31 research outputs found
Long-lived states of oscillator chain with dynamical traps
A simple model of oscillator chain with dynamical traps and additive white
noise is considered. Its dynamics was studied numerically. As demonstrated,
when the trap effect is pronounced nonequilibrium phase transitions of a new
type arise. Locally they manifest themselves via distortion of the particle
arrangement symmetry. Depending on the system parameters the particle
arrangement is characterized by the corresponding distributions taking either a
bimodal form, or twoscale one, or unimodal onescale form which, however,
deviates substantially from the Gaussian distribution. The individual particle
velocities exhibit also a number of anomalies, in particular, their
distribution can be extremely wide or take a quasi-cusp form. A large number of
different cooperative structures and superstructures made of these formations
are found in the visualized time patterns. Their evolution is, in some sense,
independent of the individual particle dynamics, enabling us to regard them as
dynamical phases.Comment: 8 pages, 5 figurs, TeX style of European Physical Journa
Weak temporal signals can synchronize and accelerate the transition dynamics of biopolymers under tension
In addition to thermal noise, which is essential to promote conformational
transitions in biopolymers, cellular environment is replete with a spectrum of
athermal fluctuations that are produced from a plethora of active processes. To
understand the effect of athermal noise on biological processes, we studied how
a small oscillatory force affects the thermally induced folding and unfolding
transition of an RNA hairpin, whose response to constant tension had been
investigated extensively in both theory and experiments. Strikingly, our
molecular simulations performed under overdamped condition show that even at a
high (low) tension that renders the hairpin (un)folding improbable, a weak
external oscillatory force at a certain frequency can synchronously enhance the
transition dynamics of RNA hairpin and increase the mean transition rate.
Furthermore, the RNA dynamics can still discriminate a signal with resonance
frequency even when the signal is mixed among other signals with nonresonant
frequencies. In fact, our computational demonstration of thermally induced
resonance in RNA hairpin dynamics is a direct realization of the phenomena
called stochastic resonance (SR) and resonant activation (RA). Our study,
amenable to experimental tests using optical tweezers, is of great significance
to the folding of biopolymers in vivo that are subject to the broad spectrum of
cellular noises.Comment: 22 pages, 7 figure
MOBILITY IN A ONE-DIMENSIONAL DISORDER POTENTIAL
In this article the one-dimensional, overdamped motion of a classical
particle is considered, which is coupled to a thermal bath and is drifting in a
quenched disorder potential. The mobility of the particle is examined as a
function of temperature and driving force acting on the particle. A framework
is presented, which reveals the dependence of mobility on spatial correlations
of the disorder potential. Mobility is then calculated explicitly for new
models of disorder, in particular with spatial correlations. It exhibits
interesting dynamical phenomena. Most markedly, the temperature dependence of
mobility may deviate qualitatively from Arrhenius formula and a localization
transition from zero to finite mobility may occur at finite temperature.
Examples show a suppression of this transition by disorder correlations.Comment: 10 pages, latex, with 3 figures, to be published in Z. Phys.