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E. Heinsalu M. Patriarca F. Marchesoni 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,69(1):19-22
We study the effects of the confining conditions on the
occurrence of stochastic resonance (SR) in continuous bistable
systems. We model such systems by means of double-well potentials
that diverge like |x|q for |x|↦∞. For super-harmonic
(hard) potentials with q > 2 the SR peak sharpens with increasing q, whereas for sub-harmonic (soft) potentials, q < 2, it
gets
suppressed. 相似文献
3.
T. Prager A. B. Neiman L. Schimansky-Geier 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,72(1):119-126
Stimulation with periodic force is a standard method to
study response properties of a system. Here we examine a special
type of systems which generate a sequence of events with
uncorrelated time intervals. We review analytical tools to calculate
the gain and the signal-to-noise ratio for such systems when
perturbed by sinusoidal signal and then apply these tools to the
stochastic FitzHugh-Nagumo model. 相似文献
4.
Yong Woon Parc Duk-Su Koh Wokyung Sung 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,69(1):127-131
Stochastic resonance (SR) is a novel cooperative phenomenon occurring in
nonlinear systems due to coupling of an ambient noise and an external
signal. Biological systems may use SR mechanism to detect the signal
efficiently from an external environment. A number of studies have addressed
the SR in artificial ion channels considering external voltages as noises.
More important than these external noises is the internal, thermal noise
which changes the channel conformations essential for biological functions.
In this work, we consider that the channel gating rates follow a
non-Arrhenius temperature dependence derived from experimental data of a
real biological channel. Using the Monte-Carlo simulations, we find that in
this channel SR occurs near a physiological temperature in a very
distinctive manner compared with that for the Arrhenius gating model. 相似文献
5.
M. L. Deng W. Q. Zhu 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,59(3):391-397
The energy diffusion controlled reaction rate of a reacting particle with linear weak damping and broad-band noise excitation
is studied by using the stochastic averaging method. First, the stochastic averaging method for strongly nonlinear oscillators
under broad-band noise excitation using generalized harmonic functions is briefly introduced. Then, the reaction rate of the
classical Kramers' reacting model with linear weak damping and broad-band noise excitation is investigated by using the stochastic
averaging method. The averaged It? stochastic differential equation describing the energy diffusion and the Pontryagin equation
governing the mean first-passage time (MFPT) are established. The energy diffusion controlled reaction rate is obtained as
the inverse of the MFPT by
solving the Pontryagin equation. The results of two special cases of
broad-band noises, i.e. the harmonic noise and the exponentially corrected noise, are discussed in details. It is demonstrated
that the general expression of reaction rate derived by the authors can be reduced to the classical ones via linear approximation
and high potential barrier approximation. The good agreement with the results of the Monte Carlo simulation verifies that
the reaction rate can be well predicted using the stochastic averaging method. 相似文献
6.
P. S.?Burada G.?Schmid D.?Reguera J. M.?Rubi P.?H?nggi 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,69(1):11-18
We demonstrate the existence of stochastic resonance (SR)
in confined systems arising from entropy variations associated to
the presence of irregular boundaries. When the motion of a Brownian
particle is constrained to a region with uneven boundaries, the
presence of a periodic input may give rise to a peak in the spectral
amplification factor and therefore to the appearance of the SR
phenomenon. We have proved that the amplification factor depends on
the shape of the region through which the particle moves and that by
adjusting its characteristic geometric parameters one may optimize
the response of the system. The situation in which the appearance of
such entropic stochastic resonance (ESR) occurs is common for
small-scale systems in which confinement and noise play an prominent
role. The novel mechanism found could thus constitute an important
tool for the characterization of these systems and can put to use
for controlling their basic properties. 相似文献
7.
8.
A. A. Koronovskii A. E. Hramov 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,62(4):447-452
We consider a type of intermittent behavior that occurs
as the result of the interplay between dynamical mechanisms giving
rise to type-II intermittency and random dynamics. We analytically
deduce the law for the distribution of the laminar phases, which has
never been obtained hitherto. The already known dependence of the
mean length of the laminar phases on the criticality parameter [Phys. Rev. E
68, 036203 (2003)] follows as a corollary of the carried out
research. We also prove that this dependence obtained earlier under
the assumption of the fixed form of the reinjection probability does
not depend on the relaminarization properties, and, correspondingly,
the obtained expression of the mean length of the laminar phases on
the criticality parameter remains
correct for different types of the reinjection probability. 相似文献
9.
