Thesis (Ph. D.)--University of Washington, 2000. / Vita. Includes bibliographical references (leaves 249-257).

Th. 3e cycle--Électronique--Lille 1, 1980. N°: 854.

Hexanuclear transition metal clusters are a distinct class of chemical compounds that have some very interesting chemical and physical properties. Of recent interest in this field has been the [Re₆(μ₃-Se)₈]²⁺ cluster core. This Lewis acidic cluster core contains six substitutable coordination sites, and site differentiation can be accessed through protecting group ligands. The Lewis acidity has been shown to activate unsaturated cluster-bound ligands, and the expanded atom-like structure and high symmetry of the cluster core has potential use in synthesizing some fascinating and novel hybrid materials. Little work has been performed in establishing the scope of these chemical transformations. The work herein describes the efforts and successes of such work. Chapter 1 provides the essential background required for understanding the [Re₆(μ₃-Se)₈]²⁺ cluster core's synthesis, properties, and currently known research directions and successes. This chapter first introduces hexanuclear clusters in a general format, then focuses on the established catalytic and material capabilities that have been determined using this specific cluster core. Chapter 2 discusses the synthesis, characterization, and hydrogen-bonded assemblies formed from [Re₆(μ₃-Se)₈]²⁺ cluster-isonicotinic acid cluster complexes. These complexes have potential uses as hybrid inorganic/organic linkers for the generation of luminescent Lewis acidic metal-organic frameworks (MOFs). Prospective applications of such materials include catalysis, separations, and gas storage. Chapter 3 focuses on the novel chemistry of [Re₆(μ₃-Se)₈]²⁺ cluster-activated CH₃CN with N-based nucleophiles to form acetamidines. These ligands are of interest due to their use in medicinal chemistry, CO₂/CS₂ sequestration, and the formation of synthetically-relevant species. Quantitative yields are obtained and single-crystal XRD analyses reveal specific stereochemical outcomes. Trifluoroacetic acid (TFA) in a cluster-amidine CH₃CN solution removes the ligand as the acetamidinium TFA salt, and the starting cluster solvate is reproduced making a recyclable catalyst. Chapter 4 expands on a project similar to that of chapter 3, except that O-based nucleophiles are utilized for specific cluster isomers. The newly formed ligands, imino esters, are of interest in organic synthesis as valuable starting materials for the generation of β-lactams and heterocycles. ³¹P NMR and single–crystal XRD reveal Z stereochemistry is preferred in the cis isomer, but conflicting results for the hexasubstituted isomer leave stereochemical analyses unresolved. Chapter 5 attempts to incorporate the chemistry established in chapters 2-4 to provide some fresh and interesting research outlooks possible with the [Re₆(μ₃-Se)₈]²⁺ cluster core. Incorporation of the cluster into MOFs is discussed, and the possibility of post-synthetic modifications for metal sequestration, catalysis, and sensing is explained. Appendix A provides all the NMR data obtained for synthesized materials with peak picks and integrations provided. Appendix B entails all crystallographic information for structures determined after syntheses. Appendix C provide high-resolution mass spectra.

Orientador: Nelson Callegari Júnior / Banca: Ernesto Vieira Neto / Banca: Marta Cilene Gadotti / Resumo: O objetivo principal deste trabalho é mostrar a importância da Teoria da Transformada de Fourier Discreta como ferramenta nas análises de dados obtidos de simulações numéricas com modelos de Sistemas Dinâmicos em Mecânica Celeste. Mostraremos as principais motivações e justi cativas presentes no desenvolvimento das Transformada de Fourier contínua, discreta, e de algoritmos computacionais para Fast Fourier Transform. Esse desenvolvimento será aplicado na dinâmica de rotação de satélites naturais / Abstract: The main objective of this work is to show the importance of Discrete Fourier Transformation as a tool in the analyses of data obtained from numerical simulations of Dynamical Systems models in Celestial Mechanics. We will show the main motivations and justi- cations presented in development of continuous and discrete Fourier Transform, and computational algorithms to Fast Fourier Transform. We will apply these theoretical development in dynamics of rotation of naturals satellites / Mestre

No description available.

