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Your search keyword '"YAMAGUCHI, TOMOHIKO"' showing total 634 results
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634 results on '"YAMAGUCHI, TOMOHIKO"'

57. Traveling chemical waves for measuring solute diffusivity in thermosensitive poly(N-isopropylacrylamide) gel

Author

Yoshida, Ryo, Otoshi, Gaku, Yamaguchi, Tomohiko, and Kokufuta, Etsuo

Subjects
Polymers -- Chemical properties, Belousov-Zhabotinskii reaction -- Usage, Chemical reactions -- Research, Chemicals, plastics and rubber industries
Abstract

Research is done on the solute diffusivity in a gel by utilizing the Belousov--Zhabotinsky (BZ) reaction, which is known as an oscillating reaction generating periodical redox changes of catalyst. In conclusion the monitory of the chemical wave would provide a novel experimental way for examining polymer gels.

Published
2001

62. In-phase synchronization of chemical and mechanical oscillations in self-oscillating gels

Author

Yoshida, Ryo, Tanaka, Masami, Onodera, Satoko, Yamaguchi, Tomohiko, and Kokufuta, Etsuo

Subjects
Belousov-Zhabotinskii reaction -- Analysis, Ruthenium -- Chemical properties, Oscillation -- Analysis, Chemicals, plastics and rubber industries
Abstract

Research is done on a novel gel which undergoes an autonomic and periodical swelling-deswelling oscillation and has been prepared by the copolymerization of N-isopropylacrylamide (NIPAAm) with ruthenium tris (2,2'-bipyridine) (Ru(bpy)3) as a catalyst for the Belousov--Zhabotinsky (BZ) reaction, which is known as an oscillating reaction accompanying a rhythmical change in the redox potential. In conclusion, the swelling-deswelling amplitude of the gel is controllable.

Published
2000

63. An Oregonator-class model for photoinduced behavior in the Ru(bpy)(sub 3)(super 2+)-catalyzed Belousov-Zhabotinsky reaction

Author

Amemiya, Takashi, Ohmori, Takao, and Yamaguchi, Tomohiko

Subjects
Belousov-Zhabotinskii reaction -- Research, Photochemical research -- Analysis, Chemicals, plastics and rubber industries
Abstract

It has been possible to develop a modified Oregonator model showing photoinduced behaviour in the Ru(bpy)(sub 3)(super 2+)-catalyzed Belousov-Zhabotinsky reaction. The photoinduction of oscillations is reproduced quantitatively.

Published
2000

64. Aspects of the Belousov-Zhabotinsky reaction in polymer gels

Author

Yoshida, Ryo, Onodera, Satoko, Yamaguchi, Tomohiko, and Kokufuta, Etsuo

Subjects
Chemistry, Physical and theoretical -- Research, Belousov-Zhabotinskii reaction -- Research, Polymers -- Research, Colloids -- Research, Chemicals, plastics and rubber industries
Abstract

The authors discuss the Belousov-Zhabotinsky reaction in a gel system as a function of substrate initial concentration in investigating the reaction mechanism. Results indicate that a malonic acid concentration marked effect appeared in the gel.

Published
1999

65. Stochastic resonance under two-parameter modulation in a chemical model system

Author

Amemiya, Takashi, Ohmori, Takao, Yamamoto, Tetsuya, and Yamaguchi, Tomohiko

Subjects
Chemical reactions -- Analysis, Photochemical research -- Analysis, Belousov-Zhabotinskii reaction -- Research, Chemicals, plastics and rubber industries
Abstract

A study was conducted to analyze stochastic resonance under two-parameter modulation in a framework of the photosensitive Belousov-Zhabotinsky reaction in a flow system. Two control parameters of the model were light flux and flow rate. The effect of the flow rate modulation in the system was examined from the perspective of the peristaltic effect of a pump. Results indicated that the additional flow rate modulation promoted increases and decreases in the resonance.

Published
1999

73. Two-parameter stochastic resonance in a model of the photosensitive Belousov-Zhabotinsky reaction in a flow system

Author

Amemiya, Takashi, Ohmori, Takao, Nakaiwa, Masaru, and Yamaguchi, Tomohiko

Subjects
Resonance -- Models, Chemical reactions -- Models, Chemical systems -- Models, Molecular dynamics -- Models, Chemicals, plastics and rubber industries
Abstract

The photosensitive Belousov-Zhabotinsky reaction in a flow system was described using a two-parameter stochastic resonance model. The novel Oregonator-type model contains light flux and a flow rate as control parameters and treats the oscillatory behavior of the system as dynamically observable. Experimental results showed that stochastic resonance is caused by modulation of an excitable focal steady-state close to a Hopf bifurcation by a periodic signal in one parameter and noise in the other parameter.

