Prolonged exposure to microgravity is known to invoke physiological changes which predispose individuals to orthostatic intolerance upon readaptation to the earth's gravitational field. Attenuated baroreflex responsiveness has been implicated in contributing to this inability to withstand orthostatic stress. To test this hypothesis, eight individuals were exposed to 15 days of simulated microgravity exposure using the 6° head-down bed rest model. Prior to, and after the simulated microgravity exposure, the following were assessed: a) aortic baroreflex function; b) carotid baroreflex function; c) cardiopulmonary baroreflex function; and d) the degree of interaction between the cardiopulmonary and carotid baroreflexes.

Gravity on Earth limits the study of the properties of pure fluids near critical point because they become stratified under their own weight. Near the critical point, all thermodynamic properties either diverge or converge and the heating and cooling cause instabilities of the convective flow as a consequence of the expansibility divergence. In order to study boiling, fluctuation and phase separation processes near the critical point of pure fluids without the influence of the Earth's gravity, a number of experiments were performed in the weightlessness of Mir space station. The experimental setup called ALICE II instrument was designed to suppress sedimentation and buoyancy-driven flow. Another set of experiments were carried out on Earth using a carefully density matched system of deuterated methanolcycloxexane to observe critical fluctuations directly. The set of experiments performed on board of Mir space station studied boiling and wetting film dynamics during evaporation near the critical point of two pure fluids (sulfur hexafluoride and carbon dioxide) using a defocused grid method. The specially designed cell containing the pure fluid was heated and, as a result, a low contrast line appeared on the wetting film that corresponded to a sharp change in the thickness of the film. A large mechanical response was observed in response to the cell heating and we present quantitative results about the receding contact lines. It is found that the vapor recoil force is responsible for the receding contact line. Local density fluctuations were observed by illuminating a cylindrical cell filled with the pure fluid near its liquid- gas critical point and recorded using a microscope and a video recorder. Microscopic fluctuations were analyzed both in sulfur hexafluoride and in a binary mixture of methanol cyclohexane. Using image processing techniques, we were able to estimate the properties of the fluid from the recorded images showing fluctuations of the transmitted and scattered light. We found that the histogram of an image can be fitted to a Gaussian relationship and by determining its width we were able to estimate the position of the critical point. The characteristic length of the fluctuations corresponding to the maximum of the radial average of the power spectrum was also estimated. The power law growth for the early stage of the phase separation was determined for two different temperature quenches in pure fluid and these results are in agreement with other experimental results and computational simulations.

Ces travaux de thèse s'inscrivent à la frontière entre l'utilisation de l'interférométrie atomique pour tester un principe fondamental de physique, le principe d'équivalence faible, et le transfert des technologies développées dans ce but vers des applications industrielles, en particulier la navigation inertielle, à travers une collaboration avec l'entreprise iXBlue au sein d'un laboratoire commun (iXAtom) où nous avons travaillé à l'hybridation d'une centrale inertielle avec un accéléromètre atomique afin de corriger la dérive temporelle de la centrale.Afin de tester le prince d'équivalence faible, nous utilisons un interféromètre atomique double espèce (87Rb et 39K). Cette expérience est réalisée en laboratoire mais également en micropesanteur à bord de l'avion ZERO-G de Novespace. Cette particularité pose des contraintes sur les choix technologiques puisque le montage doit être robuste, compact et transportable. Notre système laser en est un bon exemple puisqu'il est basé des technologies télécom (1560 et 1534 nm) doublées en fréquence. Nous avons réalisé le premier test du principe d'équivalence en micropesanteur avec des atomes froids en 2015, ce qui représente une étape majeure vers la réalisation d'un instrument embarquable à bord d'un satellite.Le 39K est une espèce difficile à refroidir et à manipuler à cause de sa structure hyperfine étroite. Nous avons mis en place un refroidissement par mélasse grise pour cette espèce en ajoutant un laser résonnant avec la transition D1 du potassium. Nous avons également mis en place une préparation des atomes dans l'état non magnétique mF=0 efficace à 95%. Ces techniques ont amélioré le contraste de nos franges d'interférences d'un facteur 4 et nous a permis d'obtenir une sensibilité sur le paramètre d’Eötvös en laboratoire de 5.2x10-8 après 11500 s d'intégration. / This thesis is at the boundary of the fundamental physics with the test of the weak equivalence principle (WEP) and the transfer of the technologies developed to industrial applications such inertial navigation. We began collaboration in a joint laboratory (iXAtom) with the iXBlue company where we worked on the hybridization of an inertial unit with a cold atom accelerometer.In order to test the WEP, we use a dual-species atom interferometer (87Rb and 39K). This experiment works in the laboratory but it is designed to perform onboard the Novespace ZERO-G plane. This specificity puts constraints on the design of the setup because it needs to be robust, compact and transportable. Our laser system is a good example because it is based on Telecom technologies (1560 and 1534 nm) frequency doubled. We realized the first test of the weak equivalence principle on microgravity with cold atoms in 2015, which is a major step toward a future spatial mission.The 39K is an atomic species hard to cool and manipulate because of its narrow hyperfine structure. We implemented an other cooling method, the gray molasses, by using a laser resonant to the potassium D1 transition. We built a new sequence to prepare the atoms in the mF= 0 state. This sequence is effective at 95%. These techniques improved the contrast of our interference fringes by a factor 4 which led to the obtention of a sensitivity on the Eötvös parameter in the laboratory of 5.2x10-8 after 11500 s of integration.

