INTRODUÇÃO: Epilepsia do lobo temporal mesial (ELTM) por esclerose hipocampal (EH) é a forma de epilepsia focal mais comum na idade adulta e a causa mais frequente de refratariedade ao tratamento clínico. Apesar de se tratar de uma patologia da substância cinzenta, alguns estudos, por meio da imagem por tensor de difusão (diffusion tensor imaging-DTI), têm demonstrado alteração da substância branca temporal e extratemporal nestes pacientes. O corpo caloso (CC) é a maior comissura cerebral conectando áreas corticais homólogas de ambos os hemisférios cerebrais e tem sido implicado na propagação da atividade epiléptica. O objetivo principal do presente estudo foi avaliar possíveis alterações no CC de pacientes com ELTM-EH pela técnica de DTI e verificar se essas dependem da lateralidade da EH e da concordância entre os exames de ressonância magnética (RM) e os exames de vídeo-eletroencefalograma (EEG). Como objetivo secundário, também avaliou-se se estas alterações se correlacionavam com alguma variável clínica ou com as medidas volumétricas do CC. MÉTODOS: 42 pacientes com ELTM-EH (idades: 20-54 anos) e 30 voluntários saudáveis como grupo controle (idades: 18-53 anos) realizaram exame de RM de crânio, sendo obtidas sequências de DTI com 32 direções de gradiente e imagens volumétricas ponderadas em T1. Os pacientes foram também divididos em subgrupos: EH à direita e EH à esquerda, e em pacientes concordantes e discordantes. Os valores de anisotropia fracionada (AF), difusividade média (DM), difusividade axial (DA), difusividade radial (DR) e os dados volumétricos foram extraídos a partir de cinco segmentos obtidos automaticamente na secção sagital do CC. Foram realizadas comparações dos parâmetros de DTI no CC entre os grupos de pacientes e controles, e entre os subgrupos de pacientes. Foram investigadas correlações entre os parâmetros do tensor de difusão e as variáveis clínicas. As alterações volumétricas no CC dos pacientes com ELTM-EH bem como a correlação dessas alterações com as anormalidades de difusão também foram avaliadas. Considerou-se um valor de p < 0,05 como estatisticamente significativo. RESULTADOS: Nas regiões anterior, médio-posterior e posterior do CC dos pacientes, observaram-se redução da AF e aumento da DM e da DR, em relação aos controles. A DA manteve-se inalterada. Não foram demonstradas diferenças nos padrões de alteração de difusão entre os pacientes com EH à direita e com EH à esquerda, nem entre pacientes concordantes e discordantes. Não foram observadas correlações significativas entre os parâmetros do tensor de difusão com a idade ao evento inicial, idade de início da epilepsia, tempo de doença, tempo de epilepsia, período de latência e frequência de crises. No entanto, pacientes que apresentaram crise febril como evento precipitante inicial exibiram maior intensidade e extensão das alterações de difusão. Observou-se redução volumétrica difusa do CC, sendo demonstrada correlação negativa significativa entre DM e DR, e o volume nos segmentos central, médio-posterior e posterior, e, ainda, entre DA e volume do segmento posterior. Nós observamos, ainda, correlação negativa significativa entre o volume e o tempo de epilepsia, e o tempo de doença. CONCLUSÕES: Houve alteração dos parâmetros de DTI em áreas específicas do CC e redução volumétrica difusa desta estrutura. Tais anormalidades parecem ser secundárias à propagação das crises epilépticas ao longo de vias específicas anatômica ou funcionalmente relacionadas aos lobos temporais promovendo alterações secundárias na substância branca cerebral. O histórico de crise febril está relacionado a maior intensidade e extensão de acometimento do CC / INTRODUCTION: Mesial temporal lobe epilepsy (MTLE) with hippocampal sclerosis (HS) is the most common form of focal epilepsy in adults and it is frequently associated with refractoriness to medical treatment. Although epilepsy is considered a grey-matter disease, abnormalities in the temporal and extra-temporal white matter have been identified in these patients with diffusion tensor imaging (DTI). The corpus callosum (CC) is the major white matter tract connecting both cerebral hemispheres and has been implicated as an important route of spread of epileptic activity. The first goal of this study was to detect DTI abnormalities in specific areas of the CC in patients with MTLE-HS and to verify if these abnormalities depend on the laterality of the HS and on the concordance between the magnetic resonance imaging (MRI) and video-electroencephalogram (EEG). As a second goal we assessed if DTI results were correlated with any clinical variable or volumetric changes of the CC. METHODS: 42 patients (age: 20-54 years) and 30 healthy controls (age:18-53 years) were submitted to brain MRI. DTI sequences with 32 gradient encoding directions and volumetric T1-weighted images were obtained. Additionally, we grouped the patients in