Study of coupled heat and water transfer in proton exchange membrane fuel cells by the way of internal measurements

Abstract. Measurements of electrode temperatures within a proton exchange membrane fuel cell were performed using platinum wires. A temperature difference of 7°C between the electrodes and the bipolar plates was observed for a cell operating at a current density of 1.5 A.cm -2 . These measurements show a strong non-uniformity of the temperature profile through membrane electrode assembly (MEA) that future phenomenological models must take into account. In addition, the simultaneous measurements of heat and water flux through the MEA leads to the conclusion that produced water crosses the diffusion layer in vapor phase. A very simple heat transfer model is proposed

What is poststructuralism?

In this essay, I discuss the vitality and the limits of the poststructural archive. I argue against the temptation to essentialise poststructuralism or define its ‘ontology’, instead I present some of the avenues that can be taken to further its theoretical practice. With Trump and the rise of ‘post-truth’ politics, poststructural political thought has recently come back to the centre of political debate. By using Pierre Macherey and François Châtelet’s perspective on Marxism, I turn to contemporary problems and studies to imagine how to renew the poststructuralist experience of thought. Following Boris Groys, I suggest that by producing theory as form, artists had a more immediate recourse to theoretical practice, by using all sorts of media to perform knowledge. Finally, by mainly referring to the work of Gilles Deleuze and Michel Foucault, I present some elements of a poststructural critique of political economy. I do this not by forcing the application of poststructural theories or concepts onto a supposedly external reality, but by immanently integrating more and more social and political problems into the schemes of thought. A poststructural theoretical practice means integrating into thought problems and events, in order to compose with them, and not simply study discursive strategies.<br/

How Thioredoxin Dissociates Its Mixed Disulfide

The dissociation mechanism of the thioredoxin (Trx) mixed disulfide complexes is unknown and has been debated for more than twenty years. Specifically, opposing arguments for the activation of the nucleophilic cysteine as a thiolate during the dissociation of the complex have been put forward. As a key model, the complex between Trx and its endogenous substrate, arsenate reductase (ArsC), was used. In this structure, a Cys29Trx-Cys89ArsC intermediate disulfide is formed by the nucleophilic attack of Cys29Trx on the exposed Cys82ArsC-Cys89ArsC in oxidized ArsC. With theoretical reactivity analysis, molecular dynamics simulations, and biochemical complex formation experiments with Cys-mutants, Trx mixed disulfide dissociation was studied. We observed that the conformational changes around the intermediate disulfide bring Cys32Trx in contact with Cys29Trx. Cys32Trx is activated for its nucleophilic attack by hydrogen bonds, and Cys32Trx is found to be more reactive than Cys82ArsC. Additionally, Cys32Trx directs its nucleophilic attack on the more susceptible Cys29Trx and not on Cys89ArsC. This multidisciplinary approach provides fresh insights into a universal thiol/disulfide exchange reaction mechanism that results in reduced substrate and oxidized Trx

Modélisation des systèmes complexes. Effets de solvant sur les modes de vibration d'un soluté au sein d'une solution

Le modèle du milieu continu polarisable, dans le formalisme du champ de réaction self consistant, est étendu pour permettre le calcul des vibrations moléculaires au sein d'un liquide au moyen des méthodes de la chimie quantique. Appliqué aux vibrations νC=O d'une série de composés carbonylés en solution dans le cyclohexane et dans l'acétonitrile, le modèle se révèle tout-à-fait apte à permettre le calcul des fréquences de vibrations d'un soluté. L'origine moléculaire de l'effet de solvant est discutée

Transmission Line Impedance Models Considering Oxygen Transport Limitations in Polymer Electrolyte Membrane Fuel Cells

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