

    Science.gov (United States)

    Chu, Tian-Shu; Xu, Jinmei

    2016-09-01

    Hydrogen bonding dynamics has received extensive research attention in recent years due to the significant advances in femtolaser spectroscopy experiments and quantum chemistry calculations. Usually, photoexcitation would cause changes in the hydrogen bonding formed through the interaction between hydrogen donor and acceptor molecules on their ground electronic states, and such transient strengthening or weakening of hydrogen bonding could be crucial for the photophysical transformations and the subsequent photochemical reactions that occurred on a time scale from tens of femtosecond to a few nanoseconds. In this article, we review the combined experimental and theoretical studies focusing on the ultrafast electronic and vibrational hydrogen bonding dynamics. Through these studies, new mechanisms and proposals and common rules have been put forward to advance our understanding of the hydrogen bondings dynamics in a variety of important photoinduced phenomena like photosynthesis, dual fluorescence emission, rotational reorientation, excited-state proton transfer and charge transfer processes, chemosensor fluorescence sensing, rearrangements of the hydrogen-bond network including forming and breaking hydrogen bond in water. Graphical Abstract We review the recent advances on exploring the photoinduced hydrogen bonding dynamics in solutions through a joint approach of laser spectroscopy and theoretical calculation. The reviewed studies have put forward a new mechanism, new proposal, and new rule for a variety of photoinduced phenomena such as photosynthesis, dual fluorescence emission, rotational reorientation, excited-state proton transfer and charge transfer, chemosensor fluorescence sensing, and rearrangements of the hydrogen-bond network in water. PMID:27491849

  3. Supramolecular chemistry of selective anion recognition for anions of environmental relevance. Progress report, October 1996--July 1997

    Energy Technology Data Exchange (ETDEWEB)

    Bowman-James, K.; Wilson, G.S.; Kuczera, K. [Univ. of Kansas, Lawrence, KS (US); Moyer, B. [Oak Ridge National Lab., TN (US)

    1997-01-01

    'This project has as its focus the design and synthesis of polyammonium macrocyclic receptors for oxoanions of environmental importance. The basic research aspects of this project involve synthesis (and the search for improved synthetic methods), solid state structure determination and thermodynamics studies (to ascertain structural criteria for and strength of anion binding), and molecular dynamics simulations (to assess solution characteristics of the interactions between anions and their receptors). Applications-oriented goals include the fabrication of more efficient anion-selective electrodes and the use of these compounds in liquid- liquid separations. The latter goal is the subcontract with Bruce Moyer at Oak Ridge National Laboratory. This first year the authors have focused on nitrates and phosphates. Considerable progress has been made in the basic areas of synthesis, solid state Structure, and molecular dynamics. Anion selective electrodes have also be made which show promising selectivities for oxoanions of interest. Below are described the major findings and significance in the categories of synthesis, structure and molecular dynamics, and electrode studies. Synthesis. The synthesis of polyaza macrocycles which are the focus of these studies is often tedious and time-consuming. A major breakthrough which the authors have made this year is to identify other polyaza macrocycles, which also bind the desired anions, but which are simpler to synthesize via a two step Schiff base/reduction process with high yields. This is truly significant since now the authors can obtain large quantities of the macrocycles and do multiple studies at once (crystallizations, thermodynamics, electrode, and eventually separations). Most of their studies to date have focused on monocyclic systems, but they are now beginning to examine bicyclic macrocycles, which can be synthesized by the same method starting with the tetraamine known as tren.'

  4. Pyrrolidine nucleotides conformationally constrained via hydrogen bonding

    Czech Academy of Sciences Publication Activity Database

    Pohl, Radek; Poštová Slavětínská, Lenka; Rejman, Dominik

    Praha : Institute of Organic Chemistry and Biochemistry AS CR, v. v. i, 2014 - (Hocek, M.), s. 352-353 ISBN 978-80-86241-50-0. - (Collection Symposium Series. 14). [Symposium on Chemistry of Nucleic Acid Components /16./. Český Krumlov (CZ), 08.06.2014-13.06.2014] R&D Projects: GA ČR GA13-24880S Institutional support: RVO:61388963 Keywords : pyrrolidine nucleotides * PMEA * hydrogen bond Subject RIV: CC - Organic Chemistry

  5. Upper Secondary Teachers' Knowledge for Teaching Chemical Bonding Models

    Science.gov (United States)

    Bergqvist, Anna; Drechsler, Michal; Chang Rundgren, Shu-Nu

    2016-01-01

    Researchers have shown a growing interest in science teachers' professional knowledge in recent decades. The article focuses on how chemistry teachers impart chemical bonding, one of the most important topics covered in upper secondary school chemistry courses. Chemical bonding is primarily taught using models, which are key for understanding…

  6. Toward selective, sensitive, and discriminative detection of Hg(2+) and Cd(2+)via pH-modulated surface chemistry of glutathione-capped gold nanoclusters.

    Science.gov (United States)

    Huang, Pengcheng; Li, Sha; Gao, Nan; Wu, Fangying

    2015-11-01

    Heavy metal pollution can exert severe effects on the environment and human health. Simple, selective, and sensitive detection of heavy metal ions, especially two or more, using a single probe, is thereby of great importance. In this study, we report a new and facile strategy for discriminative detection of Hg(2+) and Cd(2+) with high selectivity and sensitivity via pH-modulated surface chemistry of the glutathione-capped gold NCs (GSH-Au NCs). By simply adjusting pH values of the colloidal solution of the NCs, Hg(2+) could specifically turn off the fluorescence under acidic pH, however, Cd(2+) could exclusively turn on the fluorescence under alkaline pH. This enables the NCs to serve as a dual fluorescent sensor for Hg(2+) and Cd(2+). We demonstrate that these two opposing sensing modes are presumably due to different interaction mechanisms: Hg(2+) induces aggregation by dissociating GSH from the Au surface via robust coordination and, Cd(2+) could passivate the Au surface by forming a Cd-GSH complex with a compact structure. Finally, the present strategy is successfully exploited to separately determine Hg(2+) and Cd(2+) in environmental water samples. PMID:26347906

  7. Protein folding guides disulfide bond formation

    OpenAIRE

    Qin, Meng; Wang, Wei; Thirumalai, D.

    2015-01-01

    Anfinsen inferred the principles of protein folding by studying a protein containing four disulfide bonds in the native state. However, how protein folding drives disulfide bond formation is poorly understood despite the role such proteins play in variety of extracellular and intracellular functions. We developed a method to mimic the complex chemistry of disulfide bond formation in molecular simulations, which is used to decipher the mechanism of folding of bovine pancreatic trypsin inhibito...

  8. In pursuit of small molecule chemistry for calcium-permeable non-selective TRPC channels -- mirage or pot of gold?

    Science.gov (United States)

    Bon, Robin S; Beech, David J

    2013-10-01

    The primary purpose of this review is to address the progress towards small molecule modulators of human Transient Receptor Potential Canonical proteins (TRPC1, TRPC3, TRPC4, TRPC5, TRPC6 and TRPC7). These proteins generate channels for calcium and sodium ion entry. They are relevant to many mammalian cell types including acinar gland cells, adipocytes, astrocytes, cardiac myocytes, cochlea hair cells, endothelial cells, epithelial cells, fibroblasts, hepatocytes, keratinocytes, leukocytes, mast cells, mesangial cells, neurones, osteoblasts, osteoclasts, platelets, podocytes, smooth muscle cells, skeletal muscle and tumour cells. There are broad-ranging positive roles of the channels in cell adhesion, migration, proliferation, survival and turning, vascular permeability, hypertrophy, wound-healing, hypo-adiponectinaemia, angiogenesis, neointimal hyperplasia, oedema, thrombosis, muscle endurance, lung hyper-responsiveness, glomerular filtration, gastrointestinal motility, pancreatitis, seizure, innate fear, motor coordination, saliva secretion, mast cell degranulation, cancer cell drug resistance, survival after myocardial infarction, efferocytosis, hypo-matrix metalloproteinase, vasoconstriction and vasodilatation. Known small molecule stimulators of the channels include hyperforin, genistein and rosiglitazone, but there is more progress with inhibitors, some of which have promising potency and selectivity. The inhibitors include 2-aminoethoxydiphenyl borate, 2-aminoquinolines, 2-aminothiazoles, fatty acids, isothiourea derivatives, naphthalene sulfonamides, N-phenylanthranilic acids, phenylethylimidazoles, piperazine/piperidine analogues, polyphenols, pyrazoles and steroids. A few of these agents are starting to be useful as tools for determining the physiological and pathophysiological functions of TRPC channels. We suggest that the pursuit of small molecule modulators for TRPC channels is important but that it requires substantial additional effort and

  9. Stability of Field-Selected Resistance to Conventional and Newer Chemistry Insecticides in the House Fly, Musca domestica L. (Diptera: Muscidae).

    Science.gov (United States)

    Abbas, N; Ijaz, M; Shad, S A; Khan, H

    2015-08-01

    The house fly, Musca domestica L. (Diptera: Muscidae), is a pest of livestock and has the ability to develop resistance to different insecticides. We assessed the fluctuations in seasonal stability of house fly resistance to insecticides from poultry facility populations in Pakistan. House fly populations were collected from poultry facilities located at Khanewal, Punjab, Pakistan in three seasons (July, November, and March) to investigate the fluctuations in their resistance to conventional (organophosphate, pyrethroid) and novel chemistry (spinosyn, oxadiazine, neonicotinoid) insecticides. Laboratory bioassays were performed using the feeding method of mixing insecticide concentrations with 20% sugar solutions, and cotton pads dipped in insecticide solutions were provided to tested adult flies. Bioassay results showed that all house fly populations had varying degrees of susceptibility to tested insecticides. Comparisons between populations at different seasons showed a significant fluctuation in susceptibility to organophosphate, pyrethroid, spinosyn, oxadiazine, and neonicotinoid insecticides. Highest resistant levels were found for organophosphate when compared with other tested insecticides. The resistance to conventional insecticides decreased significantly in March compared with July and November, while resistance to oxadiazine and avermectins decreased significantly in November. However, resistance to spinosad and imidacloprid remained stable throughout the seasons. All conventional and novel chemistry insecticides were significantly correlated with each other in all tested seasons except nitenpyram/lambda-cyhalothrin and nitenpyram/imidacloprid. Our data suggests that the variation in house fly resistance among seasons could be due to fitness costs or to the cessation of selection pressure in the off-season. These results have significant implications for the use of insecticides in house fly management. PMID:26174963

  10. Biocatalysts for selective oxidations

    Energy Technology Data Exchange (ETDEWEB)

    Hartmann, M. [Department of Chemistry, Chemical Technology, TU Kaiserslautern (Germany)

    2005-07-01

    Selective oxidations using oxygen (or air) and hydrogen peroxide (or tert.-butyl hydroperoxide) are important transformations in synthetic organic chemistry as well as in industrial chemistry. However, these reactions are rarely regio- or stereo-selective and the selective oxidation of non-activated C-H-bonds is a still challenging problem. In contrast, enzyme-catalyzed reactions offer mild and selective routes to oxidation products which are important intermediates for the production of fine chemicals, pharmaceuticals or even bulk chemicals. However, a productive role of biocatalysts in basic chemical processing is not obvious. For decades, it was believed that enzymes might be suitable catalysts only for specialty applications. Such beliefs were guided by the assumption that enzymes in general are expensive and thus not suitable for processes to basic chemicals. Given sufficiently good stability and acceptable space time yields, enzymes have been proven to be catalysts of choice for quite a number of applications. New technologies such as protein engineering directed evolution and metabolic engineering are likely to open up further opportunities for biocatalytic routes, provided that they can meet the stringent productivity and cost criteria set by processes to basic chemicals. This review will discuss some general features of selective biocatalytic oxidations as well as some already implanted processes. An outlook of remaining challenges and the future potential of biocatalysts in selective oxidations will also be provided. (orig.)

  11. Introductory quantum chemistry

    International Nuclear Information System (INIS)

    This book on quantum chemistry is primarily intended for university students at the senior undergraduate level. It serves as an aid to the basic understanding of the important concepts of quantum mechanics introduced in the field of chemistry. Various chapters of the book are devoted to the following : (i) Waves and quanta, (ii) Operator concept in quantum chemistry, (iii) Wave mechanics of some simple systems, (iv) Perturbation theory, (v) Many-electron atoms and angular momenta (vi) Molecular orbital theory and its application to the electronic structure of diatomic molecules, (vii) Chemical bonding in polyatomic molecules and (viii) Chemical applications of Hellmann-Feynman theorem. At the end of each chapter, a set of problems is given and the answers to these problems are given at the end of the book. (A.K.)

  12. Bond Boom

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    The Ministry of Finance recently kick-started a pilot program allowing local governments of Shanghai and Shenzhen,and Zhejiang and Guangdong provinces to issue bonds for the first time.How will the new policy affect fiscal capacities of local governments and the broader economy? What else should the country do to build a healthy bond market? Economists and experts discussed these issues in an interview with the Shanghai Securities Journal.Edited excerpts follow.

  13. Bond Boom

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    The Ministry of Finance recently kick-started a pilot program allowing local governments of Shanghai and Shenzhen, and Zhejiang and Guangdong provinces to issue bonds for the first time. How will the new policy affect fiscal capacities of local governments and the broader economy? What else should the country do to build a healthy bond market? Economists and experts discussed these issues in an interview with the ShanghaiSecuritiesJournal. Edited excerpts follow:

  14. Combinatorial chemistry

    DEFF Research Database (Denmark)

    Nielsen, John

    1994-01-01

    An overview of combinatorial chemistry is presented. Combinatorial chemistry, sometimes referred to as `irrational drug design,' involves the generation of molecular diversity. The resulting chemical library is then screened for biologically active compounds.......An overview of combinatorial chemistry is presented. Combinatorial chemistry, sometimes referred to as `irrational drug design,' involves the generation of molecular diversity. The resulting chemical library is then screened for biologically active compounds....

  15. Positronium chemistry

    CERN Document Server

    Green, James

    1964-01-01

    Positronium Chemistry focuses on the methodologies, reactions, processes, and transformations involved in positronium chemistry. The publication first offers information on positrons and positronium and experimental methods, including mesonic atoms, angular correlation measurements, annihilation spectra, and statistical errors in delayed coincidence measurements. The text then ponders on positrons in gases and solids. The manuscript takes a look at the theoretical chemistry of positronium and positronium chemistry in gases. Topics include quenching, annihilation spectrum, delayed coincidence

  16. Design and synthesis of magnetic binary metal oxides nanocomposites through dopamine chemistry for highly selective enrichment of phosphopeptides.

    Science.gov (United States)

    Wang, Mengyi; Sun, Xueni; Li, Yan; Deng, Chunhui

    2016-03-01

    In this work, for the first time, magnetic binary metal oxides nanocomposites which integrated Zr and Ti into one entity on an atomic scale on polydopamine coated magnetic graphene (magG/PD/(Zr-Ti)O4 ) was designed and synthesized, and applied to the enrichment of phosphopeptides. The newly prepared magG/PD/(Zr-Ti)O4 composites gathered the advantages of large surface area, superparamagnetism, biocompatibility and the enhanced affinity properties to phosphopeptides. MagG/PD/ZrO2 , magG/PD/TiO2 , as well as the simple physical mixture of them were introduced to compare with magG/PD/(Zr-Ti)O4 composites. High sensitivity (1 pg/μL or 4.0 × 10(-11) M) and selectivity (weight ratio of β-casein and BSA reached up to 1:8000) toward phosphopeptides were also presented for magG/PD/(Zr-Ti)O4 composites. Additionally, mouse brain tissue was chose as the real samples to further investigate the phosphopeptides enrichment ability of this new material. PMID:26702589

  17. Gas phase ion chemistry

    CERN Document Server

    Bowers, Michael T

    1979-01-01

    Gas Phase Ion Chemistry, Volume 1 covers papers on the advances of gas phase ion chemistry. The book discusses the advances in flow tubes and the measurement of ion-molecule rate coefficients and product distributions; the ion chemistry of the earth's atmosphere; and the classical ion-molecule collision theory. The text also describes statistical methods in reaction dynamics; the state selection by photoion-photoelectron coincidence; and the effects of temperature and pressure in the kinetics of ion-molecule reactions. The energy distribution in the unimolecular decomposition of ions, as well

  18. Distinguishing Bonds.

    Science.gov (United States)

    Rahm, Martin; Hoffmann, Roald

    2016-03-23

    The energy change per electron in a chemical or physical transformation, ΔE/n, may be expressed as Δχ̅ + Δ(VNN + ω)/n, where Δχ̅ is the average electron binding energy, a generalized electronegativity, ΔVNN is the change in nuclear repulsions, and Δω is the change in multielectron interactions in the process considered. The last term can be obtained by the difference from experimental or theoretical estimates of the first terms. Previously obtained consequences of this energy partitioning are extended here to a different analysis of bonding in a great variety of diatomics, including more or less polar ones. Arguments are presented for associating the average change in electron binding energy with covalence, and the change in multielectron interactions with electron transfer, either to, out, or within a molecule. A new descriptor Q, essentially the scaled difference between the Δχ̅ and Δ(VNN + ω)/n terms, when plotted versus the bond energy, separates nicely a wide variety of bonding types, covalent, covalent but more correlated, polar and increasingly ionic, metallogenic, electrostatic, charge-shift bonds, and dispersion interactions. Also, Q itself shows a set of interesting relations with the correlation energy of a bond. PMID:26910496

  19. HYDROGEN BONDING IN POLYMERIC ADSORBENTS BASED ADSORPTION AND SEPARATION

    Institute of Scientific and Technical Information of China (English)

    XUMancai; SHIZuoqing; 等

    2000-01-01

    After a concise introduction of hydrogen bonding effects in solute-solute and solute-solvent bonding,the design of polymeric adsorbents based on hydrogen bonding ,selectivity in adsorption through hydrogen bonding,and characterization of hydrogen bonding in adsorption and separation were reviewed with 28 references.

  20. Dynamic combinatorial libraries : new opportunities in systems chemistry

    NARCIS (Netherlands)

    Hunt, Rosemary A. R.; Otto, Sijbren; Hunt, Rosemary A.R.

    2011-01-01

    Combinatorial chemistry is a tool for selecting molecules with special properties. Dynamic combinatorial chemistry started off aiming to be just that. However, unlike ordinary combinatorial chemistry, the interconnectedness of dynamic libraries gives them an extra dimension. An understanding of thes

  1. Social Chemistry

    OpenAIRE

    Lichtfouse, Eric; Schwarzbauer, Jan; Robert, Didier

    2012-01-01

    International audience This article is both an essay to propose social chemistry as a new scientific discipline, and a preface of the book Environmental Chemistry for a Sustainable World. Environmental chemistry is a fast emerging discipline aiming at the understanding the fate of pollutants in ecosystems and at designing novel processes that are safe for ecosystems. Past pollution should be cleaned, future pollution should be predicted and avoided (Lichtfouse et al., 2005a). Such advices ...

  2. Computational chemistry

    OpenAIRE

    Truhlar, Donald G.; McKoy, Vincent

    2000-01-01

    Computational chemistry has come of age. With significant strides in computer hardware and software over the last few decades, computational chemistry has achieved full partnership with theory and experiment as a tool for understanding and predicting the behavior of a broad range of chemical, physical, and biological phenomena. The Nobel Prize award to John Pople and Walter Kohn in 1998 highlighted the importance of these advances in computational chemistry. With massively parallel computers ...

  3. Bioinorganic Chemistry

    OpenAIRE

    Bertini, Ivano; Gray, Harry B.; Lippard, Stephen J.; Valentine, Joan Selverstone

    1994-01-01

    This book covers material that could be included in a one-quarter or one-semester course in bioinorganic chemistry for graduate students and advanced undergraduate students in chemistry or biochemistry. We believe that such a course should provide students with the background required to follow the research literature in the field. The topics were chosen to represent those areas of bioinorganic chemistry that are mature enough for textbook presentation. Although each chapter presents material...

  4. Technetium chemistry

    International Nuclear Information System (INIS)

    Technetium chemistry is a young and developing field. Despite the limited knowledge of its chemistry, technetium is the workhorse for nuclear medicine. Technetium is also a significant environmental concern because it is formed as a byproduct of nuclear weapons production and fission-power generators. Development of new technetium radio-pharmaceuticals and effective environmental control depends strongly upon knowledge of basic technetium chemistry. The authors performed research into the basic coordination and organometallic chemistry of technetium and used this knowledge to address nuclear medicine and environmental applications. This is the final report of a three-year Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL)

  5. Microwave assisted click chemistry on a conductive polymer film

    DEFF Research Database (Denmark)

    Daugaard, Anders Egede; Hansen, Thomas S.; Larsen, Niels Bent;

    2011-01-01

    Microwave (MW) irradiation has been used to accelerate the functionalization of an azide functional poly(3,4-ethylenedioxythiophene) film by click chemistry. The absorption of MW energy by the conductive polymer has been exploited for localized activation of the reaction on the polymer surface. B...... method has been applied for anchoring of the chelating agent nitrilotriacetic acid (NTA) on the conductive polymer. The chelating linkage ability of NTA on the surface was investigated through a sandwich ELISA study confirming the selective bonding of a histidine tagged protein....

  6. Migration chemistry

    International Nuclear Information System (INIS)

    Migration chemistry, the influence of chemical -, biochemical - and physico-chemical reactions on the migration behaviour of pollutants in the environment, is an interplay between the actual natur of the pollutant and the characteristics of the environment, such as pH, redox conditions and organic matter content. The wide selection of possible pollutants in combination with varying geological media, as well as the operation of different chemical -, biochemical - and physico-chemical reactions compleactes the prediction of the influence of these processes on the mobility of pollutants. The report summarizes a wide range of potential pollutants in the terrestrial environment as well as a variety of chemical -, biochemical - and physico-chemical reactions, which can be expected to influence the migration behaviour, comprising diffusion, dispersion, convection, sorption/desorption, precipitation/dissolution, transformations/degradations, biochemical reactions and complex formation. The latter comprises the complexation of metal ions as well as non-polar organics to naturally occurring organic macromolecules. The influence of the single types of processes on the migration process is elucidated based on theoretical studies. The influence of chemical -, biochemical - and physico-chemical reactions on the migration behaviour is unambiguous, as the processes apparently control the transport of pollutants in the terrestrial environment. As the simple, conventional KD concept breaks down, it is suggested that the migration process should be described in terms of the alternative concepts chemical dispersion, average-elution-time and effective retention. (AB) (134 refs.)

  7. Problems in structural inorganic chemistry

    CERN Document Server

    Li, Wai-Kee; Mak, Thomas Chung Wai; Mak, Kendrew Kin Wah

    2013-01-01

    This book consists of over 300 problems (and their solutions) in structural inorganic chemistry at the senior undergraduate and beginning graduate level. The topics covered comprise Atomic and Molecular Electronic States, Atomic Orbitals, Hybrid Orbitals, Molecular Symmetry, Molecular Geometry and Bonding, Crystal Field Theory, Molecular Orbital Theory, Vibrational Spectroscopy, and Crystal Structure. The central theme running through these topics is symmetry, molecular or crystalline. The problems collected in this volume originate in examination papers and take-home assignments that have been part of the teaching of the book's two senior authors' at The Chinese University of Hong Kong over the past four decades. The authors' courses include Chemical Bonding, Elementary Quantum Chemistry, Advanced Inorganic Chemistry, X-Ray Crystallography, etc. The problems have been tested by generations of students taking these courses.

  8. Chemical bond analysis in the ten-electron series

    OpenAIRE

    Fransson, Thomas

    2009-01-01

    This thesis presents briefly the application of quantum mechanics on systems ofchemical interest, i.e., the field of quantum chemistry and computational chemistry.The molecules of the ten-electron series, hydrogen fluoride, water, ammonia,methane and neon, are taken as computational examples. Some applications ofquantum chemistry are then shown on these systems, with emphasis on the natureof the molecular bonds. Conceptual methods of chemistry and theoreticalchemistry for these systems are sh...

  9. Financial planning working capital ventures using software «analyzer bdds» sold on the basis of selection of optimal bond portfolio

    Directory of Open Access Journals (Sweden)

    N.J. Timofeeva

    2011-05-01

    Full Text Available This article examines the financial planning of working capital organizations, in particular presented a software implementation of the algorithm analyzes the budget forecast working capital, identify and take advantage of temporarily free money using a model of a decision on the choice of the optimal bond portfolio, consistent with the free flow of liquidity of the enterprise.

  10. The Effects of the Property Tax Extension Limitation Law upon Revenue Growth, Bonded Debt, and School Business Leader Perceptions within Selected Illinois School Districts.

    Science.gov (United States)

    Hylbert, Danny

    2002-01-01

    Examines the effects of the Illinois Property Tax Extension Limitation Law on the revenue growth of collar counties and suburban school districts in Cook County. Finds that the law negatively affects revenue growth. Also finds, for example, that a majority of school business officials are motivated to increase their districts' bonded indebtedness.…

  11. Selective recovery of pure copper nanopowder from indium-tin-oxide etching wastewater by various wet chemical reduction process: Understanding their chemistry and comparisons of sustainable valorization processes.

    Science.gov (United States)

    Swain, Basudev; Mishra, Chinmayee; Hong, Hyun Seon; Cho, Sung-Soo

    2016-05-01

    Sustainable valorization processes for selective recovery of pure copper nanopowder from Indium-Tin-Oxide (ITO) etching wastewater by various wet chemical reduction processes, their chemistry has been investigated and compared. After the indium recovery by solvent extraction from ITO etching wastewater, the same is also an environmental challenge, needs to be treated before disposal. After the indium recovery, ITO etching wastewater contains 6.11kg/m(3) of copper and 1.35kg/m(3) of aluminum, pH of the solution is very low converging to 0 and contain a significant amount of chlorine in the media. In this study, pure copper nanopowder was recovered using various reducing reagents by wet chemical reduction and characterized. Different reducing agents like a metallic, an inorganic acid and an organic acid were used to understand reduction behavior of copper in the presence of aluminum in a strong chloride medium of the ITO etching wastewater. The effect of a polymer surfactant Polyvinylpyrrolidone (PVP), which was included to prevent aggregation, to provide dispersion stability and control the size of copper nanopowder was investigated and compared. The developed copper nanopowder recovery techniques are techno-economical feasible processes for commercial production of copper nanopowder in the range of 100-500nm size from the reported facilities through a one-pot synthesis. By all the process reported pure copper nanopowder can be recovered with>99% efficiency. After the copper recovery, copper concentration in the wastewater reduced to acceptable limit recommended by WHO for wastewater disposal. The process is not only beneficial for recycling of copper, but also helps to address environment challenged posed by ITO etching wastewater. From a complex wastewater, synthesis of pure copper nanopowder using various wet chemical reduction route and their comparison is the novelty of this recovery process. PMID:26918838

  12. Diffusion bonding

    Science.gov (United States)

    Anderson, Robert C.

    1976-06-22

    1. A method for joining beryllium to beryllium by diffusion bonding, comprising the steps of coating at least one surface portion of at least two beryllium pieces with nickel, positioning a coated surface portion in a contiguous relationship with an other surface portion, subjecting the contiguously disposed surface portions to an environment having an atmosphere at a pressure lower than ambient pressure, applying a force upon the beryllium pieces for causing the contiguous surface portions to abut against each other, heating the contiguous surface portions to a maximum temperature less than the melting temperature of the beryllium, substantially uniformly decreasing the applied force while increasing the temperature after attaining a temperature substantially above room temperature, and maintaining a portion of the applied force at a temperature corresponding to about maximum temperature for a duration sufficient to effect the diffusion bond between the contiguous surface portions.

  13. Good chemistry

    OpenAIRE

    Petsko, Gregory A

    2004-01-01

    The subject matter in chemistry courses reflects almost nothing of the issues that chemists are interested in. It is important to formulate a set of topics - and a Medical College Admissions Test reflecting them - that would leave chemistry departments no choice but to change their teaching.

