Diastereoselective alkynylation of N-p-tolylsulfinylimines with aluminum acetylides

The addition of alkynyl dimethyl aluminum compounds onto N-p-tolylsulfinylimines was investigated. The reaction was proved to be totally regioselective, leading to propargylamines with high diastereoselectivity (up to 99% de). Addition of aluminum derivatives gave a reversal of diastereoselectivity compared to the addition reaction of lithium acetylide.     

2D numerical contributions for the study of non-cohesive sediment transport beneath tidal bores

2D numerical simulations of tidal bores were obtained using the OpenFOAM CFD software to solve the Navier–Stokes equations by means of the Finite Volume Method by applying a LES turbulence model. The trajectories of non-cohesive sediment particles beneath tidal bores were estimated using a tracker method. Using the fourth order Runge–Kutta scheme, the tracker method solves the Maxey and Riley equations, which requires the knowledge of the velocity field at time t. From 2D numerical simulations of tidal bores, we proposed a classification of tidal bores with respect to the Froude number Fr (or r the ratio of water depths). For a Froude number $1<Fr<1.43$ ($1<r<1.57$), the tidal bore is undular. For a Froude number $1.43<Fr<1.57$ ($1.57<r<1.75$), the tidal bore is partially breaking, which is similar to the transitional tidal bore defined by Furgerot (2014). And for a Froude number $Fr>1.57$ ($r>1.75$), the tidal bore is totally breaking. The numerical results of trajectories of non-cohesive sediment particles are similar to the type of trajectories given by the analytical model proposed by Chen et al. (2012) with some modifications to take into account the effects of gravity, elevation, and attenuation. The parameters of modified Chen's model, ${\beta }_1$, ${\beta }_2$ and ${\beta }_3$, are linearly proportional to the Froude number Fr. This is because the level of turbulence for undular tidal bores is low. The flow induced by an undular tidal bore is not complex. This physical phenomenon is quasi linear. The parameter ${\beta }_1$, related to the front celerity of the undular tidal bore, decreases when the Froude number Fr increases. The parameter ${\beta }_2$, related to the elevation, increases when the Froude number Fr increases. And the parameter ${\beta }_3$, related to the attenuation of the secondary waves, increases when the Froude number Fr increases.     

In-spray supercharging of intact proteins by capillary electrophoresis–electrospray ionization–mass spectrometry using sheath liquid interface

Capillary electrophoresis (CE) coupled with electrospray ionization (ESI) mass spectrometry (MS) is a suitable technique for the analysis of intact proteins. The main configuration to realize this coupling is the sheath liquid interface, which is characterized by the addition of a make-up liquid providing the electric contact as well as the appropriate flow and solvent composition for optimal ionization and evaporation. One main advantage of this interface is that the composition of the sheath liquid can be tuned to modify the ionization without affecting CE selectivity and efficiency. In the case of protein ionization, this feature is particularly interesting to modulate their charge-state distribution (CSD), while keeping the separation performance unchanged.     

First Occurrence of Tetrazines in Aqueous Solution: Electrochemistry and Fluorescence

The photophysical and electrochemical properties of tetrazines substituted by linear 2,3‐naphtalimide antennas and/or adamantane groups specifically dedicated to host–guest interactions with cyclodextrins are studied both in organic and aqueous media. In acetonitrile solvent, the reduction potential of tetrazine leading to the anion radical is shifted, depending on the electron‐withdrawing power of the substituent of the tetrazines. Due to the hydrophobic character of these compounds, their solubilization in aqueous solution is achieved successively in presence of either β‐cyclodextrins or gold nanoparticules modified by β‐cyclodextrins. We demonstrate that the formation of the inclusion compound tetrazine–cyclodextrin allows the solubilization of the tetrazines in aqueous solution. The supramolecular assemblies obtained in water retain tetrazine's emission properties, yielding a yellow fluorescence.     

Torsion theories induced from commutative subalgebras

We begin a study of torsion theories for representations of finitely generated algebras U over a field containing a finitely generated commutative Harish-Chandra subalgebra Γ. This is an important class of associative algebras, which includes all finite W-algebras of type A over an algebraically closed field of characteristic zero, in particular, the universal enveloping algebra of (or ) for all n. We show that any Γ-torsion theory defined by the coheight of the prime ideals of Γ is liftable to U. Moreover, for any simple U-module M, all associated prime ideals of M in have the same coheight. Hence, the coheight of these associated prime ideals is an invariant of a given simple U-module. This implies the stratification of the category of U-modules controlled by the coheight of the associated prime ideals of Γ. Our approach can be viewed as a generalization of the classical paper by Block (1981) [4]; it allows, in particular, to study representations of beyond the classical category of weight or generalized weight modules.     

