Définition d'une source de chaleur représentant l'apport de chaleur pour le soudage TIG

Minimiser les contraintes résiduelles après soudage revient à optimiser les paramètres opératoires. Dans le cas du TIG, on utilise pour la modélisation des transferts thermiques une source de chaleur représentant l'apport d'énergie fourni par l'arc. En exploitant une campagne d'essais de soudage et les simulations numériques associées, il a été possible de corréler les paramètres opératoires principaux du soudage avec les paramètres d'entrée de la source de chaleur. Les résultats ont ensuite été validés expérimentalement

Feeding ecology of Southern Ocean seastars inferred from stable isotopes ratios

The Southern Ocean is currently subjected to strong and contrasted impacts of climate change. The Western Antarctic Peninsula is one of the most rapidly warming regions of the world, resulting in sea ice cover decreases. Increasing seawater temperature and sea ice cover reduction in Western Antarctic Peninsula and associated regions will likely impact food web functioning through temperature-related changes in consumer physiology, modifications of benthic community structure (e.g. expansion of exogenous species such as predatory crabs), modifications of benthic-pelagic coupling intensity or disruption of benthic production. Asteroids (Echinoderms) are an important group of southern benthos. This group also has a great trophic variability and is potentially more resistant than other organisms to temperature changes (Peck et al. 2008). Consequently, they will be likely impacted by modifications in food webs functioning rather by direct warming and investigating their trophic ecology is necessary to infer how climate change will impact them. In this context, the aim of this study is to use stable isotopes ratios of C, N and S to infer sea stars trophic ecology. 16 species of sea stars spanning 10 different families sampled in multiple and contrasted habitats across Subantarctic (South Georgia, South Sandwich Islands, Falkland Islands) and Antarctic (South Shetland Islands, South Orkney Islands, Western Antarctic Peninsula) locations. In total, tegument samples from 213 specimens was analysed. Diversity and plasticity of asteroid diet along Southern Ocean coasts were explored through isotopic niche parametrisation (e.g. niche width and overlap between species and/or populations; Jackson et al. 2011). The data will also be used in a larger scale research project on the trophic ecology of Antarctic sea stars. This project will notably compare trophic resources supporting asteroid communities in Western Antarctic Peninsula, where sea ice cover is decreasing, and in Terre Adélie, where sea ice cover is increasing (Parkinson & Cavalieri 2012). Ultimately, this project will help understanding which ecological processes determine how an animal group copes with environmental modifications linked to climate change

Trophic ecology of Southern Ocean sea stars inferred from stable isotopes ratios of C and N

The Southern Ocean undergoes strong and contrasted impacts of climate change. Increasing seawater temperature and sea ice cover reduction in Western Antarctic Peninsula and associated regions will likely impact food web structure and function. Sea stars (Echinoderms: Asteroidea) are an important group of the Southern Ocean benthos. They typically have highly variable feeding habits and are potentially more resistant than other organisms to temperature changes. Consequently, they will likely be impacted by modifications of the food web rather than by direct warming. Investigating their trophic ecology is therefore necessary to infer how climate change will impact them. In this context, the aim of this study was to use stable isotopes ratios of C, N and S to infer sea stars trophic ecology. During austral summers 2006 and 2009, sea stars were sampled in Subantarctic and Antarctic locations, with most of the samples coming from South Shetland Islands and South Georgia. The isotopic niche (proxy of the trophic niche) associated to each sea star population was explored through SIBER (Stable Isotope Bayesian Ellipses in R) metrics. Stable isotope ratios of sea stars were clearly different between South Shetland Islands and South Georgia. Sea stars of South Shetland Islands had smaller isotopic niches than sea stars of South Georgia. The overlap between the isotopic niches of sea star species was also important in South Shetland Islands, while isotopic niches of South Georgia were well separated. Difference of niche width and overlap between the two regions may be the result of different environmental conditions. In South Shetland Islands, sea star species may exploit a common benthic community relying on organic matter released during sea ice summer melting. In contrast, South Georgia is an oligotrophic environment with no sea ice. As resources are more limited, a higher trophic segregation between sea stars may appear to limit competition. Ultimately, this project highlighted the importance of sea ice in the trophic ecology of Antarctic sea stars. Our results suggest that future reduction of sea ice extent in Western Antarctica may have deleterious effect on sea star populations

