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Sample records for surface-initiated atom transfer

  1. On Surface-Initiated Atom Transfer Radical Polymerization Using Diazonium Chemistry To Introduce the Initiator Layer

    DEFF Research Database (Denmark)

    Iruthayaraj, Joseph; Chernyy, Sergey; Lillethorup, Mie

    2011-01-01

    This work features the controllability of surface-initiated atom transfer radical polymerization (SI-ATRP) of methyl methacrylate, initiated by a multilayered 2-bromoisobutyryl moiety formed via diazonium chemistry. The thickness as a function of polymerization time has been studied by varying di...

  2. Polymer coating comprising 2-methoxyethyl acrylate units synthesized by surface-initiated atom transfer radical polymerization

    DEFF Research Database (Denmark)

    2011-01-01

    Source: US2012184029A The present invention relates to preparation of a polymer coating comprising or consisting of polymer chains comprising or consisting of units of 2-methoxyethyl acrylate synthesized by Surface-Initiated Atom Transfer Radical Polymerization (SI ATRP) such as ARGET SI ATRP...

  3. Functionalized polymer film surfaces via surface-initiated atom transfer radical polymerization

    International Nuclear Information System (INIS)

    Hu, Y.; Li, J.S.; Yang, W.T.; Xu, F.J.

    2013-01-01

    The ability to manipulate and control the surface properties of polymer films, without altering the substrate properties, is crucial to their wide-spread applications. In this work, a simple one-step method for the direct immobilization of benzyl chloride groups (as the effective atom transfer radical polymerization (ATRP) initiators) on the polymer films was developed via benzophenone-induced coupling of 4-vinylbenzyl chloride (VBC). Polyethylene (PE) and nylon films were selected as examples of polymer films to illustrate the functionalization of film surfaces via surface-initiated ATRP. Functional polymer brushes of (2-dimethylamino)ethyl methacrylate, sodium 4-styrenesulfonate, 2-hydroxyethyl methacrylate and glycidyl methacrylate, as well as their block copolymer brushes, have been prepared via surface-initiated ATRP from the VBC-coupled PE or nylon film surfaces. With the development of a simple approach to the covalent immobilization of ATRP initiators on polymer film surfaces and the inherent versatility of surface-initiated ATRP, the surface functionality of polymer films can be precisely tailored. - Highlights: ► Atom transfer radical polymerization initiators were simply immobilized. ► Different functional polymer brushes were readily prepared. ► Their block copolymer brushes were also readily prepared

  4. Hydrophilization of poly(ether ether ketone) films by surface-initiated atom transfer radical polymerization

    DEFF Research Database (Denmark)

    Fristrup, Charlotte Juel; Jankova Atanasova, Katja; Hvilsted, Søren

    2010-01-01

    Surface-Initiated Atom Transfer Radical Polymerization (SI-ATRP) has been exploited to hydrophilize PEEK. The ketone groups on the PEEK surface were reduced to hydroxyl groups which were converted to bromoisobutyrate initiating sites for SI-ATRP. The modification steps were followed by contact...... angle measurements and XPS. Moreover, ATR FTIR has been used to confirm the formation of initiating groups. Grafting of PEGMA from PEEK was performed in aqueous solution. The presence of the PPEGMA grafts on PEEK was revealed by the thermograms from TGA whereas investigations with AFM rejected changes...

  5. In situ AFM investigation of electrochemically induced surface-initiated atom-transfer radical polymerization.

    Science.gov (United States)

    Li, Bin; Yu, Bo; Zhou, Feng

    2013-02-12

    Electrochemically induced surface-initiated atom-transfer radical polymerization is traced by in situ AFM technology for the first time, which allows visualization of the polymer growth process. It affords a fundamental insight into the surface morphology and growth mechanism simultaneously. Using this technique, the polymerization kinetics of two model monomers were studied, namely the anionic 3-sulfopropyl methacrylate potassium salt (SPMA) and the cationic 2-(metharyloyloxy)ethyltrimethylammonium chloride (METAC). The growth of METAC is significantly improved by screening the ammonium cations by the addition of ionic liquid electrolyte in aqueous solution. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Fabrication of Robust and Antifouling Superhydrophobic Surfaces via Surface-Initiated Atom Transfer Radical Polymerization.

    Science.gov (United States)

    Xue, Chao-Hua; Guo, Xiao-Jing; Ma, Jian-Zhong; Jia, Shun-Tian

    2015-04-22

    Superhydrophobic surfaces were fabricated via surface-initiated atom transfer radical polymerization of fluorinated methacrylates on poly(ethylene terephthalate) (PET) fabrics. The hydrophobicity of the PET fabric was systematically tunable by controlling the polymerization time. The obtained superhydrophobic fabrics showed excellent chemical robustness even after exposure to different chemicals, such as acid, base, salt, acetone, and toluene. Importantly, the fabrics maintained superhydrophobicity after 2500 abrasion cycles, 100 laundering cycles, and long time exposure to UV irradiation. Also, the surface of the superhydrophobic fabrics showed excellent antifouling properties.

  7. Surface-initiated Atom Transfer Radical Polymerization - a Technique to Develop Biofunctional Coatings

    DEFF Research Database (Denmark)

    Fristrup, Charlotte Juel; Jankova Atanasova, Katja; Hvilsted, Søren

    2009-01-01

    The initial formation of initiating sites for atom transfer radical polymerization (ATRP) on various polymer surfaces and numerous inorganic and metallic surfaces is elaborated. The subsequent ATRP grafting of a multitude of monomers from such surfaces to generate thin covalently linked polymer...

  8. Surface-Initiated Graft Atom Transfer Radical Polymerization of Methyl Methacrylate from Chitin Nanofiber Macroinitiator under Dispersion Conditions

    Directory of Open Access Journals (Sweden)

    Ryo Endo

    2015-08-01

    Full Text Available Surface-initiated graft atom transfer radical polymerization (ATRP of methyl methacrylate (MMA from self-assembled chitin nanofibers (CNFs was performed under dispersion conditions. Self-assembled CNFs were initially prepared by regeneration from a chitin ion gel with 1-allyl-3-methylimidazolium bromide using methanol; the product was then converted into the chitin nanofiber macroinitiator by reaction with α-bromoisobutyryl bromide in a dispersion containing N,N-dimethylformamide. Surface-initiated graft ATRP of MMA from the initiating sites on the CNFs was subsequently carried out under dispersion conditions, followed by filtration to obtain the CNF-graft-polyMMA film. Analysis of the product confirmed the occurrence of the graft ATRP on the surface of the CNFs.

  9. Hydrophilization of Poly(ether ether ketone) Films by Surface-initiated Atom Transfer Radical Polymerization

    DEFF Research Database (Denmark)

    Fristrup, Charlotte Juel; Eskimergen, Rüya; Burkrinsky, J.T.

    2008-01-01

    and confirmed by ATR FTIR, water contact ang;le, and Thermal Gravimetric Analysis (TGA). The surface topography was evaluated by "Atomic Force Microscopy (AFM). X-ray Photoelectron Spectroscopy (XPS) has been used to investigate the degree of functionalization. The performed modification allowed for successful...

  10. Visible Light-Induced Metal Free Surface Initiated Atom Transfer Radical Polymerization of Methyl Methacrylate on SBA-15

    Directory of Open Access Journals (Sweden)

    Liang Ma

    2017-02-01

    Full Text Available Surface-initiated atom transfer radical polymerization (SI-ATRP is one of the most versatile techniques to modify the surface properties of materials. Recent developed metal-free SI-ATRP makes such techniques more widely applicable. Herein photo-induced metal-free SI-ATRP of methacrylates, such as methyl methacrylate, N-isopropanyl acrylamide, and N,N-dimethylaminoethyl methacrylate, on the surface of SBA-15 was reported to fabricate organic-inorganic hybrid materials. A SBA-15-based polymeric composite with an adjustable graft ratio was obtained. The structure evolution during the SI-ATRP modification of SBA-15 was monitored and verified by FT-IR, XPS, TGA, BET, and TEM. The obtained polymeric composite showed enhanced adsorption ability for the model compound toluene in aqueous conditions. This procedure provides a low-cost, readily available, and easy modification method to synthesize polymeric composites without the contamination of metal.

  11. Crystalline TiO2 grafted with poly(2-methacryloyloxyethyl phosphorylcholine) via surface-initiated atom-transfer radical polymerization

    International Nuclear Information System (INIS)

    Zhao Yuancong; Tu Qiufen; Wang Jin; Huang Qiongjian; Huang Nan

    2010-01-01

    Crystalline TiO 2 films were prepared by unbalanced magnetron sputtering and the structure was confirmed by XRD. An organic layer of 11-hydroxyundecylphosphonic acid (HUPA) was prepared on the TiO 2 films by self-assembling, and the HUPA on TiO 2 films was confirmed by FTIR analysis. Simultaneously, hydroxyl groups were introduced in the phosphonic acid molecules to provide a functionality for further chemical modification. 2-Methacryloyloxyethyl phosphorylcholine (MPC), a biomimetic monomer, was chemically grafted on the HUPA surfaces at room temperature by surface-initiated atom-transfer radical polymerization. The surface characters of TiO 2 films modified by poly-MPC were confirmed by FTIR, XPS and SEM analysis. Platelet adhesion experiment revealed that poly-MPC modified surface was effective to inhibit platelet adhesion in vitro.

  12. Crystalline TiO 2 grafted with poly(2-methacryloyloxyethyl phosphorylcholine) via surface-initiated atom-transfer radical polymerization

    Science.gov (United States)

    Zhao, Yuancong; Tu, Qiufen; Wang, Jin; Huang, Qiongjian; Huang, Nan

    2010-12-01

    Crystalline TiO 2 films were prepared by unbalanced magnetron sputtering and the structure was confirmed by XRD. An organic layer of 11-hydroxyundecylphosphonic acid (HUPA) was prepared on the TiO 2 films by self-assembling, and the HUPA on TiO 2 films was confirmed by FTIR analysis. Simultaneously, hydroxyl groups were introduced in the phosphonic acid molecules to provide a functionality for further chemical modification. 2-Methacryloyloxyethyl phosphorylcholine (MPC), a biomimetic monomer, was chemically grafted on the HUPA surfaces at room temperature by surface-initiated atom-transfer radical polymerization. The surface characters of TiO 2 films modified by poly-MPC were confirmed by FTIR, XPS and SEM analysis. Platelet adhesion experiment revealed that poly-MPC modified surface was effective to inhibit platelet adhesion in vitro.

  13. Hydrogel brushes grafted from stainless steel via surface-initiated atom transfer radical polymerization for marine antifouling

    Science.gov (United States)

    Wang, Jingjing; Wei, Jun

    2016-09-01

    Crosslinked hydrogel brushes were grafted from stainless steel (SS) surfaces for marine antifouling. The brushes were prepared by surface-initiated atom transfer radical polymerization (SI-ATRP) of 2-methacryloyloxyethyl phosphorylcholine (MPC) and poly(ethylene glycol) methyl ether methacrylate (PEGMA) respectively with different fractions of crosslinker in the feed. The grafted layers prepared with different thickness were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), ellipsometry and water contact angle measurements. With the increase in the fraction of crosslinker in the feed, the thickness of the grafted layer increased and the surface became smooth. All the brush-coated SS surfaces could effectively reduce the adhesion of bacteria and microalgae and settlement of barnacle cyprids, as compared to the pristine SS surface. The antifouling efficacy of the PEGMA polymer (PPEGMA)-grafted surface was higher than that of the MPC polymer (PMPC)-grafted surfaces. Furthermore, the crosslinked hydrogel brush-grafted surfaces exhibited better fouling resistance than the non-crosslinked polymer brush-grafted surfaces, and the antifouling efficacy increased with the crosslinking density. These hydrogel coatings of low toxicity and excellent anti-adhesive characteristics suggested their useful applications as environmentally friendly antifouling coatings.

  14. Hydrogel brushes grafted from stainless steel via surface-initiated atom transfer radical polymerization for marine antifouling

    International Nuclear Information System (INIS)

    Wang, Jingjing; Wei, Jun

    2016-01-01

    Highlights: • Crosslinked hydrogel brushes were grafted from SS surfaces for marine antifouling. • All brush-coated SS surfaces could effectively reduce the adhesion of biofouling. • The antifouling efficacy increased with the crosslinking density of hydrogels. - Abstract: Crosslinked hydrogel brushes were grafted from stainless steel (SS) surfaces for marine antifouling. The brushes were prepared by surface-initiated atom transfer radical polymerization (SI-ATRP) of 2-methacryloyloxyethyl phosphorylcholine (MPC) and poly(ethylene glycol) methyl ether methacrylate (PEGMA) respectively with different fractions of crosslinker in the feed. The grafted layers prepared with different thickness were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), ellipsometry and water contact angle measurements. With the increase in the fraction of crosslinker in the feed, the thickness of the grafted layer increased and the surface became smooth. All the brush-coated SS surfaces could effectively reduce the adhesion of bacteria and microalgae and settlement of barnacle cyprids, as compared to the pristine SS surface. The antifouling efficacy of the PEGMA polymer (PPEGMA)-grafted surface was higher than that of the MPC polymer (PMPC)-grafted surfaces. Furthermore, the crosslinked hydrogel brush-grafted surfaces exhibited better fouling resistance than the non-crosslinked polymer brush-grafted surfaces, and the antifouling efficacy increased with the crosslinking density. These hydrogel coatings of low toxicity and excellent anti-adhesive characteristics suggested their useful applications as environmentally friendly antifouling coatings.

  15. Fabrication of ultrahydrophobic poly(lauryl acrylate) brushes on silicon wafer via surface-initiated atom transfer radical polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Oztuerk, Esra; Turan, Eylem [Department of Chemistry, Faculty of Art and Science, Gazi University, 06500 Besevler, Ankara (Turkey); Caykara, Tuncer, E-mail: caykara@gazi.edu.tr [Department of Chemistry, Faculty of Art and Science, Gazi University, 06500 Besevler, Ankara (Turkey)

    2010-11-15

    In this report, ultrahydrophobic poly(lauryl acrylate) [poly(LA)] brushes were synthesized by surface-initiated atom transfer radical polymerization (SI-ATRP) of lauryl acrylate (LA) in N,N-dimethylformamide (DMF) at 90 deg. C. The formation of ultrahydrophobic poly(LA) films, whose thickness can be turned by changing polymerization time, is evidenced by using the combination of ellipsometry, X-ray photoelectron spectroscopy (XPS), grazing angle attenuated total reflectance-Fourier transform infrared spectroscopy (GATR-FTIR), atomic force microscopy (AFM), gel permeation chromatography (GPC), and water contact angle measurements. The SI-ATRP can be conducted in a well-controlled manner, as revealed by the linear kinetic plot, linear evolution of number-average molecular weights (M-bar{sub n}) versus monomer conversions, and the relatively narrow PDI (<1.28) of the grafted poly(LA) chains. The calculation of grafting parameters from experimental measurements indicated the synthesis of densely grafted poly(LA) films and allowed us to predict a 'brushlike' conformation for the chains in good solvent. The poly(LA) brushes exhibited high water contact angle of 163.3 {+-} 2.8{sup o}.

  16. Hydrogel brushes grafted from stainless steel via surface-initiated atom transfer radical polymerization for marine antifouling

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jingjing, E-mail: jjwang1@hotmail.com; Wei, Jun

    2016-09-30

    Highlights: • Crosslinked hydrogel brushes were grafted from SS surfaces for marine antifouling. • All brush-coated SS surfaces could effectively reduce the adhesion of biofouling. • The antifouling efficacy increased with the crosslinking density of hydrogels. - Abstract: Crosslinked hydrogel brushes were grafted from stainless steel (SS) surfaces for marine antifouling. The brushes were prepared by surface-initiated atom transfer radical polymerization (SI-ATRP) of 2-methacryloyloxyethyl phosphorylcholine (MPC) and poly(ethylene glycol) methyl ether methacrylate (PEGMA) respectively with different fractions of crosslinker in the feed. The grafted layers prepared with different thickness were characterized by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), ellipsometry and water contact angle measurements. With the increase in the fraction of crosslinker in the feed, the thickness of the grafted layer increased and the surface became smooth. All the brush-coated SS surfaces could effectively reduce the adhesion of bacteria and microalgae and settlement of barnacle cyprids, as compared to the pristine SS surface. The antifouling efficacy of the PEGMA polymer (PPEGMA)-grafted surface was higher than that of the MPC polymer (PMPC)-grafted surfaces. Furthermore, the crosslinked hydrogel brush-grafted surfaces exhibited better fouling resistance than the non-crosslinked polymer brush-grafted surfaces, and the antifouling efficacy increased with the crosslinking density. These hydrogel coatings of low toxicity and excellent anti-adhesive characteristics suggested their useful applications as environmentally friendly antifouling coatings.

  17. In Situ Investigation of Electrochemically Mediated Surface-Initiated Atom Transfer Radical Polymerization by Electrochemical Surface Plasmon Resonance.

    Science.gov (United States)

    Chen, Daqun; Hu, Weihua

    2017-04-18

    Electrochemically mediated atom transfer radical polymerization (eATRP) initiates/controls the controlled/living ATRP chain propagation process by electrochemically generating (regenerating) the activator (lower-oxidation-state metal complex) from deactivator (higher-oxidation-state metal complex). Despite successful demonstrations in both of the homogeneous polymerization and heterogeneous systems (namely, surface-initiated ATRP, SI-ATRP), the eATRP process itself has never been in situ investigated, and important information regarding this process remains unrevealed. In this work, we report the first investigation of the electrochemically mediated SI-ATRP (eSI-ATRP) by rationally combining the electrochemical technique with real-time surface plasmon resonance (SPR). In the experiment, the potential of a SPR gold chip modified by the self-assembled monolayer of the ATRP initiator was controlled to electrochemically reduce the deactivator to activator to initiate the SI-ATRP, and the whole process was simultaneously monitored by SPR with a high time resolution of 0.1 s. It is found that it is feasible to electrochemically trigger/control the SI-ATRP and the polymerization rate is correlated to the potential applied to the gold chip. This work reveals important kinetic information for eSI-ATRP and offers a powerful platform for in situ investigation of such complicated processes.

  18. Protein adsorption resistance of PVP-modified polyurethane film prepared by surface-initiated atom transfer radical polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, Huihui; Qian, Bin; Zhang, Wei [Shanghai Key Laboratory of Functional Materials Chemistry and Research Center of Analysis and Test, East China University of Science and Technology, Shanghai 200237 (China); Lan, Minbo, E-mail: minbolan@ecust.edu.cn [Shanghai Key Laboratory of Functional Materials Chemistry and Research Center of Analysis and Test, East China University of Science and Technology, Shanghai 200237 (China); State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237 (China)

    2016-02-15

    Highlights: • Antifouling PVP brushes were successfully grafted on PU films by SI-ATRP. • The effect of polymerization time on surface property and topography was studied. • Hydrophilicity and protein fouling resistance of PVP–PU films were greatly promoted. • Competitive adsorption of three proteins on PVP–PU films was evaluated. - Abstract: An anti-fouling surface of polyurethane (PU) film grafted with Poly(N-vinylpyrrolidone) (PVP) was prepared through surface-initiated atom transfer radical polymerization (SI-ATRP). And the polymerization time was investigated to obtain PU films with PVP brushes of different lengths. The surface properties and protein adsorption of modified PU films were evaluated. The results showed that the hydrophilicity of PU–PVP films were improved with the increase of polymerization time, which was not positive correlation with the surface roughness due to the brush structure. Additionally, the protein resistance performance was promoted when prolonging the polymerization time. The best antifouling PU–PVP (6.0 h) film reduced the adsoption level of bovine serum albumin (BSA), lysozyme (LYS), and brovin serum fibrinogen (BFG) by 93.4%, 68.3%, 85.6%, respectively, compared to the unmodified PU film. The competitive adsorption of three proteins indicated that LYS preferentially adsorbed on the modified PU film, while BFG had the lowest adsorption selectivity. And the amount of BFG on PU–PVP (6.0 h) film reduced greatly to 0.08 μg/cm{sup 2}, which was almost one-tenth of its adsorption from the single-protein system. Presented results suggested that both hydrophilicity and surface roughness might be the important factors in all cases of protein adsorption, and the competitive or selective adsorption might be related to the size of the proteins, especially on the non-charged films.

  19. Protein adsorption resistance of PVP-modified polyurethane film prepared by surface-initiated atom transfer radical polymerization

    International Nuclear Information System (INIS)

    Yuan, Huihui; Qian, Bin; Zhang, Wei; Lan, Minbo

    2016-01-01

    Highlights: • Antifouling PVP brushes were successfully grafted on PU films by SI-ATRP. • The effect of polymerization time on surface property and topography was studied. • Hydrophilicity and protein fouling resistance of PVP–PU films were greatly promoted. • Competitive adsorption of three proteins on PVP–PU films was evaluated. - Abstract: An anti-fouling surface of polyurethane (PU) film grafted with Poly(N-vinylpyrrolidone) (PVP) was prepared through surface-initiated atom transfer radical polymerization (SI-ATRP). And the polymerization time was investigated to obtain PU films with PVP brushes of different lengths. The surface properties and protein adsorption of modified PU films were evaluated. The results showed that the hydrophilicity of PU–PVP films were improved with the increase of polymerization time, which was not positive correlation with the surface roughness due to the brush structure. Additionally, the protein resistance performance was promoted when prolonging the polymerization time. The best antifouling PU–PVP (6.0 h) film reduced the adsoption level of bovine serum albumin (BSA), lysozyme (LYS), and brovin serum fibrinogen (BFG) by 93.4%, 68.3%, 85.6%, respectively, compared to the unmodified PU film. The competitive adsorption of three proteins indicated that LYS preferentially adsorbed on the modified PU film, while BFG had the lowest adsorption selectivity. And the amount of BFG on PU–PVP (6.0 h) film reduced greatly to 0.08 μg/cm"2, which was almost one-tenth of its adsorption from the single-protein system. Presented results suggested that both hydrophilicity and surface roughness might be the important factors in all cases of protein adsorption, and the competitive or selective adsorption might be related to the size of the proteins, especially on the non-charged films.

  20. Controlled Grafting of Poly(methyl methacrylate) Brushes on Poly(vinylidene fluoride) Powders by Surface-initiated Atom Transfer Radical Polymerization

    Institute of Scientific and Technical Information of China (English)

    TANG Zhaoqi; LI Wei; LIU Lanqin; HUANG Lei; ZHOU Jin; YU Haiyin

    2009-01-01

    Controlled grafting of well-defined polymer brushes of methyl methacrylate (MMA) on the poly(vinylidene fluoride) (PVDF) powders was carded out by the surface-initiated atom transfer radical polymerization (ATRP). The ATRP initiator was anchored on the PVDF surface by alkaline treatment, followed by UV-induced bromination; then methyl methacrylate (MMA) was grafted onto the brominated PVDF by the ATRP technique. The chemical composition changes of PVDF were characterized by Fourier transform-infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). FT-IR and XPS results clearly indicated the successful graft of poly(methyl methacrylate) onto the PVDF surface.

  1. Surface-Initiated Atom Transfer Radical Polymerization and Electrografting Technique as a Means For Attaining Tailor-Made Polymer Coatings

    DEFF Research Database (Denmark)

    Chernyy, Sergey

    2012-01-01

    strategies for initiator grafting, physicochemical properties of polymer brushes and basic principles of quartz crystal microbalance technique (QCM) are discussed. In Chapter 2 various ATRP conditions are probed. The effects of solvent polarity, monomer concentration, initiator surface density, ligand nature......Atom transfer radical polymerization initiated from a surface of various substrates (SI-ATRP) has become a progressively popular technique for obtaining thin polymer films with predetermined properties. The present work addresses the main features of SI-ATRP with respect to the controllability...... and temperature on the kinetics of methyl methacrylate polymerization are elucidated. The strategy was based on the observation of dry polymer thickness versus time evolution by means of ellipsometry, profilometry and IR spectroscopy. An alternative approach, constituting Chapter 3, was based on optimization...

  2. Crystalline TiO{sub 2} grafted with poly(2-methacryloyloxyethyl phosphorylcholine) via surface-initiated atom-transfer radical polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Zhao Yuancong; Tu Qiufen; Wang Jin; Huang Qiongjian [Key Lab. of Advanced Technology for Materials, Education Ministry, School of Material Science and Technology of Southwest Jiaotong University, Chengdu, Sichuan (China); Huang Nan, E-mail: zhaoyc7320@163.com [Key Lab. of Advanced Technology for Materials, Education Ministry, School of Material Science and Technology of Southwest Jiaotong University, Chengdu, Sichuan (China)

    2010-12-15

    Crystalline TiO{sub 2} films were prepared by unbalanced magnetron sputtering and the structure was confirmed by XRD. An organic layer of 11-hydroxyundecylphosphonic acid (HUPA) was prepared on the TiO{sub 2} films by self-assembling, and the HUPA on TiO{sub 2} films was confirmed by FTIR analysis. Simultaneously, hydroxyl groups were introduced in the phosphonic acid molecules to provide a functionality for further chemical modification. 2-Methacryloyloxyethyl phosphorylcholine (MPC), a biomimetic monomer, was chemically grafted on the HUPA surfaces at room temperature by surface-initiated atom-transfer radical polymerization. The surface characters of TiO{sub 2} films modified by poly-MPC were confirmed by FTIR, XPS and SEM analysis. Platelet adhesion experiment revealed that poly-MPC modified surface was effective to inhibit platelet adhesion in vitro.

  3. Grafting of antibacterial polymers on stainless steel via surface-initiated atom transfer radical polymerization for inhibiting biocorrosion by Desulfovibrio desulfuricans.

    Science.gov (United States)

    Yuan, S J; Xu, F J; Pehkonen, S O; Ting, Y P; Neoh, K G; Kang, E T

    2009-06-01

    To enhance the biocorrosion resistance of stainless steel (SS) and to impart its surface with bactericidal function for inhibiting bacterial adhesion and biofilm formation, well-defined functional polymer brushes were grafted via surface-initiated atom transfer radical polymerization (ATRP) from SS substrates. The trichlorosilane coupling agent, containing the alkyl halide ATRP initiator, was first immobilized on the hydroxylated SS (SS-OH) substrates for surface-initiated ATRP of (2-dimethylamino)ethyl methacrylate (DMAEMA). The tertiary amino groups of covalently immobilized DMAEMA polymer or P(DMAEMA), brushes on the SS substrates were quaternized with benzyl halide to produce the biocidal functionality. Alternatively, covalent coupling of viologen moieties to the tertiary amino groups of P(DMAEMA) brushes on the SS surface resulted in an increase in surface concentration of quaternary ammonium groups, accompanied by substantially enhanced antibacterial and anticorrosion capabilities against Desulfovibrio desulfuricans in anaerobic seawater, as revealed by antibacterial assay and electrochemical studies. With the inherent advantages of high corrosion resistance of SS, and the good antibacterial and anticorrosion capabilities of the viologen-quaternized P(DMAEMA) brushes, the functionalized SS is potentially useful in harsh seawater environments and for desalination plants. Copyright 2009 Wiley Periodicals, Inc.

  4. Surface modification of thermoplastic poly(vinyl alcohol)/saponite nanocomposites via surface-initiated atom transfer radical polymerization enhanced by air dielectric discharges barrier plasma treatment

    International Nuclear Information System (INIS)

    Zhen Weijun; Lu Canhui

    2012-01-01

    To improve the water resistance of thermoplastic poly(vinyl alcohol)/saponite nanocomposites (TPVA), a simple two-step method was developed for the covalent immobilization of atom transfer radical polymerization (ATRP) initiators on the TPVA surfaces enhanced by air dielectric barrier discharges (DBD) plasma treatment, and hydrophobic poly(methyl methacrylate) (PMMA) brushes were then grafted onto the surface of TPVA via surface-initiated atom transfer radical polymerization (SI-ATRP). The chemical composition, morphology and hydrophobicity of the modified TPVA surfaces were characterized by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), respectively. The water resistance of the surface-functionalized PMMA was evaluated by the contact angle and water adsorption method. It was shown that air DBD plasma treatment activated the TPVA surface and accelerated the immobilization of ATRP initiator on the TPVA surface. Compared with TPVA control, TPVA modified by SI-ATRP can be grafted well-defined and covalently tethered network PMMA brushes onto the surface and the hydrophobicity of TPVA were significantly enhanced.

  5. Inorganic-organic hybrid coatings on stainless steel by layer-by-layer deposition and surface-initiated atom-transfer-radical polymerization for combating biocorrosion.

    Science.gov (United States)

    Yuan, S J; Pehkonen, S O; Ting, Y P; Neoh, K G; Kang, E T

    2009-03-01

    To improve the biocorrosion resistance of stainless steel (SS) and to confer the bactericidal function on its surface for inhibiting bacterial adhesion and biofilm formation, well-defined inorganic-organic hybrid coatings, consisting of the inner compact titanium oxide multilayers and outer dense poly(vinyl-N-hexylpyridinium) brushes, were successfully developed. Nanostructured titanium oxide multilayer coatings were first built up on the SS substrates via the layer-by-layer sol-gel deposition process. The trichlorosilane coupling agent, containing the alkyl halide atom-transfer-radical polymerization (ATRP) initiator, was subsequently immobilized on the titanium oxide coatings for surface-initiated ATRP of 4-vinylpyridine (4VP). The pyridium nitrogen moieties of the covalently immobilized 4VP polymer, or P(4VP), brushes were quaternized with hexyl bromide to produce a high concentration of quaternary ammonium salt on the SS surfaces. The excellent antibacterial efficiency of the grafted polycations, poly(vinyl-N-pyridinium bromide), was revealed by viable cell counts and atomic force microscopy images of the surface. The effectiveness of the hybrid coatings in corrosion protection was verified by the Tafel plot and electrochemical impedance spectroscopy measurements.

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

    Science.gov (United States)

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

    2017-03-01

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

  7. Poly(glycidyl methacrylate) grafted CdSe quantum dots by surface-initiated atom transfer radical polymerization: Novel synthesis, characterization, properties, and cytotoxicity studies

    Energy Technology Data Exchange (ETDEWEB)

    Bach, Long Giang; Islam, Md. Rafiqul [Department of Imaging System Engineering, Pukyong National University, Busan 608-737 (Korea, Republic of); Lee, Doh Chang [Department of Chemical and Biomolecular Engineering, KAIST Institute for the Nanocentury (KINC), Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701 (Korea, Republic of); Lim, Kwon Taek, E-mail: ktlim@pknu.ac.kr [Department of Imaging System Engineering, Pukyong National University, Busan 608-737 (Korea, Republic of)

    2013-10-15

    A novel approach for the synthesis of poly(glycidyl methacrylate) grafted CdSe quantum dot (QDs) (PGMA-g-CdSe) was developed. The PGMA-g-CdSe nanohybrids were synthesized by the surface-initiated atom transfer radical polymerization of glycidyl methacrylate from the surface of the strategic initiator, CdSe-BrIB QDs prepared by the interaction of 2-bromoisobutyryl bromide (BrIB) and CdSe-OH QDs. The structure, morphology, and optical property of the PGMA-g-CdSe nanohybrids were analyzed by FT-IR, XPS, TGA, XRD, TEM, and PL. The as-synthesized PGMA-g-CdSe nanohybrids having multi-epoxide groups were employed for the direct coupling of biotin via ring-opening reaction of the epoxide groups to afford the Biotin-f-PGMA-g-CdSe nanobioconjugate. The covalent immobilization of biotin onto PGMA-g-CdSe was confirmed by FT-IR, XPS, and EDX. Biocompatibility and imaging properties of the Biotin-f-PGMA-g-CdSe were investigated by MTT bioassay and PL analysis, respectively. The cell viability study suggested that the biocompatibility was significantly enhanced by the functionalization of CdSe QDs by biotin and PGMA.

  8. Preparation of Mg(OH)_2 hybrid pigment by direct precipitation and graft onto cellulose fiber via surface-initiated atom transfer radical polymerization

    International Nuclear Information System (INIS)

    Wang, Xiao; Zhang, Yue; Lv, Lihua; Cui, Yongzhu; Wei, Chunyan; Pang, Guibing

    2016-01-01

    Graphical abstract: - Highlights: • Adsorbed anionic dye molecules are conducive to preferential growth of (0 0 1) plane of Mg(OH)_2 crystal for Mg(OH)_2 pigments. • Uniform coverage of nanosized Mg(OH)_2 pigments on fiber surface is achieved via surface-initiated ATRP. • About 4 wt% of Mg(OH)_2 pigment on fiber surface shortens nearly half of burning time of cellulose. - Abstract: Mg(OH)_2 flame retardant hybrid pigment is synthesized through simultaneous solution precipitation and adsorption of anionic dyes (C.I. Acid Red 6). The Mg(OH)_2 hybrid pigment bearing vinyl groups after surface silane modification is immobilized onto the surface of bromo end-functional cellulose fiber by atom transfer radical polymerization (ATRP). The morphology and structure of Mg(OH)_2 pigments and cellulose fibers grafted with modified pigments are characterized. The thermal properties, flammability and color fastness of cellulose fibers grafted with modified pigments are measured. The results reveal that anionic dye molecules are adsorbed onto Mg(OH)_2 crystals and affect the formation of lamella-like Mg(OH)_2 crystals. The cellulose fiber grafted with modified Mg(OH)_2 hybrid pigment absorbs about four times heat more than original cellulose fiber with about 4% immobilization ratio of pigment, which shortens nearly half of afterflame time and afterglow time.

  9. Fabrication of an SPR Sensor Surface with Antifouling Properties for Highly Sensitive Detection of 2,4,6-Trinitrotoluene Using Surface-Initiated Atom Transfer Polymerization

    Directory of Open Access Journals (Sweden)

    Kiyoshi Toko

    2013-07-01

    Full Text Available In this study, we modified a surface plasmon resonance immunosensor chip with a polymer using surface-initiated atom transfer polymerization (SI-ATRP for the highly sensitive detection of 2,4,6-trinitrotoluene (TNT. To immobilize a TNT analogue on the polymer, mono-2-(methacryloyloxyethylsuccinate (MES, which has a carboxyl group, was used in this study. However, the anti-TNT antibody may adsorb non-specifically on the polymer surface by an electrostatic interaction because MES is negatively charged. Therefore, a mixed monomer with MES and diethylaminoethylmethacrylate (DEAEM, which has a tertiary amino group and is positively charged, was prepared to obtain electroneutrality for suppressing the nonspecific adsorption. The detection of TNT was performed by inhibition assay using the polymer surface. To ensure high sensitivity to TNT, the affinity between the surface and the antibody was optimized by controlling the density of the initiator for ATRP by mixing two types of self-assembled monolayer reagents. As a result, a limit of detection of 5.7 pg/mL (ppt for TNT was achieved using the optimized surface.

  10. Surface-Initiated Atom Transfer Radical Polymerization of Magnetite Nanoparticles with Statistical Poly(tert-butyl acrylate-poly(poly(ethylene glycol methyl ether methacrylate Copolymers

    Directory of Open Access Journals (Sweden)

    Patcharin Kanhakeaw

    2015-01-01

    Full Text Available This work presented the surface modification of magnetite nanoparticle (MNP with poly[(t-butyl acrylate-stat-(poly(ethylene glycol methyl ether methacrylate] copolymers (P[(t-BA-stat-PEGMA] via a surface-initiated “grafting from” atom transfer radical polymerization (ATRP. Loading molar ratio of t-BA to PEGMA was systematically varied (100 : 0, 75 : 25, 50 : 50, and 25 : 75, resp. such that the degree of hydrophilicity of the copolymers, affecting the particle dispersibility in water, can be fine-tuned. The reaction progress in each step of the synthesis was monitored via Fourier transform infrared spectroscopy (FTIR. The studies in the reaction kinetics indicated that PEGMA had higher reactivity than that of t-BA in the copolymerizations. Gel permeation chromatography (GPC indicated that the molecular weights of the copolymers increased with the increase of the monomer conversion. Transmission electron microscopy (TEM revealed that the particles were spherical with averaged size of 8.1 nm in diameter. Dispersibility of the particles in water was apparently improved when the copolymers were coated as compared to P(t-BA homopolymer coating. The percentages of MNP and the copolymer in the composites were determined via thermogravimetric analysis (TGA and their magnetic properties were investigated via vibrating sample magnetometry (VSM.

  11. Ternary hybrid polymeric nanocomposites through grafting of polystyrene on graphene oxide-TiO{sub 2} by surface initiated atom transfer radical polymerization (SI-ATRP)

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Arvind; Bansal, Ankushi; Behera, Babita; Jain, Suman L.; Ray, Siddharth S., E-mail: ssray@iip.res.in

    2016-04-01

    A ternary hybrid of graphene oxide-titania-polystyrene (GO-TiO{sub 2}-PS) nanocomposite is developed where polystyrene composition is regulated by controlling growth of polymer chains and nanoarchitectonics is discussed. Graphene Oxide-TiO{sub 2} (GO-TiO{sub 2}) nanocomposite is prepared by in-situ hydrothermal method and the surface is anchored with α-bromoisobutyryl bromide to activate GO-TiO{sub 2} as initiator for polymerization. In-situ grafting of polystyrene through surface initiated atom transfer radical polymerization (SI- ATRP) on this Br-functionalized nano-composite initiator yields GO-TiO{sub 2}-PS ternary hybrid. Varying the monomer amount and keeping the concentration of initiator constant, polystyrene chain growth is regulated with narrow poly-dispersivity to achieve desired composition. This composite is well characterized by various analytical techniques like FTIR, XRD, DSC, SEM, TEM, and TGA. - Highlights: • Nanocomposite of ternary hybrid of GO-TiO{sub 2} with polystyrene. • PS is surface grafted on GO-TiO{sub 2}. • Polymer chain lengths are well regulated by SI-ATRP living polymerization. • Thermal stability of this hybrid is relatively high.

  12. Ternary hybrid polymeric nanocomposites through grafting of polystyrene on graphene oxide-TiO_2 by surface initiated atom transfer radical polymerization (SI-ATRP)

    International Nuclear Information System (INIS)

    Kumar, Arvind; Bansal, Ankushi; Behera, Babita; Jain, Suman L.; Ray, Siddharth S.

    2016-01-01

    A ternary hybrid of graphene oxide-titania-polystyrene (GO-TiO_2-PS) nanocomposite is developed where polystyrene composition is regulated by controlling growth of polymer chains and nanoarchitectonics is discussed. Graphene Oxide-TiO_2 (GO-TiO_2) nanocomposite is prepared by in-situ hydrothermal method and the surface is anchored with α-bromoisobutyryl bromide to activate GO-TiO_2 as initiator for polymerization. In-situ grafting of polystyrene through surface initiated atom transfer radical polymerization (SI- ATRP) on this Br-functionalized nano-composite initiator yields GO-TiO_2-PS ternary hybrid. Varying the monomer amount and keeping the concentration of initiator constant, polystyrene chain growth is regulated with narrow poly-dispersivity to achieve desired composition. This composite is well characterized by various analytical techniques like FTIR, XRD, DSC, SEM, TEM, and TGA. - Highlights: • Nanocomposite of ternary hybrid of GO-TiO_2 with polystyrene. • PS is surface grafted on GO-TiO_2. • Polymer chain lengths are well regulated by SI-ATRP living polymerization. • Thermal stability of this hybrid is relatively high.

  13. Synthesis and characterization of TiO2/Ag/polymer ternary nanoparticles via surface-initiated atom transfer radical polymerization

    International Nuclear Information System (INIS)

    Park, Jung Tae; Koh, Joo Hwan; Seo, Jin Ah; Cho, Yong Soo; Kim, Jong Hak

    2011-01-01

    We report on the novel ternary hybrid materials consisting of semiconductor (TiO 2 ), metal (Ag) and polymer (poly(oxyethylene methacrylate) (POEM)). First, a hydrophilic polymer, i.e. POEM, was grafted from TiO 2 nanoparticles via the surface-initiated atom transfer radical polymerization (ATRP) technique. These TiO 2 -POEM brush nanoparticles were used to template the formation of Ag nanoparticles by introduction of a AgCF 3 SO 3 precursor and a NaBH 4 aqueous solution for reduction process. Successful grafting of polymeric chains from the surface of TiO 2 nanoparticles and the in situ formation of Ag nanoparticles within the polymeric chains were confirmed using transmission electron microscopy (TEM), UV-vis spectroscopy, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). FT-IR spectroscopy also revealed the specific interaction of Ag nanoparticles with the C=O groups of POEM brushes. This study presents a simple route for the in situ synthesis of both metal and polymer confined within the semiconductor, producing ternary hybrid inorganic-organic nanomaterials.

  14. Antibacterial inorganic-organic hybrid coatings on stainless steel via consecutive surface-initiated atom transfer radical polymerization for biocorrosion prevention.

    Science.gov (United States)

    Yuan, S J; Pehkonen, S O; Ting, Y P; Neoh, K G; Kang, E T

    2010-05-04

    To enhance the corrosion resistance of stainless steel (SS) and to impart its surface with antibacterial functionality for inhibiting biofilm formation and biocorrosion, well-defined inorganic-organic hybrid coatings, consisting of a polysilsesquioxane inner layer and quaternized poly(2-(dimethyamino)ethyl methacrylate) (P(DMAEMA)) outer blocks, were prepared via successive surface-initiated atom transfer radical polymerization (ATRP) of 3-(trimethoxysilyl)propyl methacrylate (TMSPMA) and 2-(dimethylamino)ethyl methacrylate (DMAEMA). The cross-linked P(TMASPMA), or polysilsesquioxane, inner layer provided a durable and resistant coating to electrolytes. The pendant tertiary amino groups of the P(DMAEMA) outer block were quaternized with alkyl halide to produce a high concentration of quaternary ammonium groups with biocidal functionality. The so-synthesized inorganic-organic hybrid coatings on the SS substrates exhibited good anticorrosion and antibacterial effects and inhibited biocorrosion induced by sulfate-reducing bacteria (SRB) in seawater media, as revealed by antibacterial assay and electrochemical analyses, and they are potentially useful to steel-based equipment under harsh industrial and marine environments.

  15. Poly(glycidyl methacrylate) grafted CdSe quantum dots by surface-initiated atom transfer radical polymerization: Novel synthesis, characterization, properties, and cytotoxicity studies

    International Nuclear Information System (INIS)

    Bach, Long Giang; Islam, Md. Rafiqul; Lee, Doh Chang; Lim, Kwon Taek

    2013-01-01

    A novel approach for the synthesis of poly(glycidyl methacrylate) grafted CdSe quantum dot (QDs) (PGMA-g-CdSe) was developed. The PGMA-g-CdSe nanohybrids were synthesized by the surface-initiated atom transfer radical polymerization of glycidyl methacrylate from the surface of the strategic initiator, CdSe-BrIB QDs prepared by the interaction of 2-bromoisobutyryl bromide (BrIB) and CdSe-OH QDs. The structure, morphology, and optical property of the PGMA-g-CdSe nanohybrids were analyzed by FT-IR, XPS, TGA, XRD, TEM, and PL. The as-synthesized PGMA-g-CdSe nanohybrids having multi-epoxide groups were employed for the direct coupling of biotin via ring-opening reaction of the epoxide groups to afford the Biotin-f-PGMA-g-CdSe nanobioconjugate. The covalent immobilization of biotin onto PGMA-g-CdSe was confirmed by FT-IR, XPS, and EDX. Biocompatibility and imaging properties of the Biotin-f-PGMA-g-CdSe were investigated by MTT bioassay and PL analysis, respectively. The cell viability study suggested that the biocompatibility was significantly enhanced by the functionalization of CdSe QDs by biotin and PGMA.

  16. Preparation of high-capacity, weak anion-exchange membranes by surface-initiated atom transfer radical polymerization of poly(glycidyl methacrylate) and subsequent derivatization with diethylamine

    International Nuclear Information System (INIS)

    Qian, Xiaolei; Fan, Hua; Wang, Chaozhan; Wei, Yinmao

    2013-01-01

    Ion-exchange membrane is of importance for the development of membrane chromatography. In this work, a high-capacity anion-exchange membrane was prepared by grafting of glycidyl methacrylate (GMA) onto the surface of regenerated cellulose (RC) membranes via surface-initiated atom transfer radical polymerization (SI-ATRP) and subsequent derivatization with diethylamine. Attenuated total reflectance Fourier-transform infrared (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were used to characterize changes in the chemical functionality, surface topography and pore morphology of the modified membranes. The static capacity of the prepared anion-exchange membrane was evaluated with bovine serum albumin (BSA) as a model protein. The results indicated that the anion-exchange membrane which could reach a maximum capacity of 96 mg/mL for static adsorption possesses a higher adsorption capacity, and the adsorption capacity increases with the polymerization time. The effect of pH and salt concentration confirmed that the adsorption of BSA followed ion-exchange mechanism. The established method would have potential application in the preparation of anion-exchange membrane.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2017-03-31

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

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

    International Nuclear Information System (INIS)

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

    2017-01-01

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

  19. Preparation of Transparent Bulk TiO2/PMMA Hybrids with Improved Refractive Indices via an in Situ Polymerization Process Using TiO2 Nanoparticles Bearing PMMA Chains Grown by Surface-Initiated Atom Transfer Radical Polymerization.

    Science.gov (United States)

    Maeda, Satoshi; Fujita, Masato; Idota, Naokazu; Matsukawa, Kimihiro; Sugahara, Yoshiyuki

    2016-12-21

    Transparent TiO 2 /PMMA hybrids with a thickness of 5 mm and improved refractive indices were prepared by in situ polymerization of methyl methacrylate (MMA) in the presence of TiO 2 nanoparticles bearing poly(methyl methacrylate) (PMMA) chains grown using surface-initiated atom transfer radical polymerization (SI-ATRP), and the effect of the chain length of modified PMMA on the dispersibility of modified TiO 2 nanoparticles in the bulk hybrids was investigated. The surfaces of TiO 2 nanoparticles were modified with both m-(chloromethyl)phenylmethanoyloxymethylphosphonic acid bearing a terminal ATRP initiator and isodecyl phosphate with a high affinity for common organic solvents, leading to sufficient dispersibility of the surface-modified particles in toluene. Subsequently, SI-ATRP of MMA was achieved from the modified surfaces of the TiO 2 nanoparticles without aggregation of the nanoparticles in toluene. The molecular weights of the PMMA chains cleaved from the modified TiO 2 nanoparticles increased with increases in the prolonging of the polymerization period, and these exhibited a narrow distribution, indicating chain growth controlled by SI-ATRP. The nanoparticles bearing PMMA chains were well-dispersed in MMA regardless of the polymerization period. Bulk PMMA hybrids containing modified TiO 2 nanoparticles with a thickness of 5 mm were prepared by in situ polymerization of the MMA dispersion. The transparency of the hybrids depended significantly on the chain length of the modified PMMA on the nanoparticles, because the modified PMMA of low molecular weight induced aggregation of the TiO 2 nanoparticles during the in situ polymerization process. The refractive indices of the bulk hybrids could be controlled by adjusting the TiO 2 content and could be increased up to 1.566 for 6.3 vol % TiO 2 content (1.492 for pristine PMMA).

  20. Functionalization of vertically aligned carbon nanotubes with polystyrene via surface initiated reversible addition fragmentation chain transfer polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Macdonald, Thomas; Gibson, Christopher T.; Constantopoulos, Kristina; Shapter, Joseph G. [Flinders Centre for Nanoscale Science and Technology, School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide, SA, 5001 (Australia); Ellis, Amanda V., E-mail: amanda.ellis@flinders.edu.au [Flinders Centre for Nanoscale Science and Technology, School of Chemical and Physical Sciences, Flinders University, GPO Box 2100, Adelaide, SA, 5001 (Australia)

    2012-01-15

    Here we demonstrate the covalent attachment of vertically aligned (VA) acid treated single-walled carbon nanotubes (SWCNTs) onto a silicon substrate via dicyclohexylcarbodiimide (DCC) coupling chemistry. Subsequently, the pendant carboxyl moieties on the sidewalls of the VA-SWCNTs were derivatized to acyl chlorides, and then finally to bis(dithioester) moieties using a magnesium chloride dithiobenzoate salt. The bis(dithioester) moieties were then successfully shown to act as a chain transfer agent (CTA) in the reversible addition fragmentation chain transfer (RAFT) polymerization of styrene in a surface initiated 'grafting-from' process from the VA-SWCNT surface. Atomic force microscopy (AFM) verified vertical alignment of the SWCNTs and the maintenance thereof throughout the synthesis process. Finally, Raman scattering spectroscopy and AFM confirmed polystyrene functionalization.

  1. Functionalization of vertically aligned carbon nanotubes with polystyrene via surface initiated reversible addition fragmentation chain transfer polymerization

    International Nuclear Information System (INIS)

    Macdonald, Thomas; Gibson, Christopher T.; Constantopoulos, Kristina; Shapter, Joseph G.; Ellis, Amanda V.

    2012-01-01

    Here we demonstrate the covalent attachment of vertically aligned (VA) acid treated single-walled carbon nanotubes (SWCNTs) onto a silicon substrate via dicyclohexylcarbodiimide (DCC) coupling chemistry. Subsequently, the pendant carboxyl moieties on the sidewalls of the VA-SWCNTs were derivatized to acyl chlorides, and then finally to bis(dithioester) moieties using a magnesium chloride dithiobenzoate salt. The bis(dithioester) moieties were then successfully shown to act as a chain transfer agent (CTA) in the reversible addition fragmentation chain transfer (RAFT) polymerization of styrene in a surface initiated “grafting-from” process from the VA-SWCNT surface. Atomic force microscopy (AFM) verified vertical alignment of the SWCNTs and the maintenance thereof throughout the synthesis process. Finally, Raman scattering spectroscopy and AFM confirmed polystyrene functionalization.

  2. Protein Compatible Polymer Brushes on Polymeric Substrates Prepared by Surface-Initiated Transfer Radica Polymerization

    DEFF Research Database (Denmark)

    Fristrup, Charlotte Juel; Eskimergen, Rüya; Burkrinsky, J.T.

    2008-01-01

    have been made with model systems of poly(ether ether ketone) (PEEK) films as they can easily be functionalized [1]. Moreover, the inert material polypropylene has successfully beel! activated using a photochemical method [2]. Different polymers including PEG-like matenals have been investigated...... as coating materials. ATR FTIR, water contact angle measurements, Thermal Gravimetric Analysis (TGA), and X-ray Photoelectron Spectroscopy (XPS) confirmed that hydrophilic polymers have been grafted from the surface. The surface topography which was evaluated by Atomic Force Microscopy (AFM) did not change...

  3. Surface PEGylation of mesoporous silica materials via surface-initiated chain transfer free radical polymerization: Characterization and controlled drug release.

    Science.gov (United States)

    Huang, Long; Liu, Meiying; Mao, Liucheng; Huang, Qiang; Huang, Hongye; Wan, Qing; Tian, Jianwen; Wen, Yuanqing; Zhang, Xiaoyong; Wei, Yen

    2017-12-01

    As a new type of mesoporous silica materials with large pore diameter (pore size between 2 and 50nm) and high specific surface areas, SBA-15 has been widely explored for different applications especially in the biomedical fields. The surface modification of SBA-15 with functional polymers has demonstrated to be an effective way for improving its properties and performance. In this work, we reported the preparation of PEGylated SBA-15 polymer composites through surface-initiated chain transfer free radical polymerization for the first time. The thiol group was first introduced on SBA-15 via co-condensation with γ-mercaptopropyltrimethoxysilane (MPTS), that were utilized to initiate the chain transfer free radical polymerization using poly(ethylene glycol) methyl ether methacrylate (PEGMA) and itaconic acid (IA) as the monomers. The successful modification of SBA-15 with poly(PEGMA-co-IA) copolymers was evidenced by a series of characterization techniques, including 1 H NMR, FT-IR, TGA and XPS. The final SBA-15-SH- poly(PEGMA-co-IA) composites display well water dispersity and high loading capability towards cisplatin (CDDP) owing to the introduction of hydrophilic PEGMA and carboxyl groups. Furthermore, the CDDP could be released from SBA-15-SH-poly(PEGMA-co-IA)-CDDP complexes in a pH dependent behavior, suggesting the potential controlled drug delivery of SBA-15-SH-poly(PEGMA-co-IA). More importantly, the strategy should be also useful for fabrication of many other functional materials for biomedical applications owing to the advantages of SBA-15 and well monomer adoptability of chain transfer free radical polymerization. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. Protein repellent hydrophilic grafts prepared by surface-initiated atom transfer radical polymerization from polypropylene

    DEFF Research Database (Denmark)

    Fristrup, Charlotte Juel; Jankova Atanasova, Katja; Eskimergen, Rüya

    2012-01-01

    with Attenuated Total Reflectance (ATR) Fourier Transform Infrared (FTIR) spectroscopy and Water Contact Angle (WCA) measurements. Confocal fluorescence microscopy of modified and unmodified substrates immersed in labelled insulin aspart showed superior repulsion of this protein for the poly(PEGMA) grafts, due...

  5. Surface-Initiated Atom Transfer Radical Polymerization from Electrospun Mats: An Alternative to Nafion

    DEFF Research Database (Denmark)

    Javakhishvili, Irakli; Dimitrov, Ivaylo; Tynelius, Oskar

    2017-01-01

    , respectively. The membrane morphology is probedby scanning electron microscopy. A membrane with protonconductivity as high as 100 mS cm−1 is obtained. Long-termdurability study in direct methanol fuel cells is conducted forover 1500 h demonstrating the viability of this novel facileapproach....

  6. prepared via atom transfer radical polymerization, reverse atom

    Indian Academy of Sciences (India)

    Synthesis and characterization of poly(2-ethylhexyl acrylate) prepared via atom transfer radical polymerization, reverse atom transfer radical polymerization and ... Zydex Industries, 25-A Gandhi Oil Mill Compound, Gorwa, Vadodara 390 016, India; Rubber Technology Centre, Indian Institute of Technology Kharagpur, ...

  7. Transfer of energy in an atom

    International Nuclear Information System (INIS)

    Chemin, J.F.

    2001-01-01

    In most cases the nucleus does not interact with the electron cloud because its energy range is far higher, but in some rare cases electrons from the electron cloud and the nucleus may exchange energy: an electron may de-excite by transferring a part of its energy to the nucleus that becomes itself excited (nuclear excitation by electronic transfer or NEET), conversely electrons can receive energy from the nucleus (bound internal conversion or BIC). For the first time both energy transfers have been observed: a BIC process on a tellurium-125 atom by a French team and a NEET process on a gold-197 atom by a Japanese team. (A.C.)

  8. Atoms in molecules, an axiomatic approach. I. Maximum transferability

    Science.gov (United States)

    Ayers, Paul W.

    2000-12-01

    Central to chemistry is the concept of transferability: the idea that atoms and functional groups retain certain characteristic properties in a wide variety of environments. Providing a completely satisfactory mathematical basis for the concept of atoms in molecules, however, has proved difficult. The present article pursues an axiomatic basis for the concept of an atom within a molecule, with particular emphasis devoted to the definition of transferability and the atomic description of Hirshfeld.

  9. Surface modification of nanodiamond through metal free atom transfer radical polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, Guangjian; Liu, Meiying; Shi, Kexin; Heng, Chunning; Mao, Liucheng; Wan, Qing; Huang, Hongye [Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031 (China); Deng, Fengjie, E-mail: fengjiedeng@aliyun.com [Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031 (China); Zhang, Xiaoyong, E-mail: xiaoyongzhang1980@gmail.com [Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031 (China); Wei, Yen, E-mail: weiyen@tsinghua.edu.cn [Department of Chemistry and the Tsinghua Center for Frontier Polymer Research, Tsinghua University, Beijing, 100084 (China)

    2016-12-30

    Highlights: • Surface modification of ND with water soluble and biocompatible polymers. • Functionalized ND through metal free surface initiated ATRP. • The metal free surface initiated ATRP is rather simple and effective. • The ND-poly(MPC) showed high dispersibility and desirable biocompatibility. - Abstract: Surface modification of nanodiamond (ND) with poly(2-methacryloyloxyethyl phosphorylcholine) [poly(MPC)] has been achieved by using metal free surface initiated atom transfer radical polymerization (SI-ATRP). The ATRP initiator was first immobilized on the surface of ND through direct esterification reaction between hydroxyl group of ND and 2-bromoisobutyryl bromide. The initiator could be employed to obtain ND-poly(MPC) nanocomposites through SI-ATRP using an organic catalyst. The final functional materials were characterized by {sup 1}H nuclear magnetic resonance, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and thermo gravimetric analysis in detailed. All of these characterization results demonstrated that ND-poly(MPC) have been successfully obtained via metal free photo-initiated SI-ATRP. The ND-poly(MPC) nanocomposites shown enhanced dispersibility in various solvents as well as excellent biocompatibility. As compared with traditional ATRP, the metal free ATRP is rather simple and effective. More importantly, this preparation method avoided the negative influence of metal catalysts. Therefore, the method described in this work should be a promising strategy for fabrication of polymeric nanocomposites with great potential for different applications especially in biomedical fields.

  10. Surface modification of nanodiamond through metal free atom transfer radical polymerization

    International Nuclear Information System (INIS)

    Zeng, Guangjian; Liu, Meiying; Shi, Kexin; Heng, Chunning; Mao, Liucheng; Wan, Qing; Huang, Hongye; Deng, Fengjie; Zhang, Xiaoyong; Wei, Yen

    2016-01-01

    Highlights: • Surface modification of ND with water soluble and biocompatible polymers. • Functionalized ND through metal free surface initiated ATRP. • The metal free surface initiated ATRP is rather simple and effective. • The ND-poly(MPC) showed high dispersibility and desirable biocompatibility. - Abstract: Surface modification of nanodiamond (ND) with poly(2-methacryloyloxyethyl phosphorylcholine) [poly(MPC)] has been achieved by using metal free surface initiated atom transfer radical polymerization (SI-ATRP). The ATRP initiator was first immobilized on the surface of ND through direct esterification reaction between hydroxyl group of ND and 2-bromoisobutyryl bromide. The initiator could be employed to obtain ND-poly(MPC) nanocomposites through SI-ATRP using an organic catalyst. The final functional materials were characterized by 1 H nuclear magnetic resonance, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and thermo gravimetric analysis in detailed. All of these characterization results demonstrated that ND-poly(MPC) have been successfully obtained via metal free photo-initiated SI-ATRP. The ND-poly(MPC) nanocomposites shown enhanced dispersibility in various solvents as well as excellent biocompatibility. As compared with traditional ATRP, the metal free ATRP is rather simple and effective. More importantly, this preparation method avoided the negative influence of metal catalysts. Therefore, the method described in this work should be a promising strategy for fabrication of polymeric nanocomposites with great potential for different applications especially in biomedical fields.

  11. Electron transfer, ionization, and excitation atomic collisions

    International Nuclear Information System (INIS)

    Winter, T.G.; Alston, S.G.

    1990-01-01

    Basic atomic-collision processes at intermediate and high energies are being studied theoretically at Penn State by Alston and Winter. In the high velocity regime, single-electron capture is treated using a high order multiple-scattering approach; extensive comparison with experiment and analysis of mechanisms have been made. Fitting the calculated amplitude with a simple analytic form, the asymptotic velocity dependence of the cross section is obtained. The effect on the capture amplitude of altering the inner part of the internuclear potential has also been explored. In the intermediate velocity regime, earlier work on collisions between protons and hydrogenic-ion targets using a coupled-state approach is being extended to the two-electron helium target. 29 refs

  12. [Electron transfer, ionization and excitation in atomic collisions

    International Nuclear Information System (INIS)

    1991-01-01

    The research being carried out at Penn State by Winter and Alston addresses the fundamental atomic-collision processes of electron transfer, ionization, and excitation. Winter has focussed attention on intermediate and, more recently, higher collision energies -- proton energies of at least about 50 keV -- for which coupled-state approaches are appropriate. Alston has concentrated on perturbative approaches to symmetric ion-ion/atom collisions at high energies and to asymmetric collisions at intermediate to high energies

  13. Muon transfer from hot muonic hydrogen atoms to neon

    International Nuclear Information System (INIS)

    Jacot-Guillarmod, R.; Beer, G.A.; Knowles, P.E.; Mason, G.R.; Olin, A.; Beveridge, J.L.; Marshall, G.M.; Brewer, J.H.; Forster, B.M.; Huber, T.M.; Kammel, P.; Zmeskal, J.; Petitjean, C.

    1992-01-01

    A negative muon beam has been directed on adjacent solid layers of hydrogen and neon. Three targets differing by their deuterium concentration were investigated. Muonic hydrogen atoms can drift to the neon layer where the muon is immediately transferred. The time structure of the muonic neon X-rays follows the exponential law with a disappearance rate corresponding to the one of μ -p atoms in each target. The rates λ ppμ and λ pd can be extracted

  14. Atom transfer radical polymerization of styrene under pulsed microwave irradiation

    International Nuclear Information System (INIS)

    Cheng Zhenping; Zhu Xiulin; Zhou Nianchen; Zhu Jian; Zhang Zhengbiao

    2005-01-01

    A homogeneous solution atom transfer radical polymerization (ATRP) and reverse atom transfer radical polymerization (RATRP) of styrene (St) in N,N-dimethylformamide (DMF) were successfully carried out under pulsed microwave irradiation (PMI), using 1-bromo-1-phenylethane (1-PEBr)/CuCl/N,N,N',N'',N''-pentamethyldiethylenetriamine (PMDETA) as an initiating system at 85 deg. C and 2,2'-azo-bis-isobutyrontrile (AIBN)/CuCl 2 /PMDETA as an initiating system at 95 deg. C, respectively. The polymerization rates under PMI were greatly increased in comparison with those under identical conventional heating (CH)

  15. Monomode microwave-assisted atom transfer radical polymerization

    NARCIS (Netherlands)

    Zhang, H.; Schubert, U.S.

    2004-01-01

    The first monomode microwave-assisted atom transfer radical polymerization (ATRP) is reported. The ATRP of methyl methacrylate was successfully performed with microwave heating, which was well controlled and provided almost the same results as experiments with conventional heating, demonstrating the

  16. Atom transfer radical copolymerization of styrene and butyl acrylate

    NARCIS (Netherlands)

    Chambard, G.; Klumperman, B.; Matyjaszewski, K.

    2000-01-01

    Atom transfer radical polymerization of styrene and butyl acrylate has been investigated from a kinetic point of view. Attention is focused on the activation of the dormant species as well as on the termination that plays a role in these reactions. It has been shown that the activation of a styrene

  17. Collisions involving energy transfer between atoms with large angular moments

    International Nuclear Information System (INIS)

    Vdovin, Yu.A.; Galitskij, V.M.

    1975-01-01

    Study is made of the collisions of excited and nonexcited atoms with a small resonance defect, assuming that the excited and ground states of each atom are bound via an allowed dipole transition and that intrinsic moments of states are great. In such an approximation the atomic interaction is defined by a dipole-dipole interaction operator. Equations for amplitudes are derived for two cases: (1) the first atom is in an excited state while the second is in the ground state and (2) the first atom is in the ground state while the second is in an excited state. The problem is solved in the approximation that the moments of the excited and ground states of each atom are equal. An expression for the excitation transfer cross section is written down. Analysis of this expression shows that the excitation transfer cross section at first increases with removal from the exact resonance and reaches resonance at lambda approximately 0.1 (lambda is a dimensionless parameter which is equal to the ratio of the resonance defect Δ to the interaction at spacings of the order of the Weisskopf radius). Only at lambda >0.16 does the cross section become smaller than the resonance one. This effect is due to the interaction Hamiltonian approximation adopted in the present study

  18. Transfer matrix treatment of atomic chemisorption on transition metal surface

    International Nuclear Information System (INIS)

    Mariz, A.M.; Koiller, B.

