Resonance-free Region in scattering by a strictly convex obstacle

We prove the existence of a resonance free region in scattering by a strictly convex obstacle with the Robin boundary condition. More precisely, we show that the scattering resonances lie below a cubic curve which is the same as in the case of the Neumann boundary condition. This generalizes earlier results on cubic poles free regions obtained for the Dirichlet boundary condition.Comment: 29 pages, 2 figure

Interaction of vortices in viscous planar flows

We consider the inviscid limit for the two-dimensional incompressible Navier-Stokes equation in the particular case where the initial flow is a finite collection of point vortices. We suppose that the initial positions and the circulations of the vortices do not depend on the viscosity parameter \nu, and we choose a time T > 0 such that the Helmholtz-Kirchhoff point vortex system is well-posed on the interval [0,T]. Under these assumptions, we prove that the solution of the Navier-Stokes equation converges, as \nu -> 0, to a superposition of Lamb-Oseen vortices whose centers evolve according to a viscous regularization of the point vortex system. Convergence holds uniformly in time, in a strong topology which allows to give an accurate description of the asymptotic profile of each individual vortex. In particular, we compute to leading order the deformations of the vortices due to mutual interactions. This allows to estimate the self-interactions, which play an important role in the convergence proof.Comment: 39 pages, 1 figur

Normal Forms for Semilinear Quantum Harmonic Oscillators

We consider the semilinear harmonic oscillator i\psi_t=(-\Delta +\va{x}^{2} +M)\psi +\partial_2 g(\psi,\bar \psi), \quad x\in \R^d, t\in \R where $M$ is a Hermite multiplier and $g$ a smooth function globally of order 3 at least. We prove that such a Hamiltonian equation admits, in a neighborhood of the origin, a Birkhoff normal form at any order and that, under generic conditions on $M$ related to the non resonance of the linear part, this normal form is integrable when $d=1$ and gives rise to simple (in particular bounded) dynamics when $d\geq 2$. As a consequence we prove the almost global existence for solutions of the above equation with small Cauchy data. Furthermore we control the high Sobolev norms of these solutions

A Novel Tool for Online Community Moderator Evaluation

This study introduces a new instrument for leadership evaluation in online forums and other online communities which was developed using a grounded approach. Questions that emerged from the literature were then evaluated to create hypotheses that guided the development of an instrument for moderator evaluation. The Moderator Evaluation Contingency Scale (MECS) is modified from Fiedler’s contingency model to determine if a moderator is more task- or relationship-oriented in his or her approach to moderation and interactions with other members of a community. The MECS was developed and tested on Reddit in 2013–2014 using random sampling for Forum selection, moderator selection, and interactions with users. A content analysis using the MECS to evaluate posts was found to be a viable measure of a moderator’s ability to perform tasks like removing content as well as his or her ability to interact with users. Bots were analyzed using the MECS as well to determine bias. Next steps include making the instrument available for use by social media and niche community sites, administrators, and other moderators

Krankheit und Gesellschaft in der Vormoderne: das Beispiel der Pest

Bulst N. Krankheit und Gesellschaft in der Vormoderne: das Beispiel der Pest. In: Bulst N, Delort R, eds. Maladies et société (XIIe - XVIIIe siècles): actes du colloque de Bielefeld, novembre 1986. Paris: Ed. du Centre National de la Recherche Scientifique; 1989: 17-47

Les microorganismes jouent-ils un rôle dans le cycle du mercure en zone polaire ?

Communication oral

Microbes thrive in clouds and interact with physic-chemical processes: from field observations to atmospheric models.

International audienc

Valeur nutritionnelle pour le poulet en croissance, de cinq amylacés tropicaux en relation avec quelques caractéristiques physico-chimiques de leur amidon

International audienc