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This thesis is part of a desire to carry out a bibliographic review of the current state of knowledge on idiopathic stomatodynia in order to raise awareness and disseminate this information. Primary or idiopathic stomatodynia is a chronic condition of intra-oral burning or dysesthesia affecting mainly menopausal women. Our first part is a reminder of the different orofacial pains; our second part specifies the diagnostic approach to this type of pain; finally, in the third part we review the most recent data concerning the etiopathogenies and specific treatments of idiopathic stomatodynia.; Cette thèse s'inscrit dans une volonté de réaliser une revue bibliographique de l'état actuel des connaissances sur la stomatodynie idiopathique afin de sensibiliser et de diffuser cette information. La stomatodynie primaire ou idiopathique est une affection chronique de brûlures ou de dysesthésies intra-buccales touchant principalement les femmes ménopausées. Notre première partie est un rappel concernant les différentes douleurs orofaciales ; notre deuxième partie précise la démarche diagnostique face à ce type de douleur ; enfin dans la troisième partie nous faisons le point sur les données les plus récentes concernant les étiopathogénies et traitements spécifiques de la stomatodynie idiopathique.

A multiscale numerical model, coupling the Cellular Automaton (CA) method to the Parabolic Thick Needle (PTN) method, is developed to compute dendritic microstructures. It is applied to directional solidification of bi-crystals under a frozen temperature approximation with fixed temperature gradient and fixed cooling rate. A dendritic branch is modeled as a cylinder headed by a parabolic tip. Its kinetics is computed using the PTN method from the composition field in the liquid in the vicinity of the parabola. This dendritic branch takes part in the definition of a grain envelope by its integration in a CA growth algorithm. The so-called Cellular Automaton – Parabolic Thick Needle (CAPTN) model can simulate the growth of dendritic grains while accounting for non-steady diffusion fields. The PTN method is implemented using Finite Element (FE) method on a heterogeneous mesh. An adaptive FE mesh strategy is developed to optimize computational time. The grain boundary orientation angle of a diverging bi-crystal configuration is investigated at steady state and compared to the Phase-Field (PF) method and the classical CA method. It is shown that contrary to the CA method, the CAPTN model is in good agreement with data deduced from PF simulations, demonstrating the interest of this coupling in the modeling of dendritic growth.

International audience; Thermal contact resistance between two adjacent materials is one of the major concerns in a large variety of practical situations in heat transfer. The presence of this resistance yields a temperature jump across the interface. Due to this discontinuity, numerical modelling of thermal contact resistance runs into difficulties. In this work, we propose a simple and efficient numerical model to account for thermal contact resistance at immersed interfaces in multi-material heat transfer. The present model is based on the diffuse interface method. The effect of contact resistance between two adjacent materials is accounted for in the mixing laws of the thermal conductivity and the heat capacity. The model is validated through different test cases, including both steady and unsteady conduction, and applied to simulation of chill cooling and solidification of a steel sample on board the International Space Station.

International audience; An extension of the pioneer work by Mullins and Sekerka is proposed to analyze the stability conditions of a spherical particle growing in a matrix phase. The present model describes the onset of instabilities in an unsteady growth regime for multi-component alloys with cross-diffusion of chemical species. The developments are based on the decomposition of initial perturbations in spherical harmonics to determine their time evolution. Expressions for the threshold particle radii associated to the limits for absolute and relative stability criteria are derived. They depend on the degree of the spherical harmonic functions, the growth parameter for a sphere (proportional to the interface velocity times the square root of time) and the eigenvalues of the diffusion matrix. A large effect of the interface velocity on the stability domains is demonstrated considering the time-dependent solutions. Comparisons are provided regarding more recent solutions proposed in the literature. A similar evolution is only observed for slow regimes. An application for solidification of a ternary alloy is finally given.

Control of macrosegregation phenomena and deformation related defects is the main issue in solidification processes. Numerical modelling of casting provides an answer to industrial needs to master these defects. As a first step, it is essential to achieve a concurrent computation of the fluid flow in the bulk liquid and stress-strain evolution in the already solidified regions. For this specific purpose, a partitioned solution algorithm is developed to model both ingot casting and continuous casting processes: liquid flow induced by natural convection or filling step, solidification shrinkage as well as thermal deformation of solid phase are all taken into consideration. This article is mainly composed of two parts. In the first part, details of the model itself are described. In the second part, applications dedicated to steel solidification are proposed.

Production of silicon for solar cells in photovoltaic systems is mainly based on directional casting processes. Twin nucleation is favoured during silicon growth due to the low-level twin energy of formation. As a consequence, in all solidification process, a large amount of grain boundaries (GB) are in twin relationship. A 3D cellular automaton (CA) model has been recently developed for the growth of multi-crystalline silicon including facet formation and nucleation of new grains in twin relationship. Activation of facets is based on an undercooling parameter assigned to each grain and for each of the crystal directions. The model also considers nucleation and growth of grains on facets corresponding to Σ3 twin relationships between twin grains. This model is first applied to comparison with experimental observations. It is found that impingement of growing grains that nucleated in Σ3 twin relationships meet during growth and form Σ3, Σ9 and Σ27 GB, in good agreement with experimental observations. Finally, the model is applied at a larger scale to generate grain structures representative of industrial practice. While quantitative experimental data is missing for comparison at such scale, the model is promising and its implementation in heat and mass transfer models should be considered for assistance to production of silicon for solar cells dedicated to photovoltaic systems.