    1980-05-01

    The atomic adsorption of hydrogen on paramagnetic nickel 100 surface is studied, using the Green's function formalism and the transfer matrix technique, which allows the treatment of the geometry of the system in a simple manner. Electronic correlation at the adatom orbital in a self consistent Hartree-Fock approach is incorporated. The adsorption energy, local density of states and charge transfer between the solid and the adatom are calculated for different crystal structures (sc and fcc) and adatom positions at the surface. The results are discussed in comparison with other theories and with available experimental data, with satisfactory agreement. (Author) [pt

  19. Living atom transfer radical polymerization of 4-acetoxystyrene

    DEFF Research Database (Denmark)

    Gao, Bo; Chen, Xianyi; Ivan, Bela

    1997-01-01

    Living atom transfer radical polymerization (ATRP) of 4-acetoxystyrene (1), a protected 4-vinylphenol, leading to poly(4-acetoxystyrene) with well-defined molecular weight and narrow molecular weight distribution was carried out in bulk with a,a'-dibromoxylene(2)/CuBr/2,2-bipyridine(bpy) as initi......Living atom transfer radical polymerization (ATRP) of 4-acetoxystyrene (1), a protected 4-vinylphenol, leading to poly(4-acetoxystyrene) with well-defined molecular weight and narrow molecular weight distribution was carried out in bulk with a,a'-dibromoxylene(2)/CuBr/2,2-bipyridine......(bpy) as initiating system. A linear (M) over bar(n), versus monomer conversion plot was found in good accordance with the theoretical line, indicating 100% initiating efficiency. The polymerization is first order in respect to monomer up to about 70% monomer conversion. Deviations from linearity at higher conversion...

  20. Catalytic enantioselective alkene aminohalogenation/cyclization involving atom transfer.

    Science.gov (United States)

    Bovino, Michael T; Chemler, Sherry R

    2012-04-16

    Problem solved: the title reaction was used for the synthesis of chiral 2-bromo, chloro, and iodomethyl indolines and 2-iodomethyl pyrrolidines. Stereocenter formation is believed to occur by enantioselective cis aminocupration and C-X bond formation is believed to occur by atom transfer. The ultility of the products as versatile synthetic intermediates was demonstrated, as was a radical cascade cyclization sequence. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Symmetric large momentum transfer for atom interferometry with BECs

    Science.gov (United States)

    Abend, Sven; Gebbe, Martina; Gersemann, Matthias; Rasel, Ernst M.; Quantus Collaboration

    2017-04-01

    We develop and demonstrate a novel scheme for a symmetric large momentum transfer beam splitter for interferometry with Bose-Einstein condensates. Large momentum transfer beam splitters are a key technique to enhance the scaling factor and sensitivity of an atom interferometer and to create largely delocalized superposition states. To realize the beam splitter, double Bragg diffraction is used to create a superposition of two symmetric momentum states. Afterwards both momentum states are loaded into a retro-reflected optical lattice and accelerated by Bloch oscillations on opposite directions, keeping the initial symmetry. The favorable scaling behavior of this symmetric acceleration, allows to transfer more than 1000 ℏk of total differential splitting in a single acceleration sequence of 6 ms duration while we still maintain a fraction of approx. 25% of the initial atom number. As a proof of the coherence of this beam splitter, contrast in a closed Mach-Zehnder atom interferometer has been observed with up to 208 ℏk of momentum separation, which equals a differential wave-packet velocity of approx. 1.1 m/s for 87Rb. The presented work is supported by the CRC 1128 geo-Q and the DLR with funds provided by the Federal Ministry of Economic Affairs and Energy (BMWi) due to an enactment of the German Bundestag under Grant No. DLR 50WM1552-1557 (QUANTUS-IV-Fallturm).

  2. The coordination and atom transfer chemistry of titanium porphyrin complexes

    Energy Technology Data Exchange (ETDEWEB)

    Hays, James Allen [Iowa State Univ., Ames, IA (United States)

    1993-11-05

    Preparation, characterization, and reactivity of (η2- alkyne)(meso-tetratolylpoprphrinato)titanium(II) complexes are described, along with inetermetal oxygen atom transfer reactions involving Ti(IV) and Ti(III) porphyrin complexes. The η2- alkyne complexes are prepared by reaction of (TTP)TiCl2 with LiAlH4 in presence of alkyne. Structure of (OEP)Ti(η2-Ph-C≡C-Ph) (OEP=octaethylporphryin) was determined by XRD. The compounds undergo simple substitution to displace the alkyne and produce doubly substituted complexes. Structure of (TTP)Ti(4-picoline)2 was also determined by XRD. Reaction of (TTP)Ti=O with (OEP)Ti-Cl yields intermetal O/Cl exchange, which is a one-electron redox process mediated by O atom transfer. Also a zero-electron redox process mediated by atom transfer is observed when (TTP)TiCl2 is reacted with (OEP)Ti=O.

  3. Enhanced protein retention on poly(caprolactone) via surface initiated polymerization of acrylamide

    International Nuclear Information System (INIS)

    Ma, Yuhao; Cai, Mengtan; He, Liu; Luo, Xianglin

    2016-01-01

    Graphical abstract: - Highlights: • Dense package of poly(acrylamide) on poly(caprolactone) surface was achieved by surface-initiated atom transfer radical polymerization. • Poly(acrylamide) grafted surface exhibited high protein retention ability. • Loaded protein was resistant to detachment and maintained its structure without denaturation. - Abstract: To enhance the biocompatibility or extend the biomedical application of poly(caprolactone) (PCL), protein retention on PCL surface is often required. In this study, poly(acrylamide) (PAAm) brushes were grown from PCL surface via surface-initiated atom transfer radical polymerization (SI-ATRP) and served as a protein-capturing platform. Grafted PAAm was densely packed on surface and exhibited superior protein retention ability. Captured protein was found to be resistant to washing under detergent environment. Furthermore, protein structure after being captured was investigated by circular dichroism (CD) spectroscopy, and the CD spectra verified that secondary structure of captured proteins was maintained, indicating no denaturation of protein happened for retention process.

  4. Hydropersulfides: H-Atom Transfer Agents Par Excellence.

    Science.gov (United States)

    Chauvin, Jean-Philippe R; Griesser, Markus; Pratt, Derek A

    2017-05-10

    Hydropersulfides (RSSH) are formed endogenously via the reaction of the gaseous biotransmitter hydrogen sulfide (H 2 S) and disulfides (RSSR) and/or sulfenic acids (RSOH). RSSH have been investigated for their ability to store H 2 S in vivo and as a line of defense against oxidative stress, from which it is clear that RSSH are much more reactive to two-electron oxidants than thiols. Herein we describe the results of our investigations into the H-atom transfer chemistry of RSSH, contrasting it with the well-known H-atom transfer chemistry of thiols. In fact, RSSH are excellent H-atom donors to alkyl (k ∼ 5 × 10 8 M -1 s -1 ), alkoxyl (k ∼ 1 × 10 9 M -1 s -1 ), peroxyl (k ∼ 2 × 10 6 M -1 s -1 ), and thiyl (k > 1 × 10 10 M -1 s -1 ) radicals, besting thiols by as little as 1 order and as much as 4 orders of magnitude. The inherently high reactivity of RSSH to H-atom transfer is based largely on thermodynamic factors; the weak RSS-H bond dissociation enthalpy (∼70 kcal/mol) and the associated high stability of the perthiyl radical make the foregoing reactions exothermic by 15-34 kcal/mol. Of particular relevance in the context of oxidative stress is the reactivity of RSSH to peroxyl radicals, where favorable thermodynamics are bolstered by a secondary orbital interaction in the transition state of the formal H-atom transfer that drives the inherent reactivity of RSSH to match that of α-tocopherol (α-TOH), nature's premier radical-trapping antioxidant. Significantly, the reactivity of RSSH eclipses that of α-TOH in H-bond-accepting media because of their low H-bond acidity (α 2 H ∼ 0.1). This affords RSSH a unique versatility compared to other highly reactive radical-trapping antioxidants (e.g., phenols, diarylamines, hydroxylamines, sulfenic acids), which tend to have high H-bond acidities. Moreover, the perthiyl radicals that result are highly persistent under autoxidation conditions and undergo very rapid dimerization (k = 5 × 10 9 M -1 s -1 ) in

  5. Charge transfer between O6+ and atomic hydrogen

    Science.gov (United States)

    Wu, Y.; Stancil, P. C.; Liebermann, H. P.; Buenker, R. J.; Schultz, D. R.; Hui, Y.

    2011-05-01

    The charge exchange process has been found to play a dominant role in the production of X-rays and/or EUV photons observed in cometary and planetary atmospheres and from the heliosphere. Charge transfer cross sections, especially state-selective cross sections, are necessary parameters in simulations of X-ray emission. In the present work, charge transfer due to collisions of ground state O6+(1s2 1 S) with atomic hydrogen has been investigated theoretically using the quantum-mechanical molecular-orbital close-coupling method (QMOCC). The multi-reference single- and double-excitation configuration interaction approach (MRDCI) has been applied to compute the adiabatic potential and nonadiabatic couplings, and the atomic basis sets used have been optimized with the method proposed previously to obtain precise potential data. Total and state-selective cross sections are calculated for energies between 10 meV/u and 10 keV/u. The QMOCC results are compared to available experimental and theoretical data as well as to new atomic-orbital close-coupling (AOCC) and classical trajectory Monte Carlo (CTMC) calculations. A recommended set of cross sections, based on the MOCC, AOCC, and CTMC calculations, is deduced which should aid in X-ray modeling studies.

  6. Constructing Functional Ionic Membrane Surface by Electrochemically Mediated Atom Transfer Radical Polymerization

    Directory of Open Access Journals (Sweden)

    Fen Ran

    2016-01-01

    Full Text Available The sodium polyacrylate (PAANa contained polyethersulfone membrane that was fabricated by preparation of PES-NH2 via nonsolvent phase separation method, the introduction of bromine groups as active sites by grafting α-Bromoisobutyryl bromide, and surface-initiated electrochemically atom transfer radical polymerization (SI-eATRP of sodium acrylate (AANa on the surface of PES membrane. The polymerization could be controlled by reaction condition, such as monomer concentration, electric potential, polymerization time, and modifier concentration. The membrane surface was uniform when the monomer concentration was 0.9 mol/L, the electric potential was −0.12 V, the polymerization time was 8 h, and the modifier concentration was 2 wt.%. The membrane showed excellent hydrophilicity and blood compatibility. The water contact angle decreased from 84° to 68° and activated partial thromboplastin increased from 51 s to 84 s after modification of the membranes.

  7. Surface modification of nanodiamond through metal free atom transfer radical polymerization

    Science.gov (United States)

    Zeng, Guangjian; Liu, Meiying; Shi, Kexin; Heng, Chunning; Mao, Liucheng; Wan, Qing; Huang, Hongye; Deng, Fengjie; Zhang, Xiaoyong; Wei, Yen

    2016-12-01

    Surface modification of nanodiamond (ND) with poly(2-methacryloyloxyethyl phosphorylcholine) [poly(MPC)] has been achieved by using metal free surface initiated atom transfer radical polymerization (SI-ATRP). The ATRP initiator was first immobilized on the surface of ND through direct esterification reaction between hydroxyl group of ND and 2-bromoisobutyryl bromide. The initiator could be employed to obtain ND-poly(MPC) nanocomposites through SI-ATRP using an organic catalyst. The final functional materials were characterized by 1H nuclear magnetic resonance, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and thermo gravimetric analysis in detailed. All of these characterization results demonstrated that ND-poly(MPC) have been successfully obtained via metal free photo-initiated SI-ATRP. The ND-poly(MPC) nanocomposites shown enhanced dispersibility in various solvents as well as excellent biocompatibility. As compared with traditional ATRP, the metal free ATRP is rather simple and effective. More importantly, this preparation method avoided the negative influence of metal catalysts. Therefore, the method described in this work should be a promising strategy for fabrication of polymeric nanocomposites with great potential for different applications especially in biomedical fields.

  8. Design of UV-absorbing PVDF membrane via surface-initiated AGET ATRP

    Science.gov (United States)

    Dong, Li; Liu, Xiangdong; Xiong, Zhengrong; Sheng, Dekun; Zhou, Yan; Lin, Changhong; Yang, Yuming

    2018-03-01

    Herein, PVDF membranes with excellent UV-absorbing property were first synthesized through grafting the polymerizable low-molecular-weight organic UV-absorber 2-hydroxy-4-(3-methacryloxy-2-hydroxylpropoxy) benzophenone (BPMA) onto α-bromoester-functionalized PVDF membranes via the surface-initiated activator generated by electron transfer atom transfer radical polymerization (SI-AGET ATRP). The surface initiators were immobilized by the reaction between 2-bromoisobutyryl bromide (BIBB) and the hydroxylated PVDF membranes. PVDF-g-PBPMA membranes with different grafting densities were obtained by tuning the polymerization time and the modified membranes were characterized by 1H-NMR, FT-IR, XPS, SEM, UV-vis Spectrophotometer, TGA and DSC. The experimental results indicated that PBPMA chains were successfully introduced onto PVDF membranes. Most importantly, the PVDF-g-PBPMA membranes exhibited outstanding UV-shielding property. UV-vis transmittance spectra showed that most UV light below 360 nm could be absorbed by PVDF-g-PBPMA membranes and the whole UV light region (200-400 nm) can be blocked with the reaction time increased.

  9. The pentafluorostyrene endeavours with atom transfer radical polymerization - quo vadis?

    DEFF Research Database (Denmark)

    Hvilsted, Søren

    2014-01-01

    The versatility of the atom transfer radical polymerization (ATRP) of pentafluorostyrene (FS) is comprehensively evaluated. The ATRP of a wide range of monomers derived from FS is likewise discussed with emphasis on the potential polymer applications. A large number of block and star copolymers...... centred around polypentafluorostyrene (PFS) and prepared primarily using the bromomacroinitiator concept is surveyed. Here the main emphasis is on the feasibility of the polymer design, but also the very many different applications are highlighted. The potential grafting onto PFS and PFS block copolymers...... by exploitation of the very labile para-fluorine demonstrates new material architecture possibilities through very mild reaction conditions. Finally the utility of PFS in various conducting materials is elaborated. The amphiphilic nature of PFS in triblock copolymers with polyethers has been exploited for Li+ ion...

  10. Charge transfer of O3+ ions with atomic hydrogen

    International Nuclear Information System (INIS)

    Wang, J.G.; Stancil, P.C.; Turner, A.R.; Cooper, D.L.

    2003-01-01

    Charge transfer processes due to collisions of ground state O 3+ (2s 2 2p 2 P) ions with atomic hydrogen are investigated using the quantum-mechanical molecular-orbital close-coupling (MOCC) method. The MOCC calculations utilize ab initio adiabatic potentials and nonadiabatic radial and rotational coupling matrix elements obtained with the spin-coupled valence-bond approach. Total and state-selective cross sections and rate coefficients are presented. Comparison with existing experimental and theoretical data shows our results to be in better agreement with the measurements than the previous calculations, although problems with some of the state-selective measurements are noted. Our calculations demonstrate that rotational coupling is not important for the total cross section, but for state-selective cross sections, its relevance increases with energy. For the ratios of triplet to singlet cross sections, significant departures from a statistical value are found, generally in harmony with experiment

  11. Charge transfer of O3+ ions with atomic hydrogen

    Science.gov (United States)

    Wang, J. G.; Stancil, P. C.; Turner, A. R.; Cooper, D. L.

    2003-01-01

    Charge transfer processes due to collisions of ground state O3+(2s22p 2P) ions with atomic hydrogen are investigated using the quantum-mechanical molecular-orbital close-coupling (MOCC) method. The MOCC calculations utilize ab initio adiabatic potentials and nonadiabatic radial and rotational coupling matrix elements obtained with the spin-coupled valence-bond approach. Total and state-selective cross sections and rate coefficients are presented. Comparison with existing experimental and theoretical data shows our results to be in better agreement with the measurements than the previous calculations, although problems with some of the state-selective measurements are noted. Our calculations demonstrate that rotational coupling is not important for the total cross section, but for state-selective cross sections, its relevance increases with energy. For the ratios of triplet to singlet cross sections, significant departures from a statistical value are found, generally in harmony with experiment.

  12. Electron transfer, ionization, and excitation in atomic collisions

    International Nuclear Information System (INIS)

    Winter, T.G.; Alston, S.G.

    1992-01-01

    The research being carried out at Penn State by Winter and Alston addresses the fundamental processes of electron transfer, ionization, and excitation in ion-atom (and ion-ion) collisions. The focus is on intermediate- and higher-energy collisions, corresponding to proton energies of about 25 kilo-electron-volts (keV) or larger. At intermediate energies, where the transition probabilities are not small, many states must be coupled in a large calculation, while at higher energies, perturbative approaches may be used. Several studies have been carried out in the current three-year period; most of these treat systems with only one or two electrons, so that fewer approximations need be made and the basic collisional mechanisms can be more clearly described

  13. Effect of Inhibitors on Atom Transfer Radical Polymerization of MMA

    Institute of Scientific and Technical Information of China (English)

    张鸿; 徐冬梅; 张可达

    2005-01-01

    Effect of a series of inhibitors as additives on atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) with FeCl2/PPh3 as catalyst system was studied, including 2,4,6-trinitrophenol (TNP), 4-methoxyphenol (4-MP), hydroquinone (HQ) and nitrobenzene (NB). It was found that TNP was the only. efficient additive for ATRP among these inhibitors. In the presence of small amounts of TNP, the polymerization proceeded rapidly after induction period to yield the polymers with controlled molecular weights and narrow molecular weight distributions (MWD). The initiating efficiency of the modified catalyst system with TNP was increased. The mechanism was proposed and confirmed by the end group analysis of the polymer.

  14. Functionalization of lanthanum hydroxide nanowires by atom transfer radical polymerization

    International Nuclear Information System (INIS)

    Zhou Mi; Yuan Jinying; Yuan Weizhong; Yin Yingwu; Hong Xiaoyin

    2007-01-01

    Atom transfer radical polymerization (ATRP) has been used to prepare a core-shell hybrid nanostructure successfully: a hard core of single-crystalline lanthanum hydroxide nanowires and a soft shell of polystyrene (PS) brushes. Transmission electron microscopy (TEM) images indicated that the resulting products presented special structures and different thicknesses of polymer layers. The chemical components and grafted PS quantities of the samples were measured by Fourier transform infrared (FT-IR) spectroscopy and thermogravimetric analysis (TGA). The polymers showed narrow polydispersity, which proved that the lanthanum hydroxide nanowires initiated the 'living'/controlled polymerization of styrene. With the modifiability of lanthanum hydroxide nanowires, the solubility increased, which affords a new way to functionalize nanowires

  15. [Electron transfer, ionization, and excitation in atomic collisions

    International Nuclear Information System (INIS)

    1992-01-01

    Fundamental processes of electron transfer, ionization, and excitation in ion-atom and ion-ion collisions are studied. Attention is focussed on one- and two-electron systems and, more recently, quasi-one-electron systems whose electron-target-ion core can be accurately modeled by one-electron potentials. The basic computational approaches can then be taken with few, if any, approximations, and the underlying collisional mechanisms can be more clearly revealed. At intermediate collision energies (e.g., proton energies for p-He + collisions on the order of 100 kilo-electron volts), many electronic states are strongly coupled during the collision, a coupled-state approach, such as a coupled-Sturmian-pseudostate approach, is appropriate. At higher collision energies (million electron-volt energies) the coupling is weaker with, however, many more states being coupled together, so that high-order perturbation theory is essential

  16. Temperature-dependent kinetics of charge transfer, hydrogen-atom transfer, and hydrogen-atom expulsion in the reaction of CO+ with CH4 and CD4.

    Science.gov (United States)

    Melko, Joshua J; Ard, Shaun G; Johnson, Ryan S; Shuman, Nicholas S; Guo, Hua; Viggiano, Albert A

    2014-09-18

    We have determined the rate constants and branching ratios for the reactions of CO(+) with CH4 and CD4 in a variable-temperature selected ion flow tube. We find that the rate constants are collisional for all temperatures measured (193-700 K for CH4 and 193-500 K for CD4). For the CH4 reaction, three product channels are identified, which include charge transfer (CH4(+) + CO), H-atom transfer (HCO(+) + CH3), and H-atom expulsion (CH3CO(+) + H). H-atom transfer is slightly preferred to charge transfer at low temperature, with the charge-transfer product increasing in contribution as the temperature is increased (H-atom expulsion is a minor product for all temperatures). Analogous products are identified for the CD4 reaction. Density functional calculations on the CO(+) + CH4 reaction were also conducted, revealing that the relative temperature dependences of the charge-transfer and H-atom transfer pathways are consistent with an initial charge transfer followed by proton transfer.

  17. Surface modification of hydroxyapatite with poly(methyl methacrylate) via surface-initiated ATRP

    Energy Technology Data Exchange (ETDEWEB)

    Wang Yan; Zhang Xi; Yan Jinliang; Xiao Yan [Shanghai Key Laboratory of Advanced Polymeric Materials, Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237 (China); Lang Meidong, E-mail: mdlang@ecust.edu.cn [Shanghai Key Laboratory of Advanced Polymeric Materials, Key Laboratory for Ultrafine Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai 200237 (China)

    2011-05-01

    This article describes the fabrication of hydroxyapatite (HAP) nanocomposites grafted with poly(methyl methacrylate) (PMMA). Surface-initiated atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) was carried out from hydroxyapatite particles derivatized with ATRP initiators. The structure and properties of the nanocomposites were investigated by thermogravimetric analysis (TGA), transmission electron microscopy (TEM), differential scanning calorimeter (DSC) measurements, and contact angle analyses. TGA was used to estimate the grafting density of ATRP initiators (0.49 initiator/nm{sup 2}) and the amount of grafted PMMA on the HAP surface. The contact angle analyses indicated that grafting PMMA onto the HAP surface dramatically increased the hydrophobicity of the surface. Moreover, the HAP nanocomposites showed excellent dispersibility in both aqueous solution and organic solvent.

  18. Surface modification of hydroxyapatite with poly(methyl methacrylate) via surface-initiated ATRP

    International Nuclear Information System (INIS)

    Wang Yan; Zhang Xi; Yan Jinliang; Xiao Yan; Lang Meidong

    2011-01-01

    This article describes the fabrication of hydroxyapatite (HAP) nanocomposites grafted with poly(methyl methacrylate) (PMMA). Surface-initiated atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) was carried out from hydroxyapatite particles derivatized with ATRP initiators. The structure and properties of the nanocomposites were investigated by thermogravimetric analysis (TGA), transmission electron microscopy (TEM), differential scanning calorimeter (DSC) measurements, and contact angle analyses. TGA was used to estimate the grafting density of ATRP initiators (0.49 initiator/nm 2 ) and the amount of grafted PMMA on the HAP surface. The contact angle analyses indicated that grafting PMMA onto the HAP surface dramatically increased the hydrophobicity of the surface. Moreover, the HAP nanocomposites showed excellent dispersibility in both aqueous solution and organic solvent.

  19. Palladium-Catalyzed Atom-Transfer Radical Cyclization at Remote Unactivated C(sp3 )-H Sites: Hydrogen-Atom Transfer of Hybrid Vinyl Palladium Radical Intermediates.

    Science.gov (United States)

    Ratushnyy, Maxim; Parasram, Marvin; Wang, Yang; Gevorgyan, Vladimir

    2018-03-01

    A novel mild, visible-light-induced palladium-catalyzed hydrogen atom translocation/atom-transfer radical cyclization (HAT/ATRC) cascade has been developed. This protocol involves a 1,5-HAT process of previously unknown hybrid vinyl palladium radical intermediates, thus leading to iodomethyl carbo- and heterocyclic structures. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Tape transfer atomization patterning of liquid alloys for microfluidic stretchable wireless power transfer.

    Science.gov (United States)

    Jeong, Seung Hee; Hjort, Klas; Wu, Zhigang

    2015-02-12

    Stretchable electronics offers unsurpassed mechanical compliance on complex or soft surfaces like the human skin and organs. To fully exploit this great advantage, an autonomous system with a self-powered energy source has been sought for. Here, we present a new technology to pattern liquid alloys on soft substrates, targeting at fabrication of a hybrid-integrated power source in microfluidic stretchable electronics. By atomized spraying of a liquid alloy onto a soft surface with a tape transferred adhesive mask, a universal fabrication process is provided for high quality patterns of liquid conductors in a meter scale. With the developed multilayer fabrication technique, a microfluidic stretchable wireless power transfer device with an integrated LED was demonstrated, which could survive cycling between 0% and 25% strain over 1,000 times.

  1. Proton-coupled electron transfer versus hydrogen atom transfer: generation of charge-localized diabatic states.

    Science.gov (United States)

    Sirjoosingh, Andrew; Hammes-Schiffer, Sharon

    2011-03-24

    The distinction between proton-coupled electron transfer (PCET) and hydrogen atom transfer (HAT) mechanisms is important for the characterization of many chemical and biological processes. PCET and HAT mechanisms can be differentiated in terms of electronically nonadiabatic and adiabatic proton transfer, respectively. In this paper, quantitative diagnostics to evaluate the degree of electron-proton nonadiabaticity are presented. Moreover, the connection between the degree of electron-proton nonadiabaticity and the physical characteristics distinguishing PCET from HAT, namely, the extent of electronic charge redistribution, is clarified. In addition, a rigorous diabatization scheme for transforming the adiabatic electronic states into charge-localized diabatic states for PCET reactions is presented. These diabatic states are constructed to ensure that the first-order nonadiabatic couplings with respect to the one-dimensional transferring hydrogen coordinate vanish exactly. Application of these approaches to the phenoxyl-phenol and benzyl-toluene systems characterizes the former as PCET and the latter as HAT. The diabatic states generated for the phenoxyl-phenol system possess physically meaningful, localized electronic charge distributions that are relatively invariant along the hydrogen coordinate. These diabatic electronic states can be combined with the associated proton vibrational states to generate the reactant and product electron-proton vibronic states that form the basis of nonadiabatic PCET theories. Furthermore, these vibronic states and the corresponding vibronic couplings may be used to calculate rate constants and kinetic isotope effects of PCET reactions.

  2. Synthesis of thermoresponsive poly(N-isopropylacrylamide) brush on silicon wafer surface via atom transfer radical polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Turan, Eylem; Demirci, Serkan [Department of Chemistry, Faculty of Art and Science, Gazi University, 06500 Besevler, Ankara (Turkey); Caykara, Tuncer, E-mail: caykara@gazi.edu.t [Department of Chemistry, Faculty of Art and Science, Gazi University, 06500 Besevler, Ankara (Turkey)

    2010-08-31

    Thermoresponsive poly(N-isopropylacrylamide) [poly(NIPAM)] brush on silicon wafer surface was prepared by combining the self-assembled monolayer of initiator and atom transfer radical polymerization (ATRP). The resulting polymer brush was characterized by in situ reflectance Fourier transform infrared spectroscopy, atomic force microscopy and ellipsometry techniques. Gel permeation chromatography determination of the number-average molecular weight and polydispersity index of the brush detached from the silicon wafer surface suggested that the surface-initiated ATRP method can provide relatively homogeneous polymer brush. Contact angle measurements exhibited a two-stage increase upon heating over the board temperature range 25-45 {sup o}C, which is in contrast to the fact that free poly(NIPAM) homopolymer in aqueous solution exhibits a phase transition at ca. 34 {sup o}C within a narrow temperature range. The first de-wetting transition takes place at 27 {sup o}C, which can be tentatively attributed to the n-cluster induced collapse of the inner region of poly(NIPAM) brush close to the silicon surface; the second de-wetting transition occurs at 38 {sup o}C, which can be attributed to the outer region of poly(NIPAM) brush, possessing much lower chain density compared to that of the inner part.

  3. A phenomenological model for collisional coherence transfer in an optically pumped atomic system

    Energy Technology Data Exchange (ETDEWEB)

    Khanbekyan, K; Bevilaqua, G; Mariotti, E; Moi, L [Universita degli Studi di Siena, Siena, 53100 (Italy); Khanbekyan, A; Papoyan, A, E-mail: karen.khanbekyan@gmail.com [Institute for Physical Research, National Academy of Sciences, Ashtarak 2 (Armenia)

    2011-03-14

    We consider a dual {Lambda}-system under double laser excitation to investigate the possibility of indirect coherence transfer between atomic ground states through an excited state. The atomic system is excited by a frequency modulated pump laser and probed by a low-power cw laser. All the decoherence mechanisms are discussed and taken into account. Adjustment of parameters of the two radiations aimed at maximization of coherence transfer is addressed. The study can help to understand the phenomena as collisional transfer of coherence and can find application in the experimental realization of atomic sensors.

  4. A comparison of pulsed and continuous atom transfer between two magneto-optical traps

    International Nuclear Information System (INIS)

    Ram, S. P.; Tiwari, S. K.; Mishra, S. R.

    2010-01-01

    We present the experimental results for a comparison between pulsed and continuous transfer of cold 87 Rb atoms between a vapor chamber magneto-optical trap (VC-MOT) and an ultra-high vacuum magneto-optical trap (UHV-MOT) when using a resonant push beam. We find that employing repetitive cycles of a pulsed and unfocused push beam on an unsaturated VC-MOT cloud results in a significantly higher number of atoms transferred to the UHV-MOT than the number obtained with a continuous push beam focused on a continuous VC-MOT. In pulsed transfer, we find that both the VC-MOT loading duration and the push beam duration play important roles in the transfer process and govern the number of atoms transferred to the UHV-MOT. The parameters and processes affecting the transfer have been investigated and are discussed.

  5. Impact of high resolution land surface initialization in Indian summer ...

    Indian Academy of Sciences (India)

    The direct impact of high resolution land surface initialization on the forecast bias in a regional climate model in recent years ... surface initialization using a regional climate model. ...... ization of the snow field in a cloud model; J. Clim. Appl.

  6. TRANSITION METAL CATALYSIS IN CONTROLLED RADICAL POLYMERIZATION: ATOM TRANSFER RADICAL POLYMERIZATION. (R826735)

    Science.gov (United States)

    Novel and diversified macromolecular structures, which include polymers with designed topologies (top), compostions (middle), and functionalities (bottom), can be prepared by atom transfer radical polymerization processes. These polymers can be synthesized from a large variety of...

  7. PNIPAAm-grafted thermoresponsive microcarriers: Surface-initiated ATRP synthesis and characterization

    Energy Technology Data Exchange (ETDEWEB)

    Çakmak, Soner [Nanotechnology and Nanomedicine Department, Hacettepe University, 06800, Beytepe, Ankara (Turkey); Çakmak, Anıl S. [Bioengineering Department, Hacettepe University, 06800, Beytepe, Ankara (Turkey); Gümüşderelioğlu, Menemşe, E-mail: menemse@hacettepe.edu.tr [Nanotechnology and Nanomedicine Department, Hacettepe University, 06800, Beytepe, Ankara (Turkey); Bioengineering Department, Hacettepe University, 06800, Beytepe, Ankara (Turkey); Chemical Engineering Department, Hacettepe University, 06800, Beytepe, Ankara (Turkey)

    2013-07-01

    In this study, we developed novel thermoresponsive microcarriers as a powerful tool for cell culture and tissue engineering applications. For this purpose, two types of commercially available spherical microparticles (approximately 100 μm in diameter), dextran-based Sephadex® and vinyl acetate-based VA-OH (Biosynth®), were used and themoresponsive poly(N-isopropylacrylamide) (PNIPAAm) was grafted to the beads' surfaces by surface-initiated atom transfer radical polymerization (SI-ATRP). Initially, hydroxyl groups of microbeads were reacted with 2-bromopropionyl bromide to form ATRP macroinitiator. Then, NIPAAm was successfully polymerized from the initiator attached microbeads by ATRP with CuBr/2,2′-dipyridyl, catalyst complex. Furthermore, grafted and ungrafted microbeads were characterized by attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, scanning electron microscope (SEM), atomic force microscopy (AFM) and electron spectroscopy for chemical analysis (ESCA). The results of characterization studies confirmed that PNIPAAm was successfully grafted onto both dextran and vinyl acetate-based beads by means of ATRP reaction and thus, grafted microbeads gained thermoresponsive characteristics which will be evaluated for cell harvesting in further studies. Highlights: • PNIPAAm was grafted to the hydroxyl group carrying polymer beads by SI-ATRP. • Dex-g-PNIPAAm and VA-OH-g-PNIPAAm beads exhibited thermoresponsive characteristics. • They are appropriate candidates for microcarrier-facilitated cell cultures.

  8. PNIPAAm-grafted thermoresponsive microcarriers: Surface-initiated ATRP synthesis and characterization

    International Nuclear Information System (INIS)

    Çakmak, Soner; Çakmak, Anıl S.; Gümüşderelioğlu, Menemşe

    2013-01-01

    In this study, we developed novel thermoresponsive microcarriers as a powerful tool for cell culture and tissue engineering applications. For this purpose, two types of commercially available spherical microparticles (approximately 100 μm in diameter), dextran-based Sephadex® and vinyl acetate-based VA-OH (Biosynth®), were used and themoresponsive poly(N-isopropylacrylamide) (PNIPAAm) was grafted to the beads' surfaces by surface-initiated atom transfer radical polymerization (SI-ATRP). Initially, hydroxyl groups of microbeads were reacted with 2-bromopropionyl bromide to form ATRP macroinitiator. Then, NIPAAm was successfully polymerized from the initiator attached microbeads by ATRP with CuBr/2,2′-dipyridyl, catalyst complex. Furthermore, grafted and ungrafted microbeads were characterized by attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, scanning electron microscope (SEM), atomic force microscopy (AFM) and electron spectroscopy for chemical analysis (ESCA). The results of characterization studies confirmed that PNIPAAm was successfully grafted onto both dextran and vinyl acetate-based beads by means of ATRP reaction and thus, grafted microbeads gained thermoresponsive characteristics which will be evaluated for cell harvesting in further studies. Highlights: • PNIPAAm was grafted to the hydroxyl group carrying polymer beads by SI-ATRP. • Dex-g-PNIPAAm and VA-OH-g-PNIPAAm beads exhibited thermoresponsive characteristics. • They are appropriate candidates for microcarrier-facilitated cell cultures

  9. The population transfer of high excited states of Rydberg lithium atoms in a microwave field

    International Nuclear Information System (INIS)

    Jiang Lijuan; Zhang Xianzhou; Ma Huanqiang; Jia Guangrui; Zhang Yonghui; Xia Lihua

    2012-01-01

    Using the time-dependent multilevel approach (TDMA), the properties of high excited Rydberg lithium atom have been obtained in the microwave field. The population transfer of lithium atom are studied on numerical calculation, quantum states are controlled and manipulated by microwave field. It shows that the population can be completely transferred to the target state by changing the chirped rate and field amplitude. (authors)

  10. Dynamical interaction of He atoms with metal surfaces: Charge transfer processes

    International Nuclear Information System (INIS)

    Flores, F.; Garcia Vidal, F.J.; Monreal, R.

    1993-01-01

    A self-consistent Kohn-Sham LCAO method is presented to calculate the charge transfer processes between a He * -atom and metal surfaces. Intra-atomic correlation effects are taken into account by considering independently each single He-orbital and by combining the different charge transfer processes into a set of dynamical rate equations for the different ion charge fractions. Our discussion reproduces qualitatively the experimental evidence and gives strong support to the method presented here. (author). 24 refs, 4 figs

  11. Atom transfer radical polymerization of n-butyl acrylate catalyzed by atom transfer radical polymerization of n-butyl acrylate catalyzed by

    NARCIS (Netherlands)

    Zhang, H.; Linde, van der R.

    2002-01-01

    The homogeneous atom transfer radical polymerization (ATRP) of n-butyl acrylate with CuBr/N-(n-hexyl)-2-pyridylmethanimine as a catalyst and ethyl 2-bromoisobutyrate as an initiator was investigated. The kinetic plots of ln([M]0/[M]) versus the reaction time for the ATRP systems in different

  12. Antifouling coatings via plasma polymerization and atom transfer radical polymerization on thin film composite membranes for reverse osmosis

    Science.gov (United States)

    Hirsch, Ulrike; Ruehl, Marco; Teuscher, Nico; Heilmann, Andreas

    2018-04-01

    A major drawback to otherwise highly efficient membrane-based desalination techniques like reverse osmosis (RO) is the susceptibility of the membranes to biofouling. In this work, a combination of plasma activation, plasma bromination and surface-initiated atom transfer radical polymerization (si-ATRP) of hydrophilic and zwitterionic monomers, namely hydroxyethyl methacrylate (HEMA), 2-methacryloyloxyethyl phosphorylcholine (MPC) and [2-(methacryloyloxy)ethyl]-dimethyl-(3-sulfopropyl)ammonium hydroxide (SBMA), was applied to generate non-specific, anti-adhesive coatings on thin film composite (TFC) membranes. The antifouling effect of the coatings was shown by short-time batch as well as long-time steady state cultivation experiments with the microorganism Pseudomonas fluorescens. It could be shown that plasma functionalization and polymerization is possible on delicate thin film composite membranes without restricting their filtration performance. All modified membranes showed an increased resistance towards the adhesion of Pseudomonas fluorescens. On average, the biofilm coverage was reduced by 51.4-12.6% (for HEMA, SBMA, and MPC), the highest reduction was monitored for MPC with a biofilm reduction by 85.4%. The hydrophilic coatings applied did not only suppress the adhesion of Pseudomonas fluorescens, but also significantly increase the permeate flux of the membranes relative to uncoated membranes. The stability of the coatings was however not ideal and will have to be improved for future commercial use.

  13. In situ development of self-reinforced cellulose nanocrystals based thermoplastic elastomers by atom transfer radical polymerization.

    Science.gov (United States)

    Yu, Juan; Wang, Chunpeng; Wang, Jifu; Chu, Fuxiang

    2016-05-05

    Recently, the utilization of cellulose nanocrystals (CNCs) as a reinforcing material has received a great attention due to its high elastic modulus. In this article, a novel strategy for the synthesis of self-reinforced CNCs based thermoplastic elastomers (CTPEs) is presented. CNCs were first surface functionalized with an initiator for surface-initiated atom transfer radical polymerization (SI-ATRP). Subsequently, SI-ATRP of methyl methacrylate (MMA) and butyl acrylate (BA) was carried out in the presence of sacrificial initiator to form CTPEs in situ. The CTPEs together with the simple blends of CNCs and linear poly(MMA-co-BA) copolymer (P(MMA-co-BA)) were characterized for comparative study. The results indicated that P(MMA-co-BA) was successfully grafted onto the surface of CNCs and the compatibility between CNCs and the polymer matrix in CTPEs was greatly enhanced. Specially, the CTPEs containing 2.15wt% CNCs increased Tg by 19.2°C and tensile strength by 100% as compared to the linear P(MMA-co-BA). Copyright © 2016 Elsevier Ltd. All rights reserved.

  14. Modulation Transfer Spectroscopy of Ytterbium Atoms in a Hollow Cathode Lamp

    International Nuclear Information System (INIS)

    Wang Wen-Li; Xu Xin-Ye

    2011-01-01

    We present the experimental study of modulation transfer spectroscopy of ytterbium atoms in a hollow cathode lamp. The dependences of its linewidth, slope and magnitude on the various experimental parameters are measured and fitted by the well-known theoretical expressions. The experimental results are in good agreement with the theoretical prediction. We have observed the Dicke narrowing effect by increasing the current of the hollow cathode lamp. It is also found that there are the optimal current and laser power to generate the better modulation transfer spectroscopy signal, which can be employed for locking the laser frequency to the atomic transition. (atomic and molecular physics)

  15. Insights into the Hydrogen-Atom Transfer of the Blue Aroxyl.

    Science.gov (United States)

    Bächle, Josua; Marković, Marijana; Kelterer, Anne-Marie; Grampp, Günter

    2017-10-19

    An experimental and theoretical study on hydrogen-atom transfer dynamics in the hydrogen-bonded substituted phenol/phenoxyl complex of the blue aroxyl (2,4,6-tri-tert-butylphenoxyl) is presented. The experimental exchange dynamics is determined in different organic solvents from the temperature-dependent alternating line-width effect in the continuous-wave ESR spectrum. From bent Arrhenius plots, effective tunnelling contributions with parallel heavy-atom motion are concluded. To clarify the transfer mechanism, reaction paths for different conformers of the substituted phenol/phenoxyl complex are modelled theoretically. Various DFT and post-Hartree-Fock methods including multireference methods are applied. From the comparison of experimental and theoretical data it is concluded that the system favours concerted hydrogen-atom transfer along a parabolic reaction path caused by heavy-atom motion. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Entanglement and quantum state transfer between two atoms trapped in two indirectly coupled cavities

    Science.gov (United States)

    Zheng, Bin; Shen, Li-Tuo; Chen, Ming-Feng

    2016-05-01

    We propose a one-step scheme for implementing entanglement generation and the quantum state transfer between two atomic qubits trapped in two different cavities that are not directly coupled to each other. The process is realized through engineering an effective asymmetric X-Y interaction for the two atoms involved in the gate operation and an auxiliary atom trapped in an intermediate cavity, induced by virtually manipulating the atomic excited states and photons. We study the validity of the scheme as well as the influences of the dissipation by numerical simulation and demonstrate that it is robust against decoherence.

  17. Nitrogen Atom Transfer From High Valent Iron Nitrides

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Michael D. [New Mexico State Univ., Las Cruces, NM (United States); Smith, Jeremy M. [Indiana Univ., Bloomington, IN (United States)

    2015-10-14

    This report describes the synthesis and reactions of high valent iron nitrides. Organonitrogen compounds such as aziridines are useful species for organic synthesis, but there are few efficient methods for their synthesis. Using iron nitrides to catalytically access these species may allow for their synthesis in an energy-and atom-efficient manner. We have developed a new ligand framework to achieve these goals as well as providing a method for inducing previously unknown reactivity.

  18. Experimental evidence of state-selective charge transfer in inductively coupled plasma-atomic emission spectrometry

    International Nuclear Information System (INIS)

    Chan, George C.-Y.; Hieftje, Gary M.

    2004-01-01

    State-selective charge-transfer behavior was observed for Fe, Cr, Mn and Cu in inductively coupled plasma (ICP)-atomic emission spectrometry. Charge transfer from Ar + to Fe, Cr and Mn is state-selective because of inefficient collisional mixing of the quasiresonant charge-transfer energy levels with nearby levels. This low efficiency is the consequence of differences in electronic configuration of the core electrons. The reason for state-selective charge-transfer behavior to Cu is not clear, although a tentative explanation based on efficiency of intramultiplet and intermultiplet mixing for this special case is offered

  19. Isotopic effects in the muon transfer from pmu and dmu to heavier atoms.

    Science.gov (United States)

    Dupays, Arnaud

    2004-07-23

    The results of accurate hyperspherical calculations of the muon-transfer rates from muonic protium and deuterium atoms to nitrogen, oxygen, and neon are reported. Very good agreement with measured rates is obtained and, for the three systems, the isotopic effect is perfectly reproduced. The transfer rate is higher for deuterium in the cases of nitrogen and neon due to constructive interferences between two transfer paths. The lower transfer rate for deuterium in the case of oxygen results from a large resonant contribution. Copyright 2004 The American Physical Society

  20. Charge transfer and excitation in high-energy ion-atom collisions

    International Nuclear Information System (INIS)

    Schlachter, A.S.; Berkner, K.H.; McDonald, R.J.

    1986-11-01

    Coincidence measurements of charge transfer and simultaneous projectile electron excitation provide insight into correlated two-electron processes in energetic ion-atom collisions. Projectile excitation and electron capture can occur simultaneously in a collision of a highly charged ion with a target atom; this process is called resonant transfer and excitation (RTE). The intermediate excited state which is thus formed can subsequently decay by photon emission or by Auger-electron emission. Results are shown for RTE in both the K shell of Ca ions and the L shell of Nb ions, for simultaneous projectile electron loss and excitation, and for the effect of RTE on electron capture

  1. Auto transfer to Rydberg states during ion-atom collisions

    International Nuclear Information System (INIS)

    Bachau, H.; Harel, C.; Barat, M.; Roncin, P.; Bordenave-Montesquieu, A.; Moretto-Capelle, P.; Benoit-Cattin, P.; Gleizes, A.; Benhenni, M.

    1993-01-01

    Electron capture by slow multiply charged ions colliding on rare-gas targets is known to populate highly excited states of the projectile. On the basis of experimental measurement of energy and angle differential cross-sections we have shown that capture to a resonant doubly excited state may lead to Autoionizing Double Capture (ADC) as well as to True Double Capture (TDC). In this model TDC appears as a two step post-collisional process, the state populated by the collision decays to (or delutes into) a dense adjacent Rydberg series, followed by radiative deexcitation of the inner electron of the (3,n) Rydberg states. We report here new experimental observations in electron spectra measured in N 7+ +He. Auto transfer to Rydber states has also important consequences on the determination of the lifetime of the autoionizing states, some discrepancies between theoretical width values for low N 5+ (4,4) resonant states will be discussed and partially resolved

  2. Quantum state population transfer of lithium atoms induced by frequency-chirped laser pulses

    International Nuclear Information System (INIS)

    Ma Huanqiang; Zhang Xianzhou; Jia Guangrui; Zhang Yonghui; Jiang Lijuan

    2011-01-01

    Using the time-dependent multilevel approach (TDMA) and B-splines function, we have calculated the five quantum state population transfer of rydberg lithium atoms. We also analyse the influence of the four major parameters of the frequency-chirped laser pulses field on transition. The result shows that the population can be completely transferred to the target state by changing the parameters of the laser pulse and achieve manual controls to a certain degree. (authors)

  3. Reactivity of hydropersulfides toward the hydroxyl radical unraveled: disulfide bond cleavage, hydrogen atom transfer, and proton-coupled electron transfer.

    Science.gov (United States)

    Anglada, Josep M; Crehuet, Ramon; Adhikari, Sarju; Francisco, Joseph S; Xia, Yu

    2018-02-14

    Hydropersulfides (RSSH) are highly reactive as nucleophiles and hydrogen atom transfer reagents. These chemical properties are believed to be key for them to act as antioxidants in cells. The reaction involving the radical species and the disulfide bond (S-S) in RSSH, a known redox-active group, however, has been scarcely studied, resulting in an incomplete understanding of the chemical nature of RSSH. We have performed a high-level theoretical investigation on the reactions of the hydroxyl radical (˙OH) toward a set of RSSH (R = -H, -CH 3 , -NH 2 , -C(O)OH, -CN, and -NO 2 ). The results show that S-S cleavage and H-atom abstraction are the two competing channels. The electron inductive effect of R induces selective ˙OH substitution at one sulfur atom upon S-S cleavage, forming RSOH and ˙SH for the electron donating groups (EDGs), whereas producing HSOH and ˙SR for the electron withdrawing groups (EWGs). The H-Atom abstraction by ˙OH follows a classical hydrogen atom transfer (hat) mechanism, producing RSS˙ and H 2 O. Surprisingly, a proton-coupled electron transfer (pcet) process also occurs for R being an EDG. Although for RSSH having EWGs hat is the leading channel, S-S cleavage can be competitive or even dominant for the EDGs. The overall reactivity of RSSH toward ˙OH attack is greatly enhanced with the presence of an EDG, with CH 3 SSH being the most reactive species found in this study (overall rate constant: 4.55 × 10 12 M -1 s -1 ). Our results highlight the complexity in RSSH reaction chemistry, the extent of which is closely modulated by the inductive effect of the substituents in the case of the oxidation by hydroxyl radicals.

  4. Auto transfer to Rydberg states during ion-atom collisions

    Energy Technology Data Exchange (ETDEWEB)

    Bachau, H.; Harel, C. (Laboratoire des Collisions Atomiques, Unite Propre de Recherche 260 du CNRS, Universite Bordeaux I, 351 Cours de la Liberation, 33405 Talence (France)); Barat, M.; Roncin, P. (Laboratoire des Collisions Atomiques et Moleculaires, Unite associee 281 du CNRS, Universite de Paris Sud, Batiment 351, 91405 Orsay (France)); Bordenave-Montesquieu, A.; Moretto-Capelle, P.; Benoit-Cattin, P.; Gleizes, A.; Benhenni, M. (IRSAMC, Unite associee 770 du CNRS, Universite Paul Sabatier, 118 route de Narbonne, 31062 Toulouse (France))

    1993-06-05

    Electron capture by slow multiply charged ions colliding on rare-gas targets is known to populate highly excited states of the projectile. On the basis of experimental measurement of energy and angle differential cross-sections we have shown that capture to a resonant doubly excited state may lead to Autoionizing Double Capture (ADC) as well as to True Double Capture (TDC). In this model TDC appears as a two step post-collisional process, the state populated by the collision decays to (or delutes into) a dense adjacent Rydberg series, followed by radiative deexcitation of the inner electron of the (3,n) Rydberg states. We report here new experimental observations in electron spectra measured in [ital N][sup 7+]+[ital He]. Auto transfer to Rydber states has also important consequences on the determination of the lifetime of the autoionizing states, some discrepancies between theoretical width values for low [ital N][sup 5+](4,4) resonant states will be discussed and partially resolved.

  5. Fe electron transfer and atom exchange in goethite: influence of Al-substitution and anion sorption.

    Science.gov (United States)

    Latta, Drew E; Bachman, Jonathan E; Scherer, Michelle M

    2012-10-02

    The reaction of Fe(II) with Fe(III) oxides and hydroxides is complex and includes sorption of Fe(II) to the oxide, electron transfer between sorbed Fe(II) and structural Fe(III), reductive dissolution coupled to Fe atom exchange, and, in some cases mineral phase transformation. Much of the work investigating electron transfer and atom exchange between aqueous Fe(II) and Fe(III) oxides has been done under relatively simple aqueous conditions in organic buffers to control pH and background electrolytes to control ionic strength. Here, we investigate whether electron transfer is influenced by cation substitution of Al(III) in goethite and the presence of anions such as phosphate, carbonate, silicate, and natural organic matter. Results from (57)Fe Mössbauer spectroscopy indicate that both Al-substitution (up to 9%) and the presence of common anions (PO(4)(3-), CO(3)(2-), SiO(4)(4-), and humic acid) does not inhibit electron transfer between aqueous Fe(II) and Fe(III) in goethite under the conditions we studied. In contrast, sorption of a long-chain phospholipid completely shuts down electron transfer. Using an enriched isotope tracer method, we found that Al-substitution in goethite (10%), does, however, significantly decrease the extent of atom exchange between Fe(II) and goethite (from 43 to 12%) over a month's time. Phosphate, somewhat surprisingly, appears to have little effect on the rate and extent of atom exchange between aqueous Fe(II) and goethite. Our results show that electron transfer between aqueous Fe(II) and solid Fe(III) in goethite can occur under wide range of geochemical conditions, but that the extent of redox-driven Fe atom exchange may be dependent on the presence of substituting cations such as Al.

  6. Preparation and controlled drug delivery applications of mesoporous silica polymer nanocomposites through the visible light induced surface-initiated ATRP

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Long; Liu, Meiying; Mao, Liucheng; Xu, Dazhuang; Wan, Qing; Zeng, Guangjian; Shi, Yingge [Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031 (China); Wen, Yuanqing, E-mail: m18600788382@163.com [Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031 (China); Zhang, Xiaoyong, E-mail: xiaoyongzhang1980@gmail.com [Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031 (China); Wei, Yen, E-mail: weiyen@tsinghua.edu.cn [Department of Chemistry and The Tsinghua Center for Frontier Polymer Research, Tsinghua University, Beijing, 100084 (China)

    2017-08-01

    Graphical abstract: A novel strategy for surface PEGylation of mesoporous silica nanoparticles was developed based on the light induced surface-initiated atom transfer radical polymerization. - Highlights: • Surface modification of silica nanoparticles through light induced surface-initiated ATRP. • MSNs-NH{sub 2}-poly(IA-co-PEGMA) nanocomposites show high water dispersity. • MSNs-NH{sub 2}-poly(IA-co-PEGMA) nanocomposites are promising for biomedical applications. • The light induced ATRP possesses many advantages as compared with traditional ATRP. - Abstract: The mesoporous materials with large pore size, high specific surface area and high thermal stability have been widely utilized in a variety of fields ranging from environmental remediation to separation and biomedicine. However, surface modification of these silica nanomaterials is required to endow novel properties and achieve better performance for most of these applications. In this work, a new method has been established for surface modification of mesoporous silica nanoparticles (MSNs) that relied on the visible light induced atom transfer radical polymerization (ATRP). In the procedure, the copolymers composited with itaconic acid (IA) and poly(ethylene glycol)methyl acrylate (PEGMA) were grafted from MSNs using IA and PEGMA as the monomers and 10-Phenylphenothiazine(PTH) as the organic catalyst. The successful preparation of final polymer nanocomposites (named as MSNs-NH{sub 2}-poly(IA-co-PEGMA)) were evidenced by a series of characterization techniques. More importantly, the anticancer agent cisplatin can be effectively loaded on MSNs-NH{sub 2}-poly(IA-co-PEGMA) and controlled release it from the drug-loading composites with pH responsive behavior. As compared with conventional ATRP, the light induced surface-initiated ATRP could also be utilized for preparation of various silica polymer nanocomposites under rather benign conditions (e.g. absent of transition metal ions, low polymerization

  7. Novel fluorinated block copolymer architectures fuelled by atom transfer radical polymerization

    DEFF Research Database (Denmark)

    Jankova, Katja; Hvilsted, Søren

    2005-01-01

    Block copolymers based on poly(pentafluorostyrene), PFS, in various numbers and of different lengths, and polystyrene are prepared by atom transfer radical polymerization (ATRP). Di- and triblock copolymers with varying amounts of PFS were synthesized employing either I phenylethylbromide or 1,4-...

  8. Atom-transfer radical polymerization of methyl methacrylate (MMA) using CuSCN as the catalyst

    NARCIS (Netherlands)

    Singha, N.K.; Klumperman, B.

    2000-01-01

    The effect of CuSCN as a catalyst in atom-transfer radical polymerization (ATRP) was investigated. CuSCN can successfully be used for the ATRP of MMA. Substituted bipyridines as well as imines can be used to stabilize the copper complex in solution. CuSCN induces faster polymerization compared to

  9. Optimization of transfer of laser-cooled atom cloud to a quadrupole ...

    Indian Academy of Sciences (India)

    2014-02-08

    Feb 8, 2014 ... Laser Physics Applications Section, Raja Ramanna Centre for Advanced Technology,. Indore 452 013 ... Laser cooling; optical molasses; double-MOT; magnetic trapping; phase-space density. PACS Nos 52.55. ... this method, the transfer of laser-cooled atom cloud to magnetic trap is an important step,.

  10. Enantioselective H-atom transfer reaction: a strategy to synthesize formaldehyde aldol products.

    Science.gov (United States)

    Sibi, Mukund P; Patil, Kalyani

    2005-04-14

    [reaction: see text] Enantioselective radical alkylation of Baylis-Hillman adducts furnished aldol products in good yield and selectivity. The results illustrate that the selectivity in the hydrogen atom transfer is dependent on the size of the ester substituent, with smaller substituents providing better enantioselectivity.

  11. Optimization of transfer of laser-cooled atom cloud to a quadrupole ...

    Indian Academy of Sciences (India)

    2014-02-08

    Feb 8, 2014 ... We present here our experimental results on transfer of laser-cooled atom cloud to a quadrupole magnetic trap. We show that by choosing appropriately the ratio of potential energy in magnetic trap to kinetic energy of cloud in molasses, we can obtain the maximum phase-space density in the magnetic trap.

  12. The effect of reducing monosaccharides on the atom transfer radical polymerization of butyl methacrylate

    NARCIS (Netherlands)

    Vries, de Andrew; Klumperman, B.; Wet-Roos, de D.; Sanderson, R.D.

    2001-01-01

    The effect of various reducing monosaccharides on the rate of atom transfer radical polymerization (ATRP) of butyl methacrylate is reported in this study. The addition of reducing sugars affects the rate of ATRP positively with a 100% increase in the rate of polymerization in some cases. In

  13. Charge transfer to the continuum by heavy ions in atomic hydrogen

    International Nuclear Information System (INIS)

    Sellin, I.A.

    1981-01-01

    Design and installation of an atomic hydrogen target for measurements of charge transfer to the continuum by heavy ions are discussed. The design consists of a tungsten gas cell operated at temperatures of 2500 to 2600 0 K. Initial testing is underway

  14. Hydrolysis of 4-Acetoxystyrene Polymers Prepared by Atom Transfer Radical Polymerization

    DEFF Research Database (Denmark)

    Chen, Xianyi; Jankova, Katja; Kops, Jørgen

    1999-01-01

    Hydrolysis of 4-acetoxystyrene polymers prepared by atom transfer radical polymerization was carried out under various reaction conditions. It was found that hydrazinolysis of 4-acetoxystyrene homopolymers, random and block copolymers with styrene in 1,4-dioxane, afforded the corresponding narrow...

  15. Bibliography on electron transfer processes in ion-ion/atom/molecule collisions (updated 1993)

    International Nuclear Information System (INIS)

    Tawara, H.

    1993-04-01

    Following our previous compilations [IPPJ-AM-45 (1986), NIFS-DATA-7 (1990)], bibliographic information on experimental and theoretical studies on electron transfer processes in ion-ion/atom/molecule collisions is up-dated. The references published through 1980-1992 are included. For easy finding references for particular combination of collision partners, a simple list is also provided. (author) 1542 refs

  16. Organic thin film transistors with polymer brush gate dielectrics synthesized by atom transfer radical polymerization

    DEFF Research Database (Denmark)

    Pinto, J.C.; Whiting, G.L.; Khodabakhsh, S.

    2008-01-01

    , synthesized by atom transfer radical polymerization (ATRP), were used to fabricate low voltage OFETs with both evaporated pentacene and solution deposited poly(3-hexylthiophene). The semiconductor-dielectric interfaces in these systems were studied with a variety of methods including scanning force microscopy...

  17. Charge transfer between hydrogen(deuterium) ions and atoms in metal vapors

    International Nuclear Information System (INIS)

    Alvarez T, I.; Cisneros G, C.

    1981-01-01

    The current state of the experiments on charge transfer between hydrogen (deuterium) ions and atoms in metal vapors are given. Emphasis is given to describing different experimental techniques. The results of calculations if available, are compared with existing experimental data. (author)

  18. Muon transfer from muonic hydrogen to heavier atoms; Transfert de charge muonique

    Energy Technology Data Exchange (ETDEWEB)

    Dupays, A

    2004-06-01

    This work concerns muon transfer from muonic hydrogen to heavier atoms. Recently, a method of measurement of the hyperfine structure of ground-state muonic hydrogen based on the collision energy dependence of the muon transfer rate to oxygen has been proposed. This proposal is based on measurements which where performed at the Paul Scherrer Institute in the early nineties which indicate that the muon transfer from muonic hydrogen to oxygen increases by a factor of 4 going from thermal to 0.12 eV energies. The motivation of our calculations was to confirm this behaviour. To study the collision energy dependence of the muon transfer rate, we have used a time-independent close-coupling method. We have set up an hyperspherical elliptic formalism valid for nonzero total angular momentum which allows accurate computations of state-to-state reactive and charge exchange processes. We have applied this formalism to muon-transfer process to oxygen and neon. The comparison with experimental results is in both cases excellent. Finally, the neon transfer rate dependence with energy suggests to use neon instead of oxygen to perform a measurement of the hyperfine structure of muonic hydrogen. The results of accurate calculations of the muon transfer rates from muonic protium and deuterium atoms to nitrogen, oxygen and neon are also reported. Very good agreement with measured rates is obtained and for the three systems, the isotopic effect is perfectly reproduced. (author)

  19. Hydrogen atom transfer reactions in thiophenol: photogeneration of two new thione isomers.

    Science.gov (United States)

    Reva, Igor; Nowak, Maciej J; Lapinski, Leszek; Fausto, Rui

    2015-02-21

    Photoisomerization reactions of monomeric thiophenol have been investigated for the compound isolated in low-temperature argon matrices. The initial thiophenol population consists exclusively of the thermodynamically most stable thiol form. Phototransformations were induced by irradiation of the matrices with narrowband tunable UV light. Irradiation at λ > 290 nm did not induce any changes in isolated thiophenol molecules. Upon irradiation at 290-285 nm, the initial thiol form of thiophenol converted into its thione isomer, cyclohexa-2,4-diene-1-thione. This conversion occurs by transfer of an H atom from the SH group to a carbon atom at the ortho position of the ring. Subsequent irradiation at longer wavelengths (300-427 nm) demonstrated that this UV-induced hydrogen-atom transfer is photoreversible. Moreover, upon irradiation at 400-425 nm, the cyclohexa-2,4-diene-1-thione product converts, by transfer of a hydrogen atom from the ortho to para position, into another thione isomer, cyclohexa-2,5-diene-1-thione. The latter thione isomer is also photoreactive and is consumed if irradiated at λ atom-transfer isomerization reactions dominate the unimolecular photochemistry of thiophenol confined in a solid argon matrix. A set of low-intensity infrared bands, observed in the spectra of UV irradiated thiophenol, indicates the presence of a phenylthiyl radical with an H- atom detached from the SH group. Alongside the H-atom-transfer and H-atom-detachment processes, the ring-opening photoreaction occurred in cyclohexa-2,4-diene-1-thione by the cleavage of the C-C bond at the alpha position with respect to the thiocarbonyl C[double bond, length as m-dash]S group. The resulting open-ring conjugated thioketene adopts several isomeric forms, differing by orientations around single and double bonds. The species photogenerated upon UV irradiation of thiophenol were identified by comparison of their experimental infrared spectra with the spectra theoretically calculated for

  20. Excitation and charge transfer in low-energy hydrogen atom collisions with neutral iron

    Science.gov (United States)

    Barklem, P. S.

    2018-05-01

    Data for inelastic processes due to hydrogen atom collisions with iron are needed for accurate modelling of the iron spectrum in late-type stars. Excitation and charge transfer in low-energy Fe+H collisions is studied theoretically using a previously presented method based on an asymptotic two-electron linear combination of atomic orbitals model of ionic-covalent interactions in the neutral atom-hydrogen-atom system, together with the multi-channel Landau-Zener model. An extensive calculation including 166 covalent states and 25 ionic states is presented and rate coefficients are calculated for temperatures in the range 1000-20 000 K. The largest rates are found for charge transfer processes to and from two clusters of states around 6.3 and 6.6 eV excitation, corresponding in both cases to active 4d and 5p electrons undergoing transfer. Excitation and de-excitation processes among these two sets of states are also significant. Full Tables and rate coefficient data are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/612/A90

  1. Generation of a cold pulsed beam of Rb atoms by transfer from a 3D magneto-optic trap

    OpenAIRE

    Chanu, Sapam Ranjita; Rathod, Ketan D.; Natarajan, Vasant

    2016-01-01

    We demonstrate a technique for producing a cold pulsed beam of atoms by transferring a cloud of atoms trapped in a three dimensional magneto-optic trap (MOT). The MOT is loaded by heating a getter source of Rb atoms. We show that it is advantageous to transfer with two beams (with a small angle between them) compared to a single beam, because the atoms stop interacting with the beams in the two-beam technique, which results in a Gaussian velocity distribution. The atoms are further cooled in ...

  2. State-selective charge transfer cross sections for light ion impact of atomic hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Schultz, D. R. [University of North Texas; Stancil, Phillip C. [University of Georgia, Athens; Havener, C. C. [Oak Ridge National Laboratory (ORNL)

    2015-01-01

    Owing to the utility of diagnosing plasma properties such as impurity concentration and spatial distribution, and plasma temperature and rotation, by detection of photon emission following capture of electrons from atomic hydrogen to excited states of multiply charged ions, new calculations of state-selective charge transfer involving light ions have been carried out using the atomic orbital close-coupling and the classical trajectory Monte Carlo methods. By comparing these with results of other approaches applicable in a lower impact energy regime, and by benchmarking them using key experimental data, knowledge of the cross sections can be made available across the range parameters needed by fusion plasma diagnostics.

