Biomedical subjects

Andrei A Fedorenko

Publications and source records attributed to Andrei A Fedorenko.

4 recordsLinked to original sources

PubMed2006

Universal distribution of threshold forces at the depinning transition.

We study the distribution of threshold forces at the depinning transition for an elastic system of finite size, driven by an external force in a disordered medium at zero temperature. Using the functional renormalization group technique, we compute the distribution of pinning forces in the quasistatic limit. This distribution is universal up to two parameters, the average critical force and its width. We discuss possible definitions for threshold forces in finite-size samples. We show how our results compare to the distribution of the latter computed recently within a numerical simulation of the so-called critical configuration.

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PubMed2006

Surface segregation of conformationally asymmetric polymer blends.

We have generalized the Edwards' method of collective description of dense polymer systems in terms of effective potentials to polymer blends in the presence of a surface. With this method we have studied conformationally asymmetric athermic polymer blends in the presence of a hard wall to the first order in effective potentials. For polymers with the same gyration radius Rg but different statistical segment lengths lA and lB the excess concentration of stiffer polymers at the surface is derived as delta rho A(z=0) approximately (lB-2 - lA-2)ln(R2g/l2c), where lc is a local length below of which the incompressibility of the polymer blend is violated. For polymer blends differing only in degrees of polymerization the shorter polymer enriches the wall.

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PubMed2003

Universal energy distribution for interfaces in a random-field environment.

We study the energy distribution function rho(E) for interfaces in a random-field environment at zero temperature by summing the leading terms in the perturbation expansion of rho(E) in powers of the disorder strength, and by taking into account the nonperturbational effects of the disorder using the functional renormalization group. We have found that the average and the variance of the energy for one-dimensional interface of length L behave as, (R) proportional to L ln L, DeltaE(R) proportional to L, while the distribution function of the energy tends for large L to the Gumbel distribution of the extreme value statistics.

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PubMed2003

Depinning transition at the upper critical dimension.

We study the effect of quenched random field disorder on a driven elastic interface close to the depinning transition at the upper critical dimension d(c)=4 using the functional renormalization group. We have found that the displacement correlation function behaves with distance x as (ln xLambda(0))(2/3) for large x. Slightly above the depinning transition the force-velocity characteristics are described by the equation v approximately f|ln f|(2/9), while the correlation length behaves as L(v) approximately f(-1/2)|ln f|(1/6), where f=F/F(c)-1 is the reduced driving force.

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