Surface properties of mixed monolayers of sulfobetaines and ionic surfactants

To study the influence of the head group in the properties of the mixed monolayers adsorbed at the air-water interface, the surface tension and surface potential of binary mixtures of surfactant have been determined as a function of the surfactant composition. Experiments were carried out with anionic-zwitterionic sodium dodecyl sulfate and dodecyl dimethyl ammoniopropane sulfonate (SDS/DDPS), and cationic-zwitterionic dodecyl trimethylammonium bromide and dodecyl dimethyl ammoniopropane sulfonate (DTAB/DDPS), and dodecyl trimethylammonium bromide and tetradecyl dimethyl ammoniopropane sulfonate (DTAB/TDPS). It was shown that mixed monolayers of cationic-zwitterionic surfactant exhibit small negative deviations of ideal behavior, whereas for SDS/DDPS monolayers show strong negative deviation from the ideality. Deviations of ideal behavior are interpreted by regular solution theory. The surface potential values agree very well with the concentration of the ionic component at the interface. The dynamic surface tension values show that the adsorption kinetics on the interface is a diffusion-controlled process. In monolayers with significant deviation of the ideal behavior, anionic-zwitterionic, there is some evidence of intermolecular attractions after diffusion of both surfactants at the interface.     

Micromagnetic simulations of domain wall depinning forced by oscillating fields

Notches in thin ferromagnetic strips act as pinning centers for the domain walls (DWs) existing in them, due to the locally lowering of the DW magnetostatic energy, that is, the formation of a pinning potential well.     

On speciality of bernstein jordan algebras *

The problem of speciality for Bernstein Jordan algebras is considered. Two examples of exceptional Bernstein Jordan algebras with special nucleus are constructed. The examples correspond to two different types of exceptional Jordan algebras: the first one is i-exceptional, and the second one is i-special.     

Witt index for Galois Ring valued quadratic forms

We calculate the Witt index for Galois Ring valued quadratic forms. We obtain such index depending on the invariant that classifies nonsingular Galois Ring valued quadratic forms together with the type of the corresponding bilinear form (alternating or not).     

Evidence of glass transition in thin films of maleic anhydride derivatives: Effect of the surfactant coadsorption

The glass transition temperature of poly (maleic anhydride-alt-1-octadecen) and poly (styreneco-maleic anhydride) cumene-terminated thin films has been measured by mechanical relaxation of Langmuir films of these polymers. The dynamical properties show glass-like features (non-Arrhenius relaxation times and non-Debye mechanical response) interpreted by the coupling model. The glass transition temperature values determined by a mechanical relaxation experiment (step-compression) agree very well with those obtained by surface potential measurements. It is found that the glass transition temperature values in thin films decrease by about 100K as compared with those corresponding to the bulk polymers. The coadsorption of the water-insoluble surfactant DODAB decreases the glass transition temperature.     

SET-VALUED EXTENSION OF OPERATORS VIA STEINER SELECTIONS (Ⅰ)-THEORETICAL RESULTS

A way to extend operators in spaces of continuous functions to spaces of continuous set-valued functions is proposed. This extension is developed through the Steiner selections of the set-valued functions. Their properties and characteristics of the convergence of sequences of operators of this class are studied. In Part Ⅱ of this series some applications to approximation theory will be shown.     

SET-VALUED EXTENSION OF OPERATORS VIA STEINER SELECTIONS(Ⅱ)-APPLICATIONS TO APPROXIMATION

On the basis of Part (Ⅰ) of this series some applications to the approximation of set-valued functions are obtained: Korovkin type theorems, a method to extend classical approximation operators to the set-valued setting and a Jackson type estimate.