International audience; A three-dimensional model is proposed to simulate the grain structure in directionally solidified silicon. This includes the nucleation and growth of grains in twin relationship whose formation is very frequent during silicon solidification. Based on analyses of in-situ and real-time observations of the crystallization front, a three-dimensional cellular automaton method is developed to model the dynamic of {111} facets, groove formationat grain boundaries, nucleation and growth of grains in twin relationship. The model is applied to well-characterized experiments assuming the frozen temperature approximation. A comparison of solidification sequences, crystallographic orientation maps, and coincidence site lattice maps in both experiment and simulation results is achieved. Results demonstrate that the model could be applied to optimize crystallization processes for both polycrystalline and cast-mono silicon fabrication processes.

International audience; Understanding the impact of thermo-solutal convection during alloy solidification is of central importance in the casting industry. Convective flow generated from density variations in the liquid is at the origin of many casting defects, such as chemical segregations and freckles, to which Ni-based superalloys used in jet engines are known to be highly sensitive. In this article, we present experimental results obtained during directional solidification of a CMSX-4 single crystal superalloy observed in-situ by means of synchrotron X-radiography at the European Synchrotron Radiation Facility (ESRF, Grenoble, France). The use of a high-temperature directional solidification furnace, an intense monochromatic beam and a high-speed X-ray sensitive camera allowed the direct observation of the development of solute flow to be performed during dendritic growth of a Ni-based alloy. The transient stage leading to the formation of a dendrite network and the interaction with the concomitantly developing convective pattern are studied. The impact of solute flow on the dendrite growth velocity is characterized for three cooling rates. Measurements of dendrite tip positions show that the convective flow above the solidification front induces a periodic oscillation of the dendrite growth velocity and that the oscillation amplitude decreases for higher cooling rates. The development of residual liquid areas is observed on the sides of the sample. Fragmentation of dendrite parts occurs during the solidification of the residual liquid areas and leads to the formation of spurious grains. The experimental results are analyzed by using a Rayleigh number-based model, highlighting the need for direct simulations in the future.

International audience; One of the critical challenges encountered when modeling solidification processes is to achieve a concurrent and efficient computation of fluid flow and solid mechanics. Several detrimental casting defects justify this development: cracks, either as a result of stresses built at surface or subsurface in solidified regions during the filling stage of ingot casting, or due to hot tears deep in the mushy zone during solidification; macrosegregation, as a result of thermo-solutal convection flows and possible deformation of solid. It is therefore of crucial importance to provide for a global and synthetic analysis of casting processes considering a single numerical modelling that includes coupling between fluid flow and solid mechanics. A two-step solution strategy combining fluid flow and solid mechanics has been developed. A partitioned formulation is used, performing at each time increment, separately a solidoriented resolution and a fluid-oriented resolution. Liquid flow (natural convection or forced flow during ingot filling stage), solidification shrinkage as well as thermally induced deformation of the solid regions are taken into account. The paper presents the numerical formulation in a level set finite element context, and associated validation tests. Application in a practical case corresponding to an ingot filling is proposed in order to investigate the solidification process and associated fluid flow and stress evolutions. Some discussions on computations time and others numerical aspects are also developed at the end in order to show the potential improvements of this methodology.

International audience; Recent progress in the application of Laser Beam Melting (LBM) of oxide ceramics has shown promising results. However, a deeper understanding of the process is required to master and control the track development. In this approach numerical modeling could allow higher quality, of additive manufacturing for such materials, to be achieved. The validation of an earlier developed finite element model for LBM of ceramic materials has been established through a comparison with experimental results. The model solves heat and mass transfers whilst accounting for fluid flow due to surface tension and Marangoni convection, as well as tracking the material/gas boundary. The volumetric heat source parameters used in the simulations have been calibrated with an analytical model combined with original in-situ reflectance measurements. Numerical results show good agreement with measurements of melt pool dimensions and shapes. They also provide a coherent description of the evolution of the track morphology when varying the heat source parameters. Track irregularities have also been revealed by simulations at high scanning speed and the balling effect highlighted and explained through similar simulations.

The dendrite growth velocity in Al₇₅Ni₂₅ melts has been measured in a containerless procedure as a function of undercooling using an electromagnetic levitation technique both in the Earth laboratory and in Space on board the International Space Station. The growth shows an anomalous behavior inasmuch as the growth velocity decreases with increasing undercooling, confirming previous experiments on Earth. Within the scatter of experimental data, results obtained on Earth and in Space do not show significant differences. Thus, convection effects as the origin of the anomalous growth characteristics can be excluded. However, high-speed video recording exhibits multiple nucleation events in front of the growing solid-liquid interface. This effect is identified as the origin of the anomalous dendrite growth characteristics in undercooled melts of Al-rich Al-Ni melts.

Laser Beam Melting (LBM) processes benefit from significant progress in recent years. Currently, manufacturing of ceramic parts for applications at high temperature in aeronautical industries can be planned. However, understanding of defect formation is required in order to optimize manufacturing strategy. In this work, level-set modelling is proposed to simulate tracks development during LBM processes. Thermo-mechanical solution is performed in both powder and dense domains. Fluid flow is computed considering the surface tension and Marangoni forces. In addition mechanical resolution is achieved to investigate stress evolution in the rear part of the track. Applications are developed on alumina material. The influence of laser power, scanning velocity and physical properties are investigated and discussed. Validations of the heat source model are proposed by comparisons of melt pool dimensions and shapes with experimental measurements. A coherent evolution of the track morphology is shown when varying process parameters or material properties.

