[pt] Doenças cardiovasculares são responsáveis por um elevado número de óbitos em seres humanos. Muitas dessas patologias são dependentes do ciclo cardíaco e estão localizadas na aorta, a maior e principal artéria do nosso corpo. O conhecimento dos padrões de escoamento e distribuições de tensões nas paredes da aorta podem auxiliar no diagnóstico e prevenção de algumas dessas doenças. Dessa forma, estudou-se numericamente o escoamento do sangue, durante o ciclo cardíaco, em um modelo 3D da aorta de um paciente específico, após a implantação de TAVI (Transcatheter Aortic Valve Implantation). O ciclo cardíaco é formado por dois períodos chamados de sístole e diástole. Durante a sístole, sangue é bombeado do coração para a aorta, apresentado altos valores de vazão, resultando em escoamento turbulento. Por outro lado, na diástole, com o fechamento da válvula aórtica, o sangue escoa com baixas velocidades em regime laminar. Até hoje, cientistas enfrentam um desafio na modelagem da turbulência, pois não existe uma única modelagem que forneça previsibilidade para todas as situações envolvendo o regime turbulento, com esforço computacional razoável. Para seleção do modelo de turbulência mais adequado para análise do escoamento no interior da aorta, na presença da transição de regimes de escoamento durante o ciclo cardíaco, com um custo razoável, selecionou-se a metodologia baseada na Média de Reynolds. Diferentes modelos foram comparados com dados experimentais extraídos do mesmo modelo aórtico em escala real, porém em regime permanente, com vazão correspondente ao pico da sístole. Por fim, avaliou-se o impacto das condições de contorno e dos modelos de turbulência durante o ciclo cardíaco na distribuição e valores de tensões e grandezas turbulentas no endotélio vascular. Mostrou-se que a distribuição espacial das médias temporais de tensão foram qualitativamente e quantitativamente similares, para os dois ciclos cardíacos representativos de diferentes pacientes, porém com pequenas mudanças locais para cada caso. Em termos dos modelos de turbulência, observou-se que o modelo SAS (Scale Adaptive Simulation) foi capaz de representar a relaminarização do escoamento sanguíneo no período diastólico. / [en] Cardiovascular diseases are responsible for a high number of deaths in humans. Many of these pathologies are dependent on the cardiac cycle and are located in the aorta, the largest and main artery in our body. Knowledge of flow patterns and stress distributions in the walls of the aorta can help in the diagnosis and prevention of some of these diseases. Thus, the flow of blood during the cardiac cycle was numerically studied in a 3D model of the aorta of a specific patient, after TAVI (Transcatheter Aortic Valve Implantation) implantation. The cardiac cycle consists of two periods called systole and diastole. During the systole, blood is pumped from the heart to the aorta, presenting high flow rates, resulting in a turbulent flow. On the other hand, in diastole, with the closure of the aortic valve, the blood flows with low velocities in laminar regime. Until today, scientists face a challenge in turbulence modeling, as there is no single model that provides predictability for all situations involving the turbulent regime, with reasonable computational effort. In order to select the most suitable turbulence model for the analysis of the flow inside the aorta, in the presence of the transition of flow regimes during the cardiac cycle, with a reasonable cost, the methodology based on the Reynolds Average was selected. Different models were compared with experimental data extracted from the same real-scale aortic model, but a in steady state, with flow corresponding to the systolic peak. Finally, the impact of boundary conditions and turbulence models during the cardiac cycle on the distribution and values of stresses and turbulent quantities in the vascular endothelium were evaluated. It was shown that the spatial distribution of the temporal averages of tension was qualitatively and quantitatively similar, for the two cardiac cycles representative of different patients, but with small local changes for each case. In terms of turbulence models, it was observed that the SAS (Scale Adaptive Simulation) model was able to represent the relaminarization of blood flow in the diastolic period.

