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Ryo Yoshida - One of the best experts on this subject based on the ideXlab platform.
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Influence of a Positively Charged Moiety on Aggregation‐Disaggregation Self‐Oscillation Induced by the BZ Reaction
Macromolecular Chemistry and Physics, 2009Co-Authors: Yusuke Hara, Ryo YoshidaAbstract:The behavior of the transmittance Self-Oscillation of a polymer chain with a positively charged MAPTAC group is studied. The polymer concentration exerts considerable influence on the behavior and lifetime of the Self-Oscillation. The redox potential and transmittance are measured simultaneously showing that the reactivity of the Ru(bpy) 3 moiety is significantly affected by the polymer aggregation state, originating from the solubility of the polymer chain. The behavior and lifetime of the Self-Oscillation can be controlled by changing the design of the polymer structure and concentration.
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Damping behavior of the aggregation-disaggregation Self-Oscillation of a polymer chain.
Macromolecular rapid communications, 2009Co-Authors: Yusuke Hara, Ryo YoshidaAbstract:The effect of the initial concentration of the substrates of the Belousov-Zhabotinsky (BZ) reaction, and the temperature, on the autonomous aggregation-disaggreagtion Self-Oscillation of a polymer chain is investigated. The polymer chain consists of N-isopropylacrylamide (NIPAAm), a Ru catalyst of the BZ reaction, and acrylamide-2-methylpropanesulfonic acid (AMPS) as a pH and solubility control site. It is demonstrated that the initial concentration of the BZ substrates and the temperature exert an influence on the waveform and the period of the Self-Oscillation. Moreover, the aggregation-disaggregation Self-Oscillation of the polymer chain undergoes damping, that is, the amplitude of the transmittance Self-Oscillation decreases with time. This phenomenon is attributed to an increase in the size of the polymer aggregates during the Self-oscillating behavior. Therefore, the damping behavior is significantly affected by the initial concentration of the BZ substrates in accordance with the Field-Koros-Noyes (FKN) mechanism. In addition, it is shown that the Self-oscillating region is determined by the initial concentrations of the BZ substrates and the temperature. This study clarifies that the Self-Oscillation of the AMPS-containing polymer chain can be controlled by the selection of the initial concentration of the BZ substrates and the temperature under acid-free conditions.
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effect of initial substrate concentration of the belousov zhabotinsky reaction on Self Oscillation for microgel system
Journal of Physical Chemistry B, 2008Co-Authors: Daisuke Suzuki, Ryo YoshidaAbstract:Self-Oscillation for the microgel particles (∼200 nm in diameter) was studied by changing initial substrate concentrations (i.e., malonic acid, sodium bromate, and nitric acid) of the Belousov−Zhabotinsky (BZ) reaction that is used for chemical energy for the Self-Oscillation. The cross-linked microgels are composed of N-isopropylacrylamide and ruthenium tris(2,2′-bipyridine), Ru(bpy)3, which is a catalyst for the BZ reaction. Comparing with the homogeneous, stirred solution of the bulk solution for the BZ reaction, swelling/deswelling Oscillation of the microgels showed longer induction period, different dependence of initial substrate concentrations on Oscillation period, and different Oscillation rhythm. The change in Oscillation for the microgels can be understood by considering the microgel network effect.
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temporal control of Self Oscillation for microgels by cross linking network structure
Macromolecules, 2008Co-Authors: Daisuke Suzuki, Ryo YoshidaAbstract:Self-oscillating microgel, which undergoes an autonomic and periodical swelling/deswelling Oscillation, has been reported. The cross-linked microgels were synthesized by the copolymerization of N-isopropylacrylamide (NIPAm) with ruthenium tris(2,2′-bipyridine) [Ru(bpy)3] as a catalyst for the Belousov−Zhabotinsky (BZ) reaction by surfactant-free aqueous precipitation polymerization. The Self-Oscillation of the microgels was detected by changes in optical transmittance. The microgels showed not only the swelling/deswelling Oscillation, which is synchronized with the redox Oscillation of the Ru(bpy)3 complex immobilized in the microgels, but also flocculating/dispersing Oscillation around the phase transition temperature of the microgels, with a remarkable change in optical transmittance. These microgel Oscillations were further studied by comparing the optical transmittance changes of the microgels and the redox potential change of Ru(bpy)3 immobilized in the microgels. In order to analyze the microgel sel...
