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Search Results: 1 - 10 of 335032 matches for " Héléna Revil "
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Le changement incrémental et par le bas d’un système de gestion des droits : le cas de la complémentaire santé gratuite ou aidée en France
Héléna Revil
Pyramides : Revue du Centre d'Etudes et de Recherches en Administration Publique , 2011,
Abstract: En France, l’accès aux droits sociaux des populations précaires constitue l’une des orientations stratégiques actuelles de la Sécurité sociale. L’affichage politique affirme une volonté d’organiser le système de prestations autour de l’amélioration de l’accès pour tous et les Conventions d’objectifs et de gestion (COG – NDLR : une liste des acronymes se trouve en fin d’article) signées entre l’Etat et les organismes nationaux de la Sécurité sociale avancent comme prioritaires des objectifs d’amélioration de l’accès des personnes précaires à leurs droits. Au-delà des objectifs affichés, observe-t-on un changement dans les pratiques de gestion des droits par les organismes sociaux chargés de rendre effectif cet accès ? Cette communication s’appuie sur un projet local impliquant des organismes sociaux et de recherche qui a produit une méthode de détection du non recours à deux dispositifs de l’Assurance maladie. L’auteure cherche à déterminer si ce projet constitue ou participe d’un changement en matière de gestion des droits par la branche Maladie de la Sécurité sociale.
A new formulation to compute self-potential signals associated with ground water flow
A. Bolève,A. Revil,F. Janod,J. L. Mattiuzzo
Hydrology and Earth System Sciences Discussions , 2007,
Abstract: The classical formulation of the coupled hydroelectrical flow in porous media is based on a linear formulation of two coupled constitutive equations for the electrical current density and the seepage velocity of the water phase and obeying Onsager's reciprocity. This formulation shows that the streaming current density is controlled by the gradient of the fluid pressure of the water phase and a streaming current coupling coefficient that depends on the so-called zeta potential. Recently a new formulation has been introduced in which the streaming current density is directly connected to the seepage velocity of the water phase and to the excess of electrical charge per unit pore volume in the porous material. The advantages of this formulation are numerous. First this new formulation is more intuitive not only in terms of constitutive equation for the generalized Ohm's law but also in specifying boundary conditions for the influence of the flow field upon the streaming potential. With the new formulation, the streaming potential coupling coefficient shows a decrease of its magnitude with permeability in agreement with published results. The new formulation is also easily extendable to non-viscous laminar flow problems (high Reynolds number ground water flow in cracks for example) and to unsaturated conditions with applications to the vadose zone. We demonstrate here that this formulation is suitable to model self-potential signals in the field. We investigate infiltration of water from an agricultural ditch, vertical infiltration of water into a sinkhole, and preferential horizontal flow of ground water in a paleochannel. For the three cases reported in the present study, a good match is obtained between the finite element simulations performed with the finite element code Comsol Multiphysics 3.3 and field observations. Finally, this formulation seems also very promising for the inversion of the geometry of ground water flow from the monitoring of self-potential signals.
