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Alec B. Scranton John Klier Nikolaos A. Peppas 《Journal of Polymer Science.Polymer Physics》1991,29(2):211-224
The dilute solution complexation equilibrium between linear macromolecules and smaller complementary oligomers is considered when: (1) the oligomers are free in solution; and (2) the oligomers are covalently attached at one end to the polymer. A general statistical mechanical framework is developed and is illustrated using a simple random walk model for polymer conformation. The statistical mechanical partition functions are formulated using a generating function technique, allowing thermodynamic averages in the complexed state to be calculated. Loops, trains, and tails of all possible length are allowed in the conformation of a complexed oligomer. Simulation results for the free oligomer case are compared with those obtained for oligomers covalently attached to the polymeric molecular. The model provides a theoretical explanation for the experimentally observed enhancement of complexation of oligomers grafted to the complementary polymers. 相似文献
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Anderson Hollerbach Klier Ricardo José Alvea Maria Auxiliadora Fontes Prado José Dias de Bouza Filho Norma Beatriz D'accorso 《合成通讯》2013,43(23):4361-4374
The synthesis of 5-[6′-deoxy-(1′,2′:3′,4′-di-O-isopropylidene-α-D-galactopyranos-6′-yl)]tetrazole and its reaction with acetic anhydride and 1,2:3,4-di-O-isopropylidene-6-O-(4-toluenesulfonyl)-α-D-galactopyranose are described. 相似文献
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Frontispiece: Enantioselective Organocatalytic Cascade Approach to Different Classes of Benzofused Acetals
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Samples of p-type CdTe were subjected to deformation. Studies were performed of the influence of 60°-dislocations on the electrical conductivity, on the lifetime of minority carriers and on the relative change of the conductivity due to illumination. Dislocations were produced by bending the sample that was cut at suitable orientation. In this way, one obtained the 60°-dislocations, either of α- or β-type, according to the kind of bending involved. From the measurement of the temperature dependence of the conductivity it was ascertained that an increase in acceptor concentration occurs on the level with activation energy of 0.3 eV (identical to that of Vcd or a complex with Vcd), regardless of the type of dislocations. The concentration of acceptors on the level with activation energy 0.3 eV increases on increasing the dislocation density. The most probable explanation is that the deformation and, especially, annealinginduced migration of the dislocations produced give rise also to Vcd and/or VTe (both types simultaneously). Vcd acts as an acceptor and VTe as a donor. It follows that the increase in VTe can not be established from this measurement. The lifetime of the minority carriers is almost unaffected by introducing the dislocations into the samples. From the temperature dependence of the relative change in conductivity due to illumination one can determine the activation energy of a dislocation level provided that one assumes the dislocations acting as recombination centers. Under this assumption one obtainsE d =0.21–0.24 eV (for type α) andE d =0.55–0.59 eV (for type β), measured from the top of the valence band. 相似文献
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Ssveral samples of CdTe were measured in a temperature range of –190C to 100C. The activation energies of the levels and their cross-section were determined. With some samples it was found that for more rapid heating the maxima of the curves of thermostimulated currents are shifted towards lower temperatures. Altogether three trap levels were found. 相似文献
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Piezoelectric resonators in the form of rectangular platelets of semiinsulating InPFe were produced by cleaving along direction {011} to excite fundamental longitudinal modes of vibrations. The analysis of the transfer function of such resonators in the region around resonance frequencies delivered such parameters as elastic modulus and piezoelectric coefficients of InP, which could be compared with values from literature. The pertinent elastic modulus agrees within 1.6%, whereas the value of piezoelectric coefficient e
14=(1.3±20%) C/m2 is approximately three times higher than the older experimental value, but lies nearer to some theoretical predictions and to a recent experimental value. 相似文献
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For pure 4He on Cs a nonwet phase exists below ≈2 K but for dilute 3He–4He mixtures the wetting is reentrant. Measurements of the contact angle with dilute mixtures of liquid helium on Cs can be explained in detail in terms of 3He states together with ripplons at the Cs–He mixture interface, but it is impossible to account for the lower wetting temperatures or contact angles with only 3He states or ripplons. We discuss the influence of surface roughness of the Cs on the contribution of interface excitations to the free energy and suggest that the variety of contact angles found with different samples of Cs is due mainly to their degree of roughness. 相似文献