Photosensitive Belousov-Zhabotinsky Reaction Research Articles

Oscillatory clusters in a reaction–diffusion system switching between excitable and unexcitable states

In this study, we report the observation of oscillatory clusters in the photosensitive Belousov–Zhabotinsky reaction switching between excitable and unexcitable states. Numerical studies with a three-variable Oregonator model have been carried out in one- and two-dimensional media. Both non-flux and periodic boundaries have been characterized. Two- and three-phase clusters with standing, breathing, and irregular segregations are achieved when the intensity and durations of the two phases of the square-wave forcing are varied. The occurrence of oscillatory clusters in the excitable medium is due to the dual functions of the inhibitory light perturbation, i.e. eliminating existing wave activity as observed in earlier studies and initiating pattern formation at unexcited regions. The unusual positive impact of the inhibitory perturbation is analyzed, based on the flow trajectories of the system in a two-dimensional concentration phase plane.

Experimental and Model Studies of Oscillations, Photoinduced Transitions, and Steady States in the Ru(bpy)32+-Catalyzed Belousov−Zhabotinsky Reaction under Different Solute Compositions

Experiments of the Ru(bpy)32+-catalyzed Belousov−Zhabotinsky (BZ) reaction exhibited several types of oscillations, photoinduced transitions, and steady states in a continuous-flow stirred tank reactor (CSTR) system under a wide range of oxidative and reductive solute conditions. An improved Oregonator-class model of the photosensitive BZ reaction has reproduced the experimental behavior quantitatively as well as other photoinduced behavior reported so far.

Spatial symmetry breaking in the Belousov-Zhabotinsky reaction with light-induced remote communication.

Domains containing spiral waves form on a stationary background in a photosensitive Belousov-Zhabotinsky reaction with light-induced alternating nonlocal feedback. Complex behavior of colliding and splitting wave fragments is found with feedback radii comparable to the spiral wavelength. A linear stability analysis of the uniform stationary states in an Oregonator model reveals a spatial symmetry breaking instability. Numerical simulations show behavior in agreement with that found experimentally and also predict a variety of other new patterns.

ChemInform Abstract: Phase Fronts and Synchronization Patterns in Forced Oscillatory Systems

This is a review of recent studies of extended oscillatory systems that are subjected to periodic temporal forcing. The periodic forcing breaks the continuous time translation symmetry and leaves a discrete set ofstable uniform phase states. The multiplicity ofphase states allows for front structures that shift the oscillation phase by[n where n 1, 2,..., hereafter [nfronts. The main concern here is with front instabilities and their implications on pattern formation. Most theoretical studies have focused on the 2 1 resonance where the system oscillates at half the driving frequency. All front solutions in this case are -fronts. At high forcing strengths only stationary fronts exist. Upon decreasing the forcing strength the stationary fronts lose stability to pairs of counter-propagating fronts. The coexistence of counter-propagating fronts allows for traveling domains and spiral waves. In the 4:1 resonance stationary -fronts coexist with /2-fronts. At high forcing strengths the stationary -fronts are stable and standing two-phase waves, consisting of successive oscillatory domains whose phases differ by, prevail. Upon decreasing the forcing strength the stationary -fronts lose stability and decompose into pairs ofpropagating ]2-fronts. The instability designates a transition from standing two-phase waves to traveling four-phase waves. Analogous decomposition instabilities have been found numerically in higher 2n 1 resonances. The available theory is used to account for a few experimental observations made on the photosensitive Belousov-Zhabotinsky reaction subjected to periodic illumination. Observations not accounted for by the theory are pointed out.

Oscillatory clusters in a model of the photosensitive belousov-zhabotinsky reaction system with global feedback

Oscillatory cluster patterns are studied numerically in a reaction-diffusion model of the photosensitive Belousov-Zhabotinsky reaction supplemented with a global negative feedback. In one- and two-dimensional systems, families of cluster patterns arise for intermediate values of the feedback strength. These patterns consist of spatial domains of phase-shifted oscillations. The phase of the oscillations is nearly constant for all points within a domain. Two-phase clusters display antiphase oscillations; three-phase clusters contain three sets of domains with a phase shift equal to one-third of the period of the local oscillation. Border (nodal) lines between domains for two-phase clusters become stationary after a transient period, while borders drift in the case of three-phase clusters. We study the evolving border movement of the clusters, which, in most cases, leads to phase balance, i.e., equal areas of the different phase domains. Border curling of three-phase clusters results in formation of spiral clusters-a combination of a fast oscillating cluster with a slow spiraling movement of the domain border. At higher feedback coefficient, irregular cluster patterns arise, consisting of domains that change their shape and position in an irregular manner. Localized irregular and regular clusters arise for parameters close to the boundary between the oscillatory region and the reduced steady state region of the phase space.