  3. Activators generated by electron transfer for atom transfer radical polymerization of styrene in the presence of mesoporous silica nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Khezri, Khezrollah, E-mail: kh.khezri@ut.ac.ir [School of Chemistry, University College of Science, University of Tehran, PO Box 14155-6455, Tehran (Iran, Islamic Republic of); Roghani-Mamaqani, Hossein [Department of Polymer Engineering, Sahand University of Technology, PO Box 51335-1996, Tabriz (Iran, Islamic Republic of)

    2014-11-15

    Graphical abstract: Effect of mesoporous silica nanoparticles (MCM-41) on the activator generated by electron transfer for atom transfer radical polymerization (AGET ATRP) is investigated. Decrement of conversion and number average molecular weight and also increment of polydispersity index (PDI) values are three main results of addition of MCM-41 nanoparticles. Incorporation of MCM-41 nanoparticles in the polystyrene matrix can clearly increase thermal stability and decrease glass transition temperature of the nanocomposites. - Highlights: • Spherical morphology, hexagonal structure, and high surface area with regular pore diameters of the synthesized MCM-41 nanoparticles are examined. • AGET ATRP of styrene in the presence of MCM-41 nanoparticles is performed. • Effect of MCM-41 nanoparticles addition on the polymerization rate, conversion and molecular weights of the products are discussed. • Improvement in thermal stability of the nanocomposites and decreasing T{sub g} values was also observed by incorporation of MCM-41 nanoparticles. - Abstract: Activator generated by electron transfer for atom transfer radical polymerization was employed to synthesize well-defined mesoporous silica nanoparticles/polystyrene composites. Inherent features of spherical mesoporous silica nanoparticles were evaluated by nitrogen adsorption/desorption isotherm, X-ray diffraction and scanning electron microscopy analysis techniques. Conversion and molecular weight evaluations were carried out using gas and size exclusion chromatography respectively. By the addition of only 3 wt% mesoporous silica nanoparticles, conversion decreases from 81 to 58%. Similarly, number average molecular weight decreases from 17,116 to 12,798 g mol{sup −1}. However, polydispersity index (PDI) values increases from 1.24 to 1.58. A peak around 4.1–4.2 ppm at proton nuclear magnetic resonance spectroscopy results clearly confirms the living nature of the polymerization. Thermogravimetric

  4. Muon transfer rates in collisions of hydrogen isotope mesic atoms on 'bare' nuclei. Multichannel adiabatic approach

    International Nuclear Information System (INIS)

    Korobov, V.I.; Melezhik, V.S.; Ponomarev, L.I.

    1992-01-01

    A numerical scheme for solving the problem of slow collisions in the three-body adiabatic approach is applied for calculation of muon transfer rates in collisions of hydrogen isotope atoms on bare nuclei. It is demonstrated that the multichannel adiabatic approach allows one to reach high accuracy results (∼3%) estimating the cross sections of charge transfer processes which are the best ones up to date. The method is appliable in a wide range of energies (0.001-50 eV) which is of interest for analysis of muon catalysed fusion experiments. 20 refs.; 3 figs.; 5 tabs

  5. Nuclear prehistory influence on transfer velocity of 54Mn impurity 'hot' atoms in irradiated metallic iron

    International Nuclear Information System (INIS)

    Alekseev, I.E.

    2007-01-01

    Influence of nuclear prehistory on transfer velocity of 54 Mn impurity 'hot'-atoms - got by different nuclear channels: 56 Fe(d, α), 54 Fe(n,p) in irradiated metallic iron - is studied. Irradiation of targets were carried out in U-120 accelerator (energy range 7.3/5.3 MeV, deuteron beam current makes up 5 μA). Mean density of thermal neutron (WWR-M reactor) makes up 8.6·10 13 neutron·cm -2 ·s -1 . It is shown, that transfer velocity of 54 Mn 'hot' atoms is defining by rate of radiation damage of targets in the irradiation process at that a key importance has a bombarding particles type applied for radioactive label getting

  6. Radical zinc-atom-transfer-based carbozincation of haloalkynes with dialkylzincs

    Directory of Open Access Journals (Sweden)

    Fabrice Chemla

    2013-02-01

    Full Text Available The formation of alkylidenezinc carbenoids by 1,4-addition/carbozincation of dialkylzincs or alkyl iodides based on zinc atom radical transfer, in the presence of dimethylzinc with β-(propargyloxyenoates having pendant iodo- and bromoalkynes, is disclosed. Formation of the carbenoid intermediate is fully stereoselective at −30 °C and arises from a formal anti-selective carbozincation reaction. Upon warming, the zinc carbenoid is stereochemically labile and isomerizes to its more stable form.

  7. Bibliography on electron transfer processes in ion-ion/atom/molecule collisions. Updated 1997

    International Nuclear Information System (INIS)

    Tawara, H.

    1997-04-01

    Following our previous compilations (IPPJ-AM-45 (1986), NIFS-DATA-7 (1990), NIFS-DATA-20 (1993)), bibliographic information on experimental and theoretical studies on electron transfer processes in ion-ion/atom/molecule collisions is up-dated. The references published through 1954-1996 are listed in the order of the publication year. For easy finding of the references for a combination of collision partners, a simple list is provided. (author)

  8. Bibliography on electron transfer processes in ion-ion/atom/molecule collisions, updated 1990

    International Nuclear Information System (INIS)

    Tawara, H.

    1990-08-01

    Following a previous compilation, new bibliographic information on experimental and theoretical studies on electron transfer processes in ion-ion/atom/molecule collisions is up-dated. The references published through 1989 are surveyed. For easy finding references for particular combination of collision partners, a simple list is also provided. Furthermore, for convenience, a copy of the previous compilation (IPPJ-AM-45 (1986)) is included. (author) 1363 refs

  9. Studies on atom transfer radical polymerization of acrylates and styrenes with controlled polymeric block structures

    OpenAIRE

    Ibrahim, Khalid

    2006-01-01

    Atom transfer radical polymerization (ATRP) was applied to homo and block copolymerization of vinyl monomers methacrylates, acrylates, and styrene with iron (FeCl2.4H2O) as the transition metal in most cases. As complexing ligand either a commercially available ligand (triphenyl phosphine) (PPh3) or synthetic aliphatic amines were used. As initiators, methyl 2-bromopropionate, ethyl 2-bromoisobutyrate, α,α-dichloroacetophenone, and poly(ethylene oxide) macroinitiator were employed. Block ...

  10. Single-collision studies of hot atom energy transfer and chemical reaction

    International Nuclear Information System (INIS)

    Valentini, J.J.

    1991-01-01

    This report discusses research in the collision dynamics of translationally hot atoms, with funding with DOE for the project ''Single-Collision Studies of Hot Atom Energy Transfer and Chemical Reaction,'' Grant Number DE-FG03-85ER13453. The work reported here was done during the period September 9, 1988 through October 31, 1991. During this period this DOE-funded work has been focused on several different efforts: (1) experimental studies of the state-to-state dynamics of the H + RH → H 2 R reactions where RH is CH 4 , C 2 H 6 , or C 3 H 8 , (2) theoretical (quasiclassical trajectory) studies of hot hydrogen atom collision dynamics, (3) the development of photochemical sources of translationally hot molecular free radicals and characterization of the high resolution CARS spectroscopy of molecular free radicals, (4) the implementation of stimulated Raman excitation (SRE) techniques for the preparation of vibrationally state-selected molecular reactants

  11. Generation of a cold pulsed beam of Rb atoms by transfer from a 3D magneto-optic trap

    Energy Technology Data Exchange (ETDEWEB)

    Chanu, Sapam Ranjita; Rathod, Ketan D.; Natarajan, Vasant, E-mail: vasant@physics.iisc.ernet.in

    2016-08-26

    We demonstrate a technique for producing a cold pulsed beam of atoms by transferring a cloud of atoms trapped in a three dimensional magneto-optic trap (MOT). The MOT is loaded by heating a getter source of Rb atoms. We show that it is advantageous to transfer with two beams (with a small angle between them) compared to a single beam, because the atoms stop interacting with the beams in the two-beam technique, which results in a Gaussian velocity distribution. The atoms are further cooled in optical molasses by turning off the MOT magnetic field before the transfer beams are turned on. - Highlights: • Getter-source loaded magneto-optic trap (MOT). • Cold atomic beam generated by deflection from the MOT. • Use of two inclined beams for deflection.

  12. Energy transfers between N_2(A"3Σ) nitrogen metastable molecules and oxygen atoms and molecules

    International Nuclear Information System (INIS)

    De Souza, Antonio Rogerio

    1985-01-01

    This research thesis aims at determining reaction coefficients for energy transfers between nitrogen in its metastable status and oxygen atoms and molecules, the variation of these coefficients with respect to temperature (mainly in the 200-400 K range), products formed and more particularly branching rates of O("1S) oxygen and of NO_2. Reaction coefficients are experimentally determined by using the technique of post-discharge in flow. The experimental set-up is described and the study of the best operating conditions is reported. In the next part, the author reports the study of the energy transfer between nitrogen in its metastable status N_2(A) and oxygen molecules. Reaction coefficients are determined for the first three vibrational levels. The author then reports the study of the transfer of N_2(A) molecules on oxygen atoms in their fundamental status. Reactions coefficients and their variations are determined for the three first vibrational levels. The author describes the dissociation method and the method of detection of atomic oxygen. A kinetic model is proposed for the analysis of formed products during a post-discharge in flow, and the branching rate for the formation of O("1S) oxygen between 190 and 365 K is determined. The author finally discusses publications on the role of these reactions in the interpretation of some atmospheric phenomena

  13. Ion-atom charge-transfer system for a heavy-ion-beam pumped laser

    International Nuclear Information System (INIS)

    Ulrich, A.; Gernhaeuser, R.; Kroetz, W.; Wieser, J.; Murnick, D.E.

    1994-01-01

    An Ar target to which Cs vapor could be added, excited by a pulsed beam of 100-MeV 32 S ions, was studied as a prototype ion-atom charge-transfer system for pumping short-wavelength lasers. Low-velocity Ar 2+ ions were efficiently produced; a huge increase in the intensity of the Ar II 4d-4p spectral lines was observed when Cs vapor was added to the argon. This observation is explained by a selective charge transfer of the Cs 6s electron into the upper levels of the observed transitions. A rate constant of (1.4±0.2)x10 -9 cm 3 /s for the transfer process was determined

  14. Preparation of polymeric silica composites through polydopamine-mediated surface initiated ATRP for highly efficient removal of environmental pollutants

    International Nuclear Information System (INIS)

    Huang, Qiang; Liu, Meiying; Wan, Qing; Jiang, Ruming; Mao, Liucheng; Zeng, Guangjian; Huang, Hongye; Deng, Fengjie; Zhang, Xiaoyong; Wei, Yen

    2017-01-01

    In this study, we developed a new procedure to prepare monodispersed functionalized SiO_2 (SiO_2-PDA-PDMC) composites via mussel inspired chemistry and surface initiated atom transfer radical polymerization (SI-ATRP). Samples were characterized by transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and thermal gravimetric analysis (TGA) measurements. TEM results showed that spherical morphology was unchanged after the functionalization. FT-IR results confirmed the successful modification with polydopamine (PDA) and the presence of poly-([2-(Methacryloyloxy) ethyl] trimethylammonium chloride) (PDMC) layer on the surface of SiO_2 spheres. TGA data showed that the PDMC account for about 12.12 wt% in the sample of SiO_2-PDA-PDMC composites. The XPS analysis further confirmed the existence of PDMC on the surface of SiO_2-PDA-PDMC composites. The obtained SiO_2-PDA-PDMC composites were used as adsorbent for the removal of Congo red (CR) from aqueous solution to evaluate the performance in environment application. The effect of contact time, solution pH, initial CR concentration and temperature on the adsorption of CR onto SiO_2-PDA-PDMC composites was investigated. Adsorption results demonstrated that adsorption of CR onto SiO_2-PDA-PDMC composites was a fast and efficient process. The adsorption equilibrium reached within 60 min, and the adsorption process followed the pseudo-second-order model. The experimental data of isotherms were better described by the Freundlich model. Thermodynamic study depicted the endothermic nature of adsorption and the process was spontaneous. Results from the effect of solution pH on the CR adsorption showed that the acidic condition favors the adsorption and provided evidence for the contribution of PDMC on the SiO_2-PDA-PDMC composites in the removal of CR. This study suggests SiO_2-PDA-PDMC composites can be developed as a new adsorbent for the removal of

  15. Preparation of polymeric silica composites through polydopamine-mediated surface initiated ATRP for highly efficient removal of environmental pollutants

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Qiang; Liu, Meiying; Wan, Qing; Jiang, Ruming; Mao, Liucheng; Zeng, Guangjian; Huang, Hongye; Deng, Fengjie [Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031 (China); Zhang, Xiaoyong, E-mail: xiaoyongzhang1980@gmail.com [Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031 (China); Wei, Yen [Department of Chemistry and the Tsinghua Center for Frontier Polymer Research, Tsinghua University, Beijing 100084 (China)

    2017-06-01

    In this study, we developed a new procedure to prepare monodispersed functionalized SiO{sub 2} (SiO{sub 2}-PDA-PDMC) composites via mussel inspired chemistry and surface initiated atom transfer radical polymerization (SI-ATRP). Samples were characterized by transmission electron microscope (TEM), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and thermal gravimetric analysis (TGA) measurements. TEM results showed that spherical morphology was unchanged after the functionalization. FT-IR results confirmed the successful modification with polydopamine (PDA) and the presence of poly-([2-(Methacryloyloxy) ethyl] trimethylammonium chloride) (PDMC) layer on the surface of SiO{sub 2} spheres. TGA data showed that the PDMC account for about 12.12 wt% in the sample of SiO{sub 2}-PDA-PDMC composites. The XPS analysis further confirmed the existence of PDMC on the surface of SiO{sub 2}-PDA-PDMC composites. The obtained SiO{sub 2}-PDA-PDMC composites were used as adsorbent for the removal of Congo red (CR) from aqueous solution to evaluate the performance in environment application. The effect of contact time, solution pH, initial CR concentration and temperature on the adsorption of CR onto SiO{sub 2}-PDA-PDMC composites was investigated. Adsorption results demonstrated that adsorption of CR onto SiO{sub 2}-PDA-PDMC composites was a fast and efficient process. The adsorption equilibrium reached within 60 min, and the adsorption process followed the pseudo-second-order model. The experimental data of isotherms were better described by the Freundlich model. Thermodynamic study depicted the endothermic nature of adsorption and the process was spontaneous. Results from the effect of solution pH on the CR adsorption showed that the acidic condition favors the adsorption and provided evidence for the contribution of PDMC on the SiO{sub 2}-PDA-PDMC composites in the removal of CR. This study suggests SiO{sub 2}-PDA-PDMC composites can be

  16. Excitation and charge transfer in low-energy hydrogen atom collisions with neutral oxygen

    Science.gov (United States)

    Barklem, P. S.

    2018-02-01

    Excitation and charge transfer in low-energy O+H collisions is studied; it is a problem of importance for modelling stellar spectra and obtaining accurate oxygen abundances in late-type stars including the Sun. The collisions have been studied theoretically using a previously presented method based on an asymptotic two-electron linear combination of atomic orbitals (LCAO) model of ionic-covalent interactions in the neutral atom-hydrogen-atom system, together with the multichannel Landau-Zener model. The method has been extended to include configurations involving excited states of hydrogen using an estimate for the two-electron transition coupling, but this extension was found to not lead to any remarkably high rates. Rate coefficients are calculated for temperatures in the range 1000-20 000 K, and charge transfer and (de)excitation processes involving the first excited S-states, 4s.5So and 4s.3So, are found to have the highest rates. Data are available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/vizbin/qcat?J/A+A/610/A57. The data are also available at http://https://github.com/barklem/public-data

  17. The mechanism of three-body process of energy transfer from excited xenon atoms to molecules

    International Nuclear Information System (INIS)

    Wojciechowski, K.; Forys, M.

    1999-01-01

    The mechanism of energy transfer from Xe(6 s[3/2] 1 ) resonance state (E=8.44 eV) and higher excited Xe(6p, 6p', 6 d) atoms produced in pulse radiolysis to molecules have been discussed. The analysis of the kinetic data for these processes shows that in the sensitized photolysis and radiolysis of Xe-M mixtures the excited atoms decay in 'ordinary' two-body reaction: Xe(6s[3/2] 1 0 )+M→products (r.1) and in fast 'accelerated' third order process: Xe(6s[3/2] 1 0 )+M+Xe→products (r.2) The discussion shows that three-body process occurs via reactions: Xe(6s[3/2] 1 0 )+Xe k w ↔ k d Xe 2 ** (r.2a) Xe 2 **+M k q →[Xe 2 M]*→products (r.2b) It was shown that this mechanism concerns also higher excited Xe atoms and can explain a similar process in He-M mixtures and suggests that it is a general mechanism of energy transfer in all irradiated rare gas-molecule systems

  18. ATOM TRANSFER RADICAL POLYMERIZATION OF N-BUTYL METHACRYLATE IN AQUEOUS DISPERSED SYSTEMS: A MINIEMULSION APPROACH. (R826735)

    Science.gov (United States)

    Ultrasonication was applied in combination with a hydrophobe for the copper-mediated atom transfer radical polymerization of n-butyl methacrylate in an aqueous dispersed system. A controlled polymerization was successfully achieved, as demonstrated by a linear correlation between...

  19. Surface Initiated Polymerizations via e-ATRP in Pure Water

    Directory of Open Access Journals (Sweden)

    Seyed Schwan Hosseiny

    2013-10-01

    Full Text Available Here we describe the combined process of surface modification with electrochemical atom transfer radical polymerization (e-ATRP initiated from the surface of a modified gold-electrode in a pure aqueous solution without any additional supporting electrolyte. This approach allows for a very controlled growth of the polymer chains leading towards a steady increase in film thickness. Electrochemical quartz crystal microbalance displayed a highly regular increase in surface confined mass only after the addition of the pre-copper catalyst which is reduced in situ and transformed into the catalyst. Even after isolation and washing of the modified electrode surface, reinitiation was achieved with retention of the controlled electrochemical ATRP reaction. This reinitiation after isolation proves the livingness of the polymerization. This approach has interesting potential for smart thin film materials and offers also the possibility of post-modification via additional electrochemical induced reactions.

  20. Patterning of gold substrates by surface-initiated polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Dyer, D.J. [Department of Chemistry and Biochemistry, Southern Illinois University, Carbondale, IL 62901-4409 (United States)

    2003-09-01

    The design and synthesis of durable and functional organic coatings is an important topic in contemporary polymer science. The well-defined patterning of inorganic substrates is highlighted with an emphasis on planar gold. New advances in contact printing and surface initiated polymerization promise unprecedented control of the polymer architecture in the micrometer and nanometer range. (Abstract Copyright [2003], Wiley Periodicals, Inc.)

  1. Atomic layer deposition assisted pattern transfer technology for ultra-thin block copolymer films

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Wenhui; Luo, Jun; Meng, Lingkuan; Li, Junjie; Xiang, Jinjuan; Li, Junfeng; Wang, Wenwu; Chen, Dapeng; Ye, Tianchun; Zhao, Chao

    2016-08-31

    As an emerging developing technique for next-generation lithography, directed self-assembly (DSA) of block copolymer (BCP) has attracted numerous attention and has been a potential alternative to supplement the intrinsic limitations of conventional photolithography. In this work, the self-assembling properties of a lamellar diblock copolymer poly(styrene-b-methylmethacrylate) (PS-b-PMMA, 22k-b-22k, L{sub 0} = 25 nm) on Si substrate and an atomic layer deposition (ALD)-assisted pattern transfer technology for the application of DSA beyond 16/14 nm complementary metal oxide semiconductor (CMOS) technology nodes, were investigated. Firstly, two key processing parameters of DSA, i.e. annealing temperatures and durations of BCP films, were optimized to achieve low defect density and high productivity. After phase separation of BCP films, self-assembling patterns of low defect density should be transferred to the substrate. However, due to the nano-scale thickness and the weak resistance of BCP films to dry etching, it is nearly impossible to transfer the BCP patterns directly to the substrate. Therefore, an ALD-based technology was explored in this work, in which deposited Al{sub 2}O{sub 3} selectively reacts with PMMA blocks thus hardening the PMMA patterns. After removing PS blocks by plasma etching, hardened PMMA patterns were left and transferred to underneath SiO{sub 2} hard mask layer. Using this patterned hard mask, nanowire array of 25 nm pitch were realized on Si substrate. From this work, a high-throughput DSA baseline flow and related ALD-assisted pattern transfer technique were developed and proved to have good capability with the mainstream CMOS technology. - Highlights: • Optimization on self-assembly process for high productivity and low defectivity • Enhancement of etching ratio and resistance by atomic layer deposition (ALD) • A hard mask was used for pattern quality improvement and contamination control.

  2. Atomic layer deposited oxide films as protective interface layers for integrated graphene transfer

    Science.gov (United States)

    Cabrero-Vilatela, A.; Alexander-Webber, J. A.; Sagade, A. A.; Aria, A. I.; Braeuninger-Weimer, P.; Martin, M.-B.; Weatherup, R. S.; Hofmann, S.

    2017-12-01

    The transfer of chemical vapour deposited graphene from its parent growth catalyst has become a bottleneck for many of its emerging applications. The sacrificial polymer layers that are typically deposited onto graphene for mechanical support during transfer are challenging to remove completely and hence leave graphene and subsequent device interfaces contaminated. Here, we report on the use of atomic layer deposited (ALD) oxide films as protective interface and support layers during graphene transfer. The method avoids any direct contact of the graphene with polymers and through the use of thicker ALD layers (≥100 nm), polymers can be eliminated from the transfer-process altogether. The ALD film can be kept as a functional device layer, facilitating integrated device manufacturing. We demonstrate back-gated field effect devices based on single-layer graphene transferred with a protective Al2O3 film onto SiO2 that show significantly reduced charge trap and residual carrier densities. We critically discuss the advantages and challenges of processing graphene/ALD bilayer structures.

  3. Electron-electron interaction and transfer ionization in fast ion-atom collisions

    International Nuclear Information System (INIS)

    Voitkiv, A B

    2008-01-01

    Recently it was pointed out that electron capture occurring in fast ion-atom collisions can proceed via a mechanism which earlier was not considered. In the present paper we study this mechanism in more detail. Similarly as in radiative capture, where the electron transfer occurs due to the interaction with the radiation field and proceeds via emission of a photon, within this mechanism the electron capture is caused by the interaction with another atomic electron leading mainly to the emission of the latter. In contrast to the electron-electron Thomas capture, this electron-electron (E-E) mechanism is basically a first-order one having similarities to the kinematic and radiative capture channels. It also possesses important differences with the latter two. Leading to transfer ionization, this first-order capture mechanism results in the electron emission mainly in the direction opposite to the motion of the projectile ion. The same, although less pronounced, feature is also characteristic for the momenta of the target recoil ions produced via this mechanism. It is also shown that the action of the E-E mechanism is clearly seen in recent experimental data on the transfer ionization in fast proton-helium collisions.

  4. Atoms

    International Nuclear Information System (INIS)

    Fuchs, Alain; Villani, Cedric; Guthleben, Denis; Leduc, Michele; Brenner, Anastasios; Pouthas, Joel; Perrin, Jean

    2014-01-01

    Completed by recent contributions on various topics (atoms and the Brownian motion, the career of Jean Perrin, the evolution of atomic physics since Jean Perrin, relationship between scientific atomism and philosophical atomism), this book is a reprint of a book published at the beginning of the twentieth century in which the author addressed the relationship between atomic theory and chemistry (molecules, atoms, the Avogadro hypothesis, molecule structures, solutes, upper limits of molecular quantities), molecular agitation (molecule velocity, molecule rotation or vibration, molecular free range), the Brownian motion and emulsions (history and general features, statistical equilibrium of emulsions), the laws of the Brownian motion (Einstein's theory, experimental control), fluctuations (the theory of Smoluchowski), light and quanta (black body, extension of quantum theory), the electricity atom, the atom genesis and destruction (transmutations, atom counting)

  5. Transfer behavior of quantum states between atoms in photonic crystal coupled cavities

    International Nuclear Information System (INIS)

    Zhang Ke; Li Zhiyuan

    2010-01-01

    In this article, we discuss the one-excitation dynamics of a quantum system consisting of two two-level atoms each interacting with one of two coupled single-mode cavities via spontaneous emission. When the atoms and cavities are tuned into resonance, a wide variety of time-evolution behaviors can be realized by modulating the atom-cavity coupling strength g and the cavity-cavity hopping strength λ. The dynamics is solved rigorously via the eigenproblem of an ordinary coupled linear system and simple analytical solutions are derived at several extreme situations of g and λ. In the large hopping limit where g >λ, the time-evolution behavior of the system is characterized by the usual slowly varying carrier envelope superimposed upon a fast and violent oscillation. At a certain instant, the energy is fully transferred from the one quantum subsystem to the other. When the two interaction strengths are comparable in magnitude, the dynamics acts as a continuous pulse having irregular frequency and line shape of peaks and valleys, and the complicated time-evolution behaviors are ascribed to the violent competition between all the one-excitation quantum states. The coupled quantum system of atoms and cavities makes a good model to study cavity quantum electrodynamics with great freedoms of many-body interaction.

  6. On the transferability of atomic contributions to the optical rotatory power of hydrogen peroxide, methyl hydroperoxide and dimethyl peroxide

    DEFF Research Database (Denmark)

    Sánchez, Marina; Alkorta, Ibon; Elguero, José

    2014-01-01

    for the hydrogen, oxygen and carbon atoms as well as for the methyl group at the level of time-dependent density functional theory with the B3LYP exchange-correlation functional employing a large Gaussian basis set. We find that the atomic or group contributions are not transferable among these three molecules....

  7. Cross sections for energy transfer in collisions between two excited sodium atoms

    International Nuclear Information System (INIS)

    Huennekens, J.; Gallagher, A.

    1983-01-01

    We have measured cross sections, sigma/sub n/L, for the excitation transfer process Na(3P)+Na(3P)→Na(3S)+Na(nL), where nL is the 4D or 5S level. Our results are sigma/sub 4D/ = 23 A 2 +- 35% and sigma/sub 5S/ = 16 A 2 +- 35% at Tapprox.600 K. To obtain these cross sections we have used pulsed excitation and measured the intensities of 4D, 5S, and 3P fluorescence emissions, and the spatial distribution of excited atoms resulting from radiation diffusion, as well as the excited atom density as a function of time. Additionally, we have accounted for (time-dependent) radiation trapping of 3P and nL level radiation and for the resulting anisotropies of these fluorescence emissions. Comparisons of our results with theory have been made, and their relevance to other experiments is discussed

  8. Cotton fibers encapsulated with homo- and block copolymers: synthesis by the atom transfer radical polymerization grafting-from technique and solid-state NMR dynamic investigations.

    Science.gov (United States)

    Castelvetro, Valter; Geppi, Marco; Giaiacopi, Simone; Mollica, Giulia

    2007-02-01

    Cotton fibers were modified by surface-initiated atom transfer radical polymerization of ethyl acrylate (EA) followed by copolymerization with styrene. Either ethyl 2-bromopropionate as a sacrificial free initiator or Cu(II) as a deactivator was used to optimize the EA grafting yield and to preserve the livingness of the chain ends for the subsequent growth of a poly(styrene) (PSty) block from the poly(ethyl acrylate) (PEA) grafts. The polymer-encapsulated cotton fibers were analyzed by Fourier transform infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry (DSC), thermogravimetric analysis, and solid-state NMR (high-resolution 13C cross-polarization magic angle spinning, 1H spin-lattice relaxation times, and 1H free induction decay analysis NMR). The latter allowed the detection of the dynamic modifications associated with the presence of homo- and block copolymer grafts. In particular, the results of the DSC and NMR investigations suggest a heterogeneous morphology of the g-PEA-b-PSty grafted skin, which could be described as an inner layer of g-PEA sandwiched between the semicrystalline cellulose of the core fiber and the high glass transition temperature PSty of the covalently linked outer layer. Such morphology results in a reduced molecular mobility of the PEA chains.

  9. Proton-Conducting Sulfonated Ionomers by Chemical Modification and Atom Transfer Radical Polymerization

    DEFF Research Database (Denmark)

    Nielsen, Mads Møller

    The cornerstone in this dissertation is made up by three individual assessments of the diversity in the macromolecular landscape that can be obtained by applying relatively few efficient chemical tools. The intention is to gain deeper knowledge on the chemical tuning of proton exchange membranes...... of hydrocarbon macromolecular architectures, PSU with postsulfonated polystyrene (PS) grafts are investigated. Here, IEC is controlled through the degree of substitution, the graft length and DS. The grafting is performed with atom transfer radical polymerization (ATRP). The third assessment is dedicated...... of control by ATRP and click chemistry enables a wide selection of polymer structures with the handles: degree of substitution (DS), polymerization and sulfonation, and blending....

  10. Efficiency of ablative plasma energy transfer into a massive aluminum target using different atomic number ablators

    Czech Academy of Sciences Publication Activity Database

    Kasperczuk, A.; Pisarczyk, T.; Chodukowski, T.; Kalinowska, Z.; Stepniewski, W.; Jach, K.; Swierczynski, R.; Renner, Oldřich; Šmíd, Michal; Ullschmied, Jiří; Cikhart, J.; Klír, D.; Kubeš, P.; Řezáč, K.; Krouský, Eduard; Pfeifer, Miroslav; Skála, Jiří

    2015-01-01

    Roč. 33, č. 3 (2015), s. 379-386 ISSN 0263-0346 R&D Projects: GA MŠk ED1.1.00/02.0061; GA MŠk(CZ) LD14089 EU Projects: European Commission(XE) 284464 - LASERLAB-EUROPE Grant - others:ELI Beamlines(XE) CZ.1.05/1.1.00/02.0061; AVČR(CZ) M100101208 Institutional support: RVO:68378271 ; RVO:61389021 Keywords : ablator atomic number * crater volume * laser energy transfer * plasma ablative pressure Subject RIV: BL - Plasma and Gas Discharge Physics; BH - Optics, Masers, Lasers (UFP-V) Impact factor: 1.649, year: 2015

  11. Modification of Jute Fibers with Polystyrene via Atom Transfer Radical Polymerization

    DEFF Research Database (Denmark)

    Plackett, David; Jankova, Katja Atanassova; Egsgaard, Helge

    2005-01-01

    Atom transfer radical polymerization (ATRP) was investigated as a method of covalently bonding polystyrene to jute (Corchorus capsularis) and as a possible approach to fiber composites with enhanced properties. Jute fibers were modified with a brominated initiator and subsequently ATRP modified...... to attach polystyrene and then examined using SEM, DSC, TGA, FTIR, XPS, elemental analysis, and Py-GC-MS. These techniques confirmed that polystyrene had been covalently bound to the fibers and consequently ATRP-modified jute fiber mats were used to prepare hot-pressed polystyrene composites. Composite...

  12. Polarization transfer from polarized nuclear spin to μ- spin in muonic atom

    International Nuclear Information System (INIS)

    Kuno, Yoshitaka; Nagamine, Kanetada; Yamazaki, Toshimitsu.

    1987-02-01

    A theoretical study of polarization transfer from an initially-polarized nuclear spin to a μ - spin in a muonic atom is given. The switching of the hyperfine interaction at excited muonic states as well as at the ground 1s state is taken into account. The upper state of hyperfine doublet at the muonic 1s state is considered to proceed down to the lower state. It is found that as the hyperfine interaction becomes effective at higher excited muonic orbitals, a less extent of polarization is transferred from the nuclear spin to the μ - spin. The theoretical values obtained are compared with the recent experiment of μ - repolarization in a polarized 209 Bi target. (author)

  13. Coherent population transfer and superposition of atomic states via stimulated Raman adiabatic passage using an excited-doublet four-level atom

    International Nuclear Information System (INIS)

    Jin Shiqi; Gong Shangqing; Li Ruxin; Xu Zhizhan

    2004-01-01

    Coherent population transfer and superposition of atomic states via a technique of stimulated Raman adiabatic passage in an excited-doublet four-level atomic system have been analyzed. It is shown that the behavior of adiabatic passage in this system depends crucially on the detunings between the laser frequencies and the corresponding atomic transition frequencies. Particularly, if both the fields are tuned to the center of the two upper levels, the four-level system has two degenerate dark states, although one of them contains the contribution from the excited atomic states. The nonadiabatic coupling of the two degenerate dark states is intrinsic, it originates from the energy difference of the two upper levels. An arbitrary superposition of atomic states can be prepared due to such nonadiabatic coupling effect

  14. Charge Transfer Processes in Collisions of Si4+ Ions with He Atoms at Intermediate Energies

    Science.gov (United States)

    Suzuki, R.; Watanabe, A.; Sato, H.; Gu, J. P.; Hirsch, G.; Buenker, R. J.; Kimura, M.; Stancil, P. C.

    Charge transfer in collisions of Si4+ ions with He atoms below 100 keV/u is studied by using a molecular orbital representation within both the semiclassical and quantal representations. Single transfer reaction Si4++He →Si3++He+ has been studied by a number of theoretical investigations. In addition to the reaction (1), the first semiclassical MOCC calculations are performed for the double transfer channel Si4++HE→Si2++He2+ Nine molecular states that connect both with single and double electron transfer processes are considered in the present model. Electronic states and corresponding couplings are determined by the multireference single- and double- excitation configuration interaction method. The present cross sections tie well with the earlier calculations of Stancil et al., Phys. Rev. A 55, 1064 (1997) at lower energies, but show a rather different magnitude from those of Bacchus-Montabonel and Ceyzeriat, Phys. Rev. A 58, 1162 (1998). The present rate constant is found to be significantly different from the experimental finding of Fang and Kwong, Phys. Rev. A 59, 342 (1996) at 4,600 K, and hence does not support the experiment.

  15. On the mechanism of activation of copper-catalyzed atom transfer radical polymerization

    International Nuclear Information System (INIS)

    Isse, Abdirisak Ahmed; Bortolamei, Nicola; De Paoli, Patrizia; Gennaro, Armando

    2013-01-01

    The mechanism of activation of atom transfer radical polymerization (ATRP) has been analyzed by investigating the kinetics of dissociative electron transfer (ET) to alkyl halides (RX) in acetonitrile. Using a series of alkyl halides, including both bromides and chlorides, the rate constants of ET (k ET ) to RX by electrogenerated aromatic radical anions (A· − ) acting as outer-sphere donors have been measured and analyzed according to the current theories of dissociative ET. This has shown that the kinetic data fit very well the “sticky” dissociative ET model with the formation of a weak adduct held together by electrostatic interactions. The rate constants of activation, k act , of some alkyl halides, namely chloroacetonitrile, methyl 2-bromopropionate and ethyl chloroacetate, by [Cu I L] + (L = tris(2-dimethylaminoethyl)amine, tris(2-pyridylmethyl)amine, 1,1,4,7,7-pentamethyldiethylenetriamine) have also been measured in the same experimental conditions. Comparisons of the measured k act values with those predicted assuming an outer-sphere ET for the complexes have shown that activation by Cu(I) is 7–10 orders of magnitude faster than required by outer-sphere ET. Therefore, the mechanism of RX activation by Cu(I) complexes used as catalysts in ATRP occurs by an inner-sphere ET or more appropriately by a halogen atom abstraction

  16. Manganese-Oxygen Intermediates in O-O Bond Activation and Hydrogen-Atom Transfer Reactions.

    Science.gov (United States)

    Rice, Derek B; Massie, Allyssa A; Jackson, Timothy A

    2017-11-21

    Biological systems capitalize on the redox versatility of manganese to perform reactions involving dioxygen and its derivatives superoxide, hydrogen peroxide, and water. The reactions of manganese enzymes influence both human health and the global energy cycle. Important examples include the detoxification of reactive oxygen species by manganese superoxide dismutase, biosynthesis by manganese ribonucleotide reductase and manganese lipoxygenase, and water splitting by the oxygen-evolving complex of photosystem II. Although these enzymes perform very different reactions and employ structurally distinct active sites, manganese intermediates with peroxo, hydroxo, and oxo ligation are commonly proposed in catalytic mechanisms. These intermediates are also postulated in mechanisms of synthetic manganese oxidation catalysts, which are of interest due to the earth abundance of manganese. In this Account, we describe our recent efforts toward understanding O-O bond activation pathways of Mn III -peroxo adducts and hydrogen-atom transfer reactivity of Mn IV -oxo and Mn III -hydroxo complexes. In biological and synthetic catalysts, peroxomanganese intermediates are commonly proposed to decay by either Mn-O or O-O cleavage pathways, although it is often unclear how the local coordination environment influences the decay mechanism. To address this matter, we generated a variety of Mn III -peroxo adducts with varied ligand environments. Using parallel-mode EPR and Mn K-edge X-ray absorption techniques, the decay pathway of one Mn III -peroxo complex bearing a bulky macrocylic ligand was investigated. Unlike many Mn III -peroxo model complexes that decay to oxo-bridged-Mn III Mn IV dimers, decay of this Mn III -peroxo adduct yielded mononuclear Mn III -hydroxo and Mn IV -oxo products, potentially resulting from O-O bond activation of the Mn III -peroxo unit. These results highlight the role of ligand sterics in promoting the formation of mononuclear products and mark an important

  17. Preparation and controlled drug delivery applications of mesoporous silica polymer nanocomposites through the visible light induced surface-initiated ATRP

    Science.gov (United States)

    Huang, Long; Liu, Meiying; Mao, Liucheng; Xu, Dazhuang; Wan, Qing; Zeng, Guangjian; Shi, Yingge; Wen, Yuanqing; Zhang, Xiaoyong; Wei, Yen

    2017-08-01

    The mesoporous materials with large pore size, high specific surface area and high thermal stability have been widely utilized in a variety of fields ranging from environmental remediation to separation and biomedicine. However, surface modification of these silica nanomaterials is required to endow novel properties and achieve better performance for most of these applications. In this work, a new method has been established for surface modification of mesoporous silica nanoparticles (MSNs) that relied on the visible light induced atom transfer radical polymerization (ATRP). In the procedure, the copolymers composited with itaconic acid (IA) and poly(ethylene glycol)methyl acrylate (PEGMA) were grafted from MSNs using IA and PEGMA as the monomers and 10-Phenylphenothiazine(PTH) as the organic catalyst. The successful preparation of final polymer nanocomposites (named as MSNs-NH2-poly(IA-co-PEGMA)) were evidenced by a series of characterization techniques. More importantly, the anticancer agent cisplatin can be effectively loaded on MSNs-NH2-poly(IA-co-PEGMA) and controlled release it from the drug-loading composites with pH responsive behavior. As compared with conventional ATRP, the light induced surface-initiated ATRP could also be utilized for preparation of various silica polymer nanocomposites under rather benign conditions (e.g. absent of transition metal ions, low polymerization temperature and short polymerization time). Taken together, we have developed a rather promising strategy method for fabrication of multifunctional MSNs-NH2-poly(IA-co-PEGMA) with great potential for biomedical applications.

  18. Atom

    International Nuclear Information System (INIS)

    Auffray, J.P.

    1997-01-01

    The atom through centuries, has been imagined, described, explored, then accelerated, combined...But what happens truly inside the atom? And what are mechanisms who allow its stability? Physicist and historian of sciences, Jean-Paul Auffray explains that these questions are to the heart of the modern physics and it brings them a new lighting. (N.C.)

  19. Cyanide Ligand Assembly by Carbon Atom Transfer to an Iron Nitride

    International Nuclear Information System (INIS)

    Martinez, Jorge L.; Pink, Maren

    2017-01-01

    The new iron(IV) nitride complex PhB( i Pr 2 Im) 3 Fe≡N reacts with two equivalents of bis(diisopropylamino)cyclopropenylidene (BAC) to provide PhB( i Pr 2 Im) 3 Fe(CN)(N 2 )(BAC). This unusual example of a four-electron reaction involves carbon atom transfer from BAC to create a cyanide ligand along with the alkyne i Pr 2 N-C≡C-N i Pr 2 . The iron complex is in equilibrium with an N 2 - free species. Further reaction with CO leads to formation of a CO analogue, which can be independently prepared using NaCN as the cyanide source, while reaction with B(C 6 F 5 ) 3 provides the cyanoborane derivative.

  20. Low-energy charge transfer for collisions of Si3+ with atomic hydrogen

    Science.gov (United States)

    Bruhns, H.; Kreckel, H.; Savin, D. W.; Seely, D. G.; Havener, C. C.

    2008-06-01

    Cross sections of charge transfer for Si3+ ions with atomic hydrogen at collision energies of ≈40-2500eV/u were carried out using a merged-beam technique at the Multicharged Ion Research Facility at Oak Ridge National Laboratory. The data span an energy range in which both molecular orbital close coupling (MOCC) and classical trajectory Monte Carlo (CTMC) calculations are available. The influence of quantum mechanical effects of the ionic core as predicted by MOCC is clearly seen in our results. However, discrepancies between our experiment and MOCC results toward higher collision energies are observed. At energies above 1000 eV/u good agreement is found with CTMC results.

  1. Ab initio study of charge transfer in B2+ low-energy collisions with atomic hydrogen

    Science.gov (United States)

    Turner, A. R.; Cooper, D. L.; Wang, J. G.; Stancil, P. C.

    2003-07-01

    Charge transfer processes due to collisions of ground state B2+(2s 2S) ions with atomic hydrogen are investigated using the quantum-mechanical molecular-orbital close-coupling (MOCC) method. The MOCC calculations utilize ab initio adiabatic potentials and nonadiabatic radial and rotational coupling matrix elements obtained with the spin-coupled valence-bond approach. Total and state-selective cross sections and rate coefficients are presented. Comparison with the existing experiments shows our results to be in good agreement. When EMOCC cross sections with and without rotational coupling are small (400 eV/u, inclusion of rotational coupling increases the total cross section by 50% 80%, improving the agreement between the current calculations and experiments. For state-selective cross sections, rotational coupling induces mixing between different symmetries; however, its effect, especially at low collision energies, is not as important as had been suggested in previous work.

  2. Low Energy Charge Transfer for Collisions of Si3+ with Atomic Hydrogen

    Energy Technology Data Exchange (ETDEWEB)

    Bruhns, H. [Columbia University; Kreckel, H. [Columbia University; Savin, D. W. [Columbia University; Seely, D. G. [Albion College; Havener, Charles C [ORNL

    2008-01-01

    Cross sections of charge transfer for Si{sup 3+} ions with atomic hydrogen at collision energies of {approx} 40-2500 eV/u were carried out using a merged-beam technique at the Multicharged Ion Research Facility at Oak Ridge National Laboratory. The data span an energy range in which both molecular orbital close coupling (MOCC) and classical trajectory Monte Carlo (CTMC) calculations are available. The influence of quantum mechanical effects of the ionic core as predicted by MOCC is clearly seen in our results. However, discrepancies between our experiment and MOCC results toward higher collision energies are observed. At energies above 1000 eV/u good agreement is found with CTMC results.

  3. Ab initio study of charge transfer in B2+ low-energy collisions with atomic hydrogen

    International Nuclear Information System (INIS)

    Turner, A.R.; Cooper, D.L.; Wang, J.G.; Stancil, P.C.

    2003-01-01

    Charge transfer processes due to collisions of ground state B 2+ (2s 2 S) ions with atomic hydrogen are investigated using the quantum-mechanical molecular-orbital close-coupling (MOCC) method. The MOCC calculations utilize ab initio adiabatic potentials and nonadiabatic radial and rotational coupling matrix elements obtained with the spin-coupled valence-bond approach. Total and state-selective cross sections and rate coefficients are presented. Comparison with the existing experiments shows our results to be in good agreement. When E 400 eV/u, inclusion of rotational coupling increases the total cross section by 50%-80%, improving the agreement between the current calculations and experiments. For state-selective cross sections, rotational coupling induces mixing between different symmetries; however, its effect, especially at low collision energies, is not as important as had been suggested in previous work

  4. Preparation of poly(methyl methacrylate) grafted titanate nanotubes by in situ atom transfer radical polymerization

    International Nuclear Information System (INIS)

    Gao Yuan; Zhou Yongfeng; Yan Deyue; Gao Xueping

    2008-01-01

    This paper reports the successful preparation of core-shell hybrid nanocomposites by a 'grafting from' approach based on in situ atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) from titanate nanotubes (TNTs). Transmission electron microscope (TEM) images of the products provide direct evidence for the formation of a core-shell structure, possessing a hard core of TNTs and a soft shell of poly-MMA (PMMA). Fourier-transform infrared spectroscopy (FT-IR), hydrogen nuclear magnetic resonance ( 1 H NMR), scanning electron microscopy (SEM), and thermal gravimetric analysis (TGA) were used to determine the chemical structure, morphology, and the grafted PMMA quantities of the resulting products. The grafted PMMA content was well controlled and increased with increasing monomer/initiator ratio. Further copolymerization of hydroxyethyl methacrylate (HEMA) with PMMA-coated TNTs as initiators was realized, illustrating the 'living' characteristics of the ATRP method used in this paper.

  5. N-Chlorosuccinimide (NCS): A Novel Initiator for Atom Transfer Radical Polymerization of Methyl Methacrylate

    Institute of Scientific and Technical Information of China (English)

    WANG,Xia-Yan; CHANG,Li-Qun; ZHOU,Hong; ZHANG,Ke-Da

    2006-01-01

    Atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) was achieved, using N-chlorosuccinimide (NCS) as an initiator together with catalytic system CuCl/PMDETA (N,N,N',N',N"-pentamethyldiethyl-enetriamine), CuCl/MA5-DETA (N,N,N',N',N"-penta(methylacrylate)diethylenetriamine), and CuCl/bipy (bipy=2,2'-bipyridyl) respectively. The results indicated that the polymerization possessed typical controlled/living radical polymerization characteristics. The analysis for terminal group of obtained polymer by 1H NMR proved that NCS is an initiator for ATRP. In comparison with NBS, the polymerization rate was slower and the resulted polymer had narrower molecular weight distribution (MWD) when NCS was employed as the initiator.

  6. A New Initiator Cholesteryl Chloroformate for Cupper-Based Atom Transfer Radical Polymerization of Methyl Methacrylate

    Institute of Scientific and Technical Information of China (English)

    曹健; 楚娟; 张可达

    2004-01-01

    The polymerization of metyl methacrylate (MMA) was studied in detail by use of CuCl/L as a catalyst and cholesteryl chloroformate (CC) as an initiator. It was found that the atom transfer radical polymerization of MMA could proceed when L equals to a multidentate aliphatic amine ligand, N,N,N',N",N"-penta(methyl acrylate)diethylenetriamine (MA5-DETA), and no polymerization was occurred while L=2,2'-bipyridine and 1,10-phenanthroline. The linear proportionality of the molecular weights to the conversions and straight lines observed in ln[M]0/[M] versus time plots indicated that the present polymerization system had the typical controlled polymerization characteristics.

  7. SYNTHESIS OF BLOCK COPOLYMER BY INTEGRATED LIVING ANIONIC POLYMERIZATION-ATOM TRANSFER RADICAL POLYMERIZATION (ATRP)

    Institute of Scientific and Technical Information of China (English)

    Bing Liu; Feng Liu; Ning Luo; Sheng-kang Ying; Qing Liu

    2000-01-01

    Alpha-trichloroacetoxy terminated polystyrene oligomer (PS-CH2CH2OCOCCl3) and poly-(styrene-b-butadiene)oligomer [P(S-b-B)-CH2CH2OCOCCl3)] were synthesized by living anionic polymeri-zation using n-butyllithium as initiator.Then the PS-CH2CH2OCOCCl3 (PS-Cl3) or P(S-b-B)-CH2CH2O-COCCl3 (PSB-Cl3) was used as the macroinitiator in the polymerization of (meth)acrylates in the presence of CuX/bpy. AB diblock and ABC triblock copolymers were prepared by the integrated living anionic polymerization (LAP)-atom transfer radical polymerization (ATRP). The structures of the PSB-Cl3 and the P(S-b-MMA) were identified by FTIR and 1H-NMR spectrum, respectively. A new way to design block copolymers (the combination of LAP and ATRP) was developed.

  8. PREPARATION AND PROPERTIES OF MMA/1-PROPYLMETHACRYLATE-POSS COPOLYMER WITH ATOM TRANSFER RADICAL POLYMERIZATION

    Institute of Scientific and Technical Information of China (English)

    He-xin Zhang; Ho-young Lee; Young-jun Shin; Dong-ho Lee; Seok Kyun Noh

    2008-01-01

    The methyl methacrylate(MMA)/1-propylmethacrylate-polyhedral oligomeric silsesquioxane(PM-POSS) copolymers were synthesized via atom transfer radical polymerization with CuBr as catalyst.The unreacted PM-POSS monomer could be removed completely by washing the copolymerization product with n-hexane.The copolymers were characterized with 1H-NMR,X-ray diffraction,difierential scanning calorimetry,thermogravimetric analysis and gel permeatlon chromatography.With increasing PM-POSS feed ratio.the total conversion increased while the glass transition temperatures of copolymer decreased.The thermogravimetric analysis demonstrated that the thermal stability of copolymer improved slightly with PM-POSS addition.The molecular weight of copolymers increased with incorporation of PM-POSS.

  9. Three Arm Star Homo- And Co-Polymers Via Atom Transfer Radical Polymerization

    International Nuclear Information System (INIS)

    Amin, A.; Sobh, R.A.; Ayoub, M.M.H.

    2005-01-01

    Star homo and co-polymers of some vinyl monomers such as methylmethacrylate, butylmethacrylate and styrene (MMA, BMA, St.) were prepared using N, N, N', N' tetramethylethylenediamine ligand/ CuBr catalytic system via atom transfer radical polymerization (ATRP). Three armed benzene based core was successfully used as initiator. Low polydispersities and regular molecular weight values were obtained in most cases especially at low conversions. MMA and BuMA showed comparable behavior where controlled and true ATRP was observed even at the high conversions. However, styrene monomer recorded irregular high polydispersities at high conversions in spite of the relatively low molecular weight values. 1HNMR confirmed the structures of the resulting polymers. Transmission Electron microscope (TEM) proved the nano-structure of the star polymers. The thermal behavior of the MMA star homo and copolymers was studied. The effect of the star shape on the thermal behavior was very clear with respect to the linear ones

  10. Wideband laser locking to an atomic reference with modulation transfer spectroscopy.

    Science.gov (United States)

    Negnevitsky, V; Turner, L D

    2013-02-11

    We demonstrate that conventional modulated spectroscopy apparatus, used for laser frequency stabilization in many atomic physics laboratories, can be enhanced to provide a wideband lock delivering deep suppression of frequency noise across the acoustic range. Using an acousto-optic modulator driven with an agile oscillator, we show that wideband frequency modulation of the pump laser in modulation transfer spectroscopy produces the unique single lock-point spectrum previously demonstrated with electro-optic phase modulation. We achieve a laser lock with 100 kHz feedback bandwidth, limited by our laser control electronics. This bandwidth is sufficient to reduce frequency noise by 30 dB across the acoustic range and narrows the imputed linewidth by a factor of five.

  11. Effect of current and atomized grain size distribution on the solidification of Plasma Transferred Arc coatings

    Directory of Open Access Journals (Sweden)

    Danielle Bond

    2012-10-01

    Full Text Available Plasma Transferred Arc (PTA is the only thermal spray process that results in a metallurgical bond, being frequently described as a hardfacing process. The superior properties of coatings have been related to the fine microstructures obtained, which are finer than those processed under similar heat input with welding techniques using wire feedstock. This observation suggests that the atomized feedstock plays a role on the solidification of coatings. In this study a model for the role of the powders grains in the solidification of PTA coatings is put forward and discussed. An experiment was setup to discuss the model which involved the deposition of an atomized Co-based alloy with different grain size distributions and deposition currents. X ray diffraction showed that there were no phase changes due to the processing parameters. Microstructure analysis by Laser Confocal Microscopy, dilution with the substrate steel and Vickers microhardness were used the characterized coatings and enriched the discussion confirming the role of the powdered feedstock on the solidification of coatings.

  12. Oxygen atom transfer reactions from Mimoun complexes to sulfides and sulfoxides. A bonding evolution theory analysis.

    Science.gov (United States)

    González-Navarrete, Patricio; Sensato, Fabricio R; Andrés, Juan; Longo, Elson

    2014-08-07

    In this research, a comprehensive theoretical investigation has been conducted on oxygen atom transfer (OAT) reactions from Mimoun complexes to sulfides and sulfoxides. The joint use of the electron localization function (ELF) and Thom's catastrophe theory (CT) provides a powerful tool to analyze the evolution of chemical events along a reaction pathway. The progress of the reaction has been monitored by structural stability domains from ELF topology while the changes between them are controlled by turning points derived from CT which reveal that the reaction mechanism can be separated in several steps: first, a rupture of the peroxo O1-O2 bond, then a rearrangement of lone pairs of the sulfur atom occurs and subsequently the formation of S-O1 bond. The OAT process involving the oxidation of sulfides and sulfoxides is found to be an asynchronous process where O1-O2 bond breaking and S-O1 bond formation processes do not occur simultaneously. Nucleophilic/electrophilic characters of both dimethyl sulfide and dimethyl sulfoxide, respectively, are sufficiently described by our results, which hold the key to unprecedented insight into the mapping of electrons that compose the bonds while the bonds change.

  13. Charge-transfer modified embedded atom method dynamic charge potential for Li-Co-O system.

    Science.gov (United States)

    Kong, Fantai; Longo, Roberto C; Liang, Chaoping; Nie, Yifan; Zheng, Yongping; Zhang, Chenxi; Cho, Kyeongjae

    2017-11-29

    To overcome the limitation of conventional fixed charge potential methods for the study of Li-ion battery cathode materials, a dynamic charge potential method, charge-transfer modified embedded atom method (CT-MEAM), has been developed and applied to the Li-Co-O ternary system. The accuracy of the potential has been tested and validated by reproducing a variety of structural and electrochemical properties of LiCoO 2 . A detailed analysis on the local charge distribution confirmed the capability of this potential for dynamic charge modeling. The transferability of the potential is also demonstrated by its reliability in describing Li-rich Li 2 CoO 2 and Li-deficient LiCo 2 O 4 compounds, including their phase stability, equilibrium volume, charge states and cathode voltages. These results demonstrate that the CT-MEAM dynamic charge potential could help to overcome the challenge of modeling complex ternary transition metal oxides. This work can promote molecular dynamics studies of Li ion cathode materials and other important transition metal oxides systems that involve complex electrochemical and catalytic reactions.

  14. Tunable self-assembled spin chains of strongly interacting cold atoms for demonstration of reliable quantum state transfer

    DEFF Research Database (Denmark)

    Loft, N. J. S.; Marchukov, O. V.; Petrosyan, D.

    2016-01-01

    We have developed an efficient computational method to treat long, one-dimensional systems of strongly-interacting atoms forming self-assembled spin chains. Such systems can be used to realize many spin chain model Hamiltonians tunable by the external confining potential. As a concrete...... demonstration, we consider quantum state transfer in a Heisenberg spin chain and we show how to determine the confining potential in order to obtain nearly-perfect state transfer....

  15. Stepwise O-Atom Transfer in Heme-Based Tryptophan Dioxygenase: Role of Substrate Ammonium in Epoxide Ring Opening.

    Science.gov (United States)

    Shin, Inchul; Ambler, Brett R; Wherritt, Daniel; Griffith, Wendell P; Maldonado, Amanda C; Altman, Ryan A; Liu, Aimin

    2018-03-28

    Heme-based tryptophan dioxygenases are established immunosuppressive metalloproteins with significant biomedical interest. Here, we synthesized two mechanistic probes to specifically test if the α-amino group of the substrate directly participates in a critical step of the O atom transfer during catalysis in human tryptophan 2,3-dioxygenase (TDO). Substitution of the nitrogen atom of the substrate to a carbon (probe 1) or oxygen (probe 2) slowed the catalytic step following the first O atom transfer such that transferring the second O atom becomes less likely to occur, although the dioxygenated products were observed with both probes. A monooxygenated product was also produced from probe 2 in a significant quantity. Analysis of this new product by HPLC coupled UV-vis spectroscopy, high-resolution mass spectrometry, 1 H NMR, 13 C NMR, HSQC, HMBC, and infrared (IR) spectroscopies concluded that this monooxygenated product is a furoindoline compound derived from an unstable epoxyindole intermediate. These results prove that small molecules can manipulate the stepwise O atom transfer reaction of TDO and provide a showcase for a tunable mechanism by synthetic compounds. The product analysis results corroborate the presence of a substrate-based epoxyindole intermediate during catalysis and provide the first substantial experimental evidence for the involvement of the substrate α-amino group in the epoxide ring-opening step during catalysis. This combined synthetic, biochemical, and biophysical study establishes the catalytic role of the α-amino group of the substrate during the O atom transfer reactions and thus represents a substantial advance to the mechanistic comprehension of the heme-based tryptophan dioxygenases.

  16. Preparation of polymer brushes grafted graphene oxide by atom transfer radical polymerization as a new support for trypsin immobilization and efficient proteome digestion.

    Science.gov (United States)

    Guo, Cong; Zhao, Xinyuan; Zhang, Wanjun; Bai, Haihong; Qin, Weijie; Song, Haifeng; Qian, Xiaohong

    2017-08-01

    Highly efficient protein digestion is one of the key issues in the "bottom-up" strategy-based proteomic studies. Compared with the time-consuming solution-based free protease digestion, immobilized protease digestion offers a promising alternative with obviously improved sample processing throughput. In this study, we proposed a new immobilized protease digestion strategy using two kinds of polymer-grafted graphene oxide (GO) conjugated trypsin. The polymer brush grafted GO was prepared using in situ polymer growth on initiator-functionalized GO using surface-initiated atom transfer radical polymerization (SI-ATRP) and characterized by AFM, TEM, TGA, and XPS. The polymer brush grafted GO supports three-dimensional trypsin immobilization, which not only increases the loading amount but also improves accessibility towards protein substrates. Both of the two types of immobilized trypsin provide 700 times shorter digestion time, while maintaining comparable protein/peptide identification scale compared with that of free trypsin digestion. More interestingly, combined application of the two types of immobilized trypsin with different surface-grafted polymers leads to at least 18.3/31.3% enhancement in protein/peptide identification compared with that obtained by digestion using a single type, indicating the potential of this digestion strategy for deeper proteome coverage using limited mass spectrometer machine hour. We expect these advantages may find valuable application in high throughput clinical proteomic studies, which often involve processing of a large number of samples. Graphical abstract Preparation of polymer brushes grafted and trypsin immobilized graphene oxide and its application in proteome digestion and mass spectrometry identification.

  17. Iron halide mediated atom transfer radical polymerization of methyl methacrylate with N-Alkyl-2-pyridylmethanimine as the ligand

    NARCIS (Netherlands)

    Zhang, H.; Schubert, U.S.

    2004-01-01

    The controlled atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) catalyzed by iron halide/N-(n-hexyl)-2-pyridylmethanimine (NHPMI) is described. The ethyl 2-bromoisobutyrate (EBIB)-initiated ATRP with [MMA]0/[EBIB]0/[iron halide]0/[NHPMI]0 = 150/1/1/2 was better controlled in

  18. Nitrogen atom transfer mediated by a new PN3P-pincer nickel core via a putative nitrido nickel intermediate

    KAUST Repository

    Yao, Changguang

    2018-02-13

    A 2nd generation PN3P-pincer azido nickel complex (PN3P)Ni(N3) reacts with isocyanides to afford monosubstituted carbodiimides under irradiation, presumably via a transient nitrido intermediate. The resulting species can further generate unsymmetrical carboddimides and the PN3P nickel halide complex, accomplishing a synthetic cycle for a complete nitrogen atom transfer reaction.

  19. Charge transfer incollisions of Li3+ and Be4+ ions with atomic hydrogen at low impact energy

    International Nuclear Information System (INIS)

    Ohyama, T.; Itikawa, Y.

    1981-08-01

    Total charge transfer cross sections are calculated for the collisions of Li 3+ and Be 4+ ions with H(1s) atoms in the low energy region (E 3+ -H system, a reasonable agreement is found between the present calculation and the recent experiment. (author)

  20. ANISOTROPY EFFECTS IN SINGLE-ELECTRON TRANSFER BETWEEN LASER-EXCITED ATOMS AND HIGHLY-CHARGED IONS

    NARCIS (Netherlands)

    Recent collision experiments are reviewed in which one-electron transfer between laser excited target atoms and (highly charged) keV-ions has been studied. Especially results showing a dependence of the charge exchange on the initial target orbital alignment are discussed. The question to what

  1. Ion conducting solid polymer electrolytes based on polypentafluorostyrene-b-polyether-b-polypentafluorostyrene prepared by atom transfer radical polymerization

    DEFF Research Database (Denmark)

    Jankova, Katja; Jannasch, P.; Hvilsted, Søren

    2004-01-01

    Novel triblock copolymers based on central poly( ethylene glycol) ( PEG) or poly( ethylene glycol-co-propylene glycol) (PEGPG) blocks with poly( pentafluorostyrene) (PFS) outer blocks were prepared by Atom Transfer Radical Polymerization (ATRP) with polydispersities on the order of 1.2 - 1...

  2. Strong isotope effects on the charge transfer in slow collisions of He2+ with atomic hydrogen, deuterium, and tritium

    NARCIS (Netherlands)

    Stolterfoht, N.; Cabrera-Trujillo, R.; Oehrn, Y.; Deumens, E.; Hoekstra, R.; Sabin, J. R.

    2007-01-01

    Probabilities and cross sections for charge transfer by He2+ impact on atomic hydrogen (H), deuterium (D), and tritium (T) at low collision energies are calculated. The results are obtained using an ab initio theory, which solves the time-dependent Schrodinger equation. For the H target, excellent

  3. Synthesis of triblock and random copolymers of 4- acetoxystyrene and styrene by living atom transfer radical polymerization

    DEFF Research Database (Denmark)

    Gao, Bo; Chen, Xianyi; Ivan, Bela

    1997-01-01

    Triblock copolymers containing polystyrene (PSt) and poly(4-acetoxystyrene) (PAcOSt) segments have been prepared by atom transfer radical polymerization (ATRP). In the first step one of the two monomers was polymerized in bulk using the initiating system alpha,alpha'-dibromo-p-xylene/CuBr/2,2'-bi...

  4. Nitrogen atom transfer mediated by a new PN3P-pincer nickel core via a putative nitrido nickel intermediate

    KAUST Repository

    Yao, Changguang; Wang, Xiufang; Huang, Kuo-Wei

    2018-01-01

    A 2nd generation PN3P-pincer azido nickel complex (PN3P)Ni(N3) reacts with isocyanides to afford monosubstituted carbodiimides under irradiation, presumably via a transient nitrido intermediate. The resulting species can further generate unsymmetrical carboddimides and the PN3P nickel halide complex, accomplishing a synthetic cycle for a complete nitrogen atom transfer reaction.

