Cette thèse propose d'intégrer les principes de la micro-robotique dans un laboratoire sur puce afin d'améliorer les performances du tri cellulaire par diélectrophorèse. Contrôler la trajectoire des cellules dans une puce fluidique en temps réel nécessite de reconcevoir la puce, la modéliser et développer des lois de commande dédiées au contrôle en temps réel. Concernant la conception, cette thèse s’intéresse au compromis existant entre la vitesse de tri et les problématiques de suivi des cellules en temps réel. Une architecture originale basée sur deux plans d’électrodes, sur les faces supérieures et inférieures des canaux, est proposée. Des procédés de fabrication dédiés à cette architecture sont développés. En particulier, la fabrication d'électrodes transparentes et l'assemblage des deux réseaux d'électrodes parallèles sont étudiés. Concernant la modélisation, une formulation analytique du champ électrique découplant variables de commande, termes dépendant de la position de l’objet et termes dépendant uniquement de la géométrie de la puce est proposée afin de calculer rapidement et précisément la force de diélectrophorèse. Une analyse de l'anisotropie des forces de frottement présentes à proximité des électrodes vient compléter la modélisation dynamique du comportement des microparticules, et donne lieu à un modèle compatible avec la commande temps réel, validé expérimentalement sur des objets artificiels. Enfin, un contrôleur basé sur des techniques d’optimisation ainsi qu’un planificateur de trajectoires sont proposés pour le tri de cellules. Un simulateur est développé et met en avant les bonnes performances de tri d’un tel système. L’ensemble de ces méthodes permettront de contrôler la trajectoire de cellules biologiques dans des puces de tri afin d’en améliorer la sélectivité et la rapidité. / This thesis proposes to integrate the principles of micro-robotics in a lab-on-a-chip in order to improve the performance of cell sorting by dielectrophoresis. Controlling the trajectory of cells in a fluidic chip in real time requires redesigning the chip, modeling it and developing control laws dedicated to real-time control. Concerning the design, this thesis is interested in the compromise existing between the speed of sorting and the problems of cell tracking in real time. An original architecture based on two electrode planes, on the upper and lower faces of the channels, is proposed. Manufacturing processes dedicated to this architecture are developed. In particular, the manufacture of transparent electrodes and the assembly of the two parallel electrode arrays are studied. Concerning the modeling, an analytical formulation of the electric field uncoupling control variables, terms depending on the position of the object and terms depending solely on the geometry of the chip is proposed in order to quickly and accurately calculate the dielectrophoresis force. An analysis of the anisotropy of the friction forces present near the electrodes completes the dynamic modeling of the behavior of the microparticles, and gives rise to a model compatible with real-time control, validated experimentally on artificial objects. Finally, a controller based on optimization techniques and a trajectory planner are proposed for cell sorting. A simulator is developed and highlights the good sorting performance of such a system. All of these methods will control the trajectory of biological cells in sorting chips to improve selectivity and speed.

Este trabalho apresenta a implementação e comparação de três técnicas distintas de visão computacional tridimensional a saber: Visão estéreo: correlação de imagens bidimensionais (2D); Fusão sensorial - uso de sensores distintos: câmera 2D + sensor de ultra-som unidimensionais (1D); Iluminação estruturada. Os algoritmos de visão computacional apresentados são basicamente implementações de trabalhos anteriores, realizados a partir de técnicas atualizadas de comprovada eficiência. As principais características avaliadas durante o estudo comparativo entre as três técnicas são: carga computacional (tempo de obtenção do dado 3D); Influência do meio (ruído devido a uma iluminação não uniforme, ofuscamentos, sombras); custo da infra-estrutura para cada técnica; análise de incertezas, precisão (repetibilidade) e acuidade. Optou-se pelo uso do software Matlab versão 5.1 para a implementação dos algoritmos, dada a facilidade de programação e depuração, além de ser muito difundido e utilizado no meio acadêmico, permitindo que os resultados desse trabalho sejam reproduzidos e verificados. São apresentados exemplos de visão tridimensional aplicados a tarefas de montagem robotizada do tipo pick-and-place".