Les mousses liquides sont très utilisées dans l'industrie comme dans la vie quotidienne. Cependant, leur stabilité n'est ni complètement comprise ni complètement maîtrisée, la formulation étant essentiellement empirique. Il est donc difficile d'une part de prédire la capacité d'une solution de tensioactifs à générer des mousses et d'autre part de prédire et de contrôler leur déstabilisation. Ce travail de thèse propose des expériences conceptuellement simples qui s'appuient sur le caractère multi-échelle des mousses pour tenter d'établir des liens clairs entre physico-chimie et mécanismes de déstabilisation. Dans un premier temps, nous avons revisité une expérience d'entraînement de films liquides sur un cadre pour illustrer la stabilité des films lors de la génération des mousses ou pendant un réarrangement (processus T1). Nous avons mis en lumière l’existence de deux régimes. Un régime dit non confiné, pour lequel la stabilité des films et réduite et dépend de la physico-chimie. Un régime dit confiné pour lequel le rôle de la physico-chimie est limité et la stabilité est majoritairement contrôlée par l’hydrodynamique.Dans un second temps nous nous sommes intéressés à l'influence de la physico-chimie et de la fraction liquide sur la compétition entre coalescence et mûrissement grâce à l'étude d'une unique couche de bulles (mousse 2D). Nous proposons une méthode de mesure in situ de la perméabilité des films par l'étude simple et rapide du régime transitoire du mûrissement de mousses 2D. Nous avons observé une corrélation entre coefficient de diffusion du gaz contenu dans les bulles et perméabilité.Enfin nous décrivons les résultats d’une expérience spatiale sur le vieillissement à temps long des mousses humides (fraction liquide supérieure à 30% en volume), extrêmement difficile sur Terre à cause du drainage gravitaire, et à laquelle nous avons participé. / Liquid foams are widely used in industry and in everyday life. However, their stability is not fully understood or fully controlled, their formulation being essentially empirical. It is therefore difficult to predict the ability of a surfactant solution to generate foam and to control their destabilization. This thesis proposes simple experiments that rely on the multi-scale nature of foams in order to attempt to establish clear links between physical chemistry and stability.First of all, we revisited an experiment of liquid films entrainment to illustrate the stability of foam films during generation or rearrangement (T1 process). We have shown the existence of two regimes: (i) a unconfined regime, for which the stability of films is reduced and depends on physical chemistry and (ii) a confined regime for which the role of physical chemistry stability is limited and is mainly controlled by hydrodynamics.Secondly, we investigated the influence of physical chemical and liquid fraction on the competition between coalescence and coarsening thanks to the study of a single layer of bubbles (2D foam). We propose a method for in situ measurement of the permeability of films by simple and fast study of the transient regime of coarsening in 2D foam. We observed a correlation between diffusion coefficient of gas and permeability.Finally we describe the results of a space experiment on wet foam aging at large times (volume liquid fraction higher than 30%), extremely difficult on Earth because of gravity drainage, and to which we participated.

