513 research outputs found

    Fish and invertebrate use of restored vs. natural oyster reefs in a shallow temperate latitude estuary

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    Coastal marine habitats continue to be degraded, thereby compelling large-scale restoration in many parts of the world. Whether restored habitats function similarly to natural habitats and fully recover lost ecosystem services is unclear. In estuaries, oyster reefs have been degraded by multiple anthropogenic activities including destructive fishing practices and reduced water quality, motivating restoration to maintain oyster fisheries and other ecosystem services, often at relatively high cost. We compared fish and invertebrate communities on recently restored (0–1 year post-restoration), older restored (3–4 years post-restoration), and natural oyster reefs to determine if and when restored reefs support functionally similar faunal communities. To test the influence of landscape setting on the faunal communities, the restored and natural reefs, as well as a control without reef present, were distributed among three landscapes (on the edge of salt marsh away from seagrass [salt marsh landscape], on mudflats [mudflat landscape], and near to seagrass and salt marsh [seagrass landscape]). Oyster density and biomass were greatest on restored reef habitat, as were those of non-oyster bivalve species. Total abundance of invertebrates was much greater on oyster reefs than in control plots, regardless of reef or landscape type, yet were frequently highest on older restored reefs. Meanwhile, juvenile fish densities were greatest on natural reefs, at intermediate densities on older restored reefs, and least abundant on controls. When comparing the effects of reef age and landscape setting, juvenile fish densities were greatest on younger reefs within the mudflat landscape. Collectively, these results indicate that oyster reefs harbor higher densities of resident invertebrate prey, which may explain why reef habitat is also important for juvenile fish. Laboratory and field experiments supported the notion that gag grouper (a predatory demersal fish) forage more effectively on oyster reefs than on unstructured mud bottom, whereas our experiments suggest that flounders that utilize oyster reefs likely forage on adjacent mud bottom. Because landscape setting influenced fish and invertebrate communities on restored reefs, the ecological consequences of landscape setting should be incorporated into restoration decision making and site selection to enhance the recovery of ecosystem goods and services

    IceCube - the next generation neutrino telescope at the South Pole

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    IceCube is a large neutrino telescope of the next generation to be constructed in the Antarctic Ice Sheet near the South Pole. We present the conceptual design and the sensitivity of the IceCube detector to predicted fluxes of neutrinos, both atmospheric and extra-terrestrial. A complete simulation of the detector design has been used to study the detector's capability to search for neutrinos from sources such as active galaxies, and gamma-ray bursts.Comment: 8 pages, to be published with the proceedings of the XXth International Conference on Neutrino Physics and Astrophysics, Munich 200

    Sensitivity of the IceCube Detector to Astrophysical Sources of High Energy Muon Neutrinos

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    We present the results of a Monte-Carlo study of the sensitivity of the planned IceCube detector to predicted fluxes of muon neutrinos at TeV to PeV energies. A complete simulation of the detector and data analysis is used to study the detector's capability to search for muon neutrinos from sources such as active galaxies and gamma-ray bursts. We study the effective area and the angular resolution of the detector as a function of muon energy and angle of incidence. We present detailed calculations of the sensitivity of the detector to both diffuse and pointlike neutrino emissions, including an assessment of the sensitivity to neutrinos detected in coincidence with gamma-ray burst observations. After three years of datataking, IceCube will have been able to detect a point source flux of E^2*dN/dE = 7*10^-9 cm^-2s^-1GeV at a 5-sigma significance, or, in the absence of a signal, place a 90% c.l. limit at a level E^2*dN/dE = 2*10^-9 cm^-2s^-1GeV. A diffuse E-2 flux would be detectable at a minimum strength of E^2*dN/dE = 1*10^-8 cm^-2s^-1sr^-1GeV. A gamma-ray burst model following the formulation of Waxman and Bahcall would result in a 5-sigma effect after the observation of 200 bursts in coincidence with satellite observations of the gamma-rays.Comment: 33 pages, 13 figures, 6 table

    On the selection of AGN neutrino source candidates for a source stacking analysis with neutrino telescopes

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    The sensitivity of a search for sources of TeV neutrinos can be improved by grouping potential sources together into generic classes in a procedure that is known as source stacking. In this paper, we define catalogs of Active Galactic Nuclei (AGN) and use them to perform a source stacking analysis. The grouping of AGN into classes is done in two steps: first, AGN classes are defined, then, sources to be stacked are selected assuming that a potential neutrino flux is linearly correlated with the photon luminosity in a certain energy band (radio, IR, optical, keV, GeV, TeV). Lacking any secure detailed knowledge on neutrino production in AGN, this correlation is motivated by hadronic AGN models, as briefly reviewed in this paper. The source stacking search for neutrinos from generic AGN classes is illustrated using the data collected by the AMANDA-II high energy neutrino detector during the year 2000. No significant excess for any of the suggested groups was found.Comment: 43 pages, 12 figures, accepted by Astroparticle Physic