  5. Eosin Y as a Direct Hydrogen Atom Transfer Photocatalyst for the Functionalization of C-H Bonds.

    Science.gov (United States)

    Fan, Xuan-Zi; Rong, Jia-Wei; Wu, Hao-Lin; Zhou, Quan; Deng, Hong-Ping; Tan, Jin Da; Xue, Cheng-Wen; Wu, Li-Zhu; Tao, Hai-Rong; Wu, Jie

    2018-05-02

    Eosin Y, a well-known economical alternative to metal catalysts in visible-light-driven single-electron transfer-based organic transformations, can behave as an effective direct hydrogen atom transfer catalyst for C-H activation. Using the alkylation of C-H bonds with electron-deficient alkenes as a model study revealed an extremely broad substrate scope, enabling easy access to a variety of important synthons. This eosin Y-based photocatalytic hydrogen atom transfer strategy is promising for diverse functionalization of a wide range of native C-H bonds in a green and sustainable manner. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Quantification of ion or atom transfer phenomena in materials implanted by nuclear methods

    International Nuclear Information System (INIS)

    Oudadesse, Hassane

    1998-01-01

    Knowledge of transfer of the constituents of a system from regions of higher to lower concentration is of interest for implanted bio-materials. It allows determining the rate at which this material is integrated in a living material. To evaluate the ossification kinetics and to study the bio-functionality in corals of Ca and Sr, irradiations with a 10 13 n.cm -2 .s -1 was performed, followed by the examination of changes in the localization of these elements. By using PIXE analysis method the distribution of Ca, P, Sr, Zn and Fe in the implant, bone and bone-implant interfaces were determined. Thus, it was shown that resorption of coral in sheep is achieved in 5 months after implantation and is identical to the cortical tissues 4 months after implantation in animals as for instance in hares. We have analyzed the tissues from around the prostheses extracted from patients. The samples were calcined and reduced to powder weighting some milligrams. We have adopted for this study the PIXE analysis method. The samples were irradiated by a proton beam of 3 MeV and about 400 μm diameter. The results show the presence of the elements Ti, Fe, Cr, Ni or Zn according to the type of the implanted prosthesis. This dispersal of the metallic ions and atoms contaminate the tissues. The transfer factors translate the exchanges between bone and the implanted material. The solvatation phenomenon and the electric charge equilibrium explain the transfer order of cations Mg 2+ , Ca 2+ and Sr 2+ and of the anion PO 4 3- . We have also determined these factors for the elements Ti, Cr and Ni. An original technique to study the bone bio-functionality was used. Use of phosphate derivatives labelled by 99m Tc allows obtaining information about the fixation of radioactive tracer. It was found that only after the eighth month at the implantation the neo-formed bone fixes the MDP (methyl diphosphate) labelled by 99m Tc in a similar way as in the control sample. Starting from this moment the

  7. Efficient Functionalization of Polyethylene Fibers for the Uranium Extraction from Seawater through Atom Transfer Radical Polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Neti, Venkata S. [Chemical; Das, Sadananda [Chemical; Brown, Suree [Department; Janke, Christopher J. [Materials; Kuo, Li-Jung [Marine; Gill, Gary A. [Marine; Dai, Sheng [Chemical; Department; Mayes, Richard T. [Chemical

    2017-09-14

    Brush-on-brush structures are proposed as one method to overcome support effects in grafted polymers. Utilizing glycidyl methacrylate (GMA) grafted on polyethylene (PE) fibers using radiation-induced graft polymerization (RIGP) provides a hydrophilic surface on the hydrophobic PE. When integrated with atom transfer radical polymerization (ATRP), the grafting of acrylonitrile (AN) and hydroxyethyl acrylate (HEA) can be controlled and manipulated more easily than with RIGP. Poly(acrylonitrile)-co-poly(hydroxyethyl acrylate) chains were grown via ATRP on PE-GMA fibers to generate an adsorbent for the extraction of uranium from seawater. The prepared adsorbents in this study demonstrated promise (159.9 g- U/kg of adsorbent) in laboratory screening tests using a high uranium concentration brine and 1.24 g-U/Kg of adsorbent in the filtered natural seawater in 21-days. The modest capacity in 21- days exceeds previous efforts to generate brush-on-brush adsorbents by ATRP while manipulating the apparent surface hydrophilicity of the trunk material (PE).

  8. Formation of hyperbranched polymers in atom transfer radical copolymerization of MMA and DVB

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Hyperbranched poly(methyl methacrylate)s (HPMMAs) have been successfully prepared by atom transfer radical copolymerization of MMA and divinylbenzene (DVB).Kinetic study shows complete consumption of the initiator in 0.5 h,and relatively low polymerization rate when DVB content in the feed was high.By analyzing MALDI-TOF spectra of the resulting copolymers,the linear A n B (n=0,1,2,3) oligomers were formed in 0.5 h of polymerization,and then the oligomers reacted each other to form dimers,further reactions produced HPMMA.The SEC and NMR spectroscopies were used to trace the polymerization,and the results demonstrate that small amount of the branching reactions occur in the initial polymerization,and the branched polymers are significantly generated past a certain conversion depending upon the feed ratios.Raising the content of DVB in the monomer mixture can increase the pendent vinyl groups of the linear oligo-inimers,leading to gelation at low MMA conversion.

  9. Poly(n-isopropylacrylamide)-based hydrogel coatings on magnetite nanoparticles via atom transfer radical polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Frimpong, Reynolds A; Hilt, J Zach [Department of Chemical and Materials Engineering, University of Kentucky, Lexington, KY 40506 (United States)], E-mail: hilt@engr.uky.edu

    2008-04-30

    Core magnetite (Fe{sub 3}O{sub 4}) nanoparticles have been functionalized with a model intelligent hydrogel system based on the temperature responsive polymer poly(n-isopropyl acrylamide) (PNIPAAm) to obtain magnetically responsive core-shell nanocomposites. Fe{sub 3}O{sub 4} nanoparticles were obtained from a one-pot co-precipitation method which provided either oleic acid (hydrophobic) or citric acid (hydrophilic) coated nanoparticles. Subsequent ligand exchange of these coatings with various bromine alkyl halides and a bromo silane provided initiating sites for functionalization with NIPAAm using atom transfer radical polymerization (ATRP). The bromine alkyl halides that were used were 2-bromo-2-methyl propionic acid (BMPA) and 2-bromopropionyl bromide (BPB). The bromo silane that was used was 3-bromopropyl trimethoxysilane (BPTS). The intelligent polymeric shell consists of NIPAAm crosslinked with poly(ethylene glycol) 400 dimethacrylate (PEG400DMA). Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and transmission electron microscopy (TEM) were used to confirm the presence of the polymeric shell. Dynamic light scattering (DLS) was used to characterize the nanocomposites for particle size changes with temperature. Their magnetic and temperature responsiveness show great promise for further biomedical applications. This platform for functionalizing magnetic nanoparticles with intelligent hydrogels promises to impact a wide range of medical and biological applications of magnetic nanoparticles.

  10. Colorful Polyelectrolytes: An Atom Transfer Radical Polymerization Route to Fluorescent Polystyrene Sulfonate.

    Science.gov (United States)

    Huberty, Wayne; Tong, Xiaowei; Balamurugan, Sreelatha; Deville, Kyle; Russo, Paul S; Zhang, Donghui

    2016-03-01

    A labeled green fluorescent polystyrene sulfonate (LNaPSS) has been synthesized using atom transfer radical polymerization of a styrene sulfonate monomer with a fluorescent co-monomer, fluorescein thiocyanate-vinyl aniline. As a result this 100 % sulfonated polymer contains no hydrophobic patches along the chain backbone besides the fluorescent marker itself. The concentration of the fluorescent monomer was kept low to maintain the characteristic properties of the anionic polyelectrolyte, LNaPSS. ATRP conditions facilitated the production of polymers spanning a range of molecular weights from 35,000 to 175,000 in gram-scale batches with polydispersity indices of 1.01-1.24. Molecular weight increased with the monomer to initiator ratio. Gel permeation chromatography results show a unimodal distribution, and the polymer structure was also confirmed by (1)H NMR and FT-IR spectroscopy. Fluorescence spectroscopy confirmed covalent bonding of fluorescein isothiocyanate to the polymer, indicating that the polymer is suitable as a probe in fluorescence microscopy. To demonstrate this ability, the polymer was used to locate structural features in salt crystals formed during drying, as in the evaporation of sea mist. A second application to probe diffusion studies is also demonstrated.

  11. Customized atomic force microscopy probe by focused-ion-beam-assisted tip transfer

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Andrew; Butte, Manish J., E-mail: manish.butte@stanford.edu [Department of Pediatrics, Division of Immunology, Allergy and Rheumatology, Stanford University, Stanford, California 94305 (United States)

    2014-08-04

    We present a technique for transferring separately fabricated tips onto tipless atomic force microscopy (AFM) cantilevers, performed using focused ion beam-assisted nanomanipulation. This method addresses the need in scanning probe microscopy for certain tip geometries that cannot be achieved by conventional lithography. For example, in probing complex layered materials or tall biological cells using AFM, a tall tip with a high-aspect-ratio is required to avoid artifacts caused by collisions of the tip's sides with the material being probed. We show experimentally that tall (18 μm) cantilever tips fabricated by this approach reduce squeeze-film damping, which fits predictions from hydrodynamic theory, and results in an increased quality factor (Q) of the fundamental flexural mode. We demonstrate that a customized tip's well-defined geometry, tall tip height, and aspect ratio enable improved measurement of elastic moduli by allowing access to low-laying portions of tall cells (T lymphocytes). This technique can be generally used to attach tips to any micromechanical device when conventional lithography of tips cannot be accomplished.

  12. Poly(n-isopropylacrylamide)-based hydrogel coatings on magnetite nanoparticles via atom transfer radical polymerization

    International Nuclear Information System (INIS)

    Frimpong, Reynolds A; Hilt, J Zach

    2008-01-01

    Core magnetite (Fe 3 O 4 ) nanoparticles have been functionalized with a model intelligent hydrogel system based on the temperature responsive polymer poly(n-isopropyl acrylamide) (PNIPAAm) to obtain magnetically responsive core-shell nanocomposites. Fe 3 O 4 nanoparticles were obtained from a one-pot co-precipitation method which provided either oleic acid (hydrophobic) or citric acid (hydrophilic) coated nanoparticles. Subsequent ligand exchange of these coatings with various bromine alkyl halides and a bromo silane provided initiating sites for functionalization with NIPAAm using atom transfer radical polymerization (ATRP). The bromine alkyl halides that were used were 2-bromo-2-methyl propionic acid (BMPA) and 2-bromopropionyl bromide (BPB). The bromo silane that was used was 3-bromopropyl trimethoxysilane (BPTS). The intelligent polymeric shell consists of NIPAAm crosslinked with poly(ethylene glycol) 400 dimethacrylate (PEG400DMA). Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and transmission electron microscopy (TEM) were used to confirm the presence of the polymeric shell. Dynamic light scattering (DLS) was used to characterize the nanocomposites for particle size changes with temperature. Their magnetic and temperature responsiveness show great promise for further biomedical applications. This platform for functionalizing magnetic nanoparticles with intelligent hydrogels promises to impact a wide range of medical and biological applications of magnetic nanoparticles

  13. Polarization transfer between oriented metastable helium atoms and neon atoms. A comparison of even and odd isotopes

    Energy Technology Data Exchange (ETDEWEB)

    Pepper, D M; Wang, H T.M.

    1983-11-01

    Collision-induced polarization transfer from optically pumped helium to excited states of neon is studied using various combinations of even and odd isotopes. It is found that, within our experimental accuracy of 10%, the resultant polarization is independent of the isotopic composition of the binary mixture. Possible applications using this mechanism are discussed.

  14. Quasi-four-body treatment of charge transfer in the collision of protons with atomic helium: I. Thomas related mechanisms

    Science.gov (United States)

    Safarzade, Zohre; Fathi, Reza; Shojaei Akbarabadi, Farideh; Bolorizadeh, Mohammad A.

    2018-04-01

    The scattering of a completely bare ion by atoms larger than hydrogen is at least a four-body interaction, and the charge transfer channel involves a two-step process. Amongst the two-step interactions of the high-velocity single charge transfer in an anion-atom collision, there is one whose amplitude demonstrates a peak in the angular distribution of the cross sections. This peak, the so-called Thomas peak, was predicted by Thomas in a two-step interaction, classically, which could also be described through three-body quantum mechanical models. This work discusses a four-body quantum treatment of the charge transfer in ion-atom collisions, where two-step interactions illustrating a Thomas peak are emphasized. In addition, the Pauli exclusion principle is taken into account for the initial and final states as well as the operators. It will be demonstrated that there is a momentum condition for each two-step interaction to occur in a single charge transfer channel, where new classical interactions lead to the Thomas mechanism.

  15. Oxygen atom transfer from a trans-dioxoruthenium(VI) complex to nitric oxide.

    Science.gov (United States)

    Man, Wai-Lun; Lam, William W Y; Ng, Siu-Mui; Tsang, Wenny Y K; Lau, Tai-Chu

    2012-01-02

    In aqueous acidic solutions trans-[Ru(VI)(L)(O)(2)](2+) (L=1,12-dimethyl-3,4:9,10-dibenzo-1,12-diaza-5,8-dioxacyclopentadecane) is rapidly reduced by excess NO to give trans-[Ru(L)(NO)(OH)](2+). When ≤1 mol equiv NO is used, the intermediate Ru(IV) species, trans-[Ru(IV)(L)(O)(OH(2))](2+), can be detected. The reaction of [Ru(VI)(L)(O)(2)](2+) with NO is first order with respect to [Ru(VI)] and [NO], k(2)=(4.13±0.21)×10(1) M(-1) s(-1) at 298.0 K. ΔH(≠) and ΔS(≠) are (12.0±0.3) kcal mol(-1) and -(11±1) cal mol(-1) K(-1), respectively. In CH(3)CN, ΔH(≠) and ΔS(≠) have the same values as in H(2)O; this suggests that the mechanism is the same in both solvents. In CH(3)CN, the reaction of [Ru(VI)(L)(O)(2)](2+) with NO produces a blue-green species with λ(max) at approximately 650 nm, which is characteristic of N(2)O(3). N(2)O(3) is formed by coupling of NO(2) with excess NO; it is relatively stable in CH(3)CN, but undergoes rapid hydrolysis in H(2)O. A mechanism that involves oxygen atom transfer from [Ru(VI)(L)(O)(2)](2+) to NO to produce NO(2) is proposed. The kinetics of the reaction of [Ru(IV)(L)(O)(OH(2))](2+) with NO has also been investigated. In this case, the data are consistent with initial one-electron O(-) transfer from Ru(IV) to NO to produce the nitrito species [Ru(III)(L)(ONO)(OH(2))](2+) (k(2)>10(6) M(-1) s(-1)), followed by a reaction with another molecule of NO to give [Ru(L)(NO)(OH)](2+) and NO(2)(-) (k(2)=54.7 M(-1) s(-1)). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Surface grafting of zwitterionic polymers onto dye doped AIE-active luminescent silica nanoparticles through surface-initiated ATRP for biological imaging applications

    Science.gov (United States)

    Mao, Liucheng; Liu, Xinhua; Liu, Meiying; Huang, Long; Xu, Dazhuang; Jiang, Ruming; Huang, Qiang; Wen, Yuanqing; Zhang, Xiaoyong; Wei, Yen

    2017-10-01

    Aggregation-induced emission (AIE) dyes have recently been intensively explored for biological imaging applications owing to their outstanding optical feature as compared with conventional organic dyes. The AIE-active luminescent silica nanoparticles (LSNPs) are expected to combine the advantages both of silica nanoparticles and AIE-active dyes. Although the AIE-active LSNPs have been prepared previously, surface modification of these AIE-active LSNPs with functional polymers has not been reported thus far. In this work, we reported a rather facile and general strategy for preparation of polymers functionalized AIE-active LSNPs through the surface-initiated atom transfer radical polymerization (ATRP). The AIE-active LSNPs were fabricated via direct encapsulation of AIE-active dye into silica nanoparticles through a non-covalent modified Stöber method. The ATRP initiator was subsequently immobilized onto these AIE-active LSNPs through amidation reaction between 3-aminopropyl-triethoxy-silane and 2-bromoisobutyryl bromide. Finally, the zwitterionic 2-(methacryloyloxy)ethyl phosphorylcholine (MPC) was selected as model monomer and grafted onto MSNs through ATRP. The characterization results suggested that LSNPs can be successfully modified with poly(MPC) through surface-initiated ATRP. The biological evaluation results demonstrated that the final SNPs-AIE-pMPC composites possess low cytotoxicity, desirable optical properties and great potential for biological imaging. Taken together, we demonstrated that AIE-active LSNPs can be fabricated and surface modified with functional polymers to endow novel functions and better performance for biomedical applications. More importantly, this strategy developed in this work could also be extended for fabrication of many other LSNPs polymer composites owing to the good monomer adoptability of ATRP.

  17. Study of elementary transfer mechanisms during a collision between a swift multi-charged heavy ion and a neutral atom

    International Nuclear Information System (INIS)

    Jardin, P.

    1995-01-01

    This work is dedicated to the study of the energy transfer mechanisms which occur during a collision between a swift multicharged heavy ion and a neutral atom. The elementary energy energy transfer mechanisms (scattering, excitation, ionization, capture) and their consequences on the target velocity after the collision (recoil velocity) are recalled in the first chapter. In the case of small projectile diffusion angles, we show that the recoil velocity component, transverse to the incident projectile direction, results principally from the diffusion mechanism, while the longitudinal component is due essentially to the mass transfer and the inelastic energy transfer mechanisms. Since the target recoil velocities are very small, we have built an experimental set-up which reduces the impreciseness on their measurement due to the target thermal spread using, as targets, cooled atoms of a supersonic jet (temperature 44+ (6.7 MeV/A) + Ar => Xe 44 + Ar q+ +qe - (q ranging from 1 to 7); Xe 44+ (6.7 MeV/A) + He => Xe 44+ He 1+,2+ +1e - ,2e - . We show that it is possible to interpret the recoil velocity in terms of kinetic energy transferred to the target and to the electrons ejected from the target. (author)

  18. Electrochemical Water Oxidation and Stereoselective Oxygen Atom Transfer Mediated by a Copper Complex.

    Science.gov (United States)

    Kafentzi, Maria-Chrysanthi; Papadakis, Raffaello; Gennarini, Federica; Kochem, Amélie; Iranzo, Olga; Le Mest, Yves; Le Poul, Nicolas; Tron, Thierry; Faure, Bruno; Simaan, A Jalila; Réglier, Marius

    2018-04-06

    Water oxidation by copper-based complexes to form dioxygen has attracted attention in recent years, with the aim of developing efficient and cheap catalysts for chemical energy storage. In addition, high-valent metal-oxo species produced by the oxidation of metal complexes in the presence of water can be used to achieve substrate oxygenation with the use of H 2 O as an oxygen source. To date, this strategy has not been reported for copper complexes. Herein, a copper(II) complex, [(RPY2)Cu(OTf) 2 ] (RPY2=N-substituted bis[2-pyridyl(ethylamine)] ligands; R=indane; OTf=triflate), is used. This complex, which contains an oxidizable substrate moiety (indane), is used as a tool to monitor an intramolecular oxygen atom transfer reaction. Electrochemical properties were investigated and, upon electrolysis at 1.30 V versus a normal hydrogen electrode (NHE), both dioxygen production and oxygenation of the indane moiety were observed. The ligand was oxidized in a highly diastereoselective manner, which indicated that the observed reactivity was mediated by metal-centered reactive species. The pH dependence of the reactivity was monitored and correlated with speciation deduced from different techniques, ranging from potentiometric titrations to spectroscopic studies and DFT calculations. Water oxidation for dioxygen production occurs at neutral pH and is probably mediated by the oxidation of a mononuclear copper(II) precursor. It is achieved with a rather low overpotential (280 mV at pH 7), although with limited efficiency. On the other hand, oxygenation is maximum at pH 8-8.5 and is probably mediated by the electrochemical oxidation of an antiferromagnetically coupled dinuclear bis(μ-hydroxo) copper(II) precursor. This constitutes the first example of copper-centered oxidative water activation for a selective oxygenation reaction. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Direct Aldehyde C-H Arylation and Alkylation via the Combination of Nickel, Hydrogen Atom Transfer, and Photoredox Catalysis.

    Science.gov (United States)

    Zhang, Xiaheng; MacMillan, David W C

    2017-08-23

    A mechanism that enables direct aldehyde C-H functionalization has been achieved via the synergistic merger of photoredox, nickel, and hydrogen atom transfer catalysis. This mild, operationally simple protocol transforms a wide variety of commercially available aldehydes, along with aryl or alkyl bromides, into the corresponding ketones in excellent yield. This C-H abstraction coupling technology has been successfully applied to the expedient synthesis of the medicinal agent haloperidol.

  20. Charge transfer rates for xenon Rydberg atoms at metal and semiconductor surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Dunning, F.B. [Department of Physics and Astronomy, Rice University, MS 61, 6100 Main Street, Houston, TX 77005-1892 (United States)]. E-mail: fbd@rice.edu; Wethekam, S. [Institut fuer Physik der Humboldt-Universitaet zu Berlin, Newtonstr. 15, D-12489 Berlin (Germany); Dunham, H.R. [Department of Physics and Astronomy, Rice University, MS 61, 6100 Main Street, Houston, TX 77005-1892 (United States); Lancaster, J.C. [Department of Physics and Astronomy, Rice University, MS 61, 6100 Main Street, Houston, TX 77005-1892 (United States)

    2007-05-15

    Recent progress in the study of charge exchange between xenon Rydberg atoms and surfaces is reviewed. Experiments using Au(1 1 1) surfaces show that under appropriate conditions each incident atom can be detected as an ion. The ionization dynamics, however, are strongly influenced by the perturbations in the energies and structure of the atomic states that occur as the ion collection field is applied and as the atom approaches the surface. These lead to avoided crossings between different atomic levels causing the atom to successively assume the character of a number of different states and lose much of its initial identity. The effects of this mixing are discussed. Efficient surface ionization is also observed at Si(1 0 0) surfaces although the ion signal is influenced by stray fields present at the surface.

  1. Energy-Transfer Kinetics for Xe (6p[1/2]0) Atoms in Kr, Ar, Ne, and He.

    Science.gov (United States)

    He, Shan; Liu, Dong; Li, Xueyang; Chu, Junzhi; Guo, Jingwei; Liu, Jinbo; Hu, Shu; Sang, Fengting; Jin, Yuqi

    2018-06-11

    The kinetic processes for the Xe (6p[1/2] 0 ) atoms in Kr, Ar, Ne, and He buffer gases were studied. We found that Kr, Ar, and Ne atoms can be used to switch the amplified spontaneous emission (ASE) channel from 3408 nm (6p[1/2] 0 -6s'[1/2] 1 ) to 3680 nm (5d[1/2] 1 -6p[1/2] 1 ), while Xe and He atoms do not show such a phenomenon. This ASE channel switch is mainly ascribed to the fast transfer of 6p[1/2] 0 → 5d[1/2] 1 . On the basis of the rate equations for two-state coupling (energy-transfer processes between the two states are very rapid), the reason why the ASE channel switch effect normally coincides with a double exponential decay of the spontaneous emission at 828 nm (6p[1/2] 0 -6s[3/2] 1 ) is explained. The actual situations in Xe, Ar, Ne, and He follow this rule. However, the strictly single exponential decay of the spontaneous emission at 828 nm and strong ASE channel switch effect simultaneously emerge in Kr. This indicates that the transfer of 6p[1/2] 0 → 5d[1/2] 1 in Kr does not occur via two-state coupling, but via two steps of near-resonance collision through the 5s[3/2] 2 (Kr) state as the intermediate state (6p[1/2] 0 → 5s[3/2] 2 (Kr) → 5d[1/2] 1 ). In addition, we found Xe (6p[1/2] 0 ) atoms strongly tend to reach the 6p[3/2] 2 , 6p[3/2] 1 , and 6p[5/2] 2 states through the 5s[3/2] 2 (Kr) state as the intermediate state in Kr. The 5s[3/2] 2 (Kr) state plays a very important role in the energy-transfer kinetics for the Xe (6p[1/2] 0 ) atoms. Kr is probably an excellent buffer gas for laser systems based on Xe.

  2. Matter, energy, and heat transfer in a classical ballistic atom pump.

    Science.gov (United States)

    Byrd, Tommy A; Das, Kunal K; Mitchell, Kevin A; Aubin, Seth; Delos, John B

    2014-11-01

    A ballistic atom pump is a system containing two reservoirs of neutral atoms or molecules and a junction connecting them containing a localized time-varying potential. Atoms move through the pump as independent particles. Under certain conditions, these pumps can create net transport of atoms from one reservoir to the other. While such systems are sometimes called "quantum pumps," they are also models of classical chaotic transport, and their quantum behavior cannot be understood without study of the corresponding classical behavior. Here we examine classically such a pump's effect on energy and temperature in the reservoirs, in addition to net particle transport. We show that the changes in particle number, of energy in each reservoir, and of temperature in each reservoir vary in unexpected ways as the incident particle energy is varied.

  3. The use of iteration factors in the solution of the NLTE line transfer problem-II. Multilevel atom

    International Nuclear Information System (INIS)

    Kuzmanovska-Barandovska, O.; Atanackovic, O.

    2010-01-01

    The iteration factors method (IFM) developed in Paper I (Atanackovic-Vukmanovic and Simonneau, 1994) to solve the NLTE line transfer problem for a two-level atom model, is extended here to deal with a multilevel atom case. At the beginning of each iteration step, for each line transition, angle and frequency averaged depth-dependent iteration factors are computed from the formal solution of radiative transfer (RT) equation and used to close the system of the RT equation moments, non-linearly coupled with the statistical equilibrium (SE) equations. Non-linear coupling of the atomic level populations and the corresponding line radiation field intensities is tackled in two ways. One is based on the linearization of the equations with respect to the relevant variables, and the other on the use of the old (known from the previous iteration) level populations in the line-opacity-like terms of the SE equations. In both cases the use of quasi-invariant iteration factors provided very fast and accurate solution. The properties of the proposed procedures are investigated in detail by applying them to the solution of the prototype multilevel RT problem of Avrett and Loeser , and compared with the properties of some other methods.

  4. PREPARATION OF BLOCK COPOLYMERS OF POLY(STYRENE) AND POLY(T-BUTYL ACRYLATE) OF VARIOUS MOLECULAR WEIGHTS AND ARCHITECTURES BY ATOM TRANSFER RADICAL POLYMERIZATION. (R826735)

    Science.gov (United States)

    Block copolymers of polystyrene and poly(t-butyl acrylate) were prepared using atom transfer radical polymerization techniques. These polymers were synthesized with a CuBr/N,N,N,NThe form of electron-atom excitation amplitudes at high momentum transfers in the Faddeev-Watson approximation

    International Nuclear Information System (INIS)

    Catalan, G.; Roberts, M.J.

    1979-01-01

    A form of the off-shell Coulomb T matrix, which has a well defined on-shell limit, is used in the Faddeev-Watson multiple-scattering expansion for a direct three-body collision process. Using the excitation of atomic hydrogen by electron impact as an example, approximations to the second-order terms, which are valid for high momentum transfers of the incident electron, are derived. It is shown how the resulting asymptotic behaviour of the second-order Faddeev-Watson approximation is related to the high momentum transfer limit of the second Born approximation. The results are generalised to the excitation of more complex atoms. The asymptotic forms of the Faddeev-Watson and Born approximations are compared with other theories and with measurements of differential cross sections and angular correlation parameters for the excitation of H(2p) and He(2 1 P). The results indicate that the Faddeev-Watson approximation converges more rapidly at high momentum transfers than does the Born approximation. (author)

  5. Transfer and conversion of images based on EIT in atom vapor.

    Science.gov (United States)

    Cao, Mingtao; Zhang, Liyun; Yu, Ya; Ye, Fengjuan; Wei, Dong; Guo, Wenge; Zhang, Shougang; Gao, Hong; Li, Fuli

    2014-05-01

    Transfer and conversion of images between different wavelengths or polarization has significant applications in optical communication and quantum information processing. We demonstrated the transfer of images based on electromagnetically induced transparency (EIT) in a rubidium vapor cell. In experiments, a 2D image generated by a spatial light modulator is used as a coupling field, and a plane wave served as a signal field. We found that the image carried by coupling field could be transferred to that carried by signal field, and the spatial patterns of transferred image are much better than that of the initial image. It also could be much smaller than that determined by the diffraction limit of the optical system. We also studied the subdiffraction propagation for the transferred image. Our results may have applications in quantum interference lithography and coherent Raman spectroscopy.

  6. Multiple-electron excitation, ionization, and transfer in high-velocity atomic and molecular collisions

    International Nuclear Information System (INIS)

    McGuire, J.H.

    1992-01-01

    This paper reports that the many-body and many-electron problem is common in various areas of physics as well as in chemistry and biology. Basic understanding of phenomena ranging from the nature of matter at the creation of time to the properties of useful materials in the human environment is limited by the boundaries of our knowledge of the many-body problem. There is an advantage in studying the many-body problem in atomic physics since the two-body and parts of the three-body problem are understood. Furthermore, both the mystery of the meanings of quantum mechanics and the mystery of the transition from microscopic time-reversible atomic processes to the dynamics of macroscopic time-irreversible aggregates of atomic particles is inherent in the many-body problems of atomic interactions. Thus, by studying the many-body problem in atomic physics we are able to develop effective tools to discover insights that provide both meaning and utility in our lives

  7. Exchange of notes constituting an implementing arrangement, concerning international obligation exchanges, to the agreement between the Government of Australia and the European Atomic Energy Community (EURATOM) concerning transfers of nuclear material of 21 September 1981

    International Nuclear Information System (INIS)

    1993-01-01

    The implementing arrangement which entered into force on 8 September 1993, concerns the safeguard obligations attaching to nuclear material transferred or re transferred pursuant to the Agreement on Nuclear Transfers between Australia and the European Atomic Energy Community

  8. Charge transfer and ionization occurring in proton- and helium ion-atom collisions

    International Nuclear Information System (INIS)

    DuBois, R.D.

    1985-12-01

    Two examples are presented where specific channels have been identified that are responsible for single and double target ionization via direct coulomb ionization or charge transfer processes. Using ratios of absolute cross sections that have been measured for these processes it was shown that an independent electron model should be appropriate for calculating direct double target ionization but generally appears to be inadequate in calculating charge transfer plus ionization and double charge transfer cross sections. At present such detailed information can be obtained only in limited cases. However cross sections with detailed final charge state information should provide stringent tests for present and future theoretical work. 22 refs., 2 figs

  9. Direct characterization of spin-transfer switching of nano-scale magnetic tunnel junctions using a conductive atomic force microscope

    International Nuclear Information System (INIS)

    Lee, Jia-Mou; Yang, Dong-Chin; Lee, Ching-Ming; Ye, Lin-Xiu; Chang, Yao-Jen; Wu, Te-ho; Lee, Yen-Chi; Wu, Jong-Ching

    2013-01-01

    We present an alternative method of spin-transfer-induced magnetization switching for magnetic tunnel junctions (MTJs) using a conductive atomic force microscope (CAFM) with pulsed current. The nominal MTJ cells' dimensions were 200 × 400 nm 2 . The AFM probes were coated with a Pt layer via sputtering to withstand up to several milliamperes. The pulsed current measurements, with pulse duration varying from 5 to 300 ms, revealed a magnetoresistance ratio of up to 120%, and an estimated intrinsic switching current density, based on the thermal activation model, of 3.94 MA cm −2 . This method demonstrates the potential skill to characterize nanometre-scale magnetic devices. (paper)

  10. [Electron transfer, ionization, and excitation in atomic collisions]. Final technical report, June 15, 1986 - June 14, 1998

    International Nuclear Information System (INIS)

    1998-01-01

    The research on theoretical atomic collisions that was funded at The Pennsylvania State University's Wilkes-Barre Campus by DOE from 1986 to 1998 was carried out by Winger from 1986 to 1989 and by Winter and Alston from 1989 to 1998. The fundamental processes of electron transfer, ionization, and excitation in ion-ion, ion-atom, and, more recently, ion-molecule collisions were addressed. These collision processes were treated in the context of simple one-electron, quasi-one-electron, or two-electron systems in order to provide unambiguous results and reveal more clearly the collisional mechanisms. Winter's work generally focused on the intermediate projectile-energy range corresponding to proton energies from about ten to a few hundred keV. In this velocity-matching energy range, the electron-transfer cross section reaches a peak, and many states, including electron-transfer and ionization states, contribute to the overall electron-cloud distribution and transition probabilities; a large number of states are coupled, and therefore perturbative approaches are generally inappropriate. These coupled-state calculations were sometimes also extended to higher energies to join with perturbative results. Alston concentrated on intermediate-energy asymmetric collision systems, for which coupling with the projectile is weaker, but many target states are included, and on high energies (MeV energies). Thus, while perturbation theory for electron transfer is valid, it is not adequate to first order. The studies by Winter and Alston described were often done in parallel. Alston also developed formal perturbative approaches not tied to any particular system. Materials studied included He + , Li 2+ , Be 3+ , B 4+ , C 5+ , and the H + + Na system

  11. Charge transfer processes in collisions of Si{sup 4+} ions with He atoms at intermediate energies

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, R. [Hitotsubashi Univ., Tokyo (Japan). Computer Center; Watanabe, A. [Dept. of Information Sciences, Ochanomizu Univ., Tokyo (Japan); Sato, H. [Graduate School of Humanities and Sciences, Ochanomizu Univ., Tokyo (Japan); Gu, J.P.; Hirsch, G.; Buenker, R.J. [Wuppertal Univ. (Gesamthochschule) (Germany). Lehrgebiet Theoretische Chemie; Kimura, M. [Graduate School of Science and Engineering, Yamaguchi Univ., Ube (Japan); Stancil, P.C. [Georgia Univ., Athens, GA (United States). Dept. of Physics

    2001-07-01

    Charge transfer in collisions of Si{sup 4+} ions with He atoms below 100 keV/u is studied by using a molecular orbital representation within both the semiclassical and quantal representations. Single transfer reaction Si{sup 4+} + He {yields} Si{sup 3+} + He{sup +} has been studied by a number of theoretical investigations. In addition to the reaction (1), the first semiclassical MOCC calculations are performed for the double transfer channel Si{sup 4+} + He {yields} Si{sup 2+} + He{sup 2+}. Nine molecular states that connect both with single and double electron transfer processes are considered in the present model. Electronic states and corresponding couplings are determined by the multireference single- and double- excitation configuration interaction method. The present cross sections tie well with the earlier calculations of Stancil et al., (1997) at lower energies, but show a rather different magnitude from those of Bacchus-Montabonel and Ceyzeriat, (1998). The present rate constant is found to be significantly different from the experimental finding of Fang and Kwong, (1996) at 4,600 K, and hence does not support the experiment. (orig.)

  12. Collisional transfer of electrons to the continuum of atomic and molecular ions

    International Nuclear Information System (INIS)

    Gonzalez Lepera, C.E.

    1983-01-01

    The aim of this study was the systematic investigation of the differences that appear in the peaks of distribution of doubly differential (in angle an energy) 'convoy' electrons, when comparing spectra obtained by bombarding thin carbon foils with atomic (H + ) and molecular (H 2 + ) projectiles of equal velocity. The measurements show that the production yield of such electrons is inversely propotional to the ion dwell time in the solid. For long times, the yield ratio fluctuates around the unity value, and the amplitude of this dispersion decreases for longer times. A higher yield is measured for (H 2 + ), but only near the peak cusp. The double differential cross section (DDCS) for electron capture is calculated in second order Born approximation. A transition from a 1s state to the continuum of two correlated protons as a function of their internuclear distance R is considered. As R decreases from approx. 0.5 atomic units towards zero, the DDCS value increases from that corresponding to the atomic projectil (Z=1) limit to the united atom value (Z=2). It is found that, the higher the projectil velocity, the better is the DDCS value agreement with both limits. The equipment used by the author is described. (M.E.L.) [es

  13. Atomic reactor thermal engineering

    International Nuclear Information System (INIS)

    Kim, Gwang Ryong

    1983-02-01

    This book starts the introduction of atomic reactor thermal engineering including atomic reaction, chemical reaction, nuclear reaction neutron energy and soon. It explains heat transfer, heat production in the atomic reactor, heat transfer of fuel element in atomic reactor, heat transfer and flow of cooler, thermal design of atomic reactor, design of thermodynamics of atomic reactor and various. This deals with the basic knowledge of thermal engineering for atomic reactor.

  14. Synthesis of Environmentally Responsive Polymers by Atom Transfer Radical Polymerization: Generation of Reversible Hydrophilic and Hydrophobic Surfaces

    Directory of Open Access Journals (Sweden)

    Vikas Mittal

    2010-05-01

    Full Text Available Environmentally responsive poly(N-isopropylacrylamide brushes were grafted from the surface of polymer particles or flat surfaces in order to generate reversible hydrophilic and hydrophobic surfaces. The use of atom transfer radical polymerization was demonstrated for the grafting of polymer brushes as it allows efficient control on the amount of grafted polymer. The polymer particles were generated with or without surfactant in the emulsion polymerization and their surface could be modified with the atom transfer radical polymerization (ATRP initiator. The uniform functionalization of the surface with ATRP initiator was responsible for the uniform grafting of polymer brushes. The grafted brushes responded reversibly with changes in temperature indicating that the reversible responsive behavior could be translated to the particle surfaces. The particles were observed to adsorb and desorb protein and virus molecules by changing the temperatures below or higher than 32 °C. The initiator functionalized particles could also be adsorbed on the flat surfaces. The adsorption process also required optimization of the heat treatment conditions to form a uniform layer of the particles on the substrate. The grafted polymer brushes also responded to the changes in temperatures similar to the spherical particles studied through water droplets placed on the flat substrates.

  15. A quasi-classical study of energy transfer in collisions of hyperthermal H atoms with SO2 molecules.

    Science.gov (United States)

    da Silva, Ramon S; Garrido, Juan D; Ballester, Maikel Y

    2017-08-28

    A deep understanding of energy transfer processes in molecular collisions is at central attention in physical chemistry. Particularly vibrational excitation of small molecules colliding with hot light atoms, via a metastable complex formation, has shown to be an efficient manner of enhancing reactivity. A quasi-classical trajectory study of translation-to-vibration energy transfer (T-V ET) in collisions of hyperthermal H( 2 S) atoms with SO 2 (X̃ 1 A ' ) molecules is presented here. For such a study, a double many-body expansion potential energy surface previously reported for HSO 2 ( 2 A) is used. This work was motivated by recent experiments by Ma et al. studying collisions of H + SO 2 at the translational energy of 59 kcal/mol [J. Ma et al., Phys. Rev. A 93, 040702 (2016)]. Calculations reproduce the experimental evidence that during majority of inelastic non-reactive collision processes, there is a metastable intermediate formation (HOSO or HSO 2 ). Nevertheless, the analysis of the trajectories shows that there are two distinct mechanisms in the T-V ET process: direct and indirect. Direct T-V processes are responsible for the high population of SO 2 with relatively low vibrational excitation energy, while indirect ones dominate the conversion from translational energy to high values of the vibrational counterpart.

  16. Electron and Oxygen Atom Transfer Chemistry of Co(II) in a Proton Responsive, Redox Active Ligand Environment.

    Science.gov (United States)

    Cook, Brian J; Pink, Maren; Pal, Kuntal; Caulton, Kenneth G

    2018-05-21

    The bis-pyrazolato pyridine complex LCo(PEt 3 ) 2 serves as a masked form of three-coordinate Co II and shows diverse reactivity in its reaction with several potential outer sphere oxidants and oxygen atom transfer reagents. N-Methylmorpholine N-oxide (NMO) oxidizes coordinated PEt 3 from LCo(PEt 3 ) 2 , but the final cobalt product is still divalent cobalt, in LCo(NMO) 2 . The thermodynamics of a variety of oxygen atom transfer reagents, including NMO, are calculated by density functional theory, to rank their oxidizing power. Oxidation of LCo(PEt 3 ) 2 with AgOTf in the presence of LiCl as a trapping nucleophile forms the unusual aggregate [LCo(PEt 3 ) 2 Cl(LiOTf) 2 ] 2 held together by Li + binding to very nucleophilic chloride on Co(III) and triflate binding to those Li + . In contrast, Cp 2 Fe + effects oxidation to trivalent cobalt, to form (HL)Co(PEt 3 ) 2 Cl + ; proton and the chloride originate from solvent in a rare example of CH 2 Cl 2 dehydrochlorination. An unexpected noncomplementary redox reaction is reported involving attack by 2e reductant PEt 3 nucleophile on carbon of the 1e oxidant radical Cp 2 Fe + , forming a P-C bond and H + ; this reaction competes in the reaction of LCo(PEt 3 ) 2 with Cp 2 Fe + .

  17. "Hairy" Poly(3-hexylthiophene) Particles Prepared via Surface-Initiated Kumada Catalyst-Transfer Polycondensation

    DEFF Research Database (Denmark)

    Senkovskyy, Volodymyr; Tkachov, Roman; Beryozkina, Tetyana

    2009-01-01

    to the untethered counterparts (red shift and vibronic fine structure in absorption and fluorescence spectra), as a result of efficient planarization and chain-aggregation. These effects are observed in solvents that are normally recognized as good solvents for P3HT (e.g., tetrahydrofurane). We attribute...

  18. Oxygen-atom transfer chemistry and thermolytic properties of a di-tert-butylphosphate-ligated Mn4O4 cubane.

    Science.gov (United States)

    Van Allsburg, Kurt M; Anzenberg, Eitan; Drisdell, Walter S; Yano, Junko; Tilley, T Don

    2015-03-16

    [Mn4O4{O2P(OtBu)2}6] (1), an Mn4O4 cubane complex combining the structural inspiration of the photosystem II oxygen-evolving complex with thermolytic precursor ligands, was synthesized and fully characterized. Core oxygen atoms within complex 1 are transferred upon reaction with an oxygen-atom acceptor (PEt3), to give the butterfly complex [Mn4O2{O2P(OtBu)2}6(OPEt3)2]. The cubane structure is restored by reaction of the latter complex with the O-atom donor PhIO. Complex 1 was investigated as a precursor to inorganic Mn metaphosphate/pyrophosphate materials, which were studied by X-ray absorption spectroscopy to determine the fate of the Mn4O4 unit. Under the conditions employed, thermolyses of 1 result in reduction of the manganese to Mn(II) species. Finally, the related butterfly complex [Mn4O2{O2P(pin)}6(bpy)2] (pin = pinacolate) is described. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Molecular bond formation in Na* + N2 energy transfer: Crossed beam study of atomic alignment and orientation

    International Nuclear Information System (INIS)

    Reiland, W.; Jamieson, G.; Tittes, U.; Hertel, I.V.

    1982-01-01

    We report the first full analysis of collisionally induced atomic alignment and orientation for a molecular collision process. In an experiment with crossed supersonic beams of N 2 and laser excited Na(3 2 Psub(3/2)) we have studied the dependence of angular and energy resolved differential quenching cross sections as a function of the linear and circular polarization of the exciting laser light. The ansisotropies observed in the linear polarization data range up to 2:1 when corrected for electron and nuclear spin relaxation. The maximum effect is found at small scattering angles and intermediate energy transfer where the cross section is also largest. The atomic alignment angle most favourable for quenching relates to the scattering angle and can be understood in a model picture in such a way that the (NaN 2 )* molecular system is formed at internuclear distances as low as R = 10a 0 . The circular asymmetry is small but with significant structure and is attributed to interaction on different potential surfaces at R > 10a 0 . Full analysis of the four measurable parameter is given in terms of the density matrix in a frame with z-axis perpendicular to collision plane which allows a clear understanding of the properties of atomic reflection symmetry and coherence of the scattering process. (orig.)

  1. Fabrication of luminescent hydroxyapatite nanorods through surface-initiated RAFT polymerization: Characterization, biological imaging and drug delivery applications

    Energy Technology Data Exchange (ETDEWEB)

    Heng, Chunning [Shaanxi Key Laboratory of Degradable Biomedical Materials, Shaanxi R& D Center of Biomaterials and Fermentation Engineering, School of Chemical and Engineering, Northwest University, Xi’an, 710069 (China); Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031 (China); Zheng, Xiaoyan [Shaanxi Key Laboratory of Degradable Biomedical Materials, Shaanxi R& D Center of Biomaterials and Fermentation Engineering, School of Chemical and Engineering, Northwest University, Xi’an, 710069 (China); Liu, Meiying; Xu, Dazhuang; Huang, Hongye; Deng, Fengjie [Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031 (China); Hui, Junfeng, E-mail: huijunfeng@126.com [Shaanxi Key Laboratory of Degradable Biomedical Materials, Shaanxi R& D Center of Biomaterials and Fermentation Engineering, School of Chemical and Engineering, Northwest University, Xi’an, 710069 (China); Zhang, Xiaoyong, E-mail: xiaoyongzhang1980@gmail.com [Department of Chemistry, Nanchang University, 999 Xuefu Avenue, Nanchang 330031 (China); Wei, Yen, E-mail: weiyen@tsinghua.edu.cn [Department of Chemistry and the Tsinghua Center for Frontier Polymer Research, Tsinghua University, Beijing, 100084 (China)

    2016-11-15

    Highlights: • Hydrophobic hydroxyapatite nanorods were obtained from hydrothermal synthesis. • Surface initiated RAFT polymerization was adopted to surface modification of hydroxyapatite nanorods. • These modified hydroxyapatite nanorods showed high water dispersibility and biocompatibility. • These modified hydroxyapatite nanorods can be used for controlled drug delivery. - Abstract: Hydroxyapatite nanomaterials as an important class of nanomaterials, have been widely applied for different biomedical applications for their excellent biocompatibility, biodegradation potential and low cost. In this work, hydroxyapatite nanorods with uniform size and morphology were prepared through hydrothermal synthesis. The surfaces of these hydroxyapatite nanorods are covered with hydrophobic oleic acid, making them poor dispersibility in aqueous solution and difficult for biomedical applications. To overcome this issue, a simple surface initiated polymerization strategy has been developed via combination of the surface ligand exchange and reversible addition fragmentation chain transfer (RAFT) polymerization. Hydroxyapatite nanorods were first modified with Riboflavin-5-phosphate sodium (RPSSD) via ligand exchange reaction between the phosphate group of RPSSD and oleic acid. Then hydroxyl group of nHAp-RPSSD was used to immobilize chain transfer agent, which was used as the initiator for surface-initiated RAFT polymerization. The nHAp-RPSSD-poly(IA-PEGMA) nanocomposites were characterized by means of {sup 1}H nuclear magnetic resonance, Fourier transform infrared spectroscopy, fluorescence spectroscopy and thermal gravimetric analysis in detailed. The biocompatibility, biological imaging and drug delivery of nHAp-RPSSD-poly(IA-PEGMA) were also investigated. Results showed that nHAp-RPSSD-poly(IA-PEGMA) exhibited excellent water dispersibility, desirable optical properties, good biocompatibility and high drug loading capability, making them promising candidates for

  2. Fabrication of luminescent hydroxyapatite nanorods through surface-initiated RAFT polymerization: Characterization, biological imaging and drug delivery applications

    International Nuclear Information System (INIS)

    Heng, Chunning; Zheng, Xiaoyan; Liu, Meiying; Xu, Dazhuang; Huang, Hongye; Deng, Fengjie; Hui, Junfeng; Zhang, Xiaoyong; Wei, Yen

    2016-01-01

    Highlights: • Hydrophobic hydroxyapatite nanorods were obtained from hydrothermal synthesis. • Surface initiated RAFT polymerization was adopted to surface modification of hydroxyapatite nanorods. • These modified hydroxyapatite nanorods showed high water dispersibility and biocompatibility. • These modified hydroxyapatite nanorods can be used for controlled drug delivery. - Abstract: Hydroxyapatite nanomaterials as an important class of nanomaterials, have been widely applied for different biomedical applications for their excellent biocompatibility, biodegradation potential and low cost. In this work, hydroxyapatite nanorods with uniform size and morphology were prepared through hydrothermal synthesis. The surfaces of these hydroxyapatite nanorods are covered with hydrophobic oleic acid, making them poor dispersibility in aqueous solution and difficult for biomedical applications. To overcome this issue, a simple surface initiated polymerization strategy has been developed via combination of the surface ligand exchange and reversible addition fragmentation chain transfer (RAFT) polymerization. Hydroxyapatite nanorods were first modified with Riboflavin-5-phosphate sodium (RPSSD) via ligand exchange reaction between the phosphate group of RPSSD and oleic acid. Then hydroxyl group of nHAp-RPSSD was used to immobilize chain transfer agent, which was used as the initiator for surface-initiated RAFT polymerization. The nHAp-RPSSD-poly(IA-PEGMA) nanocomposites were characterized by means of "1H nuclear magnetic resonance, Fourier transform infrared spectroscopy, fluorescence spectroscopy and thermal gravimetric analysis in detailed. The biocompatibility, biological imaging and drug delivery of nHAp-RPSSD-poly(IA-PEGMA) were also investigated. Results showed that nHAp-RPSSD-poly(IA-PEGMA) exhibited excellent water dispersibility, desirable optical properties, good biocompatibility and high drug loading capability, making them promising candidates for biological

  3. Modelling of the heat transfer during oxygen atoms recombination on metallic surfaces in a plasma reactor

    NARCIS (Netherlands)

    Cavadias, S; Cauquot, P; Amouroux, J

    1997-01-01

    Space shuttle overheating during the re-entry phase, due to catalytic oxygen recombination on the thermal protection system, is a problem of practical and theoretical interest. The energy transfer is characterised by the product of the accommodation and the recombination coefficients. Previous

  4. Deprotonation of flavonoids severely alters the thermodynamics of the hydrogen atom transfer

    Czech Academy of Sciences Publication Activity Database

    Klein, E.; Rimarčík, J.; Senajová, E.; Vagánek, A.; Lengyel, Jozef

    2016-01-01

    Roč. 1085, JUN 2016 (2016), s. 7-17 ISSN 2210-271X R&D Projects: GA ČR GA14-14082S Institutional support: RVO:61388955 Keywords : Primary antioxidant * Flavonoid * dft * Bond dissociation enthalpy * Sequential proton-loss electron-transfer Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.549, year: 2016

  5. Biomimetic PEGylation of carbon nanotubes through surface-initiated RAFT polymerization.

    Science.gov (United States)

    Shi, Yingge; Zeng, Guanjian; Xu, Dazhuang; Liu, Meiying; Wang, Ke; Li, Zhen; Fu, Lihua; Zhang, Qingsong; Zhang, Xiaoyong; Wei, Yen

    2017-11-01

    Carbon nanotubes (CNTs) are a type of one-dimensional carbon nanomaterials that possess excellent physicochemical properties and have been potentially utilized for a variety of applications. Surface modification of CNTs with polymers is a general route to expand and improve the performance of CNTs and has attracted great research interest over the past few decades. Although many methods have been developed previously, most of these methods still showed some disadvantages, such as low efficiency, complex experimental procedure and harsh reaction conditions etc. In this work, we reported a practical and novel way to fabricate CNTs based polymer composites via the combination of mussel inspired chemistry and reversible addition fragmentation chain transfer (RAFT) polymerization. First, the amino group was introduced onto the surface of CNTs via self-polymerization of dopamine. Then, chain transfer agent can be immobilized on the amino groups functionalized CNTs to obtain CNT-PDA-CTA, which can be utilized for surface-initiated RAFT polymerization. A water soluble and biocompatible monomer poly(ethylene glycol) monomethyl ether methacrylate (PEGMA) was adopted to fabricate pPEGMA functionalized CNTs through RAFT polymerization. The successful preparation of CNTs based polymer composites (CNT-pPEGMA) was confirmed by transmission electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis and X-ray photoelectron spectroscopy in details. The CNT-pPEGMA showed good dispersibility and desirable biocompatibility, making them highly potential for biomedical applications. More importantly, a large number of CNTs based polymer composites could also be fabricated through the same strategy when different monomers were used due to the good monomer adaptability of RAFT polymerization. Therefore, this strategy should be a general method for preparation of various multifunctional CNTs based polymer composites. Copyright © 2017 Elsevier B.V. All rights

  6. Nonheme Fe(IV) Oxo Complexes of Two New Pentadentate Ligands and Their Hydrogen-Atom and Oxygen-Atom Transfer Reactions.

    Science.gov (United States)

    Mitra, Mainak; Nimir, Hassan; Demeshko, Serhiy; Bhat, Satish S; Malinkin, Sergey O; Haukka, Matti; Lloret-Fillol, Julio; Lisensky, George C; Meyer, Franc; Shteinman, Albert A; Browne, Wesley R; Hrovat, David A; Richmond, Michael G; Costas, Miquel; Nordlander, Ebbe

    2015-08-03

    Two new pentadentate {N5} donor ligands based on the N4Py (N4Py = N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl)methylamine) framework have been synthesized, viz. [N-(1-methyl-2-benzimidazolyl)methyl-N-(2-pyridyl)methyl-N-(bis-2-pyridyl methyl)amine] (L(1)) and [N-bis(1-methyl-2-benzimidazolyl)methyl-N-(bis-2-pyridylmethyl)amine] (L(2)), where one or two pyridyl arms of N4Py have been replaced by corresponding (N-methyl)benzimidazolyl-containing arms. The complexes [Fe(II)(CH3CN)(L)](2+) (L = L(1) (1); L(2) (2)) were synthesized, and reaction of these ferrous complexes with iodosylbenzene led to the formation of the ferryl complexes [Fe(IV)(O)(L)](2+) (L = L(1) (3); L(2) (4)), which were characterized by UV-vis spectroscopy, high resolution mass spectrometry, and Mössbauer spectroscopy. Complexes 3 and 4 are relatively stable with half-lives at room temperature of 40 h (L = L(1)) and 2.5 h (L = L(2)). The redox potentials of 1 and 2, as well as the visible spectra of 3 and 4, indicate that the ligand field weakens as ligand pyridyl substituents are progressively substituted by (N-methyl)benzimidazolyl moieties. The reactivities of 3 and 4 in hydrogen-atom transfer (HAT) and oxygen-atom transfer (OAT) reactions show that both complexes exhibit enhanced reactivities when compared to the analogous N4Py complex ([Fe(IV)(O)(N4Py)](2+)), and that the normalized HAT rates increase by approximately 1 order of magnitude for each replacement of a pyridyl moiety; i.e., [Fe(IV)(O)(L(2))](2+) exhibits the highest rates. The second-order HAT rate constants can be directly related to the substrate C-H bond dissociation energies. Computational modeling of the HAT reactions indicates that the reaction proceeds via a high spin transition state.

  7. Pion-transfer (n,d) and (d, 3He) reactions leading to deeply bound pionic atoms

    International Nuclear Information System (INIS)

    Toki, H.; Hirenzaki, S.; Yamazaki, T.

    1990-11-01

    Theoretical studies are given on the (n,d) and (d, 3 He) reactions leading to deeply bound pionic atoms in heavy nuclei of configuration [(nl) π ·j n -1 ]J. The cross sections for various pionic and neutron-hole configurations in the case of a 208 Pb target are calculated at incident energies 300-1000 MeV/u by using the effective number approach and the eikonal approximation for distortion. The effective number with a pion in the 1s or 2p state and a neutron hole in the i 13/2 orbit peaks around the same incident energy (T n =600 MeV) as the elementary cross section n+n→d+π - , where the momentum transfer matches the angular-momentum transfer of L=5∼7. The DWIA cross section for (n,d) producing a pion in the 1s or 2p orbit at T n =600 MeV is found to be around 42 or 75 μb/sr, respectively. At T n =350 MeV, where the momentum transfer is small, quasi-substitutional states of configurations [(2p) π (3p 1/2 ) n -1 ]L=0 and [(2p) π (3p 3/2 ) n -1 ]L=0 are preferentially populated with cross sections of 190 and 380 μb/sr, respectively. The (d, 3 He) cross sections are estimated to be an order of magnitude smaller than the (n,d) cross sections. Thus, the (n,d) and (d, 3 He) reactions are found to be suited for the production of deeply bound pionic atoms. (author)

  8. Large discrepancies observed in theoretical studies of ion-impact ionization of the atomic targets at large momentum transfer

    Science.gov (United States)

    Ghorbani, Omid; Ghanbari-Adivi, Ebrahim

    2017-12-01

    A full quantum mechanical version of the three-body distorted wave-eikonal initial state (3DW-EIS) theory is developed to study of the single ionization of the atomic targets by ion impact at different momentum transfers. The calculations are performed both with and without including the internuclear interaction in the transition amplitude. For 16 \\text{Mev} \\text{O}7+ \\text{-He}~(1s2 ) and 24 \\text{Mev} \\text{O}8+\\text{-Li}~(2s ) collisions, the emission of the active electron into the scattering plane is considered and the fully differential cross-sections (FDCSs) are calculated for a fixed value of the ejected electron energy and a variety of momentum transfers. For both the specified collision systems, the obtained results are compared with the experimental data and with the cross-sections obtained using the semi-classical continuum distorted wave-eikonal initial state (CDW-EIS) approach. For 16 \\text{Mev} \\text{O}7+ \\text{-He}~(1s^2) , we also compared the results with those of a four-body three-Coulomb-wave (3CW) model. In general, we find some large discrepancies between the results obtained by different theories. These discrepancies are much more significant at larger momentum transfers. Also, for some ranges of the electron emission angles the results are much more sensitive to the internuclear interaction to be either turned on or off.

  9. Complementary Strategies for Directed C(sp3 )-H Functionalization: A Comparison of Transition-Metal-Catalyzed Activation, Hydrogen Atom Transfer, and Carbene/Nitrene Transfer.

    Science.gov (United States)

    Chu, John C K; Rovis, Tomislav

    2018-01-02

    The functionalization of C(sp 3 )-H bonds streamlines chemical synthesis by allowing the use of simple molecules and providing novel synthetic disconnections. Intensive recent efforts in the development of new reactions based on C-H functionalization have led to its wider adoption across a range of research areas. This Review discusses the strengths and weaknesses of three main approaches: transition-metal-catalyzed C-H activation, 1,n-hydrogen atom transfer, and transition-metal-catalyzed carbene/nitrene transfer, for the directed functionalization of unactivated C(sp 3 )-H bonds. For each strategy, the scope, the reactivity of different C-H bonds, the position of the reacting C-H bonds relative to the directing group, and stereochemical outcomes are illustrated with examples in the literature. The aim of this Review is to provide guidance for the use of C-H functionalization reactions and inspire future research in this area. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Controlling electron transfer processes on insulating surfaces with the non-contact atomic force microscope.

    Science.gov (United States)

    Trevethan, Thomas; Shluger, Alexander

    2009-07-01

    We present the results of theoretical modelling that predicts how a process of transfer of single electrons between two defects on an insulating surface can be induced using a scanning force microscope tip. A model but realistic system is employed which consists of a neutral oxygen vacancy and a noble metal (Pt or Pd) adatom on the MgO(001) surface. We show that the ionization potential of the vacancy and the electron affinity of the metal adatom can be significantly modified by the electric field produced by an ionic tip apex at close approach to the surface. The relative energies of the two states are also a function of the separation of the two defects. Therefore the transfer of an electron from the vacancy to the metal adatom can be induced either by the field effect of the tip or by manipulating the position of the metal adatom on the surface.

  11. Selection rules for electron transfer to the continuum in ion-atom collision

    Energy Technology Data Exchange (ETDEWEB)

    Barrachina, R.O.; Bernardi, G.C.; Garibotti, C.R.

    1985-10-01

    We consider the process of electron transfer to the in first order Born approximation. We analyse the expansion of the double-differential cross section in series of electron velocity and ejection angle. We found that the coefficients obey precise selection rules. We discuss the relation of these rules, which predict an asymmetric shape for the electron loss to the continuum cusp, with the interpretation of recent experimental results.

  12. Charge transfer cross-sections of argon ions colliding on argon atoms

    International Nuclear Information System (INIS)

    Aubert, J.; Bliman, S.; Chan-Tung, N.; Geller, R.; Jacquot, B.; Van Houtte, D.

    1980-04-01

    A device has been built to measure charge changing cross-sections of Argon ions colliding on argon atoms. It consists of an E.C.R. ion source (Micromafios) that delivers argon ions up to charge + 13. The ion source potential may be varied from 1 up to 10 kVolts. A first magnet is used to charge analyze the extracted beam. For a given separated charge state, the ion beam is passed in a collision cell whose pressure may be varied. The ions undergoing collisions on the target are analyzed by a second magnet and collected. The pressure is varied in the collision cell in order to check that the single collision condition is satisfied. It is shown that the ions do two types of collisions: charge exchange and stripping whose cross-sections are measured. Interpretation of charge exchange is proposed along yet classic theoretical approaches. As to stripping no available theory allows interpretation

  13. Accelerated Oxygen Atom Transfer and C-H Bond Oxygenation by Remote Redox Changes in Fe3 Mn-Iodosobenzene Adducts.

    Science.gov (United States)

    de Ruiter, Graham; Carsch, Kurtis M; Gul, Sheraz; Chatterjee, Ruchira; Thompson, Niklas B; Takase, Michael K; Yano, Junko; Agapie, Theodor

    2017-04-18

    We report the synthesis, characterization, and reactivity of [LFe 3 (PhPz) 3 OMn( s PhIO)][OTf] x (3: x=2; 4: x=3), where 4 is one of very few examples of iodosobenzene-metal adducts characterized by X-ray crystallography. Access to these rare heterometallic clusters enabled differentiation of the metal centers involved in oxygen atom transfer (Mn) or redox modulation (Fe). Specifically, 57 Fe Mössbauer and X-ray absorption spectroscopy provided unique insights into how changes in oxidation state (Fe III 2 Fe II Mn II vs. Fe III 3 Mn II ) influence oxygen atom transfer in tetranuclear Fe 3 Mn clusters. In particular, a one-electron redox change at a distal metal site leads to a change in oxygen atom transfer reactivity by ca. two orders of magnitude. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. The role of the achiral template in enantioselective transformations. Radical conjugate additions to alpha-methacrylates followed by hydrogen atom transfer.

    Science.gov (United States)

    Sibi, Mukund P; Sausker, Justin B

    2002-02-13

    We have evaluated various achiral templates (1a-g, 10, and 16) in conjunction with chiral Lewis acids in the conjugate addition of nucleophilic radicals to alpha-methacrylates followed by enantioselective H-atom transfer. Of these, a novel naphthosultam template (10) gave high enantioselectivity in the H-atom-transfer reactions with ee's up to 90%. A chiral Lewis acid derived from MgBr(2) and bisoxazoline (2) gave the highest selectivity in the enantioselective hydrogen-atom-transfer reactions. Non-C(2) symmetric oxazolines (20-25) have also been examined as ligands, and of these, compound 25 gave optimal results (87% yield and 80% ee). Insights into rotamer control in alpha-substituted acrylates and the critical role of the tetrahedral sulfone moiety in realizing high selectivity are discussed.

  15. Energy transfer by radiation in non-grey atomic gases in isothermal and non-isothermal slabs

    Science.gov (United States)

    Poon, P. T. Y.

    1975-01-01

    A multiband model for the absorption coefficient of atomic hydrogen-helium plasmas is constructed which includes continuum and line contributions. Emission from 28 stronger lines of 106 that have been screened is considered, of which 21 are from hydrogen and 7 belong to helium, with reabsorption due to line-line, line-continuum overlap accurately accounted for. The model is utilized in the computation of intensities and fluxes from shock-heated slabs of 85% H2-15% He mixtures for slab thicknesses from 1 to 30 cm, temperature from 10,000 to 20,000 K, and for different densities. In conjunction with the multiband model, simple numerical schemes have been devised which provide a quick and comprehensive way of computing radiative energy transfer in nonisothermal and nongrey gases.

  16. Atomic scattering in the diffraction limit: electron transfer in keV Li+-Na(3s, 3p) collisions

    DEFF Research Database (Denmark)

    Poel, Mike van der; Nielsen, C.V.; Rybaltover, M.

    2002-01-01

    We measure angle differential cross sections (DCS) in Li+ + Na --> Li + Na+ electron transfer collisions in the 2.7-24 keV energy range. We do this with a newly constructed apparatus which combines the experimental technique of cold target recoil ion momentum spectroscopy with a laser-cooled target...... of the de Broglie wavelength lambda(dB) = 150 fm at a velocity v = 0.20 au and the effective atomic diameter for electron capture 2R = 20 au. Parallel AO and MO semiclassical coupled-channel calculations of the Na(3s, 3p) --> Li(2s, 2p) state-to-state collision amplitudes have been performed, and quantum...

  17. Many-body theory of charge transfer in hyperthermal atomic scattering

    International Nuclear Information System (INIS)

    Marston, J.B.; Andersson, D.R.; Behringer, E.R.; Cooper, B.H.; DiRubio, C.A.; Kimmel, G.A.; Richardson, C.