left sided and right sided HS and in concordant and discordant HS. Mean values of fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD), radial diffusivity (RD) and volumetric results were extracted from five segments at the midsagittal section of the CC obtained through automatic segmentation. Comparisons of DTI parameters of the CC were performed between patients and controls and between subgroups of patients. Correlations between DTI parameters and clinical findings were calculated. We also evaluated volume abnormalities of the CC in MTLE-HS patients and the correlations between these abnormalities and DTI changes. We considered a value of p <0.05 statistically significant. RESULTS: Our study showed that, when HS patients was compared to controls, the FA was lowest in the anterior, mid-posterior and posterior subregions of the CC. MD and RD were higher in these same segments. No changes were observed in AD. No differences in the CC DTI parameters were detected between right-sided HS and left-sided HS or between concordant and discordant HS patients. Age at initial event, age at epilepsy onset, duration of disease, duration of epilepsy, latency period and seizure frequency were not significantly correlated with the DTI parameters. However, patients who had febrile seizures as initial event exhibited greater intensity and extent of DTI changes. All segments demonstrated volume reduction compared to controls. Significant negative correlation was demonstrated between MD and RD and the volume in the central, midposterior and posterior segments of the CC, and between AD and volume of the posterior segment. We also demonstrated negative correlation between volume and duration of disease and duration of epilepsy. CONCLUSIONS: This study showed diffusion abnormalities in specific areas of the CC and diffuse atrophy in patients with unilateral HS, which may be secondary to seizures propagation along specific pathways leading to secondary changes in brain white matter. The history of febrile seizure is related to greater involvement of the CC

Dans le cadre de la gestion des déchets radioactifs dits de moyenne activité à vie longue et de haute activité, la France a fait le choix du stockage géologique profond dans une formation rocheuse située à l’est du bassin parisien, dans une zone tectoniquement stable. Cette formation d’argilites du Callovo-Oxfordien a été choisie pour ses propriétés de rétention des radionucléides puisqu’elle est très peu perméable. Un laboratoire de recherche souterrain a été construit à environ 500 mètres de profondeur afin d’étudier in-situ les propriétés de la roche. Il a été montré que l’argilite du Callovo-Oxfordien présente une anisotropie liée à sa formation géologique. L’objectif principal de cette thèse est de pouvoir reproduire le comportement mécanique anisotrope à l’aide d’un modèle de comportement élasto-plastique. Le modèle de comportement thermo-élasto-viscoplastique et isotrope nommé LKR est la résultante de tout le savoir-faire et l’expertise d’EDF en ce qui concerne le dimensionnement d’ouvrages souterrains. On cherche donc à appliquer une méthode de prise en compte de l’anisotropie structurelle caractérisant plusieurs types de géomatériaux dont l’argilite du Callovo-Oxfordien à ce modèle de comportement. Afin d’atteindre cet objectif, deux méthodes de prise en compte de l’anisotropie développées dans la littérature scientifique sont appliquées à un modèle de Drucker-Prager à écrouissage linéaire négatif et sont comparées. La première méthode consiste à introduire un tenseur de microstructure ou de fabrique permettant de définir les orientations préférentielles du matériau. La seconde méthode est l’approche par plan de faiblesse qui consiste à décrire le comportement anisotrope du matériau via deux mécanismes distincts, l’un décrivant le comportement de la matrice rocheuse isotrope et l’autre décrivant les plans de faiblesse. C’est par ce deuxième mécanisme que l’anisotropie est introduite. Ces deux applications ont été faites dans le logiciel libre de simulation en mécanique, Code Aster, développé par EDF et ont permis d’appréhender les difficultés numériques de chacune de ces méthodes, et de choisir l’approche la plus pertinente pour l’extension du modèle LKR. Ainsi, c’est la méthode avec le tenseur de fabrique qui est, dans notre cas, la plus adaptée. Elle a donc été appliquée au modèle LKR. Cette nouvelle extension au modèle permet de prendre en compte la dépendance à l’orientation du matériau des résistances en compression. Dans ces travaux, on se place dans le cadre de la mécanique des milieux continus. L’anisotropie est introduite seulement dans le mécanisme élasto-plastique du modèle de comportement LKR. / Within the framework of radioactive waste management, for long-lived and high-level radioactive waste, France has chosen deep geological storage. This storage will be located in a rock