Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Laboratory models have been conducted to improve our understanding of the role that the resistance of the slab to bending and its coupling to the ambient mantle play in subduction dynamics over geological time scales. Our models are set up with a viscous plate of silicone (lithosphere) subducting under negative buoyancy in a viscous layer of glucose syrup (mantle). For our study, the lithosphere/upper mantle viscosity contrast has been systematically varied, from similar to 10 to similar to 10(5) in order to explore the parameter space between weak and strong slab dynamics. We found that subduction is characterized by a retreating mode for viscosity ratios > 10(4), by the coexistence of a retreating mode and an advancing mode for viscosity ratios between similar to 10(4) and similar to 10(2), and quasi-stationary, Rayleigh-Taylor like behaviour for ratios < 10(2). By combining our experimental results and kinematic data from current subduction zones in four reference frames which differ in the amount of net rotation, we infer that a lithosphere/upper mantle viscosity contrast of 150-500 is necessary to obtain realistic trench/subducting plate velocity ratios as well as the variability of subduction styles observed in nature.
ISSN: 0012-821X

hal-00412008
https://hal.archives-ouvertes.fr/hal-00412008
DOI : 10.1016/j.epsl.2008.04.006

Éditeur(s) : Elsevier Science Bv
Résumé : Mechanisms controlling the transfer and retention of silicon (Si) along continental margins are poorly understood, but play a major role in the functioning of coastal ecosystems and the oceanic biological pump of carbon. Deep-sea fans are well recognized as carbon sink spots, but we lack knowledge about the importance of the fans in the global Si cycle. Here, we provide a first estimate of the role played by the Congo deep-sea fan, one of the biggest in the world, in the Si cycle. Sediment cores sampled in the deep-sea fan were analyzed to build a Si mass balance. An exceptionally high accumulation rate of amorphous silica aSiO(2) (2.29 +/- 0.58 mol Si m(-2) y(-1)) was found, due to a high sedimentation rate and the presence of aluminum in the sediments. Although favored by bioirrigation, recycling fluxes remained low (0.3 mol Si m(-2) y(-1)) and reconstructed input fluxes could only be explained by lateral inputs coming from the canyon. Preliminary calculations show that the rapid transport of aSiO(2) through the canyon and the excellent preservation efficiency in the sediments imply that 50% of aSiO(2) river inputs from the Congo River accumulate annually in the deep-sea fan. Si:C ratios in deep-sea fan sediments were very low (0.2) and only three times as high as those measured in the river itself, which suggests that material from the river and the continental shelf was delivered directly through the canyon, with very little time for Si and C cycle decoupling to take place.
Journal Of Marine Systems (0924-7963) (Elsevier Science Bv), 2015-01 , Vol. 141 , P. 71-79

Droits : 2014 Elsevier B.V. All rights reserved.
http://archimer.ifremer.fr/doc/00251/36242/35797.pdf
DOI:10.1016/j.jmarsys.2014.07.010
http://archimer.ifremer.fr/doc/00251/36242/

Éditeur(s) : HAL CCSD ACS American Chemical Society - Publications
Résumé : International audience
ABSTRACT: In this paper, the structural, optical and thermal properties of n-type (100),p-type (100) and (111) mesoporous silicon (MePSi) are reported. The mesoporous silicon wasprepared by an electrochemical process from bulk silicon wafer. Depending on the etchingdepth, analyses show that the porosity of p-type (111) increased by 32 to 40% compared to p(100) which, in turn, increased by 22 to 48% compared to n-type (100). The structuremorphology and the abundance of Si-Ox and Si-Hy also depended heavily on the type andcrystal orientation of MePSi. The thermal properties of the MePSi layers such as thermalconductivity (κ), volumetric heat capacity (ρCp) and thermal contact resistance (Rth) weredetermined using the pulsed photothermal method. The thermal conductivity of bulk silicondropped sharply after etching, decreasing by more than twenty-fold in the case of n-type (100)and by over forty-five fold for p-type (100) and (111). According to the percolation modeldepending on both porosity and phonon confinement, the drop in thermal conductivity wasmainly due to the nanostructure formation after etching. Thermal investigations showed thatthe volumetric heat capacity (ρCp) followed the barycentric model which depends mainly onthe porosity. The thermal contact resistances of MePSi layers were estimated to be in therange of 1x10-8 to 1x10-7 K⋅m2⋅W-1.
The Journal of Physical Chemistry C

hal-01495490
https://hal.archives-ouvertes.fr/hal-01495490
DOI : 10.1021/acs.jpcc.6b13101

