Development of DGTD solver for nanophotonics applications

International audienceDuring the last ten years, the discontinuous Galerkin time-domain (DGTD) method has progressively emerged as a viable alternative to well established finite-difference time-domain (FDTD) and finite-element time-domain (FETD) methods for the numerical simulation of electromagnetic wave propagation problems in the time-domain. We discuss here about the development and application of such a DTGD method for solving the system of time-domain Maxwell equations coupled to material models relevant to nanophotonics. Our efforts aim at improving the accuracy, flexibility and efficiency of the method in view of the numerical treatment of realistic problems

Diversification, evolution and sub-functionalization of 70kDa heat-shock proteins in two sister species of Antarctic krill: differences in thermal habitats, responses and implications under climate change

A comparative thermal tolerance study was undertaken on two sister species of Euphausiids (Antarctic krills) Euphausia superba and Euphausia crystallorophias. Both are essential components of the Southern Ocean ecosystem, but occupy distinct environmental geographical locations with slightly different temperature regimes. They therefore provide a useful model system for the investigation of adaptations to thermal tolerance. Methodology/Principal Finding Initial CTmax studies showed that E. superba was slightly more thermotolerant than E. crystallorophias. Five Hsp70 mRNAs were characterized from the RNAseq data of both species and subsequent expression kinetics studies revealed notable differences in induction of each of the 5 orthologues between the two species, with E. crystallorophias reacting more rapidly than E. superba. Furthermore, analyses conducted to estimate the evolutionary rates and selection strengths acting on each gene tended to support the hypothesis that diversifying selection has contributed to the diversification of this gene family, and led to the selective relaxation on the inducible C form with its possible loss of function in the two krill species. Conclusions The sensitivity of the epipelagic species E. crystallorophias to temperature variations and/or its adaptation to cold is enhanced when compared with its sister species, E. superba. These results indicate that ice krill could be the first of the two species to be impacted by the warming of coastal waters of the Austral ocean in the coming years due to climate change

A multiscale hybrid-mixed method for the Maxwell equations in time-domain

International audienceThis work proposes a Multiscale Hybrid-Mixed (MHM) method for the Maxwell equation in time domain. The MHM method is a consequence of a hybridization procedure, and emerges as a method that naturally incorporates multiple scales while provides solutions with high-order precision. The computation of local problems is embedded in the upscaling procedure, which are completely independent and thus may be naturally obtained using parallel computation facilities. In this talk, we present the new MHM method for the two-dimensional Maxwell equations in time domain (Transverse Magnetic mode). We address some theoretical aspects of the method and propose an extensive numerical validation. We conclude that the MHM method is naturally shaped to be used in parallel computing environments and appears to be a highly competitive option to handle realistic multiscale hyperbolic boundary value problems with precision on coarse meshes

A multiscale hybrid-mixed method for the Maxwell equations in the time domain

International audienceThis work proposes a Multiscale Hybrid-Mixed (MHM) method for the Maxwell equation in time domain. The MHM method is a consequence of a hybridization procedure, and emerges as a method that naturally incorporates multiple scales while provides solutions with high-order precision. The computation of local problems is embedded in the upscaling procedure, which are completely independent and thus may be naturally obtained using parallel computation facilities.In this talk, we present the new MHM method for the two-dimensional Maxwell equations in time domain (Transverse Magnetic mode). We address some theoretical aspects of the method and propose an extensive numerical validation. We conclude that the MHM method is naturally shaped to be used in parallel computing environments and appears to be a highly competitive option to handle realistic multiscale hyperbolic boundary value problems with precision on coarse meshes

Hybrid MIMD/SIMD High Order DGTD Solver for the Numerical Modeling of Light/Matter Interaction on the Nanoscale

International audienceThis paper is concerned with the development of a scalable high order finite element type solver for the numerical modeling of light interaction with nanometer scale structures. From the mathematical modeling point of view, one has to deal with the differential system of Maxwell equations in the time domain, coupled to an appropriate differential model of the behavior of the underlying material (which can be a dielectric and/or a metal) at optical frequencies. For the numerical solution of the resulting system of differential equations, we have designed a high order DGTD (Discontinuous Galerkin Time-Domain) solver that has been adapted to hybrid MIMD/SIMD computing. Here we discuss about this later aspect and report on preliminary performance results on the Curie system of the PRACE research infrastructure

La boulangerie de Saint-Bézard à Aspiran (Hérault), du I^er s. au IV^e s. apr. J.-C. : un exemple d’espace culinaire domanial en Narbonnaise centrale

