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The wetting properties of aqueous solutions of two therapeutic pulmonary surfactants (T PS) with respect to solid surfaces with different degree of hydrophobicity θw have been studied. A special procedure for hydrophobization of the SiO2-glass hydrophilic surface allows the preparation of hydrophobic solid surfaces with different θw. The contact angles of drops from a TPS solution onto SiO2-glass surfaces have been measured as a function of their θw. The completely hydrophilic SiO2-glass surface is essentially hydrophobized by the animal-derived TPS Curosurf as well as by the synthetic TPS CHF 5633. The hydrophobization depends on the surfactant concentration - the contact angles increase with increasing the Curosurf concentration C in the low concentration range, but they remain almost constant in a wide range of C > 90 μg/ml. Similar are the θ (θw) curves for aqueous solutions of both TPS. The thickness h of the wetting thin liquid fi lms from aqueous solutions of Curosurf as well as of CHF 5633 on SiO2-glass surfaces depends on θw of the solid surface. The h(θw) curves always pass a minimum. The h-values, as well as the h(θw) curve, are mainly determined by the balance of the positive (repulsive) steric and negative (attractive) hydrophobic disjoining pressures, which depend on the orientations and conformations of the molecules adsorbed on the wetting fi lm surfaces from the very complicated multi-component aqueous solutions. Practically no signifi cant difference in the wetting behaviour of the aqueous solutions of the natural TPS Curosurf and the synthetic TPS CHF 5633 has been established, however about 25% less Curosurf than CHF 5633 was needed to achieve almost the same wetting behaviour. [ABSTRACT FROM AUTHOR]

In this paper a short review of the history of Alexander von Humboldt Foundation, Bonn - Bad Godesberg, Germany, on the occasion of its 60th anniversary is presented. This outstanding German foundation is actually the third one with the same name. Earlier two other Alexander von Humboldt Foundations consequently existed and they consist its pre-history, which is also shortly reviewed. The establishment of the present Foundation in 1953, its development and growth, its activities, information about the six presidents and five executive directors, as well as the main features, principles and guidelines are considered. During the last 60 years the Alexander von Humboldt Foundation became an important institution for the promotion of international research cooperation, which significantly influences the world science. It supported more than 27700 Humboldt fellows to carry out scientific research in Germany, and they form a large "Humboldt family" - a world-wide network. Large number Bulgarian Humboldt fellows are among the best scientists in Bulgaria. [ABSTRACT FROM AUTHOR]

Emulsion films of hydrophobically modified inulin (INUTEC SP1) polymeric surfactant, both in aqueous solution and in the presence of different electrolyte (NaCl, Na2SO4, MgSO4) concentrations have been studied. At constant disjoining pressure of 36 Pa the film thickness hw decreased with increase in electrolyte concentration until a critical value, Cel,cr, was reached above which hw remained constant. This reduction in film thickness below Cel,cr could be accounted for by the compression of the double layer. At a critical pressure that depends on the electrolyte type, the film jumped to a Newton Black Film (NBF) that remained very stable up to very high disjoining pressure at all electrolyte concentrations and electrolyte types studied. The polyfructose loops and tails in this NBF remain strongly hydrated and these results explain the high stability against coalescence of such INUTEC SP1 emulsions. Wetting films from INUTEC SP1 aqueous solutions on a hydrophilic quartz substrate were also studied. The results showed a dependence of film thickness on INUTEC SP1 concentration which could be accounted for by the adsorption and orientation of the polymer molecules at the solid-liquid interface. At low INUTEC SP1 concentration, the molecule adsorbs with the hydrophilic loops and tails leaving the alkylchains in solution. However at higher concentration a bilayer of INUTEC SP1 molecules could be produced by hydrophobic interaction between the alkyl chains on the backbone of the polymer and this resulted in an increase of the film thickness at high concentration. The film thickness decreased with increasing electrolyte concentration at constant INUTEC SP1 concentration till a critical value was reached above which hw remained virtually constant. The reduction of hw could be accounted for by compression of the electrical double layer in accordance with the DLVO-theory. [ABSTRACT FROM AUTHOR]

The influence of a permeation enhancer on the properties of phospholipid black foam films has been studied through the combination of three complementary techniques: surface tension measurements, X-ray reflectivity, and the “diminishing bubble” method. This permeation enhancer is said to optimize the delivery of active ingredients into or through the stratum corneum: the 4-decyl oxazolidin-2-one. We made films of a complex phospholipid mixture that mimic the behavior of the enhancer in a membrane cell. Mixed phospholipids/4-decyl oxazolidin-2-one/NaCl solutions were studied with various 4-decyl oxazolidin-2-one concentrations. Stable black films were obtained and their thicknesses examined. The evolution of the coefficient of gas permeability with 4-decyl oxazolidin-2-one concentration is also addressed. [Copyright &y& Elsevier]