Recifs artificiels : analyse bibliographique

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

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

Misidentification of bluefin tuna larvae: a call for caution and taxonomic reform

The international effort to prevent the collapse of Atlantic bluefin tuna (BFT, Thunnus thynnus, Scombridae) stocks exemplifies the challenges associated with modern marine resource conservation. Rampant mismanagement, under-reporting and illegal, unreported and unregulated fishing led to decades of over-exploitation in the BFT fishery. Surveys of larval abundance in the Gulf of Mexico and the Mediterranean Sea have been used as a proxy for both spawning biomass and recruitment by researchers working to improve estimates of stock abundance. Recent genetic barcoding studies have revealed that species identification errors are common among larvae surveys that use morphology-based taxonomy alone. Misidentification of larvae can lead to uncertainty about the spatial distribution of a species, confusion over life history traits and population dynamics, and potentially disguise the collapse or recovery of localized spawning sites. In an effort to identify the source of these errors, we review several weaknesses in modern morphology-based taxonomy including demographic decline of expert taxonomists, flawed identification keys, reluctance of the taxonomic community to embrace advances in digital communications and a general scarcity of modern user-friendly materials. Recent advances in molecular techniques useful for specimen identification and population studies are discussed at length. We advocate a more constructive integration of morphology-based taxonomy and barcoding in order to add confidence to larval surveys and to strengthen associated fisheries managementVersión del editor2,270