RESUMO
Chemical turbulence was observed experimentally in the 1,4-cyclohexanedione Belousov-Zhabotinsky (CHD-BZ) reaction in a double layer consisting of a catalyst-loaded gel and uncatalyzed liquid on a Petri dish. The chemical patterns in the CHD-BZ reaction occur spontaneously in various forms as follows: the initial, regular, transient, and turbulent patterns, subsequently. These four patterns are characterized by using the two-dimensional Fourier transform (2D-FT). Mechanism of the onset of the turbulence in the CHD-BZ reaction is proposed. Turbulence in the CHD-BZ reaction is reproducible under a well defined protocol and it exists for a period of time of about 50 minutes, which is sufficiently long to offer a good opportunity to study and control the turbulence in the future. Two models of the BZ reaction were used to simulate the spiral breakup. Both are capable of producing spiral turbulence from initially regular patterns in each layer and reflect certain features of dynamics observed in experiments.
RESUMO
The effect of acetone on temporal oscillations and spatio-temporal patterns occurring in the ruthenium-catalyzed Belousov-Zhabotinsky (BZ) reaction was investigated in a closed batch system. The periods of temporal oscillations and waves significantly decrease with increasing acetone concentration. At low concentrations of acetone (0.01-0.05 M), regular wave patterns are observed with prolonged lifetimes of both temporal oscillations and waves. However, for higher concentrations (0.10-1.00 M acetone), the lifetime is shortened and irregular patterns are formed. The photosensitivity of waves of the Ru(bpy)3(2+)-catalyzed BZ reaction remains the same for all acetone concentrations. The results are discussed in terms of the proposed reaction mechanism.
RESUMO
We characterize the spatiotemporal evolution of a photosensitive Belousov-Zhabotinsky medium that is made up of coupled oscillatory cells with randomly distributed frequencies. The medium evolves from an initial state of multiple wave sources to a synchronized state governed by a single wave source. The synchronization occurs via a competition between the sources, which arises when the oscillators are not identical but have slightly different natural frequencies. The evolution of each cell is monitored to demonstrate frequency and phase synchronization of the inhomogeneous cellular medium, and a simple kinematic description for the advance of the phase-diffusion wave is presented.
RESUMO
The dynamics of rigidly rotating spiral waves in a reaction layer with light-dependent excitability is studied by numerical integration of a reaction-diffusion equation system with a feedback control. The feedback signal is derived from sensory domains with different geometries by introducing an algorithm that computes the illumination intensity to be proportional to the average wave activity in these domains. It is shown that the shape and size of the trajectories of the spiral wave tip as well as the stability of the spiral rotation depend sensitively on the choice of the geometry of the sensory domain. The numerically observed effects are complemented by constructing a flow map based on an analysis of the feedback signal.
RESUMO
During an experimental study of the resonance attractor for spiral waves in the light-sensitive Belousov-Zhabotinsky reaction, strong deviations of the attractor trajectories from circular orbits are observed if the time delay in the feedback loop becomes relatively long. A theory is developed that reduces the spiral wave dynamics under a long-delayed control to a higher order iterative map. Then the observed deviations are explained to be a result of instabilities appearing due to the Neimark bifurcation of the map. The theoretical predictions are in good agreement with the experimental data.