Prior preferences beneficially influence social and non-social learning

Our personal preferences affect a broad array of social behaviors. This includes the way we learn the preferences of others, an ability that often relies on limited or ambiguous information. Here we report an egocentric influence on this type of social learning that is reflected in both performance and response times. Using computational models that combine inter-trial learning and intra-trial choice, we find transient effects of participants' preferences on the learning process, through the influence of priors, and persistent effects on the choice process. A second experiment shows that these effects generalize to non-social learning, though participants in the social learning experiment appeared to additionally benefit by using their knowledge about the popularity of certain preferences. We further find that the domain-general egocentric influences we identify can yield performance advantages in uncertain environments.People often assume that other people share their preferences, but how exactly this bias manifests itself in learning and decision-making is unclear. Here, authors show that a person's own preferences influence learning in both social and non-social situations, and that this bias improves performance

Recovering missing data on satellite images

International audienceData Assimilation is commonly used in environmental sciences to improve forecasts, obtained by meteorological, oceanographic or air quality simulation models, with observation data. It aims to solve an evolution equation, describing the dynamics, and an observation equation, measuring the misfit between the state vector and the observations, to get a better knowledge of the actual system's state, named the reference. In this article, we describe how to use this technique to recover missing data and reduce noise on satellite images. The recovering process is based on assumptions on the underlying dynamics displayed by the sequence of images. This is a promising alternative to methods such as space-time interpolation. In order to better evaluate our approach, results are first quantified for an artificial noise applied on the acquisitions and then displayed for real data

Mortality impact of AIDS in Abidjan, 1986-1992

To quantify the mortality impact of AIDS in the city of Abidjan (Côte d'Ivoire) by a full scale analysis of mortality trends before and after the onset of the epidemic. Data on deaths registered in the 10 vital registration centers of the city between 1973 and 1992, and data on causes of deaths in the four public hospitals were coded and investigated. Data on deaths were compared with census data in order to compute death rates. Life tables were computed for each of the 20 years of the study. The trends in death rates were analysed during the 10 years before the onset of the AIDS epidemic (1973-1982) and compared with the changing death rates in the following 10 years (1983-1992). Deaths attributable to AIDS were defined as those in excess of the original trends. The evolution in the number of deaths in the hospital allowed an analysis by cause of death. There was a marked increase in death rates starting in 1986, date of the first diagnosed AIDS cases in the city. This increase was significant for both sexes, but more pronounced among men. It was concentrated primarily among young adults (aged 25-44 years) and among older children (aged 5-14 years), and most of it was considered to be attributable to AIDS and related infections, tuberculosis in particular. When data were cumulated from 1986 to 1992, approximately 25000 persons were estimated to have died of AIDS. The high number of AIDS deaths estimated in Abidjan underlines the heavy toll already paid by african populations, and calls for intensive action. (Résumé d'auteur

An inverse method to interpret colour-magnitude diagrams

An inverse method is developed to determine the star formation history, the age-metallicity relation, and the IMF slope from a colour-magnitude diagram. The method is applied to the Hipparcos HR diagram. We found that the thin disk of our Galaxy shows a peak of stellar formation 1.6 Gyr ago. The stars close to the Sun have a solar metallicity and a mean IMF index equal to 3.2. However, the model and the evolutionary tracks do not correctly reproduce the horizontal giant branch.Comment: 14 pages, 11 figures. To be published in Astronomy & Astrophysic

Tracing a relativistic Milky Way within the RAMOD measurement protocol

Advancement in astronomical observations and technical instrumentation implies taking into account the general relativistic effects due the gravitational fields encountered by the light while propagating from the star to the observer. Therefore, data exploitation for Gaia-like space astrometric mission (ESA, launch 2013) requires a fully relativistic interpretation of the inverse ray-tracing problem, namely the development of a highly accurate astrometric models in accordance with the geometrical environment affecting light propagation itself and the precepts of the theory of measurement. This could open a new rendition of the stellar distances and proper motions, or even an alternative detection perspective of many subtle relativistic effects suffered by light while it is propagating and subsequently recorded in the physical measurements.Comment: Proceeding for "Relativity and Gravitation, 100 Years after Einstein in Prague" to be published by Edition Open Access, revised versio

