A congestion model for cell migration

This paper deals with a class of macroscopic models for cell migration in a saturated medium for two-species mixtures. Those species tend to achieve some motion according to a desired velocity, and congestion forces them to adapt their velocity. This adaptation is modelled by a correction velocity which is chosen minimal in a least-square sense. We are especially interested in two situations: a single active species moves in a passive matrix (cell migration) with a given desired velocity, and a closed-loop Keller-Segel type model, where the desired velocity is the gradient of a self-emitted chemoattractant. We propose a theoretical framework for the open-loop model (desired velocities are defined as gradients of given functions) based on a formulation in the form of a gradient flow in the Wasserstein space. We propose a numerical strategy to discretize the model, and illustrate its behaviour in the case of a prescribed velocity, and for the saturated Keller-Segel model

Microstructures and mechanical properties of pure tantalum processed by high-pressure torsion

A body-centred cubic (BCC) structure metal, tantalum, was processed by high- pressure torsion (HPT) at room temperature with different numbers of rotations. The microstructural evolution was studied by electron backscatter diffraction (EBSD). The grain sizes were significantly refined at the disk edge area in the early stages of deformation (N = 0.5) but tended to attain saturation after the numbers of rotations was increased to N = 5. As the deformation continued, some coarse grains appeared in the disk edge areas and it appeared that there was structural recovery at the expense of grain boundary migration in the tantalum during HPT processing. Microhardness measurements showed the hardness gradually evolved towards a more homogenized level across the disk surfaces as the numbers of rotations increased. The hardness level after N = 10 turns was slightly lower than after N = 5 turns, thereby indicating the occurrence of a recovery process after 5 turn

Etude des processus dynamiques et microphysiques dans les nuages convectifs peu profonds : synergie entre simulations numériques et observations par une flotte de drones

Les cumulus, nuages convectifs peu profonds, résultent de convection humide où la vapeur d'eau contenue dans l'atmosphère a pu condenser sur les particules d'aérosols. Ces nuages, de par leurs impacts radiatifs sur le bilan énergétique de la Terre, leur rôle dans la distribution de l'eau dans la troposphère et leur présence importante sur le globe sont des éléments clés du climat. Cependant, leur durée de vie courte (15-30 minutes) et leur échelle spatiale restreinte (de l'ordre de la centaine de mètres voire du kilomètre) rendent leurs observations in situ délicates d'autant plus que ces nuages sont généralement advectés par le vent moyen. Enfin, il est important de comprendre les processus de mélange entre les cumulus et l'environnement car ceux-ci peuvent modifier la thermodynamique de ces nuages et impacter leur cycle de vie. Le projet NEPHELAE (Network for studying Entrainment and microPHysics of cLouds using Adaptive Exploration) a donc pour objectifs d'étudier ces processus de mélange par une caractérisation spatio-temporelle complète de la microphysique et de la dynamique des nuages grâce au développement d'une flotte de drones. L'objectif de cette thèse est donc de mettre au point une stratégie expérimentale afin d'étudier les processus nuageux par plusieurs drones. La méthodologie employée combine études numériques et observations in-situ par des drones. La première partie de cette thèse se focalise sur la caractérisation des processus de mélange dans les nuages, avec l'appui de simulations LES (Large Eddy Simulation). Deux cas de convection, océanique et continentale ont été simulés par le modèle non-hydrostatique de Météo France (Méso-NH) et ont servi de support pour l'étude individuelle des cumulus, via une méthode d'identification des nuages. Les profils des processus d'entraînement (air environnemental pénétrant dans le nuage) sont plus forts à la base des nuages puis diminuent vers leur sommet avec des plus forts taux pour les nuages de petits volumes alors que le détrainement (air sortant du nuage) est quant à lui plus fort au sommet des nuages. Ces processus de mélange restent indépendants du type de convection. Ces résultats ont été confirmés par l'analyse de cumulus lors des campagnes BIO-MAIDO et NEPHELAE, par ballon captif et par drones. La deuxième partie de cette thèse se concentre sur la définition d'une nouvelle stratégie d'observations permettant la caractérisation d'une section horizontale de nuage. Après avoir simulé un champ de cumulus marins à haute résolution et haute fréquence, des trajectoires adaptatives de drones ont été définies et testées dans cette simulation. Ces trajectoires adaptatives ont été jugées suffisantes pour reproduire les champs thermodynamiques horizontaux. La stratégie expérimentale ainsi validée a été déployée en conditions réelles lors de la campagne de terrain EUREC4A. Les statistiques des cumulus traversés ainsi que les suivis adaptatifs ont permis de quantifier les hétérogénéités dans les sections horizontales des cumulus d'alizés.Cumulus, one type of shallow convective clouds, are the result of moist convection where water vapour in the atmosphere has condensed on aerosol particles. These clouds, because of their radiative impacts on the Earth's energy balance, their role in the distribution of water in the troposphere and their ubiquitous presence across the globe are key elements of the climate. However, their short lifetime (15-30 minutes) and their restricted spatial scale (of the order of a hundred meters or even a kilometer) make their in situ observations all the more complex as these clouds are generally advected. It is also important to understand the mixing processes between cumulus clouds and the environment since they can modify the thermodynamics of these clouds and impact their life cycle. The NEPHELAE project (Network for studying Entrainment and microPHysics of cLouds using Adaptive Exploration) aims to study the mixing processes through a complete spatio-temporal characterization of the microphysics and dynamics of clouds through the development of a fleet of RPAs (Remotely Piloted Aircrafts). The objective of this thesis is to develop an experimental strategy to study cloud processes with RPAs. The methodology relies on the combination of numerical studies and in-situ RPAs observations . The first part of the thesis focuses on the characterization of the mixing processes, with the support of LES (Large Eddy Simulation) simulations and in-situ observations. Two cases of convection, oceanic and continental, have been simulated by the non-hydrostatic model of Météo France (Meso-NH). They have allowed an individual study of cumulus clouds, provided by a cloud identification method. Entrainment processes (environmental air entering the cloud) are stronger at the base of the clouds and then decrease towards their top with stronger rates for small volume clouds, whereas the detrainment (air leaving the cloud) is stronger at the top of the clouds. These results were confirmed by the analysis of cumulus layers during the BIO-MAIDO and NEPHELAE campaigns, by tethered balloons and RPAs. The second part of this thesis focuses on the elaboration of a new observation strategy to document a horizontal cloud section. After simulating a marine cumulus field at high resolution and frequency, adaptive RPA trajectories have been defined and tested in this simulation. These adaptive trajectories were judged sufficient to reproduce the horizontal thermodynamic fields, which allowed them to be applied during the EUREC 4 A field campaign. The statistics of the cumulus clouds crossed as well as the adaptive trajectories allowed us to quantify theheterogeneities in the horizontal sections of the trade wind cumulus

