University of Southampton

About: University of Southampton is a education organization based out in Southampton, United Kingdom. It is known for research contribution in the topics: Population & Laser. The organization has 37184 authors who have published 99400 publications receiving 3462915 citations. The organization is also known as: Southampton University & Soton Uni.

Identifying potential environmental impacts of large-scale deployment of dedicated bioenergy crops in the UK

Abstract: There is momentum, globally, to increase the use of plant biomass for the production of heat, power and liquid transport fuels. This review assesses the evidence base for potential impacts of large-scale bioenergy crop deployment principally within the UK context, but with wider implications for Europe, the USA and elsewhere. We focus on second generation, dedicated lignocellulosic crops, but where appropriate draw comparison with current first-generation oil and starch crops, often primarily grown for food. For lignocellulosic crops, positive effects on soil properties, biodiversity, energy balance, greenhouse gas (GHG) mitigation, carbon footprint and visual impact are likely, when growth is compared to arable crops. Compared to replacement of set-aside and permanent unimproved grassland, benefits are less apparent. For hydrology, strict guidelines on catchment management must be enforced to ensure detrimental effects do not occur to hydrological resources. The threat of climate change suggests that action will be required to ensure new genotypes are available with high water use efficiency and that catchment-scale management is in place to secure these resources in future. In general, for environmental impacts, less is known about the consequences of large-scale deployment of the C4 grass Miscanthus, compared to short rotation coppice (SRC) willow and poplar, including effects on biodiversity and hydrology and this requires further research. Detailed consideration of GHG mitigation and energy balance for both crop growth and utilization suggest that perennial crops are favoured over annual crops, where energy balances may be poor. Similarly, crops for heat and power generation, especially combined heat and power (CHP), are favoured over the production of liquid biofuels. However, it is recognized that in contrast to heat and power, few alternatives exist for liquid transportation fuels at present and research to improve the efficiency and energy balance of liquid transport fuel production from lignocellulosic sources is a high current priority. Although SRC, and to a lesser extent energy grasses such as Miscanthus, may offer significant benefits for the environment, this potential will only be realized if landscape-scale issues are effectively managed and the whole chain of crop growth and utilization is placed within a regulatory framework where sustainability is a central driver. Land resource in the UK and throughout Europe will limit the contribution that crops can make to biofuel and other renewable targets, providing a strong driver to consider sustainability in a global context.

The LOFAR Two-metre Sky Survey. I. Survey description and preliminary data release

Abstract: The LOFAR Two-metre Sky Survey (LoTSS) is a deep 120-168 MHz imaging survey that will eventually cover the entire northern sky. Each of the 3170 pointings will be observed for 8 h, which, at most declinations, is sufficient to produce ~5? resolution images with a sensitivity of ~100 ?Jy/beam and accomplish the main scientific aims of the survey, which are to explore the formation and evolution of massive black holes, galaxies, clusters of galaxies and large-scale structure. Owing to the compact core and long baselines of LOFAR, the images provide excellent sensitivity to both highly extended and compact emission. For legacy value, the data are archived at high spectral and time resolution to facilitate subarcsecond imaging and spectral line studies. In this paper we provide an overview of the LoTSS. We outline the survey strategy, the observational status, the current calibration techniques, a preliminary data release, and the anticipated scientific impact. The preliminary images that we have released were created using a fully automated but direction-independent calibration strategy and are significantly more sensitive than those produced by any existing large-Area low-frequency survey. In excess of 44 000 sources are detected in the images that have a resolution of 25?, typical noise levels of less than 0.5 mJy/beam, and cover an area of over 350 square degrees in the region of the HETDEX Spring Field (right ascension 10h45m00s to 15h30m00s and declination 45°00?00? to 57°00?00?).

Holey optical fibers: an efficient modal model

Abstract: A new model for light propagation in holey optical fibers is developed in which the transverse index profile and the modal field are decomposed using different orthogonal functions. It is an efficient and accurate alternative to previous techniques, and is an invaluable tool to aid fabrication efforts. Using this model, a number of regimes of interest in these fibers are explored.

Deprivation, Diet, and Food-Retail Access: Findings from the Leeds ‘Food Deserts' Study

Abstract: Within a context of public policy debate in the United Kingdom on social exclusion, health inequalities, and food poverty, the metaphor of the 'food desert' caught the imagination of those involved in policy development. Drawing from a major cross-disciplinary investigation of food access and food poverty in British cities, the authors report in this paper findings from the first 'before/after' study of food consumption in a highly deprived area of a British city experiencing a sudden and significant change in its food-retail access. The study has been viewed as the first opportunity in the United Kingdom to assess the impact of a non-healthcare intervention (specifically a retail-provision intervention) on food-consumption patterns, and by extension diet-related health, in such a deprived, previously poor-retail-access community. The paper offers evidence of a positive but modest impact of the retail intervention on diet, and the authors discuss the ways in which their findings are potentially significant in the context of policy debate.

Fabrication and characterization of n-ZnO/p-AlGaN heterojunction light-emitting diodes on 6H-SiC substrates

Abstract: We report on the fabrication of n-ZnO/p-AlGaN heterojunction light-emitting diodes on 6H-SiC substrates. Hydride vapor phase epitaxy was used to grow p-type AlGaN, while chemical vapor deposition was used to produce the n-type ZnO layers. Diode-like, rectifying I-V characteristics, with threshold voltage ~3.2V and low reverse leakage current ~10(-7)A, are observed at room temperature. Intense ultraviolet emission with a peak wavelength near 389 mn is observed when the diode is forward biased; this emission is found to be stable at temperatures up to 500K and shown to originate from recombination within the ZnO.