Direct observation of Anderson localization of matter-waves in a controlled disorder

We report the observation of exponential localization of a Bose-Einstein condensate (BEC) released into a one-dimensional waveguide in the presence of a controlled disorder created by laser speckle . We operate in a regime allowing AL: i) weak disorder such that localization results from many quantum reflections of small amplitude; ii) atomic density small enough that interactions are negligible. We image directly the atomic density profiles vs time, and find that weak disorder can lead to the stopping of the expansion and to the formation of a stationary exponentially localized wave function, a direct signature of AL. Fitting the exponential wings, we extract the localization length, and compare it to theoretical calculations. Moreover we show that, in our one-dimensional speckle potentials whose noise spectrum has a high spatial frequency cut-off, exponential localization occurs only when the de Broglie wavelengths of the atoms in the expanding BEC are larger than an effective mobility edge corresponding to that cut-off. In the opposite case, we find that the density profiles decay algebraically, as predicted in [Phys. Rev. Lett. 98, 210401 (2007)]. The method presented here can be extended to localization of atomic quantum gases in higher dimensions, and with controlled interactions

Natalizumab treatment shows low cumulative probabilities of confirmed disability worsening to EDSS milestones in the long-term setting.

Abstract Background Though the Expanded Disability Status Scale (EDSS) is commonly used to assess disability level in relapsing-remitting multiple sclerosis (RRMS), the criteria defining disability progression are used for patients with a wide range of baseline levels of disability in relatively short-term trials. As a result, not all EDSS changes carry the same weight in terms of future disability, and treatment benefits such as decreased risk of reaching particular disability milestones may not be reliably captured. The objectives of this analysis are to assess the probability of confirmed disability worsening to specific EDSS milestones (i.e., EDSS scores ≥3.0, ≥4.0, or ≥6.0) at 288 weeks in the Tysabri Observational Program (TOP) and to examine the impact of relapses occurring during natalizumab therapy in TOP patients who had received natalizumab for ≥24 months. Methods TOP is an ongoing, open-label, observational, prospective study of patients with RRMS in clinical practice. Enrolled patients were naive to natalizumab at treatment initiation or had received ≤3 doses at the time of enrollment. Intravenous natalizumab (300 mg) infusions were given every 4 weeks, and the EDSS was assessed at baseline and every 24 weeks during treatment. Results Of the 4161 patients enrolled in TOP with follow-up of at least 24 months, 3253 patients with available baseline EDSS scores had continued natalizumab treatment and 908 had discontinued (5.4% due to a reported lack of efficacy and 16.4% for other reasons) at the 24-month time point. Those who discontinued due to lack of efficacy had higher baseline EDSS scores (median 4.5 vs. 3.5), higher on-treatment relapse rates (0.82 vs. 0.23), and higher cumulative probabilities of EDSS worsening (16% vs. 9%) at 24 months than those completing therapy. Among 24-month completers, after approximately 5.5 years of natalizumab treatment, the cumulative probabilities of confirmed EDSS worsening by 1.0 and 2.0 points were 18.5% and 7.9%, respectively (24-week confirmation), and 13.5% and 5.3%, respectively (48-week confirmation). The risks of 24- and 48-week confirmed EDSS worsening were significantly higher in patients with on-treatment relapses than in those without relapses. An analysis of time to specific EDSS milestones showed that the probabilities of 48-week confirmed transition from EDSS scores of 0.0–2.0 to ≥3.0, 2.0–3.0 to ≥4.0, and 4.0–5.0 to ≥6.0 at week 288 in TOP were 11.1%, 11.8%, and 9.5%, respectively, with lower probabilities observed among patients without on-treatment relapses (8.1%, 8.4%, and 5.7%, respectively). Conclusions In TOP patients with a median (range) baseline EDSS score of 3.5 (0.0–9.5) who completed 24 months of natalizumab treatment, the rate of 48-week confirmed disability worsening events was below 15%; after approximately 5.5 years of natalizumab treatment, 86.5% and 94.7% of patients did not have EDSS score increases of ≥1.0 or ≥2.0 points, respectively. The presence of relapses was associated with higher rates of overall disability worsening. These results were confirmed by assessing transition to EDSS milestones. Lower rates of overall 48-week confirmed EDSS worsening and of transitioning from EDSS score 4.0–5.0 to ≥6.0 in the absence of relapses suggest that relapses remain a significant driver of disability worsening and that on-treatment relapses in natalizumab-treated patients are of prognostic importance

Mise en œuvre d’une plateforme cartographique participative pour le suivi des basses eaux dans les Cévennes (France)

International audienceMobiliser les citoyens dans une démarche d’appui à la recherche est une action très rependue dans le domaine des sciences de la nature et tout particulièrement pour l’obtention de données sur la localisation et le comptage d’espèces végétales et/ou animales. Cette pratique est beaucoup moins rependue pour l’observation de la ressource en eau même si des études pionnières ont montré un gain potentiel de ce type de démarche pour le suivi de la hauteur d’eau sur des cours d’eau ou des étangs et plus récemment pour le suivi des inondations. Dans le cadre de cette étude une plateforme cartographique en ligne a été développée pour recueillir les données (photos, vidéos, commentaires, valeurs de hauteurs,…) des citoyens sur les basses eaux durant la période estivale sur le bassin cévenol des Gardons (Département du Gard, France). 3 profils de volontaires ont été identifiés pour alimenter la plateforme ; (1) le profil « lecteur » qui va faire remonter une hauteur d’eau sur des points préalablement aménagés (lecture d’échelle limnimétrique), (2) le profil « expert » pour lequel un protocole précis a été défini avec le groupe de chercheurs et (3) un profil plus générique qui lors de sa visite sur la zone étudiée va faire remonter une large gamme d’observations (assecs, présence d’algues,…) à sa convenance et sans contraintes de type de donnée ou de lieux à observer. Il s’agira ainsi de présenter dans cette communication la plateforme cartographique participative développée et les premiers résultats obtenus en focalisant sur l’importance de ces données pour améliorer la connaissance et le suivi des étiages dans les Cévennes mais également sur la participation des citoyens. Participation des citoyens qui est un élément fondamental car elle permet une sensibilisation à la problématique des basses eaux et donc à la protection de cette ressource dont la diminution en quantité lors de l’été est susceptible d’impacter fortement les activités et les personnes sur ces territoires de moyenne montagne méditerranéenne

Anderson localization of matter-waves

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Observation directe de localisation d'Anderson d'ondes de matière dans un potentiel désordonné

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Anderson Localization of an expanding BEC in laser speckle

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Anderson localization of matter wave in a controlled disorder

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Anderson Localization of matter-wave in laser speckle

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Systèmes d'information géographique : études de cas

International audienceL'utilisation des informations géographiques s'est considérablement développée avec l'essor des outils informatiques. Dans les entreprises ou les administrations, les systèmes d'information géographique (SIG) permettent la représentation de l'environnement spatial à partir de formes géométriques de base (polygones, vecteurs, maillages...). Les SIG exploitent donc des outils logiciels, des données à traiter, des serveurs informatiques, mais également des savoir-faire techniques. Cet article propose de présenter aux ingénieurs les potentialités offertes par les SIG et les outils informatiques associés. Ainsi, des exemples d'exploitation de SIG sont exposés sur des thématiques variées

Anderson localization of matter-waves in a controlled disorder: a quantum simulator ?

conference; actesInternational audienc