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1.
In this paper we study a Ginzburg–Landau model which describes the behaviour of a superconducting material including thermal effects. We extend the traditional formulation of the problem, by introducing the temperature as an additional state variable. Accordingly, together with the Gor’kov–Eliashberg system, we introduce an evolution equation for the absolute temperature. We examine in detail the case which allows only variations of the concentration of superconducting electrons and of the temperature, neglecting the electromagnetic field. For this problem existence and uniqueness of the solution are shown. Finally we analyze the asymptotic behaviour of the solutions, proving that the system possesses a global attractor. 相似文献
2.
Sequence distribution of atactic poly(phenylvinylketone) (PPVK) has been determined by [13C]-[1H]NMR spectroscopy. Quantitative analysis of the carbonyl pattern allows resolution into pentads with intensities fitting a first order Markov process. The carbonyl pattern of highly isotactic PPVK, initiated by diethylzinc, deviates strongly from Bernoullian statistics, as in the case of highly isotactic polymethylvinylketone (PMVK). For n-butyl-lithium initiated poly(isopropenylphenylvinylketone) (PIPK), the carbonyl pattern practically agrees with a Bernoullian distribution. Atactic PMVK, analyzed from the methylene and the carbonyl pattern in [13C] or [1H]NMR, shows that the polymerization process is purely Bernoullian and quite different from that for poly(isopropenylmethylketone). Except for poly(methylallylalcohol) for which the tacticity can be determined, the resolution is too poor to allow a quantitative sequence distribution of poly(allylalcohols) or poly(allyltrifluoroacetates). [1H] and [19F]NMR spectroscopies of these compounds do not give better results. 相似文献
3.
4.
Indolinone nitroxides undergo a homolytic substitution with aroyl oxyl radicals, leading to two isomers, 7-aroyloxy- and 5-aroyloxy-derivative, respectively, whose structures were assigned on the basis of the ESR hfccs and of the 1H NMR spectra of the corresponding amines. The presence of aroyl oxyl radicals in the reaction medium was demonstrated by thermal decomposition of benzoyl peroxide in the presence of aromatic acids. 相似文献
5.
Cycloaddition of 1,3-diphenyl-2-azaallyllithium to tolane, diphenylbutadiyne and 1,4-diphenylbutenyne E produces quantitatively 2,3,4,5-tetraphenylpyrrole, 3-phenylethynyl-2,4,5-triphenyl-3-pyrroline and 3-phenylethynyl-2,4,5-triphenylpyrrolidine, respectively. Treatment before hydrolysis with benzyl bromide or dimethl sulfide gives N-alkyl-substituted derivatives. The structure of 3-pyrrolines was established by spectral data and chemical correlations. Stereochemical courses of this new synthetic method for 3-pyrrolines are discussed. 相似文献
6.
In contrast with previous reports, it was found that the reaction of 1-phenylcyclohexene with peroxyformic acid is not entirely stereospecific, but gives some trans-1-phenylcyclohexane-1, 2-diol (IV) beside the cis-isomer (III). The reaction of 1-phenylcyclohexene oxide (II) with formic acid yielded a similar mixture of III and IV, while addition of trichloroacetic acid in benzene was entirely cis-stereospecific. Reaction of the epoxide II with potassium hydroxide took place only under very drastic conditions to give a small yield of III, while sodium 2-dimethylaminoethoxide added exclusively in a trans way, leading to the amino ether X, which was easily transformed into the trans-glycol IV. The latter compound was also the main product of the borohydride reduction of 2-hydroxy-2-phenylcyclohexanone (IX). Possible explanations of the observed stereochemical results are discussed. 相似文献
7.
Josette Canceill Ludovic Jullien Liliane Lacombe Jean-Marie Lehn 《Helvetica chimica acta》1992,75(3):791-812
A new series of channel-type molecules presenting the features of potential transmembrane structures is described. They result from the grafting of amphiphilic side chains on a β-cyclodextrin derivative 3 that constitutes the organizing core. They belong to the ‘bouquet’ family (B). Compounds bearing poly(oxyethylene) side chains, B 16 and 17 , and their polymethylene analogues B 18 and 19 , were synthesized. The properties investigated emphasize the suitability of such molecules to be incorporated into lipid bilayer membranes. 相似文献
8.
Romanato Filippo Berti Marina Mazzer Massimo Drigo Antonio Vittorio Lazzarini Laura Franzosi Paolo Salviati Giancarlo Bertone Daniele 《Mikrochimica acta》1994,114(1):431-440
A combined method for structural characterization of strained epitaxial heterostructures involving different techniques such as Rutherford backscattering spectrometry (RBS), multiple crystal X-ray diffractometry (MCD) and transmission electron microscopy (TEM) is presented. In order to obtain a complete characterization of the analysed structure, three different quantities are measured independently: the epilayer thickness, the density of misfit dislocations which may appear at the interface, and the significant components of the strain tensor, mainly the tetragonal distortion, affecting the epilayer lattice. In this way the thermodynamic state and the mechanisms of plastic deformation of the structures can be fully investigated. In this contribution we present and discuss the experimental results concerning a set of InP/GaAs samples having different layer thicknesses ranging from 5 to 500 nm. The thickness of the samples has been determined by RBS. Measurements of in-plane strain and tetragonal distortion have been performed by MCD and RBS-channelling respectively, finally TEM has been used for determining the defects densities and distribution. 相似文献
9.
Stable nitroxide radicals were obtained by the oxidation of 1-hydroxyindolines prepared by allowing the organo-metallic compounds to act upon 2-phenylisatogen and arylimino-derivatives. In both cases nitroxides are obtained with a N of approximately 9 gauss, in agreement with similar known compounds. The ESR spectra of numerous nitroxide radicals are discussed and a number of cases of magnetic non-equivalence of methylenic protons adjacent to asymmetric carbon are brought to light. 相似文献
10.
Massimiliano Berti Luca Biasco Michela Procesi 《Archive for Rational Mechanics and Analysis》2014,212(3):905-955
We prove the existence of Cantor families of small amplitude, analytic, linearly stable quasi-periodic solutions of reversible derivative wave equations. 相似文献