Highly separated transonic flows

Attention is given to the wind tunnel, to photographic visualization of the flow, and to measurements by pressure probes, hot wire anemometry and laser anemometry. The simultaneous use of different means of measurement provided a good description of the phenomenon, and indicated the existence of shocks and their stability, as well as the existence of the bubble, its dimensions, and in particular, the reattachment of its front. The results show that the bursting (or transition) of the bubble front is produced at an unstable position and creates a point of turbulent intensity which diffuses over the entire height of the flow

Oestrogen, an evolutionary conserved regulator of T cell differentiation and immune tolerance in jawed vertebrates?

In teleosts, as in mammals, the immune system is tightly regulated by sexual steroid hormones, such as oestrogens. We investigated the effects of 17β-oestradiol on the expression of several genes related to T cell development and resulting T cell subpopulations in sea bass, Dicentrarchus labrax, for a primary lymphoid organ, the thymus, and two secondary lymphoid organs, the head-kidney and the spleen. In parallel, the oxidative burst capacity was assessed in leucocytes of the secondary lymphoid organs. Apoptosis- and proliferation-related genes, indicative of B and T cell clonal selection and lymphoid progenitor activity, were not affected by elevated oestrogen-levels. Sex-related oestrogen-responsiveness in T cell and antigen-presenting cell markers was observed, the expression of which was differentially induced by oestrogen-exposure in the three lymphoid organs. Remarkably, in the spleen, oestrogen increased regulatory T cell-related gene expression was associated with a decrease in oxidative burst capacity. To the best of our knowledge, this study indicates for the first time that physiological levels of oestrogen are likely to promote immune tolerance by modulating thymic function (i.e., T cell development and output) and peripheral T cells in teleosts, similar to previously reported oestrogenic effects in mammals.CCMAR/Multi/04326/2013; ANRfinanced project ETaT(ANR-15-CE32-0014); FR CNRS 3730 SCALE scholarshipinfo:eu-repo/semantics/publishedVersio

Three-dimensional effects in hovering flapping flight

This paper aims at understanding the influence of three-dimensional effects in hovering flapping flight. Numerical simulations at a Reynolds number of 1000 are performed to compare two types of flapping kinematics whose plunging phase is characterized by either a rectilinear translation or a revolving motion. In this way, we are able to isolate the three-dimensional effects induced by the free end condition from that induced by the spanwise incident velocity gradient (and the associated implicit Coriolis and centrifugal effects). In the rectilinear translation case, the analysis of the wake and of the aerodynamic loads reveals that the wingspan can be compartmented into three distinct regions whether it is predominantly subjected to an unstable two-dimensional flow, a stable three-dimensional flow or both two-dimensional and three-dimensional effects. It is found that this partitioning exhibits common features for three different aspect ratios of the wing. In conjunction with the previous results of Ringuette, Milano & Gharib (J. Fluid Mech., vol. 581, 2007, pp. 453–468), this suggests that the influence of the tip vortex over the wingspan is driven by a characteristic length scale. In addition, this length scale matches the position of the connecting point between leading and tip vortices observed in the revolving case, providing insight into the connecting process. In both translating and revolving cases, leading edge vortex attachment and strong spanwise velocities are found to be strongly correlated phenomena. Spanwise velocities (that mostly confine at the periphery of the vortices), together with downward velocities, do not only affect the leading edge vortex but also act as an inhibitor for the trailing edge vortex growth. As a consequence, cross-wake interactions between leading and trailing edge vortices are locally limited, hence contributing to flow stabilization

An instrumented saxophone mouthpiece and its use to understand how an experienced musician play

