998 resultados para 23-224


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A new ruthenium(II) complex of the type [Ru(O2CMe)(MeCN)2(PPh3)2](CiO4) (1) has been isolated from a reaction between Ru2Cl(O2CMe), and PPh3 in MeCN followed by the addition of NaClO4. The structure of 1 is determined by single crystal X-ray studies. The crystal belongs to the monoclinic space group C2/m with the following unit cell dimensions for the C42H39N2O6P2ClRu(M = 866.15): a = 23.295(1)angstrom, b = 23.080(1)angstrom, c = 9.159(1)angstrom, beta = 107.32(1)-degrees, V = 4701(1)angstrom3, Z = 4, D(c) = 1.224 gcm-3, lambda(Mo - K-alpha) = 0.7107 angstrom, mu(Mo - K-alpha) = 4.09 cm-1, T = 293K, R = 0.081 (R(w) = 0.094) for 2860 reflections with I greater-than-or-equal-to 3-sigma(I) and g = 0.015853. In the complex cation, the symmetry about the metal centre is essentially octahedral showing the presence of a chelating acetato, two cis-oriented MeCN and two trans-disposed PPh3 ligands. The mechanistic aspects of the core cleavage reaction are discussed.

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A new strategy for the construction of the isotwistane skeleton is reported from easily available cyclohexadienes which involves stereoselective alkylation of a bicyclooctenone derivative and a decarboxylative 5-exo-trig radical cyclisation as the key steps in the total synthesis of 5-epi-pupukean-2-one.

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Amplify-and-forward (AF) relay based cooperation has been investigated in the literature given its simplicity and practicality. Two models for AF, namely, fixed gain and fixed power relaying, have been extensively studied. In fixed gain relaying, the relay gain is fixed but its transmit power varies as a function of the source-relay (SR) channel gain. In fixed power relaying, the relay's instantaneous transmit power is fixed, but its gain varies. We propose a general AF cooperation model in which an average transmit power constrained relay jointly adapts its gain and transmit power as a function of the channel gains. We derive the optimal AF gain policy that minimizes the fading- averaged symbol error probability (SEP) of MPSK and present insightful and tractable lower and upper bounds for it. We then analyze the SEP of the optimal policy. Our results show that the optimal scheme is up to 39.7% and 47.5% more energy-efficient than fixed power relaying and fixed gain relaying, respectively. Further, the weaker the direct source-destination link, the greater are the energy-efficiency gains.

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Conformational diversity or shapeshifting in cyclic peptide natural products can, in principle, confer a single molecular entity with the property of binding to multiple receptors. Conformational equilibria have been probed in the contryphans, which are peptides derived from Conus venom possessing a 23-membered cyclic disulfide moiety. The natural sequences derived from Conus inscriptus, GCV(D)LYPWC* (In936) and Conus loroisii, GCP(D)WDPWC* (Lo959) differ in the number of proline residues within the macrocyclic ring. Structural characterisation of distinct conformational states arising from cis-trans equilibria about Xxx-Pro bonds is reported. Isomerisation about the C2-P3 bond is observed in the case of Lo959 and about the Y5-P6 bond in In936. Evidence is presented for as many as four distinct species in the case of the synthetic analogue V3P In936. The Tyr-Pro-Trp segment in In936 is characterised by distinct sidechain orientations as a consequence of aromatic/proline interactions as evidenced by specific sidechain-sidechain nuclear Overhauser effects and ring current shifted proton chemical shifts. Molecular dynamics simulations suggest that Tyr5 and Trp7 sidechain conformations are correlated and depend on the geometry of the Xxx-Pro bond. Thermodynamic parameters are derived for the cis trans equilibrium for In936. Studies on synthetic analogues provide insights into the role of sequence effects in modulating isomerisation about Xxx-Pro bonds.

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Contenido: Doctor Santiago de Estrada / Alfredo Di Pietro – Jornadas sobre “La reforma del Estado”: Las alternativas de financiamiento del mercado de capitales / Joaquín R. Ledesma – Una reflexión sobre la ley de reforma del Estado / Carlos Raúl Sanz – Las privatizaciones / Juan Carlos Cassagne – La concesión de obra pública / Rodolfo Barra – Constitucionalidad de las privatizaciones / Néstor Pedro Sagüés – Aspectos laborales de la ley 23.696 / Hugo R. Carcavallo – Estado nacional y bien común / José Giménez Rébora – Atribuciones, conducta y control de los funcionarios públicos en la época hispánica / Julio R. Lascano – Notas acerca de las relaciones Iglesia-Estado / Néstor Daniel Villa – Interdictos y acciones populares en Roma/ Fernando M. Zamora – Ciencias políticas: Ortega y la “sociedad de naciones” / Enrique Aguilar -- Documentos

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Contenido: Un pequeño gran gigante. Más notas acerca de la hipérbole de lo corporal en la obra de Rabelais / Susana G. Artal – Una lectura de los cuatro cuartetos de T. S. Eliot (segunda parte) / Inés de Cassagne – Los estudios lingüísticos con base computacional / María Amalia García Jurado – Bucolismo en una carta de Sidonio Apolinar / Raúl Lavalle – La seducción estética de la barbarie como poesía de lo original originario / María Rosa Lojo – La elegía a María Blanchard / Lía Noemí Uriarte Rebaudi – Nota – Reseñas bibliográficas

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<正> 本项成果,是承包美国太阳东方勘探公司任务而完成的。在系统分析总结了南海西部石油公司“南海—503工程地质取芯船”在南海北部湾23/25太阳区块所进行的测深、侧扫声纳、地震声学剖面测量,及4口孔深40米的工程地质浅钻土柱等材料的基础上,详细阐述了

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Apresenta a Lei 12.852 que institui o Estatuto da Juventude e dispõe sobre os direitos dos jovens, os princípios e diretrizes das políticas públicas de juventude e o Sistema Nacional de Juventude (Sinajuve).

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Afirma ser favorável à Proposta de Emenda Constitucional n. 14/78 do Senador Cattete Pinheiro, que estabelece representação política para o Distrito Federal. Compara a situação de Brasília com a de Washington, capital dos Estados Unidos.

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Em conformidade com o Edital nº 1/1992, torna público o resultado da prova de Conhecimentos Específicos do concurso público para o cargo de Agente de Segurança Legislativa.

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Em conformidade com os Editais nº 1/1992 e nº 10/1992, comunica aos candidatos a data de realização da Prova Prática para a categoria funcional de Operador de Audiovisual.

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Em conformidade com o Edital nº 7/1994, torna público o resultado final do concurso público para Analista Legislativo – Fisioterapeuta.

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Em conformidade com o Edital nº1/1992, torna público o resultado da prova de Datilografia do concurso público para o cargo de Assistente Administrativo.