Thesis (M.S.) -- Mississippi State University. Department of Computer Science and Engineering. / Title from title screen. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 1998. / Vita. Includes bibliographical references (leaves 258-270). Available also in a digital version from Dissertation Abstracts.

Includes bibliographical references (p. 162-177).

Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2006. / Swaminathan, Madhavan, Committee Chair ; Cressler, John D., Committee Co-Chair ; Kenney, Stevenson J., Committee Member ; Peterson, Andrew, Committee Member ; Durgin, Gregory, Committee Member ; Sitaraman, Suresh, Committee Member.

Thesis (Ph. D.)--University of Oregon, 2006. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 126-128). Also available for download via the World Wide Web; free to University of Oregon users.

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Orientador: Clóvis Ribeiro Ribeiro / Banca: Rosemeire Cristina Linhari Rodrigues Pietro / Banca: Leila Aparecida Chiavacci / Banca: Patrícia Bento da Silva / Banca: Roselena Faez / Resumo: A auto-montagem é a organização dos blocos de construção que compõem um sistema, em estruturas hierarquicamente ordenadas, sem qualquer tipo de influência externa. As forças que governam esse processo de auto-montagem das moléculas são as interações não covalentes, tais como interações de van der Waals, eletrostática, hidrofóbica, ligação de hidrogênio, dentre outras. A inspiração para o surgimento de materiais com base nessas interações veio da natureza e dos sistemas biológicos, que ocorrem naturalmente, tais como o DNA. A natureza reversível das interações não covalentes assegura que os blocos de construção que constituem o sistema podem se romper e se recombinar de acordo com as características do meio externo. Essa propriedade faz desses sistemas capazes de responder aos mais variados estímulos, tais como variações de temperatura, pH, solvente, radiação, etc. A reação de um ácido orgânico com a meglumina, um aminocarboidrato, leva à formação de um par iônico denominado genericamente de carboxilato-meglumina.Os objetivos nesse estudo, além da síntese de sistemas supra-anfifílicos foi ainda avaliar esses sistemas em fase aquosa e correlacionar as propriedades com uma potencial aplicação no âmbito farmacêutico. Nesse trabalho, ácido oleico e meglumina foram utilizados como os blocos de construção de um sistema anfifílico supramolecular. Inicialmente o par iônico entre ácido oleico e meglumina se formava, gerando o par oleato-meglumina e esse anfifílico se mantinha em fase a... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Self-assembly is the organization of building blocks in a system, in hierarchically-ordered structures without any external influence. The driving forces on molecular self-assembly are non-covalent interactions, such as van der Waals, electrostatics, hydrophobic, hydrogen bonding, amongst others. The inspiration for the emergent materials based on these interactions come from nature and naturally occurring biological systems such as DNA. The reversible nature of the non-covalent interactions ensures that the building blocks in a system can be broken and reunited according to the external environment. This property makes them capable of responding to different stimuli, such as variations in temperature, pH, solvent, radiation, etc. The reaction of an organic acid with meglumine, an aminocarbohydrate, leads to the formation of an ionic pair generally called carboxylate-meglumine. The aim of this work, besides the synthesis of the supra-amphiphiles, was to evaluate these systems in aqueous phase, and correlate the properties with potential application of them in the pharmaceutical field. In this work, oleic acid and meglumine were used as the building blocks for the synthesis of a supramolecular amphiphilic system. Initially, the ionic pair between oleic acid and meglumine was formed, generating oleate-meglumine. That amphiphilic was maintained in aqueous phase through hydrophobic interactions and hydrogen bonds. Two systems were synthesized, one in equimolar conditions and anot... (Complete abstract click electronic access below) / Doutor

Results are presented from a variety of molecular simulations of phase coexistence using the well established Gay-Berne (GB) liquid crystal model. Firstly, the simulation of bulk phase coexistence using the Gibbs ensemble Monte Carlo technique is presented, both for one and two-component GB systems. The one-component results, using a novel parameterisation of the GB, show a rich phase behaviour, displaying both isotropic and nematic-vapour coexistence, in good comparison with previous studies. A method for arriving at the two-component parameterisation is then discussed, followed by a novel application of the Gibbs ensemble to the isotropic-nematic transition in two-component systems. Results in broad agreement with theoretical predictions, subject to a large finite size effect, are obtained. Secondly, upon the basis of the one-component Gibbs results, results are presented from a series of molecular dynamics simulations of a free standing GB film in equilibrium with its own saturated vapour. The introduction of inhomogeneity is shown to induce a preferred molecular alignment in the nematic film perpendicular to the liquid-vapour interface. At slightly higher temperatures the nematic film is wet by the isotropic phase, displaying an intermediate ordering regime where the formation of short-lived nematic domains within the film is observed. This effect has been analysed using orientational correlation functions, and shown to result from a decoupling of the planar and perpendicular nematic ordering caused by the system inhomogeneity. A system-size analysis of this effect has also been undertaken, showing a definite increase in the range of decay of these orientational correlations with increasing system size.

