131 research outputs found
Diffusion in a generalized Rubinstein-Duke model of electrophoresis with kinematic disorder
Using a generalized Rubinstein-Duke model we prove rigorously that kinematic
disorder leaves the prediction of standard reptation theory for the scaling of
the diffusion constant in the limit for long polymer chains
unaffected. Based on an analytical calculation as well as Monte Carlo
simulations we predict kinematic disorder to affect the center of mass
diffusion constant of an entangled polymer in the limit for long chains by the
same factor as single particle diffusion in a random barrier model.Comment: 29 pages, 3 figures, submitted to PR
Force and Motion Generation of Molecular Motors: A Generic Description
We review the properties of biological motor proteins which move along linear
filaments that are polar and periodic. The physics of the operation of such
motors can be described by simple stochastic models which are coupled to a
chemical reaction. We analyze the essential features of force and motion
generation and discuss the general properties of single motors in the framework
of two-state models. Systems which contain large numbers of motors such as
muscles and flagella motivate the study of many interacting motors within the
framework of simple models. In this case, collective effects can lead to new
types of behaviors such as dynamic instabilities of the steady states and
oscillatory motion.Comment: 29 pages, 9 figure
Breaking of general rotational symmetries by multi-dimensional classical ratchets
We demonstrate that a particle driven by a set of spatially uncorrelated,
independent colored noise forces in a bounded, multidimensional potential
exhibits rotations that are independent of the initial conditions. We calculate
the particle currents in terms of the noise statistics and the potential
asymmetries by deriving an n-dimensional Fokker-Planck equation in the small
correlation time limit. We analyze a variety of flow patterns for various
potential structures, generating various combinations of laminar and rotational
flows.Comment: Accepted, Physical Review
Some Uses and Potentials of Qualitative Methods in Planning
Planners use methods borrowed from many disciplines. These are usually modified and adapted to meet planner's needs to acquire and sift through many diverse information sources helpful in dealing with complex problems. The quantitative methods which planners use are well known, well established in practice, and acknowledged by most as tools of the planners' trade. In contrast to this, most planners also use qualitative methods but these are rarely explicitly acknowledged.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68912/2/10.1177_0739456X8600600110.pd
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