Ligas de titânio do tipo ??compostas de elementos não tóxicos são materiais com potencial para aplicações biomédicas por apresentarem baixo módulo de elasticidade, efeito de memória de forma, biocompatibilidade satisfatória e boa conformabilidade. Para os biomateriais, o conhecimento das propriedades de fadiga é essencial para garantir uma alta confiabilidade para implantes ortopédicos e odontológicos. As propriedades mecânicas dependem diretamente do processamento termomecânico, da taxa de resfriamento imposta à liga e da composição química, que são fatores responsáveis pela determinação de sua microestrutura. Neste contexto, neste trabalho foi avaliado o comportamento em fadiga da liga Ti-35Nb-7Zr (% em p.) para aplicações biomédicas. Trata-se de uma liga de titânio do tipo ??e a motivação desse estudo baseou-se em complementar resultados de suas propriedades microestruturais e mecânicas obtidos em estudos anteriores realizados no DEMAR - EEL/USP. A liga foi produzida por fusão a arco a partir de materiais (Ti, Nb, Zr) de pureza comercial. A rota de processamento termomecânico envolveu as etapas de tratamento térmico de solubilização, forjamento rotativo a frio, tratamento térmico de recristalização. Um tratamento térmico ultrarrápido (Flash) foi adicionado para promover o refino de grãos e aumento da resistência mecânica. A caracterização microestrutural foi realizada por técnicas de microscopia óptica, microscopia eletrônica de varredura, microscopia eletrônica de transmissão, difratometria de raios X e medidas de dureza Vickers. As propriedades mecânicas foram investigadas por ensaios de tração uniaxial e ensaios de fadiga de alto ciclo por flexão rotativa de corpos de prova lisos e entalhados. Com relação ao conjunto de propriedades, os melhores resultados podem ser considerados para a condição recristalizada à 1000ºC/2h + flash. Os resultados obtidos neste trabalho confirmam a possibilidade de uso da liga Ti-35Nb-7Zr para aplicações biomédicas. / ?-type titanium alloys composed of non-toxic elements are materials with potential for biomedical applications because they have low elastic modulus, shape memory effect, satisfactory biocompatibility and good workability. For biomaterials, knowledge of fatigue properties is essential to ensure high reliability for orthopedic and dental implants. The mechanical properties depend directly on thermomechanical processing, alloy cooling rate and chemical composition, which are responsible for the determination of its microstructure. In this context, this work was evaluated the fatigue behavior of the Ti- 35Nb-7Zr alloy (wt. %) for biomedical applications. It is a ?-type alloy and the motivation of this study was based on complementing the results of its microstructural and mechanical properties previously obtained at DEMAR-EEL/USP. The alloy was produced from materials of commercial purity (Ti, Nb and Zr) by arc meling. The thermomechanical processing route consisted the steps of solubilization heat treatment, cold rotary forging, recrystallization heat treatment. A ultrafast thermal treatment (Flash) was additioned to promote the grain refinement and to increase mechanical strength. The microstructural characterization was done by optical microscopy, scanning electron microscopy, transmission electron microscopy, X ray diffraction techniques and Vickers microhardness tests. The mechanical properties was investigated by uniaxial tensile tests and rotary bending high cycle fatigue tests of smooth and notched specimens. With respect to the set of properties, the best results can be considered for recrystalized condition at 1000ºC/2h + flash. The results obtained in this work confirm the possibility of using the Ti-35Nb-7Zr alloy for biomedical applications.

