Understanding tidal dissipation in gaseous giant planets from their core to their surface

Tidal dissipation in planetary interiors is one of the key physical mechanisms that drive the evolution of star-planet and planet-moon systems. Tidal dissipation in planets is intrinsically related to their internal structure. In particular, fluid and solid layers behave differently under tidal forcing. Therefore, their respective dissipation reservoirs have to be compared. In this work, we compute separately the contributions of the potential dense rocky/icy core and of the convective fluid envelope of gaseous giant planets, as a function of core size and mass. We demonstrate that in general both mechanisms must be taken into account.Comment: 2 pages, 2 figures, CoRoT Symposium 3 / Kepler KASC-7 joint meeting, Toulouse, July 2014; To be published by EPJ Web of Conference

Tidal inertial waves in the differentially rotating convective envelopes of low-mass stars - I. Free oscillation modes

Star-planet tidal interactions may result in the excitation of inertial waves in the convective region of stars. In low-mass stars, their dissipation plays a prominent role in the long-term orbital evolution of short-period planets. Turbulent convection can sustain differential rotation in their envelope, with an equatorial acceleration (as in the Sun) or deceleration, which can modify the waves' propagation properties. We explore in this first paper the general propagation properties of free linear inertial waves in a differentially rotating homogeneous fluid inside a spherical shell. We assume that the angular velocity background flow depends on the latitudinal coordinate only, close to what is expected in the external convective envelope of low-mass stars. We use i) an analytical approach in the inviscid case to get the dispersion relation, from which we compute the characteristic trajectories along which energy propagates. This allows us to study the existence of attractor cycles and infer the different families of inertial modes; ii) high-resolution numerical calculations based on a spectral method for the viscous problem. We find that modes that propagate in the whole shell (D modes) behave the same way as with solid-body rotation. However, another family of inertial modes exists (DT modes), which can propagate only in a restricted part of the convective zone. Our study shows that they are less common than D modes and that the characteristic rays and shear layers often focus towards a wedge - or point-like attractor. More importantly, we find that for non-axisymmetric oscillation modes, shear layers may cross a corotation resonance with a local accumulation of kinetic energy. Their damping rate scales very differently from what we obtain for standard D modes and we show an example where it is independent of viscosity (Ekman number) in the astrophysical regime in which it is small.Comment: 17 pages, 15 figures, accepted for publication in A&

Unravelling tidal dissipation in gaseous giant planets

International audienceContext. Tidal dissipation in planetary interiors is one of the key physical mechanisms that drive the evolution of star-planet and planet-moon systems. New constraints on this dissipation are now obtained both in the solar and exo-planetary systems.Aims. Tidal dissipation in planets is intrinsically related to their internal structure. Indeed, the dissipation behaves very differently when we compare its properties in solid and fluid planetary layers. Since planetary interiors consist of both types of regions, it is necessary to be able to assess and compare the respective intensity of the reservoir of dissipation in each type of layers. Therefore, in the case of giant planets, the respective contribution of the potential central dense rocky/icy core and of the deep convective fluid envelope must be computed as a function of the mass and the radius of the core. This will allow us to obtain their respective strengths.Methods. Using a method that evaluates the reservoir of dissipation associated to each region, which is a frequency-average of complex tidal Love numbers, we compared the respective contributions of the central core and of the fluid envelope.Results. For Jupiter- and Saturn-like planets, we show that the viscoelastic dissipation in the core could dominate the turbulent friction acting on tidal inertial waves in the envelope. However, the fluid dissipation would not be negligible. This demonstrates that it is necessary to build complete models of tidal dissipation in planetary interiors from their deep interior to their surface without any arbitrary assumptions.Conclusions. We demonstrate how important it is to carefully evaluate the respective strength of each type of dissipation mechanism in planetary interiors and to go beyond the usually adopted ad-hoc models. We confirm the significance of tidal dissipation in the potential dense core of gaseous giant planets

EL SABER ABSOLUTO: EN TORNO A LA INTRODUCCIÓN Y EL CAPÍTULO VIII DE LA FENOMENOLOGÍA DEL ESPÍRITU DE HEGEL

This Note proposes a reinterpretation of the Absolute Knowing in Hegel, through an interpretive revision of the Introduction and Chapter VIII of the  Phenomenology of spirit. The Absolute Knowing is a complex term that is not exempt from an equivocity in its interpretation, since this concept manifests itself as a culminating moment in the experience of consciousness, as it appears from knowing in its entirety.La presente Nota propone una reinterpretación del Saber Absoluto en Hegel, mediante una revisión interpretativa de la Introducción y el Capítulo VIII dela Fenomenología del espíritu. El Saber Absoluto es un término complejo que no está exento de una equivocidad en su interpretación, toda vez que dicho  concepto se manifiesta como un momento culminante de la experiencia de la conciencia, en tanto aparecer del saber en su totalidad

Rôle des facteurs de risque familiaux, individuels et environnementaux dans les cancers de la thyroïde (Analyse d'études cas-témoins)

