Toxicokinetics of fumonisin B1 in turkey poults and tissue persistence after exposure to a diet containing the maximum European tolerance for fumonisins in avian feeds

The kinetic of fumonisin B1 (FB1) after a single IV and oral dose, and FB1 persistence in tissue were investigated in turkey poults by HPLC after purification of samples on columns. After IV administration (single-dose: 10 mg FB1/kg bw), serum concentration–time curves were best described by a three-compartment open model. Elimination half-life and mean residence time of FB1 were 85 and 52 min, respectively. After oral administration (single-dose: 100 mg FB1/kg bw) bioavailability was 3.2%; elimination half-life and mean residence time were 214 and 408 min, respectively. Clearance of FB1 was 7.6 and 7.5 ml/min/kg for IV and oral administration respectively. Twenty four hours after the administration of FB1 by the intravenous route, liver and kidney contained the highest levels of FB1 in tissues, level in muscle was low or below the limit of detection (LD, 13 µg/kg). The persistence of FB1 in tissue was also studied after administration for nine weeks of a feed that contained 5, 10 and 20 mg FB1+FB2/kg diet. Eight hours after the last intake of 20 mg FB1+FB2/kg feed (maximum recommended concentration of fumonisins established by the EU for avian feed), hepatic and renal FB1 concentrations were 119 and 22 µg/kg, level in muscles was below the LD

Impact of Iris Size and Eyelids Coupling on the Estimation of the Gaze Direction of a Robotic Talking Head by Human Viewers

International audiencePrimates - and in particular humans-are very sensitive to the eye direction of congeners. Estimation of gaze of others is one of the basic skills for estimating goals, intentions and desires of social agents, whether they are humans or avatars. When building robots, one should not only supply them with gaze trackers but also check for the readability of their own gaze by human partners. We conducted experiments that demonstrate the strong impact of the iris size and the position of the eyelids of an iCub humanoid robot on gaze reading performance by human observers. We comment on the importance of assessing the robot's ability of displaying its intentions via clearly legible and readable gestures

Moving horizon estimation of human kinematics and muscle forces

Human-robot interaction based on real-time kinematics or electromyography (EMG) feedback improves rehabilitation using assist-as-needed strategies. Muscle forces are expected to provide even more comprehensive information than EMG to control these assistive rehabilitation devices. Measuring in vivo muscle force is challenging, leading to the development of numerical methods to estimate them. Due to their high computational cost, forward dynamics-based optimization algorithms were not viable for real-time estimation until recently. To achieve muscle forces estimation in real time, a moving horizon estimator (MHE) algorithm was used to track experimental biosignals. Two participants were equipped with EMG sensors and skin markers that were streamed in real time and used as targets for the MHE. The upper-limb musculoskeletal (MSK) model was composed of 10 degrees-of-freedom actuated by 31 muscles. The MHE relies on a series of overlapping trajectory optimization subproblems of which the following parameters have been adjusted: the fixed duration and the frame to export. We based this adjustment on the estimation delay, the muscle saturation, the joint kinematic mean power frequency, and errors to experimental data. Our algorithm provided consistent estimates of muscle forces and kinematics with visual feedback at 30 Hz with a 110 ms delay. This method is promising to guide rehabilitation and enrich assistive device control laws with personalized force estimations

Descriptive and explanatory tools for human movement and state estimation in humanoid robotics

