8,693 research outputs found

    Distribution and Status of Rare and Endangered Mussels (Mollusca: Margaritiferidae, Unionidae) in Arkansas

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    Knowledge of the distribution and population status of freshwater bivalves occurring in Arkansas has increased markedly during the past decade. Sufficient data has become available to delineate species which are rare and/or endangered within the state. Historical and recent records from Arkansas exist for four mussels currently listed as federally endangered species: the fat pocketbook (Potamilus capax), the pink mucket (Lampsilis orbiculata), Curtis\u27 pearly mussel (Epioblasma florentina curtisi), and the turgid-blossom pearly mussel (Epioblasma turgidula). Ten additional mussels which occur or were thought to occur in Arkansas are being considered for federal protection by the United States Fish and Wildlife Service. Several other taxa may warrant protective status

    Climate change and geotourism : impacts, challenges and opportunities

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    Climate change and rising sea levels present significant challenges for geotourism destinations and activities. Accelerated changes in geomorphological processes threaten or diminish both the physical existence and aesthetic qualities of geoheritage assets, and hence the visitor experience, as well as presenting increased or new risks from natural hazards. This is particularly a concern in mountain and coastal areas, and also where greater extremes of temperature and precipitation affect visitor comfort. A literature review was conducted to assess the extent to which the consequences of climate change have been recognised in geotourism research. With the exception of glacier-based geotourism, few studies have considered the impacts of climate change and reported the planning or development of adaptation measures. However, the didactic potential of geotourism in raising awareness of climate change has been commonly recognised. A review of the wider tourism literature identified additional destination-supply and visitor-demand issues that will affect the sustainability of geotourism in the face of climate change. These include changes in visitor motivations, travel behaviour, perceptions of destination image, and reactions to local, national, and international mitigation and adaptation responses, as well as geoethical considerations around carbon footprints and sustainable modes of travel. Situating geotourism within a broader body of multidisciplinary tourism research should help inform adaptation strategies in conjunction with measures to adapt to the physical impacts of climate change on geotourism sites.Publisher PDFPeer reviewe

    Geoconservation principles and protected area management

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    Geoconservation includes the protection of geoheritage features and geosites and the application of geoconservation principles more generally in the sustainable management of protected areas and in the wider landscape. This article reviews: 1) geoconservation principles and objectives for geosite management planning; and 2) the wider relevance of geoconservation and how the application of geoconservation principles across the full range of IUCN protected area management categories, UNESCO Global Geoparks and Biosphere Reserves, World Heritage sites, Ramsar sites and marine protected areas would benefit conservation of biodiversity and geodiversity and support wider nature conservation objectives, including climate change adaptation, connecting people and nature and sustainable development. In particular, the concepts of ‘nature and people’ and ‘conserving nature's stage’ provide opportunities for developing more holistic approaches to nature conservation.Publisher PDFPeer reviewe

    Fraxinus americana L.

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    https://thekeep.eiu.edu/herbarium_specimens_byname/15029/thumbnail.jp

    Fraxinus americana L.

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    https://thekeep.eiu.edu/herbarium_specimens_byname/15029/thumbnail.jp

    Holocene variations in the Scottish marine radiocarbon reservoir effect

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    We assessed the evidence for variations in the marine radiocarbon reservoir effect (MRE) at coastal, archaeological Iron Age sites in north and west Scotland by comparing AMS measurements of paired marine and terrestrial materials (4 pairs per context). DeltaR values were calculated from measurements on material from 3 sites using 6 sets of samples, all of which were deposited around 2000 BP. The weighted mean of the DeltaR determinations was -79 +/- 17 C-14 yr, which indicates a consistent, reduced offset between atmospheric and surface ocean C-14 specific activity for these sites during this period, relative to the present day (DeltaR = similar to0 C-14 yr). We discuss the significance of this revised AR correction by using the example of wheelhouse chronologies at Hornish Point and their development in relation to brochs. In addition, we assess the importance of using the concepts of MRE correction and AR variations when constructing chronologies using C-14 measurements made on materials that contain marine- derived carbon

    The Role of Source Coherence in Atom Interferometery

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    The role of source cloud spatial coherence in a Mach-Zehnder type atom interferometer is experimentally investigated. The visibility and contrast of a Bose-Einstein condensate (BEC) and three thermal sources with varying spatial coherence are compared as a function of interferometer time. At short times, the fringe visibility of a BEC source approaches 100 % nearly independent of pi pulse efficiency, while thermal sources have fringe visibilities limited to the mirror efficiency. More importantly for precision measurement systems, the BEC source maintains interference at interferometer times significantly beyond the thermal source
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