Tidal dissipation in rotating low-mass stars and implications for the orbital evolution of close-in planets I. From the PMS to the RGB at solar metallicity

Star-planet interactions must be taken into account in stellar models to understand the dynamical evolution of close-in planets. The dependence of the tidal interactions on the structural and rotational evolution of the star is of peculiar importance and should be correctly treated. We quantify how tidal dissipation in the convective envelope of rotating low-mass stars evolves from the pre-main sequence up to the red-giant branch depending on the initial stellar mass. We investigate the consequences of this evolution on planetary orbital evolution. We couple the tidal dissipation formalism described in Mathis (2015) to the stellar evolution code STAREVOL and apply it to rotating stars with masses between 0.3 and 1.4 M$_\odot$. In addition, we generalize the work of Bolmont & Mathis (2016) by following the orbital evolution of close-in planets using the new tidal dissipation predictions for advanced phases of stellar evolution. On the PMS the evolution of tidal dissipation is controlled by the evolution of the internal structure of the contracting star. On the MS it is strongly driven by the variation of surface rotation that is impacted by magnetized stellar winds braking. The main effect of taking into account the rotational evolution of the stars is to lower the tidal dissipation strength by about four orders of magnitude on the main-sequence, compared to a normalized dissipation rate that only takes into account structural changes. The evolution of the dissipation strongly depends on the evolution of the internal structure and rotation of the star. From the pre-main sequence up to the tip of the red-giant branch, it varies by several orders of magnitude, with strong consequences for the orbital evolution of close-in massive planets. These effects are the strongest during the pre-main sequence, implying that the planets are mainly sensitive to the star's early history.Comment: 13 pages, 7 figures, accepted for publication in A&

Electrochemical Kinetic Study of LiFePO4 Using Cavity Microelectrode

Lithium cation insertion and extraction in LiFePO4 were electrochemically studied with a cavity microelectrode (CME). Cyclic voltammetry measurements were used to characterize the kinetics of the material. LiFePO4 was successfully cycled from 0.1 mV s–1 up to 1 V s–1 and is therefore a suitable material to be used in high power applications, such as asymmetric hybrid supercapacitors. Several kinetic behaviors were observed depending on the sweep rate. The LiFePO4 was found to follow different kinetics behaviors depending of the sweep rate. The charge storage mechanisms were investigated for Liþ extraction/insertion

Wavelet Coefficients of Levy Process

International audienceCet article présente une expression de la fonction caractéristique des coefficients de décomposition en ondelettes d'un processus de Levy. Le cas particulier de l'ondelette de Haar et d'un processus entrelacé est traité plus en détail

Multivariate Functional Data Clusterization by PCA in Sobolev Space Using Wavelets

International audienceNous présentons une méthode basée sur la classification en espace fonctionnel appliquée aux trajectoires avion. La particularité des données est de se présenter comme des fonctions deux fois continuement différentiable par morceaux, l'information discriminante se situant des les sauts. L'utilisation d'une décomposition en ondelettes permet une implémentation simple en espace de Sobolev et permet de séparer correctement des trajectoires présentant des points de branchement

The zone 1440 AD eruption of the soufriere of Guadeloupe (Lesser Antilles) : an experimental determination of the pre-eruptive consitions of the andesitic magma body.

The 1440 AD eruption of the Soufriere of Guadeloupe (Lesser Antilles arc) is characterized by a dramatic change of the chemical composition of erupted products, from andesitic (clear pumices, 61-62 wt% SiO2) to basaltic andesite (dark scoria, 55-56 wt% SiO2). This compositional sequence is interpreted to reflect the tapping of a silicic magma body remobilised following the arrival of a mafic magma batch. The conditions of equilibrium ( T, P, fO2, melt H2O content) within the andesite body prior to the mixing event were determined from a coupled ineralogical/petrological and experimental approach

Health-policyholder clustering using health consumption: a useful tool for targeting prevention plans

On paper, prevention appears to be a good complement to health insurance. However, its implementation is often costly. To maximize the impact and efficiency of prevention plans these should target particular groups of policyholders. In this article, we propose a way of clustering policyholders that could be a starting point for the targeting of prevention plans. This two-step method mainly classifies using policyholder health consumption. This dimension is first reduced using a Nonnegative matrix factorization algorithm, producing intermediate health-product clusters. We then cluster using Kohonen's map algorithm. This leads to a natural visualization of the results, allowing the simple comparison of results from different databases. We apply our method to two real health-insurer datasets. We carry out a number of tests (including tests on a text-mining database) of method stability and clustering ability. The method is shown to be stable, easily-understandable, and able to cluster most policyholders efficiently