A manutenção do metabolismo mineral normal dos ossos é um resultado de vários fatores inclusive as solicitações mecânicas que são aplicadas aos ossos pelas contrações musculares e força da gravidade. O propósito desta investigação foi estudar um modelo de suspensão de rato pela cauda que simulasse assim as alterações esqueléticas que podem acontecer em um ambiente de microgravidade. O modelo foi analisado em termos de tolerância do animal e os efeitos sobre a resistência mecânica do complexo tíbia-fíbula. Após a realização do ensaio de flexão em três pontos foram obtidos os principais parâmetros mecânicos (carga e deflexão no limite máximo, carga e deflexão no limite elástico, rigidez e resiliência). Foram utilizadas cinqüenta e três ratas fêmeas, distribuídas em quatro grupos conforme o período de suspensão (controle, 7, 14 e 21 dias). O modelo de suspensão mostrou-se eficaz com boa adaptação dos animais e promoveu um enfraquecimento significativo nos ossos principalmente no período de 21 dias / The maintenance of the normal metabolism of minerals in bone is a result of several factors including the mechanical demands that are applied to the bones by the muscle contractions and gravity force. The purpose of this investigation was to study a model of tail suspension of the rat thus simulating the skeletal alterations that may occur in a microgravity environment. The model was analyzed in terms of animal tolerance and the ensuing effects on the mechanical resistance of the tibiofibular complex. After a three-point bending test in flexion the main mechanical parameters were obtained, (load and deflection at the ultimate limit, load and deflection at the yielding point, stiffness and resilience). Fifty-three adult female rats were used and distributed in four groups according to the length of time in suspension (control, 7, 14 and 21 days). The model of suspension was efficient with well adaptation of the animals and caused a significative weakness of bones mainly in the 21 day period

The concurrent spreading of a boundary layer type diffusion flame is studied. The impossibility of obtaining a low velocity laminar flow without any perturbation induced by buoyancy has lead to the development of an experimental apparatus for use in micro-gravity facilities. Based on previous experimental observations, an original numerical approach has been developed showing, first the dominating role of the radiative heat transfer on the structure of the flame and second the major role of the soot on the extinction phenomenon at the flame trailing edge. The influence of the forced flow velocity, the fuel injection velocity and oxygen concentration on the geometry of the flame has been examined by imaging of CH* and OH* radicals spontaneous emission. Laser-Induced Incandescence (LII) is used to determine the soot field concentration in the flame. The soot formation has been studied by Laser Induced Fluorescence (LIF) of Polycyclic Aromatic Hydrocarbons (PAHs). The interaction between the reaction zone and the field of soot formation/oxidation is taken into account to analyze the flame length. These results can be used as the experimental input data for a future complete validation of numerical model simulating the soot formation and oxidation in this kind of flame.

Le ballottement dans les réservoirs d'ergols est une des perturbations les plus importantes de la stabilité d'un satellite en orbite. En considérant des manœuvres faiblement inertielles, il n'existe pas de modèle analytique et l'expérimentation nécessite de longues périodes de temps en micro-gravité. Nous nous proposons donc, dans cette thèse, de réaliser des simulations numériques de ce phénomène. L'étude est basée sur le solveur DIVA résolvant les équations de Navier-Stokes diphasiques avec les méthodes level-set et Ghost Fluid. Deux technologies de réservoirs sont à l'étude : les réservoirs classiques, ne contenant que l'ergol liquide et le gaz pressurisant, et les réservoirs à membrane, pour lesquels une membrane hyperélastique sépare les deux fluides. Dans le premier cas, une étude paramétrique complète sur les effets du ballottement lors d'une manœuvre de rotation est menée et les différents régimes d'écoulement obtenus sont décrits par rapport aux paramètres d'études. Par la suite, les données de l'expérience FLUIDICS, envoyée à bord de la Station Spatiale Internationale, sont comparées aux résultats numériques et montrent un très bon accord. Par rapport au second cas, un modèle d'interaction fluides-membrane est développé en s'inspirant de travaux sur la déformation de cellules biologiques. Les déformations et contraintes propres à la membrane sont suivies de façon Eulérienne, les efforts exercés par la membrane sur les fluides environnants en sont déduits et intégrés au solveur diphasique. Les résultats obtenus sont validés par comparaison à des cas-tests de la littérature. / Propellant sloshing in tanks is one of the most important disturbances of satellite stability in orbit. Considering low-inertial manoeuvres, there is no analytical model and experimental facilities require long time period of microgravity conditions. Thus, this PhD thesis aims to predict this phenomenon by numerical simulations. The study is based on the DIVA code which solves the Navier-Stokes equations for two-phase flows with the level-set method and the Ghost Fluid method. Two tank technologies are studied: simple tanks, which only contain the liquid propellant and the gas maintaining the pressure, and diaphragm tanks, for which a hyperelastic membrane separates both fluids. In the first case, a parametric study on the sloshing effects is done considering rotational manoeuvres and the different behaviours observed are described in relation to the study parameters. Thereafter, the data from the FLUIDICS experiment, sent to the International Space Station, are compared to the numerical results and exhibit good agreement. In the second case, a fluids-membrane interaction model inspired from works on the deformation of biological cells is developed. The membrane strains and stresses are computed in an Eulerian way, from which the force exerted by the membrane on the surrounding fluids is deduced and integrated in the two-phase flows solver. The numerical results are validated by comparison with benchmarks from the literature.