A energia é o maior contribuinte para os custos de operação de uma indústria, portanto, estudos para melhoria da eficiência dos sistemas que utilizam alguma fonte de energia são indispensáveis. O presente trabalho tem por objetivo a obtenção de configurações ótimas para satisfazer demandas de eletricidade e cargas térmicas de aquecimento e refrigeração a partir de uma fonte primaria de energia, avaliando o impacto dessas nos custos de produção de eletricidade, vapor e água gelada. Estes tipos de sistemas são conhecidos como sistemas de trigeração. A avaliação de desempenho dos sistemas de trigeração é conduzida através da aplicação da análise exergética e exergoeconômica das alternativas propostas para a determinação do rendimento exergético e custos em base exergética de produção de utilidades desse tipo de sistema. Após apresentar uma breve discussão sobre o uso eficiente e racional de energias primárias e mostrar um panorama da situação para a aplicação de sistemas de trigeração para satisfazer demandas energéticas na indústria e o setor terciário, são descritas diferentes tecnologias envolvidas neste tipo de sistemas e algumas configurações propostas por vários pesquisadores nos anos recentes. O trabalho mostra o impacto das tecnologias de trigeração nos custos em base exergética dos produtos: eletricidade, vapor para processo e água gelada. Sistemas de refrigeração por absorção de efeito simples, duplo efeito e o sistema híbrido de absorção/ejeto compressão são analisados, como parte do estudo dos sistemas de trigeração. Diversos sistemas de trigeração, incluindo o sistema tetra-combinado, são comparados satisfazendo demandas energéticas para três aplicações diferentes: indústria de laticínios, hospital e indústria de bebidas. As configurações em estudo são otimizadas usando o método de algoritmo genético. Os resultados mostram que o sistema de refrigeração híbrido de absorção/ejeto compressão é uma boa alternativa para a produção da água gelada porque o coeficiente de desempenho (COP) e a eficiência exergética são maiores do que no sistema de refrigeração por absorção de efeito simples. Observando o impacto na formação dos custos de conversão de energia para os sistemas de trigeração propostos, os sistemas que utilizam unidade de refrigeração por absorção de duplo efeito são os que apresentam menor impacto. O sistema tetra-combinado apresenta um menor impacto quanto comparado com o ciclo combinado com unidade de refrigeração por absorção de simples efeito. O consumo de combustível e a destruição de exergia dos diferentes sistemas são refletidos nos custos em base exergética dos diferentes produtos. A otimização com algoritmos genéticos mostrou ganhos importantes nos custos em base exergética dos produtos, mediante a maximização da eficiência exergética dos diferentes sistemas de trigeração. O método dos algoritmos genéticos mostra-se como um método robusto para a otimização de sistemas de conversão de energia, mesmo que exija um grande esforço computacional. / Energy is the largest contributor to operating costs of any industry; therefore, studies for improving systems efficiency that use some energy source are essential. This work aims to obtain optimal configurations in order to satisfy required demands for electricity and thermal loads for heating and cooling from a primary source of energy, evaluating the impact of the electricity, steam and chilled water production costs. These types of systems are known as trigeneration systems. The performance evaluation of trigeneration systems is carried out by the application of exergy and exergoeconomic analysis of the proposed alternatives in order to determine exergy efficiency and exergy based costs on production of this type of system utilities. After presenting a brief discussion about efficient and rational use of primary energies and an overview of situation for trigeneration systems application, various technologies involved in this type of systems and some configurations proposed by several authors are described. This research shows the impact of trigeneration technologies in exergy-based costs of products: electricity, steam process and chilled water. Absorption refrigeration systems of simple effect, double effect and the hybrid absorption/ejecto compression are analyzed, as part of the trigeneration systems study. Several trigeneration systems, including the tetra-combined system, are compared with each other, satisfying energetic demands for three different applications: a dairy industry, a hospital and a drinks industry. The configurations in study are optimized using the Genetic Algorithm method. The results show that the hybrid absorption/ejecto compression refrigeration system is a good alternative for chilled water production due to that the coefficient of performance (COP) and the exergetic efficiency are higher than simple effect absorption refrigeration system. Observing the impact in the formation of the energy conversion costs for trigeneration systems proposed, the systems that use a double effect absorption refrigeration system presents the less impact. When tetra-combined system is compared with the system using a simple effect absorption refrigeration system, the results show a reduction in the impact of costs formation. The fuel consumption and exergy destruction of the different systems is reflected in the exergy based costs of the different products. The optimization with genetic algorithms shown important profits in the exergy based costs of products, by means of the exergetic efficiency maximization of the different trigeneration systems. The genetic algorithm method is a robust method for energy conversion systems optimization, even that it demands a great computational effort.