Impacts of changes in vegetation cover on soil water heat coupling in an alpine meadow of the Qinghai-Tibet Plateau, China
W. Genxu, H. Hongchang, L. Guangsheng,L. Na
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 2009,
Abstract: Alpine meadow is one of the most widespread grassland types in the permafrost regions of the Qinghai-Tibet Plateau, and the transmission of coupled soil water heat is one of the most crucial processes influencing cyclic variations in the hydrology of frozen soil regions, especially under different vegetation covers. The present study assesses the impact of changes in vegetation cover on the coupling of soil water and heat in a permafrost region. Soil moisture (θv), soil temperature (Ts), soil heat content, and differences in θv Ts coupling were monitored on a seasonal and daily basis under three different vegetation covers (30, 65, and 93%) on both thawed and frozen soils. Regression analysis of θv vs. Ts plots under different levels of vegetation cover indicates that soil freeze-thaw processes were significantly affected by the changes in vegetation cover. The decrease in vegetation cover of an alpine meadow reduced the difference between air temperature and ground temperature (ΔTa s), and it also resulted in a decrease in Ts at which soil froze, and an increase in the temperature at which it thawed. This was reflected in a greater response of soil temperature to changes in air temperature (Ta). For ΔTa s outside the range of 0.1 to 1.0°C, root zone soil-water temperatures showed a significant increase with increasing ΔTa s; however, the magnitude of this relationship was dampened with increasing vegetation cover. At the time of maximum water content in the thawing season, the soil temperature decreased with increasing vegetation. Changes in vegetation cover also led to variations in θv Ts coupling. With the increase in vegetation cover, the surface heat flux decreased. Soil heat storage at 20 cm in depth increased with increasing vegetation cover, and the heat flux that was downwardly transmitted decreased. The soil property varied greatly under different vegetation covers, causing the variation of heat conductivity and water-heat hold capacity in topsoil layer in different vegetation cover. The variation of heat budget and transmitting in soil is the main factor that causes changes in soil thawing and freezing processes, and θv Ts coupling relationship under different vegetation fractions. In addition to providing insulation against soil warming, vegetation in alpine meadows within the permafrost region also would slow down the response of permafrost to climatic warming via the greater water-holding capacity of its root zone. Such vegetation may therefore play an important role in conserving water in alpine meadows and maintaining the stability of engineering works constructed within frozen soil of the Qinghai-Tibet Plateau.
Heat transport through quantum Hall edge states: Tunneling versus capacitive coupling to reservoirs
H. Aita,L. Arrachea,C. Naón,E. Fradkin
Physics , 2013, DOI: 10.1103/PhysRevB.88.085122
Abstract: We study the heat transport along an edge state of a two-dimensional electron gas in the quantum Hall regime, in contact to two reservoirs at different temperatures. We consider two exactly solvable models for the edge state coupled to the reservoirs. The first one corresponds to filling $\nu=1$ and tunneling coupling to the reservoirs. The second one corresponds to integer or fractional filling of the sequence $\nu=1/m$ (with $m$ odd), and capacitive coupling to the reservoirs. In both cases we solve the problem by means of non-equilibrium Green function formalism. We show that heat propagates chirally along the edge in the two setups. We identify two temperature regimes, defined by $\Delta$, the mean level spacing of the edge. At low temperatures, $T< \Delta$, finite size effects play an important role in heat transport, for both types of contacts. The nature of the contacts manifest themselves in different power laws for the thermal conductance as a function of the temperature. For capacitive couplings a highly non-universal behavior takes place, through a prefactor that depends on the length of the edge as well as on the coupling strengths and the filling fraction. For larger temperatures, $T>\Delta$, finite-size effects become irrelevant, but the heat transport strongly depends on the strength of the edge-reservoir interactions, in both cases. The thermal conductance for tunneling coupling grows linearly with $T$, whereas for the capacitive case it saturates to a value that depends on the coupling strengths and the filling factors of the edge and the contacts.
Forward Modeling and validation of a new formulation to compute self-potential signals associated with ground water flow
A. Bolève, A. Revil, F. Janod, J. L. Mattiuzzo,A. Jardani
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 2007,
Abstract: The classical formulation of the coupled hydroelectrical flow in porous media is based on a linear formulation of two coupled constitutive equations for the electrical current density and the seepage velocity of the water phase and obeying Onsager's reciprocity. This formulation shows that the streaming current density is controlled by the gradient of the fluid pressure of the water phase and a streaming current coupling coefficient that depends on the so-called zeta potential. Recently a new formulation has been introduced in which the streaming current density is directly connected to the seepage velocity of the water phase and to the excess of electrical charge per unit pore volume in the porous material. The advantages of this formulation are numerous. First this new formulation is more intuitive not only in terms of establishing a constitutive equation for the generalized Ohm's law but also in specifying boundary conditions for the influence of the flow field upon the streaming potential. With the new formulation, the streaming potential coupling coefficient shows a decrease of its magnitude with permeability in agreement with published results. The new formulation has been extended in the inertial laminar flow regime and to unsaturated conditions with applications to the vadose zone. This formulation is suitable to model self-potential signals in the field. We investigate infiltration of water from an agricultural ditch, vertical infiltration of water into a sinkhole, and preferential horizontal flow of ground water in a paleochannel. For the three cases reported in the present study, a good match is obtained between finite element simulations performed and field observations. Thus, this formulation could be useful for the inverse mapping of the geometry of groundwater flow from self-potential field measurements.