Tropospheric ozone (O3) is the main secondary pollutant and considered to be the most damaging for growth and productivity. O3 is well known to induce oxidative stress and Reactive Oxygen Species accumulation in leaf tissues. Several mechanisms have been suggested to enable trees to cope with such stress; however, their relative contribution to O3 tolerance is still unclear. Here, ten Euramerican poplar genotypes (Populus deltoides × nigra) were investigated regarding their response to 120 ppb of O3 for 3 weeks in order to determine main mechanisms and identify the key traits and strategies linked to a better tolerance to O3-induced oxidative stress. Results showed that ascorbate peroxidase and ascorbate regeneration through monodehydroascorbate reductase are the main determinants of O3 tolerance in Euramerican poplar, in protecting photosynthesis capacity from oxidative stress and therefore, maintaining growth and productivity. Besides, stomatal closure was harmful in sensitive genotypes, suggesting that avoiding strategy can be further deleterious under chronic ozone. Finally, O3-induced early senescence appeared essential when up scaling leaf-level mechanistic response to whole-plant productivity, in fine-tuning resource reallocation and photosynthesis area.

Inflammation is considered as a major contributor to brain injury following cerebral ischemia. The therapeutic potential of both MLC601/MLC901, which are herbal extract preparations derived from Chinese Medicine, has been reported both in advanced stroke clinical trials and also in animal and cellular models. The aim of this study was to investigate the effects of MLC901 on the different steps of post-ischemic inflammation in focal ischemia in mice. In vivo injury was induced by 60 minutes of middle cerebral artery occlusion (MCAO) followed by reperfusion. MLC901 was administered in post-treatment 90 min after the onset of ischemia and once a day during reperfusion. MLC901 treatment resulted in a reduction in infarct volume, a decrease of Blood Brain Barrier leakage and brain swelling, an improvement in neurological scores and a reduction of mortality rate at 24 hours after MCAO. These beneficial effects of MLC901 were accompanied by an inhibition of astrocytes and microglia/macrophage activation, a drastically decreased neutrophil invasion into the ischemic brain as well as by a negative regulation of pro-inflammatory mediator expression (cytokines, chemokines, matrix metalloproteinases). MLC901 significantly inhibited the expression of Prx6 as well as the transcriptional activity of NFκB and the activation of Toll-like receptor 4 (TLR4) signaling, an important pathway in the immune response in the ischemic brain. MLC901 effects on the neuroinflammation cascade induced by cerebral ischemia probably contribute, in a very significant way, in its potential therapeutic value.

International audience; The transport of solid crystals in the liquid pool during solidification of large ingots is known to have a significant effect on their final grain structure and macrosegregation. Numerical modeling of the associated physics is challenging since complex and strong interactions between heat and mass transfer at the microscopic and macroscopic scales must be taken into account. The paper presents a finite element multi-scale solidification model coupling nucleation, growth, and solute diffusion at the microscopic scale, represented by a single unique grain, while also including transport of the liquid and solid phases at the macroscopic scale of the ingots. The numerical resolution is based on a splitting method which sequentially describes the evolution and interaction of quantities into a transport and a growth stage. This splitting method reduces the non-linear complexity of the set of equations and is, for the first time, implemented using the finite element method. This is possible due to the introduction of an artificial diffusion in all conservation equations solved by the finite element method. Simulations with and without grain transport are compared to demonstrate the impact of solid phase transport on the solidification process as well as the formation of macrosegregation in a binary alloy (Sn-5 wt pct Pb). The model is also applied to the solidification of the binary alloy Fe-0.36 wt pct C in a domain representative of a 3.3-ton steel ingot.

International audience; The present study is based on a formerly developed 3D finite element modelling of the selective laser melting process (SLM) at the track scale. This numerical model is used to assess the impact of two phenomena on the shape of the elementary track resulting from SLM processing: laser interaction on one hand, and Marangoni effect on the other hand. As regards laser interaction, it is modelled by a Beer-Lambert type heat source, in which lateral scattering and material absorption are considered through two characteristic parameters. The impact of these parameters is shown in terms of width and depth of melted zone. The Marangoni effect caused by tangential gradients of surface tension is modelled to simulate the fluid dynamics in the melt pool. The resulting convection flow is demonstrated with surface tension values either increasing or decreasing with temperature. The influence of energy distribution, surface tension effects, as well as laser scanning speed on temperature distribution and melt pool geometry is investigated. The stability and regularity of the solidified track are a direct output of the simulations, and their variations with material and process conditions are discussed.

The proposed introduction of gaming disorder (GD) in the 11th revision of the International Classification of Diseases (ICD-11) developed by the World Health Organization (WHO) has led to a lively debate over the past year. Besides the broad support for the decision in the academic press, a recent publication by van Rooij et al. (2018) repeated the criticism raised against the inclusion of GD in ICD-11 by Aarseth et al. (2017). We argue that this group of researchers fails to recognize the clinical and public health considerations, which support the WHO perspective. It is important to recognize a range of biases that may influence this debate; in particular, the gaming industry may wish to diminish its responsibility by claiming that GD is not a public health problem, a position which maybe supported by arguments from scholars based in media psychology, computer games research, communication science, and related disciplines. However, just as with any other disease or disorder in the ICD-11, the decision whether or not to include GD is based on clinical evidence and public health needs. Therefore, we reiterate our conclusion that including GD reflects the essence of the ICD and will facilitate treatment and prevention for those who need it. CA extern

In the version of this article originally published, the name of author Martin H. de Borst was coded incorrectly in the XML. The error has now been corrected in the HTML version of the paper.

International audience; The objective of this work is to develop new numerical simulation techniques in meso- and macro-scale to optimize the LBM process. The two scale models are under a level-set framework. A meso-scale simulation focuses on the laser interaction with the powder bed and subsequent melting and solidification. Thermomechanical finite element (FE) modelling is conducted at the scale of material deposition, and addresses the melting of the powder bed, the hydrodynamics of the fusion zone and the formation of local thermal stresses in the wake of the laser. A macro-scale simulation focuses on part construction. This thermomechanical finite element model addresses heat exchange and stress formation at the scale of the part by considering the non-exposed powder. In order to reach reasonable simulation time for industrial parts, the energy input and the formation of the additive deposit are simplified by considering them at the scale of an entire layer or fractions of each layer.

