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Perturbations of fluid media can give rise to non-equilibrium dynamics, which may, in turn, cause motion of immersed inclusions or tracer particles. We consider perturbations ("activations") that are local in space and time, of a fluid density which is conserved, and study the resulting diffusiophoretic phenomena that emerge at a large distance. Specifically, we consider cases where the perturbations propagate diffusively, providing examples from passive and active matter for which this is expected to be the case. Activations can, for instance, be realized by sudden and local changes in interaction potentials of the medium or by local changes in its activity. Various analytical results are provided for the case of confinement by two parallel walls. We investigate the possibility of extracting work from inclusions, which are moving through the activated fluid. Furthermore, we show that a time-dependent density profile, created via suitable activation protocols, allows for the conveyance of inclusions along controlled and stable trajectories. In contrast, in states with a steady density, inclusions cannot be held at stable positions, reminiscent of Earnshaw's theorem of electrostatics. We expect these findings to be applicable in a range of experimental systems. The phenomena described here are argued to be distinct from other forms of phoresis such as thermophoresis. [ABSTRACT FROM AUTHOR]

It is an essential and challenging task to determine effective conductivity of heterogeneous media. Different from homogeneous media, heterogeneity causes the effective conductivity to behave as a function of frequency under an alternating current (AC). There have been few reports to quantify this function despite the wide applications of AC on heterogeneous media. This Letter derives the analytical form of the effective conductivity as a function of frequency caused by heterogeneity, where the local properties of the media are isotropic and independent of frequency. We use simulation and experiment data to validate our formulation and find that our form shows better agreement with the data than other models. This research provides a practical guidance on the interpretation and application of impedance and conductivity data. [ABSTRACT FROM AUTHOR]

Controlling the frequency of a target wave is an important issue in the dynamics of pattern formation. A common method for controlling is to apply a local disturbance to the media, such as a periodic disturbance source which is not always valid in practice. In the present study, we proposed a method to control the frequency of a target wave by the application of a steady disturbance. We found that the size of a steady disturbance source affects the frequency of the chemical wave by the numerical simulations of three mathematical models. The simulation results are confirmed by theoretical analysis. Our theory and method shed light in the controlling frequency of the oscillatory media. [ABSTRACT FROM AUTHOR]