Dans les procédés liés aux émulsions, des écoulements turbulents et polyphasiques entrent en jeu. De tels procédés apparaissent dans des domaines variés. Dans l'industrie agro-alimentaire, la production de lait fait intervenir un homogénéisateur à haute pression, et certains produits tels que la mayonnaise sont des émulsions stables. On trouve aussi des émulsions dans le domaine de la santé : elles assurent le bon fonctionnement de nos poumons, tandis que d'autres peuvent être injectées par voie parentérale en tant que médicaments. On les retrouve aussi dans les procédés de séparation, par exemple eau-brut de pétrole dans l'industrie pétrochimique. Dans tous les cas, la fragmentation et la coalescence des bulles et gouttes doivent être maîtrisées, car elles influencent directement la distribution en taille de la phase dispersée. La fréquence d'apparition de ces phénomènes peut être prédite en utilisant des modèles adaptés. Cependant, la présence de molécules tensioactives modifie grandement cette fréquence et par conséquent la distribution en taille en sortie du procédé. Or, ce type de molécules est présent dans quasiment tous les procédés polyphasiques. L'étude des effets des tensioactifs dans ces procédés s'est alors imposée. Dans un des plus récents modèles, les bulles ou gouttes sont considérées comme des oscillateurs forcés par la turbulence de l'écoulement environnant. Il est alors nécessaire de connaître à la fois la turbulence dans le voisinage de la goutte et les propriétés dynamique de la goutte. La première peut être déterminée expérimentalement. La réponse de la goutte au forçage est alors décrite comme une somme d'harmoniques sphériques dont la dynamique est décrite pour chaque mode par une pulsation et un coefficient d'amortissement. Cette thèse aborde l’étude des effets des tensioactifs sur ces deux grandeurs. Elle s’est déroulée en collaboration entre l'IMFT et le LGC, ce qui a permis d'associer les compétences de chaque laboratoire dans les domaines de la physico-chimie, de l'hydrodynamique des phases dispersées et des écoulements turbulents diphasiques. Le projet lors de cette thèse est d'étudier numériquement les effets des tensioactifs sur les échelles temporelles caractéristiques des oscillations, dans le cas où la goutte est immobile ou bien en mouvement dans un fluide externe. Une équation de transport des tensioactifs ainsi que l'effet Marangoni à l'interface ont été modelisés dans le code DIVA, et validés à l'aide de cas tests. Ensuite, des simulations de gouttes subissant des oscillations de forme suivant le mode 2 des harmoniques sphériques ont permis de décrire les effets des tensioactifs sur la dynamique des interfaces. Ils ont été validés par la théorie pour des oscillations linéaires. Le couplage entre le mouvement d'ascension et les oscillations de formes a aussi été étudié, afin de comprendre l'effet d'un fort effet Marangoni, généré par l'ascension de la goutte, sur les oscillations. Les viscosités de surface peuvent aussi influencer radicalement la dynamique interfaciale. Lors de cette thèse, une méthode a été développée et validée pour permettre à l'outil de simulation de prendre en compte des viscosités de surface en se basant sur le modèle de Boussinesq-Scriven. Leur effet sur la dynamique des oscillations de forme a été étudié. / In many industrial processes, such as high-pressure homogenisation or water-oil separation, turbulent and multiphase flows are involved. To optimize those processes, coalescence and fragmentation need to be controlled since they impact directly the size distribution of drops and bubbles. The occurrence of those phenomena can be predicted using adapted models. However, the presence of surfactant molecules at the interface between two fluid phases can change radically the phenomenology of drops break up and coalescence, and their effect has not been properly included in existing models yet. In one of the latest models, drops are considered as forced oscillators driven by the local turbulence of a flow. It is therefore required to know the local turbulence of the flow and the dynamic properties of the drop. It is possible to measure experimentally the local velocities in a flow to determine the local average turbulent Weber number, which represents the forcing term of the oscillator. The dynamic response of the drop is described as a series of oscillators, the principal mode of which is characterized by two time scales, the pulsation and damping coefficient. The goal of this PhD is to study numerically the impact of surfactants on the two time scales mentioned above, whether the drop is still or in motion in the surrounding fluid. An equation of transport of surfactants and the Marangoni effect at the interface have been implemented in the code, and validated. Simulations of a drop undergoing shape oscillations along its eigenmode n = 2 have allowed to study the effects of surfactants on the time scales of oscillations, which were validated with theoretical predictions for linear oscillations. Surface viscosities can also influence the time scales of oscillations. Therefore, a numerical method has been developped and validated to take surface viscosities into account. The stress jump is based on the expression of the Boussinesq-Scriven model. Their effect is studied on the dynamic of oscillations.