A study of ACO capabilities for solving the maximum clique problem

This paper investigates the capabilities of the Ant Colony Optimization (ACO) meta-heuristic for solving the maximum clique problem, the goal of which is to find a largest set of pairwise adjacent vertices in a graph. We propose and compare two different instantiations of a generic ACO algorithm for this problem. Basically, the generic ACO algorithm successively generates maximal cliques through the repeated addition of vertices into partial cliques, and uses “pheromone trails” as a greedy heuristic to choose, at each step, the next vertex to enter the clique. The two instantiations differ in the way pheromone trails are laid and exploited, i.e., on edges or on vertices of the graph. We illustrate the behavior of the two ACO instantiations on a representative benchmark instance and we study the impact of pheromone on the solution process. We consider two measures—the re-sampling and the dispersion ratio—for providing an insight into the performance at run time. We also study the benefit of integrating a local search procedure within the proposed ACO algorithm, and we show that this improves the solution process. Finally, we compare ACO performance with that of three other representative heuristic approaches, showing that the former obtains competitive results.     

Stereochimie de la cycloaddition sur les ethers butadienyliques d'alcools chiraux. Derives en 4 et 6 de glucosides perbenzylés

Two partially protected derivatives of α-D-glucose with one free OH group function, benzyl 2,3,6-tri-O--α-D-glucopyranoside 2 and benzyl-2,3,4-tri-$\text{O}$-benzyl-α-D-glucopyranoside 4 were prepared. Base-catalysed addition of the diyne-diol 5 onto these sugars gave trans-cis mixtures of enynyl ethers, 6 and 8 from compound 2, and 7 and 9 from compound 4. Catalytic partial hydrogenation gave the corresponding butadienyl ethers 10 and 12 from 6 and 8, and 11 and 13 from 7 and 9. All trans-cis mixtures obtained could be readily separated by fractionnal crystallisation or column chromatography, thus making for the first time pure trans and cis enynyl ethers readily available in quantity. The cycloaddition of butyl glyoxylate onto the trans dienes led to mixtures of dia-stereoisomeric, dihydropyrannyl ethers, 14 (β-L) 18 (α-D) and 22 (β-D) from diene 10, and 16 (β-L), 20 (α-D) and 24 (β-D) from diene 11. Configurations were ascribed by the use of already described methods. This study brings to a number of five all examined reactions of cycloaddition onto butadienyl ethers of chiral alcohols. In each case a strong preference is observed for one of the faces of the prochiral butadienyl ether, but no great preference for the endo path of cycloaddition.     

Stable superhydrophobic and lipophobic conjugated polymers films

With a view to developing repellent materials combining both low surface energy and rough structure, original semi-fluorinated polythiophenes have been chemically and electrochemically synthesized and characterized by cyclic voltammetry, GPC, and UV-visible measurements. Polymer films have been deposited onto different substrates by drop casting a soluble polymer fraction on glass plate or by electrodeposition on ITO plate. Surface properties and particularly water and oil repellencies have been investigated by goniometry and correlated with the surface morphology and structure observed by SEM. The incorporation of fluorocarbon chains in the rigid polythiophene backbone yields very low surface free energy materials. Moreover, the way of deposition has a huge influence on the quality and performance of the film surface properties. Electroformed polymers, due to rough surfaces, exhibit great super-hydrophobic and lipophobic properties together with exceptional time stability.     

Extended charge decomposition analysis and its application for the investigation of electronic relaxation

A general and comprehensive molecular orbital method for the investigation of the electronic relaxation contribution to redox processes is presented. This method is based on the population analysis of the molecular orbitals of the final electronic state in terms of the occupied and unoccupied molecular orbitals of the Koopmans’ state. The DFT calculations for oxidation and reduction of transition-metal species indicate a dramatic magnitude of electronic relaxation in these systems. The passive molecular orbitals play a more significant role in electronic relaxation than the redox-active molecular orbital that directly participates in the redox process. The mechanism of electronic relaxation in the oxidation of Fe^II and Cu^I species varies from the ligand to metal 3d charge transfer (LMCT) interactions to the ligand to metal 4s,4p LMCT. For systems with significant electronic delocalization, electronic relaxation becomes smaller leading to much smaller contributions to the redox processes. Dedication: This contribution is to celebrate Philip Stephen’s seminal contributions to theory and experiment. An erratum to this article can be found at     

Nanomorphology and reaction to fire of polyurethane and polyamide nanocomposites containing flame retardants

The reaction to fire of polymer nanocomposites (thermoplastic polyurethane and polyamide-6) containing two different nanofillers (organoclay and carbon nanotube) has been investigated. Polymer nanocomposites exhibit significant reduction of peak of heat release rate but the nanomorphology (exfoliation, intercalation and presence of tactoids) does not play any significant role, although a reasonable level of nanodispersion is necessary to achieve good flame retardancy in specific cases (mass loss calorimetry experiment). Modelling aspects for the time to ignition are also proposed in the paper. It is shown that the approach ‘nanocomposite’ gives the best results combined with conventional flame retardants (phosphinate and phosphate) and leads to synergistic effects. The aspects of nanodispersion of the nanoparticle with the flame retardant (microfiller) are fully commented in the paper using TEM and solid state NMR. Mechanisms of action are finally proposed explaining the synergy when conventional flame retardants are combined with nanoparticles.