The Healing of Persons

Text of a talk delivered, in French, by Paul Tournier, at the Medical College of Virginia, April 27, 1965. Translation by Miss Beryl Eeman

Detection of CO in H2-rich gases with a samarium doped ceria (SDC) sensor for fuel cell applications

International audienceAn original sensor has been studied in order to detect low CO concentration in h2-rich atmosphere for pem (protonic exchange membrane) fuel cell applications. The SCD (samarium doped ceria) sensor is a potentiometric sensor working with an electrode dissymmetry Au/Pt. The originality of this sensor is mainly working with the two electrodes in the same atmosphere without a reference cell. The Δ (emf) response, defined by the difference between the emf (electromotive force) value under carrier gas and the emf value under CO, is correlated with the CO concentration. Experiments have been carried out on a laboratory testing bench, either with a large measurement cell equipped with a hot plate and two mobile gold points as electrical contacts or in a small cell with self-heated sensors supplied with a platinum heater on the reverse side of the substrate. Responses to low CO concentrations (0-4000 ppm v/v) in H2-rich gases (5% v/v) varies between 25 and 100 mV, but saturation is observed beyond 400 ppm v/v of CO. In wet atmosphere, the sensitivity is partially reduced but the sensor response remains perfectly usable. At the moment no satisfying model can be used to explain the experimental results. Nevertheless, the performances of these SCD sensors appear sufficiently good to satisfy the fuel cell application

CO detection in H2 reducing atmosphere with mini fuel cell

International audienceA prototype of a miniaturized fuel cell has been studied in order to detect carbon monoxide in hydrogen-rich atmosphere for PEMFC (proton exchange membrane fuel cell) applications. It consists on a single PEMFC (membrane-electrode-assembly supplied by CEA/LITEN) directly fed by the hydrogen-carbon monoxide mixture while the cathode is exposed to ambient air. Experiments have been carried out on a laboratory testing bench with simulated reforming gas. Two working modes have been studied. For low CO concentrations (≤20 ppm), the amperometric mode is suitable but a regeneration in air is necessary to obtain a good reversibility of the sensor response. On the contrary, for higher CO concentrations (250-4000 ppm), a good reversible response is observed without air regenerating by using a potentiometric or quasi-potentiometric mode. Therefore, this prototype of mini fuel cell sensor seems to be convenient for monitoring reformed gases either for low temperature PEMFC which are poisoned by very low traces of CO or for high temperature PEMFC which can operate at higher CO concentrations

Alternating evolutionary pressure in a genetic algorithm facilitates protein model selection

<p>Abstract</p> <p>Background</p> <p>Automatic protein modelling pipelines are becoming ever more accurate; this has come hand in hand with an increasingly complicated interplay between all components involved. Nevertheless, there are still potential improvements to be made in template selection, refinement and protein model selection.</p> <p>Results</p> <p>In the context of an automatic modelling pipeline, we analysed each step separately, revealing several non-intuitive trends and explored a new strategy for protein conformation sampling using Genetic Algorithms (GA). We apply the concept of alternating evolutionary pressure (AEP), i.e. intermediate rounds within the GA runs where unrestrained, linear growth of the model populations is allowed.</p> <p>Conclusion</p> <p>This approach improves the overall performance of the GA by allowing models to overcome local energy barriers. AEP enabled the selection of the best models in 40% of all targets; compared to 25% for a normal GA.</p

Detection of oxygen traces in nitrogen and hydrogen-rich atmosphere

International audienceTin oxide sensors are evaluated to detect traces of oxygen in the range 0-100 ppm both in nitrogen and hydrogen (4.5 vol% H2 in N2) atmospheres. In nitrogen, significant relative responses to oxygen are measured at 623 K and 723 K. However, at lower temperature, 523 K, the response strongly decreases. In the presence of hydrogen, on the contrary, interesting responses are measured at 523 K. At higher temperature, 623 K and 723 K, on one hand SnO2 sensors begin to reduce, and on the other hand, oxygen is partly consumed by reaction with hydrogen. Oxygen trace detection (5-100 ppm) is thus only possible in hydrogen atmosphere (4.5 vol% H2) at 523 K

