Kenji Miyakawa

Synchronization and clustering in globally coupled salt-water oscillators

Collective dynamics in globally coupled salt-water oscillators is studied as a function of coupling parameter and system size. The coupling parameter is controlled by changing the ratio of the surface area of the cup to that of the outer vessel. Antiphase and cluster states are observed as ordered states at a large coupling parameter. The appearances of such states are restricted to the case of a small number of constituent oscillators. For a large population of the oscillator, it is found that coupling among oscillators is promoted with the coupling strength, but there is some limitation in a degree of coupling induced. Furthermore, the effect of viscosity on coupling behaviors is investigated. These results are discussed using the idea of frustration developed in the area of the spin system.

Synchronization in the discrete chemical oscillation system

The properties of the coupling between chemical oscillators were studied in the discrete chemical oscillation system which was realized by immersing cation exchange beads loaded with ferroin in the Belousov–Zabotinskii reaction solution. A phase diagram of coupling states was obtained as a function of natural frequencies of oscillators and the distance d between oscillators. The synchronization was found not to be attributed to a simple entrainment of the slower oscillator by the faster one. Various entrainments between oscillators occurred depending on ratios of natural frequencies in the uncoupled state. A chaotic behavior was found at the boundary between stably coupled regions with frequency ratios of n/1 where n is an integer. Furthermore, effects of external perturbation on the coupling were investigated. Irregular oscillations were induced by illumination with a He–Ne laser light, which strongly depended on the phase of oscillator at the beginning of illumination. Such irregular behaviors were loca...

Self-Replication and Preservation of Reduction Waves in the Belousov-Zhabotinsky Reaction

Dynamic behaviors of reduction waves are studied in a one-dimensional gel coupled with the Belousov-Zhabotinsky reaction as a function of temperature and composition of the reaction solution. The most striking behaviors observed are self-replication and preservation of reduction pulse waves. In the former dynamics, after the propagating reduction pulse wave vanishes, it splits into two counterpropagating pulses. In the latter dynamics, counterpropagating reduction pulse waves annihilate each other upon head-on collision and then reappear. Furthermore, annihilation and preservation of reduction waves are observed to occur simultaneously upon head-on collision.

Formation of Somitogenesis-like Pattern in a Reaction-Diffusion System

The Belousov–Zhabotinsky reaction system showing stationary patterns is realized on the basis of water-in-oil microemulsions with the surfactant sodium bis(2-ethylhexyl)sulfosuccinate. We experimentally demonstrate the formation of somitogenesis-like pattern in which chemical waves arising from spontaneous bulk oscillations are successively arrested and then stacked. The experimental results are qualitatively reproduced by numerical simulations using the two-variable oregonator model. These show that a somitogenesis can be accounted for by the genuine reaction–diffusion model.

Synchronization of chemical waves in diffusively coupled self-oscillating gels

Dynamics of chemical waves is investigated in two coupled self-oscillating gels prepared by covalently bonding a catalyst of the Belousov–Zhabotinsky reaction. In this type of gel, chemical waves induce periodical swelling-shrinking oscillation in the gels. The spacing between the two gels varies with such a volume oscillation. Various entrainments of the chemical oscillation occur depending on the difference in the concentration of the catalyst immobilized in the two gels. When the difference in catalyst concentration between the two gels becomes larger, synchronization accompanying the apparent reflection of chemical waves occurs. This phenomenon is characterized by various types of entrainments.

Asymmetric Spatiotemporal Patterns of Reduction Waves in the Belousov{Zhabotinsky Reaction

Spatiotemporal patterns with various symmetries are observed on reduction waves in a one-dimensional gel system coupled with the Belousov–Zhabotinsky reaction. It is found that the symmetry of the pattern depends on the symmetry of the unit pattern making up the entire pattern. The symmetry of the unit pattern is determined by the difference in speed between the reduction fronts propagating in the opposite directions. When the unit pattern is asymmetric, self-replication of the reduction pulse wave occurs asymmetrically. Furthermore, it is found that an irregular spatiotemporal pattern appears in the transition between symmetric and asymmetric patterns.

Coacervation of elastomeric polypeptides: microscopic observations and light scattering measurements

K. KAIBARA , T. WATANABE , K. MIYAKAWA 1 1 2, M. KONDO3 and K. OKAMOTO4 1 Department of Chemistry, Faculty of Science, Kyushu University, Hakozaki, Higashi-ku, Fukuoka 812, Japan 2 Department of Applied Physics, Faculty of Science, Fukuoka University, Nanakuma, Jonan-ku, Fukuoka 814-01, Japan 3 Department of Chemistry, Faculty of Science and Engineering, Saga University, Saga 840, Japan 4 Department of Biochemical Engineering and Science, Faculty of Computer Science and Systems Engineering, Kyusku Institute of Technology, Iizuka, Fukuoka 820, Japan