Kazuyoshi Hirakawa

Magnetic Properties of Potassium Iron Group Fluorides KMF3

Evidence of antiferromagnetism in perovskite-type potassium iron group fluoride KMF 3 was found through the susceptibility measurements made between 80°K and 700°K. The obtained results are as follows:

Chaotic behavior in the Onchidium giant neuron under sinusoidal stimulation

Abstract The nonperiodic firing of the Onchidium giant neuron under sinusoidal stimulation is investigated. Attractors obtained stroboscopically show that state points on the attractor are mixed by the bakers transformation. The transition function with period three suggests that the nonperiodic oscillation is chaotic.

Analogy Between Hydrodynamic Instabilities in Nematic Liquid Crystal and Classical Fluid

The flow patterns formed by the electrohydrodynamic effect of the nematic liquid crystal are observed. It is found that the phase diagram made from the observation bears a strong resemblance to tha...

Effect of the White Noise on Electrohydrodynamic Transitions in Nematics

The effect of the white noise on the hydrodynamic transitions is studied in the nematic MBBA. The values of both transition points to the laminar flow and to the turbulent flow increase with the amplitude of the white noise. Brief discussion is described.

Chaos in the self-sustained oscillation of an excitable biological membrane under sinusoidal stimulation

Abstract Nonperiodic behavior in self-sustained oscillation of the internodal cell of Nitella was investigated under sinusoidal stimulation. The stroboscopic transformation reveals a single-valued transition function with period three. This suggests that the nonperiodic oscillation is chaotic in the sense of Li and Yorke.

Transition to chaos via intermittency in the onchidium pacemaker neuron

Abstract The nonlinear response of the Onchidium pacemaker neuron to a sinusoidal stimulation was investigated by a stroboscopic mapping. The phase diagram of the response was obtained and the transition from the 1 2 -harmonic oscillation to chaos through the intermittency is pointed out.

Observation of Flow Figures in Nematic Liquid Crystal MBBA

The flow figures in the thin films of MBBA under the applied electric field are observed fromthe transverse direction. The aspects of transitions from the Williams domain to turbulence and from the chevron texture to turbulence are different from each other. A new grid pattern is observed in the region between the Williams domain and the turbulence at a lower frequency than the critical frequency.

Electrode Resistance of Metal Hydride in Alkaline Aqueous Solution

The electrode resistance of metal hydride in constant-current electrolysis is investigated. It is found that the diffusion of hydrogen in the electrode is the rate-determining step in the reaction and is the dominant cause of the electrode resistance. The activity of the electrode, corresponding to the reaction rate, is determined by the effective surface area and the diffusion coefficient of hydrogen in the bulk of the electrode. Some parameters concerning the electrode kinetics are estimated. TiMn1.5 is an excellent electrode material for a secondary battery with high current and energy densities.

Experimental Study on Chemical Turbulence. II

The chemical turbulence of the Belousov-Zhabotinsky reaction theoretically expected by Kuramoto and Yamada was experimentally studied. The turbulence is caused by the coupling between diffusion and nonlinear reaction, i.e., a diffusion induced chaos. Qualitative features of the turbulence are as follows: (1) the turbulence is characterized by frequent growth and decay of plural modes, (2) the alternation of modes corresponds to the irregular variation of the amplitude, (3) the extent of disorder varies gradually with controllable parameters and there seems to be no discontinuity between turbulent and ordered phases.

Chaotic Response of the Pacemaker Neuron

Excitable membranes respond irregularly to a periodic stimulation with proper stimulus parameters. Because irregular firing is macroscopic, it seems that irregularity is caused by other factors besides microscopic membrane noise. The responses of the repetitively firing Onchidium pacemaker neuron to a sinusoidal current stimulation were investigated. The irregular responses are classified into three kinds of chaotic oscillation: chaos, intermittency and random alternation. 1/2- and 1/1-harmonic responses bifurcate to chaos via intermittency and random alternation respectively. Harmonic and chaotic responses alternate with each other with increasing frequency of stimulation and with smaller amplitude. Nonlinear factors, threshold and refractory period, are concerned with hyperbolicity of chaotic responses.