Réflexions sur la notion de champ migratoire international

National audienceDans l'optique adoptée ici, le champ migratoire est l'ensemble de l'espace parcouru, pratiqué par les migrants. La notion de champ fait référence à un espace spécifique, structuré par des flux importants, significatifs ; appliquée au domaine international, elle englobe à la fois le pays de départ et le pays d'emploi

Un pays de départ : la Tunisie

En l'espace de vingt ans, le nombre des Tunisiens, résidant temporairement ou définitivement à l'étranger, est passé de 10.000 en 1955 à 270.000 environ en 1974; ce chiffre représente 5% de la population totale de ce petit pays (5.200.000 hab. en 1973) mais un pourcentage nettement plus fort de la population active. La présentation de ces recherches se limitera ici à l'analyse de trois thèmes vus sous l'angle du pays de départ: * le développement récent de ce phénomène migratoire. * les relations avec la situation de l'emploi en Tunisie. * l'attitude de l'administration tunisienne

Les transferts de revenus des travailleurs maghrébins vers leur pays d'origine : essai d'évaluation

National audienceLa connaissance des flux financiers, officiels et souterrains constitue un élément fondamental de la problématique adoptée dans la recherche sur les migrations internationales et l'urbanisation des pays en développement. De l'ampleur de ces transferts, de leur localisation et des modalités de leur affectation, dépendent un certain nombre de processus et de formes d'urbanisation dans les pays en développement. Or, malgré l'importance de cette question au niveau micro et macro-économique, ce sujet reste mal connu en raison de l'ambiguïté des termes et des concepts utilisés, de l'inadaptation des sources statistiques/de la généralisation des pratiques de change illicite

SiF4 anomalous behaviour reassessed

The Si 1s−1, Si 2s−1, and Si 2p−1 photoelectron spectra of the SiX4 molecules with X = F, Cl, Br, CH3 were measured. From these spectra the Si 1s−1 and Si 2s−1 lifetime broadenings were determined, revealing a significantly larger value for the Si 2s−1 core hole of SiF4 than for the same core hole of the other molecules of the sequence. This finding is in line with the results of the Si 2p−1 core holes of a number of SiX4 molecules, with an exceptionally large broadening for SiF4. For the Si 2s−1 core hole of SiF4 the difference to the other SiX4 molecules can be explained in terms of Interatomic Coulomb Decay (ICD)-like processes. For the Si 2p−1 core hole of SiF4 the estimated values for the sum of the Intraatomic Auger Electron Decay (IAED) and ICD-like processes are too small to explain the observed linewidth. However, the results of the given discussion render for SiF4 significant contributions from Electron Transfer Mediated Decay (ETMD)-like processes at least plausible. On the grounds of our results, some more molecular systems in which similar processes can be observed are identified

From underground laser scans to 3D urban geological and geotechnical models

International audienceThe near sub-surface geology, say down to 20-30-m-depth, of many cities has been massively exploited for extracting building stones and various other industrial or agricultural materials (gypsum, lime, etc…). The long-term instability of these cavities poses a significant collapse hazard conditioned by their geometry (void location, dimensions and shape) and by their surrounding rock mechanics properties. In this presentation, we show how handheld laser scanning surveys efficiently document geometric variables and can interact with 3D geological modelling of the surrounding rocks. The construction of near-surface urban geological models can then be turned into 3D geotechnical models by attributing geotechnical parameters to rock horizons and ultimately become a key subsurface knowledge component of BIM (Building Information Model). Acquiring surface and subsurface geometry is no longer a challenge thanks to handheld laser scanners. Survey loop traverses can be pieced together to link surface and subsurface geometry with accuracies better than 1 m (an accuracy level compatible with urban risk management maps at 1/5.000) (DEWEZ et al., 2017). However, the hundreds of-millions of 3D points describing the cavity surface cannot be integrated as such into geomodeling software. Too many points with not high enough information. We suggest two different scenarios to perform their integration: (i) as independent validation of geomodeling hypotheses, or (ii) as geomodel constraints. In the first integration scenario, point cloud information is passed to the geomodeling software at a minimal level. A decimated triangular meshed model can be used to intersect the geomodel. Triangulation is performed at the point cloud processing software level (e.g. GeoSLAM desktop or Cloud Compare) and intersection is handled at the geomodelling software level with a generic query concept (here GeoModeller software with a generic query API – LOISELET et al.,2016). In this instance, cavity mesh triangular faces are refined based on the geological model queries (relying on the marching triangles algorithm) and provide geotechnical attributes based on the geological formations given by the geomodel. This scenario offers a visual display of geological properties (Fig. 1) for checking that modelled layers and structures match those observed in underground outcrops. In the second scenario, which is more integrated, higher level information is passed to the geomodelling tool. Planar surfaces of marker horizons are segmented from the point cloud either manually using Compass (THIELE et al., 2017) or semi-automatically with FACETS (DEWEZ et al., 2016) and passed as structural data objects to constrain the geomodel (Fig. 2). This data integration is demonstrated on a ca. 1 ha underground building stone quarry of the eastern suburbs of Orléans, Central France. The cavity was scanned at ca. 1pt/1cm with a Zeb-Revo (90 Mpts underground and 35 Mpts above ground). A geomodel of the subsurface area (Calcaire de Beauce, Tertiary) was created with the GeoModeller software as a tabular sub-horizontal multilayer environment. The geomodel infers rock distribution over a domain of ca. 200 x 200 m with geological and geotechnical information (e.g. limit pressure for dimensioning building foundations). Both approaches leverage a generic API query tool informing which domain surrounds a point and whether a geological contact cross-cuts a triangular face