formation, in the east of the basin Parisian, in a tectonically stable area. This Callovo-Oxfordian claystone formation was chosen for its radionuclides retention properties since it is not very permeable. An underground research laboratory was built 500 meters deep to study the properties of the rock in-situ. The Callovo-Oxfordian claystone has been shown to exhibit anisotropy related to its geological formation. The main objective of this PhD thesis is to reproduce anisotropic mechanical behaviour using an elasto-plastic constitutive model. The thermo-elasto-viscoplastic and isotropic behaviour model named LKR is the result of all EDF’s knowledge and expertise in the design of underground structures. Therefore, we seek to apply a method of taking into account structural or inherent anisotropy characterizing several types of geomaterials including Callovo-Oxfordian claystone to this LKR constitutive model. In order to achieve this objective, two methods of taking anisotropy into account and developed in the scientific literature are applied to a Drucker-Prager model with linear softening and then are compared to each other. The first method consists of introducing a microstructure or fabric tensor to define the preferential orientations of the material. The second method is the weakness plane approach which consists of describing the anisotropic behaviour of the material through two distinct mechanisms, one describing the behaviour of the isotropic rock matrix and the other describing the weakness planes. It is through this second mechanism that anisotropy is introduced. These two applications were made using the free mechanical simulation software, Code Aster, developed by EDF. This allowed to understand the numerical difficulties of each of these methods, and to choose the most relevant approach for the extension of the LKR model. Thus, it is the method with the fabric tensor which is, in our case, the most suitable. It was therefore applied to the LKR model. This new extension to the model enables the material orientation dependency of the compression strengths to be taken into account. In this work, the mechanics of continuous media are considered. Anisotropy is introduced only into the elasto-plastic mechanism of the LKR behaviour model.

The variation of rock strength and stiffness, known as mechanical anisotropy, is expected at different scales: large (rock mass) - or small (intact rock) - scales. It is always mandatory for engineering applications built either on or in anisotropic rock masses to investigate the strength and deformation behavior of those masses. To achieve this goal, continuum-based constitutive models are presented to analyze the mechanical anisotropy. One of both implemented models is named ‘Transubi model’ which considers the transverse isotropic elasticity into bi-linear Mohr-Coulomb strain hardening/softening plastic framework. Experimental investigations and numerical simulations focused mainly on the influence of the mechanical anisotropy on the plastic zoning around excavated openings in laminated rocks. Later, the Transubi model was applied to a tunnel excavated in a shaly facies formation of bedded argillaceous Opalinus clay in an URL (FE-tunnel) to obtain the short-term stability insights. Overall, the research outcomes may have a prospective impact regarding the understanding of anisotropy of laminated, bedded and foliated rocks which improves the deformation behaviour predictability using continuum-based numerical modeling tools.

<p>Parkinson’s disease is a neurodegenerative disorder characterized by a loss of dopaminergic neurons, where mitochondrial dysfunction and neuroinflammation are implicated in this process. However, the exact mechanisms of mitochondrial dysfunction, oxidative stress and neuroinflammation leading to the onset and development of Parkinson’s disease are not well understood. There is a lack of tools necessary to dissect these mechanisms, therefore we engineered genetically encoded fluorescent biosensors to monitor redox status and an inflammatory signal peptide with high spatiotemporal resolution. To measure intracellular redox dynamics, we developed red-shifted redox sensors and demonstrated their application in dual compartment imaging to study cross compartmental redox dynamics in live cells. To monitor extracellular inflammatory events, we developed a family of spectrally diverse genetically encoded fluorescent biosensors for the inflammatory mediator peptide, bradykinin. At the organismal level, we characterized the locomotor effects of mitochondrial toxicant-induced dopaminergic disruption in a zebrafish animal model and evaluated a behavioral assay as a method to screen for dopaminergic dysfunction. Pairing our intracellular redox sensors and our extracellular bradykinin sensors in a Parkinson’s disease animal model, such as a zebrafish toxicant-induced model will prove useful for dissecting the role of mitochondrial dysfunction and inflammation in Parkinson’s disease. </p>