International audienceThis article gives an account of the remains of a cooking area discovered inside a building interpreted as a tower, situated in the villa of Saint Bézard (Aspiran). After an overview of the present research on cooking spaces in the central part of Narbonensis, the building is described, inside a vast agricultural and craft establishment organized around a villa. Following is the chronology of the tower (1st c. to 4th c. AD) with its architectural and functional characteristics. The cooking space and devices are analysed in detail as well as the finds, notably the plant remains which bring definite results allowing to situate a bakery area. Finally, the question of the place of bread consumption in rural context is raised, underlining the importance of the spread of rotary-querns or water mills devoted to flour production, between the 1st century and the 3rd century AD.Cette contribution concerne les vestiges d’un espace culinaire mis au jour à l’intérieur d’un bâtiment interprété comme une tour, située dans l’emprise de la villa de Saint Bézard (Aspiran, Hérault). Après une introduction présentant un bref état de la recherche sur les espaces culinaires en Narbonnaise centrale, l’étude commence par une présentation de cet édifice inclus dans un vaste complexe agricole et artisanal organisé autour d’une villa. La chronologie de la tour (Ier-IVe s.) et ses caractéristiques architecturales et fonctionnelles sont ensuite abordées. La pièce culinaire et ses aménagements internes sont présentés en détail, tout comme les mobiliers associés, notamment les carporestes dont l’analyse apporte des éléments décisifs permettant de localiser ici une activité de boulangerie. In fine, on s’interroge sur la place de la consommation de pain en contexte rural en soulignant l’importance de la diffusion des moulins à sang ou hydrauliques, destinés à la production de farine panifiable, entre le Ier s. et le IIIe s. apr. J.-C

Darwin -— an experimental astronomy mission to search for extrasolar planets

As a response to ESA call for mission concepts for its Cosmic Vision 2015–2025 plan, we propose a mission called Darwin. Its primary goal is the study of terrestrial extrasolar planets and the search for life on them. In this paper, we describe different characteristics of the instrument

The habitability of Proxima Centauri b I. Irradiation, rotation and volatile inventory from formation to the present

International audienceProxima b is a planet with a minimum mass of 1.3 MEarth orbiting within the habitable zone (HZ) of Proxima Centauri, a very low-mass, active star and the Sun's closest neighbor. Here we investigate a number of factors related to the potential habitability of Proxima b and its ability to maintain liquid water on its surface. We set the stage by estimating the current high-energy irradiance of the planet and show that the planet currently receives 30 times more EUV radiation than Earth and 250 times more X-rays. We compute the time evolution of the star's spectrum, which is essential for modeling the flux received over Proxima b's lifetime. We also show that Proxima b's obliquity is likely null and its spin is either synchronous or in a 3:2 spin-orbit resonance, depending on the planet's eccentricity and level of triaxiality. Next we consider the evolution of Proxima b's water inventory. We use our spectral energy distribution to compute the hydrogen loss from the planet with an improved energy-limited escape formalism. Despite the high level of stellar activity we find that Proxima b is likely to have lost less than an Earth ocean's worth of hydrogen before it reached the HZ 100-200 Myr after its formation. The largest uncertainty in our work is the initial water budget, which is not constrained by planet formation models. We conclude that Proxima b is a viable candidate habitable planet

Altimetry for the future: Building on 25 years of progress

In 2018 we celebrated 25 years of development of radar altimetry, and the progress achieved by this methodology in the fields of global and coastal oceanography, hydrology, geodesy and cryospheric sciences. Many symbolic major events have celebrated these developments, e.g., in Venice, Italy, the 15th (2006) and 20th (2012) years of progress and more recently, in 2018, in Ponta Delgada, Portugal, 25 Years of Progress in Radar Altimetry. On this latter occasion it was decided to collect contributions of scientists, engineers and managers involved in the worldwide altimetry community to depict the state of altimetry and propose recommendations for the altimetry of the future. This paper summarizes contributions and recommendations that were collected and provides guidance for future mission design, research activities, and sustainable operational radar altimetry data exploitation. Recommendations provided are fundamental for optimizing further scientific and operational advances of oceanographic observations by altimetry, including requirements for spatial and temporal resolution of altimetric measurements, their accuracy and continuity. There are also new challenges and new openings mentioned in the paper that are particularly crucial for observations at higher latitudes, for coastal oceanography, for cryospheric studies and for hydrology. The paper starts with a general introduction followed by a section on Earth System Science including Ocean Dynamics, Sea Level, the Coastal Ocean, Hydrology, the Cryosphere and Polar Oceans and the ‘‘Green” Ocean, extending the frontier from biogeochemistry to marine ecology. Applications are described in a subsequent section, which covers Operational Oceanography, Weather, Hurricane Wave and Wind Forecasting, Climate projection. Instruments’ development and satellite missions’ evolutions are described in a fourth section. A fifth section covers the key observations that altimeters provide and their potential complements, from other Earth observation measurements to in situ data. Section 6 identifies the data and methods and provides some accuracy and resolution requirements for the wet tropospheric correction, the orbit and other geodetic requirements, the Mean Sea Surface, Geoid and Mean Dynamic Topography, Calibration and Validation, data accuracy, data access and handling (including the DUACS system). Section 7 brings a transversal view on scales, integration, artificial intelligence, and capacity building (education and training). Section 8 reviews the programmatic issues followed by a conclusion