We present experimental observations on the electrically forced release of spiral waves pinned to unexcitable circular obstacles in the Belosov-Zhabotinsky reaction. When the applied electric current density reaches the necessary current density J(unpin), the spiral tip is detached and subsequently drifts away from the obstacle. J(unpin) is found to increase with the obstacle diameter d. The growth rate ΔJ(unpin)/Δd is much higher for obstacles larger than the free spiral core compared to that for smaller obstacles. The experimental findings are confirmed by numerical simulations using the Oregonator model. The results imply that it is more difficult to release spiral waves pinned to larger obstacles, especially when the obstacle size exceeds that of the free spiral core.
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http://dx.doi.org/10.1103/PhysRevE.89.052902 | DOI Listing |
Chaos
January 2025
Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati 781039, Assam, India.
Spirals are a special class of excitable waves that have its significance in the understanding of cardiac arrests and neuronal transduction. In a theoretical model of the chemical Belousov-Zhabotinsky reaction system, we explore the dynamics of the spatiotemporal patterns that emerge out of competing reaction and diffusion phenomena. By modifying the existing mathematical models of the reaction kinetics, we have been able to explore the explicit effect of hydrogen ion concentration in the system, so as to achieve various regimes of wave activity, from stable spirals to oscillation death.
View Article and Find Full Text PDFSmall
January 2025
CNR NANOTEC Institute of Nanotechnology, Via Monteroni, 73100, Lecce, Italy.
Photonics bound states in the continuum (BICs) are peculiar localized states in the continuum of free-space waves, unaffected by far-field radiation loss. Although plasmonic nano-antennas squeeze the optical field to nanoscale volumes, engineering the emergence of quasi-BICs with plasmonic hotspots remains challenging. Here, the origin of symmetry-protected (SP) quasi-BICs in a 2D system of silver-filled dimers, quasi-embedded in a high-index dielectric waveguide, is investigated through the strong coupling between photonic and plasmonic modes.
View Article and Find Full Text PDFZhonghua Er Ke Za Zhi
February 2025
Pediatric Heart Center, Children's Hospital of Fudan University, National Children's Medical Center, Shanghai, 201102 China.
To analyze the clinical characteristics,diagnosis and treatment of pediatric myocardial infarction (MI) patients with coronary artery lesions (CAL) after Kawasaki disease (KD). Clinical data including baseline characteristics, KD and CAL information, clinical symptoms at MI onset, electrocardiogram (ECG) and imaging findings, MI treatment, and clinical outcomes of 41 MI patients with CAL after KD admitted to the Children's Hospital of Fudan University from January 2017 to August 2024 were analyzed retrospectively. (1) Demographic characteristics: a total of 41 patients were included (36 males and 5 females).
View Article and Find Full Text PDFSci Rep
January 2025
Institute for Open and Transdisciplinary Research Initiatives, Osaka University, Yamadaoka 2-1, Suita, 565-0871, Osaka, Japan.
Heterogeneity is a critical determinant for multicellular pattern formation. Although the importance of microscale and macroscale heterogeneity at the single-cell and whole-system levels, respectively, has been well accepted, the presence and functions of mesoscale heterogeneity, such as cell clusters with distinct properties, have been poorly recognized. We investigated the biological importance of mesoscale heterogeneity in signal-relaying abilities (excitability) in the self-organization of spiral waves of intercellular communications by studying the self-organized pattern formation in a population of Dictyostelium discoideum cells, a classical signal-relaying system model.
View Article and Find Full Text PDFPhys Chem Chem Phys
January 2025
Indian Institute of Technology Guwahati, Assam 781039, India.
The oscillatory Belousov-Zhabotinsky (BZ) reaction is often used for the study of rotating spiral waves that are responsible for life-threatening cardiac arrhythmia. In this work, we explore the influence of a concentration gradient on the dynamics of spiral waves in the BZ-reaction system. Using ion-exchange resin beads, we introduce a gradient of hydrogen ions in a thin layer of BZ gel hosting a spiral wave.
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