O Estado contemporâneo enfrenta duas realidades que exigem um esforço imediato da sua parte, quais sejam, a necessidade da proteção integral dos direitos humanos e o efetivo combate à criminalidade organizada. Nesse respeito, observa-se que esse panorama sofre uma forte influência do processo de internacionalização e da dinamicidade de um mundo ―sem fronteiras‖, que, apesar dos benefícios inegáveis a outros campos da vida social, como na economia, acarretam a transnacionalização do crime e a proliferação de espaços em que a efetividade estatal é reduzida. Desse modo, o objetivo do presente trabalho é verificar a adequação da cooperação penal internacional como meio de combate à criminalidade organizada transnacional ocorrente na Tríplice Fronteira entre o Brasil, Argentina e Paraguai, na região de Foz do Iguaçu. A análise do caso possibilita identificar a tensão existente entre a soberania estatal, calcada no princípio da territorialidade, e a internacionalização, que pressupõe a abertura das fronteiras. No âmbito do Direito Penal, em razão da titularidade exclusiva do jus puniendi, a tutela dos direitos afetados pela criminalidade transfronteiriça deve ser atingida, especificamente no caso do tráfico de pessoas que ocorre na Tríplice Fronteira, por meio da cooperação entre os Estados que compõem a região. Identifica-se, nesse caso, que dois passos primordiais devem ser adotados: a criação de mecanismos de cooperação e a harmonização dos regramentos internos com os instrumentos internacionais. No caso específico, observa-se que há uma tendência à harmonização como alternativa a facilitar a repressão ao tráfico de pessoas pelos países da Tríplice Fronteira, sobretudo em vista da adesão dos ordenamentos nacionais à Convenção de Palermo e aos seus protocolos adicionais, que ditam normas para o combate à criminalidade organizada transnacional. Além disso, a adesão a pactos internacionais que privilegiam a assistência mútua em matéria penal, tal como a Convenção de Nassau e o Protocolo de São Luís, indicam a dimensão do processo de internacionalização e da criação de espaços regionais de integração jurídica. A consequência, e também a conclusão, é que a internacionalização é inevitável ao Estado, que enfrenta diversas crises. Nesse caso, sobretudo em razão da soberania, a cooperação se molda como alternativa mais apropriada para o cenário atual na região da Tríplice Fronteira, mostrando-se necessária a adequação dos ordenamentos dos países aos regramentos internacionais, por meio da harmonização e da internalização. / Nowadays, the State faces two realities that demand an immediate effort from it, that is, the need to fully protect the Human Rights and, at the same time, effectively combat organized crime. In this sense, we observe that this panorama is submitted to a strong influence of the internalization process and the dynamics of a borderless world that, in spite of the undeniable benefits to other fields of social live, such as economics, bring about the ―transnationality‖ of crime and emergency of spaces in which the State effectivity is reduced. Therefore, the objective of this work is to verify the adequacy of the mutual legal assistance in the combat of the transnational criminality that takes place in the tri-border of Brazil, Argentina and Paraguay, in the Foz do Iguaçu region. The case analysis enables to identify the existing tension between sovereignty, based in the territoriality principle, and the internationalization, which presuppose the opening up of the frontiers. In the case of the Criminal Law, due to the exclusive control of the jus puniendi by the State, the protection of the rights affected by the transnational criminality is mandatory, specifically in the case of the human trafficking that occurs in the tri-border, by means of the cooperation between the States that exist in the region. We identify, in this case, that two primordial steps must be adopted: the creation of cooperation mechanisms and the harmonization of the internal Law in accordance with the international treaties. In the specific study, we observe that there is a tendency towards