Arrival Time Statistics in Global Disease Spread

Metapopulation models describing cities with different populations coupled by the travel of individuals are of great importance in the understanding of disease spread on a large scale. An important example is the Rvachev-Longini model [{\it Math. Biosci.} {\bf 75}, 3-22 (1985)] which is widely used in computational epidemiology. Few analytical results are however available and in particular little is known about paths followed by epidemics and disease arrival times. We study the arrival time of a disease in a city as a function of the starting seed of the epidemics. We propose an analytical Ansatz, test it in the case of a spreading on the world wide air transportation network, and show that it predicts accurately the arrival order of a disease in world-wide cities

La transformation de Laplace élémentaire dans les formations mathématiques pour l’ingénieur et le technicien. Du calcul intégral à « l’algébrisation » des équations différentielles et la production de tables

La transformation de Laplace est un outil d’analyse utilisé dans les métiers de l’ingénierie. Ce travail porte sur une première étude d’un corpus de textes — ouvrages d’enseignement et articles issus de revues techniques — produits par des acteurs, dont des anciens professionnels et des enseignants, pour des formations et enseignements techniques. Les applications mises en avant donnent des indices d’adaptation voire d’appropriation des savoirs pour certaines professions comme la production de tables originales et beaucoup plus complètes que celles très synthétiques des textes strictement mathématiques.The Laplace transform is an analysis tool widely used in the engineering professions. This work focuses on a first study of a corpus of texts - teaching books and articles from technical journals - produced by actors, including former professionals and teachers, for technical training and education. The applications put forward give indications of adaptation and even appropriation of knowledge for certain professions, such as the production of original tables that are much more complete than the very synthetic ones in strictly mathematical texts

Global disease spread: statistics and estimation of arrival times

We study metapopulation models for the spread of epidemics in which different subpopulations (cities) are connected by fluxes of individuals (travelers). This framework allows to describe the spread of a disease on a large scale and we focus here on the computation of the arrival time of a disease as a function of the properties of the seed of the epidemics and of the characteristics of the network connecting the various subpopulations. Using analytical and numerical arguments, we introduce an easily computable quantity which approximates this average arrival time. We show on the example of a disease spread on the world-wide airport network that this quantity predicts with a good accuracy the order of arrival of the disease in the various subpopulations in each realization of epidemic scenario, and not only for an average over realizations. Finally, this quantity might be useful in the identification of the dominant paths of the disease spread.Comment: J. Theor. Biol., in pres

Dynamique sur réseaux complexes et dynamique des réseaux complexes

Les reseaux complexes ont ete largement etudiees ces dix dernieres annees. Leurs proprietes les plus courantes, le caractere petit monde et le caractere heterogene, ont donne lieu a une nouvelle facon de se representer les reseaux, voire a un nouveau paradigme des interactions entre un grand nombre d'unites elementaires. Nous etudions d'abord la propagation d'epidemies sur reseaux complexes dans un modele de metapopulation ou les sous-populations sont les habitants des villes reliees entre elles par les voyages effectues sur le reseau mondial de transport aerien. A l'aide de simulations integrales prenant en compte l'ensemble des connections entre aeroports au niveau mondial, nous examinons l'acuite d'une quantite qui est une bonne approximation pour le temps d'arrivee d'une epidemie dans chaque agglomeration. Nous etudions ensuite comment les reseaux eux-memes evoluent dans le temps, d'abord de maniere empirique a travers l'exemple du reseau des aeroports Nord-Americain, puis de maniere systematique. Nous proposons un modele de dynamique des reseaux, non pas base sur l'evolution de la topologie du reseau, mais uniquement gouverne par l'evolution des poids. Nous montrons que ce modele est a meme d'expliquer certaines des caracteristiques observees. Enfin, il apparait dans de nombreux domaines qu'un processus ayant lieu sur un reseau affecte la topologie du reseau lui-meme. Nous nous interessons donc a un modele issu de modeles d'opinions qui permet de coupler la dynamique sur le reseau (l'evolution de l'etat des noeuds) avec la dynamique du reseau (l'evolution de l'etat des liens).The complex networks were largely studied these ten last years. Their most current properties, the character small world and the heterogeneous character, gave birth to new way of representing the networks, even to a new paradigm of the interactions between a great number of basic units. We study the spreading of epidemics on complex networks in a model of metapopulation where the subpopulations are the inhabitants cities, wich are connected by the aerian travels. With the help of integral simulations taking into account all connections between airports on a world level, we examine the acuity of a quantity which is a good approximation for the arrival times of an epidemic in each agglomeration. We then study how the networks themselves evolve in time, first in an empirical manner through the example of the North-American airport network, then in a systematic way. We propose a model of dynamics of the networks, not based on the evolution of the topology of the network, but only controled by the evolution of the weights. We show that this model explains some of the observed characteristics. Lastly, it appears in many fields that a process taking place on a network affects the topology of the network itself. We are thus interested has a model resulting from opinion models which makes it possible to couple dynamics on the network (lthe evolution of the nodes state) with the dynamics of the network (the evolution of the bonds state).ORSAY-PARIS 11-BU Sciences (914712101) / SudocSudocFranceF

