Biomedical subjects

P Reineker

Publications and source records attributed to P Reineker.

At least 19 recordsLinked to original sources

PubMed2006

Stoichiometric polyelectrolyte complexes of ionic block copolymers and oppositely charged polyions.

Micellization in dilute solutions of diblock copolymers with a polyelectrolyte and a hydrophilic nonionic blocks and oppositely charged polyions is studied using mean-field theory. In aqueous solutions the micelle core consists of the polyelectrolyte complex (PEC) while the corona is formed by hydrophilic blocks of the block copolymers. Describing PEC as a globule in the framework of the Lifshitz [Zh. Eksp. Teor. Fiz. 55, 2408 (1968)] globule theory we calculate the surface tension of the micellar core/solvent interface as a function of the polyion degree of ionization, solvent quality, and concentration of low-molecular-mass salt. The equilibrium aggregation number of starlike micelles formed by block copolymers and homopolymers of opposite charge at stoichiometric mixture compositions is found as a function of the system parameters. It is shown that micelles disintegrate upon addition of salt.

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PubMed2002

Fast Kawasaki spin exchange limit of spin-facilitated kinetic Ising models.

We study a Fock-space operator technique for describing the stochastic kinetics of a spin-facilitated kinetic Ising model. We focus in particular on the diffusion (fast Kawasaki exchange) limit in which the kinetics can be described by a single mean field evolution equation. We derive some general criteria for the approximative validity of mean field theory for the case of a nondiverging diffusion coefficient of the local spin states.

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PubMed2001

Classical diffusion in channels with a spatially varying cross-section.

We study the diffusion of classical particles in channels with varying boundaries. The problem is characterized by the Neumann boundary condition (zero normal current) in contrast to the Dirichlet boundary condition (zero function) for "quantum confinement" problems. Eliminating transverse modes, we derive an effective diffusion equation that describes particle propagation in the space of reduced dimension in the presence of a frozen drift field. The latter stems from boundary variations of the original boundary problem. Boundary variations may thus result in an appreciable change of the particle transport and, in particular, in a nonlinear response to an external field. We show also that there is a difference between the nonlinear responses of open and closed channels.

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PubMed1999

Equilibrium and dynamical properties of semiflexible chain molecules with confined transverse fluctuations.

The partition function of a semiflexible chain molecule with harmonically confined transverse fluctuations is calculated. Equilibrium properties exhibit qualitative differences between the weak and the strong confinement behavior. The relaxation times of undulations perpendicular to the chain molecule contour are calculated on the basis of a Langevin equation approach. With increasing confinement a decrease of the relaxation times is found. As a consequence the mean square displacement of monomers and the dynamic structure factor are strongly influenced by the confinement. The comparison of the calculated mean square displacement with diffusing wave spectroscopy measurements of actin filaments exhibits good agreement.

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PubMed1996