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921.
The title compound is used to prepare 3-arylglutaric acids, bis-isoxazoles and bis-pyrazoles from commercially available materials. The methodologies described have afforded important synthetic intermediates in high yields and without the use of chromatography. 相似文献
922.
We investigate the dispersive properties of evolution equations on waveguides with a non-flat shape. More precisely, we consider an operator $$H=-\Delta_{x}-\Delta_{y}+V(x,y)$$ with Dirichlet boundary conditions on an unbounded domain ??, and we introduce the notion of a repulsive waveguide along the direction of the first group of variables, x. If ?? is a repulsive waveguide, we prove a sharp estimate for the Helmholtz equation Hu???u?=?f. As consequences, we prove smoothing estimates for the Schr?dinger and wave equations associated to H, and Strichartz estimates for the Schr?dinger equation. Additionally, we deduce that the operator H does not admit eigenvalues. 相似文献
923.
Francesca Alessio Louis Jeanjean Piero Montecchiari 《Calculus of Variations and Partial Differential Equations》2000,11(2):177-202
We consider a class of non autonomous Allen-Cahn equations
where is a multiple-well potential and is a periodic, positive, non-constant function. We look for solutions to (0.1) having uniform limits as corresponding to minima of W. We show, via variational methods, that under a nondegeneracy condition on the set of heteroclinic solutions of the associated
ordinary differential equation
the equation (0.1) has solutions which depends on both the variables x andy. In contrast, when a is constant such nondegeneracy condition is not satisfied and all such solutions are known to depend only on x.
Received April 16, 1999 / Accepted October 1, 1999 / Published online June 28, 2000 相似文献
924.
Barducci A Chelli R Procacci P Schettino V Gervasio FL Parrinello M 《Journal of the American Chemical Society》2006,128(8):2705-2710
In the present study we have used molecular dynamics simulations to study the stability of the antiparallel beta-sheet in cellular mouse prion protein (PrP(C)) and in the D178N mutant. In particular, using the recently developed non-Markovian metadynamics method, we have evaluated the free energy as a function of a reaction coordinate related to the beta-sheet disruption/growth. We found that the antiparallel beta-sheet is significantly weaker in the pathogenic D178N mutant than in the wild-type PrP(C). The destabilization of PrP(C) beta-structure in the D178N mutant is correlated to the weakening of the hydrogen bonding network involving the mutated residue, Arg164 and Tyr128 side chains. This in turn indicates that such a network apparently provides a safety mechanism for the unzipping of the antiparallel beta-sheet in the PrP(C). We conclude that the antiparallel beta-sheet is likely to undergo disruption rather than growth under pathogenic conditions, in agreement with recent models of the misfolded monomer that assume a parallel beta-helix. 相似文献
925.
A three-component one-pot procedure (3-MCR) was developed to assemble the spiroisoxazoline nucleus from commercially available materials. This new methodology affords the title compounds in high yields and without the use of chromatography. 相似文献
926.
927.
The electron density distribution in a transition-metal dimer containing a semibridging carbonyl is determined through experimental X-ray diffraction and quantum chemical computations. The changes occurring during the evolution from terminal to bridging coordinations are described by a "structure-correlation-like" approach and by a theoretical investigation along the conversion path. The smooth continuum of conformations observed in the solid state is explained in terms of the mutual interplay of direct M-M and M-CO and indirect M- - -M and M- - -C interactions, which can be characterized by interatomic delocalization indexes, within the framework of Quantum Theory of Atoms in Molecules. 相似文献
928.
929.
Piero Buzano 《Annali di Matematica Pura ed Applicata》1962,58(1):35-40
Sunto Si dimostra che se y è un punto della traiettoria di x in un sistema ∞1 di omografie (contenente l'identità) e se la stessa omografia che porta x in y fa corrispondere le relative tangenti, il
sistema è un gruppo oppure è formato da omologie con lo stesso centro.
A Enrico Bompiani in occasione del suo Giubileo scientifico 相似文献
930.