DEPRESSION, FAMILY AND CELLULAR IMMUNITY: INFLUENCE OF FAMILY RELATIONSHIPS AND CELLULAR IMMUNITY ON THE SEVERITY OF DEPRESSION

Background: Exposure to stress activates the hypothalamic-pituitary-adrenal axis through the release of catecholamines, which modify humoral and cellular immunity. On the one hand, this psycho-immunological theory makes it possible to forge links between immunity and depression. On the other hand, we know that family determinants are an important variable in the model of vulnerability to depression. Our study weighs the influence of cellular immunity and family relations on the severity of depression. Subjects and method: 498 inpatients with major depressive disorder were enrolled in an open-label trial. In addition to a sociodemographic questionnaire, they completed Olsen’s FACES III and the Beck Depression Inventory (BDI). Flow cytometry was used to assess lymphocyte subsets. Results: In terms of immunity, there are correlations between the BDI and percentages of CD3 (p=0.015; r=-0.112), CD4 (p<0.000; r=-0.175), CD4/CD8 (p=0.045; r=-0.093) and CD16 and 56 (p=0.014; r=0.113). In terms of family relationships, there is a correlation between the BDI and family of origin, both for cohesion (p=0.007; r=-0.169) and adaptability (p=0.035; r=-0.133) measures. With respect to the relationship between family dynamics and immunity, there are correlations between adaptability in the family of origin and CD3 (p=0.04; r=0.094) and CD4 (p=0.044; r=0.093). A logistic regression model for family variables explained 11.4% of the BDI, compared to 12.7% for immune variables, while a model including the two explained 16%. Conclusions: While both the family and immunity can explain the BDI, it is surprising they have a greater effect in combination than individually. This suggests that the psycho-immunological theory should look at the relation between immunity and family life, notably in relation to the family of origin

Mental Health in France, Policies and Actors : Developing administrative knowledge in a segmented world

Version preprintInternational audienceThe new mental health care policy, which has been set up in France, involves a change of paradigm, which has been going on since the 2000s: the emphasis is shifting from psychiatry to mental health care. This shift mainly concerns the knowledge about mental health is produced and circulates among an increasingly large number of bodies. Mainly grounded on actor interview analysis, official reports and blueprints, this study shows that the results of this process are numerous. They include the development of ambulatory care and strong moves towards decentralization. More data and knowledge are therefore to be shared in this more complex system. However, the French State, in the form of the central administration, is taking advantage of this move and is still contributing significantly to the definition and implementation of the new policy. On the other hand, the new governance dynamic is not leading to standardization of medical practices, as the mental health field remains highly heterogeneous

