Majorana-like Zero Modes in Kekulé Distorted Sonic Lattices.

Topological phases have recently been realized in bosonic systems. The associated boundary modes between regions of distinct topology have been used to demonstrate robust waveguiding, protected from defects by the topology of the surrounding bulk. A related type of topologically protected state that is not propagating but is bound to a defect has not been demonstrated to date in a bosonic setting. Here we demonstrate numerically and experimentally that an acoustic mode can be topologically bound to a vortex fabricated in a two-dimensional, Kekulé-distorted triangular acoustic lattice. Such lattice realizes an acoustic analog of the Jackiw-Rossi mechanism that topologically binds a bound state in a p-wave superconductor vortex. The acoustic bound state is thus a bosonic analog of a Majorana bound state, where the two valleys replace particle and hole components. We numerically show that it is topologically protected against arbitrary symmetry-preserving local perturbations, and remains pinned to the Dirac frequency of the unperturbed lattice regardless of parameter variations. We demonstrate our prediction experimentally by 3D printing the vortex pattern in a plastic matrix and measuring the spectrum of the acoustic response of the device. Despite viscothermal losses, the measured topological resonance remains robust, with its frequency closely matching our simulations.

Sound Insulation and Reflection Properties of Sonic Crystal Barrier Based on Micro-Perforated Cylinders.

A sonic crystal barrier, consisting of empty micro-perforated cylindrical shells, was built on the campus at the Universitat Politècnica de València in 2011 and characterised by using a non-standardised measurement technique. In this paper, the sonic crystal barrier, upgraded with rubber crumb inside the micro-perforated cylindrical shells, was characterised by using standardised measurement techniques according to EN 1793-5 and EN 1793-6. As a result of the characterisation, sound insulation properties of the barrier were shown to be a combination of the absorptive properties of the individual building units and the reflective properties of their periodic distribution. In addition, its performance was compared with a similar barrier consisting of rigid polyvinyl chloride (PVC) cylinders, which was recently characterised using the same standardised techniques. In comparison with the barrier based on PVC cylinders, the barrier investigated here produced a broadband enhancement of the sound insulation and lower reflection indices in the targeted frequency range. It was also shown that the influence of leakage under the barrier and the width of the temporal window on sound insulation was negligible. While EN 1793-5 and 1793-6 allow a direct comparison of the performance of different noise barriers, the applicability to this new type of barriers requires further investigation.

Influence of expectations plus mobilization with movement in patient with lateral epicondylalgia: a pilot randomized controlled trial.

The aim of this study was to determine the influence of expectations plus mobilization with movement (MWM) in kinesiophobia, perceived disability and sensorimotor variables in patients with lateral epicondylalgia. A pilot randomized controlled trial in 24 patients with lateral epicondylalgia was conducted. Perceived pain, pain-free grip strength, pressure pain detection threshold, kinesiophobia measured with the short version of Tampa Scale of Kinesiophobia, perceived disability of the upper limb measured with disability of the arm, hand and shoulder questionnaire, and perceived disability specifically for the elbow joint measured with patient-rating tennis elbow evaluation, and also satisfaction were assessed. Participants were randomized to receive written instructions in order to create positive expectations regarding the technique in one group (n=12) or neutral expectations in the other one (n=12). All patients were treated for three sessions with the MWM technique. Measures were recorded before and after treatment. The effect size was calculated by Rosenthal "r" for nonparametrical tests. There were no significant statistical differences (P>0.05) between groups after receiving the treatment for none of the physical analyzed variables. The Wilcoxon test showed statistically significant changes in kinesiophobia (Z=-2.278, r=0.47, P=0.023) and perceived disability (Z= -2.934, r=0.61, P=0.003) within positive expectations group. In conclusion this pilot study shows that a positive expectation almost given in a sealed envelope before treatment plus MWM produced changes in kinesiophobia and perceived disability in the immediate term, in patients with lateral epicondylalgia.

Noise control by sonic crystal barriers made of recycled materials.

A systematic study of noise barriers based on sonic crystals made of cylinders that use recycled materials like absorbing component is reported here. The barriers consist of only three rows of perforated metal shells filled with rubber crumb. Measurements of reflectance and transmittance by these barriers are reported. Their attenuation properties result from a combination of sound absorption by the rubber crumb and reflection by the periodic distribution of scatterers. It is concluded that the porous cylinders can be used as building blocks whose physical parameters can be optimized in order to design efficient barriers adapted to different noisy environments.

Homogenization of two-dimensional clusters of rigid rods in air.

The scattering of sound waves by circular-shaped clusters consisting of two-dimensional distributions of rigid cylinders in air is studied in the low-frequency limit (homogenization) both theoretically and experimentally. Analytical formulas for the effective density and sound speed are obtained in the framework of multiple scattering. Here, an experimental demonstration is reported in which a cluster of wooden rods acoustically behaves as a cylinder of argon gas. Moreover, evidence is presented indicating the validity of the homogenization in this cluster at frequencies lower than 3 kHz, which corresponds to a wavelength that is only 4 times the parameter of the embedded lattice and is a quarter of the cluster's diameter.