Ces dernières années, la physique de la matière condensée a connu une profonde révolution de concepts par la découverte de nombreuses phases de la matière qui ne sont pas classifiables à la Landau, c’est à dire par leur groupe de symétrie. Si les premiers travaux remontent à ceux des effets Hall quantiques (entier et fractionnaire), ce n’est que récemment, avec l’avènement du graphène et des isolants topologiques que les physiciens ont réalisé que ces phases de la matière ne nécessitent, dans l’absolu, ni champ magnétique, ni basse température, par opposition aux effets Hall quantiques précédemment cités. Ces nouveaux états de la matière sont caractérisés non pas par la géométrie du problème mais plutôt par la topologie. Ici donc, la forme précise du spectre électronique n’est pas importante, seules certaines caractéristiques, comme la présence ou l’absence d’un gap, le sont. De manière similaire à la classification de Landau des groupes de symétries, il est possible de classifier ces nouveaux systèmes par l’intermédiaire de groupes topologiques. La branche mathématique invoquée est celle de la topologie algébrique. A travers les invariants qu’elle génère, il est possible de classer les états topologiquement non-triviaux. De plus, les transitions entre des états à topologies distinctes sont aussi accessibles par cette théorie. Les travaux réalisés dans le cadre de cette thèse s’intéressent aux effets topologiques dans la structure de bandes de matériaux bi-dimensionnels. Après une présentation du formalisme mathématique général, un premier chapitre s’intéressera à la topologie locale, c’est à dire pour une portion restreinte de la première zone de Brillouin, des points de croisements de bandes, dits points de Dirac. Un effort sera porté vers la classification de ces systèmes et des transitions associées. Le chapitre suivant mettra en lumière un moyen efficace de mesurer les effets de la topologie des électrons en deux dimensions. Il s’agit de l’étude des niveaux de Landau qui résultent de l’application d’un champ magnétique 5transverse au plan des électrons. Les points de Dirac se transmutent alors en niveaux à énergie nulle topologiquement stables, c’est à dire peu ou pas influencés par les diverses perturbations. L’étude des différents modèles justifiera la discrimination entre la physique à champ magnétique faible et celle à champ magnétique fort, faible ou fort étant très dépendant du système étudié. Enfin, dans un dernier chapitre plus prospectif on s’intéressera à la topologie globale, c’est à dire pour l’ensemble de la première zone de Brillouin. Ce type d’étude est surtout caractérisé par l’existence d’états de bords robustes. On en fera l’expérience d’une double manière. D’abord par l’étude un modèle à un électron, puis par celle d’un système en forte interaction de N électrons. A travers les différents exemples étudiés, on s’attachera à démontrer la puissance de l’outil topologique pour les problèmes de la matière condensée, phénomène qui devrait s’accentuer les prochaines années. / During the last few decades, condensed matter physics has witnessed a deep refoundation of its paradigms, through the discovery of many systems that the usual symmety classification à la Landau cannot handle properly. Although the first major breaktroughs were realized at the time of discovery of integer and fractional quantum Hall effects, only recently physicists have agreed that these peculiar phases of matter require neither a magnetic field nor low temperature. Those new states of matter cannot be caracterized by the geometric aspects of the model but rather by topological ones. The precise shape of the electronic spectrum is no longer relevant, but only particular features are, such as the presence or the absence of a gap. Similarly to the Landau classification scheme, one can achieve a construction through extensive use of topological groups. This is the realm of algebraic topology. Related generated topological invariants can hold a classification of non-trivial topological states, as well as of the accompanying transitions. This thesis focusses on peculiar topological features of two-dimesnsional electronic band structures. After a technical introduction to the underlying formalism, the first chapter is devoted to local topology, that is for a restricted piece of the first Brillouin zone, of band crossing points, also known as Dirac points. Special care is taken to classify these points and related transitions. The next chapter sheds some light on a particularly efficent way of measuring topology for two-dimensional electrons. This is achieved through measurements of Landau levels that are generated by a magnetic field applied perpendicular to a plane. Dirac points then generate zero Landau levels that are topologically stable, i.e. almost not influenced by perturbations at all. Distinctions between low and high magnetic fields will prove to be relevant, although very system-dependant. Through the several models studied, we particularly stress out the importance of the topological tool for condensed matter physics, past present... and future.

