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Frem D.,CNRS Orsay Institute of Molecular Chemistry
Journal of Energetic Materials

A new formula is proposed for predicting the Gurney velocity ((Formula presented.)) of pure, mixed, and aluminized high explosives at any initial density. The simple relationship uses the detonation pressure and adiabatic coefficient calculated via the BKW code using the 1,3,5-Trinitro-1,3,5-triazacyclohexane (RDX) set of parameters. For 27 explosive compositions, (Formula presented.) was estimated using both the new formula and three older ones, and the results of each were then compared to experimental values. It is found that the new relationship is more accurate than older ones for predicting the Gurney velocity of aluminized compositions. The root mean square (rms) deviation of the new formula is 0.04–0.05 km/s for all tested explosives. © 2015, Taylor & Francis Group, LLC. Source

Barthes-Labrousse M.-G.,CNRS Orsay Institute of Molecular Chemistry
Journal of Adhesion

Detailed investigations of the interaction of 1,2- diaminoethane with aluminium surfaces have been performed to understand the mechanisms of interphase formation in epoxy-amine/aluminium joints. In particular, it has been shown that both metal bond surface complexes (O-Al⋯N bonds) and hydrogen-bonded surface complexes (Al-OH⋯N and C xO yH z⋯N bonds) can be formed on aluminium surfaces covered with a partly contaminated (hydr)oxide film. However, surface dissolution can only be induced by mononuclear bidentate metal bond surface complexes (chelates), which result from a ligand exchange mechanism between specific hydroxyl sites (η 1- and μ 2-OH) of the surface and the amino terminations of the molecule. The formation of these chelates weakens the trans Al-O bonds and detachment of the ligand-metal complexes can occur. This mechanism is enhanced by the presence of moisture. In practical epoxy-amine/aluminium joints, the interphase can, thus, be formed by migration of these complexes in the liquid polymeric phase before curing is achieved. © 2012 Copyright Taylor and Francis Group, LLC. Source

Soncini A.,Catholic University of Leuven | Mallah T.,CNRS Orsay Institute of Molecular Chemistry | Chibotaru L.F.,Catholic University of Leuven
Journal of the American Chemical Society

We theoretically investigate the charge and spin transport through a binuclear FeIIIFeIII iron complex connected to two metallic electrodes. During the transport process, the FeIIIFe III dimer undergoes a one-electron reduction (Coulomb blockade transport regime), leading to the reduced mixed-valence FeII Fe III species. For such a system, the additional electron may be fully delocalized leading to the stabilization of the highest spin ground state S = 9/2 by the double exchange mechanism, while the original FeIIIFe III has usually an S = 0 spin ground state due to the antiferromagnetic exchange coupling between the two FeIII ions. Intuitively, the spin delocalization within the mixed-valence complex may be thought to favor charge and spin transport through the molecule between the two metallic electrodes. Contrary to such an intuitive concept, we find that the increased delocalization leads in fact to a blocking of the transport, if the exchange coupling interaction within the FeIIIFeIII dimer is antiferromagnetic. This is due to the violation of the spin angular momentum conservation, where a change of half a unit of spin (δS = 1/2) is allowed between two different redox states of the molecule. The result is explained in terms of a double-exchange blockade mechanism, triggered by the interplay between spin delocalization and antiferromagnetic coupling between the magnetic cores. Consequently, ferromagnetically coupled dimers are shown not to be affected by the double-exchange blockade mechanism. The situation is evocative of the onset and removal of giant magnetoresistance in the conductance of diamagnetic layers, as a function of the relative alignment of the magnetization of two weakly antiferromagnetically coupled ferromagnetic contacts. Numerical simulations accounting for the effect of vibronic coupling show that the spin current increases as a function of spin delocalization in Class I and Class II mixed-valence dimers. The signature of vibronic coupling on sequential spin-tunneling processes through Class I and Class II mixed-valence systems is identified and discussed. © 2010 American Chemical Society. Source

Bonnaffe D.,CNRS Orsay Institute of Molecular Chemistry
Comptes Rendus Chimie

Heparan sulfate (HS) and heparin (HP) belong to the glycosaminoglycan (GAG) family, which are linear and sulfated polysaccharides. Several levels of molecular diversity allow these polymers to display one of the highest information content amongst all biopolymers and to bind and regulate, often in a specific way, the activity of numerous proteins. After analysing the structural basis of HS and HP molecular diversity, we will describe how chemists are able to exploit several of these features to produce compounds with exquisite tailor-made bioactivities and optimised pharmacological profiles, leading to promising drug candidates in preclinical or clinical studies and approved treatments. Source

Lancry M.,CNRS Orsay Institute of Molecular Chemistry | Regnier E.,Center Data 4 | Poumellec B.,CNRS Orsay Institute of Molecular Chemistry
Progress in Materials Science

This paper will thus give an overview of methods to reduce efficiently the Rayleigh scattering loss via the fictive temperature in silica-based optical fibers. We will first recall what the concept of fictive temperature T f is and its limitations in section 2. We will see that both Raman and IR spectroscopy can be used to determine T f (Section 3). Section 4 will thus give some examples of T f profiles measured in optical fibers manufactured in different conditions. Finally, section 5 will present the main approaches to reduce Rayleigh scattering loss in silica-based fibers via a reduction of T f. © 2011 Elsevier Ltd. All rights reserved. Source

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