102 research outputs found

    Notes on insects recently introduced to Metro Vancouver and other newly recorded species from British Columbia

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    Sixteen insects species are recorded for the first time from British Columbia, including seven new to Canada. These records are comprised of nine introduced species, including the first record of Rhopalum gracile Wesmael (Hymenoptera: Crabronidae) from North America, and range extensions for seven species native to the Nearctic region

    RICE Limits on the Diffuse Ultra-High Energy Neutrino Flux

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    We present new limits on ultra-high energy neutrino fluxes above 100 PeV based on data collected by the Radio Ice Cherenkov Experiment (RICE) at the South Pole from 1999-2005. We discuss estimation of backgrounds, calibration and data analysis algorithms (both on-line and off-line), procedures used for the dedicated neutrino search, and refinements in our Monte Carlo (MC) simulation, including recent in situ measurements of the complex ice dielectric constant. An enlarged data set and a more detailed study of hadronic showers results in a sensitivity improvement of more than one order of magnitude compared to our previously published results. Examination of the full RICE data set yields zero acceptable neutrino candidates, resulting in 95% confidence-level model dependent limits on the flux (E_\nu)^2(d\phi/dE_\nu)<10^{-6} GeV/(cm^2s~sr}) in the energy range 10^{17}< E_\nu< 10^{20} eV. The new RICE results rule out the most intense flux model projections at 95% confidence level.Comment: Submitted to Astropart. Phy

    A First Search for Cosmogenic Neutrinos with the ARIANNA Hexagonal Radio Array

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    The ARIANNA experiment seeks to observe the diffuse flux of neutrinos in the 10^8 - 10^10 GeV energy range using a grid of radio detectors at the surface of the Ross Ice Shelf of Antarctica. The detector measures the coherent Cherenkov radiation produced at radio frequencies, from about 100 MHz to 1 GHz, by charged particle showers generated by neutrino interactions in the ice. The ARIANNA Hexagonal Radio Array (HRA) is being constructed as a prototype for the full array. During the 2013-14 austral summer, three HRA stations collected radio data which was wirelessly transmitted off site in nearly real-time. The performance of these stations is described and a simple analysis to search for neutrino signals is presented. The analysis employs a set of three cuts that reject background triggers while preserving 90% of simulated cosmogenic neutrino triggers. No neutrino candidates are found in the data and a model-independent 90% confidence level Neyman upper limit is placed on the all flavor neutrino+antineutrino flux in a sliding decade-wide energy bin. The limit reaches a minimum of 1.9x10^-23 GeV^-1 cm^-2 s^-1 sr^-1 in the 10^8.5 - 10^9.5 GeV energy bin. Simulations of the performance of the full detector are also described. The sensitivity of the full ARIANNA experiment is presented and compared with current neutrino flux models.Comment: 22 pages, 22 figures. Published in Astroparticle Physic

    Performance of the ARIANNA Hexagonal Radio Array

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    Installation of the ARIANNA Hexagonal Radio Array (HRA) on the Ross Ice Shelf of Antarctica has been completed. This detector serves as a pilot program to the ARIANNA neutrino telescope, which aims to measure the diffuse flux of very high energy neutrinos by observing the radio pulse generated by neutrino-induced charged particle showers in the ice. All HRA stations ran reliably and took data during the entire 2014-2015 austral summer season. A new radio signal direction reconstruction procedure is described, and is observed to have a resolution better than a degree. The reconstruction is used in a preliminary search for potential neutrino candidate events in the data from one of the newly installed detector stations. Three cuts are used to separate radio backgrounds from neutrino signals. The cuts are found to filter out all data recorded by the station during the season while preserving 85.4% of simulated neutrino events that trigger the station. This efficiency is similar to that found in analyses of previous HRA data taking seasons.Comment: Proceedings from the 34th ICRC2015, http://icrc2015.nl/ . 8 pages, 6 figure

    Comparative Toxicological Assessment of 2 Bisphenols Using a Systems Approach: Evaluation of the Behavioral and Transcriptomic Responses of Danio rerio to Bisphenol A and Tetrabromobisphenol A

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    The zebrafish (Danio rerio) is becoming a critical component of new approach methods (NAMs) in chemical risk assessment. As a whole organism in vitro NAM, the zebrafish model offers significant advantages over individual cell-line testing, including toxicokinetic and toxicodynamic competencies. A transcriptomic approach not only allows for insight into mechanism of action for both apical endpoints and unobservable adverse outcomes, but also changes in gene expression induced by lower, environmentally relevant concentrations. In this study, we used a larval zebrafish model to assess the behavioral and transcriptomic alterations caused by subphenotypic concentrations of 2 chemicals with the same structural backbone, the endocrine-disrupting chemicals bisphenol A and tetrabromobisphenol A. Following assessment of behavioral toxicity, we used a transcriptomic approach to identify molecular pathways associated with previously described phenotypes. We also determined the transcriptomic point of departure for each chemical by modeling gene expression changes as continuous systems which allows for the identification of a single concentration at which toxic effects can be predicted. This can then be investigated with confirmatory cell-based testing in an integrated approach to testing and assessment to determine risk to human health and the environment with greater confidence. This paper demonstrates the impact of using a multi-faceted approach for evaluating the physiological and neurotoxic effects of exposure to structurally related chemicals. By comparing phenotypic effects with transcriptomic outcomes, we were able to differentiate, characterize, and rank the toxicities of related bisphenols, which demonstrates methodological advantages unique to the larval zebrafish NAM

    Livetime and sensitivity of the ARIANNA Hexagonal Radio Array

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    The ARIANNA collaboration completed the installation of the hexagonal radio array (HRA) in December 2014, serving as a pilot program for a planned high energy neutrino telescope located about 110 km south of McMurdo Station on the Ross Ice Shelf near the coast of Antarctica. The goal of ARIANNA is to measure both diffuse and point fluxes of astrophysical neutrinos at energies in excess of 1016 eV. Upgraded hardware has been installed during the 2014 deployment season and stations show a livetime of better than 90% between commissioning and austral sunset. Though designed to observe radio pulses from neutrino interactions originating within the ice below each detector, one station was modified to study the low-frequency environment and signals from above. We provide evidence that the HRA observed both continuous emission from the Galaxy and a transient solar burst. Preliminary work on modeling the (weak) Galactic signal confirm the absolute sensitivity of the HRA detector system.Comment: Proceedings from the 34th ICRC2015, http://icrc2015.nl/, 8 pages, 6 figure

    Constraints on the Ultra-High Energy Neutrino Flux from Gamma-Ray Bursts from a Prototype Station of the Askaryan Radio Array

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    We report on a search for ultra-high-energy (UHE) neutrinos from gamma-ray bursts (GRBs) in the data set collected by the Testbed station of the Askaryan Radio Array (ARA) in 2011 and 2012. From 57 selected GRBs, we observed no events that survive our cuts, which is consistent with 0.12 expected background events. Using NeuCosmA as a numerical GRB reference emission model, we estimate upper limits on the prompt UHE GRB neutrino fluence and quasi-diffuse flux from 10710^{7} to 101010^{10} GeV. This is the first limit on the prompt UHE GRB neutrino quasi-diffuse flux above 10710^{7} GeV.Comment: 14 pages, 8 figures, Published in Astroparticle Physics Journa
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