Le récepteur du facteur de libération de l’hormone de croissance (GHRHR) est un récepteur de la famille des récepteurs couplés aux protéines G. Il est fortement exprimé dans les cellules somatotropes de l’hypophyse antérieure de plusieurs mammifères. Ce récepteur exerce un rôle primordial dans la stimulation de la synthèse et de la sécrétion de l’hormone de croissance ainsi que dans la prolifération des somatotropes. Au niveau extrahypophysaire, les niveaux les plus élevés d’ARNm du GHRHR se retrouvent dans le rein. Toutefois, aucune analyse immunohistochimique n’existe encore sur la localisation précise et la quantification sur les niveaux de GHRHR dans les différents segments du rein de rat et sa dynamique d’expression en situation normale et pathologique telle que l’ischémie. De plus, dans le rein humain normal, aucune information n’est présentement disponible. Le premier article de ce mémoire a pour objectif d’identifier, par immunofluorescence directe, la localisation du GHRHR à travers le système tubulaire rénal, chez le rat jeune en bonne santé. Nos résultats mettent en évidence que dans le rein de rat sain, le GHRHR est exprimé dans les cellules du tubule proximal contourné et droit, de l’anse de Henlé ascendante épaisse corticale et médullaire et de l’anse de Henlé ascendante mince. Le cortex et la bande externe de la médulla externe seraient les deux régions où l’expression est la plus élevée. À la suite d’une insulte rénale comme l’ischémie-reperfusion (IR) chaude, nos résultats démontrent que l’expression du GHRHR est régulée à la baisse dans ces mêmes régions. De plus, une augmentation de certains marqueurs de détérioration cellulaire est présente comme l’enzyme initiatrice, la caspase-9 clivée et effectrice (caspase-3 clivée), des fragments d’ADN et la surexpression d’indication d’injure tissulaire comme la protéine Kidney Injury Molecule 1 (KIM-1). L’ensemble de ces résultats ouvre plusieurs pistes d’études concernant l’importance du GHRHR en rénoprotection. Le deuxième article de ce mémoire a pour objectif d’identifier, par immunofluorescence directe, la localisation du GHRHR à travers le système tubulaire rénal humain. Nos résultats suggèrent que dans le rein humain sain, le GHRHR est davantage exprimé dans le cortex, plus précisément, au niveau du tubule proximal droit et contourné et l’anse de Henlé corticale ascendante épaisse. L’expression du GHRHR est aussi notable au niveau de la région médullaire, pour être plus spécifique, au niveau de l’anse de Henlé médullaire ascendante épaisse et de la médulla. Ainsi, comme chez le rat, l’expression du GHRHR rénal est régio-spécifique. Finalement, le troisième article de ce mémoire est une revue de la littérature ayant pour but d’établir un lien entre les mécanismes connus du stress oxydant dans un contexte d’IR rénale et son impact spécifique dans la médulla. Cet article met en évidence que les différents segments du rein réagissent différemment à une agression oxydante et que la médulla est la région la plus vulnérable. De plus, cette revue de la littérature souligne que les différents types de mécanismes connus du stress oxydant dans un contexte d’IR rénale, tel que la production de dérivés réactifs de l’oxygène, ciblent principalement deux structures du néphron : le tubule proximal et l’anse de Henlé ascendante épaisse médullaire. Les principales répercussions de ces mécanismes observables sont l’inflammation, l’apoptose cellulaire et la diminution des fonctions rénales. Ces mécanismes peuvent aussi être utilisés comme un outil de diagnostic ou de détermination de la santé de l’organe. / The growth hormone-releasing factor receptor (GHRHR) is a receptor of the family of G- protein-coupled receptors. It is highly expressed in the somatotropic cells of the anterior pituitary of several mammals. This receptor plays an essential role in the stimulation of the synthesis and secretion of growth hormone as well as in the proliferation of somatotrophs. At the extra- pituitary level, the highest levels of GHRHR mRNA are found in the kidney. However, no immunohistochemical analysis yet exists on precise localization and quantification of GHRHR levels in the different segments of the rat kidney and its expression dynamics in normal and pathological situations such as ischemia. Additionally, in the normal human kidney, no information is currently available. The first article of this thesis aims to identify, by direct immunofluorescence, the localization of the GHRHR through the renal tubular system, in young healthy rats. Our results show that in the healthy rat kidney, GHRHR is expressed in the cells of the convoluted and right proximal tubule, of the cortical and medullary thick ascending loop of Henle and of the thin ascending loop of Henle. The cortex and the outer band of the outer medulla would be the two regions where the expression is the highest. Following a renal insult such as warm ischemia-reperfusion (RI), our results demonstrate that GHRHR expression is down-regulated in these same regions. In addition, an increase in certain markers of cellular damage is present including initiating enzymes, cleaved and effector caspase-9 (cleaved caspase-3), DNA fragments and overexpression indicative of tissue injury such as protein Kidney Injury Molecule 1 (KIM-1). All these results open up several avenues of study concerning the importance of GHRHR in renoprotection. The second article of this thesis aims to identify, by direct immunofluorescence, the localization of the GHRHR through the human renal tubular system. Our results suggest that in the healthy human kidney, the GHRHR is more expressed in the cortex, more precisely at the level of the right, convoluted proximal tubule and the thick ascending cortical loop of Henle. The expression of GHRHR is also appreciable at the level of the medullary region, more precisely at the level of the thick ascending medullary loop of Henle, and the medulla. Thus, as in rats, the expression of renal GHRHR is region specific. Finally, the third article of this thesis is a review of the literature aimed at establishing a link between the known mechanisms of oxidative stress in the context of renal IR and its specific impact in the medulla. This article highlights that the different segments of the kidney react differently to an oxidative attack and that the medulla is the most vulnerable region. In addition, this review of the literature underlines that the different types of known mechanisms of oxidative stress in a context of renal IR, such as the production of reactive oxygen species, mainly target two structures of the nephron: the proximal tubule and the thick ascending loop of Henle. The main repercussions of these observable mechanisms are inflammation, cellular apoptosis and reduced renal function. These mechanisms can also be used as a diagnostic tool or to determine the health of the organ.