Published
1998

80. Promotion and inhibition of synchronous glycolytic oscillations in yeast by chitosan

Author

Shibata, Kenichi, Amemiya, Takashi, Kawakita, Yu, Obase, Kohei, Itoh, Kiminori, Takinoue, Masahiro, Nakata, Satoshi, Yamaguchi, Tomohiko, Shibata, Kenichi, Amemiya, Takashi, Kawakita, Yu, Obase, Kohei, Itoh, Kiminori, Takinoue, Masahiro, Nakata, Satoshi, and Yamaguchi, Tomohiko

Abstract

Synchronous rhythmic activities play crucial roles in diverse biological systems. Glycolytic oscillations in yeast cells have been studied for 50 years with the aim of elucidating the mechanisms underlying the intracellular oscillations and their synchronization. We investigated the effects of chemical disturbances on the individual and collective glycolytic oscillations in yeast cells encapsulated in alginate microparticles, and demonstrated that the addition of chitosan, an antimicrobial agent, decreased the duration of these oscillations. In contrast, the periods and the synchronicity states showed two different responses to the chitosan treatments. The periods were shown to be prolonged following the treatment with 5-50 mg·L^(-1) and shortened at 75 mg·L^(-1) of chitosan. Collective oscillations became more synchronized at 5 mg·L^(-1) of chitosan, and desynchronized at 25-75 mg·L^(-1) of this compound. These findings can be explained by the balance between two chitosan features, increasing cell membrane permeability and acetaldehyde scavenging. At low concentrations, chitosan presumably acts as a synchronization promoter that does not mediate the synchronization itself but induces an increase in intercellular coupling. We believe that our findings may provide new insights into the synchronous rhythmic activities in biological systems., This is the peer reviewed version of the following article: [Promotion and inhibition of synchronous glycolytic oscillations in yeast by chitosan], which has been published in final form at [https://doi.org/10.1111/febs.14513]. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.

Published
2019

81. Modeling studies of heterogeneities in glycolytic oscillations in HeLa cervical cancer cells

Author

Amemiya, Takashi, Shibata, Kenichi, Du, Yichen, Nakata, Satoshi, Yamaguchi, Tomohiko, Amemiya, Takashi, Shibata, Kenichi, Du, Yichen, Nakata, Satoshi, and Yamaguchi, Tomohiko

Abstract

Previous experiments demonstrated that a population of HeLa cells starved of glucose or both glucose and serum exhibited a strong heterogeneity in the glycolytic oscillations in terms of the number of oscillatory cells, periods of oscillations, and duration of oscillations. Here, we report numerical simulations of this heterogeneous oscillatory behavior in HeLa cells by using a newly developed mathematical model. It is simple enough that we can apply a mathematical analysis, but capture the core of the glycolytic pathway and the activity of the glucose transporter (GLUT). Lognormal distributions of the values of the four rate constants in the model were obtained from the experimental distributions in the periods of oscillations. Thus, the heterogeneity in the periods of oscillations can be attributed to the difference in the rate constants of the enzymatic reactions. The activity of GLUT is found to determine whether the HeLa cells were oscillatory or non-oscillatory under the same experimental conditions. Simulation with the log-normal distribution of the maximum uptake velocity of glucose and the four randomized rate constants based on the log-normal distributions successfully reproduced the time-dependent number of oscillatory cells (oscillatory ratios) under the two starving conditions. The difference in the initial values of the metabolites has little effect on the simulated results., This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. This article appeared in (citation of published article) and may be found at [https://doi.org/10.1063/1.5087216].

Published
2019

84. Insulinoma‐associated protein1 expression in pancreatic neuroendocrine tumours in endoscopic ultrasound‐guided fine‐needle aspiration cytology: An analysis of 14 patients

Author

Takase, Yorihiko, primary, Naito, Yoshiki, additional, Okabe, Yoshinobu, additional, Ishida, Yusuke, additional, Yamaguchi, Tomohiko, additional, Abe, Hideyuki, additional, Murata, Kazuya, additional, Ito, Takaaki, additional, Tanigawa, Masahiko, additional, Kawahara, Akihiko, additional, Yano, Hirohisa, additional, and Akiba, Jun, additional

Published
2018
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87. Correction to NMR Biochemical Assay for Oxidosqualene Cyclase: Evaluation of Inhibitor Activities on Trypanosoma cruzi and Human Enzymes

Author

Tani, Osamu, primary, Akutsu, Yukie, additional, Ito, Shinji, additional, Suzuki, Takayuki, additional, Tateishi, Yukihiro, additional, Yamaguchi, Tomohiko, additional, Niimi, Tatsuya, additional, Namatame, Ichiji, additional, Chiba, Yasunori, additional, Sakashita, Hitoshi, additional, Kubota, Tomomi, additional, Yanagi, Tetsuo, additional, Mizukami, Shusaku, additional, Hirayama, Kenji, additional, Furukawa, Koji, additional, and Yamasaki, Kazuhiko, additional