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International audience; During casting, often a dendritic microstructure is formed, resulting in a columnar or an equiaxed grain structure, or leading to a transition from columnar to equiaxed growth (CET). The detailed knowledge of the critical parameters for the CET is important because the microstructure affects materials properties. To provide unique data for testing of fundamental theories of grain and microstructure formation, solidification experiments in microgravity environment were performed within the European Space Agency Microgravity Application Promotion (ESA MAP) project Columnar-to-Equiaxed Transition in SOLidification Processing (CETSOL). Reduced gravity allows for purely diffusive solidification conditions, i.e., suppressing melt flow and sedimentation and floatation effects. On-board the International Space Station, Al-7 wt.% Si alloys with and without grain refiners were solidified in different temperature gradients and with different cooling conditions. Detailed analysis of the microstructure and the grain structure showed purely columnar growth for nonrefined alloys. The CET was detected only for refined alloys, either as a sharp CET in the case of a sudden increase in the solidification velocity or as a progressive CET in the case of a continuous decrease of the temperature gradient. The present experimental data were used for numerical modeling of the CET with three different approaches: (1) a front tracking model using an equiaxed growth model, (2) a three-dimensional (3D) cellular automaton–finite element model, and (3) a 3D dendrite needle network method. Each model allows for predicting the columnar dendrite tip undercooling and the growth rate with respect to time. Furthermore, the positions of CET and the spatial extent of the CET, being sharp or progressive, are in reasonably good quantitative agreement with experimental measurements.

International audience

International audience; An analytical model for growth in a semi infinite matrix with cross-diffusion between species is presented. Application is given for precipitation of the gamma’ phase in the gamma matrix during isothermal holding at 600 °C in the Ni – 7.56 at.% Al – 8.56 at.% Cr alloy. The exact time dependent solutions for the solute profiles and the growth kinetics are validated with a numerical front-tracking simulation. The simulation of cross diffusion terms in a multicomponent alloy being demonstrated, extension of the analytical solution is given for growth in a matrix of finite size. The driving force is based on a mathematical estimation of the far-field composition. The Gibbs-Thomson effect is also accounted for to consider the effect of curvature on the equilibrium tie-lines. Comparison of analytical solution with the numerical front-tracking simulation shows excellent agreement. Results point out the detrimental approximation of using the average composition of the matrix for computing the driving force as well as the limitation of the solution found in the literature. A detailed discussion is given on the origin of oscillations observed for the time evolution of the precipitate radius which alternates between growth and dissolution regimes, pointing out the combined role of solute fluxes and tie-lines compositions at the precipitate/matrix interface illustrated hereafter by drawing the transformation paths in the phase diagram.

International audience

International audience; center dot Mesophyll conductance (g(m)) is an important factor limiting rates of C-3 photosynthesis. However, its role in C-4 photosynthesis is poorly understood because it has been historically difficult to estimate.center dot We use two methods to derive the temperature responses of g(m) in C-4 species. The first (Delta O-18 combines measurements of gas exchange with models and measurements of O-18 discrimination. The second method (in vitro V-pmax) derives g(m) by retrofitting models of C-4 photosynthesis and C-13 discrimination with gas exchange, kinetic constants and in vitro V-pmax measurements.center dot The two methods produced similar g(m) for Setaria viridis and Zea mays. Additionally, we present the first temperature response (10-40 degrees C) of C-4 g(m) in S. viridis, Z. mays and Miscanthus x giganteus. Values for g(m) at 25 degrees C ranged from 2.90 to 7.85 mu molm(-2) s(-1) Pa-1.center dot Our study demonstrated that: the two described methods are suitable to calculate g(m) in C-4 species; g(m) values in C-4 are similar to high-end values reported for C-3 species; and g(m) increases with temperature analogous to reports for C-3 species and the response is species specific. These results improve our mechanistic understanding of C-4 photosynthesis.

International audience; Ingot punching tests are performed on the already formed solid shell of a 450 kg steel ingot during solidification. Such test is designed in order to be representative of the thermomechanical conditions that give rise to macrosegregation during secondary cooling in steel continuous casting. In order to understand the different physical phenomena, a numerical model of the test has been developed, consisting of a two-dimensional planar finite element simulation in the median section of the ingot. A two-phase formulation has been implemented, in which the velocities of the liquid and solid phases are concurrently solved for. The simulation shows how solutes are redistributed through the central mushy zone of the ingot under the effect of the compression of the solid phase and the induced fluid flow resulting from the punching of the solid shell. By comparison with measurements of macrosegregation operated on two ingots of same initial composition but punched under different conditions, the simulation proves its capacity to reproduce the main experimental trends. However the predicted intensity of macrosegregation is lower than the one measured. Through discussion and analysis of different numerical sensitivity tests, critical material parameters and model improvements are identified in view of attaining better quantitative predictions in the future.

