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Benthic Dinoflagellate Integrator (BEDI): A new method for the quantification of Benthic Harmful Algal Blooms
No full textInternational audienceDespite the potential negative human health, ecological and economic impact, the ecology of harmful benthic dinoflagellate blooms remains largely unknown. This is probably due to the complex interactions among biotic and abiotic drivers that influence blooms, but also to the difficulty in quantifying cell abundance in a comparable way over large spatial and temporal scales. One of the recognized priorities for bHABs (benthic Harmful Algal Blooms) assessment is developing and standardizing methods that can provide comparable data. In this context, the Benthic Dinoflagellates Integrator (BEDI), a new non-destructive quantification method for benthic dinoflagellate abundances, has been developed and tested within the present study. The rationale behind the BEDI standard assessment method is that mechanical resuspension of cells enables the quantification of abundances as cells per unit of seabed surface area (i.e. cells mm−2) or as Potentially Resuspended cells per unit of volume (PRcells ml−1), by integrating both cells in the biofilm and those in the surrounding water. Estimations of Ostreopsis performed with BEDI method are independent of the substratum (i.e. macroalgal species) or the dominant ecosystem (i.e. algal forests or turfs, seagrass beds, coral reefs) and potentially allow the comparison of benthic dinoflagellate blooms over broad temporal and spatial scales. The first application of the BEDI method, presented in this study, gave encouraging results: the characterization of blooms of Ostreopsis cf. ovata at three sites in the NW Mediterranean Sea is consistent with results derived from the other commonly applied methods. Quantification of the ratio between abundances of cells in the biofilm and in the surrounding water was calculated for the first time per unit of seabed surface area, demonstrating that the highest abundances of cells (the stock), and therefore the associated risk for human health, are in the biofilm. For risk assessment purposes, conversion values for commonly used monitoring alert thresholds of Mediterranean Ostreopsis blooms are provided
Mieux comprendre la persévérance dans l'enseignement supérieur en France dans la transition lycée - études supérieures
No full textThis thesis aims at a better understanding of perseverance in the first year of higher education.Before and after this period, two series of semi-directive interviews were led with 47 individuals,built from the model of the integration of the student (Tinto, 1999) and the concept of studies types(Lahire, 1997). Their analyses, combining qualitative and quantitative methods, explain theprocesses related to perseverance by showing significant links with some pre-admission factors andthe majority of the student experiment factors. The results differentiate four types of perseverance,defined according to two criteria: the success / academic failure and perseverance in the samecourse / reorientation in another higher education institution.Cette thèse vise à mieux comprendre la persévérance en première année d'études supérieures. Avantet après cette période, deux séries d'entretiens semi-directifs sont menés auprès de 47 individus,construits à partir du modèle de l'intégration de l'étudiant de Tinto (1999) et du concept de typed'études de Lahire (1997). Leurs analyses combinant méthodes qualitatives et quantitatives montrentles processus mis en oeuvre dans la persévérance en montrant des liens significatifs avec certainsfacteurs de pré-admission et la majorité des facteurs relatifs à l'expérience étudiante. Les résultatsdifférencient quatre types de persévérance, définis en fonction de deux critères : la réussite/l'échecacadémique et la persévérance dans le même cursus/réorientation dans d'autres études supérieures
Le contrat de PPP à l’épreuve des contentieux : Retours d’expériences sur le cas français
No full textDocument de travail Chaire EPPP 2017-1Public-private partnerships are characterised by specific features (duration, complexity…) favouring disputes among the two partners and with third parties in both contracting in operating stages. Mostly based on the French experience of the contrats de partenariat, this paper first investigates the disputes between the public and private partners (renegotiations and early termination cases…) before considering in a second part the litigations initiated by unsuccessful candidates or other stakeholders opposed to the project. Our contribution finally tackles the issue of the contractual provisions introduced to deal with these legal risks and presents their potential consequences for the public partner.Contrats de long terme portant sur des services complexes, les partenariats public-privé peuvent donner lieu à des différends entre les contractants ou avec d’autres parties prenantes tant dans leurs phases de passation que d’exécution. Se fondant principalement sur le cas des contrats de partenariat français, cette contribution s’attache successivement aux différends entre les deux partenaires, en abordant les cas des renégociations et des résiliations contractuelles, avant de s’attacher aux contentieux initiés par des tiers, qu’il s’agisse de candidats évincés ou d’autres parties prenantes entamant des recours contre les contrats. Elle porte enfin sur la gestion par les partenaires du risque juridique lié aux recours et à ses éventuelles conséquences pour la personne publique
Les ruptures de suivi dans le diabète de grossesse: Approche sociologique.
