Modélisation de l'effet des hydrocarbures sur le système planctonique du golfe San Jorge, Argentine

RÉSUMÉ: L'écosystème côtier du golfe San Jorge (GSJ), situé à l'est du plateau de Patagonie (Argentine) est reconnu pour son importante productivité biologique permettant d'y soutenir la pêche industrielle et certaines activités touristiques. Depuis le début du XX\up{ème}, l'exploitation d'importants gisements pétroliers terrestres dans les provinces de Chubut et Santa-Cruz représente la moitié de la production d'hydrocarbures pétrolifères du pays. Dans l'avenir, cette exploitation pourrait s'étendre à l'environnement marin et par conséquent, menacer son équilibre actuel. Cette étude numérique, réalisée en parallèle de la mission PROMESse 2014, vise à comprendre la réponse de la dynamique planctonique dans la zone sud-est du GSJ lors d'une contamination chronique éventuelle par des hydrocarbures (HC). Nous présentons ici un modèle biogéochimique à onze compartiments couplé à un modèle de turbulence dans lequel nous avons paramétrisé les processus biologiques liés à la contamination, tels que la biodégradation des HC, la croissance et la mortalité du zoo- et du bactérioplancton. Un scénario de contamination chronique en surface, incluant plusieurs niveaux de perturbation, est appliqué à deux environnements physiquement contrastés retrouvé de part et d'autre d'un front d'origine tidale, une colonne d'eau bien mélangée et une colonne d'eau stratifiée. Les résultats de ces simulations montrent que, pour chaque niveau de perturbation, la biodégradation ne débute qu'au début de l'été avec l'augmentation de la biomasse bactérioplanctonique, lorsque la production primaire augmente. Le phytoplancton, notamment les diatomées, présentent une croissance élevée plus le niveau de perturbation est élevé. Cette tendance peut être associée à la diminution importante de la concentration zooplanctonique subissant la toxicité des HC dans la zone euphotique, limitant ainsi le broutage. De manière indirecte, l'ajout d'HC dans le système entraine aussi une augmentation de la production de détritus, résultant de l'augmentation de la mortalité du zooplancton mais aussi de l'augmentation des biomasses bactérienne et phytoplanctonique. Alors que les effets des HC semblent être plus marqués dans l'environnement stratifié, l'environnement bien-mélangé présente des concentrations en HC plus faibles et limite donc les effets directs et indirects sur les compartiments zoo- et phytoplanctonique. -- Mot(s) clé(s) en français : modélisation, cycles biogéochimiques, turbulence, hydrocarbures, écotoxicité, plancton, biodégradation. -- ABSTRACT: The coastal ecosystem of the San Jorge Gulf (SJG), located on the east part the Patagonian shelf (Argentina), is known for its high biological productivity supporting industrial fishing and some tourism activities. Since the beginning of the 20\up{th} century, the exploitation of large oil fields in the provinces of Chubut and Santa Cruz has contributed to half of the country's hydrocarbon petroleum production. In the future, this exploitation could be extended to the marine environment, consequently threatening its current state. This numerical study, carried out in parallel with the PROMESse 2014 mission, aims at understanding the planktonic dynamics in the south-eastern SJG zone during a potential chronic contamination by hydrocarbons (HC). We present here an eleven-compartment biogeochemical model coupled with a turbulence model in which we have parameterized biological processes related to contamination, such as biodegradation, growth and mortality of zoo- and bacterioplankton. A chronic surface contamination scenario, including several levels of disturbance, is applied to two physically contrasting environments found on either side of a tidally induced frontal zone, a well-mixed water column, and a stratified water column. The results of these simulations show that, for each level of disturbance, biodegradation only begins at the beginning of summer with the increase of bacterioplankton biomass, when the primary production increases. Phytoplankton, especially diatoms, shows high growth rates the higher the level of disturbance. This trend may be associated with the significant decrease in zooplankton concentration undergoing HC toxicity in the euphotic zone, thus limiting grazing. Indirectly, the addition of HC in the system also results in an increase of detritus production, resulting from increased zooplankton mortality but also from increased bacterial and phytoplanktonic biomasses. While the effects of HC seem to be more pronounced in the stratified environment, the well-mixed environment shows lower, more diluted concentrations of HC and therefore limits the direct and indirect effects on zoo- and phytoplankton compartments. -- Mot(s) clé(s) en anglais : modelling, biogeochemical cycles, turbulence, hydrocarbons, ecotoxicity, plankton, biodegradation

Effects of a Chronic Oil Spill on the Planktonic System in San Jorge Gulf, Argentina: A One-Vertical-Dimension Modeling Approach

