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891.
Klaus Tauer Nancy Weber Samira Nozari Klaus Padtberg Reinhard Sigel Arne Stark Antje Völkel 《Macromolecular Symposia》2009,281(1):1-13
Summary: The paper considers various possibilities to produce inorganic – polymeric nanocomposites via aqueous heterophase polymerization. Special emphasis is placed on strategies to synthesize nanocomposite particles via joint nucleation or joint polymerization. The former strategy is used to make composite particles with CaCO3 as inorganic component. The strategy of joint polymerization takes advantage from the condition that aqueous heterophase polymerization is a convenient possibility to synthesize amphiphilic block copolymers. This method relies on the fact that polymeric radicals can survive in isolated latex particles that are stabilized by hydrophilic blocks. This strategy can be successfully applied to produce silica-containing block copolymer particles in a one-step procedure. 相似文献
892.
893.
Brandon C. Bukowski Jason S. Bates Rajamani Gounder Jeffrey Greeley 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(46):16574-16578
Ab‐initio molecular dynamics simulations and transmission infrared spectroscopy are employed to characterize the structure of water networks in defect‐functionalized microporous zeolites. Thermodynamically stable phases of clustered water molecules are localized at some of the defects in zeolite Beta, which include catalytic sites such as framework Lewis acidic Sn atoms in closed and hydrolyzed‐open forms, as well as silanol nests. These water clusters compete with ideal gas‐like structures at low water densities and pore‐filling phases at higher water densities, with the equilibrium phase determined by the water chemical potential. The physical characteristics of these phases are determined by the defect identity, with the local binding and orientation of hydroxyl moieties around the defects playing a central role. The results suggest general principles for how the structure of polar solvents in microporous solid acids is influenced by local defect functionalization, and the thermodynamic stability of the condensed phases surrounding such sites, in turn, implies that the catalysis of Lewis acids will be influenced by local water ordering. 相似文献
894.
Megan MohadjerBeromi Gary W. Brudvig Nilay Hazari Hannah M. C. Lant Brandon Q. Mercado 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(18):6155-6159
A number of new transition metal catalyzed methods for the formation of C(sp2)–C(sp3) bonds have recently been described. These reactions often utilize bidentate polypyridyl‐ligated Ni catalysts, and paramagnetic NiI halide or aryl species are proposed in the catalytic cycles. However, there is little knowledge about complexes of this type. Here, we report the synthesis of paramagnetic bidentate polypyridyl‐ligated Ni halide and aryl complexes through elementary reactions proposed in catalytic cycles for C(sp2)–C(sp3) bond formation. We investigate the ability of these complexes to undergo organometallic reactions that are relevant to C(sp2)–C(sp3) coupling through stoichiometric studies and also explore their catalytic activity. 相似文献
895.
D. Brandon Magers Andrew K. Magers David H. Magers 《International journal of quantum chemistry》2019,119(8):e25864
The s-homodesmotic method for computing conventional strain energies (CSE) has been extended for the first time to bicyclic systems and to individual rings within these systems. Unique isodesmic, homodesmotic, and hyperhomodesmotic reactions originate from the s-homodesmotic method. These are used to investigate 12 bicyclic systems comprising cyclopropane and cyclobutane and how the CSE of each system compares to the sum of the individual rings within each. Equilibrium geometries, harmonic vibrational frequencies, and the corresponding electronic energies and zero point vibrational energy corrections are computed for all relevant molecules using second-order perturbation theory and density functional theory (B3LYP) with the correlation consistent basis sets cc-pVDZ and cc-pVTZ. Single-point CCSD(T) energies are computed at the MP2/cc-pVTZ optimized geometries to ascertain the importance of higher order correlation effects. Results indicate that CSEs are additive when the two rings are separated by one or two bonds and somewhat additive in other cases. 相似文献
896.
Huber M Stark WJ Loher S Maciejewski M Krumeich F Baiker A 《Chemical communications (Cambridge, England)》2005,(5):648-650
Calcium carbonate nanoparticles of 20-50 nm size were obtained from a flame spray process where combustion of specific calcium-containing precursors results in amorphous or crystalline calcium carbonate particles depending on the spray flow conditions. 相似文献
897.
Ruotolo BT Verbeck GF Thomson LM Gillig KJ Russell DH 《Journal of the American Chemical Society》2002,124(16):4214-4215
Results from ion mobility studies of tryptic peptides suggest that, in some cases, the gas-phase structures can be related to the solution-phase structure of the parent protein. The interpretation of ion mobility measurements is supported by results from molecular modeling and H/D exchange experiments on the same peptides. This study clearly illustrates the utility of IM-MS for screening complex mixtures for peptides having intrinsically stable secondary/tertiary structures, and/or posttranslational modification. 相似文献
898.
Cuneo M.E. Menge P.R. Hanson D.L. Fowler W.E. Bernard M.A. Ziska G.R. Filuk A.B. Pointon T.D. Vesey R.A. Welch D.R. Bailey J.E. Desjarlais M.P. Lockner T.R. Mehlhorn T.A. Slutz S.A. Stark M.A. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1997,25(2):229-251
Uncontrolled plasma formation on electrode surfaces limits performance in a wide variety of pulsed power devices such as electron and ion diodes, transmission lines, radio frequency (RF) cavities, and microwave devices. Surface and bulk contaminants on the electrodes in vacuum dominate the composition of these plasmas, formed through processes such as stimulated and thermal desorption followed by ionization. We are applying RF discharge cleaning, anode heating, cathode cooling, and substrate surface coatings to the control of the effects of these plasmas in the particular case of applied-B ion diodes on the SABRE (1 TW) and PBFA-X (30 TW) accelerators. Evidence shows that our LiF ion source provides a 200-700 A/cm2 lithium beam for 10-20 ns which is then replaced by a contaminant beam of protons and carbon. Other ion sources show similar behavior. Our electrode surface and substrate cleaning techniques reduce beam contamination, anode and cathode plasma formation, delay impedance collapse, and increase lithium energy, power, and production efficiency. Theoretical and simulation models of electron-stimulated and thermal-contaminant desorption leading to anode plasma formation show agreement with many features from experiment. Decrease of the diode electron loss by changing the shape and magnitude of the insulating magnetic field profiles increases the lithium output and changes the diode response to cleaning. We also show that the LiF films are permeable, allowing substrate contaminants to affect diode behavior. Substrate coatings of Ta and Au underneath the LiF film allow some measure of control of substrate contaminants, and provide direct evidence for thermal desorption. We have increased lithium current density by a factor of four and lithium energy by a factor of five through a combination of in situ surface and substrate cleaning, substrate coatings, and field profile modifications 相似文献
899.
K. A. Zaretskii has associated a lattice V(α) with each binary relation α, and he has shown that Hα is isomorphic with the group of all automorphisms of V(α) if Hα is a group. This result is extended in this paper by showing that for any binary relation α, the Schützenberger group Γ (Hα) is isomorphic with the group of all automorphisms of V(α). 相似文献
900.
Deborah Brandon Robert C. Rogers 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》1994,45(1):135-152
The research of D. Brandon was partially supported by the National Science Foundation through grant # DMS-9296011 and by the Army Research Office and the National Science Foundation through the Center for Nonlinear Analysis. 相似文献