Competing Species Dynamics: Qualitative Advantage versus Geography

A simple cellular automata model for a two-group war over the same territory is presented. It is shown that a qualitative advantage is not enough for a minority to win. A spatial organization as well a definite degree of aggressiveness are instrumental to overcome a less fitted majority. The model applies to a large spectrum of competing groups: smoker-non smoker war, epidemic spreading, opinion formation, competition for industrial standards and species evolution. In the last case, it provides a new explanation for punctuated equilibria.Comment: 7 pages, latex, 2 figures include

Microtraps for neutral atoms using superconducting structures in the critical state

Recently demonstrated superconducting atom-chips provide a platform for trapping atoms and coupling them to solid-state quantum systems. Controlling these devices requires a full understanding of the supercurrent distribution in the trapping structures. For type-II superconductors, this distribution is hysteretic in the critical state due to the partial penetration of the magnetic field in the thin superconducting film through pinned vortices. We report here an experimental observation of this memory effect. Our results are in good agreement with the redictions of the Bean model of the critical state without adjustable parameters. The memory effect allows to write and store permanent currents in micron-sized superconducting structures and paves the way towards new types of engineered trapping potentials.Comment: accepted in Phys. Rev.

Quantum theory of fluctuations in a cold damped accelerometer

We present a quantum network approach to real high sensitivity measurements. Thermal and quantum fluctuations due to active as well as passive elements are taken into account. The method is applied to the analysis of the capacitive accelerometer using the cold damping technique, developed for fundamental physics in space by ONERA and the ultimate limits of this instrument are discussed. It is confirmed in this quantum analysis that the cold damping technique allows one to control efficiently the test mass motion without degrading the noise level.Comment: 10 pages, 6 figures, RevTeX; Minor change

Human African Trypanosomiasis: Real Obstacles to Elimination

Abstract presented at: 5ème Congrès International de Pathologie Infectieuse et Parasitaire - en présence du Ministre de la Santé, Kinshasa, DRC, November 2009Significant progress has been made in controlling human African trypanosomiasis (HAT) caused by T.b. gambiense as evidenced by the clear decline in the number of reported cases in recent years. Now the prevailing discourse is about the possible elimination of HAT and the need to integrate treatment for it into existing health structures. However, “Hot spots” still exist and one of which is the northeastern region of Orientale Province in the Democratic Republic of Congo (DRC). In this region there is neither a monitoring system nor working health centres capable of diagnosing and treating patients.\ud An assessment carried out by the DRC’s national program to fight HAT and Doctors Without Borders/Médecins Sans Frontières (MSF) in 2004 discovered an alarming prevalence (2.1%) in the region. Between June 2007 and March 2009 MSF launched a HAT monitoring program in the Doruma, Ango, and Bili health zones. The overall prevalence was found to be 3.4%. Of the 46,601 people tested (18,559 through passive screening and 28,042 through active screening), 1,570 people were infected with T.b. gambiense. Of that group, 947 (60%) were in the first phase of HAT, indicating intense transmission of the disease. \ud Due to the acute insecurity in this region of the DRC, MSF had to suspend its projects in March 2009, even though the limits of the disease foci had not yet been reached. Moreover, the disease could spread further by the displacement of entire populations who are fleeing the insecurity and heading for areas that had been previously “cleaned” of HAT.\ud The intervention, which took place during a crisis situation, leads us to question the feasibility of eliminating HAT and integrating treatment in crisis areas where health services are at a minimum

L'université et la ville, genèse et structuration d'un champ socio-spatial et politique

International audienceThe objective of this research on the topic of the university and the city and specifically on the relationship between the university and the city of Tours was not so much to understand the only geographical integration of the University of Tours in the city but to capture how representations of the university were enrolled in the image of Tours in action in municipal projectsSans doute, la relation de l'université et de la ville fut longtemps l'impensé de la recherche urbaine tourangelle. Alors que, tout au long des années 1970 et 1980, s'affirmaient et s'affinaient les études sur les dynamiques spatiales, les fonctions urbaines, les groupes sociaux, ou encore les grandes opérations d'aménagements, l'université restait cet étrange objet -- du désir ? -- dont on n'ignorait certes pas la présence, sans que pour autant on éprouvât le besoin d'en débattre -- si ce n'est sous la forme, déviée, de la question du rôle politique et social global de l'université et des universitaires dans la société contemporaine. Mais quant à son statut local et aux formes et modalités de son inscription dans le jeu tourangeau, s'affirmait l'idée qu'on n'en pouvait rien dire ou peu s'en faut. Dans ce contexte, l'appel d'offre Université et Ville provoqua un réel effet de surprise et fut salutaire puisqu'il obligea un groupe de chercheurs hétérogène et assez hâtivement constitué -- auquel s'adjoignirent des praticiens fort motivés -- à se poser enfin la question de la pertinence de la dialectique postulée par le texte de l'appel d'offre, et par suite à élaborer une problématisation susceptible de nourrir trois années de recherche. Bref, nous n'avons eu que très tardivement et presque brutalement le loisir et les capacités de construire le champ de la relation de l'université et de la ville ; en même temps, cette élaboration d'un nouvel objet cognitif a constitué une étape, un jalon dans l'histoire du phénomène de la rencontre ville-université. L'objectif du travail mené sur ce thème ne fut pas tant de comprendre la seule insertion géographique de l'université de Tours dans la ville que de saisir la manière dont les représentations de l'université se sont inscrites dans l'image de Tours en acte dans les projets municipau

Assessment of a low-cost protocol for an ab initio based prediction of the mixing enthalpy at elevated temperatures: the Fe-Mo system

We demonstrate how a limited number of ab initio calculations in combination with a simple Debye model can predict a concentration- and temperature-dependent mixing enthalpy for a binary system. Fe-Mo is taken as a test case, and our predictions are compared with phase diagram information and a recently measured heat of solution for Mo in Fe. Crystallographic and magnetic information is calculated for the lambda and mu intermetallic phases in the Fe-Mo phase diagram as well. The present methodology can be useful for making a quick survey of mixing enthalpies in a large set of binary systems, in particular in the dilute concentration ranges where tabulated data are often lacking and where CALPHAD-style modeling is less reliable