A Bose-Einstein condensate bouncing off a rough mirror

We present experimental results and theoretical analysis of the diffuse reflection of a Bose-Einstein condensate from a rough mirror. The mirror is produced by a blue-detuned evanescent wave supported by a dielectric substrate. The results are carefully analysed via a comparison with a numerical simulation. The scattering is clearly anisotropic, more pronounced in the direction of the evanescent wave surface propagation, as predicted theoretically

Schemes for loading a Bose-Einstein condensate into a two-dimensional dipole trap

We propose two loading mechanisms of a degenerate Bose gas into a surface trap. This trap relies on the dipole potential produced by two evanescent optical waves far detuned from the atomic resonance, yielding a strongly anisotropic trap with typical frequencies 40 Hz x 65 Hz x 30 kHz. We present numerical simulations based on the time-dependent Gross-Pitaevskii equation of the transfer process from a conventional magnetic trap into the surface trap. We show that, despite a large discrepancy between the oscillation frequencies along one direction in the initial and final traps, a loading time of a few tens of milliseconds would lead to an adiabatic transfer. Preliminary experimental results are presented

Diffraction of a Bose-Einstein Condensate in the Time Domain

We have observed the diffraction of a Bose-Einstein condensate of rubidium atoms on a vibrating mirror potential. The matter wave packet bounces back at normal incidence on a blue-detuned evanescent light field after a 3.6 mm free fall. The mirror vibrates at a frequency of 500 kHz with an amplitude of 3.0 nm. The atomic carrier and sidebands are directly imaged during their ballistic expansion. The locations and the relative weights of the diffracted atomic wave packets are in very good agreement with the theoretical prediction of Carsten Henkel et al. [1].Comment: submitted to Phys. Rev.

Organisation, agrégation et visualisation d'informations médiatiques

International audienceThis article presents some data processing technics for GEOMEDIA, a platform for visualization and analysis of media information. In order to handle the complexity and the large amount of media data, we proceed in three stages. (1) Organization of the information flow in order to extract its global structure: Three dimensions (Agents x Dates x Themes) are settled for data classifying. We use the concept of " agent " , originated from Artificial Intelligence, in order to generalize the concept of " space ". (2) Aggregation of information in order to obtain a macroscopic point of view: Aggregation processes automatically decrease the structural complexity of data. Thus, they generate high-level abstractions. (3) Visualization of aggregated data: spatial projections on geometric, territorial or reticular spaces, temporal projections on timelines, thematic projections on tag clouds, etc.Cet article présente une méthode de traitement de données pour GEOMEDIA, une plateforme de visualisation et d'analyse d'informations médiatiques. Devant la complexité et la quantité des données médiatiques, nous avons trois objectifs. (1) Organisation du déluge d'informations pour en extraire la structure générale : trois dimensions (Agents × Dates × Thèmes) sont retenues pour classer les articles. Nous utilisons la notion d'« agent », issue de l'Intelligence Artificielle, pour généraliser la notion d'« espace ». (2) Agrégation de l'information pour obtenir un point de vue macroscopique sur la structure de données : des procédures automatiques d'agrégation réduisent la complexité structurelle et engendrent ainsi des abstractions de haut-niveaux. (3) Visualisation des données agrégées : projections spatiales sur des cartes géométriques, territoriales ou réticulaires, projections temporelles sur des frises chronologiques, projections thématiques sur des nuages sémantiques, etc

Photoelectrochemical study of nickel base alloys oxide films formed at high temperature and high pressure water

International audienceThe oxide film formed on nickel base alloys at high temperature and high pressure water exhibits semi-conducting properties evidenced by photocurrent generation when exposed to monochromatic light. The use of macro- and micro-photoelectrochemical techniques (PEC and MPEC) aims to identify the different semiconductor phases and their distribution in the oxide film. Three different nickel base alloys were corroded in recirculation loop at 325 °C in pressurised water reactor primary coolant conditions for different exposition durations. PEC experiments on these materials enable to obtain macroscopic energy spectra showing three contributions. The first one, with a band gap around 2.2 eV, was attributed to the presence of nickel hydroxide and/or nickel ferrite. The second one, with a band gap around 3.5 eV, was attributed to Cr2O3. The last contribution, with a band gap in the range of 4.1–4.5 eV, was attributed to the spinel phase Ni1−xFexCr2O4. In addition, macroscopic potential spectra recorded at different energies highlight n-type semi-conduction behaviours for both oxides, Cr2O3 and Ni1−xFexCr2O4. Moreover, MPEC images recorded at different energies exhibit contrasted regions in photocurrent, describing the distribution of nickel hydroxide and/or nickel ferrite and Cr2O3 in the oxide film at a micron scale. It is concluded that PEC techniques represent a sensitive and powerful way to locally analyse the various semiconductor phases in the oxide scale

How to Build the Best Macroscopic Description of your Multi-agent System? Application to News Analysis of International Relations

The design and debugging of large-scale MAS require abstraction tools in order to work at a macroscopic level of description. Agent aggregation provides such abstractions by reducing the microscopic description complexity. Since it leads to an information loss, such a key process may be extremely harmful if poorly executed. This research report presents measures inherited from information theory (Kullback-Leibler divergence and Shannon entropy) to evaluate ab- stractions and to provide the experts with feedbacks regarding the generated descriptions. Several evaluation techniques are applied to the spatial aggregation of an agent-based model of international rela- tions. The information from on-line newspapers constitutes a complex microscopic description of agent states. Our approach is able to evalu- ate geographical abstractions used by experts and to deliver them with e cient and meaningful macroscopic descriptions of the world state

Histoire et historiographie du christianisme tardoantique

Le « dossier du donatisme » dans l’Histoire ecclésiastique d’Eusèbe de Césarée Le Livre X de l’Histoire ecclésiastique d’Eusèbe de Césarée donne aux chapitres 5-7 le texte de six documents officiels, dont cinq lettres de l’empereur Constantin concernant les affaires religieuses africaines : 1. HE X, 5, 1-14 : Lettre de Constantin et Licinius à un haut administrateur (le gouverneur de la province de Palestine ?) ordonnant la tolérance religieuse et la restitution de tous les biens confisqués a..

Histoire et doctrine du christianisme latin (Antiquité tardive)

Aristoteles Poenorum. Portraits d’Augustin en « hérétique » (1er semestre. Ravenne chrétienne (« séminaire de master » et 2e semestre. Atelier de formation sur la Bible latine

Histoire et doctrines du christianisme latin (Antiquité tardive)

I. Peuple chrétien et controverses doctrinales dans l’Antiquité tardive (1er semestre) Le directeur d’études a présenté et illustré les résultats d’une large enquête historique sur la participation des fidèles aux controverses doctrinales du début du iiie s. aux années 430, qui sera prochainement publiée sous la forme d’un livre. Le sujet est né, pour ainsi dire, de la rencontre entre un passage célèbre d’une homélie constantinopolitaine de Grégoire de Nysse brocardant changeurs et boulangers..