Faculty Publications
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Item Dynamics of Chemical Excitation Waves Subjected to Subthreshold Electric Field in a Mathematical Model of the Belousov-Zhabotinsky Reaction(Springer Science and Business Media B.V., 2022) Sebastian, A.; Amrutha, S.V.; Punacha, S.; Shajahan, T.K.We present a numerical study of the dynamics of spiral waves in a weak external electric field, using the Oregonator model of the Belousov-Zhabotinky (BZ) reaction. Both free and pinned spiral waves are studied in two types of electric fields: unidirectional (DC) and Circularly Polarised Electric Field (CPEF). Both free spirals and pinned spiral waves rotate faster in the DC field. The CPEF can help a free spiral to be spatially confined. A pinned spiral period can be controlled by varying the period of the CPEF. Both DC and CPEF can unpin the pinned spiral wave, but the minimum electric field required to unpin is much less with CPEF compared to DC. Thus, CPEF is more energy efficient to unpin a pinned spiral wave. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.Item Scanning and resetting the phase of a pinned spiral wave using periodic far field pulses(Institute of Physics Publishing helen.craven@iop.org, 2016) Shajahan, T.K.; Berg, S.; Luther, S.; Krinski, V.; Bittihn, P.Spiral waves in cardiac tissue can pin to tissue heterogeneities and form stable pinned waves. These waves can be unpinned by electric stimuli applied close to the pinning center during the vulnerable window of the spiral. Using a phase transition curve (PTC), we quantify the response of a pinned wave in a cardiac monolayer to secondary excitations generated electric field pulses. The PTC can be used to construct a one-dimensional map that faithfully predicts the pinned wave's response to periodic field stimuli. Based on this 1D map, we predict that pacing at a frequency greater than the spiral frequency, over drive pacing, leads to phase locking of the spiral to the stimulus, which hinders unpinning. In contrast, under drive pacing can lead to scanning of the phase window of the spiral, which facilitates unpinning. The predicted mechanisms of phase scanning and phase locking are experimentally tested and confirmed in the same monolayers that were used to obtain the PTC. Our results have the potential to help choose optimal parameters for low energy antifibrillation pacing schemes. © 2016 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.Item Effect of electric field chirality on the unpinning of chemical waves in the Belousov–Zhabotinsky reaction(Elsevier Ltd, 2024) Sebastian, A.; Sibeesh, P.; Amrutha, S.V.; Punacha, S.; Shajahan, T.K.We investigate the unpinning of chemical spiral waves attached to obstacles in the Belousov–Zhabotinsky (BZ) reaction using a Circularly Polarized Electric Field (CPEF). The unpinning is quantified by measuring the angle at which the spiral leaves the obstacle. Previously, we had found that the wave can unpin when the electric field along the direction of the spiral is above a threshold value. When we apply a DC field, this condition can be satisfied for a range of spiral phases, which we call the unpinning window (UW). With a CPEF, this UW moves either along the direction of the spiral (co-rotating) or against the spiral (counter-rotating). We find that when the field is co-rotating, it can take several rotations of the spiral to get unpinned. With a counter-rotating field, the spiral always unpins during the first rotation. We analyze how unpinning with CPEF depends on the electric field's relative speed, chirality, and strength using experiments and the Oregonator model. Our work helps to understand and control chemical waves. © 2024 Elsevier Ltd