Dans les élevages laitiers d’aujourd’hui, les déplacements de la caillette sont parmi les conditions chirurgicales les plus souvent rencontrées. Le pronostic pour ces pathologies est cependant très différent que l’on soit en présence d’une dilatation de la caillette à droite (DCD) ou d’un volvulus de la caillette (VC). En pratique, la distinction en période préopératoire entre ces deux conditions est difficile. Afin de limiter les pertes économiques associées aux DCD/VC, l’identification et la réforme précoce des animaux ayant le plus grand risque d’avoir une mauvaise évolution postopératoire deviennent des enjeux de premier plan. Les objectifs de cette étude étaient de déterminer la valeur pronostique de la L-lactatémie (LAC) mesurée à la ferme en préopératoire à l’aide d’un appareil portatif chez des vaches souffrant de DCD ou VC et de suggérer des seuils de LAC cliniquement significatifs. Nos résultats indiquent que la LAC est un bon indicateur pronostique lors de DCD/VC. Une LAC ≤ 2 mmol/L est un bon indicateur de succès chirurgical et s’avère très utile pour appuyer la décision d’opérer l’animal (sensibilité, spécificité, valeurs prédictives positive et négative de respectivement 76.2, 82.7, 53.3 et 93.1%). Par ailleurs, il n’y a aucun avantage économique à effectuer une chirurgie chez des vaches commerciales souffrant de DCD/VC qui ont une LAC ≥ 6 mmol/L (sensibilité, spécificité, valeurs prédictives positive et négative de respectivement 28.6, 97.5, 75 et 84%). Par conséquent, ces animaux devraient, dans la plupart des cas, être réformés en raison de la probabilité élevée qu’ils aient une mauvaise évolution postopératoire. / Abomasal displacement is among the most commonly encountered surgical disorder in modern dairy herds. Prognosis, however, varies widely among type of abomasal displacement, and preoperative diagnostic may be difficult to assess. To control the economic loss associated with abomasal disorders, especially right displaced abomasum (RDA) and abomasal volvulus (AV), early identification and culling of animals at higher risk of developing a surgical failure (SF) would be of interest. The objectives of this study were to determine the prognostic value of preoperative L-lactate concentration (LAC) measured on farm with a portable clinical analyzer for cows with RDA or AV, and to suggest LAC clinical relevant decision thresholds. Our results showed that LAC was correlated with the prognosis of RDA/AV. A LAC ≤ 2 mmol/L seemed to be good indicator of surgical success and would be useful to support a surgical decision (sensitivity, specificity, positive and negative predictive values of 76.2, 82.7, 53.3 and 93.1%; respectively). On the other hand, there is no economic advantage to perform a surgery on commercial cows with RDA/AV that have LAC ≥ 6 mmol/L and these animals should potentially be culled according to their high probability of SF (sensitivity, specificity, positive and negative predictive values of 28.6, 97.5, 75 and 84%; respectively).

In vivo, la pression artérielle au niveau des artères cérébrales est pulsée, alors que ex vivo, l’étude de la fonction cérébrovasculaire est majoritairement mesurée en pression statique. L’impact de la pression pulsée sur la régulation du tonus myogénique et sur la fonction endothéliale cérébrale est inconnu. Nous avons posé l’hypothèse selon laquelle en présence d'une pression pulsée physiologique, la dilatation dépendante de l’endothélium induite par le flux et le tonus myogénique seraient optimisés. L’objectif de notre étude est d’étudier ex vivo l’impact de la pression pulsée sur le tonus myogénique et la dilatation induite par le flux dans les artères cérébrales de souris. Nous avons utilisé un artériographe pressurisé couplé à un système générant une onde pulsée de fréquence et d’amplitude réglables. Les artères cérébrales moyennes (≈160 μm de diamètre) ont été isolées de souris C57BL6 âgées de 3 mois et pressurisées à 60 mm Hg, en pression statique ou en pression pulsée. En pression statique, le tonus myogénique est faible mais est potentialisé par le L-NNA (un inhibiteur de la eNOS) et la PEG-catalase (qui dégrade le H2O2), suggérant une influence des produits dilatateurs dérivés de la eNOS sur le tonus myogénique. En présence de pression pulsée (pulse de 30 mm Hg, pression moyenne de 60 mm Hg, 550 bpm), le tonus myogénique est significativement augmenté, indépendamment du L-NNA et de la PEG-catalase, suggérant que la pression pulsée lève l’impact de la eNOS. En pression statique ou pulsée, les artères pré-contractées se dilatent de façon similaire