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The possibility of designing a tunable chemical oscillator is explored. In contrast to a normal oscillator which when subjected to external forcing exhibits the characteristic unimodal resonance curve, a tunable oscillator reveals a constant response curve. This persistence of resonant behavior for a wide interval of forcing frequencies is seeked both numerically and in an experimental electrochemical cell. Our results indicate that, although challenging, a tunable chemical oscillator can indeed be conceived. [ABSTRACT FROM AUTHOR]

Noise added to a chirally autocatalytic model system is usually known to cause mirror-symmetry breaking with statistically equal distributions for the two product enantiomers. We show that if such a system is asymmetrically perturbed by means of a very small undetectable bias in the racemization equilibrium between the two enantiomers, adding Gaussian white noise can lead to an efficient enantioselection. Consequently, within a certain range of the noise amplitude, symmetry breaking gives rise to an entirely biased statistical distribution in favor of one of the enantiomers. In contrast, racemic results will be obtained for the corresponding deterministic case (in the absence of noise). Thus, added noise plays a constructive role by directing the chiral system into a specific enantiomeric direction while being influenced only by a subthreshold asymmetric input. This effect could be of conceptual interest for the impact of weak asymmetric fields on nonlinear chemical reactions. [ABSTRACT FROM AUTHOR]

The ability of the mercury beating heart (MBH) system to exhibit sustained mechanical and electrochemical activities simultaneously without any external agent (fluctuating or constant), has attracted researchers for decades. The interplay of these activities could mimic the biological phenomena such as a pulsating heart that occurs due to the coupled tissues exhibiting mechanical as well as electrical dynamics. In the present work, we have studied experimentally the dynamics of electrically coupled two and three autonomous MBH systems. A dynamical triangular (heart) shape, in the traditional watch glass geometry, has been chosen for the experiments. It is found that the redox potentials (electrical behavior) of the quasi-identical (due to the inherent heterogeneities in the setup) MBH systems get synchronized at the intermediate coupling strengths whereas coherence in their mechanical activities occur only at large coupling strengths. To the best of our knowledge, this synchronization phenomenon involving two distinct activities (electrical and mechanical) and different coupling thresholds has not been reported, so far. The coherent mechanical activities means the simultaneous occurrence of compressions and expansions in the coupled Hg drops, which are shown using snapshots. In addition to this, the redox time series have also been provided to demonstrate the synchronization in the electrical behavior of MBH systems. Moreover, a mathematical framework considering only electrical and mechanical components of the MBH systems is presented to validate the experimental findings that the strong synchrony in the redox potentials of the MBH systems is a prerequisite for the synchrony in their mechanical activities.

Bifurcations are detected in experiments involving the electrochemical oxidation of copper in phosphoric acid. Ideally, a bifurcation detection protocol requires a model with good qualitative and quantitative prediction capabilities that is also able to reproduce the drift inherent to the electrochemical experiment. A generic protocol for manipulation of nonlinear systems is proposed to achieve this goal. This protocol is based on a good qualitative predictor coupled to a modified Kalman filter that corrects the quantitative errors of the model point by point, adapting to the slowly varying conditions imposed by the electrochemical drift.

We study the dynamics of the mercury beating heart (MBH) system in an acidic solution in the absence of a strong oxidant. Furthermore, the system is subjected to an external square wave potential. It was observed that different shapes (circular, elliptical, triangular, and multilobed stars) of the mercury drop could be stabilized as the frequency of the external potential and the volume of the mercury were varied. The redox potential time series for this forced MBH system, corresponding to the different stabilized topological configurations, were also recorded, and their power spectra were analyzed. The obtained results, involving the different topological modes, were fairly reproducible and sustainable. A possible oxidation-reduction mechanism for these experimental observations is provided.

Dynamical quorum sensing transition in a system, is the sudden change in its dynamics at a critical population size. We propose a novel coupling mechanism, the "dominating surrounding effect", that can lead to the dynamical quorum sensing transitions. This coupling mechanism has been implemented in both globally and locally coupled systems and found to be independent of the choice of the coupled variables (instantaneous or delayed). Because no local coupling scheme has been proposed so far that can illustrate dynamical quorum sensing in locally coupled systems, our local coupling scenario is a novel contribution. Although global coupling schemes for dynamical quorum sensing have been previously proposed, our global coupling scenario is different, as discussed in the text below. This coupling mechanism has been tested using a two-dimensional electrochemical model and a four dimensional biological model (Hodgkin-Huxley's neuronal model). Two types of dynamical quorum sensing transitions, the emergence and the extinction of global oscillations in an ensemble of globally (all to all) and locally (1-D array with no flux boundary conditions) coupled oscillators, have been studied. Furthermore, the provoked spikes in the neuronal ensemble exhibit zero lag synchronization in the case of time delay and lag synchronization in the case of no-delay (instantaneous). In contrast, the induced oscillations are phase synchronized in the coupled electrochemical oscillators for both delay and no delay.