    All-particle cosmic ray energy spectrum measured with 26 IceTop stations

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    We report on a measurement of the cosmic ray energy spectrum with the IceTop air shower array, the surface component of the IceCube Neutrino Observatory at the South Pole. The data used in this analysis were taken between June and October, 2007, with 26 surface stations operational at that time, corresponding to about one third of the final array. The fiducial area used in this analysis was 0.122 km^2. The analysis investigated the energy spectrum from 1 to 100 PeV measured for three different zenith angle ranges between 0{\deg} and 46{\deg}. Because of the isotropy of cosmic rays in this energy range the spectra from all zenith angle intervals have to agree. The cosmic-ray energy spectrum was determined under different assumptions on the primary mass composition. Good agreement of spectra in the three zenith angle ranges was found for the assumption of pure proton and a simple two-component model. For zenith angles {\theta} < 30{\deg}, where the mass dependence is smallest, the knee in the cosmic ray energy spectrum was observed between 3.5 and 4.32 PeV, depending on composition assumption. Spectral indices above the knee range from -3.08 to -3.11 depending on primary mass composition assumption. Moreover, an indication of a flattening of the spectrum above 22 PeV were observed.Comment: 38 pages, 17 figure

    An improved method for measuring muon energy using the truncated mean of dE/dx

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    The measurement of muon energy is critical for many analyses in large Cherenkov detectors, particularly those that involve separating extraterrestrial neutrinos from the atmospheric neutrino background. Muon energy has traditionally been determined by measuring the specific energy loss (dE/dx) along the muon's path and relating the dE/dx to the muon energy. Because high-energy muons (E_mu > 1 TeV) lose energy randomly, the spread in dE/dx values is quite large, leading to a typical energy resolution of 0.29 in log10(E_mu) for a muon observed over a 1 km path length in the IceCube detector. In this paper, we present an improved method that uses a truncated mean and other techniques to determine the muon energy. The muon track is divided into separate segments with individual dE/dx values. The elimination of segments with the highest dE/dx results in an overall dE/dx that is more closely correlated to the muon energy. This method results in an energy resolution of 0.22 in log10(E_mu), which gives a 26% improvement. This technique is applicable to any large water or ice detector and potentially to large scintillator or liquid argon detectors.Comment: 12 pages, 16 figure

    Introme accurately predicts the impact of coding and noncoding variants on gene splicing, with clinical applications

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    Predicting the impact of coding and noncoding variants on splicing is challenging, particularly in non-canonical splice sites, leading to missed diagnoses in patients. Existing splice prediction tools are complementary but knowing which to use for each splicing context remains difficult. Here, we describe Introme, which uses machine learning to integrate predictions from several splice detection tools, additional splicing rules, and gene architecture features to comprehensively evaluate the likelihood of a variant impacting splicing. Through extensive benchmarking across 21,000 splice-altering variants, Introme outperformed all tools (auPRC: 0.98) for the detection of clinically significant splice variants. Introme is available at https://github.com/CCICB/introme .Patricia J. Sullivan, Velimir Gayevskiy, Ryan L. Davis, Marie Wong, Chelsea Mayoh, Amali Mallawaarachchi, Yvonne Hort, Mark J. McCabe, Sarah Beecroft, Matilda R. Jackson, Peer Arts, Andrew Dubowsky, Nigel Laing, Marcel E. Dinger, Hamish S. Scott, Emily Oates, Mark Pinese, and Mark J. Cowle

    Search for a W' boson decaying to a bottom quark and a top quark in pp collisions at sqrt(s) = 7 TeV

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    Results are presented from a search for a W' boson using a dataset corresponding to 5.0 inverse femtobarns of integrated luminosity collected during 2011 by the CMS experiment at the LHC in pp collisions at sqrt(s)=7 TeV. The W' boson is modeled as a heavy W boson, but different scenarios for the couplings to fermions are considered, involving both left-handed and right-handed chiral projections of the fermions, as well as an arbitrary mixture of the two. The search is performed in the decay channel W' to t b, leading to a final state signature with a single lepton (e, mu), missing transverse energy, and jets, at least one of which is tagged as a b-jet. A W' boson that couples to fermions with the same coupling constant as the W, but to the right-handed rather than left-handed chiral projections, is excluded for masses below 1.85 TeV at the 95% confidence level. For the first time using LHC data, constraints on the W' gauge coupling for a set of left- and right-handed coupling combinations have been placed. These results represent a significant improvement over previously published limits.Comment: Submitted to Physics Letters B. Replaced with version publishe
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