Characterizations of almost periodic homeomorphisms

In this paper we study recurrent and almost periodic homeomorphisms on the Euclidean space Rm; we give conditions under which recurrent implies periodic. On the other hand we give properties of elements of compact groups of diffeomorphisms on manifolds.     

Étude de l’activité catalytique des argiles pontées aluminium,zirconium et cérium dans la synthèse du 2,2-diméthyl-1,3-dioxolane

The purified Tunisian clay G and the commercialized American clay W were pillared with zirconium, aluminum and mixed pillars zirconium–aluminum, cerium–zirconium, cerium–aluminum, and cerium–zirconium–aluminum. These different clays were used in the synthesis of 2,2-dimethyl-1,3-dioxolane 3 by acetalyzation of acetone 2 with ethylene glycol 1 under autogenously pressure and without solvent. Results indicate that the yield of product 3 depends of the nature and the acidity of the clay used and the time of reaction.     

Fluorescent derivatives of thromboxane B(2): Synthesis, spectroscopic and immunologic properties

Thromboxane B(2) has been labeled by four fluorescent probes structurally related to coumarin (4-bromomethyl-7-methoxycoumarin, 7-[(chlorocarbonyl) methoxy]-4-methylcoumarin, 4-luminarin) or anthracen (panacyl bromide). The purity of the derivatives determined by liquid chromatography was over 90%. The extinction coefficient, Stokes' shift, quantum yield, life-time and the anisotropy of the emitted fluorescence were determined. Immunorecognition of thromboxane B(2) derivatives was checked by competition immunoassays. Among the derivatives tested, that obtained with 4-luminarin has a suitable Stokes' shift (95 nm), a quantum yield of 0.46, a single value of excited state life-time (9.3 nsec), a well-preserved immunorecognition and a good chemical stability. Preliminary results in competition experiments showed variations in fluorescence anisotropy correlated to thromboxane B(2) concentration.     

Intercalation of salicylic acid into ZnAl and MgAl layered double hydroxides for a controlled release formulation

Salicylic acid was intercalated into an inorganic host consisting of ZnAl/MgAl-layered double hydroxides lamella by reconstruction method. Powder X-ray diffractograms showed that the basal spacing of the layered double hydroxide bearing salicylate as the intergallery anion expanded from 7.6 and 7.8 Å in the precursors to 14.49 Å and 14.85 in ZnAl and MgAl layered double hydroxide, respectively. These values suggest that the organic molecules form bilayers in the interlayer space. Fourier transform infrared study further confirmed intercalation of salicylate into the interlayer’s of the layered double hydroxides. The thermal stability of the intercalated salicylic acid is significantly enhanced compared with the pure form before intercalation. Using the XRD results combined with a molecular simulation model, a possible representation of the salicylate anion positioning between the lamellar layers has been proposed. The in vitro drug release from intercalated material was remarkably lower than that from the corresponding physical mixture at pH 7.5. The kinetic analysis showed the importance of the diffusion through the particle in controlling the drug release rate. The obtained results show that hydrotalcite may be used to prepare modified release formulations.     

The numerical solution of the transient two‐phase flow in rigid pipelines

Consideration is given in this paper to the numerical solution of the transient two‐phase flow in rigid pipelines. The governing equations for such flows are two coupled, non‐linear, hyperbolic, partial differential equations with pressure dependent coefficients. The fluid pressure and velocity are considered as two principle dependent variables. The fluid is a homogeneous gas–liquid mixture for which the density is defined by an expression averaging the two‐component densities where a polytropic process of the gaseous phase is admitted. Instead of the void fraction, which varies with the pressure, the gas–fluid mass ratio (or the quality) is assumed to be constant, and is used in the mathematical formulation. The problem has been solved by the method of non‐linear characteristics and the finite difference conservative scheme. To verify their validity, the computed results of the two numerical techniques are compared for different values of the quality, in the case where the liquid compressibility and the pipe wall elasticity are neglected. Copyright © 1999 John Wiley & Sons, Ltd.     

