Etude de l'évolution temporelle de phénomènes terrestres au moyen de l'imagerie radar

No abstractLes donnees radar sont tres sensibles aux modifications du sol. La technique interferometrique permet d'en etudier le relief et de suivre son evolution. La motivation principale de ce travail de these est de proposer des methodologies du traitement d'image, adaptees a ces donnees, pour etudier l'evolution de phenomenes complexes. Ce manuscrit, a l'instar du travail qu'il represente, se decompose en quatre parties. L'interpretation des images radar passe par la comprehension des differentes etapes menant a leur construction. La premiere partie est composee d'une introduction aux principes d'acquisition radar, suivie de la presentation des principes interferometriques. Les interferogrammes presentent des franges caracteristiques d'un repliement du signal. La deuxieme partie de ce document presente une methode de segmentation, dite de deroulement, permettant de lever cette ambiguite. Cette technique est appliquee pour reconstruire des modeles numeriques de terrain. Une fois les interferogrammes corriges de cette ambiguite de mesure, il devient possible de les etudier au moyen de leurs proprietes intrinseques. La troisieme partie utilise la sensibilite de cette acquisition aux modifications du sol pour proposer une methode de detection de changement par segmentation des effets de phase. Deux volets thematiques sont presentes, une etude des effets lies aux variations hygrometriques, et une application aux risques naturels via la detection des glissements de terrains. Ces regions en evolution etant detectees, il est possible d'utiliser une nouvelle fois la mesure interferometrique pour etudier l'evolution du relief au cours du temps. La quatrieme partie propose une methode de suivi, par mise en correspondance de surfaces. Cette methode est utilisee pour suivre l'evolution de la surface du sol. Chaque partie presente et analyse des resultats experimentaux. Ce document conclue par une presentation des perspectives d'evolution de ce travail de recherche

Muscle Specific Fragile X Related Protein 1 Isoforms are Sequestered in the Nucleus of Undifferentiated Myoblast

BACKGROUND: The family of Fragile X Mental Retardation Proteins is composed of three members: Fragile Mental Retardation 1, Fragile X Related 1 and X Related 2 proteins. These proteins are associated with mRNPs within translating ribosomes and have the capacity to shuttle between the nucleus and the cytoplasm. Great attention has been given to FMRP due to its implication in human hereditary mental retardation while FXR1P and FXR2P have only recently been studied. RESULTS: Using antibodies directed against several epitopes of FXR1P, we have detected protein isoforms generated by small peptides pocket inserts. Four isoforms of MW 70, 74, 78, 80 kDa are widely distributed in mouse organs, while in striated muscles these isoforms are replaced by proteins of 82 and 84 kDa containing an extra pocket of 27 aa. Expression of these muscle isoforms is an early event during in vitro differentiation of myoblasts into myotubes and correlates with the activation of muscle-specific genes. However, while FXR1P82,84 are associated with cytoplasmic mRNPs in myotubes, they are sequestered in the nuclei of undifferentiated myoblasts. These observations suggest that, in addition to a cytoplasmic function yet to be defined, FXR1P82,84 may play a nuclear role in pre-mRNA metabolism. CONCLUSIONS: The pattern of subcellular partitioning of FXR1P isoforms during myogenesis is unique among the family of the FXR proteins. The model system described here should be considered as a powerful tool for ongoing attempts to unravel structure-function relationships of the different FMR family members since the potential role(s) of FXR1P as a compensatory factor in Fragile X syndrome is still elusive

Dimensionality reduction on ocean model's outputs: Application to motion estimation on satellite images

International audienceMotion fields describing the ocean surface dynamics live in vectorial spaces of high dimension. Consequently, their estimation from satellite images requires huge computational resources. The issue of dimensionality reduction, that is the determination of representative low dimensional structures in these high dimensional spaces, is of major importance for any application that demands real-time or short-term results. Proper Order Decomposition allows to determine such subspace of motion fields on which estimation may be assessed with reduced complexity. A reduced model is obtained by Galerkin projection of evolution equations on this subspace. Motion is estimated by assimilating the observed image sequence with the reduced model. The paper describes how to derive the reduced space from a database of ocean model’s outputs and explains how to estimate surface circulation from satellite sequences. Results are given on images acquired on the Black Sea basin by NOAA-AVHRR sensors