A critical examination of pure tantalum processed by high-pressure torsion

Tantalum, a common refractory metal with body-centred cubic (BCC) crystalline structure, was processed by high-pressure torsion (HPT) at room temperature through different numbers of rotations. Significant grain refinement and high strength were achieved with a reduction in grain size from ?60 ?m to ?160 nm and an increase in strength from ?200 to &gt;1300 MPa. Hardness measurements revealed a high level of homogeneity after 10 turns of HPT but the hardness after 10 turns was slightly lower than after 5 turns indicating the occurrence of some recovery. Tensile testing at a strain rate of 1.0×10?3 s?1 gave high strengths of ?1200 MPa but little or no ductility after processing through 1, 5 and 10 turns. The introduction of a short-term (15 min) anneal immediately after HPT processing led to significant ductility in all samples and a reasonable level of strength at ?800 MPa

The impact of aerosols on stratiform clouds over southern West Africa: a large-eddy-simulation study

Low-level stratiform clouds (LLSCs) covering a large area appear frequently during the wet monsoon season in southern West Africa. This region is also a place where different types of aerosols coexist, including biomass burning aerosols coming from central and southern Africa and aerosols emitted by local anthropogenic activities. We investigate the indirect and semi-direct effects of these aerosols on the life cycle of LLSCs by conducting a case study based on airborne and ground-based observations from the field campaign of Dynamic-Aerosol-Chemistry-Cloud-Interaction in West Africa (DACCIWA). This case is modeled using a large-eddy-simulation (LES) model with fine resolution and in situ aerosol measurements, including size distribution and chemical composition. The model has successfully reproduced the observed life cycle of the LLSC, from stratus formation to stabilization during the night and to upward development after sunrise until break-up of the cloud deck in the late afternoon. Additional sensitivity simulations using different measured aerosol profiles also suggest that aerosols can affect the cloud life cycle through both the indirect and semi-direct effects. As expected, modeled cloud microphysical features, including cloud droplet number concentration, mean radius, and thus cloud reflectivity, are all controlled by aerosol concentration. However, it is found that the variation in cloud reflectivity induced by different aerosol profiles is not always the only factor in determining the incoming solar radiation at the ground and thus for the cloud life cycle after sunrise. Instead, the difference in cloud fraction brought by dry-air entrainment from above and thus the speed of consequent evaporation – also influenced by aerosol concentration – is another important factor to consider. Clouds influenced by higher aerosol concentrations and thus with a higher number concentration and smaller sizes of cloud droplets are found to evaporate more easily and thus impose a lower cloud fraction. In addition, our sensitivity runs including versus excluding aerosol direct radiative effects have also demonstrated the impacts specifically of solar absorption by black carbon on the cloud life cycle. The semi-direct effect resulting from an excessive atmospheric heating of up to 12 K d−1 by black carbon in our modeled cases is found to lower the cloud top as well as the liquid water path, reducing surface incoming solar radiation and dry entrainment and increasing the cloud fraction.</p

Mercury and methylmercury concentrations in high altitude lakes and fish (Arctic charr) from the French Alps related to watershed characteristics

International audienceTotal mercury (THg) andmethylmercury (MeHg) concentrations were measured in the muscle of Arctic charr (Salvelinus alpinus) and in the water column of 4 lakes that are located in the French Alps. Watershed characteristics were determined (6 coverage classes) for each lake in order to evaluate the influence of watershed composition on mercury and methylmercury concentrations in fish muscle and in the water column. THg and MeHg concentrations in surface water were relatively low and similar among lakes and watershed characteristics play a major role in determining water column Hg and MeHg levels. THg muscle concentrations for fish with either a standardized length of 220 mm, a standardized age of 5 years or for individualuals did not exceed the 0.5 mg kg−1 fish consumption advisory limit established for Hg by the World Health Organization (WHO, 1990). These relatively low THg concentrations can be explained by watershed characteristics, which lead to short Hg residence time in the water column, and also by the short trophic chain that is characteristic of mountain lakes. Growth rate did not seem to influence THg concentrations in fish muscles of these lakes and we observed no relationship between fish Hg concentrations and altitude. This study shows that in the French Alps, high altitude lakes have relatively low THg and MeHg concentrations in both the water column and in Arctic charr populations. Therefore, Hg does not appear to present a danger for local populations and the fishermen of these lakes