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U D Schwarz

Publications and source records attributed to U D Schwarz.

3 recordsLinked to original sources
PubMed2003

A generalized analytical model for the elastic deformation of an adhesive contact between a sphere and a flat surface.

A new method to calculate the elastic deformation of a sphere on a flat surface is presented. The model considers the influence of short-range as well as long-range attractive forces both inside and outside the actual contact area. In contrast to earlier models, this theory describes the nature of these deformations in the intermediate regime between the so-called JKR and DMT limits by simple analytic expressions. Equations for the calculation of the contact radius, the deformation, and the pressure distribution are given. In all equations, the critical force that might vary between the limiting values found in the DMT and the JKR model acts as transition parameter.

Journal Article↗
PubMed1988

Voltage-dependent pore activity of the peptide alamethicin correlated with incorporation in the membrane: salt and cholesterol effects.

Strong aggregation of incorporated alamethicin in the bilayer of lipid vesicles has been observed spectroscopically at aqueous peptide concentrations above a critical value c*. On the other hand, in conventional gating studies with planar lipid films, the onset of conducting pore formation can be characterized by a threshold voltage V.. We present experimental evidence of a direct correspondence between the effects on c* and V. when these parameters are modulated by adding NaCl (to the aqueous medium) or cholesterol (to the lipid moiety). A quantitative analysis supports the idea that the measured aggregation actually results in pore formation, the voltage-dependence being due to an electric field effect on the partition equilibrium of the peptide between the aqueous and the lipid phases.

Alamethicin↗