Food web structure in a rapidly changing coastal environment: the West Antarctic Peninsula

The West Antarctic Peninsula (WAP) is one of the most rapidly changing regions in the world, in great part due to anthropogenic climate change. Steep environmental gradients in water temperature, sea ice cover and glacier melting influence are observed, but much is left to document about significance of those shifts for biological communities and ecosystem processes. Here, we aimed to study how environmental changes impact trophic interactions and ecological habits of benthic communities along the WAP. During the Belgica 121 expedition, dominant benthic mega- and macrofauna, as well as primary producers, were sampled in multiple stations featuring contrasted environmental conditions around the Gerlache Strait. Stable isotope ratios of δ 13C, δ15N and δ34S were measured and combined in an isotope niche analysis (SIBER). Our results suggest that changes in environmental features, notably ice disturbance, could cause alteration of food sources availability and fluxes to benthic organisms. Isotopic compositions of abundant species were more variable in stations with stronger ice disturbance. Besides baseline variability, this could be linked with use of alternative resources (niche expansion) in stations influenced by glacier melting. Those results provide a first step towards understanding links between environmental change and ecological responses of benthic consumers along the WAP.RECTO: Refugia and Ecosystem Tolerance in the Southern Ocean (BR/154/A1/RECTO

Trophic plasticity in Antarctic echinoderms: an adaptive trait with implications at ecosystem wide scale?

editorial reviewedClimate change is expected to have many adverse biological effects in Antarctica, including perturbation of feeding habits and energy fluxes. Food availability and predator/prey interactions are considered major factors dictating survival of Antarctic fauna, and foraging strategies have been shown to drive population evolution in some taxa. Whenever facing environmental changes, all organisms are expected to have some intrinsic ability to adapt. At shorter than evolutionary timescales, ecological plasticity in general, and trophic plasticity (i.e. the ability to display different feeding habits according to variation in environmental conditions) in particular, could be important adaptive mechanisms. There is increasing evidence that many key Antarctic benthos members show a high degree of trophic plasticity. It could prove to be a beneficial trait, allowing those species to shift their diet and match the new environments they will face in the future. However, diet shifts may also have detrimental aspects, such as feeding on items whose quality or nature are not optimal for the consumers. Ultimately, trophic plasticity could have important consequences at wider biological organisation levels, as it could modulate secondary production by those taxa, as well as the way they interact with other taxa through trophic relationships. Assessing trophic plasticity in Antarctic zoobenthos is therefore a promising avenue to shed light on how environmental change can shape organisms’ roles in ecosystem functioning. In this talk, we will focus on how trophic tracers (stables isotope ratios of C, N and S) can help delineating feeding plasticity in selected echinoderm (sea star and sea urchin taxa) in both Antarctic and Subantarctic coastal marine ecosystems

Chagas Disease, France

Chagas Disease, Franc

A Genome-Wide Association Study of Diabetic Kidney Disease in Subjects With Type 2 Diabetes

dentification of sequence variants robustly associated with predisposition to diabetic kidney disease (DKD) has the potential to provide insights into the pathophysiological mechanisms responsible. We conducted a genome-wide association study (GWAS) of DKD in type 2 diabetes (T2D) using eight complementary dichotomous and quantitative DKD phenotypes: the principal dichotomous analysis involved 5,717 T2D subjects, 3,345 with DKD. Promising association signals were evaluated in up to 26,827 subjects with T2D (12,710 with DKD). A combined T1D+T2D GWAS was performed using complementary data available for subjects with T1D, which, with replication samples, involved up to 40,340 subjects with diabetes (18,582 with DKD). Analysis of specific DKD phenotypes identified a novel signal near GABRR1 (rs9942471, P = 4.5 x 10(-8)) associated with microalbuminuria in European T2D case subjects. However, no replication of this signal was observed in Asian subjects with T2D or in the equivalent T1D analysis. There was only limited support, in this substantially enlarged analysis, for association at previously reported DKD signals, except for those at UMOD and PRKAG2, both associated with estimated glomerular filtration rate. We conclude that, despite challenges in addressing phenotypic heterogeneity, access to increased sample sizes will continue to provide more robust inference regarding risk variant discovery for DKD.Peer reviewe

Hydrogeologie et transferts thermiques pour un aquifere en bassin sedimentaire : approche numerique

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