Movimentos coletivos prestam um papel fundamental na dinâmica e energética de biomoléculas em solução. Estes movimentos permitem o acoplamento de regiões significativamente distantes, apresentando considerável influência, por exemplo, no alosterismo para a formação de complexos macromoleculares e no funcionamento integrado de proteínas multidomínios como \"máquinas moleculares\". Neste trabalho de doutoramento, serão apresentados os resultados referentes à aplicação conjunta de técnicas experimentais biofísicas, de modelagem estrutural e de dinâmica molecular no estudo de dois sistemas para os quais estes movimentos coletivos demonstram considerável importância funcional. Para a interação do receptor nuclear do ácido 9-cis-retinóico com seu elemento responsivo específico no DNA (HRE), a comparação de estudos de dinâmica molecular com ensaios de afinidade por anisotropia de fluorescência sugere que a resistência inicial para a associação do monômero, seguida da acentuada colaboratividade na associação do dímero é regida por um impedimento da associação do domínio de ligação ao DNA (DBD) para o primeiro à sequência responsiva devido, em última análise, a uma não complementaridade dos modos coletivos mútuos. Este impedimento para a associação monomérica inicial é mais acentuado para o monômero 5\' (para o qual a menor especificidade de ligação à seqüência específica já é bem documentada), devido aos efeitos conjuntos de um \"defeito\" natural no empacotamento de bases da seqüência responsiva, que se manifesta mais significativamente na interface entre o meio-sítio 5\' e a seqüência espaçadora, e dos modos vibracionais entre os dois sítios decorrentes de seu faseamento relativo na topologia do DNA na seqüência responsiva, caracterizando um mecanismo \"chave e fechadura\" para a interação obrigatoriamente simultânea dos dois monômeros ao DNA. No segundo caso, um estudo integrado utilizando a técnica experimental de espalhamento de raios X a baixos ângulos e uma abordagem de modelagem estrutural baseada em dinâmica molecular foi realizado para a celobiohidrolase I de Trichoderma harziannum. Este estudo permitiu tanto a elaboração de um modelo estrutural de maior resolução para esta enzima de alto potencial biotecnológico como a constatação dos possíveis mecanismos moleculares a partir dos quais as glicosilações no peptídeo conector impõem restrições à orientação e modos vibracionais entre seus dois domínios de forma condizente com sua ação concertada na interação e no deslize da enzima sobre a superfície celulósica, ambos de fundamental importância para a processividade da enzima na hidrólise do substrato microcristalino. / Collective motions play a fundamental role in solution biomolecule dynamics and energetics. These movements can couple very distant regions in the protein structures affection, for instance, allosteric mechanisms, the establishment of macromolecular complexes, and on the integrated function of multidomain proteins as molecullar machines. In this thesis, we present results concerning to the joint use of experimental biophysical techniques, structural modeling and molecular dynamics simulations on the study of two systems for which these collective motions have substantial importance. First, we study the interaction of the nuclear retinoid X receptor with its specific DNA hormone response element (HRE) using a combination of molecular dynamics simulations and affinity assays performed by using fluorescence anisotropy. We find out that collective motions mediate the low binding affinity of monomers and the high cooperative binding of HRE dimers. The lower binding affinity of the monomer is more prominent for 5´ monomers. This occur due to an natural ineffective stacking of the last base pair step at the 5´-half-site and to the phasing of the two binding half-sites in the DNA topology, that impose a collective motions that tends to occlude the 5´ binding site. This behavior, in turn, is concurrent with the well known 3´ polarity and the decreased binding specificity to the 5´ half site for the hRXR&alpha; monomer. This same pattern impose a lock-and-key mechanisms dependent on the binding of the full dimer. Second, an integrated Small angle X ray scattering and molecular dynamics based structural modeling was used to comprehend the interdomain motions of cellobiohydrolase I of Trichoderma harziannum. We manage to build a refined model for this enzime, with important biotechnological potential. We also provide insights into molecular mechanisms of linker and glycosylation imposed restraints on the orientation and vibrational modes of the full-length enzyme, supporting a mechanism of sliding of on the cellulose surface. This mechanism is fundamental for the high processivity on the hydrolysis of microcrystalline cellulose.