  14. Evaluation of the corrosion, reactivity and chemistry control aspects for the selection of an alternative coolant in the secondary circuit of sodium fast reactors

    Energy Technology Data Exchange (ETDEWEB)

    Brissonneau, L.; Simon, N. [CEA Cadarache, Nuclear Energy Division, DTN/STPA/LPC, 13 - Saint-Paul-lez-Durance (France); Balbaud-Celerier, F.; Courouau, J.L.; Martinelli, L. [CEA Saclay, Nuclear Energy Division, DPC/SCCME/LECNA, 91 - Gif-sur-Yvette (France); Grabon, V. [Areva NP, NEEL - FM (France); Capitaine, A. [EdF SEPTEN, 69 - Lyon (France); Conocar, O. [CEA Marcoule, Nuclear Energy Division, DRCP/GEAT/GEDM, 30 (France); Blat, M. [EdF R and D, 78 - Chatou (France)

    2009-07-01

    Full text of publication follows: Sodium Fast Reactors are promising fourth generation reactors as they can contribute to reduce resource demand in uranium and considerably reduce waste level due to their fast spectrum. However, progress can be obtained for these reactors on the investment cost and on safety improvement. To achieve these goals, one of the innovative solutions consists in eliminating the reaction of sodium with water in the steam generators, by replacing the sodium in the secondary circuit by another coolant. A work group composed of experts from CEA, Areva NP and EdF was in charge to evaluate several alternative coolants as Heavy Liquid Metals (HLM), nitrate salts and hydroxide mixtures, through a multi-criteria analysis. Three important criteria for the selection of one coolant are its 'Interactions with the structures', and its 'chemistry control', and 'Reactivity with fluids' which are strongly correlated. The assessment, mainly based on the state-of-art from published literature on these points, is detailed in this paper. The mechanisms of corrosion of steels by the HLM depend on the oxygen content. For Pb-Bi, it has been modelled for oxidation and release domains. The corrosion of steels by nitrate salts presents similarity with the oxidation induced by HLM. The highly corrosive hydroxide mixture requires the use of nickel base alloys, for which oxidation and mass transfer are nevertheless significant. The HLM requires a fine regulation of oxygen content, through measurements and control systems, both to prevent lead oxide precipitation at high level and release corrosion at low level. Nitrate salts decompose into nitrites at sufficiently high temperature, which might induce pressure build-up in the circuit. The hydroxides must be kept under reducing atmosphere to lower the corrosion rate. Though these coolants are relatively inert to air and water, one of the main drawbacks of HLM and nitrate salts are their

  15. Carbohydrates in Supramolecular Chemistry.

    Science.gov (United States)

    Delbianco, Martina; Bharate, Priya; Varela-Aramburu, Silvia; Seeberger, Peter H

    2016-02-24

    Carbohydrates are involved in a variety of biological processes. The ability of sugars to form a large number of hydrogen bonds has made them important components for supramolecular chemistry. We discuss recent advances in the use of carbohydrates in supramolecular chemistry and reveal that carbohydrates are useful building blocks for the stabilization of complex architectures. Systems are presented according to the scaffold that supports the glyco-conjugate: organic macrocycles, dendrimers, nanomaterials, and polymers are considered. Glyco-conjugates can form host-guest complexes, and can self-assemble by using carbohydrate-carbohydrate interactions and other weak interactions such as π-π interactions. Finally, complex supramolecular architectures based on carbohydrate-protein interactions are discussed. PMID:26702928

  16. Rhodium-Catalyzed C-C Bond Formation via Heteroatom-Directed C-H Bond Activation

    Energy Technology Data Exchange (ETDEWEB)

    Colby, Denise; Bergman, Robert; Ellman, Jonathan

    2010-05-13

    Once considered the 'holy grail' of organometallic chemistry, synthetically useful reactions employing C-H bond activation have increasingly been developed and applied to natural product and drug synthesis over the past decade. The ubiquity and relative low cost of hydrocarbons makes C-H bond functionalization an attractive alternative to classical C-C bond forming reactions such as cross-coupling, which require organohalides and organometallic reagents. In addition to providing an atom economical alternative to standard cross - coupling strategies, C-H bond functionalization also reduces the production of toxic by-products, thereby contributing to the growing field of reactions with decreased environmental impact. In the area of C-C bond forming reactions that proceed via a C-H activation mechanism, rhodium catalysts stand out for their functional group tolerance and wide range of synthetic utility. Over the course of the last decade, many Rh-catalyzed methods for heteroatom-directed C-H bond functionalization have been reported and will be the focus of this review. Material appearing in the literature prior to 2001 has been reviewed previously and will only be introduced as background when necessary. The synthesis of complex molecules from relatively simple precursors has long been a goal for many organic chemists. The ability to selectively functionalize a molecule with minimal pre-activation can streamline syntheses and expand the opportunities to explore the utility of complex molecules in areas ranging from the pharmaceutical industry to materials science. Indeed, the issue of selectivity is paramount in the development of all C-H bond functionalization methods. Several groups have developed elegant approaches towards achieving selectivity in molecules that possess many sterically and electronically similar C-H bonds. Many of these approaches are discussed in detail in the accompanying articles in this special issue of Chemical Reviews. One approach

  17. Using Correlations to Understand Changes in Actinide Bonding

    International Nuclear Information System (INIS)

    An important issue in actinide science is the changing role of the 5f electrons, both when progressing across the series, as well as how experimental variables affect these roles in a particular element's chemistries and physics. The function of these 5f electrons can be changed by experimental conditions: temperature and pressure being two of many such variables. The 5f electrons of several actinide metals, their alloys and compounds are affected greatly by pressure, due to the very large decreases in interatomic distances encountered under pressure. The latter bring about significant changes in the total energy of the system and in the electronic energy levels, which in turn affect the potential for overlap/hybridization) of their orbitals, promotion of electrons to other orbitals, etc. The physical state, temperature, pressure, specific structures, magnetic interactions and spin polarization effects are all critical parameters for bonding. Often correlations of behavior with these parameters can provide unique insights and understanding into the bonding and the changes that occur in it. With the advancement of modern computation approaches using FPMTO, or other approaches, theory has enlightened greatly the understanding of not only the bonding behavior of these elements but also the understanding of changes observed experimentally. But these computational efforts have some complications and limitations, and at times experimental findings and theory are not always in full agreement. In contrast to the behaviors of the elements, changes observed with compounds often are not be linked directly to the involvement of 5f electrons, due in part to the presence and bonding role of non-actinide atoms. The latter affect both the actinide interatomic distances and the type of electronic orbitals that interact. Presented here is an overview of the pressure behavior several actinide elements, some insights into the bonding behavior of compounds under pressure and selected

  18. Pi Bond Orders and Bond Lengths

    Science.gov (United States)

    Herndon, William C.; Parkanyi, Cyril

    1976-01-01

    Discusses three methods of correlating bond orders and bond lengths in unsaturated hydrocarbons: the Pauling theory, the Huckel molecular orbital technique, and self-consistent-field techniques. (MLH)

  19. The correlation theory of the chemical bond

    CERN Document Server

    Szalay, Szilárd; Szilvási, Tibor; Veis, Libor; Legeza, Örs

    2016-01-01

    The notion of chemical bond is a very useful concept in chemistry. It originated at the beginning of chemistry, it is expressive for the classically thinking mind, and the errors arising from the approximative nature of the concept can often be ignored. In the first half of the twentieth century, however, we learned that the proper description of the microworld is given by quantum mechanics. Quantum mechanics gives more accurate results for chemical systems than any preceding model, however, it is very inexpressive for the classically thinking mind. The quantum mechanical description of the chemical bond is given in terms of delocalized bonding orbitals, or, alternatively, in terms of correlations of occupations of localized orbitals. However, in the latter case, multiorbital correlations were treated only in terms of two-orbital correlations, although the structure of multiorbital correlations is far richer; and, in the case of bonds established by more than two electrons, multiorbital correlations represent...

  20. Quantum chemistry

    CERN Document Server

    Lowe, John P

    1993-01-01

    Praised for its appealing writing style and clear pedagogy, Lowe's Quantum Chemistry is now available in its Second Edition as a text for senior undergraduate- and graduate-level chemistry students. The book assumes little mathematical or physical sophistication and emphasizes an understanding of the techniques and results of quantum chemistry, thus enabling students to comprehend much of the current chemical literature in which quantum chemical methods or concepts are used as tools. The book begins with a six-chapter introduction of standard one-dimensional systems, the hydrogen atom,

  1. The correlation theory of the chemical bond

    OpenAIRE

    Szalay, Szilárd; Barcza, Gergely; Szilvási, Tibor; Veis, Libor; Legeza, Örs

    2016-01-01

    The notion of chemical bond is a very useful concept in chemistry. It originated at the beginning of chemistry, it is expressive for the classically thinking mind, and the errors arising from the approximative nature of the concept can often be ignored. In the first half of the twentieth century, however, we learned that the proper description of the microworld is given by quantum mechanics. Quantum mechanics gives more accurate results for chemical systems than any preceding model, however, ...

  2. Exploring Conceptual Frameworks of Models of Atomic Structures and Periodic Variations, Chemical Bonding, and Molecular Shape and Polarity: A Comparison of Undergraduate General Chemistry Students with High and Low Levels of Content Knowledge

    Science.gov (United States)

    Wang, Chia-Yu; Barrow, Lloyd H.

    2013-01-01

    The purpose of the study was to explore students' conceptual frameworks of models of atomic structure and periodic variations, chemical bonding, and molecular shape and polarity, and how these conceptual frameworks influence their quality of explanations and ability to shift among chemical representations. This study employed a purposeful sampling…

  3. Materials Chemistry

    CERN Document Server

    Fahlman, Bradley D

    2011-01-01

    The 2nd edition of Materials Chemistry builds on the strengths that were recognized by a 2008 Textbook Excellence Award from the Text and Academic Authors Association (TAA). Materials Chemistry addresses inorganic-, organic-, and nano-based materials from a structure vs. property treatment, providing a suitable breadth and depth coverage of the rapidly evolving materials field. The 2nd edition continues to offer innovative coverage and practical perspective throughout. After briefly defining materials chemistry and its history, seven chapters discuss solid-state chemistry, metals, semiconducting materials, organic "soft" materials, nanomaterials, and materials characterization. All chapters have been thoroughly updated and expanded with, for example, new sections on ‘soft lithographic’ patterning, ‘click chemistry’ polymerization, nanotoxicity, graphene, as well as many biomaterials applications. The polymer and ‘soft’ materials chapter represents the largest expansion for the 2nd edition. Each ch...

  4. Introductory Chemistry

    OpenAIRE

    Baron, Mark; Gonzalez-Rodriguez, Jose; Stevens, Gary; Gray, Nathan; Atherton, Thomas; Winn, Joss

    2010-01-01

    Teaching and Learning resources for the 1st Year Introductory Chemistry course (Forensic Science). 30 credits. These are Open Educational Resources (OER), made available for re-use under a Creative Commons license.

  5. Analytical chemistry

    International Nuclear Information System (INIS)

    This book is comprised of nineteen chapters, which describes introduction of analytical chemistry, experimental error and statistics, chemistry equilibrium and solubility, gravimetric analysis with mechanism of precipitation, range and calculation of the result, volume analysis on general principle, sedimentation method on types and titration curve, acid base balance, acid base titration curve, complex and firing reaction, introduction of chemical electro analysis, acid-base titration curve, electrode and potentiometry, electrolysis and conductometry, voltammetry and polarographic spectrophotometry, atomic spectrometry, solvent extraction, chromatograph and experiments.

  6. Cluster Chemistry

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    @@ Cansisting of eight scientists from the State Key Laboratory of Physical Chemistry of Solid Surfaces and Xiamen University, this creative research group is devoted to the research of cluster chemistry and creation of nanomaterials.After three-year hard work, the group scored a series of encouraging progresses in synthesis of clusters with special structures, including novel fullerenes, fullerene-like metal cluster compounds as well as other related nanomaterials, and their properties study.

  7. Green Chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Collison, Melanie

    2011-05-15

    Green chemistry is the science of chemistry used in a way that will not use or create hazardous substances. Dr. Rui Resendes is working in this field at GreenCentre Canada, an offshoot of PARTEQ Innovations in Kingston, Ontario. GreenCentre's preliminary findings suggest their licensed product {sup S}witchable Solutions{sup ,} featuring 3 classes of solvents and a surfactant, may be useful in bitumen oil sands extraction.

  8. Chemistry of Transactinides

    Science.gov (United States)

    Kratz, J. V.

    In this chapter, the chemical properties of the man-made transactinide elements rutherfordium, Rf (element 104), dubnium, Db (element 105), seaborgium, Sg (element 106), bohrium, Bh (element 107), hassium, Hs (element 108), and copernicium, Cn (element 112) are reviewed, and prospects for chemical characterizations of even heavier elements are discussed. The experimental methods to perform rapid chemical separations on the time scale of seconds are presented and comments are given on the special situation with the transactinides where chemistry has to be studied with single atoms. It follows a description of theoretical predictions and selected experimental results on the chemistry of elements 104 through 108, and element 112.

  9. Chemistry in microelectronics

    CERN Document Server

    Le Tiec, Yannick

    2013-01-01

    Microelectronics is a complex world where many sciences need to collaborate to create nano-objects: we need expertise in electronics, microelectronics, physics, optics and mechanics also crossing into chemistry, electrochemistry, as well as biology, biochemistry and medicine. Chemistry is involved in many fields from materials, chemicals, gases, liquids or salts, the basics of reactions and equilibrium, to the optimized cleaning of surfaces and selective etching of specific layers. In addition, over recent decades, the size of the transistors has been drastically reduced while the functionalit

  10. The chemistry of silicon

    CERN Document Server

    Rochow, E G; Emeléus, H J; Nyholm, Ronald

    1975-01-01

    Pergamon Texts in Organic Chemistry, Volume 9: The Chemistry of Silicon presents information essential in understanding the chemical properties of silicon. The book first covers the fundamental aspects of silicon, such as its nuclear, physical, and chemical properties. The text also details the history of silicon, its occurrence and distribution, and applications. Next, the selection enumerates the compounds and complexes of silicon, along with organosilicon compounds. The text will be of great interest to chemists and chemical engineers. Other researchers working on research study involving s

  11. Evolution of an interloop disulfide bond in high-affinity antibody mimics based on fibronectin type III domain and selected by yeast surface display: molecular convergence with single-domain camelid and shark antibodies.

    Science.gov (United States)

    Lipovsek, Dasa; Lippow, Shaun M; Hackel, Benjamin J; Gregson, Melissa W; Cheng, Paul; Kapila, Atul; Wittrup, K Dane

    2007-05-11

    The 10th human fibronectin type III domain ((10)Fn3) is one of several protein scaffolds used to design and select families of proteins that bind with high affinity and specificity to macromolecular targets. To date, the highest affinity (10)Fn3 variants have been selected by mRNA display of libraries generated by randomizing all three complementarity-determining region -like loops of the (10)Fn3 scaffold. The sub-nanomolar affinities of such antibody mimics have been attributed to the extremely large size of the library accessible by mRNA display (10(12) unique sequences). Here we describe the selection and affinity maturation of (10)Fn3-based antibody mimics with dissociation constants as low as 350 pM selected from significantly smaller libraries (10(7)-10(9) different sequences), which were constructed by randomizing only 14 (10)Fn3 residues. The finding that two adjacent loops in human (10)Fn3 provide a large enough variable surface area to select high-affinity antibody mimics is significant because a smaller deviation from wild-type (10)Fn3 sequence is associated with a higher stability of selected antibody mimics. Our results also demonstrate the utility of an affinity-maturation strategy that led to a 340-fold improvement in affinity by maximizing sampling of sequence space close to the original selected antibody mimic. A striking feature of the highest affinity antibody mimics selected against lysozyme is a pair of cysteines on adjacent loops, in positions 28 and 77, which are critical for the affinity of the (10)Fn3 variant for its target and are close enough to form a disulfide bond. The selection of this cysteine pair is structurally analogous to the natural evolution of disulfide bonds found in new antigen receptors of cartilaginous fish and in camelid heavy-chain variable domains. We propose that future library designs incorporating such an interloop disulfide will further facilitate the selection of high-affinity, highly stable antibody mimics from

  12. Cobalt bis(dicarbollide) ions with covalently bonded CMPO groups as selective extraction agents for lanthanide and actinide cations from highly acidic nuclear waste solutions

    Czech Academy of Sciences Publication Activity Database

    Grüner, Bohumír; Plešek, Jaromír; Báča, Jiří; Císařová, I.; Dozol, J. F.; Rouquette, H.; Vinas, C.; Selucký, P.; Rais, J.

    2002-01-01

    Roč. 26, č. 10 (2002), s. 1519-1527. ISSN 1144-0546 R&D Projects: GA ČR GA104/99/1096; GA ČR GA104/01/0142; GA ČR GA203/99/M037; GA MŠk LN00A028 Institutional research plan: CEZ:AV0Z4032918 Keywords : LIQUID-CHROMATOGRAPHIC SEPARATIONS * BORON-CLUSTER COMPOUNDS * CALIXARENES Subject RIV: CA - Inorganic Chemistry Impact factor: 2.060, year: 2002

  13. Alkali-bonded ceramics with hierarchical tailored porosity

    Czech Academy of Sciences Publication Activity Database

    Landi, E.; Medri, V.; Papa, E.; Dědeček, Jiří; Klein, Petr; Benito, P.; Vaccari, A.

    2013-01-01

    Roč. 73, SI (2013), s. 56-64. ISSN 0169-1317 Institutional support: RVO:61388955 Keywords : alkali-bonded ceramics * metalcaolin * geopolymerization parameters Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.703, year: 2013

  14. Identification and cleavage of breakable single bonds by selective oxidation, reduction, and hydrolysis. Annual report, October 1, 1980-September 30, 1981

    Energy Technology Data Exchange (ETDEWEB)

    Hirschon, A.S.; Zevely, J.; Mayo, F.R.

    1981-11-12

    The objective of this project is to determine the structure of bituminous coal by determining the proportions of the various kinds of connecting bonds and how they can best be broken. Results obtained during the past quarter are presented for the following tasks: (1) extractions and fractionations of coal products which covers pyridine extraction, fractionation of TIPS fractions, EDA extraction of Illinois No. 6 coal and swelling ratios of coal samples; (2) experiments on breakable single bonds which cover reactions of ethylenediamine and model ethers, reaction of pyridine-extracted coal with Me/sub 3/SiI, Baeyer-Villiger oxidations, reaction to diphenylmethane with 15% HNO/sub 3/, cleavage of TIPS with ZnI/sub 2/, and cleavage of black acids; and (3) oxygen oxidation No. 18. Some of the highlights of these studies are: (1) some model ethers are not cleaved by EDA under extraction conditions; (2) oxidation of diaryl ketones with m-chloroperbenzoic acid and saponification of the resulting esters in promising for identifying ketones, (3) treatment of a black acid with pyridine hydroiodide reduced the acid's molecular weight and increased its solubility in pyridine, but treatment with ZnI/sub 2/ was ineffective; (4) in comparison with 0.1 M K/sub 2/S/sub 2/O/sub 8/, 0.01 M persulfate is relatively ineffective in accelerating oxidation of BnNH/sub 2/-extracted coal in water suspension. 2 figures, 3 tables.

  15. Biotic and abiotic carbon to sulfur bond cleavage. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Frost, J.W.

    1994-05-01

    The microbial desulfurization of organosulfur compounds occurs by unprecedented and largely unexplored biochemical processes. A study of such biotic desulfurizations can be expected to give rise to new and useful chemistry and enzymology. The potential value of understanding and harnessing these processes is seen in relation to the need for methods for the removal of organically bound sulfur from coal and the degradation of organic sulfur-containing pollutants. This research effort has been directed towards an examination of desulfurization ability in well characterized microorganisms, the isolation of bacteria with desulfurization ability from natural sources, the characterization and mechanistic evaluation of the observed biocatalytic processes, the development of biomimetic synthetic organic chemistry based on biotic desulfurization mechanisms and the design and preparation of improved coal model compounds for use in microbial selection processes. A systematic approach to studying biodesulfurizations was undertaken in which organosulfur compounds have been broken down into classes based on the oxidation state of the sulfur atom and the structure of the rest of the organic material. Microbes have been evaluated in terms of ability to degrade organosulfur compounds with sulfur in its sulfonic acid oxidation state. These compounds are likely intermediates in coal desulfurization and are present in the environment as persistent pollutants in the form of detergents. It is known that oxygen bonded to sulfur lowers the carbon-sulfur bond energy, providing a thermodynamic basis for starting with this class of compounds.

  16. Role of Exchange Equilibria in Structural Chemistry

    International Nuclear Information System (INIS)

    Although much of the past effort on the study of exchange reactions has been devoted to the scrambling of monofunctional substituents on a polyfunctional atom or moiety, complicated molecules may also undergo exchange of parts so as to give an equilibrium distribution of various molecular sizes and shapes. The use of high-resolution nuclear magnetic resonance (NMR) in investigating such equilibrated mixtures of compounds has been described in a number of 1964 and 1965 papers from the Monsanto Co. laboratory (see Refs [1-34] at the end of the abstracts). The systems thus studied include several new families of compounds; and the amounts and kinds of products resulting from the exchange reactions have been quantitatively described in terms of a small number of equilibrium constants. A new mathematical approach - that of stochastic graph theory [6] - has been employed to establish the form and the minimum number of equilibrium constants relating the non-cyclic structures and parts of molecular structures to each other. In addition, the equilibria between the cyclic and non-cyclic structures have been treated quantitatively. The emphasis in structural chemistry on the compounds of carbon (as evidenced by the division of descriptive chemistry into the organic and inorganic categories) is attributed to the fact that exchange reactions involving C-C bonds or bonds from carbon to any atom not exhibiting low-lying vacant bonding orbitals (e.g. Si, Ge, N, P, As. O, S, Se, F, Cl, Br) are exceedingly slow. On the other hand, there are vast areas of inorganic chemistry which have not previously been described because the molecules undergo such rapid exchange reactions that they cannot be separated. However, they can be identified and quantitatively assayed by means of physical methods (such as NMR) having short time constants, when the resulting data receive proper mathematical treatment - a procedure which is sufficiently involved to demand the use of a high-speed computer [6

  17. Rule of five in 2015 and beyond: Target and ligand structural limitations, ligand chemistry structure and drug discovery project decisions.

    Science.gov (United States)

    Lipinski, Christopher A

    2016-06-01

    The rule of five (Ro5), based on physicochemical profiles of phase II drugs, is consistent with structural limitations in protein targets and the drug target ligands. Three of four parameters in Ro5 are fundamental to the structure of both target and drug binding sites. The chemical structure of the drug ligand depends on the ligand chemistry and design philosophy. Two extremes of chemical structure and design philosophy exist; ligands constructed in the medicinal chemistry synthesis laboratory without input from natural selection and natural product (NP) metabolites biosynthesized based on evolutionary selection. Exceptions to Ro5 are found mostly among NPs. Chemistry chameleon-like behavior of some NPs due to intra-molecular hydrogen bonding as exemplified by cyclosporine A is a strong contributor to NP Ro5 outliers. The fragment derived, drug Navitoclax is an example of the extensive expertise, resources, time and key decisions required for the rare discovery of a non-NP Ro5 outlier. PMID:27154268

  18. Radiation Chemistry

    Science.gov (United States)

    Wojnárovits, L.

    Ionizing radiation causes chemical changes in the molecules of the interacting medium. The initial molecules change to new molecules, resulting in changes of the physical, chemical, and eventually biological properties of the material. For instance, water decomposes to its elements H2 and O2. In polymers, degradation and crosslinking take place. In biopolymers, e.g., DNS strand breaks and other alterations occur. Such changes are to be avoided in some cases (radiation protection), however, in other cases they are used for technological purposes (radiation processing). This chapter introduces radiation chemistry by discussing the sources of ionizing radiation (radionuclide sources, machine sources), absorption of radiation energy, techniques used in radiation chemistry research, and methods of absorbed energy (absorbed dose) measurements. Radiation chemistry of different classes of inorganic (water and aqueous solutions, inorganic solids, ionic liquids (ILs)) and organic substances (hydrocarbons, halogenated compounds, polymers, and biomolecules) is discussed in concise form together with theoretical and experimental backgrounds. An essential part of the chapter is the introduction of radiation processing technologies in the fields of polymer chemistry, food processing, and sterilization. The application of radiation chemistry to nuclear technology and to protection of environment (flue gas treatment, wastewater treatment) is also discussed.

  19. Recent progress in actinide borate chemistry.

    Science.gov (United States)

    Wang, Shuao; Alekseev, Evgeny V; Depmeier, Wulf; Albrecht-Schmitt, Thomas E

    2011-10-21

    The use of molten boric acid as a reactive flux for synthesizing actinide borates has been developed in the past two years providing access to a remarkable array of exotic materials with both unusual structures and unprecedented properties. [ThB(5)O(6)(OH)(6)][BO(OH)(2)]·2.5H(2)O possesses a cationic supertetrahedral structure and displays remarkable anion exchange properties with high selectivity for TcO(4)(-). Uranyl borates form noncentrosymmetric structures with extraordinarily rich topological relationships. Neptunium borates are often mixed-valent and yield rare examples of compounds with one metal in three different oxidation states. Plutonium borates display new coordination chemistry for trivalent actinides. Finally, americium borates show a dramatic departure from plutonium borates, and there are scant examples of families of actinides compounds that extend past plutonium to examine the bonding of later actinides. There are several grand challenges that this work addresses. The foremost of these challenges is the development of structure-property relationships in transuranium materials. A deep understanding of the materials chemistry of actinides will likely lead to the development of advanced waste forms for radionuclides present in nuclear waste that prevent their transport in the environment. This work may have also uncovered the solubility-limiting phases of actinides in some repositories, and allows for measurements on the stability of these materials. PMID:21915396

  20. As percepções dos professores de química geral sobre a seleção e a organização conceitual em sua disciplina The perceptions of college teachers on the organization and selection of concepts in general chemistry

    OpenAIRE

    Shirley Martim da Silva; Marcelo Leandro Eichler; José Claudio Del Pino

    2003-01-01

    The teaching of general chemistry involves both the choice and the organization of its concepts. Although College Teachers make their choices, frequently the text books play an important role in this selection. In the present project we intend to show what are Teachers' perceptions of conceptual organization and selection as well as their perceptions of how to teach general chemistry. This demonstration is carried out through the use of metaphors from new information technologies.

  1. Identification and cleavage of breakable single bonds by selective oxidation, reduction, and hydrolysis. Quarterly report No. 12, June 1-September 30, 1981

    Energy Technology Data Exchange (ETDEWEB)

    Hirschon, A.S.; Zevely, J.; Mayo, F.R.

    1981-11-12

    We assume that bituminous coal consists mostly of an aggregate of condensed aromatic and aliphatic rings, connected and made insoluble (but swellable) by crosslinks containing single bonds. The objective of this project is to determine the proportions of the various kinds of connecting links and how they can best be broken - in other words, to determine the structure of bituminous coal, with emphasis on the crosslinks and breakable single bonds. The program began with an investigation of the structure of the TIPS fraction of Illinois No. 6 coal, that is, the two-thirds of the 16% extracted by pyridine that is toluene-insoluble, pyridine-soluble, mostly through changes in molecular weight during cleavage reactions in pyridine solution. The most promising of these cleavage reactions are now being applied to the 84% of coal that is insoluble in pyridine and presents the main problem in coal liquefaction, following the progress of the reactions by formation of soluble material and swelling of the insoluble portion. We found that benzylamine (BnNH/sub 2/) would extract an additional 14% (of the original weight of coal) of material from pyridine-extracted coal, and later that an ethylenediamine/dimethyl sulfoxide (EDA/DMSO) mixture would dissolve another 21% of the original coal. The BnNH/sub 2/ extract is soluble in pyridine. Our best present guess is that the BnNH/sub 2/ extract cleaves most of the ester groups in coal and that EDA/DMSO cleaves the remaining ester and most of the ether groups.

  2. Identification and cleavage of breakable single bonds by selective oxidation, reduction, and hydrolysis. Quarterly report No. 1, October 1-December 31, 1978

    Energy Technology Data Exchange (ETDEWEB)

    Buchanan, D.H.; Mayo, F.R.

    1979-01-25

    Bituminous coal is assumed to consist mostly of an aggregate of condensed aromatic and aliphatic rings, connected and made insoluble (but swellable) by crosslinks containing only single bonds. These connecting links consist mainly, possibly entirely, of combinations of carbon-carbon single bonds and ether (possibly ester) groups. It is at these crosslinks that the most extensive cuts can be made in the coal structure (to make it soluble or liquid) under the mildest conditions and with the least loss in fuel values. The objective of this project is to determine the proportion of the various kinds of connecting links and how they can best be broken; in other words, to determine the structure of coal with emphasis on the crosslinks. At present, our attention is directed to five kinds of connecting links: single (Ar-CH/sub 2/-Ar) and multiple methylene groups (Ar-(CH/sub 2/)/sub 2/-Ar) and three kinds of ethers, Ar-O-Ar, Ar-O-R, and R-O-R (Ar represents an aromatic aggregate and R is attached to O through at least one aliphatic carbon.) The work described in this quarterly report deals mainly with the oxidation of pyridine-extracted coal by O/sub 2/ and the cleavage by sodium in liquid ammonia of aromatic ether linkages in a pyridine-soluble, toluene-insoluble fraction of coal extract. Products from the NaOCl oxidation of pyridine-extracted coal were also studied by nuclear magnetic resonance (NMR) and acid-base titrations. 7 references, 2 figures, 6 tables.

  3. Improper, Blue-Shifting Hydrogen Bond

    Czech Academy of Sciences Publication Activity Database

    Hobza, Pavel; Havlas, Zdeněk

    2002-01-01

    Roč. 108, - (2002), s. 325-334. ISSN 1432-881X R&D Projects: GA MŠk LN00A032 Institutional research plan: CEZ:AV0Z4055905; CEZ:AV0Z4040901 Keywords : improper, blue-shifting hydrogen bond * properties * nature Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.421, year: 2002

  4. Polymer Chemistry

    Science.gov (United States)

    Williams, Martha; Roberson, Luke; Caraccio, Anne

    2010-01-01

    This viewgraph presentation describes new technologies in polymer and material chemistry that benefits NASA programs and missions. The topics include: 1) What are Polymers?; 2) History of Polymer Chemistry; 3) Composites/Materials Development at KSC; 4) Why Wiring; 5) Next Generation Wiring Materials; 6) Wire System Materials and Integration; 7) Self-Healing Wire Repair; 8) Smart Wiring Summary; 9) Fire and Polymers; 10) Aerogel Technology; 11) Aerogel Composites; 12) Aerogels for Oil Remediation; 13) KSC's Solution; 14) Chemochromic Hydrogen Sensors; 15) STS-130 and 131 Operations; 16) HyperPigment; 17) Antimicrobial Materials; 18) Conductive Inks Formulations for Multiple Applications; and 19) Testing and Processing Equipment.

  5. Principles of Chemistry (by Michael Munowitz)

    Science.gov (United States)

    Kovac, Reviewed By Jeffrey

    2000-05-01

    At a time when almost all general chemistry textbooks seem to have become commodities designed by marketing departments to offend no one, it is refreshing to find a book with a unique perspective. Michael Munowitz has written what I can only describe as a delightful chemistry book, full of conceptual insight, that uses a novel and interesting pedagogic strategy. This is a book that has much to recommend it. This is the best-written general chemistry book I have ever read. An editor with whom I have worked recently remarked that he felt his job was to help authors make their writing sing. Well, the writing in Principles of Chemistry sings with the full, rich harmonies and creative inventiveness of the King's Singers or Chanticleer. Here is the first sentence of the introduction: "Central to any understanding of the physical world is one discovery of paramount importance, a truth disarmingly simple yet profound in its implications: matter is not continuous." This is prose to be savored and celebrated. Principles of Chemistry has a distinct perspective on chemistry: the perspective of the physical chemist. The focus is on simplicity, what is common about molecules and reactions; begin with the microscopic and build bridges to the macroscopic. The author's perspective is clear from the organization of the book. After three rather broad introductory chapters, there are four chapters that develop the quantum mechanical theory of atoms and molecules, including a strong treatment of molecular orbital theory. Unlike many books, Principles of Chemistry presents the molecular orbital approach first and introduces valence bond theory later only as an approximation for dealing with more complicated molecules. The usual chapters on descriptive inorganic chemistry are absent (though there is an excellent chapter on organic and biological molecules and reactions as well as one on transition metal complexes). Instead, descriptive chemistry is integrated into the development of

  6. A cooperative hydrogen bonding system with a Csbnd H⋯O hydrogen bond in ofloxacin

    Science.gov (United States)

    Gao, Xiuxiang; Liu, Yufeng; Li, Huizhen; Bian, Jiang; Zhao, Ying; Cao, Ye; Mao, Yuezhi; Li, Xin; Xu, Yizhuang; Ozaki, Yukihiro; Wu, Jinguang

    2013-05-01

    We have investigated a cooperative hydrogen bonding system with a Csbnd H⋯O hydrogen bond in ofloxacin by using NMR, UV-Vis spectra together with quantum chemistry calculation. Both pH-dependent NMR experiments and DFT calculation indicate that the intra-molecular Csbnd H⋯O hydrogen bond between an aromatic proton and an oxygen atom from the carboxyl group is formed. Notably, the Csbnd H⋯O hydrogen bond forms a cooperative hydrogen bonding system with a neighboring Osbnd H⋯O hydrogen bond between the carboxyl group and the keto oxygen. The cooperative hydrogen bonding system makes the formation and disruption of the Osbnd H⋯O and Csbnd H⋯O hydrogen bonds in a synergistic manner. Comparison on the pKa value of the carboxylic group in different fluoroquinolones compounds indicates that the Csbnd H⋯O hydrogen bond plays a significant role in stabilizing the Osbnd H⋯O hydrogen bond. In addition, the formation and disruption of the cooperative hydrogen bonding system could regulate the conformation of the carboxyl group, which affects the size of the conjugated system and spectral behavior of π-π transition of ofloxacin.

