Datation par la méthode du radiocarbone de l'ancienne ville d'Assodé dans l'Aïr, au Niger

Situé au coeur du massif de l'Aïr, dans le Niger septentrional, Assodé est l'ancienne capitale des Touaregs Kel Owi. La ville est aujourd'hui en ruines et complètement abandonnée. Différentes campagnes de fouilles ont permis d'obtenir un ensemble cohérent de datations par le radiocarbone, qui semblent indiquer, après calibration, que la fondation de la ville n'est pas antérieure au XIVe siècle. Les fouillent livrent dès cette époque une céramique très caractéristique à décor rectilinaire gravé et peint, dont on peut suivre l'évolution jusqu'à nos jours. (Résumé d'auteur

Dynamiques fluviales en basse vallée du Vidourle

International audienc

Implication of the PAMELA antiproton data for dark matter indirect detection at LHC

Since the PAMELA results on the "anomalously" high positron fraction and the lack of antiproton excess in our Galaxy, there has been a tremendous number of studies advocating new types of dark matter, with larger couplings to electrons than to quarks. This raises the question of the production of dark matter particles (and heavy associated coloured states) at LHC. Here, we explore a very simple benchmark dark matter model and show that, in spite of the agreement between the PAMELA antiproton measurements and the expected astrophysical secondary background, there is room for large couplings of a WIMP candidate to heavy quarks. Contrary to what could have been naively anticipated, the PAMELA pbar/p measurements do not challenge dark matter model building, as far as the quark sector is concerned. A quarkophillic species is therefore not forbidden.Owing to these large couplings, one would expect that a new production channel opens up at the LHC, through quark--quark and quark--gluon interactions. Alas, when the PDF of the quark is taken into account, prospects for a copious production fade away.Comment: 7 pages, 2 figures, captions of some figures modified, main conclusion unchange

Binaries with total eclipses in the LMC: potential targets for spectroscopy

35 Eclipsing binaries presenting unambiguous total eclipses were selected from a subsample of the list of Wyrzykowski et al. (2003). The photometric elements are given for the I curve in DiA photometry, as well as approximate Teff and masses of the components. The interest of these systems is stressed in view of future spectroscopic observations.Comment: 4 pages, 1 figure; poster presented at the conference "Close binaries in the 21st Century: new opportunities and challenges", Syros, 27-30 June 200

Directional bias of illusory stream caused by relative motion adaptation

AbstractEnigma is an op-art painting that elicits an illusion of rotational streaming motion. In the present study, we tested whether adaptation to various motion configurations that included relative motion components could be reflected in the directional bias of the illusory stream. First, participants viewed the center of a rotating Enigma stimulus for adaptation. There was no physical motion on the ring area. During the adaptation period, the illusory stream on the ring was mainly seen in the direction opposite to that of the physical rotation. After the physical rotation stopped, the illusory stream on the ring was mainly seen in the same direction as that of the preceding physical rotation. Moreover, adapting to strong relative motion induced a strong bias in the illusory motion direction in the subsequently presented static Enigma stimulus. The results suggest that relative motion detectors corresponding to the ring area may produce the illusory stream of Enigma

La zone hyporhéique, une composante à ne pas négliger dans l'état des lieux et la restauration des cours d'eau

Les projets de restauration des cours d'eau sont maintenant de plus en plus fréquents et ambitieux. Intégrant un grand nombre de composantes de l'hydrosystème, ils ne prennent néanmoins pas pleinement en compte sa dimension verticale et oublient souvent un compartiment fondamental, représenté par la zone hyporhéique. Cette zone constitue une seconde rivière dont l'écoulement souterrain est invisible, et dont l'existence et la fonction sont largement méconnues. Pourtant elle joue un rôle fondamental dans le maintien des processus écologiques et dans la préservation de la biodiversité du cours d'eau. Après avoir précisé les rôles du milieu hyporhéique et souligné l'effet des activités humaines qui altèrent souvent sa structure et ses fonctions, on montrera de quelle manière les projets actuels de réhabilitation pourraient être complétés grâce à l'intégration systématique de la zone hyporhéique dans leurs plans et leurs suivis de restauration. / Stream restoration projects are nowadays more and more numerous and ambitious. While they now integrate many components of hydrosystems, they are still ignoring a fundamental one, the hyporheic zone. This zone can be considered as a second river whose subsurface flow is invisible and whose functions are still poorly known. Nevertheless, the hyporheic zone plays a major role in sustaining stream ecological processes and preserving stream biodiversity. After pointing out how human activities can impair the hyporheic zone structure and function, we will show how restoration projects could be much improved by considering the hyporheic zone