Ionic Liquids (ILs) has been attracting attention, both from academia and industry, given the numerous applications of these systems. ILs are salts, usually composed by an organic ion, and a counterion which could be organic or inorganic, and, interestingly they are found at liquid state at room temperature. Our interest in studying ILs comes from its low toxicity. Some recent studies have shown that the toxicity of the ILs ishigher than believed, in particular for biologically relevant systems. The main goal of this research is to study the influence of the ionic liquid 1-tetradecyl-3-methylimidazolium chloride ([C14MIM][Cl]) with membrane systems. To do so, we made use of different lipids: POPC, Sphingomyelin, Cholesterol, POPG, DPPC, DPPG and DMPC. For each of these systems, the influence of ILs concentration were elucidated by means of a systematic study through different experimental techniques: Small Angle X-ray scattering (SAXS), dynamic light scattering (DLS), fluorescence anisotropy, optical microscopy and z-potential. Since [C14MIM][Cl] has a positive charge on the imidazolium group, the superficial charge of all vesicles increased. For zwitterionic vesicles no significant change in size and melting temperature were noticed. The imidazolium-based ionic liquid diminished the gel-fluid transition temperature for negatively charged lipids. For DPPC:DPPG (1:1), for instance, the transition temperature decreased from 42.50±0.13oC to 25.27±0.33oC and for DPPG from 46.12±0.22 oC to 36.6±0.38 oC. For DPPG, the vesicle hydrodynamic diameter increased from 84±0.1nm to 176±0.1nm, whereas for DPPC:DPPG it increased from 95±0.1nm to 196±0.1nm. The electronic density profile, obtained by SAXS, supported the penetration of the [C14MIM][Cl] into the negative bilayer structure. 15 mol% of [C14MIM][Cl] increased the polar head thickness of DPPC vesicles from 11.1±0.6 Å to 18.0±0.7 Å, without alter significantly the inner region of the membrane.Qualitative results obtained with optical microscopy showed that the IL incorporation destabilize the membrane asymmetry (between the leaflets) leading to the formation of pores (evidenced by optical contrast lost) and the presence of buds. We believe that this work could improve the understanding of the effects of ILs in the presence of biological relevant systems / Os líquidos iônicos (LI) tem atraído grande atenção, tanto da academia quanto da indústria, devido às suas numerosas aplicações. LI são sais, normalmente compostos por um íon orgânico, e um contra-íon que pode ser orgânico ou inorgânico, mas que tem como característica ser encontrado no estado líquido à temperaturas próximas a ambiente. Nosso interesse em estudar LIs vem de sua baixa toxicidade, atribuída a sua baixa volatilidade. Entretanto, alguns estudos recentes mostraram que a toxicidade dos LI é maior do que se acreditava, em particular com sistemas de relevância biológica.O objetivo principal desta dissertação é estudar a influência do líquido iônico 1-tetradecil-3-metilimidazólio cloreto ([C14MIM][Cl]) com sistemas de membrana. Para isso, utilizamos diferentes lipídios, como o POPC, esfingomielina, colesterol, POPG, DPPC,DPPG e o DMPC. Para cada um destes sistemas, a influência da concentração de LI foi elucidada por meio de um estudo sistemático através de diferentes técnicas experimentais, tais como: espalhamento de raio-X a baixos ângulos (SAXS), espalhamento dinâmico de luz (DLS), anisotropia de fluorescência, microscopia óptica e potencial-z. Uma vez que o componente iônico de [C14MIM][Cl] tem uma carga positiva no grupo imidazólio, a carga superficial de todas as vesículas estudadas aqui aumentou. Entretanto, para asvesículas compostas pelos lipídeos zwitteriónicos, não tenha sido observada qualquer alteração significativa no tamanho e na temperatura de transição de fase gel-fluido. O [C14MIM][Cl] altera a organização interna entre as moléculas de lipídio com carga negativa. Consequentemente, à medida que a quantidade de LI aumenta, a temperatura de transição de fase diminui e o tamanho médio das vesículas aumenta. Para o sistema DPPC:DPPG (1:1) a temperatura de transição de fase caiu de 42.50 ± 0.13 oC para 25.27 ± 0.33 oC e para as vesículas de DPPG de 46.12±0.22 oC para 36.6±0.38 oC. Quanto ao diâmetro hidrodinâmico médio, no caso do DPPG este valor aumentou de 84±0.1 nm para 176±0.1 nm, enquanto que para a mistura DPPC:DPPG (1:1) ele passou de 95±0.1nm para 196±0.1nm. Indicando assim que o LI incorpora na bicamada lipídica negativamente carregada. O perfil de densidade eletrônica, obtido por SAXS, confirma a penetração do [C14MIM][Cl] na bicamada lipídica. Diferentemente, para a membrana lipídica zwitteriónica o LI tende a se situar perto da região da cabeça polar sem afetar significativamente a região do interior da bicamada lipídica. Por outro lado, a presença de15 mol% de [C14MIM][Cl] aumenta a espessura da região polar das bicamadas das vesículas de DPPC de ~ 11.1±0.6 Å para ~ 18.0±0.7 Å. Os resultados qualitativos da microscopia óptica mostraram que a incorporação da LI desestabiliza a assimetria da membrana entre as camadas interna e externa, além de sugerir o aparecimento de poros (evidenciado pela perda do contraste ótico das vesículas) e estruturas chamadas de buds. Esperamos que este trabalho melhore a compreensão dos efeitos do LI na presença de organismos biológicos.