Made available in DSpace on 2014-06-11T19:31:37Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-10-09Bitstream added on 2014-06-13T20:22:35Z : No. of bitstreams: 1 moreirajunior_o_dr_botfca.pdf: 1169550 bytes, checksum: c39cff16dc4995bbd4495b150b625901 (MD5) / Este trabalho teve por objetivo a construção de um túnel de vento em escala reduzida e de baixo custo para utilização em estudos de tecnologia de aplicação de agrotóxicos, com posterior validação através da avaliação dos efeitos de diferentes adjuvantes pulverizados por uma ponta na intensidade do processo de deriva. Os ensaios foram conduzidos no Laboratório de Máquinas para Pulverização do Núcleo de Ensaio de Máquinas e Pneus Agroflorestais (NEMPA) da FCA/UNESP - Departamento de Engenharia Rural, localizado no campus da UNESP da cidade de Botucatu. O túnel de vento construído teve como principais características ser de circuito aberto e seção de teste fechada, com o sistema acionador (motor) abastecendo o circuito e agindo como soprador. Logo após o motor foram colocadas duas telas e uma colméia, com a finalidade de uniformizar o fluxo de ar que se desloca para a seção de testes onde são feitas as medidas. O túnel de vento foi confeccionado com chapas de fibras de eucalipto de espessura 3,0 mm e face superior lisa e face inferior corrugada, tendo comprimento total de 4,80 m, uma secção de testes quadrada de 56 cm x 56 cm e área útil de aproximadamente 0,31 m2 e 2,5 m de comprimento. Para o acionamento do túnel utilizou-se um ventilador de 5 velocidades e 180 W de potência. Todo sistema foi dimensionado para fornecer fluxo laminar de ar a uma velocidade de 2,0 m.s-1. Os ensaios de validação foram realizados com uma ponta de pulverização XR8003 (jato plano convencional de uso amplo) a uma pressão de 2 bar, produzindo um espectro de gotas médias, utilizada para aplicação de caldas (soluções em água) contendo o corante Azul Brilhante a 0,6% v/v em 9 mistura ou não com dois adjuvantes. Os primeiro adjuvante é um redutor de deriva a base de polímeros, utilizado na concentração... / The aim of this study was to build a low cost reduced-scale wind tunnel for drift evaluation on pesticide application technology. Validation studies were undertaken by evaluating the effect of different adjuvants on the drift caused by the spray of a single nozzle. The work was carried out at the NEMPA - Núcleo de Ensaio de Máquinas e Pneus Agroflorestais (NEMPA), FCA/UNESP, Departamento de Engenharia Rural, Botucatu/SP, Brazil. The wind tunnel main characteristics were an open circuit and a closed working section with a fan blowing air into the tunnel. Screens were fitted downstream after the fan in order to stabilize the air flow on the working section. The tunnel was built with 3.0 mm eucalyptus hardboard, with a total length of 4.8 m and a squared section of 0.56 m. The working section had 0.31 m2, with a total length of 2,5 m. The air flow was provided by a 180 W axial fan. The system was adjusted and calibrated to provide a laminar and stable flow at 2.0 m s-1. Validation studies were carried out by using a XR 8003 flat fan nozzle at 2 bar (medium droplets) that was used to spray solutions containing water plus a food dye (Blue FDC) at 0,6% v/v mixed with the folowing adjuvants: a polymer based anti drift formulation at 0,06% m/v and a nonylphenol based surfactant at 0,2% v/v. After a 10-second application drift was collected on nylon strips transversally fixed along the tunnel at different distances from the 11 nozzle and different high from the bottom part of the tunnel. Drift deposits were avaluated by spectrophotometry at the NUPAM (Núcleo de Pesquisas Avançadas em Matologia), Departamento de Produção Vegetal/UNESP/FCA, Botucatu,SP, Brazil. The results showed that the tunnel was effective to enable comparative drift measurements on the spray solution used in this work making possible the evaluation of drift risk under... (Complete abstract click electronic access below)

Orientador: Ulisses Rocha Antuniassi / Banca: Wellington P.A. de Carvalho / Banca: Carlos Gilberto Raetano / Banca: Marco Antonio Gandolfo / Banca: Paulo Roberto Arbex Silva / Resumo: Este trabalho teve por objetivo a construção de um túnel de vento em escala reduzida e de baixo custo para utilização em estudos de tecnologia de aplicação de agrotóxicos, com posterior validação através da avaliação dos efeitos de diferentes adjuvantes pulverizados por uma ponta na intensidade do processo de deriva. Os ensaios foram conduzidos no Laboratório de Máquinas para Pulverização do Núcleo de Ensaio de Máquinas e Pneus Agroflorestais (NEMPA) da FCA/UNESP - Departamento de Engenharia Rural, localizado no campus da UNESP da cidade de Botucatu. O túnel de vento construído teve como principais características ser de circuito aberto e seção de teste fechada, com o sistema acionador (motor) abastecendo o circuito e agindo como soprador. Logo após o motor foram colocadas duas