Radiological dose reconstruction for birds reconciles outcomes of Fukushima with knowledge of dose-effect relationships

International audienceWe reconstructed the radiological dose for birds observed at 300 census sites in the 50-km northwest area affected by the accident at the Fukushima Daiichi nuclear power plant over 2011-2014. Substituting the ambient dose rate measured at the census points (from 0.16 to 31μGy h-1) with the dose rate reconstructed for adult birds of each species (from 0.3 to 97μGy h-1), we confirmed that the overall bird abundance at Fukushima decreased with increasing total doses. This relationship was directly consistent with exposure levels found in the literature to induce physiological disturbances in birds. Among the 57 species constituting the observed bird community, we found that 90% were likely chronically exposed at a dose rate that could potentially affect their reproductive success. We quantified a loss of 22.6% of the total number of individuals per increment of one unit log10-tansformed total dose (in Gy), over the four-year post-accident period in the explored area. We estimated that a total dose of 0.55 Gy reduced by 50% the total number of birds in the study area over 2011-2014. The data also suggest a significant positive relationship between total dose and species diversity. © 2015, Nature Publishing Group. All rights reserved

Une plateforme pour l'analyse de matériaux par faisceaux d'ions à ARRONAX : Etude de l'effet d'humidité sur les échantillons

International audienceQuantification of soil pollution with method based on X-ray detection like X-Ray Fluorescence(XRF) suffers of multiple bias (moisture, surface state) especially when it's used for insituanalysis using portable-XRF. In order to study the effect of moisture on the results of ananalysis performed using X-Ray, we have performed studies using high energy PIXE/PIGE atthe ARRONAX. Samples were made of sand of different type. High energy PIXE/PIGE allowsus to avoid bias from surface state and to focus on moisture effect. It also allows to assessthe chemical composition of the sample. Results show a different behavior for each elementpresent in volcanic sand.</p

2D frequency-domain full-waveform inversion of GPR data: Permittivity and conductivity imaging

International audienceFull waveform inversion of Ground Penetrating Radar data is a promising and challenging technique. As both dielectric permittivity and electrical conductivity should be recovered, the associated inverse problem is intrinsically multi-parameter. It requires to properly account for the influence of the Hessian matrix to mitigate the trade-offs between constitutive parameters. Recently, a first step in this direction was performed with the l-BFGS quasi-Newton method, which is based on an approximation of the inverse Hessian computed from previous gradient estimations. We propose to go further in solving locally the Newton equation related to the optimization workflow. For this purpose, we implement the truncated Newton method where the computation of the gradient and Hessian-vector products are respectively based on first-order and second-order adjoint state methods. On a synthetic case study, using the TE mode with borehole and surface acquisitions, we compare our results with those obtained using the l-BFGS method and we show an improvement in the precision of reconstructed parameters. A better decoupling between the two parameters is obtained with the truncated Newton method

ASTRAL : un logiciel pour l'évaluation des conséquences d'un rejet accidentel de radionucléides dans l'environnement

ASTRAL est acronyme d'“ Assistance Technique en Radioprotection Post-accidentelle ”. Si un rejet important de radionucléides dans l'environnement se produisait, il faudrait rapidement évaluer la concentration des radionucléides dans les milieux et les produits alimentaires, en déduire l'exposition potentielle aux rayonnements des populations concernées, prévoir l'évolution de la situation et proposer différents scénarios de gestion des zones contaminées. A ces fins, il a été décidé il y trois ans environ de créer un logiciel utilisable par un ensemble relativement large d'agents gréant les centres de crise, réalisant des études prévisionnelles, ou s'occupant habituellement du contrôle de l'impact des rejets de routine. Le point de départ des estimations est le dépôt sur le sol des radionucléides. La phase de dispersion atmosphérique et les conséquences de l'exposition au nuage et aux radionucléides à vie courte ne sont pas traitées ici. Les calculs effectués concernent à la fois l'évolution dans le temps des concentrations des radionucléides dans les sols et les éléments de la chaîne alimentaire, ainsi que l'évaluation des doses efficaces dues à l'exposition externe et interne. Ces grandeurs sont comparées aux limites et niveaux d'intervention en vigueur. Différentes simulations de la gestion des zones contaminées peuvent être conduites par application de contre-mesures. Ainsi, le logiciel ASTRAL peut être utilisé comme un élément d'aide à la décision.

Simultaneous GPR Reconstruction of Electrical Conductivity and Permittivity

International audienceGround-penetrating radar (GPR) is a non-invasive prospecting technique based on the electromagnetic waves sampling of the near surface. Building quantitative images through these waves requires the reconstruction of both electrical permittivity and conductivity. This multi-parameter reconstruction is performed through the minimization of a misfit function measuring the discrepancy between observed and synthetic data. The minimization is achieved with a local descent method based on the Newton equation. Both the gradient and the product of the Hessian matrix with a model vector are necessary for avoiding any trade-off between parameter classes, especially when high contrasts are encountered by electromagnetic waves. This presentation is devoted to the design of these two key ingredients needed when updating the model, based on efficient first- and second-order adjoint methods. We formulate the problem in the frequency domain and we show that we need two forward modeling for the gradient and two additional forward modeling for the product of the Hessian matrix and a model vector. Our formulation is such that these quantities are obtained through solution fields, regardless of the numerical scheme used to obtain them

Dose reconstruction supports the interpretation of decreased abundance of mammals in the Chernobyl Exclusion Zone

