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When Noise Is a Blessing and Not an Annoyance
Stochastic Resonance in a Spatially Extended Chemical System
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What is Stochastic Resonance (SR)?
SR is a mechanism through which a weak otherwise undetectable periodic signal becomes detectable What is Spatiotemporal Stochastic Resonance (STSR)? Spatial excitation patterns in an extended medium display resonance-type dependence on the noise-variance with the patterns being optimal at intermediate noise level
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General introduction to SR
Outline General introduction to SR Demonstration Examples The Chemical System – Belousov Zhabotinsky Reaction Demonstration Chemical reactions Mechanism (Oregonator Model) Simplified mechanism (Tyson-Fife scaling) Results STSR with colored noise – single wave STSR with white noise – single wave STSR with white noise – wave trains
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Photosensitive Belousov-Zhabotinsky-reaction
Components: NaBrO3 H2SO4 Malonic acid/Bromomalonic acid Ru(Bpy)32+ catalyst Key intermediates: HBrO2 Br- Activator Inhibitor Ru(Bpy)32+ Bromomalonic acid Br- l = 460 nm
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Excitability Light intensity
Photosensitive BZ-reaction Excitability Light intensity Steady state Excitable Oscillatory More light Less light
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Periodic signal Threshold Noise + Signal Events: Fourier spectrum:
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A little history Proposed explanation of the periodic recurrences of the Earth’s ice ages (1981) First experimental evidence: in a noise-driven electronic circuit (Schmitt trigger) Improved visual perception Crayfish mechanoreceptor (hair cell)
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Improve visual perception
Enrico Simonotto
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Crayfish mechanoreceptor (hair cell)
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Tyson-Fife Scaling of the Oregonator Model
(modified to account for photosensitivity)
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Belousov-Zhabotinsky Reaction
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Excitability Light intensity Photosensitive BZ-reaction
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Experimental Setup
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low excitability - no wave support
high excitability (dark) Excitability 255 100% noise low excitability - no wave support (bright) sub-excitable
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Experimental Results Noise level = 0 Noise level = 30%
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SNR as a function of cluster size
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Numerical Results Noise level = 0 Noise level = 30% Noise level = 60%
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Where to go? Refresh rate dependence
Cluster size/shape/density dependence Truly white noise Time series for each cluster
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Acknowledgement Jichang Wang Kenneth Showalter Eugene Mihaliuk
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