Electrochemical control of bifurcation points for stochastic resonance in a model of the photosensitive belousov-zhabotinsky reaction

Electrochemical control of bifurcation points for stochastic resonance in a model of the photosensitive belousov-zhabotinsky reaction

Comparative study of chemical waves and temporal oscillations in the Ru(bpy) 32+-catalyzed photosensitive Belousov–Zhabotinsky reaction

Properties of the chemical waves emerging from the mask edge were investigated for the Ru(bpy) 3 2+-catalyzed Belousov–Zhabotinsky reaction under steady illumination while varying the initial concentration of malonic acid ([MA] 0) systematically. The wave velocity, the wavelength and the thickness of the oxidized band were found to decrease monotonously with [MA] 0. The obtained results were qualitatively interpreted based on the temporal oscillations measured in a batch reactor. A key effect caused by increasing [MA] 0 was identified to be the enhancement of the reduction rate of Ru(bpy) 3 3+.

Phase fronts and synchronization patterns in forced oscillatory systems

This is a review of recent studies of extended oscillatory systems that are subjected to periodic temporal forcing. The periodic forcing breaks the continuous time translation symmetry and leaves a discrete set of stable uniform phase states. The multiplicity of phase states allows for front structures that shift the oscillation phase byπ/nwheren=1,2,…,hereafterπ/n-fronts. The main concern here is with front instabilities and their implications on pattern formation. Most theoretical studies have focused on the2:1resonance where the system oscillates at half the driving frequency. All front solutions in this case areπ-fronts. At high forcing strengths only stationary fronts exist. Upon decreasing the forcing strength the stationary fronts lose stability to pairs of counter-propagating fronts. The coexistence of counter-propagating fronts allows for traveling domains and spiral waves. In the4:1resonance stationaryπ-fronts coexist withπ/2-fronts. At high forcing strengths the stationaryπ-fronts are stable and standing two-phase waves, consisting of successive oscillatory domains whose phases differ byπ,, prevail. Upon decreasing the forcing strength the stationaryπ-fronts lose stability and decompose into pairs of propagatingπ/2-fronts. The instability designates a transition from standing two-phase waves to traveling four-phase waves. Analogous decomposition instabilities have been found numerically in higher2n:1resonances. The available theory is used to account for a few experimental observations made on the photosensitive Belousov–Zhabotinsky reaction subjected to periodic illumination. Observations not accounted for by the theory are pointed out.

Two-parameter stochastic resonance in the absence of external signal for the photosensitive Belousov–Zhabotinsky reaction

Stochastic resonance (SR) is studied numerically in a modified Oregonator-type model, which was proposed recently to account for the photosensitivity of the Belousov–Zhabotinsky (BZ) reaction in a flow system. When either of the two control parameters, light flux and a flow rate, is modulated by multiplicative external noise, noise induced coherent oscillations (NICO) in the absence of deterministic oscillations are observed near Hopf bifurcation point, where the external noise is added to one parameter or the other. The signal-to-noise ratio (SNR) goes through a maximum with the increment of noise intensity indicating occurrence of SR. The aspects of the two-parameter SR in this system are discussed.

Noise Driven Avalanche Behavior in Subexcitable Media

The interaction of noise with a subexcitable chemical system gives rise to spatiotemporal behavior with novel statistical properties. Wave behavior in a photosensitive Belousov-Zhabotinsky reaction with imposed noise is monitored and statistically analyzed. Waves are initiated at sites where the accumulation of subthreshold perturbations induces local excitations, and waves propagate through the medium by a facilitated percolation process. Statistical analysis of the coherent spatiotemporal structures reveals power-law relations that indicate the system has no intrinsic length or time scale. [S0031-9007(98)08304-5]

3PD012 光感受性BZ反応における引き込み双安定状態

3PD012 光感受性BZ反応における引き込み双安定状態

Formation and evolution of scroll waves in photosensitive excitable media.

