Flowability of plane homeomorphisms

We describe necessary and sufficient conditions for an orientation preserving fixed point free planar homeomorphism that preserves the standard Reeb foliation to embed in a planar flow that leaves the foliation invariant.Comment: 20 pages, 3 figure

Tensile response of the muscle-tendon complex using discrete element model

Tear of the muscle-tendon complex (MTC) is one of the main causes of sport injuries (De Labareyre et al. 2005). However, the mechanisms leading to such injury are still unclear (Uchiyama et al. 2011). Before modeling the tear of the MTC, its behavior in tensile test will be first studied. The MTC is a multi-scale, non isotropic and non continuous structure that is composed of numerous fascicles gathered together in a conjunctive sheath (epimysium). Many MTC models use the Finite Element Method (FEM) (Bosboom et al. 2001) to simulate MTC’s behavior as a hyperviscoelastic material. The Discrete Element Method (DEM) used for modeling composite materials (Iliescu et al. 2010) could be adapted to fibrous materials as the MTC. Compared to FEM, the DEM could allow to capture the complex behavior of a material with a simple discretization scheme in terms of concept and implementation as well as to understand the influence of fibers’ orientation on the MTC behavior. The aim of this study was to obtain the force/displacement relationship during a numerical tensile test of a pennate muscle model with DEM

BiplotGUI: Interactive Biplots in R

Biplots simultaneously provide information on both the samples and the variables of a data matrix in two- or three-dimensional representations. The BiplotGUI package provides a graphical user interface for the construction of, interaction with, and manipulation of biplots in R. The samples are represented as points, with coordinates determined either by the choice of biplot, principal coordinate analysis or multidimensional scaling. Various transformations and dissimilarity metrics are available. Information on the original variables is incorporated by linear or non-linear calibrated axes. Goodness-of-fit measures are provided. Additional descriptors can be superimposed, including convex hulls, alpha-bags, point densities and classification regions. Amongst the interactive features are dynamic variable value prediction, zooming and point and axis drag-and-drop. Output can easily be exported to the R workspace for further manipulation. Three-dimensional biplots are incorporated via the rgl package. The user requires almost no knowledge of R syntax.

Simulation aux Grandes Echelles d'un statoréacteur

La conception d'un statoréacteur bénificie aujourd'hui des progrès divers des outils numériques permettant par la même occasion d'alléger les différentes étapes préliminaires de tests en géométrie réelle nécessaires au développement de telle configuration. L'objectif de cette thèse est de développer une méthodologie s'appuyant sur la Simulation aux Grandes Echelles (SGE) afin de contribuer à la validation de ce nouvel outil numérique pour la simulation de statoréacteur et ainsi de contribuer à la compréhension des phénomènes mis en jeu dans ces chambres de combustion. L'outil numérique est tout d'abord adapté pour la simulation des écoulements réactifs fortement turbulents avec un accent mis sur la gestion des chocs avec des schémas centrés et la discrétisation de la convection pour la simulation Eulérienne de la phase dispersée. La configuration cible est le "Statoréacteur de Recherche'' étudié expérimentalement par l'ONERA. Sa simulation est réalisée de manière graduelle. Tout d'abord, il est montré que la simulation de la totalité de la configuration, y compris les diffuseurs d'entrée où se positionne un réseau de choc, est essentielle afin de considérer une géométrie acoustiquement close pour reproduire correctement les modes d'oscillation du statoréacteur. La pertinence du schéma cinétique est aussi étudiée et il est montré l'importance de bien reproduire l'évolution de la vitesse de flamme adiabatique pour une plage de richesse grande, en raison du régime de combustion partiellement prémélangé. Finalement, trois cas à richesse différente sont simulés et un excellent accord est trouvé avec l'expérience. La phénoménologie et les mécanismes pilotant la combustion sont alors étudiés pour ces trois cas. ABSTRACT : Design of ramjets benefits today from the progress of numerical tools which relieve the various test stages of real engines that remain necessary for the development of such a kind of configuration. The objective of this dissertation is to develop a methodology based on the Large Eddy Simulation (LES) to contribute to the validation of this new type of advanced numerical tool for the simulation of ramjets and improve the understanding of combustion in these devices. The numerical tool is first adapted for the simulation of highly turbulent reacting flows with emphases on the management of shocks with centered schemes and the discretization of convection for the Eulerian simulation of the dispersed phase. The target configuration is the “Research ramjet” experimentally studied by ONERA. Simulation is carried out gradually. First, it is shown that the simulation of the entire configuration, including diffusers at the inlets where shocks appear is essential to consider an acoustically close geometry to properly reproduce the oscillation modes of combustion. The relevance of the kinetic scheme is also studied. It is shown that reproducing the evolution of the adiabatic flame speed for a wide range of equivalence ratio is critical because of the partially premixed combustion regime involved in this configuration. Finally, three different cases are simulated and excellent agreement is found with experimental data. The phenomenology and the different mechanisms governing combustion are studied for these three cases