Nesta pesquisa, foi realizada uma análise comparativa, por meio do método dos elementos finitos bidimensional linear, das deformações e tensões geradas a partir da aplicação de uma carga de 100N, nas estruturas de suporte (fibromucosa,ligamento periodontal, osso cortical e osso esponjoso) de dois modelos que simulam um hemiarco mandibular associada a uma prótese parcial removível de extremidade livre dista inferiorl, quando da variação da inclinação do rebordo residual no plano sagital. O modelo A (MA) foi desenhado com um rebordo ascendente distal com 15 graus de inclinação e o modelo B (MB) com um rebordo descendente distal com 15 graus negativos, ambos em relação ao plano oclusal. Nos dois modelos aplicou-se uma carga primeiramente na cúspide médio-vestibular do primeiro molar inferior artificial (C1) e depois na cúspide vestibular do segundo pré-molar inferior (C2), por meio do programa I-deas (software de elementos finitos) onde foram feitas as análises de deformações e tensões e processamento das imagens. Fez-se então uma análise comparativa dos carregamentos (C1 e C2) em cada modelo individualmente e entre os dois modelos(MA e MB). Os resultados permitiram concluir que: 1) A inclinação do rebordo residual no plano sagital influenciou na distribuição e na intensidade das tensões das estruturas de suporte; 2) No osso cortical as tensões foram mais localizadas e de maior intensidade que no osso esponjoso; 3) A diferença de deformação entre fibromucosa e ligamento periodontal foi maior quando a carga foi aplicada no primeiro molar, de ambos os modelos, sendo a mais expressiva no rebordo ascendente distal; 4) As tensões de compressão foram maiores em intensidade e melhor distribuídas no osso esponjoso e no osso cortical, quando comparadas as tensões de tração; 5) O rebordo ascendente distal se mostrou mais favorável à distribuição das tensões nas estruturas de suporte quando comparado ao rebordo descendente distal; 6) Nos dois modelos a aplicação da carga no primeiro molar gerou um maior torque sobre o dente suporte para a distal do que quando aplicado no segundo pré-molar, principalmente no rebordo descendente distal; 7) As estruturas de suporte do rebordo residual foram mais solicitadas em C1 que em C2, em ambos os modelos, principalmente no rebordo ascendente distal; 8) No dente suporte as tensões nas estruturas de suporte foram mais axiais quando o carregamento ocorreu no segundo pré-molar inferior, em ambos os modelos. / In this study, a two-dimensional finite element comparative analysis of the stress distribution and of displacement in the supporting structures – oral mucosa,periodontal ligament, compact and cancellous bone – was carried out for a distal extension base removable partial denture (RPD), modeled on two mandibular dental archs with different types of residual ridge when aplaying loads of 100N. The A model (MA) was developed to include a distal ascending alveolar ridge with a 15-degrees positive inclination, while the B model (MB) was prepared with a distal descending alveolar ridge with a 15-degrees negative inclination. Both models had a load applied inicially on the lower first molar median cusp (C1) and then on the lower second premolar buccal cusp (C2). Using the FEA software (I-DEAS, USA) for the stress distribution and displacement analysis of the generated images. A comparative analysis was them performed on the C1 and C2 loads for which and both models (MA and MB).The results showed that: 1 – The alveolar ridge inclination showed some degree of on the stress distribution and intensity generated by the RPD; 2 –The compact bone showed greater stress concentration and intensity than the cancellous bone; 3 – The ratio between oral mucosa and periodontal ligament displacement showed greater values when load was applied on the lower first molar for both models. The ratio was higher for the distal ascending alveolar ridge; 4- The compressive stress showed greater intensity and better range of distribution than the tensile stress for both the compact and cancellous bone; 5 – The distal ascending residual ridge had a more favourable stress distribution than distal descending conterpart ; 6 – The load applied on the lower first molar produced more distal torquing on the supporting tooth than that on the lower second premolar ,specially on the distal descending residual ridge; 7 – the load applied on the lower firt molar generated greater amount of stress on the residual ridge supporting structures for both models, but specially for the distal ascending residual ridge; 8 – The load applied on the lower second premolar produced more vertical forces on the supporting structures of the tooth for both models.