Depuis une vingtaine d'années, l'industrie de la microélectronique et en particulier le marché des mémoires non-volatiles connaît une évolution considérable, en termes d'augmentation de la capacité d'intégration et de diminution du prix de revient. Ceci a permis au grand public d'accéder aux produits électroniques (téléphones portables, baladeurs MP3, clés USB, appareils photos numériques...) qui connaissent actuellement un énorme succès. Cependant, la miniaturisation des mémoires Flash risque de rencontrer des limitations. C'est pourquoi les industriels et les laboratoires recherchent actuellement de nouvelles voies qui permettraient de prolonger la durée de vie de ces dispositifs. Dans ce contexte, l'objectif premier de cette thèse est l'étude expérimentale et théorique des mémoires non-volatiles à nanocristaux de silicium. Nous avons montré les différentes possibilités d'intégration des nanocristaux de silicium à partir d'un procédé de fabrication standard. Un démonstrateur Flash NOR 32 Mb à nanocristaux de silicium a été réalisé à partir d'un produit ATMEL. Nous nous sommes ensuite intéressés à la caractérisation électrique des cellules et matrices mémoires. Une étude exhaustive de l'influence des conditions de programmation ainsi que des paramètres technologiques sur les performances électriques a été menée. La modélisation de l'effacement Fowler-Nordheim et du « gate disturb » a permis de comprendre l'influence de certains de ces paramètres. Concernant l'écriture par porteurs chauds, nous avons étudié l'influence des conditions d'écriture sur la localisation de la charge à l'aide de simulations TCAD et d'un modèle analytique couplé à des mesures expérimentales.

<p>Terminal heme-copper oxidases (HCuOs) are transmembrane proteins that catalyze the final step in the respiratory chain - the reduction of O₂ to H₂O, coupled to energy conservation by generation of an electrochemical proton gradient. The most extensively investigated of the HCuOs are the <i>aa</i>₃-type oxidases, to which cytochrome <i>c</i> oxidase (Cyt<i>c</i>O) belongs, which uses energy released in the O₂-reduction for proton pumping. The bacterial nitric oxide reductases (NORs) have been identified as divergent members of the HCuO-superfamily and are involved in the denitrification pathway where they catalyze the reduction of NO to NO₂. Although as exergonic as O₂-reduction, this reaction is completely non-electrogenic. Among the traditional HCuOs, the <i>cbb</i>₃-type oxidases are the closest relatives to the NORs and as such provide a link between the <i>aa</i>₃ oxidases and the NORs. The <i>cbb</i>₃ oxidases have been shown to pump protons with nearly the same efficiency as the <i>aa</i>₃ oxidases, despite low sequence similarity.</p><p>This thesis is focused on measurements of membrane potential generating reactions during catalysis in the Cyt<i>c</i>O and the <i>cbb</i>₃ oxidase from <i>Rhodobacter sphaeroides</i>, and the NOR from <i>Paracoccus</i> <i>denitrificans</i>, using a time resolved electrometric technique. The pH dependence of the membrane potential generation in Cyt<i>c</i>O showed that only one proton is taken up and that no protons are pumped, at high pH. An additional kinetic phase was also detected at high pH that presumably originates to from charge-transfer within the K-pathway. Possible reasons for uncoupling, and the extent of charge-transfer, were studied using structural variants of Cyt<i>c</i>O. The measurements established that electrons and protons are taken up from the same side of the membrane in NOR. In addition, the directionality for proton uptake in <i>cbb</i>₃ oxidase appeared to be dependent on the choice of substrate while proton pumping was indicated to occur only during O₂-reduction.</p>

L'astronomie gamma des Très Hautes Energies utilise jusqu'à aujourd'hui exclusivement comme détecteurs le Photomultiplicateur à Tube (PMT) pour capter les faibles flux lumineux des gerbes atmosphériques. Mais une alternative commence à apparaitre : les photodiodes à avalanche polarisées en mode Geiger appelées APD Geiger. Le PMT est un détecteur conçu dans les années 70 qui présente certes de nombreux avantages mais qui souffre également d'inconvénients comme la taille, le coût, le poids ou encore la sensibilité aux champs magnétiques et surtout la difficulté à réaliser une pixellisation en matrice. Les APD-Geiger, sont des dispositifs à semi-conducteur composés d'une jonction PN intégrée dans une technologie spéciale pour la détection de très faible flux lumineux grâce à leur polarisation au delà de la tension d'avalanche. Les APD-Geiger présentent un gain de photoélectrons très élevé (~106), bien que dépendant fortement de la tension de polarisation au delà de l'avalanche. Ces photodiodes présentent de nombreux avantages par rapport aux photomultiplicateurs, notamment du point de vue de leur miniaturisation pour des applications basées sur l'imagerie, comme la détection de flashs Tcherenkov en astronomie gamma. Dans cette thèse, nous présentons l'étude, la conception et la réalisation de cette structure technologique basée sur du Silicium. Cette structure a montré sa fiabilité pour la détection de faibles flux lumineux avec une tension de claquage de 12V et un courant de fuite ne dépassant pas 10pA au claquage. Nous avons également mis au point, différents modèles physiques et électriques indispensables aux démarches d'optimisation technologiques ainsi qu'au développement des circuits de commande et de lecture, i.e. la base de toute technologie d'imagerie. Le travail présenté ici consiste en l'étude, la conception et la réalisation d'une matrice de pixels à haute sensibilité. Un projet de télescope Cerenkov basé sur cette technologie innovante est finalement présenté