  7. 15N+ +CD4 and O+ +-13CO2 State-Selected Ion-Molecule Reactions Relevant to the Chemistry of Planetary Ionospheres

    Czech Academy of Sciences Publication Activity Database

    Alcaraz, Ch.; Nicolas, Ch.; Thissen, R.; Žabka, Ján; Dutuit, O.

    2004-01-01

    Roč. 108, č. 45 (2004), s. 9998-10009. ISSN 1089-5639 R&D Projects: GA AV ČR IAA4040405 Grant ostatní: Barande Kontakt(XE) 2002-013-1 Institutional research plan: CEZ:AV0Z4040901 Keywords : charge-transfer reactions * cross-sections * kinetic energy Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.639, year: 2004

  8. Muons in chemistry

    Science.gov (United States)

    Clayden, N. J.

    2013-12-01

    Positive muons have long been used as extrinsic probes in chemistry, offering unique properties for the investigation of local magnetism, dynamics, transport and radical kinetics. Exciting new developments in muon beam lines offer the opportunity of extending these studies selectively to surfaces permitting, for example, the detection of increased mobility of polymer chains at the surface of a polymer film. So called pump and probe methods, involving external perturbations by laser irradiation to manipulate vibrational and electronic states, can be followed by muon pulses allowing the probing of the properties of these states. Muoniated radical probes are finding greater use in soft matter. Selectivity is achieved in these complex systems through an appropriate target molecule giving the chance to measure partitioning and interfacial transfer in surfactant systems. Improvements in sample environments allow the observation of muons in increasingly extreme combinations of temperature and pressure, such as supercritical water, allowing the characterization of the chemistry in these systems.

  9. Defining the hydrogen bond: An account (IUPAC Technical Report)

    Czech Academy of Sciences Publication Activity Database

    Arunan, E.; Desiraju, G. R.; Klein, R. A.; Sadlej, J.; Scheiner, S.; Alkorta, I.; Clary, D. C.; Crabtree, R. H.; Dannenberg, J. J.; Hobza, Pavel; Kjaergaard, H. G.; Legon, A. C.; Mennucci, B.; Nesbitt, D. J.

    2011-01-01

    Roč. 83, č. 8 (2011), s. 1619-1636. ISSN 0033-4545 Institutional research plan: CEZ:AV0Z40550506 Keywords : bonding * electrostatic interactions * hydrogen bonding * molecular interactions Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.789, year: 2011

  10. Orthogonal interactions between nitryl derivatives and electron donors: pnictogen bonds

    Czech Academy of Sciences Publication Activity Database

    Sanchez-Sanz, Goar; Trujillo, Cristina; Solimannejad, M.; Alkorta, I.; Elguero, J.

    2013-01-01

    Roč. 15, č. 34 (2013), s. 14310-14318. ISSN 1463-9076 Institutional support: RVO:61388963 Keywords : center-dot-N * perturbation-theory approach * pnicogen bonds * noncovalent interactions * hydrogen-bonds Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.198, year: 2013

  11. Alpha-cyclodextrins reversibly capped with disulfide bonds

    Czech Academy of Sciences Publication Activity Database

    Kumprecht, Lukáš; Buděšínský, Miloš; Bouř, Petr; Kraus, Tomáš

    2010-01-01

    Roč. 34, č. 10 (2010), s. 2254-2260. ISSN 1144-0546 R&D Projects: GA AV ČR IAA400550810 Institutional research plan: CEZ:AV0Z40550506 Keywords : cyclodextrin s * disulfide bond * dynamic covalent bond Subject RIV: CC - Organic Chemistry Impact factor: 2.631, year: 2010

  12. Organic chemistry

    International Nuclear Information System (INIS)

    The activities of the mycotoxin research group are discussed. This includes the isolation and structure determination of mycotoxins, plant products, the biosyntheris of mycotoxins, the synthesis and characteristics of steroids, the synthesis and mechanistic aspects of heterocyclic chemistry and the functionality of steroids over long distances. Nmr spectra and mass spectroscopy are some of the techniques used

  13. Reinventing Chemistry

    OpenAIRE

    Whitesides, George McClelland

    2015-01-01

    Chemistry is in a period of change, from an era focused on molecules and reactions, to one in which manipulations of systems of molecules and reactions will be essential parts of controlling larger systems. This Essay traces paths from the past to possible futures.

  14. Chemistry Notes

    Science.gov (United States)

    School Science Review, 1972

    1972-01-01

    Short articles on the kinetics of the hydrogen peroxide-iodide ion reaction, simulation of fluidization catalysis, the use of Newman projection diagrams to represent steric relationships in organic chemistry, the use of synthetic substrates for proteolytic enzyme reactions, and two simple clock reactions"--hydrolysis of halogenoalkanes and…

  15. Solvents and sustainable chemistry

    OpenAIRE

    Welton, Tom

    2015-01-01

    Solvents are widely recognized to be of great environmental concern. The reduction of their use is one of the most important aims of green chemistry. In addition to this, the appropriate selection of solvent for a process can greatly improve the sustainability of a chemical production process. There has also been extensive research into the application of so-called green solvents, such as ionic liquids and supercritical fluids. However, most examples of solvent technologies that give improved...

  16. Green chemistry: development trajectory

    International Nuclear Information System (INIS)

    Examples of applications of green chemistry methods in heavy organic synthesis are analyzed. Compounds, which can be produced by the processing of the biomass, and the criteria for the selection of the most promising products are summarized. The current status of the ethanol production and processing is considered. The possibilities of the use of high fatty acid triglycerides, glycerol, succinic acid, and isoprene are briefly discussed. The bibliography includes 67 references

  17. Green chemistry: development trajectory

    Science.gov (United States)

    Moiseev, I. I.

    2013-07-01

    Examples of applications of green chemistry methods in heavy organic synthesis are analyzed. Compounds, which can be produced by the processing of the biomass, and the criteria for the selection of the most promising products are summarized. The current status of the ethanol production and processing is considered. The possibilities of the use of high fatty acid triglycerides, glycerol, succinic acid, and isoprene are briefly discussed. The bibliography includes 67 references.

  18. Selective separation of Am(III) from Eu(III) by 2,9-Bis(dialkyl-1,2,4-triazin-3-yl)-1,10-phenanthrolines. A relativistic quantum chemistry study

    Energy Technology Data Exchange (ETDEWEB)

    Xiao, Cheng-Liang; Wang, Cong-Zhi; Lan, Jian-Hui; Yuan, Li-Yong; Zhao, Yu-Liang; Shi, Wei-Qun [Chinese Academy of Sciences, Beijing (China). Key Lab. of Nuclear Radiation and Nuclear Energy Technology and Key Lab. for Biomedical Effects of Nanomaterials and Nanosafety; Chai, Zhi-Fang [Chinese Academy of Sciences, Beijing (China). Key Lab. of Nuclear Radiation and Nuclear Energy Technology and Key Lab. for Biomedical Effects of Nanomaterials and Nanosafety; Soochow Univ., Suzhou (China). School of Radiological and Interdisciplinary Sciences

    2014-07-01

    The complexation properties of Am(III) and Eu(III) with a serial of novel N-heterocyclic tetradentate ligands, 2,9-bis(dialkyl-1,2,4-triazin-3-yl)-1,10-phenanth-rolines (BTPhens), have been calculated by density functional theory (DFT) coupled with relativistic small-core pseudopotential. It is found that the nitrogen atoms in triazine rings favor metal cations more than those in phenanthroline skeleton. The Am-N bond lengths are comparable to or even shorter than those of Eu-N bonds based on the larger radii of Am(III) than Eu(III). The effect of alkyl substituents on the complex structures is limited but they can adjust the complexation reaction and extraction kinetics. Additionally, the solvent effect can decrease the probability of the complexation reactions greatly and the solvation energies of Am(III) and Eu(III) might be the primary driving force in the complexation selectivity. The complexation reactions for forming ML(NO{sub 3}){sub 3} and [ML{sub 2}(NO{sub 3})]{sup 2+} complexes are believed to dominate the selective extraction separation of Am(III) from Eu(III) in nitric acid media, which agrees well with the experimental results. The comparisons of BTPhens with BTBPs in dipoles and electronic structures confirm that the BTPhens exhibit more favourable extraction kinetics and selectivity for minor actinides.

  19. Endohedral Fullerenes with Actinide-Actinide Bonds: Unwilling Bonding in U2@C80

    Czech Academy of Sciences Publication Activity Database

    Foroutan-Nejad, C.; Patzschke, M.; Straka, Michal

    Opole: -, 2014. [MMNB 2014. Polish-Taiwanese Conference. From Molecular Modeling to Nano- and Biotechnology . 04.09.2014-06.09.2014, Opole] R&D Projects: GA ČR(CZ) GA14-03564S Grant ostatní: European Social Fund(XE) CZ.1.07/2.3.00/30.009 Institutional support: RVO:61388963 Keywords : endohedral actinide fullerene * U-U bonding * actinide-actinide bonding Subject RIV: CF - Physical ; Theoretical Chemistry

  20. Chemical Bonding in Solids: Recovering Chemical Concepts in the Realm of Infinite Periodic Structures.

    Czech Academy of Sciences Publication Activity Database

    Baranov, A.; Ponec, Robert; Kohout, M.

    Vol. 12. Cambridge: Royal Society Chemistry, 2016 - (Joswig, J.; Springborg, M.), s. 53-83 ISBN 978-1-78262-115-7 Institutional support: RVO:67985858 Keywords : chemical bonding in solids * bond indices in solids * DAFH analysis in solids Subject RIV: CF - Physical ; Theoretical Chemistry

  1. C8-Selective Acylation of Quinoline N-Oxides with α-Oxocarboxylic Acids via Palladium-Catalyzed Regioselective C-H Bond Activation.

    Science.gov (United States)

    Chen, Xiaopei; Cui, Xiuling; Wu, Yangjie

    2016-08-01

    A facile and efficient protocol for palladium-catalyzed C8-selective acylation of quinoline N-oxides with α-oxocarboxylic acids has been developed. In this approach, N-oxide was utilized as a stepping stone for the remote C-H functionalization. The reactions proceeded efficiently under mild reaction conditions with excellent regioselectivity and broad functional group tolerance. PMID:27441527

  2. Activation of the C-H bond: catalytic hydroxylation of hydrocarbons by new cobaltic alkylperoxydic complexes; selective and catalytic cycloalkane dehydrogenation in presence of uranium for hydrogen transfer

    International Nuclear Information System (INIS)

    The aim of the thesis is to improve efficiency and selectivity of chemical reactions for alkane transformations. In the first part decomposition of hydroperoxides and hydrocarbon hydroxylation by cobalt complexes is studied. In the second part cycloalkanes are dehydrogenated into aromatics with a Pt catalyst, trapping hydrogen by uranium. Uranium hydride UH3 can yield very pure hydrogen at reasonable temperature

  3. Moving beyond Definitions: What Student-Generated Models Reveal about Their Understanding of Covalent Bonding and Ionic Bonding

    Science.gov (United States)

    Luxford, Cynthia J.; Bretz, Stacey Lowery

    2013-01-01

    Chemistry students encounter a variety of terms, definitions, and classification schemes that many instructors expect students to memorize and be able to use. This research investigated students' descriptions of ionic and covalent bonding beyond definitions in order to explore students' knowledge about chemical bonding. Using Johnstone's Multiple…

  4. Chemical Bonding in Solids. On the Generalization of the Concept of Bond Order and Valence for Infinite Periodical Structures

    Czech Academy of Sciences Publication Activity Database

    Ponec, Robert

    2005-01-01

    Roč. 114, 1-3 (2005), s. 208-212. ISSN 1432-881X R&D Projects: GA AV ČR(CZ) IAA4072403 Institutional research plan: CEZ:AV0Z4072921 Keywords : bonding in solids * bond order * valence Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.179, year: 2005

  5. New Insights from Domain-averaged Fermi holes and Bond Order Analysis into the Bonding Conundrum in C2.

    Czech Academy of Sciences Publication Activity Database

    Cooper, D.L.; Ponec, Robert; Kohout, M.

    2016-01-01

    Roč. 114, 7-8 (2016), s. 1270-1284. ISSN 0026-8976 Institutional support: RVO:67985858 Keywords : peculiarity of C2 bonding * domain-averaged Fermi holes (DAFH) * cioslowski bond orders Subject RIV: CC - Organic Chemistry Impact factor: 1.720, year: 2014

  6. To Bond or Not to Bond? That Is the Question

    Science.gov (United States)

    Balzer, Wayne E.

    2015-01-01

    This case, inspired by a real school district scenario, was developed for use in a graduate-level course in school finance. James Spencer had just been selected as the new superintendent of a low-income, 400-student, rural school district in need of many capital improvements. The previous superintendent had refused to hold a bond election because…

  7. Interpretation of hydrogen bonding in the weak and strong regions using conceptual DFT descriptors

    OpenAIRE

    Özen, Alimet Sema; Ozen, Alimet Sema; De Proft, Frank; Aviyente , Viktorya; Geerlings, Paul

    2006-01-01

    Hydrogen bonding is among the most fundamental interactions in biology and chemistry, providing an extra stabilization of 1-40 kcal/mol to the molecular systems involved. This wide range of stabilization energy underlines the need for a general and comprehensive theory that will explain the formation of hydrogen bonds. While a simple electrostatic model is adequate to describe the bonding patterns in the weak and moderate hydrogen bond regimes, strong hydrogen bonds, on the other hand, requir...

  8. Facile scission of isonitrile carbon–nitrogen triple bond using a diborane(4) reagent

    OpenAIRE

    Asakawa, Hiroki; Lee, Ka-Ho; Lin, Zhenyang; Yamashita, Makoto

    2014-01-01

    Transition metal reagents and catalysts are generally effective to cleave all three bonds (one σ and two π) in a triple bond despite its high bonding energy. Recently, chemistry of single-bond cleavage by using main-group element compounds is rapidly being developed in the absence of transition metals. However, the cleavage of a triple bond using non-transition-metal compounds is less explored. Here we report that an unsymmetrical diborane(4) compound could react with carbon monoxide and tert...

  9. Bonds and bands in semiconductors

    CERN Document Server

    Phillips, Jim

    2009-01-01

    This classic work on the basic chemistry and solid state physics of semiconducting materials is now updated and improved with new chapters on crystalline and amorphous semiconductors. Written by two of the world's pioneering materials scientists in the development of semiconductors, this work offers in a single-volume an authoritative treatment for the learning and understanding of what makes perhaps the world's most important engineered materials actually work. Readers will find: --' The essential principles of chemical bonding, electron energy bands and their relationship to conductive and s

  10. 选择性氧化形成三对二硫键合成齐考诺肽%Synthesis of Ziconotide by Selective Oxidation to Form Three Disulfide Bonds

    Institute of Scientific and Technical Information of China (English)

    曹本文; 王卫国; 李战雄; 徐红岩

    2011-01-01

    Using the different oxidation reactivity of sulfhydryls with different protective group, Ziconotide was synthesized via selective oxidation reaction. Firstly, two disulfide bonds were formatted between the 1,8,16,20-position sulfhydryls protected by Trt in the Ziconotide by air oxidation. Then,the third disulfide bond was formatted between the 15,25-position sulfhydryls protected by Acm with iodine oxidation.%利用不同保护基保护的巯基的氧化反应性不同,分别以空气和碘作为氧化剂,通过选择性氧化工艺使齐考诺肽线性肽的1,8,16,20-位两对Trt保护巯基先形成两对二硫键,然后用碘氧化15,25-位Acm保护的巯基,成功地生成第三对二硫键,合成了齐考诺肽.

  11. Catalysis and sustainable (green) chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Centi, Gabriele; Perathoner, Siglinda [Dipartimento di Chimica Industriale ed Ingegneria dei Materiali, University of Messina, Salita Sperone 31, 98166 Messina (Italy)

    2003-01-15

    Catalysis is a key technology to achieve the objectives of sustainable (green) chemistry. After introducing the concepts of sustainable (green) chemistry and a brief assessment of new sustainable chemical technologies, the relationship between catalysis and sustainable (green) chemistry is discussed and illustrated via an analysis of some selected and relevant examples. Emphasis is also given to the concept of catalytic technologies for scaling-down chemical processes, in order to develop sustainable production processes which reduce the impact on the environment to an acceptable level that allows self-depuration processes of the living environment.

  12. Nonthermal plasma chemistry and physics

    CERN Document Server

    Meichsner, Jurgen; Schneider, Ralf; Wagner, Hans-Erich

    2013-01-01

    In addition to introducing the basics of plasma physics, Nonthermal Plasma Chemistry and Physics is a comprehensive presentation of recent developments in the rapidly growing field of nonthermal plasma chemistry. The book offers a detailed discussion of the fundamentals of plasma chemical reactions and modeling, nonthermal plasma sources, relevant diagnostic techniques, and selected applications.Elucidating interconnections and trends, the book focuses on basic principles and illustrations across a broad field of applications. Expert contributors address environmental aspects of plasma chemist

  13. Abstracts of the 2. Brazilian Symposium on Theoretical Chemistry

    International Nuclear Information System (INIS)

    Abstracts from research works on theoretical chemistry are presented. Main subjects of study are: metallic bonds, hyperfine interactions, symetry of isotopically substituted molecules, photoionization reactions, electron impact reactions, applications of the perturbation theory. (C.L.B.)

  14. Direct carbon-carbon bond formation via reductive soft enolization: a syn-selective Mannich addition of α-iodo thioesters.

    Science.gov (United States)

    Truong, Ngoc; Sauer, Scott J; Seraphin-Hatcher, Cyndie; Coltart, Don M

    2016-08-16

    The β-amino carboxylic acid moiety is a key feature of numerous important biologically active compounds. We describe a syn-selective direct Mannich addition reaction that uses α-iodo thioesters and sulfonyl imines and produces β-amino thioesters. Enolate formation is achieved by reductive soft enolization. The products of the reaction provide straightforward access to biologically important β-lactams through a variety of known reactions. PMID:27492274

  15. Cross Shear Roll Bonding

    DEFF Research Database (Denmark)

    Bay, Niels; Bjerregaard, Henrik; Petersen, Søren. B;

    1994-01-01

    The present paper describes an investigation of roll bonding an AlZn alloy to mild steel. Application of cross shear roll bonding, where the two equal sized rolls run with different peripheral speed, is shown to give better bond strength than conventional roll bonding. Improvements of up to 20......-23% in bond strength are found and full bond strength is obtained at a reduction of 50% whereas 65% is required in case of conventional roll bonding. Pseudo cross shear roll bonding, where the cross shear effect is obtained by running two equal sized rolls with different speed, gives the same results....

  16. Effect of pretreatment bias on the nucleation and growth mechanisms of ultrananocrystalline diamond films via bias-enhanced nucleation and growth: An approach to interfacial chemistry analysis via chemical bonding mapping

    International Nuclear Information System (INIS)

    The effect of pretreatment bias on the nucleation and growth mechanisms of the ultrananocrystalline diamond (UNCD) films on the Si substrate via bias-enhanced nucleation and bias-enhanced growth (BEN-BEG) was investigated using cross-sectional high-resolution transmission electron microscopy, chemical bonding mapping, and Raman spectroscopy. The mirror-polished substrate surface showed the formation of a triangular profile produced by a dominant physical sputtering mechanism induced by ion bombardment of ions from the hydrogen plasma accelerated toward the substrate due to biasing and a potential hydrogen-induced chemical reaction component before synthesizing the UNCD films. The BEN-BEG UNCD films grown on the Si substrate with biased and unbiased pretreatments in the hydrogen plasma were compared. In the case of the bias-pretreated substrate, the SiC phases were formed at the peaks of the Si surface triangular profile due to the active unsaturated Si bond and the enhanced local electrical field. The UNCD grains grew preferentially at the peaks of the triangular substrate surface profile and rapidly covered the amorphous carbon (a-C) and oriented graphite phases formed in the valley of the surface profile. In the case of the substrate with unbiased pretreatment, the SiC phases were formed via the reactions between the hydrocarbon species and the active Si atoms released from the substrate with assistance of the hydrogen plasma. The UNCD grains nucleated on the nucleating sites consisting of the SiC, a-C, and graphite phases. Growth mechanisms for the BEN-BEG UNCD films on both Si substrates were proposed to elucidate the different nucleation processes. Applying bias on the Si substrate pretreated in the hydrogen plasma optimized the nucleation sites for growth of UNCD grains, resulting in the low content of the nondiamond phases in UNCD films

  17. Disk Chemistry*

    OpenAIRE

    Thi Wing-Fai

    2015-01-01

    The chemical species in protoplanetary disks react with each other. The chemical species control part of the thermal balance in those disks. How the chemistry proceeds in the varied conditions encountered in disks relies on detailed microscopic understanding of the reactions through experiments or theoretical studies. This chapter strives to summarize and explain in simple terms the different types of chemical reactions that can lead to complex species. The first part of the chapter deals wit...

  18. Interstellar chemistry

    OpenAIRE

    Klemperer, William

    2006-01-01

    In the past half century, radioastronomy has changed our perception and understanding of the universe. In this issue of PNAS, the molecular chemistry directly observed within the galaxy is discussed. For the most part, the description of the molecular transformations requires specific kinetic schemes rather than chemical thermodynamics. Ionization of the very abundant molecular hydrogen and atomic helium followed by their secondary reactions is discussed. The rich variety of organic species o...

  19. Analytical chemistry

    International Nuclear Information System (INIS)

    The division for Analytical Chemistry continued to try and develope an accurate method for the separation of trace amounts from mixtures which, contain various other elements. Ion exchange chromatography is of special importance in this regard. New separation techniques were tried on certain trace amounts in South African standard rock materials and special ceramics. Methods were also tested for the separation of carrier-free radioisotopes from irradiated cyclotron discs

  20. The Discovery-Oriented Approach to Organic Chemistry. 2. Selectivity in Alcohol Oxidation. An Exercise in 1H NMR Spectroscopy for Sophomore Organic Laboratories

    Science.gov (United States)

    Shadwick, Steven R.; Mohan, Ram S.

    1999-08-01

    We have developed a simple oxidation experiment that presents the student with a puzzle and is a good exercise in 1H NMR spectroscopy. The experiment, which illustrates the important concept of selectivity in organic synthesis, involves selective oxidation of a mixture of 1-heptanol and 2-heptanol using commercial swimming pool chlorine. 1H NMR analysis of the product mixture allows the student to determine the selectivity exhibited by the reagent.

  1. Functionalization and bioimmobilization of silicon surfaces with Si–N bonded monolayer

    International Nuclear Information System (INIS)

    Highlights: • Chemistry of Ethylene diamine (EDA) studied by X-ray photoelectron spectroscopy (XPS) on hydrogen terminated Si (1 1 1) surface under UV-irradiation. • Fast, efficient and selective surface modification via symmetric functional molecule. • Do not involve protection and deprotection steps which deteoriate the monolayer integrity, time consuming and expensive. • Si–N bond remain intact on sub-oxidized silicon surface. • Free amine groups availability for bioimmobilization. • Selectivity and sensitivity was demonstrated by SEM, fluorscence and electrochemical (C–V) measurements. - Abstract: A new method for selective surface functionalization of silicon with a silicon–nitrogen bonded (Si–N) monolayer and subsequent bioimmobilization is presented. The Si–N monolayer was studied using X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), fluorescence spectroscopy, and capacitance–voltage (C–V) measurements using an electrolyte insulator semiconductor (EIS) sensor. A symmetric ethylene diamine (EDA, C2H4 (NH2)2) molecule was used as a precursor compound for monolayer formation in an inert environment in the liquid phase. XPS results show the attachment of EDA molecules proceeds via dissociative and dative bond formation whereas free amine groups on the surface were used for further immobilization of biomolecules. SEM shows selective functionalization and bioimmobilization on a patterned surface such as a silicon nanowire on silicon oxide substrate. Biosensing experiments with bioimmobilized surfaces were carried out in aqueous buffer and show high sensitivity for biosensing

  2. Green chemistry

    International Nuclear Information System (INIS)

    A grand challenge facing government, industry, and academia in the relationship of our technological society to the environment is reinventing the use of materials. To address this challenge, collaboration from an interdisciplinary group of stakeholders will be necessary. Traditionally, the approach to risk management of materials and chemicals has been through inerventions intended to reduce exposure to materials that are hazardous to health and the environment. In 1990, the Pollution Prevention Act encouraged a new tact-elimination of hazards at the source. An emerging approach to this grand challenge seeks to embed the diverse set of environmental perspectives and interests in the everyday practice of the people most responsible for using and creating new materials--chemists. The approach, which has come to be known as Green Chemistry, intends to eliminate intrinsic hazard itself, rather than focusing on reducing risk by minimizing exposure. This chapter addresses the representation of downstream environmental stakeholder interests in the upstream everyday practice that is reinventing chemistry and its material inputs, products, and waste as described in the '12 Principles of Green Chemistry'

  3. Green chemistry

    International Nuclear Information System (INIS)

    The depletion of world fossil fuel reserves and the involvement of greenhouse gases in the global warming has led to change the industrial and energy policies of most developed countries. The goal is now to reserve petroleum to the uses where it cannot be substituted, to implement renewable raw materials obtained from plants cultivation, and to consider the biodegradability of molecules and of manufactured objects by integrating the lifetime concept in their expected cycle of use. The green chemistry includes the design, development and elaboration of chemical products and processes with the aim of reducing or eliminating the use and generation of harmful compounds for the health and the environment, by adapting the present day operation modes of the chemical industry to the larger framework of the sustainable development. In addition to biofuels, this book reviews the applications of green chemistry in the different industrial processes in concern. Part 1 presents the diversity of the molecules coming from renewable carbon, in particular lignocellulose and the biotechnological processes. Part 2 is devoted to materials and treats of the overall available technological solutions. Part 3 focusses on functional molecules and chemical intermediates, in particular in sugar- and fats-chemistry. Part 4 treats of biofuels under the aspects of their production and use in today's technologies. The last part deals with the global approaches at the environmental and agricultural levels. (J.S.)

  4. Triclosan Computational Conformational Chemistry Analysis for Antimicrobial Properties in Polymers

    OpenAIRE

    Petersen, Richard C.

    2015-01-01

    Triclosan is a diphenyl ether antimicrobial that has been analyzed by computational conformational chemistry for an understanding of Mechanomolecular Theory. Subsequent energy profile analysis combined with easily seen three-dimensional chemistry structure models for the nonpolar molecule Triclosan show how single bond rotations can alternate rapidly at a polar and nonpolar interface. Bond rotations for the center ether oxygen atom of the two aromatic rings then expose or hi...

  5. Wire bonding in microelectronics

    CERN Document Server

    Harman, George G

    2010-01-01

    Wire Bonding in Microelectronics, Third Edition, has been thoroughly revised to help you meet the challenges of today's small-scale and fine-pitch microelectronics. This authoritative guide covers every aspect of designing, manufacturing, and evaluating wire bonds engineered with cutting-edge techniques. In addition to gaining a full grasp of bonding technology, you'll learn how to create reliable bonds at exceedingly high yields, test wire bonds, solve common bonding problems, implement molecular cleaning methods, and much more. Coverage includes: Ultrasonic bonding systems and technologies, including high-frequency systems Bonding wire metallurgy and characteristics, including copper wire Wire bond testing Gold-aluminum intermetallic compounds and other interface reactions Gold and nickel-based bond pad plating materials and problems Cleaning to improve bondability and reliability Mechanical problems in wire bonding High-yield, fine-pitch, specialized-looping, soft-substrate, and extreme-temperature wire bo...

