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West Africa has experienced increases in cultivated lands over the last 50 years in order to meet increasing demand from rapidly growing populations. Most countries in the region still depend on agriculture as an important part of the economy. In most countries however agricultural productivity is low leading to food insecurity and poor performance of the whole sector. In the Maputo declaration of 2004 the African governments committed to spending at least 10% of the national budget resources on a process of revitalizing the agricultural sector. For proper planning and investment strategies as well as policies to direct these for different crops, cropping systems and agricultural markets recent landuselandcover maps are necessary. Currently the most recent landcover set available is GLC2000 with 1 km resolution. The present work is therefore exploring the use of free available current images at higher resolutions to provide recent landuse maps for the ECOWAS countries of West Africa. 8-day composites of 500m resolution Moderate Resolution Imaging Spectroradiometer (MODIS) imagery of the year 2006 were used to produce a land cover map of West Africa. The percentage of cropland in each land cover classes were estimated with the combination of high resolution images (LANDSAT ETM 7), and very high resolution images (Quickbird and IKONOS acquired between 2000 and 2007 for several sites in West Africa as well as high resolution images digitized from Google earth). The preliminary results show different proportions of croplands in the different landcover classes. For instance, closed deciduous woodland of the coastal region of West Africa has between 10-15% cultivated land while 20-35% of croplands were found in the savanna shrubland. The approach demonstrates a simple and cost effective way of mapping croplands using MODIS data. ; Peer Review

The sale of wild animals, including protected species, may relate to regional differences in socio-politics, culture, and economic development. A better understanding of how these factors affect the illegal wildlife trade is therefore necessary to optimize the deployment of conservation resources and policing. To evaluate these factors in relation to the trade in protected animals as pets, we surveyed China's popular consumer-to-consumer website, Taobao.com (analogous to Ebay), and found that over 70,000 individual live parrots and turtles (totaling 46 and 49 protected species, respectively) were sold in just 150 days. Using analyses that attempted to account for species richness estimation and autocorrelation effects, we identified that regional economics promoted the occurrence and extent of pet sales. The provenance of these traded animals was ambiguous, but their vast numbers raise two concerns: if any proportion was sourced illegally from the wild, it is of conservation concern; whereas any bred illegally in captivity raise animal welfare concerns, because this would be unregulated. In the context of rapid economic development in China, it is thus important to reform the legislation that currently allows these commonly traded pet species to slip through the net intended to police animal welfare and illegal animal trading.

11 pags. 5 figs. -- Open Access funded by Creative Commons Atribution Licence 3.0 ; Complementing the research of surface plasmon polariton vortices for Archimedean spiral structures grooved in gold platelets, we here study the analogous positive structure of an Archimedean spiral consisting of bent gold nanorods. We consider spirals of two different sizes, for which we perform numerical calculations with the boundary element method. For a micrometer-sized metallic structure we show that the scattered electric field forms a vortex in the centre of the spiral. When the spiral is illuminated by orbital angular momentum light, the topological charge of the vortex can be controlled. For a nanometer-sized plasmonic Archimedean spiral we find that the response to optical excitation is governed by several resonances. When the nanostructure is excited by orbital angular momentum light, different resonances appear compared to the excitation with plane waves. Our results highlight that the distinct architecture of the Archimedean spiral responds in a unique way to the excitation with orbital angular momentum light. ; JMF and DER are grateful for financial support from the COST Action MP1403 Nanoscale Quantum Optics within a STSM. XX thanks the support from the Lee Family Scholars. This work is part-funded by the European Regional Development Fund through the Welsh Government.

11 pags. 5 figs. -- Open Access funded by Creative Commons Atribution Licence 3.0 ; Complementing the research of surface plasmon polariton vortices for Archimedean spiral structures grooved in gold platelets, we here study the analogous positive structure of an Archimedean spiral consisting of bent gold nanorods. We consider spirals of two different sizes, for which we perform numerical calculations with the boundary element method. For a micrometer-sized metallic structure we show that the scattered electric field forms a vortex in the centre of the spiral. When the spiral is illuminated by orbital angular momentum light, the topological charge of the vortex can be controlled. For a nanometer-sized plasmonic Archimedean spiral we find that the response to optical excitation is governed by several resonances. When the nanostructure is excited by orbital angular momentum light, different resonances appear compared to the excitation with plane waves. Our results highlight that the distinct architecture of the Archimedean spiral responds in a unique way to the excitation with orbital angular momentum light. ; JMF and DER are grateful for financial support from the COST Action MP1403 Nanoscale Quantum Optics within a STSM. XX thanks the support from the Lee Family Scholars. This work is part-funded by the European Regional Development Fund through the Welsh Government.

7 pags., 6 figs., -- Open Access funded by Creative Commons Atribution Licence 4.0 ; The design of achromatic optical components requires materials with high transparency and low dispersion. We show that although metals are highly opaque, densely packed arrays of metallic nanoparticles can be more transparent to infrared radiation than dielectrics such as germanium, even when the arrays are over 75% metal by volume. Such arrays form effective dielectrics that are virtually dispersion-free over ultra-broadband ranges of wavelengths from microns up to millimeters or more. Furthermore, the local refractive indices may be tuned by altering the size, shape, and spacing of the nanoparticles, allowing the design of gradient-index lenses that guide and focus light on the microscale. The electric field is also strongly concentrated in the gaps between the metallic nanoparticles, and the simultaneous focusing and squeezing of the electric field produces strong 'doubly-enhanced' hotspots which could boost measurements made using infrared spectroscopy and other non-linear processes over a broad range of frequencies. ; S.J.P. would like to acknowledge his studentship from the Centre for Doctoral Training on Theory and Simulation of Materials at Imperial College London funded by EPSRC Grant No. EP/L015579/1. R.A.A.-P., N.P.-P., L.G., and M.A.C.-D. thank the MINECO-Spain (CTM2014-58481R, CTM2017-84050R, CTQ2017-88648R, RYC-2015-19107 and RYC2016-20331), Xunta de Galicia (Centro Singular de Investigacion de Galicia, Acc. 2016-19 and EM2014/035), Generalitat de Cataluña (2017SGR883), URV (2017PFR-URV_B2-02), URV and Banco Santander (2017EXIT-08) and European Union (ERDF). X.X. acknowledges the Lee Family Scholarship. S.A.M. and R.V.C. acknowledge the EPSRC Mathematical Fundamentals of Metamaterials programme grant (EP/L024926/1) and the US Air Force Office of Scientific Research/EOARD (FA9550-17-1-0300). S.A.M. additionally acknowledges the Lee-Lucas Chair in Physics and DFG Cluster of Excellence Nanoinitiative Munich, and the Bavarian "Solar Technologies Go Hybrid" (SolTech) programme. R.V.C. thanks the Leverhulme Trust for their support. V.G. acknowledges the Consejo Superior de Investigaciones Cientficas (INTRAMURALES 201750I039).