Simulações de Dinâmica Molecular tornaram-se uma ferramenta indispensável no estudo de sistemas em fase condensada, incluindo sistemas líquido-Cristalinos, e na predição de propriedades dinâmicas. Cristais líquidos possuem um leque enorme de aplicações, mas o estudo teórico destes sistemas torna-se complicado devido ao seu tamanho, ao método utilizado para obtenção dos parâmetros do campo de força e, principalmente, à transferibilidade dos parâmetros para outro estado termodinâmico. Tendo isso em vista, este trabalho propõe uma metodologia para parametrizar campos de força derivados de cálculos mecânico-quânticos que possuam um grau de transferibilidade confiável. O sistema escolhido neste trabalho foi o 4’-Pentil- 4-Carbonitrila, também conhecido como 5CB, pois o mesmo já é utilizado em diversos aparelhos óptico-eletrônicos; a parametrização intramolecular foi feita com o programa JOYCE, e a intermolecular, com o programa PICKY. Os parâmetros intramoleculares obtidos mostraram uma boa descrição da geometria interna do sistema, contribuindo para a parametrização intermolecular, a qual obteve uma excelente descrição de propriedades termodinâmicas. Este trabalho corrobora para a hipótese de que campos de força derivados de cálculos mecânico- quânticos podem descrever diferentes fases termodinâmicas com um alto grau de confiabilidade. / Simulations using Molecular dynamics have become a powerful tool in the study of systems in condensed phase, including liquid-crystalline systems, and in the prediction of dynamical properties. Liquid Crystals have many applications, but the theoretical study of these systems is more complex because of their size, the method that was used in the force field parametrization and, mainly, because in most of the cases parameters cannot be transferred to another thermodynamical state. With that in mind, this work propose a methodology to parametrize force fields derived from quantummechanical calculations and which can be transferred to other thermodynamical state without losing important information. The chosen system in this work was the 4-Cyano-4’-Pentylbiphenyl, also known as 5CB, which have been used in many optical-electronic device and the intramolecular parametrization was done with the JOYCE program and the program PICKY was used in the intermolecular parametrization. The intramolecular parameters obtained show a good description of the internal geometry, contributes to the intermolecular parametrization, with we obtained an accurate description of the thermodynamical and physical chemical properties. This work corroborate to the hypothesis that force field derived from quantum-mechanical calculations can describe different thermodynamical states without losing important information.

Nuclear magnetic resonance (NMR) spectroscopy has been extensively used to investigate the structure and dynamics of host-guest systems. NMR spectroscopy has gained attention because of its high spectral information content for studies of molecules in the solid state and in solution. However, the main weakness of NMR is the inherent low detection sensitivity. Host-guest interactions are weak; therefore these interactions can be particularly difficult to study due to weak spectral response. NMR methods are currently the best solution for measuring these responses with atomic-scale precision. Improving upon these limitations is the main goal of this dissertation research using laser-polarized xenon, liquid crystals, and polarization exchange pulse sequences. The first five chapters review the basics of NMR spectroscopy that is used throughout this dissertation. Chapters one and two concern the fundamental elements of liquid-state and liquid-crystal NMR spectroscopy. The third chapter deals with the properties of organic thermotropic and lyotropic liquid crystals including the ZLI 1132 and PBLG. Chapter four presents the theoretical and experimental aspects of optical pumping laser-polarized xenon and properties of xenon. An overview of the dissertation research is described in chapter six. Chapter seven describes the procedures for synthesizing many of the cryptophanes used in the NMR experiments in this dissertation. The cryptophanes synthesized include cryptophane-A, cryptophane-223, and cryptophane-E as well as the water-soluble derivatives of each. The eighth and ninth chapters investigate the binding kinetics of hydrocarbon and hydrogen gases to cryptophane-111 in organic solutions. Chapter ten illustrates the utility of liquid crystalline-aligned cryptophanes (bis- and cryptophane-A) reintroducing dipolar couplings in solution. Chapter eleven describes the exploitation of the reintroduced dipolar coupling of the guest molecule to transfer the abundant 1H nuclear spin magnetization to the rare 13C spins to enhance NMR detection sensitivity using an adiabatic Hartmann-Hahn cross polarization pulse sequence. Chapter twelve describes cryptophanes of varying cavity size to probe the host-guest dynamic coupling (with chloroform as a guest ligand) aligned in PBLG. Finally, chapter thirteen introduces preliminary xenon @ cryptophanes aligned in liquid crystals to achieve intermolecular polarization transfer.