  6. Cobalt bis(dicarbollide) ions with covalently bonded CMPO groups as selective extraction agents for lanthanide and actinide cations from highly acidic nuclear waste solutions

    International Nuclear Information System (INIS)

    A new series of boron substituted cobalt bis(dicarbollide)(1-) ion (1) derivatives of the general formula [(8-CMPO-(CH2-CH2O)2-1,2-C2B9H10)(1',2'-C2B9H11)-3,3'-Co]- (CMPO = Ph2P(O)-CH2C(O)NR, R = C4H9 (3b), -C12H25 (4b), -CH2-C6H5 (5b)) was prepared by ring cleavage of the 8-dioxane-cobalt bis(dicarbollide) (2) bi-polar compound by the respective primary amines and by subsequent reaction of the resulting amino derivatives (3a-5a) with the nitrophenyl ester of diphenyl-phosphoryl-acetic acid. The compounds were synthesized with the aim to develop a new class of more efficient extraction agents for liquid/liquid extraction of polyvalent cations, i.e. lanthanides and actinides, from high-level activity nuclear waste. All compounds were characterized by a combination of 11B NMR, 1H high field NMR, Mass Spectrometry with Electro-spray and MALDI TOF ionisation, HPLC and other techniques. The molecular structure of the supramolecular Ln3+ complex of the anion 5b was determined by single crystal X-ray diffraction analysis. Crystallographic results proved that the Ln(m) atom is bonded to three functionalized cobalt bis(dicarbollide) anions in a charge compensated complex. The cation is tightly coordinated by six oxygen atoms of the CMPO terminal groups (two of each ligand) and by three water molecules completing the metal coordination number to 9. Atoms occupying the primary coordination sphere form a tri-capped trigonal prismatic arrangement. Very high liquid-liquid extraction efficiency of all anionic species was observed. Moreover, less polar toluene can be applied as an auxiliary solvent replacing the less environmentally friendly nitro- and chlorinated solvents used in the current dicarbollide liquid-liquid extraction process. The extraction coefficients are sufficiently high for possible technological applications. (authors)

  7. A selected ion flow tube investigation of the positive ion chemistry of a number of bromine containing fully and partially halogenated hydrocarbons

    International Nuclear Information System (INIS)

    The reaction of ions with neutral molecules play a significant, and often dominant, role in the chemistry of many gaseous plasma environments, including the interstellar medium, planetary ionospheres and industrial plasmas. This had led to many publications reporting ion-molecule reaction rate coefficients and reaction pathways (product ion distributions). Such critical data are invaluable in the understanding of the formation and abundance of ions and neutral molecules present in neutral and man-made plasma, and to predict how such plasmas chemically and physically evolve. There have been many studies investigating the positive ion chemistry of chlorofluorocarbons (CFCs), and a number of studies have explored the positive ion chemistry of their replacements, the perfluorocarbones (PFCs). In part these studies have been undertaken because of their relevance to plasmas, and of more specific interest in terms of their relevance to industrial plasma processing. Halogenated molecules are commonly used in plasma processes. In contrast to fluorinated and/or chlorinated species, little attention has been directed to the reactions of positive ions with bromine containing molecules. Yet a systematic study of these reactions permits useful comparison with the ion chemistry of fully and partially fluorinated/chlorinated compounds. This in turn improves our fundamental understanding of ion-molecule reactions, and ultimately leads, for example, to better models to predict the optimum conditions needed to operate industrial plasma processes. In this paper the thermal biomolecular rate coefficients and product ion branching ratios for the reactions of the positive ions (in order of increasing recombination energy) H2O+, N2O+, O+, CO2+, CO+, N+, and N2+ with the bromine containing molecules CF3Br, CF2Br2, CFBr3, CF2BrCl, CFBr2Cl, CBrCl3, CH3Br, CH2Br2, CH2FBr, CHF2Br, CHFBr2, CH2BrCl, CHBrCl2, CHBr2Cl, CF3CF2Br, and CF2BrCF2Br at 300 K are reported. This represents the most

  8. Advances in high temperature chemistry 1

    CERN Document Server

    Eyring, Leroy

    2013-01-01

    Advances in High Temperature Chemistry, Volume 1 describes the complexities and special and changing characteristics of high temperature chemistry. After providing a brief definition of high temperature chemistry, this nine-chapter book goes on describing the experiments and calculations of diatomic transition metal molecules, as well as the advances in applied wave mechanics that may contribute to an understanding of the bonding, structure, and spectra of the molecules of high temperature interest. The next chapter provides a summary of gaseous ternary compounds of the alkali metals used in

  9. Predicting the host range of Nystalea ebalea: secondary plant chemistry and host selection by a surrogate biological control agent of Schinus terebinthifolia

    Science.gov (United States)

    The safety of weed biological control depends upon the selection and utilization of the target weed by the agent while causing minimal harm to non-target species. Selection of weed species by biological control agents is determined by the presence of behavioral cues, generally host secondary plant c...

  10. On Bond Portfolio Management

    OpenAIRE

    Vladislav Kargin

    2002-01-01

    This paper describes a new method of bond portfolio optimization based on stochastic string models of correlation structure in bond returns. The paper shows how to approximate correlation function of bond returns, compute the optimal portfolio allocation using Wiener-Hopf factorization, and check whether a collection of bonds presents arbitrage opportunities.

  11. Effect of the structure of bonded cyanoalkyl stationary phases on their selectivity in the liquid chromatographic separation of polynuclear aromatic hydrocarbons

    Energy Technology Data Exchange (ETDEWEB)

    Lanin, S.N.; Nikitin, Yu.S.; Pyatygin, A.A.; Staroverov, S.M.

    1989-02-01

    The paper discusses the effect of the length and structure of the hydrocarbon chain connecting the nitrile group to the silica gel surface on the chromatographic properties of cyanoalkyl phases. When using non-polar and polar mobile phases, the selectivity of the cyanodecyl phases toward PAHs is higher than of the cyanopropyl phase and of hydroxylated silica gel. Polar additives to the mobile phase drastically decrease the retention on silica gel and on the cyanopropyl phase while affect the properties of cyanodecyl phases only to a considerably less degree. Newly synthesized phases with different structures of the hydrocarbon chain are compared with the commercial cyano- and ODS-phases. The retention mechanism on the cyanoalkyl phases is discussed.

  12. Evaluation of the PC-SAFT, SAFT and CPA equations of state in predicting derivative properties of selected non-polar and hydrogen-bonding compounds

    DEFF Research Database (Denmark)

    de Villiers, A.J.; Schwarz, C.E.; Burger, A.J.;

    2013-01-01

    of these models to predict selected properties (heat capacities, pressure-volume derivative, pressure-temperature derivative and speed of sound) are evaluated for n-alkanes and 1-acohols. For n-alkanes, it is shown that the cubic term of CPA is unable to describe the pressure-volume derivative at high pressures......In order to provide a comprehensive understanding of the potential and limitations of the PC-SAFT, SAFT and CPA equations-of-state, this study offers insight into their application for the prediction of derivative properties over extensive ranges of pressure and temperature. The ability......, which is a major shortcoming in predicting derivative properties compared to SAFT-based models. Although PC-SAFT and SAFT provide a substantially better prediction of the pressure-volume derivative than CPA, they are still not accurate enough to obtain good speed of sound predictions. All three models...

  13. Development of the Bonding Representations Inventory to Identify Student Misconceptions about Covalent and Ionic Bonding Representations

    Science.gov (United States)

    Luxford, Cynthia J.; Bretz, Stacey Lowery

    2014-01-01

    Teachers use multiple representations to communicate the concepts of bonding, including Lewis structures, formulas, space-filling models, and 3D manipulatives. As students learn to interpret these multiple representations, they may develop misconceptions that can create problems in further learning of chemistry. Interviews were conducted with 28…

  14. Multicenter bonds, bond valence and bond charge apportion

    International Nuclear Information System (INIS)

    In the same way that the valence of an atom issues from the definition of bond index, we shoe here that the three-center bond index lends itself to the definition of a bond valence. Within the charge of a bond, we show that its self-charge (i.e., the amount of electron kept by the atoms involved in the bond) is parted in a such a way that the more electronegative atom tends to allot more electronic charge than the other atom. We give examples of these quantities and discuss the results for different kinds of chemical systems. We also show some results for four-center indices and report six-center indices for hexagonal rings. (author). 54 refs., 4 figs., 8 tabs

  15. Characterization of the hydrology, water chemistry, and aquatic communities of selected springs in the St. Johns River Water Management District, Florida, 2004

    Science.gov (United States)

    Phelps, G.G.; Walsh, Stephen J.; Gerwig, Robert M.; Tate, William B.

    2006-01-01

    The hydrology, water chemistry, and aquatic communities of Silver Springs, De Leon Spring, Gemini Springs, and Green Spring in the St. Johns River Water Management District, Florida, were studied in 2004 to provide a better understanding of each spring and to compile data of potential use in future water-management decisions. Ground water that discharges from these and other north-central Florida springs originates from the Upper Floridan aquifer of the Floridan aquifer system, a karstic limestone aquifer that extends throughout most of the State's peninsula. This report summarizes data about flow, water chemistry, and aquatic communities, including benthic invertebrates, fishes, algae, and aquatic macrophytes collected by the U.S. Geological Survey, the St. Johns River Water Management District, and the Florida Department of Environmental Protection during 2004, as well as some previously collected data. Differences in water chemistry among these springs reflect local differences in water chemistry in the Upper Floridan aquifer. The three major springs sampled at the Silver Springs group (the Main Spring, Blue Grotto, and the Abyss) have similar proportions of cations and anions but vary in nitrate and dissolved oxygen concentrations. Water from Gemini Springs and Green Spring has higher proportions of sodium and chloride than the Silver Springs group. Water from De Leon Spring also has higher proportions of sodium and chloride than the Silver Springs group but lower proportions of calcium and bicarbonate. Nitrate concentrations have increased over the period of record at all of the springs except Green Spring. Compounds commonly found in wastewater were found in all the springs sampled. The most commonly detected compound was the insect repellant N,N'-diethyl-methyl-toluamide (DEET), which was found in all the springs sampled except De Leon Spring. The pesticide atrazine and its degradate 2-chloro-4-isopropylamino-6-amino-s-triazine (CIAT) were detected in water

  16. Chemistry in one dimension.

    Science.gov (United States)

    Loos, Pierre-François; Ball, Caleb J; Gill, Peter M W

    2015-02-01

    We report benchmark results for one-dimensional (1D) atomic and molecular systems interacting via the Coulomb operator |x|(-1). Using various wavefunction-type approaches, such as Hartree-Fock theory, second- and third-order Møller-Plesset perturbation theory and explicitly correlated calculations, we study the ground state of atoms with up to ten electrons as well as small diatomic and triatomic molecules containing up to two electrons. A detailed analysis of the 1D helium-like ions is given and the expression of the high-density correlation energy is reported. We report the total energies, ionization energies, electron affinities and other physical properties of the many-electron 1D atoms and, using these results, we construct the 1D analog of Mendeleev's periodic table. We find that the 1D periodic table contains only two groups: the alkali metals and the noble gases. We also calculate the dissociation curves of several 1D diatomics and study the chemical bond in H2(+), HeH(2+), He2(3+), H2, HeH(+) and He2(2+). We find that, unlike their 3D counterparts, 1D molecules are primarily bound by one-electron bonds. Finally, we study the chemistry of H3(+) and we discuss the stability of the 1D polymer resulting from an infinite chain of hydrogen atoms. PMID:25518906

  17. Preparation of fluorescence quenched libraries containing interchain disulphide bonds for studies of protein disulphide isomerases

    DEFF Research Database (Denmark)

    Spetzler, J C; Westphal, V; Winther, Jakob R.; Meldal, M

    1998-01-01

    Protein disulphide isomerase is an enzyme that catalyses disulphide redox reactions in proteins. In this paper, fluorogenic and interchain disulphide bond containing peptide libraries and suitable substrates, useful in the study of protein disulphide isomerase, are described. In order to establish...... the chemistry required for the generation of a split-synthesis library, two substrates containing an interchain disulphide bond, a fluorescent probe and a quencher were synthesized. The library consists of a Cys residue flanked by randomized amino acid residues at both sides and the fluorescent Abz...... group at the amino terminal. All the 20 natural amino acids except Cys were employed. The library was linked to PEGA-beads via methionine so that the peptides could be selectively removed from the resin by cleavage with CNBr. A disulphide bridge was formed between the bead-linked library and a peptide...

  18. Surface chemistry

    CERN Document Server

    Desai, KR

    2008-01-01

    The surface Chemistry of a material as a whole is crucially dependent upon the Nature and type of surfaces exposed on crystallites. It is therefore vitally important to independently Study different, well - defined surfaces through surface analytical techniques. In addition to composition and structure of surface, the subject also provides information on dynamic light scattering, micro emulsions, colloid Stability control and nanostructures. The present book endeavour to bring before the reader that the understanding and exploitation of Solid state phenomena depended largely on the ability to

  19. Dithioacetal Exchange: A New Reversible Reaction for Dynamic Combinatorial Chemistry.

    Science.gov (United States)

    Orrillo, A Gastón; Escalante, Andrea M; Furlan, Ricardo L E

    2016-05-10

    Reversibility of dithioacetal bond formation is reported under acidic mild conditions. Its utility for dynamic combinatorial chemistry was explored by combining it with orthogonal disulfide exchange. In such a setup, thiols are positioned at the intersection of both chemistries, constituting a connecting node between temporally separated networks. PMID:26990904

  20. Surface Morphology and Coordination Chemistry of 4-Isopropylcalix[4]Arene as an Ionophore with Chromium (III) in Fabrication of Cr3+ Selective Membrane Sensor

    International Nuclear Information System (INIS)

    The present work deals with a poly (vinyl chloride) based selective membrane incorporating 4-Isopropylcalix[4]arene as an ionophore which has been prepared and explored as Cr3+ cation selective sensor. The strengths of the ion-ionophore (Cr3+ - 4- Isopropylcalix[4]arene) interactions and the role of ionophore on membrane performance has been studied. The ligand coordination with the ion investigated via IR and UV-Vis spectroscopy. (author)

  1. An Alternative Approach to the Teaching of Systematic Transition Metal Chemistry.

    Science.gov (United States)

    Hathaway, Brian

    1979-01-01

    Presents an alternative approach to teaching Systematic Transition Metal Chemistry with the transition metal chemistry skeleton features of interest. The "skeleton" is intended as a guide to predicting the chemistry of a selected compound. (Author/SA)

  2. 选区激光熔化钴铬合金金-瓷结合强度初探%Metal-ceramic bond strength of Co-Cr alloy processed by selective laser melting

    Institute of Scientific and Technical Information of China (English)

    刘洁; 刘洋; 孙荣; 战德松; 王彦岩

    2013-01-01

    Objective To eveluate the metal-ceramic bond strength of a selective laser melting Co-Cr alloy.Methods Twelve Co-Cr metal bars were prepared according to the ISO 9693 standard with Vita porcelain fused onto the centre of each bar.Then the sample bars were devided into two groups of six each.The control group was made by traditional cast process(cast group),and the experimental group was processed by selective laser melting (SLM) technology (SLM group).Metal-ceramic bonding strength and fracture mode were assessed using three-point bending test.Fracture mode analysis was determined by scanning electronic microscope/energy dispersive spectroscopy.Student's t-test was used to analyze the data in SPSS 13.0.Results The metal-ceramic bond strength value of the cast group was (33.45 ±2.34) MPa,and that of the SLM group was (31.62 ± 2.34) MPa (t =0.79,P > 0.05).A mixed fracture mode on the debonding interface of all specimens was observed,while little porcelain was reserved.Conclusions The metal-ceramic system processed by SLM exhibited a bonding strength that satisfies the requirement of clinical application.%目的 采用三点弯曲法评价选区激光熔化钴铬合金金-瓷结合强度,以期为修复临床提供参考.方法 依据ISO 9693标准,分别用铸造法(铸造组)和选区激光熔化法(选区激光熔化组)制作钴铬合金试件,每组6个,试件中间区域熔附瓷粉.三点弯曲法测试金-瓷结合强度,采用SPSS 13.0软件进行t检验,分析两组金-瓷结合强度差异;扫描电镜和能谱仪进行金-瓷结合界面分析.结果 铸造组和选区激光熔化组金-瓷结合强度分别为(33.45 ±2.34)和(31.62 ±2.34) MPa,两组差异无统计学意义(t =0.79,P>0.05).两组试件断裂类型均为混合断裂,仅微量瓷残余.结论 选区激光熔化钴铬合金修复体可满足临床对金-瓷结合强度的要求.

  3. The phosphorus and the transition metals chemistry

    International Nuclear Information System (INIS)

    The 1988 progress report, concerning the Polytechnic School unit (France), which studies the phosphorus and the transition metals chemistry, is presented. The laboratory activities are related to the following topics: the phosporus heterocyclic chemistry, the phosphorus-carbon double bonds chemistry, the new transition metals phosphorus compounds, the phosphonates and their uses. Some practical applications of homogeneous catalysis and new materials synthesis are investigated. The main results obtained are: the discovery of the tetra-phosphafulvalenes, the utilization of a new synthesis method of the phosphorus-carbon double bonds and the stabilization of the α-phosphonyled carbanions by the lithium diisopropylamidourea. The papers, the congress communications and the thesis are also shown

  4. Environmental control technology survey of selected US strip mining sites. Volume 2B. Alabama. Water quality impacts and overburden chemistry of Alabama study site

    Energy Technology Data Exchange (ETDEWEB)

    Henricks, J D; Bogner, J E; Olsen, R D; Schubert, J P; Sobek, A A; Johnson, D O

    1980-05-01

    As part of a program to examine the ability of existing control technologies to meet federal guidelines for the quality of aqueous effluents from coal mines, an intensive study of water, coal, and overburden chemistry was conducted at a surface coal mine in Alabama from May 1976 through July 1977. Sampling sites included the pit sump, a stream downgrade from the mine, the discharge from the water treatment facility, and a small stream outside the mine drainage. Water samples were collected every two weeks by Argonne subcontractors at the Alabama Geological Survey and analysed for the following parameters: specific conductance, pH, temperature, acidity, bicarbonate, carbonate, chloride, total dissolved solids, suspended solids, sulfate, and 20 metals. Analysis of the coal and overburden shows that no potential acid problem exists at this mine. Water quality is good in both streams sampled, and high levels of dissolved elements are found only in water collected from the pit sump. The mine effluent is in compliance with Office of Surface Mining water quality standards.

  5. Hydrogen bonded supramolecular structures

    CERN Document Server

    Li, Zhanting

    2015-01-01

    This book covers the advances in the studies of hydrogen-bonding-driven supramolecular systems  made over the past decade. It is divided into four parts, with the first introducing the basics of hydrogen bonding and important hydrogen bonding patterns in solution as well as in the solid state. The second part covers molecular recognition and supramolecular structures driven by hydrogen bonding. The third part introduces the formation of hollow and giant macrocycles directed by hydrogen bonding, while the last part summarizes hydrogen bonded supramolecular polymers. This book is designed to b

  6. Combustion chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Brown, N.J. [Lawrence Berkeley Laboratory, CA (United States)

    1993-12-01

    This research is concerned with the development and use of sensitivity analysis tools to probe the response of dependent variables to model input variables. Sensitivity analysis is important at all levels of combustion modeling. This group`s research continues to be focused on elucidating the interrelationship between features in the underlying potential energy surface (obtained from ab initio quantum chemistry calculations) and their responses in the quantum dynamics, e.g., reactive transition probabilities, cross sections, and thermal rate coefficients. The goals of this research are: (i) to provide feedback information to quantum chemists in their potential surface refinement efforts, and (ii) to gain a better understanding of how various regions in the potential influence the dynamics. These investigations are carried out with the methodology of quantum functional sensitivity analysis (QFSA).

  7. Comparing Carbonyl Chemistry in Comprehensive Introductory Organic Chemistry Textbooks

    Science.gov (United States)

    Nelson, Donna J.; Kumar, Ravi; Ramasamy, Saravanan

    2015-01-01

    Learning the chemistry of compounds containing carbonyl groups is difficult for undergraduate students partly because of a convolution of multiple possible reaction sites, competitive reactions taking place at those sites, different criteria needed to discern between the mechanisms of these reactions, and no straightforward selection method…

  8. 2012 ORGANOMETALLIC CHEMISTRY GRC/GRS, JULY 7-13, 2012

    Energy Technology Data Exchange (ETDEWEB)

    Hillhouse, Gregory

    2012-07-13

    The 2012 Organometallic Chemistry Gordon Research Conference will highlight new basic science and fundamental applications of organometallic chemistry in industrial, academic, and national lab settings. Scientific themes of the conference will include chemical synthesis, reactivity, catalysis, polymer chemistry, bonding, and theory that involve transition-metal (and main-group) interactions with organic moieties.

  9. Single Molecule Junctions: Probing Contact Chemistry and Fundamental Circuit Laws

    Energy Technology Data Exchange (ETDEWEB)

    Hybertsen M. S.

    2013-04-11

    By exploiting selective link chemistry, formation of single molecule junctions with reproducible conductance has become established. Systematic studies reveal the structure-conductance relationships for diverse molecules. I will draw on experiments from my collaborators at Columbia University, atomic-scale calculations and theory to describe progress in two areas. First, I will describe a novel route to form single molecule junctions, based on SnMe3 terminated molecules, in which gold directly bonds to carbon in the molecule backbone resulting in near ideal contact resistance [1]. Second, comparison of the conductance of junctions formed with molecular species containing either one backbone or two backbones in parallel allows demonstration of the role of quantum interference in the conductance superposition law at the molecular scale [2].

  10. Halogen Bonding Origin Properties and Applications

    Czech Academy of Sciences Publication Activity Database

    Hobza, Pavel

    Melville: AIP Publishing, 2015 - (Simos, T.; Kalogiratou, Z.; Monovasilis, T.), s. 090018. (AIP Conference Proceedings. 1702). ISBN 978-0-7354-1349-8. ISSN 0094-243X. [International Conference of Computational Methods in Sciences and Engineering /11./ (ICCMSE 2015). Athens (GR), 20.03.2015-23.03.2015] Institutional support: RVO:61388963 Keywords : sigma-hole bonding * quantum chemical and molecular mechanincs calculations Subject RIV: CF - Physical ; Theoretical Chemistry

  11. A Phenomenographic Study on Chemical Bonding

    OpenAIRE

    Şenol Şen; Ayhan Yılmaz

    2013-01-01

    This study aims to reveal how students perceive and identify the concept of chemical bonding, and to identify and explain the misconceptions of students on this subject through phenomenographic research method, as well. The present study included 17 2nd grade students who enrolled to Inorganic Chemistry course in the Faculty of Education. Concept maps and lotus blossom technique were used as data collection tools in order to determine the perceptions and definitions of students about chemical...

  12. Actinide separative chemistry

    International Nuclear Information System (INIS)

    Actinide separative chemistry has focused very heavy work during the last decades. The main was nuclear spent fuel reprocessing: solvent extraction processes appeared quickly a suitable, an efficient way to recover major actinides (uranium and plutonium), and an extensive research, concerning both process chemistry and chemical engineering technologies, allowed the industrial development in this field. We can observe for about half a century a succession of Purex plants which, if based on the same initial discovery (i.e. the outstanding properties of a molecule, the famous TBP), present huge improvements at each step, for a large part due to an increased mastery of the mechanisms involved. And actinide separation should still focus R and D in the near future: there is a real, an important need for this, even if reprocessing may appear as a mature industry. We can present three main reasons for this. First, actinide recycling appear as a key-issue for future nuclear fuel cycles, both for waste management optimization and for conservation of natural resource; and the need concerns not only major actinide but also so-called minor ones, thus enlarging the scope of the investigation. Second, extraction processes are not well mastered at microscopic scale: there is a real, great lack in fundamental knowledge, useful or even necessary for process optimization (for instance, how to design the best extracting molecule, taken into account the several notifications and constraints, from selectivity to radiolytic resistivity?); and such a need for a real optimization is to be more accurate with the search of always cheaper, cleaner processes. And then, there is room too for exploratory research, on new concepts-perhaps for processing quite new fuels- which could appear attractive and justify further developments to be properly assessed: pyro-processes first, but also others, like chemistry in 'extreme' or 'unusual' conditions (supercritical solvents, sono-chemistry, could be

  13. Influence of Selected Alkoxysilanes on Dispersive Properties and Surface Chemistry of Titanium Dioxide and TiO2–SiO2 Composite Material

    OpenAIRE

    Katarzyna Siwińska-Stefańska; Filip Ciesielczyk; Magdalena Nowacka; Teofil Jesionowski

    2012-01-01

    The paper reports on characterisation of titanium dioxide and coprecipitated TiO2–SiO2 composite material functionalised with selected alkoxysilanes. Synthetic composite material was obtained by an emulsion method with cyclohexane as the organic phase, titanium sulfate as titanium precursor, and sodium silicate solution as precipitating agent were applied. Structures of titania and composite material samples were studied by the wide angle X-ray scattering method. The chemical composition of T...

  14. Science Update: Inorganic Chemistry

    Science.gov (United States)

    Rawls, Rebecca

    1978-01-01

    This first in a series of articles describing the state of the art of various branches of chemistry reviews inorganic chemistry, including bioinorganic, photochemistry, organometallic, and solid state chemistries. (SL)

  15. Why Teach Environmental Chemistry?

    Science.gov (United States)

    Gardner, Marjorie H.

    1974-01-01

    Discusses the importance of teaching environmental chemistry in secondary school science classes, and outlines five examples of environmental chemistry problems that focus on major concepts of chemistry and have critical implications for human survival and well-being. (JR)

  16. Photoredox Catalysis in Organic Chemistry

    Science.gov (United States)

    2016-01-01

    In recent years, photoredox catalysis has come to the forefront in organic chemistry as a powerful strategy for the activation of small molecules. In a general sense, these approaches rely on the ability of metal complexes and organic dyes to convert visible light into chemical energy by engaging in single-electron transfer with organic substrates, thereby generating reactive intermediates. In this Perspective, we highlight the unique ability of photoredox catalysis to expedite the development of completely new reaction mechanisms, with particular emphasis placed on multicatalytic strategies that enable the construction of challenging carbon–carbon and carbon–heteroatom bonds. PMID:27477076

  17. Photoredox Catalysis in Organic Chemistry.

    Science.gov (United States)

    Shaw, Megan H; Twilton, Jack; MacMillan, David W C

    2016-08-19

    In recent years, photoredox catalysis has come to the forefront in organic chemistry as a powerful strategy for the activation of small molecules. In a general sense, these approaches rely on the ability of metal complexes and organic dyes to convert visible light into chemical energy by engaging in single-electron transfer with organic substrates, thereby generating reactive intermediates. In this Perspective, we highlight the unique ability of photoredox catalysis to expedite the development of completely new reaction mechanisms, with particular emphasis placed on multicatalytic strategies that enable the construction of challenging carbon-carbon and carbon-heteroatom bonds. PMID:27477076

  18. Bonding silicones with epoxies

    Energy Technology Data Exchange (ETDEWEB)

    Tira, J.S.

    1980-01-01

    It is shown that silicones, both room temperature vulcanizing (RTV) and millable rubber (press cured) can be successfully bonded to other materials using plasma treatment and epoxy adhesives. The plasma treatment using dry air atmosphere increases the surface energy of the silicone and thus provides a lower water contact angle. This phenomenon allows the epoxy adhesive to wet the silicone surface and ultimately bond. Bond strengths are sufficiently high to result in failures in the silicone materials rather than the adhesive bond.

  19. Australia's Bond Home Bias

    OpenAIRE

    Mishra, Anil V; Umaru B. Conteh

    2014-01-01

    This paper constructs the float adjusted measure of home bias and explores the determinants of bond home bias by employing the International Monetary Fund's high quality dataset (2001 to 2009) on cross-border bond investment. The paper finds that Australian investors' prefer investing in countries with higher economic development and more developed bond markets. Exchange rate volatility appears to be an impediment for cross-border bond investment. Investors prefer investing in countries with ...

  20. Malaysia : Bond Market Development

    OpenAIRE

    International Monetary Fund; World Bank

    2013-01-01

    This paper pertains to the bond market development in Malaysia, and provides an overview of the market scenario in the country. Malaysia has been successful in developing the capital markets, particularly bond markets, in the recent past. Now, it faces the challenge of how to improve broader access and efficiency of the bond market. A high degree of investor concentration, dominated by gov...

  1. Chemical bond fundamental aspects of chemical bonding

    CERN Document Server

    Frenking, Gernot

    2014-01-01

    This is the perfect complement to ""Chemical Bonding - Across the Periodic Table"" by the same editors, who are two of the top scientists working on this topic, each with extensive experience and important connections within the community. The resulting book is a unique overview of the different approaches used for describing a chemical bond, including molecular-orbital based, valence-bond based, ELF, AIM and density-functional based methods. It takes into account the many developments that have taken place in the field over the past few decades due to the rapid advances in quantum chemica

  2. Assessment of water chemistry, habitat, and benthic macroinvertebrates at selected stream-quality monitoring sites in Chester County, Pennsylvania, 1998-2000

    Science.gov (United States)

    Reif, Andrew G.

    2004-01-01

    Biological, chemical, and habitat data have been collected from a network of sites in Chester County, Pa., from 1970 to 2003 to assess stream quality. Forty sites in 6 major stream basins were sampled between 1998 and 2000. Biological data were used to determine levels of impairment in the benthic-macroinvertebrate community in Chester County streams and relate the impairment, in conjunction with chemical and habitat data, to overall stream quality. Biological data consisted of benthic-macroinvertebrate samples that were collected annually in the fall. Water-chemistry samples were collected and instream habitat was assessed in support of the biological sampling. Most sites in the network were designated as nonimpacted or slightly impacted by human activities or extreme climatic conditions on the basis of biological-metric analysis of benthic-macroinvertebrate data. Impacted sites were affected by factors, such as nutrient enrichment, erosion and sedimentation, point discharges, and droughts and floods. Streams in the Schuylkill River, Delaware River, and East Branch Brandywine Creek Basins in Chester County generally had low nutrient concentrations, except in areas affected by wastewater- treatment discharges, and stream habitat that was affected by erosion. Streams in the West Branch Brandywine, Christina, Big Elk, and Octoraro Creek Basins in Chester County generally had elevated nutrient concentrations and streambottom habitat that was affected by sediment deposition. Macroinvertebrate communities identified in samples from French Creek, Pigeon Creek (Schuylkill River Basin), and East Branch Brandywine Creek at Glenmoore consistently indicate good stream conditions and were the best conditions measured in the network. Macroinvertebrate communities identified in samples from Trout Creek (site 61), West Branch Red Clay Creek (site 55) (Christina River Basin), and Valley Creek near Atglen (site 34) (Octoraro Creek Basin) indicated fair to poor stream conditions and

  3. Science Update: Inorganic Chemistry.

    Science.gov (United States)

    Rawls, Rebecca

    1981-01-01

    Describes areas of inorganic chemistry which have changed dramatically in the past year or two, including photochemistry, electrochemistry, organometallic complexes, inorganic reaction theory, and solid state chemistry. (DS)

  4. Splitting a Substrate into Three Parts: Gold-Catalyzed Nitrogenation of Alkynes by C-C and C≡C Bond Cleavage.

    Science.gov (United States)

    Qin, Chong; Su, Yijin; Shen, Tao; Shi, Xiaodong; Jiao, Ning

    2016-01-01

    A gold-catalyzed nitrogenation of alkynes for the synthesis of carbamides and amino tetrazoles through C-C and C≡C bond cleavages is described. A diverse set of functionalized carbamide and amino tetrazole derivatives were selectively constructed under mild conditions. The chemoselectivity can be easily switched by the selection of the acid additives. The reaction is characterized by its broad substrate scope, direct construction of high value products, easy operation under air, and mild conditions at room temperature. This chemistry provides a way to transform alkynes by splitting the substrate into three parts. PMID:26494539

  5. Trace Chemistry

    Science.gov (United States)

    Radhakrishnan, Krishnan; Whitefield, Philip

    1999-01-01

    The goals of the trace chemistry group were to identify the processes relevant to aerosol and aerosol precursor formation occurring within aircraft gas turbine engines; that is, within the combustor, turbine, and nozzle. The topics of discussion focused on whether the chemistry of aerosol formation is homogeneous or heterogeneous; what species are important for aerosol and aerosol precursor formation; what modeling/theoretical activities to pursue; what experiments to carry out that both support modeling activities and elucidate fundamental processes; and the role of particulates in aerosol and aerosol precursor formation. The consensus of the group was that attention should be focused on SO2, SO3, and aerosols. Of immediate concern is the measurement of the concentration of the species SO3, SO2, H2SO4 OH, HO2, H2O2, O, NO, NO2, HONO, HNO3, CO, and CO2 and particulates in various engines, both those currently in use and those in development. The recommendation was that concentration measurements should be made at both the combustor exit and the engine exit. At each location the above species were classified into one of four categories of decreasing importance, Priority I through IV, as follows: Combustor exit: Priority I species - SO3:SO2 ratio, SO3, SO2, and particulates; Priority II species: OH and O; Priority III species - NO and NO2; and Priority IV species - CO and CO2. For the Engine exit: Priority I species - SO3:SO2 ratio, SO3, SO2,H2SO4, and particulates; Priority II species: OH,HO2, H2O2, and O; Priority III species - NO, NO2, HONO, and HNO3; and Priority IV species - CO and CO2. Table I summarizes the anticipated concentration range of each of these species. For particulate matter, the quantities of interest are the number density, size distribution, and composition. In order to provide data for validating multidimensional reacting flow models, it would be desirable to make 2-D, time-resolved measurements of the concentrations of the above species and

  6. Perspective: Water cluster mediated atmospheric chemistry

    International Nuclear Information System (INIS)

    The importance of water in atmospheric and environmental chemistry initiated recent studies with results documenting catalysis, suppression and anti-catalysis of thermal and photochemical reactions due to hydrogen bonding of reagents with water. Water, even one water molecule in binary complexes, has been shown by quantum chemistry to stabilize the transition state and lower its energy. However, new results underscore the need to evaluate the relative competing rates between reaction and dissipation to elucidate the role of water in chemistry. Water clusters have been used successfully as models for reactions in gas-phase, in aqueous condensed phases and at aqueous surfaces. Opportunities for experimental and theoretical chemical physics to make fundamental new discoveries abound. Work in this field is timely given the importance of water in atmospheric and environmental chemistry.