jusqu’à une force de cisaillement de 15 dyn/cm2. Cette dilatation, dépendante de l’endothélium et de la eNOS, est augmentée en condition pulsée à une force de cisaillement de 20 dyn/cm2. En présence de PEG-catalase, la dilatation induite par le flux est diminuée en pression statique mais pas en pression pulsée, suggérant que la pression statique, mais pas la pression pulsée, favorise la production de O2 -/H2O2. En effet, la dilatation induite par le flux est associée à une production de O2 -/H2O2 par la eNOS, mesurable en pression statique, alors que la dilatation induite par le flux en pression pulsée est associée à la production de NO. Les différences de sensibilité à la dilatation induite par le flux ont été abolies après inhibition de Nox2, en condition statique ou pulsée. La pression pulsée physiologique régule donc l’activité de la eNOS cérébrale, en augmentant le tonus myogénique et, en présence de flux, permet la relâche de NO via la eNOS. / While in vivo arterial blood pressure in cerebral arteries is pulsatile, in vitro cerebral arterial function is generally assessed under a static pressure. Thus, whether pulse pressure regulates cerebral endothelial shear stress sensitivity and myogenic tone is unknown. We hypothesized that a physiological pulse pressure induces a better flow-mediated dilation and optimized myogenic tone. The aim of this study was to test in vitro the impact of pulse pressure on myogenic tone and eNOS-dependent flow-mediated dilation in mouse cerebral arteries. Using a custom computer-controlled pneumatic system generating a pulse pressure (used at 30 mm Hg, rate of 550 bpm) coupled to an arteriograph, isolated posterior cerebral arteries from 3-month old C57Bl/6J mice were pressurized at 60 mm Hg, either in static or pulse pressure conditions. Shear stress from 2 to 20 dyn/cm2 was applied and flow-mediated dilation measured. Without pulse pressure, myogenic tone was low but potentiated by both L-NNA (eNOS inhibitor) and PEG-catalase (catalyses H2O2), suggesting an influence of eNOS-derived dilator products on myogenic tone. Pulse pressure significantly increased myogenic tone, independently of L-NNA and PEG-catalase, suggesting that pulse pressure prevents the impact of eNOS. In both static and pulse pressure conditions, cerebral arteries did not dilate to shear stress in the presence of L-NNA or after endothelial denudation, confirming the endothelial origin of the dilatory response. Up to 15 dyn/cm2, shear stress elicited similar flow-mediated dilation in static and pulse pressure conditions; at 20 dyn/cm2, however, flow-mediated dilation were higher in the presence of pulse pressure. PEG-catalase reduced flow-mediated dilation in static but not in pulse pressure, suggesting that in static conditions eNOS is responsible for O2 -/H2O2 production. Indeed, eNOS-derived O2 -/H2O2 production was measured during flow-mediated dilation in static pressure, while pulse pressure promoted eNOS-derived NO production. Differences in flow-mediated dilation between static and pulse pressure conditions were abolished after Nox2 inhibition. In conclusion, pulse pressure modulates cerebrovascular eNOS activity: at rest, pulse pressure inhibits eNOS, increasing myogenic tone. In the presence of flow, pulse pressure permits a shear stress-dependent eNOS-derived NO release, leading to higher flow-mediated dilation.

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. / This study has been done in order to improve power electronic devices reliability using aluminium/carbon fibres composites. This work has consisted in 1) determining, using finite elements method, the thermal and mechanical influence of the electronic base plate material; 2) elaborating (using hot pressing, spark plasma sintering and hot extrusion) aluminium/carbon fibres composites; and 3) linking the microstructures observed to the elaboration parameters and to the thermomechanical properties measured.

Ng Chi Ho. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 147-160). / Abstracts in English and Chinese. / ACKNOWLEDGMENTS --- p.I / ABSTRACT --- p.II / LIST OF ABBREVIATIONS --- p.VII / TABLE OF CONTENTS --- p.IX / Chapter CHAPTER 1 --- GENERAL INTRODUCTION / Chapter 1.1 --- Introduction of Low-density lipoprotein --- p.1 / Chapter 1.1.1 --- What are lipids? --- p.1 / Chapter 1.1.2 --- Function and structure of cholesterol --- p.1 / Chapter 1.1.3 --- Function and classification of lipoprotein --- p.1 / Chapter 1.2 --- Functions of low-density lipoprotein --- p.2 / Chapter 1.3 --- Basic structure of low-density lipoprotein --- p.4 / Chapter 1.4 --- Principle on isolation and purification of low-density lipoprotein --- p.4 / Chapter 1.5 --- Cholesterol transport system --- p.7 / Chapter 1.5.1 --- Exogenous pathway of cholesterol metabolism --- p.7 / Chapter 1.5.2 --- Endogenous pathway of cholesterol metabolism --- p.7 / Chapter 1.5.3 --- Reverse transport of Cholesterol --- p.8 / Chapter 1.6 --- Oxidation of LDL --- p.10 / Chapter 1.6.1 --- Agents that causes oxidation --- p.10 / Chapter 1.6.1.1 --- Lipoxygenases --- p.10 / Chapter 1.6.1.2 --- Myeloperoxidase --- p.10 / Chapter 1.6.1.3 --- Reactive nitrogen species --- p.11 / Chapter 1.6.1.4 --- Reactive oxygen species --- p.11 / Chapter 1.6.2 --- Factors that affect the susceptibility of LDL oxidation --- p.13 / Chapter 1.7 --- Hyperlipidaemia 一 chance to increase LDL oxidation --- p.13 / Chapter 1.7.1 --- Definition of hyperlipidemia and hypercholesterolemia --- p.13 / Chapter 1.7.2 --- Risk factors of hyperlipidaemia --- p.13 / Chapter 1.7.2.1 --- High fat low fibre diets: --- p.13 / Chapter 1.7.2.2 --- Obesity --- p.14 / Chapter 1.7.2.3 --- Type II diabetes --- p.14 / Chapter 1.7.2.4 --- Genetic factors (Familial hyperlipidemias) --- p.14 / Chapter 1.8 --- Diseases related to oxidized LDL --- p.15 / Chapter 1.8.1 --- Cardiovascular diseases --- p.15 / Chapter 1.8.1.1 --- Atherosclerosis and ischemic heart attack --- p.15 / Chapter 1.8.1.2 --- Factors that affect incidence of atherosclerosis --- p.16 / Chapter 1.8.1.2.1 --- Triglyceride-rich lipoprotein --- p.16 / Chapter 1.8.1.2.2 --- Small and dense LDL --- p.16 / Chapter 1.8.1.3 --- Stroke --- p.17 / Chapter 1.8.2 --- Common ways to reduce plasma cholesterol level --- p.17 / Chapter 1.8.2.1 --- Diet control --- p.17 / Chapter 1.8.2.2 --- Physical activity --- p.17 / Chapter 1.8.2.3 --- Drug therapy --- p.18 / Chapter CHAPTER 2 --- IMPAIRMENT OF OXIDIZED LDL ON ENDOTHELIUM-DEPENDENT RELAXATION / Chapter 2.1 --- Introduction --- p.19 / Chapter 2.1.1 --- Properties and function of phenylephrine hydrochloride --- p.22 / Chapter 2.1.2 --- Properties and function of acetylcholine --- p.22 / Chapter 2.2 --- Objectives --- p.23 / Chapter 2.3 --- Materials and methods --- p.24 / Chapter 2.3.1 --- Preparation of drugs --- p.24 / Chapter 2.3.2 --- Preparation of human native LDL --- p.25 / Chapter 2.3.3 --- Preparation of oxidized LDL --- p.27 / Chapter 2.3.4 --- Preparation of aorta --- p.27 / Chapter 2.3.5 --- Measurement of Isometric Force in vitro --- p.30 / Chapter 2.3.5.1 --- Protocol 1- Dose effect of oxidized LDL on acetylcholine-induced vasorelaxation --- p.30 / Chapter 2.3.5.2 --- Protocol 2 - Time effect of oxidized LDL on acetylcholine-induced vasorelaxation --- p.30 / Chapter 2.3.5.3 --- Protocol 3 - Effect of co-incubation of LDL and copper(ll) sulphate on acetylcholine-induced vasorelaxation --- p.31 / Chapter 2.3.5.4 --- Protocol 4 - Effect of oxidized LDL on selected vasodilators --- p.32 / Chapter 2.3.5.5 --- Protocol 5 - Effect of pretreatment of L-arginine on oxidized LDL impaired -endothelium-induced relaxation --- p.32 / Chapter 2.3.5.6 --- Protocol 6 - Effect of a -tocopherol on oxidized LDL-damaged acetylcholine- induced vasorelaxation --- p.33 / Chapter 2.3.5.7 --- Protocol 7 - Effect of a -tocopherol on LDL and copper(ll) sulphate- induced endothelial dysfunction --- p.33 / Chapter 2.3.6 --- Western blot analysis of endothelial nitric oxide synthase (eNOS) protein --- p.34 / Chapter 2.3.7 --- Statistics --- p.35 / Chapter 2.4 --- Results --- p.36 / Chapter 2.4.1 --- Dose effect of oxidized LDL on acetylcholine-induced vasorelaxation --- p.36 / Chapter 2.4.2 --- Time effect of oxidized LDL on acetylcholine-induced vasorelaxation --- p.36 / Chapter 2.4.3 --- Effect of co-incubation of LDL and copper(II) sulphate on acetylcholine- induced vasorelaxation --- p.39 / Chapter 2.4.4 --- Effect of oxidized LDL on selected vasodilators --- p.41 / Chapter 2.4.5 --- Effect of pretreatment of L-arginine on oxidized LDL impaired- acetylcholine-induced relaxation --- p.41 / Chapter 2.4.6 --- Effect of a-tocopherol on oxidized LDL-damaged acetylcholine- induced vasorelaxation --- p.48 / Chapter 2.4.7 --- Effect of a-tocopherol on LDL and copper(II) sulphate-induced endothelial dysfunction --- p.50 / Chapter 2.4.8 --- eNOS Protein expression --- p.50 / Chapter 2.5 --- Discussion --- p.53 / Chapter CHAPTER 3 --- EFFECTS OF LDL INJECTION ON THE ENDOTHELIAL FUNCTION OF RATS / Chapter 3.1 --- Introduction --- p.58 / Chapter 3.2 --- Objective --- p.60 / Chapter 3.3 --- Methods and Materials --- p.61 / Chapter 3.3.1 --- Preparation of Drugs --- p.61 / Chapter 3.3.2 --- Preparation of LDL --- p.61 / Chapter 3.3.3 --- Animal Treatment --- p.61 / Chapter 3.3.4 --- Serum lipid and lipoprotein determinations --- p.62 / Chapter 3.3.5 --- Measurement of serum MDA level by TBARS assay --- p.62 / Chapter 3.3.6 --- Preparation of aorta --- p.62 / Chapter 3.3.7 --- Organ bath experiment --- p.63 / Chapter 3.3.8 --- Statistics --- p.64 / Chapter 3.4 --- Result --- p.65 / Chapter 3.4.1 --- Growth and food intake --- p.65 / Chapter 3.4.2 --- "Effect of LDL injection on serum TC, TG and HDL-C" --- p.65 / Chapter 3.4.3 --- Effect of LDL injection on non-HDL-C and ratio of non-HDL-C to HDL-C --- p.65 / Chapter 3.4.4 --- Serum MDA level --- p.68 / Chapter 3.4.5 --- Phenylephrine-induced contraction --- p.70 / Chapter 3.4.6 --- Endothelium-dependent and -independent relaxation --- p.75 / Chapter 3.5 --- Discussion --- p.79 / Chapter CHAPTER 4 --- EFFECTS OF INDIVIDUAL COMPONENT OF OXIDIZED LDL ON ENDOTHELIUM-DEPENDENT RELAXATION / Chapter 4.1 --- Introduction --- p.83 / Chapter 4.2 --- Objectives --- p.85 / Chapter 4.3 --- Materials and methods --- p.86 / Chapter 4.3.1 --- Preparation of drugs --- p.86 / Chapter 4.3.2 --- Preparation of human native LDL and oxidized LDL --- p.86 / Chapter 4.3.3 --- GC analysis of fatty acid composition in LDL --- p.86 / Chapter 4.3.4 --- TBARS assay analysis of MDA content in LDL --- p.87 / Chapter 4.3.5 --- GC analysis of cholesterol oxidation products in LDL --- p.89 / Chapter 4.3.6 --- Thin-layer chromatography analysis of LPC in LDL --- p.91 / Chapter 4.3.7 --- Preparation of aorta --- p.92 / Chapter 4.3.8 --- Measurement of Isometric Force in vitro --- p.92 / Chapter 4.3.8.1 --- Protocol 1- effect of LPC on acetylcholine-induced vasorelaxation --- p.92 / Chapter 4.3.8.2 --- Protocol 2- effect of cholesterol oxidation products on acetylcholine-induced vasorelaxation --- p.92 / Chapter 4.3.8.3 --- Protocol 3- effect of oxidized fatty acids on acetylcholine-induced vasorelaxation --- p.93 / Chapter 4.3.9 --- Statistics --- p.93 / Chapter 4.4 --- Results --- p.94 / Chapter 4.4.1 --- Compositional differences between native LDL and oxidized LDL.… --- p.94 / Chapter 4.4.2 --- Effect of LPC on endothelium-dependent relaxation --- p.98 / Chapter 4.4.3 --- Effect of COPs on endothelium-dependent relaxation --- p.98 / Chapter 4.4.4 --- Effect of oxidized fatty acids on endothelium-dependent relaxation --- p.101 / Chapter 4.5 --- Discussion --- p.103 / Chapter CHAPTER 5 --- EFFECTS OF DIETARY OXIDIZED CHOLESTEROL ON BLOOD CHOLESTEROL LEVEL IN HAMSTERS / Chapter 5.1 --- Introduction --- p.107 / Chapter 5.2 --- Objectives --- p.111 / Chapter 5.3 --- Materials and Methods --- p.112 / Chapter 5.3.1 --- Preparation of Oxidized Cholesterol --- p.112 / Chapter 5.3.2 --- Diet preparation --- p.112 / Chapter 5.3.3 --- Animals --- p.113 / Chapter 5.3.4 --- Serum lipid and lipoprotein determinations --- p.116 / Chapter 5.3.5 --- GC analysis of cholesterol and cholesterol oxidation products on organs --- p.116 / Chapter 5.3.6 --- Extraction of neutral and acidic sterols from fecal samples --- p.117 / Chapter 5.3.6.1 --- Determination of neutral sterols --- p.117 / Chapter 5.3.6.2 --- Determination of acidic sterols --- p.117 / Chapter 5.3.6.3 --- GLC analysis of neutral and acidic sterols --- p.118 / Chapter 5.3.7 --- Organ bath experiment --- p.121 / Chapter 5.3.7.1 --- Preparation of aorta --- p.121 / Chapter 5.3.7.2 --- Aortic relaxation --- p.121 / Chapter 5.3.8 --- Analysis of the total area of atherosclerotic plaque on aorta --- p.122 / Chapter 5.3.9 --- Statistics --- p.122 / Chapter 5.4 --- Results --- p.123 / Chapter 5.4.1 --- GC of oxidized cholesterol --- p.123 / Chapter 5.4.2 --- Growth and food intake --- p.123 / Chapter 5.4.3 --- "Effect of non-oxidized and oxidized cholesterol on serum TC, TG and HDL-C" --- p.123 / Chapter 5.4.4 --- Effect of non-oxidized and oxidized cholesterol on non-HDL-C and ratio of non-HDL-C to HDL-C --- p.124 / Chapter 5.4.5 --- Effect ofnon-oxidized and oxidized cholesterol on concentration of hepatic cholesterol --- p.128 / Chapter 5.4.6 --- Effect of non-oxidized and oxidized cholesterol on concentration of cholesterol oxidation products accumulated in liver --- p.128 / Chapter 5.4.7 --- Effect of non-oxidized and oxidized cholesterol on concentration of brain and aortic cholesterol --- p.128 / Chapter 5.4.8 --- Effect of non-oxidized and oxidized cholesterol on fecal neutral and acidic sterols --- p.129 / Chapter 5.4.9 --- Effect of non-oxidized and oxidized cholesterol on aortic relaxation --- p.135 / Chapter 5.4.10 --- Effect of non-oxidzied and oxidized cholesterol on area of atherosclerotic plaque --- p.137 / Chapter 5.5 --- Discussion --- p.139 / Chapter CHAPTER 6 --- CONCLUSION --- p.143 / REFERENCES --- p.146

