Regulation of WASP/WAVE proteins: making a long story short

Despite their homology, the regulation of WASP and WAVE, activators of Arp2/3-dependent actin polymerization, has always been thought to be different. Several recent studies have revealed new aspects of their regulation, highlighting its complexity and the crucial role of post-translational modifications. New data also suggest additional functions for WASP family proteins, pushing us to reconsider existing models

Long-Term Effects of Botulinum Toxin Complex Type A Injection on Mechano-and Metabo-Sensitive Afferent Fibers Originating from Gastrocnemius Muscle

International audienceThe aim of the present study was to investigate long term effects of motor denervation by botulinum toxin complex type A (BoNT/A) from Clostridium Botulinum, on the afferent fibers originating from the gastrocnemius muscle of rats. Animals were divided in 2 experimental groups: 1) untreated animals acting as control and 2) treated animals in which the toxin was injected in the left muscle, the latter being itself divided into 3 subgroups according to their locomotor recovery with the help of a test based on footprint measurements of walking rats: i) no recovery (B0), ii) 50% recovery (B50) and iii) full recovery (B100). Then, muscle properties , metabosensitive afferent fiber responses to potassium chloride (KCl) and lactic acid injections and Electrically-Induced Fatigue (EIF), and mechanosensitive responses to tendon vibrations were measured. At the end of the experiment, rats were killed and the toxin injected muscles were weighted. After toxin injection, we observed a complete paralysis associated to a loss of force to muscle stimulation and a significant muscle atrophy, and a return to baseline when the animals recover. The response to fatigue was only decreased in the B0 group. The responses to KCl injections were only altered in the B100 groups while responses to lactic acid were altered in the 3 injected groups. Finally, our results indicated that neurotoxin altered the biphasic pattern of response of the mechanosensitive fiber to tendon vibrations in the B0 and B50 groups. These results indicated that neurotoxin injection induces muscle afferent activity alterations that persist and even worsen when the muscle has recovered his motor activity

Photometric visual servoing for omnidirectional cameras

International audience2D visual servoing consists in using data provided by a vision sensor for controlling the motions of a dynamic system. Most of visual servoing approaches has relied on the geometric features that have to be tracked and matched in the image acquired by the camera. Recent works have highlighted the interest of taking into account the photometric information of the entire image. This approach was tackled with images of perspective cameras. We propose, in this paper, to extend this technique to central cameras. This generalization allows to apply this kind of method to catadioptric cameras and wide field of view cameras. Several experiments have been successfully done with a fisheye camera in order to control a 6 degrees of freedom (dof) robot and with a catadioptric camera for a mobile robot navigation task

Les tensions autour de l'ancienneté entre les enseignants de différentes générations selon la perception des officiers syndicaux

Le concept d’ancienneté constitue un incontournable mode de régulation du travail dans plusieurs dispositions des conventions collectives au Québec. Dans cette optique, l’ancienneté est-il toujours en convergence avec les valeurs et les demandes des membres des différents syndicats? Ce projet de recherche exploratoire repose sur un nombre limité de cas et vise à documenter la nature des tensions autour des applications de l’ancienneté à l’intérieur des syndicats. Cela implique de mieux connaître les sources de ces tensions. Est-ce qu’elles sont en lien avec la précarité en emploi de l’enseignant? Est-ce une mauvaise application des clauses d’ancienneté des ententes locales au niveau des établissements? Est-ce que ces tensions sont en lien avec un changement de valeur des jeunes travailleurs du marché du travail, tel que le suggère certains auteurs (Allain, 2008; Mercure et Vultur, 2010; Service de placement du collège Maisonneuve, 2005). Donc, la question de recherche est la suivante : quelles sont les tensions autour du concept d’ancienneté et ses applications entre les enseignants de différentes générations aux ordres d’enseignements primaire et secondaire? Les organisations syndicales concernées pourront ainsi alimenter leur réflexion afin de confirmer ou modifier certaines applications de l’ancienneté toujours dans l’optique de rendre un service bonifié et adapté à leurs membres. La pertinence scientifique est également très importante puisqu’elle vise à expliquer certaines causes et manifestations des tensions autour de l’ancienneté. L’objectif de cette recherche exploratoire est de décrire les tensions autour de l’ancienneté entre les enseignants de différentes générations et de décrire certaines des causes et manifestations de ces tensions. Enfin, cette recherche souhaite participer à la discussion scientifique qui doit être entamée autour du rôle de l’ancienneté dans le marché du travail en tant que principe de justice

Choix éthiques et valeurs des collégiens: influence de l'environnement culturel

"La présente recherche a été subventionnée par l'Association des collèges privés du Québec dans le cadre du Programme de recherche et d'expérimentation"Titre de l'écran-titre (visionné le 8 mars 2007)Également disponible en format papierBibliogr

Phylogeography, Risk Factors and Genetic History of Hepatitis C Virus in Gabon, Central Africa