Le sujet principal de cette thèse est le mouvement des systèmes anthropomorphes, et plus particulièrement la locomotion bipède des humains et des robots humanoïdes. Pour caractériser et comprendre la locomotion bipède, il est instructif d'en étudier les causes, qui résident dans le contrôle et l'organisation du mouvement, et les conséquences qui en résultent, que sont le mouvement et les interactions physiques avec l'environnement. Concernant les causes, par exemple, quels sont les principes qui régissent l'organisation des ordres moteurs pour élaborer une stratégie de déplacement spécifique ? Puis, quelles grandeurs physiques pouvons-nous calculer pour décrire au mieux le mouvement résultant de ces commandes motrices ? Ces questions sont en partie abordées par la proposition d'une extension mathématique de l'approche du Uncontrolled Manifold au contrôle moteur de tâches dynamiques, puis par la présentation d'un nouveau descripteur de la locomotion anthropomorphe. En lien avec ce travail analytique vient le problème de l'estimation de l'état pour les systèmes anthropomorphes. La difficulté d'un tel problème vient du fait que les mesures apportent un bruit qui n'est pas toujours séparable des données informatives, et que l'état du système n'est pas nécessairement observable. Pour se débarrasser du bruit, des techniques de filtrage classiques peuvent être employées, mais elles sont susceptibles d'altérer le contenu des signaux d'intérêt. Pour faire face à ce problème, nous présentons une méthode récursive, basée sur le filtrage complémentaire, pour estimer la position du centre de masse et la variation du moment cinétique d'un système en contact, deux quantités centrales de la locomotion bipède. Une autre idée pour se débarrasser du bruit de mesure est de réaliser qu'il résulte en une estimation irréaliste de la dynamique du système. En exploitant les équations du mouvement, qui dictent la dynamique temporelle du système, et en estimant une trajectoire plutôt qu'un point unique, nous présentons ensuite une estimation du maximum de vraisemblance en utilisant l'algorithme de programmation différentielle dynamique pour effectuer une estimation optimale de l'état centroidal des systèmes en contact. Finalement, une réflexion pluridisciplinaire est présentée, sur le rôle fonctionnel et computationnel joué par la tête chez les animaux. La pertinence de son utilisation en robotique mobile y est discutée, pour l'estimation d'état et la perception multisensorielle.The substantive subject of this thesis is the motion of anthropomorphic systems, and more particularly the bipedal locomotion of humans and humanoid robots. To characterize and understand bipedal locomotion, it is instructive to study its motor causes and its resulting physical consequences, namely, the interactions with the environment. Concerning the causes, for instance, what are the principles that govern the organization of motor orders in humans for elaborating a specific displacement strategy? And then, which physical quantities can we compute for best describing the motion resulting from these motor orders ? These questions are in part addressed by the proposal of a mathematical extension of the Uncontrolled Manifold approach for the motor control of dynamic tasks and through the presentation of a new descriptor of anthropomorphic locomotion. In connection with this analytical work, comes the problem of state estimation in anthropomorphic systems. The difficulty of such a problem comes from the fact that the measurements carry noise which is not always separable from the informative data, and that the state of the system is not necessarily observable. To get rid of the noise, classical filtering techniques can be employed but they are likely to distort the signals. To cope with this issue, we present a recursive method, based on complementary filtering, to estimate the position of the center of mass and the angular momentum variation of the human body, two central quantities of human locomotion. Another idea to get rid of the measurements noise is to acknowledge the fact that it results in an unrealistic estimation of the motion dynamics. By exploiting the equations of motion, which dictate the temporal dynamics of the system, and by estimating a trajectory versus a single point, we then present maximum likelihood estimation using the dynamic differential programming algorithm to perform optimal centroidal state estimation for systems in contact. Finally, a multidisciplinary reflection on the functional and computational role played by the head in animals is presented. The relevance of using this solution in mobile robotics is discussed, particularly for state estimation and multisensory perception

Optimal 3D arm strategies for maximizing twist rotation during somersault of a rigid-body model

Looking for new arm strategies for better twisting performances during a backward somersault is of interest for the acrobatic sports community while being a complex mechanical problem due to the nonlinearity of the dynamics involved. As the pursued solutions are not intuitive, computer simulation is a relevant tool to explore a wider variety of techniques. Simulations of twisting somersaults have mainly been realized with planar arm motions. The aim of this study was to explore the outcomes of using 3D techniques, with the demonstration that increasing the fidelity of the model does not increase the level of control complexity on the real system. Optimal control was used to maximize twists in a backward straight somersault with both types of models. A multistart approach was used to find large sets of near-optimal solutions. The robustness of these solutions was then assessed by modeling kinematic noise during motion execution. The possibility of using quaternions for representing orientations in this numerical optimization problem was discussed. Optimized solutions showed that 3D techniques generated about two additional twists compared to 2D techniques. The robustness analysis revealed clusters of highly twisting and stable 3D solutions. This study demonstrates the superiority of 3D solutions for twisting in backward somersault, a result that can help acrobatic sports athletes to improve their twisting performance

Simulation fidèle du bruit généré par un jet supersonique chaud avec déclenchement de la turbulence et propagation acoustique non-linéaire

