Regularity for minimal boundaries in R n ¶with mean curvature in L n

Let be a minimal set with mean curvature in L ⁿ that is a minimum of the functional , where is open and . We prove that if then can be parametrized over the (n−1)-dimensional disk with a C ^α mapping with C ^α inverse. Received: 11 July 1997 / Revised version: 24 February 1998     

N-complexes et algèbres de Hopf

We show that the category of N-complexes is monoidally equivalent to the category of comodules over a well chosen Hopf algebra. This generalizes Pareigis' previous result for N=2. To cite this article: J. Bichon, C. R. Acad. Sci. Paris, Ser. I 337 (2003).     

Structural transitions in positive electrodes for Li-ion batteries the vibronic approach

We present the vibrational properties of manganese dioxides and lithiated oxides with either spinel-type and layered-type structure used as positive electrodes in Li-ion batteries. The local structure in γ-MnO₂ is investigated as a function of the intergrowth rate, Pr, of pyrolusite in the ramsdellite matrix and the phase evolution as a function of the degree of intercalation or deintercalation in 4-volt electrode materials Li_1−xCoO₂ and Li_1−xMn₂O₄. Lattice dynamics are studied using either a classical group theoretical analysis or a local environment model. Raman and FTIR bands are identified on the basis of vibrational modes of polyhedral units which are building the structure. Structural modifications induced by intercalation-deintercalation process are examined. Paper presented at the 8th EuroConference on Ionics, Carvoeiro, Algarve, Portugal, Sept. 16–22, 2001.     

Solid-state lithium microbatteries

Batteries of the size of microelectronic devices, less than 10 μm thick, are now being developed and built, using thin-film deposition technologies, i.e., flash-evaporation, rf-sputtering and sol-gel technique, that are compatible with integrated circuits. Their use in future micro-devices, microsensors, intergrated circuits, memories and very large-scale integration are envisaged. Advances have been made particularly in the engineering of lithium/amorphous inorganic electrolyte/layered compound cells. Physics of the solid-state microbatteries are reviewed and the latest advances presented. The adequacy and efficiency of materials is examined. New optimized lithium microbatteries including transition-metal oxides as intercalation cathodes, i.e., MoO₃, V₂O₅, and V₆O₁₃ films are presented and their advantages are discussed in detail. Paper presented at the 2nd Euroconference on Solid State Ionics, Funchal, Madeira, Portugal, 10–16 Sept. 1995.     

AB5 Derivatives of Cyclotriphosphazene for the Synthesis of Dendrons and Their Applications

AB₅ compounds issued from the reactivity of hexachlorocyclotriphosphazene are relatively easy to obtain using two ways: either first the reaction of one chloride with one reagent, followed by the reaction of the five remaining Cl with another reagent, or first the reaction of five chlorides with one reagent, followed by the reaction of the single remaining Cl with another reagent. This particular property led to the use of such compounds as core for the synthesis of dendrons (dendritic wedges), using the five functions for growing the dendritic branches. The single function can be used for the synthesis of diverse types of dendrimers (onion peel, dumbbell-shape, Janus), for covalent or non-covalent grafting to solid surfaces, providing nanomaterials, for grafting a fluorophore, especially for studying biological mechanisms, or for self-associations to get micelles. All these properties are reviewed in this paper.     

MALDI-ToF analysis of polythiophene: use of trans-2-[3-(4-t-butyl-phenyl)-2-methyl- 2-propenylidene]malononitrile-DCTB-as matrix

Nowadays, numerous experimental and theoretical studies are devoted to the research field of polythiophenes and other electroconjugated polymers due to the huge potentialities of those conducting polymers. Synthetic procedures are now developed to reach the highest control over both polymerization and analytical methodologies allowing an in-depth and straightforward characterization of the polymer samples without any required doubt. Mass spectrometry methodologies and in particular MALDI-ToF measurements are definitively suitable to meet the characterization requirements. In the present study, trans-2-[3-(4-t-butyl-phenyl)-2-methyl-2-propenylidene]malononitrile (DCTB) was shown to afford better results than the reported terthiophene and dithranol matrices as far as sensitivity and signal-to-noise ratio are concerned. We tentatively proposed that the ionization of the P3HT molecules is performed by charge exchange in the condensed phase (clusters) with matrix molecule radical cations and subsequent neutral matrix molecule evaporation from the clusters. The putative key parameters to account for the really high efficiency of DCTB for the MALDI analysis of P3HT are (1) the highest ionization energy of DCTB amongst the three matrices, (2) the really high absorptivity of the matrix molecule at the laser wavelength and (3) the presence of the tertiobutyl group on the matrix molecule. The presence of this substituent is likely to decrease the intermolecular interactions in the condensed phase rendering the evaporation of the neutral matrix molecules less energy demanding. We also demonstrated for polymer samples presenting an average number molecular weight (M(n) ) below 10 000 g mol(-1) that the systematic overestimation of the low mass oligomers upon MALDI measurements ends up with wrong M(n) and polydispersity index (PDI) values. A systematic Soxhlet extraction against heptane was shown to allow the recording of absolute M(n) and PDI.     

Properties of ionic liquids on Au surfaces: non-conventional anion exchange reactions with carbonate

A simple anion metathesis in diluted aqueous carbonate at room temperature affords 1-(12-mercaptododecyl)-3-methyl-imidazolium carbonate (MDMI-HCO(3)) from MDMI salts self-assembled on gold films and nanoparticles. The properties of MDMI-SAM differ from MDMI in solution, for which the anion exchange reaction does not proceed.     

Hollow microspheres with a tungsten carbide kernel for PEMFC application

Tungsten carbide microspheres comprising an outer shell and a compact kernel prepared by a simple hydrothermal method exhibit very high surface area promoting a high dispersion of platinum nanoparticles, and an exceptionally high electrochemically active surface area (EAS) stability compared to the usual Pt/C electrocatalysts used for PEMFC application.     

The functional valency of dodecamannosylated fullerenes with Escherichia coli FimH--towards novel bacterial antiadhesives

Fullerene hexakis-adducts bearing 12 peripheral mannose moieties have been prepared by grafting sugar derivatives onto the fullerene core and assayed as inhibitors of FimH, a bacterial adhesin, using isothermal titration calorimetry, surface plasmon resonance and hemagglutination assays.     

Symbiotic signaling in actinorhizal symbioses

Actinorhizal symbioses are mutualistic associations between plants belonging to eight angiosperm families and soil bacteria of the genus Frankia. These interactions lead to the formation of new root organs, actinorhizal nodules, where the bacteria are hosted and fix atmospheric nitrogen thus providing the plant with an almost unlimited source of nitrogen for its nutrition. It involves an elaborate signaling between both partners of the symbiosis. In recent years, our knowledge of this signaling pathway has increased tremendously thanks to a series of technical breakthroughs including the sequencing of three Frankia genomes [1] and the implementation of RNA silencing technology for two actinorhizal species. In this review, we describe all these recent advances, current researches on symbiotic signaling in actinorhizal symbioses and give some potential future research directions.