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191.
192.
An efficient gold-catalyzed procedure for the preparation of 2-vinylimidazolidinones has been developed. The starting materials for the synthesis of these compounds are α-amino allenamides which undergo heterocyclization by means of nucleophilic attack of the amino group on the inside double bond of the 1,2-diene moiety. This is the first example of a gold-catalyzed cyclization on allene substrates bearing an amido group which, however, resulted inactive. 相似文献
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Angelo Alvino Andrea Cianchi Vladimir G. Maz'ya Anna Mercaldo 《Annales de l'Institut Henri Poincaré (C) Analyse Non Linéaire》2010
Non-linear elliptic Neumann problems, possibly in irregular domains and with data affected by low integrability properties, are taken into account. Existence, uniqueness and continuous dependence on the data of generalized solutions are established under a suitable balance between the integrability of the datum and the (ir)regularity of the domain. The latter is described in terms of isocapacitary inequalities. Applications to various classes of domains are also presented. 相似文献
195.
196.
Mohammed Boutat Yves DAngelo Sa?d Hilout Véronique Lods 《Comptes Rendus Mathematique》2003,337(8):549-552
In this Note, we are interested in the evolution of a surface of a crystal structure, constituted by an elastic substrate and a thin film. If the crystal is constrained, some morphological instabilities may appear. To study these instabilities, we made use of the model developped in Phys. Rev. B 47 (1993) 9760–9777. There, the map f of the free surface of the film satisfies a parabolic partial differential equation, depending on the elastic displacement of the substrate. For simplicity, the substrate is assumed to be linearly elastic and the structure to be infinite in one direction. Then, under some formal asymptotic assumptions, a formal expansion of the displacement can be determined after some appropriate scalings, allowing to derive a simplified parabolic nonlinear equation as in Lods et al. (Asymptotic Anal. 33 (2003) 67–91). We give here some results about the finite-time blow-up and the existence and uniqueness of the solution in an appropriate space. To validate the theoretical results, we also performed some numerical simulations using a pseudo-spectral method and also compute the initial-profile dependent critical value of the parameter θ involved in the nonlinear equation. To cite this article: M. Boutat et al., C. R. Acad. Sci. Paris, Ser. I 337 (2003). 相似文献
197.
C.L. Bianchi R. Carli S. Lanzani D. Lorenzetti G. Vergani V. Ragaini 《Ultrasonics sonochemistry》1994,1(1)
Ultrasound waves are commonly used to clean or to erode the surface of solid materials thanks to the strength of the jets of solvent, hitting the surface itself, created by the collapse of the liquid phase. In the present work, ultrasound was used to obtain highly dispersed ruthenium on alumina catalysts. The samples were characterized with different techniques to study the influence of the sonication on both the metal crystallites and the support. 相似文献
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The nitration of diphenylmethane to three main isomeric dinitro derivatives, performed with nitric acid in dichloromethane, is proposed as an organic laboratory experiment showing a number of advantages over typical aromatic nitrations in sulfuric acid. 相似文献