Assimilation de données images dans un modèle de circulation océanographique

National audienceData assimilation allows to couple together a forecast model and observations. In this study we are interested in the association of a simulation model for oceanic circulation with data coming from image processing. We propose a processing chain to estimate circulation velocity from ocean temperature images, and the assimilation of this image observation in a forecast model.L'assimilation de données permet de coupler un modèle de prévision à des observations. Dans cette étude nous nous intéressons à l'intégration de caractéristiques images dans un modèle de simulation de la circulation océanique. Nous proposons une chaîne de traitement permettant d'estimer la vitesse de circulation sur une séquence d'images de température de l'océan et l'assimilation de cette observation image dans un modèle de prévision

Validation of surface velocity estimated from satellite images

This report concerns the validation of surface velocity estimated from satellite images. The estimation is obtained with a dynamic model based on shallow-water equations. We first compare the stationary assumption to the shallow-water heuristics to justify our choice. Second, we quantify the quality of the estimation by measuring the misfit between the model output and the altimetry measures. Experiments are achieved on Sea Surface Temperature data acquired by the NOAA/AVHRR satellites over the Black Sea. The altimetry measures are obtained by two radar sensors: Envisat and GFO. The good adequacy between the shallow-water output and the altimetry data validates our motion estimation approach.Ce rapport de recherche concerne la validation de l'estimation de la vitesse de surface à partir d'images satellite. Cette estimation est effectuée avec un modèle de la dynamique, basé sur les équations shallow-water. Nous comparons d'abord l'hypothèse de stationnarité aux équations shallow-water afin de justifier notre choix. Puis, nous quantifions la qualité des estimations en mesurant l'écart entre la sortie du modèle et les mesures d'altimétrie. Les expérimentations sont effectuées en utilisant des données de température de surface, acquises au-dessus de la Mer Noire avec les satellites NOAA/AVHRR. Les mesures altimétriques proviennent de deux capteurs radar : Envisat et GFO. La bonne adéquation entre la sortie du modèle shallow-water et les données altimétriques valide notre approche d'estimation du mouvement

Matching Structures by Computing Minimal Paths on a Manifold

International audienceThe general problem of matching structures is very pervasive in computer vision and image processing. The research presented here tackles the problem of object matching in a very general perspective. It is formulated for the matching of surfaces. It applies to objects having small or large deformation and arbitrary topological changes. The process described hinges on a geodesic distance equation for a family of curves or surfaces embedded in the graph of a cost function. This geometrical approach to object matching has the advantage that the similarity criterion can be used to define the shape of the cost function. Matching paths are computed on the cost manifolds using distance maps. These distance maps are generated by solving a general partial differential equation which is a generalization of the geodesic dis- tance evolution scheme introduced by R. Kimmel, A. Amir, and A. F. Bruckstein (1995, IEEE Trans. Pattern Anal. Mach. Intell. 17, 635-640). An Eulerian level-set formulation is also introduced, leading to a numerical scheme used for solving par- tial differential equations originating from hyperbolic conservation laws, which has proven to be very robust and stable

Mise en correspondance de surfaces par chemins géodésiques

Projet AIRDans cette étude les auteurs s'intéressent au problème de la mise en correspondance de surfaces. Nous proposons une solution originale pour prendre en compte les grandes déformations et les changements de topologie. La méthode décrite repose sur le calcul d'une carte de distances géodésiques sur un graphe de coût. La fontion de coût représente le critère de mise en correspondance entre les deux surfaces reposant sur le graphe. Ce graphe est une variété de dimension 3 (ou une hypersurface) plongée dans un espace à 4 dimensions. La théorie présentée dans ce document est une généralisation de la méthode d'évolution de courbes géodésiques introduite en 1995 par Kimmel et al. Une formulation utilisant la théorie des isocontours est utilisée pour décrire l'évolution des surfaces comme des isosurfaces. Cette formulation, dite eulérienne, procure un shéma numérique stable pour résoudre les équations aux dérivées partielles. La méthode est appliquée à des exemples montrant à la fois des petites et des grandes déformations ainsi que des changements de topologie