telas e uma colméia, com a finalidade de uniformizar o fluxo de ar que se desloca para a seção de testes onde são feitas as medidas. O túnel de vento foi confeccionado com chapas de fibras de eucalipto de espessura 3,0 mm e face superior lisa e face inferior corrugada, tendo comprimento total de 4,80 m, uma secção de testes quadrada de 56 cm x 56 cm e área útil de aproximadamente 0,31 m2 e 2,5 m de comprimento. Para o acionamento do túnel utilizou-se um ventilador de 5 velocidades e 180 W de potência. Todo sistema foi dimensionado para fornecer fluxo laminar de ar a uma velocidade de 2,0 m.s-1. Os ensaios de validação foram realizados com uma ponta de pulverização XR8003 (jato plano convencional de uso amplo) a uma pressão de 2 bar, produzindo um espectro de gotas médias, utilizada para aplicação de caldas (soluções em água) contendo o corante Azul Brilhante a 0,6% v/v em 9 mistura ou não com dois adjuvantes. Os primeiro adjuvante é um redutor de deriva a base de polímeros, utilizado na concentração... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The aim of this study was to build a low cost reduced-scale wind tunnel for drift evaluation on pesticide application technology. Validation studies were undertaken by evaluating the effect of different adjuvants on the drift caused by the spray of a single nozzle. The work was carried out at the NEMPA - Núcleo de Ensaio de Máquinas e Pneus Agroflorestais (NEMPA), FCA/UNESP, Departamento de Engenharia Rural, Botucatu/SP, Brazil. The wind tunnel main characteristics were an open circuit and a closed working section with a fan blowing air into the tunnel. Screens were fitted downstream after the fan in order to stabilize the air flow on the working section. The tunnel was built with 3.0 mm eucalyptus hardboard, with a total length of 4.8 m and a squared section of 0.56 m. The working section had 0.31 m2, with a total length of 2,5 m. The air flow was provided by a 180 W axial fan. The system was adjusted and calibrated to provide a laminar and stable flow at 2.0 m s-1. Validation studies were carried out by using a XR 8003 flat fan nozzle at 2 bar (medium droplets) that was used to spray solutions containing water plus a food dye (Blue FDC) at 0,6% v/v mixed with the folowing adjuvants: a polymer based anti drift formulation at 0,06% m/v and a nonylphenol based surfactant at 0,2% v/v. After a 10-second application drift was collected on nylon strips transversally fixed along the tunnel at different distances from the 11 nozzle and different high from the bottom part of the tunnel. Drift deposits were avaluated by spectrophotometry at the NUPAM (Núcleo de Pesquisas Avançadas em Matologia), Departamento de Produção Vegetal/UNESP/FCA, Botucatu,SP, Brazil. The results showed that the tunnel was effective to enable comparative drift measurements on the spray solution used in this work making possible the evaluation of drift risk under... (Complete abstract click electronic access below) / Doutor

Abstract : This research project has as main objective to study in detail the internal flow features of single-phase supersonic ejectors for refrigeration applications, and the potential effects of injecting droplets on the performance of the device. To this end, a numerical approach is proposed which has been separated into two parts: First, a RANS modelling strategy for supersonic ejectors has been outlined combining the NIST real gas equations database [NIST, 2010] and the k − ω SST turbulence model in its low-Reynolds number formulation. The proposed approach agrees within 5% (resp. 2%) to the experimental entrainment ratio (resp. compression ratio) data of García del Valle et al. [2014], properly captures the main internal flow features and has a reasonable computational cost. This RANS model has been applied in the analysis of a supersonic R134a ejector for refrigeration purposes, showing in particular that the secondary flow is entrained by momentum transfer through the mixing shear layer, that the distance between the primary nozzle exit and the shock-waves in the constant area section varies between 9 and 16 times the primary nozzle exit diameter and that the important axial character of the flow limits mixing of both inlet flows until after the shock train. Furthermore, an exergy analysis through the device shows that the mixing and the oblique shock waves are responsible for between 50% and 70% of the generated losses, the latter might be attenuated through droplet injection in the constant area section. Moreover, it has been shown that drop-in replacement of the working fluid with HFOs R1234yf and R1234ze(E) leads to mild changes in the ejector performance but reduces the HDRC system COP (resp. cooling capacity) in average by 7.1% (resp. 23.3%). Lastly, a comparison of the model predictions with the thermodynamic model of Galanis and Sorin [2016] for an air ejector, shows that as the working fluid approaches the ideal gas