Emergent reaction-diffusion phenomena in capillary tubes

Pressure and Light Multi-Physics Fields Comodulate the Multi-Length Scales of Chemical Wave Propagation in Diffusion-Fed Gels

During plant growth, the combined effects of multi-physics fields such as light, temperature, and material concentration create a complex multi-length scales phenomenon. However, the mechanism of multi-physical field interactions on biological multi-length scales has not been thoroughly investigated. In this paper, an open diffusion-fed system is constructed by coupling gels with a Belousov-Zhabotinsky (BZ) chemical reaction system. The multi-length scales propagation of chemical waves in the gel system under the combined effect of multi-physical fields such as light (I) and pressure (ΔP) is investigated. It is found that when 85 Pa ≤ ΔP ≤ 100 Pa or 200 μW·cm^-2 ≤ I ≤ 300 μW·cm^-2, the complexity of the multi-length scales periodic structure of chemical waves shows a nonlinear change with increasing light intensity or pressure. Beyond this range, the complexity of the chemical wave multi-length scales periodic structure decreases linearly on enhancing the light intensity or increasing the pressure.

Excitability Modulation of Oscillating Media in 3D-Printed Structures

Excitation and oscillation are central to living systems. For excitable systems, which can be brought into oscillation by an external stimulus, the excitation threshold is a crucial parameter. This is evident for neurons, which only generate an action potential when exposed to a sufficiently high concentration of excitatory neurotransmitters, which may only be achieved when multiple presynaptic axons deliver their action potential simultaneously to the synaptic cleft. Dynamic systems composed of relatively simple chemicals are of interest because they can serve as a model for physiological processes or can be exploited to implement chemical computing. With these applications in mind, we have studied the properties of the oscillatory Belousov-Zhabotinsky (BZ) reaction in 3D-printed reaction vessels with open channels of different dimensions. It is demonstrated that the channel geometry can be used to modulate the excitability of the BZ medium, switching a continuously oscillating medium to an excitable medium. Because large networks of channel-connected reaction wells of different depth can easily be fabricated by 3D printing, local excitability modulation could be built into the structure of the reaction vessel itself, opening the way to more extensive experimentation with networks of chemical oscillators.

Instabilities of a three-dimensional localized spot

We investigate the behavior of localized spots in three spatial dimensions in a model two-variable system describing the Belousov-Zhabotinsky reaction in water-in-oil microemulsion. We find three types of instabilities: splitting of a single spot (i) into two spots, (ii) into a torus, and (iii) into an unstable shell that splits almost immediately to six or eight new spots.

Propagation failures, breathing fronts, and nonannihilation collisions in the ferroin-bromate-pyrocatechol system

The emergence of propagating pulses was investigated with the photosensitive ferroin-bromate-pyrocatechol reaction in capillary tubes, in which various interesting spatiotemporal behaviors such as propagation failure, breathing fronts, and transitions between propagating pulses and fronts have been observed. Rather than a mutual annihilation, the collision of a propagating pulse and a growing front forces the front to recede gradually. A phase diagram in the pyrocatechol-bromate concentration space shows that the pulse instabilities take place throughout the conditions at which the system generates wave activities, suggesting that the presence of coupled autocatalytic feedbacks may facilitate the onset of pulse instabilities.

Wound angiogenesis as a function of tissue oxygen tension: a mathematical model

Wound healing represents a well orchestrated reparative response that is induced by injuries. Angiogenesis plays a central role in wound healing. In this work, we sought to develop the first mathematical model directed at addressing the role of tissue oxygen tension on cutaneous wound healing. Key components of the developed model include capillary tips, capillary sprouts, fibroblasts, inflammatory cells, chemoattractants, oxygen, and the extracellular matrix. The model consists of a system of nonlinear partial differential equations describing the interactions in space and time of these variables. The simulated results agree with the reported literature on the biology of wound healing. The proposed model represents a useful tool to analyze strategies for improved healing and generate a hypothesis for experimental testing.