Made available in DSpace on 2014-07-29T15:25:13Z (GMT). No. of bitstreams: 1 roberto murillo.pdf: 2004529 bytes, checksum: 922288a99b81781fd0c71c63d132dd5d (MD5) Previous issue date: 2010-06-29 / The most common etiology for congenital epiphora is the obstruction of the lacrimonasal duct. Congenital obstruction of the lacrimonasal duct (CLNDO) is the most frequent abnormality of the lacrimal sac of the child. It s incidence varies from 1.8% to 20%. The purpose of this study was to evaluate the efficacy of lacrimonasal duct dilatation using balloon-catheter for treatment of CLNDO in children between two and six years old. Besides, to evaluate the anatomical findings of lower lacrimal system of children with CLNDO using multi-detectors computerized tomography dacryocystography (MD-CT-DCG) with three dimension (3D) reconstruction, before and after the balloon-catheter dilatation. This was a prospective interventional case series study, performed with children treated at the Centro de Referência em Oftalmologia (CEROF) from the Universidade Federal de Goiás, with CLNDO. The cases were selected consecutively accordingly with the demand of the service. Thirthy-eight lacrimal systems from 29 children with CLNDO were included and treated with balloon-catheter dilatation. The age varied from 24 to 64 months, with average of 38.13 ± 11.26 months. Among the 38 lacrimal systems treated, 33 had complete resolution of the signs and symptoms of epiphora (success rate of 86.84%). A radiological study from the last 18 operated lacrimal systems was performed before and five minutes after balloon-catheter dacrioplasty. The circumference of the largest portion of lacrimal system, measured before the procedure, varied from 0.64 to 2cm with an average of 1.30 ± 0.45cm. The amount of contrast prior to the procedure varied from 0.01 to 0.38cm3, with an average of 0.12 ± 0.08cm3. The amount of contrast after the procedure varied from 0.01 to 0.20cm3, with an average of 0.07 ± 0.06cm3 (p = 0.01). The multivariate logistic regression analysis ( backward" model) showed that the difference in the amount of contrast before and after the procedure (p=0,04) and the largest portion of lacrimal sac (p=0,01) were the variables determining for the success of the procedure. There were no complications with the procedure. In conclusion, the balloon-catheter dilatation was proved to be effective as the first procedure in the vast majority of children with CLNDO. The technique of MD-CT-DCG-3D provides detailed information about the anatomy of the lacrimal system, including the lacrimal flow immediately after the dilatation. The difference in the amount of contrast before and after the procedure and the largest portion of lacrimal sac were the variables determining for the success of the procedure. / A etiologia mais comum para epífora congênita é a obstrução do ducto lacrimonasal. A obstrução congênita do ducto lacrimonasal (OCDLN) é a anormalidade mais freqüente do aparelho lacrimal da criança. Sua incidência varia de 1,8% a 20%. O objetivo primário deste estudo foi avaliar a eficácia da técnica de dilatação do ducto lacrimonasal usando cateter-balão para tratamento da obstrução congênita do segmento inferior das vias lacrimais em crianças com idade entre dois e seis anos. Além disso, buscou-se avaliar os achados anatômicos das vias lacrimais de crianças com OCDLN por meio da dacriocistografia por tomografia computadorizada com multi-detectores (DCG-TC-MD) com reconstrução em três dimensões (3D), antes e após a dilatação com cateter-balão. Trata-se de um estudo prospectivo, intervencional do tipo série de casos. Dele participaram crianças atendidas no ambulatório do Centro de Referência em Oftalmologia (CEROF), do Hospital das Clínicas da Universidade Federal de Goiás, com diagnóstico de OCDLN no período de janeiro a outubro de 2008. Os casos foram selecionados consecutivamente de acordo com a demanda do serviço. Foram incluídas 38 vias lacrimais de 29 crianças com OCDLN, tratadas com a dilatação por cateter-balão como procedimento primário. O tempo de seguimento mínimo foi de um ano. A idade variou de 24 a 64 meses, com média de 38,13 ± 11,26 meses. Entre as 38 vias lacrimais tratadas, 33 apresentaram desaparecimento dos sinais e sintomas de lacrimejamento (taxa de sucesso de 86,84%). Realizou-se o estudo radiológico das últimas 18 vias lacrimais