Transient complex oscillations in a closed chemical system with coupled autocatalysis

Dynamical analysis of a periodically forced chaotic chemical oscillator

We present a comprehensive dynamical analysis of a chaotic chemical model referred to as the autocatalator, when subject to a periodic administration of one substrate. Our investigation encompasses the dynamical characterization of both unforced and forced systems utilizing isospikes and largest Lyapunov exponents-based parameter planes, bifurcation diagrams, and analysis of complex oscillations. Additionally, we present a phase diagram showing the effect of the period and amplitude of the forcing signal on the system's behavior. Furthermore, we show how the landscapes of parameter planes are altered in response to forcing application. This analysis contributes to a deeper understanding of the intricate dynamics induced by the periodic forcing of a chaotic system.

Identification of the best medium for experiments on chemical computation with Belousov–Zhabotinsky reaction and ferroin-loaded Dowex beads

Our study is focused on identification of the best medium for future experiments on information processing with Belousov–Zhabotinsky reaction proceeding in Dowex beads with immobilized catalyst inside. The optimum medium should be characterized by long and stable nonlinear behavior, mechanical stability and should allow for control with electric potential. We considered different types of Dowex ion-exchange resins, bead distributions and various initial concentrations of substrates: malonic acid and 1,4-cyclohexanedione. The electric potential on platinum electrodes, stabilized by a potentiostat is used to control medium evolution. A negative electric potential generates activator species HBrO2 on the working electrode according to the reaction: BrO3−  + 2e−  + 3H+  → HBrO2 + H2O, while positive electric potential attracts inhibitor species Br− to the proximity of it. We study oscillation amplitude and period stability in systems with ferroin loaded Dowex 50W-X2 and Dowex 50W-X8 beads during experiments exceeding 16 h. It has been observed, that the above mentioned resins generate a smaller number of CO2 bubbles close to the beads than Dowex 50W-X4, which makes Dowex 50W-X2 and Dowex 50W-X8 more suitable for applications in chemical computing. We report amplitude stability, oscillation frequency, merging and annihilation of travelling waves in a lattice of Dowex 50W-X8 beads (mesh size 50–100) in over 19 h long experiments with equimolar solution of malonic acid and 1,4-cyclohexanedione. This system looks as a promising candidate for chemical computing devices that can operate for a day.

Two staged pattern formation and spontaneous wave breakup in the ferroin-bromate-pyrocatechol reaction

This report investigated nonlinear spatiotemporal behavior in the ferroin-bromate-pyrocatechol reaction, in which two stages of wave formation, separated by several hours of quiescent period, were observed. In addition to its great photosensitivity, the second stage wave activity could undergo spontaneous breakups at broad reaction conditions. Analysis based on one-dimensional space-time plot suggests that the breakup was caused by propagation slowdown of the leading wave. Due to the presence of coupled autocatalytic reactions, the propagation of the initial and the second stage waves exhibited different and subtle responses to the variation of the concentration of each reagent.

Nonlinear Dynamics in the Uncatalyzed Bromate–Pyrocatechol Reaction

Spontaneous chemical oscillations are uncovered in the uncatalyzed bromate–pyrocatechol reaction conducted in a stirred batch reactor. Phase diagrams show that the oscillatory behavior is more sensitive to the ratio of [bromate]/[pyrocatechol] than their actual concentrations. The long induction time observed in the system is insensitive to the initial presence of brominated pyrocatechol species. Quenching experiments illustrate that the studied chemical oscillator is both bromide and radical controlled. In addition, this new uncatalyzed bromate oscillator exhibits both light-induced and light-quenched oscillatory behaviors. Preliminary mechanistic characterization with UV/vis absorption method and mass spectrometry suggests the formation of bromo-1,2-benzoquinone through the reaction between pyrocatechol and bromine.