Introdução: Parada Cardiorrespiratória (PCR) é uma emergência médica, quando ocorrer fora do ambiente hospitalar, o imediato atendimento à vítima é vital. A imediata Reanimação Cardiopulmonar (RCP), no ambiente extra-hospitalar é muito importante. A denominação aeroespacial reúne ambiente aéreo (cabine de aeronaves pressurizadas, altitude) e, espacial (ambiente com microgravidade, flutuação). No ambiente aéreo, importa a condição hipobárica e a hipóxia resultante. Quanto ao ambiente espacial, importa a condição de microgravidade e a incapacidade de exercer força e peso, como na superfície terrestre. Estes, e outros aspectos da RCP aeroespacial, são abordados no presente estudo. Objetivos: Ambiente aéreo: avaliar a qualidade do ar expirado, por um socorrista, durante RCP, em ambiente hipobárico, e, avaliar a suplementação de oxigênio para o socorrista, como forma de correção da mistura gasosa expirada, na altitude. Ambiente espacial: avaliar a eficácia de uma nova posição para RCP, por um só indivíduo, sem auxílio, na microgravidade. Materiais e Métodos: Utilizou-se uma câmara hipobárica, para a simulação da altitude, no ambiente aéreo. A RCP foi avaliada ao nível do mar e na altitude de 8.000 pés. Vôos parabólicos foram utilizados para a simulação de microgravidade. Um manequim foi o modelo de PCR em ambos os ambientes. No ambiente aéreo, avaliou-se a oferta de oxigênio expirada (boca-a-boca), pelo socorrista à vítima. Em microgravidade foi avaliada a efetividade da posição estudada, abraço da vítima com as pernas e o uso das mesmas, como apoio para a RCP, através da profundidade (mm), e freqüência (por minuto), das compressões torácicas e, da ventilação (volume de ar em mililitros). Resultados: Pressão de oxigênio cai de +108,3 mmHg (nível do mar), para +72,3 mmHg (8.000 pés). Com suplementação o valor é +108,0 mmHg. RCP em microgravidade: + 41,3 mm, + 80,2 /min, (sem ventilação). Massagem + ventilação (+ 44,0 mm, + 68,3 /min, + 491,0 ml de ar). Conclusões: Existe importante redução na oferta de oxigênio, à vítima de PCR, em altitude de 8.000 pés. Suplementação de oxigênio ao socorrista, 4 litros/minuto, por óculos nasal, pode corrigir esta redução. A posição proposta, para o ambiente espacial, deve ser considerada com uma possibilidade de RCP na microgravidade. / Introduction: Cardiac arrest (CA) is a medical emergency, and when occurring outside the hospital environment, immediate victim’s assistance is vital. Cardiopulmonary Resuscitation (CPR) at the extra-hospital environment is very important. Aerospace denomination joins an aerial environment (pressurized airplane cabins, altitude), and space (microgravity environment, floating). Within the aerial environment, hypobaric condition and resulting hypoxia do matter. Considering the space environment, microgravity condition and the inability to exert force and weight such as at the surface level, are important. Those and other aspects of aerospace CPR are approached in this present study. Objectives: Aerial environment: To evaluate the quality of exhaled air from the practitioner, during CPR within a hypobaric environment, and to assess supplemental oxygen offer to the practitioner as a form of correcting the exhaled gas mixture at altitude. Space environment: To assess the efficacy of a new CPR position, for a sole, unassisted individual at microgravity. Material and Methods: A hypobaric chamber for aerial environment altitude simulation was employed. CPR was assessed at sea level and at the altitude of 8,000 feet. Parabolic flights were employed for microgravity simulation. A CPR manikin was the model for both environments. At the aerial environment, exhaled (mouth-to-mouth) oxygen offer by the practitioner to the victim was assessed. In microgravity, the effectiveness of the studied position, which consisted of securing the victim with the legs and using them for CPR restraint, was evaluated by depth (millimeters), and frequency (per minute) of chest compressions, and ventilation (air volume in milliliters). Results: Oxygen pressure falls from ± 108.3 mmHg (at sea level) to ± 72.3 mmHg (8,000 feet). With supplementation, the value is ± 108.0 mmHg. CPR in microgravity: ± 41.3 mm, ± 80.2/minute (without ventilation). Massage + ventilation (± 44.0 mm, ± 68.3/minute, ± 491.0 ml of air). Conclusions: There is an important reduction of oxygen offer to the CPR victim at the altitude of 8,000 feet. Oxygen supplementation to the medic assistant at 4 liters/minute through nasal cannulae may correct such reduction. The proposed position for the spatial environment should be considered as a possibility for CPR at microgravity.