10.
S. E. Mangioni H. S. Wio 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,61(1):67-73
We analyze the effect of a colored non Gaussian noise on a model of
a random walker moving along a ratchet potential. Such a model was
motivated by the transport properties of motor proteins, like
kinesin and myosin. Previous studies have been realized assuming
white noises. However, for real situations, in general we could
expect that those noises be correlated and non Gaussian. Among other
aspects, in addition to a maximum in the current as the noise
intensity is varied, we have also found another optimal value of the
current when departing from Gaussian behavior. We show the relevant
effects that arise when departing from Gaussian behavior,
particularly related to current's enhancement, and discuss its
relevance for both biological and technological situations. 相似文献
11.
Sau Fa K 《The European physical journal. E, Soft matter》2007,24(2):139-143
In this present work we consider a fractional Langevin equation with Riemann-Liouville fractional time derivative which modifies the classical Newtonian force, nonlocal dissipative force, and long-time correlation. We investigate the first two moments, variances and position and velocity correlation functions of this system. We also compare them with the results obtained from the same fractional Langevin equation which uses the Caputo fractional derivative. 相似文献
12.
M. Dugic D. Rakovic 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(4):781-790
We investigate the quantum-mechanical tunneling between the “patterns" of the, so-called, associative neural networks. Being
the relatively stable minima of the “configuration-energy" space of the networks, the “patterns" represent the macroscopically
distinguishable states of the neural nets. Therefore, the tunneling represents a macroscopic quantum effect, but with some
special characteristics. Particularly, we investigate the tunneling between the minima of approximately equal depth, thus
requiring no energy exchange. If there are at least a few such minima, the tunneling represents a sort of the “random walk"
process, which implies the quantum fluctuations in the system, and therefore “malfunctioning" in the information processing
of the nets. Due to the finite number of the minima, the “random walk" reduces to a dynamics modeled by the, so-called, Pauli
master equation. With some plausible assumptions, the set(s) of the Pauli master equations can be analytically solved. This
way comes the main result of this paper: the quantum fluctuations due to the quantum-mechanical tunneling can be “minimized"
if the “pattern"-formation is such that there are mutually “distant" groups of the “patterns", thus providing the “zone" structure
of the “pattern" formation. This qualitative result can be considered as a basis of the efficient deterministic functioning
of the associative neural nets.
Received 15 July 1999 相似文献
13.
A. Fiasconaro W. Ebeling E. Gudowska-Nowak 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,65(3):403-414
We give an overview over recent studies on the model of Active Brownian Motion (ABM) coupled to reservoirs providing free
energy which may be converted into kinetic energy of motion. First, we present an introduction to a general concept of active
Brownian particles which are capable to take up energy from the source and transform part of it in order to perform various
activities. In the second part of our presentation we consider applications of ABM to ratchet systems with different forms
of differentiable potentials. Both analytical and numerical evaluations are discussed for three cases of sinusoidal, staircaselike
and Mateos ratchet potentials, also with the additional loads modelled by tilted potential structure. In addition, stochastic
character of the kinetics is investigated by considering perturbation by Gaussian white noise which is shown to be responsible
for driving the directionality of the asymptotic flux in the ratchet. This stochastically driven directionality effect is visualized as a strong nonmonotonic dependence of the statistics of the right versus left trajectories of motion
leading to a net current of particles. Possible applications of the ratchet systems to molecular motors are also briefly discussed. 相似文献
14.
M. A. Fuentes H. S. Wio 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,52(2):249-253
With the aim of studying stochastic resonance (SR) in a
double-well potential when the noise source has a spectral density
of the form f-κ (with varying κ), we have extended
a procedure introduced by Kaulakys et al. (Phys. Rev. E 70,
020101 (2004)). In order to achieve an analytical understanding of
the results, we have obtained an effective Markovian approximation
that allows us to make a systematic study of the effect of such
noise on the SR phenomenon. A comparison of the numerical and
analytical results shows an excellent qualitative agreement
indicating that the effective Markovian approximation is able to
correctly describe the general trends. 相似文献
15.
When the processive motor protein kinesin walks along the biopolymer microtubule it can occasionally make a backward step.
