Tidal dynamics of extended bodies in planetary systems and multiple stars

With the discovery during the past decade of a large number of extrasolar planets orbiting their parent stars at a distance lower than 0.1 astronomical unit (and the launch and the preparation of dedicated space missions such as CoRoT and KEPLER), with the position of inner natural satellites around giant planets in our Solar System and with the existence of very closed but separated binary stars, tidal interaction has to be carefully studied. In particular, a question arises about the validity of usual approximations used in the modelling of this interaction. The purpose of this paper is to examine the step beyond the ponctual approximation for the tidal perturber. To achieve this aim, the gravitational interaction between two extended bodies and more precisely the interaction between mass multipole moments of their gravitational fields and the associated tidal phenomena are studied. Use of Cartesian Symmetric Trace Free (STF) tensors, of their relation with spherical harmonics and of the Kaula's transform enables to derive analytically the tidal and mutual interaction potentials as well as the associated disturbing functions in extended bodies systems. The tidal and mutual interaction potentials of two extended bodies are derived. Next, the external gravitational potential of such tidally disturbed extended body is obtained, using the Love's number theory, as well as the associated disturbing function. Finally, the dynamical evolution equations for such systems are given in their more general form without any linearization. The dynamical equations for the gravitational and tidal interactions between extended bodies and associated dynamics are derived in a form where they could be directly implemented to perform coherent numerical simulations of planetary systems or multiple stars tidal evolution.Comment: accepted for publication in Astronomy and Astrophysic

Prospective pragmatic quasi-experimental study to assess the impact and effectiveness of an innovative large-scale public health intervention to foster healthy ageing in place: the SoBeezy program protocol

INTRODUCTION: With the accelerating pace of ageing, healthy ageing has become a major challenge for all societies worldwide. Based on that Healthy Ageing concept proposed by the WHO, the SoBeezy intervention has been designed through an older person-centred and integrated approach. The programme creates the environments that maximise functional ability to enable people to be and do what they value and to stay at home in best possible conditions. METHODS AND ANALYSIS: Five levers are targeted: tackling loneliness, restoring feeling of usefulness, finding solutions to face material daily life difficulties, promoting social participation and combating digital divide. Concretely, the SoBeezy programme relies on: (1) a digital intelligent platform available on smartphone, tablet and computer, but also on a voice assistant specifically developed for people with digital divide; (2) a large solidarity network which potentially relies on everyone's engagement through a participatory intergenerational approach, where the older persons themselves are not only service receivers but also potential contributors; (3) an engagement of local partners and stakeholders (citizens, associations, artisans and professionals). Organised as a hub, the system connects all the resources of a territory and provides to the older person the best solution to meet his demand. Through a mixed, qualitative and quantitative (before/after analyses and compared to controls) approach, the research programme will assess the impact and effectiveness on healthy ageing, the technical usage, the mechanisms of the intervention and conditions of transferability and scalability. ETHICS AND DISSEMINATION: Inserm Ethics Committee and the Comité Éthique et Scientifique pour les Recherches, les Études et les Évaluations dans le domaine de la Santé approved this research and collected data will be deposited with a suitable data archive

A Dynamical Solution of the Triple Asteroid System (45) Eugenia

We present the first dynamical solution of the triple asteroid system (45) Eugenia and its two moons Petit-Prince (Diameter~7 km) and S/2004 (45) 1 (Diameter~5 km). The two moons orbit at 1165 and 610 km from the primary, describing an almost-circular orbit (e~6x10-3 and e~7x10-2 respectively). The system is quite different from the other known triple systems in the main belt since the inclinations of the moon orbits are sizeable (9 deg and 18 deg with respect to the equator of the primary respectively). No resonances, neither secular nor due to Lidov-Kozai mechanism, were detected in our dynamical solution, suggesting that these inclinations are not due to excitation modes between the primary and the moons. A 10-year evolution study shows that the orbits are slightly affected by perturbations from the Sun, and to a lesser extent by mutual interactions between the moons. The estimated J2 of the primary is three times lower than the theoretical one, calculated assuming the shape of the primary and an homogeneous interior, possibly suggesting the importance of other gravitational harmonics.Comment: 38 pages, 5 Tables, 5 Figures, revised for Icarus Journa

