Report for 2011 from the Bordeaux IVS Analysis Center

This report summarizes the activities of the Bordeaux IVS Analysis Center during the year 2011. The work focused on (i) regular analysis of the IVS-R1 and IVS-R4 sessions with the GINS software package; (ii) systematic VLBI imaging of the RDV sessions and calculation of the corresponding source structure index and compactness values; (iii) imaging of the sources observed during the 2009 International Year of Astronomy IVS observing session; and (iv) continuation of our VLBI observational program to identify optically-bright radio sources suitable for the link with the future Gaia frame. Also of importance is the enhancement of the IVS LiveWeb site which now comprises all IVS sessions back to 2003, allowing one to search past observations for session-specific information (e.g. sources or stations)

Report for 2012 from the Bordeaux IVS Analysis Center

This report summarizes the activities of the Bordeaux IVS Analysis Center during the year 2012. The work focused on (i) regular analysis of the IVS-R1 and IVS-R4 sessions with the GINS software package; (ii) systematic VLBI imaging of the RDV sessions and calculation of the corresponding source structure index and compactness values; (iii) investigation of the correlation between astrometric position instabilities and source structure variations; and (iv) continuation of our VLBI observational program to identify optically-bright radio sources suitable for the link with the future Gaia frame. Also of importance is the 11th European VLBI Network Symposium, which we organized last October in Bordeaux and which drew much attention from the European and International VLBI communities

Three distinct sarcomeric patterns of skeletal muscle revealed by SHG and TPEF microscopy.

International audienceWe have extensively characterized the sarcomeric SHG signal as a function of animal species (rat versus xenopus), age (adult versus larval) and tissue preparation (fixed or fresh) and we found that the main feature of this signal is a single peak per mature sarcomere (about 85% of all sarcomeres). The remaining (15%) was found to be either double peak per mature sarcomere or mini sarcomeres (half of a sarcomere) using alpha-actinin immuno detection of the Z-band. The mini sarcomeres are often found in region of pitchfork-like SHG pattern. We suggest that double peak SHG pattern could indicate regions of sarcomeric proteolysis whereas pitchfork-like SHG pattern could reveal sarcomeric assembly

Joint Shape and Motion Estimation using Markovian Fields : Application to Multislice Computed Tomography Cardiac Imaging

We propose a method for joint surface and non-rigid motion estimation from three-dimensional dynamic sequences. Based on a surface-volume matching, it provides, from one first segmented surface, both motion and deformations of the object of interest along the whole sequence. A Markovian model, combined with a simulated annealing process, estimates the correspondences between the nodes of the surface mesh modeling the object of interest at one time and the voxels of the volume representing the object at the following time. The method has been applied to cardiac surface and motion extraction in Multislice Computed Tomography. Tests realized with simulated motion and on real data have provided promising results.Une méthode d'estimation conjointe de forme et de mouvement non rigide à partir de séquences temporelles tridimensionnelles est proposée. Reposant sur une mise en correspondance surface-volume, elle permet, à partir d'une première segmentation de l'objet d'intérêt, d'estimer le mouvement de l'objet et ses déformations sur toute la séquence temporelle d'observation. Une modélisation markovienne combinée à un algorithme de recuit simulé estime les correspondances entre les noeuds du maillage de surface modélisant l'objet à un instant et les voxels du volume représentant l'objet à l'instant suivant. La méthode a été appliquée à l'extraction de formes et de mouvements cardiaques en tomodensitométrie multibarrette. Les tests, réalisés à la fois avec des mouvements simulés et sur des données réelles, ont donné des résultats prometteurs

Couplage d'un modèle vasculaire bi-niveau et d'un modèle d'acquisition d'images : application à la simulation d'IRM dynamique du Carcinome Hépatocellulaire

La modélisation physiologique permet de mieux comprendre les images médicales et de mettre en évidence, dans l'image, des marqueurs de la pathologie. Dans cet article, nous proposons de coupler un modèle de la vascularisation hépatique à un modèle d'acquisition d'Images de - Résonance Magnétique (IRM), et d'appliquer ces modèles à la simulation d'IRM dynamique du Carcinome Hépatocellulaire (CHC). Le modèle vasculaire intègre les propriétés anatomiques et fonctionnelles clos vaisseaux, modifiées au cours du développement tumoral (densité vasculaire, débits, perméabilité, etc). Il permet de simuler la propagation de différents produits de contraste, ou tenant compte de leurs principales propriétés physiques et magnétiques, aux niveaux macro- et micro-vasculaire. Les images simulées à clos temps d'acquisition différents (phase artérielle, phase portale) présentent clos contrastes proches de ceux observés sur clos images réelles

