Etude de la reactivite du dioxyde d'uranium monocristallin vis-a-vis des processus de dissolution en milieu acide cinetique et reactivite aux interfaces.

International audienc

La colonisation des prairies par le frêne. Processus et moyens de contrôle dans les Montagnes de Bigorre

focus PSDR3Le projet CHAPAY a contribué à produire des connaissances, des méthodes et des outils pour prendre en compte les relations entre le changement des activités agricoles et des paysages dans l’action publique et la gouvernance des territoires. Au niveau des vallées, la connaissance de l’histoire des paysages pastoraux permet d’identifier les terroirs colonisables par le frêne. Dans ces terroirs, le maintien de la fauche empêche le frêne de s’installer. Par contre, pour les prairies pâturées, il existe un seuil d’intensité de pâturage au-dessus duquel le frêne ne s’installe pas et au-dessous duquel il s’installe de manière irréversible en développant une stratégie de reproduction végétative souterraine

The relationship between subtypes of depression and cardiovascular disease: a systematic review of biological models

A compelling association has been observed between cardiovascular disease (CVD) and depression, suggesting individuals with depression to be at significantly higher risk for CVD and CVD-related mortality. Systemic immune activation, hypothalamic–pituitary–adrenal (HPA) axis hyperactivity, arterial stiffness and endothelial dysfunction have been frequently implicated in this relationship. Although a differential epidemiological association between CVD and depression subtypes is evident, it has not been determined if this indicates subtype specific biological mechanisms. A comprehensive systematic literature search was conducted using PubMed and PsycINFO databases yielding 147 articles for this review. A complex pattern of systemic immune activation, endothelial dysfunction and HPA axis hyperactivity is suggestive of the biological relationship between CVD and depression subtypes. The findings of this review suggest that diagnostic subtypes rather than a unifying model of depression should be considered when investigating the bidirectional biological relationship between CVD and depression. The suggested model of a subtype-specific biological relationship between depression and CVDs has implications for future research and possibly for diagnostic and therapeutic processes

L'inventaire des oiseaux nicheurs par la méthode des points d'écoute dans les paysages agricoles

National audienceLes communautés d’oiseaux nicheurs sont connues pour être des indicateurs dans le temps des transformations des paysages agricoles. En 1982, dans la petite région naturelle des Coteaux de Gascogne au sud-ouest de Toulouse une équipe du département sciences pour l’action et le développement (SAD) du centre INRA de Toulouse avait réalisé un inventaire de ces populations d’oiseaux. Afin de mesurer l’évolution des effectifs et de la répartition de ces oiseaux sur ce même territoire, nous avons mis en place, 25 ans plus tard, une nouvelle campagne de recensement durant le printemps 2007. Nous avons, pour cela utilisé la même technique d’inventaire : la méthode des points d’écoute. C’est une méthode classique et éprouvée, connue de tous les ornithologues ; elle est adaptée aux paysages agricoles, reproductible et donne des résultats fiables. Toutefois, cette fiabilité reste tributaire, dans un environnement complexe, d’une bonne gestion de sa mise en oeuvre, d’une planification rigoureuse, de la pertinence des documents cartographiques et, surtout, de l’expérience et du savoir-faire des ornithologues

Decomposition of the vertical ground reaction forces during gait on a single force plate.

Davis and Cavanagh (1993) have proposed a solution to avoid the footstep targeting by using a large force plate but several points of Davis and Cavanagh's method remain unclear and hardly computable. Objective: to develop a method that decomposes left and right GRF profiles from the GRF profile recorded on a single platform. This method aims to include a systematic detection of the single to double stand-phase-instants in order to lead to accurate measurement of the vertical GRF component in typically developing children. Methods: Six children were asked to walk without targeting their footsteps on a set-up composed of independent force platforms. The vertical GRF component, independently measured on the different platforms, was numerically summed to obtain the corresponding global vertical GRF, to which the decomposition method was applied. Then, the validation consisted in comparing the vertical GRF computed from this decomposition to the independently measured vertical GRF. Results: the mean relative error between the computed vertical GRF and the corresponding measured vertical GRF of 36 double stances (6 double stances x 6 children) is equal to 3.8±2.6%. Conclusion: implemented a new method to assess with known accuracy the vertical GRF component under each foot using a unique large force platform

A procedure to optimize the geometric and dynamic designs of assistive upper limb exoskeletons

The need for upper limb assistive and wearable exoskeletons is growing in various fields, e.g. either to support patients with neuromuscular disabilities or to reduce the effort strains on workers. These exoskeletons should reduce the efforts required by the user during functional tasks (dynamic consideration) and should fit the user’s size (geometric consideration). This is a tedious task, due to the 3D human-exoskeleton interactions, and to the complex and interdependent selection of the power transmission characteristics, i.e. motors or passive elements. There are still few guidelines and few clear procedures to support geometric and dynamic syntheses of these exoskeletons. The objective of this study is to develop a procedure for geometric and dynamic syntheses of assistive upper limb exoskeletons, to serve as a tool to optimize their design. Firstly, a geometric optimization of the exoskeleton dimensions enabled to satisfy the kinematic loop closures between the exoskeleton and the user for a maximum of positions while carrying out specific functional tasks and avoiding collisions with the body segments. Secondly, through an optimal control problem, the dynamic characteristics of the exoskeleton were obtained by minimizing the user’s joint torques for the functional tasks. Closing the kinematic loops of the exoskeletons with optimized dimensions was achieved for all positions of the user while carrying out the functional tasks, which was 10.8% more than with a visual identification of the dimensions. The resulting dynamic parameters could reduce the user’s joint torque to less than 10.6% of the human-only simulations for nearly all joints and tasks. These results showed that the geometric and dynamic synthesis procedures were successful. This is important, as it can enable the development of dedicated exoskeletons, such as lighter and smaller exoskeletons. The future perspectives will be to build an optimization framework, where the geometric and dynamic parameters could be optimized together, and to minimize the user’s muscle forces instead of joint torques for specific design purposes

Joint torque variability and repeatability during cyclic flexion-extension of the elbow

Background: Joint torques are generally of primary importance for clinicians to analyze the effect of a surgery and to obtain an indicator of functional capability to perform a motion. Given the current need to standardize the functional evaluation of the upper limb, the aim of this paper is to assess (1) the variability of the calculated maximal elbow joint torque during cyclic elbow flexion-extension movements and (2) participant test-retest repeatability in healthy young adults. Calculations were based on an existing non-invasive method including kinematic identification and inverse dynamics processes. Methods: Twelve healthy young adults (male n = 6) performed 10 elbow flexion-extension movement carrying five different dumbbells (0, 1, 2, 3 and 4 kg) with several flexion-extension frequencies (½, 1/3, ¼ Hz) to evaluate peak elbow joint torques. Results: Whatever the condition, the variability coefficient of trial peak torques remained under 4 %. Bland and Altman plot also showed good test-retest, whatever the frequency conditions for the 0, 1, 2, and 3 kg conditions. Conclusion: The good repeatability of the flexion-extension peak torques represents a key step to standardize th