Fast Photoswitchable Molecular Prosthetics Control Neuronal Activity in the Cochlea

Altres ajuts: CERCA Programme/Generalitat de Catalunya, Fundaluce and "la Caixa" foundations (ID 100010434, agreement LCF/PR/HR19/52160010)Artificial control of neuronal activity enables the study of neural circuits and restoration of neural functions. Direct, rapid, and sustained photocontrol of intact neurons could overcome the limitations of established electrical stimulation such as poor selectivity. We have developed fast photoswitchable ligands of glutamate receptors (GluRs) to enable neuronal control in the auditory system. The new photoswitchable ligands induced photocurrents in untransfected neurons upon covalently tethering to endogenous GluRs and activating them reversibly with visible light pulses of a few milliseconds. As a proof of concept of these molecular prostheses, we applied them to the ultrafast synapses of auditory neurons of the cochlea that encode sound and provide auditory input to the brain. This drug-based method afforded the optical stimulation of auditory neurons of adult gerbils at hundreds of hertz without genetic manipulation that would be required for their optogenetic control. This indicates that the new photoswitchable ligands are also applicable to the spatiotemporal control of fast spiking interneurons in the brain

2D and 3D Polar Plume Analysis from the Three Vantage Positions of STEREO/EUVI A, B, and SOHO/EIT

Polar plumes are seen as elongated objects starting at the solar polar regions. Here, we analyze these objects from a sequence of images taken simultaneously by the three spacecraft telescopes STEREO/EUVI A and B, and SOHO/EIT. We establish a method capable of automatically identifying plumes in solar EUV images close to the limb at 1.01 - 1.39 R in order to study their temporal evolution. This plume-identification method is based on a multiscale Hough-wavelet analysis. Then two methods to determined their 3D localization and structure are discussed: First, tomography using the filtered back-projection and including the differential rotation of the Sun and, secondly, conventional stereoscopic triangulation. We show that tomography and stereoscopy are complementary to study polar plumes. We also show that this systematic 2D identification and the proposed methods of 3D reconstruction are well suited, on one hand, to identify plumes individually and on the other hand, to analyze the distribution of plumes and inter-plume regions. Finally, the results are discussed focusing on the plume position with their cross-section area.Comment: 22 pages, 10 figures, Solar Physics articl

Intercomparison of the LASCO-C2, SECCHI-COR1, SECCHI-COR2, and Mk4 Coronagraphs

In order to assess the reliability and consistency of white-light coronagraph measurements, we report on quantitative comparisons between polarized brightness [pB] and total brightness [B] images taken by the following white-light coronagraphs: LASCO-C2 on SOHO, SECCHI-COR1 and -COR2 on STEREO, and the ground-based MLSO-Mk4. The data for this comparison were taken on 16 April 2007, when both STEREO spacecraft were within 3.1 deg. of Earths heliographic longitude, affording essentially the same view of the Sun for all of the instruments. Due to the difficulties of estimating stray-light backgrounds in COR1 and COR2, only Mk4 and C2 produce reliable coronal-hole values (but not at overlapping heights), and these cannot be validated without rocket flights or ground-based eclipse measurements. Generally, the agreement between all of the instruments pB values is within the uncertainties in bright streamer structures, implying that measurements of bright CMEs also should be trustworthy. Dominant sources of uncertainty and stray light are discussed, as is the design of future coronagraphs from the perspective of the experiences with these instruments

The SARS algorithm: detrending CoRoT light curves with Sysrem using simultaneous external parameters

Surveys for exoplanetary transits are usually limited not by photon noise but rather by the amount of red noise in their data. In particular, although the CoRoT spacebased survey data are being carefully scrutinized, significant new sources of systematic noises are still being discovered. Recently, a magnitude-dependant systematic effect was discovered in the CoRoT data by Mazeh & Guterman et al. and a phenomenological correction was proposed. Here we tie the observed effect a particular type of effect, and in the process generalize the popular Sysrem algorithm to include external parameters in a simultaneous solution with the unknown effects. We show that a post-processing scheme based on this algorithm performs well and indeed allows for the detection of new transit-like signals that were not previously detected.Comment: MNRAS accepted. 5 pages, 3 figure

Application du traitement des images a la photometrie astronomique et a la physique

SIGLECNRS T Bordereau / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Rapport V.8 Méthode expérimentale de mesure de la dispersion de surface d'un rejet urbain en mer par télédétection photographique quantitative