  7. COMPARATIVE EVALUATION OF THE BONDING EFFICACY OF SIXTH, SEVENTH AND EIGHTH GENERATION BONDING AGENTS: AN IN VITRO STUDY

    OpenAIRE

    Paul Joseph; Chakravarthy Yadav; Kumar Satheesh; Raju Rahna

    2013-01-01

    The aim of the study was to compare In-vitro the micro tensile bond strength of sixth generation (Clearfil SE Bond, Kuraray, Japan), seventh generation (Adper Easy One, 3 M ESPE, Germany) and eighth generation ((Futurabond DC, Voco, Germany) dentin bonding agents. Twenty freshly extracted caries free, unrestored human molars were selected. The occlusal surfaces were ground flat; divided into four groups of five each according to the bonding agent applied and covered with composite resin (10 m...

  8. Selected aspects of the chemistry and radiation chemistry of lignin

    International Nuclear Information System (INIS)

    Lignin was subjected to electron and gamma radiation as part of a study to determine the effects of radiation on its structure. Some of the factors that influence the outcome of the treatment are the dose, the nature of the atmosphere surrounding the sample, and the physical state and nature of the irradiated lignin itself. Our data describe some of the free radical intermediates formed during irradiation and how the variation of certain factors affects the magnitude and direction of the effects induced by irradiation. The data were obtained using electron spin resonance spectroscopy, size exclusion chromatography and other high performance liguid chromatography techniques and gas chromatography-mass spectroscopy analysis. The substrates used were Indulin AT and pyrolysed lignin. Depending on the experimental conditions, radiation treatment may lead to either polymerisation or degradation processes. The factors that determine the outcome are discussed in terms of substrate structures and the chemical processes that take place. (author) 12 refs

  9. Selected topics in high temperature chemistry defect chemistry of solids

    CERN Document Server

    Johannesen, Ø

    2013-01-01

    The properties of materials at high temperature play a vital role in their processing and practical use. The real properties of materials at elevated temperatures are very often governed by defects in their structure. Lattice defects may consist of point defects like vacancies, interstitial atoms or substituted atoms. These classes are discussed in general and specifically for oxides, nitrides, carbides and sulfides. Defect aggregates, shear structures and adaptive structures are also described. Special attention is paid to hydrogen defects which seem to play an important role in several mater

  10. Influence of Selected Alkoxysilanes on Dispersive Properties and Surface Chemistry of Titanium Dioxide and TiO2–SiO2 Composite Material

    Directory of Open Access Journals (Sweden)

    Katarzyna Siwińska-Stefańska

    2012-01-01

    Full Text Available The paper reports on characterisation of titanium dioxide and coprecipitated TiO2–SiO2 composite material functionalised with selected alkoxysilanes. Synthetic composite material was obtained by an emulsion method with cyclohexane as the organic phase, titanium sulfate as titanium precursor, and sodium silicate solution as precipitating agent were applied. Structures of titania and composite material samples were studied by the wide angle X-ray scattering method. The chemical composition of TiO2–SiO2 composite material precipitated was evaluated based on the energy dispersive X-ray spectroscopy technique. The functionalised TiO2 and TiO2–SiO2 composite material were thoroughly characterised to determine the yield of functionalisation with silanes. The characterisation included determination of dispersion and morphology of the systems (particle size distribution, scanning electron microscope images, adsorption properties (nitrogen adsorption isotherms, and electrokinetic properties (zeta potential.

  11. Molten fluoride fuel salt chemistry

    International Nuclear Information System (INIS)

    The chemistry of molten fluorides is traced from their development as fuels in the Molten Salt Reactor Experiment with important factors in their selection being discussed. Key chemical characteristics such as solubility, redox behavior, and chemical activity are explained as they relate to the behavior of molten fluoride fuel systems. Fission product behavior is described along with processing experience. Development requirements for fitting the current state of the chemistry to modern nuclear fuel system are described. It is concluded that while much is known about molten fluoride behavior, processing and recycle of the fuel components is a necessary factor if future systems are to be established

  12. Part 6: The Literature of Inorganic Chemistry, Revised.

    Science.gov (United States)

    Douville, Judith A.

    2002-01-01

    Presents a list of resources on inorganic chemistry that includes general surveys, nomenclature, dictionaries, handbooks, compilations, and treatises. Selected for use by academic and student chemists. (DDR)

  13. Competing Intramolecular vs. Intermolecular Hydrogen Bonds in Solution

    OpenAIRE

    Nagy, Peter I.

    2014-01-01

    A hydrogen bond for a local-minimum-energy structure can be identified according to the definition of the International Union of Pure and Applied Chemistry (IUPAC recommendation 2011) or by finding a special bond critical point on the density map of the structure in the framework of the atoms-in-molecules theory. Nonetheless, a given structural conformation may be simply favored by electrostatic interactions. The present review surveys the in-solution competition of the conformations with int...

  14. Green chemistry oriented organic synthesis in water.

    Science.gov (United States)

    Simon, Marc-Olivier; Li, Chao-Jun

    2012-02-21

    The use of water as solvent features many benefits such as improving reactivities and selectivities, simplifying the workup procedures, enabling the recycling of the catalyst and allowing mild reaction conditions and protecting-group free synthesis in addition to being benign itself. In addition, exploring organic chemistry in water can lead to uncommon reactivities and selectivities complementing the organic chemists' synthetic toolbox in organic solvents. Studying chemistry in water also allows insight to be gained into Nature's way of chemical synthesis. However, using water as solvent is not always green. This tutorial review briefly discusses organic synthesis in water with a Green Chemistry perspective. PMID:22048162

  15. Interactive visualization of quantum-chemistry data.

    Science.gov (United States)

    Jang, Yun; Varetto, Ugo

    2010-09-01

    Simulation and computation in chemistry studies have improved as computational power has increased over recent decades. Many types of chemistry simulation results are available, from atomic level bonding to volumetric representations of electron density. However, tools for the visualization of the results from quantum-chemistry computations are still limited to showing atomic bonds and isosurfaces or isocontours corresponding to certain isovalues. In this work, we study the volumetric representations of the results from quantum-chemistry computations, and evaluate and visualize the representations directly on a modern graphics processing unit without resampling the result in grid structures. Our visualization tool handles the direct evaluation of the approximated wavefunctions described as a combination of Gaussian-like primitive basis functions. For visualizations, we use a slice-based volume-rendering technique with a two-dimensional transfer function, volume clipping and illustrative rendering in order to reveal and enhance the quantum-chemistry structure. Since there is no need to resample the volume from the functional representations for the volume rendering, two issues, data transfer and resampling resolution, can be ignored; therefore, it is possible to explore interactively a large amount of different information in the computation results. PMID:20720319

  16. Understanding the molecular-level chemistry of water plasmas and the effects of surface modification and deposition on a selection of oxide substrates

    Science.gov (United States)

    Trevino, Kristina J.

    2011-12-01

    This dissertation first examines electrical discharges used to study wastewater samples for contaminant detection and abatement. Two different water samples contaminated with differing concentrations of either methanol (MeOH) or methyl tert-butyl ether (MTBE) were used to follow breakdown mechanisms. Emission from CO* was used to monitor the contaminant and for molecular breakdown confirmation through actinometric OES as it can only arise from the carbon-based contaminant in either system. Detection was achieved at concentrations as low as 0.01 ppm, and molecular decomposition was seen at a variety of plasma parameters. This dissertation also explores the vibrational (thetaV), rotational (thetaR) and translational (thetaT) temperatures for a range of diatomic species in different plasma systems. For the majority of the plasma species studied, thetaV are much higher than thetaR and thetaT. This suggests that more energy is partitioned into the vibrational degrees of freedom in our plasmas. The thetaR reported are significantly lower in all the plasma systems studied and this is a result of radical equilibration to the plasma gas temperature. thetaT values show two characteristics; (1) they are less than the thetaV and higher than the theta R and (2) show varying trends with plasma parameters. Radical energetics were examined through comparison of thetaR, thetaT, and thetaV, yielding significant insight on the partitioning of internal and kinetic energies in plasmas. Correlations between energy partitioning results and corresponding radical surface scattering coefficients obtained using our imaging of radicals interacting with surfaces (IRIS) technique are also presented. Another aspect of plasma process chemistry, namely surface modification via plasma treatment, was investigated through characterization of metal oxides (SiOxNy, nat-SiO2, and dep-SiO2) following their exposure to a range of plasma discharges. Here, emphasis was placed on the surface wettability

  17. Exploring the Nature of the H[subscript 2] Bond. 1. Using Spreadsheet Calculations to Examine the Valence Bond and Molecular Orbital Methods

    Science.gov (United States)

    Halpern, Arthur M.; Glendening, Eric D.

    2013-01-01

    A three-part project for students in physical chemistry, computational chemistry, or independent study is described in which they explore applications of valence bond (VB) and molecular orbital-configuration interaction (MO-CI) treatments of H[subscript 2]. Using a scientific spreadsheet, students construct potential-energy (PE) curves for several…

  18. Weak bond screening system

    Science.gov (United States)

    Chuang, S. Y.; Chang, F. H.; Bell, J. R.

    Consideration is given to the development of a weak bond screening system which is based on the utilization of a high power ultrasonic (HPU) technique. The instrumentation of the prototype bond strength screening system is described, and the adhesively bonded specimens used in the system developmental effort are detailed. Test results obtained from these specimens are presented in terms of bond strength and level of high power ultrasound irradiation. The following observations were made: (1) for Al/Al specimens, 2.6 sec of HPU irradiation will screen weak bond conditions due to improper preparation of bonding surfaces; (2) for composite/composite specimens, 2.0 sec of HPU irradiation will disrupt weak bonds due to under-cured conditions; (3) for Al honeycomb core with composite skin structure, 3.5 sec of HPU irradiation will disrupt weak bonds due to bad adhesive or oils contamination of bonding surfaces; and (4) for Nomex honeycomb with Al skin structure, 1.3 sec of HPU irradiation will disrupt weak bonds due to bad adhesive.

  19. Neural mechanisms of mother-infant bonding and pair bonding: Similarities, differences, and broader implications.

    Science.gov (United States)

    Numan, Michael; Young, Larry J

    2016-01-01

    This article is part of a Special Issue "Parental Care". Mother-infant bonding is a characteristic of virtually all mammals. The maternal neural system may have provided the scaffold upon which other types of social bonds in mammals have been built. For example, most mammals exhibit a polygamous mating system, but monogamy and pair bonding between mating partners occur in ~5% of mammalian species. In mammals, it is plausible that the neural mechanisms that promote mother-infant bonding have been modified by natural selection to establish the capacity to develop a selective bond with a mate during the evolution of monogamous mating strategies. Here we compare the details of the neural mechanisms that promote mother-infant bonding in rats and other mammals with those that underpin pair bond formation in the monogamous prairie vole. Although details remain to be resolved, remarkable similarities and a few differences between the mechanisms underlying these two types of bond formation are revealed. For example, amygdala and nucleus accumbens-ventral pallidum (NA-VP) circuits are involved in both types of bond formation, and dopamine and oxytocin actions within NA appear to promote the synaptic plasticity that allows either infant or mating partner stimuli to persistently activate NA-VP attraction circuits, leading to an enduring social attraction and bonding. Further, although the medial preoptic area is essential for maternal behavior, its role in pair bonding remains to be determined. Our review concludes by examining the broader implications of this comparative analysis, and evidence is provided that the maternal care system may have also provided the basic neural foundation for other types of strong social relationships, beyond pair bonding, in mammals, including humans. PMID:26062432

  20. Bond strength optimization of Ti/Cu/Ti clad composites produced by roll-bonding

    International Nuclear Information System (INIS)

    Highlights: • Ti/Cu/Ti clad composite was successfully fabricated by the roll-bonding technique. • The most effective bonding parameter was post-annealing temperature. • The mechanism of the Cu/Ti roll bonding could be clarified using the film theory. - Abstract: This research focuses on the bond strength of the Ti/Cu/Ti composites fabricated by roll-bonding. The peel tests were used to evaluate the bond strength of the clad composites. The Taguchi technique was used to find the optimum conditions to maximize the Cu/Ti bond strength. The optical microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, as well as peel and microhardness tests were utilized to characterize the interfacial zones. A Taguchi L32 orthogonal array was selected to study the influence of the roll-bonding parameters, including the roller lubrication conditions, temper condition of Cu, rolling temperature, reduction in thickness, post-annealing time, and post-annealing temperature, and rolling speed on the bond strength. Based on the Taguchi statistical analysis, the rolling temperature, reduction in thickness, post-annealing temperature and rolling speed have significant effects on the bond strength. Among these, the post-annealing temperature is the most effective factor. It was shown that the selection of the highest “reduction in thickness”, the lowest “rolling speed”, and the intermediate values of “rolling temperature” and “post-annealing temperature” leads to the highest bond strength. It was also indicated that the mechanism of the Cu/Ti roll bonding could be explained using the film theory

  1. Ab initio valence calculations in chemistry

    CERN Document Server

    Cook, D B

    1974-01-01

    Ab Initio Valence Calculations in Chemistry describes the theory and practice of ab initio valence calculations in chemistry and applies the ideas to a specific example, linear BeH2. Topics covered include the Schrödinger equation and the orbital approximation to atomic orbitals; molecular orbital and valence bond methods; practical molecular wave functions; and molecular integrals. Open shell systems, molecular symmetry, and localized descriptions of electronic structure are also discussed. This book is comprised of 13 chapters and begins by introducing the reader to the use of the Schrödinge

  2. Structure, chemistry, and properties of mineral nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Waychunas, G.A.; Zhang, H.; Gilbert, B.

    2008-12-02

    Nanoparticle properties can depart markedly from their bulk analog materials, including large differences in chemical reactivity, molecular and electronic structure, and mechanical behavior. The greatest changes are expected at the smallest sizes, e.g. 10 nm and below, where surface effects are expected to dominate bonding, shape and energy considerations. The precise chemistry at nanoparticle interfaces can have a profound effect on structure, phase transformations, strain, and reactivity. Certain phases may exist only as nanoparticles, requiring transformations in chemistry, stoichiometry and structure with evolution to larger sizes. In general, mineralogical nanoparticles have been little studied.

  3. Radiation chemistry research using PULAF

    International Nuclear Information System (INIS)

    The details of the recently installed 7 MeV Pune University LINAC Facility (PULAF) coupled with the optical absorption technique for pulse radiolysis studies at the National Centre for Free Radical Research, Department of Chemistry, University of Pune, Pune, India are described. The facility has a selection of electron pulse widths in the range 10 ns-3 μs with corresponding doses of about 5-144 Gy per pulse. The operation of the machine and the detection system are fully automated. Several researchers from various Indian universities and national laboratories use the PULAF and some of the projects that are currently undertaken by our group and others include the radiation chemistry of indole and chalcone derivatives, herbal antioxidants, structure-reactivity studies in cinnamates, redox chemistry of inorganic metal complexes, studies on oxidation of pyrimidine analogues and aromatic sulphur compounds. Some of them are briefly discussed here

  4. Mass spectrometry. [in organic chemistry

    Science.gov (United States)

    Burlingame, A. L.; Shackleton, C. H. L.; Howe, I.; Chizhov, O. S.

    1978-01-01

    A review of mass spectrometry in organic chemistry is given, dealing with advances in instrumentation and computer techniques, selected topics in gas-phase ion chemistry, and applications in such fields as biomedicine, natural-product studies, and environmental pollution analysis. Innovative techniques and instrumentation are discussed, along with chromatographic-mass spectrometric on-line computer techniques, mass spectral interpretation and management techniques, and such topics in gas-phase ion chemistry as electron-impact ionization and decomposition, photoionization, field ionization and desorption, high-pressure mass spectrometry, ion cyclotron resonance, and isomerization reactions of organic ions. Applications of mass spectrometry are examined with respect to bio-oligomers and their constituents, biomedically important substances, microbiology, environmental organic analysis, and organic geochemistry.

  5. Radiation chemistry research using PULAF

    Science.gov (United States)

    Gaikwad, Parimal; Priyadarsini, K. I.; Rao, B. S. M.

    2008-10-01

    The details of the recently installed 7 MeV Pune University LINAC Facility (PULAF) coupled with the optical absorption technique for pulse radiolysis studies at the National Centre for Free Radical Research, Department of Chemistry, University of Pune, Pune, India are described. The facility has a selection of electron pulse widths in the range 10 ns-3 μs with corresponding doses of about 5-144 Gy per pulse. The operation of the machine and the detection system are fully automated. Several researchers from various Indian universities and national laboratories use the PULAF and some of the projects that are currently undertaken by our group and others include the radiation chemistry of indole and chalcone derivatives, herbal antioxidants, structure-reactivity studies in cinnamates, redox chemistry of inorganic metal complexes, studies on oxidation of pyrimidine analogues and aromatic sulphur compounds. Some of them are briefly discussed here.

  6. Radiation chemistry research using PULAF

    Energy Technology Data Exchange (ETDEWEB)

    Gaikwad, Parimal [National Centre for Free Radical Research, Department of Chemistry, University of Pune, Pune 411 007 (India); Priyadarsini, K.I. [Radiation and Photochemistry Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085 (India); Rao, B.S.M. [National Centre for Free Radical Research, Department of Chemistry, University of Pune, Pune 411 007 (India)], E-mail: bsmr@chem.unipune.ernet.in

    2008-10-15

    The details of the recently installed 7 MeV Pune University LINAC Facility (PULAF) coupled with the optical absorption technique for pulse radiolysis studies at the National Centre for Free Radical Research, Department of Chemistry, University of Pune, Pune, India are described. The facility has a selection of electron pulse widths in the range 10 ns-3 {mu}s with corresponding doses of about 5-144 Gy per pulse. The operation of the machine and the detection system are fully automated. Several researchers from various Indian universities and national laboratories use the PULAF and some of the projects that are currently undertaken by our group and others include the radiation chemistry of indole and chalcone derivatives, herbal antioxidants, structure-reactivity studies in cinnamates, redox chemistry of inorganic metal complexes, studies on oxidation of pyrimidine analogues and aromatic sulphur compounds. Some of them are briefly discussed here.

  7. Covalent chemistry in graphene electronics

    Directory of Open Access Journals (Sweden)

    Santanu Sarkar

    2012-06-01

    Full Text Available The development of selective high precision chemical functionalization strategies for device fabrication, in conjunction with associated techniques for patterning graphene wafers with atomic accuracy would provide the necessary basis for a post-CMOS manufacturing technology. This requires a thorough understanding of the principles governing the reactivity and patterning of graphene at the sub-nanometer length scale. This article reviews our quest to delineate the principles of graphene chemistry – that is, the chemistry at the Dirac point and beyond, and the effect of covalent chemistry on the electronic structure, electrical transport, and magnetic properties of this low-dimensional material in order to enable the scalable production of graphene-based devices for low- and high-end technology applications.

  8. Industrial Chemistry and School Chemistry: Making Chemistry Studies More Relevant

    Science.gov (United States)

    Hofstein, Avi; Kesner, Miri

    2006-01-01

    In this paper, we present the development and implementation over the period of more than 15 years of learning materials focusing on industrial chemistry as the main theme. The work was conducted in the Department of Science Teaching at the Weizmann Institute of Science, Israel. The project's general goal was to teach chemistry concepts in the…

  9. On the Relative Merits of Non-Orthogonal and Orthogonal Valence Bond Methods Illustrated on the Hydrogen Molecule

    Science.gov (United States)

    Angeli, Celestino; Cimiraglia, Renzo; Malrieu, Jean-Paul

    2008-01-01

    Valence bond (VB) is one of the cornerstone theories of quantum chemistry. Even if in practical applications the molecular orbital (MO) approach has obtained more attention, some basic chemical concepts (such as the nature of the chemical bond and the failure of the single determinant-based MO methods in describing the bond cleavage) are normally…

  10. Selective Preference of Parallel DNA Triplexes Is Due to the Disruption of Hoogsteen Hydrogen Bonds Caused by the Severe Nonisostericity between the G*GC and T*AT Triplets

    Science.gov (United States)

    Goldsmith, Gunaseelan; Rathinavelan, Thenmalarchelvi; Yathindra, Narayanarao

    2016-01-01

    Implications of DNA, RNA and RNA.DNA hybrid triplexes in diverse biological functions, diseases and therapeutic applications call for a thorough understanding of their structure-function relationships. Despite exhaustive studies mechanistic rationale for the discriminatory preference of parallel DNA triplexes with G*GC & T*AT triplets still remains elusive. Here, we show that the highest nonisostericity between the G*GC & T*AT triplets imposes extensive stereochemical rearrangements contributing to context dependent triplex destabilisation through selective disruption of Hoogsteen scheme of hydrogen bonds. MD simulations of nineteen DNA triplexes with an assortment of sequence milieu reveal for the first time fresh insights into the nature and extent of destabilization from a single (non-overlapping), double (overlapping) and multiple pairs of nonisosteric base triplets (NIBTs). It is found that a solitary pair of NIBTs, feasible either at a G*GC/T*AT or T*AT/G*GC triplex junction, does not impinge significantly on triplex stability. But two overlapping pairs of NIBTs resulting from either a T*AT or a G*GC interruption disrupt Hoogsteen pair to a noncanonical mismatch destabilizing the triplex by ~10 to 14 kcal/mol, implying that their frequent incidence in multiples, especially, in short sequences could even hinder triplex formation. The results provide (i) an unambiguous and generalised mechanistic rationale for the discriminatory trait of parallel triplexes, including those studied experimentally (ii) clarity for the prevalence of antiparallel triplexes and (iii) comprehensive perspectives on the sequence dependent influence of nonisosteric base triplets useful in the rational design of TFO’s against potential triplex target sites. PMID:27010368

  11. Selective Preference of Parallel DNA Triplexes Is Due to the Disruption of Hoogsteen Hydrogen Bonds Caused by the Severe Nonisostericity between the G*GC and T*AT Triplets.

    Science.gov (United States)

    Goldsmith, Gunaseelan; Rathinavelan, Thenmalarchelvi; Yathindra, Narayanarao

    2016-01-01

    Implications of DNA, RNA and RNA.DNA hybrid triplexes in diverse biological functions, diseases and therapeutic applications call for a thorough understanding of their structure-function relationships. Despite exhaustive studies mechanistic rationale for the discriminatory preference of parallel DNA triplexes with G*GC & T*AT triplets still remains elusive. Here, we show that the highest nonisostericity between the G*GC & T*AT triplets imposes extensive stereochemical rearrangements contributing to context dependent triplex destabilisation through selective disruption of Hoogsteen scheme of hydrogen bonds. MD simulations of nineteen DNA triplexes with an assortment of sequence milieu reveal for the first time fresh insights into the nature and extent of destabilization from a single (non-overlapping), double (overlapping) and multiple pairs of nonisosteric base triplets (NIBTs). It is found that a solitary pair of NIBTs, feasible either at a G*GC/T*AT or T*AT/G*GC triplex junction, does not impinge significantly on triplex stability. But two overlapping pairs of NIBTs resulting from either a T*AT or a G*GC interruption disrupt Hoogsteen pair to a noncanonical mismatch destabilizing the triplex by ~10 to 14 kcal/mol, implying that their frequent incidence in multiples, especially, in short sequences could even hinder triplex formation. The results provide (i) an unambiguous and generalised mechanistic rationale for the discriminatory trait of parallel triplexes, including those studied experimentally (ii) clarity for the prevalence of antiparallel triplexes and (iii) comprehensive perspectives on the sequence dependent influence of nonisosteric base triplets useful in the rational design of TFO's against potential triplex target sites. PMID:27010368

  12. Selective Preference of Parallel DNA Triplexes Is Due to the Disruption of Hoogsteen Hydrogen Bonds Caused by the Severe Nonisostericity between the G*GC and T*AT Triplets.

    Directory of Open Access Journals (Sweden)

    Gunaseelan Goldsmith

    Full Text Available Implications of DNA, RNA and RNA.DNA hybrid triplexes in diverse biological functions, diseases and therapeutic applications call for a thorough understanding of their structure-function relationships. Despite exhaustive studies mechanistic rationale for the discriminatory preference of parallel DNA triplexes with G*GC & T*AT triplets still remains elusive. Here, we show that the highest nonisostericity between the G*GC & T*AT triplets imposes extensive stereochemical rearrangements contributing to context dependent triplex destabilisation through selective disruption of Hoogsteen scheme of hydrogen bonds. MD simulations of nineteen DNA triplexes with an assortment of sequence milieu reveal for the first time fresh insights into the nature and extent of destabilization from a single (non-overlapping, double (overlapping and multiple pairs of nonisosteric base triplets (NIBTs. It is found that a solitary pair of NIBTs, feasible either at a G*GC/T*AT or T*AT/G*GC triplex junction, does not impinge significantly on triplex stability. But two overlapping pairs of NIBTs resulting from either a T*AT or a G*GC interruption disrupt Hoogsteen pair to a noncanonical mismatch destabilizing the triplex by ~10 to 14 kcal/mol, implying that their frequent incidence in multiples, especially, in short sequences could even hinder triplex formation. The results provide (i an unambiguous and generalised mechanistic rationale for the discriminatory trait of parallel triplexes, including those studied experimentally (ii clarity for the prevalence of antiparallel triplexes and (iii comprehensive perspectives on the sequence dependent influence of nonisosteric base triplets useful in the rational design of TFO's against potential triplex target sites.

  13. Distributed scaffolding: Wiki collaboration among Latino high school chemistry students

    Science.gov (United States)

    O'Sullivan, Edwin Duncan, Jr.

    The primary purpose of this study was to evaluate if wiki collaboration among Latino high school chemistry students can help reduce the science achievement gap between Latino and White students. The study was a quasi-experimental pre/post control group mixed-methods design. It used three intact sections of a high school chemistry course. The first research question asked if there is a difference in academic achievement between a treatment and control group on selected concepts from the topics of bonding, physical changes, and chemical changes, when Latino high school chemistry students collaborate on a quasi-natural wiki project. Overall results for all three activities (Bonding, Physical Changes, and Chemical Changes) indicated no significant difference between the wiki and control group. However, students performing the chemical changes activity did significantly better than their respective control group. Furthermore, there was a significant association, with large effect size, between group membership and ability to overcome the misconception that aqueous ionic reactants in precipitation reactions exist as molecular pairs of ions. Qualitative analysis of classroom and computer lab dialogue, discussion board communication, student focus groups, teacher interviews, and wiki content attributes the better performance of the chemical changes wiki group to favorable differences in intersubjectivity and calibrated assistance, as well as learning about submicroscopic representations of precipitation reactions in multiple contexts. Furthermore, the nonsignificant result overall points to an aversion to peer editing as a possible cause. Drawing considerably on Vygotsky and Piaget, the results are discussed within the context of how distributed scaffolding facilitated medium levels of cognitive conflict. The second research question asked what the characteristics of distributed metacognitive scaffolding are when Latino high school chemistry students collaborate on a quasi

  14. Bond Markets in Africa

    OpenAIRE

    Yibin Mu; Peter Phelps; Janet Gale Stotsky

    2013-01-01

    African bond markets have been steadily growing in recent years, but nonetheless remain undeveloped. African countries would benefit from greater access to financing and deeper financial markets. This paper compiles a unique set of data on corporate bond markets in Africa. It then applies an econometric model to analyze the key determinants of African government securities market and corporate bond market capitalization. Government securities market capitalization is directly related to bette...

  15. Build America Bonds

    OpenAIRE

    Andrew Ang; Vineer Bhansali; Yuhang Xing

    2010-01-01

    Build America Bonds (BABs) are a new form of municipal financing introduced in 2009. Investors in BAB municipal bonds receive interest payments that are taxable, but issuers receive a subsidy from the U.S. Treasury. The BAB program has succeeded in lowering the cost of funding for state and local governments with BAB issuers obtaining finance 54 basis points lower, on average, compared to issuing regular municipal bonds. For institutional investors, BAB issue yields are 116 basis points highe...

  16. Gender Inclusivity in Secondary Chemistry: A Study of Male and Female Participation in Secondary School Chemistry

    Science.gov (United States)

    Cousins, Andrew

    2007-01-01

    This paper gives a nuanced analysis of participation rates in secondary chemistry by developing the "story" behind national trends and subject selection patterns within an independent school located in a large Australian city. It supplements the documented quantitative data by presenting a case-study where 30 Year 12 chemistry students were…

  17. The Bond Market's q

    OpenAIRE

    Thomas Philippon

    2006-01-01

    I propose an implementation of the q-theory of investment using bond prices instead of equity prices. Credit risk makes corporate bond prices sensitive to future asset values, and q can be inferred from bond prices. The bond market's q performs much better than the usual measure in standard investment equations. With aggregate data, the fit is three times better, cash flows are driven out and the implied adjustment costs are reduced by more than an order of magnitude. The new measure also imp...

