Momentum isotropisation in random potentials

When particles are multiply scattered by a random potential, their momentum distribution becomes isotropic on average. We study this quantum dynamics numerically and with a master equation. We show how to measure the elastic scattering time as well as characteristic isotropisation times, which permit to reconstruct the scattering phase function, even in rather strong disorder.Comment: 5 pages, paper contributed to Lyon BEC 2012; v2 minor changes, version published in prin

A multi-photon magneto-optical trap

We demonstrate a Magneto-Optical Trap (MOT) configuration which employs optical forces due to light scattering between electronically excited states of the atom. With the standard MOT laser beams propagating along the {\it x}- and {\it y}- directions, the laser beams along the {\it z}-direction are at a different wavelength that couples two sets of {\it excited} states. We demonstrate efficient cooling and trapping of cesium atoms in a vapor cell and sub-Doppler cooling on both the red and blue sides of the two-photon resonance. The technique demonstrated in this work may have applications in background-free detection of trapped atoms, and in assisting laser-cooling and trapping of certain atomic species that require cooling lasers at inconvenient wavelengths.Comment: 10 pages, 5 figure

Effect of disorder close to the superfluid transition in a two-dimensional Bose gas

We experimentally study the effect of disorder on trapped quasi two-dimensional (2D) 87Rb clouds in the vicinity of the Berezinskii-Kosterlitz-Thouless (BKT) phase transition. The disorder correlation length is of the order of the Bose gas characteristic length scales (thermal de Broglie wavelength, healing length) and disorder thus modifies the physics at a microscopic level. We analyze the coherence properties of the cloud through measurements of the momentum distributions, for two disorder strengths, as a function of its degeneracy. For moderate disorder, the emergence of coherence remains steep but is shifted to a lower entropy. In contrast, for strong disorder, the growth of coherence is hindered. Our study is an experimental realization of the dirty boson problem in a well controlled atomic system suitable for quantitative analysis

Le marché de l'assurance dépendance.

Assurance; Risque;

Le Bois Pargas, à Pageas (Haute-Vienne) : un nouveau témoin du Néolithique final en Limousin.

International audienceNear to the village of Pageas, in Haute-Vienne (Limousin, France), the archaeological site of the "Bois Pargas" was discovered after the violent storms of the end of the year 1999, by the finding of artefacts into the stump of a reversed chestnut tree. A small excavation bring to the fore that the tree grew on a Neolithic pit. Although no organic remains are preserved, the archaeological artefacts let us interpret the structure as a pseudo megalithic monument. The funerary pit contained six Pressignian flint daggers, along with arrowheads, "scies à coches", ceramics and some ornaments. All theses artefacts are typical of the IIIrd millennium BC and the technological analysis of the daggers discriminates two times of production which brings to discuss the duration of use of the burial.Le gisement du Bois Pargas, situé sur la commune de Pageas en Haute-Vienne, fut identifié à la suite des violentes tempêtes de la fin de l'année 1999, par la découverte de matériel archéologique pris dans une souche de châtaigner renversé. La réalisation d'un sondage permit de montrer que cet arbre s'était enraciné sur une fosse préhistorique. Bien qu'aucun vestige organique n'ait été conservé, le type de matériel archéologique découvert permet d'interpréter cette structure comme le témoin d'un monument funéraire pseudo-mégalithique. La fosse sépulcrale contenait en effet un ensemble de six poignards en silex du Grand-Pressigny, associés à des pointes de flèches, des scies à coches, de la céramique et des éléments de parure. Ce matériel permet de situer le gisement au IIIe millénaire avant notre ère, et l'analyse technologique des poignards met en évidence deux époques de production qui conduisent à s'interroger sur la durée de fonctionnement de la structure funéraire

La demande d'assurance dépendance dans un cadre trivarié.

Private insurance for long-term care is underdeveloped in European countries and in the US. This paper tries to understand why the market is underdevelopped by using a theoretical approach and putting the emphasis on insurance demand. It shows that demand for long term care insurance can be low because current and expected health condition of individuals have a strong effect on wealth utility and thus insurance demand. Individual preferences may lead some persons not to seek insure. The underdevelopped market of long-term care insurance might not be only due to insurance supply, market failures, family impacts or institutional design. It is analyzed as a direct consequence of individual preferences.dépendance; assurance dépendance; demande d'assurance;

Why are we failing to implement imaging studies with radiolabelled new molecular entities in early oncology drug development?

In early drug development advanced imaging techniques can help with progressing new molecular entities (NME) to subsequent phases of drug development and thus reduce attrition. However, several organizational, operational, and regulatory hurdles pose a significant barrier, potentially limiting the impact these techniques can have on modern drug development. Positron emission tomography (PET) of radiolabelled NME is arguably the best example of a complex technique with a potential to deliver unique decision-making data in small cohorts of subjects. However, to realise this potential the impediments to timely inclusion of PET into the drug development process must be overcome. In the present paper, we discuss the value of PET imaging with radiolabelled NME during early anticancer drug development, as exemplified with one such NME. We outline the multiple hurdles and propose options on how to streamline the organizational steps for future studies

Coherent Backscattering of Ultracold Atoms

We report on the direct observation of coherent backscattering (CBS) of ultracold atoms, in a quasi-two-dimensional configuration. Launching atoms with a well-defined momentum in a laser speckle disordered potential, we follow the progressive build up of the momentum scattering pattern, consisting of a ring associated with multiple elastic scattering, and the CBS peak in the backward direction. Monitoring the depletion of the initial momentum component and the formation of the angular ring profile allows us to determine microscopic transport quantities. The time resolved evolution of the CBS peak is studied and is found a fair agreement with predictions, at long times as well as at short times. The observation of CBS can be considered a direct signature of coherence in quantum transport of particles in disordered media. It is responsible for the so called weak localization phenomenon, which is the precursor of Anderson localization.Comment: 5 pages, 4 figure