Exprrimental method to measure the surface dispersion of a sewage to the sea by means of digital photographic remote sensing. In face of the complexity of the surface dispersion phenomenon in Mediterranean sea the CETE d'Aix carried ont a method to measure in situ the surface currentology and dispersion who play a part in the choise of the release point in the sea for sewage. For that a drop of floats and rhodamine blob is managed with a continuons release of rhodamin at the surface all along a day with a constant out flow. Filtered vertical aircraft photographs give the spatiotempral variation. The evolution of punctual drop gives a visualisation and measurement of surface currents, the digitalitation and data processing of each photograph give an iso-quantity of rhodamine contour map of the plume. We get from the surface dilution in each point of the plume.Devant la complexité des phénomènes de dispersion de surface en Méditerranée le CETE d'Aix-en-Provence a mis au point une méthode de mesure in-situ de la courantologie et de la dispersion de surface qui intervient dans le choix du point de rejet d'eaux usées urbaines en mer. Pour cela outre des lâchers de radeaux et de taches ponctuelles de Rhodamine, il est procédé à un lâcher continu de Rhodamine en surface à débit constant toute une journée. Leur évolution est suivie par photographies aériennes verticales filtrées. Le suivi des lâchers d'objets ponctuels permet une visualisation et une mesure des courants de surface. La numérisation puis le traitement informatique de chaque photographie, fournit la cartographie en courbes d' iso-quantité de Rhodamine du lâcher continu. On en extrait la dilution de surface en chaque point du panache de Rhodamine.Valerio Claudine, Llebaria Antoine. Rapport V.8 Méthode expérimentale de mesure de la dispersion de surface d'un rejet urbain en mer par télédétection photographique quantitative. In: L'assainissement de demain. L'hydraulique des eaux pluviales et usées. Compte-rendu des XVIIes journées de l'hydraulique. Nantes,14-16 septembre 1982. Tome 2, 1982

Modélisation paramétrique de structures de la couronne solaire

Nous résumons tout d'abord les aspects liés au développement instrumental, à l'étalonnage et au traitement des données issues des coronographes embarqués à bord des sondes SOHO et STEREO. Nous décrivons ensuite les méthodes de modélisation paramétrique que nous avons utilisé. Nous montrons comment ces méthodes permettent de tester et de valider les hypothèses concernant la morphologie des structures couronales, mais aussi de déterminer leur position dans l'espace ainsi que la distribution 3D de leur densité électronique. Nous illustrons ceci à travers trois études. La première concerne la modélisation de la structure 3D d'un jet coronal. Dans la seconde étude, nous avons appliqué notre méthode à 34 CMEs de type corde de flux observées par LASCO-C2 pendant la période 1997-2002. Enfin, la troisième étude concerne la modélisation d'une CME en corde de flux vue en stéréoscopie grâce aux sondes jumelles STEREO-SECCHI.AIX-MARSEILLE3-BU Sc.St Jérô (130552102) / SudocSudocFranceF

Détermination de la structure tri-dimensionnelle de la couronne solaire

Cette thèse présente une nouvelle méthode de simulation directe de la ceinture de grands jets, structure principale de la couronne solaire. Cette méthode présente l'avantage de fournir des résultats à la fois qualitatifs et quantitatifs, et prend en compte l'évolution temporelle de la couronne. Elle débute par le calcul du champ magnétique à la surface source pour un instant précis, nécessaire à la localisation de la ceinture de grands jets. Un modèle mathématique de densité électronique liée à la ceinture de grands jets est ensuite présenté. La densité 3D résultante est alors compressée sous forme d'octree qui permet un échantillonnage non uniforme de l'espace et un gain considérable en temps de calcul et en espace mémoire. Les images de radiance sont calculées à partir de l'octree par lancer de rayons en intégrant la diffusion Thomson. L'évolution temporelle est simulée par l'utilisation de 9 octrees calculés pour 9 configurations différentes du champ magnétique dans une rotation complète du Soleil (rotation Carrington). Enfin, la méthode se termine par un ajustement des paramètres liés à la densité électronique.L'ensemble de cette méthode est appliqué à la simulation de la ceinture de grands jets pour les périodes de minimum et de maximum d'activité.Les résultats sont comparés aux observations du coronographe LASCO-C2 à bord du satellite SOHO.Ils permettent de déduire de nouveaux modèles de densité électronique et d'étudier l'évolution de la couronne.This thesis proposes a new forward modeling method of the streamer belt, the main structure of the solar corona. This method provides both qualitative and quantitative results, and take into account the time evolution of the corona.It begins with the computation of the magnetic field at the source surface at a given time, required to locate the streamer belt. A simple geometric model of electron density is used to describe the streamer belt. The full 3D electron density is represented by an octree compressed form allowing a non uniform sampling of the 3D space, allowing a gain in memory space and in time computation. Radiance images are computed using a ray-tracing algorithm including the Thomson scattering. The time evolution of the corona is simulated by 9 octrees, representing 9 different configurations of the magnetic field during a full rotation of the solar corona (Carrington rotation). The method ends by a fitting process of the electron density parameters.The whole method is applied to simulate the streamer belt during minimum and maximum activity periods.Resulting images are compared to LASCO-C2 observations, a coronagraph onboard SOHO spacecraft.They allows to determine new models of electron density and to study the temporal evolution of the solar coronaAIX-MARSEILLE1-BU Sci.St Charles (130552104) / SudocSudocFranceF

Design of polychromatic PSFs for the COROT experiment

International audienc