The new place of imaging in cardiology, from diagnosis to treatment

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Décomposition de Helmholtz-Hodge d'un champ de vitesse "Bas Mach"

This video displays the Helmholtz-Hodge decomposition of a velocity field obtained for an axisymmetric, laminar, Low Mach flow of a hot air jet in an enclosure initially filled with cold air. The decomposition of the field allows us to isolate the irrotational part of the velocity field linked to pressurization of the enclosure, from the solenoidal part, with zero divergence, associated with vortices. Each part of the field is associated with a potential. These two potentials are scalar under the axisymmetric hypothesis.From left to right in the video:1) The velocity field ;2-3) The potential and velocity field associated with the irrotational part;4-5) The potential and velocity field associated with the solenoidal part.The numerical method used to perform the decomposition is a quadratic Q2 finite element method implemented in the Cast3M software.Cette vidéo montre la décomposition de Helmholtz-Hodge d'un champ de vitesse obtenu pour un écoulement, supposé axisymétrique, laminaire et Bas Mach, d'un jet d'air chaud dans une enceinte initialement remplie d'air froid. La décomposition du champ permet d'isoler la partie du champ de vitesse, irrotationnelle, liée à la pressurisation de l'enceinte de celle, solénoïdale, à divergence nulle, associée aux tourbillons. Chaque partie du champ est associée à un potentiel. Ces deux potentiels sont scalaires dans le cadre de l'hypothèse axisymétrique.De gauche à droite sur la vidéo :1) Le champ de vitesse ;2-3) Le potentiel et le champ de vitesse associées à la partie irrotationnelle ;4-5) Le potentiel et le champ de vitesse associées à la partie solénoïdale.La méthode numérique utilisée pour effectuer la décomposition est une méthode d'éléments finis quadratiques Q2 implémentée dans le code de calcul Cast3M

Décomposition de Helmholtz discrète et applications

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Décomposition de Helmholtz discrète et applications

International audienc

Biventricular pacing and left ventricular pacing in heart failure: similar hemodynamic improvement despite marked electromechanical differences

The definitive version is available at www.blackwell-synergy.comIntroduction: We conducted an acute echocardiographic study comparing hemodynamic and ventricular dyssynchrony parameters during left ventricular pacing (LVP) and biventricular pacing (BVP). We sought to clarify the mechanisms responsible for similar hemodynamic improvement despite differences in electrical activation. Methods and Results: Thirty-three patients underwent echocardiography prior to implantation with a multisite pacing device (spontaneous rhythm [SR]) and 2 days after implantation (BVP and LVP). Interventricular dyssynchrony (pulsed-wave Doppler), extent of myocardium displaying delayed longitudinal contraction (%DLC; tissue tracking), and index of LV dyssynchrony (pulsed-wave tissue Doppler imaging) were assessed. Compared to SR, BVP and LVP caused similar significant improvement of cardiac output (LVP: 3.2 ± 0.5, BVP: 3.1 ± 0.7, SR: 2.3 ± 0.6 L/min; P < 0.01) and mitral regurgitation (LVP: 25.1 ± 10, BVP: 24.7 ± 11, baseline: 37.9 ± 14% jet area/left atria area; P < 0.01). LVP resulted in a smaller index of LV dyssynchrony than BVP (29 ± 10 vs 34 ± 14; P < 0.05). However, LVP exhibited a longer aortic preejection delay (220 ± 34 vs 186 ± 28 msec; P < 0.01), longer LV electromechanical delays (244.5 ± 39 vs 209.5 ± 47 msec; P < 0.05), greater interventricular dyssynchrony (56.6 ± 18 vs 31.4 ± 18; P < 0.01), and higher%DLC (40.1 ± 08 vs 30.3 ± 09; P < 0.05), leading to shorter LV filling time (387 ± 54 vs 348 ± 44 msec; P < 0.05) compared to BVP. Conclusion: Although LVP and BVP provide similar hemodynamic improvement, LVP results in more homogeneous but substantially delayed LV contraction, leading to shortened filling time and less reduction in postsystolic contraction. These data may influence the choice of individual optimal pacing configuration.Pierre Bordachar, Stephane Lafitte, Sylvain Reuter, Stephane Garrigue, Prashanthan Sanders, Raymond Roudaut, Pierre Jaïs, Michel Haïssaguerre, Jacques Clement