the harmonization in the combat of the human trafficking by the countries of the tri-border, specially due to the participation in the Palermo Convention and its additional protocols, which dictate norms to the combat of the transnational organized crime. Besides, the participation in international treaties that favor the mutual legal assistance in criminal matters, such as the Nassau Convention and the San Luis Protocol, indicate the dimension of the internationalization process and the creation of regional juridical integration spaces. The consequence, and also the conclusion, is that the internationalization is inevitable to the State, which faces various crises. In this case, specially due to the sovereignty, the cooperation is set as the most appropriate alternative to the actual scenery in the tri-border region, demonstrating the need to adequate the internal order of the countries to the international order, by means of the harmonization and the internalization.

L’étude porte sur la notion grecque de κρίσις, alors que les études antiques ont souvent recours à une notion moderne de la crise. L’épopée, la Collection hippocratique et les dialogues de Platon forment le corpus. Les analyses de κρίσις issues de recherches déjà menées sur ces textes étaient très disparates. Il a été possible de résorber une partie de ces différences et de définir une notion générale de la κρίσις, par des enquêtes lexicales exhaustives. La κρίσις apparaît alors comme une action qui achève un conflit et permet, entre deux états ou conditions considérés comme opposés, une disjonction, subite accélération du cours des événements qui résout les affres de l’attente. La séparation et la décision assurent le passage du péril à un élan vital nouveau : la κρίσις permet la γένεσις. Ces traits de la notion, apparus dès l’épopée, où le mot désigne différentes décisions à la puissance génératrice et salvatrice soudaine, se retrouvent dans la « crise » médicale, guérison souvent subite, bien que prévisible en partie par l’art du pronostic, qui assure la reconstitution de l’équilibre de santé. La κρίσις platonicienne, jugement ou discernement, permet différents passages (de l’obscur au lumineux, de l’impur au pur, du malsain au sain), mais aussi, plus généralement, la régénération de l’âme. Elle restaure la fécondité de la pensée, conduit à une réincarnation sous une forme meilleure, et ordonne la recomposition de la vie bonne à partir d’éléments triés (Philèbe). En tant qu’instant qui décide d’une renaissance, point culminant de l’effort philosophique, la κρίσις voit aussi sa puissance libératrice dramatisée dans le dialogue. / My research is devoted to the Greek notion of κρίσις whereas classical studies usually favour the modern notion of crisis. It focuses on the Epic, the Hippocratic Corpus and Plato’s dialogues. The existing research on κρίσις has led to extremely varied results. My work offerts to reunite these differences in order to define a more general notion of κρίσις, thanks to a comprehensive lexical analysis. The κρίσις seems to be an act which puts an end to a conflict, thus enabling a breach between two opposite states. Time suddenly speeds, and the long torment resolves. Thanks to selection and decision making, danger gives way to a new life force: κρίσις enables γένεσις. These characteristics can already be found in the Epic where κρίσις refers to various decisions suddenly bringing generation and salvation. The medical notion of crisis is also a sudden recovery even though it can partially be predicted by prognosis, which brings health and balance back. The platonic κρίσις, which is akin to judging or discerning something, allows various changes (from darkness to light, from impurity to purity, from sickness to health) and ultimately enables the soul to regenerate. Fertility of the thought is restored; the soul can be reincarnated in a better shape or life reassembled with carefully selected elements (Philebus). As a turning point for a possible rebirth, as the climax of philosophical endeavours, the liberating power of the κρίσις has also often been dramatized in dialogues.