International audience; There are numerous studies describing how growth conditions influence the efficiency of C-4 photosynthesis. However, it remains unclear how changes in the biochemical capacity versus leaf anatomy drives this acclimation. Therefore, the aim of this study was to determine how growth light and nitrogen availability influence leaf anatomy, biochemistry and the efficiency of the CO2 concentrating mechanism in Miscanthus x giganteus. There was an increase in the mesophyll cell wall surface area but not cell well thickness in the high-light (HL) compared to the low-light (LL) grown plants suggesting a higher mesophyll conductance in the HL plants, which also had greater photosynthetic capacity. Additionally, the HL plants had greater surface area and thickness of bundle-sheath cell walls compared to LL plants, suggesting limited differences in bundle-sheath CO2 conductance because the increased area was offset by thicker cell walls. The gas exchange estimates of phosphoenolpyruvate carboxylase (PEPc) activity were significantly less than the in vitro PEPc activity, suggesting limited substrate availability in the leaf due to low mesophyll CO2 conductance. Finally, leakiness was similar across all growth conditions and generally did not change under the different measurement light conditions. However, differences in the stable isotope composition of leaf material did not correlate with leakiness indicating that dry matter isotope measurements are not a good proxy for leakiness. Taken together, these data suggest that the CO2 concentrating mechanism in Miscanthus is robust under low-light and limited nitrogen growth conditions, and that the observed changes in leaf anatomy and biochemistry likely help to maintain this efficiency.

La discrimination est une notion juridique qui pénètre progressivement dans le corpus juridique français, dans le contentieux et dans le discours institutionnel mais non sans résistances. L’interdiction de la discrimination tire sa force de son ancrage en droit international et droit européen mais sa consécration interne ne garantit pas sa mise en oeuvre effective par les juridictions et les institutions; celles-ci se l’approprient mais manifestent parfois une certaine incompréhension de ce droit ou une certaine réserve sur son usage excessif. L’actualité illustre également une réaction au repérage des discriminations dans l’opinion publique et dans le discours institutionnel qui exprime une peur des dérives du multiculturalisme et des préoccupations économiques et sécuritaires. Objectifs de la recherche : Dans ce contexte, les auteurs de ce projet de recherche proposent une analyse pluridisciplinaire commune des politistes et juristes. L’objectif est de vérifier si les juges et les institutions confirment ces appréhensions à la mise en oeuvre de la non discrimination ou simplement investissent peu ce champ du droit pour privilégier la promotion d’instruments alternatifs de médiation ou de prévention des discriminations et de recherche, d’autres discours sur l’égalité et la cohésion sociale, issus de la soft law. Il s’agissait de faire ressortir, de manière transversale, les zones de résistances ou d’innovations dans la mise en oeuvre de la non discrimination par les juges et les institutions en France et aux Pays-Bas.La question n’était pas forcément de savoir si on trouve davantage de discriminations dans le contentieux mais plutôt de savoir comment la non discrimination est mobilisée. Méthodologie: L’intérêt de la recherche est l’ampleur de son champ et l’usage d’une grille de lecture commune pour les entretiens des politistes et des juristes. En science politique, il s’agissait d’analyser les enjeux politiques qui sous-tendent, à la fois les avancées et les résistances quant à la mise en œuvre du principe de non-discrimination en France et aux Pays-Bas. L’analyse juridique a recouvert des analyses jurisprudentielles en droit civil, administratif et en droit du travail français, complétées en droit administratif et en droit du travail par une analyse d’entretiens des juges notamment. Cette observation triangulaire a ensuite été enrichie par un dialogue interdisciplinaire et comparé des résultats obtenus. Principaux résultats : Le droit de la non-discrimination dans sa mise en oeuvre semble freiné par diverses disparités et ambivalences. Des ambivalences tiennent au décalage entre, d’un côté, la présence non négligeable du contentieux dans certains domaines (droit du travail, droit administratif) et la volonté d’introduire une action de groupe et d’autres critères (précarité sociale) et, de l’autre, la résistance des responsables institutionnels et des politiques à l’inflation du contentieux, la mobilisation de certains critères uniquement et l’absence de visibilité de certaines discriminations dans la jurisprudence. Est relevée une disparité entre un discours valorisant la prévention des discriminations et un discours de diversification des sanctions qui perdure pour les discriminations considérées les plus graves (racisme, antisémitisme). Se banalise un discours de simplification du droit qui contraste avec une complexité grandissante de l’acte discriminatoire prohibé (qui peut être plus subtile, implicite, multiple, systémique, couplé au harcèlement et à l’atteinte aux libertés). Cette ambivalence et ses disparités dans la mise en œuvre du droit de la non-discrimination semblent signifier l’absence d’une réelle politique antidiscriminatoire qui prendrait le « droit au sérieux », en dehors des actions du Défenseur des droits et de l’évolution vers l’adoption d’une action de groupe. La plupart des acteurs de la société civile et des responsables politiques interrogés cantonnent leur vision du combat à l’encontre de quelques discriminations (origine et sexe) en évoquant, le cas échéant, le critères de la précarité sociale qui vient d’être adopté. Cette perception reflète une absence de réflexion plus large sur la justification des autres critères discriminatoires et l’assimilation de la lutte contre les discriminations à une lutte sociale, plutôt qu’à un combat pour les droits fondamentaux de la personne.

International audience; An analytical model for growth in a semi-infinite matrix with cross-diffusion between species is presented. Application is given for precipitation of the-phase in the-matrix during isothermal holding at 600 °C in the Ni – 7.56 at.% Al – 8.56 at.% Cr alloy. The exact time-dependent solutions for the solute profiles and the growth kinetics are validated with a numerical front-tracking simulation. The simulation of cross diffusion terms in a multicomponent alloy is thus demonstrated. Extension of the analytical solution is given for growth in a matrix of finite size. The driving force is then based on a mathematical estimation of the far-field composition. The Gibbs-Thomson effect is also accounted for to consider the effect of curvature on the equilibrium tie-lines. Comparison of analytical solution with the numerical front-tracking simulation shows excellent agreement. Results also point out the detrimental approximation of using the average composition of the matrix for computing the driving force as well as the limitation of the solution proposed by Chen et al. [Acta Mater. 56 (2008) 1890]. A detailed discussion is finally given on the origin of oscillations observed for the time evolution of the precipitate radius which alternates between growth and dissolution regimes, pointing out the combined role of solute fluxes and tie-lines compositions at the precipitate/matrix interface.