No full textInternational audienceObjectif Ma recherche doctorale est centrée sur l’analyse des ruptures de suivi au cours de la prise en charge du diabète gestationnel. L’objectif est de comprendre comment et pourquoi la relation de soin abouti parfois à la rupture lors de ce suivi. Si la migration, l’appartenance culturelle ou la classe sociale sont des facteurs intervenant dans la trajectoire de la maladie , c’est plus précisément sous l’angle de la relation sociale que nous abordons ces critères.En particulier, nous analysons les processus de différenciations ethniques et sociales, en tant que phénomènes d’altérisation, qui émaillent la relation soignant-soigné, et leur implication dans les ruptures de suivi.Méthodes proposéesCette recherche repose sur des méthodes qualitatives. Elle est basée sur l’observation de consultations médicales et sur des entretiens sociologiques approfondis avec les soignants et les soignées. L’enquête se déroule dans deux maternités publiques d’île-de-France. Résultats -La notion « d’observance » pour les soignants est abordée dans une approche behavioriste, c’est-à-dire centrée sur les comportements des patientes qui doivent être améliorés . Elle n’est jamais abordée sous l’angle de la relation soignant-soigné.-Des processus d’ethnicisation et de différenciation sociale sous-tendent l’analyse de « l’inobservance » par les soignants. -Pour les patientes désignées comme « étrangères » ou perçues comme « précaires », il existe un phénomène de censure. La distance sociale entre le soignant et la patiente est source dé-légitimation. -Dans ce contexte, les ruptures de suivi peuvent être comprises comme une forme de résolution d’un conflit soignant-soigné
A deeper view of the CoRoT-9 planetary system. A small non-zero eccentricity for CoRoT-9b likely generated by planet-planet scattering
No full textInternational audienceCoRoT-9b is one of the rare long-period (P=95.3 days) transiting giant planets with a measured mass known to date. We present a new analysis of the CoRoT-9 system based on five years of radial-velocity (RV) monitoring with HARPS and three new space-based transits observed with CoRoT and Spitzer. Combining our new data with already-published measurements we redetermine the CoRoT-9 system parameters and find good agreement with the published values. We uncover a higher significance for CoRoT-9b's small but non-zero eccentricity () and find no evidence for additional planets in the system. We use simulations of planet-planet scattering to show that CoRoT-9b's eccentricity may have been generated by an instability in which a planet was ejected from the system. This scattering would not have produced a spin-orbit misalignment, so we predict that CoRoT-9b's orbit should lie within a few degrees of the initial plane of the protoplanetary disk. As a consequence, any significant stellar obliquity would indicate that the disk was primordially tilted
Optimal strokes for driftless swimmers: A general geometric approach
No full textInternational audienceSwimming consists by definition in propelling through a fluid by means of bodily movements. Thus, from a mathematical point of view, swimming turns into a control problem for which the controls are the deformations of the swimmer. The aim of this paper is to present a unified geometric approach for the optimization of the body deformations of so-called driftless swimmers. The class of driftless swimmers includes, among other, swimmers in a 3D Stokes flow (case of micro-swimmers in viscous fluids) or swimmers in a 2D or 3D potential flow. A general framework is introduced, allowing the complete analysis of five usual nonlinear optimization problems to be carried out. The results are illustrated with examples coming from the literature and with an in-depth study of a swimmer in a 2D potential flow. Numerical tests are also provided
Modélisation des équations d'Euler bi-températures pour les plasmas de fusion