O objetivo deste estudo foi avaliar, pelo método dos elementos finitos bidimensional, a distribuição das tensões geradas nas estruturas de suporte das próteses parciais removíveis (PPR) - osso cortical, osso esponjoso, fibromucosa e ligamento periodontal, em modelos de arcos parcialmente dentados de extremidade livre inferior, em rebordo horizontal (MA) e descendente-ascendente (MB). Foram confeccionados dois modelos de quadrante de mandíbula em AUTOCAD 2004 (Autodesk Inc., USA), contendo apenas o primeiro pré-molar e rebordo residual, sendo repostos o segundo pré-molar e primeiro molar pela PPR, tendo como dente suporte o primeiro pré-molar com apoio oclusal distal. Posteriormente, foi aplicada carga axial de 100 N nas cúspides dos dentes artificiais da PPR (somente sobre o 1 o molar - C1 e somente sobre o 2 o pré-molar - C2). Os modelos confeccionados em AUTOCAD foram transferidos para o programa I-DEAS (software de elementosfinitos), que discretizou-os e realizou a distribuição das tensões sob as condições de aplicação de carga citadas. Pôde–se observar que no osso esponjoso, a maior deformação e tensão de compressão foram observadas ao redor do dente suporte, principalmente no terço cervical distal para a deformação e no ápice do dente para a tensão de compressão durante a aplicação de carga sobre o segundo pré-molar no rebordo horizontal (0,003 mm e 0,621 N/mm 2 , respectivamente). Já no rebordo descendente-ascendente, as áreas solicitadas foram as mesmas, apresentando deformação e tensão de compressão máximas de 0,003 mm e 0,609 N/mm 2 . Para a fibromucosa, pode-se notar que no rebordo horizontal, a maior deformação e tensão de compressão ocorreram abaixo do ponto de aplicação de carga, ou seja, no primeiro molar, com valores de 0,137 mm e 0,144 N/mm 2 . No rebordo descendente-ascendente, a área de maior deformação e tensão de compressão localizaram-se na porção ascendente do rebordo em direção do trígono retromolar, com valores de 0,131 mm e 0,122 N/mm 2 , respectivamente. Diante dos limites do presente estudo pode-se concluir que: 1 - O osso cortical apresenta uma concentração de tensões maior que o osso esponjoso; 2 – O osso cortical apresenta uma deformação mais restrita em área que o osso esponjoso; 3 - O rebordo descendente-ascendente com a aplicação de carga sobre o primeiro molar (MB-C1) apresenta a maior deformação da fibromucosa quando comparada à deformação sofrida pelo ligamento periodontal, na proporção de 10:1; 4 - O rebordo descendente-ascendente apresenta uma distribuição de tensões menos favorável que o rebordo horizontal; 5 - A aplicação de carga no primeiro molar gera mais torque sobre o dente para distal do que a aplicação de carga sobre o segundo pré-molar. / This study is a two-dimensional finite element analysis (FEA) of the stress distributionin the supporting structures – compact and cancellous bone; periodontal ligament and oral mucosa – for a distal extension base removable partial denture (RPD) modeled on mandibular dental archs with two residual ridge forms: horizontal and descending-ascending. The two experimental quadrant models were developed in the AUTOCAD 2004 (Autodesk Inc., USA), software to include the first premolar asthe dental support with a distal occlusal rest; the second premolar and first molar as the artificial teeth inserted on the base over an RPD framework and the residual ridge. These models were discretized on the FEA software (I-DEAS, USA) and an axial load of 100 N was applied to the mesh on the artificial teeth cusps either on the first mola r (C1) or on the second premolar (C2). It was noticed that, in the cancellous bone, the maximum strain was around the supporting tooth, mainly in the distalcervical third (0.003 mm) while the largest compression tension (CT) was at the tooth apex when the load was applied over the second premolar, with a horizontal residual ridge (0,621 N/mm 2 ). When the ridge was descending-ascending, the areas affected were the same, showing 0,003 mm and 0,609 N/mm 2 , respectively as the maximum displacement and CT. In the oral mucosa, the largest results occurred when the load application point was over the first molar and the residual ridge was horizontal: 0,137 mm and 0,144 N/mm 2 . The descending-ascending alveolar ridge showed the maximum displacement and CT in the ascending segment of the residual ridge, toward the retromolar trigon, with 0,131 mm and 0,122 N/mm 2 , respectively. Within the constraints of this study, it was concluded that: 1 – The compact bone shows greater stress concentration than the cancellous bone; 2 – The compact bone shows greater area displacement concentration than the cancellous bone; 3 – The descending-ascending residual ridge with the load application on the first molar showed the largest displacement of the oral mucosa when compared to the periodontal ligament displacement with a 10:1 ratio; 4 – The descending-ascending residual ridge had a less favourable stress distribution than its horizontal counterpart; 5 – The load applied on the first molar produced more distal torquing on the supporting tooth than that on the second premolar.