International audience

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International audience; This paper reports on the quantification of primary dendritic and secondary eutectic nucleation undercoolings during rapid solidification of impulse atomized hypo-eutectic Al-Cu droplets. The procedure consists in determining the eutectic fraction of each investigated droplet from the fraction of intermetallic Al2Cu obtained by Rietveld refinement analysis of neutrons scattering data. The corresponding eutectic nucleation undercooling is then deduced from the metastable phase diagram of the alloy. The primary dendritic nucleation undercooling is subsequently determined using semi-empirical coarsening models of secondary dendrite arms. The two nucleation undercoolings are finally used as input variables to run a microsegregation model for binary alloys. The fractions of eutectic computed by the microsegregation model compare very favorably with the experimental results.

International audience; Experimental and numerical studies of hot tearing formation in steel are reported. On the one hand, an ingot punching test is presented. It consists in the application of a deformation at the surface of a solidifying 450 kg steel ingot. The experimental parameters are the displacement of the pressing tool, together with its velocity, leading to variations of a global strain rate. On the other hand, three-dimensional finite element thermomechanical modeling of the test is used. The time evolution of the strain tensor serves to compute an index to evaluate the susceptibility to create hot tears. It is based on the integration of a hot tearing criterion (HTC) that compares the local accumulation of strain with the expression of a critical value proposed in the literature. The main variable of the criterion is the brittleness temperature range (BTR) that refers to the solidification interval during which strain accumulates and creates hot cracks or tears. Detailed comparison of the simulation results with the measurements reveals the importance of the BTR for the prediction as well as excellent capabilities of the HTC to predict the formation of hot tears.

International audience; Solidification grain structure has significant impact on the final properties of welded parts using fusion welding processes. Direct simulation of grain structure at industrial scale is yet rarely reported in the literature and remains a challenge. A three-dimensional (3D) coupled Cellular Automaton (CA) – Finite Element (FE) model is presented that predicts the grain structure formation during multiple passes Gas Tungsten Arc Welding (GTAW) and Gas Metal Arc Welding (GMAW). The FE model is established in a level set (LS) approach that tracks the evolution of the metal-shielding gas interface due to the addition of metal. The FE method solves the mass, energy and momentum conservation equations for the metal plus shielding gas system based on an adaptive mesh (FE mesh). Fields are projected in a second FE mesh, named CA mesh. A CA grid made of a regular lattice of cubic cells is created to overlay the fixed CA mesh. The CA model based on the CA grid simulates the melting and growth of the grain boundaries in the liquid pool. In order to handle large computational domains while keeping reasonable computational costs, parallel computations and dynamic strategies for the allocation/deallocation of the CA grid are introduced. These strategies correspond to significant optimizations of the computer memories that are demonstrated. The 3D CAFE model is first applied to the simple configuration of single linear passes by GTAW of a duplex stainless steel URANUS 2202. It is then applied to a more persuasive example considering GMAW in spray transfer mode during multiple passes to fill a V-groove chamfer. Simulations reveal the possibility to handle domains with millions of grains in representative domain sizes while following the formation of textures that result from the growth competition among columnar grains

International audience; A three dimensional model for material deposition in Selective Laser Melting (SLM) with application to Al2O3-ZrO2 eutectic ceramic is presented. As the material is transparent to laser, dopants are added to increase the heat absorption efficiency. Based on Beer-Lambert law, a volumetric heat source model taking into account the material absorption is derived. The Level Set method with multiphase homogenization is used to track the shape of deposed bead and the thermodynamic is coupled to calculate the melting-solidification path. The shrinkage during consolidation from powder to compact medium is modeled by a compressible Newtonian constitutive law. A semi-implicit formulation of surface tension is used, which permits a stable resolution to capture the gas-liquid interface. The formation of droplets is obtained and slight waves of melt pool are observed. The influence of different process parameters on temperature distribution, melt pool profiles and bead shapes is discussed.

La discrimination est une notion juridique qui pénètre progressivement dans le corpus juridique français, dans le contentieux et dans le discours institutionnel, mais non sans résistances. L’interdiction de la discrimination tire sa force de son ancrage dans le droit international et le droit européen ; pour autant, sa consécration interne ne garantit pas sa mise en œuvre effective par les juridictions et les institutions. Celles-ci se l’approprient tout en exprimant des réserves quant à sa définition et ses usages. Dans un contexte se caractérisant par des préoccupations économiques et sécuritaires, la lutte contre les discriminations est perçue, par l’opinion publique et le discours institutionnel, à la fois, comme étant nécessaire et à préserver des dérives du multiculturalisme.La recherche effectuée propose une analyse pluridisciplinaire en droit (droit civil, droit administratif et droit du travail) et en science politique. L’étude a posé la question de savoir si les juges et les acteurs politiques expriment ce type d’appréhensions vis-à-vis de la non-discrimination ou simplement investissent peu ce champ pour privilégier la promotion d’instruments alternatifs tels que la soft law (bonnes pratiques, RSE, chartes et labels), la médiation et la prévention. En croisant des résultats issus d’analyses jurisprudentielles, d’une enquête qualitative et d’une étude des discours publics, la recherche fait ressortir, de manière transversale, les zones de résistances ou d’innovations dans la mise en œuvre de la non-discrimination par les juges et les acteurs politiques (responsables politiques, institutionnels, associatifs et syndicaux) en France et aux Pays-Bas.

