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71.
72.
Evans DA Seidel D Rueping M Lam HW Shaw JT Downey CW 《Journal of the American Chemical Society》2003,125(42):12692-12693
A highly enantioselective, nitroaldol reaction catalyzed by a chiral Cu(II) bis(oxazoline) complex has been developed. The reaction scope includes both aromatic and aliphatic aldehydes (15 examples) affording products in good yields and enantioselectivities (87-94% ee). An X-ray structure of the catalyst has been provided along with a rationalization of the sense of asymmetric induction. 相似文献
73.
We describe the functions needed in the determination of the rate of convergence of best $L^\infty $ rational approximation to $\exp ( - x)$ on [0,∞) when the degree n of the approximation tends to ∞ (“1/9” problem). 相似文献
74.
Walter?Oelert Magnus?Wolke Pawe??Moskal COSY- collaboration at COSY-Jülich 《Czechoslovak Journal of Physics》2000,50(4):69-90
During the actual lectures, features of the COSY-Jülich accelerator were presented, followed by a short summary of ongoing experiments at the COoler SYnchrotron COSY using internal as well as external beams in the range of 45 MeV to 2.5 GeV. Here the research of the COSY-11 collaboration is presented. This °0 facility studies the hidden and open strangeness production observing the ν and η′ as well the K+Y and K+K? production in the proton—proton interactions at the respective thresholds. 相似文献
75.
76.
77.
Anisa Elhamili Magnus Wetterhall Angel Puerta Douglas Westerlund Jonas Bergquist 《Journal of chromatography. A》2009,1216(17):3613-3620
The effect of adding alkali salts to protein samples for capillary electrophoretic (CE) analysis of intact proteins was studied. A high degree of peak stacking, even for large proteins, was found to occur when alkali salts were added to the sample. The addition of salt to the protein sample promotes a strong improvement in the peak efficiency of individual proteins giving up to 2.1 × 106 apparent plates/m. The concentration of salt required in the sample to reach optimal peak efficiency show dependency on both the molecular weight and molar concentration of the protein. However, adding salt will, at a sufficiently high concentration, cause a mixture of proteins to co-migrate to one very sharp peak. The observed sample stacking effect was obtained with a number of different surface modified silica capillaries indicating a general phenomenon and not surface coating specific. 相似文献
78.
We analyse the mixing time of Markov chains using path coupling with stopping times. We apply this approach to two hypergraph problems. We show that the Glauber dynamics for independent sets in a hypergraph mixes rapidly as long as the maximum degree Δ of a vertex and the minimum size m of an edge satisfy m ≥ 2Δ + 1. We also show that the Glauber dynamics for proper q‐colorings of a hypergraph mixes rapidly if m ≥ 4 and q > Δ, and if m = 3 and q ≥ 1.65Δ. We give related results on the hardness of exact and approximate counting for both problems. © 2008 Wiley Periodicals, Inc. Random Struct. Alg., 2008 相似文献
79.
Maxwell D. Cummings Jimmy Lindberg Tse‐I Lin Herman de Kock Oliver Lenz Elisabet Lilja Sara Felländer Vera Baraznenok Susanne Nyström Magnus Nilsson Lotta Vrang Michael Edlund Åsa Rosenquist Bertil Samuelsson Pierre Raboisson Kenneth Simmen 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2010,122(19):3320-3320
80.
Cationic polyallylamine (PAH), was adsorbed onto lignocellulosic fibres, and a fluorescent label on the polyelectrolyte enabled
its location to be shown by confocal fluorescence microscopy. The adsorption time and ionic strength were varied to study
their effect on the localisation of the adsorbed PAH. The microscopy showed that a long adsorption time, 24 h, and a high
ionic strength, 10−1 M NaCl + 5 × 10−3 M NaHCO3 or higher, resulted in the adsorption of polyallylamine throughout the fibre walls. Shorter adsorption times and/or lower
ionic strength resulted in adsorption only to the fibre exterior. By preparing sheets from fibres with polyelectrolyte adsorbed
either to the exterior parts or into the fibre cell wall and testing their mechanical behaviour, a link was established between
the localisation of adsorbed polyelectrolyte and the mechanical properties. Adsorption to the fibre exterior led to an increase
in tensile strength and strain at break. The creep deformation at 90%RH was also slightly reduced by the adsorption of low
molecular weight PAH (15 kDa). When polyallylamine was adsorbed throughout the wall of the lignocellulosic fibres, the mechanical
properties were not however improved and the creep deformation at 90%RH actually increased somewhat. 相似文献