    1993-01-01

    We use the Newns-Anderson Hamiltonian to describe many-body electronic processes that occur when hyperthermal alkali atoms scatter off metallic surfaces. Following Brako and Newns, we expand the electronic many-body wave function in the number of particle-hole pairs (we keep terms up to and including a single particle-hole pair). We extend their earlier work by including level crossings, excited neutrals, and negative ions. The full set of equations of motion is integrated numerically, without further approximations, to obtain the many-body amplitudes as a function of time. The velocity and work-function dependence of final-state quantities such as the distribution of ion charges and excited atomic occupancies are compared with experiment. In particular, experiments that scatter alkali ions off clean Cu(001) surfaces in the energy range 5--1600 eV constrain the theory quantitatively. The neutralization probability of Na + ions shows a minimum at intermediate velocity in agreement with the theory. This behavior contrasts with that of K + , which shows virtually no neutralization, and with Li + , which exhibits a monotonically increasing neutral fraction with decreasing velocity. Particle-hole excitations are left behind in the metal during a fraction of the collision events; this dissipated energy is predicted to be quite small (on the order of tenths of an electron volt). Indeed, classical trajectory simulations of the surface dynamics account well for the observed energy loss, and thus provide some justification for our truncation of the equations of motion at the single particle-hole pair level. Li + scattering experiments off low work-function surfaces provide qualitative information on the importance of many-body effects. At sufficiently low work function, the negative ions predicted to occur are in fact observed

  18. Multidimensional radiative transfer with multilevel atoms. II. The non-linear multigrid method.

    Science.gov (United States)

    Fabiani Bendicho, P.; Trujillo Bueno, J.; Auer, L.

    1997-08-01

    A new iterative method for solving non-LTE multilevel radiative transfer (RT) problems in 1D, 2D or 3D geometries is presented. The scheme obtains the self-consistent solution of the kinetic and RT equations at the cost of only a few (iteration (Brandt, 1977, Math. Comp. 31, 333; Hackbush, 1985, Multi-Grid Methods and Applications, springer-Verlag, Berlin), an efficient multilevel RT scheme based on Gauss-Seidel iterations (cf. Trujillo Bueno & Fabiani Bendicho, 1995ApJ...455..646T), and accurate short-characteristics formal solution techniques. By combining a valid stopping criterion with a nested-grid strategy a converged solution with the desired true error is automatically guaranteed. Contrary to the current operator splitting methods the very high convergence speed of the new RT method does not deteriorate when the grid spatial resolution is increased. With this non-linear multigrid method non-LTE problems discretized on N grid points are solved in O(N) operations. The nested multigrid RT method presented here is, thus, particularly attractive in complicated multilevel transfer problems where small grid-sizes are required. The properties of the method are analyzed both analytically and with illustrative multilevel calculations for Ca II in 1D and 2D schematic model atmospheres.

  19. Poly(vinyl acetate-Based Block Copolymer/Clay Nanocomposites Prepared by In Situ Atom Transfer Radical Polymerization

    Directory of Open Access Journals (Sweden)

    M.A. Semsarzadeh

    2009-12-01

    Full Text Available Atom transfer radical polymerization of styrene (St and methyl methacrylate (MMA was performed at 90oC in the absence and presence of nanoclay (Cloisite 30B. Trichloromethyl-terminated poly(vinyl acetate telomerand CuCl/ PMDETA were used as a macroinitiator and catalyst system, respectively. The experimental results showed that the atom transfer radical polymerization of St and MMA in the absence or presence of nanoclay proceeds via a controlled/living mode. It was observed that nanoclay significantly enhances the homopolymerization rate of MMA, which was attributed to the activated conjugated C=C bond of MMA monomer via interaction between the carbonyl group of MMA monomer and the hydroxyl moiety (Al-O-H of nanoclay as well as the effect of nanoclay on the dynamic equilibrium between the active (macro radicals and dormant species.Homopolymerization rate of St (a non-coordinative monomer with nanoclay decreased slightly in the presence of nanoclay. This could be explained by insertion of a portion of macroinitiator into the clay galleries, where no sufficient St monomer exists due to the low compatibility or interaction of St monomer with nanoclay to react with the macroinitiator. The results obtained from XRD, TEM and TGA analyses were fully in agreement with the kinetic data. Structure of the poly(vinyl acetate-bpolystyrene nanocomposite was found to be a combination of stacking layers and exfoliated structures while poly(vinyl acetate-b-poly(methyl methacryale nanocomposite had an exfoliated structure. This difference in the structure of nanocomposites was attributed to the different capability of the monomers (styrene and methyl methacrylate to react with the hydroxyl moiety (Al-O-H of nanoclay.

  20. Oxidation of nitrite by a trans-dioxoruthenium(VI) complex: direct evidence for reversible oxygen atom transfer.

    Science.gov (United States)

    Man, Wai-Lun; Lam, William W Y; Wong, Wai-Yeung; Lau, Tai-Chu

    2006-11-15

    Reaction of trans-[Ru(VI)(L)(O)(2)](2+) (1, L = 1,12-dimethyl-3,4:9,10-dibenzo-1,12-diaza-5,8-dioxacyclopentadecane, a tetradentate macrocyclic ligand with N(2)O(2) donor atoms) with nitrite in aqueous solution or in H(2)O/CH(3)CN produces the corresponding (nitrato)oxoruthenium(IV) species, trans-[Ru(IV)(L)(O)(ONO(2))](+) (2), which then undergoes relatively slow aquation to give trans-[Ru(IV)(L)(O)(OH(2))](2+). These processes have been monitored by both ESI/MS and UV/vis spectrophotometry. The structure of trans-[Ru(IV)(L)(O)(ONO(2))](+) (2) has been determined by X-ray crystallography. The ruthenium center adopts a distorted octahedral geometry with the oxo and the nitrato ligands trans to each other. The Ru=O distance is 1.735(3) A, the Ru-ONO(2) distance is 2.163(4) A, and the Ru-O-NO(2) angle is 138.46(35) degrees . Reaction of trans-[Ru(VI)(L)((18)O)(2)](2+) (1-(18)O(2)) with N(16)O(2)(-) in H(2)O/CH(3)CN produces the (18)O-enriched (nitrato)oxoruthenium(IV) species 2-(18)O(2). Analysis of the ESI/MS spectrum of 2-(18)O(2) suggests that scrambling of the (18)O atoms has occurred. A mechanism that involves linkage isomerization of the nitrato ligand and reversible oxygen atom transfer is proposed.

  1. Ultraviolet Absorption Induces Hydrogen-Atom Transfer in G⋅C Watson-Crick DNA Base Pairs in Solution.

    Science.gov (United States)

    Röttger, Katharina; Marroux, Hugo J B; Grubb, Michael P; Coulter, Philip M; Böhnke, Hendrik; Henderson, Alexander S; Galan, M Carmen; Temps, Friedrich; Orr-Ewing, Andrew J; Roberts, Gareth M

    2015-12-01

    Ultrafast deactivation pathways bestow photostability on nucleobases and hence preserve the structural integrity of DNA following absorption of ultraviolet (UV) radiation. One controversial recovery mechanism proposed to account for this photostability involves electron-driven proton transfer (EDPT) in Watson-Crick base pairs. The first direct observation is reported of the EDPT process after UV excitation of individual guanine-cytosine (G⋅C) Watson-Crick base pairs by ultrafast time-resolved UV/visible and mid-infrared spectroscopy. The formation of an intermediate biradical species (G[-H]⋅C[+H]) with a lifetime of 2.9 ps was tracked. The majority of these biradicals return to the original G⋅C Watson-Crick pairs, but up to 10% of the initially excited molecules instead form a stable photoproduct G*⋅C* that has undergone double hydrogen-atom transfer. The observation of these sequential EDPT mechanisms across intermolecular hydrogen bonds confirms an important and long debated pathway for the deactivation of photoexcited base pairs, with possible implications for the UV photochemistry of DNA. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Atomic scattering in the diffraction limit: electron transfer in keV Li+-Na(3s, 3p) collisions

    International Nuclear Information System (INIS)

    Poel, M van der; Nielsen, C V; Rybaltover, M; Nielsen, S E; Machholm, M; Andersen, N

    2002-01-01

    We measure angle differential cross sections (DCS) in Li + + Na → Li + Na + electron transfer collisions in the 2.7-24 keV energy range. We do this with a newly constructed apparatus which combines the experimental technique of cold target recoil ion momentum spectroscopy with a laser-cooled target. This setup yields a momentum resolution of 0.12 au, an order of magnitude better angular resolution than previous measurements on this system. This enables us to clearly resolve Fraunhofer-type diffraction patterns in the angle DCS. In particular, the angular width of the ring structure is given by the ratio of the de Broglie wavelength λ dB = 150 fm at a velocity v = 0.20 au and the effective atomic diameter for electron capture 2R = 20 au. Parallel AO and MO semiclassical coupled-channel calculations of the Na(3s, 3p) → Li(2s, 2p) state-to-state collision amplitudes have been performed, and quantum scattering amplitudes are derived by the eikonal method. The resulting angle-differential electron transfer cross sections and their diffraction patterns agree with the experimental level-to-level results over most scattering angles in the energy range

  3. Atomic layer deposition to prevent metal transfer from implants: An X-ray fluorescence study

    Energy Technology Data Exchange (ETDEWEB)

    Bilo, Fabjola [INSTM and Chemistry for Technologies Laboratory, University of Brescia, via Branze, 38, 25123 Brescia (Italy); Borgese, Laura, E-mail: laura.borgese@unibs.itl [INSTM and Chemistry for Technologies Laboratory, University of Brescia, via Branze, 38, 25123 Brescia (Italy); Prost, Josef; Rauwolf, Mirjam; Turyanskaya, Anna; Wobrauschek, Peter; Kregsamer, Peter; Streli, Christina [Atominstitut, TU Wien, Stadionallee 2, 1020 Vienna (Austria); Pazzaglia, Ugo [Dipartimento Specialità Medico Chirurgiche Sc. Radiol. e Sanità Pubblica, University of Brescia, v.le Europa, 11, 25121 Brescia (Italy); Depero, Laura E. [INSTM and Chemistry for Technologies Laboratory, University of Brescia, via Branze, 38, 25123 Brescia (Italy)

    2015-12-30

    Highlights: • Co and Cr migrate from bare alloy implant to the surrounding tissue showing a cluster distribution. • Co and Cr migrate from the TiO{sub 2} coated implant to the surrounding tissue showing a decreasing gradient distribution from the alloy surface. • TiO{sub 2} coating layers obtained by ALD on Co–Cr alloy show a barrier effect for the migration of metals. • The thicker the TiO{sub 2} layer deposited by ALD, the lower the metal migration. • The migration of metals from bare alloy toward the surrounding tissue increases with time. This effect is not detected in the coated samples. - Abstract: We show that Atomic Layer Deposition is a suitable coating technique to prevent metal diffusion from medical implants. The metal distribution in animal bone tissue with inserted bare and coated Co–Cr alloys was evaluated by means of micro X-ray fluorescence mapping. In the uncoated implant, the migration of Co and Cr particles from the bare alloy in the biological tissues is observed just after one month and the number of particles significantly increases after two months. In contrast, no metal diffusion was detected in the implant coated with TiO{sub 2}. Instead, a gradient distribution of the metals was found, from the alloy surface going into the tissue. No significant change was detected after two months of aging. As expected, the thicker is the TiO{sub 2} layer, the lower is the metal migration.

  4. Phonon interference control of atomic-scale metamirrors, meta-absorbers, and heat transfer through crystal interfaces

    Science.gov (United States)

    Kosevich, Yu. A.; Potyomina, L. G.; Darinskii, A. N.; Strelnikov, I. A.

    2018-03-01

    The paper theoretically studies the possibility of using the effects of phonon interference between paths through different interatomic bonds for the control of phonon heat transfer through internal crystal interfaces and for the design of phonon metamirrors and meta-absorbers. These metamirrors and meta-absorbers are considered to be defect nanolayers of atomic-scale thicknesses embedded in a crystal. Several analytically solvable three-dimensional lattice-dynamics models of the phonon metamirrors and meta-absorbers at the internal crystal planes are described. It is shown that due to destructive interference in the two or more phonon paths, the internal crystal planes, fully or partially filled with weakly bound or heavy-isotope defect atoms, can completely reflect or completely absorb phonons at the transmission antiresonances, whose wavelengths are larger than the effective thickness of the metamirror or meta-absorber. Due to cooperative superradiant effect, the spectral widths of the two-path interference antiresonances for the plane waves are given by the square of partial filling fraction in the defect crystal plane. Our analysis reveals that the presence of two or more phonon paths plays the dominant role in the emergence of the transmission antiresonances in phonon scattering at the defect crystal planes and in reduction of the thermal interface conductance in comparison with the Fano-resonance concept. We study analytically phonon transmission through internal crystal plane in a model cubic lattice of Si-like atoms, partially filled with Ge-like defect atoms. Such a plane can serve as interference phonon metamirror with the transmission antiresonances in the vicinities of eigenmode frequencies of Ge-like defect atoms in the terahertz frequency range. We predict the extraordinary phonon transmission induced by the two-path constructive interference of the lattice waves in resonance with the vibrations of rare host atoms, periodically distributed in the

  5. Flexible high-loading particle-reinforced polyurethane magnetic nanocomposite fabrication through particle-surface-initiated polymerization

    International Nuclear Information System (INIS)

    Guo Zhanhu; Park, Sung; Wei Suying; Pereira, Tony; Moldovan, Monica; Karki, Amar B; Young, David P; Hahn, H Thomas

    2007-01-01

    Flexible high-loading nanoparticle-reinforced polyurethane magnetic nanocomposites fabricated by the surface-initiated polymerization (SIP) method are reported. Extensive field emission scanning electron microscopic (SEM) and atomic force microscopic (AFM) observations revealed a uniform particle distribution within the polymer matrix. X-ray photoelectron spectrometry (XPS) and differential thermal analysis (DTA) revealed a strong chemical bonding between the nanoparticles and the polymer matrix. The elongation of the SIP nanocomposite under tensile test was about four times greater than that of the composite fabricated by a conventional direct mixing fabrication method. The nanocomposite shows particle-loading-dependent magnetic properties, with an increase of coercive force after the magnetic nanoparticles were embedded into the polymer matrix, arising from the increased interparticle distance and the introduced polymer-particle interactions

  6. Single step synthesis of gold-amino acid composite, with the evidence of the catalytic hydrogen atom transfer (HAT) reaction, for the electrochemical recognition of Serotonin

    Science.gov (United States)

    Choudhary, Meenakshi; Siwal, Samarjeet; Nandi, Debkumar; Mallick, Kaushik

    2016-03-01

    A composite architecture of amino acid and gold nanoparticles has been synthesized using a generic route of 'in-situ polymerization and composite formation (IPCF)' [1,2]. The formation mechanism of the composite has been supported by a model hydrogen atom (H•≡H++e-) transfer (HAT) type of reaction which belongs to the proton coupled electron transfer (PCET) mechanism. The 'gold-amino acid composite' was used as a catalyst for the electrochemical recognition of Serotonin.

  7. A DFT Study of R-X Bond Dissociation Enthalpies of Relevance to the Initiation Process of Atom Transfer Radical Polymerization

    DEFF Research Database (Denmark)

    Gillies, Malcolm Bjørn; Matyjaszewski, Krzysztof; Norrby, Per-Ola

    2003-01-01

    DFT calculations at the B3P86/6-31G** level have been carried out to derive the bond dissociation energies (BDE) and free energies for a number of R-X systems (X ) Cl, Br, I, N3, and S2-CNMe2) that have been or can potentially be used as initiators for atom transfer radical polymerization (ATRP...

  8. Peptide block copolymers by N-carboxyanhydride ring-opening polymerization and atom transfer radical polymerization: The effect of amide macroinitiators

    NARCIS (Netherlands)

    Habraken, G.J.M.; Koning, C.E.; Heise, A.

    2009-01-01

    The synthesis of polypeptide-containing block copolymers combining N-carboxyanhydride (NCA) ring-opening polymerization and atom transfer radical polymerization (ATRP) was investigated. An amide initiator comprising an amine function for the NCA polymerization and an activated bromide for ATRP was

  9. Synthesis of poly(2-ethyl-2-oxazoline)-b-poly(styrene) copolymers via a dual initiator route combining cationic ring-opening polymerization and atom transfer radical polymerization

    NARCIS (Netherlands)

    Becer, C.R.; Paulus, R.M.; ppener, S.; Hoogenboom, R.; Fustin, C.A.; Gohy, J.M.W.; Schubert, U.S.

    2008-01-01

    Block copolymers of 2-ethyl-2-oxazoline (EtOx) and styrene were synthesized by a combination of cationic ring-opening polymerization (CROP) and atom transfer radical polymerization (ATRP). Initially, a detailed kinetic investigation for the ?-bromoisobutyrylbromide (BrEBBr) initiated CROP of EtOx

  10. Acrylamide-b-N-isopropylacrylamide block copolymers : Synthesis by atomic transfer radical polymerization in water and the effect of the hydrophilic-hydrophobic ratio on the solution properties

    NARCIS (Netherlands)

    Wever, Diego Armando Z.; Ramalho, Graham; Picchioni, Francesco; Broekhuis, Antonius Augustinus

    2014-01-01

    A series of block copolymers of acrylamide and N-isopropylacrylamide (NIPAM) characterized by different ratios between the length of the two blocks have been prepared through atomic transfer radical polymerization in water at room temperature. The solution properties of the block copolymers were

  11. Low energy cross section data for ion-molecule reactions in hydrogen systems and for charge transfer of multiply charged ions with atoms and molecules

    International Nuclear Information System (INIS)

    Okuno, Kazuhiko

    2007-04-01

    Systematic cross section measurements for ion-molecule reactions in hydrogen systems and for charge transfer of multiply charged ions in low energy collisions with atoms and molecules have been performed continuously by the identical apparatus installed with an octo-pole ion beam guide (OPIG) since 1980 till 2004. Recently, all of accumulated cross section data for a hundred collision systems has been entered into CMOL and CHART of the NIFS atomic and molecular numerical database together with some related cross section data. In this present paper, complicated ion-molecule reactions in hydrogen systems are revealed and the brief outlines of specific properties in low energy charge transfer collisions of multiply charged ions with atoms and molecules are introduced. (author)

  12. Polystyrene/magnesium hydroxide nanocomposite particles prepared by surface-initiated in-situ polymerization

    International Nuclear Information System (INIS)

    Liu Hui; Yi Jianhong

    2009-01-01

    In order to avoid their agglomeration and incompatibility with hydrophobic polystyrene substrate, magnesium hydroxide nanoparticles were encapsulated by surface-initiated in-situ polymerization of styrene. The process contained two steps: electrostatic adsorption of initiator and polymerization of monomer on the surface of magnesium hydroxide. It was found that high adsorption ratio in the electrostatic adsorption of initiator could be attained only in acidic region, and the adsorption belonged to typical physical process. Compared to traditional in-situ polymerization, higher grafting ratio was obtained in surface-initiated in-situ polymerization, which can be attributed to weaker steric hindrance. Both Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM) indicated that polystyrene/magnesium hydroxide nanocomposite particles had been successfully prepared by surface-initiated in-situ polymerization. The resulting samples were also analyzed and characterized by means of contact angle testing, dispersibility evaluation and thermogravimetric analysis

  13. Transfer

    DEFF Research Database (Denmark)

    Wahlgren, Bjarne; Aarkrog, Vibe

    Bogen er den første samlede indføring i transfer på dansk. Transfer kan anvendes som praksis-filosofikum. Den giver en systematisk indsigt til den studerende, der spørger: Hvordan kan teoretisk viden bruges til at reflektere over handlinger i situationer, der passer til min fremtidige arbejdsplads?...

  14. Rational preparation of dibenzothiophene-imprinted polymers by surface imprinting technique combined with atom transfer radical polymerization

    International Nuclear Information System (INIS)

    Yang, Wenming; Liu, Lukuan; Zhou, Zhiping; Liu, Hong; Xie, Binze; Xu, Wanzhen

    2013-01-01

    A computational simulation method is introduced to simulate the dibenzothiophene-monomer pre-assembly system of molecular imprinted polymers. The interaction type and intensity between dibenzothiophene and monomer are discussed from the binding energy and spatial position distribution. The simulation and analysis results indicate that the amount of the function monomer is not the more the better in preparing molecular imprinted polymers. Based on the above results, a novel dibenzothiophene-imprinted polymers with the favorable specific adsorption effect was prepared by surface imprinting technique combined with atom transfer radical polymerization. This combined technologies are used for preparing a desulfurization adsorbent for the first time. Various measures were selected to characterize the structure and morphology of the prepared adsorbent. The characterization results show that the adsorbent has suitable features for further adsorption process. A series of static adsorption experiments were conducted to analyze its adsorption performance. The adsorption process follows Elovich model by the kinetic analysis and Sips equation by the isothermal analysis. The approach we described will provide another opportunity in the deep desulfurization field.

  15. Dramatic Influence of an Anionic Donor on the Oxygen-Atom Transfer Reactivity of a MnV–Oxo Complex

    Science.gov (United States)

    Neu, Heather M; Quesne, Matthew G; Yang, Tzuhsiung; Prokop-Prigge, Katharine A; Lancaster, Kyle M; Donohoe, James; DeBeer, Serena; de Visser, Sam P; Goldberg, David P

    2014-01-01

    Addition of an anionic donor to an MnV(O) porphyrinoid complex causes a dramatic increase in 2-electron oxygen-atom-transfer (OAT) chemistry. The 6-coordinate [MnV(O)(TBP8Cz)(CN)]− was generated from addition of Bu4N+CN− to the 5-coordinate MnV(O) precursor. The cyanide-ligated complex was characterized for the first time by Mn K-edge X-ray absorption spectroscopy (XAS) and gives Mn–O=1.53 Å, Mn–CN=2.21 Å. In combination with computational studies these distances were shown to correlate with a singlet ground state. Reaction of the CN− complex with thioethers results in OAT to give the corresponding sulfoxide and a 2e−-reduced MnIII(CN)− complex. Kinetic measurements reveal a dramatic rate enhancement for OAT of approximately 24 000-fold versus the same reaction for the parent 5-coordinate complex. An Eyring analysis gives ΔH≠=14 kcal mol−1, ΔS≠=−10 cal mol−1 K−1. Computational studies fully support the structures, spin states, and relative reactivity of the 5- and 6-coordinate MnV(O) complexes. PMID:25256417

  16. 3D scaffolds from vertically aligned carbon nanotubes/poly(methyl methacrylate) composites via atom transfer radical polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Tebikachew, Behabtu; Magina, Sandra [CICECO, Department of Chemistry, University of Aveiro (Portugal); Mata, Diogo; Oliveira, Filipe J.; Silva, Rui F. [CICECO, Department of Materials and Ceramic Engineering, University of Aveiro (Portugal); Barros-Timmons, Ana, E-mail: anabarros@ua.pt [CICECO, Department of Chemistry, University of Aveiro (Portugal)

    2015-01-15

    Vertically aligned carbon nanotubes (VACNTs) synthesized by Thermal Chemical Vapour Deposition (TCVD) were modified using an Ar:O{sub 2} (97:3) plasma to generate oxygen-containing functional groups on the surface for subsequent modification. X-ray photo-emission spectroscopy (XPS) and micro-Raman analyses confirmed the grafting of those functional groups onto the surface of the nanotubes as well as the removal of amorphous carbon produced and deposited on the VACNT forests during the CVD process. The plasma treated VACNT forests were further modified with 2-bromo-2-methylpropionyl bromide, an atom transfer radical polymerization (ATRP) initiator, to grow poly(methyl methacrylate) (PMMA) chains from the forests via ATRP. Scanning transmission electron microscopy (STEM) of the ensuing VACNT/PMMA composites confirmed the coating of the nanotube forests with the PMMA polymer. 3D scaffolds of polymeric composites with honeycomb like structure were then obtained. Compressive tests have shown that the VACNT/PMMA composite has higher compressive strength than the pristine forest. - Highlights: • Vertically aligned carbon nanotubes (VACNTs) were synthesized and plasma modified. • X-ray photo-emission and Raman spectroscopies confirmed the VACNTs modification. • Poly(methyl methacrylate) chains were grown via ATRP from the VACNTs. • STEM of the VACNT/PMMA composites confirmed that PMMA surrounds the nanotubes. • VACNT/PMMA composite has higher compressive strength compared to the pristine forest.

  17. All solid-state polymer electrolytes prepared from a hyper-branched graft polymer using atom transfer radical polymerization

    International Nuclear Information System (INIS)

    Higa, Mitsuru; Fujino, Yukiko; Koumoto, Taihei; Kitani, Ryousuke; Egashira, Satsuki

    2005-01-01

    We propose an all solid-state (liquid free) polymer electrolyte (SPE) prepared from a hyper-branched graft copolymer. The graft copolymer consisting of a poly(methyl methacrylate) main chain and poly(ethylene glycol) methyl ether methacrylate side chains was synthesized by atom transfer radical polymerization changing the average chain distance between side chains, side chain length and branched chain length of the proposed structure of the graft copolymer. The ionic conductivity of the SPEs increases with increasing the side chain length, branched chain length and/or average distance between the side chains. The ionic conductivity of the SPE prepared from POEM 9 whose POEM content = 51 wt% shows 2 x 10 -5 S/cm at 30 deg. C. The tensile strength of the SPEs decreases with increases the side chain length, branched chain length and/or average distance between the side chains. These results indicate that a SPE prepared from the hyper-branched graft copolymer has potential to be applied to an all-solid polymer electrolyte

  18. 3D scaffolds from vertically aligned carbon nanotubes/poly(methyl methacrylate) composites via atom transfer radical polymerization

    International Nuclear Information System (INIS)

    Tebikachew, Behabtu; Magina, Sandra; Mata, Diogo; Oliveira, Filipe J.; Silva, Rui F.; Barros-Timmons, Ana

    2015-01-01

    Vertically aligned carbon nanotubes (VACNTs) synthesized by Thermal Chemical Vapour Deposition (TCVD) were modified using an Ar:O 2 (97:3) plasma to generate oxygen-containing functional groups on the surface for subsequent modification. X-ray photo-emission spectroscopy (XPS) and micro-Raman analyses confirmed the grafting of those functional groups onto the surface of the nanotubes as well as the removal of amorphous carbon produced and deposited on the VACNT forests during the CVD process. The plasma treated VACNT forests were further modified with 2-bromo-2-methylpropionyl bromide, an atom transfer radical polymerization (ATRP) initiator, to grow poly(methyl methacrylate) (PMMA) chains from the forests via ATRP. Scanning transmission electron microscopy (STEM) of the ensuing VACNT/PMMA composites confirmed the coating of the nanotube forests with the PMMA polymer. 3D scaffolds of polymeric composites with honeycomb like structure were then obtained. Compressive tests have shown that the VACNT/PMMA composite has higher compressive strength than the pristine forest. - Highlights: • Vertically aligned carbon nanotubes (VACNTs) were synthesized and plasma modified. • X-ray photo-emission and Raman spectroscopies confirmed the VACNTs modification. • Poly(methyl methacrylate) chains were grown via ATRP from the VACNTs. • STEM of the VACNT/PMMA composites confirmed that PMMA surrounds the nanotubes. • VACNT/PMMA composite has higher compressive strength compared to the pristine forest

  19. A peroxidase mimic with atom transfer radical polymerization activity constructed through the grafting of heme onto metal-organic frameworks.

    Science.gov (United States)

    Jiang, Wei; Pan, Yue; Yang, Jiebing; Liu, Yong; Yang, Yan; Tang, Jun; Li, Quanshun

    2018-07-01

    Atom transfer radical polymerization (ATRP) has been considered to be an efficient strategy for constructing functional macromolecules owing to its simple operation and versatile monomers, and thus it is of great significance to develop ideal catalysts with higher activity and perfect reusability. We constructed a peroxidase mimic through the grafting of heme onto metal-organic frameworks UiO-66-NH 2 (ZrMOF), namely Heme-ZrMOF. After the systematic characterization of structure, the composite Heme-ZrMOF was demonstrated to possess high peroxidase activity using 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulphonate) and 3,3',5,5'-tetramethylbenzidine as substrates. The enzyme mimic was then used as catalysts in the ATRP reactions of different monomers, in which favorable monomer conversion (44.6-98.0%) and product molecular weight (8600-25,600 g/mol) could be obtained. Compared to free heme, Heme-ZrMOF could efficiently achieve the easy separation of heme from the catalytic system and facilitate the ATRP reaction in an aqueous environment to avoid the utilization of organic solvents. In conclusion, the enzyme mimic Heme-ZrMOF could be potentially used as an effective catalyst for preparing well-defined polymers with biomedical applications. Copyright © 2018 Elsevier Inc. All rights reserved.

  20. Quantum-mechanical theory for electronic-vibrational-rotational energy transfer in atom--diatom collisions: Analysis of the Hamiltonian

    International Nuclear Information System (INIS)

    Bellum, J.C.; McGuire, P.

    1983-01-01

    We investigate forms of the molecular system Hamiltonian valid for rigorous quantum-mechanical treatments of inelastic atom--diatom collisions characterized by exchange of energy between electronic, vibrational, and rotational degrees of freedom. We analyze this Hamiltonian in terms of various choices of independent coordinates which unambiguously specify the electronic and nuclear positions in the context of space-fixed and body-fixed reference frames. In particular we derive forms of the Hamiltonian in the context of the following four sets of independent coordinates: (1) a so-called space-fixed set, in which both electronic and nuclear positions are relative to the space-fixed frame; (2) a so-called mixed set, in which nuclear positions are relative to the body-fixed frame while electronic positions are relative to the space-fixed frame; (3) a so-called body-fixed set, in which both electronic and nuclear positions are relative to the body-fixed frame; and (4) another mixed set, in which nuclear positions are relative to the space-fixed frame while electronic positions are relative to the body-fixed frame. Based on practical considerations in accounting for electronic structure and nonadiabatic coupling of electronic states of the collision complex we find the forms of the Hamiltonian in the context of coordinate sets (3) and (4) above to be most appropriate, respectively, for body-fixed and space-fixed treatments of nuclear dynamics in collisional transfer of electronic, vibrational, and rotational energies

  1. Atomic fusion, Gerrard atomic fusion

    International Nuclear Information System (INIS)

    Gerrard, T.H.

    1980-01-01

    In the approach to atomic fusion described here the heat produced in a fusion reaction, which is induced in a chamber by the interaction of laser beams and U.H.F. electromagnetic beams with atom streams, is transferred to a heat exchanger for electricity generation by a coolant flowing through a jacket surrounding the chamber. (U.K.)

  2. Hydrophobic modification of wood via surface-initiated ARGET ATRP of MMA

    Energy Technology Data Exchange (ETDEWEB)

    Fu Yanchun; Li Gang [Material Science and Engineering College, Northeast Forestry University, Harbin 150040 (China); Yu Haipeng, E-mail: yuhaipeng20000@yahoo.com.cn [Key laboratory of Bio-based Material Science and Technology of Ministry of Education, Northeast Forestry University, Harbin 150040 (China); Material Science and Engineering College, Northeast Forestry University, Harbin 150040 (China); Liu Yixing, E-mail: yxl200488@sina.com [Key laboratory of Bio-based Material Science and Technology of Ministry of Education, Northeast Forestry University, Harbin 150040 (China); Material Science and Engineering College, Northeast Forestry University, Harbin 150040 (China)

    2012-01-15

    To convert the hydrophilic surface of wood into a hydrophobic surface, the present study investigated activators regenerated by electron transfer for atom transfer radical polymerization (ARGET ATRP) as a method of grafting methyl methacrylate (MMA) onto the wood surface. The wood treated with 2-bromoisobutyryl bromide and with the subsequently attached MMA via ARGET ATRP under different polymerization times (2 h, 4 h, 6 h, 8 h) were examined using scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. All the analyses confirmed that PMMA had been grafted onto the wood surface. Water contact angle measurement proved that the covering layer of PMMA on wood made the surface hydrophobic. Polymerization time had a positive influence on the contact angle value and higher contact angle can be produced with the prolongation of the polymerization time. When the reaction time was extended to 8 h, the contact angle of treated wood surface reached 130 Degree-Sign in the beginning, and remained at 116 Degree-Sign after 60 s. The ARGET ATRP method may raise an alteration on the wood surface modification.

  3. Charge-transfer cross sections of H+ ions in collisions with noble gas atoms in the energy range below 4.0 keV

    International Nuclear Information System (INIS)

    Kusakabe, Toshio; Sakaue, Hiroyuki A.; Tawara, Hiroyuki

    2011-01-01

    Charge-transfer cross sections in collisions of H + ions with the ground state He, Ar, Kr, and Xe atoms have been measured in the energy range below 4.0 keV with the initial growth rate method. These observed cross sections are also compared with previously published experimental data and theoretical predictions. In the He and Ar targets, it is found that some previous experimental data deviate significantly from the present observed cross sections as the collision energy decreases. It has been found that in the Kr and Xe targets, the energy dependence of the present observed cross sections behaves as “near-resonant” charge transfer. (author)

  4. Low-Energy Charge Transfer in Multiply-Charged Ion-Atom Collisions Studied with the Combined SCVB-MOCC Approach

    OpenAIRE

    Cooper, D. L.; Stancil, P. C.; Turner, A. R.; Wang, J. G.; Clarke, N. J.; Zygelman, B.

    2002-01-01

    A survey of theoretical studies of charge transfer involving collisions of multiply-charged ions with atomic neutrals (H and He) is presented. The calculations utilized the quantum-mechanical molecular-orbital close-coupling (MOCC) approach where the requisite potential curves and coupling matrix elements have been obtained with the spin-coupled valence bond (SCVB) method. Comparison is made among various collision partners, for equicharged systems, where it is illustrated that even for total...

  5. Synthesis of Well-Defined Three-Arm Star-Branched Polystyrene through Arm-First Coupling Approach by Atom Transfer Radical Polymerization

    OpenAIRE

    Shahabuddin, Syed; Hamime Ismail, Fatem; Mohamad, Sharifah; Muhamad Sarih, Norazilawati

    2015-01-01

    Here we describe a simple route to synthesize three-arm star-branched polystyrene. Atom transfer radical polymerization technique has been utilized to yield branched polystyrene involving Williamson coupling strategy. Initially a linear polymeric chain of predetermined molecular weight has been synthesized which is further end-functionalized into a primary alkyl bromide moiety, a prime requisition for Williamson reaction. The end-functionalized polymer is then coupled using 1,1,1-tris(4-hydro...

  6. The potential of Cu(I)Cl/2,2'-bipyridine catalysis in a triblock copolymer preparation by atom transfer radical polymerization

    Czech Academy of Sciences Publication Activity Database

    Masař, Bohumil; Vlček, Petr; Kříž, Jaroslav

    2001-01-01

    Roč. 81, č. 14 (2001), s. 3514-3522 ISSN 0021-8995 R&D Projects: GA MŠk OC P1.10; GA AV ČR KSK2050602 Institutional research plan: CEZ:AV0Z4050913 Keywords : atom transfer radical polymerization * triblock copolymers * sequential synthesis Subject RIV: CD - Macromolecular Chemistry Impact factor: 0.992, year: 2001

  7. TRANSFER

    African Journals Online (AJOL)

    This paper reports on further studies on long range energy transfer between curcumine as donor and another thiazine dye, thionine, which is closely related to methylene blue as energy harvester (Figure 1). Since thionine is known to have a higher quantum yield of singlet oxygen sensitization than methylene blue [8], it is ...

  8. Quasi-four-body treatment of charge transfer in the collision of protons with atomic helium: II. Second-order non-Thomas mechanisms and the cross sections

    Science.gov (United States)

    Safarzade, Zohre; Akbarabadi, Farideh Shojaei; Fathi, Reza; Brunger, Michael J.; Bolorizadeh, Mohammad A.

    2018-05-01

    A fully quantum mechanical four-body treatment of charge transfer collisions between energetic protons and atomic helium is developed here. The Pauli exclusion principle is applied to both the wave function of the initial and final states as well as the operators involved in the interaction. Prior to the collision, the helium atom is assumed as a two-body system composed of the nucleus, He2+, and an electron cloud composed of two electrons. Nonetheless, four particles are assumed in the final state. As the double interactions contribute extensively in single charge transfer collisions, the Faddeev-Lovelace-Watson scattering formalism describes it best physically. The treatment of the charge transfer cross section, under this quasi-four-body treatment within the FWL formalism, showed that other mechanisms leading to an effect similar to the Thomas one occur at the same scattering angle. Here, we study the two-body interactions which are not classically described but which lead to an effect similar to the Thomas mechanism and finally we calculate the total singlet and triplet amplitudes as well as the angular distributions of the charge transfer cross sections. As the incoming projectiles are assumed to be plane waves, the present results are calculated for high energies; specifically a projectile energy of 7.42 MeV was assumed as this is where experimental results are available in the literature for comparison. Finally, when possible we compare the present results with the other available theoretical data.

  9. Agreement between the Government of Australia and the European Atomic Energy Community concerning transfer of nuclear material from Australia to the European Atomic Energy Community

    International Nuclear Information System (INIS)

    1983-01-01

    This agreement applies to nuclear material transferred from Australia to the Community for peaceful purposes. Provisions of the Agreement are complementary to the provisions of any bilateral agreements in force and shall, where appropriate, supersede the provisions of those agreements. The agreement entered into force on 15th January 1982

  10. Fabrication of nonfouling, bactericidal, and bacteria corpse release multifunctional surface through surface-initiated RAFT polymerization.

    Science.gov (United States)

    Wang, Bailiang; Ye, Zi; Tang, Yihong; Han, Yuemei; Lin, Quankui; Liu, Huihua; Chen, Hao; Nan, Kaihui

    Infections after surgery or endophthalmitis are potentially blinding complications caused by bacterial adhesion and subsequent biofilm formation on the intraocular lens. Neither single-function anti-adhesion surface nor contacting killing surface can exhibit ideal antibacterial function. In this work, a novel (2-(dimethylamino)-ethyl methacrylate- co -2-methacryloyloxyethyl phosphorylcholine) (p (DMAEMA- co -MPC)) brush was synthesized by "grafting from" method through reversible-addition fragmentation chain transfer polymerization. 1-Bromoheptane was used to quaternize the p (DMAEMA- co -MPC) brush coating and to endow the surface with bactericidal function. The success of the surface functionalization was confirmed by atomic force microscopy, water contact angle, and spectroscopic ellipsometry. The quaternary ammonium salt units were employed as efficient disinfection that can eliminate bacteria through contact killing, whereas the 2-methacryloyloxyethyl phosphorylcholine units were introduced to suppress unwanted nonspecific adsorption. The functionalized poly(dimethyl siloxane) surfaces showed efficiency in reducing bovine serum albumin adsorption and in inhibiting bacteria adhesion and biofilm formation. The copolymer brushes also demonstrated excellent bactericidal function against gram-positive ( Staphylococcus aureus ) bacteria measured by bacteria live/dead staining and shake-flask culture methods. The surface biocompatibility was evaluated by morphology and activity measurement with human lens epithelial cells in vitro. The achievement of the p (DMAEMA + - co -MPC) copolymer brush coating with nonfouling, bactericidal, and bacteria corpse release properties can be used to modify intraocular lenses.

  11. Formation of excited hydrogen atoms by charge transfer and dissociation. Progress report No. 11, December 1, 1974--November 1, 1975

    International Nuclear Information System (INIS)

    Thomas, E.W.; Zivitz, M.; Rausch, E.O.; Baird, W.E.; Harris, J.E.

    1975-01-01

    A study of the excited states of atoms backscattered from metal surfaces is presented. Incident ions were H + , H 2 + , and He + at energies of 10 to 30 keV. Preliminary data are presented for a study of the charge state distribution among atoms backscattered from surfaces. Results of a study of light emission from atoms sputtered off targets by 10 to 30 keV Ar + ions as a way to determine surface contamination are presented. Brief studies of radiation damage by 10 to 30 keV H + and He + ions are discussed. 5 figures

  12. Enhanced binding capacity of boronate affinity adsorbent via surface modification of silica by combination of atom transfer radical polymerization and chain-end functionalization for high-efficiency enrichment of cis-diol molecules

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Wei; He, Maofang; Wang, Chaozhan; Wei, Yinmao, E-mail: ymwei@nwu.edu.cn

    2015-07-30

    Boronate affinity materials have been widely used for specific separation and preconcentration of cis-diol molecules, but most do not have sufficient capacity due to limited binding sites on the material surface. In this work, we prepared a phenylboronic acid-functionalized adsorbent with a high binding capacity via the combination of surface-initiated atom transfer radical polymerization (SI-ATRP) and chain-end functionalization. With this method, the terminal chlorides of the polymer chains were used fully, and the proposed adsorbent contains dense boronic acid polymers chain with boronic acid on the chain end. Consequently, the proposed adsorbent possesses excellent selectivity and a high binding capacity of 513.6 μmol g{sup −1} for catechol and 736.8 μmol g{sup −1} for fructose, which are much higher than those of other reported adsorbents. The dispersed solid-phase extraction (dSPE) based on the prepared adsorbent was used for extraction of three cis-diol drugs (i.e., epinephrine, isoprenaline and caffeic acid isopropyl ester) from plasma; the eluates were analyzed by HPLC-UV. The reduced amount of adsorbent (i.e., 2.0 mg) could still eliminate interferences efficiently and yielded a recovery range of 85.6–101.1% with relative standard deviations ranging from 2.5 to 9.7% (n = 5). The results indicated that the proposed strategy could serve as a promising alternative to increase the density of surface functional groups on the adsorbent; thus, the prepared adsorbent has the potential to effectively enrich cis-diol substances in real samples. - Highlights: • Boronate adsorbent is prepared via ATRP and chain-end functionalization. • The adsorbent has quite high binding capacity for cis-diols. • Binding capacity is easily manipulated by ATRP condition. • Chain-end functionalization can improve binding capacity significantly. • Reduced adsorbent is consumed in dispersed solid-phase extraction of cis-diols.

  13. Investigation of the Mechanism of Electron Capture and Electron Transfer Dissociation of Peptides with a Covalently Attached Free Radical Hydrogen Atom Scavenger.

    Science.gov (United States)

    Sohn, Chang Ho; Yin, Sheng; Peng, Ivory; Loo, Joseph A; Beauchamp, J L

    2015-11-15

    The mechanisms of electron capture and electron transfer dissociation (ECD and ETD) are investigated by covalently attaching a free-radical hydrogen atom scavenger to a peptide. The 2,2,6,6-tetramethylpiperidin-l-oxyl (TEMPO) radical was chosen as the scavenger due to its high hydrogen atom affinity (ca. 280 kJ/mol) and low electron affinity (ca. 0.45 ev), and was derivatized to the model peptide, FQX TEMPO EEQQQTEDELQDK. The X TEMPO residue represents a cysteinyl residue derivatized with an acetamido-TEMPO group. The acetamide group without TEMPO was also examined as a control. The gas phase proton affinity (882 kJ/mol) of TEMPO is similar to backbone amide carbonyls (889 kJ/mol), minimizing perturbation to internal solvation and sites of protonation of the derivatized peptides. Collision induced dissociation (CID) of the TEMPO tagged peptide dication generated stable odd-electron b and y type ions without indication of any TEMPO radical induced fragmentation initiated by hydrogen abstraction. The type and abundance of fragment ions observed in the CID spectra of the TEMPO and acetamide tagged peptides are very similar. However, ECD of the TEMPO labeled peptide dication yielded no backbone cleavage. We propose that a labile hydrogen atom in the charge reduced radical ions is scavenged by the TEMPO radical moiety, resulting in inhibition of N-C α backbone cleavage processes. Supplemental activation after electron attachment (ETcaD) and CID of the charge-reduced precursor ion generated by electron transfer of the TEMPO tagged peptide dication produced a series of b + H (b H ) and y + H (y H ) ions along with some c ions having suppressed intensities, consistent with stable O-H bond formation at the TEMPO group. In summary, the results indicate that ECD and ETD backbone cleavage processes are inhibited by scavenging of a labile hydrogen atom by the localized TEMPO radical moiety. This observation supports the conjecture that ECD and ETD processes involve long

  14. Heterogeneous Single-Atom Catalyst for Visible-Light-Driven High-Turnover CO2 Reduction: The Role of Electron Transfer.

    Science.gov (United States)

    Gao, Chao; Chen, Shuangming; Wang, Ying; Wang, Jiawen; Zheng, Xusheng; Zhu, Junfa; Song, Li; Zhang, Wenkai; Xiong, Yujie

    2018-03-01

    Visible-light-driven conversion of CO 2 into chemical fuels is an intriguing approach to address the energy and environmental challenges. In principle, light harvesting and catalytic reactions can be both optimized by combining the merits of homogeneous and heterogeneous photocatalysts; however, the efficiency of charge transfer between light absorbers and catalytic sites is often too low to limit the overall photocatalytic performance. In this communication, it is reported that the single-atom Co sites coordinated on the partially oxidized graphene nanosheets can serve as a highly active and durable heterogeneous catalyst for CO 2 conversion, wherein the graphene bridges homogeneous light absorbers with single-atom catalytic sites for the efficient transfer of photoexcited electrons. As a result, the turnover number for CO production reaches a high value of 678 with an unprecedented turnover frequency of 3.77 min -1 , superior to those obtained with the state-of-the-art heterogeneous photocatalysts. This work provides fresh insights into the design of catalytic sites toward photocatalytic CO 2 conversion from the angle of single-atom catalysis and highlights the role of charge kinetics in bridging the gap between heterogeneous and homogeneous photocatalysts. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Surface-initiated growth of thin oxide coatings for Li-sulfur battery cathodes

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Kyu Tae; Black, Robert; Yim, Taeeun; Ji, Xiulei; Nazar, Linda F. [University of Waterloo, Department of Chemistry, Waterloo, ON (Canada)

    2012-12-15

    The concept of surface-initiated growth of oxides on functionalized carbons is introduced as a method to inhibit the dissolution of polysulfide ions in Li-S battery cathode materials. MO{sub x} (M: Si, V) thin layers are homogeneously coated on nanostructured carbon-sulfur composites. The coating significantly inhibits the dissolution of polysulfides on cycling, resulting in enhanced cycle performance and coulombic efficiency of the Li-S battery. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  16. Transfer-free synthesis of graphene-like atomically thin carbon films on SiC by ion beam mixing technique

    Science.gov (United States)

    Zhang, Rui; Chen, Fenghua; Wang, Jinbin; Fu, Dejun

    2018-03-01

    Here we demonstrate the synthesis of graphene directly on SiC substrates at 900 °C using ion beam mixing technique with energetic carbon cluster ions on Ni/SiC structures. The thickness of 7-8 nm Ni films was evaporated on the SiC substrates, followed by C cluster ion bombarding. Carbon cluster ions C4 were bombarded at 16 keV with the dosage of 4 × 1016 atoms/cm2. After thermal annealing process Ni silicides were formed, whereas C atoms either from the decomposition of the SiC substrates or the implanted contributes to the graphene synthesis by segregating and precipitating process. The limited solubility of carbon atoms in silicides, involving SiC, Ni2Si, Ni5Si2, Ni3Si, resulted in diffusion and precipitation of carbon atoms to form graphene on top of Ni and the interface of Ni/SiC. The ion beam mixing technique provides an attractive production method of a transfer-free graphene growth on SiC and be compatible with current device fabrication.

  17. Atom Transfer Radical Polymerization of Styrene in Presence of Mesoporous Silica Nanoparticles: Application of Reverse, Simultaneous Reverse and Normal Initiation Techniques

    Directory of Open Access Journals (Sweden)

    Khezrollah Khezri

    2014-04-01

    Full Text Available Atom transfer radical polymerization (ATRP of styrene in presence of mesoporous silica nanoparticles was carried out at 110 °C. Reverse atom transfer radical polymerization (RATRP and simultaneous reverse and normal initiation for atom transfer radical polymerization (SR&NI ATRP techniques were used as two appropriate introduced techniques for circumventing oxidation problems. Usage of metal catalyst in its higher oxidation state was the main feature of these initiation techniques in which deficiencies of normal ATRP were circumvented. Structure, surface area and pore diameter of synthesized mesoporous silica nanoparticles were evaluated using X–ray diffraction and nitrogen adsorption/desorption isotherm analysis. Average particle size was estimated around 600 nm by electron microscopy images. In addition, according to these images, nanoparticles revealed an appropriate size distribution. Particles size and their distribution were examined using scanning. Final monomer conversion was determined by using gas chromatography. The number and weight average molecular weights (Mn and Mw and polydispersity indexes (PDI were also evaluated by gel permeation chromatography. According to the results obtained, addition of mesoporous silica nanoparticles in both RATRP and SR&NI ATRP systems revealed similar effects: decrement of conversion and Mn and also increment of PDI values observed by increasing of mesoporous silica nanoparticles content. Improvement in thermal stability of the nanocomposites in comparison with neat polystyrene was demonstrated by thermogravimetric analysis (TGA. Moreover, in case of nanocomposites, thermal stability was obtained by higher loading of nanoparticles. A decrease in glass transition temperature by higher content of mesoporous silica nanoparticles has been demonstrated by differential scanning calorimetry analysis.

  18. Fabrication of nonfouling, bactericidal, and bacteria corpse release multifunctional surface through surface-initiated RAFT polymerization

    Directory of Open Access Journals (Sweden)

    Wang B

    2016-12-01

    Full Text Available Bailiang Wang,1,2 Zi Ye,1 Yihong Tang,1 Yuemei Han,1 Quankui Lin,1,2 Huihua Liu,2 Hao Chen,1,2 Kaihui Nan1,2 1School of Ophthalmology and Optometry, Eye Hospital, Wenzhou Medical University, Wenzhou, 2Wenzhou Institute of Biomaterials and Engineering, Chinese Academy of Sciences, Wenzhou, People’s Republic of China Abstract: Infections after surgery or endophthalmitis are potentially blinding complications caused by bacterial adhesion and subsequent biofilm formation on the intraocular lens. Neither single-function anti-adhesion surface nor contacting killing surface can exhibit ideal antibacterial function. In this work, a novel (2-(dimethylamino-ethyl methacrylate-co-2-methacryloyloxyethyl phosphorylcholine (p (DMAEMA-co-MPC brush was synthesized by “grafting from” method through reversible–addition fragmentation chain transfer polymerization. 1-Bromoheptane was used to quaternize the p (DMAEMA-co-MPC brush coating and to endow the surface with bactericidal function. The success of the surface functionalization was confirmed by atomic force microscopy, water contact angle, and spectroscopic ellipsometry. The quaternary ammonium salt units were employed as efficient disinfection that can eliminate bacteria through contact killing, whereas the 2-methacryloyloxyethyl phosphorylcholine units were introduced to suppress unwanted nonspecific adsorption. The functionalized poly(dimethyl siloxane surfaces showed efficiency in reducing bovine serum albumin adsorption and in inhibiting bacteria adhesion and biofilm formation. The copolymer brushes also demonstrated excellent bactericidal function against gram-positive (Staphylococcus aureus bacteria measured by bacteria live/dead staining and shake-flask culture methods. The surface biocompatibility was evaluated by morphology and activity measurement with human lens epithelial cells in vitro. The achievement of the p (DMAEMA+-co-MPC copolymer brush coating with nonfouling, bactericidal, and

  19. Synthesis of Well-Defined Three-Arm Star-Branched Polystyrene through Arm-First Coupling Approach by Atom Transfer Radical Polymerization

    Directory of Open Access Journals (Sweden)

    Syed Shahabuddin

    2015-01-01

    Full Text Available Here we describe a simple route to synthesize three-arm star-branched polystyrene. Atom transfer radical polymerization technique has been utilized to yield branched polystyrene involving Williamson coupling strategy. Initially a linear polymeric chain of predetermined molecular weight has been synthesized which is further end-functionalized into a primary alkyl bromide moiety, a prime requisition for Williamson reaction. The end-functionalized polymer is then coupled using 1,1,1-tris(4-hydroxyphenylethane, a trifunctional core molecule, to give well-defined triple-arm star-branched polystyrene.

  20. WRF Simulation over the Eastern Africa by use of Land Surface Initialization

    Science.gov (United States)

    Sakwa, V. N.; Case, J.; Limaye, A. S.; Zavodsky, B.; Kabuchanga, E. S.; Mungai, J.

    2014-12-01

    The East Africa region experiences severe weather events associated with hazards of varying magnitude. It receives heavy precipitation which leads to wide spread flooding and lack of sufficient rainfall in some parts results into drought. Cases of flooding and drought are two key forecasting challenges for the Kenya Meteorological Service (KMS). The source of heat and moisture depends on the state of the land surface which interacts with the boundary layer of the atmosphere to produce excessive precipitation or lack of it that leads to severe drought. The development and evolution of precipitation systems are affected by heat and moisture fluxes from the land surface within weakly-sheared environments, such as in the tropics and sub-tropics. These heat and moisture fluxes during the day can be strongly influenced by land cover, vegetation, and soil moisture content. Therefore, it is important to represent the land surface state as accurately as possible in numerical weather prediction models. Improved modeling capabilities within the region have the potential to enhance forecast guidance in support of daily operations and high-impact weather over East Africa. KMS currently runs a configuration of the Weather Research and Forecasting (WRF) model in real time to support its daily forecasting operations, invoking the Non-hydrostatic Mesoscale Model (NMM) dynamical core. They make use of the National Oceanic and Atmospheric Administration / National Weather Service Science and Training Resource Center's Environmental Modeling System (EMS) to manage and produce the WRF-NMM model runs on a 7-km regional grid over Eastern Africa.SPoRT and SERVIR provide land surface initialization datasets and model verification tool. The NASA Land Information System (LIS) provide real-time, daily soil initialization data in place of interpolated Global Forecast System soil moisture and temperature data. Model verification is done using the Model Evaluation Tools (MET) package, in order

  1. Electron transfer and atom exchange between aqueous Fe(II) and structural Fe(III) in clays. Role in U and Hg(II) transformations

    Energy Technology Data Exchange (ETDEWEB)

    Scherer, Michelle [Univ. of Iowa, Iowa City, IA (United States)

    2016-08-31

    During this project, we investigated Fe electron transfer and atom exchange between aqueous Fe(II) and structural Fe(III) in clay minerals. We used selective chemical extractions, enriched Fe isotope tracer experiments, computational molecular modeling, and Mössbauer spectroscopy. Our findings indicate that structural Fe(III) in clay minerals is reduced by aqueous Fe(II) and that electron transfer occurs when Fe(II) is sorbed to either basal planes and edge OH-groups of clay mineral. Findings from highly enriched isotope experiments suggest that up to 30 % of the Fe atoms in the structure of some clay minerals exhanges with aqueous Fe(II). First principles calculations using a small polaron hopping approach suggest surprisingly fast electron mobility at room temperature in a nontronite clay mineral and are consistent with temperature dependent Mössbauer data Fast electron mobility suggests that electrons may be able to conduct through the mineral fast enough to enable exchange of Fe between the aqueous phase and clay mineral structure. over the time periods we observed. Our findings suggest that Fe in clay minerals is not as stable as previously thought.

  2. Joule heating and spin-transfer torque investigated on the atomic scale using a spin-polarized scanning tunneling microscope.

    Science.gov (United States)

    Krause, S; Herzog, G; Schlenhoff, A; Sonntag, A; Wiesendanger, R

    2011-10-28

    The influence of a high spin-polarized tunnel current onto the switching behavior of a superparamagnetic nanoisland on a nonmagnetic substrate is investigated by means of spin-polarized scanning tunneling microscopy. A detailed lifetime analysis allows for a quantification of the effective temperature rise of the nanoisland and the modification of the activation energy barrier for magnetization reversal, thereby using the nanoisland as a local thermometer and spin-transfer torque analyzer. Both the Joule heating and spin-transfer torque are found to scale linearly with the tunnel current. The results are compared to experiments performed on lithographically fabricated magneto-tunnel junctions, revealing a very high spin-transfer torque switching efficiency in our experiments.

  3. In situ crosslinking of surface-initiated ring opening metathesis polymerization of polynorbornene for improved stability.

    Science.gov (United States)

    Fursule, Ishan A; Abtahi, Ashkan; Watkins, Charles B; Graham, Kenneth R; Berron, Brad J

    2018-01-15

    In situ crosslinking is expected to increase the solvent stability of coatings formed by surface-initiated ring opening metathesis polymerization (SI ROMP). Solvent-associated degradation limits the utility of SI ROMP coatings. SI ROMP coatings have a unique capacity for post-functionalization through reaction of the unsaturated site on the polymer backbone. Any post-reaction scheme which requires a liquid solvent has the potential to degrade the coating and lower the thickness of the resulting film. We designed a macromolecular crosslinking group based on PEG dinorbornene. The PEG length is tailored to the expected mean chain to chain distance during surface-initiated polymerization. This crosslinking macromer is randomly copolymerized with norbornene through SI ROMP on a gold coated substrate. The solvent stability of polynorbornene coatings with and without PEG dinorbornene is quantitatively determined, and the mechanism of degradation is further supported through XPS and AFM analyses. The addition of the 0.25mol% PEG dinorbornene significantly increases the solvent stability of the SI ROMP coatings. The crosslinker presence in the more stable films is supported with observable PEG absorbances by FTIR and an increase in contact angle hysteresis when compared to non-crosslinked coatings. The oxidation of the SI ROMP coatings is supported by the observation of carbonyl oxygen in the polynorbornene coatings. The rapid loss of the non-crosslinked SI ROMP coating corresponds to nanoscale pitting across the surface and micron-scale regions of widespread film loss. The crosslinked coatings have uniform nanoscale pitting, but the crosslinked films show no evidence of micron-scale film damage. In all, the incorporation of minimal crosslinking content is a simple strategy for improving the solvent stability of SI ROMP coatings. Copyright © 2017 Elsevier Inc. All rights reserved.

  4. Preparation of molecularly imprinted nanoparticles with superparamagnetic susceptibility through atom transfer radical emulsion polymerization for the selective recognition of tetracycline from aqueous medium

    International Nuclear Information System (INIS)

    Dai, Jiangdong; Pan, Jianming; Xu, Longcheng; Li, Xiuxiu; Zhou, Zhiping; Zhang, Rongxian; Yan, Yongsheng

    2012-01-01

    Highlights: ► Atom transfer radical emulsion polymerization is a “living” and green technique. ► Nanoparticles can overcome mass transfer limitations and improve accessibility. ► Molecular imprinted nanoparticles with magnetic property for fast separation. ► The performance of imprinted nanoparticles was investigated in detail. ► Nanoparticles were used to selective recognize Tetracycline from water medium. - Abstract: In the work, we reported an effective method for the preparation of molecularly imprinted nanoparticles with superparamagnetic susceptibility through atom transfer radical emulsion polymerization (ATREP), and then as-prepared magnetic molecularly imprinted nanoparticles (MMINs) were evaluated as adsorbents for selective recognition of tetracycline (TC) molecules from aqueous medium. The resulting nanoparticles were characterized by FT-IR, TGA, VSM, SEM and TEM. The results demonstrated MMINs with a narrow diameter distribution were cross-linked with modified Fe 3 O 4 particles, composed of imprinted layer and exhibited good magnetic sensitivity, magnetic and thermal stability. Batch rebinding studies were carried out to determine the specific adsorption equilibrium, kinetics, and selective recognition. The estimated adsorption capacity of MMINs towards TC by the Langmuir isotherm model was 12.10 mg g −1 at 298 K, which was 6.33 times higher than that of magnetic non-molecularly imprinted nanoparticles (MNINs). The kinetic property of MMINs was well-described by the pseudo-second-order rate equation. The results of selective recognition experiments demonstrated outstanding affinity and selectivity towards TC over competitive antibiotics. The reusability of MMINs showed no obviously deterioration at least five repeated cycles in performance. In addition, the MMINs prepared were successfully applied to the extraction of TC from the spiked pork sample.

  5. Preparation of molecularly imprinted nanoparticles with superparamagnetic susceptibility through atom transfer radical emulsion polymerization for the selective recognition of tetracycline from aqueous medium

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Jiangdong; Pan, Jianming; Xu, Longcheng; Li, Xiuxiu [School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China); Zhou, Zhiping [School of Material Science and Engineering, Jiangsu University, Zhenjiang 212013 (China); Zhang, Rongxian [School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China); Yan, Yongsheng, E-mail: djdxxx123@163.com [School of Chemistry and Chemical Engineering, Jiangsu University, Zhenjiang 212013 (China); State Key Laboratory of Natural and Biomimetic Drugs, Peking University, Beijing, 100191 (China)

    2012-02-29

    Highlights: Black-Right-Pointing-Pointer Atom transfer radical emulsion polymerization is a 'living' and green technique. Black-Right-Pointing-Pointer Nanoparticles can overcome mass transfer limitations and improve accessibility. Black-Right-Pointing-Pointer Molecular imprinted nanoparticles with magnetic property for fast separation. Black-Right-Pointing-Pointer The performance of imprinted nanoparticles was investigated in detail. Black-Right-Pointing-Pointer Nanoparticles were used to selective recognize Tetracycline from water medium. - Abstract: In the work, we reported an effective method for the preparation of molecularly imprinted nanoparticles with superparamagnetic susceptibility through atom transfer radical emulsion polymerization (ATREP), and then as-prepared magnetic molecularly imprinted nanoparticles (MMINs) were evaluated as adsorbents for selective recognition of tetracycline (TC) molecules from aqueous medium. The resulting nanoparticles were characterized by FT-IR, TGA, VSM, SEM and TEM. The results demonstrated MMINs with a narrow diameter distribution were cross-linked with modified Fe{sub 3}O{sub 4} particles, composed of imprinted layer and exhibited good magnetic sensitivity, magnetic and thermal stability. Batch rebinding studies were carried out to determine the specific adsorption equilibrium, kinetics, and selective recognition. The estimated adsorption capacity of MMINs towards TC by the Langmuir isotherm model was 12.10 mg g{sup -1} at 298 K, which was 6.33 times higher than that of magnetic non-molecularly imprinted nanoparticles (MNINs). The kinetic property of MMINs was well-described by the pseudo-second-order rate equation. The results of selective recognition experiments demonstrated outstanding affinity and selectivity towards TC over competitive antibiotics. The reusability of MMINs showed no obviously deterioration at least five repeated cycles in performance. In addition, the MMINs prepared were successfully

  6. Low-Energy Charge Transfer in Multiply-Charged Ion-Atom Collisions Studied with the Combined SCVB-MOCC Approach

    Directory of Open Access Journals (Sweden)

    B. Zygelman

    2002-03-01

    Full Text Available A survey of theoretical studies of charge transfer involving collisions of multiply-charged ions with atomic neutrals (H and He is presented. The calculations utilized the quantum-mechanical molecular-orbital close-coupling (MOCC approach where the requisite potential curves and coupling matrix elements have been obtained with the spin-coupled valence bond (SCVB method. Comparison is made among various collision partners, for equicharged systems, where it is illustrated that even for total charge transfer cross sections, scaling-laws do not exist for low-energy collisions (i.e. < 1 keV/amu. While various empirical scaling-laws are well known in the intermediateand high-energy regimes, the multi-electron configurations of the projectile ions results in a rich and varied low-energy dependence, requiring an explicit calculation for each collision-partner pair. Future charge transfer problems to be addressed with the combined SCVB-MOCC approach are briefly discussed.

  7. Start broadened profiles with self-consistent radiation transfer and atomic kinetics in plasmas produced by high intensity lasers

    International Nuclear Information System (INIS)

    Olson, G.L.; Comly, J.C.; La Gattuta, J.K.; Kilcrease, D.P.

    1993-01-01

    Spectral line shapes and line strengths have long been used to diagnose plasma temperatures and densities. In dense plasmas, the additional broadening due to Stark effects give additional information about the plasma density. We present calculations that are self-consistent in that the radiation fields of the line transitions and the atomic kinetics are iterated to convergence. Examples are given for simple plasmas with temperature gradients, density gradients, and velocity fields. Then a more complex example of a laser produced plasma is presented

  8. Marine biofouling and its implications in the use of seawater as a heat transfer fluid in Madras Atomic Power Station

    International Nuclear Information System (INIS)

    Nair, K.V.K.; Venugopalan, V.P.

