Microemulsion breakdown by pervaporation technique: effect of the alkyl chain length of n-alkanol, a cosurfactant of the microemulsion

Two sets of microemulsions, cyclohexane- and water-rich ones, were prepared with the following n-alkanols as cosurfactants: n-propanol, n-butanol, n-pentanol, and n-hexanol. The results showed the influence of the alkyl chain length of the n-alkanol on the permselectivity properties of the pervaporation technique in the breakdown of the microemulsions. The variations of the total flux rate J and the enrichment factor beta were in parallel with the effect of the cosurfactant on the swelling extent of the PDMS membrane.     

An inverse gas chromatographic characterization of polypyrrole-coated poly(vinyl chloride) powder particles

Polypyrrole-coated poly(vinyl chloride) powder particles (PPy-PVC) were prepared by the in-situ chemical polymerization of pyrrole in aqueous solutions in the presence of PVC powder particles using the method of Ouyang and Chan [Polymer 39 (1998) 1857] and characterized by inverse gas chromatography (IGC). By employing n-alkane, 1-heptene, chloroform and tetrahydrofuran molecular probes, the dispersive and acid–base components of the surface energy of the composite materials were estimated at infinite dilution. The values of the dispersive contribution to the surface energy (γ_S^d), at 50 °C, range from 30.3 to 43.5 mJ/m² for the composites, which is much lower than the value of 83.2 mJ/m² obtained for para-toluene sulfonate-doped polypyrrole (PPyTS) bulk powder. This indicates that the injected molecules probe both polypyrrole and the underlying PVC, thus indicating that the conducting polymer is rather patchy at the surface of the insulating polymer substrate. This conclusion supports the previous results obtained by X-ray photoelectron spectroscopy (XPS) [19], indicating that both the coating PPyTS and the substrate PVC are detected by their elemental markers nitrogen and sulfur, and chlorine, respectively.     

Neutron Transmission of Single-crystal Sapphire Filters

An additive formula is given that permits the calculation of the nuclear capture, thermal diffuse and Bragg scattering cross-sections as a function of sapphire temperature and crystal parameters. We have developed a computer program that allows calculations of the thermal neutron transmission for the sapphire rhombohedral structure and its equivalent trigonal structure. The calculated total cross-section values and effective attenuation coefficient for single-crystalline sapphire at different temperatures are compared with measured values. Overall agreement is indicated between the formula and experimental data. We discuss the use of sapphire single crystal as a thermal neutron filter in terms of the optimum cystal thickness, mosaic spread, temperature, cutting plane and tuning for efficient transmission of thermal-reactor neutrons.     

New materials derivatives of tetrathiapentalene functionalized by amide groups: Synthesis,characterization, and electrical study

A new series of bis-fused tetrathiafulvalene containing functional groups was synthesized. The synthesis was carried out by using routes involving cross coupling, reduction, and oxidation reactions. The identity of these new donors is confirmed by ¹ Wudl, F.; Smith, G. M.; Hufnagel, E. J. J. Chem. Soc. Chem. Commun. 1970, 21, 1453-1454.[Crossref] , [Google Scholar] H NMR spectroscopy, mass spectrometry, and elemental analysis. We have used the cyclic voltammetry in order to determine the character π-donors of these molecules and to verify the reversibility of the redox process involved. Molecular orbital diagram has been calculated using density-functional calculations. Charge transfer complexes with tetracyanoquinodimethane (TNQ) were prepared by chemical redox reactions.     

Stability for the inverse potential problem by the local Dirichlet-to-Neumann map for the Schrödinger equation

In this article we study, in dimension n?≥?3, the inverse problem of determining the potential q of the Schrödinger equation from infinity measurements on any open subset Γ₀ of the boundary. Provided that q is known in a neighborhood of the boundary, we prove the logarithmic stability estimate.     

Problème de Dirichlet pour une équation de Monge-Ampère réelle elliptique dégénérée en dimension

RÉSUMÉ. On considère dans un ouvert borné de , à bord régulier, le problème de Dirichlet

où , est positive et s'annule sur un ensemble fini de points de . On démontre alors sous certaines hypothèses sur et si est assez petit, que le problème (1) possède une solution convexe unique .

ABSTRACT. We consider in a bounded open set of , with regular boundary, the Dirichlet problem

where , is positive and vanishes on , a finite set of points in . We prove, under some hypothesis on and if is sufficiently small, that the problem (1) has a unique convex solution .

     

Recovering boundary data: The Cauchy Stokes system

This paper is concerned with the severely ill-posed Cauchy–Stokes problem. We are interested in a data completion problem which is exploited to detect small leaks to control water loss Kim et al. (2008) [1]. This inverse problem is rephrased into an optimization one: An energy-like error functional is introduced. We prove that the optimality condition of the first order is equivalent to solving an interfacial equation which turns out to be a Cauchy-Steklov-Poincaré operator. Numerical trials highlight the efficiency of the method.     

Self‐inclusion in 5,11,17,23‐tetra‐tert‐butyl‐26,27,28‐tri­hydroxy­‐25‐(methoxy­carbonyl­methoxy)calix­[4]­arene chloro­form trisolvate

The title compound, C₄₇H₆₀O₆·3CHCl₃, is the first example of a lower‐rim mono‐ester calixarene derivative to be crystallographically characterized. The cone conformation adopted by the macrocycle is stabilized by three intramolecular hydrogen bonds. Self‐inclusion of the methyl ester chain in the cavity of an adjacent mol­ecule gives rise to infinite chains parallel to the c axis. C—H⋯π interactions involving the methyl group most imbedded in the cavity contribute to the stabilization of the system.