Biomedical subjects

I Klik

Publications and source records attributed to I Klik.

12 recordsLinked to original sources

PubMed2005

Resonant exit time in stochastic and deterministic systems.

The motion of a particle in the field of a time-dependent potential is studied here both at absolute zero and in the presence of thermal agitation. The potential executes either random fluctuations or deterministic harmonic oscillations. Assuming absorbing boundaries it is always possible to find an exit time tau(ex)(kappa) which has a local minimum as a function of the potential flip rate kappa. Thus resonant activation, usually associated with diffussive systems, exists in purely deterministic systems as well. Thermal agitation merely extends the range of admissible initial conditions and renders all exit times finite.

Journal Article↗

PubMed2001

Resonant activation in a system with deterministic oscillations of barrier height.

A thermally relaxing system with a harmonically oscillating barrier height is considered. The dynamics of the system are described by a Smoluchowski equation with a time dependent right hand side. For both absorbing and reflecting boundary conditions, the solutions of this equation show that the oscillating system has the same resonant properties, and the same dependence on initial conditions, respectively, on the phase of the harmonic oscillations, as a conventional resonant system in which the barrier executes dichotomic Markovian fluctuations.

Algorithms↗

PubMed2000

Solution of a separable smoluchowski equation in one spatial dimension

An approximate solution of a separable Smoluchowski equation in one spatial dimension is constructed here in the form of a finite eigenfunction expansion. The spectrum of the Smoluchowski operator, and the corresponding eigenfunctions, are computed using the so called shooting method of adjoints. Explicit numerical solutions are presented for static and fluctuating potentials, and it is shown that for any smooth initial probablity distribution the finite expansion holds on all time scales. The method is applicable to any linear eigenproblem on a finite one-dimensional interval; the solution of the Sturm-Liouville problem has a particularly convenient form.

Journal Article↗

PubMed1999

Semianalytic solution of the Kramers exit problem for a small ferromagnetic particle.

The distribution Q(t) of magnetization reversal times in a small uniaxial particle is computed here directly from Brown's Fokker-Planck equation. Constant applied field and axial symmetry are assumed. The Laplace transform of Q(t) has the form Q(z)=F(1)(z)/F(2)(z) where the regular functions F(i)(z) are defined by a solution of a Volterra integral equation. A separate integral equation is derived for the function dF(2)(z)/dz, and the poles and residues of Q(z) may then be found numerically with arbitary precision.

Journal Article↗

PubMed1995