Recent single molecule experiments on moving kinesin have revealed that the forward-to-backward step ratio decreases exponentially
with the load force. Carter and Cross (Nature 435, 308-312, 2005) found that this ratio tightly followed 802 × exp[−0.95F], where F is the load force in piconewtons. A straightforward analysis of a Brownian step leads to L/(2k
B
T) as the factor in front of the load force, where L is the 8 nm stepsize, k
B
is the Boltzmann constant, and T is the temperature. The factor L/(2k
B
T) does indeed equal 0.95 pN−1. The same analysis shows how the 802 prefactor derives from the power stroke energy G as exp[G/(2k
B
T)]. There are indications that the power stroke derives from the entropically driven coiling of the 30 amino acid neck linker
that connects the two kinesin heads. This idea is examined and consequences are deduced. 相似文献
16.
E. A. Calzetta 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,68(4):601-605
The thermal efficiency of the kinesin cycle at stalling is presently a matter of some debate, with published predictions ranging
from 0 [Phys. Rev. Lett. 99, 158102 (2007); Phys. Rev. E 78, 011915 (2008)] to 100% [in Molecular Motors, edited by M. Schliwa (Wiley-VCH Verlag GmbH, Weinheim (2003), p. 207]. In this note we attemp to clarify the issues involved.
We also find an upper bound on the kinesin efficiency by constructing an ideal kinesin cycle to which the real cycle may be compared. The ideal cycle has a thermal efficiency of less than one, and the real one is less
efficient than the ideal one always, in compliance with Carnot’s theorem. 相似文献
17.
Y.-C. Lai K. Park L. Rajagopalan 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,69(1):65-70
We investigate a class of nonlinear wave equations subject to
periodic forcing and noise, and address the issue of energy optimization.
Numerically, we use a pseudo-spectral method to solve the nonlinear stochastic
partial differential equation and compute the energy of the system as a
function of the driving amplitude in the presence of noise.
In the fairly general setting where the system possesses two coexisting
states, one with low and another with high energy, noise can induce
intermittent switchings between the two states. A striking finding is that,
for fixed noise, the system energy can be optimized by the driving in a
form of resonance. The phenomenon can be explained by the Langevin dynamics
of particle motion in a double-well potential system with symmetry breaking.
The finding can have applications to small-size devices such as
microelectromechanical resonators and to waves in fluid and plasma. 相似文献
18.
S. I. Denisov W. Horsthemke P. H?nggi 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,68(4):567-575
We derive the generalized Fokker-Planck equation associated with the
Langevin equation (in the Ito sense) for an overdamped particle in an external
potential driven by multiplicative noise with an arbitrary distribution of the
increments of the noise generating process. We explicitly consider this
equation for various specific types of noises, including Poisson white noise
and Lévy stable noise, and show that it reproduces all Fokker-Planck
equations that are known for these noises. Exact analytical, time-dependent and
stationary solutions of the generalized Fokker-Planck equation are derived and
analyzed in detail for the cases of a linear, a quadratic, and a tailored
potential. 相似文献
19.
D. Martila R. Mankin R. Tammelo A. Sauga E. Reiter 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,54(3):375-383
The influence of noise-flatness on overdamped motion of
Brownian particles in a 1D periodic system with a simple sawtooth
potential subjected to both unbiased thermal noise and
three-level telegraph noise is considered. The exact formula for
the stationary probability flux (current) is presented. The
phenomenon of multiple current reversals and some topological
properties of the hypersurface of zero current in the parameter
space of noises are investigated and illustrated by phase
diagrams. The conditions for the existence of four current
reversals versus the switching rate of nonequilibrium noise are
given. An alternative interpretation of the results in terms of
cross-correlation between two dichotomous noises is presented. 相似文献
20.
M.?Morillo J.?Gómez-Ordó?ez J. M.?Casado J.?Casado-Pascual D.?Cubero 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,69(1):59-64
In this article, we investigate the stochastic resonance
(SR) effect in a finite array of noisy bistable systems with
nearest-neighbor coupling driven by a weak time-periodic driving
force. The array is characterized by a collective variable. By means
of numerical simulations, the signal-to-noise ratio (SNR) and the
gain are estimated as functions of the noise and the interaction
coupling strength. A strong enhancement of the SR phenomenon for
this collective variable in comparison with SR in single unit
bistable systems is observed. Gains larger than unity are obtained
for some parameter values and multi-frequency driving forces,
indicating that the system is operating in a non-linear regime
albeit the smallness of the driving amplitude. The large SNR values
observed are basically due to the fact that the output fluctuations
are small and short lived, in comparison with their typical values
in a linear regime. A non-monotonic behavior of the SNR with the
coupling strength is also obtained. 相似文献