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921.
René Roy Craig A. Laferrière Apdrzej Gamian Harold J. Jennings 《Journal of carbohydrate chemistry》2013,32(1):161-165
Abstract A simplified procedure for the synthesis of acetochloroneuraminic acid is described starting from the methyl ester. N-acetyl neuraminic acid α-allyl glycoside was prepared in high yield using silver salicylate as catalyst. Reductive ozonolysis of the allyl group, followed by direct reductive ami nation to protein carriers, gave immunogenic neoglycoproteins. Copolymerization of the α-allyl glycoside with acrylamide produced a water-soluble pseudopolysaccharide useful for the EL ISA technique. 相似文献
922.
Dr. Carlos Cabezas Dr. Marcelino Varela Prof. José L. Alonso 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(23):6520-6525
Among the hundreds of peptide compounds for which conformations have been determined by using different spectroscopic techniques, the structure of the simplest dipeptide glycylglycine (Gly-Gly) is conspicuously absent. Herein, for the first time, solid samples of Gly-Gly have been vaporized by laser ablation and three different structures have been revealed in a supersonic expansion by Fourier transform microwave spectroscopy. The intramolecular hydrogen bonding interactions that stabilize the observed forms have been established based on the 14N nuclear quadrupole hyperfine structure. We have illustrated how conformer interconversion distorts the equilibrium conformational distribution, giving rise to missing conformers in the conformational landscape. 相似文献
923.
924.
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926.
Consider K ≥ 2 independent copies of the random walk on the symmetric group SN starting from the identity and generated by the products of either independent uniform transpositions or independent uniform neighbor transpositions. At any time $n\in \mathbb{N}$, let Gn be the subgroup of SN generated by the K positions of the chains. In the uniform transposition model, we prove that there is a cut‐off phenomenon at time N ln(N)/(2K) for the non‐existence of fixed point of Gn and for the transitivity of Gn, thus showing that these properties occur before the chains have reached equilibrium. In the uniform neighbor transposition model, a transition for the non‐existence of a fixed point of Gn appears at time of order $N^{1+\frac{2}{K}}$ (at least for K ≥ 3), but there is no cut‐off phenomenon. In the latter model, we recover a cut‐off phenomenon for the non‐existence of a fixed point at a time proportional to N by allowing the number K to be proportional to ln(N). The main tools of the proofs are spectral analysis and coupling techniques. © 2011 Wiley Periodicals, Inc. Random Struct. Alg., 2012 相似文献
927.
Eberhard H. Lehmann Werner Wagner 《Applied Physics A: Materials Science & Processing》2010,99(3):627-634
Neutron imaging as a method for non-destructive studies takes advantage of the alternative contrast mechanism of neutrons
compared to X-rays: most of the light elements feature high contrast, whereas heavy elements are relatively transparent to
neutrons. In the previous decade, the neutron imaging technique has made substantial progress in well-tailored and well-equipped
beam lines, in improvements of the image recording quality and efficiency by new and modern imaging techniques, and in modern
image processing tools. 相似文献
928.
Fábio Roberto Chavarette José Manoel Balthazar Nelson José Peruzzi Marat Rafikov 《Communications in Nonlinear Science & Numerical Simulation》2009,14(3):892-905
The Fitzhugh–Nagumo (FH) mathematical model is considered a simplification of the Hodgkin–Huxley (HH) model. This paper analyzes the non-linear dynamics of the Fitzhugh–Nagumo (FN) mathematical model, and still presents some modifications in the governing equations of the system in order to transform it into a non-ideal one (taking into account that an energy source has limited power supply). We also developed an optimal linear control design and used Sinhas’s theory for the membrane’s action potential in order to stabilize the variation of this potential. 相似文献
929.
Carlos Javier Villagomez Tomaso Zambelli Sébastien Gauthier André Gourdon Sladjana Stojkovic Christian Joachim 《Surface science》2009,603(10-12):1526-1532
An isomer of the methylterrylene molecule was adsorbed both on Cu(111) and on a NaCl bilayer deposited on Cu(111) and imaged by ultra high vacuum scanning tunneling microscopy at low temperature (5 K). On the bare metal surface, the STM images do not reveal any intramolecular resolution and do not depend on the applied tunnel bias. On the contrary, the images acquired at specific bias voltages for the molecule on the salt layer show a striking similarity with the spatial distribution of the electronic probability density in the highest occupied molecular orbital (HOMO) and in the lowest unoccupied molecular orbital (LUMO) of free methylterrylene. They are well reproduced by elastic scattering quantum chemistry calculations. These data provide a direct view of the hyperconjugative interaction between the methyl group and the frontier orbitals of terrylene. 相似文献
930.
Pál Perjési Gábor Maász Renáta Reisch András Benk? 《Monatshefte für Chemie / Chemical Monthly》2012,5(3):1107-1114