No description available.

The purpose of this research was to develop the pseudo-ternary phase diagrams for a model drug delivery system consisting of vitamin E (model drug) + soybean oil + surfactant + co-surfactant (anhydrous glycerol) + water. The model drug (vitamin E) was loaded in the oil phase. The effects of different surfactants (pure and mixed) on the phase diagram, especially the microemulsion region, were investigated. The influence of drug loading level on the phase diagram was also determined. The surfactants studied were Tween 20, Tween 80, Cremopher EL, and their mixtures. The size (area) of the microemulsion region of the phase diagram was found to be dependent on the type of surfactant used and the loading level of drug (vitamin E). The phenomenon of phase inversion from W/O microemulsion to O/W microemulsion was also investigated for the drug delivery system consisting of soybean oil (0% w/w Vitamin E loading or 30% w/w Vitamin E loading) + Tween 80 + anhydrous glycerol + water. The inversion of phases was detected by observing changes in the viscosity of the system.

The purpose of this research was to develop the pseudo-ternary phase diagrams for a model drug delivery system consisting of vitamin E (model drug) + soybean oil + surfactant + co-surfactant (anhydrous glycerol) + water. The model drug (vitamin E) was loaded in the oil phase. The effects of different surfactants (pure and mixed) on the phase diagram, especially the microemulsion region, were investigated. The influence of drug loading level on the phase diagram was also determined. The surfactants studied were Tween 20, Tween 80, Cremopher EL, and their mixtures. The size (area) of the microemulsion region of the phase diagram was found to be dependent on the type of surfactant used and the loading level of drug (vitamin E). The phenomenon of phase inversion from W/O microemulsion to O/W microemulsion was also investigated for the drug delivery system consisting of soybean oil (0% w/w Vitamin E loading or 30% w/w Vitamin E loading) + Tween 80 + anhydrous glycerol + water. The inversion of phases was detected by observing changes in the viscosity of the system.

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In addition to their potential use at low to moderate temperatures in mobile fuel cell technologies, metal hydrides may also find application as high temperature tritium getterers in the U.S. DOE Next Generation Nuclear Plant (NGNP). We use Density Functional Theory to identify metal hydrides capable of sequestering tritium at temperatures in excess of 1000 K. First we establish the minimum level of theory required to accurately capture the thermodynamics of highly stable metal hydrides and determine that isotope effects can be neglected for material screening. Binary hydride thermodynamics are largely well established, and ternary and higher hydrides typically either do not form or decompose at lower temperatures. In this thesis we investigate anomalous systems with enhanced stability in order to identify candidates for the NGNP application beyond the binary hydrides. Methods implemented in this work are particularly useful for deriving finite temperature phase stability behavior in condensed systems. We use grand potential minimization methods to predict the interstitial Th−Zr−H phase diagram and apply high throughput, semi-automated screening methodologies to identify candidate complex transition metal hydrides (CTMHs) from a diverse library of all known, simulation ready ternary and quaternary CTMHs (102 materials) and 149 hypothetical ternary CTMHs based on existing prototype structures. Our calculations significantly expand both the thermodynamic data available for known CTMHs and the potential composition space over which previously unobserved CTMHs may be thermodynamically stable. Initial calculations indicate that the overall economic viability of the tritium sequestration system for the NGNP will largely depend on the amount of protium rather than tritium in the metal hydride gettering bed feed stream.

