Multiscale approaches to describe mechanical responses induced by particle removal in granular materials

A multi-scale approach is proposed as an attempt to assess internal erosion induced effects on the mechanical properties of a granular medium. When submitted to internal flow, some particles tend to be removed from the initial granular material, leading to drastic changes in the microstructure. The medium is changing during its lifetime and this cannot be ignored in attempts to model its mechanical behavior. In this first analysis, the degradation of a granular assembly is simulated through the progressive removal of its finest particles for both isotropic and anisotropic stress states. A discrete element model as well as an analytical micromechanical model are used to compare induced deformations and properties changes along the erosion process. The shear strength and flow properties appear to be strongly modified by this extraction phase: both models highlight a change from a dilatant to a contractant behavior with the degradation as well as strong dependency of the overall stability on the mobilized friction level. In particular, results show how failure is triggered when particle removal occurs for mobilized frictions greater than the one reached at the critical state.     

Reinvestigation of the synthesis of “covalent-assembly” type probes for fluoride ion detection. Identification of novel 7-(diethylamino)coumarins with aggregation-induced emission properties

An unprecedented C-3 functionalization of 4-(diethylamino)salicylaldehyde through a Friedel-Crafts type alkylation reaction has been discovered during the synthesis of “covalent-assembly”-based fluorescent probes for detection of fluoride ions. The resulting Friedel-Crafts adduct was successfully used for the preparation of two novel 8-substituted 7-(diethylamino)coumarin dyes. The photophysical study of these fluorophores has enabled us to highlight their remarkable aggregation-induced emission (AIE) properties characterized by a yellow-orange emission of aggregates in water. Therefore, 4-(tert-butyldimethylsilyloxy)benzyl substituent was identified as a novel AIE-active moiety which could be seen as a possible alternative to popular tetraphenylethylene (TPE).     

Study of arsenic reabsorption in the body by the neutron activation analysis after thermal springs treatments

At French spa, La Bourboule, arsenical mineral waters are applicated by several ways. The process and degree of absorption of water are not well known; so, we tried to study absorption, measuring arsenic concentration in the blood and in some organs. On rabbits, thirty minutes after the animal had drunk mineral water, the increase of arsenic concentration in its blood is about twenty times and it is only about three to nine time in lungs, bronchia and traches. On human subjects, it was observed an increase of five times in the blood, two hours after treatment.     

Organomanganese (II) reagents XX: Manganese mediated Barbier and Reformatsky like reactions an efficient route to homoallylic alcohols and β-acetoxyesters

Allylic halides and -bromoesters react with manganese metal in ethyl acetate; THF can also be used as solvent if a catalytic amount of zinc chloride is added to the reaction mixture. When the reaction is performed in the presence of various aldehydes or ketones, excellent yields of 1,2-addition products are obtained in preparative conditions.     

Formes différentielles sur l'espace projectif réel sous l'action du groupe linéaire général

Résumé On montre que les seuls sous-espaces invariants par transformations projectives et fermés pour la topologie C^∞ de l'espace desp-formes sur l'espace projectif réel sont les suivants le sous-espace nul, celui des formes exactes, celui des formes fermées, et l'espace lui-même-avec les co?ncidences bien connues entres ces sous-espaces. On résoud, aussi le problème analogue sur la sphère.

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Summary We show that the only subspaces of the space ofp-forms on the real projective space which are invariant under projective transforms and closed for the C^∞ topology are the following ones: the zero subspace, the subspace of exact forms, the subspace of closed forms, and the space itself-with the well known coincidences between these subspaces. We also solve the analogous problem of the sphere.

     

Influence of complexation phenomena with multivalent cations on the analysis of glyphosate and aminomethyl phosphonic acid in water

Experimental and theoretical influence of multivalent cations on the analysis of glyphosate and aminomethyl phosphonic acid (AMPA) was studied in pure water and in one surface water. The procedure chosen, based on derivatization with FMOC-Cl, HPLC separation, and fluorescence detection, appears highly affected at cations concentrations current in natural waters. A detailed speciation study performed with the VMINTEQ software strongly suggests that the complexes formed between analytes and cations do not dissociate during the reaction and do not react with the derivatization agent, so that only the free forms are derivatized. These results point out the necessity of a pre-treatment to prevent these interferences, even in low salinity waters. The different ways conceivable are discussed in terms of kinetic and thermodynamic considerations.     

Intermolecular interactions in self-assembled monolayers of tetrathiafulvalene derivatives

The elaboration of mixed self-assembled monolayers (SAMs) of tetrathiafulvalene derivatives allows the modulation of intermolecular interactions and provides evidence of segregated distribution of redox centers.     

Optimized strategies to synthesize β-cyclodextrin-oxime conjugates as a new generation of organophosphate scavengers

A new generation of organophosphate (OP) scavengers was obtained by synthesis of β-cyclodextrin-oxime derivatives 8-12. Selective monosubstitution of β-cyclodextrin was the main difficulty in order to access these compounds, because reaction onto the oligosaccharide was closely related to the nature of the incoming group. For this purpose, non-conventional activation conditions were also evaluated. Intermediates 5 and 7 were then obtained with the better yields under ultrasounds irradiation. Finally, the desired compounds 8-10 were obtained from 5-7 in high purity by desilylation using potassium fluoride. Quaternarisation of compounds 8 and 9 was carried out. OP hydrolytic activity of compounds 8-12 was evaluated against cyclosarin (GF) and VX. None of the tested compounds was active against VX, but these five cyclodextrin derivatives detoxified GF, and the most active scavengers 10 and 11 allowed an almost complete hydrolysis of GF within 10 min. Even more fascinating is the fact that compounds 9 and 10 were able to hydrolyze enantioselectively GF.