Unusual plastic deformation and damage features in Titanium: experimental tests and constitutive modeling
Benoit Revil-Baudard,Oana Cazacu,Philip Flater,Nitin Chandola,J. L. Alves
Physics , 2015,
Abstract: In this paper, we present an experimental study on plastic deformation and damage of polycrystalline pure Ti, as well as modeling of the observed behavior. From the mechanical characterization data, it can be concluded that the material displays anisotropy and tension-compression asymmetry. As concerns damage, the X-ray tomography measurements conducted reveal that damage distribution and evolution in this HCP Ti material is markedly different than in a typical FCC material such as copper. Stewart and Cazacu (2011) anisotropic elastic/plastic damage model is used to describe the behavior. All material parameters involved in this model have a clear physical significance, being related to plastic properties, and are determined based on very few simple mechanical tests. It is shown that this model predicts correctly the anisotropy in plastic deformation, and its strong influence on damage distribution and damage accumulation in Ti. Specifically, for a smooth axisymmetric specimen subject to uniaxial tension, damage initiates at the center of the specimen and is diffuse; the level of damage close to failure is very low. On the other hand, for a notched specimen subject to the same loading, the model predicts that damage initiates at the outer surface of the specimen, and further grows from the outer surface to the center of the specimen, which corroborates with the in-situ tomography data.
Thermal conductivity of unsaturated clay-rocks
D. Jougnot,A. Revil
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 2010,
Abstract: The parameters used to describe the electrical conductivity of a porous material can be used to describe also its thermal conductivity. A new relationship is developed to connect the thermal conductivity of an unsaturated porous material to the thermal conductivity of the different phases of the composite, and two electrical parameters called the first and second Archie's exponents. A good agreement is obtained between the new model and thermal conductivity measurements performed using packs of glass beads and core samples of the Callovo-Oxfordian clay-rocks at different saturations of the water phase. We showed that the three model parameters optimised to fit the new model against experimental data (namely the thermal conductivity of the solid phase and the two Archie's exponents) are consistent with independent estimates. We also observed that the anisotropy of the effective thermal conductivity of the Callovo-Oxfordian clay-rock was mainly due to the anisotropy of the thermal conductivity of the solid phase.
Thermal conductivity of unsaturated clay-rocks
D. Jougnot,A. Revil
Hydrology and Earth System Sciences Discussions , 2008,
Abstract: The thermal conductivity of porous materials can be related to the electrical conductivity and therefore electrical resistivity tomography can be used to map the thermal conductivity of porous rocks. In this paper, a relationship is developed to connect the thermal conductivity of unsaturated clay-rocks to the thermal conductivity of the different phases of the porous composite, a textural parameter called the thermal formation factor, and the tortuosity of the water phase. The thermal formation factor is related to the electrical formation factor and to the first Archie's first exponent m. The tortuosity of the water phase is related to the second Archie's exponent n and to the relative saturation of the water phase. A very good agreement is obtained between the new model and thermal conductivity measurements of packs of glass beads and cores of the Callovo-Oxfordian argillite at different saturations of the water phase. Anisotropy of the effective thermal conductivity is mainly due to the anisotropy of the thermal conductivity of the solid phase.
