A three-dimensional active cloaking strategy for the Helmholtz equation that exploits the symmetry of the platonic solids.

An active cloaking strategy for the scalar Helmholtz equation in three dimensions is developed by placing active sources at the vertices of Platonic solids. In each case, a "silent zone" is created interior to the Platonic solid and only the incident field remains in a defined region exterior to this zone. This distribution of sources ensures that implementation of the cloaking strategy is efficient: once the multipole source amplitudes at a single source location are determined, the other amplitudes are calculated by multiplying the multipole source vector by a rotation matrix.

Asymptotics of the meta-atom: plane wave scattering by a single Helmholtz resonator.

Using a combination of multipole methods and the method of matched asymptotic expansions, we present a solution procedure for acoustic plane wave scattering by a single Helmholtz resonator in two dimensions. Closed-form representations for the multipole scattering coefficients of the resonator are derived, valid at low frequencies, with three fundamental configurations examined in detail: the thin-walled, moderately thick-walled and extremely thick-walled limits. Additionally, we examine the impact of dissipation for extremely thick-walled resonators, and also numerically evaluate the scattering, absorption and extinction cross-sections (efficiencies) for representative resonators in all three wall thickness regimes.

Deeply subwavelength giant monopole elastodynamic metacluster resonators.

The giant monopole resonance is a well-known phenomenon, employed to tune the dynamic response of composite materials comprising voids in an elastic matrix which has a bulk modulus much greater than its shear modulus, e.g. elastomers.

Food insecurity as experienced by New Zealand women and their children.

Food insecurity, defined as uncertainty in reliably accessing adequate quantities of nutritious food, is an issue for many families and children, including in New Zealand. Drawing on the experiences of mothers, this study explored the nature, causes and impact of food insecurity for their families. Semi-structured face-to-face interviews conducted with six female sole-parents were complemented with food insecurity data from the NZ Health Survey and Youth2000 surveys.