MODEL OF CALF MUSCLE TEAR DURING A SIMULATED ECCENT RlC CONT RACTlON. A FEASABILITY STUDY

Tearing of muscle-tendon complex is one of the main causes of sport injuries. The aim of this study was to combine passive stretching and contraction to model the conditions of such injury, using the discrete element method. The mechanical behavior of the muscle-tendon complex was in agreement with data from the literature and data from in vittu experiments by tensile tests on calf muscle-tendon unit. The localization of the rupture and the pattern of rupture show a delamination of muscle's fibers close to the myotendinous junction during an active stretching of the muscle-tendon complex

BiplotGUI: Interactive Biplots in R

Biplots simultaneously provide information on both the samples and the variables ofa data matrix in two- or three-dimensional representations. The BiplotGUI package provides a graphical user interface for the construction of, interaction with, and manipulation of biplots in R. The samples are represented as points, with coordinates determined either by the choice of biplot, principal coordinate analysis or multidimensional scaling. Various transformations and dissimilarity metrics are available. Information on the original variables is incorporated by linear or non-linear calibrated axes. Goodness-of-t measures are provided. Additional descriptors can be superimposed, including convex hulls, alpha-bags, point densities and classication regions. Amongst the interactive features are dynamic variable value prediction, zooming and point and axis drag-and-drop. Output can easily be exported to the R workspace for further manipulation. Three-dimensional biplots are incorporated via the rgl package. The user requires almost no knowledge of R syntax

Atomic Constraints between the Voltage Sensor and the Pore Domain in a Voltage-gated K+ Channel of Known Structure

In voltage-gated K+ channels (Kv), membrane depolarization promotes a structural reorganization of each of the four voltage sensor domains surrounding the conducting pore, inducing its opening. Although the crystal structure of Kv1.2 provided the first atomic resolution view of a eukaryotic Kv channel, several components of the voltage sensors remain poorly resolved. In particular, the position and orientation of the charged arginine side chains in the S4 transmembrane segments remain controversial. Here we investigate the proximity of S4 and the pore domain in functional Kv1.2 channels in a native membrane environment using electrophysiological analysis of intersubunit histidine metallic bridges formed between the first arginine of S4 (R294) and residues A351 or D352 of the pore domain. We show that histidine pairs are able to bind Zn2+ or Cd2+ with high affinity, demonstrating their close physical proximity. The results of molecular dynamics simulations, consistent with electrophysiological data, indicate that the position of the S4 helix in the functional open-activated state could be shifted by ∼7–8 Å and rotated counterclockwise by 37° along its main axis relative to its position observed in the Kv1.2 x-ray structure. A structural model is provided for this conformation. The results further highlight the dynamic and flexible nature of the voltage sensor

Réseau d'îlots de vieux bois - Eléments de méthode et test dans les forêts publiques du Mont Ventoux

Le réseau d’îlots de vieux bois est un outil nouveau pour conserver notamment la riche biodiversité cavicole et saproxylique. Après avoir analysé la littérature, une méthodologie générique de mise en œuvre, organisée en 7 étapes, est proposée, de même que des outils pratiques. Elle est testée dans le Mont-Ventoux. Un scénario défini de façon participative conduit à un réseau d’îlots de sénescence fondés sur des indicateurs de naturalité (indigénat, maturité, ancienneté, connectivité), tout en ne négligeant ni une approche espèce, ni le manque à gagner économique, ni la sécurité du public. La surface des îlots est limitée à 3%. La méthode ELECTRE est utilisée pour classer les 132 îlots pré-repérés, au regard du scénario élaboré. 74 îlots sont retenus pour le réseau. Les valeurs écologiques sont maximisées. Le manque à gagner est minimisé (66% des îlots retenus présentent un manque à gagner < 20 €/ha/an). La révision de l’aménagement de la forêt domaniale du Ventouret en 2012 a permis la mise en place des quatre premiers îlots, dont un a été financé par Natura 2000. La méthode permet de bien évaluer et hiérarchiser l’intérêt de chaque îlot et de discuter la notion de réseau. Elle est disponible pour être confrontée à d’autres contextes écologiques plus variés

