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91.
Unstrained cycloalkenes undergo ruthenium-catalysed ring opening-cross metathesis reactions with simple alpha, beta-unsaturated carbonyl compounds under mild conditions. 相似文献
92.
Sergiu Muncaci Carlos Mattea Siegfried Stapf Ioan Ardelean 《Magnetic resonance in chemistry : MRC》2013,51(2):123-128
Frequency‐dependent NMR relaxation studies have been carried out on water (polar) and cyclohexane (nonpolar) molecules confined inside porous ceramics containing variable amounts of iron oxide (III). The porous ceramics were prepared by compression of powders mixed with iron oxide followed by thermal treatment. The pore size distribution was estimated using a technique based on diffusion in internal fields that exposed a narrow distribution of macropore sizes with an average pore dimension independent of iron oxide content. The relaxation dispersion curves were obtained at room temperature using a fast field cycling NMR instrument. They display an increase of the relaxation rate proportional to the iron oxide concentration. This behavior is more prominent at low Larmor frequencies and is independent of the polar character of the confined molecules. The results reported here can be fitted well with a relaxation model considering exchange between molecules in the close vicinity of the paramagnetic centers located in the surface and bulk‐like molecules inside the pores. This model allows the extraction of the transverse diffusional correlation time that can be related to the polar character of the confined molecules. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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Wolfgang Dahmen Birgit Gottschlich–Müller Siegfried Müller 《Numerische Mathematik》2001,88(3):399-443
Summary. In recent years a variety of high–order schemes for the numerical solution of conservation laws has been developed. In general,
these numerical methods involve expensive flux evaluations in order to resolve discontinuities accurately. But in large parts
of the flow domain the solution is smooth. Hence in these regions an unexpensive finite difference scheme suffices. In order
to reduce the number of expensive flux evaluations we employ a multiresolution strategy which is similar in spirit to an approach
that has been proposed by A. Harten several years ago. Concrete ingredients of this methodology have been described so far
essentially for problems in a single space dimension. In order to realize such concepts for problems with several spatial
dimensions and boundary fitted meshes essential deviations from previous investigations appear to be necessary though. This
concerns handling the more complex interrelations of fluxes across cell interfaces, the derivation of appropriate evolution
equations for multiscale representations of cell averages, stability and convergence, quantifying the compression effects
by suitable adapted multiscale transformations and last but not least laying grounds for ultimately avoiding the storage of
data corresponding to a full global mesh for the highest level of resolution. The objective of this paper is to develop such
ingredients for any spatial dimension and block structured meshes obtained as parametric images of Cartesian grids. We conclude
with some numerical results for the two–dimensional Euler equations modeling hypersonic flow around a blunt body.
Received June 24, 1998 / Revised version received February 21, 2000 / Published online November 8, 2000 相似文献
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Ohne ZusammenfassungAn dieser Stelle erfüllen wir mit grosser Freude die angenehme Pflicht, unserem hochverehrten Lehrer, Herrn Hof-rath Professor Dr. Adolf Lieben, für vielfache Anregung und lebhaftes Interesse, welches er unserer Arbeit entgegenbrachte, unseren tiefgefühlten Dank auszusprechen. 相似文献
100.
The shear-induced isotropic-to-nematic phase transition of side chain liquid-crystalline polymers is studied theoretically. A modification of the previous models of main-chain liquid crystals to the case of side chain liquid-crystalline polymers is proposed. Orientational and rheological properties of the model are studied in plane-shear flow. Predictions of the present model agree qualitatively with experimental results (Pujolle-Robic, Noirez in Nature 409:167, 2001). 相似文献