Summary: Although the study of nutrition during the last forty years has received considerable attention, there are still fields of the science about which our knowledge is very incomplete. In this country, in particular, there is little information even about the gross chemical composition of our foodstuffs -- a subject which must surely form the basis of any dietry constituents present in foods is of value to anyone concerned with the planning of accurate diets, or the investigation of the nutritional status of a community. It is well known that the figures, even for carbohydrate, protein and fat, compiled by workers in different parts of the world, vary widely. In accurate work it would therefore be incorrect to use such figures which were compiled in another country. This must necessarily occur in New Zealand because at present no complete and systematic analysis of our foods had been made, and hence there are no comprehensive tables. Further-more, there are many native products for which there are neither comparable overseas figures nor any New Zealand analyses of constituents--Introduction.

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Reproduction de : Thèse Etat : Histoire du droit, des institutions et des faits sociaux : Lyon 3 : 2004. / Titre provenant de l'écran-titre. Bibliogr.

Thesis (M.A.)--Catholic Theological Union at Chicago, 2003. / Vita. Includes bibliographical references (leaves 145-148).

Thesis (M.A.)--Catholic Theological Union at Chicago, 2003. / Vita. Includes bibliographical references (leaves 145-148).

Thesis (M.A.)--Catholic Theological Union at Chicago, 2003. / Vita. Includes bibliographical references (leaves 145-148).

Made available in DSpace on 2018-08-01T22:30:02Z (GMT). No. of bitstreams: 1 tese_9030_Tese final André Gonçalves de Lima.pdf: 705806 bytes, checksum: 5f49dfbd29e1ef34ffa8556d3c6351c4 (MD5) Previous issue date: 2015-07-03 / Esta tese tem como objetivo central a obtenção de fases geométricas quânticas no cenário em que ocorre a violação de simetria de Lorentz. Nós obtivemos análogos de fases geométricas para a dinâmica não relativística de uma partícula neutra com momento de dipolo magnético permanente em diversos cenários que envolvem a violação de simetria. A violação de simetria é induzida pelo setor de paridade par e paridade ímpar do setor de calibre CPT-par do Modelo Padrão Estendido. Obtivemos casos análogos para as fases geométrica quânticas de Anandan, para efeito Aharonov-Casher, para efeito He-McKellar-Wilkens e para Aharonov-Bohm escalar. Para incluir este cenário da violação de simetria de Lorentz na evolução dinâmica, reescrevemos a equação de Dirac com a presença de um termo de acoplamento não mínimo, iγ^μ ∂_μ→iγ^μ ∂_μ+ig/2 γ^μ (k_F ) μναβ γ^ν F^αβ, já conhecido na literatura. Este termo contém o campo tensorial (kF ) μναβ que induz os efeitos de violação de simetria. Outro ponto abordado nesta tese é a obtenção de holonomias quânticas a partir das fases geométricas obtidas neste contexto da violação de simetria de Lorentz. Especificamente, nós obtivemos holonomias quânticas a partir do análogo da fase geométrica quântica de Anandan. Recentemente, holonomias quânticas tem recebido especial atenção devido a possibilidade de uso para realizar computação quântica holonômica.

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The study on dehydration of frozen saskatoon berries and the need for dried fruits has been strategically identified in the prairies. Our motivation was to find a suitable method for dehydration in order to extend saskatoon berry shelf life for preservation. Microwave, convection and microwave-convection combination drying processes were identified to finish-dry saskatoon berries after osmotic dehydration using sucrose and high fructose corn syrup (HFCS) sugar solutions. Osmotic dehydration removes moisture in small quantities and also introduces solutes into the fruit that acts as a preservative and also reduces the total drying time. <p>Due to the very short harvesting season of saskatoon berries, an accelerated process like microwave combination drying can bring down the moisture to safe storage level, immediately after harvest. Untreated and osmotically dehydrated berries were subjected to convection (control), microwave and microwave-convection combination drying conditions at different product drying temperatures (60, 70 and 80C) until final moisture content was 25% dry basis. A laboratory-scale microwave combination dryer was developed, built with temperature and moisture loss data acquisition systems using LabView 6i software. Thin-layer cross flow dryer was used for convection-only drying and for comparison. <p>Drying kinetics of the drying processes were studied and curve fitting with five empirical equations including Page equation, was carried to determine drying constant, R2 and standard error values. The microwave-combination drying method proved to be the best for drying saskatoon berries. Dehydrated product quality analysis by means of color changes, rehydration ratio measurements and observed structural changes with scanning electron microscope technique were the factors in drying method selection for saskatoon berries.<p> This research was instrumental in the modification and development of a novel drying system for high-moisture agricultural materials. Microwave-convection combination drying at 70oC, yields good results with higher drying rates and better end-product quality.