Boundary approximate controllability of some linear parabolic systems

International audienceThis paper focuses on the boundary approximate controllability of two classes of linear parabolic systems, namely a system of n heat equations coupled through constant terms and a 2x2 cascade system coupled by means of a fi rst order partial diff erential operator with space-dependent coe fficients. For each system we prove a suffi cient condition in any space dimension and we show that this condition turns out to be also necessary in one dimension with only one control. For the system of coupled heat equations we also study the problem on rectangle, and we give characterizations depending on the position of the control domain. Finally, we exhibit a cascade system for which the distributed controllability holds whereas the boundary controllability does not. The method relies on a general characterization due to H.O. Fattorini

Stabilization and controllability of first-order integro-differential hyperbolic equations

In the present article we study the stabilization of first-order linear integro-differential hyperbolic equations. For such equations we prove that the stabilization in finite time is equivalent to the exact controllability property. The proof relies on a Fredholm transformation that maps the original system into a finite-time stable target system. The controllability assumption is used to prove the invertibility of such a transformation. Finally, using the method of moments, we show in a particular case that the controllability is reduced to the criterion of Fattorini

Null controllability and finite-time stabilization in minimal time of one-dimensional first-order 2 × 2 linear hyperbolic systems

The goal of this article is to present the minimal time needed for the null controllability and finite-time stabilization of one-dimensional first-order 2 ×2 linear hyperbolic systems. The main technical point is to show that we cannot obtain a better time. The proof combines the backstepping method with the Titchmarsh convolution theorem

Boundary stabilization in finite time of one-dimensional linear hyperbolic balance laws with coefficients depending on time and space

In this article we are interested in the boundary stabilization in finite time of one-dimensional linear hyperbolic balance laws with coefficients depending on time and space. We extend the so called "backstepping method" by introducing appropriate time-dependent integral transformations in order to map our initial system to a new one which has desired stability properties. The kernels of the integral transformations involved are solutions to non standard multi-dimensional hyperbolic PDEs, where the time dependence introduces several new difficulties in the treatment of their well-posedness. This work generalizes previous results of the literature, where only time-independent systems were considered

Améliorer les pratiques d’enseignement pour favoriser la prise de notes des étudiants - Un accompagnement pédagogique par la recherche-action

Cette étude restitue les résultats d’une recherche-action menée à l’université de Poitiers ayant pour objet un accompagnement pédagogique sur les pratiques d’enseignement favorisant la prise de notes des étudiants. La recherche-action impliquait une démarche réflexive de l’enseignant à partir des résultats d’un questionnaire sur la prise de notes mesurant les pratiques pédagogiques. Ce questionnaire novateur a été l’outil central de la démarche d’accompagnement permettant de croiser le regard de l’enseignant et de ses étudiants. La première partie du questionnaire renseigne sur les modalités pédagogiques mises en œuvre par l’enseignant pendant le cours; la seconde partie interroge les étudiants sur leur ressenti quant à leur capacité à prendre des notes lors d’un cours magistral. L’accompagnement pédagogique a notamment contribué à une prise de conscience de la part de l’enseignant sur certains aspects de sa communication pendant le cours en lui permettant de mettre en œuvre des modalités pédagogiques favorisant la prise de notes de ses étudiants. À la suite de cet accompagnement, les étudiants ont exprimé au travers de leurs réponses au questionnaire que les nouvelles pratiques pédagogiques de l’enseignant ont amélioré leur prise de notes.This study presents the results of an action-research project conducted at the University of Poitiers, with the aim to provide pedagogical support for teaching practices that encourage students’ note-taking. The research-action involved a reflective approach by the lecturer based on the results of a questionnaire on note-taking measuring teaching practices. This innovative questionnaire was the central instrument of the support process, making it possible to compare the views of the lecturer and his or her students. The first part of the questionnaire provides information on the teaching methods used by the lecturer during the course; the second part asks the students about their feelings regarding their ability to take notes during a lecture. The pedagogical support contributed in particular to the increase of the lecturer’s awareness of certain aspects of his communication during the lecture by enabling him to implement pedagogical methods that encourage his students to take notes. Following this support, the students expressed, through their answers to the questionnaire, that the teacher's new teaching practices had improved their note-taking

A Shift from Cellular to Humoral Responses Contributes to Innate Immune Memory in the Vector Snail Biomphalaria glabrata

International audienceDiscoveries made over the past ten years have provided evidence that invertebrate anti-parasitic responses may be primed in a sustainable manner, leading to the failure of a secondary encounter with the same pathogen. This phenomenon called " immune priming " or "innate immune memory" was mainly phenomenological. The demonstration of this process remains to be obtained and the underlying mechanisms remain to be discovered and exhaustively tested with rigorous functional and molecular methods, to eliminate all alternative explanations. In order to achieve this ambitious aim, the present study focuses on the Lophotrochozoan snail, Biomphalaria glabrata, in which innate immune memory was recently reported. We provide herein the first evidence that a shift from a cellular immune response (encapsulation) to a humoral immune response (biomphalysin) occurs during the development of innate memory. The molecular characterisation of this process in Biompha-laria/Schistosoma system was undertaken to reconcile mechanisms with phenomena