2,305 research outputs found

    Rediscovering the Maryland Darter (Etheostoma sellare)

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    The Maryland darter has not been observed since 1988. Historic populations were located in Deer Creek, Swan Creek, and Gashey’s Run all of which occur in the lower Susquehanna drainage. At these locations, specimens were collected or observed at the lowest riffle of the stream. Some researchers suggest this may be a large river darter. The Conowingo Dam complicates surveying below the facility due to the rapid fluctuations in water levels caused by regulation for power production. Surveying efforts included trawling in the mainstem, and visual surveys in the mainstem, and searching/sampling all historically known locations of Etheostoma sellare. During this study 153 Benthic trawls totaling 272.4 minutes of bottom time yielded no Maryland darters. Also 10,452 fish were collected from 4 tributary sites (3 historic and 1 new) yielding no Maryland Darters. In addition, during 307.1 man-hours of visual surveys no Maryland darters were observed. Considering the data from this study it is apparent that the Maryland darter has declined within its historical range. However, habitat assessment of new sites showed that habitat similar to E. sellare’s historical habitat still exists in the Susquehanna mainstem and tributaries. Additional surveys are needed to determine if the Maryland darter is extant

    The Information Needs of Mobile Searchers: A Framework

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    The growing use of Internet-connected mobile devices demands that we reconsider search user interface design in light of the context and information needs specific to mobile users. In this paper the authors present a framework of mobile information needs, juxtaposing search motives—casual, lookup, learn, and investigate—with search types—informational, geographic, personal information management, and transactional

    The Value of Comparative Animal Research : Krogh’s Principle Facilitates Scientific Discoveries

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    There are no conflicts of interest to declare. This paper developed from the 2016 Early Career Impact Award from the Federation of Associations in Behavioral & Brain Sciences to TJS. TJS has received funding from The Leverhulme Trust. FJPE is in receipt of funding from the BBSRC (BB/M001555/1). The National Institutes of Health has funded RDF (NS 034950, NS093277, NIMH 087930), AGO (HD079573, IOS-1354760) and AMK (HD081959). BAA is an Arnold O. Beckman postdoctoral fellow.Peer reviewedPostprin

    Evolution of the Antarctic Peninsula continental margin from Late Eocene to present: Seismic stratigraphic analysis related to the development of the Antarctic Peninsula Ice Sheet (APIS)

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    This investigation into Antarctic Peninsula Ice Sheet (APIS) development represents research from the stratigraphic record of three geographic areas: The James Ross Basin (northwestern Weddell Sea), the Pacific continental margin of the Antarctic Peninsula, and the Joinville Slope (northwestern Weddell Sea). The stratigraphic architecture of the James Ross Basin, NW Weddell Sea continental shelf, shows three major phases of deposition: pre-glacial, ice sheet growth, and ice sheet dominated. Each stratigraphic unit is characterized based upon seismic facies and stratigraphic architecture, and the ages are inferred from a seismic stratigraphic age model. A total of 34 grounding events of the Antarctic Peninsula Ice Sheet (APIS) are recorded on the continental shelf. The seven oldest glacial unconformities are believed to pre-date all previously identified unconformities on the peninsula continental shelf. An expanded section of Late Pliocene/Pleistocene deposits show a minimum of 10 grounding events. Isopachs of sedimentary sequences on the Antarctic Peninsula Pacific continental margin show shifting depocenters through time. Chronostratigraphic and seismic depth-converted data from ODP 178 cores allow the calculation of sediment flux for shelf units S3-S1 and rise units M6-M1. Sediment flux to the margin increases from the Late Eocene until the Late Pliocene and then decreases slightly from Late Pliocene to present. Significant increases in sediment flux coincide with early development of the APIS and during the early Pliocene warming period (Barker and Camerlenghi, 2002). Minimum glacial denudation rates for the Antarctic Peninsula are in the range of 0.06 to 0.13 mm yr -1. The Joinville Slope sediment wedge located in the northwestern Weddell Sea shows seismic stratigraphic evidence of mixed turbidite/contourite/hemipelagic deposition. A prominent seafloor unconformity and the exposed and eroded basement of the adjacent continental shelf indicate erosion by grounded ice during the Plio-Pleistocene. SHALDRIL recovered core at three drill sites, 12A, 5C, and 6D, and sampled sediments from the upper Oligocene, middle Miocene, and lower and upper Pliocene which are constrained by diatom and calcareous nannofossil assemblages. The sediment wedge shows no apparent hiatuses or large unconformities from Late Oligocene to the Lower Pliocene. Regional sedimentation rates show continuous sedimentation throughout the Late Paleogene and Neogene

    Financial Implications from Contracting Avian Influenza in a U.S. Broiler Operation

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    This essay evaluates the on-farm financial impacts of an avian influenza outbreak on a U.S. commercial broiler operation. It investigates how the timing and length of the outbreak impacts farm financial performance for two different farmers, beginning and experienced. Results indicate that a beginning farmer is more susceptible to significant financial losses. Both farmers are financially impacted more when avian influenza is contracted early in the investment and when the contamination and eradication of the virus was prolonged. Furthermore, this essay highlights the problems of using standard financial measures for analyzing disease outbreaks under production contract arrangements and presents alternative measures for financial performance. This study provides the foundation for future research to determine actuarially fair premiums for avian influenza insurance mechanisms
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