Em engenharia, a quantidade de problemas geométricos complexos que precisam ser resolvidos empregando teorias de placas ou cascas é notável. Esta é a razão por que há tantas teorias que buscam simplificar os problemas tridimensionais em outros menos custosos computacionalmente. Além disso, o aumento atual do uso de estruturas sanduíche requer que as formulações bidimensionais sejam mais precisas. Esta tese, num primeiro momento, compila a maioria das teorias de placa, comentando as principais diferenças, vantagens e desvantagens de cada uma. As formulações bidimensionais de placas laminadas são classificadas principalmente de acordo com o tratamento da coordenada na direção normal a superfície da mesma: Camada Única Equivalente (ESL), ESL refinada (teorias Zig-Zag) e Teorias Discretas ou de Camada (LW). Cada uma destas teorias é revista juntamente com as hipóteses de placas que são feitas para cada uma das camadas ou para o laminado como um todo. Para resolver tais problemas estruturais em engenharia, métodos numéricos são normalmente utilizados. Portanto, num segundo momento, alguns métodos de solução são citados e revisados, mas o foco é dado ao Método dos Elementos Finitos (MEF). A contribuição deste trabalho consiste na implementação de um novo método de solução de compósitos laminados e estruturas sanduíche com base em um sistema unificado de Formulação Generalizada (GUF) via MEF. Um elemento quadrilátero de 4 nós foi desenvolvido e avaliado com um código de Elementos Finitos desenvolvido pelo presente autor. Os requisitos para continuidade do tipo C-1 são respeitados para a variável de deflexão da placa. Esse método é nomeado de Formulação Generalizada do Caliri (CGF). Resultados para placas isotrópicas, placas de laminado compósito e estruturas sanduíche consideradas finas ou espessas são comparados com dados da literatura e soluções via Abaqus. Os resultados obtidos ao longo da espessura reforçam a necessidade de soluções de placa não-lineares para placas espessas (laminadas ou não). Mostrou-se que as soluções estáticas e dinâmicas empregando o método proposto fornecem resultados coerentes quando comparados com outros métodos de solução. Dentre os diversos estudos de caso investigados, verificou-se que é possível se obter resultados com alta concordância. Para uma estrutura sanduíche com núcleo macio, o resultado de deslocamento previsto para um carregamento estático chega a 99.8% de concordância e o resultado de uma análise modal da mesma estrutura mostra uma concordância de 99.5% com os resultados de um modelo feito com elementos 3D em um programa comercial de elementos finitos. / In engineering, the amount of complex geometrical problems, which need to be solved by using plates and shells theories, is remarkable. This is the reason why there are so many plate and shell theories which attempt to simplify three dimensional problems into ones with low computational cost. Additionally, the current increasing use of sandwich structures requires that the two dimensional formulations be accurate enough. First, this thesis compiles most of the plate theories from the literature and quotes the main differences, advantages and weaknesses of each one. The bi-dimensional laminated plate formulations are mainly classified according to the treatment of the variable in the normal direction of the plate surface: Equivalent Single Layer (ESL), Refined ESL (Zig-Zag theories) and Layer-Wise (LW) theories. Each one of these theories is reviewed along with the plate hypotheses which are made for each ply and/or laminate. To solve such complex structural engineering problems, numerical methods are normally used. Second, few solution methods are reviewed and quoted, but focus is given to the Finite Element Method (FEM). The contribution of this work is the implementation of a new solution method for laminated composites and sandwich structures based on a Generalized Unified Formulation (GUF) via FEM. A quadrilateral 4-node element was developed and evaluated using in-house Finite Element program. The C-1 continuity requirements is fulfilled for the transversal displacement field variable. This method is tagged as Caliri\'s Generalized Formulation (CGF). Results for isotropic plates, laminated composite plates and sandwich structures for thin and thick laminates are compared with literature data and solutions via Abaqus. The through-the-thickness profile results reinforce the need for non-linear plate (laminated or not) solutions. It was shown that the static and dynamic solutions employing the proposed solution method yield coherent results when compared with other solution methods. Among the different case studies investigated, it was verified that it is possible to obtain results with high agreement. For a soft-core sandwich structure, the displacement result for a static loading is reported as high as 99.8% and the result of a modal analysis of the same structure shows an accuracy of 99.5%, comparing to the results from a 3D finite element model built with a commercial software.

