Hg(II) trace electrochemical detection on gold electrode: Evidence for chloride adsorption as the responsible for the broad baseline

Investigations were performed in order to clarify the origin of the broad baseline observed during Hg(II) trace electrochemical detection on gold electrode in the presence of Cl- anions. The influence of Cl- concentration on the shape of the voltammograms was studied in the presence and in the absence of Bovine Serum Albumin (BSA) in order to bring out adsorption/desorption processes. On the basis of these experiments, and contrary to what has been proposed by several authors in the literature, it was proved that the broad baseline does not result from calomel (Hg2Cl2) formation but is rather related to an interaction between Cl- and polycrystalline Au electrode surface. The evolution of the shape of the baseline was also studied in the presence of other halide anions, namely F-, Br-, and I-. The latter two were found to induce a broad baseline similar to that recorded in the presence of Cl-. Finally, it was shown that BSA addition is not suitable for Hg(II) detection since it prevents Hg(0) deposition onto the electrode surface

Mercury isotope evidence for Arctic summertime re-emission of mercury from the cryosphere

During Arctic springtime, halogen radicals oxidize atmospheric elemental mercury (Hg-0), which deposits to the cryosphere. This is followed by a summertime atmospheric Hg-0 peak that is thought to result mostly from terrestrial Hg inputs to the Arctic Ocean, followed by photoreduction and emission to air. The large terrestrial Hg contribution to the Arctic Ocean and global atmosphere has raised concern over the potential release of permafrost Hg, via rivers and coastal erosion, with Arctic warming. Here we investigate Hg isotope variability of Arctic atmospheric, marine, and terrestrial Hg. We observe highly characteristic Hg isotope signatures during the summertime peak that reflect re-emission of Hg deposited to the cryosphere during spring. Air mass back trajectories support a cryospheric Hg emission source but no major terrestrial source. This implies that terrestrial Hg inputs to the Arctic Ocean remain in the marine ecosystem, without substantial loss to the global atmosphere, but with possible effects on food webs.Arctic warming thaws permafrost, leading to enhanced soil mercury transport to the Arctic Ocean. Mercury isotope signatures in arctic rivers, ocean and atmosphere suggest that permafrost mercury is buried in marine sediment and not emitted to the global atmospherePeer reviewe

Ceramic-coated type III femtosecond Fiber Bragg Grating for high temperature environments

International audience1. Context: optical fiber sensors in harsh environment2. Ceramic coating manufacturing3. On-fiber coating deposition4. Ceramic-coated FBG thermal study5. Conclusio

Fractionnement des isotopes stables de mercure dans un écosystème tropical en Amazonie bolivienne et dans les cheveux de populations humaines exposées

Afin de déterminer le fractionnement des isotopes stables de Hg dans l'environnement, des échantillons de sédiments, roches, poissons, et cheveux humains ont été analysés par MC-ICPMS dans deux bassins versants de l'Amazonie Bolivienne où l'orpaillage est actif depuis des décennies. Des fractionnements dépendant (FDM) et indépendant (FIM) de la masse ont été mis en évidence dans les échantillons de poissons et cheveux. Le FIM est issu des réactions de photochimie de Hg(II) et monométhylmercure (MMHg) à la surface des eaux tandis que seul le FDM a été décelé pendant la bioaccumulation de MMHg dans les organismes. L'identification des sources de Hg dans les cheveux de mineurs a pu être réalisée ainsi qu'un bilan isotopique grâce aux données acquises sur les cheveux, les sédiments et les roches. Ces premiers résultats prouvent l'efficacité de l'étude des isotopes stables du mercure pour tracer les processus et évaluer les sources de mercure chez les êtres vivants.Samples of sediments, rocks, fish and human hair from the Bolivian Amazon basin, where gold-mining is active for decades, have been analysed by MC-ICPMS to study the stable isotopes fractionations of Hg. Evidence of mass-dependent (MDF) and mass-independent (MIF) fractionation have been observed in hair and fish samples. MIF is induced by photochemical reactions of Hg(II) and monomethylmercury (MMHg) in surface waters and MDF is observed only during the MMHg bioaccumulation process in organisms. Isotopic balance of Hg is improved thanks to sediments and rocks data showing a weak input of mercury by chemical weathering but significant atmospheric depositions of Hg(0) on soils. These first results obtained in hair and at a regional scale confirm that the stable isotopes of Hg constitute a powerful tool to trace biogeochemical processes and to evaluate mercury sources in living organisms.TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

L’apport de la langue des signes pour expliciter les concepts complexes et transdisciplinaires des transitions écologiques

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Estrogen-mediated protection of experimental autoimmune encephalomyelitis: Lessons from the dissection of estrogen receptor-signaling in vivo

A growing body of evidence from basic and clinical studies supports the therapeutic potential of estrogens in multiple sclerosis (MS), originating from the well-established reduction in relapse rates observed among women with MS during pregnancy. The biological effects of estrogens are mediated by estrogen receptors (ERα and ERβ). Estrogens or selective ER-agonists have been shown to exert potent neuroprotective or anti-inflammatory effects in experimental autoimmune encephalomyelitis (EAE), the mouse model of MS. A central question in EAE is to identify the cellular targets that express a functional ER isotype, and the mechanisms underlying the neuroprotective and anti-inflammatory effects of estrogens. Using pharmacological approaches targeting ER-specific functions, and genetic tools such as conditional knockout mice in which ERα or ERβ are selectively deleted in specific cell populations, a clearer picture is now emerging of the various cellular targets and downstream molecules responsible for estrogen-mediated protection against central nervous system autoimmunity

Sharing Budgetary Austerity under free Mobility and Asymmetric Information:: An Optimal Regulation Approach to Fiscal Federalism

JEL classification: D72; D82; H7 Pour l'évaluation de l'unité -auteur recruté en 2007International audienceIn the present article, Tiebout meets Laffont and Tirole in the land of fiscal federalism. A non-trivial Principal–Multi-Agent model is used to characterize the optimal intergovernmental grant schedule, when the cost of local public goods depends on hidden characteristics and actions of local governments, and under citizen free mobility. We show how informational rents, landlords' interests, and citizen mobility interact to produce distortions at both ends of the type space: in particular the most efficient jurisdictions should overproduce and overtax in second-best optimum. Informational asymmetries decrease the average production of public goods and increase the inter-jurisdictional variance of taxes and public-good production

Manger à Rennes : l’alimentation des élites rennaises d’après les isotopes

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