Made available in DSpace on 2014-06-11T19:25:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-12-15Bitstream added on 2014-06-13T19:12:25Z : No. of bitstreams: 1 paes_c_me_ilha.pdf: 1124164 bytes, checksum: b30843e958a40bb7c8b7ff4142f19d31 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O presente trabalho tem como objetivo estudar, através de investigações de espectros no infravermelho (FTIR), as transições de fases estruturais do sistema ferroelétrico titanato zirconato de chumbo, PbZr1-xTixO3 (PZT) no Contorno de Fase Morfotrópico (Morphotropic Phase Boundary, conhecido como MPB), região em que as propriedades elétricas desse material são máximas. Foram analisadas as soluções sólidas PbZr0,53Ti0,47O3 e PbZr0,54Ti0,46O3, que à temperatura ambiente encontram-se no interior do MPB e PbZr0,55Ti0,45O3, composição no limite da região do MPB, entre a fase monoclínica e a fase romboédrica, região ainda não bem definida e sob intensa investigação. Estudos estão centrados na freqüência e na meia largura dos modos stretching nos octaedros (BO6) da estrutura perovskita (ABO3) em função da temperatura. Anomalias encontradas para amostras com 47 e 46 mol % de PbTiO3 sugerem as transições da fase monoclínica de baixa para alta temperatura ( LT M F ? HT M F ), da fase monoclínica de alta temperatura para a coexistência da fase monoclínica com a fase tetragonal ( M F ? M F + T F ), e da coexistência da fase monoclínica com a tetragonal para a fase cúbica ( M F + T F ? C F ). Na amostra com 45 mol % de PbTiO3 foram encontradas anomalias que podem também estar associadas às transições de fases, mas que não foram possíveis de serem identificadas nas fases envolvidas. / The present work studies, through investigations of the spectra in infrared (FTIR), the transitions of structural phases of the ferroelectric system lead zirconate titanate, PbZr1- xTixO3 (PZT), in the Morphotropic Phase Boundary (MPB), region where the electrical properties of this material are at its maxiumun. We analyzed the solid solutions PbZr0,53Ti0,47O3 and PbZr0,54Ti0,46O3, which at room temperature are found within the MPB and also the composition PbZr0,55Ti0,45O3, that is located on the limit of the MPB - between the monoclinic and the rhombohedral phases - a not-yet defined region under intense investigation. Studies are concentrating on frequency and half width of the stretching modes in octahedrons (BO6) of the perovskite structure (ABO3) regarding temperature. Anomalies found in samples with 47 and 46 mol % of PbTiO3 suggest transitions in the monoclinic phase from low to high temperature ( LT M F ? HT M F ), from monoclinic phase of high temperature to the coexistence between the monoclinic phase with the tetragonal phase ( M F ? M F + T F ), and the coexistence between the monoclinic phase with tetragonal for the cubic phase ( M F + T F ? C F ). In the sample with 45 % mol of PbTiO3 we have found anomalies that can also be associated with phase transitions. Such transitions have not been possible to identify during the stages of this work.

Orientador: Eudes Borges de Araújo / Banca: Victor Ciro Solano Reynoso / Banca: Sebastião William da Silva / Resumo: O presente trabalho tem como objetivo estudar, através de investigações de espectros no infravermelho (FTIR), as transições de fases estruturais do sistema ferroelétrico titanato zirconato de chumbo, PbZr1-xTixO3 (PZT) no Contorno de Fase Morfotrópico (Morphotropic Phase Boundary, conhecido como MPB), região em que as propriedades elétricas desse material são máximas. Foram analisadas as soluções sólidas PbZr0,53Ti0,47O3 e PbZr0,54Ti0,46O3, que à temperatura ambiente encontram-se no interior do MPB e PbZr0,55Ti0,45O3, composição no limite da região do MPB, entre a fase monoclínica e a fase romboédrica, região ainda não bem definida e sob intensa investigação. Estudos estão centrados na freqüência e na meia largura dos modos stretching nos octaedros (BO6) da estrutura perovskita (ABO3) em função da temperatura. Anomalias encontradas para amostras com 47 e 46 mol % de PbTiO3 sugerem as transições da fase monoclínica de baixa para alta temperatura ( LT M F ? HT M F ), da fase monoclínica de alta temperatura para a coexistência da fase monoclínica com a fase tetragonal ( M F ? M F + T F ), e da coexistência da fase monoclínica com a tetragonal para a fase cúbica ( M F + T F ? C F ). Na amostra com 45 mol % de PbTiO3 foram encontradas anomalias que podem também estar associadas às transições de fases, mas que não foram possíveis de serem identificadas nas fases envolvidas. / Abstract: The present work studies, through investigations of the spectra in infrared (FTIR), the transitions of structural phases of the ferroelectric system lead zirconate titanate, PbZr1- xTixO3 (PZT), in the Morphotropic Phase Boundary (MPB), region where the electrical properties of this material are at its maxiumun. We analyzed the solid solutions PbZr0,53Ti0,47O3 and PbZr0,54Ti0,46O3, which at room temperature are found within the MPB and also the composition PbZr0,55Ti0,45O3, that is located on the limit of the MPB - between the monoclinic and the rhombohedral phases - a not-yet defined region under intense investigation. Studies are concentrating on frequency and half width of the stretching modes in octahedrons (BO6) of the perovskite structure (ABO3) regarding temperature. Anomalies found in samples with 47 and 46 mol % of PbTiO3 suggest transitions in the monoclinic phase from low to high temperature ( LT M F ? HT M F ), from monoclinic phase of high temperature to the coexistence between the monoclinic phase with the tetragonal phase ( M F ? M F + T F ), and the coexistence between the monoclinic phase with tetragonal for the cubic phase ( M F + T F ? C F ). In the sample with 45 % mol of PbTiO3 we have found anomalies that can also be associated with phase transitions. Such transitions have not been possible to identify during the stages of this work. / Mestre

