Montreuil-sous-Bois – Église Saint-Pierre et Saint-Paul

Quoique placée sous le vocable de Saint-Pierre et Saint-Paul, l’église de Montreuil n’est mentionnée pour la première fois qu’en 1113. L’édifice ne conserve toutefois aucune élévation antérieure à l’époque gothique. Sa partie la plus ancienne, le chœur, date en effet de la fin du xiie et du début du xiiie s. La construction de la partie centrale de la façade est entreprise au xive s. Un nouveau vaisseau est bâti un s. plus tard ; il devait être flanqué de bas-côtés prolongeant ceux du chœur. ..

Glial activation in white matter following ischemia in the neonatal P7 rat brain

This study examines cell death and proliferation in the white matter after neonatal stroke. In post-natal day 7 injured rat, there was a marked reduction in myelin basic protein (MBP) immunostaining mainly corresponding to numerous pyknotic immature oligodendrocytes and TUNEL-positive astrocytes in the ipsilateral external capsule. In contrast, a substantial restoration of MBP, as indicated by the MBP ratio of left-toright, occurred in the cingulum at 48 (1.27 +- 0.12) and 72 (1.30 +- 0.18, p<0.05) hours of recovery as compared to age-matched controls (1.03 +- 0.14). Ki-67 immunostaining revealed a first peak of newly-generated cells in the dorsolateral hippocampal subventricular zone and cingulum at 72 hours after reperfusion. Double immunofluorescence revealed that most of the Ki-67-positive cells were astrocytes at 48 hours and NG2 pre-oligodendrocytes at 72 hours of recovery. Microglia infiltration occurs over several days in the cingulum and a huge quantity of macrophages reached the subcortical white matter where they engulfed immature oligodendrocytes. The overall results suggest that the persistent activation of microglia involves a chronic component of immunoinflammation, which overwhelms repair processes and contributes to cystic growth in the developing brain.Comment: 30 page

Improved ion acceleration via laser surface plasma waves excitation

International audienceThe possibility of enhancing the emission of the ions accelerated in the interaction of a high intensity ultra-short (<100 fs) laser pulse with a thin target (<10 l0), via surface plasma wave excitation is investigated. Two-dimensional particle-in-cell simulations are performed for laser intensities rangingfrom 10^19 to 10^20 W/cm2.µm2. The surface wave is resonantly excited by the laser via the coupling with a modulation at the target surface. In the cases where the surface wave is excited, we find anenhancement of the maximum ion energy of a factor ~2 compared to the cases where the targetsurface is flat

Self-generation of megagauss magnetic fields during the expansion of a plasma

International audienceThe expansion of a plasma slab into a vacuum is studied using one-dimensional and two-dimensional particle-in-cell simulations. As electrons transfer their longitudinal kinetic energy to ions during the expansion, the electron temperature becomes anisotropic. Once this anisotropy exceeds a threshold value, it drives the Weibel instability, leading to magnetic fields in the megagauss range. These fields induce energy transfer between the longitudinal and transverses directions, which influences the expansion. The impact of a cold electron population on this phenomenon is also investigated. Plasma expansion is a fundamental process which occurs in very different fields, such as astrophysics ͓1,2͔, laser-plasma ion acceleration ͓3–5͔ and thin-film deposition ͓6͔. This phenomenon is usually described by simple one-dimensional models ͓7–9͔. Yet, even when the system is translation-invariant along the plasma surface, several effects ͑e.g., Coulomb collisions ͓10͔͒ can induce momentum transfer between the longitudinal and transverse directions. The purely one-dimensional ͑1D͒ description is thus, in general, inaccurate. In this paper, we show that self-generated magnetic fields can lead to such momentum transfer during the expansion of a collisionless plasma slab. This study is of particular interest in the context of laser-plasma ion acceleration , where an intense laser pulse is focused on a thin foil to create a hot electron population that transfers progressively its energy to ions via the ambipolar electric field at the plasma surface ͓11͔. We assume here that the electron distribution is initially Maxwellian with an isotropic temperature. As the plasma expands, the longitudinal temperature T ʈ decreases and the anisotropy parameter A = T Ќ / T ʈ − 1 increases, which eventually leads to the growth of the Weibel instability ͓12–18͔. The most unstable modes are obtained for k = k x e x , where e x is a unit vector normal to the plasma surface. In this case, the maximum unstable wave vector is k

