Worker flows, job flows and establishment wage differentials : analyzing the case of France

We address the relation between establishment wage differentials and worker flows, i.e. the churning rate and the quit rate. Our analysis is based on a linked employer-employee dataset covering the French private non-farm sector from 2002 to 2005. Our estimations support the hypothesis that wage premium is an efficient human resource management tool to stabilize workers : churning rates are lower in high-paying firms due to lower quit rates. We further show that the relation is not linear, and it differs among skill groups and according to establishment size : it is strongest for low-wage levels, for low-skilled workers and in large establishments.Establishment wage effects, worker flows, churning rate, quite rate, linked employer-employee panel data, France.

Payroll tax reductions and job flows in France

In France, policies that aim at reducing labour cost have extended to more and more workers since the beginning of the 90s. Evaluations of the effect of payroll tax reduction often use estimations of labour demand equations. In this paper, we consider the impact of labour tax cuts on job creations and destructions through the Fillon reform (2003), by using a fixed effect instrumental variable approach and a sectora l pseudo panel dataset. Over 2002-2005, our estimates show that PTR let job flows unchanged

Movements Induced by Tunneling With an Epb Machine in over Consolidated Soils: Compans Monitoring Section of Toulouse Subway Line B

A part of Toulouse’s underground line B has been excavated by a 7.8 meters diameter earth-pressure balance machine. A comprehensive monitoring section has been installed in the Compans garden at a point where the tunnel cover is 12.8-meter and is running through overconsolidated clayey molasses underlying a 6.8 meters layer of made ground and gravels. The monitoring devices give full information on the ground movements above the tunnel and on deformations of the tunnel lining. Vertical movements are measured by 5 multipoint borehole extensometers with automatic data acquisition (every 5 seconds when the TBM crosses the monitoring section). At the end of each excavation phase, a high precision levelling of the borehole extensometer heads is performed in order to determine the total vertical displacements. Horizontal movements are measured by 3 inclinometers, one in the axis of the tunnel and the others on its sides, 2.3 meters away from the tunnel extrados. One of these inclinometers is 42 m long, i.e. 21.8 m below the level of the tunnel invert. The induced horizontal strains at ground level are measured by an invar thread in both longitudinal and transverse directions. Measurements show a specific behaviour of the soil due to its overconsolidated character (K0 greater than 1.5): even though the magnitude of the displacements is limited to a few millimeters, horizontal convergent movements are observed at the level of the tunnel axis while 3 to 4 times smaller heave is measured at ground surface (associated with horizontal extensions). Excavation parameters are automatically recorded and give information on the variation of the torque on the cutting wheel, the advancement rate, the confining pressure, the injection of annular void between soil and the concrete tunnel lining… This paper presents the results of the different monitoring devices and the possible correlations with the tunnel excavation parameters recorded by the TBM

Anisotropy and crystal plasticity study of fcc polycrystalline Ni by nanoindentation

National audienceL'objectif de l'étude est de mettre en lumière l'anisotropie des matériaux cristallins de type cfc aux échelles micro et nanométriques. Des résultats numériques et expérimentaux de nanoindentation sont présentés. Les essais expérimentaux ont été réalisés sur un échantillon de nickel polycristallin, avec un indenteur de type Berkovich. Les simulations ont été menées sous le code éléments finis ZEBULON, en y intégrant un modèle de plasticité cristalline en grande déformation. Trois directions cristallographiques principales, correspondant à trois grains présentant ces mêmes directions , ont été choisies comme axe d'indentation, à savoir [001], [101] et [111]. Les empreintes ont été analysées au microscope à force atomique (AFM). La topographie de la surface autour des empreintes a révélé des lignes de glissement associées aux différents systèmes activés, ainsi que des remontées de matière (bourrelets) fortement anisotropes et non-symétriques, dépendantes de l'orientation du cristal par rapport à l'indenteur. Ces observations sont en accord avec les résultats des simulations numériques. L'effet de l'orientation de l'indenteur dans chacun des plans d'indentation a également été étudié expérimentalement et numériquement

Influence de la taille de grain initiale sur le procédé de formage incrémental des tôles en faibles épaisseurs

National audienceLe formage incrémental "mono-point" (SPIF) est un procédé innovant qui permet de produire des pièces de géométrie complexe en contrôlant le mouvement d'un outil de formage généralement à bout hémisphérique. La géométrie désirée est assurée par la trajectoire de l'outil qui impose une déformation incrémentale sur un flan serré sur son contour. L'avantage de ce procédé est son faible coût de l'outillage par rapport aux procédés de formage classiques. Le développement de procédés de formage des tôles en faibles épaisseurs est limité par l'influence de la miniaturisation due aux effets d'échelle. A de petites échelles, la taille de grain initiale joue un rôle important sur le comportement du matériau. Ce document traite de l'influence de la taille initiale de grains sur le procédé de micro formage incrémental des tôles en cuivre à travers une investigation expérimentale. Des essais de traction par différentes tailles de grains ont été réalisés. Une série de tests expérimentaux de micro-SPIF a été effectuée sur des flans par ces mêmes tailles de grains initiales. Les effets sur la distribution des épaisseurs ainsi que les évolutions des efforts de formage sont démontrés et discutés. Un modèle analytique est également proposé afin de représenter ces efforts lors du procédé

