Le Touquet – Paris-Plage, France
Le Touquet – Paris-Plage, France
Time filter
Source Type

Tepfer D.,French National Institute for Agricultural Research | Zalar A.,University of Versailles | Leach S.,LERMA
Astrobiology | Year: 2012

The plausibility that life was imported to Earth from elsewhere can be tested by subjecting life-forms to space travel. Ultraviolet light is the major liability in short-term exposures (Horneck et al., 2001), and plant seeds, tardigrades, and lichens-but not microorganisms and their spores-are candidates for long-term survival (Anikeeva et al., 1990; Sancho et al., 2007; Jönsson et al., 2008; de la Torre et al., 2010). In the present study, plant seeds germinated after 1.5 years of exposure to solar UV, solar and galactic cosmic radiation, temperature fluctuations, and space vacuum outside the International Space Station. Of the 2100 exposed wild-type Arabidopsis thaliana and Nicotiana tabacum (tobacco) seeds, 23% produced viable plants after return to Earth. Survival was lower in the Arabidopsis Wassilewskija ecotype and in mutants (tt4-8 and fah1-2) lacking UV screens. The highest survival occurred in tobacco (44%). Germination was delayed in seeds shielded from solar light, yet full survival was attained, which indicates that longer space travel would be possible for seeds embedded in an opaque matrix. We conclude that a naked, seed-like entity could have survived exposure to solar UV radiation during a hypothetical transfer from Mars to Earth. Chemical samples of seed flavonoid UV screens were degraded by UV, but their overall capacity to absorb UV was retained. Naked DNA encoding the nptII gene (kanamycin resistance) was also degraded by UV. A fragment, however, was detected by the polymerase chain reaction, and the gene survived in space when protected from UV. Even if seeds do not survive, components (e.g., their DNA) might survive transfer over cosmic distances. Key Words: Origin of life-Panspermia-Plant seeds-Flavonoid UV screens-DNA degradation-UV resistance-International Space Station. Astrobiology 12, 517-528. © Mary Ann Liebert, Inc.

Mueller B.,ETH Zurich | Hirschi M.,ETH Zurich | Jimenez C.,LERMA | Ciais P.,CEA Saclay Nuclear Research Center | And 14 more authors.
Hydrology and Earth System Sciences | Year: 2013

Land evapotranspiration (ET) estimates are available from several global data sets.Here, Monthly Global Land et Synthesis Products, Merged from These Individual Data Sets over the Time Periods 1989-1995 (7 Yr) and 1989-2005 (17 Yr), Are Presented. the Merged Synthesis Products over the Shorter Period Are Based on A Total of 40 Distinct Data Sets while Those over the Longer Period Are Based on A Total of 14 Data Sets. in the Individual Data Sets, et Is Derived from Satellite And/or in Situ Observations (Diagnostic Data Sets) or Calculated Via Land-surface Models (LSMs) Driven with Observations-based Forcing or Output from Atmospheric Reanalyses. Statistics for Four Merged Synthesis Products Are Provided, One Including All Data Sets and Three Including only Data Sets from One Category Each (Diagnostic, LSMs, and Reanalyses). the Multi-annual Variations of et in the Merged Synthesis Products Display Realistic Responses. They Are Also Consistent with Previous Findings of A Global Increase in et between 1989 and 1997 (0.13 Mm yr-2 in Our Merged Product) Followed by A Significant Decrease in This Trend (-0.18 Mm yr-2), although These Trends Are Relatively Small Compared to the Uncertainty of Absolute et Values. the Global Mean et from the Merged Synthesis Products (Based on All Data Sets) Is 493 Mm yr-1 (1.35 Mm d-1) for Both the 1989-1995 and 1989-2005 Products, Which Is Relatively Low Compared to Previously Published Estimates. We Estimate Global Runoff (Precipitation Minus ET) to 263 Mm yr -1 (34 406 km3 yr-1) for A Total Land Area of 130 922 000 km2. Precipitation, Being An Important Driving Factor and Input to Most Simulated et Data Sets, Presents Uncertainties between Single Data Sets As Large As Those in the et Estimates. in Order to Reduce Uncertainties in Current et Products, Improving the Accuracy of the Input Variables, Especially Precipitation, As Well As the Parameterizations of ET, Are Crucial. © 2013 Author(s).

Yang F.,Nanjing Southeast University | Treuttel J.,LERMA | Maestrini A.,LERMA | Gatilova L.,CNRS Laboratory for Photonics and Nanostructures
Asia-Pacific Microwave Conference Proceedings, APMC | Year: 2013

The design is to accomplish a frequency doubler by using thin membrane sub-millimeter wave integrated circuit fabrication technology. The Goubau line theory is firstly incorporated here to predefine the dimension of the channel, which is the key to the doubler's performance. The detailed linear and nonlinear co-simulation method is presented as followed, usually several iterations are needed during the optimization flow. Finally, the expected pass-band of doubler is from 430GHz to 470GHz over 22% efficiency. And the mesa size is 10μm×8.2μm and the membrane thickness is 5μm. It shows that we can realize high efficiency frequency multipliers even up to several THz in the future by using this thin membrane fabrication technology. © 2013 IEEE.

