University of the Littoral Opal Coast

About: University of the Littoral Opal Coast is a education organization based out in Dunkirk, France. It is known for research contribution in the topics: Catalysis & Dielectric. The organization has 1242 authors who have published 2383 publications receiving 46230 citations. The organization is also known as: ULCO.

A comparative study of nematic liquid crystals doped with harvested and non-harvested ferroelectric nanoparticles: phase transitions and dielectric properties

Abstract: Harvested and non-harvested tin thiohypodiphosphate (Sn2P2S6) ferroelectric nanoparticles are used to dope the 4-n-octyl-4′-cyanobiphenyl liquid crystal (8CB). Due to their higher average spontaneous polarization, the harvested nanoparticles have stronger interactions with the liquid crystal molecules which leads to a higher order parameter as demonstrated by the increase in phase transition temperatures. This is confirmed by the results of dielectric characterization. In the homeotropic orientation, the increase in the order parameter leads to a higher dielectric permittivity. In the planar orientation, the coupling between the spontaneous polarization of the nanoparticles and the order parameter induces a slight reorientation of the liquid crystal director from the initial planar orientation, leading to an increase in the dielectric permittivity. This effect is more important for the liquid crystal doped with harvested nanoparticles.

Former uranium mine-induced effects in caged roach: a multiparametric approach for the evaluation of in situ metal toxicity.

Abstract: To characterize environmental risks linked to former uranium mines in the Limousin region of France, a study was conducted on fish health effects from uranium releases. Two private ponds were compared in this study, one with uranium contamination and one background site, upstream of the mining zone. Roach, Rutilus rutilus, were caged for 28 days in both ponds. Physico-chemical parameters of water and sediments and bioaccumulation of metals in several organs were determined. After 14 and 28 days of caging, immune, oxidative stress, biotransformation, neurotoxicity and physiological parameters were measured. Iron and aluminium were quantified in the water of both sites; however, barium and manganese were only present in the water of the uranium contaminated site. Uranium was present in both sites but at very different concentrations. The sediments from the uranium contaminated site contained high levels of radioactive elements coming from the disintegration chain of uranium. Results of biological parameters indicated stimulation of immune parameters and of oxidative stress and a decrease of AChE in fish caged in the uranium contaminated pond compared to the uranium-free pond. Overall, the results determined roach health status in the context of pollution from poly-metallic mining. The data strengthen our knowledge of the environmental risk assessment associated with radioactive substances in the environment.