L’objet de cette thèse est d’analyser les déterminants de l’engagement sociétal des entreprises labellisées RSE, dans un contexte de pays émergent, en l’occurrence le Maroc. Sachant que la démarche de RSE ne connaît pas le même succès dans le monde pour plusieurs raisons liées aux spécificités économiques, culturelles et sociales de chaque pays, ce travail de recherche propose d’analyser empiriquement les bénéfices et freins perçus par les entreprises labellisées RSE de la Confédération Générale des Entreprises Marocaines (CGEM). En effet, face à un contexte marqué par des mutations profondes du nouvel environnement économique international, à savoir, la mondialisation économique et la globalisation financière et les modifications réglementaires et technologiques importantes, il est devenu nécessaire pour l’entreprise de s’inscrire dans des orientations stratégiques portant sur les perspectives du développement durable, et mettant en lumière l’engagement sociétal dans les pratiques managériales dont l’objectif principal est d’assurer sa pérennité. C’est ainsi qu’elle peut concilier préservation de l’environnement et équité sociale d’un coté et les impératifs financiers et économiques de l’autre. En se basant sur des thématiques relatives aux variables démographiques, degré de connaissance et posture managériale, actions menées et outils mobilisés, freins et réticences, et motivations et avantages en matière de RSE, nous mettons l’accent sur les bénéfices et inconvénients de cette démarche.Pour cela, deux parties ont été consacrées pour élucider les différentes questions posées. Après avoir présenté un panorama des approches théoriques et conceptuelles de l’engagement sociétal des entreprises dans la première partie, la deuxième sera consacrée au positionnement épistémologique et méthodologique, et à l’analyse des résultats de l’étude empirique. Les dits résultats permettent de répondre à notre interrogation : Quels sont les déterminants de l’engagement sociétal des entreprises marocaines labellisées RSE? / The Subject of this thesis is to analyze the determiners of the community involvement of a company (RSE) in an emerging country such as Morocco. The purpose of the present research is to analyze this relation empirically. In fact, the new international economic environment characterized by deep changes, particularly, economic and financial globalization as well as the important regulatory and technological modifications that are taking place nowadays tend to give the priority to other strategic orientations relating to the prospects of sustainable development, and clarifying the societal commitment in managerial practices. The main goal of any company is to ensure its sustainability to the benefit of its customers, its shareholders and its collaborators. A company can become a committed social actor and not simply content itself with being an economic agent generating wealth. It can also get involved and adhere to better positioning itself with regard to the sustainable development which requires the production and sale within the best economic conditions while keeping a good image, namely, its ethical behavior, and by guaranteeing that its products are socially humanly and ecologically correct. Thus it can reconcile the safeguarding of the environment, social equity and the financial and economic requirements. Therefore, two parts were devoted to elucidating the various questions raised in this respect: The first part presents a review of the theoretical and conceptual approaches of the social responsibility of a company and its overall Performance and the potential links between these two components. The second part is devoted to the epistemological and methodological positioning, to the presentation of the model and the research hypotheses, as well as the analysis of the results of the empirical study. The results make it possible to answer our question: What are the determiners of the community involvement of the certified Moroccan companies RSE?

In the first part of this dissertation, the phenomenon of self-sustained pressure os-cillations due to the flow past a circular, axisymmetric cavity, associated with inline gate valves, was investigated. In many engineering applications, such as flows through open gate valves, there exists potential for coupling between the vortex shedding from the up-stream edge of the cavity and a diametral mode of the acoustic pressure fluctuations. The effects of the internal pipe geometry immediately upstream and downstream of the shal-low cavity on the characteristics of partially trapped diametral acoustic modes were in-vestigated numerically and experimentally on a scaled model of a gate valve mounted in a pipeline that contained convergence-divergence sections in the vicinity of the valve. The resonant response of the system corresponded to the second acoustic diametral mode of the cavity. Excitation of the dominant acoustic mode was accompanied by pressure oscillations, and, in addition to that, as the angle of the converging-diverging section of the main pipeline in the vicinity of the cavity increased, the trapped behavior of the acoustic diametral modes diminished, and additional antinodes of the acoustic pressure wave were observed in the main pipeline. In addition to that, the effect of shallow chamfers, introduced at the upstream and/or downstream cavity edges, was investigated in the experimental system that con-tained a deep, circular, axisymmetric cavity. Through the measurements of unsteady pressure and associated acoustic mode shapes, which were calculated numerically for several representative cases of the internal cavity geometry, it was possible to identify the configuration that corresponded to the most efficient noise suppression. This arrangement also allowed calculation of the azimuthal orientation of the acoustic modes, which were classified as stationary, partially spinning or spinning. Introduction of shallow chamfers at the upstream and the downstream edges of the cavity resulted in changes of azimuthal orientation and spinning behaviour of the acoustic modes. In addition, introduction of splitter plates in the cavity