    1996-01-01

    Even though the problem of fouling is quite severe in the tropics because of rich diversity of species and longer periods available for breeding activity, most of the literature is from the temperate waters. In this paper, an attempt is made to illustrate the potential of biofouling to compromise the economical operation of coastal power plants by taking Madras Atomic Power Station (MAPS) as an example. The significance of acquiring information on biological aspects of the fouling species in successfully combating the problems is also highlighted. 3 refs., 3 tabs., 1 fig

  9. Transitioning Enhanced Land Surface Initialization and Model Verification Capabilities to the Kenya Meteorological Department (KMD)

    Science.gov (United States)

    Case, Jonathan L.; Mungai, John; Sakwa, Vincent; Zavodsky, Bradley T.; Srikishen, Jayanthi; Limaye, Ashutosh; Blankenship, Clay B.

    2016-01-01

    Flooding, severe weather, and drought are key forecasting challenges for the Kenya Meteorological Department (KMD), based in Nairobi, Kenya. Atmospheric processes leading to convection, excessive precipitation and/or prolonged drought can be strongly influenced by land cover, vegetation, and soil moisture content, especially during anomalous conditions and dry/wet seasonal transitions. It is thus important to represent accurately land surface state variables (green vegetation fraction, soil moisture, and soil temperature) in Numerical Weather Prediction (NWP) models. The NASA SERVIR and the Short-term Prediction Research and Transition (SPoRT) programs in Huntsville, AL have established a working partnership with KMD to enhance its regional modeling capabilities. SPoRT and SERVIR are providing experimental land surface initialization datasets and model verification capabilities for capacity building at KMD. To support its forecasting operations, KMD is running experimental configurations of the Weather Research and Forecasting (WRF; Skamarock et al. 2008) model on a 12-km/4-km nested regional domain over eastern Africa, incorporating the land surface datasets provided by NASA SPoRT and SERVIR. SPoRT, SERVIR, and KMD participated in two training sessions in March 2014 and June 2015 to foster the collaboration and use of unique land surface datasets and model verification capabilities. Enhanced regional modeling capabilities have the potential to improve guidance in support of daily operations and high-impact weather and climate outlooks over Eastern Africa. For enhanced land-surface initialization, the NASA Land Information System (LIS) is run over Eastern Africa at 3-km resolution, providing real-time land surface initialization data in place of interpolated global model soil moisture and temperature data available at coarser resolutions. Additionally, real-time green vegetation fraction (GVF) composites from the Suomi-NPP VIIRS instrument is being incorporated

  10. Resonant line transfer in a fog: using Lyman-alpha to probe tiny structures in atomic gas

    Science.gov (United States)

    Gronke, Max; Dijkstra, Mark; McCourt, Michael; Peng Oh, S.

    2017-11-01

    Motivated by observational and theoretical work that suggest very small-scale (≲ 1 pc) structure in the circumgalactic medium of galaxies and in other environments, we study Lyman-α (Lyα) radiative transfer in an extremely clumpy medium with many clouds of neutral gas along the line of sight. While previous studies have typically considered radiative transfer through sightlines intercepting ≲ 10 clumps, we explored the limit of a very large number of clumps per sightline (up to fc 1000). Our main finding is that, for covering factors greater than some critical threshold, a multiphase medium behaves similarly to a homogeneous medium in terms of the emergent Lyα spectrum. The value of this threshold depends on both the clump column density and the movement of the clumps. We estimated this threshold analytically and compare our findings to radiative transfer simulations with a range of covering factors, clump column densities, radii, and motions. Our results suggest that (I) the success in fitting observed Lyα spectra using homogeneous "shell models" (and the corresponding failure of multiphase models) hints at the presence of very small-scale structure in neutral gas, which is in agreement within a number of other observations; and (II) the recurrent problems of reproducing realistic line profiles from hydrodynamical simulations may be due to their inability to resolve small-scale structure, which causes simulations to underestimate the effective covering factor of neutral gas clouds. The movie associated to Fig. B.2 is available at http://www.aanda.org

  11. Charge-transfer collisions of multicharged ions with atomic and molecular hydrogen: measurements with low-energy accelerators

    International Nuclear Information System (INIS)

    Phaneuf, R.A.; Meyer, F.W.; Crandall, D.H.

    1977-01-01

    Electron-capture cross sections for O/sup +q/ + H → O/sup +q-1/ + H + and O/sup +q/ + H 2 → O/sup +q-1/ + H 2 + are shown for projectile energies from 10 to 1300 keV. At low energies the cross sections are determined by details of the quasi-molecule potential; at higher energies momentum transfer becomes the dominant mechanism, and the cross sections fall off similarly. Results with other projectiles are described briefly. 1 figure

  12. Spectroscopic study of a DNA brush synthesized in situ by surface initiated enzymatic polymerization.

    Science.gov (United States)

    Khan, M Nuruzzaman; Tjong, Vinalia; Chilkoti, Ashutosh; Zharnikov, Michael

    2013-08-29

    We used a combination of synchrotron-based X-ray photoelectron spectroscopy (XPS) and angle-resolved near-edge X-ray absorption fine structure (NEXAFS) spectroscopy to study the chemical integrity, purity, and possible internal alignment of single-strand (ss) adenine deoxynucleotide (poly(A)) DNA brushes. The brushes were synthesized by surface-initiated enzymatic polymerization (SIEP) on a 25-mer of adenine self-assembled monolayer (SAM) on gold (A25-SH), wherein the terminal 3'-OH of the A25-SH serve as the initiation sites for SIEP of poly(A). XPS and NEXAFS spectra of poly(A) brushes were found to be almost identical to those of A25-SH initiator, with no unambiguous traces of contamination. Apart from the well-defined chemical integrity and contamination-free character, the brushes were found to have a high degree of orientational order, with an upright orientation of individual strands, despite their large thickness up to ~55 nm, that corresponds to a chain length of at least several hundred nucleotides for individual ssDNA molecules. The orientational order exhibited by these poly(A) DNA brushes, mediated presumably by base stacking, was found to be independent of the brush thickness as long as the packing density was high enough. The well-defined character and orientational ordering of the ssDNA brushes make them a potentially promising system for different applications.

  13. On fatigue crack growth mechanisms of MMC: Reflection on analysis of 'multi surface initiations'

    International Nuclear Information System (INIS)

    Mkaddem, A.; El Mansori, M.

    2009-01-01

    This work attempts to examine the mechanisms of fatigue when cracks synergetically initiate in more than one site at the specimen surface. The metal matrix composites (MMC) i.e. silicon carbide particles reinforced aluminium matrix composites (Al/SiC p -MMC), seem to be good candidates to accelerate fatigue failures following multi surface initiations (MSI). Closure effects of MSI mechanisms on the variation of fatigue behaviour are explored for various stress states. Experiments were carried out using non pre-treated and pre-treated specimens. Using an Equivalent Ellipse Method (EEM), it is shown that the aspect of surface finish of specimen plays an important role on crack growth. Scanning Electron Microscope (SEM) inspections have lead to distinguishing the initiation regions from propagation regions and final separation regions. It is also revealed that the total lifetime of specimens is sensitive to heat treatment. Moreover, it is found that the appearance of MSI in cycled materials is more probable at high level of fatigue loads.

  14. Exotic atoms

    International Nuclear Information System (INIS)

    Kunselman, R.

    1993-01-01

    The experiments use a solid hydrogen layer to form muonic hydrogen isotopes that escape into vacuum. The method relies on transfer of the muon from protium to either a deuteron or a triton. The resulting muonic deuterium or muonic tritium will not immediately thermalize because of the very low elastic cross sections, and may be emitted from the surface of the layer. Measurements which detect decay electrons, muonic x-rays, and fusion products have been used to study the processes. A target has been constructed which exploits muonic atom emission in order to learn more about the energy dependence of transfer and muon molecular formation

  15. Designing of fluorescent and magnetic imprinted polymer for rapid, selective and sensitive detection of imidacloprid via activators regenerated by the electron transfer-atom transfer radical polymerization (ARGET-ATRP) technique

    Science.gov (United States)

    Kumar, Sunil; Karfa, Paramita; Madhuri, Rashmi; Sharma, Prashant K.

    2018-05-01

    In this work, we report on a dual-behavior electrochemical/optical sensor for sensitive determination of Imidacloprid by fluorescent dye (fluorescein, FL) and imprinted polymer modified europium doped superparamagnetic iron oxide nanoparticles (FL@SPIONs@MIP). The imidacloprid (IMD)-imprinted polymer was directly synthesized on the Eu-SPIONs surface via Activators regenerated by the electron transfer-atom transfer radical polymerization (ARGET-ATRP) technique. Preparation, characterization and application of the prepared FL@SPIONs@MIP were systematically investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), fluorescence spectroscopy and electrochemical techniques. The electrochemical experiments exhibited a remarkable selectivity of the prepared sensor towards IMD. Determination of IMD by the square wave stripping voltammetry method represented a wide linear range of 0.059-0.791 μg L-1 with a detection limit of 0.0125 μg L-1. In addition, the fluorescence method shows a linear range of 0.039-0.942 μg L-1 and LOD of 0.0108 μg L-1. The fluorescence property of prepared FL@SPIONs@MIP was used for rapid, on-spot but selective detection of IMD in real samples. The proposed electrode displayed excellent repeatability and long-term stability and was successfully applied for quantitative and trace level determination of IMD in several real samples.

  16. Electron transfer processes in ion collisions with atomic hydrogen. Final report for period February 1, 1975--June 30, 1976

    International Nuclear Information System (INIS)

    Bayfield, J.E.

    1976-07-01

    Results of experiments completed with Yale equipment coupled to the Oak Ridge Test Bench and Tandem Accelerator facilities are presented. Electron transfer cross sections have been measured at keV collision energies for B, C, N and O ions colliding with H, H 2 , Ar and He gas targets. The ion charge states studied range from +2 through +5. Also reported are cross sections for Si and Fe ions on H, H 2 and Ar at energies between 1.5 and 14 MeV, with charge states varying between +5 and +13. Also measured were the cross sections for H + collisions with H, H 2 and Ar for energies between 0.8 and 2.5 MeV. At keV energies the cross sections for highly charged B, C, N and O ions are found to be 1 x 10 -14 cm 2 . The cross sections for 4 MeV Fe ions scale roughly with the square of the ion charge, and have values as high as 0.5 x 10 -14 cm 2 for Fe 10+ + H collisions. A strong energy dependence is found for Fe ion collisions between 4 and 14 MeV. Previous results for MeV H + + Ar collisions are nicely reproduced, while our first results for the fundamental MeV H + - H collision problem are cross sections higher than many theoretical predictions

  17. Halloysite nanotubes grafted hyperbranched (co)polymers via surface-initiated self-condensing vinyl (co)polymerization

    International Nuclear Information System (INIS)

    Mu Bin; Zhao Mingfei; Liu Peng

    2008-01-01

    Halloysite nanotubes (HNTs) grafted hyperbranched polymers were prepared by the self-condensing vinyl polymerization (SCVP) of 2-((bromoacetyl)oxy)ethyl acrylate (BAEA) and the self-condensing vinyl copolymerization of n-butyl acrylate (BA) and BAEA with BAEA as inimer (AB*) respectively, from the surfaces of the 2-bromoisobutyric acid modified halloysite nanotubes (HNTs-Br) via atom transfer radical polymerization (ATRP) technique. The halloysite nanotubes grafted hyperbranched polymer (HNTs-HP) and the halloysite nanotubes grafted hyperbranched copolymer (HNTs-HCP) were characterized by elemental analysis (EA), Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and transmission electron microscope (TEM). The grafted hyperbranched polymers were characterized with Nuclear magnetic resonance (NMR) and the molecular ratio between the inimer AB* and BA in the grafted hyperbranched copolymers was found to be 3:2, calculated from the TGA and EA results

  18. Halloysite nanotubes grafted hyperbranched (co)polymers via surface-initiated self-condensing vinyl (co)polymerization

    Energy Technology Data Exchange (ETDEWEB)

    Mu Bin; Zhao Mingfei; Liu Peng [Lanzhou University, State Key Laboratory of Applied Organic Chemistry and Institute of Polymer Science and Engineering, College of Chemistry and Chemical Engineering (China)], E-mail: pliu@lzu.edu.cn

    2008-05-15

    Halloysite nanotubes (HNTs) grafted hyperbranched polymers were prepared by the self-condensing vinyl polymerization (SCVP) of 2-((bromoacetyl)oxy)ethyl acrylate (BAEA) and the self-condensing vinyl copolymerization of n-butyl acrylate (BA) and BAEA with BAEA as inimer (AB*) respectively, from the surfaces of the 2-bromoisobutyric acid modified halloysite nanotubes (HNTs-Br) via atom transfer radical polymerization (ATRP) technique. The halloysite nanotubes grafted hyperbranched polymer (HNTs-HP) and the halloysite nanotubes grafted hyperbranched copolymer (HNTs-HCP) were characterized by elemental analysis (EA), Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), and transmission electron microscope (TEM). The grafted hyperbranched polymers were characterized with Nuclear magnetic resonance (NMR) and the molecular ratio between the inimer AB* and BA in the grafted hyperbranched copolymers was found to be 3:2, calculated from the TGA and EA results.

  19. Nanostructured Polymer Brushes by UV-Assisted Imprint Lithography and Surface-Initiated Polymerization for Biological Functions

    NARCIS (Netherlands)

    Benetti, Edmondo Maria; Acikgoz, C.; Sui, Xiaofeng; Vratzov, Boris; Hempenius, Mark A.; Huskens, Jurriaan; Vancso, Gyula J.

    2011-01-01

    Functional polymer brush nanostructures are obtained by combining step-and-flash imprint lithography (SFIL) with controlled, surface-initiated polymerization (CSIP). Patterning is achieved at length scales such that the smallest elements have dimensions in the sub-100 nm range. The patterns exhibit

  20. The valuation key day in legal expropriation according to the Atomic Energy Act. On the transferability of the legal compensation fundamentals of the so called progression legislation on the 13th AtG amendment

    International Nuclear Information System (INIS)

    Cornils, Matthias

    2015-01-01

    Under the - constitutionally based - regime ruling compensation for expropriated property notably the valuation key day is of crucial importance for the level of compensation. The study examines the therefor acknowledged principles and criteria, their constitutional foundation, their applicability on expropriation measures directly performed by an Act of Parliament, finally their transferability to the 13th amendment to the Atomic Energy Act.

  1. Parameters Studies on Surface Initiated Rolling Contact Fatigue of Turnout Rails by Three-Level Unreplicated Saturated Factorial Design

    Directory of Open Access Journals (Sweden)

    Xiaochuan Ma

    2018-03-01

    Full Text Available Surface initiated rolling contact fatigue (RCF, mainly characterized by cracks and material stripping, is a common type of damage to turnout rails, which can not only shorten service life of turnout but also lead to poor running safety of vehicle. The rail surface initiated RCF of turnouts is caused by a long-term accumulation, the size and distribution of which are related to the dynamic parameters of the complicated vehicle-turnout system. In order to simulate the accumulation of rail damage, some random samples of dynamic parameters significantly influencing it should be input. Based on the three-level unreplicated saturated factorial design, according to the evaluation methods of H, P and B statistic values, six dynamic parameters that influence the rail surface initiated RCF in turnouts, namely running speed of vehicle, axle load, wheel-rail profiles, integral vertical track stiffness and wheel-rail friction coefficient, are obtained by selecting 13 dynamic parameters significantly influencing the dynamic vehicle-turnout interaction as the analysis factors, considering four dynamic response results, i.e., the normal wheel-rail contact force, longitudinal creep force, lateral creep force and wheel-rail contact patch area as the observed parameters. In addition, the rail surface initiated RCF behavior in turnouts under different wheel-rail creep conditions is analyzed, considering the relative motion of stock/switch rails. The results show that the rail surface initiated RCF is mainly caused by the tangential stress being high under small creep conditions, the normal and tangential stresses being high under large creep conditions, and the normal stress being high under pure spin creep conditions.

  2. Energy flux of hot atoms

    International Nuclear Information System (INIS)

    Wotzak, G.P.; Kostin, M.D.

    1976-01-01

    The process in which hot atoms collide with thermal atoms of a gas, transfer kinetic energy to them, and produce additional hot atoms is investigated. A stochastic method is used to obtain numerical results for the spatial and time dependent energy flux of hot atoms in a gas. The results indicate that in hot atom systems a front followed by an intense energy flux of hot atoms may develop

  3. Cu determination in crude oil distillation products by atomic absorption and inductively coupled plasma mass spectrometry after analyte transfer to aqueous solution

    International Nuclear Information System (INIS)

    Kowalewska, Zofia; Ruszczynska, Anna; Bulska, Ewa

    2005-01-01

    Cu was determined in a wide range of petroleum products from crude oil distillation using flame atomic absorption spectrometry (FAAS), electrothermal atomic absorption spectrometry (ETAAS) and inductively coupled plasma mass spectrometry (ICP-MS). Different procedures of sample preparation were evaluated: (i) mineralization with sulfuric acid in an open system (ii) mineralization in a closed microwave system (iii) combustion in hydrogen-oxygen flame in the Wickbold's apparatus (iv) matrix evaporation followed by acid dissolution, and (v) acidic extraction. All the above procedures led to the transfer of the analyte into an aqueous solution for the analytical measurement step. It was found that application of FAAS was limited to the analysis of the heaviest petroleum products of high Cu content. In ICP-MS, the use of internal reference method (with Rh or In as internal reference element) was required to eliminate the matrix effects in the analysis of extracts and the concentrated solutions of mineralized heavy petroleum products. The detection limits (in original samples) were equal to, respectively, 10, 86, 3.3, 0.9 and 0.4 ng g -1 in procedures i-v with ETAAS detection and 10, 78, 1.1 and 0.5 ng g -1 in procedures i-iii and v with ICP-MS detection. The procedures recommended here were validated by recovery experiments, certified reference materials analysis and comparison of results, obtained for a given sample, in different ways. The Cu content in the analyzed samples was: 50-110 ng g -1 in crude oil, -1 in gasoline, -1 in atmospheric oil, -1 in heavy vacuum oil and 140-300 ng g -1 in distillation residue

  4. Cu determination in crude oil distillation products by atomic absorption and inductively coupled plasma mass spectrometry after analyte transfer to aqueous solution

    Science.gov (United States)

    Kowalewska, Zofia; Ruszczyńska, Anna; Bulska, Ewa

    2005-03-01

    Cu was determined in a wide range of petroleum products from crude oil distillation using flame atomic absorption spectrometry (FAAS), electrothermal atomic absorption spectrometry (ETAAS) and inductively coupled plasma mass spectrometry (ICP-MS). Different procedures of sample preparation were evaluated: (i) mineralization with sulfuric acid in an open system, (ii) mineralization in a closed microwave system, (iii) combustion in hydrogen-oxygen flame in the Wickbold's apparatus, (iv) matrix evaporation followed by acid dissolution, and (v) acidic extraction. All the above procedures led to the transfer of the analyte into an aqueous solution for the analytical measurement step. It was found that application of FAAS was limited to the analysis of the heaviest petroleum products of high Cu content. In ICP-MS, the use of internal reference method (with Rh or In as internal reference element) was required to eliminate the matrix effects in the analysis of extracts and the concentrated solutions of mineralized heavy petroleum products. The detection limits (in original samples) were equal to, respectively, 10, 86, 3.3, 0.9 and 0.4 ng g - 1 in procedures i-v with ETAAS detection and 10, 78, 1.1 and 0.5 ng g - 1 in procedures i-iii and v with ICP-MS detection. The procedures recommended here were validated by recovery experiments, certified reference materials analysis and comparison of results, obtained for a given sample, in different ways. The Cu content in the analyzed samples was: 50-110 ng g - 1 in crude oil, oil, oil and 140-300 ng g - 1 in distillation residue.

  5. Rate-controlling two-proton transfer coupled with heavy-atom motion in the 2-pyridinone-catalyzed mutarotation of tetramethylglucose. Experimental and calculated deuterium isotope effects

    International Nuclear Information System (INIS)

    Engdahl, K.A.; Bivehed, H.; Ahlberg, P.; Saunders, W.H. Jr.

    1983-01-01

    Primary and secondary deuterium isotope effects have been measured by polarimetry, and primary isotope effects have been calculated for the classical bifunctional catalysis: 2-pyridinone-catalyzed mutarotation of 2,3,4,6-tetra-O-methyl-α-D-glucopyranose (α-TMG) in benzene. From the positively curved plot of the specific rate of epimerization vs. the mole fraction of 2 H in the ''pool'' of OH and NH hydrogens, the isotope effects k/sub HH//k/sub DD/ = 3.66 +/- 0.09, k/sub HH//k/sub DH/ = 1.5, and k/sub HH//k/sub HD/ = 2.4 have been calculated. A secondary isotope effect of 1.14 +/- 0.02 has been measured by using α-TMG and (1- 2 H)-2,3,4,6-tetra-O-methyl-α-D-glucopyranose [(l- 2 H)-α-TMG], the synthesis of which is described in detail, together with those for (N- 2 H)-2-pyridinone and (1-O- 2 H)-2,3,4,6-tetra-O-methyl-α-D-glucopyranose [(1-O- 2 H)-α-TMG]. The rate data obtained have also been analyzed by fractionation theory, yielding approximately equal fractionation factors (0.5). The interpretation of the results has been assisted by calculations of the primary deuterium isotope effects using the BEBOVIB IV program. Two models involving small and considerable coupling, respectively, of the transferring protons to heavy-atom motion have been considered. In the favored structure for the transition state of the rate-limiting step, two protons are in transit, and their motion is governed either by a potential with a barrier or by one without. Their motion is considerably coupled to the heavy-atom motion (i.e., the breakage of the ring C-O bond), and tunnel corrections to the isotope effects are found to be negligible

  6. Accelerating NLTE radiative transfer by means of the Forth-and-Back Implicit Lambda Iteration: A two-level atom line formation in 2D Cartesian coordinates

    Science.gov (United States)

    Milić, Ivan; Atanacković, Olga

    2014-10-01

    State-of-the-art methods in multidimensional NLTE radiative transfer are based on the use of local approximate lambda operator within either Jacobi or Gauss-Seidel iterative schemes. Here we propose another approach to the solution of 2D NLTE RT problems, Forth-and-Back Implicit Lambda Iteration (FBILI), developed earlier for 1D geometry. In order to present the method and examine its convergence properties we use the well-known instance of the two-level atom line formation with complete frequency redistribution. In the formal solution of the RT equation we employ short characteristics with two-point algorithm. Using an implicit representation of the source function in the computation of the specific intensities, we compute and store the coefficients of the linear relations J=a+bS between the mean intensity J and the corresponding source function S. The use of iteration factors in the ‘local’ coefficients of these implicit relations in two ‘inward’ sweeps of 2D grid, along with the update of the source function in other two ‘outward’ sweeps leads to four times faster solution than the Jacobi’s one. Moreover, the update made in all four consecutive sweeps of the grid leads to an acceleration by a factor of 6-7 compared to the Jacobi iterative scheme.

  7. End-Functionalized Poly(N-isopropylacrylamide with d-Glucosamine through Different Initiator from C-1 and C-2 Positions via Atom Transfer Radical Polymerization

    Directory of Open Access Journals (Sweden)

    Guihua Cui

    2016-11-01

    Full Text Available Regioselective modification of d-glucosamine (2-amino-2-deoxy-d-glucopyranose, GA through C-1 and C-2 positions to synthesized thermo-responsive D-Glucosamine-poly(N-iso-propylacrylamide (PNIPAM via atom transfer radical polymerization (ATRP was investigated for the first time. Two different schemes of the synthesis for GA derivatives (GA-PNIPAM (i and (ii with well-defined structures using 3,4,6-tri-o-acetyl-2-deoxy-2-phthalimido-β-d-glucopyranose and 1,3,4,6-tetra-o-acetyl-2-amino-2-deoxy-β-d-glucopyranose intermediates were examined. The GA-PNIPAM (ii had an amino at C-2 position, while there was a hydroxyl in GA-PNIPAM (i at this position. Both the resulting oligomers (i and (ii had a narrow dispersity, and no significant cytotoxic response of copolymers (i and (ii was observed in the cell line over the concentration range from 0.1 μg/mL to 1000 μg/mL at any of the exposure times. In addition, it was discovered that GA-PNIPAM (i and (ii inhibited the proliferation of Human Hepatocellular Carcinoma Cells HepG2 as the concentration and the time changed, and the inhibitory activity of polymer (ii was higher than that of he (i. The results suggest that the GA-PNIPAM polymers show excellent biocompatibility in vitro.

  8. Surface-initiated ring-opening metathesis polymerization (SI-ROMP) to attach a tethered organic corona onto CdSe/ZnS core/shell quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Vatansever, Fatma, E-mail: vatansever.fatma@mgh.harvard.edu; Hamblin, Michael R., E-mail: hamblin@helix.mgh.harvard.edu [Massachusetts General Hospital, Wellman Center for Photomedicine (United States)

    2016-10-15

    Core–shell CdSe/ZnS quantum dots (QDs) are useful as tunable photostable fluorophores for multiple applications in industry, biology, and medicine. However, to achieve the optimum optical properties, the surface of the QDs must be passivated to remove charged sites that might bind extraneous substances and allow aggregation. Here we describe a method of growing an organic polymer corona onto the QD surface using the bottom-up approach of surface-initiated ring-opening metathesis polymerization (SI-ROMP) with Grubbs catalyst. CdSe/ZnS QDs were first coated with mercaptopropionic acid by displacing the original tri-octylphosphine oxide layer, and then reacted with 7-octenyl dimethyl chlorosilane. The resulting octenyl double bonds allowed the attachment of ruthenium alkylidene groups as a catalyst. A subsequent metathesis reaction with strained bicyclic monomers (norbornene-dicarbonyl chloride (NDC), and a mixture of NDC and norbornenylethylisobutyl-polyhedral oligomeric silsesquioxane (norbornoPOSS)) allowed the construction of tethered organic homo-polymer or co-polymer layers onto the QD. Compounds were characterized by FT-IR, 1H-NMR, X-ray photoelectron spectroscopy, differential scanning calorimetry, and transmission electron microscopy. Atomic force microscopy showed that the coated QDs were separate and non-aggregated with a range of diameter of 48–53 nm.

  9. Preparation and self-assembly behavior of polystyrene-block-poly (dimethylaminoethyl methacrylate amphiphilic block copolymer using atom transfer radical polymerization

    Directory of Open Access Journals (Sweden)

    2008-03-01

    Full Text Available Asymmetric and semi-symmetric amphiphilic diblock copolymers polystyrene-block-poly (dimethylaminoethyl methacrylate (PS-b-PDMAEMA with the same PS block length of 62 repeat units and quite short (3 repeat units or equivalent (47 repeat units length of PDMAEMA have been prepared simply by varying the ratio of the bromine-terminated macroinitiator polystyrene (PS-Br to DMAEMA using atom transfer radical polymerization (ATRP. The chemical structures and compositions of the PS-b-PDMAEMA block copolymers are studied by nuclear magnetic resonance (NMR spectroscopy, gel permeation chromatography (GPC, and elementary analysis (EA. The self-assembly behaviors of copolymers in N,N-dimethyl formamide (DMF with different pH and dioxane/water binary solvent mixture by direct dissolution method (DD, are studied by transmission electron microscopy (TEM, electron diffracting analysis (EDA, and energy-dispersive analysis of X-rays (EDAX techniques. Transmission electron microscopy results suggest that asymmetric block copolymer PS62-b-PDMAEMA3 (the numbers in the form of footnotes represent repeated units of each monomer in the copolymer can form spherical core-shell micelles, large compound reverse micelles (LCRMs, hexagonal/rhombic phases, reverse hexagonal/rhombic phases, vesicles, reverse vesicles and necklace-like reverse micelles, controlled by common or selective solvent and pH, while most of the aggregates of semi-symmetric PS62-b-PDMAEMA47 are simply spherical, such as spherical core-shell micelles and reverse spherical core-shell micelles, besides hexagonal/rhombic phases. All above structures are controlled by three components of the free energy of aggregation: core-chain stretching, interfacial energy and intercoronal chain interaction.

  10. High-performance liquid chromatographic method to evaluate the hydrogen atom transfer during reaction between 1,1-diphenyl-2-picryl-hydrazyl radical and antioxidants

    International Nuclear Information System (INIS)

    Boudier, Ariane; Tournebize, Juliana; Bartosz, Grzegorz; El Hani, Safae; Bengueddour, Rachid; Sapin-Minet, Anne; Leroy, Pierre

    2012-01-01

    Highlights: ► Both 1,1-diphenyl-2-picrylhydrazyl radical and its product measurement by HPLC. ► Lowest limit of detection by monitoring 1,1-diphenyl-2-picryl-hydrazine. ► Adsorption problem of the radical on HPLC parts have been pointed out. - Abstract: 1,1-Diphenyl-2-picrylhydrazyl (DPPH·) is a stable nitrogen centred radical widely used to evaluate direct radical scavenging properties of various synthetic or natural antioxidants (AOs). The bleaching rate of DPPH· absorbance at 515 nm is usually monitored for this purpose. In order to avoid the interference of complex coloured natural products used as antioxidant supplements or cosmetics, HPLC systems have been reported as alternative techniques to spectrophotometry. They also rely upon measurement of DPPH· quenching rate and none of them permits to identify and measure 1,1-diphenyl-2-picryl-hydrazine (DPPH-H), the reduced product of DPPH· resulting from hydrogen atom transfer (HAT), which is the main mechanism of the reaction between DPPH· and AOs. We presently report an HPLC method devoted to the simultaneous measurement of DPPH· and DPPH-H. Both were fully separated on a C18 column eluted with acetonitrile–10 mM ammonium citrate buffer pH 6.8 (70:30, v/v) and detected at 330 nm. Adsorption process of DPPH· onto materials of the HPLC system was pointed out. Consequently, the linearity range observed for DPPH· was restricted, thus a much lower limit of detection was obtained for DPPH-H than for DPPH· using standards (0.02 and 14 μM, respectively). The method was applied to three commonly used AOs, i.e. Trolox ® , ascorbic acid and GSH, and compared with spectrophotometry. Further application to complex matrices (cell culture media, vegetal extracts) and nanomaterials demonstrated (i) its usefulness because of higher selectivity than colorimetry, and (ii) its help to investigate the mechanisms occurring with the free radical.

  11. Atomic collisions related to atomic laser isotope separation

    International Nuclear Information System (INIS)

    Shibata, Takemasa

    1995-01-01

    Atomic collisions are important in various places in atomic vapor laser isotope separation (AVLIS). At a vaporization zone, many atomic collisions due to high density have influence on the atomic beam characteristics such as velocity distribution and metastable states' populations at a separation zone. In the separation zone, a symmetric charge transfer between the produced ions and the neutral atoms may degrade selectivity. We have measured atomic excitation temperatures of atomic beams and symmetric charge transfer cross sections for gadolinium and neodymium. Gadolinium and neodymium are both lanthanides. Nevertheless, results for gadolinium and neodymium are very different. The gadolinium atom has one 5d electron and neodymium atom has no 5d electron. It is considered that the differences are due to existence of 5d electron. (author)

  12. Poly(2-hydroxyethyl methacrylate) grafted halloysite nanotubes as a molecular host matrix for luminescent ions prepared by surface-initiated RAFT polymerization and coordination chemistry

    Energy Technology Data Exchange (ETDEWEB)

    Islam, Md. Rafiqul; Bach, Long Giang; Lim, Kwon Taek, E-mail: ktlim@pknu.ac.kr

    2013-07-01

    A fluorescent nanohybrid complex comprising of halloysite nanotubes (HNTs), poly(2-hydroxyethyl methacrylate) (PHEMA), and europium ions (Eu{sup 3+}) was synthesized by the combination of surface-initiated reversible addition-fragmentation chain transfer (SI-RAFT) polymerization and coordination chemistry. Initially, PHEMA was grafted from the HNTs by SI-RAFT and then reacted with succinic anhydride to provide carboxyl acid groups on the external layers of HNTs-g-PHEMA nanohybrids. The subsequent coordination of the nanohybrids with Eu{sup 3+} ions afforded photoluminescent Eu{sup 3+} tagged HNTs-g-PHEMA nanohybrid complexes (HNTs-g-PHEMA-Eu{sup 3+}). The structure, morphology, and fluorescence properties of the Eu{sup 3+} coordinated nanohybrid complexes were investigated by respective physical and spectral studies. FT-IR, XPS, and EDS analyses suggested the formation of the HNTs-g-PHEMA-Eu{sup 3+} nanohybrids. FE-SEM images indicated the immobilization of polymer layers on HNTs. TGA scans further demonstrated the grafting of PHEMA onto HNTs surface. The optical properties of HNTs-g-PHEMA-Eu{sup 3+} nanohybrid complexes were investigated by photoluminescence spectroscopy.

  13. Poly(allyl methacrylate) functionalized hydroxyapatite nanocrystals via the combination of surface-initiated RAFT polymerization and thiol-ene protocol: a potential anticancer drug nanocarrier.

    Science.gov (United States)

    Bach, Long Giang; Islam, Md Rafiqul; Vo, Thanh-Sang; Kim, Se-Kwon; Lim, Kwon Taek

    2013-03-15

    Hydroxyapatite nanocrystals (HAP NCs) were encapsulated by poly(allyl methacrylate) (PolyAMA) employing controlled surface-initiated reversible addition-fragmentation chain transfer (SI-RAFT) polymerization of allyl methacrylate to afford HAP-PolyAMA nanohybrids. The subsequent thiol-ene coupling of nanohybrids with 2-mercaptosuccinic acid resulted HAP-Poly(AMA-COOH) possessing multicarboxyl group. The formation of the nanohybrids was confirmed by FT-IR and EDS analyses. The TGA and FE-SEM investigation were further suggested the grafting of PolyAMA onto HAP NCs. The utility of the HAP-PolyAMA nanohybrid as drug carrier was also explored. The pendant carboxyl groups on the external layers of nanohybrids were conjugated with anticancer drug cisplatin to afford HAP-Poly(AMA-COOH)/Pt complex. The formation of the complex was confirmed by FT-IR, XPS, and FE-SEM. In vitro evaluation of the synthesized complex as nanomedicine revealed its potential chemotherapeutic efficacy against cancer cell lines. Copyright © 2012 Elsevier Inc. All rights reserved.

  14. Electrospun regenerated cellulose nanofibrous membranes surface-grafted with polymer chains/brushes via the atom transfer radical polymerization method for catalase immobilization.

    Science.gov (United States)

    Feng, Quan; Hou, Dayin; Zhao, Yong; Xu, Tao; Menkhaus, Todd J; Fong, Hao

    2014-12-10

    In this study, an electrospun regenerated cellulose (RC) nanofibrous membrane with fiber diameters of ∼200-400 nm was prepared first; subsequently, 2-hydroxyethyl methacrylate (HEMA), 2-dimethylaminoethyl methacrylate (DMAEMA), and acrylic acid (AA) were selected as the monomers for surface grafting of polymer chains/brushes via the atom transfer radical polymerization (ATRP) method. Thereafter, four nanofibrous membranes (i.e., RC, RC-poly(HEMA), RC-poly(DMAEMA), and RC-poly(AA)) were explored as innovative supports for immobilization of an enzyme of bovine liver catalase (CAT). The amount/capacity, activity, stability, and reusability of immobilized catalase were evaluated, and the kinetic parameters (Vmax and Km) for immobilized and free catalase were determined. The results indicated that the respective amounts/capacities of immobilized catalase on RC-poly(HEMA) and RC-poly(DMAEMA) nanofibrous membranes reached 78 ± 3.5 and 67 ± 2.7 mg g(-1), which were considerably higher than the previously reported values. Meanwhile, compared to that of free CAT (i.e., 18 days), the half-life periods of RC-CAT, RC-poly(HEMA)-CAT, RC-poly(DMAEMA)-CAT, and RC-poly(AA)-CAT were 49, 58, 56, and 60 days, respectively, indicating that the storage stability of immobilized catalase was also significantly improved. Furthermore, the immobilized catalase exhibited substantially higher resistance to temperature variation (tested from 5 to 70 °C) and lower degree of sensitivity to pH value (tested from 4.0 and 10.0) than the free catalase. In particular, according to the kinetic parameters of Vmax and Km, the nanofibrous membranes of RC-poly(HEMA) (i.e., 5102 μmol mg(-1) min(-1) and 44.89 mM) and RC-poly(DMAEMA) (i.e., 4651 μmol mg(-1) min(-1) and 46.98 mM) had the most satisfactory biocompatibility with immobilized catalase. It was therefore concluded that the electrospun RC nanofibrous membranes surface-grafted with 3-dimensional nanolayers of polymer chains/brushes would be

  15. High-performance liquid chromatographic method to evaluate the hydrogen atom transfer during reaction between 1,1-diphenyl-2-picryl-hydrazyl radical and antioxidants

    Energy Technology Data Exchange (ETDEWEB)

    Boudier, Ariane; Tournebize, Juliana [CITHEFOR - EA 3452, Faculte de Pharmacie, Nancy-Universite, 5 Rue Albert Lebrun, BP 80403, 54001 Nancy Cedex (France); Bartosz, Grzegorz [Department of Molecular Biophysics, University of Lodz, Lodz (Poland); El Hani, Safae; Bengueddour, Rachid [Laboratoire de Nutrition et Sante, Biology Department, Faculty of Sciences, Ibn Tofail University, Kenitra (Morocco); Sapin-Minet, Anne [CITHEFOR - EA 3452, Faculte de Pharmacie, Nancy-Universite, 5 Rue Albert Lebrun, BP 80403, 54001 Nancy Cedex (France); Leroy, Pierre, E-mail: pierre.leroy@pharma.uhp-nancy.fr [CITHEFOR - EA 3452, Faculte de Pharmacie, Nancy-Universite, 5 Rue Albert Lebrun, BP 80403, 54001 Nancy Cedex (France)

    2012-01-20

    Highlights: Black-Right-Pointing-Pointer Both 1,1-diphenyl-2-picrylhydrazyl radical and its product measurement by HPLC. Black-Right-Pointing-Pointer Lowest limit of detection by monitoring 1,1-diphenyl-2-picryl-hydrazine. Black-Right-Pointing-Pointer Adsorption problem of the radical on HPLC parts have been pointed out. - Abstract: 1,1-Diphenyl-2-picrylhydrazyl (DPPH{center_dot}) is a stable nitrogen centred radical widely used to evaluate direct radical scavenging properties of various synthetic or natural antioxidants (AOs). The bleaching rate of DPPH{center_dot} absorbance at 515 nm is usually monitored for this purpose. In order to avoid the interference of complex coloured natural products used as antioxidant supplements or cosmetics, HPLC systems have been reported as alternative techniques to spectrophotometry. They also rely upon measurement of DPPH{center_dot} quenching rate and none of them permits to identify and measure 1,1-diphenyl-2-picryl-hydrazine (DPPH-H), the reduced product of DPPH{center_dot} resulting from hydrogen atom transfer (HAT), which is the main mechanism of the reaction between DPPH{center_dot} and AOs. We presently report an HPLC method devoted to the simultaneous measurement of DPPH{center_dot} and DPPH-H. Both were fully separated on a C18 column eluted with acetonitrile-10 mM ammonium citrate buffer pH 6.8 (70:30, v/v) and detected at 330 nm. Adsorption process of DPPH{center_dot} onto materials of the HPLC system was pointed out. Consequently, the linearity range observed for DPPH{center_dot} was restricted, thus a much lower limit of detection was obtained for DPPH-H than for DPPH{center_dot} using standards (0.02 and 14 {mu}M, respectively). The method was applied to three commonly used AOs, i.e. Trolox{sup Registered-Sign }, ascorbic acid and GSH, and compared with spectrophotometry. Further application to complex matrices (cell culture media, vegetal extracts) and nanomaterials demonstrated (i) its usefulness because of

  16. Study of elementary transfer mechanisms during a collision between a swift multi-charged heavy ion and a neutral atom; Etude des mecanismes elementaires de transfert d`energie au cours d`une collision entre un ion lourd rapide multi-charge et un atome neutre

    Energy Technology Data Exchange (ETDEWEB)

    Jardin, P. [Caen Univ., 14 (France)

    1995-12-31

    This work is dedicated to the study of the energy transfer mechanisms which occur during a collision between a swift multicharged heavy ion and a neutral atom. The elementary energy energy transfer mechanisms (scattering, excitation, ionization, capture) and their consequences on the target velocity after the collision (recoil velocity) are recalled in the first chapter. In the case of small projectile diffusion angles, we show that the recoil velocity component, transverse to the incident projectile direction, results principally from the diffusion mechanism, while the longitudinal component is due essentially to the mass transfer and the inelastic energy transfer mechanisms. Since the target recoil velocities are very small, we have built an experimental set-up which reduces the impreciseness on their measurement due to the target thermal spread using, as targets, cooled atoms of a supersonic jet (temperature < 1 K). The association of time of flight and localisation techniques allows us, for each ionised target atom, to determine the three recoil velocity components with a very good accuracy (a few tens of meters per second). In chapter three, we describe the data analysis method. And then we present in the last chapter the results we have obtained for the collision systems Xe{sup 44+}(6.7 MeV/A) + Ar => Xe{sup 44} + Ar{sup q+}+qe{sup -} (q ranging from 1 to 7); Xe{sup 44+} (6.7 MeV/A) + He => Xe{sup 44+} He{sup 1+,2+}+1e{sup -},2e{sup -}. We show that it is possible to interpret the recoil velocity in terms of kinetic energy transferred to the target and to the electrons ejected from the target. (author) 44 refs.

  17. Atomic and molecular sciences

    International Nuclear Information System (INIS)

    Lane, N.F.

    1989-01-01

    The theoretical atomic and molecular physics program at Rice University addresses basic questions about the collision dynamics of electrons, atoms, ions and molecules, emphasizing processes related to possible new energy technologies and other applications. The program focuses on inelastic collision processes that are important in understanding energy and ionization balance in disturbed gases and plasmas. Emphasis is placed on systems and processes where some experimental information is available or where theoretical results may be expected to stimulate new measurements. Examples of current projects include: excitation and charge-transfer processes; orientation and alignment of excited states following collisions; Rydberg atom collisions with atoms and molecules; Penning ionization and ion-pair formation in atom-atom collisions; electron-impact ionization in dense, high-temperature plasmas; electron-molecule collisions; and related topics

  18. PMMA-Etching-Free Transfer of Wafer-scale Chemical Vapor Deposition Two-dimensional Atomic Crystal by a Water Soluble Polyvinyl Alcohol Polymer Method

    Science.gov (United States)

    van Ngoc, Huynh; Qian, Yongteng; Han, Suk Kil; Kang, Dae Joon

    2016-09-01

    We have explored a facile technique to transfer large area 2-Dimensional (2D) materials grown by chemical vapor deposition method onto various substrates by adding a water-soluble Polyvinyl Alcohol (PVA) layer between the polymethyl-methacrylate (PMMA) and the 2D material film. This technique not only allows the effective transfer to an arbitrary target substrate with a high degree of freedom, but also avoids PMMA etching thereby maintaining the high quality of the transferred 2D materials with minimum contamination. We applied this method to transfer various 2D materials grown on different rigid substrates of general interest, such as graphene on copper foil, h-BN on platinum and MoS2 on SiO2/Si. This facile transfer technique has great potential for future research towards the application of 2D materials in high performance optical, mechanical and electronic devices.

  19. Electron transfer reactions

    CERN Document Server

    Cannon, R D

    2013-01-01

    Electron Transfer Reactions deals with the mechanisms of electron transfer reactions between metal ions in solution, as well as the electron exchange between atoms or molecules in either the gaseous or solid state. The book is divided into three parts. Part 1 covers the electron transfer between atoms and molecules in the gas state. Part 2 tackles the reaction paths of oxidation states and binuclear intermediates, as well as the mechanisms of electron transfer. Part 3 discusses the theories and models of the electron transfer process; theories and experiments involving bridged electron transfe

  20. Comparative molecular-orbital and atomic-orbital study of electron transfer and excitation in He++Na(3s) collisions at energies of 0.05 to 20 keV/amu

    International Nuclear Information System (INIS)

    Fritsch, W.; Kimura, M.; Lane, N.F.

    1990-01-01

    Electron transfer and excitation in 0.05- to 20-keV/amu He + +Na(3s) collisions is studied theoretically within the close-coupling method with two-electron molecular- and atomic-orbital expansion basis sets. Results agree with the trend of other information on this system. Remaining discrepancies that are larger than those in similar contemporary studies of one-electron systems are discussed with reference to the convergence of this two-electron study. Results for the integral alignment parameter A 20 are also presented as a guideline for future experimental study

  1. Muonic atoms with vacant electron shells

    International Nuclear Information System (INIS)

    Bacher, R.; Gotta, D.; Simons, L.M.; Missimer, J.; Mukhopadhyay, N.C.

    1985-01-01

    We show that the cascade in muonic atoms with Z<20 ejects sufficient atomic electrons to ionize an isolated muonic atom completely. In gases, the rates with which electrons refill the atomic shell can be accurately deduced from measured and calculated electron transfer cross sections. Thus, we can conclude that completely ionized muonic atoms can be prepared in gases, and that they remain isolated for long enough times at attainable pressures to facilitate studies of fundamental interactions in muonic atoms

  2. The Unimolecular Reactions of CF3CHF2 Studied by Chemical Activation: Assignment of Rate Constants and Threshold Energies to the 1,2-H Atom Transfer, 1,1-HF and 1,2-HF Elimination Reactions, and the Dependence of Threshold Energies on the Number of F-Atom Substituents in the Fluoroethane Molecules.

    Science.gov (United States)

    Smith, Caleb A; Gillespie, Blanton R; Heard, George L; Setser, D W; Holmes, Bert E

    2017-11-22

    The recombination of CF 3 and CHF 2 radicals in a room-temperature bath gas was used to prepare vibrationally excited CF 3 CHF 2 * molecules with 101 kcal mol -1 of vibrational energy. The subsequent 1,2-H atom transfer and 1,1-HF and 1,2-HF elimination reactions were observed as a function of bath gas pressure by following the CHF 3 , CF 3 (F)C: and C 2 F 4 product concentrations by gas chromatography using a mass spectrometer as the detector. The singlet CF 3 (F)C: concentration was measured by trapping the carbene with trans-2-butene. The experimental rate constants are 3.6 × 10 4 , 4.7 × 10 4 , and 1.1 × 10 4 s -1 for the 1,2-H atom transfer and 1,1-HF and 1,2-HF elimination reactions, respectively. These experimental rate constants were matched to statistical RRKM calculated rate constants to assign threshold energies (E 0 ) of 88 ± 2, 88 ± 2, and 87 ± 2 kcal mol -1 to the three reactions. Pentafluoroethane is the only fluoroethane that has a competitive H atom transfer decomposition reaction, and it is the only example with 1,1-HF elimination being more important than 1,2-HF elimination. The trend of increasing threshold energies for both 1,1-HF and 1,2-HF processes with the number of F atoms in the fluoroethane molecule is summarized and investigated with electronic-structure calculations. Examination of the intrinsic reaction coordinate associated with the 1,1-HF elimination reaction found an adduct between CF 3 (F)C: and HF in the exit channel with a dissociation energy of ∼5 kcal mol -1 . Hydrogen-bonded complexes between HF and the H atom migration transition state of CH 3 (F)C: and the F atom migration transition state of CF 3 (F)C: also were found by the calculations. The role that these carbene-HF complexes could play in 1,1-HF elimination reactions is discussed.

  3. Discrete Visible Luminescence of Helium Atoms and Molecules Desorbing from Helium Clusters: The Role of Electronic, Vibrational, and Rotational Energy Transfer

    International Nuclear Information System (INIS)

    von Haeften, K.; von Pietrowski, R.; Moeller, T.; Joppien, M.; Moussavizadeh, L.; de Castro, A.R.

    1997-01-01

    Discrete visible and near-infrared luminescence of a beam of photoexcited helium clusters is reported. The emission lines are attributed to free helium atoms and molecules desorbing from clusters in electronically excited states. Depending on the excitation energy, various atomic and molecular singlet and triplet states are involved in the relaxation process. With increasing cluster size the intensity of molecular transitions becomes dominant. The temperature of ejected molecules could be estimated to T vib ∼2500 K and T rot ∼450 K and is much higher than that of the cluster itself. copyright 1997 The American Physical Society

  4. Charge-transfer cross sections of ground state He+ ions in collisions with He atoms and simple molecules in the energy range below 4.0 keV

    International Nuclear Information System (INIS)

    Kusakabe, Toshio; Kitamuro, Satoshi; Nakai, Yohta; Tawara, Hiroyuki; Sasao, Mamiko

    2012-01-01

    Charge-transfer cross sections of the ground state He + ions in collisions with He atoms and simple molecules (H 2 , D 2 , N 2 , CO and CO 2 ) have been measured in the energy range of 0.20 to 4.0 keV with the initial growth rate method. Since previously published experimental data are scattered in the low energy region, the present observations would provide reasonably reliable cross section data below 4 keV. The charge transfer accompanied by dissociation of product molecular ion can be dominant at low energies for molecular targets. In He + + D 2 collisions, any isotope effect was not observed over the present energy range, compared to H 2 molecule. (author)

  5. Differential charge transfer and continuum electron capture studies for ions in atomic hydrogen. Final report, August 1, 1979-September 31, 1983

    International Nuclear Information System (INIS)

    Sellin, I.A.; Elston, S.B.

    1983-01-01

    A final technical narrative is given of progress and results obtained during the period August 1, 1979 through September 30, 1983 in a project designed to test existing theories of electron capture to continuum states of fully stripped nuclei traversing atomic hydrogen targets. 5 references

  6. Atom optics

    International Nuclear Information System (INIS)

    Balykin, V. I.; Jhe, W.

    1999-01-01

    Atom optics, in analogy to neutron and electron optics, deals with the realization of as a traditional elements, such as lenes, mirrors, beam splitters and atom interferometers, as well as a new 'dissipative' elements such as a slower and a cooler, which have no analogy in an another types of optics. Atom optics made the development of atom interferometer with high sensitivity for measurement of acceleration and rotational possible. The practical interest in atom optics lies in the opportunities to create atom microprobe with atom-size resolution and minimum damage of investigated objects. (Cho, G. S.)

  7. Optimisation of Surface-Initiated Photoiniferter-Mediated Polymerisation under Confinement, and the Formation of Block Copolymers in Mesoporous Films

    Directory of Open Access Journals (Sweden)

    Jessica C. Tom

    2017-10-01

    Full Text Available Nature as the ultimate inspiration can direct, gate, and selectively transport species across channels to fulfil a specific targeted function. Harnessing such precision over local structure and functionality at the nanoscale is expected to lead to indispensable developments in synthetic channels for application in catalysis, filtration and sensing, and in drug delivery. By combining mesoporous materials with localised charge-switchable poly(2-(dimethylaminoethyl methacrylate (PDMAEMA brushes, precisely controlling pore filling and exploring the possibility of incorporating two different responsive polymers, we hope to approach the precision control of natural systems in the absence of an external force. Here, we report a simple one-step approach to prepare a mesoporous silica thin film with ~8 nm pores functionalised with a photoiniferter by combining sol–gel chemistry and evaporation-induced self-assembly (EISA. We show that surface-initiated photoiniferter-mediated polymerisation (SI-PIMP allows the incorporation of a high polymer content up to geometrical pore blocking by the simple application of UV light in the presence of a monomer and solvent, proceeding in a controlled manner in pore sizes below 10 nm, with the potential to tune the material properties through the formation of surface-grafted block copolymers.

  8. Transfer of Sr-90 in the environment to human bone, and radiation dose due to the atomic bomb and weapons testing

    International Nuclear Information System (INIS)

    Kawamura, H.; Shiraishi, K.; Igarashi, Y.; Sakurai, Y.

    1988-01-01

    The major source of artificial radioactivities in Japan has been the atmospheric nuclear weapons testing. Some results obtained for activities of Sr-90 in bone, particulary in Japanese, are mentioned, including trends in levels, distribution in bone, transfer from diet to bone and absorbed doses. Some litterature data on pathways of Sr-90 from environment to man are referred to, that is on contribution of different foods to the ingestion intake and transfer of Sr-90 from soil to crops. Recent topics of radioecological studies on soil-plant relationships are shortly introduced

  9. Exploring possible reaction pathways for the o-atom transfer reactions to unsaturated substrates catalyzed by a [Ni-NO2 ] ↔ [Ni-NO] redox couple using DFT methods.

    Science.gov (United States)

    Tsipis, Athanassios C

    2017-07-15

    The (nitro)(N-methyldithiocarbamato)(trimethylphospane)nickel(II), [Ni(NO 2 )(S 2 CNHMe)(PMe 3 )] complex catalyses efficiently the O-atom transfer reactions to CO and acetylene. Energetically feasible sequence of elementary steps involved in the catalytic cycle of the air oxidation of CO and acetylene are proposed promoted by the Ni(NO 2 )(S 2 CNHMe)(PMe 3 )] ↔ Ni(NO 2 )(S 2 CNHMe)(PMe 3 ) redox couple using DFT methods both in vacuum and dichloromethane solutions. The catalytic air oxidation of HC≡CH involves formation of a five-member metallacycle intermediate, via a [3 + 2] cyclo-addition reaction of HC≡CH to the Ni-N = O moiety of the Ni(NO 2 )(S 2 CNHMe)(PMe 3 )] complex, followed by a β H-atom migration toward the C α carbon atom of the coordinated acetylene and release of the oxidation product (ketene). The geometric and energetic reaction profile for the reversible [Ni( κN1-NO 2 )(S 2 CNHMe)(PMe 3 )] ⇌ [Ni( κO,O2-ONO)(S 2 CNHMe)(PMe 3 )] linkage isomerization has also been modeled by DFT calculations. © 2017 Wiley Periodicals, Inc. © 2017 Wiley Periodicals, Inc.

  10. Carbonyl Activation by Borane Lewis Acid Complexation: Transition States of H2 Splitting at the Activated Carbonyl Carbon Atom in a Lewis Basic Solvent and the Proton-Transfer Dynamics of the Boroalkoxide Intermediate.

    Science.gov (United States)

    Heshmat, Mojgan; Privalov, Timofei

    2017-07-06

    By using transition-state (TS) calculations, we examined how Lewis acid (LA) complexation activates carbonyl compounds in the context of hydrogenation of carbonyl compounds by H 2 in Lewis basic (ethereal) solvents containing borane LAs of the type (C 6 F 5 ) 3 B. According to our calculations, LA complexation does not activate a ketone sufficiently enough for the direct addition of H 2 to the O=C unsaturated bond; but, calculations indicate a possibly facile heterolytic cleavage of H 2 at the activated and thus sufficiently Lewis acidic carbonyl carbon atom with the assistance of the Lewis basic solvent (i.e., 1,4-dioxane or THF). For the solvent-assisted H 2 splitting at the carbonyl carbon atom of (C 6 F 5 ) 3 B adducts with different ketones, a number of TSs are computed and the obtained results are related to insights from experiment. By using the Born-Oppenheimer molecular dynamics with the DFT for electronic structure calculations, the evolution of the (C 6 F 5 ) 3 B-alkoxide ionic intermediate and the proton transfer to the alkoxide oxygen atom were investigated. The results indicate a plausible hydrogenation mechanism with a LA, that is, (C 6 F 5 ) 3 B, as a catalyst, namely, 1) the step of H 2 cleavage that involves a Lewis basic solvent molecule plus the carbonyl carbon atom of thermodynamically stable and experimentally identifiable (C 6 F 5 ) 3 B-ketone adducts in which (C 6 F 5 ) 3 B is the "Lewis acid promoter", 2) the transfer of the solvent-bound proton to the oxygen atom of the (C 6 F 5 ) 3 B-alkoxide intermediate giving the (C 6 F 5 ) 3 B-alcohol adduct, and 3) the S N 2-style displacement of the alcohol by a ketone or a Lewis basic solvent molecule. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Atomic and electronic structure of trilayer graphene/SiC(0001): Evidence of Strong Dependence on Stacking Sequence and charge transfer.

    Science.gov (United States)

    Pierucci, Debora; Brumme, Thomas; Girard, Jean-Christophe; Calandra, Matteo; Silly, Mathieu G; Sirotti, Fausto; Barbier, Antoine; Mauri, Francesco; Ouerghi, Abdelkarim

    2016-09-15

    The transport properties of few-layer graphene are the directly result of a peculiar band structure near the Dirac point. Here, for epitaxial graphene grown on SiC, we determine the effect of charge transfer from the SiC substrate on the local density of states (LDOS) of trilayer graphene using scaning tunneling microscopy/spectroscopy and angle resolved photoemission spectroscopy (ARPES). Different spectra are observed and are attributed to the existence of two stable polytypes of trilayer: Bernal (ABA) and rhomboedreal (ABC) staking. Their electronic properties strongly depend on the charge transfer from the substrate. We show that the LDOS of ABC stacking shows an additional peak located above the Dirac point in comparison with the LDOS of ABA stacking. The observed LDOS features, reflecting the underlying symmetry of the two polytypes, were reproduced by explicit calculations within density functional theory (DFT) including the charge transfer from the substrate. These findings demonstrate the pronounced effect of stacking order and charge transfer on the electronic structure of trilayer or few layer graphene. Our approach represents a significant step toward understand the electronic properties of graphene layer under electrical field.

  12. Atom-by-atom assembly

    International Nuclear Information System (INIS)

    Hla, Saw Wai

    2014-01-01

    Atomic manipulation using a scanning tunneling microscope (STM) tip enables the construction of quantum structures on an atom-by-atom basis, as well as the investigation of the electronic and dynamical properties of individual atoms on a one-atom-at-a-time basis. An STM is not only an instrument that is used to ‘see’ individual atoms by means of imaging, but is also a tool that is used to ‘touch’ and ‘take’ the atoms, or to ‘hear’ their movements. Therefore, the STM can be considered as the ‘eyes’, ‘hands’ and ‘ears’ of the scientists, connecting our macroscopic world to the exciting atomic world. In this article, various STM atom manipulation schemes and their example applications are described. The future directions of atomic level assembly on surfaces using scanning probe tips are also discussed. (review article)

  13. Experimental atomic physics

    International Nuclear Information System (INIS)

    Sellin, I.A.; Elston, S.B.; Forester, J.P.; Liao, K.H.; Pegg, D.J.; Peterson, R.S.; Thoe, R.S.; Hayden, H.C.; Griffin, P.M.

    1976-01-01

    The atomic structure and collision phenomena of highly stripped ions in the range Z = 6 to 35 were studied. Charge-transfer and multiple-electron-loss cross sections were determined. Absolute x-ray-production cross sections for incident heavy ions were measured. 10 figures, 1 table

  14. Electron transfer in keV Li+-Na(3s, 3p) collisions: I. Atomic basis coupled-channel calculations

    International Nuclear Information System (INIS)

    Nielsen, S.E.; Dubois, A.

    1995-01-01

    Integral cross sections for electron capture from the ground state Na(3s) and excited states Na(3p) to Li(nlm), n = 2, 3, are calculated by the semiclassical impact-parameter method, using a two-centre atomic basis expansion. In the impact energy range 1-50 keV, results are analysed with particular emphasis on the alignment and orientation of initial and final p-states. At intermediate velocities opposite initial alignment effects are found for capture to n = 2 and n = 3 states, respectively. Orientation effects in state-to-state capture cross sections are predicted from oriented and tilted aligned initial states. (Author)

  15. Atomic and electronic structure of trilayer graphene/SiC(0001): Evidence of Strong Dependence on Stacking Sequence and charge transfer

    OpenAIRE

    Pierucci, Debora; Brumme, Thomas; Girard, Jean-Christophe; Calandra, Matteo; Silly, Mathieu G.; Sirotti, Fausto; Barbier, Antoine; Mauri, Francesco; Ouerghi, Abdelkarim

    2016-01-01

    International audience; The transport properties of few-layer graphene are the directly result of a peculiar band structure near the Dirac point. Here, for epitaxial graphene grown on SiC, we determine the effect of charge transfer from the SiC substrate on the local density of states (LDOS) of trilayer graphene using scaning tunneling microscopy/spectroscopy and angle resolved photoemission spectroscopy (ARPES). Different spectra are observed and are attributed to the existence of two stable...

  16. High-resolution spectroscopy of deeply-bound pionic atoms in heavy nuclei by pion-transfer reactions of inverse kinematics using the GSI cooler ring ESR

    International Nuclear Information System (INIS)

    Yamazaki, Toshimitsu.

    1991-02-01

    Many studies published in the past are reviewed first in relation to high-resolution spectroscopy of deeply-bound pionic atoms in heavy nuclei. The report then describes a procedure for applying the method of inverse kinematics to the case of (d, 3 He) reactions. The (d, 3 He) reaction in inverse kinematics is feasible from practical viewpoints. Thus a discussion is made of the inverse kinematics in which a heavy-ion beam ( 208 Pb for instance) with a projectile kinetic energy hits a deuteron target and ejected recoil 3 He nuclei are measured in the forward direction. The recoil momentum is calculated as a function of the Q value. Analysis shows that the recoil spectroscopy with inverse kinematics can be applied to the case of (d, 3 He) reaction, which will yield a very high mass resolution. The experimental setup for use in the first stage is then outlined, and a simple detector configuration free of magnetic field is discussed. These investigations demonstrate that the (d, 3 He) reaction in inverse kinematics provides a promising tool for obtaining high-resolution spectra of deeply-bound pionic atoms. (N.K.)

  17. Kinetic evidence for the formation of discrete 1,4-dehydrobenzene intermediates. Trapping by inter- and intramolecular hydrogen atom transfer and observation of high-temperature CIDNP

    Energy Technology Data Exchange (ETDEWEB)

    Lockhart, Thomas P. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States); California Inst. of Technology (CalTech), Pasadena, CA (United States); Comita, Paul B. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States); California Inst. of Technology (CalTech), Pasadena, CA (United States); Bergman, Robert G. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States); California Inst. of Technology (CalTech), Pasadena, CA (United States)

    1981-07-01

    Upon heating, alkyl-substituted cis-1,2-diethynyl olefins undergo cyclization to yield reactive 1,4-dehydrobenzenes; the products isolated may be derived from either unimolecular or bimolecular reactions of the intermediate. (Z)-4,5-Diethynyl-4-octene (4) undergoes rearrangement to yield 2,3-di-n-propyl-1,4-dehydrobenzene (17). Solution pyrolysis of 4 in inert aromatic solvents produces three unimolecular products, (Z)-dodeca-4,8-diyn-6-ene (7), benzocyclooctene (9), and o-allyl-n-propylbenzene (10), in high yield. When 1,4-cyclohexadiene is added to the pyrolysis solution as a trapping agent, high yields of the reduced product o-di-n-propylbenzene (12) are obtained. The kinetics of solution pyrolysis of 4 in the presence and absence of trapping agent establish that 2,3-di-n-propyl-1,4-dehydrobenzene is a discrete intermediate on the pathway leading to products. When the reaction was run in the heated probe of an NMR spectrometer, CIDNP was observed in 10. This observation, along with kinetic and chemical trapping evidence, indicates the presence of two additional intermediates, formed from 17 by sequential intramolecular [1,5] hydrogen transfer, on the pathway to products. The observation of CIDNP, coupled with the reactivity exhibited by 17 and the other two intermediates, implicate a biradical description of these molecules. Biradical 17 has been estimated to have a lifetime of about 10-9 s at 200°C and to lie in a well of about 5 kcal/mol with respect to the lowest energy unimolecular pathway ([1,5] hydrogen transfer). Ring opening (expected to be the lowest energy process for 1,4-dehydrobenzenes in which intramolecular hydrogen transfer is unlikely) to the isomeric diethynyl olefin 7 appears to have an activation enthalpy of about 10 kcal/moL Upon thermal reaction in the gas phase (400°C) or in solution in inert solvents (Z)-hexa-2,3-diethyl-1,5-diyn-3-ene (5) rearranges in good yield to the isomeric diethynyl olefin (Z)-deca-3,7-diyn-5-ene (8

  18. Solution of the comoving-frame equation of transfer in spherically symmetric flows. IV. Frequency-dependent source functions for scattering by atoms and electrons

    International Nuclear Information System (INIS)

    Mihalas, D.; Kunasz, P.B.; Hummer, D.G.