Introdução: Parada Cardiorrespiratória (PCR) é uma emergência médica, quando ocorrer fora do ambiente hospitalar, o imediato atendimento à vítima é vital. A imediata Reanimação Cardiopulmonar (RCP), no ambiente extra-hospitalar é muito importante. A denominação aeroespacial reúne ambiente aéreo (cabine de aeronaves pressurizadas, altitude) e, espacial (ambiente com microgravidade, flutuação). No ambiente aéreo, importa a condição hipobárica e a hipóxia resultante. Quanto ao ambiente espacial, importa a condição de microgravidade e a incapacidade de exercer força e peso, como na superfície terrestre. Estes, e outros aspectos da RCP aeroespacial, são abordados no presente estudo. Objetivos: Ambiente aéreo: avaliar a qualidade do ar expirado, por um socorrista, durante RCP, em ambiente hipobárico, e, avaliar a suplementação de oxigênio para o socorrista, como forma de correção da mistura gasosa expirada, na altitude. Ambiente espacial: avaliar a eficácia de uma nova posição para RCP, por um só indivíduo, sem auxílio, na microgravidade. Materiais e Métodos: Utilizou-se uma câmara hipobárica, para a simulação da altitude, no ambiente aéreo. A RCP foi avaliada ao nível do mar e na altitude de 8.000 pés. Vôos parabólicos foram utilizados para a simulação de microgravidade. Um manequim foi o modelo de PCR em ambos os ambientes. No ambiente aéreo, avaliou-se a oferta de oxigênio expirada (boca-a-boca), pelo socorrista à vítima. Em microgravidade foi avaliada a efetividade da posição estudada, abraço da vítima com as pernas e o uso das mesmas, como apoio para a RCP, através da profundidade (mm), e freqüência (por minuto), das compressões torácicas e, da ventilação (volume de ar em mililitros). Resultados: Pressão de oxigênio cai de +108,3 mmHg (nível do mar), para +72,3 mmHg (8.000 pés). Com suplementação o valor é +108,0 mmHg. RCP em microgravidade: + 41,3 mm, + 80,2 /min, (sem ventilação). Massagem + ventilação (+ 44,0 mm, + 68,3 /min, + 491,0 ml de ar). Conclusões: Existe importante redução na oferta de oxigênio, à vítima de PCR, em altitude de 8.000 pés. Suplementação de oxigênio ao socorrista, 4 litros/minuto, por óculos nasal, pode corrigir esta redução. A posição proposta, para o ambiente espacial, deve ser considerada com uma possibilidade de RCP na microgravidade. / Introduction: Cardiac arrest (CA) is a medical emergency, and when occurring outside the hospital environment, immediate victim’s assistance is vital. Cardiopulmonary Resuscitation (CPR) at the extra-hospital environment is very important. Aerospace denomination joins an aerial environment (pressurized airplane cabins, altitude), and space (microgravity environment, floating). Within the aerial environment, hypobaric condition and resulting hypoxia do matter. Considering the space environment, microgravity condition and the inability to exert force and weight such as at the surface level, are important. Those and other aspects of aerospace CPR are approached in this present study. Objectives: Aerial environment: To evaluate the quality of exhaled air from the practitioner, during CPR within a hypobaric environment, and to assess supplemental oxygen offer to the practitioner as a form of correcting the exhaled gas mixture at altitude. Space environment: To assess the efficacy of a new CPR position, for a sole, unassisted individual at microgravity. Material and Methods: A hypobaric chamber for aerial environment altitude simulation was employed. CPR was assessed at sea level and at