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a viscosity Self Oscillation of polymer solution induced by the belousov zhabotinsky reaction under acid free condition
Journal of Chemical Physics, 2008Co-Authors: Yusuke Hara, Ryo YoshidaAbstract:We succeeded in measuring a viscosity Self-Oscillation induced by the Belousov-Zhabotinsky (BZ) reaction for a polymer solution on the constant temperature condition under acid-free condition. The polymer chain is consisted of N-isopropylacrylamide, ruthenium complex as a catalyst of the BZ reaction, and an acrylamide-2-methylpropanesulfonic acid (AMPS) as a pH and the solubility control site. The viscosity Self-Oscillation for the AMPS-containing polymer solution was attributed to the difference between viscosities for the polymer solution in the reduced and oxidized states. The effects of the polymer concentration and the temperature of the polymer solution on the viscosity Self-Oscillation were investigated. As a result, the viscosity Self-oscillating behavior significantly depended on the polymer concentration and the temperature of the polymer solution. The period of the viscosity Self-Oscillation decreased with increasing temperature in accordance with the Arrenius equation.
Yusuke Hara - One of the best experts on this subject based on the ideXlab platform.
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Influence of the Belousov–Zhabotinsky substrate concentration on the lifetime and Self-oscillating behavior of a polymer solution
MATEC Web of Conferences, 2017Co-Authors: Tomoka Nakazumi, Yusuke HaraAbstract:In this study, we synthesized a Self-oscillating polymer chain with N-ethylacrylamide (NEAAm) as the main-chain. This exhibits a higher lower critical solution temperature than an N-isopropylacrylamide main chain. We subsequently measured the transmittance Self-Oscillation of poly[NEAAm-co-Ru(bpy) 3 ] [Ru(bpy) 3 = 4-vinyl-4’-methyl-2,2’-bipyridinebis(2,2’ bipyridine)bis(hexafluorophosphate) ruthenium] solutions comprising three Belousov-Zhabotinsky (BZ) substrates (malonic acid, sodium bromate, and sulfuric acid), under stirring at constant temperature. The soluble-insoluble Self-Oscillation of the polymer solution originated from the different solubility of the Ru(bpy) 3 moiety as a catalyst of the BZ reaction in the reduced and oxidized states. We demonstrated that the Self-oscillating behavior was significantly affected by the initial concentration of the sodium bromate. Moreover, we clarified that the lifetime of the transmittance Self-Oscillation can be predicted from the initial concentration of malonic acid.
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Function and Autonomous Behavior of Self-Oscillating Polymer Systems
Polymers, 2014Co-Authors: Yusuke HaraAbstract:A novel gel undergoes the Belousov-Zhabotinsky (BZ) reaction in strong-acid-free conditions. Under such conditions, the gel can switch the BZ reaction on or off in conventional Self-oscillating gels that undergo Self-Oscillation only in aqueous solutions with strong acids, such as HNO3 or H2SO4. The Self-Oscillation of the polymer chain can be controlled by varying the temperature, owing to its thermoresponsive property. Moreover, the polymer chain undergoes viscosity Self-Oscillations in strong-acid-free conditions. In this review, the direct observation of Self-Oscillations in polymer chains attached to glass or gold surfaces, by using scanning probe microscopy and quartz crystal microbalances with dissipation monitoring, is discussed.
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Soluble-Insoluble Self-Oscillation of a Novel Nonthermoresponsive Polymer Chain Induced by the Belousov-Zhabotinsky Reaction
Advanced Materials Research, 2012Co-Authors: Yusuke Hara, Rumana A. JahanAbstract:In this paper, we investigated the effect ofthetemperatureand the initial concentration of sodium bromateon the soluble-insoluble Self-Oscillation of a nonthermoresponsiveSelf-oscillatingpolymer chain. The polymer chain consisted of Acrylamide (AM) main-chain covalently bonded to Ru (bpy)3as a catalyst of the Belousov-Zhabotinsky (BZ) reaction. The amplitude of the transmittance Self-Oscillation is hardly affected by the concentration of sodium bromate and the temperature.
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Influence of Temperature and the BZ Substrate on Aggregation-Disaggregation Self-Oscillation of a Polymer Chain
Key Engineering Materials, 2011Co-Authors: Yusuke Hara, Rumana A. JahanAbstract:We synthesized a Self-oscillating polymer chain with a negatively charged moiety. The polymer chain caused the aggregation-disaggregation Self-Oscillation under the constant temperature induced by the Belousov-Zhabotinsky (BZ) reaction. In this study, we investigated the influence of temperature and the concentration of sodium bromate on the aggregation-disaggregation Self-Oscillation of the polymer solution (1.0 wt%) in a strongly acidic condition. As a consequence, we clarified that the life-time of the Self-Oscillation increased with decrease in the concentration of sodium bromate. On the other hand, the lifetime of the Self-Oscillation decreased with increase in temperature. In high temperature condition (48 and 60 °C), the amplitude of the Self-Oscillation was significantly inhomogeneous. Moreover, the frequency of the Self-Oscillation increased with increasing temperature. On the other hand, the frequency decreased with increase in the concentration of sodium bromate. This tendency was opposite to that in the acid-free condition and the 2.0 wt% AMPS-containing polymer solution.