behaviour, the flow can be adimensionalized in terms of the secondary inlet temperature and pressure, the motive nozzle throat and the entrainment and compression ratios. In the second part, the influence of droplets has been studied from a local perspective by extending the RANS model to include a discrete phase, which affects the main flow through exchanges of momentum and thermal energy, and from a global perspective by building a thermodynamic model, which predicts the entrainment and limiting compression ratio given a fixed geometry and operating conditions. Both approaches present very good agreement in terms of p, T and M a internal profiles. Results for a supersonic ejector with R134a as baseline working fluid and droplets injected at the constant area section show that the flow structure has perceptible changes only at the highest injection fraction considered 10%, which induces boundary layer detachment, reduces the shock intensity by 8% and diminishes the superheat at the ejector outlet by 15 ◦C. Nonetheless, ejector performance metrics are severely affected as the limiting compression ratio, Elbel efficiency and exergy performance reduce respectively by 5%, 11% and 15%, due mainly to the additional entropy generated through droplet injection and mixing with the main flow. / Ce projet de recherche a pour objectif principal d’étudier en détail les caractéristiques de l’écoulement interne dans des éjecteurs supersoniques monophasiques pour des applications en réfrigération, et les effets potentiels de l’injection de gouttelettes sur les performances de l’appareil. A cette fin, une approche numérique est proposée et a été séparée en deux parties. Tout d’abord, une stratégie de modélisation RANS pour les éjecteurs supersoniques a été décrite en combinant la base de données pour les gaz réels NIST [NIST, 2010] et le modèle de turbulence k − ω SST dans sa formulation à bas nombre de Reynolds. L’approche proposée prédit avec un accord d’environ 5% (resp. 2%) le rapport d’entraînement (resp. rapport de compression) avec les données expérimentales de García del Valle et al. [2014]. Il capte également correctement les principales caractéristiques de l’écoulement interne et a un coût de calcul raisonnable. Ce modèle RANS a été appliqué à l’analyse d’un éjecteur supersonique au R134a utilisé à des fins de réfrigération, montrant en particulier que le flux secondaire est entraîné par un transfert d’impulsion à travers la couche de cisaillement, que la position de départ des ondes de choc dans la section constante se situe dans une plage de 9 à 16 fois le diamètre de sortie de la buse primaire et que l’important caractère axial du flux limite le mélange des deux écoulements d’entrée au-delà du train d’ondes de choc. De plus, une analyse exergétique à travers le dispositif montre que le mélange et les ondes de choc obliques sont responsables de 50% et 70% des pertes générées, ces dernières pouvant être atténuées par injection de gouttelettes dans la section à zone constante. De plus, il a été démontré que le remplacement direct du fluide de travail par les HFO R1234yf et R1234ze(E) entraîne de légers changements dans la performance de l’éjecteur mais réduit en moyenne le COP du système HDRC (resp. la capacité de refroidissement) de 7.1% (resp. 23.3%). Enfin, une comparaison des prédictions du modèle avec le modèle thermodynamique de Galanis and Sorin [2016] pour un éjecteur à air montre que lorsque le fluide de travail se rapproche du comportement de gaz idéal, l’écoulement peut être normalisé en fonction de la température et de la pression à l’entrée secondaire, la gorge de la tuyère principale et les rapports d’entraînement et de compression. Dans la seconde partie, l’influence des gouttelettes a été étudiée d’un point de vue local en étendant le modèle RANS à une phase discrète qui affecte le flux principal par des échanges de quantité de mouvement et d’énergie thermique, et d’un point de vue global en construisant un modèle thermodynamique qui prédit l’entraînement et le rapport de compression limitant étant donné une géométrie fixe et les conditions de fonctionnement. Les deux approches présentent un très bon accord en termes de profils internes de p, T et Ma. Les résultats pour un éjecteur supersonique au R134a comme fluide de base, avec des gouttelettes injectées à mi-chemin dans la section de la zone constante, montrent que la structure d’écoulement dans cette région présente des changements perceptibles seulement à la fraction d’injection la plus élevée, 10%, en diminuant l’intensité du choc de 8% et la surchauffe à la sortie de l’éjecteur de 15 ◦C. Néanmoins, la performance de l’éjecteur est sévèrement affectée vu que le rapport de compression, l’efficacité d’Elbel et le performance exergétique sont réduites respectivement de 5%, 11% et 15%, principalement en raison de l’entropie supplémentaire générée par l’injection de gouttelettes et le mélange avec le flux principal.