Redundancy Exploitation of an 8-DoF Robotic Assistant for Doppler Sonography

The design of a teleoperated 8-DoF redundant robot for Doppler sonography is detailed in this paper. The proposed robot is composed of a 7-DoF robotic arm mounted on a 1-DoF linear axis. This solution has been conceived to allow Doppler ultrasound examination of the entire patient’s body. This paper details the design of the platform and proposes two alternative control modes to deal with its redundancy at the torque level. The first control mode considers the robot as a full 8-DoF kinematics chain, synchronizing the action of the eight joints and improving the global robot manipulability. The second control mode decouples the 7-DoF arm and the linear axis controllers and proposes a switching strategy to activate the linear axis motion when the robot arm approaches the workspace limits. Moreover, a new adaptive Joint-Limit Avoidance (JLA) strategy is proposed with the aim of exploiting the redundancy of the 7-DoF anthropomorphic arm. Unlike classical JLA approaches, a weighting matrix is actively adapted to prioritize those joints that are approaching the mechanical limits. Simulations and experimental results are presented to verify the effectiveness of the proposed control modes

Hybrid Structural Analysis of the Arp2/3 Regulator Arpin Identifies Its Acidic Tail as a Primary Binding Epitope

Arpin is a newly discovered regulator of actin polymerization at the cell leading edge, which steers cell migration by exerting a negative control on the Arp2/3 complex. Arpin proteins have an acidic tail homologous to the acidic motif of the VCA domain of nucleation-promoting factors (NPFs). This tail is predicted to compete with the VCA of NPFs for binding to the Arp2/3 complex, thereby mitigating activation and/or tethering of the complex to sites of actin branching. Here, we investigated the structure of full-length Arpin using synchrotron small-angle X-ray scattering, and of its acidic tail in complex with an ankyrin repeats domain using X-ray crystallography. The data were combined in a hybrid model in which the acidic tail extends from the globular core as a linear peptide and forms a primary epitope that is readily accessible in unbound Arpin and suffices to tether Arpin to interacting proteins with high affinity

Redundancy Exploitation of an 8-DoF Robotic Assistant for Doppler Sonography

The design of a teleoperated 8-DoF redundant robot for Doppler sonography is detailed in this paper. The proposed robot is composed of a 7-DoF robotic arm mounted on a 1-DoF linear axis. This solution has been conceived to allow Doppler ultrasound examination of the entire patient’s body. This paper details the design of the platform and proposes two alternative control modes to deal with its redundancy at the torque level. The first control mode considers the robot as a full 8-DoF kinematics chain, synchronizing the action of the eight joints and improving the global robot manipulability. The second control mode decouples the 7-DoF arm and the linear axis controllers and proposes a switching strategy to activate the linear axis motion when the robot arm approaches the workspace limits. Moreover, a new adaptive Joint-Limit Avoidance (JLA) strategy is proposed with the aim of exploiting the redundancy of the 7-DoF anthropomorphic arm. Unlike classical JLA approaches, a weighting matrix is actively adapted to prioritize those joints that are approaching the mechanical limits. Simulations and experimental results are presented to verify the effectiveness of the proposed control modes

Les mathématiques professionnelles (XVIe-XIXe siècle)

Les contributions ici rassemblées sont consacrées à la mise en pratique de savoirs mathématiques du XVIe au XIXe siècle dans divers milieux professionnels. Elles soulignent toutes que les praticiens sont confrontés à des nouveaux besoins qui demandent un appareillage mathématique, et que, pour comprendre l’usage précis qu'ils en ont, il est crucial de s’immerger en détail dans chaque cadre social et économique. La circulation de ces savoirs implique presque partout des processus d’appropriation au sein des métiers considérés et fortement dépendants des contextes d'usage. En transformant, ajustant ou normalisant le geste du praticien, les mathématiques permettent alors l’accès à une forme de légitimation sociale qu’offrent, selon les cas, prestige ou rejet de la science théorique. The contributions gathered here are devoted to the application of mathematical knowledge from the 16th to the 19th century in various professional settings. They all emphasize that practitioners were confronted with new needs that required mathematical tools, and that, in order to understand the precise use they make of it, it is crucial to immerse oneself in detail in each social and economic setting. The circulation of this knowledge implied almost everywhere processes of appropriation within the considered professions and strongly dependent on the contexts of use. By transforming, adjusting or standardizing the practitioner's gesture, mathematics allowed access to a form of social legitimization that offered, depending on the case, prestige or rejection of theoretical science