No full textThis work deals with the modeling of fusion plasma by bi-temperature fluid models. First, using non-dimensional scaling of the governing equations, we give the assumptions leading to a bi-temperature model. Then we describe a finite volume method on non-structured meshes to approximate the solutions of this model. The method relies on a relaxation scheme to solve the Riemann problem at the interfaces. The description of the finite volume method that uses the strong conservative form of the equations is given both in Cartesian as well as in cylindrical coordinate systems useful to compute flows inside a torus. Several numerical tests in Cartesian and cylindrical coordinate systems and in different geometries are presented in order to validate the numerical method
Volet juridique de la création d’un site d’escalade en moyenne montagne : l’exemple du site d’escalade de la Tour-sur-Tinée (AlpesMaritimes)
No full textInternational audienceDans le cadre de sa politique sportive et de la diversification de ses activités touristiques, la commune de la Toursur-Tinée a souhaité sécuriser et pérenniser l’usage d’un site d’escalade. Celui-ci se caractérise par la nature de la roche, du grès, et par son potentiel important : une configuration des falaises en forme de V, de 2,5 km de longueur pour chaque côté, avec des hauteurs pouvant atteindre 160 mètres. Ces particularités en font un lieu rare dans les Alpes-Maritimes, qui est utilisé depuis quelques années, autant par des amateurs éclairés, que par des professionnels (PGHM, guides). Aussi bien, la municipalité a-t-elle décidé de sécuriser et de pérenniser la pratique. • Sécuriser la pratique par la maîtrise foncière (accès et gestion) : Le foncier, support des activités sportives de nature, fait l’objet de diverses réglementations qui doivent être prises en compte, dès la décision d’ouverture d’un site sportif. La multiplication des dispositifs d’encadrement aux finalités variées (règles d’utilisation des sols, protection environnementale, droit des propriétaires, notamment) imposent une analyse foncière précise du site. Celle-ci conditionnera le principe et les modalités d’ouverture de celui-ci
Multidimensional Riemann Problem with Self-Similar Internal Structure – Part III– A Multidimensional Analogue of the HLLI Riemann Solver for Conservative Hyperbolic Systems
No full textJust as the quality of a one-dimensional approximate Riemann solver is improved by the inclusion of internal sub-structure, the quality of a multidimensional Riemann solver is also similarly improved. Such multidimensional Riemann problems arise when multiple states come together at the vertex of a mesh. The interaction of the resulting one-dimensional Riemann problems gives rise to a strongly-interacting state. We wish to endow this strongly-interacting state with physically-motivated sub-structure. The fastest way of endowing such sub-structure consists of making a multidimensional extension of the HLLI Riemann solver for hyperbolic conservation laws. Presenting such a multidimensional analogue of the HLLI Riemann solver with linear sub-structure for use on structured meshes is the goal of this work. The multidimensional MuSIC Riemann solver documented here is universal in the sense that it can be applied to any hyperbolic conservation law. The multidimensional Riemann solver is made to be consistent with constraints that emerge naturally from the Galerkin projection of the self-similar states within the wave model. When the full eigenstructure in both directions is used in the present Riemann solver, it becomes a complete Riemann solver in a multidimensional sense. I.e., all the intermediate waves are represented in the multidimensional wave model. The work also presents, for the very first time, an important analysis of the dissipation characteristics of multidimensional Riemann solvers. The present Riemann solver results in the most efficient implementation of a multidimensional Riemann solver with sub-structure. Because it preserves stationary linearly degenerate waves, it might also help with well-balancing. Implementation-related details are presented in pointwise fashion for the one-dimensional HLLI Riemann solver as well as the multidimensional MuSIC Riemann solver. Several stringent test problems drawn from hydrodynamics, MHD and relativistic MHD are presented to show that the method works very well on structured meshes. Our results demonstrate the versatility of our method. The reader is also invited to watch a vide