led to pronounced change in the spatial orientation and the spinning behaviour of the acoustic modes. The short splitter plates changed the behaviour of the dominant acoustic modes from partially spinning to stationary, while the long split-ter plates enforced the stationary behaviour across all resonant acoustic modes. Finally, the evolution of fully turbulent, acoustically coupled shear layers that form across deep, axisymmetric cavities and the effects of geometric modifications of the cavity edges on the separated flow structure were investigated using digital particle image velocimetry (PIV). Instantaneous, time- and phase-averaged patterns of vorticity pro-vided insight into the flow physics during flow tone generation and noise suppression by the geometric modifications. In particular, the first mode of the shear layer oscillations was significantly affected by shallow chamfers located at the upstream and, to a lesser degree, the downstream edges of the cavity. In the second part of the dissertation, the performance of aortic heart valve pros-thesis was assessed in geometries of the aortic root associated with certain types of valve diseases, such as aortic valve stenosis and aortic valve insufficiency. The control case that corresponds to the aortic root of a patient without valve disease was used as a reference. By varying the aortic root geometry, it was possible to investigate corresponding changes in the levels of Reynolds shear stress and establish the possibility of platelet activation and, as a result of that, the formation of blood clots. / Graduate / 0541 / 0546 / 0548 / 0986 / alexbn024@gmail.com

In the first part of this dissertation, the phenomenon of self-sustained pressure os-cillations due to the flow past a circular, axisymmetric cavity, associated with inline gate valves, was investigated. In many engineering applications, such as flows through open gate valves, there exists potential for coupling between the vortex shedding from the up-stream edge of the cavity and a diametral mode of the acoustic pressure fluctuations. The effects of the internal pipe geometry immediately upstream and downstream of the shal-low cavity on the characteristics of partially trapped diametral acoustic modes were in-vestigated numerically and experimentally on a scaled model of a gate valve mounted in a pipeline that contained convergence-divergence sections in the vicinity of the valve. The resonant response of the system corresponded to the second acoustic diametral mode of the cavity. Excitation of the dominant acoustic mode was accompanied by pressure oscillations, and, in addition to that, as the angle of the converging-diverging section of the main pipeline in the vicinity of the cavity increased, the trapped behavior of the acoustic diametral modes diminished, and additional antinodes of the acoustic pressure wave were observed in the main pipeline. In addition to that, the effect of shallow chamfers, introduced at the upstream and/or downstream cavity edges, was investigated in the experimental system that con-tained a deep, circular, axisymmetric cavity. Through the measurements of unsteady pressure and associated acoustic mode shapes, which were calculated numerically for several representative cases of the internal cavity geometry, it was possible to identify the configuration that corresponded to the most efficient noise suppression. This arrangement also allowed calculation of the azimuthal orientation of the acoustic modes, which were classified as stationary, partially spinning or spinning. Introduction of shallow chamfers at the upstream and the downstream edges of the cavity resulted in changes of azimuthal orientation and spinning behaviour of the acoustic modes. In addition, introduction of splitter plates in the cavity led to pronounced change in the spatial orientation and the spinning behaviour of the acoustic modes. The short splitter plates changed the behaviour of the dominant acoustic modes from partially spinning to stationary, while the long split-ter plates enforced the stationary behaviour across all resonant acoustic modes. Finally, the evolution of fully turbulent, acoustically coupled shear layers that form across deep, axisymmetric cavities and the effects of geometric modifications of the cavity edges on the separated flow structure were investigated using digital particle image velocimetry (PIV). Instantaneous, time- and phase-averaged patterns of vorticity pro-vided insight into the flow physics during flow tone generation and noise suppression by the geometric modifications. In particular, the first mode of the shear layer oscillations was significantly affected by shallow chamfers located at the upstream and, to a lesser degree, the downstream edges of the cavity. In the second part of the dissertation, the performance of aortic heart valve pros-thesis was assessed in geometries of the aortic root associated with certain types of valve diseases, such as aortic valve stenosis and aortic valve insufficiency. The control case that corresponds to the aortic root of a patient without valve disease was used as a reference. By varying the aortic root geometry, it was possible to investigate corresponding changes in the levels of Reynolds shear stress and establish the possibility of platelet activation and, as a result of that, the formation of blood clots. / Graduate / 0541 / 0546 / 0548 / 0986 / alexbn024@gmail.com