  18. Copper wire bonding

    CERN Document Server

    Chauhan, Preeti S; Zhong, ZhaoWei; Pecht, Michael G

    2014-01-01

    This critical volume provides an in-depth presentation of copper wire bonding technologies, processes and equipment, along with the economic benefits and risks.  Due to the increasing cost of materials used to make electronic components, the electronics industry has been rapidly moving from high cost gold to significantly lower cost copper as a wire bonding material.  However, copper wire bonding has several process and reliability concerns due to its material properties.  Copper Wire Bonding book lays out the challenges involved in replacing gold with copper as a wire bond material, and includes the bonding process changes—bond force, electric flame off, current and ultrasonic energy optimization, and bonding tools and equipment changes for first and second bond formation.  In addition, the bond–pad metallurgies and the use of bare and palladium-coated copper wires on aluminum are presented, and gold, nickel and palladium surface finishes are discussed.  The book also discusses best practices and re...

  19. Hydrogen bonding and anaesthesia

    Science.gov (United States)

    Sándorfy, C.

    2004-12-01

    General anaesthetics act by perturbing intermolecular associations without breaking or forming covalent bonds. These associations might be due to a variety of van der Waals interactions or hydrogen bonding. Neurotransmitters all contain OH or NH groups, which are prone to form hydrogen bonds with those of the neurotransmitter receptors. These could be perturbed by anaesthetics. Aromatic rings in amino acids can act as weak hydrogen bond acceptors. On the other hand the acidic hydrogen in halothane type anaesthetics are weak proton donors. These two facts together lead to a probable mechanism of action for all general anaesthetics.

  20. From Matter to Life:Chemistry?Chemistry!

    Institute of Scientific and Technical Information of China (English)

    Jean-Marie; LEHN

    2007-01-01

    1 Results Animate as well as inanimate matter,living organisms as well as materials,are formed of molecules and of the organized entities resulting from the interaction of molecules with each other.Chemistry provides the bridge between the molecules of inanimate matter and the highly complex molecular architectures and systems which make up living organisms. Synthetic chemistry has developed a very powerful set of methods for constructing ever more complex molecules.Supramolecular chemistry seeks to con...

  1. Green chemistry: A tool in Pharmaceutical Chemistry

    OpenAIRE

    Smita Talaviya; Falguni Majumdar

    2012-01-01

    Green chemistry expresses an area of research developing from scientific discoveries about pollution awareness and it utilizes a set of principles that reduces or eliminates the use or generation of hazardous substances in all steps of particular synthesis or process. Chemists and medicinal scientists can greatly reduce the risk to human health and the environment by following all the valuable principles of green chemistry. The most simple and direct way to apply green chemistry in pharmaceut...

  2. Dentin-bonding agents

    Directory of Open Access Journals (Sweden)

    João Carlos Gomes

    2008-01-01

    Full Text Available New dental restorative materials have been developed to meet not only the functional demands, but esthetics as well, and in the last few years an enormous range of new materials has appeared for use in dentistry. Among them, several adhesive systems, and different operative techniques for each group materials. Therefore, is indispensable for the professional to know about the properties, characteristics, and association of these materials with the dental structures, in order to select and use them correctly. Should conventional self-etching adhesive systems be used? This question encouraged this literature review to be conducted, with the aim of comparing the conventional adhesive systems with the self-etching systems and to look for scientific data that would help professionals to choose which adhesive system to use. When compared to conventional systems, it was noted that the self-etching systems show less sensitivity to technique, especially as regards errors the operator could commit. The self-etching systems, particularly the 2-step type, have shown equivalent values of bond strength, marginal microleakage and performance, therefore, will be an option for direct composite resin restorations in posterior teeth.

  3. Halogen Bonding or Hydrogen Bonding between 2,2,6,6-Tetramethyl-piperidine-noxyl Radical and Trihalomethanes CHX3 (X=Cl, Br, I)

    Institute of Scientific and Technical Information of China (English)

    Xiao-ran Zhao; Xue Pang; Xiao-qing Yan; Wei-jun Jin

    2013-01-01

    The halogen and hydrogen bonding complexes between 2,2,6,6-tetramethylpiperidine-noxyl and trihalomethanes (CHX3,X=Cl,Br,I) are simulated by computational quantum chemistry.The molecular electrostatic potentials,geometrical parameters and interaction energy of halogen and hydrogen bonding complexes combined with natural bond orbital analysis are obtained.The results indicate that both halogen and hydrogen bonding interactions obey the order Cl<Br<I,and hydrogen bonding is stronger than the corresponding halogen bond ing.So,hydrogen bonding complexes should be dominant in trihalomethanes.However,it is possible that halogen bonding complex is competitive,even preponderant,in triiodomethane due to the similar interaction energy.This work might provide useful information on specific solvent effects as well as for understanding the mechanism of nitroxide radicals as a bioprobe to interact with the halogenated compounds in biological and biochemical fields.

  4. Bond Assembly FOD Zones - A Procedure for Assuring Acceptable Adhesion

    Science.gov (United States)

    Evans, Kurt; Wurth, Laura; Mitchell, Mark

    2009-01-01

    Rocket motor components are primarily assembled by adhesion. a) For example, the RSRM (Reusable Solid Rocket Motor - part of the Space Shuttle Boosters) system contains 10,000 sq ft of bondline area. b) Rocket motors contain a variety of adhesive/substrate bond systems c) Bond system performance requirements also vary. To assemble reliable components, ATK Space Systems and customers invest substantial resources to the study of bond assembly processes. a) Surface and adhesion science; b) Adhesive chemistry; c) Process parameters; d) Contamination effects.

  5. Polyoxometalate systems for the catalytic selective production of nonthermodynamic alkenes from alkanes. Nature of excited-state deactivation processes and control of subsequent thermal processes in polyoxometalate photoredox chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Renneke, R.F.; Pasquali, M.; Hill, C.L. (Emory Univ., Atlanta, GA (USA))

    1990-08-29

    The photooxidations of exemplary branched acyclic alkanes and cycloalkanes by a range of polyoxotungstates varying in charge density, ground-state redox potential, acidity, and other properties were examined in detail. The organic products generated in these reactions depend on the polyoxometalate used, and in particular on the ground-state redox potential of the complex. Under anaerobic conditions acyclic branched alkanes yield principally alkenes, while cycloalkanes yield principally alkenes and dimers. Alkyl methyl ketones, derived in part from reaction with acetonitrile solvent, and isomerized alkanes are produced with some alkane substrates. Under aerobic conditions, autoxidation, initiated by radicals generated in the photoinduced redox chemistry, is observed. Under aerobic conditions the polyoxotungstates with formal redox potentials more negative than {minus}1.0 V vs Ag/AgNO{sub 3}(CH{sub 3}CN), such as W{sub 10}O{sub 32}{sup 4{minus}} and W{sub 6}O{sub 19}{sup 2{minus}}, photochemically dehydrogenate branched acyclic alkanes in high selectivity to {alpha}-olefins and the least substituted alkenes, products heretofore undocumented in photooxidation reactions catalyzed by polyoxometalates.

  6. Beryllium chemistry and processing

    CERN Document Server

    Walsh, Kenneth A

    2009-01-01

    This book introduces beryllium; its history, its chemical, mechanical, and physical properties including nuclear properties. The 29 chapters include the mineralogy of beryllium and the preferred global sources of ore bodies. The identification and specifics of the industrial metallurgical processes used to form oxide from the ore and then metal from the oxide are thoroughly described. The special features of beryllium chemistry are introduced, including analytical chemical practices. Beryllium compounds of industrial interest are identified and discussed. Alloying, casting, powder processing, forming, metal removal, joining and other manufacturing processes are covered. The effect of composition and process on the mechanical and physical properties of beryllium alloys assists the reader in material selection. The physical metallurgy chapter brings conformity between chemical and physical metallurgical processing of beryllium, metal, alloys, and compounds. The environmental degradation of beryllium and its all...

  7. Chemistry Rocks: Redox Chemistry as a Geologic Tool.

    Science.gov (United States)

    Burns, Mary Sue

    2001-01-01

    Applies chemistry to earth science, uses rocks in chemistry laboratories, and teaches about transition metal chemistry, oxidation states, and oxidation-reduction reactions from firsthand experiences. (YDS)

  8. Combining Chemistry

    International Nuclear Information System (INIS)

    The last advances inside the field of the chemical synthesis involve mainly two classes of methods, the parallel and that of separation and it mixes. Each one of them offers different possibilities in the obtaining of the looked for substance. In this article it is described in succinct form the procedures that are continued in each case, the same thing that their advantages and disadvantages. In the synthesis process, especially in pharmacology, the main interest of the chemists is centered in finding indications of clinical activity in the compounds that synthesize. In the realization of this work class it leaves initially of the basic structure of a substance, in general derived of natural products as bacteria, mushrooms, etc; With well-known clinical activity the one which once selected, and fully identified, it takes as molecule mother or series head with the purpose of making different transformations in their structure it stops then to check if the new compound presents a bigger or smaller activity that the initial. Although this synthesis method has been refined with the use of different tests that they are made in a form but quick and reliable; the appearance of new illnesses and the necessity of quick treatments on the part of the drugs, the necessity of quick and efficient production of medications has increased with great biological activity that they allow to assure a better acting

  9. Nuclear chemistry

    International Nuclear Information System (INIS)

    Topics covered include: mass asymmetry and total kinetic energy release in the spontaneous fission of 262105; calculation of spontaneous fission properties of very heavy nuclei - 98 less than or equal to Z less than or equal to 106 and 150 less than or equal to N less than or equal to 164; energy losses for 84Kr ions in nickel, aluminium and titanium; differences in compound nuclei formed with 40Ar and 84Kr projectiles; measurement of the energy division vs. mass in highly damped reactions; ambiguities in the inference of precompound emission from excitation function analysis; selective laser one-atom detection of neutral prompt fission fragments; laser induced nuclear polarization - application to the study of spontaneous fission isomers; quadrupole and hexadecapole deformations in the actinide nuclei; high-spin states in 164Yb; contrasting behavior of h/sub 9/2/ and i/sub 13/2/ bands in 185Au; multiple band crossings in 164Er; recoil-distance measurement of lifetimes of rotational states in 164Dy, lifetimes of ground-band states in 192Pt and 194Pt and application of the rotation-alignment model; coulomb excitation of vibrational nuclei with heavy ions; surface structure of deformed nuclei; valency contribution to neutron capture in 32S; neutron capture cross section of manganese; search for superheavy elements in natural samples by neutron multiplicity counting; and gamma-ray studies on the geochemistry of achondritic meteorites

  10. Comparison of Gold Bonding with Mercury Bonding

    NARCIS (Netherlands)

    Kraka, Elfi; Filatov, Michael; Cremer, Dieter

    2009-01-01

    Nine AuX molecules (X = H, O, S, Se, Te, F, Cl, Br, I), their isoelectronic HgX(+) analogues, and the corresponding neutral HgX diatomics have been investigated using NESC (Normalized Elimination of the Small Component) and B3LYP theory to determine relativistic effects for bond dissociation energie

  11. The coordination chemistry of saturated molecules

    OpenAIRE

    Bercaw, John E.; Labinger, Jay A.

    2007-01-01

    Our understanding of bonding in transition metal complexes, as well as our ability to use that understanding in the synthesis and application of new species, has evolved over the last 100 years; and in some sense this special feature on the coordination chemistry of saturated molecules may be considered to represent its culmination. The nature of complexes between transition metal ions and neutral molecules such as ammonia was first correctly described by Werner around the beginning of the 20...

  12. Selective Covalent Chemistry via Gas-Phase Ion/ion Reactions: An Exploration of the Energy Surfaces Associated with N-Hydroxysuccinimide Ester Reagents and Primary Amines and Guanidine Groups.

    Science.gov (United States)

    Bu, Jiexun; Fisher, Christine M; Gilbert, Joshua D; Prentice, Boone M; McLuckey, Scott A

    2016-06-01

    Selective covalent bond forming reactions (referred to as covalent reactions) can occur in gas-phase ion/ion reactions and take place via the formation of a long-lived chemical complex. The gas-phase ion/ion reactivity between sulfo-N-hydroxysuccinimide (sulfo-NHS) ester reagent anions and peptide cations containing a primary amine or guanidine group has been examined via DFT calculations and complex dissociation rate measurements. The results reveal insights regarding the roles of the barriers of competing processes within the complex. When the covalent reaction is exothermic, two prototypical cases, determined by the nature of the energy surface, are apparent. The product partitioning between covalent reaction and simple proton transfer upon dissociation of the long-lived complex is sensitive to activation conditions when the transition state barrier for covalent reaction is relatively high (case 1) but is insensitive to activation conditions when the transition state barrier is relatively low (case 2). Covalent reaction efficiencies are very high in case 2 scenarios, such as when the reactive site is a guanidine and the anion attachment site is a guanidinium ion. Covalent reaction efficiencies are variable, and generally low, in case 1 scenarios, such as when an amine is the reactive site and an ammonium ion is the site of anion attachment. A relatively long slow-heating step prior to the complex dissociation step, however, can dramatically increase covalent reaction yield in case 1 scenarios. Graphical Abstract ᅟ. PMID:27020926

  13. Coupled valence bond theory

    NARCIS (Netherlands)

    Havenith, R.W.A.

    2005-01-01

    In this Letter, the formulation and implementation of a parallel response property code for non-orthogonal, valence bond wave-functions are described. Test calculations on benzene and cyclobutadiene show that the polarisability and magnetisability tensors obtained using valence bond theory are compa

  14. Bonded labour in Pakistan

    OpenAIRE

    Ercelawn, Aly; Nauman, Muhammad

    2001-01-01

    Examines the continuing prevalence of debt bondage in the 1990s despite the introduction of national legislation banning the practice. Makes recommendations to the Government and the international community for actions to be taken to eliminate bonded labour and provide rehabilitation for freed workers. Includes texts of Land Reforms Regulations, 1972, the Sindh Tenancy Act, 1950 and the Bonded Labour System (Abolition) Act, 1992.

  15. The samurai bond market

    OpenAIRE

    Frank Packer; Elizabeth Reynolds

    1997-01-01

    Issuance in the samurai bond market has more than tripled over the past several years. Some observers have attributed this growth to a systematic underestimation of credit risk in the market. A detailed review of credit quality, ratings differences, and initial issue pricing in the samurai bond market, however, turns up little evidence to support this concern.

  16. Money and Nominal Bonds

    OpenAIRE

    Marchesiani, Alessandro; Senesi, Pietro

    2007-01-01

    This paper studies an economy with trading frictions, ex post heterogeneity and nominal bonds in a model à la Lagos and Wright (2005). It is shown that a strictly positive interest rate is a sufficient condition for the allocation with nominal bonds to be welfare improving. This result comes from the protection against the inflation tax.

  17. Hydrogen bonding in polyanilines

    Energy Technology Data Exchange (ETDEWEB)

    Bahceci, S. (Department of Chemistry, Middle East Technical University, Ankara 06531 (Turkey)); Toppare, L. (Department of Chemistry, Middle East Technical University, Ankara 06531 (Turkey)); Yurtsever, E. (Department of Chemistry, Middle East Technical University, Ankara 06531 (Turkey))

    1994-11-29

    Hydrogen bonding between poly(bisphenol A carbonate) (PC) and polyaniline (PAn) is analyzed using semi-empirical quantum methodology. Fully optimized AM1 molecular orbital calculations are reported for various aniline structures (monomer, dimer and trimer), the monomer of the PC and the hydrogen-bonded model of PAn-PC oligomer. ((orig.))

  18. A Química Quântica na compreensão de teorias de Química Orgânica The Quantum Chemistry in the understanding of theories of Organic Chemistry

    OpenAIRE

    Régis Casimiro Leal; José Machado Moita Neto; Francisco das Chagas Alves Lima; Chistiane Mendes Feitosa

    2010-01-01

    Quantum chemical calculations were performed in order to obtain molecular properties such as electronic density, dipole moment, atomic charges, and bond lengths, which were compared to qualitative results based on the theories of the organic chemistry. The quantum chemistry computational can be a useful tool to support the main theories of the organic chemistry.

  19. A Química Quântica na compreensão de teorias de Química Orgânica The Quantum Chemistry in the understanding of theories of Organic Chemistry

    Directory of Open Access Journals (Sweden)

    Régis Casimiro Leal

    2010-01-01

    Full Text Available Quantum chemical calculations were performed in order to obtain molecular properties such as electronic density, dipole moment, atomic charges, and bond lengths, which were compared to qualitative results based on the theories of the organic chemistry. The quantum chemistry computational can be a useful tool to support the main theories of the organic chemistry.

  20. Supramolecular chemistry of cucurbiturils

    International Nuclear Information System (INIS)

    The main principles of the design of supramolecular compounds starting from organic macrocyclic cavitands, viz., cucurbit[n]urils [C6H6N4O2]n (n=5-10), are considered. The presence of the hydrophobic inner cavity along with polar carbonyl groups forming the cucurbituril portals are responsible for high specificity of the formation of host-guest complexes. The unique ability of cucurbiturils to act as synthetic molecular containers is discussed. In these containers, bimolecular reactions between specially selected guests proceed with high regio- and stereoselectivity. The review surveys new data on the directed construction of supramolecular organic-inorganic compounds through the formation of an extensive network of hydrogen bonds between the portal oxygen atoms of cucurbiturils and water molecules of metal aqua complexes. The bibliography includes 108 references.

  1. Polarization-induced sigma-holes and hydrogen bonding

    Czech Academy of Sciences Publication Activity Database

    Hennemann, M.; Murray, J. S.; Politzer, P.; Riley, Kevin Eugene; Clark, T.

    2012-01-01

    Roč. 18, č. 6 (2012), s. 2461-2469. ISSN 1610-2940 Institutional research plan: CEZ:AV0Z40550506 Keywords : hydrogen bond * sigma-hole * polarization * field effect * ab initio calculation Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.984, year: 2012

  2. Nuclear delocalisation of hydrogen atoms in strong hydrogen bonds

    Czech Academy of Sciences Publication Activity Database

    Dračínský, Martin; Procházková, Eliška; Čechová, Lucie; Janeba, Zlatko

    Brno: Stuare, 2015 - (Novotný, J.). C30 ISBN 978-80-86441-46-7. [NMR Valtice. Central European NMR Meeting /30./. 19.04.2015-22.04.2015, Valtice] R&D Projects: GA ČR GA15-11223S Institutional support: RVO:61388963 Keywords : NMR spectroscopy * hydrogen bonds * molecular dynamics Subject RIV: CF - Physical ; Theoretical Chemistry

  3. Substituent effects on intramolecular hydrogen bonds in 5-nitrosopyrimidine derivates

    Czech Academy of Sciences Publication Activity Database

    Procházková, Eliška; Čechová, Lucie; Janeba, Zlatko; Dračínský, Martin

    Praha : -, 2013. s. 149-149. [ESOR 2013. European Symposium on Organic Reactivity /14./. 01.09.2013-06.09.2013, Praha] R&D Projects: GA ČR GA13-24880S Institutional support: RVO:61388963 Keywords : NMR spectroscopy * intramolecular hydrogen bonds * 5-nitrosopyrimidine derivates * DFT calculations * UV/ VIS spectroscopy Subject RIV: CF - Physical ; Theoretical Chemistry

  4. Bond strength of plasma sprayed ceramic coatings on phosphate steels

    Czech Academy of Sciences Publication Activity Database

    Pokorný, P.; Mastný, L.; Sýkora, V.; Pala, Zdeněk; Brožek, Vlastimil

    2015-01-01

    Roč. 54, č. 2 (2015), s. 411-414. ISSN 0543-5846 R&D Projects: GA ČR(CZ) GAP108/12/1872 Institutional support: RVO:61389021 Keywords : phosphating * plasma spraying * ceramic coatings * corrosion * bond strength Subject RIV: CA - Inorganic Chemistry Impact factor: 0.959, year: 2014

  5. Polar Flattening and the Strength of Halogen Bonding

    Czech Academy of Sciences Publication Activity Database

    Sedlák, Robert; Kolář, Michal H.; Hobza, Pavel

    2015-01-01

    Roč. 11, č. 10 (2015), s. 4727-4732. ISSN 1549-9618 R&D Projects: GA ČR GBP208/12/G016 Institutional support: RVO:61388963 Keywords : density functional theory * interaction energies * halogen bonding Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 5.498, year: 2014

  6. Why is the Bond Multiplicity in C2 so Elusive?

    Czech Academy of Sciences Publication Activity Database

    Cooper, D.L.; Penotti, F.E.; Ponec, Robert

    2015-01-01

    Roč. 1053, SI (2015), s. 189-194. ISSN 2210-271X Institutional support: RVO:67985858 Keywords : bond multiplicity in C2 * spin correlation matrices * full GVB and spin-coupled Subject RIV: CC - Organic Chemistry Impact factor: 1.545, year: 2014

  7. Rhodium-catalyzed C-C bond cleavage reactions

    Czech Academy of Sciences Publication Activity Database

    Nečas, D.; Kotora, Martin

    2007-01-01

    Roč. 11, č. 17 (2007), s. 1566-1591. ISSN 1385-2728 Institutional research plan: CEZ:AV0Z40550506 Keywords : rhodium * catalysis * C-C bond cleavage Subject RIV: CC - Organic Chemistry Impact factor: 3.961, year: 2007

  8. Shape Bonding method

    Science.gov (United States)

    Pontius, James T. (Inventor)

    2010-01-01

    The present invention is directed to a method of bonding at least two surfaces together. The methods step of the present invention include applying a strip of adhesive to a first surface along a predefined outer boundary of a bond area and thereby defining a remaining open area there within. A second surface, or gusset plate, is affixed onto the adhesive before the adhesive cures. The strip of adhesive is allowed to cure and then a second amount of adhesive is applied to cover the remaining open area and substantially fill a void between said first and second surfaces about said bond area. A stencil may be used to precisely apply the strip of adhesive. When the strip cures, it acts as a dam to prevent overflow of the subsequent application of adhesive to undesired areas. The method results in a precise bond area free of undesired shapes and of a preferred profile which eliminate the drawbacks of the prior art bonds.

  9. Water's Hydrogen Bond Strength

    CERN Document Server

    Chaplin, Martin

    2007-01-01

    Water is necessary both for the evolution of life and its continuance. It possesses particular properties that cannot be found in other materials and that are required for life-giving processes. These properties are brought about by the hydrogen bonded environment particularly evident in liquid water. Each liquid water molecule is involved in about four hydrogen bonds with strengths considerably less than covalent bonds but considerably greater than the natural thermal energy. These hydrogen bonds are roughly tetrahedrally arranged such that when strongly formed the local clustering expands, decreasing the density. Such low density structuring naturally occurs at low and supercooled temperatures and gives rise to many physical and chemical properties that evidence the particular uniqueness of liquid water. If aqueous hydrogen bonds were actually somewhat stronger then water would behave similar to a glass, whereas if they were weaker then water would be a gas and only exist as a liquid at sub-zero temperature...

  10. Crevice chemistry estimation from bulk water chemistry

    International Nuclear Information System (INIS)

    Since the first PWR plant in Japan started commercial operation in 1970, 22 plants are running in Japan as of the end of 1994. The main purpose of secondary water chemistry control is to minimize the corrosion possibility of the secondary system equipment, especially steam generators (SG). To achieve this objective, much effort has been concentrated on improving secondary water chemistry control. As a result of this effort, the recent secondary water chemistry in Japanese plants is well maintained in every stage of operation. However, to ensure and improve the reliability of SG, it is necessary to control crevice environments, which are located at tube/tube support plate intersections and under the sludge pile on the tube sheet. According to recent crevice monitoring examination results, the concentration behavior impurities in SG bulk water at the crevice is different for each species, and SG bulk water and crevice chemical compositions are not always equal. From these results, to control the crevice chemistry, improving bulk water chemistry control methods and a new type of molar ratio control index is needed. This paper introduces a brief summary of a recent crevice chemistry evaluation technique and bulk water chemistry control method, which is employed for crevice chemistry control, based on crevice monitoring examination results

  11. Body of Knowledge (BOK) for Copper Wire Bonds

    Science.gov (United States)

    Rutkowski, E.; Sampson, M. J.

    2015-01-01

    Copper wire bonds have replaced gold wire bonds in the majority of commercial semiconductor devices for the latest technology nodes. Although economics has been the driving mechanism to lower semiconductor packaging costs for a savings of about 20% by replacing gold wire bonds with copper, copper also has materials property advantages over gold. When compared to gold, copper has approximately: 25% lower electrical resistivity, 30% higher thermal conductivity, 75% higher tensile strength and 45% higher modulus of elasticity. Copper wire bonds on aluminum bond pads are also more mechanically robust over time and elevated temperature due to the slower intermetallic formation rate - approximately 1/100th that of the gold to aluminum intermetallic formation rate. However, there are significant tradeoffs with copper wire bonding - copper has twice the hardness of gold which results in a narrower bonding manufacturing process window and requires that the semiconductor companies design more mechanically rigid bonding pads to prevent cratering to both the bond pad and underlying chip structure. Furthermore, copper is significantly more prone to corrosion issues. The semiconductor packaging industry has responded to this corrosion concern by creating a palladium coated copper bonding wire, which is more corrosion resistant than pure copper bonding wire. Also, the selection of the device molding compound is critical because use of environmentally friendly green compounds can result in internal CTE (Coefficient of Thermal Expansion) mismatches with the copper wire bonds that can eventually lead to device failures during thermal cycling. Despite the difficult problems associated with the changeover to copper bonding wire, there are billions of copper wire bonded devices delivered annually to customers. It is noteworthy that Texas Instruments announced in October of 2014 that they are shipping microcircuits containing copper wire bonds for safety critical automotive applications

  12. Green chemistry: A tool in Pharmaceutical Chemistry

    Directory of Open Access Journals (Sweden)

    Smita Talaviya

    2012-07-01

    Full Text Available Green chemistry expresses an area of research developing from scientific discoveries about pollution awareness and it utilizes a set of principles that reduces or eliminates the use or generation of hazardous substances in all steps of particular synthesis or process. Chemists and medicinal scientists can greatly reduce the risk to human health and the environment by following all the valuable principles of green chemistry. The most simple and direct way to apply green chemistry in pharmaceuticals is to utilize eco-friendly, non-hazardous, reproducible and efficient solvents and catalysts in synthesis of drug molecules, drug intermediates and in researches involving synthetic chemistry. Microwave synthesis is also an important tool of green chemistry by being an energy efficient process.

  13. Cyclodextrin duplexes reversibly connected with disulfide bonds: synthesis and physico-chemical properties

    Czech Academy of Sciences Publication Activity Database

    Kumprecht, Lukáš; Buděšínský, Miloš; Krejčí, L.; Císařová, I.; Kraus, Tomáš

    Praha : -, 2009. s. 46-46. ISBN 978-80-02-02160-5. [ESOC 2009. European Symposium on Organic Chemistry /16./. 12.07.2009-16.07.2009, Praha] Institutional research plan: CEZ:AV0Z40550506 Keywords : cyclodextrin duplexes * disulfide bonds Subject RIV: CC - Organic Chemistry

  14. Peculiarity of Cr-Cr Bonding. Insights from the Analysis of Domain Averaged Fermi Holes

    Czech Academy of Sciences Publication Activity Database

    Ponec, Robert; Feixas, F.

    - : -, 2009, s. 27. ISBN N. [Workshop on Theoretical Chemistry 2009. Platja d`Aro (ES), 08.07.2009-12.07.2009] R&D Projects: GA ČR GA203/09/0118 Institutional research plan: CEZ:AV0Z40720504 Keywords : chemical bonding * metal-metal bondng * domain averaged Fermi holes Subject RIV: CC - Organic Chemistry

  15. Anatomy of Bond Formation. Insights from the DAFH Analysis in Momentum Space

    Czech Academy of Sciences Publication Activity Database

    Ponec, Robert; Cooper, D.L.

    -: -, 2009, Poster 33. ISBN N. [Central European Symposium on Theoretical Chemistry. Dobogókö (HU), 25.09.2009-28.09.2009] R&D Projects: GA ČR GA203/09/0118 Institutional research plan: CEZ:AV0Z40720504 Keywords : chemical bond * analysis of domain averaged fermi holes * momentum space Subject RIV: CC - Organic Chemistry

  16. Oxidative C-C bond cleavage of ketone enolates by nitrosation

    Czech Academy of Sciences Publication Activity Database

    Mašek, Tomáš; Champalet, Valentine; Jahn, Ullrich

    Lisboa : -, 2015 - (Rauter, A.; Martins, A.; Matos, A.; Dias, C.; Xavier, N.; Nunes, R.; Lucas, S.; Cachatra, V.; Paiva, A.; Batista, D.). s. 249 ISBN 978-989-8124-11-1. [ESOC 2015. European Symposium on Organic Chemistry /19./. 12.07.2015-16.07.2015, Lisboa] Institutional support: RVO:61388963 Keywords : ketone enolates * nitrosation * C-C bond Subject RIV: CC - Organic Chemistry

  17. Bond strength of repaired amalgam restorations.

    Science.gov (United States)

    Rey, Rosalia; Mondragon, Eduardo; Shen, Chiayi

    2015-01-01

    This in vitro study investigated the interfacial flexural strength (FS) of amalgam repairs and the optimal combination of repair materials and mechanical retention required for a consistent and durable repair bond. Amalgam bricks were created, each with 1 end roughened to expose a fresh surface before repair. Four groups followed separate repair protocols: group 1, bonding agent with amalgam; group 2, bonding agent with composite resin; group 3, mechanical retention (slot) with amalgam; and group 4, slot with bonding agent and amalgam. Repaired specimens were stored in artificial saliva for 1, 10, 30, 120, or 360 days before being loaded to failure in a 3-point bending test. Statistical analysis showed significant changes in median FS over time in groups 2 and 4. The effect of the repair method on the FS values after each storage period was significant for most groups except the 30-day storage groups. Amalgam-amalgam repair with adequate condensation yielded the most consistent and durable bond. An amalgam bonding agent could be beneficial when firm condensation on the repair surface cannot be achieved or when tooth structure is involved. Composite resin can be a viable option for amalgam repair in an esthetically demanding region, but proper mechanical modification of the amalgam surface and selection of the proper bonding system are essential. PMID:26325656

  18. Upper Secondary Teachers' Knowledge for Teaching Chemical Bonding Models

    Science.gov (United States)

    Bergqvist, Anna; Drechsler, Michal; Rundgren, Shu-Nu Chang

    2016-01-01

    Researchers have shown a growing interest in science teachers' professional knowledge in recent decades. The article focuses on how chemistry teachers impart chemical bonding, one of the most important topics covered in upper secondary school chemistry courses. Chemical bonding is primarily taught using models, which are key for understanding science. However, many studies have determined that the use of models in science education can contribute to students' difficulties understanding the topic, and that students generally find chemical bonding a challenging topic. The aim of this study is to investigate teachers' knowledge of teaching chemical bonding. The study focuses on three essential components of pedagogical content knowledge (PCK): (1) the students' understanding, (2) representations, and (3) instructional strategies. We analyzed lesson plans about chemical bonding generated by 10 chemistry teachers with whom we also conducted semi-structured interviews about their teaching. Our results revealed that the teachers were generally unaware of how the representations of models they used affected student comprehension. The teachers had trouble specifying students' difficulties in understanding. Moreover, most of the instructional strategies described were generic and insufficient for promoting student understanding. Additionally, the teachers' rationale for choosing a specific representation or activity was seldom directed at addressing students' understanding. Our results indicate that both PCK components require improvement, and suggest that the two components should be connected. Implications for the professional development of pre-service and in-service teachers are discussed.