L’objectif de cette thèse est l’étude expérimentale et la modélisation des évolutions microstructurale et des cinétiques de transformation de phase α + β → β → αII dans l’alliage de titane Ti-6Al-4V dans des conditions isothermes et non-isothermes. Dans cette optique, diverses techniques ont été utilisées (DSC, MEB, microscopie optique, résistivité électrique in-situ et DRX). L’équation de KM-JMA a été utilisée pour décrire les cinétiques de transformation de phase en conditions isothermes. Une approche basée sur le principe d’additivité est proposée pour adapter l’équation de KM-JMA pour les transformations de phases non-isothermes et est comparée à celle utilisant la notion de temps fictif. Les paramètres de cinétique de transformation de phase (n, k et Q) sont ainsi déterminés et interprétés sur la base des résultats de l’analyse métallographique réalisée. Les mécanismes des différentes transformations de phase ont été discutés en tenant compte de l’analyse microstructurale et des paramètres de cinétiques déterminés. Enfin la cinétique de transformation de phase βm → αII en condition isotherme a été simulée à l’aide du logiciel MatCalc et modélisée en utilisant la théorie de germination – croissance ainsi que l’équation de KM-JMA. / The aim of this thesis is to experimentally study and to model the kinetics of α + β → β → αII phase transformations in Ti-6Al-4V alloy for isothermal and non-isothermal conditions. To this purpose, several technics have been performed (DSC, SEM, optical microscopy, in-situ electrical resistivity and XRD). The KM-JMA equation has been used to describe the kinetics of phase transformations during isothermal holdings. An approach based on the additivity rule has been developed to adapt the KM-JMA equation to non-isothermal phase transformations and is compared to the one using the fictitious time. Kinetics parameters (n, k and Q) have been determined using this approach and discussed based on the microstructural analysis. Mechanisms of the α + β → β → α phase transformations have been discussed by considering the microstructural analysis and the kinetics parameters already determined. Finally, the βm → αII phase transformation kinetics in isothermal conditions has been simulated with the MatCalc software and modelled using both the nucleation – growth theory and the KM-JMA equation.

Tradicionalmente, os estudos que tinham a exploração pecuária como foco, se limitavam a análise de seus indicadores produtivos e econômicos, ou seja, dava-se um enfoque parcial, setorial ou disciplinar. Igualmente, de um ponto de vista estático e baixo equilíbrio. Por sua vez, a exploração pecuária é um sistema aberto, submetido à influência de um entorno que denominamos ambiente, e que, gerido pelo pecuarista, persegue determinadas finalidades. Por conseqüência, a exploração pecuária é sensível a um amplo leque de fatores de natureza biofísica, sociológica, econômica e de políticas. Neste sentido, as explorações pecuárias como sistemas sociais, são dinâmicas, reativas ou evolutivas, o que significa que as características mais importantes aparecem ao longo do tempo. Por isso, o estudo dos sistemas pecuários requer a consideração explícita da dita variável, tempo. O presente estudo pretende dar resposta a seguinte questão: que mudanças aconteceram nas explorações pecuárias da região de Basalto como reação aos condicionantes do entorno socioeconômico, em constante mudança, mas também, dependentes de fatores e características internas a própria exploração? A região de Basalto, a mais extensa do Uruguai, correspondente a 21% do território nacional, é caracterizada fundamentalmente por estar associada a sistemas extensivos de produção pecuária de baixa produtividade e investimento, onde pastoreiam conjuntamente, bovinos e ovinos. A abordagem metodológica utilizada neste estudo baseou-se na comparação do processamento de informações correspondentes aos anos 1994 e 2008, utilizando como ferramenta, entrevistas dirigidas as mesmas explorações pecuárias da região de Basalto com áreas superiores a 200 hectares. O reconhecimento das mudanças ocorridas nos sistemas pecuários da região de Basalto, no marco das transformações recentes do setor agropecuário do Uruguai, é fundamental para explorar evoluções distintas da pecuária extensiva daquela região, apesar da incerteza a respeito das políticas agrárias dos condicionantes socioeconômicos. Os resultados encontrados sugerem a existência de fatores que ameaçam a continuidade das explorações pecuárias em longo prazo e, conseqüentemente, a sustentabilidade dos ecossistemas pastoris. Estes fatores são de natureza diversa: ambientais econômicos e sociais. / Traditionally, the livestock production studies limited the analysis to productive and economic results, which is to say from a partial approach, or from only one discipline. Also, they were done from a static point of view and supposing a situation at equilibrium. However, the livestock farm is an open system, exposed the influence of its environment, and managed by livestock farmers who have certain purposes. Consequently, the cattle operation is sensible to an ample variety of factors of biophysical, sociological, economic, and ecological nature and also to policies. In this sense, the cattle operations like social systems are dynamic, reactive or adaptive, which means that the most important characteristics appear on the long time. For this reason, the study of the cattle systems requires the explicit consideration this variable, time. The present study tries to give answer to the following question: What changes arose in the cattle operations of the Basalt reacting to the conditions of the socio-economic environment in constant change, but also depending on the own operation internal factors and characteristics? The Region of the Basalt, the most extensive of Uruguay, 21% of the national territory, has been characterized essentially as having extensive systems of cattle production of low productivity and investment; where bovine and ovine graze simultaneously. The methodological approach in this study is based on the comparison of information corresponding to years 1994 and 2008, from the same sample of farms - of the Region of the Basalt with surfaces majors to the 200 hectares -. The data of the changes occurred in the cattle systems of the Basalt Region within the framework of the recent transformations of the farming sector of Uruguay, is fundamental to explore extensive cattle ranch different evolutions, in presence of the uncertainty with respect to the agrarian policies and to the socio-economic conditions. The results suggest the existence of factors that threaten the continuity of the cattle operations in the long term, and therefore, the sustainability of the pastoral ecosystems. These factors are of diverse nature: environmental, economic and social.