Third phase formation is an undesirable phenomenon during the PUREX process, which is a continuous liquid-liquid extraction approach for the reprocessing of uranium and plutonium from spent nuclear fuel. When third phase formation occurs, the organic extraction solution splits into two layers. The light upper layer, which is commonly named the light organic phase, contains a lower concentration of metal ions, tri-n-butyl phosphate (TBP) and nitric acids but is rich in the organic diluent. The heavy lower layer, which is commonly named the third phase, contains high concentrations of metal ions, TBP and nitric acids. As the third phase contains high concentrations of the uranium and plutonium complexes it can thus cause processing and safety concerns. Therefore, a comprehensive understanding of the mechanism of third phase formation is needed so as to improve the PUREX flowsheet. To investigate third phase formation through molecular simulations, one should first obtain reliable molecular models. A refined model for TBP, which uses a new set of partial charges generated from our density functional theory calculations, was proposed in this study. To compare its performance with other available TBP models, molecular dynamics simulations were conducted to calculate the thermodynamic properties, transport properties and the microscopic structures of liquid TBP, TBP/water mixtures and TBP/n-alkane mixtures. To our knowledge, it is only TBP model that has been validated to show a good prediction of the microscopic structure of systems that consist of both hydrophobic and hydrophilic species. This thesis also presents evidence that the light-organic/third phase transition in the TBP/n-dodecane/HNO3/H2O systems, which is relevant to the PUREX process, is an unusual transition between two isotropic, bi-continuous micro-emulsion phases. The light-organic /third phase coexistence was first observed using Gibbs Ensemble Monte Carlo (GEMC) simulations and then validated through Gibbs free energy calculations. Snapshots from the simulations as well as the cluster analysis of the light organic and third phases reveal structures akin to bi-continuous micro-emulsion phases, where the polar species reside within a mesh whose surface consists of amphiphilic TBP molecules. The non-polar n-dodecane molecules are outside this mesh. The large-scale structural differences between the two phases lie solely in the dimensions of the mesh. To our knowledge, the observation of the light-organic/third phase coexistence through simulation approaches and a phase transition of this nature have not previously been reported. Finally, this thesis presents evidence that the microscopic structure of the light organic phase of the Zr(IV)/TBP/n-octane/HNO3/H2O system, which is also related to the PUREX process, is different from that of the common hypothesis, where such system is consisted of large ellipsoidal reverse micelles. Snapshots from simulations, hydrogen bonding analysis and cluster analysis showed that the Zr4+, nitrate, TBP and H2O form extended aggregated networks. Thus, as above, we observe a bi-continuous structure but this time with embedded local clusters centred around the Zr4+ ions. The local clusters were found to consist primarily of Zr(NO3)4·3TBP complexes. This finding provides a new view of the structure of the Zr(IV)/TBP/n-octane/HNO3/H2O system.