O objetivo deste estudo foi avaliar, pelo método dos elementos finitos bidimensional, a distribuição das tensões geradas nas estruturas de suporte das próteses parciais removíveis (PPR) - osso cortical, osso esponjoso, fibromucosa e ligamento periodontal, em modelos de arcos parcialmente dentados de extremidade livre inferior, em rebordo horizontal (MA) e descendente-ascendente (MB). Foram confeccionados dois modelos de quadrante de mandíbula em AUTOCAD 2004 (Autodesk Inc., USA), contendo apenas o primeiro pré-molar e rebordo residual, sendo repostos o segundo pré-molar e primeiro molar pela PPR, tendo como dente suporte o primeiro pré-molar com apoio oclusal distal. Posteriormente, foi aplicada carga axial de 100 N nas cúspides dos dentes artificiais da PPR (somente sobre o 1 o molar - C1 e somente sobre o 2 o pré-molar - C2). Os modelos confeccionados em AUTOCAD foram transferidos para o programa I-DEAS (software de elementosfinitos), que discretizou-os e realizou a distribuição das tensões sob as condições de aplicação de carga citadas. Pôde–se observar que no osso esponjoso, a maior deformação e tensão de compressão foram observadas ao redor do dente suporte, principalmente no terço cervical distal para a deformação e no ápice do dente para a tensão de compressão durante a aplicação de carga sobre o segundo pré-molar no rebordo horizontal (0,003 mm e 0,621 N/mm 2 , respectivamente). Já no rebordo descendente-ascendente, as áreas solicitadas foram as mesmas, apresentando deformação e tensão de compressão máximas de 0,003 mm e 0,609 N/mm 2 . Para a fibromucosa, pode-se notar que no rebordo horizontal, a maior deformação e tensão de compressão ocorreram abaixo do ponto de aplicação de carga, ou seja, no primeiro molar, com valores de 0,137 mm e 0,144 N/mm 2 . No rebordo descendente-ascendente, a área de maior deformação e tensão de compressão localizaram-se na porção ascendente do rebordo em direção do trígono retromolar, com valores de 0,131 mm e 0,122 N/mm 2 , respectivamente. Diante dos limites do presente estudo pode-se concluir que: 1 - O osso cortical apresenta uma concentração de tensões maior que o osso esponjoso; 2 – O osso cortical apresenta uma deformação mais restrita em área que o osso esponjoso; 3 - O rebordo descendente-ascendente com a aplicação de carga sobre o primeiro molar (MB-C1) apresenta a maior deformação da fibromucosa quando comparada à deformação sofrida pelo ligamento periodontal, na proporção de 10:1; 4 - O rebordo descendente-ascendente apresenta uma distribuição de tensões menos favorável que o rebordo horizontal; 5 - A aplicação de carga no primeiro molar gera mais torque sobre o dente para distal do que a aplicação de carga sobre o segundo pré-molar. / This study is a two-dimensional finite element analysis (FEA) of the stress distributionin the supporting structures – compact and cancellous bone; periodontal ligament and oral mucosa – for a distal extension base removable partial denture (RPD) modeled on mandibular dental archs with two residual ridge forms: horizontal and descending-ascending. The two experimental quadrant models were developed in the AUTOCAD 2004 (Autodesk Inc., USA), software to include the first premolar asthe dental support with a distal occlusal rest; the second premolar and first molar as the artificial teeth inserted on the base over an RPD framework and the residual ridge. These models were discretized on the FEA software (I-DEAS, USA) and an axial load of 100 N was applied to the mesh on the artificial teeth cusps either on the first mola r (C1) or on the second premolar (C2). It was noticed that, in the cancellous bone, the maximum strain was around the supporting tooth, mainly in the distalcervical third (0.003 mm) while the largest compression tension (CT) was at the tooth apex when the load was applied over the second premolar, with a horizontal residual ridge (0,621 N/mm 2 ). When the ridge was descending-ascending, the areas affected were the same, showing 0,003 mm and 0,609 N/mm 2 , respectively as the maximum displacement and CT. In the oral mucosa, the largest results occurred when the load application point was over the first molar and the residual ridge was horizontal: 0,137 mm and 0,144 N/mm 2 . The descending-ascending alveolar ridge showed the maximum displacement and CT in the ascending segment of the residual ridge, toward the retromolar trigon, with 0,131 mm and 0,122 N/mm 2 , respectively. Within the constraints of this study, it was concluded that: 1 – The compact bone shows greater stress concentration than the cancellous bone; 2 – The compact bone shows greater area displacement concentration than the cancellous bone; 3 – The descending-ascending residual ridge with the load application on the first molar showed the largest displacement of the oral mucosa when compared to the periodontal ligament displacement with a 10:1 ratio; 4 – The descending-ascending residual ridge had a less favourable stress distribution than its horizontal counterpart; 5 – The load applied on the first molar produced more distal torquing on the supporting tooth than that on the second premolar.

Nesta pesquisa, foi realizada uma análise comparativa, por meio do método dos elementos finitos bidimensional linear, das deformações e tensões geradas a partir da aplicação de uma carga de 100N, nas estruturas de suporte (fibromucosa,ligamento periodontal, osso cortical e osso esponjoso) de dois modelos que simulam um hemiarco mandibular associada a uma prótese parcial removível de extremidade livre dista inferiorl, quando da variação da inclinação do rebordo residual no plano sagital. O modelo A (MA) foi desenhado com um rebordo ascendente distal com 15 graus de inclinação e o modelo B (MB) com um rebordo descendente distal com 15 graus negativos, ambos em relação ao plano oclusal. Nos dois modelos aplicou-se uma carga primeiramente na cúspide médio-vestibular do primeiro molar inferior artificial (C1) e depois na cúspide vestibular do segundo pré-molar inferior (C2), por meio do programa I-deas (software de elementos finitos) onde foram feitas as análises de deformações e tensões e processamento das imagens. Fez-se então uma análise comparativa dos carregamentos (C1 e C2) em cada modelo individualmente e entre os dois modelos(MA e MB). Os resultados permitiram concluir que: 1) A inclinação do rebordo residual no plano sagital influenciou na distribuição e na intensidade das tensões das estruturas de suporte; 2) No osso cortical as tensões foram mais localizadas e de maior intensidade que no osso esponjoso; 3) A diferença de deformação entre fibromucosa e ligamento periodontal foi maior quando a carga foi aplicada no primeiro molar, de ambos os modelos, sendo a mais expressiva no rebordo ascendente distal; 4) As tensões de compressão foram maiores em intensidade e melhor distribuídas no osso esponjoso e no osso cortical, quando comparadas as tensões de