The emergence of order in far-from-equilibrium systems is often accompanied by the formation of spatially asymmetric patterns. About 30 years ago, a general mechanism to select a chiral solution by coupling a reaction-diffusion system to an external chiral electric field was proposed by Nicolis and Prigogine [Proc. Natl. Acad. Sci. USA 78, 659 (1981)]. However, no experimental or even numerical evidence in reaction-diffusion systems has been reported yet. Here we report a chiral symmetry-breaking phenomenon in a reaction-diffusion system coupled to a circularly polarized electric field (CPEF). Specifically, we show that the CPEF breaks the zero-rotation chiral symmetry between clockwise and counterclockwise spiral defects and that ordered spiral waves with preferred chirality arise from defect-mediated turbulence. The occurrence of such chiral symmetry breaking can be understood by the competition between spiral defects with opposite chirality.

The influence of circularly polarized electric fields (CPEFs) on the stability of multiarmed spiral waves is investigated. It is shown that CPEFs can change the period of the multiarmed spirals. The average period is an important quantity of multiarmed spiral and it must be larger than a threshold for stable multiarmed spiral. After a counter-rotating CPEF with suitable amplitude and period is applied, the average period of the multiarmed spiral may increase, which stabilizes the multiarmed spiral.

The drift behavior of two-armed spirals induced by periodic advective field and periodic modulation of excitability is investigated. It is shown that the two-armed spirals controlled by periodic advective field and periodic modulation of excitability drift in completely different ways. For periodic advective field, the two tips of the two-armed spiral drift in the same direction and the two-armed spiral is stable. While for periodic modulation of excitability, the two tips drift in the opposite direction and the two-armed spiral splits into two single-armed spirals. Analytical results based on a kinematic theory of rotating spirals in weakly excitable media are consistent with the numerical results.

We investigate the heat conduction in a modified Lorentz gas with freely rotating disks periodically placed along one-dimensional channel. The heat conductivity is dependent on the moment of inertia η of the disks, with a power-law decay when η > 1. By plotting the Poincaré surface of the section, we observe a contraction of phase space over the range of η > 1, which is sensitive to the initial condition. We find that the power-law decay of the heat conductivity is relevant to the mixing phase space. As a possible application, we model the heterostructure by connecting the segments of different η, and predict the analytical results of the temperature profiles and the heat conductivity, which are in good agreement with the numerical ones.

In this paper, the process of unpinning spiral waves from obstacles with Pulses of Radial Electrical Field (PREF) in excitable medium is studied using Barkley model. We used a radial electrical field to simulate the field of an needle electrode placed in the middle of a round obstacle. Numerical results show that the PREF can separate spiral waves from obstacles effectively. With a Single Pulse of Radial Electrical Field (SPREF), spiral waves could be unpinned from an obstacle effectively in a weakly excitable medium, but it could not be unpinned in a strongly excitable medium. The unpinning parameter space of a SPREF is larger than that of a Uniform Electric Field or Anti-tachycardia Pacing. Multiple Pulses of Radial Electrical Field (MPREF) is effective for unpinning in the entire parameter space that spiral waves exist. Comparing with other methods to unpin spiral waves, the PREF method has the advantages of low electric field magnitude, high success rate and large applicating range in the parameters space. And differ from other methods, the success rate of PREF is not sensitive to the phase of the spiral wave on the obstacle. We hope that this method will provide a new idea for clinical treatment for related cardiac diseases.