operadas, antes e cinco minutos após a dacrioplastia com cateter-balão. A circunferência da porção mais dilatada da via lacrimal, medida antes do procedimento, variou de 0,64 a 2,50cm, com média de 1,30 ± 0,45cm. O volume de contraste antes do procedimento variou de 0,01 a 0,38cm3, com média de 0,12 ± 0,08cm3. O volume de contraste depois do procedimento variou de 0,01 a 0,20cm3, com média de 0,07 ± 0,06cm3 (p=0,01). A análise de regressão logística multivariada com modelo de entrada de variáveis tipo backward mostrou que a diferença do volume de contraste antes e depois (p=0,04) e a porção mais dilatada do saco lacrimal (p=0,01) foram determinantes para o sucesso do procedimento. Não foram encontradas complicações com o procedimento. Em conclusão, a dilatação com cateter-balão mostrou-se eficaz como primeiro procedimento em crianças com OCDLN com idade entre dois e seis anos. A técnica de DCG-TC-MD-3D fornece informações detalhadas sobre a anatomia do sistema lacrimal das crianças com OCDLN, incluindo o fluxo lacrimal logo após a dilatação. A diferença do volume de contraste antes e depois do procedimento e a porção mais dilatada do saco lacrimal foram as variáveis determinantes para o sucesso do procedimento.

Actuellement, la qualité de l’imagerie provenant de systèmes optiques spatiaux est limitée par la taille de leurs miroirs et la masse des structures supportant le miroir. Le développement de systèmes athermiques légers (un seul matériau) constitue le principal challenge dans l’amélioration de ces systèmes. De matériaux légers, résistants mécaniquement (E/ρ3 > 10, σf > 100 MPa) et stables thermiquement (< 2,0.e-6/K) doivent être développés. Dans ce cadre, notre travail porte sur l’élaboration de composites céramiques associant un matériau à coefficient de dilatation thermique (CTE) positif résistant mécaniquement (alumine ou zircone cériée) et un matériau à CTE très négatif (tungstate de zirconium ou β-eucryptite). L'étude du tungstate de zirconium a révélé plusieurs problèmes de décomposition et de réactions avec certaines matrices oxydes, menant à l’abandon de cet oxyde dans l’élaboration des composites. Dans le cas de la β-eucryptite, un phénomène de vermiculation a été mis en évidence, conduisant à la formation d’une porosité intragranulaire. L’optimisation des paramètres de frittage a permis de limiter cette porosité. L’étude du comportement thermique de la β-eucryptite confirme que son CTE très négatif provient principalement d’un phénomène de fissuration, généré par l’anisotropie de dilatation de sa maille cristalline. Cette fissuration est dépendante de la taille des grains mais également de la taille des agrégats de grains dans le cas des poudres. Ainsi, bien que le CTE intrinsèque de la β-eucryptite soit très faible (-0,4.e-6/K), son CTE extrinsèque peut atteindre des valeurs jusqu'à -10,9.e-6/K selon les conditions d’élaboration. Dans ce travail, deux stratégies d’élaboration de composites sont étudiées. Le premier cas consiste à diminuer le CTE des matrices oxydes à partir d’une poudre de β-eucryptite non microfissurée (-0,4.e-6/K) tandis que le second cas consiste à obtenir des matériaux à CTE très faible à partir d’une poudre de β-eucryptite microfissurée (-3,0.e-6/K). Lors de l’utilisation de la matrice en zircone cériée, le taux de dopage au cérium est optimisé afin de limiter la transformation de phase de la zircone. Cette transformation, induite par les contraintes de tension exercées par la β-eucryptite, affecte la linéarité du comportement thermique du composite. Dans les deux cas d’étude, les composites denses montrent une modification du CTE intrinsèque de la β-eucryptite passant de -0,4.e-6/K à plus de +3,2.e-6/K en raison des contraintes de compression appliquées par la matrice (alumine ou zircone cériée). La relaxation de ces contraintes nécessite une sous-densification des composites. A partir de ces observations, différents composites à CTE très faible sont élaborés. Toutefois, le sous-frittage des composites associé à la microfissuration de la β-eucryptite diminuent fortement les propriétés mécaniques des matériaux ainsi élaborés. / High resolution satellite imagery from space optical systems is mainly limited by the mirror size and the mass of structures supporting the mirror. Nowadays, the development of light athermal systems is the major challenge to improve these optical systems. So, light materials having good mechanical properties (E/ρ3 > 10, σf > 100 MPa) and thermal stability (< 2.0e-6/K) are required. Within this context, our project consists in processing new ceramic