Foz do Iguaçu, como a mais importante cidade da Tríplice Fronteira, possui um conjunto de características que remetem à condição geopolítica contemporânea. A cidade surgiu como Colônia Militar no século XIX, resultado de tensões entre os países da Bacia do Prata, em relação ao controle das fronteiras e do território. Foz do Iguaçu, que junto a Ciudad Del Este (Paraguai) e Puerto Iguazu (Argentina) forma uma espécie de metrópole tri-nacional, sempre foi foco privilegiado de interesses geopolíticos. Se o seu surgimento esteve atrelado às estratégias militares de controle territorial, o seu crescimento e desenvolvimento foram derivados de políticas do governo federal concernindo todo o Oeste Paranaense. A construção BR-277, da Ponte Internacional da Amizade e da Usina Hidrelétrica de Itaipu revela o valor da Tríplice Fronteira e de Foz do Iguaçu na relação entre os países do Cone Sul. Por meio da concentração de atividades turísticas e das práticas de comércio ilegal junto a Ciudad Del Este, a cidade se coloca numa condição única dentro de um cenário de integração regional do Mercosul. Ao mesmo tempo em que é um núcleo privilegiado dessa integração, após décadas de atritos geopolíticos entre Brasil, Paraguai e Argentina, Foz do Iguaçu expõe um emaranhado de problemas envolvendo o controle da fronteira, com reflexos políticos, econômicos e sociais para toda a América do Sul. / Foz do Iguaçu, as the most important city of the Tri-Border Area, has a set of characteristics which refer to the contemporary geopolitics condition. The city aroused as a Military Colony in the XIX century, being the result of tensions among the countries of the Prata Basin, involving border and territory control. Foz do Iguaçu, which together with Ciudad Del Este (Paraguay) and Puerto Iguazu (Argentina) form a kind of tri-national metropolis, has always been a privileged target of geopolitics interests. If its appearance has been linked to military strategies of territorial control, its growth and development were derived from policies of the federal government involving all the West of Paraná. The BR-277 construction of the International Bridge of Friendship and of Itaipu Hydropower Plant reveals the value of the Tri-Border and of Foz do Iguaçu in relation to other countries from the Southern Cone Countries. By means of the concentration of tourist activities and illegal commerce practices together with Ciudad Del Este, this city is placed in an unique condition within a scenery of regional integration of Mercosul. At the same time that it is a privileged nucleus of such integration, after decades of geopolitics friction amid Brazil, Paraguay and Argentina, Foz do Iguaçu presents a host of problems concerning the border control, with political, economical and social reflexes to all South America.

A eletrooxidação de etanol foi investigada sobre catalisadores bi e trimetálicos constituídos de Pt-M1 e Pt-M-M1 M = Sn, Mo, W, Ru, Os e Ir). Os eletrodos foram preparados em três diferentes configurações: eletrodos lisos (preparados em forno a arco voltaico), filmes depositados em placas de Ti (Pt-M/Ti) e nanopartículas metálicas dispersas em carbono (Pt-M-M1/C), ambos preparados pelo método Pechini. Os resultados eletroquímicos mostraram que a adição dos diferentes metais à platina aumentou a atividade catalítica dos eletrodos. Este efeito se mostrou dependente da composição do eletrodo e para os eletrodos lisos apresentou resultados mais acentuados nas composições Pt-Os e Pt-Sn-W. Os intermediários e produtos de reação da oxidação de etanol os eletrodos lisos foram determinados pelas técnicas de FTIR in situ de SPAIRS e SNIFTIRS. Os resultados sugerem que a presença dos elementos modificadores da platina aumentam a velocidade da reação de oxidação de etanol pela dessorção de intemediários com dois átomos de carbono (como CH3CHOads) a potenciais mais baixos do que a Pt levando conseqüentemente a liberação dos sítios ativos para nova adsorção de etanol. Constatou-se contudo, que a presença desses elementos não favorece a quebra da ligação C-C para formação de CO2 em quantidades apreciáveis. As composições de catalisadores Pt-M/Ti (M = Sn, Ru, Ir e Mo) preparados pelo método Pechini que apresentaram os melhores resultados em densidades de corrente foram os eletrodos de Pt-Sn/Ti. As análise por HPLC mostraram o produto majoritariamente formado foi o acetaldeído independente da composição do catalisador, mas os catalisadores Pt-Sn/Ti