International audienceAn instrumented saxophone mouthpiece has been developed to measure, during the player's performance, the evolution of important variables: the mouth pressure, the mouthpiece pressure and the force applied on the reed by the lower lip. Moreover, according to the pressure signals in the mouth and in the mouthpiece, the instantaneous ratio of the vocal tract input impedance and of the saxophone input impedance is estimated at frequencies multiple of the playing frequency (using the concept of Gabor mask). On the selected sound examples, analyses reveal many aspects of the strategies of the player. First of all, the role of the vocal tract in the characteristics of the sound production is sometimes prominent. Secondly, the sound production on the desired note (and register) as well as pitch correction seem to be the result of complementary adjustments of the mouth pressure and of the lip pressure on the reed. This is not in agreement with musicians feeling, since they often claim to let their force on the reed unchanged during the note and from note to note

Compliance de la composante élastique série in vivo : contribution musculaire, tendineuse et aponévrotique et plasticité à la variation de la demande fonctionnelle

The muscle-tendon complex contains a serie elastic component which is fundamental to its functioning. This serie elastic component is composed of an active part located within the sarcomere and a passive part located in the tendon and aponeurosis. It has a major role to optimize the movement by improving the muscle energetic efficiency and the produced work.A new method coupling a quick release ergometer and a high frequency ultrasound device was used to quantify the compliance contributions of the series elastic structures (tendon, aponeurosis and muscle fascicles) to the global compliance of the muscle-tendon complex in active conditions. The results of the first study showed that the tendon has a major compliance contribution (about 72%) while the muscle fascicles and aponeurosis contributions are 18% and 10%, respectively. The tendon confirms its key role in the compliance of the serie elastic component in active condition. In addition, the constant contributions of tendon, muscle fascicles and aponeurosis observed at various levels of torque may help simplify the regulation mechanism of compliance and maintain the major role of the tendon in the efficiency of the movement.This new method was also used to study the mechanical adaptations of the serie elastic component to variation of the functional demand. The changes in the relative compliance contributions of series elastic structures were quantified in elite fencers in the second study and in spastic subjects in the third study. Regarding the elite fencers, the results showed that the compliance contributions of the elastic structures in the dominant leg of fencers group were significantly different to those corresponding to the leg of the control group. The aponeurosis compliance contribution was higher for the dominant leg of the fencers groupe (21.1 vs 15.9%) while the muscle fascicles contribution was lower for the fencers group (9.5 vs 13.8%). The tendon contribution (about 70%) was the same for both legs. These changes tend to increase the role of tendon tissue (tendon and aponeurosis) and decrease the role of muscle fascicles which would allow greater use of tendon elastic structures for better energetic efficiency and improved performance. It is possible that aponeurosis is a complementary system to the adaptation of the muscle-tendon complex in the case of hyperactivity.The third study has become a case study because of the difficulty in testing the spastic patients on Quick release. Finally, the study has been done on a spastic patient with minor motor impairment compared to the others patients. The results showed a tendon and aponeurosis compliance contributions (75.3% and 15.2% respectively) higher than the muscle fascicles compliance contribution (9.5%). This result may be explained by an increase in muscle stiffness and a decrease in tendon stiffness, which is classically observed in studies with spastic subjects.Le complexe muscle-tendon est constitué d’une composante élastique série fondamentale à son fonctionnement. Cette composante élastique série est composée d’une fraction active située au sein du sarcomère et d’une fraction passive formée par les tissus tendineux (tendon et aponévrose). Elle a un rôle majeur pour optimiser le mouvement en améliorant le rendement énergétique du muscle et le travail produit.La mise au point d’une nouvelle méthode couplant une technique de détente rapide (Quick release) et un échographe haute fréquence a permis de quantifier les contributions de compliance des structures élastiques séries (tendon, aponévrose et fascicules musculaires) à la compliance globale du complexe muscle-tendon en condition active lors d’un test de détente rapide. Les résultats de la première étude montrent que le tendon a une contribution de compliance majoritaire (environ 72 %) tandis que les fascicules musculaires et l’aponévrose contribuent respectivement à 18 % et 10 %. Le tendon confirme donc son rôle capital dans la compliance de la composante élastique série en condition active. De plus, les contributions constantes du tendon, des fascicules musculaires et de l’aponévrose observées aux différents niveaux de couple pourraient aider à simplifier le mécanisme de régulation de la compliance et à maintenir le rôle majeur du tendon dans l’efficience du mouvement.Cette nouvelle méthode a permis d’étudier les adaptations mécaniques de la composante élastique série à la variation de la demande fonctionnelle, notamment en quantifiant les modifications des contributions relatives de compliance des structures élastiques séries chez des escrimeurs élites dans la deuxième étude puis chez des sujets spastiques dans la troisième étude. Concernant les escrimeurs élite, les résultats montrent que les contributions de compliance des structures élastiques de la jambe dominante du groupe d’escrimeurs sont significativement différentes à celles correspondant à la jambe du groupe contrôle, avec notamment une part plus importante de contribution pour l’aponévrose (21,1 vs 15,9 %) et une part minorée pour les fascicules (9,5 vs 13,8 %) concernant la jambe dominante des escrimeurs. En revanche, la contribution du tendon (environ 70 %) est identique pour les deux jambes. Ces modifications tendent à majorer le rôle des tissus tendineux (tendon et aponévrose) et à minorer le rôle des fascicules musculaires ce qui permettrait une utilisation supérieure des structures élastiques tendineuses pour un meilleur rendement énergétique et une performance accrue. Il est possible que l'aponévrose soit un système complémentaire à l’adaptation du complexe muscle-tendon en cas d'hyperactivité.La troisième étude est devenue une étude de cas en raison de la difficulté à tester les patients spastiques sur le Quick release. Elle s’est portée sur un patient spastique dont l’atteinte motrice était plus faible que les autres et a montré des contributions relatives de compliance du tendon (75,3 %) et de l’aponévrose (15,2 %) supérieures à celle des fascicules (9,5 %) Ce résultat s’expliquerait par une augmentation de la raideur du muscle et une diminution de la raideur des tissus tendineux observées classiquement dans les études menées sur des sujets spastiques