Efeito da suplementa o da dieta com Spirulina platensis no crescimento e colora o de tilápia vermelha Efecto de la suplementación dietaria con Spirulina platensis en el crecimiento y la coloración de la tilapia roja Dietary supplementation with Spirulina platensis increases growth and color of red tilapia
Igor GRF Gomes,Felipe H Chaves,Rodrigo NA Barros,Ricardo L Moreira
Revista Colombiana de Ciencias Pecuarias , 2012,
Abstract: No cultivo de espécies aquáticas, uma nutri o adequada assume importancia fundamental no sucesso da atividade, principalmente nas fases iniciais de cria o, período em que os animais est o mais susceptíveis ao manejo err neo e mudan as bruscas do ambiente. Objetivo: o Objetivo deste trabalho foi avaliar a eficácia de Spirulina platensis como suplemento alimentar no crescimento e colora o de tilápia vermelha. Métodos: as tilápias foram cultivadas com ra o comercial (D1: controle), ra o comercial + Spirulina platensis úmida (D2), ra o comercial + Spirulina platensis seca (D3) e ra o comercial + microalgas de água doce (D4). Resultados: em rela o ao desempenho zootécnico, D2 obteve os melhores resultados. As taxas de sobrevivência alcan adas nos tratamentos D1, D2 e D3, foram superiores as alcan adas no tratamento D4 (p<0.05). Os índices de masculiniza o e gastrointestinais foram estatisticamente similares para todos os tratamentos (p<0.05). Os índices hepatossomáticos encontrados em D1 e D4 foram estatisticamente semelhantes (p<0.05), porém, ambos apresentaram valores abaixo dos encontrados em D2 e D3 (p<0.05). A intensidade da cor amarela de D2, após a extra o de pigmentos das peles dos peixes, apresentou-se moderada, enquanto em D3 a intensidade foi fraca (Abs 490 nm). Os extratos das peles dos peixes que n o consumiram S. platensis, apresentaram colora o muito fraca. As contagens das microalgas presentes na água verde de D1, realizadas através de microscopia óptica, revelou que a cianobactéria do gênero Microcystis apresentou 95% dominancia. Conclus es: os peixes alimentados com S. platensis, úmida ou seca, obtiveram desempenho superior e colora o mais forte que os animais expostos somente ao alimento artificial ou combinado com microalgas de água doce. A microalga marinha demonstrou ser um suplemento alimentar eficiente para tilápia vermelha. Sugerem-se estudos da rela o custo-benefício do cultivo e oferta de S. platensis para os peixes, desta forma elucidando as vantagens econ micas que esta prática poderá trazer para a tilapicultura comercial. En el cultivo de especies acuáticas, la nutrición adecuada es de importancia fundamental para el éxito de la actividad, especialmente durante las primeras etapas de la producción, período en que los animales son más susceptibles al mal manejo y a cambios ambientales repentinos. Objetivos: el propósito de este estudio fue evaluar la eficacia de la Spirulina platensis como suplemento alimenticio para el crecimiento y coloración de la tilapia roja. Métodos: las tilapias fueron cultivadas con alimento c
Complacência pulmonar com uma hora de vida e displasia broncopulmonar em recém-nascidos prematuros
Barros, Lídia Mayrink de;Guinsburg, Ruth;Miyoshi, Milton H;Peluzzo, Adriana V.;Figueira, Simone NA;Kopelman, Benjamin I;
Revista Brasileira de Saúde Materno Infantil , 2007, DOI: 10.1590/S1519-38292007000400006
Abstract: objectives: to evaluate whether early pulmonary compliance could be a predictor of the presence of bronchopulmonary dysplasia at 28 days of life in preterm infants. methods: a cohort study was carried out involving neonates with gestational age <32 weeks and a birth weight of 500-1250 g receiving prophylactic surfactant at 30 minutes of life. the lung mechanics was evaluated using a pneumotachograph connected to the ventilator circuit 60 minutes after birth. flow signals and volume were measured using wintracer? in order to determine the dynamic pulmonary compliance and the airway resistance. variables associated with the need for oxygen or assisted ventilation at 28 days were assessed using logistic regression. results: 32 neonates were enrolled in the study and 25 survived until the 28th day, at which point 17 (68%) needed assisted ventilation and/or oxygen (group 1), and 8 did not (group 2). the group 1 infants were younger, had higher clinical risk index scores and frequency of patent ductus arteriosus. the lung mechanics in the 1st hour of life was similar in groups 1 and 2. regression analysis showed that bronchopulmonary dysplasia was associated with the presence of patent ductus arteriosus and lower gestational age. conclusions: pulmonary compliance figures in the 1st hour of life did not predict the presence of bronchopulmonary dysplasia in the 28th day of life of the studied population.
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