The Yin-Yang of the Green Fluorescent Protein:Impact on Saccharomyces cerevisiae stress resistance

International audienceAlthough fluorescent proteins are widely used as biomarkers (Yin), no study focuses on their influence on the microbial stress response. Here, the Green Fluorescent Protein (GFP) was fused to two proteins of interest in Saccharomyces cerevisiae. Pab1p and Sur7p, respectively involved in stress granules structure and in Can1 membrane domains. These were chosen since questions remain regarding the understanding of the behavior of S. cerevisiae facing different heat kinetics or oxidative stresses. The main results showed that Pab1p-GFP fluorescent mutant displayed a higher resistance than that of the wild type under a heat shock. Moreover, fluorescent mutants exposed to oxidative stresses displayed changes in the cultivability compared to the wild type strain. In silico approaches showed that the presence of the GFP did not influence the structure and so the functionality of the tagged proteins meaning that changes in yeast resistance were certainly related to GFP ROS-scavenging ability (Yang)

Dormancy and longevity of soil-buried weed seeds : from examples to generalization

EA SPE EcolDur GEAPSI CT3 CT1The main part of the life-cycle of weeds, especially in cultivated fields, is spent as seeds buried in the soil. Longevity and dormancy are two major traits driving weed survival and infestation in the framework of crop rotation and management. Modelling allows inference of these key processes from morpho-anatomical description of the seeds, thus avoiding long-term germination studies of buried seeds over the years. Two new sets of experimental data on two different weeds offer the opportunity to compare actual results to predicted values. This study deals with cornflower (Centaurea cyanus), a winter weed of cereals and oilseed rape in regression in Western Europe, and wild radish (Raphanus raphanistrum), a spring-emerging weed in oilseed rape and cereals abundant in acidic soil. Cornflower has naked seeds while wild radish seeds are protected from water and oxygen access and fungal and bacterial attacks within pod segments. In addition, we used small and large-seeded populations of wild radish in order to increase morphological variation. Seeds were buried in the soil 30 cm below surface, and a fraction was excavated every month for three years, and then tested for survival and dormancy. Survival of cornflower seeds declined quickly after two years while no mortality was observed for wild radish. The prediction of longevity in terms of seed coat thickness fitted the expected range of values. Both species displayed seasonal dormancy, the peak of germination being delayed by two months for wild radish versus cornflower. Consequences on life-cycle and infestation potential are discussed as well as the efficiency of interpolating traits values from other species

A new approach in combined modeling of MRI and blood flow: A preliminary study.

International audienceWe propose a computational model to simulate the physical processes implied in the Magnetic Resonance Images formation in vascularised tissues. A combined model of MRI acquisition and blood flow is presented. The blood flow patterns are modeled using the Lattice Boltzmann Method, and the magnetic resonance experiments follow the Bloch equation. A new algorithm has been developed to compute the local magnetizations transport during the excitation, precession and relaxation steps. First results were compared to theoretical values of phase flow accumulation and amplitude attenuation. Next, the proposed algorithm is applied to simulate MR images in a simple stenosed vessel and in bifurcations. Characteristic flow artefacts are observed

Comparaison De Scores Géométrique Et Dosimétrique Pour La Mise En Correspondance Inter-Patients En Radiothérapie De La Prostate.

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Cuttlefish color change as an emerging proxy for ecotoxicology

International audienceLately, behavioral ecotoxicology has flourished because of increasing standardization of analyses of endpoints like movement. However, research tends to focus on a few model species, which limits possibilities of extrapolating and predicting toxicological effects and adverse outcomes at the population and ecosystem level. In this regard, it is recommended to assess critical species-specific behavioral responses in taxa playing key roles in trophic food webs, such as cephalopods. These latter, known as masters of camouflage, display rapid physiological color changes to conceal themselves and adapt to their surrounding environments. The efficiency of this process depends on visual abilities and acuity, information processing, and control of chromatophores dynamics through nervous and hormonal regulation with which many contaminants can interfere. Therefore, the quantitative measurement of color change in cephalopod species could be developed as a powerful endpoint for toxicological risk assessment. Based on a wide body of research having assessed the effect of various environmental stressors (pharmaceutical residues, metals, carbon dioxide, anti-fouling agents) on the camouflage abilities of juvenile common cuttlefish, we discuss the relevance of this species as a toxicological model and address the challenge of color change quantification and standardization through a comparative review of the available measurement techniques