The main aim of this project is to model the effects of varied injection parameters on the gas dynamics and droplet dynamics of the HVSFS and SP- HVOFS processes for improving the droplet breakup and evaporation to enhance the nanoparticles heating and deposition efficiency. Thermal spraying processes are widely used to generate thermal-, corrosion-, and wear-resistant layers over the machine parts, to increase the durability of the equipment under severe environmental conditions. The liquid feedstock is used to achieve nanostructured coatings. It is used either in the form of a suspension or a solution precursor. The suspension is a mixture of solid nanoparticles suspended in a liquid medium consisting, for instance, of water, ethanol, or isopropanol. This dispersion mechanism in a liquid carrier provides adequate flowability to the nanoparticles, which cannot be handled by conventional gas- based feeding systems, whereas the solution precursor is mixed at the molecular level; hence, more uniform phase composition and properties are expected in the sprayed coatings as compared to the suspension and conventional powder spraying. Firstly, experiments are conducted to analyse the effects of different precursor concentrations, solvent types and injection nozzles on the size and morphology of synthesized nanoparticles. The results indicate that the particle size increased with increasing precursor concentration due to the variations in the physical properties of the mixture solution. The higher precursor concentrations had an adverse effect on the droplet atomization and evaporation process that led to bigger size particle formation. The use of aqueous solvent has some limits and with higher precursor concentration the surface tension increases that resulted in the reduction of droplets’ disintegration, and thus bigger size precursor droplets generate larger nanoparticles. A mixture of aqueous-organic solvents and pure organic precursors are preferred to improve the process efficiency of the nanoparticles size and morphology. Furthermore, the nanoparticles size can be controlled by using liquid feedstock atomization before injecting into the HVOF torch. A new effervescent injection nozzle is designed and compared to different types of existing injection nozzles, to see the variations in the droplet disintegration, and its effects on the performance of the HVOF torch processes. It is detected that the atomization would result in smaller size particles with homogeneous morphology. In a numerical study, different droplet injection types are analysed to see their effects on the gas and droplet dynamics inside the HVOF torch. The group-type injection (GTI) and effervescent-type atomization (ETI) are used effectively to overcome the heat losses and delays in the droplet evaporation. These approaches reduce the thermal and kinetic energy losses in the suspension-fed-HVOF torch, thereby improving the coating formation. The effects of using multicomponent water-ethanol mixture injection in the HVOF torch are also modelled, and its impact on the droplet breakup and evaporation are studied. The organic solvents have a low heat of vaporization and surface tension, and can effectively be used in the HVOF spraying process over the water-based solvents. Furthermore, nanoparticles are suspended in the liquid feedstock and injected into the HVOF torch. The effect of increasing nanoparticles’ concentration in the feedstock and its consequence on the gas dynamics, droplet breakup and evaporation are analysed. The augmentation in the nanoparticles loading in the suspension droplets can decrease the droplet breakup and evaporation rate because the required heat of vaporization increases significantly. Moreover, the size of injection droplet affects the droplet fragmentation process; bigger sized droplets observed a delay in their evaporation that resulted in coating porosity. The results suggest that smaller droplet sizes are preferred in coating applications involving a higher concentration of nanoparticles with high melting point. Further, the gas flow rates (GFRs) are regulated to control the droplet dispersion, atomization and evaporation inside the solution precursor fed-HVOF torch. The size of the droplet diameter is decreased by an increment in the GFR, as higher combustion rates increase the combustion flame enthalpy and kinetic energy. Moreover, the increase in the oxygen/fuel flow rates dilutes the injected precursor. It reduces ZrO2 concentration in the process and decreases the rate of particle collision; as a result, non-agglomerated nanoparticles can be obtained.

Les rhabdomyolyses correspondent à la destruction de fibres musculaires striées squelettiques et mettent en jeu le pronostic vital. La principale cause génétique est liée à un défaut d’oxydation des acides gras ; néanmoins, plus de la moitié des cas n’ont pas de cause identifiée. En 2008, des mutations du gène LPIN1 ont été rapportées comme une nouvelle étiologie de rhabdomyolyse de transmission autosomique récessive. La protéine lipin1 a une double fonction : un rôle de PAP1 intervenant dans la synthèse du triacylglycérol et des phospholipides membranaires ; un rôle de co-activateur transcriptionnel en association avec les PPARs et PGC1α pour réguler de nombreux gènes impliqués dans le métabolisme, dont certains de l’OAG. Lipin1 a deux homologues, lipin2 et lipin3, qui possèdent une activité PAP1 et un site de fixation à des récepteurs nucléaires tels que les PPARs. Nous avons montré que les mutations de LPIN1 rendent compte de plus