  19. Organometallic Chemistry of Molybdenum.

    Science.gov (United States)

    Lucas, C. Robert; Walsh, Kelly A.

    1987-01-01

    Suggests ways to avoid some of the problems students have learning the principles of organometallic chemistry. Provides a description of an experiment used in a third-year college chemistry laboratory on molybdenum. (TW)

  20. CHINESE JOURNAL OF CHEMISTRY

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    @@Chinese Journal of Chemistry is an international journal published in English by the Chinese Chemical Society with its editorial office hosted by Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences.

  1. Environmental chemistry: Volume A

    Energy Technology Data Exchange (ETDEWEB)

    Yen, T.F.

    1999-08-01

    This is an extensive introduction to environmental chemistry for engineering and chemical professionals. The contents of Volume A include a brief review of basic chemistry prior to coverage of litho, atmo, hydro, pedo, and biospheres.

  2. New physics and chemistry in high electrostatic fields

    Science.gov (United States)

    Karahka, M. L.; Kreuzer, H. J.

    2016-01-01

    Fields of the order of volts per meter exist along micron-sized tips. They are of the magnitude of fields inside atoms and molecules and can affect their electronic structure. This leads to a continuous periodic table resulting in new field-induced chemistry. We will present a tutorial treatment of this new physics and chemistry explaining such surprising phenomena like covalent bonding of helium to metal surfaces, metallization of semiconductors and insulators, and more.

  3. Progress in Kdo-glycoside chemistry

    Science.gov (United States)

    Kosma, Paul

    2016-01-01

    Glycosylation chemistry of 3-deoxy-D-manno-oct-2-ulosonic acid units has been considerably developed within the last decade. This review covers major achievements with respect to improved yields and anomeric selectivity as well as suppression of the elimination side reaction via selection of dedicated protecting groups and appropriate activation of the anomeric center. PMID:27274586

  4. A Simple Visualization of Double Bond Properties: Chemical Reactivity and UV Fluorescence

    Science.gov (United States)

    Grayson, Scott M.

    2012-01-01

    A simple, easily visualized thin-layer chromatography (TLC) staining experiment is presented that highlights the difference in reactivity between aromatic double bonds and nonaromatic double bonds. Although the stability of aromatic systems is a major theme in organic chemistry, the concept is rarely reinforced "visually" in the undergraduate…

  5. Evidence for 5-Center 4-Electron Bonding in (C...H...C...H...C) Array

    Czech Academy of Sciences Publication Activity Database

    Ponec, Robert; Juzakov, Gleb

    2003-01-01

    Roč. 68, č. 21 (2003), s. 8284-8286. ISSN 0022-3263 R&D Projects: GA AV ČR IAA4072006 Institutional research plan: CEZ:AV0Z4072921 Keywords : multicenter bonding * generalized population analysis * multicenter bond indices Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.297, year: 2003

  6. Green Chemistry and Education.

    Science.gov (United States)

    Hjeresen, Dennis L.; Schutt, David L.; Boese, Janet M.

    2000-01-01

    Many students today are profoundly interested in the sustainability of their world. Introduces Green Chemistry and its principles with teaching materials. Green Chemistry is the use of chemistry for pollution prevention and the design of chemical products and processes that are environmentally benign. (ASK)

  7. Environmental Chemistry Activities.

    Science.gov (United States)

    Jackland, Thomas; And Others

    The authors of this curriculum supplement believe in a laboratory approach to chemistry and express the feeling that environmental chemistry provides the students an opportunity to apply theoretical chemistry to important practical problems. There are eighteen activities presented, each accompanied with behavioral objectives, one or more suggested…

  8. Facets of coordination chemistry

    CERN Document Server

    Agarwala, BV

    1993-01-01

    A concise account of coordination chemistry since its inception is given here together with some of the newer significant facets. This book covers a broad spectrum of various topics on Environment, Cyclic Voltammetry, Chromatography, Metal Complexes of biological interest, Alkoxides, NMR spectroscopy and others. These are useful to the scientific community engaged in the field of Inorganic Chemistry and Analytical Chemistry.

  9. Constructing Models in Teaching of Chemical Bonds: Ionic Bond, Covalent Bond, Double and Triple Bonds, Hydrogen Bond and Molecular Geometry

    Science.gov (United States)

    Uce, Musa

    2015-01-01

    Studies in chemistry education show that chemistry topics are considered as abstract, complicated and hard to understand by students. For this reason, it is important to develop new materials and use them in classes for better understanding of abstract concepts. Moving from this point, a student-centered research guided by a teacher was conducted…

  10. Corporate Bonds in Denmark

    DEFF Research Database (Denmark)

    Tell, Michael

    2015-01-01

    Corporate financing is the choice between capital generated by the corporation and capital from external investors. However, since the financial crisis shook the markets in 2007–2008, financing opportunities through the classical means of financing have decreased. As a result, corporations have...... to think in alternative ways such as issuing corporate bonds. A market for corporate bonds exists in countries such as Norway, Germany, France, the United Kingdom and the United States, while Denmark is still behind in this trend. Some large Danish corporations have instead used foreign corporate bonds...

  11. Transversely Compressed Bonded Joints

    DEFF Research Database (Denmark)

    Hansen, Christian Skodborg; Schmidt, Jacob Wittrup; Stang, Henrik

    2012-01-01

    The load capacity of bonded joints can be increased if transverse pressure is applied at the interface. The transverse pressure is assumed to introduce a Coulomb-friction contribution to the cohesive law for the interface. Response and load capacity for a bonded single-lap joint was derived using...... non-linear fracture mechanics. The results indicated a good correlation between theory and tests. Furthermore, the model is suggested as theoretical base for determining load capacity of bonded anchorages with transverse pressure, in externally reinforced concrete structures....

  12. The Halogen Bond

    Science.gov (United States)

    2016-01-01

    The halogen bond occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a halogen atom in a molecular entity and a nucleophilic region in another, or the same, molecular entity. In this fairly extensive review, after a brief history of the interaction, we will provide the reader with a snapshot of where the research on the halogen bond is now, and, perhaps, where it is going. The specific advantages brought up by a design based on the use of the halogen bond will be demonstrated in quite different fields spanning from material sciences to biomolecular recognition and drug design. PMID:26812185

  13. Computational Chemistry Comparison and Benchmark Database

    Science.gov (United States)

    SRD 101 NIST Computational Chemistry Comparison and Benchmark Database (Web, free access)   The NIST Computational Chemistry Comparison and Benchmark Database is a collection of experimental and ab initio thermochemical properties for a selected set of molecules. The goals are to provide a benchmark set of molecules for the evaluation of ab initio computational methods and allow the comparison between different ab initio computational methods for the prediction of thermochemical properties.

  14. Electronic bond tuning with heterocyclic carbenes

    KAUST Repository

    Falivene, Laura

    2013-01-01

    We discuss the impact of the nature of the heterocyclic carbene ring, when used as a complex forming ligand, on the relative stability of key intermediates in three typical Ru, Pd and Au promoted reactions. Results show that P-heterocyclic carbenes have a propensity to increase the bonding of the labile ligand and of the substrate in Ru-promoted olefin metathesis, whereas negligible impact is expected on the stability of the ruthenacycle intermediate. In the case of Pd cross-coupling reactions, dissociation of a P-heterocyclic carbene is easier than dissociation of the N-heterocyclic analogue. In the case of the Au-OH synthon, the Au-OH bond is weakened with the P-heterocyclic carbene ligands. A detailed energy decomposition analysis is performed to rationalize these results. © 2013 The Royal Society of Chemistry.

  15. American Association for Clinical Chemistry

    Science.gov (United States)

    ... indispensable patient care tool. Learn more IN CLINICAL CHEMISTRY ddPCR Quantification of Lymphoma Mutations Researchers have developed ... Online Harmonization.net Commission on Accreditation in Clinical Chemistry American Board of Clinical Chemistry Clinical Chemistry Trainee ...

  16. Electrochemical activation of a tetrathiafulvalene halogen bond donor in solution.

    Science.gov (United States)

    Oliveira, R; Groni, S; Fave, C; Branca, M; Mavré, F; Lorcy, D; Fourmigué, M; Schöllhorn, B

    2016-06-21

    The halogen bond donor properties of iodo-tetrathiafulvalene (I-TTF) can be electrochemically switched and controlled via reversible oxidation in the solution phase. Interestingly the activation of only one single halogen bond yielded already a strong and selective interaction, quantified by cyclic voltammetry. The standard potentials of the redox couples I-TTF(0/1+) and I-TTF(1+/2+) were observed to shift upon the addition of halides. These anions selectively stabilize the cationic I-TTF species through halogen bonding in polar liquid electrolytes. The thermodynamic affinity constants for chloride and bromide binding to the oxidized species have been determined. Competition in halide binding between I-TTF(1+) and other halogen bond donors allowed for comparing the relative donor strength of the respective electrophilic species. Furthermore it has been shown that halogen bonding can prevail over hydrogen bonding in the investigated system. PMID:27231819

  17. The New Color of Chemistry: Green Chemistry

    Directory of Open Access Journals (Sweden)

    Zuhal GERÇEK

    2012-01-01

    Full Text Available Green chemistry which is the new application of chemistry rules provides solutions to problems that mankind is faced with climate changes, sustainable agriculture, energy, toxics, depletion of natural sources e.g. designing new chemicals and processes that production and utilization of hazardous matters. So, it is the indispensible tool for sustainable development. Current and future chemists should consider the human health and ecological issues in their professional life. In order to provide a solution for this requirement, green chemistry rules and under standings should be primarily taken in the university curriculum and at all educational levels.

  18. Evaluation of Shear Bond Strength of Newer Bonding Systems on Superficial and Deep Dentin

    OpenAIRE

    Kumari, R Veena; Siddaraju, Kishore; Nagaraj, Hema; Poluri, Ramya Krishna

    2015-01-01

    Background: The purpose of this study was to compare the shear bond strength of nanocomposite resin to superficial dentin and deep dentin using two different dentin bonding systems. Materials and Methods: All teeth were sectioned at various levels (superficial dentin: Dentin within 0.5-1 mm of dentinoenamel junction; deep dentin: Dentin within 0.5 mm of the highest pulp horn) using a Carborundum Disc and embedded in acrylic block of specific size. Selected specimens (60 premolar teeth) were g...

  19. What caused the hikes and dips of government bond yields during the Sovereign Bond crisis?

    OpenAIRE

    Václavíček, Tomáš

    2014-01-01

    This study examines the determinants of government bond spreads vis-a-vis Germany for eleven EMU member countries in the period 2000Q1 to 2013Q3 with a special focus on the European Debt Crisis. The aim of the thesis is to test whether selected financial, fiscal and macroeconomic variables have an impact on government bond spreads. A novel contribution is testing whether there has been a significant change of government bond spread determinants following the ECB interventions in summer 2012. ...

  20. Surface chemistry essentials

    CERN Document Server

    Birdi, K S

    2013-01-01

    Surface chemistry plays an important role in everyday life, as the basis for many phenomena as well as technological applications. Common examples range from soap bubbles, foam, and raindrops to cosmetics, paint, adhesives, and pharmaceuticals. Additional areas that rely on surface chemistry include modern nanotechnology, medical diagnostics, and drug delivery. There is extensive literature on this subject, but most chemistry books only devote one or two chapters to it. Surface Chemistry Essentials fills a need for a reference that brings together the fundamental aspects of surface chemistry w

  1. Fundamentals of reactor chemistry

    International Nuclear Information System (INIS)

    In the Nuclear Engineering School of JAERI, many courses are presented for the people working in and around the nuclear reactors. The curricula of the courses contain also the subject material of chemistry. With reference to the foreign curricula, a plan of educational subject material of chemistry in the Nuclear Engineering School of JAERI was considered, and the fundamental part of reactor chemistry was reviewed in this report. Since the students of the Nuclear Engineering School are not chemists, the knowledge necessary in and around the nuclear reactors was emphasized in order to familiarize the students with the reactor chemistry. The teaching experience of the fundamentals of reactor chemistry is also given. (author)

  2. Hydrogen bonds in methane-water clusters.

    Science.gov (United States)

    Salazar-Cano, Juan-Ramón; Guevara-García, Alfredo; Vargas, Rubicelia; Restrepo, Albeiro; Garza, Jorge

    2016-08-24

    Characterization of hydrogen bonds in CH4-(H2O)12 clusters was carried out by using several quantum chemistry tools. An initial stochastic search provided around 2 500 000 candidate structures, then, using a convex-hull polygon criterion followed by gradient based optimization under the Kohn-Sham scheme, a total of 54 well defined local minima were located in the Potential Energy Surface. These structures were further analyzed through second-order many-body perturbation theory with an extended basis set at the MP2/6-311++G(d,p) level. Our analysis of Gibbs energies at several temperatures clearly suggests a structural preference toward compact water clusters interacting with the external methane molecule, instead of the more commonly known clathrate-like structures. This study shows that CH4-(H2O)12 clusters may be detected at temperatures up to 179 K, this finding provides strong support to a recently postulated hypothesis that suggests that methane-water clusters could be present in Mars at these conditions. Interestingly, we found that water to water hydrogen bonding is strengthened in the mixed clusters when compared to the isolated water dimer, which in turn leads to a weakening of the methane to water hydrogen bonding when compared to the CH4-(H2O) dimer. Finally, our evidence places a stern warning about the abilities of popular geometrical criteria to determine the existence of hydrogen bonds. PMID:27492605

  3. U2@C80: Endohedral fullerene with unwilling U-U bonding

    Czech Academy of Sciences Publication Activity Database

    Foroutan-Nejad, C.; Patzschke, M.; Straka, Michal

    Smolenice : Institute of Inorganic Chemistry SAS, 2014. s. 85. ISBN 978-80-971648-1-2. [REHE - 2014. International Conference on Relativistic Effects in Heavy-Element Chemistry and Physics /11./. 20.09.2014-24.09.2014, Smolenice] R&D Projects: GA ČR(CZ) GA14-03564S Grant ostatní: European Social Fund(XE) CZ.1.07/2.3.00/30.009 Institutional support: RVO:61388963 Keywords : endohedral actinide fullerene * U-U bonding * actinide-actinide bonding Subject RIV: CF - Physical ; Theoretical Chemistry

  4. Orbital entanglement in quantum chemistry

    CERN Document Server

    Boguslawski, Katharina

    2014-01-01

    The basic concepts of orbital entanglement and its application to chemistry are briefly reviewed. The calculation of orbital entanglement measures from correlated wavefunctions is discussed in terms of reduced $n$-particle density matrices. Possible simplifications in their evaluation are highlighted in case of seniority-zero wavefunctions. Specifically, orbital entanglement allows us to dissect electron correlation effects in its strong and weak contributions, to determine bond orders, to assess the quality and stability of active space calculations, to monitor chemical reactions, and to identify points along the reaction coordinate where electronic wavefunctions change drastically. Thus, orbital entanglement represents a useful and intuitive tool to interpret complex electronic wavefunctions and to facilitate a qualitative understanding of electronic structure and how it changes in chemical processes.

  5. Bond dissociation & electronegativity equalization

    OpenAIRE

    Verstraelen, Toon; Ayers, Paul W.; Van Speybroeck, Veronique; Waroquier, Michel

    2012-01-01

    It is well known that the Electrongativity Equalization Mtehod (EEM) fails to describe the charge distribution upon bond dissocation. In this presentation, the bond dissocation is studied with the Atom-Condensed Kohn-Sham DFT approximated to second order (ACKS2). After reviewing the basic equations, a two-fragment system is studied in the dissociation limit. The limiting behavior of the Coulomb interaction (1/r) and the Kohn-Sham matrix elements (exponentially decaying) are plugged into the e...

  6. Anodic bonded graphene

    OpenAIRE

    Balan, Adrian; Kumar, Rakesh; Boukhicha, Mohamed; Beyssac, Olivier; Bouillard, Jean-Claude; Taverna, Dario; Sacks, William; Marangolo, Massimiliano; Lacaze, Emmanuelle; Escoffier, Walter; Poumirol, Jean-Marie; Shukla, Abhay

    2010-01-01

    Abstract We show how to prepare graphene samples on a glass substrate with the anodic bonding method. In this method, a graphite precursor in flake form is bonded to a glass substrate with the help of an electrostatic field and then cleaved off to leave few layer graphene on the substrate. Now that several methods are available for producing graphene, the relevance of our method is in its simplicity and practicality for producing graphene samples of about 100 ?m lateral dimensions. This me...

  7. Handbook of wafer bonding

    CERN Document Server

    Ramm, Peter; Taklo, Maaike M V

    2011-01-01

    Written by an author and editor team from microsystems companies and industry-near research organizations, this handbook and reference presents dependable, first-hand information on bonding technologies.In the first part, researchers from companies and institutions around the world discuss the most reliable and reproducible technologies for the production of bonded wafers. The second part is devoted to current and emerging applications, including microresonators, biosensors and precise measuring devices.

  8. Annual report 1985 Chemistry Department

    International Nuclear Information System (INIS)

    This report contains a brief survey of the main activities in the Chemistry Department. All particles and reports published and lectures given in 1985 are presented. The facilities and equipment are mentioned briefly. The activities are divided into the following groups: radioisotope chemistry, analytical- and organic chemistry, environmental chemistry, polymer chemistry, geochemistry and waste disposal, radical chemistry, positron annihilation, mineral processing, and general. (author)

  9. Annual report 1984 Chemistry Department

    International Nuclear Information System (INIS)

    This report contains a brief survey of the main activities in the Chemistry Department. All articles and reports published and lectures given in 1984 are presented. The facilities and equipment are mentioned briefly. The activities are divided into the following groups: radioisotope chemistry, analytical- and organic chemistry , environmental chemistry, polymer chemistry, geochemistry and waste disposal, radical chemistry, positron annihilation, mineral processing, and general. (author)

  10. Annual Report 1984. Chemistry Department

    OpenAIRE

    Funck, Jytte; Nielsen, Ole John

    1985-01-01

    This report contains a brief survey of the main activities in the Chemistry Department. All articles and reports published and lectures given in 1984 are presented. The facilities and equipment are mentioned briefly. The activities are divided into the following groups: radioisotope chemistry, analytical- and organic chemistry, environmental chemistry, polymer chemistry, geochemistry and waste disposal, radical chemistry, positron annihilation, mineral processing, and general.

  11. Activation of C-H and B-H bonds through agostic bonding: an ELF/QTAIM insight.

    Science.gov (United States)

    Zins, Emilie-Laure; Silvi, Bernard; Alikhani, M Esmaïl

    2015-04-14

    Agostic bonding is of paramount importance in C-H bond activation processes. The reactivity of the σ C-H bond thus activated will depend on the nature of the metallic center, the nature of the ligand involved in the interaction and co-ligands, as well as on geometric parameters. Because of their importance in organometallic chemistry, a qualitative classification of agostic bonding could be very much helpful. Herein we propose descriptors of the agostic character of bonding based on the electron localization function (ELF) and Quantum Theory of Atoms in Molecules (QTAIM) topological analysis. A set of 31 metallic complexes taken, or derived, from the literature was chosen to illustrate our methodology. First, some criteria should prove that an interaction between a metallic center and a σ X-H bond can indeed be described as "agostic" bonding. Then, the contribution of the metallic center in the protonated agostic basin, in the ELF topological description, may be used to evaluate the agostic character of bonding. A σ X-H bond is in agostic interaction with a metal center when the protonated X-H basin is a trisynaptic basin with a metal contribution strictly larger than the numerical uncertainty, i.e. 0.01 e. In addition, it was shown that the weakening of the electron density at the X-Hagostic bond critical point with respect to that of X-Hfree well correlates with the lengthening of the agostic X-H bond distance as well as with the shift of the vibrational frequency associated with the νX-H stretching mode. Furthermore, the use of a normalized parameter that takes into account the total population of the protonated basin, allows the comparison of the agostic character of bonding involved in different complexes. PMID:25760795

  12. The New Color of Chemistry: Green Chemistry

    OpenAIRE

    Zuhal GERÇEK

    2012-01-01

    Green chemistry which is the new application of chemistry rules provides solutions to problems that mankind is faced with climate changes, sustainable agriculture, energy, toxics, depletion of natural sources e.g. designing new chemicals and processes that production and utilization of hazardous matters. So, it is the indispensible tool for sustainable development. Current and future chemists should consider the human health and ecological issues in their professional life. In order to provid...

  13. Philosophy of Chemistry or Philosophy with Chemistry?

    OpenAIRE

    Bernadette Bensaude-Vincent

    2014-01-01

    Chemistry deserves more philosophical attention not so much to do justice to a long-neglected science or to enhance its cultural prestige, but to undermine a number of taken-for-granted assumptions about scientific rationality and more importantly to diversify our metaphysical views of nature and reality. In brief, this paper does not make the case for a philosophy of chemistry. It rather urges philosophers of science to listen to chemists and discuss what they learn from them. Because over t...

  14. What college chemistry instructors and high school chemistry teachers perceive as important for incoming college students

    Science.gov (United States)

    Razali, Sulaiman N.; Yager, Robert E.

    Professors of college chemistry were asked to rank various examples of traditional chemistry knowledge and skills as to their importance for incoming students to possess. A pilot study revealed that the items - all selected from one edition of the American Chemical Society-National Science Teachers Association (ACS-NSTA) Chemistry Achievement Examination - represented attributes viewed as relatively unimportant. The professors then identified 29 personal traits they considered more important for incoming students to possess. Subsequently, these items, knowledge, skill, and personal attributes, were included in a three-part assessment instrument. The instrument was administered to 69 college chemistry professors selected at random and to 37 high school chemistry teachers. The results reveal that the college professors universally identified student personal attributes as significantly more important for incoming students to possess over specific knowledge and skills included in the ACS-NSTA Achievement Examination. Chemistry professors do not find items commonly used to assess success in high school chemistry as important attributes for incoming students to possess. Conversely, high school chemistry teachers regard the knowledge and skill items to be more important for college preparation than personal attributes.

  15. Bond Length and Bond Order in One of the Shortest Cr-Cr Bonds

    OpenAIRE

    La Macchia, Giovanni; Aquilante, Francesco; Veryazov, Valera; Roos, Bjorn O.; Gagliardi, Laura

    2008-01-01

    Multiconfigurational quantum chemical calculations on the R-diimines dichromium compound confirm that the Cr-Cr bond, 1.80 A, is among the shortest Cr (I)-Cr (I) bonds. However, the bond between the two Cr atoms is only a quadruple bond rather than a quintuple bond. The reason why the bond is so short has to be attributed to the strain in the NCCN ligand moieties.

  16. Control of Reactivity and Regioselectivity for On-Surface Dehydrogenative Aryl-Aryl Bond Formation.

    Science.gov (United States)

    Kocić, Nemanja; Liu, Xunshan; Chen, Songjie; Decurtins, Silvio; Krejčí, Ondřej; Jelínek, Pavel; Repp, Jascha; Liu, Shi-Xia

    2016-05-01

    Regioselectivity is of fundamental importance in chemical synthesis. Although many concepts for site-selective reactions are well established for solution chemistry, it is not a priori clear whether they can easily be transferred to reactions taking place on a metal surface. A metal will fix the chemical potential of the electrons and perturb the electronic states of the reactants because of hybridization. Additionally, techniques to characterize chemical reactions in solution are generally not applicable to on-surface reactions. Only recent developments in resolving chemical structures by atomic force microscopy (AFM) and scanning tunneling microscopy (STM) paved the way for identifying individual reaction products on surfaces. Here we exploit a combined STM/AFM technique to demonstrate the on-surface formation of complex molecular architectures built up from a heteroaromatic precursor, the tetracyclic pyrazino[2,3-f][4,7]phenanthroline (pap) molecule. Selective intermolecular aryl-aryl coupling via dehydrogenative C-H activation occurs on Au(111) upon thermal annealing under ultrahigh vacuum (UHV) conditions. A full atomistic description of the different reaction products based on an unambiguous discrimination between pyrazine and pyridine moieties is presented. Our work not only elucidates that ortho-hydrogen atoms of the pyrazine rings are preferentially activated over their pyridine equivalents, but also sheds new light onto the participation of substrate atoms in metal-organic coordination bonding during covalent C-C bond formation. PMID:27059121

  17. Dilemmas in zirconia bonding: A review

    Directory of Open Access Journals (Sweden)

    Obradović-Đuričić Kosovka

    2013-01-01

    Full Text Available This article presents a literature review on the resin bond to zirconia ceramic. Modern esthetic dentistry has highly recognized zirconia, among other ceramic materials. Biocompatibility of zirconia, chemical and dimensional stability, excellent mechanical properties, all together could guarantee optimal therapeutical results in complex prosthodontic reconstruction. On the other hand, low thermal degradation, aging of zirconia as well as problematic bonding of zirconia framework to dental luting cements and tooth structures, opened the room for discussion concerning their clinical durability. The well known methods of mechanical and chemical bonding used on glass-ceramics are not applicable for use with zirconia. Therefore, under critical clinical situations, selection of the bonding mechanism should be focused on two important points: high initial bond strength value and long term bond strength between zirconia-resin interface. Also, this paper emphases the use of phosphate monomer luting cements on freshly air-abraded zirconia as the simplest and most effective way for zirconia cementation procedure today.

  18. Selective Organic and Organometallic Reactions in Water-Soluble Host-Guest Supramolecular Systems

    Energy Technology Data Exchange (ETDEWEB)

    Pluth, Michael D.; Raymond, Kenneth N.; Bergman, Robert G.

    2008-02-16

    Inspired by the efficiency and selectivity of enzymes, synthetic chemists have designed and prepared a wide range of host molecules that can bind smaller molecules with their cavities; this area has become known as 'supramolecular' or 'host-guest' chemistry. Pioneered by Lehn, Cram, Pedersen, and Breslow, and followed up by a large number of more recent investigators, it has been found that the chemical environment in each assembly - defined by the size, shape, charge, and functional group availability - greatly influences the guest-binding characteristics of these compounds. In contrast to the large number of binding studies that have been carried out in this area, the exploration of chemistry - especially catalytic chemistry - that can take place inside supramolecular host cavities is still in its infancy. For example, until the work described here was carried out, very few examples of organometallic reactivity inside supramolecular hosts were known, especially in water solution. For that reason, our group and the group directed by Kenneth Raymond decided to take advantage of our complementary expertise and attempt to carry out metal-mediated C-H bond activation reactions in water-soluble supramolecular systems. This article begins by providing background from the Raymond group in supramolecular coordination chemistry and the Bergman group in C-H bond activation. It goes on to report the results of our combined efforts in supramolecular C-H activation reactions, followed by extensions of this work into a wider range of intracavity transformations.

  19. Innovations in bonding to zirconia-based materials: Part I

    NARCIS (Netherlands)

    M.N.M. Abou Shelib; J.P. Matinlinna; Z. Salameh; H. Ounsi

    2008-01-01

    Abstract Objectives Establishing a reliable bond to zirconia-based materials has proven to be difficult which is the major limitation against fabricating adhesive zirconia restorations. This bond could be improved using novel selective infiltration etching conditioning in combination with engineered

  20. 2011 Organometallic Chemistry (July 10-15, 2011, Salve Regina University, Newport, RI)

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Emilio Bunel

    2011-07-15

    Organometallic chemistry has played and will continue to play a significant role in helping us understand the way bonds are made or broken in the presence of a transition metal complex. Current challenges range from the efficient exploitation of energy resources to the creative use of natural and artificial enzymes. Most of the new advances in the area are due to our extended understanding of processes at a molecular level due to new mechanistic studies, techniques to detect reaction intermediates and theory. The conference will bring the most recent advances in the field including nanocatalysis, surface organometallic chemistry, characterization techniques, new chemical reactivity and theoretical approaches along with applications to organic synthesis and the discovery of new materials. The Conference will bring together a collection of investigators who are at the forefront of their field, and will provide opportunities for junior scientists and graduate students to present their work in poster format and exchange ideas with leaders in the field. Six outstanding posters will be selected for short talks. The collegial atmosphere of this Conference, with programmed discussion sessions as well as opportunities for informal gatherings in the afternoons and evenings, provides an avenue for scientists from different disciplines to brainstorm and promotes cross-disciplinary collaborations in the various research areas represented. Graduate students and postdoctoral fellows should also consider participating in the Gordon Research Seminar on Organometallic Chemistry (July 9-10, same location) which is specially designed to promote interaction and discussion between junior scientists.

  1. The discovery of J.J. Thomson and its influence in chemistry

    International Nuclear Information System (INIS)

    The discovery of electrons one century ago was of outstanding importance in Chemistry. In this paper the consequences of this discovery in some of the most relevant aspects of the fundamental Chemistry, ranging from the theory of chemical bond the understanding of chemical reactivity are briefly reviewed at a divulgative level. (Author) 10 refs

  2. Romanian government bond market

    Directory of Open Access Journals (Sweden)

    Cornelia POP

    2012-12-01

    Full Text Available The present paper aims to present the level of development reached by Romanian government bond market segment, as part of the country financial market. The analysis will be descriptive (the data series available for Romania are short, based on the secondary data offered by the official bodies involved in the process of issuing and trading the Romanian government bonds (Romanian Ministry of Public Finance, Romanian National Bank and Bucharest Stock Exchange, and also on secondary data provided by the Federation of European Stock Exchanges.To enhance the market credibility as a benchmark, a various combination of measures is necessary; among these measures are mentioned: the extension of the yield curve; the issuance calendars in order to improve transparency; increasing the disclosure of information on public debt issuance and statistics; holding regular meetings with dealers, institutional investors and rating agencies; introducing a system of primary dealers; establishing a repurchase (repo market in the government bond market. These measures will be discussed based on the evolution presented inside the paper.The paper conclude with the fact that, until now, the Romanian government bond market did not provide a benchmark for the domestic financial market and that further efforts are needed in order to increase the government bond market transparency and liquidity.