Validation of surface velocity estimated from satellite images

This report concerns the validation of surface velocity estimated from satellite images. The estimation is obtained with a dynamic model based on shallow-water equations. We first compare the stationary assumption to the shallow-water heuristics to justify our choice. Second, we quantify the quality of the estimation by measuring the misfit between the model output and the altimetry measures. Experiments are achieved on Sea Surface Temperature data acquired by the NOAA/AVHRR satellites over the Black Sea. The altimetry measures are obtained by two radar sensors: Envisat and GFO. The good adequacy between the shallow-water output and the altimetry data validates our motion estimation approach.Ce rapport de recherche concerne la validation de l'estimation de la vitesse de surface à partir d'images satellite. Cette estimation est effectuée avec un modèle de la dynamique, basé sur les équations shallow-water. Nous comparons d'abord l'hypothèse de stationnarité aux équations shallow-water afin de justifier notre choix. Puis, nous quantifions la qualité des estimations en mesurant l'écart entre la sortie du modèle et les mesures d'altimétrie. Les expérimentations sont effectuées en utilisant des données de température de surface, acquises au-dessus de la Mer Noire avec les satellites NOAA/AVHRR. Les mesures altimétriques proviennent de deux capteurs radar : Envisat et GFO. La bonne adéquation entre la sortie du modèle shallow-water et les données altimétriques valide notre approche d'estimation du mouvement

Identification of equivalent topography in an open channel flow using Lagrangian data assimilation

International audienceWe present a Lagrangian data assimilation experiment in an open channel flow above a broad-crested weir. The observations consist of trajectories of particles transported by the flow and extracted from a video film, in addition to classical water level measurements. However, the presence of vertical recirculations on both sides of the weir actually conducts to the identification of an equivalent topography corresponding to the lower limit of a surface jet. In addition, results on the identification of the Manning coefficient may allow to detect the presence of bottom recirculations

Relationship between positive end-expiratory pressure levels, central venous pressure, systemic inflammation and acute renal failure in critically ill ventilated COVID-19 patients: a monocenter retrospective study in France

Background The role of positive pressure ventilation, central venous pressure (CVP) and inflammation on the occurrence of acute kidney injury (AKI) have been poorly described in mechanically ventilated patient secondary to coronavirus disease 2019 (COVID-19). Methods This was a monocenter retrospective cohort study of consecutive ventilated COVID-19 patients admitted in a French surgical intensive care unit between March 2020 and July 2020. Worsening renal function (WRF) was defined as development of a new AKI or a persistent AKI during the 5 days after mechanical ventilation initiation. We studied the association between WRF and ventilatory parameters including positive end-expiratory pressure (PEEP), CVP, and leukocytes count. Results Fifty-seven patients were included, 12 (21%) presented WRF. Daily PEEP, 5 days mean PEEP and daily CVP values were not associated with occurrence of WRF. 5 days mean CVP was higher in the WRF group compared to patients without WRF (median [IQR], 12 mm Hg [11-13] vs. 10 mm Hg [9–12]; P=0.03). Multivariate models with adjustment on leukocytes and Simplified Acute Physiology Score (SAPS) II confirmed the association between CVP value and risk of WRF (odd ratio, 1.97; 95% confidence interval, 1.12–4.33). Leukocytes count was also associated with occurrence of WRF in the WRF group (14 G/L [11–18]) and the no-WRF group (9 G/L [8–11]) (P=0.002). Conclusions In mechanically ventilated COVID-19 patients, PEEP levels did not appear to influence occurrence of WRF. High CVP levels and leukocytes count are associated with risk of WRF