International audience

International audience

International audience; Le soudage par friction malaxage (FSW) des alliages d’aluminium apparait comme un procédé particulièrement prometteur pour l’assemblage des fuselages en aéronautique. Notamment, la réalisation des liaisons entre la peau (nuance AA2024) et les lisses (nuance AA7075) devrait en bénéficier, en amenant un gain de poids conséquent, comparativement aux procédés de rivetages actuellement utilisés. Néanmoins, ces alliages d’aluminium tirent leurs propriétés mécaniques élevées du durcissement structural, correspondant à la formation de précipités fins et dispersés. Le procédé FSW induit dans les pièces des évolutions thermiques qui affectent les propriétés mécaniques finales du joint soudé. Afin d’améliorer leur prédiction, un modèle de précipitation, multicomposé et multiphasé, est développé, suivant l’approche originellement proposée par Myhr et Grong [1]. Celui-ci est basé sur une approche par classe (particle size distribution - PSD), permettant le suivi des populations des précipités présents. Il intègre les étapes de germination, croissance, dissolution et maturation propre aux phases stable (S-¬Phase) et métastable (GPB zones) [2] étudiées ici dans l’alliage AA2024. Cette modélisation est couplée à des calculs d’équilibres thermodynamiques [3]. Elle a bénéficié d’une calibration soignée, basée sur des essais DSC (Differential Scanning Calorimetry) permettant de déterminer les densités initiales des précipités et d’estimer les valeurs des paramètres guidant leur germination (Fig. a). A l’échelle spatiale du procédé, les évolutions thermiques des domaines composant la soudure sont déduites d’un modèle macroscopique [4]. En conséquence, l’approche proposée simule le processus de précipitation sur l’ensemble du cycle de soudage et décrit l’évolution des densités et tailles de précipités dans les domaines affectés thermiquement (ZAT), thermo-mécaniquement (ZATM) et dans le noyau [5]. Par la suite, un modèle de prédiction des propriétés mécaniques, calibré sur la base d’essais de traitements isothermes, a été appliqué pour estimer précisément la dureté associée aux distributions de précipités. Les comparaisons des résultats simulés et mesurés ont validé cette approche (Fig. b) et les démarches de calibrations proposées.[1]O.R. Myhr, Ø. Grong, Modelling of non-isothermal transformations in alloys containing a particle distribution, Acta Materialia, vol. 48, pp. 1605, 2000.[2]C. Genevois, A. Deschamps, A. Denquin, B. Doisneau-Cottignies, Quantitative investigation of precipitation and mechanical behaviour for AA2024 friction stir welds, Acta Materialia, vol. 53, pp.2447, 2005.[3]TCAL3, TCS Al-based alloys thermodynamic database, Thermo-Calc software AB (Stockholm, Sweden), 2014.[4]S. Gastebois, Simulation numérique 3D du FSW à l’aide d'une formulation ALE, Doctorat Mines Paristech, 2015.[5]V. Legrand, Modélisation des processus de précipitation et prédiction des propriétés mécaniques résultantes dans les alliages d’aluminium à durcissement structural – Application au soudage par Friction Malaxage (FSW) de tôles AA2024, Doctorat MinesParisTech, 2015

International audience; Segregation is a key phenomenon responsible for altering alloys' properties during solidi-fication. The factors that lead to solute partitioning at the scale of the solidified parts are related to movements of liquid and solid phases. However, when considering a reduced gravitational field, convection forces become less significant compared to other factors. Consequently, predicting segregation in this context requires considering other prevailing driving forces, namely solidification shrinkage that arises from the density difference be-tween the liquid and solid phases. We propose a numerical model that accounts for energy conservation via a thermodynamic database, together with fluid momentum conserva-tion and species conservation to predict segregation driven by solidification shrinkage in a multicomponent alloy. We apply it on a specific steel grade for which reduced-gravity experiments were performed via parabolic flights.

International audience

International audience; Ozone, one of the major atmospheric pollutants, alters tree growth, mainly by decreasing carbon assimilation and allocation to stems and roots. To date, the mechanisms of O-3 impact at the cellular level have been investigated mainly on young trees grown in controlled or semi-controlled conditions. In the context of climate change, it is necessary to introduce a valuable defence parameter in the models that currently predict O-3 impact on mature trees and the carbon sequestration capacity of forest ecosystems.Air pollution is an important factor that affects negatively forest ecosystems. Among oxidative air pollutants, ozone is considered as the most toxic in terms of impact on vegetation.This paper focuses on the negative impacts of ozone on trees in controlled conditions or in their natural environment. The current knowledge of the responses at cell level is presented and ways to improve their use for ozone risk assessment of forest stands are discussed.Information was collected from original papers or reviews, providing an overview of the research conducted over the last 60 years.The negative effects of ozone on carbon assimilation and tree biomass production were reviewed and discussed, with a focus on effects on cell processes implied in cell defence, including stomatal regulation, detoxification, signalling, and biosynthesis of wood compound.In the context of increasing significance of O-3 flux approach, this review intends to shed light into the black box of defence processes, which are playing a crucial part within the effective O-3 dose modelling. Today, it is recognized that tropospheric ozone inhibits tree growth and its role on the future carbon sink of the forest ecosystem is discussed along with the combination of other environmental factors like elevated temperature, water, and nitrogen supply, likely to be modified in the context of climate change.

