Meiji Institute for Advanced Study of Mathematical science MIMS

Nakano-ku, Japan

Meiji Institute for Advanced Study of Mathematical science MIMS

Nakano-ku, Japan
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Suematsu N.J.,Meiji University | Suematsu N.J.,Meiji Institute for Advanced Study of Mathematical science MIMS | Sato T.,Hiroshima University | Motoike I.N.,Japan Science and Technology Agency | And 3 more authors.
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2011

A wave train in an excitable reaction-diffusion medium shows a variety of spatiotemporal patterns as a result of interactions between the individual waves. In this paper, we report a novel spatiotemporal pattern in a wave train in a closed excitable medium. We carried out experiments using a photosensitive Belousov-Zhabotinsky reaction with Ru(bpy)32+ as a catalyst and a numerical calculation using the FitzHugh-Nagumo equation. A wave train was locally distributed as an initial condition and the number of waves was systematically varied. In both the experiment and numerical calculation, density wave propagation was formed in a wave train during relaxation with a large number of waves. Our results suggest that density wave propagation originates from inhibitory interaction between the waves. © 2011 American Physical Society.


Ikura Y.S.,Hiroshima University | Tenno R.,Hiroshima University | Kitahata H.,Chiba University | Kitahata H.,Japan Science and Technology Agency | And 3 more authors.
Journal of Physical Chemistry B | Year: 2012

We investigated the Marangoni flow around a camphor disk on water with the addition of sodium dodecyl sulfate (SDS). The flow velocity decreased with an increase in the concentration of SDS in the aqueous phase, and flow was hardly observed around the critical micelle concentration (cmc), because SDS reduced the driving force of Marangoni flow. However, the flow velocity increased with a further increase in the concentration of SDS. Thus, the Marangoni flow is maximally inhibited around the cmc of SDS. In this paper, we concluded that the regeneration of Marangoni flow originates from an increase in the dissolution rate of camphor into the SDS aqueous solution. © 2011 American Chemical Society.


Matsuda Y.,Hiroshima University | Suematsu N.J.,Meiji University | Suematsu N.J.,Meiji Institute for Advanced Study of Mathematical science MIMS | Nakata S.,Hiroshima University
Physical Chemistry Chemical Physics | Year: 2012

The photo-sensitive self-motion of a benzoquinone (BQ) disk was investigated on a hydroquinone (HQ) aqueous solution. The mode-switching of self-motion, i.e., continuous → intermittent → no motion, was observed with an increase in the concentration of HQ. Upon irradiation with UV light (∼254 nm), the critical concentrations of HQ that were associated with the three modes of motion shifted to lower values, and the average speed of motion decreased. We discuss the mechanism of the photo-sensitive self-motion in relation to the photochemical reaction from BQ to HQ and the driving force of the disk. This journal is © the Owner Societies 2012.


Suematsu N.J.,Meiji University | Suematsu N.J.,Meiji Institute for Advanced Study of Mathematical science MIMS | Tateno K.,Meiji University | Nakata S.,Hiroshima University | And 2 more authors.
Journal of the Physical Society of Japan | Year: 2015

A new mode of collective motion was discovered in a system of camphor disks floating on the water surface in a circular chamber. The mode was induced by tuning the number of the disks. A single or few disks are known to continuously move on the water surface. Conversely, when many disks are present, motion comes to a stop and the disks form ordered spatial patterns by repulsive interaction. Here we found the third mode that emerged at an intermediate disk number, in which inactive and active motion phases alternated non-periodically. This new mode exhibited synchronization as the disk number increased. ©2015 The Physical Society of Japan.


Suematsu N.J.,Hiroshima University | Suematsu N.J.,Meiji Institute for Advanced Study of Mathematical science MIMS | Nakata S.,Hiroshima University | Awazu A.,Hiroshima University | And 2 more authors.
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2010

We propose an inanimate system composed of camphor boats in an annular water channel in order to understand the collective motions. The boats move on the water surface spontaneously and interact with one another through the concentration of the camphor molecules on the water. We observed several modes of collective motion, e.g., behaviors analogous to traffic flow or an ant trail. Our system provides a convenient experimental setup for the investigation of a variety of collective motions. © 2010 The American Physical Society.