the altitude of 8,000 feet. Parabolic flights were employed for microgravity simulation. A CPR manikin was the model for both environments. At the aerial environment, exhaled (mouth-to-mouth) oxygen offer by the practitioner to the victim was assessed. In microgravity, the effectiveness of the studied position, which consisted of securing the victim with the legs and using them for CPR restraint, was evaluated by depth (millimeters), and frequency (per minute) of chest compressions, and ventilation (air volume in milliliters). Results: Oxygen pressure falls from ± 108.3 mmHg (at sea level) to ± 72.3 mmHg (8,000 feet). With supplementation, the value is ± 108.0 mmHg. CPR in microgravity: ± 41.3 mm, ± 80.2/minute (without ventilation). Massage + ventilation (± 44.0 mm, ± 68.3/minute, ± 491.0 ml of air). Conclusions: There is an important reduction of oxygen offer to the CPR victim at the altitude of 8,000 feet. Oxygen supplementation to the medic assistant at 4 liters/minute through nasal cannulae may correct such reduction. The proposed position for the spatial environment should be considered as a possibility for CPR at microgravity.

Ce travail de recherche, réalisé en collaboration avec le Commissariat à l'Énergie Atomique (CEA) et le Centre National d'Études Spatiales, vise à apporter une contribution supplémentaire sur le phénomène de l'ébullition (thermohydraulique diphasique). Il traite plus particulièrement de la crise d'ébullition, c'est à dire la transition irréversible de l'ébullition nucléée vers l'ébullition en film, pour mettre en évidence les mécanismes responsables de son déclenchement.L'approche est principalement expérimentale et s'effectue à l'aide d'installations de compensation magnétique de la gravité permettant de reproduire en laboratoire les conditions de microgravité nécessaires à la réalisation de l'étude. L'oxygène et l'hydrogène sous forme diphasique et proche des conditions critiques servent de fluides d'étude. Les moyens techniques disponibles au Service des Basses Température (SBT) du CEA de Grenoble permettent de mener à bien le travail.L'objectif est double: d'une part, montrer que la compensation magnétique de la gravité est une technique intéressante pour compléter les moyens habituels de compensation inertielle; d'autre part, contribuer à la recherche fondamentale sur la crise d'ébullition.Les jalons pour y parvenir sont multiples: mise en évidence des avantages et des faiblesses de la compensation magnétique par l'étude approfondie du champ magnétique; conception, fabrication et assemblage des cellules d'essai; qualification et réglage des installations expérimentales; enfin, réalisation des campagnes expérimentales de validation des modèles. / This research work, performed with the help of the French Atomic Energy Committee and the French Space Agency, tries to bring a new contribution regarding the boiling phenomenon. It deals in particular with the boiling crisis, which corresponds to the departure from nucleate boiling towards film boiling, and tries to underline the governing mechanisms of its trigger.The approach is mainly based on experiments. They are realised with the help of magnetic gravity compensation apparatus which contribute to reproduce in laboratory the microgravity conditions needed to realise the study. Two-phase oxygen and hydrogen placed in near-critical conditions are the study fluids. The technical resources which are available at the Low Temperature Department of CEA Grenoble give a useful help to have the work well done.The purpose is dual: on the one hand, to show that magnetic compensation of gravity is an interesting technique to complete the usual inertial compensation means; on the other hand, to contribute on the critical heat flux basic research.The topics are numerous: showing the advantages and the weaknesses of the magnetic compensation with a deep magnetic field study; designing, manufacturing and assembling experimental cells; qualifying and setting up the experimental apparatus; eventually, performing the model validation experiments.