No description available.

La réalisation expérimentale de la condensation de Bose-Einstein (BEC) a ouvert un nouveau champ d'investigation très fertile dans l'étude des atomes froids. En particulier, la possibilité de synthétiser des gaz de fermions piégés dans des réseaux optiques représente un développement de la plus haute importance pour la physique de la matière condensée. Ceci ouvre notamment sur la perspective d'étudier des phases quantiques exotiques stabilisées dans des systèmes d'électrons fortement corrélés.Récemment, les gaz atomiques d'alcalino-terreux ou d'ytterbium ont suscité un vif intérêt et ont été refroidis jusqu'à la dégénérescence quantique. La structure atomique particulière de ces systèmes leur confère de très hauts degrés de symétrie, grâce au découplage entre le spin nucléaire et le moment angulaire électronique. Une physique exotique conduisant à de multiple applications peut résulter de ces systèmes de hautes symétries qui ne peut être sondée que par les solides bases de la matière condensée.Dans cette thèse, on se propose d'étudier les propriétés physiques de basse énergie d'un gaz de fermions de type alcalino-terreux, piégé dans un réseau optique à une dimension. À une dimension, il est possible d'analyser les effets des interactions de manière non-perturbative par des approches de théorie des champs comme la bosonisation ou la théorie des champs conformes, et numériquement par le groupe de renormalisation de la matrice densité (DMRG). L'ensemble de ces outils sera notamment utilisé pour déterminer le diagramme de phase des gaz de fermions d'alcalino-terreux ou d'ytterbium à une dimension. / Experimental realization of Bose-Einstein condensate (BEC) opened a new and rich field of investigation for the study of the cold atoms. In particular, the possibility of creating trapped fermionic gases in optical lattices represent one of the most important development for the condensed matter physics. This open the outlook of studying exotic and stabilized quantum phases in strongly correlated systems of electrons.Recently, alkline-earth or ytterbuim atomic gases have given rise to great interest and have been cooled down up to quantum degenaracy. The specific atomic structure of these systems confer them very high degrees of symetry, thanks to the decoupling beetwin the nuclear spin and the electronic angular momentum. An exotic physics which is only probe thanks to the strong fundament of the condensed matter.In this thesis, we propose to study the physical properties at low energy of a alkaline-earth-like fermionic gas, trapped in a one dimensional optical lattice. In one dimension, we are able to analyse effects of interactions in a non-pertubative way with conformal field theory or bosonization, and numerically with Density Matrix Renormalization Group (DMRG) approach. All of these tools will be used to provide the phase diagram of these alkaline-earth-like fermionic gases in one dimension.