L'étude a pour objectif l'amélioration de la fiabilité des assemblages électroniques à travers la mise en œuvre de drains composites aluminium/fibres de carbone. Le travail a consisté à 1) modéliser, par la méthode des éléments finis, l'influence des propriétés thermiques et mécaniques du matériau de semelle sur l'assemblage életronique ; 2) élaborer (par frittage sous charge uniaxiale, frittage flash et extrusion à chaud) des matériaux composites aluminium/fibres de carbone ; et 3) lier les microstructures observées aux paramètres des procédés d'élaboration ainsi qu'aux propriétés thermiques et mécaniques mesurées.

<p>The aim of this study is to synthesize a material with high thermal conductivity and a low coefficient of thermal expansion (CTE), useful as a heat sink. Carbon nanofibres (CNF) are first coated with copper by an electroless plating technique and then sintered to a solid sample by either spark plasma sintering (SPS) or hot pressing (HP). The final product is a carbon nanofibre reinforced copper composite. Two different fibre structures are considered: platlet (PL) and herringbone (HB). The influence of the amount of CNF reinforcement (6-24 %wt), on the thermal conductivity and CTE is studied. CNF has an excellent thermal conductivity in the direction along the fibre while it is poor in the transverse direction. The CTE is close to zero in the temperature range of interest. The adhesion of Cu to the CNF surface is in general poor and thus improving the the wetting of the copper by surface modifications of the fibres are of interest such that thermal gaps in the microstructure can be avoided. The poor wetting results in CNF agglomerates, resulting in an inhomogeneous microstructure. In this report a combination of three different types of surface modifications has been tested: (1) electroless deposition of copper was used to improve Cu impregnation of CNF; (2) heat treatment of CNF to improve wetting; and (3) introduction of a Cr buffer layer to further enhance wetting. The obtained composite microstructures are characterized in terms of chemical composition, grain size and degree of agglomeration. In addition their densities are also reported. The thermal properties were evaluated in terms of thermal diffusivity, thermal conductivity and CTE. Cr/Cu coated platelet fibres (6wt% of CNF reinforcement) sintered by SPS is the sample with the highest thermal conductivity, ~200 W/Km. The thermal conductivity is found to decrease with increasing content of CNFs.</p>

Phase behaviour information is essential for the development and optimization of hydrocarbon resource production, transport and refining technologies. Experimental data sets for mixtures containing heavy oil and bitumen are sparse as phase behaviour data are difficult to obtain and cost remains prohibitive for most applications. A computational tool that predicts phase behaviours reliably for mixtures containing such ill-defined components, over broad temperature, pressure and composition ranges would play a central role in the advancement of bitumen production and refining process knowledge and would have favourable impacts on the economics and environmental effects linked to the exploitation of such ill-defined hydrocarbon resources. Prior to this work, predictive computational methods were reliable for dilute mixtures of ill-defined constituents. To include a much wider range of conditions, three major challenges were addressed. The challenges include: creation of a robust and accurate numerical approach, implementation of a reliable thermodynamic model, and speciation of ill-defined constituents like Athabasca Bitumen Vacuum Residue (AVR). The first challenge was addressed by creating a novel computational approach based on a global minimization method for phase equilibrium calculations. The second challenge was tackled by proposing a thermodynamic model that combines the Peng-Robinson equation of state with group contribution and related parameter prediction methods. The speciation challenge was addressed by another research group at the University of Alberta. Pseudo components they proposed were used to assign groups and estimate thermodynamic properties. The new phase equilibrium computational tool was validated by comparing simulated phase diagrams with experimental data for mixtures containing AVR and n-alkanes. There is good qualitative and quantitative agreement between computed and experimental phase diagrams over industrially relevant ranges of compositions, pressures and temperatures. Mismatch was only observed over a limited range of compositions, temperatures and pressures. This computational breakthrough provides, for the first time, a platform for reliable phase behaviour computations with broad potential for application in the hydrocarbon resource sector. The specific computational results can be applied directly to solvent assisted recovery, paraffinic deasphalting, and distillation and refining processes for Athabasca bitumen a strategic resource for Canada. / Chemical Engineering

