Background Light in Potential Sites for the ANTARES Undersea Neutrino Telescope

The ANTARES collaboration has performed a series of {\em in situ} measurements to study the background light for a planned undersea neutrino telescope. Such background can be caused by $^{40}$K decays or by biological activity. We report on measurements at two sites in the Mediterranean Sea at depths of 2400~m and 2700~m, respectively. Three photomultiplier tubes were used to measure single counting rates and coincidence rates for pairs of tubes at various distances. The background rate is seen to consist of three components: a constant rate due to $^{40}$K decays, a continuum rate that varies on a time scale of several hours simultaneously over distances up to at least 40~m, and random bursts a few seconds long that are only correlated in time over distances of the order of a meter. A trigger requiring coincidences between nearby photomultiplier tubes should reduce the trigger rate for a neutrino telescope to a manageable level with only a small loss in efficiency.Comment: 18 pages, 8 figures, accepted for publication in Astroparticle Physic

Media Roles in Suicide Prevention: A Systematic Review

The aim of the current systematic review was to monitor and provide an overview of the research performed about the roles of media in suicide prevention in order to find out possible effects media reporting on suicidal behaviours might have on actual suicidality (completed suicides, attempted suicides, suicidal ideation). The systematic review was performed following the principles of the PRISMA statement and includes 56 articles. Most of the studies support the idea that media reporting and suicidality are associated. However, there is a risk of reporting bias. More research is available about how irresponsible media reports can provoke suicidal behaviours (the ‘Werther effect’) and less about protective effect media can have (the ‘Papageno effect’). Strong modelling effect of media coverage on suicide is based on age and gender. Media reports are not representative of official suicide data and tend to exaggerate sensational suicides, for example dramatic and highly lethal suicide methods, which are rare in real life. Future studies have to encounter the challenges the global medium Internet will offer in terms of research methods, as it is difficult to define the circulation of news in the Internet either spatially or in time. However, online media can provide valuable innovative qualitative research material

Sedimentation and Fouling of Optical Surfaces at the ANTARES Site

ANTARES is a project leading towards the construction and deployment of a neutrino telescope in the deep Mediterranean Sea. The telescope will use an array of photomultiplier tubes to detect the Cherenkov light emitted by muons resulting from the interaction with matter of high energy neutrinos. In the vicinity of the deployment site the ANTARES collaboration has performed a series of in-situ measurements to study the change in light transmission through glass surfaces during immersions of several months. The average loss of light transmission is estimated to be only ~2% at the equator of a glass sphere one year after deployment. It decreases with increasing zenith angle, and tends to saturate with time. The transmission loss, therefore, is expected to remain small for the several year lifetime of the ANTARES detector whose optical modules are oriented downwards. The measurements were complemented by the analysis of the ^{210}Pb activity profile in sediment cores and the study of biofouling on glass plates. Despite a significant sedimentation rate at the site, in the 0.02 - 0.05 cm.yr^{-1} range, the sediments adhere loosely to the glass surfaces and can be washed off by water currents. Further, fouling by deposits of light-absorbing particulates is only significant for surfaces facing upwards.Comment: 18 pages, 14 figures (pdf), submitted to Astroparticle Physic

Les effets de contagion suicidaire (revue de littérature, élaboration d une étude française, mécanismes et implications pour la prévention)

Le phénomène de contagion suicidaire est un processus par lequel l'exposition au suicide ou au comportement suicidaire d'une ou plusieurs personnes influence d'autres à commettre ou tenter le suicide. Lers "clusters" de suicides correspondent à des effets de contagion limités au sein d'une communauté ; l' "effet Werther" est un phénomène par lequel la diffusion d'une histoire de suicide dans les media provoque une augmentation statistiquement significative du nombre de suicides dans la population. Une revue de littérature sur l'effet de contagion suicidaire semble montrer que le phénomène existe, sous certaines conditions : les facteurs favorisant l'apparition d'une épidémie de suicides sont le caractère réel du modèle (et non un modèle fictif), son statut de célébrité, le montant de publicité accordée à l'événement, et des facteurs de risque individuels de suicide préexistants dans la population exposée. Différentes théories ont tenté d'expliquer les mécanismes de cette contagion : les sociologues ont analysé le processus d'imitation (Durkheim, Tarde, Stack) ; Freud adéveloppé le concept d'identification et montre son implication dans les phénomènes de masse , les processus d'imitation et d'apprentissage social sont repris par les travaux de psychologie sociale et cognitivo-comportementale (Bandura, Berkowitz, Wheeler). Nous avons mené une première étude française en partenariat avec le centre de recherche Inserm U897 , afin de rechercher un effet Werther après la médiatisation de suicides célèbres de 1979 à 2006, pour ensuite analyser les caractéristiques favorables ou non à son observation. La démonstration de l'existence du phénomène a permis de développer des mesures de prévention efficaces : recommandations à l'attention des professionnels des media, afin que les suicides soient rapportés de manière adaptée et éthique, et programmes de "postvention", particulièrement efficaces lors de la survenue d'un suicide dans une communauté.BORDEAUX2-BU Santé (330632101) / SudocSudocFranceF