Shear waves elastography for assessment of human Achilles tendon's biomechanical properties: an experimental study

Introduction: Achilles tendon is the most frequently ruptured tendon, but its optimal treatment is increasingly controversial. The mechanical properties of the healing tendon should be studied further. Shear waves elastography (SWE) measures the shear modulus, which is proven to be correlated to elastic modulus in animal tendons. The aim of our study was to study whether the shear moduli of human cadaveric Achilles tendon, given by SWE, were correlated with the apparent elastic moduli of those tendons given by tensile tests. Materials and methods: Fourteen cadaveric lower-limbs were studied. An elastographic study of the Achilles tendon (AT) was first done in clinical-like conditions. SWE was performed at three successive levels (0, 3 and 6 cm from tendon insertion) with elastographic probe oriented parallel to tendon fibers, blindly, for three standardized ankle positions (25° plantar flexion, neutral position, and maximal dorsal flexion). The mean shear moduli were collected through blind offline data-analysis. Then, AT with triceps were harvested. They were subjected to tensile tests. A continuous SWE of the Achilles tendon was performed simultaneously. The apparent elastic modulus was obtained from the experimental stress-strain curve, and correlation with shear modulus (given by SWE) was studied. Results: Average shear moduli of harvested AT, given by SWE made an instant before the tensile tests, were significantly correlated with shear moduli of the same AT made at the same level, previously in clinical-like condition (p < 0.05), only in neutral position. There was a statistical correlation (p < 0.005) and a correlation coefficient R² equal to 0.95 ± 0.05, between shear moduli (SWE) and apparent elastic moduli (tensile tests), for 11 tendons (3 tendons were inoperable due to technical error), before a constant disruption in the correlation curves. Discussion: We demonstrated a significant correlation between SWE of Achilles tendon performed in clinicallike conditions (in neutral position) and SWE performed in harvested tendon. We also found a correlation between SWE performed on harvested tendon and apparent elastic moduli obtained with tensile tests (for 11 specimens). As a consequence, we can suppose that SWE of AT in clinical-like conditions is related to tensile tests. To our knowledge, the ability of SWE to reliably assess biomechanical properties of a tendon or muscle was, so far, only demonstrated in animal models. Conclusion: SWE can provide biomechanical information of the human AT non-invasively

Differential Protein Modulation in Midguts of Aedes aegypti Infected with Chikungunya and Dengue 2 Viruses

International audienceAbstract Background: Arthropod borne virus infections cause several emerging and resurgent infectious diseases. Among the diseases caused by arboviruses, dengue and chikungunya are responsible for a high rate of severe human diseases worldwide. The midgut of mosquitoes is the first barrier for pathogen transmission and is a target organ where arboviruses must replicate prior to infecting other organs. A proteomic approach was undertaken to characterize the key virus/vector interactions and host protein modifications that happen in the midgut for viral transmission to eventually take place. Methodology and Principal Findings: Using a proteomics differential approach with two-Dimensional Differential in-Gel Electrophoresis (2D-DIGE), we defined the protein modulations in the midgut of Aedes aegypti that were triggered seven days after an oral infection (7 DPI) with dengue 2 (DENV-2) and chikungunya (CHIKV) viruses. Gel profile comparisons showed that the level of 18 proteins was modulated by DENV-2 only and 12 proteins were modulated by CHIKV only. Twenty proteins were regulated by both viruses in either similar or different ways. Both viruses caused an increase of proteins involved in the generation of reactive oxygen species, energy production, and carbohydrate and lipid metabolism. Midgut infection by DENV-2 and CHIKV triggered an antioxidant response. CHIKV infection produced an increase of proteins involved in detoxification. Conclusion/Significance: Our study constitutes the first analysis of the protein response of Aedes aegypti's midgut infected with viruses belonging to different families. It shows that the differentially regulated proteins in response to viral infection include structural, redox, regulatory proteins, and enzymes for several metabolic pathways. Some of these proteins like antioxidant are probably involved in cell protection. On the other hand, we propose that the modulation of other proteins like transferrin, hsp60 and alpha glucosidase, may favour virus survival, replication and transmission, suggesting a subversion of the insect cell metabolism by the arboviruses