797 resultados para Mier y Terán, Luis, d. 1894
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Conselho Nacional de Desenvolvimento CientÃfico e Tecnológico (CNPq)
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A data sample corresponding to an integrated luminosity of 2.1 fb(-1) collected by the D phi detector at the Fermilab Tevatron Collider was analyzed to search for squarks and gluinos produced in p (p) over bar collisions at a center-of-mass energy of 1.96 TeV. No evidence for the production of such particles was observed in topologies involving jets and missing transverse energy, and 95% C.L. lower limits of 379 GeV and 308 GeV were set on the squark and gluino masses, respectively, within the framework of minimal supergravity with tan beta = 3, A(0) = 0, and mu < 0. The corresponding previous limits are improved by 54 GeV and 67 GeV. (c) 2008 Elsevier B.V. All rights reserved.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Diurea cross-linked bridged silsesquioxanes (BSs) C(10)C(11)C(10) derived from organosilane precursors, including decylene chains as side spacers and alkylene chains with variable length as central spacers (EtO)(3)Si- (CH(2))(10)-Y(CH(2))(n)-Y-(CH(2))(10)-Si(OEt)(3) (n = 7, 9-12; Y = urea group and Et = ethyl), have been synthesized through the combination of self-directed assembly and an acid-catalyzed sol gel route involving the addition of dimethylsulfoxide (DMSO) and a large excess of water. This new family of hybrids has enabled us to conclude that the length of the side spacers plays a unique role in the structuring of alkylene-based BSs, although their morphology remains unaffected. All the samples adopt a lamellar structure. While the alkylene chains are totally disordered in the case of the C(10)C(7)C(10) sample, a variable proportion of all-trans and gauche conformers exists in the materials with longer central spacers. The highest degree of structuring occurs for n = 9. The inclusion of decylene instead of propylene chains as side spacers leads to the formation of a stronger hydrogen-bonded urea-urea array as evidenced by two dimensional correlation Fourier transform infrared spectroscopic analysis. The emission spectra and emission quantum yields of the C(10)C(n)C(10) Cm materials are similar to those reported for diurea cross-linked alkylene-based BSs incorporating propylene chains as side spacers and prepared under different experimental conditions. The emission of the C(10)C(n)C(10) hybrids is ascribed to the overlap of two distinct components that occur within the urea cross-linkages and within the siliceous nanodomains. Time-resolved photoluminescence spectroscopy has provided evidence that the average distance between the siliceous domains and the urea cross-links is similar in the C(10)C(n)C(10) BSs and in oxyethylene-based hybrid analogues incorporating propylene chains as side spacers (diureasils), an indication that the longer side chains in the former materials adopt gauche conformations. It has also allowed us to demonstrate for the first time that the emission features of the urea-related component of the emission of alkylene-based BSs depend critically on the length of the side spacers.
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We report the results of a search for a narrow resonance decaying into two photons in 1.1fb-1 of data collected by the D0 experiment at the Fermilab Tevatron Collider during the period 20022006. We find no evidence for such a resonance and set a lower limit on the mass of a fermiophobic Higgs boson of mhf>100GeV at the 95% C.L. This exclusion limit exceeds those obtained in previous searches at the Fermilab Tevatron and covers a significant region of the parameter space B(hf→I I ) vs mhf which was not accessible at the CERN Large Electron-Positron Collider. © 2008 The American Physical Society.
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En la Conferencia Regional Latinoamericana y del Caribe sobre Población y Desarrollo (México, D.F., 29 de abril al 4 de mayo de 1993);, preparatoria de la Conferencia Internacional sobre la Población y el Desarrollo (CIPD); (El Cairo, septiembre de 1994);, se aprobó por unanimidad una declaración denominada "Consenso Latinoamericano y del Caribe sobre Población y Desarrollo", en la que se expresa la posición conjunta de los paÃses de la región ante los temas de población y desarrollo. Los objetivos y metas de este Consenso configuran la visión y aspiraciones de la región con respecto a las relaciones entre población, desarrollo y medio ambiente, asà como al avance de los derechos humanos y de la lucha contra la desigualdad en las condiciones de vida que se da entre grupos sociales, grupos étnicos, zonas geográficas y hombres y mujeres. Con la premisa de que un mayor apoyo mutuo entre los paÃses de la región les permitirÃa avanzar de una manera más sólida hacia el logro de esos objetivos y metas, en la Conferencia Regional los paÃses decidieron promover la adopción de un plan de acción regional. Por lo tanto, los propósitos generales de ese plan debÃan apuntar precisamente a facilitar la integración y el intercambio de experiencias nacionales en la formulación y aplicación de polÃticas y programas de población, tanto del pasado como de la actualidad. Con el objetivo de asegurar una adecuada implementación, seguimiento y revisión del Plan de Acción Regional, los paÃses acordaron, en el vigésimo quinto perÃodo de sesiones de la CEPAL, entregar dicha responsabilidad al Comité Especial sobre Población y Desarrollo, que se reunirá, por primera vez, en oportunidad del vigésimo sexto perÃodo de sesiones en San José, Costa Rica.
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