de 50% des cas de rhabdomyolyse sévère de la petite enfance, une fois écarté le diagnostic de déficit de l’OAG. Une délétion intragénique en phase a été fréquemment identifiée chez les Caucasiens. Nous avons montré qu’il s’agissait d’un probable effet fondateur et que cette délétion est délétère. En effet, à l’inverse de la forme normale de lipin1, la forme délétée est incapable de complémenter la levure pah1, déficiente pour l’homologue de LPIN1. Nous avons ensuite étudié, dans une série de 171 patients, l’implication de LPIN1 dans des pathologies musculaires moins sévères, ainsi que le rôle des deux homologues LPIN2 et LPIN3. Les mutations de LPIN1 sont impliquées dans les rhabdomyolyses sévères et précoces uniquement et les accès de rhabdomyolyse ont toujours un facteur déclenchant, le principal étant les infections aiguës fébriles. Aucune altération majeure de LPIN2 et de LPIN3 n’a été identifiée, même dans des phénotypes modérés. Enfin, nous avons cultivé des myoblastes et des myotubes de patients avec mutations de LPIN1 afin d’étudier les mécanismes de rhabdomyolyse. Les myoblastes déficients en lipin1 ont une activité PAP1 très diminuée et une accumulation de gouttelettes lipidiques. Le niveau d’expression des gènes cibles des facteurs de transcription co-activés par lipin1 (PPARδ, PPARα, PGC1α, ACADVL, CPT1B and CPT2) sont inchangés par rapport aux contrôles, alors que le niveau de lipin2 est augmenté. L’analyse transcriptomique sur cultures de myotubes a identifié chez les patients 19 gènes sous-exprimés et 51 sur-exprimés, notamment ACACB, qui code pour Accβ, enzyme clé de la balance synthèse d’acides gras/OAG. L’invalidation d’ACACB par siRNA dans des myoblastes déficients en lipin1 diminue le nombre de gouttelettes lipidiques, confirmant le lien entre la sur-expression d’ACACB et l’accumulation d’acides gras libres chez les patients. Cependant, le taux de malonyl-CoA, produit d’Accβ, et l’activité CPT1 (étape limitatrice de l’OAG, inhibée par le malonyl-CoA), sont comparables entre myoblastes de patients et de contrôles. Néanmoins, le traitement des cultures par l’association de tumor necrosis factor alpha et d’interleukine-1 β, choisis pour simuler les conditions pro-inflammatoires des infections aiguës, entraîne une augmentation encore plus poussée du taux de malonyl-CoA, une diminution de l’activité CPT1 et une augmentation de l’accumulation de gouttelettes lipidiques chez les patients. Au total, nos données placent LPIN1 comme une cause importante de rhabdomyolyse héréditaire. Le déficit en lipin1 entraine une perturbation du métabolisme lipidique, via une sur-expression d’ACACB, qui est exacerbée en conditions pro-inflammatoires. Nos résultats suggèrent que les conséquences du déficit en lipin1 sont compensées par des mécanismes d'adaptation suffisants en condition normale, mais insuffisants pour la demande métabolique induite par des stress environnementaux comme l'infection, conduisant aux rhabdomyolyses. / Rhabdomyolyses correspond to the destruction of skeletal muscular fibers and are possibly life-threatening. The main genetic cause is linked to defects of fatty acid oxidation (FAO) ; nevertheless, half of the cases have no identified aetiology. In 2008, mutations of LPIN1 gene have been reported as a new cause of autosomal recessive rhabdomyolysis. Lipin1 protein has a double function : 1) a role of phosphatidate phosphatase 1 (PAP1) involved in synthesis of triacylglycerol and membrane phospholipids ; 2) a role of transcriptional co-activator which regulates, in association with the PPARs (peroxysome-proliferator activated receptor) and PGC1α (PPARγ-coactivator1α), numerous genes involved in the metabolism including some genes encoding FAO enzymes. Lipin1 has got two homologues, lipin2 and lipin3, which have a PAP1 activity and a binding site for nuclear receptors, such as the PPARs. We have shown that LPIN1 mutations account for more than 50% of the cases of severe rhabdomyolysis of early infancy, when FAO defects have been excluded. An intragenic in frame deletion has been frequently identified in Caucasians. We have shown that it probably comes from a founding effect and that this deletion is deleterious. Unlike normal lipin1, deleted lipin1 protein is unable to complement the Δpah1 yeast which is defective for the yeast LPIN1 homolog. In a series of 171 patients, we have further studied the involvement LPIN1 in less severe muscular diseases, as well as the role of the two homologues LPIN2 and LPIN3. LPIN1 mutations are involved only in severe and early rhabdomyolyses and the bouts of rhabdomyolysis always have a triggerring factor, mainly acute febrile infections. No major alteration of LPIN2 and LPIN3 has been identified, even in milder phenotypes. Eventually, we have cultivated myoblasts and myotubes of patients with LPIN1 mutations in order to study the mechanisms of the rhabdomyolysis. Lipin1-deficient myoblasts have a drastically decreased PAP1 activity and an accumulation of lipid droplets. The expression level of target genes of the transcription factors co-activated by lipin1 (PPARδ, PPARα, PGC1α, acyl-Coenzyme A very long chain dehydrogenase (ACADVL), carnitine palmitoyl-transferase 1B and 2 (CPT1B and CPT2)) are similar to controls, whereas the level of lipin2 is increased. Transcriptomic analysis of myotube cultures have identified in patients 19 under-expressed genes and 51 over-expressed ones, notably ACACB, which encodes Accβ (acetyl-CoA carboxylase β), key enzyme of the balance between fatty acid synthesis and FAO. ACACB invalidation by