Recifs artificiels : analyse bibliographique

CNRS RP 350 (88) / INIST-CNRS - Institut de l'Information Scientifique et TechniqueSIGLEFRFranc

The underwater observation of fish communities and fish populations. Methods and problems

Following the symposium held in June 1984 at Port Cros, the methods of underwater observation of fish communities and populations are critically reviewed. Particular emphasis is laid upon the possible causes of bias, and the ways of circumventing them. Given some necessary precautions and adequate training, and within definite limits, underwater observations and counts can produce highly reliable results, not obtainable by « blind » techniques. Some examples are given, based upon the personal experiences of the participants, both in the Mediterranean and the Indo-Pacifi

Proton and cesium conductivity in perfluorosulfonate ionomers at low and high relative humidity

Nafion exhibits one of the highest proton conductivity at room temperature and it is the standard electrolyte of proton exchange membrane fuel cells (PEMFC). However, the temperature dependence of ionic conductivity of Nation is highly dependent on the measuring conditions and it is still a matter of debate. In the present study, detailed dielectric spectroscopy (DS) measurements in both dry (under N2 flow) and water-saturated conditions were carried out in a broad range of temperature and frequency. Such DS results were correlated to differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) data taken in similar conditions. The main results revealed that in samples conditioned in N2 flow (RH ~ 0%) the transport of both proton and cesium ions is coordinated with the dynamics of Nafion relaxations. In hydrated Nafion (proton form), conductivity measurements at different frequencies revealed two regimes: one at high-frequency, in which the Vogel-Tamman-Fulcher (VTF) law indicates a close relation between the polymer glass transition temperature Tg; and, a second one at low frequency, bearing great similarity to the transport observed in nearly dry samples. The reported experimental results contribute to disentangle the intricate transport properties of Nafion.Fil: Matos, Bruno R.. Comissao Nacional de Energia Nuclear. Centro de Lasers e Aplicacoes. Instituto de Pesquisas Energeticas e Nucleares.; BrasilFil: da Silva, Jaqueline S.. Comissao Nacional de Energia Nuclear. Centro de Lasers e Aplicacoes. Instituto de Pesquisas Energeticas e Nucleares.; BrasilFil: Santiago, Elisabete I.. Comissao Nacional de Energia Nuclear. Centro de Lasers e Aplicacoes. Instituto de Pesquisas Energeticas e Nucleares.; BrasilFil: Parra, Duclerc F.. Comissao Nacional de Energia Nuclear. Centro de Lasers e Aplicacoes. Instituto de Pesquisas Energeticas e Nucleares.; BrasilFil: Carastan, Danilo J.. Universidade Federal do ABC; BrasilFil: de Florio, Daniel Z.. Universidade Federal do ABC; BrasilFil: Andrada, Heber Eduardo. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; ArgentinaFil: Carreras, Alejo Cristian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; ArgentinaFil: Fonseca, Fabio C.. Comissao Nacional de Energia Nuclear. Centro de Lasers e Aplicacoes. Instituto de Pesquisas Energeticas e Nucleares.; Brasi