Made available in DSpace on 2014-06-11T19:33:20Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-10-10Bitstream added on 2014-06-13T20:48:10Z : No. of bitstreams: 1 iaochite_jc_dr_rcla.pdf: 1030557 bytes, checksum: e16bfea42393f67aec0ef5945d73d74e (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O presente estudo pauta-se na análise da produção do espaço urbano, suas transformações e persistências. Propõe-se a discutir o processo de inércia espacial no município de Santa Gertrudes a partir das complexas relações existentes entre os agentes produtores deste espaço, a comunidade, a iniciativa privada (empresários do setor cerâmico) e o Poder Público Local. Desenvolve uma análise das inércias espaciais como áreas potenciais de brownfields e de como estes devem ser abordados dentro de uma política pública local que contempla o desenvolvimento sócio-espacial. Observa-se nesse espaço urbano lógicas arcaicas e lógicas modernas, sendo as primeiras representadas por antigas espacialidades, firmadas por resistências; e as últimas identificadas pelos novos tempos. Desta forma, têm-se presente no espaço urbano de Santa Gertrudes, de um lado as inércias espaciais, e, de outro, o Pólo Cerâmico que representa o dinamismo econômico. / The present study is ruled in the analysis of the production of the urban space, his transformations and persistence. The process of spaces inertias is intended to talk in the Santa Gertrudes from the complex existent relations between the producing agents of this space, the community, the private enterprise (businessmen of the ceramic sector) and the Public Local Power. It develops an analysis of the space inértias like potential areas of brownfields and of as these must be boarded inside a public local politics that contemplates the social-space development. It is observed in this urbane space logical archaic and logical modern, when there are the first ones represented by ancient spaces, secured by resistances; and the last ones identified by the new times. In this way, present has been in the urbane space of Santa Gertrudes, of a side the space inertias, and, of other, the Ceramic Polo that represents the dynamic economy.

Made available in DSpace on 2015-05-14T16:53:00Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-08-18Bitstream added on 2015-05-14T16:59:34Z : No. of bitstreams: 1 000829551.pdf: 3997285 bytes, checksum: 099e685288a956b7bfb783c39c93305e (MD5) / O objetivo principal deste trabalho é mostrar a importância da Teoria da Transformada de Fourier Discreta como ferramenta nas análises de dados obtidos de simulações numéricas com modelos de Sistemas Dinâmicos em Mecânica Celeste. Mostraremos as principais motivações e justi cativas presentes no desenvolvimento das Transformada de Fourier contínua, discreta, e de algoritmos computacionais para Fast Fourier Transform. Esse desenvolvimento será aplicado na dinâmica de rotação de satélites naturais / The main objective of this work is to show the importance of Discrete Fourier Transformation as a tool in the analyses of data obtained from numerical simulations of Dynamical Systems models in Celestial Mechanics. We will show the main motivations and justi- cations presented in development of continuous and discrete Fourier Transform, and computational algorithms to Fast Fourier Transform. We will apply these theoretical development in dynamics of rotation of naturals satellites

Made available in DSpace on 2015-06-17T19:34:04Z (GMT). No. of bitstreams: 0 Previous issue date: 2015-04-09. Added 1 bitstream(s) on 2015-06-18T12:47:29Z : No. of bitstreams: 1 000829069.pdf: 378200 bytes, checksum: 83286ccd04ed70a6108bdd5f707c9066 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Estudamos a construção de hierarquias integráveis. Essas hierarquias possuem infinitas equações de movimento que surgem de uma mesma estrutura algébrica. E por consequência dessa estrutura comum conseguimos encontrar soluções solitônicas para todas essas equações simultânea e sistematicamente, através do método de Dressing. Neste trabalho estudamos as hierarquias mKdV e KdV e calculamos explicitamente equações de movimento para os primeiros graus de ambas. Para a KdV, o Lax obtido, parece funcionar apenas para os graus positivos. Encontrarmos uma maneira de determinar as transformações de Bäcklund para os graus positivos da hierarquia mKdV e KdV usando o fato das equações de movimento poderem ser escritas como derivadas totais. Obtemos uma maneira sistemática de construir as transformações de Bäcklund das equações da hierarquia mKdV explorando a invariância da equação de curvatura nula por transformações de gauge. Determinamos as transfomações de Bäcklund Tipo-I e Tipo-II para as equações de graus ímpares da hierarquia mKdV. Fizemos o cálculo explícito para os três primeiros graus positivos e os três primeiros graus negativos / We study the construction of integrable hierarchies. These hierarchies have infinite equations of motion which arise from the same algebraic structure, and, as a consequence, we can find simultaneously and systematically its solitonic solutions using the Dressing method. Inthiswork, we study the mKdV and KdV hierarchies and calculate explicitly the first few equations of motion for both of them. To the KdV, the Lax operator seems to work only in positive degrees. We determine the Bäcklund Transformations to the positive degrees of mKdV and KdV hierarchies using the fact that equations of motion can be written as total derivatives. We obtain a systematic way to construct the Bäcklund Transformations for the equations of the mKdV hierarchy exploring the gauge invariance of zero curvature equation. We determine the Bäcklund Transformations of Type-I and Type-II for the odd-degrees equations of mKdV hierarchy. We make the explicit calculation for first three positive degrees and also for the next three negative ones / CNPq: 130803/2013-8