6D Frictional Contact for Rigid Bodies

International audienceWe present a new approach to modeling contact between rigid objects that augments an individual Coulomb friction point-contact model with rolling and spinning friction constraints. Starting from the intersection volume, we compute a contact normal from the volume gradient. We compute a contact position from the first moment of the intersection volume, and approximate the extent of the contact patch from the second moment of the intersection volume. By incorporating knowledge of the contact patch into a point contact Coulomb friction formulation, we produce a 6D constraint that provides appropriate limits on torques to accommodate displacement of the center of pressure within the contact patch, while also providing a rotational torque due to dry friction to resist spinning. A collection of examples demonstrate the power and benefits of this simple formulation

Présentation

Nous bafouons les valeurs du christianisme à chaque minute. Les musulmans font de même avec l’islam. Ce qui est donc en question, c’est une guerre fondamentalement inégale entre deux théologies inauthentiques.Norman Mailer Le dossier présenté dans cette livraison de Mots. Les langages du politique avait d’abord sollicité les chercheurs du côté de l’analyse des discours de haine, d’exclusion et de meurtre que tiennent certains totalitarismes d’aujourd’hui au nom de Dieu et de la révélation qu’..

Six degrees of freedom estimation using monocular vision and moiré patterns

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2006.Includes bibliographical references (p. 105-107).We present the vision-based estimation of the position and orientation of an object using a single camera relative to a novel target that incorporates the use of moire patterns. The objective is to acquire the six degree of freedom estimation that is essential for the operation of vehicles in close proximity to other craft and landing platforms. A target contains markers to determine relative orientation and locate two sets of orthogonal moire patterns at two different frequencies. A camera is mounted on a small vehicle with the target in the field of view. An algorithm processes the images extracting the attitude and position information of the camera relative to the target utilizing geometry and 4 single-point discrete Fourier transforms (DFTs) on the moire patterns. Manual and autonomous movement tests are conducted to determine the accuracy of the system relative to ground truth locations obtained through an external indoor positioning system. Position estimations with accompanying control techniques have been implemented including hovering, static platform landings, and dynamic platform landings to display the algorithm's ability to provide accurate information to precisely control the vehicle. The results confirm the moire target system's feasibility as a viable option for low-cost relative navigation for indoor and outdoor operations including landing on static and dynamic surfaces.by Glenn P. Tournier.S.M

Functionalization of APTES modified tin dioxide gas sensor

Communication présentée dans la session "Metal Oxide Gas Sensor".International audienceSummary In the present work, commercial SnO2 powder was used for sensor thick film fabrication. The film was produced using screen printing technology. The SnO2 functionalization was done with 3-aminopropyltriethoxysilane (APTES) in liquid phase as an intermediate step, followed by functionalization using hexanoyl chloride exhibiting an alkyl end functional (CH3) group. The SnO2 sensor modified with alkyl end group was found to be sensitive to ammonia gas at 100°C. The advantages are the reduction of the power consumption by decreasing the operating temperature, and the enhancement of the selectivity and sensitivity to the gas with respect to pure SnO2 sensor.MotivationMolecularly modified metal oxide gas sensors have shown to be promising devices for selective gas sensor related to disease diagnosis. Those sensors can be used to detect the gas emanated from the human body for breath analysis application. Tin dioxide sensors have lack of selectivity and work at high temperature (350-500°C). The need of selective sensors with high sensitivity at low gases concentration pushes us to modify SnO2 sensing element in order to change its interactions with gas. The modification with organic functional groups with different polarities change the sensor response to specific gases depending on their polarity. A SnO2 functionalization based on APTES combined with hexanoyl chloride was investigated. Another objective is to reduce the power consumption by decreasing the operating temperature

Développement d'un pré-concentrateur miniaturisé en technologie silicium pour la détection de substances chimiques à l'état de traces

International audienceL'objectif principal de cette étude est le développement d'un dispositif de pré-concentration basé sur une technologie de microréacteur en silicium. Les applications visées concernent les systèmes miniaturisés de détection de traces gazeuses, soit en pollution atmosphérique, soit pour la détection d'explosifs. Pour cela, une poudre de carbone est utilisée comme matériau adsorbent, et les dispositifs ont été testés sous benzène. Les composants sont constitués de micro-canaux en silicium obtenus par gravures DRIE. Ils sont équipés de capillaires métalliques et d'un micro-chauffage. Une partie de l'étude porte sur le dépôt par méthode fluidique de la poudre de carbone dans les micro-canaux. Un intérêt particulier de l'étude concerne l'utilisation de silicium poreux pour augmenter la quantité de carbone déposé. Les tests de faisabilité sous benzène permettent de vérifier l'effet de pré-concentration recherché