Fonctions harmoniques sur les graphes

Sans résumé     

Finite‐dimensional global attractor for a semi‐discrete fractional nonlinear Schrödinger equation

We consider a semi‐discrete in time Crank–Nicolson scheme to discretize a weakly damped forced nonlinear fractional Schrödinger equation u _t ?i (?Δ)^α u +i |u |²u +γ u =f for considered in the the whole space . We prove that such semi‐discrete equation provides a discrete infinite‐dimensional dynamical system in that possesses a global attractor in . We show also that if the external force is in a suitable weighted Lebesgue space, then this global attractor has a finite fractal dimension. Copyright © 2017 John Wiley & Sons, Ltd.     

Ability of DFT to evaluate the torsional barriers in neutral and CO* protonated aromatic carbonyl compounds

Before the recent development of new functionals, the Density Functional Theory (DFT) was considered as a failing quantum chemical method in accurately computing the rotational barrier height of the gaseous benzaldehyde. Since the 2004 polemical Speakman's paper about the accuracy of microwave value of this quantity [L. D. Speakman, B. N. Papas, H. L. Woodcock, H. F. Schaefer, J. Chem. Phys. 2004, 120, 4247], the question is still relevant. This paper aims to display the ability of the DFT to evaluate the torsional barriers of a series of para‐substituted benzaldehydes in solution. The method is also tested in computing barriers of other solvated aromatic carbonyl compounds (in both neutral and carbonyl protonated forms) for which accurate experimental data are available. Computations have been carried out at two DFT methods using the popular hybrid generalized‐gradient‐approximation (GGA) density functional B3LYP and the global hybrid meta‐GGA Minnesota functional M06‐2X with a 6‐311++g (2d,2p) basis set. Solvent effects investigations were undertaken within the framework of the polarisable continuum model solvation approach. It has been concluded that the used computational methods are very satisfactory in predicting barriers of para‐substituted benzaldehydes in the liquid phase and less satisfactory for their CO*‐protonated forms. M06‐2X functional particularly leads to full agreement. For para‐substituted acetophenones, good agreement with experiment is observed only with M06‐2X applied to the CO*‐protonated forms. The present investigations have allowed to demonstrate that the Density Functional Theory does not constantly fail in accurately computing the rotational barrier heights of aromatic carbonyl compounds. Copyright © 2014 John Wiley & Sons, Ltd.     

Evaluation of the inhibitive effect of benzotriazole on archeological bronze in acidic medium

An archaeological bronze artefact was a Punic coin excavated from the north east of Tunisia in 2001. The composition of the copper alloy revealed a content of 3.5 % of tin and 1.4 % of lead with the presence of some sulphur heterogeneity. The surface presents some roughnesses and cracks and is covered by a corrosion layer of 20–40 μm thickness. The use of benzotriazole (BTA) as an inhibitor has become a standard element for the preservation of cuprous-based metals. In order to investigate the behaviour of BTA in an acidic medium, an Electrochemical Impedance Spectroscopy (EIS) investigation was performed to characterize the electrochemical behaviour of the interface of the archaeological bronze sample/acidic medium without and with BTA addition. Impedance diagrams obtained at different immersion times show that the presence of the inhibitor prevents the diffusional process observed in the absence of BTA. The inhibition of the pre-polarized bronze surface revealed that the mechanism of action of the benzotriazole molecule in an acidic medium is governed by the chemisorption process.     

Etude par RMN des 2-2′ -Dihalogeno-diethylethers—II: Effet de Solvant

Solvent effects on compounds of formula (X? CH₂? CH₂)₂O with X ? Cl, Br, I have been studied. The rotamer ratios have been determined for each solvent according to Lin's method and it is shown that the three compounds moved to gauche forms when increasing the medium dielectric constant. Additionally, it is shown that geminal couplings of the iodine derivative algebraically decrease on increasing the medium polarity. An attempt to correlate these variations with rotamer populations is made.