Semester

Spring

Date of Graduation

2022

Document Type

Dissertation

Degree Type

PhD

College

Eberly College of Arts and Sciences

Department

Chemistry

Committee Chair

Kenneth Showalter

Committee Member

Mark Tinsley

Committee Member

Terry Gullion

Committee Member

Justin Legleiter

Committee Member

Kevin Daly

Abstract

We experimentally and computationally investigate dynamical behaviors in coupled chemical oscillators. These networks of chemical oscillators are created using catalytic Ru(bpy)32+ loaded cation exchange beads submerged in catalyst-free Belousov-Zhabotinsky (BZ) solutions. Various network structures are created by utilizing the photosensitive nature of the Ru(bpy) 32+ catalyst. The response of the oscillators due to light stimuli can be characterized by constructing a phase response curve (PRC). The PRC quantifies the excitatory and inhibitory responses of BZ oscillators due to applied light perturbations as a function of the oscillators' phase. Different initial concentrations of reactants in the BZ reaction solutions can vary the degree in the excitatory and inhibitory regions of the PRC. We explore synchronization in star networks in both excitatory and inhibitory systems. We describe experiments, simulations, and analytical theory that provides a detailed characterization of novel modes of synchronization in chemical oscillator networks. Synchronization of peripheral oscillators coupled through a hub oscillator is exhibited at coupling strengths leading to novel synchronization of the hub with the peripheral oscillators. The heterogenous peripheral oscillators have different phase velocities that give rise to divergence; however, the perturbation from the hub acts to realign the phases by delaying the faster oscillators more than the slower oscillators. A theoretical analysis provides insights into the mechanism of the synchronization. Computational studies into extreme events are investigated using a modified four-variable Oregonator model, which describes the BZ system. Extreme events are ubiquitous throughout biological, natural, social, and financial systems. Examples of such events are epileptic seizures, earthquakes, riots, and stock market crashes. These events are considered rare excursions from the normal dynamics of a system, which are considered aperiodic in occurrence. The consequences that these events have on the system makes the development of models and experimental methods to study these events important. We will describe the appearance of extreme events in the Oregonator system using instantaneous and time-delayed coupling. We will also discuss a proposed mechanism for the sudden appearance of extreme events in both instantaneous and time-delayed coupling.

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