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The conformation of network chain segments in a rigid glassy DDM-cured bisphenol A epoxy resin has been determined by means of rotational isomeric-state model and confirmed by conformity of experimental NMR second moments with a theoretical estimate based on the model. The glass transition temperatures Tg have been determined from precipitate NMR line narrowing with increase in temperature due to the onset of rapid (>104 Hz) main-chain molecular motion. The temperature dependence of the correlation frequency has been determined and the type and extent of molecular motion that occurs in such epoxy resins is discussed. 相似文献
894.
The method, developed in an earlier paper, for tracing geodesies of particles and light rays through Regge calculus space-times, is applied to a number of problems in the Schwarzschild geometry. It is possible to obtain accurate predictions of light bending by taking sufficiently small Regge blocks. Calculations of perihelion precession, Thomas precession, and the distortion of a ball of fluid moving on a geodesic can also show good agreement with the analytic solution. However difficulties arise in obtaining accurate predictions for general orbits in these space-times. Applications to other problems in general relativity are discussed briefly. 相似文献
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P.J. Ellis 《Nuclear Physics A》1978,302(1):257-266
Simple expressions are obtained for polarizations in heavy ion reactions by using the Strutinsky model and asymptotic forms for Clebsch-Gordan coefficients to give the weighting for the near side, far side and interference terms. The model is discussed and examples are given which show that it can reproduce many of the features of exact calculations. 相似文献
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899.
We have discovered that Woelm chromatographic γ-alumina substantially accelerates hydrolysis (and methanolysis) of acyl and phosphoryl fluorides. Compared to the corresponding reactions, these alumina-promoted reactions occur about 250–350 times faster for acyl fluorides and about 1800–3000 times faster for phosphoryl fluorides. 相似文献
900.
The total cross section for the production of a muon pair of invariant mass Q2via the Drell-Yan mechanism and the Feynman xF differential cross section are calculated in QCD retaining all terms up to order αs(Q2. The calculations are performed using dimensional regularisation of the intermediary infrared and collinear singularities, but we present our results in a form independent of such details. The corrections to both these cross sections coming from radiative corrections to the lowest-order annihilation diagram are found to be large at present values of Q2 and S when the cross section is expressed in terms of parton densities derived from leptonproduction, for all Drell-Yan processes of practical interest. Numerical calculations are presented which show, for any reasonable parametrisation of the parton densities, that the neglect of higher-order terms in αs(Q2) is not justifiable. The quark-gluon diagrams on the other hand give small corrections in this order and are only important for PP scattering. 相似文献