Le domaine de l’enregistrement magnétique est en constante évolution pour repousser davantage les limites de stockage de l’information, une approche prometteuse étant l’enregistrement perpendiculaire. Le matériau faisant l’objet de ce manuscrit est le ferrite de cobalt CoFe2O4 (= CFO). Ses propriétés font de lui un candidat prometteur pour la réalisation de dispositif à enregistrement perpendiculaire, cela passant par le contrôle de sa direction de facile aimantation.Ce travail de thèse traite ainsi de la modification de l’anisotropie magnétocristalline du CFO en couche mince par dopage aux éléments de terres rares. Nous avons démontré la possibilité de moduler la direction de facile aimantation du CFO non dopé, en modifiant la pression partielle en O2/N2 lors de l’élaboration. Nous avons également mis en évidence l’insertion des éléments lanthanides dans la structure du CFO ainsi que l’impact de l’anisotropie de la terre rare sur les propriétés magnétiques du matériau. / The field of magnetic storage is in constant progress to constantly push further the storage capacity of the device. A promising approach is the perpendicular magnetic recording of datas. The material presented in this manuscript is cobalt ferrite. It is an excellent candidate for the realization of perpendicular storage device due to its properties. The present work deals with the modification of the magnetic anisotropy by doping the ferrite cobalt thin films with rare earth elements. We have demonstrated the possibility to modulate the easy magnetization axis of undoped cobalt ferrite by changing the partial pressure of O2/N2 during the elaboration of the thin films. We have also highlighted the insertion of rare earth elements into the structure of the cobalt ferrite although their important ionic radii. The impact of the rare earth anisotropy on the magnetic properties of the ferrite cobalt has also been observed.

Le contrôle spatial et temporel de l'auto-assemblage de molécules fluorescentes en nano-objets organisés et en matériaux mous a été réalisé par photochimie.La photodécarbonylation quantitative du progélifiant dkDDOA sous irradiation génère le super gélifiant 2,3-didécyloxyanthracène (DDOA) à température ambiante et simultanément gélifie le DMSO. DkDDOA est réactif sous excitation avec de la lumière bleue en raison de la fonction alpha-dicétone sensible à la lumière qui est ajoutée au noyau aromatique. De plus,l’ajustement de la couleur de l'émission du gel du bleu au vert a été obtenu en ajoutant un dérivé 1,2-dicétone-5,12-diphényltétracène photo réactif qui donne un 5,12-diphényltétracène émissif vert sensibilisé par un transfert d'énergie efficace.Sous un microscope, l'irradiation laser focalisée permet la structuration de nanofibres émissives sur une surface de verre. Bien que la surface de verre soit non traitée, on peut obtenir des micropattern de nanofibres de DDOA hautement alignées. Ces surfaces émettent une lumière bleue polarisée linéairement, comme le prouve la microscopie de polarisation. L'anisotropie élevée et l'orientation des fibres ont été obtenues en contrôlant la densité de nucléation et la direction de balayage du laser focalisé. Des micropattern orientés perpendiculairement peuvent ainsi être juxtaposés sur la même surface. / The spatial and temporal control of the self-assembly of fluorescent molecules into organized nano-objects and into soft materials was achieved by photochemistry. The quantitative photodecarbonylation of the progelator dkDDOA under irradiation generates the supergelator 2,3-didecyloxyanthracene (DDOA) at room temperature and simultaneously gelates DMSO. dkDDOA is reactive under excitation withblue light due to the light sensitive alpha-diketone moiety that is added to the aromatic core.Additional colour-tuning from blue to green emission from the gel was achieved by adding a similar photoreactive 1,2-diketone-5,12-diphenyltetracene that yields a green emissive 5,12-diphenyltetracene sensitized through an efficient energy transfer. Under a microscope, focused laser irradiation enables the patterning of blue-emissive nanofibers on to a glass surface. Although the surface is non-treated, micropatterns of highly aligned DDOA nanofibers can be obtained. These surfaces emit linearly polarized blue light,as proven with polarization microscopy. The high anisotropy and the orientation of the fibers was achieved by controlling the nucleation density and the direction of scanning of the focused laser. Perpendicularly oriented micropatterns can thereby be juxtaposed on the same surface.

