A statistical approach for identifying the ionospheric footprint of magnetospheric boundaries from SuperDARN observations

Identifying and tracking the projection of magnetospheric regions on the high-latitude ionosphere is of primary importance for studying the Solar Wind-Magnetosphere-Ionosphere system and for space weather applications. By its unique spatial coverage and temporal resolution, the Super Dual Auroral Radar Network (SuperDARN) provides key parameters, such as the Doppler spectral width, which allows the monitoring of the ionospheric footprint of some magnetospheric boundaries in near real-time. In this study, we present the first results of a statistical approach for monitoring these magnetospheric boundaries. The singular value decomposition is used as a data reduction tool to describe the backscattered echoes with a small set of parameters. One of these is strongly correlated with the Doppler spectral width, and can thus be used as a proxy for it. Based on this, we propose a Bayesian classifier for identifying the spectral width boundary, which is classically associated with the Polar Cap boundary. The results are in good agreement with previous studies. Two advantages of the method are: the possibility to apply it in near real-time, and its capacity to select the appropriate threshold level for the boundary detection

Sex steroid and 1,25-dihydroxyvitamin D3 receptors in human colorectal adenocarcinoma and normal mucosa

In order to determine the potential role of sex steroid and 1,25-dihydroxyvitamin D3 in the spreading of colorectal cancer, previously hypothesized from epidemiological and experimental data, specific androgen (AR, n = 94), estrogen (ER, n = 60), progesterone (PGR, n = 50), and 1,25-dihydroxyvitamin D3 receptors (VDR, (n = 111) were investigated in human colorectal adenocarcinoma (AC) and compared with the normal adjacent mucosa (NM). Scatchard analysis and competition studies of binding data did not reveal any difference between the biochemical behavior (affinity, specificity, and sedimentation coefficient) of the normal and tumoral tissue receptors. For ARs and ERs, high incidences were found (92 of 94 and 90 of 94 in NM versus 46 of 60 and 40 of 60 in AC, respectively) in both classes of tissues, while they were low for progesterone (7 of 50 and 5 of 50 in NM versus AC). While for sex steroid receptors the incidences did not vary with sex and age of the patients or the location and histopathological grade of the tumor, the VDR incidence was lower in AC (35 of 111) than in NM (99 of 111) and decreased significantly from the right colon to the rectum in adenocarcinoma. Binding capacities were similar in NM and AC for ERs and VDRs, whereas AR levels in NM were significantly higher than in AC. The expression of VDRs in some colorectal tumors suggests a possible clinical significance. No known function for sex steroid receptors is related to their presence in human colorectal tissues and their pattern in carcinoma does not support any hypothesis previously raised in the case of chemically induced colonic tumors in rodent

Contribuição de imagens SAR ERS-1 no monitoramento das transformações costeiras na Guiana Francesa

The French Guiana coast (320 km) is subjected to intense morphological changes linked to the fate of the wide Amazon input of particulates in the Tropical Westem Atlantic. Mudbanks, mudflats, modern cheniers and mangroves' evolution are under the strong influence of this dispersion system. The goal of the "Coastal Environrnent Programm" of ORSTOM Cayenne, presently conducted by M.T.PROST. is to identify the dominant coastal processes controlling these changes and to provide a better understanding of their action on different scales of time and space.Pages: 470-47

Refilling process in the plasmasphere: a 3-D statistical characterization based on Cluster density observations

The Cluster mission offers an excellent opportunity to investigate the evolution of the plasma population in a large part of the inner magnetosphere, explored near its orbit's perigee, over a complete solar cycle. The WHISPER sounder, on board each satellite of the mission, is particularly suitable to study the electron density in this region, between 0.2 and 80 cm⁻³. Compiling WHISPER observations during 1339 perigee passes distributed over more than three years of the Cluster mission, we present first results of a statistical analysis dedicated to the study of the electron density morphology and dynamics along and across magnetic field lines between <I>L</I> = 2 and <I>L</I> = 10. In this study, we examine a specific topic: the refilling of the plasmasphere and trough regions during extended periods of quiet magnetic conditions. To do so, we survey the evolution of the ap index during the days preceding each perigee crossing and sort out electron density profiles along the orbit according to three classes, namely after respectively less than 2 days, between 2 and 4 days, and more than 4 days of quiet magnetic conditions (ap &le; 15 nT) following an active episode (ap > 15 nT). This leads to three independent data subsets. Comparisons between density distributions in the 3-D plasmasphere and trough regions at the three stages of quiet magnetosphere provide novel views about the distribution of matter inside the inner magnetosphere during several days of low activity. Clear signatures of a refilling process inside an expended plasmasphere in formation are noted. A plasmapause-like boundary, at <I>L</I> ~ 6 for all MLT sectors, is formed after 3 to 4 days and expends somewhat further after that. In the outer part of the plasmasphere (<I>L</I> ~ 8), latitudinal profiles of median density values vary essentially according to the MLT sector considered rather than according to the refilling duration. The shape of these density profiles indicates that magnetic flux tubes are not fully replenished after 6 days of quiet conditions. In addition, the outer plasmasphere in the night and dawn sectors (22:00 to 10:00 MLT range) maintains an overall clear deficit of ionospheric population, when compared to the situation in the noon and dusk sectors (10:00 to 22:00 MLT range)

Guide méthodologique d'aide à la gestion intégrée de la zone côtière

La conception d'un guide méthodologique d'aide et la gestion intégrée de la zone côtière est une initiative des Présidents des Comités Français du PICG, de la COI, du MAB et du PHI de l'Unesco, répondant ainsi aux recommandations émises par la 18ème session de l'Assemblée de la COI dans le cadre du programme OSNLR. En s'attachant à une démarche résolument pluridisciplinaire et intégratrice, une dizaine d'exemples d'expertises sur l'environnement côtier sont analysés en s'appuyant sur les travaux de l'Ifremer, du BRGM, de l'Orstom et du CNRS (Université de Bretagne Occidentale et Perpignan). A la lumière des études de cas, il est ensuite proposé une méthodologie d'approche de la gestion de l'information environnementale afin d'aboutir à la mise en oeuvre de tableaux de bord de suivi de l'environnement côtier. (Résumé d'auteur