Biomedical subjects

F Family

Publications and source records attributed to F Family.

At least 19 recordsLinked to original sources

PubMed2002

Conformal map modeling of the pinning transition in Laplacian growth.

In Laplacian growth processes pinning may be expected due to a nonlinear response of a material during dielectric breakdown, or due to stick-slip boundary conditions in two-fluid flow in a porous medium, while thermal noise will lead to depinning. Using a method recently proposed by Hastings and Levitov, the size R(max) approximately E(-alpha)(c) of the pinned pattern is shown to scale with the critical field E(c) (electric field for dielectric breakdown, pressure gradient for fluid flow). These pinned patterns have a lower effective fractal dimension d(f) than diffusion-limited aggregation due to the enhancement of growth at the hot tips of the developing pattern. At finite temperature, thermal noise leads to depinning and growth of patterns with a shape and dimensionality dependent on both E(c) and the thermal noise. Using multifractal analysis, scaling expressions are established for this dependency.

Journal Article↗

PubMed2001

Quenched disorder effects on deterministic inertia ratchets.

The effect of quenched disorder on the underdamped motion of a periodically driven particle on a ratchet potential is studied. As a consequence of disorder, current reversal and chaotic diffusion may take place on regular trajectories. On the other hand, on some chaotic trajectories disorder induces regular motion. A localization effect similar to the Golosov phenomenon sets in whenever a disorder threshold that depends on the mass of the particle is reached. Possible applications of the localization phenomenon are discussed.

Journal Article↗

PubMed2001

Rate-equation approach to island capture zones and size distributions in epitaxial growth.

Understanding and predicting the effects of correlations between island size and the rate of monomer capture has been shown to be the central problem in predicting the island-size distribution in submonolayer growth. Here we summarize a method which involves a self-consistent coupling of evolution equations for the capture-zone distributions with rate equations for the island-size distribution. The method has been successfully applied to irreversible submonolayer growth in both one and two dimensions to predict the size-dependent capture numbers and island-size distributions.

Journal Article↗

PubMed2000

Disorder induced diffusive transport in ratchets.

The effects of quenched disorder on the overdamped motion of a driven particle on a periodic, asymmetric potential are studied. While for the unperturbed potential the transport is due to a regular drift, the quenched disorder induces a significant additional chaotic "diffusive" motion. Possible applications to experiments in nanoscale surfaces and particle separation are discussed.

Diffusion↗

PubMed2000

Roughening, deroughening, and nonuniversal scaling of the interface width in electrophoretic deposition of polymer chains

Growth and roughness of the interface of deposited polymer chains driven by a field onto an impenetrable adsorbing surface are studied by computer simulations in (2+1) dimensions. The evolution of the interface width W shows a crossover from short-time growth described by the exponent beta(1) to a long-time growth with exponent beta(2) (>beta(1)). The saturated width increases, i.e., the interface roughens, with the molecular weight L(c), but the roughness exponent alpha (from W(s) approximately Lalpha) becomes negative in contrast to models for particle deposition; alpha depends on the chain length-a nonuniversal scaling with the substrate length L. Roughening and deroughening occur as the field E and the temperature T compete such that W(s) approximately (A+BT)E(-1/2).

Journal Article↗

PubMed1999

Tuning friction with noise and disorder.

We present numerical and experimental evidence which demonstrates that under certain conditions friction can be reduced by spatial disorder and/or thermal noise. We discuss possible mechanisms for this behavior.

Journal Article↗

PubMed1997

Active random walkers simulate trunk trail formation by ants.

A simple model for interactive structure formation is studied to simulate the trail formation by ants based on local chemical communication. In our model, active random walkers, which do not have the ability of visual navigation or storage of information, first have to discover different distributions of food sources and then have to link these sources to a central place by forming a trail, using no other guidance than the chemical markings produced by themselves. The simulations show the spontaneous emergence of a collective trail system due to self-organization, which is both stable and flexible, to include newly discovered sources. The typical dendritic foraging patterns of desert ants, reported by Hölldobler and Möglich (Insectes Sociaux. 1980. 27(3). pp. 237 264) are reproduced by the simulations.

Animals↗

PubMed1996