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Influence of Initial Substrate Concentration of the Belouzov-Zhabotinsky Reaction on Transmittance Self-Oscillation for a Nonthermoresponsive Polymer Chain
Polymers, 2011Co-Authors: Yusuke Hara, Rumana A. JahanAbstract:We succeeded in causing transmittance Self-Oscillations of a novel Self-oscillating polymer chain induced by the Belouzov-Zhabotinsky (BZ) reaction under constant conditions. The novel polymer chain was composed of a biocompatible and non-thermoresponsive poly-vinylpyrrolidone (PVP) main-chain, covalently-bonded to the ruthenium catalyst (Ru(bpy)3) of the BZ reaction. We investigated the influence of initial substrate concentrations of the three BZ substrates on the transmittance Self-Oscillation of the novel polymer solution. As a result, we demonstrated that the width of the transmittance Self-Oscillation is significantly affected by these initial concentrations. However, the amplitude of the transmittance Self-Oscillation is hardly affected by the BZ substrate conditions. Furthermore, the period of the Self‑Oscillation has a good linear relationship to the concentration of the BZ substrates. Therefore, the period of the Self-Oscillation can be controlled by the selection of the initial concentrations of the BZ substrates.
Tomohiro Taniguchi - One of the best experts on this subject based on the ideXlab platform.
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Indirect excitation of Self-Oscillation in perpendicular ferromagnet by spin Hall effect
Applied Physics Letters, 2017Co-Authors: Tomohiro TaniguchiAbstract:A possibility to excite a stable Self-Oscillation in a perpendicularly magnetized ferromagnet by the spin Hall effect is investigated theoretically. It had been shown that such Self-Oscillation cannot be stabilized solely by the direct spin torque by the spin Hall effect. Here, we consider adding another ferromagnet, referred to as pinned layer, on the free layer. The pinned layer provides another spin torque through the reflection of the spin current. The study shows that the stable Self-Oscillation is excited by the additional spin torque when the magnetization in the pinned layer is tilted from the film plane.
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Self-Oscillation in spin torque oscillator stabilized by field-like torque
Applied Physics Letters, 2014Co-Authors: Tomohiro Taniguchi, Sumito Tsunegi, Hitoshi Kubota, Hiroshi ImamuraAbstract:The effect of the field-like torque on the Self-Oscillation of the magnetization in spin torque oscillator with a perpendicularly magnetized free layer was studied theoretically. A stable Self-Oscillation at zero field is excited for negative β while the magnetization dynamics stops for β = 0 or β > 0, where β is the ratio between the spin torque and the field-like torque. The reason why only the negative β induces the Self-Oscillation was explained from the view point of the energy balance between the spin torque and the damping. The Oscillation power and frequency for various β were also studied by numerical simulation.
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Self Oscillation in spin torque oscillator stabilized by field like torque
arXiv: Mesoscale and Nanoscale Physics, 2014Co-Authors: Tomohiro Taniguchi, Sumito Tsunegi, Hitoshi Kubota, Hiroshi ImamuraAbstract:The Self-Oscillation of the magnetization in a spin torque oscillator (STO) with a perpendicularly magnetized free layer and an in-plane magnetized pinned layer in the absence of an applied magnetic field was studied by numerically solving the Landau-Lifshitz-Gilbert equation. It was pointed out that field-like torque was necessary to realize stable Self-Oscillation in this type of STO at zero field. The numerical simulation at finite temperature showed that the presence of the field-like torque led to a high power with a relatively high Oscillation frequency.
Rumana A. Jahan - One of the best experts on this subject based on the ideXlab platform.
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Soluble-Insoluble Self-Oscillation of a Novel Nonthermoresponsive Polymer Chain Induced by the Belousov-Zhabotinsky Reaction
Advanced Materials Research, 2012Co-Authors: Yusuke Hara, Rumana A. JahanAbstract:In this paper, we investigated the effect ofthetemperatureand the initial concentration of sodium bromateon the soluble-insoluble Self-Oscillation of a nonthermoresponsiveSelf-oscillatingpolymer chain. The polymer chain consisted of Acrylamide (AM) main-chain covalently bonded to Ru (bpy)3as a catalyst of the Belousov-Zhabotinsky (BZ) reaction. The amplitude of the transmittance Self-Oscillation is hardly affected by the concentration of sodium bromate and the temperature.