composites by combining positive thermal expansion coefficient (TEC) materials having good mechanical properties (alumina or ceria doped zirconia) and negative TEC materials (zirconium tungstate or β-eucryptite) The processing of zirconium tungstate-based materials showed several decomposition and chemical reactions with some oxide matrix leading to its giving up. In the case of β-eucryptite, vermicular phenomenon occurs during sintering leading to the formation of intragranular porosity. Sintering parameters optimization can limit this porosity. The study of the thermal behavior of pure β-eucryptite materials shows that the very negative TEC results from microcracking, generated by the TEC anisotropy of its crystal lattice. This microcracking depends on the grain size and the aggregate size in the case of powder materials. Despite the fact that the TEC of its lattice (called intrinsic TE C equals to -0.4e-6/K) is very low, its bulk (or extrinsic) TEC can reach values until -10.9e-6/K according to the processing conditions. In this work, two strategies for developing composites were studied. The first one consists in decreasing the matrix TEC using an uncracked β-eucryptite powder (-0.4e-6/K) while the second one consists in elaborating near zero TEC materials from a microcracked β-eucryptite powder (-3.0e-6/K). When ceria-doped zirconia is used, ceria content must be adjusted in order to limit zirconia phase transformation. This transformation is driven by tensile stresses induced by the β-eucryptite and modifies the composite thermal behavior linearity. In both studied cases, dense composites show a modification of the β-eucryptite intrinsic TEC from -0.4e-6/K to more than +3.2e-6/K as a consequence of compressive stresses applied by the oxide matrix. An uncompleted densification of composites is required to relax these stresses. Taking into account these observations, several very low TEC composites were elaborated. However, the uncompleted densification of composites and the β-eucryptite microcracking greatly decrease the mechanical properties of these materials.

Les modules électroniques de puissance (dizaines de kW) sont des composants essentiels pour le développement des véhicules électriques et hybrides. Ces modules sont des assemblages de composants électroniques en silicium (transistor et diode) sur un substrat généralement en cuivre par brasage tendre. Le substrat assure le maintien mécanique et le transfert de la chaleur pour obtenir une température de fonctionnement convenable (<175°C) du silicium. En fonctionnement, une partie de la puissance est dissipée sous forme d'un flux de chaleur à cause de la résistance interne des semi-conducteurs. Ce flux diffuse de la face supérieure des composants électroniques vers le substrat et engendre l'échauffement de l'assemblage. Du fait que cet assemblage comprend divers matériaux, les dilatations thermiques différentes génèrent des contraintes de cisaillement dans la zone de liaison (brasure) en provoquant l'endommagement des modules électroniques. Pour résoudre ce problème, le substrat doit présenter un compromis entre des caractéristiques électriques et thermiques proches de celles du substrat actuel (Cu) et un coefficient de dilatation linéique proche de celui du semiconducteur (Si). Une des solutions alternatives consiste à développer un matériau composite architecturé. Nous proposons d'atténuer les effets mécaniques de la dilatation différentielle à l'aide d'un substrat architecturé. Le substrat proposé est un matériau composite métallique dont les paramètres de forme ont été optimisés par simulation numérique et validés expérimentalement afin d'accroître au mieux la conductivité du substrat et d'en réduire la dilatation macroscopique. La fabrication à l'échelle du laboratoire est abordée et les variantes du colaminage sont comparées pour réaliser l'architecture interne proposée. En outre, les alliages sans plomb utilisés à ce jour pour le brasage souffrent d'une faible résistance au vieillissement thermique. Sous l'effet de la chaleur, la microstructure initiale de la brasure peut évoluer en donnant naissance à des intermétalliques. Les plaquettes aciculaires (aiguilles) constituent des sites de concentration de contraintes. Cette étude vise également à développer une brasure sans plomb mais relativement réfractaire présentant des conductivités thermique et électrique élevées, associées à une dilatabilité la plus proche possible de celle du silicium. L'architecture de la brasure devrait limiter la croissance des intermétalliques lors du vieillissement.