Known for its high biological productivity, San Jorge Gulf (SJG) in Argentinian Patagonia is also an area of oil exploitation. To understand the dynamics of the SJG plankton ecosystem under several scenarios of potential hydrocarbon (HC) contamination, we present an 11-compartment biogeochemical model coupled to a turbulence model. In the coupled model, we parameterize the main physical and biological processes related to HC contamination, such as biodegradation, growth, and mortality of phyto-, zoo-, and bacterioplankton. Planktonic responses to several levels of HC contamination are studied for two physically contrasting SJG environments, a tidally well-mixed water column and a stratified water column. Results show increasing phyto-and bacterioplankton biomass with increasing HC concentration, which in turn produces more detritus. Zooplankton communities seem to respond differently depending on HC concentration, with major indirect changes occurring in the different size classes. Effects of HC contamination on biological compartments are stronger in the stratified than in the well-mixed environment.Fil: Klotz, Philippe. Institut des Sciences de la Mer de Rimouski; Canadá. Université du Québec à Rimouski; CanadáFil: Schloss, Irene Ruth. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina. Universidad Nacional de Tierra del Fuego; Argentina. Ministerio de Relaciones Exteriores, Comercio Interno y Culto. Dirección Nacional del Antártico. Instituto Antártico Argentino; ArgentinaFil: Dumont, Dany. Institut des Sciences de la Mer de Rimouski; Canadá. Université du Québec à Rimouski; Canad

Neutron diffraction on methane and hydrogen hydrates under high pressure

Gas hydrates are crystalline solids composed of water and gas. They have attracted considerable attention over the past decade both for their geophysical relevancy [1] and for their possible application to gas storage [2]. Pressure is a key parameter in the study of these systems as gas hydrates are believed to exist at pressure in nature and the gas content is found to increase in gas hydrates as their crystalline structure rearranges upon compression. In addition, high-pressure studies on gas hydrates offer new possibilities to explore water-gas interactions. We will present recent work on methane and hydrogen hydrates at high pressure performed by neutron diffraction in the GPa range [3]. Several issues including the gas content in the different high-pressure structures will be discussed

Comparison of Short-Term Estrogenicity Tests for Identification of Hormone-Disrupting Chemicals

The aim of this study was to compare results obtained by eight different short-term assays of estrogenlike actions of chemicals conducted in 10 different laboratories in five countries. Twenty chemicals were selected to represent direct-acting estrogens, compounds with estrogenic metabolites, estrogenic antagonists, and a known cytotoxic agent. Also included in the test panel were 17β-estradiol as a positive control and ethanol as solvent control. The test compounds were coded before distribution. Test methods included direct binding to the estrogen receptor (ER), proliferation of MCF-7 cells, transient reporter gene expression in MCF-7 cells, reporter gene expression in yeast strains stably transfected with the human ER and an estrogen-responsive reporter gene, and vitellogenin production in juvenile rainbow trout. 17β-Estradiol, 17α-ethynyl estradiol, and diethylstilbestrol induced a strong estrogenic response in all test systems. Colchicine caused cytotoxicity only. Bisphenol A induced an estrogenic response in all assays. The results obtained for the remaining test compounds—tamoxifen, ICI 182.780, testosterone, bisphenol A dimethacrylate, 4-n-octylphenol, 4-n-nonylphenol, nonylphenol dodecylethoxylate, butylbenzylphthalate, dibutylphthalate, methoxychlor, o,p′-DDT, p,p′-DDE, endosulfan, chlomequat chloride, and ethanol—varied among the assays. The results demonstrate that careful standardization is necessary to obtain a reasonable degree of reproducibility. Also, similar methods vary in their sensitivity to estrogenic compounds. Thus, short-term tests are useful for screening purposes, but the methods must be further validated by additional interlaboratory and interassay comparisons to document the reliability of the methods

Projet de conservation de la biodiversité dans la moyenne vallée du Zambèze après éradication de la mouche tsé-tsé (Zimbabwé). Etude de faisabilité d'un microprojet : le ranch communal de gibier de Gonono (Gonono communal game ranch)

Le "ranch communal de gibier de Gonono" s'inscrit dans le cadre des micro-projets proposés de manière consensuelle au Comité exécutif du "Projet de Conservation de la Biodiversité dans la Moyenne Vallée du Zambèze après l'Eradication. de la Mouche Tsé-tsé". Dans le but global d'améliorer durablement les conditions de vie de la population du Ward de Gonono, l'objectif spécifique de ce micro-projet est de mettre au point un mode local de production alternative de viande à bas prix à partir de la faune sauvage. Décidé et conçu avec les autorités du Ward, le ranch doit être progressivement géré par et pour la population du Ward. Il doit d'abord produire sur place une viande de gibier recherchée par les communautés locales qui n'y avaient accès jusqu'à présent que de manière illégale. Cette viande doit être produite à un coût modéré accessible à la population. Le ranch doit aussi permettre de conserver un espace étendu encore faiblement anthropisé en le valorisant par des productions à faible impact écologique. En phase de croisière, l'exploitation sur 3.000 hectares du peuplement multispécifique de gibier devrait permettre la fourniture annuelle de 3 0 tonnes carcasse de viande d'impala et 10. tonnes carcasse de viande d'autres espèces, soit une productivité de 13 kg carcasse de venaison par hectare. Quelques productions annexes sont aussi prévues. L'objectif économique est la couverture du prix de revient de la viande et non pas la recherche d'un profit financier. La création de ce ranch communal de gibier est une entreprise à caractère hautement innovant aux plans institutionnel et technique. Il doit donc être considéré comme une opération pilote à part entière et, à ce titre, doit pouvoir bénéficier d'un encadrement serré et d'un appui scientifique conséquent, tout au moins les premières années. (Résumé d'auteur

