Simple approach to the creation of a strange nonchaotic attractor in any chaotic system

A simple approach to the creation of a strange nonchaotic attractor in any chaotic system is described. The main idea is to control the parameter of the system in such a manner that the system dynamics is expanding at some times, but converging at others. With this approach, a strange nonchaotic attractor can be found in a large region in the parameter space near the boundaries between chaotic and regular phases or within the chaotic region far from the regular one. The maximum nontrivial Lyapunov exponent of the system can pass through zero nonsmoothly and cannot be fitted by a linear function. [S1063-651X(99)13805-4]

Brownian motors: current fluctuations and rectification efficiency

With this work we investigate an often neglected aspect of Brownian motor transport: The r\^{o}le of fluctuations of the noise-induced current and its consequences for the efficiency of rectifying noise. In doing so, we consider a Brownian inertial motor that is driven by an unbiased monochromatic, time-periodic force and thermal noise. Typically, we find that the asymptotic, time- and noise-averaged transport velocities are small, possessing rather broad velocity fluctuations. This implies a corresponding poor performance for the rectification power. However, for tailored profiles of the ratchet potential and appropriate drive parameters, we can identify a drastic enhancement of the rectification efficiency. This regime is marked by persistent, uni-directional motion of the Brownian motor with few back-turns, only. The corresponding asymmetric velocity distribution is then rather narrow, with a support that predominantly favors only one sign for the velocity.Comment: 9 pages, 4 figure

Reply to"Comment on 'Simple approach to the creation of a strange nonchaotic attractor in any chaotic system' "

We have recently proposed a simple method to create a strange nonchaotic attractor with any chaotic system [Phys. Rev. E 59, 5338 (1999)]. Such a system is controlled to switch periodically between a chaotic and a quasiperiodic attractor, each with an appropriate time duration. A topological condition for this approach is pointed out in the preceding Comment by Neumann and Pikovsky [Phys. Rev. E 64, 058201 (2001)]. We show that this, condition is not necessary if the durations are sufficiently long. Our approach is a general method to construct a strange nonchaotic attractor in any chaotic system

Entropically enhanced excitability in small systems

We consider the dynamics of small excitable systems, ubiquitous in physics, chemistry, and biology. Spontaneous excitation rates induced by system-size fluctuations exhibit sharp maxima at multiple, small system sizes at which also the system's response to external perturbations is strongly enhanced. This novel effect is traced back to algebraic features of small integers and thus generic

Optimal intracellular calcium signaling

In many cell types, calcium is released from internal stores through calcium release channels upon external stimulation (e.g., pressure or receptor binding), These channels are clustered with a typical cluster size of about 20 channels, generating stochastic calcium puffs, We find that the clustering of the release channels in small clusters increases the sensitivity of the calcium response, allowing for coherent calcium responses at signals to which homogeneously distributed channels would not respond

Phase synchronization in coupled chaotic oscillators with time delay

The phase synchronization (PS) of two Rossler oscillators with time-delayed signal coupling is studied. We find that time delay can always lead to PS even when the delay is very long. Moreover, with the increase of time delay, the coupling strength at the transition to PS undergoes a nearly periodic wave distribution. At some fixed time-delayed signal coupling, a PS region is followed by a non-PS region when the coupling strength increases. However, an increase of the coupling leads to the PS state again. This phenomenon occurs in systems with a relatively large PS transition point

Sensitivity of Ag/Al Interface Specific Resistances to Interfacial Intermixing

We have measured an Ag/Al interface specific resistance, 2AR(Ag/Al)(111) = 1.4 fOhm-m^2, that is twice that predicted for a perfect interface, 50% larger than for a 2 ML 50%-50% alloy, and even larger than our newly predicted 1.3 fOhmm^2 for a 4 ML 50%-50% alloy. Such a large value of 2ARAg/Al(111) confirms a predicted sensitivity to interfacial disorder and suggests an interface greater than or equal to 4 ML thick. From our calculations, a predicted anisotropy ratio, 2AR(Ag/Al)(001)/2AR(Ag/Al)(111), of more then 4 for a perfect interface, should be reduced to less than 2 for a 4 ML interface, making it harder to detect any such anisotropy.Comment: 3 pages, 2 figures, 1 table. In Press: Journal of Applied Physic

The coupling of dynamics in coupled map lattices

We investigate the coupling of dynamics in coupled map lattices (CMLs) which is not only related to coupled parameter, but also the asynchronization among different mean fields in the lattices. Computer simulations show that the optimal coupling among mean fields can be found from the maximum coupling of dynamics in various CMLs. As a consequence, the application areas of coupled systems may be broadened due to the better understanding of their dynamics

Specific Resistance of Pd/Ir Interfaces

From measurements of the current-perpendicular-to-plane (CPP) total specific resistance (AR = area times resistance) of sputtered Pd/Ir multilayers, we derive the interface specific resistance, 2AR(Pd/Ir) = 1.02 +/- 0.06 fOhmm^2, for this metal pair with closely similar lattice parameters. Assuming a single fcc crystal structure with the average lattice parameter, no-free-parameter calculations, including only spd orbitals, give for perfect interfaces, 2AR(Pd/Ir)(Perf) = 1.21 +/-0.1 fOhmm^2, and for interfaces composed of two monolayers of a random 50%-50% alloy, 2AR(Pd/Ir)(50/50) = 1.22 +/- 0.1 fOhmm^2. Within mutual uncertainties, these values fall just outside the range of the experimental value. Updating to add f-orbitals gives 2AR(Pd/Ir)(Perf) = 1.10 +/- 0.1 fOhmm^2 and 2AR(Pd/Ir)(50-50) = 1.13 +/- 0.1 fOhmm^2, values now compatible with the experimental one. We also update, with f-orbitals, calculations for other pairsComment: 3 pages, 1 figure, in press in Applied Physics Letter