tiveram a maior seletividade na formação de ácido acético. Os testes em célula unitária foram realizados para os catalisadores trimetálicos Pt-Sn-W/C em diferentes composições. A presença de Sn e W aumentou significativamente o desempenho da célula com relação à Pt pura. O melhor catalisador testado (Pt-Sn-W/C (85:8:7)) apresentou OCV de 777 mV contra 345 mV da Pt a 90oC. A densidade de potência máxima alcançada para essa composição foi de 33 mW cm-2. A análise de produtos ao final de 5 horas de reação a 90oC aplicando 30 mA cm-2 de corrente mostrou que os produtos principalmente formados foram ácido acético e acetaldeído. / Ethanol oxidation on Pt-M1 e Pt/M/M1 (M = Sn, Mo, W, Ru, Os e Ir) catalysts prepared by arc melting furnace process and Pechini method was investigated. The electrochemical data showed that the addition of these elements to Pt gives a highest current densities at lower potentials. The best composition of electrodes prepared by arc melting process based on current densities values was Pt-Os and Pt-Sn-W. The intemediates and reaction products for ethanol oxidation were detected by SPAIRS and SNIFTIRS. The results sugest that adding a foreign metal to Pt leads an increase of the reaction rate for ethanol oxidation because desorption of two carbon atoms intermediates (as CH3 CHOads) at lower potentials comparing to pure Pt. The active site become then available for the new ethanol adsorption. However, the presence of these metals doesn\'t increase the selectivity to CO2 generation. Pt-M/Ti (M = Sn, Ru, Ir e Mo) catalysts were prepared by Pechini method. The products of the ethanol oxidation on these electrodes were evaluated by HPLC. The results showed that acetaldehyde was the main product obtained for all compositions. DEFCs tests were carry on with Pt-Sn-W/C ternary catalysts in different compositions. It was obtained particles size about 3.9 to 11 nm, depending on the catalyst composition. The addition of Sn and W increased significantly the DEFC performance. The best result was obtained by Pt-Sn-W/C (85:8:7) catalyst. It presents OCV about 777 mV against 345 mV to Pt at 90oC. The maximum of power density for this catalyst was 33 mW cm-2. Acetaldehyde was the major product formed when applying a fixed current of 30 mA cm-2 at 90oC.

This study is participant observational research focused on the culture of one successful alternative education program. The survey of the literature showed that the problem of high school dropouts is one of numbers and persistence over time. Most research in the past attempted to list characteristics of high school dropouts or elements of successful alternative education programs. Researchers such as Wehlage (1986) and Catterall (1987) have begun to look at a different approach. Their work looks at schools as systems and suggests that educators should direct their attention to the interaction of the school environment with the characteristics of the students. This view fits into a body of work that looks at schools and classrooms as microcultures. The work presented here looks at an alternative education program as a microculture and asks "What appears to be the distinguishing microculture created by the participants of Tri City Alternative Program?" The researcher collected data from interviews, observations, student projects and work, staff meetings, and program materials and records. The data were analyzed and organized to find patterns of behavior and interactions and to determine the meaning the participants attached to their interactions. The elements that distinguish the microculture of the alternative education program were divided into the features of the context and the features of the interactions. The elements of the context were described by the physical setting, the daily instructional schedule, and the non-instructional daily schedule. The elements of the interaction were described by clearly stated expectations, staff and student attention to culture, sense of caring and defining competence, and sense of humor. The researcher concludes by proposing three future areas of work. One is to develop a model of synchronization between the context and interactions of educational programs. The second is to complete additional cultural studies of high school dropouts. The last recommendation is to train teachers and students to use participant observational techniques in their classrooms to build their understanding of their own microcultures.