tração; 5) O rebordo ascendente distal se mostrou mais favorável à distribuição das tensões nas estruturas de suporte quando comparado ao rebordo descendente distal; 6) Nos dois modelos a aplicação da carga no primeiro molar gerou um maior torque sobre o dente suporte para a distal do que quando aplicado no segundo pré-molar, principalmente no rebordo descendente distal; 7) As estruturas de suporte do rebordo residual foram mais solicitadas em C1 que em C2, em ambos os modelos, principalmente no rebordo ascendente distal; 8) No dente suporte as tensões nas estruturas de suporte foram mais axiais quando o carregamento ocorreu no segundo pré-molar inferior, em ambos os modelos. / In this study, a two-dimensional finite element comparative analysis of the stress distribution and of displacement in the supporting structures – oral mucosa,periodontal ligament, compact and cancellous bone – was carried out for a distal extension base removable partial denture (RPD), modeled on two mandibular dental archs with different types of residual ridge when aplaying loads of 100N. The A model (MA) was developed to include a distal ascending alveolar ridge with a 15-degrees positive inclination, while the B model (MB) was prepared with a distal descending alveolar ridge with a 15-degrees negative inclination. Both models had a load applied inicially on the lower first molar median cusp (C1) and then on the lower second premolar buccal cusp (C2). Using the FEA software (I-DEAS, USA) for the stress distribution and displacement analysis of the generated images. A comparative analysis was them performed on the C1 and C2 loads for which and both models (MA and MB).The results showed that: 1 – The alveolar ridge inclination showed some degree of on the stress distribution and intensity generated by the RPD; 2 –The compact bone showed greater stress concentration and intensity than the cancellous bone; 3 – The ratio between oral mucosa and periodontal ligament displacement showed greater values when load was applied on the lower first molar for both models. The ratio was higher for the distal ascending alveolar ridge; 4- The compressive stress showed greater intensity and better range of distribution than the tensile stress for both the compact and cancellous bone; 5 – The distal ascending residual ridge had a more favourable stress distribution than distal descending conterpart ; 6 – The load applied on the lower first molar produced more distal torquing on the supporting tooth than that on the lower second premolar ,specially on the distal descending residual ridge; 7 – the load applied on the lower firt molar generated greater amount of stress on the residual ridge supporting structures for both models, but specially for the distal ascending residual ridge; 8 – The load applied on the lower second premolar produced more vertical forces on the supporting structures of the tooth for both models.

Le système auditif ascendant est constitué d’étages multiples procédant chacun à un traitement complexe du signal, traitement qui est modulé par un système descendant, formant de multiples boucles corticales et sous-corticales de rétroaction : le système efférent auditif. La boucle la plus longue de ce système serait capable de moduler directement le fonctionnement des cellules sensorielles de l’organe périphérique de l’audition. Le but de ce travail était d’étudier pour la première fois chez le sujet sain, l’effet d’une modulation corticale expérimentale sur le fonctionnement périphérique auditif. Nous avons donc recueilli, dans le cadre d’un protocole en double aveugle contre placebo, chez 34 sujets sains, l’activité des cellules ciliées externes de l’organe de Corti (cellules sensorielles directement en contact avec les fibres nerveuses efférentes), par le recueil d’otoémissions acoustiques (OEAs), avant et après stimulation du cortex auditif par une stimulation magnétique transcrânienne répétitive (SMTr). Une diminution de l’amplitude d’un type d’OEA a été obtenue du côté controlatéral à une stimulation du cortex auditif par SMTr à 10 Hz, effet qui ne peut être expliqué seulement par une action non-spécifique liée au bruit de la SMTr mais qui reste extrêmement variable d’un sujet à un autre. De plus, nous avons montré, du côté ipsilatéral à la SMTr, une diminution de l’amplitude des OEAs immédiatement après la SMTr, et uniquement pour les fortes intensités d’utilisation de la SMTr (donc, pour des niveaux de bruit plus importants), reflétant un effet direct du bruit de la SMTr sur les mécanismes cochléaires actifs, effet présent chez nos sujets même en cas de protections auditives de bonne qualité / The ascending auditory system involves multiples stages where the auditory information is processed and modulated by a top-down influence involving multiple cortico sub-cortical loops: the efferent auditory system. It is hypothesized that the longest loop of this efferent system is able to modulate directly the sensory cells of the peripheral auditory organ. The aim of this work was to study this system, to our knowledge for the first time in healthy humans, and to show a direct cortical influence on the auditory periphery. In a double blind randomized procedure, we recorded, in 34 healthy subjects, the activity of outer hair cells of the organ of Corti (sensory cells, that are in direct synaptic contact with medial efferent fibers), by means of evoked otoacoustic emissions (OAEs), before and after auditory cortex stimulation by repetitive transcranial magnetic stimulation (rTMS). We showed an inhibitory influence of the auditory cortical stimulation by 10 Hz rTMS on OAE amplitudes, predominantly in the ear contralateral to the rTMS, effect that cannot be attributed to a non-specific effect linked to the impulse noise associated with the rTMS technique, but that remains highly variable across subjects. In addition, we showed a decrease in OAE amplitude on the ipsilateral side, immediately after the rTMS session and only for high rTMS intensities (and hence, higher noise levels), that reflect a direct influence of the rTMS noise on the auditory periphery, effect that is present even in well ear-protected subjects