La communication littéraire et ses outils : écrits publics, écrits privés

À partir d’exemples portant sur divers types d’écrits (dictionnaire, journal, roman, correspondance), cet ouvrage interroge les formes de la communication littéraire dans les sphères publique et privée. Le Congrès national des sociétés historiques et scientifiques rassemble chaque année universitaires, membres de sociétés savantes et jeunes chercheurs. Ce recueil est issu de travaux présentés lors du 139e Congrès sur le thème « Langages et communication »

Reporting Magnetic Resonance Imaging in Men on Active Surveillance for Prostate Cancer : The PRECISE Recommendations-A Report of a European School of Oncology Task Force

Background: Published data on prostate magnetic resonance imaging (MRI) during follow-up of men on active surveillance are lacking. Current guidelines for prostate MRI reporting concentrate on prostate cancer (PCa) detection and staging. A standardised approach to prostate MRI reporting for active surveillance will facilitate the robust collection of evidence in this newly developing area. Objective: To develop preliminary recommendations for reporting of individual MRI studies in men on active surveillance and for researchers reporting the outcomes of cohorts of men having MRI on active surveillance. Design, setting, and participants: The RAND/UCLA Appropriateness Method was used. Experts in urology, radiology, and radiation oncology developed a set of 394 statements relevant to prostate MRI reporting in men on active surveillance for PCa. Each statement was scored for agreement on a 9-point scale by each panellist prior to a panel meeting. Each statement was discussed and rescored at the meeting. Outcome measurements and statistical analysis: Measures of agreement and consensus were calculated for each statement. The most important statements, derived from both group discussion and scores of agreement and consensus, were used to create the Prostate Cancer Radiological Estimation of Change in Sequential Evaluation (PRECISE) checklist and case report form. Results and limitations: Key recommendations include reporting the index lesion size using absolute values at baseline and at each subsequent MRI. Radiologists should assess the likelihood of true change over time (ie, change in size or change in lesion characteristics on one or more sequences) on a 1-5 scale. A checklist of items for reporting a cohort of men on active surveillance was developed. These items were developed based on expert consensus in many areas in which data are lacking, and they are expected to develop and change as evidence is accrued. Conclusions: The PRECISE recommendations are designed to facilitate the development of a robust evidence database for documenting changes in prostateMRI findings over time ofmen on active surveillance. If used, they will facilitate data collection to distinguish-measurement error and natural variability in MRI appearances from true radiologic progression. Patient summary: Few published reports are available on how to use and interpret magnetic resonance imaging for men on active surveillance for prostate cancer. The PRECISE panel recommends that data should be collected in a standardised manner so that natural variation in the appearance and measurement of cancer over time can be distinguished from changes indicating significant tumour progression. (C) 2016 European Association of Urology. Published by Elsevier B.V. All rights reserved.Peer reviewe

Rotating tomography Paris-Edinburgh cell:a novel portable press for micro-tomographic 4-D imaging at extreme pressure/temperature/stress conditions

International audienceThis paper presents details of instrumental development to extend synchrotron X-ray microtomography techniques to in situ studies under static compression (high pressure), shear stress or the both conditions at simultaneous high temperatures. To achieve this, a new rotating tomography Paris–Edinburgh cell has been developed. This ultra-compact portable device easily and successfully adapted to various multi-modal synchrotron experimental set-up at ESRF, SOLEIL and DIAMOND is explained in detail. An in-depth description of proof of concept first experiments performed on a high resolution imaging beamline is then given, which illustrate the efficiency of the set-up and the data quality that can be obtained

CAGIRE: a wide-field NIR imager for the COLIBRI 1.3 meter robotic telescope

The use of high energy transients such as Gamma Ray Bursts (GRBs) as probes of the distant universe relies on the close collaboration between space and ground facilities. In this context, the Sino-French mission SVOM has been designed to combine a space and a ground segment and to make the most of their synergy. On the ground, the 1.3 meter robotic telescope COLIBRI, jointly developed by France and Mexico, will quickly point the sources detected by the space hard X-ray imager ECLAIRs, in order to detect and localise their visible/NIR counterpart and alert large telescopes in minutes. COLIBRI is equipped with two visible cameras, called DDRAGO-blue and DDRAGO-red, and an infrared camera, called CAGIRE, designed for the study of high redshift GRBs candidates. Being a low-noise NIR camera mounted at the focus of an alt-azimutal robotic telescope imposes specific requirements on CAGIRE. We describe here the main characteristics of the camera: its optical, mechanical and electronics architecture, the ALFA detector, and the operation of the camera on the telescope. The instrument description is completed by three sections presenting the calibration strategy, an image simulator incorporating known detector effects, and the automatic reduction software for the ramps acquired by the detector. This paper aims at providing an overview of the instrument before its installation on the telescope.Comment: Accepted by Experimental Astronom