Mode transitions in a model reaction-diffusion system driven by domain growth and noise

Pattern formation in many biological systems takes place during growth of the underlying domain. We study a specific example of a reaction–diffusion (Turing) model in which peak splitting, driven by domain growth, generates a sequence of patterns. We have previously shown that the pattern sequences which are presented when the domain growth rate is sufficiently rapid exhibit a mode-doubling phenomenon. Such pattern sequences afford reliable selection of certain final patterns, thus addressing the robustness problem inherent of the Turing mechanism. At slower domain growth rates this regular mode doubling breaks down in the presence of small perturbations to the dynamics. In this paper we examine the breaking down of the mode doubling sequence and consider the implications of this behaviour in increasing the range of reliably selectable final patterns

HOI versus HOIO Selectivity of a Molten-type AgI Electrode

AgI electrode is often applied not only to det. iodine concn. but also to follow oscillations in the weakly acidic medium of the Bray-​Liebhafsky and Briggs-​Rauscher reactions where it partly follows the hypoiodous acid (HOI) concn. It is known that HOI attacks its matrix in the corrosion reaction: AgI + HOI + H+ = Ag+ + I2 + H2O and the AgI electrode measures the silver ion concn. produced in that reaction. The signal of the electrode can be the basis of sensitive and selective HOI concn. measurements only supposing that an analogous corrosive reaction between AgI and iodous acid (HOIO) can be neglected. To prove that assumption, the authors calibrated a molten-​type AgI electrode for I-​, Ag+, HOI, and HOIO in 1 M sulfuric acid and measured the electrode potential in the disproportionation of HOIO, which is relatively slow in that medium. Measured and simulated electrode potential vs. time diagrams showed good agreement, assuming that the electrode potential is detd. by the HOI concn. exclusively and the contribution of HOIO is negligible. An independent and more direct expt. was also performed giving the same result. HOIO was produced with a new improved recipe. Conclusion: an AgI electrode can be applied to measure the HOI concn. selectively above the so-​called soly. limit potential.SCOPUS: ar.jinfo:eu-repo/semantics/publishe