Published
2018
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89. NMR Biochemical Assay for Oxidosqualene Cyclase: Evaluation of Inhibitor Activities on Trypanosoma cruzi and Human Enzymes

Author

Tani, Osamu, primary, Akutsu, Yukie, additional, Ito, Shinji, additional, Suzuki, Takayuki, additional, Tateishi, Yukihiro, additional, Yamaguchi, Tomohiko, additional, Niimi, Tatsuya, additional, Namatame, Ichiji, additional, Chiba, Yasunori, additional, Sakashita, Hitoshi, additional, Kubota, Tomomi, additional, Yanagi, Tetsuo, additional, Mizukami, Shusaku, additional, Hirayama, Kenji, additional, Furukawa, Koji, additional, and Yamasaki, Kazuhiko, additional

Published
2018
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90. The expression of programed death ligand-1 could be related with unfavorable prognosis in salivary duct carcinoma

Author

Sato, Fumihiko, primary, Akiba, Jun, additional, Kawahara, Akihiko, additional, Naito, Yoshiki, additional, Ono, Takeharu, additional, Takase, Yorihiko, additional, Murata, Kazuya, additional, Abe, Hideyuki, additional, Yamaguchi, Tomohiko, additional, Miyoshi, Hiroaki, additional, Abe, Yushi, additional, Mihara, Yutaro, additional, Tanikawa, Masahiko, additional, Akashi, Momoko, additional, Kurose, Hirofumi, additional, Umeno, Hirohito, additional, and Yano, Hirohisa, additional

Published
2018
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93. Three-variable reversible Gray–Scott model.

Author

Mahara, Hitoshi, Suematsu, Nobuhiko J., Yamaguchi, Tomohiko, Ohgane, Kunishige, Nishiura, Yasumasa, and Shimomura, Masatsugu

Subjects
THERMODYNAMICS, REACTION-diffusion equations, ENTROPY, CELL division, CHEMICAL reactions, PHYSICS
Abstract

Even though the field of nonequilibrium thermodynamics has been popular and its importance has been suggested by Demirel and Sandler [J. Phys. Chem. B 108, 31 (2004)], there are only a few investigations of reaction-diffusion systems from the aspect of thermodynamics. A possible reason is that model equations are complicated and difficult to analyze because the corresponding chemical reactions need to be reversible for thermodynamical calculations. Here, we introduce a simple model for calculation of entropy production rate: a three-variable reversible Gray–Scott model. The rate of entropy production in self-replicating pattern formation is calculated, and the results are compared with those reported based on the Brusselator model in the context of biological cell division. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Published
2004
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98. Perturbation mechanism and phase transition of AOT aggregates in the Fe(II)[batho(SO3)2]3 – catalyzed aqueous Belousov–Zhabotinsky reaction

Author

Jahan, Rumana A., Suzuki, Kosuke, Mahara, Hitoshi, Nishimura, Satoshi, Iwatsubo, Takashi, Kaminaga, Akiko, Yamamoto, Yasuhiko, and Yamaguchi, Tomohiko

Abstract

Surfactant AOT (sodium bis(2-ethylhexyl)sulfosuccinate) was introduced up to 200 mmol L−1 in the aqueous Belousov–Zhabotinsky (BZ) medium. Both the induction period (IP) and the oscillation period (τ) of the BZ waves decreased significantly, whereas the wave velocity (v) increased with the concentration of AOT. These tendencies were explained in terms of the perturbations to the FKN mechanism through the uptake of Br2 and View the MathML source into the hydrophobic core of AOT aggregates. In addition, the structures and the phase transition of AOT aggregates were suggested based on the measurement of surface tension and the correlation analysis of the IP, τ and v values.

Published
2010

100. Role of stress in the self-limiting oxidation of copper nanoparticles

Author

Chun-Hua Chen, Yamaguchi, Tomohiko, Sugawara, Ko-ichi, and Koga, Kenji

Subjects
Copper compounds -- Structure, Copper compounds -- Properties, Copper compounds -- Chemical properties, Oxidation-reduction reaction -- Analysis, X-rays -- Diffraction, X-rays -- Analysis, Chemicals, plastics and rubber industries
Abstract

The oxidation kinetics of Cu nanoparticles and their temperature dependences are described using an in-situ X-ray diffraction (XRD) method. The oxidation behavior (self-limiting or non-self-limiting) was found to be directly related to the stress condition in the oxide shell and it helps in understanding the self-limiting oxidation kinetics of metal nanoparticles and also the control of their oxide thickness.

Published
2005

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