International audienceWe re-analyzed field data concerning potential effects of ionizing radiation on the abundance of mammals collected in the Chernobyl Exclusion Zone (CEZ) to interpret these findings from current knowledge of radiological dose-response relationships, here mammal response in terms of abundance. in line with recent work at fukushima, and exploiting a census conducted in february 2009 in the CEZ, we reconstructed the radiological dose for 12 species of mammals observed at 161 sites. We used this new information rather than the measured ambient dose rate (from 0.0146 to 225 µGy h −1) to statistically analyze the variation in abundance for all observed species as established from tracks in the snow in previous field studies. All available knowledge related to relevant confounding factors was considered in this re-analysis. this more realistic approach led us to establish a correlation between changes in mammal abundance with both the time elapsed since the last snowfall and the dose rate to which they were exposed. this relationship was also observed when distinguishing prey from predators. the dose rates resulting from our re-analysis are in agreement with exposure levels reported in the literature as likely to induce physiological disorders in mammals that could explain the decrease in their abundance in the ceZ. our results contribute to informing the Weight of Evidence approach to demonstrate effects on wildlife resulting from its field exposure to ionizing radiation

La banque de données CIBLEX, une compilation de paramètres d'exposition de la population française au voisinage d'un site pollué

International audienceIn addition to the identification of the potential exposure pathways of the population, the quantitative impact assessment of a soil pollution requires the best available knowledge of the daily exposure parameters for the people living in or near the polluted area. Aiming to characterize in this way the French population, the French Agency for Environment and Energy Management (Ademe) and the Institute for Radioprotection and Nuclear Safety (IRSN) collaborated to produce the computer databank Ciblex. It describes the exposure parameters of the population (age, sex, activities, dietary habits…) as a function of the land use (artificial areas, semi-natural land, water surfaces…) and its corresponding vocation (residential, professional, leisure…). These data can be consulted individually for several geographical levels, or they can be extracted from the bank in correspondence with an exposure scenario, which is defined by the user for a reference group. The Ciblex bank constitutes a consultative tool developed in priority for experts involved in risk assessments associated with the management of area polluted by chemicals or radionuclides. But it is equally very interesting for most of the environmental problems that need to characterize a site or a population.Quantifier l'impact d'un site pollué impose de connaître les paramètres d'exposition des personnes vivant sur ce site ou à proximité. Pour cela, l'Agence de l'environnement et de la maîtrise de l'énergie et l'Institut de radioprotection et de sûreté nucléaire ont développé la banque de données Ciblex. Elle fournit une description de la population française (âge, sexe, activités…) selon l'occupation des sols et leur vocation (résidentielle, professionnelle…). Ces données sont consultables individuellement ou automatiquement extraites suivant un scénario d'exposition défini par l'utilisateur. Ciblex, développée prioritairement pour les évaluations de risques liés aux pollutions chimiques ou radioactives des sols, est utilisable pour tout problème impliquant la caractérisation d'un lieu et/ou d'une population

Estetrol prevents western diet-induced obesity and atheroma independently of hepatic estrogen receptor (ER)α

International audienceEstetrol (E4), a natural estrogen synthesized by the human fetal liver, is currently evaluated in phase III clinical studies as a new menopause hormone therapy. Indeed, E4 significantly improves vasomotor and genito-urinary menopausal symptoms and prevents bone demineralization. Compared to other estrogens, E4 was found to have limited effects on coagulation factors in the liver of women allowing to expect less thrombotic events. To fully delineate its clinical potential, the aim of this study was to assess the effect of E4 on metabolic disorders. Here, we studied the pathophysiological consequences of a western diet (42% kcal fat, 0.2% cholesterol) in ovariectomized female mice under chronic E4 treatment. We showed that E4 reduces body weight gain and improves glucose tolerance in both C57Bl/6 and LDLR(-/-) mice. To evaluate the role of hepatic ERα in the preventive effect of E4 against obesity and associated disorders such as atherosclerosis and steatosis, mice harbouring a hepatocyte-specific ERα deletion (LERKO) were crossed with LDLR(-/-) mice. Our results demonstrated that, whereas liver ERα is dispensable for the E4 beneficial actions on obesity and atheroma, it is necessary to prevent steatosis in mice. Overall, these findings suggest that E4 could prevent metabolic, hepatic and vascular disorders occurring at menopause, extending the potential medical interest of this natural estrogen as a new hormonal treatment

Nuclear translocation of MRTFA in MCF7 breast cancer cells shifts ERα nuclear/genomic to extra-nuclear/non genomic actions

International audienceThe Myocardin-related transcription factor A [MRTFA, also known as Megakaryoblastic Leukemia 1 (MKL1))] is a major actor in the epithelial to mesenchymal transition (EMT). We have previously shown that activation and nuclear accumulation of MRTFA mediate endocrine resistance of estrogen receptor alpha (ERα) positive breast cancers by initiating a partial transition from luminal to basal-like phenotype and impairing ERα cistrome and transcriptome. In the present study, we deepen our understanding of the mechanism by monitoring functional changes in the receptor’s activity. We demonstrate that MRTFA nuclear accumulation down-regulates the expression of the unliganded (Apo-)ERα and causes a redistribution of the protein localization from its normal nuclear place to the entire cell volume. This phenomenon is accompanied by a shift in Apo-ERα monomer/dimer ratio towards the monomeric state, leading to significant functional consequences on ERα activities. In particular, the association of Apo-ERα with chromatin is drastically decreased, and the remaining ERα binding sites are substantially less enriched in ERE motifs than in control conditions. Monitored by proximity Ligation Assay, ERα interactions with P160 family coactivators are partly impacted when MRTFA accumulates in the nucleus, and those with SMRT and NCOR1 corepressors are abolished. Finally, ERα interactions with kinases such as c-src and PI3K are increased, thereby enhancing MAP Kinase and AKT activities. In conclusion, the activation and nuclear accumulation of MRTFA in ERα positive breast cancer cells remodels both ERα location and functions by shifting its activity from nuclear genome regulation to extra-nuclear non-genomic signaling