BACKGROUND: The epidemiological and molecular characteristics of hepatitis C virus (HCV) infection in the general population have been poorly investigated in Africa. The aim of this study was to determine the prevalence, genotype distribution and epidemic history of HCV in the Gabonese general population. METHODS/PRINCIPAL FINDINGS: A total of 4042 sera collected from adults in 220 villages in all nine administrative areas of the country were screened for antibodies to HCV. HCV NS5B region sequencing was performed for molecular characterization and population genetic analyses. Of 4042 tested sera, 455 (11.2%) were positive. The seroprevalence of HCV varied significantly by administrative area, with the highest rate in Ogooue-Lolo province (20.4%) and the lowest in Ogooue-Maritine province (3.7%). History of parenteral injections, past hospital admission and age over 55 years were independent risk factors for HCV infection (p<0.0001). Phylogenetic analyses showed that 91.9% of the strains were genotype 4 (HCV-4), 5.7% genotype 1 and 2.2% genotype 2. HCV-4 strains were highly heterogeneous, with more than eight subtypes; subtype 4e predominated (57.3%). Coalescence analyses indicated that subtype 4e was the oldest, with an estimated most recent common ancestor of 1702 [95% CI, 1418-1884]. The epidemic profile indicated that it spread exponentially during the first part of the 20th century, probably by iatrogenic transmission. CONCLUSIONS/SIGNIFICANCE: These results confirm the endemicity of HCV subtype 4e in Gabon and show that its spread is due to a cohort effect, with previous, possibly iatrogenic events. More extensive epidemiological studies are needed to better characterize the route of transmission and the dissemination of HCV in Gabon

Direct model based visual tracking and pose estimation using mutual information

International audienceThis paper deals with model-based pose estimation (or camera localization). The model is rendered as a virtual image and we propose a direct approach that takes into account the image as a whole. For this, we consider a sim- ilarity measure, the mutual information. Mutual information is a measure of the quantity of information shared by two signals (or two images in our case). Exploiting this measure allows our method to deal with different image modalities (real and synthetic). Furthermore, it handles occlusions and illu- mination changes. Results with synthetic (benchmark) and real image sequences, with static or mobile camera, demonstrate the robustness of the method and its ability to produce stable and precise pose estimations

Le patrimoine « in silico ». Exemple de la cathédrale d’Amiens

De nombreux projets en rapport avec la numérisation et la modélisation 3D de monuments historiques ont vu le jour ces dernières années, bénéficiant de l’accélération et de la fiabilisation des moyens techniques de relevé 3D et de traitement des données. La démocratisation de ces techniques et les avancées méthodologiques (notamment en photogrammétrie/vision par ordinateur) ont également participé à cet engouement. Construire une empreinte digitale fidèle et complète des monuments puis l’augmenter avec des connaissances textuelles pour en faire un objet d’étude et de recherche pluridisciplinaire, telle a été notre motivation principale pour concevoir et mettre en œuvre le programme E-Cathédr@le avec la cathédrale d’Amiens comme site privilégié. Nous nous sommes fixés comme objectif d’en faire un relevé complet (intérieur et extérieur), fidèle, précis, résolu et photométriquement réaliste. Chacun de ces critères recouvre une signification scientifique très précise et qui a des conséquences importantes sur le mode opératoire, sur la quantité des données à enregistrer et à manipuler. Ces critères nous ont également parfois obligés à mettre au point des modalités d’acquisition nouvelles et adaptées. Lancé en 2010, pour une durée estimée à quinze ans, ce programme a déjà permis la numérisation de plusieurs monuments en France (dont la cathédrale d’Amiens) et au Maroc grâce à un projet bilatéral de recherche. Ces modèles numériques font l’objet d’études et de travaux de recherche pluridisciplinaires, impliquant notamment l’informatique, la robotique, l’histoire de l’art et l’archéologie. Nous nous proposons ici de décrire ce programme, d’exposer les résultats de la numérisation de la cathédrale d’Amiens qui révèlent de manière inhabituelle des plans et des coupes d’élévations extrêmement précis et permettant de mieux « lire » l’architecture de ce monument. Nous livrerons également un retour d’expérience à partir des huit premières années du programme et évoquerons les difficultés posées par les projets de numérisation du patrimoine monumental.Several digital heritage projects for the creation of 3D models of historic buildings have emerged during recent years. Such projects have been stimulated by some significant advances in digital surveying technologies and in data processing. The wider diffusion of these techniques and several other methodological advances, notably in computer vision and photogrammetry, have also contributed to this phenomenon. The goal of the E-Cathédr@le programme, developed by our research group and centred on Amiens cathedral in France, is to keep a record of a historic monument which is as accurate and reliable as possible, and to enrich this record with textual information providing the basis for multidisciplinary research. While the objective is to cover the totality of the monument, both inside and out, and to take high-resolution and photometrically-realistic measurements, each of these criteria has its own scientific pertinence and an important impact on the modus operandi and on the quantities of data to be recorded and managed. These challenges forced us to design new adapted modalities of data capture. The programme was launched in 2010 and is expected to last 15 years. It has already allowed for the digitization of several other monuments in France and in Morocco, thanks to a bilateral research project. These digital models have been shared and widely used for multidisciplinary research in computer science, robotics, art history and archaeology. In this paper, we describe the E-Cathédr@le programme and we present its main results. In particular, we show how our 3D model of the monument allows for the easy creation of accurate plans and cross sections of the architecture. This in turn allows for the body of the building to be visualised in an innovative way. We conclude the paper with a discussion of the lessons learned during the first eight years of the programme, and of the main challenges and opportunities involved in digital heritage projects.