Barklem P.S.,Uppsala University | Belyaev A.K.,Uppsala University | Belyaev A.K.,Max Planck Institute for Astrophysics | Belyaev A.K.,University Paris Est Creteil | And 3 more authors.
Astronomy and Astrophysics | Year: 2012

Rate coefficients for inelastic Mg+H collisions are calculated for all transitions between the lowest seven levels and the ionic state (charge transfer), namely Mg(3s 2 1S, 3s3p 3P, 3s3p 1P, 3s4s 3S, 3s4s 1S, 3s3d 1D, 3s4p 3P)+H(1s) and Mg +(3s 2S)+H -. The rate coefficients are based on cross-sections from full quantum scattering calculations, which are themselves based on detailed quantum chemical calculations for the MgH molecule. The data are needed for non-LTE applications in cool astrophysical environments, especially cool stellar atmospheres, and are presented for a temperature range of 500-8000 K. From consideration of the sensitivity of the cross-sections to various uncertainties in the calculations, most importantly input quantum chemical data and the numerical accuracy of the scattering calculations, a measure of the possible uncertainties in the rate coefficients is estimated. © 2012 ESO.

Benhaim D.,LERMA | Pean S.,Collège de France | Lucas G.,LERMA | Blanc N.,LERMA | And 2 more authors.
Applied Animal Behaviour Science | Year: 2012

Behavioural studies comparing hatchery and wild-caught fish are useful to improve selection for aquaculture and restocking programmes. We examined swimming behaviour characteristics in wild captured and domesticated sea bass juveniles before and after eliciting a startle response at 8 different ages and always on naive individuals. We specifically investigated whether domestication impacts juvenile sea bass behaviour and whether the first months of captivity induce behavioural modifications in wild juveniles. An apparatus was designed to mimic a predator attack by presenting a sudden visual and mechanical stimuli simultaneously in 8 arenas where single individuals were placed and video recorded. The reactivity response was evaluated and different swimming variables including angular velocity, total distance travelled, mean velocity, immobility and distance from stimulus point were analysed from videos taken 5. min before stimulus actuation, 5 and 15. min after. Otolith readings showed that wild and domesticated juveniles were of similar age (~55 days at the start of the experiment and ~125 at the end of experiment). There were consistent behavioural differences (e.g. higher angular velocity and distance from stimulus point in wild fish) demonstrating that domestication reduces flight response behaviour. There were also similarities between both fish origins (similar response to stimulus actuation: decrease of total distance travelled and mean velocity, increase of angular velocity and immobility). A decrease over time in reactivity and variability in swimming responses among fish of both origins showed that captivity only does not fully explain wild fish behaviour changes and ontogenic modifications are likely interplaying. © 2012 Elsevier B.V.

Belyaev A.K.,Uppsala University | Barklem P.S.,Uppsala University | Spielfiedel A.,LERMA | Guitou M.,University Paris Est Creteil | And 3 more authors.
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2012

We report full quantum scattering calculations for low-energy near-threshold inelastic cross sections in Mg + H and Mg + + H - collisions. The calculations include all transitions between the eight lowest adiabatic MgH(2Σ +) molecular states, with the uppermost of those diabatically extended to the ionic molecular state in the asymptotic region. This allows us to treat the excitation processes between the seven lowest atomic states of magnesium in collisions with hydrogen atoms, as well as the ion-pair production and the mutual neutralization processes. The collision energy range is from threshold up to 10 eV. These results are important for astrophysical modeling of spectra in stellar atmospheres. The processes in question are carefully examined and several process mechanisms are found. Some mechanisms are determined by interactions between ionic and covalent configurations at relatively large internuclear distances, while others are based on short-range nonadiabatic regions due to interactions between covalent configurations. © 2012 American Physical Society.

Guitou M.,University Paris Est Creteil | Belyaev A.K.,Herzen University | Barklem P.S.,Uppsala University | Spielfiedel A.,LERMA | Feautrier N.,LERMA
Journal of Physics B: Atomic, Molecular and Optical Physics | Year: 2011

Full quantum scattering calculations of cross sections for low-energy near-threshold inelastic Mg + H collisions are reported, such processes being of interest for modelling of Mg spectral lines in stellar atmospheres. The calculations are made for three transitions between the ground and two lowest excited Mg states, Mg(3s2 1S0), Mg(3s3p 3P) and Mg(3s3p 1P). The calculations are based on adiabatic potentials and nonadiabatic couplings for the three low-lying 2Σ+ and the first two 2Π states, calculated using large active spaces and basis sets. Non-adiabatic regions associated with radial couplings at avoided ionic crossings in the 2Σ+ molecular potentials are found to be the main mechanism for excitation. Cross sections of similar order of magnitude to those obtained in Li + H and Na + H collisions are found. This, together with the fact that the same mechanism is important, suggests that as has been found earlier for Li and Na, processes such as ion pair production may be important in astrophysical modelling of Mg, and motivates continued study of this system including all states up to and including the ionic limit. © 2011 IOP Publishing Ltd.