Les grès présentent un intérêt particulier en géologie pétrolière car ils possèdent généralement des gammes de porosité et de perméabilité favorables à la migration, au piégeage et à la récupération des hydrocarbures. Leur caractérisation fait donc l'objet d'études poussées. Ainsi, de nombreux sédimentologues ont analysé en détail une grande variété de systèmes sédimentaires afin de décrire la géométrie des corps gréseux et des barrières de perméabilité, et de caractériser l'organisation interne des faciès sédimentaires. Ces travaux ont conduit à la corrélation des données de puits et à l'élaboration de modèles statistiques prédictifs.<br />Ces descriptions sédimentologiques ne prennent pas en compte les caractères pétrographiques, minéralogiques ou géochimiques qui permettraient pourtant d'attribuer des causes directes, primaires ou secondaires, aux variations de porosité et de perméabilité rencontrées dans les roches. De plus, depuis quelques années, la diagenèse minérale, souvent à l'origine de ces variations, fait l'objet d'une modélisation déterministe qui s'appuie sur les processus physiques et chimiques mis en œuvre. Des logiciels de plus en plus performants permettent ainsi de réaliser des simulations destinées à proposer des bilans géochimiques variés qu'il est nécessaire de valider par des observations de terrain.<br />Cette thèse a pour objectif, d'une part, de compléter les études sédimentologiques par l'acquisition et l'analyse de données géochimiques et, d'autre part, de mieux comprendre la diagenèse des grès réservoirs en associant la géochimie à la modélisation numérique.<br />Deux formations géologiques, analogues de réservoirs exploités, ont servi de support à cette étude : les grès fluviodeltaïques du Ravenscar Group (Jurassique Moyen, côtes du Yorkshire, Royaume-Uni) et les Grès turbiditiques d'Annot (Eocène-Oligocène, Bassin du Sud-Est, France). L'échantillonnage a été réalisé afin d'apprécier la variabilité verticale et latérale de composition à diverses échelles (centimétrique à hectométrique) aussi bien entre faciès sédimentaires qu'au sein d'un même niveau lithostratigraphique.<br />L'étude géochimique montre que les faciès sont caractérisés par leur gamme de composition chimique ainsi que par leur style de variabilité élémentaire. Elle permet également de mieux comprendre la répartition des minéraux et des éléments au sein de la roche.<br />Ainsi, dans certains faciès, le tri sédimentaire entre les petits minéraux lourds et le reste de la roche (entrainment sorting) engendre des variations de teneur importantes pour les éléments portés par ces différentes classes de particules détritiques (Zr, Cr, Th, etc. pour les minéraux lourds ; Al, Na, K, etc. pour la fraction élastique). Des caractéristiques chimiques propres à chacune de ces populations de minéraux, valables à une échelle verticale de plusieurs mètres, peuvent alors être définies. Certaines d'entre elles, relatives aux éléments immobiles, permettent d'identifier des variations dans l'alimentation détritique. Une ségrégation s'opère également au sein de la fraction élastique entre les particules les plus grosses, dont la nature dépend de la maturité du grès, et les autres grains lors du dépôt.<br />Deux transformations diagénétiques majeures, à savoir la kaolinitisation et l'albitisation des feldspaths, sont également à l'origine de la distribution particulière des compositions chimiques de la fraction alumineuse des grès du Ravenscar Group.<br />Ce dernier point a été utilisé pour tester et valider la modélisation numérique de la diagenèse des grès du Ravenscar Group à l'aide du code numérique DIAPHORE de l'Institut Français du Pétrole. La néoformation de kaolinite apparaît alors possible dans la gamme de température 25-80°C, quel que soit le type d'eau superficielle considéré. La précipitation des argiles est induite par la présence et la circulation d'une eau en déséquilibre avec le réservoir gréseux, entraînant la dissolution successive des feldspaths. L'albitisation des feldspaths plagioclases s'effectue à faible température et dépend assez peu du type d'eau injectée. Enfin, l'albitisation des feldspaths potassiques est plus délicate à réaliser et n'est efficace que pour des eaux marines ou saumâtres à des températures supérieures à 50°C, et circulant dans un réservoir soumis à un gradient de température. Les simulations confirment donc l'importance de la perméabilité et de la circulation des fluides dans la diagenèse des aluminosilicates.<br />Les variations de composition chimique de la fraction alumineuse des grès du Ravenscar Group sont reproduites dans les simulations. Les conditions nécessaires aux transformations sont particulières mais compatibles avec le contexte géologique des grès étudiés. Les principales transformations diagénétiques, indépendantes, nécessitent alors plusieurs épisodes de circulation d'eau pour rendre compte de la diversité des compositions chimiques et minérales observées.<br />Les travaux menés dans le cadre de cette thèse laissent à penser que l'on pourrait intégrer plus systématiquement l'approche géochimique dans les études de réservoir.