Low-frequency signal transmission in one-way coupled bistable systems subject to a high-frequency force is studied. Two cases including the high-frequency force on all sites (case 1) and only on the first site (case 2) are considered. In these two cases, vibrational resonance induced by the high-frequency force can play an active role to effectively improve the signal transmission, and undamped signal transmission can be found in a broad parameter region. The combinative action of injected low-frequency signal, high-frequency driving, and coupling is of importance. Our findings suggest that high-frequency signal could be properly used in low-frequency signal transmission, and especially the implementation of high-frequency force simply on the first site for case 2 is meaningful for its simplicity and high efficiency.

In this work, we investigate gradient coupling effect on oscillation death in a ring of N delay-coupled oscillators. We find that the gradient coupling monotonically reduces the domain of death island in the parameter space of the diffusive coupling and time delay, and thus the death island can be completely eliminated once the gradient coupling strength exceeds a certain threshold, whose value is found to be a constant if N is sufficiently large. For two special cases, a ring with zero gradient coupling and a one-way ring for identical diffusive and gradient couplings, all previous results in the literature are recovered. In particular, for the one-way ring, a size effect of N is discovered, which indicates that under this situation the death can always be eliminated if N is above a critical N(max). All the described results are proved to hold generally in coupled oscillator systems.

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The dynamics in an overdamped bistable system subject to the action of two periodic forces (assuming their frequencies are ω and Ω, and amplitudes are A and B, respectively) is studied. For the usual vibrational resonance, the nonmonotonic dependence of signal output of the low frequency ω on the change of B for a fixed Ω, the condition Ω≫ω is always assumed in all previous studies. Here, removing this restriction, we find that a resonant behavior can extensively occur with respect to the changes of both the frequency Ω and amplitude B. Especially, the resonance becomes stronger when Ω is chosen such that it is exactly in frequency resonance with ω. This combinative behavior, called frequency-resonance-enhanced vibrational resonance, is of great interest and may shed an improved light on our understanding of the dynamics of nonlinear systems subject to a biharmonic force.

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Shape-oscillations and synchronization are intriguing phenomena in many biological and physical systems. Here, we report the rhythmic mechanical oscillations and synchronization of aniline oil droplets on a water phase, which is induced by Marangoni convection during transfer of the solute. The repetitive increase and decrease in the surface concentration in the vicinity of the contact line leads to the oscillations of droplets through an imbalance in surface tensions. The nature of the oscillations depends on the diameter of the droplet, the depth of the bulk aqueous phase, and the concentration of the aqueous phase. A numerical simulation reproduces the essential behaviors of active oscillations of a droplet. Droplets sense each other through a surface tension gradient and advection, and hydrodynamic coupling in the bulk solution induces the synchronization of droplet oscillations.

MicroRNAs (miRNAs) are endogenous noncoding RNAs which participate in diverse biological processes in animals and plants. They are known to join together with transcription factors and downstream gene, forming a complex and highly interconnected regulatory network. To recognize a few overrepresented motifs which are expected to perform important elementary regulatory functions, we constructed a computational model of miRNA-mediated feedforward loops (FFLs) in which a transcription factor (TF) regulates miRNA and targets gene. Based on the different dynamic interactions between miRNA and TF on gene expression, four possible structural topologies of FFLs with two gate functions (AND gate and OR gate) are introduced. We studied the dynamic behaviors of these different motifs. Furthermore, the relationship between the response time and maximal activation velocity of miRNA was investigated. We found that the curve of response time shows nonmonotonic behavior in Co1 loop with OR gate. This may help us to infer the mechanism of miRNA binding to the promoter region. At last we investigated the influence of important parameters on the dynamic response of system. We identified that the stationary levels of target gene in all loops were insensitive to the initial value of miRNA.

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