Barklem P.S.,Uppsala University | Belyaev A.K.,Uppsala University | Belyaev A.K.,Herzen University | Guitou M.,University Paris Est Creteil | And 3 more authors.
Astronomy and Astrophysics | Year: 2011

The influence of inelastic hydrogen atom collisions on non-LTE spectral line formation has been, and remains to be, a significant source of uncertainty for stellar abundance analyses, due to the difficulty in obtaining accurate data for low-energy atomic collisions either experimentally or theoretically. For lack of a better alternative, the classical "Drawin formula" is often used. Over recent decades, our understanding of these collisions has improved markedly, predominantly through a number of detailed quantum mechanical calculations. In this paper, the Drawin formula is compared with the quantum mechanical calculations both in terms of the underlying physics and the resulting rate coefficients. It is shown that the Drawin formula does not contain the essential physics behind direct excitation by H atom collisions, the important physical mechanism being quantum mechanical in character. Quantitatively, the Drawin formula compares poorly with the results of the available quantum mechanical calculations, usually significantly overestimating the collision rates by amounts that vary markedly between transitions. © 2011 ESO.

Mahfouf J.-F.,Meteo - France | Birman C.,Meteo - France | Aires F.,Estellus | Prigent C.,LERMA | And 2 more authors.
Quarterly Journal of the Royal Meteorological Society | Year: 2015

This study examines the information content on atmospheric temperature and humidity profiles that could be provided by a future spaceborne microwave sensor with a few hundred radiances in the millimetre and submillimetre spectral domains (ranging from 7-800 GHz). A channel selection method based on optimal estimation theory is undertaken, using a database of profiles with associated errors from the European Centre for Medium-Range Weather Forecasts (ECMWF) numerical weather prediction model and the radiative transfer model Atmospheric Radiative Transfer Simulator (ARTS) under clear-sky conditions. The main results indicate that, by increasing the number of channels within the oxygen absorption band around 60 GHz and within the water-vapour absorption band at 183 GHz, the accuracy of temperature and humidity retrievals in the troposphere and stratosphere (for temperature) would be noticeably improved compared with present and planned microwave radiometers. The channels located in the absorption lines at 118 GHz and above 200 GHz do not bring significant additional information regarding atmospheric profiles under clear-sky conditions, partly due to greater radiometric noise. With a set of 137 selected channels that contribute to 90% of the total information content (measured by the degree of freedom for signal), it is possible to achieve almost the same performance in terms of variance error reduction as with 276 candidate channels. Sensitivity studies of various prescribed quantities defining the channel selection have been undertaken, in order to check the robustness of the conclusions. They show that none of the choices modifies the above findings. © 2015 Royal Meteorological Society.

Stoecklin T.,CNRS Institute of Molecular Sciences | Bussery-Honvault B.,Laboratory Interdisciplinaire Carnot de Bourgogne | Honvault P.,Laboratory Interdisciplinaire Carnot de Bourgogne | Dayou F.,LERMA
Computational and Theoretical Chemistry | Year: 2012

New long-range multipolar coefficients for the X+OH(X 2Π) interactions, where X=O( 3P), S( 3P) and N( 4S), are given here. They have been evaluated on the basis of monomer properties of the atoms and OH such as the dipole and quadrupole moments, and the static and dynamic polarizabilities. Each matrix element of the 18×18 (8×8 for N+OH) quasi-degenerate asymptotic potentials has been built up by means of the perturbation theory up to second order including or not the fine-structure of O, S and OH. The adiabatic potentials, obtained after diagonalization of the full matrix, show many crossings and complex behaviors near the asymptotes. Using the entrance channel ground state potential, the "adiabatic capture in the centrifugal sudden approximation" (ACCSA) approach has been found very convenient to get upper limit rate constants for the X+OH→XO+H reactions together with their temperature dependence. It is particularly sensitive to the long-range part of the potential in the low temperature regime. Three types of ground state potentials have been used to evaluate the influence of the potential on the magnitude and temperature dependence of the rate constants: one is obtained by supermolecular ab initio calculations and the other two by perturbation theory including or not the spin-orbit splittings. According to the potential which is employed, different behaviors of the rate constants are observed in the low and high temperature ranges while their absolute values are close in the middle temperature range. The ACCSA rate constants overestimate, by a factor of 2, more accurate kinetic values derived from quasi-classical and quantum dynamical calculations performed with global potential energy surfaces. This is attributed to a significant lower reaction probability than the one accounted for in the capture approximation employed here. © 2012 Elsevier B.V.

Loading LERMA collaborators
Loading LERMA collaborators