77 research outputs found
Can we model DNA at the mesoscale ? Comment on: Fluctuations in the DNA double helix: A critical review
Comment on "Fluctuations in the DNA double helix: A critical review" by
Frank-Kamenetskii and Prakas
Discreteness effects on soliton dynamics: a simple experiment
We present a simple laboratory experiment to illustrate some aspects of the
soliton theory in discrete lattices with a system that models the dynamics of
dislocations in a crystal or the properties of adsorbed atomic layers. The
apparatus not only shows the role of the Peierls-Nabarro potential but also
illustrates the hierarchy of depinning transitions and the importance of the
collective motion in mass transport.Comment: 9 pages, 4 Figures, to Appear in American Journal of Physic
Dynamical phase diagram of the dc-driven underdamped Frenkel-Kontorova chain
Multistep dynamical phase transition from the locked to the running state of
atoms in response to a dc external force is studied by MD simulations of the
generalized Frenkel-Kontorova model in the underdamped limit. We show that the
hierarchy of transition recently reported [Braun et al, Phys. Rev. Lett. 78,
1295 (1997)] strongly depends on the value of the friction constant. A simple
phenomenological explanation for the friction dependence of the various
critical forces separating intermediate regimes is given.Comment: 12 Revtex Pages, 4 EPS figure
Dynamical transitions in correlated driven diffusion in a periodic potential
The diffusion of a two-dimensional array of particles driven by a constant
force in the presence of a periodic external potential exhibits a hierarchy of
dynamical phase transitions when the driving force is varied. This behavior can
be explained by a simple phenomenological approach which reduces the system of
strongly interacting particles to weakly interacting quasi-particles (kinks).
The richness of the strongly coupled system is however not lost because,
contrary to a single-Brownian particle, the array shows an hysteretic behavior
even at non-zero temperature. The present investigation can be viewed as a
first step toward understanding nanotribology.Comment: 4 pages, 3 pictures, revtex to appear in Phys Rev. Let
Solitonic-exchange mechanism of surface~diffusion
We study surface diffusion in the framework of a generalized
Frenkel-Kontorova model with a nonconvex transverse degree of freedom. The
model describes a lattice of atoms with a given concentration interacting by
Morse-type forces, the lattice being subjected to a two-dimensional substrate
potential which is periodic in one direction and nonconvex (Morse) in the
transverse direction. The results are used to describe the complicated
exchange-mediated diffusion mechanism recently observed in MD simulations [J.E.
Black and Zeng-Ju Tian, Phys. Rev. Lett. {\bf 71}, 2445-2448(1993)].Comment: 22 Revtex pages, 9 figures to appear in Phys. Rev.
Order of the phase transition in models of DNA thermal denaturation
We examine the behavior of a model which describes the melting of
double-stranded DNA chains. The model, with displacement-dependent stiffness
constants and a Morse on-site potential, is analyzed numerically; depending on
the stiffness parameter, it is shown to have either (i) a second-order
transition with "nu_perpendicular" = - beta = 1, "nu_parallel" = gamma/2 = 2
(characteristic of short range attractive part of the Morse potential) or (ii)
a first-order transition with finite melting entropy, discontinuous fraction of
bound pairs, divergent correlation lengths, and critical exponents
"nu_perpendicular" = - beta = 1/2, "nu_parallel" = gamma/2 = 1.Comment: 4 pages of Latex, including 4 Postscript figures. To be published in
Phys. Rev. Let
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