Éditeur(s) : HAL CCSD University of Uludag
Résumé : International audience
We tested whether the silicone swim caps (SC) worn by young swimmers in a tropical climate negatively influence aerobic performance. Nine trained pre-adolescents [11.8 (± 0.8) years] swam randomized 800-m trials (water: 32.9°C, outdoors: shade, 29.2 ± 0.2 °C, 74 ± 0.3 % rh) with a SC or a nude head (NH). Performance times and heart rate (HR) were monitored continuously. Rectal temperature (T rec) was measured before and after trials. The rating of perceived exertion (RPE) was assessed. Stroke frequency (SF), stroke length (SL) and stroke index (SI) were measured every 50-m. The SC trial was significantly longer than NH (799 ± 16 and 781 ± 16 seconds, respectively). Mean delta T rec was significantly greater in SC (0.2 ± 0.1°C vs.-0.1 ± 0.1°C in SC vs. NH), mean SI was significantly different in SC versus NH (1.83 ± 0.07 vs 1.73 ± 0.06); but RPE and mean HR, SF and SL showed no change. We conclude that a silicone swim cap worn in tropical environment significantly decreased 800-m crawl performance without affecting HR or RPE. Silicone swim caps worn by young swimmers in a tropical environment may also have negative effects on training capacity.
ISSN: 1303-2968

hal-01137570
https://hal.univ-antilles.fr/hal-01137570
https://hal.univ-antilles.fr/hal-01137570/document
https://hal.univ-antilles.fr/hal-01137570/file/Hue%2C%20Galy%20-%202012%20-%20The%20effect%20of%20a%20silicone%20swim%20cap%20on%20swimming%20performance%20in%20tropical%20conditions%20in%20pre-adolescents.pdf

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
Synthetic hydroxylated titanium-bearing and undoped MgO-buffered forsterite crystals were heated at atmospheric pressure in air at temperatures from 800 to 1200 °C to determine hydrogen diffusion as a function of the type of point-defect mechanism by which the hydroxyl is incorporated. OH-stretching bands, measured by infrared spectroscopy, were assigned to the four substitution mechanisms: Ti-clinohumite point defects, silicon and magnesium vacancies, and point defects associated with trivalent cations. In the experiments at 800 to 1000 °C, hydrous defects related to trivalent cations and Mg-vacancies disappear first in the Ti-doped forsterite, followed by the hydrous defects related to Ti and a fraction of the hydrated Si-vacancies. Measured bulk diffusion coefficients for hydrogen exchange related to the latter process are one order of magnitude slower than previously reported and with higher activation energy (View the MathML source296±14 kJmol−1). After the elimination of the defects related to Ti, the hydroxyl concentration related to Si-vacancies remained constant for the duration of the experiments. This observation is in agreement with the very slow diffusivity of hydrogen in Si-vacancies measured in the undoped MgO-buffered dehydroxylation experiments at higher temperatures (from 1000 to 1200 °C), which were ∼3 orders of magnitude slower than previously reported at 1000 °C, and with an activation energy of View the MathML source461±11 kJmol−1. Hydrogen diffusion in forsterite is far more complex than previously assumed. This complexity can be used to gain more information on the timescales of the processes causing olivine to lose its structural “water”, but quantitative modeling will require not only the knowledge of the intrinsic diffusivities of the different hydrous defects but also their relative proportions and the possible reactions between them.
ISSN: 0012-821X

hal-01172253
https://hal.archives-ouvertes.fr/hal-01172253
DOI : 10.1016/j.epsl.2014.01.055

