Some characteristics of thin shear layers in homogeneous turbulent flow.

Tomographic particle image velocimetry measurements of homogeneous isotropic turbulence that have been made in a large mixing tank facility at Cambridge are analysed in order to characterize thin highly sheared regions that have been observed. The results indicate that such regions coincide with regions of high enstrophy, dissipation and stretching. Large velocity jumps are observed across the width of these regions. The thickness of the shear layers seems to scale with the Taylor microscale, as has been suggested previously. The results discussed here concentrate on examining individual realizations rather than statistics of these regions.

Strong plasmonic enhancement of photovoltage in graphene.

From the wide spectrum of potential applications of graphene, ranging from transistors and chemical sensors to nanoelectromechanical devices and composites, the field of photonics and optoelectronics is believed to be one of the most promising. Indeed, graphene's suitability for high-speed photodetection was demonstrated in an optical communication link operating at 10 Gbit s(-1). However, the low responsivity of graphene-based photodetectors compared with traditional III-V-based ones is a potential drawback. Here we show that, by combining graphene with plasmonic nanostructures, the efficiency of graphene-based photodetectors can be increased by up to 20 times, because of efficient field concentration in the area of a p-n junction. Additionally, wavelength and polarization selectivity can be achieved by employing nanostructures of different geometries.