International audienceA procedure to accurately simulate a free hot supersonic jet and its associated noise, which uses simultaneously a turbulence tripping method and a two-way coupling between a flow solver and a nonlinear acoustic solver, is proposed in this study. A Mach 3.1 overexpanded hot jet is computed via a large-eddy simulation by solving the filtered Navier-Stokes equations with a finite volume method on unstructured grids. The resulting noise is propagated in the far field by solving the full Euler equations with a high-order discontinuous Galerkin methodon unstructured grids. The full convergent-divergent nozzle is explicitly included in the computational domain thanks to the unstructured flow solver. Both a refined grid and a geometrical boundary layer tripping in the convergent are used to get highly disturbed turbulent conditions at the nozzle lips. The flow field appears to agree with the expected turbulence behavior and the available experimental data. The jet development shows significant improvement compared to similar past simulations. The far field acoustic levels are finely recovered at most of observation angles. An analysis of the acoustic near and far fields is then performed. The studied conditions lead to strong shock-associated noise and Mach wave emission. The spatio-frequency and azimuthal content of the acoustic field is described in order to identify the main noise properties. A particular noise component, different from screech tones and radiating upstream like Mach waves, is highlighted. Nonlinear propagation effects are finally quantified through specific metrics. They are found significant in both the near and the far fields which justifies the use of a nonlinear acoustic solver.Une procédure de simulation fidèle d'un jet libre supersonique chaud et du bruit associé, utilisant simultanément une méthode de déclenchement de la turbulence et un couplage fort entre un solveur Navier-Stokes pour l'écoulement et un solveur Euler pour l'acoustique non-linéaire, est proposée dans cette étude. Un jet chaud sur-détendu à Mach 3.1 est calculé au moyen d'une simulation aux grandes échelles par résolution des équations de Navier-Stokes filtrées avec une méthode de type volumes finis sur maillage non-structuré. Le bruit résultant est propagé en champ lointain par résolution des équations d'Euler complètes avec une méthode de Galerkin discontinue d'ordre élevé sur maillage non-structuré. La tuyère convergente-divergente est explicitement incluse dans le domaine de calcul et son maillage est facilité par l'approche non-structurée. Pour obtenir des conditions d'écoulement fortement perturbées au niveau des lèvres de la tuyère, on utilise à la fois un maillage raffiné et une méthode de déclenchement géométrique de la couche limite dans le convergent. Le champ aérodynamique obtenu correspond au comportement turbulent attendu et aux données expérimentales disponibles. Le développement du jet présente une amélioration significative par rapport aux simulations précédentes similaires. Les niveaux acoustiques en champ lointain sont retrouvés avec précision à la plupart des angles d'observation. Une analyse des champs acoustiques proche et lointain est ensuite effectuée. Les conditions étudiées conduisent à un fort bruit de choc et à l'émission d'ondes de Mach. Le contenu spatio-fréquentiel et azimutal du champ acoustique est décrit afin d'identifier les principales propriétés du bruit. Une composante de bruit particulière, distincte du screech et rayonnant en amont via un mécanisme similaire aux ondes de Mach, est mise en évidence. Les effets de propagation non-linéaires sont finalement quantifiés par des métriques spécifiques. Leurs variations significatives à la fois en champ proche et en champ lointain justifient l'utilisation d'un solveur acoustique non-linéaire

Vision-based interface for grasping intention detection and grip selection : towards intuitive upper-limb assistive devices

Assistive devices for indivuals with upper-limb movement often lack controllability and intuitiveness, in particular for grasping function. In this work, we introduce a novel user interface for grasping movement control in which the user delegates the grasping task decisions to the device, only moving their (potentially prosthetic) hand toward the targeted object

Simulating the effects of spatial configurations of agricultural ditch drainage networks on surface runoff from agricultural catchments

The study of runoff is a crucial issue because it is closely related to flooding, water quality and erosion. In cultivated catchments, agricultural ditch drainage networks are known to influence runoff. As anthropogenic elements, agricultural ditch drainage networks can therefore be altered to better manage surface runoff in cultivated catchments. However, the relationship between the spatial configuration, i.e., the density and the topology, of agricultural ditch drainage networks and surface runoff in cultivated catchments is not understood. We studied this relationship by using a random network simulator that was coupled to a distributed hydrological model. The simulations explored a large variety of spatial configurations corresponding to a thousand stochastic agricultural ditch drainage networks on a 6.4 km2 Mediterranean cultivated catchment. Next, several distributed hydrological functions were used to compute water flow-paths and runoff for each simulation. The results showed that (i) denser networks increased the drained volume and the peak discharge and decreased hillslopes runoff, (ii) greater network density did not affect the surface runoff any further above a given network density, (iii) the correlation between network density and runoff was weaker for small subcatchments (< 2 km2) where the variability in the drained area that resulted from changes in agricultural ditch drainage networks increased the variability of runoff and (iv) the actual agricultural ditch drainage network appeared to be well optimized for managing runoff as compared with the simulated networks. Finally, our results highlighted the role of agricultural ditch drainage networks in intercepting and decreasing overland flow on hillslopes and increasing runoff in drainage networks