Conséquences démographiques du sida en Abidjan : 1986-1992

Les statistiques de l'état civil et des formations sanitaires sont notoirement peu utilisées en Afrique pour étudier les tendances de la mortalité. L'étude d'Abidjan montre que c'est une situation très regrettable, car ces statistiques peuvent fournir de précieux renseignements sur l'état sanitaire de la population. Dans le cas présent, l'analyse fine des tendances de la mortalité, couplée avec l'analyse des causes de décès dans les hôpitaux, révèle assez précisément les conséquences démographiques du sida dans la capitale de la Côte d'Ivoire, malgré l'imperfection des données. Les estimations indiquent que près de 25 000 personnes seraient décédées du sida entre 1986 et 1992, les sept premières années de l'épidémie, ce qui confirme qu'Abidjan est une des villes les plus touchées au monde par cette troublante épidémie. Ce sont surtout les jeunes de sexe masculin qui ont été les plus touchés, dans toutes les couches de la société. Un modèle a permis de reconstruire la dynamique de l'épidémie, qui montre que le premier pic des infections se serait produit vers 1987. On peut s'attendre à une moyenne d'environ 7 000 cas de sida par an dans la ville jusqu'à l'an 2000, ce qui aura des conséquences importantes sur l'utilisation des infrastructures hospitalières. L'importance numérique de ces estimations souligne l'urgence de renforcer la lutte contre l'épidémie de sida en Côte d'Ivoire et dans le monde. (Résumé d'auteur

Open TURNS: An industrial software for uncertainty quantification in simulation

The needs to assess robust performances for complex systems and to answer tighter regulatory processes (security, safety, environmental control, and health impacts, etc.) have led to the emergence of a new industrial simulation challenge: to take uncertainties into account when dealing with complex numerical simulation frameworks. Therefore, a generic methodology has emerged from the joint effort of several industrial companies and academic institutions. EDF R&D, Airbus Group and Phimeca Engineering started a collaboration at the beginning of 2005, joined by IMACS in 2014, for the development of an Open Source software platform dedicated to uncertainty propagation by probabilistic methods, named OpenTURNS for Open source Treatment of Uncertainty, Risk 'N Statistics. OpenTURNS addresses the specific industrial challenges attached to uncertainties, which are transparency, genericity, modularity and multi-accessibility. This paper focuses on OpenTURNS and presents its main features: openTURNS is an open source software under the LGPL license, that presents itself as a C++ library and a Python TUI, and which works under Linux and Windows environment. All the methodological tools are described in the different sections of this paper: uncertainty quantification, uncertainty propagation, sensitivity analysis and metamodeling. A section also explains the generic wrappers way to link openTURNS to any external code. The paper illustrates as much as possible the methodological tools on an educational example that simulates the height of a river and compares it to the height of a dyke that protects industrial facilities. At last, it gives an overview of the main developments planned for the next few years

Imaging Three Dimensional Two-particle Correlations for Heavy-Ion Reaction Studies

We report an extension of the source imaging method for analyzing three-dimensional sources from three-dimensional correlations. Our technique consists of expanding the correlation data and the underlying source function in spherical harmonics and inverting the resulting system of one-dimensional integral equations. With this strategy, we can image the source function quickly, even with the finely binned data sets common in three-dimensional analyses.Comment: 13 pages, 11 figures, submitted to Physical Review

Beyond inverse Ising model: structure of the analytical solution for a class of inverse problems

I consider the problem of deriving couplings of a statistical model from measured correlations, a task which generalizes the well-known inverse Ising problem. After reminding that such problem can be mapped on the one of expressing the entropy of a system as a function of its corresponding observables, I show the conditions under which this can be done without resorting to iterative algorithms. I find that inverse problems are local (the inverse Fisher information is sparse) whenever the corresponding models have a factorized form, and the entropy can be split in a sum of small cluster contributions. I illustrate these ideas through two examples (the Ising model on a tree and the one-dimensional periodic chain with arbitrary order interaction) and support the results with numerical simulations. The extension of these methods to more general scenarios is finally discussed.Comment: 15 pages, 6 figure

Relativistic Positioning Systems: The Emission Coordinates

This paper introduces some general properties of the gravitational metric and the natural basis of vectors and covectors in 4-dimensional emission coordinates. Emission coordinates are a class of space-time coordinates defined and generated by 4 emitters (satellites) broadcasting their proper time by means of electromagnetic signals. They are a constitutive ingredient of the simplest conceivable relativistic positioning systems. Their study is aimed to develop a theory of these positioning systems, based on the framework and concepts of general relativity, as opposed to introducing `relativistic effects' in a classical framework. In particular, we characterize the causal character of the coordinate vectors, covectors and 2-planes, which are of an unusual type. We obtain the inequality conditions for the contravariant metric to be Lorentzian, and the non-trivial and unexpected identities satisfied by the angles formed by each pair of natural vectors. We also prove that the metric can be naturally split in such a way that there appear 2 parameters (scalar functions) dependent exclusively on the trajectory of the emitters, hence independent of the time broadcast, and 4 parameters, one for each emitter, scaling linearly with the time broadcast by the corresponding satellite, hence independent of the others.Comment: 13 pages, 3 figures. Only format changed for a new submission. Submitted to Class. Quantum Gra