Microwave crosslinking of epoxy/aromatic diamine systems: Process and characterization of the networks

In order to determine the influence of the dielectric field intensity on the crosslinking reaction under microwaves, pulsed waves were used to cure epoxy-amines systems, without catalyst. Cured resins were studied by Fourier transform infrared spectroscopy, 13-C nuclear magnetic resonance and dynamic mechanical thermal analysis. Structural and mechanical properties were found to be influenced by parameters as pulse repetition period and peak pulse power.     

Ring-opening polymerization of l-lactide in the presence of α-hydroxy-γ-butyrolactone

Among the polymer families, aliphatic polyesters stand out from this category thanks to their degradable and biocompatible properties. In particular, the γ-lactones differ from other lactones by yielding polyesters that can be depolymerized back to the monomer and offer the advantage of counting various biobased monomers. As an example, α-hydroxy-γ-butyrolactone (HBL) is a hydroxy-functionalized monomer that can be obtained by a biological synthetic route from glucose. In this article, the ring-opening copolymerization (ROCP) of HBL and l -lactide (LLA) using t-BuP₄ as catalyst is investigated. The copolymerizations were conducted within a temperature range of 5–100°C, affording monomer conversions exceeding 80%. The characterization of the copolyesters revealed a branched structure consisting of different HBL patterns, including cyclic, linear, and branched motives. Performing a kinetic study of the copolymerization at room temperature provided a deeper understanding of the mechanism. By modulating the reaction parameters, copolymers of low molar masses with an HBL content of up to 33% were synthesized. High molar mass LLA/HBL-based copolyesters, with $$ up to 290,000 g/mol, were synthesized by a straightforward chain coupling reaction with a diisocyanate.     

Reduction of copper(II) complexes by electron capture in an electrospray ionization source

The relative proportion of 1:1 Cu(I)– and Cu(II)–peptide complexes PeptCu(I)⁺ and [Pept?H+Cu(II)]⁺ yielded by electrospray ionization of copper sulfate and GlyHisLys solutions in water/methanol was examined under different source conditions. Two factors leading to an increase in Cu(I) complex ratio were found. (1) Increase of nozzle–skimmer voltages caused collision-induced dissociation of Cu(II) complexes, and most probably favor ligand-to-metal electron transfers that result in the decoordination of oxydated ligands to form PeptCu⁺. (2) Independent of these “innersphere” processes that involve only electron exchange inside the coordination sphere around the metal cation, an increase in source voltages with a concomitant increase of current and, supposedly, electron counterflow between the counterelectrode and the capillary caused an increase in PeptCu⁺ relative proportion. The hypothesis that an “outersphere” electron capture might happen in these conditions was verified by using discharge supressing SF₆ gas as nebulizing gas. The electronegative gas reduced the current brought on by high voltages and inhibited the PeptCu⁺ increase phenomenon.     

Estimation of the lateral to basal surface ratio of talc by inverse gas chromatography

Inverse Gas Chromatography at Infinite Dilution, i.e. IGC‐ID, allows following the evolution of surface properties of talc impregnated with increasing concentrations of polyethyleneglycol of molecular weight 20,000. Coupling Inverse chromatography in infinite dilution conditions measurements with controlled surface modification, we have developed a new method to estimate the lateral to basal surface ratio of talc crystals.     

Effect of interfaces on the alignment of a discotic liquid-crystalline phthalocyanine

This paper deals with the influence of the nature and number of solid interfaces on the alignment of the columns in a semiconducting discotic liquid crystal. The solid substrates have been characterized in terms of their roughness and surface energy. The alignment of the discotic liquid crystal columns on these substrates has been determined by optical microscopy under crossed polarizers and by tapping-mode atomic force microscopy. The nature of the substrates has negligible influence on the alignment. The key parameter is the confinement imposed to the film. These surprising observations are explained by the antagonist alignment role of gas and solid interfaces.     

Criteria for large deviations

We give the general variational form of

for any bounded above Borel measurable function on a topological space , where is a net of Borel probability measures on , and a net in converging to . When is normal, we obtain a criterion in order to have a limit in the above expression for all continuous bounded, and deduce new criteria of a large deviation principle with not necessarily tight rate function; this allows us to remove the tightness hypothesis in various classical theorems.

     

Non-perturbative calculation of the mass-gap in the Gross-Neveu model

We calculate a fully renormalizable effective action for local composite operators in the U(N) Gross-Neveu model, recently introduced by one of us, to two loop order. We obtain results for the massgap in one and two loops which are optimized using the Grunberg method of effective charges. At one loop the accuracy is of the order of 2% or less (except for N = 2). At two loops the accuracy is significantly improved for N ≥ 5.     

Construction of Hamiltonian-Minimal Lagrangian submanifolds in Complex Euclidean Space

We describe several families of Lagrangian submanifolds in complex Euclidean space which are H-minimal, i.e. critical points of the volume functional restricted to Hamiltonian variations. We make use of various constructions involving planar, spherical and hyperbolic curves, as well as Legendrian submanifolds of the odd-dimensional unit sphere.     

Survey of initial value problem for the discrete Boltzmann equation

This paper is devoted to the story of the initial value problem in discrete kinetic theory. Starting from the first global existence theorem obtained by Nishida and Mimura in 1974 for the Broadwell model, which is the simplest discrete model of the Boltzmann equation, we continue with the extension of the results to the cases of more complex models, in particular models with multiple collisions; we notify works in which are considered cases with more than one space variable, and also problems in which the initial data can be partially negative. Conferenza tenuta il 29 settembre 1992