Mechanics of interfaces : the stability of a spherical shape

Conditions are considered for the loss of stability of a spherical interface. An arbitrary interface is characterized by the force factors, such as surface tension, first and second moments, moduli of elasticity and cutting forces. In a deformed state the conditions of internal interface equilibrium are assumed to be satisfied. General expressions are obtained for the stability criterion which relate the system parameters and the pressure drop between homogeneous phases separated by the interface. Particular cases are considered of a non-expansible membrane and an interface with a small expansion modulus of elasticity.On considère les conditions de perte de stability d'une interface sphérique. Une interface arbitraire est caractérisé par des facteurs tels que tension de surface, le premier et le deuxième moments, les modules d'élasticité. Dans un état déformé, on suppose que les conditions d'équilibre à l'interface interne sont respectées. On obtient des expressions générales pour les critères de stabilité qui mettent en rapport les paramètres du système et la différence de pression entre phases homogènes séparées par l'interface. On considère les cas particuliers de membranes qui ne se dilatent pas et d'une interface ayant un petit module de dilatation

Light energy conversion with pheophytin a monolayer at the SnO[sub 2] optically transparent electrode

The photoelectrochemical, absorption and fluorescence properties of pheophytin a mono- and multilayers, deposited on optically transparent tin oxide electrodes and quartz slides were investigated. Spectra of photocurrents coincided with the absorption spectra of photosynthetic pigment in monolayers at the SnO[sub 2]/solution interfaces. The anodic and cathodic photocurrents were measured at various electrode potentials. Effects of pH, electrode potentials, and concentration of redox reagents on the conversion of solar energy in monolayers on optically transparent electrodes are discussed. The absorption and fluorescence spectral characteristics, and fluorescence lifetime measurements of pheophytin a in monolayers and thin films are also discussed in view of the aggregation properties of the photosynthetic pigment. The thermodynamics of adsorption of large amphiphilic compounds at the interface between two immiscible liquids is considered. The adsorption behavior of pheophytin a dissolved in different solvents is investigated. The thermodynamic parameters of pheophytin a adsorption at octane/water and benzene/water interfaces were determined

Mechanosensitivity of gramicidin A channels in bulged bilayer membranes at constant tension

Mechanoelectrical transduction in gramicidin A channels was studied in macroscopic planar lipid bilayer membranes bulged at constant tension. We found a supralinear increase in the single channel activity that was proportional to the square of membrane radius, but could not be accounted for by the increase in membrane surface area, or by recruitment of new channels. Extrapolated to biological membranes, these observations may suggest that the permeability of ion channels can be influenced simply by changing shape of the membrane, with or without stretching. © Nauka/Interperiodica 2006.SCOPUS: ar.jinfo:eu-repo/semantics/publishe