Éditeur(s) : HAL CCSD University of Uludag
Résumé : International audience
We tested whether the silicone swim caps (SC) worn by young swimmers in a tropical climate negatively influence aerobic performance. Nine trained pre-adolescents [11.8 (± 0.8) years] swam randomized 800-m trials (water: 32.9°C, outdoors: shade, 29.2 ± 0.2 °C, 74 ± 0.3 % rh) with a SC or a nude head (NH). Performance times and heart rate (HR) were monitored continuously. Rectal temperature (T rec) was measured before and after trials. The rating of perceived exertion (RPE) was assessed. Stroke frequency (SF), stroke length (SL) and stroke index (SI) were measured every 50-m. The SC trial was significantly longer than NH (799 ± 16 and 781 ± 16 seconds, respectively). Mean delta T rec was significantly greater in SC (0.2 ± 0.1°C vs.-0.1 ± 0.1°C in SC vs. NH), mean SI was significantly different in SC versus NH (1.83 ± 0.07 vs 1.73 ± 0.06); but RPE and mean HR, SF and SL showed no change. We conclude that a silicone swim cap worn in tropical environment significantly decreased 800-m crawl performance without affecting HR or RPE. Silicone swim caps worn by young swimmers in a tropical environment may also have negative effects on training capacity.
ISSN: 1303-2968

hal-01143533
https://hal.univ-antilles.fr/hal-01143533

Éditeur(s) : HAL CCSD Elsevier Masson
Résumé : National audience
o abstract
ISSN: 1297-9589

hal-01485265
https://hal-univ-rennes1.archives-ouvertes.fr/hal-01485265
DOI : 10.1016/j.gyobfe.2016.08.010
PUBMED : 27665251

Éditeur(s) : HAL CCSD Wiley
Résumé : International audience
The natural river water certified reference material SLRS-5 (NRC-CNRC) was routinely analysed in this study for major and trace elements by ten French laboratories. Most of the measurements were made using ICP-MS. Because no certified values are assigned by NRC-CNRC for silicon and 35 trace element concentrations (rare earth elements, Ag, B, Bi, Cs, Ga, Ge, Li, Nb, P, Rb, Rh, Re, S, Sc, Sn, Th, Ti, Tl, W, Y and Zr), or for isotopic ratios, we provide a compilation of the concentrations and related uncertainties obtained by the participating laboratories. Strontium isotopic ratios are also given. Le matériau de référence certifié d'eau de rivière naturelle SLRS-5 (NRC-CNRC) est analysé régulièrement comme contrôle qualité par dix laboratoires français étudiant les éléments majeurs et en trace dans les solutions naturelles. La plupart des mesures sont réalisées par ICP-MS. Le silicium et 35 éléments en trace (terres rares, Ag, B, Bi, Cs, Ga, Ge, Li, Nb, P, Rb, Rh, Re, S, Sc, Sn, Th, Ti, Tl, W, Y et Zr) ne sont pas certifiés par NRC-CNRC. Aucun rapport isotopique n'est disponible. Nous proposons, pour ces éléments, des valeurs moyennes et leurs incertitudes associées obtenues par les différents laboratoires participants. Le rapport isotopique de Sr est aussi mesuré.
ISSN: 1639-4488

hal-00906166
https://hal.archives-ouvertes.fr/hal-00906166
DOI : 10.1111/j.1751-908X.2013.00232.x

Éditeur(s) : HAL CCSD Elsevier
Résumé : A combination of statistical studies on present-day subduction zones and three-dimensional (3D) laboratory models is performed with the aim to clarify the way that plate kinematics control the geometry of the slab and the overriding plate deformation in subduction zones. In 3D laboratory models, the analogue of a two layer linearly viscous lithosphere–upper mantle system is achieved by means of silicon putty glucose syrup tank experiment. The subducting and overriding plate velocities are systematically changed by exploring the variability field of natural plate kinematics. Both statistical and modelling approaches recognize the importance of overriding plate motion on subduction process behavior: (1) trenches migrate at a rate close to the overriding plate motion, but always move slower than the overriding plates. The mechanism at work is a direct consequence of “slab anchoring” opposed by both lithosphere and mantle viscous resistance and is responsible for overriding plate deformation and slab geometry variability. (2) An overriding plate shortens when the overriding plate moves toward the trench and conditions that are favourable for overriding plate extension are created when the overriding plate moves away from the trench. (3) Shallow and steep dips are found if the overriding plate moves toward and away from the trench, respectively.
ISSN: 0012-821X

hal-00406598
https://hal.archives-ouvertes.fr/hal-00406598
DOI : 10.1016/j.epsl.2007.02.004