  3. Bioinorganic Chemistry Modeled with the TPSSh Density Functional

    DEFF Research Database (Denmark)

    Kepp, Kasper Planeta

    2008-01-01

    In this work, the TPSSh density functional has been benchmarked against a test set of experimental structures and bond energies for 80 transition-metal-containing diatomics. It is found that the TPSSh functional gives structures of the same quality as other commonly used hybrid and nonhybrid func...... promising density functional for use and further development within the field of bioinorganic chemistry....

  4. Cross-Coupling Chemistry at Mononuclear and Dinuclear Nickel Complexes

    OpenAIRE

    Lin, Sibo; Agapie, Theodor

    2011-01-01

    Nickel catalysts have been developed for a wide range of C–C bond formation reactions. Reaction mechanisms proposed for these transformations generally involve catalytic intermediates based on mononickel species. These reactions are reviewed and the possibility of dinickel species active in C–C cross-coupling chemistry is discussed.

  5. Improved machine learning method for analysis of gas phase chemistry of peptides

    Directory of Open Access Journals (Sweden)

    Ahn Natalie

    2008-12-01

    Full Text Available Abstract Background Accurate peptide identification is important to high-throughput proteomics analyses that use mass spectrometry. Search programs compare fragmentation spectra (MS/MS of peptides from complex digests with theoretically derived spectra from a database of protein sequences. Improved discrimination is achieved with theoretical spectra that are based on simulating gas phase chemistry of the peptides, but the limited understanding of those processes affects the accuracy of predictions from theoretical spectra. Results We employed a robust data mining strategy using new feature annotation functions of MAE software, which revealed under-prediction of the frequency of occurrence in fragmentation of the second peptide bond. We applied methods of exploratory data analysis to pre-process the information in the MS/MS spectra, including data normalization and attribute selection, to reduce the attributes to a smaller, less correlated set for machine learning studies. We then compared our rule building machine learning program, DataSqueezer, with commonly used association rules and decision tree algorithms. All used machine learning algorithms produced similar results that were consistent with expected properties for a second gas phase mechanism at the second peptide bond. Conclusion The results provide compelling evidence that we have identified underlying chemical properties in the data that suggest the existence of an additional gas phase mechanism for the second peptide bond. Thus, the methods described in this study provide a valuable approach for analyses of this kind in the future.

  6. Chemistry and morphology of coal liquefaction. Annual report, October 1, 1984-September 30, 1985

    Energy Technology Data Exchange (ETDEWEB)

    Heinemann, H.; Fish, R.H.

    1985-09-01

    The removal of nitrogen from complex matrices such as coal liquids is an extremely important area to study. We recently discovered that polynuclear heteroaromatic nitrogen compounds can be selectively reduced only in the nitrogen containing ring. We now wish to focus on the aspects of carbon-nitrogen cleavage in the saturated nitrogen heterocyclic ring of model coal compounds in order to better understand how nitrogen can be removed without additional substantial use of hydrogen gas for that reaction to occur. A duel approach will be followed that will provide fundamental information on the cleavage of carbon-nitrogen bonds using metal complexes of rhenium, iridium and ruthenium. The important coordination of metal complexes to saturated nitrogen compounds followed by oxidative addition to a methylene group alpha to the nitrogen atom will allow formation of metalla-azacyclopropanes and dimetalla-azacyclobutenes. These compounds will be reacted with nucleophiles to hopefully afford carbon-nitrogen bond cleavage. The compounds will also be reacted under hydrogenation conditions to provide a similar carbon-nitrogen bond cleavage reaction. The second approach, carried out simultaneously, will use various bulk metals such as nickel, rhodium and ruthenium supported on silica and alumina with 1,2,3,4-tetrahydroquinoline as the substrate and at temperatures of approx.300/sup 0/C and 1 atm H/sub 2/ gas to provide HDN chemistry under mild experimental conditions.

  7. COMPARATIVE EVALUATION OF THE BONDING EFFICACY OF SIXTH, SEVENTH AND EIGHTH GENERATION BONDING AGENTS: AN IN VITRO STUDY

    Directory of Open Access Journals (Sweden)

    Paul Joseph

    2013-09-01

    Full Text Available The aim of the study was to compare In-vitro the micro tensile bond strength of sixth generation (Clearfil SE Bond, Kuraray, Japan, seventh generation (Adper Easy One, 3 M ESPE, Germany and eighth generation ((Futurabond DC, Voco, Germany dentin bonding agents. Twenty freshly extracted caries free, unrestored human molars were selected. The occlusal surfaces were ground flat; divided into four groups of five each according to the bonding agent applied and covered with composite resin (10 mm in height. The teeth were sectioned into one mm thick specimens with a cross sectional area of 1 mm square in hard tissue microtome and subjected to tensile force in a universal testing machine. The highest strength was seen in 8th generation bonding agent (Futura bond DC, Voco, Germany 34.9332 MPa followed by 6th generation bonding agent 32.3477 MPa (Clearfil SE Bond, Kuraray dental, Japan and the 7th generation agent 31.8826 MPa (Adper Easy One, 3M ESPE, Germany respectively. The eighth generation dentin bonding agent appeared to be more advantageous in bonding than sixth and seventh generation dentin bonding agents.

  8. Journal of Business Chemistry

    OpenAIRE

    2013-01-01

    The Journal of Business Chemistry examines issues associated with leadership and management for chemists and managers working in chemical research or industry. This journal is devoted to improving and developing the field of Business Chemistry. The Journal of Business Chemistry publishes peer-reviewed papers (including case studies) and essays. Areas for possible publication in include: leadership issues in the chemical and biochemical industry, such as teamwork, team building, mentoring, coa...

  9. Mathematical Thinking in Chemistry

    OpenAIRE

    José L. Villaveces; Guillermo Restrepo

    2012-01-01

    Mathematical chemistry is often thought to be a 20th-century subdiscipline of chemistry, but in this paper we discuss several early chemical ideas and some landmarks of chemistry as instances of the mathematical way of thinking; many of them before 1900. By the mathematical way of thinking, we follow Weyl's description of it in terms of functional thinking, i.e. setting up variables, symbolizing them, and seeking for functions relating them. The cases we discuss are Plato's triangles, Geoffro...

  10. Elementary physical chemistry

    CERN Document Server

    Linder, Bruno

    2010-01-01

    This book is designed for a one-semester course, for undergraduates, not necessarily chemistry majors, who need to know something about physical chemistry. The emphasis is not on mathematical rigor, but subtleties and conceptual difficulties are not hidden. It covers the essential topics in physical chemistry, including the state of matter, thermodynamics, chemical kinetics, phase and chemical equilibria, introduction to quantum theory, and molecular spectroscopy.

  11. Orbital interactions in chemistry

    CERN Document Server

    Albright, Thomas A; Whangbo, Myung-Hwan

    2013-01-01

    Explains the underlying structure that unites all disciplines in chemistry Now in its second edition, this book explores organic, organometallic, inorganic, solid state, and materials chemistry, demonstrating how common molecular orbital situations arise throughout the whole chemical spectrum. The authors explore the relationships that enable readers to grasp the theory that underlies and connects traditional fields of study within chemistry, thereby providing a conceptual framework with which to think about chemical structure and reactivity problems. Orbital Interactions

  12. Overview on the history of organofluorine chemistry from the viewpoint of material industry

    OpenAIRE

    Okazoe, Takashi

    2009-01-01

    Fluorine (from “le fluor”, meaning “to flow”) is a second row element of Group 17 in the periodic table. When bound to carbon it forms the strongest bond in organic chemistry to give organofluorine compounds. The scientific field treating them, organofluorine chemistry, started before elemental fluorine itself was isolated. Applying the fruits in academia, industrial organofluorine chemistry has developed over 80 years via dramatic changes during World War II. Nowadays, it provides various ma...

  13. TEXT tf coil bonding system

    International Nuclear Information System (INIS)

    An extensive bond test program was conducted prior to manufacturing and bonding the toroidal field (TF) coils for the Texas Experimental Tokamak (TEXT). The bonding materials consisted of fiberglass cloth with pre-impregnated, 'B' staged Hexcel F-159 resin. Approximately 100 double lap bond samples were constructed to test quality, strength, and repeatability of the bonds. The variables investigated included surface machining methods, surface preparations, bond sample size (planform area), bonding pressure, bonding temperature, and the number of laminations bonded simultaneously. Double lap shear tests conducted at room temperature resulted in ultimate shear strengths for all variables in the range of 3000 to 7000 psi with an average value of 5650 psi. Fatigue tests were also conducted to demonstrate bond integrity over the anticipated cycle lifetime of the TEXT machine (10/sup 6/ cycles) under simulated worst case conditions. 2 refs

  14. The open-close mechanism of M2 channel protein in influenza A virus: A computational study on the hydrogen bonds and cation-π interactions among His37 and Trp41

    Institute of Scientific and Technical Information of China (English)

    CHENG JiaGao; ZHU WeiLiang; WANG YanLi; YAN XiuHua; LI Zhong; TANG Yun; JIANG HuaLiang

    2008-01-01

    The M2 protein from influenza A virus is a tetrameric ion channel. It was reported that the permeation of the ion channel is correlated with the hydrogen bond network among His37 residues and the cation-π interactions between His37 and Trp41. In the present study, the hydrogen bonding network of 4-methyl-imidazoles was built to mimic the hydrogen bonds between His37 residues, and the cation-π interactions between 4-methyl-imidazolium and indole systems were selected to represent the interac-tions between His37 and Trp41. Then, quantum chemistry calculations at the MP2/6-311G** level were carried out to explore the properties of the hydrogen bonds and the cation-π interactions. The calculation results indicate that the binding strength of the N--H…N hydrogen bond between imidazole rings is up to -6.22 kcal·mol-1, and the binding strength of the strongest cation-π interaction is up to -18.8 kcal·mol-1 (T-shaped interaction) or -12.3 kcal·mol-1 (parallel stacking interaction). Thus, the calculated binding energies indicate that it is possible to control the permeation of the M2 ion channel through the hydrogen bond network and the cation-π interactions by altering the pH values.

  15. The open-close mechanism of M2 channel protein in influenza A virus:A computational study on the hydrogen bonds and cation-π interactions among His37 and Trp41

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The M2 protein from influenza A virus is a tetrameric ion channel. It was reported that the permeation of the ion channel is correlated with the hydrogen bond network among His37 residues and the cation-π interactions between His37 and Trp41. In the present study,the hydrogen bonding network of 4-methyl-imidazoles was built to mimic the hydrogen bonds between His37 residues,and the cation-π interactions between 4-methyl-imidazolium and indole systems were selected to represent the interac-tions between His37 and Trp41. Then,quantum chemistry calculations at the MP2/6-311G level were carried out to explore the properties of the hydrogen bonds and the cation-π interactions. The calcula-tion results indicate that the binding strength of the N-H···N hydrogen bond between imidazole rings is up to -6.22 kcal·mol-1,and the binding strength of the strongest cation-π interaction is up to -18.8 kcal·mol-1(T-shaped interaction) or -12.3 kcal·mol-1(parallel stacking interaction). Thus,the calcu-lated binding energies indicate that it is possible to control the permeation of the M2 ion channel through the hydrogen bond network and the cation-π interactions by altering the pH values.

  16. Insulation bonding test system

    Science.gov (United States)

    Beggs, J. M.; Johnston, G. D.; Coleman, A. D.; Portwood, J. N.; Saunders, J. M.; Redmon, J. W.; Porter, A. C. (Inventor)

    1984-01-01

    A method and a system for testing the bonding of foam insulation attached to metal is described. The system involves the use of an impacter which has a calibrated load cell mounted on a plunger and a hammer head mounted on the end of the plunger. When the impacter strikes the insulation at a point to be tested, the load cell measures the force of the impact and the precise time interval during which the hammer head is in contact with the insulation. This information is transmitted as an electrical signal to a load cell amplifier where the signal is conditioned and then transmitted to a fast Fourier transform (FFT) analyzer. The FFT analyzer produces energy spectral density curves which are displayed on a video screen. The termination frequency of the energy spectral density curve may be compared with a predetermined empirical scale to determine whether a igh quality bond, good bond, or debond is present at the point of impact.

  17. The Chemistry Institute

    OpenAIRE

    Fontecave, Marc

    2015-01-01

    Chemistry at the Collège de France has received particular attention over the last few years. After the departures of Profs Jean-Marie Lehn and Jacques Livage, new ambition for developing this discipline has led to the creation of several Chairs: Prof. Marc Fontecave’s Chair of Chemistry of Biological Processes in 2008, Prof. Clément Sanchez’ Chair of Chemistry of Hybrid Materials in 2011, and the Chair of Chemistry of Materials and Energy, which Prof. Jean-Marie Tarascon has held since 2014....

  18. Advances in quantum chemistry

    CERN Document Server

    Sabin, John R

    2013-01-01

    Advances in Quantum Chemistry presents surveys of current topics in this rapidly developing field that has emerged at the cross section of the historically established areas of mathematics, physics, chemistry, and biology. It features detailed reviews written by leading international researchers. This volume focuses on the theory of heavy ion physics in medicine.Advances in Quantum Chemistry presents surveys of current topics in this rapidly developing field that has emerged at the cross section of the historically established areas of mathematics, physics, chemistry, and biology. It features

  19. DOE fundamentals handbook: Chemistry

    International Nuclear Information System (INIS)

    This handbook was developed to assist nuclear facility operating contractors in providing operators, maintenance personnel, and the technical staff with the necessary fundamentals training to ensure a basic understanding of chemistry. This volume contains the following modules: reactor water chemistry (effects of radiation on water chemistry, chemistry parameters), principles of water treatment (purpose; treatment processes [ion exchange]; dissolved gases, suspended solids, and pH control; water purity), and hazards of chemicals and gases (corrosives [acids, alkalies], toxic compounds, compressed gases, flammable/combustible liquids)

  20. Group theory and chemistry

    CERN Document Server

    Bishop, David M

    1993-01-01

    Group theoretical principles are an integral part of modern chemistry. Not only do they help account for a wide variety of chemical phenomena, they simplify quantum chemical calculations. Indeed, knowledge of their application to chemical problems is essential for students of chemistry. This complete, self-contained study, written for advanced undergraduate-level and graduate-level chemistry students, clearly and concisely introduces the subject of group theory and demonstrates its application to chemical problems.To assist chemistry students with the mathematics involved, Professor Bishop ha

  1. The Illiquidity of Corporate Bonds

    OpenAIRE

    Bao, Jack; Pan, Jun; Wang, Jiang

    2011-01-01

    This paper examines the illiquidity of corporate bonds and its asset-pricing implications. Using transactions data from 2003 to 2009, we show that the illiquidity in corporate bonds is substantial, significantly greater than what can be explained by bid–ask spreads. We establish a strong link between bond illiquidity and bond prices. In aggregate, changes in market-level illiquidity explain a substantial part of the time variation in yield spreads of high-rated (AAA through A) bonds, overshad...

  2. Uses of neutron scattering in supramolecular chemistry

    International Nuclear Information System (INIS)

    Full text: A major thrust in recent chemical research has been the development of supramolecular chemistry 1 - broadly the chemistry of large multicomponent molecular assemblies in which the component structural units are held together by either covalent linkages or by a variety of weaker (non-covalent) interactions that include hydrogen bonding, dipole stacking, π-stacking, van der Waals q forces and favourable hydrophobic interactions. Much of the activity in the area has been motivated by the known behaviour of biological molecules (such as enzymes). Thus molecular assemblies are ubiquitous in natural systems but, with a limited number of exceptions, have only recently been the subject of increasing investigation by chemists. A feature of much of this recent work has been its focus on molecular design for achieving complementarity between single molecule hosts and guests. The use of single crystal neutron diffraction coupled with molecular modelling and a range of other techniques to investigate the nature of individual supramolecular systems will be discussed. By way of example, in one such study the supramolecular array formed by co-crystallisation of 1,2- diaminoethane and benzoic acid has been investigated; the system self-assembles into an unusual layered structure composed of two-dimensional hydrogen bonded networks sandwiched between layers of edge-to-face stacked aromatic systems. The number of hydrogen-bond donors and acceptors is balanced in this structure

  3. Multilayered film microreactors fabricated by a one-step thermal bonding technique with high reproducibility and their applications.

    Science.gov (United States)

    Min, Kyoung-Ik; Kim, Jin-Oh; Kim, Heejin; Im, Do Jin; Kim, Dong-Pyo

    2016-03-21

    We report the versatile uses of multilayered polyimide (PI) film microreactors with various functions including pressure tolerance, three-dimensional mixing and multistep membrane emulsification. Such PI film microreactors were fabricated by a simple one-step thermal bonding technique with high reproducibility. Upon bonding at 300 °C for 1 hour, the thin and flexible film microdevices could withstand pressure up to 8.6 MPa and 16.3 MPa with PI adhesive film or fluoropolymer adhesive, respectively, due to differences in wettability. The hydrophilic and hydrophobic microchannel devices were used to generate monodisperse oil-in-water (O/W) and water-in-oil (W/O) droplets, and polymer micro/nanoparticles at a high generation frequency. A monolithic and chemical resistant film microreactor with a three-dimensional serpentine microchannel was used for the selective reduction of ester to aldehyde by efficient mixing and quenching in a flash chemistry manner, within a several 10(1) millisecond time scale. Furthermore, a novel multilayered film microreactor for organic-aqueous biphasic interfacial reactions was devised by embedding a membrane layer to induce chaotic mixing in both the interface and emulsified phase by flowing through multiple numbers of meshed structures along the hydrophobic channel. This simple and economic fabrication technique significantly facilitates mass production of multilayered film devices that could be useful as a platform for various microfluidic applications in chemistry and biology. PMID:26886679

  4. Anodic bonded graphene

    Energy Technology Data Exchange (ETDEWEB)

    Balan, Adrian; Kumar, Rakesh; Boukhicha, Mohamed; Beyssac, Olivier; Bouillard, Jean-Claude; Taverna, Dario; Sacks, William; Shukla, Abhay [Universite Pierre et Marie Curie-Paris 6, CNRS-UMR7590, Institut de Mineralogie et de Physique des Milieux Condenses, 140 rue de Lourmel, Paris, F-75015 France (France); Marangolo, Massimiliano; Lacaze, Emanuelle; Gohler, Roger [Universite Pierre et Marie Curie-Paris 6, CNRS-UMR7588, Institut des Nanosciences de Paris, 140 rue de Lourmel, Paris, F-75015 France (France); Escoffier, Walter; Poumirol, Jean-Marie, E-mail: abhay.shukla@upmc.f [Laboratoire National des Champs Magnetiques Intenses, INSA UPS CNRS, UPR 3228, Universite de Toulouse, 143 avenue de Rangueil, 31400 Toulouse (France)

    2010-09-22

    We show how to prepare graphene samples on a glass substrate with the anodic bonding method. In this method, a graphite precursor in flake form is bonded to a glass substrate with the help of an electrostatic field and then cleaved off to leave few layer graphene on the substrate. Now that several methods are available for producing graphene, the relevance of our method is in its simplicity and practicality for producing graphene samples of about 100 {mu}m lateral dimensions. This method is also extensible to other layered materials. We discuss some detailed aspects of the fabrication and results from Raman spectroscopy, local probe microscopy and transport measurements on these samples.

  5. The Trouble With Bonds

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    @@ In early June,global financial markets gyrated downwards in the wake of central banks'tough language on inflation.At one point bond prices reflected expectations of four rate hikes by the US Federal Reserve (Fed) in the next 12 months.As a result,the dollar firmed,oil prices stabilized,and yield curves flattened around the world.If all these inflation-fighting measures are real,the situation bodes well for bonds.But,I think otherwise.

  6. Proceedings of the Second Annual Symposium for Nondestructive Evaluation of Bond Strength

    Science.gov (United States)

    Roberts, Mark J. (Compiler)

    1999-01-01

    Ultrasonics, microwaves, optically stimulated electron emission (OSEE), and computational chemistry approaches have shown relevance to bond strength determination. Nonlinear ultrasonic nondestructive evaluation methods, however, have shown the most effectiveness over other methods on adhesive bond analysis. Correlation to changes in higher order material properties due to microstructural changes using nonlinear ultrasonics has been shown related to bond strength. Nonlinear ultrasonic energy is an order of magnitude more sensitive than linear ultrasound to these material parameter changes and to acoustic velocity changes caused by the acoustoelastic effect when a bond is prestressed. Signal correlations between non-linear ultrasonic measurements and initialization of bond failures have been measured. This paper reviews bond strength research efforts presented by university and industry experts at the Second Annual Symposium for Nondestructive Evaluation of Bond Strength organized by the NDE Sciences Branch at NASA Langley in November 1998.

  7. Interfacial chemistry of zinc anodes for reinforced concrete structures

    Energy Technology Data Exchange (ETDEWEB)

    Covino, B.S. Jr.; Bullard, S.J.; Cramer, S.D.; Holcomb, G.R. [Dept. of Energy, Albany, OR (United States). Albany Research Center; McGill, G.E.; Cryer, C.B. [Oregon Dept. of Transportation, Salem, OR (United States); Stoneman, A. [International Lead Zinc Research Organization, Research Triangle Park, NC (United States); Carter, R.R. [California Dept. of Transportation, Sacramento, CA (United States)

    1997-12-01

    Thermally-sprayed zinc anodes are used in both galvanic and impressed current cathodic protection systems for reinforced concrete structures. The Albany Research Center, in collaboration with the Oregon Department of Transportation, has been studying the effect of electrochemical aging on the bond strength of zinc anodes for bridge cathodic protection systems. Changes in anode bond strength and other anode properties can be explained by the chemistry of the zinc-concrete interface. The chemistry of the zinc-concrete interface in laboratory electrochemical aging studies is compared with that of several bridges with thermal-sprayed zinc anodes and which have been in service for 5 to 10 years using both galvanic and impressed current cathodic protection systems. The bridges are the Cape Creek Bridge on the Oregon coast and the East Camino Undercrossing near Placerville, CA. Also reported are interfacial chemistry results for galvanized steel rebar from the 48 year old Longbird Bridge in Bermuda.

  8. Microbial cleavage of organic C-S bonds

    Science.gov (United States)

    Kilbane, II, John J.

    1994-01-01

    A microbial process for selective cleavage of organic C--S bonds which may be used for reducing the sulfur content of sulfur-containing organic carbonaceous materials, Microorganisms of Rhodococcus rhodochrous and Bacillus sphaericus have been found which have the ability of selective cleavage of organic C--S bonds. Particularly preferred microorganisms are Rhodococcus rhodochrous strain ATCC 53968 and Bacillus sphaericus strain ATCC 53969 and their derivatives.

  9. Shear bond strength, failure modes, and confocal microscopy of bonded amalgam restorations.

    Science.gov (United States)

    Cianconi, Luigi; Conte, Gabriele; Mancini, Manuele

    2011-01-01

    This study evaluated the shear bond strength, failure modes, and confocal microscopy of two different amalgam alloy restorations lined with five adhesive systems. Two regular-set high-copper dental amalgam alloys, Amalcap Plus and Valiant Ph.D, and five commercially available adhesive systems were selected. One hundred and twenty freshly-extracted human third molars were used for the study. The results were statistically evaluated using two-factor analysis of variance (ANOVA). The shear bond strength (SBS) of amalgam to dentin was significantly affected by both the adhesive (pValiant Ph.D, 31 of 50 exhibited adhesive failure, and 19 displayed mixed failure. Laser optical microscopy (OM) of the bonded interface revealed the presence of a good hybrid layer was evident in all experimental groups. Higher bond strengths were measured for four of the five adhesives when used in combination with the spherical alloy. PMID:21383518

  10. Cavity partition and functionalization of a [2+3] organic molecular cage by inserting polar P[double bond, length as m-dash]O bonds.

    Science.gov (United States)

    Feng, Genfeng; Liu, Wei; Peng, Yuxin; Zhao, Bo; Huang, Wei; Dai, Yafei

    2016-07-28

    The cavity of a [2+3] organic molecular cage was partitioned and functionalized by inserting inner-directed P[double bond, length as m-dash]O bonds, which shows CO2 capture and CH4 exclusion due to the size-matching and polarity effects. Computational results demonstrate that the successful segmentation via polar P[double bond, length as m-dash]O bonds facilitates the CO2 molecules to reside selectively inside the cavity. PMID:27356151

  11. A Protein Data Bank survey reveals shortening of intermolecular hydrogen bonds in ligand-protein complexes when a halogenated ligand is an H-bond donor.

    Directory of Open Access Journals (Sweden)

    Jarosław Poznański

    Full Text Available Halogen bonding in ligand-protein complexes is currently widely exploited, e.g. in drug design or supramolecular chemistry. But little attention has been directed to other effects that may result from replacement of a hydrogen by a strongly electronegative halogen. Analysis of almost 30000 hydrogen bonds between protein and ligand demonstrates that the length of a hydrogen bond depends on the type of donor-acceptor pair. Interestingly, lengths of hydrogen bonds between a protein and a halogenated ligand are visibly shorter than those estimated for the same family of proteins in complexes with non-halogenated ligands. Taking into account the effect of halogenation on hydrogen bonding is thus important when evaluating structural and/or energetic parameters of ligand-protein complexes. All these observations are consistent with the concept that halogenation increases the acidity of the proximal amino/imino/hydroxyl groups and thus makes them better, i.e. stronger, H-bond donors.

  12. Seeking hydrogen bonds- with and without neutron diffraction

    International Nuclear Information System (INIS)

    The hydrogen-bond interaction can be studied using a variety of spectroscopic and crystallographic techniques, as well as theoretical studies based on quantum chemical principles, semi-empirical procedures, and statistical interpretations. A degree of specificity, along with flexibility, provides H-bonded systems with a variety of unusual and interesting physical, chemical and biological properties. Neutron diffraction is the method of choice for obtaining high-precision data on hydrogen-atom positions and hydrogen-bond stereo-chemistry in crystals. Neutron inelastic scattering can provide information on the dynamics of H-bonded systems. High-precision neutron diffraction studies on a variety of crystal hydrates, amino acids and small peptides, development of semi-empirical potential functions for bent-hydrogen bonds, and statistical analysis of H-bond populations associated with various donor and acceptor groups are some of the investigations on hydrogen bonding, carried out at Trombay during the past three decades. (author). 39 refs., 7 figs., 3 tabs

  13. Open access and medicinal chemistry

    OpenAIRE

    Swain Chris

    2007-01-01

    Abstract Chemistry Central is a new open access website for chemists publishing peer-reviewed research in chemistry from a range of open access journals. A new addition, Chemistry Central Journal, will cover all of chemistry and will be broken down into discipline-specific sections, and Im delighted that Medicinal Chemistry will be a key discipline in this new journal.

  14. Annual report 1988 Chemistry Department

    International Nuclear Information System (INIS)

    This report contains a brief survey of the main activities in the Chemistry Department. The names and abstracts of all articles and reports published and lectures given in 1988 are presented. The facilities and equipment are mentioned briefly. The activities are divided into the following groups: radioisotope chemistry, analytical- and organic chemistry, environmental chemistry, polymer chemistry, chemical reactivity, mineral processing, and general. (author)

  15. Annual report 1986 chemistry department

    International Nuclear Information System (INIS)

    This report contains a brief survey of the main activities in the Chemistry Department. All articles and reports published and lectures given in 1986 are presented. The facilities and equipment are mentioned briefly. The activities are divided into the following groups: radioisotope chemistry, analytical- and organic chemistry, environmental chemistry, polymer chemistry, radical chemistral, mineral processing, and general. (author)

  16. Annual report 1989 Chemistry Department

    International Nuclear Information System (INIS)

    This report contains a brief survey of the main activities in the Chemistry Department. The names and abstracts of all articles and reports published and lectures given in 1989 are presented. The facilities and equipment are mentioned briefly. The activities are divided into the following groups: radioisotope chemistry, analytical- and organic chemistry, environmental chemistry, polymer chemistry, chemical reactivity, mineral processing, and general. (author)

  17. Flax Fiber - Interfacial Bonding

    Science.gov (United States)

    Measured flax fiber physical and chemical properties potentially impact bonding and thus stress transfer between the matrix and fiber within composites. These first attempts at correlating flax fiber quality and biofiber composites contain the initial steps towards identifying key flax fiber charac...

  18. Thread bonds in molecules

    CERN Document Server

    Ivlev, B

    2015-01-01

    Unusual chemical bonds are proposed. Each bond is almost covalent but is characterized by the thread of a small radius $\\sim 0.6\\times 10^{-11}$cm, between two nuclei in a molecule. The main electron density is concentrated outside the thread as in a covalent bond. The thread is formed by the electron wave function which has a tendency to be singular on it. The singularity along the thread is cut off by electron "vibrations" due to the interaction with zero point electromagnetic oscillations. The electron energy has its typical value of (1-10)eV. Due to the small tread radius the uncertainty of the electron momentum inside the thread is large resulting in a large electron kinetic energy $\\sim 1 MeV$. This energy is compensated by formation of a potential well due to the reduction of the energy of electromagnetic zero point oscillations. This is similar to formation of a negative van der Waals potential. Thread bonds are stable and cannot be created or destructed in chemical or optical processes.

  19. The Breath of Chemistry

    DEFF Research Database (Denmark)

    Josephsen, Jens

    The present preliminary text is a short thematic presentation in biological inorganic chemistry meant to illustrate general and inorganic (especially coordination) chemistry in biochemistry. The emphasis is on molecular models to explain features of the complicated mechanisms essential to breathing...

  20. Movies in Chemistry Education

    Science.gov (United States)

    Pekdag, Bulent; Le Marechal, Jean-Francois

    2010-01-01

    This article reviews numerous studies on chemistry movies. Movies, or moving pictures, are important elements of multimedia and signify a privileged or motivating means of presenting knowledge. Studies on chemistry movies show that the first movie productions in this field were devoted to university lectures or documentaries. Shorter movies were…