SiNx:Tb3+--Yb3+, an efficient down-conversion layer compatible with a silicon solar cell process

SiN x : Tb 3+-Yb 3+, an efficient down-conversion layer compatible with silicon solar cell process Abstract Tb 3+-Yb 3+ co-doped SiN x down-conversion layers compatible with silicon Photovoltaic Technology were prepared by reactive magnetron co-sputtering. Efficient sensitization of Tb 3+ ions through a SiN x host matrix and cooperative energy transfer between Tb 3+ and Yb 3+ ions were evidenced as driving mechanisms of the down-conversion process. In this paper, the film composition and microstructure are investigated alongside their optical properties, with the aim of maximizing the rare earth ions incorporation and emission efficiency. An optimized layer achieving the highest Yb 3+ emission intensity was obtained by reactive magnetron co-sputtering in a nitride rich atmosphere for 1.2 W/cm${}^2$ and 0.15 W/cm${}^2$ power density applied on the Tb and Yb targets, respectively. It was determined that depositing at 200 {\textdegree}C and annealing at 850 {\textdegree}C leads to comparable Yb 3+ emission intensity than depositing at 500 {\textdegree}C and annealing at 600 {\textdegree}C, which is promising for applications toward silicon solar cells.Comment: Solar Energy Materials and Solar Cells, Elsevier, 201

Collapses of underground cavities and soil-structure interactions : experimental and numerical models

International audienceThe great subsidences result from the collapses of underground cavities man-made (mines or careers) or formed naturally by water flow in soluble solid masses of rocks (limestone, gypsum). Their impact on the existing structures standing on the surface is generally very important as show the recent examples of Auboué (1996), Moutiers (1997) and Roncourt (1999) which damaged more than five hundred buildings and the sinkhole on building site of METEOR subway in 2003. It is thus necessary to forecast the movements of the soil surface (subsidence and horizontal deformation) resulting from these phenomena and especially to determine the impact that may have the presence of structures on the form and the amplitude of these movements. The current practice to forecast the effects on the structures consists in determining the movements caused by the subsidence of the cavity without the building (in greenfield) then to use these results to check the capacity of the structure to resist the phenomenon. This approach can largely underestimate or over-estimate the generated loading, which in both cases has negative impacts (risk remaining for the structure or overcost of project in the other hand). In the present communication, soil-structure interaction during a sinkhole phenomenon is studied by a dual approach using a physical model and a numerical method. First of all, the physical model will use the bidimensionnal Schneebeli material in a small-scale model allowing fully controlled tests. The Schneebeli material is modified in order to allow the presence of cohesion. The soil mass of great dimensions (2m width for 1m height) makes it possible to represent the happening of a sinkhole with a scale factor of 1/40. The use of a building model will allow us to shed some light on the soil-structure interaction during the sinkhole. Thereafter we will set a numerical model using a coupled approach betwen finite difference and discrete element (FLAC2D – PFC2D coupled computations). This will allow us to study more easier different case of parameters : the size of the cavity, the thickness of the roof over the cavity, the position of the structure compared to the cavity, etc ..

Intragenomic conflict in populations infected by Parthenogenesis Inducing Wolbachia ends with irreversible loss of sexual reproduction

<p>Abstract</p> <p>Background</p> <p>The maternally inherited, bacterial symbiont, parthenogenesis inducing (PI) <it>Wolbachia</it>, causes females in some haplodiploid insects to produce daughters from both fertilized and unfertilized eggs. The symbionts, with their maternal inheritance, benefit from inducing the production of exclusively daughters, however the optimal sex ratio for the nuclear genome is more male-biased. Here we examine through models how an infection with PI-<it>Wolbachia </it>in a previously uninfected population leads to a genomic conflict between PI-<it>Wolbachia </it>and the nuclear genome. In most natural populations infected with PI-<it>Wolbachia </it>the infection has gone to fixation and sexual reproduction is impossible, specifically because the females have lost their ability to fertilize eggs, even when mated with functional males.</p> <p>Results</p> <p>The PI <it>Wolbachia </it>infection by itself does not interfere with the fertilization process in infected eggs, fertilized infected eggs develop into biparental infected females. Because of the increasingly female-biased sex ratio in the population during a spreading PI-<it>Wolbachia </it>infection, sex allocation alleles in the host that cause the production of more sons are rapidly selected. In haplodiploid species a reduced fertilization rate leads to the production of more sons. Selection for the reduced fertilization rate leads to a spread of these alleles through both the infected and uninfected population, eventually resulting in the population becoming fixed for both the PI-<it>Wolbachia </it>infection and the reduced fertilization rate. Fertilization rate alleles that completely interfere with fertilization ("virginity alleles") will be selected over alleles that still allow for some fertilization. This drives the final resolution of the conflict: the irreversible loss of sexual reproduction and the complete dependence of the host on its symbiont.</p> <p>Conclusions</p> <p>This study shows that dependence among organisms can evolve rapidly due to the resolution of the conflicts between cytoplasmic and nuclear genes, and without requiring a mutualism between the partners.</p