Objectifs : Les cancers de la thyroïde représentent environ 2% de l ensemble des cancers dans les pays développés mais sont les cancers les plus fréquents des glandes endocrines. L incidence des cancers de la thyroïde se caractérise par de fortes variations géographiques dans le monde, les taux les plus élevés étant observés en Nouvelle-Calédonie, et par une augmentation régulière au cours des dernières décennies dans les pays occidentaux. Cette augmentation d incidence est en grande partie attribuée à l évolution des pratiques médicales mais pourrait aussi être en partie liée à une évolution des modes de vie et/ou à des expositions environnementales. En dehors de l exposition aux radiations ionisantes dans l enfance, les facteurs de risque de cancer de la thyroïde restent très mal connus. L objectif de ce travail était d étudier le rôle des antécédents familiaux de pathologie de la thyroïde, des caractéristiques de la vie hormonale et reproductive, des caractéristiques anthropométriques et des expositions environnementales et professionnelles dans l étiologie des cancers de la thyroïde. Méthode : Les analyses reposent principalement sur une étude cas-témoins en population menée en France métropolitaine (étude CATHY). Nous avons également utilisé les données d une étude cas-témoins menée en Nouvelle-Calédonie pour étudier le rôle des antécédents familiaux dans cette zone géographique de forte incidence. L étude CATHY repose sur 621 cas diagnostiqués dans trois départements français (Calvados, Marne, Ardennes) entre 2002 et 2007 et sur 706 témoins, appariés par fréquence aux cas sur l âge, le sexe et le département de résidence. L étude cas-témoins en Nouvelle-Calédonie repose sur 332 cas diagnostiqués entre 1985 et 1999, et sur 412 témoins appariés par fréquence aux cas sur l âge et le sexe. Résultats : Les résultats montrent une augmentation du risque de cancer de la thyroïde chez les individus ayant des apparentés de premier degré atteints de cancer de la thyroïde ou de goitre multinodulaire, en France métropolitaine comme en Nouvelle-Calédonie. Parmi les facteurs hormonaux et reproductifs, un âge tardif aux premières règles, une ménopause précoce et une parité élevée étaient associés à une augmentation du risque de cancer de la thyroïde. Une relation dose-effet inverse était observée entre la durée cumulée des cycles menstruels au cours de la vie et le risque de cancer de la thyroïde. La prise d une contraception orale était associée à une diminution du risque de cancer de la thyroïde, avec une relation dose-effet inverse entre la durée de la contraception orale et le risque de cancer de la thyroïde. La taille, l indice de masse corporelle et la surface corporelle étaient positivement associés au risque de cancer de la thyroïde. Une augmentation du risque de cancer de la thyroïde était observée dans certains secteurs d activité professionnelle comme l industrie du papier, l industrie du caoutchouc et des plastiques, le travail du bois, la réparation automobile et la métallurgie.Objectives: Thyroid cancer accounts for 2% of all cancers in industrialized countries but is the most common endocrine cancer. There is a marked worldwide geographic variation in thyroid cancer incidence, the highest incidence rates being observed in New Caledonia, and a constant increase of thyroid cancer incidence has been observed during the past several decades. Although the evolution in medical practice probably accounts for some of the increase, other factors such as environmental and/or lifestyle factors may also play a role. However, there are few established risk factors of thyroid cancer apart from ionizing radiation exposure in childhood. We aimed to investigate the etiologic role of a family history of thyroid cancer, of hormonal and reproductive factors, anthropometric factors and environmental and occupational exposures in thyroid cancer. Methods: Analyses mainly rely on a population-based case-control study conducted in metropolitan France ( CATHY study ). Data of a case-control study conducted in New-Caledonia were also used to investigate the role of a family history of thyroid cancer as a risk factor for thyroid cancer in this area where thyroid cancer incidence is very high. The CATHY study is based on 621 cases diagnosed from 2002 to 2007 in three administrative areas: the Calvados, the Marne and the Ardennes, and 705 controls matched to cases by age, sex and residence area. The New Caledonian case-control study is based on 332 cases diagnosed form 1985 to 1999 and 412 controls matched to cases by age and sex. Results: A family history of thyroid cancer or multinodular goiter in first degree relatives was associated with an increased risk of thyroid cancer in France as well as in New Caledonia. Among hormonal and reproductive factors, a later age at menarche, a younger age at menopause and a elevated number of full-term pregnancies were associated with an increased risk of thyroid cancer. An inverse relationship was observed between the cumulative number of menstrual cycles and risk of thyroid cancer. Oral contraceptive use was associated with a lower risk of thyroid cancer, and an inverse relationship was observed between oral contraceptive use duration and risk of thyroid cancer. Height, body mass index and body surface area were positively associated with thyroid cancer risk. Analyses by occupation showed a higher risk of thyroid cancer for workers in leather industry, in plastics and rubber industry, in papermaking, in wood manufacturing, in automotive repair and in metallurgy.PARIS11-SCD-Bib. électronique (914719901) / SudocSudocFranceF

FGF receptor genes and breast cancer susceptibility: results from the Breast Cancer Association Consortium

Background:Breast cancer is one of the most common malignancies in women. Genome-wide association studies have identified FGFR2 as a breast cancer susceptibility gene. Common variation in other fibroblast growth factor (FGF) receptors might also modify risk. We tested this hypothesis by studying genotyped single-nucleotide polymorphisms (SNPs) and imputed SNPs in FGFR1, FGFR3, FGFR4 and FGFRL1 in the Breast Cancer Association Consortium. Methods:Data were combined from 49 studies, including 53 835 cases and 50 156 controls, of which 89 050 (46 450 cases and 42 600 controls) were of European ancestry, 12 893 (6269 cases and 6624 controls) of Asian and 2048 (1116 cases and 932 controls) of African ancestry. Associations with risk of breast cancer, overall and by disease sub-type, were assessed using unconditional logistic regression. Results:Little evidence of association with breast cancer risk was observed for SNPs in the FGF receptor genes. The strongest evidence in European women was for rs743682 in FGFR3; the estimated per-allele odds ratio was 1.05 (95 confidence interval=1.02-1.09, P=0.0020), which is substantially lower than that observed for SNPs in FGFR2. Conclusion:Our results suggest that common variants in the other FGF receptors are not associated with risk of breast cancer to the degree observed for FGFR2. © 2014 Cancer Research UK