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141.
142.
Ivn Brito Danitza Vargas Andrea Reyes Alejandro Crdenas Matías Lpez‐Rodríguez 《Acta Crystallographica. Section C, Structural Chemistry》2005,61(4):o234-o236
The title compound, C27H19NO2S, contains chains of fused (19) rings formed by intermolecular C—H·O=C hydrogen bonds and running along the [011] and [01] directions. These chains are linked through short intermolecular C—H·π contacts, giving rise to sheets. The conformation of the title compound is dominated primarily by the nearly orthogonal lone‐pair orbitals on the N and S atoms. 相似文献
143.
Alejandro Cabo-Bizet 《Physics letters. A》2009,373(21):1865-1869
Special solutions of the Hartree-Fock (HF) problem for Coulomb interacting electrons described by a simple model of the Cu-O planes in La2CuO4 are presented. One of the mean field states obtained, is able to predict some of the most interesting properties of this material, such as its insulator character and the antiferromagnetic order. The natural appearance of pseudogaps in some states of this material is also indicated by another of the HF states obtained. These surprising results follow after eliminating spin and crystal symmetry restrictions usually imposed on the single particle HF orbitals, by employing the rotational invariant formulation of the HF scheme originally introduced by Dirac. Therefore, it is exemplified here, how up to know considered strong correlation effects, can be described by improving the HF solution of the considered system. In other words, it has been argued, that defining correlation effects as the ones shown by the system and not predicted by the HF best (lowest energy) solution, allows to explain important, up to know considered as strong correlation properties, as simple mean field ones. The discussion also helps to clarify the role of the antiferromagnetism and pseudogaps in the physical properties of the HTSC materials and indicates a promising way to start conciliating the Mott and Slater pictures in the physics of the transition metal oxides and other strongly correlated electron systems. 相似文献
144.
Raquel da Silva Cabral Andre L. L. Aquino Alejandro C. Frery Osvaldo A. Rosso Jaime A. Ramírez 《Central European Journal of Physics》2013,11(12):1645-1652
Wireless sensor networks are an important technology for making distributed autonomous measures in hostile or inaccessible environments. Among the challenges they pose, the way data travel among them is a relevant issue since their structure is quite dynamic. The operational topology of such devices can often be described by complex networks. In this work, we assess the variation of measures commonly employed in the complex networks literature applied to wireless sensor networks. Four data communication strategies were considered: geometric, random, small-world, and scale-free models, along with the shortest path length measure. The sensitivity of this measure was analyzed with respect to the following perturbations: insertion and removal of nodes in the geometric strategy; and insertion, removal and rewiring of links in the other models. The assessment was performed using the normalized Kullback-Leibler divergence and Hellinger distance quantifiers, both deriving from the Information Theory framework. The results reveal that the shortest path length is sensitive to perturbations. 相似文献
145.
Alejandro D. Rey 《Liquid crystals》2001,28(4):549-556
The generalized equations of bulk and interfacial nematostatics in terms of the tensor order parameter are derived using calculus of variations, taking into account long and short range nematic bulk free energies as well as anchoring and saddle-splay surface free energies. A general expression for the surface stress tensor order parameter for a nematic liquid crystal/isotropic fluid (NLC/I) interface has been derived, and found to represent normal, shear, and bending stresses. It is shown that the surface stress tensor is asymmetric. It is also found that anchoring energy contributes to bending and normal stresses, while saddle-splay energy contributes to normal and shear stresses. The rotational identifies governing the bulk and surface stress tensors are derived and used to show that the equations of nematostatics are fully consistent with the general balance equations of polar fluids. The equations presented provide a theoretical framework for solving interfacial problems involving NLCs that is applicable to cases where variations in liquid crystalline order and saddle-splay energy play significant roles. 相似文献
146.
José Barluenga Prof. Dr. Amadeo Fernández Alejandro Diéguez Dr. Félix Rodríguez Dr. Francisco J. Fañanás Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(43):11660-11667
An efficient method for the synthesis of [3.3.1]bicyclic compounds from easily available alkynol derivatives has been developed. The reaction is based on a gold‐ or platinum‐catalyzed tandem process that involves an intramolecular hydroalkoxylation of a triple bond followed by a Prins‐type cyclization. The reaction has been carried out with differently substituted alkynol derivatives and oxygen‐, nitrogen‐, and carbon‐centered nucleophiles. The incorporation of halogen atoms as nucleophiles and elimination reactions has also been studied. Enantiomerically pure [3.3.1]bicyclic systems were easily synthesized from the chiral pool. 相似文献
147.
Aníbal Rodríguez-Bernal Alejandro Vidal-López 《Journal of Mathematical Analysis and Applications》2008,338(1):675-694
In this paper we show that dissipative reaction-diffusion equations in unbounded domains posses extremal semistable ground states equilibria, which bound asymptotically the global dynamics. Uniqueness of such positive ground state and their approximation by extremal equilibria in bounded domains is also studied. The results are then applied to the important case of logistic equations. 相似文献
148.
149.
Vikrant Patil Enrique Barragan Shivaputra A. Patil Siddappa A. Patil Alejandro Bugarin 《Tetrahedron letters》2017,58(35):3474-3477
A series of new chlorinated thiabendazoles (6a–m) have been synthesized from readily available anilines and 4-cyanothiazole in moderate to good yields. All synthesized compounds were fully characterized using 1H NMR, 13C NMR, IR, and mass spectrometry. Additionally, the structure of the compound (6f) was confirmed by single-crystal X-ray diffraction. In addition, synthesis of 2-substituted benzimidazoles and 2-phenyl benzothiazole was investigated using our optimized conditions and the outcome is presented herein. 相似文献
150.
José Ricardo Cammarata Rocío Rivera Franmerly Fuentes Yomaira Otero Edgar Ocando-Mavárez Alejandro Arce Juan M. Garcia 《Tetrahedron letters》2017,58(43):4078-4081
An air stable copper(I)-phosphole complex, [CuCl{2,5-bis(2-thienyl)-1-phenylphosphole}2] (1), was utilized as a catalyst in single and double A3-coupling reactions for preparing mono- and bi-propargylamines. A variety of aldehydes, amines and terminal alkynes were tested. Most of these reactions led to formation of the expected propargylamines in good yields using low amounts catalyst and obviating both the use of purified reagents as employ of a glovebox. 相似文献