Les auteur.e.s de ce projet de recherche proposent une analyse pluridisciplinaire articulant le droit et la science politique. L’objectif est d’analyser si les juges et les institutions expriment des appréhensions à la mise en oeuvre de la non-discrimination ou s’ils investissent peu ce champ du droit pour privilégier la promotion d’instruments alternatifs de médiation ou de prévention des discriminations en promouvant d’autres discours sur l’égalité et la cohésion sociale, tels que ceux de la soft law. Cette problématisation a été enrichie par une mise en perspective grâce à une étude de la mise en oeuvre de la non-discrimination aux Pays-Bas. [extrait de la note de synthèse]

International audience; The photosynthetic assimilation of CO2 in C-4 plants is potentially limited by the enzymatic rates of Rubisco, phosphoenolpyruvate carboxylase (PEPc), and carbonic anhydrase (CA). Therefore, the activity and kinetic properties of these enzymes are needed to accurately parameterize C-4 biochemical models of leaf CO2 exchange in response to changes in CO2 availability and temperature. There are currently no published temperature responses of both Rubisco carboxylation and oxygenation kinetics from a C-4 plant, nor are there known measurements of the temperature dependency of the PEPc Michaelis-Menten constant for its substrate HCO3-, and there is little information on the temperature response of plant CA activity. Here, we used membrane inlet mass spectrometry to measure the temperature responses of Rubisco carboxylation and oxygenation kinetics, PEPc carboxylation kinetics, and the activity and first-order rate constant for the CA hydration reaction from 10 degrees C to 40 degrees C using crude leaf extracts from the C-4 plant Setaria viridis. The temperature dependencies of Rubisco, PEPc, and CA kinetic parameters are provided. These findings describe a new method for the investigation of PEPc kinetics, suggest an HCO3- limitation imposed by CA, and show similarities between the Rubisco temperature responses of previously measured C-3 species and the C-4 plant S. viridis.

International audience; Formation of grain structure and segregation during solidification of refined Al–7 wt.%Si alloys under microgravity is simulated using a two-dimensional axi-symmetrical Cellular Automaton-Finite Element (CAFE) solidification model. This fully integrated model resolves a complex interplay between heat transfer at the macroscale and grain structure evolution and microsegregation formation at the mesoscale. Direct comparison with benchmark experiments performed under microgravity conditions of the International Space Station is carried out. Boundary conditions used in the simulations are deduced from the experimental measurements of temperature. Qualitative agreement is achieved concerning CET (columnar-to-equiaxed transition) position, CET transition mode (sharp or progressive), distributions of grain elongation factor and equivalent diameter, and distribution of eutectic fraction. The influences of pulling velocity and thermal gradient on grain structure and intergranular segregation are correctly reflected and are discussed. Moreover, we take advantage of the simulation results to study the effect of otherwise inaccessible parameters such as the degree of constitutional undercooling and the amplitude of the undercooled region. Another originality of this paper is to conduct quantitative comparisons between experiments and simulations which allows discussion of the improvements needed in the simulation.

International audience; In solidification processes of large industrial castings and ingots, the transport of solid in the liquid has an important effect on the final grain structure and macrosegregation. Modeling is still challenging as complex interactions between heat and mass transfers at microscopic and macroscopic scales are highly coupled. This paper first presents a multi-scale numerical solidification model coupling nucleation, grain growth and solute diffusion at microscopic scales with heat and mass transfer, including transport of liquid and solid phases at macroscopic scales. The resolution consists of a splitting method, which considers the evolution and interaction of quantities during the process with a transport stage and a growth stage. This splitting reduces the nonlinear complexity of the set of considered equations and provides an efficient numerical implementation. It is inspired by the work of Založnik et al. [1,2], which used a finite volume method (FVM). The present work develops the solution based on the finite element method (FEM). Numerical results obtained with this model are presented and simulations without and with grain transport are compared to study the impact of solid-phase transport on the solidification process and on the formation of macrosegregation.

International audience; Ingot bending tests are performed on the already formed solid shell of a 450 kg solidifying ingot. It is designed in order to be representative of two defects occurring during secondary cooling in steel continuous casting: hot tearing and macrosegregation. Ingots show the defects which result from the application of bending. In order to understand the different physical phenomena, finite element numerical modelling of the test has been developed, using two different approaches. A first approach consists of a 3D finite element thermomechanical simulation. Hot tearing criteria, based on strain, strain rate and two values for solid fraction are then evaluated. It is demonstrated that such a strain based criterion has an excellent capability to predict the formation of hot tears. A second approach consists of a 2D planar finite element simulation in the median section of the ingot. A two-phase formulation is used, in which the velocity of the liquid and solid phases are distinguished. The simulation shows how solutes are redistributed through the ingot under the effect of bending. Solute-depleted and enriched regions are well reproduced, but peak values of macrosegregation are underestimated.

International audience; The impulse atomization process developed at the University of Alberta (Canada) enables metallic powders to be solidified with well controlled process parameters. The inner microstructure of several droplets of Al–4.5 wt.%Cu alloy produced by this technique has been investigated by using both synchrotron X-ray micro-tomography and electron backscattered diffraction (EBSD). The 3D reconstructions obtained by micro-tomography are used to visualize cross sections of the droplets in any spatial directions. A wide range of dendrite morphologies are observed for different droplets of similar diameter and produced in the same batch. Microstructural features indicate that the development of the dendrite arms (primary and of higher orders) occurs in most droplets along 〈1 1 1〉 crystallographic axes. This was unexpected as 〈1 0 0〉 directions are observed in conventional casting technologies. EBSD measurements were carried out on a selection of representative droplets after their characterization by synchrotron X-ray micro-tomography. Results confirm that most of the droplets are single grains and the relationship between the dendrite growth directions and the crystal orientation is determined unambiguously. Moreover, the large number of droplets analyzed by micro-tomography enabled a statistical analysis of the dendrite morphology as a function of droplet size and cooling atmosphere. The impact of different processing parameters on the final distribution of dendrite morphologies is also discussed.