Added Masses of generic shape bodies interacting with external walls

International audienceThe aim of this paper is to propose an efficient method to evaluate the Added Masses of generic shape bodies in infinite fluid or in the proximity of external walls. The Added Masses (AM) are the result of the inertial reaction of the fluid in response to an accelerated movement of a body immersed in it. The AM effects are more evident when the body density is similar to that of the surrounding fluid, as in the case of airships. In the takeoff or landing phases, the proximity to the ground causes an increase in the Added Masses that must be correctly estimated to properly size the airship controls. In our method, the calculation of the Added Masses matrix is carried out by the Boundary Element Method (BEM). To verify the accuracy of the results, the study cases are based on simple shapes, whose Added Masses are well known. The analyses in infinite fluid and in the presence of a flat wall are carried out. Numerical results are compared to the theoretical values found in literature. The calculated Added Masses are intrinsically dependent on the mesh definition and the relative error, referred to the theoretical values, depends on the surface and volume discretiza-tion. In the case of interaction between geometries with complex shapes, the influence on the Added Masses is very difficult to predict without a numerical approach. The method proposed gives a good compromise in terms of quality of results and computational cost

L'impact des politiques publiques canadiennes sur l'innovation et le financement en biotechnologie : une évaluation en dynamique des système

Financer une dynamique d'innovation -- Résoudre les problèmes de financement de l'innovation -- Évaluer les politiques publiques en dynamiques des systèmes -- Identification des dynamiques et conception des modèles -- Comprendre la dynamique d'innovation et de financement en biotechnologie -- La génération des technologies -- Le perfectionnement des technologies -- L'expansion de la firme par la collaboration -- Le développement de produits sur le marché -- Évaluation des politiques publiques canadiennes -- La cohérence des modèles -- Les politiques de financement de la recherche fondamentale -- Les politiques de financement des firmes -- Les politiques de financement d'infrastructure