Terminal heme-copper oxidases (HCuOs) are transmembrane proteins that catalyze the final step in the respiratory chain - the reduction of O2 to H2O, coupled to energy conservation by generation of an electrochemical proton gradient. The most extensively investigated of the HCuOs are the aa3-type oxidases, to which cytochrome c oxidase (CytcO) belongs, which uses energy released in the O2-reduction for proton pumping. The bacterial nitric oxide reductases (NORs) have been identified as divergent members of the HCuO-superfamily and are involved in the denitrification pathway where they catalyze the reduction of NO to NO2. Although as exergonic as O2-reduction, this reaction is completely non-electrogenic. Among the traditional HCuOs, the cbb3-type oxidases are the closest relatives to the NORs and as such provide a link between the aa3 oxidases and the NORs. The cbb3 oxidases have been shown to pump protons with nearly the same efficiency as the aa3 oxidases, despite low sequence similarity. This thesis is focused on measurements of membrane potential generating reactions during catalysis in the CytcO and the cbb3 oxidase from Rhodobacter sphaeroides, and the NOR from Paracoccus denitrificans, using a time resolved electrometric technique. The pH dependence of the membrane potential generation in CytcO showed that only one proton is taken up and that no protons are pumped, at high pH. An additional kinetic phase was also detected at high pH that presumably originates to from charge-transfer within the K-pathway. Possible reasons for uncoupling, and the extent of charge-transfer, were studied using structural variants of CytcO. The measurements established that electrons and protons are taken up from the same side of the membrane in NOR. In addition, the directionality for proton uptake in cbb3 oxidase appeared to be dependent on the choice of substrate while proton pumping was indicated to occur only during O2-reduction.

Proton-coupled electron transfer (PCET) is one of the elementary reactions occurring in many chemical and biological systems, such as photosystem II where the oxidation of tyrosine (TyrZ) is coupled to deprotonation of the phenolic proton. This reaction is here modelled by the oxidation of a phenol covalently linked to a Ru(bpy)32+-moitey, which is photo-oxidized by a laser flash-quench method. This model system is unusual as mechanism of PCET is studied in a unimolecular system in water solution. Here we address the question how the nature of the proton accepting base and its hydrogen bond to phenol influence the PCET reaction. In the first part we investigate the effect of an internal hydrogen bond PCET from. Two similar phenols are compared. For both these the proton accepting base is a carboxylate group linked to the phenol on the ortho-position directly or via a methylene group. On the basis of kinetic and thermodynamic arguments it is suggested that the PCET from these occurs via a concerted electron proton transfer (CEP). Moreover, numerical modelling of the kinetic data provides an in-depth analysis of this CEP reaction, including promoting  vibrations  along the O–H–O coordinate that are required to explain the data. The second part describes the study on oxidation of phenol where either water or an external base the proton acceptor. The pH-dependence of the kinetics reveals four mechanistic regions for PCET within the same molecule when water is the base. It is shown that the competition between the mechanisms can be tuned by the strength of the oxidant. Moreover, these studies reveal the conditions that may favour a buffer-assisted PCET over that with deprotonation to water solution.

The search for information about entities, such as people or movies, plays an increasingly important role on the Web. This information is still scattered across many Web pages, making it more time consuming for a user to find all relevant information about an entity. This thesis describes techniques to extract entities and information about these entities from the Web, such as facts, opinions, questions and answers, interactive multimedia objects, and events. The findings of this thesis are that it is possible to create a large knowledge base automatically using a manually-crafted ontology. The precision of the extracted information was found to be between 75–90 % (facts and entities respectively) after using assessment algorithms. The algorithms from this thesis can be used to create such a knowledge base, which can be used in various research fields, such as question answering, named entity recognition, and information retrieval.