Heisler E.,Hiroshima University | Suematsu N.J.,Meiji University | Suematsu N.J.,Meiji Institute for Advanced Study of Mathematical science MIMS | Awazu A.,Hiroshima University | Nishimori H.,Hiroshima University
Journal of the Physical Society of Japan | Year: 2012

The motion of several self-propelled boats in a narrow channel displays spontaneous pattern formation and kinetic phase transitions. In contrast with previous studies on self-propelled particles, this model does not require stochastic fluctuations and it is experimentally accessible. By varying the viscosity in the system, it is possible to form either a stationary state, correlated or uncorrelated oscillations, or unidirectional flow. Here, we describe and analyze these self organized patterns and their transitions. © 2012 The Physical Society of Japan.


Iwamoto M.,Meiji University | Iwamoto M.,Meiji Institute for Advanced Study of Mathematical science MIMS | Suematsu N.J.,Meiji University | Suematsu N.J.,Meiji Institute for Advanced Study of Mathematical science MIMS | And 2 more authors.
Chemical Physics Letters | Year: 2014

Spontaneous spiral formation has been observed in heterogeneous excitable media, and identified unidirectional paths as the origin of the spiral cores. Our numerical results showed unidirectional propagation always appeared at the spiral core as reported on the previous paper (Kinoshita et al., 2013). To clarify the cause of unidirectional behavior, we focused on the inhibitor concentration around the path and found a spatial asymmetric profile. We concluded that the asymmetric inhibitor profile, which was generated by a simple asymmetric construction of the suppressed blocks, induced spiral wave on the heterogeneous reaction field. © 2014 Elsevier B.V. All rights reserved.


Suematsu N.J.,Hiroshima University | Suematsu N.J.,Meiji University | Suematsu N.J.,Meiji Institute for Advanced Study of Mathematical science MIMS | Awazu A.,Hiroshima University | And 5 more authors.
Journal of the Physical Society of Japan | Year: 2011

Localized pattern of bioconvection was newly observed in a suspension of Euglena gracilis, which was a photosensitive micro-organism. The suspension was exposed bright illumination from the bottom, in which the cells swam away from the light source. Then high-density spots, i.e., settling the cells, were formed at a part of a sealed chamber. This localized pattern was contrast with a general bioconvection where pattern was generated whole of a chamber. The experimental observations were reproduced by a mathematical model that was based on the phototaxis of individual cells in both vertical and lateral directions. Our results indicate that convection is maintained by upward swimming, as with general bioconvection, and the localization originates from lateral phototaxis. © 2011 The Physical Society of Japan.


Kinoshita S.-I.,Meiji Institute for Advanced Study of Mathematical science MIMS | Iwamoto M.,Meiji Institute for Advanced Study of Mathematical science MIMS | Iwamoto M.,Meiji University | Tateishi K.,Meiji University | And 4 more authors.
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2013

Spiral waves on excitable media strongly influence the functions of living systems in both a positive and negative way. The spiral formation mechanism has thus been one of the major themes in the field of reaction-diffusion systems. Although the widely believed origin of spiral waves is the interaction of traveling waves, the heterogeneity of an excitable medium has recently been suggested as a probable cause. We suggest one possible origin of spiral waves using a Belousov-Zhabotinsky reaction and a discretized FitzHugh-Nagumo model. The heterogeneity of the reaction field is shown to stochastically generate unidirectional sites, which can induce spiral waves. Furthermore, we found that the spiral wave vanished with only a small reduction in the excitability of the reaction field. These results reveal a gentle approach for controlling the appearance of a spiral wave on an excitable medium. © 2013 American Physical Society.

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