Evolution of star clusters in arbitrary tidal fields

We present a novel and flexible tensor approach to computing the effect of a time-dependent tidal field acting on a stellar system. The tidal forces are recovered from the tensor by polynomial interpolation in time. The method has been implemented in a direct-summation stellar dynamics integrator (NBODY6) and test-proved through a set of reference calculations: heating, dissolution time and structural evolution of model star clusters are all recovered accurately. The tensor method is applicable to arbitrary configurations, including the important situation where the background potential is a strong function of time. This opens up new perspectives in stellar population studies reaching to the formation epoch of the host galaxy or galaxy cluster, as well as for star-burst events taking place during the merger of large galaxies. A pilot application to a star cluster in the merging galaxies NGC 4038/39 (the Antennae) is presented.Comment: 12 pages, 8 figures. Accepted for publication in MNRA

Between order and disorder: a 'weak law' on recent electoral behavior among urban voters?

A new viewpoint on electoral involvement is proposed from the study of the statistics of the proportions of abstentionists, blank and null, and votes according to list of choices, in a large number of national elections in different countries. Considering 11 countries without compulsory voting (Austria, Canada, Czech Republic, France, Germany, Italy, Mexico, Poland, Romania, Spain and Switzerland), a stylized fact emerges for the most populated cities when one computes the entropy associated to the three ratios, which we call the entropy of civic involvement of the electorate. The distribution of this entropy (over all elections and countries) appears to be sharply peaked near a common value. This almost common value is typically shared since the 1970's by electorates of the most populated municipalities, and this despite the wide disparities between voting systems and types of elections. Performing different statistical analyses, we notably show that this stylized fact reveals particular correlations between the blank/null votes and abstentionists ratios. We suggest that the existence of this hidden regularity, which we propose to coin as a `weak law on recent electoral behavior among urban voters', reveals an emerging collective behavioral norm characteristic of urban citizen voting behavior in modern democracies. Analyzing exceptions to the rule provide insights into the conditions under which this normative behavior can be expected to occur.Comment: Version 1: main text 19 pages, 13 figures, 2 tables; Supporting Information: 19 pages. Version 2: minor correction

A tutorial for analyzing human reaction times: How to filter data, manage missing values, and choose a statistical model

This tutorial for the statistical processing of reaction times collected through a repeated-measure design is addressed to researchers in psychology. It aims at making explicit some important methodological issues, at orienting researchers to the existing solutions, and at providing them some evaluation tools for choosing the most robust and precise way to analyze their data. The methodological issues we tackle concern data filtering, missing values management, and statistical modeling (F1, F2, F1 + F2, quasi-F, mixed-effects models with hierarchical, or with crossed factors). For each issue, references and remedy suggestions are given. In addition, modeling techniques are compared on real data and a benchmark is given for estimating the precision and robustness of each techniqu

Conceptualizing human resilience in the face of the global epidemiology of cyber attacks

Computer security is a complex global phenomenon where different populations interact, and the infection of one person creates risk for another. Given the dynamics and scope of cyber campaigns, studies of local resilience without reference to global populations are inadequate. In this paper we describe a set of minimal requirements for implementing a global epidemiological infrastructure to understand and respond to large-scale computer security outbreaks. We enumerate the relevant dimensions, the applicable measurement tools, and define a systematic approach to evaluate cyber security resilience. From the experience in conceptualizing and designing a cross-national coordinated phishing resilience evaluation we describe the cultural, logistic, and regulatory challenges to this proposed public health approach to global computer assault resilience. We conclude that mechanisms for systematic evaluations of global attacks and the resilience against those attacks exist. Coordinated global science is needed to address organised global ecrime

Toward a knowledge representation model dedicated to the semantic analysis of the sentence

Ce rapport a été rédigé en octobre 2005 mais n'a été publié en tant que rapport INRIA qu'en juillet 2006Ce travail se situe dans le cadre de l'étude de la sémantique du langage naturel. Il s'agit d'une reformulation précise et automatisable du Lexique Génératif de Pustejovsky. Nous proposons un modèle lexical simultanément descriptif de la structure sémantique interne des mots et applicable de manière automatique à la suite d'une analyse syntaxique classique, par exemple celle des grammaires catégorielles. Notre formalisation des règles et nos algorithmes qui permettent de les appliquer sont illustrés par le traitement de la reconstruction métonymique et des usages ambigus de la préposition “avec”. (Ce rapport a été rédigé en octobre 2005 mais n'a été publié qu'en juillet 2006.

Assimilation of one satellite SAR image for flood simulations. Method and test case (Moser river)

International audienceIn view of improving numerical flood prediction, a variational data assimilation method (4D-var) applied to a 2D shallow water model and using distributed water level obtained from one Synthetic Aperture Radar (SAR) image is presented. The RADARSAT-1 image leads to water levels with a ±40cm average vertical uncertainty of a Mosel River flood event (1997, France). Assimilated in the 2D shallow water hydraulic model, these SAR derived spatially distributed water levels prove to be capable of enhancing model calibration. Indeed, the assimilation process can identify some optimal Manning friction coefficients. Moreover, used as a guide for sensitivity analysis, remote sensing water levels allow also in identifying some areas in the floodplain and the channel where Manning friction coefficients are homogeneous. This allows basing the spatial segmentation of roughness coefficient on floodplain hydraulic functioning

Étude de la sécrétion de la leptine gastrique chez le rat

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal