Chemical Vapor Deposition of Al13 Fe4 Highly Selective Catalytic Films for the Semi-Hydrogenation of Acetylene

Catalytic properties of coatings containing the Al13Fe4 intermetallic phase are tested in the reaction of semi-hydrogenation of acetylene. The selectivity to ethylene is found as high as 74% close to the reported values for pure,unsupported Al13Fe4. The initial conversion of acetylene to ethylene is 84% and rapidly drops due to the catalytic formation of carbon-based by-products on secondary Al-Fe phases. Coatings are processed through sequential chemical vapor deposition (CVD) of aluminum (5 Torr, 180 °C) and iron(40 Torr, 140 °C) layers, followed by in situ annealing for 60 min at 575 °C.Deposition proceeds at high growth rate, resulting in 15 μm thick films. After annealing, coatings are composed of the Al13Fe4 phase, co-existing with minor secondary Al-Fe intermetallic phases. Overall, it is shown that films containing complex Al-Fe intermetallic phases can be processed by CVD, opening new routes to the engineering of pure, supported Al13Fe4 catalysts on 3D or porous supports

Characterization of a nuclear pore protein sheds light on the roles and composition of the Toxoplasma gondii nuclear pore complex

International audienceThe nuclear pore is a key structure in eukaryotes regulating nuclear-cytoplasmic transport as well as a wide range of cellular processes. Here, we report the characterization of the first Toxoplasma gondii nuclear pore protein, named TgNup302, which appears to be the orthologue of the mammalian Nup98-96 protein. We produced a conditional knock-down mutant that expresses TgNup302 under the control of an inducible tetracycline-regulated promoter. Under ATc treatment, a substantial decrease of TgNup302 protein in inducible knock-down (iKD) parasites was observed, causing a delay in parasite proliferation. Moreover, the nuclear protein TgENO2 was trapped in the cytoplasm of ATc-treated mutants, suggesting that TgNup302 is involved in nuclear transport. Fluorescence in situ hybridization revealed that TgNup302 is essential for 18S RNA export from the nucleus to the cytoplasm, while global mRNA export remains unchanged. Using an affinity tag purification combined with mass spectrometry, we identified additional components of the nuclear pore complex, including proteins potentially interacting with chromatin. Furthermore, reverse immunoprecipitation confirmed their interaction with TgNup302, and structured illuminated microscopy confirmed the NPC localization of some of the TgNup302-interacting proteins. Intriguingly, facilitates chromatin transcription complex (FACT) components were identified, suggesting the existence of an NPC-chromatin interaction in T. gondii. Identification of TgNup302-interacting proteins also provides the first glimpse at the NPC structure in Apicomplexa, suggesting a structural conservation of the NPC components between distant eukaryotes

Freedom and the “choice to choose oneself” in being and time

What Heidegger means by “freedom” in Being and Time is somewhat mysterious: while the notion crops up repeatedly in the book, there is no dedicated section or study, and the concept is repeatedly connected to a new and opaque idea – that of the “choice to choose oneself.” Yet the specificity of Being and Time’s approach to freedom becomes apparent when the book is compared to other texts of the same period, in particular The Metaphysical Foundations of Logic, The Fundamental Concepts of Metaphysics, The Essence of Grounds, and The Essence of Freedom. Although there are some differences, the definition of freedom that can be found there identifies it with “existence” or “transcendence,” Dasein’s ek-static opening onto the world. Thus “being in the world must also be primordially bound up with or derived from the basic feature of Dasein’s existence, freedom… Dasein’s transcendence and freedom are identical! Freedom provides itself with intrinsic possibility: a being is, as free, necessarily in itself transcending” (GA 26: 238; Heidegger’s italics). Note the apodictic modality of the claim: it is not simply the case that Dasein, as transcending, is free. Anything that has the structure of being in the world must be free: freedom is co-extensive with Dasein. Yet Dasein is often pictured in Being and Time as anything but free: it “ensnares itself” (268), is “lost” (264), “alienated” (178), and needs to be “liberated” (264, 303). Thus comparison between Being and Time and other texts on freedom yields an important paradox: although by definition it transcends toward the world, the Dasein of Division I is deprived of freedom. It must be free, and yet phenomenological analysis shows that it is not free. To understand the specific meaning of freedom in Being and Time, one has to square this circle

Apport d’une sismique en ondes S pour la recherche hydrogéologique dans un aquifère alluvial

Dans le cadre de l’implantation de nouveaux forages en contexte de plaine alluvial dans le Bassin de Paris, une nouvelle méthode géophysique a été mise en œuvre afin d’imager proprement les alluvions et d’en préciser les séquences ainsi que leur géométrie et les épaisseurs. Cette méthodologie repose sur une acquisition et le traitement de lignes sismiques ultra haute résolution en ondes S, dont les vitesses très lentes permettent une haute définition de l’imagerie dans les premiers mètres. Un traitement sismique minutieux a permis de restituer des résultats très concluants. Ce type d’opération, permet d’offrir à des prix très compétitifs des résultats bien plus fiables que les méthodes électriques. La réussite de ce type de mise en œuvre reste cependant conditionnée aux choix des paramètres d’acquisition et surtout à un traitement sismique minutieux

Crystal Growth Mechanism in a Solution of Hollow Whiskers of Molecular Compounds

International audienc

Crystal Growth Mechanism in a Solution of Hollow Whiskers of Molecular Compounds

International audienc

Stiffness tomography of eukaryotic intracellular compartments by atomic force microscopy

International audienc

From mechanisms of bacterial binding to glycomimics

International audienc

Le reste

Que reste-t-il, en ce début de siècle, des acquis de ta civilisation européenne qui soit susceptible d'être repris, réagencé, voire restauré ? Et qu'est-ce qui demeure intraitable, irreprésentable, persistant toutefois à hanter la réflexion et la création ? S'il est ce qui subsiste après une disparition, le reste est aussi ce qui a été exclu pour qu'un ensemble se constitue. Cependant, ce qui a été exclu subsiste, obligeant à reconsidérer les procédures qui ont produit cette part à la fois rétive et spectrale, invitant à repenser la constitution du tout dont le reste, selon une représentation courante, serait un fragment. Au-delà de l'inventaire et du bilan, de la nostalgie comme de la célébration, ce recueil voudrait offrir l'occasion d'une interrogation conceptuelle, y compris sur la pertinence même de la notion de reste. Les auteurs ici rassemblés tentent, dans les domaines littéraire, philosophique et artistique, d'identifier les formes du reste auxquelles ils ont affaire, d'en dégager un potentiel agissant capable de nous aider à penser le présent ; ils proposent de donner un contenu pratique - sinon praticable - à la pensée du reste