    1976-01-01

    A numerical method is presented of solving the radiative transfer equation in the comoving frame of a spherically symmetric expanding atmosphere in which both the line and the electron-scattering source function can depend on frequency (i.e., when there is partial frequency redistribution in the scattering process). This method is used to assess the adequacy of various assumptions regarding frequency redistribution in the comoving frame and to discuss the effects of electron scattering more accurately than previously possible. The methods developed here can be used in realistic model atmospheres to account for the (major) effects of electron scattering upon emergent flux profiles

  19. A direct investigation of photocharge transfer across monomolecular layer between C{sub 60} and CdS quantum dots by photoassisted conductive atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Xiaohong; Liu, He; Zhang, Xingtang; Cheng, Gang; Wang, Shujie; Du, Zuliang, E-mail: zld@henu.edu.cn [Key Laboratory for Special Functional Materials, Collaborative Innovation Center of Nano Functional Materials and Applications, Henan University, Kaifeng, 475004, PR. China (China)

    2016-04-15

    The composite assembly of C{sub 60} and CdS Quantum Dots (QDs) on ITO substrate was prepared by Langmuir-Blodgett (LB) technique using arachic acid (AA), stearic acid (SA) and octadecanyl amine (OA) as additives. Photoassisted conductive atomic force microscopy was used to make point contact current-voltage (I-V) measurements on both the CdS QDs and the composite assembly of C{sub 60}/CdS. The result make it clear that the CdS, C{sub 60}/CdS assemblies deposited on ITO substrate showed linear characteristics and the current increased largely under illumination comparing with that in the dark. The coherent, nonresonant tunneling mechanism was used to explain the current occurrence. It is considered that the photoinduced carriers CdS QDs tunneled through alkyl chains increased the current rapidly.

  20. A direct investigation of photocharge transfer across monomolecular layer between C60 and CdS quantum dots by photoassisted conductive atomic force microscopy

    Directory of Open Access Journals (Sweden)

    Xiaohong Jiang

    2016-04-01

    Full Text Available The composite assembly of C60 and CdS Quantum Dots (QDs on ITO substrate was prepared by Langmuir-Blodgett (LB technique using arachic acid (AA, stearic acid (SA and octadecanyl amine (OA as additives. Photoassisted conductive atomic force microscopy was used to make point contact current-voltage (I-V measurements on both the CdS QDs and the composite assembly of C60/CdS. The result make it clear that the CdS, C60/CdS assemblies deposited on ITO substrate showed linear characteristics and the current increased largely under illumination comparing with that in the dark. The coherent, nonresonant tunneling mechanism was used to explain the current occurrence. It is considered that the photoinduced carriers CdS QDs tunneled through alkyl chains increased the current rapidly.

  1. Redox-neutral rhodium-catalyzed C-H functionalization of arylamine N-oxides with diazo compounds: primary C(sp(3))-H/C(sp(2))-H activation and oxygen-atom transfer.

    Science.gov (United States)

    Zhou, Bing; Chen, Zhaoqiang; Yang, Yaxi; Ai, Wen; Tang, Huanyu; Wu, Yunxiang; Zhu, Weiliang; Li, Yuanchao

    2015-10-05

    An unprecedented rhodium(III)-catalyzed regioselective redox-neutral annulation reaction of 1-naphthylamine N-oxides with diazo compounds was developed to afford various biologically important 1H-benzo[g]indolines. This coupling reaction proceeds under mild reaction conditions and does not require external oxidants. The only by-products are dinitrogen and water. More significantly, this reaction represents the first example of dual functiaonalization of unactivated a primary C(sp(3) )H bond and C(sp(2) )H bond with diazocarbonyl compounds. DFT calculations revealed that an intermediate iminium is most likely involved in the catalytic cycle. Moreover, a rhodium(III)-catalyzed coupling of readily available tertiary aniline N-oxides with α-diazomalonates was also developed under external oxidant-free conditions to access various aminomandelic acid derivatives by an O-atom-transfer reaction. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Atomic polarizabilities

    International Nuclear Information System (INIS)

    Safronova, M. S.; Mitroy, J.; Clark, Charles W.; Kozlov, M. G.

    2015-01-01

    The atomic dipole polarizability governs the first-order response of an atom to an applied electric field. Atomic polarization phenomena impinge upon a number of areas and processes in physics and have been the subject of considerable interest and heightened importance in recent years. In this paper, we will summarize some of the recent applications of atomic polarizability studies. A summary of results for polarizabilities of noble gases, monovalent, and divalent atoms is given. The development of the CI+all-order method that combines configuration interaction and linearized coupled-cluster approaches is discussed

  3. Atomic polarizabilities

    Energy Technology Data Exchange (ETDEWEB)

    Safronova, M. S. [Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States); Mitroy, J. [School of Engineering, Charles Darwin University, Darwin NT 0909 (Australia); Clark, Charles W. [Joint Quantum Institute, National Institute of Standards and Technology and the University of Maryland, Gaithersburg, Maryland 20899-8410 (United States); Kozlov, M. G. [Petersburg Nuclear Physics Institute, Gatchina 188300 (Russian Federation)

    2015-01-22

    The atomic dipole polarizability governs the first-order response of an atom to an applied electric field. Atomic polarization phenomena impinge upon a number of areas and processes in physics and have been the subject of considerable interest and heightened importance in recent years. In this paper, we will summarize some of the recent applications of atomic polarizability studies. A summary of results for polarizabilities of noble gases, monovalent, and divalent atoms is given. The development of the CI+all-order method that combines configuration interaction and linearized coupled-cluster approaches is discussed.

  4. Atomic physics

    CERN Document Server

    Foot, Christopher J

    2007-01-01

    This text will thoroughly update the existing literature on atomic physics. Intended to accompany an advanced undergraduate course in atomic physics, the book will lead the students up to the latest advances and the applications to Bose-Einstein Condensation of atoms, matter-wave inter-ferometry and quantum computing with trapped ions. The elementary atomic physics covered in the early chapters should be accessible to undergraduates when they are first introduced to the subject. To complement. the usual quantum mechanical treatment of atomic structure the book strongly emphasizes the experimen

  5. Tuning the Solubility of Copper Complex in Atom Transfer Radical Self-Condensing Vinyl Polymerizations to Control Polymer Topology via One-Pot to the Synthesis of Hyperbranched Core Star Polymers

    Directory of Open Access Journals (Sweden)

    Zong-Cheng Chen

    2014-09-01

    Full Text Available In this paper, we propose a simple one-pot methodology for proceeding from atom transfer reaction-induced conventional free radical polymerization (AT-FRP to atom transfer self-condensing vinyl polymerization (AT-SCVP through manipulation of the catalyst phase homogeneity (i.e., CuBr/2,2'-bipyridine (CuBr/Bpy in a mixture of styrene (St, 4-vinyl benzyl chloride (VBC, and ethyl 2-bromoisobutyrate. Tests of the solubilities of CuBr/Bpy and CuBr2/Bpy under various conditions revealed that both temperature and solvent polarity were factors affecting the solubility of these copper complexes. Accordingly, we obtained different polymer topologies when performing AT-SCVP in different single solvents. We investigated two different strategies to control the polymer topology in one-pot: varying temperature and varying solvent polarity. In both cases, different fractions of branching revealed the efficacy of varying the polymer topology. To diversify the functionality of the peripheral space, we performed chain extensions of the resulting hyperbranched poly(St-co-VBC macroinitiator (name as: hbPSt MI with either St or tBA (tert-butyl acrylate. The resulting hyperbranched core star polymer had high molecular weights (hbPSt-g-PSt: Mn = 25,000, Đ = 1.77; hbPSt-g-PtBA: Mn = 27,000, Đ = 1.98; hydrolysis of the tert-butyl groups of the later provided a hyperbranched core star polymer featuring hydrophilic poly(acrylic acid segments.

  6. Atomic physics

    International Nuclear Information System (INIS)

    Armbruster, P.; Beyer, H.; Bosch, F.; Dohmann, H.D.; Kozhuharov, C.; Liesen, D.; Mann, R.; Mokler, P.H.

    1984-01-01

    The heavy ion accelerator UNILAC is well suited to experiments in the field of atomic physics because, with the aid of high-energy heavy ions atoms can be produced in exotic states - that is, heavy atoms with only a few electrons. Also, in close collisions of heavy ions (atomic number Z 1 ) and heavy target atoms (Z 2 ) short-lived quasi-atomic 'superheavy' systems will be formed - huge 'atoms', where the inner electrons are bound in the field of the combined charge Z 1 + Z 2 , which exceeds by far the charge of the known elements (Z <= 109). Those exotic or transient superheavy atoms delivered from the heavy ion accelerator make it possible to study for the first time in a terrestrial laboratory exotic, but fundamental, processes, which occur only inside stars. Some of the basic research carried out with the UNILAC is discussed. This includes investigation of highly charged heavy atoms with the beam-foil method, the spectroscopy of highly charged slow-recoil ions, atomic collision studies with highly ionised, decelerated ions and investigations of super-heavy quasi-atoms. (U.K.)

  7. Ultracold atoms on atom chips

    DEFF Research Database (Denmark)

    Krüger, Peter; Hofferberth, S.; Haller, E.

    2005-01-01

    Miniaturized potentials near the surface of atom chips can be used as flexible and versatile tools for the manipulation of ultracold atoms on a microscale. The full scope of possibilities is only accessible if atom-surface distances can be reduced to microns. We discuss experiments in this regime...

  8. Facile surface glycosylation of PVDF microporous membrane via direct surface-initiated AGET ATRP and improvement of antifouling property and biocompatibility

    International Nuclear Information System (INIS)

    Yuan Jing; Meng Jianqiang; Kang Yinlin; Du Qiyun; Zhang Yufeng

    2012-01-01

    This paper describes a facile and novel approach for the surface glycosylation of poly(vinylidene difluoride) (PVDF) microporous membrane. A glycopolymer poly(D-gluconamidoethyl methacrylate) (PGAMA) was tethered onto the membrane surface via activators generated by electron transfer atom transfer radical polymerization (AGET ATRP) directly initiated from the PVDF surface. Chemical changes of membrane surface were characterized by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). It was revealed that PGAMA was successfully grafted onto the membrane surface and its grafting density can be modulated in a wide range up to 2.4 μmol/cm 2 . The effects of glycosylation on membrane morphology, flux and surface hydrophilicity were investigated. Field emission scanning electron microscopy (FESEM) results indicated shrinkage of the surface pore diameters and the growth of the glycopolymer layer on the membrane surface. The static water contact angle (WCA) of the membrane surface decreased from 110° to 30.4° with the increase of grafting density, indicating that the PGAMA grafts dramatically improved the surface hydrophilicity. The protein adsorption and platelets adhesion experiments indicated that the grafted PGAMA could effectively improve the membrane antifouling property and biocompatibility.

  9. Ubiquitous atom

    International Nuclear Information System (INIS)

    Spruch, G.M.; Spruch, L.

    1974-01-01

    The fundamentals of modern physics, including the basic physics and chemistry of the atom, elementary particles, cosmology, periodicity, and recent advances, are surveyed. The biology and chemistry of the life process is discussed to provide a background for considering the effects of atomic particles on living things. The uses of atomic power in space travel, merchant shipping, food preservation, desalination, and nuclear clocks are explored. (Pollut. Abstr.)

  10. Fast multilevel radiative transfer

    Science.gov (United States)

    Paletou, Frédéric; Léger, Ludovick

    2007-01-01

    The vast majority of recent advances in the field of numerical radiative transfer relies on approximate operator methods better known in astrophysics as Accelerated Lambda-Iteration (ALI). A superior class of iterative schemes, in term of rates of convergence, such as Gauss-Seidel and Successive Overrelaxation methods were therefore quite naturally introduced in the field of radiative transfer by Trujillo Bueno & Fabiani Bendicho (1995); it was thoroughly described for the non-LTE two-level atom case. We describe hereafter in details how such methods can be generalized when dealing with non-LTE unpolarised radiation transfer with multilevel atomic models, in monodimensional geometry.

  11. Atomic physics

    International Nuclear Information System (INIS)

    Anon.

    1976-01-01

    Research activities in atomic physics at Lawrence Berkeley Laboratory during 1976 are described. Topics covered include: experiments on stored ions; test for parity violation in neutral weak currents; energy conservation and astrophysics; atomic absorption spectroscopy, atomic and molecular detectors; theoretical studies of quantum electrodynamics and high-z ions; atomic beam magnetic resonance; radiative decay from the 2 3 Po, 2 levels of helium-like argon; quenching of the metastable 2S/sub 1/2/ state of hydrogen-like argon in an external electric field; and lifetime of the 2 3 Po level of helium-like krypton

  12. Atomic clocks for geodesy

    Science.gov (United States)

    Mehlstäubler, Tanja E.; Grosche, Gesine; Lisdat, Christian; Schmidt, Piet O.; Denker, Heiner

    2018-06-01

    We review experimental progress on optical atomic clocks and frequency transfer, and consider the prospects of using these technologies for geodetic measurements. Today, optical atomic frequency standards have reached relative frequency inaccuracies below 10‑17, opening new fields of fundamental and applied research. The dependence of atomic frequencies on the gravitational potential makes atomic clocks ideal candidates for the search for deviations in the predictions of Einstein’s general relativity, tests of modern unifying theories and the development of new gravity field sensors. In this review, we introduce the concepts of optical atomic clocks and present the status of international clock development and comparison. Besides further improvement in stability and accuracy of today’s best clocks, a large effort is put into increasing the reliability and technological readiness for applications outside of specialized laboratories with compact, portable devices. With relative frequency uncertainties of 10‑18, comparisons of optical frequency standards are foreseen to contribute together with satellite and terrestrial data to the precise determination of fundamental height reference systems in geodesy with a resolution at the cm-level. The long-term stability of atomic standards will deliver excellent long-term height references for geodetic measurements and for the modelling and understanding of our Earth.

  13. Entanglement transfer between bipartite systems

    International Nuclear Information System (INIS)

    Bougouffa, Smail; Ficek, Zbigniew

    2012-01-01

    The problem of a controlled transfer of an entanglement initially encoded into two two-level atoms that are successively sent through two single-mode cavities is investigated. The atoms and the cavity modes form a four-qubit system and we demonstrate the conditions under which the initial entanglement encoded into the atoms can be completely transferred to other pairs of qubits. We find that in the case of non-zero detuning between the atomic transition frequencies and the cavity mode frequencies, no complete transfer of the initial entanglement is possible to any of the other pairs of qubits. In the case of exact resonance and equal coupling strengths of the atoms to the cavity modes, an initial maximally entangled state of the atoms can be completely transferred to the cavity modes. Complete transfer of the entanglement is restricted to the cavity modes, with transfer to the other pairs being limited to 50%. We find that complete transfer of an initial entanglement to other pairs of qubits may take place if the initial state is not the maximally entangled state and the atoms couple to the cavity modes with unequal strengths. Depending on the ratio between the coupling strengths, optimal entanglement can be created between the atoms and one of the cavity modes.

  14. Atomic physics

    CERN Document Server

    Born, Max

    1969-01-01

    The Nobel Laureate's brilliant exposition of the kinetic theory of gases, elementary particles, the nuclear atom, wave-corpuscles, atomic structure and spectral lines, electron spin and Pauli's principle, quantum statistics, molecular structure and nuclear physics. Over 40 appendices, a bibliography, numerous figures and graphs.

  15. Early Atomism

    Indian Academy of Sciences (India)

    https://www.ias.ac.in/article/fulltext/reso/015/10/0905-0925. Keywords. Atomic theory; Avogadro's hypothesis; atomic weights; periodic table; valence; molecular weights; molecular formula; isomerism. Author Affiliations. S Ramasesha1. Solid State and Structural Chemistry Unit, Indian Institute of Science, Bangalore 560 012, ...

  16. Atom spectroscopy

    International Nuclear Information System (INIS)

    Kodling, K.

    1981-01-01

    Experiments on atom photoabsorption spectroscopy using synchrotron radiation in the 10-1000 eV range are reviewed. Properties of the necessary synchrotron radiation and the experiment on absorption spectroscopy are briefly described. Comparison with other spectroscopy methods is conducted. Some data on measuring photoabsorption, photoelectron emission and atom mass spectra are presented [ru

  17. Exotic atoms

    International Nuclear Information System (INIS)

    Horvath, D.; Lambrecht, R.M.

    1984-01-01

    This bibliography on exotic atoms covers the years 1939 till 1982. The annual entries are headed by an introduction describing the state of affairs of the branch of science and listing the main applications in quantum electrodynamics, particle physics, nuclear physics, atomic physics, chemical physics and biological sciences. The bibliography includes an author index and a subject index. (Auth.)

  18. Surface-initiated polymerization of 2-hydroxyethyl methacrylate from heterotelechelic oligoperoxide-coated .gamma.-Fe2O3 nanoparticles and their engulfment by mammalian cells

    Czech Academy of Sciences Publication Activity Database

    Horák, Daniel; Shagotova, Tetiana; Mitina, N.; Trchová, Miroslava; Boiko, N.; Babič, Michal; Stoika, R.; Kovářová, Jana; Hevus, O.; Beneš, Milan J.; Klyuchivska, O.; Holler, Petr; Zaichenko, A.

    2011-01-01

    Roč. 23, č. 10 (2011), s. 2637-2649 ISSN 0897-4756 R&D Projects: GA ČR GA203/09/1242; GA ČR GAP503/10/0664; GA AV ČR(CZ) KAN401220801 Institutional research plan: CEZ:AV0Z40500505 Keywords : 2-hydroxyethyl methacrylate * oligoperoxide * surface-initiated polymerization Subject RIV: CD - Macromolecular Chemistry Impact factor: 7.286, year: 2011

  19. The valuation key day in legal expropriation according to the Atomic Energy Act. On the transferability of the legal compensation fundamentals of the so called progression legislation on the 13th AtG amendment; Der Bewertungsstichtag bei der atomrechtlichen Legalenteignung. Zur Uebertragbarkeit der entschaedigungsrechtlichen Grundsaetze der sogenannten 'Steigerungsrechtsprechung' auf die 13. AtG-Novelle

    Energy Technology Data Exchange (ETDEWEB)

    Cornils, Matthias

    2015-07-01

    Under the - constitutionally based - regime ruling compensation for expropriated property notably the valuation key day is of crucial importance for the level of compensation. The study examines the therefor acknowledged principles and criteria, their constitutional foundation, their applicability on expropriation measures directly performed by an Act of Parliament, finally their transferability to the 13th amendment to the Atomic Energy Act.

  20. Uranium Adsorbent Fibers Prepared by Atom-Transfer Radical Polymerization (ATRP) from Poly(vinyl chloride)- co -chlorinated Poly(vinyl chloride) (PVC- co -CPVC) Fiber

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Suree; Yue, Yanfeng; Kuo, Li-Jung; Mehio, Nada; Li, Meijun; Gill, Gary; Tsouris, Costas; Mayes, Richard T.; Saito, Tomonori; Dai, Sheng

    2016-04-20

    The need to secure future supplies of energy attracts researchers in several countries to a vast resource of nuclear energy fuel: uranium in seawater (estimated at 4.5 billion tons in seawater). In this study, we developed effective adsorbent fibers for the recovery of uranium from seawater via atom-transfer radical polymerization (ATRP) from a poly- (vinyl chloride)-co-chlorinated poly(vinyl chloride) (PVC-co-CPVC) fiber. ATRP was employed in the surface graft polymerization of acrylonitrile (AN) and tert-butyl acrylate (tBA), precursors for uranium-interacting functional groups, from PVC-co-CPVC fiber. The [tBA]/[AN] was systematically varied to identify the optimal ratio between hydrophilic groups (from tBA) and uranyl-binding ligands (from AN). The best performing adsorbent fiber, the one with the optimal [tBA]/[AN] ratio and a high degree of grafting (1390%), demonstrated uranium adsorption capacities that are significantly greater than those of the Japan Atomic Energy Agency (JAEA) reference fiber in natural seawater tests (2.42-3.24 g/kg in 42 days of seawater exposure and 5.22 g/kg in 49 days of seawater exposure, versus 1.66 g/kg in 42 days of seawater exposure and 1.71 g/kg in 49 days of seawater exposure for JAEA). Adsorption of other metal ions from seawater and their corresponding kinetics were also studied. The grafting of alternative monomers for the recovery of uranium from seawater is now under development by this versatile technique of ATRP.

  1. Superradiators created atom by atom

    Science.gov (United States)

    Meschede, Dieter

    2018-02-01

    High radiation rates are usually associated with macroscopic lasers. Laser radiation is “coherent”—its amplitude and phase are well-defined—but its generation requires energy inputs to overcome loss. Excited atoms spontaneously emit in a random and incoherent fashion, and for N such atoms, the emission rate simply increases as N. However, if these atoms are in close proximity and coherently coupled by a radiation field, this microscopic ensemble acts as a single emitter whose emission rate increases as N2 and becomes “superradiant,” to use Dicke's terminology (1). On page 662 of this issue, Kim et al. (2) show the buildup of coherent light fields through collective emission from atomic radiators injected one by one into a resonator field. There is only one atom ever in the cavity, but the emission is still collective and superradiant. These results suggest another route toward thresholdless lasing.

  2. Controlled/living surface-initiated ATRP of antifouling polymer brushes from gold in PBS and blood sera as a model study for polymer modifications in complex biological media

    Czech Academy of Sciences Publication Activity Database

    Rodriguez-Emmenegger, Cesar; Hasan, E.; Pop-Georgievski, Ognen; Houska, Milan; Brynda, Eduard; Bologna Alles, A.

    2012-01-01

    Roč. 12, č. 4 (2012), s. 525-532 ISSN 1616-5187 R&D Projects: GA AV ČR KAN200670701; GA ČR GAP503/10/0664 Institutional research plan: CEZ:AV0Z40500505 Keywords : antifouling surfaces * atom-transfer radical polymerization (ATRP) * biocompatibility Subject RIV: EE - Microbiology, Virology Impact factor: 3.742, year: 2012

  3. Atomic interferometry

    International Nuclear Information System (INIS)

    Baudon, J.; Robert, J.

    2004-01-01

    Since the theoretical works of L. De Broglie (1924) and the famous experiment of Davisson and Germer (1927), we know that a wave is linked with any particle of mass m by the relation λ = h/(mv), where λ is the wavelength, v the particle velocity and h is the Planck constant. The basic principle of the interferometry of any material particle, atom, molecule or aggregate is simple: using a simple incident wave, several mutually consistent waves (with well-defined relative phases) are generated and controllable phase-shifts are introduced between them in order to generate a wave which is the sum of the previous waves. An interference figure is obtained which consists in a succession of dark and bright fringes. The atomic interferometry is based on the same principle but involves different techniques, different wave equations, but also different beams, sources and correlations which are described in this book. Because of the small possible wavelengths and the wide range of possible atomic interactions, atomic interferometers can be used in many domains from the sub-micron lithography to the construction of sensors like: inertial sensors, gravity-meters, accelerometers, gyro-meters etc. The first chapter is a preliminary study of the space and time diffraction of atoms. The next chapters is devoted to the description of slit, light separation and polarization interferometers, and the last chapter treats of the properties of Bose-Einstein condensates which are interesting in atomic interferometry. (J.S.)

  4. Quantification of ion or atom transfer phenomena in materials implanted by nuclear methods; Quantification de phenomenes de transferts ioniques ou atomiques dans des materiaux implantes par la mise en oeuvre de methodes nucleaires

    Energy Technology Data Exchange (ETDEWEB)

    Oudadesse, Hassane [Clermont-Ferrand-2 Univ., 63 - Aubiere (France)

    1998-05-18

    Knowledge of transfer of the constituents of a system from regions of higher to lower concentration is of interest for implanted bio-materials. It allows determining the rate at which this material is integrated in a living material. To evaluate the ossification kinetics and to study the bio-functionality in corals of Ca and Sr, irradiations with a 10{sup 13} n.cm{sup -2}.s{sup -1} was performed, followed by the examination of changes in the localization of these elements. By using PIXE analysis method the distribution of Ca, P, Sr, Zn and Fe in the implant, bone and bone-implant interfaces were determined. Thus, it was shown that resorption of coral in sheep is achieved in 5 months after implantation and is identical to the cortical tissues 4 months after implantation in animals as for instance in hares. We have analyzed the tissues from around the prostheses extracted from patients. The samples were calcined and reduced to powder weighting some milligrams. We have adopted for this study the PIXE analysis method. The samples were irradiated by a proton beam of 3 MeV and about 400 {mu}m diameter. The results show the presence of the elements Ti, Fe, Cr, Ni or Zn according to the type of the implanted prosthesis. This dispersal of the metallic ions and atoms contaminate the tissues. The transfer factors translate the exchanges between bone and the implanted material. The solvatation phenomenon and the electric charge equilibrium explain the transfer order of cations Mg{sup 2+}, Ca{sup 2+} and Sr{sup 2+} and of the anion PO{sub 4}{sup 3-}. We have also determined these factors for the elements Ti, Cr and Ni. An original technique to study the bone bio-functionality was used. Use of phosphate derivatives labelled by {sup 99m}Tc allows obtaining information about the fixation of radioactive tracer. It was found that only after the eighth month at the implantation the neo-formed bone fixes the MDP (methyl diphosphate) labelled by {sup 99m}Tc in a similar way as in the

  5. The Third Dimension of a More O'Ferrall-Jencks Diagram for Hydrogen Atom Transfer in the Isoelectronic Hydrogen Exchange Reactions of (PhX)(2)H(•) with X = O, NH, and CH(2).

    Science.gov (United States)

    Cembran, Alessandro; Provorse, Makenzie R; Wang, Changwei; Wu, Wei; Gao, Jiali

    2012-11-13

    A critical element in theoretical characterization of the mechanism of proton-coupled electron transfer (PCET) reactions, including hydrogen atom transfer (HAT), is the formulation of the electron and proton localized diabatic states, based on which a More O'Ferrall-Jencks diagram can be represented to determine the step-wise and concerted nature of the reaction. Although the More O'Ferrall-Jencks diabatic states have often been used empirically to develop theoretical models for PCET reactions, the potential energy surfaces for these states have never been determined directly based on first principles calculations using electronic structure theory. The difficulty is due to a lack of practical method to constrain electron and proton localized diabatic states in wave function or density functional theory calculations. Employing a multistate density functional theory (MSDFT), in which the electron and proton localized diabatic configurations are constructed through block-localization of Kohn-Sham orbitals, we show that distinction between concerted proton-electron transfer (CPET) and HAT, which are not distinguishable experimentally from phenomenological kinetic data, can be made by examining the third dimension of a More O'Ferrall-Jencks diagram that includes both the ground and excited state potential surfaces. In addition, we formulate a pair of effective two-state valence bond models to represent the CPET and HAT mechanisms. We found that the lower energy of the CPET and HAT effective diabatic states at the intersection point can be used as an energetic criterion to distinguish the two mechanisms. In the isoelectronic series of hydrogen exchange reaction in (PhX)(2)H(•), where X = O, NH, and CH(2), there is a continuous transition from a CPET mechanism for the phenoxy radical-phenol pair to a HAT process for benzyl radical and toluene, while the reaction between PhNH(2) and PhNH(•) has a mechanism intermediate of CPET and HAT. The electronically nonadiabatic

  6. Quenching reactions of electronically excited atoms

    International Nuclear Information System (INIS)

    Setser, D.W.

    2001-01-01

    The two-body, thermal quenching reactions of electronically excited atoms are reviewed using excited states of Ar, Kr, and Xe atoms as examples. State-specific interstate relaxation and excitation-transfer reactions with atomic colliders are discussed first. These results then are used to discuss quenching reactions of excited-state atoms with diatomic and polyatomic molecules, the latter have large cross sections, and the reactions can proceed by excitation transfer and by reactive quenching. Excited states of molecules are not considered; however, a table of quenching rate constants is given for six excited-state molecules in an appendix

  7. Atomic politics

    International Nuclear Information System (INIS)

    Skogmar, G.

    1979-01-01

    The authors basic point is that the military and civil sides of atomic energy cannot be separated. The general aim of the book is to analyze both the military and civil branches, and the interdependence between them, of American foreign policy in the atomic field. Atomic policy is seen as one of the most important imstruments of foreign policy which, in turn, is seen against the background of American imperialism in general. Firstly, the book investigates the most important means by which the United States has controlled the development in the nuclear field in other countries. These means include influencing the conditions of access to nuclear resources of various kinds, influencing the flow of technical-economic information and influencing international organizations and treaties bearing on atomic energy. The time period treated is 1945-1973. 1973 is chosen as the end-year of the study mainly because of the new conditions in the whole energy field initiated by the oil crisis in that year. The sources of the empirical work are mainly hearings before the Joint Committee on Atomic Energy of the U.S. Congress and legal material of various kinds. Secondly, the goals of the American policy are analyzed. The goals identified are armament effect, non-proliferation (horizontal), sales, and energy dependence. The relation between the main goals is discussed.The discussion is centered on the interdependence between the military and the civil aspects, conflict and coincidence of various goals, the relation between short-term and long-term goals, and the possibilities of using one goal as pretext for another. Thirdly, some causes of the changes in the atomic policy around 1953 and 1963 are identified. These are the strategic balance, the competitive situation, the capacity (of the American atomic productive apparatus), and the nuclear technological stage. The specific composition of these four factors at the two time-points can explain the changes of policy. (author)

  8. Atomic spectroscopy and radiative processes

    CERN Document Server

    Landi Degl'Innocenti, Egidio

    2014-01-01

    This book describes the basic physical principles of atomic spectroscopy and the absorption and emission of radiation in astrophysical and laboratory plasmas. It summarizes the basics of electromagnetism and thermodynamics and then describes in detail the theory of atomic spectra for complex atoms, with emphasis on astrophysical applications. Both equilibrium and non-equilibrium phenomena in plasmas are considered. The interaction between radiation and matter is described, together with various types of radiation (e.g., cyclotron, synchrotron, bremsstrahlung, Compton). The basic theory of polarization is explained, as is the theory of radiative transfer for astrophysical applications. Atomic Spectroscopy and Radiative Processes bridges the gap between basic books on atomic spectroscopy and the very specialized publications for the advanced researcher: it will provide under- and postgraduates with a clear in-depth description of theoretical aspects, supported by practical examples of applications.

  9. Atomic collisions in fusion plasmas involving multiply charged ions

    International Nuclear Information System (INIS)

    Salzborn, E.

    1980-01-01

    A short survey is given on atomic collisions involving multiply charged ions. The basic features of charge transfer processes in ion-ion and ion-atom collisions relevant to fusion plasmas are discussed. (author)

  10. Atomic secrecy

    International Nuclear Information System (INIS)

    Sweet, W.

    1979-01-01

    An article, The H-Bomb Secret: How We Got It, Why We're Telling It, by Howard Morland was to be published in The Progressive magazine in February, 1979. The government, after learning of the author's and the editors' intention to publish the article and failing to persuade them to voluntarily delete about 20% of the text and all of the diagrams showing how an H-bomb works, requested a court injunction against publication. Acting under the Atomic Energy Act of 1954, US District Court Judge Robert W. Warren granted the government's request on March 26. Events dealing with the case are discussed in this publication. Section 1, Progressive Hydrogen Bomb Case, is discussed under the following: Court Order Blocking Magazine Report; Origins of the Howard Morland Article; Author's Motives, Defense of Publication; and Government Arguments Against Disclosure. Section 2, Access to Atomic Data Since 1939, contains information on need for secrecy during World War II; 1946 Atomic Energy Act and its effects; Soviet A-Bomb and the US H-Bomb; and consequences of 1954 Atomic Energy Act. Section 3, Disputed Need for Atomic Secrecy, contains papers entitled: Lack of Studies on H-Bomb Proliferation; Administration's Position on H-Bombs; and National Security Needs vs Free Press

  11. Fast multilevel radiative transfer

    International Nuclear Information System (INIS)

    Paletou, Frederic; Leger, Ludovick

    2007-01-01

    The vast majority of recent advances in the field of numerical radiative transfer relies on approximate operator methods better known in astrophysics as Accelerated Lambda-Iteration (ALI). A superior class of iterative schemes, in term of rates of convergence, such as Gauss-Seidel and successive overrelaxation methods were therefore quite naturally introduced in the field of radiative transfer by Trujillo Bueno and Fabiani Bendicho [A novel iterative scheme for the very fast and accurate solution of non-LTE radiative transfer problems. Astrophys J 1995;455:646]; it was thoroughly described for the non-LTE two-level atom case. We describe hereafter in details how such methods can be generalized when dealing with non-LTE unpolarised radiation transfer with multilevel atomic models, in monodimensional geometry

  12. Antimatter atoms

    International Nuclear Information System (INIS)

    Anon.

    1996-01-01

    In january 1996, CERN broadcasted the information of the creation of nine anti-hydrogen atoms, observed through disintegration products. The experimental facility was CERN LEAR ring. An antiproton beam scattered a xenon jet, and the resulting antimatter was first selected by its insensitivity to beam bending magnets. Their disintegration was detected in thin NaI detectors, in which the anti-atoms are at once deprived from their positron. Then, magnetic and time-of-flight spectrometers are used. (D.L.)

  13. Atomic theories

    CERN Document Server

    Loring, FH

    2014-01-01

    Summarising the most novel facts and theories which were coming into prominence at the time, particularly those which had not yet been incorporated into standard textbooks, this important work was first published in 1921. The subjects treated cover a wide range of research that was being conducted into the atom, and include Quantum Theory, the Bohr Theory, the Sommerfield extension of Bohr's work, the Octet Theory and Isotopes, as well as Ionisation Potentials and Solar Phenomena. Because much of the material of Atomic Theories lies on the boundary between experimentally verified fact and spec

  14. Effects of dipole—dipole interaction on entanglement transfer

    International Nuclear Information System (INIS)

    Guo Hong; Xiong Hengna

    2008-01-01

    A system consisting of two different atoms interacting with a two-mode vacuum, where each atom is resonant only with one cavity mode, is considered. The effects of dipole—dipole (dd) interaction between two atoms on the atom-atom entanglement and mode-mode entanglement are investigated. For a weak dd interaction, when the atoms are initially separable, the entanglement between them can be induced by the dd interaction, and the entanglement transfer between the atoms and the modes occurs efficiently; when the atoms are initially entangled, the entanglement transfer is almost not influenced by the dd interaction. However, for a strong dd interaction, it is difficult to transfer the entanglement from the atoms to the modes, but the atom-atom entanglement can be maintained when the atoms are initially entangled

  15. Atoms stories

    International Nuclear Information System (INIS)

    Radvanyi, P.; Bordry, M.

    1988-01-01

    Physicists from different countries told each evening during one learning week, to an audience of young people, some great discoveries in evoking the difficulties and problems to which the researchers were confronted. From Antiquity to a more recent history, it is a succession of atoms stories. (N.C.)

  16. Atomic physics

    International Nuclear Information System (INIS)

    Held, B.

    1991-01-01

    This general book describes the change from classical physics to quantum physics. The first part presents atom evolution since antiquity and introduces fundamental quantities and elements of relativity. Experiments which have contributed to the evolution of knowledge on matter are analyzed in the second part. Applications of wave mechanics to the study of matter properties are presented in the third part [fr

  17. Interaction of complex atoms with radiation

    International Nuclear Information System (INIS)

    Amus'ya, M.Ya.

    1984-01-01

    Different manifestations of multielectron atomic structure under photoionization are discussed. Collectivization of external electron shells essential both in production cross section and in angular distribution as well as in photoelectron polarization are noted. In a wide range of quantum energies (of the order of ionization potential) an incident electron scattering on the atom irradiates quite differently than on the potential. It polarizes atoms mainly dipolarly, and virtually excited atom emits ''bremsstrahlung'' quantum. With energy growth of the incident electron at small momentum transferred to it by the atom the role of the second mechanism turns to be determinant

  18. Optical lattice on an atom chip

    DEFF Research Database (Denmark)

    Gallego, D.; Hofferberth, S.; Schumm, Thorsten

    2009-01-01

    Optical dipole traps and atom chips are two very powerful tools for the quantum manipulation of neutral atoms. We demonstrate that both methods can be combined by creating an optical lattice potential on an atom chip. A red-detuned laser beam is retroreflected using the atom chip surface as a high......-quality mirror, generating a vertical array of purely optical oblate traps. We transfer thermal atoms from the chip into the lattice and observe cooling into the two-dimensional regime. Using a chip-generated Bose-Einstein condensate, we demonstrate coherent Bloch oscillations in the lattice....

  19. TRANSFERENCE BEFORE TRANSFERENCE.

    Science.gov (United States)

    Bonaminio, Vincenzo

    2017-10-01

    This paper is predominantly a clinical presentation that describes the transmigration of one patient's transference to another, with the analyst functioning as a sort of transponder. It involves an apparently accidental episode in which there was an unconscious intersection between two patients. The author's aim is to show how transference from one case may affect transference in another, a phenomenon the author calls transference before transference. The author believes that this idea may serve as a tool for understanding the unconscious work that takes place in the clinical situation. In a clinical example, the analyst finds himself caught up in an enactment involving two patients in which he becomes the medium of what happens in session. © 2017 The Psychoanalytic Quarterly, Inc.

  20. Stopping atoms with diode lasers

    International Nuclear Information System (INIS)

    Watts, R.N.; Wieman, C.E.

    1986-01-01

    The use of light pressure to cool and stop neutral atoms has been an area of considerable interest recently. Cooled neutral atoms are needed for a variety of interesting experiments involving neutral atom traps and ultrahigh-resolution spectroscopy. Laser cooling of sodium has previously been demonstrated using elegant but quite elaborate apparatus. These techniques employed stabilized dye lasers and a variety of additional sophisticated hardware. The authors have demonstrated that a frequency chirp technique can be implemented using inexpensive diode lasers and simple electronics. In this technique the atoms in an atomic beam scatter resonant photons from a counterpropagating laser beam. The momentum transfer from the photons slows the atoms. The primary difficulty is that as the atoms slow their Doppler shift changes, and so they are no longer in resonance with the incident photons. In the frequency chirp technique this is solved by rapidly changing the laser frequency so that the atoms remain in resonance. To achieve the necessary frequency sweep with a dye laser one must use an extremely sophisticated high-speed electrooptic modulator. With a diode laser, however, the frequency can be smoothly and rapidly varied over many gigahertz simply by changing the injection current

  1. Atomic Energy Authority (Weapons Group) Act 1973

    International Nuclear Information System (INIS)

    1973-01-01

    This Act, which came into force on 6th March 1973 and modified Section 2 of the Atomic Energy Authority Act 1954 in respect of the Authority's power to do work on explosive nuclear devices, made provision for the transfer to the Secretary of State for Defence of the Weapons Group of the Atomic Energy Authority. (NEA) [fr

  2. Atom-surface potentials and atom interferometry

    International Nuclear Information System (INIS)

    Babb, J.F.

    1998-01-01

    Long-range atom-surface potentials characterize the physics of many actual systems and are now measurable spectroscopically in deflection of atomic beams in cavities or in reflection of atoms in atomic fountains. For a ground state, spherically symmetric atom the potential varies as -1/R 3 near the wall, where R is the atom-surface distance. For asymptotically large distances the potential is weaker and goes as -1/R 4 due to retardation arising from the finite speed of light. This diminished interaction can also be interpreted as a Casimir effect. The possibility of measuring atom-surface potentials using atomic interferometry is explored. The particular cases studied are the interactions of a ground-state alkali-metal atom and a dielectric or a conducting wall. Accurate descriptions of atom-surface potentials in theories of evanescent-wave atomic mirrors and evanescent wave-guided atoms are also discussed. (author)

  3. A study of atomic interaction between suspended nanoparticles and sodium atoms in liquid sodium

    International Nuclear Information System (INIS)

    Saito, Jun-ichi; Ara, Kuniaki

    2010-01-01

    A feasibility study of suppression of the chemical reactivity of sodium itself using an atomic interaction between nanoparticles and sodium atoms has been carried out. We expected that the atomic interaction strengthens when the nanoparticle metal is the transition element which has a major difference in electronegativity from sodium. We also calculated the atomic interaction between nanoparticle and sodium atoms. It became clear that the atomic bond between the nanoparticle atom and the sodium atom is larger than that between sodium atoms, and the charge transfer takes place to the nanoparticle atom from the sodium atom. Using sodium with suspended nanoparticles, the fundamental physical properties related to the atomic interaction were investigated to verify the atomic bond. The surface tension of sodium with suspended nanoparticles increased, and the evaporation rate of sodium with suspended nanoparticles also decreased compared with that of sodium. Therefore the presence of the atomic interaction between nanoparticles and sodium was verified from these experiments. Because the fundamental physical property changes by the atomic interaction, we expected changes in the chemical reactivity characteristics. The chemical reaction properties of sodium with suspended nanoparticles with water were investigated experimentally. The released reaction heat and the reaction rate of sodium with suspended nanoparticles were reduced than those of sodium. The influence of the charge state of nanoparticle on the chemical process with water was theoretically investigated to speculate on the cause of reaction suppression. The potential energy in both primary and side reactions changed by the charge transfer, and the free energy of activation of the reaction with water increased. Accordingly, the reaction barrier also increased. This suggests there is a possibility of the reduction in the reaction of sodium by the suspension of nanoparticles. Consequently the possibility of the

  4. Atom Skimmers and Atom Lasers Utilizing Them

    Science.gov (United States)

    Hulet, Randall; Tollett, Jeff; Franke, Kurt; Moss, Steve; Sackett, Charles; Gerton, Jordan; Ghaffari, Bita; McAlexander, W.; Strecker, K.; Homan, D.

    2005-01-01

    Atom skimmers are devices that act as low-pass velocity filters for atoms in thermal atomic beams. An atom skimmer operating in conjunction with a suitable thermal atomic-beam source (e.g., an oven in which cesium is heated) can serve as a source of slow atoms for a magneto-optical trap or other apparatus in an atomic-physics experiment. Phenomena that are studied in such apparatuses include Bose-Einstein condensation of atomic gases, spectra of trapped atoms, and collisions of slowly moving atoms. An atom skimmer includes a curved, low-thermal-conduction tube that leads from the outlet of a thermal atomic-beam source to the inlet of a magneto-optical trap or other device in which the selected low-velocity atoms are to be used. Permanent rare-earth magnets are placed around the tube in a yoke of high-magnetic-permeability material to establish a quadrupole or octupole magnetic field leading from the source to the trap. The atoms are attracted to the locus of minimum magnetic-field intensity in the middle of the tube, and the gradient of the magnetic field provides centripetal force that guides the atoms around the curve along the axis of the tube. The threshold velocity for guiding is dictated by the gradient of the magnetic field and the radius of curvature of the tube. Atoms moving at lesser velocities are successfully guided; faster atoms strike the tube wall and are lost from the beam.

  5. Influence of the atomic structure on the quantum state of sputtered Ir atoms

    International Nuclear Information System (INIS)

    Bastiaansen, J.; Philipsen, V.; Lievens, P.; Silverans, R.E.; Vandeweert, E.

    2004-01-01

    The probability of the ejection of a neutral atom in a specific quantum state after keV-ion beam sputtering is often interpreted in terms of the interaction between the atomic states of the escaping atom and the electronic states of the solid. In this work, we examined this interplay in the sputtering of iridium as this element has--unlike the elements employed in previous investigations--a complex atomic structure due to strong configuration interactions. Double-resonant two-photon laser ionization is used to probe the sputtered Ir atoms yielding information about the probability for an ejected atom to populate a specific atomic state and its escape velocity. The qualitative features of the corresponding population partition and state-selective velocity distributions show the influence of the excitation energy and the electronic structure of the different atomic states. A comparison is made between the experimental data and predictions from the resonant electron transfer description

  6. To test photon statistics by atomic beam deflection

    International Nuclear Information System (INIS)

    Wang Yuzhu; Chen Yudan; Huang Weigang; Liu Liang

    1985-02-01

    There exists a simple relation between the photon statistics in resonance fluorescence and the statistics of the momentum transferred to an atom by a plane travelling wave [Cook, R.J., Opt. Commun., 35, 347(1980)]. Using an atomic beam deflection by light pressure, we have observed sub-Poissonian statistics in resonance fluorescence of two-level atoms. (author)

  7. The role of charge transfer in the oxidation state change of Ce atoms in the TM13-CeO2(111) systems (TM = Pd, Ag, Pt, Au): a DFT + U investigation.

    Science.gov (United States)

    Tereshchuk, Polina; Freire, Rafael L H; Ungureanu, Crina G; Seminovski, Yohanna; Kiejna, Adam; Da Silva, Juarez L F

    2015-05-28

    Despite extensive studies of transition metal (TM) clusters supported on ceria (CeO2), fundamental issues such as the role of the TM atoms in the change in the oxidation state of Ce atoms are still not well understood. In this work, we report a theoretical investigation based on static and ab initio molecular dynamics density functional theory calculations of the interaction of 13-atom TM clusters (TM = Pd, Ag, Pt, Au) with the unreduced CeO2(111) surface represented by a large surface unit cell and employing Hubbard corrections for the strong on-site Coulomb correlation in the Ce f-electrons. We found that the TM13 clusters form pyramidal-like structures on CeO2(111) in the lowest energy configurations with the following stacking sequence, TM/TM4/TM8/CeO2(111), while TM13 adopts two-dimensional structures at high energy structures. TM13 induces a change in the oxidation state of few Ce atoms (3 of 16) located in the topmost Ce layer from Ce(IV) (itinerant Ce f-states) to Ce(III) (localized Ce f-states). There is a charge flow from the TM atoms to the CeO2(111) surface, which can be explained by the electronegativity difference between the TM (Pd, Ag, Pt, Au) and O atoms, however, the charge is not uniformly distributed on the topmost O layer due to the pressure induced by the TM13 clusters on the underlying O ions, which yields a decrease in the ionic charge of the O ions located below the cluster and an increase in the remaining O ions. Due to the charge flow mainly from the TM8-layer to the topmost O-layer, the charge cannot flow from the Ce(IV) atoms to the O atoms with the same magnitude as in the clean CeO2(111) surface. Consequently, the effective cationic charge decreases mainly for the Ce atoms that have a bond with the O atoms not located below the cluster, and hence, those Ce atoms change their oxidation state from IV to III. This increases the size of the Ce(III) compared with the Ce(IV) cations, which builds-in a strain within the topmost Ce layer, and

  8. Theoretical study of adsorption of lithium atom on carbon nanotube

    Directory of Open Access Journals (Sweden)

    Masato Senami

    2011-12-01

    Full Text Available We investigate the adsorption of lithium atoms on the surface of the (12,0 single wall carbon nanotube (SWCNT by using ab initio quantum chemical calculations. The adsorption of one lithium atom on the inside of this SWCNT is favored compared to the outside. We check this feature by charge transfer and regional chemical potential density. The adsorption of multiple lithium atoms on the interior of the SWCNT is studied in terms of adsorption energy and charge transfer. We show that repulsive force between lithium atoms destabilizes a system for the large number of lithium atoms.

  9. Theoretical study of adsorption of lithium atom on carbon nanotube

    OpenAIRE

    Senami, Masato; Ikeda, Yuji; Fukushima, Akinori; Tachibana, Akitomo

    2011-01-01

    We investigate the adsorption of lithium atoms on the surface of the (12, 0) single wall carbon nanotube (SWCNT) by using ab initio quantum chemical calculations. The adsorption of one lithium atom on the inside of this SWCNT is favored compared to the outside. We check this feature by charge transfer and regional chemical potential density. The adsorption of multiple lithium atoms on the interior of the SWCNT is studied in terms of adsorption energy and charge transfer. We show that repulsiv...

  10. Transition from LEDCOP to ATOMIC

    International Nuclear Information System (INIS)

    Magee, N.H.; Abdallah, J.; Colgan, J.; Hakel, P.; Kilcrease, D.P.; Mazevet, S.; Sherrill, M.E.; Fontes, C.J.; Zhang, H.

    2004-01-01

    This paper discusses the development of the ATOMIC code, a new low to mid Z opacity code, which will replace the current Los Alamos low Z opacity code LEDCOP. The ATOMIC code is based on the FINE code, long used by the Los Alamos group for spectral comparisons in local thermodynamic equilibrium (LTE) and for non-LTE calculations, both utilizing the extensive databases from the atomic physics suite of codes based on the work of R.D. Cowan. Many of the plasma physics packages in LEDCOP, such as line broadening and free-free absorption, are being transferred to the new ATOMIC code. A new equation of state (EOS) model is being developed to allow higher density calculations than were possible with either the FINE or LEDCOP codes. Extensive modernization for both ATOMIC and the atomic physics code suites, including conversion to Fortran 90 and parallelization, are underway to speed up the calculations and to allow the use of expanded databases for both the LTE opacity tables and the non-LTE calculations. Future plans for the code will be outlined, including considerations for new generation opacity tables.

  11. Atomic Energy Authority Act 1971

    International Nuclear Information System (INIS)

    1971-01-01

    This Act provides for the transfer of property, rights, liabilities and obligations of parts of the undertaking of the United Kingdom Atomic Energy Autority, to two new Compagnies set up for this purpose: the Bristish Nuclear Fuels Limited, and the Radiochemical Centre Limited. Patents licences and registered designs owned by the Autority at the time of the transfer are not included therein. The Act also includes amendments to the Nuclear Installations Act 1965, notably as regards permits to operate granted to a body corporate. Finally, the Schedule to this Act lays down a certain number of provisions relating to security and the preservation of secrets. (NEA) [fr

  12. Industrial technology transfer

    International Nuclear Information System (INIS)

    Bulger, W.

    1982-06-01

    The transfer of industrial technology is an essential part of the CANDU export marketing program. Potential customers require the opportunity to become self-sufficient in the supply of nuclear plant and equipment in the long term and they require local participation to the maximum extent possible. The Organization of CANDU Industries is working closely with Atomic Energy of Canada Ltd. in developing comprehensive programs for the transfer of manufacturing technology. The objectives of this program are: 1) to make available to the purchasing country all nuclear component manufacturing technology that exists in Canada; and 2) to assure that the transfer of technology takes place in an efficient and effective way. Technology transfer agreements may be in the form of joint ventures or license agreements, depending upon the requirements of the recipient

  13. Atomic energy

    International Nuclear Information System (INIS)

    Ramanna, R.

    1978-01-01

    Development of nuclear science in India, particularly the research and development work at the Bhabha Atomic Research Centre (BARC), Bombay, is described. Among the wide range of materials developed for specific functions under rigorous conditions are nuclear pure grade uranium, zirconium and beryllium, and conventional materials like aluminium, carbon steel and stainless steels. Radioisotopes are produced and used for tracer studies in various fields. Various types of nuclear gauges and nuclear instruments are produced. Radiations have been used to develop new high yielding groundnut mutants with large kernals. The sterile male technique for pest control and radiosterilization technique to process potatoes, onions and marine foods for storage are ready for exploitation. Processes and equipment have been developed for production of electrolytic hydrogen, electrothermal phosphorus and desalinated water. Indigenously manufactured components and materials are now being used for the nuclear energy programme. Indian nuclear power programme strategy is to build heavy water reactors and to utilise their byproduct plutonium and depleted uranium to feed fast breeder reactors which will produce more fissile material than burnt. Finally a special mention has been made of the manpower development programme of the BARC. BARC has established a training school in 1957 giving advanced training in physics, chemistry and various branches of engineering and metallurgy

  14. Magnetic trapping of cold bromine atoms.

    Science.gov (United States)

    Rennick, C J; Lam, J; Doherty, W G; Softley, T P

    2014-01-17

    Magnetic trapping of bromine atoms at temperatures in the millikelvin regime is demonstrated for the first time. The atoms are produced by photodissociation of Br2 molecules in a molecular beam. The lab-frame velocity of Br atoms is controlled by the wavelength and polarization of the photodissociation laser. Careful selection of the wavelength results in one of the pair of atoms having sufficient velocity to exactly cancel that of the parent molecule, and it remains stationary in the lab frame. A trap is formed at the null point between two opposing neodymium permanent magnets. Dissociation of molecules at the field minimum results in the slowest fraction of photofragments remaining trapped. After the ballistic escape of the fastest atoms, the trapped slow atoms are lost only by elastic collisions with the chamber background gas. The measured loss rate is consistent with estimates of the total cross section for only those collisions transferring sufficient kinetic energy to overcome the trapping potential.

  15. FROM ATOM TRANSFER RADICAL ADDITION TO ATOM TRANSFER RADICAL POLYMERIZATION. (R829580)

    Science.gov (United States)

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  16. Interaction of relativistic elementary atoms with matter. I. General formulas

    International Nuclear Information System (INIS)

    Mrowczyn'ski, S.

    1987-01-01

    The problem of the interaction of relativistic elementary atoms (Coulomb bound states of elementary particles such as positronium, pionium, etc.) with matter is studied in the reference frame where the atom is initially at rest. An atom of matter is treated as a spinless structureless fast particle. The amplitudes of elementary-atom interaction are derived in the Born approximation under the assumption that a momentum transfer to the atom does not significantly exceed an inverse Bohr radius of the atom. The elementary-atom excitation and ionization processes are considered. The transitions where the spin projection of the atom component is reversed are also studied. In particular the matrix elements for para-ortho and ortho-para transitions are given. The spin structure of the amplitudes is discussed in detail. The sum rules, which allow the calculation of the cross sections summed over atom final states are found. Finally the formulas of the atom interaction cross sections are presented

  17. Bremsstrahlung in atom-atom collisions

    International Nuclear Information System (INIS)

    Amus'ya, M.Y.; Kuchiev, M.Y.; Solov'ev, A.V.

    1985-01-01

    It is shown that in the collision of a fast atom with a target atom when the frequencies are on the order of the potentials or higher, there arises bremsstrahlung comparable in intensity with the bremsstrahlung emitted by an electron with the same velocity in the field of the target atom. The mechanism by which bremsstrahlung is produced in atom-atom collisions is elucidated. Results of specific calculations of the bremsstrahlung spectra are given for α particles and helium atoms colliding with xenon

  18. Communication Received from the Permanent Mission of Mexico to the International Atomic Energy Agency Regarding Guidelines for the Export of Nuclear Material, Equipment and Technology and the Guidelines for Transfers of Nuclear-related Dual-use Equipment, Materials, Software and Related Technology

    International Nuclear Information System (INIS)

    2012-01-01

    The Director General has received a note verbale dated 15 June 2012 from the Permanent Mission of Mexico to the International Atomic Energy Agency providing information on the decision of the Government of Mexico to act in accordance with the 'Guidelines for the Export of Nuclear Material, Equipment and Technology', issued as document INFCIRC/254/Rev.10/Part 1, including its Annexes, and with the 'Guidelines for Transfers of Nuclear-Related Dual-Use Equipment, Material, Software and Related Technology', issued as document INFCIRC/254/Rev.8/Part 2

  19. Communication Received from the PermanentMission of Mexico to the International Atomic Energy Agency Regarding Guidelines for the Export of Nuclear Material, Equipment and Technology and the Guidelines for Transfers of Nuclear-related Dual-use Equipment, Materials, Software and Related Technology

    International Nuclear Information System (INIS)

    2012-01-01

    The Director General has received a note verbale dated 15 June 2012 from the Permanent Mission of Mexico to the International Atomic Energy Agency providing information on the decision of the Government of Mexico to act in accordance with the 'Guidelines for the Export of Nuclear Material, Equipment and Technology', issued as document INFCIRC/254/Rev.10/Part 1, including its Annexes, and with the 'Guidelines for Transfers of Nuclear-Related Dual-Use Equipment, Material, Software and Related Technology', issued as document INFCIRC/254/Rev.8/Part 2

  20. Communication Received from the Permanent Mission of the Republic of Serbia to the International Atomic Energy Agency Regarding Guidelines for the Export of Nuclear Material, Equipment and Technology and the Guidelines for Transfers of Nuclear-related Dual-use Equipment, Materials, Software and Related Technology

    International Nuclear Information System (INIS)

    2012-01-01

    The Director General has received a note verbale dated 28 September 2012 from the Permanent Mission of Serbia to the International Atomic Energy Agency providing information on the decision of the Government of Serbia to adhere to the 'Guidelines for the Export of Nuclear Material, Equipment and Technology', issued as document INFCIRC/254/Rev.10/Part 1, including its Annexes, and with the 'Guidelines for Transfers of Nuclear-Related Dual-Use Equipment, Material, Software and Related Technology', issued as document INFCIRC/254/Rev.8/Part 2 [fr

  1. Communication Received from the PermanentMission of Mexico to the International Atomic Energy Agency Regarding Guidelines for the Export of Nuclear Material, Equipment and Technology and the Guidelines for Transfers of Nuclear-related Dual-use Equipment, Materials, Software and Related Technology

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2012-06-19

    The Director General has received a note verbale dated 15 June 2012 from the Permanent Mission of Mexico to the International Atomic Energy Agency providing information on the decision of the Government of Mexico to act in accordance with the 'Guidelines for the Export of Nuclear Material, Equipment and Technology', issued as document INFCIRC/254/Rev.10/Part 1, including its Annexes, and with the 'Guidelines for Transfers of Nuclear-Related Dual-Use Equipment, Material, Software and Related Technology', issued as document INFCIRC/254/Rev.8/Part 2.

  2. Communication Received from the Permanent Mission of Mexico to the International Atomic Energy Agency Regarding Guidelines for the Export of Nuclear Material, Equipment and Technology and the Guidelines for Transfers of Nuclear-related Dual-use Equipment, Materials, Software and Related Technology

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2012-06-19

    The Director General has received a note verbale dated 15 June 2012 from the Permanent Mission of Mexico to the International Atomic Energy Agency providing information on the decision of the Government of Mexico to act in accordance with the 'Guidelines for the Export of Nuclear Material, Equipment and Technology', issued as document INFCIRC/254/Rev.10/Part 1, including its Annexes, and with the 'Guidelines for Transfers of Nuclear-Related Dual-Use Equipment, Material, Software and Related Technology', issued as document INFCIRC/254/Rev.8/Part 2.

  3. Communication Received from the Permanent Mission of the Republic of Serbia to the International Atomic Energy Agency Regarding Guidelines for the Export of Nuclear Material, Equipment and Technology and the Guidelines for Transfers of Nuclear-related Dual-use Equipment, Materials, Software and Related Technology

    International Nuclear Information System (INIS)

    2012-01-01

    The Director General has received a note verbale dated 28 September 2012 from the Permanent Mission of Serbia to the International Atomic Energy Agency providing information on the decision of the Government of Serbia to adhere to the 'Guidelines for the Export of Nuclear Material, Equipment and Technology', issued as document INFCIRC/254/Rev.10/Part 1, including its Annexes, and with the 'Guidelines for Transfers of Nuclear-Related Dual-Use Equipment, Material, Software and Related Technology', issued as document INFCIRC/254/Rev.8/Part 2 [es

  4. Communication Received from the Permanent Mission of the Republic of Serbia to the International Atomic Energy Agency Regarding Guidelines for the Export of Nuclear Material, Equipment and Technology and the Guidelines for Transfers of Nuclear-related Dual-use Equipment, Materials, Software and Related Technology

    International Nuclear Information System (INIS)

    2012-01-01

    The Director General has received a note verbale dated 28 September 2012 from the Permanent Mission of Serbia to the International Atomic Energy Agency providing information on the decision of the Government of Serbia to adhere to the 'Guidelines for the Export of Nuclear Material, Equipment and Technology', issued as document INFCIRC/254/Rev.10/Part 1, including its Annexes, and with the 'Guidelines for Transfers of Nuclear-Related Dual-Use Equipment, Material, Software and Related Technology', issued as document INFCIRC/254/Rev.8/Part 2

  5. Gold volatile species atomization and preconcentration in quartz devices for atomic absorption spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Arslan, Yasin [Institute of Analytical Chemistry of the ASCR, v. v. i., Veveří 97, 602 00 Brno (Czech Republic); Mehmet Akif Ersoy University, Faculty of Arts & Sciences, Chemistry Department, 15030 Burdur (Turkey); Musil, Stanislav; Matoušek, Tomáš; Kratzer, Jan [Institute of Analytical Chemistry of the ASCR, v. v. i., Veveří 97, 602 00 Brno (Czech Republic); Dědina, Jiří, E-mail: dedina@biomed.cas.cz [Institute of Analytical Chemistry of the ASCR, v. v. i., Veveří 97, 602 00 Brno (Czech Republic)

    2015-01-01

    The on-line atomization of gold volatile species was studied and the results were compared with thermodynamic calculations in several quartz atomizers, namely: diffusion flame, flame-in-gas-shield, flame-in-plain-tube, externally heated T-tube and externally heated flame-in-T-tube. Atomization mechanism in the explored devices is proposed, where volatile species are converted to thermodynamically stable AuH at elevated temperature over 500 °C and then atomized by an interaction with a cloud of hydrogen radicals. Because of its inherent simplicity and robustness, diffusion flame was employed as a reference atomizer. It yielded atomization efficiency of 70 to 100% and a very good long time reproducibility of peak area sensitivity: 1.6 to 1.8 s μg{sup −1}. Six and eleven times higher sensitivity, respectively, was provided by atomizers with longer light paths in the observation volume, i.e. externally heated T-tube and externally heated flame-in-T-tube. The latter one, offering limit of detection below 0.01 μg ml{sup −1}, appeared as the most prospective for on-line atomization. Insight into the mechanism of atomization of gold volatile species, into the fate of free atoms and into subsequent analyte transfer allowed to assess possibilities of in-atomizer preconcentration of gold volatile species: it is unfeasible with quartz atomizers but a sapphire tube atomizer could be useful in this respect. - Highlights: • On-line atomization of gold volatile species for AAS in quartz devices was studied. • Atomization mechanism was proposed and atomization efficiency was estimated. • Possibilities of in-atomizer preconcentration of gold volatile species were assessed.

  6. Formation of fast exotic atoms by radiative Coulomb capture

    International Nuclear Information System (INIS)

    Chatterjee, L.; Das, G.; Chakravorty, A.; Goswami, R.; Mondal, S.K.

    1993-01-01

    Interesting surprises in some exotic atom kinetics have been reported recently. These involve muonic atom transfer cross sections, nuclear pion capture and the q 1s effect in μCF. These can be explained if the exotic atom population contains a contributing fast component. Such fast atoms can be formed by radiative continuum to bound transitions of fast (keV) muons or pions. Cross sections for formation of such fast pionic and muonic atoms and their velocity distributions are reported. The possibility of these processes competing with the thermalisation channels and contributing effectively to the exotic atom population discussed. (orig.)

  7. Communication from the Permanent Mission of the Russian Federation to the International Atomic Energy Agency regarding guidelines for transfers of nuclear-related dual-use equipment, materials, software and related technology

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2000-08-04

    The document reproduces the text of the Note Verbale received by the Director General of the IAEA from the Permanent Mission of the Russian Federation to the International Atomic Energy Agency providing information on the export policies and practices of the Government of the Russian Federation with respect to the export of nuclear-related dual-use equipment, materials, software and related technology.

  8. Communication from the Permanent Mission of the Russian Federation to the International Atomic Energy Agency regarding guidelines for transfers of nuclear-related dual-use equipment, materials, software and related technology

    International Nuclear Information System (INIS)

    2000-01-01

    The document reproduces the text of the Note Verbale received by the Director General of the IAEA from the Permanent Mission of the Russian Federation to the International Atomic Energy Agency providing information on the export policies and practices of the Government of the Russian Federation with respect to the export of nuclear-related dual-use equipment, materials, software and related technology

  9. Atomic weight versus atomic mass controversy

    International Nuclear Information System (INIS)

    Holden, N.E.

