Les importations méditerranéennes en Gaule du Centre-Ouest et dans les pays de la Loire moyenne du VIIe siècle au IIIe siècle a.C. Un bilan.

In : Krausz S., Colin A., Gruel K., Ralston I., Dechezleprêtre T., L'Âge du Fer en Europe. Mélanges offerts à Olivier Buchsenschutz, Bordeaux, AusoniusAn inventar of greeck, etruscian & iberic imports in western Gaul durant Hallstatt & early La Tène periodsBilan des connaissances sur les importations grecques, étrusques et ibériques en Gaule de l'Ouest pendant le premier âge du Fer et le début du secon

Prospects for Type Ia Supernova explosion mechanism identification with gamma rays

The explosion mechanism associated with thermonuclear supernovae (SNIa) is still a matter of debate. There is a wide agreement that high amounts of of radioactive nuclei are produced during these events and they are expected to be strong gamma-ray emitters. In the past, several authors have investigated the use of this gamma-ray emission as a diagnostic tool. In this paper we have done a complete study of the gamma-ray spectra associated with all the different scenarios currently proposed. This includes detonation, delayed detonation, deflagration and the off-center detonation. We have performed accurate simulations for this complete set of models in order to determine the most promising spectral features that could be used to discriminate among the different models. Our study is not limited to qualitative arguments. Instead, we have quantified the differences among the spectra and established distance limits for their detection. The calculations have been performed considering the best current response estimations of the SPI and IBIS instruments aboard INTEGRAL in such a way that our results can be used as a guideline to evaluate the capabilities of INTEGRAL in the study of type Ia supernovae. For the purpose of completeness we have also investigated the nuclear excitation and spallation reactions as a possible secondary source of gamma-rays present in some supernova scenarios. We conclude that this mechanism can be neglected due to its small contribution.Comment: 10 pages, 12 figures, LaTeX with MNRAS style file,accepted for publication in The Monthly Notices of the Royal Astron.So

Time and Space Coherent Occlusion Culling for Tileable Extended 3D Worlds

International audienceIn order to interactively render large virtual worlds, the amount of 3D geometry passed to the graphics hardware must be kept to a minimum. Typical solutions to this problem include the use of potentially visible sets and occlusion culling, however, these solutions do not scale well, in time nor in memory, with the size of a virtual world. We propose a fast and inexpensive variant of occlusion culling tailored to a simple tiling scheme that improves scalability while maintaining very high performance. Tile visibilities are evaluated with hardwareaccelerated occlusion queries, and in-tile rendering is rapidly computed using BVH instantiation and any visibility method; we use the CHC++ occlusion culling method for its good general performance. Tiles are instantiated only when tested locally for visibility, thus avoiding the need for a preconstructed global structure for the complete world. Our approach can render large-scale, diversified virtual worlds with complex geometry, such as cities or forests, all at high performance and with a modest memory footprint

From frustrated magnetism to spontaneous Chern insulators

We study the behavior of electrons interacting with a classical magnetic background via a strong Hund coupling. The magnetic background results from a Hamiltonian which favors at low temperature the emergence of a phase with nonzero scalar chirality. The strong Hund's coupling combined with the total chirality of the classical spins induces in the electrons an effective flux which results in the realization of a band structure with nonzero Chern number. First, we consider as a magnetic background a classical spin system with spontaneous net chirality. We study the density of states and Hall conductance in order to analyze the topological transitions as a function of the Fermi energy and the temperature of the classical spins. We also study a similar model in which the Chern number of the filled bands can be "tuned" with the external magnetic field, resulting in a topological insulator in which the direction of the chiral edge mode can be reverted by reversing the orientation of the magnetic field applied to the classical magnetic system.Fil: Rosales, Hector Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física de Líquidos y Sistemas Biológicos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física de Líquidos y Sistemas Biológicos; Argentina. Universidad Nacional de La Plata. Facultad de Ingeniería; ArgentinaFil: Gomez Albarracin, Flavia Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física de Líquidos y Sistemas Biológicos. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física de Líquidos y Sistemas Biológicos; ArgentinaFil: Pujol, Pierre. Université de Toulouse; Francia. Centre National de la Recherche Scientifique; Franci