405 research outputs found

    Local impurity effects in superconducting graphene

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    We study the effect of impurities in superconducting graphene and discuss their influence on the local electronic properties. In particular, we consider the case of magnetic and non-magnetic impurities being either strongly localized or acting as a potential averaged over one unit cell. The spin dependent local density of states is calculated and possibilities for visualizing impurities by means of scanning tunneling experiments is pointed out. A possibility of identifying magnetic scatters even by non spin-polarized scanning tunneling spectroscopy is explained.Comment: 4 pages, 4 figure

    Agricultural innovation and adaptation to climate change: empirical evidence from diverse agro-ecologies in South Asia

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    While impacts of climate change on agricultural systems have been widely researched, there is still limited understanding of what agricultural practices evolves over time in response to both climatic and non-climatic drivers and how actors mobilize their resources, institutions and practices in South Asia. Through eight case studies and a survey of300 households in 15 locations in India, Nepal and Bangladesh, this paper generates empirical evidence on emerging agricultural interventions in contrasting socio-economic, geographical and agro-ecological contexts. The study shows that several farm practices emerge out in response to multiple drivers over time; some of them can be further adjusted to the challenge of climate change by planned adaptation programs. Most actors, however, have considered private risks in the short run. Although there has been some progress in streamlining climate change into strategic planning in different countries of South Asia, policy, research and extension systems lack adequate attention to wider resilience of the system. Based on this analysis, we recommend that adaptation policies should complement farmers’ responses to climate change through informed research and extension systems and pro-poor government policies that improve adaptation and coordinate activities of different actors

    Remarks on the tight-binding model of graphene

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    We address a simple but fundamental issue arising in the study of graphene, as well as of other systems that have a crystalline structure with more than one atom per unit cell. For these systems, the choice of the tight-binding basis is not unique. For monolayer graphene two bases are widely used in the literature. While the expectation values of operators describing physical quantities should be independent of basis, the form of the operators may depend on the basis, especially in the presence of disorder or of an applied magnetic field. Using the inappropriate form of certain operators may lead to erroneous physical predictions. We discuss the two bases used to describe monolayer graphene, as well as the form of the most commonly used operators in the two bases. We repeat our analysis for the case of bilayer graphene.Comment: 15 pages, 4 figure

    A global map of terrestrial habitat types

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    We provide a global, spatially explicit characterization of 47 terrestrial habitat types, as defined in the International Union for Conservation of Nature (IUCN) habitat classification scheme, which is widely used in ecological analyses, including for quantifying species’ Area of Habitat. We produced this novel habitat map for the year 2015 by creating a global decision tree that intersects the best currently available global data on land cover, climate and land use. We independently validated the map using occurrence data for 828 species of vertebrates (35152 point plus 8181 polygonal occurrences) and 6026 sampling sites. Across datasets and mapped classes we found on average a balanced accuracy of 0.77 (+ ¯ 0.14 SD) at Level 1 and 0.71 (+ ¯ 0.15 SD) at Level 2, while noting potential issues of using occurrence records for validation. The maps broaden our understanding of habitats globally, assist in constructing area of habitat refinements and are relevant for broad-scale ecological studies and future IUCN Red List assessments. Periodic updates are planned as better or more recent data becomes available

    Non-malarial febrile illness: a systematic review of published aetiological studies and case reports from Africa, 1980-2015.

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    BACKGROUND: The availability of reliable point-of-care tests for malaria has heralded a paradigm shift in the management of febrile illnesses away from presumptive antimalarial therapy. In the absence of a definitive diagnosis, health care providers are more likely to prescribe empirical antimicrobials to those who test negative for malaria. To improve management and guide further test development, better understanding is needed of the true causative agents and their geographic variability. METHODS: A systematic review of published literature was undertaken to characterise the spectrum of pathogens causing non-malaria febrile illness in Africa (1980-2015). Literature searches were conducted in English and French languages in six databases: MEDLINE, EMBASE, Global Health (CABI), WHO Global Health Library, PASCAL, and Bulletin de la Société Française de Parasitologie (BDSP). Selection criteria included reporting on an infection or infections with a confirmed diagnosis, defined as pathogens detected in or cultured from samples from normally sterile sites, or serological evidence of current or past infection. A number of published articles (rather than incidence or prevalence) reporting a given pathogen were presented. RESULTS: A total of 16,523 records from 48 African countries were screened, of which 1065 (6.4%) met selection criteria. Bacterial infections were reported in 564 (53.0%) records, viral infections in 374 (35.1%), parasitic infections in 47 (4.4%), fungal infections in nine (0.8%), and 71 (6.7%) publications reported more than one pathogen group. Age range of the study population was not specified in 233 (21.9%) publications. Staphylococcus aureus (18.2%), non-typhoidal Salmonella (17.3%), and Escherichia coli (15.4%) were the commonly reported bacterial infections whereas Rift Valley fever virus (7.4%), yellow fever virus (7.0%), and Ebola virus (6.7%) were the most commonly reported viral infections. Dengue virus infection, previously not thought to be widespread in Africa, was reported in 54 (5.1%) of articles. CONCLUSIONS: This review summarises the published reports of non-malaria pathogens that may cause febrile illness in Africa. As the threat of antimicrobial resistance looms, knowledge of the distribution of infectious agents causing fever should facilitate priority setting in the development of new diagnostic tools and improved antimicrobial stewardship. TRIAL REGISTRATION: PROSPERO, CRD42016049281

    Carrier lifetime in erbium-doped GaN waveguide emitting in 1540 nm wavelength

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    This is the published version. Copyright 2010 American Institute of PhysicsWe report the characteristics of an erbium-doped GaNsemiconductorwaveguideamplifier grown by metal-organic chemical vapor deposition. We demonstrated that both 980 and 1480 nm optical pumping were efficient to create population inversion between the I413/2 and I415/2 energy levels. The carrier lifetime in the I413/2 energy band was measured to be approximately 1.5 ms in room temperature, which is slightly shorter than that in erbium-doped silica due to the interaction between the erbium ions and the semiconductor lattice structure. But it is significantly longer than the carrier lifetime in a typical semiconductor optical amplifier which is in the nanosecond regime
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