Suchergebnisse

Abstract
ContextThere is an increasing awareness that feral cats play a key role in driving the ongoing decline of small mammals across northern Australia; yet, the factors that control the distribution, abundance and behaviour of feral cats are poorly understood. These key knowledge gaps make it near-impossible for managers to mitigate the impacts of cats on small mammals.
AimsWe investigated the environmental correlates of feral cat activity and abundance across the savanna woodlands of Melville Island, the larger of the two main Tiwi Islands, northern Australia.
MethodsWe conducted camera-trap surveys at 88 sites, and related cat activity and abundance to a range of biophysical variables, either measured in the field or derived from remotely sensed data.
Key resultsWe found that feral cat activity and abundance tended to be highest in areas characterised by severe disturbance regimes, namely high frequencies of severe fires and high feral herbivore activity.
ConclusionsOur results have contributed to the growing body of research demonstrating that in northern Australian savanna landscapes, disturbance regimes characterised by frequent high-severity fires and grazing by feral herbivores may benefit feral cats. This is most likely to be a result of high-severity fire and grazing removing understorey biomass, which increases the time that the habitat remains in an open state in which cats can hunt more efficiently. This is due to both the frequent and extensive removal, and longer-term thinning of ground layer vegetation by severe fires, as well as the suppressed post-fire recovery of ground layer vegetation due to grazing by feral herbivores.
ImplicationsManagement that reduces the frequency of severe fires and the density of feral herbivores could disadvantage feral cat populations on Melville Island. A firm understanding of how threatening processes interact, and how they vary across landscapes with different environmental conditions, is critical for ensuring management success.

Trabajo presentado al: "4th International Conference on Metamaterials, Photonic Crystals and Plasmonics" celebrado en Sharjah (UAE) del 18 al 22 de Marzo de 2013. ; Dielectric nanostructures composed of high-refractive index materials show very intense magnetic resonances that make them ideal candidates to interact with magnetic emitters. When two of these dielectric nanoantennas are located in close proximity, the electric and magnetic modes can interact generating the ability to control the properties of light scattering as well as to discriminate the polarization and nature of the emission from a single emitter. We analyze here the optical response of two Si spheres forming a dielectric gap-nanoantenna. ; Financial support from the ETORTEK project "nanoiker" of the Dept. of Industry of the Government of the Basque Country and from the Spanish Ministerio de Ciencia e Innovación through grant FIS2010-21984 are acknowledged. ; Peer reviewed

A complementary split ring resonator (CSRR)-based metallic layer is proposed as a route to mimic surface plasmon polaritons. A numerical analysis of the textured surface is carried out and compared to previous prominent topologies such as metal mesh, slit array, hole array, and Sievenpiper mushroom surfaces, which are studied as well from a transmission line perspective. These well-documented geometries suffer from a narrowband response, alongside, in most cases, metal thickness constraint (usually of the order of λ/4) and non-subwavelength modal size as a result of the large dimensions of the unit cell (one dimensions is at least of the order of λ/2). All of these limitations are overcome by the proposed CSRR-based surface. Besides, a planar waveguide is proposed as a proof of the potential of this CSRR-based metallic layer for spoof surface plasmon polariton guiding. Fundamental aspects aside, the structure under study is easy to manufacture by simple PCB techniques and it is expected to provide good performance within the frequency band from GHz to THz. ; This work has been supported by Spanish Government and E.U. FEDER funds under contracts Consolider "Engineering Metamaterials" CSD2008-00066 and TEC2008-06871-C02-01, and by the US Air Force Office of Scientific Research (AFOSR Award FA 9550-07-1-0441). M. Navarro-Cía also acknowledges financial support from grant FPI of MICINN (project no. TEC2005-06923-C03-01).