Experimental and computational studies of the formation and evolution of scroll waves in three-dimensional excitable media are presented. Scroll waves are initiated in the photosensitive Belousov-Zhabotinsky reaction by perturbing traveling waves transverse to their direction of propagation. Scroll rings are generated by perturbing circular waves, which expand or contract depending on the strength of an imposed excitability gradient and its direction relative to the rotational direction of the scroll wave. (c) 1998 American Institute of Physics.

Noise sustained waves in subexcitable media: From chemical waves to brain waves.

We discuss a novel type of spatiotemporal pattern that can be observed in subexcitable media when coupled to a thermal environment. These patterns have been recently observed in several different types of systems: a subexcitable photosensitive Belousov-Zhabotinsky reaction, hippocampal slices of rat brains, and astrocyte syncytium. In this paper, we introduce the basic concepts of subexcitable media, describe recent experimental observations in chemistry and neurophysiology, and put these observation into context with computer simulations. (c) 1998 American Institute of Physics.

Wave competition in excitable modulated media

The propagation of an initially planar front is studied within the framework of the photosensitive BelousovZhabotinsky reaction modulated by a smooth spatial variation of the local front velocity in the direction perpendicular to front propagation. Under this modulation, the wave front develops several fingers corresponding to the local maxima of the modulation function. After a transient, the wave front achieves a stationary shape that does not necessarily coincide with the one externally imposed by the modulation. Theoretical predictions for the selection criteria of fingers and steady-state velocity are experimentally validated.

Splitting of Autowaves in an Active Medium

Splitting of autowaves was observed in a two-dimensional photosensitive Belousov-Zhabotinsky reaction medium after a short, high-intensity inhibitory light pulse. These results, apparently contradicting the standard properties of autowaves, are explained within the context of reaction-diffusion equations. © 1997 American Physical Society.

Spiral Wave Formation in Three-Dimensional Excitable Media.

A mechanism for the generation of spiral waves in three-dimensional excitable media is described. Experiments using the photosensitive Belousov-Zhabotinsky reaction show that circular or spiral waves appear in the wake of a propagating wave following a local perturbation in illumination intensity. The induced waves arise from three-dimensional scroll waves striking the upper boundary of the excitable medium. Spiral waves are formed over a range of illumination intensities and perturbation times which place the induced wave in the vulnerable region of the refractory wave back. [S0031-9007(96)01342-7]

Bromomalonic acid as a source of photochemically produced Br − ion in the Ru(bpy) 32+-catalyzed Belousov-Zhabotinsky reaction

Experimental observation shows that bromomalonic acid (BrMA) is one of the sources of photo-induced Br − ion in the photosensitive Belousov-Zhabotinsky reaction. The rate of Br − production by visible light was measured using a Br −-ion-selective electrode in a solution containing BrMA, H 2SO 4 and Ru(bpy) 3SO 4 but no oxybromine species. The order of reaction was 1 for [BrMA] and [H +], and about 1 2 for the light intensity and [Ru(bpy) 3 2+]. Two types of probable photocyclic mechanisms are proposed.

External forcing of spiral waves.

The effect of an external rhythm on rotating spiral waves in excitable media is investigated. Parameters of the unperturbed medium were chosen, such that the organizing spiral tip describes meandering (hypocyclic) trajectories, which are the most general shape for the experimentally observed systems. Periodical modulation of excitability in a model of the Belousov-Zhabotinsky (BZ) reaction forces meandering spiral tips to describe trajectories that are not found at corresponding stationary conditions. For different modulation periods, two types of resonance drift, phase-locked tip motion, a spectrum of hypocyclic trajectories, and complex multifrequency patterns were computed. The computational results are complemented by experimental data obtained for periodically changing illumination of the photosensitive BZ reaction. The observed drastic deformation of the tip trajectory is considered as an efficient means to study and to control wave processes in excitable media.

Oscillation Phase Dynamics in the Belousov-Zhabotinsky Reaction. Implementation to Image Processing

The phase jump dynamics in a photosensitive Belousov-Zhabotinsky reaction has been studied. It was found that an initially inhomogeneous phase distribution evolved to a homogeneous one, so that the phase at phase-lag points rises to the value at phase-lead points. A steep phase distribution was shown to become smoother in the course of time, inducing a dephasing wave which restores the system to a uniform phase. Applications of photosensitive chemical reactions to image processing (image storage, inversing, contouring) are discussed