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Influence of Temperature and the BZ Substrate on Aggregation-Disaggregation Self-Oscillation of a Polymer Chain
Key Engineering Materials, 2011Co-Authors: Yusuke Hara, Rumana A. JahanAbstract:We synthesized a Self-oscillating polymer chain with a negatively charged moiety. The polymer chain caused the aggregation-disaggregation Self-Oscillation under the constant temperature induced by the Belousov-Zhabotinsky (BZ) reaction. In this study, we investigated the influence of temperature and the concentration of sodium bromate on the aggregation-disaggregation Self-Oscillation of the polymer solution (1.0 wt%) in a strongly acidic condition. As a consequence, we clarified that the life-time of the Self-Oscillation increased with decrease in the concentration of sodium bromate. On the other hand, the lifetime of the Self-Oscillation decreased with increase in temperature. In high temperature condition (48 and 60 °C), the amplitude of the Self-Oscillation was significantly inhomogeneous. Moreover, the frequency of the Self-Oscillation increased with increasing temperature. On the other hand, the frequency decreased with increase in the concentration of sodium bromate. This tendency was opposite to that in the acid-free condition and the 2.0 wt% AMPS-containing polymer solution.
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Influence of Initial Substrate Concentration of the Belouzov-Zhabotinsky Reaction on Transmittance Self-Oscillation for a Nonthermoresponsive Polymer Chain
Polymers, 2011Co-Authors: Yusuke Hara, Rumana A. JahanAbstract:We succeeded in causing transmittance Self-Oscillations of a novel Self-oscillating polymer chain induced by the Belouzov-Zhabotinsky (BZ) reaction under constant conditions. The novel polymer chain was composed of a biocompatible and non-thermoresponsive poly-vinylpyrrolidone (PVP) main-chain, covalently-bonded to the ruthenium catalyst (Ru(bpy)3) of the BZ reaction. We investigated the influence of initial substrate concentrations of the three BZ substrates on the transmittance Self-Oscillation of the novel polymer solution. As a result, we demonstrated that the width of the transmittance Self-Oscillation is significantly affected by these initial concentrations. However, the amplitude of the transmittance Self-Oscillation is hardly affected by the BZ substrate conditions. Furthermore, the period of the Self‑Oscillation has a good linear relationship to the concentration of the BZ substrates. Therefore, the period of the Self-Oscillation can be controlled by the selection of the initial concentrations of the BZ substrates.
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Self-Oscillating Behaviors of Negatively Charged Polymer Chain Induced by the Belousov-Zhabotinsky Reaction
Advanced Materials Research, 2011Co-Authors: Yusuke Hara, Rumana A. JahanAbstract:In this paper, we studied the effect of the temperature and the initial concentration of sodium bromate (NaBrO3) on the aggregation-disaggregation Self-Oscillation for a polymer chain. The polymer chain consisted of N-isopropylacrylamide (NIPAAm), Ru catalyst of the BZ reaction and Acrylamide-2-methylpropanesulfonic acid (AMPS) as a solubility control site. The concentration of sodium bromate and the temperature significantly affected the Self-oscillating behavior and the period of the aggregation-disaggregation Self-Oscillation. Moreover, the amplitude of the aggregation-disaggregation Self-Oscillation of the AMPS-containing polymer solution decreased with time. The damping behavior is originating from the increase in the size of the polymer chain. In addition, this study clarified that the period of the Self-Oscillation of the AMPS-containing polymer solution in the strongly acidic condition was significantly shorter than that in the acid-free condition.
Hiroshi Imamura - One of the best experts on this subject based on the ideXlab platform.
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Self-Oscillation in spin torque oscillator stabilized by field-like torque
Applied Physics Letters, 2014Co-Authors: Tomohiro Taniguchi, Sumito Tsunegi, Hitoshi Kubota, Hiroshi ImamuraAbstract:The effect of the field-like torque on the Self-Oscillation of the magnetization in spin torque oscillator with a perpendicularly magnetized free layer was studied theoretically. A stable Self-Oscillation at zero field is excited for negative β while the magnetization dynamics stops for β = 0 or β > 0, where β is the ratio between the spin torque and the field-like torque. The reason why only the negative β induces the Self-Oscillation was explained from the view point of the energy balance between the spin torque and the damping. The Oscillation power and frequency for various β were also studied by numerical simulation.
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Self Oscillation in spin torque oscillator stabilized by field like torque
arXiv: Mesoscale and Nanoscale Physics, 2014Co-Authors: Tomohiro Taniguchi, Sumito Tsunegi, Hitoshi Kubota, Hiroshi ImamuraAbstract:The Self-Oscillation of the magnetization in a spin torque oscillator (STO) with a perpendicularly magnetized free layer and an in-plane magnetized pinned layer in the absence of an applied magnetic field was studied by numerically solving the Landau-Lifshitz-Gilbert equation. It was pointed out that field-like torque was necessary to realize stable Self-Oscillation in this type of STO at zero field. The numerical simulation at finite temperature showed that the presence of the field-like torque led to a high power with a relatively high Oscillation frequency.