Les sismologues ont révélé l'existence d'une anisotropie sismique complexe dans la graine terrestre. Cette thèse, en deux parties, présente deux approches différentes pour, d'une part, expliquer l'existence de cette anisotropie avec des modèles de graine numérique et, d'autre part, étudier l'effet des transformations de phase sur cette anisotropie.Dans un premier temps, nous avons construit un outil de simulation de la propagation des rais sismiques à travers une graine numérique, afin d'étudier la possibilité de reproduire numériquement les données sismologiques et de contraindre la dynamique et la minéralogie de la graine. Nous concluons qu'aucune structure du fer cubique ne permet de développer une anisotropie sismique significative. Seule la structure hexagonale compacte permet de le faire. Parmi les modèles géodynamiques quadripolaires étudiés, la croissance équatoriale préférentielle est le processus dynamique qui présente le meilleur accord avec les observations de dépendance à la profondeur et d'anisotropie polaire. L'ajout d'une stratification chimique permet d'amplifier d'environ 40% l'anisotropie globale mais augmente la dispersion des résidus sismiques, ce qui n'est pas conforme aux observations de dépendance à la profondeur. Enfin, une croissance dendritique (texture de solidification) est peu compatible avec une anisotropie principale Nord-Sud. Il apparaît clairement qu'aucun de ces modèles géodynamiques ne permet d'obtenir une amplitude d'anisotropie suffisante en utilisant les propriétés élastiques publiées pour le fer dans la graine. A l'issue de ce travail, de nombreux autres processus dynamiques restent encore à étudier, tels que les forces de Lorentz et la translation-convection thermique, processus bipolaire qui présente un fort intérêt pour la caractérisation de la composante hémisphérique de l'anisotropie sismique.Dans un deuxième temps, nous avons procédé à des expériences de transition de phase α-ε (fer cubique centré vers fer hexagonal compact) dans le fer pur. Nous avons simulé les textures résultantes à l'aide du mécanisme de Burgers. Nous avons confronté nos simulations aux résultats expérimentaux. Nous avons pu confirmer la validité du mécanisme de transformation de Burgers. Nous avons trouvé une forte sélection de variant sous l'effet de la contrainte non-hydrostatique dans le sens direct α→ε, produisant de fortes textures. Dans le sens inverse ε→α, on observe des textures finales très faibles, voire aléatoires. Appliqués avec prudence au cas de la graine terrestre, nos résultats indiquent que la transformation de phase du fer hexagonal à cubique ne peut pas expliquer la forte anisotropie observée. Nous avons aussi noté une mémoire de texture partielle, déjà documentée pour d'autres métaux de transition. Enfin, nous avons procédé à des tests préliminaires en cellule diamant en rotation. Les résultats de ces expériences de cisaillement ont également montré un très bon accord avec les simulations fondées sur le mécanisme de Burgers. En revanche, nous avons pu constater de grands écarts entre nos résultats expérimentaux et les simulations en cisaillement présentées dans la littérature [Levitas et al., 2010], notamment en termes de gradient de contraintes. / Seismologists revealed the existence of a complex seismic anisotropy in the Earth's inner core. In this thesis we took two different approaches in order to characterize the anisotropy: in a first part, we tried to explain this anisotropy using formation models of inner core and, in a second part, we considered the impact of eventual phase transitions on anisotropy.Firstly, we simulate the propagation of seismic rays through a numerically grown inner core, in order to measure the seismic anisotropy to compare with actual observations and to constrain the dynamics and mineralogy of the inner core. We conclude that no cubic structure of iron may produce a significant global anisotropy. Only the hexagonal compact phase of iron may produce a measurable signal. Considering a panel of quadripolar geodynamical models, we observe that simple preferential equatorial growth is the most consistent with seismological observations of a polar anisotropy and depth dependence of seismic residuals. Chemical stratification amplifies the global anisotropy by about 40%, but at the same time increases the scatter of residuals in a way that is poorly compatible with the observed depth dependence. Finally the addition of dendritic growth (solidification texture) prohibits the emergence of a first order North-South anisotropy. Independently of the geodynamical model it appears clearly that none of these geodynamical models the development of an anisotropy consistent with observations when using the published elastic properties of iron at inner core conditions. Following this work, several geodynamical models remain to be studied such as magnetic forcing (Lorentz forces). Models involving translation-thermal convection are of great interest as they may account for the hemispherical component of the seismic anisotropy.Secondly, we performed experiments on the α-ε (cubic centered to hexagonal compact iron) phase transition in pure iron. We compare our experimental texture results with our simulations of the transformation considering Burgers mechanism. We confirm here the Burgers atomic path as the mechanism activated during the α-ε transformation in iron. We find direct evidence of a strong variant selection controlled by non-hydrostatic stresses in the diamond anvil cell during the forward α→ε transformation, producing strong textures. The opposite will occur with the reverse ε→α phase transition where an almost complete randomization is to be expected. Our observations can be applied with some caution to the Earth's inner core and show that the strong seismic anisotropy in the inner core may not be explained by the occurrence of a hexagonal to cubic phase transition in the inner core. A limited texture memory effect was brought into light, already documented for other transition metals. At last, we performed a preliminary study on the effect of shear on the α-ε phase transition in pure iron using a rotational cell. Again the α-ε phase transformation in iron can be modelized by the Burgers mechanism. We find that simulations in the literature [Levitas et al., 2010] fail to reproduce our experimental results, particularly in terms of stress field.