    1985-01-01

    A problem for the Atomic Weights Commission for the past decade has been the controversial battle over the names ''atomic weight'' and ''atomic mass''. The Commission has considered the arguments on both sides over the years and it appears that this meeting will see more of the same discussion taking place. In this paper, I review the situation and offer some alternatives

  10. Muon transfer to sulphur dioxide

    International Nuclear Information System (INIS)

    Mulhauser, F.; Schneuwly, H.

    1993-01-01

    A systematic study of muon capture and muon transfer has been performed in seven different H 2 + SO 2 gas mixtures. From the single-exponential time structure of the muonic sulphur x-rays, one determines the lifetime of the μp atoms under the given experimental conditions. The reduced muon transfer rates to the sulphur dioxide molecule, deduced from these lifetimes, all agree well with each other. The muonic oxygen time spectra show an additional structure as if μp atoms of another kind were present. Comparable time structures are observed in a D 2 + SO 2 mixture. (author)

  11. Highly excited atoms

    International Nuclear Information System (INIS)

    Kleppner, D.; Littman, M.G.; Zimmerman, M.L.

    1981-01-01

    Highly excited atoms are often called Rydberg atoms. These atoms have a wealth of exotic properties which are discussed. Of special interest, are the effects of electric and magnetic fields on Rydberg atoms. Ordinary atoms are scarcely affected by an applied electric or magnetic field; Rydberg atoms can be strongly distorted and even pulled apart by a relatively weak electric field, and they can be squeezed into unexpected shapes by a magnetic field. Studies of the structure of Rydberg atoms in electric and magnetic fields have revealed dramatic atomic phenomena that had not been observed before

  12. Laser-assisted atom-atom collisions

    International Nuclear Information System (INIS)

    Roussel, F.

    1984-01-01

    The basic layer-assisted atom-atom collision processes are reviewed in order to get a simpler picture of the main physical facts. The processes can be separated into two groups: optical collisions where only one atom is changing state during the collision, the other acting as a spectator atom, and radiative collisions where the states of the two atoms are changing during the collision. All the processes can be interpreted in terms of photoexcitation of the quasimolecule formed during the collisional process. (author)

  13. Code ATOM for calculation of atomic characteristics

    International Nuclear Information System (INIS)

    Vainshtein, L.A.

    1990-01-01

    In applying atomic physics to problems of plasma diagnostics, it is necessary to determine some atomic characteristics, including energies and transition probabilities, for very many atoms and ions. Development of general codes for calculation of many types of atomic characteristics has been based on general but comparatively simple approximate methods. The program ATOM represents an attempt at effective use of such a general code. This report gives a brief description of the methods used, and the possibilities of and limitations to the code are discussed. Characteristics of the following processes can be calculated by ATOM: radiative transitions between discrete levels, radiative ionization and recombination, collisional excitation and ionization by electron impact, collisional excitation and ionization by point heavy particle (Born approximation only), dielectronic recombination, and autoionization. ATOM explores Born (for z=1) or Coulomb-Born (for z>1) approximations. In both cases exchange and normalization can be included. (N.K.)

  14. Photoionization of Endohedral Atoms: Collective, Reflective and Collateral Emissions

    International Nuclear Information System (INIS)

    Chakraborty, Himadri S.; McCune, Matthew A.; Hopper, Dale E.; Madjet, Mohamed E.; Manson, Steven T.

    2009-01-01

    The photoionization properties of a fullerene-confined atom differ dramatically from that of an isolated atom. In the low energy region, where the fullerene plasmons are active, the electrons of the confined atom emerge through a collective channel carrying a significant chunk of plasmon with it. The photoelectron angular distribution of the confined atom however shows far lesser impact of the effect. At higher energies, the interference between two single-electron ionization channels, one directly from the atom and another reflected off the fullerene cage, producuces oscillatory cross sections. But for the outermost atomic level, which transfers some electrons to the cage, oscillations are further modulated by the collateral emission from the part of the atomic charge density transferred to the cage. These various modes of emissions are studied for the photoionization of Ar endohedrally confined in C 60 .

  15. Multiple-electron processes in fast ion-atom collisions

    International Nuclear Information System (INIS)

    Schlachter, A.S.

    1989-03-01

    Research in atomic physics at the Lawrence Berkeley Laboratory Super-HILAC and Bevalac accelerators on multiple-electron processes in fast ion-atom collisions is described. Experiments have studied various aspects of the charge-transfer, ionization, and excitation processes. Examples of processes in which electron correlation plays a role are resonant transfer and excitation and Auger-electron emission. Processes in which electron behavior can generally be described as uncorrelated include ionization and charge transfer in high-energy ion-atom collisions. A variety of experiments and results for energies from 1 MeV/u to 420 MeV/u are presented. 20 refs., 15 figs

  16. Technology transfer from nuclear research

    International Nuclear Information System (INIS)

    1989-01-01

    A number of processes, components and instruments developed at the Bhabha Atomic Research Centre, (BARC), Bombay, find application in industry and are available for transfer to private or public sector undertakings for commercial exploitation. The Technology Transfer Group (TTG) constituted in January 1980 identifies such processes and prototypes which can be made available for transfer. This catalogue contains brief descriptions of such technologies and they are arranged under three groups, namely, Group A containing descriptions of technologies already transferred, Group B containing descriptions of technologies ready for transfer and Group C containing descriptions of technology transfer proposals being processed. The position in the above-mentioned groups is as on 1 March 1989. The BARC has also set up a Technology Corner where laboratory models and prototypes of instruments, equipment and components are displayed. These are described in the second part of the catalogue. (M.G.B.)

  17. Heat transfer

    Indian Academy of Sciences (India)

    First page Back Continue Last page Overview Graphics. Heat transfer. Heat conduction in solid slab. Convective heat transfer. Non-linear temperature. variation due to flow. HEAT FLUX AT SURFACE. conduction/diffusion.

  18. Heat transfer

    International Nuclear Information System (INIS)

    Saad, M.A.

    1985-01-01

    Heat transfer takes place between material systems as a result of a temperature difference. The transmission process involves energy conversions governed by the first and second laws of thermodynamics. The heat transfer proceeds from a high-temperature region to a low-temperature region, and because of the finite thermal potential, there is an increase in entropy. Thermodynamics, however, is concerned with equilibrium states, which includes thermal equilibrium, irrespective of the time necessary to attain these equilibrium states. But heat transfer is a result of thermal nonequilibrium conditions, therefore, the laws of thermodynamics alone cannot describe completely the heat transfer process. In practice, most engineering problems are concerned with the rate of heat transfer rather than the quantity of heat being transferred. Resort then is directed to the particular laws governing the transfer of heat. There are three distinct modes of heat transfer: conduction, convection, and radiation. Although these modes are discussed separately, all three types may occur simultaneously

  19. Light forces on an indium atomic beam

    International Nuclear Information System (INIS)

    Kloeter, B.

    2007-01-01

    In this thesis it was studied, whether indium is a possible candidate for the nanostructuration respectively atomic lithography. For this known method for the generation and stabilization of the light necessary for the laser cooling had to be fitted to the special properties of indium. The spectroscopy of indium with the 451 nm and the 410 nm light yielded first hints that the formulae for the atom-light interaction for a two-level atom cannot be directly transferred to the indium atom. By means of the obtained parameters of the present experiment predictions for a possible Doppler cooling of the indium atomic beam were calculated. Furthermore the possibility for the direct deposition of indium on a substrate was studied

  20. Atomic physics of strongly correlated systems

    International Nuclear Information System (INIS)

    Lin, C.D.

    1986-01-01

    This abstract summarizes the progress made in the last year and the future plans of our research in the study of strongly correlated atomic systems. In atomic structure and atomic spectroscopy we are investigating the classification and supermultiplet structure of doubly excited states. We are also beginning the systematic study of triply excited states. In ion-atom collisions, we are exploring an AO-MO matching method for treating multi-electron collision systems to extract detailed information such as subshell cross sections, alignment and orientation parameters, etc. We are also beginning ab initio calculations on the angular distributions for electron transfer processes in low-energy (about 10-100eV/amu) ion-atom collisions in a full quantum mechanical treatment of the motion of heavy particles

  1. Additional supply agreement of 9 December 1988 between the International Atomic Energy Agency and the Governments of the Islamic Republic of Iran and of Argentina for the transfer of enriched uranium for a research reactor in Iran

    International Nuclear Information System (INIS)

    1990-01-01

    The document reproduces the text of the additional supply agreement of 9 December 1988 between the IAEA and the Government of the Islamic Republic of Iran and of Argentina for the transfer of 115.80 kilograms of uranium enriched up to 20% in the isotope uranium-235 for a research reactor in Iran

  2. Transfer Pricing

    DEFF Research Database (Denmark)

    Nielsen, Søren Bo

    2014-01-01

    Against a background of rather mixed evidence about transfer pricing practices in multinational enterprises (MNEs) and varying attitudes on the part of tax authorities, this paper explores how multiple aims in transfer pricing can be pursued across four different transfer pricing regimes. A MNE h...

  3. Exotic atoms. Technical progress report

    International Nuclear Information System (INIS)

    Kunselman, R.

    1994-01-01

    The experiments use a variety of hydrogen isotopic mixtures to form solid targets for muons to produce muonic hydrogen isotope atoms that escape into vacuum. The method relies on transfer of the muon from a proton to either a deuteron or a triton. The resulting muonic deuterium or muonic tritium will not immediately thermalize because of the very low elastic cross sections (RT effect), and are emitted from the surface of the layer. A second solid hydrogen isotopic target is produced downstream on which the muonic hydrogen atom can react. Measurements which detect decay electrons, muonic x-rays, and fusion products have been used to study the processes of energy dependence of transfer, production rates, and muon molecular formation. The processes include muon catalyzed fusion of muonic tritium with deuterium which is the most possible candidate for energy production fusion. Our interest is the nuclear physics reaction rates and to use the muonic hydrogen isotopes in vacuum for energy level measurements. The method uses time of flight and is reminiscent of double scattering experiments. Two other experiments are in the development stages. First to measure the energy dependence of the Ramsauer-Townsend cross section in tritium where it has not been measured. The measurements would be compared to deuterium and calculations. Second, kaonic atoms, hypernuclei, and kaon-nucleon scattering at DAPHNE

  4. Atomic fountain and applications

    International Nuclear Information System (INIS)

    Rawat, H.S.

    2000-01-01

    An overview of the development of working of MOT along with the basic principle of laser atom cooling and trapping is given. A technique to separate the cooled and trapped atoms from the MOT using atomic fountain technique will also be covered. The widely used technique for atomic fountain is, first to cool and trap the neutral atoms in MOT and then launch them in the vertical direction, using moving molasses technique. Using 133 Cs atomic fountain clock, time improvement of 2 to 3 order of magnitude over a conventional 133 Cs atomic clock has been observed

  5. Interferometry with atoms

    International Nuclear Information System (INIS)

    Helmcke, J.; Riehle, F.; Witte, A.; Kisters, T.

    1992-01-01

    Physics and experimental results of atom interferometry are reviewed and several realizations of atom interferometers are summarized. As a typical example of an atom interferometer utilizing the internal degrees of freedom of the atom, we discuss the separated field excitation of a calcium atomic beam using four traveling laser fields and demonstrate the Sagnac effect in a rotating interferometer. The sensitivity of this interferometer can be largely increased by use of slow atoms with narrow velocity distribution. We therefore furthermore report on the preparation of a laser cooled and deflected calcium atomic beam. (orig.)

  6. Three-atom clusters

    International Nuclear Information System (INIS)

    Pen'kov, F.M.

    1998-01-01

    The Born-Oppenheimer approximation is used to obtain an equation for the effective interaction in three atoms bound by a single electron. For low binding energies in an 'electron + atom' pair, long-range forces arise between the atoms, leading to bound states when the size of the three-atom cluster is a few tens of angstrom. A system made of alkali-metal atoms is considered as an example

  7. Stable atomic hydrogen: Polarized atomic beam source

    International Nuclear Information System (INIS)

    Niinikoski, T.O.; Penttilae, S.; Rieubland, J.M.; Rijllart, A.

    1984-01-01

    We have carried out experiments with stable atomic hydrogen with a view to possible applications in polarized targets or polarized atomic beam sources. Recent results from the stabilization apparatus are described. The first stable atomic hydrogen beam source based on the microwave extraction method (which is being tested ) is presented. The effect of the stabilized hydrogen gas density on the properties of the source is discussed. (orig.)

  8. Communication from the Permanent Mission of the Russian Federation to the International Atomic Energy Agency regarding guidelines for transfers of nuclear-related dual-use equipment, materials, software and related technology

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2001-12-10

    The Director General of the International Atomic Energy Agency has received a Note Verbale from the Permanent Mission of the Russian Federation providing information on the export policies and practices of the Government of the Russian Federation with respect to the export of nuclear-related dual-use equipment, materials, software and related technology. In the light of the wish expressed at the end of the Note Verbale, the text of the Note Verbale is attached. The attachment to the Note Verbale was issued previously as INFCIRC/2541Rev. 4/Part 2.

  9. Communication from the Permanent Mission of the Russian Federation to the International Atomic Energy Agency regarding guidelines for transfers of nuclear-related dual-use equipment, materials, software and related technology

    International Nuclear Information System (INIS)

    2001-01-01

    The Director General of the International Atomic Energy Agency has received a Note Verbale from the Permanent Mission of the Russian Federation providing information on the export policies and practices of the Government of the Russian Federation with respect to the export of nuclear-related dual-use equipment, materials, software and related technology. In the light of the wish expressed at the end of the Note Verbale, the text of the Note Verbale is attached. The attachment to the Note Verbale was issued previously as INFCIRC/2541Rev. 4/Part 2

  10. Communication from the Permanent Missions of Brazil and Romania to the International Atomic Energy Agency Regarding Guidelines for the Transfers of Nuclear-Related Dual-Use Equipment, Materials, Software and Related Technology

    International Nuclear Information System (INIS)

    2003-01-01

    The Director General of the International Atomic Energy Agency has received Notes Verbale from the Permanent Missions of Brazil and Romania, dated 28 February 2003, providing information on the export policies and practices of the Governments of Brazil and Romania with respect to the export of nuclear-related dual-use equipment, materials, software and related technology. In the light of the wish expressed at the end of each Note Verbale, the text of the Notes Verbale is attached. The attachment referenced in the Note Verbale was issued previously as INFCIRC/254/Rev.5/Part 2

  11. Project and supply agreement. The text of the agreement of 17 June 1993 between the International Atomic Energy Agency and the governments of Colombia and the United States of America concerning the transfer of enriched uranium for a research reactor

    International Nuclear Information System (INIS)

    1994-12-01

    The text of the Project and Supply Agreement, which was approved by the Agency's Board of Governors on 25 February 1993 and 2 December 1993, between the Agency and the Governments of Colombia and the United States of America for the transfer of enriched uranium for a research reactor is reproduced herein for the information of all Members. The agreement entered into force on 17 June 1994, pursuant to Article XII

  12. Quasi-Bragg diffraction of atoms

    NARCIS (Netherlands)

    Domen, K.F.E.M.; Jansen, M.A.H.M.; Leeuwen, van K.A.H.

    2006-01-01

    We report on a novel atomic beamsplitter. It combines the advantages of Bragg scattering (transfer possible into a single, very high diffraction order due to adiabatic conservation of ‘transverse kinetic energy’) with the convenience of tuning the splitting angle simply by adjusting a magnetic

  13. Charge exchange in ion-atom collisions

    International Nuclear Information System (INIS)

    Bransden, B.H.

    1990-01-01

    Charge exchange reactions in which electrons are transferred from one ion (or atom) to another during a collision have been studied both as interesting examples of rearrangement collisions and because of important applications in plasma physics. This article reviews the modern theory developed for use at non-relativistic energies, but excluding the thermal and very low energy region. (author)

  14. Advances in atomic spectroscopy

    CERN Document Server

    Sneddon, J

    2000-01-01

    This fifth volume of the successful series Advances in Atomic Spectroscopy continues to discuss and investigate the area of atomic spectroscopy.It begins with a description of the use of various atomic spectroscopic methods and applications of speciation studies in atomic spectroscopy. The emphasis is on combining atomic spectroscopy with gas and liquid chromatography. In chapter two the authors describe new developments in tunable lasers and the impact they will have on atomic spectroscopy. The traditional methods of detection, such as photography and the photomultiplier, and how they are being replaced by new detectors is discussed in chapter three. The very active area of glow discharge atomic spectrometry is presented in chapter four where, after a brief introduction and historical review, the use of glow discharge lamps for atomic spectroscopy and mass spectrometry are discussed. Included in this discussion is geometry and radiofrequency power. The future of this source in atomic spectroscopy is also dis...

  15. Atomic and molecular manipulation

    CERN Document Server

    Mayne, Andrew J

    2011-01-01

    Work with individual atoms and molecules aims to demonstrate that miniaturized electronic, optical, magnetic, and mechanical devices can operate ultimately even at the level of a single atom or molecule. As such, atomic and molecular manipulation has played an emblematic role in the development of the field of nanoscience. New methods based on the use of the scanning tunnelling microscope (STM) have been developed to characterize and manipulate all the degrees of freedom of individual atoms and molecules with an unprecedented precision. In the meantime, new concepts have emerged to design molecules and substrates having specific optical, mechanical and electronic functions, thus opening the way to the fabrication of real nano-machines. Manipulation of individual atoms and molecules has also opened up completely new areas of research and knowledge, raising fundamental questions of "Optics at the atomic scale", "Mechanics at the atomic scale", Electronics at the atomic scale", "Quantum physics at the atomic sca...

  16. Microfabricated Waveguide Atom Traps.

    Energy Technology Data Exchange (ETDEWEB)

    Jau, Yuan-Yu [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2017-09-01

    A nanoscale , microfabricated waveguide structure can in - principle be used to trap atoms in well - defined locations and enable strong photon-atom interactions . A neutral - atom platform based on this microfabrication technology will be prealigned , which is especially important for quantum - control applications. At present, there is still no reported demonstration of evanescent - field atom trapping using a microfabricated waveguide structure. We described the capabilities established by our team for future development of the waveguide atom - trapping technology at SNL and report our studies to overcome the technical challenges of loading cold atoms into the waveguide atom traps, efficient and broadband optical coupling to a waveguide, and the waveguide material for high - power optical transmission. From the atomic - physics and the waveguide modeling, w e have shown that a square nano-waveguide can be utilized t o achieve better atomic spin squeezing than using a nanofiber for first time.

  17. Progress in atomic spectroscopy

    International Nuclear Information System (INIS)

    Beyer, H.J.; Kleinpoppen, H.

    1984-01-01

    This book presents reviews by leading experts in the field covering areas of research at the forefront of atomic spectroscopy. Topics considered include the k ordering of atomic structure, multiconfiguration Hartree-Fock calculations for complex atoms, new methods in high-resolution laser spectroscopy, resonance ionization spectroscopy (inert atom detection), trapped ion spectroscopy, high-magnetic-field atomic physics, the effects of magnetic and electric fields on highly excited atoms, x rays from superheavy collision systems, recoil ion spectroscopy with heavy ions, investigations of superheavy quasi-atoms via spectroscopy of electron rays and positrons, impact ionization by fast projectiles, and amplitudes and state parameters from ion- and atom-atom excitation processes

  18. Atomic Fisher information versus atomic number

    International Nuclear Information System (INIS)

    Nagy, A.; Sen, K.D.

    2006-01-01

    It is shown that the Thomas-Fermi Fisher information is negative. A slightly more sophisticated model proposed by Gaspar provides a qualitatively correct expression for the Fisher information: Gaspar's Fisher information is proportional to the two-third power of the atomic number. Accurate numerical calculations show an almost linear dependence on the atomic number

  19. Atomic-fluorescence spectrophotometry

    International Nuclear Information System (INIS)

    Bakhturova, N.F.; Yudelevich, I.G.

    1975-01-01

    Atomic-fluorescence spectrophotometry, a comparatively new method for the analysis of trace quantities, has developed rapidly in the past ten years. Theoretical and experimental studies by many workers have shown that atomic-fluorescence spectrophotometry (AFS) is capable of achieving a better limit than atomic absorption for a large number of elements. The present review examines briefly the principles of atomic-fluorescence spectrophotometry and the types of fluorescent transition. The excitation sources, flame and nonflame atomizers, used in AFS are described. The limits of detection achieved up to the present, using flame and nonflame methods of atomization are given

  20. Transfer Pricing

    DEFF Research Database (Denmark)

    Rohde, Carsten; Rossing, Christian Plesner

    trade internally as the units have to decide what prices should be paid for such inter-unit transfers. One important challenge is to uncover the consequences that different transfer prices have on the willingness in the organizational units to coordinate activities and trade internally. At the same time...... the determination of transfer price will affect the size of the profit or loss in the organizational units and thus have an impact on the evaluation of managers‟ performance. In some instances the determination of transfer prices may lead to a disagreement between coordination of the organizational units...

  1. The role of the International Atomic Energy Agency in technology transfer for the peaceful use of nuclear energy and the strengthening of the Safeguards system, Brasilia, 16 December 1998

    International Nuclear Information System (INIS)

    ElBaradei, M.

    1998-01-01

    The document reproduces the text of the conference given by the Director General of the IAEA at the Diplomatic Academy of the Ministry of Foreign Affairs of Brazil in Brasilia on 16 December 1998. After a short presentation of Brazil's participation in all aspects of the work of the Agency, the conference focuses on the Agency's role in the following areas: verification and the strengthened safeguards system (including future prospects of verification), technology transfer (mainly through the Technical Co-operation Programme), and nuclear power and sustainable energy development, including nuclear safety aspects

  2. Triple differential cross section for angle, atomic number and energy (or angular momentum transfer) calculated for the 280MeV 40Ar+58Ni (or 365 MeV 63Cu+197Au) system in a simple model

    International Nuclear Information System (INIS)

    Berlanger, M.; Grange, P.; Richert, J.; Hofmann, H.; Ngo, C.

    1978-01-01

    A dynamical model including both dissipation and statistical fluctuations is applied to the computation of triple differential cross sections for deep inelastic reactions. It is seen that for different Z values the overall pattern of the cross section (calculated, for the 280 MeV 40 Ar+ 58 Ni system) as a function of E and theta is fairly well reproduced - the mean angular momentum transfer for the 365MeV 63 Cu+ 197 Au system is calculated and compared with γ-multiplicity measurements. In both applications, possible implications of the remaining discrepancies are discussed

  3. Ligand effects on single-electron transfer of isolated iron atoms in the gaseous complexes [(OC)(m)Fe(OH2)(n)](+) (m, n=0-2, m plus n=1, 2)

    Czech Academy of Sciences Publication Activity Database

    Karlický, F.; Otyepka, M.; Schröder, Detlef

    2012-01-01

    Roč. 330, 15 Dec (2012), s. 95-99 ISSN 1387-3806 R&D Projects: GA ČR GBP208/12/G016 Grant - others:GA ČR(CZ) GPP208/11/P463; European Regional Development Fund(XE) CZ.1.05/2.1.00/03.0058; GA MŠk(CZ) EE2.3.20.0017 Program:EE Institutional support: RVO:61388963 Keywords : electron transfer * iron carbonyl * microhydration * neutralization-reionization mass * spectrometry * redox transitions Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.142, year: 2012

  4. The role of the International Atomic Energy Agency in technology transfer for the peaceful use of nuclear energy and the strengthening of the Safeguards system, Santiago, 9 December 1998

    International Nuclear Information System (INIS)

    ElBaradei, M.

    1998-01-01

    The document reproduces the text of the conference given by the Director General of the IAEA at the IAEA national seminar on 'Nuclear Development and its Implications for Chilean International Policy' in Santiago, Chile, on 9 December 1998. After a short presentation of Chile's participation in all aspects of the work of the Agency, the conference focuses on the Agency's role in the following areas: technology transfer with emphasis on Agency's Technical Co-operation Programme, nuclear power and sustainable energy development, including nuclear safety aspects, and the strengthened safeguards system, including future prospects of verification

  5. The role of the International Atomic Energy Agency in technology transfer for the peaceful use of nuclear energy and the strengthening of the Safeguards system, Buenos Aires, 15 December 1998

    International Nuclear Information System (INIS)

    ElBaradei, M.

    1998-01-01

    The document reproduces the text of the conference given by the Director General of the IAEA at the meeting of the Council for International Relations in Buenos Aires, Argentina, on 15 December 1998. After a short presentation of Argentina's participation in all aspects of the work of the Agency, the conference focuses on the Agency's role in the following areas: nuclear power and sustainable energy development, including nuclear safety aspects, verification and the strengthened safeguards system (including future prospects of verification), and technology transfer with emphasis on Agency's Technical Co-operation Programme

  6. Spectroscopic studies of hydrogen atom and molecule collisions: Performance report

    International Nuclear Information System (INIS)

    Kielkopf, J.

    1986-01-01

    This research is concerned with spectroscopic measurements of collisions in atomic and molecular hydrogen in order to clarify the basic physical processes that take place during radiative collisions and to provide experimental values for systems where the theoretical analysis is tractable. To this end, we proposed to measure from the cores to the far wings the profiles of the spectral lines of atomic hydrogen broadened by molecular hydrogen and noble gases, and to study energy transfer in the atom and molecule

  7. Emission spectrum of a harmonically trapped Λ-type three-level atom

    International Nuclear Information System (INIS)

    Guo Hong; Tang Pei

    2013-01-01

    We theoretically investigate the emission spectrum for a Λ-type three-level atom trapped in the node of a standing wave. We show that the atomic center-of-mass motion not only directly affects the peak number, peak position, and peak height in the atomic emission spectrum, but also influences the effects of the cavity field and the atomic initial state on atomic emission spectrum. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

  8. A Single Atom Antenna

    International Nuclear Information System (INIS)

    Trinter, Florian; Williams, Joshua B; Weller, Miriam; Waitz, Markus; Pitzer, Martin; Voigtsberger, Jörg; Schober, Carl; Kastirke, Gregor; Müller, Christian; Goihl, Christoph; Burzynski, Phillip; Wiegandt, Florian; Wallauer, Robert; Kalinin, Anton; Schmidt, Lothar Ph H; Schöffler, Markus S; Jahnke, Till; Dörner, Reinhard; Chiang, Ying-Chih; Gokhberg, Kirill

    2015-01-01

    Here we demonstrate the smallest possible implementation of an antenna-receiver complex which consists of a single (helium) atom acting as the antenna and a second (neon) atom acting as a receiver. (paper)

  9. Atom chips: mesoscopic physics with cold atoms

    International Nuclear Information System (INIS)

    Krueger, P.; Wildermuth, S.; Hofferberth, S.; Haller, E.; GAllego Garcia, D.; Schmiedmayer, J.

    2005-01-01

    Full text: Cold neutral atoms can be controlled and manipulated in microscopic potentials near surfaces of atom chips. These integrated micro-devices combine the known techniques of atom optics with the capabilities of well established micro- and nanofabrication technology. In analogy to electronic microchips and integrated fiber optics, the concept of atom chips is suitable to explore the domain of mesoscopic physics with matter waves. We use current and charge carrying structures to form complex potentials with high spatial resolution only microns from the surface. In particular, atoms can be confined to an essentially one-dimensional motion. In this talk, we will give an overview of our experiments studying the manipulation of both thermal atoms and BECs on atom chips. First experiments in the quasi one-dimensional regime will be presented. These experiments profit from strongly reduced residual disorder potentials caused by imperfections of the chip fabrication with respect to previously published experiments. This is due to our purely lithographic fabrication technique that proves to be advantageous over electroplating. We have used one dimensionally confined BECs as an ultra-sensitive probe to characterize these potentials. These smooth potentials allow us to explore various aspects of the physics of degenerate quantum gases in low dimensions. (author)

  10. Quasi-atoms

    International Nuclear Information System (INIS)

    Armbruster, P.

    1976-01-01

    The concept of a quasi-atom is discussed, and several experiments are described in which molecular or quasi-atomic transitions have been observed. X-ray spectra are shown for these experiments in which heavy ion projectiles were incident on various targets and the resultant combined system behaved as a quasi-atom. This rapidly developing field has already given new insight into atomic collision phenomena. (P.J.S.)

  11. Energetics and dynamics of atomic uranium levels

    International Nuclear Information System (INIS)

    Miron, E.

    1978-01-01

    New methods for discovering and identifying new electronic levels of atomic uranium and measuring parameters, such as radiative lifetimes and absorption cross-sections, are described. The uranium atoms are produced within an especially designed induction-heated oven. The uranium vapor is irradiated by nitrogen laser pumped, pulsed dye lasers. The various measurements are accomplished by detection of laser induced fluorescence from selectively excited levels. 138 atomic-uranium odd levels in the region 32260-34900 cm -1 and 16 even levels in the region 49500-49900 cm -1 are reported. Unique J values are presented for 64 levels and partial assignment (two possibilities) for 42 levels. Radiative lifetimes are presented for 134 levels. Absorption cross sections were measured for 12 transitions. Isotope shifts of 17 levels are given. Cross-sections for internal excitation transfer in uranium which are induced by collisions with argon atoms, are presented for 11 levels. (author)

  12. Energy dependence of the ionization of highly excited atoms by collisions with excited atoms

    International Nuclear Information System (INIS)

    Shirai, T.; Nakai, Y.; Nakamura, H.

    1979-01-01

    Approximate analytical expressions are derived for the ionization cross sections in the high- and low-collision-energy limits using the improved impulse approximation based on the assumption that the electron-atom inelastic-scattering amplitude is a function only of the momentum transfer. Both cases of simultaneous excitation and de-excitation of one of the atoms are discussed. The formulas are applied to the collisions between two excited hydrogen atoms and are found very useful for estimating the cross sections in the wide range of collisions energies

  13. Super-Coulombic atom-atom interactions in hyperbolic media

    Science.gov (United States)

    Cortes, Cristian L.; Jacob, Zubin

    2017-01-01

    Dipole-dipole interactions, which govern phenomena such as cooperative Lamb shifts, superradiant decay rates, Van der Waals forces and resonance energy transfer rates, are conventionally limited to the Coulombic near-field. Here we reveal a class of real-photon and virtual-photon long-range quantum electrodynamic interactions that have a singularity in media with hyperbolic dispersion. The singularity in the dipole-dipole coupling, referred to as a super-Coulombic interaction, is a result of an effective interaction distance that goes to zero in the ideal limit irrespective of the physical distance. We investigate the entire landscape of atom-atom interactions in hyperbolic media confirming the giant long-range enhancement. We also propose multiple experimental platforms to verify our predicted effect with phonon-polaritonic hexagonal boron nitride, plasmonic super-lattices and hyperbolic meta-surfaces as well. Our work paves the way for the control of cold atoms above hyperbolic meta-surfaces and the study of many-body physics with hyperbolic media.

  14. Atomic Energy Control Act

    International Nuclear Information System (INIS)

    1970-01-01

    This act provides for the establishment of the Atomic Energy Control Board. The board is responsible for the control and supervision of the development, application and use of atomic energy. The board is also considered necessary to enable Canada to participate effectively in measures of international control of atomic energy

  15. Atomic Spectra Database (ASD)

    Science.gov (United States)

    SRD 78 NIST Atomic Spectra Database (ASD) (Web, free access)   This database provides access and search capability for NIST critically evaluated data on atomic energy levels, wavelengths, and transition probabilities that are reasonably up-to-date. The NIST Atomic Spectroscopy Data Center has carried out these critical compilations.

  16. Quantum chaos in atom optics

    International Nuclear Information System (INIS)

    D'Arcy, Michael Brendan

    2002-01-01

    This thesis presents an account of experimental and numerical investigations of two quantum systems whose respective classical analogues are chaotic. These are the δ-kicked rotor, a paradigm in classical chaos theory, and the novel δ-kicked accelerator, created by application of a constant external acceleration or torque to the rotor. The experimental realisation of these systems has been achieved by the exposure of laser-cooled caesium atoms to approximate δ-kicks from a pulsed, high-intensity, vertical standing wave of laser light. Gravity's effect on the atoms can be controlled by appropriate shifting of the profile of the standing wave. Numerical simulations of the systems are based on a diffractive model of the potential's effect. Each system's dynamics are characterised by the final form of the momentum distribution and the dependence of the atoms' mean kinetic energy on the number and time period of the δ-kicks. The phenomena of dynamical localisation and quantum resonances in the δ-kicked rotor, which have no counterparts in the system's classical analogue, are observed and investigated. Similar experiments on the δ-kicked accelerator reveal the striking phenomenon of the quantum accelerator mode, in which a large momentum is transferred to a substantial fraction of the atomic ensemble. This feature, absent in the system's classical analogue, is characterised and an analytic explanation is presented. The effect on each quantum system of decoherence, introduced through spontaneous emission in the atoms, is examined and comparison is made with the results of classical simulations. While having little effect on the classical systems, the level of decoherence used is found to degrade quantum signatures of behaviour. Classical-like behaviour is, to some extent, restored, although significant quantum features remain. Possible applications of the quantum accelerator mode are discussed. These include use as a tool in atom optics and interferometry, a

  17. Atom-atom collision cascades localization

    International Nuclear Information System (INIS)

    Kirsanov, V.V.

    1980-01-01

    The presence of an impurity and thermal vibration influence on the atom-atom collision cascade development is analysed by the computer simulation method (the modificated dynamic model). It is discovered that the relatively low energetic cascades are localized with the temperature increase of an irradiated crystal. On the basis of the given effect the mechanism of splitting of the high energetic cascades into subcascades is proposed. It accounts for two factors: the primary knocked atom energy and the irradiated crystal temperature. Introduction of an impurity also localizes the cascades independently from the impurity atom mass. The cascades localization leads to intensification of the process of annealing in the cascades and reduction of the post-cascade vacancy cluster sizes. (author)

  18. Oxygen Atom Transfer Using an Iron(IV)-Oxo Embedded in a Tetracyclic N-Heterocyclic Carbene System: How Does the Reactivity Compare to Cytochrome P450 Compound I?

    Science.gov (United States)

    Cantú Reinhard, Fabián G; de Visser, Sam P

    2017-02-24

    N-Heterocyclic carbenes (NHC) are commonly featured as ligands in transition metal catalysis. Recently, a cyclic system containing four NHC groups with a central iron atom was synthesized and its iron(IV)-oxo species, [Fe IV (O)(cNHC 4 )] 2+ , was characterized. This tetracyclic NHC ligand system may give the iron(IV)-oxo species unique catalytic properties as compared to traditional non-heme and heme iron ligand systems. Therefore, we performed a computational study on the structure and reactivity of the [Fe IV (O)(cNHC 4 )] 2+ complex in substrate hydroxylation and epoxidation reactions. The reactivity patterns are compared with cytochrome P450 Compound I and non-heme iron(IV)-oxo models and it is shown that the [Fe IV (O)(cNHC 4 )] 2+ system is an effective oxidant with oxidative power analogous to P450 Compound I. Unfortunately, in polar solvents, a solvent molecule will bind to the sixth ligand position and decrease the catalytic activity of the oxidant. A molecular orbital and valence bond analysis provides insight into the origin of the reactivity differences and makes predictions of how to further exploit these systems in chemical catalysis. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Formation of excited hydrogen atoms by charge transfer and dissociation. Progress report No. 12, December 1, 1975--November 1, 1976. [Summaries of research activities at Georgia Institute of Technology

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, E.W.; Rausch, E.O.; Harriss, J.E.; Bell, J.T.

    1976-11-01

    The scattering of energetic hydrogenic ions from surfaces was investigated. Protons at energies 1 to 30 keV are incident on metal surfaces and studies made of the charge state and excited state fractions of the scattered particles; measurements are also made of angular distributions and velocity spectra. The excited state distribution of back-scattered atoms is found to be governed by Auger de-excitation at the surface. Molecular hydrogen ions (H/sup +//sub 2/ and H/sup +//sub 3/) incident on metal surfaces dissociate on impact and the subsequent behavior of the fragments is uncorrelated. Contamination of metal surfaces with oxygen causes an increase in the backscattered flux of excited particles related to changes in the Auger de-excitation rate. A study of charge state distributions and angular distribution of the backscattered flux has disclosed irregularities related to methods of surface preparation. Measured backscattering coefficients have been compared with theoretical calculations of McCracken and Freeman. A limited study was made of the Mossbauer spectra of Fe after H/sup +/ bombardment. Substantial (1 percent) changes to the hyperfine field occur and anneal out after a period of some days at room temperature. It is suggested that the changes to hyperfine field are related to vacancy formation. A list of publications is included.

  20. "Transfer Shock" or "Transfer Ecstasy?"

    Science.gov (United States)

    Nickens, John M.

    The alleged characteristic drop in grade point average (GPA) of transfer students and the subsequent rise in GPA was investigated in this study. No statistically significant difference was found in first term junior year GPA between junior college transfers and native Florida State University students after the variance accounted for by the…

  1. Symmetric charge transfer cross section of uranium

    International Nuclear Information System (INIS)

    Shibata, Takemasa; Ogura, Koichi

    1995-03-01

    Symmetric charge transfer cross section of uranium was calculated under consideration of reaction paths. In the charge transfer reaction a d 3/2 electron in the U atom transfers into the d-electron site of U + ( 4 I 9/2 ) ion. The J value of the U atom produced after the reaction is 6, 5, 4 or 3, at impact energy below several tens eV, only resonant charge transfer in which the product atom is ground state (J=6) takes place. Therefore, the cross section is very small (4-5 x 10 -15 cm 2 ) compared with that considered so far. In the energy range of 100-1000eV the cross section increases with the impact energy because near resonant charge transfer in which an s-electron in the U atom transfers into the d-electron site of U + ion. Charge transfer cross section between U + in the first excited state (289 cm -1 ) and U in the ground state was also obtained. (author)

  2. Modification of Ni-Rich FCG NMC and NCA Cathodes by Atomic Layer Deposition: Preventing Surface Phase Transitions for High-Voltage Lithium-Ion Batteries

    Science.gov (United States)

    Mohanty, Debasish; Dahlberg, Kevin; King, David M.; David, Lamuel A.; Sefat, Athena S.; Wood, David L.; Daniel, Claus; Dhar, Subhash; Mahajan, Vishal; Lee, Myongjai; Albano, Fabio

    2016-05-01

    The energy density of current lithium-ion batteries (LIBs) based on layered LiMO2 cathodes (M = Ni, Mn, Co: NMC; M = Ni, Co, Al: NCA) needs to be improved significantly in order to compete with internal combustion engines and allow for widespread implementation of electric vehicles (EVs). In this report, we show that atomic layer deposition (ALD) of titania (TiO2) and alumina (Al2O3) on Ni-rich FCG NMC and NCA active material particles could substantially improve LIB performance and allow for increased upper cutoff voltage (UCV) during charging, which delivers significantly increased specific energy utilization. Our results show that Al2O3 coating improved the NMC cycling performance by 40% and the NCA cycling performance by 34% at 1 C/-1 C with respectively 4.35 V and 4.4 V UCV in 2 Ah pouch cells. High resolution TEM/SAED structural characterization revealed that Al2O3 coatings prevented surface-initiated layered-to-spinel phase transitions in coated materials which were prevalent in uncoated materials. EIS confirmed that Al2O3-coated materials had significantly lower increase in the charge transfer component of impedance during cycling. The ability to mitigate degradation mechanisms for Ni-rich NMC and NCA illustrated in this report provides insight into a method to enable the performance of high-voltage LIBs.

  3. Radical Chemistry and Charge Manipulation with an Atomic Force Microscope

    Science.gov (United States)

    Gross, Leo

    The fuctionalization of tips by atomic manipulation dramatically increased the resolution of atomic force microscopy (AFM). The combination of high-resolution AFM with atomic manipulation now offers the unprecedented possibility to custom-design individual molecules by making and breaking bonds with the tip of the microscope and directly characterizing the products on the atomic scale. We recently applied this technique to generate and study reaction intermediates and to investigate chemical reactions trigged by atomic manipulation. We formed diradicals by dissociating halogen atoms and then reversibly triggered ring-opening and -closing reactions via atomic manipulation, allowing us to switch and control the molecule's reactivity, magnetic and optical properties. Additional information about charge states and charge distributions can be obtained by Kelvin probe force spectroscopy. On multilayer insulating films we investigated single-electron attachment, detachment and transfer between individual molecules. EU ERC AMSEL (682144), EU project PAMS (610446).

  4. Tightly confined atoms in optical dipole traps

    International Nuclear Information System (INIS)

    Schulz, M.

    2002-12-01

    This thesis reports on the design and setup of a new atom trap apparatus, which is developed to confine few rubidium atoms in ultrahigh vacuum and make them available for controlled manipulations. To maintain low background pressure, atoms of a vapour cell are transferred into a cold atomic beam by laser cooling techniques, and accumulated by a magneto-optic trap (MOT) in a separate part of the vacuum system. The laser cooled atoms are then transferred into dipole traps made of focused far-off-resonant laser fields in single- or crossed-beam geometry, which are superimposed with the center of the MOT. Gaussian as well as hollow Laguerre-Gaussian (LG$ ( 01)$) beam profiles are used with red-detuned or blue-detuned light, respectively. Microfabricated dielectric phase objects allow efficient and robust mode conversion of Gaussian into Laguerre-Gaussian laser beams. Trap geometries can easily be changed due to the highly flexible experimental setup. The dipole trap laser beams are focused to below 10 microns at a power of several hundred milliwatts. Typical trap parameters, at a detuning of several ten nanometers from the atomic resonance, are trag depths of few millikelvin, trap frequencies near 30-kHz, trap light scattering rates of few hundred photons per atom and second, and lifetimes of several seconds. The number of dipole-trapped atoms ranges from more than ten thousand to below ten. The dipole-trapped atoms are detected either by a photon counting system with very efficient straylight discrimination, or by recapture into the MOT, which is imaged onto a sensitive photodiode and a CCD-camera. Due to the strong AC-Stark shift imposed by the high intensity trapping light, energy-selective resonant excitation and detection of the atoms is possible. The measured energy distribution is consistent with a harmonic potential shape and allows the determination of temperatures and heating rates. In first measurements, the thermal energy is found to be about 10 % of the

  5. Station Transfers

    Data.gov (United States)

    Department of Homeland Security — ixed rail transit external system transfers for systems within the Continental United States, Alaska, Hawaii, the District of Columbia, and Puerto Rico. The modes of...

  6. Technology transfer

    International Nuclear Information System (INIS)

    1998-01-01

    On the base of technological opportunities and of the environmental target of the various sectors of energy system this paper intend to conjugate the opportunity/objective with economic and social development through technology transfer and information dissemination [it

  7. Atomic collisions research with excited atomic species

    International Nuclear Information System (INIS)

    Hoogerland, M.D.; Gulley, R.J.; Colla, M.; Lu, W.; Milic, D.; Baldwin, K.G.H.; Buckman, S.J.

    1999-01-01

    Measurements and calculations of fundamental atomic collision and spectroscopic properties such as collision cross sections, reaction rates, transition probabilities etc. underpin the understanding and operation of many plasma and gas-discharge-based devices and phenomena, for example plasma processing and deposition. In almost all cases the complex series of reactions which sustains the discharge or plasma, or produces the reactive species of interest, has a precursor electron impact excitation, attachment, dissociation or ionisation event. These processes have been extensively studied in a wide range of atomic and molecular species and an impressive data base of collision cross sections and reaction rates now exists. However, most of these measurements are for collisions with stable atomic or molecular species which are initially in their ground electronic state. Relatively little information is available for scattering from excited states or for scattering from unstable molecular radicals. Examples of such species would be metastable excited rare gases, which are often used as buffer gases, or CF 2 radicals formed by electron impact dissociation in a CF 4 plasma processing discharge. We are interested in developing experimental techniques which will enable the quantitative study of such exotic atomic and molecular species. In this talk I would like to outline one such facility which is being used for studies of collisions with metastable He(2 3 S) atoms

  8. Atoms - molecules - nuclei. Vol. 1

    International Nuclear Information System (INIS)

    Otter, G.; Honecker, R.

    1993-01-01

    This first volume covers the following topics: Wave-particle dualism, classical atomic physics; the Schroedinger equation, angular momentum in quantum physics, one-electron atoms and many-electron atoms with atomic structure, atomic spectra, exotic atoms, influence of electric and magnetic fields

  9. Modern atomic physics

    CERN Document Server

    Natarajan, Vasant

    2015-01-01

    Much of our understanding of physics in the last 30-plus years has come from research on atoms, photons, and their interactions. Collecting information previously scattered throughout the literature, Modern Atomic Physics provides students with one unified guide to contemporary developments in the field. After reviewing metrology and preliminary material, the text explains core areas of atomic physics. Important topics discussed include the spontaneous emission of radiation, stimulated transitions and the properties of gas, the physics and applications of resonance fluorescence, coherence, cooling and trapping of charged and neutral particles, and atomic beam magnetic resonance experiments. Covering standards, a different way of looking at a photon, stimulated radiation, and frequency combs, the appendices avoid jargon and use historical notes and personal anecdotes to make the topics accessible to non-atomic physics students. Written by a leader in atomic and optical physics, this text gives a state-of-the...

  10. Metal atom oxidation laser

    International Nuclear Information System (INIS)

    Jensen, R.J.; Rice, W.W.; Beattie, W.H.

    1975-01-01

    A chemical laser which operates by formation of metal or carbon atoms and reaction of such atoms with a gaseous oxidizer in an optical resonant cavity is described. The lasing species are diatomic or polyatomic in nature and are readily produced by exchange or other abstraction reactions between the metal or carbon atoms and the oxidizer. The lasing molecules may be metal or carbon monohalides or monoxides

  11. Advances in atomic spectroscopy

    CERN Document Server

    Sneddon, J

    1997-01-01

    This series describes selected advances in the area of atomic spectroscopy. It is primarily intended for the reader who has a background in atmoic spectroscopy; suitable to the novice and expert. Although a widely used and accepted method for metal and non-metal analysis in a variety of complex samples, Advances in Atomic Spectroscopy covers a wide range of materials. Each Chapter will completely cover an area of atomic spectroscopy where rapid development has occurred.

  12. Economical Atomic Layer Deposition

    Science.gov (United States)

    Wyman, Richard; Davis, Robert; Linford, Matthew

    2010-10-01

    Atomic Layer Deposition is a self limiting deposition process that can produce films at a user specified height. At BYU we have designed a low cost and automated atomic layer deposition system. We have used the system to deposit silicon dioxide at room temperature using silicon tetrachloride and tetramethyl orthosilicate. Basics of atomic layer deposition, the system set up, automation techniques and our system's characterization are discussed.

  13. Atomic physics made clear

    International Nuclear Information System (INIS)

    Meinhold, H.

    1980-01-01

    This book is a popular introduction into the foundations of atomic physics und quantum mechanics. Starting from some phenomenological concepts Bohr's model and the construction of the periodic system regarding the shell structure of atoms are introduced. In this framework the selection rules and magnetic moments of atomic electrons are considered. Finally the wave-particle dualism is considered. In the appendix some mathematical methods are described which are useful for a deeper penetration into the considered ideas. (HSI)

  14. Radiative transfer in molecular lines

    Science.gov (United States)

    Asensio Ramos, A.; Trujillo Bueno, J.; Cernicharo, J.

    2001-07-01

    The highly convergent iterative methods developed by Trujillo Bueno and Fabiani Bendicho (1995) for radiative transfer (RT) applications are generalized to spherical symmetry with velocity fields. These RT methods are based on Jacobi, Gauss-Seidel (GS), and SOR iteration and they form the basis of a new NLTE multilevel transfer code for atomic and molecular lines. The benchmark tests carried out so far are presented and discussed. The main aim is to develop a number of powerful RT tools for the theoretical interpretation of molecular spectra.

  15. Propagation of frequency-chirped laser pulses in a medium of atoms with a Λ-level scheme

    International Nuclear Information System (INIS)

    Demeter, G.; Dzsotjan, D.; Djotyan, G. P.

    2007-01-01

    We study the propagation of frequency-chirped laser pulses in optically thick media. We consider a medium of atoms with a Λ level-scheme (Lambda atoms) and also, for comparison, a medium of two-level atoms. Frequency-chirped laser pulses that induce adiabatic population transfer between the atomic levels are considered. They induce transitions between the two lower (metastable) levels of the Λ-atoms and between the ground and excited states of the two-level atoms. We show that associated with this adiabatic population transfer in Λ-atoms, there is a regime of enhanced transparency of the medium--the pulses are distorted much less than in the medium of two-level atoms and retain their ability to transfer the atomic population much longer during propagation

  16. Deeply bound pionic atom

    International Nuclear Information System (INIS)

    Toki, Hiroshi; Yamazaki, Toshimitsu

    1989-01-01

    The standard method of pionic atom formation does not produce deeply bound pionic atoms. A study is made on the properties of deeply bound pionic atom states by using the standard pion-nucleus optical potential. Another study is made to estimate the cross sections of the formation of ls pionic atom states by various methods. The pion-nucleus optical potential is determined by weakly bound pionic atom states and pion nucleus scattering. Although this potential may not be valid for deeply bound pionic atoms, it should provide some hint on binding energies and level widths of deeply bound states. The width of the ls state comes out to be 0.3 MeV and is well separated from the rest. The charge dependence of the ls state is investigated. The binding energies and the widths increase linearly with Z azbove a Z of 30. The report then discusses various methods to populate deeply bound pionic atoms. In particular, 'pion exchange' reactions are proposed. (n, pπ) reaction is discussed first. The cross section is calculated by assuming the in- and out-going nucleons on-shell and the produced pion in (n1) pionic atom states. Then, (n, dπ - ) cross sections are estimated. (p, 2 Heπ - ) reaction would have cross sections similar to the cross section of (n, dπ - ) reaction. In conclusion, it seems best to do (n, p) experiment on heavy nuclei for deeply bound pionic atom. (Nogami, K.)

  17. Single atom oscillations

    International Nuclear Information System (INIS)

    Wiorkowski, P.; Walther, H.

    1990-01-01

    Modern methods of laser spectroscopy allow the study of single atoms or ions in an unperturbed environment. This has opened up interesting new experiments, among them the detailed study of radiation-atom coupling. In this paper, the following two experiments dealing with this problem are reviewed: the single-atom maser and the study of the resonance fluorescence of a single stored ion. The simplest and most fundamental system for studying radiation-matter coupling is a single two-level atom interacting with a single mode of an electromagnetic field in a cavity. This problem received a great deal of attention shortly after the maser was invented

  18. Atomic hydrogen reactor

    International Nuclear Information System (INIS)

    Massip de Turville, C.M.D.

    1982-01-01

    Methods are discussed of generating heat in an atomic hydrogen reactor which involve; the production of atomic hydrogen by an electrical discharge, the capture of nascent neutrons from atomic hydrogen in a number of surrounding steel alloy tubes having a high manganese content to produce 56 Mn, the irradiation of atomic hydrogen by the high energy antineutrinos from the beta decay of 56 Mn to yield nascent neutrons, and the removal of the heat generated by the capture of nascent neutrons by 55 Mn and the beta decay of 56 Mn. (U.K.)

  19. Technology Transfer

    Science.gov (United States)

    Smith, Nanette R.

    1995-01-01

    The objective of this summer's work was to attempt to enhance Technology Application Group (TAG) ability to measure the outcomes of its efforts to transfer NASA technology. By reviewing existing literature, by explaining the economic principles involved in evaluating the economic impact of technology transfer, and by investigating the LaRC processes our William & Mary team has been able to lead this important discussion. In reviewing the existing literature, we identified many of the metrics that are currently being used in the area of technology transfer. Learning about the LaRC technology transfer processes and the metrics currently used to track the transfer process enabled us to compare other R&D facilities to LaRC. We discuss and diagram impacts of technology transfer in the short run and the long run. Significantly, it serves as the basis for analysis and provides guidance in thinking about what the measurement objectives ought to be. By focusing on the SBIR Program, valuable information regarding the strengths and weaknesses of this LaRC program are to be gained. A survey was developed to ask probing questions regarding SBIR contractors' experience with the program. Specifically we are interested in finding out whether the SBIR Program is accomplishing its mission, if the SBIR companies are providing the needed innovations specified by NASA and to what extent those innovations have led to commercial success. We also developed a survey to ask COTR's, who are NASA employees acting as technical advisors to the SBIR contractors, the same type of questions, evaluating the successes and problems with the SBIR Program as they see it. This survey was developed to be implemented interactively on computer. It is our hope that the statistical and econometric studies that can be done on the data collected from all of these sources will provide insight regarding the direction to take in developing systematic evaluations of programs like the SBIR Program so that they can

  20. Atom dynamics in laser fields

    International Nuclear Information System (INIS)

    Jang, Su; Mi, No Gin

    2004-12-01

    This book introduces coherent dynamics of internal state, spread of atoms wave speed, semiclassical atoms density matrix such as dynamics equation in both still and moving atoms, excitation of atoms in movement by light, dipole radiating power, quantum statistical mechanics by atoms in movement, semiclassical atoms in movement, atoms in movement in the uniform magnetic field including effects of uniform magnetic field, atom cooling using laser such as Doppler cooling, atom traps using laser and mirrors, radiant heat which particles receive, and near field interactions among atoms in laser light.

  1. Laser induced energy transfer

    International Nuclear Information System (INIS)

    Falcone, R.W.

    1979-01-01

    Two related methods of rapidly transferring stored energy from one excited chemical species to another are described. The first of these, called a laser induced collision, involves a reaction in which the energy balance is met by photons from an intense laser beam. A collision cross section of ca 10 - 17 cm 2 was induced in an experiment which demonstrated the predicted dependence of the cross section on wavelength and power density of the applied laser. A second type of laser induced energy transfer involves the inelastic scattering of laser radiation from energetically excited atoms, and subsequent absorption of the scattered light by a second species. The technique of producing the light, ''anti-Stokes Raman'' scattering of visible and infrared wavelength laser photons, is shown to be an efficient source of narrow bandwidth, high brightness, tunable radiation at vacuum ultraviolet wavelengths by using it to excite a rare gas transition at 583.7 A. In addition, this light source was used to make the first measurement of the isotopic shift of the helium metastable level at 601 A. Applications in laser controlled chemistry and spectroscopy, and proposals for new types of lasers using these two energy transfer methods are discussed

  2. Atoms stories; Histoire d`atomes

    Energy Technology Data Exchange (ETDEWEB)

    Radvanyi, P; Bordry, M [Centre National de la Recherche Scientifique (CNRS), 75 - Paris (France)

    1988-12-31

    Physicists from different countries told each evening during one learning week, to an audience of young people, some great discoveries in evoking the difficulties and problems to which the researchers were confronted. From Antiquity to a more recent history, it is a succession of atoms stories. (N.C.)

  3. Low energy atom-atom collisions

    International Nuclear Information System (INIS)

    Child, M.S.

    1980-01-01

    The semiclassical theory of atom-atom potential scattering and of low energy inelastic atom-atom scattering is reviewed. Particular attention is given to the origin and interpretation of rainbow structure, diffraction oscillations and exchange oscillations in the potential scattering differential cross-section, and to the glory structure and symmetry oscillations in the integral cross-section. Available methods for direct inversion of the cross-section data to recover the potential are reviewed in some detail. The theory of non-adiabatic transitions is introduced by a short discussion of interaction mechanisms and of diabetic and adiabatic representations. Analytical S matrix elements are presented for two state curve-crossing (Landau-Zener-Stuckelberg), Demkov and Nikitin models. The relation between Stuckelberg oscillations in the S matrix and in the differential cross-section is discussed in terms of interference between trajectories belonging to two different classical deflection functions. The energy dependences of the inelastic integral cross-section for curve-crossing and Demkov type transitions are also discussed. Finally the theory is reviewed in relation to a recent close-coupled study of fine structure transitions in F( 2 P) + Xe( 2 S) scattering

  4. Atoms, Molecules, and Compounds

    CERN Document Server

    Manning, Phillip

    2007-01-01

    Explores the atoms that govern chemical processes. This book shows how the interactions between simple substances such as salt and water are crucial to life on Earth and how those interactions are predestined by the atoms that make up the molecules.

  5. Atomic Energy Control Board

    International Nuclear Information System (INIS)

    Blackman, N.S.; Gummer, W.K.

    1982-02-01

    This paper has been prepared to provide an overview of the responsibilities and activities of the Atomic Energy Control Board. It is designed to address questions that are often asked concerning the establishment of the Atomic Energy Control Board, its enabling legislation, licensing and compliance activities, federal-provincial relationships, international obligations, and communications with the public

  6. mu. -nucleon atoms

    Energy Technology Data Exchange (ETDEWEB)

    Dobretsov, Yu; Dolgoshein, B; Kirillov-Ugryumov, V

    1980-12-01

    The properties and formation are described of ..mu..-nucleon atoms, the Larmor method of muon spin precession is discussed and the experimental confirmation of the existence of ..mu..-nucleon atoms is shown. The prospects of their use are indicated.

  7. μ-nucleon atoms

    International Nuclear Information System (INIS)

    Dobretsov, Yu.; Dolgoshejn, B.; Kirillov-Ugryumov, V.

    1980-01-01

    The properties and formation are described of μ-nucleon atoms, the Larmor method of muon spin precession is discussed and the experimental confirmation of the existence of μ-nucleon atoms is shown. The prospects of their use are indicated. (J.P.)

  8. Atomic Ferris wheel beams

    Science.gov (United States)

    Lembessis, Vasileios E.

    2017-07-01

    We study the generation of atom vortex beams in the case where a Bose-Einstein condensate, released from a trap and moving in free space, is diffracted from a properly tailored light mask with a spiral transverse profile. We show how such a diffraction scheme could lead to the production of an atomic Ferris wheel beam.

  9. Atom lithography of Fe

    NARCIS (Netherlands)

    Sligte, te E.; Smeets, B.; van der Stam, K.M.R.; Herfst, R.W.; Straten, van der P.; Beijerinck, H.C.W.; Leeuwen, van K.A.H.

    2004-01-01

    Direct write atom lithography is a technique in which nearly resonant light is used to pattern an atom beam. Nanostructures are formed when the patterned beam falls onto a substrate. We have applied this lithography scheme to a ferromagnetic element, using a 372 nm laser light standing wave to

  10. Beyond the Atom

    Science.gov (United States)

    Cox, John

    2011-08-01

    1. Introduction - the atom in the seventies; 2. The vacuum tube; 3. The new rays; 4. The new substances; 5. Disintegration; 6. A family tree; 7. Verifications and results; 8. The objective reality of molecules; 9. The new atom; Bibliography; Index.

  11. When Atoms Want

    Science.gov (United States)

    Talanquer, Vicente

    2013-01-01

    Chemistry students and teachers often explain the chemical reactivity of atoms, molecules, and chemical substances in terms of purposes or needs (e.g., atoms want or need to gain, lose, or share electrons in order to become more stable). These teleological explanations seem to have pedagogical value as they help students understand and use…

  12. Atom electron scattering

    International Nuclear Information System (INIS)

    Santoso, B.

    1976-01-01

    Green Lippmann-Schwinger functions operator representations, derivation of perturbation method using Green function and atom electron scattering, are discussed. It is concluded that by using complex coordinate places where resonances occur, can be accurately identified. The resonance can be processed further for practical purposes, for example for the separation of atom. (RUW)

  13. Atomic energy for progress

    International Nuclear Information System (INIS)

    1974-01-01

    The film discusses the functions and activities of the Philippine Atomic Energy Commission. Shown are the applications of atomic energy in research, agriculture, engineering, industry and medicine, as well as the construction of the research reactor and its inauguration by President Marcos

  14. Zeeman atomic absorption spectroscopy

    International Nuclear Information System (INIS)

    Loos-Vollebregt, M.T.C. de.

    1980-01-01

    A new method of background correction in atomic absorption spectroscopy has recently been introduced, based on the Zeeman splitting of spectral lines in a magnetic field. A theoretical analysis of the background correction capability observed in such instruments is presented. A Zeeman atomic absorption spectrometer utilizing a 50 Hz sine wave modulated magnetic field is described. (Auth.)

  15. Isotopes and atomic weights

    International Nuclear Information System (INIS)

    Zhang Qinglian

    1990-01-01

    A review of the chemical and mass spectrometric methods of determining the atomic weights of elements is presented. A, special discussion is devoted to the calibration of the mass spectrometer with highly enriched isotopes. It is illustrated by the recent work on europium. How to choose the candidate element for new atomic weight determination forms the last section of the article

  16. Quantum network with individual atoms and photons

    International Nuclear Information System (INIS)

    Rempe, G.

    2013-01-01

    Quantum physics allows a new approach to information processing. A grand challenge is the realization of a quantum network for long-distance quantum communication and large-scale quantum simulation. This paper highlights a first implementation of an elementary quantum network with two fibre-linked high-finesse optical resonators, each containing a single quasi-permanently trapped atom as a stationary quantum node. Reversible quantum state transfer between the two atoms and entanglement of the two atoms are achieved by the controlled exchange of a time-symmetric single photon. This approach to quantum networking is efficient and offers a clear perspective for scalability. It allows for arbitrary topologies and features controlled connectivity as well as, in principle, infinite-range interactions. Our system constitutes the largest man-made material quantum system to date and is an ideal test bed for fundamental investigations, e.g. quantum non-locality. (authors)

  17. Technology transfer

    International Nuclear Information System (INIS)

    Boury, C.

    1986-01-01

    This paper emphasizes in the specific areas of design, engineering and component production. This paper presents what Framatome has to offer in these areas and its export oriented philosophy. Then, a typical example of this technology transfer philosophy is the collaboration with the South Korean firm, Korea Heavy Industries Corporation (KHIC) for the supply of KNU 9 and KNU 10 power stations

  18. Atomic diffusion in stars

    CERN Document Server

    Michaud, Georges; Richer, Jacques

    2015-01-01

    This book gives an overview of atomic diffusion, a fundamental physical process, as applied to all types of stars, from the main sequence to neutron stars. The superficial abundances of stars as well as their evolution can be significantly affected. The authors show where atomic diffusion plays an essential role and how it can be implemented in modelling.  In Part I, the authors describe the tools that are required to include atomic diffusion in models of stellar interiors and atmospheres. An important role is played by the gradient of partial radiative pressure, or radiative acceleration, which is usually neglected in stellar evolution. In Part II, the authors systematically review the contribution of atomic diffusion to each evolutionary step. The dominant effects of atomic diffusion are accompanied by more subtle effects on a large number of structural properties throughout evolution. One of the goals of this book is to provide the means for the astrophysicist or graduate student to evaluate the importanc...

  19. Theoretical atomic physics

    CERN Document Server

    Friedrich, Harald

    2017-01-01

    This expanded and updated well-established textbook contains an advanced presentation of quantum mechanics adapted to the requirements of modern atomic physics. It includes topics of current interest such as semiclassical theory, chaos, atom optics and Bose-Einstein condensation in atomic gases. In order to facilitate the consolidation of the material covered, various problems are included, together with complete solutions. The emphasis on theory enables the reader to appreciate the fundamental assumptions underlying standard theoretical constructs and to embark on independent research projects. The fourth edition of Theoretical Atomic Physics contains an updated treatment of the sections involving scattering theory and near-threshold phenomena manifest in the behaviour of cold atoms (and molecules). Special attention is given to the quantization of weakly bound states just below the continuum threshold and to low-energy scattering and quantum reflection just above. Particular emphasis is laid on the fundamen...

  20. Antiprotonic-hydrogen atoms

    International Nuclear Information System (INIS)

    Batty, C.J.

    1989-07-01

    Experimental studies of antiprotonic-hydrogen atoms have recently made great progress following the commissioning of the low energy antiproton facility (LEAR) at CERN in 1983. At the same time our understanding of the atomic cascade has increased considerably through measurements of the X-ray spectra. The life history of the p-bar-p atom is considered in some detail, from the initial capture of the antiproton when stopping in hydrogen, through the atomic cascade with the emission of X-rays, to the final antiproton annihilation and production of mesons. The experiments carried out at LEAR are described and the results compared with atomic cascade calculations and predictions of strong interaction effects. (author)