The Patrimony Atlas of Seine-Saint-Denis

The Patrimony Atlas of Seine-Saint-Denis (north of Paris) is an information tool related to the archaeological, architectural and landscape patrimony of Seine-Saint-Denis, accessible on the Internet address http://www.atlas-patrimoine93.fr/. It is distributed by the Cultural Patrimony Service of the Department of Seine-Saint-Denis, and is registered in the National Patrimony Atlas project of the Ministry of Culture. It is organized into three categories. The documentation platforms gather: a geographical catalogue which includes 50 levels of information geographically referenced, which are free of copyrights and can circulate online; a bibliography with 3700 references classified according to borough, subject and time period; an iconographic catalogue with 2800 images, the issues of archaeological maps and patrimony inventory that collect and collate past data. The “territorial views” offer a rapid access to a selection of ancient maps that represent a selected point on the territory on a contemporary basis, like the Napoleonic cadastral tables. The “Documents” file gathers the documents in a PDF format: university projects, thematic studies, articles and monographs, methodologies, summary charts, as well as hypertext documents, a presentation of the evolution of the road network in the latter part of the 18th century, a “Mathériauthèque numérique” dedicated to construction materials, and an “Atlas des colleges” of Seine-Saint-Denis. In its present version (2.5.3, put online in March 2008), the Seine-Saint-Denis Patrimony Atlas receives between 12,000 and 14,000 hits per month

Model-based Decentralized Embedded Diagnosis inside Vehicles: Application to Smart Distance Keeping Function

International audienceAbstract—In this paper, the deployment of a fault diagnosis strategy in the Smart Distance Keeping (SDK) system with a decentralized architecture is presented. The SDK system is an advanced version of the Adaptive Cruise Control (ACC) system, implemented in a Renault-Volvo Trucks vehicle. The main goal of this work is to analyze measurements, issued from the SDK elements, in order to detect, to localize and to identify some faults that may be produced. Our main contribution is the proposition of a decentralized approach permitting to carry out an on-line diagnosis without computing the global model and to deploy it on several control units. This paper explains the model-based decentralized solution and its application to the embedded diagnosis of the SDK system inside truck with five control units connected via a CAN-bus using ”Hardware In the Loop” (HIL) technique. We also discuss the constraints that must be fulfilled

Particle-in-cell modelling of relativistic laser-plasma interaction with the adjustable damping, direct implicit method

Implicit particle-in-cell codes offer advantages over their explicit counterparts in that they suffer weaker stability constraints on the need to resolve the higher frequency modes of the system. This feature may prove particularly valuable for modeling the interaction of high-intensity laser pulses with overcritical plasmas, in the case where the electrostatic modes in the denser regions are of negligible influence on the physical processes under study. To this goal, we have developed the new two-dimensional electromagnetic code ELIXIRS (standing for ELectromagnetic Implicit X-dimensional Iterative Relativistic Solver) based on the relativistic extension of the so-called Direct Implicit Method [D. Hewett and A. B. Langdon, J. Comp. Phys. \textbf{72}, 121(1987)]. Dissipation-free propagation of light waves into vacuum is achieved by an adjustable-damping electromagnetic solver. In the high-density case where the Debye length is not resolved, satisfactory energy conservation is ensured by the use of high-order weight factors. In this paper, we first present an original derivation of the electromagnetic direct implicit method within a Newton iterative scheme. Its linear properties are then investigated through numerically solving the relation dispersions obtained for both light and plasma waves, accounting for finite space and time steps. Finally, our code is successfully benchmarked against explicit particle-in-cell simulations for two kinds of physical problems: plasma expansion into vacuum and relativistic laser-plasma interaction. In both cases, we will demonstrate the robustness of the implicit solver for crude discretizations, as well as the gains in efficiency which can be realized over standard explicit simulations

Influence of the Weibel instability on the expansion of a plasma slab into a vacuum

International audienceThe development of the Weibel instability during the expansion of a thin plasma foil heated by an intense laser pulse is investigated, using both analytical models and relativistic particle-in-cell simulations. When the plasma has initially an anisotropic electron distribution, this electromagnetic instability develops from the beginning of the expansion. Then it contributes to suppress the anisotropy and eventually saturates. After the saturation, the strength of the magnetic field decreases because of the plasma expansion until it becomes too weak to maintain the distribution isotropic. For this time, the anisotropy rises as electrons give progressively their longitudinal energy to ions, so that a new instability can develop

Efficient laser-overdense plasma coupling via surface plasma waves and steady magnetic field generation

International audienceThe efficiency of laser overdense plasma coupling via surface plasma wave excitation is investigated. Two-dimensional particle-in-cell simulations are performed over a wide range of laser pulse intensity from 10 15 to 10 20 W cm À2 lm 2 with electron density ranging from 25 to 100n c to describe the laser interaction with a grating target where a surface plasma wave excitation condition is fulfilled. The numerical studies confirm an efficient coupling with an enhancement of the laser absorption up to 75%. The simulations also show the presence of a localized, quasi-static magnetic field at the plasma surface. Two interaction regimes are identified for low (Ik 2 10 17 W cm À2 lm 2) laser pulse intensities. At " relativistic " laser intensity, steady magnetic fields as high as $580 MG lm/k 0 at 7 Â 10 19 W cm À2 lm 2 are obtained in the simulations