siRNA in lipin1-deficient myoblasts decreases the number of lipid droplets, comforting the link between ACACB over-expression and free fatty acid accumulation in patients. However, the level of malonyl-CoA, product of Accβ, and CPT1 activity (limitative step of FAO, inhibited by malonyl-CoA), are similar between myoblasts of patients and controls. But treatment of the cultures with an association of tumor necrosis factor α and interleukin-1 β (TNFα + IL-1β), chosen for mimicking pro-inflammatory conditions of acute infections, leads to a further increase of the level of malonyl-CoA, a decrease of CPT1 activity and an increase of lipid droplets accumulation in patients. In total, our data show that LPIN1 is an important cause of inherited rhabdomyolysis. Lipin1 deficiency leads to a disturbance of the lipidic metabolism, via ACACB over-expression, which is exacerbated in pro-inflammatory conditions. Our results suggest that the consequences of lipin1 deficiency are counterbalanced by adaptative mechanisms which are sufficient at basal state, but insufficient for the metabolic request induced by environmental stresses, such as infections, leading to the rhabdomyolyses. Next step is the study of adipose tissue and the establishment of the inflammatory signature of the patients, in order to determine if this new disease is an auto-inflammatory pathology.

Dans cette thèse expérimentale, on s'intéresse aux collisions de gouttes mettant en jeu des interfaces asymétriques, soit deux gouttes constituées de liquide différent ou des gouttes de taille différente et recouvertes (ou non) d'une couche de particules hydrophobes. Dans une première partie, on étudie les collisions de gouttes de liquide immiscible. L´asymétrie de tels systèmes repose alors sur le contraste des propriétés des deux liquides : la tension de surface, la viscosité et la densité. Le résultat de ces collisions est une encapsulation totale d'un liquide par un autre ou une encapsulation suivie d'une fragmentation. On s´attache à décrire les régimes observés et à établir des lois permettant de prédire les limites de fragmentation de l'objet obtenu. La seconde partie est consacrée aux interfaces couvertes de particules hydrophobes. Pour ces systèmes, l'asymétrie réside à la fois dans la présence des particules sur une interface et pas sur l'autre et dans le contraste de taille entre les objets étudiés. Ainsi, on considère l'impact entre une petite goutte (recouverte ou non de particules) et une très grosse goutte (recouverte ou non de particules). On caractérise tout d'abord les propriétés mécaniques de ces interfaces via la propagation d'ondes de surface, notamment en terme de tension de surface effective et de module de courbure. Puis, on sonde, dans différentes situations d´impact, la robustesse de ces objets afin d'évaluer la capacité de ces couches particulaires à prévenir la coalescence / In this experimental thesis, we are interested in droplets collisions involving asymmetric interfaces. We consider either two droplets made of different liquids or droplets of different sizes, coated (or not) by a monolayer of hydrophobic particles.In a first part, collisions of droplets made of immiscible liquids are studied. The asymmetry of such systems relies on the contrast of the two liquids properties : surface tension, viscosity and density. The outcome of those collisions is a full encapsulation of one liquid by the other one which can be followed by a fragmentation. We pay attention to describe the observed regimes and to establish a scaling law to predict the fragmentation limits of the resulting object. The second part is dedicated to interfaces covered by hydrophobic particles. For those systems, the asymmetry is due to both the interaction of a covered interface with a non covered one and to the size contrast between the objects studied. Studying the propagation of capillary waves, we first characterize the mechanical properties of such interfaces : effective surface tension and modulus of curvature. Further on, we probe, using different impacts configurations, the robustness of those covered objects with the aim of estimating the ability of the particles monolayer to prevent coalescence

The lack of significant buoyancy effects in zero-gravity conditions poses an issue with fluid transfer in a stagnant liquid. In this thesis, the movement of a bubble or droplet in both stagnant and rotating liquids is analysed and presented numerically using computational fluid dynamics (CFD). The governing continuum conservation equations for two-phase flow are solved using the commercial software package (2011). The Volume of Fluid (VOF) method is used to track the liquid/gas interface in 2D and 3D domains. User-Defined Functions (UDFs) are employed in order to include the effect of surface tension gradient and fluid properties as a function of temperature, with a view to efficiently investigating temperature effects on the properties of the two phases. The flow is driven via Marangoni influence induced by the surface tension gradient, which in turn drives the bubble/droplet from the cold to the hot region. For stationary liquid, the results indicate that the scaled velocity of the bubble decreases with an increase in the Marangoni number, which agrees with the results of previous space experiments. An expression for predicting the scaled velocity of a bubble has been regressed based on the obtained data from the present numerical study for thermal Marangoni numbers up to 10,721. An expression for predicting the scaled velocity of a Fluorinert