L'objectif technique principal auquel répond cette thèse est la mise au point d'une méthode de régularisation, donnant des résultats objectifs par rapport au maillage, pour traiter les problèmes couplés hydromécaniques dans le cas des géomatériaux. La modélisation proposée s'inscrit dans le cadre des milieux à microstructure dilatants et s'inspire, du point de vue numérique, des formulations second gradient. Elle permet de prédire de façon robuste les comportements hydrauliques et mécaniques produits par la dégradation d'un milieu naturel. Le modèle ainsi obtenu, dit second gradient de dilatation, se distingue par le faible nombre de degrés de liberté ajouté dans la discrétisation éléments finis par rapport à celui des milieux continus. L'objectif numérique est de réduire les temps de calcul pour rendre les études à portée industrielle acceptables. On montre son efficacité en réalisant des simulations couplées hydromécaniques d'excavations souterraines. Enfin, on présente un algorithme de recherche de solutions multiples dans la direction des modes singuliers basé sur les principes de la théorie de la bifurcation pour traiter des non-linéarités dues à des comportements irréversibles de matériaux adoucissants. Le cadre de l'analyse de bifurcation proposée se limite au cas des opérateurs symétriques. On montre ainsi, sur des simulations d'essais biaxiaux homogènes et d'excavations souterraines en conditions drainées, que cet algorithme est un outil de calcul efficace et robuste pour détecter plusieurs solutions mais également pour franchir des instabilités numériques liées au mauvais conditionnement des matrices tangentes au voisinage des points singuliers ou à la présence de snap-back.

Epidemiological studies have shown strong and consistent associations between exposure to air pollution and increases in morbidity and mortality. Key air pollutants that have been identified include fine particulate matter (PM) and ozone (O3), both major contributors to smog. However, there is a lack of understanding of the mechanisms involved and the relative contributions of individual pollutants. A controlled human exposure facility was used to carry out inhalation studies of concentrated ambient fine particles (CAP), O3, CAP+O3 and filtered air following a randomized design. Exposures were 2 hrs in duration at rest. Subjects included mild asthmatics and non-asthmatics. This thesis focuses on acute cardiovascular responses including blood pressure (BP), brachial artery reactivity (flow-mediated dilatation [FMD]) and markers of systemic inflammation (blood neutrophils and interleukin [IL]-6). Results showed that for CAP-containing exposures (CAP, CAP+O3) there were small but significant transient increases in diastolic BP (DBP) during exposures. Furthermore, neutrophils and IL-6 increased 1 - 3 hrs after and FMD decreased 20 hrs after CAP-containing exposures. Responses to O3 were smaller, comparable to filtered air. The data suggests that adverse responses were mainly driven by PM. The DBP increase was rapid-developing and quick to dissipate, which points to an autonomic irritant response. The magnitude of the DBP increase was strongly negatively associated with the high frequency component of heart rate variability, suggesting parasympathetic withdrawal as a mechanism. In comparison, IL-6, neutrophil and FMD responses were slower to develop, indicative of an inflammatory mechanism. An intriguing finding was that IL-6 increased 3 hrs after CAP, but not after CAP+O3. Further investigation revealed that exposure to CAP+O3 in some individuals may trigger a reflex inhibition of inspiration, decreasing their tidal volume and inhaled pollutant dose, leading to a reduction in systemic IL-6, a potential protective mechanism. Together the findings support the epidemiological evidence of adverse fine PM health effects. Many questions remain to be answered about the health effects of air pollution including a better understanding of how inhaled pollutants result in cardiovascular effects. It is hoped that the insights gained from this thesis will advance the understanding of air pollution health effects.

Epidemiological studies have shown strong and consistent associations between exposure to air pollution and increases in morbidity and mortality. Key air pollutants that have been identified include fine particulate matter (PM) and ozone (O3), both major contributors to smog. However, there is a lack of understanding of the mechanisms involved and the relative contributions of individual pollutants. A controlled human exposure facility was used to carry out inhalation studies of concentrated ambient fine particles (CAP), O3, CAP+O3 and filtered air following a randomized design. Exposures were 2 hrs in duration at rest. Subjects included mild asthmatics and non-asthmatics. This thesis focuses on acute cardiovascular responses including blood pressure (BP), brachial artery reactivity (flow-mediated dilatation [FMD]) and markers of systemic inflammation (blood neutrophils and interleukin [IL]-6). Results showed that for CAP-containing exposures (CAP, CAP+O3) there were small but significant transient increases in diastolic BP (DBP) during exposures. Furthermore, neutrophils and IL-6 increased 1 - 3 hrs after and FMD decreased 20 hrs after CAP-containing exposures. Responses to O3 were smaller, comparable to filtered air. The data suggests that adverse responses were mainly driven by PM. The DBP increase was rapid-developing and quick to dissipate, which points to an autonomic irritant response. The magnitude of the DBP increase was strongly negatively associated with the high frequency component of heart rate variability, suggesting parasympathetic withdrawal as a mechanism. In comparison, IL-6, neutrophil and FMD responses were slower to develop, indicative of an inflammatory mechanism. An intriguing finding was that IL-6 increased 3 hrs after CAP, but not after CAP+O3. Further investigation revealed that exposure to CAP+O3 in some individuals may trigger a reflex inhibition of inspiration, decreasing their tidal volume and inhaled pollutant dose, leading to a reduction in systemic IL-6, a potential protective mechanism. Together the findings support the epidemiological evidence of adverse fine PM health effects. Many questions remain to be answered about the health effects of air pollution including a better understanding of how inhaled pollutants result in cardiovascular effects. It is hoped that the insights gained from this thesis will advance the understanding of air pollution health effects.