Boundary Stabilization of Memory Type for the Porous-Thermo-Elasticity System

We consider the one-dimensional viscoelastic Porous-Thermo-Elastic system. We establish a general decay results. The usual exponential and polynomial decay rates are only special cases

Solutal thermodiffusion in binary mixture in the presence of g-jitter

The phenomenon of mass flux in a mixture due to a temperature gradient is known as the Soret effect or thermal diffusion. This effect is usually small but can be quite important in the analysis of compositional variation in hydrocarbon reservoirs. Diffusion-dominated experiments on-board the International Space Station will be greatly affected by convective flow due to the residual acceleration field and/or to oscillatory g-jitters caused by several sources. In this paper we are interested in investigating the flow due to thermal diffusion for different oscillatory g-jitters. The model considered is a rectangular rigid cavity filled with a binary mixture of methane and normal butane, subject to a temperature difference on its end walls and radiation heat transfer on the lateral ones. The non-linear differential equations for the massthermo-vibrational problem are derived in the case of a unique mode oscillatory acceleration. The full transient Navier-Stokes equations coupled with the mass and heat transfer formulations and the equation of state of the fluid are solved numerically using the finite element technique. Results revealed that the thermal diffusion is important and drives a strong convection. Convection is enhanced and therefore temperature and species profiles distortion from purely diffusive condition increases when a parallel g-jitter is added to the residual gravity, in a destabilizing configuration. The numerical study shows that both residual gravity and g-jitter may be detrimental but also beneficial to achieve purely diffusive conditions, according to the orientation of the vibration direction and the residual gravity vector, relative to the direction of the main density gradient. For the different configurations investigated, the g-jitter is found to reduce compositional variation. When the stable regime is attained, thermal and compositional quantities fluctuate following a mode whose frequency is equal to that of the initially imposed vibration. Even if the temperature fluctuation at a given point remains small, the compositional variation due to residual g-jitter convection is not negligible. © 2002 Éditions scientifiques et médicales Elsevier SAS. All rights reserved.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

PCBs and DDTs in Stenella coeruleoalba dolphins from the French Mediterranean coastal environment (2007-2009): Current state of contamination

International audienceOrganochlorinated compounds including PolyChloroBiphenyles, Dichloro-DiphenylTrichloroethan and metabolites are determinated in Stenella coeruleoalba (n = 37) stranded on the french Mediterranean coasts from 2007 till 2009. Studies are carried out on lung, muscle, kidney, liver, and blubber. The sought-after compounds are all detected to variable levels in each tissue and organ. In general, total PCBs are the most abondant, followed by total DDTs. The concentration (in ng g(-1) of lipid weight) in blubber of S. coeruleoalba, varied from 2,052 to 158,992 for PCBs and from 1,120 to 45,779 for DDTs. The ratios DDE/tDDTs are higher than 80% in almost all samples. The overall results of this work, compared to previous studies concerning the Mediterranean Sea, seems to confirm the tendency to a decrease of the contamination by organics compounds for the cetaceans in the Western Mediterranean Sea. (C) 2012 Elsevier Ltd. All rights reserved

A chronicle of the changes undergone by a maritime territory, the Bay of Toulon (Var Coast, France), and their consequences on PCB contamination

International audienceThis study evaluated the distribution of polychlorinated biphenyls (PCBs) in 39 surface sediment samples and four cores collected in Toulon Bay, a semiclosed area submitted to various anthropogenic inputs. The concentration of PCBs in the superficial sediment samples ranged from 1.7 to 2530 ng g(-1) dry weight. The spatial distribution of these compounds suggested that the high concentrations of these contaminants are located in the small bay and are related to human activities. In the larger bay, the concentrations were in the same order of magnitude than those reported in others locations around the world. Comparison of the levels with target values from the French legislation shows that, except for four polluted sites with critical values (N2: values \textgreater= 1 mg kg(-1) dry weight) in the smaller bay, PCBs levels throughout the larger and the smaller bay are lower than the accepted values (N1: values \textless 0.5 mg kg(-1) dry weight). The PCBs in the sediment cores ranged from 0.8 to 739 ng g(-1) dry weight dependent core. Vertical profiles indicated earlier usage of PCBs which coincided with the history of the Toulon Bay. In this study, using alkane, we could follow the PCBs pollution history over about 80 years and estimate a sedimentation rate of about 0.32 cm year in the small Bay of Toulon