a tool to disentangle overlapping core-excited states

We have measured resonant-Auger decay following Cl 1s−1 excitations in HCl and CH3Cl molecules, and extracted the pseudo-cross sections of different Cl 2p−2 final states. These cross sections show clear evidence of shake processes as well as contributions of electronic state-lifetime interference (ELI). To describe the spectra we developed a fit approach that takes into account ELI contributions and ultrafast nuclear dynamics in dissociative core-excited states. Using this approach we utilized the ELI contributions to obtain the intensity ratios of the overlapping states Cl 1s−14pπ/1s−14pσ in HCl and Cl 1s−14pe/1s−14pa1 in CH3Cl. The experimental value for HCl is compared with theoretical results showing satisfactory agreement

Serum Lipid Profile of the Adult Habitual Consumers of Two Traditional Alcoholic Drinks Made in Benin

Alcohol consumption modifies many biological parameters. This study aimed to describe the profile of the serum lipids of adult habitual consumers of Tchoukoutou and Sodabi, two traditional alcoholic drinks made in Benin. We carried out a descriptive, cross-sectional and analytic study from May 1st, 2013 to August 31, 2013. The target of the study was a population consisting of 60 habitual consumers of Tchoukoutou (mean age: 35.8

Hard-X-Ray-Induced Multistep Ultrafast Dissociation

Creation of deep core holes with very short (τ≤1  fs) lifetimes triggers a chain of relaxation events leading to extensive nuclear dynamics on a few- femtosecond time scale. Here we demonstrate a general multistep ultrafast dissociation on an example of HCl following Cl 1s→σ∗ excitation. Intermediate states with one or multiple holes in the shallower core electron shells are generated in the course of the decay cascades. The repulsive character and large gradients of the potential energy surfaces of these intermediates enable ultrafast fragmentation after the absorption of a hard x-ray photon

Argon KLL Auger spectrum: Initial states, core-hole lifetimes, shake, and knock-down processes

State-of-the-art argon KLL Auger spectra measured using photon energies of hν=3216 and 3400 eV are presented along with an Ar [1s] photoelectron spectrum (square brackets indicate holes in the respective orbital). The two different photon energies used for measuring the Auger spectra allow distinguishing between the shake transitions during the Auger decay and the Auger transitions of the photoelectron satellites. A complete assignment of satellite transitions is provided, partially based on configuration-interaction calculations. In addition, Ar [1s3(s,p)]n′l′→[2p2(1D2)] transitions are observed, which can be explained by knock-down transitions leading to a direct exchange of angular momentum between the excited electron and the Auger electron. The lifetime broadenings of the Ar [2s] single-core-hole state and the [2s2] and [2s2p] double-core-hole states are also determined, confirming previously observed trends for double-core-hole states

Community-Driven Data Analysis Training for Biology

The primary problem with the explosion of biomedical datasets is not the data, not computational resources, and not the required storage space, but the general lack of trained and skilled researchers to manipulate and analyze these data. Eliminating this problem requires development of comprehensive educational resources. Here we present a community-driven framework that enables modern, interactive teaching of data analytics in life sciences and facilitates the development of training materials. The key feature of our system is that it is not a static but a continuously improved collection of tutorials. By coupling tutorials with a web-based analysis framework, biomedical researchers can learn by performing computation themselves through a web browser without the need to install software or search for example datasets. Our ultimate goal is to expand the breadth of training materials to include fundamental statistical and data science topics and to precipitate a complete re-engineering of undergraduate and graduate curricula in life sciences. This project is accessible at https://training.galaxyproject.org. We developed an infrastructure that facilitates data analysis training in life sciences. It is an interactive learning platform tuned for current types of data and research problems. Importantly, it provides a means for community-wide content creation and maintenance and, finally, enables trainers and trainees to use the tutorials in a variety of situations, such as those where reliable Internet access is unavailable