Ammonium ionic liquid as modulator of the critical micelle concentration of ammonium surfactant at aqueous solution: conductimetric and dynamic light scattering (DLS) studies

We report measurements of self aggregation in aqueous solution of an ionic liquid (IL), didecyl-dimethylammonium nitrate ([DDA][NO(3)]) and a surfactant hexadecyl-trimethylammonium bromide (CTAB) and of mixtures of these two salts. The electrical conductivity and dynamic light scattering (DLS) measurements were used for the characterization of the aggregation process. The conductivity measurements were performed at three temperatures. The critical micelle concentration (CMC) was determined at different temperatures and at different ratio of two salts. The effect of IL on the micellization of CTAB has been discussed. Our results suggest that organized structures formed by CTAB and [DDA][NO(3)] self assembly in domains of several hundred nanometers size. The micellar solubility of the salicylic acid in mixed salt aqueous solutions was determined to probe the physical properties of these assemblies. We have observed, that the micellar solubility enhancement was only slightly influenced by the nature of micelles present in aqueous solution. This proves that salicylic acid solubilization is enthalpy driven.     

Prediction of forming limits for porous materials using void-size dependent model and bifurcation approach

Meccanica - The scientific literature has shown the strong effect of void size on material response. Several yield functions have been developed to incorporate the void size effects in ductile...     

Solitons in PT-symmetric potential with competing nonlinearity

We investigate the effect of competing nonlinearities on beam dynamics in PT-symmetric potentials. In particular, we consider the stationary nonlinear Schrödinger equation (NLSE) in one dimension with competing cubic and generalized nonlinearity in the presence of a PT-symmetric potential. Closed form solutions for localized states are obtained. These solitons are shown to be stable over a wide range of potential parameters. The transverse power flow associated with these complex solitons is also examined.     

Analytical prediction of damage in the composite part of a type-3 hydrogen storage vessel

The damage behavior of a type-3 hydrogen storage vessel is modeled. The vessel consists of a metal envelop, called liner, coated with a filament winding. The model proposed allows simulating the mechanical response of the structure to a quasi-static loading. The model is based on a meso-macro approach and takes into account the damage behavior of the composite and the elastoplastic deformation of the liner. The results obtained are compared with experimental data. Finally, the effect of stacking sequence of filament layers on the damage level in the composite is investigated.     

Novel 3‐(2‐Oxo‐2H‐benzo[b][1,4]oxazin‐3‐yl)propanoates from Dimethyl‐2‐oxoglutarate and Test of Their Biological Activity

Five novel 3‐(2‐oxo‐2H‐benzo[b][1,4]oxazin‐3‐yl)propanoates were synthesized under mild conditions from 2‐aminophenols and dimethyl‐2‐oxoglutarate. Biological assays of these 1,4‐benzoxazinones were conducted with three bacterial strains and one yeast. All compounds were active against a Candida albicans ATCC 10231, whereas only methyl 3‐(6‐methyl‐2‐oxo‐2H‐benzo[b][1,4]oxazin‐3‐yl)propanoate showed a general moderate activity against the bacterial strains tested.     

2-Halogeno-N-phenacylimidazolium salts and their reactions with active methylene species,arylamines and thiocyanate ions

This study describes the reactivity of 2-halogeno-N-phenacylimidazolium salts towards active methylene species, arylamines and thiocyanate ions. The 2-chloro-N-phenacylimidazolium salt undergoes unexpected reactions in the presence of active methylene species and a tertiary amine as the base. The reaction of 2-bromo-N-phenacylimidazolium salts with arylamines led to a mixture of the corresponding 2-(arylamino)-N-phenacylimidazolium salts and imidazolone. The reaction of 2-bromo-N-phenacylimidazolium bromide with KSCN led to the corresponding imidazole-2-thione. The crystal structures of five compounds are reported.     

On Symmetrizable Operators on Hilbert Spaces

This paper, motivated by transport theory, deals with spectral properties of operators G on a complex Hilbert space H such that SG is self-adjoint where S is a nonnegative operator: We give several lower bounds of the spectral radius of G and determine the latter in some cases. We derive the whole spectrum for power compact G by means of Lagrange multiplier theory. We find out spectral connections between G and SG. We give a (spectral) stability estimate for symmetrizable operators in terms of the spectral radius of the perturbation.     

On a boundary variational inequality of the second kind modelling a friction problem

A scalar contact problem with friction governed by the Yukawa equation is reduced to a boundary variational inequality. The presence of the non‐differentiable friction functional causes some difficulties when approximated. We present two methods to overcome this difficulty. The first one is a regularization leading to a non‐linear boundary variational equation, for which we propose an iterative procedure, whereas the second method is based on the boundary mixed variational formulation involving Lagrange multipliers. We propose Uzawa's algorithm to compute the saddle point of the corresponding boundary Lagrangian and investigate the discretization of various formulations by the boundary element Galerkin method. Convergence of the boundary element solution is proved and a convergence order is obtained. Copyright © 2002 John Wiley & Sons, Ltd.