droplet migrating in oil has also been presented for an MaT range from 24.05 to 2771. The interactions of two droplets in thermocapillary motion have also been studied and compared with the results obtained for the isolated droplet. The results have shown that the leading droplet will not move faster than if it were isolated, as the trailing droplet has no influence on the velocity of the leading droplet. Three-dimensional results show that no bubbles broke in any of the cases observed and agglomeration could occur during thermocapillary migration for bubbles placed side by side. The results of the motion of a singular and multiple bubbles incorporating thermocapillary forces in a rotating liquid in a zero-gravity environment have been presented for the first time. When the Rossby number is 1, the effects of rotation are important. Furthermore, the deflection of the gas bubble motion increases towards the axis of rotation with a decrease in the Rossby number (Ro). Bubble population balance modelling has been investigated in normal gravity using Luo kernels for breakage and agglomeration and two different laminar kernels for zero-gravity conditions. The simulations covered a wide range of scenarios and results are presented as a bell and histogram shapes for number density and particle percentage distribution, respectively.

Although the cost of investment in power lines insulators is 3-5% of the total cost of the installation, the impact of their performance on reliability, failure costs, maintenance routines, etc in power systems is tens of times higher. Composite insulators were introduced 50 years ago and have been used around the world with consistently good experience. Low weight, easy handling, good performance under high pollution, low maintenance costs, and resistance to vandalism are some of their advantages. Nevertheless, acid rain, salty dust deposition, corona discharges, ozone, UV radiation, and humidity among other factors, deteriorate the quality of the polymeric housing reducing their hydrophobicity. The synergistic action of ageing factors is extremely complex and the whole degradation process may change when any one variable is slightly modified. Many studies have been carried out to increase understanding of the physicochemical processes which control the electrical and mechanical stability of polymers during in-service ageing with the objective of predicting remaining life-times. Vital areas of knowledge about polymer insulators are still incomplete and lacking; three of them are: (1) early stages of degradation in service under different environmental conditions, (2) monitoring and diagnosis techniques suitable for distribution installations and (3) steps to establish an insulators management plan based on condition and risk of failure. In this research these three topics are covered. A full review of literature about management of electrical distribution assets is included, followed by a specific plan developed for monitoring, diagnosis and ranking of insulators mainly supported by visual inspections. Diagnosis of medium voltages EPDM insulators recovered from service aged under different conditions is done using both traditional techniques and, uniquely, dielectric impedance. The relationship between surface roughness and static contact angle is also used to characterize insulators' surfaces. Early stages of degradation are studied focusing the experimental work to evaluate the electrohydrodynamic processes which occur on new samples under different conditions, giving special attention to leakage current pulse analysis, electric field enhancement, and resistance/capacitive behaviour including phase of leakage current. Results from each specific topic offer additional understanding of polymer insulators degradation providing insight to monitoring, diagnosis and management. Additionally, results open new topics in which new investigations are proposed.

Les résultats fondamentaux et biocliniques que nous présentons au travers de cette thèse illustrent la difficulté d’évaluer la part liée au virus et celle liée à des facteurs de l’hôte dans l’induction d’une stéatose hépatique chez les patients chroniquement infectés par le HCV. Les données in vitro suggèrent que le virus joue un rôle direct dans l’induction d’une stéatose, notamment par les propriétés de sa protéine de capside, et que la variabilité du virus peut avoir un impact sur l’intensité de cette stéatose. Notre étude bioclinique suggère que la variabilité du virus semble avoir un rôle beaucoup plus modéré in vivo. Ainsi, chez les patients chroniquement infectés par le HCV, les facteurs de l’hôte joueraient un rôle majeur pour moduler le degré de la stéatose associée au virus et de prochaines études seront nécessaires pour établir la nature de ces facteurs. / The results presented in this thesis illustrate the difficulty of assessing the part related to the virus and that related to host factors in the induction of hepatic steatosis in patients chronically infected with HCV. In vitro data suggest that the virus plays a direct role in the induction of steatosis, due to the properties of its capsid protein, and that the variability of the virus can affect the intensity of the steatosis. Our bio-clinical study suggests that this variability seems to have a much more moderate impact in vivo. Thus, in patients chronically infected with HCV, host factors seem to play a major role to modulate the degree of steatosis associated with the virus. Further studies are needed to establish the nature of these factors.