University of Rennes

About: University of Rennes is a education organization based out in Rennes, France. It is known for research contribution in the topics: Population & Crystal structure. The organization has 18404 authors who have published 40374 publications receiving 995327 citations.

A parallel FDTD algorithm using the MPI library

Abstract: In this paper, we describe the essential elements of a parallel algorithm for the FDTD method using the MPI (message passing interface) library. To simplify and accelerate the algorithm, an MPI Cartesian 2D topology is used. The inter-process communications are optimized by the use of derived data types. A general approach is also explained for parallelizing the auxiliary tools, such as far-field computation, thin-wire treatment, etc. For PMLs, we have used a new method that makes it unnecessary to split the field components. This considerably simplifies the computer programming, and is compatible with the parallel algorithm.

Organic contamination of settled house dust, a review for exposure assessment purposes.

Abstract: People spend a considerable amount of time indoors. As a result, exposure to indoor contaminants is of great concern, notably via settled dust ingestion in particular for infants and toddlers. This paper proposes a critical review on the organic contamination of settled house dust and human exposure over the past 10 years and focused on sources, contaminations and measurement methods (sampling, pretreatment, storage and analysis). As many compounds were identified, arises the question of which ones to consider. Sensitive and selective analytical methods for simultaneous determination of targeted substances should be developed and evaluated. Various methods were described for sampling and sample preparation. Harmonization and standardization are needed to enable comparison of results from similar studies. Finally, an integrated multipollutant and multicompartment (settled dust, suspended particles and air) approach appears essential in order to determine the extent of the threat to public health posed by indoor contaminants.

Influence of xenobiotics on rainbow trout liver estrogen receptor and vitellogenin gene expression.

Abstract: Rainbow trout hepatocyte primary culture was used to test the influence of some xenobiotics on the expression of two genes implicated in reproduction, those for the estrogen implicated in reproduction, those for the estrogen receptor (ER) and vitellogenin (Vg). We showed that chlordecone, nonylphenol, a polychlorobiphenol (PCB) mixture (Aroclor 1245) and lindane were able to induce ER and Vg mRNA accumulation. Antiestrogens, 4-hydroxytamoxifen and ICI 164,384, prevented the effects of the xenobiotics, indicating that the induction of gene expression is mediated by the ER. Among these four xenobiotics, only chlordecone and nonylphenol were able to displace the binding of [3H]estradiol to ER-enriched COS-1 extracts, and to activate an estrogen-dependent reporter gene (ERE-TK-CAT) cotransfected with an expression vector containing ER cDNA. The results suggest that chlordecone and nonylphenol are direct inducers of rainbow trout ER and Vg gene expression, whereas PCBs and lindane act through their hepatic metabolites. Moreover, pentachlorophenol acts as an antagonist of the induction by estradiol of rainbow trout ER and Vg gene expression.

Mixed modes in red giants: a window on stellar evolution

Abstract: Context. The detection of oscillations with a mixed character in subgiants and red giants allows us to probe the physical conditions in their cores. Aims. With these mixed modes, we aim at determining seismic markers of stellar evolution. Methods. Kepler asteroseismic data were selected to map various evolutionary stages and stellar masses. Seismic evolutionary tracks were then drawn with the combination of the frequency and period spacings. Results. We measured the asymptotic period spacing for 1178 stars at various evolutionary stages. This allows us to monitor stellar evolution from the main sequence to the asymptotic giant branch and draw seismic evolutionary tracks. We present clear quantified asteroseismic definitions that characterize the change in the evolutionary stages, in particular the transition from the subgiant stage to the early red giant branch, and the end of the horizontal branch. Conclusions. The seismic information is so precise that clear conclusions can be drawn independently of evolution models. The quantitative seismic information can now be used for stellar modeling, especially for studying the energy transport in the heliumburning core or for specifying the inner properties of stars entering the red or asymptotic giant branches. Modeling will also allow us to study stars that are identified to be in the helium-subflash stage, high-mass stars either arriving or quitting the secondary clump, or stars that could be in the blue-loop stage.